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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 21:38:05 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
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1247not 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
1248not 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
1249otherwise 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
1250the stat buffer having unspecified contents.</p> 1251the stat buffer having unspecified contents.</p>
1251<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
1252calls <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
1253can specify a recommended polling interval for this case. If you specify 1254can specify a recommended polling interval for this case. If you specify
1254a 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,
1255unspecified 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
1256five seconds, although this might change dynamically). Libev will also 1257five seconds, although this might change dynamically). Libev will also
1257impose 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
1258usually overkill.</p> 1259usually overkill.</p>
1259<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,
1260as even with OS-supported change notifications, this can be 1261as even with OS-supported change notifications, this can be
1261resource-intensive.</p> 1262resource-intensive.</p>
1262<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
1263if 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>
1264<dl> 1270<dl>
1265 <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>
1266 <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>
1267 <dd> 1273 <dd>
1268 <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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2015 </dd> 2021 </dd>
2016 <dt>EV_USE_DEVPOLL</dt> 2022 <dt>EV_USE_DEVPOLL</dt>
2017 <dd> 2023 <dd>
2018 <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>
2019 </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>
2020 <dt>EV_H</dt> 2032 <dt>EV_H</dt>
2021 <dd> 2033 <dd>
2022 <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
2023undefined 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
2024can 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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2079 <dt>EV_PID_HASHSIZE</dt> 2091 <dt>EV_PID_HASHSIZE</dt>
2080 <dd> 2092 <dd>
2081 <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
2082pid. 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
2083than 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
2084increase 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>
2085 </dd> 2105 </dd>
2086 <dt>EV_COMMON</dt> 2106 <dt>EV_COMMON</dt>
2087 <dd> 2107 <dd>
2088 <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
2089this 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
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2146 <dl> 2166 <dl>
2147 <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>
2148 <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>
2149 <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>
2150 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2170 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2151 <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>
2152 <dt>Finding the next timer per loop iteration: O(1)</dt> 2172 <dt>Finding the next timer per loop iteration: O(1)</dt>
2153 <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>
2154 <dt>Activating one watcher: O(1)</dt> 2174 <dt>Activating one watcher: O(1)</dt>
2155 </dl> 2175 </dl>
2156 </p> 2176 </p>

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