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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 11:20:35 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>
55<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
40<li><a href="#AUTHOR">AUTHOR</a> 56<li><a href="#AUTHOR">AUTHOR</a>
41</li> 57</li>
42</ul><hr /> 58</ul><hr />
43<!-- INDEX END --> 59<!-- INDEX END -->
44 60
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94<div id="TIME_REPRESENTATION_CONTENT"> 110<div id="TIME_REPRESENTATION_CONTENT">
95<p>Libev represents time as a single floating point number, representing the 111<p>Libev represents time as a single floating point number, representing the
96(fractional) number of seconds since the (POSIX) epoch (somewhere near 112(fractional) number of seconds since the (POSIX) epoch (somewhere near
97the beginning of 1970, details are complicated, don't ask). This type is 113the 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 114called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
99to the double type in C.</p> 115to the <code>double</code> type in C, and when you need to do any calculations on
116it, you should treat it as such.</p>
117
118
119
120
100 121
101</div> 122</div>
102<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 123<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
103<div id="GLOBAL_FUNCTIONS_CONTENT"> 124<div id="GLOBAL_FUNCTIONS_CONTENT">
125<p>These functions can be called anytime, even before initialising the
126library in any way.</p>
104<dl> 127<dl>
105 <dt>ev_tstamp ev_time ()</dt> 128 <dt>ev_tstamp ev_time ()</dt>
106 <dd> 129 <dd>
107 <p>Returns the current time as libev would use it.</p> 130 <p>Returns the current time as libev would use it. Please note that the
131<code>ev_now</code> function is usually faster and also often returns the timestamp
132you actually want to know.</p>
108 </dd> 133 </dd>
109 <dt>int ev_version_major ()</dt> 134 <dt>int ev_version_major ()</dt>
110 <dt>int ev_version_minor ()</dt> 135 <dt>int ev_version_minor ()</dt>
111 <dd> 136 <dd>
112 <p>You can find out the major and minor version numbers of the library 137 <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> 141version of the library your program was compiled against.</p>
117 <p>Usually, it's a good idea to terminate if the major versions mismatch, 142 <p>Usually, it's a good idea to terminate if the major versions mismatch,
118as this indicates an incompatible change. Minor versions are usually 143as this indicates an incompatible change. Minor versions are usually
119compatible to older versions, so a larger minor version alone is usually 144compatible to older versions, so a larger minor version alone is usually
120not a problem.</p> 145not a problem.</p>
146 <p>Example: make sure we haven't accidentally been linked against the wrong
147version:</p>
148<pre> assert ((&quot;libev version mismatch&quot;,
149 ev_version_major () == EV_VERSION_MAJOR
150 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
151
152</pre>
153 </dd>
154 <dt>unsigned int ev_supported_backends ()</dt>
155 <dd>
156 <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
157value) compiled into this binary of libev (independent of their
158availability on the system you are running on). See <code>ev_default_loop</code> for
159a description of the set values.</p>
160 <p>Example: make sure we have the epoll method, because yeah this is cool and
161a must have and can we have a torrent of it please!!!11</p>
162<pre> assert ((&quot;sorry, no epoll, no sex&quot;,
163 ev_supported_backends () &amp; EVBACKEND_EPOLL));
164
165</pre>
166 </dd>
167 <dt>unsigned int ev_recommended_backends ()</dt>
168 <dd>
169 <p>Return the set of all backends compiled into this binary of libev and also
170recommended for this platform. This set is often smaller than the one
171returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
172most BSDs and will not be autodetected unless you explicitly request it
173(assuming you know what you are doing). This is the set of backends that
174libev will probe for if you specify no backends explicitly.</p>
175 </dd>
176 <dt>unsigned int ev_embeddable_backends ()</dt>
177 <dd>
178 <p>Returns the set of backends that are embeddable in other event loops. This
179is the theoretical, all-platform, value. To find which backends
180might be supported on the current system, you would need to look at
181<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
182recommended ones.</p>
183 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
121 </dd> 184 </dd>
122 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 185 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
123 <dd> 186 <dd>
124 <p>Sets the allocation function to use (the prototype is similar to the 187 <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 188realloc 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 190needs to be allocated, the library might abort or take some potentially
128destructive action. The default is your system realloc function.</p> 191destructive action. The default is your system realloc function.</p>
129 <p>You could override this function in high-availability programs to, say, 192 <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, 193free 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> 194or even to sleep a while and retry until some memory is available.</p>
195 <p>Example: replace the libev allocator with one that waits a bit and then
196retries: better than mine).</p>
197<pre> static void *
198 persistent_realloc (void *ptr, long size)
199 {
200 for (;;)
201 {
202 void *newptr = realloc (ptr, size);
203
204 if (newptr)
205 return newptr;
206
207 sleep (60);
208 }
209 }
210
211 ...
212 ev_set_allocator (persistent_realloc);
213
214</pre>
132 </dd> 215 </dd>
133 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 216 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
134 <dd> 217 <dd>
135 <p>Set the callback function to call on a retryable syscall error (such 218 <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 219as failed select, poll, epoll_wait). The message is a printable string
137indicating the system call or subsystem causing the problem. If this 220indicating the system call or subsystem causing the problem. If this
138callback is set, then libev will expect it to remedy the sitution, no 221callback is set, then libev will expect it to remedy the sitution, no
139matter what, when it returns. That is, libev will generally retry the 222matter what, when it returns. That is, libev will generally retry the
140requested operation, or, if the condition doesn't go away, do bad stuff 223requested operation, or, if the condition doesn't go away, do bad stuff
141(such as abort).</p> 224(such as abort).</p>
225 <p>Example: do the same thing as libev does internally:</p>
226<pre> static void
227 fatal_error (const char *msg)
228 {
229 perror (msg);
230 abort ();
231 }
232
233 ...
234 ev_set_syserr_cb (fatal_error);
235
236</pre>
142 </dd> 237 </dd>
143</dl> 238</dl>
144 239
145</div> 240</div>
146<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 241<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> 253 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
159 <dd> 254 <dd>
160 <p>This will initialise the default event loop if it hasn't been initialised 255 <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 256yet 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 257false. If it already was initialised it simply returns it (and ignores the
163flags).</p> 258flags. 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 259 <p>If you don't know what event loop to use, use the one returned from this
165function.</p> 260function.</p>
166 <p>The flags argument can be used to specify special behaviour or specific 261 <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> 262backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
168 <p>It supports the following flags:</p> 263 <p>The following flags are supported:</p>
169 <p> 264 <p>
170 <dl> 265 <dl>
171 <dt><code>EVFLAG_AUTO</code></dt> 266 <dt><code>EVFLAG_AUTO</code></dt>
172 <dd> 267 <dd>
173 <p>The default flags value. Use this if you have no clue (it's the right 268 <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 275<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181override the flags completely if it is found in the environment. This is 276override 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 277useful to try out specific backends to test their performance, or to work
183around bugs.</p> 278around bugs.</p>
184 </dd> 279 </dd>
185 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> 280 <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> 281 <dd>
187 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> 282 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
188 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> 283libev 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> 284but if that fails, expect a fairly low limit on the number of fds when
190 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> 285using this backend. It doesn't scale too well (O(highest_fd)), but its usually
286the fastest backend for a low number of fds.</p>
191 <dd> 287 </dd>
192 <p>If one or more of these are ored into the flags value, then only these 288 <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 289 <dd>
194specified, any backend will do.</p> 290 <p>And this is your standard poll(2) backend. It's more complicated than
291select, but handles sparse fds better and has no artificial limit on the
292number of fds you can use (except it will slow down considerably with a
293lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
294 </dd>
295 <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
296 <dd>
297 <p>For few fds, this backend is a bit little slower than poll and select,
298but it scales phenomenally better. While poll and select usually scale like
299O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
300either O(1) or O(active_fds).</p>
301 <p>While stopping and starting an I/O watcher in the same iteration will
302result in some caching, there is still a syscall per such incident
303(because the fd could point to a different file description now), so its
304best to avoid that. Also, dup()ed file descriptors might not work very
305well if you register events for both fds.</p>
306 <p>Please note that epoll sometimes generates spurious notifications, so you
307need to use non-blocking I/O or other means to avoid blocking when no data
308(or space) is available.</p>
309 </dd>
310 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
311 <dd>
312 <p>Kqueue deserves special mention, as at the time of this writing, it
313was broken on all BSDs except NetBSD (usually it doesn't work with
314anything but sockets and pipes, except on Darwin, where of course its
315completely useless). For this reason its not being &quot;autodetected&quot;
316unless you explicitly specify it explicitly in the flags (i.e. using
317<code>EVBACKEND_KQUEUE</code>).</p>
318 <p>It scales in the same way as the epoll backend, but the interface to the
319kernel is more efficient (which says nothing about its actual speed, of
320course). While starting and stopping an I/O watcher does not cause an
321extra syscall as with epoll, it still adds up to four event changes per
322incident, so its best to avoid that.</p>
323 </dd>
324 <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
325 <dd>
326 <p>This is not implemented yet (and might never be).</p>
327 </dd>
328 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
329 <dd>
330 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
331it's really slow, but it still scales very well (O(active_fds)).</p>
332 <p>Please note that solaris ports can result in a lot of spurious
333notifications, so you need to use non-blocking I/O or other means to avoid
334blocking when no data (or space) is available.</p>
335 </dd>
336 <dt><code>EVBACKEND_ALL</code></dt>
337 <dd>
338 <p>Try all backends (even potentially broken ones that wouldn't be tried
339with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
340<code>EVBACKEND_ALL &amp; ~EVBACKEND_KQUEUE</code>.</p>
195 </dd> 341 </dd>
196 </dl> 342 </dl>
197 </p> 343 </p>
344 <p>If one or more of these are ored into the flags value, then only these
345backends will be tried (in the reverse order as given here). If none are
346specified, most compiled-in backend will be tried, usually in reverse
347order of their flag values :)</p>
348 <p>The most typical usage is like this:</p>
349<pre> if (!ev_default_loop (0))
350 fatal (&quot;could not initialise libev, bad $LIBEV_FLAGS in environment?&quot;);
351
352</pre>
353 <p>Restrict libev to the select and poll backends, and do not allow
354environment settings to be taken into account:</p>
355<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
356
357</pre>
358 <p>Use whatever libev has to offer, but make sure that kqueue is used if
359available (warning, breaks stuff, best use only with your own private
360event loop and only if you know the OS supports your types of fds):</p>
361<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
362
363</pre>
198 </dd> 364 </dd>
199 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 365 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200 <dd> 366 <dd>
201 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 367 <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 368always 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 369handle signal and child watchers, and attempts to do so will be greeted by
204undefined behaviour (or a failed assertion if assertions are enabled).</p> 370undefined behaviour (or a failed assertion if assertions are enabled).</p>
371 <p>Example: try to create a event loop that uses epoll and nothing else.</p>
372<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
373 if (!epoller)
374 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
375
376</pre>
205 </dd> 377 </dd>
206 <dt>ev_default_destroy ()</dt> 378 <dt>ev_default_destroy ()</dt>
207 <dd> 379 <dd>
208 <p>Destroys the default loop again (frees all memory and kernel state 380 <p>Destroys the default loop again (frees all memory and kernel state
209etc.). This stops all registered event watchers (by not touching them in 381etc.). None of the active event watchers will be stopped in the normal
210any way whatsoever, although you cannot rely on this :).</p> 382sense, so e.g. <code>ev_is_active</code> might still return true. It is your
383responsibility to either stop all watchers cleanly yoursef <i>before</i>
384calling this function, or cope with the fact afterwards (which is usually
385the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
386for example).</p>
211 </dd> 387 </dd>
212 <dt>ev_loop_destroy (loop)</dt> 388 <dt>ev_loop_destroy (loop)</dt>
213 <dd> 389 <dd>
214 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 390 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
215earlier call to <code>ev_loop_new</code>.</p> 391earlier call to <code>ev_loop_new</code>.</p>
… …
218 <dd> 394 <dd>
219 <p>This function reinitialises the kernel state for backends that have 395 <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 396one. 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 397after forking, in either the parent or child process (or both, but that
222again makes little sense).</p> 398again makes little sense).</p>
223 <p>You <i>must</i> call this function after forking if and only if you want to 399 <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 400only if you want to use the event library in both processes. If you just
225have to call it.</p> 401fork+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 402 <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 403it 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> 404quite nicely into a call to <code>pthread_atfork</code>:</p>
229<pre> pthread_atfork (0, 0, ev_default_fork); 405<pre> pthread_atfork (0, 0, ev_default_fork);
230 406
231</pre> 407</pre>
408 <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
409without calling this function, so if you force one of those backends you
410do not need to care.</p>
232 </dd> 411 </dd>
233 <dt>ev_loop_fork (loop)</dt> 412 <dt>ev_loop_fork (loop)</dt>
234 <dd> 413 <dd>
235 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 414 <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 415<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> 416after fork, and how you do this is entirely your own problem.</p>
238 </dd> 417 </dd>
239 <dt>unsigned int ev_method (loop)</dt> 418 <dt>unsigned int ev_backend (loop)</dt>
240 <dd> 419 <dd>
241 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 420 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
242use.</p> 421use.</p>
243 </dd> 422 </dd>
244 <dt>ev_tstamp ev_now (loop)</dt> 423 <dt>ev_tstamp ev_now (loop)</dt>
245 <dd> 424 <dd>
246 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 425 <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 426received events and started processing them. This timestamp does not
248as long as callbacks are being processed, and this is also the base time 427change 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 428time used for relative timers. You can treat it as the timestamp of the
250occuring (or more correctly, the mainloop finding out about it).</p> 429event occuring (or more correctly, libev finding out about it).</p>
251 </dd> 430 </dd>
252 <dt>ev_loop (loop, int flags)</dt> 431 <dt>ev_loop (loop, int flags)</dt>
253 <dd> 432 <dd>
254 <p>Finally, this is it, the event handler. This function usually is called 433 <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 434after you initialised all your watchers and you want to start handling
256events.</p> 435events.</p>
257 <p>If the flags argument is specified as 0, it will not return until either 436 <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> 437either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
438 <p>Please note that an explicit <code>ev_unloop</code> is usually better than
439relying on all watchers to be stopped when deciding when a program has
440finished (especially in interactive programs), but having a program that
441automatically loops as long as it has to and no longer by virtue of
442relying 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 443 <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 444those 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> 445case 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 446 <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 447neccessary) and will handle those and any outstanding ones. It will block
264your process until at least one new event arrives, and will return after 448your process until at least one new event arrives, and will return after
265one iteration of the loop.</p> 449one 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 450external event in conjunction with something not expressible using other
267constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 451libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
268more generic mechanism.</p> 452usually a better approach for this kind of thing.</p>
453 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
454<pre> * If there are no active watchers (reference count is zero), return.
455 - Queue prepare watchers and then call all outstanding watchers.
456 - If we have been forked, recreate the kernel state.
457 - Update the kernel state with all outstanding changes.
458 - Update the &quot;event loop time&quot;.
459 - Calculate for how long to block.
460 - Block the process, waiting for any events.
461 - Queue all outstanding I/O (fd) events.
462 - Update the &quot;event loop time&quot; and do time jump handling.
463 - Queue all outstanding timers.
464 - Queue all outstanding periodics.
465 - If no events are pending now, queue all idle watchers.
466 - Queue all check watchers.
467 - Call all queued watchers in reverse order (i.e. check watchers first).
468 Signals and child watchers are implemented as I/O watchers, and will
469 be handled here by queueing them when their watcher gets executed.
470 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
471 were used, return, otherwise continue with step *.
472
473</pre>
474 <p>Example: queue some jobs and then loop until no events are outsanding
475anymore.</p>
476<pre> ... queue jobs here, make sure they register event watchers as long
477 ... as they still have work to do (even an idle watcher will do..)
478 ev_loop (my_loop, 0);
479 ... jobs done. yeah!
480
481</pre>
269 </dd> 482 </dd>
270 <dt>ev_unloop (loop, how)</dt> 483 <dt>ev_unloop (loop, how)</dt>
271 <dd> 484 <dd>
272 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it 485 <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 486has 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 487<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> 488<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276 </dd> 489 </dd>
277 <dt>ev_ref (loop)</dt> 490 <dt>ev_ref (loop)</dt>
278 <dt>ev_unref (loop)</dt> 491 <dt>ev_unref (loop)</dt>
279 <dd> 492 <dd>
… …
285example, libev itself uses this for its internal signal pipe: It is not 498example, 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 499visible 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 500no 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 501way 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> 502libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
503 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
504running when nothing else is active.</p>
505<pre> struct dv_signal exitsig;
506 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
507 ev_signal_start (myloop, &amp;exitsig);
508 evf_unref (myloop);
509
510</pre>
511 <p>Example: for some weird reason, unregister the above signal handler again.</p>
512<pre> ev_ref (myloop);
513 ev_signal_stop (myloop, &amp;exitsig);
514
515</pre>
290 </dd> 516 </dd>
291</dl> 517</dl>
518
519
520
521
292 522
293</div> 523</div>
294<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 524<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"> 525<div id="ANATOMY_OF_A_WATCHER_CONTENT">
296<p>A watcher is a structure that you create and register to record your 526<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 556with 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 557*)</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> 558corresponding 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 559<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 560must not touch the values stored in it. Most specifically you must never
331reinitialise it or call its set method.</p> 561reinitialise 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 562<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 563registered watcher structure as second, and a bitset of received events as
338third argument.</p> 564third argument.</p>
339<p>The received events usually include a single bit per event type received 565<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 566(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 615your 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 616with the error from read() or write(). This will not work in multithreaded
391programs, though, so beware.</p> 617programs, though, so beware.</p>
392 </dd> 618 </dd>
393</dl> 619</dl>
620
621</div>
622<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
623<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
624<p>In the following description, <code>TYPE</code> stands for the watcher type,
625e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
626<dl>
627 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
628 <dd>
629 <p>This macro initialises the generic portion of a watcher. The contents
630of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
631the generic parts of the watcher are initialised, you <i>need</i> to call
632the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
633type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
634which rolls both calls into one.</p>
635 <p>You can reinitialise a watcher at any time as long as it has been stopped
636(or never started) and there are no pending events outstanding.</p>
637 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
638int revents)</code>.</p>
639 </dd>
640 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
641 <dd>
642 <p>This macro initialises the type-specific parts of a watcher. You need to
643call <code>ev_init</code> at least once before you call this macro, but you can
644call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
645macro on a watcher that is active (it can be pending, however, which is a
646difference to the <code>ev_init</code> macro).</p>
647 <p>Although some watcher types do not have type-specific arguments
648(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
649 </dd>
650 <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
651 <dd>
652 <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
653calls into a single call. This is the most convinient method to initialise
654a watcher. The same limitations apply, of course.</p>
655 </dd>
656 <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
657 <dd>
658 <p>Starts (activates) the given watcher. Only active watchers will receive
659events. If the watcher is already active nothing will happen.</p>
660 </dd>
661 <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
662 <dd>
663 <p>Stops the given watcher again (if active) and clears the pending
664status. It is possible that stopped watchers are pending (for example,
665non-repeating timers are being stopped when they become pending), but
666<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
667you want to free or reuse the memory used by the watcher it is therefore a
668good idea to always call its <code>ev_TYPE_stop</code> function.</p>
669 </dd>
670 <dt>bool ev_is_active (ev_TYPE *watcher)</dt>
671 <dd>
672 <p>Returns a true value iff the watcher is active (i.e. it has been started
673and not yet been stopped). As long as a watcher is active you must not modify
674it.</p>
675 </dd>
676 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
677 <dd>
678 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
679events but its callback has not yet been invoked). As long as a watcher
680is pending (but not active) you must not call an init function on it (but
681<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
682libev (e.g. you cnanot <code>free ()</code> it).</p>
683 </dd>
684 <dt>callback = ev_cb (ev_TYPE *watcher)</dt>
685 <dd>
686 <p>Returns the callback currently set on the watcher.</p>
687 </dd>
688 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
689 <dd>
690 <p>Change the callback. You can change the callback at virtually any time
691(modulo threads).</p>
692 </dd>
693</dl>
694
695
696
697
394 698
395</div> 699</div>
396<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 700<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"> 701<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 702<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> 734<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
431<div id="WATCHER_TYPES_CONTENT"> 735<div id="WATCHER_TYPES_CONTENT">
432<p>This section describes each watcher in detail, but will not repeat 736<p>This section describes each watcher in detail, but will not repeat
433information given in the last section.</p> 737information given in the last section.</p>
434 738
739
740
741
742
435</div> 743</div>
436<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 744<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"> 745<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 746<p>I/O watchers check whether a file descriptor is readable or writable
439in each iteration of the event loop (This behaviour is called 747in each iteration of the event loop, or, more precisely, when reading
440level-triggering because you keep receiving events as long as the 748would 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 749some data. This behaviour is called level-triggering because you keep
442act on the event and neither want to receive future events).</p> 750receiving events as long as the condition persists. Remember you can stop
751the watcher if you don't want to act on the event and neither want to
752receive future events.</p>
443<p>In general you can register as many read and/or write event watchers oer 753<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 754fd 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 755descriptors to non-blocking mode is also usually a good idea (but not
446required if you know what you are doing).</p> 756required if you know what you are doing).</p>
447<p>You have to be careful with dup'ed file descriptors, though. Some backends 757<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 758(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 759descriptors correctly if you register interest in two or more fds pointing
450to the same file/socket etc. description.</p> 760to the same underlying file/socket/etc. description (that is, they share
761the 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 762<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 763(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453EVMETHOD_POLL).</p> 764<code>EVBACKEND_POLL</code>).</p>
765<p>Another thing you have to watch out for is that it is quite easy to
766receive &quot;spurious&quot; readyness notifications, that is your callback might
767be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
768because there is no data. Not only are some backends known to create a
769lot of those (for example solaris ports), it is very easy to get into
770this situation even with a relatively standard program structure. Thus
771it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
772<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
773<p>If you cannot run the fd in non-blocking mode (for example you should not
774play around with an Xlib connection), then you have to seperately re-test
775wether a file descriptor is really ready with a known-to-be good interface
776such as poll (fortunately in our Xlib example, Xlib already does this on
777its own, so its quite safe to use).</p>
454<dl> 778<dl>
455 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 779 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
456 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 780 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
457 <dd> 781 <dd>
458 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 782 <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 | 783rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
460EV_WRITE</code> to receive the given events.</p> 784<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
461 </dd> 785 </dd>
462</dl> 786</dl>
787<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
788readable, but only once. Since it is likely line-buffered, you could
789attempt to read a whole line in the callback:</p>
790<pre> static void
791 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
792 {
793 ev_io_stop (loop, w);
794 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
795 }
463 796
797 ...
798 struct ev_loop *loop = ev_default_init (0);
799 struct ev_io stdin_readable;
800 ev_io_init (&amp;stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
801 ev_io_start (loop, &amp;stdin_readable);
802 ev_loop (loop, 0);
803
804
805
806
807</pre>
808
464</div> 809</div>
465<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 810<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"> 811<div id="code_ev_timer_code_relative_and_opti-2">
467<p>Timer watchers are simple relative timers that generate an event after a 812<p>Timer watchers are simple relative timers that generate an event after a
468given time, and optionally repeating in regular intervals after that.</p> 813given 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 814<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 815times 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 816time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
472detecting time jumps is hard, and soem inaccuracies are unavoidable (the 817detecting time jumps is hard, and some inaccuracies are unavoidable (the
473monotonic clock option helps a lot here).</p> 818monotonic clock option helps a lot here).</p>
474<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> 819<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 820time. This is usually the right thing as this timestamp refers to the time
476of the event triggering whatever timeout you are modifying/starting. If 821of the event triggering whatever timeout you are modifying/starting. If
477you suspect event processing to be delayed and you *need* to base the timeout 822you 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> 823on 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.); 824<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
480 825
481</pre> 826</pre>
827<p>The callback is guarenteed to be invoked only when its timeout has passed,
828but if multiple timers become ready during the same loop iteration then
829order of execution is undefined.</p>
482<dl> 830<dl>
483 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 831 <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> 832 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485 <dd> 833 <dd>
486 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 834 <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 836timer will automatically be configured to trigger again <code>repeat</code> seconds
489later, again, and again, until stopped manually.</p> 837later, again, and again, until stopped manually.</p>
490 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 838 <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 839configure a timer to trigger every 10 seconds, then it will trigger at
492exactly 10 second intervals. If, however, your program cannot keep up with 840exactly 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 841the 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> 842timer will not fire more than once per event loop iteration.</p>
495 </dd> 843 </dd>
496 <dt>ev_timer_again (loop)</dt> 844 <dt>ev_timer_again (loop)</dt>
497 <dd> 845 <dd>
498 <p>This will act as if the timer timed out and restart it again if it is 846 <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 856time 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 857state 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> 858the timer, and again will automatically restart it if need be.</p>
511 </dd> 859 </dd>
512</dl> 860</dl>
861<p>Example: create a timer that fires after 60 seconds.</p>
862<pre> static void
863 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
864 {
865 .. one minute over, w is actually stopped right here
866 }
513 867
868 struct ev_timer mytimer;
869 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
870 ev_timer_start (loop, &amp;mytimer);
871
872</pre>
873<p>Example: create a timeout timer that times out after 10 seconds of
874inactivity.</p>
875<pre> static void
876 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
877 {
878 .. ten seconds without any activity
879 }
880
881 struct ev_timer mytimer;
882 ev_timer_init (&amp;mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
883 ev_timer_again (&amp;mytimer); /* start timer */
884 ev_loop (loop, 0);
885
886 // and in some piece of code that gets executed on any &quot;activity&quot;:
887 // reset the timeout to start ticking again at 10 seconds
888 ev_timer_again (&amp;mytimer);
889
890
891
892
893</pre>
894
514</div> 895</div>
515<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 896<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"> 897<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 898<p>Periodic watchers are also timers of a kind, but they are very versatile
518(and unfortunately a bit complex).</p> 899(and unfortunately a bit complex).</p>
519<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 900<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 901but 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 902to 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 () 903periodic 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 904+ 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 905take 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 906roughly 10 seconds later and of course not if you reset your system time
526again).</p> 907again).</p>
527<p>They can also be used to implement vastly more complex timers, such as 908<p>They can also be used to implement vastly more complex timers, such as
528triggering an event on eahc midnight, local time.</p> 909triggering an event on eahc midnight, local time.</p>
910<p>As with timers, the callback is guarenteed to be invoked only when the
911time (<code>at</code>) has been passed, but if multiple periodic timers become ready
912during the same loop iteration then order of execution is undefined.</p>
529<dl> 913<dl>
530 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 914 <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> 915 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532 <dd> 916 <dd>
533 <p>Lots of arguments, lets sort it out... There are basically three modes of 917 <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> 918operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539 <p> 919 <p>
540 <dl> 920 <dl>
541 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 921 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
542 <dd> 922 <dd>
543 <p>In this configuration the watcher triggers an event at the wallclock time 923 <p>In this configuration the watcher triggers an event at the wallclock time
… …
567 <dd> 947 <dd>
568 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 948 <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 949ignored. Instead, each time the periodic watcher gets scheduled, the
570reschedule callback will be called with the watcher as first, and the 950reschedule callback will be called with the watcher as first, and the
571current time as second argument.</p> 951current time as second argument.</p>
572 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 952 <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 953ever, 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> 954return <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 955starting 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, 956 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
578ev_tstamp now)</code>, e.g.:</p> 957ev_tstamp now)</code>, e.g.:</p>
579<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 958<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580 { 959 {
581 return now + 60.; 960 return now + 60.;
… …
584</pre> 963</pre>
585 <p>It must return the next time to trigger, based on the passed time value 964 <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 965(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 966will usually be called just before the callback will be triggered, but
588might be called at other times, too.</p> 967might be called at other times, too.</p>
968 <p>NOTE: <i>This callback must always return a time that is later than the
969passed <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 970 <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 971triggers 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 972next midnight after <code>now</code> and return the timestamp value for this. How
592is, again, up to you (but it is not trivial).</p> 973you do this is, again, up to you (but it is not trivial, which is the main
974reason I omitted it as an example).</p>
593 </dd> 975 </dd>
594 </dl> 976 </dl>
595 </p> 977 </p>
596 </dd> 978 </dd>
597 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 979 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
600when you changed some parameters or the reschedule callback would return 982when 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 983a different time than the last time it was called (e.g. in a crond like
602program when the crontabs have changed).</p> 984program when the crontabs have changed).</p>
603 </dd> 985 </dd>
604</dl> 986</dl>
987<p>Example: call a callback every hour, or, more precisely, whenever the
988system clock is divisible by 3600. The callback invocation times have
989potentially a lot of jittering, but good long-term stability.</p>
990<pre> static void
991 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
992 {
993 ... its now a full hour (UTC, or TAI or whatever your clock follows)
994 }
605 995
996 struct ev_periodic hourly_tick;
997 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
998 ev_periodic_start (loop, &amp;hourly_tick);
999
1000</pre>
1001<p>Example: the same as above, but use a reschedule callback to do it:</p>
1002<pre> #include &lt;math.h&gt;
1003
1004 static ev_tstamp
1005 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1006 {
1007 return fmod (now, 3600.) + 3600.;
1008 }
1009
1010 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1011
1012</pre>
1013<p>Example: call a callback every hour, starting now:</p>
1014<pre> struct ev_periodic hourly_tick;
1015 ev_periodic_init (&amp;hourly_tick, clock_cb,
1016 fmod (ev_now (loop), 3600.), 3600., 0);
1017 ev_periodic_start (loop, &amp;hourly_tick);
1018
1019
1020
1021
1022</pre>
1023
606</div> 1024</div>
607<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1025<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"> 1026<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 1027<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 1028signal 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 1029will try it's best to deliver signals synchronously, i.e. as part of the
612normal event processing, like any other event.</p> 1030normal event processing, like any other event.</p>
… …
623 <p>Configures the watcher to trigger on the given signal number (usually one 1041 <p>Configures the watcher to trigger on the given signal number (usually one
624of the <code>SIGxxx</code> constants).</p> 1042of the <code>SIGxxx</code> constants).</p>
625 </dd> 1043 </dd>
626</dl> 1044</dl>
627 1045
1046
1047
1048
1049
628</div> 1050</div>
629<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1051<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"> 1052<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 1053<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> 1054some child status changes (most typically when a child of yours dies).</p>
633<dl> 1055<dl>
634 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1056 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
635 <dt>ev_child_set (ev_child *, int pid)</dt> 1057 <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 1062the 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 1063<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
642process causing the status change.</p> 1064process causing the status change.</p>
643 </dd> 1065 </dd>
644</dl> 1066</dl>
1067<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
1068<pre> static void
1069 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1070 {
1071 ev_unloop (loop, EVUNLOOP_ALL);
1072 }
645 1073
1074 struct ev_signal signal_watcher;
1075 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
1076 ev_signal_start (loop, &amp;sigint_cb);
1077
1078
1079
1080
1081</pre>
1082
646</div> 1083</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> 1084<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"> 1085<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 1086<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 1087(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, 1088as 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 1089imagine) 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 1102 <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, 1103kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
667believe me.</p> 1104believe me.</p>
668 </dd> 1105 </dd>
669</dl> 1106</dl>
1107<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
1108callback, free it. Alos, use no error checking, as usual.</p>
1109<pre> static void
1110 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1111 {
1112 free (w);
1113 // now do something you wanted to do when the program has
1114 // no longer asnything immediate to do.
1115 }
670 1116
1117 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1118 ev_idle_init (idle_watcher, idle_cb);
1119 ev_idle_start (loop, idle_cb);
1120
1121
1122
1123
1124</pre>
1125
671</div> 1126</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> 1127<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"> 1128<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: 1129<p>Prepare and check watchers are usually (but not always) used in tandem:
675Prepare watchers get invoked before the process blocks and check watchers 1130prepare watchers get invoked before the process blocks and check watchers
676afterwards.</p> 1131afterwards.</p>
1132<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1133the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1134watchers. Other loops than the current one are fine, however. The
1135rationale behind this is that you do not need to check for recursion in
1136those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1137<code>ev_check</code> so if you have one watcher of each kind they will always be
1138called in pairs bracketing the blocking call.</p>
677<p>Their main purpose is to integrate other event mechanisms into libev. This 1139<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 1140their use is somewhat advanced. This could be used, for example, to track
679watchers, integrate net-snmp or a coroutine library and lots more.</p> 1141variable changes, implement your own watchers, integrate net-snmp or a
1142coroutine library and lots more. They are also occasionally useful if
1143you cache some data and want to flush it before blocking (for example,
1144in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1145watcher).</p>
680<p>This is done by examining in each prepare call which file descriptors need 1146<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 1147to 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 1148them 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 1149provide just this functionality). Then, in the check watcher you check for
684any events that occured (by checking the pending status of all watchers 1150any 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 1151and stopping them) and call back into the library. The I/O and timer
686callbacks will never actually be called (but must be valid neverthelles, 1152callbacks will never actually be called (but must be valid nevertheless,
687because you never know, you know?).</p> 1153because you never know, you know?).</p>
688<p>As another example, the Perl Coro module uses these hooks to integrate 1154<p>As another example, the Perl Coro module uses these hooks to integrate
689coroutines into libev programs, by yielding to other active coroutines 1155coroutines into libev programs, by yielding to other active coroutines
690during each prepare and only letting the process block if no coroutines 1156during each prepare and only letting the process block if no coroutines
691are ready to run (its actually more complicated, it only runs coroutines 1157are ready to run (it's actually more complicated: it only runs coroutines
692with priority higher than the event loop and one lower priority once, 1158with 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 1159of lower priority, but only once, using idle watchers to keep the event
694coroutines exist, thus mapping low-priority coroutines to idle/background 1160loop from blocking if lower-priority coroutines are active, thus mapping
695tasks).</p> 1161low-priority coroutines to idle/background tasks).</p>
696<dl> 1162<dl>
697 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1163 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
698 <dt>ev_check_init (ev_check *, callback)</dt> 1164 <dt>ev_check_init (ev_check *, callback)</dt>
699 <dd> 1165 <dd>
700 <p>Initialises and configures the prepare or check watcher - they have no 1166 <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> 1167parameters 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> 1168macros, but using them is utterly, utterly and completely pointless.</p>
703 </dd> 1169 </dd>
704</dl> 1170</dl>
1171<p>Example: To include a library such as adns, you would add IO watchers
1172and a timeout watcher in a prepare handler, as required by libadns, and
1173in a check watcher, destroy them and call into libadns. What follows is
1174pseudo-code only of course:</p>
1175<pre> static ev_io iow [nfd];
1176 static ev_timer tw;
1177
1178 static void
1179 io_cb (ev_loop *loop, ev_io *w, int revents)
1180 {
1181 // set the relevant poll flags
1182 // could also call adns_processreadable etc. here
1183 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1184 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1185 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1186 }
1187
1188 // create io watchers for each fd and a timer before blocking
1189 static void
1190 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1191 {
1192 int timeout = 3600000;truct pollfd fds [nfd];
1193 // actual code will need to loop here and realloc etc.
1194 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1195
1196 /* the callback is illegal, but won't be called as we stop during check */
1197 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1198 ev_timer_start (loop, &amp;tw);
1199
1200 // create on ev_io per pollfd
1201 for (int i = 0; i &lt; nfd; ++i)
1202 {
1203 ev_io_init (iow + i, io_cb, fds [i].fd,
1204 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1205 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1206
1207 fds [i].revents = 0;
1208 iow [i].data = fds + i;
1209 ev_io_start (loop, iow + i);
1210 }
1211 }
1212
1213 // stop all watchers after blocking
1214 static void
1215 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1216 {
1217 ev_timer_stop (loop, &amp;tw);
1218
1219 for (int i = 0; i &lt; nfd; ++i)
1220 ev_io_stop (loop, iow + i);
1221
1222 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1223 }
1224
1225
1226
1227
1228</pre>
1229
1230</div>
1231<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1232<div id="code_ev_embed_code_when_one_backend_-2">
1233<p>This is a rather advanced watcher type that lets you embed one event loop
1234into another (currently only <code>ev_io</code> events are supported in the embedded
1235loop, other types of watchers might be handled in a delayed or incorrect
1236fashion and must not be used).</p>
1237<p>There are primarily two reasons you would want that: work around bugs and
1238prioritise I/O.</p>
1239<p>As an example for a bug workaround, the kqueue backend might only support
1240sockets on some platform, so it is unusable as generic backend, but you
1241still want to make use of it because you have many sockets and it scales
1242so nicely. In this case, you would create a kqueue-based loop and embed it
1243into your default loop (which might use e.g. poll). Overall operation will
1244be a bit slower because first libev has to poll and then call kevent, but
1245at least you can use both at what they are best.</p>
1246<p>As for prioritising I/O: rarely you have the case where some fds have
1247to be watched and handled very quickly (with low latency), and even
1248priorities and idle watchers might have too much overhead. In this case
1249you would put all the high priority stuff in one loop and all the rest in
1250a second one, and embed the second one in the first.</p>
1251<p>As long as the watcher is active, the callback will be invoked every time
1252there might be events pending in the embedded loop. The callback must then
1253call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1254their callbacks (you could also start an idle watcher to give the embedded
1255loop strictly lower priority for example). You can also set the callback
1256to <code>0</code>, in which case the embed watcher will automatically execute the
1257embedded loop sweep.</p>
1258<p>As long as the watcher is started it will automatically handle events. The
1259callback will be invoked whenever some events have been handled. You can
1260set the callback to <code>0</code> to avoid having to specify one if you are not
1261interested in that.</p>
1262<p>Also, there have not currently been made special provisions for forking:
1263when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
1264but you will also have to stop and restart any <code>ev_embed</code> watchers
1265yourself.</p>
1266<p>Unfortunately, not all backends are embeddable, only the ones returned by
1267<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
1268portable one.</p>
1269<p>So when you want to use this feature you will always have to be prepared
1270that you cannot get an embeddable loop. The recommended way to get around
1271this is to have a separate variables for your embeddable loop, try to
1272create it, and if that fails, use the normal loop for everything:</p>
1273<pre> struct ev_loop *loop_hi = ev_default_init (0);
1274 struct ev_loop *loop_lo = 0;
1275 struct ev_embed embed;
1276
1277 // see if there is a chance of getting one that works
1278 // (remember that a flags value of 0 means autodetection)
1279 loop_lo = ev_embeddable_backends () &amp; ev_recommended_backends ()
1280 ? ev_loop_new (ev_embeddable_backends () &amp; ev_recommended_backends ())
1281 : 0;
1282
1283 // if we got one, then embed it, otherwise default to loop_hi
1284 if (loop_lo)
1285 {
1286 ev_embed_init (&amp;embed, 0, loop_lo);
1287 ev_embed_start (loop_hi, &amp;embed);
1288 }
1289 else
1290 loop_lo = loop_hi;
1291
1292</pre>
1293<dl>
1294 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1295 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1296 <dd>
1297 <p>Configures the watcher to embed the given loop, which must be
1298embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1299invoked automatically, otherwise it is the responsibility of the callback
1300to invoke it (it will continue to be called until the sweep has been done,
1301if you do not want thta, you need to temporarily stop the embed watcher).</p>
1302 </dd>
1303 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1304 <dd>
1305 <p>Make a single, non-blocking sweep over the embedded loop. This works
1306similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1307apropriate way for embedded loops.</p>
1308 </dd>
1309</dl>
1310
1311
1312
1313
705 1314
706</div> 1315</div>
707<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1316<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
708<div id="OTHER_FUNCTIONS_CONTENT"> 1317<div id="OTHER_FUNCTIONS_CONTENT">
709<p>There are some other functions of possible interest. Described. Here. Now.</p> 1318<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> 1320 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712 <dd> 1321 <dd>
713 <p>This function combines a simple timer and an I/O watcher, calls your 1322 <p>This function combines a simple timer and an I/O watcher, calls your
714callback on whichever event happens first and automatically stop both 1323callback 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 1324watchers. 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 1325or timeout without having to allocate/configure/start/stop/free one or
717more watchers yourself.</p> 1326more watchers yourself.</p>
718 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events 1327 <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 1328is 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> 1329<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 1330 <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 1331started. 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 1332repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724dubious value.</p> 1333dubious value.</p>
725 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets 1334 <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 1335passed 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> 1336<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> 1337value passed to <code>ev_once</code>:</p>
729<pre> static void stdin_ready (int revents, void *arg) 1338<pre> static void stdin_ready (int revents, void *arg)
730 { 1339 {
731 if (revents &amp; EV_TIMEOUT) 1340 if (revents &amp; EV_TIMEOUT)
… …
736 1345
737 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1346 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738 1347
739</pre> 1348</pre>
740 </dd> 1349 </dd>
741 <dt>ev_feed_event (loop, watcher, int events)</dt> 1350 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
742 <dd> 1351 <dd>
743 <p>Feeds the given event set into the event loop, as if the specified event 1352 <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 1353had happened for the specified watcher (which must be a pointer to an
745initialised but not necessarily started event watcher).</p> 1354initialised but not necessarily started event watcher).</p>
746 </dd> 1355 </dd>
747 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1356 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
748 <dd> 1357 <dd>
749 <p>Feed an event on the given fd, as if a file descriptor backend detected 1358 <p>Feed an event on the given fd, as if a file descriptor backend detected
750the given events it.</p> 1359the given events it.</p>
751 </dd> 1360 </dd>
752 <dt>ev_feed_signal_event (loop, int signum)</dt> 1361 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
753 <dd> 1362 <dd>
754 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1363 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1364loop!).</p>
755 </dd> 1365 </dd>
756</dl> 1366</dl>
1367
1368
1369
1370
1371
1372</div>
1373<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
1374<div id="LIBEVENT_EMULATION_CONTENT">
1375<p>Libev offers a compatibility emulation layer for libevent. It cannot
1376emulate the internals of libevent, so here are some usage hints:</p>
1377<dl>
1378 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
1379 <dt>* The following members are fully supported: ev_base, ev_callback,
1380ev_arg, ev_fd, ev_res, ev_events.</dt>
1381 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
1382maintained by libev, it does not work exactly the same way as in libevent (consider
1383it a private API).</dt>
1384 <dt>* Priorities are not currently supported. Initialising priorities
1385will fail and all watchers will have the same priority, even though there
1386is an ev_pri field.</dt>
1387 <dt>* Other members are not supported.</dt>
1388 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1389to use the libev header file and library.</dt>
1390</dl>
1391
1392</div>
1393<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
1394<div id="C_SUPPORT_CONTENT">
1395<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1396you to use some convinience methods to start/stop watchers and also change
1397the callback model to a model using method callbacks on objects.</p>
1398<p>To use it,</p>
1399<pre> #include &lt;ev++.h&gt;
1400
1401</pre>
1402<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1403and puts all of its definitions (many of them macros) into the global
1404namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1405<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1406<code>EV_MULTIPLICITY</code>.</p>
1407<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1408<dl>
1409 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1410 <dd>
1411 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1412macros from <cite>ev.h</cite>.</p>
1413 </dd>
1414 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1415 <dd>
1416 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1417 </dd>
1418 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1419 <dd>
1420 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1421the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1422which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1423defines by many implementations.</p>
1424 <p>All of those classes have these methods:</p>
1425 <p>
1426 <dl>
1427 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1428 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1429 <dt>ev::TYPE::~TYPE</dt>
1430 <dd>
1431 <p>The constructor takes a pointer to an object and a method pointer to
1432the event handler callback to call in this class. The constructor calls
1433<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1434before starting it. If you do not specify a loop then the constructor
1435automatically associates the default loop with this watcher.</p>
1436 <p>The destructor automatically stops the watcher if it is active.</p>
1437 </dd>
1438 <dt>w-&gt;set (struct ev_loop *)</dt>
1439 <dd>
1440 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1441do this when the watcher is inactive (and not pending either).</p>
1442 </dd>
1443 <dt>w-&gt;set ([args])</dt>
1444 <dd>
1445 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1446called at least once. Unlike the C counterpart, an active watcher gets
1447automatically stopped and restarted.</p>
1448 </dd>
1449 <dt>w-&gt;start ()</dt>
1450 <dd>
1451 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1452constructor already takes the loop.</p>
1453 </dd>
1454 <dt>w-&gt;stop ()</dt>
1455 <dd>
1456 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1457 </dd>
1458 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1459 <dd>
1460 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1461<code>ev_TYPE_again</code> function.</p>
1462 </dd>
1463 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1464 <dd>
1465 <p>Invokes <code>ev_embed_sweep</code>.</p>
1466 </dd>
1467 </dl>
1468 </p>
1469 </dd>
1470</dl>
1471<p>Example: Define a class with an IO and idle watcher, start one of them in
1472the constructor.</p>
1473<pre> class myclass
1474 {
1475 ev_io io; void io_cb (ev::io &amp;w, int revents);
1476 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1477
1478 myclass ();
1479 }
1480
1481 myclass::myclass (int fd)
1482 : io (this, &amp;myclass::io_cb),
1483 idle (this, &amp;myclass::idle_cb)
1484 {
1485 io.start (fd, ev::READ);
1486 }
1487
1488</pre>
1489
1490</div>
1491<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
1492<div id="EMBEDDING_CONTENT">
1493<p>Libev can (and often is) directly embedded into host
1494applications. Examples of applications that embed it include the Deliantra
1495Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1496and rxvt-unicode.</p>
1497<p>The goal is to enable you to just copy the neecssary files into your
1498source directory without having to change even a single line in them, so
1499you can easily upgrade by simply copying (or having a checked-out copy of
1500libev somewhere in your source tree).</p>
1501
1502</div>
1503<h2 id="FILESETS">FILESETS</h2>
1504<div id="FILESETS_CONTENT">
1505<p>Depending on what features you need you need to include one or more sets of files
1506in your app.</p>
1507
1508</div>
1509<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1510<div id="CORE_EVENT_LOOP_CONTENT">
1511<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1512configuration (no autoconf):</p>
1513<pre> #define EV_STANDALONE 1
1514 #include &quot;ev.c&quot;
1515
1516</pre>
1517<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1518single C source file only to provide the function implementations. To use
1519it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1520done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1521where you can put other configuration options):</p>
1522<pre> #define EV_STANDALONE 1
1523 #include &quot;ev.h&quot;
1524
1525</pre>
1526<p>Both header files and implementation files can be compiled with a C++
1527compiler (at least, thats a stated goal, and breakage will be treated
1528as a bug).</p>
1529<p>You need the following files in your source tree, or in a directory
1530in your include path (e.g. in libev/ when using -Ilibev):</p>
1531<pre> ev.h
1532 ev.c
1533 ev_vars.h
1534 ev_wrap.h
1535
1536 ev_win32.c required on win32 platforms only
1537
1538 ev_select.c only when select backend is enabled (which is by default)
1539 ev_poll.c only when poll backend is enabled (disabled by default)
1540 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1541 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1542 ev_port.c only when the solaris port backend is enabled (disabled by default)
1543
1544</pre>
1545<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1546to compile this single file.</p>
1547
1548</div>
1549<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1550<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1551<p>To include the libevent compatibility API, also include:</p>
1552<pre> #include &quot;event.c&quot;
1553
1554</pre>
1555<p>in the file including <cite>ev.c</cite>, and:</p>
1556<pre> #include &quot;event.h&quot;
1557
1558</pre>
1559<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1560<p>You need the following additional files for this:</p>
1561<pre> event.h
1562 event.c
1563
1564</pre>
1565
1566</div>
1567<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1568<div id="AUTOCONF_SUPPORT_CONTENT">
1569<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1570whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1571<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1572include <cite>config.h</cite> and configure itself accordingly.</p>
1573<p>For this of course you need the m4 file:</p>
1574<pre> libev.m4
1575
1576</pre>
1577
1578</div>
1579<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1580<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1581<p>Libev can be configured via a variety of preprocessor symbols you have to define
1582before including any of its files. The default is not to build for multiplicity
1583and only include the select backend.</p>
1584<dl>
1585 <dt>EV_STANDALONE</dt>
1586 <dd>
1587 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1588keeps libev from including <cite>config.h</cite>, and it also defines dummy
1589implementations for some libevent functions (such as logging, which is not
1590supported). It will also not define any of the structs usually found in
1591<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1592 </dd>
1593 <dt>EV_USE_MONOTONIC</dt>
1594 <dd>
1595 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1596monotonic clock option at both compiletime and runtime. Otherwise no use
1597of the monotonic clock option will be attempted. If you enable this, you
1598usually have to link against librt or something similar. Enabling it when
1599the functionality isn't available is safe, though, althoguh you have
1600to make sure you link against any libraries where the <code>clock_gettime</code>
1601function is hiding in (often <cite>-lrt</cite>).</p>
1602 </dd>
1603 <dt>EV_USE_REALTIME</dt>
1604 <dd>
1605 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1606realtime clock option at compiletime (and assume its availability at
1607runtime if successful). Otherwise no use of the realtime clock option will
1608be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1609(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1610in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1611 </dd>
1612 <dt>EV_USE_SELECT</dt>
1613 <dd>
1614 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1615<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1616other method takes over, select will be it. Otherwise the select backend
1617will not be compiled in.</p>
1618 </dd>
1619 <dt>EV_SELECT_USE_FD_SET</dt>
1620 <dd>
1621 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1622structure. This is useful if libev doesn't compile due to a missing
1623<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1624exotic systems. This usually limits the range of file descriptors to some
1625low limit such as 1024 or might have other limitations (winsocket only
1626allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1627influence the size of the <code>fd_set</code> used.</p>
1628 </dd>
1629 <dt>EV_SELECT_IS_WINSOCKET</dt>
1630 <dd>
1631 <p>When defined to <code>1</code>, the select backend will assume that
1632select/socket/connect etc. don't understand file descriptors but
1633wants osf handles on win32 (this is the case when the select to
1634be used is the winsock select). This means that it will call
1635<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1636it is assumed that all these functions actually work on fds, even
1637on win32. Should not be defined on non-win32 platforms.</p>
1638 </dd>
1639 <dt>EV_USE_POLL</dt>
1640 <dd>
1641 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1642backend. Otherwise it will be enabled on non-win32 platforms. It
1643takes precedence over select.</p>
1644 </dd>
1645 <dt>EV_USE_EPOLL</dt>
1646 <dd>
1647 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
1648<code>epoll</code>(7) backend. Its availability will be detected at runtime,
1649otherwise another method will be used as fallback. This is the
1650preferred backend for GNU/Linux systems.</p>
1651 </dd>
1652 <dt>EV_USE_KQUEUE</dt>
1653 <dd>
1654 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
1655<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
1656otherwise another method will be used as fallback. This is the preferred
1657backend for BSD and BSD-like systems, although on most BSDs kqueue only
1658supports some types of fds correctly (the only platform we found that
1659supports ptys for example was NetBSD), so kqueue might be compiled in, but
1660not be used unless explicitly requested. The best way to use it is to find
1661out whether kqueue supports your type of fd properly and use an embedded
1662kqueue loop.</p>
1663 </dd>
1664 <dt>EV_USE_PORT</dt>
1665 <dd>
1666 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
166710 port style backend. Its availability will be detected at runtime,
1668otherwise another method will be used as fallback. This is the preferred
1669backend for Solaris 10 systems.</p>
1670 </dd>
1671 <dt>EV_USE_DEVPOLL</dt>
1672 <dd>
1673 <p>reserved for future expansion, works like the USE symbols above.</p>
1674 </dd>
1675 <dt>EV_H</dt>
1676 <dd>
1677 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1678undefined 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
1679can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
1680 </dd>
1681 <dt>EV_CONFIG_H</dt>
1682 <dd>
1683 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
1684<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
1685<code>EV_H</code>, above.</p>
1686 </dd>
1687 <dt>EV_EVENT_H</dt>
1688 <dd>
1689 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
1690of how the <cite>event.h</cite> header can be found.</p>
1691 </dd>
1692 <dt>EV_PROTOTYPES</dt>
1693 <dd>
1694 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
1695prototypes, but still define all the structs and other symbols. This is
1696occasionally useful if you want to provide your own wrapper functions
1697around libev functions.</p>
1698 </dd>
1699 <dt>EV_MULTIPLICITY</dt>
1700 <dd>
1701 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
1702will have the <code>struct ev_loop *</code> as first argument, and you can create
1703additional independent event loops. Otherwise there will be no support
1704for multiple event loops and there is no first event loop pointer
1705argument. Instead, all functions act on the single default loop.</p>
1706 </dd>
1707 <dt>EV_PERIODICS</dt>
1708 <dd>
1709 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported,
1710otherwise not. This saves a few kb of code.</p>
1711 </dd>
1712 <dt>EV_COMMON</dt>
1713 <dd>
1714 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1715this macro to a something else you can include more and other types of
1716members. You have to define it each time you include one of the files,
1717though, and it must be identical each time.</p>
1718 <p>For example, the perl EV module uses something like this:</p>
1719<pre> #define EV_COMMON \
1720 SV *self; /* contains this struct */ \
1721 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
1722
1723</pre>
1724 </dd>
1725 <dt>EV_CB_DECLARE (type)</dt>
1726 <dt>EV_CB_INVOKE (watcher, revents)</dt>
1727 <dt>ev_set_cb (ev, cb)</dt>
1728 <dd>
1729 <p>Can be used to change the callback member declaration in each watcher,
1730and the way callbacks are invoked and set. Must expand to a struct member
1731definition and a statement, respectively. See the <cite>ev.v</cite> header file for
1732their default definitions. One possible use for overriding these is to
1733avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
1734method calls instead of plain function calls in C++.</p>
1735
1736</div>
1737<h2 id="EXAMPLES">EXAMPLES</h2>
1738<div id="EXAMPLES_CONTENT">
1739 <p>For a real-world example of a program the includes libev
1740verbatim, you can have a look at the EV perl module
1741(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
1742the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
1743interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
1744will be compiled. It is pretty complex because it provides its own header
1745file.</p>
1746 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
1747that everybody includes and which overrides some autoconf choices:</p>
1748<pre> #define EV_USE_POLL 0
1749 #define EV_MULTIPLICITY 0
1750 #define EV_PERIODICS 0
1751 #define EV_CONFIG_H &lt;config.h&gt;
1752
1753 #include &quot;ev++.h&quot;
1754
1755</pre>
1756 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1757<pre> #include &quot;ev_cpp.h&quot;
1758 #include &quot;ev.c&quot;
1759
1760
1761
1762
1763</pre>
1764
1765</div>
1766<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
1767<div id="COMPLEXITIES_CONTENT">
1768 <p>In this section the complexities of (many of) the algorithms used inside
1769libev will be explained. For complexity discussions about backends see the
1770documentation for <code>ev_default_init</code>.</p>
1771 <p>
1772 <dl>
1773 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
1774 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
1775 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
1776 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
1777 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
1778 <dt>Finding the next timer per loop iteration: O(1)</dt>
1779 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
1780 <dt>Activating one watcher: O(1)</dt>
1781 </dl>
1782 </p>
1783
1784
1785
1786
757 1787
758</div> 1788</div>
759<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1789<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
760<div id="AUTHOR_CONTENT"> 1790<div id="AUTHOR_CONTENT">
761<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 1791 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
762 1792
763</div> 1793</div>
764</div></body> 1794</div></body>
765</html> 1795</html>

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