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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="<standard input>" />	7	<meta name="inputfile" content="<standard input>" />
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9	<meta name="created" content="Mon Nov 12 09:58:24 2007" />	9	<meta name="created" content="Sat Nov 24 05:58:35 2007" />
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12	<body>	12	<body>
13	<div class="pod">	13	<div class="pod">
14	<!-- INDEX START -->	14	<!-- INDEX START -->
…		…
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="#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>	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_child_code_wait_for_pid_stat"><code>ev_child</code> - 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>
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="#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>	36	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>
		37	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li>
37	</ul>	38	</ul>
38	</li>	39	</li>
39	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	40	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
		41	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
		42	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
40	<li><a href="#AUTHOR">AUTHOR</a>	43	<li><a href="#AUTHOR">AUTHOR</a>
41	</li>	44	</li>
42	</ul><hr />	45	</ul><hr />
43	<!-- INDEX END -->	46	<!-- INDEX END -->
44		47
…		…
94	<div id="TIME_REPRESENTATION_CONTENT">	97	<div id="TIME_REPRESENTATION_CONTENT">
95	<p>Libev represents time as a single floating point number, representing the	98	<p>Libev represents time as a single floating point number, representing the
96	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
97	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
98	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	101	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
99	to the double type in C.</p>	102	to the <code>double</code> type in C, and when you need to do any calculations on
		103	it, you should treat it as such.</p>
		104
		105
		106
		107
100		108
101	</div>	109	</div>
102	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	110	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
103	<div id="GLOBAL_FUNCTIONS_CONTENT">	111	<div id="GLOBAL_FUNCTIONS_CONTENT">
		112	<p>These functions can be called anytime, even before initialising the
		113	library in any way.</p>
104	<dl>	114	<dl>
105	<dt>ev_tstamp ev_time ()</dt>	115	<dt>ev_tstamp ev_time ()</dt>
106	<dd>	116	<dd>
107	<p>Returns the current time as libev would use it.</p>	117	<p>Returns the current time as libev would use it. Please note that the
		118	<code>ev_now</code> function is usually faster and also often returns the timestamp
		119	you actually want to know.</p>
108	</dd>	120	</dd>
109	<dt>int ev_version_major ()</dt>	121	<dt>int ev_version_major ()</dt>
110	<dt>int ev_version_minor ()</dt>	122	<dt>int ev_version_minor ()</dt>
111	<dd>	123	<dd>
112	<p>You can find out the major and minor version numbers of the library	124	<p>You can find out the major and minor version numbers of the library
…		…
116	version of the library your program was compiled against.</p>	128	version of the library your program was compiled against.</p>
117	<p>Usually, it's a good idea to terminate if the major versions mismatch,	129	<p>Usually, it's a good idea to terminate if the major versions mismatch,
118	as this indicates an incompatible change. Minor versions are usually	130	as this indicates an incompatible change. Minor versions are usually
119	compatible to older versions, so a larger minor version alone is usually	131	compatible to older versions, so a larger minor version alone is usually
120	not a problem.</p>	132	not a problem.</p>
		133	<p>Example: make sure we haven't accidentally been linked against the wrong
		134	version:</p>
		135	<pre> assert (("libev version mismatch",
		136	ev_version_major () == EV_VERSION_MAJOR
		137	&& ev_version_minor () >= EV_VERSION_MINOR));
		138
		139	</pre>
		140	</dd>
		141	<dt>unsigned int ev_supported_backends ()</dt>
		142	<dd>
		143	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		144	value) compiled into this binary of libev (independent of their
		145	availability on the system you are running on). See <code>ev_default_loop</code> for
		146	a description of the set values.</p>
		147	<p>Example: make sure we have the epoll method, because yeah this is cool and
		148	a must have and can we have a torrent of it please!!!11</p>
		149	<pre> assert (("sorry, no epoll, no sex",
		150	ev_supported_backends () & EVBACKEND_EPOLL));
		151
		152	</pre>
		153	</dd>
		154	<dt>unsigned int ev_recommended_backends ()</dt>
		155	<dd>
		156	<p>Return the set of all backends compiled into this binary of libev and also
		157	recommended for this platform. This set is often smaller than the one
		158	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		159	most BSDs and will not be autodetected unless you explicitly request it
		160	(assuming you know what you are doing). This is the set of backends that
		161	libev will probe for if you specify no backends explicitly.</p>
		162	</dd>
		163	<dt>unsigned int ev_embeddable_backends ()</dt>
		164	<dd>
		165	<p>Returns the set of backends that are embeddable in other event loops. This
		166	is the theoretical, all-platform, value. To find which backends
		167	might be supported on the current system, you would need to look at
		168	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		169	recommended ones.</p>
		170	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
121	</dd>	171	</dd>
122	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	172	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
123	<dd>	173	<dd>
124	<p>Sets the allocation function to use (the prototype is similar to the	174	<p>Sets the allocation function to use (the prototype is similar to the
125	realloc C function, the semantics are identical). It is used to allocate	175	realloc C function, the semantics are identical). It is used to allocate
…		…
127	needs to be allocated, the library might abort or take some potentially	177	needs to be allocated, the library might abort or take some potentially
128	destructive action. The default is your system realloc function.</p>	178	destructive action. The default is your system realloc function.</p>
129	<p>You could override this function in high-availability programs to, say,	179	<p>You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	180	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.</p>	181	or even to sleep a while and retry until some memory is available.</p>
		182	<p>Example: replace the libev allocator with one that waits a bit and then
		183	retries: better than mine).</p>
		184	<pre> static void *
		185	persistent_realloc (void *ptr, long size)
		186	{
		187	for (;;)
		188	{
		189	void *newptr = realloc (ptr, size);
		190
		191	if (newptr)
		192	return newptr;
		193
		194	sleep (60);
		195	}
		196	}
		197
		198	...
		199	ev_set_allocator (persistent_realloc);
		200
		201	</pre>
132	</dd>	202	</dd>
133	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	203	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
134	<dd>	204	<dd>
135	<p>Set the callback function to call on a retryable syscall error (such	205	<p>Set the callback function to call on a retryable syscall error (such
136	as failed select, poll, epoll_wait). The message is a printable string	206	as failed select, poll, epoll_wait). The message is a printable string
137	indicating the system call or subsystem causing the problem. If this	207	indicating the system call or subsystem causing the problem. If this
138	callback is set, then libev will expect it to remedy the sitution, no	208	callback is set, then libev will expect it to remedy the sitution, no
139	matter what, when it returns. That is, libev will generally retry the	209	matter what, when it returns. That is, libev will generally retry the
140	requested operation, or, if the condition doesn't go away, do bad stuff	210	requested operation, or, if the condition doesn't go away, do bad stuff
141	(such as abort).</p>	211	(such as abort).</p>
		212	<p>Example: do the same thing as libev does internally:</p>
		213	<pre> static void
		214	fatal_error (const char *msg)
		215	{
		216	perror (msg);
		217	abort ();
		218	}
		219
		220	...
		221	ev_set_syserr_cb (fatal_error);
		222
		223	</pre>
142	</dd>	224	</dd>
143	</dl>	225	</dl>
144		226
145	</div>	227	</div>
146	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	228	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
…		…
158	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	240	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
159	<dd>	241	<dd>
160	<p>This will initialise the default event loop if it hasn't been initialised	242	<p>This will initialise the default event loop if it hasn't been initialised
161	yet and return it. If the default loop could not be initialised, returns	243	yet and return it. If the default loop could not be initialised, returns
162	false. If it already was initialised it simply returns it (and ignores the	244	false. If it already was initialised it simply returns it (and ignores the
163	flags).</p>	245	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
164	<p>If you don't know what event loop to use, use the one returned from this	246	<p>If you don't know what event loop to use, use the one returned from this
165	function.</p>	247	function.</p>
166	<p>The flags argument can be used to specify special behaviour or specific	248	<p>The flags argument can be used to specify special behaviour or specific
167	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>	249	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
168	<p>It supports the following flags:</p>	250	<p>The following flags are supported:</p>
169	<p>	251	<p>
170	<dl>	252	<dl>
171	<dt><code>EVFLAG_AUTO</code></dt>	253	<dt><code>EVFLAG_AUTO</code></dt>
172	<dd>	254	<dd>
173	<p>The default flags value. Use this if you have no clue (it's the right	255	<p>The default flags value. Use this if you have no clue (it's the right
…		…
180	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will	262	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181	override the flags completely if it is found in the environment. This is	263	override the flags completely if it is found in the environment. This is
182	useful to try out specific backends to test their performance, or to work	264	useful to try out specific backends to test their performance, or to work
183	around bugs.</p>	265	around bugs.</p>
184	</dd>	266	</dd>
185	<dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>	267	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
186	<dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
187	<dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
188	<dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
189	<dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
190	<dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
191	<dd>	268	<dd>
192	<p>If one or more of these are ored into the flags value, then only these	269	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
193	backends will be tried (in the reverse order as given here). If one are	270	libev tries to roll its own fd_set with no limits on the number of fds,
194	specified, any backend will do.</p>	271	but if that fails, expect a fairly low limit on the number of fds when
		272	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		273	the fastest backend for a low number of fds.</p>
		274	</dd>
		275	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		276	<dd>
		277	<p>And this is your standard poll(2) backend. It's more complicated than
		278	select, but handles sparse fds better and has no artificial limit on the
		279	number of fds you can use (except it will slow down considerably with a
		280	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		281	</dd>
		282	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		283	<dd>
		284	<p>For few fds, this backend is a bit little slower than poll and select,
		285	but it scales phenomenally better. While poll and select usually scale like
		286	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		287	either O(1) or O(active_fds).</p>
		288	<p>While stopping and starting an I/O watcher in the same iteration will
		289	result in some caching, there is still a syscall per such incident
		290	(because the fd could point to a different file description now), so its
		291	best to avoid that. Also, dup()ed file descriptors might not work very
		292	well if you register events for both fds.</p>
		293	<p>Please note that epoll sometimes generates spurious notifications, so you
		294	need to use non-blocking I/O or other means to avoid blocking when no data
		295	(or space) is available.</p>
		296	</dd>
		297	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		298	<dd>
		299	<p>Kqueue deserves special mention, as at the time of this writing, it
		300	was broken on all BSDs except NetBSD (usually it doesn't work with
		301	anything but sockets and pipes, except on Darwin, where of course its
		302	completely useless). For this reason its not being "autodetected"
		303	unless you explicitly specify it explicitly in the flags (i.e. using
		304	<code>EVBACKEND_KQUEUE</code>).</p>
		305	<p>It scales in the same way as the epoll backend, but the interface to the
		306	kernel is more efficient (which says nothing about its actual speed, of
		307	course). While starting and stopping an I/O watcher does not cause an
		308	extra syscall as with epoll, it still adds up to four event changes per
		309	incident, so its best to avoid that.</p>
		310	</dd>
		311	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		312	<dd>
		313	<p>This is not implemented yet (and might never be).</p>
		314	</dd>
		315	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		316	<dd>
		317	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		318	it's really slow, but it still scales very well (O(active_fds)).</p>
		319	<p>Please note that solaris ports can result in a lot of spurious
		320	notifications, so you need to use non-blocking I/O or other means to avoid
		321	blocking when no data (or space) is available.</p>
		322	</dd>
		323	<dt><code>EVBACKEND_ALL</code></dt>
		324	<dd>
		325	<p>Try all backends (even potentially broken ones that wouldn't be tried
		326	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		327	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
195	</dd>	328	</dd>
196	</dl>	329	</dl>
197	</p>	330	</p>
		331	<p>If one or more of these are ored into the flags value, then only these
		332	backends will be tried (in the reverse order as given here). If none are
		333	specified, most compiled-in backend will be tried, usually in reverse
		334	order of their flag values :)</p>
		335	<p>The most typical usage is like this:</p>
		336	<pre> if (!ev_default_loop (0))
		337	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		338
		339	</pre>
		340	<p>Restrict libev to the select and poll backends, and do not allow
		341	environment settings to be taken into account:</p>
		342	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		343
		344	</pre>
		345	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		346	available (warning, breaks stuff, best use only with your own private
		347	event loop and only if you know the OS supports your types of fds):</p>
		348	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		349
		350	</pre>
198	</dd>	351	</dd>
199	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	352	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200	<dd>	353	<dd>
201	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	354	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
202	always distinct from the default loop. Unlike the default loop, it cannot	355	always distinct from the default loop. Unlike the default loop, it cannot
203	handle signal and child watchers, and attempts to do so will be greeted by	356	handle signal and child watchers, and attempts to do so will be greeted by
204	undefined behaviour (or a failed assertion if assertions are enabled).</p>	357	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		358	<p>Example: try to create a event loop that uses epoll and nothing else.</p>
		359	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		360	if (!epoller)
		361	fatal ("no epoll found here, maybe it hides under your chair");
		362
		363	</pre>
205	</dd>	364	</dd>
206	<dt>ev_default_destroy ()</dt>	365	<dt>ev_default_destroy ()</dt>
207	<dd>	366	<dd>
208	<p>Destroys the default loop again (frees all memory and kernel state	367	<p>Destroys the default loop again (frees all memory and kernel state
209	etc.). This stops all registered event watchers (by not touching them in	368	etc.). This stops all registered event watchers (by not touching them in
…		…
218	<dd>	377	<dd>
219	<p>This function reinitialises the kernel state for backends that have	378	<p>This function reinitialises the kernel state for backends that have
220	one. Despite the name, you can call it anytime, but it makes most sense	379	one. Despite the name, you can call it anytime, but it makes most sense
221	after forking, in either the parent or child process (or both, but that	380	after forking, in either the parent or child process (or both, but that
222	again makes little sense).</p>	381	again makes little sense).</p>
223	<p>You <i>must</i> call this function after forking if and only if you want to	382	<p>You <i>must</i> call this function in the child process after forking if and
224	use the event library in both processes. If you just fork+exec, you don't	383	only if you want to use the event library in both processes. If you just
225	have to call it.</p>	384	fork+exec, you don't have to call it.</p>
226	<p>The function itself is quite fast and it's usually not a problem to call	385	<p>The function itself is quite fast and it's usually not a problem to call
227	it just in case after a fork. To make this easy, the function will fit in	386	it just in case after a fork. To make this easy, the function will fit in
228	quite nicely into a call to <code>pthread_atfork</code>:</p>	387	quite nicely into a call to <code>pthread_atfork</code>:</p>
229	<pre> pthread_atfork (0, 0, ev_default_fork);	388	<pre> pthread_atfork (0, 0, ev_default_fork);
230		389
231	</pre>	390	</pre>
		391	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		392	without calling this function, so if you force one of those backends you
		393	do not need to care.</p>
232	</dd>	394	</dd>
233	<dt>ev_loop_fork (loop)</dt>	395	<dt>ev_loop_fork (loop)</dt>
234	<dd>	396	<dd>
235	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	397	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
236	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	398	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
237	after fork, and how you do this is entirely your own problem.</p>	399	after fork, and how you do this is entirely your own problem.</p>
238	</dd>	400	</dd>
239	<dt>unsigned int ev_method (loop)</dt>	401	<dt>unsigned int ev_backend (loop)</dt>
240	<dd>	402	<dd>
241	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	403	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
242	use.</p>	404	use.</p>
243	</dd>	405	</dd>
244	<dt>ev_tstamp ev_now (loop)</dt>	406	<dt>ev_tstamp ev_now (loop)</dt>
245	<dd>	407	<dd>
246	<p>Returns the current "event loop time", which is the time the event loop	408	<p>Returns the current "event loop time", which is the time the event loop
247	got events and started processing them. This timestamp does not change	409	received events and started processing them. This timestamp does not
248	as long as callbacks are being processed, and this is also the base time	410	change as long as callbacks are being processed, and this is also the base
249	used for relative timers. You can treat it as the timestamp of the event	411	time used for relative timers. You can treat it as the timestamp of the
250	occuring (or more correctly, the mainloop finding out about it).</p>	412	event occuring (or more correctly, libev finding out about it).</p>
251	</dd>	413	</dd>
252	<dt>ev_loop (loop, int flags)</dt>	414	<dt>ev_loop (loop, int flags)</dt>
253	<dd>	415	<dd>
254	<p>Finally, this is it, the event handler. This function usually is called	416	<p>Finally, this is it, the event handler. This function usually is called
255	after you initialised all your watchers and you want to start handling	417	after you initialised all your watchers and you want to start handling
256	events.</p>	418	events.</p>
257	<p>If the flags argument is specified as 0, it will not return until either	419	<p>If the flags argument is specified as <code>0</code>, it will not return until
258	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	420	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		421	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		422	relying on all watchers to be stopped when deciding when a program has
		423	finished (especially in interactive programs), but having a program that
		424	automatically loops as long as it has to and no longer by virtue of
		425	relying on its watchers stopping correctly is a thing of beauty.</p>
259	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	426	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
260	those events and any outstanding ones, but will not block your process in	427	those events and any outstanding ones, but will not block your process in
261	case there are no events and will return after one iteration of the loop.</p>	428	case there are no events and will return after one iteration of the loop.</p>
262	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	429	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
263	neccessary) and will handle those and any outstanding ones. It will block	430	neccessary) and will handle those and any outstanding ones. It will block
264	your process until at least one new event arrives, and will return after	431	your process until at least one new event arrives, and will return after
265	one iteration of the loop.</p>	432	one iteration of the loop. This is useful if you are waiting for some
266	<p>This flags value could be used to implement alternative looping	433	external event in conjunction with something not expressible using other
267	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	434	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
268	more generic mechanism.</p>	435	usually a better approach for this kind of thing.</p>
		436	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		437	<pre> * If there are no active watchers (reference count is zero), return.
		438	- Queue prepare watchers and then call all outstanding watchers.
		439	- If we have been forked, recreate the kernel state.
		440	- Update the kernel state with all outstanding changes.
		441	- Update the "event loop time".
		442	- Calculate for how long to block.
		443	- Block the process, waiting for any events.
		444	- Queue all outstanding I/O (fd) events.
		445	- Update the "event loop time" and do time jump handling.
		446	- Queue all outstanding timers.
		447	- Queue all outstanding periodics.
		448	- If no events are pending now, queue all idle watchers.
		449	- Queue all check watchers.
		450	- Call all queued watchers in reverse order (i.e. check watchers first).
		451	Signals and child watchers are implemented as I/O watchers, and will
		452	be handled here by queueing them when their watcher gets executed.
		453	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		454	were used, return, otherwise continue with step *.
		455
		456	</pre>
		457	<p>Example: queue some jobs and then loop until no events are outsanding
		458	anymore.</p>
		459	<pre> ... queue jobs here, make sure they register event watchers as long
		460	... as they still have work to do (even an idle watcher will do..)
		461	ev_loop (my_loop, 0);
		462	... jobs done. yeah!
		463
		464	</pre>
269	</dd>	465	</dd>
270	<dt>ev_unloop (loop, how)</dt>	466	<dt>ev_unloop (loop, how)</dt>
271	<dd>	467	<dd>
272	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it	468	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
273	has processed all outstanding events). The <code>how</code> argument must be either	469	has processed all outstanding events). The <code>how</code> argument must be either
274	<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or	470	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
275	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>	471	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276	</dd>	472	</dd>
277	<dt>ev_ref (loop)</dt>	473	<dt>ev_ref (loop)</dt>
278	<dt>ev_unref (loop)</dt>	474	<dt>ev_unref (loop)</dt>
279	<dd>	475	<dd>
…		…
285	example, libev itself uses this for its internal signal pipe: It is not	481	example, libev itself uses this for its internal signal pipe: It is not
286	visible to the libev user and should not keep <code>ev_loop</code> from exiting if	482	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
287	no event watchers registered by it are active. It is also an excellent	483	no event watchers registered by it are active. It is also an excellent
288	way to do this for generic recurring timers or from within third-party	484	way to do this for generic recurring timers or from within third-party
289	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>	485	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		486	<p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
		487	running when nothing else is active.</p>
		488	<pre> struct dv_signal exitsig;
		489	ev_signal_init (&exitsig, sig_cb, SIGINT);
		490	ev_signal_start (myloop, &exitsig);
		491	evf_unref (myloop);
		492
		493	</pre>
		494	<p>Example: for some weird reason, unregister the above signal handler again.</p>
		495	<pre> ev_ref (myloop);
		496	ev_signal_stop (myloop, &exitsig);
		497
		498	</pre>
290	</dd>	499	</dd>
291	</dl>	500	</dl>
292		501
293	</div>	502	</div>
294	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	503	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
…		…
326	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	535	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
327	*)</code>), and you can stop watching for events at any time by calling the	536	*)</code>), and you can stop watching for events at any time by calling the
328	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	537	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
329	<p>As long as your watcher is active (has been started but not stopped) you	538	<p>As long as your watcher is active (has been started but not stopped) you
330	must not touch the values stored in it. Most specifically you must never	539	must not touch the values stored in it. Most specifically you must never
331	reinitialise it or call its set method.</p>	540	reinitialise it or call its set macro.</p>
332	<p>You can check whether an event is active by calling the <code>ev_is_active	541	<p>You can check whether an event is active by calling the <code>ev_is_active
333	(watcher *)</code> macro. To see whether an event is outstanding (but the	542	(watcher *)</code> macro. To see whether an event is outstanding (but the
334	callback for it has not been called yet) you can use the <code>ev_is_pending	543	callback for it has not been called yet) you can use the <code>ev_is_pending
335	(watcher *)</code> macro.</p>	544	(watcher *)</code> macro.</p>
336	<p>Each and every callback receives the event loop pointer as first, the	545	<p>Each and every callback receives the event loop pointer as first, the
…		…
430	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	639	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
431	<div id="WATCHER_TYPES_CONTENT">	640	<div id="WATCHER_TYPES_CONTENT">
432	<p>This section describes each watcher in detail, but will not repeat	641	<p>This section describes each watcher in detail, but will not repeat
433	information given in the last section.</p>	642	information given in the last section.</p>
434		643
		644
		645
		646
		647
435	</div>	648	</div>
436	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>	649	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
437	<div id="code_ev_io_code_is_this_file_descrip-2">	650	<div id="code_ev_io_code_is_this_file_descrip-2">
438	<p>I/O watchers check whether a file descriptor is readable or writable	651	<p>I/O watchers check whether a file descriptor is readable or writable
439	in each iteration of the event loop (This behaviour is called	652	in each iteration of the event loop (This behaviour is called
440	level-triggering because you keep receiving events as long as the	653	level-triggering because you keep receiving events as long as the
441	condition persists. Remember you can stop the watcher if you don't want to	654	condition persists. Remember you can stop the watcher if you don't want to
442	act on the event and neither want to receive future events).</p>	655	act on the event and neither want to receive future events).</p>
443	<p>In general you can register as many read and/or write event watchers oer	656	<p>In general you can register as many read and/or write event watchers per
444	fd as you want (as long as you don't confuse yourself). Setting all file	657	fd as you want (as long as you don't confuse yourself). Setting all file
445	descriptors to non-blocking mode is also usually a good idea (but not	658	descriptors to non-blocking mode is also usually a good idea (but not
446	required if you know what you are doing).</p>	659	required if you know what you are doing).</p>
447	<p>You have to be careful with dup'ed file descriptors, though. Some backends	660	<p>You have to be careful with dup'ed file descriptors, though. Some backends
448	(the linux epoll backend is a notable example) cannot handle dup'ed file	661	(the linux epoll backend is a notable example) cannot handle dup'ed file
449	descriptors correctly if you register interest in two or more fds pointing	662	descriptors correctly if you register interest in two or more fds pointing
450	to the same file/socket etc. description.</p>	663	to the same underlying file/socket etc. description (that is, they share
		664	the same underlying "file open").</p>
451	<p>If you must do this, then force the use of a known-to-be-good backend	665	<p>If you must do this, then force the use of a known-to-be-good backend
452	(at the time of this writing, this includes only EVMETHOD_SELECT and	666	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453	EVMETHOD_POLL).</p>	667	<code>EVBACKEND_POLL</code>).</p>
454	<dl>	668	<dl>
455	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	669	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
456	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	670	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
457	<dd>	671	<dd>
458	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive	672	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
459	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	673	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|
460	EV_WRITE</code> to receive the given events.</p>	674	EV_WRITE</code> to receive the given events.</p>
		675	<p>Please note that most of the more scalable backend mechanisms (for example
		676	epoll and solaris ports) can result in spurious readyness notifications
		677	for file descriptors, so you practically need to use non-blocking I/O (and
		678	treat callback invocation as hint only), or retest separately with a safe
		679	interface before doing I/O (XLib can do this), or force the use of either
		680	<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
		681	problem. Also note that it is quite easy to have your callback invoked
		682	when the readyness condition is no longer valid even when employing
		683	typical ways of handling events, so its a good idea to use non-blocking
		684	I/O unconditionally.</p>
461	</dd>	685	</dd>
462	</dl>	686	</dl>
		687	<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		688	readable, but only once. Since it is likely line-buffered, you could
		689	attempt to read a whole line in the callback:</p>
		690	<pre> static void
		691	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		692	{
		693	ev_io_stop (loop, w);
		694	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		695	}
		696
		697	...
		698	struct ev_loop *loop = ev_default_init (0);
		699	struct ev_io stdin_readable;
		700	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		701	ev_io_start (loop, &stdin_readable);
		702	ev_loop (loop, 0);
		703
		704
		705
		706
		707	</pre>
463		708
464	</div>	709	</div>
465	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>	710	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
466	<div id="code_ev_timer_code_relative_and_opti-2">	711	<div id="code_ev_timer_code_relative_and_opti-2">
467	<p>Timer watchers are simple relative timers that generate an event after a	712	<p>Timer watchers are simple relative timers that generate an event after a
468	given time, and optionally repeating in regular intervals after that.</p>	713	given time, and optionally repeating in regular intervals after that.</p>
469	<p>The timers are based on real time, that is, if you register an event that	714	<p>The timers are based on real time, that is, if you register an event that
470	times out after an hour and youreset your system clock to last years	715	times out after an hour and you reset your system clock to last years
471	time, it will still time out after (roughly) and hour. "Roughly" because	716	time, it will still time out after (roughly) and hour. "Roughly" because
472	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	717	detecting time jumps is hard, and some inaccuracies are unavoidable (the
473	monotonic clock option helps a lot here).</p>	718	monotonic clock option helps a lot here).</p>
474	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>	719	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
475	time. This is usually the right thing as this timestamp refers to the time	720	time. This is usually the right thing as this timestamp refers to the time
476	of the event triggering whatever timeout you are modifying/starting. If	721	of the event triggering whatever timeout you are modifying/starting. If
477	you suspect event processing to be delayed and you need to base the timeout	722	you suspect event processing to be delayed and you <i>need</i> to base the timeout
478	ion the current time, use something like this to adjust for this:</p>	723	on the current time, use something like this to adjust for this:</p>
479	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	724	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
480		725
481	</pre>	726	</pre>
		727	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		728	but if multiple timers become ready during the same loop iteration then
		729	order of execution is undefined.</p>
482	<dl>	730	<dl>
483	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	731	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
484	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	732	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485	<dd>	733	<dd>
486	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	734	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
488	timer will automatically be configured to trigger again <code>repeat</code> seconds	736	timer will automatically be configured to trigger again <code>repeat</code> seconds
489	later, again, and again, until stopped manually.</p>	737	later, again, and again, until stopped manually.</p>
490	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	738	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
491	configure a timer to trigger every 10 seconds, then it will trigger at	739	configure a timer to trigger every 10 seconds, then it will trigger at
492	exactly 10 second intervals. If, however, your program cannot keep up with	740	exactly 10 second intervals. If, however, your program cannot keep up with
493	the timer (ecause it takes longer than those 10 seconds to do stuff) the	741	the timer (because it takes longer than those 10 seconds to do stuff) the
494	timer will not fire more than once per event loop iteration.</p>	742	timer will not fire more than once per event loop iteration.</p>
495	</dd>	743	</dd>
496	<dt>ev_timer_again (loop)</dt>	744	<dt>ev_timer_again (loop)</dt>
497	<dd>	745	<dd>
498	<p>This will act as if the timer timed out and restart it again if it is	746	<p>This will act as if the timer timed out and restart it again if it is
…		…
508	time you successfully read or write some data. If you go into an idle	756	time you successfully read or write some data. If you go into an idle
509	state where you do not expect data to travel on the socket, you can stop	757	state where you do not expect data to travel on the socket, you can stop
510	the timer, and again will automatically restart it if need be.</p>	758	the timer, and again will automatically restart it if need be.</p>
511	</dd>	759	</dd>
512	</dl>	760	</dl>
		761	<p>Example: create a timer that fires after 60 seconds.</p>
		762	<pre> static void
		763	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		764	{
		765	.. one minute over, w is actually stopped right here
		766	}
		767
		768	struct ev_timer mytimer;
		769	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		770	ev_timer_start (loop, &mytimer);
		771
		772	</pre>
		773	<p>Example: create a timeout timer that times out after 10 seconds of
		774	inactivity.</p>
		775	<pre> static void
		776	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		777	{
		778	.. ten seconds without any activity
		779	}
		780
		781	struct ev_timer mytimer;
		782	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		783	ev_timer_again (&mytimer); /* start timer */
		784	ev_loop (loop, 0);
		785
		786	// and in some piece of code that gets executed on any "activity":
		787	// reset the timeout to start ticking again at 10 seconds
		788	ev_timer_again (&mytimer);
		789
		790
		791
		792
		793	</pre>
513		794
514	</div>	795	</div>
515	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>	796	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
516	<div id="code_ev_periodic_code_to_cron_or_not-2">	797	<div id="code_ev_periodic_code_to_cron_or_not-2">
517	<p>Periodic watchers are also timers of a kind, but they are very versatile	798	<p>Periodic watchers are also timers of a kind, but they are very versatile
…		…
524	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger	805	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
525	roughly 10 seconds later and of course not if you reset your system time	806	roughly 10 seconds later and of course not if you reset your system time
526	again).</p>	807	again).</p>
527	<p>They can also be used to implement vastly more complex timers, such as	808	<p>They can also be used to implement vastly more complex timers, such as
528	triggering an event on eahc midnight, local time.</p>	809	triggering an event on eahc midnight, local time.</p>
		810	<p>As with timers, the callback is guarenteed to be invoked only when the
		811	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		812	during the same loop iteration then order of execution is undefined.</p>
529	<dl>	813	<dl>
530	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	814	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
531	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	815	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532	<dd>	816	<dd>
533	<p>Lots of arguments, lets sort it out... There are basically three modes of	817	<p>Lots of arguments, lets sort it out... There are basically three modes of
534	operation, and we will explain them from simplest to complex:</p>	818	operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539	<p>	819	<p>
540	<dl>	820	<dl>
541	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	821	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
542	<dd>	822	<dd>
543	<p>In this configuration the watcher triggers an event at the wallclock time	823	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
567	<dd>	847	<dd>
568	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	848	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
569	ignored. Instead, each time the periodic watcher gets scheduled, the	849	ignored. Instead, each time the periodic watcher gets scheduled, the
570	reschedule callback will be called with the watcher as first, and the	850	reschedule callback will be called with the watcher as first, and the
571	current time as second argument.</p>	851	current time as second argument.</p>
572	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	852	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
573	periodic watcher, ever, or make any event loop modifications</i>. If you need	853	ever, or make any event loop modifications</i>. If you need to stop it,
574	to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p>	854	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
575	<p>Also, <i>this callback must always return a time that is later than the	855	starting a prepare watcher).</p>
576	passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
577	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,	856	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
578	ev_tstamp now)</code>, e.g.:</p>	857	ev_tstamp now)</code>, e.g.:</p>
579	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	858	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580	{	859	{
581	return now + 60.;	860	return now + 60.;
…		…
584	</pre>	863	</pre>
585	<p>It must return the next time to trigger, based on the passed time value	864	<p>It must return the next time to trigger, based on the passed time value
586	(that is, the lowest time value larger than to the second argument). It	865	(that is, the lowest time value larger than to the second argument). It
587	will usually be called just before the callback will be triggered, but	866	will usually be called just before the callback will be triggered, but
588	might be called at other times, too.</p>	867	might be called at other times, too.</p>
		868	<p>NOTE: <i>This callback must always return a time that is later than the
		869	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
589	<p>This can be used to create very complex timers, such as a timer that	870	<p>This can be used to create very complex timers, such as a timer that
590	triggers on each midnight, local time. To do this, you would calculate the	871	triggers on each midnight, local time. To do this, you would calculate the
591	next midnight after <code>now</code> and return the timestamp value for this. How you do this	872	next midnight after <code>now</code> and return the timestamp value for this. How
592	is, again, up to you (but it is not trivial).</p>	873	you do this is, again, up to you (but it is not trivial, which is the main
		874	reason I omitted it as an example).</p>
593	</dd>	875	</dd>
594	</dl>	876	</dl>
595	</p>	877	</p>
596	</dd>	878	</dd>
597	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	879	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
600	when you changed some parameters or the reschedule callback would return	882	when you changed some parameters or the reschedule callback would return
601	a different time than the last time it was called (e.g. in a crond like	883	a different time than the last time it was called (e.g. in a crond like
602	program when the crontabs have changed).</p>	884	program when the crontabs have changed).</p>
603	</dd>	885	</dd>
604	</dl>	886	</dl>
		887	<p>Example: call a callback every hour, or, more precisely, whenever the
		888	system clock is divisible by 3600. The callback invocation times have
		889	potentially a lot of jittering, but good long-term stability.</p>
		890	<pre> static void
		891	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		892	{
		893	... its now a full hour (UTC, or TAI or whatever your clock follows)
		894	}
		895
		896	struct ev_periodic hourly_tick;
		897	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		898	ev_periodic_start (loop, &hourly_tick);
		899
		900	</pre>
		901	<p>Example: the same as above, but use a reschedule callback to do it:</p>
		902	<pre> #include <math.h>
		903
		904	static ev_tstamp
		905	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		906	{
		907	return fmod (now, 3600.) + 3600.;
		908	}
		909
		910	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		911
		912	</pre>
		913	<p>Example: call a callback every hour, starting now:</p>
		914	<pre> struct ev_periodic hourly_tick;
		915	ev_periodic_init (&hourly_tick, clock_cb,
		916	fmod (ev_now (loop), 3600.), 3600., 0);
		917	ev_periodic_start (loop, &hourly_tick);
		918
		919
		920
		921
		922	</pre>
605		923
606	</div>	924	</div>
607	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>	925	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
608	<div id="code_ev_signal_code_signal_me_when_a-2">	926	<div id="code_ev_signal_code_signal_me_when_a-2">
609	<p>Signal watchers will trigger an event when the process receives a specific	927	<p>Signal watchers will trigger an event when the process receives a specific
…		…
623	<p>Configures the watcher to trigger on the given signal number (usually one	941	<p>Configures the watcher to trigger on the given signal number (usually one
624	of the <code>SIGxxx</code> constants).</p>	942	of the <code>SIGxxx</code> constants).</p>
625	</dd>	943	</dd>
626	</dl>	944	</dl>
627		945
		946
		947
		948
		949
628	</div>	950	</div>
629	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>	951	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
630	<div id="code_ev_child_code_wait_for_pid_stat-2">	952	<div id="code_ev_child_code_wait_for_pid_stat-2">
631	<p>Child watchers trigger when your process receives a SIGCHLD in response to	953	<p>Child watchers trigger when your process receives a SIGCHLD in response to
632	some child status changes (most typically when a child of yours dies).</p>	954	some child status changes (most typically when a child of yours dies).</p>
…		…
640	the status word (use the macros from <code>sys/wait.h</code> and see your systems	962	the status word (use the macros from <code>sys/wait.h</code> and see your systems
641	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the	963	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
642	process causing the status change.</p>	964	process causing the status change.</p>
643	</dd>	965	</dd>
644	</dl>	966	</dl>
		967	<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
		968	<pre> static void
		969	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		970	{
		971	ev_unloop (loop, EVUNLOOP_ALL);
		972	}
		973
		974	struct ev_signal signal_watcher;
		975	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		976	ev_signal_start (loop, &sigint_cb);
		977
		978
		979
		980
		981	</pre>
645		982
646	</div>	983	</div>
647	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>	984	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
648	<div id="code_ev_idle_code_when_you_ve_got_no-2">	985	<div id="code_ev_idle_code_when_you_ve_got_no-2">
649	<p>Idle watchers trigger events when there are no other events are pending	986	<p>Idle watchers trigger events when there are no other events are pending
…		…
665	<p>Initialises and configures the idle watcher - it has no parameters of any	1002	<p>Initialises and configures the idle watcher - it has no parameters of any
666	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1003	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
667	believe me.</p>	1004	believe me.</p>
668	</dd>	1005	</dd>
669	</dl>	1006	</dl>
		1007	<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
		1008	callback, free it. Alos, use no error checking, as usual.</p>
		1009	<pre> static void
		1010	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1011	{
		1012	free (w);
		1013	// now do something you wanted to do when the program has
		1014	// no longer asnything immediate to do.
		1015	}
		1016
		1017	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1018	ev_idle_init (idle_watcher, idle_cb);
		1019	ev_idle_start (loop, idle_cb);
		1020
		1021
		1022
		1023
		1024	</pre>
670		1025
671	</div>	1026	</div>
672	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>	1027	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
673	<div id="code_ev_prepare_code_and_code_ev_che-2">	1028	<div id="code_ev_prepare_code_and_code_ev_che-2">
674	<p>Prepare and check watchers are usually (but not always) used in tandem:	1029	<p>Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	1030	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.</p>	1031	afterwards.</p>
677	<p>Their main purpose is to integrate other event mechanisms into libev. This	1032	<p>Their main purpose is to integrate other event mechanisms into libev and
678	could be used, for example, to track variable changes, implement your own	1033	their use is somewhat advanced. This could be used, for example, to track
679	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1034	variable changes, implement your own watchers, integrate net-snmp or a
		1035	coroutine library and lots more.</p>
680	<p>This is done by examining in each prepare call which file descriptors need	1036	<p>This is done by examining in each prepare call which file descriptors need
681	to be watched by the other library, registering <code>ev_io</code> watchers for	1037	to be watched by the other library, registering <code>ev_io</code> watchers for
682	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries	1038	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
683	provide just this functionality). Then, in the check watcher you check for	1039	provide just this functionality). Then, in the check watcher you check for
684	any events that occured (by checking the pending status of all watchers	1040	any events that occured (by checking the pending status of all watchers
685	and stopping them) and call back into the library. The I/O and timer	1041	and stopping them) and call back into the library. The I/O and timer
686	callbacks will never actually be called (but must be valid neverthelles,	1042	callbacks will never actually be called (but must be valid nevertheless,
687	because you never know, you know?).</p>	1043	because you never know, you know?).</p>
688	<p>As another example, the Perl Coro module uses these hooks to integrate	1044	<p>As another example, the Perl Coro module uses these hooks to integrate
689	coroutines into libev programs, by yielding to other active coroutines	1045	coroutines into libev programs, by yielding to other active coroutines
690	during each prepare and only letting the process block if no coroutines	1046	during each prepare and only letting the process block if no coroutines
691	are ready to run (its actually more complicated, it only runs coroutines	1047	are ready to run (it's actually more complicated: it only runs coroutines
692	with priority higher than the event loop and one lower priority once,	1048	with priority higher than or equal to the event loop and one coroutine
693	using idle watchers to keep the event loop from blocking if lower-priority	1049	of lower priority, but only once, using idle watchers to keep the event
694	coroutines exist, thus mapping low-priority coroutines to idle/background	1050	loop from blocking if lower-priority coroutines are active, thus mapping
695	tasks).</p>	1051	low-priority coroutines to idle/background tasks).</p>
696	<dl>	1052	<dl>
697	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1053	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
698	<dt>ev_check_init (ev_check *, callback)</dt>	1054	<dt>ev_check_init (ev_check *, callback)</dt>
699	<dd>	1055	<dd>
700	<p>Initialises and configures the prepare or check watcher - they have no	1056	<p>Initialises and configures the prepare or check watcher - they have no
701	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1057	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
702	macros, but using them is utterly, utterly and completely pointless.</p>	1058	macros, but using them is utterly, utterly and completely pointless.</p>
703	</dd>	1059	</dd>
704	</dl>	1060	</dl>
		1061	<p>Example: TODO.</p>
		1062
		1063
		1064
		1065
		1066
		1067	</div>
		1068	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2>
		1069	<div id="code_ev_embed_code_when_one_backend_-2">
		1070	<p>This is a rather advanced watcher type that lets you embed one event loop
		1071	into another.</p>
		1072	<p>There are primarily two reasons you would want that: work around bugs and
		1073	prioritise I/O.</p>
		1074	<p>As an example for a bug workaround, the kqueue backend might only support
		1075	sockets on some platform, so it is unusable as generic backend, but you
		1076	still want to make use of it because you have many sockets and it scales
		1077	so nicely. In this case, you would create a kqueue-based loop and embed it
		1078	into your default loop (which might use e.g. poll). Overall operation will
		1079	be a bit slower because first libev has to poll and then call kevent, but
		1080	at least you can use both at what they are best.</p>
		1081	<p>As for prioritising I/O: rarely you have the case where some fds have
		1082	to be watched and handled very quickly (with low latency), and even
		1083	priorities and idle watchers might have too much overhead. In this case
		1084	you would put all the high priority stuff in one loop and all the rest in
		1085	a second one, and embed the second one in the first.</p>
		1086	<p>As long as the watcher is started it will automatically handle events. The
		1087	callback will be invoked whenever some events have been handled. You can
		1088	set the callback to <code>0</code> to avoid having to specify one if you are not
		1089	interested in that.</p>
		1090	<p>Also, there have not currently been made special provisions for forking:
		1091	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1092	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1093	yourself.</p>
		1094	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1095	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1096	portable one.</p>
		1097	<p>So when you want to use this feature you will always have to be prepared
		1098	that you cannot get an embeddable loop. The recommended way to get around
		1099	this is to have a separate variables for your embeddable loop, try to
		1100	create it, and if that fails, use the normal loop for everything:</p>
		1101	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1102	struct ev_loop *loop_lo = 0;
		1103	struct ev_embed embed;
		1104
		1105	// see if there is a chance of getting one that works
		1106	// (remember that a flags value of 0 means autodetection)
		1107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1109	: 0;
		1110
		1111	// if we got one, then embed it, otherwise default to loop_hi
		1112	if (loop_lo)
		1113	{
		1114	ev_embed_init (&embed, 0, loop_lo);
		1115	ev_embed_start (loop_hi, &embed);
		1116	}
		1117	else
		1118	loop_lo = loop_hi;
		1119
		1120	</pre>
		1121	<dl>
		1122	<dt>ev_embed_init (ev_embed , callback, struct ev_loop loop)</dt>
		1123	<dt>ev_embed_set (ev_embed , callback, struct ev_loop loop)</dt>
		1124	<dd>
		1125	<p>Configures the watcher to embed the given loop, which must be embeddable.</p>
		1126	</dd>
		1127	</dl>
		1128
		1129
		1130
		1131
705		1132
706	</div>	1133	</div>
707	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1134	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
708	<div id="OTHER_FUNCTIONS_CONTENT">	1135	<div id="OTHER_FUNCTIONS_CONTENT">
709	<p>There are some other functions of possible interest. Described. Here. Now.</p>	1136	<p>There are some other functions of possible interest. Described. Here. Now.</p>
…		…
711	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1138	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712	<dd>	1139	<dd>
713	<p>This function combines a simple timer and an I/O watcher, calls your	1140	<p>This function combines a simple timer and an I/O watcher, calls your
714	callback on whichever event happens first and automatically stop both	1141	callback on whichever event happens first and automatically stop both
715	watchers. This is useful if you want to wait for a single event on an fd	1142	watchers. This is useful if you want to wait for a single event on an fd
716	or timeout without havign to allocate/configure/start/stop/free one or	1143	or timeout without having to allocate/configure/start/stop/free one or
717	more watchers yourself.</p>	1144	more watchers yourself.</p>
718	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events	1145	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
719	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and	1146	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
720	<code>events</code> set will be craeted and started.</p>	1147	<code>events</code> set will be craeted and started.</p>
721	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1148	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
722	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and	1149	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
723	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of	1150	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724	dubious value.</p>	1151	dubious value.</p>
725	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets	1152	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
726	passed an events set like normal event callbacks (with a combination of	1153	passed an <code>revents</code> set like normal event callbacks (a combination of
727	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>	1154	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
728	value passed to <code>ev_once</code>:</p>	1155	value passed to <code>ev_once</code>:</p>
729	<pre> static void stdin_ready (int revents, void *arg)	1156	<pre> static void stdin_ready (int revents, void *arg)
730	{	1157	{
731	if (revents & EV_TIMEOUT)	1158	if (revents & EV_TIMEOUT)
…		…
753	<dd>	1180	<dd>
754	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1181	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
755	</dd>	1182	</dd>
756	</dl>	1183	</dl>
757		1184
		1185
		1186
		1187
		1188
		1189	</div>
		1190	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1191	<div id="LIBEVENT_EMULATION_CONTENT">
		1192	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1193	emulate the internals of libevent, so here are some usage hints:</p>
		1194	<dl>
		1195	<dt>* Use it by including <event.h>, as usual.</dt>
		1196	<dt>* The following members are fully supported: ev_base, ev_callback,
		1197	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1198	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1199	maintained by libev, it does not work exactly the same way as in libevent (consider
		1200	it a private API).</dt>
		1201	<dt>* Priorities are not currently supported. Initialising priorities
		1202	will fail and all watchers will have the same priority, even though there
		1203	is an ev_pri field.</dt>
		1204	<dt>* Other members are not supported.</dt>
		1205	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1206	to use the libev header file and library.</dt>
		1207	</dl>
		1208
		1209	</div>
		1210	<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1211	<div id="C_SUPPORT_CONTENT">
		1212	<p>TBD.</p>
		1213
758	</div>	1214	</div>
759	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1215	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
760	<div id="AUTHOR_CONTENT">	1216	<div id="AUTHOR_CONTENT">
761	<p>Marc Lehmann <libev@schmorp.de>.</p>	1217	<p>Marc Lehmann <libev@schmorp.de>.</p>
762		1218

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