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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="Sat Nov 24 08:20:38 2007" /> 9 <meta name="created" content="Mon Nov 26 10:52:13 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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21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 21<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
26<ul><li><a href="#SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</a></li> 26<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
27<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 27<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
28</ul> 28</ul>
29</li> 29</li>
30<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 30<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
31<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> 31<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<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> 32<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
33<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> 33<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
34<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> 34<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
35<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
36<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> 36<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>
37<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> 37<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>
38<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li> 38<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
39</ul> 39</ul>
40</li> 40</li>
41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
44<li><a href="#EMBEDDING">EMBEDDING</a>
45<ul><li><a href="#FILESETS">FILESETS</a>
46<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
47<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
48<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
49</ul>
50</li>
51<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
52<li><a href="#EXAMPLES">EXAMPLES</a></li>
53</ul>
54</li>
44<li><a href="#AUTHOR">AUTHOR</a> 55<li><a href="#AUTHOR">AUTHOR</a>
45</li> 56</li>
46</ul><hr /> 57</ul><hr />
47<!-- INDEX END --> 58<!-- INDEX END -->
48 59
… …
502 513
503</pre> 514</pre>
504 </dd> 515 </dd>
505</dl> 516</dl>
506 517
518
519
520
521
507</div> 522</div>
508<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 523<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
509<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 524<div id="ANATOMY_OF_A_WATCHER_CONTENT">
510<p>A watcher is a structure that you create and register to record your 525<p>A watcher is a structure that you create and register to record your
511interest in some event. For instance, if you want to wait for STDIN to 526interest in some event. For instance, if you want to wait for STDIN to
… …
601programs, though, so beware.</p> 616programs, though, so beware.</p>
602 </dd> 617 </dd>
603</dl> 618</dl>
604 619
605</div> 620</div>
606<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2> 621<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
607<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2"> 622<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
608<p>In the following description, <code>TYPE</code> stands for the watcher type, 623<p>In the following description, <code>TYPE</code> stands for the watcher type,
609e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p> 624e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
610<dl> 625<dl>
611 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt> 626 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
612 <dd> 627 <dd>
… …
616the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the 631the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
617type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro 632type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
618which rolls both calls into one.</p> 633which rolls both calls into one.</p>
619 <p>You can reinitialise a watcher at any time as long as it has been stopped 634 <p>You can reinitialise a watcher at any time as long as it has been stopped
620(or never started) and there are no pending events outstanding.</p> 635(or never started) and there are no pending events outstanding.</p>
621 <p>The callbakc is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher, 636 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
622int revents)</code>.</p> 637int revents)</code>.</p>
623 </dd> 638 </dd>
624 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt> 639 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
625 <dd> 640 <dd>
626 <p>This macro initialises the type-specific parts of a watcher. You need to 641 <p>This macro initialises the type-specific parts of a watcher. You need to
… …
723 738
724 739
725 740
726 741
727</div> 742</div>
728<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 743<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
729<div id="code_ev_io_code_is_this_file_descrip-2"> 744<div id="code_ev_io_code_is_this_file_descrip-2">
730<p>I/O watchers check whether a file descriptor is readable or writable 745<p>I/O watchers check whether a file descriptor is readable or writable
731in each iteration of the event loop (This behaviour is called 746in each iteration of the event loop, or, more precisely, when reading
732level-triggering because you keep receiving events as long as the 747would not block the process and writing would at least be able to write
733condition persists. Remember you can stop the watcher if you don't want to 748some data. This behaviour is called level-triggering because you keep
734act on the event and neither want to receive future events).</p> 749receiving events as long as the condition persists. Remember you can stop
750the watcher if you don't want to act on the event and neither want to
751receive future events.</p>
735<p>In general you can register as many read and/or write event watchers per 752<p>In general you can register as many read and/or write event watchers per
736fd as you want (as long as you don't confuse yourself). Setting all file 753fd as you want (as long as you don't confuse yourself). Setting all file
737descriptors to non-blocking mode is also usually a good idea (but not 754descriptors to non-blocking mode is also usually a good idea (but not
738required if you know what you are doing).</p> 755required if you know what you are doing).</p>
739<p>You have to be careful with dup'ed file descriptors, though. Some backends 756<p>You have to be careful with dup'ed file descriptors, though. Some backends
740(the linux epoll backend is a notable example) cannot handle dup'ed file 757(the linux epoll backend is a notable example) cannot handle dup'ed file
741descriptors correctly if you register interest in two or more fds pointing 758descriptors correctly if you register interest in two or more fds pointing
742to the same underlying file/socket etc. description (that is, they share 759to the same underlying file/socket/etc. description (that is, they share
743the same underlying &quot;file open&quot;).</p> 760the same underlying &quot;file open&quot;).</p>
744<p>If you must do this, then force the use of a known-to-be-good backend 761<p>If you must do this, then force the use of a known-to-be-good backend
745(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and 762(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
746<code>EVBACKEND_POLL</code>).</p> 763<code>EVBACKEND_POLL</code>).</p>
764<p>Another thing you have to watch out for is that it is quite easy to
765receive &quot;spurious&quot; readyness notifications, that is your callback might
766be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
767because there is no data. Not only are some backends known to create a
768lot of those (for example solaris ports), it is very easy to get into
769this situation even with a relatively standard program structure. Thus
770it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
771<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
772<p>If you cannot run the fd in non-blocking mode (for example you should not
773play around with an Xlib connection), then you have to seperately re-test
774wether a file descriptor is really ready with a known-to-be good interface
775such as poll (fortunately in our Xlib example, Xlib already does this on
776its own, so its quite safe to use).</p>
747<dl> 777<dl>
748 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 778 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
749 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 779 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
750 <dd> 780 <dd>
751 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 781 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
752events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 782rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
753EV_WRITE</code> to receive the given events.</p> 783<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
754 <p>Please note that most of the more scalable backend mechanisms (for example
755epoll and solaris ports) can result in spurious readyness notifications
756for file descriptors, so you practically need to use non-blocking I/O (and
757treat callback invocation as hint only), or retest separately with a safe
758interface before doing I/O (XLib can do this), or force the use of either
759<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
760problem. Also note that it is quite easy to have your callback invoked
761when the readyness condition is no longer valid even when employing
762typical ways of handling events, so its a good idea to use non-blocking
763I/O unconditionally.</p>
764 </dd> 784 </dd>
765</dl> 785</dl>
766<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 786<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
767readable, but only once. Since it is likely line-buffered, you could 787readable, but only once. Since it is likely line-buffered, you could
768attempt to read a whole line in the callback:</p> 788attempt to read a whole line in the callback:</p>
… …
784 804
785 805
786</pre> 806</pre>
787 807
788</div> 808</div>
789<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 809<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
790<div id="code_ev_timer_code_relative_and_opti-2"> 810<div id="code_ev_timer_code_relative_and_opti-2">
791<p>Timer watchers are simple relative timers that generate an event after a 811<p>Timer watchers are simple relative timers that generate an event after a
792given time, and optionally repeating in regular intervals after that.</p> 812given time, and optionally repeating in regular intervals after that.</p>
793<p>The timers are based on real time, that is, if you register an event that 813<p>The timers are based on real time, that is, if you register an event that
794times out after an hour and you reset your system clock to last years 814times out after an hour and you reset your system clock to last years
… …
870 890
871 891
872</pre> 892</pre>
873 893
874</div> 894</div>
875<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 895<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
876<div id="code_ev_periodic_code_to_cron_or_not-2"> 896<div id="code_ev_periodic_code_to_cron_or_not-2">
877<p>Periodic watchers are also timers of a kind, but they are very versatile 897<p>Periodic watchers are also timers of a kind, but they are very versatile
878(and unfortunately a bit complex).</p> 898(and unfortunately a bit complex).</p>
879<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 899<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
880but on wallclock time (absolute time). You can tell a periodic watcher 900but on wallclock time (absolute time). You can tell a periodic watcher
881to trigger &quot;at&quot; some specific point in time. For example, if you tell a 901to trigger &quot;at&quot; some specific point in time. For example, if you tell a
882periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 902periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
883+ 10.&gt;) and then reset your system clock to the last year, then it will 903+ 10.</code>) and then reset your system clock to the last year, then it will
884take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 904take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
885roughly 10 seconds later and of course not if you reset your system time 905roughly 10 seconds later and of course not if you reset your system time
886again).</p> 906again).</p>
887<p>They can also be used to implement vastly more complex timers, such as 907<p>They can also be used to implement vastly more complex timers, such as
888triggering an event on eahc midnight, local time.</p> 908triggering an event on eahc midnight, local time.</p>
… …
999 1019
1000 1020
1001</pre> 1021</pre>
1002 1022
1003</div> 1023</div>
1004<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1024<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
1005<div id="code_ev_signal_code_signal_me_when_a-2"> 1025<div id="code_ev_signal_code_signal_me_when_a-2">
1006<p>Signal watchers will trigger an event when the process receives a specific 1026<p>Signal watchers will trigger an event when the process receives a specific
1007signal one or more times. Even though signals are very asynchronous, libev 1027signal one or more times. Even though signals are very asynchronous, libev
1008will try it's best to deliver signals synchronously, i.e. as part of the 1028will try it's best to deliver signals synchronously, i.e. as part of the
1009normal event processing, like any other event.</p> 1029normal event processing, like any other event.</p>
… …
1025 1045
1026 1046
1027 1047
1028 1048
1029</div> 1049</div>
1030<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1050<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
1031<div id="code_ev_child_code_wait_for_pid_stat-2"> 1051<div id="code_ev_child_code_watch_out_for_pro-2">
1032<p>Child watchers trigger when your process receives a SIGCHLD in response to 1052<p>Child watchers trigger when your process receives a SIGCHLD in response to
1033some child status changes (most typically when a child of yours dies).</p> 1053some child status changes (most typically when a child of yours dies).</p>
1034<dl> 1054<dl>
1035 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1055 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1036 <dt>ev_child_set (ev_child *, int pid)</dt> 1056 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
1058 1078
1059 1079
1060</pre> 1080</pre>
1061 1081
1062</div> 1082</div>
1063<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1083<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1064<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1084<div id="code_ev_idle_code_when_you_ve_got_no-2">
1065<p>Idle watchers trigger events when there are no other events are pending 1085<p>Idle watchers trigger events when there are no other events are pending
1066(prepare, check and other idle watchers do not count). That is, as long 1086(prepare, check and other idle watchers do not count). That is, as long
1067as your process is busy handling sockets or timeouts (or even signals, 1087as your process is busy handling sockets or timeouts (or even signals,
1068imagine) it will not be triggered. But when your process is idle all idle 1088imagine) it will not be triggered. But when your process is idle all idle
… …
1101 1121
1102 1122
1103</pre> 1123</pre>
1104 1124
1105</div> 1125</div>
1106<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1126<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1107<div id="code_ev_prepare_code_and_code_ev_che-2"> 1127<div id="code_ev_prepare_code_and_code_ev_che-2">
1108<p>Prepare and check watchers are usually (but not always) used in tandem: 1128<p>Prepare and check watchers are usually (but not always) used in tandem:
1109prepare watchers get invoked before the process blocks and check watchers 1129prepare watchers get invoked before the process blocks and check watchers
1110afterwards.</p> 1130afterwards.</p>
1131<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1132the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1133watchers. Other loops than the current one are fine, however. The
1134rationale behind this is that you do not need to check for recursion in
1135those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1136<code>ev_check</code> so if you have one watcher of each kind they will always be
1137called in pairs bracketing the blocking call.</p>
1111<p>Their main purpose is to integrate other event mechanisms into libev and 1138<p>Their main purpose is to integrate other event mechanisms into libev and
1112their use is somewhat advanced. This could be used, for example, to track 1139their use is somewhat advanced. This could be used, for example, to track
1113variable changes, implement your own watchers, integrate net-snmp or a 1140variable changes, implement your own watchers, integrate net-snmp or a
1114coroutine library and lots more.</p> 1141coroutine library and lots more. They are also occasionally useful if
1142you cache some data and want to flush it before blocking (for example,
1143in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1144watcher).</p>
1115<p>This is done by examining in each prepare call which file descriptors need 1145<p>This is done by examining in each prepare call which file descriptors need
1116to be watched by the other library, registering <code>ev_io</code> watchers for 1146to be watched by the other library, registering <code>ev_io</code> watchers for
1117them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1147them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1118provide just this functionality). Then, in the check watcher you check for 1148provide just this functionality). Then, in the check watcher you check for
1119any events that occured (by checking the pending status of all watchers 1149any events that occured (by checking the pending status of all watchers
… …
1135 <p>Initialises and configures the prepare or check watcher - they have no 1165 <p>Initialises and configures the prepare or check watcher - they have no
1136parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1166parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1137macros, but using them is utterly, utterly and completely pointless.</p> 1167macros, but using them is utterly, utterly and completely pointless.</p>
1138 </dd> 1168 </dd>
1139</dl> 1169</dl>
1140<p>Example: *TODO*.</p> 1170<p>Example: To include a library such as adns, you would add IO watchers
1171and a timeout watcher in a prepare handler, as required by libadns, and
1172in a check watcher, destroy them and call into libadns. What follows is
1173pseudo-code only of course:</p>
1174<pre> static ev_io iow [nfd];
1175 static ev_timer tw;
1141 1176
1177 static void
1178 io_cb (ev_loop *loop, ev_io *w, int revents)
1179 {
1180 // set the relevant poll flags
1181 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1182 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1183 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1184 }
1142 1185
1186 // create io watchers for each fd and a timer before blocking
1187 static void
1188 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1189 {
1190 int timeout = 3600000;truct pollfd fds [nfd];
1191 // actual code will need to loop here and realloc etc.
1192 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1143 1193
1194 /* the callback is illegal, but won't be called as we stop during check */
1195 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1196 ev_timer_start (loop, &amp;tw);
1144 1197
1198 // create on ev_io per pollfd
1199 for (int i = 0; i &lt; nfd; ++i)
1200 {
1201 ev_io_init (iow + i, io_cb, fds [i].fd,
1202 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1203 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1145 1204
1205 fds [i].revents = 0;
1206 iow [i].data = fds + i;
1207 ev_io_start (loop, iow + i);
1208 }
1209 }
1210
1211 // stop all watchers after blocking
1212 static void
1213 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1214 {
1215 ev_timer_stop (loop, &amp;tw);
1216
1217 for (int i = 0; i &lt; nfd; ++i)
1218 ev_io_stop (loop, iow + i);
1219
1220 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1221 }
1222
1223
1224
1225
1226</pre>
1227
1146</div> 1228</div>
1147<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1229<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1148<div id="code_ev_embed_code_when_one_backend_-2"> 1230<div id="code_ev_embed_code_when_one_backend_-2">
1149<p>This is a rather advanced watcher type that lets you embed one event loop 1231<p>This is a rather advanced watcher type that lets you embed one event loop
1150into another (currently only <code>ev_io</code> events are supported in the embedded 1232into another (currently only <code>ev_io</code> events are supported in the embedded
1151loop, other types of watchers might be handled in a delayed or incorrect 1233loop, other types of watchers might be handled in a delayed or incorrect
1152fashion and must not be used).</p> 1234fashion and must not be used).</p>
… …
1306</dl> 1388</dl>
1307 1389
1308</div> 1390</div>
1309<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1391<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
1310<div id="C_SUPPORT_CONTENT"> 1392<div id="C_SUPPORT_CONTENT">
1311<p>TBD.</p> 1393<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1394you to use some convinience methods to start/stop watchers and also change
1395the callback model to a model using method callbacks on objects.</p>
1396<p>To use it,</p>
1397<pre> #include &lt;ev++.h&gt;
1398
1399</pre>
1400<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1401and puts all of its definitions (many of them macros) into the global
1402namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1403<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1404<code>EV_MULTIPLICITY</code>.</p>
1405<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1406<dl>
1407 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1408 <dd>
1409 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1410macros from <cite>ev.h</cite>.</p>
1411 </dd>
1412 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1413 <dd>
1414 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1415 </dd>
1416 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1417 <dd>
1418 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1419the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1420which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1421defines by many implementations.</p>
1422 <p>All of those classes have these methods:</p>
1423 <p>
1424 <dl>
1425 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1426 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1427 <dt>ev::TYPE::~TYPE</dt>
1428 <dd>
1429 <p>The constructor takes a pointer to an object and a method pointer to
1430the event handler callback to call in this class. The constructor calls
1431<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1432before starting it. If you do not specify a loop then the constructor
1433automatically associates the default loop with this watcher.</p>
1434 <p>The destructor automatically stops the watcher if it is active.</p>
1435 </dd>
1436 <dt>w-&gt;set (struct ev_loop *)</dt>
1437 <dd>
1438 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1439do this when the watcher is inactive (and not pending either).</p>
1440 </dd>
1441 <dt>w-&gt;set ([args])</dt>
1442 <dd>
1443 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1444called at least once. Unlike the C counterpart, an active watcher gets
1445automatically stopped and restarted.</p>
1446 </dd>
1447 <dt>w-&gt;start ()</dt>
1448 <dd>
1449 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1450constructor already takes the loop.</p>
1451 </dd>
1452 <dt>w-&gt;stop ()</dt>
1453 <dd>
1454 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1455 </dd>
1456 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1457 <dd>
1458 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1459<code>ev_TYPE_again</code> function.</p>
1460 </dd>
1461 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1462 <dd>
1463 <p>Invokes <code>ev_embed_sweep</code>.</p>
1464 </dd>
1465 </dl>
1466 </p>
1467 </dd>
1468</dl>
1469<p>Example: Define a class with an IO and idle watcher, start one of them in
1470the constructor.</p>
1471<pre> class myclass
1472 {
1473 ev_io io; void io_cb (ev::io &amp;w, int revents);
1474 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1475
1476 myclass ();
1477 }
1478
1479 myclass::myclass (int fd)
1480 : io (this, &amp;myclass::io_cb),
1481 idle (this, &amp;myclass::idle_cb)
1482 {
1483 io.start (fd, ev::READ);
1484 }
1485
1486</pre>
1487
1488</div>
1489<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
1490<div id="EMBEDDING_CONTENT">
1491<p>Libev can (and often is) directly embedded into host
1492applications. Examples of applications that embed it include the Deliantra
1493Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1494and rxvt-unicode.</p>
1495<p>The goal is to enable you to just copy the neecssary files into your
1496source directory without having to change even a single line in them, so
1497you can easily upgrade by simply copying (or having a checked-out copy of
1498libev somewhere in your source tree).</p>
1499
1500</div>
1501<h2 id="FILESETS">FILESETS</h2>
1502<div id="FILESETS_CONTENT">
1503<p>Depending on what features you need you need to include one or more sets of files
1504in your app.</p>
1505
1506</div>
1507<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1508<div id="CORE_EVENT_LOOP_CONTENT">
1509<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1510configuration (no autoconf):</p>
1511<pre> #define EV_STANDALONE 1
1512 #include &quot;ev.c&quot;
1513
1514</pre>
1515<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1516single C source file only to provide the function implementations. To use
1517it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1518done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1519where you can put other configuration options):</p>
1520<pre> #define EV_STANDALONE 1
1521 #include &quot;ev.h&quot;
1522
1523</pre>
1524<p>Both header files and implementation files can be compiled with a C++
1525compiler (at least, thats a stated goal, and breakage will be treated
1526as a bug).</p>
1527<p>You need the following files in your source tree, or in a directory
1528in your include path (e.g. in libev/ when using -Ilibev):</p>
1529<pre> ev.h
1530 ev.c
1531 ev_vars.h
1532 ev_wrap.h
1533
1534 ev_win32.c required on win32 platforms only
1535
1536 ev_select.c only when select backend is enabled (which is by default)
1537 ev_poll.c only when poll backend is enabled (disabled by default)
1538 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1539 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1540 ev_port.c only when the solaris port backend is enabled (disabled by default)
1541
1542</pre>
1543<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1544to compile this single file.</p>
1545
1546</div>
1547<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1548<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1549<p>To include the libevent compatibility API, also include:</p>
1550<pre> #include &quot;event.c&quot;
1551
1552</pre>
1553<p>in the file including <cite>ev.c</cite>, and:</p>
1554<pre> #include &quot;event.h&quot;
1555
1556</pre>
1557<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1558<p>You need the following additional files for this:</p>
1559<pre> event.h
1560 event.c
1561
1562</pre>
1563
1564</div>
1565<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1566<div id="AUTOCONF_SUPPORT_CONTENT">
1567<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1568whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1569<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1570include <cite>config.h</cite> and configure itself accordingly.</p>
1571<p>For this of course you need the m4 file:</p>
1572<pre> libev.m4
1573
1574</pre>
1575
1576</div>
1577<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1578<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1579<p>Libev can be configured via a variety of preprocessor symbols you have to define
1580before including any of its files. The default is not to build for multiplicity
1581and only include the select backend.</p>
1582<dl>
1583 <dt>EV_STANDALONE</dt>
1584 <dd>
1585 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1586keeps libev from including <cite>config.h</cite>, and it also defines dummy
1587implementations for some libevent functions (such as logging, which is not
1588supported). It will also not define any of the structs usually found in
1589<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1590 </dd>
1591 <dt>EV_USE_MONOTONIC</dt>
1592 <dd>
1593 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1594monotonic clock option at both compiletime and runtime. Otherwise no use
1595of the monotonic clock option will be attempted. If you enable this, you
1596usually have to link against librt or something similar. Enabling it when
1597the functionality isn't available is safe, though, althoguh you have
1598to make sure you link against any libraries where the <code>clock_gettime</code>
1599function is hiding in (often <cite>-lrt</cite>).</p>
1600 </dd>
1601 <dt>EV_USE_REALTIME</dt>
1602 <dd>
1603 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1604realtime clock option at compiletime (and assume its availability at
1605runtime if successful). Otherwise no use of the realtime clock option will
1606be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1607(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1608in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1609 </dd>
1610 <dt>EV_USE_SELECT</dt>
1611 <dd>
1612 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1613<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1614other method takes over, select will be it. Otherwise the select backend
1615will not be compiled in.</p>
1616 </dd>
1617 <dt>EV_SELECT_USE_FD_SET</dt>
1618 <dd>
1619 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1620structure. This is useful if libev doesn't compile due to a missing
1621<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1622exotic systems. This usually limits the range of file descriptors to some
1623low limit such as 1024 or might have other limitations (winsocket only
1624allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1625influence the size of the <code>fd_set</code> used.</p>
1626 </dd>
1627 <dt>EV_SELECT_IS_WINSOCKET</dt>
1628 <dd>
1629 <p>When defined to <code>1</code>, the select backend will assume that
1630select/socket/connect etc. don't understand file descriptors but
1631wants osf handles on win32 (this is the case when the select to
1632be used is the winsock select). This means that it will call
1633<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1634it is assumed that all these functions actually work on fds, even
1635on win32. Should not be defined on non-win32 platforms.</p>
1636 </dd>
1637 <dt>EV_USE_POLL</dt>
1638 <dd>
1639 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1640backend. Otherwise it will be enabled on non-win32 platforms. It
1641takes precedence over select.</p>
1642 </dd>
1643 <dt>EV_USE_EPOLL</dt>
1644 <dd>
1645 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
1646<code>epoll</code>(7) backend. Its availability will be detected at runtime,
1647otherwise another method will be used as fallback. This is the
1648preferred backend for GNU/Linux systems.</p>
1649 </dd>
1650 <dt>EV_USE_KQUEUE</dt>
1651 <dd>
1652 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
1653<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
1654otherwise another method will be used as fallback. This is the preferred
1655backend for BSD and BSD-like systems, although on most BSDs kqueue only
1656supports some types of fds correctly (the only platform we found that
1657supports ptys for example was NetBSD), so kqueue might be compiled in, but
1658not be used unless explicitly requested. The best way to use it is to find
1659out whether kqueue supports your type of fd properly and use an embedded
1660kqueue loop.</p>
1661 </dd>
1662 <dt>EV_USE_PORT</dt>
1663 <dd>
1664 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
166510 port style backend. Its availability will be detected at runtime,
1666otherwise another method will be used as fallback. This is the preferred
1667backend for Solaris 10 systems.</p>
1668 </dd>
1669 <dt>EV_USE_DEVPOLL</dt>
1670 <dd>
1671 <p>reserved for future expansion, works like the USE symbols above.</p>
1672 </dd>
1673 <dt>EV_H</dt>
1674 <dd>
1675 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1676undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This
1677can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
1678 </dd>
1679 <dt>EV_CONFIG_H</dt>
1680 <dd>
1681 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
1682<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
1683<code>EV_H</code>, above.</p>
1684 </dd>
1685 <dt>EV_EVENT_H</dt>
1686 <dd>
1687 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
1688of how the <cite>event.h</cite> header can be found.</p>
1689 </dd>
1690 <dt>EV_PROTOTYPES</dt>
1691 <dd>
1692 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
1693prototypes, but still define all the structs and other symbols. This is
1694occasionally useful if you want to provide your own wrapper functions
1695around libev functions.</p>
1696 </dd>
1697 <dt>EV_MULTIPLICITY</dt>
1698 <dd>
1699 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
1700will have the <code>struct ev_loop *</code> as first argument, and you can create
1701additional independent event loops. Otherwise there will be no support
1702for multiple event loops and there is no first event loop pointer
1703argument. Instead, all functions act on the single default loop.</p>
1704 </dd>
1705 <dt>EV_PERIODICS</dt>
1706 <dd>
1707 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported,
1708otherwise not. This saves a few kb of code.</p>
1709 </dd>
1710 <dt>EV_COMMON</dt>
1711 <dd>
1712 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1713this macro to a something else you can include more and other types of
1714members. You have to define it each time you include one of the files,
1715though, and it must be identical each time.</p>
1716 <p>For example, the perl EV module uses something like this:</p>
1717<pre> #define EV_COMMON \
1718 SV *self; /* contains this struct */ \
1719 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
1720
1721</pre>
1722 </dd>
1723 <dt>EV_CB_DECLARE (type)</dt>
1724 <dt>EV_CB_INVOKE (watcher, revents)</dt>
1725 <dt>ev_set_cb (ev, cb)</dt>
1726 <dd>
1727 <p>Can be used to change the callback member declaration in each watcher,
1728and the way callbacks are invoked and set. Must expand to a struct member
1729definition and a statement, respectively. See the <cite>ev.v</cite> header file for
1730their default definitions. One possible use for overriding these is to
1731avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
1732method calls instead of plain function calls in C++.</p>
1733
1734</div>
1735<h2 id="EXAMPLES">EXAMPLES</h2>
1736<div id="EXAMPLES_CONTENT">
1737 <p>For a real-world example of a program the includes libev
1738verbatim, you can have a look at the EV perl module
1739(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
1740the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
1741interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
1742will be compiled. It is pretty complex because it provides its own header
1743file.</p>
1744 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
1745that everybody includes and which overrides some autoconf choices:</p>
1746<pre> #define EV_USE_POLL 0
1747 #define EV_MULTIPLICITY 0
1748 #define EV_PERIODICS 0
1749 #define EV_CONFIG_H &lt;config.h&gt;
1750
1751 #include &quot;ev++.h&quot;
1752
1753</pre>
1754 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1755<pre> #include &quot;ev_cpp.h&quot;
1756 #include &quot;ev.c&quot;
1757
1758</pre>
1312 1759
1313</div> 1760</div>
1314<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1761<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
1315<div id="AUTHOR_CONTENT"> 1762<div id="AUTHOR_CONTENT">
1316<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 1763 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1317 1764
1318</div> 1765</div>
1319</div></body> 1766</div></body>
1320</html> 1767</html>

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