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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 08:13:46 2007" /> 9 <meta name="created" content="Tue Nov 27 20:23:27 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 -->
… …
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>
40<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
39</ul> 41</ul>
40</li> 42</li>
41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 43<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 44<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 45<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
46<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
47<li><a href="#EMBEDDING">EMBEDDING</a>
48<ul><li><a href="#FILESETS">FILESETS</a>
49<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
50<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
51<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
52</ul>
53</li>
54<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
55<li><a href="#EXAMPLES">EXAMPLES</a></li>
56</ul>
57</li>
58<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
44<li><a href="#AUTHOR">AUTHOR</a> 59<li><a href="#AUTHOR">AUTHOR</a>
45</li> 60</li>
46</ul><hr /> 61</ul><hr />
47<!-- INDEX END --> 62<!-- INDEX END -->
48 63
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100(fractional) number of seconds since the (POSIX) epoch (somewhere near 115(fractional) number of seconds since the (POSIX) epoch (somewhere near
101the beginning of 1970, details are complicated, don't ask). This type is 116the beginning of 1970, details are complicated, don't ask). This type is
102called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 117called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
103to the <code>double</code> type in C, and when you need to do any calculations on 118to the <code>double</code> type in C, and when you need to do any calculations on
104it, you should treat it as such.</p> 119it, you should treat it as such.</p>
105
106
107
108
109 120
110</div> 121</div>
111<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
112<div id="GLOBAL_FUNCTIONS_CONTENT"> 123<div id="GLOBAL_FUNCTIONS_CONTENT">
113<p>These functions can be called anytime, even before initialising the 124<p>These functions can be called anytime, even before initialising the
… …
364</pre> 375</pre>
365 </dd> 376 </dd>
366 <dt>ev_default_destroy ()</dt> 377 <dt>ev_default_destroy ()</dt>
367 <dd> 378 <dd>
368 <p>Destroys the default loop again (frees all memory and kernel state 379 <p>Destroys the default loop again (frees all memory and kernel state
369etc.). This stops all registered event watchers (by not touching them in 380etc.). None of the active event watchers will be stopped in the normal
370any way whatsoever, although you cannot rely on this :).</p> 381sense, so e.g. <code>ev_is_active</code> might still return true. It is your
382responsibility to either stop all watchers cleanly yoursef <i>before</i>
383calling this function, or cope with the fact afterwards (which is usually
384the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
385for example).</p>
371 </dd> 386 </dd>
372 <dt>ev_loop_destroy (loop)</dt> 387 <dt>ev_loop_destroy (loop)</dt>
373 <dd> 388 <dd>
374 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 389 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
375earlier call to <code>ev_loop_new</code>.</p> 390earlier call to <code>ev_loop_new</code>.</p>
… …
498 513
499</pre> 514</pre>
500 </dd> 515 </dd>
501</dl> 516</dl>
502 517
518
519
520
521
503</div> 522</div>
504<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>
505<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 524<div id="ANATOMY_OF_A_WATCHER_CONTENT">
506<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
507interest 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
… …
566 </dd> 585 </dd>
567 <dt><code>EV_CHILD</code></dt> 586 <dt><code>EV_CHILD</code></dt>
568 <dd> 587 <dd>
569 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 588 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
570 </dd> 589 </dd>
590 <dt><code>EV_STAT</code></dt>
591 <dd>
592 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
593 </dd>
571 <dt><code>EV_IDLE</code></dt> 594 <dt><code>EV_IDLE</code></dt>
572 <dd> 595 <dd>
573 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 596 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
574 </dd> 597 </dd>
575 <dt><code>EV_PREPARE</code></dt> 598 <dt><code>EV_PREPARE</code></dt>
… …
580<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 603<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
581received events. Callbacks of both watcher types can start and stop as 604received events. Callbacks of both watcher types can start and stop as
582many watchers as they want, and all of them will be taken into account 605many watchers as they want, and all of them will be taken into account
583(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 606(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
584<code>ev_loop</code> from blocking).</p> 607<code>ev_loop</code> from blocking).</p>
608 </dd>
609 <dt><code>EV_EMBED</code></dt>
610 <dd>
611 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
612 </dd>
613 <dt><code>EV_FORK</code></dt>
614 <dd>
615 <p>The event loop has been resumed in the child process after fork (see
616<code>ev_fork</code>).</p>
585 </dd> 617 </dd>
586 <dt><code>EV_ERROR</code></dt> 618 <dt><code>EV_ERROR</code></dt>
587 <dd> 619 <dd>
588 <p>An unspecified error has occured, the watcher has been stopped. This might 620 <p>An unspecified error has occured, the watcher has been stopped. This might
589happen because the watcher could not be properly started because libev 621happen because the watcher could not be properly started because libev
… …
597programs, though, so beware.</p> 629programs, though, so beware.</p>
598 </dd> 630 </dd>
599</dl> 631</dl>
600 632
601</div> 633</div>
602<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2> 634<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
603<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2"> 635<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
604<p>In the following description, <code>TYPE</code> stands for the watcher type, 636<p>In the following description, <code>TYPE</code> stands for the watcher type,
605e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p> 637e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
606<dl> 638<dl>
607 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt> 639 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
608 <dd> 640 <dd>
… …
612the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the 644the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
613type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro 645type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
614which rolls both calls into one.</p> 646which rolls both calls into one.</p>
615 <p>You can reinitialise a watcher at any time as long as it has been stopped 647 <p>You can reinitialise a watcher at any time as long as it has been stopped
616(or never started) and there are no pending events outstanding.</p> 648(or never started) and there are no pending events outstanding.</p>
617 <p>The callbakc is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher, 649 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
618int revents)</code>.</p> 650int revents)</code>.</p>
619 </dd> 651 </dd>
620 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt> 652 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
621 <dd> 653 <dd>
622 <p>This macro initialises the type-specific parts of a watcher. You need to 654 <p>This macro initialises the type-specific parts of a watcher. You need to
… …
712 744
713</div> 745</div>
714<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 746<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
715<div id="WATCHER_TYPES_CONTENT"> 747<div id="WATCHER_TYPES_CONTENT">
716<p>This section describes each watcher in detail, but will not repeat 748<p>This section describes each watcher in detail, but will not repeat
717information given in the last section.</p> 749information given in the last section. Any initialisation/set macros,
750functions and members specific to the watcher type are explained.</p>
751<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
752while the watcher is active, you can look at the member and expect some
753sensible content, but you must not modify it (you can modify it while the
754watcher is stopped to your hearts content), or <i>[read-write]</i>, which
755means you can expect it to have some sensible content while the watcher
756is active, but you can also modify it. Modifying it may not do something
757sensible or take immediate effect (or do anything at all), but libev will
758not crash or malfunction in any way.</p>
718 759
719 760
720 761
721 762
722 763
723</div> 764</div>
724<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 765<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
725<div id="code_ev_io_code_is_this_file_descrip-2"> 766<div id="code_ev_io_code_is_this_file_descrip-2">
726<p>I/O watchers check whether a file descriptor is readable or writable 767<p>I/O watchers check whether a file descriptor is readable or writable
727in each iteration of the event loop (This behaviour is called 768in each iteration of the event loop, or, more precisely, when reading
728level-triggering because you keep receiving events as long as the 769would not block the process and writing would at least be able to write
729condition persists. Remember you can stop the watcher if you don't want to 770some data. This behaviour is called level-triggering because you keep
730act on the event and neither want to receive future events).</p> 771receiving events as long as the condition persists. Remember you can stop
772the watcher if you don't want to act on the event and neither want to
773receive future events.</p>
731<p>In general you can register as many read and/or write event watchers per 774<p>In general you can register as many read and/or write event watchers per
732fd as you want (as long as you don't confuse yourself). Setting all file 775fd as you want (as long as you don't confuse yourself). Setting all file
733descriptors to non-blocking mode is also usually a good idea (but not 776descriptors to non-blocking mode is also usually a good idea (but not
734required if you know what you are doing).</p> 777required if you know what you are doing).</p>
735<p>You have to be careful with dup'ed file descriptors, though. Some backends 778<p>You have to be careful with dup'ed file descriptors, though. Some backends
736(the linux epoll backend is a notable example) cannot handle dup'ed file 779(the linux epoll backend is a notable example) cannot handle dup'ed file
737descriptors correctly if you register interest in two or more fds pointing 780descriptors correctly if you register interest in two or more fds pointing
738to the same underlying file/socket etc. description (that is, they share 781to the same underlying file/socket/etc. description (that is, they share
739the same underlying &quot;file open&quot;).</p> 782the same underlying &quot;file open&quot;).</p>
740<p>If you must do this, then force the use of a known-to-be-good backend 783<p>If you must do this, then force the use of a known-to-be-good backend
741(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and 784(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
742<code>EVBACKEND_POLL</code>).</p> 785<code>EVBACKEND_POLL</code>).</p>
786<p>Another thing you have to watch out for is that it is quite easy to
787receive &quot;spurious&quot; readyness notifications, that is your callback might
788be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
789because there is no data. Not only are some backends known to create a
790lot of those (for example solaris ports), it is very easy to get into
791this situation even with a relatively standard program structure. Thus
792it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
793<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
794<p>If you cannot run the fd in non-blocking mode (for example you should not
795play around with an Xlib connection), then you have to seperately re-test
796wether a file descriptor is really ready with a known-to-be good interface
797such as poll (fortunately in our Xlib example, Xlib already does this on
798its own, so its quite safe to use).</p>
743<dl> 799<dl>
744 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 800 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
745 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 801 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
746 <dd> 802 <dd>
747 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 803 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
748events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 804rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
749EV_WRITE</code> to receive the given events.</p> 805<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
750 <p>Please note that most of the more scalable backend mechanisms (for example 806 </dd>
751epoll and solaris ports) can result in spurious readyness notifications 807 <dt>int fd [read-only]</dt>
752for file descriptors, so you practically need to use non-blocking I/O (and 808 <dd>
753treat callback invocation as hint only), or retest separately with a safe 809 <p>The file descriptor being watched.</p>
754interface before doing I/O (XLib can do this), or force the use of either 810 </dd>
755<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 811 <dt>int events [read-only]</dt>
756problem. Also note that it is quite easy to have your callback invoked 812 <dd>
757when the readyness condition is no longer valid even when employing 813 <p>The events being watched.</p>
758typical ways of handling events, so its a good idea to use non-blocking
759I/O unconditionally.</p>
760 </dd> 814 </dd>
761</dl> 815</dl>
762<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 816<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
763readable, but only once. Since it is likely line-buffered, you could 817readable, but only once. Since it is likely line-buffered, you could
764attempt to read a whole line in the callback:</p> 818attempt to read a whole line in the callback:</p>
… …
780 834
781 835
782</pre> 836</pre>
783 837
784</div> 838</div>
785<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 839<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
786<div id="code_ev_timer_code_relative_and_opti-2"> 840<div id="code_ev_timer_code_relative_and_opti-2">
787<p>Timer watchers are simple relative timers that generate an event after a 841<p>Timer watchers are simple relative timers that generate an event after a
788given time, and optionally repeating in regular intervals after that.</p> 842given time, and optionally repeating in regular intervals after that.</p>
789<p>The timers are based on real time, that is, if you register an event that 843<p>The timers are based on real time, that is, if you register an event that
790times out after an hour and you reset your system clock to last years 844times out after an hour and you reset your system clock to last years
… …
822repeating. The exact semantics are:</p> 876repeating. The exact semantics are:</p>
823 <p>If the timer is started but nonrepeating, stop it.</p> 877 <p>If the timer is started but nonrepeating, stop it.</p>
824 <p>If the timer is repeating, either start it if necessary (with the repeat 878 <p>If the timer is repeating, either start it if necessary (with the repeat
825value), or reset the running timer to the repeat value.</p> 879value), or reset the running timer to the repeat value.</p>
826 <p>This sounds a bit complicated, but here is a useful and typical 880 <p>This sounds a bit complicated, but here is a useful and typical
827example: Imagine you have a tcp connection and you want a so-called idle 881example: Imagine you have a tcp connection and you want a so-called
828timeout, that is, you want to be called when there have been, say, 60 882idle timeout, that is, you want to be called when there have been,
829seconds of inactivity on the socket. The easiest way to do this is to 883say, 60 seconds of inactivity on the socket. The easiest way to do
830configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 884this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
831time you successfully read or write some data. If you go into an idle 885<code>ev_timer_again</code> each time you successfully read or write some data. If
832state where you do not expect data to travel on the socket, you can stop 886you go into an idle state where you do not expect data to travel on the
833the timer, and again will automatically restart it if need be.</p> 887socket, you can stop the timer, and again will automatically restart it if
888need be.</p>
889 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
890and only ever use the <code>repeat</code> value:</p>
891<pre> ev_timer_init (timer, callback, 0., 5.);
892 ev_timer_again (loop, timer);
893 ...
894 timer-&gt;again = 17.;
895 ev_timer_again (loop, timer);
896 ...
897 timer-&gt;again = 10.;
898 ev_timer_again (loop, timer);
899
900</pre>
901 <p>This is more efficient then stopping/starting the timer eahc time you want
902to modify its timeout value.</p>
903 </dd>
904 <dt>ev_tstamp repeat [read-write]</dt>
905 <dd>
906 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
907or <code>ev_timer_again</code> is called and determines the next timeout (if any),
908which is also when any modifications are taken into account.</p>
834 </dd> 909 </dd>
835</dl> 910</dl>
836<p>Example: create a timer that fires after 60 seconds.</p> 911<p>Example: create a timer that fires after 60 seconds.</p>
837<pre> static void 912<pre> static void
838 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 913 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
866 941
867 942
868</pre> 943</pre>
869 944
870</div> 945</div>
871<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 946<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
872<div id="code_ev_periodic_code_to_cron_or_not-2"> 947<div id="code_ev_periodic_code_to_cron_or_not-2">
873<p>Periodic watchers are also timers of a kind, but they are very versatile 948<p>Periodic watchers are also timers of a kind, but they are very versatile
874(and unfortunately a bit complex).</p> 949(and unfortunately a bit complex).</p>
875<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 950<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
876but on wallclock time (absolute time). You can tell a periodic watcher 951but on wallclock time (absolute time). You can tell a periodic watcher
877to trigger &quot;at&quot; some specific point in time. For example, if you tell a 952to trigger &quot;at&quot; some specific point in time. For example, if you tell a
878periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 953periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
879+ 10.&gt;) and then reset your system clock to the last year, then it will 954+ 10.</code>) and then reset your system clock to the last year, then it will
880take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 955take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
881roughly 10 seconds later and of course not if you reset your system time 956roughly 10 seconds later and of course not if you reset your system time
882again).</p> 957again).</p>
883<p>They can also be used to implement vastly more complex timers, such as 958<p>They can also be used to implement vastly more complex timers, such as
884triggering an event on eahc midnight, local time.</p> 959triggering an event on eahc midnight, local time.</p>
… …
956 <p>Simply stops and restarts the periodic watcher again. This is only useful 1031 <p>Simply stops and restarts the periodic watcher again. This is only useful
957when you changed some parameters or the reschedule callback would return 1032when you changed some parameters or the reschedule callback would return
958a different time than the last time it was called (e.g. in a crond like 1033a different time than the last time it was called (e.g. in a crond like
959program when the crontabs have changed).</p> 1034program when the crontabs have changed).</p>
960 </dd> 1035 </dd>
1036 <dt>ev_tstamp interval [read-write]</dt>
1037 <dd>
1038 <p>The current interval value. Can be modified any time, but changes only
1039take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1040called.</p>
1041 </dd>
1042 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1043 <dd>
1044 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1045switched off. Can be changed any time, but changes only take effect when
1046the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1047 </dd>
961</dl> 1048</dl>
962<p>Example: call a callback every hour, or, more precisely, whenever the 1049<p>Example: call a callback every hour, or, more precisely, whenever the
963system clock is divisible by 3600. The callback invocation times have 1050system clock is divisible by 3600. The callback invocation times have
964potentially a lot of jittering, but good long-term stability.</p> 1051potentially a lot of jittering, but good long-term stability.</p>
965<pre> static void 1052<pre> static void
… …
995 1082
996 1083
997</pre> 1084</pre>
998 1085
999</div> 1086</div>
1000<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1087<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
1001<div id="code_ev_signal_code_signal_me_when_a-2"> 1088<div id="code_ev_signal_code_signal_me_when_a-2">
1002<p>Signal watchers will trigger an event when the process receives a specific 1089<p>Signal watchers will trigger an event when the process receives a specific
1003signal one or more times. Even though signals are very asynchronous, libev 1090signal one or more times. Even though signals are very asynchronous, libev
1004will try it's best to deliver signals synchronously, i.e. as part of the 1091will try it's best to deliver signals synchronously, i.e. as part of the
1005normal event processing, like any other event.</p> 1092normal event processing, like any other event.</p>
… …
1014 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1101 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1015 <dd> 1102 <dd>
1016 <p>Configures the watcher to trigger on the given signal number (usually one 1103 <p>Configures the watcher to trigger on the given signal number (usually one
1017of the <code>SIGxxx</code> constants).</p> 1104of the <code>SIGxxx</code> constants).</p>
1018 </dd> 1105 </dd>
1106 <dt>int signum [read-only]</dt>
1107 <dd>
1108 <p>The signal the watcher watches out for.</p>
1109 </dd>
1019</dl> 1110</dl>
1020 1111
1021 1112
1022 1113
1023 1114
1024 1115
1025</div> 1116</div>
1026<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1117<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
1027<div id="code_ev_child_code_wait_for_pid_stat-2"> 1118<div id="code_ev_child_code_watch_out_for_pro-2">
1028<p>Child watchers trigger when your process receives a SIGCHLD in response to 1119<p>Child watchers trigger when your process receives a SIGCHLD in response to
1029some child status changes (most typically when a child of yours dies).</p> 1120some child status changes (most typically when a child of yours dies).</p>
1030<dl> 1121<dl>
1031 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1122 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1032 <dt>ev_child_set (ev_child *, int pid)</dt> 1123 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
1035<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 1126<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
1036at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1127at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1037the status word (use the macros from <code>sys/wait.h</code> and see your systems 1128the status word (use the macros from <code>sys/wait.h</code> and see your systems
1038<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1129<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1039process causing the status change.</p> 1130process causing the status change.</p>
1131 </dd>
1132 <dt>int pid [read-only]</dt>
1133 <dd>
1134 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1135 </dd>
1136 <dt>int rpid [read-write]</dt>
1137 <dd>
1138 <p>The process id that detected a status change.</p>
1139 </dd>
1140 <dt>int rstatus [read-write]</dt>
1141 <dd>
1142 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1143<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1040 </dd> 1144 </dd>
1041</dl> 1145</dl>
1042<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1146<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
1043<pre> static void 1147<pre> static void
1044 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1148 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1054 1158
1055 1159
1056</pre> 1160</pre>
1057 1161
1058</div> 1162</div>
1163<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1164<div id="code_ev_stat_code_did_the_file_attri-2">
1165<p>This watches a filesystem path for attribute changes. That is, it calls
1166<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1167compared to the last time, invoking the callback if it did.</p>
1168<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1169not exist&quot; is a status change like any other. The condition &quot;path does
1170not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1171otherwise always forced to be at least one) and all the other fields of
1172the stat buffer having unspecified contents.</p>
1173<p>Since there is no standard to do this, the portable implementation simply
1174calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You
1175can specify a recommended polling interval for this case. If you specify
1176a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1177unspecified default</i> value will be used (which you can expect to be around
1178five seconds, although this might change dynamically). Libev will also
1179impose a minimum interval which is currently around <code>0.1</code>, but thats
1180usually overkill.</p>
1181<p>This watcher type is not meant for massive numbers of stat watchers,
1182as even with OS-supported change notifications, this can be
1183resource-intensive.</p>
1184<p>At the time of this writing, no specific OS backends are implemented, but
1185if demand increases, at least a kqueue and inotify backend will be added.</p>
1186<dl>
1187 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1188 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1189 <dd>
1190 <p>Configures the watcher to wait for status changes of the given
1191<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1192be detected and should normally be specified as <code>0</code> to let libev choose
1193a suitable value. The memory pointed to by <code>path</code> must point to the same
1194path for as long as the watcher is active.</p>
1195 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1196relative to the attributes at the time the watcher was started (or the
1197last change was detected).</p>
1198 </dd>
1199 <dt>ev_stat_stat (ev_stat *)</dt>
1200 <dd>
1201 <p>Updates the stat buffer immediately with new values. If you change the
1202watched path in your callback, you could call this fucntion to avoid
1203detecting this change (while introducing a race condition). Can also be
1204useful simply to find out the new values.</p>
1205 </dd>
1206 <dt>ev_statdata attr [read-only]</dt>
1207 <dd>
1208 <p>The most-recently detected attributes of the file. Although the type is of
1209<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1210suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1211was some error while <code>stat</code>ing the file.</p>
1212 </dd>
1213 <dt>ev_statdata prev [read-only]</dt>
1214 <dd>
1215 <p>The previous attributes of the file. The callback gets invoked whenever
1216<code>prev</code> != <code>attr</code>.</p>
1217 </dd>
1218 <dt>ev_tstamp interval [read-only]</dt>
1219 <dd>
1220 <p>The specified interval.</p>
1221 </dd>
1222 <dt>const char *path [read-only]</dt>
1223 <dd>
1224 <p>The filesystem path that is being watched.</p>
1225 </dd>
1226</dl>
1227<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1228<pre> static void
1229 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1230 {
1231 /* /etc/passwd changed in some way */
1232 if (w-&gt;attr.st_nlink)
1233 {
1234 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1235 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1236 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1237 }
1238 else
1239 /* you shalt not abuse printf for puts */
1240 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1241 &quot;if this is windows, they already arrived\n&quot;);
1242 }
1243
1244 ...
1245 ev_stat passwd;
1246
1247 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1248 ev_stat_start (loop, &amp;passwd);
1249
1250
1251
1252
1253</pre>
1254
1255</div>
1059<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1256<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1060<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1257<div id="code_ev_idle_code_when_you_ve_got_no-2">
1061<p>Idle watchers trigger events when there are no other events are pending 1258<p>Idle watchers trigger events when there are no other events are pending
1062(prepare, check and other idle watchers do not count). That is, as long 1259(prepare, check and other idle watchers do not count). That is, as long
1063as your process is busy handling sockets or timeouts (or even signals, 1260as your process is busy handling sockets or timeouts (or even signals,
1064imagine) it will not be triggered. But when your process is idle all idle 1261imagine) it will not be triggered. But when your process is idle all idle
… …
1097 1294
1098 1295
1099</pre> 1296</pre>
1100 1297
1101</div> 1298</div>
1102<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1299<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1103<div id="code_ev_prepare_code_and_code_ev_che-2"> 1300<div id="code_ev_prepare_code_and_code_ev_che-2">
1104<p>Prepare and check watchers are usually (but not always) used in tandem: 1301<p>Prepare and check watchers are usually (but not always) used in tandem:
1105prepare watchers get invoked before the process blocks and check watchers 1302prepare watchers get invoked before the process blocks and check watchers
1106afterwards.</p> 1303afterwards.</p>
1304<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1305the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1306watchers. Other loops than the current one are fine, however. The
1307rationale behind this is that you do not need to check for recursion in
1308those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1309<code>ev_check</code> so if you have one watcher of each kind they will always be
1310called in pairs bracketing the blocking call.</p>
1107<p>Their main purpose is to integrate other event mechanisms into libev and 1311<p>Their main purpose is to integrate other event mechanisms into libev and
1108their use is somewhat advanced. This could be used, for example, to track 1312their use is somewhat advanced. This could be used, for example, to track
1109variable changes, implement your own watchers, integrate net-snmp or a 1313variable changes, implement your own watchers, integrate net-snmp or a
1110coroutine library and lots more.</p> 1314coroutine library and lots more. They are also occasionally useful if
1315you cache some data and want to flush it before blocking (for example,
1316in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1317watcher).</p>
1111<p>This is done by examining in each prepare call which file descriptors need 1318<p>This is done by examining in each prepare call which file descriptors need
1112to be watched by the other library, registering <code>ev_io</code> watchers for 1319to be watched by the other library, registering <code>ev_io</code> watchers for
1113them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1320them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1114provide just this functionality). Then, in the check watcher you check for 1321provide just this functionality). Then, in the check watcher you check for
1115any events that occured (by checking the pending status of all watchers 1322any events that occured (by checking the pending status of all watchers
… …
1131 <p>Initialises and configures the prepare or check watcher - they have no 1338 <p>Initialises and configures the prepare or check watcher - they have no
1132parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1339parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1133macros, but using them is utterly, utterly and completely pointless.</p> 1340macros, but using them is utterly, utterly and completely pointless.</p>
1134 </dd> 1341 </dd>
1135</dl> 1342</dl>
1136<p>Example: *TODO*.</p> 1343<p>Example: To include a library such as adns, you would add IO watchers
1344and a timeout watcher in a prepare handler, as required by libadns, and
1345in a check watcher, destroy them and call into libadns. What follows is
1346pseudo-code only of course:</p>
1347<pre> static ev_io iow [nfd];
1348 static ev_timer tw;
1137 1349
1350 static void
1351 io_cb (ev_loop *loop, ev_io *w, int revents)
1352 {
1353 // set the relevant poll flags
1354 // could also call adns_processreadable etc. here
1355 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1356 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1357 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1358 }
1138 1359
1360 // create io watchers for each fd and a timer before blocking
1361 static void
1362 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1363 {
1364 int timeout = 3600000;truct pollfd fds [nfd];
1365 // actual code will need to loop here and realloc etc.
1366 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1139 1367
1368 /* the callback is illegal, but won't be called as we stop during check */
1369 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1370 ev_timer_start (loop, &amp;tw);
1140 1371
1372 // create on ev_io per pollfd
1373 for (int i = 0; i &lt; nfd; ++i)
1374 {
1375 ev_io_init (iow + i, io_cb, fds [i].fd,
1376 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1377 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1141 1378
1379 fds [i].revents = 0;
1380 iow [i].data = fds + i;
1381 ev_io_start (loop, iow + i);
1382 }
1383 }
1384
1385 // stop all watchers after blocking
1386 static void
1387 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1388 {
1389 ev_timer_stop (loop, &amp;tw);
1390
1391 for (int i = 0; i &lt; nfd; ++i)
1392 ev_io_stop (loop, iow + i);
1393
1394 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1395 }
1396
1397
1398
1399
1400</pre>
1401
1142</div> 1402</div>
1143<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1403<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1144<div id="code_ev_embed_code_when_one_backend_-2"> 1404<div id="code_ev_embed_code_when_one_backend_-2">
1145<p>This is a rather advanced watcher type that lets you embed one event loop 1405<p>This is a rather advanced watcher type that lets you embed one event loop
1146into another (currently only <code>ev_io</code> events are supported in the embedded 1406into another (currently only <code>ev_io</code> events are supported in the embedded
1147loop, other types of watchers might be handled in a delayed or incorrect 1407loop, other types of watchers might be handled in a delayed or incorrect
1148fashion and must not be used).</p> 1408fashion and must not be used).</p>
… …
1216 <dd> 1476 <dd>
1217 <p>Make a single, non-blocking sweep over the embedded loop. This works 1477 <p>Make a single, non-blocking sweep over the embedded loop. This works
1218similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1478similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1219apropriate way for embedded loops.</p> 1479apropriate way for embedded loops.</p>
1220 </dd> 1480 </dd>
1481 <dt>struct ev_loop *loop [read-only]</dt>
1482 <dd>
1483 <p>The embedded event loop.</p>
1484 </dd>
1485</dl>
1486
1487
1488
1489
1490
1491</div>
1492<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
1493<div id="code_ev_fork_code_the_audacity_to_re-2">
1494<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1495whoever is a good citizen cared to tell libev about it by calling
1496<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1497event loop blocks next and before <code>ev_check</code> watchers are being called,
1498and only in the child after the fork. If whoever good citizen calling
1499<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1500handlers will be invoked, too, of course.</p>
1501<dl>
1502 <dt>ev_fork_init (ev_signal *, callback)</dt>
1503 <dd>
1504 <p>Initialises and configures the fork watcher - it has no parameters of any
1505kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1506believe me.</p>
1507 </dd>
1221</dl> 1508</dl>
1222 1509
1223 1510
1224 1511
1225 1512
… …
1302</dl> 1589</dl>
1303 1590
1304</div> 1591</div>
1305<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1592<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
1306<div id="C_SUPPORT_CONTENT"> 1593<div id="C_SUPPORT_CONTENT">
1307<p>TBD.</p> 1594<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1595you to use some convinience methods to start/stop watchers and also change
1596the callback model to a model using method callbacks on objects.</p>
1597<p>To use it,</p>
1598<pre> #include &lt;ev++.h&gt;
1599
1600</pre>
1601<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1602and puts all of its definitions (many of them macros) into the global
1603namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1604<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1605<code>EV_MULTIPLICITY</code>.</p>
1606<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1607<dl>
1608 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1609 <dd>
1610 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1611macros from <cite>ev.h</cite>.</p>
1612 </dd>
1613 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1614 <dd>
1615 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1616 </dd>
1617 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1618 <dd>
1619 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1620the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1621which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1622defines by many implementations.</p>
1623 <p>All of those classes have these methods:</p>
1624 <p>
1625 <dl>
1626 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1627 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1628 <dt>ev::TYPE::~TYPE</dt>
1629 <dd>
1630 <p>The constructor takes a pointer to an object and a method pointer to
1631the event handler callback to call in this class. The constructor calls
1632<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1633before starting it. If you do not specify a loop then the constructor
1634automatically associates the default loop with this watcher.</p>
1635 <p>The destructor automatically stops the watcher if it is active.</p>
1636 </dd>
1637 <dt>w-&gt;set (struct ev_loop *)</dt>
1638 <dd>
1639 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1640do this when the watcher is inactive (and not pending either).</p>
1641 </dd>
1642 <dt>w-&gt;set ([args])</dt>
1643 <dd>
1644 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1645called at least once. Unlike the C counterpart, an active watcher gets
1646automatically stopped and restarted.</p>
1647 </dd>
1648 <dt>w-&gt;start ()</dt>
1649 <dd>
1650 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1651constructor already takes the loop.</p>
1652 </dd>
1653 <dt>w-&gt;stop ()</dt>
1654 <dd>
1655 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1656 </dd>
1657 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1658 <dd>
1659 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1660<code>ev_TYPE_again</code> function.</p>
1661 </dd>
1662 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1663 <dd>
1664 <p>Invokes <code>ev_embed_sweep</code>.</p>
1665 </dd>
1666 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1667 <dd>
1668 <p>Invokes <code>ev_stat_stat</code>.</p>
1669 </dd>
1670 </dl>
1671 </p>
1672 </dd>
1673</dl>
1674<p>Example: Define a class with an IO and idle watcher, start one of them in
1675the constructor.</p>
1676<pre> class myclass
1677 {
1678 ev_io io; void io_cb (ev::io &amp;w, int revents);
1679 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1680
1681 myclass ();
1682 }
1683
1684 myclass::myclass (int fd)
1685 : io (this, &amp;myclass::io_cb),
1686 idle (this, &amp;myclass::idle_cb)
1687 {
1688 io.start (fd, ev::READ);
1689 }
1690
1691
1692
1693
1694</pre>
1695
1696</div>
1697<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p>
1698<div id="MACRO_MAGIC_CONTENT">
1699<p>Libev can be compiled with a variety of options, the most fundemantal is
1700<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1701callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1702<p>To make it easier to write programs that cope with either variant, the
1703following macros are defined:</p>
1704<dl>
1705 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1706 <dd>
1707 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1708loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1709<code>EV_A_</code> is used when other arguments are following. Example:</p>
1710<pre> ev_unref (EV_A);
1711 ev_timer_add (EV_A_ watcher);
1712 ev_loop (EV_A_ 0);
1713
1714</pre>
1715 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1716which is often provided by the following macro.</p>
1717 </dd>
1718 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1719 <dd>
1720 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1721loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1722<code>EV_P_</code> is used when other parameters are following. Example:</p>
1723<pre> // this is how ev_unref is being declared
1724 static void ev_unref (EV_P);
1725
1726 // this is how you can declare your typical callback
1727 static void cb (EV_P_ ev_timer *w, int revents)
1728
1729</pre>
1730 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1731suitable for use with <code>EV_A</code>.</p>
1732 </dd>
1733 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1734 <dd>
1735 <p>Similar to the other two macros, this gives you the value of the default
1736loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1737 </dd>
1738</dl>
1739<p>Example: Declare and initialise a check watcher, working regardless of
1740wether multiple loops are supported or not.</p>
1741<pre> static void
1742 check_cb (EV_P_ ev_timer *w, int revents)
1743 {
1744 ev_check_stop (EV_A_ w);
1745 }
1746
1747 ev_check check;
1748 ev_check_init (&amp;check, check_cb);
1749 ev_check_start (EV_DEFAULT_ &amp;check);
1750 ev_loop (EV_DEFAULT_ 0);
1751
1752
1753
1754
1755</pre>
1756
1757</div>
1758<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
1759<div id="EMBEDDING_CONTENT">
1760<p>Libev can (and often is) directly embedded into host
1761applications. Examples of applications that embed it include the Deliantra
1762Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1763and rxvt-unicode.</p>
1764<p>The goal is to enable you to just copy the neecssary files into your
1765source directory without having to change even a single line in them, so
1766you can easily upgrade by simply copying (or having a checked-out copy of
1767libev somewhere in your source tree).</p>
1768
1769</div>
1770<h2 id="FILESETS">FILESETS</h2>
1771<div id="FILESETS_CONTENT">
1772<p>Depending on what features you need you need to include one or more sets of files
1773in your app.</p>
1774
1775</div>
1776<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1777<div id="CORE_EVENT_LOOP_CONTENT">
1778<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1779configuration (no autoconf):</p>
1780<pre> #define EV_STANDALONE 1
1781 #include &quot;ev.c&quot;
1782
1783</pre>
1784<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1785single C source file only to provide the function implementations. To use
1786it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1787done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1788where you can put other configuration options):</p>
1789<pre> #define EV_STANDALONE 1
1790 #include &quot;ev.h&quot;
1791
1792</pre>
1793<p>Both header files and implementation files can be compiled with a C++
1794compiler (at least, thats a stated goal, and breakage will be treated
1795as a bug).</p>
1796<p>You need the following files in your source tree, or in a directory
1797in your include path (e.g. in libev/ when using -Ilibev):</p>
1798<pre> ev.h
1799 ev.c
1800 ev_vars.h
1801 ev_wrap.h
1802
1803 ev_win32.c required on win32 platforms only
1804
1805 ev_select.c only when select backend is enabled (which is by default)
1806 ev_poll.c only when poll backend is enabled (disabled by default)
1807 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1808 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1809 ev_port.c only when the solaris port backend is enabled (disabled by default)
1810
1811</pre>
1812<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1813to compile this single file.</p>
1814
1815</div>
1816<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1817<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1818<p>To include the libevent compatibility API, also include:</p>
1819<pre> #include &quot;event.c&quot;
1820
1821</pre>
1822<p>in the file including <cite>ev.c</cite>, and:</p>
1823<pre> #include &quot;event.h&quot;
1824
1825</pre>
1826<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1827<p>You need the following additional files for this:</p>
1828<pre> event.h
1829 event.c
1830
1831</pre>
1832
1833</div>
1834<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1835<div id="AUTOCONF_SUPPORT_CONTENT">
1836<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1837whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1838<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1839include <cite>config.h</cite> and configure itself accordingly.</p>
1840<p>For this of course you need the m4 file:</p>
1841<pre> libev.m4
1842
1843</pre>
1844
1845</div>
1846<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1847<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1848<p>Libev can be configured via a variety of preprocessor symbols you have to define
1849before including any of its files. The default is not to build for multiplicity
1850and only include the select backend.</p>
1851<dl>
1852 <dt>EV_STANDALONE</dt>
1853 <dd>
1854 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1855keeps libev from including <cite>config.h</cite>, and it also defines dummy
1856implementations for some libevent functions (such as logging, which is not
1857supported). It will also not define any of the structs usually found in
1858<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1859 </dd>
1860 <dt>EV_USE_MONOTONIC</dt>
1861 <dd>
1862 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1863monotonic clock option at both compiletime and runtime. Otherwise no use
1864of the monotonic clock option will be attempted. If you enable this, you
1865usually have to link against librt or something similar. Enabling it when
1866the functionality isn't available is safe, though, althoguh you have
1867to make sure you link against any libraries where the <code>clock_gettime</code>
1868function is hiding in (often <cite>-lrt</cite>).</p>
1869 </dd>
1870 <dt>EV_USE_REALTIME</dt>
1871 <dd>
1872 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1873realtime clock option at compiletime (and assume its availability at
1874runtime if successful). Otherwise no use of the realtime clock option will
1875be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1876(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1877in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1878 </dd>
1879 <dt>EV_USE_SELECT</dt>
1880 <dd>
1881 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1882<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1883other method takes over, select will be it. Otherwise the select backend
1884will not be compiled in.</p>
1885 </dd>
1886 <dt>EV_SELECT_USE_FD_SET</dt>
1887 <dd>
1888 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1889structure. This is useful if libev doesn't compile due to a missing
1890<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1891exotic systems. This usually limits the range of file descriptors to some
1892low limit such as 1024 or might have other limitations (winsocket only
1893allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1894influence the size of the <code>fd_set</code> used.</p>
1895 </dd>
1896 <dt>EV_SELECT_IS_WINSOCKET</dt>
1897 <dd>
1898 <p>When defined to <code>1</code>, the select backend will assume that
1899select/socket/connect etc. don't understand file descriptors but
1900wants osf handles on win32 (this is the case when the select to
1901be used is the winsock select). This means that it will call
1902<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1903it is assumed that all these functions actually work on fds, even
1904on win32. Should not be defined on non-win32 platforms.</p>
1905 </dd>
1906 <dt>EV_USE_POLL</dt>
1907 <dd>
1908 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1909backend. Otherwise it will be enabled on non-win32 platforms. It
1910takes precedence over select.</p>
1911 </dd>
1912 <dt>EV_USE_EPOLL</dt>
1913 <dd>
1914 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
1915<code>epoll</code>(7) backend. Its availability will be detected at runtime,
1916otherwise another method will be used as fallback. This is the
1917preferred backend for GNU/Linux systems.</p>
1918 </dd>
1919 <dt>EV_USE_KQUEUE</dt>
1920 <dd>
1921 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
1922<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
1923otherwise another method will be used as fallback. This is the preferred
1924backend for BSD and BSD-like systems, although on most BSDs kqueue only
1925supports some types of fds correctly (the only platform we found that
1926supports ptys for example was NetBSD), so kqueue might be compiled in, but
1927not be used unless explicitly requested. The best way to use it is to find
1928out whether kqueue supports your type of fd properly and use an embedded
1929kqueue loop.</p>
1930 </dd>
1931 <dt>EV_USE_PORT</dt>
1932 <dd>
1933 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
193410 port style backend. Its availability will be detected at runtime,
1935otherwise another method will be used as fallback. This is the preferred
1936backend for Solaris 10 systems.</p>
1937 </dd>
1938 <dt>EV_USE_DEVPOLL</dt>
1939 <dd>
1940 <p>reserved for future expansion, works like the USE symbols above.</p>
1941 </dd>
1942 <dt>EV_H</dt>
1943 <dd>
1944 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1945undefined 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
1946can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
1947 </dd>
1948 <dt>EV_CONFIG_H</dt>
1949 <dd>
1950 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
1951<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
1952<code>EV_H</code>, above.</p>
1953 </dd>
1954 <dt>EV_EVENT_H</dt>
1955 <dd>
1956 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
1957of how the <cite>event.h</cite> header can be found.</p>
1958 </dd>
1959 <dt>EV_PROTOTYPES</dt>
1960 <dd>
1961 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
1962prototypes, but still define all the structs and other symbols. This is
1963occasionally useful if you want to provide your own wrapper functions
1964around libev functions.</p>
1965 </dd>
1966 <dt>EV_MULTIPLICITY</dt>
1967 <dd>
1968 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
1969will have the <code>struct ev_loop *</code> as first argument, and you can create
1970additional independent event loops. Otherwise there will be no support
1971for multiple event loops and there is no first event loop pointer
1972argument. Instead, all functions act on the single default loop.</p>
1973 </dd>
1974 <dt>EV_PERIODIC_ENABLE</dt>
1975 <dd>
1976 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1977defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
1978code.</p>
1979 </dd>
1980 <dt>EV_EMBED_ENABLE</dt>
1981 <dd>
1982 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
1983defined to be <code>0</code>, then they are not.</p>
1984 </dd>
1985 <dt>EV_STAT_ENABLE</dt>
1986 <dd>
1987 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
1988defined to be <code>0</code>, then they are not.</p>
1989 </dd>
1990 <dt>EV_FORK_ENABLE</dt>
1991 <dd>
1992 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
1993defined to be <code>0</code>, then they are not.</p>
1994 </dd>
1995 <dt>EV_MINIMAL</dt>
1996 <dd>
1997 <p>If you need to shave off some kilobytes of code at the expense of some
1998speed, define this symbol to <code>1</code>. Currently only used for gcc to override
1999some inlining decisions, saves roughly 30% codesize of amd64.</p>
2000 </dd>
2001 <dt>EV_PID_HASHSIZE</dt>
2002 <dd>
2003 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2004pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2005than enough. If you need to manage thousands of children you might want to
2006increase this value.</p>
2007 </dd>
2008 <dt>EV_COMMON</dt>
2009 <dd>
2010 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2011this macro to a something else you can include more and other types of
2012members. You have to define it each time you include one of the files,
2013though, and it must be identical each time.</p>
2014 <p>For example, the perl EV module uses something like this:</p>
2015<pre> #define EV_COMMON \
2016 SV *self; /* contains this struct */ \
2017 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2018
2019</pre>
2020 </dd>
2021 <dt>EV_CB_DECLARE (type)</dt>
2022 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2023 <dt>ev_set_cb (ev, cb)</dt>
2024 <dd>
2025 <p>Can be used to change the callback member declaration in each watcher,
2026and the way callbacks are invoked and set. Must expand to a struct member
2027definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2028their default definitions. One possible use for overriding these is to
2029avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2030method calls instead of plain function calls in C++.</p>
2031
2032</div>
2033<h2 id="EXAMPLES">EXAMPLES</h2>
2034<div id="EXAMPLES_CONTENT">
2035 <p>For a real-world example of a program the includes libev
2036verbatim, you can have a look at the EV perl module
2037(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2038the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2039interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2040will be compiled. It is pretty complex because it provides its own header
2041file.</p>
2042 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2043that everybody includes and which overrides some autoconf choices:</p>
2044<pre> #define EV_USE_POLL 0
2045 #define EV_MULTIPLICITY 0
2046 #define EV_PERIODICS 0
2047 #define EV_CONFIG_H &lt;config.h&gt;
2048
2049 #include &quot;ev++.h&quot;
2050
2051</pre>
2052 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2053<pre> #include &quot;ev_cpp.h&quot;
2054 #include &quot;ev.c&quot;
2055
2056
2057
2058
2059</pre>
2060
2061</div>
2062<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
2063<div id="COMPLEXITIES_CONTENT">
2064 <p>In this section the complexities of (many of) the algorithms used inside
2065libev will be explained. For complexity discussions about backends see the
2066documentation for <code>ev_default_init</code>.</p>
2067 <p>
2068 <dl>
2069 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2070 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2071 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2072 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2073 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
2074 <dt>Finding the next timer per loop iteration: O(1)</dt>
2075 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2076 <dt>Activating one watcher: O(1)</dt>
2077 </dl>
2078 </p>
2079
2080
2081
2082
1308 2083
1309</div> 2084</div>
1310<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2085<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
1311<div id="AUTHOR_CONTENT"> 2086<div id="AUTHOR_CONTENT">
1312<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2087 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1313 2088
1314</div> 2089</div>
1315</div></body> 2090</div></body>
1316</html> 2091</html>

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