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…		…
4	<head>	4	<head>
5	<title>libev</title>	5	<title>libev</title>
6	<meta name="description" content="Pod documentation for libev" />	6	<meta name="description" content="Pod documentation for libev" />
7	<meta name="inputfile" content="<standard input>" />	7	<meta name="inputfile" content="<standard input>" />
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9	<meta name="created" content="Mon Nov 12 09:12:14 2007" />	9	<meta name="created" content="Sat Nov 24 08:13:46 2007" />
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12	<body>	12	<body>
13	<div class="pod">	13	<div class="pod">
14	<!-- INDEX START -->	14	<!-- INDEX START -->
…		…
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="#SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF 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 recurring 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_wait_for_pid_stat"><code>ev_child</code> - wait for pid 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>
39	<li><a href="#AUTHOR">AUTHOR</a>	44	<li><a href="#AUTHOR">AUTHOR</a>
40	</li>	45	</li>
41	</ul><hr />	46	</ul><hr />
42	<!-- INDEX END -->	47	<!-- INDEX END -->
43		48
…		…
72	<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific	77	<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific
73	kqueue mechanisms for file descriptor events, relative timers, absolute	78	kqueue mechanisms for file descriptor events, relative timers, absolute
74	timers with customised rescheduling, signal events, process status change	79	timers with customised rescheduling, signal events, process status change
75	events (related to SIGCHLD), and event watchers dealing with the event	80	events (related to SIGCHLD), and event watchers dealing with the event
76	loop mechanism itself (idle, prepare and check watchers). It also is quite	81	loop mechanism itself (idle, prepare and check watchers). It also is quite
77	fast (see a <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it	82	fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing
78	to libevent).</p>	83	it to libevent for example).</p>
79		84
80	</div>	85	</div>
81	<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	86	<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
82	<div id="CONVENTIONS_CONTENT">	87	<div id="CONVENTIONS_CONTENT">
83	<p>Libev is very configurable. In this manual the default configuration	88	<p>Libev is very configurable. In this manual the default configuration
84	will be described, which supports multiple event loops. For more info	89	will be described, which supports multiple event loops. For more info
85	about various configuraiton options please have a look at the file	90	about various configuration options please have a look at the file
86	<cite>README.embed</cite> in the libev distribution. If libev was configured without	91	<cite>README.embed</cite> in the libev distribution. If libev was configured without
87	support for multiple event loops, then all functions taking an initial	92	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>)	93	argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
89	will not have this argument.</p>	94	will not have this argument.</p>
90		95
91	</div>	96	</div>
92	<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	97	<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">	98	<div id="TIME_REPRESENTATION_CONTENT">
94	<p>Libev represents time as a single floating point number, representing the	99	<p>Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	100	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	the beginning of 1970, details are complicated, don't ask). This type is	101	the beginning of 1970, details are complicated, don't ask). This type is
97	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	102	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
98	to the double type in C.</p>	103	to the <code>double</code> type in C, and when you need to do any calculations on
		104	it, you should treat it as such.</p>
		105
		106
		107
		108
		109
		110	</div>
		111	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
		112	<div id="GLOBAL_FUNCTIONS_CONTENT">
		113	<p>These functions can be called anytime, even before initialising the
		114	library in any way.</p>
99	<dl>	115	<dl>
100	<dt>ev_tstamp ev_time ()</dt>	116	<dt>ev_tstamp ev_time ()</dt>
101	<dd>	117	<dd>
102	<p>Returns the current time as libev would use it.</p>	118	<p>Returns the current time as libev would use it. Please note that the
		119	<code>ev_now</code> function is usually faster and also often returns the timestamp
		120	you actually want to know.</p>
103	</dd>	121	</dd>
104	<dt>int ev_version_major ()</dt>	122	<dt>int ev_version_major ()</dt>
105	<dt>int ev_version_minor ()</dt>	123	<dt>int ev_version_minor ()</dt>
106	<dd>	124	<dd>
107	<p>You can find out the major and minor version numbers of the library	125	<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	126	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	127	<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	128	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>	129	version of the library your program was compiled against.</p>
112	<p>Usually, its a good idea to terminate if the major versions mismatch,	130	<p>Usually, it's a good idea to terminate if the major versions mismatch,
113	as this indicates an incompatible change. Minor versions are usually	131	as this indicates an incompatible change. Minor versions are usually
114	compatible to older versions, so a larger minor version alone is usually	132	compatible to older versions, so a larger minor version alone is usually
115	not a problem.</p>	133	not a problem.</p>
		134	<p>Example: make sure we haven't accidentally been linked against the wrong
		135	version:</p>
		136	<pre> assert (("libev version mismatch",
		137	ev_version_major () == EV_VERSION_MAJOR
		138	&& ev_version_minor () >= EV_VERSION_MINOR));
		139
		140	</pre>
		141	</dd>
		142	<dt>unsigned int ev_supported_backends ()</dt>
		143	<dd>
		144	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
		145	value) compiled into this binary of libev (independent of their
		146	availability on the system you are running on). See <code>ev_default_loop</code> for
		147	a description of the set values.</p>
		148	<p>Example: make sure we have the epoll method, because yeah this is cool and
		149	a must have and can we have a torrent of it please!!!11</p>
		150	<pre> assert (("sorry, no epoll, no sex",
		151	ev_supported_backends () & EVBACKEND_EPOLL));
		152
		153	</pre>
		154	</dd>
		155	<dt>unsigned int ev_recommended_backends ()</dt>
		156	<dd>
		157	<p>Return the set of all backends compiled into this binary of libev and also
		158	recommended for this platform. This set is often smaller than the one
		159	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
		160	most BSDs and will not be autodetected unless you explicitly request it
		161	(assuming you know what you are doing). This is the set of backends that
		162	libev will probe for if you specify no backends explicitly.</p>
		163	</dd>
		164	<dt>unsigned int ev_embeddable_backends ()</dt>
		165	<dd>
		166	<p>Returns the set of backends that are embeddable in other event loops. This
		167	is the theoretical, all-platform, value. To find which backends
		168	might be supported on the current system, you would need to look at
		169	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		170	recommended ones.</p>
		171	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
116	</dd>	172	</dd>
117	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	173	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
118	<dd>	174	<dd>
119	<p>Sets the allocation function to use (the prototype is similar to the	175	<p>Sets the allocation function to use (the prototype is similar to the
120	realloc function). It is used to allocate and free memory (no surprises	176	realloc C function, the semantics are identical). It is used to allocate
121	here). If it returns zero when memory needs to be allocated, the library	177	and free memory (no surprises here). If it returns zero when memory
122	might abort or take some potentially destructive action. The default is	178	needs to be allocated, the library might abort or take some potentially
123	your system realloc function.</p>	179	destructive action. The default is your system realloc function.</p>
124	<p>You could override this function in high-availability programs to, say,	180	<p>You could override this function in high-availability programs to, say,
125	free some memory if it cannot allocate memory, to use a special allocator,	181	free some memory if it cannot allocate memory, to use a special allocator,
126	or even to sleep a while and retry until some memory is available.</p>	182	or even to sleep a while and retry until some memory is available.</p>
		183	<p>Example: replace the libev allocator with one that waits a bit and then
		184	retries: better than mine).</p>
		185	<pre> static void *
		186	persistent_realloc (void *ptr, long size)
		187	{
		188	for (;;)
		189	{
		190	void *newptr = realloc (ptr, size);
		191
		192	if (newptr)
		193	return newptr;
		194
		195	sleep (60);
		196	}
		197	}
		198
		199	...
		200	ev_set_allocator (persistent_realloc);
		201
		202	</pre>
127	</dd>	203	</dd>
128	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	204	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
129	<dd>	205	<dd>
130	<p>Set the callback function to call on a retryable syscall error (such	206	<p>Set the callback function to call on a retryable syscall error (such
131	as failed select, poll, epoll_wait). The message is a printable string	207	as failed select, poll, epoll_wait). The message is a printable string
132	indicating the system call or subsystem causing the problem. If this	208	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	209	callback is set, then libev will expect it to remedy the sitution, no
134	matter what, when it returns. That is, libev will geenrally retry the	210	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	211	requested operation, or, if the condition doesn't go away, do bad stuff
136	(such as abort).</p>	212	(such as abort).</p>
		213	<p>Example: do the same thing as libev does internally:</p>
		214	<pre> static void
		215	fatal_error (const char *msg)
		216	{
		217	perror (msg);
		218	abort ();
		219	}
		220
		221	...
		222	ev_set_syserr_cb (fatal_error);
		223
		224	</pre>
137	</dd>	225	</dd>
138	</dl>	226	</dl>
139		227
140	</div>	228	</div>
141	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	229	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
142	<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">	230	<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	231	<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	232	types of such loops, the <i>default</i> loop, which supports signals and child
145	events, and dynamically created loops which do not.</p>	233	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	234	<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	235	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 lockign	236	create, you also create another event loop. Libev itself does no locking
149	whatsoever, so if you mix calls to different event loops, make sure you	237	whatsoever, so if you mix calls to the same event loop in different
150	lock (this is usually a bad idea, though, even if done right).</p>	238	threads, make sure you lock (this is usually a bad idea, though, even if
		239	done correctly, because it's hideous and inefficient).</p>
151	<dl>	240	<dl>
152	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>	241	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
153	<dd>	242	<dd>
154	<p>This will initialise the default event loop if it hasn't been initialised	243	<p>This will initialise the default event loop if it hasn't been initialised
155	yet and return it. If the default loop could not be initialised, returns	244	yet and return it. If the default loop could not be initialised, returns
156	false. If it already was initialised it simply returns it (and ignores the	245	false. If it already was initialised it simply returns it (and ignores the
157	flags).</p>	246	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
158	<p>If you don't know what event loop to use, use the one returned from this	247	<p>If you don't know what event loop to use, use the one returned from this
159	function.</p>	248	function.</p>
160	<p>The flags argument can be used to specify special behaviour or specific	249	<p>The flags argument can be used to specify special behaviour or specific
161	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p>	250	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
162	<p>It supports the following flags:</p>	251	<p>The following flags are supported:</p>
163	<p>	252	<p>
164	<dl>	253	<dl>
165	<dt>EVFLAG_AUTO</dt>	254	<dt><code>EVFLAG_AUTO</code></dt>
166	<dd>	255	<dd>
167	<p>The default flags value. Use this if you have no clue (its the right	256	<p>The default flags value. Use this if you have no clue (it's the right
168	thing, believe me).</p>	257	thing, believe me).</p>
169	</dd>	258	</dd>
170	<dt>EVFLAG_NOENV</dt>	259	<dt><code>EVFLAG_NOENV</code></dt>
171	<dd>	260	<dd>
172	<p>If this flag bit is ored into the flag value then libev will <i>not</i> look	261	<p>If this flag bit is ored into the flag value (or the program runs setuid
173	at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this	262	or setgid) then libev will <i>not</i> look at the environment variable
174	environment variable will override the flags completely. This is useful	263	<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
		264	override the flags completely if it is found in the environment. This is
175	to try out specific backends to tets their performance, or to work around	265	useful to try out specific backends to test their performance, or to work
176	bugs.</p>	266	around bugs.</p>
177	</dd>	267	</dd>
178	<dt>EVMETHOD_SELECT portable select backend</dt>	268	<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
179	<dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt>
180	<dt>EVMETHOD_EPOLL linux only</dt>
181	<dt>EVMETHOD_KQUEUE some bsds only</dt>
182	<dt>EVMETHOD_DEVPOLL solaris 8 only</dt>
183	<dt>EVMETHOD_PORT solaris 10 only</dt>
184	<dd>	269	<dd>
185	<p>If one or more of these are ored into the flags value, then only these	270	<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
186	backends will be tried (in the reverse order as given here). If one are	271	libev tries to roll its own fd_set with no limits on the number of fds,
187	specified, any backend will do.</p>	272	but if that fails, expect a fairly low limit on the number of fds when
		273	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		274	the fastest backend for a low number of fds.</p>
		275	</dd>
		276	<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
		277	<dd>
		278	<p>And this is your standard poll(2) backend. It's more complicated than
		279	select, but handles sparse fds better and has no artificial limit on the
		280	number of fds you can use (except it will slow down considerably with a
		281	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
		282	</dd>
		283	<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
		284	<dd>
		285	<p>For few fds, this backend is a bit little slower than poll and select,
		286	but it scales phenomenally better. While poll and select usually scale like
		287	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		288	either O(1) or O(active_fds).</p>
		289	<p>While stopping and starting an I/O watcher in the same iteration will
		290	result in some caching, there is still a syscall per such incident
		291	(because the fd could point to a different file description now), so its
		292	best to avoid that. Also, dup()ed file descriptors might not work very
		293	well if you register events for both fds.</p>
		294	<p>Please note that epoll sometimes generates spurious notifications, so you
		295	need to use non-blocking I/O or other means to avoid blocking when no data
		296	(or space) is available.</p>
		297	</dd>
		298	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
		299	<dd>
		300	<p>Kqueue deserves special mention, as at the time of this writing, it
		301	was broken on all BSDs except NetBSD (usually it doesn't work with
		302	anything but sockets and pipes, except on Darwin, where of course its
		303	completely useless). For this reason its not being "autodetected"
		304	unless you explicitly specify it explicitly in the flags (i.e. using
		305	<code>EVBACKEND_KQUEUE</code>).</p>
		306	<p>It scales in the same way as the epoll backend, but the interface to the
		307	kernel is more efficient (which says nothing about its actual speed, of
		308	course). While starting and stopping an I/O watcher does not cause an
		309	extra syscall as with epoll, it still adds up to four event changes per
		310	incident, so its best to avoid that.</p>
		311	</dd>
		312	<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
		313	<dd>
		314	<p>This is not implemented yet (and might never be).</p>
		315	</dd>
		316	<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
		317	<dd>
		318	<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
		319	it's really slow, but it still scales very well (O(active_fds)).</p>
		320	<p>Please note that solaris ports can result in a lot of spurious
		321	notifications, so you need to use non-blocking I/O or other means to avoid
		322	blocking when no data (or space) is available.</p>
		323	</dd>
		324	<dt><code>EVBACKEND_ALL</code></dt>
		325	<dd>
		326	<p>Try all backends (even potentially broken ones that wouldn't be tried
		327	with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
		328	<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
188	</dd>	329	</dd>
189	</dl>	330	</dl>
190	</p>	331	</p>
		332	<p>If one or more of these are ored into the flags value, then only these
		333	backends will be tried (in the reverse order as given here). If none are
		334	specified, most compiled-in backend will be tried, usually in reverse
		335	order of their flag values :)</p>
		336	<p>The most typical usage is like this:</p>
		337	<pre> if (!ev_default_loop (0))
		338	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		339
		340	</pre>
		341	<p>Restrict libev to the select and poll backends, and do not allow
		342	environment settings to be taken into account:</p>
		343	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		344
		345	</pre>
		346	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		347	available (warning, breaks stuff, best use only with your own private
		348	event loop and only if you know the OS supports your types of fds):</p>
		349	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		350
		351	</pre>
191	</dd>	352	</dd>
192	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	353	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
193	<dd>	354	<dd>
194	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	355	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
195	always distinct from the default loop. Unlike the default loop, it cannot	356	always distinct from the default loop. Unlike the default loop, it cannot
196	handle signal and child watchers, and attempts to do so will be greeted by	357	handle signal and child watchers, and attempts to do so will be greeted by
197	undefined behaviour (or a failed assertion if assertions are enabled).</p>	358	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		359	<p>Example: try to create a event loop that uses epoll and nothing else.</p>
		360	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		361	if (!epoller)
		362	fatal ("no epoll found here, maybe it hides under your chair");
		363
		364	</pre>
198	</dd>	365	</dd>
199	<dt>ev_default_destroy ()</dt>	366	<dt>ev_default_destroy ()</dt>
200	<dd>	367	<dd>
201	<p>Destroys the default loop again (frees all memory and kernel state	368	<p>Destroys the default loop again (frees all memory and kernel state
202	etc.). This stops all registered event watchers (by not touching them in	369	etc.). This stops all registered event watchers (by not touching them in
203	any way whatsoever, although you cnanot rely on this :).</p>	370	any way whatsoever, although you cannot rely on this :).</p>
204	</dd>	371	</dd>
205	<dt>ev_loop_destroy (loop)</dt>	372	<dt>ev_loop_destroy (loop)</dt>
206	<dd>	373	<dd>
207	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an	374	<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
208	earlier call to <code>ev_loop_new</code>.</p>	375	earlier call to <code>ev_loop_new</code>.</p>
…		…
211	<dd>	378	<dd>
212	<p>This function reinitialises the kernel state for backends that have	379	<p>This function reinitialises the kernel state for backends that have
213	one. Despite the name, you can call it anytime, but it makes most sense	380	one. Despite the name, you can call it anytime, but it makes most sense
214	after forking, in either the parent or child process (or both, but that	381	after forking, in either the parent or child process (or both, but that
215	again makes little sense).</p>	382	again makes little sense).</p>
216	<p>You <i>must</i> call this function after forking if and only if you want to	383	<p>You <i>must</i> call this function in the child process after forking if and
217	use the event library in both processes. If you just fork+exec, you don't	384	only if you want to use the event library in both processes. If you just
218	have to call it.</p>	385	fork+exec, you don't have to call it.</p>
219	<p>The function itself is quite fast and its usually not a problem to call	386	<p>The function itself is quite fast and it's usually not a problem to call
220	it just in case after a fork. To make this easy, the function will fit in	387	it just in case after a fork. To make this easy, the function will fit in
221	quite nicely into a call to <code>pthread_atfork</code>:</p>	388	quite nicely into a call to <code>pthread_atfork</code>:</p>
222	<pre> pthread_atfork (0, 0, ev_default_fork);	389	<pre> pthread_atfork (0, 0, ev_default_fork);
223		390
224	</pre>	391	</pre>
		392	<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
		393	without calling this function, so if you force one of those backends you
		394	do not need to care.</p>
225	</dd>	395	</dd>
226	<dt>ev_loop_fork (loop)</dt>	396	<dt>ev_loop_fork (loop)</dt>
227	<dd>	397	<dd>
228	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by	398	<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
229	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop	399	<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
230	after fork, and how you do this is entirely your own problem.</p>	400	after fork, and how you do this is entirely your own problem.</p>
231	</dd>	401	</dd>
232	<dt>unsigned int ev_method (loop)</dt>	402	<dt>unsigned int ev_backend (loop)</dt>
233	<dd>	403	<dd>
234	<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in	404	<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
235	use.</p>	405	use.</p>
236	</dd>	406	</dd>
237	<dt>ev_tstamp = ev_now (loop)</dt>	407	<dt>ev_tstamp ev_now (loop)</dt>
238	<dd>	408	<dd>
239	<p>Returns the current "event loop time", which is the time the event loop	409	<p>Returns the current "event loop time", which is the time the event loop
240	got events and started processing them. This timestamp does not change	410	received events and started processing them. This timestamp does not
241	as long as callbacks are being processed, and this is also the base time	411	change as long as callbacks are being processed, and this is also the base
242	used for relative timers. You can treat it as the timestamp of the event	412	time used for relative timers. You can treat it as the timestamp of the
243	occuring (or more correctly, the mainloop finding out about it).</p>	413	event occuring (or more correctly, libev finding out about it).</p>
244	</dd>	414	</dd>
245	<dt>ev_loop (loop, int flags)</dt>	415	<dt>ev_loop (loop, int flags)</dt>
246	<dd>	416	<dd>
247	<p>Finally, this is it, the event handler. This function usually is called	417	<p>Finally, this is it, the event handler. This function usually is called
248	after you initialised all your watchers and you want to start handling	418	after you initialised all your watchers and you want to start handling
249	events.</p>	419	events.</p>
250	<p>If the flags argument is specified as 0, it will not return until either	420	<p>If the flags argument is specified as <code>0</code>, it will not return until
251	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	421	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		422	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		423	relying on all watchers to be stopped when deciding when a program has
		424	finished (especially in interactive programs), but having a program that
		425	automatically loops as long as it has to and no longer by virtue of
		426	relying on its watchers stopping correctly is a thing of beauty.</p>
252	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	427	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
253	those events and any outstanding ones, but will not block your process in	428	those events and any outstanding ones, but will not block your process in
254	case there are no events.</p>	429	case there are no events and will return after one iteration of the loop.</p>
255	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	430	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
256	neccessary) and will handle those and any outstanding ones. It will block	431	neccessary) and will handle those and any outstanding ones. It will block
257	your process until at least one new event arrives.</p>	432	your process until at least one new event arrives, and will return after
258	<p>This flags value could be used to implement alternative looping	433	one iteration of the loop. This is useful if you are waiting for some
259	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	434	external event in conjunction with something not expressible using other
260	more generic mechanism.</p>	435	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
		436	usually a better approach for this kind of thing.</p>
		437	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
		438	<pre> * If there are no active watchers (reference count is zero), return.
		439	- Queue prepare watchers and then call all outstanding watchers.
		440	- If we have been forked, recreate the kernel state.
		441	- Update the kernel state with all outstanding changes.
		442	- Update the "event loop time".
		443	- Calculate for how long to block.
		444	- Block the process, waiting for any events.
		445	- Queue all outstanding I/O (fd) events.
		446	- Update the "event loop time" and do time jump handling.
		447	- Queue all outstanding timers.
		448	- Queue all outstanding periodics.
		449	- If no events are pending now, queue all idle watchers.
		450	- Queue all check watchers.
		451	- Call all queued watchers in reverse order (i.e. check watchers first).
		452	Signals and child watchers are implemented as I/O watchers, and will
		453	be handled here by queueing them when their watcher gets executed.
		454	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		455	were used, return, otherwise continue with step *.
		456
		457	</pre>
		458	<p>Example: queue some jobs and then loop until no events are outsanding
		459	anymore.</p>
		460	<pre> ... queue jobs here, make sure they register event watchers as long
		461	... as they still have work to do (even an idle watcher will do..)
		462	ev_loop (my_loop, 0);
		463	... jobs done. yeah!
		464
		465	</pre>
261	</dd>	466	</dd>
262	<dt>ev_unloop (loop, how)</dt>	467	<dt>ev_unloop (loop, how)</dt>
263	<dd>	468	<dd>
264	<p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument	469	<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
		470	has processed all outstanding events). The <code>how</code> argument must be either
265	must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code>	471	<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
266	call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code>	472	<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
267	calls return.</p>
268	</dd>	473	</dd>
269	<dt>ev_ref (loop)</dt>	474	<dt>ev_ref (loop)</dt>
270	<dt>ev_unref (loop)</dt>	475	<dt>ev_unref (loop)</dt>
271	<dd>	476	<dd>
272	<p>Ref/unref can be used to add or remove a refcount on the event loop: Every	477	<p>Ref/unref can be used to add or remove a reference count on the event
273	watcher keeps one reference. If you have a long-runing watcher you never	478	loop: Every watcher keeps one reference, and as long as the reference
274	unregister that should not keep ev_loop from running, ev_unref() after	479	count is nonzero, <code>ev_loop</code> will not return on its own. If you have
275	starting, and ev_ref() before stopping it. Libev itself uses this for	480	a watcher you never unregister that should not keep <code>ev_loop</code> from
276	example for its internal signal pipe: It is not visible to you as a user	481	returning, ev_unref() after starting, and ev_ref() before stopping it. For
277	and should not keep <code>ev_loop</code> from exiting if the work is done. It is	482	example, libev itself uses this for its internal signal pipe: It is not
278	also an excellent way to do this for generic recurring timers or from	483	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
279	within third-party libraries. Just remember to unref after start and ref	484	no event watchers registered by it are active. It is also an excellent
280	before stop.</p>	485	way to do this for generic recurring timers or from within third-party
		486	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		487	<p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
		488	running when nothing else is active.</p>
		489	<pre> struct dv_signal exitsig;
		490	ev_signal_init (&exitsig, sig_cb, SIGINT);
		491	ev_signal_start (myloop, &exitsig);
		492	evf_unref (myloop);
		493
		494	</pre>
		495	<p>Example: for some weird reason, unregister the above signal handler again.</p>
		496	<pre> ev_ref (myloop);
		497	ev_signal_stop (myloop, &exitsig);
		498
		499	</pre>
281	</dd>	500	</dd>
282	</dl>	501	</dl>
283		502
284	</div>	503	</div>
285	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	504	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
286	<div id="ANATOMY_OF_A_WATCHER_CONTENT">	505	<div id="ANATOMY_OF_A_WATCHER_CONTENT">
287	<p>A watcher is a structure that you create and register to record your	506	<p>A watcher is a structure that you create and register to record your
288	interest in some event. For instance, if you want to wait for STDIN to	507	interest in some event. For instance, if you want to wait for STDIN to
289	become readable, you would create an ev_io watcher for that:</p>	508	become readable, you would create an <code>ev_io</code> watcher for that:</p>
290	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	509	<pre> static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
291	{	510	{
292	ev_io_stop (w);	511	ev_io_stop (w);
293	ev_unloop (loop, EVUNLOOP_ALL);	512	ev_unloop (loop, EVUNLOOP_ALL);
294	}	513	}
…		…
317	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher	536	with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
318	*)</code>), and you can stop watching for events at any time by calling the	537	*)</code>), and you can stop watching for events at any time by calling the
319	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>	538	corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
320	<p>As long as your watcher is active (has been started but not stopped) you	539	<p>As long as your watcher is active (has been started but not stopped) you
321	must not touch the values stored in it. Most specifically you must never	540	must not touch the values stored in it. Most specifically you must never
322	reinitialise it or call its set method.</p>	541	reinitialise it or call its <code>set</code> macro.</p>
323	<p>You cna check whether an event is active by calling the <code>ev_is_active
324	(watcher *)</code> macro. To see whether an event is outstanding (but the
325	callback for it has not been called yet) you cna use the <code>ev_is_pending
326	(watcher *)</code> macro.</p>
327	<p>Each and every callback receives the event loop pointer as first, the	542	<p>Each and every callback receives the event loop pointer as first, the
328	registered watcher structure as second, and a bitset of received events as	543	registered watcher structure as second, and a bitset of received events as
329	third argument.</p>	544	third argument.</p>
330	<p>The rceeived events usually include a single bit per event type received	545	<p>The received events usually include a single bit per event type received
331	(you can receive multiple events at the same time). The possible bit masks	546	(you can receive multiple events at the same time). The possible bit masks
332	are:</p>	547	are:</p>
333	<dl>	548	<dl>
334	<dt>EV_READ</dt>	549	<dt><code>EV_READ</code></dt>
335	<dt>EV_WRITE</dt>	550	<dt><code>EV_WRITE</code></dt>
336	<dd>	551	<dd>
337	<p>The file descriptor in the ev_io watcher has become readable and/or	552	<p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
338	writable.</p>	553	writable.</p>
339	</dd>	554	</dd>
340	<dt>EV_TIMEOUT</dt>	555	<dt><code>EV_TIMEOUT</code></dt>
341	<dd>
342	<p>The ev_timer watcher has timed out.</p>
343	</dd>	556	<dd>
344	<dt>EV_PERIODIC</dt>	557	<p>The <code>ev_timer</code> watcher has timed out.</p>
345	<dd>	558	</dd>
346	<p>The ev_periodic watcher has timed out.</p>	559	<dt><code>EV_PERIODIC</code></dt>
347	</dd>	560	<dd>
348	<dt>EV_SIGNAL</dt>	561	<p>The <code>ev_periodic</code> watcher has timed out.</p>
349	<dd>	562	</dd>
		563	<dt><code>EV_SIGNAL</code></dt>
		564	<dd>
350	<p>The signal specified in the ev_signal watcher has been received by a thread.</p>	565	<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
351	</dd>
352	<dt>EV_CHILD</dt>
353	<dd>	566	</dd>
		567	<dt><code>EV_CHILD</code></dt>
		568	<dd>
354	<p>The pid specified in the ev_child watcher has received a status change.</p>	569	<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
355	</dd>
356	<dt>EV_IDLE</dt>
357	<dd>	570	</dd>
		571	<dt><code>EV_IDLE</code></dt>
		572	<dd>
358	<p>The ev_idle watcher has determined that you have nothing better to do.</p>	573	<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
359	</dd>
360	<dt>EV_PREPARE</dt>
361	<dt>EV_CHECK</dt>
362	<dd>	574	</dd>
		575	<dt><code>EV_PREPARE</code></dt>
		576	<dt><code>EV_CHECK</code></dt>
		577	<dd>
363	<p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts	578	<p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
364	to gather new events, and all ev_check watchers are invoked just after	579	to gather new events, and all <code>ev_check</code> watchers are invoked just after
365	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any	580	<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
366	received events. Callbacks of both watcher types can start and stop as	581	received events. Callbacks of both watcher types can start and stop as
367	many watchers as they want, and all of them will be taken into account	582	many watchers as they want, and all of them will be taken into account
368	(for example, a ev_prepare watcher might start an idle watcher to keep	583	(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
369	<code>ev_loop</code> from blocking).</p>	584	<code>ev_loop</code> from blocking).</p>
370	</dd>	585	</dd>
371	<dt>EV_ERROR</dt>	586	<dt><code>EV_ERROR</code></dt>
372	<dd>	587	<dd>
373	<p>An unspecified error has occured, the watcher has been stopped. This might	588	<p>An unspecified error has occured, the watcher has been stopped. This might
374	happen because the watcher could not be properly started because libev	589	happen because the watcher could not be properly started because libev
375	ran out of memory, a file descriptor was found to be closed or any other	590	ran out of memory, a file descriptor was found to be closed or any other
376	problem. You best act on it by reporting the problem and somehow coping	591	problem. You best act on it by reporting the problem and somehow coping
…		…
382	programs, though, so beware.</p>	597	programs, though, so beware.</p>
383	</dd>	598	</dd>
384	</dl>	599	</dl>
385		600
386	</div>	601	</div>
		602	<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2>
		603	<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2">
		604	<p>In the following description, <code>TYPE</code> stands for the watcher type,
		605	e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
		606	<dl>
		607	<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
		608	<dd>
		609	<p>This macro initialises the generic portion of a watcher. The contents
		610	of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
		611	the generic parts of the watcher are initialised, you <i>need</i> to call
		612	the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
		613	type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
		614	which rolls both calls into one.</p>
		615	<p>You can reinitialise a watcher at any time as long as it has been stopped
		616	(or never started) and there are no pending events outstanding.</p>
		617	<p>The callbakc is always of type <code>void ()(ev_loop loop, ev_TYPE *watcher,
		618	int revents)</code>.</p>
		619	</dd>
		620	<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
		621	<dd>
		622	<p>This macro initialises the type-specific parts of a watcher. You need to
		623	call <code>ev_init</code> at least once before you call this macro, but you can
		624	call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
		625	macro on a watcher that is active (it can be pending, however, which is a
		626	difference to the <code>ev_init</code> macro).</p>
		627	<p>Although some watcher types do not have type-specific arguments
		628	(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
		629	</dd>
		630	<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
		631	<dd>
		632	<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
		633	calls into a single call. This is the most convinient method to initialise
		634	a watcher. The same limitations apply, of course.</p>
		635	</dd>
		636	<dt><code>ev_TYPE_start</code> (loop , ev_TYPE watcher)</dt>
		637	<dd>
		638	<p>Starts (activates) the given watcher. Only active watchers will receive
		639	events. If the watcher is already active nothing will happen.</p>
		640	</dd>
		641	<dt><code>ev_TYPE_stop</code> (loop , ev_TYPE watcher)</dt>
		642	<dd>
		643	<p>Stops the given watcher again (if active) and clears the pending
		644	status. It is possible that stopped watchers are pending (for example,
		645	non-repeating timers are being stopped when they become pending), but
		646	<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
		647	you want to free or reuse the memory used by the watcher it is therefore a
		648	good idea to always call its <code>ev_TYPE_stop</code> function.</p>
		649	</dd>
		650	<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
		651	<dd>
		652	<p>Returns a true value iff the watcher is active (i.e. it has been started
		653	and not yet been stopped). As long as a watcher is active you must not modify
		654	it.</p>
		655	</dd>
		656	<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
		657	<dd>
		658	<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
		659	events but its callback has not yet been invoked). As long as a watcher
		660	is pending (but not active) you must not call an init function on it (but
		661	<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
		662	libev (e.g. you cnanot <code>free ()</code> it).</p>
		663	</dd>
		664	<dt>callback = ev_cb (ev_TYPE *watcher)</dt>
		665	<dd>
		666	<p>Returns the callback currently set on the watcher.</p>
		667	</dd>
		668	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
		669	<dd>
		670	<p>Change the callback. You can change the callback at virtually any time
		671	(modulo threads).</p>
		672	</dd>
		673	</dl>
		674
		675
		676
		677
		678
		679	</div>
387	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>	680	<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
388	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">	681	<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
389	<p>Each watcher has, by default, a member <code>void *data</code> that you can change	682	<p>Each watcher has, by default, a member <code>void *data</code> that you can change
390	and read at any time, libev will completely ignore it. This cna be used	683	and read at any time, libev will completely ignore it. This can be used
391	to associate arbitrary data with your watcher. If you need more data and	684	to associate arbitrary data with your watcher. If you need more data and
392	don't want to allocate memory and store a pointer to it in that data	685	don't want to allocate memory and store a pointer to it in that data
393	member, you can also "subclass" the watcher type and provide your own	686	member, you can also "subclass" the watcher type and provide your own
394	data:</p>	687	data:</p>
395	<pre> struct my_io	688	<pre> struct my_io
…		…
421	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	714	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
422	<div id="WATCHER_TYPES_CONTENT">	715	<div id="WATCHER_TYPES_CONTENT">
423	<p>This section describes each watcher in detail, but will not repeat	716	<p>This section describes each watcher in detail, but will not repeat
424	information given in the last section.</p>	717	information given in the last section.</p>
425		718
		719
		720
		721
		722
426	</div>	723	</div>
427	<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2>	724	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
428	<div id="struct_ev_io_is_my_file_descriptor_r-2">	725	<div id="code_ev_io_code_is_this_file_descrip-2">
429	<p>I/O watchers check whether a file descriptor is readable or writable	726	<p>I/O watchers check whether a file descriptor is readable or writable
430	in each iteration of the event loop (This behaviour is called	727	in each iteration of the event loop (This behaviour is called
431	level-triggering because you keep receiving events as long as the	728	level-triggering because you keep receiving events as long as the
432	condition persists. Remember you cna stop the watcher if you don't want to	729	condition persists. Remember you can stop the watcher if you don't want to
433	act on the event and neither want to receive future events).</p>	730	act on the event and neither want to receive future events).</p>
		731	<p>In general you can register as many read and/or write event watchers per
		732	fd as you want (as long as you don't confuse yourself). Setting all file
		733	descriptors to non-blocking mode is also usually a good idea (but not
		734	required if you know what you are doing).</p>
		735	<p>You have to be careful with dup'ed file descriptors, though. Some backends
		736	(the linux epoll backend is a notable example) cannot handle dup'ed file
		737	descriptors correctly if you register interest in two or more fds pointing
		738	to the same underlying file/socket etc. description (that is, they share
		739	the same underlying "file open").</p>
		740	<p>If you must do this, then force the use of a known-to-be-good backend
		741	(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
		742	<code>EVBACKEND_POLL</code>).</p>
434	<dl>	743	<dl>
435	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>	744	<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
436	<dt>ev_io_set (ev_io *, int fd, int events)</dt>	745	<dt>ev_io_set (ev_io *, int fd, int events)</dt>
437	<dd>	746	<dd>
438	<p>Configures an ev_io watcher. The fd is the file descriptor to rceeive	747	<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
439	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|	748	events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ \|
440	EV_WRITE</code> to receive the given events.</p>	749	EV_WRITE</code> to receive the given events.</p>
		750	<p>Please note that most of the more scalable backend mechanisms (for example
		751	epoll and solaris ports) can result in spurious readyness notifications
		752	for file descriptors, so you practically need to use non-blocking I/O (and
		753	treat callback invocation as hint only), or retest separately with a safe
		754	interface before doing I/O (XLib can do this), or force the use of either
		755	<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
		756	problem. Also note that it is quite easy to have your callback invoked
		757	when the readyness condition is no longer valid even when employing
		758	typical ways of handling events, so its a good idea to use non-blocking
		759	I/O unconditionally.</p>
441	</dd>	760	</dd>
442	</dl>	761	</dl>
		762	<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		763	readable, but only once. Since it is likely line-buffered, you could
		764	attempt to read a whole line in the callback:</p>
		765	<pre> static void
		766	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		767	{
		768	ev_io_stop (loop, w);
		769	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		770	}
443		771
		772	...
		773	struct ev_loop *loop = ev_default_init (0);
		774	struct ev_io stdin_readable;
		775	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		776	ev_io_start (loop, &stdin_readable);
		777	ev_loop (loop, 0);
		778
		779
		780
		781
		782	</pre>
		783
444	</div>	784	</div>
445	<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2>	785	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
446	<div id="struct_ev_timer_relative_and_optiona-2">	786	<div id="code_ev_timer_code_relative_and_opti-2">
447	<p>Timer watchers are simple relative timers that generate an event after a	787	<p>Timer watchers are simple relative timers that generate an event after a
448	given time, and optionally repeating in regular intervals after that.</p>	788	given time, and optionally repeating in regular intervals after that.</p>
449	<p>The timers are based on real time, that is, if you register an event that	789	<p>The timers are based on real time, that is, if you register an event that
450	times out after an hour and youreset your system clock to last years	790	times out after an hour and you reset your system clock to last years
451	time, it will still time out after (roughly) and hour. "Roughly" because	791	time, it will still time out after (roughly) and hour. "Roughly" because
452	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	792	detecting time jumps is hard, and some inaccuracies are unavoidable (the
453	monotonic clock option helps a lot here).</p>	793	monotonic clock option helps a lot here).</p>
		794	<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
		795	time. This is usually the right thing as this timestamp refers to the time
		796	of the event triggering whatever timeout you are modifying/starting. If
		797	you suspect event processing to be delayed and you <i>need</i> to base the timeout
		798	on the current time, use something like this to adjust for this:</p>
		799	<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		800
		801	</pre>
		802	<p>The callback is guarenteed to be invoked only when its timeout has passed,
		803	but if multiple timers become ready during the same loop iteration then
		804	order of execution is undefined.</p>
454	<dl>	805	<dl>
455	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>	806	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
456	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>	807	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
457	<dd>	808	<dd>
458	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is	809	<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
…		…
460	timer will automatically be configured to trigger again <code>repeat</code> seconds	811	timer will automatically be configured to trigger again <code>repeat</code> seconds
461	later, again, and again, until stopped manually.</p>	812	later, again, and again, until stopped manually.</p>
462	<p>The timer itself will do a best-effort at avoiding drift, that is, if you	813	<p>The timer itself will do a best-effort at avoiding drift, that is, if you
463	configure a timer to trigger every 10 seconds, then it will trigger at	814	configure a timer to trigger every 10 seconds, then it will trigger at
464	exactly 10 second intervals. If, however, your program cannot keep up with	815	exactly 10 second intervals. If, however, your program cannot keep up with
465	the timer (ecause it takes longer than those 10 seconds to do stuff) the	816	the timer (because it takes longer than those 10 seconds to do stuff) the
466	timer will not fire more than once per event loop iteration.</p>	817	timer will not fire more than once per event loop iteration.</p>
467	</dd>	818	</dd>
468	<dt>ev_timer_again (loop)</dt>	819	<dt>ev_timer_again (loop)</dt>
469	<dd>	820	<dd>
470	<p>This will act as if the timer timed out and restart it again if it is	821	<p>This will act as if the timer timed out and restart it again if it is
…		…
474	value), or reset the running timer to the repeat value.</p>	825	value), or reset the running timer to the repeat value.</p>
475	<p>This sounds a bit complicated, but here is a useful and typical	826	<p>This sounds a bit complicated, but here is a useful and typical
476	example: Imagine you have a tcp connection and you want a so-called idle	827	example: Imagine you have a tcp connection and you want a so-called idle
477	timeout, that is, you want to be called when there have been, say, 60	828	timeout, that is, you want to be called when there have been, say, 60
478	seconds of inactivity on the socket. The easiest way to do this is to	829	seconds of inactivity on the socket. The easiest way to do this is to
479	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	830	configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
480	time you successfully read or write some data. If you go into an idle	831	time you successfully read or write some data. If you go into an idle
481	state where you do not expect data to travel on the socket, you can stop	832	state where you do not expect data to travel on the socket, you can stop
482	the timer, and again will automatically restart it if need be.</p>	833	the timer, and again will automatically restart it if need be.</p>
483	</dd>	834	</dd>
484	</dl>	835	</dl>
		836	<p>Example: create a timer that fires after 60 seconds.</p>
		837	<pre> static void
		838	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		839	{
		840	.. one minute over, w is actually stopped right here
		841	}
485		842
		843	struct ev_timer mytimer;
		844	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		845	ev_timer_start (loop, &mytimer);
		846
		847	</pre>
		848	<p>Example: create a timeout timer that times out after 10 seconds of
		849	inactivity.</p>
		850	<pre> static void
		851	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		852	{
		853	.. ten seconds without any activity
		854	}
		855
		856	struct ev_timer mytimer;
		857	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		858	ev_timer_again (&mytimer); /* start timer */
		859	ev_loop (loop, 0);
		860
		861	// and in some piece of code that gets executed on any "activity":
		862	// reset the timeout to start ticking again at 10 seconds
		863	ev_timer_again (&mytimer);
		864
		865
		866
		867
		868	</pre>
		869
486	</div>	870	</div>
487	<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2>	871	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
488	<div id="ev_periodic_to_cron_or_not_to_cron_i-2">	872	<div id="code_ev_periodic_code_to_cron_or_not-2">
489	<p>Periodic watchers are also timers of a kind, but they are very versatile	873	<p>Periodic watchers are also timers of a kind, but they are very versatile
490	(and unfortunately a bit complex).</p>	874	(and unfortunately a bit complex).</p>
491	<p>Unlike ev_timer's, they are not based on real time (or relative time)	875	<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
492	but on wallclock time (absolute time). You can tell a periodic watcher	876	but on wallclock time (absolute time). You can tell a periodic watcher
493	to trigger "at" some specific point in time. For example, if you tell a	877	to trigger "at" some specific point in time. For example, if you tell a
494	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	878	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
495	+ 10.>) and then reset your system clock to the last year, then it will	879	+ 10.>) and then reset your system clock to the last year, then it will
496	take a year to trigger the event (unlike an ev_timer, which would trigger	880	take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
497	roughly 10 seconds later and of course not if you reset your system time	881	roughly 10 seconds later and of course not if you reset your system time
498	again).</p>	882	again).</p>
499	<p>They can also be used to implement vastly more complex timers, such as	883	<p>They can also be used to implement vastly more complex timers, such as
500	triggering an event on eahc midnight, local time.</p>	884	triggering an event on eahc midnight, local time.</p>
		885	<p>As with timers, the callback is guarenteed to be invoked only when the
		886	time (<code>at</code>) has been passed, but if multiple periodic timers become ready
		887	during the same loop iteration then order of execution is undefined.</p>
501	<dl>	888	<dl>
502	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>	889	<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
503	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>	890	<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
504	<dd>	891	<dd>
505	<p>Lots of arguments, lets sort it out... There are basically three modes of	892	<p>Lots of arguments, lets sort it out... There are basically three modes of
506	operation, and we will explain them from simplest to complex:</p>	893	operation, and we will explain them from simplest to complex:</p>
507
508
509
510
511	<p>	894	<p>
512	<dl>	895	<dl>
513	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>	896	<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
514	<dd>	897	<dd>
515	<p>In this configuration the watcher triggers an event at the wallclock time	898	<p>In this configuration the watcher triggers an event at the wallclock time
…		…
527	<pre> ev_periodic_set (&periodic, 0., 3600., 0);	910	<pre> ev_periodic_set (&periodic, 0., 3600., 0);
528		911
529	</pre>	912	</pre>
530	<p>This doesn't mean there will always be 3600 seconds in between triggers,	913	<p>This doesn't mean there will always be 3600 seconds in between triggers,
531	but only that the the callback will be called when the system time shows a	914	but only that the the callback will be called when the system time shows a
532	full hour (UTC), or more correct, when the system time is evenly divisible	915	full hour (UTC), or more correctly, when the system time is evenly divisible
533	by 3600.</p>	916	by 3600.</p>
534	<p>Another way to think about it (for the mathematically inclined) is that	917	<p>Another way to think about it (for the mathematically inclined) is that
535	ev_periodic will try to run the callback in this mode at the next possible	918	<code>ev_periodic</code> will try to run the callback in this mode at the next possible
536	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>	919	time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
537	</dd>	920	</dd>
538	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>	921	<dt>* manual reschedule mode (reschedule_cb = callback)</dt>
539	<dd>	922	<dd>
540	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being	923	<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
541	ignored. Instead, each time the periodic watcher gets scheduled, the	924	ignored. Instead, each time the periodic watcher gets scheduled, the
542	reschedule callback will be called with the watcher as first, and the	925	reschedule callback will be called with the watcher as first, and the
543	current time as second argument.</p>	926	current time as second argument.</p>
544	<p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other	927	<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
545	periodic watcher, ever, or make any event loop modificstions</i>. If you need	928	ever, or make any event loop modifications</i>. If you need to stop it,
546	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p>	929	return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
		930	starting a prepare watcher).</p>
547	<p>Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	931	<p>Its prototype is <code>ev_tstamp (reschedule_cb)(struct ev_periodic w,
548	ev_tstamp now)>, e.g.:</p>	932	ev_tstamp now)</code>, e.g.:</p>
549	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	933	<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
550	{	934	{
551	return now + 60.;	935	return now + 60.;
552	}	936	}
553		937
554	</pre>	938	</pre>
555	<p>It must return the next time to trigger, based on the passed time value	939	<p>It must return the next time to trigger, based on the passed time value
556	(that is, the lowest time value larger than to the second argument). It	940	(that is, the lowest time value larger than to the second argument). It
557	will usually be called just before the callback will be triggered, but	941	will usually be called just before the callback will be triggered, but
558	might be called at other times, too.</p>	942	might be called at other times, too.</p>
		943	<p>NOTE: <i>This callback must always return a time that is later than the
		944	passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
559	<p>This can be used to create very complex timers, such as a timer that	945	<p>This can be used to create very complex timers, such as a timer that
560	triggers on each midnight, local time. To do this, you would calculate the	946	triggers on each midnight, local time. To do this, you would calculate the
561	next midnight after <code>now</code> and return the timestamp value for this. How you do this	947	next midnight after <code>now</code> and return the timestamp value for this. How
562	is, again, up to you (but it is not trivial).</p>	948	you do this is, again, up to you (but it is not trivial, which is the main
		949	reason I omitted it as an example).</p>
563	</dd>	950	</dd>
564	</dl>	951	</dl>
565	</p>	952	</p>
566	</dd>	953	</dd>
567	<dt>ev_periodic_again (loop, ev_periodic *)</dt>	954	<dt>ev_periodic_again (loop, ev_periodic *)</dt>
…		…
570	when you changed some parameters or the reschedule callback would return	957	when you changed some parameters or the reschedule callback would return
571	a different time than the last time it was called (e.g. in a crond like	958	a different time than the last time it was called (e.g. in a crond like
572	program when the crontabs have changed).</p>	959	program when the crontabs have changed).</p>
573	</dd>	960	</dd>
574	</dl>	961	</dl>
		962	<p>Example: call a callback every hour, or, more precisely, whenever the
		963	system clock is divisible by 3600. The callback invocation times have
		964	potentially a lot of jittering, but good long-term stability.</p>
		965	<pre> static void
		966	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		967	{
		968	... its now a full hour (UTC, or TAI or whatever your clock follows)
		969	}
575		970
		971	struct ev_periodic hourly_tick;
		972	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		973	ev_periodic_start (loop, &hourly_tick);
		974
		975	</pre>
		976	<p>Example: the same as above, but use a reschedule callback to do it:</p>
		977	<pre> #include <math.h>
		978
		979	static ev_tstamp
		980	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		981	{
		982	return fmod (now, 3600.) + 3600.;
		983	}
		984
		985	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		986
		987	</pre>
		988	<p>Example: call a callback every hour, starting now:</p>
		989	<pre> struct ev_periodic hourly_tick;
		990	ev_periodic_init (&hourly_tick, clock_cb,
		991	fmod (ev_now (loop), 3600.), 3600., 0);
		992	ev_periodic_start (loop, &hourly_tick);
		993
		994
		995
		996
		997	</pre>
		998
576	</div>	999	</div>
577	<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2>	1000	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
578	<div id="ev_signal_signal_me_when_a_signal_ge-2">	1001	<div id="code_ev_signal_code_signal_me_when_a-2">
579	<p>Signal watchers will trigger an event when the process receives a specific	1002	<p>Signal watchers will trigger an event when the process receives a specific
580	signal one or more times. Even though signals are very asynchronous, libev	1003	signal one or more times. Even though signals are very asynchronous, libev
581	will try its best to deliver signals synchronously, i.e. as part of the	1004	will try it's best to deliver signals synchronously, i.e. as part of the
582	normal event processing, like any other event.</p>	1005	normal event processing, like any other event.</p>
583	<p>You cna configure as many watchers as you like per signal. Only when the	1006	<p>You can configure as many watchers as you like per signal. Only when the
584	first watcher gets started will libev actually register a signal watcher	1007	first watcher gets started will libev actually register a signal watcher
585	with the kernel (thus it coexists with your own signal handlers as long	1008	with the kernel (thus it coexists with your own signal handlers as long
586	as you don't register any with libev). Similarly, when the last signal	1009	as you don't register any with libev). Similarly, when the last signal
587	watcher for a signal is stopped libev will reset the signal handler to	1010	watcher for a signal is stopped libev will reset the signal handler to
588	SIG_DFL (regardless of what it was set to before).</p>	1011	SIG_DFL (regardless of what it was set to before).</p>
…		…
593	<p>Configures the watcher to trigger on the given signal number (usually one	1016	<p>Configures the watcher to trigger on the given signal number (usually one
594	of the <code>SIGxxx</code> constants).</p>	1017	of the <code>SIGxxx</code> constants).</p>
595	</dd>	1018	</dd>
596	</dl>	1019	</dl>
597		1020
		1021
		1022
		1023
		1024
598	</div>	1025	</div>
599	<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2>	1026	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
600	<div id="ev_child_wait_for_pid_status_changes-2">	1027	<div id="code_ev_child_code_wait_for_pid_stat-2">
601	<p>Child watchers trigger when your process receives a SIGCHLD in response to	1028	<p>Child watchers trigger when your process receives a SIGCHLD in response to
602	some child status changes (most typically when a child of yours dies).</p>	1029	some child status changes (most typically when a child of yours dies).</p>
603	<dl>	1030	<dl>
604	<dt>ev_child_init (ev_child *, callback, int pid)</dt>	1031	<dt>ev_child_init (ev_child *, callback, int pid)</dt>
605	<dt>ev_child_set (ev_child *, int pid)</dt>	1032	<dt>ev_child_set (ev_child *, int pid)</dt>
606	<dd>	1033	<dd>
607	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or	1034	<p>Configures the watcher to wait for status changes of process <code>pid</code> (or
608	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look	1035	<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
609	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see	1036	at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
610	the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member	1037	the status word (use the macros from <code>sys/wait.h</code> and see your systems
		1038	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
611	contains the pid of the process causing the status change.</p>	1039	process causing the status change.</p>
612	</dd>	1040	</dd>
613	</dl>	1041	</dl>
		1042	<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
		1043	<pre> static void
		1044	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1045	{
		1046	ev_unloop (loop, EVUNLOOP_ALL);
		1047	}
614		1048
		1049	struct ev_signal signal_watcher;
		1050	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1051	ev_signal_start (loop, &sigint_cb);
		1052
		1053
		1054
		1055
		1056	</pre>
		1057
615	</div>	1058	</div>
616	<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2>	1059	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
617	<div id="ev_idle_when_you_ve_got_nothing_bett-2">	1060	<div id="code_ev_idle_code_when_you_ve_got_no-2">
618	<p>Idle watchers trigger events when there are no other I/O or timer (or	1061	<p>Idle watchers trigger events when there are no other events are pending
619	periodic) events pending. That is, as long as your process is busy	1062	(prepare, check and other idle watchers do not count). That is, as long
620	handling sockets or timeouts it will not be called. But when your process	1063	as your process is busy handling sockets or timeouts (or even signals,
621	is idle all idle watchers are being called again and again - until	1064	imagine) it will not be triggered. But when your process is idle all idle
		1065	watchers are being called again and again, once per event loop iteration -
622	stopped, that is, or your process receives more events.</p>	1066	until stopped, that is, or your process receives more events and becomes
		1067	busy.</p>
623	<p>The most noteworthy effect is that as long as any idle watchers are	1068	<p>The most noteworthy effect is that as long as any idle watchers are
624	active, the process will not block when waiting for new events.</p>	1069	active, the process will not block when waiting for new events.</p>
625	<p>Apart from keeping your process non-blocking (which is a useful	1070	<p>Apart from keeping your process non-blocking (which is a useful
626	effect on its own sometimes), idle watchers are a good place to do	1071	effect on its own sometimes), idle watchers are a good place to do
627	"pseudo-background processing", or delay processing stuff to after the	1072	"pseudo-background processing", or delay processing stuff to after the
…		…
632	<p>Initialises and configures the idle watcher - it has no parameters of any	1077	<p>Initialises and configures the idle watcher - it has no parameters of any
633	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1078	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
634	believe me.</p>	1079	believe me.</p>
635	</dd>	1080	</dd>
636	</dl>	1081	</dl>
		1082	<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
		1083	callback, free it. Alos, use no error checking, as usual.</p>
		1084	<pre> static void
		1085	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1086	{
		1087	free (w);
		1088	// now do something you wanted to do when the program has
		1089	// no longer asnything immediate to do.
		1090	}
637		1091
		1092	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1093	ev_idle_init (idle_watcher, idle_cb);
		1094	ev_idle_start (loop, idle_cb);
		1095
		1096
		1097
		1098
		1099	</pre>
		1100
638	</div>	1101	</div>
639	<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2>	1102	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
640	<div id="prepare_and_check_your_hooks_into_th-2">	1103	<div id="code_ev_prepare_code_and_code_ev_che-2">
641	<p>Prepare and check watchers usually (but not always) are used in	1104	<p>Prepare and check watchers are usually (but not always) used in tandem:
642	tandom. Prepare watchers get invoked before the process blocks and check	1105	prepare watchers get invoked before the process blocks and check watchers
643	watchers afterwards.</p>	1106	afterwards.</p>
644	<p>Their main purpose is to integrate other event mechanisms into libev. This	1107	<p>Their main purpose is to integrate other event mechanisms into libev and
645	could be used, for example, to track variable changes, implement your own	1108	their use is somewhat advanced. This could be used, for example, to track
646	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1109	variable changes, implement your own watchers, integrate net-snmp or a
		1110	coroutine library and lots more.</p>
647	<p>This is done by examining in each prepare call which file descriptors need	1111	<p>This is done by examining in each prepare call which file descriptors need
648	to be watched by the other library, registering ev_io watchers for them	1112	to be watched by the other library, registering <code>ev_io</code> watchers for
649	and starting an ev_timer watcher for any timeouts (many libraries provide	1113	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
650	just this functionality). Then, in the check watcher you check for any	1114	provide just this functionality). Then, in the check watcher you check for
651	events that occured (by making your callbacks set soem flags for example)	1115	any events that occured (by checking the pending status of all watchers
652	and call back into the library.</p>	1116	and stopping them) and call back into the library. The I/O and timer
		1117	callbacks will never actually be called (but must be valid nevertheless,
		1118	because you never know, you know?).</p>
653	<p>As another example, the perl Coro module uses these hooks to integrate	1119	<p>As another example, the Perl Coro module uses these hooks to integrate
654	coroutines into libev programs, by yielding to other active coroutines	1120	coroutines into libev programs, by yielding to other active coroutines
655	during each prepare and only letting the process block if no coroutines	1121	during each prepare and only letting the process block if no coroutines
656	are ready to run.</p>	1122	are ready to run (it's actually more complicated: it only runs coroutines
		1123	with priority higher than or equal to the event loop and one coroutine
		1124	of lower priority, but only once, using idle watchers to keep the event
		1125	loop from blocking if lower-priority coroutines are active, thus mapping
		1126	low-priority coroutines to idle/background tasks).</p>
657	<dl>	1127	<dl>
658	<dt>ev_prepare_init (ev_prepare *, callback)</dt>	1128	<dt>ev_prepare_init (ev_prepare *, callback)</dt>
659	<dt>ev_check_init (ev_check *, callback)</dt>	1129	<dt>ev_check_init (ev_check *, callback)</dt>
660	<dd>	1130	<dd>
661	<p>Initialises and configures the prepare or check watcher - they have no	1131	<p>Initialises and configures the prepare or check watcher - they have no
662	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1132	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
663	macros, but using them is utterly, utterly pointless.</p>	1133	macros, but using them is utterly, utterly and completely pointless.</p>
664	</dd>	1134	</dd>
665	</dl>	1135	</dl>
		1136	<p>Example: TODO.</p>
		1137
		1138
		1139
		1140
		1141
		1142	</div>
		1143	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2>
		1144	<div id="code_ev_embed_code_when_one_backend_-2">
		1145	<p>This is a rather advanced watcher type that lets you embed one event loop
		1146	into another (currently only <code>ev_io</code> events are supported in the embedded
		1147	loop, other types of watchers might be handled in a delayed or incorrect
		1148	fashion and must not be used).</p>
		1149	<p>There are primarily two reasons you would want that: work around bugs and
		1150	prioritise I/O.</p>
		1151	<p>As an example for a bug workaround, the kqueue backend might only support
		1152	sockets on some platform, so it is unusable as generic backend, but you
		1153	still want to make use of it because you have many sockets and it scales
		1154	so nicely. In this case, you would create a kqueue-based loop and embed it
		1155	into your default loop (which might use e.g. poll). Overall operation will
		1156	be a bit slower because first libev has to poll and then call kevent, but
		1157	at least you can use both at what they are best.</p>
		1158	<p>As for prioritising I/O: rarely you have the case where some fds have
		1159	to be watched and handled very quickly (with low latency), and even
		1160	priorities and idle watchers might have too much overhead. In this case
		1161	you would put all the high priority stuff in one loop and all the rest in
		1162	a second one, and embed the second one in the first.</p>
		1163	<p>As long as the watcher is active, the callback will be invoked every time
		1164	there might be events pending in the embedded loop. The callback must then
		1165	call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
		1166	their callbacks (you could also start an idle watcher to give the embedded
		1167	loop strictly lower priority for example). You can also set the callback
		1168	to <code>0</code>, in which case the embed watcher will automatically execute the
		1169	embedded loop sweep.</p>
		1170	<p>As long as the watcher is started it will automatically handle events. The
		1171	callback will be invoked whenever some events have been handled. You can
		1172	set the callback to <code>0</code> to avoid having to specify one if you are not
		1173	interested in that.</p>
		1174	<p>Also, there have not currently been made special provisions for forking:
		1175	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1176	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1177	yourself.</p>
		1178	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1179	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1180	portable one.</p>
		1181	<p>So when you want to use this feature you will always have to be prepared
		1182	that you cannot get an embeddable loop. The recommended way to get around
		1183	this is to have a separate variables for your embeddable loop, try to
		1184	create it, and if that fails, use the normal loop for everything:</p>
		1185	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1186	struct ev_loop *loop_lo = 0;
		1187	struct ev_embed embed;
		1188
		1189	// see if there is a chance of getting one that works
		1190	// (remember that a flags value of 0 means autodetection)
		1191	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1192	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1193	: 0;
		1194
		1195	// if we got one, then embed it, otherwise default to loop_hi
		1196	if (loop_lo)
		1197	{
		1198	ev_embed_init (&embed, 0, loop_lo);
		1199	ev_embed_start (loop_hi, &embed);
		1200	}
		1201	else
		1202	loop_lo = loop_hi;
		1203
		1204	</pre>
		1205	<dl>
		1206	<dt>ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1207	<dt>ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)</dt>
		1208	<dd>
		1209	<p>Configures the watcher to embed the given loop, which must be
		1210	embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
		1211	invoked automatically, otherwise it is the responsibility of the callback
		1212	to invoke it (it will continue to be called until the sweep has been done,
		1213	if you do not want thta, you need to temporarily stop the embed watcher).</p>
		1214	</dd>
		1215	<dt>ev_embed_sweep (loop, ev_embed *)</dt>
		1216	<dd>
		1217	<p>Make a single, non-blocking sweep over the embedded loop. This works
		1218	similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
		1219	apropriate way for embedded loops.</p>
		1220	</dd>
		1221	</dl>
		1222
		1223
		1224
		1225
666		1226
667	</div>	1227	</div>
668	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1228	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
669	<div id="OTHER_FUNCTIONS_CONTENT">	1229	<div id="OTHER_FUNCTIONS_CONTENT">
670	<p>There are some other fucntions of possible interest. Described. Here. Now.</p>	1230	<p>There are some other functions of possible interest. Described. Here. Now.</p>
671	<dl>	1231	<dl>
672	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>	1232	<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
673	<dd>	1233	<dd>
674	<p>This function combines a simple timer and an I/O watcher, calls your	1234	<p>This function combines a simple timer and an I/O watcher, calls your
675	callback on whichever event happens first and automatically stop both	1235	callback on whichever event happens first and automatically stop both
676	watchers. This is useful if you want to wait for a single event on an fd	1236	watchers. This is useful if you want to wait for a single event on an fd
677	or timeout without havign to allocate/configure/start/stop/free one or	1237	or timeout without having to allocate/configure/start/stop/free one or
678	more watchers yourself.</p>	1238	more watchers yourself.</p>
679	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is	1239	<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
680	ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set	1240	is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
681	will be craeted and started.</p>	1241	<code>events</code> set will be craeted and started.</p>
682	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be	1242	<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
683	started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat	1243	started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
684	= 0) will be started.</p>	1244	repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
		1245	dubious value.</p>
685	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and	1246	<p>The callback has the type <code>void (cb)(int revents, void arg)</code> and gets
686	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1247	passed an <code>revents</code> set like normal event callbacks (a combination of
687	EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p>	1248	<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
		1249	value passed to <code>ev_once</code>:</p>
688	<pre> static void stdin_ready (int revents, void *arg)	1250	<pre> static void stdin_ready (int revents, void *arg)
689	{	1251	{
690	if (revents & EV_TIMEOUT)	1252	if (revents & EV_TIMEOUT)
691	/* doh, nothing entered */	1253	/* doh, nothing entered */;
692	else if (revents & EV_READ)	1254	else if (revents & EV_READ)
693	/* stdin might have data for us, joy! */	1255	/* stdin might have data for us, joy! */;
694	}	1256	}
695		1257
696	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1258	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
697		1259
698	</pre>	1260	</pre>
699	</dd>	1261	</dd>
700	<dt>ev_feed_event (loop, watcher, int events)</dt>	1262	<dt>ev_feed_event (ev_loop , watcher , int revents)</dt>
701	<dd>	1263	<dd>
702	<p>Feeds the given event set into the event loop, as if the specified event	1264	<p>Feeds the given event set into the event loop, as if the specified event
703	has happened for the specified watcher (which must be a pointer to an	1265	had happened for the specified watcher (which must be a pointer to an
704	initialised but not necessarily active event watcher).</p>	1266	initialised but not necessarily started event watcher).</p>
705	</dd>	1267	</dd>
706	<dt>ev_feed_fd_event (loop, int fd, int revents)</dt>	1268	<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
707	<dd>	1269	<dd>
708	<p>Feed an event on the given fd, as if a file descriptor backend detected it.</p>	1270	<p>Feed an event on the given fd, as if a file descriptor backend detected
		1271	the given events it.</p>
709	</dd>	1272	</dd>
710	<dt>ev_feed_signal_event (loop, int signum)</dt>	1273	<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
711	<dd>	1274	<dd>
712	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1275	<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
		1276	loop!).</p>
713	</dd>	1277	</dd>
714	</dl>	1278	</dl>
		1279
		1280
		1281
		1282
		1283
		1284	</div>
		1285	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1286	<div id="LIBEVENT_EMULATION_CONTENT">
		1287	<p>Libev offers a compatibility emulation layer for libevent. It cannot
		1288	emulate the internals of libevent, so here are some usage hints:</p>
		1289	<dl>
		1290	<dt>* Use it by including <event.h>, as usual.</dt>
		1291	<dt>* The following members are fully supported: ev_base, ev_callback,
		1292	ev_arg, ev_fd, ev_res, ev_events.</dt>
		1293	<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
		1294	maintained by libev, it does not work exactly the same way as in libevent (consider
		1295	it a private API).</dt>
		1296	<dt>* Priorities are not currently supported. Initialising priorities
		1297	will fail and all watchers will have the same priority, even though there
		1298	is an ev_pri field.</dt>
		1299	<dt>* Other members are not supported.</dt>
		1300	<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
		1301	to use the libev header file and library.</dt>
		1302	</dl>
		1303
		1304	</div>
		1305	<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
		1306	<div id="C_SUPPORT_CONTENT">
		1307	<p>TBD.</p>
715		1308
716	</div>	1309	</div>
717	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>	1310	<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
718	<div id="AUTHOR_CONTENT">	1311	<div id="AUTHOR_CONTENT">
719	<p>Marc Lehmann <libev@schmorp.de>.</p>	1312	<p>Marc Lehmann <libev@schmorp.de>.</p>

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Comparing libev/ev.html (file contents): Revision 1.6 by root, Mon Nov 12 08:12:14 2007 UTC vs. Revision 1.37 by root, Sat Nov 24 07:14:26 2007 UTC

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Comparing libev/ev.html (file contents):
Revision 1.6 by root, Mon Nov 12 08:12:14 2007 UTC vs.
Revision 1.37 by root, Sat Nov 24 07:14:26 2007 UTC