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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="Fri Dec 7 20:07:44 2007" /> 9 <meta name="created" content="Wed Dec 12 05:53:55 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li> 27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
29</ul> 29</ul>
30</li> 30</li>
31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li> 32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a>
33<ul><li><a href="#The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</a></li>
34</ul>
35</li>
33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> 36<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
34<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li> 37<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
35<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li> 38<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> 39<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li> 40<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
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185you actually want to know.</p> 188you actually want to know.</p>
186 </dd> 189 </dd>
187 <dt>int ev_version_major ()</dt> 190 <dt>int ev_version_major ()</dt>
188 <dt>int ev_version_minor ()</dt> 191 <dt>int ev_version_minor ()</dt>
189 <dd> 192 <dd>
190 <p>You can find out the major and minor version numbers of the library 193 <p>You can find out the major and minor ABI version numbers of the library
191you linked against by calling the functions <code>ev_version_major</code> and 194you linked against by calling the functions <code>ev_version_major</code> and
192<code>ev_version_minor</code>. If you want, you can compare against the global 195<code>ev_version_minor</code>. If you want, you can compare against the global
193symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 196symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
194version of the library your program was compiled against.</p> 197version of the library your program was compiled against.</p>
198 <p>These version numbers refer to the ABI version of the library, not the
199release version.</p>
195 <p>Usually, it's a good idea to terminate if the major versions mismatch, 200 <p>Usually, it's a good idea to terminate if the major versions mismatch,
196as this indicates an incompatible change. Minor versions are usually 201as this indicates an incompatible change. Minor versions are usually
197compatible to older versions, so a larger minor version alone is usually 202compatible to older versions, so a larger minor version alone is usually
198not a problem.</p> 203not a problem.</p>
199 <p>Example: Make sure we haven't accidentally been linked against the wrong 204 <p>Example: Make sure we haven't accidentally been linked against the wrong
200version.</p> 205version.</p>
201<pre> assert ((&quot;libev version mismatch&quot;, 206<pre> assert ((&quot;libev version mismatch&quot;,
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529one iteration of the loop. This is useful if you are waiting for some 534one iteration of the loop. This is useful if you are waiting for some
530external event in conjunction with something not expressible using other 535external event in conjunction with something not expressible using other
531libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is 536libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
532usually a better approach for this kind of thing.</p> 537usually a better approach for this kind of thing.</p>
533 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 538 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
539<pre> - Before the first iteration, call any pending watchers.
534<pre> * If there are no active watchers (reference count is zero), return. 540 * If there are no active watchers (reference count is zero), return.
535 - Queue prepare watchers and then call all outstanding watchers. 541 - Queue all prepare watchers and then call all outstanding watchers.
536 - If we have been forked, recreate the kernel state. 542 - If we have been forked, recreate the kernel state.
537 - Update the kernel state with all outstanding changes. 543 - Update the kernel state with all outstanding changes.
538 - Update the &quot;event loop time&quot;. 544 - Update the &quot;event loop time&quot;.
539 - Calculate for how long to block. 545 - Calculate for how long to block.
540 - Block the process, waiting for any events. 546 - Block the process, waiting for any events.
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769 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 775 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
770 <dd> 776 <dd>
771 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 777 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
772events but its callback has not yet been invoked). As long as a watcher 778events but its callback has not yet been invoked). As long as a watcher
773is pending (but not active) you must not call an init function on it (but 779is pending (but not active) you must not call an init function on it (but
774<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 780<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
775libev (e.g. you cnanot <code>free ()</code> it).</p> 781make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
782it).</p>
776 </dd> 783 </dd>
777 <dt>callback ev_cb (ev_TYPE *watcher)</dt> 784 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
778 <dd> 785 <dd>
779 <p>Returns the callback currently set on the watcher.</p> 786 <p>Returns the callback currently set on the watcher.</p>
780 </dd> 787 </dd>
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795invocation after new events have been received. This is useful, for 802invocation after new events have been received. This is useful, for
796example, to reduce latency after idling, or more often, to bind two 803example, to reduce latency after idling, or more often, to bind two
797watchers on the same event and make sure one is called first.</p> 804watchers 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 805 <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> 806you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
807 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
808pending.</p>
800 <p>The default priority used by watchers when no priority has been set is 809 <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> 810always <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 811 <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 812fine, 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> 813or might not have been adjusted to be within valid range.</p>
814 </dd>
815 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
816 <dd>
817 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
818<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
819can deal with that fact.</p>
820 </dd>
821 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
822 <dd>
823 <p>If the watcher is pending, this function returns clears its pending status
824and returns its <code>revents</code> bitset (as if its callback was invoked). If the
825watcher isn't pending it does nothing and returns <code>0</code>.</p>
805 </dd> 826 </dd>
806</dl> 827</dl>
807 828
808 829
809 830
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923<p>If you cannot run the fd in non-blocking mode (for example you should not 944<p>If you cannot run the fd in non-blocking mode (for example you should not
924play around with an Xlib connection), then you have to seperately re-test 945play around with an Xlib connection), then you have to seperately re-test
925whether a file descriptor is really ready with a known-to-be good interface 946whether a file descriptor is really ready with a known-to-be good interface
926such as poll (fortunately in our Xlib example, Xlib already does this on 947such as poll (fortunately in our Xlib example, Xlib already does this on
927its own, so its quite safe to use).</p> 948its own, so its quite safe to use).</p>
949
950</div>
951<h3 id="The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</h3>
952<div id="The_special_problem_of_disappearing_-2">
953<p>Some backends (e.g kqueue, epoll) need to be told about closing a file
954descriptor (either by calling <code>close</code> explicitly or by any other means,
955such as <code>dup</code>). The reason is that you register interest in some file
956descriptor, but when it goes away, the operating system will silently drop
957this interest. If another file descriptor with the same number then is
958registered with libev, there is no efficient way to see that this is, in
959fact, a different file descriptor.</p>
960<p>To avoid having to explicitly tell libev about such cases, libev follows
961the following policy: Each time <code>ev_io_set</code> is being called, libev
962will assume that this is potentially a new file descriptor, otherwise
963it is assumed that the file descriptor stays the same. That means that
964you <i>have</i> to call <code>ev_io_set</code> (or <code>ev_io_init</code>) when you change the
965descriptor even if the file descriptor number itself did not change.</p>
966<p>This is how one would do it normally anyway, the important point is that
967the libev application should not optimise around libev but should leave
968optimisations to libev.</p>
969
970
971
972
928<dl> 973<dl>
929 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 974 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
930 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 975 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
931 <dd> 976 <dd>
932 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 977 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
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1081but on wallclock time (absolute time). You can tell a periodic watcher 1126but on wallclock time (absolute time). You can tell a periodic watcher
1082to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1127to trigger &quot;at&quot; some specific point in time. For example, if you tell a
1083periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () 1128periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
1084+ 10.</code>) and then reset your system clock to the last year, then it will 1129+ 10.</code>) and then reset your system clock to the last year, then it will
1085take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1130take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
1086roughly 10 seconds later and of course not if you reset your system time 1131roughly 10 seconds later).</p>
1087again).</p>
1088<p>They can also be used to implement vastly more complex timers, such as 1132<p>They can also be used to implement vastly more complex timers, such as
1089triggering an event on eahc midnight, local time.</p> 1133triggering an event on each midnight, local time or other, complicated,
1134rules.</p>
1090<p>As with timers, the callback is guarenteed to be invoked only when the 1135<p>As with timers, the callback is guarenteed to be invoked only when the
1091time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1136time (<code>at</code>) has been passed, but if multiple periodic timers become ready
1092during the same loop iteration then order of execution is undefined.</p> 1137during the same loop iteration then order of execution is undefined.</p>
1093<dl> 1138<dl>
1094 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1139 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
… …
1096 <dd> 1141 <dd>
1097 <p>Lots of arguments, lets sort it out... There are basically three modes of 1142 <p>Lots of arguments, lets sort it out... There are basically three modes of
1098operation, and we will explain them from simplest to complex:</p> 1143operation, and we will explain them from simplest to complex:</p>
1099 <p> 1144 <p>
1100 <dl> 1145 <dl>
1101 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1146 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
1102 <dd> 1147 <dd>
1103 <p>In this configuration the watcher triggers an event at the wallclock time 1148 <p>In this configuration the watcher triggers an event at the wallclock time
1104<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1149<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
1105that is, if it is to be run at January 1st 2011 then it will run when the 1150that is, if it is to be run at January 1st 2011 then it will run when the
1106system time reaches or surpasses this time.</p> 1151system time reaches or surpasses this time.</p>
1107 </dd> 1152 </dd>
1108 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1153 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
1109 <dd> 1154 <dd>
1110 <p>In this mode the watcher will always be scheduled to time out at the next 1155 <p>In this mode the watcher will always be scheduled to time out at the next
1111<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1156<code>at + N * interval</code> time (for some integer N, which can also be negative)
1112of any time jumps.</p> 1157and then repeat, regardless of any time jumps.</p>
1113 <p>This can be used to create timers that do not drift with respect to system 1158 <p>This can be used to create timers that do not drift with respect to system
1114time:</p> 1159time:</p>
1115<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1160<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
1116 1161
1117</pre> 1162</pre>
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1120full hour (UTC), or more correctly, when the system time is evenly divisible 1165full hour (UTC), or more correctly, when the system time is evenly divisible
1121by 3600.</p> 1166by 3600.</p>
1122 <p>Another way to think about it (for the mathematically inclined) is that 1167 <p>Another way to think about it (for the mathematically inclined) is that
1123<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1168<code>ev_periodic</code> will try to run the callback in this mode at the next possible
1124time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1169time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1170 <p>For numerical stability it is preferable that the <code>at</code> value is near
1171<code>ev_now ()</code> (the current time), but there is no range requirement for
1172this value.</p>
1125 </dd> 1173 </dd>
1126 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1174 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
1127 <dd> 1175 <dd>
1128 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1176 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
1129ignored. Instead, each time the periodic watcher gets scheduled, the 1177ignored. Instead, each time the periodic watcher gets scheduled, the
1130reschedule callback will be called with the watcher as first, and the 1178reschedule callback will be called with the watcher as first, and the
1131current time as second argument.</p> 1179current time as second argument.</p>
1132 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1180 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
1133ever, or make any event loop modifications</i>. If you need to stop it, 1181ever, or make any event loop modifications</i>. If you need to stop it,
1134return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1182return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
1135starting a prepare watcher).</p> 1183starting an <code>ev_prepare</code> watcher, which is legal).</p>
1136 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1184 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1137ev_tstamp now)</code>, e.g.:</p> 1185ev_tstamp now)</code>, e.g.:</p>
1138<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1186<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1139 { 1187 {
1140 return now + 60.; 1188 return now + 60.;
… …
1160 <dd> 1208 <dd>
1161 <p>Simply stops and restarts the periodic watcher again. This is only useful 1209 <p>Simply stops and restarts the periodic watcher again. This is only useful
1162when you changed some parameters or the reschedule callback would return 1210when you changed some parameters or the reschedule callback would return
1163a different time than the last time it was called (e.g. in a crond like 1211a different time than the last time it was called (e.g. in a crond like
1164program when the crontabs have changed).</p> 1212program when the crontabs have changed).</p>
1213 </dd>
1214 <dt>ev_tstamp offset [read-write]</dt>
1215 <dd>
1216 <p>When repeating, this contains the offset value, otherwise this is the
1217absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1218 <p>Can be modified any time, but changes only take effect when the periodic
1219timer fires or <code>ev_periodic_again</code> is being called.</p>
1165 </dd> 1220 </dd>
1166 <dt>ev_tstamp interval [read-write]</dt> 1221 <dt>ev_tstamp interval [read-write]</dt>
1167 <dd> 1222 <dd>
1168 <p>The current interval value. Can be modified any time, but changes only 1223 <p>The current interval value. Can be modified any time, but changes only
1169take effect when the periodic timer fires or <code>ev_periodic_again</code> is being 1224take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
… …
1468are ready to run (it's actually more complicated: it only runs coroutines 1523are ready to run (it's actually more complicated: it only runs coroutines
1469with priority higher than or equal to the event loop and one coroutine 1524with priority higher than or equal to the event loop and one coroutine
1470of lower priority, but only once, using idle watchers to keep the event 1525of lower priority, but only once, using idle watchers to keep the event
1471loop from blocking if lower-priority coroutines are active, thus mapping 1526loop from blocking if lower-priority coroutines are active, thus mapping
1472low-priority coroutines to idle/background tasks).</p> 1527low-priority coroutines to idle/background tasks).</p>
1528<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1529priority, to ensure that they are being run before any other watchers
1530after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1531too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1532supports this, they will be called before other <code>ev_check</code> watchers did
1533their job. As <code>ev_check</code> watchers are often used to embed other event
1534loops those other event loops might be in an unusable state until their
1535<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1536others).</p>
1473<dl> 1537<dl>
1474 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1538 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1475 <dt>ev_check_init (ev_check *, callback)</dt> 1539 <dt>ev_check_init (ev_check *, callback)</dt>
1476 <dd> 1540 <dd>
1477 <p>Initialises and configures the prepare or check watcher - they have no 1541 <p>Initialises and configures the prepare or check watcher - they have no
1478parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1542parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1479macros, but using them is utterly, utterly and completely pointless.</p> 1543macros, but using them is utterly, utterly and completely pointless.</p>
1480 </dd> 1544 </dd>
1481</dl> 1545</dl>
1482<p>Example: To include a library such as adns, you would add IO watchers 1546<p>There are a number of principal ways to embed other event loops or modules
1483and a timeout watcher in a prepare handler, as required by libadns, and 1547into libev. Here are some ideas on how to include libadns into libev
1548(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1549use for an actually working example. Another Perl module named <code>EV::Glib</code>
1550embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1551into the Glib event loop).</p>
1552<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1484in a check watcher, destroy them and call into libadns. What follows is 1553and in a check watcher, destroy them and call into libadns. What follows
1485pseudo-code only of course:</p> 1554is pseudo-code only of course. This requires you to either use a low
1555priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1556the callbacks for the IO/timeout watchers might not have been called yet.</p>
1486<pre> static ev_io iow [nfd]; 1557<pre> static ev_io iow [nfd];
1487 static ev_timer tw; 1558 static ev_timer tw;
1488 1559
1489 static void 1560 static void
1490 io_cb (ev_loop *loop, ev_io *w, int revents) 1561 io_cb (ev_loop *loop, ev_io *w, int revents)
1491 { 1562 {
1492 // set the relevant poll flags
1493 // could also call adns_processreadable etc. here
1494 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1495 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1496 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1497 } 1563 }
1498 1564
1499 // create io watchers for each fd and a timer before blocking 1565 // create io watchers for each fd and a timer before blocking
1500 static void 1566 static void
1501 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1567 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
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1507 1573
1508 /* the callback is illegal, but won't be called as we stop during check */ 1574 /* the callback is illegal, but won't be called as we stop during check */
1509 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1575 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1510 ev_timer_start (loop, &amp;tw); 1576 ev_timer_start (loop, &amp;tw);
1511 1577
1512 // create on ev_io per pollfd 1578 // create one ev_io per pollfd
1513 for (int i = 0; i &lt; nfd; ++i) 1579 for (int i = 0; i &lt; nfd; ++i)
1514 { 1580 {
1515 ev_io_init (iow + i, io_cb, fds [i].fd, 1581 ev_io_init (iow + i, io_cb, fds [i].fd,
1516 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1582 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1517 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1583 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1518 1584
1519 fds [i].revents = 0; 1585 fds [i].revents = 0;
1520 iow [i].data = fds + i;
1521 ev_io_start (loop, iow + i); 1586 ev_io_start (loop, iow + i);
1522 } 1587 }
1523 } 1588 }
1524 1589
1525 // stop all watchers after blocking 1590 // stop all watchers after blocking
… …
1527 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1592 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1528 { 1593 {
1529 ev_timer_stop (loop, &amp;tw); 1594 ev_timer_stop (loop, &amp;tw);
1530 1595
1531 for (int i = 0; i &lt; nfd; ++i) 1596 for (int i = 0; i &lt; nfd; ++i)
1597 {
1598 // set the relevant poll flags
1599 // could also call adns_processreadable etc. here
1600 struct pollfd *fd = fds + i;
1601 int revents = ev_clear_pending (iow + i);
1602 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1603 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1604
1605 // now stop the watcher
1532 ev_io_stop (loop, iow + i); 1606 ev_io_stop (loop, iow + i);
1607 }
1533 1608
1534 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1609 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1610 }
1611
1612</pre>
1613<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1614in the prepare watcher and would dispose of the check watcher.</p>
1615<p>Method 3: If the module to be embedded supports explicit event
1616notification (adns does), you can also make use of the actual watcher
1617callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1618<pre> static void
1619 timer_cb (EV_P_ ev_timer *w, int revents)
1620 {
1621 adns_state ads = (adns_state)w-&gt;data;
1622 update_now (EV_A);
1623
1624 adns_processtimeouts (ads, &amp;tv_now);
1625 }
1626
1627 static void
1628 io_cb (EV_P_ ev_io *w, int revents)
1629 {
1630 adns_state ads = (adns_state)w-&gt;data;
1631 update_now (EV_A);
1632
1633 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1634 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1635 }
1636
1637 // do not ever call adns_afterpoll
1638
1639</pre>
1640<p>Method 4: Do not use a prepare or check watcher because the module you
1641want to embed is too inflexible to support it. Instead, youc na override
1642their poll function. The drawback with this solution is that the main
1643loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1644this.</p>
1645<pre> static gint
1646 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1647 {
1648 int got_events = 0;
1649
1650 for (n = 0; n &lt; nfds; ++n)
1651 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1652
1653 if (timeout &gt;= 0)
1654 // create/start timer
1655
1656 // poll
1657 ev_loop (EV_A_ 0);
1658
1659 // stop timer again
1660 if (timeout &gt;= 0)
1661 ev_timer_stop (EV_A_ &amp;to);
1662
1663 // stop io watchers again - their callbacks should have set
1664 for (n = 0; n &lt; nfds; ++n)
1665 ev_io_stop (EV_A_ iow [n]);
1666
1667 return got_events;
1535 } 1668 }
1536 1669
1537 1670
1538 1671
1539 1672
… …
1736the callback model to a model using method callbacks on objects.</p> 1869the callback model to a model using method callbacks on objects.</p>
1737<p>To use it,</p> 1870<p>To use it,</p>
1738<pre> #include &lt;ev++.h&gt; 1871<pre> #include &lt;ev++.h&gt;
1739 1872
1740</pre> 1873</pre>
1741<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1874<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1742and puts all of its definitions (many of them macros) into the global 1875of them macros) into the global namespace. All C++ specific things are
1743namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1876put into the <code>ev</code> namespace. It should support all the same embedding
1744<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1877options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1745<code>EV_MULTIPLICITY</code>.</p> 1878<p>Care has been taken to keep the overhead low. The only data member the C++
1879classes add (compared to plain C-style watchers) is the event loop pointer
1880that the watcher is associated with (or no additional members at all if
1881you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1882<p>Currently, functions, and static and non-static member functions can be
1883used as callbacks. Other types should be easy to add as long as they only
1884need one additional pointer for context. If you need support for other
1885types of functors please contact the author (preferably after implementing
1886it).</p>
1746<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1887<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1747<dl> 1888<dl>
1748 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1889 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1749 <dd> 1890 <dd>
1750 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1891 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1761which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1902which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1762defines by many implementations.</p> 1903defines by many implementations.</p>
1763 <p>All of those classes have these methods:</p> 1904 <p>All of those classes have these methods:</p>
1764 <p> 1905 <p>
1765 <dl> 1906 <dl>
1766 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1907 <dt>ev::TYPE::TYPE ()</dt>
1767 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1908 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1768 <dt>ev::TYPE::~TYPE</dt> 1909 <dt>ev::TYPE::~TYPE</dt>
1769 <dd> 1910 <dd>
1770 <p>The constructor takes a pointer to an object and a method pointer to 1911 <p>The constructor (optionally) takes an event loop to associate the watcher
1771the event handler callback to call in this class. The constructor calls 1912with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1772<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1913 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1773before starting it. If you do not specify a loop then the constructor 1914<code>set</code> method before starting it.</p>
1774automatically associates the default loop with this watcher.</p> 1915 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1916method to set a callback before you can start the watcher.</p>
1917 <p>(The reason why you have to use a method is a limitation in C++ which does
1918not allow explicit template arguments for constructors).</p>
1775 <p>The destructor automatically stops the watcher if it is active.</p> 1919 <p>The destructor automatically stops the watcher if it is active.</p>
1920 </dd>
1921 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1922 <dd>
1923 <p>This method sets the callback method to call. The method has to have a
1924signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1925first argument and the <code>revents</code> as second. The object must be given as
1926parameter and is stored in the <code>data</code> member of the watcher.</p>
1927 <p>This method synthesizes efficient thunking code to call your method from
1928the C callback that libev requires. If your compiler can inline your
1929callback (i.e. it is visible to it at the place of the <code>set</code> call and
1930your compiler is good :), then the method will be fully inlined into the
1931thunking function, making it as fast as a direct C callback.</p>
1932 <p>Example: simple class declaration and watcher initialisation</p>
1933<pre> struct myclass
1934 {
1935 void io_cb (ev::io &amp;w, int revents) { }
1936 }
1937
1938 myclass obj;
1939 ev::io iow;
1940 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1941
1942</pre>
1943 </dd>
1944 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1945 <dd>
1946 <p>Also sets a callback, but uses a static method or plain function as
1947callback. The optional <code>data</code> argument will be stored in the watcher's
1948<code>data</code> member and is free for you to use.</p>
1949 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1950 <p>See the method-<code>set</code> above for more details.</p>
1951 <p>Example:</p>
1952<pre> static void io_cb (ev::io &amp;w, int revents) { }
1953 iow.set &lt;io_cb&gt; ();
1954
1955</pre>
1776 </dd> 1956 </dd>
1777 <dt>w-&gt;set (struct ev_loop *)</dt> 1957 <dt>w-&gt;set (struct ev_loop *)</dt>
1778 <dd> 1958 <dd>
1779 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1959 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1780do this when the watcher is inactive (and not pending either).</p> 1960do this when the watcher is inactive (and not pending either).</p>
1781 </dd> 1961 </dd>
1782 <dt>w-&gt;set ([args])</dt> 1962 <dt>w-&gt;set ([args])</dt>
1783 <dd> 1963 <dd>
1784 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1964 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1785called at least once. Unlike the C counterpart, an active watcher gets 1965called at least once. Unlike the C counterpart, an active watcher gets
1786automatically stopped and restarted.</p> 1966automatically stopped and restarted when reconfiguring it with this
1967method.</p>
1787 </dd> 1968 </dd>
1788 <dt>w-&gt;start ()</dt> 1969 <dt>w-&gt;start ()</dt>
1789 <dd> 1970 <dd>
1790 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1971 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1791constructor already takes the loop.</p> 1972constructor already stores the event loop.</p>
1792 </dd> 1973 </dd>
1793 <dt>w-&gt;stop ()</dt> 1974 <dt>w-&gt;stop ()</dt>
1794 <dd> 1975 <dd>
1795 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1976 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1796 </dd> 1977 </dd>
… …
1820 2001
1821 myclass (); 2002 myclass ();
1822 } 2003 }
1823 2004
1824 myclass::myclass (int fd) 2005 myclass::myclass (int fd)
1825 : io (this, &amp;myclass::io_cb),
1826 idle (this, &amp;myclass::idle_cb)
1827 { 2006 {
2007 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
2008 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
2009
1828 io.start (fd, ev::READ); 2010 io.start (fd, ev::READ);
1829 } 2011 }
1830 2012
1831 2013
1832 2014
… …
2239<h1 id="COMPLEXITIES">COMPLEXITIES</h1> 2421<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2240<div id="COMPLEXITIES_CONTENT"> 2422<div id="COMPLEXITIES_CONTENT">
2241 <p>In this section the complexities of (many of) the algorithms used inside 2423 <p>In this section the complexities of (many of) the algorithms used inside
2242libev will be explained. For complexity discussions about backends see the 2424libev will be explained. For complexity discussions about backends see the
2243documentation for <code>ev_default_init</code>.</p> 2425documentation for <code>ev_default_init</code>.</p>
2426 <p>All of the following are about amortised time: If an array needs to be
2427extended, libev needs to realloc and move the whole array, but this
2428happens asymptotically never with higher number of elements, so O(1) might
2429mean it might do a lengthy realloc operation in rare cases, but on average
2430it is much faster and asymptotically approaches constant time.</p>
2244 <p> 2431 <p>
2245 <dl> 2432 <dl>
2246 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2433 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2247 <dd> 2434 <dd>
2248 <p>This means that, when you have a watcher that triggers in one hour and 2435 <p>This means that, when you have a watcher that triggers in one hour and
… …
2254 <p>That means that for changing a timer costs less than removing/adding them 2441 <p>That means that for changing a timer costs less than removing/adding them
2255as only the relative motion in the event queue has to be paid for.</p> 2442as only the relative motion in the event queue has to be paid for.</p>
2256 </dd> 2443 </dd>
2257 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2444 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2258 <dd> 2445 <dd>
2259 <p>These just add the watcher into an array or at the head of a list. If 2446 <p>These just add the watcher into an array or at the head of a list.
2260the array needs to be extended libev needs to realloc and move the whole
2261array, but this happen asymptotically less and less with more watchers,
2262thus amortised O(1).</p>
2263 </dd>
2264 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2447=item Stopping check/prepare/idle watchers: O(1)</p>
2448 </dd>
2265 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> 2449 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2266 <dd> 2450 <dd>
2267 <p>These watchers are stored in lists then need to be walked to find the 2451 <p>These watchers are stored in lists then need to be walked to find the
2268correct watcher to remove. The lists are usually short (you don't usually 2452correct watcher to remove. The lists are usually short (you don't usually
2269have many watchers waiting for the same fd or signal).</p> 2453have many watchers waiting for the same fd or signal).</p>

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