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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Fri Nov 23 06:14:47 2007" /> 9 <meta name="created" content="Tue Nov 27 11:59:06 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>
36<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
35<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> 37<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> 38<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
39<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
40<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
37</ul> 41</ul>
38</li> 42</li>
39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 43<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 44<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 45<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
46<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
47<li><a href="#EMBEDDING">EMBEDDING</a>
48<ul><li><a href="#FILESETS">FILESETS</a>
49<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
50<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
51<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
52</ul>
53</li>
54<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
55<li><a href="#EXAMPLES">EXAMPLES</a></li>
56</ul>
57</li>
58<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
42<li><a href="#AUTHOR">AUTHOR</a> 59<li><a href="#AUTHOR">AUTHOR</a>
43</li> 60</li>
44</ul><hr /> 61</ul><hr />
45<!-- INDEX END --> 62<!-- INDEX END -->
46 63
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96<div id="TIME_REPRESENTATION_CONTENT"> 113<div id="TIME_REPRESENTATION_CONTENT">
97<p>Libev represents time as a single floating point number, representing the 114<p>Libev represents time as a single floating point number, representing the
98(fractional) number of seconds since the (POSIX) epoch (somewhere near 115(fractional) number of seconds since the (POSIX) epoch (somewhere near
99the beginning of 1970, details are complicated, don't ask). This type is 116the beginning of 1970, details are complicated, don't ask). This type is
100called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 117called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
101to the double type in C.</p> 118to the <code>double</code> type in C, and when you need to do any calculations on
119it, you should treat it as such.</p>
102 120
103</div> 121</div>
104<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105<div id="GLOBAL_FUNCTIONS_CONTENT"> 123<div id="GLOBAL_FUNCTIONS_CONTENT">
106<p>These functions can be called anytime, even before initialising the 124<p>These functions can be called anytime, even before initialising the
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122version of the library your program was compiled against.</p> 140version of the library your program was compiled against.</p>
123 <p>Usually, it's a good idea to terminate if the major versions mismatch, 141 <p>Usually, it's a good idea to terminate if the major versions mismatch,
124as this indicates an incompatible change. Minor versions are usually 142as this indicates an incompatible change. Minor versions are usually
125compatible to older versions, so a larger minor version alone is usually 143compatible to older versions, so a larger minor version alone is usually
126not a problem.</p> 144not a problem.</p>
145 <p>Example: make sure we haven't accidentally been linked against the wrong
146version:</p>
147<pre> assert ((&quot;libev version mismatch&quot;,
148 ev_version_major () == EV_VERSION_MAJOR
149 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
150
151</pre>
127 </dd> 152 </dd>
128 <dt>unsigned int ev_supported_backends ()</dt> 153 <dt>unsigned int ev_supported_backends ()</dt>
129 <dd> 154 <dd>
130 <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> 155 <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
131value) compiled into this binary of libev (independent of their 156value) compiled into this binary of libev (independent of their
132availability on the system you are running on). See <code>ev_default_loop</code> for 157availability on the system you are running on). See <code>ev_default_loop</code> for
133a description of the set values.</p> 158a description of the set values.</p>
159 <p>Example: make sure we have the epoll method, because yeah this is cool and
160a must have and can we have a torrent of it please!!!11</p>
161<pre> assert ((&quot;sorry, no epoll, no sex&quot;,
162 ev_supported_backends () &amp; EVBACKEND_EPOLL));
163
164</pre>
134 </dd> 165 </dd>
135 <dt>unsigned int ev_recommended_backends ()</dt> 166 <dt>unsigned int ev_recommended_backends ()</dt>
136 <dd> 167 <dd>
137 <p>Return the set of all backends compiled into this binary of libev and also 168 <p>Return the set of all backends compiled into this binary of libev and also
138recommended for this platform. This set is often smaller than the one 169recommended for this platform. This set is often smaller than the one
139returned by <code>ev_supported_backends</code>, as for example kqueue is broken on 170returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
140most BSDs and will not be autodetected unless you explicitly request it 171most BSDs and will not be autodetected unless you explicitly request it
141(assuming you know what you are doing). This is the set of backends that 172(assuming you know what you are doing). This is the set of backends that
142<code>EVFLAG_AUTO</code> will probe for.</p> 173libev will probe for if you specify no backends explicitly.</p>
174 </dd>
175 <dt>unsigned int ev_embeddable_backends ()</dt>
176 <dd>
177 <p>Returns the set of backends that are embeddable in other event loops. This
178is the theoretical, all-platform, value. To find which backends
179might be supported on the current system, you would need to look at
180<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
181recommended ones.</p>
182 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
143 </dd> 183 </dd>
144 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 184 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
145 <dd> 185 <dd>
146 <p>Sets the allocation function to use (the prototype is similar to the 186 <p>Sets the allocation function to use (the prototype is similar to the
147realloc C function, the semantics are identical). It is used to allocate 187realloc C function, the semantics are identical). It is used to allocate
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149needs to be allocated, the library might abort or take some potentially 189needs to be allocated, the library might abort or take some potentially
150destructive action. The default is your system realloc function.</p> 190destructive action. The default is your system realloc function.</p>
151 <p>You could override this function in high-availability programs to, say, 191 <p>You could override this function in high-availability programs to, say,
152free some memory if it cannot allocate memory, to use a special allocator, 192free some memory if it cannot allocate memory, to use a special allocator,
153or even to sleep a while and retry until some memory is available.</p> 193or even to sleep a while and retry until some memory is available.</p>
194 <p>Example: replace the libev allocator with one that waits a bit and then
195retries: better than mine).</p>
196<pre> static void *
197 persistent_realloc (void *ptr, long size)
198 {
199 for (;;)
200 {
201 void *newptr = realloc (ptr, size);
202
203 if (newptr)
204 return newptr;
205
206 sleep (60);
207 }
208 }
209
210 ...
211 ev_set_allocator (persistent_realloc);
212
213</pre>
154 </dd> 214 </dd>
155 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 215 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
156 <dd> 216 <dd>
157 <p>Set the callback function to call on a retryable syscall error (such 217 <p>Set the callback function to call on a retryable syscall error (such
158as failed select, poll, epoll_wait). The message is a printable string 218as failed select, poll, epoll_wait). The message is a printable string
159indicating the system call or subsystem causing the problem. If this 219indicating the system call or subsystem causing the problem. If this
160callback is set, then libev will expect it to remedy the sitution, no 220callback is set, then libev will expect it to remedy the sitution, no
161matter what, when it returns. That is, libev will generally retry the 221matter what, when it returns. That is, libev will generally retry the
162requested operation, or, if the condition doesn't go away, do bad stuff 222requested operation, or, if the condition doesn't go away, do bad stuff
163(such as abort).</p> 223(such as abort).</p>
224 <p>Example: do the same thing as libev does internally:</p>
225<pre> static void
226 fatal_error (const char *msg)
227 {
228 perror (msg);
229 abort ();
230 }
231
232 ...
233 ev_set_syserr_cb (fatal_error);
234
235</pre>
164 </dd> 236 </dd>
165</dl> 237</dl>
166 238
167</div> 239</div>
168<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 240<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
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184false. If it already was initialised it simply returns it (and ignores the 256false. If it already was initialised it simply returns it (and ignores the
185flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p> 257flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
186 <p>If you don't know what event loop to use, use the one returned from this 258 <p>If you don't know what event loop to use, use the one returned from this
187function.</p> 259function.</p>
188 <p>The flags argument can be used to specify special behaviour or specific 260 <p>The flags argument can be used to specify special behaviour or specific
189backends to use, and is usually specified as <code>0</code> (or EVFLAG_AUTO).</p> 261backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
190 <p>It supports the following flags:</p> 262 <p>The following flags are supported:</p>
191 <p> 263 <p>
192 <dl> 264 <dl>
193 <dt><code>EVFLAG_AUTO</code></dt> 265 <dt><code>EVFLAG_AUTO</code></dt>
194 <dd> 266 <dd>
195 <p>The default flags value. Use this if you have no clue (it's the right 267 <p>The default flags value. Use this if you have no clue (it's the right
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228 <p>While stopping and starting an I/O watcher in the same iteration will 300 <p>While stopping and starting an I/O watcher in the same iteration will
229result in some caching, there is still a syscall per such incident 301result in some caching, there is still a syscall per such incident
230(because the fd could point to a different file description now), so its 302(because the fd could point to a different file description now), so its
231best to avoid that. Also, dup()ed file descriptors might not work very 303best to avoid that. Also, dup()ed file descriptors might not work very
232well if you register events for both fds.</p> 304well if you register events for both fds.</p>
305 <p>Please note that epoll sometimes generates spurious notifications, so you
306need to use non-blocking I/O or other means to avoid blocking when no data
307(or space) is available.</p>
233 </dd> 308 </dd>
234 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt> 309 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
235 <dd> 310 <dd>
236 <p>Kqueue deserves special mention, as at the time of this writing, it 311 <p>Kqueue deserves special mention, as at the time of this writing, it
237was broken on all BSDs except NetBSD (usually it doesn't work with 312was broken on all BSDs except NetBSD (usually it doesn't work with
238anything but sockets and pipes, except on Darwin, where of course its 313anything but sockets and pipes, except on Darwin, where of course its
239completely useless). For this reason its not being &quot;autodetected&quot; unless 314completely useless). For this reason its not being &quot;autodetected&quot;
240you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p> 315unless you explicitly specify it explicitly in the flags (i.e. using
316<code>EVBACKEND_KQUEUE</code>).</p>
241 <p>It scales in the same way as the epoll backend, but the interface to the 317 <p>It scales in the same way as the epoll backend, but the interface to the
242kernel is more efficient (which says nothing about its actual speed, of 318kernel is more efficient (which says nothing about its actual speed, of
243course). While starting and stopping an I/O watcher does not cause an 319course). While starting and stopping an I/O watcher does not cause an
244extra syscall as with epoll, it still adds up to four event changes per 320extra syscall as with epoll, it still adds up to four event changes per
245incident, so its best to avoid that.</p> 321incident, so its best to avoid that.</p>
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250 </dd> 326 </dd>
251 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt> 327 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
252 <dd> 328 <dd>
253 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, 329 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
254it's really slow, but it still scales very well (O(active_fds)).</p> 330it's really slow, but it still scales very well (O(active_fds)).</p>
331 <p>Please note that solaris ports can result in a lot of spurious
332notifications, so you need to use non-blocking I/O or other means to avoid
333blocking when no data (or space) is available.</p>
255 </dd> 334 </dd>
256 <dt><code>EVBACKEND_ALL</code></dt> 335 <dt><code>EVBACKEND_ALL</code></dt>
257 <dd> 336 <dd>
258 <p>Try all backends (even potentially broken ones that wouldn't be tried 337 <p>Try all backends (even potentially broken ones that wouldn't be tried
259with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as 338with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
… …
263 </p> 342 </p>
264 <p>If one or more of these are ored into the flags value, then only these 343 <p>If one or more of these are ored into the flags value, then only these
265backends will be tried (in the reverse order as given here). If none are 344backends will be tried (in the reverse order as given here). If none are
266specified, most compiled-in backend will be tried, usually in reverse 345specified, most compiled-in backend will be tried, usually in reverse
267order of their flag values :)</p> 346order of their flag values :)</p>
347 <p>The most typical usage is like this:</p>
348<pre> if (!ev_default_loop (0))
349 fatal (&quot;could not initialise libev, bad $LIBEV_FLAGS in environment?&quot;);
350
351</pre>
352 <p>Restrict libev to the select and poll backends, and do not allow
353environment settings to be taken into account:</p>
354<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
355
356</pre>
357 <p>Use whatever libev has to offer, but make sure that kqueue is used if
358available (warning, breaks stuff, best use only with your own private
359event loop and only if you know the OS supports your types of fds):</p>
360<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
361
362</pre>
268 </dd> 363 </dd>
269 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 364 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
270 <dd> 365 <dd>
271 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 366 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
272always distinct from the default loop. Unlike the default loop, it cannot 367always distinct from the default loop. Unlike the default loop, it cannot
273handle signal and child watchers, and attempts to do so will be greeted by 368handle signal and child watchers, and attempts to do so will be greeted by
274undefined behaviour (or a failed assertion if assertions are enabled).</p> 369undefined behaviour (or a failed assertion if assertions are enabled).</p>
370 <p>Example: try to create a event loop that uses epoll and nothing else.</p>
371<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
372 if (!epoller)
373 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
374
375</pre>
275 </dd> 376 </dd>
276 <dt>ev_default_destroy ()</dt> 377 <dt>ev_default_destroy ()</dt>
277 <dd> 378 <dd>
278 <p>Destroys the default loop again (frees all memory and kernel state 379 <p>Destroys the default loop again (frees all memory and kernel state
279etc.). This stops all registered event watchers (by not touching them in 380etc.). None of the active event watchers will be stopped in the normal
280any way whatsoever, although you cannot rely on this :).</p> 381sense, so e.g. <code>ev_is_active</code> might still return true. It is your
382responsibility to either stop all watchers cleanly yoursef <i>before</i>
383calling this function, or cope with the fact afterwards (which is usually
384the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
385for example).</p>
281 </dd> 386 </dd>
282 <dt>ev_loop_destroy (loop)</dt> 387 <dt>ev_loop_destroy (loop)</dt>
283 <dd> 388 <dd>
284 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 389 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
285earlier call to <code>ev_loop_new</code>.</p> 390earlier call to <code>ev_loop_new</code>.</p>
… …
315use.</p> 420use.</p>
316 </dd> 421 </dd>
317 <dt>ev_tstamp ev_now (loop)</dt> 422 <dt>ev_tstamp ev_now (loop)</dt>
318 <dd> 423 <dd>
319 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 424 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
320got events and started processing them. This timestamp does not change 425received events and started processing them. This timestamp does not
321as long as callbacks are being processed, and this is also the base time 426change as long as callbacks are being processed, and this is also the base
322used for relative timers. You can treat it as the timestamp of the event 427time used for relative timers. You can treat it as the timestamp of the
323occuring (or more correctly, the mainloop finding out about it).</p> 428event occuring (or more correctly, libev finding out about it).</p>
324 </dd> 429 </dd>
325 <dt>ev_loop (loop, int flags)</dt> 430 <dt>ev_loop (loop, int flags)</dt>
326 <dd> 431 <dd>
327 <p>Finally, this is it, the event handler. This function usually is called 432 <p>Finally, this is it, the event handler. This function usually is called
328after you initialised all your watchers and you want to start handling 433after you initialised all your watchers and you want to start handling
329events.</p> 434events.</p>
330 <p>If the flags argument is specified as 0, it will not return until either 435 <p>If the flags argument is specified as <code>0</code>, it will not return until
331no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 436either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
437 <p>Please note that an explicit <code>ev_unloop</code> is usually better than
438relying on all watchers to be stopped when deciding when a program has
439finished (especially in interactive programs), but having a program that
440automatically loops as long as it has to and no longer by virtue of
441relying on its watchers stopping correctly is a thing of beauty.</p>
332 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 442 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
333those events and any outstanding ones, but will not block your process in 443those events and any outstanding ones, but will not block your process in
334case there are no events and will return after one iteration of the loop.</p> 444case there are no events and will return after one iteration of the loop.</p>
335 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 445 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
336neccessary) and will handle those and any outstanding ones. It will block 446neccessary) and will handle those and any outstanding ones. It will block
337your process until at least one new event arrives, and will return after 447your process until at least one new event arrives, and will return after
338one iteration of the loop.</p> 448one iteration of the loop. This is useful if you are waiting for some
339 <p>This flags value could be used to implement alternative looping 449external event in conjunction with something not expressible using other
340constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 450libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
341more generic mechanism.</p> 451usually a better approach for this kind of thing.</p>
342 <p>Here are the gory details of what ev_loop does:</p> 452 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
343<pre> 1. If there are no active watchers (reference count is zero), return. 453<pre> * If there are no active watchers (reference count is zero), return.
344 2. Queue and immediately call all prepare watchers. 454 - Queue prepare watchers and then call all outstanding watchers.
345 3. If we have been forked, recreate the kernel state. 455 - If we have been forked, recreate the kernel state.
346 4. Update the kernel state with all outstanding changes. 456 - Update the kernel state with all outstanding changes.
347 5. Update the &quot;event loop time&quot;. 457 - Update the &quot;event loop time&quot;.
348 6. Calculate for how long to block. 458 - Calculate for how long to block.
349 7. Block the process, waiting for events. 459 - Block the process, waiting for any events.
460 - Queue all outstanding I/O (fd) events.
350 8. Update the &quot;event loop time&quot; and do time jump handling. 461 - Update the &quot;event loop time&quot; and do time jump handling.
351 9. Queue all outstanding timers. 462 - Queue all outstanding timers.
352 10. Queue all outstanding periodics. 463 - Queue all outstanding periodics.
353 11. If no events are pending now, queue all idle watchers. 464 - If no events are pending now, queue all idle watchers.
354 12. Queue all check watchers. 465 - Queue all check watchers.
355 13. Call all queued watchers in reverse order (i.e. check watchers first). 466 - Call all queued watchers in reverse order (i.e. check watchers first).
467 Signals and child watchers are implemented as I/O watchers, and will
468 be handled here by queueing them when their watcher gets executed.
356 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 469 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
357 was used, return, otherwise continue with step #1. 470 were used, return, otherwise continue with step *.
471
472</pre>
473 <p>Example: queue some jobs and then loop until no events are outsanding
474anymore.</p>
475<pre> ... queue jobs here, make sure they register event watchers as long
476 ... as they still have work to do (even an idle watcher will do..)
477 ev_loop (my_loop, 0);
478 ... jobs done. yeah!
358 479
359</pre> 480</pre>
360 </dd> 481 </dd>
361 <dt>ev_unloop (loop, how)</dt> 482 <dt>ev_unloop (loop, how)</dt>
362 <dd> 483 <dd>
… …
376example, libev itself uses this for its internal signal pipe: It is not 497example, libev itself uses this for its internal signal pipe: It is not
377visible to the libev user and should not keep <code>ev_loop</code> from exiting if 498visible to the libev user and should not keep <code>ev_loop</code> from exiting if
378no event watchers registered by it are active. It is also an excellent 499no event watchers registered by it are active. It is also an excellent
379way to do this for generic recurring timers or from within third-party 500way to do this for generic recurring timers or from within third-party
380libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 501libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
502 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
503running when nothing else is active.</p>
504<pre> struct dv_signal exitsig;
505 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
506 ev_signal_start (myloop, &amp;exitsig);
507 evf_unref (myloop);
508
509</pre>
510 <p>Example: for some weird reason, unregister the above signal handler again.</p>
511<pre> ev_ref (myloop);
512 ev_signal_stop (myloop, &amp;exitsig);
513
514</pre>
381 </dd> 515 </dd>
382</dl> 516</dl>
517
518
519
520
383 521
384</div> 522</div>
385<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 523<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
386<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 524<div id="ANATOMY_OF_A_WATCHER_CONTENT">
387<p>A watcher is a structure that you create and register to record your 525<p>A watcher is a structure that you create and register to record your
… …
417with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 555with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
418*)</code>), and you can stop watching for events at any time by calling the 556*)</code>), and you can stop watching for events at any time by calling the
419corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 557corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
420<p>As long as your watcher is active (has been started but not stopped) you 558<p>As long as your watcher is active (has been started but not stopped) you
421must not touch the values stored in it. Most specifically you must never 559must not touch the values stored in it. Most specifically you must never
422reinitialise it or call its set macro.</p> 560reinitialise it or call its <code>set</code> macro.</p>
423<p>You can check whether an event is active by calling the <code>ev_is_active
424(watcher *)</code> macro. To see whether an event is outstanding (but the
425callback for it has not been called yet) you can use the <code>ev_is_pending
426(watcher *)</code> macro.</p>
427<p>Each and every callback receives the event loop pointer as first, the 561<p>Each and every callback receives the event loop pointer as first, the
428registered watcher structure as second, and a bitset of received events as 562registered watcher structure as second, and a bitset of received events as
429third argument.</p> 563third argument.</p>
430<p>The received events usually include a single bit per event type received 564<p>The received events usually include a single bit per event type received
431(you can receive multiple events at the same time). The possible bit masks 565(you can receive multiple events at the same time). The possible bit masks
… …
451 </dd> 585 </dd>
452 <dt><code>EV_CHILD</code></dt> 586 <dt><code>EV_CHILD</code></dt>
453 <dd> 587 <dd>
454 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 588 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
455 </dd> 589 </dd>
590 <dt><code>EV_STAT</code></dt>
591 <dd>
592 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
593 </dd>
456 <dt><code>EV_IDLE</code></dt> 594 <dt><code>EV_IDLE</code></dt>
457 <dd> 595 <dd>
458 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 596 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
459 </dd> 597 </dd>
460 <dt><code>EV_PREPARE</code></dt> 598 <dt><code>EV_PREPARE</code></dt>
… …
465<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 603<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
466received events. Callbacks of both watcher types can start and stop as 604received events. Callbacks of both watcher types can start and stop as
467many watchers as they want, and all of them will be taken into account 605many watchers as they want, and all of them will be taken into account
468(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 606(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
469<code>ev_loop</code> from blocking).</p> 607<code>ev_loop</code> from blocking).</p>
608 </dd>
609 <dt><code>EV_EMBED</code></dt>
610 <dd>
611 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
612 </dd>
613 <dt><code>EV_FORK</code></dt>
614 <dd>
615 <p>The event loop has been resumed in the child process after fork (see
616<code>ev_fork</code>).</p>
470 </dd> 617 </dd>
471 <dt><code>EV_ERROR</code></dt> 618 <dt><code>EV_ERROR</code></dt>
472 <dd> 619 <dd>
473 <p>An unspecified error has occured, the watcher has been stopped. This might 620 <p>An unspecified error has occured, the watcher has been stopped. This might
474happen because the watcher could not be properly started because libev 621happen because the watcher could not be properly started because libev
… …
480your callbacks is well-written it can just attempt the operation and cope 627your callbacks is well-written it can just attempt the operation and cope
481with the error from read() or write(). This will not work in multithreaded 628with the error from read() or write(). This will not work in multithreaded
482programs, though, so beware.</p> 629programs, though, so beware.</p>
483 </dd> 630 </dd>
484</dl> 631</dl>
632
633</div>
634<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
635<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
636<p>In the following description, <code>TYPE</code> stands for the watcher type,
637e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
638<dl>
639 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
640 <dd>
641 <p>This macro initialises the generic portion of a watcher. The contents
642of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
643the generic parts of the watcher are initialised, you <i>need</i> to call
644the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
645type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
646which rolls both calls into one.</p>
647 <p>You can reinitialise a watcher at any time as long as it has been stopped
648(or never started) and there are no pending events outstanding.</p>
649 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
650int revents)</code>.</p>
651 </dd>
652 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
653 <dd>
654 <p>This macro initialises the type-specific parts of a watcher. You need to
655call <code>ev_init</code> at least once before you call this macro, but you can
656call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
657macro on a watcher that is active (it can be pending, however, which is a
658difference to the <code>ev_init</code> macro).</p>
659 <p>Although some watcher types do not have type-specific arguments
660(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
661 </dd>
662 <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
663 <dd>
664 <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
665calls into a single call. This is the most convinient method to initialise
666a watcher. The same limitations apply, of course.</p>
667 </dd>
668 <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
669 <dd>
670 <p>Starts (activates) the given watcher. Only active watchers will receive
671events. If the watcher is already active nothing will happen.</p>
672 </dd>
673 <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
674 <dd>
675 <p>Stops the given watcher again (if active) and clears the pending
676status. It is possible that stopped watchers are pending (for example,
677non-repeating timers are being stopped when they become pending), but
678<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
679you want to free or reuse the memory used by the watcher it is therefore a
680good idea to always call its <code>ev_TYPE_stop</code> function.</p>
681 </dd>
682 <dt>bool ev_is_active (ev_TYPE *watcher)</dt>
683 <dd>
684 <p>Returns a true value iff the watcher is active (i.e. it has been started
685and not yet been stopped). As long as a watcher is active you must not modify
686it.</p>
687 </dd>
688 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
689 <dd>
690 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
691events but its callback has not yet been invoked). As long as a watcher
692is pending (but not active) you must not call an init function on it (but
693<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
694libev (e.g. you cnanot <code>free ()</code> it).</p>
695 </dd>
696 <dt>callback = ev_cb (ev_TYPE *watcher)</dt>
697 <dd>
698 <p>Returns the callback currently set on the watcher.</p>
699 </dd>
700 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
701 <dd>
702 <p>Change the callback. You can change the callback at virtually any time
703(modulo threads).</p>
704 </dd>
705</dl>
706
707
708
709
485 710
486</div> 711</div>
487<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 712<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
488<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 713<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
489<p>Each watcher has, by default, a member <code>void *data</code> that you can change 714<p>Each watcher has, by default, a member <code>void *data</code> that you can change
… …
519 744
520</div> 745</div>
521<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 746<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
522<div id="WATCHER_TYPES_CONTENT"> 747<div id="WATCHER_TYPES_CONTENT">
523<p>This section describes each watcher in detail, but will not repeat 748<p>This section describes each watcher in detail, but will not repeat
524information given in the last section.</p> 749information given in the last section. Any initialisation/set macros,
750functions and members specific to the watcher type are explained.</p>
751<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
752while the watcher is active, you can look at the member and expect some
753sensible content, but you must not modify it (you can modify it while the
754watcher is stopped to your hearts content), or <i>[read-write]</i>, which
755means you can expect it to have some sensible content while the watcher
756is active, but you can also modify it. Modifying it may not do something
757sensible or take immediate effect (or do anything at all), but libev will
758not crash or malfunction in any way.</p>
525 759
760
761
762
763
526</div> 764</div>
527<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 765<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
528<div id="code_ev_io_code_is_this_file_descrip-2"> 766<div id="code_ev_io_code_is_this_file_descrip-2">
529<p>I/O watchers check whether a file descriptor is readable or writable 767<p>I/O watchers check whether a file descriptor is readable or writable
530in each iteration of the event loop (This behaviour is called 768in each iteration of the event loop, or, more precisely, when reading
531level-triggering because you keep receiving events as long as the 769would not block the process and writing would at least be able to write
532condition persists. Remember you can stop the watcher if you don't want to 770some data. This behaviour is called level-triggering because you keep
533act on the event and neither want to receive future events).</p> 771receiving events as long as the condition persists. Remember you can stop
772the watcher if you don't want to act on the event and neither want to
773receive future events.</p>
534<p>In general you can register as many read and/or write event watchers per 774<p>In general you can register as many read and/or write event watchers per
535fd as you want (as long as you don't confuse yourself). Setting all file 775fd as you want (as long as you don't confuse yourself). Setting all file
536descriptors to non-blocking mode is also usually a good idea (but not 776descriptors to non-blocking mode is also usually a good idea (but not
537required if you know what you are doing).</p> 777required if you know what you are doing).</p>
538<p>You have to be careful with dup'ed file descriptors, though. Some backends 778<p>You have to be careful with dup'ed file descriptors, though. Some backends
539(the linux epoll backend is a notable example) cannot handle dup'ed file 779(the linux epoll backend is a notable example) cannot handle dup'ed file
540descriptors correctly if you register interest in two or more fds pointing 780descriptors correctly if you register interest in two or more fds pointing
541to the same underlying file/socket etc. description (that is, they share 781to the same underlying file/socket/etc. description (that is, they share
542the same underlying &quot;file open&quot;).</p> 782the same underlying &quot;file open&quot;).</p>
543<p>If you must do this, then force the use of a known-to-be-good backend 783<p>If you must do this, then force the use of a known-to-be-good backend
544(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and 784(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
545<code>EVBACKEND_POLL</code>).</p> 785<code>EVBACKEND_POLL</code>).</p>
786<p>Another thing you have to watch out for is that it is quite easy to
787receive &quot;spurious&quot; readyness notifications, that is your callback might
788be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
789because there is no data. Not only are some backends known to create a
790lot of those (for example solaris ports), it is very easy to get into
791this situation even with a relatively standard program structure. Thus
792it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
793<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
794<p>If you cannot run the fd in non-blocking mode (for example you should not
795play around with an Xlib connection), then you have to seperately re-test
796wether a file descriptor is really ready with a known-to-be good interface
797such as poll (fortunately in our Xlib example, Xlib already does this on
798its own, so its quite safe to use).</p>
546<dl> 799<dl>
547 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 800 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
548 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 801 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
549 <dd> 802 <dd>
550 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 803 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
551events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 804rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
552EV_WRITE</code> to receive the given events.</p> 805<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
806 </dd>
807 <dt>int fd [read-only]</dt>
808 <dd>
809 <p>The file descriptor being watched.</p>
810 </dd>
811 <dt>int events [read-only]</dt>
812 <dd>
813 <p>The events being watched.</p>
553 </dd> 814 </dd>
554</dl> 815</dl>
816<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
817readable, but only once. Since it is likely line-buffered, you could
818attempt to read a whole line in the callback:</p>
819<pre> static void
820 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
821 {
822 ev_io_stop (loop, w);
823 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
824 }
555 825
826 ...
827 struct ev_loop *loop = ev_default_init (0);
828 struct ev_io stdin_readable;
829 ev_io_init (&amp;stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
830 ev_io_start (loop, &amp;stdin_readable);
831 ev_loop (loop, 0);
832
833
834
835
836</pre>
837
556</div> 838</div>
557<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 839<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
558<div id="code_ev_timer_code_relative_and_opti-2"> 840<div id="code_ev_timer_code_relative_and_opti-2">
559<p>Timer watchers are simple relative timers that generate an event after a 841<p>Timer watchers are simple relative timers that generate an event after a
560given time, and optionally repeating in regular intervals after that.</p> 842given time, and optionally repeating in regular intervals after that.</p>
561<p>The timers are based on real time, that is, if you register an event that 843<p>The timers are based on real time, that is, if you register an event that
562times out after an hour and you reset your system clock to last years 844times out after an hour and you reset your system clock to last years
… …
594repeating. The exact semantics are:</p> 876repeating. The exact semantics are:</p>
595 <p>If the timer is started but nonrepeating, stop it.</p> 877 <p>If the timer is started but nonrepeating, stop it.</p>
596 <p>If the timer is repeating, either start it if necessary (with the repeat 878 <p>If the timer is repeating, either start it if necessary (with the repeat
597value), or reset the running timer to the repeat value.</p> 879value), or reset the running timer to the repeat value.</p>
598 <p>This sounds a bit complicated, but here is a useful and typical 880 <p>This sounds a bit complicated, but here is a useful and typical
599example: Imagine you have a tcp connection and you want a so-called idle 881example: Imagine you have a tcp connection and you want a so-called
600timeout, that is, you want to be called when there have been, say, 60 882idle timeout, that is, you want to be called when there have been,
601seconds of inactivity on the socket. The easiest way to do this is to 883say, 60 seconds of inactivity on the socket. The easiest way to do
602configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 884this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
603time you successfully read or write some data. If you go into an idle 885<code>ev_timer_again</code> each time you successfully read or write some data. If
604state where you do not expect data to travel on the socket, you can stop 886you go into an idle state where you do not expect data to travel on the
605the timer, and again will automatically restart it if need be.</p> 887socket, you can stop the timer, and again will automatically restart it if
888need be.</p>
889 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
890and only ever use the <code>repeat</code> value:</p>
891<pre> ev_timer_init (timer, callback, 0., 5.);
892 ev_timer_again (loop, timer);
893 ...
894 timer-&gt;again = 17.;
895 ev_timer_again (loop, timer);
896 ...
897 timer-&gt;again = 10.;
898 ev_timer_again (loop, timer);
899
900</pre>
901 <p>This is more efficient then stopping/starting the timer eahc time you want
902to modify its timeout value.</p>
903 </dd>
904 <dt>ev_tstamp repeat [read-write]</dt>
905 <dd>
906 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
907or <code>ev_timer_again</code> is called and determines the next timeout (if any),
908which is also when any modifications are taken into account.</p>
606 </dd> 909 </dd>
607</dl> 910</dl>
911<p>Example: create a timer that fires after 60 seconds.</p>
912<pre> static void
913 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
914 {
915 .. one minute over, w is actually stopped right here
916 }
608 917
918 struct ev_timer mytimer;
919 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
920 ev_timer_start (loop, &amp;mytimer);
921
922</pre>
923<p>Example: create a timeout timer that times out after 10 seconds of
924inactivity.</p>
925<pre> static void
926 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
927 {
928 .. ten seconds without any activity
929 }
930
931 struct ev_timer mytimer;
932 ev_timer_init (&amp;mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
933 ev_timer_again (&amp;mytimer); /* start timer */
934 ev_loop (loop, 0);
935
936 // and in some piece of code that gets executed on any &quot;activity&quot;:
937 // reset the timeout to start ticking again at 10 seconds
938 ev_timer_again (&amp;mytimer);
939
940
941
942
943</pre>
944
609</div> 945</div>
610<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 946<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
611<div id="code_ev_periodic_code_to_cron_or_not-2"> 947<div id="code_ev_periodic_code_to_cron_or_not-2">
612<p>Periodic watchers are also timers of a kind, but they are very versatile 948<p>Periodic watchers are also timers of a kind, but they are very versatile
613(and unfortunately a bit complex).</p> 949(and unfortunately a bit complex).</p>
614<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 950<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
615but on wallclock time (absolute time). You can tell a periodic watcher 951but on wallclock time (absolute time). You can tell a periodic watcher
616to trigger &quot;at&quot; some specific point in time. For example, if you tell a 952to trigger &quot;at&quot; some specific point in time. For example, if you tell a
617periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 953periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
618+ 10.&gt;) and then reset your system clock to the last year, then it will 954+ 10.</code>) and then reset your system clock to the last year, then it will
619take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 955take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
620roughly 10 seconds later and of course not if you reset your system time 956roughly 10 seconds later and of course not if you reset your system time
621again).</p> 957again).</p>
622<p>They can also be used to implement vastly more complex timers, such as 958<p>They can also be used to implement vastly more complex timers, such as
623triggering an event on eahc midnight, local time.</p> 959triggering an event on eahc midnight, local time.</p>
… …
695 <p>Simply stops and restarts the periodic watcher again. This is only useful 1031 <p>Simply stops and restarts the periodic watcher again. This is only useful
696when you changed some parameters or the reschedule callback would return 1032when you changed some parameters or the reschedule callback would return
697a different time than the last time it was called (e.g. in a crond like 1033a different time than the last time it was called (e.g. in a crond like
698program when the crontabs have changed).</p> 1034program when the crontabs have changed).</p>
699 </dd> 1035 </dd>
1036 <dt>ev_tstamp interval [read-write]</dt>
1037 <dd>
1038 <p>The current interval value. Can be modified any time, but changes only
1039take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1040called.</p>
1041 </dd>
1042 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1043 <dd>
1044 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1045switched off. Can be changed any time, but changes only take effect when
1046the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1047 </dd>
700</dl> 1048</dl>
1049<p>Example: call a callback every hour, or, more precisely, whenever the
1050system clock is divisible by 3600. The callback invocation times have
1051potentially a lot of jittering, but good long-term stability.</p>
1052<pre> static void
1053 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1054 {
1055 ... its now a full hour (UTC, or TAI or whatever your clock follows)
1056 }
701 1057
1058 struct ev_periodic hourly_tick;
1059 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
1060 ev_periodic_start (loop, &amp;hourly_tick);
1061
1062</pre>
1063<p>Example: the same as above, but use a reschedule callback to do it:</p>
1064<pre> #include &lt;math.h&gt;
1065
1066 static ev_tstamp
1067 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1068 {
1069 return fmod (now, 3600.) + 3600.;
1070 }
1071
1072 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1073
1074</pre>
1075<p>Example: call a callback every hour, starting now:</p>
1076<pre> struct ev_periodic hourly_tick;
1077 ev_periodic_init (&amp;hourly_tick, clock_cb,
1078 fmod (ev_now (loop), 3600.), 3600., 0);
1079 ev_periodic_start (loop, &amp;hourly_tick);
1080
1081
1082
1083
1084</pre>
1085
702</div> 1086</div>
703<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1087<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
704<div id="code_ev_signal_code_signal_me_when_a-2"> 1088<div id="code_ev_signal_code_signal_me_when_a-2">
705<p>Signal watchers will trigger an event when the process receives a specific 1089<p>Signal watchers will trigger an event when the process receives a specific
706signal one or more times. Even though signals are very asynchronous, libev 1090signal one or more times. Even though signals are very asynchronous, libev
707will try it's best to deliver signals synchronously, i.e. as part of the 1091will try it's best to deliver signals synchronously, i.e. as part of the
708normal event processing, like any other event.</p> 1092normal event processing, like any other event.</p>
… …
717 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1101 <dt>ev_signal_set (ev_signal *, int signum)</dt>
718 <dd> 1102 <dd>
719 <p>Configures the watcher to trigger on the given signal number (usually one 1103 <p>Configures the watcher to trigger on the given signal number (usually one
720of the <code>SIGxxx</code> constants).</p> 1104of the <code>SIGxxx</code> constants).</p>
721 </dd> 1105 </dd>
1106 <dt>int signum [read-only]</dt>
1107 <dd>
1108 <p>The signal the watcher watches out for.</p>
1109 </dd>
722</dl> 1110</dl>
723 1111
1112
1113
1114
1115
724</div> 1116</div>
725<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1117<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
726<div id="code_ev_child_code_wait_for_pid_stat-2"> 1118<div id="code_ev_child_code_watch_out_for_pro-2">
727<p>Child watchers trigger when your process receives a SIGCHLD in response to 1119<p>Child watchers trigger when your process receives a SIGCHLD in response to
728some child status changes (most typically when a child of yours dies).</p> 1120some child status changes (most typically when a child of yours dies).</p>
729<dl> 1121<dl>
730 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1122 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
731 <dt>ev_child_set (ev_child *, int pid)</dt> 1123 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
735at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1127at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
736the status word (use the macros from <code>sys/wait.h</code> and see your systems 1128the status word (use the macros from <code>sys/wait.h</code> and see your systems
737<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1129<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
738process causing the status change.</p> 1130process causing the status change.</p>
739 </dd> 1131 </dd>
1132 <dt>int pid [read-only]</dt>
1133 <dd>
1134 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1135 </dd>
1136 <dt>int rpid [read-write]</dt>
1137 <dd>
1138 <p>The process id that detected a status change.</p>
1139 </dd>
1140 <dt>int rstatus [read-write]</dt>
1141 <dd>
1142 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1143<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1144 </dd>
740</dl> 1145</dl>
1146<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
1147<pre> static void
1148 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1149 {
1150 ev_unloop (loop, EVUNLOOP_ALL);
1151 }
741 1152
1153 struct ev_signal signal_watcher;
1154 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
1155 ev_signal_start (loop, &amp;sigint_cb);
1156
1157
1158
1159
1160</pre>
1161
742</div> 1162</div>
1163<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1164<div id="code_ev_stat_code_did_the_file_attri-2">
1165<p>This watches a filesystem path for attribute changes. That is, it calls
1166<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1167compared to the last time, invoking the callback if it did.</p>
1168<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1169not exist&quot; is a status change like any other. The condition &quot;path does
1170not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1171otherwise always forced to be at least one) and all the other fields of
1172the stat buffer having unspecified contents.</p>
1173<p>Since there is no standard to do this, the portable implementation simply
1174calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You
1175can specify a recommended polling interval for this case. If you specify
1176a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1177unspecified default</i> value will be used (which you can expect to be around
1178five seconds, although this might change dynamically). Libev will also
1179impose a minimum interval which is currently around <code>0.1</code>, but thats
1180usually overkill.</p>
1181<p>This watcher type is not meant for massive numbers of stat watchers,
1182as even with OS-supported change notifications, this can be
1183resource-intensive.</p>
1184<p>At the time of this writing, no specific OS backends are implemented, but
1185if demand increases, at least a kqueue and inotify backend will be added.</p>
1186<dl>
1187 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1188 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1189 <dd>
1190 <p>Configures the watcher to wait for status changes of the given
1191<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1192be detected and should normally be specified as <code>0</code> to let libev choose
1193a suitable value. The memory pointed to by <code>path</code> must point to the same
1194path for as long as the watcher is active.</p>
1195 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1196relative to the attributes at the time the watcher was started (or the
1197last change was detected).</p>
1198 </dd>
1199 <dt>ev_stat_stat (ev_stat *)</dt>
1200 <dd>
1201 <p>Updates the stat buffer immediately with new values. If you change the
1202watched path in your callback, you could call this fucntion to avoid
1203detecting this change (while introducing a race condition). Can also be
1204useful simply to find out the new values.</p>
1205 </dd>
1206 <dt>ev_statdata attr [read-only]</dt>
1207 <dd>
1208 <p>The most-recently detected attributes of the file. Although the type is of
1209<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1210suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1211was some error while <code>stat</code>ing the file.</p>
1212 </dd>
1213 <dt>ev_statdata prev [read-only]</dt>
1214 <dd>
1215 <p>The previous attributes of the file. The callback gets invoked whenever
1216<code>prev</code> != <code>attr</code>.</p>
1217 </dd>
1218 <dt>ev_tstamp interval [read-only]</dt>
1219 <dd>
1220 <p>The specified interval.</p>
1221 </dd>
1222 <dt>const char *path [read-only]</dt>
1223 <dd>
1224 <p>The filesystem path that is being watched.</p>
1225 </dd>
1226</dl>
1227<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1228<pre> static void
1229 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1230 {
1231 /* /etc/passwd changed in some way */
1232 if (w-&gt;attr.st_nlink)
1233 {
1234 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1235 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1236 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1237 }
1238 else
1239 /* you shalt not abuse printf for puts */
1240 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1241 &quot;if this is windows, they already arrived\n&quot;);
1242 }
1243
1244 ...
1245 ev_stat passwd;
1246
1247 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1248 ev_stat_start (loop, &amp;passwd);
1249
1250
1251
1252
1253</pre>
1254
1255</div>
743<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1256<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
744<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1257<div id="code_ev_idle_code_when_you_ve_got_no-2">
745<p>Idle watchers trigger events when there are no other events are pending 1258<p>Idle watchers trigger events when there are no other events are pending
746(prepare, check and other idle watchers do not count). That is, as long 1259(prepare, check and other idle watchers do not count). That is, as long
747as your process is busy handling sockets or timeouts (or even signals, 1260as your process is busy handling sockets or timeouts (or even signals,
748imagine) it will not be triggered. But when your process is idle all idle 1261imagine) it will not be triggered. But when your process is idle all idle
… …
761 <p>Initialises and configures the idle watcher - it has no parameters of any 1274 <p>Initialises and configures the idle watcher - it has no parameters of any
762kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1275kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
763believe me.</p> 1276believe me.</p>
764 </dd> 1277 </dd>
765</dl> 1278</dl>
1279<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
1280callback, free it. Alos, use no error checking, as usual.</p>
1281<pre> static void
1282 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1283 {
1284 free (w);
1285 // now do something you wanted to do when the program has
1286 // no longer asnything immediate to do.
1287 }
766 1288
1289 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1290 ev_idle_init (idle_watcher, idle_cb);
1291 ev_idle_start (loop, idle_cb);
1292
1293
1294
1295
1296</pre>
1297
767</div> 1298</div>
768<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1299<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
769<div id="code_ev_prepare_code_and_code_ev_che-2"> 1300<div id="code_ev_prepare_code_and_code_ev_che-2">
770<p>Prepare and check watchers are usually (but not always) used in tandem: 1301<p>Prepare and check watchers are usually (but not always) used in tandem:
771prepare watchers get invoked before the process blocks and check watchers 1302prepare watchers get invoked before the process blocks and check watchers
772afterwards.</p> 1303afterwards.</p>
1304<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1305the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1306watchers. Other loops than the current one are fine, however. The
1307rationale behind this is that you do not need to check for recursion in
1308those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1309<code>ev_check</code> so if you have one watcher of each kind they will always be
1310called in pairs bracketing the blocking call.</p>
773<p>Their main purpose is to integrate other event mechanisms into libev. This 1311<p>Their main purpose is to integrate other event mechanisms into libev and
774could be used, for example, to track variable changes, implement your own 1312their use is somewhat advanced. This could be used, for example, to track
775watchers, integrate net-snmp or a coroutine library and lots more.</p> 1313variable changes, implement your own watchers, integrate net-snmp or a
1314coroutine library and lots more. They are also occasionally useful if
1315you cache some data and want to flush it before blocking (for example,
1316in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1317watcher).</p>
776<p>This is done by examining in each prepare call which file descriptors need 1318<p>This is done by examining in each prepare call which file descriptors need
777to be watched by the other library, registering <code>ev_io</code> watchers for 1319to be watched by the other library, registering <code>ev_io</code> watchers for
778them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1320them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
779provide just this functionality). Then, in the check watcher you check for 1321provide just this functionality). Then, in the check watcher you check for
780any events that occured (by checking the pending status of all watchers 1322any events that occured (by checking the pending status of all watchers
… …
796 <p>Initialises and configures the prepare or check watcher - they have no 1338 <p>Initialises and configures the prepare or check watcher - they have no
797parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1339parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
798macros, but using them is utterly, utterly and completely pointless.</p> 1340macros, but using them is utterly, utterly and completely pointless.</p>
799 </dd> 1341 </dd>
800</dl> 1342</dl>
1343<p>Example: To include a library such as adns, you would add IO watchers
1344and a timeout watcher in a prepare handler, as required by libadns, and
1345in a check watcher, destroy them and call into libadns. What follows is
1346pseudo-code only of course:</p>
1347<pre> static ev_io iow [nfd];
1348 static ev_timer tw;
1349
1350 static void
1351 io_cb (ev_loop *loop, ev_io *w, int revents)
1352 {
1353 // set the relevant poll flags
1354 // could also call adns_processreadable etc. here
1355 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1356 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1357 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1358 }
1359
1360 // create io watchers for each fd and a timer before blocking
1361 static void
1362 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1363 {
1364 int timeout = 3600000;truct pollfd fds [nfd];
1365 // actual code will need to loop here and realloc etc.
1366 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1367
1368 /* the callback is illegal, but won't be called as we stop during check */
1369 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1370 ev_timer_start (loop, &amp;tw);
1371
1372 // create on ev_io per pollfd
1373 for (int i = 0; i &lt; nfd; ++i)
1374 {
1375 ev_io_init (iow + i, io_cb, fds [i].fd,
1376 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1377 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1378
1379 fds [i].revents = 0;
1380 iow [i].data = fds + i;
1381 ev_io_start (loop, iow + i);
1382 }
1383 }
1384
1385 // stop all watchers after blocking
1386 static void
1387 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1388 {
1389 ev_timer_stop (loop, &amp;tw);
1390
1391 for (int i = 0; i &lt; nfd; ++i)
1392 ev_io_stop (loop, iow + i);
1393
1394 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1395 }
1396
1397
1398
1399
1400</pre>
1401
1402</div>
1403<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1404<div id="code_ev_embed_code_when_one_backend_-2">
1405<p>This is a rather advanced watcher type that lets you embed one event loop
1406into another (currently only <code>ev_io</code> events are supported in the embedded
1407loop, other types of watchers might be handled in a delayed or incorrect
1408fashion and must not be used).</p>
1409<p>There are primarily two reasons you would want that: work around bugs and
1410prioritise I/O.</p>
1411<p>As an example for a bug workaround, the kqueue backend might only support
1412sockets on some platform, so it is unusable as generic backend, but you
1413still want to make use of it because you have many sockets and it scales
1414so nicely. In this case, you would create a kqueue-based loop and embed it
1415into your default loop (which might use e.g. poll). Overall operation will
1416be a bit slower because first libev has to poll and then call kevent, but
1417at least you can use both at what they are best.</p>
1418<p>As for prioritising I/O: rarely you have the case where some fds have
1419to be watched and handled very quickly (with low latency), and even
1420priorities and idle watchers might have too much overhead. In this case
1421you would put all the high priority stuff in one loop and all the rest in
1422a second one, and embed the second one in the first.</p>
1423<p>As long as the watcher is active, the callback will be invoked every time
1424there might be events pending in the embedded loop. The callback must then
1425call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1426their callbacks (you could also start an idle watcher to give the embedded
1427loop strictly lower priority for example). You can also set the callback
1428to <code>0</code>, in which case the embed watcher will automatically execute the
1429embedded loop sweep.</p>
1430<p>As long as the watcher is started it will automatically handle events. The
1431callback will be invoked whenever some events have been handled. You can
1432set the callback to <code>0</code> to avoid having to specify one if you are not
1433interested in that.</p>
1434<p>Also, there have not currently been made special provisions for forking:
1435when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
1436but you will also have to stop and restart any <code>ev_embed</code> watchers
1437yourself.</p>
1438<p>Unfortunately, not all backends are embeddable, only the ones returned by
1439<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
1440portable one.</p>
1441<p>So when you want to use this feature you will always have to be prepared
1442that you cannot get an embeddable loop. The recommended way to get around
1443this is to have a separate variables for your embeddable loop, try to
1444create it, and if that fails, use the normal loop for everything:</p>
1445<pre> struct ev_loop *loop_hi = ev_default_init (0);
1446 struct ev_loop *loop_lo = 0;
1447 struct ev_embed embed;
1448
1449 // see if there is a chance of getting one that works
1450 // (remember that a flags value of 0 means autodetection)
1451 loop_lo = ev_embeddable_backends () &amp; ev_recommended_backends ()
1452 ? ev_loop_new (ev_embeddable_backends () &amp; ev_recommended_backends ())
1453 : 0;
1454
1455 // if we got one, then embed it, otherwise default to loop_hi
1456 if (loop_lo)
1457 {
1458 ev_embed_init (&amp;embed, 0, loop_lo);
1459 ev_embed_start (loop_hi, &amp;embed);
1460 }
1461 else
1462 loop_lo = loop_hi;
1463
1464</pre>
1465<dl>
1466 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1467 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1468 <dd>
1469 <p>Configures the watcher to embed the given loop, which must be
1470embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1471invoked automatically, otherwise it is the responsibility of the callback
1472to invoke it (it will continue to be called until the sweep has been done,
1473if you do not want thta, you need to temporarily stop the embed watcher).</p>
1474 </dd>
1475 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1476 <dd>
1477 <p>Make a single, non-blocking sweep over the embedded loop. This works
1478similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1479apropriate way for embedded loops.</p>
1480 </dd>
1481 <dt>struct ev_loop *loop [read-only]</dt>
1482 <dd>
1483 <p>The embedded event loop.</p>
1484 </dd>
1485</dl>
1486
1487
1488
1489
1490
1491</div>
1492<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
1493<div id="code_ev_fork_code_the_audacity_to_re-2">
1494<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1495whoever is a good citizen cared to tell libev about it by calling
1496<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1497event loop blocks next and before <code>ev_check</code> watchers are being called,
1498and only in the child after the fork. If whoever good citizen calling
1499<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1500handlers will be invoked, too, of course.</p>
1501<dl>
1502 <dt>ev_fork_init (ev_signal *, callback)</dt>
1503 <dd>
1504 <p>Initialises and configures the fork watcher - it has no parameters of any
1505kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1506believe me.</p>
1507 </dd>
1508</dl>
1509
1510
1511
1512
801 1513
802</div> 1514</div>
803<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1515<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
804<div id="OTHER_FUNCTIONS_CONTENT"> 1516<div id="OTHER_FUNCTIONS_CONTENT">
805<p>There are some other functions of possible interest. Described. Here. Now.</p> 1517<p>There are some other functions of possible interest. Described. Here. Now.</p>
… …
832 1544
833 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1545 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
834 1546
835</pre> 1547</pre>
836 </dd> 1548 </dd>
837 <dt>ev_feed_event (loop, watcher, int events)</dt> 1549 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
838 <dd> 1550 <dd>
839 <p>Feeds the given event set into the event loop, as if the specified event 1551 <p>Feeds the given event set into the event loop, as if the specified event
840had happened for the specified watcher (which must be a pointer to an 1552had happened for the specified watcher (which must be a pointer to an
841initialised but not necessarily started event watcher).</p> 1553initialised but not necessarily started event watcher).</p>
842 </dd> 1554 </dd>
843 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1555 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
844 <dd> 1556 <dd>
845 <p>Feed an event on the given fd, as if a file descriptor backend detected 1557 <p>Feed an event on the given fd, as if a file descriptor backend detected
846the given events it.</p> 1558the given events it.</p>
847 </dd> 1559 </dd>
848 <dt>ev_feed_signal_event (loop, int signum)</dt> 1560 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
849 <dd> 1561 <dd>
850 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1562 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1563loop!).</p>
851 </dd> 1564 </dd>
852</dl> 1565</dl>
1566
1567
1568
1569
853 1570
854</div> 1571</div>
855<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1572<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
856<div id="LIBEVENT_EMULATION_CONTENT"> 1573<div id="LIBEVENT_EMULATION_CONTENT">
857<p>Libev offers a compatibility emulation layer for libevent. It cannot 1574<p>Libev offers a compatibility emulation layer for libevent. It cannot
… …
872</dl> 1589</dl>
873 1590
874</div> 1591</div>
875<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1592<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
876<div id="C_SUPPORT_CONTENT"> 1593<div id="C_SUPPORT_CONTENT">
877<p>TBD.</p> 1594<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1595you to use some convinience methods to start/stop watchers and also change
1596the callback model to a model using method callbacks on objects.</p>
1597<p>To use it,</p>
1598<pre> #include &lt;ev++.h&gt;
1599
1600</pre>
1601<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1602and puts all of its definitions (many of them macros) into the global
1603namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1604<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1605<code>EV_MULTIPLICITY</code>.</p>
1606<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1607<dl>
1608 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1609 <dd>
1610 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1611macros from <cite>ev.h</cite>.</p>
1612 </dd>
1613 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1614 <dd>
1615 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1616 </dd>
1617 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1618 <dd>
1619 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1620the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1621which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1622defines by many implementations.</p>
1623 <p>All of those classes have these methods:</p>
1624 <p>
1625 <dl>
1626 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1627 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1628 <dt>ev::TYPE::~TYPE</dt>
1629 <dd>
1630 <p>The constructor takes a pointer to an object and a method pointer to
1631the event handler callback to call in this class. The constructor calls
1632<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1633before starting it. If you do not specify a loop then the constructor
1634automatically associates the default loop with this watcher.</p>
1635 <p>The destructor automatically stops the watcher if it is active.</p>
1636 </dd>
1637 <dt>w-&gt;set (struct ev_loop *)</dt>
1638 <dd>
1639 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1640do this when the watcher is inactive (and not pending either).</p>
1641 </dd>
1642 <dt>w-&gt;set ([args])</dt>
1643 <dd>
1644 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1645called at least once. Unlike the C counterpart, an active watcher gets
1646automatically stopped and restarted.</p>
1647 </dd>
1648 <dt>w-&gt;start ()</dt>
1649 <dd>
1650 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1651constructor already takes the loop.</p>
1652 </dd>
1653 <dt>w-&gt;stop ()</dt>
1654 <dd>
1655 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1656 </dd>
1657 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1658 <dd>
1659 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1660<code>ev_TYPE_again</code> function.</p>
1661 </dd>
1662 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1663 <dd>
1664 <p>Invokes <code>ev_embed_sweep</code>.</p>
1665 </dd>
1666 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1667 <dd>
1668 <p>Invokes <code>ev_stat_stat</code>.</p>
1669 </dd>
1670 </dl>
1671 </p>
1672 </dd>
1673</dl>
1674<p>Example: Define a class with an IO and idle watcher, start one of them in
1675the constructor.</p>
1676<pre> class myclass
1677 {
1678 ev_io io; void io_cb (ev::io &amp;w, int revents);
1679 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1680
1681 myclass ();
1682 }
1683
1684 myclass::myclass (int fd)
1685 : io (this, &amp;myclass::io_cb),
1686 idle (this, &amp;myclass::idle_cb)
1687 {
1688 io.start (fd, ev::READ);
1689 }
1690
1691
1692
1693
1694</pre>
1695
1696</div>
1697<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p>
1698<div id="MACRO_MAGIC_CONTENT">
1699<p>Libev can be compiled with a variety of options, the most fundemantal is
1700<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1701callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1702<p>To make it easier to write programs that cope with either variant, the
1703following macros are defined:</p>
1704<dl>
1705 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1706 <dd>
1707 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1708loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1709<code>EV_A_</code> is used when other arguments are following. Example:</p>
1710<pre> ev_unref (EV_A);
1711 ev_timer_add (EV_A_ watcher);
1712 ev_loop (EV_A_ 0);
1713
1714</pre>
1715 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1716which is often provided by the following macro.</p>
1717 </dd>
1718 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1719 <dd>
1720 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1721loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1722<code>EV_P_</code> is used when other parameters are following. Example:</p>
1723<pre> // this is how ev_unref is being declared
1724 static void ev_unref (EV_P);
1725
1726 // this is how you can declare your typical callback
1727 static void cb (EV_P_ ev_timer *w, int revents)
1728
1729</pre>
1730 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1731suitable for use with <code>EV_A</code>.</p>
1732 </dd>
1733 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1734 <dd>
1735 <p>Similar to the other two macros, this gives you the value of the default
1736loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1737 </dd>
1738</dl>
1739<p>Example: Declare and initialise a check watcher, working regardless of
1740wether multiple loops are supported or not.</p>
1741<pre> static void
1742 check_cb (EV_P_ ev_timer *w, int revents)
1743 {
1744 ev_check_stop (EV_A_ w);
1745 }
1746
1747 ev_check check;
1748 ev_check_init (&amp;check, check_cb);
1749 ev_check_start (EV_DEFAULT_ &amp;check);
1750 ev_loop (EV_DEFAULT_ 0);
1751
1752
1753
1754
1755</pre>
1756
1757</div>
1758<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
1759<div id="EMBEDDING_CONTENT">
1760<p>Libev can (and often is) directly embedded into host
1761applications. Examples of applications that embed it include the Deliantra
1762Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1763and rxvt-unicode.</p>
1764<p>The goal is to enable you to just copy the neecssary files into your
1765source directory without having to change even a single line in them, so
1766you can easily upgrade by simply copying (or having a checked-out copy of
1767libev somewhere in your source tree).</p>
1768
1769</div>
1770<h2 id="FILESETS">FILESETS</h2>
1771<div id="FILESETS_CONTENT">
1772<p>Depending on what features you need you need to include one or more sets of files
1773in your app.</p>
1774
1775</div>
1776<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1777<div id="CORE_EVENT_LOOP_CONTENT">
1778<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1779configuration (no autoconf):</p>
1780<pre> #define EV_STANDALONE 1
1781 #include &quot;ev.c&quot;
1782
1783</pre>
1784<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1785single C source file only to provide the function implementations. To use
1786it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1787done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1788where you can put other configuration options):</p>
1789<pre> #define EV_STANDALONE 1
1790 #include &quot;ev.h&quot;
1791
1792</pre>
1793<p>Both header files and implementation files can be compiled with a C++
1794compiler (at least, thats a stated goal, and breakage will be treated
1795as a bug).</p>
1796<p>You need the following files in your source tree, or in a directory
1797in your include path (e.g. in libev/ when using -Ilibev):</p>
1798<pre> ev.h
1799 ev.c
1800 ev_vars.h
1801 ev_wrap.h
1802
1803 ev_win32.c required on win32 platforms only
1804
1805 ev_select.c only when select backend is enabled (which is by default)
1806 ev_poll.c only when poll backend is enabled (disabled by default)
1807 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1808 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1809 ev_port.c only when the solaris port backend is enabled (disabled by default)
1810
1811</pre>
1812<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1813to compile this single file.</p>
1814
1815</div>
1816<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1817<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1818<p>To include the libevent compatibility API, also include:</p>
1819<pre> #include &quot;event.c&quot;
1820
1821</pre>
1822<p>in the file including <cite>ev.c</cite>, and:</p>
1823<pre> #include &quot;event.h&quot;
1824
1825</pre>
1826<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1827<p>You need the following additional files for this:</p>
1828<pre> event.h
1829 event.c
1830
1831</pre>
1832
1833</div>
1834<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1835<div id="AUTOCONF_SUPPORT_CONTENT">
1836<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1837whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1838<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1839include <cite>config.h</cite> and configure itself accordingly.</p>
1840<p>For this of course you need the m4 file:</p>
1841<pre> libev.m4
1842
1843</pre>
1844
1845</div>
1846<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1847<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1848<p>Libev can be configured via a variety of preprocessor symbols you have to define
1849before including any of its files. The default is not to build for multiplicity
1850and only include the select backend.</p>
1851<dl>
1852 <dt>EV_STANDALONE</dt>
1853 <dd>
1854 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1855keeps libev from including <cite>config.h</cite>, and it also defines dummy
1856implementations for some libevent functions (such as logging, which is not
1857supported). It will also not define any of the structs usually found in
1858<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1859 </dd>
1860 <dt>EV_USE_MONOTONIC</dt>
1861 <dd>
1862 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1863monotonic clock option at both compiletime and runtime. Otherwise no use
1864of the monotonic clock option will be attempted. If you enable this, you
1865usually have to link against librt or something similar. Enabling it when
1866the functionality isn't available is safe, though, althoguh you have
1867to make sure you link against any libraries where the <code>clock_gettime</code>
1868function is hiding in (often <cite>-lrt</cite>).</p>
1869 </dd>
1870 <dt>EV_USE_REALTIME</dt>
1871 <dd>
1872 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1873realtime clock option at compiletime (and assume its availability at
1874runtime if successful). Otherwise no use of the realtime clock option will
1875be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1876(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1877in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1878 </dd>
1879 <dt>EV_USE_SELECT</dt>
1880 <dd>
1881 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1882<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1883other method takes over, select will be it. Otherwise the select backend
1884will not be compiled in.</p>
1885 </dd>
1886 <dt>EV_SELECT_USE_FD_SET</dt>
1887 <dd>
1888 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1889structure. This is useful if libev doesn't compile due to a missing
1890<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1891exotic systems. This usually limits the range of file descriptors to some
1892low limit such as 1024 or might have other limitations (winsocket only
1893allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1894influence the size of the <code>fd_set</code> used.</p>
1895 </dd>
1896 <dt>EV_SELECT_IS_WINSOCKET</dt>
1897 <dd>
1898 <p>When defined to <code>1</code>, the select backend will assume that
1899select/socket/connect etc. don't understand file descriptors but
1900wants osf handles on win32 (this is the case when the select to
1901be used is the winsock select). This means that it will call
1902<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1903it is assumed that all these functions actually work on fds, even
1904on win32. Should not be defined on non-win32 platforms.</p>
1905 </dd>
1906 <dt>EV_USE_POLL</dt>
1907 <dd>
1908 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1909backend. Otherwise it will be enabled on non-win32 platforms. It
1910takes precedence over select.</p>
1911 </dd>
1912 <dt>EV_USE_EPOLL</dt>
1913 <dd>
1914 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
1915<code>epoll</code>(7) backend. Its availability will be detected at runtime,
1916otherwise another method will be used as fallback. This is the
1917preferred backend for GNU/Linux systems.</p>
1918 </dd>
1919 <dt>EV_USE_KQUEUE</dt>
1920 <dd>
1921 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
1922<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
1923otherwise another method will be used as fallback. This is the preferred
1924backend for BSD and BSD-like systems, although on most BSDs kqueue only
1925supports some types of fds correctly (the only platform we found that
1926supports ptys for example was NetBSD), so kqueue might be compiled in, but
1927not be used unless explicitly requested. The best way to use it is to find
1928out whether kqueue supports your type of fd properly and use an embedded
1929kqueue loop.</p>
1930 </dd>
1931 <dt>EV_USE_PORT</dt>
1932 <dd>
1933 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
193410 port style backend. Its availability will be detected at runtime,
1935otherwise another method will be used as fallback. This is the preferred
1936backend for Solaris 10 systems.</p>
1937 </dd>
1938 <dt>EV_USE_DEVPOLL</dt>
1939 <dd>
1940 <p>reserved for future expansion, works like the USE symbols above.</p>
1941 </dd>
1942 <dt>EV_H</dt>
1943 <dd>
1944 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1945undefined 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
1946can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
1947 </dd>
1948 <dt>EV_CONFIG_H</dt>
1949 <dd>
1950 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
1951<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
1952<code>EV_H</code>, above.</p>
1953 </dd>
1954 <dt>EV_EVENT_H</dt>
1955 <dd>
1956 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
1957of how the <cite>event.h</cite> header can be found.</p>
1958 </dd>
1959 <dt>EV_PROTOTYPES</dt>
1960 <dd>
1961 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
1962prototypes, but still define all the structs and other symbols. This is
1963occasionally useful if you want to provide your own wrapper functions
1964around libev functions.</p>
1965 </dd>
1966 <dt>EV_MULTIPLICITY</dt>
1967 <dd>
1968 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
1969will have the <code>struct ev_loop *</code> as first argument, and you can create
1970additional independent event loops. Otherwise there will be no support
1971for multiple event loops and there is no first event loop pointer
1972argument. Instead, all functions act on the single default loop.</p>
1973 </dd>
1974 <dt>EV_PERIODIC_ENABLE</dt>
1975 <dd>
1976 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1977defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
1978code.</p>
1979 </dd>
1980 <dt>EV_EMBED_ENABLE</dt>
1981 <dd>
1982 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
1983defined to be <code>0</code>, then they are not.</p>
1984 </dd>
1985 <dt>EV_STAT_ENABLE</dt>
1986 <dd>
1987 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
1988defined to be <code>0</code>, then they are not.</p>
1989 </dd>
1990 <dt>EV_FORK_ENABLE</dt>
1991 <dd>
1992 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
1993defined to be <code>0</code>, then they are not.</p>
1994 </dd>
1995 <dt>EV_MINIMAL</dt>
1996 <dd>
1997 <p>If you need to shave off some kilobytes of code at the expense of some
1998speed, define this symbol to <code>1</code>. Currently only used for gcc to override
1999some inlining decisions, saves roughly 30% codesize of amd64.</p>
2000 </dd>
2001 <dt>EV_COMMON</dt>
2002 <dd>
2003 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2004this macro to a something else you can include more and other types of
2005members. You have to define it each time you include one of the files,
2006though, and it must be identical each time.</p>
2007 <p>For example, the perl EV module uses something like this:</p>
2008<pre> #define EV_COMMON \
2009 SV *self; /* contains this struct */ \
2010 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2011
2012</pre>
2013 </dd>
2014 <dt>EV_CB_DECLARE (type)</dt>
2015 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2016 <dt>ev_set_cb (ev, cb)</dt>
2017 <dd>
2018 <p>Can be used to change the callback member declaration in each watcher,
2019and the way callbacks are invoked and set. Must expand to a struct member
2020definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2021their default definitions. One possible use for overriding these is to
2022avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2023method calls instead of plain function calls in C++.</p>
2024
2025</div>
2026<h2 id="EXAMPLES">EXAMPLES</h2>
2027<div id="EXAMPLES_CONTENT">
2028 <p>For a real-world example of a program the includes libev
2029verbatim, you can have a look at the EV perl module
2030(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2031the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2032interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2033will be compiled. It is pretty complex because it provides its own header
2034file.</p>
2035 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2036that everybody includes and which overrides some autoconf choices:</p>
2037<pre> #define EV_USE_POLL 0
2038 #define EV_MULTIPLICITY 0
2039 #define EV_PERIODICS 0
2040 #define EV_CONFIG_H &lt;config.h&gt;
2041
2042 #include &quot;ev++.h&quot;
2043
2044</pre>
2045 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2046<pre> #include &quot;ev_cpp.h&quot;
2047 #include &quot;ev.c&quot;
2048
2049
2050
2051
2052</pre>
2053
2054</div>
2055<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
2056<div id="COMPLEXITIES_CONTENT">
2057 <p>In this section the complexities of (many of) the algorithms used inside
2058libev will be explained. For complexity discussions about backends see the
2059documentation for <code>ev_default_init</code>.</p>
2060 <p>
2061 <dl>
2062 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2063 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2064 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2065 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2066 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
2067 <dt>Finding the next timer per loop iteration: O(1)</dt>
2068 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2069 <dt>Activating one watcher: O(1)</dt>
2070 </dl>
2071 </p>
2072
2073
2074
2075
878 2076
879</div> 2077</div>
880<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2078<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
881<div id="AUTHOR_CONTENT"> 2079<div id="AUTHOR_CONTENT">
882<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2080 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
883 2081
884</div> 2082</div>
885</div></body> 2083</div></body>
886</html> 2084</html>

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