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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="Thu Nov 29 13:21:20 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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229might be supported on the current system, you would need to look at 230might be supported on the current system, you would need to look at
230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 231<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
231recommended ones.</p> 232recommended ones.</p>
232 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 233 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
233 </dd> 234 </dd>
234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
235 <dd> 236 <dd>
236 <p>Sets the allocation function to use (the prototype and semantics are 237 <p>Sets the allocation function to use (the prototype is similar - the
237identical to the realloc C function). It is used to allocate and free 238semantics is identical - to the realloc C function). It is used to
238memory (no surprises here). If it returns zero when memory needs to be 239allocate and free memory (no surprises here). If it returns zero when
239allocated, the library might abort or take some potentially destructive 240memory needs to be allocated, the library might abort or take some
240action. The default is your system realloc function.</p> 241potentially destructive action. The default is your system realloc
242function.</p>
241 <p>You could override this function in high-availability programs to, say, 243 <p>You could override this function in high-availability programs to, say,
242free some memory if it cannot allocate memory, to use a special allocator, 244free some memory if it cannot allocate memory, to use a special allocator,
243or even to sleep a while and retry until some memory is available.</p> 245or even to sleep a while and retry until some memory is available.</p>
244 <p>Example: Replace the libev allocator with one that waits a bit and then 246 <p>Example: Replace the libev allocator with one that waits a bit and then
245retries).</p> 247retries).</p>
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741events but its callback has not yet been invoked). As long as a watcher 743events 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 744is 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 745<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> 746libev (e.g. you cnanot <code>free ()</code> it).</p>
745 </dd> 747 </dd>
746 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 748 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd> 749 <dd>
748 <p>Returns the callback currently set on the watcher.</p> 750 <p>Returns the callback currently set on the watcher.</p>
749 </dd> 751 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 752 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 753 <dd>
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783 struct my_io *w = (struct my_io *)w_; 785 struct my_io *w = (struct my_io *)w_;
784 ... 786 ...
785 } 787 }
786 788
787</pre> 789</pre>
788<p>More interesting and less C-conformant ways of catsing your callback type 790<p>More interesting and less C-conformant ways of casting your callback type
789have been omitted....</p> 791instead have been omitted.</p>
792<p>Another common scenario is having some data structure with multiple
793watchers:</p>
794<pre> struct my_biggy
795 {
796 int some_data;
797 ev_timer t1;
798 ev_timer t2;
799 }
790 800
801</pre>
802<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
803you need to use <code>offsetof</code>:</p>
804<pre> #include &lt;stddef.h&gt;
791 805
806 static void
807 t1_cb (EV_P_ struct ev_timer *w, int revents)
808 {
809 struct my_biggy big = (struct my_biggy *
810 (((char *)w) - offsetof (struct my_biggy, t1));
811 }
792 812
813 static void
814 t2_cb (EV_P_ struct ev_timer *w, int revents)
815 {
816 struct my_biggy big = (struct my_biggy *
817 (((char *)w) - offsetof (struct my_biggy, t2));
818 }
793 819
820
821
822
823</pre>
794 824
795</div> 825</div>
796<h1 id="WATCHER_TYPES">WATCHER TYPES</h1> 826<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
797<div id="WATCHER_TYPES_CONTENT"> 827<div id="WATCHER_TYPES_CONTENT">
798<p>This section describes each watcher in detail, but will not repeat 828<p>This section describes each watcher in detail, but will not repeat
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922 </dd> 952 </dd>
923 <dt>ev_timer_again (loop)</dt> 953 <dt>ev_timer_again (loop)</dt>
924 <dd> 954 <dd>
925 <p>This will act as if the timer timed out and restart it again if it is 955 <p>This will act as if the timer timed out and restart it again if it is
926repeating. The exact semantics are:</p> 956repeating. The exact semantics are:</p>
957 <p>If the timer is pending, its pending status is cleared.</p>
927 <p>If the timer is started but nonrepeating, stop it.</p> 958 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
928 <p>If the timer is repeating, either start it if necessary (with the repeat 959 <p>If the timer is repeating, either start it if necessary (with the
929value), or reset the running timer to the repeat value.</p> 960<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
930 <p>This sounds a bit complicated, but here is a useful and typical 961 <p>This sounds a bit complicated, but here is a useful and typical
931example: Imagine you have a tcp connection and you want a so-called 962example: Imagine you have a tcp connection and you want a so-called idle
932idle timeout, that is, you want to be called when there have been, 963timeout, that is, you want to be called when there have been, say, 60
933say, 60 seconds of inactivity on the socket. The easiest way to do 964seconds of inactivity on the socket. The easiest way to do this is to
934this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling 965configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
935<code>ev_timer_again</code> each time you successfully read or write some data. If 966<code>ev_timer_again</code> each time you successfully read or write some data. If
936you go into an idle state where you do not expect data to travel on the 967you go into an idle state where you do not expect data to travel on the
937socket, you can stop the timer, and again will automatically restart it if 968socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
938need be.</p> 969automatically restart it if need be.</p>
939 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 970 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
940and only ever use the <code>repeat</code> value:</p> 971altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
941<pre> ev_timer_init (timer, callback, 0., 5.); 972<pre> ev_timer_init (timer, callback, 0., 5.);
942 ev_timer_again (loop, timer); 973 ev_timer_again (loop, timer);
943 ... 974 ...
944 timer-&gt;again = 17.; 975 timer-&gt;again = 17.;
945 ev_timer_again (loop, timer); 976 ev_timer_again (loop, timer);
946 ... 977 ...
947 timer-&gt;again = 10.; 978 timer-&gt;again = 10.;
948 ev_timer_again (loop, timer); 979 ev_timer_again (loop, timer);
949 980
950</pre> 981</pre>
951 <p>This is more efficient then stopping/starting the timer eahc time you want 982 <p>This is more slightly efficient then stopping/starting the timer each time
952to modify its timeout value.</p> 983you want to modify its timeout value.</p>
953 </dd> 984 </dd>
954 <dt>ev_tstamp repeat [read-write]</dt> 985 <dt>ev_tstamp repeat [read-write]</dt>
955 <dd> 986 <dd>
956 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 987 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
957or <code>ev_timer_again</code> is called and determines the next timeout (if any), 988or <code>ev_timer_again</code> is called and determines the next timeout (if any),
… …
1218<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1249<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1219not exist&quot; is a status change like any other. The condition &quot;path does 1250not 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 1251not 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 1252otherwise always forced to be at least one) and all the other fields of
1222the stat buffer having unspecified contents.</p> 1253the stat buffer having unspecified contents.</p>
1254<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1255relative and your working directory changes, the behaviour is undefined.</p>
1223<p>Since there is no standard to do this, the portable implementation simply 1256<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 1257calls <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 1258can specify a recommended polling interval for this case. If you specify
1226a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1259a 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 1260unspecified default</i> value will be used (which you can expect to be around
1228five seconds, although this might change dynamically). Libev will also 1261five seconds, although this might change dynamically). Libev will also
1229impose a minimum interval which is currently around <code>0.1</code>, but thats 1262impose a minimum interval which is currently around <code>0.1</code>, but thats
1230usually overkill.</p> 1263usually overkill.</p>
1231<p>This watcher type is not meant for massive numbers of stat watchers, 1264<p>This watcher type is not meant for massive numbers of stat watchers,
1232as even with OS-supported change notifications, this can be 1265as even with OS-supported change notifications, this can be
1233resource-intensive.</p> 1266resource-intensive.</p>
1234<p>At the time of this writing, no specific OS backends are implemented, but 1267<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> 1268implemented (implementing kqueue support is left as an exercise for the
1269reader). Inotify will be used to give hints only and should not change the
1270semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1271to fall back to regular polling again even with inotify, but changes are
1272usually detected immediately, and if the file exists there will be no
1273polling.</p>
1236<dl> 1274<dl>
1237 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1275 <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> 1276 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1239 <dd> 1277 <dd>
1240 <p>Configures the watcher to wait for status changes of the given 1278 <p>Configures the watcher to wait for status changes of the given
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1987 </dd> 2025 </dd>
1988 <dt>EV_USE_DEVPOLL</dt> 2026 <dt>EV_USE_DEVPOLL</dt>
1989 <dd> 2027 <dd>
1990 <p>reserved for future expansion, works like the USE symbols above.</p> 2028 <p>reserved for future expansion, works like the USE symbols above.</p>
1991 </dd> 2029 </dd>
2030 <dt>EV_USE_INOTIFY</dt>
2031 <dd>
2032 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2033interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2034be detected at runtime.</p>
2035 </dd>
1992 <dt>EV_H</dt> 2036 <dt>EV_H</dt>
1993 <dd> 2037 <dd>
1994 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2038 <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 2039undefined 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> 2040can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
2051 <dt>EV_PID_HASHSIZE</dt> 2095 <dt>EV_PID_HASHSIZE</dt>
2052 <dd> 2096 <dd>
2053 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2097 <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 2098pid. 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 2099than enough. If you need to manage thousands of children you might want to
2056increase this value.</p> 2100increase this value (<i>must</i> be a power of two).</p>
2101 </dd>
2102 <dt>EV_INOTIFY_HASHSIZE</dt>
2103 <dd>
2104 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2105inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2106usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2107watchers you might want to increase this value (<i>must</i> be a power of
2108two).</p>
2057 </dd> 2109 </dd>
2058 <dt>EV_COMMON</dt> 2110 <dt>EV_COMMON</dt>
2059 <dd> 2111 <dd>
2060 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2112 <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 2113this macro to a something else you can include more and other types of
… …
2118 <dl> 2170 <dl>
2119 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2171 <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> 2172 <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> 2173 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2122 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2174 <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> 2175 <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> 2176 <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> 2177 <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> 2178 <dt>Activating one watcher: O(1)</dt>
2127 </dl> 2179 </dl>
2128 </p> 2180 </p>

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