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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="Fri Nov 23 17:17:04 2007" /> 9 <meta name="created" content="Thu Nov 29 13:21:20 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>
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>
37</ul> 42</ul>
38</li> 43</li>
39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41<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>
42<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
43</li> 61</li>
44</ul><hr /> 62</ul><hr />
45<!-- INDEX END --> 63<!-- INDEX END -->
46 64
47<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
48<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
49<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>
50 68
51</div> 69</div>
52<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
53<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
54<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
55 73
56</pre> 74</pre>
57 75
58</div> 76</div>
59<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>
60<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
61<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
62file descriptor being readable or a timeout occuring), and it will manage 125file descriptor being readable or a timeout occuring), and it will manage
63these event sources and provide your program with events.</p> 126these event sources and provide your program with events.</p>
64<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
… …
68watchers</i>, which are relatively small C structures you initialise with the 131watchers</i>, which are relatively small C structures you initialise with the
69details 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
70watcher.</p> 133watcher.</p>
71 134
72</div> 135</div>
73<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1>
74<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
75<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
76kqueue mechanisms for file descriptor events, relative timers, absolute 139BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
77timers with customised rescheduling, signal events, process status change 140for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
78events (related to SIGCHLD), and event watchers dealing with the event 141(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
79loop 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
80fast (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
81it to libevent for example).</p> 150for example).</p>
82 151
83</div> 152</div>
84<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 153<h1 id="CONVENTIONS">CONVENTIONS</h1>
85<div id="CONVENTIONS_CONTENT"> 154<div id="CONVENTIONS_CONTENT">
86<p>Libev is very configurable. In this manual the default configuration 155<p>Libev is very configurable. In this manual the default configuration will
87will be described, which supports multiple event loops. For more info 156be described, which supports multiple event loops. For more info about
88about various configuration options please have a look at the file 157various configuration options please have a look at <strong>EMBED</strong> section in
89<cite>README.embed</cite> in the libev distribution. If libev was configured without 158this manual. If libev was configured without support for multiple event
90support for multiple event loops, then all functions taking an initial 159loops, then all functions taking an initial argument of name <code>loop</code>
91argument 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>
92will not have this argument.</p>
93 161
94</div> 162</div>
95<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 163<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
96<div id="TIME_REPRESENTATION_CONTENT"> 164<div id="TIME_REPRESENTATION_CONTENT">
97<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
98(fractional) number of seconds since the (POSIX) epoch (somewhere near 166(fractional) number of seconds since the (POSIX) epoch (somewhere near
99the 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
100called <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
101to 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
102it, you should treat it as such.</p> 170it, you should treat it as such.</p>
103 171
104
105
106
107
108</div> 172</div>
109<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 173<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
110<div id="GLOBAL_FUNCTIONS_CONTENT"> 174<div id="GLOBAL_FUNCTIONS_CONTENT">
111<p>These functions can be called anytime, even before initialising the 175<p>These functions can be called anytime, even before initialising the
112library in any way.</p> 176library in any way.</p>
113<dl> 177<dl>
114 <dt>ev_tstamp ev_time ()</dt> 178 <dt>ev_tstamp ev_time ()</dt>
… …
127version of the library your program was compiled against.</p> 191version of the library your program was compiled against.</p>
128 <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,
129as this indicates an incompatible change. Minor versions are usually 193as this indicates an incompatible change. Minor versions are usually
130compatible to older versions, so a larger minor version alone is usually 194compatible to older versions, so a larger minor version alone is usually
131not a problem.</p> 195not a problem.</p>
132 <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
133version:</p> 197version.</p>
134<pre> assert ((&quot;libev version mismatch&quot;, 198<pre> assert ((&quot;libev version mismatch&quot;,
135 ev_version_major () == EV_VERSION_MAJOR 199 ev_version_major () == EV_VERSION_MAJOR
136 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 200 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
137 201
138</pre> 202</pre>
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157returned by <code>ev_supported_backends</code>, as for example kqueue is broken on 221returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
158most BSDs and will not be autodetected unless you explicitly request it 222most BSDs and will not be autodetected unless you explicitly request it
159(assuming you know what you are doing). This is the set of backends that 223(assuming you know what you are doing). This is the set of backends that
160libev will probe for if you specify no backends explicitly.</p> 224libev will probe for if you specify no backends explicitly.</p>
161 </dd> 225 </dd>
226 <dt>unsigned int ev_embeddable_backends ()</dt>
227 <dd>
228 <p>Returns the set of backends that are embeddable in other event loops. This
229is the theoretical, all-platform, value. To find which backends
230might be supported on the current system, you would need to look at
231<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
232recommended ones.</p>
233 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
234 </dd>
162 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
163 <dd> 236 <dd>
164 <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
165realloc C function, the semantics are identical). It is used to allocate 238semantics is identical - to the realloc C function). It is used to
166and free memory (no surprises here). If it returns zero when memory 239allocate and free memory (no surprises here). If it returns zero when
167needs to be allocated, the library might abort or take some potentially 240memory needs to be allocated, the library might abort or take some
168destructive action. The default is your system realloc function.</p> 241potentially destructive action. The default is your system realloc
242function.</p>
169 <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,
170free 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,
171or 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>
172 <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
173retries: better than mine).</p> 247retries).</p>
174<pre> static void * 248<pre> static void *
175 persistent_realloc (void *ptr, long size) 249 persistent_realloc (void *ptr, size_t size)
176 { 250 {
177 for (;;) 251 for (;;)
178 { 252 {
179 void *newptr = realloc (ptr, size); 253 void *newptr = realloc (ptr, size);
180 254
… …
197indicating the system call or subsystem causing the problem. If this 271indicating the system call or subsystem causing the problem. If this
198callback 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
199matter what, when it returns. That is, libev will generally retry the 273matter what, when it returns. That is, libev will generally retry the
200requested 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
201(such as abort).</p> 275(such as abort).</p>
202 <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>
203<pre> static void 277<pre> static void
204 fatal_error (const char *msg) 278 fatal_error (const char *msg)
205 { 279 {
206 perror (msg); 280 perror (msg);
207 abort (); 281 abort ();
… …
213</pre> 287</pre>
214 </dd> 288 </dd>
215</dl> 289</dl>
216 290
217</div> 291</div>
218<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>
219<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 293<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
220<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
221types 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
222events, and dynamically created loops which do not.</p> 296events, and dynamically created loops which do not.</p>
223<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
… …
343 <dd> 417 <dd>
344 <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
345always distinct from the default loop. Unlike the default loop, it cannot 419always distinct from the default loop. Unlike the default loop, it cannot
346handle 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
347undefined behaviour (or a failed assertion if assertions are enabled).</p> 421undefined behaviour (or a failed assertion if assertions are enabled).</p>
348 <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>
349<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);
350 if (!epoller) 424 if (!epoller)
351 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;);
352 426
353</pre> 427</pre>
354 </dd> 428 </dd>
355 <dt>ev_default_destroy ()</dt> 429 <dt>ev_default_destroy ()</dt>
356 <dd> 430 <dd>
357 <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
358etc.). This stops all registered event watchers (by not touching them in 432etc.). None of the active event watchers will be stopped in the normal
359any 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>
360 </dd> 438 </dd>
361 <dt>ev_loop_destroy (loop)</dt> 439 <dt>ev_loop_destroy (loop)</dt>
362 <dd> 440 <dd>
363 <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
364earlier call to <code>ev_loop_new</code>.</p> 442earlier call to <code>ev_loop_new</code>.</p>
… …
442 be handled here by queueing them when their watcher gets executed. 520 be handled here by queueing them when their watcher gets executed.
443 - 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
444 were used, return, otherwise continue with step *. 522 were used, return, otherwise continue with step *.
445 523
446</pre> 524</pre>
447 <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
448anymore.</p> 526anymore.</p>
449<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
450 ... 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..)
451 ev_loop (my_loop, 0); 529 ev_loop (my_loop, 0);
452 ... jobs done. yeah! 530 ... jobs done. yeah!
… …
471example, 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
472visible 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
473no 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
474way 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
475libraries. 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>
476 <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>
477running when nothing else is active.</p> 555running when nothing else is active.</p>
478<pre> struct dv_signal exitsig; 556<pre> struct ev_signal exitsig;
479 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 557 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
480 ev_signal_start (myloop, &amp;exitsig); 558 ev_signal_start (loop, &amp;exitsig);
481 evf_unref (myloop); 559 evf_unref (loop);
482 560
483</pre> 561</pre>
484 <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>
485<pre> ev_ref (myloop); 563<pre> ev_ref (loop);
486 ev_signal_stop (myloop, &amp;exitsig); 564 ev_signal_stop (loop, &amp;exitsig);
487 565
488</pre> 566</pre>
489 </dd> 567 </dd>
490</dl> 568</dl>
491 569
570
571
572
573
492</div> 574</div>
493<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>
494<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 576<div id="ANATOMY_OF_A_WATCHER_CONTENT">
495<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
496interest 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
497become 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>
498<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)
… …
525with 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
526*)</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
527corresponding 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>
528<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
529must 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
530reinitialise it or call its set macro.</p> 612reinitialise it or call its <code>set</code> macro.</p>
531<p>You can check whether an event is active by calling the <code>ev_is_active
532(watcher *)</code> macro. To see whether an event is outstanding (but the
533callback for it has not been called yet) you can use the <code>ev_is_pending
534(watcher *)</code> macro.</p>
535<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
536registered watcher structure as second, and a bitset of received events as 614registered watcher structure as second, and a bitset of received events as
537third argument.</p> 615third argument.</p>
538<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
539(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
… …
559 </dd> 637 </dd>
560 <dt><code>EV_CHILD</code></dt> 638 <dt><code>EV_CHILD</code></dt>
561 <dd> 639 <dd>
562 <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>
563 </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>
564 <dt><code>EV_IDLE</code></dt> 646 <dt><code>EV_IDLE</code></dt>
565 <dd> 647 <dd>
566 <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>
567 </dd> 649 </dd>
568 <dt><code>EV_PREPARE</code></dt> 650 <dt><code>EV_PREPARE</code></dt>
… …
573<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
574received events. Callbacks of both watcher types can start and stop as 656received events. Callbacks of both watcher types can start and stop as
575many 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
576(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
577<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>
578 </dd> 669 </dd>
579 <dt><code>EV_ERROR</code></dt> 670 <dt><code>EV_ERROR</code></dt>
580 <dd> 671 <dd>
581 <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
582happen because the watcher could not be properly started because libev 673happen because the watcher could not be properly started because libev
… …
590programs, though, so beware.</p> 681programs, though, so beware.</p>
591 </dd> 682 </dd>
592</dl> 683</dl>
593 684
594</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>
595<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>
596<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 765<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
597<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
598and 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
599to 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
… …
616 struct my_io *w = (struct my_io *)w_; 785 struct my_io *w = (struct my_io *)w_;
617 ... 786 ...
618 } 787 }
619 788
620</pre> 789</pre>
621<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
622have 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 }
623 800
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;
624 805
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 }
625 812
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 }
626 819
627 820
821
822
823</pre>
824
628</div> 825</div>
629<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 826<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
630<div id="WATCHER_TYPES_CONTENT"> 827<div id="WATCHER_TYPES_CONTENT">
631<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
632information 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>
633 839
634 840
635 841
636 842
637 843
638</div> 844</div>
639<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>
640<div id="code_ev_io_code_is_this_file_descrip-2"> 846<div id="code_ev_io_code_is_this_file_descrip-2">
641<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
642in each iteration of the event loop (This behaviour is called 848in each iteration of the event loop, or, more precisely, when reading
643level-triggering because you keep receiving events as long as the 849would not block the process and writing would at least be able to write
644condition persists. Remember you can stop the watcher if you don't want to 850some data. This behaviour is called level-triggering because you keep
645act 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>
646<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
647fd 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
648descriptors 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
649required if you know what you are doing).</p> 857required if you know what you are doing).</p>
650<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
651(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
652descriptors correctly if you register interest in two or more fds pointing 860descriptors correctly if you register interest in two or more fds pointing
653to the same underlying file/socket etc. description (that is, they share 861to the same underlying file/socket/etc. description (that is, they share
654the same underlying &quot;file open&quot;).</p> 862the same underlying &quot;file open&quot;).</p>
655<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
656(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
657<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>
658<dl> 879<dl>
659 <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>
660 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 881 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
661 <dd> 882 <dd>
662 <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
663events 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
664EV_WRITE</code> to receive the given events.</p> 885<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
665 <p>Please note that most of the more scalable backend mechanisms (for example 886 </dd>
666epoll and solaris ports) can result in spurious readyness notifications 887 <dt>int fd [read-only]</dt>
667for file descriptors, so you practically need to use non-blocking I/O (and 888 <dd>
668treat callback invocation as hint only), or retest separately with a safe 889 <p>The file descriptor being watched.</p>
669interface before doing I/O (XLib can do this), or force the use of either 890 </dd>
670<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 891 <dt>int events [read-only]</dt>
671problem. Also note that it is quite easy to have your callback invoked 892 <dd>
672when the readyness condition is no longer valid even when employing 893 <p>The events being watched.</p>
673typical ways of handling events, so its a good idea to use non-blocking
674I/O unconditionally.</p>
675 </dd> 894 </dd>
676</dl> 895</dl>
677<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
678readable, but only once. Since it is likely line-buffered, you could 897readable, but only once. Since it is likely line-buffered, you could
679attempt to read a whole line in the callback:</p> 898attempt to read a whole line in the callback.</p>
680<pre> static void 899<pre> static void
681 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)
682 { 901 {
683 ev_io_stop (loop, w); 902 ev_io_stop (loop, w);
684 .. 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
… …
695 914
696 915
697</pre> 916</pre>
698 917
699</div> 918</div>
700<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>
701<div id="code_ev_timer_code_relative_and_opti-2"> 920<div id="code_ev_timer_code_relative_and_opti-2">
702<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
703given time, and optionally repeating in regular intervals after that.</p> 922given time, and optionally repeating in regular intervals after that.</p>
704<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
705times 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
… …
733 </dd> 952 </dd>
734 <dt>ev_timer_again (loop)</dt> 953 <dt>ev_timer_again (loop)</dt>
735 <dd> 954 <dd>
736 <p>This will act as if the timer timed out and restart it again if it is 955 <p>This will act as if the timer timed out and restart it again if it is
737repeating. The exact semantics are:</p> 956repeating. The exact semantics are:</p>
957 <p>If the timer is pending, its pending status is cleared.</p>
738 <p>If the timer is started but nonrepeating, stop it.</p> 958 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
739 <p>If the timer is repeating, either start it if necessary (with the repeat 959 <p>If the timer is repeating, either start it if necessary (with the
740value), or reset the running timer to the repeat value.</p> 960<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
741 <p>This sounds a bit complicated, but here is a useful and typical 961 <p>This sounds a bit complicated, but here is a useful and typical
742example: Imagine you have a tcp connection and you want a so-called idle 962example: Imagine you have a tcp connection and you want a so-called idle
743timeout, that is, you want to be called when there have been, say, 60 963timeout, that is, you want to be called when there have been, say, 60
744seconds of inactivity on the socket. The easiest way to do this is to 964seconds of inactivity on the socket. The easiest way to do this is to
745configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 965configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
746time you successfully read or write some data. If you go into an idle 966<code>ev_timer_again</code> each time you successfully read or write some data. If
747state where you do not expect data to travel on the socket, you can stop 967you go into an idle state where you do not expect data to travel on the
968socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
748the timer, and again will automatically restart it if need be.</p> 969automatically restart it if need be.</p>
970 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
971altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
972<pre> ev_timer_init (timer, callback, 0., 5.);
973 ev_timer_again (loop, timer);
974 ...
975 timer-&gt;again = 17.;
976 ev_timer_again (loop, timer);
977 ...
978 timer-&gt;again = 10.;
979 ev_timer_again (loop, timer);
980
981</pre>
982 <p>This is more slightly efficient then stopping/starting the timer each time
983you want to modify its timeout value.</p>
984 </dd>
985 <dt>ev_tstamp repeat [read-write]</dt>
986 <dd>
987 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
988or <code>ev_timer_again</code> is called and determines the next timeout (if any),
989which is also when any modifications are taken into account.</p>
749 </dd> 990 </dd>
750</dl> 991</dl>
751<p>Example: create a timer that fires after 60 seconds.</p> 992<p>Example: Create a timer that fires after 60 seconds.</p>
752<pre> static void 993<pre> static void
753 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 994 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
754 { 995 {
755 .. one minute over, w is actually stopped right here 996 .. one minute over, w is actually stopped right here
756 } 997 }
… …
758 struct ev_timer mytimer; 999 struct ev_timer mytimer;
759 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1000 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
760 ev_timer_start (loop, &amp;mytimer); 1001 ev_timer_start (loop, &amp;mytimer);
761 1002
762</pre> 1003</pre>
763<p>Example: create a timeout timer that times out after 10 seconds of 1004<p>Example: Create a timeout timer that times out after 10 seconds of
764inactivity.</p> 1005inactivity.</p>
765<pre> static void 1006<pre> static void
766 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1007 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
767 { 1008 {
768 .. ten seconds without any activity 1009 .. ten seconds without any activity
… …
781 1022
782 1023
783</pre> 1024</pre>
784 1025
785</div> 1026</div>
786<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 1027<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
787<div id="code_ev_periodic_code_to_cron_or_not-2"> 1028<div id="code_ev_periodic_code_to_cron_or_not-2">
788<p>Periodic watchers are also timers of a kind, but they are very versatile 1029<p>Periodic watchers are also timers of a kind, but they are very versatile
789(and unfortunately a bit complex).</p> 1030(and unfortunately a bit complex).</p>
790<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 1031<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
791but on wallclock time (absolute time). You can tell a periodic watcher 1032but on wallclock time (absolute time). You can tell a periodic watcher
792to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1033to trigger &quot;at&quot; some specific point in time. For example, if you tell a
793periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 1034periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
794+ 10.&gt;) and then reset your system clock to the last year, then it will 1035+ 10.</code>) and then reset your system clock to the last year, then it will
795take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1036take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
796roughly 10 seconds later and of course not if you reset your system time 1037roughly 10 seconds later and of course not if you reset your system time
797again).</p> 1038again).</p>
798<p>They can also be used to implement vastly more complex timers, such as 1039<p>They can also be used to implement vastly more complex timers, such as
799triggering an event on eahc midnight, local time.</p> 1040triggering an event on eahc midnight, local time.</p>
… …
871 <p>Simply stops and restarts the periodic watcher again. This is only useful 1112 <p>Simply stops and restarts the periodic watcher again. This is only useful
872when you changed some parameters or the reschedule callback would return 1113when you changed some parameters or the reschedule callback would return
873a different time than the last time it was called (e.g. in a crond like 1114a different time than the last time it was called (e.g. in a crond like
874program when the crontabs have changed).</p> 1115program when the crontabs have changed).</p>
875 </dd> 1116 </dd>
1117 <dt>ev_tstamp interval [read-write]</dt>
1118 <dd>
1119 <p>The current interval value. Can be modified any time, but changes only
1120take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1121called.</p>
1122 </dd>
1123 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1124 <dd>
1125 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1126switched off. Can be changed any time, but changes only take effect when
1127the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1128 </dd>
876</dl> 1129</dl>
877<p>Example: call a callback every hour, or, more precisely, whenever the 1130<p>Example: Call a callback every hour, or, more precisely, whenever the
878system clock is divisible by 3600. The callback invocation times have 1131system clock is divisible by 3600. The callback invocation times have
879potentially a lot of jittering, but good long-term stability.</p> 1132potentially a lot of jittering, but good long-term stability.</p>
880<pre> static void 1133<pre> static void
881 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1134 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
882 { 1135 {
… …
886 struct ev_periodic hourly_tick; 1139 struct ev_periodic hourly_tick;
887 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1140 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
888 ev_periodic_start (loop, &amp;hourly_tick); 1141 ev_periodic_start (loop, &amp;hourly_tick);
889 1142
890</pre> 1143</pre>
891<p>Example: the same as above, but use a reschedule callback to do it:</p> 1144<p>Example: The same as above, but use a reschedule callback to do it:</p>
892<pre> #include &lt;math.h&gt; 1145<pre> #include &lt;math.h&gt;
893 1146
894 static ev_tstamp 1147 static ev_tstamp
895 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1148 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
896 { 1149 {
… …
898 } 1151 }
899 1152
900 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1153 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
901 1154
902</pre> 1155</pre>
903<p>Example: call a callback every hour, starting now:</p> 1156<p>Example: Call a callback every hour, starting now:</p>
904<pre> struct ev_periodic hourly_tick; 1157<pre> struct ev_periodic hourly_tick;
905 ev_periodic_init (&amp;hourly_tick, clock_cb, 1158 ev_periodic_init (&amp;hourly_tick, clock_cb,
906 fmod (ev_now (loop), 3600.), 3600., 0); 1159 fmod (ev_now (loop), 3600.), 3600., 0);
907 ev_periodic_start (loop, &amp;hourly_tick); 1160 ev_periodic_start (loop, &amp;hourly_tick);
908 1161
… …
910 1163
911 1164
912</pre> 1165</pre>
913 1166
914</div> 1167</div>
915<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1168<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
916<div id="code_ev_signal_code_signal_me_when_a-2"> 1169<div id="code_ev_signal_code_signal_me_when_a-2">
917<p>Signal watchers will trigger an event when the process receives a specific 1170<p>Signal watchers will trigger an event when the process receives a specific
918signal one or more times. Even though signals are very asynchronous, libev 1171signal one or more times. Even though signals are very asynchronous, libev
919will try it's best to deliver signals synchronously, i.e. as part of the 1172will try it's best to deliver signals synchronously, i.e. as part of the
920normal event processing, like any other event.</p> 1173normal event processing, like any other event.</p>
… …
929 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1182 <dt>ev_signal_set (ev_signal *, int signum)</dt>
930 <dd> 1183 <dd>
931 <p>Configures the watcher to trigger on the given signal number (usually one 1184 <p>Configures the watcher to trigger on the given signal number (usually one
932of the <code>SIGxxx</code> constants).</p> 1185of the <code>SIGxxx</code> constants).</p>
933 </dd> 1186 </dd>
1187 <dt>int signum [read-only]</dt>
1188 <dd>
1189 <p>The signal the watcher watches out for.</p>
1190 </dd>
934</dl> 1191</dl>
935 1192
1193
1194
1195
1196
936</div> 1197</div>
937<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1198<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
938<div id="code_ev_child_code_wait_for_pid_stat-2"> 1199<div id="code_ev_child_code_watch_out_for_pro-2">
939<p>Child watchers trigger when your process receives a SIGCHLD in response to 1200<p>Child watchers trigger when your process receives a SIGCHLD in response to
940some child status changes (most typically when a child of yours dies).</p> 1201some child status changes (most typically when a child of yours dies).</p>
941<dl> 1202<dl>
942 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1203 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
943 <dt>ev_child_set (ev_child *, int pid)</dt> 1204 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
947at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1208at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
948the status word (use the macros from <code>sys/wait.h</code> and see your systems 1209the status word (use the macros from <code>sys/wait.h</code> and see your systems
949<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1210<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
950process causing the status change.</p> 1211process causing the status change.</p>
951 </dd> 1212 </dd>
1213 <dt>int pid [read-only]</dt>
1214 <dd>
1215 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1216 </dd>
1217 <dt>int rpid [read-write]</dt>
1218 <dd>
1219 <p>The process id that detected a status change.</p>
1220 </dd>
1221 <dt>int rstatus [read-write]</dt>
1222 <dd>
1223 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1224<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1225 </dd>
952</dl> 1226</dl>
953<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1227<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
954<pre> static void 1228<pre> static void
955 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1229 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
956 { 1230 {
957 ev_unloop (loop, EVUNLOOP_ALL); 1231 ev_unloop (loop, EVUNLOOP_ALL);
958 } 1232 }
… …
965 1239
966 1240
967</pre> 1241</pre>
968 1242
969</div> 1243</div>
1244<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1245<div id="code_ev_stat_code_did_the_file_attri-2">
1246<p>This watches a filesystem path for attribute changes. That is, it calls
1247<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1248compared to the last time, invoking the callback if it did.</p>
1249<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1250not exist&quot; is a status change like any other. The condition &quot;path does
1251not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1252otherwise always forced to be at least one) and all the other fields of
1253the stat buffer having unspecified contents.</p>
1254<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1255relative and your working directory changes, the behaviour is undefined.</p>
1256<p>Since there is no standard to do this, the portable implementation simply
1257calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1258can specify a recommended polling interval for this case. If you specify
1259a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1260unspecified default</i> value will be used (which you can expect to be around
1261five seconds, although this might change dynamically). Libev will also
1262impose a minimum interval which is currently around <code>0.1</code>, but thats
1263usually overkill.</p>
1264<p>This watcher type is not meant for massive numbers of stat watchers,
1265as even with OS-supported change notifications, this can be
1266resource-intensive.</p>
1267<p>At the time of this writing, only the Linux inotify interface is
1268implemented (implementing kqueue support is left as an exercise for the
1269reader). Inotify will be used to give hints only and should not change the
1270semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1271to fall back to regular polling again even with inotify, but changes are
1272usually detected immediately, and if the file exists there will be no
1273polling.</p>
1274<dl>
1275 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1276 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1277 <dd>
1278 <p>Configures the watcher to wait for status changes of the given
1279<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1280be detected and should normally be specified as <code>0</code> to let libev choose
1281a suitable value. The memory pointed to by <code>path</code> must point to the same
1282path for as long as the watcher is active.</p>
1283 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1284relative to the attributes at the time the watcher was started (or the
1285last change was detected).</p>
1286 </dd>
1287 <dt>ev_stat_stat (ev_stat *)</dt>
1288 <dd>
1289 <p>Updates the stat buffer immediately with new values. If you change the
1290watched path in your callback, you could call this fucntion to avoid
1291detecting this change (while introducing a race condition). Can also be
1292useful simply to find out the new values.</p>
1293 </dd>
1294 <dt>ev_statdata attr [read-only]</dt>
1295 <dd>
1296 <p>The most-recently detected attributes of the file. Although the type is of
1297<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1298suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1299was some error while <code>stat</code>ing the file.</p>
1300 </dd>
1301 <dt>ev_statdata prev [read-only]</dt>
1302 <dd>
1303 <p>The previous attributes of the file. The callback gets invoked whenever
1304<code>prev</code> != <code>attr</code>.</p>
1305 </dd>
1306 <dt>ev_tstamp interval [read-only]</dt>
1307 <dd>
1308 <p>The specified interval.</p>
1309 </dd>
1310 <dt>const char *path [read-only]</dt>
1311 <dd>
1312 <p>The filesystem path that is being watched.</p>
1313 </dd>
1314</dl>
1315<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1316<pre> static void
1317 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1318 {
1319 /* /etc/passwd changed in some way */
1320 if (w-&gt;attr.st_nlink)
1321 {
1322 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1323 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1324 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1325 }
1326 else
1327 /* you shalt not abuse printf for puts */
1328 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1329 &quot;if this is windows, they already arrived\n&quot;);
1330 }
1331
1332 ...
1333 ev_stat passwd;
1334
1335 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1336 ev_stat_start (loop, &amp;passwd);
1337
1338
1339
1340
1341</pre>
1342
1343</div>
970<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1344<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
971<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1345<div id="code_ev_idle_code_when_you_ve_got_no-2">
972<p>Idle watchers trigger events when there are no other events are pending 1346<p>Idle watchers trigger events when there are no other events are pending
973(prepare, check and other idle watchers do not count). That is, as long 1347(prepare, check and other idle watchers do not count). That is, as long
974as your process is busy handling sockets or timeouts (or even signals, 1348as your process is busy handling sockets or timeouts (or even signals,
975imagine) it will not be triggered. But when your process is idle all idle 1349imagine) it will not be triggered. But when your process is idle all idle
… …
988 <p>Initialises and configures the idle watcher - it has no parameters of any 1362 <p>Initialises and configures the idle watcher - it has no parameters of any
989kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1363kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
990believe me.</p> 1364believe me.</p>
991 </dd> 1365 </dd>
992</dl> 1366</dl>
993<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1367<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
994callback, free it. Alos, use no error checking, as usual.</p> 1368callback, free it. Also, use no error checking, as usual.</p>
995<pre> static void 1369<pre> static void
996 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1370 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
997 { 1371 {
998 free (w); 1372 free (w);
999 // now do something you wanted to do when the program has 1373 // now do something you wanted to do when the program has
… …
1008 1382
1009 1383
1010</pre> 1384</pre>
1011 1385
1012</div> 1386</div>
1013<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1387<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1014<div id="code_ev_prepare_code_and_code_ev_che-2"> 1388<div id="code_ev_prepare_code_and_code_ev_che-2">
1015<p>Prepare and check watchers are usually (but not always) used in tandem: 1389<p>Prepare and check watchers are usually (but not always) used in tandem:
1016prepare watchers get invoked before the process blocks and check watchers 1390prepare watchers get invoked before the process blocks and check watchers
1017afterwards.</p> 1391afterwards.</p>
1392<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1393the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1394watchers. Other loops than the current one are fine, however. The
1395rationale behind this is that you do not need to check for recursion in
1396those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1397<code>ev_check</code> so if you have one watcher of each kind they will always be
1398called in pairs bracketing the blocking call.</p>
1018<p>Their main purpose is to integrate other event mechanisms into libev. This 1399<p>Their main purpose is to integrate other event mechanisms into libev and
1019could be used, for example, to track variable changes, implement your own 1400their use is somewhat advanced. This could be used, for example, to track
1020watchers, integrate net-snmp or a coroutine library and lots more.</p> 1401variable changes, implement your own watchers, integrate net-snmp or a
1402coroutine library and lots more. They are also occasionally useful if
1403you cache some data and want to flush it before blocking (for example,
1404in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1405watcher).</p>
1021<p>This is done by examining in each prepare call which file descriptors need 1406<p>This is done by examining in each prepare call which file descriptors need
1022to be watched by the other library, registering <code>ev_io</code> watchers for 1407to be watched by the other library, registering <code>ev_io</code> watchers for
1023them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1408them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1024provide just this functionality). Then, in the check watcher you check for 1409provide just this functionality). Then, in the check watcher you check for
1025any events that occured (by checking the pending status of all watchers 1410any events that occured (by checking the pending status of all watchers
… …
1041 <p>Initialises and configures the prepare or check watcher - they have no 1426 <p>Initialises and configures the prepare or check watcher - they have no
1042parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1427parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1043macros, but using them is utterly, utterly and completely pointless.</p> 1428macros, but using them is utterly, utterly and completely pointless.</p>
1044 </dd> 1429 </dd>
1045</dl> 1430</dl>
1046<p>Example: *TODO*.</p> 1431<p>Example: To include a library such as adns, you would add IO watchers
1432and a timeout watcher in a prepare handler, as required by libadns, and
1433in a check watcher, destroy them and call into libadns. What follows is
1434pseudo-code only of course:</p>
1435<pre> static ev_io iow [nfd];
1436 static ev_timer tw;
1047 1437
1438 static void
1439 io_cb (ev_loop *loop, ev_io *w, int revents)
1440 {
1441 // set the relevant poll flags
1442 // could also call adns_processreadable etc. here
1443 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1444 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1445 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1446 }
1048 1447
1448 // create io watchers for each fd and a timer before blocking
1449 static void
1450 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1451 {
1452 int timeout = 3600000;truct pollfd fds [nfd];
1453 // actual code will need to loop here and realloc etc.
1454 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1049 1455
1456 /* the callback is illegal, but won't be called as we stop during check */
1457 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1458 ev_timer_start (loop, &amp;tw);
1050 1459
1460 // create on ev_io per pollfd
1461 for (int i = 0; i &lt; nfd; ++i)
1462 {
1463 ev_io_init (iow + i, io_cb, fds [i].fd,
1464 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1465 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1051 1466
1467 fds [i].revents = 0;
1468 iow [i].data = fds + i;
1469 ev_io_start (loop, iow + i);
1470 }
1471 }
1472
1473 // stop all watchers after blocking
1474 static void
1475 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1476 {
1477 ev_timer_stop (loop, &amp;tw);
1478
1479 for (int i = 0; i &lt; nfd; ++i)
1480 ev_io_stop (loop, iow + i);
1481
1482 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1483 }
1484
1485
1486
1487
1488</pre>
1489
1052</div> 1490</div>
1053<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1491<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1492<div id="code_ev_embed_code_when_one_backend_-2">
1493<p>This is a rather advanced watcher type that lets you embed one event loop
1494into another (currently only <code>ev_io</code> events are supported in the embedded
1495loop, other types of watchers might be handled in a delayed or incorrect
1496fashion and must not be used).</p>
1497<p>There are primarily two reasons you would want that: work around bugs and
1498prioritise I/O.</p>
1499<p>As an example for a bug workaround, the kqueue backend might only support
1500sockets on some platform, so it is unusable as generic backend, but you
1501still want to make use of it because you have many sockets and it scales
1502so nicely. In this case, you would create a kqueue-based loop and embed it
1503into your default loop (which might use e.g. poll). Overall operation will
1504be a bit slower because first libev has to poll and then call kevent, but
1505at least you can use both at what they are best.</p>
1506<p>As for prioritising I/O: rarely you have the case where some fds have
1507to be watched and handled very quickly (with low latency), and even
1508priorities and idle watchers might have too much overhead. In this case
1509you would put all the high priority stuff in one loop and all the rest in
1510a second one, and embed the second one in the first.</p>
1511<p>As long as the watcher is active, the callback will be invoked every time
1512there might be events pending in the embedded loop. The callback must then
1513call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1514their callbacks (you could also start an idle watcher to give the embedded
1515loop strictly lower priority for example). You can also set the callback
1516to <code>0</code>, in which case the embed watcher will automatically execute the
1517embedded loop sweep.</p>
1518<p>As long as the watcher is started it will automatically handle events. The
1519callback will be invoked whenever some events have been handled. You can
1520set the callback to <code>0</code> to avoid having to specify one if you are not
1521interested in that.</p>
1522<p>Also, there have not currently been made special provisions for forking:
1523when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
1524but you will also have to stop and restart any <code>ev_embed</code> watchers
1525yourself.</p>
1526<p>Unfortunately, not all backends are embeddable, only the ones returned by
1527<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
1528portable one.</p>
1529<p>So when you want to use this feature you will always have to be prepared
1530that you cannot get an embeddable loop. The recommended way to get around
1531this is to have a separate variables for your embeddable loop, try to
1532create it, and if that fails, use the normal loop for everything:</p>
1533<pre> struct ev_loop *loop_hi = ev_default_init (0);
1534 struct ev_loop *loop_lo = 0;
1535 struct ev_embed embed;
1536
1537 // see if there is a chance of getting one that works
1538 // (remember that a flags value of 0 means autodetection)
1539 loop_lo = ev_embeddable_backends () &amp; ev_recommended_backends ()
1540 ? ev_loop_new (ev_embeddable_backends () &amp; ev_recommended_backends ())
1541 : 0;
1542
1543 // if we got one, then embed it, otherwise default to loop_hi
1544 if (loop_lo)
1545 {
1546 ev_embed_init (&amp;embed, 0, loop_lo);
1547 ev_embed_start (loop_hi, &amp;embed);
1548 }
1549 else
1550 loop_lo = loop_hi;
1551
1552</pre>
1553<dl>
1554 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1555 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1556 <dd>
1557 <p>Configures the watcher to embed the given loop, which must be
1558embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1559invoked automatically, otherwise it is the responsibility of the callback
1560to invoke it (it will continue to be called until the sweep has been done,
1561if you do not want thta, you need to temporarily stop the embed watcher).</p>
1562 </dd>
1563 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1564 <dd>
1565 <p>Make a single, non-blocking sweep over the embedded loop. This works
1566similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1567apropriate way for embedded loops.</p>
1568 </dd>
1569 <dt>struct ev_loop *loop [read-only]</dt>
1570 <dd>
1571 <p>The embedded event loop.</p>
1572 </dd>
1573</dl>
1574
1575
1576
1577
1578
1579</div>
1580<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>
1581<div id="code_ev_fork_code_the_audacity_to_re-2">
1582<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1583whoever is a good citizen cared to tell libev about it by calling
1584<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1585event loop blocks next and before <code>ev_check</code> watchers are being called,
1586and only in the child after the fork. If whoever good citizen calling
1587<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1588handlers will be invoked, too, of course.</p>
1589<dl>
1590 <dt>ev_fork_init (ev_signal *, callback)</dt>
1591 <dd>
1592 <p>Initialises and configures the fork watcher - it has no parameters of any
1593kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1594believe me.</p>
1595 </dd>
1596</dl>
1597
1598
1599
1600
1601
1602</div>
1603<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1054<div id="OTHER_FUNCTIONS_CONTENT"> 1604<div id="OTHER_FUNCTIONS_CONTENT">
1055<p>There are some other functions of possible interest. Described. Here. Now.</p> 1605<p>There are some other functions of possible interest. Described. Here. Now.</p>
1056<dl> 1606<dl>
1057 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1607 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1058 <dd> 1608 <dd>
… …
1082 1632
1083 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1633 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1084 1634
1085</pre> 1635</pre>
1086 </dd> 1636 </dd>
1087 <dt>ev_feed_event (loop, watcher, int events)</dt> 1637 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
1088 <dd> 1638 <dd>
1089 <p>Feeds the given event set into the event loop, as if the specified event 1639 <p>Feeds the given event set into the event loop, as if the specified event
1090had happened for the specified watcher (which must be a pointer to an 1640had happened for the specified watcher (which must be a pointer to an
1091initialised but not necessarily started event watcher).</p> 1641initialised but not necessarily started event watcher).</p>
1092 </dd> 1642 </dd>
1093 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1643 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
1094 <dd> 1644 <dd>
1095 <p>Feed an event on the given fd, as if a file descriptor backend detected 1645 <p>Feed an event on the given fd, as if a file descriptor backend detected
1096the given events it.</p> 1646the given events it.</p>
1097 </dd> 1647 </dd>
1098 <dt>ev_feed_signal_event (loop, int signum)</dt> 1648 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
1099 <dd> 1649 <dd>
1100 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1650 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1651loop!).</p>
1101 </dd> 1652 </dd>
1102</dl> 1653</dl>
1103 1654
1104 1655
1105 1656
1106 1657
1107 1658
1108</div> 1659</div>
1109<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1660<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1110<div id="LIBEVENT_EMULATION_CONTENT"> 1661<div id="LIBEVENT_EMULATION_CONTENT">
1111<p>Libev offers a compatibility emulation layer for libevent. It cannot 1662<p>Libev offers a compatibility emulation layer for libevent. It cannot
1112emulate the internals of libevent, so here are some usage hints:</p> 1663emulate the internals of libevent, so here are some usage hints:</p>
1113<dl> 1664<dl>
1114 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1665 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1124 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1675 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1125to use the libev header file and library.</dt> 1676to use the libev header file and library.</dt>
1126</dl> 1677</dl>
1127 1678
1128</div> 1679</div>
1129<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1680<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1130<div id="C_SUPPORT_CONTENT"> 1681<div id="C_SUPPORT_CONTENT">
1131<p>TBD.</p> 1682<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1683you to use some convinience methods to start/stop watchers and also change
1684the callback model to a model using method callbacks on objects.</p>
1685<p>To use it,</p>
1686<pre> #include &lt;ev++.h&gt;
1132 1687
1688</pre>
1689<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1690and puts all of its definitions (many of them macros) into the global
1691namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1692<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1693<code>EV_MULTIPLICITY</code>.</p>
1694<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1695<dl>
1696 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1697 <dd>
1698 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1699macros from <cite>ev.h</cite>.</p>
1700 </dd>
1701 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1702 <dd>
1703 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1704 </dd>
1705 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1706 <dd>
1707 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1708the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1709which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1710defines by many implementations.</p>
1711 <p>All of those classes have these methods:</p>
1712 <p>
1713 <dl>
1714 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1715 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1716 <dt>ev::TYPE::~TYPE</dt>
1717 <dd>
1718 <p>The constructor takes a pointer to an object and a method pointer to
1719the event handler callback to call in this class. The constructor calls
1720<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1721before starting it. If you do not specify a loop then the constructor
1722automatically associates the default loop with this watcher.</p>
1723 <p>The destructor automatically stops the watcher if it is active.</p>
1724 </dd>
1725 <dt>w-&gt;set (struct ev_loop *)</dt>
1726 <dd>
1727 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1728do this when the watcher is inactive (and not pending either).</p>
1729 </dd>
1730 <dt>w-&gt;set ([args])</dt>
1731 <dd>
1732 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1733called at least once. Unlike the C counterpart, an active watcher gets
1734automatically stopped and restarted.</p>
1735 </dd>
1736 <dt>w-&gt;start ()</dt>
1737 <dd>
1738 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1739constructor already takes the loop.</p>
1740 </dd>
1741 <dt>w-&gt;stop ()</dt>
1742 <dd>
1743 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1744 </dd>
1745 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1746 <dd>
1747 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1748<code>ev_TYPE_again</code> function.</p>
1749 </dd>
1750 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1751 <dd>
1752 <p>Invokes <code>ev_embed_sweep</code>.</p>
1753 </dd>
1754 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1755 <dd>
1756 <p>Invokes <code>ev_stat_stat</code>.</p>
1757 </dd>
1758 </dl>
1759 </p>
1760 </dd>
1761</dl>
1762<p>Example: Define a class with an IO and idle watcher, start one of them in
1763the constructor.</p>
1764<pre> class myclass
1765 {
1766 ev_io io; void io_cb (ev::io &amp;w, int revents);
1767 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1768
1769 myclass ();
1770 }
1771
1772 myclass::myclass (int fd)
1773 : io (this, &amp;myclass::io_cb),
1774 idle (this, &amp;myclass::idle_cb)
1775 {
1776 io.start (fd, ev::READ);
1777 }
1778
1779
1780
1781
1782</pre>
1783
1133</div> 1784</div>
1134<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1785<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1786<div id="MACRO_MAGIC_CONTENT">
1787<p>Libev can be compiled with a variety of options, the most fundemantal is
1788<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1789callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1790<p>To make it easier to write programs that cope with either variant, the
1791following macros are defined:</p>
1792<dl>
1793 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1794 <dd>
1795 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1796loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1797<code>EV_A_</code> is used when other arguments are following. Example:</p>
1798<pre> ev_unref (EV_A);
1799 ev_timer_add (EV_A_ watcher);
1800 ev_loop (EV_A_ 0);
1801
1802</pre>
1803 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1804which is often provided by the following macro.</p>
1805 </dd>
1806 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1807 <dd>
1808 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1809loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1810<code>EV_P_</code> is used when other parameters are following. Example:</p>
1811<pre> // this is how ev_unref is being declared
1812 static void ev_unref (EV_P);
1813
1814 // this is how you can declare your typical callback
1815 static void cb (EV_P_ ev_timer *w, int revents)
1816
1817</pre>
1818 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1819suitable for use with <code>EV_A</code>.</p>
1820 </dd>
1821 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1822 <dd>
1823 <p>Similar to the other two macros, this gives you the value of the default
1824loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1825 </dd>
1826</dl>
1827<p>Example: Declare and initialise a check watcher, working regardless of
1828wether multiple loops are supported or not.</p>
1829<pre> static void
1830 check_cb (EV_P_ ev_timer *w, int revents)
1831 {
1832 ev_check_stop (EV_A_ w);
1833 }
1834
1835 ev_check check;
1836 ev_check_init (&amp;check, check_cb);
1837 ev_check_start (EV_DEFAULT_ &amp;check);
1838 ev_loop (EV_DEFAULT_ 0);
1839
1840
1841
1842
1843</pre>
1844
1845</div>
1846<h1 id="EMBEDDING">EMBEDDING</h1>
1847<div id="EMBEDDING_CONTENT">
1848<p>Libev can (and often is) directly embedded into host
1849applications. Examples of applications that embed it include the Deliantra
1850Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1851and rxvt-unicode.</p>
1852<p>The goal is to enable you to just copy the neecssary files into your
1853source directory without having to change even a single line in them, so
1854you can easily upgrade by simply copying (or having a checked-out copy of
1855libev somewhere in your source tree).</p>
1856
1857</div>
1858<h2 id="FILESETS">FILESETS</h2>
1859<div id="FILESETS_CONTENT">
1860<p>Depending on what features you need you need to include one or more sets of files
1861in your app.</p>
1862
1863</div>
1864<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1865<div id="CORE_EVENT_LOOP_CONTENT">
1866<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1867configuration (no autoconf):</p>
1868<pre> #define EV_STANDALONE 1
1869 #include &quot;ev.c&quot;
1870
1871</pre>
1872<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1873single C source file only to provide the function implementations. To use
1874it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1875done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1876where you can put other configuration options):</p>
1877<pre> #define EV_STANDALONE 1
1878 #include &quot;ev.h&quot;
1879
1880</pre>
1881<p>Both header files and implementation files can be compiled with a C++
1882compiler (at least, thats a stated goal, and breakage will be treated
1883as a bug).</p>
1884<p>You need the following files in your source tree, or in a directory
1885in your include path (e.g. in libev/ when using -Ilibev):</p>
1886<pre> ev.h
1887 ev.c
1888 ev_vars.h
1889 ev_wrap.h
1890
1891 ev_win32.c required on win32 platforms only
1892
1893 ev_select.c only when select backend is enabled (which is by default)
1894 ev_poll.c only when poll backend is enabled (disabled by default)
1895 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1896 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1897 ev_port.c only when the solaris port backend is enabled (disabled by default)
1898
1899</pre>
1900<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1901to compile this single file.</p>
1902
1903</div>
1904<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1905<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1906<p>To include the libevent compatibility API, also include:</p>
1907<pre> #include &quot;event.c&quot;
1908
1909</pre>
1910<p>in the file including <cite>ev.c</cite>, and:</p>
1911<pre> #include &quot;event.h&quot;
1912
1913</pre>
1914<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1915<p>You need the following additional files for this:</p>
1916<pre> event.h
1917 event.c
1918
1919</pre>
1920
1921</div>
1922<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1923<div id="AUTOCONF_SUPPORT_CONTENT">
1924<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1925whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1926<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1927include <cite>config.h</cite> and configure itself accordingly.</p>
1928<p>For this of course you need the m4 file:</p>
1929<pre> libev.m4
1930
1931</pre>
1932
1933</div>
1934<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1935<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1936<p>Libev can be configured via a variety of preprocessor symbols you have to define
1937before including any of its files. The default is not to build for multiplicity
1938and only include the select backend.</p>
1939<dl>
1940 <dt>EV_STANDALONE</dt>
1941 <dd>
1942 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1943keeps libev from including <cite>config.h</cite>, and it also defines dummy
1944implementations for some libevent functions (such as logging, which is not
1945supported). It will also not define any of the structs usually found in
1946<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1947 </dd>
1948 <dt>EV_USE_MONOTONIC</dt>
1949 <dd>
1950 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1951monotonic clock option at both compiletime and runtime. Otherwise no use
1952of the monotonic clock option will be attempted. If you enable this, you
1953usually have to link against librt or something similar. Enabling it when
1954the functionality isn't available is safe, though, althoguh you have
1955to make sure you link against any libraries where the <code>clock_gettime</code>
1956function is hiding in (often <cite>-lrt</cite>).</p>
1957 </dd>
1958 <dt>EV_USE_REALTIME</dt>
1959 <dd>
1960 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1961realtime clock option at compiletime (and assume its availability at
1962runtime if successful). Otherwise no use of the realtime clock option will
1963be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1964(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1965in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1966 </dd>
1967 <dt>EV_USE_SELECT</dt>
1968 <dd>
1969 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1970<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1971other method takes over, select will be it. Otherwise the select backend
1972will not be compiled in.</p>
1973 </dd>
1974 <dt>EV_SELECT_USE_FD_SET</dt>
1975 <dd>
1976 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1977structure. This is useful if libev doesn't compile due to a missing
1978<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1979exotic systems. This usually limits the range of file descriptors to some
1980low limit such as 1024 or might have other limitations (winsocket only
1981allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1982influence the size of the <code>fd_set</code> used.</p>
1983 </dd>
1984 <dt>EV_SELECT_IS_WINSOCKET</dt>
1985 <dd>
1986 <p>When defined to <code>1</code>, the select backend will assume that
1987select/socket/connect etc. don't understand file descriptors but
1988wants osf handles on win32 (this is the case when the select to
1989be used is the winsock select). This means that it will call
1990<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1991it is assumed that all these functions actually work on fds, even
1992on win32. Should not be defined on non-win32 platforms.</p>
1993 </dd>
1994 <dt>EV_USE_POLL</dt>
1995 <dd>
1996 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1997backend. Otherwise it will be enabled on non-win32 platforms. It
1998takes precedence over select.</p>
1999 </dd>
2000 <dt>EV_USE_EPOLL</dt>
2001 <dd>
2002 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
2003<code>epoll</code>(7) backend. Its availability will be detected at runtime,
2004otherwise another method will be used as fallback. This is the
2005preferred backend for GNU/Linux systems.</p>
2006 </dd>
2007 <dt>EV_USE_KQUEUE</dt>
2008 <dd>
2009 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
2010<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
2011otherwise another method will be used as fallback. This is the preferred
2012backend for BSD and BSD-like systems, although on most BSDs kqueue only
2013supports some types of fds correctly (the only platform we found that
2014supports ptys for example was NetBSD), so kqueue might be compiled in, but
2015not be used unless explicitly requested. The best way to use it is to find
2016out whether kqueue supports your type of fd properly and use an embedded
2017kqueue loop.</p>
2018 </dd>
2019 <dt>EV_USE_PORT</dt>
2020 <dd>
2021 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
202210 port style backend. Its availability will be detected at runtime,
2023otherwise another method will be used as fallback. This is the preferred
2024backend for Solaris 10 systems.</p>
2025 </dd>
2026 <dt>EV_USE_DEVPOLL</dt>
2027 <dd>
2028 <p>reserved for future expansion, works like the USE symbols above.</p>
2029 </dd>
2030 <dt>EV_USE_INOTIFY</dt>
2031 <dd>
2032 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2033interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2034be detected at runtime.</p>
2035 </dd>
2036 <dt>EV_H</dt>
2037 <dd>
2038 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
2039undefined 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
2040can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
2041 </dd>
2042 <dt>EV_CONFIG_H</dt>
2043 <dd>
2044 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
2045<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
2046<code>EV_H</code>, above.</p>
2047 </dd>
2048 <dt>EV_EVENT_H</dt>
2049 <dd>
2050 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
2051of how the <cite>event.h</cite> header can be found.</p>
2052 </dd>
2053 <dt>EV_PROTOTYPES</dt>
2054 <dd>
2055 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
2056prototypes, but still define all the structs and other symbols. This is
2057occasionally useful if you want to provide your own wrapper functions
2058around libev functions.</p>
2059 </dd>
2060 <dt>EV_MULTIPLICITY</dt>
2061 <dd>
2062 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
2063will have the <code>struct ev_loop *</code> as first argument, and you can create
2064additional independent event loops. Otherwise there will be no support
2065for multiple event loops and there is no first event loop pointer
2066argument. Instead, all functions act on the single default loop.</p>
2067 </dd>
2068 <dt>EV_PERIODIC_ENABLE</dt>
2069 <dd>
2070 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2071defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2072code.</p>
2073 </dd>
2074 <dt>EV_EMBED_ENABLE</dt>
2075 <dd>
2076 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2077defined to be <code>0</code>, then they are not.</p>
2078 </dd>
2079 <dt>EV_STAT_ENABLE</dt>
2080 <dd>
2081 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2082defined to be <code>0</code>, then they are not.</p>
2083 </dd>
2084 <dt>EV_FORK_ENABLE</dt>
2085 <dd>
2086 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2087defined to be <code>0</code>, then they are not.</p>
2088 </dd>
2089 <dt>EV_MINIMAL</dt>
2090 <dd>
2091 <p>If you need to shave off some kilobytes of code at the expense of some
2092speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2093some inlining decisions, saves roughly 30% codesize of amd64.</p>
2094 </dd>
2095 <dt>EV_PID_HASHSIZE</dt>
2096 <dd>
2097 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2098pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2099than enough. If you need to manage thousands of children you might want to
2100increase this value (<i>must</i> be a power of two).</p>
2101 </dd>
2102 <dt>EV_INOTIFY_HASHSIZE</dt>
2103 <dd>
2104 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2105inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2106usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2107watchers you might want to increase this value (<i>must</i> be a power of
2108two).</p>
2109 </dd>
2110 <dt>EV_COMMON</dt>
2111 <dd>
2112 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2113this macro to a something else you can include more and other types of
2114members. You have to define it each time you include one of the files,
2115though, and it must be identical each time.</p>
2116 <p>For example, the perl EV module uses something like this:</p>
2117<pre> #define EV_COMMON \
2118 SV *self; /* contains this struct */ \
2119 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2120
2121</pre>
2122 </dd>
2123 <dt>EV_CB_DECLARE (type)</dt>
2124 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2125 <dt>ev_set_cb (ev, cb)</dt>
2126 <dd>
2127 <p>Can be used to change the callback member declaration in each watcher,
2128and the way callbacks are invoked and set. Must expand to a struct member
2129definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2130their default definitions. One possible use for overriding these is to
2131avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2132method calls instead of plain function calls in C++.</p>
2133
2134</div>
2135<h2 id="EXAMPLES">EXAMPLES</h2>
2136<div id="EXAMPLES_CONTENT">
2137 <p>For a real-world example of a program the includes libev
2138verbatim, you can have a look at the EV perl module
2139(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2140the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2141interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2142will be compiled. It is pretty complex because it provides its own header
2143file.</p>
2144 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2145that everybody includes and which overrides some autoconf choices:</p>
2146<pre> #define EV_USE_POLL 0
2147 #define EV_MULTIPLICITY 0
2148 #define EV_PERIODICS 0
2149 #define EV_CONFIG_H &lt;config.h&gt;
2150
2151 #include &quot;ev++.h&quot;
2152
2153</pre>
2154 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2155<pre> #include &quot;ev_cpp.h&quot;
2156 #include &quot;ev.c&quot;
2157
2158
2159
2160
2161</pre>
2162
2163</div>
2164<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2165<div id="COMPLEXITIES_CONTENT">
2166 <p>In this section the complexities of (many of) the algorithms used inside
2167libev will be explained. For complexity discussions about backends see the
2168documentation for <code>ev_default_init</code>.</p>
2169 <p>
2170 <dl>
2171 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2172 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2173 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2174 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2175 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2176 <dt>Finding the next timer per loop iteration: O(1)</dt>
2177 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2178 <dt>Activating one watcher: O(1)</dt>
2179 </dl>
2180 </p>
2181
2182
2183
2184
2185
2186</div>
2187<h1 id="AUTHOR">AUTHOR</h1>
1135<div id="AUTHOR_CONTENT"> 2188<div id="AUTHOR_CONTENT">
1136<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2189 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1137 2190
1138</div> 2191</div>
1139</div></body> 2192</div></body>
1140</html> 2193</html>

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