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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="Fri Nov 23 06:14:47 2007" />	9	<meta name="created" content="Sat Nov 24 10:48:32 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>
127	</dd>	141	</dd>
128	<dt>unsigned int ev_supported_backends ()</dt>	142	<dt>unsigned int ev_supported_backends ()</dt>
129	<dd>	143	<dd>
130	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>	144	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
131	value) compiled into this binary of libev (independent of their	145	value) compiled into this binary of libev (independent of their
132	availability on the system you are running on). See <code>ev_default_loop</code> for	146	availability on the system you are running on). See <code>ev_default_loop</code> for
133	a description of the set values.</p>	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>
134	</dd>	154	</dd>
135	<dt>unsigned int ev_recommended_backends ()</dt>	155	<dt>unsigned int ev_recommended_backends ()</dt>
136	<dd>	156	<dd>
137	<p>Return the set of all backends compiled into this binary of libev and also	157	<p>Return the set of all backends compiled into this binary of libev and also
138	recommended for this platform. This set is often smaller than the one	158	recommended for this platform. This set is often smaller than the one
139	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on	159	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
140	most BSDs and will not be autodetected unless you explicitly request it	160	most BSDs and will not be autodetected unless you explicitly request it
141	(assuming you know what you are doing). This is the set of backends that	161	(assuming you know what you are doing). This is the set of backends that
142	<code>EVFLAG_AUTO</code> will probe for.</p>	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>
143	</dd>	172	</dd>
144	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	173	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
145	<dd>	174	<dd>
146	<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
147	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
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149	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
150	destructive action. The default is your system realloc function.</p>	179	destructive action. The default is your system realloc function.</p>
151	<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,
152	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,
153	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>
154	</dd>	203	</dd>
155	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	204	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
156	<dd>	205	<dd>
157	<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
158	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
159	indicating the system call or subsystem causing the problem. If this	208	indicating the system call or subsystem causing the problem. If this
160	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
161	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
162	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
163	(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>
164	</dd>	225	</dd>
165	</dl>	226	</dl>
166		227
167	</div>	228	</div>
168	<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>
…		…
184	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
185	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>	246	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
186	<p>If you don't know what event loop to use, use the one returned from this	247	<p>If you don't know what event loop to use, use the one returned from this
187	function.</p>	248	function.</p>
188	<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
189	backends to use, and is usually specified as <code>0</code> (or EVFLAG_AUTO).</p>	250	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
190	<p>It supports the following flags:</p>	251	<p>The following flags are supported:</p>
191	<p>	252	<p>
192	<dl>	253	<dl>
193	<dt><code>EVFLAG_AUTO</code></dt>	254	<dt><code>EVFLAG_AUTO</code></dt>
194	<dd>	255	<dd>
195	<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
…		…
228	<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
229	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
230	(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
231	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
232	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>
233	</dd>	297	</dd>
234	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>	298	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
235	<dd>	299	<dd>
236	<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
237	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
238	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
239	completely useless). For this reason its not being "autodetected" unless	303	completely useless). For this reason its not being "autodetected"
240	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>
241	<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
242	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
243	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
244	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
245	incident, so its best to avoid that.</p>	310	incident, so its best to avoid that.</p>
…		…
250	</dd>	315	</dd>
251	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>	316	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
252	<dd>	317	<dd>
253	<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,
254	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>
255	</dd>	323	</dd>
256	<dt><code>EVBACKEND_ALL</code></dt>	324	<dt><code>EVBACKEND_ALL</code></dt>
257	<dd>	325	<dd>
258	<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
259	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
…		…
263	</p>	331	</p>
264	<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
265	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
266	specified, most compiled-in backend will be tried, usually in reverse	334	specified, most compiled-in backend will be tried, usually in reverse
267	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>
268	</dd>	352	</dd>
269	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	353	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
270	<dd>	354	<dd>
271	<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
272	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
273	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
274	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>
275	</dd>	365	</dd>
276	<dt>ev_default_destroy ()</dt>	366	<dt>ev_default_destroy ()</dt>
277	<dd>	367	<dd>
278	<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
279	etc.). This stops all registered event watchers (by not touching them in	369	etc.). None of the active event watchers will be stopped in the normal
280	any way whatsoever, although you cannot rely on this :).</p>	370	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		371	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		372	calling this function, or cope with the fact afterwards (which is usually
		373	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		374	for example).</p>
281	</dd>	375	</dd>
282	<dt>ev_loop_destroy (loop)</dt>	376	<dt>ev_loop_destroy (loop)</dt>
283	<dd>	377	<dd>
284	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	378	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
285	earlier call to <code>ev_loop_new</code>.</p>	379	earlier call to <code>ev_loop_new</code>.</p>
…		…
315	use.</p>	409	use.</p>
316	</dd>	410	</dd>
317	<dt>ev_tstamp ev_now (loop)</dt>	411	<dt>ev_tstamp ev_now (loop)</dt>
318	<dd>	412	<dd>
319	<p>Returns the current "event loop time", which is the time the event loop	413	<p>Returns the current "event loop time", which is the time the event loop
320	got events and started processing them. This timestamp does not change	414	received events and started processing them. This timestamp does not
321	as long as callbacks are being processed, and this is also the base time	415	change as long as callbacks are being processed, and this is also the base
322	used for relative timers. You can treat it as the timestamp of the event	416	time used for relative timers. You can treat it as the timestamp of the
323	occuring (or more correctly, the mainloop finding out about it).</p>	417	event occuring (or more correctly, libev finding out about it).</p>
324	</dd>	418	</dd>
325	<dt>ev_loop (loop, int flags)</dt>	419	<dt>ev_loop (loop, int flags)</dt>
326	<dd>	420	<dd>
327	<p>Finally, this is it, the event handler. This function usually is called	421	<p>Finally, this is it, the event handler. This function usually is called
328	after you initialised all your watchers and you want to start handling	422	after you initialised all your watchers and you want to start handling
329	events.</p>	423	events.</p>
330	<p>If the flags argument is specified as 0, it will not return until either	424	<p>If the flags argument is specified as <code>0</code>, it will not return until
331	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	425	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		426	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		427	relying on all watchers to be stopped when deciding when a program has
		428	finished (especially in interactive programs), but having a program that
		429	automatically loops as long as it has to and no longer by virtue of
		430	relying on its watchers stopping correctly is a thing of beauty.</p>
332	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	431	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
333	those events and any outstanding ones, but will not block your process in	432	those events and any outstanding ones, but will not block your process in
334	case there are no events and will return after one iteration of the loop.</p>	433	case there are no events and will return after one iteration of the loop.</p>
335	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	434	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
336	neccessary) and will handle those and any outstanding ones. It will block	435	neccessary) and will handle those and any outstanding ones. It will block
337	your process until at least one new event arrives, and will return after	436	your process until at least one new event arrives, and will return after
338	one iteration of the loop.</p>	437	one iteration of the loop. This is useful if you are waiting for some
339	<p>This flags value could be used to implement alternative looping	438	external event in conjunction with something not expressible using other
340	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	439	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
341	more generic mechanism.</p>	440	usually a better approach for this kind of thing.</p>
342	<p>Here are the gory details of what ev_loop does:</p>	441	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
343	<pre> 1. If there are no active watchers (reference count is zero), return.	442	<pre> * If there are no active watchers (reference count is zero), return.
344	2. Queue and immediately call all prepare watchers.	443	- Queue prepare watchers and then call all outstanding watchers.
345	3. If we have been forked, recreate the kernel state.	444	- If we have been forked, recreate the kernel state.
346	4. Update the kernel state with all outstanding changes.	445	- Update the kernel state with all outstanding changes.
347	5. Update the "event loop time".	446	- Update the "event loop time".
348	6. Calculate for how long to block.	447	- Calculate for how long to block.
349	7. Block the process, waiting for events.	448	- Block the process, waiting for any events.
		449	- Queue all outstanding I/O (fd) events.
350	8. Update the "event loop time" and do time jump handling.	450	- Update the "event loop time" and do time jump handling.
351	9. Queue all outstanding timers.	451	- Queue all outstanding timers.
352	10. Queue all outstanding periodics.	452	- Queue all outstanding periodics.
353	11. If no events are pending now, queue all idle watchers.	453	- If no events are pending now, queue all idle watchers.
354	12. Queue all check watchers.	454	- Queue all check watchers.
355	13. Call all queued watchers in reverse order (i.e. check watchers first).	455	- Call all queued watchers in reverse order (i.e. check watchers first).
		456	Signals and child watchers are implemented as I/O watchers, and will
		457	be handled here by queueing them when their watcher gets executed.
356	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	458	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
357	was used, return, otherwise continue with step #1.	459	were used, return, otherwise continue with step *.
		460
		461	</pre>
		462	<p>Example: queue some jobs and then loop until no events are outsanding
		463	anymore.</p>
		464	<pre> ... queue jobs here, make sure they register event watchers as long
		465	... as they still have work to do (even an idle watcher will do..)
		466	ev_loop (my_loop, 0);
		467	... jobs done. yeah!
358		468
359	</pre>	469	</pre>
360	</dd>	470	</dd>
361	<dt>ev_unloop (loop, how)</dt>	471	<dt>ev_unloop (loop, how)</dt>
362	<dd>	472	<dd>
…		…
376	example, libev itself uses this for its internal signal pipe: It is not	486	example, libev itself uses this for its internal signal pipe: It is not
377	visible to the libev user and should not keep <code>ev_loop</code> from exiting if	487	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
378	no event watchers registered by it are active. It is also an excellent	488	no event watchers registered by it are active. It is also an excellent
379	way to do this for generic recurring timers or from within third-party	489	way to do this for generic recurring timers or from within third-party
380	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>	490	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		491	<p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
		492	running when nothing else is active.</p>
		493	<pre> struct dv_signal exitsig;
		494	ev_signal_init (&exitsig, sig_cb, SIGINT);
		495	ev_signal_start (myloop, &exitsig);
		496	evf_unref (myloop);
		497
		498	</pre>
		499	<p>Example: for some weird reason, unregister the above signal handler again.</p>
		500	<pre> ev_ref (myloop);
		501	ev_signal_stop (myloop, &exitsig);
		502
		503	</pre>
381	</dd>	504	</dd>
382	</dl>	505	</dl>
383		506
384	</div>	507	</div>
385	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	508	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
…		…
417	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	540	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
418	*)</code>), and you can stop watching for events at any time by calling the	541	*)</code>), and you can stop watching for events at any time by calling the
419	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	542	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
420	<p>As long as your watcher is active (has been started but not stopped) you	543	<p>As long as your watcher is active (has been started but not stopped) you
421	must not touch the values stored in it. Most specifically you must never	544	must not touch the values stored in it. Most specifically you must never
422	reinitialise it or call its set macro.</p>	545	reinitialise it or call its <code>set</code> macro.</p>
423	<p>You can check whether an event is active by calling the <code>ev_is_active
424	(watcher *)</code> macro. To see whether an event is outstanding (but the
425	callback for it has not been called yet) you can use the <code>ev_is_pending
426	(watcher *)</code> macro.</p>
427	<p>Each and every callback receives the event loop pointer as first, the	546	<p>Each and every callback receives the event loop pointer as first, the
428	registered watcher structure as second, and a bitset of received events as	547	registered watcher structure as second, and a bitset of received events as
429	third argument.</p>	548	third argument.</p>
430	<p>The received events usually include a single bit per event type received	549	<p>The received events usually include a single bit per event type received
431	(you can receive multiple events at the same time). The possible bit masks	550	(you can receive multiple events at the same time). The possible bit masks
…		…
480	your callbacks is well-written it can just attempt the operation and cope	599	your callbacks is well-written it can just attempt the operation and cope
481	with the error from read() or write(). This will not work in multithreaded	600	with the error from read() or write(). This will not work in multithreaded
482	programs, though, so beware.</p>	601	programs, though, so beware.</p>
483	</dd>	602	</dd>
484	</dl>	603	</dl>
		604
		605	</div>
		606	<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2>
		607	<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2">
		608	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		609	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		610	<dl>
		611	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		612	<dd>
		613	<p>This macro initialises the generic portion of a watcher. The contents
		614	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		615	the generic parts of the watcher are initialised, you <i>need</i> to call
		616	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		617	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		618	which rolls both calls into one.</p>
		619	<p>You can reinitialise a watcher at any time as long as it has been stopped
		620	(or never started) and there are no pending events outstanding.</p>
		621	<p>The callbakc is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		622	int revents)</code>.</p>
		623	</dd>
		624	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		625	<dd>
		626	<p>This macro initialises the type-specific parts of a watcher. You need to
		627	call <code>ev_init</code> at least once before you call this macro, but you can
		628	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		629	macro on a watcher that is active (it can be pending, however, which is a
		630	difference to the <code>ev_init</code> macro).</p>
		631	<p>Although some watcher types do not have type-specific arguments
		632	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		633	</dd>
		634	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		635	<dd>
		636	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		637	calls into a single call. This is the most convinient method to initialise
		638	a watcher. The same limitations apply, of course.</p>
		639	</dd>
		640	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		641	<dd>
		642	<p>Starts (activates) the given watcher. Only active watchers will receive
		643	events. If the watcher is already active nothing will happen.</p>
		644	</dd>
		645	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		646	<dd>
		647	<p>Stops the given watcher again (if active) and clears the pending
		648	status. It is possible that stopped watchers are pending (for example,
		649	non-repeating timers are being stopped when they become pending), but
		650	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		651	you want to free or reuse the memory used by the watcher it is therefore a
		652	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		653	</dd>
		654	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		655	<dd>
		656	<p>Returns a true value iff the watcher is active (i.e. it has been started
		657	and not yet been stopped). As long as a watcher is active you must not modify
		658	it.</p>
		659	</dd>
		660	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		661	<dd>
		662	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		663	events but its callback has not yet been invoked). As long as a watcher
		664	is pending (but not active) you must not call an init function on it (but
		665	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		666	libev (e.g. you cnanot <code>free ()</code> it).</p>
		667	</dd>
		668	<dt>callback = ev_cb (ev_TYPE *watcher)</dt>
		669	<dd>
		670	<p>Returns the callback currently set on the watcher.</p>
		671	</dd>
		672	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		673	<dd>
		674	<p>Change the callback. You can change the callback at virtually any time
		675	(modulo threads).</p>
		676	</dd>
		677	</dl>
		678
		679
		680
		681
485		682
486	</div>	683	</div>
487	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	684	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
488	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	685	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
489	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	686	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
…		…
520	</div>	717	</div>
521	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	718	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
522	<div id="WATCHER_TYPES_CONTENT">	719	<div id="WATCHER_TYPES_CONTENT">
523	<p>This section describes each watcher in detail, but will not repeat	720	<p>This section describes each watcher in detail, but will not repeat
524	information given in the last section.</p>	721	information given in the last section.</p>
		722
		723
		724
		725
525		726
526	</div>	727	</div>
527	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>	728	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
528	<div id="code_ev_io_code_is_this_file_descrip-2">	729	<div id="code_ev_io_code_is_this_file_descrip-2">
529	<p>I/O watchers check whether a file descriptor is readable or writable	730	<p>I/O watchers check whether a file descriptor is readable or writable
…		…
548	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	749	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
549	<dd>	750	<dd>
550	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive	751	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
551	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	752	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|
552	EV_WRITE</code> to receive the given events.</p>	753	EV_WRITE</code> to receive the given events.</p>
		754	<p>Please note that most of the more scalable backend mechanisms (for example
		755	epoll and solaris ports) can result in spurious readyness notifications
		756	for file descriptors, so you practically need to use non-blocking I/O (and
		757	treat callback invocation as hint only), or retest separately with a safe
		758	interface before doing I/O (XLib can do this), or force the use of either
		759	<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
		760	problem. Also note that it is quite easy to have your callback invoked
		761	when the readyness condition is no longer valid even when employing
		762	typical ways of handling events, so its a good idea to use non-blocking
		763	I/O unconditionally.</p>
553	</dd>	764	</dd>
554	</dl>	765	</dl>
		766	<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		767	readable, but only once. Since it is likely line-buffered, you could
		768	attempt to read a whole line in the callback:</p>
		769	<pre> static void
		770	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		771	{
		772	ev_io_stop (loop, w);
		773	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		774	}
		775
		776	...
		777	struct ev_loop *loop = ev_default_init (0);
		778	struct ev_io stdin_readable;
		779	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		780	ev_io_start (loop, &stdin_readable);
		781	ev_loop (loop, 0);
		782
		783
		784
		785
		786	</pre>
555		787
556	</div>	788	</div>
557	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>	789	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
558	<div id="code_ev_timer_code_relative_and_opti-2">	790	<div id="code_ev_timer_code_relative_and_opti-2">
559	<p>Timer watchers are simple relative timers that generate an event after a	791	<p>Timer watchers are simple relative timers that generate an event after a
…		…
603	time you successfully read or write some data. If you go into an idle	835	time you successfully read or write some data. If you go into an idle
604	state where you do not expect data to travel on the socket, you can stop	836	state where you do not expect data to travel on the socket, you can stop
605	the timer, and again will automatically restart it if need be.</p>	837	the timer, and again will automatically restart it if need be.</p>
606	</dd>	838	</dd>
607	</dl>	839	</dl>
		840	<p>Example: create a timer that fires after 60 seconds.</p>
		841	<pre> static void
		842	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		843	{
		844	.. one minute over, w is actually stopped right here
		845	}
		846
		847	struct ev_timer mytimer;
		848	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		849	ev_timer_start (loop, &mytimer);
		850
		851	</pre>
		852	<p>Example: create a timeout timer that times out after 10 seconds of
		853	inactivity.</p>
		854	<pre> static void
		855	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		856	{
		857	.. ten seconds without any activity
		858	}
		859
		860	struct ev_timer mytimer;
		861	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		862	ev_timer_again (&mytimer); /* start timer */
		863	ev_loop (loop, 0);
		864
		865	// and in some piece of code that gets executed on any "activity":
		866	// reset the timeout to start ticking again at 10 seconds
		867	ev_timer_again (&mytimer);
		868
		869
		870
		871
		872	</pre>
608		873
609	</div>	874	</div>
610	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>	875	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
611	<div id="code_ev_periodic_code_to_cron_or_not-2">	876	<div id="code_ev_periodic_code_to_cron_or_not-2">
612	<p>Periodic watchers are also timers of a kind, but they are very versatile	877	<p>Periodic watchers are also timers of a kind, but they are very versatile
613	(and unfortunately a bit complex).</p>	878	(and unfortunately a bit complex).</p>
614	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)	879	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
615	but on wallclock time (absolute time). You can tell a periodic watcher	880	but on wallclock time (absolute time). You can tell a periodic watcher
616	to trigger "at" some specific point in time. For example, if you tell a	881	to trigger "at" some specific point in time. For example, if you tell a
617	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	882	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
618	+ 10.>) and then reset your system clock to the last year, then it will	883	+ 10.</code>) and then reset your system clock to the last year, then it will
619	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger	884	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
620	roughly 10 seconds later and of course not if you reset your system time	885	roughly 10 seconds later and of course not if you reset your system time
621	again).</p>	886	again).</p>
622	<p>They can also be used to implement vastly more complex timers, such as	887	<p>They can also be used to implement vastly more complex timers, such as
623	triggering an event on eahc midnight, local time.</p>	888	triggering an event on eahc midnight, local time.</p>
…		…
696	when you changed some parameters or the reschedule callback would return	961	when you changed some parameters or the reschedule callback would return
697	a different time than the last time it was called (e.g. in a crond like	962	a different time than the last time it was called (e.g. in a crond like
698	program when the crontabs have changed).</p>	963	program when the crontabs have changed).</p>
699	</dd>	964	</dd>
700	</dl>	965	</dl>
		966	<p>Example: call a callback every hour, or, more precisely, whenever the
		967	system clock is divisible by 3600. The callback invocation times have
		968	potentially a lot of jittering, but good long-term stability.</p>
		969	<pre> static void
		970	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		971	{
		972	... its now a full hour (UTC, or TAI or whatever your clock follows)
		973	}
		974
		975	struct ev_periodic hourly_tick;
		976	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		977	ev_periodic_start (loop, &hourly_tick);
		978
		979	</pre>
		980	<p>Example: the same as above, but use a reschedule callback to do it:</p>
		981	<pre> #include <math.h>
		982
		983	static ev_tstamp
		984	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		985	{
		986	return fmod (now, 3600.) + 3600.;
		987	}
		988
		989	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		990
		991	</pre>
		992	<p>Example: call a callback every hour, starting now:</p>
		993	<pre> struct ev_periodic hourly_tick;
		994	ev_periodic_init (&hourly_tick, clock_cb,
		995	fmod (ev_now (loop), 3600.), 3600., 0);
		996	ev_periodic_start (loop, &hourly_tick);
		997
		998
		999
		1000
		1001	</pre>
701		1002
702	</div>	1003	</div>
703	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>	1004	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
704	<div id="code_ev_signal_code_signal_me_when_a-2">	1005	<div id="code_ev_signal_code_signal_me_when_a-2">
705	<p>Signal watchers will trigger an event when the process receives a specific	1006	<p>Signal watchers will trigger an event when the process receives a specific
…		…
719	<p>Configures the watcher to trigger on the given signal number (usually one	1020	<p>Configures the watcher to trigger on the given signal number (usually one
720	of the <code>SIGxxx</code> constants).</p>	1021	of the <code>SIGxxx</code> constants).</p>
721	</dd>	1022	</dd>
722	</dl>	1023	</dl>
723		1024
		1025
		1026
		1027
		1028
724	</div>	1029	</div>
725	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>	1030	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
726	<div id="code_ev_child_code_wait_for_pid_stat-2">	1031	<div id="code_ev_child_code_wait_for_pid_stat-2">
727	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1032	<p>Child watchers trigger when your process receives a SIGCHLD in response to
728	some child status changes (most typically when a child of yours dies).</p>	1033	some child status changes (most typically when a child of yours dies).</p>
…		…
736	the status word (use the macros from <code>sys/wait.h</code> and see your systems	1041	the status word (use the macros from <code>sys/wait.h</code> and see your systems
737	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the	1042	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
738	process causing the status change.</p>	1043	process causing the status change.</p>
739	</dd>	1044	</dd>
740	</dl>	1045	</dl>
		1046	<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
		1047	<pre> static void
		1048	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1049	{
		1050	ev_unloop (loop, EVUNLOOP_ALL);
		1051	}
		1052
		1053	struct ev_signal signal_watcher;
		1054	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1055	ev_signal_start (loop, &sigint_cb);
		1056
		1057
		1058
		1059
		1060	</pre>
741		1061
742	</div>	1062	</div>
743	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>	1063	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
744	<div id="code_ev_idle_code_when_you_ve_got_no-2">	1064	<div id="code_ev_idle_code_when_you_ve_got_no-2">
745	<p>Idle watchers trigger events when there are no other events are pending	1065	<p>Idle watchers trigger events when there are no other events are pending
…		…
761	<p>Initialises and configures the idle watcher - it has no parameters of any	1081	<p>Initialises and configures the idle watcher - it has no parameters of any
762	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1082	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
763	believe me.</p>	1083	believe me.</p>
764	</dd>	1084	</dd>
765	</dl>	1085	</dl>
		1086	<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
		1087	callback, free it. Alos, use no error checking, as usual.</p>
		1088	<pre> static void
		1089	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1090	{
		1091	free (w);
		1092	// now do something you wanted to do when the program has
		1093	// no longer asnything immediate to do.
		1094	}
		1095
		1096	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1097	ev_idle_init (idle_watcher, idle_cb);
		1098	ev_idle_start (loop, idle_cb);
		1099
		1100
		1101
		1102
		1103	</pre>
766		1104
767	</div>	1105	</div>
768	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>	1106	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
769	<div id="code_ev_prepare_code_and_code_ev_che-2">	1107	<div id="code_ev_prepare_code_and_code_ev_che-2">
770	<p>Prepare and check watchers are usually (but not always) used in tandem:	1108	<p>Prepare and check watchers are usually (but not always) used in tandem:
771	prepare watchers get invoked before the process blocks and check watchers	1109	prepare watchers get invoked before the process blocks and check watchers
772	afterwards.</p>	1110	afterwards.</p>
773	<p>Their main purpose is to integrate other event mechanisms into libev. This	1111	<p>Their main purpose is to integrate other event mechanisms into libev and
774	could be used, for example, to track variable changes, implement your own	1112	their use is somewhat advanced. This could be used, for example, to track
775	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1113	variable changes, implement your own watchers, integrate net-snmp or a
		1114	coroutine library and lots more.</p>
776	<p>This is done by examining in each prepare call which file descriptors need	1115	<p>This is done by examining in each prepare call which file descriptors need
777	to be watched by the other library, registering <code>ev_io</code> watchers for	1116	to be watched by the other library, registering <code>ev_io</code> watchers for
778	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries	1117	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
779	provide just this functionality). Then, in the check watcher you check for	1118	provide just this functionality). Then, in the check watcher you check for
780	any events that occured (by checking the pending status of all watchers	1119	any events that occured (by checking the pending status of all watchers
…		…
796	<p>Initialises and configures the prepare or check watcher - they have no	1135	<p>Initialises and configures the prepare or check watcher - they have no
797	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1136	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
798	macros, but using them is utterly, utterly and completely pointless.</p>	1137	macros, but using them is utterly, utterly and completely pointless.</p>
799	</dd>	1138	</dd>
800	</dl>	1139	</dl>
		1140	<p>Example: TODO.</p>
		1141
		1142
		1143
		1144
		1145
		1146	</div>
		1147	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2>
		1148	<div id="code_ev_embed_code_when_one_backend_-2">
		1149	<p>This is a rather advanced watcher type that lets you embed one event loop
		1150	into another (currently only <code>ev_io</code> events are supported in the embedded
		1151	loop, other types of watchers might be handled in a delayed or incorrect
		1152	fashion and must not be used).</p>
		1153	<p>There are primarily two reasons you would want that: work around bugs and
		1154	prioritise I/O.</p>
		1155	<p>As an example for a bug workaround, the kqueue backend might only support
		1156	sockets on some platform, so it is unusable as generic backend, but you
		1157	still want to make use of it because you have many sockets and it scales
		1158	so nicely. In this case, you would create a kqueue-based loop and embed it
		1159	into your default loop (which might use e.g. poll). Overall operation will
		1160	be a bit slower because first libev has to poll and then call kevent, but
		1161	at least you can use both at what they are best.</p>
		1162	<p>As for prioritising I/O: rarely you have the case where some fds have
		1163	to be watched and handled very quickly (with low latency), and even
		1164	priorities and idle watchers might have too much overhead. In this case
		1165	you would put all the high priority stuff in one loop and all the rest in
		1166	a second one, and embed the second one in the first.</p>
		1167	<p>As long as the watcher is active, the callback will be invoked every time
		1168	there might be events pending in the embedded loop. The callback must then
		1169	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1170	their callbacks (you could also start an idle watcher to give the embedded
		1171	loop strictly lower priority for example). You can also set the callback
		1172	to <code>0</code>, in which case the embed watcher will automatically execute the
		1173	embedded loop sweep.</p>
		1174	<p>As long as the watcher is started it will automatically handle events. The
		1175	callback will be invoked whenever some events have been handled. You can
		1176	set the callback to <code>0</code> to avoid having to specify one if you are not
		1177	interested in that.</p>
		1178	<p>Also, there have not currently been made special provisions for forking:
		1179	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1180	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1181	yourself.</p>
		1182	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1183	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1184	portable one.</p>
		1185	<p>So when you want to use this feature you will always have to be prepared
		1186	that you cannot get an embeddable loop. The recommended way to get around
		1187	this is to have a separate variables for your embeddable loop, try to
		1188	create it, and if that fails, use the normal loop for everything:</p>
		1189	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1190	struct ev_loop *loop_lo = 0;
		1191	struct ev_embed embed;
		1192
		1193	// see if there is a chance of getting one that works
		1194	// (remember that a flags value of 0 means autodetection)
		1195	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1196	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1197	: 0;
		1198
		1199	// if we got one, then embed it, otherwise default to loop_hi
		1200	if (loop_lo)
		1201	{
		1202	ev_embed_init (&embed, 0, loop_lo);
		1203	ev_embed_start (loop_hi, &embed);
		1204	}
		1205	else
		1206	loop_lo = loop_hi;
		1207
		1208	</pre>
		1209	<dl>
		1210	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1211	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1212	<dd>
		1213	<p>Configures the watcher to embed the given loop, which must be
		1214	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1215	invoked automatically, otherwise it is the responsibility of the callback
		1216	to invoke it (it will continue to be called until the sweep has been done,
		1217	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1218	</dd>
		1219	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1220	<dd>
		1221	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1222	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1223	apropriate way for embedded loops.</p>
		1224	</dd>
		1225	</dl>
		1226
		1227
		1228
		1229
801		1230
802	</div>	1231	</div>
803	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1232	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
804	<div id="OTHER_FUNCTIONS_CONTENT">	1233	<div id="OTHER_FUNCTIONS_CONTENT">
805	<p>There are some other functions of possible interest. Described. Here. Now.</p>	1234	<p>There are some other functions of possible interest. Described. Here. Now.</p>
…		…
832		1261
833	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1262	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
834		1263
835	</pre>	1264	</pre>
836	</dd>	1265	</dd>
837	<dt>ev_feed_event (loop, watcher, int events)</dt>	1266	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
838	<dd>	1267	<dd>
839	<p>Feeds the given event set into the event loop, as if the specified event	1268	<p>Feeds the given event set into the event loop, as if the specified event
840	had happened for the specified watcher (which must be a pointer to an	1269	had happened for the specified watcher (which must be a pointer to an
841	initialised but not necessarily started event watcher).</p>	1270	initialised but not necessarily started event watcher).</p>
842	</dd>	1271	</dd>
843	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1272	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
844	<dd>	1273	<dd>
845	<p>Feed an event on the given fd, as if a file descriptor backend detected	1274	<p>Feed an event on the given fd, as if a file descriptor backend detected
846	the given events it.</p>	1275	the given events it.</p>
847	</dd>	1276	</dd>
848	<dt>ev_feed_signal_event (loop, int signum)</dt>	1277	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
849	<dd>	1278	<dd>
850	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1279	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1280	loop!).</p>
851	</dd>	1281	</dd>
852	</dl>	1282	</dl>
		1283
		1284
		1285
		1286
853		1287
854	</div>	1288	</div>
855	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>	1289	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
856	<div id="LIBEVENT_EMULATION_CONTENT">	1290	<div id="LIBEVENT_EMULATION_CONTENT">
857	<p>Libev offers a compatibility emulation layer for libevent. It cannot	1291	<p>Libev offers a compatibility emulation layer for libevent. It cannot
…		…
872	</dl>	1306	</dl>
873		1307
874	</div>	1308	</div>
875	<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>	1309	<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
876	<div id="C_SUPPORT_CONTENT">	1310	<div id="C_SUPPORT_CONTENT">
877	<p>TBD.</p>	1311	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1312	you to use some convinience methods to start/stop watchers and also change
		1313	the callback model to a model using method callbacks on objects.</p>
		1314	<p>To use it,</p>
		1315	<pre> #include <ev++.h>
		1316
		1317	</pre>
		1318	<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
		1319	and puts all of its definitions (many of them macros) into the global
		1320	namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
		1321	<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
		1322	<code>EV_MULTIPLICITY</code>.</p>
		1323	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1324	<dl>
		1325	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1326	<dd>
		1327	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1328	macros from <cite>ev.h</cite>.</p>
		1329	</dd>
		1330	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1331	<dd>
		1332	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1333	</dd>
		1334	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1335	<dd>
		1336	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1337	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1338	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1339	defines by many implementations.</p>
		1340	<p>All of those classes have these methods:</p>
		1341	<p>
		1342	<dl>
		1343	<dt>ev::TYPE::TYPE (object , object::method )</dt>
		1344	<dt>ev::TYPE::TYPE (object , object::method , struct ev_loop *)</dt>
		1345	<dt>ev::TYPE::~TYPE</dt>
		1346	<dd>
		1347	<p>The constructor takes a pointer to an object and a method pointer to
		1348	the event handler callback to call in this class. The constructor calls
		1349	<code>ev_init</code> for you, which means you have to call the <code>set</code> method
		1350	before starting it. If you do not specify a loop then the constructor
		1351	automatically associates the default loop with this watcher.</p>
		1352	<p>The destructor automatically stops the watcher if it is active.</p>
		1353	</dd>
		1354	<dt>w->set (struct ev_loop *)</dt>
		1355	<dd>
		1356	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1357	do this when the watcher is inactive (and not pending either).</p>
		1358	</dd>
		1359	<dt>w->set ([args])</dt>
		1360	<dd>
		1361	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1362	called at least once. Unlike the C counterpart, an active watcher gets
		1363	automatically stopped and restarted.</p>
		1364	</dd>
		1365	<dt>w->start ()</dt>
		1366	<dd>
		1367	<p>Starts the watcher. Note that there is no <code>loop</code> argument as the
		1368	constructor already takes the loop.</p>
		1369	</dd>
		1370	<dt>w->stop ()</dt>
		1371	<dd>
		1372	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1373	</dd>
		1374	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1375	<dd>
		1376	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1377	<code>ev_TYPE_again</code> function.</p>
		1378	</dd>
		1379	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1380	<dd>
		1381	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1382	</dd>
		1383	</dl>
		1384	</p>
		1385	</dd>
		1386	</dl>
		1387	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1388	the constructor.</p>
		1389	<pre> class myclass
		1390	{
		1391	ev_io io; void io_cb (ev::io &w, int revents);
		1392	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1393
		1394	myclass ();
		1395	}
		1396
		1397	myclass::myclass (int fd)
		1398	: io (this, &myclass::io_cb),
		1399	idle (this, &myclass::idle_cb)
		1400	{
		1401	io.start (fd, ev::READ);
		1402	}
		1403
		1404	</pre>
878		1405
879	</div>	1406	</div>
880	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1407	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
881	<div id="AUTHOR_CONTENT">	1408	<div id="AUTHOR_CONTENT">
882	<p>Marc Lehmann <libev@schmorp.de>.</p>	1409	<p>Marc Lehmann <libev@schmorp.de>.</p>

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