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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 09:16:01 2007" />	9	<meta name="created" content="Mon Nov 26 11:20:35 2007" />
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12	<body>	12	<body>
13	<div class="pod">	13	<div class="pod">
14	<!-- INDEX START -->	14	<!-- INDEX START -->
…		…
17	<ul><li><a href="#NAME">NAME</a></li>	17	<ul><li><a href="#NAME">NAME</a></li>
18	<li><a href="#SYNOPSIS">SYNOPSIS</a></li>	18	<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19	<li><a href="#DESCRIPTION">DESCRIPTION</a></li>	19	<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20	<li><a href="#FEATURES">FEATURES</a></li>	20	<li><a href="#FEATURES">FEATURES</a></li>
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_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li>	23	<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
23	<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>
24	<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>
25	<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>
26	</ul>	28	</ul>
27	</li>	29	</li>
28	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>	30	<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
29	<ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my 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>
30	<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - 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>
31	<li><a href="#ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</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>
32	<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - 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>
33	<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - 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>
34	<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li>	36	<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
35	<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li>	37	<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
		38	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
36	</ul>	39	</ul>
37	</li>	40	</li>
38	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	41	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
		42	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
		43	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
		44	<li><a href="#EMBEDDING">EMBEDDING</a>
		45	<ul><li><a href="#FILESETS">FILESETS</a>
		46	<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
		47	<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
		48	<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
		49	</ul>
		50	</li>
		51	<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
		52	<li><a href="#EXAMPLES">EXAMPLES</a></li>
		53	</ul>
		54	</li>
		55	<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
39	<li><a href="#AUTHOR">AUTHOR</a>	56	<li><a href="#AUTHOR">AUTHOR</a>
40	</li>	57	</li>
41	</ul><hr />	58	</ul><hr />
42	<!-- INDEX END -->	59	<!-- INDEX END -->
43		60
…		…
87	support for multiple event loops, then all functions taking an initial	104	support for multiple event loops, then all functions taking an initial
88	argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)	105	argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
89	will not have this argument.</p>	106	will not have this argument.</p>
90		107
91	</div>	108	</div>
92	<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	109	<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
93	<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT">	110	<div id="TIME_REPRESENTATION_CONTENT">
94	<p>Libev represents time as a single floating point number, representing the	111	<p>Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	112	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	the beginning of 1970, details are complicated, don't ask). This type is	113	the beginning of 1970, details are complicated, don't ask). This type is
97	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	114	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
98	to the double type in C.</p>	115	to the <code>double</code> type in C, and when you need to do any calculations on
		116	it, you should treat it as such.</p>
		117
		118
		119
		120
		121
		122	</div>
		123	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
		124	<div id="GLOBAL_FUNCTIONS_CONTENT">
		125	<p>These functions can be called anytime, even before initialising the
		126	library in any way.</p>
99	<dl>	127	<dl>
100	<dt>ev_tstamp ev_time ()</dt>	128	<dt>ev_tstamp ev_time ()</dt>
101	<dd>	129	<dd>
102	<p>Returns the current time as libev would use it.</p>	130	<p>Returns the current time as libev would use it. Please note that the
		131	<code>ev_now</code> function is usually faster and also often returns the timestamp
		132	you actually want to know.</p>
103	</dd>	133	</dd>
104	<dt>int ev_version_major ()</dt>	134	<dt>int ev_version_major ()</dt>
105	<dt>int ev_version_minor ()</dt>	135	<dt>int ev_version_minor ()</dt>
106	<dd>	136	<dd>
107	<p>You can find out the major and minor version numbers of the library	137	<p>You can find out the major and minor version numbers of the library
108	you linked against by calling the functions <code>ev_version_major</code> and	138	you linked against by calling the functions <code>ev_version_major</code> and
109	<code>ev_version_minor</code>. If you want, you can compare against the global	139	<code>ev_version_minor</code>. If you want, you can compare against the global
110	symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the	140	symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
111	version of the library your program was compiled against.</p>	141	version of the library your program was compiled against.</p>
112	<p>Usually, its a good idea to terminate if the major versions mismatch,	142	<p>Usually, it's a good idea to terminate if the major versions mismatch,
113	as this indicates an incompatible change. Minor versions are usually	143	as this indicates an incompatible change. Minor versions are usually
114	compatible to older versions, so a larger minor version alone is usually	144	compatible to older versions, so a larger minor version alone is usually
115	not a problem.</p>	145	not a problem.</p>
		146	<p>Example: make sure we haven't accidentally been linked against the wrong
		147	version:</p>
		148	<pre> assert (("libev version mismatch",
		149	ev_version_major () == EV_VERSION_MAJOR
		150	&& ev_version_minor () >= EV_VERSION_MINOR));
		151
		152	</pre>
		153	</dd>
		154	<dt>unsigned int ev_supported_backends ()</dt>
		155	<dd>
		156	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		157	value) compiled into this binary of libev (independent of their
		158	availability on the system you are running on). See <code>ev_default_loop</code> for
		159	a description of the set values.</p>
		160	<p>Example: make sure we have the epoll method, because yeah this is cool and
		161	a must have and can we have a torrent of it please!!!11</p>
		162	<pre> assert (("sorry, no epoll, no sex",
		163	ev_supported_backends () & EVBACKEND_EPOLL));
		164
		165	</pre>
		166	</dd>
		167	<dt>unsigned int ev_recommended_backends ()</dt>
		168	<dd>
		169	<p>Return the set of all backends compiled into this binary of libev and also
		170	recommended for this platform. This set is often smaller than the one
		171	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		172	most BSDs and will not be autodetected unless you explicitly request it
		173	(assuming you know what you are doing). This is the set of backends that
		174	libev will probe for if you specify no backends explicitly.</p>
		175	</dd>
		176	<dt>unsigned int ev_embeddable_backends ()</dt>
		177	<dd>
		178	<p>Returns the set of backends that are embeddable in other event loops. This
		179	is the theoretical, all-platform, value. To find which backends
		180	might be supported on the current system, you would need to look at
		181	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		182	recommended ones.</p>
		183	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
116	</dd>	184	</dd>
117	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	185	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
118	<dd>	186	<dd>
119	<p>Sets the allocation function to use (the prototype is similar to the	187	<p>Sets the allocation function to use (the prototype is similar to the
120	realloc C function, the semantics are identical). It is used to allocate	188	realloc C function, the semantics are identical). It is used to allocate
…		…
122	needs to be allocated, the library might abort or take some potentially	190	needs to be allocated, the library might abort or take some potentially
123	destructive action. The default is your system realloc function.</p>	191	destructive action. The default is your system realloc function.</p>
124	<p>You could override this function in high-availability programs to, say,	192	<p>You could override this function in high-availability programs to, say,
125	free some memory if it cannot allocate memory, to use a special allocator,	193	free some memory if it cannot allocate memory, to use a special allocator,
126	or even to sleep a while and retry until some memory is available.</p>	194	or even to sleep a while and retry until some memory is available.</p>
		195	<p>Example: replace the libev allocator with one that waits a bit and then
		196	retries: better than mine).</p>
		197	<pre> static void *
		198	persistent_realloc (void *ptr, long size)
		199	{
		200	for (;;)
		201	{
		202	void *newptr = realloc (ptr, size);
		203
		204	if (newptr)
		205	return newptr;
		206
		207	sleep (60);
		208	}
		209	}
		210
		211	...
		212	ev_set_allocator (persistent_realloc);
		213
		214	</pre>
127	</dd>	215	</dd>
128	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	216	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
129	<dd>	217	<dd>
130	<p>Set the callback function to call on a retryable syscall error (such	218	<p>Set the callback function to call on a retryable syscall error (such
131	as failed select, poll, epoll_wait). The message is a printable string	219	as failed select, poll, epoll_wait). The message is a printable string
132	indicating the system call or subsystem causing the problem. If this	220	indicating the system call or subsystem causing the problem. If this
133	callback is set, then libev will expect it to remedy the sitution, no	221	callback is set, then libev will expect it to remedy the sitution, no
134	matter what, when it returns. That is, libev will generally retry the	222	matter what, when it returns. That is, libev will generally retry the
135	requested operation, or, if the condition doesn't go away, do bad stuff	223	requested operation, or, if the condition doesn't go away, do bad stuff
136	(such as abort).</p>	224	(such as abort).</p>
		225	<p>Example: do the same thing as libev does internally:</p>
		226	<pre> static void
		227	fatal_error (const char *msg)
		228	{
		229	perror (msg);
		230	abort ();
		231	}
		232
		233	...
		234	ev_set_syserr_cb (fatal_error);
		235
		236	</pre>
137	</dd>	237	</dd>
138	</dl>	238	</dl>
139		239
140	</div>	240	</div>
141	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	241	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
142	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">	242	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
143	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two	243	<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
144	types of such loops, the <i>default</i> loop, which supports signals and child	244	types of such loops, the <i>default</i> loop, which supports signals and child
145	events, and dynamically created loops which do not.</p>	245	events, and dynamically created loops which do not.</p>
146	<p>If you use threads, a common model is to run the default event loop	246	<p>If you use threads, a common model is to run the default event loop
147	in your main thread (or in a separate thrad) and for each thread you	247	in your main thread (or in a separate thread) and for each thread you
148	create, you also create another event loop. Libev itself does no locking	248	create, you also create another event loop. Libev itself does no locking
149	whatsoever, so if you mix calls to the same event loop in different	249	whatsoever, so if you mix calls to the same event loop in different
150	threads, make sure you lock (this is usually a bad idea, though, even if	250	threads, make sure you lock (this is usually a bad idea, though, even if
151	done correctly, because its hideous and inefficient).</p>	251	done correctly, because it's hideous and inefficient).</p>
152	<dl>	252	<dl>
153	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	253	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
154	<dd>	254	<dd>
155	<p>This will initialise the default event loop if it hasn't been initialised	255	<p>This will initialise the default event loop if it hasn't been initialised
156	yet and return it. If the default loop could not be initialised, returns	256	yet and return it. If the default loop could not be initialised, returns
157	false. If it already was initialised it simply returns it (and ignores the	257	false. If it already was initialised it simply returns it (and ignores the
158	flags).</p>	258	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
159	<p>If you don't know what event loop to use, use the one returned from this	259	<p>If you don't know what event loop to use, use the one returned from this
160	function.</p>	260	function.</p>
161	<p>The flags argument can be used to specify special behaviour or specific	261	<p>The flags argument can be used to specify special behaviour or specific
162	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p>	262	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
163	<p>It supports the following flags:</p>	263	<p>The following flags are supported:</p>
164	<p>	264	<p>
165	<dl>	265	<dl>
166	<dt>EVFLAG_AUTO</dt>	266	<dt><code>EVFLAG_AUTO</code></dt>
167	<dd>	267	<dd>
168	<p>The default flags value. Use this if you have no clue (its the right	268	<p>The default flags value. Use this if you have no clue (it's the right
169	thing, believe me).</p>	269	thing, believe me).</p>
170	</dd>	270	</dd>
171	<dt>EVFLAG_NOENV</dt>	271	<dt><code>EVFLAG_NOENV</code></dt>
172	<dd>
173	<p>If this flag bit is ored into the flag value then libev will <i>not</i> look
174	at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this
175	environment variable will override the flags completely. This is useful
176	to try out specific backends to tets their performance, or to work around
177	bugs.</p>
178	</dd>	272	<dd>
179	<dt>EVMETHOD_SELECT portable select backend</dt>	273	<p>If this flag bit is ored into the flag value (or the program runs setuid
180	<dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt>	274	or setgid) then libev will <i>not</i> look at the environment variable
181	<dt>EVMETHOD_EPOLL linux only</dt>	275	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
182	<dt>EVMETHOD_KQUEUE some bsds only</dt>	276	override the flags completely if it is found in the environment. This is
183	<dt>EVMETHOD_DEVPOLL solaris 8 only</dt>	277	useful to try out specific backends to test their performance, or to work
184	<dt>EVMETHOD_PORT solaris 10 only</dt>	278	around bugs.</p>
185	<dd>	279	</dd>
186	<p>If one or more of these are ored into the flags value, then only these	280	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
187	backends will be tried (in the reverse order as given here). If one are	281	<dd>
188	specified, any backend will do.</p>	282	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
		283	libev tries to roll its own fd_set with no limits on the number of fds,
		284	but if that fails, expect a fairly low limit on the number of fds when
		285	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		286	the fastest backend for a low number of fds.</p>
		287	</dd>
		288	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		289	<dd>
		290	<p>And this is your standard poll(2) backend. It's more complicated than
		291	select, but handles sparse fds better and has no artificial limit on the
		292	number of fds you can use (except it will slow down considerably with a
		293	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		294	</dd>
		295	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		296	<dd>
		297	<p>For few fds, this backend is a bit little slower than poll and select,
		298	but it scales phenomenally better. While poll and select usually scale like
		299	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		300	either O(1) or O(active_fds).</p>
		301	<p>While stopping and starting an I/O watcher in the same iteration will
		302	result in some caching, there is still a syscall per such incident
		303	(because the fd could point to a different file description now), so its
		304	best to avoid that. Also, dup()ed file descriptors might not work very
		305	well if you register events for both fds.</p>
		306	<p>Please note that epoll sometimes generates spurious notifications, so you
		307	need to use non-blocking I/O or other means to avoid blocking when no data
		308	(or space) is available.</p>
		309	</dd>
		310	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		311	<dd>
		312	<p>Kqueue deserves special mention, as at the time of this writing, it
		313	was broken on all BSDs except NetBSD (usually it doesn't work with
		314	anything but sockets and pipes, except on Darwin, where of course its
		315	completely useless). For this reason its not being "autodetected"
		316	unless you explicitly specify it explicitly in the flags (i.e. using
		317	<code>EVBACKEND_KQUEUE</code>).</p>
		318	<p>It scales in the same way as the epoll backend, but the interface to the
		319	kernel is more efficient (which says nothing about its actual speed, of
		320	course). While starting and stopping an I/O watcher does not cause an
		321	extra syscall as with epoll, it still adds up to four event changes per
		322	incident, so its best to avoid that.</p>
		323	</dd>
		324	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		325	<dd>
		326	<p>This is not implemented yet (and might never be).</p>
		327	</dd>
		328	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		329	<dd>
		330	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		331	it's really slow, but it still scales very well (O(active_fds)).</p>
		332	<p>Please note that solaris ports can result in a lot of spurious
		333	notifications, so you need to use non-blocking I/O or other means to avoid
		334	blocking when no data (or space) is available.</p>
		335	</dd>
		336	<dt><code>EVBACKEND_ALL</code></dt>
		337	<dd>
		338	<p>Try all backends (even potentially broken ones that wouldn't be tried
		339	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		340	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
189	</dd>	341	</dd>
190	</dl>	342	</dl>
191	</p>	343	</p>
		344	<p>If one or more of these are ored into the flags value, then only these
		345	backends will be tried (in the reverse order as given here). If none are
		346	specified, most compiled-in backend will be tried, usually in reverse
		347	order of their flag values :)</p>
		348	<p>The most typical usage is like this:</p>
		349	<pre> if (!ev_default_loop (0))
		350	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		351
		352	</pre>
		353	<p>Restrict libev to the select and poll backends, and do not allow
		354	environment settings to be taken into account:</p>
		355	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		356
		357	</pre>
		358	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		359	available (warning, breaks stuff, best use only with your own private
		360	event loop and only if you know the OS supports your types of fds):</p>
		361	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		362
		363	</pre>
192	</dd>	364	</dd>
193	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	365	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
194	<dd>	366	<dd>
195	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	367	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
196	always distinct from the default loop. Unlike the default loop, it cannot	368	always distinct from the default loop. Unlike the default loop, it cannot
197	handle signal and child watchers, and attempts to do so will be greeted by	369	handle signal and child watchers, and attempts to do so will be greeted by
198	undefined behaviour (or a failed assertion if assertions are enabled).</p>	370	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		371	<p>Example: try to create a event loop that uses epoll and nothing else.</p>
		372	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		373	if (!epoller)
		374	fatal ("no epoll found here, maybe it hides under your chair");
		375
		376	</pre>
199	</dd>	377	</dd>
200	<dt>ev_default_destroy ()</dt>	378	<dt>ev_default_destroy ()</dt>
201	<dd>	379	<dd>
202	<p>Destroys the default loop again (frees all memory and kernel state	380	<p>Destroys the default loop again (frees all memory and kernel state
203	etc.). This stops all registered event watchers (by not touching them in	381	etc.). None of the active event watchers will be stopped in the normal
204	any way whatsoever, although you cnanot rely on this :).</p>	382	sense, so e.g. <code>ev_is_active</code> might still return true. It is your
		383	responsibility to either stop all watchers cleanly yoursef <i>before</i>
		384	calling this function, or cope with the fact afterwards (which is usually
		385	the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
		386	for example).</p>
205	</dd>	387	</dd>
206	<dt>ev_loop_destroy (loop)</dt>	388	<dt>ev_loop_destroy (loop)</dt>
207	<dd>	389	<dd>
208	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	390	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
209	earlier call to <code>ev_loop_new</code>.</p>	391	earlier call to <code>ev_loop_new</code>.</p>
…		…
212	<dd>	394	<dd>
213	<p>This function reinitialises the kernel state for backends that have	395	<p>This function reinitialises the kernel state for backends that have
214	one. Despite the name, you can call it anytime, but it makes most sense	396	one. Despite the name, you can call it anytime, but it makes most sense
215	after forking, in either the parent or child process (or both, but that	397	after forking, in either the parent or child process (or both, but that
216	again makes little sense).</p>	398	again makes little sense).</p>
217	<p>You <i>must</i> call this function after forking if and only if you want to	399	<p>You <i>must</i> call this function in the child process after forking if and
218	use the event library in both processes. If you just fork+exec, you don't	400	only if you want to use the event library in both processes. If you just
219	have to call it.</p>	401	fork+exec, you don't have to call it.</p>
220	<p>The function itself is quite fast and its usually not a problem to call	402	<p>The function itself is quite fast and it's usually not a problem to call
221	it just in case after a fork. To make this easy, the function will fit in	403	it just in case after a fork. To make this easy, the function will fit in
222	quite nicely into a call to <code>pthread_atfork</code>:</p>	404	quite nicely into a call to <code>pthread_atfork</code>:</p>
223	<pre> pthread_atfork (0, 0, ev_default_fork);	405	<pre> pthread_atfork (0, 0, ev_default_fork);
224		406
225	</pre>	407	</pre>
		408	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		409	without calling this function, so if you force one of those backends you
		410	do not need to care.</p>
226	</dd>	411	</dd>
227	<dt>ev_loop_fork (loop)</dt>	412	<dt>ev_loop_fork (loop)</dt>
228	<dd>	413	<dd>
229	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	414	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
230	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	415	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
231	after fork, and how you do this is entirely your own problem.</p>	416	after fork, and how you do this is entirely your own problem.</p>
232	</dd>	417	</dd>
233	<dt>unsigned int ev_method (loop)</dt>	418	<dt>unsigned int ev_backend (loop)</dt>
234	<dd>	419	<dd>
235	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	420	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
236	use.</p>	421	use.</p>
237	</dd>	422	</dd>
238	<dt>ev_tstamp = ev_now (loop)</dt>	423	<dt>ev_tstamp ev_now (loop)</dt>
239	<dd>	424	<dd>
240	<p>Returns the current "event loop time", which is the time the event loop	425	<p>Returns the current "event loop time", which is the time the event loop
241	got events and started processing them. This timestamp does not change	426	received events and started processing them. This timestamp does not
242	as long as callbacks are being processed, and this is also the base time	427	change as long as callbacks are being processed, and this is also the base
243	used for relative timers. You can treat it as the timestamp of the event	428	time used for relative timers. You can treat it as the timestamp of the
244	occuring (or more correctly, the mainloop finding out about it).</p>	429	event occuring (or more correctly, libev finding out about it).</p>
245	</dd>	430	</dd>
246	<dt>ev_loop (loop, int flags)</dt>	431	<dt>ev_loop (loop, int flags)</dt>
247	<dd>	432	<dd>
248	<p>Finally, this is it, the event handler. This function usually is called	433	<p>Finally, this is it, the event handler. This function usually is called
249	after you initialised all your watchers and you want to start handling	434	after you initialised all your watchers and you want to start handling
250	events.</p>	435	events.</p>
251	<p>If the flags argument is specified as 0, it will not return until either	436	<p>If the flags argument is specified as <code>0</code>, it will not return until
252	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	437	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		438	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		439	relying on all watchers to be stopped when deciding when a program has
		440	finished (especially in interactive programs), but having a program that
		441	automatically loops as long as it has to and no longer by virtue of
		442	relying on its watchers stopping correctly is a thing of beauty.</p>
253	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	443	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
254	those events and any outstanding ones, but will not block your process in	444	those events and any outstanding ones, but will not block your process in
255	case there are no events.</p>	445	case there are no events and will return after one iteration of the loop.</p>
256	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	446	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
257	neccessary) and will handle those and any outstanding ones. It will block	447	neccessary) and will handle those and any outstanding ones. It will block
258	your process until at least one new event arrives.</p>	448	your process until at least one new event arrives, and will return after
259	<p>This flags value could be used to implement alternative looping	449	one iteration of the loop. This is useful if you are waiting for some
260	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	450	external event in conjunction with something not expressible using other
261	more generic mechanism.</p>	451	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
		452	usually a better approach for this kind of thing.</p>
		453	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		454	<pre> * If there are no active watchers (reference count is zero), return.
		455	- Queue prepare watchers and then call all outstanding watchers.
		456	- If we have been forked, recreate the kernel state.
		457	- Update the kernel state with all outstanding changes.
		458	- Update the "event loop time".
		459	- Calculate for how long to block.
		460	- Block the process, waiting for any events.
		461	- Queue all outstanding I/O (fd) events.
		462	- Update the "event loop time" and do time jump handling.
		463	- Queue all outstanding timers.
		464	- Queue all outstanding periodics.
		465	- If no events are pending now, queue all idle watchers.
		466	- Queue all check watchers.
		467	- Call all queued watchers in reverse order (i.e. check watchers first).
		468	Signals and child watchers are implemented as I/O watchers, and will
		469	be handled here by queueing them when their watcher gets executed.
		470	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		471	were used, return, otherwise continue with step *.
		472
		473	</pre>
		474	<p>Example: queue some jobs and then loop until no events are outsanding
		475	anymore.</p>
		476	<pre> ... queue jobs here, make sure they register event watchers as long
		477	... as they still have work to do (even an idle watcher will do..)
		478	ev_loop (my_loop, 0);
		479	... jobs done. yeah!
		480
		481	</pre>
262	</dd>	482	</dd>
263	<dt>ev_unloop (loop, how)</dt>	483	<dt>ev_unloop (loop, how)</dt>
264	<dd>	484	<dd>
265	<p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument	485	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
		486	has processed all outstanding events). The <code>how</code> argument must be either
266	must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code>	487	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
267	call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code>	488	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
268	calls return.</p>
269	</dd>	489	</dd>
270	<dt>ev_ref (loop)</dt>	490	<dt>ev_ref (loop)</dt>
271	<dt>ev_unref (loop)</dt>	491	<dt>ev_unref (loop)</dt>
272	<dd>	492	<dd>
273	<p>Ref/unref can be used to add or remove a refcount on the event loop: Every	493	<p>Ref/unref can be used to add or remove a reference count on the event
274	watcher keeps one reference. If you have a long-runing watcher you never	494	loop: Every watcher keeps one reference, and as long as the reference
275	unregister that should not keep ev_loop from running, ev_unref() after	495	count is nonzero, <code>ev_loop</code> will not return on its own. If you have
276	starting, and ev_ref() before stopping it. Libev itself uses this for	496	a watcher you never unregister that should not keep <code>ev_loop</code> from
277	example for its internal signal pipe: It is not visible to you as a user	497	returning, ev_unref() after starting, and ev_ref() before stopping it. For
278	and should not keep <code>ev_loop</code> from exiting if the work is done. It is	498	example, libev itself uses this for its internal signal pipe: It is not
279	also an excellent way to do this for generic recurring timers or from	499	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
280	within third-party libraries. Just remember to unref after start and ref	500	no event watchers registered by it are active. It is also an excellent
281	before stop.</p>	501	way to do this for generic recurring timers or from within third-party
		502	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		503	<p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
		504	running when nothing else is active.</p>
		505	<pre> struct dv_signal exitsig;
		506	ev_signal_init (&exitsig, sig_cb, SIGINT);
		507	ev_signal_start (myloop, &exitsig);
		508	evf_unref (myloop);
		509
		510	</pre>
		511	<p>Example: for some weird reason, unregister the above signal handler again.</p>
		512	<pre> ev_ref (myloop);
		513	ev_signal_stop (myloop, &exitsig);
		514
		515	</pre>
282	</dd>	516	</dd>
283	</dl>	517	</dl>
		518
		519
		520
		521
284		522
285	</div>	523	</div>
286	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	524	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
287	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	525	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
288	<p>A watcher is a structure that you create and register to record your	526	<p>A watcher is a structure that you create and register to record your
289	interest in some event. For instance, if you want to wait for STDIN to	527	interest in some event. For instance, if you want to wait for STDIN to
290	become readable, you would create an ev_io watcher for that:</p>	528	become readable, you would create an <code>ev_io</code> watcher for that:</p>
291	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	529	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
292	{	530	{
293	ev_io_stop (w);	531	ev_io_stop (w);
294	ev_unloop (loop, EVUNLOOP_ALL);	532	ev_unloop (loop, EVUNLOOP_ALL);
295	}	533	}
…		…
318	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	556	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
319	*)</code>), and you can stop watching for events at any time by calling the	557	*)</code>), and you can stop watching for events at any time by calling the
320	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	558	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
321	<p>As long as your watcher is active (has been started but not stopped) you	559	<p>As long as your watcher is active (has been started but not stopped) you
322	must not touch the values stored in it. Most specifically you must never	560	must not touch the values stored in it. Most specifically you must never
323	reinitialise it or call its set method.</p>	561	reinitialise it or call its <code>set</code> macro.</p>
324	<p>You cna check whether an event is active by calling the <code>ev_is_active
325	(watcher *)</code> macro. To see whether an event is outstanding (but the
326	callback for it has not been called yet) you cna use the <code>ev_is_pending
327	(watcher *)</code> macro.</p>
328	<p>Each and every callback receives the event loop pointer as first, the	562	<p>Each and every callback receives the event loop pointer as first, the
329	registered watcher structure as second, and a bitset of received events as	563	registered watcher structure as second, and a bitset of received events as
330	third argument.</p>	564	third argument.</p>
331	<p>The rceeived events usually include a single bit per event type received	565	<p>The received events usually include a single bit per event type received
332	(you can receive multiple events at the same time). The possible bit masks	566	(you can receive multiple events at the same time). The possible bit masks
333	are:</p>	567	are:</p>
334	<dl>	568	<dl>
335	<dt>EV_READ</dt>	569	<dt><code>EV_READ</code></dt>
336	<dt>EV_WRITE</dt>	570	<dt><code>EV_WRITE</code></dt>
337	<dd>	571	<dd>
338	<p>The file descriptor in the ev_io watcher has become readable and/or	572	<p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
339	writable.</p>	573	writable.</p>
340	</dd>	574	</dd>
341	<dt>EV_TIMEOUT</dt>	575	<dt><code>EV_TIMEOUT</code></dt>
342	<dd>
343	<p>The ev_timer watcher has timed out.</p>
344	</dd>	576	<dd>
345	<dt>EV_PERIODIC</dt>	577	<p>The <code>ev_timer</code> watcher has timed out.</p>
346	<dd>	578	</dd>
347	<p>The ev_periodic watcher has timed out.</p>	579	<dt><code>EV_PERIODIC</code></dt>
348	</dd>	580	<dd>
349	<dt>EV_SIGNAL</dt>	581	<p>The <code>ev_periodic</code> watcher has timed out.</p>
350	<dd>	582	</dd>
		583	<dt><code>EV_SIGNAL</code></dt>
		584	<dd>
351	<p>The signal specified in the ev_signal watcher has been received by a thread.</p>	585	<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
352	</dd>
353	<dt>EV_CHILD</dt>
354	<dd>	586	</dd>
		587	<dt><code>EV_CHILD</code></dt>
		588	<dd>
355	<p>The pid specified in the ev_child watcher has received a status change.</p>	589	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
356	</dd>
357	<dt>EV_IDLE</dt>
358	<dd>	590	</dd>
		591	<dt><code>EV_IDLE</code></dt>
		592	<dd>
359	<p>The ev_idle watcher has determined that you have nothing better to do.</p>	593	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
360	</dd>
361	<dt>EV_PREPARE</dt>
362	<dt>EV_CHECK</dt>
363	<dd>	594	</dd>
		595	<dt><code>EV_PREPARE</code></dt>
		596	<dt><code>EV_CHECK</code></dt>
		597	<dd>
364	<p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts	598	<p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
365	to gather new events, and all ev_check watchers are invoked just after	599	to gather new events, and all <code>ev_check</code> watchers are invoked just after
366	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	600	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
367	received events. Callbacks of both watcher types can start and stop as	601	received events. Callbacks of both watcher types can start and stop as
368	many watchers as they want, and all of them will be taken into account	602	many watchers as they want, and all of them will be taken into account
369	(for example, a ev_prepare watcher might start an idle watcher to keep	603	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
370	<code>ev_loop</code> from blocking).</p>	604	<code>ev_loop</code> from blocking).</p>
371	</dd>	605	</dd>
372	<dt>EV_ERROR</dt>	606	<dt><code>EV_ERROR</code></dt>
373	<dd>	607	<dd>
374	<p>An unspecified error has occured, the watcher has been stopped. This might	608	<p>An unspecified error has occured, the watcher has been stopped. This might
375	happen because the watcher could not be properly started because libev	609	happen because the watcher could not be properly started because libev
376	ran out of memory, a file descriptor was found to be closed or any other	610	ran out of memory, a file descriptor was found to be closed or any other
377	problem. You best act on it by reporting the problem and somehow coping	611	problem. You best act on it by reporting the problem and somehow coping
…		…
383	programs, though, so beware.</p>	617	programs, though, so beware.</p>
384	</dd>	618	</dd>
385	</dl>	619	</dl>
386		620
387	</div>	621	</div>
		622	<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
		623	<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
		624	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		625	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		626	<dl>
		627	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		628	<dd>
		629	<p>This macro initialises the generic portion of a watcher. The contents
		630	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		631	the generic parts of the watcher are initialised, you <i>need</i> to call
		632	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		633	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		634	which rolls both calls into one.</p>
		635	<p>You can reinitialise a watcher at any time as long as it has been stopped
		636	(or never started) and there are no pending events outstanding.</p>
		637	<p>The callback is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		638	int revents)</code>.</p>
		639	</dd>
		640	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		641	<dd>
		642	<p>This macro initialises the type-specific parts of a watcher. You need to
		643	call <code>ev_init</code> at least once before you call this macro, but you can
		644	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		645	macro on a watcher that is active (it can be pending, however, which is a
		646	difference to the <code>ev_init</code> macro).</p>
		647	<p>Although some watcher types do not have type-specific arguments
		648	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		649	</dd>
		650	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		651	<dd>
		652	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		653	calls into a single call. This is the most convinient method to initialise
		654	a watcher. The same limitations apply, of course.</p>
		655	</dd>
		656	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		657	<dd>
		658	<p>Starts (activates) the given watcher. Only active watchers will receive
		659	events. If the watcher is already active nothing will happen.</p>
		660	</dd>
		661	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		662	<dd>
		663	<p>Stops the given watcher again (if active) and clears the pending
		664	status. It is possible that stopped watchers are pending (for example,
		665	non-repeating timers are being stopped when they become pending), but
		666	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		667	you want to free or reuse the memory used by the watcher it is therefore a
		668	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		669	</dd>
		670	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		671	<dd>
		672	<p>Returns a true value iff the watcher is active (i.e. it has been started
		673	and not yet been stopped). As long as a watcher is active you must not modify
		674	it.</p>
		675	</dd>
		676	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		677	<dd>
		678	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		679	events but its callback has not yet been invoked). As long as a watcher
		680	is pending (but not active) you must not call an init function on it (but
		681	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		682	libev (e.g. you cnanot <code>free ()</code> it).</p>
		683	</dd>
		684	<dt>callback = ev_cb (ev_TYPE *watcher)</dt>
		685	<dd>
		686	<p>Returns the callback currently set on the watcher.</p>
		687	</dd>
		688	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		689	<dd>
		690	<p>Change the callback. You can change the callback at virtually any time
		691	(modulo threads).</p>
		692	</dd>
		693	</dl>
		694
		695
		696
		697
		698
		699	</div>
388	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	700	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
389	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	701	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
390	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	702	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
391	and read at any time, libev will completely ignore it. This cna be used	703	and read at any time, libev will completely ignore it. This can be used
392	to associate arbitrary data with your watcher. If you need more data and	704	to associate arbitrary data with your watcher. If you need more data and
393	don't want to allocate memory and store a pointer to it in that data	705	don't want to allocate memory and store a pointer to it in that data
394	member, you can also "subclass" the watcher type and provide your own	706	member, you can also "subclass" the watcher type and provide your own
395	data:</p>	707	data:</p>
396	<pre> struct my_io	708	<pre> struct my_io
…		…
422	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	734	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
423	<div id="WATCHER_TYPES_CONTENT">	735	<div id="WATCHER_TYPES_CONTENT">
424	<p>This section describes each watcher in detail, but will not repeat	736	<p>This section describes each watcher in detail, but will not repeat
425	information given in the last section.</p>	737	information given in the last section.</p>
426		738
		739
		740
		741
		742
427	</div>	743	</div>
428	<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2>	744	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
429	<div id="struct_ev_io_is_my_file_descriptor_r-2">	745	<div id="code_ev_io_code_is_this_file_descrip-2">
430	<p>I/O watchers check whether a file descriptor is readable or writable	746	<p>I/O watchers check whether a file descriptor is readable or writable
431	in each iteration of the event loop (This behaviour is called	747	in each iteration of the event loop, or, more precisely, when reading
432	level-triggering because you keep receiving events as long as the	748	would not block the process and writing would at least be able to write
433	condition persists. Remember you cna stop the watcher if you don't want to	749	some data. This behaviour is called level-triggering because you keep
434	act on the event and neither want to receive future events).</p>	750	receiving events as long as the condition persists. Remember you can stop
		751	the watcher if you don't want to act on the event and neither want to
		752	receive future events.</p>
		753	<p>In general you can register as many read and/or write event watchers per
		754	fd as you want (as long as you don't confuse yourself). Setting all file
		755	descriptors to non-blocking mode is also usually a good idea (but not
		756	required if you know what you are doing).</p>
		757	<p>You have to be careful with dup'ed file descriptors, though. Some backends
		758	(the linux epoll backend is a notable example) cannot handle dup'ed file
		759	descriptors correctly if you register interest in two or more fds pointing
		760	to the same underlying file/socket/etc. description (that is, they share
		761	the same underlying "file open").</p>
		762	<p>If you must do this, then force the use of a known-to-be-good backend
		763	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
		764	<code>EVBACKEND_POLL</code>).</p>
		765	<p>Another thing you have to watch out for is that it is quite easy to
		766	receive "spurious" readyness notifications, that is your callback might
		767	be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
		768	because there is no data. Not only are some backends known to create a
		769	lot of those (for example solaris ports), it is very easy to get into
		770	this situation even with a relatively standard program structure. Thus
		771	it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
		772	<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
		773	<p>If you cannot run the fd in non-blocking mode (for example you should not
		774	play around with an Xlib connection), then you have to seperately re-test
		775	wether a file descriptor is really ready with a known-to-be good interface
		776	such as poll (fortunately in our Xlib example, Xlib already does this on
		777	its own, so its quite safe to use).</p>
435	<dl>	778	<dl>
436	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	779	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
437	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	780	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
438	<dd>	781	<dd>
439	<p>Configures an ev_io watcher. The fd is the file descriptor to rceeive	782	<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
440	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	783	rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
441	EV_WRITE</code> to receive the given events.</p>	784	<code>EV_READ \| EV_WRITE</code> to receive the given events.</p>
442	</dd>	785	</dd>
443	</dl>	786	</dl>
		787	<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		788	readable, but only once. Since it is likely line-buffered, you could
		789	attempt to read a whole line in the callback:</p>
		790	<pre> static void
		791	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		792	{
		793	ev_io_stop (loop, w);
		794	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		795	}
444		796
		797	...
		798	struct ev_loop *loop = ev_default_init (0);
		799	struct ev_io stdin_readable;
		800	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		801	ev_io_start (loop, &stdin_readable);
		802	ev_loop (loop, 0);
		803
		804
		805
		806
		807	</pre>
		808
445	</div>	809	</div>
446	<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2>	810	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
447	<div id="struct_ev_timer_relative_and_optiona-2">	811	<div id="code_ev_timer_code_relative_and_opti-2">
448	<p>Timer watchers are simple relative timers that generate an event after a	812	<p>Timer watchers are simple relative timers that generate an event after a
449	given time, and optionally repeating in regular intervals after that.</p>	813	given time, and optionally repeating in regular intervals after that.</p>
450	<p>The timers are based on real time, that is, if you register an event that	814	<p>The timers are based on real time, that is, if you register an event that
451	times out after an hour and youreset your system clock to last years	815	times out after an hour and you reset your system clock to last years
452	time, it will still time out after (roughly) and hour. "Roughly" because	816	time, it will still time out after (roughly) and hour. "Roughly" because
453	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	817	detecting time jumps is hard, and some inaccuracies are unavoidable (the
454	monotonic clock option helps a lot here).</p>	818	monotonic clock option helps a lot here).</p>
		819	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
		820	time. This is usually the right thing as this timestamp refers to the time
		821	of the event triggering whatever timeout you are modifying/starting. If
		822	you suspect event processing to be delayed and you <i>need</i> to base the timeout
		823	on the current time, use something like this to adjust for this:</p>
		824	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		825
		826	</pre>
		827	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		828	but if multiple timers become ready during the same loop iteration then
		829	order of execution is undefined.</p>
455	<dl>	830	<dl>
456	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	831	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
457	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	832	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
458	<dd>	833	<dd>
459	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	834	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
461	timer will automatically be configured to trigger again <code>repeat</code> seconds	836	timer will automatically be configured to trigger again <code>repeat</code> seconds
462	later, again, and again, until stopped manually.</p>	837	later, again, and again, until stopped manually.</p>
463	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	838	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
464	configure a timer to trigger every 10 seconds, then it will trigger at	839	configure a timer to trigger every 10 seconds, then it will trigger at
465	exactly 10 second intervals. If, however, your program cannot keep up with	840	exactly 10 second intervals. If, however, your program cannot keep up with
466	the timer (ecause it takes longer than those 10 seconds to do stuff) the	841	the timer (because it takes longer than those 10 seconds to do stuff) the
467	timer will not fire more than once per event loop iteration.</p>	842	timer will not fire more than once per event loop iteration.</p>
468	</dd>	843	</dd>
469	<dt>ev_timer_again (loop)</dt>	844	<dt>ev_timer_again (loop)</dt>
470	<dd>	845	<dd>
471	<p>This will act as if the timer timed out and restart it again if it is	846	<p>This will act as if the timer timed out and restart it again if it is
…		…
475	value), or reset the running timer to the repeat value.</p>	850	value), or reset the running timer to the repeat value.</p>
476	<p>This sounds a bit complicated, but here is a useful and typical	851	<p>This sounds a bit complicated, but here is a useful and typical
477	example: Imagine you have a tcp connection and you want a so-called idle	852	example: Imagine you have a tcp connection and you want a so-called idle
478	timeout, that is, you want to be called when there have been, say, 60	853	timeout, that is, you want to be called when there have been, say, 60
479	seconds of inactivity on the socket. The easiest way to do this is to	854	seconds of inactivity on the socket. The easiest way to do this is to
480	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	855	configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
481	time you successfully read or write some data. If you go into an idle	856	time you successfully read or write some data. If you go into an idle
482	state where you do not expect data to travel on the socket, you can stop	857	state where you do not expect data to travel on the socket, you can stop
483	the timer, and again will automatically restart it if need be.</p>	858	the timer, and again will automatically restart it if need be.</p>
484	</dd>	859	</dd>
485	</dl>	860	</dl>
		861	<p>Example: create a timer that fires after 60 seconds.</p>
		862	<pre> static void
		863	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		864	{
		865	.. one minute over, w is actually stopped right here
		866	}
486		867
		868	struct ev_timer mytimer;
		869	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		870	ev_timer_start (loop, &mytimer);
		871
		872	</pre>
		873	<p>Example: create a timeout timer that times out after 10 seconds of
		874	inactivity.</p>
		875	<pre> static void
		876	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		877	{
		878	.. ten seconds without any activity
		879	}
		880
		881	struct ev_timer mytimer;
		882	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		883	ev_timer_again (&mytimer); /* start timer */
		884	ev_loop (loop, 0);
		885
		886	// and in some piece of code that gets executed on any "activity":
		887	// reset the timeout to start ticking again at 10 seconds
		888	ev_timer_again (&mytimer);
		889
		890
		891
		892
		893	</pre>
		894
487	</div>	895	</div>
488	<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2>	896	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
489	<div id="ev_periodic_to_cron_or_not_to_cron_i-2">	897	<div id="code_ev_periodic_code_to_cron_or_not-2">
490	<p>Periodic watchers are also timers of a kind, but they are very versatile	898	<p>Periodic watchers are also timers of a kind, but they are very versatile
491	(and unfortunately a bit complex).</p>	899	(and unfortunately a bit complex).</p>
492	<p>Unlike ev_timer's, they are not based on real time (or relative time)	900	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
493	but on wallclock time (absolute time). You can tell a periodic watcher	901	but on wallclock time (absolute time). You can tell a periodic watcher
494	to trigger "at" some specific point in time. For example, if you tell a	902	to trigger "at" some specific point in time. For example, if you tell a
495	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	903	periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
496	+ 10.>) and then reset your system clock to the last year, then it will	904	+ 10.</code>) and then reset your system clock to the last year, then it will
497	take a year to trigger the event (unlike an ev_timer, which would trigger	905	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
498	roughly 10 seconds later and of course not if you reset your system time	906	roughly 10 seconds later and of course not if you reset your system time
499	again).</p>	907	again).</p>
500	<p>They can also be used to implement vastly more complex timers, such as	908	<p>They can also be used to implement vastly more complex timers, such as
501	triggering an event on eahc midnight, local time.</p>	909	triggering an event on eahc midnight, local time.</p>
		910	<p>As with timers, the callback is guarenteed to be invoked only when the
		911	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		912	during the same loop iteration then order of execution is undefined.</p>
502	<dl>	913	<dl>
503	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	914	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
504	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	915	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
505	<dd>	916	<dd>
506	<p>Lots of arguments, lets sort it out... There are basically three modes of	917	<p>Lots of arguments, lets sort it out... There are basically three modes of
507	operation, and we will explain them from simplest to complex:</p>	918	operation, and we will explain them from simplest to complex:</p>
508
509
510
511
512	<p>	919	<p>
513	<dl>	920	<dl>
514	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	921	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
515	<dd>	922	<dd>
516	<p>In this configuration the watcher triggers an event at the wallclock time	923	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
528	<pre> ev_periodic_set (&periodic, 0., 3600., 0);	935	<pre> ev_periodic_set (&periodic, 0., 3600., 0);
529		936
530	</pre>	937	</pre>
531	<p>This doesn't mean there will always be 3600 seconds in between triggers,	938	<p>This doesn't mean there will always be 3600 seconds in between triggers,
532	but only that the the callback will be called when the system time shows a	939	but only that the the callback will be called when the system time shows a
533	full hour (UTC), or more correct, when the system time is evenly divisible	940	full hour (UTC), or more correctly, when the system time is evenly divisible
534	by 3600.</p>	941	by 3600.</p>
535	<p>Another way to think about it (for the mathematically inclined) is that	942	<p>Another way to think about it (for the mathematically inclined) is that
536	ev_periodic will try to run the callback in this mode at the next possible	943	<code>ev_periodic</code> will try to run the callback in this mode at the next possible
537	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>	944	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
538	</dd>	945	</dd>
539	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>	946	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>
540	<dd>	947	<dd>
541	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	948	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
542	ignored. Instead, each time the periodic watcher gets scheduled, the	949	ignored. Instead, each time the periodic watcher gets scheduled, the
543	reschedule callback will be called with the watcher as first, and the	950	reschedule callback will be called with the watcher as first, and the
544	current time as second argument.</p>	951	current time as second argument.</p>
545	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	952	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
546	periodic watcher, ever, or make any event loop modificstions</i>. If you need	953	ever, or make any event loop modifications</i>. If you need to stop it,
547	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p>	954	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
		955	starting a prepare watcher).</p>
548	<p>Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	956	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
549	ev_tstamp now)>, e.g.:</p>	957	ev_tstamp now)</code>, e.g.:</p>
550	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	958	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
551	{	959	{
552	return now + 60.;	960	return now + 60.;
553	}	961	}
554		962
555	</pre>	963	</pre>
556	<p>It must return the next time to trigger, based on the passed time value	964	<p>It must return the next time to trigger, based on the passed time value
557	(that is, the lowest time value larger than to the second argument). It	965	(that is, the lowest time value larger than to the second argument). It
558	will usually be called just before the callback will be triggered, but	966	will usually be called just before the callback will be triggered, but
559	might be called at other times, too.</p>	967	might be called at other times, too.</p>
		968	<p>NOTE: <i>This callback must always return a time that is later than the
		969	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
560	<p>This can be used to create very complex timers, such as a timer that	970	<p>This can be used to create very complex timers, such as a timer that
561	triggers on each midnight, local time. To do this, you would calculate the	971	triggers on each midnight, local time. To do this, you would calculate the
562	next midnight after <code>now</code> and return the timestamp value for this. How you do this	972	next midnight after <code>now</code> and return the timestamp value for this. How
563	is, again, up to you (but it is not trivial).</p>	973	you do this is, again, up to you (but it is not trivial, which is the main
		974	reason I omitted it as an example).</p>
564	</dd>	975	</dd>
565	</dl>	976	</dl>
566	</p>	977	</p>
567	</dd>	978	</dd>
568	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	979	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
571	when you changed some parameters or the reschedule callback would return	982	when you changed some parameters or the reschedule callback would return
572	a different time than the last time it was called (e.g. in a crond like	983	a different time than the last time it was called (e.g. in a crond like
573	program when the crontabs have changed).</p>	984	program when the crontabs have changed).</p>
574	</dd>	985	</dd>
575	</dl>	986	</dl>
		987	<p>Example: call a callback every hour, or, more precisely, whenever the
		988	system clock is divisible by 3600. The callback invocation times have
		989	potentially a lot of jittering, but good long-term stability.</p>
		990	<pre> static void
		991	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		992	{
		993	... its now a full hour (UTC, or TAI or whatever your clock follows)
		994	}
576		995
		996	struct ev_periodic hourly_tick;
		997	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		998	ev_periodic_start (loop, &hourly_tick);
		999
		1000	</pre>
		1001	<p>Example: the same as above, but use a reschedule callback to do it:</p>
		1002	<pre> #include <math.h>
		1003
		1004	static ev_tstamp
		1005	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1006	{
		1007	return fmod (now, 3600.) + 3600.;
		1008	}
		1009
		1010	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1011
		1012	</pre>
		1013	<p>Example: call a callback every hour, starting now:</p>
		1014	<pre> struct ev_periodic hourly_tick;
		1015	ev_periodic_init (&hourly_tick, clock_cb,
		1016	fmod (ev_now (loop), 3600.), 3600., 0);
		1017	ev_periodic_start (loop, &hourly_tick);
		1018
		1019
		1020
		1021
		1022	</pre>
		1023
577	</div>	1024	</div>
578	<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2>	1025	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
579	<div id="ev_signal_signal_me_when_a_signal_ge-2">	1026	<div id="code_ev_signal_code_signal_me_when_a-2">
580	<p>Signal watchers will trigger an event when the process receives a specific	1027	<p>Signal watchers will trigger an event when the process receives a specific
581	signal one or more times. Even though signals are very asynchronous, libev	1028	signal one or more times. Even though signals are very asynchronous, libev
582	will try its best to deliver signals synchronously, i.e. as part of the	1029	will try it's best to deliver signals synchronously, i.e. as part of the
583	normal event processing, like any other event.</p>	1030	normal event processing, like any other event.</p>
584	<p>You cna configure as many watchers as you like per signal. Only when the	1031	<p>You can configure as many watchers as you like per signal. Only when the
585	first watcher gets started will libev actually register a signal watcher	1032	first watcher gets started will libev actually register a signal watcher
586	with the kernel (thus it coexists with your own signal handlers as long	1033	with the kernel (thus it coexists with your own signal handlers as long
587	as you don't register any with libev). Similarly, when the last signal	1034	as you don't register any with libev). Similarly, when the last signal
588	watcher for a signal is stopped libev will reset the signal handler to	1035	watcher for a signal is stopped libev will reset the signal handler to
589	SIG_DFL (regardless of what it was set to before).</p>	1036	SIG_DFL (regardless of what it was set to before).</p>
…		…
594	<p>Configures the watcher to trigger on the given signal number (usually one	1041	<p>Configures the watcher to trigger on the given signal number (usually one
595	of the <code>SIGxxx</code> constants).</p>	1042	of the <code>SIGxxx</code> constants).</p>
596	</dd>	1043	</dd>
597	</dl>	1044	</dl>
598		1045
		1046
		1047
		1048
		1049
599	</div>	1050	</div>
600	<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2>	1051	<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
601	<div id="ev_child_wait_for_pid_status_changes-2">	1052	<div id="code_ev_child_code_watch_out_for_pro-2">
602	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1053	<p>Child watchers trigger when your process receives a SIGCHLD in response to
603	some child status changes (most typically when a child of yours dies).</p>	1054	some child status changes (most typically when a child of yours dies).</p>
604	<dl>	1055	<dl>
605	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1056	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
606	<dt>ev_child_set (ev_child *, int pid)</dt>	1057	<dt>ev_child_set (ev_child *, int pid)</dt>
607	<dd>	1058	<dd>
608	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or	1059	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or
609	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look	1060	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
610	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1061	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
611	the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member	1062	the status word (use the macros from <code>sys/wait.h</code> and see your systems
		1063	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
612	contains the pid of the process causing the status change.</p>	1064	process causing the status change.</p>
613	</dd>	1065	</dd>
614	</dl>	1066	</dl>
		1067	<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
		1068	<pre> static void
		1069	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1070	{
		1071	ev_unloop (loop, EVUNLOOP_ALL);
		1072	}
615		1073
		1074	struct ev_signal signal_watcher;
		1075	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1076	ev_signal_start (loop, &sigint_cb);
		1077
		1078
		1079
		1080
		1081	</pre>
		1082
616	</div>	1083	</div>
617	<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2>	1084	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
618	<div id="ev_idle_when_you_ve_got_nothing_bett-2">	1085	<div id="code_ev_idle_code_when_you_ve_got_no-2">
619	<p>Idle watchers trigger events when there are no other I/O or timer (or	1086	<p>Idle watchers trigger events when there are no other events are pending
620	periodic) events pending. That is, as long as your process is busy	1087	(prepare, check and other idle watchers do not count). That is, as long
621	handling sockets or timeouts it will not be called. But when your process	1088	as your process is busy handling sockets or timeouts (or even signals,
622	is idle all idle watchers are being called again and again - until	1089	imagine) it will not be triggered. But when your process is idle all idle
		1090	watchers are being called again and again, once per event loop iteration -
623	stopped, that is, or your process receives more events.</p>	1091	until stopped, that is, or your process receives more events and becomes
		1092	busy.</p>
624	<p>The most noteworthy effect is that as long as any idle watchers are	1093	<p>The most noteworthy effect is that as long as any idle watchers are
625	active, the process will not block when waiting for new events.</p>	1094	active, the process will not block when waiting for new events.</p>
626	<p>Apart from keeping your process non-blocking (which is a useful	1095	<p>Apart from keeping your process non-blocking (which is a useful
627	effect on its own sometimes), idle watchers are a good place to do	1096	effect on its own sometimes), idle watchers are a good place to do
628	"pseudo-background processing", or delay processing stuff to after the	1097	"pseudo-background processing", or delay processing stuff to after the
…		…
633	<p>Initialises and configures the idle watcher - it has no parameters of any	1102	<p>Initialises and configures the idle watcher - it has no parameters of any
634	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1103	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
635	believe me.</p>	1104	believe me.</p>
636	</dd>	1105	</dd>
637	</dl>	1106	</dl>
		1107	<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
		1108	callback, free it. Alos, use no error checking, as usual.</p>
		1109	<pre> static void
		1110	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1111	{
		1112	free (w);
		1113	// now do something you wanted to do when the program has
		1114	// no longer asnything immediate to do.
		1115	}
638		1116
		1117	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1118	ev_idle_init (idle_watcher, idle_cb);
		1119	ev_idle_start (loop, idle_cb);
		1120
		1121
		1122
		1123
		1124	</pre>
		1125
639	</div>	1126	</div>
640	<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2>	1127	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
641	<div id="prepare_and_check_your_hooks_into_th-2">	1128	<div id="code_ev_prepare_code_and_code_ev_che-2">
642	<p>Prepare and check watchers usually (but not always) are used in	1129	<p>Prepare and check watchers are usually (but not always) used in tandem:
643	tandom. Prepare watchers get invoked before the process blocks and check	1130	prepare watchers get invoked before the process blocks and check watchers
644	watchers afterwards.</p>	1131	afterwards.</p>
		1132	<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
		1133	the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
		1134	watchers. Other loops than the current one are fine, however. The
		1135	rationale behind this is that you do not need to check for recursion in
		1136	those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
		1137	<code>ev_check</code> so if you have one watcher of each kind they will always be
		1138	called in pairs bracketing the blocking call.</p>
645	<p>Their main purpose is to integrate other event mechanisms into libev. This	1139	<p>Their main purpose is to integrate other event mechanisms into libev and
646	could be used, for example, to track variable changes, implement your own	1140	their use is somewhat advanced. This could be used, for example, to track
647	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1141	variable changes, implement your own watchers, integrate net-snmp or a
		1142	coroutine library and lots more. They are also occasionally useful if
		1143	you cache some data and want to flush it before blocking (for example,
		1144	in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
		1145	watcher).</p>
648	<p>This is done by examining in each prepare call which file descriptors need	1146	<p>This is done by examining in each prepare call which file descriptors need
649	to be watched by the other library, registering ev_io watchers for them	1147	to be watched by the other library, registering <code>ev_io</code> watchers for
650	and starting an ev_timer watcher for any timeouts (many libraries provide	1148	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
651	just this functionality). Then, in the check watcher you check for any	1149	provide just this functionality). Then, in the check watcher you check for
652	events that occured (by making your callbacks set soem flags for example)	1150	any events that occured (by checking the pending status of all watchers
653	and call back into the library.</p>	1151	and stopping them) and call back into the library. The I/O and timer
		1152	callbacks will never actually be called (but must be valid nevertheless,
		1153	because you never know, you know?).</p>
654	<p>As another example, the perl Coro module uses these hooks to integrate	1154	<p>As another example, the Perl Coro module uses these hooks to integrate
655	coroutines into libev programs, by yielding to other active coroutines	1155	coroutines into libev programs, by yielding to other active coroutines
656	during each prepare and only letting the process block if no coroutines	1156	during each prepare and only letting the process block if no coroutines
657	are ready to run.</p>	1157	are ready to run (it's actually more complicated: it only runs coroutines
		1158	with priority higher than or equal to the event loop and one coroutine
		1159	of lower priority, but only once, using idle watchers to keep the event
		1160	loop from blocking if lower-priority coroutines are active, thus mapping
		1161	low-priority coroutines to idle/background tasks).</p>
658	<dl>	1162	<dl>
659	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1163	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
660	<dt>ev_check_init (ev_check *, callback)</dt>	1164	<dt>ev_check_init (ev_check *, callback)</dt>
661	<dd>	1165	<dd>
662	<p>Initialises and configures the prepare or check watcher - they have no	1166	<p>Initialises and configures the prepare or check watcher - they have no
663	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1167	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
664	macros, but using them is utterly, utterly pointless.</p>	1168	macros, but using them is utterly, utterly and completely pointless.</p>
665	</dd>	1169	</dd>
666	</dl>	1170	</dl>
		1171	<p>Example: To include a library such as adns, you would add IO watchers
		1172	and a timeout watcher in a prepare handler, as required by libadns, and
		1173	in a check watcher, destroy them and call into libadns. What follows is
		1174	pseudo-code only of course:</p>
		1175	<pre> static ev_io iow [nfd];
		1176	static ev_timer tw;
		1177
		1178	static void
		1179	io_cb (ev_loop loop, ev_io w, int revents)
		1180	{
		1181	// set the relevant poll flags
		1182	// could also call adns_processreadable etc. here
		1183	struct pollfd fd = (struct pollfd )w->data;
		1184	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1185	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1186	}
		1187
		1188	// create io watchers for each fd and a timer before blocking
		1189	static void
		1190	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1191	{
		1192	int timeout = 3600000;truct pollfd fds [nfd];
		1193	// actual code will need to loop here and realloc etc.
		1194	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1195
		1196	/* the callback is illegal, but won't be called as we stop during check */
		1197	ev_timer_init (&tw, 0, timeout * 1e-3);
		1198	ev_timer_start (loop, &tw);
		1199
		1200	// create on ev_io per pollfd
		1201	for (int i = 0; i < nfd; ++i)
		1202	{
		1203	ev_io_init (iow + i, io_cb, fds [i].fd,
		1204	((fds [i].events & POLLIN ? EV_READ : 0)
		1205	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1206
		1207	fds [i].revents = 0;
		1208	iow [i].data = fds + i;
		1209	ev_io_start (loop, iow + i);
		1210	}
		1211	}
		1212
		1213	// stop all watchers after blocking
		1214	static void
		1215	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1216	{
		1217	ev_timer_stop (loop, &tw);
		1218
		1219	for (int i = 0; i < nfd; ++i)
		1220	ev_io_stop (loop, iow + i);
		1221
		1222	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1223	}
		1224
		1225
		1226
		1227
		1228	</pre>
		1229
		1230	</div>
		1231	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
		1232	<div id="code_ev_embed_code_when_one_backend_-2">
		1233	<p>This is a rather advanced watcher type that lets you embed one event loop
		1234	into another (currently only <code>ev_io</code> events are supported in the embedded
		1235	loop, other types of watchers might be handled in a delayed or incorrect
		1236	fashion and must not be used).</p>
		1237	<p>There are primarily two reasons you would want that: work around bugs and
		1238	prioritise I/O.</p>
		1239	<p>As an example for a bug workaround, the kqueue backend might only support
		1240	sockets on some platform, so it is unusable as generic backend, but you
		1241	still want to make use of it because you have many sockets and it scales
		1242	so nicely. In this case, you would create a kqueue-based loop and embed it
		1243	into your default loop (which might use e.g. poll). Overall operation will
		1244	be a bit slower because first libev has to poll and then call kevent, but
		1245	at least you can use both at what they are best.</p>
		1246	<p>As for prioritising I/O: rarely you have the case where some fds have
		1247	to be watched and handled very quickly (with low latency), and even
		1248	priorities and idle watchers might have too much overhead. In this case
		1249	you would put all the high priority stuff in one loop and all the rest in
		1250	a second one, and embed the second one in the first.</p>
		1251	<p>As long as the watcher is active, the callback will be invoked every time
		1252	there might be events pending in the embedded loop. The callback must then
		1253	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1254	their callbacks (you could also start an idle watcher to give the embedded
		1255	loop strictly lower priority for example). You can also set the callback
		1256	to <code>0</code>, in which case the embed watcher will automatically execute the
		1257	embedded loop sweep.</p>
		1258	<p>As long as the watcher is started it will automatically handle events. The
		1259	callback will be invoked whenever some events have been handled. You can
		1260	set the callback to <code>0</code> to avoid having to specify one if you are not
		1261	interested in that.</p>
		1262	<p>Also, there have not currently been made special provisions for forking:
		1263	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1264	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1265	yourself.</p>
		1266	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1267	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1268	portable one.</p>
		1269	<p>So when you want to use this feature you will always have to be prepared
		1270	that you cannot get an embeddable loop. The recommended way to get around
		1271	this is to have a separate variables for your embeddable loop, try to
		1272	create it, and if that fails, use the normal loop for everything:</p>
		1273	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1274	struct ev_loop *loop_lo = 0;
		1275	struct ev_embed embed;
		1276
		1277	// see if there is a chance of getting one that works
		1278	// (remember that a flags value of 0 means autodetection)
		1279	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1280	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1281	: 0;
		1282
		1283	// if we got one, then embed it, otherwise default to loop_hi
		1284	if (loop_lo)
		1285	{
		1286	ev_embed_init (&embed, 0, loop_lo);
		1287	ev_embed_start (loop_hi, &embed);
		1288	}
		1289	else
		1290	loop_lo = loop_hi;
		1291
		1292	</pre>
		1293	<dl>
		1294	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1295	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1296	<dd>
		1297	<p>Configures the watcher to embed the given loop, which must be
		1298	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1299	invoked automatically, otherwise it is the responsibility of the callback
		1300	to invoke it (it will continue to be called until the sweep has been done,
		1301	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1302	</dd>
		1303	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1304	<dd>
		1305	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1306	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1307	apropriate way for embedded loops.</p>
		1308	</dd>
		1309	</dl>
		1310
		1311
		1312
		1313
667		1314
668	</div>	1315	</div>
669	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1316	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
670	<div id="OTHER_FUNCTIONS_CONTENT">	1317	<div id="OTHER_FUNCTIONS_CONTENT">
671	<p>There are some other fucntions of possible interest. Described. Here. Now.</p>	1318	<p>There are some other functions of possible interest. Described. Here. Now.</p>
672	<dl>	1319	<dl>
673	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1320	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
674	<dd>	1321	<dd>
675	<p>This function combines a simple timer and an I/O watcher, calls your	1322	<p>This function combines a simple timer and an I/O watcher, calls your
676	callback on whichever event happens first and automatically stop both	1323	callback on whichever event happens first and automatically stop both
677	watchers. This is useful if you want to wait for a single event on an fd	1324	watchers. This is useful if you want to wait for a single event on an fd
678	or timeout without havign to allocate/configure/start/stop/free one or	1325	or timeout without having to allocate/configure/start/stop/free one or
679	more watchers yourself.</p>	1326	more watchers yourself.</p>
680	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is	1327	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
681	ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set	1328	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
682	will be craeted and started.</p>	1329	<code>events</code> set will be craeted and started.</p>
683	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1330	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
684	started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat	1331	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
685	= 0) will be started.</p>	1332	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
		1333	dubious value.</p>
686	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and	1334	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
687	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1335	passed an <code>revents</code> set like normal event callbacks (a combination of
688	EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p>	1336	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
		1337	value passed to <code>ev_once</code>:</p>
689	<pre> static void stdin_ready (int revents, void *arg)	1338	<pre> static void stdin_ready (int revents, void *arg)
690	{	1339	{
691	if (revents & EV_TIMEOUT)	1340	if (revents & EV_TIMEOUT)
692	/* doh, nothing entered */	1341	/* doh, nothing entered */;
693	else if (revents & EV_READ)	1342	else if (revents & EV_READ)
694	/* stdin might have data for us, joy! */	1343	/* stdin might have data for us, joy! */;
695	}	1344	}
696		1345
697	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1346	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
698		1347
699	</pre>	1348	</pre>
700	</dd>	1349	</dd>
701	<dt>ev_feed_event (loop, watcher, int events)</dt>	1350	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
702	<dd>	1351	<dd>
703	<p>Feeds the given event set into the event loop, as if the specified event	1352	<p>Feeds the given event set into the event loop, as if the specified event
704	has happened for the specified watcher (which must be a pointer to an	1353	had happened for the specified watcher (which must be a pointer to an
705	initialised but not necessarily active event watcher).</p>	1354	initialised but not necessarily started event watcher).</p>
706	</dd>	1355	</dd>
707	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1356	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
708	<dd>	1357	<dd>
709	<p>Feed an event on the given fd, as if a file descriptor backend detected it.</p>	1358	<p>Feed an event on the given fd, as if a file descriptor backend detected
		1359	the given events it.</p>
710	</dd>	1360	</dd>
711	<dt>ev_feed_signal_event (loop, int signum)</dt>	1361	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
712	<dd>	1362	<dd>
713	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1363	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1364	loop!).</p>
714	</dd>	1365	</dd>
715	</dl>	1366	</dl>
		1367
		1368
		1369
		1370
		1371
		1372	</div>
		1373	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1374	<div id="LIBEVENT_EMULATION_CONTENT">
		1375	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1376	emulate the internals of libevent, so here are some usage hints:</p>
		1377	<dl>
		1378	<dt>* Use it by including <event.h>, as usual.</dt>
		1379	<dt>* The following members are fully supported: ev_base, ev_callback,
		1380	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1381	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1382	maintained by libev, it does not work exactly the same way as in libevent (consider
		1383	it a private API).</dt>
		1384	<dt>* Priorities are not currently supported. Initialising priorities
		1385	will fail and all watchers will have the same priority, even though there
		1386	is an ev_pri field.</dt>
		1387	<dt>* Other members are not supported.</dt>
		1388	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1389	to use the libev header file and library.</dt>
		1390	</dl>
		1391
		1392	</div>
		1393	<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1394	<div id="C_SUPPORT_CONTENT">
		1395	<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1396	you to use some convinience methods to start/stop watchers and also change
		1397	the callback model to a model using method callbacks on objects.</p>
		1398	<p>To use it,</p>
		1399	<pre> #include <ev++.h>
		1400
		1401	</pre>
		1402	<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
		1403	and puts all of its definitions (many of them macros) into the global
		1404	namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
		1405	<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
		1406	<code>EV_MULTIPLICITY</code>.</p>
		1407	<p>Here is a list of things available in the <code>ev</code> namespace:</p>
		1408	<dl>
		1409	<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
		1410	<dd>
		1411	<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
		1412	macros from <cite>ev.h</cite>.</p>
		1413	</dd>
		1414	<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
		1415	<dd>
		1416	<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
		1417	</dd>
		1418	<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
		1419	<dd>
		1420	<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
		1421	the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
		1422	which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
		1423	defines by many implementations.</p>
		1424	<p>All of those classes have these methods:</p>
		1425	<p>
		1426	<dl>
		1427	<dt>ev::TYPE::TYPE (object , object::method )</dt>
		1428	<dt>ev::TYPE::TYPE (object , object::method , struct ev_loop *)</dt>
		1429	<dt>ev::TYPE::~TYPE</dt>
		1430	<dd>
		1431	<p>The constructor takes a pointer to an object and a method pointer to
		1432	the event handler callback to call in this class. The constructor calls
		1433	<code>ev_init</code> for you, which means you have to call the <code>set</code> method
		1434	before starting it. If you do not specify a loop then the constructor
		1435	automatically associates the default loop with this watcher.</p>
		1436	<p>The destructor automatically stops the watcher if it is active.</p>
		1437	</dd>
		1438	<dt>w->set (struct ev_loop *)</dt>
		1439	<dd>
		1440	<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
		1441	do this when the watcher is inactive (and not pending either).</p>
		1442	</dd>
		1443	<dt>w->set ([args])</dt>
		1444	<dd>
		1445	<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
		1446	called at least once. Unlike the C counterpart, an active watcher gets
		1447	automatically stopped and restarted.</p>
		1448	</dd>
		1449	<dt>w->start ()</dt>
		1450	<dd>
		1451	<p>Starts the watcher. Note that there is no <code>loop</code> argument as the
		1452	constructor already takes the loop.</p>
		1453	</dd>
		1454	<dt>w->stop ()</dt>
		1455	<dd>
		1456	<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
		1457	</dd>
		1458	<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
		1459	<dd>
		1460	<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
		1461	<code>ev_TYPE_again</code> function.</p>
		1462	</dd>
		1463	<dt>w->sweep () <code>ev::embed</code> only</dt>
		1464	<dd>
		1465	<p>Invokes <code>ev_embed_sweep</code>.</p>
		1466	</dd>
		1467	</dl>
		1468	</p>
		1469	</dd>
		1470	</dl>
		1471	<p>Example: Define a class with an IO and idle watcher, start one of them in
		1472	the constructor.</p>
		1473	<pre> class myclass
		1474	{
		1475	ev_io io; void io_cb (ev::io &w, int revents);
		1476	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1477
		1478	myclass ();
		1479	}
		1480
		1481	myclass::myclass (int fd)
		1482	: io (this, &myclass::io_cb),
		1483	idle (this, &myclass::idle_cb)
		1484	{
		1485	io.start (fd, ev::READ);
		1486	}
		1487
		1488	</pre>
		1489
		1490	</div>
		1491	<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1492	<div id="EMBEDDING_CONTENT">
		1493	<p>Libev can (and often is) directly embedded into host
		1494	applications. Examples of applications that embed it include the Deliantra
		1495	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1496	and rxvt-unicode.</p>
		1497	<p>The goal is to enable you to just copy the neecssary files into your
		1498	source directory without having to change even a single line in them, so
		1499	you can easily upgrade by simply copying (or having a checked-out copy of
		1500	libev somewhere in your source tree).</p>
		1501
		1502	</div>
		1503	<h2 id="FILESETS">FILESETS</h2>
		1504	<div id="FILESETS_CONTENT">
		1505	<p>Depending on what features you need you need to include one or more sets of files
		1506	in your app.</p>
		1507
		1508	</div>
		1509	<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
		1510	<div id="CORE_EVENT_LOOP_CONTENT">
		1511	<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
		1512	configuration (no autoconf):</p>
		1513	<pre> #define EV_STANDALONE 1
		1514	#include "ev.c"
		1515
		1516	</pre>
		1517	<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
		1518	single C source file only to provide the function implementations. To use
		1519	it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
		1520	done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
		1521	where you can put other configuration options):</p>
		1522	<pre> #define EV_STANDALONE 1
		1523	#include "ev.h"
		1524
		1525	</pre>
		1526	<p>Both header files and implementation files can be compiled with a C++
		1527	compiler (at least, thats a stated goal, and breakage will be treated
		1528	as a bug).</p>
		1529	<p>You need the following files in your source tree, or in a directory
		1530	in your include path (e.g. in libev/ when using -Ilibev):</p>
		1531	<pre> ev.h
		1532	ev.c
		1533	ev_vars.h
		1534	ev_wrap.h
		1535
		1536	ev_win32.c required on win32 platforms only
		1537
		1538	ev_select.c only when select backend is enabled (which is by default)
		1539	ev_poll.c only when poll backend is enabled (disabled by default)
		1540	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1541	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1542	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1543
		1544	</pre>
		1545	<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
		1546	to compile this single file.</p>
		1547
		1548	</div>
		1549	<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
		1550	<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
		1551	<p>To include the libevent compatibility API, also include:</p>
		1552	<pre> #include "event.c"
		1553
		1554	</pre>
		1555	<p>in the file including <cite>ev.c</cite>, and:</p>
		1556	<pre> #include "event.h"
		1557
		1558	</pre>
		1559	<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
		1560	<p>You need the following additional files for this:</p>
		1561	<pre> event.h
		1562	event.c
		1563
		1564	</pre>
		1565
		1566	</div>
		1567	<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
		1568	<div id="AUTOCONF_SUPPORT_CONTENT">
		1569	<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
		1570	whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
		1571	<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
		1572	include <cite>config.h</cite> and configure itself accordingly.</p>
		1573	<p>For this of course you need the m4 file:</p>
		1574	<pre> libev.m4
		1575
		1576	</pre>
		1577
		1578	</div>
		1579	<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
		1580	<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
		1581	<p>Libev can be configured via a variety of preprocessor symbols you have to define
		1582	before including any of its files. The default is not to build for multiplicity
		1583	and only include the select backend.</p>
		1584	<dl>
		1585	<dt>EV_STANDALONE</dt>
		1586	<dd>
		1587	<p>Must always be <code>1</code> if you do not use autoconf configuration, which
		1588	keeps libev from including <cite>config.h</cite>, and it also defines dummy
		1589	implementations for some libevent functions (such as logging, which is not
		1590	supported). It will also not define any of the structs usually found in
		1591	<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
		1592	</dd>
		1593	<dt>EV_USE_MONOTONIC</dt>
		1594	<dd>
		1595	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1596	monotonic clock option at both compiletime and runtime. Otherwise no use
		1597	of the monotonic clock option will be attempted. If you enable this, you
		1598	usually have to link against librt or something similar. Enabling it when
		1599	the functionality isn't available is safe, though, althoguh you have
		1600	to make sure you link against any libraries where the <code>clock_gettime</code>
		1601	function is hiding in (often <cite>-lrt</cite>).</p>
		1602	</dd>
		1603	<dt>EV_USE_REALTIME</dt>
		1604	<dd>
		1605	<p>If defined to be <code>1</code>, libev will try to detect the availability of the
		1606	realtime clock option at compiletime (and assume its availability at
		1607	runtime if successful). Otherwise no use of the realtime clock option will
		1608	be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
		1609	(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
		1610	in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
		1611	</dd>
		1612	<dt>EV_USE_SELECT</dt>
		1613	<dd>
		1614	<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
		1615	<code>select</code>(2) backend. No attempt at autodetection will be done: if no
		1616	other method takes over, select will be it. Otherwise the select backend
		1617	will not be compiled in.</p>
		1618	</dd>
		1619	<dt>EV_SELECT_USE_FD_SET</dt>
		1620	<dd>
		1621	<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
		1622	structure. This is useful if libev doesn't compile due to a missing
		1623	<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
		1624	exotic systems. This usually limits the range of file descriptors to some
		1625	low limit such as 1024 or might have other limitations (winsocket only
		1626	allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
		1627	influence the size of the <code>fd_set</code> used.</p>
		1628	</dd>
		1629	<dt>EV_SELECT_IS_WINSOCKET</dt>
		1630	<dd>
		1631	<p>When defined to <code>1</code>, the select backend will assume that
		1632	select/socket/connect etc. don't understand file descriptors but
		1633	wants osf handles on win32 (this is the case when the select to
		1634	be used is the winsock select). This means that it will call
		1635	<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
		1636	it is assumed that all these functions actually work on fds, even
		1637	on win32. Should not be defined on non-win32 platforms.</p>
		1638	</dd>
		1639	<dt>EV_USE_POLL</dt>
		1640	<dd>
		1641	<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
		1642	backend. Otherwise it will be enabled on non-win32 platforms. It
		1643	takes precedence over select.</p>
		1644	</dd>
		1645	<dt>EV_USE_EPOLL</dt>
		1646	<dd>
		1647	<p>If defined to be <code>1</code>, libev will compile in support for the Linux
		1648	<code>epoll</code>(7) backend. Its availability will be detected at runtime,
		1649	otherwise another method will be used as fallback. This is the
		1650	preferred backend for GNU/Linux systems.</p>
		1651	</dd>
		1652	<dt>EV_USE_KQUEUE</dt>
		1653	<dd>
		1654	<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
		1655	<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
		1656	otherwise another method will be used as fallback. This is the preferred
		1657	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		1658	supports some types of fds correctly (the only platform we found that
		1659	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		1660	not be used unless explicitly requested. The best way to use it is to find
		1661	out whether kqueue supports your type of fd properly and use an embedded
		1662	kqueue loop.</p>
		1663	</dd>
		1664	<dt>EV_USE_PORT</dt>
		1665	<dd>
		1666	<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
		1667	10 port style backend. Its availability will be detected at runtime,
		1668	otherwise another method will be used as fallback. This is the preferred
		1669	backend for Solaris 10 systems.</p>
		1670	</dd>
		1671	<dt>EV_USE_DEVPOLL</dt>
		1672	<dd>
		1673	<p>reserved for future expansion, works like the USE symbols above.</p>
		1674	</dd>
		1675	<dt>EV_H</dt>
		1676	<dd>
		1677	<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
		1678	undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
		1679	can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
		1680	</dd>
		1681	<dt>EV_CONFIG_H</dt>
		1682	<dd>
		1683	<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
		1684	<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
		1685	<code>EV_H</code>, above.</p>
		1686	</dd>
		1687	<dt>EV_EVENT_H</dt>
		1688	<dd>
		1689	<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
		1690	of how the <cite>event.h</cite> header can be found.</p>
		1691	</dd>
		1692	<dt>EV_PROTOTYPES</dt>
		1693	<dd>
		1694	<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
		1695	prototypes, but still define all the structs and other symbols. This is
		1696	occasionally useful if you want to provide your own wrapper functions
		1697	around libev functions.</p>
		1698	</dd>
		1699	<dt>EV_MULTIPLICITY</dt>
		1700	<dd>
		1701	<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
		1702	will have the <code>struct ev_loop *</code> as first argument, and you can create
		1703	additional independent event loops. Otherwise there will be no support
		1704	for multiple event loops and there is no first event loop pointer
		1705	argument. Instead, all functions act on the single default loop.</p>
		1706	</dd>
		1707	<dt>EV_PERIODICS</dt>
		1708	<dd>
		1709	<p>If undefined or defined to be <code>1</code>, then periodic timers are supported,
		1710	otherwise not. This saves a few kb of code.</p>
		1711	</dd>
		1712	<dt>EV_COMMON</dt>
		1713	<dd>
		1714	<p>By default, all watchers have a <code>void *data</code> member. By redefining
		1715	this macro to a something else you can include more and other types of
		1716	members. You have to define it each time you include one of the files,
		1717	though, and it must be identical each time.</p>
		1718	<p>For example, the perl EV module uses something like this:</p>
		1719	<pre> #define EV_COMMON \
		1720	SV self; / contains this struct */ \
		1721	SV cb_sv, fh /* note no trailing ";" */
		1722
		1723	</pre>
		1724	</dd>
		1725	<dt>EV_CB_DECLARE (type)</dt>
		1726	<dt>EV_CB_INVOKE (watcher, revents)</dt>
		1727	<dt>ev_set_cb (ev, cb)</dt>
		1728	<dd>
		1729	<p>Can be used to change the callback member declaration in each watcher,
		1730	and the way callbacks are invoked and set. Must expand to a struct member
		1731	definition and a statement, respectively. See the <cite>ev.v</cite> header file for
		1732	their default definitions. One possible use for overriding these is to
		1733	avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
		1734	method calls instead of plain function calls in C++.</p>
		1735
		1736	</div>
		1737	<h2 id="EXAMPLES">EXAMPLES</h2>
		1738	<div id="EXAMPLES_CONTENT">
		1739	<p>For a real-world example of a program the includes libev
		1740	verbatim, you can have a look at the EV perl module
		1741	(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
		1742	the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
		1743	interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
		1744	will be compiled. It is pretty complex because it provides its own header
		1745	file.</p>
		1746	<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
		1747	that everybody includes and which overrides some autoconf choices:</p>
		1748	<pre> #define EV_USE_POLL 0
		1749	#define EV_MULTIPLICITY 0
		1750	#define EV_PERIODICS 0
		1751	#define EV_CONFIG_H <config.h>
		1752
		1753	#include "ev++.h"
		1754
		1755	</pre>
		1756	<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
		1757	<pre> #include "ev_cpp.h"
		1758	#include "ev.c"
		1759
		1760
		1761
		1762
		1763	</pre>
		1764
		1765	</div>
		1766	<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1767	<div id="COMPLEXITIES_CONTENT">
		1768	<p>In this section the complexities of (many of) the algorithms used inside
		1769	libev will be explained. For complexity discussions about backends see the
		1770	documentation for <code>ev_default_init</code>.</p>
		1771	<p>
		1772	<dl>
		1773	<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
		1774	<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
		1775	<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
		1776	<dt>Stopping check/prepare/idle watchers: O(1)</dt>
		1777	<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
		1778	<dt>Finding the next timer per loop iteration: O(1)</dt>
		1779	<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
		1780	<dt>Activating one watcher: O(1)</dt>
		1781	</dl>
		1782	</p>
		1783
		1784
		1785
		1786
716		1787
717	</div>	1788	</div>
718	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1789	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
719	<div id="AUTHOR_CONTENT">	1790	<div id="AUTHOR_CONTENT">
720	<p>Marc Lehmann <libev@schmorp.de>.</p>	1791	<p>Marc Lehmann <libev@schmorp.de>.</p>
721		1792
722	</div>	1793	</div>
723	</div></body>	1794	</div></body>
724	</html>	1795	</html>

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Comparing libev/ev.html (file contents): Revision 1.7 by root, Mon Nov 12 08:16:02 2007 UTC vs. Revision 1.47 by root, Mon Nov 26 10:20:43 2007 UTC

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Comparing libev/ev.html (file contents):
Revision 1.7 by root, Mon Nov 12 08:16:02 2007 UTC vs.
Revision 1.47 by root, Mon Nov 26 10:20:43 2007 UTC