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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>" />
8	<meta name="outputfile" content="<standard output>" />	8	<meta name="outputfile" content="<standard output>" />
9	<meta name="created" content="Thu Nov 22 13:28:34 2007" />	9	<meta name="created" content="Sat Nov 24 08:13:46 2007" />
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12	<body>	12	<body>
13	<div class="pod">	13	<div class="pod">
14	<!-- INDEX START -->	14	<!-- INDEX START -->
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21	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>	21	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>	22	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>	23	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
24	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>	24	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>	25	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
		26	<ul><li><a href="#SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</a></li>
26	<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>	27	<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
27	</ul>	28	</ul>
28	</li>	29	</li>
29	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>	30	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
30	<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>	31	<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>
31	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>	32	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
32	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>	33	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
33	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>	34	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
34	<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>	35	<li><a href="#code_ev_child_code_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>	36	<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>
36	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>	37	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>
		38	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li>
37	</ul>	39	</ul>
38	</li>	40	</li>
39	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	41	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>	42	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>	43	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
…		…
96	<div id="TIME_REPRESENTATION_CONTENT">	98	<div id="TIME_REPRESENTATION_CONTENT">
97	<p>Libev represents time as a single floating point number, representing the	99	<p>Libev represents time as a single floating point number, representing the
98	(fractional) number of seconds since the (POSIX) epoch (somewhere near	100	(fractional) number of seconds since the (POSIX) epoch (somewhere near
99	the beginning of 1970, details are complicated, don't ask). This type is	101	the beginning of 1970, details are complicated, don't ask). This type is
100	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	102	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
101	to the double type in C.</p>	103	to the <code>double</code> type in C, and when you need to do any calculations on
		104	it, you should treat it as such.</p>
		105
		106
		107
		108
102		109
103	</div>	110	</div>
104	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	111	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105	<div id="GLOBAL_FUNCTIONS_CONTENT">	112	<div id="GLOBAL_FUNCTIONS_CONTENT">
106	<p>These functions can be called anytime, even before initialising the	113	<p>These functions can be called anytime, even before initialising the
…		…
122	version of the library your program was compiled against.</p>	129	version of the library your program was compiled against.</p>
123	<p>Usually, it's a good idea to terminate if the major versions mismatch,	130	<p>Usually, it's a good idea to terminate if the major versions mismatch,
124	as this indicates an incompatible change. Minor versions are usually	131	as this indicates an incompatible change. Minor versions are usually
125	compatible to older versions, so a larger minor version alone is usually	132	compatible to older versions, so a larger minor version alone is usually
126	not a problem.</p>	133	not a problem.</p>
		134	<p>Example: make sure we haven't accidentally been linked against the wrong
		135	version:</p>
		136	<pre> assert (("libev version mismatch",
		137	ev_version_major () == EV_VERSION_MAJOR
		138	&& ev_version_minor () >= EV_VERSION_MINOR));
		139
		140	</pre>
		141	</dd>
		142	<dt>unsigned int ev_supported_backends ()</dt>
		143	<dd>
		144	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		145	value) compiled into this binary of libev (independent of their
		146	availability on the system you are running on). See <code>ev_default_loop</code> for
		147	a description of the set values.</p>
		148	<p>Example: make sure we have the epoll method, because yeah this is cool and
		149	a must have and can we have a torrent of it please!!!11</p>
		150	<pre> assert (("sorry, no epoll, no sex",
		151	ev_supported_backends () & EVBACKEND_EPOLL));
		152
		153	</pre>
		154	</dd>
		155	<dt>unsigned int ev_recommended_backends ()</dt>
		156	<dd>
		157	<p>Return the set of all backends compiled into this binary of libev and also
		158	recommended for this platform. This set is often smaller than the one
		159	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		160	most BSDs and will not be autodetected unless you explicitly request it
		161	(assuming you know what you are doing). This is the set of backends that
		162	libev will probe for if you specify no backends explicitly.</p>
		163	</dd>
		164	<dt>unsigned int ev_embeddable_backends ()</dt>
		165	<dd>
		166	<p>Returns the set of backends that are embeddable in other event loops. This
		167	is the theoretical, all-platform, value. To find which backends
		168	might be supported on the current system, you would need to look at
		169	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		170	recommended ones.</p>
		171	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
127	</dd>	172	</dd>
128	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	173	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
129	<dd>	174	<dd>
130	<p>Sets the allocation function to use (the prototype is similar to the	175	<p>Sets the allocation function to use (the prototype is similar to the
131	realloc C function, the semantics are identical). It is used to allocate	176	realloc C function, the semantics are identical). It is used to allocate
…		…
133	needs to be allocated, the library might abort or take some potentially	178	needs to be allocated, the library might abort or take some potentially
134	destructive action. The default is your system realloc function.</p>	179	destructive action. The default is your system realloc function.</p>
135	<p>You could override this function in high-availability programs to, say,	180	<p>You could override this function in high-availability programs to, say,
136	free some memory if it cannot allocate memory, to use a special allocator,	181	free some memory if it cannot allocate memory, to use a special allocator,
137	or even to sleep a while and retry until some memory is available.</p>	182	or even to sleep a while and retry until some memory is available.</p>
		183	<p>Example: replace the libev allocator with one that waits a bit and then
		184	retries: better than mine).</p>
		185	<pre> static void *
		186	persistent_realloc (void *ptr, long size)
		187	{
		188	for (;;)
		189	{
		190	void *newptr = realloc (ptr, size);
		191
		192	if (newptr)
		193	return newptr;
		194
		195	sleep (60);
		196	}
		197	}
		198
		199	...
		200	ev_set_allocator (persistent_realloc);
		201
		202	</pre>
138	</dd>	203	</dd>
139	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	204	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
140	<dd>	205	<dd>
141	<p>Set the callback function to call on a retryable syscall error (such	206	<p>Set the callback function to call on a retryable syscall error (such
142	as failed select, poll, epoll_wait). The message is a printable string	207	as failed select, poll, epoll_wait). The message is a printable string
143	indicating the system call or subsystem causing the problem. If this	208	indicating the system call or subsystem causing the problem. If this
144	callback is set, then libev will expect it to remedy the sitution, no	209	callback is set, then libev will expect it to remedy the sitution, no
145	matter what, when it returns. That is, libev will generally retry the	210	matter what, when it returns. That is, libev will generally retry the
146	requested operation, or, if the condition doesn't go away, do bad stuff	211	requested operation, or, if the condition doesn't go away, do bad stuff
147	(such as abort).</p>	212	(such as abort).</p>
		213	<p>Example: do the same thing as libev does internally:</p>
		214	<pre> static void
		215	fatal_error (const char *msg)
		216	{
		217	perror (msg);
		218	abort ();
		219	}
		220
		221	...
		222	ev_set_syserr_cb (fatal_error);
		223
		224	</pre>
148	</dd>	225	</dd>
149	</dl>	226	</dl>
150		227
151	</div>	228	</div>
152	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	229	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
…		…
164	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	241	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
165	<dd>	242	<dd>
166	<p>This will initialise the default event loop if it hasn't been initialised	243	<p>This will initialise the default event loop if it hasn't been initialised
167	yet and return it. If the default loop could not be initialised, returns	244	yet and return it. If the default loop could not be initialised, returns
168	false. If it already was initialised it simply returns it (and ignores the	245	false. If it already was initialised it simply returns it (and ignores the
169	flags).</p>	246	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
170	<p>If you don't know what event loop to use, use the one returned from this	247	<p>If you don't know what event loop to use, use the one returned from this
171	function.</p>	248	function.</p>
172	<p>The flags argument can be used to specify special behaviour or specific	249	<p>The flags argument can be used to specify special behaviour or specific
173	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>	250	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
174	<p>It supports the following flags:</p>	251	<p>The following flags are supported:</p>
175	<p>	252	<p>
176	<dl>	253	<dl>
177	<dt><code>EVFLAG_AUTO</code></dt>	254	<dt><code>EVFLAG_AUTO</code></dt>
178	<dd>	255	<dd>
179	<p>The default flags value. Use this if you have no clue (it's the right	256	<p>The default flags value. Use this if you have no clue (it's the right
…		…
186	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will	263	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
187	override the flags completely if it is found in the environment. This is	264	override the flags completely if it is found in the environment. This is
188	useful to try out specific backends to test their performance, or to work	265	useful to try out specific backends to test their performance, or to work
189	around bugs.</p>	266	around bugs.</p>
190	</dd>	267	</dd>
191	<dt><code>EVMETHOD_SELECT</code> (value 1, portable select backend)</dt>	268	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
192	<dd>	269	<dd>
193	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as	270	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
194	libev tries to roll its own fd_set with no limits on the number of fds,	271	libev tries to roll its own fd_set with no limits on the number of fds,
195	but if that fails, expect a fairly low limit on the number of fds when	272	but if that fails, expect a fairly low limit on the number of fds when
196	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	273	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
197	the fastest backend for a low number of fds.</p>	274	the fastest backend for a low number of fds.</p>
198	</dd>	275	</dd>
199	<dt><code>EVMETHOD_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>	276	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
200	<dd>	277	<dd>
201	<p>And this is your standard poll(2) backend. It's more complicated than	278	<p>And this is your standard poll(2) backend. It's more complicated than
202	select, but handles sparse fds better and has no artificial limit on the	279	select, but handles sparse fds better and has no artificial limit on the
203	number of fds you can use (except it will slow down considerably with a	280	number of fds you can use (except it will slow down considerably with a
204	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>	281	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
205	</dd>	282	</dd>
206	<dt><code>EVMETHOD_EPOLL</code> (value 4, Linux)</dt>	283	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
207	<dd>	284	<dd>
208	<p>For few fds, this backend is a bit little slower than poll and select,	285	<p>For few fds, this backend is a bit little slower than poll and select,
209	but it scales phenomenally better. While poll and select usually scale like	286	but it scales phenomenally better. While poll and select usually scale like
210	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	287	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
211	either O(1) or O(active_fds).</p>	288	either O(1) or O(active_fds).</p>
212	<p>While stopping and starting an I/O watcher in the same iteration will	289	<p>While stopping and starting an I/O watcher in the same iteration will
213	result in some caching, there is still a syscall per such incident	290	result 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	291	(because the fd could point to a different file description now), so its
215	best to avoid that. Also, dup()ed file descriptors might not work very	292	best to avoid that. Also, dup()ed file descriptors might not work very
216	well if you register events for both fds.</p>	293	well if you register events for both fds.</p>
		294	<p>Please note that epoll sometimes generates spurious notifications, so you
		295	need to use non-blocking I/O or other means to avoid blocking when no data
		296	(or space) is available.</p>
217	</dd>	297	</dd>
218	<dt><code>EVMETHOD_KQUEUE</code> (value 8, most BSD clones)</dt>	298	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
219	<dd>	299	<dd>
220	<p>Kqueue deserves special mention, as at the time of this writing, it	300	<p>Kqueue deserves special mention, as at the time of this writing, it
221	was broken on all BSDs except NetBSD (usually it doesn't work with	301	was broken on all BSDs except NetBSD (usually it doesn't work with
222	anything but sockets and pipes, except on Darwin, where of course its	302	anything but sockets and pipes, except on Darwin, where of course its
223	completely useless). For this reason its not being "autodetected" unless	303	completely useless). For this reason its not being "autodetected"
224	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p>	304	unless you explicitly specify it explicitly in the flags (i.e. using
		305	<code>EVBACKEND_KQUEUE</code>).</p>
225	<p>It scales in the same way as the epoll backend, but the interface to the	306	<p>It scales in the same way as the epoll backend, but the interface to the
226	kernel is more efficient (which says nothing about its actual speed, of	307	kernel is more efficient (which says nothing about its actual speed, of
227	course). While starting and stopping an I/O watcher does not cause an	308	course). While starting and stopping an I/O watcher does not cause an
228	extra syscall as with epoll, it still adds up to four event changes per	309	extra syscall as with epoll, it still adds up to four event changes per
229	incident, so its best to avoid that.</p>	310	incident, so its best to avoid that.</p>
230	</dd>	311	</dd>
231	<dt><code>EVMETHOD_DEVPOLL</code> (value 16, Solaris 8)</dt>	312	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
232	<dd>	313	<dd>
233	<p>This is not implemented yet (and might never be).</p>	314	<p>This is not implemented yet (and might never be).</p>
234	</dd>	315	</dd>
235	<dt><code>EVMETHOD_PORT</code> (value 32, Solaris 10)</dt>	316	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
236	<dd>	317	<dd>
237	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,	318	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
238	it's really slow, but it still scales very well (O(active_fds)).</p>	319	it's really slow, but it still scales very well (O(active_fds)).</p>
		320	<p>Please note that solaris ports can result in a lot of spurious
		321	notifications, so you need to use non-blocking I/O or other means to avoid
		322	blocking when no data (or space) is available.</p>
239	</dd>	323	</dd>
240	<dt><code>EVMETHOD_ALL</code></dt>	324	<dt><code>EVBACKEND_ALL</code></dt>
241	<dd>	325	<dd>
242	<p>Try all backends (even potentially broken ones that wouldn't be tried	326	<p>Try all backends (even potentially broken ones that wouldn't be tried
243	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as	327	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
244	<code>EVMETHOD_ALL & ~EVMETHOD_KQUEUE</code>.</p>	328	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
245	</dd>	329	</dd>
246	</dl>	330	</dl>
247	</p>	331	</p>
248	<p>If one or more of these are ored into the flags value, then only these	332	<p>If one or more of these are ored into the flags value, then only these
249	backends will be tried (in the reverse order as given here). If none are	333	backends will be tried (in the reverse order as given here). If none are
250	specified, most compiled-in backend will be tried, usually in reverse	334	specified, most compiled-in backend will be tried, usually in reverse
251	order of their flag values :)</p>	335	order of their flag values :)</p>
		336	<p>The most typical usage is like this:</p>
		337	<pre> if (!ev_default_loop (0))
		338	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		339
		340	</pre>
		341	<p>Restrict libev to the select and poll backends, and do not allow
		342	environment settings to be taken into account:</p>
		343	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		344
		345	</pre>
		346	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		347	available (warning, breaks stuff, best use only with your own private
		348	event loop and only if you know the OS supports your types of fds):</p>
		349	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		350
		351	</pre>
252	</dd>	352	</dd>
253	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	353	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
254	<dd>	354	<dd>
255	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	355	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
256	always distinct from the default loop. Unlike the default loop, it cannot	356	always distinct from the default loop. Unlike the default loop, it cannot
257	handle signal and child watchers, and attempts to do so will be greeted by	357	handle signal and child watchers, and attempts to do so will be greeted by
258	undefined behaviour (or a failed assertion if assertions are enabled).</p>	358	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		359	<p>Example: try to create a event loop that uses epoll and nothing else.</p>
		360	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		361	if (!epoller)
		362	fatal ("no epoll found here, maybe it hides under your chair");
		363
		364	</pre>
259	</dd>	365	</dd>
260	<dt>ev_default_destroy ()</dt>	366	<dt>ev_default_destroy ()</dt>
261	<dd>	367	<dd>
262	<p>Destroys the default loop again (frees all memory and kernel state	368	<p>Destroys the default loop again (frees all memory and kernel state
263	etc.). This stops all registered event watchers (by not touching them in	369	etc.). This stops all registered event watchers (by not touching them in
…		…
272	<dd>	378	<dd>
273	<p>This function reinitialises the kernel state for backends that have	379	<p>This function reinitialises the kernel state for backends that have
274	one. Despite the name, you can call it anytime, but it makes most sense	380	one. Despite the name, you can call it anytime, but it makes most sense
275	after forking, in either the parent or child process (or both, but that	381	after forking, in either the parent or child process (or both, but that
276	again makes little sense).</p>	382	again makes little sense).</p>
277	<p>You <i>must</i> call this function after forking if and only if you want to	383	<p>You <i>must</i> call this function in the child process after forking if and
278	use the event library in both processes. If you just fork+exec, you don't	384	only if you want to use the event library in both processes. If you just
279	have to call it.</p>	385	fork+exec, you don't have to call it.</p>
280	<p>The function itself is quite fast and it's usually not a problem to call	386	<p>The function itself is quite fast and it's usually not a problem to call
281	it just in case after a fork. To make this easy, the function will fit in	387	it just in case after a fork. To make this easy, the function will fit in
282	quite nicely into a call to <code>pthread_atfork</code>:</p>	388	quite nicely into a call to <code>pthread_atfork</code>:</p>
283	<pre> pthread_atfork (0, 0, ev_default_fork);	389	<pre> pthread_atfork (0, 0, ev_default_fork);
284		390
285	</pre>	391	</pre>
		392	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		393	without calling this function, so if you force one of those backends you
		394	do not need to care.</p>
286	</dd>	395	</dd>
287	<dt>ev_loop_fork (loop)</dt>	396	<dt>ev_loop_fork (loop)</dt>
288	<dd>	397	<dd>
289	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	398	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
290	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	399	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
291	after fork, and how you do this is entirely your own problem.</p>	400	after fork, and how you do this is entirely your own problem.</p>
292	</dd>	401	</dd>
293	<dt>unsigned int ev_method (loop)</dt>	402	<dt>unsigned int ev_backend (loop)</dt>
294	<dd>	403	<dd>
295	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	404	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
296	use.</p>	405	use.</p>
297	</dd>	406	</dd>
298	<dt>ev_tstamp ev_now (loop)</dt>	407	<dt>ev_tstamp ev_now (loop)</dt>
299	<dd>	408	<dd>
300	<p>Returns the current "event loop time", which is the time the event loop	409	<p>Returns the current "event loop time", which is the time the event loop
301	got events and started processing them. This timestamp does not change	410	received events and started processing them. This timestamp does not
302	as long as callbacks are being processed, and this is also the base time	411	change as long as callbacks are being processed, and this is also the base
303	used for relative timers. You can treat it as the timestamp of the event	412	time used for relative timers. You can treat it as the timestamp of the
304	occuring (or more correctly, the mainloop finding out about it).</p>	413	event occuring (or more correctly, libev finding out about it).</p>
305	</dd>	414	</dd>
306	<dt>ev_loop (loop, int flags)</dt>	415	<dt>ev_loop (loop, int flags)</dt>
307	<dd>	416	<dd>
308	<p>Finally, this is it, the event handler. This function usually is called	417	<p>Finally, this is it, the event handler. This function usually is called
309	after you initialised all your watchers and you want to start handling	418	after you initialised all your watchers and you want to start handling
310	events.</p>	419	events.</p>
311	<p>If the flags argument is specified as 0, it will not return until either	420	<p>If the flags argument is specified as <code>0</code>, it will not return until
312	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	421	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		422	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		423	relying on all watchers to be stopped when deciding when a program has
		424	finished (especially in interactive programs), but having a program that
		425	automatically loops as long as it has to and no longer by virtue of
		426	relying on its watchers stopping correctly is a thing of beauty.</p>
313	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	427	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
314	those events and any outstanding ones, but will not block your process in	428	those events and any outstanding ones, but will not block your process in
315	case there are no events and will return after one iteration of the loop.</p>	429	case there are no events and will return after one iteration of the loop.</p>
316	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	430	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
317	neccessary) and will handle those and any outstanding ones. It will block	431	neccessary) and will handle those and any outstanding ones. It will block
318	your process until at least one new event arrives, and will return after	432	your process until at least one new event arrives, and will return after
319	one iteration of the loop.</p>	433	one iteration of the loop. This is useful if you are waiting for some
320	<p>This flags value could be used to implement alternative looping	434	external event in conjunction with something not expressible using other
321	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	435	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
322	more generic mechanism.</p>	436	usually a better approach for this kind of thing.</p>
323	<p>Here are the gory details of what ev_loop does:</p>	437	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
324	<pre> 1. If there are no active watchers (reference count is zero), return.	438	<pre> * If there are no active watchers (reference count is zero), return.
325	2. Queue and immediately call all prepare watchers.	439	- Queue prepare watchers and then call all outstanding watchers.
326	3. If we have been forked, recreate the kernel state.	440	- If we have been forked, recreate the kernel state.
327	4. Update the kernel state with all outstanding changes.	441	- Update the kernel state with all outstanding changes.
328	5. Update the "event loop time".	442	- Update the "event loop time".
329	6. Calculate for how long to block.	443	- Calculate for how long to block.
330	7. Block the process, waiting for events.	444	- Block the process, waiting for any events.
		445	- Queue all outstanding I/O (fd) events.
331	8. Update the "event loop time" and do time jump handling.	446	- Update the "event loop time" and do time jump handling.
332	9. Queue all outstanding timers.	447	- Queue all outstanding timers.
333	10. Queue all outstanding periodics.	448	- Queue all outstanding periodics.
334	11. If no events are pending now, queue all idle watchers.	449	- If no events are pending now, queue all idle watchers.
335	12. Queue all check watchers.	450	- Queue all check watchers.
336	13. Call all queued watchers in reverse order (i.e. check watchers first).	451	- Call all queued watchers in reverse order (i.e. check watchers first).
		452	Signals and child watchers are implemented as I/O watchers, and will
		453	be handled here by queueing them when their watcher gets executed.
337	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	454	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
338	was used, return, otherwise continue with step #1.	455	were used, return, otherwise continue with step *.
		456
		457	</pre>
		458	<p>Example: queue some jobs and then loop until no events are outsanding
		459	anymore.</p>
		460	<pre> ... queue jobs here, make sure they register event watchers as long
		461	... as they still have work to do (even an idle watcher will do..)
		462	ev_loop (my_loop, 0);
		463	... jobs done. yeah!
339		464
340	</pre>	465	</pre>
341	</dd>	466	</dd>
342	<dt>ev_unloop (loop, how)</dt>	467	<dt>ev_unloop (loop, how)</dt>
343	<dd>	468	<dd>
…		…
357	example, libev itself uses this for its internal signal pipe: It is not	482	example, libev itself uses this for its internal signal pipe: It is not
358	visible to the libev user and should not keep <code>ev_loop</code> from exiting if	483	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
359	no event watchers registered by it are active. It is also an excellent	484	no event watchers registered by it are active. It is also an excellent
360	way to do this for generic recurring timers or from within third-party	485	way to do this for generic recurring timers or from within third-party
361	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>	486	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		487	<p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
		488	running when nothing else is active.</p>
		489	<pre> struct dv_signal exitsig;
		490	ev_signal_init (&exitsig, sig_cb, SIGINT);
		491	ev_signal_start (myloop, &exitsig);
		492	evf_unref (myloop);
		493
		494	</pre>
		495	<p>Example: for some weird reason, unregister the above signal handler again.</p>
		496	<pre> ev_ref (myloop);
		497	ev_signal_stop (myloop, &exitsig);
		498
		499	</pre>
362	</dd>	500	</dd>
363	</dl>	501	</dl>
364		502
365	</div>	503	</div>
366	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	504	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
…		…
398	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	536	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
399	*)</code>), and you can stop watching for events at any time by calling the	537	*)</code>), and you can stop watching for events at any time by calling the
400	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	538	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
401	<p>As long as your watcher is active (has been started but not stopped) you	539	<p>As long as your watcher is active (has been started but not stopped) you
402	must not touch the values stored in it. Most specifically you must never	540	must not touch the values stored in it. Most specifically you must never
403	reinitialise it or call its set method.</p>	541	reinitialise it or call its <code>set</code> macro.</p>
404	<p>You can check whether an event is active by calling the <code>ev_is_active
405	(watcher *)</code> macro. To see whether an event is outstanding (but the
406	callback for it has not been called yet) you can use the <code>ev_is_pending
407	(watcher *)</code> macro.</p>
408	<p>Each and every callback receives the event loop pointer as first, the	542	<p>Each and every callback receives the event loop pointer as first, the
409	registered watcher structure as second, and a bitset of received events as	543	registered watcher structure as second, and a bitset of received events as
410	third argument.</p>	544	third argument.</p>
411	<p>The received events usually include a single bit per event type received	545	<p>The received events usually include a single bit per event type received
412	(you can receive multiple events at the same time). The possible bit masks	546	(you can receive multiple events at the same time). The possible bit masks
…		…
461	your callbacks is well-written it can just attempt the operation and cope	595	your callbacks is well-written it can just attempt the operation and cope
462	with the error from read() or write(). This will not work in multithreaded	596	with the error from read() or write(). This will not work in multithreaded
463	programs, though, so beware.</p>	597	programs, though, so beware.</p>
464	</dd>	598	</dd>
465	</dl>	599	</dl>
		600
		601	</div>
		602	<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2>
		603	<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2">
		604	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		605	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		606	<dl>
		607	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		608	<dd>
		609	<p>This macro initialises the generic portion of a watcher. The contents
		610	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		611	the generic parts of the watcher are initialised, you <i>need</i> to call
		612	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		613	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		614	which rolls both calls into one.</p>
		615	<p>You can reinitialise a watcher at any time as long as it has been stopped
		616	(or never started) and there are no pending events outstanding.</p>
		617	<p>The callbakc is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		618	int revents)</code>.</p>
		619	</dd>
		620	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		621	<dd>
		622	<p>This macro initialises the type-specific parts of a watcher. You need to
		623	call <code>ev_init</code> at least once before you call this macro, but you can
		624	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		625	macro on a watcher that is active (it can be pending, however, which is a
		626	difference to the <code>ev_init</code> macro).</p>
		627	<p>Although some watcher types do not have type-specific arguments
		628	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		629	</dd>
		630	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		631	<dd>
		632	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		633	calls into a single call. This is the most convinient method to initialise
		634	a watcher. The same limitations apply, of course.</p>
		635	</dd>
		636	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		637	<dd>
		638	<p>Starts (activates) the given watcher. Only active watchers will receive
		639	events. If the watcher is already active nothing will happen.</p>
		640	</dd>
		641	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		642	<dd>
		643	<p>Stops the given watcher again (if active) and clears the pending
		644	status. It is possible that stopped watchers are pending (for example,
		645	non-repeating timers are being stopped when they become pending), but
		646	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		647	you want to free or reuse the memory used by the watcher it is therefore a
		648	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		649	</dd>
		650	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		651	<dd>
		652	<p>Returns a true value iff the watcher is active (i.e. it has been started
		653	and not yet been stopped). As long as a watcher is active you must not modify
		654	it.</p>
		655	</dd>
		656	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		657	<dd>
		658	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		659	events but its callback has not yet been invoked). As long as a watcher
		660	is pending (but not active) you must not call an init function on it (but
		661	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		662	libev (e.g. you cnanot <code>free ()</code> it).</p>
		663	</dd>
		664	<dt>callback = ev_cb (ev_TYPE *watcher)</dt>
		665	<dd>
		666	<p>Returns the callback currently set on the watcher.</p>
		667	</dd>
		668	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		669	<dd>
		670	<p>Change the callback. You can change the callback at virtually any time
		671	(modulo threads).</p>
		672	</dd>
		673	</dl>
		674
		675
		676
		677
466		678
467	</div>	679	</div>
468	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	680	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
469	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	681	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
470	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	682	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
…		…
501	</div>	713	</div>
502	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	714	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
503	<div id="WATCHER_TYPES_CONTENT">	715	<div id="WATCHER_TYPES_CONTENT">
504	<p>This section describes each watcher in detail, but will not repeat	716	<p>This section describes each watcher in detail, but will not repeat
505	information given in the last section.</p>	717	information given in the last section.</p>
		718
		719
		720
		721
506		722
507	</div>	723	</div>
508	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>	724	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
509	<div id="code_ev_io_code_is_this_file_descrip-2">	725	<div id="code_ev_io_code_is_this_file_descrip-2">
510	<p>I/O watchers check whether a file descriptor is readable or writable	726	<p>I/O watchers check whether a file descriptor is readable or writable
…		…
520	(the linux epoll backend is a notable example) cannot handle dup'ed file	736	(the linux epoll backend is a notable example) cannot handle dup'ed file
521	descriptors correctly if you register interest in two or more fds pointing	737	descriptors correctly if you register interest in two or more fds pointing
522	to the same underlying file/socket etc. description (that is, they share	738	to the same underlying file/socket etc. description (that is, they share
523	the same underlying "file open").</p>	739	the same underlying "file open").</p>
524	<p>If you must do this, then force the use of a known-to-be-good backend	740	<p>If you must do this, then force the use of a known-to-be-good backend
525	(at the time of this writing, this includes only EVMETHOD_SELECT and	741	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
526	EVMETHOD_POLL).</p>	742	<code>EVBACKEND_POLL</code>).</p>
527	<dl>	743	<dl>
528	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	744	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
529	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	745	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
530	<dd>	746	<dd>
531	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive	747	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
532	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	748	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|
533	EV_WRITE</code> to receive the given events.</p>	749	EV_WRITE</code> to receive the given events.</p>
		750	<p>Please note that most of the more scalable backend mechanisms (for example
		751	epoll and solaris ports) can result in spurious readyness notifications
		752	for file descriptors, so you practically need to use non-blocking I/O (and
		753	treat callback invocation as hint only), or retest separately with a safe
		754	interface before doing I/O (XLib can do this), or force the use of either
		755	<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
		756	problem. Also note that it is quite easy to have your callback invoked
		757	when the readyness condition is no longer valid even when employing
		758	typical ways of handling events, so its a good idea to use non-blocking
		759	I/O unconditionally.</p>
534	</dd>	760	</dd>
535	</dl>	761	</dl>
		762	<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		763	readable, but only once. Since it is likely line-buffered, you could
		764	attempt to read a whole line in the callback:</p>
		765	<pre> static void
		766	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		767	{
		768	ev_io_stop (loop, w);
		769	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		770	}
		771
		772	...
		773	struct ev_loop *loop = ev_default_init (0);
		774	struct ev_io stdin_readable;
		775	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		776	ev_io_start (loop, &stdin_readable);
		777	ev_loop (loop, 0);
		778
		779
		780
		781
		782	</pre>
536		783
537	</div>	784	</div>
538	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>	785	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
539	<div id="code_ev_timer_code_relative_and_opti-2">	786	<div id="code_ev_timer_code_relative_and_opti-2">
540	<p>Timer watchers are simple relative timers that generate an event after a	787	<p>Timer watchers are simple relative timers that generate an event after a
…		…
584	time you successfully read or write some data. If you go into an idle	831	time you successfully read or write some data. If you go into an idle
585	state where you do not expect data to travel on the socket, you can stop	832	state where you do not expect data to travel on the socket, you can stop
586	the timer, and again will automatically restart it if need be.</p>	833	the timer, and again will automatically restart it if need be.</p>
587	</dd>	834	</dd>
588	</dl>	835	</dl>
		836	<p>Example: create a timer that fires after 60 seconds.</p>
		837	<pre> static void
		838	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		839	{
		840	.. one minute over, w is actually stopped right here
		841	}
		842
		843	struct ev_timer mytimer;
		844	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		845	ev_timer_start (loop, &mytimer);
		846
		847	</pre>
		848	<p>Example: create a timeout timer that times out after 10 seconds of
		849	inactivity.</p>
		850	<pre> static void
		851	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		852	{
		853	.. ten seconds without any activity
		854	}
		855
		856	struct ev_timer mytimer;
		857	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		858	ev_timer_again (&mytimer); /* start timer */
		859	ev_loop (loop, 0);
		860
		861	// and in some piece of code that gets executed on any "activity":
		862	// reset the timeout to start ticking again at 10 seconds
		863	ev_timer_again (&mytimer);
		864
		865
		866
		867
		868	</pre>
589		869
590	</div>	870	</div>
591	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>	871	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
592	<div id="code_ev_periodic_code_to_cron_or_not-2">	872	<div id="code_ev_periodic_code_to_cron_or_not-2">
593	<p>Periodic watchers are also timers of a kind, but they are very versatile	873	<p>Periodic watchers are also timers of a kind, but they are very versatile
…		…
677	when you changed some parameters or the reschedule callback would return	957	when you changed some parameters or the reschedule callback would return
678	a different time than the last time it was called (e.g. in a crond like	958	a different time than the last time it was called (e.g. in a crond like
679	program when the crontabs have changed).</p>	959	program when the crontabs have changed).</p>
680	</dd>	960	</dd>
681	</dl>	961	</dl>
		962	<p>Example: call a callback every hour, or, more precisely, whenever the
		963	system clock is divisible by 3600. The callback invocation times have
		964	potentially a lot of jittering, but good long-term stability.</p>
		965	<pre> static void
		966	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		967	{
		968	... its now a full hour (UTC, or TAI or whatever your clock follows)
		969	}
		970
		971	struct ev_periodic hourly_tick;
		972	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		973	ev_periodic_start (loop, &hourly_tick);
		974
		975	</pre>
		976	<p>Example: the same as above, but use a reschedule callback to do it:</p>
		977	<pre> #include <math.h>
		978
		979	static ev_tstamp
		980	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		981	{
		982	return fmod (now, 3600.) + 3600.;
		983	}
		984
		985	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		986
		987	</pre>
		988	<p>Example: call a callback every hour, starting now:</p>
		989	<pre> struct ev_periodic hourly_tick;
		990	ev_periodic_init (&hourly_tick, clock_cb,
		991	fmod (ev_now (loop), 3600.), 3600., 0);
		992	ev_periodic_start (loop, &hourly_tick);
		993
		994
		995
		996
		997	</pre>
682		998
683	</div>	999	</div>
684	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>	1000	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
685	<div id="code_ev_signal_code_signal_me_when_a-2">	1001	<div id="code_ev_signal_code_signal_me_when_a-2">
686	<p>Signal watchers will trigger an event when the process receives a specific	1002	<p>Signal watchers will trigger an event when the process receives a specific
…		…
700	<p>Configures the watcher to trigger on the given signal number (usually one	1016	<p>Configures the watcher to trigger on the given signal number (usually one
701	of the <code>SIGxxx</code> constants).</p>	1017	of the <code>SIGxxx</code> constants).</p>
702	</dd>	1018	</dd>
703	</dl>	1019	</dl>
704		1020
		1021
		1022
		1023
		1024
705	</div>	1025	</div>
706	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>	1026	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
707	<div id="code_ev_child_code_wait_for_pid_stat-2">	1027	<div id="code_ev_child_code_wait_for_pid_stat-2">
708	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1028	<p>Child watchers trigger when your process receives a SIGCHLD in response to
709	some child status changes (most typically when a child of yours dies).</p>	1029	some child status changes (most typically when a child of yours dies).</p>
…		…
717	the status word (use the macros from <code>sys/wait.h</code> and see your systems	1037	the status word (use the macros from <code>sys/wait.h</code> and see your systems
718	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the	1038	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
719	process causing the status change.</p>	1039	process causing the status change.</p>
720	</dd>	1040	</dd>
721	</dl>	1041	</dl>
		1042	<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
		1043	<pre> static void
		1044	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1045	{
		1046	ev_unloop (loop, EVUNLOOP_ALL);
		1047	}
		1048
		1049	struct ev_signal signal_watcher;
		1050	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1051	ev_signal_start (loop, &sigint_cb);
		1052
		1053
		1054
		1055
		1056	</pre>
722		1057
723	</div>	1058	</div>
724	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>	1059	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
725	<div id="code_ev_idle_code_when_you_ve_got_no-2">	1060	<div id="code_ev_idle_code_when_you_ve_got_no-2">
726	<p>Idle watchers trigger events when there are no other events are pending	1061	<p>Idle watchers trigger events when there are no other events are pending
…		…
742	<p>Initialises and configures the idle watcher - it has no parameters of any	1077	<p>Initialises and configures the idle watcher - it has no parameters of any
743	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1078	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
744	believe me.</p>	1079	believe me.</p>
745	</dd>	1080	</dd>
746	</dl>	1081	</dl>
		1082	<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
		1083	callback, free it. Alos, use no error checking, as usual.</p>
		1084	<pre> static void
		1085	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1086	{
		1087	free (w);
		1088	// now do something you wanted to do when the program has
		1089	// no longer asnything immediate to do.
		1090	}
		1091
		1092	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1093	ev_idle_init (idle_watcher, idle_cb);
		1094	ev_idle_start (loop, idle_cb);
		1095
		1096
		1097
		1098
		1099	</pre>
747		1100
748	</div>	1101	</div>
749	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>	1102	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
750	<div id="code_ev_prepare_code_and_code_ev_che-2">	1103	<div id="code_ev_prepare_code_and_code_ev_che-2">
751	<p>Prepare and check watchers are usually (but not always) used in tandem:	1104	<p>Prepare and check watchers are usually (but not always) used in tandem:
752	prepare watchers get invoked before the process blocks and check watchers	1105	prepare watchers get invoked before the process blocks and check watchers
753	afterwards.</p>	1106	afterwards.</p>
754	<p>Their main purpose is to integrate other event mechanisms into libev. This	1107	<p>Their main purpose is to integrate other event mechanisms into libev and
755	could be used, for example, to track variable changes, implement your own	1108	their use is somewhat advanced. This could be used, for example, to track
756	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1109	variable changes, implement your own watchers, integrate net-snmp or a
		1110	coroutine library and lots more.</p>
757	<p>This is done by examining in each prepare call which file descriptors need	1111	<p>This is done by examining in each prepare call which file descriptors need
758	to be watched by the other library, registering <code>ev_io</code> watchers for	1112	to be watched by the other library, registering <code>ev_io</code> watchers for
759	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries	1113	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
760	provide just this functionality). Then, in the check watcher you check for	1114	provide just this functionality). Then, in the check watcher you check for
761	any events that occured (by checking the pending status of all watchers	1115	any events that occured (by checking the pending status of all watchers
…		…
777	<p>Initialises and configures the prepare or check watcher - they have no	1131	<p>Initialises and configures the prepare or check watcher - they have no
778	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1132	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
779	macros, but using them is utterly, utterly and completely pointless.</p>	1133	macros, but using them is utterly, utterly and completely pointless.</p>
780	</dd>	1134	</dd>
781	</dl>	1135	</dl>
		1136	<p>Example: TODO.</p>
		1137
		1138
		1139
		1140
		1141
		1142	</div>
		1143	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2>
		1144	<div id="code_ev_embed_code_when_one_backend_-2">
		1145	<p>This is a rather advanced watcher type that lets you embed one event loop
		1146	into another (currently only <code>ev_io</code> events are supported in the embedded
		1147	loop, other types of watchers might be handled in a delayed or incorrect
		1148	fashion and must not be used).</p>
		1149	<p>There are primarily two reasons you would want that: work around bugs and
		1150	prioritise I/O.</p>
		1151	<p>As an example for a bug workaround, the kqueue backend might only support
		1152	sockets on some platform, so it is unusable as generic backend, but you
		1153	still want to make use of it because you have many sockets and it scales
		1154	so nicely. In this case, you would create a kqueue-based loop and embed it
		1155	into your default loop (which might use e.g. poll). Overall operation will
		1156	be a bit slower because first libev has to poll and then call kevent, but
		1157	at least you can use both at what they are best.</p>
		1158	<p>As for prioritising I/O: rarely you have the case where some fds have
		1159	to be watched and handled very quickly (with low latency), and even
		1160	priorities and idle watchers might have too much overhead. In this case
		1161	you would put all the high priority stuff in one loop and all the rest in
		1162	a second one, and embed the second one in the first.</p>
		1163	<p>As long as the watcher is active, the callback will be invoked every time
		1164	there might be events pending in the embedded loop. The callback must then
		1165	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1166	their callbacks (you could also start an idle watcher to give the embedded
		1167	loop strictly lower priority for example). You can also set the callback
		1168	to <code>0</code>, in which case the embed watcher will automatically execute the
		1169	embedded loop sweep.</p>
		1170	<p>As long as the watcher is started it will automatically handle events. The
		1171	callback will be invoked whenever some events have been handled. You can
		1172	set the callback to <code>0</code> to avoid having to specify one if you are not
		1173	interested in that.</p>
		1174	<p>Also, there have not currently been made special provisions for forking:
		1175	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1176	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1177	yourself.</p>
		1178	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1179	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1180	portable one.</p>
		1181	<p>So when you want to use this feature you will always have to be prepared
		1182	that you cannot get an embeddable loop. The recommended way to get around
		1183	this is to have a separate variables for your embeddable loop, try to
		1184	create it, and if that fails, use the normal loop for everything:</p>
		1185	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1186	struct ev_loop *loop_lo = 0;
		1187	struct ev_embed embed;
		1188
		1189	// see if there is a chance of getting one that works
		1190	// (remember that a flags value of 0 means autodetection)
		1191	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1192	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1193	: 0;
		1194
		1195	// if we got one, then embed it, otherwise default to loop_hi
		1196	if (loop_lo)
		1197	{
		1198	ev_embed_init (&embed, 0, loop_lo);
		1199	ev_embed_start (loop_hi, &embed);
		1200	}
		1201	else
		1202	loop_lo = loop_hi;
		1203
		1204	</pre>
		1205	<dl>
		1206	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1207	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1208	<dd>
		1209	<p>Configures the watcher to embed the given loop, which must be
		1210	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1211	invoked automatically, otherwise it is the responsibility of the callback
		1212	to invoke it (it will continue to be called until the sweep has been done,
		1213	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1214	</dd>
		1215	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1216	<dd>
		1217	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1218	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1219	apropriate way for embedded loops.</p>
		1220	</dd>
		1221	</dl>
		1222
		1223
		1224
		1225
782		1226
783	</div>	1227	</div>
784	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1228	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
785	<div id="OTHER_FUNCTIONS_CONTENT">	1229	<div id="OTHER_FUNCTIONS_CONTENT">
786	<p>There are some other functions of possible interest. Described. Here. Now.</p>	1230	<p>There are some other functions of possible interest. Described. Here. Now.</p>
…		…
813		1257
814	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1258	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
815		1259
816	</pre>	1260	</pre>
817	</dd>	1261	</dd>
818	<dt>ev_feed_event (loop, watcher, int events)</dt>	1262	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
819	<dd>	1263	<dd>
820	<p>Feeds the given event set into the event loop, as if the specified event	1264	<p>Feeds the given event set into the event loop, as if the specified event
821	had happened for the specified watcher (which must be a pointer to an	1265	had happened for the specified watcher (which must be a pointer to an
822	initialised but not necessarily started event watcher).</p>	1266	initialised but not necessarily started event watcher).</p>
823	</dd>	1267	</dd>
824	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1268	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
825	<dd>	1269	<dd>
826	<p>Feed an event on the given fd, as if a file descriptor backend detected	1270	<p>Feed an event on the given fd, as if a file descriptor backend detected
827	the given events it.</p>	1271	the given events it.</p>
828	</dd>	1272	</dd>
829	<dt>ev_feed_signal_event (loop, int signum)</dt>	1273	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
830	<dd>	1274	<dd>
831	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1275	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1276	loop!).</p>
832	</dd>	1277	</dd>
833	</dl>	1278	</dl>
		1279
		1280
		1281
		1282
834		1283
835	</div>	1284	</div>
836	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>	1285	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
837	<div id="LIBEVENT_EMULATION_CONTENT">	1286	<div id="LIBEVENT_EMULATION_CONTENT">
838	<p>Libev offers a compatibility emulation layer for libevent. It cannot	1287	<p>Libev offers a compatibility emulation layer for libevent. It cannot

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Revision 1.30 by root, Thu Nov 22 12:28:35 2007 UTC vs.
Revision 1.37 by root, Sat Nov 24 07:14:26 2007 UTC