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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 11:15:15 2007" /> 9 <meta name="created" content="Tue Nov 27 21:14:27 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 -->
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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>
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>
44<li><a href="#EMBEDDING">EMBEDDING</a> 47<li><a href="#EMBEDDING">EMBEDDING</a>
45<ul><li><a href="#FILESETS">FILESETS</a> 48<ul><li><a href="#FILESETS">FILESETS</a>
46<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> 49<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
47<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> 50<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
48<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> 51<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
… …
50</li> 53</li>
51<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li> 54<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
52<li><a href="#EXAMPLES">EXAMPLES</a></li> 55<li><a href="#EXAMPLES">EXAMPLES</a></li>
53</ul> 56</ul>
54</li> 57</li>
58<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
55<li><a href="#AUTHOR">AUTHOR</a> 59<li><a href="#AUTHOR">AUTHOR</a>
56</li> 60</li>
57</ul><hr /> 61</ul><hr />
58<!-- INDEX END --> 62<!-- INDEX END -->
59 63
… …
62<p>libev - a high performance full-featured event loop written in C</p> 66<p>libev - a high performance full-featured event loop written in C</p>
63 67
64</div> 68</div>
65<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 69<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>
66<div id="SYNOPSIS_CONTENT"> 70<div id="SYNOPSIS_CONTENT">
71<pre> /* this is the only header you need */
67<pre> #include &lt;ev.h&gt; 72 #include &lt;ev.h&gt;
73
74 /* what follows is a fully working example program */
75 ev_io stdin_watcher;
76 ev_timer timeout_watcher;
77
78 /* called when data readable on stdin */
79 static void
80 stdin_cb (EV_P_ struct ev_io *w, int revents)
81 {
82 /* puts (&quot;stdin ready&quot;); */
83 ev_io_stop (EV_A_ w); /* just a syntax example */
84 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
85 }
86
87 static void
88 timeout_cb (EV_P_ struct ev_timer *w, int revents)
89 {
90 /* puts (&quot;timeout&quot;); */
91 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
92 }
93
94 int
95 main (void)
96 {
97 struct ev_loop *loop = ev_default_loop (0);
98
99 /* initialise an io watcher, then start it */
100 ev_io_init (&amp;stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
101 ev_io_start (loop, &amp;stdin_watcher);
102
103 /* simple non-repeating 5.5 second timeout */
104 ev_timer_init (&amp;timeout_watcher, timeout_cb, 5.5, 0.);
105 ev_timer_start (loop, &amp;timeout_watcher);
106
107 /* loop till timeout or data ready */
108 ev_loop (loop, 0);
109
110 return 0;
111 }
68 112
69</pre> 113</pre>
70 114
71</div> 115</div>
72<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 116<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>
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111(fractional) number of seconds since the (POSIX) epoch (somewhere near 155(fractional) number of seconds since the (POSIX) epoch (somewhere near
112the beginning of 1970, details are complicated, don't ask). This type is 156the beginning of 1970, details are complicated, don't ask). This type is
113called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 157called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
114to the <code>double</code> type in C, and when you need to do any calculations on 158to the <code>double</code> type in C, and when you need to do any calculations on
115it, you should treat it as such.</p> 159it, you should treat it as such.</p>
116
117
118
119
120 160
121</div> 161</div>
122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 162<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
123<div id="GLOBAL_FUNCTIONS_CONTENT"> 163<div id="GLOBAL_FUNCTIONS_CONTENT">
124<p>These functions can be called anytime, even before initialising the 164<p>These functions can be called anytime, even before initialising the
… …
179might be supported on the current system, you would need to look at 219might be supported on the current system, you would need to look at
180<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 220<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
181recommended ones.</p> 221recommended ones.</p>
182 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 222 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
183 </dd> 223 </dd>
184 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 224 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt>
185 <dd> 225 <dd>
186 <p>Sets the allocation function to use (the prototype is similar to the 226 <p>Sets the allocation function to use (the prototype and semantics are
187realloc C function, the semantics are identical). It is used to allocate 227identical to the realloc C function). It is used to allocate and free
188and free memory (no surprises here). If it returns zero when memory 228memory (no surprises here). If it returns zero when memory needs to be
189needs to be allocated, the library might abort or take some potentially 229allocated, the library might abort or take some potentially destructive
190destructive action. The default is your system realloc function.</p> 230action. The default is your system realloc function.</p>
191 <p>You could override this function in high-availability programs to, say, 231 <p>You could override this function in high-availability programs to, say,
192free some memory if it cannot allocate memory, to use a special allocator, 232free some memory if it cannot allocate memory, to use a special allocator,
193or even to sleep a while and retry until some memory is available.</p> 233or even to sleep a while and retry until some memory is available.</p>
194 <p>Example: replace the libev allocator with one that waits a bit and then 234 <p>Example: replace the libev allocator with one that waits a bit and then
195retries: better than mine).</p> 235retries: better than mine).</p>
196<pre> static void * 236<pre> static void *
197 persistent_realloc (void *ptr, long size) 237 persistent_realloc (void *ptr, size_t size)
198 { 238 {
199 for (;;) 239 for (;;)
200 { 240 {
201 void *newptr = realloc (ptr, size); 241 void *newptr = realloc (ptr, size);
202 242
… …
513 553
514</pre> 554</pre>
515 </dd> 555 </dd>
516</dl> 556</dl>
517 557
558
559
560
561
518</div> 562</div>
519<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 563<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
520<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 564<div id="ANATOMY_OF_A_WATCHER_CONTENT">
521<p>A watcher is a structure that you create and register to record your 565<p>A watcher is a structure that you create and register to record your
522interest in some event. For instance, if you want to wait for STDIN to 566interest in some event. For instance, if you want to wait for STDIN to
… …
581 </dd> 625 </dd>
582 <dt><code>EV_CHILD</code></dt> 626 <dt><code>EV_CHILD</code></dt>
583 <dd> 627 <dd>
584 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 628 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
585 </dd> 629 </dd>
630 <dt><code>EV_STAT</code></dt>
631 <dd>
632 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
633 </dd>
586 <dt><code>EV_IDLE</code></dt> 634 <dt><code>EV_IDLE</code></dt>
587 <dd> 635 <dd>
588 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 636 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
589 </dd> 637 </dd>
590 <dt><code>EV_PREPARE</code></dt> 638 <dt><code>EV_PREPARE</code></dt>
… …
595<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 643<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
596received events. Callbacks of both watcher types can start and stop as 644received events. Callbacks of both watcher types can start and stop as
597many watchers as they want, and all of them will be taken into account 645many watchers as they want, and all of them will be taken into account
598(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 646(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
599<code>ev_loop</code> from blocking).</p> 647<code>ev_loop</code> from blocking).</p>
648 </dd>
649 <dt><code>EV_EMBED</code></dt>
650 <dd>
651 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
652 </dd>
653 <dt><code>EV_FORK</code></dt>
654 <dd>
655 <p>The event loop has been resumed in the child process after fork (see
656<code>ev_fork</code>).</p>
600 </dd> 657 </dd>
601 <dt><code>EV_ERROR</code></dt> 658 <dt><code>EV_ERROR</code></dt>
602 <dd> 659 <dd>
603 <p>An unspecified error has occured, the watcher has been stopped. This might 660 <p>An unspecified error has occured, the watcher has been stopped. This might
604happen because the watcher could not be properly started because libev 661happen because the watcher could not be properly started because libev
… …
612programs, though, so beware.</p> 669programs, though, so beware.</p>
613 </dd> 670 </dd>
614</dl> 671</dl>
615 672
616</div> 673</div>
617<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2> 674<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
618<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2"> 675<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
619<p>In the following description, <code>TYPE</code> stands for the watcher type, 676<p>In the following description, <code>TYPE</code> stands for the watcher type,
620e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p> 677e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
621<dl> 678<dl>
622 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt> 679 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
623 <dd> 680 <dd>
… …
627the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the 684the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
628type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro 685type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
629which rolls both calls into one.</p> 686which rolls both calls into one.</p>
630 <p>You can reinitialise a watcher at any time as long as it has been stopped 687 <p>You can reinitialise a watcher at any time as long as it has been stopped
631(or never started) and there are no pending events outstanding.</p> 688(or never started) and there are no pending events outstanding.</p>
632 <p>The callbakc is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher, 689 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
633int revents)</code>.</p> 690int revents)</code>.</p>
634 </dd> 691 </dd>
635 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt> 692 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
636 <dd> 693 <dd>
637 <p>This macro initialises the type-specific parts of a watcher. You need to 694 <p>This macro initialises the type-specific parts of a watcher. You need to
… …
727 784
728</div> 785</div>
729<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 786<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
730<div id="WATCHER_TYPES_CONTENT"> 787<div id="WATCHER_TYPES_CONTENT">
731<p>This section describes each watcher in detail, but will not repeat 788<p>This section describes each watcher in detail, but will not repeat
732information given in the last section.</p> 789information given in the last section. Any initialisation/set macros,
790functions and members specific to the watcher type are explained.</p>
791<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
792while the watcher is active, you can look at the member and expect some
793sensible content, but you must not modify it (you can modify it while the
794watcher is stopped to your hearts content), or <i>[read-write]</i>, which
795means you can expect it to have some sensible content while the watcher
796is active, but you can also modify it. Modifying it may not do something
797sensible or take immediate effect (or do anything at all), but libev will
798not crash or malfunction in any way.</p>
733 799
734 800
735 801
736 802
737 803
738</div> 804</div>
739<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 805<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
740<div id="code_ev_io_code_is_this_file_descrip-2"> 806<div id="code_ev_io_code_is_this_file_descrip-2">
741<p>I/O watchers check whether a file descriptor is readable or writable 807<p>I/O watchers check whether a file descriptor is readable or writable
742in each iteration of the event loop (This behaviour is called 808in each iteration of the event loop, or, more precisely, when reading
743level-triggering because you keep receiving events as long as the 809would not block the process and writing would at least be able to write
744condition persists. Remember you can stop the watcher if you don't want to 810some data. This behaviour is called level-triggering because you keep
745act on the event and neither want to receive future events).</p> 811receiving events as long as the condition persists. Remember you can stop
812the watcher if you don't want to act on the event and neither want to
813receive future events.</p>
746<p>In general you can register as many read and/or write event watchers per 814<p>In general you can register as many read and/or write event watchers per
747fd as you want (as long as you don't confuse yourself). Setting all file 815fd as you want (as long as you don't confuse yourself). Setting all file
748descriptors to non-blocking mode is also usually a good idea (but not 816descriptors to non-blocking mode is also usually a good idea (but not
749required if you know what you are doing).</p> 817required if you know what you are doing).</p>
750<p>You have to be careful with dup'ed file descriptors, though. Some backends 818<p>You have to be careful with dup'ed file descriptors, though. Some backends
751(the linux epoll backend is a notable example) cannot handle dup'ed file 819(the linux epoll backend is a notable example) cannot handle dup'ed file
752descriptors correctly if you register interest in two or more fds pointing 820descriptors correctly if you register interest in two or more fds pointing
753to the same underlying file/socket etc. description (that is, they share 821to the same underlying file/socket/etc. description (that is, they share
754the same underlying &quot;file open&quot;).</p> 822the same underlying &quot;file open&quot;).</p>
755<p>If you must do this, then force the use of a known-to-be-good backend 823<p>If you must do this, then force the use of a known-to-be-good backend
756(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and 824(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
757<code>EVBACKEND_POLL</code>).</p> 825<code>EVBACKEND_POLL</code>).</p>
826<p>Another thing you have to watch out for is that it is quite easy to
827receive &quot;spurious&quot; readyness notifications, that is your callback might
828be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
829because there is no data. Not only are some backends known to create a
830lot of those (for example solaris ports), it is very easy to get into
831this situation even with a relatively standard program structure. Thus
832it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
833<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
834<p>If you cannot run the fd in non-blocking mode (for example you should not
835play around with an Xlib connection), then you have to seperately re-test
836wether a file descriptor is really ready with a known-to-be good interface
837such as poll (fortunately in our Xlib example, Xlib already does this on
838its own, so its quite safe to use).</p>
758<dl> 839<dl>
759 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 840 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
760 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 841 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
761 <dd> 842 <dd>
762 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 843 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
763events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 844rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
764EV_WRITE</code> to receive the given events.</p> 845<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
765 <p>Please note that most of the more scalable backend mechanisms (for example 846 </dd>
766epoll and solaris ports) can result in spurious readyness notifications 847 <dt>int fd [read-only]</dt>
767for file descriptors, so you practically need to use non-blocking I/O (and 848 <dd>
768treat callback invocation as hint only), or retest separately with a safe 849 <p>The file descriptor being watched.</p>
769interface before doing I/O (XLib can do this), or force the use of either 850 </dd>
770<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 851 <dt>int events [read-only]</dt>
771problem. Also note that it is quite easy to have your callback invoked 852 <dd>
772when the readyness condition is no longer valid even when employing 853 <p>The events being watched.</p>
773typical ways of handling events, so its a good idea to use non-blocking
774I/O unconditionally.</p>
775 </dd> 854 </dd>
776</dl> 855</dl>
777<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 856<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
778readable, but only once. Since it is likely line-buffered, you could 857readable, but only once. Since it is likely line-buffered, you could
779attempt to read a whole line in the callback:</p> 858attempt to read a whole line in the callback:</p>
… …
795 874
796 875
797</pre> 876</pre>
798 877
799</div> 878</div>
800<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 879<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
801<div id="code_ev_timer_code_relative_and_opti-2"> 880<div id="code_ev_timer_code_relative_and_opti-2">
802<p>Timer watchers are simple relative timers that generate an event after a 881<p>Timer watchers are simple relative timers that generate an event after a
803given time, and optionally repeating in regular intervals after that.</p> 882given time, and optionally repeating in regular intervals after that.</p>
804<p>The timers are based on real time, that is, if you register an event that 883<p>The timers are based on real time, that is, if you register an event that
805times out after an hour and you reset your system clock to last years 884times out after an hour and you reset your system clock to last years
… …
837repeating. The exact semantics are:</p> 916repeating. The exact semantics are:</p>
838 <p>If the timer is started but nonrepeating, stop it.</p> 917 <p>If the timer is started but nonrepeating, stop it.</p>
839 <p>If the timer is repeating, either start it if necessary (with the repeat 918 <p>If the timer is repeating, either start it if necessary (with the repeat
840value), or reset the running timer to the repeat value.</p> 919value), or reset the running timer to the repeat value.</p>
841 <p>This sounds a bit complicated, but here is a useful and typical 920 <p>This sounds a bit complicated, but here is a useful and typical
842example: Imagine you have a tcp connection and you want a so-called idle 921example: Imagine you have a tcp connection and you want a so-called
843timeout, that is, you want to be called when there have been, say, 60 922idle timeout, that is, you want to be called when there have been,
844seconds of inactivity on the socket. The easiest way to do this is to 923say, 60 seconds of inactivity on the socket. The easiest way to do
845configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 924this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
846time you successfully read or write some data. If you go into an idle 925<code>ev_timer_again</code> each time you successfully read or write some data. If
847state where you do not expect data to travel on the socket, you can stop 926you go into an idle state where you do not expect data to travel on the
848the timer, and again will automatically restart it if need be.</p> 927socket, you can stop the timer, and again will automatically restart it if
928need be.</p>
929 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
930and only ever use the <code>repeat</code> value:</p>
931<pre> ev_timer_init (timer, callback, 0., 5.);
932 ev_timer_again (loop, timer);
933 ...
934 timer-&gt;again = 17.;
935 ev_timer_again (loop, timer);
936 ...
937 timer-&gt;again = 10.;
938 ev_timer_again (loop, timer);
939
940</pre>
941 <p>This is more efficient then stopping/starting the timer eahc time you want
942to modify its timeout value.</p>
943 </dd>
944 <dt>ev_tstamp repeat [read-write]</dt>
945 <dd>
946 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
947or <code>ev_timer_again</code> is called and determines the next timeout (if any),
948which is also when any modifications are taken into account.</p>
849 </dd> 949 </dd>
850</dl> 950</dl>
851<p>Example: create a timer that fires after 60 seconds.</p> 951<p>Example: create a timer that fires after 60 seconds.</p>
852<pre> static void 952<pre> static void
853 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 953 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
881 981
882 982
883</pre> 983</pre>
884 984
885</div> 985</div>
886<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 986<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
887<div id="code_ev_periodic_code_to_cron_or_not-2"> 987<div id="code_ev_periodic_code_to_cron_or_not-2">
888<p>Periodic watchers are also timers of a kind, but they are very versatile 988<p>Periodic watchers are also timers of a kind, but they are very versatile
889(and unfortunately a bit complex).</p> 989(and unfortunately a bit complex).</p>
890<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 990<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
891but on wallclock time (absolute time). You can tell a periodic watcher 991but on wallclock time (absolute time). You can tell a periodic watcher
… …
971 <p>Simply stops and restarts the periodic watcher again. This is only useful 1071 <p>Simply stops and restarts the periodic watcher again. This is only useful
972when you changed some parameters or the reschedule callback would return 1072when you changed some parameters or the reschedule callback would return
973a different time than the last time it was called (e.g. in a crond like 1073a different time than the last time it was called (e.g. in a crond like
974program when the crontabs have changed).</p> 1074program when the crontabs have changed).</p>
975 </dd> 1075 </dd>
1076 <dt>ev_tstamp interval [read-write]</dt>
1077 <dd>
1078 <p>The current interval value. Can be modified any time, but changes only
1079take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1080called.</p>
1081 </dd>
1082 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1083 <dd>
1084 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1085switched off. Can be changed any time, but changes only take effect when
1086the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1087 </dd>
976</dl> 1088</dl>
977<p>Example: call a callback every hour, or, more precisely, whenever the 1089<p>Example: call a callback every hour, or, more precisely, whenever the
978system clock is divisible by 3600. The callback invocation times have 1090system clock is divisible by 3600. The callback invocation times have
979potentially a lot of jittering, but good long-term stability.</p> 1091potentially a lot of jittering, but good long-term stability.</p>
980<pre> static void 1092<pre> static void
… …
1010 1122
1011 1123
1012</pre> 1124</pre>
1013 1125
1014</div> 1126</div>
1015<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1127<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
1016<div id="code_ev_signal_code_signal_me_when_a-2"> 1128<div id="code_ev_signal_code_signal_me_when_a-2">
1017<p>Signal watchers will trigger an event when the process receives a specific 1129<p>Signal watchers will trigger an event when the process receives a specific
1018signal one or more times. Even though signals are very asynchronous, libev 1130signal one or more times. Even though signals are very asynchronous, libev
1019will try it's best to deliver signals synchronously, i.e. as part of the 1131will try it's best to deliver signals synchronously, i.e. as part of the
1020normal event processing, like any other event.</p> 1132normal event processing, like any other event.</p>
… …
1029 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1141 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1030 <dd> 1142 <dd>
1031 <p>Configures the watcher to trigger on the given signal number (usually one 1143 <p>Configures the watcher to trigger on the given signal number (usually one
1032of the <code>SIGxxx</code> constants).</p> 1144of the <code>SIGxxx</code> constants).</p>
1033 </dd> 1145 </dd>
1146 <dt>int signum [read-only]</dt>
1147 <dd>
1148 <p>The signal the watcher watches out for.</p>
1149 </dd>
1034</dl> 1150</dl>
1035 1151
1036 1152
1037 1153
1038 1154
1039 1155
1040</div> 1156</div>
1041<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1157<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
1042<div id="code_ev_child_code_wait_for_pid_stat-2"> 1158<div id="code_ev_child_code_watch_out_for_pro-2">
1043<p>Child watchers trigger when your process receives a SIGCHLD in response to 1159<p>Child watchers trigger when your process receives a SIGCHLD in response to
1044some child status changes (most typically when a child of yours dies).</p> 1160some child status changes (most typically when a child of yours dies).</p>
1045<dl> 1161<dl>
1046 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1162 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1047 <dt>ev_child_set (ev_child *, int pid)</dt> 1163 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
1050<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 1166<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
1051at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1167at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1052the status word (use the macros from <code>sys/wait.h</code> and see your systems 1168the status word (use the macros from <code>sys/wait.h</code> and see your systems
1053<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1169<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1054process causing the status change.</p> 1170process causing the status change.</p>
1171 </dd>
1172 <dt>int pid [read-only]</dt>
1173 <dd>
1174 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1175 </dd>
1176 <dt>int rpid [read-write]</dt>
1177 <dd>
1178 <p>The process id that detected a status change.</p>
1179 </dd>
1180 <dt>int rstatus [read-write]</dt>
1181 <dd>
1182 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1183<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1055 </dd> 1184 </dd>
1056</dl> 1185</dl>
1057<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1186<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
1058<pre> static void 1187<pre> static void
1059 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1188 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1069 1198
1070 1199
1071</pre> 1200</pre>
1072 1201
1073</div> 1202</div>
1203<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1204<div id="code_ev_stat_code_did_the_file_attri-2">
1205<p>This watches a filesystem path for attribute changes. That is, it calls
1206<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1207compared to the last time, invoking the callback if it did.</p>
1208<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1209not exist&quot; is a status change like any other. The condition &quot;path does
1210not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1211otherwise always forced to be at least one) and all the other fields of
1212the stat buffer having unspecified contents.</p>
1213<p>Since there is no standard to do this, the portable implementation simply
1214calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You
1215can specify a recommended polling interval for this case. If you specify
1216a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1217unspecified default</i> value will be used (which you can expect to be around
1218five seconds, although this might change dynamically). Libev will also
1219impose a minimum interval which is currently around <code>0.1</code>, but thats
1220usually overkill.</p>
1221<p>This watcher type is not meant for massive numbers of stat watchers,
1222as even with OS-supported change notifications, this can be
1223resource-intensive.</p>
1224<p>At the time of this writing, no specific OS backends are implemented, but
1225if demand increases, at least a kqueue and inotify backend will be added.</p>
1226<dl>
1227 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1228 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1229 <dd>
1230 <p>Configures the watcher to wait for status changes of the given
1231<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1232be detected and should normally be specified as <code>0</code> to let libev choose
1233a suitable value. The memory pointed to by <code>path</code> must point to the same
1234path for as long as the watcher is active.</p>
1235 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1236relative to the attributes at the time the watcher was started (or the
1237last change was detected).</p>
1238 </dd>
1239 <dt>ev_stat_stat (ev_stat *)</dt>
1240 <dd>
1241 <p>Updates the stat buffer immediately with new values. If you change the
1242watched path in your callback, you could call this fucntion to avoid
1243detecting this change (while introducing a race condition). Can also be
1244useful simply to find out the new values.</p>
1245 </dd>
1246 <dt>ev_statdata attr [read-only]</dt>
1247 <dd>
1248 <p>The most-recently detected attributes of the file. Although the type is of
1249<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1250suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1251was some error while <code>stat</code>ing the file.</p>
1252 </dd>
1253 <dt>ev_statdata prev [read-only]</dt>
1254 <dd>
1255 <p>The previous attributes of the file. The callback gets invoked whenever
1256<code>prev</code> != <code>attr</code>.</p>
1257 </dd>
1258 <dt>ev_tstamp interval [read-only]</dt>
1259 <dd>
1260 <p>The specified interval.</p>
1261 </dd>
1262 <dt>const char *path [read-only]</dt>
1263 <dd>
1264 <p>The filesystem path that is being watched.</p>
1265 </dd>
1266</dl>
1267<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1268<pre> static void
1269 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1270 {
1271 /* /etc/passwd changed in some way */
1272 if (w-&gt;attr.st_nlink)
1273 {
1274 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1275 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1276 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1277 }
1278 else
1279 /* you shalt not abuse printf for puts */
1280 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1281 &quot;if this is windows, they already arrived\n&quot;);
1282 }
1283
1284 ...
1285 ev_stat passwd;
1286
1287 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1288 ev_stat_start (loop, &amp;passwd);
1289
1290
1291
1292
1293</pre>
1294
1295</div>
1074<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1296<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1075<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1297<div id="code_ev_idle_code_when_you_ve_got_no-2">
1076<p>Idle watchers trigger events when there are no other events are pending 1298<p>Idle watchers trigger events when there are no other events are pending
1077(prepare, check and other idle watchers do not count). That is, as long 1299(prepare, check and other idle watchers do not count). That is, as long
1078as your process is busy handling sockets or timeouts (or even signals, 1300as your process is busy handling sockets or timeouts (or even signals,
1079imagine) it will not be triggered. But when your process is idle all idle 1301imagine) it will not be triggered. But when your process is idle all idle
… …
1112 1334
1113 1335
1114</pre> 1336</pre>
1115 1337
1116</div> 1338</div>
1117<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1339<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1118<div id="code_ev_prepare_code_and_code_ev_che-2"> 1340<div id="code_ev_prepare_code_and_code_ev_che-2">
1119<p>Prepare and check watchers are usually (but not always) used in tandem: 1341<p>Prepare and check watchers are usually (but not always) used in tandem:
1120prepare watchers get invoked before the process blocks and check watchers 1342prepare watchers get invoked before the process blocks and check watchers
1121afterwards.</p> 1343afterwards.</p>
1344<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1345the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1346watchers. Other loops than the current one are fine, however. The
1347rationale behind this is that you do not need to check for recursion in
1348those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1349<code>ev_check</code> so if you have one watcher of each kind they will always be
1350called in pairs bracketing the blocking call.</p>
1122<p>Their main purpose is to integrate other event mechanisms into libev and 1351<p>Their main purpose is to integrate other event mechanisms into libev and
1123their use is somewhat advanced. This could be used, for example, to track 1352their use is somewhat advanced. This could be used, for example, to track
1124variable changes, implement your own watchers, integrate net-snmp or a 1353variable changes, implement your own watchers, integrate net-snmp or a
1125coroutine library and lots more.</p> 1354coroutine library and lots more. They are also occasionally useful if
1355you cache some data and want to flush it before blocking (for example,
1356in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1357watcher).</p>
1126<p>This is done by examining in each prepare call which file descriptors need 1358<p>This is done by examining in each prepare call which file descriptors need
1127to be watched by the other library, registering <code>ev_io</code> watchers for 1359to be watched by the other library, registering <code>ev_io</code> watchers for
1128them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1360them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1129provide just this functionality). Then, in the check watcher you check for 1361provide just this functionality). Then, in the check watcher you check for
1130any events that occured (by checking the pending status of all watchers 1362any events that occured (by checking the pending status of all watchers
… …
1146 <p>Initialises and configures the prepare or check watcher - they have no 1378 <p>Initialises and configures the prepare or check watcher - they have no
1147parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1379parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1148macros, but using them is utterly, utterly and completely pointless.</p> 1380macros, but using them is utterly, utterly and completely pointless.</p>
1149 </dd> 1381 </dd>
1150</dl> 1382</dl>
1151<p>Example: *TODO*.</p> 1383<p>Example: To include a library such as adns, you would add IO watchers
1384and a timeout watcher in a prepare handler, as required by libadns, and
1385in a check watcher, destroy them and call into libadns. What follows is
1386pseudo-code only of course:</p>
1387<pre> static ev_io iow [nfd];
1388 static ev_timer tw;
1152 1389
1390 static void
1391 io_cb (ev_loop *loop, ev_io *w, int revents)
1392 {
1393 // set the relevant poll flags
1394 // could also call adns_processreadable etc. here
1395 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1396 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1397 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1398 }
1153 1399
1400 // create io watchers for each fd and a timer before blocking
1401 static void
1402 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1403 {
1404 int timeout = 3600000;truct pollfd fds [nfd];
1405 // actual code will need to loop here and realloc etc.
1406 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1154 1407
1408 /* the callback is illegal, but won't be called as we stop during check */
1409 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1410 ev_timer_start (loop, &amp;tw);
1155 1411
1412 // create on ev_io per pollfd
1413 for (int i = 0; i &lt; nfd; ++i)
1414 {
1415 ev_io_init (iow + i, io_cb, fds [i].fd,
1416 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1417 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1156 1418
1419 fds [i].revents = 0;
1420 iow [i].data = fds + i;
1421 ev_io_start (loop, iow + i);
1422 }
1423 }
1424
1425 // stop all watchers after blocking
1426 static void
1427 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1428 {
1429 ev_timer_stop (loop, &amp;tw);
1430
1431 for (int i = 0; i &lt; nfd; ++i)
1432 ev_io_stop (loop, iow + i);
1433
1434 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1435 }
1436
1437
1438
1439
1440</pre>
1441
1157</div> 1442</div>
1158<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1443<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1159<div id="code_ev_embed_code_when_one_backend_-2"> 1444<div id="code_ev_embed_code_when_one_backend_-2">
1160<p>This is a rather advanced watcher type that lets you embed one event loop 1445<p>This is a rather advanced watcher type that lets you embed one event loop
1161into another (currently only <code>ev_io</code> events are supported in the embedded 1446into another (currently only <code>ev_io</code> events are supported in the embedded
1162loop, other types of watchers might be handled in a delayed or incorrect 1447loop, other types of watchers might be handled in a delayed or incorrect
1163fashion and must not be used).</p> 1448fashion and must not be used).</p>
… …
1230 <dt>ev_embed_sweep (loop, ev_embed *)</dt> 1515 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1231 <dd> 1516 <dd>
1232 <p>Make a single, non-blocking sweep over the embedded loop. This works 1517 <p>Make a single, non-blocking sweep over the embedded loop. This works
1233similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1518similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1234apropriate way for embedded loops.</p> 1519apropriate way for embedded loops.</p>
1520 </dd>
1521 <dt>struct ev_loop *loop [read-only]</dt>
1522 <dd>
1523 <p>The embedded event loop.</p>
1524 </dd>
1525</dl>
1526
1527
1528
1529
1530
1531</div>
1532<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>
1533<div id="code_ev_fork_code_the_audacity_to_re-2">
1534<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1535whoever is a good citizen cared to tell libev about it by calling
1536<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1537event loop blocks next and before <code>ev_check</code> watchers are being called,
1538and only in the child after the fork. If whoever good citizen calling
1539<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1540handlers will be invoked, too, of course.</p>
1541<dl>
1542 <dt>ev_fork_init (ev_signal *, callback)</dt>
1543 <dd>
1544 <p>Initialises and configures the fork watcher - it has no parameters of any
1545kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1546believe me.</p>
1235 </dd> 1547 </dd>
1236</dl> 1548</dl>
1237 1549
1238 1550
1239 1551
… …
1389 </dd> 1701 </dd>
1390 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1702 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1391 <dd> 1703 <dd>
1392 <p>Invokes <code>ev_embed_sweep</code>.</p> 1704 <p>Invokes <code>ev_embed_sweep</code>.</p>
1393 </dd> 1705 </dd>
1706 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1707 <dd>
1708 <p>Invokes <code>ev_stat_stat</code>.</p>
1709 </dd>
1394 </dl> 1710 </dl>
1395 </p> 1711 </p>
1396 </dd> 1712 </dd>
1397</dl> 1713</dl>
1398<p>Example: Define a class with an IO and idle watcher, start one of them in 1714<p>Example: Define a class with an IO and idle watcher, start one of them in
… …
1409 : io (this, &amp;myclass::io_cb), 1725 : io (this, &amp;myclass::io_cb),
1410 idle (this, &amp;myclass::idle_cb) 1726 idle (this, &amp;myclass::idle_cb)
1411 { 1727 {
1412 io.start (fd, ev::READ); 1728 io.start (fd, ev::READ);
1413 } 1729 }
1730
1731
1732
1733
1734</pre>
1735
1736</div>
1737<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p>
1738<div id="MACRO_MAGIC_CONTENT">
1739<p>Libev can be compiled with a variety of options, the most fundemantal is
1740<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1741callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1742<p>To make it easier to write programs that cope with either variant, the
1743following macros are defined:</p>
1744<dl>
1745 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1746 <dd>
1747 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1748loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1749<code>EV_A_</code> is used when other arguments are following. Example:</p>
1750<pre> ev_unref (EV_A);
1751 ev_timer_add (EV_A_ watcher);
1752 ev_loop (EV_A_ 0);
1753
1754</pre>
1755 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1756which is often provided by the following macro.</p>
1757 </dd>
1758 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1759 <dd>
1760 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1761loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1762<code>EV_P_</code> is used when other parameters are following. Example:</p>
1763<pre> // this is how ev_unref is being declared
1764 static void ev_unref (EV_P);
1765
1766 // this is how you can declare your typical callback
1767 static void cb (EV_P_ ev_timer *w, int revents)
1768
1769</pre>
1770 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1771suitable for use with <code>EV_A</code>.</p>
1772 </dd>
1773 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1774 <dd>
1775 <p>Similar to the other two macros, this gives you the value of the default
1776loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1777 </dd>
1778</dl>
1779<p>Example: Declare and initialise a check watcher, working regardless of
1780wether multiple loops are supported or not.</p>
1781<pre> static void
1782 check_cb (EV_P_ ev_timer *w, int revents)
1783 {
1784 ev_check_stop (EV_A_ w);
1785 }
1786
1787 ev_check check;
1788 ev_check_init (&amp;check, check_cb);
1789 ev_check_start (EV_DEFAULT_ &amp;check);
1790 ev_loop (EV_DEFAULT_ 0);
1791
1792
1793
1414 1794
1415</pre> 1795</pre>
1416 1796
1417</div> 1797</div>
1418<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1798<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
… …
1460 ev_vars.h 1840 ev_vars.h
1461 ev_wrap.h 1841 ev_wrap.h
1462 1842
1463 ev_win32.c required on win32 platforms only 1843 ev_win32.c required on win32 platforms only
1464 1844
1465 ev_select.c only when select backend is enabled (which is is by default) 1845 ev_select.c only when select backend is enabled (which is by default)
1466 ev_poll.c only when poll backend is enabled (disabled by default) 1846 ev_poll.c only when poll backend is enabled (disabled by default)
1467 ev_epoll.c only when the epoll backend is enabled (disabled by default) 1847 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1468 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 1848 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1469 ev_port.c only when the solaris port backend is enabled (disabled by default) 1849 ev_port.c only when the solaris port backend is enabled (disabled by default)
1470 1850
1471</pre> 1851</pre>
1472<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need 1852<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1473to compile a single file.</p> 1853to compile this single file.</p>
1474 1854
1475</div> 1855</div>
1476<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3> 1856<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1477<div id="LIBEVENT_COMPATIBILITY_API_CONTENT"> 1857<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1478<p>To include the libevent compatibility API, also include:</p> 1858<p>To include the libevent compatibility API, also include:</p>
… …
1493</div> 1873</div>
1494<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3> 1874<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1495<div id="AUTOCONF_SUPPORT_CONTENT"> 1875<div id="AUTOCONF_SUPPORT_CONTENT">
1496<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in 1876<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1497whatever way you want, you can also <code>m4_include([libev.m4])</code> in your 1877whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1498<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> off. <cite>ev.c</cite> will then include 1878<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1499<cite>config.h</cite> and configure itself accordingly.</p> 1879include <cite>config.h</cite> and configure itself accordingly.</p>
1500<p>For this of course you need the m4 file:</p> 1880<p>For this of course you need the m4 file:</p>
1501<pre> libev.m4 1881<pre> libev.m4
1502 1882
1503</pre> 1883</pre>
1504 1884
… …
1583otherwise another method will be used as fallback. This is the preferred 1963otherwise another method will be used as fallback. This is the preferred
1584backend for BSD and BSD-like systems, although on most BSDs kqueue only 1964backend for BSD and BSD-like systems, although on most BSDs kqueue only
1585supports some types of fds correctly (the only platform we found that 1965supports some types of fds correctly (the only platform we found that
1586supports ptys for example was NetBSD), so kqueue might be compiled in, but 1966supports ptys for example was NetBSD), so kqueue might be compiled in, but
1587not be used unless explicitly requested. The best way to use it is to find 1967not be used unless explicitly requested. The best way to use it is to find
1588out wether kqueue supports your type of fd properly and use an embedded 1968out whether kqueue supports your type of fd properly and use an embedded
1589kqueue loop.</p> 1969kqueue loop.</p>
1590 </dd> 1970 </dd>
1591 <dt>EV_USE_PORT</dt> 1971 <dt>EV_USE_PORT</dt>
1592 <dd> 1972 <dd>
1593 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris 1973 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
… …
1629will have the <code>struct ev_loop *</code> as first argument, and you can create 2009will have the <code>struct ev_loop *</code> as first argument, and you can create
1630additional independent event loops. Otherwise there will be no support 2010additional independent event loops. Otherwise there will be no support
1631for multiple event loops and there is no first event loop pointer 2011for multiple event loops and there is no first event loop pointer
1632argument. Instead, all functions act on the single default loop.</p> 2012argument. Instead, all functions act on the single default loop.</p>
1633 </dd> 2013 </dd>
1634 <dt>EV_PERIODICS</dt> 2014 <dt>EV_PERIODIC_ENABLE</dt>
1635 <dd> 2015 <dd>
1636 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported, 2016 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1637otherwise not. This saves a few kb of code.</p> 2017defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2018code.</p>
2019 </dd>
2020 <dt>EV_EMBED_ENABLE</dt>
2021 <dd>
2022 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2023defined to be <code>0</code>, then they are not.</p>
2024 </dd>
2025 <dt>EV_STAT_ENABLE</dt>
2026 <dd>
2027 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2028defined to be <code>0</code>, then they are not.</p>
2029 </dd>
2030 <dt>EV_FORK_ENABLE</dt>
2031 <dd>
2032 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2033defined to be <code>0</code>, then they are not.</p>
2034 </dd>
2035 <dt>EV_MINIMAL</dt>
2036 <dd>
2037 <p>If you need to shave off some kilobytes of code at the expense of some
2038speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2039some inlining decisions, saves roughly 30% codesize of amd64.</p>
2040 </dd>
2041 <dt>EV_PID_HASHSIZE</dt>
2042 <dd>
2043 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2044pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2045than enough. If you need to manage thousands of children you might want to
2046increase this value.</p>
1638 </dd> 2047 </dd>
1639 <dt>EV_COMMON</dt> 2048 <dt>EV_COMMON</dt>
1640 <dd> 2049 <dd>
1641 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2050 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1642this macro to a something else you can include more and other types of 2051this macro to a something else you can include more and other types of
… …
1647 SV *self; /* contains this struct */ \ 2056 SV *self; /* contains this struct */ \
1648 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */ 2057 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
1649 2058
1650</pre> 2059</pre>
1651 </dd> 2060 </dd>
1652 <dt>EV_CB_DECLARE(type)</dt> 2061 <dt>EV_CB_DECLARE (type)</dt>
1653 <dt>EV_CB_INVOKE(watcher,revents)</dt> 2062 <dt>EV_CB_INVOKE (watcher, revents)</dt>
1654 <dt>ev_set_cb(ev,cb)</dt> 2063 <dt>ev_set_cb (ev, cb)</dt>
1655 <dd> 2064 <dd>
1656 <p>Can be used to change the callback member declaration in each watcher, 2065 <p>Can be used to change the callback member declaration in each watcher,
1657and the way callbacks are invoked and set. Must expand to a struct member 2066and the way callbacks are invoked and set. Must expand to a struct member
1658definition and a statement, respectively. See the <cite>ev.v</cite> header file for 2067definition and a statement, respectively. See the <cite>ev.v</cite> header file for
1659their default definitions. One possible use for overriding these is to 2068their default definitions. One possible use for overriding these is to
1660avoid the ev_loop pointer as first argument in all cases, or to use method 2069avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
1661calls instead of plain function calls in C++.</p> 2070method calls instead of plain function calls in C++.</p>
1662 2071
1663</div> 2072</div>
1664<h2 id="EXAMPLES">EXAMPLES</h2> 2073<h2 id="EXAMPLES">EXAMPLES</h2>
1665<div id="EXAMPLES_CONTENT"> 2074<div id="EXAMPLES_CONTENT">
1666 <p>For a real-world example of a program the includes libev 2075 <p>For a real-world example of a program the includes libev
… …
1682</pre> 2091</pre>
1683 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2092 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1684<pre> #include &quot;ev_cpp.h&quot; 2093<pre> #include &quot;ev_cpp.h&quot;
1685 #include &quot;ev.c&quot; 2094 #include &quot;ev.c&quot;
1686 2095
2096
2097
2098
1687</pre> 2099</pre>
2100
2101</div>
2102<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
2103<div id="COMPLEXITIES_CONTENT">
2104 <p>In this section the complexities of (many of) the algorithms used inside
2105libev will be explained. For complexity discussions about backends see the
2106documentation for <code>ev_default_init</code>.</p>
2107 <p>
2108 <dl>
2109 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2110 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2111 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2112 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2113 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
2114 <dt>Finding the next timer per loop iteration: O(1)</dt>
2115 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2116 <dt>Activating one watcher: O(1)</dt>
2117 </dl>
2118 </p>
2119
2120
2121
2122
1688 2123
1689</div> 2124</div>
1690<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2125<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
1691<div id="AUTHOR_CONTENT"> 2126<div id="AUTHOR_CONTENT">
1692 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2127 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

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