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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="Wed Nov 28 19:29:25 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>), the Linux <code>inotify</code> interface
79events (related to SIGCHLD), and event watchers dealing with the event 141(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
80loop mechanism itself (idle, prepare and check watchers). It also is quite 142with customised rescheduling (<code>ev_periodic</code>), synchronous signals
143(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
144watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
145<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
146file watchers (<code>ev_stat</code>) and even limited support for fork events
147(<code>ev_fork</code>).</p>
148<p>It also is quite fast (see this
81fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 149<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
82it to libevent for example).</p> 150for example).</p>
83 151
84</div> 152</div>
85<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 153<h1 id="CONVENTIONS">CONVENTIONS</h1>
86<div id="CONVENTIONS_CONTENT"> 154<div id="CONVENTIONS_CONTENT">
87<p>Libev is very configurable. In this manual the default configuration 155<p>Libev is very configurable. In this manual the default configuration will
88will be described, which supports multiple event loops. For more info 156be described, which supports multiple event loops. For more info about
89about various configuration options please have a look at the file 157various 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 158this manual. If libev was configured without support for multiple event
91support for multiple event loops, then all functions taking an initial 159loops, 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>) 160(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
93will not have this argument.</p>
94 161
95</div> 162</div>
96<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 163<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
97<div id="TIME_REPRESENTATION_CONTENT"> 164<div id="TIME_REPRESENTATION_CONTENT">
98<p>Libev represents time as a single floating point number, representing the 165<p>Libev represents time as a single floating point number, representing the
99(fractional) number of seconds since the (POSIX) epoch (somewhere near 166(fractional) number of seconds since the (POSIX) epoch (somewhere near
100the beginning of 1970, details are complicated, don't ask). This type is 167the 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 168called <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 169to the <code>double</code> type in C, and when you need to do any calculations on
103it, you should treat it as such.</p> 170it, you should treat it as such.</p>
104 171
105
106
107
108
109</div> 172</div>
110<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 173<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
111<div id="GLOBAL_FUNCTIONS_CONTENT"> 174<div id="GLOBAL_FUNCTIONS_CONTENT">
112<p>These functions can be called anytime, even before initialising the 175<p>These functions can be called anytime, even before initialising the
113library in any way.</p> 176library in any way.</p>
114<dl> 177<dl>
115 <dt>ev_tstamp ev_time ()</dt> 178 <dt>ev_tstamp ev_time ()</dt>
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128version of the library your program was compiled against.</p> 191version of the library your program was compiled against.</p>
129 <p>Usually, it's a good idea to terminate if the major versions mismatch, 192 <p>Usually, it's a good idea to terminate if the major versions mismatch,
130as this indicates an incompatible change. Minor versions are usually 193as this indicates an incompatible change. Minor versions are usually
131compatible to older versions, so a larger minor version alone is usually 194compatible to older versions, so a larger minor version alone is usually
132not a problem.</p> 195not a problem.</p>
133 <p>Example: make sure we haven't accidentally been linked against the wrong 196 <p>Example: Make sure we haven't accidentally been linked against the wrong
134version:</p> 197version.</p>
135<pre> assert ((&quot;libev version mismatch&quot;, 198<pre> assert ((&quot;libev version mismatch&quot;,
136 ev_version_major () == EV_VERSION_MAJOR 199 ev_version_major () == EV_VERSION_MAJOR
137 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 200 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
138 201
139</pre> 202</pre>
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169recommended ones.</p> 232recommended ones.</p>
170 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 233 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
171 </dd> 234 </dd>
172 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
173 <dd> 236 <dd>
174 <p>Sets the allocation function to use (the prototype is similar to the 237 <p>Sets the allocation function to use (the prototype is similar - the
175realloc C function, the semantics are identical). It is used to allocate 238semantics is identical - to the realloc C function). It is used to
176and free memory (no surprises here). If it returns zero when memory 239allocate and free memory (no surprises here). If it returns zero when
177needs to be allocated, the library might abort or take some potentially 240memory needs to be allocated, the library might abort or take some
178destructive action. The default is your system realloc function.</p> 241potentially destructive action. The default is your system realloc
242function.</p>
179 <p>You could override this function in high-availability programs to, say, 243 <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, 244free 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> 245or 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 246 <p>Example: Replace the libev allocator with one that waits a bit and then
183retries: better than mine).</p> 247retries).</p>
184<pre> static void * 248<pre> static void *
185 persistent_realloc (void *ptr, long size) 249 persistent_realloc (void *ptr, size_t size)
186 { 250 {
187 for (;;) 251 for (;;)
188 { 252 {
189 void *newptr = realloc (ptr, size); 253 void *newptr = realloc (ptr, size);
190 254
… …
207indicating the system call or subsystem causing the problem. If this 271indicating the system call or subsystem causing the problem. If this
208callback is set, then libev will expect it to remedy the sitution, no 272callback is set, then libev will expect it to remedy the sitution, no
209matter what, when it returns. That is, libev will generally retry the 273matter what, when it returns. That is, libev will generally retry the
210requested operation, or, if the condition doesn't go away, do bad stuff 274requested operation, or, if the condition doesn't go away, do bad stuff
211(such as abort).</p> 275(such as abort).</p>
212 <p>Example: do the same thing as libev does internally:</p> 276 <p>Example: This is basically the same thing that libev does internally, too.</p>
213<pre> static void 277<pre> static void
214 fatal_error (const char *msg) 278 fatal_error (const char *msg)
215 { 279 {
216 perror (msg); 280 perror (msg);
217 abort (); 281 abort ();
… …
223</pre> 287</pre>
224 </dd> 288 </dd>
225</dl> 289</dl>
226 290
227</div> 291</div>
228<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 292<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
229<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 293<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 294<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 295types of such loops, the <i>default</i> loop, which supports signals and child
232events, and dynamically created loops which do not.</p> 296events, and dynamically created loops which do not.</p>
233<p>If you use threads, a common model is to run the default event loop 297<p>If you use threads, a common model is to run the default event loop
… …
353 <dd> 417 <dd>
354 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 418 <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 419always 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 420handle signal and child watchers, and attempts to do so will be greeted by
357undefined behaviour (or a failed assertion if assertions are enabled).</p> 421undefined 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> 422 <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); 423<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
360 if (!epoller) 424 if (!epoller)
361 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 425 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
362 426
363</pre> 427</pre>
364 </dd> 428 </dd>
365 <dt>ev_default_destroy ()</dt> 429 <dt>ev_default_destroy ()</dt>
366 <dd> 430 <dd>
367 <p>Destroys the default loop again (frees all memory and kernel state 431 <p>Destroys the default loop again (frees all memory and kernel state
368etc.). This stops all registered event watchers (by not touching them in 432etc.). None of the active event watchers will be stopped in the normal
369any way whatsoever, although you cannot rely on this :).</p> 433sense, so e.g. <code>ev_is_active</code> might still return true. It is your
434responsibility to either stop all watchers cleanly yoursef <i>before</i>
435calling this function, or cope with the fact afterwards (which is usually
436the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
437for example).</p>
370 </dd> 438 </dd>
371 <dt>ev_loop_destroy (loop)</dt> 439 <dt>ev_loop_destroy (loop)</dt>
372 <dd> 440 <dd>
373 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 441 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
374earlier call to <code>ev_loop_new</code>.</p> 442earlier call to <code>ev_loop_new</code>.</p>
… …
452 be handled here by queueing them when their watcher gets executed. 520 be handled here by queueing them when their watcher gets executed.
453 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 521 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
454 were used, return, otherwise continue with step *. 522 were used, return, otherwise continue with step *.
455 523
456</pre> 524</pre>
457 <p>Example: queue some jobs and then loop until no events are outsanding 525 <p>Example: Queue some jobs and then loop until no events are outsanding
458anymore.</p> 526anymore.</p>
459<pre> ... queue jobs here, make sure they register event watchers as long 527<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..) 528 ... as they still have work to do (even an idle watcher will do..)
461 ev_loop (my_loop, 0); 529 ev_loop (my_loop, 0);
462 ... jobs done. yeah! 530 ... jobs done. yeah!
… …
481example, libev itself uses this for its internal signal pipe: It is not 549example, 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 550visible 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 551no 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 552way 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> 553libraries. 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> 554 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
487running when nothing else is active.</p> 555running when nothing else is active.</p>
488<pre> struct dv_signal exitsig; 556<pre> struct ev_signal exitsig;
489 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 557 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
490 ev_signal_start (myloop, &amp;exitsig); 558 ev_signal_start (loop, &amp;exitsig);
491 evf_unref (myloop); 559 evf_unref (loop);
492 560
493</pre> 561</pre>
494 <p>Example: for some weird reason, unregister the above signal handler again.</p> 562 <p>Example: For some weird reason, unregister the above signal handler again.</p>
495<pre> ev_ref (myloop); 563<pre> ev_ref (loop);
496 ev_signal_stop (myloop, &amp;exitsig); 564 ev_signal_stop (loop, &amp;exitsig);
497 565
498</pre> 566</pre>
499 </dd> 567 </dd>
500</dl> 568</dl>
501 569
570
571
572
573
502</div> 574</div>
503<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 575<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
504<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 576<div id="ANATOMY_OF_A_WATCHER_CONTENT">
505<p>A watcher is a structure that you create and register to record your 577<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 578interest 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> 579become 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) 580<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 607with 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 608*)</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> 609corresponding 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 610<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 611must not touch the values stored in it. Most specifically you must never
540reinitialise it or call its set macro.</p> 612reinitialise 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 613<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 614registered watcher structure as second, and a bitset of received events as
547third argument.</p> 615third argument.</p>
548<p>The received events usually include a single bit per event type received 616<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 617(you can receive multiple events at the same time). The possible bit masks
… …
569 </dd> 637 </dd>
570 <dt><code>EV_CHILD</code></dt> 638 <dt><code>EV_CHILD</code></dt>
571 <dd> 639 <dd>
572 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 640 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
573 </dd> 641 </dd>
642 <dt><code>EV_STAT</code></dt>
643 <dd>
644 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
645 </dd>
574 <dt><code>EV_IDLE</code></dt> 646 <dt><code>EV_IDLE</code></dt>
575 <dd> 647 <dd>
576 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 648 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
577 </dd> 649 </dd>
578 <dt><code>EV_PREPARE</code></dt> 650 <dt><code>EV_PREPARE</code></dt>
… …
583<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 655<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 656received 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 657many 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 658(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
587<code>ev_loop</code> from blocking).</p> 659<code>ev_loop</code> from blocking).</p>
660 </dd>
661 <dt><code>EV_EMBED</code></dt>
662 <dd>
663 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
664 </dd>
665 <dt><code>EV_FORK</code></dt>
666 <dd>
667 <p>The event loop has been resumed in the child process after fork (see
668<code>ev_fork</code>).</p>
588 </dd> 669 </dd>
589 <dt><code>EV_ERROR</code></dt> 670 <dt><code>EV_ERROR</code></dt>
590 <dd> 671 <dd>
591 <p>An unspecified error has occured, the watcher has been stopped. This might 672 <p>An unspecified error has occured, the watcher has been stopped. This might
592happen because the watcher could not be properly started because libev 673happen because the watcher could not be properly started because libev
… …
600programs, though, so beware.</p> 681programs, though, so beware.</p>
601 </dd> 682 </dd>
602</dl> 683</dl>
603 684
604</div> 685</div>
686<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
687<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
688<p>In the following description, <code>TYPE</code> stands for the watcher type,
689e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
690<dl>
691 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
692 <dd>
693 <p>This macro initialises the generic portion of a watcher. The contents
694of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
695the generic parts of the watcher are initialised, you <i>need</i> to call
696the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
697type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
698which rolls both calls into one.</p>
699 <p>You can reinitialise a watcher at any time as long as it has been stopped
700(or never started) and there are no pending events outstanding.</p>
701 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
702int revents)</code>.</p>
703 </dd>
704 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
705 <dd>
706 <p>This macro initialises the type-specific parts of a watcher. You need to
707call <code>ev_init</code> at least once before you call this macro, but you can
708call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
709macro on a watcher that is active (it can be pending, however, which is a
710difference to the <code>ev_init</code> macro).</p>
711 <p>Although some watcher types do not have type-specific arguments
712(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
713 </dd>
714 <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
715 <dd>
716 <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
717calls into a single call. This is the most convinient method to initialise
718a watcher. The same limitations apply, of course.</p>
719 </dd>
720 <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
721 <dd>
722 <p>Starts (activates) the given watcher. Only active watchers will receive
723events. If the watcher is already active nothing will happen.</p>
724 </dd>
725 <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
726 <dd>
727 <p>Stops the given watcher again (if active) and clears the pending
728status. It is possible that stopped watchers are pending (for example,
729non-repeating timers are being stopped when they become pending), but
730<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
731you want to free or reuse the memory used by the watcher it is therefore a
732good idea to always call its <code>ev_TYPE_stop</code> function.</p>
733 </dd>
734 <dt>bool ev_is_active (ev_TYPE *watcher)</dt>
735 <dd>
736 <p>Returns a true value iff the watcher is active (i.e. it has been started
737and not yet been stopped). As long as a watcher is active you must not modify
738it.</p>
739 </dd>
740 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
741 <dd>
742 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
743events but its callback has not yet been invoked). As long as a watcher
744is pending (but not active) you must not call an init function on it (but
745<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
746libev (e.g. you cnanot <code>free ()</code> it).</p>
747 </dd>
748 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
749 <dd>
750 <p>Returns the callback currently set on the watcher.</p>
751 </dd>
752 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
753 <dd>
754 <p>Change the callback. You can change the callback at virtually any time
755(modulo threads).</p>
756 </dd>
757</dl>
758
759
760
761
762
763</div>
605<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 764<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"> 765<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 766<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 767and 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 768to associate arbitrary data with your watcher. If you need more data and
… …
626 struct my_io *w = (struct my_io *)w_; 785 struct my_io *w = (struct my_io *)w_;
627 ... 786 ...
628 } 787 }
629 788
630</pre> 789</pre>
631<p>More interesting and less C-conformant ways of catsing your callback type 790<p>More interesting and less C-conformant ways of casting your callback type
632have been omitted....</p> 791instead have been omitted.</p>
792<p>Another common scenario is having some data structure with multiple
793watchers:</p>
794<pre> struct my_biggy
795 {
796 int some_data;
797 ev_timer t1;
798 ev_timer t2;
799 }
633 800
801</pre>
802<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
803you need to use <code>offsetof</code>:</p>
804<pre> #include &lt;stddef.h&gt;
634 805
806 static void
807 t1_cb (EV_P_ struct ev_timer *w, int revents)
808 {
809 struct my_biggy big = (struct my_biggy *
810 (((char *)w) - offsetof (struct my_biggy, t1));
811 }
635 812
813 static void
814 t2_cb (EV_P_ struct ev_timer *w, int revents)
815 {
816 struct my_biggy big = (struct my_biggy *
817 (((char *)w) - offsetof (struct my_biggy, t2));
818 }
636 819
637 820
821
822
823</pre>
824
638</div> 825</div>
639<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 826<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
640<div id="WATCHER_TYPES_CONTENT"> 827<div id="WATCHER_TYPES_CONTENT">
641<p>This section describes each watcher in detail, but will not repeat 828<p>This section describes each watcher in detail, but will not repeat
642information given in the last section.</p> 829information given in the last section. Any initialisation/set macros,
830functions and members specific to the watcher type are explained.</p>
831<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
832while the watcher is active, you can look at the member and expect some
833sensible content, but you must not modify it (you can modify it while the
834watcher is stopped to your hearts content), or <i>[read-write]</i>, which
835means you can expect it to have some sensible content while the watcher
836is active, but you can also modify it. Modifying it may not do something
837sensible or take immediate effect (or do anything at all), but libev will
838not crash or malfunction in any way.</p>
643 839
644 840
645 841
646 842
647 843
648</div> 844</div>
649<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 845<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"> 846<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 847<p>I/O watchers check whether a file descriptor is readable or writable
652in each iteration of the event loop (This behaviour is called 848in each iteration of the event loop, or, more precisely, when reading
653level-triggering because you keep receiving events as long as the 849would 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 850some data. This behaviour is called level-triggering because you keep
655act on the event and neither want to receive future events).</p> 851receiving events as long as the condition persists. Remember you can stop
852the watcher if you don't want to act on the event and neither want to
853receive future events.</p>
656<p>In general you can register as many read and/or write event watchers per 854<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 855fd 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 856descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing).</p> 857required if you know what you are doing).</p>
660<p>You have to be careful with dup'ed file descriptors, though. Some backends 858<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 859(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 860descriptors correctly if you register interest in two or more fds pointing
663to the same underlying file/socket etc. description (that is, they share 861to the same underlying file/socket/etc. description (that is, they share
664the same underlying &quot;file open&quot;).</p> 862the 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 863<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 864(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
667<code>EVBACKEND_POLL</code>).</p> 865<code>EVBACKEND_POLL</code>).</p>
866<p>Another thing you have to watch out for is that it is quite easy to
867receive &quot;spurious&quot; readyness notifications, that is your callback might
868be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
869because there is no data. Not only are some backends known to create a
870lot of those (for example solaris ports), it is very easy to get into
871this situation even with a relatively standard program structure. Thus
872it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
873<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
874<p>If you cannot run the fd in non-blocking mode (for example you should not
875play around with an Xlib connection), then you have to seperately re-test
876wether a file descriptor is really ready with a known-to-be good interface
877such as poll (fortunately in our Xlib example, Xlib already does this on
878its own, so its quite safe to use).</p>
668<dl> 879<dl>
669 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 880 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
670 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 881 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
671 <dd> 882 <dd>
672 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 883 <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 | 884rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
674EV_WRITE</code> to receive the given events.</p> 885<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 886 </dd>
676epoll and solaris ports) can result in spurious readyness notifications 887 <dt>int fd [read-only]</dt>
677for file descriptors, so you practically need to use non-blocking I/O (and 888 <dd>
678treat callback invocation as hint only), or retest separately with a safe 889 <p>The file descriptor being watched.</p>
679interface before doing I/O (XLib can do this), or force the use of either 890 </dd>
680<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 891 <dt>int events [read-only]</dt>
681problem. Also note that it is quite easy to have your callback invoked 892 <dd>
682when the readyness condition is no longer valid even when employing 893 <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> 894 </dd>
686</dl> 895</dl>
687<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 896<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 897readable, but only once. Since it is likely line-buffered, you could
689attempt to read a whole line in the callback:</p> 898attempt to read a whole line in the callback.</p>
690<pre> static void 899<pre> static void
691 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 900 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
692 { 901 {
693 ev_io_stop (loop, w); 902 ev_io_stop (loop, w);
694 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 903 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
705 914
706 915
707</pre> 916</pre>
708 917
709</div> 918</div>
710<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 919<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"> 920<div id="code_ev_timer_code_relative_and_opti-2">
712<p>Timer watchers are simple relative timers that generate an event after a 921<p>Timer watchers are simple relative timers that generate an event after a
713given time, and optionally repeating in regular intervals after that.</p> 922given 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 923<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 924times out after an hour and you reset your system clock to last years
… …
747repeating. The exact semantics are:</p> 956repeating. The exact semantics are:</p>
748 <p>If the timer is started but nonrepeating, stop it.</p> 957 <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 958 <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> 959value), or reset the running timer to the repeat value.</p>
751 <p>This sounds a bit complicated, but here is a useful and typical 960 <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 961example: 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 962idle 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 963say, 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 964this 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 965<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 966you 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> 967socket, you can stop the timer, and again will automatically restart it if
968need be.</p>
969 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
970and only ever use the <code>repeat</code> value:</p>
971<pre> ev_timer_init (timer, callback, 0., 5.);
972 ev_timer_again (loop, timer);
973 ...
974 timer-&gt;again = 17.;
975 ev_timer_again (loop, timer);
976 ...
977 timer-&gt;again = 10.;
978 ev_timer_again (loop, timer);
979
980</pre>
981 <p>This is more efficient then stopping/starting the timer eahc time you want
982to modify its timeout value.</p>
983 </dd>
984 <dt>ev_tstamp repeat [read-write]</dt>
985 <dd>
986 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
987or <code>ev_timer_again</code> is called and determines the next timeout (if any),
988which is also when any modifications are taken into account.</p>
759 </dd> 989 </dd>
760</dl> 990</dl>
761<p>Example: create a timer that fires after 60 seconds.</p> 991<p>Example: Create a timer that fires after 60 seconds.</p>
762<pre> static void 992<pre> static void
763 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 993 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
764 { 994 {
765 .. one minute over, w is actually stopped right here 995 .. one minute over, w is actually stopped right here
766 } 996 }
… …
768 struct ev_timer mytimer; 998 struct ev_timer mytimer;
769 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 999 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
770 ev_timer_start (loop, &amp;mytimer); 1000 ev_timer_start (loop, &amp;mytimer);
771 1001
772</pre> 1002</pre>
773<p>Example: create a timeout timer that times out after 10 seconds of 1003<p>Example: Create a timeout timer that times out after 10 seconds of
774inactivity.</p> 1004inactivity.</p>
775<pre> static void 1005<pre> static void
776 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1006 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
777 { 1007 {
778 .. ten seconds without any activity 1008 .. ten seconds without any activity
… …
791 1021
792 1022
793</pre> 1023</pre>
794 1024
795</div> 1025</div>
796<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 1026<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"> 1027<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 1028<p>Periodic watchers are also timers of a kind, but they are very versatile
799(and unfortunately a bit complex).</p> 1029(and unfortunately a bit complex).</p>
800<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 1030<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 1031but 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 1032to 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 () 1033periodic 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 1034+ 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 1035take 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 1036roughly 10 seconds later and of course not if you reset your system time
807again).</p> 1037again).</p>
808<p>They can also be used to implement vastly more complex timers, such as 1038<p>They can also be used to implement vastly more complex timers, such as
809triggering an event on eahc midnight, local time.</p> 1039triggering an event on eahc midnight, local time.</p>
… …
881 <p>Simply stops and restarts the periodic watcher again. This is only useful 1111 <p>Simply stops and restarts the periodic watcher again. This is only useful
882when you changed some parameters or the reschedule callback would return 1112when 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 1113a different time than the last time it was called (e.g. in a crond like
884program when the crontabs have changed).</p> 1114program when the crontabs have changed).</p>
885 </dd> 1115 </dd>
1116 <dt>ev_tstamp interval [read-write]</dt>
1117 <dd>
1118 <p>The current interval value. Can be modified any time, but changes only
1119take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1120called.</p>
1121 </dd>
1122 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1123 <dd>
1124 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1125switched off. Can be changed any time, but changes only take effect when
1126the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1127 </dd>
886</dl> 1128</dl>
887<p>Example: call a callback every hour, or, more precisely, whenever the 1129<p>Example: Call a callback every hour, or, more precisely, whenever the
888system clock is divisible by 3600. The callback invocation times have 1130system clock is divisible by 3600. The callback invocation times have
889potentially a lot of jittering, but good long-term stability.</p> 1131potentially a lot of jittering, but good long-term stability.</p>
890<pre> static void 1132<pre> static void
891 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1133 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
892 { 1134 {
… …
896 struct ev_periodic hourly_tick; 1138 struct ev_periodic hourly_tick;
897 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1139 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
898 ev_periodic_start (loop, &amp;hourly_tick); 1140 ev_periodic_start (loop, &amp;hourly_tick);
899 1141
900</pre> 1142</pre>
901<p>Example: the same as above, but use a reschedule callback to do it:</p> 1143<p>Example: The same as above, but use a reschedule callback to do it:</p>
902<pre> #include &lt;math.h&gt; 1144<pre> #include &lt;math.h&gt;
903 1145
904 static ev_tstamp 1146 static ev_tstamp
905 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1147 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
906 { 1148 {
… …
908 } 1150 }
909 1151
910 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1152 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
911 1153
912</pre> 1154</pre>
913<p>Example: call a callback every hour, starting now:</p> 1155<p>Example: Call a callback every hour, starting now:</p>
914<pre> struct ev_periodic hourly_tick; 1156<pre> struct ev_periodic hourly_tick;
915 ev_periodic_init (&amp;hourly_tick, clock_cb, 1157 ev_periodic_init (&amp;hourly_tick, clock_cb,
916 fmod (ev_now (loop), 3600.), 3600., 0); 1158 fmod (ev_now (loop), 3600.), 3600., 0);
917 ev_periodic_start (loop, &amp;hourly_tick); 1159 ev_periodic_start (loop, &amp;hourly_tick);
918 1160
… …
920 1162
921 1163
922</pre> 1164</pre>
923 1165
924</div> 1166</div>
925<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1167<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"> 1168<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 1169<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 1170signal 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 1171will try it's best to deliver signals synchronously, i.e. as part of the
930normal event processing, like any other event.</p> 1172normal event processing, like any other event.</p>
… …
939 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1181 <dt>ev_signal_set (ev_signal *, int signum)</dt>
940 <dd> 1182 <dd>
941 <p>Configures the watcher to trigger on the given signal number (usually one 1183 <p>Configures the watcher to trigger on the given signal number (usually one
942of the <code>SIGxxx</code> constants).</p> 1184of the <code>SIGxxx</code> constants).</p>
943 </dd> 1185 </dd>
1186 <dt>int signum [read-only]</dt>
1187 <dd>
1188 <p>The signal the watcher watches out for.</p>
1189 </dd>
944</dl> 1190</dl>
945 1191
946 1192
947 1193
948 1194
949 1195
950</div> 1196</div>
951<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1197<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"> 1198<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 1199<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> 1200some child status changes (most typically when a child of yours dies).</p>
955<dl> 1201<dl>
956 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1202 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
957 <dt>ev_child_set (ev_child *, int pid)</dt> 1203 <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 1207at 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 1208the 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 1209<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
964process causing the status change.</p> 1210process causing the status change.</p>
965 </dd> 1211 </dd>
1212 <dt>int pid [read-only]</dt>
1213 <dd>
1214 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1215 </dd>
1216 <dt>int rpid [read-write]</dt>
1217 <dd>
1218 <p>The process id that detected a status change.</p>
1219 </dd>
1220 <dt>int rstatus [read-write]</dt>
1221 <dd>
1222 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1223<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1224 </dd>
966</dl> 1225</dl>
967<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1226<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
968<pre> static void 1227<pre> static void
969 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1228 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
970 { 1229 {
971 ev_unloop (loop, EVUNLOOP_ALL); 1230 ev_unloop (loop, EVUNLOOP_ALL);
972 } 1231 }
… …
979 1238
980 1239
981</pre> 1240</pre>
982 1241
983</div> 1242</div>
1243<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1244<div id="code_ev_stat_code_did_the_file_attri-2">
1245<p>This watches a filesystem path for attribute changes. That is, it calls
1246<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1247compared to the last time, invoking the callback if it did.</p>
1248<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1249not exist&quot; is a status change like any other. The condition &quot;path does
1250not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1251otherwise always forced to be at least one) and all the other fields of
1252the stat buffer having unspecified contents.</p>
1253<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1254relative and your working directory changes, the behaviour is undefined.</p>
1255<p>Since there is no standard to do this, the portable implementation simply
1256calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1257can specify a recommended polling interval for this case. If you specify
1258a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1259unspecified default</i> value will be used (which you can expect to be around
1260five seconds, although this might change dynamically). Libev will also
1261impose a minimum interval which is currently around <code>0.1</code>, but thats
1262usually overkill.</p>
1263<p>This watcher type is not meant for massive numbers of stat watchers,
1264as even with OS-supported change notifications, this can be
1265resource-intensive.</p>
1266<p>At the time of this writing, only the Linux inotify interface is
1267implemented (implementing kqueue support is left as an exercise for the
1268reader). Inotify will be used to give hints only and should not change the
1269semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1270to fall back to regular polling again even with inotify, but changes are
1271usually detected immediately, and if the file exists there will be no
1272polling.</p>
1273<dl>
1274 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1275 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1276 <dd>
1277 <p>Configures the watcher to wait for status changes of the given
1278<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1279be detected and should normally be specified as <code>0</code> to let libev choose
1280a suitable value. The memory pointed to by <code>path</code> must point to the same
1281path for as long as the watcher is active.</p>
1282 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1283relative to the attributes at the time the watcher was started (or the
1284last change was detected).</p>
1285 </dd>
1286 <dt>ev_stat_stat (ev_stat *)</dt>
1287 <dd>
1288 <p>Updates the stat buffer immediately with new values. If you change the
1289watched path in your callback, you could call this fucntion to avoid
1290detecting this change (while introducing a race condition). Can also be
1291useful simply to find out the new values.</p>
1292 </dd>
1293 <dt>ev_statdata attr [read-only]</dt>
1294 <dd>
1295 <p>The most-recently detected attributes of the file. Although the type is of
1296<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1297suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1298was some error while <code>stat</code>ing the file.</p>
1299 </dd>
1300 <dt>ev_statdata prev [read-only]</dt>
1301 <dd>
1302 <p>The previous attributes of the file. The callback gets invoked whenever
1303<code>prev</code> != <code>attr</code>.</p>
1304 </dd>
1305 <dt>ev_tstamp interval [read-only]</dt>
1306 <dd>
1307 <p>The specified interval.</p>
1308 </dd>
1309 <dt>const char *path [read-only]</dt>
1310 <dd>
1311 <p>The filesystem path that is being watched.</p>
1312 </dd>
1313</dl>
1314<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1315<pre> static void
1316 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1317 {
1318 /* /etc/passwd changed in some way */
1319 if (w-&gt;attr.st_nlink)
1320 {
1321 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1322 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1323 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1324 }
1325 else
1326 /* you shalt not abuse printf for puts */
1327 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1328 &quot;if this is windows, they already arrived\n&quot;);
1329 }
1330
1331 ...
1332 ev_stat passwd;
1333
1334 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1335 ev_stat_start (loop, &amp;passwd);
1336
1337
1338
1339
1340</pre>
1341
1342</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> 1343<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"> 1344<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 1345<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 1346(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, 1347as 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 1348imagine) 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 1361 <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, 1362kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1004believe me.</p> 1363believe me.</p>
1005 </dd> 1364 </dd>
1006</dl> 1365</dl>
1007<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1366<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> 1367callback, free it. Also, use no error checking, as usual.</p>
1009<pre> static void 1368<pre> static void
1010 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1369 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1011 { 1370 {
1012 free (w); 1371 free (w);
1013 // now do something you wanted to do when the program has 1372 // now do something you wanted to do when the program has
… …
1022 1381
1023 1382
1024</pre> 1383</pre>
1025 1384
1026</div> 1385</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> 1386<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"> 1387<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: 1388<p>Prepare and check watchers are usually (but not always) used in tandem:
1030prepare watchers get invoked before the process blocks and check watchers 1389prepare watchers get invoked before the process blocks and check watchers
1031afterwards.</p> 1390afterwards.</p>
1391<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1392the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1393watchers. Other loops than the current one are fine, however. The
1394rationale behind this is that you do not need to check for recursion in
1395those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1396<code>ev_check</code> so if you have one watcher of each kind they will always be
1397called in pairs bracketing the blocking call.</p>
1032<p>Their main purpose is to integrate other event mechanisms into libev and 1398<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 1399their use is somewhat advanced. This could be used, for example, to track
1034variable changes, implement your own watchers, integrate net-snmp or a 1400variable changes, implement your own watchers, integrate net-snmp or a
1035coroutine library and lots more.</p> 1401coroutine library and lots more. They are also occasionally useful if
1402you cache some data and want to flush it before blocking (for example,
1403in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1404watcher).</p>
1036<p>This is done by examining in each prepare call which file descriptors need 1405<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 1406to 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 1407them 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 1408provide just this functionality). Then, in the check watcher you check for
1040any events that occured (by checking the pending status of all watchers 1409any events that occured (by checking the pending status of all watchers
… …
1056 <p>Initialises and configures the prepare or check watcher - they have no 1425 <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> 1426parameters 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> 1427macros, but using them is utterly, utterly and completely pointless.</p>
1059 </dd> 1428 </dd>
1060</dl> 1429</dl>
1061<p>Example: *TODO*.</p> 1430<p>Example: To include a library such as adns, you would add IO watchers
1431and a timeout watcher in a prepare handler, as required by libadns, and
1432in a check watcher, destroy them and call into libadns. What follows is
1433pseudo-code only of course:</p>
1434<pre> static ev_io iow [nfd];
1435 static ev_timer tw;
1062 1436
1437 static void
1438 io_cb (ev_loop *loop, ev_io *w, int revents)
1439 {
1440 // set the relevant poll flags
1441 // could also call adns_processreadable etc. here
1442 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1443 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1444 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1445 }
1063 1446
1447 // create io watchers for each fd and a timer before blocking
1448 static void
1449 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1450 {
1451 int timeout = 3600000;truct pollfd fds [nfd];
1452 // actual code will need to loop here and realloc etc.
1453 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1064 1454
1455 /* the callback is illegal, but won't be called as we stop during check */
1456 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1457 ev_timer_start (loop, &amp;tw);
1065 1458
1459 // create on ev_io per pollfd
1460 for (int i = 0; i &lt; nfd; ++i)
1461 {
1462 ev_io_init (iow + i, io_cb, fds [i].fd,
1463 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1464 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1066 1465
1466 fds [i].revents = 0;
1467 iow [i].data = fds + i;
1468 ev_io_start (loop, iow + i);
1469 }
1470 }
1471
1472 // stop all watchers after blocking
1473 static void
1474 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1475 {
1476 ev_timer_stop (loop, &amp;tw);
1477
1478 for (int i = 0; i &lt; nfd; ++i)
1479 ev_io_stop (loop, iow + i);
1480
1481 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1482 }
1483
1484
1485
1486
1487</pre>
1488
1067</div> 1489</div>
1068<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1490<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"> 1491<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 1492<p>This is a rather advanced watcher type that lets you embed one event loop
1071into another.</p> 1493into another (currently only <code>ev_io</code> events are supported in the embedded
1494loop, other types of watchers might be handled in a delayed or incorrect
1495fashion and must not be used).</p>
1072<p>There are primarily two reasons you would want that: work around bugs and 1496<p>There are primarily two reasons you would want that: work around bugs and
1073prioritise I/O.</p> 1497prioritise I/O.</p>
1074<p>As an example for a bug workaround, the kqueue backend might only support 1498<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 1499sockets 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 1500still 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 1505<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 1506to be watched and handled very quickly (with low latency), and even
1083priorities and idle watchers might have too much overhead. In this case 1507priorities 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 1508you 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> 1509a second one, and embed the second one in the first.</p>
1510<p>As long as the watcher is active, the callback will be invoked every time
1511there might be events pending in the embedded loop. The callback must then
1512call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1513their callbacks (you could also start an idle watcher to give the embedded
1514loop strictly lower priority for example). You can also set the callback
1515to <code>0</code>, in which case the embed watcher will automatically execute the
1516embedded loop sweep.</p>
1086<p>As long as the watcher is started it will automatically handle events. The 1517<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 1518callback 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 1519set the callback to <code>0</code> to avoid having to specify one if you are not
1089interested in that.</p> 1520interested in that.</p>
1090<p>Also, there have not currently been made special provisions for forking: 1521<p>Also, there have not currently been made special provisions for forking:
… …
1117 else 1548 else
1118 loop_lo = loop_hi; 1549 loop_lo = loop_hi;
1119 1550
1120</pre> 1551</pre>
1121<dl> 1552<dl>
1122 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *loop)</dt> 1553 <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> 1554 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1555 <dd>
1556 <p>Configures the watcher to embed the given loop, which must be
1557embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1558invoked automatically, otherwise it is the responsibility of the callback
1559to invoke it (it will continue to be called until the sweep has been done,
1560if you do not want thta, you need to temporarily stop the embed watcher).</p>
1124 <dd> 1561 </dd>
1125 <p>Configures the watcher to embed the given loop, which must be embeddable.</p> 1562 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1563 <dd>
1564 <p>Make a single, non-blocking sweep over the embedded loop. This works
1565similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1566apropriate way for embedded loops.</p>
1567 </dd>
1568 <dt>struct ev_loop *loop [read-only]</dt>
1569 <dd>
1570 <p>The embedded event loop.</p>
1126 </dd> 1571 </dd>
1127</dl> 1572</dl>
1128 1573
1129 1574
1130 1575
1131 1576
1132 1577
1133</div> 1578</div>
1134<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1579<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>
1580<div id="code_ev_fork_code_the_audacity_to_re-2">
1581<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1582whoever is a good citizen cared to tell libev about it by calling
1583<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1584event loop blocks next and before <code>ev_check</code> watchers are being called,
1585and only in the child after the fork. If whoever good citizen calling
1586<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1587handlers will be invoked, too, of course.</p>
1588<dl>
1589 <dt>ev_fork_init (ev_signal *, callback)</dt>
1590 <dd>
1591 <p>Initialises and configures the fork watcher - it has no parameters of any
1592kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1593believe me.</p>
1594 </dd>
1595</dl>
1596
1597
1598
1599
1600
1601</div>
1602<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1135<div id="OTHER_FUNCTIONS_CONTENT"> 1603<div id="OTHER_FUNCTIONS_CONTENT">
1136<p>There are some other functions of possible interest. Described. Here. Now.</p> 1604<p>There are some other functions of possible interest. Described. Here. Now.</p>
1137<dl> 1605<dl>
1138 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1606 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1139 <dd> 1607 <dd>
… …
1163 1631
1164 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1632 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1165 1633
1166</pre> 1634</pre>
1167 </dd> 1635 </dd>
1168 <dt>ev_feed_event (loop, watcher, int events)</dt> 1636 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
1169 <dd> 1637 <dd>
1170 <p>Feeds the given event set into the event loop, as if the specified event 1638 <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 1639had happened for the specified watcher (which must be a pointer to an
1172initialised but not necessarily started event watcher).</p> 1640initialised but not necessarily started event watcher).</p>
1173 </dd> 1641 </dd>
1174 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1642 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
1175 <dd> 1643 <dd>
1176 <p>Feed an event on the given fd, as if a file descriptor backend detected 1644 <p>Feed an event on the given fd, as if a file descriptor backend detected
1177the given events it.</p> 1645the given events it.</p>
1178 </dd> 1646 </dd>
1179 <dt>ev_feed_signal_event (loop, int signum)</dt> 1647 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
1180 <dd> 1648 <dd>
1181 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1649 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1650loop!).</p>
1182 </dd> 1651 </dd>
1183</dl> 1652</dl>
1184 1653
1185 1654
1186 1655
1187 1656
1188 1657
1189</div> 1658</div>
1190<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1659<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1191<div id="LIBEVENT_EMULATION_CONTENT"> 1660<div id="LIBEVENT_EMULATION_CONTENT">
1192<p>Libev offers a compatibility emulation layer for libevent. It cannot 1661<p>Libev offers a compatibility emulation layer for libevent. It cannot
1193emulate the internals of libevent, so here are some usage hints:</p> 1662emulate the internals of libevent, so here are some usage hints:</p>
1194<dl> 1663<dl>
1195 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1664 <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 1674 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1206to use the libev header file and library.</dt> 1675to use the libev header file and library.</dt>
1207</dl> 1676</dl>
1208 1677
1209</div> 1678</div>
1210<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1679<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1211<div id="C_SUPPORT_CONTENT"> 1680<div id="C_SUPPORT_CONTENT">
1212<p>TBD.</p> 1681<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1682you to use some convinience methods to start/stop watchers and also change
1683the callback model to a model using method callbacks on objects.</p>
1684<p>To use it,</p>
1685<pre> #include &lt;ev++.h&gt;
1213 1686
1687</pre>
1688<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1689and puts all of its definitions (many of them macros) into the global
1690namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1691<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1692<code>EV_MULTIPLICITY</code>.</p>
1693<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1694<dl>
1695 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1696 <dd>
1697 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1698macros from <cite>ev.h</cite>.</p>
1699 </dd>
1700 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1701 <dd>
1702 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1703 </dd>
1704 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1705 <dd>
1706 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1707the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1708which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1709defines by many implementations.</p>
1710 <p>All of those classes have these methods:</p>
1711 <p>
1712 <dl>
1713 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1714 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1715 <dt>ev::TYPE::~TYPE</dt>
1716 <dd>
1717 <p>The constructor takes a pointer to an object and a method pointer to
1718the event handler callback to call in this class. The constructor calls
1719<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1720before starting it. If you do not specify a loop then the constructor
1721automatically associates the default loop with this watcher.</p>
1722 <p>The destructor automatically stops the watcher if it is active.</p>
1723 </dd>
1724 <dt>w-&gt;set (struct ev_loop *)</dt>
1725 <dd>
1726 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1727do this when the watcher is inactive (and not pending either).</p>
1728 </dd>
1729 <dt>w-&gt;set ([args])</dt>
1730 <dd>
1731 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1732called at least once. Unlike the C counterpart, an active watcher gets
1733automatically stopped and restarted.</p>
1734 </dd>
1735 <dt>w-&gt;start ()</dt>
1736 <dd>
1737 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1738constructor already takes the loop.</p>
1739 </dd>
1740 <dt>w-&gt;stop ()</dt>
1741 <dd>
1742 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1743 </dd>
1744 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1745 <dd>
1746 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1747<code>ev_TYPE_again</code> function.</p>
1748 </dd>
1749 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1750 <dd>
1751 <p>Invokes <code>ev_embed_sweep</code>.</p>
1752 </dd>
1753 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1754 <dd>
1755 <p>Invokes <code>ev_stat_stat</code>.</p>
1756 </dd>
1757 </dl>
1758 </p>
1759 </dd>
1760</dl>
1761<p>Example: Define a class with an IO and idle watcher, start one of them in
1762the constructor.</p>
1763<pre> class myclass
1764 {
1765 ev_io io; void io_cb (ev::io &amp;w, int revents);
1766 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1767
1768 myclass ();
1769 }
1770
1771 myclass::myclass (int fd)
1772 : io (this, &amp;myclass::io_cb),
1773 idle (this, &amp;myclass::idle_cb)
1774 {
1775 io.start (fd, ev::READ);
1776 }
1777
1778
1779
1780
1781</pre>
1782
1214</div> 1783</div>
1215<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1784<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1785<div id="MACRO_MAGIC_CONTENT">
1786<p>Libev can be compiled with a variety of options, the most fundemantal is
1787<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1788callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1789<p>To make it easier to write programs that cope with either variant, the
1790following macros are defined:</p>
1791<dl>
1792 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1793 <dd>
1794 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1795loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1796<code>EV_A_</code> is used when other arguments are following. Example:</p>
1797<pre> ev_unref (EV_A);
1798 ev_timer_add (EV_A_ watcher);
1799 ev_loop (EV_A_ 0);
1800
1801</pre>
1802 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1803which is often provided by the following macro.</p>
1804 </dd>
1805 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1806 <dd>
1807 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1808loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1809<code>EV_P_</code> is used when other parameters are following. Example:</p>
1810<pre> // this is how ev_unref is being declared
1811 static void ev_unref (EV_P);
1812
1813 // this is how you can declare your typical callback
1814 static void cb (EV_P_ ev_timer *w, int revents)
1815
1816</pre>
1817 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1818suitable for use with <code>EV_A</code>.</p>
1819 </dd>
1820 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1821 <dd>
1822 <p>Similar to the other two macros, this gives you the value of the default
1823loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1824 </dd>
1825</dl>
1826<p>Example: Declare and initialise a check watcher, working regardless of
1827wether multiple loops are supported or not.</p>
1828<pre> static void
1829 check_cb (EV_P_ ev_timer *w, int revents)
1830 {
1831 ev_check_stop (EV_A_ w);
1832 }
1833
1834 ev_check check;
1835 ev_check_init (&amp;check, check_cb);
1836 ev_check_start (EV_DEFAULT_ &amp;check);
1837 ev_loop (EV_DEFAULT_ 0);
1838
1839
1840
1841
1842</pre>
1843
1844</div>
1845<h1 id="EMBEDDING">EMBEDDING</h1>
1846<div id="EMBEDDING_CONTENT">
1847<p>Libev can (and often is) directly embedded into host
1848applications. Examples of applications that embed it include the Deliantra
1849Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1850and rxvt-unicode.</p>
1851<p>The goal is to enable you to just copy the neecssary files into your
1852source directory without having to change even a single line in them, so
1853you can easily upgrade by simply copying (or having a checked-out copy of
1854libev somewhere in your source tree).</p>
1855
1856</div>
1857<h2 id="FILESETS">FILESETS</h2>
1858<div id="FILESETS_CONTENT">
1859<p>Depending on what features you need you need to include one or more sets of files
1860in your app.</p>
1861
1862</div>
1863<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1864<div id="CORE_EVENT_LOOP_CONTENT">
1865<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1866configuration (no autoconf):</p>
1867<pre> #define EV_STANDALONE 1
1868 #include &quot;ev.c&quot;
1869
1870</pre>
1871<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1872single C source file only to provide the function implementations. To use
1873it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1874done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1875where you can put other configuration options):</p>
1876<pre> #define EV_STANDALONE 1
1877 #include &quot;ev.h&quot;
1878
1879</pre>
1880<p>Both header files and implementation files can be compiled with a C++
1881compiler (at least, thats a stated goal, and breakage will be treated
1882as a bug).</p>
1883<p>You need the following files in your source tree, or in a directory
1884in your include path (e.g. in libev/ when using -Ilibev):</p>
1885<pre> ev.h
1886 ev.c
1887 ev_vars.h
1888 ev_wrap.h
1889
1890 ev_win32.c required on win32 platforms only
1891
1892 ev_select.c only when select backend is enabled (which is by default)
1893 ev_poll.c only when poll backend is enabled (disabled by default)
1894 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1895 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1896 ev_port.c only when the solaris port backend is enabled (disabled by default)
1897
1898</pre>
1899<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1900to compile this single file.</p>
1901
1902</div>
1903<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1904<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1905<p>To include the libevent compatibility API, also include:</p>
1906<pre> #include &quot;event.c&quot;
1907
1908</pre>
1909<p>in the file including <cite>ev.c</cite>, and:</p>
1910<pre> #include &quot;event.h&quot;
1911
1912</pre>
1913<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1914<p>You need the following additional files for this:</p>
1915<pre> event.h
1916 event.c
1917
1918</pre>
1919
1920</div>
1921<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1922<div id="AUTOCONF_SUPPORT_CONTENT">
1923<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1924whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1925<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1926include <cite>config.h</cite> and configure itself accordingly.</p>
1927<p>For this of course you need the m4 file:</p>
1928<pre> libev.m4
1929
1930</pre>
1931
1932</div>
1933<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1934<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1935<p>Libev can be configured via a variety of preprocessor symbols you have to define
1936before including any of its files. The default is not to build for multiplicity
1937and only include the select backend.</p>
1938<dl>
1939 <dt>EV_STANDALONE</dt>
1940 <dd>
1941 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1942keeps libev from including <cite>config.h</cite>, and it also defines dummy
1943implementations for some libevent functions (such as logging, which is not
1944supported). It will also not define any of the structs usually found in
1945<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1946 </dd>
1947 <dt>EV_USE_MONOTONIC</dt>
1948 <dd>
1949 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1950monotonic clock option at both compiletime and runtime. Otherwise no use
1951of the monotonic clock option will be attempted. If you enable this, you
1952usually have to link against librt or something similar. Enabling it when
1953the functionality isn't available is safe, though, althoguh you have
1954to make sure you link against any libraries where the <code>clock_gettime</code>
1955function is hiding in (often <cite>-lrt</cite>).</p>
1956 </dd>
1957 <dt>EV_USE_REALTIME</dt>
1958 <dd>
1959 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1960realtime clock option at compiletime (and assume its availability at
1961runtime if successful). Otherwise no use of the realtime clock option will
1962be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1963(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1964in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1965 </dd>
1966 <dt>EV_USE_SELECT</dt>
1967 <dd>
1968 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1969<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1970other method takes over, select will be it. Otherwise the select backend
1971will not be compiled in.</p>
1972 </dd>
1973 <dt>EV_SELECT_USE_FD_SET</dt>
1974 <dd>
1975 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1976structure. This is useful if libev doesn't compile due to a missing
1977<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1978exotic systems. This usually limits the range of file descriptors to some
1979low limit such as 1024 or might have other limitations (winsocket only
1980allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1981influence the size of the <code>fd_set</code> used.</p>
1982 </dd>
1983 <dt>EV_SELECT_IS_WINSOCKET</dt>
1984 <dd>
1985 <p>When defined to <code>1</code>, the select backend will assume that
1986select/socket/connect etc. don't understand file descriptors but
1987wants osf handles on win32 (this is the case when the select to
1988be used is the winsock select). This means that it will call
1989<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1990it is assumed that all these functions actually work on fds, even
1991on win32. Should not be defined on non-win32 platforms.</p>
1992 </dd>
1993 <dt>EV_USE_POLL</dt>
1994 <dd>
1995 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1996backend. Otherwise it will be enabled on non-win32 platforms. It
1997takes precedence over select.</p>
1998 </dd>
1999 <dt>EV_USE_EPOLL</dt>
2000 <dd>
2001 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
2002<code>epoll</code>(7) backend. Its availability will be detected at runtime,
2003otherwise another method will be used as fallback. This is the
2004preferred backend for GNU/Linux systems.</p>
2005 </dd>
2006 <dt>EV_USE_KQUEUE</dt>
2007 <dd>
2008 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
2009<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
2010otherwise another method will be used as fallback. This is the preferred
2011backend for BSD and BSD-like systems, although on most BSDs kqueue only
2012supports some types of fds correctly (the only platform we found that
2013supports ptys for example was NetBSD), so kqueue might be compiled in, but
2014not be used unless explicitly requested. The best way to use it is to find
2015out whether kqueue supports your type of fd properly and use an embedded
2016kqueue loop.</p>
2017 </dd>
2018 <dt>EV_USE_PORT</dt>
2019 <dd>
2020 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
202110 port style backend. Its availability will be detected at runtime,
2022otherwise another method will be used as fallback. This is the preferred
2023backend for Solaris 10 systems.</p>
2024 </dd>
2025 <dt>EV_USE_DEVPOLL</dt>
2026 <dd>
2027 <p>reserved for future expansion, works like the USE symbols above.</p>
2028 </dd>
2029 <dt>EV_USE_INOTIFY</dt>
2030 <dd>
2031 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2032interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2033be detected at runtime.</p>
2034 </dd>
2035 <dt>EV_H</dt>
2036 <dd>
2037 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
2038undefined 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
2039can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
2040 </dd>
2041 <dt>EV_CONFIG_H</dt>
2042 <dd>
2043 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
2044<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
2045<code>EV_H</code>, above.</p>
2046 </dd>
2047 <dt>EV_EVENT_H</dt>
2048 <dd>
2049 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
2050of how the <cite>event.h</cite> header can be found.</p>
2051 </dd>
2052 <dt>EV_PROTOTYPES</dt>
2053 <dd>
2054 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
2055prototypes, but still define all the structs and other symbols. This is
2056occasionally useful if you want to provide your own wrapper functions
2057around libev functions.</p>
2058 </dd>
2059 <dt>EV_MULTIPLICITY</dt>
2060 <dd>
2061 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
2062will have the <code>struct ev_loop *</code> as first argument, and you can create
2063additional independent event loops. Otherwise there will be no support
2064for multiple event loops and there is no first event loop pointer
2065argument. Instead, all functions act on the single default loop.</p>
2066 </dd>
2067 <dt>EV_PERIODIC_ENABLE</dt>
2068 <dd>
2069 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2070defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2071code.</p>
2072 </dd>
2073 <dt>EV_EMBED_ENABLE</dt>
2074 <dd>
2075 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2076defined to be <code>0</code>, then they are not.</p>
2077 </dd>
2078 <dt>EV_STAT_ENABLE</dt>
2079 <dd>
2080 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2081defined to be <code>0</code>, then they are not.</p>
2082 </dd>
2083 <dt>EV_FORK_ENABLE</dt>
2084 <dd>
2085 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2086defined to be <code>0</code>, then they are not.</p>
2087 </dd>
2088 <dt>EV_MINIMAL</dt>
2089 <dd>
2090 <p>If you need to shave off some kilobytes of code at the expense of some
2091speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2092some inlining decisions, saves roughly 30% codesize of amd64.</p>
2093 </dd>
2094 <dt>EV_PID_HASHSIZE</dt>
2095 <dd>
2096 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2097pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2098than enough. If you need to manage thousands of children you might want to
2099increase this value (<i>must</i> be a power of two).</p>
2100 </dd>
2101 <dt>EV_INOTIFY_HASHSIZE</dt>
2102 <dd>
2103 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2104inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2105usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2106watchers you might want to increase this value (<i>must</i> be a power of
2107two).</p>
2108 </dd>
2109 <dt>EV_COMMON</dt>
2110 <dd>
2111 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2112this macro to a something else you can include more and other types of
2113members. You have to define it each time you include one of the files,
2114though, and it must be identical each time.</p>
2115 <p>For example, the perl EV module uses something like this:</p>
2116<pre> #define EV_COMMON \
2117 SV *self; /* contains this struct */ \
2118 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2119
2120</pre>
2121 </dd>
2122 <dt>EV_CB_DECLARE (type)</dt>
2123 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2124 <dt>ev_set_cb (ev, cb)</dt>
2125 <dd>
2126 <p>Can be used to change the callback member declaration in each watcher,
2127and the way callbacks are invoked and set. Must expand to a struct member
2128definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2129their default definitions. One possible use for overriding these is to
2130avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2131method calls instead of plain function calls in C++.</p>
2132
2133</div>
2134<h2 id="EXAMPLES">EXAMPLES</h2>
2135<div id="EXAMPLES_CONTENT">
2136 <p>For a real-world example of a program the includes libev
2137verbatim, you can have a look at the EV perl module
2138(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2139the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2140interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2141will be compiled. It is pretty complex because it provides its own header
2142file.</p>
2143 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2144that everybody includes and which overrides some autoconf choices:</p>
2145<pre> #define EV_USE_POLL 0
2146 #define EV_MULTIPLICITY 0
2147 #define EV_PERIODICS 0
2148 #define EV_CONFIG_H &lt;config.h&gt;
2149
2150 #include &quot;ev++.h&quot;
2151
2152</pre>
2153 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2154<pre> #include &quot;ev_cpp.h&quot;
2155 #include &quot;ev.c&quot;
2156
2157
2158
2159
2160</pre>
2161
2162</div>
2163<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2164<div id="COMPLEXITIES_CONTENT">
2165 <p>In this section the complexities of (many of) the algorithms used inside
2166libev will be explained. For complexity discussions about backends see the
2167documentation for <code>ev_default_init</code>.</p>
2168 <p>
2169 <dl>
2170 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2171 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2172 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2173 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2174 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2175 <dt>Finding the next timer per loop iteration: O(1)</dt>
2176 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2177 <dt>Activating one watcher: O(1)</dt>
2178 </dl>
2179 </p>
2180
2181
2182
2183
2184
2185</div>
2186<h1 id="AUTHOR">AUTHOR</h1>
1216<div id="AUTHOR_CONTENT"> 2187<div id="AUTHOR_CONTENT">
1217<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2188 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1218 2189
1219</div> 2190</div>
1220</div></body> 2191</div></body>
1221</html> 2192</html>

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