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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 15:31:35 2007" /> 9 <meta name="created" content="Wed Dec 12 18:55:28 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<li><a href="#Watcher_Specific_Functions">Watcher-Specific Functions</a></li>
35</ul>
36</li>
33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> 37<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a>
38<ul><li><a href="#Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</a></li>
39</ul>
40</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> 41<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a>
42<ul><li><a href="#Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</a></li>
43</ul>
44</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> 45<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a>
46<ul><li><a href="#Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</a></li>
47</ul>
48</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> 49<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a>
50<ul><li><a href="#Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</a></li>
51</ul>
52</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> 53<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a>
54<ul><li><a href="#Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</a></li>
55</ul>
56</li>
38<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li> 57<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a>
58<ul><li><a href="#Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</a></li>
59</ul>
60</li>
39<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li> 61<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a>
62<ul><li><a href="#Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</a></li>
63</ul>
64</li>
40<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> 65<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a>
66<ul><li><a href="#Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</a></li>
67</ul>
68</li>
41<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li> 69<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a>
70<ul><li><a href="#Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</a></li>
71</ul>
72</li>
42</ul> 73</ul>
43</li> 74</li>
44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 75<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 76<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
46<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 77<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
… …
185you actually want to know.</p> 216you actually want to know.</p>
186 </dd> 217 </dd>
187 <dt>int ev_version_major ()</dt> 218 <dt>int ev_version_major ()</dt>
188 <dt>int ev_version_minor ()</dt> 219 <dt>int ev_version_minor ()</dt>
189 <dd> 220 <dd>
190 <p>You can find out the major and minor version numbers of the library 221 <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 222you 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 223<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 224symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
194version of the library your program was compiled against.</p> 225version of the library your program was compiled against.</p>
226 <p>These version numbers refer to the ABI version of the library, not the
227release version.</p>
195 <p>Usually, it's a good idea to terminate if the major versions mismatch, 228 <p>Usually, it's a good idea to terminate if the major versions mismatch,
196as this indicates an incompatible change. Minor versions are usually 229as this indicates an incompatible change. Minor versions are usually
197compatible to older versions, so a larger minor version alone is usually 230compatible to older versions, so a larger minor version alone is usually
198not a problem.</p> 231not a problem.</p>
199 <p>Example: Make sure we haven't accidentally been linked against the wrong 232 <p>Example: Make sure we haven't accidentally been linked against the wrong
200version.</p> 233version.</p>
201<pre> assert ((&quot;libev version mismatch&quot;, 234<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 562one iteration of the loop. This is useful if you are waiting for some
530external event in conjunction with something not expressible using other 563external 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 564libev 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> 565usually a better approach for this kind of thing.</p>
533 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 566 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
567<pre> - Before the first iteration, call any pending watchers.
534<pre> * If there are no active watchers (reference count is zero), return. 568 * If there are no active watchers (reference count is zero), return.
535 - Queue prepare watchers and then call all outstanding watchers. 569 - Queue all prepare watchers and then call all outstanding watchers.
536 - If we have been forked, recreate the kernel state. 570 - If we have been forked, recreate the kernel state.
537 - Update the kernel state with all outstanding changes. 571 - Update the kernel state with all outstanding changes.
538 - Update the &quot;event loop time&quot;. 572 - Update the &quot;event loop time&quot;.
539 - Calculate for how long to block. 573 - Calculate for how long to block.
540 - Block the process, waiting for any events. 574 - Block the process, waiting for any events.
… …
938<p>If you cannot run the fd in non-blocking mode (for example you should not 972<p>If you cannot run the fd in non-blocking mode (for example you should not
939play around with an Xlib connection), then you have to seperately re-test 973play around with an Xlib connection), then you have to seperately re-test
940whether a file descriptor is really ready with a known-to-be good interface 974whether a file descriptor is really ready with a known-to-be good interface
941such as poll (fortunately in our Xlib example, Xlib already does this on 975such as poll (fortunately in our Xlib example, Xlib already does this on
942its own, so its quite safe to use).</p> 976its own, so its quite safe to use).</p>
977
978</div>
979<h3 id="The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</h3>
980<div id="The_special_problem_of_disappearing_-2">
981<p>Some backends (e.g kqueue, epoll) need to be told about closing a file
982descriptor (either by calling <code>close</code> explicitly or by any other means,
983such as <code>dup</code>). The reason is that you register interest in some file
984descriptor, but when it goes away, the operating system will silently drop
985this interest. If another file descriptor with the same number then is
986registered with libev, there is no efficient way to see that this is, in
987fact, a different file descriptor.</p>
988<p>To avoid having to explicitly tell libev about such cases, libev follows
989the following policy: Each time <code>ev_io_set</code> is being called, libev
990will assume that this is potentially a new file descriptor, otherwise
991it is assumed that the file descriptor stays the same. That means that
992you <i>have</i> to call <code>ev_io_set</code> (or <code>ev_io_init</code>) when you change the
993descriptor even if the file descriptor number itself did not change.</p>
994<p>This is how one would do it normally anyway, the important point is that
995the libev application should not optimise around libev but should leave
996optimisations to libev.</p>
997
998
999
1000
1001
1002</div>
1003<h3 id="Watcher_Specific_Functions">Watcher-Specific Functions</h3>
1004<div id="Watcher_Specific_Functions_CONTENT">
943<dl> 1005<dl>
944 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 1006 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
945 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 1007 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
946 <dd> 1008 <dd>
947 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 1009 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
… …
998 1060
999</pre> 1061</pre>
1000<p>The callback is guarenteed to be invoked only when its timeout has passed, 1062<p>The callback is guarenteed to be invoked only when its timeout has passed,
1001but if multiple timers become ready during the same loop iteration then 1063but if multiple timers become ready during the same loop iteration then
1002order of execution is undefined.</p> 1064order of execution is undefined.</p>
1065
1066</div>
1067<h3 id="Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</h3>
1068<div id="Watcher_Specific_Functions_and_Data_-2">
1003<dl> 1069<dl>
1004 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 1070 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
1005 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 1071 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
1006 <dd> 1072 <dd>
1007 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 1073 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
1096but on wallclock time (absolute time). You can tell a periodic watcher 1162but on wallclock time (absolute time). You can tell a periodic watcher
1097to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1163to trigger &quot;at&quot; some specific point in time. For example, if you tell a
1098periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () 1164periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
1099+ 10.</code>) and then reset your system clock to the last year, then it will 1165+ 10.</code>) and then reset your system clock to the last year, then it will
1100take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1166take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
1101roughly 10 seconds later and of course not if you reset your system time 1167roughly 10 seconds later).</p>
1102again).</p>
1103<p>They can also be used to implement vastly more complex timers, such as 1168<p>They can also be used to implement vastly more complex timers, such as
1104triggering an event on eahc midnight, local time.</p> 1169triggering an event on each midnight, local time or other, complicated,
1170rules.</p>
1105<p>As with timers, the callback is guarenteed to be invoked only when the 1171<p>As with timers, the callback is guarenteed to be invoked only when the
1106time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1172time (<code>at</code>) has been passed, but if multiple periodic timers become ready
1107during the same loop iteration then order of execution is undefined.</p> 1173during the same loop iteration then order of execution is undefined.</p>
1174
1175</div>
1176<h3 id="Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</h3>
1177<div id="Watcher_Specific_Functions_and_Data_-2">
1108<dl> 1178<dl>
1109 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1179 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
1110 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 1180 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
1111 <dd> 1181 <dd>
1112 <p>Lots of arguments, lets sort it out... There are basically three modes of 1182 <p>Lots of arguments, lets sort it out... There are basically three modes of
1113operation, and we will explain them from simplest to complex:</p> 1183operation, and we will explain them from simplest to complex:</p>
1114 <p> 1184 <p>
1115 <dl> 1185 <dl>
1116 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1186 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
1117 <dd> 1187 <dd>
1118 <p>In this configuration the watcher triggers an event at the wallclock time 1188 <p>In this configuration the watcher triggers an event at the wallclock time
1119<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1189<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
1120that is, if it is to be run at January 1st 2011 then it will run when the 1190that is, if it is to be run at January 1st 2011 then it will run when the
1121system time reaches or surpasses this time.</p> 1191system time reaches or surpasses this time.</p>
1122 </dd> 1192 </dd>
1123 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1193 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
1124 <dd> 1194 <dd>
1125 <p>In this mode the watcher will always be scheduled to time out at the next 1195 <p>In this mode the watcher will always be scheduled to time out at the next
1126<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1196<code>at + N * interval</code> time (for some integer N, which can also be negative)
1127of any time jumps.</p> 1197and then repeat, regardless of any time jumps.</p>
1128 <p>This can be used to create timers that do not drift with respect to system 1198 <p>This can be used to create timers that do not drift with respect to system
1129time:</p> 1199time:</p>
1130<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1200<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
1131 1201
1132</pre> 1202</pre>
… …
1135full hour (UTC), or more correctly, when the system time is evenly divisible 1205full hour (UTC), or more correctly, when the system time is evenly divisible
1136by 3600.</p> 1206by 3600.</p>
1137 <p>Another way to think about it (for the mathematically inclined) is that 1207 <p>Another way to think about it (for the mathematically inclined) is that
1138<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1208<code>ev_periodic</code> will try to run the callback in this mode at the next possible
1139time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1209time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1210 <p>For numerical stability it is preferable that the <code>at</code> value is near
1211<code>ev_now ()</code> (the current time), but there is no range requirement for
1212this value.</p>
1140 </dd> 1213 </dd>
1141 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1214 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
1142 <dd> 1215 <dd>
1143 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1216 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
1144ignored. Instead, each time the periodic watcher gets scheduled, the 1217ignored. Instead, each time the periodic watcher gets scheduled, the
1145reschedule callback will be called with the watcher as first, and the 1218reschedule callback will be called with the watcher as first, and the
1146current time as second argument.</p> 1219current time as second argument.</p>
1147 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1220 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
1148ever, or make any event loop modifications</i>. If you need to stop it, 1221ever, or make any event loop modifications</i>. If you need to stop it,
1149return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1222return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
1150starting a prepare watcher).</p> 1223starting an <code>ev_prepare</code> watcher, which is legal).</p>
1151 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1224 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1152ev_tstamp now)</code>, e.g.:</p> 1225ev_tstamp now)</code>, e.g.:</p>
1153<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1226<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1154 { 1227 {
1155 return now + 60.; 1228 return now + 60.;
… …
1175 <dd> 1248 <dd>
1176 <p>Simply stops and restarts the periodic watcher again. This is only useful 1249 <p>Simply stops and restarts the periodic watcher again. This is only useful
1177when you changed some parameters or the reschedule callback would return 1250when you changed some parameters or the reschedule callback would return
1178a different time than the last time it was called (e.g. in a crond like 1251a different time than the last time it was called (e.g. in a crond like
1179program when the crontabs have changed).</p> 1252program when the crontabs have changed).</p>
1253 </dd>
1254 <dt>ev_tstamp offset [read-write]</dt>
1255 <dd>
1256 <p>When repeating, this contains the offset value, otherwise this is the
1257absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1258 <p>Can be modified any time, but changes only take effect when the periodic
1259timer fires or <code>ev_periodic_again</code> is being called.</p>
1180 </dd> 1260 </dd>
1181 <dt>ev_tstamp interval [read-write]</dt> 1261 <dt>ev_tstamp interval [read-write]</dt>
1182 <dd> 1262 <dd>
1183 <p>The current interval value. Can be modified any time, but changes only 1263 <p>The current interval value. Can be modified any time, but changes only
1184take effect when the periodic timer fires or <code>ev_periodic_again</code> is being 1264take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
… …
1239first watcher gets started will libev actually register a signal watcher 1319first watcher gets started will libev actually register a signal watcher
1240with the kernel (thus it coexists with your own signal handlers as long 1320with the kernel (thus it coexists with your own signal handlers as long
1241as you don't register any with libev). Similarly, when the last signal 1321as you don't register any with libev). Similarly, when the last signal
1242watcher for a signal is stopped libev will reset the signal handler to 1322watcher for a signal is stopped libev will reset the signal handler to
1243SIG_DFL (regardless of what it was set to before).</p> 1323SIG_DFL (regardless of what it was set to before).</p>
1324
1325</div>
1326<h3 id="Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</h3>
1327<div id="Watcher_Specific_Functions_and_Data_-2-2">
1244<dl> 1328<dl>
1245 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt> 1329 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt>
1246 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1330 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1247 <dd> 1331 <dd>
1248 <p>Configures the watcher to trigger on the given signal number (usually one 1332 <p>Configures the watcher to trigger on the given signal number (usually one
… …
1261</div> 1345</div>
1262<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2> 1346<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
1263<div id="code_ev_child_code_watch_out_for_pro-2"> 1347<div id="code_ev_child_code_watch_out_for_pro-2">
1264<p>Child watchers trigger when your process receives a SIGCHLD in response to 1348<p>Child watchers trigger when your process receives a SIGCHLD in response to
1265some child status changes (most typically when a child of yours dies).</p> 1349some child status changes (most typically when a child of yours dies).</p>
1350
1351</div>
1352<h3 id="Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</h3>
1353<div id="Watcher_Specific_Functions_and_Data_-2-3">
1266<dl> 1354<dl>
1267 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1355 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1268 <dt>ev_child_set (ev_child *, int pid)</dt> 1356 <dt>ev_child_set (ev_child *, int pid)</dt>
1269 <dd> 1357 <dd>
1270 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 1358 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
… …
1333reader). Inotify will be used to give hints only and should not change the 1421reader). Inotify will be used to give hints only and should not change the
1334semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs 1422semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1335to fall back to regular polling again even with inotify, but changes are 1423to fall back to regular polling again even with inotify, but changes are
1336usually detected immediately, and if the file exists there will be no 1424usually detected immediately, and if the file exists there will be no
1337polling.</p> 1425polling.</p>
1426
1427</div>
1428<h3 id="Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</h3>
1429<div id="Watcher_Specific_Functions_and_Data_-2-4">
1338<dl> 1430<dl>
1339 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1431 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1340 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> 1432 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1341 <dd> 1433 <dd>
1342 <p>Configures the watcher to wait for status changes of the given 1434 <p>Configures the watcher to wait for status changes of the given
… …
1420active, the process will not block when waiting for new events.</p> 1512active, the process will not block when waiting for new events.</p>
1421<p>Apart from keeping your process non-blocking (which is a useful 1513<p>Apart from keeping your process non-blocking (which is a useful
1422effect on its own sometimes), idle watchers are a good place to do 1514effect on its own sometimes), idle watchers are a good place to do
1423&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1515&quot;pseudo-background processing&quot;, or delay processing stuff to after the
1424event loop has handled all outstanding events.</p> 1516event loop has handled all outstanding events.</p>
1517
1518</div>
1519<h3 id="Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</h3>
1520<div id="Watcher_Specific_Functions_and_Data_-2-5">
1425<dl> 1521<dl>
1426 <dt>ev_idle_init (ev_signal *, callback)</dt> 1522 <dt>ev_idle_init (ev_signal *, callback)</dt>
1427 <dd> 1523 <dd>
1428 <p>Initialises and configures the idle watcher - it has no parameters of any 1524 <p>Initialises and configures the idle watcher - it has no parameters of any
1429kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1525kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
… …
1483are ready to run (it's actually more complicated: it only runs coroutines 1579are ready to run (it's actually more complicated: it only runs coroutines
1484with priority higher than or equal to the event loop and one coroutine 1580with priority higher than or equal to the event loop and one coroutine
1485of lower priority, but only once, using idle watchers to keep the event 1581of lower priority, but only once, using idle watchers to keep the event
1486loop from blocking if lower-priority coroutines are active, thus mapping 1582loop from blocking if lower-priority coroutines are active, thus mapping
1487low-priority coroutines to idle/background tasks).</p> 1583low-priority coroutines to idle/background tasks).</p>
1584<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1585priority, to ensure that they are being run before any other watchers
1586after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1587too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1588supports this, they will be called before other <code>ev_check</code> watchers did
1589their job. As <code>ev_check</code> watchers are often used to embed other event
1590loops those other event loops might be in an unusable state until their
1591<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1592others).</p>
1593
1594</div>
1595<h3 id="Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</h3>
1596<div id="Watcher_Specific_Functions_and_Data_-2-6">
1488<dl> 1597<dl>
1489 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1598 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1490 <dt>ev_check_init (ev_check *, callback)</dt> 1599 <dt>ev_check_init (ev_check *, callback)</dt>
1491 <dd> 1600 <dd>
1492 <p>Initialises and configures the prepare or check watcher - they have no 1601 <p>Initialises and configures the prepare or check watcher - they have no
1493parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1602parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1494macros, but using them is utterly, utterly and completely pointless.</p> 1603macros, but using them is utterly, utterly and completely pointless.</p>
1495 </dd> 1604 </dd>
1496</dl> 1605</dl>
1497<p>Example: To include a library such as adns, you would add IO watchers 1606<p>There are a number of principal ways to embed other event loops or modules
1498and a timeout watcher in a prepare handler, as required by libadns, and 1607into libev. Here are some ideas on how to include libadns into libev
1608(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1609use for an actually working example. Another Perl module named <code>EV::Glib</code>
1610embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1611into the Glib event loop).</p>
1612<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1499in a check watcher, destroy them and call into libadns. What follows is 1613and in a check watcher, destroy them and call into libadns. What follows
1500pseudo-code only of course:</p> 1614is pseudo-code only of course. This requires you to either use a low
1615priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1616the callbacks for the IO/timeout watchers might not have been called yet.</p>
1501<pre> static ev_io iow [nfd]; 1617<pre> static ev_io iow [nfd];
1502 static ev_timer tw; 1618 static ev_timer tw;
1503 1619
1504 static void 1620 static void
1505 io_cb (ev_loop *loop, ev_io *w, int revents) 1621 io_cb (ev_loop *loop, ev_io *w, int revents)
1506 { 1622 {
1507 // set the relevant poll flags
1508 // could also call adns_processreadable etc. here
1509 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1510 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1511 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1512 } 1623 }
1513 1624
1514 // create io watchers for each fd and a timer before blocking 1625 // create io watchers for each fd and a timer before blocking
1515 static void 1626 static void
1516 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1627 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
… …
1522 1633
1523 /* the callback is illegal, but won't be called as we stop during check */ 1634 /* the callback is illegal, but won't be called as we stop during check */
1524 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1635 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1525 ev_timer_start (loop, &amp;tw); 1636 ev_timer_start (loop, &amp;tw);
1526 1637
1527 // create on ev_io per pollfd 1638 // create one ev_io per pollfd
1528 for (int i = 0; i &lt; nfd; ++i) 1639 for (int i = 0; i &lt; nfd; ++i)
1529 { 1640 {
1530 ev_io_init (iow + i, io_cb, fds [i].fd, 1641 ev_io_init (iow + i, io_cb, fds [i].fd,
1531 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1642 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1532 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1643 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1533 1644
1534 fds [i].revents = 0; 1645 fds [i].revents = 0;
1535 iow [i].data = fds + i;
1536 ev_io_start (loop, iow + i); 1646 ev_io_start (loop, iow + i);
1537 } 1647 }
1538 } 1648 }
1539 1649
1540 // stop all watchers after blocking 1650 // stop all watchers after blocking
… …
1542 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1652 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1543 { 1653 {
1544 ev_timer_stop (loop, &amp;tw); 1654 ev_timer_stop (loop, &amp;tw);
1545 1655
1546 for (int i = 0; i &lt; nfd; ++i) 1656 for (int i = 0; i &lt; nfd; ++i)
1657 {
1658 // set the relevant poll flags
1659 // could also call adns_processreadable etc. here
1660 struct pollfd *fd = fds + i;
1661 int revents = ev_clear_pending (iow + i);
1662 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1663 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1664
1665 // now stop the watcher
1547 ev_io_stop (loop, iow + i); 1666 ev_io_stop (loop, iow + i);
1667 }
1548 1668
1549 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1669 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1670 }
1671
1672</pre>
1673<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1674in the prepare watcher and would dispose of the check watcher.</p>
1675<p>Method 3: If the module to be embedded supports explicit event
1676notification (adns does), you can also make use of the actual watcher
1677callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1678<pre> static void
1679 timer_cb (EV_P_ ev_timer *w, int revents)
1680 {
1681 adns_state ads = (adns_state)w-&gt;data;
1682 update_now (EV_A);
1683
1684 adns_processtimeouts (ads, &amp;tv_now);
1685 }
1686
1687 static void
1688 io_cb (EV_P_ ev_io *w, int revents)
1689 {
1690 adns_state ads = (adns_state)w-&gt;data;
1691 update_now (EV_A);
1692
1693 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1694 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1695 }
1696
1697 // do not ever call adns_afterpoll
1698
1699</pre>
1700<p>Method 4: Do not use a prepare or check watcher because the module you
1701want to embed is too inflexible to support it. Instead, youc na override
1702their poll function. The drawback with this solution is that the main
1703loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1704this.</p>
1705<pre> static gint
1706 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1707 {
1708 int got_events = 0;
1709
1710 for (n = 0; n &lt; nfds; ++n)
1711 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1712
1713 if (timeout &gt;= 0)
1714 // create/start timer
1715
1716 // poll
1717 ev_loop (EV_A_ 0);
1718
1719 // stop timer again
1720 if (timeout &gt;= 0)
1721 ev_timer_stop (EV_A_ &amp;to);
1722
1723 // stop io watchers again - their callbacks should have set
1724 for (n = 0; n &lt; nfds; ++n)
1725 ev_io_stop (EV_A_ iow [n]);
1726
1727 return got_events;
1550 } 1728 }
1551 1729
1552 1730
1553 1731
1554 1732
… …
1615 } 1793 }
1616 else 1794 else
1617 loop_lo = loop_hi; 1795 loop_lo = loop_hi;
1618 1796
1619</pre> 1797</pre>
1798
1799</div>
1800<h3 id="Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</h3>
1801<div id="Watcher_Specific_Functions_and_Data_-2-7">
1620<dl> 1802<dl>
1621 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> 1803 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1622 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> 1804 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1623 <dd> 1805 <dd>
1624 <p>Configures the watcher to embed the given loop, which must be 1806 <p>Configures the watcher to embed the given loop, which must be
… …
1651<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the 1833<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1652event loop blocks next and before <code>ev_check</code> watchers are being called, 1834event loop blocks next and before <code>ev_check</code> watchers are being called,
1653and only in the child after the fork. If whoever good citizen calling 1835and only in the child after the fork. If whoever good citizen calling
1654<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork 1836<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1655handlers will be invoked, too, of course.</p> 1837handlers will be invoked, too, of course.</p>
1838
1839</div>
1840<h3 id="Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</h3>
1841<div id="Watcher_Specific_Functions_and_Data_-2-8">
1656<dl> 1842<dl>
1657 <dt>ev_fork_init (ev_signal *, callback)</dt> 1843 <dt>ev_fork_init (ev_signal *, callback)</dt>
1658 <dd> 1844 <dd>
1659 <p>Initialises and configures the fork watcher - it has no parameters of any 1845 <p>Initialises and configures the fork watcher - it has no parameters of any
1660kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless, 1846kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,

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