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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;" />
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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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181you actually want to know.</p> 185you actually want to know.</p>
182 </dd> 186 </dd>
183 <dt>int ev_version_major ()</dt> 187 <dt>int ev_version_major ()</dt>
184 <dt>int ev_version_minor ()</dt> 188 <dt>int ev_version_minor ()</dt>
185 <dd> 189 <dd>
186 <p>You can find out the major and minor version numbers of the library 190 <p>You can find out the major and minor API/ABI version numbers of the library
187you linked against by calling the functions <code>ev_version_major</code> and 191you linked against by calling the functions <code>ev_version_major</code> and
188<code>ev_version_minor</code>. If you want, you can compare against the global 192<code>ev_version_minor</code>. If you want, you can compare against the global
189symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 193symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
190version of the library your program was compiled against.</p> 194version of the library your program was compiled against.</p>
195 <p>These version numbers refer to the API and ABI version of the library, not
196the release version.</p>
191 <p>Usually, it's a good idea to terminate if the major versions mismatch, 197 <p>Usually, it's a good idea to terminate if the major versions mismatch,
192as this indicates an incompatible change. Minor versions are usually 198as this indicates an incompatible change. Minor versions are usually
193compatible to older versions, so a larger minor version alone is usually 199compatible to older versions, so a larger minor version alone is usually
194not a problem.</p> 200not a problem.</p>
195 <p>Example: Make sure we haven't accidentally been linked against the wrong 201 <p>Example: Make sure we haven't accidentally been linked against the wrong
196version.</p> 202version.</p>
197<pre> assert ((&quot;libev version mismatch&quot;, 203<pre> assert ((&quot;libev version mismatch&quot;,
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229might be supported on the current system, you would need to look at 235might be supported on the current system, you would need to look at
230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 236<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
231recommended ones.</p> 237recommended ones.</p>
232 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 238 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
233 </dd> 239 </dd>
234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 240 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
235 <dd> 241 <dd>
236 <p>Sets the allocation function to use (the prototype and semantics are 242 <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 243semantics is identical - to the realloc C function). It is used to
238memory (no surprises here). If it returns zero when memory needs to be 244allocate and free memory (no surprises here). If it returns zero when
239allocated, the library might abort or take some potentially destructive 245memory needs to be allocated, the library might abort or take some
240action. The default is your system realloc function.</p> 246potentially destructive action. The default is your system realloc
247function.</p>
241 <p>You could override this function in high-availability programs to, say, 248 <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, 249free 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> 250or 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 251 <p>Example: Replace the libev allocator with one that waits a bit and then
245retries).</p> 252retries).</p>
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324<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 331<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
325override the flags completely if it is found in the environment. This is 332override 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 333useful to try out specific backends to test their performance, or to work
327around bugs.</p> 334around bugs.</p>
328 </dd> 335 </dd>
336 <dt><code>EVFLAG_FORKCHECK</code></dt>
337 <dd>
338 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
339a fork, you can also make libev check for a fork in each iteration by
340enabling this flag.</p>
341 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
342and thus this might slow down your event loop if you do a lot of loop
343iterations and little real work, but is usually not noticeable (on my
344Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
345without a syscall and thus <i>very</i> fast, but my Linux system also has
346<code>pthread_atfork</code> which is even faster).</p>
347 <p>The big advantage of this flag is that you can forget about fork (and
348forget about forgetting to tell libev about forking) when you use this
349flag.</p>
350 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
351environment variable.</p>
352 </dd>
329 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 353 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
330 <dd> 354 <dd>
331 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 355 <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, 356libev 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 357but 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> 485 <dt>ev_loop_fork (loop)</dt>
462 <dd> 486 <dd>
463 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 487 <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 488<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> 489after fork, and how you do this is entirely your own problem.</p>
490 </dd>
491 <dt>unsigned int ev_loop_count (loop)</dt>
492 <dd>
493 <p>Returns the count of loop iterations for the loop, which is identical to
494the number of times libev did poll for new events. It starts at <code>0</code> and
495happily wraps around with enough iterations.</p>
496 <p>This value can sometimes be useful as a generation counter of sorts (it
497&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
498<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
466 </dd> 499 </dd>
467 <dt>unsigned int ev_backend (loop)</dt> 500 <dt>unsigned int ev_backend (loop)</dt>
468 <dd> 501 <dd>
469 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 502 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
470use.</p> 503use.</p>
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498one iteration of the loop. This is useful if you are waiting for some 531one iteration of the loop. This is useful if you are waiting for some
499external event in conjunction with something not expressible using other 532external 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 533libev 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> 534usually a better approach for this kind of thing.</p>
502 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 535 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
536<pre> - Before the first iteration, call any pending watchers.
503<pre> * If there are no active watchers (reference count is zero), return. 537 * If there are no active watchers (reference count is zero), return.
504 - Queue prepare watchers and then call all outstanding watchers. 538 - Queue all prepare watchers and then call all outstanding watchers.
505 - If we have been forked, recreate the kernel state. 539 - If we have been forked, recreate the kernel state.
506 - Update the kernel state with all outstanding changes. 540 - Update the kernel state with all outstanding changes.
507 - Update the &quot;event loop time&quot;. 541 - Update the &quot;event loop time&quot;.
508 - Calculate for how long to block. 542 - Calculate for how long to block.
509 - Block the process, waiting for any events. 543 - Block the process, waiting for any events.
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738 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 772 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
739 <dd> 773 <dd>
740 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 774 <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 775events 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 776is 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 777<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> 778make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
779it).</p>
745 </dd> 780 </dd>
746 <dt>callback ev_cb (ev_TYPE *watcher)</dt> 781 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd> 782 <dd>
748 <p>Returns the callback currently set on the watcher.</p> 783 <p>Returns the callback currently set on the watcher.</p>
749 </dd> 784 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 785 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 786 <dd>
752 <p>Change the callback. You can change the callback at virtually any time 787 <p>Change the callback. You can change the callback at virtually any time
753(modulo threads).</p> 788(modulo threads).</p>
789 </dd>
790 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
791 <dt>int ev_priority (ev_TYPE *watcher)</dt>
792 <dd>
793 <p>Set and query the priority of the watcher. The priority is a small
794integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
795(default: <code>-2</code>). Pending watchers with higher priority will be invoked
796before watchers with lower priority, but priority will not keep watchers
797from being executed (except for <code>ev_idle</code> watchers).</p>
798 <p>This means that priorities are <i>only</i> used for ordering callback
799invocation after new events have been received. This is useful, for
800example, to reduce latency after idling, or more often, to bind two
801watchers on the same event and make sure one is called first.</p>
802 <p>If you need to suppress invocation when higher priority events are pending
803you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
804 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
805pending.</p>
806 <p>The default priority used by watchers when no priority has been set is
807always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
808 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
809fine, as long as you do not mind that the priority value you query might
810or might not have been adjusted to be within valid range.</p>
811 </dd>
812 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
813 <dd>
814 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
815<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
816can deal with that fact.</p>
817 </dd>
818 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
819 <dd>
820 <p>If the watcher is pending, this function returns clears its pending status
821and returns its <code>revents</code> bitset (as if its callback was invoked). If the
822watcher isn't pending it does nothing and returns <code>0</code>.</p>
754 </dd> 823 </dd>
755</dl> 824</dl>
756 825
757 826
758 827
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869this situation even with a relatively standard program structure. Thus 938this situation even with a relatively standard program structure. Thus
870it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 939it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
871<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 940<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
872<p>If you cannot run the fd in non-blocking mode (for example you should not 941<p>If you cannot run the fd in non-blocking mode (for example you should not
873play around with an Xlib connection), then you have to seperately re-test 942play around with an Xlib connection), then you have to seperately re-test
874wether a file descriptor is really ready with a known-to-be good interface 943whether a file descriptor is really ready with a known-to-be good interface
875such as poll (fortunately in our Xlib example, Xlib already does this on 944such as poll (fortunately in our Xlib example, Xlib already does this on
876its own, so its quite safe to use).</p> 945its own, so its quite safe to use).</p>
877<dl> 946<dl>
878 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 947 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
879 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 948 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
950 </dd> 1019 </dd>
951 <dt>ev_timer_again (loop)</dt> 1020 <dt>ev_timer_again (loop)</dt>
952 <dd> 1021 <dd>
953 <p>This will act as if the timer timed out and restart it again if it is 1022 <p>This will act as if the timer timed out and restart it again if it is
954repeating. The exact semantics are:</p> 1023repeating. The exact semantics are:</p>
1024 <p>If the timer is pending, its pending status is cleared.</p>
955 <p>If the timer is started but nonrepeating, stop it.</p> 1025 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
956 <p>If the timer is repeating, either start it if necessary (with the repeat 1026 <p>If the timer is repeating, either start it if necessary (with the
957value), or reset the running timer to the repeat value.</p> 1027<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
958 <p>This sounds a bit complicated, but here is a useful and typical 1028 <p>This sounds a bit complicated, but here is a useful and typical
959example: Imagine you have a tcp connection and you want a so-called 1029example: Imagine you have a tcp connection and you want a so-called idle
960idle timeout, that is, you want to be called when there have been, 1030timeout, that is, you want to be called when there have been, say, 60
961say, 60 seconds of inactivity on the socket. The easiest way to do 1031seconds of inactivity on the socket. The easiest way to do this is to
962this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling 1032configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
963<code>ev_timer_again</code> each time you successfully read or write some data. If 1033<code>ev_timer_again</code> each time you successfully read or write some data. If
964you go into an idle state where you do not expect data to travel on the 1034you go into an idle state where you do not expect data to travel on the
965socket, you can stop the timer, and again will automatically restart it if 1035socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
966need be.</p> 1036automatically restart it if need be.</p>
967 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1037 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
968and only ever use the <code>repeat</code> value:</p> 1038altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
969<pre> ev_timer_init (timer, callback, 0., 5.); 1039<pre> ev_timer_init (timer, callback, 0., 5.);
970 ev_timer_again (loop, timer); 1040 ev_timer_again (loop, timer);
971 ... 1041 ...
972 timer-&gt;again = 17.; 1042 timer-&gt;again = 17.;
973 ev_timer_again (loop, timer); 1043 ev_timer_again (loop, timer);
974 ... 1044 ...
975 timer-&gt;again = 10.; 1045 timer-&gt;again = 10.;
976 ev_timer_again (loop, timer); 1046 ev_timer_again (loop, timer);
977 1047
978</pre> 1048</pre>
979 <p>This is more efficient then stopping/starting the timer eahc time you want 1049 <p>This is more slightly efficient then stopping/starting the timer each time
980to modify its timeout value.</p> 1050you want to modify its timeout value.</p>
981 </dd> 1051 </dd>
982 <dt>ev_tstamp repeat [read-write]</dt> 1052 <dt>ev_tstamp repeat [read-write]</dt>
983 <dd> 1053 <dd>
984 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1054 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
985or <code>ev_timer_again</code> is called and determines the next timeout (if any), 1055or <code>ev_timer_again</code> is called and determines the next timeout (if any),
… …
1029but on wallclock time (absolute time). You can tell a periodic watcher 1099but on wallclock time (absolute time). You can tell a periodic watcher
1030to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1100to trigger &quot;at&quot; some specific point in time. For example, if you tell a
1031periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () 1101periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
1032+ 10.</code>) and then reset your system clock to the last year, then it will 1102+ 10.</code>) and then reset your system clock to the last year, then it will
1033take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1103take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
1034roughly 10 seconds later and of course not if you reset your system time 1104roughly 10 seconds later).</p>
1035again).</p>
1036<p>They can also be used to implement vastly more complex timers, such as 1105<p>They can also be used to implement vastly more complex timers, such as
1037triggering an event on eahc midnight, local time.</p> 1106triggering an event on each midnight, local time or other, complicated,
1107rules.</p>
1038<p>As with timers, the callback is guarenteed to be invoked only when the 1108<p>As with timers, the callback is guarenteed to be invoked only when the
1039time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1109time (<code>at</code>) has been passed, but if multiple periodic timers become ready
1040during the same loop iteration then order of execution is undefined.</p> 1110during the same loop iteration then order of execution is undefined.</p>
1041<dl> 1111<dl>
1042 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1112 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
… …
1044 <dd> 1114 <dd>
1045 <p>Lots of arguments, lets sort it out... There are basically three modes of 1115 <p>Lots of arguments, lets sort it out... There are basically three modes of
1046operation, and we will explain them from simplest to complex:</p> 1116operation, and we will explain them from simplest to complex:</p>
1047 <p> 1117 <p>
1048 <dl> 1118 <dl>
1049 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1119 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
1050 <dd> 1120 <dd>
1051 <p>In this configuration the watcher triggers an event at the wallclock time 1121 <p>In this configuration the watcher triggers an event at the wallclock time
1052<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1122<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
1053that is, if it is to be run at January 1st 2011 then it will run when the 1123that is, if it is to be run at January 1st 2011 then it will run when the
1054system time reaches or surpasses this time.</p> 1124system time reaches or surpasses this time.</p>
1055 </dd> 1125 </dd>
1056 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1126 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
1057 <dd> 1127 <dd>
1058 <p>In this mode the watcher will always be scheduled to time out at the next 1128 <p>In this mode the watcher will always be scheduled to time out at the next
1059<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1129<code>at + N * interval</code> time (for some integer N, which can also be negative)
1060of any time jumps.</p> 1130and then repeat, regardless of any time jumps.</p>
1061 <p>This can be used to create timers that do not drift with respect to system 1131 <p>This can be used to create timers that do not drift with respect to system
1062time:</p> 1132time:</p>
1063<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1133<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
1064 1134
1065</pre> 1135</pre>
… …
1068full hour (UTC), or more correctly, when the system time is evenly divisible 1138full hour (UTC), or more correctly, when the system time is evenly divisible
1069by 3600.</p> 1139by 3600.</p>
1070 <p>Another way to think about it (for the mathematically inclined) is that 1140 <p>Another way to think about it (for the mathematically inclined) is that
1071<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1141<code>ev_periodic</code> will try to run the callback in this mode at the next possible
1072time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1142time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1143 <p>For numerical stability it is preferable that the <code>at</code> value is near
1144<code>ev_now ()</code> (the current time), but there is no range requirement for
1145this value.</p>
1073 </dd> 1146 </dd>
1074 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1147 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
1075 <dd> 1148 <dd>
1076 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1149 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
1077ignored. Instead, each time the periodic watcher gets scheduled, the 1150ignored. Instead, each time the periodic watcher gets scheduled, the
1078reschedule callback will be called with the watcher as first, and the 1151reschedule callback will be called with the watcher as first, and the
1079current time as second argument.</p> 1152current time as second argument.</p>
1080 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1153 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
1081ever, or make any event loop modifications</i>. If you need to stop it, 1154ever, or make any event loop modifications</i>. If you need to stop it,
1082return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1155return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
1083starting a prepare watcher).</p> 1156starting an <code>ev_prepare</code> watcher, which is legal).</p>
1084 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1157 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1085ev_tstamp now)</code>, e.g.:</p> 1158ev_tstamp now)</code>, e.g.:</p>
1086<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1159<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1087 { 1160 {
1088 return now + 60.; 1161 return now + 60.;
… …
1108 <dd> 1181 <dd>
1109 <p>Simply stops and restarts the periodic watcher again. This is only useful 1182 <p>Simply stops and restarts the periodic watcher again. This is only useful
1110when you changed some parameters or the reschedule callback would return 1183when you changed some parameters or the reschedule callback would return
1111a different time than the last time it was called (e.g. in a crond like 1184a different time than the last time it was called (e.g. in a crond like
1112program when the crontabs have changed).</p> 1185program when the crontabs have changed).</p>
1186 </dd>
1187 <dt>ev_tstamp offset [read-write]</dt>
1188 <dd>
1189 <p>When repeating, this contains the offset value, otherwise this is the
1190absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1191 <p>Can be modified any time, but changes only take effect when the periodic
1192timer fires or <code>ev_periodic_again</code> is being called.</p>
1113 </dd> 1193 </dd>
1114 <dt>ev_tstamp interval [read-write]</dt> 1194 <dt>ev_tstamp interval [read-write]</dt>
1115 <dd> 1195 <dd>
1116 <p>The current interval value. Can be modified any time, but changes only 1196 <p>The current interval value. Can be modified any time, but changes only
1117take effect when the periodic timer fires or <code>ev_periodic_again</code> is being 1197take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
… …
1246<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1326<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1247not exist&quot; is a status change like any other. The condition &quot;path does 1327not 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 1328not 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 1329otherwise always forced to be at least one) and all the other fields of
1250the stat buffer having unspecified contents.</p> 1330the stat buffer having unspecified contents.</p>
1331<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1332relative and your working directory changes, the behaviour is undefined.</p>
1251<p>Since there is no standard to do this, the portable implementation simply 1333<p>Since there is no standard to do this, the portable implementation simply
1252calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You 1334calls <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 1335can specify a recommended polling interval for this case. If you specify
1254a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1336a 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 1337unspecified default</i> value will be used (which you can expect to be around
… …
1336</pre> 1418</pre>
1337 1419
1338</div> 1420</div>
1339<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1421<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1340<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1422<div id="code_ev_idle_code_when_you_ve_got_no-2">
1341<p>Idle watchers trigger events when there are no other events are pending 1423<p>Idle watchers trigger events when no other events of the same or higher
1342(prepare, check and other idle watchers do not count). That is, as long 1424priority are pending (prepare, check and other idle watchers do not
1343as your process is busy handling sockets or timeouts (or even signals, 1425count).</p>
1344imagine) it will not be triggered. But when your process is idle all idle 1426<p>That is, as long as your process is busy handling sockets or timeouts
1345watchers are being called again and again, once per event loop iteration - 1427(or even signals, imagine) of the same or higher priority it will not be
1428triggered. But when your process is idle (or only lower-priority watchers
1429are pending), the idle watchers are being called once per event loop
1346until stopped, that is, or your process receives more events and becomes 1430iteration - until stopped, that is, or your process receives more events
1347busy.</p> 1431and becomes busy again with higher priority stuff.</p>
1348<p>The most noteworthy effect is that as long as any idle watchers are 1432<p>The most noteworthy effect is that as long as any idle watchers are
1349active, the process will not block when waiting for new events.</p> 1433active, the process will not block when waiting for new events.</p>
1350<p>Apart from keeping your process non-blocking (which is a useful 1434<p>Apart from keeping your process non-blocking (which is a useful
1351effect on its own sometimes), idle watchers are a good place to do 1435effect on its own sometimes), idle watchers are a good place to do
1352&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1436&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1412are ready to run (it's actually more complicated: it only runs coroutines 1496are ready to run (it's actually more complicated: it only runs coroutines
1413with priority higher than or equal to the event loop and one coroutine 1497with priority higher than or equal to the event loop and one coroutine
1414of lower priority, but only once, using idle watchers to keep the event 1498of lower priority, but only once, using idle watchers to keep the event
1415loop from blocking if lower-priority coroutines are active, thus mapping 1499loop from blocking if lower-priority coroutines are active, thus mapping
1416low-priority coroutines to idle/background tasks).</p> 1500low-priority coroutines to idle/background tasks).</p>
1501<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1502priority, to ensure that they are being run before any other watchers
1503after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1504too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1505supports this, they will be called before other <code>ev_check</code> watchers did
1506their job. As <code>ev_check</code> watchers are often used to embed other event
1507loops those other event loops might be in an unusable state until their
1508<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1509others).</p>
1417<dl> 1510<dl>
1418 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1511 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1419 <dt>ev_check_init (ev_check *, callback)</dt> 1512 <dt>ev_check_init (ev_check *, callback)</dt>
1420 <dd> 1513 <dd>
1421 <p>Initialises and configures the prepare or check watcher - they have no 1514 <p>Initialises and configures the prepare or check watcher - they have no
1422parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1515parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1423macros, but using them is utterly, utterly and completely pointless.</p> 1516macros, but using them is utterly, utterly and completely pointless.</p>
1424 </dd> 1517 </dd>
1425</dl> 1518</dl>
1426<p>Example: To include a library such as adns, you would add IO watchers 1519<p>There are a number of principal ways to embed other event loops or modules
1427and a timeout watcher in a prepare handler, as required by libadns, and 1520into libev. Here are some ideas on how to include libadns into libev
1521(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1522use for an actually working example. Another Perl module named <code>EV::Glib</code>
1523embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1524into the Glib event loop).</p>
1525<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1428in a check watcher, destroy them and call into libadns. What follows is 1526and in a check watcher, destroy them and call into libadns. What follows
1429pseudo-code only of course:</p> 1527is pseudo-code only of course. This requires you to either use a low
1528priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1529the callbacks for the IO/timeout watchers might not have been called yet.</p>
1430<pre> static ev_io iow [nfd]; 1530<pre> static ev_io iow [nfd];
1431 static ev_timer tw; 1531 static ev_timer tw;
1432 1532
1433 static void 1533 static void
1434 io_cb (ev_loop *loop, ev_io *w, int revents) 1534 io_cb (ev_loop *loop, ev_io *w, int revents)
1435 { 1535 {
1436 // set the relevant poll flags
1437 // could also call adns_processreadable etc. here
1438 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1439 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1440 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1441 } 1536 }
1442 1537
1443 // create io watchers for each fd and a timer before blocking 1538 // create io watchers for each fd and a timer before blocking
1444 static void 1539 static void
1445 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1540 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1446 { 1541 {
1447 int timeout = 3600000;truct pollfd fds [nfd]; 1542 int timeout = 3600000;
1543 struct pollfd fds [nfd];
1448 // actual code will need to loop here and realloc etc. 1544 // actual code will need to loop here and realloc etc.
1449 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1545 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1450 1546
1451 /* the callback is illegal, but won't be called as we stop during check */ 1547 /* the callback is illegal, but won't be called as we stop during check */
1452 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1548 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1453 ev_timer_start (loop, &amp;tw); 1549 ev_timer_start (loop, &amp;tw);
1454 1550
1455 // create on ev_io per pollfd 1551 // create one ev_io per pollfd
1456 for (int i = 0; i &lt; nfd; ++i) 1552 for (int i = 0; i &lt; nfd; ++i)
1457 { 1553 {
1458 ev_io_init (iow + i, io_cb, fds [i].fd, 1554 ev_io_init (iow + i, io_cb, fds [i].fd,
1459 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1555 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1460 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1556 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1461 1557
1462 fds [i].revents = 0; 1558 fds [i].revents = 0;
1463 iow [i].data = fds + i;
1464 ev_io_start (loop, iow + i); 1559 ev_io_start (loop, iow + i);
1465 } 1560 }
1466 } 1561 }
1467 1562
1468 // stop all watchers after blocking 1563 // stop all watchers after blocking
… …
1470 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1565 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1471 { 1566 {
1472 ev_timer_stop (loop, &amp;tw); 1567 ev_timer_stop (loop, &amp;tw);
1473 1568
1474 for (int i = 0; i &lt; nfd; ++i) 1569 for (int i = 0; i &lt; nfd; ++i)
1570 {
1571 // set the relevant poll flags
1572 // could also call adns_processreadable etc. here
1573 struct pollfd *fd = fds + i;
1574 int revents = ev_clear_pending (iow + i);
1575 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1576 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1577
1578 // now stop the watcher
1475 ev_io_stop (loop, iow + i); 1579 ev_io_stop (loop, iow + i);
1580 }
1476 1581
1477 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1582 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1583 }
1584
1585</pre>
1586<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1587in the prepare watcher and would dispose of the check watcher.</p>
1588<p>Method 3: If the module to be embedded supports explicit event
1589notification (adns does), you can also make use of the actual watcher
1590callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1591<pre> static void
1592 timer_cb (EV_P_ ev_timer *w, int revents)
1593 {
1594 adns_state ads = (adns_state)w-&gt;data;
1595 update_now (EV_A);
1596
1597 adns_processtimeouts (ads, &amp;tv_now);
1598 }
1599
1600 static void
1601 io_cb (EV_P_ ev_io *w, int revents)
1602 {
1603 adns_state ads = (adns_state)w-&gt;data;
1604 update_now (EV_A);
1605
1606 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1607 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1608 }
1609
1610 // do not ever call adns_afterpoll
1611
1612</pre>
1613<p>Method 4: Do not use a prepare or check watcher because the module you
1614want to embed is too inflexible to support it. Instead, youc na override
1615their poll function. The drawback with this solution is that the main
1616loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1617this.</p>
1618<pre> static gint
1619 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1620 {
1621 int got_events = 0;
1622
1623 for (n = 0; n &lt; nfds; ++n)
1624 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1625
1626 if (timeout &gt;= 0)
1627 // create/start timer
1628
1629 // poll
1630 ev_loop (EV_A_ 0);
1631
1632 // stop timer again
1633 if (timeout &gt;= 0)
1634 ev_timer_stop (EV_A_ &amp;to);
1635
1636 // stop io watchers again - their callbacks should have set
1637 for (n = 0; n &lt; nfds; ++n)
1638 ev_io_stop (EV_A_ iow [n]);
1639
1640 return got_events;
1478 } 1641 }
1479 1642
1480 1643
1481 1644
1482 1645
… …
1679the callback model to a model using method callbacks on objects.</p> 1842the callback model to a model using method callbacks on objects.</p>
1680<p>To use it,</p> 1843<p>To use it,</p>
1681<pre> #include &lt;ev++.h&gt; 1844<pre> #include &lt;ev++.h&gt;
1682 1845
1683</pre> 1846</pre>
1684<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1847<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1685and puts all of its definitions (many of them macros) into the global 1848of them macros) into the global namespace. All C++ specific things are
1686namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1849put into the <code>ev</code> namespace. It should support all the same embedding
1687<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1850options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1688<code>EV_MULTIPLICITY</code>.</p> 1851<p>Care has been taken to keep the overhead low. The only data member the C++
1852classes add (compared to plain C-style watchers) is the event loop pointer
1853that the watcher is associated with (or no additional members at all if
1854you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1855<p>Currently, functions, and static and non-static member functions can be
1856used as callbacks. Other types should be easy to add as long as they only
1857need one additional pointer for context. If you need support for other
1858types of functors please contact the author (preferably after implementing
1859it).</p>
1689<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1860<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1690<dl> 1861<dl>
1691 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1862 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1692 <dd> 1863 <dd>
1693 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1864 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1704which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1875which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1705defines by many implementations.</p> 1876defines by many implementations.</p>
1706 <p>All of those classes have these methods:</p> 1877 <p>All of those classes have these methods:</p>
1707 <p> 1878 <p>
1708 <dl> 1879 <dl>
1709 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1880 <dt>ev::TYPE::TYPE ()</dt>
1710 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1881 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1711 <dt>ev::TYPE::~TYPE</dt> 1882 <dt>ev::TYPE::~TYPE</dt>
1712 <dd> 1883 <dd>
1713 <p>The constructor takes a pointer to an object and a method pointer to 1884 <p>The constructor (optionally) takes an event loop to associate the watcher
1714the event handler callback to call in this class. The constructor calls 1885with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1715<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1886 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1716before starting it. If you do not specify a loop then the constructor 1887<code>set</code> method before starting it.</p>
1717automatically associates the default loop with this watcher.</p> 1888 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1889method to set a callback before you can start the watcher.</p>
1890 <p>(The reason why you have to use a method is a limitation in C++ which does
1891not allow explicit template arguments for constructors).</p>
1718 <p>The destructor automatically stops the watcher if it is active.</p> 1892 <p>The destructor automatically stops the watcher if it is active.</p>
1893 </dd>
1894 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1895 <dd>
1896 <p>This method sets the callback method to call. The method has to have a
1897signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1898first argument and the <code>revents</code> as second. The object must be given as
1899parameter and is stored in the <code>data</code> member of the watcher.</p>
1900 <p>This method synthesizes efficient thunking code to call your method from
1901the C callback that libev requires. If your compiler can inline your
1902callback (i.e. it is visible to it at the place of the <code>set</code> call and
1903your compiler is good :), then the method will be fully inlined into the
1904thunking function, making it as fast as a direct C callback.</p>
1905 <p>Example: simple class declaration and watcher initialisation</p>
1906<pre> struct myclass
1907 {
1908 void io_cb (ev::io &amp;w, int revents) { }
1909 }
1910
1911 myclass obj;
1912 ev::io iow;
1913 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1914
1915</pre>
1916 </dd>
1917 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1918 <dd>
1919 <p>Also sets a callback, but uses a static method or plain function as
1920callback. The optional <code>data</code> argument will be stored in the watcher's
1921<code>data</code> member and is free for you to use.</p>
1922 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1923 <p>See the method-<code>set</code> above for more details.</p>
1924 <p>Example:</p>
1925<pre> static void io_cb (ev::io &amp;w, int revents) { }
1926 iow.set &lt;io_cb&gt; ();
1927
1928</pre>
1719 </dd> 1929 </dd>
1720 <dt>w-&gt;set (struct ev_loop *)</dt> 1930 <dt>w-&gt;set (struct ev_loop *)</dt>
1721 <dd> 1931 <dd>
1722 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1932 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1723do this when the watcher is inactive (and not pending either).</p> 1933do this when the watcher is inactive (and not pending either).</p>
1724 </dd> 1934 </dd>
1725 <dt>w-&gt;set ([args])</dt> 1935 <dt>w-&gt;set ([args])</dt>
1726 <dd> 1936 <dd>
1727 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1937 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1728called at least once. Unlike the C counterpart, an active watcher gets 1938called at least once. Unlike the C counterpart, an active watcher gets
1729automatically stopped and restarted.</p> 1939automatically stopped and restarted when reconfiguring it with this
1940method.</p>
1730 </dd> 1941 </dd>
1731 <dt>w-&gt;start ()</dt> 1942 <dt>w-&gt;start ()</dt>
1732 <dd> 1943 <dd>
1733 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1944 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1734constructor already takes the loop.</p> 1945constructor already stores the event loop.</p>
1735 </dd> 1946 </dd>
1736 <dt>w-&gt;stop ()</dt> 1947 <dt>w-&gt;stop ()</dt>
1737 <dd> 1948 <dd>
1738 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1949 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1739 </dd> 1950 </dd>
… …
1763 1974
1764 myclass (); 1975 myclass ();
1765 } 1976 }
1766 1977
1767 myclass::myclass (int fd) 1978 myclass::myclass (int fd)
1768 : io (this, &amp;myclass::io_cb),
1769 idle (this, &amp;myclass::idle_cb)
1770 { 1979 {
1980 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1981 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1982
1771 io.start (fd, ev::READ); 1983 io.start (fd, ev::READ);
1772 } 1984 }
1773 1985
1774 1986
1775 1987
… …
1778 1990
1779</div> 1991</div>
1780<h1 id="MACRO_MAGIC">MACRO MAGIC</h1> 1992<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1781<div id="MACRO_MAGIC_CONTENT"> 1993<div id="MACRO_MAGIC_CONTENT">
1782<p>Libev can be compiled with a variety of options, the most fundemantal is 1994<p>Libev can be compiled with a variety of options, the most fundemantal is
1783<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 1995<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1784callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1996callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1785<p>To make it easier to write programs that cope with either variant, the 1997<p>To make it easier to write programs that cope with either variant, the
1786following macros are defined:</p> 1998following macros are defined:</p>
1787<dl> 1999<dl>
1788 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 2000 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1817 <dd> 2029 <dd>
1818 <p>Similar to the other two macros, this gives you the value of the default 2030 <p>Similar to the other two macros, this gives you the value of the default
1819loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 2031loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1820 </dd> 2032 </dd>
1821</dl> 2033</dl>
1822<p>Example: Declare and initialise a check watcher, working regardless of 2034<p>Example: Declare and initialise a check watcher, utilising the above
1823wether multiple loops are supported or not.</p> 2035macros so it will work regardless of whether multiple loops are supported
2036or not.</p>
1824<pre> static void 2037<pre> static void
1825 check_cb (EV_P_ ev_timer *w, int revents) 2038 check_cb (EV_P_ ev_timer *w, int revents)
1826 { 2039 {
1827 ev_check_stop (EV_A_ w); 2040 ev_check_stop (EV_A_ w);
1828 } 2041 }
1829 2042
1830 ev_check check; 2043 ev_check check;
1831 ev_check_init (&amp;check, check_cb); 2044 ev_check_init (&amp;check, check_cb);
1832 ev_check_start (EV_DEFAULT_ &amp;check); 2045 ev_check_start (EV_DEFAULT_ &amp;check);
1833 ev_loop (EV_DEFAULT_ 0); 2046 ev_loop (EV_DEFAULT_ 0);
1834
1835
1836
1837 2047
1838</pre> 2048</pre>
1839 2049
1840</div> 2050</div>
1841<h1 id="EMBEDDING">EMBEDDING</h1> 2051<h1 id="EMBEDDING">EMBEDDING</h1>
… …
1883 ev_vars.h 2093 ev_vars.h
1884 ev_wrap.h 2094 ev_wrap.h
1885 2095
1886 ev_win32.c required on win32 platforms only 2096 ev_win32.c required on win32 platforms only
1887 2097
1888 ev_select.c only when select backend is enabled (which is by default) 2098 ev_select.c only when select backend is enabled (which is enabled by default)
1889 ev_poll.c only when poll backend is enabled (disabled by default) 2099 ev_poll.c only when poll backend is enabled (disabled by default)
1890 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2100 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1891 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2101 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1892 ev_port.c only when the solaris port backend is enabled (disabled by default) 2102 ev_port.c only when the solaris port backend is enabled (disabled by default)
1893 2103
… …
2058will have the <code>struct ev_loop *</code> as first argument, and you can create 2268will have the <code>struct ev_loop *</code> as first argument, and you can create
2059additional independent event loops. Otherwise there will be no support 2269additional independent event loops. Otherwise there will be no support
2060for multiple event loops and there is no first event loop pointer 2270for multiple event loops and there is no first event loop pointer
2061argument. Instead, all functions act on the single default loop.</p> 2271argument. Instead, all functions act on the single default loop.</p>
2062 </dd> 2272 </dd>
2273 <dt>EV_MINPRI</dt>
2274 <dt>EV_MAXPRI</dt>
2275 <dd>
2276 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2277<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2278provide for more priorities by overriding those symbols (usually defined
2279to be <code>-2</code> and <code>2</code>, respectively).</p>
2280 <p>When doing priority-based operations, libev usually has to linearly search
2281all the priorities, so having many of them (hundreds) uses a lot of space
2282and time, so using the defaults of five priorities (-2 .. +2) is usually
2283fine.</p>
2284 <p>If your embedding app does not need any priorities, defining these both to
2285<code>0</code> will save some memory and cpu.</p>
2286 </dd>
2063 <dt>EV_PERIODIC_ENABLE</dt> 2287 <dt>EV_PERIODIC_ENABLE</dt>
2064 <dd> 2288 <dd>
2065 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2289 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2290defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2291code.</p>
2292 </dd>
2293 <dt>EV_IDLE_ENABLE</dt>
2294 <dd>
2295 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2066defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2296defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2067code.</p> 2297code.</p>
2068 </dd> 2298 </dd>
2069 <dt>EV_EMBED_ENABLE</dt> 2299 <dt>EV_EMBED_ENABLE</dt>
2070 <dd> 2300 <dd>
… …
2135the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2365the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2136interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2366interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2137will be compiled. It is pretty complex because it provides its own header 2367will be compiled. It is pretty complex because it provides its own header
2138file.</p> 2368file.</p>
2139 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2369 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2140that everybody includes and which overrides some autoconf choices:</p> 2370that everybody includes and which overrides some configure choices:</p>
2371<pre> #define EV_MINIMAL 1
2141<pre> #define EV_USE_POLL 0 2372 #define EV_USE_POLL 0
2142 #define EV_MULTIPLICITY 0 2373 #define EV_MULTIPLICITY 0
2143 #define EV_PERIODICS 0 2374 #define EV_PERIODIC_ENABLE 0
2375 #define EV_STAT_ENABLE 0
2376 #define EV_FORK_ENABLE 0
2144 #define EV_CONFIG_H &lt;config.h&gt; 2377 #define EV_CONFIG_H &lt;config.h&gt;
2378 #define EV_MINPRI 0
2379 #define EV_MAXPRI 0
2145 2380
2146 #include &quot;ev++.h&quot; 2381 #include &quot;ev++.h&quot;
2147 2382
2148</pre> 2383</pre>
2149 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2384 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2159<h1 id="COMPLEXITIES">COMPLEXITIES</h1> 2394<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2160<div id="COMPLEXITIES_CONTENT"> 2395<div id="COMPLEXITIES_CONTENT">
2161 <p>In this section the complexities of (many of) the algorithms used inside 2396 <p>In this section the complexities of (many of) the algorithms used inside
2162libev will be explained. For complexity discussions about backends see the 2397libev will be explained. For complexity discussions about backends see the
2163documentation for <code>ev_default_init</code>.</p> 2398documentation for <code>ev_default_init</code>.</p>
2399 <p>All of the following are about amortised time: If an array needs to be
2400extended, libev needs to realloc and move the whole array, but this
2401happens asymptotically never with higher number of elements, so O(1) might
2402mean it might do a lengthy realloc operation in rare cases, but on average
2403it is much faster and asymptotically approaches constant time.</p>
2164 <p> 2404 <p>
2165 <dl> 2405 <dl>
2166 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2406 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2407 <dd>
2408 <p>This means that, when you have a watcher that triggers in one hour and
2409there are 100 watchers that would trigger before that then inserting will
2410have to skip those 100 watchers.</p>
2411 </dd>
2167 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2412 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2413 <dd>
2414 <p>That means that for changing a timer costs less than removing/adding them
2415as only the relative motion in the event queue has to be paid for.</p>
2416 </dd>
2168 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2417 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2418 <dd>
2419 <p>These just add the watcher into an array or at the head of a list.
2169 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2420=item Stopping check/prepare/idle watchers: O(1)</p>
2421 </dd>
2170 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> 2422 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2423 <dd>
2424 <p>These watchers are stored in lists then need to be walked to find the
2425correct watcher to remove. The lists are usually short (you don't usually
2426have many watchers waiting for the same fd or signal).</p>
2427 </dd>
2171 <dt>Finding the next timer per loop iteration: O(1)</dt> 2428 <dt>Finding the next timer per loop iteration: O(1)</dt>
2172 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2429 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2430 <dd>
2431 <p>A change means an I/O watcher gets started or stopped, which requires
2432libev to recalculate its status (and possibly tell the kernel).</p>
2433 </dd>
2173 <dt>Activating one watcher: O(1)</dt> 2434 <dt>Activating one watcher: O(1)</dt>
2435 <dt>Priority handling: O(number_of_priorities)</dt>
2436 <dd>
2437 <p>Priorities are implemented by allocating some space for each
2438priority. When doing priority-based operations, libev usually has to
2439linearly search all the priorities.</p>
2440 </dd>
2174 </dl> 2441 </dl>
2175 </p> 2442 </p>
2176 2443
2177 2444
2178 2445

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