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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Mon Nov 12 09:20:02 2007" /> 9 <meta name="created" content="Thu Nov 22 13:26:17 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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17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 19<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 20<li><a href="#FEATURES">FEATURES</a></li>
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_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li> 23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
23<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>
24<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>
25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 26<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
26</ul> 27</ul>
27</li> 28</li>
28<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 29<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
29<ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li> 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>
30<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li> 31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
31<li><a href="#ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</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>
32<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</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>
33<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</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>
34<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</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>
35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</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>
36</ul> 37</ul>
37</li> 38</li>
38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
39<li><a href="#AUTHOR">AUTHOR</a> 42<li><a href="#AUTHOR">AUTHOR</a>
40</li> 43</li>
41</ul><hr /> 44</ul><hr />
42<!-- INDEX END --> 45<!-- INDEX END -->
43 46
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87support for multiple event loops, then all functions taking an initial 90support for multiple event loops, then all functions taking an initial
88argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 91argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
89will not have this argument.</p> 92will not have this argument.</p>
90 93
91</div> 94</div>
92<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 95<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
93<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> 96<div id="TIME_REPRESENTATION_CONTENT">
94<p>Libev represents time as a single floating point number, representing the 97<p>Libev represents time as a single floating point number, representing the
95(fractional) number of seconds since the (POSIX) epoch (somewhere near 98(fractional) number of seconds since the (POSIX) epoch (somewhere near
96the beginning of 1970, details are complicated, don't ask). This type is 99the beginning of 1970, details are complicated, don't ask). This type is
97called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 100called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
98to the double type in C.</p> 101to the double type in C.</p>
102
103</div>
104<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105<div id="GLOBAL_FUNCTIONS_CONTENT">
106<p>These functions can be called anytime, even before initialising the
107library in any way.</p>
99<dl> 108<dl>
100 <dt>ev_tstamp ev_time ()</dt> 109 <dt>ev_tstamp ev_time ()</dt>
101 <dd> 110 <dd>
102 <p>Returns the current time as libev would use it.</p> 111 <p>Returns the current time as libev would use it. Please note that the
112<code>ev_now</code> function is usually faster and also often returns the timestamp
113you actually want to know.</p>
103 </dd> 114 </dd>
104 <dt>int ev_version_major ()</dt> 115 <dt>int ev_version_major ()</dt>
105 <dt>int ev_version_minor ()</dt> 116 <dt>int ev_version_minor ()</dt>
106 <dd> 117 <dd>
107 <p>You can find out the major and minor version numbers of the library 118 <p>You can find out the major and minor version numbers of the library
108you linked against by calling the functions <code>ev_version_major</code> and 119you linked against by calling the functions <code>ev_version_major</code> and
109<code>ev_version_minor</code>. If you want, you can compare against the global 120<code>ev_version_minor</code>. If you want, you can compare against the global
110symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 121symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
111version of the library your program was compiled against.</p> 122version of the library your program was compiled against.</p>
112 <p>Usually, its a good idea to terminate if the major versions mismatch, 123 <p>Usually, it's a good idea to terminate if the major versions mismatch,
113as this indicates an incompatible change. Minor versions are usually 124as this indicates an incompatible change. Minor versions are usually
114compatible to older versions, so a larger minor version alone is usually 125compatible to older versions, so a larger minor version alone is usually
115not a problem.</p> 126not a problem.</p>
116 </dd> 127 </dd>
117 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 128 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
… …
142<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 153<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
143<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 154<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
144types of such loops, the <i>default</i> loop, which supports signals and child 155types of such loops, the <i>default</i> loop, which supports signals and child
145events, and dynamically created loops which do not.</p> 156events, and dynamically created loops which do not.</p>
146<p>If you use threads, a common model is to run the default event loop 157<p>If you use threads, a common model is to run the default event loop
147in your main thread (or in a separate thrad) and for each thread you 158in your main thread (or in a separate thread) and for each thread you
148create, you also create another event loop. Libev itself does no locking 159create, you also create another event loop. Libev itself does no locking
149whatsoever, so if you mix calls to the same event loop in different 160whatsoever, so if you mix calls to the same event loop in different
150threads, make sure you lock (this is usually a bad idea, though, even if 161threads, make sure you lock (this is usually a bad idea, though, even if
151done correctly, because its hideous and inefficient).</p> 162done correctly, because it's hideous and inefficient).</p>
152<dl> 163<dl>
153 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 164 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
154 <dd> 165 <dd>
155 <p>This will initialise the default event loop if it hasn't been initialised 166 <p>This will initialise the default event loop if it hasn't been initialised
156yet and return it. If the default loop could not be initialised, returns 167yet and return it. If the default loop could not be initialised, returns
… …
161 <p>The flags argument can be used to specify special behaviour or specific 172 <p>The flags argument can be used to specify special behaviour or specific
162backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> 173backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>
163 <p>It supports the following flags:</p> 174 <p>It supports the following flags:</p>
164 <p> 175 <p>
165 <dl> 176 <dl>
166 <dt>EVFLAG_AUTO</dt> 177 <dt><code>EVFLAG_AUTO</code></dt>
167 <dd> 178 <dd>
168 <p>The default flags value. Use this if you have no clue (its the right 179 <p>The default flags value. Use this if you have no clue (it's the right
169thing, believe me).</p> 180thing, believe me).</p>
170 </dd> 181 </dd>
171 <dt>EVFLAG_NOENV</dt> 182 <dt><code>EVFLAG_NOENV</code></dt>
172 <dd> 183 <dd>
173 <p>If this flag bit is ored into the flag value (or the program runs setuid 184 <p>If this flag bit is ored into the flag value (or the program runs setuid
174or setgid) then libev will <i>not</i> look at the environment variable 185or setgid) then libev will <i>not</i> look at the environment variable
175<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 186<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
176override the flags completely if it is found in the environment. This is 187override the flags completely if it is found in the environment. This is
177useful to try out specific backends to test their performance, or to work 188useful to try out specific backends to test their performance, or to work
178around bugs.</p> 189around bugs.</p>
179 </dd> 190 </dd>
180 <dt>EVMETHOD_SELECT portable select backend</dt> 191 <dt><code>EVMETHOD_SELECT</code> (value 1, portable select backend)</dt>
181 <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> 192 <dd>
182 <dt>EVMETHOD_EPOLL linux only</dt> 193 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
183 <dt>EVMETHOD_KQUEUE some bsds only</dt> 194libev tries to roll its own fd_set with no limits on the number of fds,
184 <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> 195but if that fails, expect a fairly low limit on the number of fds when
185 <dt>EVMETHOD_PORT solaris 10 only</dt> 196using this backend. It doesn't scale too well (O(highest_fd)), but its usually
197the fastest backend for a low number of fds.</p>
186 <dd> 198 </dd>
187 <p>If one or more of these are ored into the flags value, then only these 199 <dt><code>EVMETHOD_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
188backends will be tried (in the reverse order as given here). If one are 200 <dd>
189specified, any backend will do.</p> 201 <p>And this is your standard poll(2) backend. It's more complicated than
202select, but handles sparse fds better and has no artificial limit on the
203number of fds you can use (except it will slow down considerably with a
204lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
205 </dd>
206 <dt><code>EVMETHOD_EPOLL</code> (value 4, Linux)</dt>
207 <dd>
208 <p>For few fds, this backend is a bit little slower than poll and select,
209but it scales phenomenally better. While poll and select usually scale like
210O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
211either O(1) or O(active_fds).</p>
212 <p>While stopping and starting an I/O watcher in the same iteration will
213result in some caching, there is still a syscall per such incident
214(because the fd could point to a different file description now), so its
215best to avoid that. Also, dup()ed file descriptors might not work very
216well if you register events for both fds.</p>
217 </dd>
218 <dt><code>EVMETHOD_KQUEUE</code> (value 8, most BSD clones)</dt>
219 <dd>
220 <p>Kqueue deserves special mention, as at the time of this writing, it
221was broken on all BSDs except NetBSD (usually it doesn't work with
222anything but sockets and pipes, except on Darwin, where of course its
223completely useless). For this reason its not being &quot;autodetected&quot; unless
224you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p>
225 <p>It scales in the same way as the epoll backend, but the interface to the
226kernel is more efficient (which says nothing about its actual speed, of
227course). While starting and stopping an I/O watcher does not cause an
228extra syscall as with epoll, it still adds up to four event changes per
229incident, so its best to avoid that.</p>
230 </dd>
231 <dt><code>EVMETHOD_DEVPOLL</code> (value 16, Solaris 8)</dt>
232 <dd>
233 <p>This is not implemented yet (and might never be).</p>
234 </dd>
235 <dt><code>EVMETHOD_PORT</code> (value 32, Solaris 10)</dt>
236 <dd>
237 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
238it's really slow, but it still scales very well (O(active_fds)).</p>
239 </dd>
240 <dt><code>EVMETHOD_ALL</code></dt>
241 <dd>
242 <p>Try all backends (even potentially broken ones). Since this is a mask, you
243can do stuff like <code>EVMETHOD_ALL &amp; ~EVMETHOD_KQUEUE</code>.</p>
190 </dd> 244 </dd>
191 </dl> 245 </dl>
192 </p> 246 </p>
247 <p>If one or more of these are ored into the flags value, then only these
248backends will be tried (in the reverse order as given here). If none are
249specified, most compiled-in backend will be tried, usually in reverse
250order of their flag values :)</p>
193 </dd> 251 </dd>
194 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 252 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
195 <dd> 253 <dd>
196 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 254 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
197always distinct from the default loop. Unlike the default loop, it cannot 255always distinct from the default loop. Unlike the default loop, it cannot
… …
200 </dd> 258 </dd>
201 <dt>ev_default_destroy ()</dt> 259 <dt>ev_default_destroy ()</dt>
202 <dd> 260 <dd>
203 <p>Destroys the default loop again (frees all memory and kernel state 261 <p>Destroys the default loop again (frees all memory and kernel state
204etc.). This stops all registered event watchers (by not touching them in 262etc.). This stops all registered event watchers (by not touching them in
205any way whatsoever, although you cnanot rely on this :).</p> 263any way whatsoever, although you cannot rely on this :).</p>
206 </dd> 264 </dd>
207 <dt>ev_loop_destroy (loop)</dt> 265 <dt>ev_loop_destroy (loop)</dt>
208 <dd> 266 <dd>
209 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 267 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
210earlier call to <code>ev_loop_new</code>.</p> 268earlier call to <code>ev_loop_new</code>.</p>
… …
216after forking, in either the parent or child process (or both, but that 274after forking, in either the parent or child process (or both, but that
217again makes little sense).</p> 275again makes little sense).</p>
218 <p>You <i>must</i> call this function after forking if and only if you want to 276 <p>You <i>must</i> call this function after forking if and only if you want to
219use the event library in both processes. If you just fork+exec, you don't 277use the event library in both processes. If you just fork+exec, you don't
220have to call it.</p> 278have to call it.</p>
221 <p>The function itself is quite fast and its usually not a problem to call 279 <p>The function itself is quite fast and it's usually not a problem to call
222it just in case after a fork. To make this easy, the function will fit in 280it just in case after a fork. To make this easy, the function will fit in
223quite nicely into a call to <code>pthread_atfork</code>:</p> 281quite nicely into a call to <code>pthread_atfork</code>:</p>
224<pre> pthread_atfork (0, 0, ev_default_fork); 282<pre> pthread_atfork (0, 0, ev_default_fork);
225 283
226</pre> 284</pre>
… …
234 <dt>unsigned int ev_method (loop)</dt> 292 <dt>unsigned int ev_method (loop)</dt>
235 <dd> 293 <dd>
236 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 294 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in
237use.</p> 295use.</p>
238 </dd> 296 </dd>
239 <dt>ev_tstamp = ev_now (loop)</dt> 297 <dt>ev_tstamp ev_now (loop)</dt>
240 <dd> 298 <dd>
241 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 299 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
242got events and started processing them. This timestamp does not change 300got events and started processing them. This timestamp does not change
243as long as callbacks are being processed, and this is also the base time 301as long as callbacks are being processed, and this is also the base time
244used for relative timers. You can treat it as the timestamp of the event 302used for relative timers. You can treat it as the timestamp of the event
… …
251events.</p> 309events.</p>
252 <p>If the flags argument is specified as 0, it will not return until either 310 <p>If the flags argument is specified as 0, it will not return until either
253no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 311no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
254 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 312 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
255those events and any outstanding ones, but will not block your process in 313those events and any outstanding ones, but will not block your process in
256case there are no events.</p> 314case there are no events and will return after one iteration of the loop.</p>
257 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 315 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
258neccessary) and will handle those and any outstanding ones. It will block 316neccessary) and will handle those and any outstanding ones. It will block
259your process until at least one new event arrives.</p> 317your process until at least one new event arrives, and will return after
318one iteration of the loop.</p>
260 <p>This flags value could be used to implement alternative looping 319 <p>This flags value could be used to implement alternative looping
261constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 320constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
262more generic mechanism.</p> 321more generic mechanism.</p>
322 <p>Here are the gory details of what ev_loop does:</p>
323<pre> 1. If there are no active watchers (reference count is zero), return.
324 2. Queue and immediately call all prepare watchers.
325 3. If we have been forked, recreate the kernel state.
326 4. Update the kernel state with all outstanding changes.
327 5. Update the &quot;event loop time&quot;.
328 6. Calculate for how long to block.
329 7. Block the process, waiting for events.
330 8. Update the &quot;event loop time&quot; and do time jump handling.
331 9. Queue all outstanding timers.
332 10. Queue all outstanding periodics.
333 11. If no events are pending now, queue all idle watchers.
334 12. Queue all check watchers.
335 13. Call all queued watchers in reverse order (i.e. check watchers first).
336 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
337 was used, return, otherwise continue with step #1.
338
339</pre>
263 </dd> 340 </dd>
264 <dt>ev_unloop (loop, how)</dt> 341 <dt>ev_unloop (loop, how)</dt>
265 <dd> 342 <dd>
266 <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument 343 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
344has processed all outstanding events). The <code>how</code> argument must be either
267must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> 345<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
268call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> 346<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
269calls return.</p>
270 </dd> 347 </dd>
271 <dt>ev_ref (loop)</dt> 348 <dt>ev_ref (loop)</dt>
272 <dt>ev_unref (loop)</dt> 349 <dt>ev_unref (loop)</dt>
273 <dd> 350 <dd>
274 <p>Ref/unref can be used to add or remove a refcount on the event loop: Every 351 <p>Ref/unref can be used to add or remove a reference count on the event
275watcher keeps one reference. If you have a long-runing watcher you never 352loop: Every watcher keeps one reference, and as long as the reference
276unregister that should not keep ev_loop from running, ev_unref() after 353count is nonzero, <code>ev_loop</code> will not return on its own. If you have
277starting, and ev_ref() before stopping it. Libev itself uses this for 354a watcher you never unregister that should not keep <code>ev_loop</code> from
278example for its internal signal pipe: It is not visible to you as a user 355returning, ev_unref() after starting, and ev_ref() before stopping it. For
279and should not keep <code>ev_loop</code> from exiting if the work is done. It is 356example, libev itself uses this for its internal signal pipe: It is not
280also an excellent way to do this for generic recurring timers or from 357visible to the libev user and should not keep <code>ev_loop</code> from exiting if
281within third-party libraries. Just remember to unref after start and ref 358no event watchers registered by it are active. It is also an excellent
282before stop.</p> 359way to do this for generic recurring timers or from within third-party
360libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
283 </dd> 361 </dd>
284</dl> 362</dl>
285 363
286</div> 364</div>
287<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 365<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
288<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 366<div id="ANATOMY_OF_A_WATCHER_CONTENT">
289<p>A watcher is a structure that you create and register to record your 367<p>A watcher is a structure that you create and register to record your
290interest in some event. For instance, if you want to wait for STDIN to 368interest in some event. For instance, if you want to wait for STDIN to
291become readable, you would create an ev_io watcher for that:</p> 369become readable, you would create an <code>ev_io</code> watcher for that:</p>
292<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 370<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
293 { 371 {
294 ev_io_stop (w); 372 ev_io_stop (w);
295 ev_unloop (loop, EVUNLOOP_ALL); 373 ev_unloop (loop, EVUNLOOP_ALL);
296 } 374 }
… …
320*)</code>), and you can stop watching for events at any time by calling the 398*)</code>), and you can stop watching for events at any time by calling the
321corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 399corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
322<p>As long as your watcher is active (has been started but not stopped) you 400<p>As long as your watcher is active (has been started but not stopped) you
323must not touch the values stored in it. Most specifically you must never 401must not touch the values stored in it. Most specifically you must never
324reinitialise it or call its set method.</p> 402reinitialise it or call its set method.</p>
325<p>You cna check whether an event is active by calling the <code>ev_is_active 403<p>You can check whether an event is active by calling the <code>ev_is_active
326(watcher *)</code> macro. To see whether an event is outstanding (but the 404(watcher *)</code> macro. To see whether an event is outstanding (but the
327callback for it has not been called yet) you cna use the <code>ev_is_pending 405callback for it has not been called yet) you can use the <code>ev_is_pending
328(watcher *)</code> macro.</p> 406(watcher *)</code> macro.</p>
329<p>Each and every callback receives the event loop pointer as first, the 407<p>Each and every callback receives the event loop pointer as first, the
330registered watcher structure as second, and a bitset of received events as 408registered watcher structure as second, and a bitset of received events as
331third argument.</p> 409third argument.</p>
332<p>The rceeived events usually include a single bit per event type received 410<p>The received events usually include a single bit per event type received
333(you can receive multiple events at the same time). The possible bit masks 411(you can receive multiple events at the same time). The possible bit masks
334are:</p> 412are:</p>
335<dl> 413<dl>
336 <dt>EV_READ</dt> 414 <dt><code>EV_READ</code></dt>
337 <dt>EV_WRITE</dt> 415 <dt><code>EV_WRITE</code></dt>
338 <dd> 416 <dd>
339 <p>The file descriptor in the ev_io watcher has become readable and/or 417 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
340writable.</p> 418writable.</p>
341 </dd> 419 </dd>
342 <dt>EV_TIMEOUT</dt> 420 <dt><code>EV_TIMEOUT</code></dt>
343 <dd>
344 <p>The ev_timer watcher has timed out.</p>
345 </dd> 421 <dd>
346 <dt>EV_PERIODIC</dt> 422 <p>The <code>ev_timer</code> watcher has timed out.</p>
347 <dd> 423 </dd>
348 <p>The ev_periodic watcher has timed out.</p> 424 <dt><code>EV_PERIODIC</code></dt>
349 </dd> 425 <dd>
350 <dt>EV_SIGNAL</dt> 426 <p>The <code>ev_periodic</code> watcher has timed out.</p>
351 <dd> 427 </dd>
428 <dt><code>EV_SIGNAL</code></dt>
429 <dd>
352 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 430 <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
353 </dd>
354 <dt>EV_CHILD</dt>
355 <dd> 431 </dd>
432 <dt><code>EV_CHILD</code></dt>
433 <dd>
356 <p>The pid specified in the ev_child watcher has received a status change.</p> 434 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
357 </dd>
358 <dt>EV_IDLE</dt>
359 <dd> 435 </dd>
436 <dt><code>EV_IDLE</code></dt>
437 <dd>
360 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 438 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
361 </dd>
362 <dt>EV_PREPARE</dt>
363 <dt>EV_CHECK</dt>
364 <dd> 439 </dd>
440 <dt><code>EV_PREPARE</code></dt>
441 <dt><code>EV_CHECK</code></dt>
442 <dd>
365 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 443 <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
366to gather new events, and all ev_check watchers are invoked just after 444to gather new events, and all <code>ev_check</code> watchers are invoked just after
367<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 445<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
368received events. Callbacks of both watcher types can start and stop as 446received events. Callbacks of both watcher types can start and stop as
369many watchers as they want, and all of them will be taken into account 447many watchers as they want, and all of them will be taken into account
370(for example, a ev_prepare watcher might start an idle watcher to keep 448(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
371<code>ev_loop</code> from blocking).</p> 449<code>ev_loop</code> from blocking).</p>
372 </dd> 450 </dd>
373 <dt>EV_ERROR</dt> 451 <dt><code>EV_ERROR</code></dt>
374 <dd> 452 <dd>
375 <p>An unspecified error has occured, the watcher has been stopped. This might 453 <p>An unspecified error has occured, the watcher has been stopped. This might
376happen because the watcher could not be properly started because libev 454happen because the watcher could not be properly started because libev
377ran out of memory, a file descriptor was found to be closed or any other 455ran out of memory, a file descriptor was found to be closed or any other
378problem. You best act on it by reporting the problem and somehow coping 456problem. You best act on it by reporting the problem and somehow coping
… …
387 465
388</div> 466</div>
389<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 467<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
390<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 468<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
391<p>Each watcher has, by default, a member <code>void *data</code> that you can change 469<p>Each watcher has, by default, a member <code>void *data</code> that you can change
392and read at any time, libev will completely ignore it. This cna be used 470and read at any time, libev will completely ignore it. This can be used
393to associate arbitrary data with your watcher. If you need more data and 471to associate arbitrary data with your watcher. If you need more data and
394don't want to allocate memory and store a pointer to it in that data 472don't want to allocate memory and store a pointer to it in that data
395member, you can also &quot;subclass&quot; the watcher type and provide your own 473member, you can also &quot;subclass&quot; the watcher type and provide your own
396data:</p> 474data:</p>
397<pre> struct my_io 475<pre> struct my_io
… …
424<div id="WATCHER_TYPES_CONTENT"> 502<div id="WATCHER_TYPES_CONTENT">
425<p>This section describes each watcher in detail, but will not repeat 503<p>This section describes each watcher in detail, but will not repeat
426information given in the last section.</p> 504information given in the last section.</p>
427 505
428</div> 506</div>
429<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 507<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
430<div id="struct_ev_io_is_my_file_descriptor_r-2"> 508<div id="code_ev_io_code_is_this_file_descrip-2">
431<p>I/O watchers check whether a file descriptor is readable or writable 509<p>I/O watchers check whether a file descriptor is readable or writable
432in each iteration of the event loop (This behaviour is called 510in each iteration of the event loop (This behaviour is called
433level-triggering because you keep receiving events as long as the 511level-triggering because you keep receiving events as long as the
434condition persists. Remember you cna stop the watcher if you don't want to 512condition persists. Remember you can stop the watcher if you don't want to
435act on the event and neither want to receive future events).</p> 513act on the event and neither want to receive future events).</p>
436<p>In general you can register as many read and/or write event watchers oer 514<p>In general you can register as many read and/or write event watchers per
437fd as you want (as long as you don't confuse yourself). Setting all file 515fd as you want (as long as you don't confuse yourself). Setting all file
438descriptors to non-blocking mode is also usually a good idea (but not 516descriptors to non-blocking mode is also usually a good idea (but not
439required if you know what you are doing).</p> 517required if you know what you are doing).</p>
440<p>You have to be careful with dup'ed file descriptors, though. Some backends 518<p>You have to be careful with dup'ed file descriptors, though. Some backends
441(the linux epoll backend is a notable example) cannot handle dup'ed file 519(the linux epoll backend is a notable example) cannot handle dup'ed file
442descriptors correctly if you register interest in two or more fds pointing 520descriptors correctly if you register interest in two or more fds pointing
443to the same file/socket etc. description.</p> 521to the same underlying file/socket etc. description (that is, they share
522the same underlying &quot;file open&quot;).</p>
444<p>If you must do this, then force the use of a known-to-be-good backend 523<p>If you must do this, then force the use of a known-to-be-good backend
445(at the time of this writing, this includes only EVMETHOD_SELECT and 524(at the time of this writing, this includes only EVMETHOD_SELECT and
446EVMETHOD_POLL).</p> 525EVMETHOD_POLL).</p>
447<dl> 526<dl>
448 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 527 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
449 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 528 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
450 <dd> 529 <dd>
451 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 530 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
452events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 531events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
453EV_WRITE</code> to receive the given events.</p> 532EV_WRITE</code> to receive the given events.</p>
454 </dd> 533 </dd>
455</dl> 534</dl>
456 535
457</div> 536</div>
458<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 537<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
459<div id="struct_ev_timer_relative_and_optiona-2"> 538<div id="code_ev_timer_code_relative_and_opti-2">
460<p>Timer watchers are simple relative timers that generate an event after a 539<p>Timer watchers are simple relative timers that generate an event after a
461given time, and optionally repeating in regular intervals after that.</p> 540given time, and optionally repeating in regular intervals after that.</p>
462<p>The timers are based on real time, that is, if you register an event that 541<p>The timers are based on real time, that is, if you register an event that
463times out after an hour and youreset your system clock to last years 542times out after an hour and you reset your system clock to last years
464time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 543time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
465detecting time jumps is hard, and soem inaccuracies are unavoidable (the 544detecting time jumps is hard, and some inaccuracies are unavoidable (the
466monotonic clock option helps a lot here).</p> 545monotonic clock option helps a lot here).</p>
546<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
547time. This is usually the right thing as this timestamp refers to the time
548of the event triggering whatever timeout you are modifying/starting. If
549you suspect event processing to be delayed and you <i>need</i> to base the timeout
550on the current time, use something like this to adjust for this:</p>
551<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
552
553</pre>
554<p>The callback is guarenteed to be invoked only when its timeout has passed,
555but if multiple timers become ready during the same loop iteration then
556order of execution is undefined.</p>
467<dl> 557<dl>
468 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 558 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
469 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 559 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
470 <dd> 560 <dd>
471 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 561 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
473timer will automatically be configured to trigger again <code>repeat</code> seconds 563timer will automatically be configured to trigger again <code>repeat</code> seconds
474later, again, and again, until stopped manually.</p> 564later, again, and again, until stopped manually.</p>
475 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 565 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
476configure a timer to trigger every 10 seconds, then it will trigger at 566configure a timer to trigger every 10 seconds, then it will trigger at
477exactly 10 second intervals. If, however, your program cannot keep up with 567exactly 10 second intervals. If, however, your program cannot keep up with
478the timer (ecause it takes longer than those 10 seconds to do stuff) the 568the timer (because it takes longer than those 10 seconds to do stuff) the
479timer will not fire more than once per event loop iteration.</p> 569timer will not fire more than once per event loop iteration.</p>
480 </dd> 570 </dd>
481 <dt>ev_timer_again (loop)</dt> 571 <dt>ev_timer_again (loop)</dt>
482 <dd> 572 <dd>
483 <p>This will act as if the timer timed out and restart it again if it is 573 <p>This will act as if the timer timed out and restart it again if it is
… …
487value), or reset the running timer to the repeat value.</p> 577value), or reset the running timer to the repeat value.</p>
488 <p>This sounds a bit complicated, but here is a useful and typical 578 <p>This sounds a bit complicated, but here is a useful and typical
489example: Imagine you have a tcp connection and you want a so-called idle 579example: Imagine you have a tcp connection and you want a so-called idle
490timeout, that is, you want to be called when there have been, say, 60 580timeout, that is, you want to be called when there have been, say, 60
491seconds of inactivity on the socket. The easiest way to do this is to 581seconds of inactivity on the socket. The easiest way to do this is to
492configure an ev_timer with after=repeat=60 and calling ev_timer_again each 582configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
493time you successfully read or write some data. If you go into an idle 583time you successfully read or write some data. If you go into an idle
494state where you do not expect data to travel on the socket, you can stop 584state where you do not expect data to travel on the socket, you can stop
495the timer, and again will automatically restart it if need be.</p> 585the timer, and again will automatically restart it if need be.</p>
496 </dd> 586 </dd>
497</dl> 587</dl>
498 588
499</div> 589</div>
500<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2> 590<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
501<div id="ev_periodic_to_cron_or_not_to_cron_i-2"> 591<div id="code_ev_periodic_code_to_cron_or_not-2">
502<p>Periodic watchers are also timers of a kind, but they are very versatile 592<p>Periodic watchers are also timers of a kind, but they are very versatile
503(and unfortunately a bit complex).</p> 593(and unfortunately a bit complex).</p>
504<p>Unlike ev_timer's, they are not based on real time (or relative time) 594<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
505but on wallclock time (absolute time). You can tell a periodic watcher 595but on wallclock time (absolute time). You can tell a periodic watcher
506to trigger &quot;at&quot; some specific point in time. For example, if you tell a 596to trigger &quot;at&quot; some specific point in time. For example, if you tell a
507periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 597periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now ()
508+ 10.&gt;) and then reset your system clock to the last year, then it will 598+ 10.&gt;) and then reset your system clock to the last year, then it will
509take a year to trigger the event (unlike an ev_timer, which would trigger 599take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
510roughly 10 seconds later and of course not if you reset your system time 600roughly 10 seconds later and of course not if you reset your system time
511again).</p> 601again).</p>
512<p>They can also be used to implement vastly more complex timers, such as 602<p>They can also be used to implement vastly more complex timers, such as
513triggering an event on eahc midnight, local time.</p> 603triggering an event on eahc midnight, local time.</p>
604<p>As with timers, the callback is guarenteed to be invoked only when the
605time (<code>at</code>) has been passed, but if multiple periodic timers become ready
606during the same loop iteration then order of execution is undefined.</p>
514<dl> 607<dl>
515 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 608 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
516 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 609 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
517 <dd> 610 <dd>
518 <p>Lots of arguments, lets sort it out... There are basically three modes of 611 <p>Lots of arguments, lets sort it out... There are basically three modes of
519operation, and we will explain them from simplest to complex:</p> 612operation, and we will explain them from simplest to complex:</p>
520
521
522
523
524 <p> 613 <p>
525 <dl> 614 <dl>
526 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 615 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
527 <dd> 616 <dd>
528 <p>In this configuration the watcher triggers an event at the wallclock time 617 <p>In this configuration the watcher triggers an event at the wallclock time
… …
540<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 629<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
541 630
542</pre> 631</pre>
543 <p>This doesn't mean there will always be 3600 seconds in between triggers, 632 <p>This doesn't mean there will always be 3600 seconds in between triggers,
544but only that the the callback will be called when the system time shows a 633but only that the the callback will be called when the system time shows a
545full hour (UTC), or more correct, when the system time is evenly divisible 634full hour (UTC), or more correctly, when the system time is evenly divisible
546by 3600.</p> 635by 3600.</p>
547 <p>Another way to think about it (for the mathematically inclined) is that 636 <p>Another way to think about it (for the mathematically inclined) is that
548ev_periodic will try to run the callback in this mode at the next possible 637<code>ev_periodic</code> will try to run the callback in this mode at the next possible
549time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 638time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
550 </dd> 639 </dd>
551 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 640 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
552 <dd> 641 <dd>
553 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 642 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
554ignored. Instead, each time the periodic watcher gets scheduled, the 643ignored. Instead, each time the periodic watcher gets scheduled, the
555reschedule callback will be called with the watcher as first, and the 644reschedule callback will be called with the watcher as first, and the
556current time as second argument.</p> 645current time as second argument.</p>
557 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 646 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
558periodic watcher, ever, or make any event loop modificstions</i>. If you need 647ever, or make any event loop modifications</i>. If you need to stop it,
559to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 648return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
649starting a prepare watcher).</p>
560 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 650 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
561ev_tstamp now)&gt;, e.g.:</p> 651ev_tstamp now)</code>, e.g.:</p>
562<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 652<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
563 { 653 {
564 return now + 60.; 654 return now + 60.;
565 } 655 }
566 656
567</pre> 657</pre>
568 <p>It must return the next time to trigger, based on the passed time value 658 <p>It must return the next time to trigger, based on the passed time value
569(that is, the lowest time value larger than to the second argument). It 659(that is, the lowest time value larger than to the second argument). It
570will usually be called just before the callback will be triggered, but 660will usually be called just before the callback will be triggered, but
571might be called at other times, too.</p> 661might be called at other times, too.</p>
662 <p>NOTE: <i>This callback must always return a time that is later than the
663passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
572 <p>This can be used to create very complex timers, such as a timer that 664 <p>This can be used to create very complex timers, such as a timer that
573triggers on each midnight, local time. To do this, you would calculate the 665triggers on each midnight, local time. To do this, you would calculate the
574next midnight after <code>now</code> and return the timestamp value for this. How you do this 666next midnight after <code>now</code> and return the timestamp value for this. How
575is, again, up to you (but it is not trivial).</p> 667you do this is, again, up to you (but it is not trivial, which is the main
668reason I omitted it as an example).</p>
576 </dd> 669 </dd>
577 </dl> 670 </dl>
578 </p> 671 </p>
579 </dd> 672 </dd>
580 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 673 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
585program when the crontabs have changed).</p> 678program when the crontabs have changed).</p>
586 </dd> 679 </dd>
587</dl> 680</dl>
588 681
589</div> 682</div>
590<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 683<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
591<div id="ev_signal_signal_me_when_a_signal_ge-2"> 684<div id="code_ev_signal_code_signal_me_when_a-2">
592<p>Signal watchers will trigger an event when the process receives a specific 685<p>Signal watchers will trigger an event when the process receives a specific
593signal one or more times. Even though signals are very asynchronous, libev 686signal one or more times. Even though signals are very asynchronous, libev
594will try its best to deliver signals synchronously, i.e. as part of the 687will try it's best to deliver signals synchronously, i.e. as part of the
595normal event processing, like any other event.</p> 688normal event processing, like any other event.</p>
596<p>You cna configure as many watchers as you like per signal. Only when the 689<p>You can configure as many watchers as you like per signal. Only when the
597first watcher gets started will libev actually register a signal watcher 690first watcher gets started will libev actually register a signal watcher
598with the kernel (thus it coexists with your own signal handlers as long 691with the kernel (thus it coexists with your own signal handlers as long
599as you don't register any with libev). Similarly, when the last signal 692as you don't register any with libev). Similarly, when the last signal
600watcher for a signal is stopped libev will reset the signal handler to 693watcher for a signal is stopped libev will reset the signal handler to
601SIG_DFL (regardless of what it was set to before).</p> 694SIG_DFL (regardless of what it was set to before).</p>
… …
607of the <code>SIGxxx</code> constants).</p> 700of the <code>SIGxxx</code> constants).</p>
608 </dd> 701 </dd>
609</dl> 702</dl>
610 703
611</div> 704</div>
612<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 705<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
613<div id="ev_child_wait_for_pid_status_changes-2"> 706<div id="code_ev_child_code_wait_for_pid_stat-2">
614<p>Child watchers trigger when your process receives a SIGCHLD in response to 707<p>Child watchers trigger when your process receives a SIGCHLD in response to
615some child status changes (most typically when a child of yours dies).</p> 708some child status changes (most typically when a child of yours dies).</p>
616<dl> 709<dl>
617 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 710 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
618 <dt>ev_child_set (ev_child *, int pid)</dt> 711 <dt>ev_child_set (ev_child *, int pid)</dt>
619 <dd> 712 <dd>
620 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 713 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
621<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 714<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
622at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 715at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
623the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 716the status word (use the macros from <code>sys/wait.h</code> and see your systems
717<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
624contains the pid of the process causing the status change.</p> 718process causing the status change.</p>
625 </dd> 719 </dd>
626</dl> 720</dl>
627 721
628</div> 722</div>
629<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 723<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
630<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 724<div id="code_ev_idle_code_when_you_ve_got_no-2">
631<p>Idle watchers trigger events when there are no other I/O or timer (or 725<p>Idle watchers trigger events when there are no other events are pending
632periodic) events pending. That is, as long as your process is busy 726(prepare, check and other idle watchers do not count). That is, as long
633handling sockets or timeouts it will not be called. But when your process 727as your process is busy handling sockets or timeouts (or even signals,
634is idle all idle watchers are being called again and again - until 728imagine) it will not be triggered. But when your process is idle all idle
729watchers are being called again and again, once per event loop iteration -
635stopped, that is, or your process receives more events.</p> 730until stopped, that is, or your process receives more events and becomes
731busy.</p>
636<p>The most noteworthy effect is that as long as any idle watchers are 732<p>The most noteworthy effect is that as long as any idle watchers are
637active, the process will not block when waiting for new events.</p> 733active, the process will not block when waiting for new events.</p>
638<p>Apart from keeping your process non-blocking (which is a useful 734<p>Apart from keeping your process non-blocking (which is a useful
639effect on its own sometimes), idle watchers are a good place to do 735effect on its own sometimes), idle watchers are a good place to do
640&quot;pseudo-background processing&quot;, or delay processing stuff to after the 736&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
647believe me.</p> 743believe me.</p>
648 </dd> 744 </dd>
649</dl> 745</dl>
650 746
651</div> 747</div>
652<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 748<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
653<div id="prepare_and_check_your_hooks_into_th-2"> 749<div id="code_ev_prepare_code_and_code_ev_che-2">
654<p>Prepare and check watchers usually (but not always) are used in 750<p>Prepare and check watchers are usually (but not always) used in tandem:
655tandom. Prepare watchers get invoked before the process blocks and check 751prepare watchers get invoked before the process blocks and check watchers
656watchers afterwards.</p> 752afterwards.</p>
657<p>Their main purpose is to integrate other event mechanisms into libev. This 753<p>Their main purpose is to integrate other event mechanisms into libev. This
658could be used, for example, to track variable changes, implement your own 754could be used, for example, to track variable changes, implement your own
659watchers, integrate net-snmp or a coroutine library and lots more.</p> 755watchers, integrate net-snmp or a coroutine library and lots more.</p>
660<p>This is done by examining in each prepare call which file descriptors need 756<p>This is done by examining in each prepare call which file descriptors need
661to be watched by the other library, registering ev_io watchers for them 757to be watched by the other library, registering <code>ev_io</code> watchers for
662and starting an ev_timer watcher for any timeouts (many libraries provide 758them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
663just this functionality). Then, in the check watcher you check for any 759provide just this functionality). Then, in the check watcher you check for
664events that occured (by making your callbacks set soem flags for example) 760any events that occured (by checking the pending status of all watchers
665and call back into the library.</p> 761and stopping them) and call back into the library. The I/O and timer
762callbacks will never actually be called (but must be valid nevertheless,
763because you never know, you know?).</p>
666<p>As another example, the perl Coro module uses these hooks to integrate 764<p>As another example, the Perl Coro module uses these hooks to integrate
667coroutines into libev programs, by yielding to other active coroutines 765coroutines into libev programs, by yielding to other active coroutines
668during each prepare and only letting the process block if no coroutines 766during each prepare and only letting the process block if no coroutines
669are ready to run.</p> 767are ready to run (it's actually more complicated: it only runs coroutines
768with priority higher than or equal to the event loop and one coroutine
769of lower priority, but only once, using idle watchers to keep the event
770loop from blocking if lower-priority coroutines are active, thus mapping
771low-priority coroutines to idle/background tasks).</p>
670<dl> 772<dl>
671 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 773 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
672 <dt>ev_check_init (ev_check *, callback)</dt> 774 <dt>ev_check_init (ev_check *, callback)</dt>
673 <dd> 775 <dd>
674 <p>Initialises and configures the prepare or check watcher - they have no 776 <p>Initialises and configures the prepare or check watcher - they have no
675parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 777parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
676macros, but using them is utterly, utterly pointless.</p> 778macros, but using them is utterly, utterly and completely pointless.</p>
677 </dd> 779 </dd>
678</dl> 780</dl>
679 781
680</div> 782</div>
681<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 783<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
682<div id="OTHER_FUNCTIONS_CONTENT"> 784<div id="OTHER_FUNCTIONS_CONTENT">
683<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 785<p>There are some other functions of possible interest. Described. Here. Now.</p>
684<dl> 786<dl>
685 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 787 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
686 <dd> 788 <dd>
687 <p>This function combines a simple timer and an I/O watcher, calls your 789 <p>This function combines a simple timer and an I/O watcher, calls your
688callback on whichever event happens first and automatically stop both 790callback on whichever event happens first and automatically stop both
689watchers. This is useful if you want to wait for a single event on an fd 791watchers. This is useful if you want to wait for a single event on an fd
690or timeout without havign to allocate/configure/start/stop/free one or 792or timeout without having to allocate/configure/start/stop/free one or
691more watchers yourself.</p> 793more watchers yourself.</p>
692 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 794 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
693ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 795is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
694will be craeted and started.</p> 796<code>events</code> set will be craeted and started.</p>
695 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 797 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
696started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 798started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
697= 0) will be started.</p> 799repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
800dubious value.</p>
698 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 801 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
699gets passed an events set (normally a combination of EV_ERROR, EV_READ, 802passed an <code>revents</code> set like normal event callbacks (a combination of
700EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 803<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
804value passed to <code>ev_once</code>:</p>
701<pre> static void stdin_ready (int revents, void *arg) 805<pre> static void stdin_ready (int revents, void *arg)
702 { 806 {
703 if (revents &amp; EV_TIMEOUT) 807 if (revents &amp; EV_TIMEOUT)
704 /* doh, nothing entered */ 808 /* doh, nothing entered */;
705 else if (revents &amp; EV_READ) 809 else if (revents &amp; EV_READ)
706 /* stdin might have data for us, joy! */ 810 /* stdin might have data for us, joy! */;
707 } 811 }
708 812
709 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 813 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
710 814
711</pre> 815</pre>
712 </dd> 816 </dd>
713 <dt>ev_feed_event (loop, watcher, int events)</dt> 817 <dt>ev_feed_event (loop, watcher, int events)</dt>
714 <dd> 818 <dd>
715 <p>Feeds the given event set into the event loop, as if the specified event 819 <p>Feeds the given event set into the event loop, as if the specified event
716has happened for the specified watcher (which must be a pointer to an 820had happened for the specified watcher (which must be a pointer to an
717initialised but not necessarily active event watcher).</p> 821initialised but not necessarily started event watcher).</p>
718 </dd> 822 </dd>
719 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 823 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
720 <dd> 824 <dd>
721 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 825 <p>Feed an event on the given fd, as if a file descriptor backend detected
826the given events it.</p>
722 </dd> 827 </dd>
723 <dt>ev_feed_signal_event (loop, int signum)</dt> 828 <dt>ev_feed_signal_event (loop, int signum)</dt>
724 <dd> 829 <dd>
725 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 830 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
726 </dd> 831 </dd>
727</dl> 832</dl>
833
834</div>
835<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
836<div id="LIBEVENT_EMULATION_CONTENT">
837<p>Libev offers a compatibility emulation layer for libevent. It cannot
838emulate the internals of libevent, so here are some usage hints:</p>
839<dl>
840 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
841 <dt>* The following members are fully supported: ev_base, ev_callback,
842ev_arg, ev_fd, ev_res, ev_events.</dt>
843 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
844maintained by libev, it does not work exactly the same way as in libevent (consider
845it a private API).</dt>
846 <dt>* Priorities are not currently supported. Initialising priorities
847will fail and all watchers will have the same priority, even though there
848is an ev_pri field.</dt>
849 <dt>* Other members are not supported.</dt>
850 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
851to use the libev header file and library.</dt>
852</dl>
853
854</div>
855<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
856<div id="C_SUPPORT_CONTENT">
857<p>TBD.</p>
728 858
729</div> 859</div>
730<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 860<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
731<div id="AUTHOR_CONTENT"> 861<div id="AUTHOR_CONTENT">
732<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 862<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

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