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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 10:48:32 2007" /> 9 <meta name="created" content="Tue Nov 27 09:20:40 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_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</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_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> 38<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> 39<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
39</ul> 40</ul>
40</li> 41</li>
41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 42<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 43<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 44<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
45<li><a href="#EMBEDDING">EMBEDDING</a>
46<ul><li><a href="#FILESETS">FILESETS</a>
47<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
48<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
49<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
50</ul>
51</li>
52<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
53<li><a href="#EXAMPLES">EXAMPLES</a></li>
54</ul>
55</li>
56<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
44<li><a href="#AUTHOR">AUTHOR</a> 57<li><a href="#AUTHOR">AUTHOR</a>
45</li> 58</li>
46</ul><hr /> 59</ul><hr />
47<!-- INDEX END --> 60<!-- INDEX END -->
48 61
… …
502 515
503</pre> 516</pre>
504 </dd> 517 </dd>
505</dl> 518</dl>
506 519
520
521
522
523
507</div> 524</div>
508<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 525<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"> 526<div id="ANATOMY_OF_A_WATCHER_CONTENT">
510<p>A watcher is a structure that you create and register to record your 527<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 528interest in some event. For instance, if you want to wait for STDIN to
… …
570 </dd> 587 </dd>
571 <dt><code>EV_CHILD</code></dt> 588 <dt><code>EV_CHILD</code></dt>
572 <dd> 589 <dd>
573 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 590 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
574 </dd> 591 </dd>
592 <dt><code>EV_STAT</code></dt>
593 <dd>
594 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
595 </dd>
575 <dt><code>EV_IDLE</code></dt> 596 <dt><code>EV_IDLE</code></dt>
576 <dd> 597 <dd>
577 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 598 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
578 </dd> 599 </dd>
579 <dt><code>EV_PREPARE</code></dt> 600 <dt><code>EV_PREPARE</code></dt>
… …
601programs, though, so beware.</p> 622programs, though, so beware.</p>
602 </dd> 623 </dd>
603</dl> 624</dl>
604 625
605</div> 626</div>
606<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2> 627<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
607<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2"> 628<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
608<p>In the following description, <code>TYPE</code> stands for the watcher type, 629<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> 630e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
610<dl> 631<dl>
611 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt> 632 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
612 <dd> 633 <dd>
… …
616the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the 637the 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 638type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
618which rolls both calls into one.</p> 639which rolls both calls into one.</p>
619 <p>You can reinitialise a watcher at any time as long as it has been stopped 640 <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> 641(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, 642 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
622int revents)</code>.</p> 643int revents)</code>.</p>
623 </dd> 644 </dd>
624 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt> 645 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
625 <dd> 646 <dd>
626 <p>This macro initialises the type-specific parts of a watcher. You need to 647 <p>This macro initialises the type-specific parts of a watcher. You need to
… …
716 737
717</div> 738</div>
718<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 739<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
719<div id="WATCHER_TYPES_CONTENT"> 740<div id="WATCHER_TYPES_CONTENT">
720<p>This section describes each watcher in detail, but will not repeat 741<p>This section describes each watcher in detail, but will not repeat
721information given in the last section.</p> 742information given in the last section. Any initialisation/set macros,
743functions and members specific to the watcher type are explained.</p>
744<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
745while the watcher is active, you can look at the member and expect some
746sensible content, but you must not modify it (you can modify it while the
747watcher is stopped to your hearts content), or <i>[read-write]</i>, which
748means you can expect it to have some sensible content while the watcher
749is active, but you can also modify it. Modifying it may not do something
750sensible or take immediate effect (or do anything at all), but libev will
751not crash or malfunction in any way.</p>
722 752
723 753
724 754
725 755
726 756
727</div> 757</div>
728<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 758<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"> 759<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 760<p>I/O watchers check whether a file descriptor is readable or writable
731in each iteration of the event loop (This behaviour is called 761in each iteration of the event loop, or, more precisely, when reading
732level-triggering because you keep receiving events as long as the 762would 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 763some data. This behaviour is called level-triggering because you keep
734act on the event and neither want to receive future events).</p> 764receiving events as long as the condition persists. Remember you can stop
765the watcher if you don't want to act on the event and neither want to
766receive future events.</p>
735<p>In general you can register as many read and/or write event watchers per 767<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 768fd 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 769descriptors to non-blocking mode is also usually a good idea (but not
738required if you know what you are doing).</p> 770required if you know what you are doing).</p>
739<p>You have to be careful with dup'ed file descriptors, though. Some backends 771<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 772(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 773descriptors correctly if you register interest in two or more fds pointing
742to the same underlying file/socket etc. description (that is, they share 774to the same underlying file/socket/etc. description (that is, they share
743the same underlying &quot;file open&quot;).</p> 775the 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 776<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 777(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
746<code>EVBACKEND_POLL</code>).</p> 778<code>EVBACKEND_POLL</code>).</p>
779<p>Another thing you have to watch out for is that it is quite easy to
780receive &quot;spurious&quot; readyness notifications, that is your callback might
781be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
782because there is no data. Not only are some backends known to create a
783lot of those (for example solaris ports), it is very easy to get into
784this situation even with a relatively standard program structure. Thus
785it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
786<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
787<p>If you cannot run the fd in non-blocking mode (for example you should not
788play around with an Xlib connection), then you have to seperately re-test
789wether a file descriptor is really ready with a known-to-be good interface
790such as poll (fortunately in our Xlib example, Xlib already does this on
791its own, so its quite safe to use).</p>
747<dl> 792<dl>
748 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 793 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
749 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 794 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
750 <dd> 795 <dd>
751 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 796 <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 | 797rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
753EV_WRITE</code> to receive the given events.</p> 798<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 799 </dd>
755epoll and solaris ports) can result in spurious readyness notifications 800 <dt>int fd [read-only]</dt>
756for file descriptors, so you practically need to use non-blocking I/O (and 801 <dd>
757treat callback invocation as hint only), or retest separately with a safe 802 <p>The file descriptor being watched.</p>
758interface before doing I/O (XLib can do this), or force the use of either 803 </dd>
759<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 804 <dt>int events [read-only]</dt>
760problem. Also note that it is quite easy to have your callback invoked 805 <dd>
761when the readyness condition is no longer valid even when employing 806 <p>The events being watched.</p>
762typical ways of handling events, so its a good idea to use non-blocking
763I/O unconditionally.</p>
764 </dd> 807 </dd>
765</dl> 808</dl>
766<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 809<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 810readable, but only once. Since it is likely line-buffered, you could
768attempt to read a whole line in the callback:</p> 811attempt to read a whole line in the callback:</p>
… …
784 827
785 828
786</pre> 829</pre>
787 830
788</div> 831</div>
789<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 832<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"> 833<div id="code_ev_timer_code_relative_and_opti-2">
791<p>Timer watchers are simple relative timers that generate an event after a 834<p>Timer watchers are simple relative timers that generate an event after a
792given time, and optionally repeating in regular intervals after that.</p> 835given 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 836<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 837times out after an hour and you reset your system clock to last years
… …
826repeating. The exact semantics are:</p> 869repeating. The exact semantics are:</p>
827 <p>If the timer is started but nonrepeating, stop it.</p> 870 <p>If the timer is started but nonrepeating, stop it.</p>
828 <p>If the timer is repeating, either start it if necessary (with the repeat 871 <p>If the timer is repeating, either start it if necessary (with the repeat
829value), or reset the running timer to the repeat value.</p> 872value), or reset the running timer to the repeat value.</p>
830 <p>This sounds a bit complicated, but here is a useful and typical 873 <p>This sounds a bit complicated, but here is a useful and typical
831example: Imagine you have a tcp connection and you want a so-called idle 874example: Imagine you have a tcp connection and you want a so-called
832timeout, that is, you want to be called when there have been, say, 60 875idle timeout, that is, you want to be called when there have been,
833seconds of inactivity on the socket. The easiest way to do this is to 876say, 60 seconds of inactivity on the socket. The easiest way to do
834configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 877this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
835time you successfully read or write some data. If you go into an idle 878<code>ev_timer_again</code> each time you successfully read or write some data. If
836state where you do not expect data to travel on the socket, you can stop 879you go into an idle state where you do not expect data to travel on the
837the timer, and again will automatically restart it if need be.</p> 880socket, you can stop the timer, and again will automatically restart it if
881need be.</p>
882 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
883and only ever use the <code>repeat</code> value:</p>
884<pre> ev_timer_init (timer, callback, 0., 5.);
885 ev_timer_again (loop, timer);
886 ...
887 timer-&gt;again = 17.;
888 ev_timer_again (loop, timer);
889 ...
890 timer-&gt;again = 10.;
891 ev_timer_again (loop, timer);
892
893</pre>
894 <p>This is more efficient then stopping/starting the timer eahc time you want
895to modify its timeout value.</p>
896 </dd>
897 <dt>ev_tstamp repeat [read-write]</dt>
898 <dd>
899 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
900or <code>ev_timer_again</code> is called and determines the next timeout (if any),
901which is also when any modifications are taken into account.</p>
838 </dd> 902 </dd>
839</dl> 903</dl>
840<p>Example: create a timer that fires after 60 seconds.</p> 904<p>Example: create a timer that fires after 60 seconds.</p>
841<pre> static void 905<pre> static void
842 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 906 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
870 934
871 935
872</pre> 936</pre>
873 937
874</div> 938</div>
875<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 939<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"> 940<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 941<p>Periodic watchers are also timers of a kind, but they are very versatile
878(and unfortunately a bit complex).</p> 942(and unfortunately a bit complex).</p>
879<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 943<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 944but on wallclock time (absolute time). You can tell a periodic watcher
… …
960 <p>Simply stops and restarts the periodic watcher again. This is only useful 1024 <p>Simply stops and restarts the periodic watcher again. This is only useful
961when you changed some parameters or the reschedule callback would return 1025when you changed some parameters or the reschedule callback would return
962a different time than the last time it was called (e.g. in a crond like 1026a different time than the last time it was called (e.g. in a crond like
963program when the crontabs have changed).</p> 1027program when the crontabs have changed).</p>
964 </dd> 1028 </dd>
1029 <dt>ev_tstamp interval [read-write]</dt>
1030 <dd>
1031 <p>The current interval value. Can be modified any time, but changes only
1032take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1033called.</p>
1034 </dd>
1035 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1036 <dd>
1037 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1038switched off. Can be changed any time, but changes only take effect when
1039the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1040 </dd>
965</dl> 1041</dl>
966<p>Example: call a callback every hour, or, more precisely, whenever the 1042<p>Example: call a callback every hour, or, more precisely, whenever the
967system clock is divisible by 3600. The callback invocation times have 1043system clock is divisible by 3600. The callback invocation times have
968potentially a lot of jittering, but good long-term stability.</p> 1044potentially a lot of jittering, but good long-term stability.</p>
969<pre> static void 1045<pre> static void
… …
999 1075
1000 1076
1001</pre> 1077</pre>
1002 1078
1003</div> 1079</div>
1004<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1080<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"> 1081<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 1082<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 1083signal 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 1084will try it's best to deliver signals synchronously, i.e. as part of the
1009normal event processing, like any other event.</p> 1085normal event processing, like any other event.</p>
… …
1018 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1094 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1019 <dd> 1095 <dd>
1020 <p>Configures the watcher to trigger on the given signal number (usually one 1096 <p>Configures the watcher to trigger on the given signal number (usually one
1021of the <code>SIGxxx</code> constants).</p> 1097of the <code>SIGxxx</code> constants).</p>
1022 </dd> 1098 </dd>
1099 <dt>int signum [read-only]</dt>
1100 <dd>
1101 <p>The signal the watcher watches out for.</p>
1102 </dd>
1023</dl> 1103</dl>
1024 1104
1025 1105
1026 1106
1027 1107
1028 1108
1029</div> 1109</div>
1030<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1110<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"> 1111<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 1112<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> 1113some child status changes (most typically when a child of yours dies).</p>
1034<dl> 1114<dl>
1035 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1115 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1036 <dt>ev_child_set (ev_child *, int pid)</dt> 1116 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
1039<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 1119<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
1040at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1120at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1041the status word (use the macros from <code>sys/wait.h</code> and see your systems 1121the status word (use the macros from <code>sys/wait.h</code> and see your systems
1042<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1122<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1043process causing the status change.</p> 1123process causing the status change.</p>
1124 </dd>
1125 <dt>int pid [read-only]</dt>
1126 <dd>
1127 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1128 </dd>
1129 <dt>int rpid [read-write]</dt>
1130 <dd>
1131 <p>The process id that detected a status change.</p>
1132 </dd>
1133 <dt>int rstatus [read-write]</dt>
1134 <dd>
1135 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1136<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1044 </dd> 1137 </dd>
1045</dl> 1138</dl>
1046<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1139<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
1047<pre> static void 1140<pre> static void
1048 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1141 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1058 1151
1059 1152
1060</pre> 1153</pre>
1061 1154
1062</div> 1155</div>
1156<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1157<div id="code_ev_stat_code_did_the_file_attri-2">
1158<p>This watches a filesystem path for attribute changes. That is, it calls
1159<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1160compared to the last time, invoking the callback if it did.</p>
1161<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1162not exist&quot; is a status change like any other. The condition &quot;path does
1163not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1164otherwise always forced to be at least one) and all the other fields of
1165the stat buffer having unspecified contents.</p>
1166<p>Since there is no standard to do this, the portable implementation simply
1167calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You
1168can specify a recommended polling interval for this case. If you specify
1169a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1170unspecified default</i> value will be used (which you can expect to be around
1171five seconds, although this might change dynamically). Libev will also
1172impose a minimum interval which is currently around <code>0.1</code>, but thats
1173usually overkill.</p>
1174<p>This watcher type is not meant for massive numbers of stat watchers,
1175as even with OS-supported change notifications, this can be
1176resource-intensive.</p>
1177<p>At the time of this writing, no specific OS backends are implemented, but
1178if demand increases, at least a kqueue and inotify backend will be added.</p>
1179<dl>
1180 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1181 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1182 <dd>
1183 <p>Configures the watcher to wait for status changes of the given
1184<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1185be detected and should normally be specified as <code>0</code> to let libev choose
1186a suitable value. The memory pointed to by <code>path</code> must point to the same
1187path for as long as the watcher is active.</p>
1188 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1189relative to the attributes at the time the watcher was started (or the
1190last change was detected).</p>
1191 </dd>
1192 <dt>ev_stat_stat (ev_stat *)</dt>
1193 <dd>
1194 <p>Updates the stat buffer immediately with new values. If you change the
1195watched path in your callback, you could call this fucntion to avoid
1196detecting this change (while introducing a race condition). Can also be
1197useful simply to find out the new values.</p>
1198 </dd>
1199 <dt>ev_statdata attr [read-only]</dt>
1200 <dd>
1201 <p>The most-recently detected attributes of the file. Although the type is of
1202<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1203suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1204was some error while <code>stat</code>ing the file.</p>
1205 </dd>
1206 <dt>ev_statdata prev [read-only]</dt>
1207 <dd>
1208 <p>The previous attributes of the file. The callback gets invoked whenever
1209<code>prev</code> != <code>attr</code>.</p>
1210 </dd>
1211 <dt>ev_tstamp interval [read-only]</dt>
1212 <dd>
1213 <p>The specified interval.</p>
1214 </dd>
1215 <dt>const char *path [read-only]</dt>
1216 <dd>
1217 <p>The filesystem path that is being watched.</p>
1218 </dd>
1219</dl>
1220<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1221<pre> static void
1222 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1223 {
1224 /* /etc/passwd changed in some way */
1225 if (w-&gt;attr.st_nlink)
1226 {
1227 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1228 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1229 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1230 }
1231 else
1232 /* you shalt not abuse printf for puts */
1233 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1234 &quot;if this is windows, they already arrived\n&quot;);
1235 }
1236
1237 ...
1238 ev_stat passwd;
1239
1240 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1241 ev_stat_start (loop, &amp;passwd);
1242
1243
1244
1245
1246</pre>
1247
1248</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> 1249<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"> 1250<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 1251<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 1252(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, 1253as 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 1254imagine) it will not be triggered. But when your process is idle all idle
… …
1101 1287
1102 1288
1103</pre> 1289</pre>
1104 1290
1105</div> 1291</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> 1292<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"> 1293<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: 1294<p>Prepare and check watchers are usually (but not always) used in tandem:
1109prepare watchers get invoked before the process blocks and check watchers 1295prepare watchers get invoked before the process blocks and check watchers
1110afterwards.</p> 1296afterwards.</p>
1297<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1298the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1299watchers. Other loops than the current one are fine, however. The
1300rationale behind this is that you do not need to check for recursion in
1301those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1302<code>ev_check</code> so if you have one watcher of each kind they will always be
1303called in pairs bracketing the blocking call.</p>
1111<p>Their main purpose is to integrate other event mechanisms into libev and 1304<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 1305their use is somewhat advanced. This could be used, for example, to track
1113variable changes, implement your own watchers, integrate net-snmp or a 1306variable changes, implement your own watchers, integrate net-snmp or a
1114coroutine library and lots more.</p> 1307coroutine library and lots more. They are also occasionally useful if
1308you cache some data and want to flush it before blocking (for example,
1309in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1310watcher).</p>
1115<p>This is done by examining in each prepare call which file descriptors need 1311<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 1312to 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 1313them 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 1314provide just this functionality). Then, in the check watcher you check for
1119any events that occured (by checking the pending status of all watchers 1315any events that occured (by checking the pending status of all watchers
… …
1135 <p>Initialises and configures the prepare or check watcher - they have no 1331 <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> 1332parameters 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> 1333macros, but using them is utterly, utterly and completely pointless.</p>
1138 </dd> 1334 </dd>
1139</dl> 1335</dl>
1140<p>Example: *TODO*.</p> 1336<p>Example: To include a library such as adns, you would add IO watchers
1337and a timeout watcher in a prepare handler, as required by libadns, and
1338in a check watcher, destroy them and call into libadns. What follows is
1339pseudo-code only of course:</p>
1340<pre> static ev_io iow [nfd];
1341 static ev_timer tw;
1141 1342
1343 static void
1344 io_cb (ev_loop *loop, ev_io *w, int revents)
1345 {
1346 // set the relevant poll flags
1347 // could also call adns_processreadable etc. here
1348 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1349 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1350 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1351 }
1142 1352
1353 // create io watchers for each fd and a timer before blocking
1354 static void
1355 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1356 {
1357 int timeout = 3600000;truct pollfd fds [nfd];
1358 // actual code will need to loop here and realloc etc.
1359 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1143 1360
1361 /* the callback is illegal, but won't be called as we stop during check */
1362 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1363 ev_timer_start (loop, &amp;tw);
1144 1364
1365 // create on ev_io per pollfd
1366 for (int i = 0; i &lt; nfd; ++i)
1367 {
1368 ev_io_init (iow + i, io_cb, fds [i].fd,
1369 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1370 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1145 1371
1372 fds [i].revents = 0;
1373 iow [i].data = fds + i;
1374 ev_io_start (loop, iow + i);
1375 }
1376 }
1377
1378 // stop all watchers after blocking
1379 static void
1380 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1381 {
1382 ev_timer_stop (loop, &amp;tw);
1383
1384 for (int i = 0; i &lt; nfd; ++i)
1385 ev_io_stop (loop, iow + i);
1386
1387 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1388 }
1389
1390
1391
1392
1393</pre>
1394
1146</div> 1395</div>
1147<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1396<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"> 1397<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 1398<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 1399into 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 1400loop, other types of watchers might be handled in a delayed or incorrect
1152fashion and must not be used).</p> 1401fashion and must not be used).</p>
… …
1219 <dt>ev_embed_sweep (loop, ev_embed *)</dt> 1468 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1220 <dd> 1469 <dd>
1221 <p>Make a single, non-blocking sweep over the embedded loop. This works 1470 <p>Make a single, non-blocking sweep over the embedded loop. This works
1222similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1471similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1223apropriate way for embedded loops.</p> 1472apropriate way for embedded loops.</p>
1473 </dd>
1474 <dt>struct ev_loop *loop [read-only]</dt>
1475 <dd>
1476 <p>The embedded event loop.</p>
1224 </dd> 1477 </dd>
1225</dl> 1478</dl>
1226 1479
1227 1480
1228 1481
… …
1378 </dd> 1631 </dd>
1379 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1632 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1380 <dd> 1633 <dd>
1381 <p>Invokes <code>ev_embed_sweep</code>.</p> 1634 <p>Invokes <code>ev_embed_sweep</code>.</p>
1382 </dd> 1635 </dd>
1636 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1637 <dd>
1638 <p>Invokes <code>ev_stat_stat</code>.</p>
1639 </dd>
1383 </dl> 1640 </dl>
1384 </p> 1641 </p>
1385 </dd> 1642 </dd>
1386</dl> 1643</dl>
1387<p>Example: Define a class with an IO and idle watcher, start one of them in 1644<p>Example: Define a class with an IO and idle watcher, start one of them in
… …
1402 } 1659 }
1403 1660
1404</pre> 1661</pre>
1405 1662
1406</div> 1663</div>
1664<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
1665<div id="EMBEDDING_CONTENT">
1666<p>Libev can (and often is) directly embedded into host
1667applications. Examples of applications that embed it include the Deliantra
1668Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1669and rxvt-unicode.</p>
1670<p>The goal is to enable you to just copy the neecssary files into your
1671source directory without having to change even a single line in them, so
1672you can easily upgrade by simply copying (or having a checked-out copy of
1673libev somewhere in your source tree).</p>
1674
1675</div>
1676<h2 id="FILESETS">FILESETS</h2>
1677<div id="FILESETS_CONTENT">
1678<p>Depending on what features you need you need to include one or more sets of files
1679in your app.</p>
1680
1681</div>
1682<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1683<div id="CORE_EVENT_LOOP_CONTENT">
1684<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1685configuration (no autoconf):</p>
1686<pre> #define EV_STANDALONE 1
1687 #include &quot;ev.c&quot;
1688
1689</pre>
1690<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1691single C source file only to provide the function implementations. To use
1692it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1693done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1694where you can put other configuration options):</p>
1695<pre> #define EV_STANDALONE 1
1696 #include &quot;ev.h&quot;
1697
1698</pre>
1699<p>Both header files and implementation files can be compiled with a C++
1700compiler (at least, thats a stated goal, and breakage will be treated
1701as a bug).</p>
1702<p>You need the following files in your source tree, or in a directory
1703in your include path (e.g. in libev/ when using -Ilibev):</p>
1704<pre> ev.h
1705 ev.c
1706 ev_vars.h
1707 ev_wrap.h
1708
1709 ev_win32.c required on win32 platforms only
1710
1711 ev_select.c only when select backend is enabled (which is by default)
1712 ev_poll.c only when poll backend is enabled (disabled by default)
1713 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1714 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1715 ev_port.c only when the solaris port backend is enabled (disabled by default)
1716
1717</pre>
1718<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1719to compile this single file.</p>
1720
1721</div>
1722<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1723<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1724<p>To include the libevent compatibility API, also include:</p>
1725<pre> #include &quot;event.c&quot;
1726
1727</pre>
1728<p>in the file including <cite>ev.c</cite>, and:</p>
1729<pre> #include &quot;event.h&quot;
1730
1731</pre>
1732<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1733<p>You need the following additional files for this:</p>
1734<pre> event.h
1735 event.c
1736
1737</pre>
1738
1739</div>
1740<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1741<div id="AUTOCONF_SUPPORT_CONTENT">
1742<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1743whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1744<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1745include <cite>config.h</cite> and configure itself accordingly.</p>
1746<p>For this of course you need the m4 file:</p>
1747<pre> libev.m4
1748
1749</pre>
1750
1751</div>
1752<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1753<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1754<p>Libev can be configured via a variety of preprocessor symbols you have to define
1755before including any of its files. The default is not to build for multiplicity
1756and only include the select backend.</p>
1757<dl>
1758 <dt>EV_STANDALONE</dt>
1759 <dd>
1760 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1761keeps libev from including <cite>config.h</cite>, and it also defines dummy
1762implementations for some libevent functions (such as logging, which is not
1763supported). It will also not define any of the structs usually found in
1764<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1765 </dd>
1766 <dt>EV_USE_MONOTONIC</dt>
1767 <dd>
1768 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1769monotonic clock option at both compiletime and runtime. Otherwise no use
1770of the monotonic clock option will be attempted. If you enable this, you
1771usually have to link against librt or something similar. Enabling it when
1772the functionality isn't available is safe, though, althoguh you have
1773to make sure you link against any libraries where the <code>clock_gettime</code>
1774function is hiding in (often <cite>-lrt</cite>).</p>
1775 </dd>
1776 <dt>EV_USE_REALTIME</dt>
1777 <dd>
1778 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1779realtime clock option at compiletime (and assume its availability at
1780runtime if successful). Otherwise no use of the realtime clock option will
1781be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1782(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1783in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1784 </dd>
1785 <dt>EV_USE_SELECT</dt>
1786 <dd>
1787 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1788<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1789other method takes over, select will be it. Otherwise the select backend
1790will not be compiled in.</p>
1791 </dd>
1792 <dt>EV_SELECT_USE_FD_SET</dt>
1793 <dd>
1794 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1795structure. This is useful if libev doesn't compile due to a missing
1796<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1797exotic systems. This usually limits the range of file descriptors to some
1798low limit such as 1024 or might have other limitations (winsocket only
1799allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1800influence the size of the <code>fd_set</code> used.</p>
1801 </dd>
1802 <dt>EV_SELECT_IS_WINSOCKET</dt>
1803 <dd>
1804 <p>When defined to <code>1</code>, the select backend will assume that
1805select/socket/connect etc. don't understand file descriptors but
1806wants osf handles on win32 (this is the case when the select to
1807be used is the winsock select). This means that it will call
1808<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1809it is assumed that all these functions actually work on fds, even
1810on win32. Should not be defined on non-win32 platforms.</p>
1811 </dd>
1812 <dt>EV_USE_POLL</dt>
1813 <dd>
1814 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1815backend. Otherwise it will be enabled on non-win32 platforms. It
1816takes precedence over select.</p>
1817 </dd>
1818 <dt>EV_USE_EPOLL</dt>
1819 <dd>
1820 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
1821<code>epoll</code>(7) backend. Its availability will be detected at runtime,
1822otherwise another method will be used as fallback. This is the
1823preferred backend for GNU/Linux systems.</p>
1824 </dd>
1825 <dt>EV_USE_KQUEUE</dt>
1826 <dd>
1827 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
1828<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
1829otherwise another method will be used as fallback. This is the preferred
1830backend for BSD and BSD-like systems, although on most BSDs kqueue only
1831supports some types of fds correctly (the only platform we found that
1832supports ptys for example was NetBSD), so kqueue might be compiled in, but
1833not be used unless explicitly requested. The best way to use it is to find
1834out whether kqueue supports your type of fd properly and use an embedded
1835kqueue loop.</p>
1836 </dd>
1837 <dt>EV_USE_PORT</dt>
1838 <dd>
1839 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
184010 port style backend. Its availability will be detected at runtime,
1841otherwise another method will be used as fallback. This is the preferred
1842backend for Solaris 10 systems.</p>
1843 </dd>
1844 <dt>EV_USE_DEVPOLL</dt>
1845 <dd>
1846 <p>reserved for future expansion, works like the USE symbols above.</p>
1847 </dd>
1848 <dt>EV_H</dt>
1849 <dd>
1850 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1851undefined 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
1852can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
1853 </dd>
1854 <dt>EV_CONFIG_H</dt>
1855 <dd>
1856 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
1857<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
1858<code>EV_H</code>, above.</p>
1859 </dd>
1860 <dt>EV_EVENT_H</dt>
1861 <dd>
1862 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
1863of how the <cite>event.h</cite> header can be found.</p>
1864 </dd>
1865 <dt>EV_PROTOTYPES</dt>
1866 <dd>
1867 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
1868prototypes, but still define all the structs and other symbols. This is
1869occasionally useful if you want to provide your own wrapper functions
1870around libev functions.</p>
1871 </dd>
1872 <dt>EV_MULTIPLICITY</dt>
1873 <dd>
1874 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
1875will have the <code>struct ev_loop *</code> as first argument, and you can create
1876additional independent event loops. Otherwise there will be no support
1877for multiple event loops and there is no first event loop pointer
1878argument. Instead, all functions act on the single default loop.</p>
1879 </dd>
1880 <dt>EV_PERIODIC_ENABLE</dt>
1881 <dd>
1882 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1883defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
1884code.</p>
1885 </dd>
1886 <dt>EV_EMBED_ENABLE</dt>
1887 <dd>
1888 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
1889defined to be <code>0</code>, then they are not.</p>
1890 </dd>
1891 <dt>EV_STAT_ENABLE</dt>
1892 <dd>
1893 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
1894defined to be <code>0</code>, then they are not.</p>
1895 </dd>
1896 <dt>EV_MINIMAL</dt>
1897 <dd>
1898 <p>If you need to shave off some kilobytes of code at the expense of some
1899speed, define this symbol to <code>1</code>. Currently only used for gcc to override
1900some inlining decisions, saves roughly 30% codesize of amd64.</p>
1901 </dd>
1902 <dt>EV_COMMON</dt>
1903 <dd>
1904 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1905this macro to a something else you can include more and other types of
1906members. You have to define it each time you include one of the files,
1907though, and it must be identical each time.</p>
1908 <p>For example, the perl EV module uses something like this:</p>
1909<pre> #define EV_COMMON \
1910 SV *self; /* contains this struct */ \
1911 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
1912
1913</pre>
1914 </dd>
1915 <dt>EV_CB_DECLARE (type)</dt>
1916 <dt>EV_CB_INVOKE (watcher, revents)</dt>
1917 <dt>ev_set_cb (ev, cb)</dt>
1918 <dd>
1919 <p>Can be used to change the callback member declaration in each watcher,
1920and the way callbacks are invoked and set. Must expand to a struct member
1921definition and a statement, respectively. See the <cite>ev.v</cite> header file for
1922their default definitions. One possible use for overriding these is to
1923avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
1924method calls instead of plain function calls in C++.</p>
1925
1926</div>
1927<h2 id="EXAMPLES">EXAMPLES</h2>
1928<div id="EXAMPLES_CONTENT">
1929 <p>For a real-world example of a program the includes libev
1930verbatim, you can have a look at the EV perl module
1931(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
1932the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
1933interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
1934will be compiled. It is pretty complex because it provides its own header
1935file.</p>
1936 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
1937that everybody includes and which overrides some autoconf choices:</p>
1938<pre> #define EV_USE_POLL 0
1939 #define EV_MULTIPLICITY 0
1940 #define EV_PERIODICS 0
1941 #define EV_CONFIG_H &lt;config.h&gt;
1942
1943 #include &quot;ev++.h&quot;
1944
1945</pre>
1946 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1947<pre> #include &quot;ev_cpp.h&quot;
1948 #include &quot;ev.c&quot;
1949
1950
1951
1952
1953</pre>
1954
1955</div>
1956<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
1957<div id="COMPLEXITIES_CONTENT">
1958 <p>In this section the complexities of (many of) the algorithms used inside
1959libev will be explained. For complexity discussions about backends see the
1960documentation for <code>ev_default_init</code>.</p>
1961 <p>
1962 <dl>
1963 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
1964 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
1965 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
1966 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
1967 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
1968 <dt>Finding the next timer per loop iteration: O(1)</dt>
1969 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
1970 <dt>Activating one watcher: O(1)</dt>
1971 </dl>
1972 </p>
1973
1974
1975
1976
1977
1978</div>
1407<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1979<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
1408<div id="AUTHOR_CONTENT"> 1980<div id="AUTHOR_CONTENT">
1409<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 1981 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1410 1982
1411</div> 1983</div>
1412</div></body> 1984</div></body>
1413</html> 1985</html>

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