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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="Thu Nov 29 13:21:20 2007" /> 9 <meta name="created" content="Wed Dec 12 18:55:28 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li> 27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
29</ul> 29</ul>
30</li> 30</li>
31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li> 32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a>
33<ul><li><a href="#The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</a></li>
34<li><a href="#Watcher_Specific_Functions">Watcher-Specific Functions</a></li>
35</ul>
36</li>
33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> 37<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a>
38<ul><li><a href="#Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</a></li>
39</ul>
40</li>
34<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li> 41<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a>
42<ul><li><a href="#Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</a></li>
43</ul>
44</li>
35<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li> 45<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a>
46<ul><li><a href="#Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</a></li>
47</ul>
48</li>
36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> 49<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a>
50<ul><li><a href="#Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</a></li>
51</ul>
52</li>
37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li> 53<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a>
54<ul><li><a href="#Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</a></li>
55</ul>
56</li>
38<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li> 57<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a>
58<ul><li><a href="#Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</a></li>
59</ul>
60</li>
39<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li> 61<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a>
62<ul><li><a href="#Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</a></li>
63</ul>
64</li>
40<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> 65<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a>
66<ul><li><a href="#Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</a></li>
67</ul>
68</li>
41<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li> 69<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a>
70<ul><li><a href="#Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</a></li>
71</ul>
72</li>
42</ul> 73</ul>
43</li> 74</li>
44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 75<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 76<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
46<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 77<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
… …
119</pre> 150</pre>
120 151
121</div> 152</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1> 153<h1 id="DESCRIPTION">DESCRIPTION</h1>
123<div id="DESCRIPTION_CONTENT"> 154<div id="DESCRIPTION_CONTENT">
155<p>The newest version of this document is also available as a html-formatted
156web page you might find easier to navigate when reading it for the first
157time: <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 158<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 159file descriptor being readable or a timeout occuring), and it will manage
126these event sources and provide your program with events.</p> 160these 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 161<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 162(or thread) by executing the <i>event loop</i> handler, and will then
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182you actually want to know.</p> 216you actually want to know.</p>
183 </dd> 217 </dd>
184 <dt>int ev_version_major ()</dt> 218 <dt>int ev_version_major ()</dt>
185 <dt>int ev_version_minor ()</dt> 219 <dt>int ev_version_minor ()</dt>
186 <dd> 220 <dd>
187 <p>You can find out the major and minor version numbers of the library 221 <p>You can find out the major and minor ABI version numbers of the library
188you linked against by calling the functions <code>ev_version_major</code> and 222you linked against by calling the functions <code>ev_version_major</code> and
189<code>ev_version_minor</code>. If you want, you can compare against the global 223<code>ev_version_minor</code>. If you want, you can compare against the global
190symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 224symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
191version of the library your program was compiled against.</p> 225version of the library your program was compiled against.</p>
226 <p>These version numbers refer to the ABI version of the library, not the
227release version.</p>
192 <p>Usually, it's a good idea to terminate if the major versions mismatch, 228 <p>Usually, it's a good idea to terminate if the major versions mismatch,
193as this indicates an incompatible change. Minor versions are usually 229as this indicates an incompatible change. Minor versions are usually
194compatible to older versions, so a larger minor version alone is usually 230compatible to older versions, so a larger minor version alone is usually
195not a problem.</p> 231not a problem.</p>
196 <p>Example: Make sure we haven't accidentally been linked against the wrong 232 <p>Example: Make sure we haven't accidentally been linked against the wrong
197version.</p> 233version.</p>
198<pre> assert ((&quot;libev version mismatch&quot;, 234<pre> assert ((&quot;libev version mismatch&quot;,
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326<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 362<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
327override the flags completely if it is found in the environment. This is 363override the flags completely if it is found in the environment. This is
328useful to try out specific backends to test their performance, or to work 364useful to try out specific backends to test their performance, or to work
329around bugs.</p> 365around bugs.</p>
330 </dd> 366 </dd>
367 <dt><code>EVFLAG_FORKCHECK</code></dt>
368 <dd>
369 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
370a fork, you can also make libev check for a fork in each iteration by
371enabling this flag.</p>
372 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
373and thus this might slow down your event loop if you do a lot of loop
374iterations and little real work, but is usually not noticeable (on my
375Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
376without a syscall and thus <i>very</i> fast, but my Linux system also has
377<code>pthread_atfork</code> which is even faster).</p>
378 <p>The big advantage of this flag is that you can forget about fork (and
379forget about forgetting to tell libev about forking) when you use this
380flag.</p>
381 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
382environment variable.</p>
383 </dd>
331 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 384 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
332 <dd> 385 <dd>
333 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 386 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
334libev tries to roll its own fd_set with no limits on the number of fds, 387libev tries to roll its own fd_set with no limits on the number of fds,
335but if that fails, expect a fairly low limit on the number of fds when 388but if that fails, expect a fairly low limit on the number of fds when
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463 <dt>ev_loop_fork (loop)</dt> 516 <dt>ev_loop_fork (loop)</dt>
464 <dd> 517 <dd>
465 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 518 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
466<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 519<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
467after fork, and how you do this is entirely your own problem.</p> 520after fork, and how you do this is entirely your own problem.</p>
521 </dd>
522 <dt>unsigned int ev_loop_count (loop)</dt>
523 <dd>
524 <p>Returns the count of loop iterations for the loop, which is identical to
525the number of times libev did poll for new events. It starts at <code>0</code> and
526happily wraps around with enough iterations.</p>
527 <p>This value can sometimes be useful as a generation counter of sorts (it
528&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
529<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
468 </dd> 530 </dd>
469 <dt>unsigned int ev_backend (loop)</dt> 531 <dt>unsigned int ev_backend (loop)</dt>
470 <dd> 532 <dd>
471 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 533 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
472use.</p> 534use.</p>
… …
500one iteration of the loop. This is useful if you are waiting for some 562one iteration of the loop. This is useful if you are waiting for some
501external event in conjunction with something not expressible using other 563external event in conjunction with something not expressible using other
502libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is 564libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
503usually a better approach for this kind of thing.</p> 565usually a better approach for this kind of thing.</p>
504 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 566 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
567<pre> - Before the first iteration, call any pending watchers.
505<pre> * If there are no active watchers (reference count is zero), return. 568 * If there are no active watchers (reference count is zero), return.
506 - Queue prepare watchers and then call all outstanding watchers. 569 - Queue all prepare watchers and then call all outstanding watchers.
507 - If we have been forked, recreate the kernel state. 570 - If we have been forked, recreate the kernel state.
508 - Update the kernel state with all outstanding changes. 571 - Update the kernel state with all outstanding changes.
509 - Update the &quot;event loop time&quot;. 572 - Update the &quot;event loop time&quot;.
510 - Calculate for how long to block. 573 - Calculate for how long to block.
511 - Block the process, waiting for any events. 574 - Block the process, waiting for any events.
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740 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 803 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
741 <dd> 804 <dd>
742 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 805 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
743events but its callback has not yet been invoked). As long as a watcher 806events but its callback has not yet been invoked). As long as a watcher
744is pending (but not active) you must not call an init function on it (but 807is pending (but not active) you must not call an init function on it (but
745<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 808<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
746libev (e.g. you cnanot <code>free ()</code> it).</p> 809make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
810it).</p>
747 </dd> 811 </dd>
748 <dt>callback ev_cb (ev_TYPE *watcher)</dt> 812 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
749 <dd> 813 <dd>
750 <p>Returns the callback currently set on the watcher.</p> 814 <p>Returns the callback currently set on the watcher.</p>
751 </dd> 815 </dd>
752 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 816 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
753 <dd> 817 <dd>
754 <p>Change the callback. You can change the callback at virtually any time 818 <p>Change the callback. You can change the callback at virtually any time
755(modulo threads).</p> 819(modulo threads).</p>
820 </dd>
821 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
822 <dt>int ev_priority (ev_TYPE *watcher)</dt>
823 <dd>
824 <p>Set and query the priority of the watcher. The priority is a small
825integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
826(default: <code>-2</code>). Pending watchers with higher priority will be invoked
827before watchers with lower priority, but priority will not keep watchers
828from being executed (except for <code>ev_idle</code> watchers).</p>
829 <p>This means that priorities are <i>only</i> used for ordering callback
830invocation after new events have been received. This is useful, for
831example, to reduce latency after idling, or more often, to bind two
832watchers on the same event and make sure one is called first.</p>
833 <p>If you need to suppress invocation when higher priority events are pending
834you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
835 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
836pending.</p>
837 <p>The default priority used by watchers when no priority has been set is
838always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
839 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
840fine, as long as you do not mind that the priority value you query might
841or might not have been adjusted to be within valid range.</p>
842 </dd>
843 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
844 <dd>
845 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
846<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
847can deal with that fact.</p>
848 </dd>
849 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
850 <dd>
851 <p>If the watcher is pending, this function returns clears its pending status
852and returns its <code>revents</code> bitset (as if its callback was invoked). If the
853watcher isn't pending it does nothing and returns <code>0</code>.</p>
756 </dd> 854 </dd>
757</dl> 855</dl>
758 856
759 857
760 858
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871this situation even with a relatively standard program structure. Thus 969this situation even with a relatively standard program structure. Thus
872it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 970it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
873<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 971<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
874<p>If you cannot run the fd in non-blocking mode (for example you should not 972<p>If you cannot run the fd in non-blocking mode (for example you should not
875play around with an Xlib connection), then you have to seperately re-test 973play around with an Xlib connection), then you have to seperately re-test
876wether a file descriptor is really ready with a known-to-be good interface 974whether a file descriptor is really ready with a known-to-be good interface
877such as poll (fortunately in our Xlib example, Xlib already does this on 975such as poll (fortunately in our Xlib example, Xlib already does this on
878its own, so its quite safe to use).</p> 976its own, so its quite safe to use).</p>
977
978</div>
979<h3 id="The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</h3>
980<div id="The_special_problem_of_disappearing_-2">
981<p>Some backends (e.g kqueue, epoll) need to be told about closing a file
982descriptor (either by calling <code>close</code> explicitly or by any other means,
983such as <code>dup</code>). The reason is that you register interest in some file
984descriptor, but when it goes away, the operating system will silently drop
985this interest. If another file descriptor with the same number then is
986registered with libev, there is no efficient way to see that this is, in
987fact, a different file descriptor.</p>
988<p>To avoid having to explicitly tell libev about such cases, libev follows
989the following policy: Each time <code>ev_io_set</code> is being called, libev
990will assume that this is potentially a new file descriptor, otherwise
991it is assumed that the file descriptor stays the same. That means that
992you <i>have</i> to call <code>ev_io_set</code> (or <code>ev_io_init</code>) when you change the
993descriptor even if the file descriptor number itself did not change.</p>
994<p>This is how one would do it normally anyway, the important point is that
995the libev application should not optimise around libev but should leave
996optimisations to libev.</p>
997
998
999
1000
1001
1002</div>
1003<h3 id="Watcher_Specific_Functions">Watcher-Specific Functions</h3>
1004<div id="Watcher_Specific_Functions_CONTENT">
879<dl> 1005<dl>
880 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 1006 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
881 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 1007 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
882 <dd> 1008 <dd>
883 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 1009 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
… …
934 1060
935</pre> 1061</pre>
936<p>The callback is guarenteed to be invoked only when its timeout has passed, 1062<p>The callback is guarenteed to be invoked only when its timeout has passed,
937but if multiple timers become ready during the same loop iteration then 1063but if multiple timers become ready during the same loop iteration then
938order of execution is undefined.</p> 1064order of execution is undefined.</p>
1065
1066</div>
1067<h3 id="Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</h3>
1068<div id="Watcher_Specific_Functions_and_Data_-2">
939<dl> 1069<dl>
940 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 1070 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
941 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 1071 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
942 <dd> 1072 <dd>
943 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 1073 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
1032but on wallclock time (absolute time). You can tell a periodic watcher 1162but on wallclock time (absolute time). You can tell a periodic watcher
1033to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1163to trigger &quot;at&quot; some specific point in time. For example, if you tell a
1034periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () 1164periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
1035+ 10.</code>) and then reset your system clock to the last year, then it will 1165+ 10.</code>) and then reset your system clock to the last year, then it will
1036take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1166take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
1037roughly 10 seconds later and of course not if you reset your system time 1167roughly 10 seconds later).</p>
1038again).</p>
1039<p>They can also be used to implement vastly more complex timers, such as 1168<p>They can also be used to implement vastly more complex timers, such as
1040triggering an event on eahc midnight, local time.</p> 1169triggering an event on each midnight, local time or other, complicated,
1170rules.</p>
1041<p>As with timers, the callback is guarenteed to be invoked only when the 1171<p>As with timers, the callback is guarenteed to be invoked only when the
1042time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1172time (<code>at</code>) has been passed, but if multiple periodic timers become ready
1043during the same loop iteration then order of execution is undefined.</p> 1173during the same loop iteration then order of execution is undefined.</p>
1174
1175</div>
1176<h3 id="Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</h3>
1177<div id="Watcher_Specific_Functions_and_Data_-2">
1044<dl> 1178<dl>
1045 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1179 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
1046 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 1180 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
1047 <dd> 1181 <dd>
1048 <p>Lots of arguments, lets sort it out... There are basically three modes of 1182 <p>Lots of arguments, lets sort it out... There are basically three modes of
1049operation, and we will explain them from simplest to complex:</p> 1183operation, and we will explain them from simplest to complex:</p>
1050 <p> 1184 <p>
1051 <dl> 1185 <dl>
1052 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1186 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
1053 <dd> 1187 <dd>
1054 <p>In this configuration the watcher triggers an event at the wallclock time 1188 <p>In this configuration the watcher triggers an event at the wallclock time
1055<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1189<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
1056that is, if it is to be run at January 1st 2011 then it will run when the 1190that is, if it is to be run at January 1st 2011 then it will run when the
1057system time reaches or surpasses this time.</p> 1191system time reaches or surpasses this time.</p>
1058 </dd> 1192 </dd>
1059 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1193 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
1060 <dd> 1194 <dd>
1061 <p>In this mode the watcher will always be scheduled to time out at the next 1195 <p>In this mode the watcher will always be scheduled to time out at the next
1062<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1196<code>at + N * interval</code> time (for some integer N, which can also be negative)
1063of any time jumps.</p> 1197and then repeat, regardless of any time jumps.</p>
1064 <p>This can be used to create timers that do not drift with respect to system 1198 <p>This can be used to create timers that do not drift with respect to system
1065time:</p> 1199time:</p>
1066<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1200<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
1067 1201
1068</pre> 1202</pre>
… …
1071full hour (UTC), or more correctly, when the system time is evenly divisible 1205full hour (UTC), or more correctly, when the system time is evenly divisible
1072by 3600.</p> 1206by 3600.</p>
1073 <p>Another way to think about it (for the mathematically inclined) is that 1207 <p>Another way to think about it (for the mathematically inclined) is that
1074<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1208<code>ev_periodic</code> will try to run the callback in this mode at the next possible
1075time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1209time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1210 <p>For numerical stability it is preferable that the <code>at</code> value is near
1211<code>ev_now ()</code> (the current time), but there is no range requirement for
1212this value.</p>
1076 </dd> 1213 </dd>
1077 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1214 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
1078 <dd> 1215 <dd>
1079 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1216 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
1080ignored. Instead, each time the periodic watcher gets scheduled, the 1217ignored. Instead, each time the periodic watcher gets scheduled, the
1081reschedule callback will be called with the watcher as first, and the 1218reschedule callback will be called with the watcher as first, and the
1082current time as second argument.</p> 1219current time as second argument.</p>
1083 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1220 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
1084ever, or make any event loop modifications</i>. If you need to stop it, 1221ever, or make any event loop modifications</i>. If you need to stop it,
1085return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1222return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
1086starting a prepare watcher).</p> 1223starting an <code>ev_prepare</code> watcher, which is legal).</p>
1087 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1224 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1088ev_tstamp now)</code>, e.g.:</p> 1225ev_tstamp now)</code>, e.g.:</p>
1089<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1226<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1090 { 1227 {
1091 return now + 60.; 1228 return now + 60.;
… …
1111 <dd> 1248 <dd>
1112 <p>Simply stops and restarts the periodic watcher again. This is only useful 1249 <p>Simply stops and restarts the periodic watcher again. This is only useful
1113when you changed some parameters or the reschedule callback would return 1250when you changed some parameters or the reschedule callback would return
1114a different time than the last time it was called (e.g. in a crond like 1251a different time than the last time it was called (e.g. in a crond like
1115program when the crontabs have changed).</p> 1252program when the crontabs have changed).</p>
1253 </dd>
1254 <dt>ev_tstamp offset [read-write]</dt>
1255 <dd>
1256 <p>When repeating, this contains the offset value, otherwise this is the
1257absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1258 <p>Can be modified any time, but changes only take effect when the periodic
1259timer fires or <code>ev_periodic_again</code> is being called.</p>
1116 </dd> 1260 </dd>
1117 <dt>ev_tstamp interval [read-write]</dt> 1261 <dt>ev_tstamp interval [read-write]</dt>
1118 <dd> 1262 <dd>
1119 <p>The current interval value. Can be modified any time, but changes only 1263 <p>The current interval value. Can be modified any time, but changes only
1120take effect when the periodic timer fires or <code>ev_periodic_again</code> is being 1264take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
… …
1175first watcher gets started will libev actually register a signal watcher 1319first watcher gets started will libev actually register a signal watcher
1176with the kernel (thus it coexists with your own signal handlers as long 1320with the kernel (thus it coexists with your own signal handlers as long
1177as you don't register any with libev). Similarly, when the last signal 1321as you don't register any with libev). Similarly, when the last signal
1178watcher for a signal is stopped libev will reset the signal handler to 1322watcher for a signal is stopped libev will reset the signal handler to
1179SIG_DFL (regardless of what it was set to before).</p> 1323SIG_DFL (regardless of what it was set to before).</p>
1324
1325</div>
1326<h3 id="Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</h3>
1327<div id="Watcher_Specific_Functions_and_Data_-2-2">
1180<dl> 1328<dl>
1181 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt> 1329 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt>
1182 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1330 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1183 <dd> 1331 <dd>
1184 <p>Configures the watcher to trigger on the given signal number (usually one 1332 <p>Configures the watcher to trigger on the given signal number (usually one
… …
1197</div> 1345</div>
1198<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2> 1346<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
1199<div id="code_ev_child_code_watch_out_for_pro-2"> 1347<div id="code_ev_child_code_watch_out_for_pro-2">
1200<p>Child watchers trigger when your process receives a SIGCHLD in response to 1348<p>Child watchers trigger when your process receives a SIGCHLD in response to
1201some child status changes (most typically when a child of yours dies).</p> 1349some child status changes (most typically when a child of yours dies).</p>
1350
1351</div>
1352<h3 id="Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</h3>
1353<div id="Watcher_Specific_Functions_and_Data_-2-3">
1202<dl> 1354<dl>
1203 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1355 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1204 <dt>ev_child_set (ev_child *, int pid)</dt> 1356 <dt>ev_child_set (ev_child *, int pid)</dt>
1205 <dd> 1357 <dd>
1206 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 1358 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
… …
1269reader). Inotify will be used to give hints only and should not change the 1421reader). Inotify will be used to give hints only and should not change the
1270semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs 1422semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1271to fall back to regular polling again even with inotify, but changes are 1423to fall back to regular polling again even with inotify, but changes are
1272usually detected immediately, and if the file exists there will be no 1424usually detected immediately, and if the file exists there will be no
1273polling.</p> 1425polling.</p>
1426
1427</div>
1428<h3 id="Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</h3>
1429<div id="Watcher_Specific_Functions_and_Data_-2-4">
1274<dl> 1430<dl>
1275 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1431 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1276 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> 1432 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1277 <dd> 1433 <dd>
1278 <p>Configures the watcher to wait for status changes of the given 1434 <p>Configures the watcher to wait for status changes of the given
… …
1341</pre> 1497</pre>
1342 1498
1343</div> 1499</div>
1344<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1500<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1345<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1501<div id="code_ev_idle_code_when_you_ve_got_no-2">
1346<p>Idle watchers trigger events when there are no other events are pending 1502<p>Idle watchers trigger events when no other events of the same or higher
1347(prepare, check and other idle watchers do not count). That is, as long 1503priority are pending (prepare, check and other idle watchers do not
1348as your process is busy handling sockets or timeouts (or even signals, 1504count).</p>
1349imagine) it will not be triggered. But when your process is idle all idle 1505<p>That is, as long as your process is busy handling sockets or timeouts
1350watchers are being called again and again, once per event loop iteration - 1506(or even signals, imagine) of the same or higher priority it will not be
1507triggered. But when your process is idle (or only lower-priority watchers
1508are pending), the idle watchers are being called once per event loop
1351until stopped, that is, or your process receives more events and becomes 1509iteration - until stopped, that is, or your process receives more events
1352busy.</p> 1510and becomes busy again with higher priority stuff.</p>
1353<p>The most noteworthy effect is that as long as any idle watchers are 1511<p>The most noteworthy effect is that as long as any idle watchers are
1354active, the process will not block when waiting for new events.</p> 1512active, the process will not block when waiting for new events.</p>
1355<p>Apart from keeping your process non-blocking (which is a useful 1513<p>Apart from keeping your process non-blocking (which is a useful
1356effect on its own sometimes), idle watchers are a good place to do 1514effect on its own sometimes), idle watchers are a good place to do
1357&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1515&quot;pseudo-background processing&quot;, or delay processing stuff to after the
1358event loop has handled all outstanding events.</p> 1516event loop has handled all outstanding events.</p>
1517
1518</div>
1519<h3 id="Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</h3>
1520<div id="Watcher_Specific_Functions_and_Data_-2-5">
1359<dl> 1521<dl>
1360 <dt>ev_idle_init (ev_signal *, callback)</dt> 1522 <dt>ev_idle_init (ev_signal *, callback)</dt>
1361 <dd> 1523 <dd>
1362 <p>Initialises and configures the idle watcher - it has no parameters of any 1524 <p>Initialises and configures the idle watcher - it has no parameters of any
1363kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1525kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
… …
1417are ready to run (it's actually more complicated: it only runs coroutines 1579are ready to run (it's actually more complicated: it only runs coroutines
1418with priority higher than or equal to the event loop and one coroutine 1580with priority higher than or equal to the event loop and one coroutine
1419of lower priority, but only once, using idle watchers to keep the event 1581of lower priority, but only once, using idle watchers to keep the event
1420loop from blocking if lower-priority coroutines are active, thus mapping 1582loop from blocking if lower-priority coroutines are active, thus mapping
1421low-priority coroutines to idle/background tasks).</p> 1583low-priority coroutines to idle/background tasks).</p>
1584<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1585priority, to ensure that they are being run before any other watchers
1586after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1587too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1588supports this, they will be called before other <code>ev_check</code> watchers did
1589their job. As <code>ev_check</code> watchers are often used to embed other event
1590loops those other event loops might be in an unusable state until their
1591<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1592others).</p>
1593
1594</div>
1595<h3 id="Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</h3>
1596<div id="Watcher_Specific_Functions_and_Data_-2-6">
1422<dl> 1597<dl>
1423 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1598 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1424 <dt>ev_check_init (ev_check *, callback)</dt> 1599 <dt>ev_check_init (ev_check *, callback)</dt>
1425 <dd> 1600 <dd>
1426 <p>Initialises and configures the prepare or check watcher - they have no 1601 <p>Initialises and configures the prepare or check watcher - they have no
1427parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1602parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1428macros, but using them is utterly, utterly and completely pointless.</p> 1603macros, but using them is utterly, utterly and completely pointless.</p>
1429 </dd> 1604 </dd>
1430</dl> 1605</dl>
1431<p>Example: To include a library such as adns, you would add IO watchers 1606<p>There are a number of principal ways to embed other event loops or modules
1432and a timeout watcher in a prepare handler, as required by libadns, and 1607into libev. Here are some ideas on how to include libadns into libev
1608(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1609use for an actually working example. Another Perl module named <code>EV::Glib</code>
1610embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1611into the Glib event loop).</p>
1612<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1433in a check watcher, destroy them and call into libadns. What follows is 1613and in a check watcher, destroy them and call into libadns. What follows
1434pseudo-code only of course:</p> 1614is pseudo-code only of course. This requires you to either use a low
1615priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1616the callbacks for the IO/timeout watchers might not have been called yet.</p>
1435<pre> static ev_io iow [nfd]; 1617<pre> static ev_io iow [nfd];
1436 static ev_timer tw; 1618 static ev_timer tw;
1437 1619
1438 static void 1620 static void
1439 io_cb (ev_loop *loop, ev_io *w, int revents) 1621 io_cb (ev_loop *loop, ev_io *w, int revents)
1440 { 1622 {
1441 // set the relevant poll flags
1442 // could also call adns_processreadable etc. here
1443 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1444 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1445 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1446 } 1623 }
1447 1624
1448 // create io watchers for each fd and a timer before blocking 1625 // create io watchers for each fd and a timer before blocking
1449 static void 1626 static void
1450 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1627 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1451 { 1628 {
1452 int timeout = 3600000;truct pollfd fds [nfd]; 1629 int timeout = 3600000;
1630 struct pollfd fds [nfd];
1453 // actual code will need to loop here and realloc etc. 1631 // actual code will need to loop here and realloc etc.
1454 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1632 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1455 1633
1456 /* the callback is illegal, but won't be called as we stop during check */ 1634 /* the callback is illegal, but won't be called as we stop during check */
1457 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1635 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1458 ev_timer_start (loop, &amp;tw); 1636 ev_timer_start (loop, &amp;tw);
1459 1637
1460 // create on ev_io per pollfd 1638 // create one ev_io per pollfd
1461 for (int i = 0; i &lt; nfd; ++i) 1639 for (int i = 0; i &lt; nfd; ++i)
1462 { 1640 {
1463 ev_io_init (iow + i, io_cb, fds [i].fd, 1641 ev_io_init (iow + i, io_cb, fds [i].fd,
1464 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1642 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1465 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1643 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1466 1644
1467 fds [i].revents = 0; 1645 fds [i].revents = 0;
1468 iow [i].data = fds + i;
1469 ev_io_start (loop, iow + i); 1646 ev_io_start (loop, iow + i);
1470 } 1647 }
1471 } 1648 }
1472 1649
1473 // stop all watchers after blocking 1650 // stop all watchers after blocking
… …
1475 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1652 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1476 { 1653 {
1477 ev_timer_stop (loop, &amp;tw); 1654 ev_timer_stop (loop, &amp;tw);
1478 1655
1479 for (int i = 0; i &lt; nfd; ++i) 1656 for (int i = 0; i &lt; nfd; ++i)
1657 {
1658 // set the relevant poll flags
1659 // could also call adns_processreadable etc. here
1660 struct pollfd *fd = fds + i;
1661 int revents = ev_clear_pending (iow + i);
1662 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1663 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1664
1665 // now stop the watcher
1480 ev_io_stop (loop, iow + i); 1666 ev_io_stop (loop, iow + i);
1667 }
1481 1668
1482 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1669 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1670 }
1671
1672</pre>
1673<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1674in the prepare watcher and would dispose of the check watcher.</p>
1675<p>Method 3: If the module to be embedded supports explicit event
1676notification (adns does), you can also make use of the actual watcher
1677callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1678<pre> static void
1679 timer_cb (EV_P_ ev_timer *w, int revents)
1680 {
1681 adns_state ads = (adns_state)w-&gt;data;
1682 update_now (EV_A);
1683
1684 adns_processtimeouts (ads, &amp;tv_now);
1685 }
1686
1687 static void
1688 io_cb (EV_P_ ev_io *w, int revents)
1689 {
1690 adns_state ads = (adns_state)w-&gt;data;
1691 update_now (EV_A);
1692
1693 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1694 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1695 }
1696
1697 // do not ever call adns_afterpoll
1698
1699</pre>
1700<p>Method 4: Do not use a prepare or check watcher because the module you
1701want to embed is too inflexible to support it. Instead, youc na override
1702their poll function. The drawback with this solution is that the main
1703loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1704this.</p>
1705<pre> static gint
1706 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1707 {
1708 int got_events = 0;
1709
1710 for (n = 0; n &lt; nfds; ++n)
1711 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1712
1713 if (timeout &gt;= 0)
1714 // create/start timer
1715
1716 // poll
1717 ev_loop (EV_A_ 0);
1718
1719 // stop timer again
1720 if (timeout &gt;= 0)
1721 ev_timer_stop (EV_A_ &amp;to);
1722
1723 // stop io watchers again - their callbacks should have set
1724 for (n = 0; n &lt; nfds; ++n)
1725 ev_io_stop (EV_A_ iow [n]);
1726
1727 return got_events;
1483 } 1728 }
1484 1729
1485 1730
1486 1731
1487 1732
… …
1548 } 1793 }
1549 else 1794 else
1550 loop_lo = loop_hi; 1795 loop_lo = loop_hi;
1551 1796
1552</pre> 1797</pre>
1798
1799</div>
1800<h3 id="Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</h3>
1801<div id="Watcher_Specific_Functions_and_Data_-2-7">
1553<dl> 1802<dl>
1554 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> 1803 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1555 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> 1804 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1556 <dd> 1805 <dd>
1557 <p>Configures the watcher to embed the given loop, which must be 1806 <p>Configures the watcher to embed the given loop, which must be
… …
1584<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the 1833<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1585event loop blocks next and before <code>ev_check</code> watchers are being called, 1834event loop blocks next and before <code>ev_check</code> watchers are being called,
1586and only in the child after the fork. If whoever good citizen calling 1835and only in the child after the fork. If whoever good citizen calling
1587<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork 1836<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1588handlers will be invoked, too, of course.</p> 1837handlers will be invoked, too, of course.</p>
1838
1839</div>
1840<h3 id="Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</h3>
1841<div id="Watcher_Specific_Functions_and_Data_-2-8">
1589<dl> 1842<dl>
1590 <dt>ev_fork_init (ev_signal *, callback)</dt> 1843 <dt>ev_fork_init (ev_signal *, callback)</dt>
1591 <dd> 1844 <dd>
1592 <p>Initialises and configures the fork watcher - it has no parameters of any 1845 <p>Initialises and configures the fork watcher - it has no parameters of any
1593kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless, 1846kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
… …
1684the callback model to a model using method callbacks on objects.</p> 1937the callback model to a model using method callbacks on objects.</p>
1685<p>To use it,</p> 1938<p>To use it,</p>
1686<pre> #include &lt;ev++.h&gt; 1939<pre> #include &lt;ev++.h&gt;
1687 1940
1688</pre> 1941</pre>
1689<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1942<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1690and puts all of its definitions (many of them macros) into the global 1943of them macros) into the global namespace. All C++ specific things are
1691namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1944put into the <code>ev</code> namespace. It should support all the same embedding
1692<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1945options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1693<code>EV_MULTIPLICITY</code>.</p> 1946<p>Care has been taken to keep the overhead low. The only data member the C++
1947classes add (compared to plain C-style watchers) is the event loop pointer
1948that the watcher is associated with (or no additional members at all if
1949you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1950<p>Currently, functions, and static and non-static member functions can be
1951used as callbacks. Other types should be easy to add as long as they only
1952need one additional pointer for context. If you need support for other
1953types of functors please contact the author (preferably after implementing
1954it).</p>
1694<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1955<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1695<dl> 1956<dl>
1696 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1957 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1697 <dd> 1958 <dd>
1698 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1959 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1709which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1970which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1710defines by many implementations.</p> 1971defines by many implementations.</p>
1711 <p>All of those classes have these methods:</p> 1972 <p>All of those classes have these methods:</p>
1712 <p> 1973 <p>
1713 <dl> 1974 <dl>
1714 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1975 <dt>ev::TYPE::TYPE ()</dt>
1715 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1976 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1716 <dt>ev::TYPE::~TYPE</dt> 1977 <dt>ev::TYPE::~TYPE</dt>
1717 <dd> 1978 <dd>
1718 <p>The constructor takes a pointer to an object and a method pointer to 1979 <p>The constructor (optionally) takes an event loop to associate the watcher
1719the event handler callback to call in this class. The constructor calls 1980with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1720<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1981 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1721before starting it. If you do not specify a loop then the constructor 1982<code>set</code> method before starting it.</p>
1722automatically associates the default loop with this watcher.</p> 1983 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1984method to set a callback before you can start the watcher.</p>
1985 <p>(The reason why you have to use a method is a limitation in C++ which does
1986not allow explicit template arguments for constructors).</p>
1723 <p>The destructor automatically stops the watcher if it is active.</p> 1987 <p>The destructor automatically stops the watcher if it is active.</p>
1988 </dd>
1989 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1990 <dd>
1991 <p>This method sets the callback method to call. The method has to have a
1992signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1993first argument and the <code>revents</code> as second. The object must be given as
1994parameter and is stored in the <code>data</code> member of the watcher.</p>
1995 <p>This method synthesizes efficient thunking code to call your method from
1996the C callback that libev requires. If your compiler can inline your
1997callback (i.e. it is visible to it at the place of the <code>set</code> call and
1998your compiler is good :), then the method will be fully inlined into the
1999thunking function, making it as fast as a direct C callback.</p>
2000 <p>Example: simple class declaration and watcher initialisation</p>
2001<pre> struct myclass
2002 {
2003 void io_cb (ev::io &amp;w, int revents) { }
2004 }
2005
2006 myclass obj;
2007 ev::io iow;
2008 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
2009
2010</pre>
2011 </dd>
2012 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
2013 <dd>
2014 <p>Also sets a callback, but uses a static method or plain function as
2015callback. The optional <code>data</code> argument will be stored in the watcher's
2016<code>data</code> member and is free for you to use.</p>
2017 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
2018 <p>See the method-<code>set</code> above for more details.</p>
2019 <p>Example:</p>
2020<pre> static void io_cb (ev::io &amp;w, int revents) { }
2021 iow.set &lt;io_cb&gt; ();
2022
2023</pre>
1724 </dd> 2024 </dd>
1725 <dt>w-&gt;set (struct ev_loop *)</dt> 2025 <dt>w-&gt;set (struct ev_loop *)</dt>
1726 <dd> 2026 <dd>
1727 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 2027 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1728do this when the watcher is inactive (and not pending either).</p> 2028do this when the watcher is inactive (and not pending either).</p>
1729 </dd> 2029 </dd>
1730 <dt>w-&gt;set ([args])</dt> 2030 <dt>w-&gt;set ([args])</dt>
1731 <dd> 2031 <dd>
1732 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 2032 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1733called at least once. Unlike the C counterpart, an active watcher gets 2033called at least once. Unlike the C counterpart, an active watcher gets
1734automatically stopped and restarted.</p> 2034automatically stopped and restarted when reconfiguring it with this
2035method.</p>
1735 </dd> 2036 </dd>
1736 <dt>w-&gt;start ()</dt> 2037 <dt>w-&gt;start ()</dt>
1737 <dd> 2038 <dd>
1738 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 2039 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1739constructor already takes the loop.</p> 2040constructor already stores the event loop.</p>
1740 </dd> 2041 </dd>
1741 <dt>w-&gt;stop ()</dt> 2042 <dt>w-&gt;stop ()</dt>
1742 <dd> 2043 <dd>
1743 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 2044 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1744 </dd> 2045 </dd>
… …
1768 2069
1769 myclass (); 2070 myclass ();
1770 } 2071 }
1771 2072
1772 myclass::myclass (int fd) 2073 myclass::myclass (int fd)
1773 : io (this, &amp;myclass::io_cb),
1774 idle (this, &amp;myclass::idle_cb)
1775 { 2074 {
2075 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
2076 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
2077
1776 io.start (fd, ev::READ); 2078 io.start (fd, ev::READ);
1777 } 2079 }
1778 2080
1779 2081
1780 2082
… …
1783 2085
1784</div> 2086</div>
1785<h1 id="MACRO_MAGIC">MACRO MAGIC</h1> 2087<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1786<div id="MACRO_MAGIC_CONTENT"> 2088<div id="MACRO_MAGIC_CONTENT">
1787<p>Libev can be compiled with a variety of options, the most fundemantal is 2089<p>Libev can be compiled with a variety of options, the most fundemantal is
1788<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 2090<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1789callbacks have an initial <code>struct ev_loop *</code> argument.</p> 2091callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1790<p>To make it easier to write programs that cope with either variant, the 2092<p>To make it easier to write programs that cope with either variant, the
1791following macros are defined:</p> 2093following macros are defined:</p>
1792<dl> 2094<dl>
1793 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 2095 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1822 <dd> 2124 <dd>
1823 <p>Similar to the other two macros, this gives you the value of the default 2125 <p>Similar to the other two macros, this gives you the value of the default
1824loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 2126loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1825 </dd> 2127 </dd>
1826</dl> 2128</dl>
1827<p>Example: Declare and initialise a check watcher, working regardless of 2129<p>Example: Declare and initialise a check watcher, utilising the above
1828wether multiple loops are supported or not.</p> 2130macros so it will work regardless of whether multiple loops are supported
2131or not.</p>
1829<pre> static void 2132<pre> static void
1830 check_cb (EV_P_ ev_timer *w, int revents) 2133 check_cb (EV_P_ ev_timer *w, int revents)
1831 { 2134 {
1832 ev_check_stop (EV_A_ w); 2135 ev_check_stop (EV_A_ w);
1833 } 2136 }
1834 2137
1835 ev_check check; 2138 ev_check check;
1836 ev_check_init (&amp;check, check_cb); 2139 ev_check_init (&amp;check, check_cb);
1837 ev_check_start (EV_DEFAULT_ &amp;check); 2140 ev_check_start (EV_DEFAULT_ &amp;check);
1838 ev_loop (EV_DEFAULT_ 0); 2141 ev_loop (EV_DEFAULT_ 0);
1839
1840
1841
1842 2142
1843</pre> 2143</pre>
1844 2144
1845</div> 2145</div>
1846<h1 id="EMBEDDING">EMBEDDING</h1> 2146<h1 id="EMBEDDING">EMBEDDING</h1>
… …
1888 ev_vars.h 2188 ev_vars.h
1889 ev_wrap.h 2189 ev_wrap.h
1890 2190
1891 ev_win32.c required on win32 platforms only 2191 ev_win32.c required on win32 platforms only
1892 2192
1893 ev_select.c only when select backend is enabled (which is by default) 2193 ev_select.c only when select backend is enabled (which is enabled by default)
1894 ev_poll.c only when poll backend is enabled (disabled by default) 2194 ev_poll.c only when poll backend is enabled (disabled by default)
1895 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2195 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1896 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2196 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1897 ev_port.c only when the solaris port backend is enabled (disabled by default) 2197 ev_port.c only when the solaris port backend is enabled (disabled by default)
1898 2198
… …
2063will have the <code>struct ev_loop *</code> as first argument, and you can create 2363will have the <code>struct ev_loop *</code> as first argument, and you can create
2064additional independent event loops. Otherwise there will be no support 2364additional independent event loops. Otherwise there will be no support
2065for multiple event loops and there is no first event loop pointer 2365for multiple event loops and there is no first event loop pointer
2066argument. Instead, all functions act on the single default loop.</p> 2366argument. Instead, all functions act on the single default loop.</p>
2067 </dd> 2367 </dd>
2368 <dt>EV_MINPRI</dt>
2369 <dt>EV_MAXPRI</dt>
2370 <dd>
2371 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2372<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2373provide for more priorities by overriding those symbols (usually defined
2374to be <code>-2</code> and <code>2</code>, respectively).</p>
2375 <p>When doing priority-based operations, libev usually has to linearly search
2376all the priorities, so having many of them (hundreds) uses a lot of space
2377and time, so using the defaults of five priorities (-2 .. +2) is usually
2378fine.</p>
2379 <p>If your embedding app does not need any priorities, defining these both to
2380<code>0</code> will save some memory and cpu.</p>
2381 </dd>
2068 <dt>EV_PERIODIC_ENABLE</dt> 2382 <dt>EV_PERIODIC_ENABLE</dt>
2069 <dd> 2383 <dd>
2070 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2384 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2385defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2386code.</p>
2387 </dd>
2388 <dt>EV_IDLE_ENABLE</dt>
2389 <dd>
2390 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2071defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2391defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2072code.</p> 2392code.</p>
2073 </dd> 2393 </dd>
2074 <dt>EV_EMBED_ENABLE</dt> 2394 <dt>EV_EMBED_ENABLE</dt>
2075 <dd> 2395 <dd>
… …
2140the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2460the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2141interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2461interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2142will be compiled. It is pretty complex because it provides its own header 2462will be compiled. It is pretty complex because it provides its own header
2143file.</p> 2463file.</p>
2144 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2464 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2145that everybody includes and which overrides some autoconf choices:</p> 2465that everybody includes and which overrides some configure choices:</p>
2466<pre> #define EV_MINIMAL 1
2146<pre> #define EV_USE_POLL 0 2467 #define EV_USE_POLL 0
2147 #define EV_MULTIPLICITY 0 2468 #define EV_MULTIPLICITY 0
2148 #define EV_PERIODICS 0 2469 #define EV_PERIODIC_ENABLE 0
2470 #define EV_STAT_ENABLE 0
2471 #define EV_FORK_ENABLE 0
2149 #define EV_CONFIG_H &lt;config.h&gt; 2472 #define EV_CONFIG_H &lt;config.h&gt;
2473 #define EV_MINPRI 0
2474 #define EV_MAXPRI 0
2150 2475
2151 #include &quot;ev++.h&quot; 2476 #include &quot;ev++.h&quot;
2152 2477
2153</pre> 2478</pre>
2154 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2479 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2164<h1 id="COMPLEXITIES">COMPLEXITIES</h1> 2489<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2165<div id="COMPLEXITIES_CONTENT"> 2490<div id="COMPLEXITIES_CONTENT">
2166 <p>In this section the complexities of (many of) the algorithms used inside 2491 <p>In this section the complexities of (many of) the algorithms used inside
2167libev will be explained. For complexity discussions about backends see the 2492libev will be explained. For complexity discussions about backends see the
2168documentation for <code>ev_default_init</code>.</p> 2493documentation for <code>ev_default_init</code>.</p>
2494 <p>All of the following are about amortised time: If an array needs to be
2495extended, libev needs to realloc and move the whole array, but this
2496happens asymptotically never with higher number of elements, so O(1) might
2497mean it might do a lengthy realloc operation in rare cases, but on average
2498it is much faster and asymptotically approaches constant time.</p>
2169 <p> 2499 <p>
2170 <dl> 2500 <dl>
2171 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2501 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2502 <dd>
2503 <p>This means that, when you have a watcher that triggers in one hour and
2504there are 100 watchers that would trigger before that then inserting will
2505have to skip those 100 watchers.</p>
2506 </dd>
2172 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2507 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2508 <dd>
2509 <p>That means that for changing a timer costs less than removing/adding them
2510as only the relative motion in the event queue has to be paid for.</p>
2511 </dd>
2173 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2512 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2513 <dd>
2514 <p>These just add the watcher into an array or at the head of a list.
2174 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2515=item Stopping check/prepare/idle watchers: O(1)</p>
2516 </dd>
2175 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> 2517 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2518 <dd>
2519 <p>These watchers are stored in lists then need to be walked to find the
2520correct watcher to remove. The lists are usually short (you don't usually
2521have many watchers waiting for the same fd or signal).</p>
2522 </dd>
2176 <dt>Finding the next timer per loop iteration: O(1)</dt> 2523 <dt>Finding the next timer per loop iteration: O(1)</dt>
2177 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2524 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2525 <dd>
2526 <p>A change means an I/O watcher gets started or stopped, which requires
2527libev to recalculate its status (and possibly tell the kernel).</p>
2528 </dd>
2178 <dt>Activating one watcher: O(1)</dt> 2529 <dt>Activating one watcher: O(1)</dt>
2530 <dt>Priority handling: O(number_of_priorities)</dt>
2531 <dd>
2532 <p>Priorities are implemented by allocating some space for each
2533priority. When doing priority-based operations, libev usually has to
2534linearly search all the priorities.</p>
2535 </dd>
2179 </dl> 2536 </dl>
2180 </p> 2537 </p>
2181 2538
2182 2539
2183 2540

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