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Revision 1.76 by root, Sun Dec 9 19:47:29 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 20:47:27 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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185you actually want to know.</p> 185you actually want to know.</p>
186 </dd> 186 </dd>
187 <dt>int ev_version_major ()</dt> 187 <dt>int ev_version_major ()</dt>
188 <dt>int ev_version_minor ()</dt> 188 <dt>int ev_version_minor ()</dt>
189 <dd> 189 <dd>
190 <p>You can find out the major and minor version numbers of the library 190 <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 191you 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 192<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 193symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
194version of the library your program was compiled against.</p> 194version of the library your program was compiled against.</p>
195 <p>These version numbers refer to the ABI version of the library, not the
196release version.</p>
195 <p>Usually, it's a good idea to terminate if the major versions mismatch, 197 <p>Usually, it's a good idea to terminate if the major versions mismatch,
196as this indicates an incompatible change. Minor versions are usually 198as this indicates an incompatible change. Minor versions are usually
197compatible to older versions, so a larger minor version alone is usually 199compatible to older versions, so a larger minor version alone is usually
198not a problem.</p> 200not a problem.</p>
199 <p>Example: Make sure we haven't accidentally been linked against the wrong 201 <p>Example: Make sure we haven't accidentally been linked against the wrong
200version.</p> 202version.</p>
201<pre> assert ((&quot;libev version mismatch&quot;, 203<pre> assert ((&quot;libev version mismatch&quot;,
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1097but on wallclock time (absolute time). You can tell a periodic watcher 1099but 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 1100to 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 () 1101periodic 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 1102+ 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 1103take 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 1104roughly 10 seconds later).</p>
1103again).</p>
1104<p>They can also be used to implement vastly more complex timers, such as 1105<p>They can also be used to implement vastly more complex timers, such as
1105triggering an event on eahc midnight, local time.</p> 1106triggering an event on each midnight, local time or other, complicated,
1107rules.</p>
1106<p>As with timers, the callback is guarenteed to be invoked only when the 1108<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 1109time (<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> 1110during the same loop iteration then order of execution is undefined.</p>
1109<dl> 1111<dl>
1110 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1112 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
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1112 <dd> 1114 <dd>
1113 <p>Lots of arguments, lets sort it out... There are basically three modes of 1115 <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> 1116operation, and we will explain them from simplest to complex:</p>
1115 <p> 1117 <p>
1116 <dl> 1118 <dl>
1117 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1119 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
1118 <dd> 1120 <dd>
1119 <p>In this configuration the watcher triggers an event at the wallclock time 1121 <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, 1122<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 1123that 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> 1124system time reaches or surpasses this time.</p>
1123 </dd> 1125 </dd>
1124 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1126 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
1125 <dd> 1127 <dd>
1126 <p>In this mode the watcher will always be scheduled to time out at the next 1128 <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 1129<code>at + N * interval</code> time (for some integer N, which can also be negative)
1128of any time jumps.</p> 1130and 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 1131 <p>This can be used to create timers that do not drift with respect to system
1130time:</p> 1132time:</p>
1131<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1133<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
1132 1134
1133</pre> 1135</pre>
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1136full hour (UTC), or more correctly, when the system time is evenly divisible 1138full hour (UTC), or more correctly, when the system time is evenly divisible
1137by 3600.</p> 1139by 3600.</p>
1138 <p>Another way to think about it (for the mathematically inclined) is that 1140 <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 1141<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> 1142time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1143 <p>For numerical stability it is preferable that the <code>at</code> value is near
1144<code>ev_now ()</code> (the current time), but there is no range requirement for
1145this value.</p>
1141 </dd> 1146 </dd>
1142 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1147 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
1143 <dd> 1148 <dd>
1144 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1149 <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 1150ignored. Instead, each time the periodic watcher gets scheduled, the
1146reschedule callback will be called with the watcher as first, and the 1151reschedule callback will be called with the watcher as first, and the
1147current time as second argument.</p> 1152current time as second argument.</p>
1148 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1153 <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, 1154ever, 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 1155return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
1151starting a prepare watcher).</p> 1156starting an <code>ev_prepare</code> watcher, which is legal).</p>
1152 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1157 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1153ev_tstamp now)</code>, e.g.:</p> 1158ev_tstamp now)</code>, e.g.:</p>
1154<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1159<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1155 { 1160 {
1156 return now + 60.; 1161 return now + 60.;
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1176 <dd> 1181 <dd>
1177 <p>Simply stops and restarts the periodic watcher again. This is only useful 1182 <p>Simply stops and restarts the periodic watcher again. This is only useful
1178when you changed some parameters or the reschedule callback would return 1183when 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 1184a different time than the last time it was called (e.g. in a crond like
1180program when the crontabs have changed).</p> 1185program when the crontabs have changed).</p>
1186 </dd>
1187 <dt>ev_tstamp offset [read-write]</dt>
1188 <dd>
1189 <p>When repeating, this contains the offset value, otherwise this is the
1190absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1191 <p>Can be modified any time, but changes only take effect when the periodic
1192timer fires or <code>ev_periodic_again</code> is being called.</p>
1181 </dd> 1193 </dd>
1182 <dt>ev_tstamp interval [read-write]</dt> 1194 <dt>ev_tstamp interval [read-write]</dt>
1183 <dd> 1195 <dd>
1184 <p>The current interval value. Can be modified any time, but changes only 1196 <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 1197take effect when the periodic timer fires or <code>ev_periodic_again</code> is being

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