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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="Sat Dec 8 23:11:11 2007" />
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12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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119</pre> 119</pre>
120 120
121</div> 121</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1> 122<h1 id="DESCRIPTION">DESCRIPTION</h1>
123<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
124<p>The newest version of this document is also available as a html-formatted
125web page you might find easier to navigate when reading it for the first
126time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
124<p>Libev is an event loop: you register interest in certain events (such as a 127<p>Libev is an event loop: you register interest in certain events (such as a
125file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
126these event sources and provide your program with events.</p> 129these event sources and provide your program with events.</p>
127<p>To do this, it must take more or less complete control over your process 130<p>To do this, it must take more or less complete control over your process
128(or thread) by executing the <i>event loop</i> handler, and will then 131(or thread) by executing the <i>event loop</i> handler, and will then
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133watcher.</p> 136watcher.</p>
134 137
135</div> 138</div>
136<h1 id="FEATURES">FEATURES</h1> 139<h1 id="FEATURES">FEATURES</h1>
137<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
138<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the 141<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 142BSD-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>), 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
144(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous 145with customised rescheduling (<code>ev_periodic</code>), synchronous signals
142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and 146(<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>, 147watchers 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 148<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 149file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p> 150(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this 151<p>It also is quite fast (see this
148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent 152<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 233might be supported on the current system, you would need to look at
230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 234<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
231recommended ones.</p> 235recommended ones.</p>
232 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 236 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
233 </dd> 237 </dd>
234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 238 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
235 <dd> 239 <dd>
236 <p>Sets the allocation function to use (the prototype and semantics are 240 <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 241semantics is identical - to the realloc C function). It is used to
238memory (no surprises here). If it returns zero when memory needs to be 242allocate and free memory (no surprises here). If it returns zero when
239allocated, the library might abort or take some potentially destructive 243memory needs to be allocated, the library might abort or take some
240action. The default is your system realloc function.</p> 244potentially destructive action. The default is your system realloc
245function.</p>
241 <p>You could override this function in high-availability programs to, say, 246 <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, 247free 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> 248or 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 249 <p>Example: Replace the libev allocator with one that waits a bit and then
245retries).</p> 250retries).</p>
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324<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 329<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
325override the flags completely if it is found in the environment. This is 330override the flags completely if it is found in the environment. This is
326useful to try out specific backends to test their performance, or to work 331useful to try out specific backends to test their performance, or to work
327around bugs.</p> 332around bugs.</p>
328 </dd> 333 </dd>
334 <dt><code>EVFLAG_FORKCHECK</code></dt>
335 <dd>
336 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
337a fork, you can also make libev check for a fork in each iteration by
338enabling this flag.</p>
339 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
340and thus this might slow down your event loop if you do a lot of loop
341iterations and little real work, but is usually not noticeable (on my
342Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
343without a syscall and thus <i>very</i> fast, but my Linux system also has
344<code>pthread_atfork</code> which is even faster).</p>
345 <p>The big advantage of this flag is that you can forget about fork (and
346forget about forgetting to tell libev about forking) when you use this
347flag.</p>
348 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
349environment variable.</p>
350 </dd>
329 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 351 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
330 <dd> 352 <dd>
331 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 353 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
332libev tries to roll its own fd_set with no limits on the number of fds, 354libev tries to roll its own fd_set with no limits on the number of fds,
333but if that fails, expect a fairly low limit on the number of fds when 355but if that fails, expect a fairly low limit on the number of fds when
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461 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
462 <dd> 484 <dd>
463 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 485 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
464<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 486<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
465after fork, and how you do this is entirely your own problem.</p> 487after fork, and how you do this is entirely your own problem.</p>
488 </dd>
489 <dt>unsigned int ev_loop_count (loop)</dt>
490 <dd>
491 <p>Returns the count of loop iterations for the loop, which is identical to
492the number of times libev did poll for new events. It starts at <code>0</code> and
493happily wraps around with enough iterations.</p>
494 <p>This value can sometimes be useful as a generation counter of sorts (it
495&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
496<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
466 </dd> 497 </dd>
467 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
468 <dd> 499 <dd>
469 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 500 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
470use.</p> 501use.</p>
… …
498one iteration of the loop. This is useful if you are waiting for some 529one iteration of the loop. This is useful if you are waiting for some
499external event in conjunction with something not expressible using other 530external event in conjunction with something not expressible using other
500libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is 531libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
501usually a better approach for this kind of thing.</p> 532usually a better approach for this kind of thing.</p>
502 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 533 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
534<pre> - Before the first iteration, call any pending watchers.
503<pre> * If there are no active watchers (reference count is zero), return. 535 * If there are no active watchers (reference count is zero), return.
504 - Queue prepare watchers and then call all outstanding watchers. 536 - Queue all prepare watchers and then call all outstanding watchers.
505 - If we have been forked, recreate the kernel state. 537 - If we have been forked, recreate the kernel state.
506 - Update the kernel state with all outstanding changes. 538 - Update the kernel state with all outstanding changes.
507 - Update the &quot;event loop time&quot;. 539 - Update the &quot;event loop time&quot;.
508 - Calculate for how long to block. 540 - Calculate for how long to block.
509 - Block the process, waiting for any events. 541 - Block the process, waiting for any events.
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738 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 770 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
739 <dd> 771 <dd>
740 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 772 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
741events but its callback has not yet been invoked). As long as a watcher 773events 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 774is 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 775<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
744libev (e.g. you cnanot <code>free ()</code> it).</p> 776make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
777it).</p>
745 </dd> 778 </dd>
746 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 779 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd> 780 <dd>
748 <p>Returns the callback currently set on the watcher.</p> 781 <p>Returns the callback currently set on the watcher.</p>
749 </dd> 782 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 783 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 784 <dd>
752 <p>Change the callback. You can change the callback at virtually any time 785 <p>Change the callback. You can change the callback at virtually any time
753(modulo threads).</p> 786(modulo threads).</p>
787 </dd>
788 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
789 <dt>int ev_priority (ev_TYPE *watcher)</dt>
790 <dd>
791 <p>Set and query the priority of the watcher. The priority is a small
792integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
793(default: <code>-2</code>). Pending watchers with higher priority will be invoked
794before watchers with lower priority, but priority will not keep watchers
795from being executed (except for <code>ev_idle</code> watchers).</p>
796 <p>This means that priorities are <i>only</i> used for ordering callback
797invocation after new events have been received. This is useful, for
798example, to reduce latency after idling, or more often, to bind two
799watchers on the same event and make sure one is called first.</p>
800 <p>If you need to suppress invocation when higher priority events are pending
801you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
802 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
803pending.</p>
804 <p>The default priority used by watchers when no priority has been set is
805always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
806 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
807fine, as long as you do not mind that the priority value you query might
808or might not have been adjusted to be within valid range.</p>
809 </dd>
810 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
811 <dd>
812 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
813<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
814can deal with that fact.</p>
815 </dd>
816 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
817 <dd>
818 <p>If the watcher is pending, this function returns clears its pending status
819and returns its <code>revents</code> bitset (as if its callback was invoked). If the
820watcher isn't pending it does nothing and returns <code>0</code>.</p>
754 </dd> 821 </dd>
755</dl> 822</dl>
756 823
757 824
758 825
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783 struct my_io *w = (struct my_io *)w_; 850 struct my_io *w = (struct my_io *)w_;
784 ... 851 ...
785 } 852 }
786 853
787</pre> 854</pre>
788<p>More interesting and less C-conformant ways of catsing your callback type 855<p>More interesting and less C-conformant ways of casting your callback type
789have been omitted....</p> 856instead have been omitted.</p>
857<p>Another common scenario is having some data structure with multiple
858watchers:</p>
859<pre> struct my_biggy
860 {
861 int some_data;
862 ev_timer t1;
863 ev_timer t2;
864 }
790 865
866</pre>
867<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
868you need to use <code>offsetof</code>:</p>
869<pre> #include &lt;stddef.h&gt;
791 870
871 static void
872 t1_cb (EV_P_ struct ev_timer *w, int revents)
873 {
874 struct my_biggy big = (struct my_biggy *
875 (((char *)w) - offsetof (struct my_biggy, t1));
876 }
792 877
878 static void
879 t2_cb (EV_P_ struct ev_timer *w, int revents)
880 {
881 struct my_biggy big = (struct my_biggy *
882 (((char *)w) - offsetof (struct my_biggy, t2));
883 }
793 884
885
886
887
888</pre>
794 889
795</div> 890</div>
796<h1 id="WATCHER_TYPES">WATCHER TYPES</h1> 891<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
797<div id="WATCHER_TYPES_CONTENT"> 892<div id="WATCHER_TYPES_CONTENT">
798<p>This section describes each watcher in detail, but will not repeat 893<p>This section describes each watcher in detail, but will not repeat
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841this situation even with a relatively standard program structure. Thus 936this situation even with a relatively standard program structure. Thus
842it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 937it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
843<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 938<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
844<p>If you cannot run the fd in non-blocking mode (for example you should not 939<p>If you cannot run the fd in non-blocking mode (for example you should not
845play around with an Xlib connection), then you have to seperately re-test 940play around with an Xlib connection), then you have to seperately re-test
846wether a file descriptor is really ready with a known-to-be good interface 941whether a file descriptor is really ready with a known-to-be good interface
847such as poll (fortunately in our Xlib example, Xlib already does this on 942such as poll (fortunately in our Xlib example, Xlib already does this on
848its own, so its quite safe to use).</p> 943its own, so its quite safe to use).</p>
849<dl> 944<dl>
850 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 945 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
851 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 946 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
922 </dd> 1017 </dd>
923 <dt>ev_timer_again (loop)</dt> 1018 <dt>ev_timer_again (loop)</dt>
924 <dd> 1019 <dd>
925 <p>This will act as if the timer timed out and restart it again if it is 1020 <p>This will act as if the timer timed out and restart it again if it is
926repeating. The exact semantics are:</p> 1021repeating. The exact semantics are:</p>
1022 <p>If the timer is pending, its pending status is cleared.</p>
927 <p>If the timer is started but nonrepeating, stop it.</p> 1023 <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 1024 <p>If the timer is repeating, either start it if necessary (with the
929value), or reset the running timer to the repeat value.</p> 1025<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 1026 <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 1027example: 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, 1028timeout, 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 1029seconds 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 1030configure 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 1031<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 1032you 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 1033socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
938need be.</p> 1034automatically restart it if need be.</p>
939 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1035 <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> 1036altogether 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.); 1037<pre> ev_timer_init (timer, callback, 0., 5.);
942 ev_timer_again (loop, timer); 1038 ev_timer_again (loop, timer);
943 ... 1039 ...
944 timer-&gt;again = 17.; 1040 timer-&gt;again = 17.;
945 ev_timer_again (loop, timer); 1041 ev_timer_again (loop, timer);
946 ... 1042 ...
947 timer-&gt;again = 10.; 1043 timer-&gt;again = 10.;
948 ev_timer_again (loop, timer); 1044 ev_timer_again (loop, timer);
949 1045
950</pre> 1046</pre>
951 <p>This is more efficient then stopping/starting the timer eahc time you want 1047 <p>This is more slightly efficient then stopping/starting the timer each time
952to modify its timeout value.</p> 1048you want to modify its timeout value.</p>
953 </dd> 1049 </dd>
954 <dt>ev_tstamp repeat [read-write]</dt> 1050 <dt>ev_tstamp repeat [read-write]</dt>
955 <dd> 1051 <dd>
956 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1052 <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), 1053or <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 1314<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 1315not 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 1316not 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 1317otherwise always forced to be at least one) and all the other fields of
1222the stat buffer having unspecified contents.</p> 1318the stat buffer having unspecified contents.</p>
1319<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1320relative and your working directory changes, the behaviour is undefined.</p>
1223<p>Since there is no standard to do this, the portable implementation simply 1321<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 1322calls <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 1323can specify a recommended polling interval for this case. If you specify
1226a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1324a 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 1325unspecified default</i> value will be used (which you can expect to be around
1228five seconds, although this might change dynamically). Libev will also 1326five seconds, although this might change dynamically). Libev will also
1229impose a minimum interval which is currently around <code>0.1</code>, but thats 1327impose a minimum interval which is currently around <code>0.1</code>, but thats
1230usually overkill.</p> 1328usually overkill.</p>
1231<p>This watcher type is not meant for massive numbers of stat watchers, 1329<p>This watcher type is not meant for massive numbers of stat watchers,
1232as even with OS-supported change notifications, this can be 1330as even with OS-supported change notifications, this can be
1233resource-intensive.</p> 1331resource-intensive.</p>
1234<p>At the time of this writing, no specific OS backends are implemented, but 1332<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> 1333implemented (implementing kqueue support is left as an exercise for the
1334reader). Inotify will be used to give hints only and should not change the
1335semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1336to fall back to regular polling again even with inotify, but changes are
1337usually detected immediately, and if the file exists there will be no
1338polling.</p>
1236<dl> 1339<dl>
1237 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1340 <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> 1341 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1239 <dd> 1342 <dd>
1240 <p>Configures the watcher to wait for status changes of the given 1343 <p>Configures the watcher to wait for status changes of the given
… …
1303</pre> 1406</pre>
1304 1407
1305</div> 1408</div>
1306<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1409<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1307<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1410<div id="code_ev_idle_code_when_you_ve_got_no-2">
1308<p>Idle watchers trigger events when there are no other events are pending 1411<p>Idle watchers trigger events when no other events of the same or higher
1309(prepare, check and other idle watchers do not count). That is, as long 1412priority are pending (prepare, check and other idle watchers do not
1310as your process is busy handling sockets or timeouts (or even signals, 1413count).</p>
1311imagine) it will not be triggered. But when your process is idle all idle 1414<p>That is, as long as your process is busy handling sockets or timeouts
1312watchers are being called again and again, once per event loop iteration - 1415(or even signals, imagine) of the same or higher priority it will not be
1416triggered. But when your process is idle (or only lower-priority watchers
1417are pending), the idle watchers are being called once per event loop
1313until stopped, that is, or your process receives more events and becomes 1418iteration - until stopped, that is, or your process receives more events
1314busy.</p> 1419and becomes busy again with higher priority stuff.</p>
1315<p>The most noteworthy effect is that as long as any idle watchers are 1420<p>The most noteworthy effect is that as long as any idle watchers are
1316active, the process will not block when waiting for new events.</p> 1421active, the process will not block when waiting for new events.</p>
1317<p>Apart from keeping your process non-blocking (which is a useful 1422<p>Apart from keeping your process non-blocking (which is a useful
1318effect on its own sometimes), idle watchers are a good place to do 1423effect on its own sometimes), idle watchers are a good place to do
1319&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1424&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1379are ready to run (it's actually more complicated: it only runs coroutines 1484are ready to run (it's actually more complicated: it only runs coroutines
1380with priority higher than or equal to the event loop and one coroutine 1485with priority higher than or equal to the event loop and one coroutine
1381of lower priority, but only once, using idle watchers to keep the event 1486of lower priority, but only once, using idle watchers to keep the event
1382loop from blocking if lower-priority coroutines are active, thus mapping 1487loop from blocking if lower-priority coroutines are active, thus mapping
1383low-priority coroutines to idle/background tasks).</p> 1488low-priority coroutines to idle/background tasks).</p>
1489<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1490priority, to ensure that they are being run before any other watchers
1491after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1492too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1493supports this, they will be called before other <code>ev_check</code> watchers did
1494their job. As <code>ev_check</code> watchers are often used to embed other event
1495loops those other event loops might be in an unusable state until their
1496<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1497others).</p>
1384<dl> 1498<dl>
1385 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1499 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1386 <dt>ev_check_init (ev_check *, callback)</dt> 1500 <dt>ev_check_init (ev_check *, callback)</dt>
1387 <dd> 1501 <dd>
1388 <p>Initialises and configures the prepare or check watcher - they have no 1502 <p>Initialises and configures the prepare or check watcher - they have no
1389parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1503parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1390macros, but using them is utterly, utterly and completely pointless.</p> 1504macros, but using them is utterly, utterly and completely pointless.</p>
1391 </dd> 1505 </dd>
1392</dl> 1506</dl>
1393<p>Example: To include a library such as adns, you would add IO watchers 1507<p>There are a number of principal ways to embed other event loops or modules
1394and a timeout watcher in a prepare handler, as required by libadns, and 1508into libev. Here are some ideas on how to include libadns into libev
1509(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1510use for an actually working example. Another Perl module named <code>EV::Glib</code>
1511embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1512into the Glib event loop).</p>
1513<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1395in a check watcher, destroy them and call into libadns. What follows is 1514and in a check watcher, destroy them and call into libadns. What follows
1396pseudo-code only of course:</p> 1515is pseudo-code only of course. This requires you to either use a low
1516priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1517the callbacks for the IO/timeout watchers might not have been called yet.</p>
1397<pre> static ev_io iow [nfd]; 1518<pre> static ev_io iow [nfd];
1398 static ev_timer tw; 1519 static ev_timer tw;
1399 1520
1400 static void 1521 static void
1401 io_cb (ev_loop *loop, ev_io *w, int revents) 1522 io_cb (ev_loop *loop, ev_io *w, int revents)
1402 { 1523 {
1403 // set the relevant poll flags
1404 // could also call adns_processreadable etc. here
1405 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1406 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1407 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1408 } 1524 }
1409 1525
1410 // create io watchers for each fd and a timer before blocking 1526 // create io watchers for each fd and a timer before blocking
1411 static void 1527 static void
1412 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1528 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1413 { 1529 {
1414 int timeout = 3600000;truct pollfd fds [nfd]; 1530 int timeout = 3600000;
1531 struct pollfd fds [nfd];
1415 // actual code will need to loop here and realloc etc. 1532 // actual code will need to loop here and realloc etc.
1416 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1533 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1417 1534
1418 /* the callback is illegal, but won't be called as we stop during check */ 1535 /* the callback is illegal, but won't be called as we stop during check */
1419 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1536 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1420 ev_timer_start (loop, &amp;tw); 1537 ev_timer_start (loop, &amp;tw);
1421 1538
1422 // create on ev_io per pollfd 1539 // create one ev_io per pollfd
1423 for (int i = 0; i &lt; nfd; ++i) 1540 for (int i = 0; i &lt; nfd; ++i)
1424 { 1541 {
1425 ev_io_init (iow + i, io_cb, fds [i].fd, 1542 ev_io_init (iow + i, io_cb, fds [i].fd,
1426 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1543 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1427 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1544 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1428 1545
1429 fds [i].revents = 0; 1546 fds [i].revents = 0;
1430 iow [i].data = fds + i;
1431 ev_io_start (loop, iow + i); 1547 ev_io_start (loop, iow + i);
1432 } 1548 }
1433 } 1549 }
1434 1550
1435 // stop all watchers after blocking 1551 // stop all watchers after blocking
… …
1437 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1553 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1438 { 1554 {
1439 ev_timer_stop (loop, &amp;tw); 1555 ev_timer_stop (loop, &amp;tw);
1440 1556
1441 for (int i = 0; i &lt; nfd; ++i) 1557 for (int i = 0; i &lt; nfd; ++i)
1558 {
1559 // set the relevant poll flags
1560 // could also call adns_processreadable etc. here
1561 struct pollfd *fd = fds + i;
1562 int revents = ev_clear_pending (iow + i);
1563 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1564 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1565
1566 // now stop the watcher
1442 ev_io_stop (loop, iow + i); 1567 ev_io_stop (loop, iow + i);
1568 }
1443 1569
1444 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1570 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1571 }
1572
1573</pre>
1574<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1575in the prepare watcher and would dispose of the check watcher.</p>
1576<p>Method 3: If the module to be embedded supports explicit event
1577notification (adns does), you can also make use of the actual watcher
1578callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1579<pre> static void
1580 timer_cb (EV_P_ ev_timer *w, int revents)
1581 {
1582 adns_state ads = (adns_state)w-&gt;data;
1583 update_now (EV_A);
1584
1585 adns_processtimeouts (ads, &amp;tv_now);
1586 }
1587
1588 static void
1589 io_cb (EV_P_ ev_io *w, int revents)
1590 {
1591 adns_state ads = (adns_state)w-&gt;data;
1592 update_now (EV_A);
1593
1594 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1595 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1596 }
1597
1598 // do not ever call adns_afterpoll
1599
1600</pre>
1601<p>Method 4: Do not use a prepare or check watcher because the module you
1602want to embed is too inflexible to support it. Instead, youc na override
1603their poll function. The drawback with this solution is that the main
1604loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1605this.</p>
1606<pre> static gint
1607 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1608 {
1609 int got_events = 0;
1610
1611 for (n = 0; n &lt; nfds; ++n)
1612 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1613
1614 if (timeout &gt;= 0)
1615 // create/start timer
1616
1617 // poll
1618 ev_loop (EV_A_ 0);
1619
1620 // stop timer again
1621 if (timeout &gt;= 0)
1622 ev_timer_stop (EV_A_ &amp;to);
1623
1624 // stop io watchers again - their callbacks should have set
1625 for (n = 0; n &lt; nfds; ++n)
1626 ev_io_stop (EV_A_ iow [n]);
1627
1628 return got_events;
1445 } 1629 }
1446 1630
1447 1631
1448 1632
1449 1633
… …
1646the callback model to a model using method callbacks on objects.</p> 1830the callback model to a model using method callbacks on objects.</p>
1647<p>To use it,</p> 1831<p>To use it,</p>
1648<pre> #include &lt;ev++.h&gt; 1832<pre> #include &lt;ev++.h&gt;
1649 1833
1650</pre> 1834</pre>
1651<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1835<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1652and puts all of its definitions (many of them macros) into the global 1836of them macros) into the global namespace. All C++ specific things are
1653namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1837put into the <code>ev</code> namespace. It should support all the same embedding
1654<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1838options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1655<code>EV_MULTIPLICITY</code>.</p> 1839<p>Care has been taken to keep the overhead low. The only data member the C++
1840classes add (compared to plain C-style watchers) is the event loop pointer
1841that the watcher is associated with (or no additional members at all if
1842you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1843<p>Currently, functions, and static and non-static member functions can be
1844used as callbacks. Other types should be easy to add as long as they only
1845need one additional pointer for context. If you need support for other
1846types of functors please contact the author (preferably after implementing
1847it).</p>
1656<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1848<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1657<dl> 1849<dl>
1658 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1850 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1659 <dd> 1851 <dd>
1660 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1852 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1671which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1863which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1672defines by many implementations.</p> 1864defines by many implementations.</p>
1673 <p>All of those classes have these methods:</p> 1865 <p>All of those classes have these methods:</p>
1674 <p> 1866 <p>
1675 <dl> 1867 <dl>
1676 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1868 <dt>ev::TYPE::TYPE ()</dt>
1677 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1869 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1678 <dt>ev::TYPE::~TYPE</dt> 1870 <dt>ev::TYPE::~TYPE</dt>
1679 <dd> 1871 <dd>
1680 <p>The constructor takes a pointer to an object and a method pointer to 1872 <p>The constructor (optionally) takes an event loop to associate the watcher
1681the event handler callback to call in this class. The constructor calls 1873with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1682<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1874 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1683before starting it. If you do not specify a loop then the constructor 1875<code>set</code> method before starting it.</p>
1684automatically associates the default loop with this watcher.</p> 1876 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1877method to set a callback before you can start the watcher.</p>
1878 <p>(The reason why you have to use a method is a limitation in C++ which does
1879not allow explicit template arguments for constructors).</p>
1685 <p>The destructor automatically stops the watcher if it is active.</p> 1880 <p>The destructor automatically stops the watcher if it is active.</p>
1881 </dd>
1882 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1883 <dd>
1884 <p>This method sets the callback method to call. The method has to have a
1885signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1886first argument and the <code>revents</code> as second. The object must be given as
1887parameter and is stored in the <code>data</code> member of the watcher.</p>
1888 <p>This method synthesizes efficient thunking code to call your method from
1889the C callback that libev requires. If your compiler can inline your
1890callback (i.e. it is visible to it at the place of the <code>set</code> call and
1891your compiler is good :), then the method will be fully inlined into the
1892thunking function, making it as fast as a direct C callback.</p>
1893 <p>Example: simple class declaration and watcher initialisation</p>
1894<pre> struct myclass
1895 {
1896 void io_cb (ev::io &amp;w, int revents) { }
1897 }
1898
1899 myclass obj;
1900 ev::io iow;
1901 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1902
1903</pre>
1904 </dd>
1905 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1906 <dd>
1907 <p>Also sets a callback, but uses a static method or plain function as
1908callback. The optional <code>data</code> argument will be stored in the watcher's
1909<code>data</code> member and is free for you to use.</p>
1910 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1911 <p>See the method-<code>set</code> above for more details.</p>
1912 <p>Example:</p>
1913<pre> static void io_cb (ev::io &amp;w, int revents) { }
1914 iow.set &lt;io_cb&gt; ();
1915
1916</pre>
1686 </dd> 1917 </dd>
1687 <dt>w-&gt;set (struct ev_loop *)</dt> 1918 <dt>w-&gt;set (struct ev_loop *)</dt>
1688 <dd> 1919 <dd>
1689 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1920 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1690do this when the watcher is inactive (and not pending either).</p> 1921do this when the watcher is inactive (and not pending either).</p>
1691 </dd> 1922 </dd>
1692 <dt>w-&gt;set ([args])</dt> 1923 <dt>w-&gt;set ([args])</dt>
1693 <dd> 1924 <dd>
1694 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1925 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1695called at least once. Unlike the C counterpart, an active watcher gets 1926called at least once. Unlike the C counterpart, an active watcher gets
1696automatically stopped and restarted.</p> 1927automatically stopped and restarted when reconfiguring it with this
1928method.</p>
1697 </dd> 1929 </dd>
1698 <dt>w-&gt;start ()</dt> 1930 <dt>w-&gt;start ()</dt>
1699 <dd> 1931 <dd>
1700 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1932 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1701constructor already takes the loop.</p> 1933constructor already stores the event loop.</p>
1702 </dd> 1934 </dd>
1703 <dt>w-&gt;stop ()</dt> 1935 <dt>w-&gt;stop ()</dt>
1704 <dd> 1936 <dd>
1705 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1937 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1706 </dd> 1938 </dd>
… …
1730 1962
1731 myclass (); 1963 myclass ();
1732 } 1964 }
1733 1965
1734 myclass::myclass (int fd) 1966 myclass::myclass (int fd)
1735 : io (this, &amp;myclass::io_cb),
1736 idle (this, &amp;myclass::idle_cb)
1737 { 1967 {
1968 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1969 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1970
1738 io.start (fd, ev::READ); 1971 io.start (fd, ev::READ);
1739 } 1972 }
1740 1973
1741 1974
1742 1975
… …
1745 1978
1746</div> 1979</div>
1747<h1 id="MACRO_MAGIC">MACRO MAGIC</h1> 1980<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1748<div id="MACRO_MAGIC_CONTENT"> 1981<div id="MACRO_MAGIC_CONTENT">
1749<p>Libev can be compiled with a variety of options, the most fundemantal is 1982<p>Libev can be compiled with a variety of options, the most fundemantal is
1750<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 1983<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1751callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1984callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1752<p>To make it easier to write programs that cope with either variant, the 1985<p>To make it easier to write programs that cope with either variant, the
1753following macros are defined:</p> 1986following macros are defined:</p>
1754<dl> 1987<dl>
1755 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1988 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1784 <dd> 2017 <dd>
1785 <p>Similar to the other two macros, this gives you the value of the default 2018 <p>Similar to the other two macros, this gives you the value of the default
1786loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 2019loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1787 </dd> 2020 </dd>
1788</dl> 2021</dl>
1789<p>Example: Declare and initialise a check watcher, working regardless of 2022<p>Example: Declare and initialise a check watcher, utilising the above
1790wether multiple loops are supported or not.</p> 2023macros so it will work regardless of whether multiple loops are supported
2024or not.</p>
1791<pre> static void 2025<pre> static void
1792 check_cb (EV_P_ ev_timer *w, int revents) 2026 check_cb (EV_P_ ev_timer *w, int revents)
1793 { 2027 {
1794 ev_check_stop (EV_A_ w); 2028 ev_check_stop (EV_A_ w);
1795 } 2029 }
1796 2030
1797 ev_check check; 2031 ev_check check;
1798 ev_check_init (&amp;check, check_cb); 2032 ev_check_init (&amp;check, check_cb);
1799 ev_check_start (EV_DEFAULT_ &amp;check); 2033 ev_check_start (EV_DEFAULT_ &amp;check);
1800 ev_loop (EV_DEFAULT_ 0); 2034 ev_loop (EV_DEFAULT_ 0);
1801
1802
1803
1804 2035
1805</pre> 2036</pre>
1806 2037
1807</div> 2038</div>
1808<h1 id="EMBEDDING">EMBEDDING</h1> 2039<h1 id="EMBEDDING">EMBEDDING</h1>
… …
1850 ev_vars.h 2081 ev_vars.h
1851 ev_wrap.h 2082 ev_wrap.h
1852 2083
1853 ev_win32.c required on win32 platforms only 2084 ev_win32.c required on win32 platforms only
1854 2085
1855 ev_select.c only when select backend is enabled (which is by default) 2086 ev_select.c only when select backend is enabled (which is enabled by default)
1856 ev_poll.c only when poll backend is enabled (disabled by default) 2087 ev_poll.c only when poll backend is enabled (disabled by default)
1857 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2088 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1858 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2089 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1859 ev_port.c only when the solaris port backend is enabled (disabled by default) 2090 ev_port.c only when the solaris port backend is enabled (disabled by default)
1860 2091
… …
1987 </dd> 2218 </dd>
1988 <dt>EV_USE_DEVPOLL</dt> 2219 <dt>EV_USE_DEVPOLL</dt>
1989 <dd> 2220 <dd>
1990 <p>reserved for future expansion, works like the USE symbols above.</p> 2221 <p>reserved for future expansion, works like the USE symbols above.</p>
1991 </dd> 2222 </dd>
2223 <dt>EV_USE_INOTIFY</dt>
2224 <dd>
2225 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2226interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2227be detected at runtime.</p>
2228 </dd>
1992 <dt>EV_H</dt> 2229 <dt>EV_H</dt>
1993 <dd> 2230 <dd>
1994 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2231 <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 2232undefined 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> 2233can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
2019will have the <code>struct ev_loop *</code> as first argument, and you can create 2256will have the <code>struct ev_loop *</code> as first argument, and you can create
2020additional independent event loops. Otherwise there will be no support 2257additional independent event loops. Otherwise there will be no support
2021for multiple event loops and there is no first event loop pointer 2258for multiple event loops and there is no first event loop pointer
2022argument. Instead, all functions act on the single default loop.</p> 2259argument. Instead, all functions act on the single default loop.</p>
2023 </dd> 2260 </dd>
2261 <dt>EV_MINPRI</dt>
2262 <dt>EV_MAXPRI</dt>
2263 <dd>
2264 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2265<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2266provide for more priorities by overriding those symbols (usually defined
2267to be <code>-2</code> and <code>2</code>, respectively).</p>
2268 <p>When doing priority-based operations, libev usually has to linearly search
2269all the priorities, so having many of them (hundreds) uses a lot of space
2270and time, so using the defaults of five priorities (-2 .. +2) is usually
2271fine.</p>
2272 <p>If your embedding app does not need any priorities, defining these both to
2273<code>0</code> will save some memory and cpu.</p>
2274 </dd>
2024 <dt>EV_PERIODIC_ENABLE</dt> 2275 <dt>EV_PERIODIC_ENABLE</dt>
2025 <dd> 2276 <dd>
2026 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2277 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2027defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2278defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2028code.</p> 2279code.</p>
2029 </dd> 2280 </dd>
2281 <dt>EV_IDLE_ENABLE</dt>
2282 <dd>
2283 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2284defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2285code.</p>
2286 </dd>
2030 <dt>EV_EMBED_ENABLE</dt> 2287 <dt>EV_EMBED_ENABLE</dt>
2031 <dd> 2288 <dd>
2032 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If 2289 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2033defined to be <code>0</code>, then they are not.</p> 2290defined to be <code>0</code>, then they are not.</p>
2034 </dd> 2291 </dd>
… …
2051 <dt>EV_PID_HASHSIZE</dt> 2308 <dt>EV_PID_HASHSIZE</dt>
2052 <dd> 2309 <dd>
2053 <p><code>ev_child</code> watchers use a small hash table to distribute workload by 2310 <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 2311pid. 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 2312than enough. If you need to manage thousands of children you might want to
2056increase this value.</p> 2313increase this value (<i>must</i> be a power of two).</p>
2314 </dd>
2315 <dt>EV_INOTIFY_HASHSIZE</dt>
2316 <dd>
2317 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2318inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2319usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2320watchers you might want to increase this value (<i>must</i> be a power of
2321two).</p>
2057 </dd> 2322 </dd>
2058 <dt>EV_COMMON</dt> 2323 <dt>EV_COMMON</dt>
2059 <dd> 2324 <dd>
2060 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2325 <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 2326this macro to a something else you can include more and other types of
… …
2088the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2353the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2089interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2354interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2090will be compiled. It is pretty complex because it provides its own header 2355will be compiled. It is pretty complex because it provides its own header
2091file.</p> 2356file.</p>
2092 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2357 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2093that everybody includes and which overrides some autoconf choices:</p> 2358that everybody includes and which overrides some configure choices:</p>
2359<pre> #define EV_MINIMAL 1
2094<pre> #define EV_USE_POLL 0 2360 #define EV_USE_POLL 0
2095 #define EV_MULTIPLICITY 0 2361 #define EV_MULTIPLICITY 0
2096 #define EV_PERIODICS 0 2362 #define EV_PERIODIC_ENABLE 0
2363 #define EV_STAT_ENABLE 0
2364 #define EV_FORK_ENABLE 0
2097 #define EV_CONFIG_H &lt;config.h&gt; 2365 #define EV_CONFIG_H &lt;config.h&gt;
2366 #define EV_MINPRI 0
2367 #define EV_MAXPRI 0
2098 2368
2099 #include &quot;ev++.h&quot; 2369 #include &quot;ev++.h&quot;
2100 2370
2101</pre> 2371</pre>
2102 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2372 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2112<h1 id="COMPLEXITIES">COMPLEXITIES</h1> 2382<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2113<div id="COMPLEXITIES_CONTENT"> 2383<div id="COMPLEXITIES_CONTENT">
2114 <p>In this section the complexities of (many of) the algorithms used inside 2384 <p>In this section the complexities of (many of) the algorithms used inside
2115libev will be explained. For complexity discussions about backends see the 2385libev will be explained. For complexity discussions about backends see the
2116documentation for <code>ev_default_init</code>.</p> 2386documentation for <code>ev_default_init</code>.</p>
2387 <p>All of the following are about amortised time: If an array needs to be
2388extended, libev needs to realloc and move the whole array, but this
2389happens asymptotically never with higher number of elements, so O(1) might
2390mean it might do a lengthy realloc operation in rare cases, but on average
2391it is much faster and asymptotically approaches constant time.</p>
2117 <p> 2392 <p>
2118 <dl> 2393 <dl>
2119 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2394 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2395 <dd>
2396 <p>This means that, when you have a watcher that triggers in one hour and
2397there are 100 watchers that would trigger before that then inserting will
2398have to skip those 100 watchers.</p>
2399 </dd>
2120 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2400 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2401 <dd>
2402 <p>That means that for changing a timer costs less than removing/adding them
2403as only the relative motion in the event queue has to be paid for.</p>
2404 </dd>
2121 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2405 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2406 <dd>
2407 <p>These just add the watcher into an array or at the head of a list.
2122 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2408=item Stopping check/prepare/idle watchers: O(1)</p>
2409 </dd>
2123 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2410 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2411 <dd>
2412 <p>These watchers are stored in lists then need to be walked to find the
2413correct watcher to remove. The lists are usually short (you don't usually
2414have many watchers waiting for the same fd or signal).</p>
2415 </dd>
2124 <dt>Finding the next timer per loop iteration: O(1)</dt> 2416 <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> 2417 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2418 <dd>
2419 <p>A change means an I/O watcher gets started or stopped, which requires
2420libev to recalculate its status (and possibly tell the kernel).</p>
2421 </dd>
2126 <dt>Activating one watcher: O(1)</dt> 2422 <dt>Activating one watcher: O(1)</dt>
2423 <dt>Priority handling: O(number_of_priorities)</dt>
2424 <dd>
2425 <p>Priorities are implemented by allocating some space for each
2426priority. When doing priority-based operations, libev usually has to
2427linearly search all the priorities.</p>
2428 </dd>
2127 </dl> 2429 </dl>
2128 </p> 2430 </p>
2129 2431
2130 2432
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