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Revision 1.14 by root, Sat Nov 24 10:10:26 2007 UTC vs.
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129	.\" ========================================================================	133	.\" ========================================================================
130	.\"	134	.\"
131	.IX Title ""<STANDARD INPUT>" 1"	135	.IX Title "LIBEV 3"
132	.TH "<STANDARD INPUT>" 1 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation"	136	.TH LIBEV 3 "2019-06-25" "libev-4.25" "libev - high performance full featured event loop"
		137	.\" For nroff, turn off justification. Always turn off hyphenation; it makes
		138	.\" way too many mistakes in technical documents.
		139	.if n .ad l
		140	.nh
133	.SH "NAME"	141	.SH "NAME"
134	libev \- a high performance full\-featured event loop written in C	142	libev \- a high performance full\-featured event loop written in C
135	.SH "SYNOPSIS"	143	.SH "SYNOPSIS"
136	.IX Header "SYNOPSIS"	144	.IX Header "SYNOPSIS"
137	.Vb 1	145	.Vb 1
138	\& #include <ev.h>	146	\& #include <ev.h>
139	.Ve	147	.Ve
140	.SH "DESCRIPTION"	148	.SS "\s-1EXAMPLE PROGRAM\s0"
141	.IX Header "DESCRIPTION"	149	.IX Subsection "EXAMPLE PROGRAM"
		150	.Vb 2
		151	\& // a single header file is required
		152	\& #include <ev.h>
		153	\&
		154	\& #include <stdio.h> // for puts
		155	\&
		156	\& // every watcher type has its own typedef\*(Aqd struct
		157	\& // with the name ev_TYPE
		158	\& ev_io stdin_watcher;
		159	\& ev_timer timeout_watcher;
		160	\&
		161	\& // all watcher callbacks have a similar signature
		162	\& // this callback is called when data is readable on stdin
		163	\& static void
		164	\& stdin_cb (EV_P_ ev_io *w, int revents)
		165	\& {
		166	\& puts ("stdin ready");
		167	\& // for one\-shot events, one must manually stop the watcher
		168	\& // with its corresponding stop function.
		169	\& ev_io_stop (EV_A_ w);
		170	\&
		171	\& // this causes all nested ev_run\*(Aqs to stop iterating
		172	\& ev_break (EV_A_ EVBREAK_ALL);
		173	\& }
		174	\&
		175	\& // another callback, this time for a time\-out
		176	\& static void
		177	\& timeout_cb (EV_P_ ev_timer *w, int revents)
		178	\& {
		179	\& puts ("timeout");
		180	\& // this causes the innermost ev_run to stop iterating
		181	\& ev_break (EV_A_ EVBREAK_ONE);
		182	\& }
		183	\&
		184	\& int
		185	\& main (void)
		186	\& {
		187	\& // use the default event loop unless you have special needs
		188	\& struct ev_loop *loop = EV_DEFAULT;
		189	\&
		190	\& // initialise an io watcher, then start it
		191	\& // this one will watch for stdin to become readable
		192	\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		193	\& ev_io_start (loop, &stdin_watcher);
		194	\&
		195	\& // initialise a timer watcher, then start it
		196	\& // simple non\-repeating 5.5 second timeout
		197	\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		198	\& ev_timer_start (loop, &timeout_watcher);
		199	\&
		200	\& // now wait for events to arrive
		201	\& ev_run (loop, 0);
		202	\&
		203	\& // break was called, so exit
		204	\& return 0;
		205	\& }
		206	.Ve
		207	.SH "ABOUT THIS DOCUMENT"
		208	.IX Header "ABOUT THIS DOCUMENT"
		209	This document documents the libev software package.
		210	.PP
		211	The newest version of this document is also available as an html-formatted
		212	web page you might find easier to navigate when reading it for the first
		213	time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		214	.PP
		215	While this document tries to be as complete as possible in documenting
		216	libev, its usage and the rationale behind its design, it is not a tutorial
		217	on event-based programming, nor will it introduce event-based programming
		218	with libev.
		219	.PP
		220	Familiarity with event based programming techniques in general is assumed
		221	throughout this document.
		222	.SH "WHAT TO READ WHEN IN A HURRY"
		223	.IX Header "WHAT TO READ WHEN IN A HURRY"
		224	This manual tries to be very detailed, but unfortunately, this also makes
		225	it very long. If you just want to know the basics of libev, I suggest
		226	reading \*(L"\s-1ANATOMY OF A WATCHER\*(R"\s0, then the \*(L"\s-1EXAMPLE PROGRAM\*(R"\s0 above and
		227	look up the missing functions in \*(L"\s-1GLOBAL FUNCTIONS\*(R"\s0 and the \f(CW\*(C`ev_io\*(C'\fR and
		228	\&\f(CW\*(C`ev_timer\*(C'\fR sections in \*(L"\s-1WATCHER TYPES\*(R"\s0.
		229	.SH "ABOUT LIBEV"
		230	.IX Header "ABOUT LIBEV"
142	Libev is an event loop: you register interest in certain events (such as a	231	Libev is an event loop: you register interest in certain events (such as a
143	file descriptor being readable or a timeout occuring), and it will manage	232	file descriptor being readable or a timeout occurring), and it will manage
144	these event sources and provide your program with events.	233	these event sources and provide your program with events.
145	.PP	234	.PP
146	To do this, it must take more or less complete control over your process	235	To do this, it must take more or less complete control over your process
147	(or thread) by executing the \fIevent loop\fR handler, and will then	236	(or thread) by executing the \fIevent loop\fR handler, and will then
148	communicate events via a callback mechanism.	237	communicate events via a callback mechanism.
149	.PP	238	.PP
150	You register interest in certain events by registering so-called \fIevent	239	You register interest in certain events by registering so-called \fIevent
151	watchers\fR, which are relatively small C structures you initialise with the	240	watchers\fR, which are relatively small C structures you initialise with the
152	details of the event, and then hand it over to libev by \fIstarting\fR the	241	details of the event, and then hand it over to libev by \fIstarting\fR the
153	watcher.	242	watcher.
154	.SH "FEATURES"	243	.SS "\s-1FEATURES\s0"
155	.IX Header "FEATURES"	244	.IX Subsection "FEATURES"
156	Libev supports select, poll, the linux-specific epoll and the bsd-specific	245	Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific aio and \f(CW\*(C`epoll\*(C'\fR
157	kqueue mechanisms for file descriptor events, relative timers, absolute	246	interfaces, the BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port
158	timers with customised rescheduling, signal events, process status change	247	mechanisms for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR
159	events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event	248	interface (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner
160	loop mechanism itself (idle, prepare and check watchers). It also is quite	249	inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative
161	fast (see this benchmark comparing	250	timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling
162	it to libevent for example).	251	(\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status
		252	change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event
		253	loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and
		254	\&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even
		255	limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR).
		256	.PP
		257	It also is quite fast (see this
		258	benchmark <http://libev.schmorp.de/bench.html> comparing it to libevent
		259	for example).
163	.SH "CONVENTIONS"	260	.SS "\s-1CONVENTIONS\s0"
164	.IX Header "CONVENTIONS"	261	.IX Subsection "CONVENTIONS"
165	Libev is very configurable. In this manual the default configuration	262	Libev is very configurable. In this manual the default (and most common)
166	will be described, which supports multiple event loops. For more info	263	configuration will be described, which supports multiple event loops. For
167	about various configuration options please have a look at the file	264	more info about various configuration options please have a look at
168	\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without	265	\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support
169	support for multiple event loops, then all functions taking an initial	266	for multiple event loops, then all functions taking an initial argument of
170	argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR)	267	name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have
171	will not have this argument.	268	this argument.
172	.SH "TIME REPRESENTATION"	269	.SS "\s-1TIME REPRESENTATION\s0"
173	.IX Header "TIME REPRESENTATION"	270	.IX Subsection "TIME REPRESENTATION"
174	Libev represents time as a single floating point number, representing the	271	Libev represents time as a single floating point number, representing
175	(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near	272	the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (in practice
176	the beginning of 1970, details are complicated, don't ask). This type is	273	somewhere near the beginning of 1970, details are complicated, don't
177	called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases	274	ask). This type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use
178	to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on	275	too. It usually aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do
179	it, you should treat it as such.	276	any calculations on it, you should treat it as some floating point value.
		277	.PP
		278	Unlike the name component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for
		279	time differences (e.g. delays) throughout libev.
		280	.SH "ERROR HANDLING"
		281	.IX Header "ERROR HANDLING"
		282	Libev knows three classes of errors: operating system errors, usage errors
		283	and internal errors (bugs).
		284	.PP
		285	When libev catches an operating system error it cannot handle (for example
		286	a system call indicating a condition libev cannot fix), it calls the callback
		287	set via \f(CW\*(C`ev_set_syserr_cb\*(C'\fR, which is supposed to fix the problem or
		288	abort. The default is to print a diagnostic message and to call \f(CW\*(C`abort
		289	()\*(C'\fR.
		290	.PP
		291	When libev detects a usage error such as a negative timer interval, then
		292	it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism,
		293	so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in
		294	the libev caller and need to be fixed there.
		295	.PP
		296	Via the \f(CW\*(C`EV_FREQUENT\*(C'\fR macro you can compile in and/or enable extensive
		297	consistency checking code inside libev that can be used to check for
		298	internal inconsistencies, suually caused by application bugs.
		299	.PP
		300	Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions. These do not
		301	trigger under normal circumstances, as they indicate either a bug in libev
		302	or worse.
180	.SH "GLOBAL FUNCTIONS"	303	.SH "GLOBAL FUNCTIONS"
181	.IX Header "GLOBAL FUNCTIONS"	304	.IX Header "GLOBAL FUNCTIONS"
182	These functions can be called anytime, even before initialising the	305	These functions can be called anytime, even before initialising the
183	library in any way.	306	library in any way.
184	.IP "ev_tstamp ev_time ()" 4	307	.IP "ev_tstamp ev_time ()" 4
185	.IX Item "ev_tstamp ev_time ()"	308	.IX Item "ev_tstamp ev_time ()"
186	Returns the current time as libev would use it. Please note that the	309	Returns the current time as libev would use it. Please note that the
187	\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp	310	\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
188	you actually want to know.	311	you actually want to know. Also interesting is the combination of
		312	\&\f(CW\*(C`ev_now_update\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR.
		313	.IP "ev_sleep (ev_tstamp interval)" 4
		314	.IX Item "ev_sleep (ev_tstamp interval)"
		315	Sleep for the given interval: The current thread will be blocked
		316	until either it is interrupted or the given time interval has
		317	passed (approximately \- it might return a bit earlier even if not
		318	interrupted). Returns immediately if \f(CW\*(C`interval <= 0\*(C'\fR.
		319	.Sp
		320	Basically this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR.
		321	.Sp
		322	The range of the \f(CW\*(C`interval\*(C'\fR is limited \- libev only guarantees to work
		323	with sleep times of up to one day (\f(CW\*(C`interval <= 86400\*(C'\fR).
189	.IP "int ev_version_major ()" 4	324	.IP "int ev_version_major ()" 4
190	.IX Item "int ev_version_major ()"	325	.IX Item "int ev_version_major ()"
191	.PD 0	326	.PD 0
192	.IP "int ev_version_minor ()" 4	327	.IP "int ev_version_minor ()" 4
193	.IX Item "int ev_version_minor ()"	328	.IX Item "int ev_version_minor ()"
194	.PD	329	.PD
195	You can find out the major and minor version numbers of the library	330	You can find out the major and minor \s-1ABI\s0 version numbers of the library
196	you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and	331	you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
197	\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global	332	\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
198	symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the	333	symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
199	version of the library your program was compiled against.	334	version of the library your program was compiled against.
200	.Sp	335	.Sp
		336	These version numbers refer to the \s-1ABI\s0 version of the library, not the
		337	release version.
		338	.Sp
201	Usually, it's a good idea to terminate if the major versions mismatch,	339	Usually, it's a good idea to terminate if the major versions mismatch,
202	as this indicates an incompatible change. Minor versions are usually	340	as this indicates an incompatible change. Minor versions are usually
203	compatible to older versions, so a larger minor version alone is usually	341	compatible to older versions, so a larger minor version alone is usually
204	not a problem.	342	not a problem.
205	.Sp	343	.Sp
206	Example: make sure we haven't accidentally been linked against the wrong	344	Example: Make sure we haven't accidentally been linked against the wrong
207	version:	345	version (note, however, that this will not detect other \s-1ABI\s0 mismatches,
		346	such as \s-1LFS\s0 or reentrancy).
208	.Sp	347	.Sp
209	.Vb 3	348	.Vb 3
210	\& assert (("libev version mismatch",	349	\& assert (("libev version mismatch",
211	\& ev_version_major () == EV_VERSION_MAJOR	350	\& ev_version_major () == EV_VERSION_MAJOR
212	\& && ev_version_minor () >= EV_VERSION_MINOR));	351	\& && ev_version_minor () >= EV_VERSION_MINOR));
213	.Ve	352	.Ve
214	.IP "unsigned int ev_supported_backends ()" 4	353	.IP "unsigned int ev_supported_backends ()" 4
215	.IX Item "unsigned int ev_supported_backends ()"	354	.IX Item "unsigned int ev_supported_backends ()"
216	Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR	355	Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
217	value) compiled into this binary of libev (independent of their	356	value) compiled into this binary of libev (independent of their
…		…
220	.Sp	359	.Sp
221	Example: make sure we have the epoll method, because yeah this is cool and	360	Example: make sure we have the epoll method, because yeah this is cool and
222	a must have and can we have a torrent of it please!!!11	361	a must have and can we have a torrent of it please!!!11
223	.Sp	362	.Sp
224	.Vb 2	363	.Vb 2
225	\& assert (("sorry, no epoll, no sex",	364	\& assert (("sorry, no epoll, no sex",
226	\& ev_supported_backends () & EVBACKEND_EPOLL));	365	\& ev_supported_backends () & EVBACKEND_EPOLL));
227	.Ve	366	.Ve
228	.IP "unsigned int ev_recommended_backends ()" 4	367	.IP "unsigned int ev_recommended_backends ()" 4
229	.IX Item "unsigned int ev_recommended_backends ()"	368	.IX Item "unsigned int ev_recommended_backends ()"
230	Return the set of all backends compiled into this binary of libev and also	369	Return the set of all backends compiled into this binary of libev and
231	recommended for this platform. This set is often smaller than the one	370	also recommended for this platform, meaning it will work for most file
		371	descriptor types. This set is often smaller than the one returned by
232	returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on	372	\&\f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on most BSDs
233	most BSDs and will not be autodetected unless you explicitly request it	373	and will not be auto-detected unless you explicitly request it (assuming
234	(assuming you know what you are doing). This is the set of backends that	374	you know what you are doing). This is the set of backends that libev will
235	libev will probe for if you specify no backends explicitly.	375	probe for if you specify no backends explicitly.
236	.IP "unsigned int ev_embeddable_backends ()" 4	376	.IP "unsigned int ev_embeddable_backends ()" 4
237	.IX Item "unsigned int ev_embeddable_backends ()"	377	.IX Item "unsigned int ev_embeddable_backends ()"
238	Returns the set of backends that are embeddable in other event loops. This	378	Returns the set of backends that are embeddable in other event loops. This
239	is the theoretical, all\-platform, value. To find which backends	379	value is platform-specific but can include backends not available on the
240	might be supported on the current system, you would need to look at	380	current system. To find which embeddable backends might be supported on
241	\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for	381	the current system, you would need to look at \f(CW\*(C`ev_embeddable_backends ()
242	recommended ones.	382	& ev_supported_backends ()\*(C'\fR, likewise for recommended ones.
243	.Sp	383	.Sp
244	See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.	384	See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
245	.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4	385	.IP "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())" 4
246	.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"	386	.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())"
247	Sets the allocation function to use (the prototype is similar to the	387	Sets the allocation function to use (the prototype is similar \- the
248	realloc C function, the semantics are identical). It is used to allocate	388	semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is
249	and free memory (no surprises here). If it returns zero when memory	389	used to allocate and free memory (no surprises here). If it returns zero
250	needs to be allocated, the library might abort or take some potentially	390	when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort
251	destructive action. The default is your system realloc function.	391	or take some potentially destructive action.
		392	.Sp
		393	Since some systems (at least OpenBSD and Darwin) fail to implement
		394	correct \f(CW\*(C`realloc\*(C'\fR semantics, libev will use a wrapper around the system
		395	\&\f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions by default.
252	.Sp	396	.Sp
253	You could override this function in high-availability programs to, say,	397	You could override this function in high-availability programs to, say,
254	free some memory if it cannot allocate memory, to use a special allocator,	398	free some memory if it cannot allocate memory, to use a special allocator,
255	or even to sleep a while and retry until some memory is available.	399	or even to sleep a while and retry until some memory is available.
256	.Sp	400	.Sp
257	Example: replace the libev allocator with one that waits a bit and then	401	Example: The following is the \f(CW\*(C`realloc\*(C'\fR function that libev itself uses
258	retries: better than mine).	402	which should work with \f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions of all kinds and
		403	is probably a good basis for your own implementation.
259	.Sp	404	.Sp
260	.Vb 6	405	.Vb 5
261	\& static void *	406	\& static void *
262	\& persistent_realloc (void *ptr, long size)	407	\& ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
263	\& {	408	\& {
		409	\& if (size)
		410	\& return realloc (ptr, size);
		411	\&
		412	\& free (ptr);
		413	\& return 0;
		414	\& }
		415	.Ve
		416	.Sp
		417	Example: Replace the libev allocator with one that waits a bit and then
		418	retries.
		419	.Sp
		420	.Vb 8
		421	\& static void *
		422	\& persistent_realloc (void *ptr, size_t size)
		423	\& {
		424	\& if (!size)
		425	\& {
		426	\& free (ptr);
		427	\& return 0;
		428	\& }
		429	\&
264	\& for (;;)	430	\& for (;;)
265	\& {	431	\& {
266	\& void *newptr = realloc (ptr, size);	432	\& void *newptr = realloc (ptr, size);
267	.Ve	433	\&
268	.Sp
269	.Vb 2
270	\& if (newptr)	434	\& if (newptr)
271	\& return newptr;	435	\& return newptr;
272	.Ve	436	\&
273	.Sp
274	.Vb 3
275	\& sleep (60);	437	\& sleep (60);
276	\& }	438	\& }
277	\& }	439	\& }
278	.Ve	440	\&
279	.Sp
280	.Vb 2
281	\& ...	441	\& ...
282	\& ev_set_allocator (persistent_realloc);	442	\& ev_set_allocator (persistent_realloc);
283	.Ve	443	.Ve
284	.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4	444	.IP "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())" 4
285	.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"	445	.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())"
286	Set the callback function to call on a retryable syscall error (such	446	Set the callback function to call on a retryable system call error (such
287	as failed select, poll, epoll_wait). The message is a printable string	447	as failed select, poll, epoll_wait). The message is a printable string
288	indicating the system call or subsystem causing the problem. If this	448	indicating the system call or subsystem causing the problem. If this
289	callback is set, then libev will expect it to remedy the sitution, no	449	callback is set, then libev will expect it to remedy the situation, no
290	matter what, when it returns. That is, libev will generally retry the	450	matter what, when it returns. That is, libev will generally retry the
291	requested operation, or, if the condition doesn't go away, do bad stuff	451	requested operation, or, if the condition doesn't go away, do bad stuff
292	(such as abort).	452	(such as abort).
293	.Sp	453	.Sp
294	Example: do the same thing as libev does internally:	454	Example: This is basically the same thing that libev does internally, too.
295	.Sp	455	.Sp
296	.Vb 6	456	.Vb 6
297	\& static void	457	\& static void
298	\& fatal_error (const char *msg)	458	\& fatal_error (const char *msg)
299	\& {	459	\& {
300	\& perror (msg);	460	\& perror (msg);
301	\& abort ();	461	\& abort ();
302	\& }	462	\& }
303	.Ve	463	\&
304	.Sp
305	.Vb 2
306	\& ...	464	\& ...
307	\& ev_set_syserr_cb (fatal_error);	465	\& ev_set_syserr_cb (fatal_error);
308	.Ve	466	.Ve
		467	.IP "ev_feed_signal (int signum)" 4
		468	.IX Item "ev_feed_signal (int signum)"
		469	This function can be used to \*(L"simulate\*(R" a signal receive. It is completely
		470	safe to call this function at any time, from any context, including signal
		471	handlers or random threads.
		472	.Sp
		473	Its main use is to customise signal handling in your process, especially
		474	in the presence of threads. For example, you could block signals
		475	by default in all threads (and specifying \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when
		476	creating any loops), and in one thread, use \f(CW\*(C`sigwait\*(C'\fR or any other
		477	mechanism to wait for signals, then \*(L"deliver\*(R" them to libev by calling
		478	\&\f(CW\*(C`ev_feed_signal\*(C'\fR.
309	.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"	479	.SH "FUNCTIONS CONTROLLING EVENT LOOPS"
310	.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"	480	.IX Header "FUNCTIONS CONTROLLING EVENT LOOPS"
311	An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two	481	An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR is
312	types of such loops, the \fIdefault\fR loop, which supports signals and child	482	\&\fInot\fR optional in this case unless libev 3 compatibility is disabled, as
313	events, and dynamically created loops which do not.	483	libev 3 had an \f(CW\*(C`ev_loop\*(C'\fR function colliding with the struct name).
314	.PP	484	.PP
315	If you use threads, a common model is to run the default event loop	485	The library knows two types of such loops, the \fIdefault\fR loop, which
316	in your main thread (or in a separate thread) and for each thread you	486	supports child process events, and dynamically created event loops which
317	create, you also create another event loop. Libev itself does no locking	487	do not.
318	whatsoever, so if you mix calls to the same event loop in different
319	threads, make sure you lock (this is usually a bad idea, though, even if
320	done correctly, because it's hideous and inefficient).
321	.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4	488	.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
322	.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"	489	.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
323	This will initialise the default event loop if it hasn't been initialised	490	This returns the \*(L"default\*(R" event loop object, which is what you should
324	yet and return it. If the default loop could not be initialised, returns	491	normally use when you just need \*(L"the event loop\*(R". Event loop objects and
325	false. If it already was initialised it simply returns it (and ignores the	492	the \f(CW\*(C`flags\*(C'\fR parameter are described in more detail in the entry for
326	flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).	493	\&\f(CW\*(C`ev_loop_new\*(C'\fR.
		494	.Sp
		495	If the default loop is already initialised then this function simply
		496	returns it (and ignores the flags. If that is troubling you, check
		497	\&\f(CW\*(C`ev_backend ()\*(C'\fR afterwards). Otherwise it will create it with the given
		498	flags, which should almost always be \f(CW0\fR, unless the caller is also the
		499	one calling \f(CW\*(C`ev_run\*(C'\fR or otherwise qualifies as \*(L"the main program\*(R".
327	.Sp	500	.Sp
328	If you don't know what event loop to use, use the one returned from this	501	If you don't know what event loop to use, use the one returned from this
329	function.	502	function (or via the \f(CW\*(C`EV_DEFAULT\*(C'\fR macro).
		503	.Sp
		504	Note that this function is \fInot\fR thread-safe, so if you want to use it
		505	from multiple threads, you have to employ some kind of mutex (note also
		506	that this case is unlikely, as loops cannot be shared easily between
		507	threads anyway).
		508	.Sp
		509	The default loop is the only loop that can handle \f(CW\*(C`ev_child\*(C'\fR watchers,
		510	and to do this, it always registers a handler for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is
		511	a problem for your application you can either create a dynamic loop with
		512	\&\f(CW\*(C`ev_loop_new\*(C'\fR which doesn't do that, or you can simply overwrite the
		513	\&\f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling \f(CW\*(C`ev_default_init\*(C'\fR.
		514	.Sp
		515	Example: This is the most typical usage.
		516	.Sp
		517	.Vb 2
		518	\& if (!ev_default_loop (0))
		519	\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		520	.Ve
		521	.Sp
		522	Example: Restrict libev to the select and poll backends, and do not allow
		523	environment settings to be taken into account:
		524	.Sp
		525	.Vb 1
		526	\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		527	.Ve
		528	.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
		529	.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
		530	This will create and initialise a new event loop object. If the loop
		531	could not be initialised, returns false.
		532	.Sp
		533	This function is thread-safe, and one common way to use libev with
		534	threads is indeed to create one loop per thread, and using the default
		535	loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread.
330	.Sp	536	.Sp
331	The flags argument can be used to specify special behaviour or specific	537	The flags argument can be used to specify special behaviour or specific
332	backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).	538	backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
333	.Sp	539	.Sp
334	The following flags are supported:	540	The following flags are supported:
…		…
339	The default flags value. Use this if you have no clue (it's the right	545	The default flags value. Use this if you have no clue (it's the right
340	thing, believe me).	546	thing, believe me).
341	.ie n .IP """EVFLAG_NOENV""" 4	547	.ie n .IP """EVFLAG_NOENV""" 4
342	.el .IP "\f(CWEVFLAG_NOENV\fR" 4	548	.el .IP "\f(CWEVFLAG_NOENV\fR" 4
343	.IX Item "EVFLAG_NOENV"	549	.IX Item "EVFLAG_NOENV"
344	If this flag bit is ored into the flag value (or the program runs setuid	550	If this flag bit is or'ed into the flag value (or the program runs setuid
345	or setgid) then libev will \fInot\fR look at the environment variable	551	or setgid) then libev will \fInot\fR look at the environment variable
346	\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will	552	\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
347	override the flags completely if it is found in the environment. This is	553	override the flags completely if it is found in the environment. This is
348	useful to try out specific backends to test their performance, or to work	554	useful to try out specific backends to test their performance, to work
349	around bugs.	555	around bugs, or to make libev threadsafe (accessing environment variables
		556	cannot be done in a threadsafe way, but usually it works if no other
		557	thread modifies them).
		558	.ie n .IP """EVFLAG_FORKCHECK""" 4
		559	.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
		560	.IX Item "EVFLAG_FORKCHECK"
		561	Instead of calling \f(CW\*(C`ev_loop_fork\*(C'\fR manually after a fork, you can also
		562	make libev check for a fork in each iteration by enabling this flag.
		563	.Sp
		564	This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
		565	and thus this might slow down your event loop if you do a lot of loop
		566	iterations and little real work, but is usually not noticeable (on my
		567	GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn
		568	sequence without a system call and thus \fIvery\fR fast, but my GNU/Linux
		569	system also has \f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). (Update: glibc
		570	versions 2.25 apparently removed the \f(CW\*(C`getpid\*(C'\fR optimisation again).
		571	.Sp
		572	The big advantage of this flag is that you can forget about fork (and
		573	forget about forgetting to tell libev about forking, although you still
		574	have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR) when you use this flag.
		575	.Sp
		576	This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
		577	environment variable.
		578	.ie n .IP """EVFLAG_NOINOTIFY""" 4
		579	.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
		580	.IX Item "EVFLAG_NOINOTIFY"
		581	When this flag is specified, then libev will not attempt to use the
		582	\&\fIinotify\fR \s-1API\s0 for its \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and
		583	testing, this flag can be useful to conserve inotify file descriptors, as
		584	otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle.
		585	.ie n .IP """EVFLAG_SIGNALFD""" 4
		586	.el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4
		587	.IX Item "EVFLAG_SIGNALFD"
		588	When this flag is specified, then libev will attempt to use the
		589	\&\fIsignalfd\fR \s-1API\s0 for its \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This \s-1API\s0
		590	delivers signals synchronously, which makes it both faster and might make
		591	it possible to get the queued signal data. It can also simplify signal
		592	handling with threads, as long as you properly block signals in your
		593	threads that are not interested in handling them.
		594	.Sp
		595	Signalfd will not be used by default as this changes your signal mask, and
		596	there are a lot of shoddy libraries and programs (glib's threadpool for
		597	example) that can't properly initialise their signal masks.
		598	.ie n .IP """EVFLAG_NOSIGMASK""" 4
		599	.el .IP "\f(CWEVFLAG_NOSIGMASK\fR" 4
		600	.IX Item "EVFLAG_NOSIGMASK"
		601	When this flag is specified, then libev will avoid to modify the signal
		602	mask. Specifically, this means you have to make sure signals are unblocked
		603	when you want to receive them.
		604	.Sp
		605	This behaviour is useful when you want to do your own signal handling, or
		606	want to handle signals only in specific threads and want to avoid libev
		607	unblocking the signals.
		608	.Sp
		609	It's also required by \s-1POSIX\s0 in a threaded program, as libev calls
		610	\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified.
		611	.Sp
		612	This flag's behaviour will become the default in future versions of libev.
350	.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4	613	.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
351	.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4	614	.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
352	.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"	615	.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
353	This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as	616	This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
354	libev tries to roll its own fd_set with no limits on the number of fds,	617	libev tries to roll its own fd_set with no limits on the number of fds,
355	but if that fails, expect a fairly low limit on the number of fds when	618	but if that fails, expect a fairly low limit on the number of fds when
356	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	619	using this backend. It doesn't scale too well (O(highest_fd)), but its
357	the fastest backend for a low number of fds.	620	usually the fastest backend for a low number of (low-numbered :) fds.
		621	.Sp
		622	To get good performance out of this backend you need a high amount of
		623	parallelism (most of the file descriptors should be busy). If you are
		624	writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many
		625	connections as possible during one iteration. You might also want to have
		626	a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of
		627	readiness notifications you get per iteration.
		628	.Sp
		629	This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the
		630	\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the
		631	\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform).
358	.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4	632	.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
359	.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4	633	.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
360	.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"	634	.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
361	And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than	635	And this is your standard \fBpoll\fR\|(2) backend. It's more complicated
362	select, but handles sparse fds better and has no artificial limit on the	636	than select, but handles sparse fds better and has no artificial
363	number of fds you can use (except it will slow down considerably with a	637	limit on the number of fds you can use (except it will slow down
364	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	638	considerably with a lot of inactive fds). It scales similarly to select,
		639	i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
		640	performance tips.
		641	.Sp
		642	This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
		643	\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
365	.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4	644	.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
366	.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4	645	.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
367	.IX Item "EVBACKEND_EPOLL (value 4, Linux)"	646	.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
		647	Use the Linux-specific \fBepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
		648	kernels).
		649	.Sp
368	For few fds, this backend is a bit little slower than poll and select,	650	For few fds, this backend is a bit little slower than poll and select, but
369	but it scales phenomenally better. While poll and select usually scale like	651	it scales phenomenally better. While poll and select usually scale like
370	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	652	O(total_fds) where total_fds is the total number of fds (or the highest
371	either O(1) or O(active_fds).	653	fd), epoll scales either O(1) or O(active_fds).
372	.Sp	654	.Sp
		655	The epoll mechanism deserves honorable mention as the most misdesigned
		656	of the more advanced event mechanisms: mere annoyances include silently
		657	dropping file descriptors, requiring a system call per change per file
		658	descriptor (and unnecessary guessing of parameters), problems with dup,
		659	returning before the timeout value, resulting in additional iterations
		660	(and only giving 5ms accuracy while select on the same platform gives
		661	0.1ms) and so on. The biggest issue is fork races, however \- if a program
		662	forks then \fIboth\fR parent and child process have to recreate the epoll
		663	set, which can take considerable time (one syscall per file descriptor)
		664	and is of course hard to detect.
		665	.Sp
		666	Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work,
		667	but of course \fIdoesn't\fR, and epoll just loves to report events for
		668	totally \fIdifferent\fR file descriptors (even already closed ones, so
		669	one cannot even remove them from the set) than registered in the set
		670	(especially on \s-1SMP\s0 systems). Libev tries to counter these spurious
		671	notifications by employing an additional generation counter and comparing
		672	that against the events to filter out spurious ones, recreating the set
		673	when required. Epoll also erroneously rounds down timeouts, but gives you
		674	no way to know when and by how much, so sometimes you have to busy-wait
		675	because epoll returns immediately despite a nonzero timeout. And last
		676	not least, it also refuses to work with some file descriptors which work
		677	perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...).
		678	.Sp
		679	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		680	cobbled together in a hurry, no thought to design or interaction with
		681	others. Oh, the pain, will it ever stop...
		682	.Sp
373	While stopping and starting an I/O watcher in the same iteration will	683	While stopping, setting and starting an I/O watcher in the same iteration
374	result in some caching, there is still a syscall per such incident	684	will result in some caching, there is still a system call per such
375	(because the fd could point to a different file description now), so its	685	incident (because the same \fIfile descriptor\fR could point to a different
376	best to avoid that. Also, \fIdup()\fRed file descriptors might not work very	686	\&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed
377	well if you register events for both fds.	687	file descriptors might not work very well if you register events for both
		688	file descriptors.
378	.Sp	689	.Sp
379	Please note that epoll sometimes generates spurious notifications, so you	690	Best performance from this backend is achieved by not unregistering all
380	need to use non-blocking I/O or other means to avoid blocking when no data	691	watchers for a file descriptor until it has been closed, if possible,
381	(or space) is available.	692	i.e. keep at least one watcher active per fd at all times. Stopping and
		693	starting a watcher (without re-setting it) also usually doesn't cause
		694	extra overhead. A fork can both result in spurious notifications as well
		695	as in libev having to destroy and recreate the epoll object, which can
		696	take considerable time and thus should be avoided.
		697	.Sp
		698	All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or
		699	faster than epoll for maybe up to a hundred file descriptors, depending on
		700	the usage. So sad.
		701	.Sp
		702	While nominally embeddable in other event loops, this feature is broken in
		703	a lot of kernel revisions, but probably(!) works in current versions.
		704	.Sp
		705	This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
		706	\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
		707	.ie n .IP """EVBACKEND_LINUXAIO"" (value 64, Linux)" 4
		708	.el .IP "\f(CWEVBACKEND_LINUXAIO\fR (value 64, Linux)" 4
		709	.IX Item "EVBACKEND_LINUXAIO (value 64, Linux)"
		710	Use the Linux-specific Linux \s-1AIO\s0 (\fInot\fR \f(CWaio(7)\fR but \f(CWio_submit(2)\fR) event interface available in post\-4.18 kernels (but libev
		711	only tries to use it in 4.19+).
		712	.Sp
		713	This is another Linux train wreck of an event interface.
		714	.Sp
		715	If this backend works for you (as of this writing, it was very
		716	experimental), it is the best event interface available on Linux and might
		717	be well worth enabling it \- if it isn't available in your kernel this will
		718	be detected and this backend will be skipped.
		719	.Sp
		720	This backend can batch oneshot requests and supports a user-space ring
		721	buffer to receive events. It also doesn't suffer from most of the design
		722	problems of epoll (such as not being able to remove event sources from
		723	the epoll set), and generally sounds too good to be true. Because, this
		724	being the Linux kernel, of course it suffers from a whole new set of
		725	limitations, forcing you to fall back to epoll, inheriting all its design
		726	issues.
		727	.Sp
		728	For one, it is not easily embeddable (but probably could be done using
		729	an event fd at some extra overhead). It also is subject to a system wide
		730	limit that can be configured in \fI/proc/sys/fs/aio\-max\-nr\fR. If no \s-1AIO\s0
		731	requests are left, this backend will be skipped during initialisation, and
		732	will switch to epoll when the loop is active.
		733	.Sp
		734	Most problematic in practice, however, is that not all file descriptors
		735	work with it. For example, in Linux 5.1, \s-1TCP\s0 sockets, pipes, event fds,
		736	files, \fI/dev/null\fR and many others are supported, but ttys do not work
		737	properly (a known bug that the kernel developers don't care about, see
		738	<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		739	(yet?) a generic event polling interface.
		740	.Sp
		741	Overall, it seems the Linux developers just don't want it to have a
		742	generic event handling mechanism other than \f(CW\*(C`select\*(C'\fR or \f(CW\*(C`poll\*(C'\fR.
		743	.Sp
		744	To work around all these problem, the current version of libev uses its
		745	epoll backend as a fallback for file descriptor types that do not work. Or
		746	falls back completely to epoll if the kernel acts up.
		747	.Sp
		748	This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
		749	\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
382	.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4	750	.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
383	.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4	751	.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
384	.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"	752	.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
385	Kqueue deserves special mention, as at the time of this writing, it	753	Kqueue deserves special mention, as at the time this backend was
386	was broken on all BSDs except NetBSD (usually it doesn't work with	754	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
387	anything but sockets and pipes, except on Darwin, where of course its	755	work reliably with anything but sockets and pipes, except on Darwin,
388	completely useless). For this reason its not being \*(L"autodetected\*(R"	756	where of course it's completely useless). Unlike epoll, however, whose
389	unless you explicitly specify it explicitly in the flags (i.e. using	757	brokenness is by design, these kqueue bugs can be (and mostly have been)
390	\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).	758	fixed without \s-1API\s0 changes to existing programs. For this reason it's not
		759	being \*(L"auto-detected\*(R" on all platforms unless you explicitly specify it
		760	in the flags (i.e. using \f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a
		761	known-to-be-good (\-enough) system like NetBSD.
		762	.Sp
		763	You still can embed kqueue into a normal poll or select backend and use it
		764	only for sockets (after having made sure that sockets work with kqueue on
		765	the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
391	.Sp	766	.Sp
392	It scales in the same way as the epoll backend, but the interface to the	767	It scales in the same way as the epoll backend, but the interface to the
393	kernel is more efficient (which says nothing about its actual speed, of	768	kernel is more efficient (which says nothing about its actual speed, of
394	course). While starting and stopping an I/O watcher does not cause an	769	course). While stopping, setting and starting an I/O watcher does never
395	extra syscall as with epoll, it still adds up to four event changes per	770	cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
396	incident, so its best to avoid that.	771	two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you
		772	might have to leak fds on fork, but it's more sane than epoll) and it
		773	drops fds silently in similarly hard-to-detect cases.
		774	.Sp
		775	This backend usually performs well under most conditions.
		776	.Sp
		777	While nominally embeddable in other event loops, this doesn't work
		778	everywhere, so you might need to test for this. And since it is broken
		779	almost everywhere, you should only use it when you have a lot of sockets
		780	(for which it usually works), by embedding it into another event loop
		781	(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course
		782	also broken on \s-1OS X\s0)) and, did I mention it, using it only for sockets.
		783	.Sp
		784	This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with
		785	\&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with
		786	\&\f(CW\*(C`NOTE_EOF\*(C'\fR.
397	.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4	787	.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
398	.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4	788	.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
399	.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"	789	.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
400	This is not implemented yet (and might never be).	790	This is not implemented yet (and might never be, unless you send me an
		791	implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets
		792	and is not embeddable, which would limit the usefulness of this backend
		793	immensely.
401	.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4	794	.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
402	.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4	795	.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
403	.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"	796	.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
404	This uses the Solaris 10 port mechanism. As with everything on Solaris,	797	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
405	it's really slow, but it still scales very well (O(active_fds)).	798	it's really slow, but it still scales very well (O(active_fds)).
406	.Sp	799	.Sp
407	Please note that solaris ports can result in a lot of spurious	800	While this backend scales well, it requires one system call per active
408	notifications, so you need to use non-blocking I/O or other means to avoid	801	file descriptor per loop iteration. For small and medium numbers of file
409	blocking when no data (or space) is available.	802	descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
		803	might perform better.
		804	.Sp
		805	On the positive side, this backend actually performed fully to
		806	specification in all tests and is fully embeddable, which is a rare feat
		807	among the OS-specific backends (I vastly prefer correctness over speed
		808	hacks).
		809	.Sp
		810	On the negative side, the interface is \fIbizarre\fR \- so bizarre that
		811	even sun itself gets it wrong in their code examples: The event polling
		812	function sometimes returns events to the caller even though an error
		813	occurred, but with no indication whether it has done so or not (yes, it's
		814	even documented that way) \- deadly for edge-triggered interfaces where you
		815	absolutely have to know whether an event occurred or not because you have
		816	to re-arm the watcher.
		817	.Sp
		818	Fortunately libev seems to be able to work around these idiocies.
		819	.Sp
		820	This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
		821	\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
410	.ie n .IP """EVBACKEND_ALL""" 4	822	.ie n .IP """EVBACKEND_ALL""" 4
411	.el .IP "\f(CWEVBACKEND_ALL\fR" 4	823	.el .IP "\f(CWEVBACKEND_ALL\fR" 4
412	.IX Item "EVBACKEND_ALL"	824	.IX Item "EVBACKEND_ALL"
413	Try all backends (even potentially broken ones that wouldn't be tried	825	Try all backends (even potentially broken ones that wouldn't be tried
414	with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as	826	with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
415	\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.	827	\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
		828	.Sp
		829	It is definitely not recommended to use this flag, use whatever
		830	\&\f(CW\*(C`ev_recommended_backends ()\*(C'\fR returns, or simply do not specify a backend
		831	at all.
		832	.ie n .IP """EVBACKEND_MASK""" 4
		833	.el .IP "\f(CWEVBACKEND_MASK\fR" 4
		834	.IX Item "EVBACKEND_MASK"
		835	Not a backend at all, but a mask to select all backend bits from a
		836	\&\f(CW\*(C`flags\*(C'\fR value, in case you want to mask out any backends from a flags
		837	value (e.g. when modifying the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR environment variable).
416	.RE	838	.RE
417	.RS 4	839	.RS 4
418	.Sp	840	.Sp
419	If one or more of these are ored into the flags value, then only these	841	If one or more of the backend flags are or'ed into the flags value,
420	backends will be tried (in the reverse order as given here). If none are	842	then only these backends will be tried (in the reverse order as listed
421	specified, most compiled-in backend will be tried, usually in reverse	843	here). If none are specified, all backends in \f(CW\*(C`ev_recommended_backends
422	order of their flag values :)	844	()\*(C'\fR will be tried.
423	.Sp	845	.Sp
424	The most typical usage is like this:	846	Example: Try to create a event loop that uses epoll and nothing else.
425	.Sp	847	.Sp
426	.Vb 2	848	.Vb 3
427	\& if (!ev_default_loop (0))	849	\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
428	\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	850	\& if (!epoller)
		851	\& fatal ("no epoll found here, maybe it hides under your chair");
429	.Ve	852	.Ve
430	.Sp	853	.Sp
431	Restrict libev to the select and poll backends, and do not allow	854	Example: Use whatever libev has to offer, but make sure that kqueue is
432	environment settings to be taken into account:	855	used if available.
433	.Sp	856	.Sp
434	.Vb 1	857	.Vb 1
435	\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	858	\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
436	.Ve	859	.Ve
437	.Sp	860	.Sp
438	Use whatever libev has to offer, but make sure that kqueue is used if	861	Example: Similarly, on linux, you mgiht want to take advantage of the
439	available (warning, breaks stuff, best use only with your own private	862	linux aio backend if possible, but fall back to something else if that
440	event loop and only if you know the \s-1OS\s0 supports your types of fds):	863	isn't available.
441	.Sp	864	.Sp
442	.Vb 1	865	.Vb 1
443	\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	866	\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
444	.Ve	867	.Ve
445	.RE	868	.RE
446	.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
447	.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
448	Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
449	always distinct from the default loop. Unlike the default loop, it cannot
450	handle signal and child watchers, and attempts to do so will be greeted by
451	undefined behaviour (or a failed assertion if assertions are enabled).
452	.Sp
453	Example: try to create a event loop that uses epoll and nothing else.
454	.Sp
455	.Vb 3
456	\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457	\& if (!epoller)
458	\& fatal ("no epoll found here, maybe it hides under your chair");
459	.Ve
460	.IP "ev_default_destroy ()" 4	869	.IP "ev_loop_destroy (loop)" 4
461	.IX Item "ev_default_destroy ()"	870	.IX Item "ev_loop_destroy (loop)"
462	Destroys the default loop again (frees all memory and kernel state	871	Destroys an event loop object (frees all memory and kernel state
463	etc.). None of the active event watchers will be stopped in the normal	872	etc.). None of the active event watchers will be stopped in the normal
464	sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your	873	sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
465	responsibility to either stop all watchers cleanly yoursef \fIbefore\fR	874	responsibility to either stop all watchers cleanly yourself \fIbefore\fR
466	calling this function, or cope with the fact afterwards (which is usually	875	calling this function, or cope with the fact afterwards (which is usually
467	the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them	876	the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
468	for example).	877	for example).
469	.IP "ev_loop_destroy (loop)" 4
470	.IX Item "ev_loop_destroy (loop)"
471	Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
472	earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
473	.IP "ev_default_fork ()" 4
474	.IX Item "ev_default_fork ()"
475	This function reinitialises the kernel state for backends that have
476	one. Despite the name, you can call it anytime, but it makes most sense
477	after forking, in either the parent or child process (or both, but that
478	again makes little sense).
479	.Sp	878	.Sp
480	You \fImust\fR call this function in the child process after forking if and	879	Note that certain global state, such as signal state (and installed signal
481	only if you want to use the event library in both processes. If you just	880	handlers), will not be freed by this function, and related watchers (such
482	fork+exec, you don't have to call it.	881	as signal and child watchers) would need to be stopped manually.
483	.Sp	882	.Sp
484	The function itself is quite fast and it's usually not a problem to call	883	This function is normally used on loop objects allocated by
485	it just in case after a fork. To make this easy, the function will fit in	884	\&\f(CW\*(C`ev_loop_new\*(C'\fR, but it can also be used on the default loop returned by
486	quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:	885	\&\f(CW\*(C`ev_default_loop\*(C'\fR, in which case it is not thread-safe.
487	.Sp	886	.Sp
488	.Vb 1	887	Note that it is not advisable to call this function on the default loop
489	\& pthread_atfork (0, 0, ev_default_fork);	888	except in the rare occasion where you really need to free its resources.
490	.Ve	889	If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR
491	.Sp	890	and \f(CW\*(C`ev_loop_destroy\*(C'\fR.
492	At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
493	without calling this function, so if you force one of those backends you
494	do not need to care.
495	.IP "ev_loop_fork (loop)" 4	891	.IP "ev_loop_fork (loop)" 4
496	.IX Item "ev_loop_fork (loop)"	892	.IX Item "ev_loop_fork (loop)"
497	Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by	893	This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations
498	\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop	894	to reinitialise the kernel state for backends that have one. Despite
499	after fork, and how you do this is entirely your own problem.	895	the name, you can call it anytime you are allowed to start or stop
		896	watchers (except inside an \f(CW\*(C`ev_prepare\*(C'\fR callback), but it makes most
		897	sense after forking, in the child process. You \fImust\fR call it (or use
		898	\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR.
		899	.Sp
		900	In addition, if you want to reuse a loop (via this function or
		901	\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR), you \fIalso\fR have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR.
		902	.Sp
		903	Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after
		904	a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is
		905	because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things
		906	during fork.
		907	.Sp
		908	On the other hand, you only need to call this function in the child
		909	process if and only if you want to use the event loop in the child. If
		910	you just fork+exec or create a new loop in the child, you don't have to
		911	call it at all (in fact, \f(CW\*(C`epoll\*(C'\fR is so badly broken that it makes a
		912	difference, but libev will usually detect this case on its own and do a
		913	costly reset of the backend).
		914	.Sp
		915	The function itself is quite fast and it's usually not a problem to call
		916	it just in case after a fork.
		917	.Sp
		918	Example: Automate calling \f(CW\*(C`ev_loop_fork\*(C'\fR on the default loop when
		919	using pthreads.
		920	.Sp
		921	.Vb 5
		922	\& static void
		923	\& post_fork_child (void)
		924	\& {
		925	\& ev_loop_fork (EV_DEFAULT);
		926	\& }
		927	\&
		928	\& ...
		929	\& pthread_atfork (0, 0, post_fork_child);
		930	.Ve
		931	.IP "int ev_is_default_loop (loop)" 4
		932	.IX Item "int ev_is_default_loop (loop)"
		933	Returns true when the given loop is, in fact, the default loop, and false
		934	otherwise.
		935	.IP "unsigned int ev_iteration (loop)" 4
		936	.IX Item "unsigned int ev_iteration (loop)"
		937	Returns the current iteration count for the event loop, which is identical
		938	to the number of times libev did poll for new events. It starts at \f(CW0\fR
		939	and happily wraps around with enough iterations.
		940	.Sp
		941	This value can sometimes be useful as a generation counter of sorts (it
		942	\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
		943	\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls \- and is incremented between the
		944	prepare and check phases.
		945	.IP "unsigned int ev_depth (loop)" 4
		946	.IX Item "unsigned int ev_depth (loop)"
		947	Returns the number of times \f(CW\*(C`ev_run\*(C'\fR was entered minus the number of
		948	times \f(CW\*(C`ev_run\*(C'\fR was exited normally, in other words, the recursion depth.
		949	.Sp
		950	Outside \f(CW\*(C`ev_run\*(C'\fR, this number is zero. In a callback, this number is
		951	\&\f(CW1\fR, unless \f(CW\*(C`ev_run\*(C'\fR was invoked recursively (or from another thread),
		952	in which case it is higher.
		953	.Sp
		954	Leaving \f(CW\*(C`ev_run\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread,
		955	throwing an exception etc.), doesn't count as \*(L"exit\*(R" \- consider this
		956	as a hint to avoid such ungentleman-like behaviour unless it's really
		957	convenient, in which case it is fully supported.
500	.IP "unsigned int ev_backend (loop)" 4	958	.IP "unsigned int ev_backend (loop)" 4
501	.IX Item "unsigned int ev_backend (loop)"	959	.IX Item "unsigned int ev_backend (loop)"
502	Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in	960	Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
503	use.	961	use.
504	.IP "ev_tstamp ev_now (loop)" 4	962	.IP "ev_tstamp ev_now (loop)" 4
505	.IX Item "ev_tstamp ev_now (loop)"	963	.IX Item "ev_tstamp ev_now (loop)"
506	Returns the current \*(L"event loop time\*(R", which is the time the event loop	964	Returns the current \*(L"event loop time\*(R", which is the time the event loop
507	received events and started processing them. This timestamp does not	965	received events and started processing them. This timestamp does not
508	change as long as callbacks are being processed, and this is also the base	966	change as long as callbacks are being processed, and this is also the base
509	time used for relative timers. You can treat it as the timestamp of the	967	time used for relative timers. You can treat it as the timestamp of the
510	event occuring (or more correctly, libev finding out about it).	968	event occurring (or more correctly, libev finding out about it).
		969	.IP "ev_now_update (loop)" 4
		970	.IX Item "ev_now_update (loop)"
		971	Establishes the current time by querying the kernel, updating the time
		972	returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and
		973	is usually done automatically within \f(CW\*(C`ev_run ()\*(C'\fR.
		974	.Sp
		975	This function is rarely useful, but when some event callback runs for a
		976	very long time without entering the event loop, updating libev's idea of
		977	the current time is a good idea.
		978	.Sp
		979	See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section.
		980	.IP "ev_suspend (loop)" 4
		981	.IX Item "ev_suspend (loop)"
		982	.PD 0
		983	.IP "ev_resume (loop)" 4
		984	.IX Item "ev_resume (loop)"
		985	.PD
		986	These two functions suspend and resume an event loop, for use when the
		987	loop is not used for a while and timeouts should not be processed.
		988	.Sp
		989	A typical use case would be an interactive program such as a game: When
		990	the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it
		991	would be best to handle timeouts as if no time had actually passed while
		992	the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR
		993	in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling
		994	\&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing.
		995	.Sp
		996	Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend
		997	between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers
		998	will be rescheduled (that is, they will lose any events that would have
		999	occurred while suspended).
		1000	.Sp
		1001	After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the
		1002	given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR
		1003	without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR.
		1004	.Sp
		1005	Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the
		1006	event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR).
511	.IP "ev_loop (loop, int flags)" 4	1007	.IP "bool ev_run (loop, int flags)" 4
512	.IX Item "ev_loop (loop, int flags)"	1008	.IX Item "bool ev_run (loop, int flags)"
513	Finally, this is it, the event handler. This function usually is called	1009	Finally, this is it, the event handler. This function usually is called
514	after you initialised all your watchers and you want to start handling	1010	after you have initialised all your watchers and you want to start
515	events.	1011	handling events. It will ask the operating system for any new events, call
		1012	the watcher callbacks, and then repeat the whole process indefinitely: This
		1013	is why event loops are called \fIloops\fR.
516	.Sp	1014	.Sp
517	If the flags argument is specified as \f(CW0\fR, it will not return until	1015	If the flags argument is specified as \f(CW0\fR, it will keep handling events
518	either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.	1016	until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was
		1017	called.
519	.Sp	1018	.Sp
		1019	The return value is false if there are no more active watchers (which
		1020	usually means \*(L"all jobs done\*(R" or \*(L"deadlock\*(R"), and true in all other cases
		1021	(which usually means " you should call \f(CW\*(C`ev_run\*(C'\fR again").
		1022	.Sp
520	Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than	1023	Please note that an explicit \f(CW\*(C`ev_break\*(C'\fR is usually better than
521	relying on all watchers to be stopped when deciding when a program has	1024	relying on all watchers to be stopped when deciding when a program has
522	finished (especially in interactive programs), but having a program that	1025	finished (especially in interactive programs), but having a program
523	automatically loops as long as it has to and no longer by virtue of	1026	that automatically loops as long as it has to and no longer by virtue
524	relying on its watchers stopping correctly is a thing of beauty.	1027	of relying on its watchers stopping correctly, that is truly a thing of
		1028	beauty.
525	.Sp	1029	.Sp
		1030	This function is \fImostly\fR exception-safe \- you can break out of a
		1031	\&\f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+
		1032	exception and so on. This does not decrement the \f(CW\*(C`ev_depth\*(C'\fR value, nor
		1033	will it clear any outstanding \f(CW\*(C`EVBREAK_ONE\*(C'\fR breaks.
		1034	.Sp
526	A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle	1035	A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle
527	those events and any outstanding ones, but will not block your process in	1036	those events and any already outstanding ones, but will not wait and
528	case there are no events and will return after one iteration of the loop.	1037	block your process in case there are no events and will return after one
		1038	iteration of the loop. This is sometimes useful to poll and handle new
		1039	events while doing lengthy calculations, to keep the program responsive.
529	.Sp	1040	.Sp
530	A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if	1041	A flags value of \f(CW\*(C`EVRUN_ONCE\*(C'\fR will look for new events (waiting if
531	neccessary) and will handle those and any outstanding ones. It will block	1042	necessary) and will handle those and any already outstanding ones. It
532	your process until at least one new event arrives, and will return after	1043	will block your process until at least one new event arrives (which could
533	one iteration of the loop. This is useful if you are waiting for some	1044	be an event internal to libev itself, so there is no guarantee that a
534	external event in conjunction with something not expressible using other	1045	user-registered callback will be called), and will return after one
		1046	iteration of the loop.
		1047	.Sp
		1048	This is useful if you are waiting for some external event in conjunction
		1049	with something not expressible using other libev watchers (i.e. "roll your
535	libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is	1050	own \f(CW\*(C`ev_run\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
536	usually a better approach for this kind of thing.	1051	usually a better approach for this kind of thing.
537	.Sp	1052	.Sp
538	Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:	1053	Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does (this is for your
		1054	understanding, not a guarantee that things will work exactly like this in
		1055	future versions):
539	.Sp	1056	.Sp
540	.Vb 18	1057	.Vb 10
541	\& * If there are no active watchers (reference count is zero), return.	1058	\& \- Increment loop depth.
542	\& - Queue prepare watchers and then call all outstanding watchers.	1059	\& \- Reset the ev_break status.
		1060	\& \- Before the first iteration, call any pending watchers.
		1061	\& LOOP:
		1062	\& \- If EVFLAG_FORKCHECK was used, check for a fork.
		1063	\& \- If a fork was detected (by any means), queue and call all fork watchers.
		1064	\& \- Queue and call all prepare watchers.
		1065	\& \- If ev_break was called, goto FINISH.
543	\& - If we have been forked, recreate the kernel state.	1066	\& \- If we have been forked, detach and recreate the kernel state
		1067	\& as to not disturb the other process.
544	\& - Update the kernel state with all outstanding changes.	1068	\& \- Update the kernel state with all outstanding changes.
545	\& - Update the "event loop time".	1069	\& \- Update the "event loop time" (ev_now ()).
546	\& - Calculate for how long to block.	1070	\& \- Calculate for how long to sleep or block, if at all
		1071	\& (active idle watchers, EVRUN_NOWAIT or not having
		1072	\& any active watchers at all will result in not sleeping).
		1073	\& \- Sleep if the I/O and timer collect interval say so.
		1074	\& \- Increment loop iteration counter.
547	\& - Block the process, waiting for any events.	1075	\& \- Block the process, waiting for any events.
548	\& - Queue all outstanding I/O (fd) events.	1076	\& \- Queue all outstanding I/O (fd) events.
549	\& - Update the "event loop time" and do time jump handling.	1077	\& \- Update the "event loop time" (ev_now ()), and do time jump adjustments.
550	\& - Queue all outstanding timers.	1078	\& \- Queue all expired timers.
551	\& - Queue all outstanding periodics.	1079	\& \- Queue all expired periodics.
552	\& - If no events are pending now, queue all idle watchers.	1080	\& \- Queue all idle watchers with priority higher than that of pending events.
553	\& - Queue all check watchers.	1081	\& \- Queue all check watchers.
554	\& - Call all queued watchers in reverse order (i.e. check watchers first).	1082	\& \- Call all queued watchers in reverse order (i.e. check watchers first).
555	\& Signals and child watchers are implemented as I/O watchers, and will	1083	\& Signals and child watchers are implemented as I/O watchers, and will
556	\& be handled here by queueing them when their watcher gets executed.	1084	\& be handled here by queueing them when their watcher gets executed.
557	\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	1085	\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
558	\& were used, return, otherwise continue with step *.	1086	\& were used, or there are no active watchers, goto FINISH, otherwise
		1087	\& continue with step LOOP.
		1088	\& FINISH:
		1089	\& \- Reset the ev_break status iff it was EVBREAK_ONE.
		1090	\& \- Decrement the loop depth.
		1091	\& \- Return.
559	.Ve	1092	.Ve
560	.Sp	1093	.Sp
561	Example: queue some jobs and then loop until no events are outsanding	1094	Example: Queue some jobs and then loop until no events are outstanding
562	anymore.	1095	anymore.
563	.Sp	1096	.Sp
564	.Vb 4	1097	.Vb 4
565	\& ... queue jobs here, make sure they register event watchers as long	1098	\& ... queue jobs here, make sure they register event watchers as long
566	\& ... as they still have work to do (even an idle watcher will do..)	1099	\& ... as they still have work to do (even an idle watcher will do..)
567	\& ev_loop (my_loop, 0);	1100	\& ev_run (my_loop, 0);
568	\& ... jobs done. yeah!	1101	\& ... jobs done or somebody called break. yeah!
569	.Ve	1102	.Ve
570	.IP "ev_unloop (loop, how)" 4	1103	.IP "ev_break (loop, how)" 4
571	.IX Item "ev_unloop (loop, how)"	1104	.IX Item "ev_break (loop, how)"
572	Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it	1105	Can be used to make a call to \f(CW\*(C`ev_run\*(C'\fR return early (but only after it
573	has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either	1106	has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
574	\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or	1107	\&\f(CW\*(C`EVBREAK_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_run\*(C'\fR call return, or
575	\&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return.	1108	\&\f(CW\*(C`EVBREAK_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_run\*(C'\fR calls return.
		1109	.Sp
		1110	This \*(L"break state\*(R" will be cleared on the next call to \f(CW\*(C`ev_run\*(C'\fR.
		1111	.Sp
		1112	It is safe to call \f(CW\*(C`ev_break\*(C'\fR from outside any \f(CW\*(C`ev_run\*(C'\fR calls, too, in
		1113	which case it will have no effect.
576	.IP "ev_ref (loop)" 4	1114	.IP "ev_ref (loop)" 4
577	.IX Item "ev_ref (loop)"	1115	.IX Item "ev_ref (loop)"
578	.PD 0	1116	.PD 0
579	.IP "ev_unref (loop)" 4	1117	.IP "ev_unref (loop)" 4
580	.IX Item "ev_unref (loop)"	1118	.IX Item "ev_unref (loop)"
581	.PD	1119	.PD
582	Ref/unref can be used to add or remove a reference count on the event	1120	Ref/unref can be used to add or remove a reference count on the event
583	loop: Every watcher keeps one reference, and as long as the reference	1121	loop: Every watcher keeps one reference, and as long as the reference
584	count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have	1122	count is nonzero, \f(CW\*(C`ev_run\*(C'\fR will not return on its own.
585	a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from	1123	.Sp
586	returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For	1124	This is useful when you have a watcher that you never intend to
		1125	unregister, but that nevertheless should not keep \f(CW\*(C`ev_run\*(C'\fR from
		1126	returning. In such a case, call \f(CW\*(C`ev_unref\*(C'\fR after starting, and \f(CW\*(C`ev_ref\*(C'\fR
		1127	before stopping it.
		1128	.Sp
587	example, libev itself uses this for its internal signal pipe: It is not	1129	As an example, libev itself uses this for its internal signal pipe: It
588	visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if	1130	is not visible to the libev user and should not keep \f(CW\*(C`ev_run\*(C'\fR from
589	no event watchers registered by it are active. It is also an excellent	1131	exiting if no event watchers registered by it are active. It is also an
590	way to do this for generic recurring timers or from within third-party	1132	excellent way to do this for generic recurring timers or from within
591	libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.	1133	third-party libraries. Just remember to \fIunref after start\fR and \fIref
		1134	before stop\fR (but only if the watcher wasn't active before, or was active
		1135	before, respectively. Note also that libev might stop watchers itself
		1136	(e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR
		1137	in the callback).
592	.Sp	1138	.Sp
593	Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR	1139	Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_run\*(C'\fR
594	running when nothing else is active.	1140	running when nothing else is active.
595	.Sp	1141	.Sp
596	.Vb 4	1142	.Vb 4
597	\& struct dv_signal exitsig;	1143	\& ev_signal exitsig;
598	\& ev_signal_init (&exitsig, sig_cb, SIGINT);	1144	\& ev_signal_init (&exitsig, sig_cb, SIGINT);
599	\& ev_signal_start (myloop, &exitsig);	1145	\& ev_signal_start (loop, &exitsig);
600	\& evf_unref (myloop);	1146	\& ev_unref (loop);
601	.Ve	1147	.Ve
602	.Sp	1148	.Sp
603	Example: for some weird reason, unregister the above signal handler again.	1149	Example: For some weird reason, unregister the above signal handler again.
604	.Sp	1150	.Sp
605	.Vb 2	1151	.Vb 2
606	\& ev_ref (myloop);	1152	\& ev_ref (loop);
607	\& ev_signal_stop (myloop, &exitsig);	1153	\& ev_signal_stop (loop, &exitsig);
608	.Ve	1154	.Ve
		1155	.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
		1156	.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
		1157	.PD 0
		1158	.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
		1159	.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
		1160	.PD
		1161	These advanced functions influence the time that libev will spend waiting
		1162	for events. Both time intervals are by default \f(CW0\fR, meaning that libev
		1163	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		1164	latency.
		1165	.Sp
		1166	Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
		1167	allows libev to delay invocation of I/O and timer/periodic callbacks
		1168	to increase efficiency of loop iterations (or to increase power-saving
		1169	opportunities).
		1170	.Sp
		1171	The idea is that sometimes your program runs just fast enough to handle
		1172	one (or very few) event(s) per loop iteration. While this makes the
		1173	program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
		1174	events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
		1175	overhead for the actual polling but can deliver many events at once.
		1176	.Sp
		1177	By setting a higher \fIio collect interval\fR you allow libev to spend more
		1178	time collecting I/O events, so you can handle more events per iteration,
		1179	at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
		1180	\&\f(CW\*(C`ev_timer\*(C'\fR) will not be affected. Setting this to a non-null value will
		1181	introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The
		1182	sleep time ensures that libev will not poll for I/O events more often then
		1183	once per this interval, on average (as long as the host time resolution is
		1184	good enough).
		1185	.Sp
		1186	Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
		1187	to spend more time collecting timeouts, at the expense of increased
		1188	latency/jitter/inexactness (the watcher callback will be called
		1189	later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null
		1190	value will not introduce any overhead in libev.
		1191	.Sp
		1192	Many (busy) programs can usually benefit by setting the I/O collect
		1193	interval to a value near \f(CW0.1\fR or so, which is often enough for
		1194	interactive servers (of course not for games), likewise for timeouts. It
		1195	usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR,
		1196	as this approaches the timing granularity of most systems. Note that if
		1197	you do transactions with the outside world and you can't increase the
		1198	parallelity, then this setting will limit your transaction rate (if you
		1199	need to poll once per transaction and the I/O collect interval is 0.01,
		1200	then you can't do more than 100 transactions per second).
		1201	.Sp
		1202	Setting the \fItimeout collect interval\fR can improve the opportunity for
		1203	saving power, as the program will \*(L"bundle\*(R" timer callback invocations that
		1204	are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of
		1205	times the process sleeps and wakes up again. Another useful technique to
		1206	reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure
		1207	they fire on, say, one-second boundaries only.
		1208	.Sp
		1209	Example: we only need 0.1s timeout granularity, and we wish not to poll
		1210	more often than 100 times per second:
		1211	.Sp
		1212	.Vb 2
		1213	\& ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1214	\& ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1215	.Ve
		1216	.IP "ev_invoke_pending (loop)" 4
		1217	.IX Item "ev_invoke_pending (loop)"
		1218	This call will simply invoke all pending watchers while resetting their
		1219	pending state. Normally, \f(CW\*(C`ev_run\*(C'\fR does this automatically when required,
		1220	but when overriding the invoke callback this call comes handy. This
		1221	function can be invoked from a watcher \- this can be useful for example
		1222	when you want to do some lengthy calculation and want to pass further
		1223	event handling to another thread (you still have to make sure only one
		1224	thread executes within \f(CW\*(C`ev_invoke_pending\*(C'\fR or \f(CW\*(C`ev_run\*(C'\fR of course).
		1225	.IP "int ev_pending_count (loop)" 4
		1226	.IX Item "int ev_pending_count (loop)"
		1227	Returns the number of pending watchers \- zero indicates that no watchers
		1228	are pending.
		1229	.IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4
		1230	.IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))"
		1231	This overrides the invoke pending functionality of the loop: Instead of
		1232	invoking all pending watchers when there are any, \f(CW\*(C`ev_run\*(C'\fR will call
		1233	this callback instead. This is useful, for example, when you want to
		1234	invoke the actual watchers inside another context (another thread etc.).
		1235	.Sp
		1236	If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new
		1237	callback.
		1238	.IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0) throw (), void (*acquire)(\s-1EV_P\s0) throw ())" 4
		1239	.IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())"
		1240	Sometimes you want to share the same loop between multiple threads. This
		1241	can be done relatively simply by putting mutex_lock/unlock calls around
		1242	each call to a libev function.
		1243	.Sp
		1244	However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible
		1245	to wait for it to return. One way around this is to wake up the event
		1246	loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`ev_async_send\*(C'\fR, another way is to set these
		1247	\&\fIrelease\fR and \fIacquire\fR callbacks on the loop.
		1248	.Sp
		1249	When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is
		1250	suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just
		1251	afterwards.
		1252	.Sp
		1253	Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and
		1254	\&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again.
		1255	.Sp
		1256	While event loop modifications are allowed between invocations of
		1257	\&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no
		1258	modifications done will affect the event loop, i.e. adding watchers will
		1259	have no effect on the set of file descriptors being watched, or the time
		1260	waited. Use an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_run\*(C'\fR when you want it
		1261	to take note of any changes you made.
		1262	.Sp
		1263	In theory, threads executing \f(CW\*(C`ev_run\*(C'\fR will be async-cancel safe between
		1264	invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR.
		1265	.Sp
		1266	See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this
		1267	document.
		1268	.IP "ev_set_userdata (loop, void *data)" 4
		1269	.IX Item "ev_set_userdata (loop, void *data)"
		1270	.PD 0
		1271	.IP "void *ev_userdata (loop)" 4
		1272	.IX Item "void *ev_userdata (loop)"
		1273	.PD
		1274	Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When
		1275	\&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns
		1276	\&\f(CW0\fR.
		1277	.Sp
		1278	These two functions can be used to associate arbitrary data with a loop,
		1279	and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and
		1280	\&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for
		1281	any other purpose as well.
		1282	.IP "ev_verify (loop)" 4
		1283	.IX Item "ev_verify (loop)"
		1284	This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been
		1285	compiled in, which is the default for non-minimal builds. It tries to go
		1286	through all internal structures and checks them for validity. If anything
		1287	is found to be inconsistent, it will print an error message to standard
		1288	error and call \f(CW\*(C`abort ()\*(C'\fR.
		1289	.Sp
		1290	This can be used to catch bugs inside libev itself: under normal
		1291	circumstances, this function will never abort as of course libev keeps its
		1292	data structures consistent.
609	.SH "ANATOMY OF A WATCHER"	1293	.SH "ANATOMY OF A WATCHER"
610	.IX Header "ANATOMY OF A WATCHER"	1294	.IX Header "ANATOMY OF A WATCHER"
		1295	In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the
		1296	watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer
		1297	watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers.
		1298	.PP
611	A watcher is a structure that you create and register to record your	1299	A watcher is an opaque structure that you allocate and register to record
612	interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to	1300	your interest in some event. To make a concrete example, imagine you want
613	become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:	1301	to wait for \s-1STDIN\s0 to become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher
		1302	for that:
614	.PP	1303	.PP
615	.Vb 5	1304	.Vb 5
616	\& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1305	\& static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
617	\& {	1306	\& {
618	\& ev_io_stop (w);	1307	\& ev_io_stop (w);
619	\& ev_unloop (loop, EVUNLOOP_ALL);	1308	\& ev_break (loop, EVBREAK_ALL);
620	\& }	1309	\& }
621	.Ve	1310	\&
622	.PP
623	.Vb 6
624	\& struct ev_loop *loop = ev_default_loop (0);	1311	\& struct ev_loop *loop = ev_default_loop (0);
		1312	\&
625	\& struct ev_io stdin_watcher;	1313	\& ev_io stdin_watcher;
		1314	\&
626	\& ev_init (&stdin_watcher, my_cb);	1315	\& ev_init (&stdin_watcher, my_cb);
627	\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1316	\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
628	\& ev_io_start (loop, &stdin_watcher);	1317	\& ev_io_start (loop, &stdin_watcher);
		1318	\&
629	\& ev_loop (loop, 0);	1319	\& ev_run (loop, 0);
630	.Ve	1320	.Ve
631	.PP	1321	.PP
632	As you can see, you are responsible for allocating the memory for your	1322	As you can see, you are responsible for allocating the memory for your
633	watcher structures (and it is usually a bad idea to do this on the stack,	1323	watcher structures (and it is \fIusually\fR a bad idea to do this on the
634	although this can sometimes be quite valid).	1324	stack).
635	.PP	1325	.PP
		1326	Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR
		1327	or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs).
		1328	.PP
636	Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init	1329	Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init (watcher
637	(watcher *, callback)\*(C'\fR, which expects a callback to be provided. This	1330	*, callback)\*(C'\fR, which expects a callback to be provided. This callback is
638	callback gets invoked each time the event occurs (or, in the case of io	1331	invoked each time the event occurs (or, in the case of I/O watchers, each
639	watchers, each time the event loop detects that the file descriptor given	1332	time the event loop detects that the file descriptor given is readable
640	is readable and/or writable).	1333	and/or writable).
641	.PP	1334	.PP
642	Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro	1335	Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR
643	with arguments specific to this watcher type. There is also a macro	1336	macro to configure it, with arguments specific to the watcher type. There
644	to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init	1337	is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR.
645	(watcher *, callback, ...)\*(C'\fR.
646	.PP	1338	.PP
647	To make the watcher actually watch out for events, you have to start it	1339	To make the watcher actually watch out for events, you have to start it
648	with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher	1340	with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher
649	*)\*(C'\fR), and you can stop watching for events at any time by calling the	1341	*)\*(C'\fR), and you can stop watching for events at any time by calling the
650	corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.	1342	corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR.
651	.PP	1343	.PP
652	As long as your watcher is active (has been started but not stopped) you	1344	As long as your watcher is active (has been started but not stopped) you
653	must not touch the values stored in it. Most specifically you must never	1345	must not touch the values stored in it. Most specifically you must never
654	reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.	1346	reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
655	.PP	1347	.PP
656	Each and every callback receives the event loop pointer as first, the	1348	Each and every callback receives the event loop pointer as first, the
657	registered watcher structure as second, and a bitset of received events as	1349	registered watcher structure as second, and a bitset of received events as
658	third argument.	1350	third argument.
659	.PP	1351	.PP
…		…
668	.el .IP "\f(CWEV_WRITE\fR" 4	1360	.el .IP "\f(CWEV_WRITE\fR" 4
669	.IX Item "EV_WRITE"	1361	.IX Item "EV_WRITE"
670	.PD	1362	.PD
671	The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or	1363	The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or
672	writable.	1364	writable.
673	.ie n .IP """EV_TIMEOUT""" 4	1365	.ie n .IP """EV_TIMER""" 4
674	.el .IP "\f(CWEV_TIMEOUT\fR" 4	1366	.el .IP "\f(CWEV_TIMER\fR" 4
675	.IX Item "EV_TIMEOUT"	1367	.IX Item "EV_TIMER"
676	The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out.	1368	The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out.
677	.ie n .IP """EV_PERIODIC""" 4	1369	.ie n .IP """EV_PERIODIC""" 4
678	.el .IP "\f(CWEV_PERIODIC\fR" 4	1370	.el .IP "\f(CWEV_PERIODIC\fR" 4
679	.IX Item "EV_PERIODIC"	1371	.IX Item "EV_PERIODIC"
680	The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out.	1372	The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out.
…		…
684	The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.	1376	The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
685	.ie n .IP """EV_CHILD""" 4	1377	.ie n .IP """EV_CHILD""" 4
686	.el .IP "\f(CWEV_CHILD\fR" 4	1378	.el .IP "\f(CWEV_CHILD\fR" 4
687	.IX Item "EV_CHILD"	1379	.IX Item "EV_CHILD"
688	The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.	1380	The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
		1381	.ie n .IP """EV_STAT""" 4
		1382	.el .IP "\f(CWEV_STAT\fR" 4
		1383	.IX Item "EV_STAT"
		1384	The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
689	.ie n .IP """EV_IDLE""" 4	1385	.ie n .IP """EV_IDLE""" 4
690	.el .IP "\f(CWEV_IDLE\fR" 4	1386	.el .IP "\f(CWEV_IDLE\fR" 4
691	.IX Item "EV_IDLE"	1387	.IX Item "EV_IDLE"
692	The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.	1388	The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
693	.ie n .IP """EV_PREPARE""" 4	1389	.ie n .IP """EV_PREPARE""" 4
…		…
696	.PD 0	1392	.PD 0
697	.ie n .IP """EV_CHECK""" 4	1393	.ie n .IP """EV_CHECK""" 4
698	.el .IP "\f(CWEV_CHECK\fR" 4	1394	.el .IP "\f(CWEV_CHECK\fR" 4
699	.IX Item "EV_CHECK"	1395	.IX Item "EV_CHECK"
700	.PD	1396	.PD
701	All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts	1397	All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_run\*(C'\fR starts to
702	to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after	1398	gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are queued (not invoked)
703	\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any	1399	just after \f(CW\*(C`ev_run\*(C'\fR has gathered them, but before it queues any callbacks
		1400	for any received events. That means \f(CW\*(C`ev_prepare\*(C'\fR watchers are the last
		1401	watchers invoked before the event loop sleeps or polls for new events, and
		1402	\&\f(CW\*(C`ev_check\*(C'\fR watchers will be invoked before any other watchers of the same
		1403	or lower priority within an event loop iteration.
		1404	.Sp
704	received events. Callbacks of both watcher types can start and stop as	1405	Callbacks of both watcher types can start and stop as many watchers as
705	many watchers as they want, and all of them will be taken into account	1406	they want, and all of them will be taken into account (for example, a
706	(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep	1407	\&\f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep \f(CW\*(C`ev_run\*(C'\fR from
707	\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).	1408	blocking).
		1409	.ie n .IP """EV_EMBED""" 4
		1410	.el .IP "\f(CWEV_EMBED\fR" 4
		1411	.IX Item "EV_EMBED"
		1412	The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
		1413	.ie n .IP """EV_FORK""" 4
		1414	.el .IP "\f(CWEV_FORK\fR" 4
		1415	.IX Item "EV_FORK"
		1416	The event loop has been resumed in the child process after fork (see
		1417	\&\f(CW\*(C`ev_fork\*(C'\fR).
		1418	.ie n .IP """EV_CLEANUP""" 4
		1419	.el .IP "\f(CWEV_CLEANUP\fR" 4
		1420	.IX Item "EV_CLEANUP"
		1421	The event loop is about to be destroyed (see \f(CW\*(C`ev_cleanup\*(C'\fR).
		1422	.ie n .IP """EV_ASYNC""" 4
		1423	.el .IP "\f(CWEV_ASYNC\fR" 4
		1424	.IX Item "EV_ASYNC"
		1425	The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR).
		1426	.ie n .IP """EV_CUSTOM""" 4
		1427	.el .IP "\f(CWEV_CUSTOM\fR" 4
		1428	.IX Item "EV_CUSTOM"
		1429	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1430	by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR).
708	.ie n .IP """EV_ERROR""" 4	1431	.ie n .IP """EV_ERROR""" 4
709	.el .IP "\f(CWEV_ERROR\fR" 4	1432	.el .IP "\f(CWEV_ERROR\fR" 4
710	.IX Item "EV_ERROR"	1433	.IX Item "EV_ERROR"
711	An unspecified error has occured, the watcher has been stopped. This might	1434	An unspecified error has occurred, the watcher has been stopped. This might
712	happen because the watcher could not be properly started because libev	1435	happen because the watcher could not be properly started because libev
713	ran out of memory, a file descriptor was found to be closed or any other	1436	ran out of memory, a file descriptor was found to be closed or any other
		1437	problem. Libev considers these application bugs.
		1438	.Sp
714	problem. You best act on it by reporting the problem and somehow coping	1439	You best act on it by reporting the problem and somehow coping with the
715	with the watcher being stopped.	1440	watcher being stopped. Note that well-written programs should not receive
		1441	an error ever, so when your watcher receives it, this usually indicates a
		1442	bug in your program.
716	.Sp	1443	.Sp
717	Libev will usually signal a few \*(L"dummy\*(R" events together with an error,	1444	Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for
718	for example it might indicate that a fd is readable or writable, and if	1445	example it might indicate that a fd is readable or writable, and if your
719	your callbacks is well-written it can just attempt the operation and cope	1446	callbacks is well-written it can just attempt the operation and cope with
720	with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded	1447	the error from \fBread()\fR or \fBwrite()\fR. This will not work in multi-threaded
721	programs, though, so beware.	1448	programs, though, as the fd could already be closed and reused for another
722	.Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"	1449	thing, so beware.
		1450	.SS "\s-1GENERIC WATCHER FUNCTIONS\s0"
723	.IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS"	1451	.IX Subsection "GENERIC WATCHER FUNCTIONS"
724	In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
725	e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
726	.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4	1452	.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
727	.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4	1453	.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
728	.IX Item "ev_init (ev_TYPE *watcher, callback)"	1454	.IX Item "ev_init (ev_TYPE *watcher, callback)"
729	This macro initialises the generic portion of a watcher. The contents	1455	This macro initialises the generic portion of a watcher. The contents
730	of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only	1456	of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
…		…
734	which rolls both calls into one.	1460	which rolls both calls into one.
735	.Sp	1461	.Sp
736	You can reinitialise a watcher at any time as long as it has been stopped	1462	You can reinitialise a watcher at any time as long as it has been stopped
737	(or never started) and there are no pending events outstanding.	1463	(or never started) and there are no pending events outstanding.
738	.Sp	1464	.Sp
739	The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,	1465	The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher,
740	int revents)\*(C'\fR.	1466	int revents)\*(C'\fR.
		1467	.Sp
		1468	Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps.
		1469	.Sp
		1470	.Vb 3
		1471	\& ev_io w;
		1472	\& ev_init (&w, my_cb);
		1473	\& ev_io_set (&w, STDIN_FILENO, EV_READ);
		1474	.Ve
741	.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4	1475	.ie n .IP """ev_TYPE_set"" (ev_TYPE *watcher, [args])" 4
742	.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4	1476	.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *watcher, [args])" 4
743	.IX Item "ev_TYPE_set (ev_TYPE *, [args])"	1477	.IX Item "ev_TYPE_set (ev_TYPE *watcher, [args])"
744	This macro initialises the type-specific parts of a watcher. You need to	1478	This macro initialises the type-specific parts of a watcher. You need to
745	call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can	1479	call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
746	call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this	1480	call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
747	macro on a watcher that is active (it can be pending, however, which is a	1481	macro on a watcher that is active (it can be pending, however, which is a
748	difference to the \f(CW\*(C`ev_init\*(C'\fR macro).	1482	difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
749	.Sp	1483	.Sp
750	Although some watcher types do not have type-specific arguments	1484	Although some watcher types do not have type-specific arguments
751	(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.	1485	(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
		1486	.Sp
		1487	See \f(CW\*(C`ev_init\*(C'\fR, above, for an example.
752	.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4	1488	.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
753	.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4	1489	.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
754	.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"	1490	.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
755	This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro	1491	This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
756	calls into a single call. This is the most convinient method to initialise	1492	calls into a single call. This is the most convenient method to initialise
757	a watcher. The same limitations apply, of course.	1493	a watcher. The same limitations apply, of course.
		1494	.Sp
		1495	Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step.
		1496	.Sp
		1497	.Vb 1
		1498	\& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1499	.Ve
758	.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4	1500	.ie n .IP """ev_TYPE_start"" (loop, ev_TYPE *watcher)" 4
759	.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4	1501	.el .IP "\f(CWev_TYPE_start\fR (loop, ev_TYPE *watcher)" 4
760	.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"	1502	.IX Item "ev_TYPE_start (loop, ev_TYPE *watcher)"
761	Starts (activates) the given watcher. Only active watchers will receive	1503	Starts (activates) the given watcher. Only active watchers will receive
762	events. If the watcher is already active nothing will happen.	1504	events. If the watcher is already active nothing will happen.
		1505	.Sp
		1506	Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this
		1507	whole section.
		1508	.Sp
		1509	.Vb 1
		1510	\& ev_io_start (EV_DEFAULT_UC, &w);
		1511	.Ve
763	.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4	1512	.ie n .IP """ev_TYPE_stop"" (loop, ev_TYPE *watcher)" 4
764	.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4	1513	.el .IP "\f(CWev_TYPE_stop\fR (loop, ev_TYPE *watcher)" 4
765	.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"	1514	.IX Item "ev_TYPE_stop (loop, ev_TYPE *watcher)"
766	Stops the given watcher again (if active) and clears the pending	1515	Stops the given watcher if active, and clears the pending status (whether
		1516	the watcher was active or not).
		1517	.Sp
767	status. It is possible that stopped watchers are pending (for example,	1518	It is possible that stopped watchers are pending \- for example,
768	non-repeating timers are being stopped when they become pending), but	1519	non-repeating timers are being stopped when they become pending \- but
769	\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If	1520	calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor
770	you want to free or reuse the memory used by the watcher it is therefore a	1521	pending. If you want to free or reuse the memory used by the watcher it is
771	good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.	1522	therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
772	.IP "bool ev_is_active (ev_TYPE *watcher)" 4	1523	.IP "bool ev_is_active (ev_TYPE *watcher)" 4
773	.IX Item "bool ev_is_active (ev_TYPE *watcher)"	1524	.IX Item "bool ev_is_active (ev_TYPE *watcher)"
774	Returns a true value iff the watcher is active (i.e. it has been started	1525	Returns a true value iff the watcher is active (i.e. it has been started
775	and not yet been stopped). As long as a watcher is active you must not modify	1526	and not yet been stopped). As long as a watcher is active you must not modify
776	it.	1527	it.
777	.IP "bool ev_is_pending (ev_TYPE *watcher)" 4	1528	.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
778	.IX Item "bool ev_is_pending (ev_TYPE *watcher)"	1529	.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
779	Returns a true value iff the watcher is pending, (i.e. it has outstanding	1530	Returns a true value iff the watcher is pending, (i.e. it has outstanding
780	events but its callback has not yet been invoked). As long as a watcher	1531	events but its callback has not yet been invoked). As long as a watcher
781	is pending (but not active) you must not call an init function on it (but	1532	is pending (but not active) you must not call an init function on it (but
782	\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to	1533	\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
783	libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).	1534	make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
		1535	it).
784	.IP "callback = ev_cb (ev_TYPE *watcher)" 4	1536	.IP "callback ev_cb (ev_TYPE *watcher)" 4
785	.IX Item "callback = ev_cb (ev_TYPE *watcher)"	1537	.IX Item "callback ev_cb (ev_TYPE *watcher)"
786	Returns the callback currently set on the watcher.	1538	Returns the callback currently set on the watcher.
787	.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4	1539	.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4
788	.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"	1540	.IX Item "ev_set_cb (ev_TYPE *watcher, callback)"
789	Change the callback. You can change the callback at virtually any time	1541	Change the callback. You can change the callback at virtually any time
790	(modulo threads).	1542	(modulo threads).
791	.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"	1543	.IP "ev_set_priority (ev_TYPE *watcher, int priority)" 4
792	.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"	1544	.IX Item "ev_set_priority (ev_TYPE *watcher, int priority)"
793	Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change	1545	.PD 0
794	and read at any time, libev will completely ignore it. This can be used	1546	.IP "int ev_priority (ev_TYPE *watcher)" 4
795	to associate arbitrary data with your watcher. If you need more data and	1547	.IX Item "int ev_priority (ev_TYPE *watcher)"
796	don't want to allocate memory and store a pointer to it in that data	1548	.PD
797	member, you can also \*(L"subclass\*(R" the watcher type and provide your own	1549	Set and query the priority of the watcher. The priority is a small
798	data:	1550	integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
		1551	(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
		1552	before watchers with lower priority, but priority will not keep watchers
		1553	from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
		1554	.Sp
		1555	If you need to suppress invocation when higher priority events are pending
		1556	you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
		1557	.Sp
		1558	You \fImust not\fR change the priority of a watcher as long as it is active or
		1559	pending.
		1560	.Sp
		1561	Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
		1562	fine, as long as you do not mind that the priority value you query might
		1563	or might not have been clamped to the valid range.
		1564	.Sp
		1565	The default priority used by watchers when no priority has been set is
		1566	always \f(CW0\fR, which is supposed to not be too high and not be too low :).
		1567	.Sp
		1568	See \*(L"\s-1WATCHER PRIORITY MODELS\*(R"\s0, below, for a more thorough treatment of
		1569	priorities.
		1570	.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
		1571	.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
		1572	Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
		1573	\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
		1574	can deal with that fact, as both are simply passed through to the
		1575	callback.
		1576	.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
		1577	.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
		1578	If the watcher is pending, this function clears its pending status and
		1579	returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
		1580	watcher isn't pending it does nothing and returns \f(CW0\fR.
		1581	.Sp
		1582	Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its
		1583	callback to be invoked, which can be accomplished with this function.
		1584	.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4
		1585	.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)"
		1586	Feeds the given event set into the event loop, as if the specified event
		1587	had happened for the specified watcher (which must be a pointer to an
		1588	initialised but not necessarily started event watcher). Obviously you must
		1589	not free the watcher as long as it has pending events.
		1590	.Sp
		1591	Stopping the watcher, letting libev invoke it, or calling
		1592	\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was
		1593	not started in the first place.
		1594	.Sp
		1595	See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related
		1596	functions that do not need a watcher.
799	.PP	1597	.PP
		1598	See also the \*(L"\s-1ASSOCIATING CUSTOM DATA WITH A WATCHER\*(R"\s0 and \*(L"\s-1BUILDING YOUR
		1599	OWN COMPOSITE WATCHERS\*(R"\s0 idioms.
		1600	.SS "\s-1WATCHER STATES\s0"
		1601	.IX Subsection "WATCHER STATES"
		1602	There are various watcher states mentioned throughout this manual \-
		1603	active, pending and so on. In this section these states and the rules to
		1604	transition between them will be described in more detail \- and while these
		1605	rules might look complicated, they usually do \*(L"the right thing\*(R".
		1606	.IP "initialised" 4
		1607	.IX Item "initialised"
		1608	Before a watcher can be registered with the event loop it has to be
		1609	initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to
		1610	\&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function.
		1611	.Sp
		1612	In this state it is simply some block of memory that is suitable for
		1613	use in an event loop. It can be moved around, freed, reused etc. at
		1614	will \- as long as you either keep the memory contents intact, or call
		1615	\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again.
		1616	.IP "started/running/active" 4
		1617	.IX Item "started/running/active"
		1618	Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes
		1619	property of the event loop, and is actively waiting for events. While in
		1620	this state it cannot be accessed (except in a few documented ways), moved,
		1621	freed or anything else \- the only legal thing is to keep a pointer to it,
		1622	and call libev functions on it that are documented to work on active watchers.
		1623	.IP "pending" 4
		1624	.IX Item "pending"
		1625	If a watcher is active and libev determines that an event it is interested
		1626	in has occurred (such as a timer expiring), it will become pending. It will
		1627	stay in this pending state until either it is stopped or its callback is
		1628	about to be invoked, so it is not normally pending inside the watcher
		1629	callback.
		1630	.Sp
		1631	The watcher might or might not be active while it is pending (for example,
		1632	an expired non-repeating timer can be pending but no longer active). If it
		1633	is stopped, it can be freely accessed (e.g. by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR),
		1634	but it is still property of the event loop at this time, so cannot be
		1635	moved, freed or reused. And if it is active the rules described in the
		1636	previous item still apply.
		1637	.Sp
		1638	It is also possible to feed an event on a watcher that is not active (e.g.
		1639	via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being
		1640	active.
		1641	.IP "stopped" 4
		1642	.IX Item "stopped"
		1643	A watcher can be stopped implicitly by libev (in which case it might still
		1644	be pending), or explicitly by calling its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. The
		1645	latter will clear any pending state the watcher might be in, regardless
		1646	of whether it was active or not, so stopping a watcher explicitly before
		1647	freeing it is often a good idea.
		1648	.Sp
		1649	While stopped (and not pending) the watcher is essentially in the
		1650	initialised state, that is, it can be reused, moved, modified in any way
		1651	you wish (but when you trash the memory block, you need to \f(CW\*(C`ev_TYPE_init\*(C'\fR
		1652	it again).
		1653	.SS "\s-1WATCHER PRIORITY MODELS\s0"
		1654	.IX Subsection "WATCHER PRIORITY MODELS"
		1655	Many event loops support \fIwatcher priorities\fR, which are usually small
		1656	integers that influence the ordering of event callback invocation
		1657	between watchers in some way, all else being equal.
		1658	.PP
		1659	In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
		1660	description for the more technical details such as the actual priority
		1661	range.
		1662	.PP
		1663	There are two common ways how these these priorities are being interpreted
		1664	by event loops:
		1665	.PP
		1666	In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation
		1667	of lower priority watchers, which means as long as higher priority
		1668	watchers receive events, lower priority watchers are not being invoked.
		1669	.PP
		1670	The less common only-for-ordering model uses priorities solely to order
		1671	callback invocation within a single event loop iteration: Higher priority
		1672	watchers are invoked before lower priority ones, but they all get invoked
		1673	before polling for new events.
		1674	.PP
		1675	Libev uses the second (only-for-ordering) model for all its watchers
		1676	except for idle watchers (which use the lock-out model).
		1677	.PP
		1678	The rationale behind this is that implementing the lock-out model for
		1679	watchers is not well supported by most kernel interfaces, and most event
		1680	libraries will just poll for the same events again and again as long as
		1681	their callbacks have not been executed, which is very inefficient in the
		1682	common case of one high-priority watcher locking out a mass of lower
		1683	priority ones.
		1684	.PP
		1685	Static (ordering) priorities are most useful when you have two or more
		1686	watchers handling the same resource: a typical usage example is having an
		1687	\&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle
		1688	timeouts. Under load, data might be received while the program handles
		1689	other jobs, but since timers normally get invoked first, the timeout
		1690	handler will be executed before checking for data. In that case, giving
		1691	the timer a lower priority than the I/O watcher ensures that I/O will be
		1692	handled first even under adverse conditions (which is usually, but not
		1693	always, what you want).
		1694	.PP
		1695	Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers
		1696	will only be executed when no same or higher priority watchers have
		1697	received events, they can be used to implement the \*(L"lock-out\*(R" model when
		1698	required.
		1699	.PP
		1700	For example, to emulate how many other event libraries handle priorities,
		1701	you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in
		1702	the normal watcher callback, you just start the idle watcher. The real
		1703	processing is done in the idle watcher callback. This causes libev to
		1704	continuously poll and process kernel event data for the watcher, but when
		1705	the lock-out case is known to be rare (which in turn is rare :), this is
		1706	workable.
		1707	.PP
		1708	Usually, however, the lock-out model implemented that way will perform
		1709	miserably under the type of load it was designed to handle. In that case,
		1710	it might be preferable to stop the real watcher before starting the
		1711	idle watcher, so the kernel will not have to process the event in case
		1712	the actual processing will be delayed for considerable time.
		1713	.PP
		1714	Here is an example of an I/O watcher that should run at a strictly lower
		1715	priority than the default, and which should only process data when no
		1716	other events are pending:
		1717	.PP
800	.Vb 7	1718	.Vb 2
801	\& struct my_io	1719	\& ev_idle idle; // actual processing watcher
		1720	\& ev_io io; // actual event watcher
		1721	\&
		1722	\& static void
		1723	\& io_cb (EV_P_ ev_io *w, int revents)
802	\& {	1724	\& {
803	\& struct ev_io io;	1725	\& // stop the I/O watcher, we received the event, but
804	\& int otherfd;	1726	\& // are not yet ready to handle it.
805	\& void *somedata;	1727	\& ev_io_stop (EV_A_ w);
806	\& struct whatever *mostinteresting;	1728	\&
		1729	\& // start the idle watcher to handle the actual event.
		1730	\& // it will not be executed as long as other watchers
		1731	\& // with the default priority are receiving events.
		1732	\& ev_idle_start (EV_A_ &idle);
807	\& }	1733	\& }
808	.Ve	1734	\&
809	.PP	1735	\& static void
810	And since your callback will be called with a pointer to the watcher, you	1736	\& idle_cb (EV_P_ ev_idle *w, int revents)
811	can cast it back to your own type:
812	.PP
813	.Vb 5
814	\& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
815	\& {	1737	\& {
816	\& struct my_io *w = (struct my_io *)w_;	1738	\& // actual processing
817	\& ...	1739	\& read (STDIN_FILENO, ...);
		1740	\&
		1741	\& // have to start the I/O watcher again, as
		1742	\& // we have handled the event
		1743	\& ev_io_start (EV_P_ &io);
818	\& }	1744	\& }
		1745	\&
		1746	\& // initialisation
		1747	\& ev_idle_init (&idle, idle_cb);
		1748	\& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1749	\& ev_io_start (EV_DEFAULT_ &io);
819	.Ve	1750	.Ve
820	.PP	1751	.PP
821	More interesting and less C\-conformant ways of catsing your callback type	1752	In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that
822	have been omitted....	1753	low-priority connections can not be locked out forever under load. This
		1754	enables your program to keep a lower latency for important connections
		1755	during short periods of high load, while not completely locking out less
		1756	important ones.
823	.SH "WATCHER TYPES"	1757	.SH "WATCHER TYPES"
824	.IX Header "WATCHER TYPES"	1758	.IX Header "WATCHER TYPES"
825	This section describes each watcher in detail, but will not repeat	1759	This section describes each watcher in detail, but will not repeat
826	information given in the last section.	1760	information given in the last section. Any initialisation/set macros,
		1761	functions and members specific to the watcher type are explained.
		1762	.PP
		1763	Members are additionally marked with either \fI[read\-only]\fR, meaning that,
		1764	while the watcher is active, you can look at the member and expect some
		1765	sensible content, but you must not modify it (you can modify it while the
		1766	watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
		1767	means you can expect it to have some sensible content while the watcher
		1768	is active, but you can also modify it. Modifying it may not do something
		1769	sensible or take immediate effect (or do anything at all), but libev will
		1770	not crash or malfunction in any way.
827	.ie n .Sh """ev_io"" \- is this file descriptor readable or writable"	1771	.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
828	.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable"	1772	.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
829	.IX Subsection "ev_io - is this file descriptor readable or writable"	1773	.IX Subsection "ev_io - is this file descriptor readable or writable?"
830	I/O watchers check whether a file descriptor is readable or writable	1774	I/O watchers check whether a file descriptor is readable or writable
831	in each iteration of the event loop (This behaviour is called	1775	in each iteration of the event loop, or, more precisely, when reading
832	level-triggering because you keep receiving events as long as the	1776	would not block the process and writing would at least be able to write
833	condition persists. Remember you can stop the watcher if you don't want to	1777	some data. This behaviour is called level-triggering because you keep
834	act on the event and neither want to receive future events).	1778	receiving events as long as the condition persists. Remember you can stop
		1779	the watcher if you don't want to act on the event and neither want to
		1780	receive future events.
835	.PP	1781	.PP
836	In general you can register as many read and/or write event watchers per	1782	In general you can register as many read and/or write event watchers per
837	fd as you want (as long as you don't confuse yourself). Setting all file	1783	fd as you want (as long as you don't confuse yourself). Setting all file
838	descriptors to non-blocking mode is also usually a good idea (but not	1784	descriptors to non-blocking mode is also usually a good idea (but not
839	required if you know what you are doing).	1785	required if you know what you are doing).
840	.PP	1786	.PP
841	You have to be careful with dup'ed file descriptors, though. Some backends	1787	Another thing you have to watch out for is that it is quite easy to
842	(the linux epoll backend is a notable example) cannot handle dup'ed file	1788	receive \*(L"spurious\*(R" readiness notifications, that is, your callback might
843	descriptors correctly if you register interest in two or more fds pointing	1789	be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
844	to the same underlying file/socket etc. description (that is, they share	1790	because there is no data. It is very easy to get into this situation even
845	the same underlying \*(L"file open\*(R").	1791	with a relatively standard program structure. Thus it is best to always
		1792	use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning \f(CW\*(C`EAGAIN\*(C'\fR is far
		1793	preferable to a program hanging until some data arrives.
846	.PP	1794	.PP
847	If you must do this, then force the use of a known-to-be-good backend	1795	If you cannot run the fd in non-blocking mode (for example you should
848	(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and	1796	not play around with an Xlib connection), then you have to separately
849	\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).	1797	re-test whether a file descriptor is really ready with a known-to-be good
		1798	interface such as poll (fortunately in the case of Xlib, it already does
		1799	this on its own, so its quite safe to use). Some people additionally
		1800	use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block
		1801	indefinitely.
		1802	.PP
		1803	But really, best use non-blocking mode.
		1804	.PP
		1805	\fIThe special problem of disappearing file descriptors\fR
		1806	.IX Subsection "The special problem of disappearing file descriptors"
		1807	.PP
		1808	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
		1809	a file descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other
		1810	means, such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some
		1811	file descriptor, but when it goes away, the operating system will silently
		1812	drop this interest. If another file descriptor with the same number then
		1813	is registered with libev, there is no efficient way to see that this is,
		1814	in fact, a different file descriptor.
		1815	.PP
		1816	To avoid having to explicitly tell libev about such cases, libev follows
		1817	the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
		1818	will assume that this is potentially a new file descriptor, otherwise
		1819	it is assumed that the file descriptor stays the same. That means that
		1820	you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the
		1821	descriptor even if the file descriptor number itself did not change.
		1822	.PP
		1823	This is how one would do it normally anyway, the important point is that
		1824	the libev application should not optimise around libev but should leave
		1825	optimisations to libev.
		1826	.PP
		1827	\fIThe special problem of dup'ed file descriptors\fR
		1828	.IX Subsection "The special problem of dup'ed file descriptors"
		1829	.PP
		1830	Some backends (e.g. epoll), cannot register events for file descriptors,
		1831	but only events for the underlying file descriptions. That means when you
		1832	have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register
		1833	events for them, only one file descriptor might actually receive events.
		1834	.PP
		1835	There is no workaround possible except not registering events
		1836	for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to
		1837	\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
		1838	.PP
		1839	\fIThe special problem of files\fR
		1840	.IX Subsection "The special problem of files"
		1841	.PP
		1842	Many people try to use \f(CW\*(C`select\*(C'\fR (or libev) on file descriptors
		1843	representing files, and expect it to become ready when their program
		1844	doesn't block on disk accesses (which can take a long time on their own).
		1845	.PP
		1846	However, this cannot ever work in the \*(L"expected\*(R" way \- you get a readiness
		1847	notification as soon as the kernel knows whether and how much data is
		1848	there, and in the case of open files, that's always the case, so you
		1849	always get a readiness notification instantly, and your read (or possibly
		1850	write) will still block on the disk I/O.
		1851	.PP
		1852	Another way to view it is that in the case of sockets, pipes, character
		1853	devices and so on, there is another party (the sender) that delivers data
		1854	on its own, but in the case of files, there is no such thing: the disk
		1855	will not send data on its own, simply because it doesn't know what you
		1856	wish to read \- you would first have to request some data.
		1857	.PP
		1858	Since files are typically not-so-well supported by advanced notification
		1859	mechanism, libev tries hard to emulate \s-1POSIX\s0 behaviour with respect
		1860	to files, even though you should not use it. The reason for this is
		1861	convenience: sometimes you want to watch \s-1STDIN\s0 or \s-1STDOUT,\s0 which is
		1862	usually a tty, often a pipe, but also sometimes files or special devices
		1863	(for example, \f(CW\*(C`epoll\*(C'\fR on Linux works with \fI/dev/random\fR but not with
		1864	\&\fI/dev/urandom\fR), and even though the file might better be served with
		1865	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1866	it \*(L"just works\*(R" instead of freezing.
		1867	.PP
		1868	So avoid file descriptors pointing to files when you know it (e.g. use
		1869	libeio), but use them when it is convenient, e.g. for \s-1STDIN/STDOUT,\s0 or
		1870	when you rarely read from a file instead of from a socket, and want to
		1871	reuse the same code path.
		1872	.PP
		1873	\fIThe special problem of fork\fR
		1874	.IX Subsection "The special problem of fork"
		1875	.PP
		1876	Some backends (epoll, kqueue, probably linuxaio) do not support \f(CW\*(C`fork ()\*(C'\fR
		1877	at all or exhibit useless behaviour. Libev fully supports fork, but needs
		1878	to be told about it in the child if you want to continue to use it in the
		1879	child.
		1880	.PP
		1881	To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
		1882	()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to
		1883	\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
		1884	.PP
		1885	\fIThe special problem of \s-1SIGPIPE\s0\fR
		1886	.IX Subsection "The special problem of SIGPIPE"
		1887	.PP
		1888	While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR:
		1889	when writing to a pipe whose other end has been closed, your program gets
		1890	sent a \s-1SIGPIPE,\s0 which, by default, aborts your program. For most programs
		1891	this is sensible behaviour, for daemons, this is usually undesirable.
		1892	.PP
		1893	So when you encounter spurious, unexplained daemon exits, make sure you
		1894	ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon
		1895	somewhere, as that would have given you a big clue).
		1896	.PP
		1897	\fIThe special problem of \f(BIaccept()\fIing when you can't\fR
		1898	.IX Subsection "The special problem of accept()ing when you can't"
		1899	.PP
		1900	Many implementations of the \s-1POSIX\s0 \f(CW\*(C`accept\*(C'\fR function (for example,
		1901	found in post\-2004 Linux) have the peculiar behaviour of not removing a
		1902	connection from the pending queue in all error cases.
		1903	.PP
		1904	For example, larger servers often run out of file descriptors (because
		1905	of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not
		1906	rejecting the connection, leading to libev signalling readiness on
		1907	the next iteration again (the connection still exists after all), and
		1908	typically causing the program to loop at 100% \s-1CPU\s0 usage.
		1909	.PP
		1910	Unfortunately, the set of errors that cause this issue differs between
		1911	operating systems, there is usually little the app can do to remedy the
		1912	situation, and no known thread-safe method of removing the connection to
		1913	cope with overload is known (to me).
		1914	.PP
		1915	One of the easiest ways to handle this situation is to just ignore it
		1916	\&\- when the program encounters an overload, it will just loop until the
		1917	situation is over. While this is a form of busy waiting, no \s-1OS\s0 offers an
		1918	event-based way to handle this situation, so it's the best one can do.
		1919	.PP
		1920	A better way to handle the situation is to log any errors other than
		1921	\&\f(CW\*(C`EAGAIN\*(C'\fR and \f(CW\*(C`EWOULDBLOCK\*(C'\fR, making sure not to flood the log with such
		1922	messages, and continue as usual, which at least gives the user an idea of
		1923	what could be wrong (\*(L"raise the ulimit!\*(R"). For extra points one could stop
		1924	the \f(CW\*(C`ev_io\*(C'\fR watcher on the listening fd \*(L"for a while\*(R", which reduces \s-1CPU\s0
		1925	usage.
		1926	.PP
		1927	If your program is single-threaded, then you could also keep a dummy file
		1928	descriptor for overload situations (e.g. by opening \fI/dev/null\fR), and
		1929	when you run into \f(CW\*(C`ENFILE\*(C'\fR or \f(CW\*(C`EMFILE\*(C'\fR, close it, run \f(CW\*(C`accept\*(C'\fR,
		1930	close that fd, and create a new dummy fd. This will gracefully refuse
		1931	clients under typical overload conditions.
		1932	.PP
		1933	The last way to handle it is to simply log the error and \f(CW\*(C`exit\*(C'\fR, as
		1934	is often done with \f(CW\*(C`malloc\*(C'\fR failures, but this results in an easy
		1935	opportunity for a DoS attack.
		1936	.PP
		1937	\fIWatcher-Specific Functions\fR
		1938	.IX Subsection "Watcher-Specific Functions"
850	.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4	1939	.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
851	.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"	1940	.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
852	.PD 0	1941	.PD 0
853	.IP "ev_io_set (ev_io *, int fd, int events)" 4	1942	.IP "ev_io_set (ev_io *, int fd, int events)" 4
854	.IX Item "ev_io_set (ev_io *, int fd, int events)"	1943	.IX Item "ev_io_set (ev_io *, int fd, int events)"
855	.PD	1944	.PD
856	Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive	1945	Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
857	events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ |	1946	receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
858	EV_WRITE\*(C'\fR to receive the given events.	1947	\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events.
859	.Sp	1948	.IP "int fd [read\-only]" 4
860	Please note that most of the more scalable backend mechanisms (for example	1949	.IX Item "int fd [read-only]"
861	epoll and solaris ports) can result in spurious readyness notifications	1950	The file descriptor being watched.
862	for file descriptors, so you practically need to use non-blocking I/O (and	1951	.IP "int events [read\-only]" 4
863	treat callback invocation as hint only), or retest separately with a safe	1952	.IX Item "int events [read-only]"
864	interface before doing I/O (XLib can do this), or force the use of either	1953	The events being watched.
865	\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
866	problem. Also note that it is quite easy to have your callback invoked
867	when the readyness condition is no longer valid even when employing
868	typical ways of handling events, so its a good idea to use non-blocking
869	I/O unconditionally.
870	.PP	1954	.PP
		1955	\fIExamples\fR
		1956	.IX Subsection "Examples"
		1957	.PP
871	Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well	1958	Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
872	readable, but only once. Since it is likely line\-buffered, you could	1959	readable, but only once. Since it is likely line-buffered, you could
873	attempt to read a whole line in the callback:	1960	attempt to read a whole line in the callback.
874	.PP	1961	.PP
875	.Vb 6	1962	.Vb 6
876	\& static void	1963	\& static void
877	\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1964	\& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
878	\& {	1965	\& {
879	\& ev_io_stop (loop, w);	1966	\& ev_io_stop (loop, w);
880	\& .. read from stdin here (or from w->fd) and haqndle any I/O errors	1967	\& .. read from stdin here (or from w\->fd) and handle any I/O errors
881	\& }	1968	\& }
882	.Ve	1969	\&
883	.PP
884	.Vb 6
885	\& ...	1970	\& ...
886	\& struct ev_loop *loop = ev_default_init (0);	1971	\& struct ev_loop *loop = ev_default_init (0);
887	\& struct ev_io stdin_readable;	1972	\& ev_io stdin_readable;
888	\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1973	\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
889	\& ev_io_start (loop, &stdin_readable);	1974	\& ev_io_start (loop, &stdin_readable);
890	\& ev_loop (loop, 0);	1975	\& ev_run (loop, 0);
891	.Ve	1976	.Ve
892	.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts"	1977	.ie n .SS """ev_timer"" \- relative and optionally repeating timeouts"
893	.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts"	1978	.el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
894	.IX Subsection "ev_timer - relative and optionally recurring timeouts"	1979	.IX Subsection "ev_timer - relative and optionally repeating timeouts"
895	Timer watchers are simple relative timers that generate an event after a	1980	Timer watchers are simple relative timers that generate an event after a
896	given time, and optionally repeating in regular intervals after that.	1981	given time, and optionally repeating in regular intervals after that.
897	.PP	1982	.PP
898	The timers are based on real time, that is, if you register an event that	1983	The timers are based on real time, that is, if you register an event that
899	times out after an hour and you reset your system clock to last years	1984	times out after an hour and you reset your system clock to January last
900	time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because	1985	year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because
901	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1986	detecting time jumps is hard, and some inaccuracies are unavoidable (the
902	monotonic clock option helps a lot here).	1987	monotonic clock option helps a lot here).
		1988	.PP
		1989	The callback is guaranteed to be invoked only \fIafter\fR its timeout has
		1990	passed (not \fIat\fR, so on systems with very low-resolution clocks this
		1991	might introduce a small delay, see \*(L"the special problem of being too
		1992	early\*(R", below). If multiple timers become ready during the same loop
		1993	iteration then the ones with earlier time-out values are invoked before
		1994	ones of the same priority with later time-out values (but this is no
		1995	longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
		1996	.PP
		1997	\fIBe smart about timeouts\fR
		1998	.IX Subsection "Be smart about timeouts"
		1999	.PP
		2000	Many real-world problems involve some kind of timeout, usually for error
		2001	recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs,
		2002	you want to raise some error after a while.
		2003	.PP
		2004	What follows are some ways to handle this problem, from obvious and
		2005	inefficient to smart and efficient.
		2006	.PP
		2007	In the following, a 60 second activity timeout is assumed \- a timeout that
		2008	gets reset to 60 seconds each time there is activity (e.g. each time some
		2009	data or other life sign was received).
		2010	.IP "1. Use a timer and stop, reinitialise and start it on activity." 4
		2011	.IX Item "1. Use a timer and stop, reinitialise and start it on activity."
		2012	This is the most obvious, but not the most simple way: In the beginning,
		2013	start the watcher:
		2014	.Sp
		2015	.Vb 2
		2016	\& ev_timer_init (timer, callback, 60., 0.);
		2017	\& ev_timer_start (loop, timer);
		2018	.Ve
		2019	.Sp
		2020	Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it
		2021	and start it again:
		2022	.Sp
		2023	.Vb 3
		2024	\& ev_timer_stop (loop, timer);
		2025	\& ev_timer_set (timer, 60., 0.);
		2026	\& ev_timer_start (loop, timer);
		2027	.Ve
		2028	.Sp
		2029	This is relatively simple to implement, but means that each time there is
		2030	some activity, libev will first have to remove the timer from its internal
		2031	data structure and then add it again. Libev tries to be fast, but it's
		2032	still not a constant-time operation.
		2033	.ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4
		2034	.el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4
		2035	.IX Item "2. Use a timer and re-start it with ev_timer_again inactivity."
		2036	This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of
		2037	\&\f(CW\*(C`ev_timer_start\*(C'\fR.
		2038	.Sp
		2039	To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value
		2040	of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you
		2041	successfully read or write some data. If you go into an idle state where
		2042	you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR
		2043	the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be.
		2044	.Sp
		2045	That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the
		2046	\&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR
		2047	member and \f(CW\*(C`ev_timer_again\*(C'\fR.
		2048	.Sp
		2049	At start:
		2050	.Sp
		2051	.Vb 3
		2052	\& ev_init (timer, callback);
		2053	\& timer\->repeat = 60.;
		2054	\& ev_timer_again (loop, timer);
		2055	.Ve
		2056	.Sp
		2057	Each time there is some activity:
		2058	.Sp
		2059	.Vb 1
		2060	\& ev_timer_again (loop, timer);
		2061	.Ve
		2062	.Sp
		2063	It is even possible to change the time-out on the fly, regardless of
		2064	whether the watcher is active or not:
		2065	.Sp
		2066	.Vb 2
		2067	\& timer\->repeat = 30.;
		2068	\& ev_timer_again (loop, timer);
		2069	.Ve
		2070	.Sp
		2071	This is slightly more efficient then stopping/starting the timer each time
		2072	you want to modify its timeout value, as libev does not have to completely
		2073	remove and re-insert the timer from/into its internal data structure.
		2074	.Sp
		2075	It is, however, even simpler than the \*(L"obvious\*(R" way to do it.
		2076	.IP "3. Let the timer time out, but then re-arm it as required." 4
		2077	.IX Item "3. Let the timer time out, but then re-arm it as required."
		2078	This method is more tricky, but usually most efficient: Most timeouts are
		2079	relatively long compared to the intervals between other activity \- in
		2080	our example, within 60 seconds, there are usually many I/O events with
		2081	associated activity resets.
		2082	.Sp
		2083	In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone,
		2084	but remember the time of last activity, and check for a real timeout only
		2085	within the callback:
		2086	.Sp
		2087	.Vb 3
		2088	\& ev_tstamp timeout = 60.;
		2089	\& ev_tstamp last_activity; // time of last activity
		2090	\& ev_timer timer;
		2091	\&
		2092	\& static void
		2093	\& callback (EV_P_ ev_timer *w, int revents)
		2094	\& {
		2095	\& // calculate when the timeout would happen
		2096	\& ev_tstamp after = last_activity \- ev_now (EV_A) + timeout;
		2097	\&
		2098	\& // if negative, it means we the timeout already occurred
		2099	\& if (after < 0.)
		2100	\& {
		2101	\& // timeout occurred, take action
		2102	\& }
		2103	\& else
		2104	\& {
		2105	\& // callback was invoked, but there was some recent
		2106	\& // activity. simply restart the timer to time out
		2107	\& // after "after" seconds, which is the earliest time
		2108	\& // the timeout can occur.
		2109	\& ev_timer_set (w, after, 0.);
		2110	\& ev_timer_start (EV_A_ w);
		2111	\& }
		2112	\& }
		2113	.Ve
		2114	.Sp
		2115	To summarise the callback: first calculate in how many seconds the
		2116	timeout will occur (by calculating the absolute time when it would occur,
		2117	\&\f(CW\*(C`last_activity + timeout\*(C'\fR, and subtracting the current time, \f(CW\*(C`ev_now
		2118	(EV_A)\*(C'\fR from that).
		2119	.Sp
		2120	If this value is negative, then we are already past the timeout, i.e. we
		2121	timed out, and need to do whatever is needed in this case.
		2122	.Sp
		2123	Otherwise, we now the earliest time at which the timeout would trigger,
		2124	and simply start the timer with this timeout value.
		2125	.Sp
		2126	In other words, each time the callback is invoked it will check whether
		2127	the timeout occurred. If not, it will simply reschedule itself to check
		2128	again at the earliest time it could time out. Rinse. Repeat.
		2129	.Sp
		2130	This scheme causes more callback invocations (about one every 60 seconds
		2131	minus half the average time between activity), but virtually no calls to
		2132	libev to change the timeout.
		2133	.Sp
		2134	To start the machinery, simply initialise the watcher and set
		2135	\&\f(CW\*(C`last_activity\*(C'\fR to the current time (meaning there was some activity just
		2136	now), then call the callback, which will \*(L"do the right thing\*(R" and start
		2137	the timer:
		2138	.Sp
		2139	.Vb 3
		2140	\& last_activity = ev_now (EV_A);
		2141	\& ev_init (&timer, callback);
		2142	\& callback (EV_A_ &timer, 0);
		2143	.Ve
		2144	.Sp
		2145	When there is some activity, simply store the current time in
		2146	\&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all:
		2147	.Sp
		2148	.Vb 2
		2149	\& if (activity detected)
		2150	\& last_activity = ev_now (EV_A);
		2151	.Ve
		2152	.Sp
		2153	When your timeout value changes, then the timeout can be changed by simply
		2154	providing a new value, stopping the timer and calling the callback, which
		2155	will again do the right thing (for example, time out immediately :).
		2156	.Sp
		2157	.Vb 3
		2158	\& timeout = new_value;
		2159	\& ev_timer_stop (EV_A_ &timer);
		2160	\& callback (EV_A_ &timer, 0);
		2161	.Ve
		2162	.Sp
		2163	This technique is slightly more complex, but in most cases where the
		2164	time-out is unlikely to be triggered, much more efficient.
		2165	.IP "4. Wee, just use a double-linked list for your timeouts." 4
		2166	.IX Item "4. Wee, just use a double-linked list for your timeouts."
		2167	If there is not one request, but many thousands (millions...), all
		2168	employing some kind of timeout with the same timeout value, then one can
		2169	do even better:
		2170	.Sp
		2171	When starting the timeout, calculate the timeout value and put the timeout
		2172	at the \fIend\fR of the list.
		2173	.Sp
		2174	Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of
		2175	the list is expected to fire (for example, using the technique #3).
		2176	.Sp
		2177	When there is some activity, remove the timer from the list, recalculate
		2178	the timeout, append it to the end of the list again, and make sure to
		2179	update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list.
		2180	.Sp
		2181	This way, one can manage an unlimited number of timeouts in O(1) time for
		2182	starting, stopping and updating the timers, at the expense of a major
		2183	complication, and having to use a constant timeout. The constant timeout
		2184	ensures that the list stays sorted.
		2185	.PP
		2186	So which method the best?
		2187	.PP
		2188	Method #2 is a simple no-brain-required solution that is adequate in most
		2189	situations. Method #3 requires a bit more thinking, but handles many cases
		2190	better, and isn't very complicated either. In most case, choosing either
		2191	one is fine, with #3 being better in typical situations.
		2192	.PP
		2193	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		2194	rather complicated, but extremely efficient, something that really pays
		2195	off after the first million or so of active timers, i.e. it's usually
		2196	overkill :)
		2197	.PP
		2198	\fIThe special problem of being too early\fR
		2199	.IX Subsection "The special problem of being too early"
		2200	.PP
		2201	If you ask a timer to call your callback after three seconds, then
		2202	you expect it to be invoked after three seconds \- but of course, this
		2203	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2204	guaranteed to any precision by libev \- imagine somebody suspending the
		2205	process with a \s-1STOP\s0 signal for a few hours for example.
		2206	.PP
		2207	So, libev tries to invoke your callback as soon as possible \fIafter\fR the
		2208	delay has occurred, but cannot guarantee this.
		2209	.PP
		2210	A less obvious failure mode is calling your callback too early: many event
		2211	loops compare timestamps with a \*(L"elapsed delay >= requested delay\*(R", but
		2212	this can cause your callback to be invoked much earlier than you would
		2213	expect.
		2214	.PP
		2215	To see why, imagine a system with a clock that only offers full second
		2216	resolution (think windows if you can't come up with a broken enough \s-1OS\s0
		2217	yourself). If you schedule a one-second timer at the time 500.9, then the
		2218	event loop will schedule your timeout to elapse at a system time of 500
		2219	(500.9 truncated to the resolution) + 1, or 501.
		2220	.PP
		2221	If an event library looks at the timeout 0.1s later, it will see \*(L"501 >=
		2222	501\*(R" and invoke the callback 0.1s after it was started, even though a
		2223	one-second delay was requested \- this is being \*(L"too early\*(R", despite best
		2224	intentions.
		2225	.PP
		2226	This is the reason why libev will never invoke the callback if the elapsed
		2227	delay equals the requested delay, but only when the elapsed delay is
		2228	larger than the requested delay. In the example above, libev would only invoke
		2229	the callback at system time 502, or 1.1s after the timer was started.
		2230	.PP
		2231	So, while libev cannot guarantee that your callback will be invoked
		2232	exactly when requested, it \fIcan\fR and \fIdoes\fR guarantee that the requested
		2233	delay has actually elapsed, or in other words, it always errs on the \*(L"too
		2234	late\*(R" side of things.
		2235	.PP
		2236	\fIThe special problem of time updates\fR
		2237	.IX Subsection "The special problem of time updates"
		2238	.PP
		2239	Establishing the current time is a costly operation (it usually takes
		2240	at least one system call): \s-1EV\s0 therefore updates its idea of the current
		2241	time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a
		2242	growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling
		2243	lots of events in one iteration.
903	.PP	2244	.PP
904	The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR	2245	The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
905	time. This is usually the right thing as this timestamp refers to the time	2246	time. This is usually the right thing as this timestamp refers to the time
906	of the event triggering whatever timeout you are modifying/starting. If	2247	of the event triggering whatever timeout you are modifying/starting. If
907	you suspect event processing to be delayed and you \fIneed\fR to base the timeout	2248	you suspect event processing to be delayed and you \fIneed\fR to base the
908	on the current time, use something like this to adjust for this:	2249	timeout on the current time, use something like the following to adjust
		2250	for it:
909	.PP	2251	.PP
910	.Vb 1	2252	.Vb 1
911	\& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2253	\& ev_timer_set (&timer, after + (ev_time () \- ev_now ()), 0.);
912	.Ve	2254	.Ve
913	.PP	2255	.PP
914	The callback is guarenteed to be invoked only when its timeout has passed,	2256	If the event loop is suspended for a long time, you can also force an
915	but if multiple timers become ready during the same loop iteration then	2257	update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update
916	order of execution is undefined.	2258	()\*(C'\fR, although that will push the event time of all outstanding events
		2259	further into the future.
		2260	.PP
		2261	\fIThe special problem of unsynchronised clocks\fR
		2262	.IX Subsection "The special problem of unsynchronised clocks"
		2263	.PP
		2264	Modern systems have a variety of clocks \- libev itself uses the normal
		2265	\&\*(L"wall clock\*(R" clock and, if available, the monotonic clock (to avoid time
		2266	jumps).
		2267	.PP
		2268	Neither of these clocks is synchronised with each other or any other clock
		2269	on the system, so \f(CW\*(C`ev_time ()\*(C'\fR might return a considerably different time
		2270	than \f(CW\*(C`gettimeofday ()\*(C'\fR or \f(CW\*(C`time ()\*(C'\fR. On a GNU/Linux system, for example,
		2271	a call to \f(CW\*(C`gettimeofday\*(C'\fR might return a second count that is one higher
		2272	than a directly following call to \f(CW\*(C`time\*(C'\fR.
		2273	.PP
		2274	The moral of this is to only compare libev-related timestamps with
		2275	\&\f(CW\*(C`ev_time ()\*(C'\fR and \f(CW\*(C`ev_now ()\*(C'\fR, at least if you want better precision than
		2276	a second or so.
		2277	.PP
		2278	One more problem arises due to this lack of synchronisation: if libev uses
		2279	the system monotonic clock and you compare timestamps from \f(CW\*(C`ev_time\*(C'\fR
		2280	or \f(CW\*(C`ev_now\*(C'\fR from when you started your timer and when your callback is
		2281	invoked, you will find that sometimes the callback is a bit \*(L"early\*(R".
		2282	.PP
		2283	This is because \f(CW\*(C`ev_timer\*(C'\fRs work in real time, not wall clock time, so
		2284	libev makes sure your callback is not invoked before the delay happened,
		2285	\&\fImeasured according to the real time\fR, not the system clock.
		2286	.PP
		2287	If your timeouts are based on a physical timescale (e.g. \*(L"time out this
		2288	connection after 100 seconds\*(R") then this shouldn't bother you as it is
		2289	exactly the right behaviour.
		2290	.PP
		2291	If you want to compare wall clock/system timestamps to your timers, then
		2292	you need to use \f(CW\*(C`ev_periodic\*(C'\fRs, as these are based on the wall clock
		2293	time, where your comparisons will always generate correct results.
		2294	.PP
		2295	\fIThe special problems of suspended animation\fR
		2296	.IX Subsection "The special problems of suspended animation"
		2297	.PP
		2298	When you leave the server world it is quite customary to hit machines that
		2299	can suspend/hibernate \- what happens to the clocks during such a suspend?
		2300	.PP
		2301	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2302	all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue
		2303	to run until the system is suspended, but they will not advance while the
		2304	system is suspended. That means, on resume, it will be as if the program
		2305	was frozen for a few seconds, but the suspend time will not be counted
		2306	towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time
		2307	clock advanced as expected, but if it is used as sole clocksource, then a
		2308	long suspend would be detected as a time jump by libev, and timers would
		2309	be adjusted accordingly.
		2310	.PP
		2311	I would not be surprised to see different behaviour in different between
		2312	operating systems, \s-1OS\s0 versions or even different hardware.
		2313	.PP
		2314	The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a
		2315	time jump in the monotonic clocks and the realtime clock. If the program
		2316	is suspended for a very long time, and monotonic clock sources are in use,
		2317	then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time
		2318	will be counted towards the timers. When no monotonic clock source is in
		2319	use, then libev will again assume a timejump and adjust accordingly.
		2320	.PP
		2321	It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR
		2322	and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get
		2323	deterministic behaviour in this case (you can do nothing against
		2324	\&\f(CW\*(C`SIGSTOP\*(C'\fR).
		2325	.PP
		2326	\fIWatcher-Specific Functions and Data Members\fR
		2327	.IX Subsection "Watcher-Specific Functions and Data Members"
917	.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4	2328	.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
918	.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"	2329	.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
919	.PD 0	2330	.PD 0
920	.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4	2331	.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
921	.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"	2332	.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
922	.PD	2333	.PD
923	Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is	2334	Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds (fractional and
924	\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the	2335	negative values are supported). If \f(CW\*(C`repeat\*(C'\fR is \f(CW0.\fR, then it will
		2336	automatically be stopped once the timeout is reached. If it is positive,
925	timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds	2337	then the timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR
926	later, again, and again, until stopped manually.	2338	seconds later, again, and again, until stopped manually.
927	.Sp	2339	.Sp
928	The timer itself will do a best-effort at avoiding drift, that is, if you	2340	The timer itself will do a best-effort at avoiding drift, that is, if
929	configure a timer to trigger every 10 seconds, then it will trigger at	2341	you configure a timer to trigger every 10 seconds, then it will normally
930	exactly 10 second intervals. If, however, your program cannot keep up with	2342	trigger at exactly 10 second intervals. If, however, your program cannot
931	the timer (because it takes longer than those 10 seconds to do stuff) the	2343	keep up with the timer (because it takes longer than those 10 seconds to
932	timer will not fire more than once per event loop iteration.	2344	do stuff) the timer will not fire more than once per event loop iteration.
933	.IP "ev_timer_again (loop)" 4	2345	.IP "ev_timer_again (loop, ev_timer *)" 4
934	.IX Item "ev_timer_again (loop)"	2346	.IX Item "ev_timer_again (loop, ev_timer *)"
935	This will act as if the timer timed out and restart it again if it is	2347	This will act as if the timer timed out, and restarts it again if it is
936	repeating. The exact semantics are:	2348	repeating. It basically works like calling \f(CW\*(C`ev_timer_stop\*(C'\fR, updating the
		2349	timeout to the \f(CW\*(C`repeat\*(C'\fR value and calling \f(CW\*(C`ev_timer_start\*(C'\fR.
937	.Sp	2350	.Sp
938	If the timer is started but nonrepeating, stop it.	2351	The exact semantics are as in the following rules, all of which will be
		2352	applied to the watcher:
		2353	.RS 4
		2354	.IP "If the timer is pending, the pending status is always cleared." 4
		2355	.IX Item "If the timer is pending, the pending status is always cleared."
		2356	.PD 0
		2357	.IP "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." 4
		2358	.IX Item "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)."
		2359	.ie n .IP "If the timer is repeating, make the ""repeat"" value the new timeout and start the timer, if necessary." 4
		2360	.el .IP "If the timer is repeating, make the \f(CWrepeat\fR value the new timeout and start the timer, if necessary." 4
		2361	.IX Item "If the timer is repeating, make the repeat value the new timeout and start the timer, if necessary."
		2362	.RE
		2363	.RS 4
		2364	.PD
939	.Sp	2365	.Sp
940	If the timer is repeating, either start it if necessary (with the repeat	2366	This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a
941	value), or reset the running timer to the repeat value.	2367	usage example.
		2368	.RE
		2369	.IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4
		2370	.IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)"
		2371	Returns the remaining time until a timer fires. If the timer is active,
		2372	then this time is relative to the current event loop time, otherwise it's
		2373	the timeout value currently configured.
942	.Sp	2374	.Sp
943	This sounds a bit complicated, but here is a useful and typical	2375	That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns
944	example: Imagine you have a tcp connection and you want a so-called idle	2376	\&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remaining\*(C'\fR
945	timeout, that is, you want to be called when there have been, say, 60	2377	will return \f(CW4\fR. When the timer expires and is restarted, it will return
946	seconds of inactivity on the socket. The easiest way to do this is to	2378	roughly \f(CW7\fR (likely slightly less as callback invocation takes some time,
947	configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each	2379	too), and so on.
948	time you successfully read or write some data. If you go into an idle	2380	.IP "ev_tstamp repeat [read\-write]" 4
949	state where you do not expect data to travel on the socket, you can stop	2381	.IX Item "ev_tstamp repeat [read-write]"
950	the timer, and again will automatically restart it if need be.	2382	The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
		2383	or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any),
		2384	which is also when any modifications are taken into account.
951	.PP	2385	.PP
		2386	\fIExamples\fR
		2387	.IX Subsection "Examples"
		2388	.PP
952	Example: create a timer that fires after 60 seconds.	2389	Example: Create a timer that fires after 60 seconds.
953	.PP	2390	.PP
954	.Vb 5	2391	.Vb 5
955	\& static void	2392	\& static void
956	\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2393	\& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
957	\& {	2394	\& {
958	\& .. one minute over, w is actually stopped right here	2395	\& .. one minute over, w is actually stopped right here
959	\& }	2396	\& }
960	.Ve	2397	\&
961	.PP
962	.Vb 3
963	\& struct ev_timer mytimer;	2398	\& ev_timer mytimer;
964	\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2399	\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
965	\& ev_timer_start (loop, &mytimer);	2400	\& ev_timer_start (loop, &mytimer);
966	.Ve	2401	.Ve
967	.PP	2402	.PP
968	Example: create a timeout timer that times out after 10 seconds of	2403	Example: Create a timeout timer that times out after 10 seconds of
969	inactivity.	2404	inactivity.
970	.PP	2405	.PP
971	.Vb 5	2406	.Vb 5
972	\& static void	2407	\& static void
973	\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2408	\& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
974	\& {	2409	\& {
975	\& .. ten seconds without any activity	2410	\& .. ten seconds without any activity
976	\& }	2411	\& }
977	.Ve	2412	\&
978	.PP
979	.Vb 4
980	\& struct ev_timer mytimer;	2413	\& ev_timer mytimer;
981	\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2414	\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
982	\& ev_timer_again (&mytimer); /* start timer */	2415	\& ev_timer_again (&mytimer); /* start timer */
983	\& ev_loop (loop, 0);	2416	\& ev_run (loop, 0);
984	.Ve	2417	\&
985	.PP
986	.Vb 3
987	\& // and in some piece of code that gets executed on any "activity":	2418	\& // and in some piece of code that gets executed on any "activity":
988	\& // reset the timeout to start ticking again at 10 seconds	2419	\& // reset the timeout to start ticking again at 10 seconds
989	\& ev_timer_again (&mytimer);	2420	\& ev_timer_again (&mytimer);
990	.Ve	2421	.Ve
991	.ie n .Sh """ev_periodic"" \- to cron or not to cron"	2422	.ie n .SS """ev_periodic"" \- to cron or not to cron?"
992	.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron"	2423	.el .SS "\f(CWev_periodic\fP \- to cron or not to cron?"
993	.IX Subsection "ev_periodic - to cron or not to cron"	2424	.IX Subsection "ev_periodic - to cron or not to cron?"
994	Periodic watchers are also timers of a kind, but they are very versatile	2425	Periodic watchers are also timers of a kind, but they are very versatile
995	(and unfortunately a bit complex).	2426	(and unfortunately a bit complex).
996	.PP	2427	.PP
997	Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)	2428	Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or
998	but on wallclock time (absolute time). You can tell a periodic watcher	2429	relative time, the physical time that passes) but on wall clock time
999	to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a	2430	(absolute time, the thing you can read on your calendar or clock). The
1000	periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()	2431	difference is that wall clock time can run faster or slower than real
1001	+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will	2432	time, and time jumps are not uncommon (e.g. when you adjust your
1002	take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger	2433	wrist-watch).
1003	roughly 10 seconds later and of course not if you reset your system time
1004	again).
1005	.PP	2434	.PP
1006	They can also be used to implement vastly more complex timers, such as	2435	You can tell a periodic watcher to trigger after some specific point
1007	triggering an event on eahc midnight, local time.	2436	in time: for example, if you tell a periodic watcher to trigger \*(L"in 10
		2437	seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time
		2438	not a delay) and then reset your system clock to January of the previous
		2439	year, then it will take a year or more to trigger the event (unlike an
		2440	\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting
		2441	it, as it uses a relative timeout).
1008	.PP	2442	.PP
		2443	\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex
		2444	timers, such as triggering an event on each \*(L"midnight, local time\*(R", or
		2445	other complicated rules. This cannot easily be done with \f(CW\*(C`ev_timer\*(C'\fR
		2446	watchers, as those cannot react to time jumps.
		2447	.PP
1009	As with timers, the callback is guarenteed to be invoked only when the	2448	As with timers, the callback is guaranteed to be invoked only when the
1010	time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready	2449	point in time where it is supposed to trigger has passed. If multiple
1011	during the same loop iteration then order of execution is undefined.	2450	timers become ready during the same loop iteration then the ones with
		2451	earlier time-out values are invoked before ones with later time-out values
		2452	(but this is no longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
		2453	.PP
		2454	\fIWatcher-Specific Functions and Data Members\fR
		2455	.IX Subsection "Watcher-Specific Functions and Data Members"
1012	.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4	2456	.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
1013	.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"	2457	.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
1014	.PD 0	2458	.PD 0
1015	.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4	2459	.IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
1016	.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"	2460	.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
1017	.PD	2461	.PD
1018	Lots of arguments, lets sort it out... There are basically three modes of	2462	Lots of arguments, let's sort it out... There are basically three modes of
1019	operation, and we will explain them from simplest to complex:	2463	operation, and we will explain them from simplest to most complex:
1020	.RS 4	2464	.RS 4
1021	.IP "* absolute timer (interval = reschedule_cb = 0)" 4	2465	.IP "\(bu" 4
1022	.IX Item "absolute timer (interval = reschedule_cb = 0)"	2466	absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
		2467	.Sp
1023	In this configuration the watcher triggers an event at the wallclock time	2468	In this configuration the watcher triggers an event after the wall clock
1024	\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,	2469	time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a
1025	that is, if it is to be run at January 1st 2011 then it will run when the	2470	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1026	system time reaches or surpasses this time.	2471	will be stopped and invoked when the system clock reaches or surpasses
1027	.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4	2472	this point in time.
1028	.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)"	2473	.IP "\(bu" 4
		2474	repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
		2475	.Sp
1029	In this mode the watcher will always be scheduled to time out at the next	2476	In this mode the watcher will always be scheduled to time out at the next
1030	\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless	2477	\&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be
1031	of any time jumps.	2478	negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR
		2479	argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods.
1032	.Sp	2480	.Sp
1033	This can be used to create timers that do not drift with respect to system	2481	This can be used to create timers that do not drift with respect to the
1034	time:	2482	system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each
		2483	hour, on the hour (with respect to \s-1UTC\s0):
1035	.Sp	2484	.Sp
1036	.Vb 1	2485	.Vb 1
1037	\& ev_periodic_set (&periodic, 0., 3600., 0);	2486	\& ev_periodic_set (&periodic, 0., 3600., 0);
1038	.Ve	2487	.Ve
1039	.Sp	2488	.Sp
1040	This doesn't mean there will always be 3600 seconds in between triggers,	2489	This doesn't mean there will always be 3600 seconds in between triggers,
1041	but only that the the callback will be called when the system time shows a	2490	but only that the callback will be called when the system time shows a
1042	full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible	2491	full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
1043	by 3600.	2492	by 3600.
1044	.Sp	2493	.Sp
1045	Another way to think about it (for the mathematically inclined) is that	2494	Another way to think about it (for the mathematically inclined) is that
1046	\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible	2495	\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1047	time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.	2496	time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps.
1048	.IP "* manual reschedule mode (reschedule_cb = callback)" 4	2497	.Sp
1049	.IX Item "manual reschedule mode (reschedule_cb = callback)"	2498	The \f(CW\*(C`interval\*(C'\fR \fI\s-1MUST\s0\fR be positive, and for numerical stability, the
		2499	interval value should be higher than \f(CW\*(C`1/8192\*(C'\fR (which is around 100
		2500	microseconds) and \f(CW\*(C`offset\*(C'\fR should be higher than \f(CW0\fR and should have
		2501	at most a similar magnitude as the current time (say, within a factor of
		2502	ten). Typical values for offset are, in fact, \f(CW0\fR or something between
		2503	\&\f(CW0\fR and \f(CW\*(C`interval\*(C'\fR, which is also the recommended range.
		2504	.Sp
		2505	Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0
		2506	speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability
		2507	will of course deteriorate. Libev itself tries to be exact to be about one
		2508	millisecond (if the \s-1OS\s0 supports it and the machine is fast enough).
		2509	.IP "\(bu" 4
		2510	manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
		2511	.Sp
1050	In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being	2512	In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being
1051	ignored. Instead, each time the periodic watcher gets scheduled, the	2513	ignored. Instead, each time the periodic watcher gets scheduled, the
1052	reschedule callback will be called with the watcher as first, and the	2514	reschedule callback will be called with the watcher as first, and the
1053	current time as second argument.	2515	current time as second argument.
1054	.Sp	2516	.Sp
1055	\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,	2517	\&\s-1NOTE:\s0 \fIThis callback \s-1MUST NOT\s0 stop or destroy any periodic watcher, ever,
1056	ever, or make any event loop modifications\fR. If you need to stop it,	2518	or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly
1057	return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by	2519	allowed by documentation here\fR.
1058	starting a prepare watcher).
1059	.Sp	2520	.Sp
		2521	If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop
		2522	it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the
		2523	only event loop modification you are allowed to do).
		2524	.Sp
1060	Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	2525	The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic
1061	ev_tstamp now)\*(C'\fR, e.g.:	2526	*w, ev_tstamp now)\*(C'\fR, e.g.:
1062	.Sp	2527	.Sp
1063	.Vb 4	2528	.Vb 5
		2529	\& static ev_tstamp
1064	\& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2530	\& my_rescheduler (ev_periodic *w, ev_tstamp now)
1065	\& {	2531	\& {
1066	\& return now + 60.;	2532	\& return now + 60.;
1067	\& }	2533	\& }
1068	.Ve	2534	.Ve
1069	.Sp	2535	.Sp
1070	It must return the next time to trigger, based on the passed time value	2536	It must return the next time to trigger, based on the passed time value
1071	(that is, the lowest time value larger than to the second argument). It	2537	(that is, the lowest time value larger than to the second argument). It
1072	will usually be called just before the callback will be triggered, but	2538	will usually be called just before the callback will be triggered, but
1073	might be called at other times, too.	2539	might be called at other times, too.
1074	.Sp	2540	.Sp
1075	\&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the	2541	\&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or
1076	passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger.	2542	equal to the passed \f(CI\*(C`now\*(C'\fI value\fR.
1077	.Sp	2543	.Sp
1078	This can be used to create very complex timers, such as a timer that	2544	This can be used to create very complex timers, such as a timer that
1079	triggers on each midnight, local time. To do this, you would calculate the	2545	triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate
1080	next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How	2546	the next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for
1081	you do this is, again, up to you (but it is not trivial, which is the main	2547	this. Here is a (completely untested, no error checking) example on how to
1082	reason I omitted it as an example).	2548	do this:
		2549	.Sp
		2550	.Vb 1
		2551	\& #include <time.h>
		2552	\&
		2553	\& static ev_tstamp
		2554	\& my_rescheduler (ev_periodic *w, ev_tstamp now)
		2555	\& {
		2556	\& time_t tnow = (time_t)now;
		2557	\& struct tm tm;
		2558	\& localtime_r (&tnow, &tm);
		2559	\&
		2560	\& tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2561	\& ++tm.tm_mday; // midnight next day
		2562	\&
		2563	\& return mktime (&tm);
		2564	\& }
		2565	.Ve
		2566	.Sp
		2567	Note: this code might run into trouble on days that have more then two
		2568	midnights (beginning and end).
1083	.RE	2569	.RE
1084	.RS 4	2570	.RS 4
1085	.RE	2571	.RE
1086	.IP "ev_periodic_again (loop, ev_periodic *)" 4	2572	.IP "ev_periodic_again (loop, ev_periodic *)" 4
1087	.IX Item "ev_periodic_again (loop, ev_periodic *)"	2573	.IX Item "ev_periodic_again (loop, ev_periodic *)"
1088	Simply stops and restarts the periodic watcher again. This is only useful	2574	Simply stops and restarts the periodic watcher again. This is only useful
1089	when you changed some parameters or the reschedule callback would return	2575	when you changed some parameters or the reschedule callback would return
1090	a different time than the last time it was called (e.g. in a crond like	2576	a different time than the last time it was called (e.g. in a crond like
1091	program when the crontabs have changed).	2577	program when the crontabs have changed).
		2578	.IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4
		2579	.IX Item "ev_tstamp ev_periodic_at (ev_periodic *)"
		2580	When active, returns the absolute time that the watcher is supposed
		2581	to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to
		2582	\&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual
		2583	rescheduling modes.
		2584	.IP "ev_tstamp offset [read\-write]" 4
		2585	.IX Item "ev_tstamp offset [read-write]"
		2586	When repeating, this contains the offset value, otherwise this is the
		2587	absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR,
		2588	although libev might modify this value for better numerical stability).
		2589	.Sp
		2590	Can be modified any time, but changes only take effect when the periodic
		2591	timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
		2592	.IP "ev_tstamp interval [read\-write]" 4
		2593	.IX Item "ev_tstamp interval [read-write]"
		2594	The current interval value. Can be modified any time, but changes only
		2595	take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
		2596	called.
		2597	.IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4
		2598	.IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]"
		2599	The current reschedule callback, or \f(CW0\fR, if this functionality is
		2600	switched off. Can be changed any time, but changes only take effect when
		2601	the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1092	.PP	2602	.PP
		2603	\fIExamples\fR
		2604	.IX Subsection "Examples"
		2605	.PP
1093	Example: call a callback every hour, or, more precisely, whenever the	2606	Example: Call a callback every hour, or, more precisely, whenever the
1094	system clock is divisible by 3600. The callback invocation times have	2607	system time is divisible by 3600. The callback invocation times have
1095	potentially a lot of jittering, but good long-term stability.	2608	potentially a lot of jitter, but good long-term stability.
1096	.PP	2609	.PP
1097	.Vb 5	2610	.Vb 5
1098	\& static void	2611	\& static void
1099	\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2612	\& clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1100	\& {	2613	\& {
1101	\& ... its now a full hour (UTC, or TAI or whatever your clock follows)	2614	\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1102	\& }	2615	\& }
1103	.Ve	2616	\&
1104	.PP
1105	.Vb 3
1106	\& struct ev_periodic hourly_tick;	2617	\& ev_periodic hourly_tick;
1107	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2618	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1108	\& ev_periodic_start (loop, &hourly_tick);	2619	\& ev_periodic_start (loop, &hourly_tick);
1109	.Ve	2620	.Ve
1110	.PP	2621	.PP
1111	Example: the same as above, but use a reschedule callback to do it:	2622	Example: The same as above, but use a reschedule callback to do it:
1112	.PP	2623	.PP
1113	.Vb 1	2624	.Vb 1
1114	\& #include <math.h>	2625	\& #include <math.h>
1115	.Ve	2626	\&
1116	.PP
1117	.Vb 5
1118	\& static ev_tstamp	2627	\& static ev_tstamp
1119	\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2628	\& my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1120	\& {	2629	\& {
1121	\& return fmod (now, 3600.) + 3600.;	2630	\& return now + (3600. \- fmod (now, 3600.));
1122	\& }	2631	\& }
1123	.Ve	2632	\&
1124	.PP
1125	.Vb 1
1126	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2633	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1127	.Ve	2634	.Ve
1128	.PP	2635	.PP
1129	Example: call a callback every hour, starting now:	2636	Example: Call a callback every hour, starting now:
1130	.PP	2637	.PP
1131	.Vb 4	2638	.Vb 4
1132	\& struct ev_periodic hourly_tick;	2639	\& ev_periodic hourly_tick;
1133	\& ev_periodic_init (&hourly_tick, clock_cb,	2640	\& ev_periodic_init (&hourly_tick, clock_cb,
1134	\& fmod (ev_now (loop), 3600.), 3600., 0);	2641	\& fmod (ev_now (loop), 3600.), 3600., 0);
1135	\& ev_periodic_start (loop, &hourly_tick);	2642	\& ev_periodic_start (loop, &hourly_tick);
1136	.Ve	2643	.Ve
1137	.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled"	2644	.ie n .SS """ev_signal"" \- signal me when a signal gets signalled!"
1138	.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled"	2645	.el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1139	.IX Subsection "ev_signal - signal me when a signal gets signalled"	2646	.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1140	Signal watchers will trigger an event when the process receives a specific	2647	Signal watchers will trigger an event when the process receives a specific
1141	signal one or more times. Even though signals are very asynchronous, libev	2648	signal one or more times. Even though signals are very asynchronous, libev
1142	will try it's best to deliver signals synchronously, i.e. as part of the	2649	will try its best to deliver signals synchronously, i.e. as part of the
1143	normal event processing, like any other event.	2650	normal event processing, like any other event.
1144	.PP	2651	.PP
		2652	If you want signals to be delivered truly asynchronously, just use
		2653	\&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing
		2654	the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to
		2655	synchronously wake up an event loop.
		2656	.PP
1145	You can configure as many watchers as you like per signal. Only when the	2657	You can configure as many watchers as you like for the same signal, but
1146	first watcher gets started will libev actually register a signal watcher	2658	only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your
1147	with the kernel (thus it coexists with your own signal handlers as long	2659	default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for
1148	as you don't register any with libev). Similarly, when the last signal	2660	\&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At
1149	watcher for a signal is stopped libev will reset the signal handler to	2661	the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop.
1150	\&\s-1SIG_DFL\s0 (regardless of what it was set to before).	2662	.PP
		2663	Only after the first watcher for a signal is started will libev actually
		2664	register something with the kernel. It thus coexists with your own signal
		2665	handlers as long as you don't register any with libev for the same signal.
		2666	.PP
		2667	If possible and supported, libev will install its handlers with
		2668	\&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should
		2669	not be unduly interrupted. If you have a problem with system calls getting
		2670	interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher
		2671	and unblock them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
		2672	.PP
		2673	\fIThe special problem of inheritance over fork/execve/pthread_create\fR
		2674	.IX Subsection "The special problem of inheritance over fork/execve/pthread_create"
		2675	.PP
		2676	Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition
		2677	(\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after
		2678	stopping it again), that is, libev might or might not block the signal,
		2679	and might or might not set or restore the installed signal handler (but
		2680	see \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR).
		2681	.PP
		2682	While this does not matter for the signal disposition (libev never
		2683	sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on
		2684	\&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect
		2685	certain signals to be blocked.
		2686	.PP
		2687	This means that before calling \f(CW\*(C`exec\*(C'\fR (from the child) you should reset
		2688	the signal mask to whatever \*(L"default\*(R" you expect (all clear is a good
		2689	choice usually).
		2690	.PP
		2691	The simplest way to ensure that the signal mask is reset in the child is
		2692	to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will
		2693	catch fork calls done by libraries (such as the libc) as well.
		2694	.PP
		2695	In current versions of libev, the signal will not be blocked indefinitely
		2696	unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API\s0 (\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces
		2697	the window of opportunity for problems, it will not go away, as libev
		2698	\&\fIhas\fR to modify the signal mask, at least temporarily.
		2699	.PP
		2700	So I can't stress this enough: \fIIf you do not reset your signal mask when
		2701	you expect it to be empty, you have a race condition in your code\fR. This
		2702	is not a libev-specific thing, this is true for most event libraries.
		2703	.PP
		2704	\fIThe special problem of threads signal handling\fR
		2705	.IX Subsection "The special problem of threads signal handling"
		2706	.PP
		2707	\&\s-1POSIX\s0 threads has problematic signal handling semantics, specifically,
		2708	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2709	threads in a process block signals, which is hard to achieve.
		2710	.PP
		2711	When you want to use sigwait (or mix libev signal handling with your own
		2712	for the same signals), you can tackle this problem by globally blocking
		2713	all signals before creating any threads (or creating them with a fully set
		2714	sigprocmask) and also specifying the \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when creating
		2715	loops. Then designate one thread as \*(L"signal receiver thread\*(R" which handles
		2716	these signals. You can pass on any signals that libev might be interested
		2717	in by calling \f(CW\*(C`ev_feed_signal\*(C'\fR.
		2718	.PP
		2719	\fIWatcher-Specific Functions and Data Members\fR
		2720	.IX Subsection "Watcher-Specific Functions and Data Members"
1151	.IP "ev_signal_init (ev_signal *, callback, int signum)" 4	2721	.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1152	.IX Item "ev_signal_init (ev_signal *, callback, int signum)"	2722	.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1153	.PD 0	2723	.PD 0
1154	.IP "ev_signal_set (ev_signal *, int signum)" 4	2724	.IP "ev_signal_set (ev_signal *, int signum)" 4
1155	.IX Item "ev_signal_set (ev_signal *, int signum)"	2725	.IX Item "ev_signal_set (ev_signal *, int signum)"
1156	.PD	2726	.PD
1157	Configures the watcher to trigger on the given signal number (usually one	2727	Configures the watcher to trigger on the given signal number (usually one
1158	of the \f(CW\*(C`SIGxxx\*(C'\fR constants).	2728	of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
		2729	.IP "int signum [read\-only]" 4
		2730	.IX Item "int signum [read-only]"
		2731	The signal the watcher watches out for.
		2732	.PP
		2733	\fIExamples\fR
		2734	.IX Subsection "Examples"
		2735	.PP
		2736	Example: Try to exit cleanly on \s-1SIGINT.\s0
		2737	.PP
		2738	.Vb 5
		2739	\& static void
		2740	\& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		2741	\& {
		2742	\& ev_break (loop, EVBREAK_ALL);
		2743	\& }
		2744	\&
		2745	\& ev_signal signal_watcher;
		2746	\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		2747	\& ev_signal_start (loop, &signal_watcher);
		2748	.Ve
1159	.ie n .Sh """ev_child"" \- wait for pid status changes"	2749	.ie n .SS """ev_child"" \- watch out for process status changes"
1160	.el .Sh "\f(CWev_child\fP \- wait for pid status changes"	2750	.el .SS "\f(CWev_child\fP \- watch out for process status changes"
1161	.IX Subsection "ev_child - wait for pid status changes"	2751	.IX Subsection "ev_child - watch out for process status changes"
1162	Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to	2752	Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1163	some child status changes (most typically when a child of yours dies).	2753	some child status changes (most typically when a child of yours dies or
		2754	exits). It is permissible to install a child watcher \fIafter\fR the child
		2755	has been forked (which implies it might have already exited), as long
		2756	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2757	forking and then immediately registering a watcher for the child is fine,
		2758	but forking and registering a watcher a few event loop iterations later or
		2759	in the next callback invocation is not.
		2760	.PP
		2761	Only the default event loop is capable of handling signals, and therefore
		2762	you can only register child watchers in the default event loop.
		2763	.PP
		2764	Due to some design glitches inside libev, child watchers will always be
		2765	handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by
		2766	libev)
		2767	.PP
		2768	\fIProcess Interaction\fR
		2769	.IX Subsection "Process Interaction"
		2770	.PP
		2771	Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is
		2772	initialised. This is necessary to guarantee proper behaviour even if the
		2773	first child watcher is started after the child exits. The occurrence
		2774	of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done
		2775	synchronously as part of the event loop processing. Libev always reaps all
		2776	children, even ones not watched.
		2777	.PP
		2778	\fIOverriding the Built-In Processing\fR
		2779	.IX Subsection "Overriding the Built-In Processing"
		2780	.PP
		2781	Libev offers no special support for overriding the built-in child
		2782	processing, but if your application collides with libev's default child
		2783	handler, you can override it easily by installing your own handler for
		2784	\&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the
		2785	default loop never gets destroyed. You are encouraged, however, to use an
		2786	event-based approach to child reaping and thus use libev's support for
		2787	that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely.
		2788	.PP
		2789	\fIStopping the Child Watcher\fR
		2790	.IX Subsection "Stopping the Child Watcher"
		2791	.PP
		2792	Currently, the child watcher never gets stopped, even when the
		2793	child terminates, so normally one needs to stop the watcher in the
		2794	callback. Future versions of libev might stop the watcher automatically
		2795	when a child exit is detected (calling \f(CW\*(C`ev_child_stop\*(C'\fR twice is not a
		2796	problem).
		2797	.PP
		2798	\fIWatcher-Specific Functions and Data Members\fR
		2799	.IX Subsection "Watcher-Specific Functions and Data Members"
1164	.IP "ev_child_init (ev_child *, callback, int pid)" 4	2800	.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
1165	.IX Item "ev_child_init (ev_child *, callback, int pid)"	2801	.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
1166	.PD 0	2802	.PD 0
1167	.IP "ev_child_set (ev_child *, int pid)" 4	2803	.IP "ev_child_set (ev_child *, int pid, int trace)" 4
1168	.IX Item "ev_child_set (ev_child *, int pid)"	2804	.IX Item "ev_child_set (ev_child *, int pid, int trace)"
1169	.PD	2805	.PD
1170	Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or	2806	Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
1171	\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look	2807	\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1172	at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see	2808	at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1173	the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems	2809	the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1174	\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the	2810	\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1175	process causing the status change.	2811	process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only
		2812	activate the watcher when the process terminates) or \f(CW1\fR (additionally
		2813	activate the watcher when the process is stopped or continued).
		2814	.IP "int pid [read\-only]" 4
		2815	.IX Item "int pid [read-only]"
		2816	The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
		2817	.IP "int rpid [read\-write]" 4
		2818	.IX Item "int rpid [read-write]"
		2819	The process id that detected a status change.
		2820	.IP "int rstatus [read\-write]" 4
		2821	.IX Item "int rstatus [read-write]"
		2822	The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
		2823	\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1176	.PP	2824	.PP
1177	Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.	2825	\fIExamples\fR
		2826	.IX Subsection "Examples"
1178	.PP	2827	.PP
		2828	Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for
		2829	its completion.
		2830	.PP
1179	.Vb 5	2831	.Vb 1
		2832	\& ev_child cw;
		2833	\&
1180	\& static void	2834	\& static void
1181	\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2835	\& child_cb (EV_P_ ev_child *w, int revents)
1182	\& {	2836	\& {
1183	\& ev_unloop (loop, EVUNLOOP_ALL);	2837	\& ev_child_stop (EV_A_ w);
		2838	\& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
1184	\& }	2839	\& }
		2840	\&
		2841	\& pid_t pid = fork ();
		2842	\&
		2843	\& if (pid < 0)
		2844	\& // error
		2845	\& else if (pid == 0)
		2846	\& {
		2847	\& // the forked child executes here
		2848	\& exit (1);
		2849	\& }
		2850	\& else
		2851	\& {
		2852	\& ev_child_init (&cw, child_cb, pid, 0);
		2853	\& ev_child_start (EV_DEFAULT_ &cw);
		2854	\& }
1185	.Ve	2855	.Ve
		2856	.ie n .SS """ev_stat"" \- did the file attributes just change?"
		2857	.el .SS "\f(CWev_stat\fP \- did the file attributes just change?"
		2858	.IX Subsection "ev_stat - did the file attributes just change?"
		2859	This watches a file system path for attribute changes. That is, it calls
		2860	\&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed)
		2861	and sees if it changed compared to the last time, invoking the callback
		2862	if it did. Starting the watcher \f(CW\*(C`stat\*(C'\fR's the file, so only changes that
		2863	happen after the watcher has been started will be reported.
1186	.PP	2864	.PP
		2865	The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
		2866	not exist\*(R" is a status change like any other. The condition \*(L"path does not
		2867	exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the
		2868	\&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at
		2869	least one) and all the other fields of the stat buffer having unspecified
		2870	contents.
		2871	.PP
		2872	The path \fImust not\fR end in a slash or contain special components such as
		2873	\&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and
		2874	your working directory changes, then the behaviour is undefined.
		2875	.PP
		2876	Since there is no portable change notification interface available, the
		2877	portable implementation simply calls \f(CWstat(2)\fR regularly on the path
		2878	to see if it changed somehow. You can specify a recommended polling
		2879	interval for this case. If you specify a polling interval of \f(CW0\fR (highly
		2880	recommended!) then a \fIsuitable, unspecified default\fR value will be used
		2881	(which you can expect to be around five seconds, although this might
		2882	change dynamically). Libev will also impose a minimum interval which is
		2883	currently around \f(CW0.1\fR, but that's usually overkill.
		2884	.PP
		2885	This watcher type is not meant for massive numbers of stat watchers,
		2886	as even with OS-supported change notifications, this can be
		2887	resource-intensive.
		2888	.PP
		2889	At the time of this writing, the only OS-specific interface implemented
		2890	is the Linux inotify interface (implementing kqueue support is left as an
		2891	exercise for the reader. Note, however, that the author sees no way of
		2892	implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint).
		2893	.PP
		2894	\fI\s-1ABI\s0 Issues (Largefile Support)\fR
		2895	.IX Subsection "ABI Issues (Largefile Support)"
		2896	.PP
		2897	Libev by default (unless the user overrides this) uses the default
		2898	compilation environment, which means that on systems with large file
		2899	support disabled by default, you get the 32 bit version of the stat
		2900	structure. When using the library from programs that change the \s-1ABI\s0 to
		2901	use 64 bit file offsets the programs will fail. In that case you have to
		2902	compile libev with the same flags to get binary compatibility. This is
		2903	obviously the case with any flags that change the \s-1ABI,\s0 but the problem is
		2904	most noticeably displayed with ev_stat and large file support.
		2905	.PP
		2906	The solution for this is to lobby your distribution maker to make large
		2907	file interfaces available by default (as e.g. FreeBSD does) and not
		2908	optional. Libev cannot simply switch on large file support because it has
		2909	to exchange stat structures with application programs compiled using the
		2910	default compilation environment.
		2911	.PP
		2912	\fIInotify and Kqueue\fR
		2913	.IX Subsection "Inotify and Kqueue"
		2914	.PP
		2915	When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at
		2916	runtime, it will be used to speed up change detection where possible. The
		2917	inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR
		2918	watcher is being started.
		2919	.PP
		2920	Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers
		2921	except that changes might be detected earlier, and in some cases, to avoid
		2922	making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support
		2923	there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling,
		2924	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2925	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2926	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2927	xfs are fully working) libev usually gets away without polling.
		2928	.PP
		2929	There is no support for kqueue, as apparently it cannot be used to
		2930	implement this functionality, due to the requirement of having a file
		2931	descriptor open on the object at all times, and detecting renames, unlinks
		2932	etc. is difficult.
		2933	.PP
		2934	\fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR
		2935	.IX Subsection "stat () is a synchronous operation"
		2936	.PP
		2937	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2938	the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat
		2939	()\*(C'\fR, which is a synchronous operation.
		2940	.PP
		2941	For local paths, this usually doesn't matter: unless the system is very
		2942	busy or the intervals between stat's are large, a stat call will be fast,
		2943	as the path data is usually in memory already (except when starting the
		2944	watcher).
		2945	.PP
		2946	For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite
		2947	time due to network issues, and even under good conditions, a stat call
		2948	often takes multiple milliseconds.
		2949	.PP
		2950	Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked
		2951	paths, although this is fully supported by libev.
		2952	.PP
		2953	\fIThe special problem of stat time resolution\fR
		2954	.IX Subsection "The special problem of stat time resolution"
		2955	.PP
		2956	The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably,
		2957	and even on systems where the resolution is higher, most file systems
		2958	still only support whole seconds.
		2959	.PP
		2960	That means that, if the time is the only thing that changes, you can
		2961	easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and
		2962	calls your callback, which does something. When there is another update
		2963	within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the
		2964	stat data does change in other ways (e.g. file size).
		2965	.PP
		2966	The solution to this is to delay acting on a change for slightly more
		2967	than a second (or till slightly after the next full second boundary), using
		2968	a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02);
		2969	ev_timer_again (loop, w)\*(C'\fR).
		2970	.PP
		2971	The \f(CW.02\fR offset is added to work around small timing inconsistencies
		2972	of some operating systems (where the second counter of the current time
		2973	might be be delayed. One such system is the Linux kernel, where a call to
		2974	\&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than
		2975	a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to
		2976	update file times then there will be a small window where the kernel uses
		2977	the previous second to update file times but libev might already execute
		2978	the timer callback).
		2979	.PP
		2980	\fIWatcher-Specific Functions and Data Members\fR
		2981	.IX Subsection "Watcher-Specific Functions and Data Members"
		2982	.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
		2983	.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
		2984	.PD 0
		2985	.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
		2986	.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
		2987	.PD
		2988	Configures the watcher to wait for status changes of the given
		2989	\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
		2990	be detected and should normally be specified as \f(CW0\fR to let libev choose
		2991	a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
		2992	path for as long as the watcher is active.
		2993	.Sp
		2994	The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event when a change was detected,
		2995	relative to the attributes at the time the watcher was started (or the
		2996	last change was detected).
		2997	.IP "ev_stat_stat (loop, ev_stat *)" 4
		2998	.IX Item "ev_stat_stat (loop, ev_stat *)"
		2999	Updates the stat buffer immediately with new values. If you change the
		3000	watched path in your callback, you could call this function to avoid
		3001	detecting this change (while introducing a race condition if you are not
		3002	the only one changing the path). Can also be useful simply to find out the
		3003	new values.
		3004	.IP "ev_statdata attr [read\-only]" 4
		3005	.IX Item "ev_statdata attr [read-only]"
		3006	The most-recently detected attributes of the file. Although the type is
		3007	\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
		3008	suitable for your system, but you can only rely on the POSIX-standardised
		3009	members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was
		3010	some error while \f(CW\*(C`stat\*(C'\fRing the file.
		3011	.IP "ev_statdata prev [read\-only]" 4
		3012	.IX Item "ev_statdata prev [read-only]"
		3013	The previous attributes of the file. The callback gets invoked whenever
		3014	\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members
		3015	differ: \f(CW\*(C`st_dev\*(C'\fR, \f(CW\*(C`st_ino\*(C'\fR, \f(CW\*(C`st_mode\*(C'\fR, \f(CW\*(C`st_nlink\*(C'\fR, \f(CW\*(C`st_uid\*(C'\fR,
		3016	\&\f(CW\*(C`st_gid\*(C'\fR, \f(CW\*(C`st_rdev\*(C'\fR, \f(CW\*(C`st_size\*(C'\fR, \f(CW\*(C`st_atime\*(C'\fR, \f(CW\*(C`st_mtime\*(C'\fR, \f(CW\*(C`st_ctime\*(C'\fR.
		3017	.IP "ev_tstamp interval [read\-only]" 4
		3018	.IX Item "ev_tstamp interval [read-only]"
		3019	The specified interval.
		3020	.IP "const char *path [read\-only]" 4
		3021	.IX Item "const char *path [read-only]"
		3022	The file system path that is being watched.
		3023	.PP
		3024	\fIExamples\fR
		3025	.IX Subsection "Examples"
		3026	.PP
		3027	Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
		3028	.PP
		3029	.Vb 10
		3030	\& static void
		3031	\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		3032	\& {
		3033	\& /* /etc/passwd changed in some way */
		3034	\& if (w\->attr.st_nlink)
		3035	\& {
		3036	\& printf ("passwd current size %ld\en", (long)w\->attr.st_size);
		3037	\& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime);
		3038	\& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime);
		3039	\& }
		3040	\& else
		3041	\& /* you shalt not abuse printf for puts */
		3042	\& puts ("wow, /etc/passwd is not there, expect problems. "
		3043	\& "if this is windows, they already arrived\en");
		3044	\& }
		3045	\&
		3046	\& ...
		3047	\& ev_stat passwd;
		3048	\&
		3049	\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		3050	\& ev_stat_start (loop, &passwd);
		3051	.Ve
		3052	.PP
		3053	Example: Like above, but additionally use a one-second delay so we do not
		3054	miss updates (however, frequent updates will delay processing, too, so
		3055	one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on
		3056	\&\f(CW\*(C`ev_timer\*(C'\fR callback invocation).
		3057	.PP
1187	.Vb 3	3058	.Vb 2
1188	\& struct ev_signal signal_watcher;	3059	\& static ev_stat passwd;
1189	\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	3060	\& static ev_timer timer;
1190	\& ev_signal_start (loop, &sigint_cb);	3061	\&
		3062	\& static void
		3063	\& timer_cb (EV_P_ ev_timer *w, int revents)
		3064	\& {
		3065	\& ev_timer_stop (EV_A_ w);
		3066	\&
		3067	\& /* now it\*(Aqs one second after the most recent passwd change */
		3068	\& }
		3069	\&
		3070	\& static void
		3071	\& stat_cb (EV_P_ ev_stat *w, int revents)
		3072	\& {
		3073	\& /* reset the one\-second timer */
		3074	\& ev_timer_again (EV_A_ &timer);
		3075	\& }
		3076	\&
		3077	\& ...
		3078	\& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		3079	\& ev_stat_start (loop, &passwd);
		3080	\& ev_timer_init (&timer, timer_cb, 0., 1.02);
1191	.Ve	3081	.Ve
1192	.ie n .Sh """ev_idle"" \- when you've got nothing better to do"	3082	.ie n .SS """ev_idle"" \- when you've got nothing better to do..."
1193	.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do"	3083	.el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..."
1194	.IX Subsection "ev_idle - when you've got nothing better to do"	3084	.IX Subsection "ev_idle - when you've got nothing better to do..."
1195	Idle watchers trigger events when there are no other events are pending	3085	Idle watchers trigger events when no other events of the same or higher
1196	(prepare, check and other idle watchers do not count). That is, as long	3086	priority are pending (prepare, check and other idle watchers do not count
1197	as your process is busy handling sockets or timeouts (or even signals,	3087	as receiving \*(L"events\*(R").
1198	imagine) it will not be triggered. But when your process is idle all idle	3088	.PP
1199	watchers are being called again and again, once per event loop iteration \-	3089	That is, as long as your process is busy handling sockets or timeouts
		3090	(or even signals, imagine) of the same or higher priority it will not be
		3091	triggered. But when your process is idle (or only lower-priority watchers
		3092	are pending), the idle watchers are being called once per event loop
1200	until stopped, that is, or your process receives more events and becomes	3093	iteration \- until stopped, that is, or your process receives more events
1201	busy.	3094	and becomes busy again with higher priority stuff.
1202	.PP	3095	.PP
1203	The most noteworthy effect is that as long as any idle watchers are	3096	The most noteworthy effect is that as long as any idle watchers are
1204	active, the process will not block when waiting for new events.	3097	active, the process will not block when waiting for new events.
1205	.PP	3098	.PP
1206	Apart from keeping your process non-blocking (which is a useful	3099	Apart from keeping your process non-blocking (which is a useful
1207	effect on its own sometimes), idle watchers are a good place to do	3100	effect on its own sometimes), idle watchers are a good place to do
1208	\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the	3101	\&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the
1209	event loop has handled all outstanding events.	3102	event loop has handled all outstanding events.
		3103	.PP
		3104	\fIAbusing an \f(CI\*(C`ev_idle\*(C'\fI watcher for its side-effect\fR
		3105	.IX Subsection "Abusing an ev_idle watcher for its side-effect"
		3106	.PP
		3107	As long as there is at least one active idle watcher, libev will never
		3108	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		3109	For this to work, the idle watcher doesn't need to be invoked at all \- the
		3110	lowest priority will do.
		3111	.PP
		3112	This mode of operation can be useful together with an \f(CW\*(C`ev_check\*(C'\fR watcher,
		3113	to do something on each event loop iteration \- for example to balance load
		3114	between different connections.
		3115	.PP
		3116	See \*(L"Abusing an ev_check watcher for its side-effect\*(R" for a longer
		3117	example.
		3118	.PP
		3119	\fIWatcher-Specific Functions and Data Members\fR
		3120	.IX Subsection "Watcher-Specific Functions and Data Members"
1210	.IP "ev_idle_init (ev_signal *, callback)" 4	3121	.IP "ev_idle_init (ev_idle *, callback)" 4
1211	.IX Item "ev_idle_init (ev_signal *, callback)"	3122	.IX Item "ev_idle_init (ev_idle *, callback)"
1212	Initialises and configures the idle watcher \- it has no parameters of any	3123	Initialises and configures the idle watcher \- it has no parameters of any
1213	kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,	3124	kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1214	believe me.	3125	believe me.
1215	.PP	3126	.PP
		3127	\fIExamples\fR
		3128	.IX Subsection "Examples"
		3129	.PP
1216	Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the	3130	Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1217	callback, free it. Alos, use no error checking, as usual.	3131	callback, free it. Also, use no error checking, as usual.
1218	.PP	3132	.PP
1219	.Vb 7	3133	.Vb 5
1220	\& static void	3134	\& static void
1221	\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	3135	\& idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1222	\& {	3136	\& {
		3137	\& // stop the watcher
		3138	\& ev_idle_stop (loop, w);
		3139	\&
		3140	\& // now we can free it
1223	\& free (w);	3141	\& free (w);
		3142	\&
1224	\& // now do something you wanted to do when the program has	3143	\& // now do something you wanted to do when the program has
1225	\& // no longer asnything immediate to do.	3144	\& // no longer anything immediate to do.
1226	\& }	3145	\& }
1227	.Ve	3146	\&
1228	.PP
1229	.Vb 3
1230	\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	3147	\& ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1231	\& ev_idle_init (idle_watcher, idle_cb);	3148	\& ev_idle_init (idle_watcher, idle_cb);
1232	\& ev_idle_start (loop, idle_cb);	3149	\& ev_idle_start (loop, idle_watcher);
1233	.Ve	3150	.Ve
1234	.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop"	3151	.ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!"
1235	.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop"	3152	.el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1236	.IX Subsection "ev_prepare and ev_check - customise your event loop"	3153	.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1237	Prepare and check watchers are usually (but not always) used in tandem:	3154	Prepare and check watchers are often (but not always) used in pairs:
1238	prepare watchers get invoked before the process blocks and check watchers	3155	prepare watchers get invoked before the process blocks and check watchers
1239	afterwards.	3156	afterwards.
1240	.PP	3157	.PP
		3158	You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR (or similar functions that enter the
		3159	current event loop) or \f(CW\*(C`ev_loop_fork\*(C'\fR from either \f(CW\*(C`ev_prepare\*(C'\fR or
		3160	\&\f(CW\*(C`ev_check\*(C'\fR watchers. Other loops than the current one are fine,
		3161	however. The rationale behind this is that you do not need to check
		3162	for recursion in those watchers, i.e. the sequence will always be
		3163	\&\f(CW\*(C`ev_prepare\*(C'\fR, blocking, \f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each
		3164	kind they will always be called in pairs bracketing the blocking call.
		3165	.PP
1241	Their main purpose is to integrate other event mechanisms into libev and	3166	Their main purpose is to integrate other event mechanisms into libev and
1242	their use is somewhat advanced. This could be used, for example, to track	3167	their use is somewhat advanced. They could be used, for example, to track
1243	variable changes, implement your own watchers, integrate net-snmp or a	3168	variable changes, implement your own watchers, integrate net-snmp or a
1244	coroutine library and lots more.	3169	coroutine library and lots more. They are also occasionally useful if
		3170	you cache some data and want to flush it before blocking (for example,
		3171	in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
		3172	watcher).
1245	.PP	3173	.PP
1246	This is done by examining in each prepare call which file descriptors need	3174	This is done by examining in each prepare call which file descriptors
1247	to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for	3175	need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers
1248	them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries	3176	for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many
1249	provide just this functionality). Then, in the check watcher you check for	3177	libraries provide exactly this functionality). Then, in the check watcher,
1250	any events that occured (by checking the pending status of all watchers	3178	you check for any events that occurred (by checking the pending status
1251	and stopping them) and call back into the library. The I/O and timer	3179	of all watchers and stopping them) and call back into the library. The
1252	callbacks will never actually be called (but must be valid nevertheless,	3180	I/O and timer callbacks will never actually be called (but must be valid
1253	because you never know, you know?).	3181	nevertheless, because you never know, you know?).
1254	.PP	3182	.PP
1255	As another example, the Perl Coro module uses these hooks to integrate	3183	As another example, the Perl Coro module uses these hooks to integrate
1256	coroutines into libev programs, by yielding to other active coroutines	3184	coroutines into libev programs, by yielding to other active coroutines
1257	during each prepare and only letting the process block if no coroutines	3185	during each prepare and only letting the process block if no coroutines
1258	are ready to run (it's actually more complicated: it only runs coroutines	3186	are ready to run (it's actually more complicated: it only runs coroutines
1259	with priority higher than or equal to the event loop and one coroutine	3187	with priority higher than or equal to the event loop and one coroutine
1260	of lower priority, but only once, using idle watchers to keep the event	3188	of lower priority, but only once, using idle watchers to keep the event
1261	loop from blocking if lower-priority coroutines are active, thus mapping	3189	loop from blocking if lower-priority coroutines are active, thus mapping
1262	low-priority coroutines to idle/background tasks).	3190	low-priority coroutines to idle/background tasks).
		3191	.PP
		3192	When used for this purpose, it is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers
		3193	highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) priority, to ensure that they are being run before
		3194	any other watchers after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR
		3195	watchers).
		3196	.PP
		3197	Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not
		3198	activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they
		3199	might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As
		3200	\&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event
		3201	loops those other event loops might be in an unusable state until their
		3202	\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
		3203	others).
		3204	.PP
		3205	\fIAbusing an \f(CI\*(C`ev_check\*(C'\fI watcher for its side-effect\fR
		3206	.IX Subsection "Abusing an ev_check watcher for its side-effect"
		3207	.PP
		3208	\&\f(CW\*(C`ev_check\*(C'\fR (and less often also \f(CW\*(C`ev_prepare\*(C'\fR) watchers can also be
		3209	useful because they are called once per event loop iteration. For
		3210	example, if you want to handle a large number of connections fairly, you
		3211	normally only do a bit of work for each active connection, and if there
		3212	is more work to do, you wait for the next event loop iteration, so other
		3213	connections have a chance of making progress.
		3214	.PP
		3215	Using an \f(CW\*(C`ev_check\*(C'\fR watcher is almost enough: it will be called on the
		3216	next event loop iteration. However, that isn't as soon as possible \-
		3217	without external events, your \f(CW\*(C`ev_check\*(C'\fR watcher will not be invoked.
		3218	.PP
		3219	This is where \f(CW\*(C`ev_idle\*(C'\fR watchers come in handy \- all you need is a
		3220	single global idle watcher that is active as long as you have one active
		3221	\&\f(CW\*(C`ev_check\*(C'\fR watcher. The \f(CW\*(C`ev_idle\*(C'\fR watcher makes sure the event loop
		3222	will not sleep, and the \f(CW\*(C`ev_check\*(C'\fR watcher makes sure a callback gets
		3223	invoked. Neither watcher alone can do that.
		3224	.PP
		3225	\fIWatcher-Specific Functions and Data Members\fR
		3226	.IX Subsection "Watcher-Specific Functions and Data Members"
1263	.IP "ev_prepare_init (ev_prepare *, callback)" 4	3227	.IP "ev_prepare_init (ev_prepare *, callback)" 4
1264	.IX Item "ev_prepare_init (ev_prepare *, callback)"	3228	.IX Item "ev_prepare_init (ev_prepare *, callback)"
1265	.PD 0	3229	.PD 0
1266	.IP "ev_check_init (ev_check *, callback)" 4	3230	.IP "ev_check_init (ev_check *, callback)" 4
1267	.IX Item "ev_check_init (ev_check *, callback)"	3231	.IX Item "ev_check_init (ev_check *, callback)"
1268	.PD	3232	.PD
1269	Initialises and configures the prepare or check watcher \- they have no	3233	Initialises and configures the prepare or check watcher \- they have no
1270	parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR	3234	parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1271	macros, but using them is utterly, utterly and completely pointless.	3235	macros, but using them is utterly, utterly, utterly and completely
		3236	pointless.
1272	.PP	3237	.PP
1273	Example: *TODO*.	3238	\fIExamples\fR
		3239	.IX Subsection "Examples"
		3240	.PP
		3241	There are a number of principal ways to embed other event loops or modules
		3242	into libev. Here are some ideas on how to include libadns into libev
		3243	(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
		3244	use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a
		3245	Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the
		3246	Glib event loop).
		3247	.PP
		3248	Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
		3249	and in a check watcher, destroy them and call into libadns. What follows
		3250	is pseudo-code only of course. This requires you to either use a low
		3251	priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
		3252	the callbacks for the IO/timeout watchers might not have been called yet.
		3253	.PP
		3254	.Vb 2
		3255	\& static ev_io iow [nfd];
		3256	\& static ev_timer tw;
		3257	\&
		3258	\& static void
		3259	\& io_cb (struct ev_loop *loop, ev_io *w, int revents)
		3260	\& {
		3261	\& }
		3262	\&
		3263	\& // create io watchers for each fd and a timer before blocking
		3264	\& static void
		3265	\& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
		3266	\& {
		3267	\& int timeout = 3600000;
		3268	\& struct pollfd fds [nfd];
		3269	\& // actual code will need to loop here and realloc etc.
		3270	\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		3271	\&
		3272	\& /* the callback is illegal, but won\*(Aqt be called as we stop during check */
		3273	\& ev_timer_init (&tw, 0, timeout * 1e\-3, 0.);
		3274	\& ev_timer_start (loop, &tw);
		3275	\&
		3276	\& // create one ev_io per pollfd
		3277	\& for (int i = 0; i < nfd; ++i)
		3278	\& {
		3279	\& ev_io_init (iow + i, io_cb, fds [i].fd,
		3280	\& ((fds [i].events & POLLIN ? EV_READ : 0)
		3281	\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		3282	\&
		3283	\& fds [i].revents = 0;
		3284	\& ev_io_start (loop, iow + i);
		3285	\& }
		3286	\& }
		3287	\&
		3288	\& // stop all watchers after blocking
		3289	\& static void
		3290	\& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
		3291	\& {
		3292	\& ev_timer_stop (loop, &tw);
		3293	\&
		3294	\& for (int i = 0; i < nfd; ++i)
		3295	\& {
		3296	\& // set the relevant poll flags
		3297	\& // could also call adns_processreadable etc. here
		3298	\& struct pollfd *fd = fds + i;
		3299	\& int revents = ev_clear_pending (iow + i);
		3300	\& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
		3301	\& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
		3302	\&
		3303	\& // now stop the watcher
		3304	\& ev_io_stop (loop, iow + i);
		3305	\& }
		3306	\&
		3307	\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		3308	\& }
		3309	.Ve
		3310	.PP
		3311	Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
		3312	in the prepare watcher and would dispose of the check watcher.
		3313	.PP
		3314	Method 3: If the module to be embedded supports explicit event
		3315	notification (libadns does), you can also make use of the actual watcher
		3316	callbacks, and only destroy/create the watchers in the prepare watcher.
		3317	.PP
		3318	.Vb 5
		3319	\& static void
		3320	\& timer_cb (EV_P_ ev_timer *w, int revents)
		3321	\& {
		3322	\& adns_state ads = (adns_state)w\->data;
		3323	\& update_now (EV_A);
		3324	\&
		3325	\& adns_processtimeouts (ads, &tv_now);
		3326	\& }
		3327	\&
		3328	\& static void
		3329	\& io_cb (EV_P_ ev_io *w, int revents)
		3330	\& {
		3331	\& adns_state ads = (adns_state)w\->data;
		3332	\& update_now (EV_A);
		3333	\&
		3334	\& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now);
		3335	\& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
		3336	\& }
		3337	\&
		3338	\& // do not ever call adns_afterpoll
		3339	.Ve
		3340	.PP
		3341	Method 4: Do not use a prepare or check watcher because the module you
		3342	want to embed is not flexible enough to support it. Instead, you can
		3343	override their poll function. The drawback with this solution is that the
		3344	main loop is now no longer controllable by \s-1EV.\s0 The \f(CW\*(C`Glib::EV\*(C'\fR module uses
		3345	this approach, effectively embedding \s-1EV\s0 as a client into the horrible
		3346	libglib event loop.
		3347	.PP
		3348	.Vb 4
		3349	\& static gint
		3350	\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		3351	\& {
		3352	\& int got_events = 0;
		3353	\&
		3354	\& for (n = 0; n < nfds; ++n)
		3355	\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		3356	\&
		3357	\& if (timeout >= 0)
		3358	\& // create/start timer
		3359	\&
		3360	\& // poll
		3361	\& ev_run (EV_A_ 0);
		3362	\&
		3363	\& // stop timer again
		3364	\& if (timeout >= 0)
		3365	\& ev_timer_stop (EV_A_ &to);
		3366	\&
		3367	\& // stop io watchers again \- their callbacks should have set
		3368	\& for (n = 0; n < nfds; ++n)
		3369	\& ev_io_stop (EV_A_ iow [n]);
		3370	\&
		3371	\& return got_events;
		3372	\& }
		3373	.Ve
1274	.ie n .Sh """ev_embed"" \- when one backend isn't enough"	3374	.ie n .SS """ev_embed"" \- when one backend isn't enough..."
1275	.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough"	3375	.el .SS "\f(CWev_embed\fP \- when one backend isn't enough..."
1276	.IX Subsection "ev_embed - when one backend isn't enough"	3376	.IX Subsection "ev_embed - when one backend isn't enough..."
1277	This is a rather advanced watcher type that lets you embed one event loop	3377	This is a rather advanced watcher type that lets you embed one event loop
1278	into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded	3378	into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1279	loop, other types of watchers might be handled in a delayed or incorrect	3379	loop, other types of watchers might be handled in a delayed or incorrect
1280	fashion and must not be used).	3380	fashion and must not be used).
1281	.PP	3381	.PP
…		…
1283	prioritise I/O.	3383	prioritise I/O.
1284	.PP	3384	.PP
1285	As an example for a bug workaround, the kqueue backend might only support	3385	As an example for a bug workaround, the kqueue backend might only support
1286	sockets on some platform, so it is unusable as generic backend, but you	3386	sockets on some platform, so it is unusable as generic backend, but you
1287	still want to make use of it because you have many sockets and it scales	3387	still want to make use of it because you have many sockets and it scales
1288	so nicely. In this case, you would create a kqueue-based loop and embed it	3388	so nicely. In this case, you would create a kqueue-based loop and embed
1289	into your default loop (which might use e.g. poll). Overall operation will	3389	it into your default loop (which might use e.g. poll). Overall operation
1290	be a bit slower because first libev has to poll and then call kevent, but	3390	will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then
1291	at least you can use both at what they are best.	3391	\&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are
		3392	best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :)
1292	.PP	3393	.PP
1293	As for prioritising I/O: rarely you have the case where some fds have	3394	As for prioritising I/O: under rare circumstances you have the case where
1294	to be watched and handled very quickly (with low latency), and even	3395	some fds have to be watched and handled very quickly (with low latency),
1295	priorities and idle watchers might have too much overhead. In this case	3396	and even priorities and idle watchers might have too much overhead. In
1296	you would put all the high priority stuff in one loop and all the rest in	3397	this case you would put all the high priority stuff in one loop and all
1297	a second one, and embed the second one in the first.	3398	the rest in a second one, and embed the second one in the first.
1298	.PP	3399	.PP
1299	As long as the watcher is active, the callback will be invoked every time	3400	As long as the watcher is active, the callback will be invoked every
1300	there might be events pending in the embedded loop. The callback must then	3401	time there might be events pending in the embedded loop. The callback
1301	call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke	3402	must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single
1302	their callbacks (you could also start an idle watcher to give the embedded	3403	sweep and invoke their callbacks (the callback doesn't need to invoke the
1303	loop strictly lower priority for example). You can also set the callback	3404	\&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher
1304	to \f(CW0\fR, in which case the embed watcher will automatically execute the	3405	to give the embedded loop strictly lower priority for example).
1305	embedded loop sweep.
1306	.PP	3406	.PP
1307	As long as the watcher is started it will automatically handle events. The	3407	You can also set the callback to \f(CW0\fR, in which case the embed watcher
1308	callback will be invoked whenever some events have been handled. You can	3408	will automatically execute the embedded loop sweep whenever necessary.
1309	set the callback to \f(CW0\fR to avoid having to specify one if you are not
1310	interested in that.
1311	.PP	3409	.PP
1312	Also, there have not currently been made special provisions for forking:	3410	Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher
1313	when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,	3411	is active, i.e., the embedded loop will automatically be forked when the
1314	but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers	3412	embedding loop forks. In other cases, the user is responsible for calling
1315	yourself.	3413	\&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop.
1316	.PP	3414	.PP
1317	Unfortunately, not all backends are embeddable, only the ones returned by	3415	Unfortunately, not all backends are embeddable: only the ones returned by
1318	\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any	3416	\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1319	portable one.	3417	portable one.
1320	.PP	3418	.PP
1321	So when you want to use this feature you will always have to be prepared	3419	So when you want to use this feature you will always have to be prepared
1322	that you cannot get an embeddable loop. The recommended way to get around	3420	that you cannot get an embeddable loop. The recommended way to get around
1323	this is to have a separate variables for your embeddable loop, try to	3421	this is to have a separate variables for your embeddable loop, try to
1324	create it, and if that fails, use the normal loop for everything:	3422	create it, and if that fails, use the normal loop for everything.
1325	.PP	3423	.PP
1326	.Vb 3	3424	\fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR
1327	\& struct ev_loop *loop_hi = ev_default_init (0);	3425	.IX Subsection "ev_embed and fork"
1328	\& struct ev_loop *loop_lo = 0;
1329	\& struct ev_embed embed;
1330	.Ve
1331	.PP	3426	.PP
1332	.Vb 5	3427	While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will
1333	\& // see if there is a chance of getting one that works	3428	automatically be applied to the embedded loop as well, so no special
1334	\& // (remember that a flags value of 0 means autodetection)	3429	fork handling is required in that case. When the watcher is not running,
1335	\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3430	however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR
1336	\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3431	as applicable.
1337	\& : 0;
1338	.Ve
1339	.PP	3432	.PP
1340	.Vb 8	3433	\fIWatcher-Specific Functions and Data Members\fR
1341	\& // if we got one, then embed it, otherwise default to loop_hi	3434	.IX Subsection "Watcher-Specific Functions and Data Members"
1342	\& if (loop_lo)
1343	\& {
1344	\& ev_embed_init (&embed, 0, loop_lo);
1345	\& ev_embed_start (loop_hi, &embed);
1346	\& }
1347	\& else
1348	\& loop_lo = loop_hi;
1349	.Ve
1350	.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4	3435	.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1351	.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"	3436	.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1352	.PD 0	3437	.PD 0
1353	.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4	3438	.IP "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)" 4
1354	.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"	3439	.IX Item "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)"
1355	.PD	3440	.PD
1356	Configures the watcher to embed the given loop, which must be	3441	Configures the watcher to embed the given loop, which must be
1357	embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be	3442	embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1358	invoked automatically, otherwise it is the responsibility of the callback	3443	invoked automatically, otherwise it is the responsibility of the callback
1359	to invoke it (it will continue to be called until the sweep has been done,	3444	to invoke it (it will continue to be called until the sweep has been done,
1360	if you do not want thta, you need to temporarily stop the embed watcher).	3445	if you do not want that, you need to temporarily stop the embed watcher).
1361	.IP "ev_embed_sweep (loop, ev_embed *)" 4	3446	.IP "ev_embed_sweep (loop, ev_embed *)" 4
1362	.IX Item "ev_embed_sweep (loop, ev_embed *)"	3447	.IX Item "ev_embed_sweep (loop, ev_embed *)"
1363	Make a single, non-blocking sweep over the embedded loop. This works	3448	Make a single, non-blocking sweep over the embedded loop. This works
1364	similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most	3449	similarly to \f(CW\*(C`ev_run (embedded_loop, EVRUN_NOWAIT)\*(C'\fR, but in the most
1365	apropriate way for embedded loops.	3450	appropriate way for embedded loops.
		3451	.IP "struct ev_loop *other [read\-only]" 4
		3452	.IX Item "struct ev_loop *other [read-only]"
		3453	The embedded event loop.
		3454	.PP
		3455	\fIExamples\fR
		3456	.IX Subsection "Examples"
		3457	.PP
		3458	Example: Try to get an embeddable event loop and embed it into the default
		3459	event loop. If that is not possible, use the default loop. The default
		3460	loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable loop is stored in
		3461	\&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the case no embeddable loop can be
		3462	used).
		3463	.PP
		3464	.Vb 3
		3465	\& struct ev_loop *loop_hi = ev_default_init (0);
		3466	\& struct ev_loop *loop_lo = 0;
		3467	\& ev_embed embed;
		3468	\&
		3469	\& // see if there is a chance of getting one that works
		3470	\& // (remember that a flags value of 0 means autodetection)
		3471	\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		3472	\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		3473	\& : 0;
		3474	\&
		3475	\& // if we got one, then embed it, otherwise default to loop_hi
		3476	\& if (loop_lo)
		3477	\& {
		3478	\& ev_embed_init (&embed, 0, loop_lo);
		3479	\& ev_embed_start (loop_hi, &embed);
		3480	\& }
		3481	\& else
		3482	\& loop_lo = loop_hi;
		3483	.Ve
		3484	.PP
		3485	Example: Check if kqueue is available but not recommended and create
		3486	a kqueue backend for use with sockets (which usually work with any
		3487	kqueue implementation). Store the kqueue/socket\-only event loop in
		3488	\&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too).
		3489	.PP
		3490	.Vb 3
		3491	\& struct ev_loop *loop = ev_default_init (0);
		3492	\& struct ev_loop *loop_socket = 0;
		3493	\& ev_embed embed;
		3494	\&
		3495	\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		3496	\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		3497	\& {
		3498	\& ev_embed_init (&embed, 0, loop_socket);
		3499	\& ev_embed_start (loop, &embed);
		3500	\& }
		3501	\&
		3502	\& if (!loop_socket)
		3503	\& loop_socket = loop;
		3504	\&
		3505	\& // now use loop_socket for all sockets, and loop for everything else
		3506	.Ve
		3507	.ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork"
		3508	.el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
		3509	.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
		3510	Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
		3511	whoever is a good citizen cared to tell libev about it by calling
		3512	\&\f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the event loop blocks next
		3513	and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, and only in the child
		3514	after the fork. If whoever good citizen calling \f(CW\*(C`ev_default_fork\*(C'\fR cheats
		3515	and calls it in the wrong process, the fork handlers will be invoked, too,
		3516	of course.
		3517	.PP
		3518	\fIThe special problem of life after fork \- how is it possible?\fR
		3519	.IX Subsection "The special problem of life after fork - how is it possible?"
		3520	.PP
		3521	Most uses of \f(CW\*(C`fork ()\*(C'\fR consist of forking, then some simple calls to set
		3522	up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This
		3523	sequence should be handled by libev without any problems.
		3524	.PP
		3525	This changes when the application actually wants to do event handling
		3526	in the child, or both parent in child, in effect \*(L"continuing\*(R" after the
		3527	fork.
		3528	.PP
		3529	The default mode of operation (for libev, with application help to detect
		3530	forks) is to duplicate all the state in the child, as would be expected
		3531	when \fIeither\fR the parent \fIor\fR the child process continues.
		3532	.PP
		3533	When both processes want to continue using libev, then this is usually the
		3534	wrong result. In that case, usually one process (typically the parent) is
		3535	supposed to continue with all watchers in place as before, while the other
		3536	process typically wants to start fresh, i.e. without any active watchers.
		3537	.PP
		3538	The cleanest and most efficient way to achieve that with libev is to
		3539	simply create a new event loop, which of course will be \*(L"empty\*(R", and
		3540	use that for new watchers. This has the advantage of not touching more
		3541	memory than necessary, and thus avoiding the copy-on-write, and the
		3542	disadvantage of having to use multiple event loops (which do not support
		3543	signal watchers).
		3544	.PP
		3545	When this is not possible, or you want to use the default loop for
		3546	other reasons, then in the process that wants to start \*(L"fresh\*(R", call
		3547	\&\f(CW\*(C`ev_loop_destroy (EV_DEFAULT)\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR.
		3548	Destroying the default loop will \*(L"orphan\*(R" (not stop) all registered
		3549	watchers, so you have to be careful not to execute code that modifies
		3550	those watchers. Note also that in that case, you have to re-register any
		3551	signal watchers.
		3552	.PP
		3553	\fIWatcher-Specific Functions and Data Members\fR
		3554	.IX Subsection "Watcher-Specific Functions and Data Members"
		3555	.IP "ev_fork_init (ev_fork *, callback)" 4
		3556	.IX Item "ev_fork_init (ev_fork *, callback)"
		3557	Initialises and configures the fork watcher \- it has no parameters of any
		3558	kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
		3559	really.
		3560	.ie n .SS """ev_cleanup"" \- even the best things end"
		3561	.el .SS "\f(CWev_cleanup\fP \- even the best things end"
		3562	.IX Subsection "ev_cleanup - even the best things end"
		3563	Cleanup watchers are called just before the event loop is being destroyed
		3564	by a call to \f(CW\*(C`ev_loop_destroy\*(C'\fR.
		3565	.PP
		3566	While there is no guarantee that the event loop gets destroyed, cleanup
		3567	watchers provide a convenient method to install cleanup hooks for your
		3568	program, worker threads and so on \- you just to make sure to destroy the
		3569	loop when you want them to be invoked.
		3570	.PP
		3571	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3572	all other watchers, they do not keep a reference to the event loop (which
		3573	makes a lot of sense if you think about it). Like all other watchers, you
		3574	can call libev functions in the callback, except \f(CW\*(C`ev_cleanup_start\*(C'\fR.
		3575	.PP
		3576	\fIWatcher-Specific Functions and Data Members\fR
		3577	.IX Subsection "Watcher-Specific Functions and Data Members"
		3578	.IP "ev_cleanup_init (ev_cleanup *, callback)" 4
		3579	.IX Item "ev_cleanup_init (ev_cleanup *, callback)"
		3580	Initialises and configures the cleanup watcher \- it has no parameters of
		3581	any kind. There is a \f(CW\*(C`ev_cleanup_set\*(C'\fR macro, but using it is utterly
		3582	pointless, I assure you.
		3583	.PP
		3584	Example: Register an atexit handler to destroy the default loop, so any
		3585	cleanup functions are called.
		3586	.PP
		3587	.Vb 5
		3588	\& static void
		3589	\& program_exits (void)
		3590	\& {
		3591	\& ev_loop_destroy (EV_DEFAULT_UC);
		3592	\& }
		3593	\&
		3594	\& ...
		3595	\& atexit (program_exits);
		3596	.Ve
		3597	.ie n .SS """ev_async"" \- how to wake up an event loop"
		3598	.el .SS "\f(CWev_async\fP \- how to wake up an event loop"
		3599	.IX Subsection "ev_async - how to wake up an event loop"
		3600	In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other
		3601	asynchronous sources such as signal handlers (as opposed to multiple event
		3602	loops \- those are of course safe to use in different threads).
		3603	.PP
		3604	Sometimes, however, you need to wake up an event loop you do not control,
		3605	for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR
		3606	watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you can signal
		3607	it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe.
		3608	.PP
		3609	This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals,
		3610	too, are asynchronous in nature, and signals, too, will be compressed
		3611	(i.e. the number of callback invocations may be less than the number of
		3612	\&\f(CW\*(C`ev_async_send\*(C'\fR calls). In fact, you could use signal watchers as a kind
		3613	of \*(L"global async watchers\*(R" by using a watcher on an otherwise unused
		3614	signal, and \f(CW\*(C`ev_feed_signal\*(C'\fR to signal this watcher from another thread,
		3615	even without knowing which loop owns the signal.
		3616	.PP
		3617	\fIQueueing\fR
		3618	.IX Subsection "Queueing"
		3619	.PP
		3620	\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason
		3621	is that the author does not know of a simple (or any) algorithm for a
		3622	multiple-writer-single-reader queue that works in all cases and doesn't
		3623	need elaborate support such as pthreads or unportable memory access
		3624	semantics.
		3625	.PP
		3626	That means that if you want to queue data, you have to provide your own
		3627	queue. But at least I can tell you how to implement locking around your
		3628	queue:
		3629	.IP "queueing from a signal handler context" 4
		3630	.IX Item "queueing from a signal handler context"
		3631	To implement race-free queueing, you simply add to the queue in the signal
		3632	handler but you block the signal handler in the watcher callback. Here is
		3633	an example that does that for some fictitious \s-1SIGUSR1\s0 handler:
		3634	.Sp
		3635	.Vb 1
		3636	\& static ev_async mysig;
		3637	\&
		3638	\& static void
		3639	\& sigusr1_handler (void)
		3640	\& {
		3641	\& sometype data;
		3642	\&
		3643	\& // no locking etc.
		3644	\& queue_put (data);
		3645	\& ev_async_send (EV_DEFAULT_ &mysig);
		3646	\& }
		3647	\&
		3648	\& static void
		3649	\& mysig_cb (EV_P_ ev_async *w, int revents)
		3650	\& {
		3651	\& sometype data;
		3652	\& sigset_t block, prev;
		3653	\&
		3654	\& sigemptyset (&block);
		3655	\& sigaddset (&block, SIGUSR1);
		3656	\& sigprocmask (SIG_BLOCK, &block, &prev);
		3657	\&
		3658	\& while (queue_get (&data))
		3659	\& process (data);
		3660	\&
		3661	\& if (sigismember (&prev, SIGUSR1)
		3662	\& sigprocmask (SIG_UNBLOCK, &block, 0);
		3663	\& }
		3664	.Ve
		3665	.Sp
		3666	(Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR
		3667	instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it
		3668	either...).
		3669	.IP "queueing from a thread context" 4
		3670	.IX Item "queueing from a thread context"
		3671	The strategy for threads is different, as you cannot (easily) block
		3672	threads but you can easily preempt them, so to queue safely you need to
		3673	employ a traditional mutex lock, such as in this pthread example:
		3674	.Sp
		3675	.Vb 2
		3676	\& static ev_async mysig;
		3677	\& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		3678	\&
		3679	\& static void
		3680	\& otherthread (void)
		3681	\& {
		3682	\& // only need to lock the actual queueing operation
		3683	\& pthread_mutex_lock (&mymutex);
		3684	\& queue_put (data);
		3685	\& pthread_mutex_unlock (&mymutex);
		3686	\&
		3687	\& ev_async_send (EV_DEFAULT_ &mysig);
		3688	\& }
		3689	\&
		3690	\& static void
		3691	\& mysig_cb (EV_P_ ev_async *w, int revents)
		3692	\& {
		3693	\& pthread_mutex_lock (&mymutex);
		3694	\&
		3695	\& while (queue_get (&data))
		3696	\& process (data);
		3697	\&
		3698	\& pthread_mutex_unlock (&mymutex);
		3699	\& }
		3700	.Ve
		3701	.PP
		3702	\fIWatcher-Specific Functions and Data Members\fR
		3703	.IX Subsection "Watcher-Specific Functions and Data Members"
		3704	.IP "ev_async_init (ev_async *, callback)" 4
		3705	.IX Item "ev_async_init (ev_async *, callback)"
		3706	Initialises and configures the async watcher \- it has no parameters of any
		3707	kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless,
		3708	trust me.
		3709	.IP "ev_async_send (loop, ev_async *)" 4
		3710	.IX Item "ev_async_send (loop, ev_async *)"
		3711	Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds
		3712	an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop, and instantly
		3713	returns.
		3714	.Sp
		3715	Unlike \f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads,
		3716	signal or similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the
		3717	embedding section below on what exactly this means).
		3718	.Sp
		3719	Note that, as with other watchers in libev, multiple events might get
		3720	compressed into a single callback invocation (another way to look at
		3721	this is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered: they are set on
		3722	\&\f(CW\*(C`ev_async_send\*(C'\fR, reset when the event loop detects that).
		3723	.Sp
		3724	This call incurs the overhead of at most one extra system call per event
		3725	loop iteration, if the event loop is blocked, and no syscall at all if
		3726	the event loop (or your program) is processing events. That means that
		3727	repeated calls are basically free (there is no need to avoid calls for
		3728	performance reasons) and that the overhead becomes smaller (typically
		3729	zero) under load.
		3730	.IP "bool = ev_async_pending (ev_async *)" 4
		3731	.IX Item "bool = ev_async_pending (ev_async *)"
		3732	Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the
		3733	watcher but the event has not yet been processed (or even noted) by the
		3734	event loop.
		3735	.Sp
		3736	\&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When
		3737	the loop iterates next and checks for the watcher to have become active,
		3738	it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very
		3739	quickly check whether invoking the loop might be a good idea.
		3740	.Sp
		3741	Not that this does \fInot\fR check whether the watcher itself is pending,
		3742	only whether it has been requested to make this watcher pending: there
		3743	is a time window between the event loop checking and resetting the async
		3744	notification, and the callback being invoked.
1366	.SH "OTHER FUNCTIONS"	3745	.SH "OTHER FUNCTIONS"
1367	.IX Header "OTHER FUNCTIONS"	3746	.IX Header "OTHER FUNCTIONS"
1368	There are some other functions of possible interest. Described. Here. Now.	3747	There are some other functions of possible interest. Described. Here. Now.
1369	.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4	3748	.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)" 4
1370	.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"	3749	.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)"
1371	This function combines a simple timer and an I/O watcher, calls your	3750	This function combines a simple timer and an I/O watcher, calls your
1372	callback on whichever event happens first and automatically stop both	3751	callback on whichever event happens first and automatically stops both
1373	watchers. This is useful if you want to wait for a single event on an fd	3752	watchers. This is useful if you want to wait for a single event on an fd
1374	or timeout without having to allocate/configure/start/stop/free one or	3753	or timeout without having to allocate/configure/start/stop/free one or
1375	more watchers yourself.	3754	more watchers yourself.
1376	.Sp	3755	.Sp
1377	If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events	3756	If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the
1378	is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and	3757	\&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for
1379	\&\f(CW\*(C`events\*(C'\fR set will be craeted and started.	3758	the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started.
1380	.Sp	3759	.Sp
1381	If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be	3760	If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be
1382	started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and	3761	started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and
1383	repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of	3762	repeat = 0) will be started. \f(CW0\fR is a valid timeout.
1384	dubious value.
1385	.Sp	3763	.Sp
1386	The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets	3764	The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and is
1387	passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of	3765	passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
1388	\&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR	3766	\&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMER\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR
1389	value passed to \f(CW\*(C`ev_once\*(C'\fR:	3767	value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR
		3768	a timeout and an io event at the same time \- you probably should give io
		3769	events precedence.
		3770	.Sp
		3771	Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO.\s0
1390	.Sp	3772	.Sp
1391	.Vb 7	3773	.Vb 7
1392	\& static void stdin_ready (int revents, void *arg)	3774	\& static void stdin_ready (int revents, void *arg)
		3775	\& {
		3776	\& if (revents & EV_READ)
		3777	\& /* stdin might have data for us, joy! */;
		3778	\& else if (revents & EV_TIMER)
		3779	\& /* doh, nothing entered */;
		3780	\& }
		3781	\&
		3782	\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
		3783	.Ve
		3784	.IP "ev_feed_fd_event (loop, int fd, int revents)" 4
		3785	.IX Item "ev_feed_fd_event (loop, int fd, int revents)"
		3786	Feed an event on the given fd, as if a file descriptor backend detected
		3787	the given events.
		3788	.IP "ev_feed_signal_event (loop, int signum)" 4
		3789	.IX Item "ev_feed_signal_event (loop, int signum)"
		3790	Feed an event as if the given signal occurred. See also \f(CW\*(C`ev_feed_signal\*(C'\fR,
		3791	which is async-safe.
		3792	.SH "COMMON OR USEFUL IDIOMS (OR BOTH)"
		3793	.IX Header "COMMON OR USEFUL IDIOMS (OR BOTH)"
		3794	This section explains some common idioms that are not immediately
		3795	obvious. Note that examples are sprinkled over the whole manual, and this
		3796	section only contains stuff that wouldn't fit anywhere else.
		3797	.SS "\s-1ASSOCIATING CUSTOM DATA WITH A WATCHER\s0"
		3798	.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
		3799	Each watcher has, by default, a \f(CW\*(C`void *data\*(C'\fR member that you can read
		3800	or modify at any time: libev will completely ignore it. This can be used
		3801	to associate arbitrary data with your watcher. If you need more data and
		3802	don't want to allocate memory separately and store a pointer to it in that
		3803	data member, you can also \*(L"subclass\*(R" the watcher type and provide your own
		3804	data:
		3805	.PP
		3806	.Vb 7
		3807	\& struct my_io
		3808	\& {
		3809	\& ev_io io;
		3810	\& int otherfd;
		3811	\& void *somedata;
		3812	\& struct whatever *mostinteresting;
		3813	\& };
		3814	\&
		3815	\& ...
		3816	\& struct my_io w;
		3817	\& ev_io_init (&w.io, my_cb, fd, EV_READ);
		3818	.Ve
		3819	.PP
		3820	And since your callback will be called with a pointer to the watcher, you
		3821	can cast it back to your own type:
		3822	.PP
		3823	.Vb 5
		3824	\& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3825	\& {
		3826	\& struct my_io *w = (struct my_io *)w_;
		3827	\& ...
		3828	\& }
		3829	.Ve
		3830	.PP
		3831	More interesting and less C\-conformant ways of casting your callback
		3832	function type instead have been omitted.
		3833	.SS "\s-1BUILDING YOUR OWN COMPOSITE WATCHERS\s0"
		3834	.IX Subsection "BUILDING YOUR OWN COMPOSITE WATCHERS"
		3835	Another common scenario is to use some data structure with multiple
		3836	embedded watchers, in effect creating your own watcher that combines
		3837	multiple libev event sources into one \*(L"super-watcher\*(R":
		3838	.PP
		3839	.Vb 6
		3840	\& struct my_biggy
		3841	\& {
		3842	\& int some_data;
		3843	\& ev_timer t1;
		3844	\& ev_timer t2;
		3845	\& }
		3846	.Ve
		3847	.PP
		3848	In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more
		3849	complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct in
		3850	the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies or \*(C+ coders), or you need
		3851	to use some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for
		3852	real programmers):
		3853	.PP
		3854	.Vb 1
		3855	\& #include <stddef.h>
		3856	\&
		3857	\& static void
		3858	\& t1_cb (EV_P_ ev_timer *w, int revents)
		3859	\& {
		3860	\& struct my_biggy big = (struct my_biggy *)
		3861	\& (((char *)w) \- offsetof (struct my_biggy, t1));
		3862	\& }
		3863	\&
		3864	\& static void
		3865	\& t2_cb (EV_P_ ev_timer *w, int revents)
		3866	\& {
		3867	\& struct my_biggy big = (struct my_biggy *)
		3868	\& (((char *)w) \- offsetof (struct my_biggy, t2));
		3869	\& }
		3870	.Ve
		3871	.SS "\s-1AVOIDING FINISHING BEFORE RETURNING\s0"
		3872	.IX Subsection "AVOIDING FINISHING BEFORE RETURNING"
		3873	Often you have structures like this in event-based programs:
		3874	.PP
		3875	.Vb 4
		3876	\& callback ()
1393	\& {	3877	\& {
1394	\& if (revents & EV_TIMEOUT)	3878	\& free (request);
1395	\& /* doh, nothing entered */;
1396	\& else if (revents & EV_READ)
1397	\& /* stdin might have data for us, joy! */;
1398	\& }	3879	\& }
		3880	\&
		3881	\& request = start_new_request (..., callback);
1399	.Ve	3882	.Ve
1400	.Sp	3883	.PP
		3884	The intent is to start some \*(L"lengthy\*(R" operation. The \f(CW\*(C`request\*(C'\fR could be
		3885	used to cancel the operation, or do other things with it.
		3886	.PP
		3887	It's not uncommon to have code paths in \f(CW\*(C`start_new_request\*(C'\fR that
		3888	immediately invoke the callback, for example, to report errors. Or you add
		3889	some caching layer that finds that it can skip the lengthy aspects of the
		3890	operation and simply invoke the callback with the result.
		3891	.PP
		3892	The problem here is that this will happen \fIbefore\fR \f(CW\*(C`start_new_request\*(C'\fR
		3893	has returned, so \f(CW\*(C`request\*(C'\fR is not set.
		3894	.PP
		3895	Even if you pass the request by some safer means to the callback, you
		3896	might want to do something to the request after starting it, such as
		3897	canceling it, which probably isn't working so well when the callback has
		3898	already been invoked.
		3899	.PP
		3900	A common way around all these issues is to make sure that
		3901	\&\f(CW\*(C`start_new_request\*(C'\fR \fIalways\fR returns before the callback is invoked. If
		3902	\&\f(CW\*(C`start_new_request\*(C'\fR immediately knows the result, it can artificially
		3903	delay invoking the callback by using a \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`idle\*(C'\fR watcher for
		3904	example, or more sneakily, by reusing an existing (stopped) watcher and
		3905	pushing it into the pending queue:
		3906	.PP
1401	.Vb 1	3907	.Vb 2
1402	\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3908	\& ev_set_cb (watcher, callback);
		3909	\& ev_feed_event (EV_A_ watcher, 0);
1403	.Ve	3910	.Ve
1404	.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4	3911	.PP
1405	.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"	3912	This way, \f(CW\*(C`start_new_request\*(C'\fR can safely return before the callback is
1406	Feeds the given event set into the event loop, as if the specified event	3913	invoked, while not delaying callback invocation too much.
1407	had happened for the specified watcher (which must be a pointer to an	3914	.SS "\s-1MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS\s0"
1408	initialised but not necessarily started event watcher).	3915	.IX Subsection "MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS"
1409	.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4	3916	Often (especially in \s-1GUI\s0 toolkits) there are places where you have
1410	.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"	3917	\&\fImodal\fR interaction, which is most easily implemented by recursively
1411	Feed an event on the given fd, as if a file descriptor backend detected	3918	invoking \f(CW\*(C`ev_run\*(C'\fR.
1412	the given events it.	3919	.PP
1413	.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4	3920	This brings the problem of exiting \- a callback might want to finish the
1414	.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"	3921	main \f(CW\*(C`ev_run\*(C'\fR call, but not the nested one (e.g. user clicked \*(L"Quit\*(R", but
1415	Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default	3922	a modal \*(L"Are you sure?\*(R" dialog is still waiting), or just the nested one
1416	loop!).	3923	and not the main one (e.g. user clocked \*(L"Ok\*(R" in a modal dialog), or some
		3924	other combination: In these cases, a simple \f(CW\*(C`ev_break\*(C'\fR will not work.
		3925	.PP
		3926	The solution is to maintain \*(L"break this loop\*(R" variable for each \f(CW\*(C`ev_run\*(C'\fR
		3927	invocation, and use a loop around \f(CW\*(C`ev_run\*(C'\fR until the condition is
		3928	triggered, using \f(CW\*(C`EVRUN_ONCE\*(C'\fR:
		3929	.PP
		3930	.Vb 2
		3931	\& // main loop
		3932	\& int exit_main_loop = 0;
		3933	\&
		3934	\& while (!exit_main_loop)
		3935	\& ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3936	\&
		3937	\& // in a modal watcher
		3938	\& int exit_nested_loop = 0;
		3939	\&
		3940	\& while (!exit_nested_loop)
		3941	\& ev_run (EV_A_ EVRUN_ONCE);
		3942	.Ve
		3943	.PP
		3944	To exit from any of these loops, just set the corresponding exit variable:
		3945	.PP
		3946	.Vb 2
		3947	\& // exit modal loop
		3948	\& exit_nested_loop = 1;
		3949	\&
		3950	\& // exit main program, after modal loop is finished
		3951	\& exit_main_loop = 1;
		3952	\&
		3953	\& // exit both
		3954	\& exit_main_loop = exit_nested_loop = 1;
		3955	.Ve
		3956	.SS "\s-1THREAD LOCKING EXAMPLE\s0"
		3957	.IX Subsection "THREAD LOCKING EXAMPLE"
		3958	Here is a fictitious example of how to run an event loop in a different
		3959	thread from where callbacks are being invoked and watchers are
		3960	created/added/removed.
		3961	.PP
		3962	For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module,
		3963	which uses exactly this technique (which is suited for many high-level
		3964	languages).
		3965	.PP
		3966	The example uses a pthread mutex to protect the loop data, a condition
		3967	variable to wait for callback invocations, an async watcher to notify the
		3968	event loop thread and an unspecified mechanism to wake up the main thread.
		3969	.PP
		3970	First, you need to associate some data with the event loop:
		3971	.PP
		3972	.Vb 6
		3973	\& typedef struct {
		3974	\& mutex_t lock; /* global loop lock */
		3975	\& ev_async async_w;
		3976	\& thread_t tid;
		3977	\& cond_t invoke_cv;
		3978	\& } userdata;
		3979	\&
		3980	\& void prepare_loop (EV_P)
		3981	\& {
		3982	\& // for simplicity, we use a static userdata struct.
		3983	\& static userdata u;
		3984	\&
		3985	\& ev_async_init (&u\->async_w, async_cb);
		3986	\& ev_async_start (EV_A_ &u\->async_w);
		3987	\&
		3988	\& pthread_mutex_init (&u\->lock, 0);
		3989	\& pthread_cond_init (&u\->invoke_cv, 0);
		3990	\&
		3991	\& // now associate this with the loop
		3992	\& ev_set_userdata (EV_A_ u);
		3993	\& ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3994	\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3995	\&
		3996	\& // then create the thread running ev_run
		3997	\& pthread_create (&u\->tid, 0, l_run, EV_A);
		3998	\& }
		3999	.Ve
		4000	.PP
		4001	The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
		4002	solely to wake up the event loop so it takes notice of any new watchers
		4003	that might have been added:
		4004	.PP
		4005	.Vb 5
		4006	\& static void
		4007	\& async_cb (EV_P_ ev_async *w, int revents)
		4008	\& {
		4009	\& // just used for the side effects
		4010	\& }
		4011	.Ve
		4012	.PP
		4013	The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex
		4014	protecting the loop data, respectively.
		4015	.PP
		4016	.Vb 6
		4017	\& static void
		4018	\& l_release (EV_P)
		4019	\& {
		4020	\& userdata *u = ev_userdata (EV_A);
		4021	\& pthread_mutex_unlock (&u\->lock);
		4022	\& }
		4023	\&
		4024	\& static void
		4025	\& l_acquire (EV_P)
		4026	\& {
		4027	\& userdata *u = ev_userdata (EV_A);
		4028	\& pthread_mutex_lock (&u\->lock);
		4029	\& }
		4030	.Ve
		4031	.PP
		4032	The event loop thread first acquires the mutex, and then jumps straight
		4033	into \f(CW\*(C`ev_run\*(C'\fR:
		4034	.PP
		4035	.Vb 4
		4036	\& void *
		4037	\& l_run (void *thr_arg)
		4038	\& {
		4039	\& struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4040	\&
		4041	\& l_acquire (EV_A);
		4042	\& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4043	\& ev_run (EV_A_ 0);
		4044	\& l_release (EV_A);
		4045	\&
		4046	\& return 0;
		4047	\& }
		4048	.Ve
		4049	.PP
		4050	Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will
		4051	signal the main thread via some unspecified mechanism (signals? pipe
		4052	writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers
		4053	have been called (in a while loop because a) spurious wakeups are possible
		4054	and b) skipping inter-thread-communication when there are no pending
		4055	watchers is very beneficial):
		4056	.PP
		4057	.Vb 4
		4058	\& static void
		4059	\& l_invoke (EV_P)
		4060	\& {
		4061	\& userdata *u = ev_userdata (EV_A);
		4062	\&
		4063	\& while (ev_pending_count (EV_A))
		4064	\& {
		4065	\& wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4066	\& pthread_cond_wait (&u\->invoke_cv, &u\->lock);
		4067	\& }
		4068	\& }
		4069	.Ve
		4070	.PP
		4071	Now, whenever the main thread gets told to invoke pending watchers, it
		4072	will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop
		4073	thread to continue:
		4074	.PP
		4075	.Vb 4
		4076	\& static void
		4077	\& real_invoke_pending (EV_P)
		4078	\& {
		4079	\& userdata *u = ev_userdata (EV_A);
		4080	\&
		4081	\& pthread_mutex_lock (&u\->lock);
		4082	\& ev_invoke_pending (EV_A);
		4083	\& pthread_cond_signal (&u\->invoke_cv);
		4084	\& pthread_mutex_unlock (&u\->lock);
		4085	\& }
		4086	.Ve
		4087	.PP
		4088	Whenever you want to start/stop a watcher or do other modifications to an
		4089	event loop, you will now have to lock:
		4090	.PP
		4091	.Vb 2
		4092	\& ev_timer timeout_watcher;
		4093	\& userdata *u = ev_userdata (EV_A);
		4094	\&
		4095	\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4096	\&
		4097	\& pthread_mutex_lock (&u\->lock);
		4098	\& ev_timer_start (EV_A_ &timeout_watcher);
		4099	\& ev_async_send (EV_A_ &u\->async_w);
		4100	\& pthread_mutex_unlock (&u\->lock);
		4101	.Ve
		4102	.PP
		4103	Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise
		4104	an event loop currently blocking in the kernel will have no knowledge
		4105	about the newly added timer. By waking up the loop it will pick up any new
		4106	watchers in the next event loop iteration.
		4107	.SS "\s-1THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS\s0"
		4108	.IX Subsection "THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS"
		4109	While the overhead of a callback that e.g. schedules a thread is small, it
		4110	is still an overhead. If you embed libev, and your main usage is with some
		4111	kind of threads or coroutines, you might want to customise libev so that
		4112	doesn't need callbacks anymore.
		4113	.PP
		4114	Imagine you have coroutines that you can switch to using a function
		4115	\&\f(CW\*(C`switch_to (coro)\*(C'\fR, that libev runs in a coroutine called \f(CW\*(C`libev_coro\*(C'\fR
		4116	and that due to some magic, the currently active coroutine is stored in a
		4117	global called \f(CW\*(C`current_coro\*(C'\fR. Then you can build your own \*(L"wait for libev
		4118	event\*(R" primitive by changing \f(CW\*(C`EV_CB_DECLARE\*(C'\fR and \f(CW\*(C`EV_CB_INVOKE\*(C'\fR (note
		4119	the differing \f(CW\*(C`;\*(C'\fR conventions):
		4120	.PP
		4121	.Vb 2
		4122	\& #define EV_CB_DECLARE(type) struct my_coro *cb;
		4123	\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
		4124	.Ve
		4125	.PP
		4126	That means instead of having a C callback function, you store the
		4127	coroutine to switch to in each watcher, and instead of having libev call
		4128	your callback, you instead have it switch to that coroutine.
		4129	.PP
		4130	A coroutine might now wait for an event with a function called
		4131	\&\f(CW\*(C`wait_for_event\*(C'\fR. (the watcher needs to be started, as always, but it doesn't
		4132	matter when, or whether the watcher is active or not when this function is
		4133	called):
		4134	.PP
		4135	.Vb 6
		4136	\& void
		4137	\& wait_for_event (ev_watcher *w)
		4138	\& {
		4139	\& ev_set_cb (w, current_coro);
		4140	\& switch_to (libev_coro);
		4141	\& }
		4142	.Ve
		4143	.PP
		4144	That basically suspends the coroutine inside \f(CW\*(C`wait_for_event\*(C'\fR and
		4145	continues the libev coroutine, which, when appropriate, switches back to
		4146	this or any other coroutine.
		4147	.PP
		4148	You can do similar tricks if you have, say, threads with an event queue \-
		4149	instead of storing a coroutine, you store the queue object and instead of
		4150	switching to a coroutine, you push the watcher onto the queue and notify
		4151	any waiters.
		4152	.PP
		4153	To embed libev, see \*(L"\s-1EMBEDDING\*(R"\s0, but in short, it's easiest to create two
		4154	files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files:
		4155	.PP
		4156	.Vb 4
		4157	\& // my_ev.h
		4158	\& #define EV_CB_DECLARE(type) struct my_coro *cb;
		4159	\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
		4160	\& #include "../libev/ev.h"
		4161	\&
		4162	\& // my_ev.c
		4163	\& #define EV_H "my_ev.h"
		4164	\& #include "../libev/ev.c"
		4165	.Ve
		4166	.PP
		4167	And then use \fImy_ev.h\fR when you would normally use \fIev.h\fR, and compile
		4168	\&\fImy_ev.c\fR into your project. When properly specifying include paths, you
		4169	can even use \fIev.h\fR as header file name directly.
1417	.SH "LIBEVENT EMULATION"	4170	.SH "LIBEVENT EMULATION"
1418	.IX Header "LIBEVENT EMULATION"	4171	.IX Header "LIBEVENT EMULATION"
1419	Libev offers a compatibility emulation layer for libevent. It cannot	4172	Libev offers a compatibility emulation layer for libevent. It cannot
1420	emulate the internals of libevent, so here are some usage hints:	4173	emulate the internals of libevent, so here are some usage hints:
		4174	.IP "\(bu" 4
		4175	Only the libevent\-1.4.1\-beta \s-1API\s0 is being emulated.
		4176	.Sp
		4177	This was the newest libevent version available when libev was implemented,
		4178	and is still mostly unchanged in 2010.
		4179	.IP "\(bu" 4
1421	.IP "* Use it by including <event.h>, as usual." 4	4180	Use it by including <event.h>, as usual.
1422	.IX Item "Use it by including <event.h>, as usual."	4181	.IP "\(bu" 4
1423	.PD 0	4182	The following members are fully supported: ev_base, ev_callback,
1424	.IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4	4183	ev_arg, ev_fd, ev_res, ev_events.
1425	.IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events."	4184	.IP "\(bu" 4
1426	.IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4	4185	Avoid using ev_flags and the EVLIST_*\-macros, while it is
1427	.IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)."	4186	maintained by libev, it does not work exactly the same way as in libevent (consider
1428	.IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4	4187	it a private \s-1API\s0).
1429	.IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field."	4188	.IP "\(bu" 4
		4189	Priorities are not currently supported. Initialising priorities
		4190	will fail and all watchers will have the same priority, even though there
		4191	is an ev_pri field.
		4192	.IP "\(bu" 4
		4193	In libevent, the last base created gets the signals, in libev, the
		4194	base that registered the signal gets the signals.
		4195	.IP "\(bu" 4
1430	.IP "* Other members are not supported." 4	4196	Other members are not supported.
1431	.IX Item "Other members are not supported."	4197	.IP "\(bu" 4
1432	.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4	4198	The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
1433	.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."	4199	to use the libev header file and library.
1434	.PD
1435	.SH "\*(C+ SUPPORT"	4200	.SH "\*(C+ SUPPORT"
1436	.IX Header " SUPPORT"	4201	.IX Header " SUPPORT"
		4202	.SS "C \s-1API\s0"
		4203	.IX Subsection "C API"
		4204	The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the
		4205	libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0
		4206	will work fine.
		4207	.PP
		4208	Proper exception specifications might have to be added to callbacks passed
		4209	to libev: exceptions may be thrown only from watcher callbacks, all other
		4210	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4211	callbacks) must not throw exceptions, and might need a \f(CW\*(C`noexcept\*(C'\fR
		4212	specification. If you have code that needs to be compiled as both C and
		4213	\&\*(C+ you can use the \f(CW\*(C`EV_NOEXCEPT\*(C'\fR macro for this:
		4214	.PP
		4215	.Vb 6
		4216	\& static void
		4217	\& fatal_error (const char *msg) EV_NOEXCEPT
		4218	\& {
		4219	\& perror (msg);
		4220	\& abort ();
		4221	\& }
		4222	\&
		4223	\& ...
		4224	\& ev_set_syserr_cb (fatal_error);
		4225	.Ve
		4226	.PP
		4227	The only \s-1API\s0 functions that can currently throw exceptions are \f(CW\*(C`ev_run\*(C'\fR,
		4228	\&\f(CW\*(C`ev_invoke\*(C'\fR, \f(CW\*(C`ev_invoke_pending\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR (the latter
		4229	because it runs cleanup watchers).
		4230	.PP
		4231	Throwing exceptions in watcher callbacks is only supported if libev itself
		4232	is compiled with a \*(C+ compiler or your C and \*(C+ environments allow
		4233	throwing exceptions through C libraries (most do).
		4234	.SS "\*(C+ \s-1API\s0"
		4235	.IX Subsection " API"
1437	Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow	4236	Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1438	you to use some convinience methods to start/stop watchers and also change	4237	you to use some convenience methods to start/stop watchers and also change
1439	the callback model to a model using method callbacks on objects.	4238	the callback model to a model using method callbacks on objects.
1440	.PP	4239	.PP
1441	To use it,	4240	To use it,
1442	.PP	4241	.PP
1443	.Vb 1	4242	.Vb 1
1444	\& #include <ev++.h>	4243	\& #include <ev++.h>
1445	.Ve	4244	.Ve
1446	.PP	4245	.PP
1447	(it is not installed by default). This automatically includes \fIev.h\fR	4246	This automatically includes \fIev.h\fR and puts all of its definitions (many
1448	and puts all of its definitions (many of them macros) into the global	4247	of them macros) into the global namespace. All \*(C+ specific things are
1449	namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.	4248	put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
		4249	options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1450	.PP	4250	.PP
1451	It should support all the same embedding options as \fIev.h\fR, most notably	4251	Care has been taken to keep the overhead low. The only data member the \*(C+
1452	\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.	4252	classes add (compared to plain C\-style watchers) is the event loop pointer
		4253	that the watcher is associated with (or no additional members at all if
		4254	you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
		4255	.PP
		4256	Currently, functions, static and non-static member functions and classes
		4257	with \f(CW\*(C`operator ()\*(C'\fR can be used as callbacks. Other types should be easy
		4258	to add as long as they only need one additional pointer for context. If
		4259	you need support for other types of functors please contact the author
		4260	(preferably after implementing it).
		4261	.PP
		4262	For all this to work, your \*(C+ compiler either has to use the same calling
		4263	conventions as your C compiler (for static member functions), or you have
		4264	to embed libev and compile libev itself as \*(C+.
1453	.PP	4265	.PP
1454	Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:	4266	Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1455	.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4	4267	.ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4
1456	.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4	4268	.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1457	.IX Item "ev::READ, ev::WRITE etc."	4269	.IX Item "ev::READ, ev::WRITE etc."
1458	These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.	4270	These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1459	macros from \fIev.h\fR.	4271	macros from \fIev.h\fR.
1460	.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4	4272	.ie n .IP """ev::tstamp"", ""ev::now""" 4
1461	.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4	4273	.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1462	.IX Item "ev::tstamp, ev::now"	4274	.IX Item "ev::tstamp, ev::now"
1463	Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.	4275	Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1464	.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4	4276	.ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4
1465	.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4	4277	.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1466	.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."	4278	.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1467	For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of	4279	For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1468	the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR	4280	the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1469	which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro	4281	which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1470	defines by many implementations.	4282	defined by many implementations.
1471	.Sp	4283	.Sp
1472	All of those classes have these methods:	4284	All of those classes have these methods:
1473	.RS 4	4285	.RS 4
1474	.IP "ev::TYPE::TYPE (object *, object::method *)" 4	4286	.IP "ev::TYPE::TYPE ()" 4
1475	.IX Item "ev::TYPE::TYPE (object *, object::method *)"	4287	.IX Item "ev::TYPE::TYPE ()"
1476	.PD 0	4288	.PD 0
1477	.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4	4289	.IP "ev::TYPE::TYPE (loop)" 4
1478	.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"	4290	.IX Item "ev::TYPE::TYPE (loop)"
1479	.IP "ev::TYPE::~TYPE" 4	4291	.IP "ev::TYPE::~TYPE" 4
1480	.IX Item "ev::TYPE::~TYPE"	4292	.IX Item "ev::TYPE::~TYPE"
1481	.PD	4293	.PD
1482	The constructor takes a pointer to an object and a method pointer to	4294	The constructor (optionally) takes an event loop to associate the watcher
1483	the event handler callback to call in this class. The constructor calls	4295	with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
1484	\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method	4296	.Sp
1485	before starting it. If you do not specify a loop then the constructor	4297	The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
1486	automatically associates the default loop with this watcher.	4298	\&\f(CW\*(C`set\*(C'\fR method before starting it.
		4299	.Sp
		4300	It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
		4301	method to set a callback before you can start the watcher.
		4302	.Sp
		4303	(The reason why you have to use a method is a limitation in \*(C+ which does
		4304	not allow explicit template arguments for constructors).
1487	.Sp	4305	.Sp
1488	The destructor automatically stops the watcher if it is active.	4306	The destructor automatically stops the watcher if it is active.
		4307	.IP "w\->set<class, &class::method> (object *)" 4
		4308	.IX Item "w->set<class, &class::method> (object *)"
		4309	This method sets the callback method to call. The method has to have a
		4310	signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
		4311	first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
		4312	parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
		4313	.Sp
		4314	This method synthesizes efficient thunking code to call your method from
		4315	the C callback that libev requires. If your compiler can inline your
		4316	callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
		4317	your compiler is good :), then the method will be fully inlined into the
		4318	thunking function, making it as fast as a direct C callback.
		4319	.Sp
		4320	Example: simple class declaration and watcher initialisation
		4321	.Sp
		4322	.Vb 4
		4323	\& struct myclass
		4324	\& {
		4325	\& void io_cb (ev::io &w, int revents) { }
		4326	\& }
		4327	\&
		4328	\& myclass obj;
		4329	\& ev::io iow;
		4330	\& iow.set <myclass, &myclass::io_cb> (&obj);
		4331	.Ve
		4332	.IP "w\->set (object *)" 4
		4333	.IX Item "w->set (object *)"
		4334	This is a variation of a method callback \- leaving out the method to call
		4335	will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use
		4336	functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all
		4337	the time. Incidentally, you can then also leave out the template argument
		4338	list.
		4339	.Sp
		4340	The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w,
		4341	int revents)\*(C'\fR.
		4342	.Sp
		4343	See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
		4344	.Sp
		4345	Example: use a functor object as callback.
		4346	.Sp
		4347	.Vb 7
		4348	\& struct myfunctor
		4349	\& {
		4350	\& void operator() (ev::io &w, int revents)
		4351	\& {
		4352	\& ...
		4353	\& }
		4354	\& }
		4355	\&
		4356	\& myfunctor f;
		4357	\&
		4358	\& ev::io w;
		4359	\& w.set (&f);
		4360	.Ve
		4361	.IP "w\->set<function> (void *data = 0)" 4
		4362	.IX Item "w->set<function> (void *data = 0)"
		4363	Also sets a callback, but uses a static method or plain function as
		4364	callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
		4365	\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
		4366	.Sp
		4367	The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
		4368	.Sp
		4369	See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
		4370	.Sp
		4371	Example: Use a plain function as callback.
		4372	.Sp
		4373	.Vb 2
		4374	\& static void io_cb (ev::io &w, int revents) { }
		4375	\& iow.set <io_cb> ();
		4376	.Ve
1489	.IP "w\->set (struct ev_loop *)" 4	4377	.IP "w\->set (loop)" 4
1490	.IX Item "w->set (struct ev_loop *)"	4378	.IX Item "w->set (loop)"
1491	Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only	4379	Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1492	do this when the watcher is inactive (and not pending either).	4380	do this when the watcher is inactive (and not pending either).
1493	.IP "w\->set ([args])" 4	4381	.IP "w\->set ([arguments])" 4
1494	.IX Item "w->set ([args])"	4382	.IX Item "w->set ([arguments])"
1495	Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be	4383	Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR (except for \f(CW\*(C`ev::embed\*(C'\fR watchers>),
		4384	with the same arguments. Either this method or a suitable start method
1496	called at least once. Unlike the C counterpart, an active watcher gets	4385	must be called at least once. Unlike the C counterpart, an active watcher
1497	automatically stopped and restarted.	4386	gets automatically stopped and restarted when reconfiguring it with this
		4387	method.
		4388	.Sp
		4389	For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
		4390	clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
1498	.IP "w\->start ()" 4	4391	.IP "w\->start ()" 4
1499	.IX Item "w->start ()"	4392	.IX Item "w->start ()"
1500	Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the	4393	Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
1501	constructor already takes the loop.	4394	constructor already stores the event loop.
		4395	.IP "w\->start ([arguments])" 4
		4396	.IX Item "w->start ([arguments])"
		4397	Instead of calling \f(CW\*(C`set\*(C'\fR and \f(CW\*(C`start\*(C'\fR methods separately, it is often
		4398	convenient to wrap them in one call. Uses the same type of arguments as
		4399	the configure \f(CW\*(C`set\*(C'\fR method of the watcher.
1502	.IP "w\->stop ()" 4	4400	.IP "w\->stop ()" 4
1503	.IX Item "w->stop ()"	4401	.IX Item "w->stop ()"
1504	Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.	4402	Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1505	.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4	4403	.ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4
1506	.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4	4404	.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
1507	.IX Item "w->again () ev::timer, ev::periodic only"	4405	.IX Item "w->again () (ev::timer, ev::periodic only)"
1508	For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding	4406	For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1509	\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.	4407	\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1510	.ie n .IP "w\->sweep () ""ev::embed"" only" 4	4408	.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
1511	.el .IP "w\->sweep () \f(CWev::embed\fR only" 4	4409	.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
1512	.IX Item "w->sweep () ev::embed only"	4410	.IX Item "w->sweep () (ev::embed only)"
1513	Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.	4411	Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
		4412	.ie n .IP "w\->update () (""ev::stat"" only)" 4
		4413	.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
		4414	.IX Item "w->update () (ev::stat only)"
		4415	Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1514	.RE	4416	.RE
1515	.RS 4	4417	.RS 4
1516	.RE	4418	.RE
1517	.PP	4419	.PP
1518	Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in	4420	Example: Define a class with two I/O and idle watchers, start the I/O
1519	the constructor.	4421	watchers in the constructor.
1520	.PP	4422	.PP
1521	.Vb 4	4423	.Vb 5
1522	\& class myclass	4424	\& class myclass
1523	\& {	4425	\& {
1524	\& ev_io io; void io_cb (ev::io &w, int revents);	4426	\& ev::io io ; void io_cb (ev::io &w, int revents);
		4427	\& ev::io io2 ; void io2_cb (ev::io &w, int revents);
1525	\& ev_idle idle void idle_cb (ev::idle &w, int revents);	4428	\& ev::idle idle; void idle_cb (ev::idle &w, int revents);
		4429	\&
		4430	\& myclass (int fd)
		4431	\& {
		4432	\& io .set <myclass, &myclass::io_cb > (this);
		4433	\& io2 .set <myclass, &myclass::io2_cb > (this);
		4434	\& idle.set <myclass, &myclass::idle_cb> (this);
		4435	\&
		4436	\& io.set (fd, ev::WRITE); // configure the watcher
		4437	\& io.start (); // start it whenever convenient
		4438	\&
		4439	\& io2.start (fd, ev::READ); // set + start in one call
		4440	\& }
		4441	\& };
1526	.Ve	4442	.Ve
		4443	.SH "OTHER LANGUAGE BINDINGS"
		4444	.IX Header "OTHER LANGUAGE BINDINGS"
		4445	Libev does not offer other language bindings itself, but bindings for a
		4446	number of languages exist in the form of third-party packages. If you know
		4447	any interesting language binding in addition to the ones listed here, drop
		4448	me a note.
		4449	.IP "Perl" 4
		4450	.IX Item "Perl"
		4451	The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test
		4452	libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module,
		4453	there are additional modules that implement libev-compatible interfaces
		4454	to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays),
		4455	\&\f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the \f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR
		4456	and \f(CW\*(C`EV::Glib\*(C'\fR).
		4457	.Sp
		4458	It can be found and installed via \s-1CPAN,\s0 its homepage is at
		4459	<http://software.schmorp.de/pkg/EV>.
		4460	.IP "Python" 4
		4461	.IX Item "Python"
		4462	Python bindings can be found at <http://code.google.com/p/pyev/>. It
		4463	seems to be quite complete and well-documented.
		4464	.IP "Ruby" 4
		4465	.IX Item "Ruby"
		4466	Tony Arcieri has written a ruby extension that offers access to a subset
		4467	of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and
		4468	more on top of it. It can be found via gem servers. Its homepage is at
		4469	<http://rev.rubyforge.org/>.
		4470	.Sp
		4471	Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR
		4472	makes rev work even on mingw.
		4473	.IP "Haskell" 4
		4474	.IX Item "Haskell"
		4475	A haskell binding to libev is available at
		4476	<http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>.
		4477	.IP "D" 4
		4478	.IX Item "D"
		4479	Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
		4480	be found at <http://www.llucax.com.ar/proj/ev.d/index.html>.
		4481	.IP "Ocaml" 4
		4482	.IX Item "Ocaml"
		4483	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4484	<http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>.
		4485	.IP "Lua" 4
		4486	.IX Item "Lua"
		4487	Brian Maher has written a partial interface to libev for lua (at the
		4488	time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at
		4489	<http://github.com/brimworks/lua\-ev>.
		4490	.IP "Javascript" 4
		4491	.IX Item "Javascript"
		4492	Node.js (<http://nodejs.org>) uses libev as the underlying event library.
		4493	.IP "Others" 4
		4494	.IX Item "Others"
		4495	There are others, and I stopped counting.
		4496	.SH "MACRO MAGIC"
		4497	.IX Header "MACRO MAGIC"
		4498	Libev can be compiled with a variety of options, the most fundamental
		4499	of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
		4500	functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1527	.PP	4501	.PP
		4502	To make it easier to write programs that cope with either variant, the
		4503	following macros are defined:
		4504	.ie n .IP """EV_A"", ""EV_A_""" 4
		4505	.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
		4506	.IX Item "EV_A, EV_A_"
		4507	This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
		4508	loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
		4509	\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
		4510	.Sp
		4511	.Vb 3
		4512	\& ev_unref (EV_A);
		4513	\& ev_timer_add (EV_A_ watcher);
		4514	\& ev_run (EV_A_ 0);
		4515	.Ve
		4516	.Sp
		4517	It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
		4518	which is often provided by the following macro.
		4519	.ie n .IP """EV_P"", ""EV_P_""" 4
		4520	.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
		4521	.IX Item "EV_P, EV_P_"
		4522	This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
		4523	loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
		4524	\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
		4525	.Sp
1528	.Vb 2	4526	.Vb 2
1529	\& myclass ();	4527	\& // this is how ev_unref is being declared
1530	\& }	4528	\& static void ev_unref (EV_P);
		4529	\&
		4530	\& // this is how you can declare your typical callback
		4531	\& static void cb (EV_P_ ev_timer *w, int revents)
1531	.Ve	4532	.Ve
		4533	.Sp
		4534	It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
		4535	suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
		4536	.ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4
		4537	.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
		4538	.IX Item "EV_DEFAULT, EV_DEFAULT_"
		4539	Similar to the other two macros, this gives you the value of the default
		4540	loop, if multiple loops are supported (\*(L"ev loop default\*(R"). The default loop
		4541	will be initialised if it isn't already initialised.
		4542	.Sp
		4543	For non-multiplicity builds, these macros do nothing, so you always have
		4544	to initialise the loop somewhere.
		4545	.ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4
		4546	.el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4
		4547	.IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_"
		4548	Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the
		4549	default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour
		4550	is undefined when the default loop has not been initialised by a previous
		4551	execution of \f(CW\*(C`EV_DEFAULT\*(C'\fR, \f(CW\*(C`EV_DEFAULT_\*(C'\fR or \f(CW\*(C`ev_default_init (...)\*(C'\fR.
		4552	.Sp
		4553	It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first
		4554	watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards.
1532	.PP	4555	.PP
		4556	Example: Declare and initialise a check watcher, utilising the above
		4557	macros so it will work regardless of whether multiple loops are supported
		4558	or not.
		4559	.PP
1533	.Vb 6	4560	.Vb 5
1534	\& myclass::myclass (int fd)	4561	\& static void
1535	\& : io (this, &myclass::io_cb),	4562	\& check_cb (EV_P_ ev_timer *w, int revents)
1536	\& idle (this, &myclass::idle_cb)
1537	\& {	4563	\& {
1538	\& io.start (fd, ev::READ);	4564	\& ev_check_stop (EV_A_ w);
1539	\& }	4565	\& }
		4566	\&
		4567	\& ev_check check;
		4568	\& ev_check_init (&check, check_cb);
		4569	\& ev_check_start (EV_DEFAULT_ &check);
		4570	\& ev_run (EV_DEFAULT_ 0);
1540	.Ve	4571	.Ve
1541	.SH "EMBEDDING"	4572	.SH "EMBEDDING"
1542	.IX Header "EMBEDDING"	4573	.IX Header "EMBEDDING"
1543	Libev can (and often is) directly embedded into host	4574	Libev can (and often is) directly embedded into host
1544	applications. Examples of applications that embed it include the Deliantra	4575	applications. Examples of applications that embed it include the Deliantra
1545	Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)	4576	Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
1546	and rxvt\-unicode.	4577	and rxvt-unicode.
1547	.PP	4578	.PP
1548	The goal is to enable you to just copy the neecssary files into your	4579	The goal is to enable you to just copy the necessary files into your
1549	source directory without having to change even a single line in them, so	4580	source directory without having to change even a single line in them, so
1550	you can easily upgrade by simply copying (or having a checked-out copy of	4581	you can easily upgrade by simply copying (or having a checked-out copy of
1551	libev somewhere in your source tree).	4582	libev somewhere in your source tree).
1552	.Sh "\s-1FILESETS\s0"	4583	.SS "\s-1FILESETS\s0"
1553	.IX Subsection "FILESETS"	4584	.IX Subsection "FILESETS"
1554	Depending on what features you need you need to include one or more sets of files	4585	Depending on what features you need you need to include one or more sets of files
1555	in your app.	4586	in your application.
1556	.PP	4587	.PP
1557	\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR	4588	\fI\s-1CORE EVENT LOOP\s0\fR
1558	.IX Subsection "CORE EVENT LOOP"	4589	.IX Subsection "CORE EVENT LOOP"
1559	.PP	4590	.PP
1560	To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual	4591	To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
1561	configuration (no autoconf):	4592	configuration (no autoconf):
1562	.PP	4593	.PP
1563	.Vb 2	4594	.Vb 2
1564	\& #define EV_STANDALONE 1	4595	\& #define EV_STANDALONE 1
1565	\& #include "ev.c"	4596	\& #include "ev.c"
1566	.Ve	4597	.Ve
1567	.PP	4598	.PP
1568	This will automatically include \fIev.h\fR, too, and should be done in a	4599	This will automatically include \fIev.h\fR, too, and should be done in a
1569	single C source file only to provide the function implementations. To use	4600	single C source file only to provide the function implementations. To use
1570	it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best	4601	it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
1571	done by writing a wrapper around \fIev.h\fR that you can include instead and	4602	done by writing a wrapper around \fIev.h\fR that you can include instead and
1572	where you can put other configuration options):	4603	where you can put other configuration options):
1573	.PP	4604	.PP
1574	.Vb 2	4605	.Vb 2
1575	\& #define EV_STANDALONE 1	4606	\& #define EV_STANDALONE 1
1576	\& #include "ev.h"	4607	\& #include "ev.h"
1577	.Ve	4608	.Ve
1578	.PP	4609	.PP
1579	Both header files and implementation files can be compiled with a \*(C+	4610	Both header files and implementation files can be compiled with a \*(C+
1580	compiler (at least, thats a stated goal, and breakage will be treated	4611	compiler (at least, that's a stated goal, and breakage will be treated
1581	as a bug).	4612	as a bug).
1582	.PP	4613	.PP
1583	You need the following files in your source tree, or in a directory	4614	You need the following files in your source tree, or in a directory
1584	in your include path (e.g. in libev/ when using \-Ilibev):	4615	in your include path (e.g. in libev/ when using \-Ilibev):
1585	.PP	4616	.PP
1586	.Vb 4	4617	.Vb 4
1587	\& ev.h	4618	\& ev.h
1588	\& ev.c	4619	\& ev.c
1589	\& ev_vars.h	4620	\& ev_vars.h
1590	\& ev_wrap.h	4621	\& ev_wrap.h
		4622	\&
		4623	\& ev_win32.c required on win32 platforms only
		4624	\&
		4625	\& ev_select.c only when select backend is enabled
		4626	\& ev_poll.c only when poll backend is enabled
		4627	\& ev_epoll.c only when the epoll backend is enabled
		4628	\& ev_linuxaio.c only when the linux aio backend is enabled
		4629	\& ev_kqueue.c only when the kqueue backend is enabled
		4630	\& ev_port.c only when the solaris port backend is enabled
1591	.Ve	4631	.Ve
		4632	.PP
		4633	\&\fIev.c\fR includes the backend files directly when enabled, so you only need
		4634	to compile this single file.
		4635	.PP
		4636	\fI\s-1LIBEVENT COMPATIBILITY API\s0\fR
		4637	.IX Subsection "LIBEVENT COMPATIBILITY API"
		4638	.PP
		4639	To include the libevent compatibility \s-1API,\s0 also include:
1592	.PP	4640	.PP
1593	.Vb 1	4641	.Vb 1
1594	\& ev_win32.c required on win32 platforms only	4642	\& #include "event.c"
1595	.Ve	4643	.Ve
1596	.PP	4644	.PP
1597	.Vb 5	4645	in the file including \fIev.c\fR, and:
1598	\& ev_select.c only when select backend is enabled (which is is by default)
1599	\& ev_poll.c only when poll backend is enabled (disabled by default)
1600	\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
1601	\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1602	\& ev_port.c only when the solaris port backend is enabled (disabled by default)
1603	.Ve
1604	.PP
1605	\&\fIev.c\fR includes the backend files directly when enabled, so you only need
1606	to compile a single file.
1607	.PP
1608	\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
1609	.IX Subsection "LIBEVENT COMPATIBILITY API"
1610	.PP
1611	To include the libevent compatibility \s-1API\s0, also include:
1612	.PP	4646	.PP
1613	.Vb 1	4647	.Vb 1
1614	\& #include "event.c"	4648	\& #include "event.h"
1615	.Ve	4649	.Ve
1616	.PP	4650	.PP
1617	in the file including \fIev.c\fR, and:	4651	in the files that want to use the libevent \s-1API.\s0 This also includes \fIev.h\fR.
		4652	.PP
		4653	You need the following additional files for this:
		4654	.PP
		4655	.Vb 2
		4656	\& event.h
		4657	\& event.c
		4658	.Ve
		4659	.PP
		4660	\fI\s-1AUTOCONF SUPPORT\s0\fR
		4661	.IX Subsection "AUTOCONF SUPPORT"
		4662	.PP
		4663	Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in
		4664	whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
		4665	\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
		4666	include \fIconfig.h\fR and configure itself accordingly.
		4667	.PP
		4668	For this of course you need the m4 file:
1618	.PP	4669	.PP
1619	.Vb 1	4670	.Vb 1
1620	\& #include "event.h"
1621	.Ve
1622	.PP
1623	in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
1624	.PP
1625	You need the following additional files for this:
1626	.PP
1627	.Vb 2
1628	\& event.h
1629	\& event.c
1630	.Ve
1631	.PP
1632	\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
1633	.IX Subsection "AUTOCONF SUPPORT"
1634	.PP
1635	Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
1636	whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
1637	\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR off. \fIev.c\fR will then include
1638	\&\fIconfig.h\fR and configure itself accordingly.
1639	.PP
1640	For this of course you need the m4 file:
1641	.PP
1642	.Vb 1
1643	\& libev.m4	4671	\& libev.m4
1644	.Ve	4672	.Ve
1645	.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"	4673	.SS "\s-1PREPROCESSOR SYMBOLS/MACROS\s0"
1646	.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"	4674	.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
1647	Libev can be configured via a variety of preprocessor symbols you have to define	4675	Libev can be configured via a variety of preprocessor symbols you have to
1648	before including any of its files. The default is not to build for multiplicity	4676	define before including (or compiling) any of its files. The default in
1649	and only include the select backend.	4677	the absence of autoconf is documented for every option.
		4678	.PP
		4679	Symbols marked with \*(L"(h)\*(R" do not change the \s-1ABI,\s0 and can have different
		4680	values when compiling libev vs. including \fIev.h\fR, so it is permissible
		4681	to redefine them before including \fIev.h\fR without breaking compatibility
		4682	to a compiled library. All other symbols change the \s-1ABI,\s0 which means all
		4683	users of libev and the libev code itself must be compiled with compatible
		4684	settings.
		4685	.IP "\s-1EV_COMPAT3\s0 (h)" 4
		4686	.IX Item "EV_COMPAT3 (h)"
		4687	Backwards compatibility is a major concern for libev. This is why this
		4688	release of libev comes with wrappers for the functions and symbols that
		4689	have been renamed between libev version 3 and 4.
		4690	.Sp
		4691	You can disable these wrappers (to test compatibility with future
		4692	versions) by defining \f(CW\*(C`EV_COMPAT3\*(C'\fR to \f(CW0\fR when compiling your
		4693	sources. This has the additional advantage that you can drop the \f(CW\*(C`struct\*(C'\fR
		4694	from \f(CW\*(C`struct ev_loop\*(C'\fR declarations, as libev will provide an \f(CW\*(C`ev_loop\*(C'\fR
		4695	typedef in that case.
		4696	.Sp
		4697	In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR,
		4698	and in some even more future version the compatibility code will be
		4699	removed completely.
1650	.IP "\s-1EV_STANDALONE\s0" 4	4700	.IP "\s-1EV_STANDALONE\s0 (h)" 4
1651	.IX Item "EV_STANDALONE"	4701	.IX Item "EV_STANDALONE (h)"
1652	Must always be \f(CW1\fR if you do not use autoconf configuration, which	4702	Must always be \f(CW1\fR if you do not use autoconf configuration, which
1653	keeps libev from including \fIconfig.h\fR, and it also defines dummy	4703	keeps libev from including \fIconfig.h\fR, and it also defines dummy
1654	implementations for some libevent functions (such as logging, which is not	4704	implementations for some libevent functions (such as logging, which is not
1655	supported). It will also not define any of the structs usually found in	4705	supported). It will also not define any of the structs usually found in
1656	\&\fIevent.h\fR that are not directly supported by the libev core alone.	4706	\&\fIevent.h\fR that are not directly supported by the libev core alone.
		4707	.Sp
		4708	In standalone mode, libev will still try to automatically deduce the
		4709	configuration, but has to be more conservative.
		4710	.IP "\s-1EV_USE_FLOOR\s0" 4
		4711	.IX Item "EV_USE_FLOOR"
		4712	If defined to be \f(CW1\fR, libev will use the \f(CW\*(C`floor ()\*(C'\fR function for its
		4713	periodic reschedule calculations, otherwise libev will fall back on a
		4714	portable (slower) implementation. If you enable this, you usually have to
		4715	link against libm or something equivalent. Enabling this when the \f(CW\*(C`floor\*(C'\fR
		4716	function is not available will fail, so the safe default is to not enable
		4717	this.
1657	.IP "\s-1EV_USE_MONOTONIC\s0" 4	4718	.IP "\s-1EV_USE_MONOTONIC\s0" 4
1658	.IX Item "EV_USE_MONOTONIC"	4719	.IX Item "EV_USE_MONOTONIC"
1659	If defined to be \f(CW1\fR, libev will try to detect the availability of the	4720	If defined to be \f(CW1\fR, libev will try to detect the availability of the
1660	monotonic clock option at both compiletime and runtime. Otherwise no use	4721	monotonic clock option at both compile time and runtime. Otherwise no
1661	of the monotonic clock option will be attempted. If you enable this, you	4722	use of the monotonic clock option will be attempted. If you enable this,
1662	usually have to link against librt or something similar. Enabling it when	4723	you usually have to link against librt or something similar. Enabling it
1663	the functionality isn't available is safe, though, althoguh you have	4724	when the functionality isn't available is safe, though, although you have
1664	to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR	4725	to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
1665	function is hiding in (often \fI\-lrt\fR).	4726	function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
1666	.IP "\s-1EV_USE_REALTIME\s0" 4	4727	.IP "\s-1EV_USE_REALTIME\s0" 4
1667	.IX Item "EV_USE_REALTIME"	4728	.IX Item "EV_USE_REALTIME"
1668	If defined to be \f(CW1\fR, libev will try to detect the availability of the	4729	If defined to be \f(CW1\fR, libev will try to detect the availability of the
1669	realtime clock option at compiletime (and assume its availability at	4730	real-time clock option at compile time (and assume its availability
1670	runtime if successful). Otherwise no use of the realtime clock option will	4731	at runtime if successful). Otherwise no use of the real-time clock
1671	be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get	4732	option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR
1672	(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries	4733	by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect
1673	in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.	4734	correctness. See the note about libraries in the description of
		4735	\&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of
		4736	\&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
		4737	.IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4
		4738	.IX Item "EV_USE_CLOCK_SYSCALL"
		4739	If defined to be \f(CW1\fR, libev will try to use a direct syscall instead
		4740	of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option
		4741	exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR
		4742	unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded
		4743	programs needlessly. Using a direct syscall is slightly slower (in
		4744	theory), because no optimised vdso implementation can be used, but avoids
		4745	the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or
		4746	higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
		4747	.IP "\s-1EV_USE_NANOSLEEP\s0" 4
		4748	.IX Item "EV_USE_NANOSLEEP"
		4749	If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
		4750	and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
		4751	.IP "\s-1EV_USE_EVENTFD\s0" 4
		4752	.IX Item "EV_USE_EVENTFD"
		4753	If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
		4754	available and will probe for kernel support at runtime. This will improve
		4755	\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
		4756	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4757	2.7 or newer, otherwise disabled.
1674	.IP "\s-1EV_USE_SELECT\s0" 4	4758	.IP "\s-1EV_USE_SELECT\s0" 4
1675	.IX Item "EV_USE_SELECT"	4759	.IX Item "EV_USE_SELECT"
1676	If undefined or defined to be \f(CW1\fR, libev will compile in support for the	4760	If undefined or defined to be \f(CW1\fR, libev will compile in support for the
1677	\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no	4761	\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at auto-detection will be done: if no
1678	other method takes over, select will be it. Otherwise the select backend	4762	other method takes over, select will be it. Otherwise the select backend
1679	will not be compiled in.	4763	will not be compiled in.
1680	.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4	4764	.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
1681	.IX Item "EV_SELECT_USE_FD_SET"	4765	.IX Item "EV_SELECT_USE_FD_SET"
1682	If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR	4766	If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
1683	structure. This is useful if libev doesn't compile due to a missing	4767	structure. This is useful if libev doesn't compile due to a missing
1684	\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on	4768	\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout
1685	exotic systems. This usually limits the range of file descriptors to some	4769	on exotic systems. This usually limits the range of file descriptors to
1686	low limit such as 1024 or might have other limitations (winsocket only	4770	some low limit such as 1024 or might have other limitations (winsocket
1687	allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might	4771	only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation,
1688	influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.	4772	configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR.
1689	.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4	4773	.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
1690	.IX Item "EV_SELECT_IS_WINSOCKET"	4774	.IX Item "EV_SELECT_IS_WINSOCKET"
1691	When defined to \f(CW1\fR, the select backend will assume that	4775	When defined to \f(CW1\fR, the select backend will assume that
1692	select/socket/connect etc. don't understand file descriptors but	4776	select/socket/connect etc. don't understand file descriptors but
1693	wants osf handles on win32 (this is the case when the select to	4777	wants osf handles on win32 (this is the case when the select to
1694	be used is the winsock select). This means that it will call	4778	be used is the winsock select). This means that it will call
1695	\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,	4779	\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
1696	it is assumed that all these functions actually work on fds, even	4780	it is assumed that all these functions actually work on fds, even
1697	on win32. Should not be defined on non\-win32 platforms.	4781	on win32. Should not be defined on non\-win32 platforms.
		4782	.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0(fd)" 4
		4783	.IX Item "EV_FD_TO_WIN32_HANDLE(fd)"
		4784	If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map
		4785	file descriptors to socket handles. When not defining this symbol (the
		4786	default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually
		4787	correct. In some cases, programs use their own file descriptor management,
		4788	in which case they can provide this function to map fds to socket handles.
		4789	.IP "\s-1EV_WIN32_HANDLE_TO_FD\s0(handle)" 4
		4790	.IX Item "EV_WIN32_HANDLE_TO_FD(handle)"
		4791	If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR then libev maps handles to file descriptors
		4792	using the standard \f(CW\*(C`_open_osfhandle\*(C'\fR function. For programs implementing
		4793	their own fd to handle mapping, overwriting this function makes it easier
		4794	to do so. This can be done by defining this macro to an appropriate value.
		4795	.IP "\s-1EV_WIN32_CLOSE_FD\s0(fd)" 4
		4796	.IX Item "EV_WIN32_CLOSE_FD(fd)"
		4797	If programs implement their own fd to handle mapping on win32, then this
		4798	macro can be used to override the \f(CW\*(C`close\*(C'\fR function, useful to unregister
		4799	file descriptors again. Note that the replacement function has to close
		4800	the underlying \s-1OS\s0 handle.
		4801	.IP "\s-1EV_USE_WSASOCKET\s0" 4
		4802	.IX Item "EV_USE_WSASOCKET"
		4803	If defined to be \f(CW1\fR, libev will use \f(CW\*(C`WSASocket\*(C'\fR to create its internal
		4804	communication socket, which works better in some environments. Otherwise,
		4805	the normal \f(CW\*(C`socket\*(C'\fR function will be used, which works better in other
		4806	environments.
1698	.IP "\s-1EV_USE_POLL\s0" 4	4807	.IP "\s-1EV_USE_POLL\s0" 4
1699	.IX Item "EV_USE_POLL"	4808	.IX Item "EV_USE_POLL"
1700	If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)	4809	If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
1701	backend. Otherwise it will be enabled on non\-win32 platforms. It	4810	backend. Otherwise it will be enabled on non\-win32 platforms. It
1702	takes precedence over select.	4811	takes precedence over select.
1703	.IP "\s-1EV_USE_EPOLL\s0" 4	4812	.IP "\s-1EV_USE_EPOLL\s0" 4
1704	.IX Item "EV_USE_EPOLL"	4813	.IX Item "EV_USE_EPOLL"
1705	If defined to be \f(CW1\fR, libev will compile in support for the Linux	4814	If defined to be \f(CW1\fR, libev will compile in support for the Linux
1706	\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,	4815	\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
1707	otherwise another method will be used as fallback. This is the	4816	otherwise another method will be used as fallback. This is the preferred
1708	preferred backend for GNU/Linux systems.	4817	backend for GNU/Linux systems. If undefined, it will be enabled if the
		4818	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4819	.IP "\s-1EV_USE_LINUXAIO\s0" 4
		4820	.IX Item "EV_USE_LINUXAIO"
		4821	If defined to be \f(CW1\fR, libev will compile in support for the Linux
		4822	aio backend. Due to it's currenbt limitations it has to be requested
		4823	explicitly. If undefined, it will be enabled on linux, otherwise
		4824	disabled.
1709	.IP "\s-1EV_USE_KQUEUE\s0" 4	4825	.IP "\s-1EV_USE_KQUEUE\s0" 4
1710	.IX Item "EV_USE_KQUEUE"	4826	.IX Item "EV_USE_KQUEUE"
1711	If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style	4827	If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
1712	\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,	4828	\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
1713	otherwise another method will be used as fallback. This is the preferred	4829	otherwise another method will be used as fallback. This is the preferred
1714	backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only	4830	backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
1715	supports some types of fds correctly (the only platform we found that	4831	supports some types of fds correctly (the only platform we found that
1716	supports ptys for example was NetBSD), so kqueue might be compiled in, but	4832	supports ptys for example was NetBSD), so kqueue might be compiled in, but
1717	not be used unless explicitly requested. The best way to use it is to find	4833	not be used unless explicitly requested. The best way to use it is to find
1718	out wether kqueue supports your type of fd properly and use an embedded	4834	out whether kqueue supports your type of fd properly and use an embedded
1719	kqueue loop.	4835	kqueue loop.
1720	.IP "\s-1EV_USE_PORT\s0" 4	4836	.IP "\s-1EV_USE_PORT\s0" 4
1721	.IX Item "EV_USE_PORT"	4837	.IX Item "EV_USE_PORT"
1722	If defined to be \f(CW1\fR, libev will compile in support for the Solaris	4838	If defined to be \f(CW1\fR, libev will compile in support for the Solaris
1723	10 port style backend. Its availability will be detected at runtime,	4839	10 port style backend. Its availability will be detected at runtime,
1724	otherwise another method will be used as fallback. This is the preferred	4840	otherwise another method will be used as fallback. This is the preferred
1725	backend for Solaris 10 systems.	4841	backend for Solaris 10 systems.
1726	.IP "\s-1EV_USE_DEVPOLL\s0" 4	4842	.IP "\s-1EV_USE_DEVPOLL\s0" 4
1727	.IX Item "EV_USE_DEVPOLL"	4843	.IX Item "EV_USE_DEVPOLL"
1728	reserved for future expansion, works like the \s-1USE\s0 symbols above.	4844	Reserved for future expansion, works like the \s-1USE\s0 symbols above.
		4845	.IP "\s-1EV_USE_INOTIFY\s0" 4
		4846	.IX Item "EV_USE_INOTIFY"
		4847	If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
		4848	interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
		4849	be detected at runtime. If undefined, it will be enabled if the headers
		4850	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4851	.IP "\s-1EV_NO_SMP\s0" 4
		4852	.IX Item "EV_NO_SMP"
		4853	If defined to be \f(CW1\fR, libev will assume that memory is always coherent
		4854	between threads, that is, threads can be used, but threads never run on
		4855	different cpus (or different cpu cores). This reduces dependencies
		4856	and makes libev faster.
		4857	.IP "\s-1EV_NO_THREADS\s0" 4
		4858	.IX Item "EV_NO_THREADS"
		4859	If defined to be \f(CW1\fR, libev will assume that it will never be called from
		4860	different threads (that includes signal handlers), which is a stronger
		4861	assumption than \f(CW\*(C`EV_NO_SMP\*(C'\fR, above. This reduces dependencies and makes
		4862	libev faster.
		4863	.IP "\s-1EV_ATOMIC_T\s0" 4
		4864	.IX Item "EV_ATOMIC_T"
		4865	Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose
		4866	access is atomic with respect to other threads or signal contexts. No
		4867	such type is easily found in the C language, so you can provide your own
		4868	type that you know is safe for your purposes. It is used both for signal
		4869	handler \*(L"locking\*(R" as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR
		4870	watchers.
		4871	.Sp
		4872	In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR
		4873	(from \fIsignal.h\fR), which is usually good enough on most platforms.
1729	.IP "\s-1EV_H\s0" 4	4874	.IP "\s-1EV_H\s0 (h)" 4
1730	.IX Item "EV_H"	4875	.IX Item "EV_H (h)"
1731	The name of the \fIev.h\fR header file used to include it. The default if	4876	The name of the \fIev.h\fR header file used to include it. The default if
1732	undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This	4877	undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
1733	can be used to virtually rename the \fIev.h\fR header file in case of conflicts.	4878	used to virtually rename the \fIev.h\fR header file in case of conflicts.
1734	.IP "\s-1EV_CONFIG_H\s0" 4	4879	.IP "\s-1EV_CONFIG_H\s0 (h)" 4
1735	.IX Item "EV_CONFIG_H"	4880	.IX Item "EV_CONFIG_H (h)"
1736	If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override	4881	If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
1737	\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to	4882	\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
1738	\&\f(CW\*(C`EV_H\*(C'\fR, above.	4883	\&\f(CW\*(C`EV_H\*(C'\fR, above.
1739	.IP "\s-1EV_EVENT_H\s0" 4	4884	.IP "\s-1EV_EVENT_H\s0 (h)" 4
1740	.IX Item "EV_EVENT_H"	4885	.IX Item "EV_EVENT_H (h)"
1741	Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea	4886	Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
1742	of how the \fIevent.h\fR header can be found.	4887	of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
1743	.IP "\s-1EV_PROTOTYPES\s0" 4	4888	.IP "\s-1EV_PROTOTYPES\s0 (h)" 4
1744	.IX Item "EV_PROTOTYPES"	4889	.IX Item "EV_PROTOTYPES (h)"
1745	If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function	4890	If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
1746	prototypes, but still define all the structs and other symbols. This is	4891	prototypes, but still define all the structs and other symbols. This is
1747	occasionally useful if you want to provide your own wrapper functions	4892	occasionally useful if you want to provide your own wrapper functions
1748	around libev functions.	4893	around libev functions.
1749	.IP "\s-1EV_MULTIPLICITY\s0" 4	4894	.IP "\s-1EV_MULTIPLICITY\s0" 4
…		…
1751	If undefined or defined to \f(CW1\fR, then all event-loop-specific functions	4896	If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
1752	will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create	4897	will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
1753	additional independent event loops. Otherwise there will be no support	4898	additional independent event loops. Otherwise there will be no support
1754	for multiple event loops and there is no first event loop pointer	4899	for multiple event loops and there is no first event loop pointer
1755	argument. Instead, all functions act on the single default loop.	4900	argument. Instead, all functions act on the single default loop.
		4901	.Sp
		4902	Note that \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR will no longer provide a
		4903	default loop when multiplicity is switched off \- you always have to
		4904	initialise the loop manually in this case.
1756	.IP "\s-1EV_PERIODICS\s0" 4	4905	.IP "\s-1EV_MINPRI\s0" 4
1757	.IX Item "EV_PERIODICS"	4906	.IX Item "EV_MINPRI"
1758	If undefined or defined to be \f(CW1\fR, then periodic timers are supported,	4907	.PD 0
1759	otherwise not. This saves a few kb of code.	4908	.IP "\s-1EV_MAXPRI\s0" 4
		4909	.IX Item "EV_MAXPRI"
		4910	.PD
		4911	The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
		4912	\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
		4913	provide for more priorities by overriding those symbols (usually defined
		4914	to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
		4915	.Sp
		4916	When doing priority-based operations, libev usually has to linearly search
		4917	all the priorities, so having many of them (hundreds) uses a lot of space
		4918	and time, so using the defaults of five priorities (\-2 .. +2) is usually
		4919	fine.
		4920	.Sp
		4921	If your embedding application does not need any priorities, defining these
		4922	both to \f(CW0\fR will save some memory and \s-1CPU.\s0
		4923	.IP "\s-1EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE.\s0" 4
		4924	.IX Item "EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE."
		4925	If undefined or defined to be \f(CW1\fR (and the platform supports it), then
		4926	the respective watcher type is supported. If defined to be \f(CW0\fR, then it
		4927	is not. Disabling watcher types mainly saves code size.
		4928	.IP "\s-1EV_FEATURES\s0" 4
		4929	.IX Item "EV_FEATURES"
		4930	If you need to shave off some kilobytes of code at the expense of some
		4931	speed (but with the full \s-1API\s0), you can define this symbol to request
		4932	certain subsets of functionality. The default is to enable all features
		4933	that can be enabled on the platform.
		4934	.Sp
		4935	A typical way to use this symbol is to define it to \f(CW0\fR (or to a bitset
		4936	with some broad features you want) and then selectively re-enable
		4937	additional parts you want, for example if you want everything minimal,
		4938	but multiple event loop support, async and child watchers and the poll
		4939	backend, use this:
		4940	.Sp
		4941	.Vb 5
		4942	\& #define EV_FEATURES 0
		4943	\& #define EV_MULTIPLICITY 1
		4944	\& #define EV_USE_POLL 1
		4945	\& #define EV_CHILD_ENABLE 1
		4946	\& #define EV_ASYNC_ENABLE 1
		4947	.Ve
		4948	.Sp
		4949	The actual value is a bitset, it can be a combination of the following
		4950	values (by default, all of these are enabled):
		4951	.RS 4
		4952	.ie n .IP "1 \- faster/larger code" 4
		4953	.el .IP "\f(CW1\fR \- faster/larger code" 4
		4954	.IX Item "1 - faster/larger code"
		4955	Use larger code to speed up some operations.
		4956	.Sp
		4957	Currently this is used to override some inlining decisions (enlarging the
		4958	code size by roughly 30% on amd64).
		4959	.Sp
		4960	When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with
		4961	gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of
		4962	assertions.
		4963	.Sp
		4964	The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
		4965	(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
		4966	.ie n .IP "2 \- faster/larger data structures" 4
		4967	.el .IP "\f(CW2\fR \- faster/larger data structures" 4
		4968	.IX Item "2 - faster/larger data structures"
		4969	Replaces the small 2\-heap for timer management by a faster 4\-heap, larger
		4970	hash table sizes and so on. This will usually further increase code size
		4971	and can additionally have an effect on the size of data structures at
		4972	runtime.
		4973	.Sp
		4974	The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
		4975	(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
		4976	.ie n .IP "4 \- full \s-1API\s0 configuration" 4
		4977	.el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4
		4978	.IX Item "4 - full API configuration"
		4979	This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and
		4980	enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1).
		4981	.ie n .IP "8 \- full \s-1API\s0" 4
		4982	.el .IP "\f(CW8\fR \- full \s-1API\s0" 4
		4983	.IX Item "8 - full API"
		4984	This enables a lot of the \*(L"lesser used\*(R" \s-1API\s0 functions. See \f(CW\*(C`ev.h\*(C'\fR for
		4985	details on which parts of the \s-1API\s0 are still available without this
		4986	feature, and do not complain if this subset changes over time.
		4987	.ie n .IP "16 \- enable all optional watcher types" 4
		4988	.el .IP "\f(CW16\fR \- enable all optional watcher types" 4
		4989	.IX Item "16 - enable all optional watcher types"
		4990	Enables all optional watcher types. If you want to selectively enable
		4991	only some watcher types other than I/O and timers (e.g. prepare,
		4992	embed, async, child...) you can enable them manually by defining
		4993	\&\f(CW\*(C`EV_watchertype_ENABLE\*(C'\fR to \f(CW1\fR instead.
		4994	.ie n .IP "32 \- enable all backends" 4
		4995	.el .IP "\f(CW32\fR \- enable all backends" 4
		4996	.IX Item "32 - enable all backends"
		4997	This enables all backends \- without this feature, you need to enable at
		4998	least one backend manually (\f(CW\*(C`EV_USE_SELECT\*(C'\fR is a good choice).
		4999	.ie n .IP "64 \- enable OS-specific ""helper"" APIs" 4
		5000	.el .IP "\f(CW64\fR \- enable OS-specific ``helper'' APIs" 4
		5001	.IX Item "64 - enable OS-specific helper APIs"
		5002	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		5003	default.
		5004	.RE
		5005	.RS 4
		5006	.Sp
		5007	Compiling with \f(CW\*(C`gcc \-Os \-DEV_STANDALONE \-DEV_USE_EPOLL=1 \-DEV_FEATURES=0\*(C'\fR
		5008	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		5009	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		5010	watchers, timers and monotonic clock support.
		5011	.Sp
		5012	With an intelligent-enough linker (gcc+binutils are intelligent enough
		5013	when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by
		5014	your program might be left out as well \- a binary starting a timer and an
		5015	I/O watcher then might come out at only 5Kb.
		5016	.RE
		5017	.IP "\s-1EV_API_STATIC\s0" 4
		5018	.IX Item "EV_API_STATIC"
		5019	If this symbol is defined (by default it is not), then all identifiers
		5020	will have static linkage. This means that libev will not export any
		5021	identifiers, and you cannot link against libev anymore. This can be useful
		5022	when you embed libev, only want to use libev functions in a single file,
		5023	and do not want its identifiers to be visible.
		5024	.Sp
		5025	To use this, define \f(CW\*(C`EV_API_STATIC\*(C'\fR and include \fIev.c\fR in the file that
		5026	wants to use libev.
		5027	.Sp
		5028	This option only works when libev is compiled with a C compiler, as \*(C+
		5029	doesn't support the required declaration syntax.
		5030	.IP "\s-1EV_AVOID_STDIO\s0" 4
		5031	.IX Item "EV_AVOID_STDIO"
		5032	If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio
		5033	functions (printf, scanf, perror etc.). This will increase the code size
		5034	somewhat, but if your program doesn't otherwise depend on stdio and your
		5035	libc allows it, this avoids linking in the stdio library which is quite
		5036	big.
		5037	.Sp
		5038	Note that error messages might become less precise when this option is
		5039	enabled.
		5040	.IP "\s-1EV_NSIG\s0" 4
		5041	.IX Item "EV_NSIG"
		5042	The highest supported signal number, +1 (or, the number of
		5043	signals): Normally, libev tries to deduce the maximum number of signals
		5044	automatically, but sometimes this fails, in which case it can be
		5045	specified. Also, using a lower number than detected (\f(CW32\fR should be
		5046	good for about any system in existence) can save some memory, as libev
		5047	statically allocates some 12\-24 bytes per signal number.
		5048	.IP "\s-1EV_PID_HASHSIZE\s0" 4
		5049	.IX Item "EV_PID_HASHSIZE"
		5050	\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
		5051	pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR disabled),
		5052	usually more than enough. If you need to manage thousands of children you
		5053	might want to increase this value (\fImust\fR be a power of two).
		5054	.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
		5055	.IX Item "EV_INOTIFY_HASHSIZE"
		5056	\&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by
		5057	inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR
		5058	disabled), usually more than enough. If you need to manage thousands of
		5059	\&\f(CW\*(C`ev_stat\*(C'\fR watchers you might want to increase this value (\fImust\fR be a
		5060	power of two).
		5061	.IP "\s-1EV_USE_4HEAP\s0" 4
		5062	.IX Item "EV_USE_4HEAP"
		5063	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		5064	timer and periodics heaps, libev uses a 4\-heap when this symbol is defined
		5065	to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably
		5066	faster performance with many (thousands) of watchers.
		5067	.Sp
		5068	The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
		5069	will be \f(CW0\fR.
		5070	.IP "\s-1EV_HEAP_CACHE_AT\s0" 4
		5071	.IX Item "EV_HEAP_CACHE_AT"
		5072	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		5073	timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within
		5074	the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR),
		5075	which uses 8\-12 bytes more per watcher and a few hundred bytes more code,
		5076	but avoids random read accesses on heap changes. This improves performance
		5077	noticeably with many (hundreds) of watchers.
		5078	.Sp
		5079	The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
		5080	will be \f(CW0\fR.
		5081	.IP "\s-1EV_VERIFY\s0" 4
		5082	.IX Item "EV_VERIFY"
		5083	Controls how much internal verification (see \f(CW\*(C`ev_verify ()\*(C'\fR) will
		5084	be done: If set to \f(CW0\fR, no internal verification code will be compiled
		5085	in. If set to \f(CW1\fR, then verification code will be compiled in, but not
		5086	called. If set to \f(CW2\fR, then the internal verification code will be
		5087	called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
		5088	verification code will be called very frequently, which will slow down
		5089	libev considerably.
		5090	.Sp
		5091	Verification errors are reported via C's \f(CW\*(C`assert\*(C'\fR mechanism, so if you
		5092	disable that (e.g. by defining \f(CW\*(C`NDEBUG\*(C'\fR) then no errors will be reported.
		5093	.Sp
		5094	The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
		5095	will be \f(CW0\fR.
1760	.IP "\s-1EV_COMMON\s0" 4	5096	.IP "\s-1EV_COMMON\s0" 4
1761	.IX Item "EV_COMMON"	5097	.IX Item "EV_COMMON"
1762	By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining	5098	By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
1763	this macro to a something else you can include more and other types of	5099	this macro to something else you can include more and other types of
1764	members. You have to define it each time you include one of the files,	5100	members. You have to define it each time you include one of the files,
1765	though, and it must be identical each time.	5101	though, and it must be identical each time.
1766	.Sp	5102	.Sp
1767	For example, the perl \s-1EV\s0 module uses something like this:	5103	For example, the perl \s-1EV\s0 module uses something like this:
1768	.Sp	5104	.Sp
1769	.Vb 3	5105	.Vb 3
1770	\& #define EV_COMMON \e	5106	\& #define EV_COMMON \e
1771	\& SV *self; /* contains this struct */ \e	5107	\& SV *self; /* contains this struct */ \e
1772	\& SV *cb_sv, *fh /* note no trailing ";" */	5108	\& SV *cb_sv, *fh /* note no trailing ";" */
1773	.Ve	5109	.Ve
1774	.IP "\s-1EV_CB_DECLARE\s0(type)" 4	5110	.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
1775	.IX Item "EV_CB_DECLARE(type)"	5111	.IX Item "EV_CB_DECLARE (type)"
1776	.PD 0	5112	.PD 0
1777	.IP "\s-1EV_CB_INVOKE\s0(watcher,revents)" 4	5113	.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
1778	.IX Item "EV_CB_INVOKE(watcher,revents)"	5114	.IX Item "EV_CB_INVOKE (watcher, revents)"
1779	.IP "ev_set_cb(ev,cb)" 4	5115	.IP "ev_set_cb (ev, cb)" 4
1780	.IX Item "ev_set_cb(ev,cb)"	5116	.IX Item "ev_set_cb (ev, cb)"
1781	.PD	5117	.PD
1782	Can be used to change the callback member declaration in each watcher,	5118	Can be used to change the callback member declaration in each watcher,
1783	and the way callbacks are invoked and set. Must expand to a struct member	5119	and the way callbacks are invoked and set. Must expand to a struct member
1784	definition and a statement, respectively. See the \fIev.v\fR header file for	5120	definition and a statement, respectively. See the \fIev.h\fR header file for
1785	their default definitions. One possible use for overriding these is to	5121	their default definitions. One possible use for overriding these is to
1786	avoid the ev_loop pointer as first argument in all cases, or to use method	5122	avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
1787	calls instead of plain function calls in \*(C+.	5123	method calls instead of plain function calls in \*(C+.
		5124	.SS "\s-1EXPORTED API SYMBOLS\s0"
		5125	.IX Subsection "EXPORTED API SYMBOLS"
		5126	If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of
		5127	exported symbols, you can use the provided \fISymbol.*\fR files which list
		5128	all public symbols, one per line:
		5129	.PP
		5130	.Vb 2
		5131	\& Symbols.ev for libev proper
		5132	\& Symbols.event for the libevent emulation
		5133	.Ve
		5134	.PP
		5135	This can also be used to rename all public symbols to avoid clashes with
		5136	multiple versions of libev linked together (which is obviously bad in
		5137	itself, but sometimes it is inconvenient to avoid this).
		5138	.PP
		5139	A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
		5140	include before including \fIev.h\fR:
		5141	.PP
		5142	.Vb 1
		5143	\& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h
		5144	.Ve
		5145	.PP
		5146	This would create a file \fIwrap.h\fR which essentially looks like this:
		5147	.PP
		5148	.Vb 4
		5149	\& #define ev_backend myprefix_ev_backend
		5150	\& #define ev_check_start myprefix_ev_check_start
		5151	\& #define ev_check_stop myprefix_ev_check_stop
		5152	\& ...
		5153	.Ve
1788	.Sh "\s-1EXAMPLES\s0"	5154	.SS "\s-1EXAMPLES\s0"
1789	.IX Subsection "EXAMPLES"	5155	.IX Subsection "EXAMPLES"
1790	For a real-world example of a program the includes libev	5156	For a real-world example of a program the includes libev
1791	verbatim, you can have a look at the \s-1EV\s0 perl module	5157	verbatim, you can have a look at the \s-1EV\s0 perl module
1792	(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in	5158	(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
1793	the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public	5159	the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
1794	interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file	5160	interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
1795	will be compiled. It is pretty complex because it provides its own header	5161	will be compiled. It is pretty complex because it provides its own header
1796	file.	5162	file.
1797	.Sp	5163	.PP
1798	The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file	5164	The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
1799	that everybody includes and which overrides some autoconf choices:	5165	that everybody includes and which overrides some configure choices:
1800	.Sp	5166	.PP
1801	.Vb 4	5167	.Vb 8
		5168	\& #define EV_FEATURES 8
		5169	\& #define EV_USE_SELECT 1
		5170	\& #define EV_PREPARE_ENABLE 1
		5171	\& #define EV_IDLE_ENABLE 1
		5172	\& #define EV_SIGNAL_ENABLE 1
		5173	\& #define EV_CHILD_ENABLE 1
1802	\& #define EV_USE_POLL 0	5174	\& #define EV_USE_STDEXCEPT 0
1803	\& #define EV_MULTIPLICITY 0
1804	\& #define EV_PERIODICS 0
1805	\& #define EV_CONFIG_H <config.h>	5175	\& #define EV_CONFIG_H <config.h>
1806	.Ve	5176	\&
1807	.Sp
1808	.Vb 1
1809	\& #include "ev++.h"	5177	\& #include "ev++.h"
1810	.Ve	5178	.Ve
1811	.Sp	5179	.PP
1812	And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:	5180	And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
1813	.Sp	5181	.PP
1814	.Vb 1
1815	\& #include "rxvttoolkit.h"
1816	.Ve
1817	.Sp
1818	.Vb 2	5182	.Vb 2
1819	\& /* darwin has problems with its header files in C++, requiring this namespace juggling */	5183	\& #include "ev_cpp.h"
1820	\& using namespace ev;
1821	.Ve
1822	.Sp
1823	.Vb 1
1824	\& #include "ev.c"	5184	\& #include "ev.c"
1825	.Ve	5185	.Ve
		5186	.SH "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
		5187	.IX Header "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
		5188	.SS "\s-1THREADS AND COROUTINES\s0"
		5189	.IX Subsection "THREADS AND COROUTINES"
		5190	\fI\s-1THREADS\s0\fR
		5191	.IX Subsection "THREADS"
		5192	.PP
		5193	All libev functions are reentrant and thread-safe unless explicitly
		5194	documented otherwise, but libev implements no locking itself. This means
		5195	that you can use as many loops as you want in parallel, as long as there
		5196	are no concurrent calls into any libev function with the same loop
		5197	parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter,
		5198	of course): libev guarantees that different event loops share no data
		5199	structures that need any locking.
		5200	.PP
		5201	Or to put it differently: calls with different loop parameters can be done
		5202	concurrently from multiple threads, calls with the same loop parameter
		5203	must be done serially (but can be done from different threads, as long as
		5204	only one thread ever is inside a call at any point in time, e.g. by using
		5205	a mutex per loop).
		5206	.PP
		5207	Specifically to support threads (and signal handlers), libev implements
		5208	so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of
		5209	concurrency on the same event loop, namely waking it up \*(L"from the
		5210	outside\*(R".
		5211	.PP
		5212	If you want to know which design (one loop, locking, or multiple loops
		5213	without or something else still) is best for your problem, then I cannot
		5214	help you, but here is some generic advice:
		5215	.IP "\(bu" 4
		5216	most applications have a main thread: use the default libev loop
		5217	in that thread, or create a separate thread running only the default loop.
		5218	.Sp
		5219	This helps integrating other libraries or software modules that use libev
		5220	themselves and don't care/know about threading.
		5221	.IP "\(bu" 4
		5222	one loop per thread is usually a good model.
		5223	.Sp
		5224	Doing this is almost never wrong, sometimes a better-performance model
		5225	exists, but it is always a good start.
		5226	.IP "\(bu" 4
		5227	other models exist, such as the leader/follower pattern, where one
		5228	loop is handed through multiple threads in a kind of round-robin fashion.
		5229	.Sp
		5230	Choosing a model is hard \- look around, learn, know that usually you can do
		5231	better than you currently do :\-)
		5232	.IP "\(bu" 4
		5233	often you need to talk to some other thread which blocks in the
		5234	event loop.
		5235	.Sp
		5236	\&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely
		5237	(or from signal contexts...).
		5238	.Sp
		5239	An example use would be to communicate signals or other events that only
		5240	work in the default loop by registering the signal watcher with the
		5241	default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop
		5242	watcher callback into the event loop interested in the signal.
		5243	.PP
		5244	See also \*(L"\s-1THREAD LOCKING EXAMPLE\*(R"\s0.
		5245	.PP
		5246	\fI\s-1COROUTINES\s0\fR
		5247	.IX Subsection "COROUTINES"
		5248	.PP
		5249	Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"):
		5250	libev fully supports nesting calls to its functions from different
		5251	coroutines (e.g. you can call \f(CW\*(C`ev_run\*(C'\fR on the same loop from two
		5252	different coroutines, and switch freely between both coroutines running
		5253	the loop, as long as you don't confuse yourself). The only exception is
		5254	that you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks.
		5255	.PP
		5256	Care has been taken to ensure that libev does not keep local state inside
		5257	\&\f(CW\*(C`ev_run\*(C'\fR, and other calls do not usually allow for coroutine switches as
		5258	they do not call any callbacks.
		5259	.SS "\s-1COMPILER WARNINGS\s0"
		5260	.IX Subsection "COMPILER WARNINGS"
		5261	Depending on your compiler and compiler settings, you might get no or a
		5262	lot of warnings when compiling libev code. Some people are apparently
		5263	scared by this.
		5264	.PP
		5265	However, these are unavoidable for many reasons. For one, each compiler
		5266	has different warnings, and each user has different tastes regarding
		5267	warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when
		5268	targeting a specific compiler and compiler-version.
		5269	.PP
		5270	Another reason is that some compiler warnings require elaborate
		5271	workarounds, or other changes to the code that make it less clear and less
		5272	maintainable.
		5273	.PP
		5274	And of course, some compiler warnings are just plain stupid, or simply
		5275	wrong (because they don't actually warn about the condition their message
		5276	seems to warn about). For example, certain older gcc versions had some
		5277	warnings that resulted in an extreme number of false positives. These have
		5278	been fixed, but some people still insist on making code warn-free with
		5279	such buggy versions.
		5280	.PP
		5281	While libev is written to generate as few warnings as possible,
		5282	\&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev
		5283	with any compiler warnings enabled unless you are prepared to cope with
		5284	them (e.g. by ignoring them). Remember that warnings are just that:
		5285	warnings, not errors, or proof of bugs.
		5286	.SS "\s-1VALGRIND\s0"
		5287	.IX Subsection "VALGRIND"
		5288	Valgrind has a special section here because it is a popular tool that is
		5289	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		5290	.PP
		5291	If you think you found a bug (memory leak, uninitialised data access etc.)
		5292	in libev, then check twice: If valgrind reports something like:
		5293	.PP
		5294	.Vb 3
		5295	\& ==2274== definitely lost: 0 bytes in 0 blocks.
		5296	\& ==2274== possibly lost: 0 bytes in 0 blocks.
		5297	\& ==2274== still reachable: 256 bytes in 1 blocks.
		5298	.Ve
		5299	.PP
		5300	Then there is no memory leak, just as memory accounted to global variables
		5301	is not a memleak \- the memory is still being referenced, and didn't leak.
		5302	.PP
		5303	Similarly, under some circumstances, valgrind might report kernel bugs
		5304	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		5305	although an acceptable workaround has been found here), or it might be
		5306	confused.
		5307	.PP
		5308	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		5309	make it into some kind of religion.
		5310	.PP
		5311	If you are unsure about something, feel free to contact the mailing list
		5312	with the full valgrind report and an explanation on why you think this
		5313	is a bug in libev (best check the archives, too :). However, don't be
		5314	annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance
		5315	of learning how to interpret valgrind properly.
		5316	.PP
		5317	If you need, for some reason, empty reports from valgrind for your project
		5318	I suggest using suppression lists.
		5319	.SH "PORTABILITY NOTES"
		5320	.IX Header "PORTABILITY NOTES"
		5321	.SS "\s-1GNU/LINUX 32 BIT LIMITATIONS\s0"
		5322	.IX Subsection "GNU/LINUX 32 BIT LIMITATIONS"
		5323	GNU/Linux is the only common platform that supports 64 bit file/large file
		5324	interfaces but \fIdisables\fR them by default.
		5325	.PP
		5326	That means that libev compiled in the default environment doesn't support
		5327	files larger than 2GiB or so, which mainly affects \f(CW\*(C`ev_stat\*(C'\fR watchers.
		5328	.PP
		5329	Unfortunately, many programs try to work around this GNU/Linux issue
		5330	by enabling the large file \s-1API,\s0 which makes them incompatible with the
		5331	standard libev compiled for their system.
		5332	.PP
		5333	Likewise, libev cannot enable the large file \s-1API\s0 itself as this would
		5334	suddenly make it incompatible to the default compile time environment,
		5335	i.e. all programs not using special compile switches.
		5336	.SS "\s-1OS/X AND DARWIN BUGS\s0"
		5337	.IX Subsection "OS/X AND DARWIN BUGS"
		5338	The whole thing is a bug if you ask me \- basically any system interface
		5339	you touch is broken, whether it is locales, poll, kqueue or even the
		5340	OpenGL drivers.
		5341	.PP
		5342	\fI\f(CI\*(C`kqueue\*(C'\fI is buggy\fR
		5343	.IX Subsection "kqueue is buggy"
		5344	.PP
		5345	The kqueue syscall is broken in all known versions \- most versions support
		5346	only sockets, many support pipes.
		5347	.PP
		5348	Libev tries to work around this by not using \f(CW\*(C`kqueue\*(C'\fR by default on this
		5349	rotten platform, but of course you can still ask for it when creating a
		5350	loop \- embedding a socket-only kqueue loop into a select-based one is
		5351	probably going to work well.
		5352	.PP
		5353	\fI\f(CI\*(C`poll\*(C'\fI is buggy\fR
		5354	.IX Subsection "poll is buggy"
		5355	.PP
		5356	Instead of fixing \f(CW\*(C`kqueue\*(C'\fR, Apple replaced their (working) \f(CW\*(C`poll\*(C'\fR
		5357	implementation by something calling \f(CW\*(C`kqueue\*(C'\fR internally around the 10.5.6
		5358	release, so now \f(CW\*(C`kqueue\*(C'\fR \fIand\fR \f(CW\*(C`poll\*(C'\fR are broken.
		5359	.PP
		5360	Libev tries to work around this by not using \f(CW\*(C`poll\*(C'\fR by default on
		5361	this rotten platform, but of course you can still ask for it when creating
		5362	a loop.
		5363	.PP
		5364	\fI\f(CI\*(C`select\*(C'\fI is buggy\fR
		5365	.IX Subsection "select is buggy"
		5366	.PP
		5367	All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this
		5368	one up as well: On \s-1OS/X,\s0 \f(CW\*(C`select\*(C'\fR actively limits the number of file
		5369	descriptors you can pass in to 1024 \- your program suddenly crashes when
		5370	you use more.
		5371	.PP
		5372	There is an undocumented \*(L"workaround\*(R" for this \- defining
		5373	\&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR
		5374	work on \s-1OS/X.\s0
		5375	.SS "\s-1SOLARIS PROBLEMS AND WORKAROUNDS\s0"
		5376	.IX Subsection "SOLARIS PROBLEMS AND WORKAROUNDS"
		5377	\fI\f(CI\*(C`errno\*(C'\fI reentrancy\fR
		5378	.IX Subsection "errno reentrancy"
		5379	.PP
		5380	The default compile environment on Solaris is unfortunately so
		5381	thread-unsafe that you can't even use components/libraries compiled
		5382	without \f(CW\*(C`\-D_REENTRANT\*(C'\fR in a threaded program, which, of course, isn't
		5383	defined by default. A valid, if stupid, implementation choice.
		5384	.PP
		5385	If you want to use libev in threaded environments you have to make sure
		5386	it's compiled with \f(CW\*(C`_REENTRANT\*(C'\fR defined.
		5387	.PP
		5388	\fIEvent port backend\fR
		5389	.IX Subsection "Event port backend"
		5390	.PP
		5391	The scalable event interface for Solaris is called \*(L"event
		5392	ports\*(R". Unfortunately, this mechanism is very buggy in all major
		5393	releases. If you run into high \s-1CPU\s0 usage, your program freezes or you get
		5394	a large number of spurious wakeups, make sure you have all the relevant
		5395	and latest kernel patches applied. No, I don't know which ones, but there
		5396	are multiple ones to apply, and afterwards, event ports actually work
		5397	great.
		5398	.PP
		5399	If you can't get it to work, you can try running the program by setting
		5400	the environment variable \f(CW\*(C`LIBEV_FLAGS=3\*(C'\fR to only allow \f(CW\*(C`poll\*(C'\fR and
		5401	\&\f(CW\*(C`select\*(C'\fR backends.
		5402	.SS "\s-1AIX POLL BUG\s0"
		5403	.IX Subsection "AIX POLL BUG"
		5404	\&\s-1AIX\s0 unfortunately has a broken \f(CW\*(C`poll.h\*(C'\fR header. Libev works around
		5405	this by trying to avoid the poll backend altogether (i.e. it's not even
		5406	compiled in), which normally isn't a big problem as \f(CW\*(C`select\*(C'\fR works fine
		5407	with large bitsets on \s-1AIX,\s0 and \s-1AIX\s0 is dead anyway.
		5408	.SS "\s-1WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS\s0"
		5409	.IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
		5410	\fIGeneral issues\fR
		5411	.IX Subsection "General issues"
		5412	.PP
		5413	Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
		5414	requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
		5415	model. Libev still offers limited functionality on this platform in
		5416	the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
		5417	descriptors. This only applies when using Win32 natively, not when using
		5418	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5419	as every compiler comes with a slightly differently broken/incompatible
		5420	environment.
		5421	.PP
		5422	Lifting these limitations would basically require the full
		5423	re-implementation of the I/O system. If you are into this kind of thing,
		5424	then note that glib does exactly that for you in a very portable way (note
		5425	also that glib is the slowest event library known to man).
		5426	.PP
		5427	There is no supported compilation method available on windows except
		5428	embedding it into other applications.
		5429	.PP
		5430	Sensible signal handling is officially unsupported by Microsoft \- libev
		5431	tries its best, but under most conditions, signals will simply not work.
		5432	.PP
		5433	Not a libev limitation but worth mentioning: windows apparently doesn't
		5434	accept large writes: instead of resulting in a partial write, windows will
		5435	either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large,
		5436	so make sure you only write small amounts into your sockets (less than a
		5437	megabyte seems safe, but this apparently depends on the amount of memory
		5438	available).
		5439	.PP
		5440	Due to the many, low, and arbitrary limits on the win32 platform and
		5441	the abysmal performance of winsockets, using a large number of sockets
		5442	is not recommended (and not reasonable). If your program needs to use
		5443	more than a hundred or so sockets, then likely it needs to use a totally
		5444	different implementation for windows, as libev offers the \s-1POSIX\s0 readiness
		5445	notification model, which cannot be implemented efficiently on windows
		5446	(due to Microsoft monopoly games).
		5447	.PP
		5448	A typical way to use libev under windows is to embed it (see the embedding
		5449	section for details) and use the following \fIevwrap.h\fR header file instead
		5450	of \fIev.h\fR:
		5451	.PP
		5452	.Vb 2
		5453	\& #define EV_STANDALONE /* keeps ev from requiring config.h */
		5454	\& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		5455	\&
		5456	\& #include "ev.h"
		5457	.Ve
		5458	.PP
		5459	And compile the following \fIevwrap.c\fR file into your project (make sure
		5460	you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!):
		5461	.PP
		5462	.Vb 2
		5463	\& #include "evwrap.h"
		5464	\& #include "ev.c"
		5465	.Ve
		5466	.PP
		5467	\fIThe winsocket \f(CI\*(C`select\*(C'\fI function\fR
		5468	.IX Subsection "The winsocket select function"
		5469	.PP
		5470	The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it
		5471	requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is
		5472	also extremely buggy). This makes select very inefficient, and also
		5473	requires a mapping from file descriptors to socket handles (the Microsoft
		5474	C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the
		5475	discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and
		5476	\&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info.
		5477	.PP
		5478	The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime
		5479	libraries and raw winsocket select is:
		5480	.PP
		5481	.Vb 2
		5482	\& #define EV_USE_SELECT 1
		5483	\& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		5484	.Ve
		5485	.PP
		5486	Note that winsockets handling of fd sets is O(n), so you can easily get a
		5487	complexity in the O(nX) range when using win32.
		5488	.PP
		5489	\fILimited number of file descriptors\fR
		5490	.IX Subsection "Limited number of file descriptors"
		5491	.PP
		5492	Windows has numerous arbitrary (and low) limits on things.
		5493	.PP
		5494	Early versions of winsocket's select only supported waiting for a maximum
		5495	of \f(CW64\fR handles (probably owning to the fact that all windows kernels
		5496	can only wait for \f(CW64\fR things at the same time internally; Microsoft
		5497	recommends spawning a chain of threads and wait for 63 handles and the
		5498	previous thread in each. Sounds great!).
		5499	.PP
		5500	Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
		5501	to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
		5502	call (which might be in libev or elsewhere, for example, perl and many
		5503	other interpreters do their own select emulation on windows).
		5504	.PP
		5505	Another limit is the number of file descriptors in the Microsoft runtime
		5506	libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR
		5507	fetish or something like this inside Microsoft). You can increase this
		5508	by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR
		5509	(another arbitrary limit), but is broken in many versions of the Microsoft
		5510	runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets
		5511	(depending on windows version and/or the phase of the moon). To get more,
		5512	you need to wrap all I/O functions and provide your own fd management, but
		5513	the cost of calling select (O(nX)) will likely make this unworkable.
		5514	.SS "\s-1PORTABILITY REQUIREMENTS\s0"
		5515	.IX Subsection "PORTABILITY REQUIREMENTS"
		5516	In addition to a working ISO-C implementation and of course the
		5517	backend-specific APIs, libev relies on a few additional extensions:
		5518	.ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4
		5519	.el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4
		5520	.IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *."
		5521	Libev assumes not only that all watcher pointers have the same internal
		5522	structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO C\s0 for example), but it also
		5523	assumes that the same (machine) code can be used to call any watcher
		5524	callback: The watcher callbacks have different type signatures, but libev
		5525	calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
		5526	.IP "null pointers and integer zero are represented by 0 bytes" 4
		5527	.IX Item "null pointers and integer zero are represented by 0 bytes"
		5528	Libev uses \f(CW\*(C`memset\*(C'\fR to initialise structs and arrays to \f(CW0\fR bytes, and
		5529	relies on this setting pointers and integers to null.
		5530	.IP "pointer accesses must be thread-atomic" 4
		5531	.IX Item "pointer accesses must be thread-atomic"
		5532	Accessing a pointer value must be atomic, it must both be readable and
		5533	writable in one piece \- this is the case on all current architectures.
		5534	.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4
		5535	.el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4
		5536	.IX Item "sig_atomic_t volatile must be thread-atomic as well"
		5537	The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as
		5538	\&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different
		5539	threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is
		5540	believed to be sufficiently portable.
		5541	.ie n .IP """sigprocmask"" must work in a threaded environment" 4
		5542	.el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4
		5543	.IX Item "sigprocmask must work in a threaded environment"
		5544	Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not
		5545	allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical
		5546	pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main
		5547	thread\*(R" or will block signals process-wide, both behaviours would
		5548	be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and
		5549	\&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however.
		5550	.Sp
		5551	The most portable way to handle signals is to block signals in all threads
		5552	except the initial one, and run the signal handling loop in the initial
		5553	thread as well.
		5554	.ie n .IP """long"" must be large enough for common memory allocation sizes" 4
		5555	.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
		5556	.IX Item "long must be large enough for common memory allocation sizes"
		5557	To improve portability and simplify its \s-1API,\s0 libev uses \f(CW\*(C`long\*(C'\fR internally
		5558	instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX
		5559	systems (Microsoft...) this might be unexpectedly low, but is still at
		5560	least 31 bits everywhere, which is enough for hundreds of millions of
		5561	watchers.
		5562	.ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4
		5563	.el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4
		5564	.IX Item "double must hold a time value in seconds with enough accuracy"
		5565	The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to
		5566	have at least 51 bits of mantissa (and 9 bits of exponent), which is
		5567	good enough for at least into the year 4000 with millisecond accuracy
		5568	(the design goal for libev). This requirement is overfulfilled by
		5569	implementations using \s-1IEEE 754,\s0 which is basically all existing ones.
		5570	.Sp
		5571	With \s-1IEEE 754\s0 doubles, you get microsecond accuracy until at least the
		5572	year 2255 (and millisecond accuracy till the year 287396 \- by then, libev
		5573	is either obsolete or somebody patched it to use \f(CW\*(C`long double\*(C'\fR or
		5574	something like that, just kidding).
		5575	.PP
		5576	If you know of other additional requirements drop me a note.
		5577	.SH "ALGORITHMIC COMPLEXITIES"
		5578	.IX Header "ALGORITHMIC COMPLEXITIES"
		5579	In this section the complexities of (many of) the algorithms used inside
		5580	libev will be documented. For complexity discussions about backends see
		5581	the documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
		5582	.PP
		5583	All of the following are about amortised time: If an array needs to be
		5584	extended, libev needs to realloc and move the whole array, but this
		5585	happens asymptotically rarer with higher number of elements, so O(1) might
		5586	mean that libev does a lengthy realloc operation in rare cases, but on
		5587	average it is much faster and asymptotically approaches constant time.
		5588	.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
		5589	.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
		5590	This means that, when you have a watcher that triggers in one hour and
		5591	there are 100 watchers that would trigger before that, then inserting will
		5592	have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers.
		5593	.IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4
		5594	.IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)"
		5595	That means that changing a timer costs less than removing/adding them,
		5596	as only the relative motion in the event queue has to be paid for.
		5597	.IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4
		5598	.IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)"
		5599	These just add the watcher into an array or at the head of a list.
		5600	.IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4
		5601	.IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)"
		5602	.PD 0
		5603	.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
		5604	.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
		5605	.PD
		5606	These watchers are stored in lists, so they need to be walked to find the
		5607	correct watcher to remove. The lists are usually short (you don't usually
		5608	have many watchers waiting for the same fd or signal: one is typical, two
		5609	is rare).
		5610	.IP "Finding the next timer in each loop iteration: O(1)" 4
		5611	.IX Item "Finding the next timer in each loop iteration: O(1)"
		5612	By virtue of using a binary or 4\-heap, the next timer is always found at a
		5613	fixed position in the storage array.
		5614	.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
		5615	.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
		5616	A change means an I/O watcher gets started or stopped, which requires
		5617	libev to recalculate its status (and possibly tell the kernel, depending
		5618	on backend and whether \f(CW\*(C`ev_io_set\*(C'\fR was used).
		5619	.IP "Activating one watcher (putting it into the pending state): O(1)" 4
		5620	.IX Item "Activating one watcher (putting it into the pending state): O(1)"
		5621	.PD 0
		5622	.IP "Priority handling: O(number_of_priorities)" 4
		5623	.IX Item "Priority handling: O(number_of_priorities)"
		5624	.PD
		5625	Priorities are implemented by allocating some space for each
		5626	priority. When doing priority-based operations, libev usually has to
		5627	linearly search all the priorities, but starting/stopping and activating
		5628	watchers becomes O(1) with respect to priority handling.
		5629	.IP "Sending an ev_async: O(1)" 4
		5630	.IX Item "Sending an ev_async: O(1)"
		5631	.PD 0
		5632	.IP "Processing ev_async_send: O(number_of_async_watchers)" 4
		5633	.IX Item "Processing ev_async_send: O(number_of_async_watchers)"
		5634	.IP "Processing signals: O(max_signal_number)" 4
		5635	.IX Item "Processing signals: O(max_signal_number)"
		5636	.PD
		5637	Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR
		5638	calls in the current loop iteration and the loop is currently
		5639	blocked. Checking for async and signal events involves iterating over all
		5640	running async watchers or all signal numbers.
		5641	.SH "PORTING FROM LIBEV 3.X TO 4.X"
		5642	.IX Header "PORTING FROM LIBEV 3.X TO 4.X"
		5643	The major version 4 introduced some incompatible changes to the \s-1API.\s0
		5644	.PP
		5645	At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions
		5646	for all changes, so most programs should still compile. The compatibility
		5647	layer might be removed in later versions of libev, so better update to the
		5648	new \s-1API\s0 early than late.
		5649	.ie n .IP """EV_COMPAT3"" backwards compatibility mechanism" 4
		5650	.el .IP "\f(CWEV_COMPAT3\fR backwards compatibility mechanism" 4
		5651	.IX Item "EV_COMPAT3 backwards compatibility mechanism"
		5652	The backward compatibility mechanism can be controlled by
		5653	\&\f(CW\*(C`EV_COMPAT3\*(C'\fR. See \*(L"\s-1PREPROCESSOR SYMBOLS/MACROS\*(R"\s0 in the \*(L"\s-1EMBEDDING\*(R"\s0
		5654	section.
		5655	.ie n .IP """ev_default_destroy"" and ""ev_default_fork"" have been removed" 4
		5656	.el .IP "\f(CWev_default_destroy\fR and \f(CWev_default_fork\fR have been removed" 4
		5657	.IX Item "ev_default_destroy and ev_default_fork have been removed"
		5658	These calls can be replaced easily by their \f(CW\*(C`ev_loop_xxx\*(C'\fR counterparts:
		5659	.Sp
		5660	.Vb 2
		5661	\& ev_loop_destroy (EV_DEFAULT_UC);
		5662	\& ev_loop_fork (EV_DEFAULT);
		5663	.Ve
		5664	.IP "function/symbol renames" 4
		5665	.IX Item "function/symbol renames"
		5666	A number of functions and symbols have been renamed:
		5667	.Sp
		5668	.Vb 3
		5669	\& ev_loop => ev_run
		5670	\& EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5671	\& EVLOOP_ONESHOT => EVRUN_ONCE
		5672	\&
		5673	\& ev_unloop => ev_break
		5674	\& EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5675	\& EVUNLOOP_ONE => EVBREAK_ONE
		5676	\& EVUNLOOP_ALL => EVBREAK_ALL
		5677	\&
		5678	\& EV_TIMEOUT => EV_TIMER
		5679	\&
		5680	\& ev_loop_count => ev_iteration
		5681	\& ev_loop_depth => ev_depth
		5682	\& ev_loop_verify => ev_verify
		5683	.Ve
		5684	.Sp
		5685	Most functions working on \f(CW\*(C`struct ev_loop\*(C'\fR objects don't have an
		5686	\&\f(CW\*(C`ev_loop_\*(C'\fR prefix, so it was removed; \f(CW\*(C`ev_loop\*(C'\fR, \f(CW\*(C`ev_unloop\*(C'\fR and
		5687	associated constants have been renamed to not collide with the \f(CW\*(C`struct
		5688	ev_loop\*(C'\fR anymore and \f(CW\*(C`EV_TIMER\*(C'\fR now follows the same naming scheme
		5689	as all other watcher types. Note that \f(CW\*(C`ev_loop_fork\*(C'\fR is still called
		5690	\&\f(CW\*(C`ev_loop_fork\*(C'\fR because it would otherwise clash with the \f(CW\*(C`ev_fork\*(C'\fR
		5691	typedef.
		5692	.ie n .IP """EV_MINIMAL"" mechanism replaced by ""EV_FEATURES""" 4
		5693	.el .IP "\f(CWEV_MINIMAL\fR mechanism replaced by \f(CWEV_FEATURES\fR" 4
		5694	.IX Item "EV_MINIMAL mechanism replaced by EV_FEATURES"
		5695	The preprocessor symbol \f(CW\*(C`EV_MINIMAL\*(C'\fR has been replaced by a different
		5696	mechanism, \f(CW\*(C`EV_FEATURES\*(C'\fR. Programs using \f(CW\*(C`EV_MINIMAL\*(C'\fR usually compile
		5697	and work, but the library code will of course be larger.
		5698	.SH "GLOSSARY"
		5699	.IX Header "GLOSSARY"
		5700	.IP "active" 4
		5701	.IX Item "active"
		5702	A watcher is active as long as it has been started and not yet stopped.
		5703	See \*(L"\s-1WATCHER STATES\*(R"\s0 for details.
		5704	.IP "application" 4
		5705	.IX Item "application"
		5706	In this document, an application is whatever is using libev.
		5707	.IP "backend" 4
		5708	.IX Item "backend"
		5709	The part of the code dealing with the operating system interfaces.
		5710	.IP "callback" 4
		5711	.IX Item "callback"
		5712	The address of a function that is called when some event has been
		5713	detected. Callbacks are being passed the event loop, the watcher that
		5714	received the event, and the actual event bitset.
		5715	.IP "callback/watcher invocation" 4
		5716	.IX Item "callback/watcher invocation"
		5717	The act of calling the callback associated with a watcher.
		5718	.IP "event" 4
		5719	.IX Item "event"
		5720	A change of state of some external event, such as data now being available
		5721	for reading on a file descriptor, time having passed or simply not having
		5722	any other events happening anymore.
		5723	.Sp
		5724	In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or
		5725	\&\f(CW\*(C`EV_TIMER\*(C'\fR).
		5726	.IP "event library" 4
		5727	.IX Item "event library"
		5728	A software package implementing an event model and loop.
		5729	.IP "event loop" 4
		5730	.IX Item "event loop"
		5731	An entity that handles and processes external events and converts them
		5732	into callback invocations.
		5733	.IP "event model" 4
		5734	.IX Item "event model"
		5735	The model used to describe how an event loop handles and processes
		5736	watchers and events.
		5737	.IP "pending" 4
		5738	.IX Item "pending"
		5739	A watcher is pending as soon as the corresponding event has been
		5740	detected. See \*(L"\s-1WATCHER STATES\*(R"\s0 for details.
		5741	.IP "real time" 4
		5742	.IX Item "real time"
		5743	The physical time that is observed. It is apparently strictly monotonic :)
		5744	.IP "wall-clock time" 4
		5745	.IX Item "wall-clock time"
		5746	The time and date as shown on clocks. Unlike real time, it can actually
		5747	be wrong and jump forwards and backwards, e.g. when you adjust your
		5748	clock.
		5749	.IP "watcher" 4
		5750	.IX Item "watcher"
		5751	A data structure that describes interest in certain events. Watchers need
		5752	to be started (attached to an event loop) before they can receive events.
1826	.SH "AUTHOR"	5753	.SH "AUTHOR"
1827	.IX Header "AUTHOR"	5754	.IX Header "AUTHOR"
1828	Marc Lehmann <libev@schmorp.de>.	5755	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5756	Magnusson and Emanuele Giaquinta, and minor corrections by many others.

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