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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 05:58:35 2007" /> 9 <meta name="created" content="Tue Nov 27 21:38:05 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 -->
15<h3 id="TOP">Index</h3> 15<h3 id="TOP">Index</h3>
16 16
17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 20<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 21<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 22<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 23<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 24<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> 25<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> 26<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
26<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
27</ul> 29</ul>
28</li> 30</li>
29<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
30<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> 32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> 33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
32<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_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
33<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_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_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
35<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> 38<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
36<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> 39<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
37<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_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
41<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
38</ul> 42</ul>
39</li> 43</li>
40<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
41<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
42<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 46<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
47<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
48<li><a href="#EMBEDDING">EMBEDDING</a>
49<ul><li><a href="#FILESETS">FILESETS</a>
50<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
51<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
52<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
53</ul>
54</li>
55<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
56<li><a href="#EXAMPLES">EXAMPLES</a></li>
57</ul>
58</li>
59<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
43<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
44</li> 61</li>
45</ul><hr /> 62</ul><hr />
46<!-- INDEX END --> 63<!-- INDEX END -->
47 64
48<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
49<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
50<p>libev - a high performance full-featured event loop written in C</p> 67<p>libev - a high performance full-featured event loop written in C</p>
51 68
52</div> 69</div>
53<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
54<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
55<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
56 73
57</pre> 74</pre>
58 75
59</div> 76</div>
60<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
78<div id="EXAMPLE_PROGRAM_CONTENT">
79<pre> #include &lt;ev.h&gt;
80
81 ev_io stdin_watcher;
82 ev_timer timeout_watcher;
83
84 /* called when data readable on stdin */
85 static void
86 stdin_cb (EV_P_ struct ev_io *w, int revents)
87 {
88 /* puts (&quot;stdin ready&quot;); */
89 ev_io_stop (EV_A_ w); /* just a syntax example */
90 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
91 }
92
93 static void
94 timeout_cb (EV_P_ struct ev_timer *w, int revents)
95 {
96 /* puts (&quot;timeout&quot;); */
97 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
98 }
99
100 int
101 main (void)
102 {
103 struct ev_loop *loop = ev_default_loop (0);
104
105 /* initialise an io watcher, then start it */
106 ev_io_init (&amp;stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
107 ev_io_start (loop, &amp;stdin_watcher);
108
109 /* simple non-repeating 5.5 second timeout */
110 ev_timer_init (&amp;timeout_watcher, timeout_cb, 5.5, 0.);
111 ev_timer_start (loop, &amp;timeout_watcher);
112
113 /* loop till timeout or data ready */
114 ev_loop (loop, 0);
115
116 return 0;
117 }
118
119</pre>
120
121</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1>
61<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
62<p>Libev is an event loop: you register interest in certain events (such as a 124<p>Libev is an event loop: you register interest in certain events (such as a
63file descriptor being readable or a timeout occuring), and it will manage 125file descriptor being readable or a timeout occuring), and it will manage
64these event sources and provide your program with events.</p> 126these event sources and provide your program with events.</p>
65<p>To do this, it must take more or less complete control over your process 127<p>To do this, it must take more or less complete control over your process
… …
69watchers</i>, which are relatively small C structures you initialise with the 131watchers</i>, which are relatively small C structures you initialise with the
70details of the event, and then hand it over to libev by <i>starting</i> the 132details of the event, and then hand it over to libev by <i>starting</i> the
71watcher.</p> 133watcher.</p>
72 134
73</div> 135</div>
74<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1>
75<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
76<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 138<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the
77kqueue mechanisms for file descriptor events, relative timers, absolute 139bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms
78timers with customised rescheduling, signal events, process status change 140for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>),
79events (related to SIGCHLD), and event watchers dealing with the event 141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous
80loop mechanism itself (idle, prepare and check watchers). It also is quite 142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and
143event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
144<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
145file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this
81fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
82it to libevent for example).</p> 149for example).</p>
83 150
84</div> 151</div>
85<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 152<h1 id="CONVENTIONS">CONVENTIONS</h1>
86<div id="CONVENTIONS_CONTENT"> 153<div id="CONVENTIONS_CONTENT">
87<p>Libev is very configurable. In this manual the default configuration 154<p>Libev is very configurable. In this manual the default configuration will
88will be described, which supports multiple event loops. For more info 155be described, which supports multiple event loops. For more info about
89about various configuration options please have a look at the file 156various configuration options please have a look at <strong>EMBED</strong> section in
90<cite>README.embed</cite> in the libev distribution. If libev was configured without 157this manual. If libev was configured without support for multiple event
91support for multiple event loops, then all functions taking an initial 158loops, then all functions taking an initial argument of name <code>loop</code>
92argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 159(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
93will not have this argument.</p>
94 160
95</div> 161</div>
96<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 162<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
97<div id="TIME_REPRESENTATION_CONTENT"> 163<div id="TIME_REPRESENTATION_CONTENT">
98<p>Libev represents time as a single floating point number, representing the 164<p>Libev represents time as a single floating point number, representing the
99(fractional) number of seconds since the (POSIX) epoch (somewhere near 165(fractional) number of seconds since the (POSIX) epoch (somewhere near
100the beginning of 1970, details are complicated, don't ask). This type is 166the beginning of 1970, details are complicated, don't ask). This type is
101called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 167called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
102to the <code>double</code> type in C, and when you need to do any calculations on 168to the <code>double</code> type in C, and when you need to do any calculations on
103it, you should treat it as such.</p> 169it, you should treat it as such.</p>
104 170
105
106
107
108
109</div> 171</div>
110<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 172<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
111<div id="GLOBAL_FUNCTIONS_CONTENT"> 173<div id="GLOBAL_FUNCTIONS_CONTENT">
112<p>These functions can be called anytime, even before initialising the 174<p>These functions can be called anytime, even before initialising the
113library in any way.</p> 175library in any way.</p>
114<dl> 176<dl>
115 <dt>ev_tstamp ev_time ()</dt> 177 <dt>ev_tstamp ev_time ()</dt>
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128version of the library your program was compiled against.</p> 190version of the library your program was compiled against.</p>
129 <p>Usually, it's a good idea to terminate if the major versions mismatch, 191 <p>Usually, it's a good idea to terminate if the major versions mismatch,
130as this indicates an incompatible change. Minor versions are usually 192as this indicates an incompatible change. Minor versions are usually
131compatible to older versions, so a larger minor version alone is usually 193compatible to older versions, so a larger minor version alone is usually
132not a problem.</p> 194not a problem.</p>
133 <p>Example: make sure we haven't accidentally been linked against the wrong 195 <p>Example: Make sure we haven't accidentally been linked against the wrong
134version:</p> 196version.</p>
135<pre> assert ((&quot;libev version mismatch&quot;, 197<pre> assert ((&quot;libev version mismatch&quot;,
136 ev_version_major () == EV_VERSION_MAJOR 198 ev_version_major () == EV_VERSION_MAJOR
137 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 199 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
138 200
139</pre> 201</pre>
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167might be supported on the current system, you would need to look at 229might be supported on the current system, you would need to look at
168<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
169recommended ones.</p> 231recommended ones.</p>
170 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 232 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
171 </dd> 233 </dd>
172 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt>
173 <dd> 235 <dd>
174 <p>Sets the allocation function to use (the prototype is similar to the 236 <p>Sets the allocation function to use (the prototype and semantics are
175realloc C function, the semantics are identical). It is used to allocate 237identical to the realloc C function). It is used to allocate and free
176and free memory (no surprises here). If it returns zero when memory 238memory (no surprises here). If it returns zero when memory needs to be
177needs to be allocated, the library might abort or take some potentially 239allocated, the library might abort or take some potentially destructive
178destructive action. The default is your system realloc function.</p> 240action. The default is your system realloc function.</p>
179 <p>You could override this function in high-availability programs to, say, 241 <p>You could override this function in high-availability programs to, say,
180free some memory if it cannot allocate memory, to use a special allocator, 242free some memory if it cannot allocate memory, to use a special allocator,
181or even to sleep a while and retry until some memory is available.</p> 243or even to sleep a while and retry until some memory is available.</p>
182 <p>Example: replace the libev allocator with one that waits a bit and then 244 <p>Example: Replace the libev allocator with one that waits a bit and then
183retries: better than mine).</p> 245retries).</p>
184<pre> static void * 246<pre> static void *
185 persistent_realloc (void *ptr, long size) 247 persistent_realloc (void *ptr, size_t size)
186 { 248 {
187 for (;;) 249 for (;;)
188 { 250 {
189 void *newptr = realloc (ptr, size); 251 void *newptr = realloc (ptr, size);
190 252
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207indicating the system call or subsystem causing the problem. If this 269indicating the system call or subsystem causing the problem. If this
208callback is set, then libev will expect it to remedy the sitution, no 270callback is set, then libev will expect it to remedy the sitution, no
209matter what, when it returns. That is, libev will generally retry the 271matter what, when it returns. That is, libev will generally retry the
210requested operation, or, if the condition doesn't go away, do bad stuff 272requested operation, or, if the condition doesn't go away, do bad stuff
211(such as abort).</p> 273(such as abort).</p>
212 <p>Example: do the same thing as libev does internally:</p> 274 <p>Example: This is basically the same thing that libev does internally, too.</p>
213<pre> static void 275<pre> static void
214 fatal_error (const char *msg) 276 fatal_error (const char *msg)
215 { 277 {
216 perror (msg); 278 perror (msg);
217 abort (); 279 abort ();
… …
223</pre> 285</pre>
224 </dd> 286 </dd>
225</dl> 287</dl>
226 288
227</div> 289</div>
228<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 290<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
229<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 291<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
230<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 292<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
231types of such loops, the <i>default</i> loop, which supports signals and child 293types of such loops, the <i>default</i> loop, which supports signals and child
232events, and dynamically created loops which do not.</p> 294events, and dynamically created loops which do not.</p>
233<p>If you use threads, a common model is to run the default event loop 295<p>If you use threads, a common model is to run the default event loop
… …
353 <dd> 415 <dd>
354 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 416 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
355always distinct from the default loop. Unlike the default loop, it cannot 417always distinct from the default loop. Unlike the default loop, it cannot
356handle signal and child watchers, and attempts to do so will be greeted by 418handle signal and child watchers, and attempts to do so will be greeted by
357undefined behaviour (or a failed assertion if assertions are enabled).</p> 419undefined behaviour (or a failed assertion if assertions are enabled).</p>
358 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 420 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
359<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 421<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
360 if (!epoller) 422 if (!epoller)
361 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 423 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
362 424
363</pre> 425</pre>
364 </dd> 426 </dd>
365 <dt>ev_default_destroy ()</dt> 427 <dt>ev_default_destroy ()</dt>
366 <dd> 428 <dd>
367 <p>Destroys the default loop again (frees all memory and kernel state 429 <p>Destroys the default loop again (frees all memory and kernel state
368etc.). This stops all registered event watchers (by not touching them in 430etc.). None of the active event watchers will be stopped in the normal
369any way whatsoever, although you cannot rely on this :).</p> 431sense, so e.g. <code>ev_is_active</code> might still return true. It is your
432responsibility to either stop all watchers cleanly yoursef <i>before</i>
433calling this function, or cope with the fact afterwards (which is usually
434the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
435for example).</p>
370 </dd> 436 </dd>
371 <dt>ev_loop_destroy (loop)</dt> 437 <dt>ev_loop_destroy (loop)</dt>
372 <dd> 438 <dd>
373 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 439 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
374earlier call to <code>ev_loop_new</code>.</p> 440earlier call to <code>ev_loop_new</code>.</p>
… …
452 be handled here by queueing them when their watcher gets executed. 518 be handled here by queueing them when their watcher gets executed.
453 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 519 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
454 were used, return, otherwise continue with step *. 520 were used, return, otherwise continue with step *.
455 521
456</pre> 522</pre>
457 <p>Example: queue some jobs and then loop until no events are outsanding 523 <p>Example: Queue some jobs and then loop until no events are outsanding
458anymore.</p> 524anymore.</p>
459<pre> ... queue jobs here, make sure they register event watchers as long 525<pre> ... queue jobs here, make sure they register event watchers as long
460 ... as they still have work to do (even an idle watcher will do..) 526 ... as they still have work to do (even an idle watcher will do..)
461 ev_loop (my_loop, 0); 527 ev_loop (my_loop, 0);
462 ... jobs done. yeah! 528 ... jobs done. yeah!
… …
481example, libev itself uses this for its internal signal pipe: It is not 547example, libev itself uses this for its internal signal pipe: It is not
482visible to the libev user and should not keep <code>ev_loop</code> from exiting if 548visible to the libev user and should not keep <code>ev_loop</code> from exiting if
483no event watchers registered by it are active. It is also an excellent 549no event watchers registered by it are active. It is also an excellent
484way to do this for generic recurring timers or from within third-party 550way to do this for generic recurring timers or from within third-party
485libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 551libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
486 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 552 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
487running when nothing else is active.</p> 553running when nothing else is active.</p>
488<pre> struct dv_signal exitsig; 554<pre> struct ev_signal exitsig;
489 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 555 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
490 ev_signal_start (myloop, &amp;exitsig); 556 ev_signal_start (loop, &amp;exitsig);
491 evf_unref (myloop); 557 evf_unref (loop);
492 558
493</pre> 559</pre>
494 <p>Example: for some weird reason, unregister the above signal handler again.</p> 560 <p>Example: For some weird reason, unregister the above signal handler again.</p>
495<pre> ev_ref (myloop); 561<pre> ev_ref (loop);
496 ev_signal_stop (myloop, &amp;exitsig); 562 ev_signal_stop (loop, &amp;exitsig);
497 563
498</pre> 564</pre>
499 </dd> 565 </dd>
500</dl> 566</dl>
501 567
568
569
570
571
502</div> 572</div>
503<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 573<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
504<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 574<div id="ANATOMY_OF_A_WATCHER_CONTENT">
505<p>A watcher is a structure that you create and register to record your 575<p>A watcher is a structure that you create and register to record your
506interest in some event. For instance, if you want to wait for STDIN to 576interest in some event. For instance, if you want to wait for STDIN to
507become readable, you would create an <code>ev_io</code> watcher for that:</p> 577become readable, you would create an <code>ev_io</code> watcher for that:</p>
508<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 578<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
535with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 605with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
536*)</code>), and you can stop watching for events at any time by calling the 606*)</code>), and you can stop watching for events at any time by calling the
537corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 607corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
538<p>As long as your watcher is active (has been started but not stopped) you 608<p>As long as your watcher is active (has been started but not stopped) you
539must not touch the values stored in it. Most specifically you must never 609must not touch the values stored in it. Most specifically you must never
540reinitialise it or call its set macro.</p> 610reinitialise it or call its <code>set</code> macro.</p>
541<p>You can check whether an event is active by calling the <code>ev_is_active
542(watcher *)</code> macro. To see whether an event is outstanding (but the
543callback for it has not been called yet) you can use the <code>ev_is_pending
544(watcher *)</code> macro.</p>
545<p>Each and every callback receives the event loop pointer as first, the 611<p>Each and every callback receives the event loop pointer as first, the
546registered watcher structure as second, and a bitset of received events as 612registered watcher structure as second, and a bitset of received events as
547third argument.</p> 613third argument.</p>
548<p>The received events usually include a single bit per event type received 614<p>The received events usually include a single bit per event type received
549(you can receive multiple events at the same time). The possible bit masks 615(you can receive multiple events at the same time). The possible bit masks
… …
569 </dd> 635 </dd>
570 <dt><code>EV_CHILD</code></dt> 636 <dt><code>EV_CHILD</code></dt>
571 <dd> 637 <dd>
572 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 638 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
573 </dd> 639 </dd>
640 <dt><code>EV_STAT</code></dt>
641 <dd>
642 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
643 </dd>
574 <dt><code>EV_IDLE</code></dt> 644 <dt><code>EV_IDLE</code></dt>
575 <dd> 645 <dd>
576 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 646 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
577 </dd> 647 </dd>
578 <dt><code>EV_PREPARE</code></dt> 648 <dt><code>EV_PREPARE</code></dt>
… …
583<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 653<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
584received events. Callbacks of both watcher types can start and stop as 654received events. Callbacks of both watcher types can start and stop as
585many watchers as they want, and all of them will be taken into account 655many watchers as they want, and all of them will be taken into account
586(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 656(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
587<code>ev_loop</code> from blocking).</p> 657<code>ev_loop</code> from blocking).</p>
658 </dd>
659 <dt><code>EV_EMBED</code></dt>
660 <dd>
661 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
662 </dd>
663 <dt><code>EV_FORK</code></dt>
664 <dd>
665 <p>The event loop has been resumed in the child process after fork (see
666<code>ev_fork</code>).</p>
588 </dd> 667 </dd>
589 <dt><code>EV_ERROR</code></dt> 668 <dt><code>EV_ERROR</code></dt>
590 <dd> 669 <dd>
591 <p>An unspecified error has occured, the watcher has been stopped. This might 670 <p>An unspecified error has occured, the watcher has been stopped. This might
592happen because the watcher could not be properly started because libev 671happen because the watcher could not be properly started because libev
… …
600programs, though, so beware.</p> 679programs, though, so beware.</p>
601 </dd> 680 </dd>
602</dl> 681</dl>
603 682
604</div> 683</div>
684<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
685<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
686<p>In the following description, <code>TYPE</code> stands for the watcher type,
687e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
688<dl>
689 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
690 <dd>
691 <p>This macro initialises the generic portion of a watcher. The contents
692of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
693the generic parts of the watcher are initialised, you <i>need</i> to call
694the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
695type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
696which rolls both calls into one.</p>
697 <p>You can reinitialise a watcher at any time as long as it has been stopped
698(or never started) and there are no pending events outstanding.</p>
699 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
700int revents)</code>.</p>
701 </dd>
702 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
703 <dd>
704 <p>This macro initialises the type-specific parts of a watcher. You need to
705call <code>ev_init</code> at least once before you call this macro, but you can
706call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
707macro on a watcher that is active (it can be pending, however, which is a
708difference to the <code>ev_init</code> macro).</p>
709 <p>Although some watcher types do not have type-specific arguments
710(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
711 </dd>
712 <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
713 <dd>
714 <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
715calls into a single call. This is the most convinient method to initialise
716a watcher. The same limitations apply, of course.</p>
717 </dd>
718 <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
719 <dd>
720 <p>Starts (activates) the given watcher. Only active watchers will receive
721events. If the watcher is already active nothing will happen.</p>
722 </dd>
723 <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
724 <dd>
725 <p>Stops the given watcher again (if active) and clears the pending
726status. It is possible that stopped watchers are pending (for example,
727non-repeating timers are being stopped when they become pending), but
728<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
729you want to free or reuse the memory used by the watcher it is therefore a
730good idea to always call its <code>ev_TYPE_stop</code> function.</p>
731 </dd>
732 <dt>bool ev_is_active (ev_TYPE *watcher)</dt>
733 <dd>
734 <p>Returns a true value iff the watcher is active (i.e. it has been started
735and not yet been stopped). As long as a watcher is active you must not modify
736it.</p>
737 </dd>
738 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
739 <dd>
740 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
741events but its callback has not yet been invoked). As long as a watcher
742is pending (but not active) you must not call an init function on it (but
743<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
744libev (e.g. you cnanot <code>free ()</code> it).</p>
745 </dd>
746 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd>
748 <p>Returns the callback currently set on the watcher.</p>
749 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd>
752 <p>Change the callback. You can change the callback at virtually any time
753(modulo threads).</p>
754 </dd>
755</dl>
756
757
758
759
760
761</div>
605<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 762<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
606<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 763<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
607<p>Each watcher has, by default, a member <code>void *data</code> that you can change 764<p>Each watcher has, by default, a member <code>void *data</code> that you can change
608and read at any time, libev will completely ignore it. This can be used 765and read at any time, libev will completely ignore it. This can be used
609to associate arbitrary data with your watcher. If you need more data and 766to associate arbitrary data with your watcher. If you need more data and
… …
626 struct my_io *w = (struct my_io *)w_; 783 struct my_io *w = (struct my_io *)w_;
627 ... 784 ...
628 } 785 }
629 786
630</pre> 787</pre>
631<p>More interesting and less C-conformant ways of catsing your callback type 788<p>More interesting and less C-conformant ways of casting your callback type
632have been omitted....</p> 789instead have been omitted.</p>
790<p>Another common scenario is having some data structure with multiple
791watchers:</p>
792<pre> struct my_biggy
793 {
794 int some_data;
795 ev_timer t1;
796 ev_timer t2;
797 }
633 798
799</pre>
800<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
801you need to use <code>offsetof</code>:</p>
802<pre> #include &lt;stddef.h&gt;
634 803
804 static void
805 t1_cb (EV_P_ struct ev_timer *w, int revents)
806 {
807 struct my_biggy big = (struct my_biggy *
808 (((char *)w) - offsetof (struct my_biggy, t1));
809 }
635 810
811 static void
812 t2_cb (EV_P_ struct ev_timer *w, int revents)
813 {
814 struct my_biggy big = (struct my_biggy *
815 (((char *)w) - offsetof (struct my_biggy, t2));
816 }
636 817
637 818
819
820
821</pre>
822
638</div> 823</div>
639<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 824<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
640<div id="WATCHER_TYPES_CONTENT"> 825<div id="WATCHER_TYPES_CONTENT">
641<p>This section describes each watcher in detail, but will not repeat 826<p>This section describes each watcher in detail, but will not repeat
642information given in the last section.</p> 827information given in the last section. Any initialisation/set macros,
828functions and members specific to the watcher type are explained.</p>
829<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
830while the watcher is active, you can look at the member and expect some
831sensible content, but you must not modify it (you can modify it while the
832watcher is stopped to your hearts content), or <i>[read-write]</i>, which
833means you can expect it to have some sensible content while the watcher
834is active, but you can also modify it. Modifying it may not do something
835sensible or take immediate effect (or do anything at all), but libev will
836not crash or malfunction in any way.</p>
643 837
644 838
645 839
646 840
647 841
648</div> 842</div>
649<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 843<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
650<div id="code_ev_io_code_is_this_file_descrip-2"> 844<div id="code_ev_io_code_is_this_file_descrip-2">
651<p>I/O watchers check whether a file descriptor is readable or writable 845<p>I/O watchers check whether a file descriptor is readable or writable
652in each iteration of the event loop (This behaviour is called 846in each iteration of the event loop, or, more precisely, when reading
653level-triggering because you keep receiving events as long as the 847would not block the process and writing would at least be able to write
654condition persists. Remember you can stop the watcher if you don't want to 848some data. This behaviour is called level-triggering because you keep
655act on the event and neither want to receive future events).</p> 849receiving events as long as the condition persists. Remember you can stop
850the watcher if you don't want to act on the event and neither want to
851receive future events.</p>
656<p>In general you can register as many read and/or write event watchers per 852<p>In general you can register as many read and/or write event watchers per
657fd as you want (as long as you don't confuse yourself). Setting all file 853fd as you want (as long as you don't confuse yourself). Setting all file
658descriptors to non-blocking mode is also usually a good idea (but not 854descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing).</p> 855required if you know what you are doing).</p>
660<p>You have to be careful with dup'ed file descriptors, though. Some backends 856<p>You have to be careful with dup'ed file descriptors, though. Some backends
661(the linux epoll backend is a notable example) cannot handle dup'ed file 857(the linux epoll backend is a notable example) cannot handle dup'ed file
662descriptors correctly if you register interest in two or more fds pointing 858descriptors correctly if you register interest in two or more fds pointing
663to the same underlying file/socket etc. description (that is, they share 859to the same underlying file/socket/etc. description (that is, they share
664the same underlying &quot;file open&quot;).</p> 860the same underlying &quot;file open&quot;).</p>
665<p>If you must do this, then force the use of a known-to-be-good backend 861<p>If you must do this, then force the use of a known-to-be-good backend
666(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and 862(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
667<code>EVBACKEND_POLL</code>).</p> 863<code>EVBACKEND_POLL</code>).</p>
864<p>Another thing you have to watch out for is that it is quite easy to
865receive &quot;spurious&quot; readyness notifications, that is your callback might
866be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
867because there is no data. Not only are some backends known to create a
868lot of those (for example solaris ports), it is very easy to get into
869this situation even with a relatively standard program structure. Thus
870it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
871<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
872<p>If you cannot run the fd in non-blocking mode (for example you should not
873play around with an Xlib connection), then you have to seperately re-test
874wether a file descriptor is really ready with a known-to-be good interface
875such as poll (fortunately in our Xlib example, Xlib already does this on
876its own, so its quite safe to use).</p>
668<dl> 877<dl>
669 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 878 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
670 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 879 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
671 <dd> 880 <dd>
672 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 881 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
673events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 882rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
674EV_WRITE</code> to receive the given events.</p> 883<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
675 <p>Please note that most of the more scalable backend mechanisms (for example 884 </dd>
676epoll and solaris ports) can result in spurious readyness notifications 885 <dt>int fd [read-only]</dt>
677for file descriptors, so you practically need to use non-blocking I/O (and 886 <dd>
678treat callback invocation as hint only), or retest separately with a safe 887 <p>The file descriptor being watched.</p>
679interface before doing I/O (XLib can do this), or force the use of either 888 </dd>
680<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 889 <dt>int events [read-only]</dt>
681problem. Also note that it is quite easy to have your callback invoked 890 <dd>
682when the readyness condition is no longer valid even when employing 891 <p>The events being watched.</p>
683typical ways of handling events, so its a good idea to use non-blocking
684I/O unconditionally.</p>
685 </dd> 892 </dd>
686</dl> 893</dl>
687<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 894<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
688readable, but only once. Since it is likely line-buffered, you could 895readable, but only once. Since it is likely line-buffered, you could
689attempt to read a whole line in the callback:</p> 896attempt to read a whole line in the callback.</p>
690<pre> static void 897<pre> static void
691 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 898 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
692 { 899 {
693 ev_io_stop (loop, w); 900 ev_io_stop (loop, w);
694 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 901 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
705 912
706 913
707</pre> 914</pre>
708 915
709</div> 916</div>
710<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 917<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
711<div id="code_ev_timer_code_relative_and_opti-2"> 918<div id="code_ev_timer_code_relative_and_opti-2">
712<p>Timer watchers are simple relative timers that generate an event after a 919<p>Timer watchers are simple relative timers that generate an event after a
713given time, and optionally repeating in regular intervals after that.</p> 920given time, and optionally repeating in regular intervals after that.</p>
714<p>The timers are based on real time, that is, if you register an event that 921<p>The timers are based on real time, that is, if you register an event that
715times out after an hour and you reset your system clock to last years 922times out after an hour and you reset your system clock to last years
… …
747repeating. The exact semantics are:</p> 954repeating. The exact semantics are:</p>
748 <p>If the timer is started but nonrepeating, stop it.</p> 955 <p>If the timer is started but nonrepeating, stop it.</p>
749 <p>If the timer is repeating, either start it if necessary (with the repeat 956 <p>If the timer is repeating, either start it if necessary (with the repeat
750value), or reset the running timer to the repeat value.</p> 957value), or reset the running timer to the repeat value.</p>
751 <p>This sounds a bit complicated, but here is a useful and typical 958 <p>This sounds a bit complicated, but here is a useful and typical
752example: Imagine you have a tcp connection and you want a so-called idle 959example: Imagine you have a tcp connection and you want a so-called
753timeout, that is, you want to be called when there have been, say, 60 960idle timeout, that is, you want to be called when there have been,
754seconds of inactivity on the socket. The easiest way to do this is to 961say, 60 seconds of inactivity on the socket. The easiest way to do
755configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 962this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
756time you successfully read or write some data. If you go into an idle 963<code>ev_timer_again</code> each time you successfully read or write some data. If
757state where you do not expect data to travel on the socket, you can stop 964you go into an idle state where you do not expect data to travel on the
758the timer, and again will automatically restart it if need be.</p> 965socket, you can stop the timer, and again will automatically restart it if
966need be.</p>
967 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
968and only ever use the <code>repeat</code> value:</p>
969<pre> ev_timer_init (timer, callback, 0., 5.);
970 ev_timer_again (loop, timer);
971 ...
972 timer-&gt;again = 17.;
973 ev_timer_again (loop, timer);
974 ...
975 timer-&gt;again = 10.;
976 ev_timer_again (loop, timer);
977
978</pre>
979 <p>This is more efficient then stopping/starting the timer eahc time you want
980to modify its timeout value.</p>
981 </dd>
982 <dt>ev_tstamp repeat [read-write]</dt>
983 <dd>
984 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
985or <code>ev_timer_again</code> is called and determines the next timeout (if any),
986which is also when any modifications are taken into account.</p>
759 </dd> 987 </dd>
760</dl> 988</dl>
761<p>Example: create a timer that fires after 60 seconds.</p> 989<p>Example: Create a timer that fires after 60 seconds.</p>
762<pre> static void 990<pre> static void
763 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 991 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
764 { 992 {
765 .. one minute over, w is actually stopped right here 993 .. one minute over, w is actually stopped right here
766 } 994 }
… …
768 struct ev_timer mytimer; 996 struct ev_timer mytimer;
769 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 997 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
770 ev_timer_start (loop, &amp;mytimer); 998 ev_timer_start (loop, &amp;mytimer);
771 999
772</pre> 1000</pre>
773<p>Example: create a timeout timer that times out after 10 seconds of 1001<p>Example: Create a timeout timer that times out after 10 seconds of
774inactivity.</p> 1002inactivity.</p>
775<pre> static void 1003<pre> static void
776 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1004 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
777 { 1005 {
778 .. ten seconds without any activity 1006 .. ten seconds without any activity
… …
791 1019
792 1020
793</pre> 1021</pre>
794 1022
795</div> 1023</div>
796<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 1024<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
797<div id="code_ev_periodic_code_to_cron_or_not-2"> 1025<div id="code_ev_periodic_code_to_cron_or_not-2">
798<p>Periodic watchers are also timers of a kind, but they are very versatile 1026<p>Periodic watchers are also timers of a kind, but they are very versatile
799(and unfortunately a bit complex).</p> 1027(and unfortunately a bit complex).</p>
800<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 1028<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
801but on wallclock time (absolute time). You can tell a periodic watcher 1029but on wallclock time (absolute time). You can tell a periodic watcher
802to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1030to trigger &quot;at&quot; some specific point in time. For example, if you tell a
803periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 1031periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
804+ 10.&gt;) and then reset your system clock to the last year, then it will 1032+ 10.</code>) and then reset your system clock to the last year, then it will
805take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1033take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
806roughly 10 seconds later and of course not if you reset your system time 1034roughly 10 seconds later and of course not if you reset your system time
807again).</p> 1035again).</p>
808<p>They can also be used to implement vastly more complex timers, such as 1036<p>They can also be used to implement vastly more complex timers, such as
809triggering an event on eahc midnight, local time.</p> 1037triggering an event on eahc midnight, local time.</p>
… …
881 <p>Simply stops and restarts the periodic watcher again. This is only useful 1109 <p>Simply stops and restarts the periodic watcher again. This is only useful
882when you changed some parameters or the reschedule callback would return 1110when you changed some parameters or the reschedule callback would return
883a different time than the last time it was called (e.g. in a crond like 1111a different time than the last time it was called (e.g. in a crond like
884program when the crontabs have changed).</p> 1112program when the crontabs have changed).</p>
885 </dd> 1113 </dd>
1114 <dt>ev_tstamp interval [read-write]</dt>
1115 <dd>
1116 <p>The current interval value. Can be modified any time, but changes only
1117take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1118called.</p>
1119 </dd>
1120 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1121 <dd>
1122 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1123switched off. Can be changed any time, but changes only take effect when
1124the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1125 </dd>
886</dl> 1126</dl>
887<p>Example: call a callback every hour, or, more precisely, whenever the 1127<p>Example: Call a callback every hour, or, more precisely, whenever the
888system clock is divisible by 3600. The callback invocation times have 1128system clock is divisible by 3600. The callback invocation times have
889potentially a lot of jittering, but good long-term stability.</p> 1129potentially a lot of jittering, but good long-term stability.</p>
890<pre> static void 1130<pre> static void
891 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1131 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
892 { 1132 {
… …
896 struct ev_periodic hourly_tick; 1136 struct ev_periodic hourly_tick;
897 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1137 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
898 ev_periodic_start (loop, &amp;hourly_tick); 1138 ev_periodic_start (loop, &amp;hourly_tick);
899 1139
900</pre> 1140</pre>
901<p>Example: the same as above, but use a reschedule callback to do it:</p> 1141<p>Example: The same as above, but use a reschedule callback to do it:</p>
902<pre> #include &lt;math.h&gt; 1142<pre> #include &lt;math.h&gt;
903 1143
904 static ev_tstamp 1144 static ev_tstamp
905 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1145 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
906 { 1146 {
… …
908 } 1148 }
909 1149
910 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1150 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
911 1151
912</pre> 1152</pre>
913<p>Example: call a callback every hour, starting now:</p> 1153<p>Example: Call a callback every hour, starting now:</p>
914<pre> struct ev_periodic hourly_tick; 1154<pre> struct ev_periodic hourly_tick;
915 ev_periodic_init (&amp;hourly_tick, clock_cb, 1155 ev_periodic_init (&amp;hourly_tick, clock_cb,
916 fmod (ev_now (loop), 3600.), 3600., 0); 1156 fmod (ev_now (loop), 3600.), 3600., 0);
917 ev_periodic_start (loop, &amp;hourly_tick); 1157 ev_periodic_start (loop, &amp;hourly_tick);
918 1158
… …
920 1160
921 1161
922</pre> 1162</pre>
923 1163
924</div> 1164</div>
925<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1165<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
926<div id="code_ev_signal_code_signal_me_when_a-2"> 1166<div id="code_ev_signal_code_signal_me_when_a-2">
927<p>Signal watchers will trigger an event when the process receives a specific 1167<p>Signal watchers will trigger an event when the process receives a specific
928signal one or more times. Even though signals are very asynchronous, libev 1168signal one or more times. Even though signals are very asynchronous, libev
929will try it's best to deliver signals synchronously, i.e. as part of the 1169will try it's best to deliver signals synchronously, i.e. as part of the
930normal event processing, like any other event.</p> 1170normal event processing, like any other event.</p>
… …
939 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1179 <dt>ev_signal_set (ev_signal *, int signum)</dt>
940 <dd> 1180 <dd>
941 <p>Configures the watcher to trigger on the given signal number (usually one 1181 <p>Configures the watcher to trigger on the given signal number (usually one
942of the <code>SIGxxx</code> constants).</p> 1182of the <code>SIGxxx</code> constants).</p>
943 </dd> 1183 </dd>
1184 <dt>int signum [read-only]</dt>
1185 <dd>
1186 <p>The signal the watcher watches out for.</p>
1187 </dd>
944</dl> 1188</dl>
945 1189
946 1190
947 1191
948 1192
949 1193
950</div> 1194</div>
951<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1195<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
952<div id="code_ev_child_code_wait_for_pid_stat-2"> 1196<div id="code_ev_child_code_watch_out_for_pro-2">
953<p>Child watchers trigger when your process receives a SIGCHLD in response to 1197<p>Child watchers trigger when your process receives a SIGCHLD in response to
954some child status changes (most typically when a child of yours dies).</p> 1198some child status changes (most typically when a child of yours dies).</p>
955<dl> 1199<dl>
956 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1200 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
957 <dt>ev_child_set (ev_child *, int pid)</dt> 1201 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
961at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1205at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
962the status word (use the macros from <code>sys/wait.h</code> and see your systems 1206the status word (use the macros from <code>sys/wait.h</code> and see your systems
963<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1207<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
964process causing the status change.</p> 1208process causing the status change.</p>
965 </dd> 1209 </dd>
1210 <dt>int pid [read-only]</dt>
1211 <dd>
1212 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1213 </dd>
1214 <dt>int rpid [read-write]</dt>
1215 <dd>
1216 <p>The process id that detected a status change.</p>
1217 </dd>
1218 <dt>int rstatus [read-write]</dt>
1219 <dd>
1220 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1221<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1222 </dd>
966</dl> 1223</dl>
967<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1224<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
968<pre> static void 1225<pre> static void
969 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1226 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
970 { 1227 {
971 ev_unloop (loop, EVUNLOOP_ALL); 1228 ev_unloop (loop, EVUNLOOP_ALL);
972 } 1229 }
… …
979 1236
980 1237
981</pre> 1238</pre>
982 1239
983</div> 1240</div>
1241<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1242<div id="code_ev_stat_code_did_the_file_attri-2">
1243<p>This watches a filesystem path for attribute changes. That is, it calls
1244<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1245compared to the last time, invoking the callback if it did.</p>
1246<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1247not exist&quot; is a status change like any other. The condition &quot;path does
1248not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1249otherwise always forced to be at least one) and all the other fields of
1250the stat buffer having unspecified contents.</p>
1251<p>Since there is no standard to do this, the portable implementation simply
1252calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You
1253can specify a recommended polling interval for this case. If you specify
1254a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1255unspecified default</i> value will be used (which you can expect to be around
1256five seconds, although this might change dynamically). Libev will also
1257impose a minimum interval which is currently around <code>0.1</code>, but thats
1258usually overkill.</p>
1259<p>This watcher type is not meant for massive numbers of stat watchers,
1260as even with OS-supported change notifications, this can be
1261resource-intensive.</p>
1262<p>At the time of this writing, no specific OS backends are implemented, but
1263if demand increases, at least a kqueue and inotify backend will be added.</p>
1264<dl>
1265 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1266 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1267 <dd>
1268 <p>Configures the watcher to wait for status changes of the given
1269<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1270be detected and should normally be specified as <code>0</code> to let libev choose
1271a suitable value. The memory pointed to by <code>path</code> must point to the same
1272path for as long as the watcher is active.</p>
1273 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1274relative to the attributes at the time the watcher was started (or the
1275last change was detected).</p>
1276 </dd>
1277 <dt>ev_stat_stat (ev_stat *)</dt>
1278 <dd>
1279 <p>Updates the stat buffer immediately with new values. If you change the
1280watched path in your callback, you could call this fucntion to avoid
1281detecting this change (while introducing a race condition). Can also be
1282useful simply to find out the new values.</p>
1283 </dd>
1284 <dt>ev_statdata attr [read-only]</dt>
1285 <dd>
1286 <p>The most-recently detected attributes of the file. Although the type is of
1287<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1288suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1289was some error while <code>stat</code>ing the file.</p>
1290 </dd>
1291 <dt>ev_statdata prev [read-only]</dt>
1292 <dd>
1293 <p>The previous attributes of the file. The callback gets invoked whenever
1294<code>prev</code> != <code>attr</code>.</p>
1295 </dd>
1296 <dt>ev_tstamp interval [read-only]</dt>
1297 <dd>
1298 <p>The specified interval.</p>
1299 </dd>
1300 <dt>const char *path [read-only]</dt>
1301 <dd>
1302 <p>The filesystem path that is being watched.</p>
1303 </dd>
1304</dl>
1305<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1306<pre> static void
1307 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1308 {
1309 /* /etc/passwd changed in some way */
1310 if (w-&gt;attr.st_nlink)
1311 {
1312 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1313 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1314 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1315 }
1316 else
1317 /* you shalt not abuse printf for puts */
1318 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1319 &quot;if this is windows, they already arrived\n&quot;);
1320 }
1321
1322 ...
1323 ev_stat passwd;
1324
1325 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1326 ev_stat_start (loop, &amp;passwd);
1327
1328
1329
1330
1331</pre>
1332
1333</div>
984<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1334<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
985<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1335<div id="code_ev_idle_code_when_you_ve_got_no-2">
986<p>Idle watchers trigger events when there are no other events are pending 1336<p>Idle watchers trigger events when there are no other events are pending
987(prepare, check and other idle watchers do not count). That is, as long 1337(prepare, check and other idle watchers do not count). That is, as long
988as your process is busy handling sockets or timeouts (or even signals, 1338as your process is busy handling sockets or timeouts (or even signals,
989imagine) it will not be triggered. But when your process is idle all idle 1339imagine) it will not be triggered. But when your process is idle all idle
… …
1002 <p>Initialises and configures the idle watcher - it has no parameters of any 1352 <p>Initialises and configures the idle watcher - it has no parameters of any
1003kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1353kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1004believe me.</p> 1354believe me.</p>
1005 </dd> 1355 </dd>
1006</dl> 1356</dl>
1007<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1357<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1008callback, free it. Alos, use no error checking, as usual.</p> 1358callback, free it. Also, use no error checking, as usual.</p>
1009<pre> static void 1359<pre> static void
1010 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1360 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1011 { 1361 {
1012 free (w); 1362 free (w);
1013 // now do something you wanted to do when the program has 1363 // now do something you wanted to do when the program has
… …
1022 1372
1023 1373
1024</pre> 1374</pre>
1025 1375
1026</div> 1376</div>
1027<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1377<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1028<div id="code_ev_prepare_code_and_code_ev_che-2"> 1378<div id="code_ev_prepare_code_and_code_ev_che-2">
1029<p>Prepare and check watchers are usually (but not always) used in tandem: 1379<p>Prepare and check watchers are usually (but not always) used in tandem:
1030prepare watchers get invoked before the process blocks and check watchers 1380prepare watchers get invoked before the process blocks and check watchers
1031afterwards.</p> 1381afterwards.</p>
1382<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1383the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1384watchers. Other loops than the current one are fine, however. The
1385rationale behind this is that you do not need to check for recursion in
1386those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1387<code>ev_check</code> so if you have one watcher of each kind they will always be
1388called in pairs bracketing the blocking call.</p>
1032<p>Their main purpose is to integrate other event mechanisms into libev and 1389<p>Their main purpose is to integrate other event mechanisms into libev and
1033their use is somewhat advanced. This could be used, for example, to track 1390their use is somewhat advanced. This could be used, for example, to track
1034variable changes, implement your own watchers, integrate net-snmp or a 1391variable changes, implement your own watchers, integrate net-snmp or a
1035coroutine library and lots more.</p> 1392coroutine library and lots more. They are also occasionally useful if
1393you cache some data and want to flush it before blocking (for example,
1394in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1395watcher).</p>
1036<p>This is done by examining in each prepare call which file descriptors need 1396<p>This is done by examining in each prepare call which file descriptors need
1037to be watched by the other library, registering <code>ev_io</code> watchers for 1397to be watched by the other library, registering <code>ev_io</code> watchers for
1038them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1398them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1039provide just this functionality). Then, in the check watcher you check for 1399provide just this functionality). Then, in the check watcher you check for
1040any events that occured (by checking the pending status of all watchers 1400any events that occured (by checking the pending status of all watchers
… …
1056 <p>Initialises and configures the prepare or check watcher - they have no 1416 <p>Initialises and configures the prepare or check watcher - they have no
1057parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1417parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1058macros, but using them is utterly, utterly and completely pointless.</p> 1418macros, but using them is utterly, utterly and completely pointless.</p>
1059 </dd> 1419 </dd>
1060</dl> 1420</dl>
1061<p>Example: *TODO*.</p> 1421<p>Example: To include a library such as adns, you would add IO watchers
1422and a timeout watcher in a prepare handler, as required by libadns, and
1423in a check watcher, destroy them and call into libadns. What follows is
1424pseudo-code only of course:</p>
1425<pre> static ev_io iow [nfd];
1426 static ev_timer tw;
1062 1427
1428 static void
1429 io_cb (ev_loop *loop, ev_io *w, int revents)
1430 {
1431 // set the relevant poll flags
1432 // could also call adns_processreadable etc. here
1433 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1434 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1435 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1436 }
1063 1437
1438 // create io watchers for each fd and a timer before blocking
1439 static void
1440 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1441 {
1442 int timeout = 3600000;truct pollfd fds [nfd];
1443 // actual code will need to loop here and realloc etc.
1444 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1064 1445
1446 /* the callback is illegal, but won't be called as we stop during check */
1447 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1448 ev_timer_start (loop, &amp;tw);
1065 1449
1450 // create on ev_io per pollfd
1451 for (int i = 0; i &lt; nfd; ++i)
1452 {
1453 ev_io_init (iow + i, io_cb, fds [i].fd,
1454 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1455 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1066 1456
1457 fds [i].revents = 0;
1458 iow [i].data = fds + i;
1459 ev_io_start (loop, iow + i);
1460 }
1461 }
1462
1463 // stop all watchers after blocking
1464 static void
1465 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1466 {
1467 ev_timer_stop (loop, &amp;tw);
1468
1469 for (int i = 0; i &lt; nfd; ++i)
1470 ev_io_stop (loop, iow + i);
1471
1472 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1473 }
1474
1475
1476
1477
1478</pre>
1479
1067</div> 1480</div>
1068<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1481<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1069<div id="code_ev_embed_code_when_one_backend_-2"> 1482<div id="code_ev_embed_code_when_one_backend_-2">
1070<p>This is a rather advanced watcher type that lets you embed one event loop 1483<p>This is a rather advanced watcher type that lets you embed one event loop
1071into another.</p> 1484into another (currently only <code>ev_io</code> events are supported in the embedded
1485loop, other types of watchers might be handled in a delayed or incorrect
1486fashion and must not be used).</p>
1072<p>There are primarily two reasons you would want that: work around bugs and 1487<p>There are primarily two reasons you would want that: work around bugs and
1073prioritise I/O.</p> 1488prioritise I/O.</p>
1074<p>As an example for a bug workaround, the kqueue backend might only support 1489<p>As an example for a bug workaround, the kqueue backend might only support
1075sockets on some platform, so it is unusable as generic backend, but you 1490sockets on some platform, so it is unusable as generic backend, but you
1076still want to make use of it because you have many sockets and it scales 1491still want to make use of it because you have many sockets and it scales
… …
1081<p>As for prioritising I/O: rarely you have the case where some fds have 1496<p>As for prioritising I/O: rarely you have the case where some fds have
1082to be watched and handled very quickly (with low latency), and even 1497to be watched and handled very quickly (with low latency), and even
1083priorities and idle watchers might have too much overhead. In this case 1498priorities and idle watchers might have too much overhead. In this case
1084you would put all the high priority stuff in one loop and all the rest in 1499you would put all the high priority stuff in one loop and all the rest in
1085a second one, and embed the second one in the first.</p> 1500a second one, and embed the second one in the first.</p>
1501<p>As long as the watcher is active, the callback will be invoked every time
1502there might be events pending in the embedded loop. The callback must then
1503call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1504their callbacks (you could also start an idle watcher to give the embedded
1505loop strictly lower priority for example). You can also set the callback
1506to <code>0</code>, in which case the embed watcher will automatically execute the
1507embedded loop sweep.</p>
1086<p>As long as the watcher is started it will automatically handle events. The 1508<p>As long as the watcher is started it will automatically handle events. The
1087callback will be invoked whenever some events have been handled. You can 1509callback will be invoked whenever some events have been handled. You can
1088set the callback to <code>0</code> to avoid having to specify one if you are not 1510set the callback to <code>0</code> to avoid having to specify one if you are not
1089interested in that.</p> 1511interested in that.</p>
1090<p>Also, there have not currently been made special provisions for forking: 1512<p>Also, there have not currently been made special provisions for forking:
… …
1117 else 1539 else
1118 loop_lo = loop_hi; 1540 loop_lo = loop_hi;
1119 1541
1120</pre> 1542</pre>
1121<dl> 1543<dl>
1122 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *loop)</dt> 1544 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1123 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *loop)</dt> 1545 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1546 <dd>
1547 <p>Configures the watcher to embed the given loop, which must be
1548embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1549invoked automatically, otherwise it is the responsibility of the callback
1550to invoke it (it will continue to be called until the sweep has been done,
1551if you do not want thta, you need to temporarily stop the embed watcher).</p>
1124 <dd> 1552 </dd>
1125 <p>Configures the watcher to embed the given loop, which must be embeddable.</p> 1553 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1554 <dd>
1555 <p>Make a single, non-blocking sweep over the embedded loop. This works
1556similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1557apropriate way for embedded loops.</p>
1558 </dd>
1559 <dt>struct ev_loop *loop [read-only]</dt>
1560 <dd>
1561 <p>The embedded event loop.</p>
1126 </dd> 1562 </dd>
1127</dl> 1563</dl>
1128 1564
1129 1565
1130 1566
1131 1567
1132 1568
1133</div> 1569</div>
1134<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1570<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>
1571<div id="code_ev_fork_code_the_audacity_to_re-2">
1572<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1573whoever is a good citizen cared to tell libev about it by calling
1574<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1575event loop blocks next and before <code>ev_check</code> watchers are being called,
1576and only in the child after the fork. If whoever good citizen calling
1577<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1578handlers will be invoked, too, of course.</p>
1579<dl>
1580 <dt>ev_fork_init (ev_signal *, callback)</dt>
1581 <dd>
1582 <p>Initialises and configures the fork watcher - it has no parameters of any
1583kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1584believe me.</p>
1585 </dd>
1586</dl>
1587
1588
1589
1590
1591
1592</div>
1593<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1135<div id="OTHER_FUNCTIONS_CONTENT"> 1594<div id="OTHER_FUNCTIONS_CONTENT">
1136<p>There are some other functions of possible interest. Described. Here. Now.</p> 1595<p>There are some other functions of possible interest. Described. Here. Now.</p>
1137<dl> 1596<dl>
1138 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1597 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1139 <dd> 1598 <dd>
… …
1163 1622
1164 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1623 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1165 1624
1166</pre> 1625</pre>
1167 </dd> 1626 </dd>
1168 <dt>ev_feed_event (loop, watcher, int events)</dt> 1627 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
1169 <dd> 1628 <dd>
1170 <p>Feeds the given event set into the event loop, as if the specified event 1629 <p>Feeds the given event set into the event loop, as if the specified event
1171had happened for the specified watcher (which must be a pointer to an 1630had happened for the specified watcher (which must be a pointer to an
1172initialised but not necessarily started event watcher).</p> 1631initialised but not necessarily started event watcher).</p>
1173 </dd> 1632 </dd>
1174 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1633 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
1175 <dd> 1634 <dd>
1176 <p>Feed an event on the given fd, as if a file descriptor backend detected 1635 <p>Feed an event on the given fd, as if a file descriptor backend detected
1177the given events it.</p> 1636the given events it.</p>
1178 </dd> 1637 </dd>
1179 <dt>ev_feed_signal_event (loop, int signum)</dt> 1638 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
1180 <dd> 1639 <dd>
1181 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1640 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1641loop!).</p>
1182 </dd> 1642 </dd>
1183</dl> 1643</dl>
1184 1644
1185 1645
1186 1646
1187 1647
1188 1648
1189</div> 1649</div>
1190<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1650<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1191<div id="LIBEVENT_EMULATION_CONTENT"> 1651<div id="LIBEVENT_EMULATION_CONTENT">
1192<p>Libev offers a compatibility emulation layer for libevent. It cannot 1652<p>Libev offers a compatibility emulation layer for libevent. It cannot
1193emulate the internals of libevent, so here are some usage hints:</p> 1653emulate the internals of libevent, so here are some usage hints:</p>
1194<dl> 1654<dl>
1195 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1655 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1205 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1665 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1206to use the libev header file and library.</dt> 1666to use the libev header file and library.</dt>
1207</dl> 1667</dl>
1208 1668
1209</div> 1669</div>
1210<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1670<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1211<div id="C_SUPPORT_CONTENT"> 1671<div id="C_SUPPORT_CONTENT">
1212<p>TBD.</p> 1672<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1673you to use some convinience methods to start/stop watchers and also change
1674the callback model to a model using method callbacks on objects.</p>
1675<p>To use it,</p>
1676<pre> #include &lt;ev++.h&gt;
1213 1677
1678</pre>
1679<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1680and puts all of its definitions (many of them macros) into the global
1681namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1682<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1683<code>EV_MULTIPLICITY</code>.</p>
1684<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1685<dl>
1686 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1687 <dd>
1688 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1689macros from <cite>ev.h</cite>.</p>
1690 </dd>
1691 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1692 <dd>
1693 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1694 </dd>
1695 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1696 <dd>
1697 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1698the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1699which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1700defines by many implementations.</p>
1701 <p>All of those classes have these methods:</p>
1702 <p>
1703 <dl>
1704 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1705 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1706 <dt>ev::TYPE::~TYPE</dt>
1707 <dd>
1708 <p>The constructor takes a pointer to an object and a method pointer to
1709the event handler callback to call in this class. The constructor calls
1710<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1711before starting it. If you do not specify a loop then the constructor
1712automatically associates the default loop with this watcher.</p>
1713 <p>The destructor automatically stops the watcher if it is active.</p>
1714 </dd>
1715 <dt>w-&gt;set (struct ev_loop *)</dt>
1716 <dd>
1717 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1718do this when the watcher is inactive (and not pending either).</p>
1719 </dd>
1720 <dt>w-&gt;set ([args])</dt>
1721 <dd>
1722 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1723called at least once. Unlike the C counterpart, an active watcher gets
1724automatically stopped and restarted.</p>
1725 </dd>
1726 <dt>w-&gt;start ()</dt>
1727 <dd>
1728 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1729constructor already takes the loop.</p>
1730 </dd>
1731 <dt>w-&gt;stop ()</dt>
1732 <dd>
1733 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1734 </dd>
1735 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1736 <dd>
1737 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1738<code>ev_TYPE_again</code> function.</p>
1739 </dd>
1740 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1741 <dd>
1742 <p>Invokes <code>ev_embed_sweep</code>.</p>
1743 </dd>
1744 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1745 <dd>
1746 <p>Invokes <code>ev_stat_stat</code>.</p>
1747 </dd>
1748 </dl>
1749 </p>
1750 </dd>
1751</dl>
1752<p>Example: Define a class with an IO and idle watcher, start one of them in
1753the constructor.</p>
1754<pre> class myclass
1755 {
1756 ev_io io; void io_cb (ev::io &amp;w, int revents);
1757 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1758
1759 myclass ();
1760 }
1761
1762 myclass::myclass (int fd)
1763 : io (this, &amp;myclass::io_cb),
1764 idle (this, &amp;myclass::idle_cb)
1765 {
1766 io.start (fd, ev::READ);
1767 }
1768
1769
1770
1771
1772</pre>
1773
1214</div> 1774</div>
1215<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1775<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1776<div id="MACRO_MAGIC_CONTENT">
1777<p>Libev can be compiled with a variety of options, the most fundemantal is
1778<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1779callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1780<p>To make it easier to write programs that cope with either variant, the
1781following macros are defined:</p>
1782<dl>
1783 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1784 <dd>
1785 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1786loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1787<code>EV_A_</code> is used when other arguments are following. Example:</p>
1788<pre> ev_unref (EV_A);
1789 ev_timer_add (EV_A_ watcher);
1790 ev_loop (EV_A_ 0);
1791
1792</pre>
1793 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1794which is often provided by the following macro.</p>
1795 </dd>
1796 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1797 <dd>
1798 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1799loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1800<code>EV_P_</code> is used when other parameters are following. Example:</p>
1801<pre> // this is how ev_unref is being declared
1802 static void ev_unref (EV_P);
1803
1804 // this is how you can declare your typical callback
1805 static void cb (EV_P_ ev_timer *w, int revents)
1806
1807</pre>
1808 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1809suitable for use with <code>EV_A</code>.</p>
1810 </dd>
1811 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1812 <dd>
1813 <p>Similar to the other two macros, this gives you the value of the default
1814loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1815 </dd>
1816</dl>
1817<p>Example: Declare and initialise a check watcher, working regardless of
1818wether multiple loops are supported or not.</p>
1819<pre> static void
1820 check_cb (EV_P_ ev_timer *w, int revents)
1821 {
1822 ev_check_stop (EV_A_ w);
1823 }
1824
1825 ev_check check;
1826 ev_check_init (&amp;check, check_cb);
1827 ev_check_start (EV_DEFAULT_ &amp;check);
1828 ev_loop (EV_DEFAULT_ 0);
1829
1830
1831
1832
1833</pre>
1834
1835</div>
1836<h1 id="EMBEDDING">EMBEDDING</h1>
1837<div id="EMBEDDING_CONTENT">
1838<p>Libev can (and often is) directly embedded into host
1839applications. Examples of applications that embed it include the Deliantra
1840Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1841and rxvt-unicode.</p>
1842<p>The goal is to enable you to just copy the neecssary files into your
1843source directory without having to change even a single line in them, so
1844you can easily upgrade by simply copying (or having a checked-out copy of
1845libev somewhere in your source tree).</p>
1846
1847</div>
1848<h2 id="FILESETS">FILESETS</h2>
1849<div id="FILESETS_CONTENT">
1850<p>Depending on what features you need you need to include one or more sets of files
1851in your app.</p>
1852
1853</div>
1854<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1855<div id="CORE_EVENT_LOOP_CONTENT">
1856<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1857configuration (no autoconf):</p>
1858<pre> #define EV_STANDALONE 1
1859 #include &quot;ev.c&quot;
1860
1861</pre>
1862<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1863single C source file only to provide the function implementations. To use
1864it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1865done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1866where you can put other configuration options):</p>
1867<pre> #define EV_STANDALONE 1
1868 #include &quot;ev.h&quot;
1869
1870</pre>
1871<p>Both header files and implementation files can be compiled with a C++
1872compiler (at least, thats a stated goal, and breakage will be treated
1873as a bug).</p>
1874<p>You need the following files in your source tree, or in a directory
1875in your include path (e.g. in libev/ when using -Ilibev):</p>
1876<pre> ev.h
1877 ev.c
1878 ev_vars.h
1879 ev_wrap.h
1880
1881 ev_win32.c required on win32 platforms only
1882
1883 ev_select.c only when select backend is enabled (which is by default)
1884 ev_poll.c only when poll backend is enabled (disabled by default)
1885 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1886 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1887 ev_port.c only when the solaris port backend is enabled (disabled by default)
1888
1889</pre>
1890<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1891to compile this single file.</p>
1892
1893</div>
1894<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1895<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1896<p>To include the libevent compatibility API, also include:</p>
1897<pre> #include &quot;event.c&quot;
1898
1899</pre>
1900<p>in the file including <cite>ev.c</cite>, and:</p>
1901<pre> #include &quot;event.h&quot;
1902
1903</pre>
1904<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1905<p>You need the following additional files for this:</p>
1906<pre> event.h
1907 event.c
1908
1909</pre>
1910
1911</div>
1912<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1913<div id="AUTOCONF_SUPPORT_CONTENT">
1914<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1915whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1916<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1917include <cite>config.h</cite> and configure itself accordingly.</p>
1918<p>For this of course you need the m4 file:</p>
1919<pre> libev.m4
1920
1921</pre>
1922
1923</div>
1924<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1925<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1926<p>Libev can be configured via a variety of preprocessor symbols you have to define
1927before including any of its files. The default is not to build for multiplicity
1928and only include the select backend.</p>
1929<dl>
1930 <dt>EV_STANDALONE</dt>
1931 <dd>
1932 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1933keeps libev from including <cite>config.h</cite>, and it also defines dummy
1934implementations for some libevent functions (such as logging, which is not
1935supported). It will also not define any of the structs usually found in
1936<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1937 </dd>
1938 <dt>EV_USE_MONOTONIC</dt>
1939 <dd>
1940 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1941monotonic clock option at both compiletime and runtime. Otherwise no use
1942of the monotonic clock option will be attempted. If you enable this, you
1943usually have to link against librt or something similar. Enabling it when
1944the functionality isn't available is safe, though, althoguh you have
1945to make sure you link against any libraries where the <code>clock_gettime</code>
1946function is hiding in (often <cite>-lrt</cite>).</p>
1947 </dd>
1948 <dt>EV_USE_REALTIME</dt>
1949 <dd>
1950 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1951realtime clock option at compiletime (and assume its availability at
1952runtime if successful). Otherwise no use of the realtime clock option will
1953be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1954(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1955in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1956 </dd>
1957 <dt>EV_USE_SELECT</dt>
1958 <dd>
1959 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1960<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1961other method takes over, select will be it. Otherwise the select backend
1962will not be compiled in.</p>
1963 </dd>
1964 <dt>EV_SELECT_USE_FD_SET</dt>
1965 <dd>
1966 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1967structure. This is useful if libev doesn't compile due to a missing
1968<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1969exotic systems. This usually limits the range of file descriptors to some
1970low limit such as 1024 or might have other limitations (winsocket only
1971allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1972influence the size of the <code>fd_set</code> used.</p>
1973 </dd>
1974 <dt>EV_SELECT_IS_WINSOCKET</dt>
1975 <dd>
1976 <p>When defined to <code>1</code>, the select backend will assume that
1977select/socket/connect etc. don't understand file descriptors but
1978wants osf handles on win32 (this is the case when the select to
1979be used is the winsock select). This means that it will call
1980<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1981it is assumed that all these functions actually work on fds, even
1982on win32. Should not be defined on non-win32 platforms.</p>
1983 </dd>
1984 <dt>EV_USE_POLL</dt>
1985 <dd>
1986 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1987backend. Otherwise it will be enabled on non-win32 platforms. It
1988takes precedence over select.</p>
1989 </dd>
1990 <dt>EV_USE_EPOLL</dt>
1991 <dd>
1992 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
1993<code>epoll</code>(7) backend. Its availability will be detected at runtime,
1994otherwise another method will be used as fallback. This is the
1995preferred backend for GNU/Linux systems.</p>
1996 </dd>
1997 <dt>EV_USE_KQUEUE</dt>
1998 <dd>
1999 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
2000<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
2001otherwise another method will be used as fallback. This is the preferred
2002backend for BSD and BSD-like systems, although on most BSDs kqueue only
2003supports some types of fds correctly (the only platform we found that
2004supports ptys for example was NetBSD), so kqueue might be compiled in, but
2005not be used unless explicitly requested. The best way to use it is to find
2006out whether kqueue supports your type of fd properly and use an embedded
2007kqueue loop.</p>
2008 </dd>
2009 <dt>EV_USE_PORT</dt>
2010 <dd>
2011 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
201210 port style backend. Its availability will be detected at runtime,
2013otherwise another method will be used as fallback. This is the preferred
2014backend for Solaris 10 systems.</p>
2015 </dd>
2016 <dt>EV_USE_DEVPOLL</dt>
2017 <dd>
2018 <p>reserved for future expansion, works like the USE symbols above.</p>
2019 </dd>
2020 <dt>EV_H</dt>
2021 <dd>
2022 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
2023undefined 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
2024can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
2025 </dd>
2026 <dt>EV_CONFIG_H</dt>
2027 <dd>
2028 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
2029<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
2030<code>EV_H</code>, above.</p>
2031 </dd>
2032 <dt>EV_EVENT_H</dt>
2033 <dd>
2034 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
2035of how the <cite>event.h</cite> header can be found.</p>
2036 </dd>
2037 <dt>EV_PROTOTYPES</dt>
2038 <dd>
2039 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
2040prototypes, but still define all the structs and other symbols. This is
2041occasionally useful if you want to provide your own wrapper functions
2042around libev functions.</p>
2043 </dd>
2044 <dt>EV_MULTIPLICITY</dt>
2045 <dd>
2046 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
2047will have the <code>struct ev_loop *</code> as first argument, and you can create
2048additional independent event loops. Otherwise there will be no support
2049for multiple event loops and there is no first event loop pointer
2050argument. Instead, all functions act on the single default loop.</p>
2051 </dd>
2052 <dt>EV_PERIODIC_ENABLE</dt>
2053 <dd>
2054 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2055defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2056code.</p>
2057 </dd>
2058 <dt>EV_EMBED_ENABLE</dt>
2059 <dd>
2060 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2061defined to be <code>0</code>, then they are not.</p>
2062 </dd>
2063 <dt>EV_STAT_ENABLE</dt>
2064 <dd>
2065 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2066defined to be <code>0</code>, then they are not.</p>
2067 </dd>
2068 <dt>EV_FORK_ENABLE</dt>
2069 <dd>
2070 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2071defined to be <code>0</code>, then they are not.</p>
2072 </dd>
2073 <dt>EV_MINIMAL</dt>
2074 <dd>
2075 <p>If you need to shave off some kilobytes of code at the expense of some
2076speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2077some inlining decisions, saves roughly 30% codesize of amd64.</p>
2078 </dd>
2079 <dt>EV_PID_HASHSIZE</dt>
2080 <dd>
2081 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2082pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2083than enough. If you need to manage thousands of children you might want to
2084increase this value.</p>
2085 </dd>
2086 <dt>EV_COMMON</dt>
2087 <dd>
2088 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2089this macro to a something else you can include more and other types of
2090members. You have to define it each time you include one of the files,
2091though, and it must be identical each time.</p>
2092 <p>For example, the perl EV module uses something like this:</p>
2093<pre> #define EV_COMMON \
2094 SV *self; /* contains this struct */ \
2095 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2096
2097</pre>
2098 </dd>
2099 <dt>EV_CB_DECLARE (type)</dt>
2100 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2101 <dt>ev_set_cb (ev, cb)</dt>
2102 <dd>
2103 <p>Can be used to change the callback member declaration in each watcher,
2104and the way callbacks are invoked and set. Must expand to a struct member
2105definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2106their default definitions. One possible use for overriding these is to
2107avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2108method calls instead of plain function calls in C++.</p>
2109
2110</div>
2111<h2 id="EXAMPLES">EXAMPLES</h2>
2112<div id="EXAMPLES_CONTENT">
2113 <p>For a real-world example of a program the includes libev
2114verbatim, you can have a look at the EV perl module
2115(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2116the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2117interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2118will be compiled. It is pretty complex because it provides its own header
2119file.</p>
2120 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2121that everybody includes and which overrides some autoconf choices:</p>
2122<pre> #define EV_USE_POLL 0
2123 #define EV_MULTIPLICITY 0
2124 #define EV_PERIODICS 0
2125 #define EV_CONFIG_H &lt;config.h&gt;
2126
2127 #include &quot;ev++.h&quot;
2128
2129</pre>
2130 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2131<pre> #include &quot;ev_cpp.h&quot;
2132 #include &quot;ev.c&quot;
2133
2134
2135
2136
2137</pre>
2138
2139</div>
2140<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2141<div id="COMPLEXITIES_CONTENT">
2142 <p>In this section the complexities of (many of) the algorithms used inside
2143libev will be explained. For complexity discussions about backends see the
2144documentation for <code>ev_default_init</code>.</p>
2145 <p>
2146 <dl>
2147 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2148 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2149 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2150 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2151 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
2152 <dt>Finding the next timer per loop iteration: O(1)</dt>
2153 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2154 <dt>Activating one watcher: O(1)</dt>
2155 </dl>
2156 </p>
2157
2158
2159
2160
2161
2162</div>
2163<h1 id="AUTHOR">AUTHOR</h1>
1216<div id="AUTHOR_CONTENT"> 2164<div id="AUTHOR_CONTENT">
1217<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2165 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1218 2166
1219</div> 2167</div>
1220</div></body> 2168</div></body>
1221</html> 2169</html>

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