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Revision 1.73 by root, Sat Dec 8 22:11:14 2007 UTC vs.
Revision 1.74 by root, Sun Dec 9 19:42:57 2007 UTC

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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="Sat Dec 8 23:11:11 2007" /> 9 <meta name="created" content="Sun Dec 9 20:30:11 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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1097but on wallclock time (absolute time). You can tell a periodic watcher 1097but on wallclock time (absolute time). You can tell a periodic watcher
1098to 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
1099periodic 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 ()
1100+ 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
1101take 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
1102roughly 10 seconds later and of course not if you reset your system time 1102roughly 10 seconds later).</p>
1103again).</p>
1104<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
1105triggering an event on eahc midnight, local time.</p> 1104triggering an event on each midnight, local time or other, complicated,
1105rules.</p>
1106<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
1107time (<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
1108during the same loop iteration then order of execution is undefined.</p> 1108during the same loop iteration then order of execution is undefined.</p>
1109<dl> 1109<dl>
1110 <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>
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1112 <dd> 1112 <dd>
1113 <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
1114operation, and we will explain them from simplest to complex:</p> 1114operation, and we will explain them from simplest to complex:</p>
1115 <p> 1115 <p>
1116 <dl> 1116 <dl>
1117 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1117 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
1118 <dd> 1118 <dd>
1119 <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
1120<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,
1121that 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
1122system time reaches or surpasses this time.</p> 1122system time reaches or surpasses this time.</p>
1123 </dd> 1123 </dd>
1124 <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>
1125 <dd> 1125 <dd>
1126 <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
1127<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)
1128of any time jumps.</p> 1128and then repeat, regardless of any time jumps.</p>
1129 <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
1130time:</p> 1130time:</p>
1131<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1131<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
1132 1132
1133</pre> 1133</pre>
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1136full 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
1137by 3600.</p> 1137by 3600.</p>
1138 <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
1139<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
1140time 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>
1141 </dd> 1144 </dd>
1142 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1145 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
1143 <dd> 1146 <dd>
1144 <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
1145ignored. Instead, each time the periodic watcher gets scheduled, the 1148ignored. Instead, each time the periodic watcher gets scheduled, the
1146reschedule callback will be called with the watcher as first, and the 1149reschedule callback will be called with the watcher as first, and the
1147current time as second argument.</p> 1150current time as second argument.</p>
1148 <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,
1149ever, 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,
1150return <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
1151starting a prepare watcher).</p> 1154starting an <code>ev_prepare</code> watcher, which is legal).</p>
1152 <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,
1153ev_tstamp now)</code>, e.g.:</p> 1156ev_tstamp now)</code>, e.g.:</p>
1154<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)
1155 { 1158 {
1156 return now + 60.; 1159 return now + 60.;
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1176 <dd> 1179 <dd>
1177 <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
1178when you changed some parameters or the reschedule callback would return 1181when you changed some parameters or the reschedule callback would return
1179a 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
1180program 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>
1181 </dd> 1191 </dd>
1182 <dt>ev_tstamp interval [read-write]</dt> 1192 <dt>ev_tstamp interval [read-write]</dt>
1183 <dd> 1193 <dd>
1184 <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
1185take 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

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