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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 09:58:24 2007" />	9	<meta name="created" content="Tue Nov 27 09:11:42 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>
37	</ul>	40	</ul>
38	</li>	41	</li>
39	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	42	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
		43	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
		44	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
		45	<li><a href="#EMBEDDING">EMBEDDING</a>
		46	<ul><li><a href="#FILESETS">FILESETS</a>
		47	<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
		48	<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
		49	<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
		50	</ul>
		51	</li>
		52	<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
		53	<li><a href="#EXAMPLES">EXAMPLES</a></li>
		54	</ul>
		55	</li>
		56	<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
40	<li><a href="#AUTHOR">AUTHOR</a>	57	<li><a href="#AUTHOR">AUTHOR</a>
41	</li>	58	</li>
42	</ul><hr />	59	</ul><hr />
43	<!-- INDEX END -->	60	<!-- INDEX END -->
44		61
…		…
94	<div id="TIME_REPRESENTATION_CONTENT">	111	<div id="TIME_REPRESENTATION_CONTENT">
95	<p>Libev represents time as a single floating point number, representing the	112	<p>Libev represents time as a single floating point number, representing the
96	(fractional) number of seconds since the (POSIX) epoch (somewhere near	113	(fractional) number of seconds since the (POSIX) epoch (somewhere near
97	the beginning of 1970, details are complicated, don't ask). This type is	114	the beginning of 1970, details are complicated, don't ask). This type is
98	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	115	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
99	to the double type in C.</p>	116	to the <code>double</code> type in C, and when you need to do any calculations on
		117	it, you should treat it as such.</p>
		118
		119
		120
		121
100		122
101	</div>	123	</div>
102	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	124	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
103	<div id="GLOBAL_FUNCTIONS_CONTENT">	125	<div id="GLOBAL_FUNCTIONS_CONTENT">
		126	<p>These functions can be called anytime, even before initialising the
		127	library in any way.</p>
104	<dl>	128	<dl>
105	<dt>ev_tstamp ev_time ()</dt>	129	<dt>ev_tstamp ev_time ()</dt>
106	<dd>	130	<dd>
107	<p>Returns the current time as libev would use it.</p>	131	<p>Returns the current time as libev would use it. Please note that the
		132	<code>ev_now</code> function is usually faster and also often returns the timestamp
		133	you actually want to know.</p>
108	</dd>	134	</dd>
109	<dt>int ev_version_major ()</dt>	135	<dt>int ev_version_major ()</dt>
110	<dt>int ev_version_minor ()</dt>	136	<dt>int ev_version_minor ()</dt>
111	<dd>	137	<dd>
112	<p>You can find out the major and minor version numbers of the library	138	<p>You can find out the major and minor version numbers of the library
…		…
116	version of the library your program was compiled against.</p>	142	version of the library your program was compiled against.</p>
117	<p>Usually, it's a good idea to terminate if the major versions mismatch,	143	<p>Usually, it's a good idea to terminate if the major versions mismatch,
118	as this indicates an incompatible change. Minor versions are usually	144	as this indicates an incompatible change. Minor versions are usually
119	compatible to older versions, so a larger minor version alone is usually	145	compatible to older versions, so a larger minor version alone is usually
120	not a problem.</p>	146	not a problem.</p>
		147	<p>Example: make sure we haven't accidentally been linked against the wrong
		148	version:</p>
		149	<pre> assert (("libev version mismatch",
		150	ev_version_major () == EV_VERSION_MAJOR
		151	&& ev_version_minor () >= EV_VERSION_MINOR));
		152
		153	</pre>
		154	</dd>
		155	<dt>unsigned int ev_supported_backends ()</dt>
		156	<dd>
		157	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		158	value) compiled into this binary of libev (independent of their
		159	availability on the system you are running on). See <code>ev_default_loop</code> for
		160	a description of the set values.</p>
		161	<p>Example: make sure we have the epoll method, because yeah this is cool and
		162	a must have and can we have a torrent of it please!!!11</p>
		163	<pre> assert (("sorry, no epoll, no sex",
		164	ev_supported_backends () & EVBACKEND_EPOLL));
		165
		166	</pre>
		167	</dd>
		168	<dt>unsigned int ev_recommended_backends ()</dt>
		169	<dd>
		170	<p>Return the set of all backends compiled into this binary of libev and also
		171	recommended for this platform. This set is often smaller than the one
		172	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		173	most BSDs and will not be autodetected unless you explicitly request it
		174	(assuming you know what you are doing). This is the set of backends that
		175	libev will probe for if you specify no backends explicitly.</p>
		176	</dd>
		177	<dt>unsigned int ev_embeddable_backends ()</dt>
		178	<dd>
		179	<p>Returns the set of backends that are embeddable in other event loops. This
		180	is the theoretical, all-platform, value. To find which backends
		181	might be supported on the current system, you would need to look at
		182	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		183	recommended ones.</p>
		184	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
121	</dd>	185	</dd>
122	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	186	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
123	<dd>	187	<dd>
124	<p>Sets the allocation function to use (the prototype is similar to the	188	<p>Sets the allocation function to use (the prototype is similar to the
125	realloc C function, the semantics are identical). It is used to allocate	189	realloc C function, the semantics are identical). It is used to allocate
…		…
127	needs to be allocated, the library might abort or take some potentially	191	needs to be allocated, the library might abort or take some potentially
128	destructive action. The default is your system realloc function.</p>	192	destructive action. The default is your system realloc function.</p>
129	<p>You could override this function in high-availability programs to, say,	193	<p>You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	194	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.</p>	195	or even to sleep a while and retry until some memory is available.</p>
		196	<p>Example: replace the libev allocator with one that waits a bit and then
		197	retries: better than mine).</p>
		198	<pre> static void *
		199	persistent_realloc (void *ptr, long size)
		200	{
		201	for (;;)
		202	{
		203	void *newptr = realloc (ptr, size);
		204
		205	if (newptr)
		206	return newptr;
		207
		208	sleep (60);
		209	}
		210	}
		211
		212	...
		213	ev_set_allocator (persistent_realloc);
		214
		215	</pre>
132	</dd>	216	</dd>
133	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	217	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
134	<dd>	218	<dd>
135	<p>Set the callback function to call on a retryable syscall error (such	219	<p>Set the callback function to call on a retryable syscall error (such
136	as failed select, poll, epoll_wait). The message is a printable string	220	as failed select, poll, epoll_wait). The message is a printable string
137	indicating the system call or subsystem causing the problem. If this	221	indicating the system call or subsystem causing the problem. If this
138	callback is set, then libev will expect it to remedy the sitution, no	222	callback is set, then libev will expect it to remedy the sitution, no
139	matter what, when it returns. That is, libev will generally retry the	223	matter what, when it returns. That is, libev will generally retry the
140	requested operation, or, if the condition doesn't go away, do bad stuff	224	requested operation, or, if the condition doesn't go away, do bad stuff
141	(such as abort).</p>	225	(such as abort).</p>
		226	<p>Example: do the same thing as libev does internally:</p>
		227	<pre> static void
		228	fatal_error (const char *msg)
		229	{
		230	perror (msg);
		231	abort ();
		232	}
		233
		234	...
		235	ev_set_syserr_cb (fatal_error);
		236
		237	</pre>
142	</dd>	238	</dd>
143	</dl>	239	</dl>
144		240
145	</div>	241	</div>
146	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	242	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
…		…
158	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	254	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
159	<dd>	255	<dd>
160	<p>This will initialise the default event loop if it hasn't been initialised	256	<p>This will initialise the default event loop if it hasn't been initialised
161	yet and return it. If the default loop could not be initialised, returns	257	yet and return it. If the default loop could not be initialised, returns
162	false. If it already was initialised it simply returns it (and ignores the	258	false. If it already was initialised it simply returns it (and ignores the
163	flags).</p>	259	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
164	<p>If you don't know what event loop to use, use the one returned from this	260	<p>If you don't know what event loop to use, use the one returned from this
165	function.</p>	261	function.</p>
166	<p>The flags argument can be used to specify special behaviour or specific	262	<p>The flags argument can be used to specify special behaviour or specific
167	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>	263	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
168	<p>It supports the following flags:</p>	264	<p>The following flags are supported:</p>
169	<p>	265	<p>
170	<dl>	266	<dl>
171	<dt><code>EVFLAG_AUTO</code></dt>	267	<dt><code>EVFLAG_AUTO</code></dt>
172	<dd>	268	<dd>
173	<p>The default flags value. Use this if you have no clue (it's the right	269	<p>The default flags value. Use this if you have no clue (it's the right
…		…
180	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will	276	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181	override the flags completely if it is found in the environment. This is	277	override the flags completely if it is found in the environment. This is
182	useful to try out specific backends to test their performance, or to work	278	useful to try out specific backends to test their performance, or to work
183	around bugs.</p>	279	around bugs.</p>
184	</dd>	280	</dd>
185	<dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>	281	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
186	<dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
187	<dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
188	<dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
189	<dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
190	<dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
191	<dd>	282	<dd>
192	<p>If one or more of these are ored into the flags value, then only these	283	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
193	backends will be tried (in the reverse order as given here). If one are	284	libev tries to roll its own fd_set with no limits on the number of fds,
194	specified, any backend will do.</p>	285	but if that fails, expect a fairly low limit on the number of fds when
		286	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		287	the fastest backend for a low number of fds.</p>
		288	</dd>
		289	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		290	<dd>
		291	<p>And this is your standard poll(2) backend. It's more complicated than
		292	select, but handles sparse fds better and has no artificial limit on the
		293	number of fds you can use (except it will slow down considerably with a
		294	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		295	</dd>
		296	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		297	<dd>
		298	<p>For few fds, this backend is a bit little slower than poll and select,
		299	but it scales phenomenally better. While poll and select usually scale like
		300	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		301	either O(1) or O(active_fds).</p>
		302	<p>While stopping and starting an I/O watcher in the same iteration will
		303	result in some caching, there is still a syscall per such incident
		304	(because the fd could point to a different file description now), so its
		305	best to avoid that. Also, dup()ed file descriptors might not work very
		306	well if you register events for both fds.</p>
		307	<p>Please note that epoll sometimes generates spurious notifications, so you
		308	need to use non-blocking I/O or other means to avoid blocking when no data
		309	(or space) is available.</p>
		310	</dd>
		311	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		312	<dd>
		313	<p>Kqueue deserves special mention, as at the time of this writing, it
		314	was broken on all BSDs except NetBSD (usually it doesn't work with
		315	anything but sockets and pipes, except on Darwin, where of course its
		316	completely useless). For this reason its not being "autodetected"
		317	unless you explicitly specify it explicitly in the flags (i.e. using
		318	<code>EVBACKEND_KQUEUE</code>).</p>
		319	<p>It scales in the same way as the epoll backend, but the interface to the
		320	kernel is more efficient (which says nothing about its actual speed, of
		321	course). While starting and stopping an I/O watcher does not cause an
		322	extra syscall as with epoll, it still adds up to four event changes per
		323	incident, so its best to avoid that.</p>
		324	</dd>
		325	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		326	<dd>
		327	<p>This is not implemented yet (and might never be).</p>
		328	</dd>
		329	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		330	<dd>
		331	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		332	it's really slow, but it still scales very well (O(active_fds)).</p>
		333	<p>Please note that solaris ports can result in a lot of spurious
		334	notifications, so you need to use non-blocking I/O or other means to avoid
		335	blocking when no data (or space) is available.</p>
		336	</dd>
		337	<dt><code>EVBACKEND_ALL</code></dt>
		338	<dd>
		339	<p>Try all backends (even potentially broken ones that wouldn't be tried
		340	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		341	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
195	</dd>	342	</dd>
196	</dl>	343	</dl>
197	</p>	344	</p>
		345	<p>If one or more of these are ored into the flags value, then only these
		346	backends will be tried (in the reverse order as given here). If none are
		347	specified, most compiled-in backend will be tried, usually in reverse
		348	order of their flag values :)</p>
		349	<p>The most typical usage is like this:</p>
		350	<pre> if (!ev_default_loop (0))
		351	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		352
		353	</pre>
		354	<p>Restrict libev to the select and poll backends, and do not allow
		355	environment settings to be taken into account:</p>
		356	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		357
		358	</pre>
		359	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		360	available (warning, breaks stuff, best use only with your own private
		361	event loop and only if you know the OS supports your types of fds):</p>
		362	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		363
		364	</pre>
198	</dd>	365	</dd>
199	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	366	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200	<dd>	367	<dd>
201	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	368	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
202	always distinct from the default loop. Unlike the default loop, it cannot	369	always distinct from the default loop. Unlike the default loop, it cannot
203	handle signal and child watchers, and attempts to do so will be greeted by	370	handle signal and child watchers, and attempts to do so will be greeted by
204	undefined behaviour (or a failed assertion if assertions are enabled).</p>	371	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		372	<p>Example: try to create a event loop that uses epoll and nothing else.</p>
		373	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		374	if (!epoller)
		375	fatal ("no epoll found here, maybe it hides under your chair");
		376
		377	</pre>
205	</dd>	378	</dd>
206	<dt>ev_default_destroy ()</dt>	379	<dt>ev_default_destroy ()</dt>
207	<dd>	380	<dd>
208	<p>Destroys the default loop again (frees all memory and kernel state	381	<p>Destroys the default loop again (frees all memory and kernel state
209	etc.). This stops all registered event watchers (by not touching them in	382	etc.). None of the active event watchers will be stopped in the normal
210	any way whatsoever, although you cannot rely on this :).</p>	383	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		384	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		385	calling this function, or cope with the fact afterwards (which is usually
		386	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		387	for example).</p>
211	</dd>	388	</dd>
212	<dt>ev_loop_destroy (loop)</dt>	389	<dt>ev_loop_destroy (loop)</dt>
213	<dd>	390	<dd>
214	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	391	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
215	earlier call to <code>ev_loop_new</code>.</p>	392	earlier call to <code>ev_loop_new</code>.</p>
…		…
218	<dd>	395	<dd>
219	<p>This function reinitialises the kernel state for backends that have	396	<p>This function reinitialises the kernel state for backends that have
220	one. Despite the name, you can call it anytime, but it makes most sense	397	one. Despite the name, you can call it anytime, but it makes most sense
221	after forking, in either the parent or child process (or both, but that	398	after forking, in either the parent or child process (or both, but that
222	again makes little sense).</p>	399	again makes little sense).</p>
223	<p>You <i>must</i> call this function after forking if and only if you want to	400	<p>You <i>must</i> call this function in the child process after forking if and
224	use the event library in both processes. If you just fork+exec, you don't	401	only if you want to use the event library in both processes. If you just
225	have to call it.</p>	402	fork+exec, you don't have to call it.</p>
226	<p>The function itself is quite fast and it's usually not a problem to call	403	<p>The function itself is quite fast and it's usually not a problem to call
227	it just in case after a fork. To make this easy, the function will fit in	404	it just in case after a fork. To make this easy, the function will fit in
228	quite nicely into a call to <code>pthread_atfork</code>:</p>	405	quite nicely into a call to <code>pthread_atfork</code>:</p>
229	<pre> pthread_atfork (0, 0, ev_default_fork);	406	<pre> pthread_atfork (0, 0, ev_default_fork);
230		407
231	</pre>	408	</pre>
		409	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		410	without calling this function, so if you force one of those backends you
		411	do not need to care.</p>
232	</dd>	412	</dd>
233	<dt>ev_loop_fork (loop)</dt>	413	<dt>ev_loop_fork (loop)</dt>
234	<dd>	414	<dd>
235	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	415	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
236	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	416	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
237	after fork, and how you do this is entirely your own problem.</p>	417	after fork, and how you do this is entirely your own problem.</p>
238	</dd>	418	</dd>
239	<dt>unsigned int ev_method (loop)</dt>	419	<dt>unsigned int ev_backend (loop)</dt>
240	<dd>	420	<dd>
241	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	421	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
242	use.</p>	422	use.</p>
243	</dd>	423	</dd>
244	<dt>ev_tstamp ev_now (loop)</dt>	424	<dt>ev_tstamp ev_now (loop)</dt>
245	<dd>	425	<dd>
246	<p>Returns the current "event loop time", which is the time the event loop	426	<p>Returns the current "event loop time", which is the time the event loop
247	got events and started processing them. This timestamp does not change	427	received events and started processing them. This timestamp does not
248	as long as callbacks are being processed, and this is also the base time	428	change as long as callbacks are being processed, and this is also the base
249	used for relative timers. You can treat it as the timestamp of the event	429	time used for relative timers. You can treat it as the timestamp of the
250	occuring (or more correctly, the mainloop finding out about it).</p>	430	event occuring (or more correctly, libev finding out about it).</p>
251	</dd>	431	</dd>
252	<dt>ev_loop (loop, int flags)</dt>	432	<dt>ev_loop (loop, int flags)</dt>
253	<dd>	433	<dd>
254	<p>Finally, this is it, the event handler. This function usually is called	434	<p>Finally, this is it, the event handler. This function usually is called
255	after you initialised all your watchers and you want to start handling	435	after you initialised all your watchers and you want to start handling
256	events.</p>	436	events.</p>
257	<p>If the flags argument is specified as 0, it will not return until either	437	<p>If the flags argument is specified as <code>0</code>, it will not return until
258	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	438	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		439	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		440	relying on all watchers to be stopped when deciding when a program has
		441	finished (especially in interactive programs), but having a program that
		442	automatically loops as long as it has to and no longer by virtue of
		443	relying on its watchers stopping correctly is a thing of beauty.</p>
259	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	444	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
260	those events and any outstanding ones, but will not block your process in	445	those events and any outstanding ones, but will not block your process in
261	case there are no events and will return after one iteration of the loop.</p>	446	case there are no events and will return after one iteration of the loop.</p>
262	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	447	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
263	neccessary) and will handle those and any outstanding ones. It will block	448	neccessary) and will handle those and any outstanding ones. It will block
264	your process until at least one new event arrives, and will return after	449	your process until at least one new event arrives, and will return after
265	one iteration of the loop.</p>	450	one iteration of the loop. This is useful if you are waiting for some
266	<p>This flags value could be used to implement alternative looping	451	external event in conjunction with something not expressible using other
267	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	452	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
268	more generic mechanism.</p>	453	usually a better approach for this kind of thing.</p>
		454	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		455	<pre> * If there are no active watchers (reference count is zero), return.
		456	- Queue prepare watchers and then call all outstanding watchers.
		457	- If we have been forked, recreate the kernel state.
		458	- Update the kernel state with all outstanding changes.
		459	- Update the "event loop time".
		460	- Calculate for how long to block.
		461	- Block the process, waiting for any events.
		462	- Queue all outstanding I/O (fd) events.
		463	- Update the "event loop time" and do time jump handling.
		464	- Queue all outstanding timers.
		465	- Queue all outstanding periodics.
		466	- If no events are pending now, queue all idle watchers.
		467	- Queue all check watchers.
		468	- Call all queued watchers in reverse order (i.e. check watchers first).
		469	Signals and child watchers are implemented as I/O watchers, and will
		470	be handled here by queueing them when their watcher gets executed.
		471	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		472	were used, return, otherwise continue with step *.
		473
		474	</pre>
		475	<p>Example: queue some jobs and then loop until no events are outsanding
		476	anymore.</p>
		477	<pre> ... queue jobs here, make sure they register event watchers as long
		478	... as they still have work to do (even an idle watcher will do..)
		479	ev_loop (my_loop, 0);
		480	... jobs done. yeah!
		481
		482	</pre>
269	</dd>	483	</dd>
270	<dt>ev_unloop (loop, how)</dt>	484	<dt>ev_unloop (loop, how)</dt>
271	<dd>	485	<dd>
272	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it	486	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
273	has processed all outstanding events). The <code>how</code> argument must be either	487	has processed all outstanding events). The <code>how</code> argument must be either
274	<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or	488	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
275	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>	489	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276	</dd>	490	</dd>
277	<dt>ev_ref (loop)</dt>	491	<dt>ev_ref (loop)</dt>
278	<dt>ev_unref (loop)</dt>	492	<dt>ev_unref (loop)</dt>
279	<dd>	493	<dd>
…		…
285	example, libev itself uses this for its internal signal pipe: It is not	499	example, libev itself uses this for its internal signal pipe: It is not
286	visible to the libev user and should not keep <code>ev_loop</code> from exiting if	500	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
287	no event watchers registered by it are active. It is also an excellent	501	no event watchers registered by it are active. It is also an excellent
288	way to do this for generic recurring timers or from within third-party	502	way to do this for generic recurring timers or from within third-party
289	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>	503	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		504	<p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
		505	running when nothing else is active.</p>
		506	<pre> struct dv_signal exitsig;
		507	ev_signal_init (&exitsig, sig_cb, SIGINT);
		508	ev_signal_start (myloop, &exitsig);
		509	evf_unref (myloop);
		510
		511	</pre>
		512	<p>Example: for some weird reason, unregister the above signal handler again.</p>
		513	<pre> ev_ref (myloop);
		514	ev_signal_stop (myloop, &exitsig);
		515
		516	</pre>
290	</dd>	517	</dd>
291	</dl>	518	</dl>
		519
		520
		521
		522
292		523
293	</div>	524	</div>
294	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	525	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
295	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	526	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
296	<p>A watcher is a structure that you create and register to record your	527	<p>A watcher is a structure that you create and register to record your
…		…
326	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	557	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
327	*)</code>), and you can stop watching for events at any time by calling the	558	*)</code>), and you can stop watching for events at any time by calling the
328	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	559	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
329	<p>As long as your watcher is active (has been started but not stopped) you	560	<p>As long as your watcher is active (has been started but not stopped) you
330	must not touch the values stored in it. Most specifically you must never	561	must not touch the values stored in it. Most specifically you must never
331	reinitialise it or call its set method.</p>	562	reinitialise it or call its <code>set</code> macro.</p>
332	<p>You can check whether an event is active by calling the <code>ev_is_active
333	(watcher *)</code> macro. To see whether an event is outstanding (but the
334	callback for it has not been called yet) you can use the <code>ev_is_pending
335	(watcher *)</code> macro.</p>
336	<p>Each and every callback receives the event loop pointer as first, the	563	<p>Each and every callback receives the event loop pointer as first, the
337	registered watcher structure as second, and a bitset of received events as	564	registered watcher structure as second, and a bitset of received events as
338	third argument.</p>	565	third argument.</p>
339	<p>The received events usually include a single bit per event type received	566	<p>The received events usually include a single bit per event type received
340	(you can receive multiple events at the same time). The possible bit masks	567	(you can receive multiple events at the same time). The possible bit masks
…		…
359	<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>	586	<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
360	</dd>	587	</dd>
361	<dt><code>EV_CHILD</code></dt>	588	<dt><code>EV_CHILD</code></dt>
362	<dd>	589	<dd>
363	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>	590	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
		591	</dd>
		592	<dt><code>EV_STAT</code></dt>
		593	<dd>
		594	<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
364	</dd>	595	</dd>
365	<dt><code>EV_IDLE</code></dt>	596	<dt><code>EV_IDLE</code></dt>
366	<dd>	597	<dd>
367	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>	598	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
368	</dd>	599	</dd>
…		…
389	your callbacks is well-written it can just attempt the operation and cope	620	your callbacks is well-written it can just attempt the operation and cope
390	with the error from read() or write(). This will not work in multithreaded	621	with the error from read() or write(). This will not work in multithreaded
391	programs, though, so beware.</p>	622	programs, though, so beware.</p>
392	</dd>	623	</dd>
393	</dl>	624	</dl>
		625
		626	</div>
		627	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		628	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		629	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		630	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		631	<dl>
		632	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		633	<dd>
		634	<p>This macro initialises the generic portion of a watcher. The contents
		635	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		636	the generic parts of the watcher are initialised, you <i>need</i> to call
		637	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		638	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		639	which rolls both calls into one.</p>
		640	<p>You can reinitialise a watcher at any time as long as it has been stopped
		641	(or never started) and there are no pending events outstanding.</p>
		642	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		643	int revents)</code>.</p>
		644	</dd>
		645	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		646	<dd>
		647	<p>This macro initialises the type-specific parts of a watcher. You need to
		648	call <code>ev_init</code> at least once before you call this macro, but you can
		649	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		650	macro on a watcher that is active (it can be pending, however, which is a
		651	difference to the <code>ev_init</code> macro).</p>
		652	<p>Although some watcher types do not have type-specific arguments
		653	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		654	</dd>
		655	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		656	<dd>
		657	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		658	calls into a single call. This is the most convinient method to initialise
		659	a watcher. The same limitations apply, of course.</p>
		660	</dd>
		661	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		662	<dd>
		663	<p>Starts (activates) the given watcher. Only active watchers will receive
		664	events. If the watcher is already active nothing will happen.</p>
		665	</dd>
		666	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		667	<dd>
		668	<p>Stops the given watcher again (if active) and clears the pending
		669	status. It is possible that stopped watchers are pending (for example,
		670	non-repeating timers are being stopped when they become pending), but
		671	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		672	you want to free or reuse the memory used by the watcher it is therefore a
		673	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		674	</dd>
		675	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		676	<dd>
		677	<p>Returns a true value iff the watcher is active (i.e. it has been started
		678	and not yet been stopped). As long as a watcher is active you must not modify
		679	it.</p>
		680	</dd>
		681	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		682	<dd>
		683	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		684	events but its callback has not yet been invoked). As long as a watcher
		685	is pending (but not active) you must not call an init function on it (but
		686	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		687	libev (e.g. you cnanot <code>free ()</code> it).</p>
		688	</dd>
		689	<dt>callback = ev_cb (ev_TYPE *watcher)</dt>
		690	<dd>
		691	<p>Returns the callback currently set on the watcher.</p>
		692	</dd>
		693	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		694	<dd>
		695	<p>Change the callback. You can change the callback at virtually any time
		696	(modulo threads).</p>
		697	</dd>
		698	</dl>
		699
		700
		701
		702
394		703
395	</div>	704	</div>
396	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	705	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
397	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	706	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
398	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	707	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
…		…
428		737
429	</div>	738	</div>
430	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	739	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
431	<div id="WATCHER_TYPES_CONTENT">	740	<div id="WATCHER_TYPES_CONTENT">
432	<p>This section describes each watcher in detail, but will not repeat	741	<p>This section describes each watcher in detail, but will not repeat
433	information given in the last section.</p>	742	information given in the last section. Any initialisation/set macros,
		743	functions and members specific to the watcher type are explained.</p>
		744	<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
		745	while the watcher is active, you can look at the member and expect some
		746	sensible content, but you must not modify it (you can modify it while the
		747	watcher is stopped to your hearts content), or <i>[read-write]</i>, which
		748	means you can expect it to have some sensible content while the watcher
		749	is active, but you can also modify it. Modifying it may not do something
		750	sensible or take immediate effect (or do anything at all), but libev will
		751	not crash or malfunction in any way.</p>
434		752
		753
		754
		755
		756
435	</div>	757	</div>
436	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>	758	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
437	<div id="code_ev_io_code_is_this_file_descrip-2">	759	<div id="code_ev_io_code_is_this_file_descrip-2">
438	<p>I/O watchers check whether a file descriptor is readable or writable	760	<p>I/O watchers check whether a file descriptor is readable or writable
439	in each iteration of the event loop (This behaviour is called	761	in each iteration of the event loop, or, more precisely, when reading
440	level-triggering because you keep receiving events as long as the	762	would not block the process and writing would at least be able to write
441	condition persists. Remember you can stop the watcher if you don't want to	763	some data. This behaviour is called level-triggering because you keep
442	act on the event and neither want to receive future events).</p>	764	receiving events as long as the condition persists. Remember you can stop
		765	the watcher if you don't want to act on the event and neither want to
		766	receive future events.</p>
443	<p>In general you can register as many read and/or write event watchers oer	767	<p>In general you can register as many read and/or write event watchers per
444	fd as you want (as long as you don't confuse yourself). Setting all file	768	fd as you want (as long as you don't confuse yourself). Setting all file
445	descriptors to non-blocking mode is also usually a good idea (but not	769	descriptors to non-blocking mode is also usually a good idea (but not
446	required if you know what you are doing).</p>	770	required if you know what you are doing).</p>
447	<p>You have to be careful with dup'ed file descriptors, though. Some backends	771	<p>You have to be careful with dup'ed file descriptors, though. Some backends
448	(the linux epoll backend is a notable example) cannot handle dup'ed file	772	(the linux epoll backend is a notable example) cannot handle dup'ed file
449	descriptors correctly if you register interest in two or more fds pointing	773	descriptors correctly if you register interest in two or more fds pointing
450	to the same file/socket etc. description.</p>	774	to the same underlying file/socket/etc. description (that is, they share
		775	the same underlying "file open").</p>
451	<p>If you must do this, then force the use of a known-to-be-good backend	776	<p>If you must do this, then force the use of a known-to-be-good backend
452	(at the time of this writing, this includes only EVMETHOD_SELECT and	777	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453	EVMETHOD_POLL).</p>	778	<code>EVBACKEND_POLL</code>).</p>
		779	<p>Another thing you have to watch out for is that it is quite easy to
		780	receive "spurious" readyness notifications, that is your callback might
		781	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		782	because there is no data. Not only are some backends known to create a
		783	lot of those (for example solaris ports), it is very easy to get into
		784	this situation even with a relatively standard program structure. Thus
		785	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		786	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		787	<p>If you cannot run the fd in non-blocking mode (for example you should not
		788	play around with an Xlib connection), then you have to seperately re-test
		789	wether a file descriptor is really ready with a known-to-be good interface
		790	such as poll (fortunately in our Xlib example, Xlib already does this on
		791	its own, so its quite safe to use).</p>
454	<dl>	792	<dl>
455	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	793	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
456	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	794	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
457	<dd>	795	<dd>
458	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive	796	<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
459	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	797	rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
460	EV_WRITE</code> to receive the given events.</p>	798	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
		799	</dd>
		800	<dt>int fd [read-only]</dt>
		801	<dd>
		802	<p>The file descriptor being watched.</p>
		803	</dd>
		804	<dt>int events [read-only]</dt>
		805	<dd>
		806	<p>The events being watched.</p>
461	</dd>	807	</dd>
462	</dl>	808	</dl>
		809	<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		810	readable, but only once. Since it is likely line-buffered, you could
		811	attempt to read a whole line in the callback:</p>
		812	<pre> static void
		813	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		814	{
		815	ev_io_stop (loop, w);
		816	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		817	}
463		818
		819	...
		820	struct ev_loop *loop = ev_default_init (0);
		821	struct ev_io stdin_readable;
		822	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		823	ev_io_start (loop, &stdin_readable);
		824	ev_loop (loop, 0);
		825
		826
		827
		828
		829	</pre>
		830
464	</div>	831	</div>
465	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>	832	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
466	<div id="code_ev_timer_code_relative_and_opti-2">	833	<div id="code_ev_timer_code_relative_and_opti-2">
467	<p>Timer watchers are simple relative timers that generate an event after a	834	<p>Timer watchers are simple relative timers that generate an event after a
468	given time, and optionally repeating in regular intervals after that.</p>	835	given time, and optionally repeating in regular intervals after that.</p>
469	<p>The timers are based on real time, that is, if you register an event that	836	<p>The timers are based on real time, that is, if you register an event that
470	times out after an hour and youreset your system clock to last years	837	times out after an hour and you reset your system clock to last years
471	time, it will still time out after (roughly) and hour. "Roughly" because	838	time, it will still time out after (roughly) and hour. "Roughly" because
472	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	839	detecting time jumps is hard, and some inaccuracies are unavoidable (the
473	monotonic clock option helps a lot here).</p>	840	monotonic clock option helps a lot here).</p>
474	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>	841	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
475	time. This is usually the right thing as this timestamp refers to the time	842	time. This is usually the right thing as this timestamp refers to the time
476	of the event triggering whatever timeout you are modifying/starting. If	843	of the event triggering whatever timeout you are modifying/starting. If
477	you suspect event processing to be delayed and you need to base the timeout	844	you suspect event processing to be delayed and you <i>need</i> to base the timeout
478	ion the current time, use something like this to adjust for this:</p>	845	on the current time, use something like this to adjust for this:</p>
479	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	846	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
480		847
481	</pre>	848	</pre>
		849	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		850	but if multiple timers become ready during the same loop iteration then
		851	order of execution is undefined.</p>
482	<dl>	852	<dl>
483	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	853	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
484	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	854	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485	<dd>	855	<dd>
486	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	856	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
488	timer will automatically be configured to trigger again <code>repeat</code> seconds	858	timer will automatically be configured to trigger again <code>repeat</code> seconds
489	later, again, and again, until stopped manually.</p>	859	later, again, and again, until stopped manually.</p>
490	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	860	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
491	configure a timer to trigger every 10 seconds, then it will trigger at	861	configure a timer to trigger every 10 seconds, then it will trigger at
492	exactly 10 second intervals. If, however, your program cannot keep up with	862	exactly 10 second intervals. If, however, your program cannot keep up with
493	the timer (ecause it takes longer than those 10 seconds to do stuff) the	863	the timer (because it takes longer than those 10 seconds to do stuff) the
494	timer will not fire more than once per event loop iteration.</p>	864	timer will not fire more than once per event loop iteration.</p>
495	</dd>	865	</dd>
496	<dt>ev_timer_again (loop)</dt>	866	<dt>ev_timer_again (loop)</dt>
497	<dd>	867	<dd>
498	<p>This will act as if the timer timed out and restart it again if it is	868	<p>This will act as if the timer timed out and restart it again if it is
499	repeating. The exact semantics are:</p>	869	repeating. The exact semantics are:</p>
500	<p>If the timer is started but nonrepeating, stop it.</p>	870	<p>If the timer is started but nonrepeating, stop it.</p>
501	<p>If the timer is repeating, either start it if necessary (with the repeat	871	<p>If the timer is repeating, either start it if necessary (with the repeat
502	value), or reset the running timer to the repeat value.</p>	872	value), or reset the running timer to the repeat value.</p>
503	<p>This sounds a bit complicated, but here is a useful and typical	873	<p>This sounds a bit complicated, but here is a useful and typical
504	example: Imagine you have a tcp connection and you want a so-called idle	874	example: Imagine you have a tcp connection and you want a so-called
505	timeout, that is, you want to be called when there have been, say, 60	875	idle timeout, that is, you want to be called when there have been,
506	seconds of inactivity on the socket. The easiest way to do this is to	876	say, 60 seconds of inactivity on the socket. The easiest way to do
507	configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each	877	this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
508	time you successfully read or write some data. If you go into an idle	878	<code>ev_timer_again</code> each time you successfully read or write some data. If
509	state where you do not expect data to travel on the socket, you can stop	879	you go into an idle state where you do not expect data to travel on the
510	the timer, and again will automatically restart it if need be.</p>	880	socket, you can stop the timer, and again will automatically restart it if
		881	need be.</p>
		882	<p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
		883	and only ever use the <code>repeat</code> value:</p>
		884	<pre> ev_timer_init (timer, callback, 0., 5.);
		885	ev_timer_again (loop, timer);
		886	...
		887	timer->again = 17.;
		888	ev_timer_again (loop, timer);
		889	...
		890	timer->again = 10.;
		891	ev_timer_again (loop, timer);
		892
		893	</pre>
		894	<p>This is more efficient then stopping/starting the timer eahc time you want
		895	to modify its timeout value.</p>
		896	</dd>
		897	<dt>ev_tstamp repeat [read-write]</dt>
		898	<dd>
		899	<p>The current <code>repeat</code> value. Will be used each time the watcher times out
		900	or <code>ev_timer_again</code> is called and determines the next timeout (if any),
		901	which is also when any modifications are taken into account.</p>
511	</dd>	902	</dd>
512	</dl>	903	</dl>
		904	<p>Example: create a timer that fires after 60 seconds.</p>
		905	<pre> static void
		906	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		907	{
		908	.. one minute over, w is actually stopped right here
		909	}
513		910
		911	struct ev_timer mytimer;
		912	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		913	ev_timer_start (loop, &mytimer);
		914
		915	</pre>
		916	<p>Example: create a timeout timer that times out after 10 seconds of
		917	inactivity.</p>
		918	<pre> static void
		919	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		920	{
		921	.. ten seconds without any activity
		922	}
		923
		924	struct ev_timer mytimer;
		925	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		926	ev_timer_again (&mytimer); /* start timer */
		927	ev_loop (loop, 0);
		928
		929	// and in some piece of code that gets executed on any "activity":
		930	// reset the timeout to start ticking again at 10 seconds
		931	ev_timer_again (&mytimer);
		932
		933
		934
		935
		936	</pre>
		937
514	</div>	938	</div>
515	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>	939	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
516	<div id="code_ev_periodic_code_to_cron_or_not-2">	940	<div id="code_ev_periodic_code_to_cron_or_not-2">
517	<p>Periodic watchers are also timers of a kind, but they are very versatile	941	<p>Periodic watchers are also timers of a kind, but they are very versatile
518	(and unfortunately a bit complex).</p>	942	(and unfortunately a bit complex).</p>
519	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)	943	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
520	but on wallclock time (absolute time). You can tell a periodic watcher	944	but on wallclock time (absolute time). You can tell a periodic watcher
521	to trigger "at" some specific point in time. For example, if you tell a	945	to trigger "at" some specific point in time. For example, if you tell a
522	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	946	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
523	+ 10.>) and then reset your system clock to the last year, then it will	947	+ 10.</code>) and then reset your system clock to the last year, then it will
524	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger	948	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
525	roughly 10 seconds later and of course not if you reset your system time	949	roughly 10 seconds later and of course not if you reset your system time
526	again).</p>	950	again).</p>
527	<p>They can also be used to implement vastly more complex timers, such as	951	<p>They can also be used to implement vastly more complex timers, such as
528	triggering an event on eahc midnight, local time.</p>	952	triggering an event on eahc midnight, local time.</p>
		953	<p>As with timers, the callback is guarenteed to be invoked only when the
		954	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		955	during the same loop iteration then order of execution is undefined.</p>
529	<dl>	956	<dl>
530	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	957	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
531	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	958	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532	<dd>	959	<dd>
533	<p>Lots of arguments, lets sort it out... There are basically three modes of	960	<p>Lots of arguments, lets sort it out... There are basically three modes of
534	operation, and we will explain them from simplest to complex:</p>	961	operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539	<p>	962	<p>
540	<dl>	963	<dl>
541	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	964	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
542	<dd>	965	<dd>
543	<p>In this configuration the watcher triggers an event at the wallclock time	966	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
567	<dd>	990	<dd>
568	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	991	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
569	ignored. Instead, each time the periodic watcher gets scheduled, the	992	ignored. Instead, each time the periodic watcher gets scheduled, the
570	reschedule callback will be called with the watcher as first, and the	993	reschedule callback will be called with the watcher as first, and the
571	current time as second argument.</p>	994	current time as second argument.</p>
572	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	995	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
573	periodic watcher, ever, or make any event loop modifications</i>. If you need	996	ever, or make any event loop modifications</i>. If you need to stop it,
574	to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p>	997	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
575	<p>Also, <i>this callback must always return a time that is later than the	998	starting a prepare watcher).</p>
576	passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
577	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,	999	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
578	ev_tstamp now)</code>, e.g.:</p>	1000	ev_tstamp now)</code>, e.g.:</p>
579	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1001	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580	{	1002	{
581	return now + 60.;	1003	return now + 60.;
…		…
584	</pre>	1006	</pre>
585	<p>It must return the next time to trigger, based on the passed time value	1007	<p>It must return the next time to trigger, based on the passed time value
586	(that is, the lowest time value larger than to the second argument). It	1008	(that is, the lowest time value larger than to the second argument). It
587	will usually be called just before the callback will be triggered, but	1009	will usually be called just before the callback will be triggered, but
588	might be called at other times, too.</p>	1010	might be called at other times, too.</p>
		1011	<p>NOTE: <i>This callback must always return a time that is later than the
		1012	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
589	<p>This can be used to create very complex timers, such as a timer that	1013	<p>This can be used to create very complex timers, such as a timer that
590	triggers on each midnight, local time. To do this, you would calculate the	1014	triggers on each midnight, local time. To do this, you would calculate the
591	next midnight after <code>now</code> and return the timestamp value for this. How you do this	1015	next midnight after <code>now</code> and return the timestamp value for this. How
592	is, again, up to you (but it is not trivial).</p>	1016	you do this is, again, up to you (but it is not trivial, which is the main
		1017	reason I omitted it as an example).</p>
593	</dd>	1018	</dd>
594	</dl>	1019	</dl>
595	</p>	1020	</p>
596	</dd>	1021	</dd>
597	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	1022	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
599	<p>Simply stops and restarts the periodic watcher again. This is only useful	1024	<p>Simply stops and restarts the periodic watcher again. This is only useful
600	when you changed some parameters or the reschedule callback would return	1025	when you changed some parameters or the reschedule callback would return
601	a different time than the last time it was called (e.g. in a crond like	1026	a different time than the last time it was called (e.g. in a crond like
602	program when the crontabs have changed).</p>	1027	program when the crontabs have changed).</p>
603	</dd>	1028	</dd>
		1029	<dt>ev_tstamp interval [read-write]</dt>
		1030	<dd>
		1031	<p>The current interval value. Can be modified any time, but changes only
		1032	take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
		1033	called.</p>
		1034	</dd>
		1035	<dt>ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]</dt>
		1036	<dd>
		1037	<p>The current reschedule callback, or <code>0</code>, if this functionality is
		1038	switched off. Can be changed any time, but changes only take effect when
		1039	the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
		1040	</dd>
604	</dl>	1041	</dl>
		1042	<p>Example: call a callback every hour, or, more precisely, whenever the
		1043	system clock is divisible by 3600. The callback invocation times have
		1044	potentially a lot of jittering, but good long-term stability.</p>
		1045	<pre> static void
		1046	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1047	{
		1048	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1049	}
605		1050
		1051	struct ev_periodic hourly_tick;
		1052	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1053	ev_periodic_start (loop, &hourly_tick);
		1054
		1055	</pre>
		1056	<p>Example: the same as above, but use a reschedule callback to do it:</p>
		1057	<pre> #include <math.h>
		1058
		1059	static ev_tstamp
		1060	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1061	{
		1062	return fmod (now, 3600.) + 3600.;
		1063	}
		1064
		1065	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1066
		1067	</pre>
		1068	<p>Example: call a callback every hour, starting now:</p>
		1069	<pre> struct ev_periodic hourly_tick;
		1070	ev_periodic_init (&hourly_tick, clock_cb,
		1071	fmod (ev_now (loop), 3600.), 3600., 0);
		1072	ev_periodic_start (loop, &hourly_tick);
		1073
		1074
		1075
		1076
		1077	</pre>
		1078
606	</div>	1079	</div>
607	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>	1080	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
608	<div id="code_ev_signal_code_signal_me_when_a-2">	1081	<div id="code_ev_signal_code_signal_me_when_a-2">
609	<p>Signal watchers will trigger an event when the process receives a specific	1082	<p>Signal watchers will trigger an event when the process receives a specific
610	signal one or more times. Even though signals are very asynchronous, libev	1083	signal one or more times. Even though signals are very asynchronous, libev
611	will try it's best to deliver signals synchronously, i.e. as part of the	1084	will try it's best to deliver signals synchronously, i.e. as part of the
612	normal event processing, like any other event.</p>	1085	normal event processing, like any other event.</p>
…		…
621	<dt>ev_signal_set (ev_signal *, int signum)</dt>	1094	<dt>ev_signal_set (ev_signal *, int signum)</dt>
622	<dd>	1095	<dd>
623	<p>Configures the watcher to trigger on the given signal number (usually one	1096	<p>Configures the watcher to trigger on the given signal number (usually one
624	of the <code>SIGxxx</code> constants).</p>	1097	of the <code>SIGxxx</code> constants).</p>
625	</dd>	1098	</dd>
		1099	<dt>int signum [read-only]</dt>
		1100	<dd>
		1101	<p>The signal the watcher watches out for.</p>
		1102	</dd>
626	</dl>	1103	</dl>
627		1104
		1105
		1106
		1107
		1108
628	</div>	1109	</div>
629	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>	1110	<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
630	<div id="code_ev_child_code_wait_for_pid_stat-2">	1111	<div id="code_ev_child_code_watch_out_for_pro-2">
631	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1112	<p>Child watchers trigger when your process receives a SIGCHLD in response to
632	some child status changes (most typically when a child of yours dies).</p>	1113	some child status changes (most typically when a child of yours dies).</p>
633	<dl>	1114	<dl>
634	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1115	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
635	<dt>ev_child_set (ev_child *, int pid)</dt>	1116	<dt>ev_child_set (ev_child *, int pid)</dt>
…		…
639	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1120	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
640	the status word (use the macros from <code>sys/wait.h</code> and see your systems	1121	the status word (use the macros from <code>sys/wait.h</code> and see your systems
641	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the	1122	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
642	process causing the status change.</p>	1123	process causing the status change.</p>
643	</dd>	1124	</dd>
		1125	<dt>int pid [read-only]</dt>
		1126	<dd>
		1127	<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
		1128	</dd>
		1129	<dt>int rpid [read-write]</dt>
		1130	<dd>
		1131	<p>The process id that detected a status change.</p>
		1132	</dd>
		1133	<dt>int rstatus [read-write]</dt>
		1134	<dd>
		1135	<p>The process exit/trace status caused by <code>rpid</code> (see your systems
		1136	<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
		1137	</dd>
644	</dl>	1138	</dl>
		1139	<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
		1140	<pre> static void
		1141	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1142	{
		1143	ev_unloop (loop, EVUNLOOP_ALL);
		1144	}
645		1145
		1146	struct ev_signal signal_watcher;
		1147	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1148	ev_signal_start (loop, &sigint_cb);
		1149
		1150
		1151
		1152
		1153	</pre>
		1154
646	</div>	1155	</div>
		1156	<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
		1157	<div id="code_ev_stat_code_did_the_file_attri-2">
		1158	<p>This watches a filesystem path for attribute changes. That is, it calls
		1159	<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
		1160	compared to the last time, invoking the callback if it did.</p>
		1161	<p>The path does not need to exist: changing from "path exists" to "path does
		1162	not exist" is a status change like any other. The condition "path does
		1163	not exist" is signified by the <code>st_nlink</code> field being zero (which is
		1164	otherwise always forced to be at least one) and all the other fields of
		1165	the stat buffer having unspecified contents.</p>
		1166	<p>Since there is no standard to do this, the portable implementation simply
		1167	calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You
		1168	can specify a recommended polling interval for this case. If you specify
		1169	a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
		1170	unspecified default</i> value will be used (which you can expect to be around
		1171	five seconds, although this might change dynamically). Libev will also
		1172	impose a minimum interval which is currently around <code>0.1</code>, but thats
		1173	usually overkill.</p>
		1174	<p>This watcher type is not meant for massive numbers of stat watchers,
		1175	as even with OS-supported change notifications, this can be
		1176	resource-intensive.</p>
		1177	<p>At the time of this writing, no specific OS backends are implemented, but
		1178	if demand increases, at least a kqueue and inotify backend will be added.</p>
		1179	<dl>
		1180	<dt>ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)</dt>
		1181	<dt>ev_stat_set (ev_stat , const char path, ev_tstamp interval)</dt>
		1182	<dd>
		1183	<p>Configures the watcher to wait for status changes of the given
		1184	<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
		1185	be detected and should normally be specified as <code>0</code> to let libev choose
		1186	a suitable value. The memory pointed to by <code>path</code> must point to the same
		1187	path for as long as the watcher is active.</p>
		1188	<p>The callback will be receive <code>EV_STAT</code> when a change was detected,
		1189	relative to the attributes at the time the watcher was started (or the
		1190	last change was detected).</p>
		1191	</dd>
		1192	<dt>ev_stat_stat (ev_stat *)</dt>
		1193	<dd>
		1194	<p>Updates the stat buffer immediately with new values. If you change the
		1195	watched path in your callback, you could call this fucntion to avoid
		1196	detecting this change (while introducing a race condition). Can also be
		1197	useful simply to find out the new values.</p>
		1198	</dd>
		1199	<dt>ev_statdata attr [read-only]</dt>
		1200	<dd>
		1201	<p>The most-recently detected attributes of the file. Although the type is of
		1202	<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
		1203	suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
		1204	was some error while <code>stat</code>ing the file.</p>
		1205	</dd>
		1206	<dt>ev_statdata prev [read-only]</dt>
		1207	<dd>
		1208	<p>The previous attributes of the file. The callback gets invoked whenever
		1209	<code>prev</code> != <code>attr</code>.</p>
		1210	</dd>
		1211	<dt>ev_tstamp interval [read-only]</dt>
		1212	<dd>
		1213	<p>The specified interval.</p>
		1214	</dd>
		1215	<dt>const char *path [read-only]</dt>
		1216	<dd>
		1217	<p>The filesystem path that is being watched.</p>
		1218	</dd>
		1219	</dl>
		1220	<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
		1221	<pre> static void
		1222	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1223	{
		1224	/* /etc/passwd changed in some way */
		1225	if (w->attr.st_nlink)
		1226	{
		1227	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1228	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1229	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1230	}
		1231	else
		1232	/* you shalt not abuse printf for puts */
		1233	puts ("wow, /etc/passwd is not there, expect problems. "
		1234	"if this is windows, they already arrived\n");
		1235	}
		1236
		1237	...
		1238	ev_stat passwd;
		1239
		1240	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1241	ev_stat_start (loop, &passwd);
		1242
		1243
		1244
		1245
		1246	</pre>
		1247
		1248	</div>
647	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>	1249	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
648	<div id="code_ev_idle_code_when_you_ve_got_no-2">	1250	<div id="code_ev_idle_code_when_you_ve_got_no-2">
649	<p>Idle watchers trigger events when there are no other events are pending	1251	<p>Idle watchers trigger events when there are no other events are pending
650	(prepare, check and other idle watchers do not count). That is, as long	1252	(prepare, check and other idle watchers do not count). That is, as long
651	as your process is busy handling sockets or timeouts (or even signals,	1253	as your process is busy handling sockets or timeouts (or even signals,
652	imagine) it will not be triggered. But when your process is idle all idle	1254	imagine) it will not be triggered. But when your process is idle all idle
…		…
665	<p>Initialises and configures the idle watcher - it has no parameters of any	1267	<p>Initialises and configures the idle watcher - it has no parameters of any
666	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1268	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
667	believe me.</p>	1269	believe me.</p>
668	</dd>	1270	</dd>
669	</dl>	1271	</dl>
		1272	<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
		1273	callback, free it. Alos, use no error checking, as usual.</p>
		1274	<pre> static void
		1275	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1276	{
		1277	free (w);
		1278	// now do something you wanted to do when the program has
		1279	// no longer asnything immediate to do.
		1280	}
670		1281
		1282	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1283	ev_idle_init (idle_watcher, idle_cb);
		1284	ev_idle_start (loop, idle_cb);
		1285
		1286
		1287
		1288
		1289	</pre>
		1290
671	</div>	1291	</div>
672	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>	1292	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
673	<div id="code_ev_prepare_code_and_code_ev_che-2">	1293	<div id="code_ev_prepare_code_and_code_ev_che-2">
674	<p>Prepare and check watchers are usually (but not always) used in tandem:	1294	<p>Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	1295	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.</p>	1296	afterwards.</p>
		1297	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1298	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1299	watchers. Other loops than the current one are fine, however. The
		1300	rationale behind this is that you do not need to check for recursion in
		1301	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1302	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1303	called in pairs bracketing the blocking call.</p>
677	<p>Their main purpose is to integrate other event mechanisms into libev. This	1304	<p>Their main purpose is to integrate other event mechanisms into libev and
678	could be used, for example, to track variable changes, implement your own	1305	their use is somewhat advanced. This could be used, for example, to track
679	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1306	variable changes, implement your own watchers, integrate net-snmp or a
		1307	coroutine library and lots more. They are also occasionally useful if
		1308	you cache some data and want to flush it before blocking (for example,
		1309	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1310	watcher).</p>
680	<p>This is done by examining in each prepare call which file descriptors need	1311	<p>This is done by examining in each prepare call which file descriptors need
681	to be watched by the other library, registering <code>ev_io</code> watchers for	1312	to be watched by the other library, registering <code>ev_io</code> watchers for
682	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries	1313	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
683	provide just this functionality). Then, in the check watcher you check for	1314	provide just this functionality). Then, in the check watcher you check for
684	any events that occured (by checking the pending status of all watchers	1315	any events that occured (by checking the pending status of all watchers
685	and stopping them) and call back into the library. The I/O and timer	1316	and stopping them) and call back into the library. The I/O and timer
686	callbacks will never actually be called (but must be valid neverthelles,	1317	callbacks will never actually be called (but must be valid nevertheless,
687	because you never know, you know?).</p>	1318	because you never know, you know?).</p>
688	<p>As another example, the Perl Coro module uses these hooks to integrate	1319	<p>As another example, the Perl Coro module uses these hooks to integrate
689	coroutines into libev programs, by yielding to other active coroutines	1320	coroutines into libev programs, by yielding to other active coroutines
690	during each prepare and only letting the process block if no coroutines	1321	during each prepare and only letting the process block if no coroutines
691	are ready to run (its actually more complicated, it only runs coroutines	1322	are ready to run (it's actually more complicated: it only runs coroutines
692	with priority higher than the event loop and one lower priority once,	1323	with priority higher than or equal to the event loop and one coroutine
693	using idle watchers to keep the event loop from blocking if lower-priority	1324	of lower priority, but only once, using idle watchers to keep the event
694	coroutines exist, thus mapping low-priority coroutines to idle/background	1325	loop from blocking if lower-priority coroutines are active, thus mapping
695	tasks).</p>	1326	low-priority coroutines to idle/background tasks).</p>
696	<dl>	1327	<dl>
697	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1328	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
698	<dt>ev_check_init (ev_check *, callback)</dt>	1329	<dt>ev_check_init (ev_check *, callback)</dt>
699	<dd>	1330	<dd>
700	<p>Initialises and configures the prepare or check watcher - they have no	1331	<p>Initialises and configures the prepare or check watcher - they have no
701	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1332	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
702	macros, but using them is utterly, utterly and completely pointless.</p>	1333	macros, but using them is utterly, utterly and completely pointless.</p>
703	</dd>	1334	</dd>
704	</dl>	1335	</dl>
		1336	<p>Example: To include a library such as adns, you would add IO watchers
		1337	and a timeout watcher in a prepare handler, as required by libadns, and
		1338	in a check watcher, destroy them and call into libadns. What follows is
		1339	pseudo-code only of course:</p>
		1340	<pre> static ev_io iow [nfd];
		1341	static ev_timer tw;
		1342
		1343	static void
		1344	io_cb (ev_loop loop, ev_io w, int revents)
		1345	{
		1346	// set the relevant poll flags
		1347	// could also call adns_processreadable etc. here
		1348	struct pollfd fd = (struct pollfd )w->data;
		1349	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1350	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1351	}
		1352
		1353	// create io watchers for each fd and a timer before blocking
		1354	static void
		1355	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1356	{
		1357	int timeout = 3600000;truct pollfd fds [nfd];
		1358	// actual code will need to loop here and realloc etc.
		1359	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1360
		1361	/* the callback is illegal, but won't be called as we stop during check */
		1362	ev_timer_init (&tw, 0, timeout * 1e-3);
		1363	ev_timer_start (loop, &tw);
		1364
		1365	// create on ev_io per pollfd
		1366	for (int i = 0; i < nfd; ++i)
		1367	{
		1368	ev_io_init (iow + i, io_cb, fds [i].fd,
		1369	((fds [i].events & POLLIN ? EV_READ : 0)
		1370	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1371
		1372	fds [i].revents = 0;
		1373	iow [i].data = fds + i;
		1374	ev_io_start (loop, iow + i);
		1375	}
		1376	}
		1377
		1378	// stop all watchers after blocking
		1379	static void
		1380	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1381	{
		1382	ev_timer_stop (loop, &tw);
		1383
		1384	for (int i = 0; i < nfd; ++i)
		1385	ev_io_stop (loop, iow + i);
		1386
		1387	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1388	}
		1389
		1390
		1391
		1392
		1393	</pre>
		1394
		1395	</div>
		1396	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1397	<div id="code_ev_embed_code_when_one_backend_-2">
		1398	<p>This is a rather advanced watcher type that lets you embed one event loop
		1399	into another (currently only <code>ev_io</code> events are supported in the embedded
		1400	loop, other types of watchers might be handled in a delayed or incorrect
		1401	fashion and must not be used).</p>
		1402	<p>There are primarily two reasons you would want that: work around bugs and
		1403	prioritise I/O.</p>
		1404	<p>As an example for a bug workaround, the kqueue backend might only support
		1405	sockets on some platform, so it is unusable as generic backend, but you
		1406	still want to make use of it because you have many sockets and it scales
		1407	so nicely. In this case, you would create a kqueue-based loop and embed it
		1408	into your default loop (which might use e.g. poll). Overall operation will
		1409	be a bit slower because first libev has to poll and then call kevent, but
		1410	at least you can use both at what they are best.</p>
		1411	<p>As for prioritising I/O: rarely you have the case where some fds have
		1412	to be watched and handled very quickly (with low latency), and even
		1413	priorities and idle watchers might have too much overhead. In this case
		1414	you would put all the high priority stuff in one loop and all the rest in
		1415	a second one, and embed the second one in the first.</p>
		1416	<p>As long as the watcher is active, the callback will be invoked every time
		1417	there might be events pending in the embedded loop. The callback must then
		1418	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1419	their callbacks (you could also start an idle watcher to give the embedded
		1420	loop strictly lower priority for example). You can also set the callback
		1421	to <code>0</code>, in which case the embed watcher will automatically execute the
		1422	embedded loop sweep.</p>
		1423	<p>As long as the watcher is started it will automatically handle events. The
		1424	callback will be invoked whenever some events have been handled. You can
		1425	set the callback to <code>0</code> to avoid having to specify one if you are not
		1426	interested in that.</p>
		1427	<p>Also, there have not currently been made special provisions for forking:
		1428	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1429	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1430	yourself.</p>
		1431	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1432	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1433	portable one.</p>
		1434	<p>So when you want to use this feature you will always have to be prepared
		1435	that you cannot get an embeddable loop. The recommended way to get around
		1436	this is to have a separate variables for your embeddable loop, try to
		1437	create it, and if that fails, use the normal loop for everything:</p>
		1438	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1439	struct ev_loop *loop_lo = 0;
		1440	struct ev_embed embed;
		1441
		1442	// see if there is a chance of getting one that works
		1443	// (remember that a flags value of 0 means autodetection)
		1444	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1445	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1446	: 0;
		1447
		1448	// if we got one, then embed it, otherwise default to loop_hi
		1449	if (loop_lo)
		1450	{
		1451	ev_embed_init (&embed, 0, loop_lo);
		1452	ev_embed_start (loop_hi, &embed);
		1453	}
		1454	else
		1455	loop_lo = loop_hi;
		1456
		1457	</pre>
		1458	<dl>
		1459	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1460	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1461	<dd>
		1462	<p>Configures the watcher to embed the given loop, which must be
		1463	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1464	invoked automatically, otherwise it is the responsibility of the callback
		1465	to invoke it (it will continue to be called until the sweep has been done,
		1466	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1467	</dd>
		1468	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1469	<dd>
		1470	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1471	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1472	apropriate way for embedded loops.</p>
		1473	</dd>
		1474	<dt>struct ev_loop *loop [read-only]</dt>
		1475	<dd>
		1476	<p>The embedded event loop.</p>
		1477	</dd>
		1478	</dl>
		1479
		1480
		1481
		1482
705		1483
706	</div>	1484	</div>
707	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1485	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
708	<div id="OTHER_FUNCTIONS_CONTENT">	1486	<div id="OTHER_FUNCTIONS_CONTENT">
709	<p>There are some other functions of possible interest. Described. Here. Now.</p>	1487	<p>There are some other functions of possible interest. Described. Here. Now.</p>
…		…
711	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1489	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712	<dd>	1490	<dd>
713	<p>This function combines a simple timer and an I/O watcher, calls your	1491	<p>This function combines a simple timer and an I/O watcher, calls your
714	callback on whichever event happens first and automatically stop both	1492	callback on whichever event happens first and automatically stop both
715	watchers. This is useful if you want to wait for a single event on an fd	1493	watchers. This is useful if you want to wait for a single event on an fd
716	or timeout without havign to allocate/configure/start/stop/free one or	1494	or timeout without having to allocate/configure/start/stop/free one or
717	more watchers yourself.</p>	1495	more watchers yourself.</p>
718	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events	1496	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
719	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and	1497	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
720	<code>events</code> set will be craeted and started.</p>	1498	<code>events</code> set will be craeted and started.</p>
721	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1499	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
722	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and	1500	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
723	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of	1501	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724	dubious value.</p>	1502	dubious value.</p>
725	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets	1503	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
726	passed an events set like normal event callbacks (with a combination of	1504	passed an <code>revents</code> set like normal event callbacks (a combination of
727	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>	1505	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
728	value passed to <code>ev_once</code>:</p>	1506	value passed to <code>ev_once</code>:</p>
729	<pre> static void stdin_ready (int revents, void *arg)	1507	<pre> static void stdin_ready (int revents, void *arg)
730	{	1508	{
731	if (revents & EV_TIMEOUT)	1509	if (revents & EV_TIMEOUT)
…		…
736		1514
737	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1515	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738		1516
739	</pre>	1517	</pre>
740	</dd>	1518	</dd>
741	<dt>ev_feed_event (loop, watcher, int events)</dt>	1519	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
742	<dd>	1520	<dd>
743	<p>Feeds the given event set into the event loop, as if the specified event	1521	<p>Feeds the given event set into the event loop, as if the specified event
744	had happened for the specified watcher (which must be a pointer to an	1522	had happened for the specified watcher (which must be a pointer to an
745	initialised but not necessarily started event watcher).</p>	1523	initialised but not necessarily started event watcher).</p>
746	</dd>	1524	</dd>
747	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1525	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
748	<dd>	1526	<dd>
749	<p>Feed an event on the given fd, as if a file descriptor backend detected	1527	<p>Feed an event on the given fd, as if a file descriptor backend detected
750	the given events it.</p>	1528	the given events it.</p>
751	</dd>	1529	</dd>
752	<dt>ev_feed_signal_event (loop, int signum)</dt>	1530	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
753	<dd>	1531	<dd>
754	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1532	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1533	loop!).</p>
755	</dd>	1534	</dd>
756	</dl>	1535	</dl>
		1536
		1537
		1538
		1539
		1540
		1541	</div>
		1542	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1543	<div id="LIBEVENT_EMULATION_CONTENT">
		1544	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1545	emulate the internals of libevent, so here are some usage hints:</p>
		1546	<dl>
		1547	<dt>* Use it by including <event.h>, as usual.</dt>
		1548	<dt>* The following members are fully supported: ev_base, ev_callback,
		1549	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1550	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1551	maintained by libev, it does not work exactly the same way as in libevent (consider
		1552	it a private API).</dt>
		1553	<dt>* Priorities are not currently supported. Initialising priorities
		1554	will fail and all watchers will have the same priority, even though there
		1555	is an ev_pri field.</dt>
		1556	<dt>* Other members are not supported.</dt>
		1557	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1558	to use the libev header file and library.</dt>
		1559	</dl>
		1560
		1561	</div>
		1562	<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1563	<div id="C_SUPPORT_CONTENT">
		1564	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1565	you to use some convinience methods to start/stop watchers and also change
		1566	the callback model to a model using method callbacks on objects.</p>
		1567	<p>To use it,</p>
		1568	<pre> #include <ev++.h>
		1569
		1570	</pre>
		1571	<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
		1572	and puts all of its definitions (many of them macros) into the global
		1573	namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
		1574	<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
		1575	<code>EV_MULTIPLICITY</code>.</p>
		1576	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1577	<dl>
		1578	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1579	<dd>
		1580	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1581	macros from <cite>ev.h</cite>.</p>
		1582	</dd>
		1583	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1584	<dd>
		1585	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1586	</dd>
		1587	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1588	<dd>
		1589	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1590	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1591	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1592	defines by many implementations.</p>
		1593	<p>All of those classes have these methods:</p>
		1594	<p>
		1595	<dl>
		1596	<dt>ev::TYPE::TYPE (object , object::method )</dt>
		1597	<dt>ev::TYPE::TYPE (object , object::method , struct ev_loop *)</dt>
		1598	<dt>ev::TYPE::~TYPE</dt>
		1599	<dd>
		1600	<p>The constructor takes a pointer to an object and a method pointer to
		1601	the event handler callback to call in this class. The constructor calls
		1602	<code>ev_init</code> for you, which means you have to call the <code>set</code> method
		1603	before starting it. If you do not specify a loop then the constructor
		1604	automatically associates the default loop with this watcher.</p>
		1605	<p>The destructor automatically stops the watcher if it is active.</p>
		1606	</dd>
		1607	<dt>w->set (struct ev_loop *)</dt>
		1608	<dd>
		1609	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1610	do this when the watcher is inactive (and not pending either).</p>
		1611	</dd>
		1612	<dt>w->set ([args])</dt>
		1613	<dd>
		1614	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1615	called at least once. Unlike the C counterpart, an active watcher gets
		1616	automatically stopped and restarted.</p>
		1617	</dd>
		1618	<dt>w->start ()</dt>
		1619	<dd>
		1620	<p>Starts the watcher. Note that there is no <code>loop</code> argument as the
		1621	constructor already takes the loop.</p>
		1622	</dd>
		1623	<dt>w->stop ()</dt>
		1624	<dd>
		1625	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1626	</dd>
		1627	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1628	<dd>
		1629	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1630	<code>ev_TYPE_again</code> function.</p>
		1631	</dd>
		1632	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1633	<dd>
		1634	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1635	</dd>
		1636	</dl>
		1637	</p>
		1638	</dd>
		1639	</dl>
		1640	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1641	the constructor.</p>
		1642	<pre> class myclass
		1643	{
		1644	ev_io io; void io_cb (ev::io &w, int revents);
		1645	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1646
		1647	myclass ();
		1648	}
		1649
		1650	myclass::myclass (int fd)
		1651	: io (this, &myclass::io_cb),
		1652	idle (this, &myclass::idle_cb)
		1653	{
		1654	io.start (fd, ev::READ);
		1655	}
		1656
		1657	</pre>
		1658
		1659	</div>
		1660	<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1661	<div id="EMBEDDING_CONTENT">
		1662	<p>Libev can (and often is) directly embedded into host
		1663	applications. Examples of applications that embed it include the Deliantra
		1664	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1665	and rxvt-unicode.</p>
		1666	<p>The goal is to enable you to just copy the neecssary files into your
		1667	source directory without having to change even a single line in them, so
		1668	you can easily upgrade by simply copying (or having a checked-out copy of
		1669	libev somewhere in your source tree).</p>
		1670
		1671	</div>
		1672	<h2 id="FILESETS">FILESETS</h2>
		1673	<div id="FILESETS_CONTENT">
		1674	<p>Depending on what features you need you need to include one or more sets of files
		1675	in your app.</p>
		1676
		1677	</div>
		1678	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		1679	<div id="CORE_EVENT_LOOP_CONTENT">
		1680	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		1681	configuration (no autoconf):</p>
		1682	<pre> #define EV_STANDALONE 1
		1683	#include "ev.c"
		1684
		1685	</pre>
		1686	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		1687	single C source file only to provide the function implementations. To use
		1688	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		1689	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		1690	where you can put other configuration options):</p>
		1691	<pre> #define EV_STANDALONE 1
		1692	#include "ev.h"
		1693
		1694	</pre>
		1695	<p>Both header files and implementation files can be compiled with a C++
		1696	compiler (at least, thats a stated goal, and breakage will be treated
		1697	as a bug).</p>
		1698	<p>You need the following files in your source tree, or in a directory
		1699	in your include path (e.g. in libev/ when using -Ilibev):</p>
		1700	<pre> ev.h
		1701	ev.c
		1702	ev_vars.h
		1703	ev_wrap.h
		1704
		1705	ev_win32.c required on win32 platforms only
		1706
		1707	ev_select.c only when select backend is enabled (which is by default)
		1708	ev_poll.c only when poll backend is enabled (disabled by default)
		1709	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1710	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1711	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1712
		1713	</pre>
		1714	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		1715	to compile this single file.</p>
		1716
		1717	</div>
		1718	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		1719	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		1720	<p>To include the libevent compatibility API, also include:</p>
		1721	<pre> #include "event.c"
		1722
		1723	</pre>
		1724	<p>in the file including <cite>ev.c</cite>, and:</p>
		1725	<pre> #include "event.h"
		1726
		1727	</pre>
		1728	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		1729	<p>You need the following additional files for this:</p>
		1730	<pre> event.h
		1731	event.c
		1732
		1733	</pre>
		1734
		1735	</div>
		1736	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		1737	<div id="AUTOCONF_SUPPORT_CONTENT">
		1738	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		1739	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		1740	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		1741	include <cite>config.h</cite> and configure itself accordingly.</p>
		1742	<p>For this of course you need the m4 file:</p>
		1743	<pre> libev.m4
		1744
		1745	</pre>
		1746
		1747	</div>
		1748	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		1749	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		1750	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		1751	before including any of its files. The default is not to build for multiplicity
		1752	and only include the select backend.</p>
		1753	<dl>
		1754	<dt>EV_STANDALONE</dt>
		1755	<dd>
		1756	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		1757	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		1758	implementations for some libevent functions (such as logging, which is not
		1759	supported). It will also not define any of the structs usually found in
		1760	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		1761	</dd>
		1762	<dt>EV_USE_MONOTONIC</dt>
		1763	<dd>
		1764	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1765	monotonic clock option at both compiletime and runtime. Otherwise no use
		1766	of the monotonic clock option will be attempted. If you enable this, you
		1767	usually have to link against librt or something similar. Enabling it when
		1768	the functionality isn't available is safe, though, althoguh you have
		1769	to make sure you link against any libraries where the <code>clock_gettime</code>
		1770	function is hiding in (often <cite>-lrt</cite>).</p>
		1771	</dd>
		1772	<dt>EV_USE_REALTIME</dt>
		1773	<dd>
		1774	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1775	realtime clock option at compiletime (and assume its availability at
		1776	runtime if successful). Otherwise no use of the realtime clock option will
		1777	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		1778	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		1779	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		1780	</dd>
		1781	<dt>EV_USE_SELECT</dt>
		1782	<dd>
		1783	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		1784	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		1785	other method takes over, select will be it. Otherwise the select backend
		1786	will not be compiled in.</p>
		1787	</dd>
		1788	<dt>EV_SELECT_USE_FD_SET</dt>
		1789	<dd>
		1790	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		1791	structure. This is useful if libev doesn't compile due to a missing
		1792	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		1793	exotic systems. This usually limits the range of file descriptors to some
		1794	low limit such as 1024 or might have other limitations (winsocket only
		1795	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		1796	influence the size of the <code>fd_set</code> used.</p>
		1797	</dd>
		1798	<dt>EV_SELECT_IS_WINSOCKET</dt>
		1799	<dd>
		1800	<p>When defined to <code>1</code>, the select backend will assume that
		1801	select/socket/connect etc. don't understand file descriptors but
		1802	wants osf handles on win32 (this is the case when the select to
		1803	be used is the winsock select). This means that it will call
		1804	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		1805	it is assumed that all these functions actually work on fds, even
		1806	on win32. Should not be defined on non-win32 platforms.</p>
		1807	</dd>
		1808	<dt>EV_USE_POLL</dt>
		1809	<dd>
		1810	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		1811	backend. Otherwise it will be enabled on non-win32 platforms. It
		1812	takes precedence over select.</p>
		1813	</dd>
		1814	<dt>EV_USE_EPOLL</dt>
		1815	<dd>
		1816	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		1817	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		1818	otherwise another method will be used as fallback. This is the
		1819	preferred backend for GNU/Linux systems.</p>
		1820	</dd>
		1821	<dt>EV_USE_KQUEUE</dt>
		1822	<dd>
		1823	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		1824	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		1825	otherwise another method will be used as fallback. This is the preferred
		1826	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		1827	supports some types of fds correctly (the only platform we found that
		1828	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		1829	not be used unless explicitly requested. The best way to use it is to find
		1830	out whether kqueue supports your type of fd properly and use an embedded
		1831	kqueue loop.</p>
		1832	</dd>
		1833	<dt>EV_USE_PORT</dt>
		1834	<dd>
		1835	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		1836	10 port style backend. Its availability will be detected at runtime,
		1837	otherwise another method will be used as fallback. This is the preferred
		1838	backend for Solaris 10 systems.</p>
		1839	</dd>
		1840	<dt>EV_USE_DEVPOLL</dt>
		1841	<dd>
		1842	<p>reserved for future expansion, works like the USE symbols above.</p>
		1843	</dd>
		1844	<dt>EV_H</dt>
		1845	<dd>
		1846	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		1847	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		1848	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		1849	</dd>
		1850	<dt>EV_CONFIG_H</dt>
		1851	<dd>
		1852	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		1853	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		1854	<code>EV_H</code>, above.</p>
		1855	</dd>
		1856	<dt>EV_EVENT_H</dt>
		1857	<dd>
		1858	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		1859	of how the <cite>event.h</cite> header can be found.</p>
		1860	</dd>
		1861	<dt>EV_PROTOTYPES</dt>
		1862	<dd>
		1863	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		1864	prototypes, but still define all the structs and other symbols. This is
		1865	occasionally useful if you want to provide your own wrapper functions
		1866	around libev functions.</p>
		1867	</dd>
		1868	<dt>EV_MULTIPLICITY</dt>
		1869	<dd>
		1870	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		1871	will have the <code>struct ev_loop *</code> as first argument, and you can create
		1872	additional independent event loops. Otherwise there will be no support
		1873	for multiple event loops and there is no first event loop pointer
		1874	argument. Instead, all functions act on the single default loop.</p>
		1875	</dd>
		1876	<dt>EV_PERIODIC_ENABLE</dt>
		1877	<dd>
		1878	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
		1879	defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
		1880	code.</p>
		1881	</dd>
		1882	<dt>EV_EMBED_ENABLE</dt>
		1883	<dd>
		1884	<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
		1885	defined to be <code>0</code>, then they are not.</p>
		1886	</dd>
		1887	<dt>EV_STAT_ENABLE</dt>
		1888	<dd>
		1889	<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
		1890	defined to be <code>0</code>, then they are not.</p>
		1891	</dd>
		1892	<dt>EV_MINIMAL</dt>
		1893	<dd>
		1894	<p>If you need to shave off some kilobytes of code at the expense of some
		1895	speed, define this symbol to <code>1</code>. Currently only used for gcc to override
		1896	some inlining decisions, saves roughly 30% codesize of amd64.</p>
		1897	</dd>
		1898	<dt>EV_COMMON</dt>
		1899	<dd>
		1900	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		1901	this macro to a something else you can include more and other types of
		1902	members. You have to define it each time you include one of the files,
		1903	though, and it must be identical each time.</p>
		1904	<p>For example, the perl EV module uses something like this:</p>
		1905	<pre> #define EV_COMMON \
		1906	SV self; / contains this struct */ \
		1907	SV cb_sv, fh /* note no trailing ";" */
		1908
		1909	</pre>
		1910	</dd>
		1911	<dt>EV_CB_DECLARE (type)</dt>
		1912	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		1913	<dt>ev_set_cb (ev, cb)</dt>
		1914	<dd>
		1915	<p>Can be used to change the callback member declaration in each watcher,
		1916	and the way callbacks are invoked and set. Must expand to a struct member
		1917	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		1918	their default definitions. One possible use for overriding these is to
		1919	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		1920	method calls instead of plain function calls in C++.</p>
		1921
		1922	</div>
		1923	<h2 id="EXAMPLES">EXAMPLES</h2>
		1924	<div id="EXAMPLES_CONTENT">
		1925	<p>For a real-world example of a program the includes libev
		1926	verbatim, you can have a look at the EV perl module
		1927	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		1928	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		1929	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		1930	will be compiled. It is pretty complex because it provides its own header
		1931	file.</p>
		1932	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		1933	that everybody includes and which overrides some autoconf choices:</p>
		1934	<pre> #define EV_USE_POLL 0
		1935	#define EV_MULTIPLICITY 0
		1936	#define EV_PERIODICS 0
		1937	#define EV_CONFIG_H <config.h>
		1938
		1939	#include "ev++.h"
		1940
		1941	</pre>
		1942	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		1943	<pre> #include "ev_cpp.h"
		1944	#include "ev.c"
		1945
		1946
		1947
		1948
		1949	</pre>
		1950
		1951	</div>
		1952	<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1953	<div id="COMPLEXITIES_CONTENT">
		1954	<p>In this section the complexities of (many of) the algorithms used inside
		1955	libev will be explained. For complexity discussions about backends see the
		1956	documentation for <code>ev_default_init</code>.</p>
		1957	<p>
		1958	<dl>
		1959	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		1960	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		1961	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		1962	<dt>Stopping check/prepare/idle watchers: O(1)</dt>
		1963	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
		1964	<dt>Finding the next timer per loop iteration: O(1)</dt>
		1965	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		1966	<dt>Activating one watcher: O(1)</dt>
		1967	</dl>
		1968	</p>
		1969
		1970
		1971
		1972
757		1973
758	</div>	1974	</div>
759	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1975	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
760	<div id="AUTHOR_CONTENT">	1976	<div id="AUTHOR_CONTENT">
761	<p>Marc Lehmann <libev@schmorp.de>.</p>	1977	<p>Marc Lehmann <libev@schmorp.de>.</p>
762		1978
763	</div>	1979	</div>
764	</div></body>	1980	</div></body>
765	</html>	1981	</html>

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Revision 1.48 by root, Tue Nov 27 08:11:52 2007 UTC