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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="Mon Nov 12 10:06:08 2007" />	9	<meta name="created" content="Tue Nov 27 21:14:27 2007" />
10	<meta name="generator" content="Pod::Xhtml 1.57" />	10	<meta name="generator" content="Pod::Xhtml 1.57" />
11	<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>	11	<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12	<body>	12	<body>
13	<div class="pod">	13	<div class="pod">
14	<!-- INDEX START -->	14	<!-- INDEX START -->
…		…
21	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>	21	<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>	22	<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>	23	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
24	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>	24	<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>	25	<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
		26	<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
26	<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>	27	<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
27	</ul>	28	</ul>
28	</li>	29	</li>
29	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>	30	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
30	<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>	31	<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
31	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>	32	<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
32	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>	33	<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
33	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>	34	<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
34	<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>	35	<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
		36	<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
35	<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>	37	<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
36	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>	38	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
		39	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
		40	<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
37	</ul>	41	</ul>
38	</li>	42	</li>
39	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	43	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>	44	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>	45	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
		46	<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
		47	<li><a href="#EMBEDDING">EMBEDDING</a>
		48	<ul><li><a href="#FILESETS">FILESETS</a>
		49	<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
		50	<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
		51	<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
		52	</ul>
		53	</li>
		54	<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
		55	<li><a href="#EXAMPLES">EXAMPLES</a></li>
		56	</ul>
		57	</li>
		58	<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
42	<li><a href="#AUTHOR">AUTHOR</a>	59	<li><a href="#AUTHOR">AUTHOR</a>
43	</li>	60	</li>
44	</ul><hr />	61	</ul><hr />
45	<!-- INDEX END -->	62	<!-- INDEX END -->
46		63
…		…
49	<p>libev - a high performance full-featured event loop written in C</p>	66	<p>libev - a high performance full-featured event loop written in C</p>
50		67
51	</div>	68	</div>
52	<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>	69	<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>
53	<div id="SYNOPSIS_CONTENT">	70	<div id="SYNOPSIS_CONTENT">
		71	<pre> /* this is the only header you need */
54	<pre> #include <ev.h>	72	#include <ev.h>
		73
		74	/* what follows is a fully working example program */
		75	ev_io stdin_watcher;
		76	ev_timer timeout_watcher;
		77
		78	/* called when data readable on stdin */
		79	static void
		80	stdin_cb (EV_P_ struct ev_io *w, int revents)
		81	{
		82	/* puts ("stdin ready"); */
		83	ev_io_stop (EV_A_ w); /* just a syntax example */
		84	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		85	}
		86
		87	static void
		88	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		89	{
		90	/* puts ("timeout"); */
		91	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		92	}
		93
		94	int
		95	main (void)
		96	{
		97	struct ev_loop *loop = ev_default_loop (0);
		98
		99	/* initialise an io watcher, then start it */
		100	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
		101	ev_io_start (loop, &stdin_watcher);
		102
		103	/* simple non-repeating 5.5 second timeout */
		104	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		105	ev_timer_start (loop, &timeout_watcher);
		106
		107	/* loop till timeout or data ready */
		108	ev_loop (loop, 0);
		109
		110	return 0;
		111	}
55		112
56	</pre>	113	</pre>
57		114
58	</div>	115	</div>
59	<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>	116	<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>
…		…
96	<div id="TIME_REPRESENTATION_CONTENT">	153	<div id="TIME_REPRESENTATION_CONTENT">
97	<p>Libev represents time as a single floating point number, representing the	154	<p>Libev represents time as a single floating point number, representing the
98	(fractional) number of seconds since the (POSIX) epoch (somewhere near	155	(fractional) number of seconds since the (POSIX) epoch (somewhere near
99	the beginning of 1970, details are complicated, don't ask). This type is	156	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	157	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
101	to the double type in C.</p>	158	to the <code>double</code> type in C, and when you need to do any calculations on
		159	it, you should treat it as such.</p>
102		160
103	</div>	161	</div>
104	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	162	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105	<div id="GLOBAL_FUNCTIONS_CONTENT">	163	<div id="GLOBAL_FUNCTIONS_CONTENT">
106	<p>These functions can be called anytime, even before initialising the	164	<p>These functions can be called anytime, even before initialising the
107	library in any way.</p>	165	library in any way.</p>
108	<dl>	166	<dl>
109	<dt>ev_tstamp ev_time ()</dt>	167	<dt>ev_tstamp ev_time ()</dt>
110	<dd>	168	<dd>
111	<p>Returns the current time as libev would use it.</p>	169	<p>Returns the current time as libev would use it. Please note that the
		170	<code>ev_now</code> function is usually faster and also often returns the timestamp
		171	you actually want to know.</p>
112	</dd>	172	</dd>
113	<dt>int ev_version_major ()</dt>	173	<dt>int ev_version_major ()</dt>
114	<dt>int ev_version_minor ()</dt>	174	<dt>int ev_version_minor ()</dt>
115	<dd>	175	<dd>
116	<p>You can find out the major and minor version numbers of the library	176	<p>You can find out the major and minor version numbers of the library
…		…
120	version of the library your program was compiled against.</p>	180	version of the library your program was compiled against.</p>
121	<p>Usually, it's a good idea to terminate if the major versions mismatch,	181	<p>Usually, it's a good idea to terminate if the major versions mismatch,
122	as this indicates an incompatible change. Minor versions are usually	182	as this indicates an incompatible change. Minor versions are usually
123	compatible to older versions, so a larger minor version alone is usually	183	compatible to older versions, so a larger minor version alone is usually
124	not a problem.</p>	184	not a problem.</p>
		185	<p>Example: make sure we haven't accidentally been linked against the wrong
		186	version:</p>
		187	<pre> assert (("libev version mismatch",
		188	ev_version_major () == EV_VERSION_MAJOR
		189	&& ev_version_minor () >= EV_VERSION_MINOR));
		190
		191	</pre>
		192	</dd>
		193	<dt>unsigned int ev_supported_backends ()</dt>
125	</dd>	194	<dd>
		195	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		196	value) compiled into this binary of libev (independent of their
		197	availability on the system you are running on). See <code>ev_default_loop</code> for
		198	a description of the set values.</p>
		199	<p>Example: make sure we have the epoll method, because yeah this is cool and
		200	a must have and can we have a torrent of it please!!!11</p>
		201	<pre> assert (("sorry, no epoll, no sex",
		202	ev_supported_backends () & EVBACKEND_EPOLL));
		203
		204	</pre>
		205	</dd>
		206	<dt>unsigned int ev_recommended_backends ()</dt>
		207	<dd>
		208	<p>Return the set of all backends compiled into this binary of libev and also
		209	recommended for this platform. This set is often smaller than the one
		210	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		211	most BSDs and will not be autodetected unless you explicitly request it
		212	(assuming you know what you are doing). This is the set of backends that
		213	libev will probe for if you specify no backends explicitly.</p>
		214	</dd>
		215	<dt>unsigned int ev_embeddable_backends ()</dt>
		216	<dd>
		217	<p>Returns the set of backends that are embeddable in other event loops. This
		218	is the theoretical, all-platform, value. To find which backends
		219	might be supported on the current system, you would need to look at
		220	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		221	recommended ones.</p>
		222	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
		223	</dd>
126	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	224	<dt>ev_set_allocator (void (cb)(void *ptr, size_t size))</dt>
127	<dd>	225	<dd>
128	<p>Sets the allocation function to use (the prototype is similar to the	226	<p>Sets the allocation function to use (the prototype and semantics are
129	realloc C function, the semantics are identical). It is used to allocate	227	identical to the realloc C function). It is used to allocate and free
130	and free memory (no surprises here). If it returns zero when memory	228	memory (no surprises here). If it returns zero when memory needs to be
131	needs to be allocated, the library might abort or take some potentially	229	allocated, the library might abort or take some potentially destructive
132	destructive action. The default is your system realloc function.</p>	230	action. The default is your system realloc function.</p>
133	<p>You could override this function in high-availability programs to, say,	231	<p>You could override this function in high-availability programs to, say,
134	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
135	or even to sleep a while and retry until some memory is available.</p>	233	or even to sleep a while and retry until some memory is available.</p>
		234	<p>Example: replace the libev allocator with one that waits a bit and then
		235	retries: better than mine).</p>
		236	<pre> static void *
		237	persistent_realloc (void *ptr, size_t size)
		238	{
		239	for (;;)
		240	{
		241	void *newptr = realloc (ptr, size);
		242
		243	if (newptr)
		244	return newptr;
		245
		246	sleep (60);
		247	}
		248	}
		249
		250	...
		251	ev_set_allocator (persistent_realloc);
		252
		253	</pre>
136	</dd>	254	</dd>
137	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	255	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
138	<dd>	256	<dd>
139	<p>Set the callback function to call on a retryable syscall error (such	257	<p>Set the callback function to call on a retryable syscall error (such
140	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
141	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
142	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the sitution, no
143	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
144	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
145	(such as abort).</p>	263	(such as abort).</p>
		264	<p>Example: do the same thing as libev does internally:</p>
		265	<pre> static void
		266	fatal_error (const char *msg)
		267	{
		268	perror (msg);
		269	abort ();
		270	}
		271
		272	...
		273	ev_set_syserr_cb (fatal_error);
		274
		275	</pre>
146	</dd>	276	</dd>
147	</dl>	277	</dl>
148		278
149	</div>	279	</div>
150	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	280	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
…		…
162	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	292	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
163	<dd>	293	<dd>
164	<p>This will initialise the default event loop if it hasn't been initialised	294	<p>This will initialise the default event loop if it hasn't been initialised
165	yet and return it. If the default loop could not be initialised, returns	295	yet and return it. If the default loop could not be initialised, returns
166	false. If it already was initialised it simply returns it (and ignores the	296	false. If it already was initialised it simply returns it (and ignores the
167	flags).</p>	297	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
168	<p>If you don't know what event loop to use, use the one returned from this	298	<p>If you don't know what event loop to use, use the one returned from this
169	function.</p>	299	function.</p>
170	<p>The flags argument can be used to specify special behaviour or specific	300	<p>The flags argument can be used to specify special behaviour or specific
171	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>	301	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
172	<p>It supports the following flags:</p>	302	<p>The following flags are supported:</p>
173	<p>	303	<p>
174	<dl>	304	<dl>
175	<dt><code>EVFLAG_AUTO</code></dt>	305	<dt><code>EVFLAG_AUTO</code></dt>
176	<dd>	306	<dd>
177	<p>The default flags value. Use this if you have no clue (it's the right	307	<p>The default flags value. Use this if you have no clue (it's the right
…		…
184	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will	314	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
185	override the flags completely if it is found in the environment. This is	315	override the flags completely if it is found in the environment. This is
186	useful to try out specific backends to test their performance, or to work	316	useful to try out specific backends to test their performance, or to work
187	around bugs.</p>	317	around bugs.</p>
188	</dd>	318	</dd>
189	<dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>	319	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
190	<dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
191	<dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
192	<dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
193	<dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
194	<dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
195	<dd>	320	<dd>
196	<p>If one or more of these are ored into the flags value, then only these	321	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
197	backends will be tried (in the reverse order as given here). If one are	322	libev tries to roll its own fd_set with no limits on the number of fds,
198	specified, any backend will do.</p>	323	but if that fails, expect a fairly low limit on the number of fds when
		324	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		325	the fastest backend for a low number of fds.</p>
		326	</dd>
		327	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		328	<dd>
		329	<p>And this is your standard poll(2) backend. It's more complicated than
		330	select, but handles sparse fds better and has no artificial limit on the
		331	number of fds you can use (except it will slow down considerably with a
		332	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		333	</dd>
		334	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		335	<dd>
		336	<p>For few fds, this backend is a bit little slower than poll and select,
		337	but it scales phenomenally better. While poll and select usually scale like
		338	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		339	either O(1) or O(active_fds).</p>
		340	<p>While stopping and starting an I/O watcher in the same iteration will
		341	result in some caching, there is still a syscall per such incident
		342	(because the fd could point to a different file description now), so its
		343	best to avoid that. Also, dup()ed file descriptors might not work very
		344	well if you register events for both fds.</p>
		345	<p>Please note that epoll sometimes generates spurious notifications, so you
		346	need to use non-blocking I/O or other means to avoid blocking when no data
		347	(or space) is available.</p>
		348	</dd>
		349	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		350	<dd>
		351	<p>Kqueue deserves special mention, as at the time of this writing, it
		352	was broken on all BSDs except NetBSD (usually it doesn't work with
		353	anything but sockets and pipes, except on Darwin, where of course its
		354	completely useless). For this reason its not being "autodetected"
		355	unless you explicitly specify it explicitly in the flags (i.e. using
		356	<code>EVBACKEND_KQUEUE</code>).</p>
		357	<p>It scales in the same way as the epoll backend, but the interface to the
		358	kernel is more efficient (which says nothing about its actual speed, of
		359	course). While starting and stopping an I/O watcher does not cause an
		360	extra syscall as with epoll, it still adds up to four event changes per
		361	incident, so its best to avoid that.</p>
		362	</dd>
		363	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		364	<dd>
		365	<p>This is not implemented yet (and might never be).</p>
		366	</dd>
		367	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		368	<dd>
		369	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		370	it's really slow, but it still scales very well (O(active_fds)).</p>
		371	<p>Please note that solaris ports can result in a lot of spurious
		372	notifications, so you need to use non-blocking I/O or other means to avoid
		373	blocking when no data (or space) is available.</p>
		374	</dd>
		375	<dt><code>EVBACKEND_ALL</code></dt>
		376	<dd>
		377	<p>Try all backends (even potentially broken ones that wouldn't be tried
		378	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		379	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
199	</dd>	380	</dd>
200	</dl>	381	</dl>
201	</p>	382	</p>
		383	<p>If one or more of these are ored into the flags value, then only these
		384	backends will be tried (in the reverse order as given here). If none are
		385	specified, most compiled-in backend will be tried, usually in reverse
		386	order of their flag values :)</p>
		387	<p>The most typical usage is like this:</p>
		388	<pre> if (!ev_default_loop (0))
		389	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		390
		391	</pre>
		392	<p>Restrict libev to the select and poll backends, and do not allow
		393	environment settings to be taken into account:</p>
		394	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		395
		396	</pre>
		397	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		398	available (warning, breaks stuff, best use only with your own private
		399	event loop and only if you know the OS supports your types of fds):</p>
		400	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		401
		402	</pre>
202	</dd>	403	</dd>
203	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	404	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
204	<dd>	405	<dd>
205	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	406	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
206	always distinct from the default loop. Unlike the default loop, it cannot	407	always distinct from the default loop. Unlike the default loop, it cannot
207	handle signal and child watchers, and attempts to do so will be greeted by	408	handle signal and child watchers, and attempts to do so will be greeted by
208	undefined behaviour (or a failed assertion if assertions are enabled).</p>	409	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		410	<p>Example: try to create a event loop that uses epoll and nothing else.</p>
		411	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		412	if (!epoller)
		413	fatal ("no epoll found here, maybe it hides under your chair");
		414
		415	</pre>
209	</dd>	416	</dd>
210	<dt>ev_default_destroy ()</dt>	417	<dt>ev_default_destroy ()</dt>
211	<dd>	418	<dd>
212	<p>Destroys the default loop again (frees all memory and kernel state	419	<p>Destroys the default loop again (frees all memory and kernel state
213	etc.). This stops all registered event watchers (by not touching them in	420	etc.). None of the active event watchers will be stopped in the normal
214	any way whatsoever, although you cannot rely on this :).</p>	421	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		422	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		423	calling this function, or cope with the fact afterwards (which is usually
		424	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		425	for example).</p>
215	</dd>	426	</dd>
216	<dt>ev_loop_destroy (loop)</dt>	427	<dt>ev_loop_destroy (loop)</dt>
217	<dd>	428	<dd>
218	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	429	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
219	earlier call to <code>ev_loop_new</code>.</p>	430	earlier call to <code>ev_loop_new</code>.</p>
…		…
222	<dd>	433	<dd>
223	<p>This function reinitialises the kernel state for backends that have	434	<p>This function reinitialises the kernel state for backends that have
224	one. Despite the name, you can call it anytime, but it makes most sense	435	one. Despite the name, you can call it anytime, but it makes most sense
225	after forking, in either the parent or child process (or both, but that	436	after forking, in either the parent or child process (or both, but that
226	again makes little sense).</p>	437	again makes little sense).</p>
227	<p>You <i>must</i> call this function after forking if and only if you want to	438	<p>You <i>must</i> call this function in the child process after forking if and
228	use the event library in both processes. If you just fork+exec, you don't	439	only if you want to use the event library in both processes. If you just
229	have to call it.</p>	440	fork+exec, you don't have to call it.</p>
230	<p>The function itself is quite fast and it's usually not a problem to call	441	<p>The function itself is quite fast and it's usually not a problem to call
231	it just in case after a fork. To make this easy, the function will fit in	442	it just in case after a fork. To make this easy, the function will fit in
232	quite nicely into a call to <code>pthread_atfork</code>:</p>	443	quite nicely into a call to <code>pthread_atfork</code>:</p>
233	<pre> pthread_atfork (0, 0, ev_default_fork);	444	<pre> pthread_atfork (0, 0, ev_default_fork);
234		445
235	</pre>	446	</pre>
		447	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		448	without calling this function, so if you force one of those backends you
		449	do not need to care.</p>
236	</dd>	450	</dd>
237	<dt>ev_loop_fork (loop)</dt>	451	<dt>ev_loop_fork (loop)</dt>
238	<dd>	452	<dd>
239	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	453	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
240	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	454	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
241	after fork, and how you do this is entirely your own problem.</p>	455	after fork, and how you do this is entirely your own problem.</p>
242	</dd>	456	</dd>
243	<dt>unsigned int ev_method (loop)</dt>	457	<dt>unsigned int ev_backend (loop)</dt>
244	<dd>	458	<dd>
245	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	459	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
246	use.</p>	460	use.</p>
247	</dd>	461	</dd>
248	<dt>ev_tstamp ev_now (loop)</dt>	462	<dt>ev_tstamp ev_now (loop)</dt>
249	<dd>	463	<dd>
250	<p>Returns the current "event loop time", which is the time the event loop	464	<p>Returns the current "event loop time", which is the time the event loop
251	got events and started processing them. This timestamp does not change	465	received events and started processing them. This timestamp does not
252	as long as callbacks are being processed, and this is also the base time	466	change as long as callbacks are being processed, and this is also the base
253	used for relative timers. You can treat it as the timestamp of the event	467	time used for relative timers. You can treat it as the timestamp of the
254	occuring (or more correctly, the mainloop finding out about it).</p>	468	event occuring (or more correctly, libev finding out about it).</p>
255	</dd>	469	</dd>
256	<dt>ev_loop (loop, int flags)</dt>	470	<dt>ev_loop (loop, int flags)</dt>
257	<dd>	471	<dd>
258	<p>Finally, this is it, the event handler. This function usually is called	472	<p>Finally, this is it, the event handler. This function usually is called
259	after you initialised all your watchers and you want to start handling	473	after you initialised all your watchers and you want to start handling
260	events.</p>	474	events.</p>
261	<p>If the flags argument is specified as 0, it will not return until either	475	<p>If the flags argument is specified as <code>0</code>, it will not return until
262	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	476	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		477	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		478	relying on all watchers to be stopped when deciding when a program has
		479	finished (especially in interactive programs), but having a program that
		480	automatically loops as long as it has to and no longer by virtue of
		481	relying on its watchers stopping correctly is a thing of beauty.</p>
263	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	482	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
264	those events and any outstanding ones, but will not block your process in	483	those events and any outstanding ones, but will not block your process in
265	case there are no events and will return after one iteration of the loop.</p>	484	case there are no events and will return after one iteration of the loop.</p>
266	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	485	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
267	neccessary) and will handle those and any outstanding ones. It will block	486	neccessary) and will handle those and any outstanding ones. It will block
268	your process until at least one new event arrives, and will return after	487	your process until at least one new event arrives, and will return after
269	one iteration of the loop.</p>	488	one iteration of the loop. This is useful if you are waiting for some
270	<p>This flags value could be used to implement alternative looping	489	external event in conjunction with something not expressible using other
271	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	490	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
272	more generic mechanism.</p>	491	usually a better approach for this kind of thing.</p>
		492	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		493	<pre> * If there are no active watchers (reference count is zero), return.
		494	- Queue prepare watchers and then call all outstanding watchers.
		495	- If we have been forked, recreate the kernel state.
		496	- Update the kernel state with all outstanding changes.
		497	- Update the "event loop time".
		498	- Calculate for how long to block.
		499	- Block the process, waiting for any events.
		500	- Queue all outstanding I/O (fd) events.
		501	- Update the "event loop time" and do time jump handling.
		502	- Queue all outstanding timers.
		503	- Queue all outstanding periodics.
		504	- If no events are pending now, queue all idle watchers.
		505	- Queue all check watchers.
		506	- Call all queued watchers in reverse order (i.e. check watchers first).
		507	Signals and child watchers are implemented as I/O watchers, and will
		508	be handled here by queueing them when their watcher gets executed.
		509	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		510	were used, return, otherwise continue with step *.
		511
		512	</pre>
		513	<p>Example: queue some jobs and then loop until no events are outsanding
		514	anymore.</p>
		515	<pre> ... queue jobs here, make sure they register event watchers as long
		516	... as they still have work to do (even an idle watcher will do..)
		517	ev_loop (my_loop, 0);
		518	... jobs done. yeah!
		519
		520	</pre>
273	</dd>	521	</dd>
274	<dt>ev_unloop (loop, how)</dt>	522	<dt>ev_unloop (loop, how)</dt>
275	<dd>	523	<dd>
276	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it	524	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
277	has processed all outstanding events). The <code>how</code> argument must be either	525	has processed all outstanding events). The <code>how</code> argument must be either
278	<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or	526	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
279	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>	527	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
280	</dd>	528	</dd>
281	<dt>ev_ref (loop)</dt>	529	<dt>ev_ref (loop)</dt>
282	<dt>ev_unref (loop)</dt>	530	<dt>ev_unref (loop)</dt>
283	<dd>	531	<dd>
…		…
289	example, libev itself uses this for its internal signal pipe: It is not	537	example, libev itself uses this for its internal signal pipe: It is not
290	visible to the libev user and should not keep <code>ev_loop</code> from exiting if	538	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
291	no event watchers registered by it are active. It is also an excellent	539	no event watchers registered by it are active. It is also an excellent
292	way to do this for generic recurring timers or from within third-party	540	way to do this for generic recurring timers or from within third-party
293	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>	541	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		542	<p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
		543	running when nothing else is active.</p>
		544	<pre> struct dv_signal exitsig;
		545	ev_signal_init (&exitsig, sig_cb, SIGINT);
		546	ev_signal_start (myloop, &exitsig);
		547	evf_unref (myloop);
		548
		549	</pre>
		550	<p>Example: for some weird reason, unregister the above signal handler again.</p>
		551	<pre> ev_ref (myloop);
		552	ev_signal_stop (myloop, &exitsig);
		553
		554	</pre>
294	</dd>	555	</dd>
295	</dl>	556	</dl>
		557
		558
		559
		560
296		561
297	</div>	562	</div>
298	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	563	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
299	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	564	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
300	<p>A watcher is a structure that you create and register to record your	565	<p>A watcher is a structure that you create and register to record your
…		…
330	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	595	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
331	*)</code>), and you can stop watching for events at any time by calling the	596	*)</code>), and you can stop watching for events at any time by calling the
332	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	597	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
333	<p>As long as your watcher is active (has been started but not stopped) you	598	<p>As long as your watcher is active (has been started but not stopped) you
334	must not touch the values stored in it. Most specifically you must never	599	must not touch the values stored in it. Most specifically you must never
335	reinitialise it or call its set method.</p>	600	reinitialise it or call its <code>set</code> macro.</p>
336	<p>You can check whether an event is active by calling the <code>ev_is_active
337	(watcher *)</code> macro. To see whether an event is outstanding (but the
338	callback for it has not been called yet) you can use the <code>ev_is_pending
339	(watcher *)</code> macro.</p>
340	<p>Each and every callback receives the event loop pointer as first, the	601	<p>Each and every callback receives the event loop pointer as first, the
341	registered watcher structure as second, and a bitset of received events as	602	registered watcher structure as second, and a bitset of received events as
342	third argument.</p>	603	third argument.</p>
343	<p>The received events usually include a single bit per event type received	604	<p>The received events usually include a single bit per event type received
344	(you can receive multiple events at the same time). The possible bit masks	605	(you can receive multiple events at the same time). The possible bit masks
…		…
364	</dd>	625	</dd>
365	<dt><code>EV_CHILD</code></dt>	626	<dt><code>EV_CHILD</code></dt>
366	<dd>	627	<dd>
367	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>	628	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
368	</dd>	629	</dd>
		630	<dt><code>EV_STAT</code></dt>
		631	<dd>
		632	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
		633	</dd>
369	<dt><code>EV_IDLE</code></dt>	634	<dt><code>EV_IDLE</code></dt>
370	<dd>	635	<dd>
371	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>	636	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
372	</dd>	637	</dd>
373	<dt><code>EV_PREPARE</code></dt>	638	<dt><code>EV_PREPARE</code></dt>
…		…
378	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	643	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
379	received events. Callbacks of both watcher types can start and stop as	644	received events. Callbacks of both watcher types can start and stop as
380	many watchers as they want, and all of them will be taken into account	645	many watchers as they want, and all of them will be taken into account
381	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep	646	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
382	<code>ev_loop</code> from blocking).</p>	647	<code>ev_loop</code> from blocking).</p>
		648	</dd>
		649	<dt><code>EV_EMBED</code></dt>
		650	<dd>
		651	<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
		652	</dd>
		653	<dt><code>EV_FORK</code></dt>
		654	<dd>
		655	<p>The event loop has been resumed in the child process after fork (see
		656	<code>ev_fork</code>).</p>
383	</dd>	657	</dd>
384	<dt><code>EV_ERROR</code></dt>	658	<dt><code>EV_ERROR</code></dt>
385	<dd>	659	<dd>
386	<p>An unspecified error has occured, the watcher has been stopped. This might	660	<p>An unspecified error has occured, the watcher has been stopped. This might
387	happen because the watcher could not be properly started because libev	661	happen because the watcher could not be properly started because libev
…		…
393	your callbacks is well-written it can just attempt the operation and cope	667	your callbacks is well-written it can just attempt the operation and cope
394	with the error from read() or write(). This will not work in multithreaded	668	with the error from read() or write(). This will not work in multithreaded
395	programs, though, so beware.</p>	669	programs, though, so beware.</p>
396	</dd>	670	</dd>
397	</dl>	671	</dl>
		672
		673	</div>
		674	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		675	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		676	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		677	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		678	<dl>
		679	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		680	<dd>
		681	<p>This macro initialises the generic portion of a watcher. The contents
		682	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		683	the generic parts of the watcher are initialised, you <i>need</i> to call
		684	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		685	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		686	which rolls both calls into one.</p>
		687	<p>You can reinitialise a watcher at any time as long as it has been stopped
		688	(or never started) and there are no pending events outstanding.</p>
		689	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		690	int revents)</code>.</p>
		691	</dd>
		692	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		693	<dd>
		694	<p>This macro initialises the type-specific parts of a watcher. You need to
		695	call <code>ev_init</code> at least once before you call this macro, but you can
		696	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		697	macro on a watcher that is active (it can be pending, however, which is a
		698	difference to the <code>ev_init</code> macro).</p>
		699	<p>Although some watcher types do not have type-specific arguments
		700	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		701	</dd>
		702	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		703	<dd>
		704	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		705	calls into a single call. This is the most convinient method to initialise
		706	a watcher. The same limitations apply, of course.</p>
		707	</dd>
		708	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		709	<dd>
		710	<p>Starts (activates) the given watcher. Only active watchers will receive
		711	events. If the watcher is already active nothing will happen.</p>
		712	</dd>
		713	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		714	<dd>
		715	<p>Stops the given watcher again (if active) and clears the pending
		716	status. It is possible that stopped watchers are pending (for example,
		717	non-repeating timers are being stopped when they become pending), but
		718	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		719	you want to free or reuse the memory used by the watcher it is therefore a
		720	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		721	</dd>
		722	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		723	<dd>
		724	<p>Returns a true value iff the watcher is active (i.e. it has been started
		725	and not yet been stopped). As long as a watcher is active you must not modify
		726	it.</p>
		727	</dd>
		728	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		729	<dd>
		730	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		731	events but its callback has not yet been invoked). As long as a watcher
		732	is pending (but not active) you must not call an init function on it (but
		733	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		734	libev (e.g. you cnanot <code>free ()</code> it).</p>
		735	</dd>
		736	<dt>callback = ev_cb (ev_TYPE *watcher)</dt>
		737	<dd>
		738	<p>Returns the callback currently set on the watcher.</p>
		739	</dd>
		740	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		741	<dd>
		742	<p>Change the callback. You can change the callback at virtually any time
		743	(modulo threads).</p>
		744	</dd>
		745	</dl>
		746
		747
		748
		749
398		750
399	</div>	751	</div>
400	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	752	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
401	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	753	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
402	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	754	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
…		…
432		784
433	</div>	785	</div>
434	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	786	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
435	<div id="WATCHER_TYPES_CONTENT">	787	<div id="WATCHER_TYPES_CONTENT">
436	<p>This section describes each watcher in detail, but will not repeat	788	<p>This section describes each watcher in detail, but will not repeat
437	information given in the last section.</p>	789	information given in the last section. Any initialisation/set macros,
		790	functions and members specific to the watcher type are explained.</p>
		791	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		792	while the watcher is active, you can look at the member and expect some
		793	sensible content, but you must not modify it (you can modify it while the
		794	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		795	means you can expect it to have some sensible content while the watcher
		796	is active, but you can also modify it. Modifying it may not do something
		797	sensible or take immediate effect (or do anything at all), but libev will
		798	not crash or malfunction in any way.</p>
438		799
		800
		801
		802
		803
439	</div>	804	</div>
440	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>	805	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
441	<div id="code_ev_io_code_is_this_file_descrip-2">	806	<div id="code_ev_io_code_is_this_file_descrip-2">
442	<p>I/O watchers check whether a file descriptor is readable or writable	807	<p>I/O watchers check whether a file descriptor is readable or writable
443	in each iteration of the event loop (This behaviour is called	808	in each iteration of the event loop, or, more precisely, when reading
444	level-triggering because you keep receiving events as long as the	809	would not block the process and writing would at least be able to write
445	condition persists. Remember you can stop the watcher if you don't want to	810	some data. This behaviour is called level-triggering because you keep
446	act on the event and neither want to receive future events).</p>	811	receiving events as long as the condition persists. Remember you can stop
		812	the watcher if you don't want to act on the event and neither want to
		813	receive future events.</p>
447	<p>In general you can register as many read and/or write event watchers oer	814	<p>In general you can register as many read and/or write event watchers per
448	fd as you want (as long as you don't confuse yourself). Setting all file	815	fd as you want (as long as you don't confuse yourself). Setting all file
449	descriptors to non-blocking mode is also usually a good idea (but not	816	descriptors to non-blocking mode is also usually a good idea (but not
450	required if you know what you are doing).</p>	817	required if you know what you are doing).</p>
451	<p>You have to be careful with dup'ed file descriptors, though. Some backends	818	<p>You have to be careful with dup'ed file descriptors, though. Some backends
452	(the linux epoll backend is a notable example) cannot handle dup'ed file	819	(the linux epoll backend is a notable example) cannot handle dup'ed file
453	descriptors correctly if you register interest in two or more fds pointing	820	descriptors correctly if you register interest in two or more fds pointing
454	to the same file/socket etc. description.</p>	821	to the same underlying file/socket/etc. description (that is, they share
		822	the same underlying "file open").</p>
455	<p>If you must do this, then force the use of a known-to-be-good backend	823	<p>If you must do this, then force the use of a known-to-be-good backend
456	(at the time of this writing, this includes only EVMETHOD_SELECT and	824	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
457	EVMETHOD_POLL).</p>	825	<code>EVBACKEND_POLL</code>).</p>
		826	<p>Another thing you have to watch out for is that it is quite easy to
		827	receive "spurious" readyness notifications, that is your callback might
		828	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		829	because there is no data. Not only are some backends known to create a
		830	lot of those (for example solaris ports), it is very easy to get into
		831	this situation even with a relatively standard program structure. Thus
		832	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		833	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		834	<p>If you cannot run the fd in non-blocking mode (for example you should not
		835	play around with an Xlib connection), then you have to seperately re-test
		836	wether a file descriptor is really ready with a known-to-be good interface
		837	such as poll (fortunately in our Xlib example, Xlib already does this on
		838	its own, so its quite safe to use).</p>
458	<dl>	839	<dl>
459	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	840	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
460	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	841	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
461	<dd>	842	<dd>
462	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive	843	<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
463	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	844	rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
464	EV_WRITE</code> to receive the given events.</p>	845	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		846	</dd>
		847	<dt>int fd [read-only]</dt>
		848	<dd>
		849	<p>The file descriptor being watched.</p>
		850	</dd>
		851	<dt>int events [read-only]</dt>
		852	<dd>
		853	<p>The events being watched.</p>
465	</dd>	854	</dd>
466	</dl>	855	</dl>
		856	<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		857	readable, but only once. Since it is likely line-buffered, you could
		858	attempt to read a whole line in the callback:</p>
		859	<pre> static void
		860	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		861	{
		862	ev_io_stop (loop, w);
		863	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		864	}
467		865
		866	...
		867	struct ev_loop *loop = ev_default_init (0);
		868	struct ev_io stdin_readable;
		869	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		870	ev_io_start (loop, &stdin_readable);
		871	ev_loop (loop, 0);
		872
		873
		874
		875
		876	</pre>
		877
468	</div>	878	</div>
469	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>	879	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
470	<div id="code_ev_timer_code_relative_and_opti-2">	880	<div id="code_ev_timer_code_relative_and_opti-2">
471	<p>Timer watchers are simple relative timers that generate an event after a	881	<p>Timer watchers are simple relative timers that generate an event after a
472	given time, and optionally repeating in regular intervals after that.</p>	882	given time, and optionally repeating in regular intervals after that.</p>
473	<p>The timers are based on real time, that is, if you register an event that	883	<p>The timers are based on real time, that is, if you register an event that
474	times out after an hour and youreset your system clock to last years	884	times out after an hour and you reset your system clock to last years
475	time, it will still time out after (roughly) and hour. "Roughly" because	885	time, it will still time out after (roughly) and hour. "Roughly" because
476	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	886	detecting time jumps is hard, and some inaccuracies are unavoidable (the
477	monotonic clock option helps a lot here).</p>	887	monotonic clock option helps a lot here).</p>
478	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>	888	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
479	time. This is usually the right thing as this timestamp refers to the time	889	time. This is usually the right thing as this timestamp refers to the time
480	of the event triggering whatever timeout you are modifying/starting. If	890	of the event triggering whatever timeout you are modifying/starting. If
481	you suspect event processing to be delayed and you need to base the timeout	891	you suspect event processing to be delayed and you <i>need</i> to base the timeout
482	ion the current time, use something like this to adjust for this:</p>	892	on the current time, use something like this to adjust for this:</p>
483	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	893	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
484		894
485	</pre>	895	</pre>
		896	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		897	but if multiple timers become ready during the same loop iteration then
		898	order of execution is undefined.</p>
486	<dl>	899	<dl>
487	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	900	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
488	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	901	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
489	<dd>	902	<dd>
490	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	903	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
492	timer will automatically be configured to trigger again <code>repeat</code> seconds	905	timer will automatically be configured to trigger again <code>repeat</code> seconds
493	later, again, and again, until stopped manually.</p>	906	later, again, and again, until stopped manually.</p>
494	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	907	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
495	configure a timer to trigger every 10 seconds, then it will trigger at	908	configure a timer to trigger every 10 seconds, then it will trigger at
496	exactly 10 second intervals. If, however, your program cannot keep up with	909	exactly 10 second intervals. If, however, your program cannot keep up with
497	the timer (ecause it takes longer than those 10 seconds to do stuff) the	910	the timer (because it takes longer than those 10 seconds to do stuff) the
498	timer will not fire more than once per event loop iteration.</p>	911	timer will not fire more than once per event loop iteration.</p>
499	</dd>	912	</dd>
500	<dt>ev_timer_again (loop)</dt>	913	<dt>ev_timer_again (loop)</dt>
501	<dd>	914	<dd>
502	<p>This will act as if the timer timed out and restart it again if it is	915	<p>This will act as if the timer timed out and restart it again if it is
503	repeating. The exact semantics are:</p>	916	repeating. The exact semantics are:</p>
504	<p>If the timer is started but nonrepeating, stop it.</p>	917	<p>If the timer is started but nonrepeating, stop it.</p>
505	<p>If the timer is repeating, either start it if necessary (with the repeat	918	<p>If the timer is repeating, either start it if necessary (with the repeat
506	value), or reset the running timer to the repeat value.</p>	919	value), or reset the running timer to the repeat value.</p>
507	<p>This sounds a bit complicated, but here is a useful and typical	920	<p>This sounds a bit complicated, but here is a useful and typical
508	example: Imagine you have a tcp connection and you want a so-called idle	921	example: Imagine you have a tcp connection and you want a so-called
509	timeout, that is, you want to be called when there have been, say, 60	922	idle timeout, that is, you want to be called when there have been,
510	seconds of inactivity on the socket. The easiest way to do this is to	923	say, 60 seconds of inactivity on the socket. The easiest way to do
511	configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each	924	this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
512	time you successfully read or write some data. If you go into an idle	925	<code>ev_timer_again</code> each time you successfully read or write some data. If
513	state where you do not expect data to travel on the socket, you can stop	926	you go into an idle state where you do not expect data to travel on the
514	the timer, and again will automatically restart it if need be.</p>	927	socket, you can stop the timer, and again will automatically restart it if
		928	need be.</p>
		929	<p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
		930	and only ever use the <code>repeat</code> value:</p>
		931	<pre> ev_timer_init (timer, callback, 0., 5.);
		932	ev_timer_again (loop, timer);
		933	...
		934	timer->again = 17.;
		935	ev_timer_again (loop, timer);
		936	...
		937	timer->again = 10.;
		938	ev_timer_again (loop, timer);
		939
		940	</pre>
		941	<p>This is more efficient then stopping/starting the timer eahc time you want
		942	to modify its timeout value.</p>
		943	</dd>
		944	<dt>ev_tstamp repeat [read-write]</dt>
		945	<dd>
		946	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		947	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		948	which is also when any modifications are taken into account.</p>
515	</dd>	949	</dd>
516	</dl>	950	</dl>
		951	<p>Example: create a timer that fires after 60 seconds.</p>
		952	<pre> static void
		953	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		954	{
		955	.. one minute over, w is actually stopped right here
		956	}
517		957
		958	struct ev_timer mytimer;
		959	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		960	ev_timer_start (loop, &mytimer);
		961
		962	</pre>
		963	<p>Example: create a timeout timer that times out after 10 seconds of
		964	inactivity.</p>
		965	<pre> static void
		966	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		967	{
		968	.. ten seconds without any activity
		969	}
		970
		971	struct ev_timer mytimer;
		972	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		973	ev_timer_again (&mytimer); /* start timer */
		974	ev_loop (loop, 0);
		975
		976	// and in some piece of code that gets executed on any "activity":
		977	// reset the timeout to start ticking again at 10 seconds
		978	ev_timer_again (&mytimer);
		979
		980
		981
		982
		983	</pre>
		984
518	</div>	985	</div>
519	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>	986	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
520	<div id="code_ev_periodic_code_to_cron_or_not-2">	987	<div id="code_ev_periodic_code_to_cron_or_not-2">
521	<p>Periodic watchers are also timers of a kind, but they are very versatile	988	<p>Periodic watchers are also timers of a kind, but they are very versatile
522	(and unfortunately a bit complex).</p>	989	(and unfortunately a bit complex).</p>
523	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)	990	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
524	but on wallclock time (absolute time). You can tell a periodic watcher	991	but on wallclock time (absolute time). You can tell a periodic watcher
525	to trigger "at" some specific point in time. For example, if you tell a	992	to trigger "at" some specific point in time. For example, if you tell a
526	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	993	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
527	+ 10.>) and then reset your system clock to the last year, then it will	994	+ 10.</code>) and then reset your system clock to the last year, then it will
528	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger	995	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
529	roughly 10 seconds later and of course not if you reset your system time	996	roughly 10 seconds later and of course not if you reset your system time
530	again).</p>	997	again).</p>
531	<p>They can also be used to implement vastly more complex timers, such as	998	<p>They can also be used to implement vastly more complex timers, such as
532	triggering an event on eahc midnight, local time.</p>	999	triggering an event on eahc midnight, local time.</p>
		1000	<p>As with timers, the callback is guarenteed to be invoked only when the
		1001	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		1002	during the same loop iteration then order of execution is undefined.</p>
533	<dl>	1003	<dl>
534	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	1004	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
535	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	1005	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
536	<dd>	1006	<dd>
537	<p>Lots of arguments, lets sort it out... There are basically three modes of	1007	<p>Lots of arguments, lets sort it out... There are basically three modes of
538	operation, and we will explain them from simplest to complex:</p>	1008	operation, and we will explain them from simplest to complex:</p>
539
540
541
542
543	<p>	1009	<p>
544	<dl>	1010	<dl>
545	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	1011	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
546	<dd>	1012	<dd>
547	<p>In this configuration the watcher triggers an event at the wallclock time	1013	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
605	<p>Simply stops and restarts the periodic watcher again. This is only useful	1071	<p>Simply stops and restarts the periodic watcher again. This is only useful
606	when you changed some parameters or the reschedule callback would return	1072	when you changed some parameters or the reschedule callback would return
607	a different time than the last time it was called (e.g. in a crond like	1073	a different time than the last time it was called (e.g. in a crond like
608	program when the crontabs have changed).</p>	1074	program when the crontabs have changed).</p>
609	</dd>	1075	</dd>
		1076	<dt>ev_tstamp interval [read-write]</dt>
		1077	<dd>
		1078	<p>The current interval value. Can be modified any time, but changes only
		1079	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1080	called.</p>
		1081	</dd>
		1082	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1083	<dd>
		1084	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1085	switched off. Can be changed any time, but changes only take effect when
		1086	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1087	</dd>
610	</dl>	1088	</dl>
		1089	<p>Example: call a callback every hour, or, more precisely, whenever the
		1090	system clock is divisible by 3600. The callback invocation times have
		1091	potentially a lot of jittering, but good long-term stability.</p>
		1092	<pre> static void
		1093	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1094	{
		1095	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1096	}
611		1097
		1098	struct ev_periodic hourly_tick;
		1099	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1100	ev_periodic_start (loop, &hourly_tick);
		1101
		1102	</pre>
		1103	<p>Example: the same as above, but use a reschedule callback to do it:</p>
		1104	<pre> #include <math.h>
		1105
		1106	static ev_tstamp
		1107	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1108	{
		1109	return fmod (now, 3600.) + 3600.;
		1110	}
		1111
		1112	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1113
		1114	</pre>
		1115	<p>Example: call a callback every hour, starting now:</p>
		1116	<pre> struct ev_periodic hourly_tick;
		1117	ev_periodic_init (&hourly_tick, clock_cb,
		1118	fmod (ev_now (loop), 3600.), 3600., 0);
		1119	ev_periodic_start (loop, &hourly_tick);
		1120
		1121
		1122
		1123
		1124	</pre>
		1125
612	</div>	1126	</div>
613	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>	1127	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
614	<div id="code_ev_signal_code_signal_me_when_a-2">	1128	<div id="code_ev_signal_code_signal_me_when_a-2">
615	<p>Signal watchers will trigger an event when the process receives a specific	1129	<p>Signal watchers will trigger an event when the process receives a specific
616	signal one or more times. Even though signals are very asynchronous, libev	1130	signal one or more times. Even though signals are very asynchronous, libev
617	will try it's best to deliver signals synchronously, i.e. as part of the	1131	will try it's best to deliver signals synchronously, i.e. as part of the
618	normal event processing, like any other event.</p>	1132	normal event processing, like any other event.</p>
…		…
627	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1141	<dt>ev_signal_set (ev_signal *, int signum)</dt>
628	<dd>	1142	<dd>
629	<p>Configures the watcher to trigger on the given signal number (usually one	1143	<p>Configures the watcher to trigger on the given signal number (usually one
630	of the <code>SIGxxx</code> constants).</p>	1144	of the <code>SIGxxx</code> constants).</p>
631	</dd>	1145	</dd>
		1146	<dt>int signum [read-only]</dt>
		1147	<dd>
		1148	<p>The signal the watcher watches out for.</p>
		1149	</dd>
632	</dl>	1150	</dl>
633		1151
		1152
		1153
		1154
		1155
634	</div>	1156	</div>
635	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>	1157	<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
636	<div id="code_ev_child_code_wait_for_pid_stat-2">	1158	<div id="code_ev_child_code_watch_out_for_pro-2">
637	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1159	<p>Child watchers trigger when your process receives a SIGCHLD in response to
638	some child status changes (most typically when a child of yours dies).</p>	1160	some child status changes (most typically when a child of yours dies).</p>
639	<dl>	1161	<dl>
640	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1162	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
641	<dt>ev_child_set (ev_child *, int pid)</dt>	1163	<dt>ev_child_set (ev_child *, int pid)</dt>
…		…
645	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1167	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
646	the status word (use the macros from <code>sys/wait.h</code> and see your systems	1168	the status word (use the macros from <code>sys/wait.h</code> and see your systems
647	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the	1169	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
648	process causing the status change.</p>	1170	process causing the status change.</p>
649	</dd>	1171	</dd>
		1172	<dt>int pid [read-only]</dt>
		1173	<dd>
		1174	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1175	</dd>
		1176	<dt>int rpid [read-write]</dt>
		1177	<dd>
		1178	<p>The process id that detected a status change.</p>
		1179	</dd>
		1180	<dt>int rstatus [read-write]</dt>
		1181	<dd>
		1182	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1183	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
		1184	</dd>
650	</dl>	1185	</dl>
		1186	<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
		1187	<pre> static void
		1188	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1189	{
		1190	ev_unloop (loop, EVUNLOOP_ALL);
		1191	}
651		1192
		1193	struct ev_signal signal_watcher;
		1194	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1195	ev_signal_start (loop, &sigint_cb);
		1196
		1197
		1198
		1199
		1200	</pre>
		1201
652	</div>	1202	</div>
		1203	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1204	<div id="code_ev_stat_code_did_the_file_attri-2">
		1205	<p>This watches a filesystem path for attribute changes. That is, it calls
		1206	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1207	compared to the last time, invoking the callback if it did.</p>
		1208	<p>The path does not need to exist: changing from "path exists" to "path does
		1209	not exist" is a status change like any other. The condition "path does
		1210	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1211	otherwise always forced to be at least one) and all the other fields of
		1212	the stat buffer having unspecified contents.</p>
		1213	<p>Since there is no standard to do this, the portable implementation simply
		1214	calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You
		1215	can specify a recommended polling interval for this case. If you specify
		1216	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1217	unspecified default</i> value will be used (which you can expect to be around
		1218	five seconds, although this might change dynamically). Libev will also
		1219	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1220	usually overkill.</p>
		1221	<p>This watcher type is not meant for massive numbers of stat watchers,
		1222	as even with OS-supported change notifications, this can be
		1223	resource-intensive.</p>
		1224	<p>At the time of this writing, no specific OS backends are implemented, but
		1225	if demand increases, at least a kqueue and inotify backend will be added.</p>
		1226	<dl>
		1227	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1228	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1229	<dd>
		1230	<p>Configures the watcher to wait for status changes of the given
		1231	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1232	be detected and should normally be specified as <code>0</code> to let libev choose
		1233	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1234	path for as long as the watcher is active.</p>
		1235	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1236	relative to the attributes at the time the watcher was started (or the
		1237	last change was detected).</p>
		1238	</dd>
		1239	<dt>ev_stat_stat (ev_stat *)</dt>
		1240	<dd>
		1241	<p>Updates the stat buffer immediately with new values. If you change the
		1242	watched path in your callback, you could call this fucntion to avoid
		1243	detecting this change (while introducing a race condition). Can also be
		1244	useful simply to find out the new values.</p>
		1245	</dd>
		1246	<dt>ev_statdata attr [read-only]</dt>
		1247	<dd>
		1248	<p>The most-recently detected attributes of the file. Although the type is of
		1249	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1250	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1251	was some error while <code>stat</code>ing the file.</p>
		1252	</dd>
		1253	<dt>ev_statdata prev [read-only]</dt>
		1254	<dd>
		1255	<p>The previous attributes of the file. The callback gets invoked whenever
		1256	<code>prev</code> != <code>attr</code>.</p>
		1257	</dd>
		1258	<dt>ev_tstamp interval [read-only]</dt>
		1259	<dd>
		1260	<p>The specified interval.</p>
		1261	</dd>
		1262	<dt>const char *path [read-only]</dt>
		1263	<dd>
		1264	<p>The filesystem path that is being watched.</p>
		1265	</dd>
		1266	</dl>
		1267	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1268	<pre> static void
		1269	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1270	{
		1271	/* /etc/passwd changed in some way */
		1272	if (w->attr.st_nlink)
		1273	{
		1274	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1275	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1276	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1277	}
		1278	else
		1279	/* you shalt not abuse printf for puts */
		1280	puts ("wow, /etc/passwd is not there, expect problems. "
		1281	"if this is windows, they already arrived\n");
		1282	}
		1283
		1284	...
		1285	ev_stat passwd;
		1286
		1287	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1288	ev_stat_start (loop, &passwd);
		1289
		1290
		1291
		1292
		1293	</pre>
		1294
		1295	</div>
653	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>	1296	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
654	<div id="code_ev_idle_code_when_you_ve_got_no-2">	1297	<div id="code_ev_idle_code_when_you_ve_got_no-2">
655	<p>Idle watchers trigger events when there are no other events are pending	1298	<p>Idle watchers trigger events when there are no other events are pending
656	(prepare, check and other idle watchers do not count). That is, as long	1299	(prepare, check and other idle watchers do not count). That is, as long
657	as your process is busy handling sockets or timeouts (or even signals,	1300	as your process is busy handling sockets or timeouts (or even signals,
658	imagine) it will not be triggered. But when your process is idle all idle	1301	imagine) it will not be triggered. But when your process is idle all idle
…		…
671	<p>Initialises and configures the idle watcher - it has no parameters of any	1314	<p>Initialises and configures the idle watcher - it has no parameters of any
672	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1315	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
673	believe me.</p>	1316	believe me.</p>
674	</dd>	1317	</dd>
675	</dl>	1318	</dl>
		1319	<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
		1320	callback, free it. Alos, use no error checking, as usual.</p>
		1321	<pre> static void
		1322	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1323	{
		1324	free (w);
		1325	// now do something you wanted to do when the program has
		1326	// no longer asnything immediate to do.
		1327	}
676		1328
		1329	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1330	ev_idle_init (idle_watcher, idle_cb);
		1331	ev_idle_start (loop, idle_cb);
		1332
		1333
		1334
		1335
		1336	</pre>
		1337
677	</div>	1338	</div>
678	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>	1339	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
679	<div id="code_ev_prepare_code_and_code_ev_che-2">	1340	<div id="code_ev_prepare_code_and_code_ev_che-2">
680	<p>Prepare and check watchers are usually (but not always) used in tandem:	1341	<p>Prepare and check watchers are usually (but not always) used in tandem:
681	prepare watchers get invoked before the process blocks and check watchers	1342	prepare watchers get invoked before the process blocks and check watchers
682	afterwards.</p>	1343	afterwards.</p>
		1344	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1345	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1346	watchers. Other loops than the current one are fine, however. The
		1347	rationale behind this is that you do not need to check for recursion in
		1348	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1349	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1350	called in pairs bracketing the blocking call.</p>
683	<p>Their main purpose is to integrate other event mechanisms into libev. This	1351	<p>Their main purpose is to integrate other event mechanisms into libev and
684	could be used, for example, to track variable changes, implement your own	1352	their use is somewhat advanced. This could be used, for example, to track
685	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1353	variable changes, implement your own watchers, integrate net-snmp or a
		1354	coroutine library and lots more. They are also occasionally useful if
		1355	you cache some data and want to flush it before blocking (for example,
		1356	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1357	watcher).</p>
686	<p>This is done by examining in each prepare call which file descriptors need	1358	<p>This is done by examining in each prepare call which file descriptors need
687	to be watched by the other library, registering <code>ev_io</code> watchers for	1359	to be watched by the other library, registering <code>ev_io</code> watchers for
688	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries	1360	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
689	provide just this functionality). Then, in the check watcher you check for	1361	provide just this functionality). Then, in the check watcher you check for
690	any events that occured (by checking the pending status of all watchers	1362	any events that occured (by checking the pending status of all watchers
…		…
706	<p>Initialises and configures the prepare or check watcher - they have no	1378	<p>Initialises and configures the prepare or check watcher - they have no
707	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1379	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
708	macros, but using them is utterly, utterly and completely pointless.</p>	1380	macros, but using them is utterly, utterly and completely pointless.</p>
709	</dd>	1381	</dd>
710	</dl>	1382	</dl>
		1383	<p>Example: To include a library such as adns, you would add IO watchers
		1384	and a timeout watcher in a prepare handler, as required by libadns, and
		1385	in a check watcher, destroy them and call into libadns. What follows is
		1386	pseudo-code only of course:</p>
		1387	<pre> static ev_io iow [nfd];
		1388	static ev_timer tw;
		1389
		1390	static void
		1391	io_cb (ev_loop loop, ev_io w, int revents)
		1392	{
		1393	// set the relevant poll flags
		1394	// could also call adns_processreadable etc. here
		1395	struct pollfd fd = (struct pollfd )w->data;
		1396	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1397	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1398	}
		1399
		1400	// create io watchers for each fd and a timer before blocking
		1401	static void
		1402	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1403	{
		1404	int timeout = 3600000;truct pollfd fds [nfd];
		1405	// actual code will need to loop here and realloc etc.
		1406	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1407
		1408	/* the callback is illegal, but won't be called as we stop during check */
		1409	ev_timer_init (&tw, 0, timeout * 1e-3);
		1410	ev_timer_start (loop, &tw);
		1411
		1412	// create on ev_io per pollfd
		1413	for (int i = 0; i < nfd; ++i)
		1414	{
		1415	ev_io_init (iow + i, io_cb, fds [i].fd,
		1416	((fds [i].events & POLLIN ? EV_READ : 0)
		1417	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1418
		1419	fds [i].revents = 0;
		1420	iow [i].data = fds + i;
		1421	ev_io_start (loop, iow + i);
		1422	}
		1423	}
		1424
		1425	// stop all watchers after blocking
		1426	static void
		1427	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1428	{
		1429	ev_timer_stop (loop, &tw);
		1430
		1431	for (int i = 0; i < nfd; ++i)
		1432	ev_io_stop (loop, iow + i);
		1433
		1434	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1435	}
		1436
		1437
		1438
		1439
		1440	</pre>
		1441
		1442	</div>
		1443	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1444	<div id="code_ev_embed_code_when_one_backend_-2">
		1445	<p>This is a rather advanced watcher type that lets you embed one event loop
		1446	into another (currently only <code>ev_io</code> events are supported in the embedded
		1447	loop, other types of watchers might be handled in a delayed or incorrect
		1448	fashion and must not be used).</p>
		1449	<p>There are primarily two reasons you would want that: work around bugs and
		1450	prioritise I/O.</p>
		1451	<p>As an example for a bug workaround, the kqueue backend might only support
		1452	sockets on some platform, so it is unusable as generic backend, but you
		1453	still want to make use of it because you have many sockets and it scales
		1454	so nicely. In this case, you would create a kqueue-based loop and embed it
		1455	into your default loop (which might use e.g. poll). Overall operation will
		1456	be a bit slower because first libev has to poll and then call kevent, but
		1457	at least you can use both at what they are best.</p>
		1458	<p>As for prioritising I/O: rarely you have the case where some fds have
		1459	to be watched and handled very quickly (with low latency), and even
		1460	priorities and idle watchers might have too much overhead. In this case
		1461	you would put all the high priority stuff in one loop and all the rest in
		1462	a second one, and embed the second one in the first.</p>
		1463	<p>As long as the watcher is active, the callback will be invoked every time
		1464	there might be events pending in the embedded loop. The callback must then
		1465	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1466	their callbacks (you could also start an idle watcher to give the embedded
		1467	loop strictly lower priority for example). You can also set the callback
		1468	to <code>0</code>, in which case the embed watcher will automatically execute the
		1469	embedded loop sweep.</p>
		1470	<p>As long as the watcher is started it will automatically handle events. The
		1471	callback will be invoked whenever some events have been handled. You can
		1472	set the callback to <code>0</code> to avoid having to specify one if you are not
		1473	interested in that.</p>
		1474	<p>Also, there have not currently been made special provisions for forking:
		1475	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1476	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1477	yourself.</p>
		1478	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1479	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1480	portable one.</p>
		1481	<p>So when you want to use this feature you will always have to be prepared
		1482	that you cannot get an embeddable loop. The recommended way to get around
		1483	this is to have a separate variables for your embeddable loop, try to
		1484	create it, and if that fails, use the normal loop for everything:</p>
		1485	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1486	struct ev_loop *loop_lo = 0;
		1487	struct ev_embed embed;
		1488
		1489	// see if there is a chance of getting one that works
		1490	// (remember that a flags value of 0 means autodetection)
		1491	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1492	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1493	: 0;
		1494
		1495	// if we got one, then embed it, otherwise default to loop_hi
		1496	if (loop_lo)
		1497	{
		1498	ev_embed_init (&embed, 0, loop_lo);
		1499	ev_embed_start (loop_hi, &embed);
		1500	}
		1501	else
		1502	loop_lo = loop_hi;
		1503
		1504	</pre>
		1505	<dl>
		1506	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1507	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1508	<dd>
		1509	<p>Configures the watcher to embed the given loop, which must be
		1510	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1511	invoked automatically, otherwise it is the responsibility of the callback
		1512	to invoke it (it will continue to be called until the sweep has been done,
		1513	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1514	</dd>
		1515	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1516	<dd>
		1517	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1518	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1519	apropriate way for embedded loops.</p>
		1520	</dd>
		1521	<dt>struct ev_loop *loop [read-only]</dt>
		1522	<dd>
		1523	<p>The embedded event loop.</p>
		1524	</dd>
		1525	</dl>
		1526
		1527
		1528
		1529
		1530
		1531	</div>
		1532	<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
		1533	<div id="code_ev_fork_code_the_audacity_to_re-2">
		1534	<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
		1535	whoever is a good citizen cared to tell libev about it by calling
		1536	<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
		1537	event loop blocks next and before <code>ev_check</code> watchers are being called,
		1538	and only in the child after the fork. If whoever good citizen calling
		1539	<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
		1540	handlers will be invoked, too, of course.</p>
		1541	<dl>
		1542	<dt>ev_fork_init (ev_signal *, callback)</dt>
		1543	<dd>
		1544	<p>Initialises and configures the fork watcher - it has no parameters of any
		1545	kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
		1546	believe me.</p>
		1547	</dd>
		1548	</dl>
		1549
		1550
		1551
		1552
711		1553
712	</div>	1554	</div>
713	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1555	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
714	<div id="OTHER_FUNCTIONS_CONTENT">	1556	<div id="OTHER_FUNCTIONS_CONTENT">
715	<p>There are some other functions of possible interest. Described. Here. Now.</p>	1557	<p>There are some other functions of possible interest. Described. Here. Now.</p>
…		…
717	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1559	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
718	<dd>	1560	<dd>
719	<p>This function combines a simple timer and an I/O watcher, calls your	1561	<p>This function combines a simple timer and an I/O watcher, calls your
720	callback on whichever event happens first and automatically stop both	1562	callback on whichever event happens first and automatically stop both
721	watchers. This is useful if you want to wait for a single event on an fd	1563	watchers. This is useful if you want to wait for a single event on an fd
722	or timeout without havign to allocate/configure/start/stop/free one or	1564	or timeout without having to allocate/configure/start/stop/free one or
723	more watchers yourself.</p>	1565	more watchers yourself.</p>
724	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events	1566	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
725	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and	1567	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
726	<code>events</code> set will be craeted and started.</p>	1568	<code>events</code> set will be craeted and started.</p>
727	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1569	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
728	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and	1570	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
729	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of	1571	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
730	dubious value.</p>	1572	dubious value.</p>
731	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets	1573	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
732	passed an events set like normal event callbacks (with a combination of	1574	passed an <code>revents</code> set like normal event callbacks (a combination of
733	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>	1575	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
734	value passed to <code>ev_once</code>:</p>	1576	value passed to <code>ev_once</code>:</p>
735	<pre> static void stdin_ready (int revents, void *arg)	1577	<pre> static void stdin_ready (int revents, void *arg)
736	{	1578	{
737	if (revents & EV_TIMEOUT)	1579	if (revents & EV_TIMEOUT)
…		…
742		1584
743	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1585	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
744		1586
745	</pre>	1587	</pre>
746	</dd>	1588	</dd>
747	<dt>ev_feed_event (loop, watcher, int events)</dt>	1589	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
748	<dd>	1590	<dd>
749	<p>Feeds the given event set into the event loop, as if the specified event	1591	<p>Feeds the given event set into the event loop, as if the specified event
750	had happened for the specified watcher (which must be a pointer to an	1592	had happened for the specified watcher (which must be a pointer to an
751	initialised but not necessarily started event watcher).</p>	1593	initialised but not necessarily started event watcher).</p>
752	</dd>	1594	</dd>
753	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1595	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
754	<dd>	1596	<dd>
755	<p>Feed an event on the given fd, as if a file descriptor backend detected	1597	<p>Feed an event on the given fd, as if a file descriptor backend detected
756	the given events it.</p>	1598	the given events it.</p>
757	</dd>	1599	</dd>
758	<dt>ev_feed_signal_event (loop, int signum)</dt>	1600	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
759	<dd>	1601	<dd>
760	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1602	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1603	loop!).</p>
761	</dd>	1604	</dd>
762	</dl>	1605	</dl>
		1606
		1607
		1608
		1609
763		1610
764	</div>	1611	</div>
765	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>	1612	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
766	<div id="LIBEVENT_EMULATION_CONTENT">	1613	<div id="LIBEVENT_EMULATION_CONTENT">
767	<p>TBD.</p>	1614	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1615	emulate the internals of libevent, so here are some usage hints:</p>
		1616	<dl>
		1617	<dt>* Use it by including <event.h>, as usual.</dt>
		1618	<dt>* The following members are fully supported: ev_base, ev_callback,
		1619	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1620	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1621	maintained by libev, it does not work exactly the same way as in libevent (consider
		1622	it a private API).</dt>
		1623	<dt>* Priorities are not currently supported. Initialising priorities
		1624	will fail and all watchers will have the same priority, even though there
		1625	is an ev_pri field.</dt>
		1626	<dt>* Other members are not supported.</dt>
		1627	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1628	to use the libev header file and library.</dt>
		1629	</dl>
768		1630
769	</div>	1631	</div>
770	<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>	1632	<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
771	<div id="C_SUPPORT_CONTENT">	1633	<div id="C_SUPPORT_CONTENT">
772	<p>TBD.</p>	1634	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1635	you to use some convinience methods to start/stop watchers and also change
		1636	the callback model to a model using method callbacks on objects.</p>
		1637	<p>To use it,</p>
		1638	<pre> #include <ev++.h>
		1639
		1640	</pre>
		1641	<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
		1642	and puts all of its definitions (many of them macros) into the global
		1643	namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
		1644	<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
		1645	<code>EV_MULTIPLICITY</code>.</p>
		1646	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1647	<dl>
		1648	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1649	<dd>
		1650	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1651	macros from <cite>ev.h</cite>.</p>
		1652	</dd>
		1653	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1654	<dd>
		1655	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1656	</dd>
		1657	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1658	<dd>
		1659	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1660	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1661	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1662	defines by many implementations.</p>
		1663	<p>All of those classes have these methods:</p>
		1664	<p>
		1665	<dl>
		1666	<dt>ev::TYPE::TYPE (object , object::method )</dt>
		1667	<dt>ev::TYPE::TYPE (object , object::method , struct ev_loop *)</dt>
		1668	<dt>ev::TYPE::~TYPE</dt>
		1669	<dd>
		1670	<p>The constructor takes a pointer to an object and a method pointer to
		1671	the event handler callback to call in this class. The constructor calls
		1672	<code>ev_init</code> for you, which means you have to call the <code>set</code> method
		1673	before starting it. If you do not specify a loop then the constructor
		1674	automatically associates the default loop with this watcher.</p>
		1675	<p>The destructor automatically stops the watcher if it is active.</p>
		1676	</dd>
		1677	<dt>w->set (struct ev_loop *)</dt>
		1678	<dd>
		1679	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1680	do this when the watcher is inactive (and not pending either).</p>
		1681	</dd>
		1682	<dt>w->set ([args])</dt>
		1683	<dd>
		1684	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1685	called at least once. Unlike the C counterpart, an active watcher gets
		1686	automatically stopped and restarted.</p>
		1687	</dd>
		1688	<dt>w->start ()</dt>
		1689	<dd>
		1690	<p>Starts the watcher. Note that there is no <code>loop</code> argument as the
		1691	constructor already takes the loop.</p>
		1692	</dd>
		1693	<dt>w->stop ()</dt>
		1694	<dd>
		1695	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1696	</dd>
		1697	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1698	<dd>
		1699	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1700	<code>ev_TYPE_again</code> function.</p>
		1701	</dd>
		1702	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1703	<dd>
		1704	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1705	</dd>
		1706	<dt>w->update () <code>ev::stat</code> only</dt>
		1707	<dd>
		1708	<p>Invokes <code>ev_stat_stat</code>.</p>
		1709	</dd>
		1710	</dl>
		1711	</p>
		1712	</dd>
		1713	</dl>
		1714	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1715	the constructor.</p>
		1716	<pre> class myclass
		1717	{
		1718	ev_io io; void io_cb (ev::io &w, int revents);
		1719	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1720
		1721	myclass ();
		1722	}
		1723
		1724	myclass::myclass (int fd)
		1725	: io (this, &myclass::io_cb),
		1726	idle (this, &myclass::idle_cb)
		1727	{
		1728	io.start (fd, ev::READ);
		1729	}
		1730
		1731
		1732
		1733
		1734	</pre>
		1735
		1736	</div>
		1737	<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1738	<div id="MACRO_MAGIC_CONTENT">
		1739	<p>Libev can be compiled with a variety of options, the most fundemantal is
		1740	<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
		1741	callbacks have an initial <code>struct ev_loop *</code> argument.</p>
		1742	<p>To make it easier to write programs that cope with either variant, the
		1743	following macros are defined:</p>
		1744	<dl>
		1745	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
		1746	<dd>
		1747	<p>This provides the loop <i>argument</i> for functions, if one is required ("ev
		1748	loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
		1749	<code>EV_A_</code> is used when other arguments are following. Example:</p>
		1750	<pre> ev_unref (EV_A);
		1751	ev_timer_add (EV_A_ watcher);
		1752	ev_loop (EV_A_ 0);
		1753
		1754	</pre>
		1755	<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
		1756	which is often provided by the following macro.</p>
		1757	</dd>
		1758	<dt><code>EV_P</code>, <code>EV_P_</code></dt>
		1759	<dd>
		1760	<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
		1761	loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
		1762	<code>EV_P_</code> is used when other parameters are following. Example:</p>
		1763	<pre> // this is how ev_unref is being declared
		1764	static void ev_unref (EV_P);
		1765
		1766	// this is how you can declare your typical callback
		1767	static void cb (EV_P_ ev_timer *w, int revents)
		1768
		1769	</pre>
		1770	<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
		1771	suitable for use with <code>EV_A</code>.</p>
		1772	</dd>
		1773	<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
		1774	<dd>
		1775	<p>Similar to the other two macros, this gives you the value of the default
		1776	loop, if multiple loops are supported ("ev loop default").</p>
		1777	</dd>
		1778	</dl>
		1779	<p>Example: Declare and initialise a check watcher, working regardless of
		1780	wether multiple loops are supported or not.</p>
		1781	<pre> static void
		1782	check_cb (EV_P_ ev_timer *w, int revents)
		1783	{
		1784	ev_check_stop (EV_A_ w);
		1785	}
		1786
		1787	ev_check check;
		1788	ev_check_init (&check, check_cb);
		1789	ev_check_start (EV_DEFAULT_ &check);
		1790	ev_loop (EV_DEFAULT_ 0);
		1791
		1792
		1793
		1794
		1795	</pre>
		1796
		1797	</div>
		1798	<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1799	<div id="EMBEDDING_CONTENT">
		1800	<p>Libev can (and often is) directly embedded into host
		1801	applications. Examples of applications that embed it include the Deliantra
		1802	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1803	and rxvt-unicode.</p>
		1804	<p>The goal is to enable you to just copy the neecssary files into your
		1805	source directory without having to change even a single line in them, so
		1806	you can easily upgrade by simply copying (or having a checked-out copy of
		1807	libev somewhere in your source tree).</p>
		1808
		1809	</div>
		1810	<h2 id="FILESETS">FILESETS</h2>
		1811	<div id="FILESETS_CONTENT">
		1812	<p>Depending on what features you need you need to include one or more sets of files
		1813	in your app.</p>
		1814
		1815	</div>
		1816	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		1817	<div id="CORE_EVENT_LOOP_CONTENT">
		1818	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		1819	configuration (no autoconf):</p>
		1820	<pre> #define EV_STANDALONE 1
		1821	#include "ev.c"
		1822
		1823	</pre>
		1824	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		1825	single C source file only to provide the function implementations. To use
		1826	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		1827	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		1828	where you can put other configuration options):</p>
		1829	<pre> #define EV_STANDALONE 1
		1830	#include "ev.h"
		1831
		1832	</pre>
		1833	<p>Both header files and implementation files can be compiled with a C++
		1834	compiler (at least, thats a stated goal, and breakage will be treated
		1835	as a bug).</p>
		1836	<p>You need the following files in your source tree, or in a directory
		1837	in your include path (e.g. in libev/ when using -Ilibev):</p>
		1838	<pre> ev.h
		1839	ev.c
		1840	ev_vars.h
		1841	ev_wrap.h
		1842
		1843	ev_win32.c required on win32 platforms only
		1844
		1845	ev_select.c only when select backend is enabled (which is by default)
		1846	ev_poll.c only when poll backend is enabled (disabled by default)
		1847	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1848	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1849	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1850
		1851	</pre>
		1852	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		1853	to compile this single file.</p>
		1854
		1855	</div>
		1856	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		1857	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		1858	<p>To include the libevent compatibility API, also include:</p>
		1859	<pre> #include "event.c"
		1860
		1861	</pre>
		1862	<p>in the file including <cite>ev.c</cite>, and:</p>
		1863	<pre> #include "event.h"
		1864
		1865	</pre>
		1866	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		1867	<p>You need the following additional files for this:</p>
		1868	<pre> event.h
		1869	event.c
		1870
		1871	</pre>
		1872
		1873	</div>
		1874	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		1875	<div id="AUTOCONF_SUPPORT_CONTENT">
		1876	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		1877	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		1878	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		1879	include <cite>config.h</cite> and configure itself accordingly.</p>
		1880	<p>For this of course you need the m4 file:</p>
		1881	<pre> libev.m4
		1882
		1883	</pre>
		1884
		1885	</div>
		1886	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		1887	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		1888	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		1889	before including any of its files. The default is not to build for multiplicity
		1890	and only include the select backend.</p>
		1891	<dl>
		1892	<dt>EV_STANDALONE</dt>
		1893	<dd>
		1894	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		1895	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		1896	implementations for some libevent functions (such as logging, which is not
		1897	supported). It will also not define any of the structs usually found in
		1898	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		1899	</dd>
		1900	<dt>EV_USE_MONOTONIC</dt>
		1901	<dd>
		1902	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1903	monotonic clock option at both compiletime and runtime. Otherwise no use
		1904	of the monotonic clock option will be attempted. If you enable this, you
		1905	usually have to link against librt or something similar. Enabling it when
		1906	the functionality isn't available is safe, though, althoguh you have
		1907	to make sure you link against any libraries where the <code>clock_gettime</code>
		1908	function is hiding in (often <cite>-lrt</cite>).</p>
		1909	</dd>
		1910	<dt>EV_USE_REALTIME</dt>
		1911	<dd>
		1912	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1913	realtime clock option at compiletime (and assume its availability at
		1914	runtime if successful). Otherwise no use of the realtime clock option will
		1915	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		1916	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		1917	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		1918	</dd>
		1919	<dt>EV_USE_SELECT</dt>
		1920	<dd>
		1921	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		1922	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		1923	other method takes over, select will be it. Otherwise the select backend
		1924	will not be compiled in.</p>
		1925	</dd>
		1926	<dt>EV_SELECT_USE_FD_SET</dt>
		1927	<dd>
		1928	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		1929	structure. This is useful if libev doesn't compile due to a missing
		1930	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		1931	exotic systems. This usually limits the range of file descriptors to some
		1932	low limit such as 1024 or might have other limitations (winsocket only
		1933	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		1934	influence the size of the <code>fd_set</code> used.</p>
		1935	</dd>
		1936	<dt>EV_SELECT_IS_WINSOCKET</dt>
		1937	<dd>
		1938	<p>When defined to <code>1</code>, the select backend will assume that
		1939	select/socket/connect etc. don't understand file descriptors but
		1940	wants osf handles on win32 (this is the case when the select to
		1941	be used is the winsock select). This means that it will call
		1942	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		1943	it is assumed that all these functions actually work on fds, even
		1944	on win32. Should not be defined on non-win32 platforms.</p>
		1945	</dd>
		1946	<dt>EV_USE_POLL</dt>
		1947	<dd>
		1948	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		1949	backend. Otherwise it will be enabled on non-win32 platforms. It
		1950	takes precedence over select.</p>
		1951	</dd>
		1952	<dt>EV_USE_EPOLL</dt>
		1953	<dd>
		1954	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		1955	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		1956	otherwise another method will be used as fallback. This is the
		1957	preferred backend for GNU/Linux systems.</p>
		1958	</dd>
		1959	<dt>EV_USE_KQUEUE</dt>
		1960	<dd>
		1961	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		1962	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		1963	otherwise another method will be used as fallback. This is the preferred
		1964	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		1965	supports some types of fds correctly (the only platform we found that
		1966	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		1967	not be used unless explicitly requested. The best way to use it is to find
		1968	out whether kqueue supports your type of fd properly and use an embedded
		1969	kqueue loop.</p>
		1970	</dd>
		1971	<dt>EV_USE_PORT</dt>
		1972	<dd>
		1973	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		1974	10 port style backend. Its availability will be detected at runtime,
		1975	otherwise another method will be used as fallback. This is the preferred
		1976	backend for Solaris 10 systems.</p>
		1977	</dd>
		1978	<dt>EV_USE_DEVPOLL</dt>
		1979	<dd>
		1980	<p>reserved for future expansion, works like the USE symbols above.</p>
		1981	</dd>
		1982	<dt>EV_H</dt>
		1983	<dd>
		1984	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		1985	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		1986	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		1987	</dd>
		1988	<dt>EV_CONFIG_H</dt>
		1989	<dd>
		1990	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		1991	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		1992	<code>EV_H</code>, above.</p>
		1993	</dd>
		1994	<dt>EV_EVENT_H</dt>
		1995	<dd>
		1996	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		1997	of how the <cite>event.h</cite> header can be found.</p>
		1998	</dd>
		1999	<dt>EV_PROTOTYPES</dt>
		2000	<dd>
		2001	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		2002	prototypes, but still define all the structs and other symbols. This is
		2003	occasionally useful if you want to provide your own wrapper functions
		2004	around libev functions.</p>
		2005	</dd>
		2006	<dt>EV_MULTIPLICITY</dt>
		2007	<dd>
		2008	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		2009	will have the <code>struct ev_loop *</code> as first argument, and you can create
		2010	additional independent event loops. Otherwise there will be no support
		2011	for multiple event loops and there is no first event loop pointer
		2012	argument. Instead, all functions act on the single default loop.</p>
		2013	</dd>
		2014	<dt>EV_PERIODIC_ENABLE</dt>
		2015	<dd>
		2016	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		2017	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		2018	code.</p>
		2019	</dd>
		2020	<dt>EV_EMBED_ENABLE</dt>
		2021	<dd>
		2022	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		2023	defined to be <code>0</code>, then they are not.</p>
		2024	</dd>
		2025	<dt>EV_STAT_ENABLE</dt>
		2026	<dd>
		2027	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		2028	defined to be <code>0</code>, then they are not.</p>
		2029	</dd>
		2030	<dt>EV_FORK_ENABLE</dt>
		2031	<dd>
		2032	<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
		2033	defined to be <code>0</code>, then they are not.</p>
		2034	</dd>
		2035	<dt>EV_MINIMAL</dt>
		2036	<dd>
		2037	<p>If you need to shave off some kilobytes of code at the expense of some
		2038	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		2039	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		2040	</dd>
		2041	<dt>EV_PID_HASHSIZE</dt>
		2042	<dd>
		2043	<p><code>ev_child</code> watchers use a small hash table to distribute workload by
		2044	pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
		2045	than enough. If you need to manage thousands of children you might want to
		2046	increase this value.</p>
		2047	</dd>
		2048	<dt>EV_COMMON</dt>
		2049	<dd>
		2050	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		2051	this macro to a something else you can include more and other types of
		2052	members. You have to define it each time you include one of the files,
		2053	though, and it must be identical each time.</p>
		2054	<p>For example, the perl EV module uses something like this:</p>
		2055	<pre> #define EV_COMMON \
		2056	SV self; / contains this struct */ \
		2057	SV cb_sv, fh /* note no trailing ";" */
		2058
		2059	</pre>
		2060	</dd>
		2061	<dt>EV_CB_DECLARE (type)</dt>
		2062	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		2063	<dt>ev_set_cb (ev, cb)</dt>
		2064	<dd>
		2065	<p>Can be used to change the callback member declaration in each watcher,
		2066	and the way callbacks are invoked and set. Must expand to a struct member
		2067	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		2068	their default definitions. One possible use for overriding these is to
		2069	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		2070	method calls instead of plain function calls in C++.</p>
		2071
		2072	</div>
		2073	<h2 id="EXAMPLES">EXAMPLES</h2>
		2074	<div id="EXAMPLES_CONTENT">
		2075	<p>For a real-world example of a program the includes libev
		2076	verbatim, you can have a look at the EV perl module
		2077	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		2078	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		2079	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		2080	will be compiled. It is pretty complex because it provides its own header
		2081	file.</p>
		2082	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		2083	that everybody includes and which overrides some autoconf choices:</p>
		2084	<pre> #define EV_USE_POLL 0
		2085	#define EV_MULTIPLICITY 0
		2086	#define EV_PERIODICS 0
		2087	#define EV_CONFIG_H <config.h>
		2088
		2089	#include "ev++.h"
		2090
		2091	</pre>
		2092	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		2093	<pre> #include "ev_cpp.h"
		2094	#include "ev.c"
		2095
		2096
		2097
		2098
		2099	</pre>
		2100
		2101	</div>
		2102	<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
		2103	<div id="COMPLEXITIES_CONTENT">
		2104	<p>In this section the complexities of (many of) the algorithms used inside
		2105	libev will be explained. For complexity discussions about backends see the
		2106	documentation for <code>ev_default_init</code>.</p>
		2107	<p>
		2108	<dl>
		2109	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		2110	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		2111	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		2112	<dt>Stopping check/prepare/idle watchers: O(1)</dt>
		2113	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
		2114	<dt>Finding the next timer per loop iteration: O(1)</dt>
		2115	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		2116	<dt>Activating one watcher: O(1)</dt>
		2117	</dl>
		2118	</p>
		2119
		2120
		2121
		2122
773		2123
774	</div>	2124	</div>
775	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	2125	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
776	<div id="AUTHOR_CONTENT">	2126	<div id="AUTHOR_CONTENT">
777	<p>Marc Lehmann <libev@schmorp.de>.</p>	2127	<p>Marc Lehmann <libev@schmorp.de>.</p>
778		2128
779	</div>	2129	</div>
780	</div></body>	2130	</div></body>
781	</html>	2131	</html>

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Revision 1.53 by root, Tue Nov 27 20:15:02 2007 UTC