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Revision 1.55 by root, Tue Nov 27 20:29:12 2007 UTC vs.
Revision 1.58 by root, Wed Nov 28 11:31:34 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="Tue Nov 27 21:29:04 2007" /> 9 <meta name="created" content="Wed Nov 28 12:31:29 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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133watcher.</p> 133watcher.</p>
134 134
135</div> 135</div>
136<h1 id="FEATURES">FEATURES</h1> 136<h1 id="FEATURES">FEATURES</h1>
137<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
138<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the 138<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
139bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms 139BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
140for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>), 140for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
141(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous 142with customised rescheduling (<code>ev_periodic</code>), synchronous signals
142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and 143(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
143event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>, 144watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
144<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as 145<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
145file watchers (<code>ev_stat</code>) and even limited support for fork events 146file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p> 147(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this 148<p>It also is quite fast (see this
148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent 149<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
… …
741events but its callback has not yet been invoked). As long as a watcher 742events but its callback has not yet been invoked). As long as a watcher
742is pending (but not active) you must not call an init function on it (but 743is pending (but not active) you must not call an init function on it (but
743<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 744<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
744libev (e.g. you cnanot <code>free ()</code> it).</p> 745libev (e.g. you cnanot <code>free ()</code> it).</p>
745 </dd> 746 </dd>
746 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 747 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd> 748 <dd>
748 <p>Returns the callback currently set on the watcher.</p> 749 <p>Returns the callback currently set on the watcher.</p>
749 </dd> 750 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 751 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 752 <dd>
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783 struct my_io *w = (struct my_io *)w_; 784 struct my_io *w = (struct my_io *)w_;
784 ... 785 ...
785 } 786 }
786 787
787</pre> 788</pre>
788<p>More interesting and less C-conformant ways of catsing your callback type 789<p>More interesting and less C-conformant ways of casting your callback type
789have been omitted....</p> 790instead have been omitted.</p>
791<p>Another common scenario is having some data structure with multiple
792watchers:</p>
793<pre> struct my_biggy
794 {
795 int some_data;
796 ev_timer t1;
797 ev_timer t2;
798 }
790 799
800</pre>
801<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
802you need to use <code>offsetof</code>:</p>
803<pre> #include &lt;stddef.h&gt;
791 804
805 static void
806 t1_cb (EV_P_ struct ev_timer *w, int revents)
807 {
808 struct my_biggy big = (struct my_biggy *
809 (((char *)w) - offsetof (struct my_biggy, t1));
810 }
792 811
812 static void
813 t2_cb (EV_P_ struct ev_timer *w, int revents)
814 {
815 struct my_biggy big = (struct my_biggy *
816 (((char *)w) - offsetof (struct my_biggy, t2));
817 }
793 818
819
820
821
822</pre>
794 823
795</div> 824</div>
796<h1 id="WATCHER_TYPES">WATCHER TYPES</h1> 825<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
797<div id="WATCHER_TYPES_CONTENT"> 826<div id="WATCHER_TYPES_CONTENT">
798<p>This section describes each watcher in detail, but will not repeat 827<p>This section describes each watcher in detail, but will not repeat
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1219not exist&quot; is a status change like any other. The condition &quot;path does 1248not exist&quot; is a status change like any other. The condition &quot;path does
1220not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is 1249not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1221otherwise always forced to be at least one) and all the other fields of 1250otherwise always forced to be at least one) and all the other fields of
1222the stat buffer having unspecified contents.</p> 1251the stat buffer having unspecified contents.</p>
1223<p>Since there is no standard to do this, the portable implementation simply 1252<p>Since there is no standard to do this, the portable implementation simply
1224calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You 1253calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1225can specify a recommended polling interval for this case. If you specify 1254can specify a recommended polling interval for this case. If you specify
1226a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1255a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1227unspecified default</i> value will be used (which you can expect to be around 1256unspecified default</i> value will be used (which you can expect to be around
1228five seconds, although this might change dynamically). Libev will also 1257five seconds, although this might change dynamically). Libev will also
1229impose a minimum interval which is currently around <code>0.1</code>, but thats 1258impose a minimum interval which is currently around <code>0.1</code>, but thats
1230usually overkill.</p> 1259usually overkill.</p>
1231<p>This watcher type is not meant for massive numbers of stat watchers, 1260<p>This watcher type is not meant for massive numbers of stat watchers,
1232as even with OS-supported change notifications, this can be 1261as even with OS-supported change notifications, this can be
1233resource-intensive.</p> 1262resource-intensive.</p>
1234<p>At the time of this writing, no specific OS backends are implemented, but 1263<p>At the time of this writing, only the Linux inotify interface is
1235if demand increases, at least a kqueue and inotify backend will be added.</p> 1264implemented (implementing kqueue support is left as an exercise for the
1265reader). Inotify will be used to give hints only and should not change the
1266semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1267to fall back to regular polling again even with inotify, but changes are
1268usually detected immediately, and if the file exists there will be no
1269polling.</p>
1236<dl> 1270<dl>
1237 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1271 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1238 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> 1272 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1239 <dd> 1273 <dd>
1240 <p>Configures the watcher to wait for status changes of the given 1274 <p>Configures the watcher to wait for status changes of the given
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1987 </dd> 2021 </dd>
1988 <dt>EV_USE_DEVPOLL</dt> 2022 <dt>EV_USE_DEVPOLL</dt>
1989 <dd> 2023 <dd>
1990 <p>reserved for future expansion, works like the USE symbols above.</p> 2024 <p>reserved for future expansion, works like the USE symbols above.</p>
1991 </dd> 2025 </dd>
2026 <dt>EV_USE_INOTIFY</dt>
2027 <dd>
2028 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2029interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2030be detected at runtime.</p>
2031 </dd>
1992 <dt>EV_H</dt> 2032 <dt>EV_H</dt>
1993 <dd> 2033 <dd>
1994 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2034 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1995undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This 2035undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This
1996can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2036can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
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2051 <dt>EV_PID_HASHSIZE</dt> 2091 <dt>EV_PID_HASHSIZE</dt>
2052 <dd> 2092 <dd>
2053 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2093 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2054pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more 2094pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2055than enough. If you need to manage thousands of children you might want to 2095than enough. If you need to manage thousands of children you might want to
2056increase this value.</p> 2096increase this value (<i>must</i> be a power of two).</p>
2097 </dd>
2098 <dt>EV_INOTIFY_HASHSIZE</dt>
2099 <dd>
2100 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2101inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2102usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2103watchers you might want to increase this value (<i>must</i> be a power of
2104two).</p>
2057 </dd> 2105 </dd>
2058 <dt>EV_COMMON</dt> 2106 <dt>EV_COMMON</dt>
2059 <dd> 2107 <dd>
2060 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2108 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2061this macro to a something else you can include more and other types of 2109this macro to a something else you can include more and other types of
… …
2118 <dl> 2166 <dl>
2119 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2167 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2120 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2168 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2121 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2169 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2122 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2170 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2123 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2171 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2124 <dt>Finding the next timer per loop iteration: O(1)</dt> 2172 <dt>Finding the next timer per loop iteration: O(1)</dt>
2125 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2173 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2126 <dt>Activating one watcher: O(1)</dt> 2174 <dt>Activating one watcher: O(1)</dt>
2127 </dl> 2175 </dl>
2128 </p> 2176 </p>

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