[ViewVC] Diff of: cvs/libev/ev.3

Comparing libev/ev.3 (file contents):
Revision 1.42 by root, Fri Dec 7 20:19:16 2007 UTC vs.
Revision 1.80 by root, Sun Aug 9 12:34:46 2009 UTC

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129	.\" ========================================================================	124	.\" ========================================================================
130	.\"	125	.\"
131	.IX Title ""<STANDARD INPUT>" 1"	126	.IX Title "LIBEV 3"
132	.TH "<STANDARD INPUT>" 1 "2007-12-07" "perl v5.8.8" "User Contributed Perl Documentation"	127	.TH LIBEV 3 "2009-07-27" "libev-3.8" "libev - high performance full featured event loop"
		128	.\" For nroff, turn off justification. Always turn off hyphenation; it makes
		129	.\" way too many mistakes in technical documents.
		130	.if n .ad l
		131	.nh
133	.SH "NAME"	132	.SH "NAME"
134	libev \- a high performance full\-featured event loop written in C	133	libev \- a high performance full\-featured event loop written in C
135	.SH "SYNOPSIS"	134	.SH "SYNOPSIS"
136	.IX Header "SYNOPSIS"	135	.IX Header "SYNOPSIS"
137	.Vb 1	136	.Vb 1
138	\& #include <ev.h>	137	\& #include <ev.h>
139	.Ve	138	.Ve
140	.SH "EXAMPLE PROGRAM"	139	.SS "\s-1EXAMPLE\s0 \s-1PROGRAM\s0"
141	.IX Header "EXAMPLE PROGRAM"	140	.IX Subsection "EXAMPLE PROGRAM"
142	.Vb 1
143	\& #include <ev.h>
144	.Ve
145	.PP
146	.Vb 2	141	.Vb 2
		142	\& // a single header file is required
		143	\& #include <ev.h>
		144	\&
		145	\& #include <stdio.h> // for puts
		146	\&
		147	\& // every watcher type has its own typedef\*(Aqd struct
		148	\& // with the name ev_TYPE
147	\& ev_io stdin_watcher;	149	\& ev_io stdin_watcher;
148	\& ev_timer timeout_watcher;	150	\& ev_timer timeout_watcher;
149	.Ve	151	\&
150	.PP	152	\& // all watcher callbacks have a similar signature
151	.Vb 8
152	\& /* called when data readable on stdin */	153	\& // this callback is called when data is readable on stdin
153	\& static void	154	\& static void
154	\& stdin_cb (EV_P_ struct ev_io *w, int revents)	155	\& stdin_cb (EV_P_ ev_io *w, int revents)
155	\& {	156	\& {
156	\& /* puts ("stdin ready"); */	157	\& puts ("stdin ready");
157	\& ev_io_stop (EV_A_ w); /* just a syntax example */	158	\& // for one\-shot events, one must manually stop the watcher
158	\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	159	\& // with its corresponding stop function.
		160	\& ev_io_stop (EV_A_ w);
		161	\&
		162	\& // this causes all nested ev_loop\*(Aqs to stop iterating
		163	\& ev_unloop (EV_A_ EVUNLOOP_ALL);
159	\& }	164	\& }
160	.Ve	165	\&
161	.PP	166	\& // another callback, this time for a time\-out
162	.Vb 6
163	\& static void	167	\& static void
164	\& timeout_cb (EV_P_ struct ev_timer *w, int revents)	168	\& timeout_cb (EV_P_ ev_timer *w, int revents)
165	\& {	169	\& {
166	\& /* puts ("timeout"); */	170	\& puts ("timeout");
167	\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	171	\& // this causes the innermost ev_loop to stop iterating
		172	\& ev_unloop (EV_A_ EVUNLOOP_ONE);
168	\& }	173	\& }
169	.Ve	174	\&
170	.PP
171	.Vb 4
172	\& int	175	\& int
173	\& main (void)	176	\& main (void)
174	\& {	177	\& {
		178	\& // use the default event loop unless you have special needs
175	\& struct ev_loop *loop = ev_default_loop (0);	179	\& struct ev_loop *loop = ev_default_loop (0);
176	.Ve	180	\&
177	.PP
178	.Vb 3
179	\& /* initialise an io watcher, then start it */	181	\& // initialise an io watcher, then start it
		182	\& // this one will watch for stdin to become readable
180	\& ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	183	\& ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
181	\& ev_io_start (loop, &stdin_watcher);	184	\& ev_io_start (loop, &stdin_watcher);
182	.Ve	185	\&
183	.PP	186	\& // initialise a timer watcher, then start it
184	.Vb 3
185	\& /* simple non-repeating 5.5 second timeout */	187	\& // simple non\-repeating 5.5 second timeout
186	\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	188	\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
187	\& ev_timer_start (loop, &timeout_watcher);	189	\& ev_timer_start (loop, &timeout_watcher);
188	.Ve	190	\&
189	.PP	191	\& // now wait for events to arrive
190	.Vb 2
191	\& /* loop till timeout or data ready */
192	\& ev_loop (loop, 0);	192	\& ev_loop (loop, 0);
193	.Ve	193	\&
194	.PP	194	\& // unloop was called, so exit
195	.Vb 2
196	\& return 0;	195	\& return 0;
197	\& }	196	\& }
198	.Ve	197	.Ve
199	.SH "DESCRIPTION"	198	.SH "ABOUT THIS DOCUMENT"
200	.IX Header "DESCRIPTION"	199	.IX Header "ABOUT THIS DOCUMENT"
		200	This document documents the libev software package.
		201	.PP
201	The newest version of this document is also available as a html-formatted	202	The newest version of this document is also available as an html-formatted
202	web page you might find easier to navigate when reading it for the first	203	web page you might find easier to navigate when reading it for the first
203	time: <http://cvs.schmorp.de/libev/ev.html>.	204	time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
204	.PP	205	.PP
		206	While this document tries to be as complete as possible in documenting
		207	libev, its usage and the rationale behind its design, it is not a tutorial
		208	on event-based programming, nor will it introduce event-based programming
		209	with libev.
		210	.PP
		211	Familarity with event based programming techniques in general is assumed
		212	throughout this document.
		213	.SH "ABOUT LIBEV"
		214	.IX Header "ABOUT LIBEV"
205	Libev is an event loop: you register interest in certain events (such as a	215	Libev is an event loop: you register interest in certain events (such as a
206	file descriptor being readable or a timeout occuring), and it will manage	216	file descriptor being readable or a timeout occurring), and it will manage
207	these event sources and provide your program with events.	217	these event sources and provide your program with events.
208	.PP	218	.PP
209	To do this, it must take more or less complete control over your process	219	To do this, it must take more or less complete control over your process
210	(or thread) by executing the \fIevent loop\fR handler, and will then	220	(or thread) by executing the \fIevent loop\fR handler, and will then
211	communicate events via a callback mechanism.	221	communicate events via a callback mechanism.
212	.PP	222	.PP
213	You register interest in certain events by registering so-called \fIevent	223	You register interest in certain events by registering so-called \fIevent
214	watchers\fR, which are relatively small C structures you initialise with the	224	watchers\fR, which are relatively small C structures you initialise with the
215	details of the event, and then hand it over to libev by \fIstarting\fR the	225	details of the event, and then hand it over to libev by \fIstarting\fR the
216	watcher.	226	watcher.
217	.SH "FEATURES"	227	.SS "\s-1FEATURES\s0"
218	.IX Header "FEATURES"	228	.IX Subsection "FEATURES"
219	Libev supports \f(CW\(C`select\(C'\fR, \f(CW\(C`poll\(C'\fR, the Linux-specific \f(CW\(C`epoll\(C'\fR, the	229	Libev supports \f(CW\(C`select\(C'\fR, \f(CW\(C`poll\(C'\fR, the Linux-specific \f(CW\(C`epoll\(C'\fR, the
220	BSD-specific \f(CW\(C`kqueue\(C'\fR and the Solaris-specific event port mechanisms	230	BSD-specific \f(CW\(C`kqueue\(C'\fR and the Solaris-specific event port mechanisms
221	for file descriptor events (\f(CW\(C`ev_io\(C'\fR), the Linux \f(CW\(C`inotify\(C'\fR interface	231	for file descriptor events (\f(CW\(C`ev_io\(C'\fR), the Linux \f(CW\(C`inotify\(C'\fR interface
222	(for \f(CW\(C`ev_stat\(C'\fR), relative timers (\f(CW\(C`ev_timer\(C'\fR), absolute timers	232	(for \f(CW\(C`ev_stat\(C'\fR), Linux eventfd/signalfd (for faster and cleaner
223	with customised rescheduling (\f(CW\(C`ev_periodic\(C'\fR), synchronous signals	233	inter-thread wakeup (\f(CW\(C`ev_async\(C'\fR)/signal handling (\f(CW\(C`ev_signal\(C'\fR)) relative
224	(\f(CW\(C`ev_signal\(C'\fR), process status change events (\f(CW\(C`ev_child\(C'\fR), and event	234	timers (\f(CW\(C`ev_timer\(C'\fR), absolute timers with customised rescheduling
225	watchers dealing with the event loop mechanism itself (\f(CW\(C`ev_idle\(C'\fR,	235	(\f(CW\(C`ev_periodic\(C'\fR), synchronous signals (\f(CW\(C`ev_signal\(C'\fR), process status
226	\&\f(CW\(C`ev_embed\(C'\fR, \f(CW\(C`ev_prepare\(C'\fR and \f(CW\(C`ev_check\(C'\fR watchers) as well as	236	change events (\f(CW\(C`ev_child\(C'\fR), and event watchers dealing with the event
227	file watchers (\f(CW\(C`ev_stat\(C'\fR) and even limited support for fork events	237	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
228	(\f(CW\(C`ev_fork\(C'\fR).	238	\&\f(CW\(C`ev_check\(C'\fR watchers) as well as file watchers (\f(CW\(C`ev_stat\(C'\fR) and even
		239	limited support for fork events (\f(CW\(C`ev_fork\(C'\fR).
229	.PP	240	.PP
230	It also is quite fast (see this	241	It also is quite fast (see this
231	benchmark comparing it to libevent	242	<benchmark> comparing it to libevent
232	for example).	243	for example).
233	.SH "CONVENTIONS"	244	.SS "\s-1CONVENTIONS\s0"
234	.IX Header "CONVENTIONS"	245	.IX Subsection "CONVENTIONS"
235	Libev is very configurable. In this manual the default configuration will	246	Libev is very configurable. In this manual the default (and most common)
236	be described, which supports multiple event loops. For more info about	247	configuration will be described, which supports multiple event loops. For
237	various configuration options please have a look at \fB\s-1EMBED\s0\fR section in	248	more info about various configuration options please have a look at
238	this manual. If libev was configured without support for multiple event	249	\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support
239	loops, then all functions taking an initial argument of name \f(CW\(C`loop\(C'\fR	250	for multiple event loops, then all functions taking an initial argument of
240	(which is always of type \f(CW\(C`struct ev_loop \*(C'\fR) will not have this argument.	251	name \f(CW\(C`loop\(C'\fR (which is always of type \f(CW\(C`ev_loop \*(C'\fR) will not have
241	.SH "TIME REPRESENTATION"	252	this argument.
		253	.SS "\s-1TIME\s0 \s-1REPRESENTATION\s0"
242	.IX Header "TIME REPRESENTATION"	254	.IX Subsection "TIME REPRESENTATION"
243	Libev represents time as a single floating point number, representing the	255	Libev represents time as a single floating point number, representing
244	(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near	256	the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere
245	the beginning of 1970, details are complicated, don't ask). This type is	257	near the beginning of 1970, details are complicated, don't ask). This
246	called \f(CW\(C`ev_tstamp\(C'\fR, which is what you should use too. It usually aliases	258	type is called \f(CW\(C`ev_tstamp\(C'\fR, which is what you should use too. It usually
247	to the \f(CW\(C`double\(C'\fR type in C, and when you need to do any calculations on	259	aliases to the \f(CW\(C`double\(C'\fR type in C. When you need to do any calculations
248	it, you should treat it as such.	260	on it, you should treat it as some floating point value. Unlike the name
		261	component \f(CW\(C`stamp\(C'\fR might indicate, it is also used for time differences
		262	throughout libev.
		263	.SH "ERROR HANDLING"
		264	.IX Header "ERROR HANDLING"
		265	Libev knows three classes of errors: operating system errors, usage errors
		266	and internal errors (bugs).
		267	.PP
		268	When libev catches an operating system error it cannot handle (for example
		269	a system call indicating a condition libev cannot fix), it calls the callback
		270	set via \f(CW\(C`ev_set_syserr_cb\(C'\fR, which is supposed to fix the problem or
		271	abort. The default is to print a diagnostic message and to call \f(CW\*(C`abort
		272	()\*(C'\fR.
		273	.PP
		274	When libev detects a usage error such as a negative timer interval, then
		275	it will print a diagnostic message and abort (via the \f(CW\(C`assert\(C'\fR mechanism,
		276	so \f(CW\(C`NDEBUG\(C'\fR will disable this checking): these are programming errors in
		277	the libev caller and need to be fixed there.
		278	.PP
		279	Libev also has a few internal error-checking \f(CW\(C`assert\(C'\fRions, and also has
		280	extensive consistency checking code. These do not trigger under normal
		281	circumstances, as they indicate either a bug in libev or worse.
249	.SH "GLOBAL FUNCTIONS"	282	.SH "GLOBAL FUNCTIONS"
250	.IX Header "GLOBAL FUNCTIONS"	283	.IX Header "GLOBAL FUNCTIONS"
251	These functions can be called anytime, even before initialising the	284	These functions can be called anytime, even before initialising the
252	library in any way.	285	library in any way.
253	.IP "ev_tstamp ev_time ()" 4	286	.IP "ev_tstamp ev_time ()" 4
254	.IX Item "ev_tstamp ev_time ()"	287	.IX Item "ev_tstamp ev_time ()"
255	Returns the current time as libev would use it. Please note that the	288	Returns the current time as libev would use it. Please note that the
256	\&\f(CW\(C`ev_now\(C'\fR function is usually faster and also often returns the timestamp	289	\&\f(CW\(C`ev_now\(C'\fR function is usually faster and also often returns the timestamp
257	you actually want to know.	290	you actually want to know.
		291	.IP "ev_sleep (ev_tstamp interval)" 4
		292	.IX Item "ev_sleep (ev_tstamp interval)"
		293	Sleep for the given interval: The current thread will be blocked until
		294	either it is interrupted or the given time interval has passed. Basically
		295	this is a sub-second-resolution \f(CW\(C`sleep ()\(C'\fR.
258	.IP "int ev_version_major ()" 4	296	.IP "int ev_version_major ()" 4
259	.IX Item "int ev_version_major ()"	297	.IX Item "int ev_version_major ()"
260	.PD 0	298	.PD 0
261	.IP "int ev_version_minor ()" 4	299	.IP "int ev_version_minor ()" 4
262	.IX Item "int ev_version_minor ()"	300	.IX Item "int ev_version_minor ()"
263	.PD	301	.PD
264	You can find out the major and minor version numbers of the library	302	You can find out the major and minor \s-1ABI\s0 version numbers of the library
265	you linked against by calling the functions \f(CW\(C`ev_version_major\(C'\fR and	303	you linked against by calling the functions \f(CW\(C`ev_version_major\(C'\fR and
266	\&\f(CW\(C`ev_version_minor\(C'\fR. If you want, you can compare against the global	304	\&\f(CW\(C`ev_version_minor\(C'\fR. If you want, you can compare against the global
267	symbols \f(CW\(C`EV_VERSION_MAJOR\(C'\fR and \f(CW\(C`EV_VERSION_MINOR\(C'\fR, which specify the	305	symbols \f(CW\(C`EV_VERSION_MAJOR\(C'\fR and \f(CW\(C`EV_VERSION_MINOR\(C'\fR, which specify the
268	version of the library your program was compiled against.	306	version of the library your program was compiled against.
269	.Sp	307	.Sp
		308	These version numbers refer to the \s-1ABI\s0 version of the library, not the
		309	release version.
		310	.Sp
270	Usually, it's a good idea to terminate if the major versions mismatch,	311	Usually, it's a good idea to terminate if the major versions mismatch,
271	as this indicates an incompatible change. Minor versions are usually	312	as this indicates an incompatible change. Minor versions are usually
272	compatible to older versions, so a larger minor version alone is usually	313	compatible to older versions, so a larger minor version alone is usually
273	not a problem.	314	not a problem.
274	.Sp	315	.Sp
275	Example: Make sure we haven't accidentally been linked against the wrong	316	Example: Make sure we haven't accidentally been linked against the wrong
276	version.	317	version.
277	.Sp	318	.Sp
278	.Vb 3	319	.Vb 3
279	\& assert (("libev version mismatch",	320	\& assert (("libev version mismatch",
280	\& ev_version_major () == EV_VERSION_MAJOR	321	\& ev_version_major () == EV_VERSION_MAJOR
281	\& && ev_version_minor () >= EV_VERSION_MINOR));	322	\& && ev_version_minor () >= EV_VERSION_MINOR));
282	.Ve	323	.Ve
283	.IP "unsigned int ev_supported_backends ()" 4	324	.IP "unsigned int ev_supported_backends ()" 4
284	.IX Item "unsigned int ev_supported_backends ()"	325	.IX Item "unsigned int ev_supported_backends ()"
285	Return the set of all backends (i.e. their corresponding \f(CW\(C`EV_BACKEND_\*(C'\fR	326	Return the set of all backends (i.e. their corresponding \f(CW\(C`EV_BACKEND_\*(C'\fR
286	value) compiled into this binary of libev (independent of their	327	value) compiled into this binary of libev (independent of their
…		…
289	.Sp	330	.Sp
290	Example: make sure we have the epoll method, because yeah this is cool and	331	Example: make sure we have the epoll method, because yeah this is cool and
291	a must have and can we have a torrent of it please!!!11	332	a must have and can we have a torrent of it please!!!11
292	.Sp	333	.Sp
293	.Vb 2	334	.Vb 2
294	\& assert (("sorry, no epoll, no sex",	335	\& assert (("sorry, no epoll, no sex",
295	\& ev_supported_backends () & EVBACKEND_EPOLL));	336	\& ev_supported_backends () & EVBACKEND_EPOLL));
296	.Ve	337	.Ve
297	.IP "unsigned int ev_recommended_backends ()" 4	338	.IP "unsigned int ev_recommended_backends ()" 4
298	.IX Item "unsigned int ev_recommended_backends ()"	339	.IX Item "unsigned int ev_recommended_backends ()"
299	Return the set of all backends compiled into this binary of libev and also	340	Return the set of all backends compiled into this binary of libev and also
300	recommended for this platform. This set is often smaller than the one	341	recommended for this platform. This set is often smaller than the one
301	returned by \f(CW\(C`ev_supported_backends\(C'\fR, as for example kqueue is broken on	342	returned by \f(CW\(C`ev_supported_backends\(C'\fR, as for example kqueue is broken on
302	most BSDs and will not be autodetected unless you explicitly request it	343	most BSDs and will not be auto-detected unless you explicitly request it
303	(assuming you know what you are doing). This is the set of backends that	344	(assuming you know what you are doing). This is the set of backends that
304	libev will probe for if you specify no backends explicitly.	345	libev will probe for if you specify no backends explicitly.
305	.IP "unsigned int ev_embeddable_backends ()" 4	346	.IP "unsigned int ev_embeddable_backends ()" 4
306	.IX Item "unsigned int ev_embeddable_backends ()"	347	.IX Item "unsigned int ev_embeddable_backends ()"
307	Returns the set of backends that are embeddable in other event loops. This	348	Returns the set of backends that are embeddable in other event loops. This
308	is the theoretical, all\-platform, value. To find which backends	349	is the theoretical, all-platform, value. To find which backends
309	might be supported on the current system, you would need to look at	350	might be supported on the current system, you would need to look at
310	\&\f(CW\(C`ev_embeddable_backends () & ev_supported_backends ()\(C'\fR, likewise for	351	\&\f(CW\(C`ev_embeddable_backends () & ev_supported_backends ()\(C'\fR, likewise for
311	recommended ones.	352	recommended ones.
312	.Sp	353	.Sp
313	See the description of \f(CW\(C`ev_embed\(C'\fR watchers for more info.	354	See the description of \f(CW\(C`ev_embed\(C'\fR watchers for more info.
314	.IP "ev_set_allocator (void (cb)(void *ptr, long size))" 4	355	.IP "ev_set_allocator (void (cb)(void *ptr, long size)) [\s-1NOT\s0 \s-1REENTRANT\s0]" 4
315	.IX Item "ev_set_allocator (void (cb)(void *ptr, long size))"	356	.IX Item "ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]"
316	Sets the allocation function to use (the prototype is similar \- the	357	Sets the allocation function to use (the prototype is similar \- the
317	semantics is identical \- to the realloc C function). It is used to	358	semantics are identical to the \f(CW\(C`realloc\(C'\fR C89/SuS/POSIX function). It is
318	allocate and free memory (no surprises here). If it returns zero when	359	used to allocate and free memory (no surprises here). If it returns zero
319	memory needs to be allocated, the library might abort or take some	360	when memory needs to be allocated (\f(CW\(C`size != 0\(C'\fR), the library might abort
320	potentially destructive action. The default is your system realloc	361	or take some potentially destructive action.
321	function.	362	.Sp
		363	Since some systems (at least OpenBSD and Darwin) fail to implement
		364	correct \f(CW\(C`realloc\(C'\fR semantics, libev will use a wrapper around the system
		365	\&\f(CW\(C`realloc\(C'\fR and \f(CW\(C`free\(C'\fR functions by default.
322	.Sp	366	.Sp
323	You could override this function in high-availability programs to, say,	367	You could override this function in high-availability programs to, say,
324	free some memory if it cannot allocate memory, to use a special allocator,	368	free some memory if it cannot allocate memory, to use a special allocator,
325	or even to sleep a while and retry until some memory is available.	369	or even to sleep a while and retry until some memory is available.
326	.Sp	370	.Sp
327	Example: Replace the libev allocator with one that waits a bit and then	371	Example: Replace the libev allocator with one that waits a bit and then
328	retries).	372	retries (example requires a standards-compliant \f(CW\(C`realloc\(C'\fR).
329	.Sp	373	.Sp
330	.Vb 6	374	.Vb 6
331	\& static void *	375	\& static void *
332	\& persistent_realloc (void *ptr, size_t size)	376	\& persistent_realloc (void *ptr, size_t size)
333	\& {	377	\& {
334	\& for (;;)	378	\& for (;;)
335	\& {	379	\& {
336	\& void *newptr = realloc (ptr, size);	380	\& void *newptr = realloc (ptr, size);
337	.Ve	381	\&
338	.Sp
339	.Vb 2
340	\& if (newptr)	382	\& if (newptr)
341	\& return newptr;	383	\& return newptr;
342	.Ve	384	\&
343	.Sp
344	.Vb 3
345	\& sleep (60);	385	\& sleep (60);
346	\& }	386	\& }
347	\& }	387	\& }
348	.Ve	388	\&
349	.Sp
350	.Vb 2
351	\& ...	389	\& ...
352	\& ev_set_allocator (persistent_realloc);	390	\& ev_set_allocator (persistent_realloc);
353	.Ve	391	.Ve
354	.IP "ev_set_syserr_cb (void (cb)(const char msg));" 4	392	.IP "ev_set_syserr_cb (void (cb)(const char msg)); [\s-1NOT\s0 \s-1REENTRANT\s0]" 4
355	.IX Item "ev_set_syserr_cb (void (cb)(const char msg));"	393	.IX Item "ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]"
356	Set the callback function to call on a retryable syscall error (such	394	Set the callback function to call on a retryable system call error (such
357	as failed select, poll, epoll_wait). The message is a printable string	395	as failed select, poll, epoll_wait). The message is a printable string
358	indicating the system call or subsystem causing the problem. If this	396	indicating the system call or subsystem causing the problem. If this
359	callback is set, then libev will expect it to remedy the sitution, no	397	callback is set, then libev will expect it to remedy the situation, no
360	matter what, when it returns. That is, libev will generally retry the	398	matter what, when it returns. That is, libev will generally retry the
361	requested operation, or, if the condition doesn't go away, do bad stuff	399	requested operation, or, if the condition doesn't go away, do bad stuff
362	(such as abort).	400	(such as abort).
363	.Sp	401	.Sp
364	Example: This is basically the same thing that libev does internally, too.	402	Example: This is basically the same thing that libev does internally, too.
…		…
368	\& fatal_error (const char *msg)	406	\& fatal_error (const char *msg)
369	\& {	407	\& {
370	\& perror (msg);	408	\& perror (msg);
371	\& abort ();	409	\& abort ();
372	\& }	410	\& }
373	.Ve	411	\&
374	.Sp
375	.Vb 2
376	\& ...	412	\& ...
377	\& ev_set_syserr_cb (fatal_error);	413	\& ev_set_syserr_cb (fatal_error);
378	.Ve	414	.Ve
379	.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"	415	.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
380	.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"	416	.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
381	An event loop is described by a \f(CW\(C`struct ev_loop \*(C'\fR. The library knows two	417	An event loop is described by a \f(CW\(C`struct ev_loop \(C'\fR (the \f(CW\(C`struct\*(C'\fR
382	types of such loops, the \fIdefault\fR loop, which supports signals and child	418	is \fInot\fR optional in this case, as there is also an \f(CW\(C`ev_loop\(C'\fR
383	events, and dynamically created loops which do not.	419	\&\fIfunction\fR).
384	.PP	420	.PP
385	If you use threads, a common model is to run the default event loop	421	The library knows two types of such loops, the \fIdefault\fR loop, which
386	in your main thread (or in a separate thread) and for each thread you	422	supports signals and child events, and dynamically created loops which do
387	create, you also create another event loop. Libev itself does no locking	423	not.
388	whatsoever, so if you mix calls to the same event loop in different
389	threads, make sure you lock (this is usually a bad idea, though, even if
390	done correctly, because it's hideous and inefficient).
391	.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4	424	.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
392	.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"	425	.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
393	This will initialise the default event loop if it hasn't been initialised	426	This will initialise the default event loop if it hasn't been initialised
394	yet and return it. If the default loop could not be initialised, returns	427	yet and return it. If the default loop could not be initialised, returns
395	false. If it already was initialised it simply returns it (and ignores the	428	false. If it already was initialised it simply returns it (and ignores the
396	flags. If that is troubling you, check \f(CW\(C`ev_backend ()\(C'\fR afterwards).	429	flags. If that is troubling you, check \f(CW\(C`ev_backend ()\(C'\fR afterwards).
397	.Sp	430	.Sp
398	If you don't know what event loop to use, use the one returned from this	431	If you don't know what event loop to use, use the one returned from this
399	function.	432	function.
		433	.Sp
		434	Note that this function is \fInot\fR thread-safe, so if you want to use it
		435	from multiple threads, you have to lock (note also that this is unlikely,
		436	as loops cannot be shared easily between threads anyway).
		437	.Sp
		438	The default loop is the only loop that can handle \f(CW\(C`ev_signal\(C'\fR and
		439	\&\f(CW\(C`ev_child\(C'\fR watchers, and to do this, it always registers a handler
		440	for \f(CW\(C`SIGCHLD\(C'\fR. If this is a problem for your application you can either
		441	create a dynamic loop with \f(CW\(C`ev_loop_new\(C'\fR that doesn't do that, or you
		442	can simply overwrite the \f(CW\(C`SIGCHLD\(C'\fR signal handler \fIafter\fR calling
		443	\&\f(CW\(C`ev_default_init\(C'\fR.
400	.Sp	444	.Sp
401	The flags argument can be used to specify special behaviour or specific	445	The flags argument can be used to specify special behaviour or specific
402	backends to use, and is usually specified as \f(CW0\fR (or \f(CW\(C`EVFLAG_AUTO\(C'\fR).	446	backends to use, and is usually specified as \f(CW0\fR (or \f(CW\(C`EVFLAG_AUTO\(C'\fR).
403	.Sp	447	.Sp
404	The following flags are supported:	448	The following flags are supported:
…		…
409	The default flags value. Use this if you have no clue (it's the right	453	The default flags value. Use this if you have no clue (it's the right
410	thing, believe me).	454	thing, believe me).
411	.ie n .IP """EVFLAG_NOENV""" 4	455	.ie n .IP """EVFLAG_NOENV""" 4
412	.el .IP "\f(CWEVFLAG_NOENV\fR" 4	456	.el .IP "\f(CWEVFLAG_NOENV\fR" 4
413	.IX Item "EVFLAG_NOENV"	457	.IX Item "EVFLAG_NOENV"
414	If this flag bit is ored into the flag value (or the program runs setuid	458	If this flag bit is or'ed into the flag value (or the program runs setuid
415	or setgid) then libev will \fInot\fR look at the environment variable	459	or setgid) then libev will \fInot\fR look at the environment variable
416	\&\f(CW\(C`LIBEV_FLAGS\(C'\fR. Otherwise (the default), this environment variable will	460	\&\f(CW\(C`LIBEV_FLAGS\(C'\fR. Otherwise (the default), this environment variable will
417	override the flags completely if it is found in the environment. This is	461	override the flags completely if it is found in the environment. This is
418	useful to try out specific backends to test their performance, or to work	462	useful to try out specific backends to test their performance, or to work
419	around bugs.	463	around bugs.
…		…
425	enabling this flag.	469	enabling this flag.
426	.Sp	470	.Sp
427	This works by calling \f(CW\(C`getpid ()\(C'\fR on every iteration of the loop,	471	This works by calling \f(CW\(C`getpid ()\(C'\fR on every iteration of the loop,
428	and thus this might slow down your event loop if you do a lot of loop	472	and thus this might slow down your event loop if you do a lot of loop
429	iterations and little real work, but is usually not noticeable (on my	473	iterations and little real work, but is usually not noticeable (on my
430	Linux system for example, \f(CW\(C`getpid\(C'\fR is actually a simple 5\-insn sequence	474	GNU/Linux system for example, \f(CW\(C`getpid\(C'\fR is actually a simple 5\-insn sequence
431	without a syscall and thus \fIvery\fR fast, but my Linux system also has	475	without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has
432	\&\f(CW\(C`pthread_atfork\(C'\fR which is even faster).	476	\&\f(CW\(C`pthread_atfork\(C'\fR which is even faster).
433	.Sp	477	.Sp
434	The big advantage of this flag is that you can forget about fork (and	478	The big advantage of this flag is that you can forget about fork (and
435	forget about forgetting to tell libev about forking) when you use this	479	forget about forgetting to tell libev about forking) when you use this
436	flag.	480	flag.
437	.Sp	481	.Sp
438	This flag setting cannot be overriden or specified in the \f(CW\(C`LIBEV_FLAGS\(C'\fR	482	This flag setting cannot be overridden or specified in the \f(CW\(C`LIBEV_FLAGS\(C'\fR
439	environment variable.	483	environment variable.
		484	.ie n .IP """EVFLAG_NOINOTIFY""" 4
		485	.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
		486	.IX Item "EVFLAG_NOINOTIFY"
		487	When this flag is specified, then libev will not attempt to use the
		488	\&\fIinotify\fR \s-1API\s0 for it's \f(CW\(C`ev_stat\(C'\fR watchers. Apart from debugging and
		489	testing, this flag can be useful to conserve inotify file descriptors, as
		490	otherwise each loop using \f(CW\(C`ev_stat\(C'\fR watchers consumes one inotify handle.
		491	.ie n .IP """EVFLAG_NOSIGNALFD""" 4
		492	.el .IP "\f(CWEVFLAG_NOSIGNALFD\fR" 4
		493	.IX Item "EVFLAG_NOSIGNALFD"
		494	When this flag is specified, then libev will not attempt to use the
		495	\&\fIsignalfd\fR \s-1API\s0 for it's \f(CW\(C`ev_signal\(C'\fR (and \f(CW\(C`ev_child\(C'\fR) watchers. This is
		496	probably only useful to work around any bugs in libev. Consequently, this
		497	flag might go away once the signalfd functionality is considered stable,
		498	so it's useful mostly in environment variables and not in program code.
440	.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4	499	.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
441	.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4	500	.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
442	.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"	501	.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
443	This is your standard \fIselect\fR\\|(2) backend. Not \fIcompletely\fR standard, as	502	This is your standard \fIselect\fR\\|(2) backend. Not \fIcompletely\fR standard, as
444	libev tries to roll its own fd_set with no limits on the number of fds,	503	libev tries to roll its own fd_set with no limits on the number of fds,
445	but if that fails, expect a fairly low limit on the number of fds when	504	but if that fails, expect a fairly low limit on the number of fds when
446	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	505	using this backend. It doesn't scale too well (O(highest_fd)), but its
447	the fastest backend for a low number of fds.	506	usually the fastest backend for a low number of (low-numbered :) fds.
		507	.Sp
		508	To get good performance out of this backend you need a high amount of
		509	parallelism (most of the file descriptors should be busy). If you are
		510	writing a server, you should \f(CW\(C`accept ()\(C'\fR in a loop to accept as many
		511	connections as possible during one iteration. You might also want to have
		512	a look at \f(CW\(C`ev_set_io_collect_interval ()\(C'\fR to increase the amount of
		513	readiness notifications you get per iteration.
		514	.Sp
		515	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
		516	\&\f(CW\(C`writefds\(C'\fR set (and to work around Microsoft Windows bugs, also onto the
		517	\&\f(CW\(C`exceptfds\(C'\fR set on that platform).
448	.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4	518	.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
449	.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4	519	.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
450	.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"	520	.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
451	And this is your standard \fIpoll\fR\\|(2) backend. It's more complicated than	521	And this is your standard \fIpoll\fR\\|(2) backend. It's more complicated
452	select, but handles sparse fds better and has no artificial limit on the	522	than select, but handles sparse fds better and has no artificial
453	number of fds you can use (except it will slow down considerably with a	523	limit on the number of fds you can use (except it will slow down
454	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	524	considerably with a lot of inactive fds). It scales similarly to select,
		525	i.e. O(total_fds). See the entry for \f(CW\(C`EVBACKEND_SELECT\(C'\fR, above, for
		526	performance tips.
		527	.Sp
		528	This backend maps \f(CW\(C`EV_READ\(C'\fR to \f(CW\(C`POLLIN \| POLLERR \| POLLHUP\(C'\fR, and
		529	\&\f(CW\(C`EV_WRITE\(C'\fR to \f(CW\(C`POLLOUT \| POLLERR \| POLLHUP\(C'\fR.
455	.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4	530	.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
456	.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4	531	.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
457	.IX Item "EVBACKEND_EPOLL (value 4, Linux)"	532	.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
458	For few fds, this backend is a bit little slower than poll and select,	533	For few fds, this backend is a bit little slower than poll and select,
459	but it scales phenomenally better. While poll and select usually scale like	534	but it scales phenomenally better. While poll and select usually scale
460	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	535	like O(total_fds) where n is the total number of fds (or the highest fd),
461	either O(1) or O(active_fds).	536	epoll scales either O(1) or O(active_fds).
462	.Sp	537	.Sp
		538	The epoll mechanism deserves honorable mention as the most misdesigned
		539	of the more advanced event mechanisms: mere annoyances include silently
		540	dropping file descriptors, requiring a system call per change per file
		541	descriptor (and unnecessary guessing of parameters), problems with dup and
		542	so on. The biggest issue is fork races, however \- if a program forks then
		543	\&\fIboth\fR parent and child process have to recreate the epoll set, which can
		544	take considerable time (one syscall per file descriptor) and is of course
		545	hard to detect.
		546	.Sp
		547	Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, but
		548	of course \fIdoesn't\fR, and epoll just loves to report events for totally
		549	\&\fIdifferent\fR file descriptors (even already closed ones, so one cannot
		550	even remove them from the set) than registered in the set (especially
		551	on \s-1SMP\s0 systems). Libev tries to counter these spurious notifications by
		552	employing an additional generation counter and comparing that against the
		553	events to filter out spurious ones, recreating the set when required.
		554	.Sp
463	While stopping and starting an I/O watcher in the same iteration will	555	While stopping, setting and starting an I/O watcher in the same iteration
464	result in some caching, there is still a syscall per such incident	556	will result in some caching, there is still a system call per such
465	(because the fd could point to a different file description now), so its	557	incident (because the same \fIfile descriptor\fR could point to a different
466	best to avoid that. Also, \fIdup()\fRed file descriptors might not work very	558	\&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\(C`dup ()\(C'\fR'ed
467	well if you register events for both fds.	559	file descriptors might not work very well if you register events for both
		560	file descriptors.
468	.Sp	561	.Sp
469	Please note that epoll sometimes generates spurious notifications, so you	562	Best performance from this backend is achieved by not unregistering all
470	need to use non-blocking I/O or other means to avoid blocking when no data	563	watchers for a file descriptor until it has been closed, if possible,
471	(or space) is available.	564	i.e. keep at least one watcher active per fd at all times. Stopping and
		565	starting a watcher (without re-setting it) also usually doesn't cause
		566	extra overhead. A fork can both result in spurious notifications as well
		567	as in libev having to destroy and recreate the epoll object, which can
		568	take considerable time and thus should be avoided.
		569	.Sp
		570	All this means that, in practice, \f(CW\(C`EVBACKEND_SELECT\(C'\fR can be as fast or
		571	faster than epoll for maybe up to a hundred file descriptors, depending on
		572	the usage. So sad.
		573	.Sp
		574	While nominally embeddable in other event loops, this feature is broken in
		575	all kernel versions tested so far.
		576	.Sp
		577	This backend maps \f(CW\(C`EV_READ\(C'\fR and \f(CW\(C`EV_WRITE\(C'\fR in the same way as
		578	\&\f(CW\(C`EVBACKEND_POLL\(C'\fR.
472	.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4	579	.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
473	.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4	580	.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
474	.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"	581	.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
475	Kqueue deserves special mention, as at the time of this writing, it	582	Kqueue deserves special mention, as at the time of this writing, it
476	was broken on all BSDs except NetBSD (usually it doesn't work with	583	was broken on all BSDs except NetBSD (usually it doesn't work reliably
477	anything but sockets and pipes, except on Darwin, where of course its	584	with anything but sockets and pipes, except on Darwin, where of course
478	completely useless). For this reason its not being \(L"autodetected\(R"	585	it's completely useless). Unlike epoll, however, whose brokenness
		586	is by design, these kqueue bugs can (and eventually will) be fixed
		587	without \s-1API\s0 changes to existing programs. For this reason it's not being
479	unless you explicitly specify it explicitly in the flags (i.e. using	588	\&\(L"auto-detected\(R" unless you explicitly specify it in the flags (i.e. using
480	\&\f(CW\(C`EVBACKEND_KQUEUE\(C'\fR).	589	\&\f(CW\(C`EVBACKEND_KQUEUE\(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
		590	system like NetBSD.
		591	.Sp
		592	You still can embed kqueue into a normal poll or select backend and use it
		593	only for sockets (after having made sure that sockets work with kqueue on
		594	the target platform). See \f(CW\(C`ev_embed\(C'\fR watchers for more info.
481	.Sp	595	.Sp
482	It scales in the same way as the epoll backend, but the interface to the	596	It scales in the same way as the epoll backend, but the interface to the
483	kernel is more efficient (which says nothing about its actual speed, of	597	kernel is more efficient (which says nothing about its actual speed, of
484	course). While starting and stopping an I/O watcher does not cause an	598	course). While stopping, setting and starting an I/O watcher does never
485	extra syscall as with epoll, it still adds up to four event changes per	599	cause an extra system call as with \f(CW\(C`EVBACKEND_EPOLL\(C'\fR, it still adds up to
486	incident, so its best to avoid that.	600	two event changes per incident. Support for \f(CW\(C`fork ()\(C'\fR is very bad (but
		601	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		602	cases
		603	.Sp
		604	This backend usually performs well under most conditions.
		605	.Sp
		606	While nominally embeddable in other event loops, this doesn't work
		607	everywhere, so you might need to test for this. And since it is broken
		608	almost everywhere, you should only use it when you have a lot of sockets
		609	(for which it usually works), by embedding it into another event loop
		610	(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
		611	also broken on \s-1OS\s0 X)) and, did I mention it, using it only for sockets.
		612	.Sp
		613	This backend maps \f(CW\(C`EV_READ\(C'\fR into an \f(CW\(C`EVFILT_READ\(C'\fR kevent with
		614	\&\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
		615	\&\f(CW\(C`NOTE_EOF\(C'\fR.
487	.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4	616	.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
488	.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4	617	.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
489	.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"	618	.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
490	This is not implemented yet (and might never be).	619	This is not implemented yet (and might never be, unless you send me an
		620	implementation). According to reports, \f(CW\(C`/dev/poll\(C'\fR only supports sockets
		621	and is not embeddable, which would limit the usefulness of this backend
		622	immensely.
491	.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4	623	.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
492	.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4	624	.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
493	.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"	625	.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
494	This uses the Solaris 10 port mechanism. As with everything on Solaris,	626	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
495	it's really slow, but it still scales very well (O(active_fds)).	627	it's really slow, but it still scales very well (O(active_fds)).
496	.Sp	628	.Sp
497	Please note that solaris ports can result in a lot of spurious	629	Please note that Solaris event ports can deliver a lot of spurious
498	notifications, so you need to use non-blocking I/O or other means to avoid	630	notifications, so you need to use non-blocking I/O or other means to avoid
499	blocking when no data (or space) is available.	631	blocking when no data (or space) is available.
		632	.Sp
		633	While this backend scales well, it requires one system call per active
		634	file descriptor per loop iteration. For small and medium numbers of file
		635	descriptors a \(L"slow\(R" \f(CW\(C`EVBACKEND_SELECT\(C'\fR or \f(CW\(C`EVBACKEND_POLL\(C'\fR backend
		636	might perform better.
		637	.Sp
		638	On the positive side, with the exception of the spurious readiness
		639	notifications, this backend actually performed fully to specification
		640	in all tests and is fully embeddable, which is a rare feat among the
		641	OS-specific backends (I vastly prefer correctness over speed hacks).
		642	.Sp
		643	This backend maps \f(CW\(C`EV_READ\(C'\fR and \f(CW\(C`EV_WRITE\(C'\fR in the same way as
		644	\&\f(CW\(C`EVBACKEND_POLL\(C'\fR.
500	.ie n .IP """EVBACKEND_ALL""" 4	645	.ie n .IP """EVBACKEND_ALL""" 4
501	.el .IP "\f(CWEVBACKEND_ALL\fR" 4	646	.el .IP "\f(CWEVBACKEND_ALL\fR" 4
502	.IX Item "EVBACKEND_ALL"	647	.IX Item "EVBACKEND_ALL"
503	Try all backends (even potentially broken ones that wouldn't be tried	648	Try all backends (even potentially broken ones that wouldn't be tried
504	with \f(CW\(C`EVFLAG_AUTO\(C'\fR). Since this is a mask, you can do stuff such as	649	with \f(CW\(C`EVFLAG_AUTO\(C'\fR). Since this is a mask, you can do stuff such as
505	\&\f(CW\(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\(C'\fR.	650	\&\f(CW\(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\(C'\fR.
		651	.Sp
		652	It is definitely not recommended to use this flag.
506	.RE	653	.RE
507	.RS 4	654	.RS 4
508	.Sp	655	.Sp
509	If one or more of these are ored into the flags value, then only these	656	If one or more of the backend flags are or'ed into the flags value,
510	backends will be tried (in the reverse order as given here). If none are	657	then only these backends will be tried (in the reverse order as listed
511	specified, most compiled-in backend will be tried, usually in reverse	658	here). If none are specified, all backends in \f(CW\*(C`ev_recommended_backends
512	order of their flag values :)	659	()\*(C'\fR will be tried.
513	.Sp	660	.Sp
514	The most typical usage is like this:	661	Example: This is the most typical usage.
515	.Sp	662	.Sp
516	.Vb 2	663	.Vb 2
517	\& if (!ev_default_loop (0))	664	\& if (!ev_default_loop (0))
518	\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	665	\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519	.Ve	666	.Ve
520	.Sp	667	.Sp
521	Restrict libev to the select and poll backends, and do not allow	668	Example: Restrict libev to the select and poll backends, and do not allow
522	environment settings to be taken into account:	669	environment settings to be taken into account:
523	.Sp	670	.Sp
524	.Vb 1	671	.Vb 1
525	\& ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);	672	\& ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
526	.Ve	673	.Ve
527	.Sp	674	.Sp
528	Use whatever libev has to offer, but make sure that kqueue is used if	675	Example: Use whatever libev has to offer, but make sure that kqueue is
529	available (warning, breaks stuff, best use only with your own private	676	used if available (warning, breaks stuff, best use only with your own
530	event loop and only if you know the \s-1OS\s0 supports your types of fds):	677	private event loop and only if you know the \s-1OS\s0 supports your types of
		678	fds):
531	.Sp	679	.Sp
532	.Vb 1	680	.Vb 1
533	\& ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);	681	\& ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
534	.Ve	682	.Ve
535	.RE	683	.RE
536	.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4	684	.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
537	.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"	685	.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
538	Similar to \f(CW\(C`ev_default_loop\(C'\fR, but always creates a new event loop that is	686	Similar to \f(CW\(C`ev_default_loop\(C'\fR, but always creates a new event loop that is
539	always distinct from the default loop. Unlike the default loop, it cannot	687	always distinct from the default loop. Unlike the default loop, it cannot
540	handle signal and child watchers, and attempts to do so will be greeted by	688	handle signal and child watchers, and attempts to do so will be greeted by
541	undefined behaviour (or a failed assertion if assertions are enabled).	689	undefined behaviour (or a failed assertion if assertions are enabled).
542	.Sp	690	.Sp
		691	Note that this function \fIis\fR thread-safe, and the recommended way to use
		692	libev with threads is indeed to create one loop per thread, and using the
		693	default loop in the \(L"main\(R" or \(L"initial\(R" thread.
		694	.Sp
543	Example: Try to create a event loop that uses epoll and nothing else.	695	Example: Try to create a event loop that uses epoll and nothing else.
544	.Sp	696	.Sp
545	.Vb 3	697	.Vb 3
546	\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	698	\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
547	\& if (!epoller)	699	\& if (!epoller)
548	\& fatal ("no epoll found here, maybe it hides under your chair");	700	\& fatal ("no epoll found here, maybe it hides under your chair");
549	.Ve	701	.Ve
550	.IP "ev_default_destroy ()" 4	702	.IP "ev_default_destroy ()" 4
551	.IX Item "ev_default_destroy ()"	703	.IX Item "ev_default_destroy ()"
552	Destroys the default loop again (frees all memory and kernel state	704	Destroys the default loop again (frees all memory and kernel state
553	etc.). None of the active event watchers will be stopped in the normal	705	etc.). None of the active event watchers will be stopped in the normal
554	sense, so e.g. \f(CW\(C`ev_is_active\(C'\fR might still return true. It is your	706	sense, so e.g. \f(CW\(C`ev_is_active\(C'\fR might still return true. It is your
555	responsibility to either stop all watchers cleanly yoursef \fIbefore\fR	707	responsibility to either stop all watchers cleanly yourself \fIbefore\fR
556	calling this function, or cope with the fact afterwards (which is usually	708	calling this function, or cope with the fact afterwards (which is usually
557	the easiest thing, youc na just ignore the watchers and/or \f(CW\(C`free ()\(C'\fR them	709	the easiest thing, you can just ignore the watchers and/or \f(CW\(C`free ()\(C'\fR them
558	for example).	710	for example).
		711	.Sp
		712	Note that certain global state, such as signal state (and installed signal
		713	handlers), will not be freed by this function, and related watchers (such
		714	as signal and child watchers) would need to be stopped manually.
		715	.Sp
		716	In general it is not advisable to call this function except in the
		717	rare occasion where you really need to free e.g. the signal handling
		718	pipe fds. If you need dynamically allocated loops it is better to use
		719	\&\f(CW\(C`ev_loop_new\(C'\fR and \f(CW\(C`ev_loop_destroy\(C'\fR).
559	.IP "ev_loop_destroy (loop)" 4	720	.IP "ev_loop_destroy (loop)" 4
560	.IX Item "ev_loop_destroy (loop)"	721	.IX Item "ev_loop_destroy (loop)"
561	Like \f(CW\(C`ev_default_destroy\(C'\fR, but destroys an event loop created by an	722	Like \f(CW\(C`ev_default_destroy\(C'\fR, but destroys an event loop created by an
562	earlier call to \f(CW\(C`ev_loop_new\(C'\fR.	723	earlier call to \f(CW\(C`ev_loop_new\(C'\fR.
563	.IP "ev_default_fork ()" 4	724	.IP "ev_default_fork ()" 4
564	.IX Item "ev_default_fork ()"	725	.IX Item "ev_default_fork ()"
		726	This function sets a flag that causes subsequent \f(CW\(C`ev_loop\(C'\fR iterations
565	This function reinitialises the kernel state for backends that have	727	to reinitialise the kernel state for backends that have one. Despite the
566	one. Despite the name, you can call it anytime, but it makes most sense	728	name, you can call it anytime, but it makes most sense after forking, in
567	after forking, in either the parent or child process (or both, but that	729	the child process (or both child and parent, but that again makes little
568	again makes little sense).	730	sense). You \fImust\fR call it in the child before using any of the libev
		731	functions, and it will only take effect at the next \f(CW\(C`ev_loop\(C'\fR iteration.
569	.Sp	732	.Sp
570	You \fImust\fR call this function in the child process after forking if and	733	On the other hand, you only need to call this function in the child
571	only if you want to use the event library in both processes. If you just	734	process if and only if you want to use the event library in the child. If
572	fork+exec, you don't have to call it.	735	you just fork+exec, you don't have to call it at all.
573	.Sp	736	.Sp
574	The function itself is quite fast and it's usually not a problem to call	737	The function itself is quite fast and it's usually not a problem to call
575	it just in case after a fork. To make this easy, the function will fit in	738	it just in case after a fork. To make this easy, the function will fit in
576	quite nicely into a call to \f(CW\(C`pthread_atfork\(C'\fR:	739	quite nicely into a call to \f(CW\(C`pthread_atfork\(C'\fR:
577	.Sp	740	.Sp
578	.Vb 1	741	.Vb 1
579	\& pthread_atfork (0, 0, ev_default_fork);	742	\& pthread_atfork (0, 0, ev_default_fork);
580	.Ve	743	.Ve
581	.Sp
582	At the moment, \f(CW\(C`EVBACKEND_SELECT\(C'\fR and \f(CW\(C`EVBACKEND_POLL\(C'\fR are safe to use
583	without calling this function, so if you force one of those backends you
584	do not need to care.
585	.IP "ev_loop_fork (loop)" 4	744	.IP "ev_loop_fork (loop)" 4
586	.IX Item "ev_loop_fork (loop)"	745	.IX Item "ev_loop_fork (loop)"
587	Like \f(CW\(C`ev_default_fork\(C'\fR, but acts on an event loop created by	746	Like \f(CW\(C`ev_default_fork\(C'\fR, but acts on an event loop created by
588	\&\f(CW\(C`ev_loop_new\(C'\fR. Yes, you have to call this on every allocated event loop	747	\&\f(CW\(C`ev_loop_new\(C'\fR. Yes, you have to call this on every allocated event loop
589	after fork, and how you do this is entirely your own problem.	748	after fork that you want to re-use in the child, and how you do this is
		749	entirely your own problem.
		750	.IP "int ev_is_default_loop (loop)" 4
		751	.IX Item "int ev_is_default_loop (loop)"
		752	Returns true when the given loop is, in fact, the default loop, and false
		753	otherwise.
590	.IP "unsigned int ev_loop_count (loop)" 4	754	.IP "unsigned int ev_loop_count (loop)" 4
591	.IX Item "unsigned int ev_loop_count (loop)"	755	.IX Item "unsigned int ev_loop_count (loop)"
592	Returns the count of loop iterations for the loop, which is identical to	756	Returns the count of loop iterations for the loop, which is identical to
593	the number of times libev did poll for new events. It starts at \f(CW0\fR and	757	the number of times libev did poll for new events. It starts at \f(CW0\fR and
594	happily wraps around with enough iterations.	758	happily wraps around with enough iterations.
595	.Sp	759	.Sp
596	This value can sometimes be useful as a generation counter of sorts (it	760	This value can sometimes be useful as a generation counter of sorts (it
597	\&\(L"ticks\(R" the number of loop iterations), as it roughly corresponds with	761	\&\(L"ticks\(R" the number of loop iterations), as it roughly corresponds with
598	\&\f(CW\(C`ev_prepare\(C'\fR and \f(CW\(C`ev_check\(C'\fR calls.	762	\&\f(CW\(C`ev_prepare\(C'\fR and \f(CW\(C`ev_check\(C'\fR calls.
		763	.IP "unsigned int ev_loop_depth (loop)" 4
		764	.IX Item "unsigned int ev_loop_depth (loop)"
		765	Returns the number of times \f(CW\(C`ev_loop\(C'\fR was entered minus the number of
		766	times \f(CW\(C`ev_loop\(C'\fR was exited, in other words, the recursion depth.
		767	.Sp
		768	Outside \f(CW\(C`ev_loop\(C'\fR, this number is zero. In a callback, this number is
		769	\&\f(CW1\fR, unless \f(CW\(C`ev_loop\(C'\fR was invoked recursively (or from another thread),
		770	in which case it is higher.
		771	.Sp
		772	Leaving \f(CW\(C`ev_loop\(C'\fR abnormally (setjmp/longjmp, cancelling the thread
		773	etc.), doesn't count as exit.
599	.IP "unsigned int ev_backend (loop)" 4	774	.IP "unsigned int ev_backend (loop)" 4
600	.IX Item "unsigned int ev_backend (loop)"	775	.IX Item "unsigned int ev_backend (loop)"
601	Returns one of the \f(CW\(C`EVBACKEND_\*(C'\fR flags indicating the event backend in	776	Returns one of the \f(CW\(C`EVBACKEND_\*(C'\fR flags indicating the event backend in
602	use.	777	use.
603	.IP "ev_tstamp ev_now (loop)" 4	778	.IP "ev_tstamp ev_now (loop)" 4
604	.IX Item "ev_tstamp ev_now (loop)"	779	.IX Item "ev_tstamp ev_now (loop)"
605	Returns the current \(L"event loop time\(R", which is the time the event loop	780	Returns the current \(L"event loop time\(R", which is the time the event loop
606	received events and started processing them. This timestamp does not	781	received events and started processing them. This timestamp does not
607	change as long as callbacks are being processed, and this is also the base	782	change as long as callbacks are being processed, and this is also the base
608	time used for relative timers. You can treat it as the timestamp of the	783	time used for relative timers. You can treat it as the timestamp of the
609	event occuring (or more correctly, libev finding out about it).	784	event occurring (or more correctly, libev finding out about it).
		785	.IP "ev_now_update (loop)" 4
		786	.IX Item "ev_now_update (loop)"
		787	Establishes the current time by querying the kernel, updating the time
		788	returned by \f(CW\(C`ev_now ()\(C'\fR in the progress. This is a costly operation and
		789	is usually done automatically within \f(CW\(C`ev_loop ()\(C'\fR.
		790	.Sp
		791	This function is rarely useful, but when some event callback runs for a
		792	very long time without entering the event loop, updating libev's idea of
		793	the current time is a good idea.
		794	.Sp
		795	See also \(L"The special problem of time updates\(R" in the \f(CW\(C`ev_timer\(C'\fR section.
		796	.IP "ev_suspend (loop)" 4
		797	.IX Item "ev_suspend (loop)"
		798	.PD 0
		799	.IP "ev_resume (loop)" 4
		800	.IX Item "ev_resume (loop)"
		801	.PD
		802	These two functions suspend and resume a loop, for use when the loop is
		803	not used for a while and timeouts should not be processed.
		804	.Sp
		805	A typical use case would be an interactive program such as a game: When
		806	the user presses \f(CW\(C`^Z\(C'\fR to suspend the game and resumes it an hour later it
		807	would be best to handle timeouts as if no time had actually passed while
		808	the program was suspended. This can be achieved by calling \f(CW\(C`ev_suspend\(C'\fR
		809	in your \f(CW\(C`SIGTSTP\(C'\fR handler, sending yourself a \f(CW\(C`SIGSTOP\(C'\fR and calling
		810	\&\f(CW\(C`ev_resume\(C'\fR directly afterwards to resume timer processing.
		811	.Sp
		812	Effectively, all \f(CW\(C`ev_timer\(C'\fR watchers will be delayed by the time spend
		813	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
		814	will be rescheduled (that is, they will lose any events that would have
		815	occured while suspended).
		816	.Sp
		817	After calling \f(CW\(C`ev_suspend\(C'\fR you \fBmust not\fR call \fIany\fR function on the
		818	given loop other than \f(CW\(C`ev_resume\(C'\fR, and you \fBmust not\fR call \f(CW\(C`ev_resume\(C'\fR
		819	without a previous call to \f(CW\(C`ev_suspend\(C'\fR.
		820	.Sp
		821	Calling \f(CW\(C`ev_suspend\(C'\fR/\f(CW\(C`ev_resume\(C'\fR has the side effect of updating the
		822	event loop time (see \f(CW\(C`ev_now_update\(C'\fR).
610	.IP "ev_loop (loop, int flags)" 4	823	.IP "ev_loop (loop, int flags)" 4
611	.IX Item "ev_loop (loop, int flags)"	824	.IX Item "ev_loop (loop, int flags)"
612	Finally, this is it, the event handler. This function usually is called	825	Finally, this is it, the event handler. This function usually is called
613	after you initialised all your watchers and you want to start handling	826	after you initialised all your watchers and you want to start handling
614	events.	827	events.
…		…
616	If the flags argument is specified as \f(CW0\fR, it will not return until	829	If the flags argument is specified as \f(CW0\fR, it will not return until
617	either no event watchers are active anymore or \f(CW\(C`ev_unloop\(C'\fR was called.	830	either no event watchers are active anymore or \f(CW\(C`ev_unloop\(C'\fR was called.
618	.Sp	831	.Sp
619	Please note that an explicit \f(CW\(C`ev_unloop\(C'\fR is usually better than	832	Please note that an explicit \f(CW\(C`ev_unloop\(C'\fR is usually better than
620	relying on all watchers to be stopped when deciding when a program has	833	relying on all watchers to be stopped when deciding when a program has
621	finished (especially in interactive programs), but having a program that	834	finished (especially in interactive programs), but having a program
622	automatically loops as long as it has to and no longer by virtue of	835	that automatically loops as long as it has to and no longer by virtue
623	relying on its watchers stopping correctly is a thing of beauty.	836	of relying on its watchers stopping correctly, that is truly a thing of
		837	beauty.
624	.Sp	838	.Sp
625	A flags value of \f(CW\(C`EVLOOP_NONBLOCK\(C'\fR will look for new events, will handle	839	A flags value of \f(CW\(C`EVLOOP_NONBLOCK\(C'\fR will look for new events, will handle
626	those events and any outstanding ones, but will not block your process in	840	those events and any already outstanding ones, but will not block your
627	case there are no events and will return after one iteration of the loop.	841	process in case there are no events and will return after one iteration of
		842	the loop.
628	.Sp	843	.Sp
629	A flags value of \f(CW\(C`EVLOOP_ONESHOT\(C'\fR will look for new events (waiting if	844	A flags value of \f(CW\(C`EVLOOP_ONESHOT\(C'\fR will look for new events (waiting if
630	neccessary) and will handle those and any outstanding ones. It will block	845	necessary) and will handle those and any already outstanding ones. It
631	your process until at least one new event arrives, and will return after	846	will block your process until at least one new event arrives (which could
632	one iteration of the loop. This is useful if you are waiting for some	847	be an event internal to libev itself, so there is no guarantee that a
633	external event in conjunction with something not expressible using other	848	user-registered callback will be called), and will return after one
		849	iteration of the loop.
		850	.Sp
		851	This is useful if you are waiting for some external event in conjunction
		852	with something not expressible using other libev watchers (i.e. "roll your
634	libev watchers. However, a pair of \f(CW\(C`ev_prepare\(C'\fR/\f(CW\(C`ev_check\(C'\fR watchers is	853	own \f(CW\(C`ev_loop\(C'\fR"). However, a pair of \f(CW\(C`ev_prepare\(C'\fR/\f(CW\(C`ev_check\(C'\fR watchers is
635	usually a better approach for this kind of thing.	854	usually a better approach for this kind of thing.
636	.Sp	855	.Sp
637	Here are the gory details of what \f(CW\(C`ev_loop\(C'\fR does:	856	Here are the gory details of what \f(CW\(C`ev_loop\(C'\fR does:
638	.Sp	857	.Sp
639	.Vb 18	858	.Vb 10
640	\& * If there are no active watchers (reference count is zero), return.	859	\& \- Before the first iteration, call any pending watchers.
641	\& - Queue prepare watchers and then call all outstanding watchers.	860	\& * If EVFLAG_FORKCHECK was used, check for a fork.
		861	\& \- If a fork was detected (by any means), queue and call all fork watchers.
		862	\& \- Queue and call all prepare watchers.
642	\& - If we have been forked, recreate the kernel state.	863	\& \- If we have been forked, detach and recreate the kernel state
		864	\& as to not disturb the other process.
643	\& - Update the kernel state with all outstanding changes.	865	\& \- Update the kernel state with all outstanding changes.
644	\& - Update the "event loop time".	866	\& \- Update the "event loop time" (ev_now ()).
645	\& - Calculate for how long to block.	867	\& \- Calculate for how long to sleep or block, if at all
		868	\& (active idle watchers, EVLOOP_NONBLOCK or not having
		869	\& any active watchers at all will result in not sleeping).
		870	\& \- Sleep if the I/O and timer collect interval say so.
646	\& - Block the process, waiting for any events.	871	\& \- Block the process, waiting for any events.
647	\& - Queue all outstanding I/O (fd) events.	872	\& \- Queue all outstanding I/O (fd) events.
648	\& - Update the "event loop time" and do time jump handling.	873	\& \- Update the "event loop time" (ev_now ()), and do time jump adjustments.
649	\& - Queue all outstanding timers.	874	\& \- Queue all expired timers.
650	\& - Queue all outstanding periodics.	875	\& \- Queue all expired periodics.
651	\& - If no events are pending now, queue all idle watchers.	876	\& \- Unless any events are pending now, queue all idle watchers.
652	\& - Queue all check watchers.	877	\& \- Queue all check watchers.
653	\& - Call all queued watchers in reverse order (i.e. check watchers first).	878	\& \- Call all queued watchers in reverse order (i.e. check watchers first).
654	\& Signals and child watchers are implemented as I/O watchers, and will	879	\& Signals and child watchers are implemented as I/O watchers, and will
655	\& be handled here by queueing them when their watcher gets executed.	880	\& be handled here by queueing them when their watcher gets executed.
656	\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	881	\& \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
657	\& were used, return, otherwise continue with step *.	882	\& were used, or there are no active watchers, return, otherwise
		883	\& continue with step *.
658	.Ve	884	.Ve
659	.Sp	885	.Sp
660	Example: Queue some jobs and then loop until no events are outsanding	886	Example: Queue some jobs and then loop until no events are outstanding
661	anymore.	887	anymore.
662	.Sp	888	.Sp
663	.Vb 4	889	.Vb 4
664	\& ... queue jobs here, make sure they register event watchers as long	890	\& ... queue jobs here, make sure they register event watchers as long
665	\& ... as they still have work to do (even an idle watcher will do..)	891	\& ... as they still have work to do (even an idle watcher will do..)
666	\& ev_loop (my_loop, 0);	892	\& ev_loop (my_loop, 0);
667	\& ... jobs done. yeah!	893	\& ... jobs done or somebody called unloop. yeah!
668	.Ve	894	.Ve
669	.IP "ev_unloop (loop, how)" 4	895	.IP "ev_unloop (loop, how)" 4
670	.IX Item "ev_unloop (loop, how)"	896	.IX Item "ev_unloop (loop, how)"
671	Can be used to make a call to \f(CW\(C`ev_loop\(C'\fR return early (but only after it	897	Can be used to make a call to \f(CW\(C`ev_loop\(C'\fR return early (but only after it
672	has processed all outstanding events). The \f(CW\(C`how\(C'\fR argument must be either	898	has processed all outstanding events). The \f(CW\(C`how\(C'\fR argument must be either
673	\&\f(CW\(C`EVUNLOOP_ONE\(C'\fR, which will make the innermost \f(CW\(C`ev_loop\(C'\fR call return, or	899	\&\f(CW\(C`EVUNLOOP_ONE\(C'\fR, which will make the innermost \f(CW\(C`ev_loop\(C'\fR call return, or
674	\&\f(CW\(C`EVUNLOOP_ALL\(C'\fR, which will make all nested \f(CW\(C`ev_loop\(C'\fR calls return.	900	\&\f(CW\(C`EVUNLOOP_ALL\(C'\fR, which will make all nested \f(CW\(C`ev_loop\(C'\fR calls return.
		901	.Sp
		902	This \(L"unloop state\(R" will be cleared when entering \f(CW\(C`ev_loop\(C'\fR again.
		903	.Sp
		904	It is safe to call \f(CW\(C`ev_unloop\(C'\fR from otuside any \f(CW\(C`ev_loop\(C'\fR calls.
675	.IP "ev_ref (loop)" 4	905	.IP "ev_ref (loop)" 4
676	.IX Item "ev_ref (loop)"	906	.IX Item "ev_ref (loop)"
677	.PD 0	907	.PD 0
678	.IP "ev_unref (loop)" 4	908	.IP "ev_unref (loop)" 4
679	.IX Item "ev_unref (loop)"	909	.IX Item "ev_unref (loop)"
680	.PD	910	.PD
681	Ref/unref can be used to add or remove a reference count on the event	911	Ref/unref can be used to add or remove a reference count on the event
682	loop: Every watcher keeps one reference, and as long as the reference	912	loop: Every watcher keeps one reference, and as long as the reference
683	count is nonzero, \f(CW\(C`ev_loop\(C'\fR will not return on its own. If you have	913	count is nonzero, \f(CW\(C`ev_loop\(C'\fR will not return on its own.
		914	.Sp
684	a watcher you never unregister that should not keep \f(CW\(C`ev_loop\(C'\fR from	915	If you have a watcher you never unregister that should not keep \f(CW\(C`ev_loop\(C'\fR
685	returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For	916	from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\fR before
		917	stopping it.
		918	.Sp
686	example, libev itself uses this for its internal signal pipe: It is not	919	As an example, libev itself uses this for its internal signal pipe: It
687	visible to the libev user and should not keep \f(CW\(C`ev_loop\(C'\fR from exiting if	920	is not visible to the libev user and should not keep \f(CW\(C`ev_loop\(C'\fR from
688	no event watchers registered by it are active. It is also an excellent	921	exiting if no event watchers registered by it are active. It is also an
689	way to do this for generic recurring timers or from within third-party	922	excellent way to do this for generic recurring timers or from within
690	libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.	923	third-party libraries. Just remember to \fIunref after start\fR and \fIref
		924	before stop\fR (but only if the watcher wasn't active before, or was active
		925	before, respectively. Note also that libev might stop watchers itself
		926	(e.g. non-repeating timers) in which case you have to \f(CW\(C`ev_ref\(C'\fR
		927	in the callback).
691	.Sp	928	.Sp
692	Example: Create a signal watcher, but keep it from keeping \f(CW\(C`ev_loop\(C'\fR	929	Example: Create a signal watcher, but keep it from keeping \f(CW\(C`ev_loop\(C'\fR
693	running when nothing else is active.	930	running when nothing else is active.
694	.Sp	931	.Sp
695	.Vb 4	932	.Vb 4
696	\& struct ev_signal exitsig;	933	\& ev_signal exitsig;
697	\& ev_signal_init (&exitsig, sig_cb, SIGINT);	934	\& ev_signal_init (&exitsig, sig_cb, SIGINT);
698	\& ev_signal_start (loop, &exitsig);	935	\& ev_signal_start (loop, &exitsig);
699	\& evf_unref (loop);	936	\& evf_unref (loop);
700	.Ve	937	.Ve
701	.Sp	938	.Sp
702	Example: For some weird reason, unregister the above signal handler again.	939	Example: For some weird reason, unregister the above signal handler again.
703	.Sp	940	.Sp
704	.Vb 2	941	.Vb 2
705	\& ev_ref (loop);	942	\& ev_ref (loop);
706	\& ev_signal_stop (loop, &exitsig);	943	\& ev_signal_stop (loop, &exitsig);
707	.Ve	944	.Ve
		945	.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
		946	.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
		947	.PD 0
		948	.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
		949	.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
		950	.PD
		951	These advanced functions influence the time that libev will spend waiting
		952	for events. Both time intervals are by default \f(CW0\fR, meaning that libev
		953	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		954	latency.
		955	.Sp
		956	Setting these to a higher value (the \f(CW\(C`interval\(C'\fR \fImust\fR be >= \f(CW0\fR)
		957	allows libev to delay invocation of I/O and timer/periodic callbacks
		958	to increase efficiency of loop iterations (or to increase power-saving
		959	opportunities).
		960	.Sp
		961	The idea is that sometimes your program runs just fast enough to handle
		962	one (or very few) event(s) per loop iteration. While this makes the
		963	program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
		964	events, especially with backends like \f(CW\(C`select ()\(C'\fR which have a high
		965	overhead for the actual polling but can deliver many events at once.
		966	.Sp
		967	By setting a higher \fIio collect interval\fR you allow libev to spend more
		968	time collecting I/O events, so you can handle more events per iteration,
		969	at the cost of increasing latency. Timeouts (both \f(CW\(C`ev_periodic\(C'\fR and
		970	\&\f(CW\(C`ev_timer\(C'\fR) will be not affected. Setting this to a non-null value will
		971	introduce an additional \f(CW\(C`ev_sleep ()\(C'\fR call into most loop iterations. The
		972	sleep time ensures that libev will not poll for I/O events more often then
		973	once per this interval, on average.
		974	.Sp
		975	Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
		976	to spend more time collecting timeouts, at the expense of increased
		977	latency/jitter/inexactness (the watcher callback will be called
		978	later). \f(CW\(C`ev_io\(C'\fR watchers will not be affected. Setting this to a non-null
		979	value will not introduce any overhead in libev.
		980	.Sp
		981	Many (busy) programs can usually benefit by setting the I/O collect
		982	interval to a value near \f(CW0.1\fR or so, which is often enough for
		983	interactive servers (of course not for games), likewise for timeouts. It
		984	usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR,
		985	as this approaches the timing granularity of most systems. Note that if
		986	you do transactions with the outside world and you can't increase the
		987	parallelity, then this setting will limit your transaction rate (if you
		988	need to poll once per transaction and the I/O collect interval is 0.01,
		989	then you can't do more than 100 transations per second).
		990	.Sp
		991	Setting the \fItimeout collect interval\fR can improve the opportunity for
		992	saving power, as the program will \(L"bundle\(R" timer callback invocations that
		993	are \(L"near\(R" in time together, by delaying some, thus reducing the number of
		994	times the process sleeps and wakes up again. Another useful technique to
		995	reduce iterations/wake\-ups is to use \f(CW\(C`ev_periodic\(C'\fR watchers and make sure
		996	they fire on, say, one-second boundaries only.
		997	.Sp
		998	Example: we only need 0.1s timeout granularity, and we wish not to poll
		999	more often than 100 times per second:
		1000	.Sp
		1001	.Vb 2
		1002	\& ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1003	\& ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1004	.Ve
		1005	.IP "ev_invoke_pending (loop)" 4
		1006	.IX Item "ev_invoke_pending (loop)"
		1007	This call will simply invoke all pending watchers while resetting their
		1008	pending state. Normally, \f(CW\(C`ev_loop\(C'\fR does this automatically when required,
		1009	but when overriding the invoke callback this call comes handy.
		1010	.IP "int ev_pending_count (loop)" 4
		1011	.IX Item "int ev_pending_count (loop)"
		1012	Returns the number of pending watchers \- zero indicates that no watchers
		1013	are pending.
		1014	.IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4
		1015	.IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))"
		1016	This overrides the invoke pending functionality of the loop: Instead of
		1017	invoking all pending watchers when there are any, \f(CW\(C`ev_loop\(C'\fR will call
		1018	this callback instead. This is useful, for example, when you want to
		1019	invoke the actual watchers inside another context (another thread etc.).
		1020	.Sp
		1021	If you want to reset the callback, use \f(CW\(C`ev_invoke_pending\(C'\fR as new
		1022	callback.
		1023	.IP "ev_set_loop_release_cb (loop, void (release)(\s-1EV_P\s0), void (acquire)(\s-1EV_P\s0))" 4
		1024	.IX Item "ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))"
		1025	Sometimes you want to share the same loop between multiple threads. This
		1026	can be done relatively simply by putting mutex_lock/unlock calls around
		1027	each call to a libev function.
		1028	.Sp
		1029	However, \f(CW\(C`ev_loop\(C'\fR can run an indefinite time, so it is not feasible to
		1030	wait for it to return. One way around this is to wake up the loop via
		1031	\&\f(CW\(C`ev_unloop\(C'\fR and \f(CW\(C`av_async_send\(C'\fR, another way is to set these \fIrelease\fR
		1032	and \fIacquire\fR callbacks on the loop.
		1033	.Sp
		1034	When set, then \f(CW\(C`release\(C'\fR will be called just before the thread is
		1035	suspended waiting for new events, and \f(CW\(C`acquire\(C'\fR is called just
		1036	afterwards.
		1037	.Sp
		1038	Ideally, \f(CW\(C`release\(C'\fR will just call your mutex_unlock function, and
		1039	\&\f(CW\(C`acquire\(C'\fR will just call the mutex_lock function again.
		1040	.Sp
		1041	While event loop modifications are allowed between invocations of
		1042	\&\f(CW\(C`release\(C'\fR and \f(CW\(C`acquire\(C'\fR (that's their only purpose after all), no
		1043	modifications done will affect the event loop, i.e. adding watchers will
		1044	have no effect on the set of file descriptors being watched, or the time
		1045	waited. USe an \f(CW\(C`ev_async\(C'\fR watcher to wake up \f(CW\(C`ev_loop\(C'\fR when you want it
		1046	to take note of any changes you made.
		1047	.Sp
		1048	In theory, threads executing \f(CW\(C`ev_loop\(C'\fR will be async-cancel safe between
		1049	invocations of \f(CW\(C`release\(C'\fR and \f(CW\(C`acquire\(C'\fR.
		1050	.Sp
		1051	See also the locking example in the \f(CW\(C`THREADS\(C'\fR section later in this
		1052	document.
		1053	.IP "ev_set_userdata (loop, void *data)" 4
		1054	.IX Item "ev_set_userdata (loop, void *data)"
		1055	.PD 0
		1056	.IP "ev_userdata (loop)" 4
		1057	.IX Item "ev_userdata (loop)"
		1058	.PD
		1059	Set and retrieve a single \f(CW\(C`void \*(C'\fR associated with a loop. When
		1060	\&\f(CW\(C`ev_set_userdata\(C'\fR has never been called, then \f(CW\(C`ev_userdata\(C'\fR returns
		1061	\&\f(CW0.\fR
		1062	.Sp
		1063	These two functions can be used to associate arbitrary data with a loop,
		1064	and are intended solely for the \f(CW\(C`invoke_pending_cb\(C'\fR, \f(CW\(C`release\(C'\fR and
		1065	\&\f(CW\(C`acquire\(C'\fR callbacks described above, but of course can be (ab\-)used for
		1066	any other purpose as well.
		1067	.IP "ev_loop_verify (loop)" 4
		1068	.IX Item "ev_loop_verify (loop)"
		1069	This function only does something when \f(CW\(C`EV_VERIFY\(C'\fR support has been
		1070	compiled in, which is the default for non-minimal builds. It tries to go
		1071	through all internal structures and checks them for validity. If anything
		1072	is found to be inconsistent, it will print an error message to standard
		1073	error and call \f(CW\(C`abort ()\(C'\fR.
		1074	.Sp
		1075	This can be used to catch bugs inside libev itself: under normal
		1076	circumstances, this function will never abort as of course libev keeps its
		1077	data structures consistent.
708	.SH "ANATOMY OF A WATCHER"	1078	.SH "ANATOMY OF A WATCHER"
709	.IX Header "ANATOMY OF A WATCHER"	1079	.IX Header "ANATOMY OF A WATCHER"
		1080	In the following description, uppercase \f(CW\(C`TYPE\(C'\fR in names stands for the
		1081	watcher type, e.g. \f(CW\(C`ev_TYPE_start\(C'\fR can mean \f(CW\(C`ev_timer_start\(C'\fR for timer
		1082	watchers and \f(CW\(C`ev_io_start\(C'\fR for I/O watchers.
		1083	.PP
710	A watcher is a structure that you create and register to record your	1084	A watcher is a structure that you create and register to record your
711	interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to	1085	interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
712	become readable, you would create an \f(CW\(C`ev_io\(C'\fR watcher for that:	1086	become readable, you would create an \f(CW\(C`ev_io\(C'\fR watcher for that:
713	.PP	1087	.PP
714	.Vb 5	1088	.Vb 5
715	\& static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	1089	\& static void my_cb (struct ev_loop loop, ev_io w, int revents)
716	\& {	1090	\& {
717	\& ev_io_stop (w);	1091	\& ev_io_stop (w);
718	\& ev_unloop (loop, EVUNLOOP_ALL);	1092	\& ev_unloop (loop, EVUNLOOP_ALL);
719	\& }	1093	\& }
720	.Ve	1094	\&
721	.PP
722	.Vb 6
723	\& struct ev_loop *loop = ev_default_loop (0);	1095	\& struct ev_loop *loop = ev_default_loop (0);
		1096	\&
724	\& struct ev_io stdin_watcher;	1097	\& ev_io stdin_watcher;
		1098	\&
725	\& ev_init (&stdin_watcher, my_cb);	1099	\& ev_init (&stdin_watcher, my_cb);
726	\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1100	\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
727	\& ev_io_start (loop, &stdin_watcher);	1101	\& ev_io_start (loop, &stdin_watcher);
		1102	\&
728	\& ev_loop (loop, 0);	1103	\& ev_loop (loop, 0);
729	.Ve	1104	.Ve
730	.PP	1105	.PP
731	As you can see, you are responsible for allocating the memory for your	1106	As you can see, you are responsible for allocating the memory for your
732	watcher structures (and it is usually a bad idea to do this on the stack,	1107	watcher structures (and it is \fIusually\fR a bad idea to do this on the
733	although this can sometimes be quite valid).	1108	stack).
		1109	.PP
		1110	Each watcher has an associated watcher structure (called \f(CW\(C`struct ev_TYPE\(C'\fR
		1111	or simply \f(CW\(C`ev_TYPE\(C'\fR, as typedefs are provided for all watcher structs).
734	.PP	1112	.PP
735	Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init	1113	Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init
736	(watcher , callback)\(C'\fR, which expects a callback to be provided. This	1114	(watcher , callback)\(C'\fR, which expects a callback to be provided. This
737	callback gets invoked each time the event occurs (or, in the case of io	1115	callback gets invoked each time the event occurs (or, in the case of I/O
738	watchers, each time the event loop detects that the file descriptor given	1116	watchers, each time the event loop detects that the file descriptor given
739	is readable and/or writable).	1117	is readable and/or writable).
740	.PP	1118	.PP
741	Each watcher type has its own \f(CW\(C`ev_<type>_set (watcher , ...)\*(C'\fR macro	1119	Each watcher type further has its own \f(CW\(C`ev_TYPE_set (watcher , ...)\*(C'\fR
742	with arguments specific to this watcher type. There is also a macro	1120	macro to configure it, with arguments specific to the watcher type. There
743	to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init	1121	is also a macro to combine initialisation and setting in one call: \f(CW\(C`ev_TYPE_init (watcher , callback, ...)\*(C'\fR.
744	(watcher , callback, ...)\(C'\fR.
745	.PP	1122	.PP
746	To make the watcher actually watch out for events, you have to start it	1123	To make the watcher actually watch out for events, you have to start it
747	with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher	1124	with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher
748	)\(C'\fR), and you can stop watching for events at any time by calling the	1125	)\(C'\fR), and you can stop watching for events at any time by calling the
749	corresponding stop function (\f(CW\(C`ev_<type>_stop (loop, watcher )\*(C'\fR.	1126	corresponding stop function (\f(CW\(C`ev_TYPE_stop (loop, watcher )\*(C'\fR.
750	.PP	1127	.PP
751	As long as your watcher is active (has been started but not stopped) you	1128	As long as your watcher is active (has been started but not stopped) you
752	must not touch the values stored in it. Most specifically you must never	1129	must not touch the values stored in it. Most specifically you must never
753	reinitialise it or call its \f(CW\(C`set\(C'\fR macro.	1130	reinitialise it or call its \f(CW\(C`ev_TYPE_set\(C'\fR macro.
754	.PP	1131	.PP
755	Each and every callback receives the event loop pointer as first, the	1132	Each and every callback receives the event loop pointer as first, the
756	registered watcher structure as second, and a bitset of received events as	1133	registered watcher structure as second, and a bitset of received events as
757	third argument.	1134	third argument.
758	.PP	1135	.PP
…		…
815	.ie n .IP """EV_FORK""" 4	1192	.ie n .IP """EV_FORK""" 4
816	.el .IP "\f(CWEV_FORK\fR" 4	1193	.el .IP "\f(CWEV_FORK\fR" 4
817	.IX Item "EV_FORK"	1194	.IX Item "EV_FORK"
818	The event loop has been resumed in the child process after fork (see	1195	The event loop has been resumed in the child process after fork (see
819	\&\f(CW\(C`ev_fork\(C'\fR).	1196	\&\f(CW\(C`ev_fork\(C'\fR).
		1197	.ie n .IP """EV_ASYNC""" 4
		1198	.el .IP "\f(CWEV_ASYNC\fR" 4
		1199	.IX Item "EV_ASYNC"
		1200	The given async watcher has been asynchronously notified (see \f(CW\(C`ev_async\(C'\fR).
		1201	.ie n .IP """EV_CUSTOM""" 4
		1202	.el .IP "\f(CWEV_CUSTOM\fR" 4
		1203	.IX Item "EV_CUSTOM"
		1204	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1205	by libev users to signal watchers (e.g. via \f(CW\(C`ev_feed_event\(C'\fR).
820	.ie n .IP """EV_ERROR""" 4	1206	.ie n .IP """EV_ERROR""" 4
821	.el .IP "\f(CWEV_ERROR\fR" 4	1207	.el .IP "\f(CWEV_ERROR\fR" 4
822	.IX Item "EV_ERROR"	1208	.IX Item "EV_ERROR"
823	An unspecified error has occured, the watcher has been stopped. This might	1209	An unspecified error has occurred, the watcher has been stopped. This might
824	happen because the watcher could not be properly started because libev	1210	happen because the watcher could not be properly started because libev
825	ran out of memory, a file descriptor was found to be closed or any other	1211	ran out of memory, a file descriptor was found to be closed or any other
		1212	problem. Libev considers these application bugs.
		1213	.Sp
826	problem. You best act on it by reporting the problem and somehow coping	1214	You best act on it by reporting the problem and somehow coping with the
827	with the watcher being stopped.	1215	watcher being stopped. Note that well-written programs should not receive
		1216	an error ever, so when your watcher receives it, this usually indicates a
		1217	bug in your program.
828	.Sp	1218	.Sp
829	Libev will usually signal a few \(L"dummy\(R" events together with an error,	1219	Libev will usually signal a few \(L"dummy\(R" events together with an error, for
830	for example it might indicate that a fd is readable or writable, and if	1220	example it might indicate that a fd is readable or writable, and if your
831	your callbacks is well-written it can just attempt the operation and cope	1221	callbacks is well-written it can just attempt the operation and cope with
832	with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded	1222	the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded
833	programs, though, so beware.	1223	programs, though, as the fd could already be closed and reused for another
		1224	thing, so beware.
834	.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"	1225	.SS "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
835	.IX Subsection "GENERIC WATCHER FUNCTIONS"	1226	.IX Subsection "GENERIC WATCHER FUNCTIONS"
836	In the following description, \f(CW\(C`TYPE\(C'\fR stands for the watcher type,
837	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.
838	.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4	1227	.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
839	.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4	1228	.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
840	.IX Item "ev_init (ev_TYPE *watcher, callback)"	1229	.IX Item "ev_init (ev_TYPE *watcher, callback)"
841	This macro initialises the generic portion of a watcher. The contents	1230	This macro initialises the generic portion of a watcher. The contents
842	of the watcher object can be arbitrary (so \f(CW\(C`malloc\(C'\fR will do). Only	1231	of the watcher object can be arbitrary (so \f(CW\(C`malloc\(C'\fR will do). Only
…		…
846	which rolls both calls into one.	1235	which rolls both calls into one.
847	.Sp	1236	.Sp
848	You can reinitialise a watcher at any time as long as it has been stopped	1237	You can reinitialise a watcher at any time as long as it has been stopped
849	(or never started) and there are no pending events outstanding.	1238	(or never started) and there are no pending events outstanding.
850	.Sp	1239	.Sp
851	The callback is always of type \f(CW\(C`void ()(ev_loop loop, ev_TYPE watcher,	1240	The callback is always of type \f(CW\(C`void ()(struct ev_loop loop, ev_TYPE watcher,
852	int revents)\*(C'\fR.	1241	int revents)\*(C'\fR.
		1242	.Sp
		1243	Example: Initialise an \f(CW\(C`ev_io\(C'\fR watcher in two steps.
		1244	.Sp
		1245	.Vb 3
		1246	\& ev_io w;
		1247	\& ev_init (&w, my_cb);
		1248	\& ev_io_set (&w, STDIN_FILENO, EV_READ);
		1249	.Ve
853	.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4	1250	.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
854	.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4	1251	.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
855	.IX Item "ev_TYPE_set (ev_TYPE *, [args])"	1252	.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
856	This macro initialises the type-specific parts of a watcher. You need to	1253	This macro initialises the type-specific parts of a watcher. You need to
857	call \f(CW\(C`ev_init\(C'\fR at least once before you call this macro, but you can	1254	call \f(CW\(C`ev_init\(C'\fR at least once before you call this macro, but you can
…		…
859	macro on a watcher that is active (it can be pending, however, which is a	1256	macro on a watcher that is active (it can be pending, however, which is a
860	difference to the \f(CW\(C`ev_init\(C'\fR macro).	1257	difference to the \f(CW\(C`ev_init\(C'\fR macro).
861	.Sp	1258	.Sp
862	Although some watcher types do not have type-specific arguments	1259	Although some watcher types do not have type-specific arguments
863	(e.g. \f(CW\(C`ev_prepare\(C'\fR) you still need to call its \f(CW\(C`set\(C'\fR macro.	1260	(e.g. \f(CW\(C`ev_prepare\(C'\fR) you still need to call its \f(CW\(C`set\(C'\fR macro.
		1261	.Sp
		1262	See \f(CW\(C`ev_init\(C'\fR, above, for an example.
864	.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4	1263	.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
865	.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4	1264	.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
866	.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"	1265	.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
867	This convinience macro rolls both \f(CW\(C`ev_init\(C'\fR and \f(CW\(C`ev_TYPE_set\(C'\fR macro	1266	This convenience macro rolls both \f(CW\(C`ev_init\(C'\fR and \f(CW\(C`ev_TYPE_set\(C'\fR macro
868	calls into a single call. This is the most convinient method to initialise	1267	calls into a single call. This is the most convenient method to initialise
869	a watcher. The same limitations apply, of course.	1268	a watcher. The same limitations apply, of course.
		1269	.Sp
		1270	Example: Initialise and set an \f(CW\(C`ev_io\(C'\fR watcher in one step.
		1271	.Sp
		1272	.Vb 1
		1273	\& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1274	.Ve
870	.ie n .IP """ev_TYPE_start"" (loop , ev_TYPE watcher)" 4	1275	.ie n .IP """ev_TYPE_start"" (loop , ev_TYPE watcher)" 4
871	.el .IP "\f(CWev_TYPE_start\fR (loop , ev_TYPE watcher)" 4	1276	.el .IP "\f(CWev_TYPE_start\fR (loop , ev_TYPE watcher)" 4
872	.IX Item "ev_TYPE_start (loop , ev_TYPE watcher)"	1277	.IX Item "ev_TYPE_start (loop , ev_TYPE watcher)"
873	Starts (activates) the given watcher. Only active watchers will receive	1278	Starts (activates) the given watcher. Only active watchers will receive
874	events. If the watcher is already active nothing will happen.	1279	events. If the watcher is already active nothing will happen.
		1280	.Sp
		1281	Example: Start the \f(CW\(C`ev_io\(C'\fR watcher that is being abused as example in this
		1282	whole section.
		1283	.Sp
		1284	.Vb 1
		1285	\& ev_io_start (EV_DEFAULT_UC, &w);
		1286	.Ve
875	.ie n .IP """ev_TYPE_stop"" (loop , ev_TYPE watcher)" 4	1287	.ie n .IP """ev_TYPE_stop"" (loop , ev_TYPE watcher)" 4
876	.el .IP "\f(CWev_TYPE_stop\fR (loop , ev_TYPE watcher)" 4	1288	.el .IP "\f(CWev_TYPE_stop\fR (loop , ev_TYPE watcher)" 4
877	.IX Item "ev_TYPE_stop (loop , ev_TYPE watcher)"	1289	.IX Item "ev_TYPE_stop (loop , ev_TYPE watcher)"
878	Stops the given watcher again (if active) and clears the pending	1290	Stops the given watcher if active, and clears the pending status (whether
		1291	the watcher was active or not).
		1292	.Sp
879	status. It is possible that stopped watchers are pending (for example,	1293	It is possible that stopped watchers are pending \- for example,
880	non-repeating timers are being stopped when they become pending), but	1294	non-repeating timers are being stopped when they become pending \- but
881	\&\f(CW\(C`ev_TYPE_stop\(C'\fR ensures that the watcher is neither active nor pending. If	1295	calling \f(CW\(C`ev_TYPE_stop\(C'\fR ensures that the watcher is neither active nor
882	you want to free or reuse the memory used by the watcher it is therefore a	1296	pending. If you want to free or reuse the memory used by the watcher it is
883	good idea to always call its \f(CW\(C`ev_TYPE_stop\(C'\fR function.	1297	therefore a good idea to always call its \f(CW\(C`ev_TYPE_stop\(C'\fR function.
884	.IP "bool ev_is_active (ev_TYPE *watcher)" 4	1298	.IP "bool ev_is_active (ev_TYPE *watcher)" 4
885	.IX Item "bool ev_is_active (ev_TYPE *watcher)"	1299	.IX Item "bool ev_is_active (ev_TYPE *watcher)"
886	Returns a true value iff the watcher is active (i.e. it has been started	1300	Returns a true value iff the watcher is active (i.e. it has been started
887	and not yet been stopped). As long as a watcher is active you must not modify	1301	and not yet been stopped). As long as a watcher is active you must not modify
888	it.	1302	it.
889	.IP "bool ev_is_pending (ev_TYPE *watcher)" 4	1303	.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
890	.IX Item "bool ev_is_pending (ev_TYPE *watcher)"	1304	.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
891	Returns a true value iff the watcher is pending, (i.e. it has outstanding	1305	Returns a true value iff the watcher is pending, (i.e. it has outstanding
892	events but its callback has not yet been invoked). As long as a watcher	1306	events but its callback has not yet been invoked). As long as a watcher
893	is pending (but not active) you must not call an init function on it (but	1307	is pending (but not active) you must not call an init function on it (but
894	\&\f(CW\(C`ev_TYPE_set\(C'\fR is safe) and you must make sure the watcher is available to	1308	\&\f(CW\(C`ev_TYPE_set\(C'\fR is safe), you must not change its priority, and you must
895	libev (e.g. you cnanot \f(CW\(C`free ()\(C'\fR it).	1309	make sure the watcher is available to libev (e.g. you cannot \f(CW\(C`free ()\(C'\fR
		1310	it).
896	.IP "callback ev_cb (ev_TYPE *watcher)" 4	1311	.IP "callback ev_cb (ev_TYPE *watcher)" 4
897	.IX Item "callback ev_cb (ev_TYPE *watcher)"	1312	.IX Item "callback ev_cb (ev_TYPE *watcher)"
898	Returns the callback currently set on the watcher.	1313	Returns the callback currently set on the watcher.
899	.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4	1314	.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
900	.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"	1315	.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
…		…
910	integer between \f(CW\(C`EV_MAXPRI\(C'\fR (default: \f(CW2\fR) and \f(CW\(C`EV_MINPRI\(C'\fR	1325	integer between \f(CW\(C`EV_MAXPRI\(C'\fR (default: \f(CW2\fR) and \f(CW\(C`EV_MINPRI\(C'\fR
911	(default: \f(CW\(C`\-2\(C'\fR). Pending watchers with higher priority will be invoked	1326	(default: \f(CW\(C`\-2\(C'\fR). Pending watchers with higher priority will be invoked
912	before watchers with lower priority, but priority will not keep watchers	1327	before watchers with lower priority, but priority will not keep watchers
913	from being executed (except for \f(CW\(C`ev_idle\(C'\fR watchers).	1328	from being executed (except for \f(CW\(C`ev_idle\(C'\fR watchers).
914	.Sp	1329	.Sp
915	This means that priorities are \fIonly\fR used for ordering callback
916	invocation after new events have been received. This is useful, for
917	example, to reduce latency after idling, or more often, to bind two
918	watchers on the same event and make sure one is called first.
919	.Sp
920	If you need to suppress invocation when higher priority events are pending	1330	If you need to suppress invocation when higher priority events are pending
921	you need to look at \f(CW\(C`ev_idle\(C'\fR watchers, which provide this functionality.	1331	you need to look at \f(CW\(C`ev_idle\(C'\fR watchers, which provide this functionality.
922	.Sp	1332	.Sp
		1333	You \fImust not\fR change the priority of a watcher as long as it is active or
		1334	pending.
		1335	.Sp
		1336	Setting a priority outside the range of \f(CW\(C`EV_MINPRI\(C'\fR to \f(CW\(C`EV_MAXPRI\(C'\fR is
		1337	fine, as long as you do not mind that the priority value you query might
		1338	or might not have been clamped to the valid range.
		1339	.Sp
923	The default priority used by watchers when no priority has been set is	1340	The default priority used by watchers when no priority has been set is
924	always \f(CW0\fR, which is supposed to not be too high and not be too low :).	1341	always \f(CW0\fR, which is supposed to not be too high and not be too low :).
925	.Sp	1342	.Sp
926	Setting a priority outside the range of \f(CW\(C`EV_MINPRI\(C'\fR to \f(CW\(C`EV_MAXPRI\(C'\fR is	1343	See \(L"\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0\(R", below, for a more thorough treatment of
927	fine, as long as you do not mind that the priority value you query might	1344	priorities.
928	or might not have been adjusted to be within valid range.	1345	.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
		1346	.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
		1347	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
		1348	\&\f(CW\(C`loop\(C'\fR nor \f(CW\(C`revents\(C'\fR need to be valid as long as the watcher callback
		1349	can deal with that fact, as both are simply passed through to the
		1350	callback.
		1351	.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
		1352	.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
		1353	If the watcher is pending, this function clears its pending status and
		1354	returns its \f(CW\(C`revents\(C'\fR bitset (as if its callback was invoked). If the
		1355	watcher isn't pending it does nothing and returns \f(CW0\fR.
		1356	.Sp
		1357	Sometimes it can be useful to \(L"poll\(R" a watcher instead of waiting for its
		1358	callback to be invoked, which can be accomplished with this function.
929	.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"	1359	.SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
930	.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"	1360	.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
931	Each watcher has, by default, a member \f(CW\(C`void data\*(C'\fR that you can change	1361	Each watcher has, by default, a member \f(CW\(C`void data\*(C'\fR that you can change
932	and read at any time, libev will completely ignore it. This can be used	1362	and read at any time: libev will completely ignore it. This can be used
933	to associate arbitrary data with your watcher. If you need more data and	1363	to associate arbitrary data with your watcher. If you need more data and
934	don't want to allocate memory and store a pointer to it in that data	1364	don't want to allocate memory and store a pointer to it in that data
935	member, you can also \(L"subclass\(R" the watcher type and provide your own	1365	member, you can also \(L"subclass\(R" the watcher type and provide your own
936	data:	1366	data:
937	.PP	1367	.PP
938	.Vb 7	1368	.Vb 7
939	\& struct my_io	1369	\& struct my_io
940	\& {	1370	\& {
941	\& struct ev_io io;	1371	\& ev_io io;
942	\& int otherfd;	1372	\& int otherfd;
943	\& void *somedata;	1373	\& void *somedata;
944	\& struct whatever *mostinteresting;	1374	\& struct whatever *mostinteresting;
945	\& }	1375	\& };
		1376	\&
		1377	\& ...
		1378	\& struct my_io w;
		1379	\& ev_io_init (&w.io, my_cb, fd, EV_READ);
946	.Ve	1380	.Ve
947	.PP	1381	.PP
948	And since your callback will be called with a pointer to the watcher, you	1382	And since your callback will be called with a pointer to the watcher, you
949	can cast it back to your own type:	1383	can cast it back to your own type:
950	.PP	1384	.PP
951	.Vb 5	1385	.Vb 5
952	\& static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1386	\& static void my_cb (struct ev_loop loop, ev_io w_, int revents)
953	\& {	1387	\& {
954	\& struct my_io w = (struct my_io )w_;	1388	\& struct my_io w = (struct my_io )w_;
955	\& ...	1389	\& ...
956	\& }	1390	\& }
957	.Ve	1391	.Ve
958	.PP	1392	.PP
959	More interesting and less C\-conformant ways of casting your callback type	1393	More interesting and less C\-conformant ways of casting your callback type
960	instead have been omitted.	1394	instead have been omitted.
961	.PP	1395	.PP
962	Another common scenario is having some data structure with multiple	1396	Another common scenario is to use some data structure with multiple
963	watchers:	1397	embedded watchers:
964	.PP	1398	.PP
965	.Vb 6	1399	.Vb 6
966	\& struct my_biggy	1400	\& struct my_biggy
967	\& {	1401	\& {
968	\& int some_data;	1402	\& int some_data;
969	\& ev_timer t1;	1403	\& ev_timer t1;
970	\& ev_timer t2;	1404	\& ev_timer t2;
971	\& }	1405	\& }
972	.Ve	1406	.Ve
973	.PP	1407	.PP
974	In this case getting the pointer to \f(CW\(C`my_biggy\(C'\fR is a bit more complicated,	1408	In this case getting the pointer to \f(CW\(C`my_biggy\(C'\fR is a bit more
975	you need to use \f(CW\(C`offsetof\(C'\fR:	1409	complicated: Either you store the address of your \f(CW\(C`my_biggy\(C'\fR struct
		1410	in the \f(CW\(C`data\(C'\fR member of the watcher (for woozies), or you need to use
		1411	some pointer arithmetic using \f(CW\(C`offsetof\(C'\fR inside your watchers (for real
		1412	programmers):
976	.PP	1413	.PP
977	.Vb 1	1414	.Vb 1
978	\& #include <stddef.h>	1415	\& #include <stddef.h>
979	.Ve	1416	\&
980	.PP
981	.Vb 6
982	\& static void	1417	\& static void
983	\& t1_cb (EV_P_ struct ev_timer *w, int revents)	1418	\& t1_cb (EV_P_ ev_timer *w, int revents)
984	\& {	1419	\& {
985	\& struct my_biggy big = (struct my_biggy *	1420	\& struct my_biggy big = (struct my_biggy *)
986	\& (((char *)w) - offsetof (struct my_biggy, t1));	1421	\& (((char *)w) \- offsetof (struct my_biggy, t1));
987	\& }	1422	\& }
988	.Ve	1423	\&
989	.PP
990	.Vb 6
991	\& static void	1424	\& static void
992	\& t2_cb (EV_P_ struct ev_timer *w, int revents)	1425	\& t2_cb (EV_P_ ev_timer *w, int revents)
993	\& {	1426	\& {
994	\& struct my_biggy big = (struct my_biggy *	1427	\& struct my_biggy big = (struct my_biggy *)
995	\& (((char *)w) - offsetof (struct my_biggy, t2));	1428	\& (((char *)w) \- offsetof (struct my_biggy, t2));
996	\& }	1429	\& }
997	.Ve	1430	.Ve
		1431	.SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0"
		1432	.IX Subsection "WATCHER PRIORITY MODELS"
		1433	Many event loops support \fIwatcher priorities\fR, which are usually small
		1434	integers that influence the ordering of event callback invocation
		1435	between watchers in some way, all else being equal.
		1436	.PP
		1437	In libev, Watcher priorities can be set using \f(CW\(C`ev_set_priority\(C'\fR. See its
		1438	description for the more technical details such as the actual priority
		1439	range.
		1440	.PP
		1441	There are two common ways how these these priorities are being interpreted
		1442	by event loops:
		1443	.PP
		1444	In the more common lock-out model, higher priorities \(L"lock out\(R" invocation
		1445	of lower priority watchers, which means as long as higher priority
		1446	watchers receive events, lower priority watchers are not being invoked.
		1447	.PP
		1448	The less common only-for-ordering model uses priorities solely to order
		1449	callback invocation within a single event loop iteration: Higher priority
		1450	watchers are invoked before lower priority ones, but they all get invoked
		1451	before polling for new events.
		1452	.PP
		1453	Libev uses the second (only-for-ordering) model for all its watchers
		1454	except for idle watchers (which use the lock-out model).
		1455	.PP
		1456	The rationale behind this is that implementing the lock-out model for
		1457	watchers is not well supported by most kernel interfaces, and most event
		1458	libraries will just poll for the same events again and again as long as
		1459	their callbacks have not been executed, which is very inefficient in the
		1460	common case of one high-priority watcher locking out a mass of lower
		1461	priority ones.
		1462	.PP
		1463	Static (ordering) priorities are most useful when you have two or more
		1464	watchers handling the same resource: a typical usage example is having an
		1465	\&\f(CW\(C`ev_io\(C'\fR watcher to receive data, and an associated \f(CW\(C`ev_timer\(C'\fR to handle
		1466	timeouts. Under load, data might be received while the program handles
		1467	other jobs, but since timers normally get invoked first, the timeout
		1468	handler will be executed before checking for data. In that case, giving
		1469	the timer a lower priority than the I/O watcher ensures that I/O will be
		1470	handled first even under adverse conditions (which is usually, but not
		1471	always, what you want).
		1472	.PP
		1473	Since idle watchers use the \(L"lock-out\(R" model, meaning that idle watchers
		1474	will only be executed when no same or higher priority watchers have
		1475	received events, they can be used to implement the \(L"lock-out\(R" model when
		1476	required.
		1477	.PP
		1478	For example, to emulate how many other event libraries handle priorities,
		1479	you can associate an \f(CW\(C`ev_idle\(C'\fR watcher to each such watcher, and in
		1480	the normal watcher callback, you just start the idle watcher. The real
		1481	processing is done in the idle watcher callback. This causes libev to
		1482	continously poll and process kernel event data for the watcher, but when
		1483	the lock-out case is known to be rare (which in turn is rare :), this is
		1484	workable.
		1485	.PP
		1486	Usually, however, the lock-out model implemented that way will perform
		1487	miserably under the type of load it was designed to handle. In that case,
		1488	it might be preferable to stop the real watcher before starting the
		1489	idle watcher, so the kernel will not have to process the event in case
		1490	the actual processing will be delayed for considerable time.
		1491	.PP
		1492	Here is an example of an I/O watcher that should run at a strictly lower
		1493	priority than the default, and which should only process data when no
		1494	other events are pending:
		1495	.PP
		1496	.Vb 2
		1497	\& ev_idle idle; // actual processing watcher
		1498	\& ev_io io; // actual event watcher
		1499	\&
		1500	\& static void
		1501	\& io_cb (EV_P_ ev_io *w, int revents)
		1502	\& {
		1503	\& // stop the I/O watcher, we received the event, but
		1504	\& // are not yet ready to handle it.
		1505	\& ev_io_stop (EV_A_ w);
		1506	\&
		1507	\& // start the idle watcher to ahndle the actual event.
		1508	\& // it will not be executed as long as other watchers
		1509	\& // with the default priority are receiving events.
		1510	\& ev_idle_start (EV_A_ &idle);
		1511	\& }
		1512	\&
		1513	\& static void
		1514	\& idle_cb (EV_P_ ev_idle *w, int revents)
		1515	\& {
		1516	\& // actual processing
		1517	\& read (STDIN_FILENO, ...);
		1518	\&
		1519	\& // have to start the I/O watcher again, as
		1520	\& // we have handled the event
		1521	\& ev_io_start (EV_P_ &io);
		1522	\& }
		1523	\&
		1524	\& // initialisation
		1525	\& ev_idle_init (&idle, idle_cb);
		1526	\& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1527	\& ev_io_start (EV_DEFAULT_ &io);
		1528	.Ve
		1529	.PP
		1530	In the \(L"real\(R" world, it might also be beneficial to start a timer, so that
		1531	low-priority connections can not be locked out forever under load. This
		1532	enables your program to keep a lower latency for important connections
		1533	during short periods of high load, while not completely locking out less
		1534	important ones.
998	.SH "WATCHER TYPES"	1535	.SH "WATCHER TYPES"
999	.IX Header "WATCHER TYPES"	1536	.IX Header "WATCHER TYPES"
1000	This section describes each watcher in detail, but will not repeat	1537	This section describes each watcher in detail, but will not repeat
1001	information given in the last section. Any initialisation/set macros,	1538	information given in the last section. Any initialisation/set macros,
1002	functions and members specific to the watcher type are explained.	1539	functions and members specific to the watcher type are explained.
…		…
1007	watcher is stopped to your hearts content), or \fI[read\-write]\fR, which	1544	watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1008	means you can expect it to have some sensible content while the watcher	1545	means you can expect it to have some sensible content while the watcher
1009	is active, but you can also modify it. Modifying it may not do something	1546	is active, but you can also modify it. Modifying it may not do something
1010	sensible or take immediate effect (or do anything at all), but libev will	1547	sensible or take immediate effect (or do anything at all), but libev will
1011	not crash or malfunction in any way.	1548	not crash or malfunction in any way.
1012	.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"	1549	.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
1013	.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"	1550	.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
1014	.IX Subsection "ev_io - is this file descriptor readable or writable?"	1551	.IX Subsection "ev_io - is this file descriptor readable or writable?"
1015	I/O watchers check whether a file descriptor is readable or writable	1552	I/O watchers check whether a file descriptor is readable or writable
1016	in each iteration of the event loop, or, more precisely, when reading	1553	in each iteration of the event loop, or, more precisely, when reading
1017	would not block the process and writing would at least be able to write	1554	would not block the process and writing would at least be able to write
1018	some data. This behaviour is called level-triggering because you keep	1555	some data. This behaviour is called level-triggering because you keep
…		…
1023	In general you can register as many read and/or write event watchers per	1560	In general you can register as many read and/or write event watchers per
1024	fd as you want (as long as you don't confuse yourself). Setting all file	1561	fd as you want (as long as you don't confuse yourself). Setting all file
1025	descriptors to non-blocking mode is also usually a good idea (but not	1562	descriptors to non-blocking mode is also usually a good idea (but not
1026	required if you know what you are doing).	1563	required if you know what you are doing).
1027	.PP	1564	.PP
1028	You have to be careful with dup'ed file descriptors, though. Some backends	1565	If you cannot use non-blocking mode, then force the use of a
1029	(the linux epoll backend is a notable example) cannot handle dup'ed file	1566	known-to-be-good backend (at the time of this writing, this includes only
1030	descriptors correctly if you register interest in two or more fds pointing	1567	\&\f(CW\(C`EVBACKEND_SELECT\(C'\fR and \f(CW\(C`EVBACKEND_POLL\(C'\fR). The same applies to file
1031	to the same underlying file/socket/etc. description (that is, they share	1568	descriptors for which non-blocking operation makes no sense (such as
1032	the same underlying \(L"file open\(R").	1569	files) \- libev doesn't guarentee any specific behaviour in that case.
1033	.PP
1034	If you must do this, then force the use of a known-to-be-good backend
1035	(at the time of this writing, this includes only \f(CW\(C`EVBACKEND_SELECT\(C'\fR and
1036	\&\f(CW\(C`EVBACKEND_POLL\(C'\fR).
1037	.PP	1570	.PP
1038	Another thing you have to watch out for is that it is quite easy to	1571	Another thing you have to watch out for is that it is quite easy to
1039	receive \(L"spurious\(R" readyness notifications, that is your callback might	1572	receive \(L"spurious\(R" readiness notifications, that is your callback might
1040	be called with \f(CW\(C`EV_READ\(C'\fR but a subsequent \f(CW\(C`read\(C'\fR(2) will actually block	1573	be called with \f(CW\(C`EV_READ\(C'\fR but a subsequent \f(CW\(C`read\(C'\fR(2) will actually block
1041	because there is no data. Not only are some backends known to create a	1574	because there is no data. Not only are some backends known to create a
1042	lot of those (for example solaris ports), it is very easy to get into	1575	lot of those (for example Solaris ports), it is very easy to get into
1043	this situation even with a relatively standard program structure. Thus	1576	this situation even with a relatively standard program structure. Thus
1044	it is best to always use non-blocking I/O: An extra \f(CW\(C`read\(C'\fR(2) returning	1577	it is best to always use non-blocking I/O: An extra \f(CW\(C`read\(C'\fR(2) returning
1045	\&\f(CW\(C`EAGAIN\(C'\fR is far preferable to a program hanging until some data arrives.	1578	\&\f(CW\(C`EAGAIN\(C'\fR is far preferable to a program hanging until some data arrives.
1046	.PP	1579	.PP
1047	If you cannot run the fd in non-blocking mode (for example you should not	1580	If you cannot run the fd in non-blocking mode (for example you should
1048	play around with an Xlib connection), then you have to seperately re-test	1581	not play around with an Xlib connection), then you have to separately
1049	whether a file descriptor is really ready with a known-to-be good interface	1582	re-test whether a file descriptor is really ready with a known-to-be good
1050	such as poll (fortunately in our Xlib example, Xlib already does this on	1583	interface such as poll (fortunately in our Xlib example, Xlib already
1051	its own, so its quite safe to use).	1584	does this on its own, so its quite safe to use). Some people additionally
		1585	use \f(CW\(C`SIGALRM\(C'\fR and an interval timer, just to be sure you won't block
		1586	indefinitely.
		1587	.PP
		1588	But really, best use non-blocking mode.
		1589	.PP
		1590	\fIThe special problem of disappearing file descriptors\fR
		1591	.IX Subsection "The special problem of disappearing file descriptors"
		1592	.PP
		1593	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1594	descriptor (either due to calling \f(CW\(C`close\(C'\fR explicitly or any other means,
		1595	such as \f(CW\(C`dup2\(C'\fR). The reason is that you register interest in some file
		1596	descriptor, but when it goes away, the operating system will silently drop
		1597	this interest. If another file descriptor with the same number then is
		1598	registered with libev, there is no efficient way to see that this is, in
		1599	fact, a different file descriptor.
		1600	.PP
		1601	To avoid having to explicitly tell libev about such cases, libev follows
		1602	the following policy: Each time \f(CW\(C`ev_io_set\(C'\fR is being called, libev
		1603	will assume that this is potentially a new file descriptor, otherwise
		1604	it is assumed that the file descriptor stays the same. That means that
		1605	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
		1606	descriptor even if the file descriptor number itself did not change.
		1607	.PP
		1608	This is how one would do it normally anyway, the important point is that
		1609	the libev application should not optimise around libev but should leave
		1610	optimisations to libev.
		1611	.PP
		1612	\fIThe special problem of dup'ed file descriptors\fR
		1613	.IX Subsection "The special problem of dup'ed file descriptors"
		1614	.PP
		1615	Some backends (e.g. epoll), cannot register events for file descriptors,
		1616	but only events for the underlying file descriptions. That means when you
		1617	have \f(CW\(C`dup ()\(C'\fR'ed file descriptors or weirder constellations, and register
		1618	events for them, only one file descriptor might actually receive events.
		1619	.PP
		1620	There is no workaround possible except not registering events
		1621	for potentially \f(CW\(C`dup ()\(C'\fR'ed file descriptors, or to resort to
		1622	\&\f(CW\(C`EVBACKEND_SELECT\(C'\fR or \f(CW\(C`EVBACKEND_POLL\(C'\fR.
		1623	.PP
		1624	\fIThe special problem of fork\fR
		1625	.IX Subsection "The special problem of fork"
		1626	.PP
		1627	Some backends (epoll, kqueue) do not support \f(CW\(C`fork ()\(C'\fR at all or exhibit
		1628	useless behaviour. Libev fully supports fork, but needs to be told about
		1629	it in the child.
		1630	.PP
		1631	To support fork in your programs, you either have to call
		1632	\&\f(CW\(C`ev_default_fork ()\(C'\fR or \f(CW\(C`ev_loop_fork ()\(C'\fR after a fork in the child,
		1633	enable \f(CW\(C`EVFLAG_FORKCHECK\(C'\fR, or resort to \f(CW\(C`EVBACKEND_SELECT\(C'\fR or
		1634	\&\f(CW\(C`EVBACKEND_POLL\(C'\fR.
		1635	.PP
		1636	\fIThe special problem of \s-1SIGPIPE\s0\fR
		1637	.IX Subsection "The special problem of SIGPIPE"
		1638	.PP
		1639	While not really specific to libev, it is easy to forget about \f(CW\(C`SIGPIPE\(C'\fR:
		1640	when writing to a pipe whose other end has been closed, your program gets
		1641	sent a \s-1SIGPIPE\s0, which, by default, aborts your program. For most programs
		1642	this is sensible behaviour, for daemons, this is usually undesirable.
		1643	.PP
		1644	So when you encounter spurious, unexplained daemon exits, make sure you
		1645	ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon
		1646	somewhere, as that would have given you a big clue).
		1647	.PP
		1648	\fIWatcher-Specific Functions\fR
		1649	.IX Subsection "Watcher-Specific Functions"
1052	.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4	1650	.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
1053	.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"	1651	.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
1054	.PD 0	1652	.PD 0
1055	.IP "ev_io_set (ev_io *, int fd, int events)" 4	1653	.IP "ev_io_set (ev_io *, int fd, int events)" 4
1056	.IX Item "ev_io_set (ev_io *, int fd, int events)"	1654	.IX Item "ev_io_set (ev_io *, int fd, int events)"
1057	.PD	1655	.PD
1058	Configures an \f(CW\(C`ev_io\(C'\fR watcher. The \f(CW\(C`fd\(C'\fR is the file descriptor to	1656	Configures an \f(CW\(C`ev_io\(C'\fR watcher. The \f(CW\(C`fd\(C'\fR is the file descriptor to
1059	rceeive events for and events is either \f(CW\(C`EV_READ\(C'\fR, \f(CW\(C`EV_WRITE\(C'\fR or	1657	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
1060	\&\f(CW\(C`EV_READ \| EV_WRITE\(C'\fR to receive the given events.	1658	\&\f(CW\(C`EV_READ \| EV_WRITE\(C'\fR, to express the desire to receive the given events.
1061	.IP "int fd [read\-only]" 4	1659	.IP "int fd [read\-only]" 4
1062	.IX Item "int fd [read-only]"	1660	.IX Item "int fd [read-only]"
1063	The file descriptor being watched.	1661	The file descriptor being watched.
1064	.IP "int events [read\-only]" 4	1662	.IP "int events [read\-only]" 4
1065	.IX Item "int events [read-only]"	1663	.IX Item "int events [read-only]"
1066	The events being watched.	1664	The events being watched.
1067	.PP	1665	.PP
		1666	\fIExamples\fR
		1667	.IX Subsection "Examples"
		1668	.PP
1068	Example: Call \f(CW\(C`stdin_readable_cb\(C'\fR when \s-1STDIN_FILENO\s0 has become, well	1669	Example: Call \f(CW\(C`stdin_readable_cb\(C'\fR when \s-1STDIN_FILENO\s0 has become, well
1069	readable, but only once. Since it is likely line\-buffered, you could	1670	readable, but only once. Since it is likely line-buffered, you could
1070	attempt to read a whole line in the callback.	1671	attempt to read a whole line in the callback.
1071	.PP	1672	.PP
1072	.Vb 6	1673	.Vb 6
1073	\& static void	1674	\& static void
1074	\& stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1675	\& stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1075	\& {	1676	\& {
1076	\& ev_io_stop (loop, w);	1677	\& ev_io_stop (loop, w);
1077	\& .. read from stdin here (or from w->fd) and haqndle any I/O errors	1678	\& .. read from stdin here (or from w\->fd) and handle any I/O errors
1078	\& }	1679	\& }
1079	.Ve	1680	\&
1080	.PP
1081	.Vb 6
1082	\& ...	1681	\& ...
1083	\& struct ev_loop *loop = ev_default_init (0);	1682	\& struct ev_loop *loop = ev_default_init (0);
1084	\& struct ev_io stdin_readable;	1683	\& ev_io stdin_readable;
1085	\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1684	\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1086	\& ev_io_start (loop, &stdin_readable);	1685	\& ev_io_start (loop, &stdin_readable);
1087	\& ev_loop (loop, 0);	1686	\& ev_loop (loop, 0);
1088	.Ve	1687	.Ve
1089	.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"	1688	.ie n .SS """ev_timer"" \- relative and optionally repeating timeouts"
1090	.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"	1689	.el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
1091	.IX Subsection "ev_timer - relative and optionally repeating timeouts"	1690	.IX Subsection "ev_timer - relative and optionally repeating timeouts"
1092	Timer watchers are simple relative timers that generate an event after a	1691	Timer watchers are simple relative timers that generate an event after a
1093	given time, and optionally repeating in regular intervals after that.	1692	given time, and optionally repeating in regular intervals after that.
1094	.PP	1693	.PP
1095	The timers are based on real time, that is, if you register an event that	1694	The timers are based on real time, that is, if you register an event that
1096	times out after an hour and you reset your system clock to last years	1695	times out after an hour and you reset your system clock to January last
1097	time, it will still time out after (roughly) and hour. \(L"Roughly\(R" because	1696	year, it will still time out after (roughly) one hour. \(L"Roughly\(R" because
1098	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1697	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1099	monotonic clock option helps a lot here).	1698	monotonic clock option helps a lot here).
		1699	.PP
		1700	The callback is guaranteed to be invoked only \fIafter\fR its timeout has
		1701	passed (not \fIat\fR, so on systems with very low-resolution clocks this
		1702	might introduce a small delay). If multiple timers become ready during the
		1703	same loop iteration then the ones with earlier time-out values are invoked
		1704	before ones of the same priority with later time-out values (but this is
		1705	no longer true when a callback calls \f(CW\(C`ev_loop\(C'\fR recursively).
		1706	.PP
		1707	\fIBe smart about timeouts\fR
		1708	.IX Subsection "Be smart about timeouts"
		1709	.PP
		1710	Many real-world problems involve some kind of timeout, usually for error
		1711	recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs,
		1712	you want to raise some error after a while.
		1713	.PP
		1714	What follows are some ways to handle this problem, from obvious and
		1715	inefficient to smart and efficient.
		1716	.PP
		1717	In the following, a 60 second activity timeout is assumed \- a timeout that
		1718	gets reset to 60 seconds each time there is activity (e.g. each time some
		1719	data or other life sign was received).
		1720	.IP "1. Use a timer and stop, reinitialise and start it on activity." 4
		1721	.IX Item "1. Use a timer and stop, reinitialise and start it on activity."
		1722	This is the most obvious, but not the most simple way: In the beginning,
		1723	start the watcher:
		1724	.Sp
		1725	.Vb 2
		1726	\& ev_timer_init (timer, callback, 60., 0.);
		1727	\& ev_timer_start (loop, timer);
		1728	.Ve
		1729	.Sp
		1730	Then, each time there is some activity, \f(CW\(C`ev_timer_stop\(C'\fR it, initialise it
		1731	and start it again:
		1732	.Sp
		1733	.Vb 3
		1734	\& ev_timer_stop (loop, timer);
		1735	\& ev_timer_set (timer, 60., 0.);
		1736	\& ev_timer_start (loop, timer);
		1737	.Ve
		1738	.Sp
		1739	This is relatively simple to implement, but means that each time there is
		1740	some activity, libev will first have to remove the timer from its internal
		1741	data structure and then add it again. Libev tries to be fast, but it's
		1742	still not a constant-time operation.
		1743	.ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4
		1744	.el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4
		1745	.IX Item "2. Use a timer and re-start it with ev_timer_again inactivity."
		1746	This is the easiest way, and involves using \f(CW\(C`ev_timer_again\(C'\fR instead of
		1747	\&\f(CW\(C`ev_timer_start\(C'\fR.
		1748	.Sp
		1749	To implement this, configure an \f(CW\(C`ev_timer\(C'\fR with a \f(CW\(C`repeat\(C'\fR value
		1750	of \f(CW60\fR and then call \f(CW\(C`ev_timer_again\(C'\fR at start and each time you
		1751	successfully read or write some data. If you go into an idle state where
		1752	you do not expect data to travel on the socket, you can \f(CW\(C`ev_timer_stop\(C'\fR
		1753	the timer, and \f(CW\(C`ev_timer_again\(C'\fR will automatically restart it if need be.
		1754	.Sp
		1755	That means you can ignore both the \f(CW\(C`ev_timer_start\(C'\fR function and the
		1756	\&\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
		1757	member and \f(CW\(C`ev_timer_again\(C'\fR.
		1758	.Sp
		1759	At start:
		1760	.Sp
		1761	.Vb 3
		1762	\& ev_init (timer, callback);
		1763	\& timer\->repeat = 60.;
		1764	\& ev_timer_again (loop, timer);
		1765	.Ve
		1766	.Sp
		1767	Each time there is some activity:
		1768	.Sp
		1769	.Vb 1
		1770	\& ev_timer_again (loop, timer);
		1771	.Ve
		1772	.Sp
		1773	It is even possible to change the time-out on the fly, regardless of
		1774	whether the watcher is active or not:
		1775	.Sp
		1776	.Vb 2
		1777	\& timer\->repeat = 30.;
		1778	\& ev_timer_again (loop, timer);
		1779	.Ve
		1780	.Sp
		1781	This is slightly more efficient then stopping/starting the timer each time
		1782	you want to modify its timeout value, as libev does not have to completely
		1783	remove and re-insert the timer from/into its internal data structure.
		1784	.Sp
		1785	It is, however, even simpler than the \(L"obvious\(R" way to do it.
		1786	.IP "3. Let the timer time out, but then re-arm it as required." 4
		1787	.IX Item "3. Let the timer time out, but then re-arm it as required."
		1788	This method is more tricky, but usually most efficient: Most timeouts are
		1789	relatively long compared to the intervals between other activity \- in
		1790	our example, within 60 seconds, there are usually many I/O events with
		1791	associated activity resets.
		1792	.Sp
		1793	In this case, it would be more efficient to leave the \f(CW\(C`ev_timer\(C'\fR alone,
		1794	but remember the time of last activity, and check for a real timeout only
		1795	within the callback:
		1796	.Sp
		1797	.Vb 1
		1798	\& ev_tstamp last_activity; // time of last activity
		1799	\&
		1800	\& static void
		1801	\& callback (EV_P_ ev_timer *w, int revents)
		1802	\& {
		1803	\& ev_tstamp now = ev_now (EV_A);
		1804	\& ev_tstamp timeout = last_activity + 60.;
		1805	\&
		1806	\& // if last_activity + 60. is older than now, we did time out
		1807	\& if (timeout < now)
		1808	\& {
		1809	\& // timeout occured, take action
		1810	\& }
		1811	\& else
		1812	\& {
		1813	\& // callback was invoked, but there was some activity, re\-arm
		1814	\& // the watcher to fire in last_activity + 60, which is
		1815	\& // guaranteed to be in the future, so "again" is positive:
		1816	\& w\->repeat = timeout \- now;
		1817	\& ev_timer_again (EV_A_ w);
		1818	\& }
		1819	\& }
		1820	.Ve
		1821	.Sp
		1822	To summarise the callback: first calculate the real timeout (defined
		1823	as \(L"60 seconds after the last activity\(R"), then check if that time has
		1824	been reached, which means something \fIdid\fR, in fact, time out. Otherwise
		1825	the callback was invoked too early (\f(CW\(C`timeout\(C'\fR is in the future), so
		1826	re-schedule the timer to fire at that future time, to see if maybe we have
		1827	a timeout then.
		1828	.Sp
		1829	Note how \f(CW\(C`ev_timer_again\(C'\fR is used, taking advantage of the
		1830	\&\f(CW\(C`ev_timer_again\(C'\fR optimisation when the timer is already running.
		1831	.Sp
		1832	This scheme causes more callback invocations (about one every 60 seconds
		1833	minus half the average time between activity), but virtually no calls to
		1834	libev to change the timeout.
		1835	.Sp
		1836	To start the timer, simply initialise the watcher and set \f(CW\(C`last_activity\(C'\fR
		1837	to the current time (meaning we just have some activity :), then call the
		1838	callback, which will \(L"do the right thing\(R" and start the timer:
		1839	.Sp
		1840	.Vb 3
		1841	\& ev_init (timer, callback);
		1842	\& last_activity = ev_now (loop);
		1843	\& callback (loop, timer, EV_TIMEOUT);
		1844	.Ve
		1845	.Sp
		1846	And when there is some activity, simply store the current time in
		1847	\&\f(CW\(C`last_activity\(C'\fR, no libev calls at all:
		1848	.Sp
		1849	.Vb 1
		1850	\& last_actiivty = ev_now (loop);
		1851	.Ve
		1852	.Sp
		1853	This technique is slightly more complex, but in most cases where the
		1854	time-out is unlikely to be triggered, much more efficient.
		1855	.Sp
		1856	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1857	callback :) \- just change the timeout and invoke the callback, which will
		1858	fix things for you.
		1859	.IP "4. Wee, just use a double-linked list for your timeouts." 4
		1860	.IX Item "4. Wee, just use a double-linked list for your timeouts."
		1861	If there is not one request, but many thousands (millions...), all
		1862	employing some kind of timeout with the same timeout value, then one can
		1863	do even better:
		1864	.Sp
		1865	When starting the timeout, calculate the timeout value and put the timeout
		1866	at the \fIend\fR of the list.
		1867	.Sp
		1868	Then use an \f(CW\(C`ev_timer\(C'\fR to fire when the timeout at the \fIbeginning\fR of
		1869	the list is expected to fire (for example, using the technique #3).
		1870	.Sp
		1871	When there is some activity, remove the timer from the list, recalculate
		1872	the timeout, append it to the end of the list again, and make sure to
		1873	update the \f(CW\(C`ev_timer\(C'\fR if it was taken from the beginning of the list.
		1874	.Sp
		1875	This way, one can manage an unlimited number of timeouts in O(1) time for
		1876	starting, stopping and updating the timers, at the expense of a major
		1877	complication, and having to use a constant timeout. The constant timeout
		1878	ensures that the list stays sorted.
		1879	.PP
		1880	So which method the best?
		1881	.PP
		1882	Method #2 is a simple no-brain-required solution that is adequate in most
		1883	situations. Method #3 requires a bit more thinking, but handles many cases
		1884	better, and isn't very complicated either. In most case, choosing either
		1885	one is fine, with #3 being better in typical situations.
		1886	.PP
		1887	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1888	rather complicated, but extremely efficient, something that really pays
		1889	off after the first million or so of active timers, i.e. it's usually
		1890	overkill :)
		1891	.PP
		1892	\fIThe special problem of time updates\fR
		1893	.IX Subsection "The special problem of time updates"
		1894	.PP
		1895	Establishing the current time is a costly operation (it usually takes at
		1896	least two system calls): \s-1EV\s0 therefore updates its idea of the current
		1897	time only before and after \f(CW\(C`ev_loop\(C'\fR collects new events, which causes a
		1898	growing difference between \f(CW\(C`ev_now ()\(C'\fR and \f(CW\(C`ev_time ()\(C'\fR when handling
		1899	lots of events in one iteration.
1100	.PP	1900	.PP
1101	The relative timeouts are calculated relative to the \f(CW\(C`ev_now ()\(C'\fR	1901	The relative timeouts are calculated relative to the \f(CW\(C`ev_now ()\(C'\fR
1102	time. This is usually the right thing as this timestamp refers to the time	1902	time. This is usually the right thing as this timestamp refers to the time
1103	of the event triggering whatever timeout you are modifying/starting. If	1903	of the event triggering whatever timeout you are modifying/starting. If
1104	you suspect event processing to be delayed and you \fIneed\fR to base the timeout	1904	you suspect event processing to be delayed and you \fIneed\fR to base the
1105	on the current time, use something like this to adjust for this:	1905	timeout on the current time, use something like this to adjust for this:
1106	.PP	1906	.PP
1107	.Vb 1	1907	.Vb 1
1108	\& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1908	\& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.);
1109	.Ve	1909	.Ve
1110	.PP	1910	.PP
1111	The callback is guarenteed to be invoked only when its timeout has passed,	1911	If the event loop is suspended for a long time, you can also force an
1112	but if multiple timers become ready during the same loop iteration then	1912	update of the time returned by \f(CW\(C`ev_now ()\(C'\fR by calling \f(CW\*(C`ev_now_update
1113	order of execution is undefined.	1913	()\*(C'\fR.
		1914	.PP
		1915	\fIThe special problems of suspended animation\fR
		1916	.IX Subsection "The special problems of suspended animation"
		1917	.PP
		1918	When you leave the server world it is quite customary to hit machines that
		1919	can suspend/hibernate \- what happens to the clocks during such a suspend?
		1920	.PP
		1921	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1922	all processes, while the clocks (\f(CW\(C`times\(C'\fR, \f(CW\(C`CLOCK_MONOTONIC\(C'\fR) continue
		1923	to run until the system is suspended, but they will not advance while the
		1924	system is suspended. That means, on resume, it will be as if the program
		1925	was frozen for a few seconds, but the suspend time will not be counted
		1926	towards \f(CW\(C`ev_timer\(C'\fR when a monotonic clock source is used. The real time
		1927	clock advanced as expected, but if it is used as sole clocksource, then a
		1928	long suspend would be detected as a time jump by libev, and timers would
		1929	be adjusted accordingly.
		1930	.PP
		1931	I would not be surprised to see different behaviour in different between
		1932	operating systems, \s-1OS\s0 versions or even different hardware.
		1933	.PP
		1934	The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a
		1935	time jump in the monotonic clocks and the realtime clock. If the program
		1936	is suspended for a very long time, and monotonic clock sources are in use,
		1937	then you can expect \f(CW\(C`ev_timer\(C'\fRs to expire as the full suspension time
		1938	will be counted towards the timers. When no monotonic clock source is in
		1939	use, then libev will again assume a timejump and adjust accordingly.
		1940	.PP
		1941	It might be beneficial for this latter case to call \f(CW\(C`ev_suspend\(C'\fR
		1942	and \f(CW\(C`ev_resume\(C'\fR in code that handles \f(CW\(C`SIGTSTP\(C'\fR, to at least get
		1943	deterministic behaviour in this case (you can do nothing against
		1944	\&\f(CW\(C`SIGSTOP\(C'\fR).
		1945	.PP
		1946	\fIWatcher-Specific Functions and Data Members\fR
		1947	.IX Subsection "Watcher-Specific Functions and Data Members"
1114	.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4	1948	.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
1115	.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"	1949	.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
1116	.PD 0	1950	.PD 0
1117	.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4	1951	.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
1118	.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"	1952	.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
1119	.PD	1953	.PD
1120	Configure the timer to trigger after \f(CW\(C`after\(C'\fR seconds. If \f(CW\(C`repeat\(C'\fR is	1954	Configure the timer to trigger after \f(CW\(C`after\(C'\fR seconds. If \f(CW\(C`repeat\(C'\fR
1121	\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the	1955	is \f(CW0.\fR, then it will automatically be stopped once the timeout is
1122	timer will automatically be configured to trigger again \f(CW\(C`repeat\(C'\fR seconds	1956	reached. If it is positive, then the timer will automatically be
1123	later, again, and again, until stopped manually.	1957	configured to trigger again \f(CW\(C`repeat\(C'\fR seconds later, again, and again,
		1958	until stopped manually.
1124	.Sp	1959	.Sp
1125	The timer itself will do a best-effort at avoiding drift, that is, if you	1960	The timer itself will do a best-effort at avoiding drift, that is, if
1126	configure a timer to trigger every 10 seconds, then it will trigger at	1961	you configure a timer to trigger every 10 seconds, then it will normally
1127	exactly 10 second intervals. If, however, your program cannot keep up with	1962	trigger at exactly 10 second intervals. If, however, your program cannot
1128	the timer (because it takes longer than those 10 seconds to do stuff) the	1963	keep up with the timer (because it takes longer than those 10 seconds to
1129	timer will not fire more than once per event loop iteration.	1964	do stuff) the timer will not fire more than once per event loop iteration.
1130	.IP "ev_timer_again (loop)" 4	1965	.IP "ev_timer_again (loop, ev_timer *)" 4
1131	.IX Item "ev_timer_again (loop)"	1966	.IX Item "ev_timer_again (loop, ev_timer *)"
1132	This will act as if the timer timed out and restart it again if it is	1967	This will act as if the timer timed out and restart it again if it is
1133	repeating. The exact semantics are:	1968	repeating. The exact semantics are:
1134	.Sp	1969	.Sp
1135	If the timer is pending, its pending status is cleared.	1970	If the timer is pending, its pending status is cleared.
1136	.Sp	1971	.Sp
1137	If the timer is started but nonrepeating, stop it (as if it timed out).	1972	If the timer is started but non-repeating, stop it (as if it timed out).
1138	.Sp	1973	.Sp
1139	If the timer is repeating, either start it if necessary (with the	1974	If the timer is repeating, either start it if necessary (with the
1140	\&\f(CW\(C`repeat\(C'\fR value), or reset the running timer to the \f(CW\(C`repeat\(C'\fR value.	1975	\&\f(CW\(C`repeat\(C'\fR value), or reset the running timer to the \f(CW\(C`repeat\(C'\fR value.
1141	.Sp	1976	.Sp
1142	This sounds a bit complicated, but here is a useful and typical	1977	This sounds a bit complicated, see \(L"Be smart about timeouts\(R", above, for a
1143	example: Imagine you have a tcp connection and you want a so-called idle	1978	usage example.
1144	timeout, that is, you want to be called when there have been, say, 60	1979	.IP "ev_timer_remaining (loop, ev_timer *)" 4
1145	seconds of inactivity on the socket. The easiest way to do this is to	1980	.IX Item "ev_timer_remaining (loop, ev_timer *)"
1146	configure an \f(CW\(C`ev_timer\(C'\fR with a \f(CW\(C`repeat\(C'\fR value of \f(CW60\fR and then call	1981	Returns the remaining time until a timer fires. If the timer is active,
1147	\&\f(CW\(C`ev_timer_again\(C'\fR each time you successfully read or write some data. If	1982	then this time is relative to the current event loop time, otherwise it's
1148	you go into an idle state where you do not expect data to travel on the	1983	the timeout value currently configured.
1149	socket, you can \f(CW\(C`ev_timer_stop\(C'\fR the timer, and \f(CW\(C`ev_timer_again\(C'\fR will
1150	automatically restart it if need be.
1151	.Sp	1984	.Sp
1152	That means you can ignore the \f(CW\(C`after\(C'\fR value and \f(CW\(C`ev_timer_start\(C'\fR	1985	That is, after an \f(CW\(C`ev_timer_set (w, 5, 7)\(C'\fR, \f(CW\(C`ev_timer_remaining\(C'\fR returns
1153	altogether and only ever use the \f(CW\(C`repeat\(C'\fR value and \f(CW\(C`ev_timer_again\(C'\fR:	1986	\&\f(CW5\fR. When the timer is started and one second passes, \f(CW\(C`ev_timer_remain\(C'\fR
1154	.Sp	1987	will return \f(CW4\fR. When the timer expires and is restarted, it will return
1155	.Vb 8	1988	roughly \f(CW7\fR (likely slightly less as callback invocation takes some time,
1156	\& ev_timer_init (timer, callback, 0., 5.);	1989	too), and so on.
1157	\& ev_timer_again (loop, timer);
1158	\& ...
1159	\& timer->again = 17.;
1160	\& ev_timer_again (loop, timer);
1161	\& ...
1162	\& timer->again = 10.;
1163	\& ev_timer_again (loop, timer);
1164	.Ve
1165	.Sp
1166	This is more slightly efficient then stopping/starting the timer each time
1167	you want to modify its timeout value.
1168	.IP "ev_tstamp repeat [read\-write]" 4	1990	.IP "ev_tstamp repeat [read\-write]" 4
1169	.IX Item "ev_tstamp repeat [read-write]"	1991	.IX Item "ev_tstamp repeat [read-write]"
1170	The current \f(CW\(C`repeat\(C'\fR value. Will be used each time the watcher times out	1992	The current \f(CW\(C`repeat\(C'\fR value. Will be used each time the watcher times out
1171	or \f(CW\(C`ev_timer_again\(C'\fR is called and determines the next timeout (if any),	1993	or \f(CW\(C`ev_timer_again\(C'\fR is called, and determines the next timeout (if any),
1172	which is also when any modifications are taken into account.	1994	which is also when any modifications are taken into account.
1173	.PP	1995	.PP
		1996	\fIExamples\fR
		1997	.IX Subsection "Examples"
		1998	.PP
1174	Example: Create a timer that fires after 60 seconds.	1999	Example: Create a timer that fires after 60 seconds.
1175	.PP	2000	.PP
1176	.Vb 5	2001	.Vb 5
1177	\& static void	2002	\& static void
1178	\& one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	2003	\& one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1179	\& {	2004	\& {
1180	\& .. one minute over, w is actually stopped right here	2005	\& .. one minute over, w is actually stopped right here
1181	\& }	2006	\& }
1182	.Ve	2007	\&
1183	.PP
1184	.Vb 3
1185	\& struct ev_timer mytimer;	2008	\& ev_timer mytimer;
1186	\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2009	\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1187	\& ev_timer_start (loop, &mytimer);	2010	\& ev_timer_start (loop, &mytimer);
1188	.Ve	2011	.Ve
1189	.PP	2012	.PP
1190	Example: Create a timeout timer that times out after 10 seconds of	2013	Example: Create a timeout timer that times out after 10 seconds of
1191	inactivity.	2014	inactivity.
1192	.PP	2015	.PP
1193	.Vb 5	2016	.Vb 5
1194	\& static void	2017	\& static void
1195	\& timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	2018	\& timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1196	\& {	2019	\& {
1197	\& .. ten seconds without any activity	2020	\& .. ten seconds without any activity
1198	\& }	2021	\& }
1199	.Ve	2022	\&
1200	.PP
1201	.Vb 4
1202	\& struct ev_timer mytimer;	2023	\& ev_timer mytimer;
1203	\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2024	\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1204	\& ev_timer_again (&mytimer); /* start timer */	2025	\& ev_timer_again (&mytimer); /* start timer */
1205	\& ev_loop (loop, 0);	2026	\& ev_loop (loop, 0);
1206	.Ve	2027	\&
1207	.PP
1208	.Vb 3
1209	\& // and in some piece of code that gets executed on any "activity":	2028	\& // and in some piece of code that gets executed on any "activity":
1210	\& // reset the timeout to start ticking again at 10 seconds	2029	\& // reset the timeout to start ticking again at 10 seconds
1211	\& ev_timer_again (&mytimer);	2030	\& ev_timer_again (&mytimer);
1212	.Ve	2031	.Ve
1213	.ie n .Sh """ev_periodic"" \- to cron or not to cron?"	2032	.ie n .SS """ev_periodic"" \- to cron or not to cron?"
1214	.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"	2033	.el .SS "\f(CWev_periodic\fP \- to cron or not to cron?"
1215	.IX Subsection "ev_periodic - to cron or not to cron?"	2034	.IX Subsection "ev_periodic - to cron or not to cron?"
1216	Periodic watchers are also timers of a kind, but they are very versatile	2035	Periodic watchers are also timers of a kind, but they are very versatile
1217	(and unfortunately a bit complex).	2036	(and unfortunately a bit complex).
1218	.PP	2037	.PP
1219	Unlike \f(CW\(C`ev_timer\(C'\fR's, they are not based on real time (or relative time)	2038	Unlike \f(CW\(C`ev_timer\(C'\fR, periodic watchers are not based on real time (or
1220	but on wallclock time (absolute time). You can tell a periodic watcher	2039	relative time, the physical time that passes) but on wall clock time
1221	to trigger \(L"at\(R" some specific point in time. For example, if you tell a	2040	(absolute time, the thing you can read on your calender or clock). The
1222	periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()	2041	difference is that wall clock time can run faster or slower than real
1223	+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will	2042	time, and time jumps are not uncommon (e.g. when you adjust your
1224	take a year to trigger the event (unlike an \f(CW\(C`ev_timer\(C'\fR, which would trigger	2043	wrist-watch).
1225	roughly 10 seconds later and of course not if you reset your system time
1226	again).
1227	.PP	2044	.PP
1228	They can also be used to implement vastly more complex timers, such as	2045	You can tell a periodic watcher to trigger after some specific point
1229	triggering an event on eahc midnight, local time.	2046	in time: for example, if you tell a periodic watcher to trigger \*(L"in 10
		2047	seconds\(R" (by specifying e.g. \f(CW\(C`ev_now () + 10.\*(C'\fR, that is, an absolute time
		2048	not a delay) and then reset your system clock to January of the previous
		2049	year, then it will take a year or more to trigger the event (unlike an
		2050	\&\f(CW\(C`ev_timer\(C'\fR, which would still trigger roughly 10 seconds after starting
		2051	it, as it uses a relative timeout).
1230	.PP	2052	.PP
		2053	\&\f(CW\(C`ev_periodic\(C'\fR watchers can also be used to implement vastly more complex
		2054	timers, such as triggering an event on each \(L"midnight, local time\(R", or
		2055	other complicated rules. This cannot be done with \f(CW\(C`ev_timer\(C'\fR watchers, as
		2056	those cannot react to time jumps.
		2057	.PP
1231	As with timers, the callback is guarenteed to be invoked only when the	2058	As with timers, the callback is guaranteed to be invoked only when the
1232	time (\f(CW\(C`at\(C'\fR) has been passed, but if multiple periodic timers become ready	2059	point in time where it is supposed to trigger has passed. If multiple
1233	during the same loop iteration then order of execution is undefined.	2060	timers become ready during the same loop iteration then the ones with
		2061	earlier time-out values are invoked before ones with later time-out values
		2062	(but this is no longer true when a callback calls \f(CW\(C`ev_loop\(C'\fR recursively).
		2063	.PP
		2064	\fIWatcher-Specific Functions and Data Members\fR
		2065	.IX Subsection "Watcher-Specific Functions and Data Members"
1234	.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4	2066	.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
1235	.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"	2067	.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
1236	.PD 0	2068	.PD 0
1237	.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4	2069	.IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
1238	.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"	2070	.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
1239	.PD	2071	.PD
1240	Lots of arguments, lets sort it out... There are basically three modes of	2072	Lots of arguments, let's sort it out... There are basically three modes of
1241	operation, and we will explain them from simplest to complex:	2073	operation, and we will explain them from simplest to most complex:
1242	.RS 4	2074	.RS 4
1243	.IP "* absolute timer (interval = reschedule_cb = 0)" 4	2075	.IP "\(bu" 4
1244	.IX Item "absolute timer (interval = reschedule_cb = 0)"	2076	absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
		2077	.Sp
1245	In this configuration the watcher triggers an event at the wallclock time	2078	In this configuration the watcher triggers an event after the wall clock
1246	\&\f(CW\(C`at\(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,	2079	time \f(CW\(C`offset\(C'\fR has passed. It will not repeat and will not adjust when a
1247	that is, if it is to be run at January 1st 2011 then it will run when the	2080	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1248	system time reaches or surpasses this time.	2081	will be stopped and invoked when the system clock reaches or surpasses
1249	.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4	2082	this point in time.
1250	.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)"	2083	.IP "\(bu" 4
		2084	repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
		2085	.Sp
1251	In this mode the watcher will always be scheduled to time out at the next	2086	In this mode the watcher will always be scheduled to time out at the next
1252	\&\f(CW\(C`at + N interval\*(C'\fR time (for some integer N) and then repeat, regardless	2087	\&\f(CW\(C`offset + N interval\*(C'\fR time (for some integer N, which can also be
1253	of any time jumps.	2088	negative) and then repeat, regardless of any time jumps. The \f(CW\(C`offset\(C'\fR
		2089	argument is merely an offset into the \f(CW\(C`interval\(C'\fR periods.
1254	.Sp	2090	.Sp
1255	This can be used to create timers that do not drift with respect to system	2091	This can be used to create timers that do not drift with respect to the
1256	time:	2092	system clock, for example, here is an \f(CW\(C`ev_periodic\(C'\fR that triggers each
		2093	hour, on the hour (with respect to \s-1UTC\s0):
1257	.Sp	2094	.Sp
1258	.Vb 1	2095	.Vb 1
1259	\& ev_periodic_set (&periodic, 0., 3600., 0);	2096	\& ev_periodic_set (&periodic, 0., 3600., 0);
1260	.Ve	2097	.Ve
1261	.Sp	2098	.Sp
1262	This doesn't mean there will always be 3600 seconds in between triggers,	2099	This doesn't mean there will always be 3600 seconds in between triggers,
1263	but only that the the callback will be called when the system time shows a	2100	but only that the callback will be called when the system time shows a
1264	full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible	2101	full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
1265	by 3600.	2102	by 3600.
1266	.Sp	2103	.Sp
1267	Another way to think about it (for the mathematically inclined) is that	2104	Another way to think about it (for the mathematically inclined) is that
1268	\&\f(CW\(C`ev_periodic\(C'\fR will try to run the callback in this mode at the next possible	2105	\&\f(CW\(C`ev_periodic\(C'\fR will try to run the callback in this mode at the next possible
1269	time where \f(CW\(C`time = at (mod interval)\(C'\fR, regardless of any time jumps.	2106	time where \f(CW\(C`time = offset (mod interval)\(C'\fR, regardless of any time jumps.
1270	.IP "* manual reschedule mode (reschedule_cb = callback)" 4	2107	.Sp
1271	.IX Item "manual reschedule mode (reschedule_cb = callback)"	2108	For numerical stability it is preferable that the \f(CW\(C`offset\(C'\fR value is near
		2109	\&\f(CW\(C`ev_now ()\(C'\fR (the current time), but there is no range requirement for
		2110	this value, and in fact is often specified as zero.
		2111	.Sp
		2112	Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0
		2113	speed for example), so if \f(CW\(C`interval\(C'\fR is very small then timing stability
		2114	will of course deteriorate. Libev itself tries to be exact to be about one
		2115	millisecond (if the \s-1OS\s0 supports it and the machine is fast enough).
		2116	.IP "\(bu" 4
		2117	manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
		2118	.Sp
1272	In this mode the values for \f(CW\(C`interval\(C'\fR and \f(CW\(C`at\(C'\fR are both being	2119	In this mode the values for \f(CW\(C`interval\(C'\fR and \f(CW\(C`offset\(C'\fR are both being
1273	ignored. Instead, each time the periodic watcher gets scheduled, the	2120	ignored. Instead, each time the periodic watcher gets scheduled, the
1274	reschedule callback will be called with the watcher as first, and the	2121	reschedule callback will be called with the watcher as first, and the
1275	current time as second argument.	2122	current time as second argument.
1276	.Sp	2123	.Sp
1277	\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,	2124	\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, ever,
1278	ever, or make any event loop modifications\fR. If you need to stop it,	2125	or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly
1279	return \f(CW\(C`now + 1e30\(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by	2126	allowed by documentation here\fR.
1280	starting a prepare watcher).
1281	.Sp	2127	.Sp
		2128	If you need to stop it, return \f(CW\(C`now + 1e30\(C'\fR (or so, fudge fudge) and stop
		2129	it afterwards (e.g. by starting an \f(CW\(C`ev_prepare\(C'\fR watcher, which is the
		2130	only event loop modification you are allowed to do).
		2131	.Sp
1282	Its prototype is \f(CW\(C`ev_tstamp (reschedule_cb)(struct ev_periodic *w,	2132	The callback prototype is \f(CW\(C`ev_tstamp (reschedule_cb)(ev_periodic
1283	ev_tstamp now)\*(C'\fR, e.g.:	2133	w, ev_tstamp now)\(C'\fR, e.g.:
1284	.Sp	2134	.Sp
1285	.Vb 4	2135	.Vb 5
		2136	\& static ev_tstamp
1286	\& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2137	\& my_rescheduler (ev_periodic *w, ev_tstamp now)
1287	\& {	2138	\& {
1288	\& return now + 60.;	2139	\& return now + 60.;
1289	\& }	2140	\& }
1290	.Ve	2141	.Ve
1291	.Sp	2142	.Sp
1292	It must return the next time to trigger, based on the passed time value	2143	It must return the next time to trigger, based on the passed time value
1293	(that is, the lowest time value larger than to the second argument). It	2144	(that is, the lowest time value larger than to the second argument). It
1294	will usually be called just before the callback will be triggered, but	2145	will usually be called just before the callback will be triggered, but
1295	might be called at other times, too.	2146	might be called at other times, too.
1296	.Sp	2147	.Sp
1297	\&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the	2148	\&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or
1298	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.	2149	equal to the passed \f(CI\(C`now\(C'\fI value\fR.
1299	.Sp	2150	.Sp
1300	This can be used to create very complex timers, such as a timer that	2151	This can be used to create very complex timers, such as a timer that
1301	triggers on each midnight, local time. To do this, you would calculate the	2152	triggers on \(L"next midnight, local time\(R". To do this, you would calculate the
1302	next midnight after \f(CW\(C`now\(C'\fR and return the timestamp value for this. How	2153	next midnight after \f(CW\(C`now\(C'\fR and return the timestamp value for this. How
1303	you do this is, again, up to you (but it is not trivial, which is the main	2154	you do this is, again, up to you (but it is not trivial, which is the main
1304	reason I omitted it as an example).	2155	reason I omitted it as an example).
1305	.RE	2156	.RE
1306	.RS 4	2157	.RS 4
…		…
1309	.IX Item "ev_periodic_again (loop, ev_periodic *)"	2160	.IX Item "ev_periodic_again (loop, ev_periodic *)"
1310	Simply stops and restarts the periodic watcher again. This is only useful	2161	Simply stops and restarts the periodic watcher again. This is only useful
1311	when you changed some parameters or the reschedule callback would return	2162	when you changed some parameters or the reschedule callback would return
1312	a different time than the last time it was called (e.g. in a crond like	2163	a different time than the last time it was called (e.g. in a crond like
1313	program when the crontabs have changed).	2164	program when the crontabs have changed).
		2165	.IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4
		2166	.IX Item "ev_tstamp ev_periodic_at (ev_periodic *)"
		2167	When active, returns the absolute time that the watcher is supposed
		2168	to trigger next. This is not the same as the \f(CW\(C`offset\(C'\fR argument to
		2169	\&\f(CW\(C`ev_periodic_set\(C'\fR, but indeed works even in interval and manual
		2170	rescheduling modes.
		2171	.IP "ev_tstamp offset [read\-write]" 4
		2172	.IX Item "ev_tstamp offset [read-write]"
		2173	When repeating, this contains the offset value, otherwise this is the
		2174	absolute point in time (the \f(CW\(C`offset\(C'\fR value passed to \f(CW\(C`ev_periodic_set\(C'\fR,
		2175	although libev might modify this value for better numerical stability).
		2176	.Sp
		2177	Can be modified any time, but changes only take effect when the periodic
		2178	timer fires or \f(CW\(C`ev_periodic_again\(C'\fR is being called.
1314	.IP "ev_tstamp interval [read\-write]" 4	2179	.IP "ev_tstamp interval [read\-write]" 4
1315	.IX Item "ev_tstamp interval [read-write]"	2180	.IX Item "ev_tstamp interval [read-write]"
1316	The current interval value. Can be modified any time, but changes only	2181	The current interval value. Can be modified any time, but changes only
1317	take effect when the periodic timer fires or \f(CW\(C`ev_periodic_again\(C'\fR is being	2182	take effect when the periodic timer fires or \f(CW\(C`ev_periodic_again\(C'\fR is being
1318	called.	2183	called.
1319	.IP "ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read\-write]" 4	2184	.IP "ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read\-write]" 4
1320	.IX Item "ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]"	2185	.IX Item "ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]"
1321	The current reschedule callback, or \f(CW0\fR, if this functionality is	2186	The current reschedule callback, or \f(CW0\fR, if this functionality is
1322	switched off. Can be changed any time, but changes only take effect when	2187	switched off. Can be changed any time, but changes only take effect when
1323	the periodic timer fires or \f(CW\(C`ev_periodic_again\(C'\fR is being called.	2188	the periodic timer fires or \f(CW\(C`ev_periodic_again\(C'\fR is being called.
1324	.PP	2189	.PP
		2190	\fIExamples\fR
		2191	.IX Subsection "Examples"
		2192	.PP
1325	Example: Call a callback every hour, or, more precisely, whenever the	2193	Example: Call a callback every hour, or, more precisely, whenever the
1326	system clock is divisible by 3600. The callback invocation times have	2194	system time is divisible by 3600. The callback invocation times have
1327	potentially a lot of jittering, but good long-term stability.	2195	potentially a lot of jitter, but good long-term stability.
1328	.PP	2196	.PP
1329	.Vb 5	2197	.Vb 5
1330	\& static void	2198	\& static void
1331	\& clock_cb (struct ev_loop loop, struct ev_io w, int revents)	2199	\& clock_cb (struct ev_loop loop, ev_io w, int revents)
1332	\& {	2200	\& {
1333	\& ... its now a full hour (UTC, or TAI or whatever your clock follows)	2201	\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1334	\& }	2202	\& }
1335	.Ve	2203	\&
1336	.PP
1337	.Vb 3
1338	\& struct ev_periodic hourly_tick;	2204	\& ev_periodic hourly_tick;
1339	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2205	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1340	\& ev_periodic_start (loop, &hourly_tick);	2206	\& ev_periodic_start (loop, &hourly_tick);
1341	.Ve	2207	.Ve
1342	.PP	2208	.PP
1343	Example: The same as above, but use a reschedule callback to do it:	2209	Example: The same as above, but use a reschedule callback to do it:
1344	.PP	2210	.PP
1345	.Vb 1	2211	.Vb 1
1346	\& #include <math.h>	2212	\& #include <math.h>
1347	.Ve	2213	\&
1348	.PP
1349	.Vb 5
1350	\& static ev_tstamp	2214	\& static ev_tstamp
1351	\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2215	\& my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1352	\& {	2216	\& {
1353	\& return fmod (now, 3600.) + 3600.;	2217	\& return now + (3600. \- fmod (now, 3600.));
1354	\& }	2218	\& }
1355	.Ve	2219	\&
1356	.PP
1357	.Vb 1
1358	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2220	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1359	.Ve	2221	.Ve
1360	.PP	2222	.PP
1361	Example: Call a callback every hour, starting now:	2223	Example: Call a callback every hour, starting now:
1362	.PP	2224	.PP
1363	.Vb 4	2225	.Vb 4
1364	\& struct ev_periodic hourly_tick;	2226	\& ev_periodic hourly_tick;
1365	\& ev_periodic_init (&hourly_tick, clock_cb,	2227	\& ev_periodic_init (&hourly_tick, clock_cb,
1366	\& fmod (ev_now (loop), 3600.), 3600., 0);	2228	\& fmod (ev_now (loop), 3600.), 3600., 0);
1367	\& ev_periodic_start (loop, &hourly_tick);	2229	\& ev_periodic_start (loop, &hourly_tick);
1368	.Ve	2230	.Ve
1369	.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"	2231	.ie n .SS """ev_signal"" \- signal me when a signal gets signalled!"
1370	.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"	2232	.el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1371	.IX Subsection "ev_signal - signal me when a signal gets signalled!"	2233	.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1372	Signal watchers will trigger an event when the process receives a specific	2234	Signal watchers will trigger an event when the process receives a specific
1373	signal one or more times. Even though signals are very asynchronous, libev	2235	signal one or more times. Even though signals are very asynchronous, libev
1374	will try it's best to deliver signals synchronously, i.e. as part of the	2236	will try it's best to deliver signals synchronously, i.e. as part of the
1375	normal event processing, like any other event.	2237	normal event processing, like any other event.
1376	.PP	2238	.PP
		2239	If you want signals to be delivered truly asynchronously, just use
		2240	\&\f(CW\(C`sigaction\(C'\fR as you would do without libev and forget about sharing
		2241	the signal. You can even use \f(CW\(C`ev_async\(C'\fR from a signal handler to
		2242	synchronously wake up an event loop.
		2243	.PP
1377	You can configure as many watchers as you like per signal. Only when the	2244	You can configure as many watchers as you like for the same signal, but
		2245	only within the same loop, i.e. you can watch for \f(CW\(C`SIGINT\(C'\fR in your
		2246	default loop and for \f(CW\(C`SIGIO\(C'\fR in another loop, but you cannot watch for
		2247	\&\f(CW\(C`SIGINT\(C'\fR in both the default loop and another loop at the same time. At
		2248	the moment, \f(CW\(C`SIGCHLD\(C'\fR is permanently tied to the default loop.
		2249	.PP
1378	first watcher gets started will libev actually register a signal watcher	2250	When the first watcher gets started will libev actually register something
1379	with the kernel (thus it coexists with your own signal handlers as long	2251	with the kernel (thus it coexists with your own signal handlers as long as
1380	as you don't register any with libev). Similarly, when the last signal	2252	you don't register any with libev for the same signal).
1381	watcher for a signal is stopped libev will reset the signal handler to	2253	.PP
1382	\&\s-1SIG_DFL\s0 (regardless of what it was set to before).	2254	Both the signal mask state (\f(CW\(C`sigprocmask\(C'\fR) and the signal handler state
		2255	(\f(CW\(C`sigaction\(C'\fR) are unspecified after starting a signal watcher (and after
		2256	sotpping it again), that is, libev might or might not block the signal,
		2257	and might or might not set or restore the installed signal handler.
		2258	.PP
		2259	If possible and supported, libev will install its handlers with
		2260	\&\f(CW\(C`SA_RESTART\(C'\fR (or equivalent) behaviour enabled, so system calls should
		2261	not be unduly interrupted. If you have a problem with system calls getting
		2262	interrupted by signals you can block all signals in an \f(CW\(C`ev_check\(C'\fR watcher
		2263	and unblock them in an \f(CW\(C`ev_prepare\(C'\fR watcher.
		2264	.PP
		2265	\fIWatcher-Specific Functions and Data Members\fR
		2266	.IX Subsection "Watcher-Specific Functions and Data Members"
1383	.IP "ev_signal_init (ev_signal *, callback, int signum)" 4	2267	.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1384	.IX Item "ev_signal_init (ev_signal *, callback, int signum)"	2268	.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1385	.PD 0	2269	.PD 0
1386	.IP "ev_signal_set (ev_signal *, int signum)" 4	2270	.IP "ev_signal_set (ev_signal *, int signum)" 4
1387	.IX Item "ev_signal_set (ev_signal *, int signum)"	2271	.IX Item "ev_signal_set (ev_signal *, int signum)"
…		…
1389	Configures the watcher to trigger on the given signal number (usually one	2273	Configures the watcher to trigger on the given signal number (usually one
1390	of the \f(CW\(C`SIGxxx\(C'\fR constants).	2274	of the \f(CW\(C`SIGxxx\(C'\fR constants).
1391	.IP "int signum [read\-only]" 4	2275	.IP "int signum [read\-only]" 4
1392	.IX Item "int signum [read-only]"	2276	.IX Item "int signum [read-only]"
1393	The signal the watcher watches out for.	2277	The signal the watcher watches out for.
		2278	.PP
		2279	\fIExamples\fR
		2280	.IX Subsection "Examples"
		2281	.PP
		2282	Example: Try to exit cleanly on \s-1SIGINT\s0.
		2283	.PP
		2284	.Vb 5
		2285	\& static void
		2286	\& sigint_cb (struct ev_loop loop, ev_signal w, int revents)
		2287	\& {
		2288	\& ev_unloop (loop, EVUNLOOP_ALL);
		2289	\& }
		2290	\&
		2291	\& ev_signal signal_watcher;
		2292	\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		2293	\& ev_signal_start (loop, &signal_watcher);
		2294	.Ve
1394	.ie n .Sh """ev_child"" \- watch out for process status changes"	2295	.ie n .SS """ev_child"" \- watch out for process status changes"
1395	.el .Sh "\f(CWev_child\fP \- watch out for process status changes"	2296	.el .SS "\f(CWev_child\fP \- watch out for process status changes"
1396	.IX Subsection "ev_child - watch out for process status changes"	2297	.IX Subsection "ev_child - watch out for process status changes"
1397	Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to	2298	Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1398	some child status changes (most typically when a child of yours dies).	2299	some child status changes (most typically when a child of yours dies or
		2300	exits). It is permissible to install a child watcher \fIafter\fR the child
		2301	has been forked (which implies it might have already exited), as long
		2302	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2303	forking and then immediately registering a watcher for the child is fine,
		2304	but forking and registering a watcher a few event loop iterations later or
		2305	in the next callback invocation is not.
		2306	.PP
		2307	Only the default event loop is capable of handling signals, and therefore
		2308	you can only register child watchers in the default event loop.
		2309	.PP
		2310	Due to some design glitches inside libev, child watchers will always be
		2311	handled at maximum priority (their priority is set to \f(CW\(C`EV_MAXPRI\(C'\fR by
		2312	libev)
		2313	.PP
		2314	\fIProcess Interaction\fR
		2315	.IX Subsection "Process Interaction"
		2316	.PP
		2317	Libev grabs \f(CW\(C`SIGCHLD\(C'\fR as soon as the default event loop is
		2318	initialised. This is necessary to guarantee proper behaviour even if the
		2319	first child watcher is started after the child exits. The occurrence
		2320	of \f(CW\(C`SIGCHLD\(C'\fR is recorded asynchronously, but child reaping is done
		2321	synchronously as part of the event loop processing. Libev always reaps all
		2322	children, even ones not watched.
		2323	.PP
		2324	\fIOverriding the Built-In Processing\fR
		2325	.IX Subsection "Overriding the Built-In Processing"
		2326	.PP
		2327	Libev offers no special support for overriding the built-in child
		2328	processing, but if your application collides with libev's default child
		2329	handler, you can override it easily by installing your own handler for
		2330	\&\f(CW\(C`SIGCHLD\(C'\fR after initialising the default loop, and making sure the
		2331	default loop never gets destroyed. You are encouraged, however, to use an
		2332	event-based approach to child reaping and thus use libev's support for
		2333	that, so other libev users can use \f(CW\(C`ev_child\(C'\fR watchers freely.
		2334	.PP
		2335	\fIStopping the Child Watcher\fR
		2336	.IX Subsection "Stopping the Child Watcher"
		2337	.PP
		2338	Currently, the child watcher never gets stopped, even when the
		2339	child terminates, so normally one needs to stop the watcher in the
		2340	callback. Future versions of libev might stop the watcher automatically
		2341	when a child exit is detected (calling \f(CW\(C`ev_child_stop\(C'\fR twice is not a
		2342	problem).
		2343	.PP
		2344	\fIWatcher-Specific Functions and Data Members\fR
		2345	.IX Subsection "Watcher-Specific Functions and Data Members"
1399	.IP "ev_child_init (ev_child *, callback, int pid)" 4	2346	.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
1400	.IX Item "ev_child_init (ev_child *, callback, int pid)"	2347	.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
1401	.PD 0	2348	.PD 0
1402	.IP "ev_child_set (ev_child *, int pid)" 4	2349	.IP "ev_child_set (ev_child *, int pid, int trace)" 4
1403	.IX Item "ev_child_set (ev_child *, int pid)"	2350	.IX Item "ev_child_set (ev_child *, int pid, int trace)"
1404	.PD	2351	.PD
1405	Configures the watcher to wait for status changes of process \f(CW\(C`pid\(C'\fR (or	2352	Configures the watcher to wait for status changes of process \f(CW\(C`pid\(C'\fR (or
1406	\&\fIany\fR process if \f(CW\(C`pid\(C'\fR is specified as \f(CW0\fR). The callback can look	2353	\&\fIany\fR process if \f(CW\(C`pid\(C'\fR is specified as \f(CW0\fR). The callback can look
1407	at the \f(CW\(C`rstatus\(C'\fR member of the \f(CW\(C`ev_child\(C'\fR watcher structure to see	2354	at the \f(CW\(C`rstatus\(C'\fR member of the \f(CW\(C`ev_child\(C'\fR watcher structure to see
1408	the status word (use the macros from \f(CW\(C`sys/wait.h\(C'\fR and see your systems	2355	the status word (use the macros from \f(CW\(C`sys/wait.h\(C'\fR and see your systems
1409	\&\f(CW\(C`waitpid\(C'\fR documentation). The \f(CW\(C`rpid\(C'\fR member contains the pid of the	2356	\&\f(CW\(C`waitpid\(C'\fR documentation). The \f(CW\(C`rpid\(C'\fR member contains the pid of the
1410	process causing the status change.	2357	process causing the status change. \f(CW\(C`trace\(C'\fR must be either \f(CW0\fR (only
		2358	activate the watcher when the process terminates) or \f(CW1\fR (additionally
		2359	activate the watcher when the process is stopped or continued).
1411	.IP "int pid [read\-only]" 4	2360	.IP "int pid [read\-only]" 4
1412	.IX Item "int pid [read-only]"	2361	.IX Item "int pid [read-only]"
1413	The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.	2362	The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1414	.IP "int rpid [read\-write]" 4	2363	.IP "int rpid [read\-write]" 4
1415	.IX Item "int rpid [read-write]"	2364	.IX Item "int rpid [read-write]"
…		…
1417	.IP "int rstatus [read\-write]" 4	2366	.IP "int rstatus [read\-write]" 4
1418	.IX Item "int rstatus [read-write]"	2367	.IX Item "int rstatus [read-write]"
1419	The process exit/trace status caused by \f(CW\(C`rpid\(C'\fR (see your systems	2368	The process exit/trace status caused by \f(CW\(C`rpid\(C'\fR (see your systems
1420	\&\f(CW\(C`waitpid\(C'\fR and \f(CW\(C`sys/wait.h\(C'\fR documentation for details).	2369	\&\f(CW\(C`waitpid\(C'\fR and \f(CW\(C`sys/wait.h\(C'\fR documentation for details).
1421	.PP	2370	.PP
1422	Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.	2371	\fIExamples\fR
		2372	.IX Subsection "Examples"
1423	.PP	2373	.PP
		2374	Example: \f(CW\(C`fork()\(C'\fR a new process and install a child handler to wait for
		2375	its completion.
		2376	.PP
1424	.Vb 5	2377	.Vb 1
		2378	\& ev_child cw;
		2379	\&
1425	\& static void	2380	\& static void
1426	\& sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	2381	\& child_cb (EV_P_ ev_child *w, int revents)
1427	\& {	2382	\& {
1428	\& ev_unloop (loop, EVUNLOOP_ALL);	2383	\& ev_child_stop (EV_A_ w);
		2384	\& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
1429	\& }	2385	\& }
		2386	\&
		2387	\& pid_t pid = fork ();
		2388	\&
		2389	\& if (pid < 0)
		2390	\& // error
		2391	\& else if (pid == 0)
		2392	\& {
		2393	\& // the forked child executes here
		2394	\& exit (1);
		2395	\& }
		2396	\& else
		2397	\& {
		2398	\& ev_child_init (&cw, child_cb, pid, 0);
		2399	\& ev_child_start (EV_DEFAULT_ &cw);
		2400	\& }
1430	.Ve	2401	.Ve
1431	.PP
1432	.Vb 3
1433	\& struct ev_signal signal_watcher;
1434	\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1435	\& ev_signal_start (loop, &sigint_cb);
1436	.Ve
1437	.ie n .Sh """ev_stat"" \- did the file attributes just change?"	2402	.ie n .SS """ev_stat"" \- did the file attributes just change?"
1438	.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"	2403	.el .SS "\f(CWev_stat\fP \- did the file attributes just change?"
1439	.IX Subsection "ev_stat - did the file attributes just change?"	2404	.IX Subsection "ev_stat - did the file attributes just change?"
1440	This watches a filesystem path for attribute changes. That is, it calls	2405	This watches a file system path for attribute changes. That is, it calls
1441	\&\f(CW\(C`stat\(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed	2406	\&\f(CW\(C`stat\(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed)
1442	compared to the last time, invoking the callback if it did.	2407	and sees if it changed compared to the last time, invoking the callback if
		2408	it did.
1443	.PP	2409	.PP
1444	The path does not need to exist: changing from \(L"path exists\(R" to \*(L"path does	2410	The path does not need to exist: changing from \(L"path exists\(R" to \*(L"path does
1445	not exist\(R" is a status change like any other. The condition \(L"path does	2411	not exist\(R" is a status change like any other. The condition \(L"path does not
1446	not exist\(R" is signified by the \f(CW\(C`st_nlink\*(C'\fR field being zero (which is	2412	exist\(R" (or more correctly \(L"path cannot be stat'ed\*(R") is signified by the
1447	otherwise always forced to be at least one) and all the other fields of	2413	\&\f(CW\(C`st_nlink\(C'\fR field being zero (which is otherwise always forced to be at
1448	the stat buffer having unspecified contents.	2414	least one) and all the other fields of the stat buffer having unspecified
		2415	contents.
1449	.PP	2416	.PP
1450	The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is	2417	The path \fImust not\fR end in a slash or contain special components such as
		2418	\&\f(CW\(C`.\(C'\fR or \f(CW\(C`..\(C'\fR. The path \fIshould\fR be absolute: If it is relative and
1451	relative and your working directory changes, the behaviour is undefined.	2419	your working directory changes, then the behaviour is undefined.
1452	.PP	2420	.PP
1453	Since there is no standard to do this, the portable implementation simply	2421	Since there is no portable change notification interface available, the
1454	calls \f(CW\(C`stat (2)\(C'\fR regularly on the path to see if it changed somehow. You	2422	portable implementation simply calls \f(CWstat(2)\fR regularly on the path
1455	can specify a recommended polling interval for this case. If you specify	2423	to see if it changed somehow. You can specify a recommended polling
1456	a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,	2424	interval for this case. If you specify a polling interval of \f(CW0\fR (highly
1457	unspecified default\fR value will be used (which you can expect to be around	2425	recommended!) then a \fIsuitable, unspecified default\fR value will be used
1458	five seconds, although this might change dynamically). Libev will also	2426	(which you can expect to be around five seconds, although this might
1459	impose a minimum interval which is currently around \f(CW0.1\fR, but thats	2427	change dynamically). Libev will also impose a minimum interval which is
1460	usually overkill.	2428	currently around \f(CW0.1\fR, but that's usually overkill.
1461	.PP	2429	.PP
1462	This watcher type is not meant for massive numbers of stat watchers,	2430	This watcher type is not meant for massive numbers of stat watchers,
1463	as even with OS-supported change notifications, this can be	2431	as even with OS-supported change notifications, this can be
1464	resource\-intensive.	2432	resource-intensive.
1465	.PP	2433	.PP
1466	At the time of this writing, only the Linux inotify interface is	2434	At the time of this writing, the only OS-specific interface implemented
1467	implemented (implementing kqueue support is left as an exercise for the	2435	is the Linux inotify interface (implementing kqueue support is left as an
1468	reader). Inotify will be used to give hints only and should not change the	2436	exercise for the reader. Note, however, that the author sees no way of
1469	semantics of \f(CW\(C`ev_stat\(C'\fR watchers, which means that libev sometimes needs	2437	implementing \f(CW\(C`ev_stat\(C'\fR semantics with kqueue, except as a hint).
1470	to fall back to regular polling again even with inotify, but changes are	2438	.PP
1471	usually detected immediately, and if the file exists there will be no	2439	\fI\s-1ABI\s0 Issues (Largefile Support)\fR
1472	polling.	2440	.IX Subsection "ABI Issues (Largefile Support)"
		2441	.PP
		2442	Libev by default (unless the user overrides this) uses the default
		2443	compilation environment, which means that on systems with large file
		2444	support disabled by default, you get the 32 bit version of the stat
		2445	structure. When using the library from programs that change the \s-1ABI\s0 to
		2446	use 64 bit file offsets the programs will fail. In that case you have to
		2447	compile libev with the same flags to get binary compatibility. This is
		2448	obviously the case with any flags that change the \s-1ABI\s0, but the problem is
		2449	most noticeably displayed with ev_stat and large file support.
		2450	.PP
		2451	The solution for this is to lobby your distribution maker to make large
		2452	file interfaces available by default (as e.g. FreeBSD does) and not
		2453	optional. Libev cannot simply switch on large file support because it has
		2454	to exchange stat structures with application programs compiled using the
		2455	default compilation environment.
		2456	.PP
		2457	\fIInotify and Kqueue\fR
		2458	.IX Subsection "Inotify and Kqueue"
		2459	.PP
		2460	When \f(CW\(C`inotify (7)\(C'\fR support has been compiled into libev and present at
		2461	runtime, it will be used to speed up change detection where possible. The
		2462	inotify descriptor will be created lazily when the first \f(CW\(C`ev_stat\(C'\fR
		2463	watcher is being started.
		2464	.PP
		2465	Inotify presence does not change the semantics of \f(CW\(C`ev_stat\(C'\fR watchers
		2466	except that changes might be detected earlier, and in some cases, to avoid
		2467	making regular \f(CW\(C`stat\(C'\fR calls. Even in the presence of inotify support
		2468	there are many cases where libev has to resort to regular \f(CW\(C`stat\(C'\fR polling,
		2469	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2470	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2471	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2472	xfs are fully working) libev usually gets away without polling.
		2473	.PP
		2474	There is no support for kqueue, as apparently it cannot be used to
		2475	implement this functionality, due to the requirement of having a file
		2476	descriptor open on the object at all times, and detecting renames, unlinks
		2477	etc. is difficult.
		2478	.PP
		2479	\fI\f(CI\(C`stat ()\(C'\fI is a synchronous operation\fR
		2480	.IX Subsection "stat () is a synchronous operation"
		2481	.PP
		2482	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2483	the process. The exception are \f(CW\(C`ev_stat\(C'\fR watchers \- those call \f(CW\*(C`stat
		2484	()\*(C'\fR, which is a synchronous operation.
		2485	.PP
		2486	For local paths, this usually doesn't matter: unless the system is very
		2487	busy or the intervals between stat's are large, a stat call will be fast,
		2488	as the path data is usually in memory already (except when starting the
		2489	watcher).
		2490	.PP
		2491	For networked file systems, calling \f(CW\(C`stat ()\(C'\fR can block an indefinite
		2492	time due to network issues, and even under good conditions, a stat call
		2493	often takes multiple milliseconds.
		2494	.PP
		2495	Therefore, it is best to avoid using \f(CW\(C`ev_stat\(C'\fR watchers on networked
		2496	paths, although this is fully supported by libev.
		2497	.PP
		2498	\fIThe special problem of stat time resolution\fR
		2499	.IX Subsection "The special problem of stat time resolution"
		2500	.PP
		2501	The \f(CW\(C`stat ()\(C'\fR system call only supports full-second resolution portably,
		2502	and even on systems where the resolution is higher, most file systems
		2503	still only support whole seconds.
		2504	.PP
		2505	That means that, if the time is the only thing that changes, you can
		2506	easily miss updates: on the first update, \f(CW\(C`ev_stat\(C'\fR detects a change and
		2507	calls your callback, which does something. When there is another update
		2508	within the same second, \f(CW\(C`ev_stat\(C'\fR will be unable to detect unless the
		2509	stat data does change in other ways (e.g. file size).
		2510	.PP
		2511	The solution to this is to delay acting on a change for slightly more
		2512	than a second (or till slightly after the next full second boundary), using
		2513	a roughly one-second-delay \f(CW\(C`ev_timer\(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02);
		2514	ev_timer_again (loop, w)\*(C'\fR).
		2515	.PP
		2516	The \f(CW.02\fR offset is added to work around small timing inconsistencies
		2517	of some operating systems (where the second counter of the current time
		2518	might be be delayed. One such system is the Linux kernel, where a call to
		2519	\&\f(CW\(C`gettimeofday\(C'\fR might return a timestamp with a full second later than
		2520	a subsequent \f(CW\(C`time\(C'\fR call \- if the equivalent of \f(CW\(C`time ()\(C'\fR is used to
		2521	update file times then there will be a small window where the kernel uses
		2522	the previous second to update file times but libev might already execute
		2523	the timer callback).
		2524	.PP
		2525	\fIWatcher-Specific Functions and Data Members\fR
		2526	.IX Subsection "Watcher-Specific Functions and Data Members"
1473	.IP "ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)" 4	2527	.IP "ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)" 4
1474	.IX Item "ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)"	2528	.IX Item "ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)"
1475	.PD 0	2529	.PD 0
1476	.IP "ev_stat_set (ev_stat , const char path, ev_tstamp interval)" 4	2530	.IP "ev_stat_set (ev_stat , const char path, ev_tstamp interval)" 4
1477	.IX Item "ev_stat_set (ev_stat , const char path, ev_tstamp interval)"	2531	.IX Item "ev_stat_set (ev_stat , const char path, ev_tstamp interval)"
…		…
1480	\&\f(CW\(C`path\(C'\fR. The \f(CW\(C`interval\(C'\fR is a hint on how quickly a change is expected to	2534	\&\f(CW\(C`path\(C'\fR. The \f(CW\(C`interval\(C'\fR is a hint on how quickly a change is expected to
1481	be detected and should normally be specified as \f(CW0\fR to let libev choose	2535	be detected and should normally be specified as \f(CW0\fR to let libev choose
1482	a suitable value. The memory pointed to by \f(CW\(C`path\(C'\fR must point to the same	2536	a suitable value. The memory pointed to by \f(CW\(C`path\(C'\fR must point to the same
1483	path for as long as the watcher is active.	2537	path for as long as the watcher is active.
1484	.Sp	2538	.Sp
1485	The callback will be receive \f(CW\(C`EV_STAT\(C'\fR when a change was detected,	2539	The callback will receive an \f(CW\(C`EV_STAT\(C'\fR event when a change was detected,
1486	relative to the attributes at the time the watcher was started (or the	2540	relative to the attributes at the time the watcher was started (or the
1487	last change was detected).	2541	last change was detected).
1488	.IP "ev_stat_stat (ev_stat *)" 4	2542	.IP "ev_stat_stat (loop, ev_stat *)" 4
1489	.IX Item "ev_stat_stat (ev_stat *)"	2543	.IX Item "ev_stat_stat (loop, ev_stat *)"
1490	Updates the stat buffer immediately with new values. If you change the	2544	Updates the stat buffer immediately with new values. If you change the
1491	watched path in your callback, you could call this fucntion to avoid	2545	watched path in your callback, you could call this function to avoid
1492	detecting this change (while introducing a race condition). Can also be	2546	detecting this change (while introducing a race condition if you are not
1493	useful simply to find out the new values.	2547	the only one changing the path). Can also be useful simply to find out the
		2548	new values.
1494	.IP "ev_statdata attr [read\-only]" 4	2549	.IP "ev_statdata attr [read\-only]" 4
1495	.IX Item "ev_statdata attr [read-only]"	2550	.IX Item "ev_statdata attr [read-only]"
1496	The most-recently detected attributes of the file. Although the type is of	2551	The most-recently detected attributes of the file. Although the type is
1497	\&\f(CW\(C`ev_statdata\(C'\fR, this is usually the (or one of the) \f(CW\(C`struct stat\(C'\fR types	2552	\&\f(CW\(C`ev_statdata\(C'\fR, this is usually the (or one of the) \f(CW\(C`struct stat\(C'\fR types
		2553	suitable for your system, but you can only rely on the POSIX-standardised
1498	suitable for your system. If the \f(CW\(C`st_nlink\(C'\fR member is \f(CW0\fR, then there	2554	members to be present. If the \f(CW\(C`st_nlink\(C'\fR member is \f(CW0\fR, then there was
1499	was some error while \f(CW\(C`stat\(C'\fRing the file.	2555	some error while \f(CW\(C`stat\(C'\fRing the file.
1500	.IP "ev_statdata prev [read\-only]" 4	2556	.IP "ev_statdata prev [read\-only]" 4
1501	.IX Item "ev_statdata prev [read-only]"	2557	.IX Item "ev_statdata prev [read-only]"
1502	The previous attributes of the file. The callback gets invoked whenever	2558	The previous attributes of the file. The callback gets invoked whenever
1503	\&\f(CW\(C`prev\(C'\fR != \f(CW\(C`attr\(C'\fR.	2559	\&\f(CW\(C`prev\(C'\fR != \f(CW\(C`attr\(C'\fR, or, more precisely, one or more of these members
		2560	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,
		2561	\&\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.
1504	.IP "ev_tstamp interval [read\-only]" 4	2562	.IP "ev_tstamp interval [read\-only]" 4
1505	.IX Item "ev_tstamp interval [read-only]"	2563	.IX Item "ev_tstamp interval [read-only]"
1506	The specified interval.	2564	The specified interval.
1507	.IP "const char *path [read\-only]" 4	2565	.IP "const char *path [read\-only]" 4
1508	.IX Item "const char *path [read-only]"	2566	.IX Item "const char *path [read-only]"
1509	The filesystem path that is being watched.	2567	The file system path that is being watched.
		2568	.PP
		2569	\fIExamples\fR
		2570	.IX Subsection "Examples"
1510	.PP	2571	.PP
1511	Example: Watch \f(CW\(C`/etc/passwd\(C'\fR for attribute changes.	2572	Example: Watch \f(CW\(C`/etc/passwd\(C'\fR for attribute changes.
1512	.PP	2573	.PP
1513	.Vb 15	2574	.Vb 10
1514	\& static void	2575	\& static void
1515	\& passwd_cb (struct ev_loop loop, ev_stat w, int revents)	2576	\& passwd_cb (struct ev_loop loop, ev_stat w, int revents)
1516	\& {	2577	\& {
1517	\& /* /etc/passwd changed in some way */	2578	\& /* /etc/passwd changed in some way */
1518	\& if (w->attr.st_nlink)	2579	\& if (w\->attr.st_nlink)
1519	\& {	2580	\& {
1520	\& printf ("passwd current size %ld\en", (long)w->attr.st_size);	2581	\& printf ("passwd current size %ld\en", (long)w\->attr.st_size);
1521	\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);	2582	\& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime);
1522	\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);	2583	\& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime);
1523	\& }	2584	\& }
1524	\& else	2585	\& else
1525	\& /* you shalt not abuse printf for puts */	2586	\& /* you shalt not abuse printf for puts */
1526	\& puts ("wow, /etc/passwd is not there, expect problems. "	2587	\& puts ("wow, /etc/passwd is not there, expect problems. "
1527	\& "if this is windows, they already arrived\en");	2588	\& "if this is windows, they already arrived\en");
1528	\& }	2589	\& }
		2590	\&
		2591	\& ...
		2592	\& ev_stat passwd;
		2593	\&
		2594	\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		2595	\& ev_stat_start (loop, &passwd);
1529	.Ve	2596	.Ve
		2597	.PP
		2598	Example: Like above, but additionally use a one-second delay so we do not
		2599	miss updates (however, frequent updates will delay processing, too, so
		2600	one might do the work both on \f(CW\(C`ev_stat\(C'\fR callback invocation \fIand\fR on
		2601	\&\f(CW\(C`ev_timer\(C'\fR callback invocation).
1530	.PP	2602	.PP
1531	.Vb 2	2603	.Vb 2
		2604	\& static ev_stat passwd;
		2605	\& static ev_timer timer;
		2606	\&
		2607	\& static void
		2608	\& timer_cb (EV_P_ ev_timer *w, int revents)
		2609	\& {
		2610	\& ev_timer_stop (EV_A_ w);
		2611	\&
		2612	\& /* now it\(Aqs one second after the most recent passwd change /
		2613	\& }
		2614	\&
		2615	\& static void
		2616	\& stat_cb (EV_P_ ev_stat *w, int revents)
		2617	\& {
		2618	\& /* reset the one\-second timer */
		2619	\& ev_timer_again (EV_A_ &timer);
		2620	\& }
		2621	\&
1532	\& ...	2622	\& ...
1533	\& ev_stat passwd;
1534	.Ve
1535	.PP
1536	.Vb 2
1537	\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2623	\& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1538	\& ev_stat_start (loop, &passwd);	2624	\& ev_stat_start (loop, &passwd);
		2625	\& ev_timer_init (&timer, timer_cb, 0., 1.02);
1539	.Ve	2626	.Ve
1540	.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."	2627	.ie n .SS """ev_idle"" \- when you've got nothing better to do..."
1541	.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."	2628	.el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..."
1542	.IX Subsection "ev_idle - when you've got nothing better to do..."	2629	.IX Subsection "ev_idle - when you've got nothing better to do..."
1543	Idle watchers trigger events when no other events of the same or higher	2630	Idle watchers trigger events when no other events of the same or higher
1544	priority are pending (prepare, check and other idle watchers do not	2631	priority are pending (prepare, check and other idle watchers do not count
1545	count).	2632	as receiving \(L"events\(R").
1546	.PP	2633	.PP
1547	That is, as long as your process is busy handling sockets or timeouts	2634	That is, as long as your process is busy handling sockets or timeouts
1548	(or even signals, imagine) of the same or higher priority it will not be	2635	(or even signals, imagine) of the same or higher priority it will not be
1549	triggered. But when your process is idle (or only lower-priority watchers	2636	triggered. But when your process is idle (or only lower-priority watchers
1550	are pending), the idle watchers are being called once per event loop	2637	are pending), the idle watchers are being called once per event loop
…		…
1554	The most noteworthy effect is that as long as any idle watchers are	2641	The most noteworthy effect is that as long as any idle watchers are
1555	active, the process will not block when waiting for new events.	2642	active, the process will not block when waiting for new events.
1556	.PP	2643	.PP
1557	Apart from keeping your process non-blocking (which is a useful	2644	Apart from keeping your process non-blocking (which is a useful
1558	effect on its own sometimes), idle watchers are a good place to do	2645	effect on its own sometimes), idle watchers are a good place to do
1559	\&\(L"pseudo\-background processing\(R", or delay processing stuff to after the	2646	\&\(L"pseudo-background processing\(R", or delay processing stuff to after the
1560	event loop has handled all outstanding events.	2647	event loop has handled all outstanding events.
		2648	.PP
		2649	\fIWatcher-Specific Functions and Data Members\fR
		2650	.IX Subsection "Watcher-Specific Functions and Data Members"
1561	.IP "ev_idle_init (ev_signal *, callback)" 4	2651	.IP "ev_idle_init (ev_idle *, callback)" 4
1562	.IX Item "ev_idle_init (ev_signal *, callback)"	2652	.IX Item "ev_idle_init (ev_idle *, callback)"
1563	Initialises and configures the idle watcher \- it has no parameters of any	2653	Initialises and configures the idle watcher \- it has no parameters of any
1564	kind. There is a \f(CW\(C`ev_idle_set\(C'\fR macro, but using it is utterly pointless,	2654	kind. There is a \f(CW\(C`ev_idle_set\(C'\fR macro, but using it is utterly pointless,
1565	believe me.	2655	believe me.
1566	.PP	2656	.PP
		2657	\fIExamples\fR
		2658	.IX Subsection "Examples"
		2659	.PP
1567	Example: Dynamically allocate an \f(CW\(C`ev_idle\(C'\fR watcher, start it, and in the	2660	Example: Dynamically allocate an \f(CW\(C`ev_idle\(C'\fR watcher, start it, and in the
1568	callback, free it. Also, use no error checking, as usual.	2661	callback, free it. Also, use no error checking, as usual.
1569	.PP	2662	.PP
1570	.Vb 7	2663	.Vb 7
1571	\& static void	2664	\& static void
1572	\& idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2665	\& idle_cb (struct ev_loop loop, ev_idle w, int revents)
1573	\& {	2666	\& {
1574	\& free (w);	2667	\& free (w);
1575	\& // now do something you wanted to do when the program has	2668	\& // now do something you wanted to do when the program has
1576	\& // no longer asnything immediate to do.	2669	\& // no longer anything immediate to do.
1577	\& }	2670	\& }
1578	.Ve	2671	\&
1579	.PP
1580	.Vb 3
1581	\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2672	\& ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1582	\& ev_idle_init (idle_watcher, idle_cb);	2673	\& ev_idle_init (idle_watcher, idle_cb);
1583	\& ev_idle_start (loop, idle_cb);	2674	\& ev_idle_start (loop, idle_watcher);
1584	.Ve	2675	.Ve
1585	.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"	2676	.ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!"
1586	.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"	2677	.el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1587	.IX Subsection "ev_prepare and ev_check - customise your event loop!"	2678	.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1588	Prepare and check watchers are usually (but not always) used in tandem:	2679	Prepare and check watchers are usually (but not always) used in pairs:
1589	prepare watchers get invoked before the process blocks and check watchers	2680	prepare watchers get invoked before the process blocks and check watchers
1590	afterwards.	2681	afterwards.
1591	.PP	2682	.PP
1592	You \fImust not\fR call \f(CW\(C`ev_loop\(C'\fR or similar functions that enter	2683	You \fImust not\fR call \f(CW\(C`ev_loop\(C'\fR or similar functions that enter
1593	the current event loop from either \f(CW\(C`ev_prepare\(C'\fR or \f(CW\(C`ev_check\(C'\fR	2684	the current event loop from either \f(CW\(C`ev_prepare\(C'\fR or \f(CW\(C`ev_check\(C'\fR
…		…
1596	those watchers, i.e. the sequence will always be \f(CW\(C`ev_prepare\(C'\fR, blocking,	2687	those watchers, i.e. the sequence will always be \f(CW\(C`ev_prepare\(C'\fR, blocking,
1597	\&\f(CW\(C`ev_check\(C'\fR so if you have one watcher of each kind they will always be	2688	\&\f(CW\(C`ev_check\(C'\fR so if you have one watcher of each kind they will always be
1598	called in pairs bracketing the blocking call.	2689	called in pairs bracketing the blocking call.
1599	.PP	2690	.PP
1600	Their main purpose is to integrate other event mechanisms into libev and	2691	Their main purpose is to integrate other event mechanisms into libev and
1601	their use is somewhat advanced. This could be used, for example, to track	2692	their use is somewhat advanced. They could be used, for example, to track
1602	variable changes, implement your own watchers, integrate net-snmp or a	2693	variable changes, implement your own watchers, integrate net-snmp or a
1603	coroutine library and lots more. They are also occasionally useful if	2694	coroutine library and lots more. They are also occasionally useful if
1604	you cache some data and want to flush it before blocking (for example,	2695	you cache some data and want to flush it before blocking (for example,
1605	in X programs you might want to do an \f(CW\(C`XFlush ()\(C'\fR in an \f(CW\(C`ev_prepare\(C'\fR	2696	in X programs you might want to do an \f(CW\(C`XFlush ()\(C'\fR in an \f(CW\(C`ev_prepare\(C'\fR
1606	watcher).	2697	watcher).
1607	.PP	2698	.PP
1608	This is done by examining in each prepare call which file descriptors need	2699	This is done by examining in each prepare call which file descriptors
1609	to be watched by the other library, registering \f(CW\(C`ev_io\(C'\fR watchers for	2700	need to be watched by the other library, registering \f(CW\(C`ev_io\(C'\fR watchers
1610	them and starting an \f(CW\(C`ev_timer\(C'\fR watcher for any timeouts (many libraries	2701	for them and starting an \f(CW\(C`ev_timer\(C'\fR watcher for any timeouts (many
1611	provide just this functionality). Then, in the check watcher you check for	2702	libraries provide exactly this functionality). Then, in the check watcher,
1612	any events that occured (by checking the pending status of all watchers	2703	you check for any events that occurred (by checking the pending status
1613	and stopping them) and call back into the library. The I/O and timer	2704	of all watchers and stopping them) and call back into the library. The
1614	callbacks will never actually be called (but must be valid nevertheless,	2705	I/O and timer callbacks will never actually be called (but must be valid
1615	because you never know, you know?).	2706	nevertheless, because you never know, you know?).
1616	.PP	2707	.PP
1617	As another example, the Perl Coro module uses these hooks to integrate	2708	As another example, the Perl Coro module uses these hooks to integrate
1618	coroutines into libev programs, by yielding to other active coroutines	2709	coroutines into libev programs, by yielding to other active coroutines
1619	during each prepare and only letting the process block if no coroutines	2710	during each prepare and only letting the process block if no coroutines
1620	are ready to run (it's actually more complicated: it only runs coroutines	2711	are ready to run (it's actually more complicated: it only runs coroutines
1621	with priority higher than or equal to the event loop and one coroutine	2712	with priority higher than or equal to the event loop and one coroutine
1622	of lower priority, but only once, using idle watchers to keep the event	2713	of lower priority, but only once, using idle watchers to keep the event
1623	loop from blocking if lower-priority coroutines are active, thus mapping	2714	loop from blocking if lower-priority coroutines are active, thus mapping
1624	low-priority coroutines to idle/background tasks).	2715	low-priority coroutines to idle/background tasks).
		2716	.PP
		2717	It is recommended to give \f(CW\(C`ev_check\(C'\fR watchers highest (\f(CW\(C`EV_MAXPRI\(C'\fR)
		2718	priority, to ensure that they are being run before any other watchers
		2719	after the poll (this doesn't matter for \f(CW\(C`ev_prepare\(C'\fR watchers).
		2720	.PP
		2721	Also, \f(CW\(C`ev_check\(C'\fR watchers (and \f(CW\(C`ev_prepare\(C'\fR watchers, too) should not
		2722	activate (\(L"feed\(R") events into libev. While libev fully supports this, they
		2723	might get executed before other \f(CW\(C`ev_check\(C'\fR watchers did their job. As
		2724	\&\f(CW\(C`ev_check\(C'\fR watchers are often used to embed other (non-libev) event
		2725	loops those other event loops might be in an unusable state until their
		2726	\&\f(CW\(C`ev_check\(C'\fR watcher ran (always remind yourself to coexist peacefully with
		2727	others).
		2728	.PP
		2729	\fIWatcher-Specific Functions and Data Members\fR
		2730	.IX Subsection "Watcher-Specific Functions and Data Members"
1625	.IP "ev_prepare_init (ev_prepare *, callback)" 4	2731	.IP "ev_prepare_init (ev_prepare *, callback)" 4
1626	.IX Item "ev_prepare_init (ev_prepare *, callback)"	2732	.IX Item "ev_prepare_init (ev_prepare *, callback)"
1627	.PD 0	2733	.PD 0
1628	.IP "ev_check_init (ev_check *, callback)" 4	2734	.IP "ev_check_init (ev_check *, callback)" 4
1629	.IX Item "ev_check_init (ev_check *, callback)"	2735	.IX Item "ev_check_init (ev_check *, callback)"
1630	.PD	2736	.PD
1631	Initialises and configures the prepare or check watcher \- they have no	2737	Initialises and configures the prepare or check watcher \- they have no
1632	parameters of any kind. There are \f(CW\(C`ev_prepare_set\(C'\fR and \f(CW\(C`ev_check_set\(C'\fR	2738	parameters of any kind. There are \f(CW\(C`ev_prepare_set\(C'\fR and \f(CW\(C`ev_check_set\(C'\fR
1633	macros, but using them is utterly, utterly and completely pointless.	2739	macros, but using them is utterly, utterly, utterly and completely
		2740	pointless.
1634	.PP	2741	.PP
1635	Example: To include a library such as adns, you would add \s-1IO\s0 watchers	2742	\fIExamples\fR
1636	and a timeout watcher in a prepare handler, as required by libadns, and	2743	.IX Subsection "Examples"
		2744	.PP
		2745	There are a number of principal ways to embed other event loops or modules
		2746	into libev. Here are some ideas on how to include libadns into libev
		2747	(there is a Perl module named \f(CW\(C`EV::ADNS\(C'\fR that does this, which you could
		2748	use as a working example. Another Perl module named \f(CW\(C`EV::Glib\(C'\fR embeds a
		2749	Glib main context into libev, and finally, \f(CW\(C`Glib::EV\(C'\fR embeds \s-1EV\s0 into the
		2750	Glib event loop).
		2751	.PP
		2752	Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1637	in a check watcher, destroy them and call into libadns. What follows is	2753	and in a check watcher, destroy them and call into libadns. What follows
1638	pseudo-code only of course:	2754	is pseudo-code only of course. This requires you to either use a low
		2755	priority for the check watcher or use \f(CW\(C`ev_clear_pending\(C'\fR explicitly, as
		2756	the callbacks for the IO/timeout watchers might not have been called yet.
1639	.PP	2757	.PP
1640	.Vb 2	2758	.Vb 2
1641	\& static ev_io iow [nfd];	2759	\& static ev_io iow [nfd];
1642	\& static ev_timer tw;	2760	\& static ev_timer tw;
1643	.Ve	2761	\&
1644	.PP
1645	.Vb 9
1646	\& static void	2762	\& static void
1647	\& io_cb (ev_loop loop, ev_io w, int revents)	2763	\& io_cb (struct ev_loop loop, ev_io w, int revents)
1648	\& {	2764	\& {
1649	\& // set the relevant poll flags
1650	\& // could also call adns_processreadable etc. here
1651	\& struct pollfd fd = (struct pollfd )w->data;
1652	\& if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1653	\& if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1654	\& }	2765	\& }
1655	.Ve	2766	\&
1656	.PP
1657	.Vb 8
1658	\& // create io watchers for each fd and a timer before blocking	2767	\& // create io watchers for each fd and a timer before blocking
1659	\& static void	2768	\& static void
1660	\& adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2769	\& adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
1661	\& {	2770	\& {
1662	\& int timeout = 3600000;	2771	\& int timeout = 3600000;
1663	\& struct pollfd fds [nfd];	2772	\& struct pollfd fds [nfd];
1664	\& // actual code will need to loop here and realloc etc.	2773	\& // actual code will need to loop here and realloc etc.
1665	\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2774	\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1666	.Ve	2775	\&
1667	.PP
1668	.Vb 3
1669	\& /* the callback is illegal, but won't be called as we stop during check */	2776	\& /* the callback is illegal, but won\(Aqt be called as we stop during check /
1670	\& ev_timer_init (&tw, 0, timeout * 1e-3);	2777	\& ev_timer_init (&tw, 0, timeout * 1e\-3, 0.);
1671	\& ev_timer_start (loop, &tw);	2778	\& ev_timer_start (loop, &tw);
1672	.Ve	2779	\&
1673	.PP
1674	.Vb 6
1675	\& // create on ev_io per pollfd	2780	\& // create one ev_io per pollfd
1676	\& for (int i = 0; i < nfd; ++i)	2781	\& for (int i = 0; i < nfd; ++i)
1677	\& {	2782	\& {
1678	\& ev_io_init (iow + i, io_cb, fds [i].fd,	2783	\& ev_io_init (iow + i, io_cb, fds [i].fd,
1679	\& ((fds [i].events & POLLIN ? EV_READ : 0)	2784	\& ((fds [i].events & POLLIN ? EV_READ : 0)
1680	\& \| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2785	\& \| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		2786	\&
		2787	\& fds [i].revents = 0;
		2788	\& ev_io_start (loop, iow + i);
		2789	\& }
		2790	\& }
		2791	\&
		2792	\& // stop all watchers after blocking
		2793	\& static void
		2794	\& adns_check_cb (struct ev_loop loop, ev_check w, int revents)
		2795	\& {
		2796	\& ev_timer_stop (loop, &tw);
		2797	\&
		2798	\& for (int i = 0; i < nfd; ++i)
		2799	\& {
		2800	\& // set the relevant poll flags
		2801	\& // could also call adns_processreadable etc. here
		2802	\& struct pollfd *fd = fds + i;
		2803	\& int revents = ev_clear_pending (iow + i);
		2804	\& if (revents & EV_READ ) fd\->revents \|= fd\->events & POLLIN;
		2805	\& if (revents & EV_WRITE) fd\->revents \|= fd\->events & POLLOUT;
		2806	\&
		2807	\& // now stop the watcher
		2808	\& ev_io_stop (loop, iow + i);
		2809	\& }
		2810	\&
		2811	\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		2812	\& }
1681	.Ve	2813	.Ve
		2814	.PP
		2815	Method 2: This would be just like method 1, but you run \f(CW\(C`adns_afterpoll\(C'\fR
		2816	in the prepare watcher and would dispose of the check watcher.
		2817	.PP
		2818	Method 3: If the module to be embedded supports explicit event
		2819	notification (libadns does), you can also make use of the actual watcher
		2820	callbacks, and only destroy/create the watchers in the prepare watcher.
1682	.PP	2821	.PP
1683	.Vb 5	2822	.Vb 5
1684	\& fds [i].revents = 0;
1685	\& iow [i].data = fds + i;
1686	\& ev_io_start (loop, iow + i);
1687	\& }
1688	\& }
1689	.Ve
1690	.PP
1691	.Vb 5
1692	\& // stop all watchers after blocking
1693	\& static void	2823	\& static void
1694	\& adns_check_cb (ev_loop loop, ev_check w, int revents)	2824	\& timer_cb (EV_P_ ev_timer *w, int revents)
1695	\& {	2825	\& {
1696	\& ev_timer_stop (loop, &tw);	2826	\& adns_state ads = (adns_state)w\->data;
1697	.Ve	2827	\& update_now (EV_A);
1698	.PP	2828	\&
1699	.Vb 2	2829	\& adns_processtimeouts (ads, &tv_now);
1700	\& for (int i = 0; i < nfd; ++i)
1701	\& ev_io_stop (loop, iow + i);
1702	.Ve
1703	.PP
1704	.Vb 2
1705	\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1706	\& }	2830	\& }
		2831	\&
		2832	\& static void
		2833	\& io_cb (EV_P_ ev_io *w, int revents)
		2834	\& {
		2835	\& adns_state ads = (adns_state)w\->data;
		2836	\& update_now (EV_A);
		2837	\&
		2838	\& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now);
		2839	\& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
		2840	\& }
		2841	\&
		2842	\& // do not ever call adns_afterpoll
1707	.Ve	2843	.Ve
		2844	.PP
		2845	Method 4: Do not use a prepare or check watcher because the module you
		2846	want to embed is not flexible enough to support it. Instead, you can
		2847	override their poll function. The drawback with this solution is that the
		2848	main loop is now no longer controllable by \s-1EV\s0. The \f(CW\(C`Glib::EV\(C'\fR module uses
		2849	this approach, effectively embedding \s-1EV\s0 as a client into the horrible
		2850	libglib event loop.
		2851	.PP
		2852	.Vb 4
		2853	\& static gint
		2854	\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2855	\& {
		2856	\& int got_events = 0;
		2857	\&
		2858	\& for (n = 0; n < nfds; ++n)
		2859	\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2860	\&
		2861	\& if (timeout >= 0)
		2862	\& // create/start timer
		2863	\&
		2864	\& // poll
		2865	\& ev_loop (EV_A_ 0);
		2866	\&
		2867	\& // stop timer again
		2868	\& if (timeout >= 0)
		2869	\& ev_timer_stop (EV_A_ &to);
		2870	\&
		2871	\& // stop io watchers again \- their callbacks should have set
		2872	\& for (n = 0; n < nfds; ++n)
		2873	\& ev_io_stop (EV_A_ iow [n]);
		2874	\&
		2875	\& return got_events;
		2876	\& }
		2877	.Ve
1708	.ie n .Sh """ev_embed"" \- when one backend isn't enough..."	2878	.ie n .SS """ev_embed"" \- when one backend isn't enough..."
1709	.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."	2879	.el .SS "\f(CWev_embed\fP \- when one backend isn't enough..."
1710	.IX Subsection "ev_embed - when one backend isn't enough..."	2880	.IX Subsection "ev_embed - when one backend isn't enough..."
1711	This is a rather advanced watcher type that lets you embed one event loop	2881	This is a rather advanced watcher type that lets you embed one event loop
1712	into another (currently only \f(CW\(C`ev_io\(C'\fR events are supported in the embedded	2882	into another (currently only \f(CW\(C`ev_io\(C'\fR events are supported in the embedded
1713	loop, other types of watchers might be handled in a delayed or incorrect	2883	loop, other types of watchers might be handled in a delayed or incorrect
1714	fashion and must not be used).	2884	fashion and must not be used).
…		…
1717	prioritise I/O.	2887	prioritise I/O.
1718	.PP	2888	.PP
1719	As an example for a bug workaround, the kqueue backend might only support	2889	As an example for a bug workaround, the kqueue backend might only support
1720	sockets on some platform, so it is unusable as generic backend, but you	2890	sockets on some platform, so it is unusable as generic backend, but you
1721	still want to make use of it because you have many sockets and it scales	2891	still want to make use of it because you have many sockets and it scales
1722	so nicely. In this case, you would create a kqueue-based loop and embed it	2892	so nicely. In this case, you would create a kqueue-based loop and embed
1723	into your default loop (which might use e.g. poll). Overall operation will	2893	it into your default loop (which might use e.g. poll). Overall operation
1724	be a bit slower because first libev has to poll and then call kevent, but	2894	will be a bit slower because first libev has to call \f(CW\(C`poll\(C'\fR and then
1725	at least you can use both at what they are best.	2895	\&\f(CW\(C`kevent\(C'\fR, but at least you can use both mechanisms for what they are
		2896	best: \f(CW\(C`kqueue\(C'\fR for scalable sockets and \f(CW\(C`poll\(C'\fR if you want it to work :)
1726	.PP	2897	.PP
1727	As for prioritising I/O: rarely you have the case where some fds have	2898	As for prioritising I/O: under rare circumstances you have the case where
1728	to be watched and handled very quickly (with low latency), and even	2899	some fds have to be watched and handled very quickly (with low latency),
1729	priorities and idle watchers might have too much overhead. In this case	2900	and even priorities and idle watchers might have too much overhead. In
1730	you would put all the high priority stuff in one loop and all the rest in	2901	this case you would put all the high priority stuff in one loop and all
1731	a second one, and embed the second one in the first.	2902	the rest in a second one, and embed the second one in the first.
1732	.PP	2903	.PP
1733	As long as the watcher is active, the callback will be invoked every time	2904	As long as the watcher is active, the callback will be invoked every
1734	there might be events pending in the embedded loop. The callback must then	2905	time there might be events pending in the embedded loop. The callback
1735	call \f(CW\(C`ev_embed_sweep (mainloop, watcher)\(C'\fR to make a single sweep and invoke	2906	must then call \f(CW\(C`ev_embed_sweep (mainloop, watcher)\(C'\fR to make a single
1736	their callbacks (you could also start an idle watcher to give the embedded	2907	sweep and invoke their callbacks (the callback doesn't need to invoke the
1737	loop strictly lower priority for example). You can also set the callback	2908	\&\f(CW\(C`ev_embed_sweep\(C'\fR function directly, it could also start an idle watcher
1738	to \f(CW0\fR, in which case the embed watcher will automatically execute the	2909	to give the embedded loop strictly lower priority for example).
1739	embedded loop sweep.
1740	.PP	2910	.PP
1741	As long as the watcher is started it will automatically handle events. The	2911	You can also set the callback to \f(CW0\fR, in which case the embed watcher
1742	callback will be invoked whenever some events have been handled. You can	2912	will automatically execute the embedded loop sweep whenever necessary.
1743	set the callback to \f(CW0\fR to avoid having to specify one if you are not
1744	interested in that.
1745	.PP	2913	.PP
1746	Also, there have not currently been made special provisions for forking:	2914	Fork detection will be handled transparently while the \f(CW\(C`ev_embed\(C'\fR watcher
1747	when you fork, you not only have to call \f(CW\(C`ev_loop_fork\(C'\fR on both loops,	2915	is active, i.e., the embedded loop will automatically be forked when the
1748	but you will also have to stop and restart any \f(CW\(C`ev_embed\(C'\fR watchers	2916	embedding loop forks. In other cases, the user is responsible for calling
1749	yourself.	2917	\&\f(CW\(C`ev_loop_fork\(C'\fR on the embedded loop.
1750	.PP	2918	.PP
1751	Unfortunately, not all backends are embeddable, only the ones returned by	2919	Unfortunately, not all backends are embeddable: only the ones returned by
1752	\&\f(CW\(C`ev_embeddable_backends\(C'\fR are, which, unfortunately, does not include any	2920	\&\f(CW\(C`ev_embeddable_backends\(C'\fR are, which, unfortunately, does not include any
1753	portable one.	2921	portable one.
1754	.PP	2922	.PP
1755	So when you want to use this feature you will always have to be prepared	2923	So when you want to use this feature you will always have to be prepared
1756	that you cannot get an embeddable loop. The recommended way to get around	2924	that you cannot get an embeddable loop. The recommended way to get around
1757	this is to have a separate variables for your embeddable loop, try to	2925	this is to have a separate variables for your embeddable loop, try to
1758	create it, and if that fails, use the normal loop for everything:	2926	create it, and if that fails, use the normal loop for everything.
1759	.PP	2927	.PP
1760	.Vb 3	2928	\fI\f(CI\(C`ev_embed\(C'\fI and fork\fR
1761	\& struct ev_loop *loop_hi = ev_default_init (0);	2929	.IX Subsection "ev_embed and fork"
1762	\& struct ev_loop *loop_lo = 0;
1763	\& struct ev_embed embed;
1764	.Ve
1765	.PP	2930	.PP
1766	.Vb 5	2931	While the \f(CW\(C`ev_embed\(C'\fR watcher is running, forks in the embedding loop will
1767	\& // see if there is a chance of getting one that works	2932	automatically be applied to the embedded loop as well, so no special
1768	\& // (remember that a flags value of 0 means autodetection)	2933	fork handling is required in that case. When the watcher is not running,
1769	\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2934	however, it is still the task of the libev user to call \f(CW\(C`ev_loop_fork ()\(C'\fR
1770	\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2935	as applicable.
1771	\& : 0;
1772	.Ve
1773	.PP	2936	.PP
1774	.Vb 8	2937	\fIWatcher-Specific Functions and Data Members\fR
1775	\& // if we got one, then embed it, otherwise default to loop_hi	2938	.IX Subsection "Watcher-Specific Functions and Data Members"
1776	\& if (loop_lo)
1777	\& {
1778	\& ev_embed_init (&embed, 0, loop_lo);
1779	\& ev_embed_start (loop_hi, &embed);
1780	\& }
1781	\& else
1782	\& loop_lo = loop_hi;
1783	.Ve
1784	.IP "ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)" 4	2939	.IP "ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)" 4
1785	.IX Item "ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)"	2940	.IX Item "ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)"
1786	.PD 0	2941	.PD 0
1787	.IP "ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)" 4	2942	.IP "ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)" 4
1788	.IX Item "ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)"	2943	.IX Item "ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)"
1789	.PD	2944	.PD
1790	Configures the watcher to embed the given loop, which must be	2945	Configures the watcher to embed the given loop, which must be
1791	embeddable. If the callback is \f(CW0\fR, then \f(CW\(C`ev_embed_sweep\(C'\fR will be	2946	embeddable. If the callback is \f(CW0\fR, then \f(CW\(C`ev_embed_sweep\(C'\fR will be
1792	invoked automatically, otherwise it is the responsibility of the callback	2947	invoked automatically, otherwise it is the responsibility of the callback
1793	to invoke it (it will continue to be called until the sweep has been done,	2948	to invoke it (it will continue to be called until the sweep has been done,
1794	if you do not want thta, you need to temporarily stop the embed watcher).	2949	if you do not want that, you need to temporarily stop the embed watcher).
1795	.IP "ev_embed_sweep (loop, ev_embed *)" 4	2950	.IP "ev_embed_sweep (loop, ev_embed *)" 4
1796	.IX Item "ev_embed_sweep (loop, ev_embed *)"	2951	.IX Item "ev_embed_sweep (loop, ev_embed *)"
1797	Make a single, non-blocking sweep over the embedded loop. This works	2952	Make a single, non-blocking sweep over the embedded loop. This works
1798	similarly to \f(CW\(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\(C'\fR, but in the most	2953	similarly to \f(CW\(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\(C'\fR, but in the most
1799	apropriate way for embedded loops.	2954	appropriate way for embedded loops.
1800	.IP "struct ev_loop *loop [read\-only]" 4	2955	.IP "struct ev_loop *other [read\-only]" 4
1801	.IX Item "struct ev_loop *loop [read-only]"	2956	.IX Item "struct ev_loop *other [read-only]"
1802	The embedded event loop.	2957	The embedded event loop.
		2958	.PP
		2959	\fIExamples\fR
		2960	.IX Subsection "Examples"
		2961	.PP
		2962	Example: Try to get an embeddable event loop and embed it into the default
		2963	event loop. If that is not possible, use the default loop. The default
		2964	loop is stored in \f(CW\(C`loop_hi\(C'\fR, while the embeddable loop is stored in
		2965	\&\f(CW\(C`loop_lo\(C'\fR (which is \f(CW\(C`loop_hi\(C'\fR in the case no embeddable loop can be
		2966	used).
		2967	.PP
		2968	.Vb 3
		2969	\& struct ev_loop *loop_hi = ev_default_init (0);
		2970	\& struct ev_loop *loop_lo = 0;
		2971	\& ev_embed embed;
		2972	\&
		2973	\& // see if there is a chance of getting one that works
		2974	\& // (remember that a flags value of 0 means autodetection)
		2975	\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2976	\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2977	\& : 0;
		2978	\&
		2979	\& // if we got one, then embed it, otherwise default to loop_hi
		2980	\& if (loop_lo)
		2981	\& {
		2982	\& ev_embed_init (&embed, 0, loop_lo);
		2983	\& ev_embed_start (loop_hi, &embed);
		2984	\& }
		2985	\& else
		2986	\& loop_lo = loop_hi;
		2987	.Ve
		2988	.PP
		2989	Example: Check if kqueue is available but not recommended and create
		2990	a kqueue backend for use with sockets (which usually work with any
		2991	kqueue implementation). Store the kqueue/socket\-only event loop in
		2992	\&\f(CW\(C`loop_socket\(C'\fR. (One might optionally use \f(CW\(C`EVFLAG_NOENV\(C'\fR, too).
		2993	.PP
		2994	.Vb 3
		2995	\& struct ev_loop *loop = ev_default_init (0);
		2996	\& struct ev_loop *loop_socket = 0;
		2997	\& ev_embed embed;
		2998	\&
		2999	\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		3000	\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		3001	\& {
		3002	\& ev_embed_init (&embed, 0, loop_socket);
		3003	\& ev_embed_start (loop, &embed);
		3004	\& }
		3005	\&
		3006	\& if (!loop_socket)
		3007	\& loop_socket = loop;
		3008	\&
		3009	\& // now use loop_socket for all sockets, and loop for everything else
		3010	.Ve
1803	.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"	3011	.ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork"
1804	.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"	3012	.el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1805	.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"	3013	.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1806	Fork watchers are called when a \f(CW\(C`fork ()\(C'\fR was detected (usually because	3014	Fork watchers are called when a \f(CW\(C`fork ()\(C'\fR was detected (usually because
1807	whoever is a good citizen cared to tell libev about it by calling	3015	whoever is a good citizen cared to tell libev about it by calling
1808	\&\f(CW\(C`ev_default_fork\(C'\fR or \f(CW\(C`ev_loop_fork\(C'\fR). The invocation is done before the	3016	\&\f(CW\(C`ev_default_fork\(C'\fR or \f(CW\(C`ev_loop_fork\(C'\fR). The invocation is done before the
1809	event loop blocks next and before \f(CW\(C`ev_check\(C'\fR watchers are being called,	3017	event loop blocks next and before \f(CW\(C`ev_check\(C'\fR watchers are being called,
1810	and only in the child after the fork. If whoever good citizen calling	3018	and only in the child after the fork. If whoever good citizen calling
1811	\&\f(CW\(C`ev_default_fork\(C'\fR cheats and calls it in the wrong process, the fork	3019	\&\f(CW\(C`ev_default_fork\(C'\fR cheats and calls it in the wrong process, the fork
1812	handlers will be invoked, too, of course.	3020	handlers will be invoked, too, of course.
		3021	.PP
		3022	\fIThe special problem of life after fork \- how is it possible?\fR
		3023	.IX Subsection "The special problem of life after fork - how is it possible?"
		3024	.PP
		3025	Most uses of \f(CW\(C`fork()\(C'\fR consist of forking, then some simple calls to ste
		3026	up/change the process environment, followed by a call to \f(CW\(C`exec()\(C'\fR. This
		3027	sequence should be handled by libev without any problems.
		3028	.PP
		3029	This changes when the application actually wants to do event handling
		3030	in the child, or both parent in child, in effect \(L"continuing\(R" after the
		3031	fork.
		3032	.PP
		3033	The default mode of operation (for libev, with application help to detect
		3034	forks) is to duplicate all the state in the child, as would be expected
		3035	when \fIeither\fR the parent \fIor\fR the child process continues.
		3036	.PP
		3037	When both processes want to continue using libev, then this is usually the
		3038	wrong result. In that case, usually one process (typically the parent) is
		3039	supposed to continue with all watchers in place as before, while the other
		3040	process typically wants to start fresh, i.e. without any active watchers.
		3041	.PP
		3042	The cleanest and most efficient way to achieve that with libev is to
		3043	simply create a new event loop, which of course will be \(L"empty\(R", and
		3044	use that for new watchers. This has the advantage of not touching more
		3045	memory than necessary, and thus avoiding the copy-on-write, and the
		3046	disadvantage of having to use multiple event loops (which do not support
		3047	signal watchers).
		3048	.PP
		3049	When this is not possible, or you want to use the default loop for
		3050	other reasons, then in the process that wants to start \(L"fresh\(R", call
		3051	\&\f(CW\(C`ev_default_destroy ()\(C'\fR followed by \f(CW\(C`ev_default_loop (...)\(C'\fR. Destroying
		3052	the default loop will \(L"orphan\(R" (not stop) all registered watchers, so you
		3053	have to be careful not to execute code that modifies those watchers. Note
		3054	also that in that case, you have to re-register any signal watchers.
		3055	.PP
		3056	\fIWatcher-Specific Functions and Data Members\fR
		3057	.IX Subsection "Watcher-Specific Functions and Data Members"
1813	.IP "ev_fork_init (ev_signal *, callback)" 4	3058	.IP "ev_fork_init (ev_signal *, callback)" 4
1814	.IX Item "ev_fork_init (ev_signal *, callback)"	3059	.IX Item "ev_fork_init (ev_signal *, callback)"
1815	Initialises and configures the fork watcher \- it has no parameters of any	3060	Initialises and configures the fork watcher \- it has no parameters of any
1816	kind. There is a \f(CW\(C`ev_fork_set\(C'\fR macro, but using it is utterly pointless,	3061	kind. There is a \f(CW\(C`ev_fork_set\(C'\fR macro, but using it is utterly pointless,
1817	believe me.	3062	believe me.
		3063	.ie n .SS """ev_async"" \- how to wake up another event loop"
		3064	.el .SS "\f(CWev_async\fP \- how to wake up another event loop"
		3065	.IX Subsection "ev_async - how to wake up another event loop"
		3066	In general, you cannot use an \f(CW\(C`ev_loop\(C'\fR from multiple threads or other
		3067	asynchronous sources such as signal handlers (as opposed to multiple event
		3068	loops \- those are of course safe to use in different threads).
		3069	.PP
		3070	Sometimes, however, you need to wake up another event loop you do not
		3071	control, for example because it belongs to another thread. This is what
		3072	\&\f(CW\(C`ev_async\(C'\fR watchers do: as long as the \f(CW\(C`ev_async\(C'\fR watcher is active, you
		3073	can signal it by calling \f(CW\(C`ev_async_send\(C'\fR, which is thread\- and signal
		3074	safe.
		3075	.PP
		3076	This functionality is very similar to \f(CW\(C`ev_signal\(C'\fR watchers, as signals,
		3077	too, are asynchronous in nature, and signals, too, will be compressed
		3078	(i.e. the number of callback invocations may be less than the number of
		3079	\&\f(CW\(C`ev_async_sent\(C'\fR calls).
		3080	.PP
		3081	Unlike \f(CW\(C`ev_signal\(C'\fR watchers, \f(CW\(C`ev_async\(C'\fR works with any event loop, not
		3082	just the default loop.
		3083	.PP
		3084	\fIQueueing\fR
		3085	.IX Subsection "Queueing"
		3086	.PP
		3087	\&\f(CW\(C`ev_async\(C'\fR does not support queueing of data in any way. The reason
		3088	is that the author does not know of a simple (or any) algorithm for a
		3089	multiple-writer-single-reader queue that works in all cases and doesn't
		3090	need elaborate support such as pthreads.
		3091	.PP
		3092	That means that if you want to queue data, you have to provide your own
		3093	queue. But at least I can tell you how to implement locking around your
		3094	queue:
		3095	.IP "queueing from a signal handler context" 4
		3096	.IX Item "queueing from a signal handler context"
		3097	To implement race-free queueing, you simply add to the queue in the signal
		3098	handler but you block the signal handler in the watcher callback. Here is
		3099	an example that does that for some fictitious \s-1SIGUSR1\s0 handler:
		3100	.Sp
		3101	.Vb 1
		3102	\& static ev_async mysig;
		3103	\&
		3104	\& static void
		3105	\& sigusr1_handler (void)
		3106	\& {
		3107	\& sometype data;
		3108	\&
		3109	\& // no locking etc.
		3110	\& queue_put (data);
		3111	\& ev_async_send (EV_DEFAULT_ &mysig);
		3112	\& }
		3113	\&
		3114	\& static void
		3115	\& mysig_cb (EV_P_ ev_async *w, int revents)
		3116	\& {
		3117	\& sometype data;
		3118	\& sigset_t block, prev;
		3119	\&
		3120	\& sigemptyset (&block);
		3121	\& sigaddset (&block, SIGUSR1);
		3122	\& sigprocmask (SIG_BLOCK, &block, &prev);
		3123	\&
		3124	\& while (queue_get (&data))
		3125	\& process (data);
		3126	\&
		3127	\& if (sigismember (&prev, SIGUSR1)
		3128	\& sigprocmask (SIG_UNBLOCK, &block, 0);
		3129	\& }
		3130	.Ve
		3131	.Sp
		3132	(Note: pthreads in theory requires you to use \f(CW\(C`pthread_setmask\(C'\fR
		3133	instead of \f(CW\(C`sigprocmask\(C'\fR when you use threads, but libev doesn't do it
		3134	either...).
		3135	.IP "queueing from a thread context" 4
		3136	.IX Item "queueing from a thread context"
		3137	The strategy for threads is different, as you cannot (easily) block
		3138	threads but you can easily preempt them, so to queue safely you need to
		3139	employ a traditional mutex lock, such as in this pthread example:
		3140	.Sp
		3141	.Vb 2
		3142	\& static ev_async mysig;
		3143	\& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		3144	\&
		3145	\& static void
		3146	\& otherthread (void)
		3147	\& {
		3148	\& // only need to lock the actual queueing operation
		3149	\& pthread_mutex_lock (&mymutex);
		3150	\& queue_put (data);
		3151	\& pthread_mutex_unlock (&mymutex);
		3152	\&
		3153	\& ev_async_send (EV_DEFAULT_ &mysig);
		3154	\& }
		3155	\&
		3156	\& static void
		3157	\& mysig_cb (EV_P_ ev_async *w, int revents)
		3158	\& {
		3159	\& pthread_mutex_lock (&mymutex);
		3160	\&
		3161	\& while (queue_get (&data))
		3162	\& process (data);
		3163	\&
		3164	\& pthread_mutex_unlock (&mymutex);
		3165	\& }
		3166	.Ve
		3167	.PP
		3168	\fIWatcher-Specific Functions and Data Members\fR
		3169	.IX Subsection "Watcher-Specific Functions and Data Members"
		3170	.IP "ev_async_init (ev_async *, callback)" 4
		3171	.IX Item "ev_async_init (ev_async *, callback)"
		3172	Initialises and configures the async watcher \- it has no parameters of any
		3173	kind. There is a \f(CW\(C`ev_async_set\(C'\fR macro, but using it is utterly pointless,
		3174	trust me.
		3175	.IP "ev_async_send (loop, ev_async *)" 4
		3176	.IX Item "ev_async_send (loop, ev_async *)"
		3177	Sends/signals/activates the given \f(CW\(C`ev_async\(C'\fR watcher, that is, feeds
		3178	an \f(CW\(C`EV_ASYNC\(C'\fR event on the watcher into the event loop. Unlike
		3179	\&\f(CW\(C`ev_feed_event\(C'\fR, this call is safe to do from other threads, signal or
		3180	similar contexts (see the discussion of \f(CW\(C`EV_ATOMIC_T\(C'\fR in the embedding
		3181	section below on what exactly this means).
		3182	.Sp
		3183	Note that, as with other watchers in libev, multiple events might get
		3184	compressed into a single callback invocation (another way to look at this
		3185	is that \f(CW\(C`ev_async\(C'\fR watchers are level-triggered, set on \f(CW\(C`ev_async_send\(C'\fR,
		3186	reset when the event loop detects that).
		3187	.Sp
		3188	This call incurs the overhead of a system call only once per event loop
		3189	iteration, so while the overhead might be noticeable, it doesn't apply to
		3190	repeated calls to \f(CW\(C`ev_async_send\(C'\fR for the same event loop.
		3191	.IP "bool = ev_async_pending (ev_async *)" 4
		3192	.IX Item "bool = ev_async_pending (ev_async *)"
		3193	Returns a non-zero value when \f(CW\(C`ev_async_send\(C'\fR has been called on the
		3194	watcher but the event has not yet been processed (or even noted) by the
		3195	event loop.
		3196	.Sp
		3197	\&\f(CW\(C`ev_async_send\(C'\fR sets a flag in the watcher and wakes up the loop. When
		3198	the loop iterates next and checks for the watcher to have become active,
		3199	it will reset the flag again. \f(CW\(C`ev_async_pending\(C'\fR can be used to very
		3200	quickly check whether invoking the loop might be a good idea.
		3201	.Sp
		3202	Not that this does \fInot\fR check whether the watcher itself is pending,
		3203	only whether it has been requested to make this watcher pending: there
		3204	is a time window between the event loop checking and resetting the async
		3205	notification, and the callback being invoked.
1818	.SH "OTHER FUNCTIONS"	3206	.SH "OTHER FUNCTIONS"
1819	.IX Header "OTHER FUNCTIONS"	3207	.IX Header "OTHER FUNCTIONS"
1820	There are some other functions of possible interest. Described. Here. Now.	3208	There are some other functions of possible interest. Described. Here. Now.
1821	.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4	3209	.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1822	.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"	3210	.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
1823	This function combines a simple timer and an I/O watcher, calls your	3211	This function combines a simple timer and an I/O watcher, calls your
1824	callback on whichever event happens first and automatically stop both	3212	callback on whichever event happens first and automatically stops both
1825	watchers. This is useful if you want to wait for a single event on an fd	3213	watchers. This is useful if you want to wait for a single event on an fd
1826	or timeout without having to allocate/configure/start/stop/free one or	3214	or timeout without having to allocate/configure/start/stop/free one or
1827	more watchers yourself.	3215	more watchers yourself.
1828	.Sp	3216	.Sp
1829	If \f(CW\(C`fd\(C'\fR is less than 0, then no I/O watcher will be started and events	3217	If \f(CW\(C`fd\(C'\fR is less than 0, then no I/O watcher will be started and the
1830	is being ignored. Otherwise, an \f(CW\(C`ev_io\(C'\fR watcher for the given \f(CW\(C`fd\(C'\fR and	3218	\&\f(CW\(C`events\(C'\fR argument is being ignored. Otherwise, an \f(CW\(C`ev_io\(C'\fR watcher for
1831	\&\f(CW\(C`events\(C'\fR set will be craeted and started.	3219	the given \f(CW\(C`fd\(C'\fR and \f(CW\(C`events\(C'\fR set will be created and started.
1832	.Sp	3220	.Sp
1833	If \f(CW\(C`timeout\(C'\fR is less than 0, then no timeout watcher will be	3221	If \f(CW\(C`timeout\(C'\fR is less than 0, then no timeout watcher will be
1834	started. Otherwise an \f(CW\(C`ev_timer\(C'\fR watcher with after = \f(CW\(C`timeout\(C'\fR (and	3222	started. Otherwise an \f(CW\(C`ev_timer\(C'\fR watcher with after = \f(CW\(C`timeout\(C'\fR (and
1835	repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of	3223	repeat = 0) will be started. \f(CW0\fR is a valid timeout.
1836	dubious value.
1837	.Sp	3224	.Sp
1838	The callback has the type \f(CW\(C`void (cb)(int revents, void arg)\(C'\fR and gets	3225	The callback has the type \f(CW\(C`void (cb)(int revents, void arg)\(C'\fR and gets
1839	passed an \f(CW\(C`revents\(C'\fR set like normal event callbacks (a combination of	3226	passed an \f(CW\(C`revents\(C'\fR set like normal event callbacks (a combination of
1840	\&\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	3227	\&\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
1841	value passed to \f(CW\(C`ev_once\(C'\fR:	3228	value passed to \f(CW\(C`ev_once\(C'\fR. Note that it is possible to receive \fIboth\fR
		3229	a timeout and an io event at the same time \- you probably should give io
		3230	events precedence.
		3231	.Sp
		3232	Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO\s0.
1842	.Sp	3233	.Sp
1843	.Vb 7	3234	.Vb 7
1844	\& static void stdin_ready (int revents, void *arg)	3235	\& static void stdin_ready (int revents, void *arg)
1845	\& {	3236	\& {
1846	\& if (revents & EV_TIMEOUT)
1847	\& /* doh, nothing entered */;
1848	\& else if (revents & EV_READ)	3237	\& if (revents & EV_READ)
1849	\& /* stdin might have data for us, joy! */;	3238	\& /* stdin might have data for us, joy! */;
		3239	\& else if (revents & EV_TIMEOUT)
		3240	\& /* doh, nothing entered */;
1850	\& }	3241	\& }
1851	.Ve	3242	\&
1852	.Sp
1853	.Vb 1
1854	\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3243	\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1855	.Ve	3244	.Ve
1856	.IP "ev_feed_event (ev_loop , watcher , int revents)" 4	3245	.IP "ev_feed_event (struct ev_loop , watcher , int revents)" 4
1857	.IX Item "ev_feed_event (ev_loop , watcher , int revents)"	3246	.IX Item "ev_feed_event (struct ev_loop , watcher , int revents)"
1858	Feeds the given event set into the event loop, as if the specified event	3247	Feeds the given event set into the event loop, as if the specified event
1859	had happened for the specified watcher (which must be a pointer to an	3248	had happened for the specified watcher (which must be a pointer to an
1860	initialised but not necessarily started event watcher).	3249	initialised but not necessarily started event watcher).
1861	.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4	3250	.IP "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" 4
1862	.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"	3251	.IX Item "ev_feed_fd_event (struct ev_loop *, int fd, int revents)"
1863	Feed an event on the given fd, as if a file descriptor backend detected	3252	Feed an event on the given fd, as if a file descriptor backend detected
1864	the given events it.	3253	the given events it.
1865	.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4	3254	.IP "ev_feed_signal_event (struct ev_loop *loop, int signum)" 4
1866	.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"	3255	.IX Item "ev_feed_signal_event (struct ev_loop *loop, int signum)"
1867	Feed an event as if the given signal occured (\f(CW\(C`loop\(C'\fR must be the default	3256	Feed an event as if the given signal occurred (\f(CW\(C`loop\(C'\fR must be the default
1868	loop!).	3257	loop!).
1869	.SH "LIBEVENT EMULATION"	3258	.SH "LIBEVENT EMULATION"
1870	.IX Header "LIBEVENT EMULATION"	3259	.IX Header "LIBEVENT EMULATION"
1871	Libev offers a compatibility emulation layer for libevent. It cannot	3260	Libev offers a compatibility emulation layer for libevent. It cannot
1872	emulate the internals of libevent, so here are some usage hints:	3261	emulate the internals of libevent, so here are some usage hints:
		3262	.IP "\(bu" 4
1873	.IP "* Use it by including <event.h>, as usual." 4	3263	Use it by including <event.h>, as usual.
1874	.IX Item "Use it by including <event.h>, as usual."	3264	.IP "\(bu" 4
1875	.PD 0	3265	The following members are fully supported: ev_base, ev_callback,
1876	.IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4	3266	ev_arg, ev_fd, ev_res, ev_events.
1877	.IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events."	3267	.IP "\(bu" 4
1878	.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	3268	Avoid using ev_flags and the EVLIST_*\-macros, while it is
1879	.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)."	3269	maintained by libev, it does not work exactly the same way as in libevent (consider
1880	.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	3270	it a private \s-1API\s0).
1881	.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."	3271	.IP "\(bu" 4
		3272	Priorities are not currently supported. Initialising priorities
		3273	will fail and all watchers will have the same priority, even though there
		3274	is an ev_pri field.
		3275	.IP "\(bu" 4
		3276	In libevent, the last base created gets the signals, in libev, the
		3277	first base created (== the default loop) gets the signals.
		3278	.IP "\(bu" 4
1882	.IP "* Other members are not supported." 4	3279	Other members are not supported.
1883	.IX Item "Other members are not supported."	3280	.IP "\(bu" 4
1884	.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4	3281	The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
1885	.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."	3282	to use the libev header file and library.
1886	.PD
1887	.SH "\*(C+ SUPPORT"	3283	.SH "\*(C+ SUPPORT"
1888	.IX Header " SUPPORT"	3284	.IX Header " SUPPORT"
1889	Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow	3285	Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1890	you to use some convinience methods to start/stop watchers and also change	3286	you to use some convenience methods to start/stop watchers and also change
1891	the callback model to a model using method callbacks on objects.	3287	the callback model to a model using method callbacks on objects.
1892	.PP	3288	.PP
1893	To use it,	3289	To use it,
1894	.PP	3290	.PP
1895	.Vb 1	3291	.Vb 1
1896	\& #include <ev++.h>	3292	\& #include <ev++.h>
1897	.Ve	3293	.Ve
1898	.PP	3294	.PP
1899	This automatically includes \fIev.h\fR and puts all of its definitions (many	3295	This automatically includes \fIev.h\fR and puts all of its definitions (many
1900	of them macros) into the global namespace. All \*(C+ specific things are	3296	of them macros) into the global namespace. All \*(C+ specific things are
1901	put into the \f(CW\(C`ev\(C'\fR namespace. It should support all the same embedding	3297	put into the \f(CW\(C`ev\(C'\fR namespace. It should support all the same embedding
…		…
1911	need one additional pointer for context. If you need support for other	3307	need one additional pointer for context. If you need support for other
1912	types of functors please contact the author (preferably after implementing	3308	types of functors please contact the author (preferably after implementing
1913	it).	3309	it).
1914	.PP	3310	.PP
1915	Here is a list of things available in the \f(CW\(C`ev\(C'\fR namespace:	3311	Here is a list of things available in the \f(CW\(C`ev\(C'\fR namespace:
1916	.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4	3312	.ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4
1917	.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4	3313	.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1918	.IX Item "ev::READ, ev::WRITE etc."	3314	.IX Item "ev::READ, ev::WRITE etc."
1919	These are just enum values with the same values as the \f(CW\(C`EV_READ\(C'\fR etc.	3315	These are just enum values with the same values as the \f(CW\(C`EV_READ\(C'\fR etc.
1920	macros from \fIev.h\fR.	3316	macros from \fIev.h\fR.
1921	.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4	3317	.ie n .IP """ev::tstamp"", ""ev::now""" 4
1922	.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4	3318	.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1923	.IX Item "ev::tstamp, ev::now"	3319	.IX Item "ev::tstamp, ev::now"
1924	Aliases to the same types/functions as with the \f(CW\(C`ev_\(C'\fR prefix.	3320	Aliases to the same types/functions as with the \f(CW\(C`ev_\(C'\fR prefix.
1925	.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	3321	.ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4
1926	.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4	3322	.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1927	.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."	3323	.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1928	For each \f(CW\(C`ev_TYPE\(C'\fR watcher in \fIev.h\fR there is a corresponding class of	3324	For each \f(CW\(C`ev_TYPE\(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1929	the same name in the \f(CW\(C`ev\(C'\fR namespace, with the exception of \f(CW\(C`ev_signal\(C'\fR	3325	the same name in the \f(CW\(C`ev\(C'\fR namespace, with the exception of \f(CW\(C`ev_signal\(C'\fR
1930	which is called \f(CW\(C`ev::sig\(C'\fR to avoid clashes with the \f(CW\(C`signal\(C'\fR macro	3326	which is called \f(CW\(C`ev::sig\(C'\fR to avoid clashes with the \f(CW\(C`signal\(C'\fR macro
…		…
1967	thunking function, making it as fast as a direct C callback.	3363	thunking function, making it as fast as a direct C callback.
1968	.Sp	3364	.Sp
1969	Example: simple class declaration and watcher initialisation	3365	Example: simple class declaration and watcher initialisation
1970	.Sp	3366	.Sp
1971	.Vb 4	3367	.Vb 4
1972	\& struct myclass	3368	\& struct myclass
1973	\& {	3369	\& {
1974	\& void io_cb (ev::io &w, int revents) { }	3370	\& void io_cb (ev::io &w, int revents) { }
1975	\& }	3371	\& }
1976	.Ve	3372	\&
1977	.Sp
1978	.Vb 3
1979	\& myclass obj;	3373	\& myclass obj;
1980	\& ev::io iow;	3374	\& ev::io iow;
1981	\& iow.set <myclass, &myclass::io_cb> (&obj);	3375	\& iow.set <myclass, &myclass::io_cb> (&obj);
1982	.Ve	3376	.Ve
1983	.IP "w\->set (void (function)(watcher &w, int), void data = 0)" 4	3377	.IP "w\->set (object *)" 4
1984	.IX Item "w->set (void (function)(watcher &w, int), void data = 0)"	3378	.IX Item "w->set (object *)"
		3379	This is an \fBexperimental\fR feature that might go away in a future version.
		3380	.Sp
		3381	This is a variation of a method callback \- leaving out the method to call
		3382	will default the method to \f(CW\(C`operator ()\(C'\fR, which makes it possible to use
		3383	functor objects without having to manually specify the \f(CW\(C`operator ()\(C'\fR all
		3384	the time. Incidentally, you can then also leave out the template argument
		3385	list.
		3386	.Sp
		3387	The \f(CW\(C`operator ()\(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w,
		3388	int revents)\*(C'\fR.
		3389	.Sp
		3390	See the method\-\f(CW\(C`set\(C'\fR above for more details.
		3391	.Sp
		3392	Example: use a functor object as callback.
		3393	.Sp
		3394	.Vb 7
		3395	\& struct myfunctor
		3396	\& {
		3397	\& void operator() (ev::io &w, int revents)
		3398	\& {
		3399	\& ...
		3400	\& }
		3401	\& }
		3402	\&
		3403	\& myfunctor f;
		3404	\&
		3405	\& ev::io w;
		3406	\& w.set (&f);
		3407	.Ve
		3408	.IP "w\->set<function> (void *data = 0)" 4
		3409	.IX Item "w->set<function> (void *data = 0)"
1985	Also sets a callback, but uses a static method or plain function as	3410	Also sets a callback, but uses a static method or plain function as
1986	callback. The optional \f(CW\(C`data\(C'\fR argument will be stored in the watcher's	3411	callback. The optional \f(CW\(C`data\(C'\fR argument will be stored in the watcher's
1987	\&\f(CW\(C`data\(C'\fR member and is free for you to use.	3412	\&\f(CW\(C`data\(C'\fR member and is free for you to use.
1988	.Sp	3413	.Sp
		3414	The prototype of the \f(CW\(C`function\(C'\fR must be \f(CW\(C`void ()(ev::TYPE &w, int)\*(C'\fR.
		3415	.Sp
1989	See the method\-\f(CW\(C`set\(C'\fR above for more details.	3416	See the method\-\f(CW\(C`set\(C'\fR above for more details.
		3417	.Sp
		3418	Example: Use a plain function as callback.
		3419	.Sp
		3420	.Vb 2
		3421	\& static void io_cb (ev::io &w, int revents) { }
		3422	\& iow.set <io_cb> ();
		3423	.Ve
1990	.IP "w\->set (struct ev_loop *)" 4	3424	.IP "w\->set (struct ev_loop *)" 4
1991	.IX Item "w->set (struct ev_loop *)"	3425	.IX Item "w->set (struct ev_loop *)"
1992	Associates a different \f(CW\(C`struct ev_loop\(C'\fR with this watcher. You can only	3426	Associates a different \f(CW\(C`struct ev_loop\(C'\fR with this watcher. You can only
1993	do this when the watcher is inactive (and not pending either).	3427	do this when the watcher is inactive (and not pending either).
1994	.IP "w\->set ([args])" 4	3428	.IP "w\->set ([arguments])" 4
1995	.IX Item "w->set ([args])"	3429	.IX Item "w->set ([arguments])"
1996	Basically the same as \f(CW\(C`ev_TYPE_set\(C'\fR, with the same args. Must be	3430	Basically the same as \f(CW\(C`ev_TYPE_set\(C'\fR, with the same arguments. Must be
1997	called at least once. Unlike the C counterpart, an active watcher gets	3431	called at least once. Unlike the C counterpart, an active watcher gets
1998	automatically stopped and restarted when reconfiguring it with this	3432	automatically stopped and restarted when reconfiguring it with this
1999	method.	3433	method.
2000	.IP "w\->start ()" 4	3434	.IP "w\->start ()" 4
2001	.IX Item "w->start ()"	3435	.IX Item "w->start ()"
2002	Starts the watcher. Note that there is no \f(CW\(C`loop\(C'\fR argument, as the	3436	Starts the watcher. Note that there is no \f(CW\(C`loop\(C'\fR argument, as the
2003	constructor already stores the event loop.	3437	constructor already stores the event loop.
2004	.IP "w\->stop ()" 4	3438	.IP "w\->stop ()" 4
2005	.IX Item "w->stop ()"	3439	.IX Item "w->stop ()"
2006	Stops the watcher if it is active. Again, no \f(CW\(C`loop\(C'\fR argument.	3440	Stops the watcher if it is active. Again, no \f(CW\(C`loop\(C'\fR argument.
2007	.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4	3441	.ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4
2008	.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4	3442	.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
2009	.IX Item "w->again () ev::timer, ev::periodic only"	3443	.IX Item "w->again () (ev::timer, ev::periodic only)"
2010	For \f(CW\(C`ev::timer\(C'\fR and \f(CW\(C`ev::periodic\(C'\fR, this invokes the corresponding	3444	For \f(CW\(C`ev::timer\(C'\fR and \f(CW\(C`ev::periodic\(C'\fR, this invokes the corresponding
2011	\&\f(CW\(C`ev_TYPE_again\(C'\fR function.	3445	\&\f(CW\(C`ev_TYPE_again\(C'\fR function.
2012	.ie n .IP "w\->sweep () ""ev::embed"" only" 4	3446	.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
2013	.el .IP "w\->sweep () \f(CWev::embed\fR only" 4	3447	.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
2014	.IX Item "w->sweep () ev::embed only"	3448	.IX Item "w->sweep () (ev::embed only)"
2015	Invokes \f(CW\(C`ev_embed_sweep\(C'\fR.	3449	Invokes \f(CW\(C`ev_embed_sweep\(C'\fR.
2016	.ie n .IP "w\->update () ""ev::stat"" only" 4	3450	.ie n .IP "w\->update () (""ev::stat"" only)" 4
2017	.el .IP "w\->update () \f(CWev::stat\fR only" 4	3451	.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
2018	.IX Item "w->update () ev::stat only"	3452	.IX Item "w->update () (ev::stat only)"
2019	Invokes \f(CW\(C`ev_stat_stat\(C'\fR.	3453	Invokes \f(CW\(C`ev_stat_stat\(C'\fR.
2020	.RE	3454	.RE
2021	.RS 4	3455	.RS 4
2022	.RE	3456	.RE
2023	.PP	3457	.PP
2024	Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in	3458	Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
2025	the constructor.	3459	the constructor.
2026	.PP	3460	.PP
2027	.Vb 4	3461	.Vb 4
2028	\& class myclass	3462	\& class myclass
2029	\& {	3463	\& {
2030	\& ev_io io; void io_cb (ev::io &w, int revents);	3464	\& ev::io io ; void io_cb (ev::io &w, int revents);
2031	\& ev_idle idle void idle_cb (ev::idle &w, int revents);	3465	\& ev::idle idle; void idle_cb (ev::idle &w, int revents);
2032	.Ve	3466	\&
2033	.PP
2034	.Vb 2
2035	\& myclass ();	3467	\& myclass (int fd)
2036	\& }
2037	.Ve
2038	.PP
2039	.Vb 4
2040	\& myclass::myclass (int fd)
2041	\& {	3468	\& {
2042	\& io .set <myclass, &myclass::io_cb > (this);	3469	\& io .set <myclass, &myclass::io_cb > (this);
2043	\& idle.set <myclass, &myclass::idle_cb> (this);	3470	\& idle.set <myclass, &myclass::idle_cb> (this);
2044	.Ve	3471	\&
2045	.PP
2046	.Vb 2
2047	\& io.start (fd, ev::READ);	3472	\& io.start (fd, ev::READ);
		3473	\& }
2048	\& }	3474	\& };
2049	.Ve	3475	.Ve
		3476	.SH "OTHER LANGUAGE BINDINGS"
		3477	.IX Header "OTHER LANGUAGE BINDINGS"
		3478	Libev does not offer other language bindings itself, but bindings for a
		3479	number of languages exist in the form of third-party packages. If you know
		3480	any interesting language binding in addition to the ones listed here, drop
		3481	me a note.
		3482	.IP "Perl" 4
		3483	.IX Item "Perl"
		3484	The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test
		3485	libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module,
		3486	there are additional modules that implement libev-compatible interfaces
		3487	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),
		3488	\&\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
		3489	and \f(CW\(C`EV::Glib\(C'\fR).
		3490	.Sp
		3491	It can be found and installed via \s-1CPAN\s0, its homepage is at
		3492	<http://software.schmorp.de/pkg/EV>.
		3493	.IP "Python" 4
		3494	.IX Item "Python"
		3495	Python bindings can be found at <http://code.google.com/p/pyev/>. It
		3496	seems to be quite complete and well-documented.
		3497	.IP "Ruby" 4
		3498	.IX Item "Ruby"
		3499	Tony Arcieri has written a ruby extension that offers access to a subset
		3500	of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and
		3501	more on top of it. It can be found via gem servers. Its homepage is at
		3502	<http://rev.rubyforge.org/>.
		3503	.Sp
		3504	Roger Pack reports that using the link order \f(CW\(C`\-lws2_32 \-lmsvcrt\-ruby\-190\(C'\fR
		3505	makes rev work even on mingw.
		3506	.IP "Haskell" 4
		3507	.IX Item "Haskell"
		3508	A haskell binding to libev is available at
		3509	<http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>.
		3510	.IP "D" 4
		3511	.IX Item "D"
		3512	Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
		3513	be found at <http://proj.llucax.com.ar/wiki/evd>.
		3514	.IP "Ocaml" 4
		3515	.IX Item "Ocaml"
		3516	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3517	<http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>.
		3518	.IP "Lua" 4
		3519	.IX Item "Lua"
		3520	Brian Maher has written a partial interface to libev
		3521	for lua (only \f(CW\(C`ev_io\(C'\fR and \f(CW\(C`ev_timer\(C'\fR), to be found at
		3522	<http://github.com/brimworks/lua\-ev>.
2050	.SH "MACRO MAGIC"	3523	.SH "MACRO MAGIC"
2051	.IX Header "MACRO MAGIC"	3524	.IX Header "MACRO MAGIC"
2052	Libev can be compiled with a variety of options, the most fundemantal is	3525	Libev can be compiled with a variety of options, the most fundamental
2053	\&\f(CW\(C`EV_MULTIPLICITY\(C'\fR. This option determines whether (most) functions and	3526	of which is \f(CW\(C`EV_MULTIPLICITY\(C'\fR. This option determines whether (most)
2054	callbacks have an initial \f(CW\(C`struct ev_loop \*(C'\fR argument.	3527	functions and callbacks have an initial \f(CW\(C`struct ev_loop \*(C'\fR argument.
2055	.PP	3528	.PP
2056	To make it easier to write programs that cope with either variant, the	3529	To make it easier to write programs that cope with either variant, the
2057	following macros are defined:	3530	following macros are defined:
2058	.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4	3531	.ie n .IP """EV_A"", ""EV_A_""" 4
2059	.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4	3532	.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2060	.IX Item "EV_A, EV_A_"	3533	.IX Item "EV_A, EV_A_"
2061	This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev	3534	This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2062	loop argument\(R"). The \f(CW\(C`EV_A\*(C'\fR form is used when this is the sole argument,	3535	loop argument\(R"). The \f(CW\(C`EV_A\*(C'\fR form is used when this is the sole argument,
2063	\&\f(CW\(C`EV_A_\(C'\fR is used when other arguments are following. Example:	3536	\&\f(CW\(C`EV_A_\(C'\fR is used when other arguments are following. Example:
2064	.Sp	3537	.Sp
2065	.Vb 3	3538	.Vb 3
2066	\& ev_unref (EV_A);	3539	\& ev_unref (EV_A);
2067	\& ev_timer_add (EV_A_ watcher);	3540	\& ev_timer_add (EV_A_ watcher);
2068	\& ev_loop (EV_A_ 0);	3541	\& ev_loop (EV_A_ 0);
2069	.Ve	3542	.Ve
2070	.Sp	3543	.Sp
2071	It assumes the variable \f(CW\(C`loop\(C'\fR of type \f(CW\(C`struct ev_loop \*(C'\fR is in scope,	3544	It assumes the variable \f(CW\(C`loop\(C'\fR of type \f(CW\(C`struct ev_loop \*(C'\fR is in scope,
2072	which is often provided by the following macro.	3545	which is often provided by the following macro.
2073	.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4	3546	.ie n .IP """EV_P"", ""EV_P_""" 4
2074	.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4	3547	.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2075	.IX Item "EV_P, EV_P_"	3548	.IX Item "EV_P, EV_P_"
2076	This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev	3549	This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2077	loop parameter\(R"). The \f(CW\(C`EV_P\*(C'\fR form is used when this is the sole parameter,	3550	loop parameter\(R"). The \f(CW\(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2078	\&\f(CW\(C`EV_P_\(C'\fR is used when other parameters are following. Example:	3551	\&\f(CW\(C`EV_P_\(C'\fR is used when other parameters are following. Example:
2079	.Sp	3552	.Sp
2080	.Vb 2	3553	.Vb 2
2081	\& // this is how ev_unref is being declared	3554	\& // this is how ev_unref is being declared
2082	\& static void ev_unref (EV_P);	3555	\& static void ev_unref (EV_P);
2083	.Ve	3556	\&
2084	.Sp
2085	.Vb 2
2086	\& // this is how you can declare your typical callback	3557	\& // this is how you can declare your typical callback
2087	\& static void cb (EV_P_ ev_timer *w, int revents)	3558	\& static void cb (EV_P_ ev_timer *w, int revents)
2088	.Ve	3559	.Ve
2089	.Sp	3560	.Sp
2090	It declares a parameter \f(CW\(C`loop\(C'\fR of type \f(CW\(C`struct ev_loop \*(C'\fR, quite	3561	It declares a parameter \f(CW\(C`loop\(C'\fR of type \f(CW\(C`struct ev_loop \*(C'\fR, quite
2091	suitable for use with \f(CW\(C`EV_A\(C'\fR.	3562	suitable for use with \f(CW\(C`EV_A\(C'\fR.
2092	.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4	3563	.ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4
2093	.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4	3564	.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2094	.IX Item "EV_DEFAULT, EV_DEFAULT_"	3565	.IX Item "EV_DEFAULT, EV_DEFAULT_"
2095	Similar to the other two macros, this gives you the value of the default	3566	Similar to the other two macros, this gives you the value of the default
2096	loop, if multiple loops are supported (\(L"ev loop default\(R").	3567	loop, if multiple loops are supported (\(L"ev loop default\(R").
		3568	.ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4
		3569	.el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4
		3570	.IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_"
		3571	Usage identical to \f(CW\(C`EV_DEFAULT\(C'\fR and \f(CW\(C`EV_DEFAULT_\(C'\fR, but requires that the
		3572	default loop has been initialised (\f(CW\(C`UC\(C'\fR == unchecked). Their behaviour
		3573	is undefined when the default loop has not been initialised by a previous
		3574	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.
		3575	.Sp
		3576	It is often prudent to use \f(CW\(C`EV_DEFAULT\(C'\fR when initialising the first
		3577	watcher in a function but use \f(CW\(C`EV_DEFAULT_UC\(C'\fR afterwards.
2097	.PP	3578	.PP
2098	Example: Declare and initialise a check watcher, utilising the above	3579	Example: Declare and initialise a check watcher, utilising the above
2099	macros so it will work regardless of whether multiple loops are supported	3580	macros so it will work regardless of whether multiple loops are supported
2100	or not.	3581	or not.
2101	.PP	3582	.PP
2102	.Vb 5	3583	.Vb 5
2103	\& static void	3584	\& static void
2104	\& check_cb (EV_P_ ev_timer *w, int revents)	3585	\& check_cb (EV_P_ ev_timer *w, int revents)
2105	\& {	3586	\& {
2106	\& ev_check_stop (EV_A_ w);	3587	\& ev_check_stop (EV_A_ w);
2107	\& }	3588	\& }
2108	.Ve	3589	\&
2109	.PP
2110	.Vb 4
2111	\& ev_check check;	3590	\& ev_check check;
2112	\& ev_check_init (&check, check_cb);	3591	\& ev_check_init (&check, check_cb);
2113	\& ev_check_start (EV_DEFAULT_ &check);	3592	\& ev_check_start (EV_DEFAULT_ &check);
2114	\& ev_loop (EV_DEFAULT_ 0);	3593	\& ev_loop (EV_DEFAULT_ 0);
2115	.Ve	3594	.Ve
2116	.SH "EMBEDDING"	3595	.SH "EMBEDDING"
2117	.IX Header "EMBEDDING"	3596	.IX Header "EMBEDDING"
2118	Libev can (and often is) directly embedded into host	3597	Libev can (and often is) directly embedded into host
2119	applications. Examples of applications that embed it include the Deliantra	3598	applications. Examples of applications that embed it include the Deliantra
2120	Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)	3599	Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2121	and rxvt\-unicode.	3600	and rxvt-unicode.
2122	.PP	3601	.PP
2123	The goal is to enable you to just copy the neecssary files into your	3602	The goal is to enable you to just copy the necessary files into your
2124	source directory without having to change even a single line in them, so	3603	source directory without having to change even a single line in them, so
2125	you can easily upgrade by simply copying (or having a checked-out copy of	3604	you can easily upgrade by simply copying (or having a checked-out copy of
2126	libev somewhere in your source tree).	3605	libev somewhere in your source tree).
2127	.Sh "\s-1FILESETS\s0"	3606	.SS "\s-1FILESETS\s0"
2128	.IX Subsection "FILESETS"	3607	.IX Subsection "FILESETS"
2129	Depending on what features you need you need to include one or more sets of files	3608	Depending on what features you need you need to include one or more sets of files
2130	in your app.	3609	in your application.
2131	.PP	3610	.PP
2132	\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR	3611	\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2133	.IX Subsection "CORE EVENT LOOP"	3612	.IX Subsection "CORE EVENT LOOP"
2134	.PP	3613	.PP
2135	To include only the libev core (all the \f(CW\(C`ev_\*(C'\fR functions), with manual	3614	To include only the libev core (all the \f(CW\(C`ev_\*(C'\fR functions), with manual
2136	configuration (no autoconf):	3615	configuration (no autoconf):
2137	.PP	3616	.PP
2138	.Vb 2	3617	.Vb 2
2139	\& #define EV_STANDALONE 1	3618	\& #define EV_STANDALONE 1
2140	\& #include "ev.c"	3619	\& #include "ev.c"
2141	.Ve	3620	.Ve
2142	.PP	3621	.PP
2143	This will automatically include \fIev.h\fR, too, and should be done in a	3622	This will automatically include \fIev.h\fR, too, and should be done in a
2144	single C source file only to provide the function implementations. To use	3623	single C source file only to provide the function implementations. To use
2145	it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best	3624	it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2146	done by writing a wrapper around \fIev.h\fR that you can include instead and	3625	done by writing a wrapper around \fIev.h\fR that you can include instead and
2147	where you can put other configuration options):	3626	where you can put other configuration options):
2148	.PP	3627	.PP
2149	.Vb 2	3628	.Vb 2
2150	\& #define EV_STANDALONE 1	3629	\& #define EV_STANDALONE 1
2151	\& #include "ev.h"	3630	\& #include "ev.h"
2152	.Ve	3631	.Ve
2153	.PP	3632	.PP
2154	Both header files and implementation files can be compiled with a \*(C+	3633	Both header files and implementation files can be compiled with a \*(C+
2155	compiler (at least, thats a stated goal, and breakage will be treated	3634	compiler (at least, that's a stated goal, and breakage will be treated
2156	as a bug).	3635	as a bug).
2157	.PP	3636	.PP
2158	You need the following files in your source tree, or in a directory	3637	You need the following files in your source tree, or in a directory
2159	in your include path (e.g. in libev/ when using \-Ilibev):	3638	in your include path (e.g. in libev/ when using \-Ilibev):
2160	.PP	3639	.PP
2161	.Vb 4	3640	.Vb 4
2162	\& ev.h	3641	\& ev.h
2163	\& ev.c	3642	\& ev.c
2164	\& ev_vars.h	3643	\& ev_vars.h
2165	\& ev_wrap.h	3644	\& ev_wrap.h
2166	.Ve	3645	\&
2167	.PP
2168	.Vb 1
2169	\& ev_win32.c required on win32 platforms only	3646	\& ev_win32.c required on win32 platforms only
2170	.Ve	3647	\&
2171	.PP
2172	.Vb 5
2173	\& ev_select.c only when select backend is enabled (which is enabled by default)	3648	\& ev_select.c only when select backend is enabled (which is enabled by default)
2174	\& ev_poll.c only when poll backend is enabled (disabled by default)	3649	\& ev_poll.c only when poll backend is enabled (disabled by default)
2175	\& ev_epoll.c only when the epoll backend is enabled (disabled by default)	3650	\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2176	\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3651	\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2177	\& ev_port.c only when the solaris port backend is enabled (disabled by default)	3652	\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2178	.Ve	3653	.Ve
2179	.PP	3654	.PP
2180	\&\fIev.c\fR includes the backend files directly when enabled, so you only need	3655	\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2181	to compile this single file.	3656	to compile this single file.
2182	.PP	3657	.PP
…		…
2184	.IX Subsection "LIBEVENT COMPATIBILITY API"	3659	.IX Subsection "LIBEVENT COMPATIBILITY API"
2185	.PP	3660	.PP
2186	To include the libevent compatibility \s-1API\s0, also include:	3661	To include the libevent compatibility \s-1API\s0, also include:
2187	.PP	3662	.PP
2188	.Vb 1	3663	.Vb 1
2189	\& #include "event.c"	3664	\& #include "event.c"
2190	.Ve	3665	.Ve
2191	.PP	3666	.PP
2192	in the file including \fIev.c\fR, and:	3667	in the file including \fIev.c\fR, and:
2193	.PP	3668	.PP
2194	.Vb 1	3669	.Vb 1
2195	\& #include "event.h"	3670	\& #include "event.h"
2196	.Ve	3671	.Ve
2197	.PP	3672	.PP
2198	in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.	3673	in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2199	.PP	3674	.PP
2200	You need the following additional files for this:	3675	You need the following additional files for this:
2201	.PP	3676	.PP
2202	.Vb 2	3677	.Vb 2
2203	\& event.h	3678	\& event.h
2204	\& event.c	3679	\& event.c
2205	.Ve	3680	.Ve
2206	.PP	3681	.PP
2207	\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR	3682	\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2208	.IX Subsection "AUTOCONF SUPPORT"	3683	.IX Subsection "AUTOCONF SUPPORT"
2209	.PP	3684	.PP
2210	Instead of using \f(CW\(C`EV_STANDALONE=1\(C'\fR and providing your config in	3685	Instead of using \f(CW\(C`EV_STANDALONE=1\(C'\fR and providing your configuration in
2211	whatever way you want, you can also \f(CW\(C`m4_include([libev.m4])\(C'\fR in your	3686	whatever way you want, you can also \f(CW\(C`m4_include([libev.m4])\(C'\fR in your
2212	\&\fIconfigure.ac\fR and leave \f(CW\(C`EV_STANDALONE\(C'\fR undefined. \fIev.c\fR will then	3687	\&\fIconfigure.ac\fR and leave \f(CW\(C`EV_STANDALONE\(C'\fR undefined. \fIev.c\fR will then
2213	include \fIconfig.h\fR and configure itself accordingly.	3688	include \fIconfig.h\fR and configure itself accordingly.
2214	.PP	3689	.PP
2215	For this of course you need the m4 file:	3690	For this of course you need the m4 file:
2216	.PP	3691	.PP
2217	.Vb 1	3692	.Vb 1
2218	\& libev.m4	3693	\& libev.m4
2219	.Ve	3694	.Ve
2220	.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"	3695	.SS "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2221	.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"	3696	.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2222	Libev can be configured via a variety of preprocessor symbols you have to define	3697	Libev can be configured via a variety of preprocessor symbols you have to
2223	before including any of its files. The default is not to build for multiplicity	3698	define before including any of its files. The default in the absence of
2224	and only include the select backend.	3699	autoconf is documented for every option.
2225	.IP "\s-1EV_STANDALONE\s0" 4	3700	.IP "\s-1EV_STANDALONE\s0" 4
2226	.IX Item "EV_STANDALONE"	3701	.IX Item "EV_STANDALONE"
2227	Must always be \f(CW1\fR if you do not use autoconf configuration, which	3702	Must always be \f(CW1\fR if you do not use autoconf configuration, which
2228	keeps libev from including \fIconfig.h\fR, and it also defines dummy	3703	keeps libev from including \fIconfig.h\fR, and it also defines dummy
2229	implementations for some libevent functions (such as logging, which is not	3704	implementations for some libevent functions (such as logging, which is not
2230	supported). It will also not define any of the structs usually found in	3705	supported). It will also not define any of the structs usually found in
2231	\&\fIevent.h\fR that are not directly supported by the libev core alone.	3706	\&\fIevent.h\fR that are not directly supported by the libev core alone.
		3707	.Sp
		3708	In standalone mode, libev will still try to automatically deduce the
		3709	configuration, but has to be more conservative.
2232	.IP "\s-1EV_USE_MONOTONIC\s0" 4	3710	.IP "\s-1EV_USE_MONOTONIC\s0" 4
2233	.IX Item "EV_USE_MONOTONIC"	3711	.IX Item "EV_USE_MONOTONIC"
2234	If defined to be \f(CW1\fR, libev will try to detect the availability of the	3712	If defined to be \f(CW1\fR, libev will try to detect the availability of the
2235	monotonic clock option at both compiletime and runtime. Otherwise no use	3713	monotonic clock option at both compile time and runtime. Otherwise no
2236	of the monotonic clock option will be attempted. If you enable this, you	3714	use of the monotonic clock option will be attempted. If you enable this,
2237	usually have to link against librt or something similar. Enabling it when	3715	you usually have to link against librt or something similar. Enabling it
2238	the functionality isn't available is safe, though, althoguh you have	3716	when the functionality isn't available is safe, though, although you have
2239	to make sure you link against any libraries where the \f(CW\(C`clock_gettime\(C'\fR	3717	to make sure you link against any libraries where the \f(CW\(C`clock_gettime\(C'\fR
2240	function is hiding in (often \fI\-lrt\fR).	3718	function is hiding in (often \fI\-lrt\fR). See also \f(CW\(C`EV_USE_CLOCK_SYSCALL\(C'\fR.
2241	.IP "\s-1EV_USE_REALTIME\s0" 4	3719	.IP "\s-1EV_USE_REALTIME\s0" 4
2242	.IX Item "EV_USE_REALTIME"	3720	.IX Item "EV_USE_REALTIME"
2243	If defined to be \f(CW1\fR, libev will try to detect the availability of the	3721	If defined to be \f(CW1\fR, libev will try to detect the availability of the
2244	realtime clock option at compiletime (and assume its availability at	3722	real-time clock option at compile time (and assume its availability
2245	runtime if successful). Otherwise no use of the realtime clock option will	3723	at runtime if successful). Otherwise no use of the real-time clock
2246	be attempted. This effectively replaces \f(CW\(C`gettimeofday\(C'\fR by \f(CW\*(C`clock_get	3724	option will be attempted. This effectively replaces \f(CW\(C`gettimeofday\(C'\fR
2247	(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries	3725	by \f(CW\(C`clock_get (CLOCK_REALTIME, ...)\(C'\fR and will not normally affect
2248	in the description of \f(CW\(C`EV_USE_MONOTONIC\(C'\fR, though.	3726	correctness. See the note about libraries in the description of
		3727	\&\f(CW\(C`EV_USE_MONOTONIC\(C'\fR, though. Defaults to the opposite value of
		3728	\&\f(CW\(C`EV_USE_CLOCK_SYSCALL\(C'\fR.
		3729	.IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4
		3730	.IX Item "EV_USE_CLOCK_SYSCALL"
		3731	If defined to be \f(CW1\fR, libev will try to use a direct syscall instead
		3732	of calling the system-provided \f(CW\(C`clock_gettime\(C'\fR function. This option
		3733	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
		3734	unconditionally pulls in \f(CW\(C`libpthread\(C'\fR, slowing down single-threaded
		3735	programs needlessly. Using a direct syscall is slightly slower (in
		3736	theory), because no optimised vdso implementation can be used, but avoids
		3737	the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or
		3738	higher, as it simplifies linking (no need for \f(CW\(C`\-lrt\(C'\fR).
		3739	.IP "\s-1EV_USE_NANOSLEEP\s0" 4
		3740	.IX Item "EV_USE_NANOSLEEP"
		3741	If defined to be \f(CW1\fR, libev will assume that \f(CW\(C`nanosleep ()\(C'\fR is available
		3742	and will use it for delays. Otherwise it will use \f(CW\(C`select ()\(C'\fR.
		3743	.IP "\s-1EV_USE_EVENTFD\s0" 4
		3744	.IX Item "EV_USE_EVENTFD"
		3745	If defined to be \f(CW1\fR, then libev will assume that \f(CW\(C`eventfd ()\(C'\fR is
		3746	available and will probe for kernel support at runtime. This will improve
		3747	\&\f(CW\(C`ev_signal\(C'\fR and \f(CW\(C`ev_async\(C'\fR performance and reduce resource consumption.
		3748	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3749	2.7 or newer, otherwise disabled.
2249	.IP "\s-1EV_USE_SELECT\s0" 4	3750	.IP "\s-1EV_USE_SELECT\s0" 4
2250	.IX Item "EV_USE_SELECT"	3751	.IX Item "EV_USE_SELECT"
2251	If undefined or defined to be \f(CW1\fR, libev will compile in support for the	3752	If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2252	\&\f(CW\(C`select\(C'\fR(2) backend. No attempt at autodetection will be done: if no	3753	\&\f(CW\(C`select\(C'\fR(2) backend. No attempt at auto-detection will be done: if no
2253	other method takes over, select will be it. Otherwise the select backend	3754	other method takes over, select will be it. Otherwise the select backend
2254	will not be compiled in.	3755	will not be compiled in.
2255	.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4	3756	.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2256	.IX Item "EV_SELECT_USE_FD_SET"	3757	.IX Item "EV_SELECT_USE_FD_SET"
2257	If defined to \f(CW1\fR, then the select backend will use the system \f(CW\(C`fd_set\(C'\fR	3758	If defined to \f(CW1\fR, then the select backend will use the system \f(CW\(C`fd_set\(C'\fR
2258	structure. This is useful if libev doesn't compile due to a missing	3759	structure. This is useful if libev doesn't compile due to a missing
2259	\&\f(CW\(C`NFDBITS\(C'\fR or \f(CW\(C`fd_mask\(C'\fR definition or it misguesses the bitset layout on	3760	\&\f(CW\(C`NFDBITS\(C'\fR or \f(CW\(C`fd_mask\(C'\fR definition or it mis-guesses the bitset layout
2260	exotic systems. This usually limits the range of file descriptors to some	3761	on exotic systems. This usually limits the range of file descriptors to
2261	low limit such as 1024 or might have other limitations (winsocket only	3762	some low limit such as 1024 or might have other limitations (winsocket
2262	allows 64 sockets). The \f(CW\(C`FD_SETSIZE\(C'\fR macro, set before compilation, might	3763	only allows 64 sockets). The \f(CW\(C`FD_SETSIZE\(C'\fR macro, set before compilation,
2263	influence the size of the \f(CW\(C`fd_set\(C'\fR used.	3764	configures the maximum size of the \f(CW\(C`fd_set\(C'\fR.
2264	.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4	3765	.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2265	.IX Item "EV_SELECT_IS_WINSOCKET"	3766	.IX Item "EV_SELECT_IS_WINSOCKET"
2266	When defined to \f(CW1\fR, the select backend will assume that	3767	When defined to \f(CW1\fR, the select backend will assume that
2267	select/socket/connect etc. don't understand file descriptors but	3768	select/socket/connect etc. don't understand file descriptors but
2268	wants osf handles on win32 (this is the case when the select to	3769	wants osf handles on win32 (this is the case when the select to
2269	be used is the winsock select). This means that it will call	3770	be used is the winsock select). This means that it will call
2270	\&\f(CW\(C`_get_osfhandle\(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,	3771	\&\f(CW\(C`_get_osfhandle\(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2271	it is assumed that all these functions actually work on fds, even	3772	it is assumed that all these functions actually work on fds, even
2272	on win32. Should not be defined on non\-win32 platforms.	3773	on win32. Should not be defined on non\-win32 platforms.
		3774	.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4
		3775	.IX Item "EV_FD_TO_WIN32_HANDLE"
		3776	If \f(CW\(C`EV_SELECT_IS_WINSOCKET\(C'\fR is enabled, then libev needs a way to map
		3777	file descriptors to socket handles. When not defining this symbol (the
		3778	default), then libev will call \f(CW\(C`_get_osfhandle\(C'\fR, which is usually
		3779	correct. In some cases, programs use their own file descriptor management,
		3780	in which case they can provide this function to map fds to socket handles.
2273	.IP "\s-1EV_USE_POLL\s0" 4	3781	.IP "\s-1EV_USE_POLL\s0" 4
2274	.IX Item "EV_USE_POLL"	3782	.IX Item "EV_USE_POLL"
2275	If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\(C`poll\(C'\fR(2)	3783	If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\(C`poll\(C'\fR(2)
2276	backend. Otherwise it will be enabled on non\-win32 platforms. It	3784	backend. Otherwise it will be enabled on non\-win32 platforms. It
2277	takes precedence over select.	3785	takes precedence over select.
2278	.IP "\s-1EV_USE_EPOLL\s0" 4	3786	.IP "\s-1EV_USE_EPOLL\s0" 4
2279	.IX Item "EV_USE_EPOLL"	3787	.IX Item "EV_USE_EPOLL"
2280	If defined to be \f(CW1\fR, libev will compile in support for the Linux	3788	If defined to be \f(CW1\fR, libev will compile in support for the Linux
2281	\&\f(CW\(C`epoll\(C'\fR(7) backend. Its availability will be detected at runtime,	3789	\&\f(CW\(C`epoll\(C'\fR(7) backend. Its availability will be detected at runtime,
2282	otherwise another method will be used as fallback. This is the	3790	otherwise another method will be used as fallback. This is the preferred
2283	preferred backend for GNU/Linux systems.	3791	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3792	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2284	.IP "\s-1EV_USE_KQUEUE\s0" 4	3793	.IP "\s-1EV_USE_KQUEUE\s0" 4
2285	.IX Item "EV_USE_KQUEUE"	3794	.IX Item "EV_USE_KQUEUE"
2286	If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style	3795	If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2287	\&\f(CW\(C`kqueue\(C'\fR(2) backend. Its actual availability will be detected at runtime,	3796	\&\f(CW\(C`kqueue\(C'\fR(2) backend. Its actual availability will be detected at runtime,
2288	otherwise another method will be used as fallback. This is the preferred	3797	otherwise another method will be used as fallback. This is the preferred
…		…
2298	10 port style backend. Its availability will be detected at runtime,	3807	10 port style backend. Its availability will be detected at runtime,
2299	otherwise another method will be used as fallback. This is the preferred	3808	otherwise another method will be used as fallback. This is the preferred
2300	backend for Solaris 10 systems.	3809	backend for Solaris 10 systems.
2301	.IP "\s-1EV_USE_DEVPOLL\s0" 4	3810	.IP "\s-1EV_USE_DEVPOLL\s0" 4
2302	.IX Item "EV_USE_DEVPOLL"	3811	.IX Item "EV_USE_DEVPOLL"
2303	reserved for future expansion, works like the \s-1USE\s0 symbols above.	3812	Reserved for future expansion, works like the \s-1USE\s0 symbols above.
2304	.IP "\s-1EV_USE_INOTIFY\s0" 4	3813	.IP "\s-1EV_USE_INOTIFY\s0" 4
2305	.IX Item "EV_USE_INOTIFY"	3814	.IX Item "EV_USE_INOTIFY"
2306	If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify	3815	If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2307	interface to speed up \f(CW\(C`ev_stat\(C'\fR watchers. Its actual availability will	3816	interface to speed up \f(CW\(C`ev_stat\(C'\fR watchers. Its actual availability will
2308	be detected at runtime.	3817	be detected at runtime. If undefined, it will be enabled if the headers
		3818	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3819	.IP "\s-1EV_ATOMIC_T\s0" 4
		3820	.IX Item "EV_ATOMIC_T"
		3821	Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose
		3822	access is atomic with respect to other threads or signal contexts. No such
		3823	type is easily found in the C language, so you can provide your own type
		3824	that you know is safe for your purposes. It is used both for signal handler \(L"locking\(R"
		3825	as well as for signal and thread safety in \f(CW\(C`ev_async\(C'\fR watchers.
		3826	.Sp
		3827	In the absence of this define, libev will use \f(CW\(C`sig_atomic_t volatile\(C'\fR
		3828	(from \fIsignal.h\fR), which is usually good enough on most platforms.
2309	.IP "\s-1EV_H\s0" 4	3829	.IP "\s-1EV_H\s0" 4
2310	.IX Item "EV_H"	3830	.IX Item "EV_H"
2311	The name of the \fIev.h\fR header file used to include it. The default if	3831	The name of the \fIev.h\fR header file used to include it. The default if
2312	undefined is \f(CW\(C`<ev.h>\(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This	3832	undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
2313	can be used to virtually rename the \fIev.h\fR header file in case of conflicts.	3833	used to virtually rename the \fIev.h\fR header file in case of conflicts.
2314	.IP "\s-1EV_CONFIG_H\s0" 4	3834	.IP "\s-1EV_CONFIG_H\s0" 4
2315	.IX Item "EV_CONFIG_H"	3835	.IX Item "EV_CONFIG_H"
2316	If \f(CW\(C`EV_STANDALONE\(C'\fR isn't \f(CW1\fR, this variable can be used to override	3836	If \f(CW\(C`EV_STANDALONE\(C'\fR isn't \f(CW1\fR, this variable can be used to override
2317	\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to	3837	\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2318	\&\f(CW\(C`EV_H\(C'\fR, above.	3838	\&\f(CW\(C`EV_H\(C'\fR, above.
2319	.IP "\s-1EV_EVENT_H\s0" 4	3839	.IP "\s-1EV_EVENT_H\s0" 4
2320	.IX Item "EV_EVENT_H"	3840	.IX Item "EV_EVENT_H"
2321	Similarly to \f(CW\(C`EV_H\(C'\fR, this macro can be used to override \fIevent.c\fR's idea	3841	Similarly to \f(CW\(C`EV_H\(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2322	of how the \fIevent.h\fR header can be found.	3842	of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
2323	.IP "\s-1EV_PROTOTYPES\s0" 4	3843	.IP "\s-1EV_PROTOTYPES\s0" 4
2324	.IX Item "EV_PROTOTYPES"	3844	.IX Item "EV_PROTOTYPES"
2325	If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function	3845	If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2326	prototypes, but still define all the structs and other symbols. This is	3846	prototypes, but still define all the structs and other symbols. This is
2327	occasionally useful if you want to provide your own wrapper functions	3847	occasionally useful if you want to provide your own wrapper functions
…		…
2347	When doing priority-based operations, libev usually has to linearly search	3867	When doing priority-based operations, libev usually has to linearly search
2348	all the priorities, so having many of them (hundreds) uses a lot of space	3868	all the priorities, so having many of them (hundreds) uses a lot of space
2349	and time, so using the defaults of five priorities (\-2 .. +2) is usually	3869	and time, so using the defaults of five priorities (\-2 .. +2) is usually
2350	fine.	3870	fine.
2351	.Sp	3871	.Sp
2352	If your embedding app does not need any priorities, defining these both to	3872	If your embedding application does not need any priorities, defining these
2353	\&\f(CW0\fR will save some memory and cpu.	3873	both to \f(CW0\fR will save some memory and \s-1CPU\s0.
2354	.IP "\s-1EV_PERIODIC_ENABLE\s0" 4	3874	.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2355	.IX Item "EV_PERIODIC_ENABLE"	3875	.IX Item "EV_PERIODIC_ENABLE"
2356	If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If	3876	If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2357	defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of	3877	defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2358	code.	3878	code.
…		…
2362	defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of	3882	defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2363	code.	3883	code.
2364	.IP "\s-1EV_EMBED_ENABLE\s0" 4	3884	.IP "\s-1EV_EMBED_ENABLE\s0" 4
2365	.IX Item "EV_EMBED_ENABLE"	3885	.IX Item "EV_EMBED_ENABLE"
2366	If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If	3886	If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2367	defined to be \f(CW0\fR, then they are not.	3887	defined to be \f(CW0\fR, then they are not. Embed watchers rely on most other
		3888	watcher types, which therefore must not be disabled.
2368	.IP "\s-1EV_STAT_ENABLE\s0" 4	3889	.IP "\s-1EV_STAT_ENABLE\s0" 4
2369	.IX Item "EV_STAT_ENABLE"	3890	.IX Item "EV_STAT_ENABLE"
2370	If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If	3891	If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2371	defined to be \f(CW0\fR, then they are not.	3892	defined to be \f(CW0\fR, then they are not.
2372	.IP "\s-1EV_FORK_ENABLE\s0" 4	3893	.IP "\s-1EV_FORK_ENABLE\s0" 4
2373	.IX Item "EV_FORK_ENABLE"	3894	.IX Item "EV_FORK_ENABLE"
2374	If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If	3895	If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2375	defined to be \f(CW0\fR, then they are not.	3896	defined to be \f(CW0\fR, then they are not.
		3897	.IP "\s-1EV_ASYNC_ENABLE\s0" 4
		3898	.IX Item "EV_ASYNC_ENABLE"
		3899	If undefined or defined to be \f(CW1\fR, then async watchers are supported. If
		3900	defined to be \f(CW0\fR, then they are not.
2376	.IP "\s-1EV_MINIMAL\s0" 4	3901	.IP "\s-1EV_MINIMAL\s0" 4
2377	.IX Item "EV_MINIMAL"	3902	.IX Item "EV_MINIMAL"
2378	If you need to shave off some kilobytes of code at the expense of some	3903	If you need to shave off some kilobytes of code at the expense of some
2379	speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override	3904	speed (but with the full \s-1API\s0), define this symbol to \f(CW1\fR. Currently this
2380	some inlining decisions, saves roughly 30% codesize of amd64.	3905	is used to override some inlining decisions, saves roughly 30% code size
		3906	on amd64. It also selects a much smaller 2\-heap for timer management over
		3907	the default 4\-heap.
		3908	.Sp
		3909	You can save even more by disabling watcher types you do not need
		3910	and setting \f(CW\(C`EV_MAXPRI\(C'\fR == \f(CW\(C`EV_MINPRI\(C'\fR. Also, disabling \f(CW\(C`assert\(C'\fR
		3911	(\f(CW\(C`\-DNDEBUG\(C'\fR) will usually reduce code size a lot.
		3912	.Sp
		3913	Defining \f(CW\(C`EV_MINIMAL\(C'\fR to \f(CW2\fR will additionally reduce the core \s-1API\s0 to
		3914	provide a bare-bones event library. See \f(CW\(C`ev.h\(C'\fR for details on what parts
		3915	of the \s-1API\s0 are still available, and do not complain if this subset changes
		3916	over time.
		3917	.IP "\s-1EV_NSIG\s0" 4
		3918	.IX Item "EV_NSIG"
		3919	The highest supported signal number, +1 (or, the number of
		3920	signals): Normally, libev tries to deduce the maximum number of signals
		3921	automatically, but sometimes this fails, in which case it can be
		3922	specified. Also, using a lower number than detected (\f(CW32\fR should be
		3923	good for about any system in existance) can save some memory, as libev
		3924	statically allocates some 12\-24 bytes per signal number.
2381	.IP "\s-1EV_PID_HASHSIZE\s0" 4	3925	.IP "\s-1EV_PID_HASHSIZE\s0" 4
2382	.IX Item "EV_PID_HASHSIZE"	3926	.IX Item "EV_PID_HASHSIZE"
2383	\&\f(CW\(C`ev_child\(C'\fR watchers use a small hash table to distribute workload by	3927	\&\f(CW\(C`ev_child\(C'\fR watchers use a small hash table to distribute workload by
2384	pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\(C`EV_MINIMAL\(C'\fR), usually more	3928	pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\(C`EV_MINIMAL\(C'\fR), usually more
2385	than enough. If you need to manage thousands of children you might want to	3929	than enough. If you need to manage thousands of children you might want to
2386	increase this value (\fImust\fR be a power of two).	3930	increase this value (\fImust\fR be a power of two).
2387	.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4	3931	.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2388	.IX Item "EV_INOTIFY_HASHSIZE"	3932	.IX Item "EV_INOTIFY_HASHSIZE"
2389	\&\f(CW\(C`ev_staz\(C'\fR watchers use a small hash table to distribute workload by	3933	\&\f(CW\(C`ev_stat\(C'\fR watchers use a small hash table to distribute workload by
2390	inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\(C`EV_MINIMAL\(C'\fR),	3934	inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\(C`EV_MINIMAL\(C'\fR),
2391	usually more than enough. If you need to manage thousands of \f(CW\(C`ev_stat\(C'\fR	3935	usually more than enough. If you need to manage thousands of \f(CW\(C`ev_stat\(C'\fR
2392	watchers you might want to increase this value (\fImust\fR be a power of	3936	watchers you might want to increase this value (\fImust\fR be a power of
2393	two).	3937	two).
		3938	.IP "\s-1EV_USE_4HEAP\s0" 4
		3939	.IX Item "EV_USE_4HEAP"
		3940	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3941	timer and periodics heaps, libev uses a 4\-heap when this symbol is defined
		3942	to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably
		3943	faster performance with many (thousands) of watchers.
		3944	.Sp
		3945	The default is \f(CW1\fR unless \f(CW\(C`EV_MINIMAL\(C'\fR is set in which case it is \f(CW0\fR
		3946	(disabled).
		3947	.IP "\s-1EV_HEAP_CACHE_AT\s0" 4
		3948	.IX Item "EV_HEAP_CACHE_AT"
		3949	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3950	timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within
		3951	the heap structure (selected by defining \f(CW\(C`EV_HEAP_CACHE_AT\(C'\fR to \f(CW1\fR),
		3952	which uses 8\-12 bytes more per watcher and a few hundred bytes more code,
		3953	but avoids random read accesses on heap changes. This improves performance
		3954	noticeably with many (hundreds) of watchers.
		3955	.Sp
		3956	The default is \f(CW1\fR unless \f(CW\(C`EV_MINIMAL\(C'\fR is set in which case it is \f(CW0\fR
		3957	(disabled).
		3958	.IP "\s-1EV_VERIFY\s0" 4
		3959	.IX Item "EV_VERIFY"
		3960	Controls how much internal verification (see \f(CW\(C`ev_loop_verify ()\(C'\fR) will
		3961	be done: If set to \f(CW0\fR, no internal verification code will be compiled
		3962	in. If set to \f(CW1\fR, then verification code will be compiled in, but not
		3963	called. If set to \f(CW2\fR, then the internal verification code will be
		3964	called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
		3965	verification code will be called very frequently, which will slow down
		3966	libev considerably.
		3967	.Sp
		3968	The default is \f(CW1\fR, unless \f(CW\(C`EV_MINIMAL\(C'\fR is set, in which case it will be
		3969	\&\f(CW0\fR.
2394	.IP "\s-1EV_COMMON\s0" 4	3970	.IP "\s-1EV_COMMON\s0" 4
2395	.IX Item "EV_COMMON"	3971	.IX Item "EV_COMMON"
2396	By default, all watchers have a \f(CW\(C`void data\*(C'\fR member. By redefining	3972	By default, all watchers have a \f(CW\(C`void data\*(C'\fR member. By redefining
2397	this macro to a something else you can include more and other types of	3973	this macro to a something else you can include more and other types of
2398	members. You have to define it each time you include one of the files,	3974	members. You have to define it each time you include one of the files,
2399	though, and it must be identical each time.	3975	though, and it must be identical each time.
2400	.Sp	3976	.Sp
2401	For example, the perl \s-1EV\s0 module uses something like this:	3977	For example, the perl \s-1EV\s0 module uses something like this:
2402	.Sp	3978	.Sp
2403	.Vb 3	3979	.Vb 3
2404	\& #define EV_COMMON \e	3980	\& #define EV_COMMON \e
2405	\& SV self; / contains this struct */ \e	3981	\& SV self; / contains this struct */ \e
2406	\& SV cb_sv, fh /* note no trailing ";" */	3982	\& SV cb_sv, fh /* note no trailing ";" */
2407	.Ve	3983	.Ve
2408	.IP "\s-1EV_CB_DECLARE\s0 (type)" 4	3984	.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2409	.IX Item "EV_CB_DECLARE (type)"	3985	.IX Item "EV_CB_DECLARE (type)"
2410	.PD 0	3986	.PD 0
2411	.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4	3987	.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
…		…
2413	.IP "ev_set_cb (ev, cb)" 4	3989	.IP "ev_set_cb (ev, cb)" 4
2414	.IX Item "ev_set_cb (ev, cb)"	3990	.IX Item "ev_set_cb (ev, cb)"
2415	.PD	3991	.PD
2416	Can be used to change the callback member declaration in each watcher,	3992	Can be used to change the callback member declaration in each watcher,
2417	and the way callbacks are invoked and set. Must expand to a struct member	3993	and the way callbacks are invoked and set. Must expand to a struct member
2418	definition and a statement, respectively. See the \fIev.v\fR header file for	3994	definition and a statement, respectively. See the \fIev.h\fR header file for
2419	their default definitions. One possible use for overriding these is to	3995	their default definitions. One possible use for overriding these is to
2420	avoid the \f(CW\(C`struct ev_loop \*(C'\fR as first argument in all cases, or to use	3996	avoid the \f(CW\(C`struct ev_loop \*(C'\fR as first argument in all cases, or to use
2421	method calls instead of plain function calls in \*(C+.	3997	method calls instead of plain function calls in \*(C+.
		3998	.SS "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
		3999	.IX Subsection "EXPORTED API SYMBOLS"
		4000	If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of
		4001	exported symbols, you can use the provided \fISymbol.*\fR files which list
		4002	all public symbols, one per line:
		4003	.PP
		4004	.Vb 2
		4005	\& Symbols.ev for libev proper
		4006	\& Symbols.event for the libevent emulation
		4007	.Ve
		4008	.PP
		4009	This can also be used to rename all public symbols to avoid clashes with
		4010	multiple versions of libev linked together (which is obviously bad in
		4011	itself, but sometimes it is inconvenient to avoid this).
		4012	.PP
		4013	A sed command like this will create wrapper \f(CW\(C`#define\(C'\fR's that you need to
		4014	include before including \fIev.h\fR:
		4015	.PP
		4016	.Vb 1
		4017	\& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h
		4018	.Ve
		4019	.PP
		4020	This would create a file \fIwrap.h\fR which essentially looks like this:
		4021	.PP
		4022	.Vb 4
		4023	\& #define ev_backend myprefix_ev_backend
		4024	\& #define ev_check_start myprefix_ev_check_start
		4025	\& #define ev_check_stop myprefix_ev_check_stop
		4026	\& ...
		4027	.Ve
2422	.Sh "\s-1EXAMPLES\s0"	4028	.SS "\s-1EXAMPLES\s0"
2423	.IX Subsection "EXAMPLES"	4029	.IX Subsection "EXAMPLES"
2424	For a real-world example of a program the includes libev	4030	For a real-world example of a program the includes libev
2425	verbatim, you can have a look at the \s-1EV\s0 perl module	4031	verbatim, you can have a look at the \s-1EV\s0 perl module
2426	(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in	4032	(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2427	the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public	4033	the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2428	interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file	4034	interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2429	will be compiled. It is pretty complex because it provides its own header	4035	will be compiled. It is pretty complex because it provides its own header
2430	file.	4036	file.
2431	.Sp	4037	.PP
2432	The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file	4038	The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2433	that everybody includes and which overrides some configure choices:	4039	that everybody includes and which overrides some configure choices:
2434	.Sp	4040	.PP
2435	.Vb 9	4041	.Vb 9
2436	\& #define EV_MINIMAL 1	4042	\& #define EV_MINIMAL 1
2437	\& #define EV_USE_POLL 0	4043	\& #define EV_USE_POLL 0
2438	\& #define EV_MULTIPLICITY 0	4044	\& #define EV_MULTIPLICITY 0
2439	\& #define EV_PERIODIC_ENABLE 0	4045	\& #define EV_PERIODIC_ENABLE 0
2440	\& #define EV_STAT_ENABLE 0	4046	\& #define EV_STAT_ENABLE 0
2441	\& #define EV_FORK_ENABLE 0	4047	\& #define EV_FORK_ENABLE 0
2442	\& #define EV_CONFIG_H <config.h>	4048	\& #define EV_CONFIG_H <config.h>
2443	\& #define EV_MINPRI 0	4049	\& #define EV_MINPRI 0
2444	\& #define EV_MAXPRI 0	4050	\& #define EV_MAXPRI 0
2445	.Ve	4051	\&
2446	.Sp
2447	.Vb 1
2448	\& #include "ev++.h"	4052	\& #include "ev++.h"
2449	.Ve	4053	.Ve
2450	.Sp	4054	.PP
2451	And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:	4055	And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2452	.Sp	4056	.PP
2453	.Vb 2	4057	.Vb 2
2454	\& #include "ev_cpp.h"	4058	\& #include "ev_cpp.h"
2455	\& #include "ev.c"	4059	\& #include "ev.c"
2456	.Ve	4060	.Ve
		4061	.SH "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES"
		4062	.IX Header "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES"
		4063	.SS "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0"
		4064	.IX Subsection "THREADS AND COROUTINES"
		4065	\fI\s-1THREADS\s0\fR
		4066	.IX Subsection "THREADS"
		4067	.PP
		4068	All libev functions are reentrant and thread-safe unless explicitly
		4069	documented otherwise, but libev implements no locking itself. This means
		4070	that you can use as many loops as you want in parallel, as long as there
		4071	are no concurrent calls into any libev function with the same loop
		4072	parameter (\f(CW\(C`ev_default_\*(C'\fR calls have an implicit default loop parameter,
		4073	of course): libev guarantees that different event loops share no data
		4074	structures that need any locking.
		4075	.PP
		4076	Or to put it differently: calls with different loop parameters can be done
		4077	concurrently from multiple threads, calls with the same loop parameter
		4078	must be done serially (but can be done from different threads, as long as
		4079	only one thread ever is inside a call at any point in time, e.g. by using
		4080	a mutex per loop).
		4081	.PP
		4082	Specifically to support threads (and signal handlers), libev implements
		4083	so-called \f(CW\(C`ev_async\(C'\fR watchers, which allow some limited form of
		4084	concurrency on the same event loop, namely waking it up \*(L"from the
		4085	outside\*(R".
		4086	.PP
		4087	If you want to know which design (one loop, locking, or multiple loops
		4088	without or something else still) is best for your problem, then I cannot
		4089	help you, but here is some generic advice:
		4090	.IP "\(bu" 4
		4091	most applications have a main thread: use the default libev loop
		4092	in that thread, or create a separate thread running only the default loop.
		4093	.Sp
		4094	This helps integrating other libraries or software modules that use libev
		4095	themselves and don't care/know about threading.
		4096	.IP "\(bu" 4
		4097	one loop per thread is usually a good model.
		4098	.Sp
		4099	Doing this is almost never wrong, sometimes a better-performance model
		4100	exists, but it is always a good start.
		4101	.IP "\(bu" 4
		4102	other models exist, such as the leader/follower pattern, where one
		4103	loop is handed through multiple threads in a kind of round-robin fashion.
		4104	.Sp
		4105	Choosing a model is hard \- look around, learn, know that usually you can do
		4106	better than you currently do :\-)
		4107	.IP "\(bu" 4
		4108	often you need to talk to some other thread which blocks in the
		4109	event loop.
		4110	.Sp
		4111	\&\f(CW\(C`ev_async\(C'\fR watchers can be used to wake them up from other threads safely
		4112	(or from signal contexts...).
		4113	.Sp
		4114	An example use would be to communicate signals or other events that only
		4115	work in the default loop by registering the signal watcher with the
		4116	default loop and triggering an \f(CW\(C`ev_async\(C'\fR watcher from the default loop
		4117	watcher callback into the event loop interested in the signal.
		4118	.PP
		4119	\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0
		4120	.IX Subsection "THREAD LOCKING EXAMPLE"
		4121	.PP
		4122	Here is a fictitious example of how to run an event loop in a different
		4123	thread than where callbacks are being invoked and watchers are
		4124	created/added/removed.
		4125	.PP
		4126	For a real-world example, see the \f(CW\(C`EV::Loop::Async\(C'\fR perl module,
		4127	which uses exactly this technique (which is suited for many high-level
		4128	languages).
		4129	.PP
		4130	The example uses a pthread mutex to protect the loop data, a condition
		4131	variable to wait for callback invocations, an async watcher to notify the
		4132	event loop thread and an unspecified mechanism to wake up the main thread.
		4133	.PP
		4134	First, you need to associate some data with the event loop:
		4135	.PP
		4136	.Vb 6
		4137	\& typedef struct {
		4138	\& mutex_t lock; /* global loop lock */
		4139	\& ev_async async_w;
		4140	\& thread_t tid;
		4141	\& cond_t invoke_cv;
		4142	\& } userdata;
		4143	\&
		4144	\& void prepare_loop (EV_P)
		4145	\& {
		4146	\& // for simplicity, we use a static userdata struct.
		4147	\& static userdata u;
		4148	\&
		4149	\& ev_async_init (&u\->async_w, async_cb);
		4150	\& ev_async_start (EV_A_ &u\->async_w);
		4151	\&
		4152	\& pthread_mutex_init (&u\->lock, 0);
		4153	\& pthread_cond_init (&u\->invoke_cv, 0);
		4154	\&
		4155	\& // now associate this with the loop
		4156	\& ev_set_userdata (EV_A_ u);
		4157	\& ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4158	\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4159	\&
		4160	\& // then create the thread running ev_loop
		4161	\& pthread_create (&u\->tid, 0, l_run, EV_A);
		4162	\& }
		4163	.Ve
		4164	.PP
		4165	The callback for the \f(CW\(C`ev_async\(C'\fR watcher does nothing: the watcher is used
		4166	solely to wake up the event loop so it takes notice of any new watchers
		4167	that might have been added:
		4168	.PP
		4169	.Vb 5
		4170	\& static void
		4171	\& async_cb (EV_P_ ev_async *w, int revents)
		4172	\& {
		4173	\& // just used for the side effects
		4174	\& }
		4175	.Ve
		4176	.PP
		4177	The \f(CW\(C`l_release\(C'\fR and \f(CW\(C`l_acquire\(C'\fR callbacks simply unlock/lock the mutex
		4178	protecting the loop data, respectively.
		4179	.PP
		4180	.Vb 6
		4181	\& static void
		4182	\& l_release (EV_P)
		4183	\& {
		4184	\& userdata *u = ev_userdata (EV_A);
		4185	\& pthread_mutex_unlock (&u\->lock);
		4186	\& }
		4187	\&
		4188	\& static void
		4189	\& l_acquire (EV_P)
		4190	\& {
		4191	\& userdata *u = ev_userdata (EV_A);
		4192	\& pthread_mutex_lock (&u\->lock);
		4193	\& }
		4194	.Ve
		4195	.PP
		4196	The event loop thread first acquires the mutex, and then jumps straight
		4197	into \f(CW\(C`ev_loop\(C'\fR:
		4198	.PP
		4199	.Vb 4
		4200	\& void *
		4201	\& l_run (void *thr_arg)
		4202	\& {
		4203	\& struct ev_loop loop = (struct ev_loop )thr_arg;
		4204	\&
		4205	\& l_acquire (EV_A);
		4206	\& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4207	\& ev_loop (EV_A_ 0);
		4208	\& l_release (EV_A);
		4209	\&
		4210	\& return 0;
		4211	\& }
		4212	.Ve
		4213	.PP
		4214	Instead of invoking all pending watchers, the \f(CW\(C`l_invoke\(C'\fR callback will
		4215	signal the main thread via some unspecified mechanism (signals? pipe
		4216	writes? \f(CW\(C`Async::Interrupt\(C'\fR?) and then waits until all pending watchers
		4217	have been called (in a while loop because a) spurious wakeups are possible
		4218	and b) skipping inter-thread-communication when there are no pending
		4219	watchers is very beneficial):
		4220	.PP
		4221	.Vb 4
		4222	\& static void
		4223	\& l_invoke (EV_P)
		4224	\& {
		4225	\& userdata *u = ev_userdata (EV_A);
		4226	\&
		4227	\& while (ev_pending_count (EV_A))
		4228	\& {
		4229	\& wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4230	\& pthread_cond_wait (&u\->invoke_cv, &u\->lock);
		4231	\& }
		4232	\& }
		4233	.Ve
		4234	.PP
		4235	Now, whenever the main thread gets told to invoke pending watchers, it
		4236	will grab the lock, call \f(CW\(C`ev_invoke_pending\(C'\fR and then signal the loop
		4237	thread to continue:
		4238	.PP
		4239	.Vb 4
		4240	\& static void
		4241	\& real_invoke_pending (EV_P)
		4242	\& {
		4243	\& userdata *u = ev_userdata (EV_A);
		4244	\&
		4245	\& pthread_mutex_lock (&u\->lock);
		4246	\& ev_invoke_pending (EV_A);
		4247	\& pthread_cond_signal (&u\->invoke_cv);
		4248	\& pthread_mutex_unlock (&u\->lock);
		4249	\& }
		4250	.Ve
		4251	.PP
		4252	Whenever you want to start/stop a watcher or do other modifications to an
		4253	event loop, you will now have to lock:
		4254	.PP
		4255	.Vb 2
		4256	\& ev_timer timeout_watcher;
		4257	\& userdata *u = ev_userdata (EV_A);
		4258	\&
		4259	\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4260	\&
		4261	\& pthread_mutex_lock (&u\->lock);
		4262	\& ev_timer_start (EV_A_ &timeout_watcher);
		4263	\& ev_async_send (EV_A_ &u\->async_w);
		4264	\& pthread_mutex_unlock (&u\->lock);
		4265	.Ve
		4266	.PP
		4267	Note that sending the \f(CW\(C`ev_async\(C'\fR watcher is required because otherwise
		4268	an event loop currently blocking in the kernel will have no knowledge
		4269	about the newly added timer. By waking up the loop it will pick up any new
		4270	watchers in the next event loop iteration.
		4271	.PP
		4272	\fI\s-1COROUTINES\s0\fR
		4273	.IX Subsection "COROUTINES"
		4274	.PP
		4275	Libev is very accommodating to coroutines (\(L"cooperative threads\(R"):
		4276	libev fully supports nesting calls to its functions from different
		4277	coroutines (e.g. you can call \f(CW\(C`ev_loop\(C'\fR on the same loop from two
		4278	different coroutines, and switch freely between both coroutines running
		4279	the loop, as long as you don't confuse yourself). The only exception is
		4280	that you must not do this from \f(CW\(C`ev_periodic\(C'\fR reschedule callbacks.
		4281	.PP
		4282	Care has been taken to ensure that libev does not keep local state inside
		4283	\&\f(CW\(C`ev_loop\(C'\fR, and other calls do not usually allow for coroutine switches as
		4284	they do not call any callbacks.
		4285	.SS "\s-1COMPILER\s0 \s-1WARNINGS\s0"
		4286	.IX Subsection "COMPILER WARNINGS"
		4287	Depending on your compiler and compiler settings, you might get no or a
		4288	lot of warnings when compiling libev code. Some people are apparently
		4289	scared by this.
		4290	.PP
		4291	However, these are unavoidable for many reasons. For one, each compiler
		4292	has different warnings, and each user has different tastes regarding
		4293	warning options. \(L"Warn-free\(R" code therefore cannot be a goal except when
		4294	targeting a specific compiler and compiler-version.
		4295	.PP
		4296	Another reason is that some compiler warnings require elaborate
		4297	workarounds, or other changes to the code that make it less clear and less
		4298	maintainable.
		4299	.PP
		4300	And of course, some compiler warnings are just plain stupid, or simply
		4301	wrong (because they don't actually warn about the condition their message
		4302	seems to warn about). For example, certain older gcc versions had some
		4303	warnings that resulted an extreme number of false positives. These have
		4304	been fixed, but some people still insist on making code warn-free with
		4305	such buggy versions.
		4306	.PP
		4307	While libev is written to generate as few warnings as possible,
		4308	\&\(L"warn-free\(R" code is not a goal, and it is recommended not to build libev
		4309	with any compiler warnings enabled unless you are prepared to cope with
		4310	them (e.g. by ignoring them). Remember that warnings are just that:
		4311	warnings, not errors, or proof of bugs.
		4312	.SS "\s-1VALGRIND\s0"
		4313	.IX Subsection "VALGRIND"
		4314	Valgrind has a special section here because it is a popular tool that is
		4315	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		4316	.PP
		4317	If you think you found a bug (memory leak, uninitialised data access etc.)
		4318	in libev, then check twice: If valgrind reports something like:
		4319	.PP
		4320	.Vb 3
		4321	\& ==2274== definitely lost: 0 bytes in 0 blocks.
		4322	\& ==2274== possibly lost: 0 bytes in 0 blocks.
		4323	\& ==2274== still reachable: 256 bytes in 1 blocks.
		4324	.Ve
		4325	.PP
		4326	Then there is no memory leak, just as memory accounted to global variables
		4327	is not a memleak \- the memory is still being referenced, and didn't leak.
		4328	.PP
		4329	Similarly, under some circumstances, valgrind might report kernel bugs
		4330	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4331	although an acceptable workaround has been found here), or it might be
		4332	confused.
		4333	.PP
		4334	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		4335	make it into some kind of religion.
		4336	.PP
		4337	If you are unsure about something, feel free to contact the mailing list
		4338	with the full valgrind report and an explanation on why you think this
		4339	is a bug in libev (best check the archives, too :). However, don't be
		4340	annoyed when you get a brisk \(L"this is no bug\(R" answer and take the chance
		4341	of learning how to interpret valgrind properly.
		4342	.PP
		4343	If you need, for some reason, empty reports from valgrind for your project
		4344	I suggest using suppression lists.
		4345	.SH "PORTABILITY NOTES"
		4346	.IX Header "PORTABILITY NOTES"
		4347	.SS "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0"
		4348	.IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
		4349	Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
		4350	requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
		4351	model. Libev still offers limited functionality on this platform in
		4352	the form of the \f(CW\(C`EVBACKEND_SELECT\(C'\fR backend, and only supports socket
		4353	descriptors. This only applies when using Win32 natively, not when using
		4354	e.g. cygwin.
		4355	.PP
		4356	Lifting these limitations would basically require the full
		4357	re-implementation of the I/O system. If you are into these kinds of
		4358	things, then note that glib does exactly that for you in a very portable
		4359	way (note also that glib is the slowest event library known to man).
		4360	.PP
		4361	There is no supported compilation method available on windows except
		4362	embedding it into other applications.
		4363	.PP
		4364	Sensible signal handling is officially unsupported by Microsoft \- libev
		4365	tries its best, but under most conditions, signals will simply not work.
		4366	.PP
		4367	Not a libev limitation but worth mentioning: windows apparently doesn't
		4368	accept large writes: instead of resulting in a partial write, windows will
		4369	either accept everything or return \f(CW\(C`ENOBUFS\(C'\fR if the buffer is too large,
		4370	so make sure you only write small amounts into your sockets (less than a
		4371	megabyte seems safe, but this apparently depends on the amount of memory
		4372	available).
		4373	.PP
		4374	Due to the many, low, and arbitrary limits on the win32 platform and
		4375	the abysmal performance of winsockets, using a large number of sockets
		4376	is not recommended (and not reasonable). If your program needs to use
		4377	more than a hundred or so sockets, then likely it needs to use a totally
		4378	different implementation for windows, as libev offers the \s-1POSIX\s0 readiness
		4379	notification model, which cannot be implemented efficiently on windows
		4380	(due to Microsoft monopoly games).
		4381	.PP
		4382	A typical way to use libev under windows is to embed it (see the embedding
		4383	section for details) and use the following \fIevwrap.h\fR header file instead
		4384	of \fIev.h\fR:
		4385	.PP
		4386	.Vb 2
		4387	\& #define EV_STANDALONE /* keeps ev from requiring config.h */
		4388	\& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4389	\&
		4390	\& #include "ev.h"
		4391	.Ve
		4392	.PP
		4393	And compile the following \fIevwrap.c\fR file into your project (make sure
		4394	you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!):
		4395	.PP
		4396	.Vb 2
		4397	\& #include "evwrap.h"
		4398	\& #include "ev.c"
		4399	.Ve
		4400	.IP "The winsocket select function" 4
		4401	.IX Item "The winsocket select function"
		4402	The winsocket \f(CW\(C`select\(C'\fR function doesn't follow \s-1POSIX\s0 in that it
		4403	requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is
		4404	also extremely buggy). This makes select very inefficient, and also
		4405	requires a mapping from file descriptors to socket handles (the Microsoft
		4406	C runtime provides the function \f(CW\(C`_open_osfhandle\(C'\fR for this). See the
		4407	discussion of the \f(CW\(C`EV_SELECT_USE_FD_SET\(C'\fR, \f(CW\(C`EV_SELECT_IS_WINSOCKET\(C'\fR and
		4408	\&\f(CW\(C`EV_FD_TO_WIN32_HANDLE\(C'\fR preprocessor symbols for more info.
		4409	.Sp
		4410	The configuration for a \(L"naked\(R" win32 using the Microsoft runtime
		4411	libraries and raw winsocket select is:
		4412	.Sp
		4413	.Vb 2
		4414	\& #define EV_USE_SELECT 1
		4415	\& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		4416	.Ve
		4417	.Sp
		4418	Note that winsockets handling of fd sets is O(n), so you can easily get a
		4419	complexity in the O(nA\*^X) range when using win32.
		4420	.IP "Limited number of file descriptors" 4
		4421	.IX Item "Limited number of file descriptors"
		4422	Windows has numerous arbitrary (and low) limits on things.
		4423	.Sp
		4424	Early versions of winsocket's select only supported waiting for a maximum
		4425	of \f(CW64\fR handles (probably owning to the fact that all windows kernels
		4426	can only wait for \f(CW64\fR things at the same time internally; Microsoft
		4427	recommends spawning a chain of threads and wait for 63 handles and the
		4428	previous thread in each. Sounds great!).
		4429	.Sp
		4430	Newer versions support more handles, but you need to define \f(CW\(C`FD_SETSIZE\(C'\fR
		4431	to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
		4432	call (which might be in libev or elsewhere, for example, perl and many
		4433	other interpreters do their own select emulation on windows).
		4434	.Sp
		4435	Another limit is the number of file descriptors in the Microsoft runtime
		4436	libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR
		4437	fetish or something like this inside Microsoft). You can increase this
		4438	by calling \f(CW\(C`_setmaxstdio\(C'\fR, which can increase this limit to \f(CW2048\fR
		4439	(another arbitrary limit), but is broken in many versions of the Microsoft
		4440	runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets
		4441	(depending on windows version and/or the phase of the moon). To get more,
		4442	you need to wrap all I/O functions and provide your own fd management, but
		4443	the cost of calling select (O(nA\*^X)) will likely make this unworkable.
		4444	.SS "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\s0"
		4445	.IX Subsection "PORTABILITY REQUIREMENTS"
		4446	In addition to a working ISO-C implementation and of course the
		4447	backend-specific APIs, libev relies on a few additional extensions:
		4448	.ie n .IP """void ()(ev_watcher_type , int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4
		4449	.el .IP "\f(CWvoid ()(ev_watcher_type , int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4
		4450	.IX Item "void ()(ev_watcher_type , int revents) must have compatible calling conventions regardless of ev_watcher_type *."
		4451	Libev assumes not only that all watcher pointers have the same internal
		4452	structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also
		4453	assumes that the same (machine) code can be used to call any watcher
		4454	callback: The watcher callbacks have different type signatures, but libev
		4455	calls them using an \f(CW\(C`ev_watcher \*(C'\fR internally.
		4456	.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4
		4457	.el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4
		4458	.IX Item "sig_atomic_t volatile must be thread-atomic as well"
		4459	The type \f(CW\(C`sig_atomic_t volatile\(C'\fR (or whatever is defined as
		4460	\&\f(CW\(C`EV_ATOMIC_T\(C'\fR) must be atomic with respect to accesses from different
		4461	threads. This is not part of the specification for \f(CW\(C`sig_atomic_t\(C'\fR, but is
		4462	believed to be sufficiently portable.
		4463	.ie n .IP """sigprocmask"" must work in a threaded environment" 4
		4464	.el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4
		4465	.IX Item "sigprocmask must work in a threaded environment"
		4466	Libev uses \f(CW\(C`sigprocmask\(C'\fR to temporarily block signals. This is not
		4467	allowed in a threaded program (\f(CW\(C`pthread_sigmask\(C'\fR has to be used). Typical
		4468	pthread implementations will either allow \f(CW\(C`sigprocmask\(C'\fR in the \*(L"main
		4469	thread\*(R" or will block signals process-wide, both behaviours would
		4470	be compatible with libev. Interaction between \f(CW\(C`sigprocmask\(C'\fR and
		4471	\&\f(CW\(C`pthread_sigmask\(C'\fR could complicate things, however.
		4472	.Sp
		4473	The most portable way to handle signals is to block signals in all threads
		4474	except the initial one, and run the default loop in the initial thread as
		4475	well.
		4476	.ie n .IP """long"" must be large enough for common memory allocation sizes" 4
		4477	.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
		4478	.IX Item "long must be large enough for common memory allocation sizes"
		4479	To improve portability and simplify its \s-1API\s0, libev uses \f(CW\(C`long\(C'\fR internally
		4480	instead of \f(CW\(C`size_t\(C'\fR when allocating its data structures. On non-POSIX
		4481	systems (Microsoft...) this might be unexpectedly low, but is still at
		4482	least 31 bits everywhere, which is enough for hundreds of millions of
		4483	watchers.
		4484	.ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4
		4485	.el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4
		4486	.IX Item "double must hold a time value in seconds with enough accuracy"
		4487	The type \f(CW\(C`double\(C'\fR is used to represent timestamps. It is required to
		4488	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4489	enough for at least into the year 4000. This requirement is fulfilled by
		4490	implementations implementing \s-1IEEE\s0 754, which is basically all existing
		4491	ones. With \s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least
		4492	2200.
		4493	.PP
		4494	If you know of other additional requirements drop me a note.
2457	.SH "COMPLEXITIES"	4495	.SH "ALGORITHMIC COMPLEXITIES"
2458	.IX Header "COMPLEXITIES"	4496	.IX Header "ALGORITHMIC COMPLEXITIES"
2459	In this section the complexities of (many of) the algorithms used inside	4497	In this section the complexities of (many of) the algorithms used inside
2460	libev will be explained. For complexity discussions about backends see the	4498	libev will be documented. For complexity discussions about backends see
2461	documentation for \f(CW\(C`ev_default_init\(C'\fR.	4499	the documentation for \f(CW\(C`ev_default_init\(C'\fR.
2462	.Sp	4500	.PP
2463	All of the following are about amortised time: If an array needs to be	4501	All of the following are about amortised time: If an array needs to be
2464	extended, libev needs to realloc and move the whole array, but this	4502	extended, libev needs to realloc and move the whole array, but this
2465	happens asymptotically never with higher number of elements, so O(1) might	4503	happens asymptotically rarer with higher number of elements, so O(1) might
2466	mean it might do a lengthy realloc operation in rare cases, but on average	4504	mean that libev does a lengthy realloc operation in rare cases, but on
2467	it is much faster and asymptotically approaches constant time.	4505	average it is much faster and asymptotically approaches constant time.
2468	.RS 4
2469	.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4	4506	.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2470	.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"	4507	.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2471	This means that, when you have a watcher that triggers in one hour and	4508	This means that, when you have a watcher that triggers in one hour and
2472	there are 100 watchers that would trigger before that then inserting will	4509	there are 100 watchers that would trigger before that, then inserting will
2473	have to skip those 100 watchers.	4510	have to skip roughly seven (\f(CW\(C`ld 100\(C'\fR) of these watchers.
2474	.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4	4511	.IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4
2475	.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"	4512	.IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)"
2476	That means that for changing a timer costs less than removing/adding them	4513	That means that changing a timer costs less than removing/adding them,
2477	as only the relative motion in the event queue has to be paid for.	4514	as only the relative motion in the event queue has to be paid for.
2478	.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4	4515	.IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4
2479	.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"	4516	.IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)"
2480	These just add the watcher into an array or at the head of a list.	4517	These just add the watcher into an array or at the head of a list.
		4518	.IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4
2481	=item Stopping check/prepare/idle watchers: O(1)	4519	.IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)"
		4520	.PD 0
2482	.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4	4521	.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2483	.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"	4522	.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
		4523	.PD
2484	These watchers are stored in lists then need to be walked to find the	4524	These watchers are stored in lists, so they need to be walked to find the
2485	correct watcher to remove. The lists are usually short (you don't usually	4525	correct watcher to remove. The lists are usually short (you don't usually
2486	have many watchers waiting for the same fd or signal).	4526	have many watchers waiting for the same fd or signal: one is typical, two
		4527	is rare).
2487	.IP "Finding the next timer per loop iteration: O(1)" 4	4528	.IP "Finding the next timer in each loop iteration: O(1)" 4
2488	.IX Item "Finding the next timer per loop iteration: O(1)"	4529	.IX Item "Finding the next timer in each loop iteration: O(1)"
2489	.PD 0	4530	By virtue of using a binary or 4\-heap, the next timer is always found at a
		4531	fixed position in the storage array.
2490	.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4	4532	.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2491	.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"	4533	.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2492	.PD
2493	A change means an I/O watcher gets started or stopped, which requires	4534	A change means an I/O watcher gets started or stopped, which requires
2494	libev to recalculate its status (and possibly tell the kernel).	4535	libev to recalculate its status (and possibly tell the kernel, depending
2495	.IP "Activating one watcher: O(1)" 4	4536	on backend and whether \f(CW\(C`ev_io_set\(C'\fR was used).
2496	.IX Item "Activating one watcher: O(1)"	4537	.IP "Activating one watcher (putting it into the pending state): O(1)" 4
		4538	.IX Item "Activating one watcher (putting it into the pending state): O(1)"
2497	.PD 0	4539	.PD 0
2498	.IP "Priority handling: O(number_of_priorities)" 4	4540	.IP "Priority handling: O(number_of_priorities)" 4
2499	.IX Item "Priority handling: O(number_of_priorities)"	4541	.IX Item "Priority handling: O(number_of_priorities)"
2500	.PD	4542	.PD
2501	Priorities are implemented by allocating some space for each	4543	Priorities are implemented by allocating some space for each
2502	priority. When doing priority-based operations, libev usually has to	4544	priority. When doing priority-based operations, libev usually has to
2503	linearly search all the priorities.	4545	linearly search all the priorities, but starting/stopping and activating
2504	.RE	4546	watchers becomes O(1) with respect to priority handling.
2505	.RS 4	4547	.IP "Sending an ev_async: O(1)" 4
		4548	.IX Item "Sending an ev_async: O(1)"
		4549	.PD 0
		4550	.IP "Processing ev_async_send: O(number_of_async_watchers)" 4
		4551	.IX Item "Processing ev_async_send: O(number_of_async_watchers)"
		4552	.IP "Processing signals: O(max_signal_number)" 4
		4553	.IX Item "Processing signals: O(max_signal_number)"
		4554	.PD
		4555	Sending involves a system call \fIiff\fR there were no other \f(CW\(C`ev_async_send\(C'\fR
		4556	calls in the current loop iteration. Checking for async and signal events
		4557	involves iterating over all running async watchers or all signal numbers.
		4558	.SH "GLOSSARY"
		4559	.IX Header "GLOSSARY"
		4560	.IP "active" 4
		4561	.IX Item "active"
		4562	A watcher is active as long as it has been started (has been attached to
		4563	an event loop) but not yet stopped (disassociated from the event loop).
		4564	.IP "application" 4
		4565	.IX Item "application"
		4566	In this document, an application is whatever is using libev.
		4567	.IP "callback" 4
		4568	.IX Item "callback"
		4569	The address of a function that is called when some event has been
		4570	detected. Callbacks are being passed the event loop, the watcher that
		4571	received the event, and the actual event bitset.
		4572	.IP "callback invocation" 4
		4573	.IX Item "callback invocation"
		4574	The act of calling the callback associated with a watcher.
		4575	.IP "event" 4
		4576	.IX Item "event"
		4577	A change of state of some external event, such as data now being available
		4578	for reading on a file descriptor, time having passed or simply not having
		4579	any other events happening anymore.
		4580	.Sp
		4581	In libev, events are represented as single bits (such as \f(CW\(C`EV_READ\(C'\fR or
		4582	\&\f(CW\(C`EV_TIMEOUT\(C'\fR).
		4583	.IP "event library" 4
		4584	.IX Item "event library"
		4585	A software package implementing an event model and loop.
		4586	.IP "event loop" 4
		4587	.IX Item "event loop"
		4588	An entity that handles and processes external events and converts them
		4589	into callback invocations.
		4590	.IP "event model" 4
		4591	.IX Item "event model"
		4592	The model used to describe how an event loop handles and processes
		4593	watchers and events.
		4594	.IP "pending" 4
		4595	.IX Item "pending"
		4596	A watcher is pending as soon as the corresponding event has been detected,
		4597	and stops being pending as soon as the watcher will be invoked or its
		4598	pending status is explicitly cleared by the application.
		4599	.Sp
		4600	A watcher can be pending, but not active. Stopping a watcher also clears
		4601	its pending status.
		4602	.IP "real time" 4
		4603	.IX Item "real time"
		4604	The physical time that is observed. It is apparently strictly monotonic :)
		4605	.IP "wall-clock time" 4
		4606	.IX Item "wall-clock time"
		4607	The time and date as shown on clocks. Unlike real time, it can actually
		4608	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4609	clock.
		4610	.IP "watcher" 4
		4611	.IX Item "watcher"
		4612	A data structure that describes interest in certain events. Watchers need
		4613	to be started (attached to an event loop) before they can receive events.
		4614	.IP "watcher invocation" 4
		4615	.IX Item "watcher invocation"
		4616	The act of calling the callback associated with a watcher.
2506	.SH "AUTHOR"	4617	.SH "AUTHOR"
2507	.IX Header "AUTHOR"	4618	.IX Header "AUTHOR"
2508	Marc Lehmann <libev@schmorp.de>.	4619	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.

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Comparing libev/ev.3 (file contents): Revision 1.42 by root, Fri Dec 7 20:19:16 2007 UTC vs. Revision 1.80 by root, Sun Aug 9 12:34:46 2009 UTC

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Comparing libev/ev.3 (file contents):
Revision 1.42 by root, Fri Dec 7 20:19:16 2007 UTC vs.
Revision 1.80 by root, Sun Aug 9 12:34:46 2009 UTC