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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="Mon Nov 12 09:57:02 2007" /> 9 <meta name="created" content="Mon Nov 26 10:52:13 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 21<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
26<ul><li><a href="#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> 27<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
27</ul> 28</ul>
28</li> 29</li>
29<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 30<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> 31<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> 32<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> 33<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
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> 34<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
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> 36<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
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> 37<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
38<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
37</ul> 39</ul>
38</li> 40</li>
39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
44<li><a href="#EMBEDDING">EMBEDDING</a>
45<ul><li><a href="#FILESETS">FILESETS</a>
46<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
47<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
48<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
49</ul>
50</li>
51<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
52<li><a href="#EXAMPLES">EXAMPLES</a></li>
53</ul>
54</li>
40<li><a href="#AUTHOR">AUTHOR</a> 55<li><a href="#AUTHOR">AUTHOR</a>
41</li> 56</li>
42</ul><hr /> 57</ul><hr />
43<!-- INDEX END --> 58<!-- INDEX END -->
44 59
… …
94<div id="TIME_REPRESENTATION_CONTENT"> 109<div id="TIME_REPRESENTATION_CONTENT">
95<p>Libev represents time as a single floating point number, representing the 110<p>Libev represents time as a single floating point number, representing the
96(fractional) number of seconds since the (POSIX) epoch (somewhere near 111(fractional) number of seconds since the (POSIX) epoch (somewhere near
97the beginning of 1970, details are complicated, don't ask). This type is 112the beginning of 1970, details are complicated, don't ask). This type is
98called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 113called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
99to the double type in C.</p> 114to the <code>double</code> type in C, and when you need to do any calculations on
115it, you should treat it as such.</p>
116
117
118
119
100 120
101</div> 121</div>
102<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
103<div id="GLOBAL_FUNCTIONS_CONTENT"> 123<div id="GLOBAL_FUNCTIONS_CONTENT">
124<p>These functions can be called anytime, even before initialising the
125library in any way.</p>
104<dl> 126<dl>
105 <dt>ev_tstamp ev_time ()</dt> 127 <dt>ev_tstamp ev_time ()</dt>
106 <dd> 128 <dd>
107 <p>Returns the current time as libev would use it.</p> 129 <p>Returns the current time as libev would use it. Please note that the
130<code>ev_now</code> function is usually faster and also often returns the timestamp
131you actually want to know.</p>
108 </dd> 132 </dd>
109 <dt>int ev_version_major ()</dt> 133 <dt>int ev_version_major ()</dt>
110 <dt>int ev_version_minor ()</dt> 134 <dt>int ev_version_minor ()</dt>
111 <dd> 135 <dd>
112 <p>You can find out the major and minor version numbers of the library 136 <p>You can find out the major and minor version numbers of the library
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116version of the library your program was compiled against.</p> 140version of the library your program was compiled against.</p>
117 <p>Usually, it's a good idea to terminate if the major versions mismatch, 141 <p>Usually, it's a good idea to terminate if the major versions mismatch,
118as this indicates an incompatible change. Minor versions are usually 142as this indicates an incompatible change. Minor versions are usually
119compatible to older versions, so a larger minor version alone is usually 143compatible to older versions, so a larger minor version alone is usually
120not a problem.</p> 144not a problem.</p>
145 <p>Example: make sure we haven't accidentally been linked against the wrong
146version:</p>
147<pre> assert ((&quot;libev version mismatch&quot;,
148 ev_version_major () == EV_VERSION_MAJOR
149 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
150
151</pre>
152 </dd>
153 <dt>unsigned int ev_supported_backends ()</dt>
154 <dd>
155 <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
156value) compiled into this binary of libev (independent of their
157availability on the system you are running on). See <code>ev_default_loop</code> for
158a description of the set values.</p>
159 <p>Example: make sure we have the epoll method, because yeah this is cool and
160a must have and can we have a torrent of it please!!!11</p>
161<pre> assert ((&quot;sorry, no epoll, no sex&quot;,
162 ev_supported_backends () &amp; EVBACKEND_EPOLL));
163
164</pre>
165 </dd>
166 <dt>unsigned int ev_recommended_backends ()</dt>
167 <dd>
168 <p>Return the set of all backends compiled into this binary of libev and also
169recommended for this platform. This set is often smaller than the one
170returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
171most BSDs and will not be autodetected unless you explicitly request it
172(assuming you know what you are doing). This is the set of backends that
173libev will probe for if you specify no backends explicitly.</p>
174 </dd>
175 <dt>unsigned int ev_embeddable_backends ()</dt>
176 <dd>
177 <p>Returns the set of backends that are embeddable in other event loops. This
178is the theoretical, all-platform, value. To find which backends
179might be supported on the current system, you would need to look at
180<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
181recommended ones.</p>
182 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
121 </dd> 183 </dd>
122 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 184 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
123 <dd> 185 <dd>
124 <p>Sets the allocation function to use (the prototype is similar to the 186 <p>Sets the allocation function to use (the prototype is similar to the
125realloc C function, the semantics are identical). It is used to allocate 187realloc C function, the semantics are identical). It is used to allocate
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127needs to be allocated, the library might abort or take some potentially 189needs to be allocated, the library might abort or take some potentially
128destructive action. The default is your system realloc function.</p> 190destructive action. The default is your system realloc function.</p>
129 <p>You could override this function in high-availability programs to, say, 191 <p>You could override this function in high-availability programs to, say,
130free some memory if it cannot allocate memory, to use a special allocator, 192free some memory if it cannot allocate memory, to use a special allocator,
131or even to sleep a while and retry until some memory is available.</p> 193or even to sleep a while and retry until some memory is available.</p>
194 <p>Example: replace the libev allocator with one that waits a bit and then
195retries: better than mine).</p>
196<pre> static void *
197 persistent_realloc (void *ptr, long size)
198 {
199 for (;;)
200 {
201 void *newptr = realloc (ptr, size);
202
203 if (newptr)
204 return newptr;
205
206 sleep (60);
207 }
208 }
209
210 ...
211 ev_set_allocator (persistent_realloc);
212
213</pre>
132 </dd> 214 </dd>
133 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 215 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
134 <dd> 216 <dd>
135 <p>Set the callback function to call on a retryable syscall error (such 217 <p>Set the callback function to call on a retryable syscall error (such
136as failed select, poll, epoll_wait). The message is a printable string 218as failed select, poll, epoll_wait). The message is a printable string
137indicating the system call or subsystem causing the problem. If this 219indicating the system call or subsystem causing the problem. If this
138callback is set, then libev will expect it to remedy the sitution, no 220callback is set, then libev will expect it to remedy the sitution, no
139matter what, when it returns. That is, libev will generally retry the 221matter what, when it returns. That is, libev will generally retry the
140requested operation, or, if the condition doesn't go away, do bad stuff 222requested operation, or, if the condition doesn't go away, do bad stuff
141(such as abort).</p> 223(such as abort).</p>
224 <p>Example: do the same thing as libev does internally:</p>
225<pre> static void
226 fatal_error (const char *msg)
227 {
228 perror (msg);
229 abort ();
230 }
231
232 ...
233 ev_set_syserr_cb (fatal_error);
234
235</pre>
142 </dd> 236 </dd>
143</dl> 237</dl>
144 238
145</div> 239</div>
146<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 240<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
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158 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 252 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
159 <dd> 253 <dd>
160 <p>This will initialise the default event loop if it hasn't been initialised 254 <p>This will initialise the default event loop if it hasn't been initialised
161yet and return it. If the default loop could not be initialised, returns 255yet and return it. If the default loop could not be initialised, returns
162false. If it already was initialised it simply returns it (and ignores the 256false. If it already was initialised it simply returns it (and ignores the
163flags).</p> 257flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
164 <p>If you don't know what event loop to use, use the one returned from this 258 <p>If you don't know what event loop to use, use the one returned from this
165function.</p> 259function.</p>
166 <p>The flags argument can be used to specify special behaviour or specific 260 <p>The flags argument can be used to specify special behaviour or specific
167backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> 261backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
168 <p>It supports the following flags:</p> 262 <p>The following flags are supported:</p>
169 <p> 263 <p>
170 <dl> 264 <dl>
171 <dt><code>EVFLAG_AUTO</code></dt> 265 <dt><code>EVFLAG_AUTO</code></dt>
172 <dd> 266 <dd>
173 <p>The default flags value. Use this if you have no clue (it's the right 267 <p>The default flags value. Use this if you have no clue (it's the right
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180<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 274<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181override the flags completely if it is found in the environment. This is 275override the flags completely if it is found in the environment. This is
182useful to try out specific backends to test their performance, or to work 276useful to try out specific backends to test their performance, or to work
183around bugs.</p> 277around bugs.</p>
184 </dd> 278 </dd>
185 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> 279 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
186 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt> 280 <dd>
187 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> 281 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
188 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> 282libev tries to roll its own fd_set with no limits on the number of fds,
189 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> 283but if that fails, expect a fairly low limit on the number of fds when
190 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> 284using this backend. It doesn't scale too well (O(highest_fd)), but its usually
285the fastest backend for a low number of fds.</p>
191 <dd> 286 </dd>
192 <p>If one or more of these are ored into the flags value, then only these 287 <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
193backends will be tried (in the reverse order as given here). If one are 288 <dd>
194specified, any backend will do.</p> 289 <p>And this is your standard poll(2) backend. It's more complicated than
290select, but handles sparse fds better and has no artificial limit on the
291number of fds you can use (except it will slow down considerably with a
292lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
293 </dd>
294 <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
295 <dd>
296 <p>For few fds, this backend is a bit little slower than poll and select,
297but it scales phenomenally better. While poll and select usually scale like
298O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
299either O(1) or O(active_fds).</p>
300 <p>While stopping and starting an I/O watcher in the same iteration will
301result in some caching, there is still a syscall per such incident
302(because the fd could point to a different file description now), so its
303best to avoid that. Also, dup()ed file descriptors might not work very
304well if you register events for both fds.</p>
305 <p>Please note that epoll sometimes generates spurious notifications, so you
306need to use non-blocking I/O or other means to avoid blocking when no data
307(or space) is available.</p>
308 </dd>
309 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
310 <dd>
311 <p>Kqueue deserves special mention, as at the time of this writing, it
312was broken on all BSDs except NetBSD (usually it doesn't work with
313anything but sockets and pipes, except on Darwin, where of course its
314completely useless). For this reason its not being &quot;autodetected&quot;
315unless you explicitly specify it explicitly in the flags (i.e. using
316<code>EVBACKEND_KQUEUE</code>).</p>
317 <p>It scales in the same way as the epoll backend, but the interface to the
318kernel is more efficient (which says nothing about its actual speed, of
319course). While starting and stopping an I/O watcher does not cause an
320extra syscall as with epoll, it still adds up to four event changes per
321incident, so its best to avoid that.</p>
322 </dd>
323 <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
324 <dd>
325 <p>This is not implemented yet (and might never be).</p>
326 </dd>
327 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
328 <dd>
329 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
330it's really slow, but it still scales very well (O(active_fds)).</p>
331 <p>Please note that solaris ports can result in a lot of spurious
332notifications, so you need to use non-blocking I/O or other means to avoid
333blocking when no data (or space) is available.</p>
334 </dd>
335 <dt><code>EVBACKEND_ALL</code></dt>
336 <dd>
337 <p>Try all backends (even potentially broken ones that wouldn't be tried
338with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
339<code>EVBACKEND_ALL &amp; ~EVBACKEND_KQUEUE</code>.</p>
195 </dd> 340 </dd>
196 </dl> 341 </dl>
197 </p> 342 </p>
343 <p>If one or more of these are ored into the flags value, then only these
344backends will be tried (in the reverse order as given here). If none are
345specified, most compiled-in backend will be tried, usually in reverse
346order of their flag values :)</p>
347 <p>The most typical usage is like this:</p>
348<pre> if (!ev_default_loop (0))
349 fatal (&quot;could not initialise libev, bad $LIBEV_FLAGS in environment?&quot;);
350
351</pre>
352 <p>Restrict libev to the select and poll backends, and do not allow
353environment settings to be taken into account:</p>
354<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
355
356</pre>
357 <p>Use whatever libev has to offer, but make sure that kqueue is used if
358available (warning, breaks stuff, best use only with your own private
359event loop and only if you know the OS supports your types of fds):</p>
360<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
361
362</pre>
198 </dd> 363 </dd>
199 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 364 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200 <dd> 365 <dd>
201 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 366 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
202always distinct from the default loop. Unlike the default loop, it cannot 367always distinct from the default loop. Unlike the default loop, it cannot
203handle signal and child watchers, and attempts to do so will be greeted by 368handle signal and child watchers, and attempts to do so will be greeted by
204undefined behaviour (or a failed assertion if assertions are enabled).</p> 369undefined behaviour (or a failed assertion if assertions are enabled).</p>
370 <p>Example: try to create a event loop that uses epoll and nothing else.</p>
371<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
372 if (!epoller)
373 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
374
375</pre>
205 </dd> 376 </dd>
206 <dt>ev_default_destroy ()</dt> 377 <dt>ev_default_destroy ()</dt>
207 <dd> 378 <dd>
208 <p>Destroys the default loop again (frees all memory and kernel state 379 <p>Destroys the default loop again (frees all memory and kernel state
209etc.). This stops all registered event watchers (by not touching them in 380etc.). None of the active event watchers will be stopped in the normal
210any way whatsoever, although you cannot rely on this :).</p> 381sense, so e.g. <code>ev_is_active</code> might still return true. It is your
382responsibility to either stop all watchers cleanly yoursef <i>before</i>
383calling this function, or cope with the fact afterwards (which is usually
384the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
385for example).</p>
211 </dd> 386 </dd>
212 <dt>ev_loop_destroy (loop)</dt> 387 <dt>ev_loop_destroy (loop)</dt>
213 <dd> 388 <dd>
214 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 389 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
215earlier call to <code>ev_loop_new</code>.</p> 390earlier call to <code>ev_loop_new</code>.</p>
… …
218 <dd> 393 <dd>
219 <p>This function reinitialises the kernel state for backends that have 394 <p>This function reinitialises the kernel state for backends that have
220one. Despite the name, you can call it anytime, but it makes most sense 395one. Despite the name, you can call it anytime, but it makes most sense
221after forking, in either the parent or child process (or both, but that 396after forking, in either the parent or child process (or both, but that
222again makes little sense).</p> 397again makes little sense).</p>
223 <p>You <i>must</i> call this function after forking if and only if you want to 398 <p>You <i>must</i> call this function in the child process after forking if and
224use the event library in both processes. If you just fork+exec, you don't 399only if you want to use the event library in both processes. If you just
225have to call it.</p> 400fork+exec, you don't have to call it.</p>
226 <p>The function itself is quite fast and it's usually not a problem to call 401 <p>The function itself is quite fast and it's usually not a problem to call
227it just in case after a fork. To make this easy, the function will fit in 402it just in case after a fork. To make this easy, the function will fit in
228quite nicely into a call to <code>pthread_atfork</code>:</p> 403quite nicely into a call to <code>pthread_atfork</code>:</p>
229<pre> pthread_atfork (0, 0, ev_default_fork); 404<pre> pthread_atfork (0, 0, ev_default_fork);
230 405
231</pre> 406</pre>
407 <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
408without calling this function, so if you force one of those backends you
409do not need to care.</p>
232 </dd> 410 </dd>
233 <dt>ev_loop_fork (loop)</dt> 411 <dt>ev_loop_fork (loop)</dt>
234 <dd> 412 <dd>
235 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 413 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
236<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 414<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
237after fork, and how you do this is entirely your own problem.</p> 415after fork, and how you do this is entirely your own problem.</p>
238 </dd> 416 </dd>
239 <dt>unsigned int ev_method (loop)</dt> 417 <dt>unsigned int ev_backend (loop)</dt>
240 <dd> 418 <dd>
241 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 419 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
242use.</p> 420use.</p>
243 </dd> 421 </dd>
244 <dt>ev_tstamp ev_now (loop)</dt> 422 <dt>ev_tstamp ev_now (loop)</dt>
245 <dd> 423 <dd>
246 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 424 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
247got events and started processing them. This timestamp does not change 425received events and started processing them. This timestamp does not
248as long as callbacks are being processed, and this is also the base time 426change as long as callbacks are being processed, and this is also the base
249used for relative timers. You can treat it as the timestamp of the event 427time used for relative timers. You can treat it as the timestamp of the
250occuring (or more correctly, the mainloop finding out about it).</p> 428event occuring (or more correctly, libev finding out about it).</p>
251 </dd> 429 </dd>
252 <dt>ev_loop (loop, int flags)</dt> 430 <dt>ev_loop (loop, int flags)</dt>
253 <dd> 431 <dd>
254 <p>Finally, this is it, the event handler. This function usually is called 432 <p>Finally, this is it, the event handler. This function usually is called
255after you initialised all your watchers and you want to start handling 433after you initialised all your watchers and you want to start handling
256events.</p> 434events.</p>
257 <p>If the flags argument is specified as 0, it will not return until either 435 <p>If the flags argument is specified as <code>0</code>, it will not return until
258no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 436either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
437 <p>Please note that an explicit <code>ev_unloop</code> is usually better than
438relying on all watchers to be stopped when deciding when a program has
439finished (especially in interactive programs), but having a program that
440automatically loops as long as it has to and no longer by virtue of
441relying on its watchers stopping correctly is a thing of beauty.</p>
259 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 442 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
260those events and any outstanding ones, but will not block your process in 443those events and any outstanding ones, but will not block your process in
261case there are no events and will return after one iteration of the loop.</p> 444case there are no events and will return after one iteration of the loop.</p>
262 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 445 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
263neccessary) and will handle those and any outstanding ones. It will block 446neccessary) and will handle those and any outstanding ones. It will block
264your process until at least one new event arrives, and will return after 447your process until at least one new event arrives, and will return after
265one iteration of the loop.</p> 448one iteration of the loop. This is useful if you are waiting for some
266 <p>This flags value could be used to implement alternative looping 449external event in conjunction with something not expressible using other
267constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 450libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
268more generic mechanism.</p> 451usually a better approach for this kind of thing.</p>
452 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
453<pre> * If there are no active watchers (reference count is zero), return.
454 - Queue prepare watchers and then call all outstanding watchers.
455 - If we have been forked, recreate the kernel state.
456 - Update the kernel state with all outstanding changes.
457 - Update the &quot;event loop time&quot;.
458 - Calculate for how long to block.
459 - Block the process, waiting for any events.
460 - Queue all outstanding I/O (fd) events.
461 - Update the &quot;event loop time&quot; and do time jump handling.
462 - Queue all outstanding timers.
463 - Queue all outstanding periodics.
464 - If no events are pending now, queue all idle watchers.
465 - Queue all check watchers.
466 - Call all queued watchers in reverse order (i.e. check watchers first).
467 Signals and child watchers are implemented as I/O watchers, and will
468 be handled here by queueing them when their watcher gets executed.
469 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
470 were used, return, otherwise continue with step *.
471
472</pre>
473 <p>Example: queue some jobs and then loop until no events are outsanding
474anymore.</p>
475<pre> ... queue jobs here, make sure they register event watchers as long
476 ... as they still have work to do (even an idle watcher will do..)
477 ev_loop (my_loop, 0);
478 ... jobs done. yeah!
479
480</pre>
269 </dd> 481 </dd>
270 <dt>ev_unloop (loop, how)</dt> 482 <dt>ev_unloop (loop, how)</dt>
271 <dd> 483 <dd>
272 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it 484 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
273has processed all outstanding events). The <code>how</code> argument must be either 485has processed all outstanding events). The <code>how</code> argument must be either
274<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or 486<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
275<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> 487<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276 </dd> 488 </dd>
277 <dt>ev_ref (loop)</dt> 489 <dt>ev_ref (loop)</dt>
278 <dt>ev_unref (loop)</dt> 490 <dt>ev_unref (loop)</dt>
279 <dd> 491 <dd>
… …
285example, libev itself uses this for its internal signal pipe: It is not 497example, libev itself uses this for its internal signal pipe: It is not
286visible to the libev user and should not keep <code>ev_loop</code> from exiting if 498visible to the libev user and should not keep <code>ev_loop</code> from exiting if
287no event watchers registered by it are active. It is also an excellent 499no event watchers registered by it are active. It is also an excellent
288way to do this for generic recurring timers or from within third-party 500way to do this for generic recurring timers or from within third-party
289libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 501libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
502 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
503running when nothing else is active.</p>
504<pre> struct dv_signal exitsig;
505 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
506 ev_signal_start (myloop, &amp;exitsig);
507 evf_unref (myloop);
508
509</pre>
510 <p>Example: for some weird reason, unregister the above signal handler again.</p>
511<pre> ev_ref (myloop);
512 ev_signal_stop (myloop, &amp;exitsig);
513
514</pre>
290 </dd> 515 </dd>
291</dl> 516</dl>
517
518
519
520
292 521
293</div> 522</div>
294<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 523<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
295<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 524<div id="ANATOMY_OF_A_WATCHER_CONTENT">
296<p>A watcher is a structure that you create and register to record your 525<p>A watcher is a structure that you create and register to record your
… …
326with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 555with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
327*)</code>), and you can stop watching for events at any time by calling the 556*)</code>), and you can stop watching for events at any time by calling the
328corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 557corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
329<p>As long as your watcher is active (has been started but not stopped) you 558<p>As long as your watcher is active (has been started but not stopped) you
330must not touch the values stored in it. Most specifically you must never 559must not touch the values stored in it. Most specifically you must never
331reinitialise it or call its set method.</p> 560reinitialise it or call its <code>set</code> macro.</p>
332<p>You can check whether an event is active by calling the <code>ev_is_active
333(watcher *)</code> macro. To see whether an event is outstanding (but the
334callback for it has not been called yet) you can use the <code>ev_is_pending
335(watcher *)</code> macro.</p>
336<p>Each and every callback receives the event loop pointer as first, the 561<p>Each and every callback receives the event loop pointer as first, the
337registered watcher structure as second, and a bitset of received events as 562registered watcher structure as second, and a bitset of received events as
338third argument.</p> 563third argument.</p>
339<p>The received events usually include a single bit per event type received 564<p>The received events usually include a single bit per event type received
340(you can receive multiple events at the same time). The possible bit masks 565(you can receive multiple events at the same time). The possible bit masks
… …
389your callbacks is well-written it can just attempt the operation and cope 614your callbacks is well-written it can just attempt the operation and cope
390with the error from read() or write(). This will not work in multithreaded 615with the error from read() or write(). This will not work in multithreaded
391programs, though, so beware.</p> 616programs, though, so beware.</p>
392 </dd> 617 </dd>
393</dl> 618</dl>
619
620</div>
621<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
622<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
623<p>In the following description, <code>TYPE</code> stands for the watcher type,
624e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
625<dl>
626 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
627 <dd>
628 <p>This macro initialises the generic portion of a watcher. The contents
629of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
630the generic parts of the watcher are initialised, you <i>need</i> to call
631the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
632type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
633which rolls both calls into one.</p>
634 <p>You can reinitialise a watcher at any time as long as it has been stopped
635(or never started) and there are no pending events outstanding.</p>
636 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
637int revents)</code>.</p>
638 </dd>
639 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
640 <dd>
641 <p>This macro initialises the type-specific parts of a watcher. You need to
642call <code>ev_init</code> at least once before you call this macro, but you can
643call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
644macro on a watcher that is active (it can be pending, however, which is a
645difference to the <code>ev_init</code> macro).</p>
646 <p>Although some watcher types do not have type-specific arguments
647(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
648 </dd>
649 <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
650 <dd>
651 <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
652calls into a single call. This is the most convinient method to initialise
653a watcher. The same limitations apply, of course.</p>
654 </dd>
655 <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
656 <dd>
657 <p>Starts (activates) the given watcher. Only active watchers will receive
658events. If the watcher is already active nothing will happen.</p>
659 </dd>
660 <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
661 <dd>
662 <p>Stops the given watcher again (if active) and clears the pending
663status. It is possible that stopped watchers are pending (for example,
664non-repeating timers are being stopped when they become pending), but
665<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
666you want to free or reuse the memory used by the watcher it is therefore a
667good idea to always call its <code>ev_TYPE_stop</code> function.</p>
668 </dd>
669 <dt>bool ev_is_active (ev_TYPE *watcher)</dt>
670 <dd>
671 <p>Returns a true value iff the watcher is active (i.e. it has been started
672and not yet been stopped). As long as a watcher is active you must not modify
673it.</p>
674 </dd>
675 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
676 <dd>
677 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
678events but its callback has not yet been invoked). As long as a watcher
679is pending (but not active) you must not call an init function on it (but
680<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
681libev (e.g. you cnanot <code>free ()</code> it).</p>
682 </dd>
683 <dt>callback = ev_cb (ev_TYPE *watcher)</dt>
684 <dd>
685 <p>Returns the callback currently set on the watcher.</p>
686 </dd>
687 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
688 <dd>
689 <p>Change the callback. You can change the callback at virtually any time
690(modulo threads).</p>
691 </dd>
692</dl>
693
694
695
696
394 697
395</div> 698</div>
396<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 699<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
397<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 700<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
398<p>Each watcher has, by default, a member <code>void *data</code> that you can change 701<p>Each watcher has, by default, a member <code>void *data</code> that you can change
… …
430<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 733<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
431<div id="WATCHER_TYPES_CONTENT"> 734<div id="WATCHER_TYPES_CONTENT">
432<p>This section describes each watcher in detail, but will not repeat 735<p>This section describes each watcher in detail, but will not repeat
433information given in the last section.</p> 736information given in the last section.</p>
434 737
738
739
740
741
435</div> 742</div>
436<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 743<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
437<div id="code_ev_io_code_is_this_file_descrip-2"> 744<div id="code_ev_io_code_is_this_file_descrip-2">
438<p>I/O watchers check whether a file descriptor is readable or writable 745<p>I/O watchers check whether a file descriptor is readable or writable
439in each iteration of the event loop (This behaviour is called 746in each iteration of the event loop, or, more precisely, when reading
440level-triggering because you keep receiving events as long as the 747would not block the process and writing would at least be able to write
441condition persists. Remember you can stop the watcher if you don't want to 748some data. This behaviour is called level-triggering because you keep
442act on the event and neither want to receive future events).</p> 749receiving events as long as the condition persists. Remember you can stop
750the watcher if you don't want to act on the event and neither want to
751receive future events.</p>
443<p>In general you can register as many read and/or write event watchers oer 752<p>In general you can register as many read and/or write event watchers per
444fd as you want (as long as you don't confuse yourself). Setting all file 753fd as you want (as long as you don't confuse yourself). Setting all file
445descriptors to non-blocking mode is also usually a good idea (but not 754descriptors to non-blocking mode is also usually a good idea (but not
446required if you know what you are doing).</p> 755required if you know what you are doing).</p>
447<p>You have to be careful with dup'ed file descriptors, though. Some backends 756<p>You have to be careful with dup'ed file descriptors, though. Some backends
448(the linux epoll backend is a notable example) cannot handle dup'ed file 757(the linux epoll backend is a notable example) cannot handle dup'ed file
449descriptors correctly if you register interest in two or more fds pointing 758descriptors correctly if you register interest in two or more fds pointing
450to the same file/socket etc. description.</p> 759to the same underlying file/socket/etc. description (that is, they share
760the same underlying &quot;file open&quot;).</p>
451<p>If you must do this, then force the use of a known-to-be-good backend 761<p>If you must do this, then force the use of a known-to-be-good backend
452(at the time of this writing, this includes only EVMETHOD_SELECT and 762(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453EVMETHOD_POLL).</p> 763<code>EVBACKEND_POLL</code>).</p>
764<p>Another thing you have to watch out for is that it is quite easy to
765receive &quot;spurious&quot; readyness notifications, that is your callback might
766be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
767because there is no data. Not only are some backends known to create a
768lot of those (for example solaris ports), it is very easy to get into
769this situation even with a relatively standard program structure. Thus
770it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
771<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
772<p>If you cannot run the fd in non-blocking mode (for example you should not
773play around with an Xlib connection), then you have to seperately re-test
774wether a file descriptor is really ready with a known-to-be good interface
775such as poll (fortunately in our Xlib example, Xlib already does this on
776its own, so its quite safe to use).</p>
454<dl> 777<dl>
455 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 778 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
456 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 779 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
457 <dd> 780 <dd>
458 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 781 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
459events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 782rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
460EV_WRITE</code> to receive the given events.</p> 783<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
461 </dd> 784 </dd>
462</dl> 785</dl>
786<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
787readable, but only once. Since it is likely line-buffered, you could
788attempt to read a whole line in the callback:</p>
789<pre> static void
790 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
791 {
792 ev_io_stop (loop, w);
793 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
794 }
463 795
796 ...
797 struct ev_loop *loop = ev_default_init (0);
798 struct ev_io stdin_readable;
799 ev_io_init (&amp;stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
800 ev_io_start (loop, &amp;stdin_readable);
801 ev_loop (loop, 0);
802
803
804
805
806</pre>
807
464</div> 808</div>
465<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 809<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
466<div id="code_ev_timer_code_relative_and_opti-2"> 810<div id="code_ev_timer_code_relative_and_opti-2">
467<p>Timer watchers are simple relative timers that generate an event after a 811<p>Timer watchers are simple relative timers that generate an event after a
468given time, and optionally repeating in regular intervals after that.</p> 812given time, and optionally repeating in regular intervals after that.</p>
469<p>The timers are based on real time, that is, if you register an event that 813<p>The timers are based on real time, that is, if you register an event that
470times out after an hour and youreset your system clock to last years 814times out after an hour and you reset your system clock to last years
471time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 815time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
472detecting time jumps is hard, and soem inaccuracies are unavoidable (the 816detecting time jumps is hard, and some inaccuracies are unavoidable (the
473monotonic clock option helps a lot here).</p> 817monotonic clock option helps a lot here).</p>
474<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> 818<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
475time. This is usually the right thing as this timestamp refers to the time 819time. This is usually the right thing as this timestamp refers to the time
476of the event triggering whatever timeout you are modifying/starting. If 820of the event triggering whatever timeout you are modifying/starting. If
477you suspect event processing to be delayed and you *need* to base the timeout 821you suspect event processing to be delayed and you <i>need</i> to base the timeout
478ion the current time, use something like this to adjust for this:</p> 822on the current time, use something like this to adjust for this:</p>
479<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.); 823<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
480 824
481</pre> 825</pre>
826<p>The callback is guarenteed to be invoked only when its timeout has passed,
827but if multiple timers become ready during the same loop iteration then
828order of execution is undefined.</p>
482<dl> 829<dl>
483 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 830 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
484 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 831 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485 <dd> 832 <dd>
486 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 833 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
488timer will automatically be configured to trigger again <code>repeat</code> seconds 835timer will automatically be configured to trigger again <code>repeat</code> seconds
489later, again, and again, until stopped manually.</p> 836later, again, and again, until stopped manually.</p>
490 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 837 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
491configure a timer to trigger every 10 seconds, then it will trigger at 838configure a timer to trigger every 10 seconds, then it will trigger at
492exactly 10 second intervals. If, however, your program cannot keep up with 839exactly 10 second intervals. If, however, your program cannot keep up with
493the timer (ecause it takes longer than those 10 seconds to do stuff) the 840the timer (because it takes longer than those 10 seconds to do stuff) the
494timer will not fire more than once per event loop iteration.</p> 841timer will not fire more than once per event loop iteration.</p>
495 </dd> 842 </dd>
496 <dt>ev_timer_again (loop)</dt> 843 <dt>ev_timer_again (loop)</dt>
497 <dd> 844 <dd>
498 <p>This will act as if the timer timed out and restart it again if it is 845 <p>This will act as if the timer timed out and restart it again if it is
… …
508time you successfully read or write some data. If you go into an idle 855time you successfully read or write some data. If you go into an idle
509state where you do not expect data to travel on the socket, you can stop 856state where you do not expect data to travel on the socket, you can stop
510the timer, and again will automatically restart it if need be.</p> 857the timer, and again will automatically restart it if need be.</p>
511 </dd> 858 </dd>
512</dl> 859</dl>
860<p>Example: create a timer that fires after 60 seconds.</p>
861<pre> static void
862 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
863 {
864 .. one minute over, w is actually stopped right here
865 }
513 866
867 struct ev_timer mytimer;
868 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
869 ev_timer_start (loop, &amp;mytimer);
870
871</pre>
872<p>Example: create a timeout timer that times out after 10 seconds of
873inactivity.</p>
874<pre> static void
875 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
876 {
877 .. ten seconds without any activity
878 }
879
880 struct ev_timer mytimer;
881 ev_timer_init (&amp;mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
882 ev_timer_again (&amp;mytimer); /* start timer */
883 ev_loop (loop, 0);
884
885 // and in some piece of code that gets executed on any &quot;activity&quot;:
886 // reset the timeout to start ticking again at 10 seconds
887 ev_timer_again (&amp;mytimer);
888
889
890
891
892</pre>
893
514</div> 894</div>
515<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 895<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
516<div id="code_ev_periodic_code_to_cron_or_not-2"> 896<div id="code_ev_periodic_code_to_cron_or_not-2">
517<p>Periodic watchers are also timers of a kind, but they are very versatile 897<p>Periodic watchers are also timers of a kind, but they are very versatile
518(and unfortunately a bit complex).</p> 898(and unfortunately a bit complex).</p>
519<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 899<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
520but on wallclock time (absolute time). You can tell a periodic watcher 900but on wallclock time (absolute time). You can tell a periodic watcher
521to trigger &quot;at&quot; some specific point in time. For example, if you tell a 901to trigger &quot;at&quot; some specific point in time. For example, if you tell a
522periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 902periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
523+ 10.&gt;) and then reset your system clock to the last year, then it will 903+ 10.</code>) and then reset your system clock to the last year, then it will
524take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 904take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
525roughly 10 seconds later and of course not if you reset your system time 905roughly 10 seconds later and of course not if you reset your system time
526again).</p> 906again).</p>
527<p>They can also be used to implement vastly more complex timers, such as 907<p>They can also be used to implement vastly more complex timers, such as
528triggering an event on eahc midnight, local time.</p> 908triggering an event on eahc midnight, local time.</p>
909<p>As with timers, the callback is guarenteed to be invoked only when the
910time (<code>at</code>) has been passed, but if multiple periodic timers become ready
911during the same loop iteration then order of execution is undefined.</p>
529<dl> 912<dl>
530 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 913 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
531 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 914 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532 <dd> 915 <dd>
533 <p>Lots of arguments, lets sort it out... There are basically three modes of 916 <p>Lots of arguments, lets sort it out... There are basically three modes of
534operation, and we will explain them from simplest to complex:</p> 917operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539 <p> 918 <p>
540 <dl> 919 <dl>
541 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 920 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
542 <dd> 921 <dd>
543 <p>In this configuration the watcher triggers an event at the wallclock time 922 <p>In this configuration the watcher triggers an event at the wallclock time
… …
567 <dd> 946 <dd>
568 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 947 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
569ignored. Instead, each time the periodic watcher gets scheduled, the 948ignored. Instead, each time the periodic watcher gets scheduled, the
570reschedule callback will be called with the watcher as first, and the 949reschedule callback will be called with the watcher as first, and the
571current time as second argument.</p> 950current time as second argument.</p>
572 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 951 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
573periodic watcher, ever, or make any event loop modifications</i>. If you need 952ever, or make any event loop modifications</i>. If you need to stop it,
574to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p> 953return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
575 <p>Also, <i>this callback must always return a time that is later than the 954starting a prepare watcher).</p>
576passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
577 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 955 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
578ev_tstamp now)</code>, e.g.:</p> 956ev_tstamp now)</code>, e.g.:</p>
579<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 957<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580 { 958 {
581 return now + 60.; 959 return now + 60.;
… …
584</pre> 962</pre>
585 <p>It must return the next time to trigger, based on the passed time value 963 <p>It must return the next time to trigger, based on the passed time value
586(that is, the lowest time value larger than to the second argument). It 964(that is, the lowest time value larger than to the second argument). It
587will usually be called just before the callback will be triggered, but 965will usually be called just before the callback will be triggered, but
588might be called at other times, too.</p> 966might be called at other times, too.</p>
967 <p>NOTE: <i>This callback must always return a time that is later than the
968passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
589 <p>This can be used to create very complex timers, such as a timer that 969 <p>This can be used to create very complex timers, such as a timer that
590triggers on each midnight, local time. To do this, you would calculate the 970triggers on each midnight, local time. To do this, you would calculate the
591next midnight after <code>now</code> and return the timestamp value for this. How you do this 971next midnight after <code>now</code> and return the timestamp value for this. How
592is, again, up to you (but it is not trivial).</p> 972you do this is, again, up to you (but it is not trivial, which is the main
973reason I omitted it as an example).</p>
593 </dd> 974 </dd>
594 </dl> 975 </dl>
595 </p> 976 </p>
596 </dd> 977 </dd>
597 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 978 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
600when you changed some parameters or the reschedule callback would return 981when you changed some parameters or the reschedule callback would return
601a different time than the last time it was called (e.g. in a crond like 982a different time than the last time it was called (e.g. in a crond like
602program when the crontabs have changed).</p> 983program when the crontabs have changed).</p>
603 </dd> 984 </dd>
604</dl> 985</dl>
986<p>Example: call a callback every hour, or, more precisely, whenever the
987system clock is divisible by 3600. The callback invocation times have
988potentially a lot of jittering, but good long-term stability.</p>
989<pre> static void
990 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
991 {
992 ... its now a full hour (UTC, or TAI or whatever your clock follows)
993 }
605 994
995 struct ev_periodic hourly_tick;
996 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
997 ev_periodic_start (loop, &amp;hourly_tick);
998
999</pre>
1000<p>Example: the same as above, but use a reschedule callback to do it:</p>
1001<pre> #include &lt;math.h&gt;
1002
1003 static ev_tstamp
1004 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1005 {
1006 return fmod (now, 3600.) + 3600.;
1007 }
1008
1009 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1010
1011</pre>
1012<p>Example: call a callback every hour, starting now:</p>
1013<pre> struct ev_periodic hourly_tick;
1014 ev_periodic_init (&amp;hourly_tick, clock_cb,
1015 fmod (ev_now (loop), 3600.), 3600., 0);
1016 ev_periodic_start (loop, &amp;hourly_tick);
1017
1018
1019
1020
1021</pre>
1022
606</div> 1023</div>
607<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1024<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
608<div id="code_ev_signal_code_signal_me_when_a-2"> 1025<div id="code_ev_signal_code_signal_me_when_a-2">
609<p>Signal watchers will trigger an event when the process receives a specific 1026<p>Signal watchers will trigger an event when the process receives a specific
610signal one or more times. Even though signals are very asynchronous, libev 1027signal one or more times. Even though signals are very asynchronous, libev
611will try it's best to deliver signals synchronously, i.e. as part of the 1028will try it's best to deliver signals synchronously, i.e. as part of the
612normal event processing, like any other event.</p> 1029normal event processing, like any other event.</p>
… …
623 <p>Configures the watcher to trigger on the given signal number (usually one 1040 <p>Configures the watcher to trigger on the given signal number (usually one
624of the <code>SIGxxx</code> constants).</p> 1041of the <code>SIGxxx</code> constants).</p>
625 </dd> 1042 </dd>
626</dl> 1043</dl>
627 1044
1045
1046
1047
1048
628</div> 1049</div>
629<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1050<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
630<div id="code_ev_child_code_wait_for_pid_stat-2"> 1051<div id="code_ev_child_code_watch_out_for_pro-2">
631<p>Child watchers trigger when your process receives a SIGCHLD in response to 1052<p>Child watchers trigger when your process receives a SIGCHLD in response to
632some child status changes (most typically when a child of yours dies).</p> 1053some child status changes (most typically when a child of yours dies).</p>
633<dl> 1054<dl>
634 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1055 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
635 <dt>ev_child_set (ev_child *, int pid)</dt> 1056 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
640the status word (use the macros from <code>sys/wait.h</code> and see your systems 1061the status word (use the macros from <code>sys/wait.h</code> and see your systems
641<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1062<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
642process causing the status change.</p> 1063process causing the status change.</p>
643 </dd> 1064 </dd>
644</dl> 1065</dl>
1066<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
1067<pre> static void
1068 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1069 {
1070 ev_unloop (loop, EVUNLOOP_ALL);
1071 }
645 1072
1073 struct ev_signal signal_watcher;
1074 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
1075 ev_signal_start (loop, &amp;sigint_cb);
1076
1077
1078
1079
1080</pre>
1081
646</div> 1082</div>
647<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1083<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
648<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1084<div id="code_ev_idle_code_when_you_ve_got_no-2">
649<p>Idle watchers trigger events when there are no other events are pending 1085<p>Idle watchers trigger events when there are no other events are pending
650(prepare, check and other idle watchers do not count). That is, as long 1086(prepare, check and other idle watchers do not count). That is, as long
651as your process is busy handling sockets or timeouts (or even signals, 1087as your process is busy handling sockets or timeouts (or even signals,
652imagine) it will not be triggered. But when your process is idle all idle 1088imagine) it will not be triggered. But when your process is idle all idle
… …
665 <p>Initialises and configures the idle watcher - it has no parameters of any 1101 <p>Initialises and configures the idle watcher - it has no parameters of any
666kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1102kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
667believe me.</p> 1103believe me.</p>
668 </dd> 1104 </dd>
669</dl> 1105</dl>
1106<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
1107callback, free it. Alos, use no error checking, as usual.</p>
1108<pre> static void
1109 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1110 {
1111 free (w);
1112 // now do something you wanted to do when the program has
1113 // no longer asnything immediate to do.
1114 }
670 1115
1116 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1117 ev_idle_init (idle_watcher, idle_cb);
1118 ev_idle_start (loop, idle_cb);
1119
1120
1121
1122
1123</pre>
1124
671</div> 1125</div>
672<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1126<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
673<div id="code_ev_prepare_code_and_code_ev_che-2"> 1127<div id="code_ev_prepare_code_and_code_ev_che-2">
674<p>Prepare and check watchers are usually (but not always) used in tandem: 1128<p>Prepare and check watchers are usually (but not always) used in tandem:
675Prepare watchers get invoked before the process blocks and check watchers 1129prepare watchers get invoked before the process blocks and check watchers
676afterwards.</p> 1130afterwards.</p>
1131<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1132the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1133watchers. Other loops than the current one are fine, however. The
1134rationale behind this is that you do not need to check for recursion in
1135those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1136<code>ev_check</code> so if you have one watcher of each kind they will always be
1137called in pairs bracketing the blocking call.</p>
677<p>Their main purpose is to integrate other event mechanisms into libev. This 1138<p>Their main purpose is to integrate other event mechanisms into libev and
678could be used, for example, to track variable changes, implement your own 1139their use is somewhat advanced. This could be used, for example, to track
679watchers, integrate net-snmp or a coroutine library and lots more.</p> 1140variable changes, implement your own watchers, integrate net-snmp or a
1141coroutine library and lots more. They are also occasionally useful if
1142you cache some data and want to flush it before blocking (for example,
1143in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1144watcher).</p>
680<p>This is done by examining in each prepare call which file descriptors need 1145<p>This is done by examining in each prepare call which file descriptors need
681to be watched by the other library, registering <code>ev_io</code> watchers for 1146to be watched by the other library, registering <code>ev_io</code> watchers for
682them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1147them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
683provide just this functionality). Then, in the check watcher you check for 1148provide just this functionality). Then, in the check watcher you check for
684any events that occured (by checking the pending status of all watchers 1149any events that occured (by checking the pending status of all watchers
685and stopping them) and call back into the library. The I/O and timer 1150and stopping them) and call back into the library. The I/O and timer
686callbacks will never actually be called (but must be valid neverthelles, 1151callbacks will never actually be called (but must be valid nevertheless,
687because you never know, you know?).</p> 1152because you never know, you know?).</p>
688<p>As another example, the Perl Coro module uses these hooks to integrate 1153<p>As another example, the Perl Coro module uses these hooks to integrate
689coroutines into libev programs, by yielding to other active coroutines 1154coroutines into libev programs, by yielding to other active coroutines
690during each prepare and only letting the process block if no coroutines 1155during each prepare and only letting the process block if no coroutines
691are ready to run (its actually more complicated, it only runs coroutines 1156are ready to run (it's actually more complicated: it only runs coroutines
692with priority higher than the event loop and one lower priority once, 1157with priority higher than or equal to the event loop and one coroutine
693using idle watchers to keep the event loop from blocking if lower-priority 1158of lower priority, but only once, using idle watchers to keep the event
694coroutines exist, thus mapping low-priority coroutines to idle/background 1159loop from blocking if lower-priority coroutines are active, thus mapping
695tasks).</p> 1160low-priority coroutines to idle/background tasks).</p>
696<dl> 1161<dl>
697 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1162 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
698 <dt>ev_check_init (ev_check *, callback)</dt> 1163 <dt>ev_check_init (ev_check *, callback)</dt>
699 <dd> 1164 <dd>
700 <p>Initialises and configures the prepare or check watcher - they have no 1165 <p>Initialises and configures the prepare or check watcher - they have no
701parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1166parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
702macros, but using them is utterly, utterly and completely pointless.</p> 1167macros, but using them is utterly, utterly and completely pointless.</p>
703 </dd> 1168 </dd>
704</dl> 1169</dl>
1170<p>Example: To include a library such as adns, you would add IO watchers
1171and a timeout watcher in a prepare handler, as required by libadns, and
1172in a check watcher, destroy them and call into libadns. What follows is
1173pseudo-code only of course:</p>
1174<pre> static ev_io iow [nfd];
1175 static ev_timer tw;
1176
1177 static void
1178 io_cb (ev_loop *loop, ev_io *w, int revents)
1179 {
1180 // set the relevant poll flags
1181 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1182 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1183 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1184 }
1185
1186 // create io watchers for each fd and a timer before blocking
1187 static void
1188 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1189 {
1190 int timeout = 3600000;truct pollfd fds [nfd];
1191 // actual code will need to loop here and realloc etc.
1192 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1193
1194 /* the callback is illegal, but won't be called as we stop during check */
1195 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1196 ev_timer_start (loop, &amp;tw);
1197
1198 // create on ev_io per pollfd
1199 for (int i = 0; i &lt; nfd; ++i)
1200 {
1201 ev_io_init (iow + i, io_cb, fds [i].fd,
1202 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1203 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1204
1205 fds [i].revents = 0;
1206 iow [i].data = fds + i;
1207 ev_io_start (loop, iow + i);
1208 }
1209 }
1210
1211 // stop all watchers after blocking
1212 static void
1213 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1214 {
1215 ev_timer_stop (loop, &amp;tw);
1216
1217 for (int i = 0; i &lt; nfd; ++i)
1218 ev_io_stop (loop, iow + i);
1219
1220 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1221 }
1222
1223
1224
1225
1226</pre>
1227
1228</div>
1229<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1230<div id="code_ev_embed_code_when_one_backend_-2">
1231<p>This is a rather advanced watcher type that lets you embed one event loop
1232into another (currently only <code>ev_io</code> events are supported in the embedded
1233loop, other types of watchers might be handled in a delayed or incorrect
1234fashion and must not be used).</p>
1235<p>There are primarily two reasons you would want that: work around bugs and
1236prioritise I/O.</p>
1237<p>As an example for a bug workaround, the kqueue backend might only support
1238sockets on some platform, so it is unusable as generic backend, but you
1239still want to make use of it because you have many sockets and it scales
1240so nicely. In this case, you would create a kqueue-based loop and embed it
1241into your default loop (which might use e.g. poll). Overall operation will
1242be a bit slower because first libev has to poll and then call kevent, but
1243at least you can use both at what they are best.</p>
1244<p>As for prioritising I/O: rarely you have the case where some fds have
1245to be watched and handled very quickly (with low latency), and even
1246priorities and idle watchers might have too much overhead. In this case
1247you would put all the high priority stuff in one loop and all the rest in
1248a second one, and embed the second one in the first.</p>
1249<p>As long as the watcher is active, the callback will be invoked every time
1250there might be events pending in the embedded loop. The callback must then
1251call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1252their callbacks (you could also start an idle watcher to give the embedded
1253loop strictly lower priority for example). You can also set the callback
1254to <code>0</code>, in which case the embed watcher will automatically execute the
1255embedded loop sweep.</p>
1256<p>As long as the watcher is started it will automatically handle events. The
1257callback will be invoked whenever some events have been handled. You can
1258set the callback to <code>0</code> to avoid having to specify one if you are not
1259interested in that.</p>
1260<p>Also, there have not currently been made special provisions for forking:
1261when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
1262but you will also have to stop and restart any <code>ev_embed</code> watchers
1263yourself.</p>
1264<p>Unfortunately, not all backends are embeddable, only the ones returned by
1265<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
1266portable one.</p>
1267<p>So when you want to use this feature you will always have to be prepared
1268that you cannot get an embeddable loop. The recommended way to get around
1269this is to have a separate variables for your embeddable loop, try to
1270create it, and if that fails, use the normal loop for everything:</p>
1271<pre> struct ev_loop *loop_hi = ev_default_init (0);
1272 struct ev_loop *loop_lo = 0;
1273 struct ev_embed embed;
1274
1275 // see if there is a chance of getting one that works
1276 // (remember that a flags value of 0 means autodetection)
1277 loop_lo = ev_embeddable_backends () &amp; ev_recommended_backends ()
1278 ? ev_loop_new (ev_embeddable_backends () &amp; ev_recommended_backends ())
1279 : 0;
1280
1281 // if we got one, then embed it, otherwise default to loop_hi
1282 if (loop_lo)
1283 {
1284 ev_embed_init (&amp;embed, 0, loop_lo);
1285 ev_embed_start (loop_hi, &amp;embed);
1286 }
1287 else
1288 loop_lo = loop_hi;
1289
1290</pre>
1291<dl>
1292 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1293 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1294 <dd>
1295 <p>Configures the watcher to embed the given loop, which must be
1296embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1297invoked automatically, otherwise it is the responsibility of the callback
1298to invoke it (it will continue to be called until the sweep has been done,
1299if you do not want thta, you need to temporarily stop the embed watcher).</p>
1300 </dd>
1301 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1302 <dd>
1303 <p>Make a single, non-blocking sweep over the embedded loop. This works
1304similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1305apropriate way for embedded loops.</p>
1306 </dd>
1307</dl>
1308
1309
1310
1311
705 1312
706</div> 1313</div>
707<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1314<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
708<div id="OTHER_FUNCTIONS_CONTENT"> 1315<div id="OTHER_FUNCTIONS_CONTENT">
709<p>There are some other functions of possible interest. Described. Here. Now.</p> 1316<p>There are some other functions of possible interest. Described. Here. Now.</p>
… …
711 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1318 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712 <dd> 1319 <dd>
713 <p>This function combines a simple timer and an I/O watcher, calls your 1320 <p>This function combines a simple timer and an I/O watcher, calls your
714callback on whichever event happens first and automatically stop both 1321callback on whichever event happens first and automatically stop both
715watchers. This is useful if you want to wait for a single event on an fd 1322watchers. This is useful if you want to wait for a single event on an fd
716or timeout without havign to allocate/configure/start/stop/free one or 1323or timeout without having to allocate/configure/start/stop/free one or
717more watchers yourself.</p> 1324more watchers yourself.</p>
718 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events 1325 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
719is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and 1326is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
720<code>events</code> set will be craeted and started.</p> 1327<code>events</code> set will be craeted and started.</p>
721 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 1328 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
722started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and 1329started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
723repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of 1330repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724dubious value.</p> 1331dubious value.</p>
725 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets 1332 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
726passed an events set like normal event callbacks (with a combination of 1333passed an <code>revents</code> set like normal event callbacks (a combination of
727<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> 1334<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
728value passed to <code>ev_once</code>:</p> 1335value passed to <code>ev_once</code>:</p>
729<pre> static void stdin_ready (int revents, void *arg) 1336<pre> static void stdin_ready (int revents, void *arg)
730 { 1337 {
731 if (revents &amp; EV_TIMEOUT) 1338 if (revents &amp; EV_TIMEOUT)
… …
736 1343
737 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1344 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738 1345
739</pre> 1346</pre>
740 </dd> 1347 </dd>
741 <dt>ev_feed_event (loop, watcher, int events)</dt> 1348 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
742 <dd> 1349 <dd>
743 <p>Feeds the given event set into the event loop, as if the specified event 1350 <p>Feeds the given event set into the event loop, as if the specified event
744had happened for the specified watcher (which must be a pointer to an 1351had happened for the specified watcher (which must be a pointer to an
745initialised but not necessarily started event watcher).</p> 1352initialised but not necessarily started event watcher).</p>
746 </dd> 1353 </dd>
747 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1354 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
748 <dd> 1355 <dd>
749 <p>Feed an event on the given fd, as if a file descriptor backend detected 1356 <p>Feed an event on the given fd, as if a file descriptor backend detected
750the given events it.</p> 1357the given events it.</p>
751 </dd> 1358 </dd>
752 <dt>ev_feed_signal_event (loop, int signum)</dt> 1359 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
753 <dd> 1360 <dd>
754 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1361 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1362loop!).</p>
755 </dd> 1363 </dd>
756</dl> 1364</dl>
1365
1366
1367
1368
1369
1370</div>
1371<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
1372<div id="LIBEVENT_EMULATION_CONTENT">
1373<p>Libev offers a compatibility emulation layer for libevent. It cannot
1374emulate the internals of libevent, so here are some usage hints:</p>
1375<dl>
1376 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
1377 <dt>* The following members are fully supported: ev_base, ev_callback,
1378ev_arg, ev_fd, ev_res, ev_events.</dt>
1379 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
1380maintained by libev, it does not work exactly the same way as in libevent (consider
1381it a private API).</dt>
1382 <dt>* Priorities are not currently supported. Initialising priorities
1383will fail and all watchers will have the same priority, even though there
1384is an ev_pri field.</dt>
1385 <dt>* Other members are not supported.</dt>
1386 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1387to use the libev header file and library.</dt>
1388</dl>
1389
1390</div>
1391<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
1392<div id="C_SUPPORT_CONTENT">
1393<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1394you to use some convinience methods to start/stop watchers and also change
1395the callback model to a model using method callbacks on objects.</p>
1396<p>To use it,</p>
1397<pre> #include &lt;ev++.h&gt;
1398
1399</pre>
1400<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1401and puts all of its definitions (many of them macros) into the global
1402namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1403<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1404<code>EV_MULTIPLICITY</code>.</p>
1405<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1406<dl>
1407 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1408 <dd>
1409 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1410macros from <cite>ev.h</cite>.</p>
1411 </dd>
1412 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1413 <dd>
1414 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1415 </dd>
1416 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1417 <dd>
1418 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1419the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1420which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1421defines by many implementations.</p>
1422 <p>All of those classes have these methods:</p>
1423 <p>
1424 <dl>
1425 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1426 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1427 <dt>ev::TYPE::~TYPE</dt>
1428 <dd>
1429 <p>The constructor takes a pointer to an object and a method pointer to
1430the event handler callback to call in this class. The constructor calls
1431<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1432before starting it. If you do not specify a loop then the constructor
1433automatically associates the default loop with this watcher.</p>
1434 <p>The destructor automatically stops the watcher if it is active.</p>
1435 </dd>
1436 <dt>w-&gt;set (struct ev_loop *)</dt>
1437 <dd>
1438 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1439do this when the watcher is inactive (and not pending either).</p>
1440 </dd>
1441 <dt>w-&gt;set ([args])</dt>
1442 <dd>
1443 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1444called at least once. Unlike the C counterpart, an active watcher gets
1445automatically stopped and restarted.</p>
1446 </dd>
1447 <dt>w-&gt;start ()</dt>
1448 <dd>
1449 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1450constructor already takes the loop.</p>
1451 </dd>
1452 <dt>w-&gt;stop ()</dt>
1453 <dd>
1454 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1455 </dd>
1456 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1457 <dd>
1458 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1459<code>ev_TYPE_again</code> function.</p>
1460 </dd>
1461 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1462 <dd>
1463 <p>Invokes <code>ev_embed_sweep</code>.</p>
1464 </dd>
1465 </dl>
1466 </p>
1467 </dd>
1468</dl>
1469<p>Example: Define a class with an IO and idle watcher, start one of them in
1470the constructor.</p>
1471<pre> class myclass
1472 {
1473 ev_io io; void io_cb (ev::io &amp;w, int revents);
1474 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1475
1476 myclass ();
1477 }
1478
1479 myclass::myclass (int fd)
1480 : io (this, &amp;myclass::io_cb),
1481 idle (this, &amp;myclass::idle_cb)
1482 {
1483 io.start (fd, ev::READ);
1484 }
1485
1486</pre>
1487
1488</div>
1489<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
1490<div id="EMBEDDING_CONTENT">
1491<p>Libev can (and often is) directly embedded into host
1492applications. Examples of applications that embed it include the Deliantra
1493Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1494and rxvt-unicode.</p>
1495<p>The goal is to enable you to just copy the neecssary files into your
1496source directory without having to change even a single line in them, so
1497you can easily upgrade by simply copying (or having a checked-out copy of
1498libev somewhere in your source tree).</p>
1499
1500</div>
1501<h2 id="FILESETS">FILESETS</h2>
1502<div id="FILESETS_CONTENT">
1503<p>Depending on what features you need you need to include one or more sets of files
1504in your app.</p>
1505
1506</div>
1507<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1508<div id="CORE_EVENT_LOOP_CONTENT">
1509<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1510configuration (no autoconf):</p>
1511<pre> #define EV_STANDALONE 1
1512 #include &quot;ev.c&quot;
1513
1514</pre>
1515<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1516single C source file only to provide the function implementations. To use
1517it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1518done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1519where you can put other configuration options):</p>
1520<pre> #define EV_STANDALONE 1
1521 #include &quot;ev.h&quot;
1522
1523</pre>
1524<p>Both header files and implementation files can be compiled with a C++
1525compiler (at least, thats a stated goal, and breakage will be treated
1526as a bug).</p>
1527<p>You need the following files in your source tree, or in a directory
1528in your include path (e.g. in libev/ when using -Ilibev):</p>
1529<pre> ev.h
1530 ev.c
1531 ev_vars.h
1532 ev_wrap.h
1533
1534 ev_win32.c required on win32 platforms only
1535
1536 ev_select.c only when select backend is enabled (which is by default)
1537 ev_poll.c only when poll backend is enabled (disabled by default)
1538 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1539 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1540 ev_port.c only when the solaris port backend is enabled (disabled by default)
1541
1542</pre>
1543<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1544to compile this single file.</p>
1545
1546</div>
1547<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1548<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1549<p>To include the libevent compatibility API, also include:</p>
1550<pre> #include &quot;event.c&quot;
1551
1552</pre>
1553<p>in the file including <cite>ev.c</cite>, and:</p>
1554<pre> #include &quot;event.h&quot;
1555
1556</pre>
1557<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1558<p>You need the following additional files for this:</p>
1559<pre> event.h
1560 event.c
1561
1562</pre>
1563
1564</div>
1565<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1566<div id="AUTOCONF_SUPPORT_CONTENT">
1567<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1568whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1569<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1570include <cite>config.h</cite> and configure itself accordingly.</p>
1571<p>For this of course you need the m4 file:</p>
1572<pre> libev.m4
1573
1574</pre>
1575
1576</div>
1577<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1578<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1579<p>Libev can be configured via a variety of preprocessor symbols you have to define
1580before including any of its files. The default is not to build for multiplicity
1581and only include the select backend.</p>
1582<dl>
1583 <dt>EV_STANDALONE</dt>
1584 <dd>
1585 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1586keeps libev from including <cite>config.h</cite>, and it also defines dummy
1587implementations for some libevent functions (such as logging, which is not
1588supported). It will also not define any of the structs usually found in
1589<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1590 </dd>
1591 <dt>EV_USE_MONOTONIC</dt>
1592 <dd>
1593 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1594monotonic clock option at both compiletime and runtime. Otherwise no use
1595of the monotonic clock option will be attempted. If you enable this, you
1596usually have to link against librt or something similar. Enabling it when
1597the functionality isn't available is safe, though, althoguh you have
1598to make sure you link against any libraries where the <code>clock_gettime</code>
1599function is hiding in (often <cite>-lrt</cite>).</p>
1600 </dd>
1601 <dt>EV_USE_REALTIME</dt>
1602 <dd>
1603 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1604realtime clock option at compiletime (and assume its availability at
1605runtime if successful). Otherwise no use of the realtime clock option will
1606be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1607(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1608in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1609 </dd>
1610 <dt>EV_USE_SELECT</dt>
1611 <dd>
1612 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1613<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1614other method takes over, select will be it. Otherwise the select backend
1615will not be compiled in.</p>
1616 </dd>
1617 <dt>EV_SELECT_USE_FD_SET</dt>
1618 <dd>
1619 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1620structure. This is useful if libev doesn't compile due to a missing
1621<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1622exotic systems. This usually limits the range of file descriptors to some
1623low limit such as 1024 or might have other limitations (winsocket only
1624allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1625influence the size of the <code>fd_set</code> used.</p>
1626 </dd>
1627 <dt>EV_SELECT_IS_WINSOCKET</dt>
1628 <dd>
1629 <p>When defined to <code>1</code>, the select backend will assume that
1630select/socket/connect etc. don't understand file descriptors but
1631wants osf handles on win32 (this is the case when the select to
1632be used is the winsock select). This means that it will call
1633<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1634it is assumed that all these functions actually work on fds, even
1635on win32. Should not be defined on non-win32 platforms.</p>
1636 </dd>
1637 <dt>EV_USE_POLL</dt>
1638 <dd>
1639 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1640backend. Otherwise it will be enabled on non-win32 platforms. It
1641takes precedence over select.</p>
1642 </dd>
1643 <dt>EV_USE_EPOLL</dt>
1644 <dd>
1645 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
1646<code>epoll</code>(7) backend. Its availability will be detected at runtime,
1647otherwise another method will be used as fallback. This is the
1648preferred backend for GNU/Linux systems.</p>
1649 </dd>
1650 <dt>EV_USE_KQUEUE</dt>
1651 <dd>
1652 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
1653<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
1654otherwise another method will be used as fallback. This is the preferred
1655backend for BSD and BSD-like systems, although on most BSDs kqueue only
1656supports some types of fds correctly (the only platform we found that
1657supports ptys for example was NetBSD), so kqueue might be compiled in, but
1658not be used unless explicitly requested. The best way to use it is to find
1659out whether kqueue supports your type of fd properly and use an embedded
1660kqueue loop.</p>
1661 </dd>
1662 <dt>EV_USE_PORT</dt>
1663 <dd>
1664 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
166510 port style backend. Its availability will be detected at runtime,
1666otherwise another method will be used as fallback. This is the preferred
1667backend for Solaris 10 systems.</p>
1668 </dd>
1669 <dt>EV_USE_DEVPOLL</dt>
1670 <dd>
1671 <p>reserved for future expansion, works like the USE symbols above.</p>
1672 </dd>
1673 <dt>EV_H</dt>
1674 <dd>
1675 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1676undefined 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
1677can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
1678 </dd>
1679 <dt>EV_CONFIG_H</dt>
1680 <dd>
1681 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
1682<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
1683<code>EV_H</code>, above.</p>
1684 </dd>
1685 <dt>EV_EVENT_H</dt>
1686 <dd>
1687 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
1688of how the <cite>event.h</cite> header can be found.</p>
1689 </dd>
1690 <dt>EV_PROTOTYPES</dt>
1691 <dd>
1692 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
1693prototypes, but still define all the structs and other symbols. This is
1694occasionally useful if you want to provide your own wrapper functions
1695around libev functions.</p>
1696 </dd>
1697 <dt>EV_MULTIPLICITY</dt>
1698 <dd>
1699 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
1700will have the <code>struct ev_loop *</code> as first argument, and you can create
1701additional independent event loops. Otherwise there will be no support
1702for multiple event loops and there is no first event loop pointer
1703argument. Instead, all functions act on the single default loop.</p>
1704 </dd>
1705 <dt>EV_PERIODICS</dt>
1706 <dd>
1707 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported,
1708otherwise not. This saves a few kb of code.</p>
1709 </dd>
1710 <dt>EV_COMMON</dt>
1711 <dd>
1712 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1713this macro to a something else you can include more and other types of
1714members. You have to define it each time you include one of the files,
1715though, and it must be identical each time.</p>
1716 <p>For example, the perl EV module uses something like this:</p>
1717<pre> #define EV_COMMON \
1718 SV *self; /* contains this struct */ \
1719 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
1720
1721</pre>
1722 </dd>
1723 <dt>EV_CB_DECLARE (type)</dt>
1724 <dt>EV_CB_INVOKE (watcher, revents)</dt>
1725 <dt>ev_set_cb (ev, cb)</dt>
1726 <dd>
1727 <p>Can be used to change the callback member declaration in each watcher,
1728and the way callbacks are invoked and set. Must expand to a struct member
1729definition and a statement, respectively. See the <cite>ev.v</cite> header file for
1730their default definitions. One possible use for overriding these is to
1731avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
1732method calls instead of plain function calls in C++.</p>
1733
1734</div>
1735<h2 id="EXAMPLES">EXAMPLES</h2>
1736<div id="EXAMPLES_CONTENT">
1737 <p>For a real-world example of a program the includes libev
1738verbatim, you can have a look at the EV perl module
1739(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
1740the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
1741interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
1742will be compiled. It is pretty complex because it provides its own header
1743file.</p>
1744 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
1745that everybody includes and which overrides some autoconf choices:</p>
1746<pre> #define EV_USE_POLL 0
1747 #define EV_MULTIPLICITY 0
1748 #define EV_PERIODICS 0
1749 #define EV_CONFIG_H &lt;config.h&gt;
1750
1751 #include &quot;ev++.h&quot;
1752
1753</pre>
1754 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1755<pre> #include &quot;ev_cpp.h&quot;
1756 #include &quot;ev.c&quot;
1757
1758</pre>
757 1759
758</div> 1760</div>
759<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1761<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
760<div id="AUTHOR_CONTENT"> 1762<div id="AUTHOR_CONTENT">
761<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 1763 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
762 1764
763</div> 1765</div>
764</div></body> 1766</div></body>
765</html> 1767</html>

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