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Revision 1.265 by root, Wed Aug 26 17:11:42 2009 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
103	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	132	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	133	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
121		136
122	=head1 ERROR HANDLING	137	=head1 ERROR HANDLING
123		138
…		…
178	not a problem.	193	not a problem.
179		194
180	Example: Make sure we haven't accidentally been linked against the wrong	195	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	196	version.
182		197
183	assert (("libev version mismatch",	198	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	199	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	200	&& ev_version_minor () >= EV_VERSION_MINOR));
186		201
187	=item unsigned int ev_supported_backends ()	202	=item unsigned int ev_supported_backends ()
188		203
189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	204	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
190	value) compiled into this binary of libev (independent of their	205	value) compiled into this binary of libev (independent of their
…		…
192	a description of the set values.	207	a description of the set values.
193		208
194	Example: make sure we have the epoll method, because yeah this is cool and	209	Example: make sure we have the epoll method, because yeah this is cool and
195	a must have and can we have a torrent of it please!!!11	210	a must have and can we have a torrent of it please!!!11
196		211
197	assert (("sorry, no epoll, no sex",	212	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	213	ev_supported_backends () & EVBACKEND_EPOLL));
199		214
200	=item unsigned int ev_recommended_backends ()	215	=item unsigned int ev_recommended_backends ()
201		216
202	Return the set of all backends compiled into this binary of libev and also	217	Return the set of all backends compiled into this binary of libev and also
203	recommended for this platform. This set is often smaller than the one	218	recommended for this platform. This set is often smaller than the one
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	230	recommended ones.
216		231
217	See the description of C<ev_embed> watchers for more info.	232	See the description of C<ev_embed> watchers for more info.
218		233
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		235
221	Sets the allocation function to use (the prototype is similar - the	236	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	238	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	239	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	265	}
251		266
252	...	267	...
253	ev_set_allocator (persistent_realloc);	268	ev_set_allocator (persistent_realloc);
254		269
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		271
257	Set the callback function to call on a retryable system call error (such	272	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	273	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	274	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	275	callback is set, then libev will expect it to remedy the situation, no
…		…
276		291
277	=back	292	=back
278		293
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		295
281	An event loop is described by a C<struct ev_loop *>. The library knows two	296	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	297	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	298	I<function>).
		299
		300	The library knows two types of such loops, the I<default> loop, which
		301	supports signals and child events, and dynamically created loops which do
		302	not.
284		303
285	=over 4	304	=over 4
286		305
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		307
…		…
294	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
295	function.	314	function.
296		315
297	Note that this function is I<not> thread-safe, so if you want to use it	316	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	317	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
300		319
301	The default loop is the only loop that can handle C<ev_signal> and	320	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	321	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	322	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_NOSIGNALFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
		382
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		384
351	This is your standard select(2) backend. Not I<completely> standard, as	385	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	386	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	387	but if that fails, expect a fairly low limit on the number of fds when
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	393	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	394	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	395	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	396	readiness notifications you get per iteration.
363		397
		398	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		399	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		400	C<exceptfds> set on that platform).
		401
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	402	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		403
366	And this is your standard poll(2) backend. It's more complicated	404	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	405	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	406	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	407	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	408	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	409	performance tips.
372		410
		411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		413
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		415
375	For few fds, this backend is a bit little slower than poll and select,	416	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	417	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	418	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	419	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	420
380	cases and requiring a system call per fd change, no fork support and bad	421	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	422	of the more advanced event mechanisms: mere annoyances include silently
		423	dropping file descriptors, requiring a system call per change per file
		424	descriptor (and unnecessary guessing of parameters), problems with dup and
		425	so on. The biggest issue is fork races, however - if a program forks then
		426	I<both> parent and child process have to recreate the epoll set, which can
		427	take considerable time (one syscall per file descriptor) and is of course
		428	hard to detect.
		429
		430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		431	of course I<doesn't>, and epoll just loves to report events for totally
		432	I<different> file descriptors (even already closed ones, so one cannot
		433	even remove them from the set) than registered in the set (especially
		434	on SMP systems). Libev tries to counter these spurious notifications by
		435	employing an additional generation counter and comparing that against the
		436	events to filter out spurious ones, recreating the set when required.
382		437
383	While stopping, setting and starting an I/O watcher in the same iteration	438	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	439	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	440	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	441	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	442	file descriptors might not work very well if you register events for both
388		443	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		444
393	Best performance from this backend is achieved by not unregistering all	445	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	446	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	447	i.e. keep at least one watcher active per fd at all times. Stopping and
		448	starting a watcher (without re-setting it) also usually doesn't cause
		449	extra overhead. A fork can both result in spurious notifications as well
		450	as in libev having to destroy and recreate the epoll object, which can
		451	take considerable time and thus should be avoided.
		452
		453	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		454	faster than epoll for maybe up to a hundred file descriptors, depending on
		455	the usage. So sad.
396		456
397	While nominally embeddable in other event loops, this feature is broken in	457	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	458	all kernel versions tested so far.
		459
		460	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		461	C<EVBACKEND_POLL>.
399		462
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	463	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		464
402	Kqueue deserves special mention, as at the time of this writing, it	465	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	466	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	467	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	468	it's completely useless). Unlike epoll, however, whose brokenness
		469	is by design, these kqueue bugs can (and eventually will) be fixed
		470	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	471	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	472	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	473	system like NetBSD.
409		474
410	You still can embed kqueue into a normal poll or select backend and use it	475	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	476	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		478
414	It scales in the same way as the epoll backend, but the interface to the	479	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	480	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	481	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	482	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	483	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	484	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		485	cases
420		486
421	This backend usually performs well under most conditions.	487	This backend usually performs well under most conditions.
422		488
423	While nominally embeddable in other event loops, this doesn't work	489	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	490	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	491	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	492	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	493	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	494	also broken on OS X)) and, did I mention it, using it only for sockets.
		495
		496	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		497	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		498	C<NOTE_EOF>.
429		499
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	500	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		501
432	This is not implemented yet (and might never be, unless you send me an	502	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	503	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	516	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	517	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	518	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	519	might perform better.
450		520
451	On the positive side, ignoring the spurious readiness notifications, this	521	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	522	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	523	in all tests and is fully embeddable, which is a rare feat among the
		524	OS-specific backends (I vastly prefer correctness over speed hacks).
		525
		526	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		527	C<EVBACKEND_POLL>.
454		528
455	=item C<EVBACKEND_ALL>	529	=item C<EVBACKEND_ALL>
456		530
457	Try all backends (even potentially broken ones that wouldn't be tried	531	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	532	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		534
461	It is definitely not recommended to use this flag.	535	It is definitely not recommended to use this flag.
462		536
463	=back	537	=back
464		538
465	If one or more of these are or'ed into the flags value, then only these	539	If one or more of the backend flags are or'ed into the flags value,
466	backends will be tried (in the reverse order as listed here). If none are	540	then only these backends will be tried (in the reverse order as listed
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	541	here). If none are specified, all backends in C<ev_recommended_backends
		542	()> will be tried.
468		543
469	The most typical usage is like this:	544	Example: This is the most typical usage.
470		545
471	if (!ev_default_loop (0))	546	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		548
474	Restrict libev to the select and poll backends, and do not allow	549	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	550	environment settings to be taken into account:
476		551
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	552	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		553
479	Use whatever libev has to offer, but make sure that kqueue is used if	554	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	555	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	556	private event loop and only if you know the OS supports your types of
		557	fds):
482		558
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	559	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		560
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	561	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		562
487	Similar to C<ev_default_loop>, but always creates a new event loop that is	563	Similar to C<ev_default_loop>, but always creates a new event loop that is
488	always distinct from the default loop. Unlike the default loop, it cannot	564	always distinct from the default loop. Unlike the default loop, it cannot
…		…
493	libev with threads is indeed to create one loop per thread, and using the	569	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.	570	default loop in the "main" or "initial" thread.
495		571
496	Example: Try to create a event loop that uses epoll and nothing else.	572	Example: Try to create a event loop that uses epoll and nothing else.
497		573
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	574	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	575	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	576	fatal ("no epoll found here, maybe it hides under your chair");
501		577
502	=item ev_default_destroy ()	578	=item ev_default_destroy ()
503		579
504	Destroys the default loop again (frees all memory and kernel state	580	Destroys the default loop again (frees all memory and kernel state
505	etc.). None of the active event watchers will be stopped in the normal	581	etc.). None of the active event watchers will be stopped in the normal
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	583	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	584	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	585	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	586	for example).
511		587
512	Note that certain global state, such as signal state, will not be freed by	588	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	589	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	590	as signal and child watchers) would need to be stopped manually.
515		591
516	In general it is not advisable to call this function except in the	592	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	593	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	594	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	595	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		620
545	=item ev_loop_fork (loop)	621	=item ev_loop_fork (loop)
546		622
547	Like C<ev_default_fork>, but acts on an event loop created by	623	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	624	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	625	after fork that you want to re-use in the child, and how you do this is
		626	entirely your own problem.
550		627
551	=item int ev_is_default_loop (loop)	628	=item int ev_is_default_loop (loop)
552		629
553	Returns true when the given loop actually is the default loop, false otherwise.	630	Returns true when the given loop is, in fact, the default loop, and false
		631	otherwise.
554		632
555	=item unsigned int ev_loop_count (loop)	633	=item unsigned int ev_loop_count (loop)
556		634
557	Returns the count of loop iterations for the loop, which is identical to	635	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	636	the number of times libev did poll for new events. It starts at C<0> and
559	happily wraps around with enough iterations.	637	happily wraps around with enough iterations.
560		638
561	This value can sometimes be useful as a generation counter of sorts (it	639	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	640	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	641	C<ev_prepare> and C<ev_check> calls.
		642
		643	=item unsigned int ev_loop_depth (loop)
		644
		645	Returns the number of times C<ev_loop> was entered minus the number of
		646	times C<ev_loop> was exited, in other words, the recursion depth.
		647
		648	Outside C<ev_loop>, this number is zero. In a callback, this number is
		649	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		650	in which case it is higher.
		651
		652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		653	etc.), doesn't count as exit.
564		654
565	=item unsigned int ev_backend (loop)	655	=item unsigned int ev_backend (loop)
566		656
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	657	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	658	use.
…		…
573	received events and started processing them. This timestamp does not	663	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	664	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	665	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	666	event occurring (or more correctly, libev finding out about it).
577		667
		668	=item ev_now_update (loop)
		669
		670	Establishes the current time by querying the kernel, updating the time
		671	returned by C<ev_now ()> in the progress. This is a costly operation and
		672	is usually done automatically within C<ev_loop ()>.
		673
		674	This function is rarely useful, but when some event callback runs for a
		675	very long time without entering the event loop, updating libev's idea of
		676	the current time is a good idea.
		677
		678	See also L<The special problem of time updates> in the C<ev_timer> section.
		679
		680	=item ev_suspend (loop)
		681
		682	=item ev_resume (loop)
		683
		684	These two functions suspend and resume a loop, for use when the loop is
		685	not used for a while and timeouts should not be processed.
		686
		687	A typical use case would be an interactive program such as a game: When
		688	the user presses C<^Z> to suspend the game and resumes it an hour later it
		689	would be best to handle timeouts as if no time had actually passed while
		690	the program was suspended. This can be achieved by calling C<ev_suspend>
		691	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		692	C<ev_resume> directly afterwards to resume timer processing.
		693
		694	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		695	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		696	will be rescheduled (that is, they will lose any events that would have
		697	occured while suspended).
		698
		699	After calling C<ev_suspend> you B<must not> call I<any> function on the
		700	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		701	without a previous call to C<ev_suspend>.
		702
		703	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		704	event loop time (see C<ev_now_update>).
		705
578	=item ev_loop (loop, int flags)	706	=item ev_loop (loop, int flags)
579		707
580	Finally, this is it, the event handler. This function usually is called	708	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	709	after you initialised all your watchers and you want to start handling
582	events.	710	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	712	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	713	either no event watchers are active anymore or C<ev_unloop> was called.
586		714
587	Please note that an explicit C<ev_unloop> is usually better than	715	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	716	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	717	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	718	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	719	of relying on its watchers stopping correctly, that is truly a thing of
		720	beauty.
592		721
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	722	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	723	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	724	process in case there are no events and will return after one iteration of
		725	the loop.
596		726
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	727	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	728	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	729	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	730	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	731	user-registered callback will be called), and will return after one
		732	iteration of the loop.
		733
		734	This is useful if you are waiting for some external event in conjunction
		735	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	736	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	737	usually a better approach for this kind of thing.
604		738
605	Here are the gory details of what C<ev_loop> does:	739	Here are the gory details of what C<ev_loop> does:
606		740
607	- Before the first iteration, call any pending watchers.	741	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	742	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	743	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	744	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	745	- If we have been forked, detach and recreate the kernel state
		746	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	747	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	748	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	749	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	750	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	751	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	752	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	753	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	754	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	755	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	756	- Queue all expired timers.
622	- Queue all outstanding periodics.	757	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	758	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	759	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	760	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	761	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	762	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	763	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	768	anymore.
634		769
635	... queue jobs here, make sure they register event watchers as long	770	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	771	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	772	ev_loop (my_loop, 0);
638	... jobs done. yeah!	773	... jobs done or somebody called unloop. yeah!
639		774
640	=item ev_unloop (loop, how)	775	=item ev_unloop (loop, how)
641		776
642	Can be used to make a call to C<ev_loop> return early (but only after it	777	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	778	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	779	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	780	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		781
647	This "unloop state" will be cleared when entering C<ev_loop> again.	782	This "unloop state" will be cleared when entering C<ev_loop> again.
648		783
		784	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		785
649	=item ev_ref (loop)	786	=item ev_ref (loop)
650		787
651	=item ev_unref (loop)	788	=item ev_unref (loop)
652		789
653	Ref/unref can be used to add or remove a reference count on the event	790	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	791	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	792	count is nonzero, C<ev_loop> will not return on its own.
		793
656	a watcher you never unregister that should not keep C<ev_loop> from	794	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	795	from returning, call ev_unref() after starting, and ev_ref() before
		796	stopping it.
		797
658	example, libev itself uses this for its internal signal pipe: It is not	798	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	799	is not visible to the libev user and should not keep C<ev_loop> from
660	no event watchers registered by it are active. It is also an excellent	800	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	801	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	802	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	803	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	804	before, respectively. Note also that libev might stop watchers itself
		805	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		806	in the callback).
665		807
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	808	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	809	running when nothing else is active.
668		810
669	struct ev_signal exitsig;	811	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	812	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	813	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	814	evf_unref (loop);
673		815
674	Example: For some weird reason, unregister the above signal handler again.	816	Example: For some weird reason, unregister the above signal handler again.
675		817
676	ev_ref (loop);	818	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	819	ev_signal_stop (loop, &exitsig);
678		820
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	821	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		822
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	823	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		824
683	These advanced functions influence the time that libev will spend waiting	825	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	826	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	827	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		828	latency.
686		829
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	830	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	831	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	832	to increase efficiency of loop iterations (or to increase power-saving
		833	opportunities).
690		834
691	The background is that sometimes your program runs just fast enough to	835	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	836	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	837	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	838	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	839	overhead for the actual polling but can deliver many events at once.
696		840
697	By setting a higher I<io collect interval> you allow libev to spend more	841	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	842	time collecting I/O events, so you can handle more events per iteration,
699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	843	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	844	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	845	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		846	sleep time ensures that libev will not poll for I/O events more often then
		847	once per this interval, on average.
702		848
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	849	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	850	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	851	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	852	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	853	value will not introduce any overhead in libev.
708		854
709	Many (busy) programs can usually benefit by setting the I/O collect	855	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	856	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	857	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	858	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	859	as this approaches the timing granularity of most systems. Note that if
		860	you do transactions with the outside world and you can't increase the
		861	parallelity, then this setting will limit your transaction rate (if you
		862	need to poll once per transaction and the I/O collect interval is 0.01,
		863	then you can't do more than 100 transations per second).
		864
		865	Setting the I<timeout collect interval> can improve the opportunity for
		866	saving power, as the program will "bundle" timer callback invocations that
		867	are "near" in time together, by delaying some, thus reducing the number of
		868	times the process sleeps and wakes up again. Another useful technique to
		869	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		870	they fire on, say, one-second boundaries only.
		871
		872	Example: we only need 0.1s timeout granularity, and we wish not to poll
		873	more often than 100 times per second:
		874
		875	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		877
		878	=item ev_invoke_pending (loop)
		879
		880	This call will simply invoke all pending watchers while resetting their
		881	pending state. Normally, C<ev_loop> does this automatically when required,
		882	but when overriding the invoke callback this call comes handy.
		883
		884	=item int ev_pending_count (loop)
		885
		886	Returns the number of pending watchers - zero indicates that no watchers
		887	are pending.
		888
		889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		890
		891	This overrides the invoke pending functionality of the loop: Instead of
		892	invoking all pending watchers when there are any, C<ev_loop> will call
		893	this callback instead. This is useful, for example, when you want to
		894	invoke the actual watchers inside another context (another thread etc.).
		895
		896	If you want to reset the callback, use C<ev_invoke_pending> as new
		897	callback.
		898
		899	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		900
		901	Sometimes you want to share the same loop between multiple threads. This
		902	can be done relatively simply by putting mutex_lock/unlock calls around
		903	each call to a libev function.
		904
		905	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		906	wait for it to return. One way around this is to wake up the loop via
		907	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		908	and I<acquire> callbacks on the loop.
		909
		910	When set, then C<release> will be called just before the thread is
		911	suspended waiting for new events, and C<acquire> is called just
		912	afterwards.
		913
		914	Ideally, C<release> will just call your mutex_unlock function, and
		915	C<acquire> will just call the mutex_lock function again.
		916
		917	While event loop modifications are allowed between invocations of
		918	C<release> and C<acquire> (that's their only purpose after all), no
		919	modifications done will affect the event loop, i.e. adding watchers will
		920	have no effect on the set of file descriptors being watched, or the time
		921	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		922	to take note of any changes you made.
		923
		924	In theory, threads executing C<ev_loop> will be async-cancel safe between
		925	invocations of C<release> and C<acquire>.
		926
		927	See also the locking example in the C<THREADS> section later in this
		928	document.
		929
		930	=item ev_set_userdata (loop, void *data)
		931
		932	=item ev_userdata (loop)
		933
		934	Set and retrieve a single C<void *> associated with a loop. When
		935	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		936	C<0.>
		937
		938	These two functions can be used to associate arbitrary data with a loop,
		939	and are intended solely for the C<invoke_pending_cb>, C<release> and
		940	C<acquire> callbacks described above, but of course can be (ab-)used for
		941	any other purpose as well.
714		942
715	=item ev_loop_verify (loop)	943	=item ev_loop_verify (loop)
716		944
717	This function only does something when C<EV_VERIFY> support has been	945	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	946	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	947	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	948	is found to be inconsistent, it will print an error message to standard
		949	error and call C<abort ()>.
721		950
722	This can be used to catch bugs inside libev itself: under normal	951	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	952	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	953	data structures consistent.
725		954
726	=back	955	=back
727		956
728		957
729	=head1 ANATOMY OF A WATCHER	958	=head1 ANATOMY OF A WATCHER
730		959
		960	In the following description, uppercase C<TYPE> in names stands for the
		961	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		962	watchers and C<ev_io_start> for I/O watchers.
		963
731	A watcher is a structure that you create and register to record your	964	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	965	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	966	become readable, you would create an C<ev_io> watcher for that:
734		967
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	968	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	969	{
737	ev_io_stop (w);	970	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	971	ev_unloop (loop, EVUNLOOP_ALL);
739	}	972	}
740		973
741	struct ev_loop *loop = ev_default_loop (0);	974	struct ev_loop *loop = ev_default_loop (0);
		975
742	struct ev_io stdin_watcher;	976	ev_io stdin_watcher;
		977
743	ev_init (&stdin_watcher, my_cb);	978	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	980	ev_io_start (loop, &stdin_watcher);
		981
746	ev_loop (loop, 0);	982	ev_loop (loop, 0);
747		983
748	As you can see, you are responsible for allocating the memory for your	984	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	985	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	986	stack).
		987
		988	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		989	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		990
752	Each watcher structure must be initialised by a call to C<ev_init	991	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	992	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	993	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	994	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	995	is readable and/or writable).
757		996
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	997	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	998	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	999	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	1000	ev_TYPE_init (watcher *, callback, ...) >>.
762		1001
763	To make the watcher actually watch out for events, you have to start it	1002	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1003	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	1004	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1005	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		1006
768	As long as your watcher is active (has been started but not stopped) you	1007	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	1008	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	1009	reinitialise it or call its C<ev_TYPE_set> macro.
771		1010
772	Each and every callback receives the event loop pointer as first, the	1011	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	1012	registered watcher structure as second, and a bitset of received events as
774	third argument.	1013	third argument.
775		1014
…		…
833		1072
834	=item C<EV_ASYNC>	1073	=item C<EV_ASYNC>
835		1074
836	The given async watcher has been asynchronously notified (see C<ev_async>).	1075	The given async watcher has been asynchronously notified (see C<ev_async>).
837		1076
		1077	=item C<EV_CUSTOM>
		1078
		1079	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1080	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1081
838	=item C<EV_ERROR>	1082	=item C<EV_ERROR>
839		1083
840	An unspecified error has occurred, the watcher has been stopped. This might	1084	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	1085	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	1086	ran out of memory, a file descriptor was found to be closed or any other
		1087	problem. Libev considers these application bugs.
		1088
843	problem. You best act on it by reporting the problem and somehow coping	1089	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	1090	watcher being stopped. Note that well-written programs should not receive
		1091	an error ever, so when your watcher receives it, this usually indicates a
		1092	bug in your program.
845		1093
846	Libev will usually signal a few "dummy" events together with an error,	1094	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	1095	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	1096	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	1097	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	1098	programs, though, as the fd could already be closed and reused for another
		1099	thing, so beware.
851		1100
852	=back	1101	=back
853		1102
854	=head2 GENERIC WATCHER FUNCTIONS	1103	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		1104
859	=over 4	1105	=over 4
860		1106
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1107	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1108
…		…
868	which rolls both calls into one.	1114	which rolls both calls into one.
869		1115
870	You can reinitialise a watcher at any time as long as it has been stopped	1116	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1117	(or never started) and there are no pending events outstanding.
872		1118
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1119	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1120	int revents)>.
		1121
		1122	Example: Initialise an C<ev_io> watcher in two steps.
		1123
		1124	ev_io w;
		1125	ev_init (&w, my_cb);
		1126	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		1127
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		1129
878	This macro initialises the type-specific parts of a watcher. You need to	1130	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1131	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	1134	difference to the C<ev_init> macro).
883		1135
884	Although some watcher types do not have type-specific arguments	1136	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1137	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1138
		1139	See C<ev_init>, above, for an example.
		1140
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1141	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1142
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1143	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1144	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1145	a watcher. The same limitations apply, of course.
892		1146
		1147	Example: Initialise and set an C<ev_io> watcher in one step.
		1148
		1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1150
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		1152
895	Starts (activates) the given watcher. Only active watchers will receive	1153	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1154	events. If the watcher is already active nothing will happen.
897		1155
		1156	Example: Start the C<ev_io> watcher that is being abused as example in this
		1157	whole section.
		1158
		1159	ev_io_start (EV_DEFAULT_UC, &w);
		1160
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		1162
900	Stops the given watcher again (if active) and clears the pending	1163	Stops the given watcher if active, and clears the pending status (whether
		1164	the watcher was active or not).
		1165
901	status. It is possible that stopped watchers are pending (for example,	1166	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1167	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1168	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1169	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1170	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1171
907	=item bool ev_is_active (ev_TYPE *watcher)	1172	=item bool ev_is_active (ev_TYPE *watcher)
908		1173
909	Returns a true value iff the watcher is active (i.e. it has been started	1174	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1175	and not yet been stopped). As long as a watcher is active you must not modify
…		…
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1201	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1202	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1203	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1204	from being executed (except for C<ev_idle> watchers).
940		1205
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1206	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1207	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1208
949	You I<must not> change the priority of a watcher as long as it is active or	1209	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1210	pending.
951		1211
		1212	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1213	fine, as long as you do not mind that the priority value you query might
		1214	or might not have been clamped to the valid range.
		1215
952	The default priority used by watchers when no priority has been set is	1216	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1217	always C<0>, which is supposed to not be too high and not be too low :).
954		1218
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1219	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1220	priorities.
957	or might not have been adjusted to be within valid range.
958		1221
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1223
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1224	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1225	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1226	can deal with that fact, as both are simply passed through to the
		1227	callback.
964		1228
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1229	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1230
967	If the watcher is pending, this function returns clears its pending status	1231	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1232	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1233	watcher isn't pending it does nothing and returns C<0>.
970		1234
		1235	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1236	callback to be invoked, which can be accomplished with this function.
		1237
971	=back	1238	=back
972		1239
973		1240
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1242
976	Each watcher has, by default, a member C<void *data> that you can change	1243	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1244	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1245	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1246	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1247	member, you can also "subclass" the watcher type and provide your own
981	data:	1248	data:
982		1249
983	struct my_io	1250	struct my_io
984	{	1251	{
985	struct ev_io io;	1252	ev_io io;
986	int otherfd;	1253	int otherfd;
987	void *somedata;	1254	void *somedata;
988	struct whatever *mostinteresting;	1255	struct whatever *mostinteresting;
989	}	1256	};
		1257
		1258	...
		1259	struct my_io w;
		1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1261
991	And since your callback will be called with a pointer to the watcher, you	1262	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1263	can cast it back to your own type:
993		1264
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1265	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1266	{
996	struct my_io *w = (struct my_io *)w_;	1267	struct my_io *w = (struct my_io *)w_;
997	...	1268	...
998	}	1269	}
999		1270
1000	More interesting and less C-conformant ways of casting your callback type	1271	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1272	instead have been omitted.
1002		1273
1003	Another common scenario is having some data structure with multiple	1274	Another common scenario is to use some data structure with multiple
1004	watchers:	1275	embedded watchers:
1005		1276
1006	struct my_biggy	1277	struct my_biggy
1007	{	1278	{
1008	int some_data;	1279	int some_data;
1009	ev_timer t1;	1280	ev_timer t1;
1010	ev_timer t2;	1281	ev_timer t2;
1011	}	1282	}
1012		1283
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1284	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1285	complicated: Either you store the address of your C<my_biggy> struct
		1286	in the C<data> member of the watcher (for woozies), or you need to use
		1287	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1288	programmers):
1015		1289
1016	#include <stddef.h>	1290	#include <stddef.h>
1017		1291
1018	static void	1292	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1293	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1294	{
1021	struct my_biggy big = (struct my_biggy *	1295	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1296	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1297	}
1024		1298
1025	static void	1299	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1300	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1301	{
1028	struct my_biggy big = (struct my_biggy *	1302	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1303	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1304	}
		1305
		1306	=head2 WATCHER PRIORITY MODELS
		1307
		1308	Many event loops support I<watcher priorities>, which are usually small
		1309	integers that influence the ordering of event callback invocation
		1310	between watchers in some way, all else being equal.
		1311
		1312	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1313	description for the more technical details such as the actual priority
		1314	range.
		1315
		1316	There are two common ways how these these priorities are being interpreted
		1317	by event loops:
		1318
		1319	In the more common lock-out model, higher priorities "lock out" invocation
		1320	of lower priority watchers, which means as long as higher priority
		1321	watchers receive events, lower priority watchers are not being invoked.
		1322
		1323	The less common only-for-ordering model uses priorities solely to order
		1324	callback invocation within a single event loop iteration: Higher priority
		1325	watchers are invoked before lower priority ones, but they all get invoked
		1326	before polling for new events.
		1327
		1328	Libev uses the second (only-for-ordering) model for all its watchers
		1329	except for idle watchers (which use the lock-out model).
		1330
		1331	The rationale behind this is that implementing the lock-out model for
		1332	watchers is not well supported by most kernel interfaces, and most event
		1333	libraries will just poll for the same events again and again as long as
		1334	their callbacks have not been executed, which is very inefficient in the
		1335	common case of one high-priority watcher locking out a mass of lower
		1336	priority ones.
		1337
		1338	Static (ordering) priorities are most useful when you have two or more
		1339	watchers handling the same resource: a typical usage example is having an
		1340	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1341	timeouts. Under load, data might be received while the program handles
		1342	other jobs, but since timers normally get invoked first, the timeout
		1343	handler will be executed before checking for data. In that case, giving
		1344	the timer a lower priority than the I/O watcher ensures that I/O will be
		1345	handled first even under adverse conditions (which is usually, but not
		1346	always, what you want).
		1347
		1348	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1349	will only be executed when no same or higher priority watchers have
		1350	received events, they can be used to implement the "lock-out" model when
		1351	required.
		1352
		1353	For example, to emulate how many other event libraries handle priorities,
		1354	you can associate an C<ev_idle> watcher to each such watcher, and in
		1355	the normal watcher callback, you just start the idle watcher. The real
		1356	processing is done in the idle watcher callback. This causes libev to
		1357	continously poll and process kernel event data for the watcher, but when
		1358	the lock-out case is known to be rare (which in turn is rare :), this is
		1359	workable.
		1360
		1361	Usually, however, the lock-out model implemented that way will perform
		1362	miserably under the type of load it was designed to handle. In that case,
		1363	it might be preferable to stop the real watcher before starting the
		1364	idle watcher, so the kernel will not have to process the event in case
		1365	the actual processing will be delayed for considerable time.
		1366
		1367	Here is an example of an I/O watcher that should run at a strictly lower
		1368	priority than the default, and which should only process data when no
		1369	other events are pending:
		1370
		1371	ev_idle idle; // actual processing watcher
		1372	ev_io io; // actual event watcher
		1373
		1374	static void
		1375	io_cb (EV_P_ ev_io *w, int revents)
		1376	{
		1377	// stop the I/O watcher, we received the event, but
		1378	// are not yet ready to handle it.
		1379	ev_io_stop (EV_A_ w);
		1380
		1381	// start the idle watcher to ahndle the actual event.
		1382	// it will not be executed as long as other watchers
		1383	// with the default priority are receiving events.
		1384	ev_idle_start (EV_A_ &idle);
		1385	}
		1386
		1387	static void
		1388	idle_cb (EV_P_ ev_idle *w, int revents)
		1389	{
		1390	// actual processing
		1391	read (STDIN_FILENO, ...);
		1392
		1393	// have to start the I/O watcher again, as
		1394	// we have handled the event
		1395	ev_io_start (EV_P_ &io);
		1396	}
		1397
		1398	// initialisation
		1399	ev_idle_init (&idle, idle_cb);
		1400	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1401	ev_io_start (EV_DEFAULT_ &io);
		1402
		1403	In the "real" world, it might also be beneficial to start a timer, so that
		1404	low-priority connections can not be locked out forever under load. This
		1405	enables your program to keep a lower latency for important connections
		1406	during short periods of high load, while not completely locking out less
		1407	important ones.
1031		1408
1032		1409
1033	=head1 WATCHER TYPES	1410	=head1 WATCHER TYPES
1034		1411
1035	This section describes each watcher in detail, but will not repeat	1412	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1436	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1437	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1438	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1439	required if you know what you are doing).
1063		1440
1064	If you must do this, then force the use of a known-to-be-good backend	1441	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1442	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1443	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1444	descriptors for which non-blocking operation makes no sense (such as
		1445	files) - libev doesn't guarentee any specific behaviour in that case.
1067		1446
1068	Another thing you have to watch out for is that it is quite easy to	1447	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1448	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1449	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1450	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1451	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1452	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1453	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1454	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1455
1077	If you cannot run the fd in non-blocking mode (for example you should not	1456	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1457	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1458	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1459	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1460	does this on its own, so its quite safe to use). Some people additionally
		1461	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1462	indefinitely.
		1463
		1464	But really, best use non-blocking mode.
1082		1465
1083	=head3 The special problem of disappearing file descriptors	1466	=head3 The special problem of disappearing file descriptors
1084		1467
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1468	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1469	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1470	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1471	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1472	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1473	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1474	fact, a different file descriptor.
1092		1475
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1506	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1507	C<EVBACKEND_POLL>.
1125		1508
1126	=head3 The special problem of SIGPIPE	1509	=head3 The special problem of SIGPIPE
1127		1510
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1511	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1512	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1513	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1514	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1515
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1516	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1517	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1518	somewhere, as that would have given you a big clue).
1137		1519
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1525	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1526
1145	=item ev_io_set (ev_io *, int fd, int events)	1527	=item ev_io_set (ev_io *, int fd, int events)
1146		1528
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1529	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1530	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1531	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1532
1151	=item int fd [read-only]	1533	=item int fd [read-only]
1152		1534
1153	The file descriptor being watched.	1535	The file descriptor being watched.
1154		1536
…		…
1162		1544
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1545	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1546	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1547	attempt to read a whole line in the callback.
1166		1548
1167	static void	1549	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1550	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1551	{
1170	ev_io_stop (loop, w);	1552	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1553	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1554	}
1173		1555
1174	...	1556	...
1175	struct ev_loop *loop = ev_default_init (0);	1557	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1558	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1559	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1560	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1561	ev_loop (loop, 0);
1180		1562
1181		1563
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1564	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1565
1184	Timer watchers are simple relative timers that generate an event after a	1566	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1567	given time, and optionally repeating in regular intervals after that.
1186		1568
1187	The timers are based on real time, that is, if you register an event that	1569	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1570	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1571	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1573	monotonic clock option helps a lot here).
		1574
		1575	The callback is guaranteed to be invoked only I<after> its timeout has
		1576	passed (not I<at>, so on systems with very low-resolution clocks this
		1577	might introduce a small delay). If multiple timers become ready during the
		1578	same loop iteration then the ones with earlier time-out values are invoked
		1579	before ones of the same priority with later time-out values (but this is
		1580	no longer true when a callback calls C<ev_loop> recursively).
		1581
		1582	=head3 Be smart about timeouts
		1583
		1584	Many real-world problems involve some kind of timeout, usually for error
		1585	recovery. A typical example is an HTTP request - if the other side hangs,
		1586	you want to raise some error after a while.
		1587
		1588	What follows are some ways to handle this problem, from obvious and
		1589	inefficient to smart and efficient.
		1590
		1591	In the following, a 60 second activity timeout is assumed - a timeout that
		1592	gets reset to 60 seconds each time there is activity (e.g. each time some
		1593	data or other life sign was received).
		1594
		1595	=over 4
		1596
		1597	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1598
		1599	This is the most obvious, but not the most simple way: In the beginning,
		1600	start the watcher:
		1601
		1602	ev_timer_init (timer, callback, 60., 0.);
		1603	ev_timer_start (loop, timer);
		1604
		1605	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1606	and start it again:
		1607
		1608	ev_timer_stop (loop, timer);
		1609	ev_timer_set (timer, 60., 0.);
		1610	ev_timer_start (loop, timer);
		1611
		1612	This is relatively simple to implement, but means that each time there is
		1613	some activity, libev will first have to remove the timer from its internal
		1614	data structure and then add it again. Libev tries to be fast, but it's
		1615	still not a constant-time operation.
		1616
		1617	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1618
		1619	This is the easiest way, and involves using C<ev_timer_again> instead of
		1620	C<ev_timer_start>.
		1621
		1622	To implement this, configure an C<ev_timer> with a C<repeat> value
		1623	of C<60> and then call C<ev_timer_again> at start and each time you
		1624	successfully read or write some data. If you go into an idle state where
		1625	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1626	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1627
		1628	That means you can ignore both the C<ev_timer_start> function and the
		1629	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1630	member and C<ev_timer_again>.
		1631
		1632	At start:
		1633
		1634	ev_init (timer, callback);
		1635	timer->repeat = 60.;
		1636	ev_timer_again (loop, timer);
		1637
		1638	Each time there is some activity:
		1639
		1640	ev_timer_again (loop, timer);
		1641
		1642	It is even possible to change the time-out on the fly, regardless of
		1643	whether the watcher is active or not:
		1644
		1645	timer->repeat = 30.;
		1646	ev_timer_again (loop, timer);
		1647
		1648	This is slightly more efficient then stopping/starting the timer each time
		1649	you want to modify its timeout value, as libev does not have to completely
		1650	remove and re-insert the timer from/into its internal data structure.
		1651
		1652	It is, however, even simpler than the "obvious" way to do it.
		1653
		1654	=item 3. Let the timer time out, but then re-arm it as required.
		1655
		1656	This method is more tricky, but usually most efficient: Most timeouts are
		1657	relatively long compared to the intervals between other activity - in
		1658	our example, within 60 seconds, there are usually many I/O events with
		1659	associated activity resets.
		1660
		1661	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1662	but remember the time of last activity, and check for a real timeout only
		1663	within the callback:
		1664
		1665	ev_tstamp last_activity; // time of last activity
		1666
		1667	static void
		1668	callback (EV_P_ ev_timer *w, int revents)
		1669	{
		1670	ev_tstamp now = ev_now (EV_A);
		1671	ev_tstamp timeout = last_activity + 60.;
		1672
		1673	// if last_activity + 60. is older than now, we did time out
		1674	if (timeout < now)
		1675	{
		1676	// timeout occured, take action
		1677	}
		1678	else
		1679	{
		1680	// callback was invoked, but there was some activity, re-arm
		1681	// the watcher to fire in last_activity + 60, which is
		1682	// guaranteed to be in the future, so "again" is positive:
		1683	w->repeat = timeout - now;
		1684	ev_timer_again (EV_A_ w);
		1685	}
		1686	}
		1687
		1688	To summarise the callback: first calculate the real timeout (defined
		1689	as "60 seconds after the last activity"), then check if that time has
		1690	been reached, which means something I<did>, in fact, time out. Otherwise
		1691	the callback was invoked too early (C<timeout> is in the future), so
		1692	re-schedule the timer to fire at that future time, to see if maybe we have
		1693	a timeout then.
		1694
		1695	Note how C<ev_timer_again> is used, taking advantage of the
		1696	C<ev_timer_again> optimisation when the timer is already running.
		1697
		1698	This scheme causes more callback invocations (about one every 60 seconds
		1699	minus half the average time between activity), but virtually no calls to
		1700	libev to change the timeout.
		1701
		1702	To start the timer, simply initialise the watcher and set C<last_activity>
		1703	to the current time (meaning we just have some activity :), then call the
		1704	callback, which will "do the right thing" and start the timer:
		1705
		1706	ev_init (timer, callback);
		1707	last_activity = ev_now (loop);
		1708	callback (loop, timer, EV_TIMEOUT);
		1709
		1710	And when there is some activity, simply store the current time in
		1711	C<last_activity>, no libev calls at all:
		1712
		1713	last_actiivty = ev_now (loop);
		1714
		1715	This technique is slightly more complex, but in most cases where the
		1716	time-out is unlikely to be triggered, much more efficient.
		1717
		1718	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1719	callback :) - just change the timeout and invoke the callback, which will
		1720	fix things for you.
		1721
		1722	=item 4. Wee, just use a double-linked list for your timeouts.
		1723
		1724	If there is not one request, but many thousands (millions...), all
		1725	employing some kind of timeout with the same timeout value, then one can
		1726	do even better:
		1727
		1728	When starting the timeout, calculate the timeout value and put the timeout
		1729	at the I<end> of the list.
		1730
		1731	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1732	the list is expected to fire (for example, using the technique #3).
		1733
		1734	When there is some activity, remove the timer from the list, recalculate
		1735	the timeout, append it to the end of the list again, and make sure to
		1736	update the C<ev_timer> if it was taken from the beginning of the list.
		1737
		1738	This way, one can manage an unlimited number of timeouts in O(1) time for
		1739	starting, stopping and updating the timers, at the expense of a major
		1740	complication, and having to use a constant timeout. The constant timeout
		1741	ensures that the list stays sorted.
		1742
		1743	=back
		1744
		1745	So which method the best?
		1746
		1747	Method #2 is a simple no-brain-required solution that is adequate in most
		1748	situations. Method #3 requires a bit more thinking, but handles many cases
		1749	better, and isn't very complicated either. In most case, choosing either
		1750	one is fine, with #3 being better in typical situations.
		1751
		1752	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1753	rather complicated, but extremely efficient, something that really pays
		1754	off after the first million or so of active timers, i.e. it's usually
		1755	overkill :)
		1756
		1757	=head3 The special problem of time updates
		1758
		1759	Establishing the current time is a costly operation (it usually takes at
		1760	least two system calls): EV therefore updates its idea of the current
		1761	time only before and after C<ev_loop> collects new events, which causes a
		1762	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1763	lots of events in one iteration.
1192		1764
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1765	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1766	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1767	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1768	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1769	timeout on the current time, use something like this to adjust for this:
1198		1770
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1772
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1773	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1774	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1775	()>.
		1776
		1777	=head3 The special problems of suspended animation
		1778
		1779	When you leave the server world it is quite customary to hit machines that
		1780	can suspend/hibernate - what happens to the clocks during such a suspend?
		1781
		1782	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1783	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1784	to run until the system is suspended, but they will not advance while the
		1785	system is suspended. That means, on resume, it will be as if the program
		1786	was frozen for a few seconds, but the suspend time will not be counted
		1787	towards C<ev_timer> when a monotonic clock source is used. The real time
		1788	clock advanced as expected, but if it is used as sole clocksource, then a
		1789	long suspend would be detected as a time jump by libev, and timers would
		1790	be adjusted accordingly.
		1791
		1792	I would not be surprised to see different behaviour in different between
		1793	operating systems, OS versions or even different hardware.
		1794
		1795	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1796	time jump in the monotonic clocks and the realtime clock. If the program
		1797	is suspended for a very long time, and monotonic clock sources are in use,
		1798	then you can expect C<ev_timer>s to expire as the full suspension time
		1799	will be counted towards the timers. When no monotonic clock source is in
		1800	use, then libev will again assume a timejump and adjust accordingly.
		1801
		1802	It might be beneficial for this latter case to call C<ev_suspend>
		1803	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1804	deterministic behaviour in this case (you can do nothing against
		1805	C<SIGSTOP>).
1204		1806
1205	=head3 Watcher-Specific Functions and Data Members	1807	=head3 Watcher-Specific Functions and Data Members
1206		1808
1207	=over 4	1809	=over 4
1208		1810
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1834	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1835
1234	If the timer is repeating, either start it if necessary (with the	1836	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1837	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1838
1237	This sounds a bit complicated, but here is a useful and typical	1839	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1840	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246		1841
1247	That means you can ignore the C<after> value and C<ev_timer_start>	1842	=item ev_timer_remaining (loop, ev_timer *)
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249		1843
1250	ev_timer_init (timer, callback, 0., 5.);	1844	Returns the remaining time until a timer fires. If the timer is active,
1251	ev_timer_again (loop, timer);	1845	then this time is relative to the current event loop time, otherwise it's
1252	...	1846	the timeout value currently configured.
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258		1847
1259	This is more slightly efficient then stopping/starting the timer each time	1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1260	you want to modify its timeout value.	1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1850	will return C<4>. When the timer expires and is restarted, it will return
		1851	roughly C<7> (likely slightly less as callback invocation takes some time,
		1852	too), and so on.
1261		1853
1262	=item ev_tstamp repeat [read-write]	1854	=item ev_tstamp repeat [read-write]
1263		1855
1264	The current C<repeat> value. Will be used each time the watcher times out	1856	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1857	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1858	which is also when any modifications are taken into account.
1267		1859
1268	=back	1860	=back
1269		1861
1270	=head3 Examples	1862	=head3 Examples
1271		1863
1272	Example: Create a timer that fires after 60 seconds.	1864	Example: Create a timer that fires after 60 seconds.
1273		1865
1274	static void	1866	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1867	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1868	{
1277	.. one minute over, w is actually stopped right here	1869	.. one minute over, w is actually stopped right here
1278	}	1870	}
1279		1871
1280	struct ev_timer mytimer;	1872	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1873	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1874	ev_timer_start (loop, &mytimer);
1283		1875
1284	Example: Create a timeout timer that times out after 10 seconds of	1876	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1877	inactivity.
1286		1878
1287	static void	1879	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1880	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1881	{
1290	.. ten seconds without any activity	1882	.. ten seconds without any activity
1291	}	1883	}
1292		1884
1293	struct ev_timer mytimer;	1885	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1886	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1887	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1888	ev_loop (loop, 0);
1297		1889
1298	// and in some piece of code that gets executed on any "activity":	1890	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	1891	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	1892	ev_timer_again (&mytimer);
1301		1893
1302		1894
1303	=head2 C<ev_periodic> - to cron or not to cron?	1895	=head2 C<ev_periodic> - to cron or not to cron?
1304		1896
1305	Periodic watchers are also timers of a kind, but they are very versatile	1897	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	1898	(and unfortunately a bit complex).
1307		1899
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1900	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	1901	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	1902	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1903	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	1904	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	1905	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		1906
		1907	You can tell a periodic watcher to trigger after some specific point
		1908	in time: for example, if you tell a periodic watcher to trigger "in 10
		1909	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1910	not a delay) and then reset your system clock to January of the previous
		1911	year, then it will take a year or more to trigger the event (unlike an
		1912	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1913	it, as it uses a relative timeout).
		1914
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1915	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	1916	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	1917	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1918	those cannot react to time jumps.
1320		1919
1321	As with timers, the callback is guaranteed to be invoked only when the	1920	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1921	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	1922	timers become ready during the same loop iteration then the ones with
		1923	earlier time-out values are invoked before ones with later time-out values
		1924	(but this is no longer true when a callback calls C<ev_loop> recursively).
1324		1925
1325	=head3 Watcher-Specific Functions and Data Members	1926	=head3 Watcher-Specific Functions and Data Members
1326		1927
1327	=over 4	1928	=over 4
1328		1929
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1930	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		1931
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1932	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		1933
1333	Lots of arguments, lets sort it out... There are basically three modes of	1934	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1935	operation, and we will explain them from simplest to most complex:
1335		1936
1336	=over 4	1937	=over 4
1337		1938
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1939	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		1940
1340	In this configuration the watcher triggers an event after the wall clock	1941	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1942	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1943	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	1944	will be stopped and invoked when the system clock reaches or surpasses
		1945	this point in time.
1344		1946
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1947	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		1948
1347	In this mode the watcher will always be scheduled to time out at the next	1949	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1950	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	1951	negative) and then repeat, regardless of any time jumps. The C<offset>
		1952	argument is merely an offset into the C<interval> periods.
1350		1953
1351	This can be used to create timers that do not drift with respect to system	1954	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1955	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	1956	hour, on the hour (with respect to UTC):
1354		1957
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1958	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1959
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1960	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1961	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	1962	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	1963	by 3600.
1361		1964
1362	Another way to think about it (for the mathematically inclined) is that	1965	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	1966	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	1967	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		1968
1366	For numerical stability it is preferable that the C<at> value is near	1969	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	1970	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	1971	this value, and in fact is often specified as zero.
1369		1972
1370	Note also that there is an upper limit to how often a timer can fire (CPU	1973	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	1974	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	1975	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	1976	millisecond (if the OS supports it and the machine is fast enough).
1374		1977
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1978	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		1979
1377	In this mode the values for C<interval> and C<at> are both being	1980	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	1981	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	1982	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	1983	current time as second argument.
1381		1984
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1985	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	1986	or make ANY other event loop modifications whatsoever, unless explicitly
		1987	allowed by documentation here>.
1384		1988
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1989	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1990	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1991	only event loop modification you are allowed to do).
1388		1992
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1993	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1994	*w, ev_tstamp now)>, e.g.:
1391		1995
		1996	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1997	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1998	{
1394	return now + 60.;	1999	return now + 60.;
1395	}	2000	}
1396		2001
1397	It must return the next time to trigger, based on the passed time value	2002	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	2022	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	2023	program when the crontabs have changed).
1419		2024
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	2025	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		2026
1422	When active, returns the absolute time that the watcher is supposed to	2027	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	2028	to trigger next. This is not the same as the C<offset> argument to
		2029	C<ev_periodic_set>, but indeed works even in interval and manual
		2030	rescheduling modes.
1424		2031
1425	=item ev_tstamp offset [read-write]	2032	=item ev_tstamp offset [read-write]
1426		2033
1427	When repeating, this contains the offset value, otherwise this is the	2034	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2035	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2036	although libev might modify this value for better numerical stability).
1429		2037
1430	Can be modified any time, but changes only take effect when the periodic	2038	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	2039	timer fires or C<ev_periodic_again> is being called.
1432		2040
1433	=item ev_tstamp interval [read-write]	2041	=item ev_tstamp interval [read-write]
1434		2042
1435	The current interval value. Can be modified any time, but changes only	2043	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	2044	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	2045	called.
1438		2046
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2047	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		2048
1441	The current reschedule callback, or C<0>, if this functionality is	2049	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	2050	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	2051	the periodic timer fires or C<ev_periodic_again> is being called.
1444		2052
1445	=back	2053	=back
1446		2054
1447	=head3 Examples	2055	=head3 Examples
1448		2056
1449	Example: Call a callback every hour, or, more precisely, whenever the	2057	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	2058	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	2059	potentially a lot of jitter, but good long-term stability.
1452		2060
1453	static void	2061	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	2063	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	2064	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	2065	}
1458		2066
1459	struct ev_periodic hourly_tick;	2067	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2068	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	2069	ev_periodic_start (loop, &hourly_tick);
1462		2070
1463	Example: The same as above, but use a reschedule callback to do it:	2071	Example: The same as above, but use a reschedule callback to do it:
1464		2072
1465	#include <math.h>	2073	#include <math.h>
1466		2074
1467	static ev_tstamp	2075	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2076	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	2077	{
1470	return fmod (now, 3600.) + 3600.;	2078	return now + (3600. - fmod (now, 3600.));
1471	}	2079	}
1472		2080
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2081	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		2082
1475	Example: Call a callback every hour, starting now:	2083	Example: Call a callback every hour, starting now:
1476		2084
1477	struct ev_periodic hourly_tick;	2085	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	2086	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	2087	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	2088	ev_periodic_start (loop, &hourly_tick);
1481		2089
1482		2090
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	2091	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		2092
1485	Signal watchers will trigger an event when the process receives a specific	2093	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	2094	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	2095	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	2096	normal event processing, like any other event.
1489		2097
		2098	If you want signals to be delivered truly asynchronously, just use
		2099	C<sigaction> as you would do without libev and forget about sharing
		2100	the signal. You can even use C<ev_async> from a signal handler to
		2101	synchronously wake up an event loop.
		2102
1490	You can configure as many watchers as you like per signal. Only when the	2103	You can configure as many watchers as you like for the same signal, but
		2104	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2105	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2106	C<SIGINT> in both the default loop and another loop at the same time. At
		2107	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2108
1491	first watcher gets started will libev actually register a signal watcher	2109	When the first watcher gets started will libev actually register something
1492	with the kernel (thus it coexists with your own signal handlers as long	2110	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	2111	you don't register any with libev for the same signal).
1494	watcher for a signal is stopped libev will reset the signal handler to
1495	SIG_DFL (regardless of what it was set to before).
1496		2112
1497	If possible and supported, libev will install its handlers with	2113	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2114	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1499	interrupted. If you have a problem with system calls getting interrupted by	2115	not be unduly interrupted. If you have a problem with system calls getting
1500	signals you can block all signals in an C<ev_check> watcher and unblock	2116	interrupted by signals you can block all signals in an C<ev_check> watcher
1501	them in an C<ev_prepare> watcher.	2117	and unblock them in an C<ev_prepare> watcher.
		2118
		2119	=head3 The special problem of inheritance over execve
		2120
		2121	Both the signal mask (C<sigprocmask>) and the signal disposition
		2122	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2123	stopping it again), that is, libev might or might not block the signal,
		2124	and might or might not set or restore the installed signal handler.
		2125
		2126	While this does not matter for the signal disposition (libev never
		2127	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2128	C<execve>), this matters for the signal mask: many programs do not expect
		2129	many signals to be blocked.
		2130
		2131	This means that before calling C<exec> (from the child) you should reset
		2132	the signal mask to whatever "default" you expect (all clear is a good
		2133	choice usually).
1502		2134
1503	=head3 Watcher-Specific Functions and Data Members	2135	=head3 Watcher-Specific Functions and Data Members
1504		2136
1505	=over 4	2137	=over 4
1506		2138
…		…
1517		2149
1518	=back	2150	=back
1519		2151
1520	=head3 Examples	2152	=head3 Examples
1521		2153
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	2154	Example: Try to exit cleanly on SIGINT.
1523		2155
1524	static void	2156	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2157	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	2158	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	2159	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	2160	}
1529		2161
1530	struct ev_signal signal_watcher;	2162	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2163	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	2164	ev_signal_start (loop, &signal_watcher);
1533		2165
1534		2166
1535	=head2 C<ev_child> - watch out for process status changes	2167	=head2 C<ev_child> - watch out for process status changes
1536		2168
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2169	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2170	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2171	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2172	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2173	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2174	forking and then immediately registering a watcher for the child is fine,
		2175	but forking and registering a watcher a few event loop iterations later or
		2176	in the next callback invocation is not.
1542		2177
1543	Only the default event loop is capable of handling signals, and therefore	2178	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2179	you can only register child watchers in the default event loop.
1545		2180
		2181	Due to some design glitches inside libev, child watchers will always be
		2182	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2183	libev)
		2184
1546	=head3 Process Interaction	2185	=head3 Process Interaction
1547		2186
1548	Libev grabs C<SIGCHLD> as soon as the default event loop is	2187	Libev grabs C<SIGCHLD> as soon as the default event loop is
1549	initialised. This is necessary to guarantee proper behaviour even if	2188	initialised. This is necessary to guarantee proper behaviour even if the
1550	the first child watcher is started after the child exits. The occurrence	2189	first child watcher is started after the child exits. The occurrence
1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2190	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1552	synchronously as part of the event loop processing. Libev always reaps all	2191	synchronously as part of the event loop processing. Libev always reaps all
1553	children, even ones not watched.	2192	children, even ones not watched.
1554		2193
1555	=head3 Overriding the Built-In Processing	2194	=head3 Overriding the Built-In Processing
…		…
1559	handler, you can override it easily by installing your own handler for	2198	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2199	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2200	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2201	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2202	that, so other libev users can use C<ev_child> watchers freely.
		2203
		2204	=head3 Stopping the Child Watcher
		2205
		2206	Currently, the child watcher never gets stopped, even when the
		2207	child terminates, so normally one needs to stop the watcher in the
		2208	callback. Future versions of libev might stop the watcher automatically
		2209	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2210	problem).
1564		2211
1565	=head3 Watcher-Specific Functions and Data Members	2212	=head3 Watcher-Specific Functions and Data Members
1566		2213
1567	=over 4	2214	=over 4
1568		2215
…		…
1597	=head3 Examples	2244	=head3 Examples
1598		2245
1599	Example: C<fork()> a new process and install a child handler to wait for	2246	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	2247	its completion.
1601		2248
1602	ev_child cw;	2249	ev_child cw;
1603		2250
1604	static void	2251	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2252	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2253	{
1607	ev_child_stop (EV_A_ w);	2254	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2255	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2256	}
1610		2257
1611	pid_t pid = fork ();	2258	pid_t pid = fork ();
1612		2259
1613	if (pid < 0)	2260	if (pid < 0)
1614	// error	2261	// error
1615	else if (pid == 0)	2262	else if (pid == 0)
1616	{	2263	{
1617	// the forked child executes here	2264	// the forked child executes here
1618	exit (1);	2265	exit (1);
1619	}	2266	}
1620	else	2267	else
1621	{	2268	{
1622	ev_child_init (&cw, child_cb, pid, 0);	2269	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	2270	ev_child_start (EV_DEFAULT_ &cw);
1624	}	2271	}
1625		2272
1626		2273
1627	=head2 C<ev_stat> - did the file attributes just change?	2274	=head2 C<ev_stat> - did the file attributes just change?
1628		2275
1629	This watches a file system path for attribute changes. That is, it calls	2276	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2277	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2278	and sees if it changed compared to the last time, invoking the callback if
		2279	it did.
1632		2280
1633	The path does not need to exist: changing from "path exists" to "path does	2281	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2282	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2283	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2284	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2285	least one) and all the other fields of the stat buffer having unspecified
		2286	contents.
1638		2287
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2288	The path I<must not> end in a slash or contain special components such as
		2289	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2290	your working directory changes, then the behaviour is undefined.
1641		2291
1642	Since there is no standard to do this, the portable implementation simply	2292	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2293	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2294	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2295	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2296	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2297	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2298	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2299	currently around C<0.1>, but that's usually overkill.
1650		2300
1651	This watcher type is not meant for massive numbers of stat watchers,	2301	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2302	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2303	resource-intensive.
1654		2304
1655	At the time of this writing, only the Linux inotify interface is	2305	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2306	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2307	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2308	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2309
1664	=head3 ABI Issues (Largefile Support)	2310	=head3 ABI Issues (Largefile Support)
1665		2311
1666	Libev by default (unless the user overrides this) uses the default	2312	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2313	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2314	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2315	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2316	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2317	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2318	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2319	most noticeably displayed with ev_stat and large file support.
1674		2320
1675	=head3 Inotify	2321	The solution for this is to lobby your distribution maker to make large
		2322	file interfaces available by default (as e.g. FreeBSD does) and not
		2323	optional. Libev cannot simply switch on large file support because it has
		2324	to exchange stat structures with application programs compiled using the
		2325	default compilation environment.
1676		2326
		2327	=head3 Inotify and Kqueue
		2328
1677	When C<inotify (7)> support has been compiled into libev (generally only	2329	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2330	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2331	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2332	watcher is being started.
1681		2333
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2334	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2335	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2336	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2337	there are many cases where libev has to resort to regular C<stat> polling,
		2338	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2339	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2340	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2341	xfs are fully working) libev usually gets away without polling.
1686		2342
1687	(There is no support for kqueue, as apparently it cannot be used to	2343	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2344	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2345	descriptor open on the object at all times, and detecting renames, unlinks
		2346	etc. is difficult.
		2347
		2348	=head3 C<stat ()> is a synchronous operation
		2349
		2350	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2351	the process. The exception are C<ev_stat> watchers - those call C<stat
		2352	()>, which is a synchronous operation.
		2353
		2354	For local paths, this usually doesn't matter: unless the system is very
		2355	busy or the intervals between stat's are large, a stat call will be fast,
		2356	as the path data is usually in memory already (except when starting the
		2357	watcher).
		2358
		2359	For networked file systems, calling C<stat ()> can block an indefinite
		2360	time due to network issues, and even under good conditions, a stat call
		2361	often takes multiple milliseconds.
		2362
		2363	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2364	paths, although this is fully supported by libev.
1690		2365
1691	=head3 The special problem of stat time resolution	2366	=head3 The special problem of stat time resolution
1692		2367
1693	The C<stat ()> system call only supports full-second resolution portably, and	2368	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2369	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2370	still only support whole seconds.
1696		2371
1697	That means that, if the time is the only thing that changes, you can	2372	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2373	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2374	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2375	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2376	stat data does change in other ways (e.g. file size).
1702		2377
1703	The solution to this is to delay acting on a change for slightly more	2378	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2379	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2380	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2381	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2401	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2402	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2403	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2404	path for as long as the watcher is active.
1730		2405
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2406	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2407	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2408	last change was detected).
1734		2409
1735	=item ev_stat_stat (loop, ev_stat *)	2410	=item ev_stat_stat (loop, ev_stat *)
1736		2411
1737	Updates the stat buffer immediately with new values. If you change the	2412	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2413	watched path in your callback, you could call this function to avoid
…		…
1767		2442
1768	=head3 Examples	2443	=head3 Examples
1769		2444
1770	Example: Watch C</etc/passwd> for attribute changes.	2445	Example: Watch C</etc/passwd> for attribute changes.
1771		2446
1772	static void	2447	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2448	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	2449	{
1775	/* /etc/passwd changed in some way */	2450	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	2451	if (w->attr.st_nlink)
1777	{	2452	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2453	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2454	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2455	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	2456	}
1782	else	2457	else
1783	/* you shalt not abuse printf for puts */	2458	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	2459	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	2460	"if this is windows, they already arrived\n");
1786	}	2461	}
1787		2462
1788	...	2463	...
1789	ev_stat passwd;	2464	ev_stat passwd;
1790		2465
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2466	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	2467	ev_stat_start (loop, &passwd);
1793		2468
1794	Example: Like above, but additionally use a one-second delay so we do not	2469	Example: Like above, but additionally use a one-second delay so we do not
1795	miss updates (however, frequent updates will delay processing, too, so	2470	miss updates (however, frequent updates will delay processing, too, so
1796	one might do the work both on C<ev_stat> callback invocation I<and> on	2471	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	2472	C<ev_timer> callback invocation).
1798		2473
1799	static ev_stat passwd;	2474	static ev_stat passwd;
1800	static ev_timer timer;	2475	static ev_timer timer;
1801		2476
1802	static void	2477	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	2478	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	2479	{
1805	ev_timer_stop (EV_A_ w);	2480	ev_timer_stop (EV_A_ w);
1806		2481
1807	/* now it's one second after the most recent passwd change */	2482	/* now it's one second after the most recent passwd change */
1808	}	2483	}
1809		2484
1810	static void	2485	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	2486	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	2487	{
1813	/* reset the one-second timer */	2488	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	2489	ev_timer_again (EV_A_ &timer);
1815	}	2490	}
1816		2491
1817	...	2492	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2493	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	2494	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	2495	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		2496
1822		2497
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2498	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2499
1825	Idle watchers trigger events when no other events of the same or higher	2500	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2501	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2502	as receiving "events").
1828		2503
1829	That is, as long as your process is busy handling sockets or timeouts	2504	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2505	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2506	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2507	are pending), the idle watchers are being called once per event loop
…		…
1843		2518
1844	=head3 Watcher-Specific Functions and Data Members	2519	=head3 Watcher-Specific Functions and Data Members
1845		2520
1846	=over 4	2521	=over 4
1847		2522
1848	=item ev_idle_init (ev_signal *, callback)	2523	=item ev_idle_init (ev_idle *, callback)
1849		2524
1850	Initialises and configures the idle watcher - it has no parameters of any	2525	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2526	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2527	believe me.
1853		2528
…		…
1856	=head3 Examples	2531	=head3 Examples
1857		2532
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2533	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2534	callback, free it. Also, use no error checking, as usual.
1860		2535
1861	static void	2536	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2537	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2538	{
1864	free (w);	2539	free (w);
1865	// now do something you wanted to do when the program has	2540	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2541	// no longer anything immediate to do.
1867	}	2542	}
1868		2543
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2544	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2545	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2546	ev_idle_start (loop, idle_watcher);
1872		2547
1873		2548
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2549	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2550
1876	Prepare and check watchers are usually (but not always) used in tandem:	2551	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2552	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2553	afterwards.
1879		2554
1880	You I<must not> call C<ev_loop> or similar functions that enter	2555	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2556	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2559	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2560	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2561	called in pairs bracketing the blocking call.
1887		2562
1888	Their main purpose is to integrate other event mechanisms into libev and	2563	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2564	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2565	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2566	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2567	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2568	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2569	watcher).
1895		2570
1896	This is done by examining in each prepare call which file descriptors need	2571	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2572	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2573	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2574	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2575	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2576	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2577	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2578	nevertheless, because you never know, you know?).
1904		2579
1905	As another example, the Perl Coro module uses these hooks to integrate	2580	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2581	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2582	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2583	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2586	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2587	low-priority coroutines to idle/background tasks).
1913		2588
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2589	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2590	priority, to ensure that they are being run before any other watchers
		2591	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2592
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2593	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2594	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2595	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2596	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2597	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2598	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2599	others).
1923		2600
1924	=head3 Watcher-Specific Functions and Data Members	2601	=head3 Watcher-Specific Functions and Data Members
1925		2602
1926	=over 4	2603	=over 4
1927		2604
…		…
1929		2606
1930	=item ev_check_init (ev_check *, callback)	2607	=item ev_check_init (ev_check *, callback)
1931		2608
1932	Initialises and configures the prepare or check watcher - they have no	2609	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2610	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2611	macros, but using them is utterly, utterly, utterly and completely
		2612	pointless.
1935		2613
1936	=back	2614	=back
1937		2615
1938	=head3 Examples	2616	=head3 Examples
1939		2617
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2626	and in a check watcher, destroy them and call into libadns. What follows
1949	is pseudo-code only of course. This requires you to either use a low	2627	is pseudo-code only of course. This requires you to either use a low
1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2628	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1951	the callbacks for the IO/timeout watchers might not have been called yet.	2629	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2630
1953	static ev_io iow [nfd];	2631	static ev_io iow [nfd];
1954	static ev_timer tw;	2632	static ev_timer tw;
1955		2633
1956	static void	2634	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2635	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2636	{
1959	}	2637	}
1960		2638
1961	// create io watchers for each fd and a timer before blocking	2639	// create io watchers for each fd and a timer before blocking
1962	static void	2640	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2641	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2642	{
1965	int timeout = 3600000;	2643	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2644	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2645	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2646	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2647
1970	/* the callback is illegal, but won't be called as we stop during check */	2648	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2649	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2650	ev_timer_start (loop, &tw);
1973		2651
1974	// create one ev_io per pollfd	2652	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2653	for (int i = 0; i < nfd; ++i)
1976	{	2654	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2655	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2656	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2657	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2658
1981	fds [i].revents = 0;	2659	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2660	ev_io_start (loop, iow + i);
1983	}	2661	}
1984	}	2662	}
1985		2663
1986	// stop all watchers after blocking	2664	// stop all watchers after blocking
1987	static void	2665	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2666	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2667	{
1990	ev_timer_stop (loop, &tw);	2668	ev_timer_stop (loop, &tw);
1991		2669
1992	for (int i = 0; i < nfd; ++i)	2670	for (int i = 0; i < nfd; ++i)
1993	{	2671	{
1994	// set the relevant poll flags	2672	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2673	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2674	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2675	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2676	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2677	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2678
2001	// now stop the watcher	2679	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2680	ev_io_stop (loop, iow + i);
2003	}	2681	}
2004		2682
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2683	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2684	}
2007		2685
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2686	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
2009	in the prepare watcher and would dispose of the check watcher.	2687	in the prepare watcher and would dispose of the check watcher.
2010		2688
2011	Method 3: If the module to be embedded supports explicit event	2689	Method 3: If the module to be embedded supports explicit event
2012	notification (libadns does), you can also make use of the actual watcher	2690	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2691	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2692
2015	static void	2693	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2694	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2695	{
2018	adns_state ads = (adns_state)w->data;	2696	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2697	update_now (EV_A);
2020		2698
2021	adns_processtimeouts (ads, &tv_now);	2699	adns_processtimeouts (ads, &tv_now);
2022	}	2700	}
2023		2701
2024	static void	2702	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2703	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2704	{
2027	adns_state ads = (adns_state)w->data;	2705	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2706	update_now (EV_A);
2029		2707
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2708	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2709	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2710	}
2033		2711
2034	// do not ever call adns_afterpoll	2712	// do not ever call adns_afterpoll
2035		2713
2036	Method 4: Do not use a prepare or check watcher because the module you	2714	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2715	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2716	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2717	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2718	this approach, effectively embedding EV as a client into the horrible
		2719	libglib event loop.
2041		2720
2042	static gint	2721	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2722	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2723	{
2045	int got_events = 0;	2724	int got_events = 0;
2046		2725
2047	for (n = 0; n < nfds; ++n)	2726	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2727	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2728
2050	if (timeout >= 0)	2729	if (timeout >= 0)
2051	// create/start timer	2730	// create/start timer
2052		2731
2053	// poll	2732	// poll
2054	ev_loop (EV_A_ 0);	2733	ev_loop (EV_A_ 0);
2055		2734
2056	// stop timer again	2735	// stop timer again
2057	if (timeout >= 0)	2736	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2737	ev_timer_stop (EV_A_ &to);
2059		2738
2060	// stop io watchers again - their callbacks should have set	2739	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	2740	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	2741	ev_io_stop (EV_A_ iow [n]);
2063		2742
2064	return got_events;	2743	return got_events;
2065	}	2744	}
2066		2745
2067		2746
2068	=head2 C<ev_embed> - when one backend isn't enough...	2747	=head2 C<ev_embed> - when one backend isn't enough...
2069		2748
2070	This is a rather advanced watcher type that lets you embed one event loop	2749	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	2755	prioritise I/O.
2077		2756
2078	As an example for a bug workaround, the kqueue backend might only support	2757	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2758	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2759	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2760	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2761	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2762	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2763	C<kevent>, but at least you can use both mechanisms for what they are
		2764	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2765
2086	As for prioritising I/O: rarely you have the case where some fds have	2766	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2767	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2768	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2769	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2770	the rest in a second one, and embed the second one in the first.
2091		2771
2092	As long as the watcher is active, the callback will be invoked every time	2772	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2773	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2774	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2775	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2776	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2777	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2778
2100	As long as the watcher is started it will automatically handle events. The	2779	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2780	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2781
2105	Also, there have not currently been made special provisions for forking:	2782	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2783	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2784	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2785	C<ev_loop_fork> on the embedded loop.
2109		2786
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2787	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2788	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2789	portable one.
2113		2790
2114	So when you want to use this feature you will always have to be prepared	2791	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2792	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2793	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2794	create it, and if that fails, use the normal loop for everything.
		2795
		2796	=head3 C<ev_embed> and fork
		2797
		2798	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2799	automatically be applied to the embedded loop as well, so no special
		2800	fork handling is required in that case. When the watcher is not running,
		2801	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2802	as applicable.
2118		2803
2119	=head3 Watcher-Specific Functions and Data Members	2804	=head3 Watcher-Specific Functions and Data Members
2120		2805
2121	=over 4	2806	=over 4
2122		2807
…		…
2148	event loop. If that is not possible, use the default loop. The default	2833	event loop. If that is not possible, use the default loop. The default
2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in	2834	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2835	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2836	used).
2152		2837
2153	struct ev_loop *loop_hi = ev_default_init (0);	2838	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2839	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2840	ev_embed embed;
2156		2841
2157	// see if there is a chance of getting one that works	2842	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2843	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2844	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2845	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	2846	: 0;
2162		2847
2163	// if we got one, then embed it, otherwise default to loop_hi	2848	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	2849	if (loop_lo)
2165	{	2850	{
2166	ev_embed_init (&embed, 0, loop_lo);	2851	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	2852	ev_embed_start (loop_hi, &embed);
2168	}	2853	}
2169	else	2854	else
2170	loop_lo = loop_hi;	2855	loop_lo = loop_hi;
2171		2856
2172	Example: Check if kqueue is available but not recommended and create	2857	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	2858	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2859	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2860	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2861
2177	struct ev_loop *loop = ev_default_init (0);	2862	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2863	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2864	ev_embed embed;
2180		2865
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2866	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2867	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2868	{
2184	ev_embed_init (&embed, 0, loop_socket);	2869	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	2870	ev_embed_start (loop, &embed);
2186	}	2871	}
2187		2872
2188	if (!loop_socket)	2873	if (!loop_socket)
2189	loop_socket = loop;	2874	loop_socket = loop;
2190		2875
2191	// now use loop_socket for all sockets, and loop for everything else	2876	// now use loop_socket for all sockets, and loop for everything else
2192		2877
2193		2878
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2879	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		2880
2196	Fork watchers are called when a C<fork ()> was detected (usually because	2881	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	2884	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	2885	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2886	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	2887	handlers will be invoked, too, of course.
2203		2888
		2889	=head3 The special problem of life after fork - how is it possible?
		2890
		2891	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2892	up/change the process environment, followed by a call to C<exec()>. This
		2893	sequence should be handled by libev without any problems.
		2894
		2895	This changes when the application actually wants to do event handling
		2896	in the child, or both parent in child, in effect "continuing" after the
		2897	fork.
		2898
		2899	The default mode of operation (for libev, with application help to detect
		2900	forks) is to duplicate all the state in the child, as would be expected
		2901	when I<either> the parent I<or> the child process continues.
		2902
		2903	When both processes want to continue using libev, then this is usually the
		2904	wrong result. In that case, usually one process (typically the parent) is
		2905	supposed to continue with all watchers in place as before, while the other
		2906	process typically wants to start fresh, i.e. without any active watchers.
		2907
		2908	The cleanest and most efficient way to achieve that with libev is to
		2909	simply create a new event loop, which of course will be "empty", and
		2910	use that for new watchers. This has the advantage of not touching more
		2911	memory than necessary, and thus avoiding the copy-on-write, and the
		2912	disadvantage of having to use multiple event loops (which do not support
		2913	signal watchers).
		2914
		2915	When this is not possible, or you want to use the default loop for
		2916	other reasons, then in the process that wants to start "fresh", call
		2917	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2918	the default loop will "orphan" (not stop) all registered watchers, so you
		2919	have to be careful not to execute code that modifies those watchers. Note
		2920	also that in that case, you have to re-register any signal watchers.
		2921
2204	=head3 Watcher-Specific Functions and Data Members	2922	=head3 Watcher-Specific Functions and Data Members
2205		2923
2206	=over 4	2924	=over 4
2207		2925
2208	=item ev_fork_init (ev_signal *, callback)	2926	=item ev_fork_init (ev_signal *, callback)
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2958	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2959	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2960	need elaborate support such as pthreads.
2243		2961
2244	That means that if you want to queue data, you have to provide your own	2962	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2963	queue. But at least I can tell you how to implement locking around your
2246	queue:	2964	queue:
2247		2965
2248	=over 4	2966	=over 4
2249		2967
2250	=item queueing from a signal handler context	2968	=item queueing from a signal handler context
2251		2969
2252	To implement race-free queueing, you simply add to the queue in the signal	2970	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2971	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2972	an example that does that for some fictitious SIGUSR1 handler:
2255		2973
2256	static ev_async mysig;	2974	static ev_async mysig;
2257		2975
2258	static void	2976	static void
2259	sigusr1_handler (void)	2977	sigusr1_handler (void)
…		…
2325	=over 4	3043	=over 4
2326		3044
2327	=item ev_async_init (ev_async *, callback)	3045	=item ev_async_init (ev_async *, callback)
2328		3046
2329	Initialises and configures the async watcher - it has no parameters of any	3047	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3048	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	3049	trust me.
2332		3050
2333	=item ev_async_send (loop, ev_async *)	3051	=item ev_async_send (loop, ev_async *)
2334		3052
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3053	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3054	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	3055	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3056	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	3057	section below on what exactly this means).
2340		3058
		3059	Note that, as with other watchers in libev, multiple events might get
		3060	compressed into a single callback invocation (another way to look at this
		3061	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3062	reset when the event loop detects that).
		3063
2341	This call incurs the overhead of a system call only once per loop iteration,	3064	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	3065	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	3066	repeated calls to C<ev_async_send> for the same event loop.
2344		3067
2345	=item bool = ev_async_pending (ev_async *)	3068	=item bool = ev_async_pending (ev_async *)
2346		3069
2347	Returns a non-zero value when C<ev_async_send> has been called on the	3070	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	3071	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3074	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	3075	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	3076	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	3077	quickly check whether invoking the loop might be a good idea.
2355		3078
2356	Not that this does I<not> check whether the watcher itself is pending, only	3079	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	3080	only whether it has been requested to make this watcher pending: there
		3081	is a time window between the event loop checking and resetting the async
		3082	notification, and the callback being invoked.
2358		3083
2359	=back	3084	=back
2360		3085
2361		3086
2362	=head1 OTHER FUNCTIONS	3087	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	3091	=over 4
2367		3092
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3093	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		3094
2370	This function combines a simple timer and an I/O watcher, calls your	3095	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	3096	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	3097	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	3098	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	3099	more watchers yourself.
2375		3100
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	3101	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3102	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	3103	the given C<fd> and C<events> set will be created and started.
2379		3104
2380	If C<timeout> is less than 0, then no timeout watcher will be	3105	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3106	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3107	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		3108
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3109	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	3110	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3111	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	3112	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3113	a timeout and an io event at the same time - you probably should give io
		3114	events precedence.
2389		3115
		3116	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3117
2390	static void stdin_ready (int revents, void *arg)	3118	static void stdin_ready (int revents, void *arg)
2391	{	3119	{
2392	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	3120	if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	3121	/* stdin might have data for us, joy! */;
		3122	else if (revents & EV_TIMEOUT)
		3123	/* doh, nothing entered */;
2396	}	3124	}
2397		3125
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3126	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		3127
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	3128	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		3129
2402	Feeds the given event set into the event loop, as if the specified event	3130	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an	3131	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	3132	initialised but not necessarily started event watcher).
2405		3133
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3134	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		3135
2408	Feed an event on the given fd, as if a file descriptor backend detected	3136	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	3137	the given events it.
2410		3138
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	3139	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		3140
2413	Feed an event as if the given signal occurred (C<loop> must be the default	3141	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	3142	loop!).
2415		3143
2416	=back	3144	=back
…		…
2452	you to use some convenience methods to start/stop watchers and also change	3180	you to use some convenience methods to start/stop watchers and also change
2453	the callback model to a model using method callbacks on objects.	3181	the callback model to a model using method callbacks on objects.
2454		3182
2455	To use it,	3183	To use it,
2456		3184
2457	#include <ev++.h>	3185	#include <ev++.h>
2458		3186
2459	This automatically includes F<ev.h> and puts all of its definitions (many	3187	This automatically includes F<ev.h> and puts all of its definitions (many
2460	of them macros) into the global namespace. All C++ specific things are	3188	of them macros) into the global namespace. All C++ specific things are
2461	put into the C<ev> namespace. It should support all the same embedding	3189	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3190	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	3257	your compiler is good :), then the method will be fully inlined into the
2530	thunking function, making it as fast as a direct C callback.	3258	thunking function, making it as fast as a direct C callback.
2531		3259
2532	Example: simple class declaration and watcher initialisation	3260	Example: simple class declaration and watcher initialisation
2533		3261
2534	struct myclass	3262	struct myclass
2535	{	3263	{
2536	void io_cb (ev::io &w, int revents) { }	3264	void io_cb (ev::io &w, int revents) { }
2537	}	3265	}
2538		3266
2539	myclass obj;	3267	myclass obj;
2540	ev::io iow;	3268	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3269	iow.set <myclass, &myclass::io_cb> (&obj);
		3270
		3271	=item w->set (object *)
		3272
		3273	This is an B<experimental> feature that might go away in a future version.
		3274
		3275	This is a variation of a method callback - leaving out the method to call
		3276	will default the method to C<operator ()>, which makes it possible to use
		3277	functor objects without having to manually specify the C<operator ()> all
		3278	the time. Incidentally, you can then also leave out the template argument
		3279	list.
		3280
		3281	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3282	int revents)>.
		3283
		3284	See the method-C<set> above for more details.
		3285
		3286	Example: use a functor object as callback.
		3287
		3288	struct myfunctor
		3289	{
		3290	void operator() (ev::io &w, int revents)
		3291	{
		3292	...
		3293	}
		3294	}
		3295
		3296	myfunctor f;
		3297
		3298	ev::io w;
		3299	w.set (&f);
2542		3300
2543	=item w->set<function> (void *data = 0)	3301	=item w->set<function> (void *data = 0)
2544		3302
2545	Also sets a callback, but uses a static method or plain function as	3303	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3304	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		3306
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3307	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3308
2551	See the method-C<set> above for more details.	3309	See the method-C<set> above for more details.
2552		3310
2553	Example:	3311	Example: Use a plain function as callback.
2554		3312
2555	static void io_cb (ev::io &w, int revents) { }	3313	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3314	iow.set <io_cb> ();
2557		3315
2558	=item w->set (struct ev_loop *)	3316	=item w->set (struct ev_loop *)
2559		3317
2560	Associates a different C<struct ev_loop> with this watcher. You can only	3318	Associates a different C<struct ev_loop> with this watcher. You can only
2561	do this when the watcher is inactive (and not pending either).	3319	do this when the watcher is inactive (and not pending either).
…		…
2594	=back	3352	=back
2595		3353
2596	Example: Define a class with an IO and idle watcher, start one of them in	3354	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	3355	the constructor.
2598		3356
2599	class myclass	3357	class myclass
2600	{	3358	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3359	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3360	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3361
2604	myclass (int fd)	3362	myclass (int fd)
2605	{	3363	{
2606	io .set <myclass, &myclass::io_cb > (this);	3364	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3365	idle.set <myclass, &myclass::idle_cb> (this);
2608		3366
2609	io.start (fd, ev::READ);	3367	io.start (fd, ev::READ);
2610	}	3368	}
2611	};	3369	};
2612		3370
2613		3371
2614	=head1 OTHER LANGUAGE BINDINGS	3372	=head1 OTHER LANGUAGE BINDINGS
2615		3373
2616	Libev does not offer other language bindings itself, but bindings for a	3374	Libev does not offer other language bindings itself, but bindings for a
…		…
2623	=item Perl	3381	=item Perl
2624		3382
2625	The EV module implements the full libev API and is actually used to test	3383	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3384	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3385	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3386	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3387	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3388	and C<EV::Glib>).
2630		3389
2631	It can be found and installed via CPAN, its homepage is found at	3390	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3391	L<http://software.schmorp.de/pkg/EV>.
		3392
		3393	=item Python
		3394
		3395	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3396	seems to be quite complete and well-documented.
2633		3397
2634	=item Ruby	3398	=item Ruby
2635		3399
2636	Tony Arcieri has written a ruby extension that offers access to a subset	3400	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds file handle abstractions, asynchronous DNS and	3401	of the libev API and adds file handle abstractions, asynchronous DNS and
2638	more on top of it. It can be found via gem servers. Its homepage is at	3402	more on top of it. It can be found via gem servers. Its homepage is at
2639	L<http://rev.rubyforge.org/>.	3403	L<http://rev.rubyforge.org/>.
2640		3404
		3405	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3406	makes rev work even on mingw.
		3407
		3408	=item Haskell
		3409
		3410	A haskell binding to libev is available at
		3411	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3412
2641	=item D	3413	=item D
2642		3414
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3415	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3416	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3417
		3418	=item Ocaml
		3419
		3420	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3421	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3422
		3423	=item Lua
		3424
		3425	Brian Maher has written a partial interface to libev
		3426	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3427	L<http://github.com/brimworks/lua-ev>.
2645		3428
2646	=back	3429	=back
2647		3430
2648		3431
2649	=head1 MACRO MAGIC	3432	=head1 MACRO MAGIC
…		…
2661		3444
2662	This provides the loop I<argument> for functions, if one is required ("ev	3445	This provides the loop I<argument> for functions, if one is required ("ev
2663	loop argument"). The C<EV_A> form is used when this is the sole argument,	3446	loop argument"). The C<EV_A> form is used when this is the sole argument,
2664	C<EV_A_> is used when other arguments are following. Example:	3447	C<EV_A_> is used when other arguments are following. Example:
2665		3448
2666	ev_unref (EV_A);	3449	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	3450	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	3451	ev_loop (EV_A_ 0);
2669		3452
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3453	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	3454	which is often provided by the following macro.
2672		3455
2673	=item C<EV_P>, C<EV_P_>	3456	=item C<EV_P>, C<EV_P_>
2674		3457
2675	This provides the loop I<parameter> for functions, if one is required ("ev	3458	This provides the loop I<parameter> for functions, if one is required ("ev
2676	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3459	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2677	C<EV_P_> is used when other parameters are following. Example:	3460	C<EV_P_> is used when other parameters are following. Example:
2678		3461
2679	// this is how ev_unref is being declared	3462	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	3463	static void ev_unref (EV_P);
2681		3464
2682	// this is how you can declare your typical callback	3465	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	3466	static void cb (EV_P_ ev_timer *w, int revents)
2684		3467
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3468	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	3469	suitable for use with C<EV_A>.
2687		3470
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3471	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		3487
2705	Example: Declare and initialise a check watcher, utilising the above	3488	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	3489	macros so it will work regardless of whether multiple loops are supported
2707	or not.	3490	or not.
2708		3491
2709	static void	3492	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	3493	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	3494	{
2712	ev_check_stop (EV_A_ w);	3495	ev_check_stop (EV_A_ w);
2713	}	3496	}
2714		3497
2715	ev_check check;	3498	ev_check check;
2716	ev_check_init (&check, check_cb);	3499	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	3500	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	3501	ev_loop (EV_DEFAULT_ 0);
2719		3502
2720	=head1 EMBEDDING	3503	=head1 EMBEDDING
2721		3504
2722	Libev can (and often is) directly embedded into host	3505	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	3506	applications. Examples of applications that embed it include the Deliantra
…		…
2737	=head3 CORE EVENT LOOP	3520	=head3 CORE EVENT LOOP
2738		3521
2739	To include only the libev core (all the C<ev_*> functions), with manual	3522	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	3523	configuration (no autoconf):
2741		3524
2742	#define EV_STANDALONE 1	3525	#define EV_STANDALONE 1
2743	#include "ev.c"	3526	#include "ev.c"
2744		3527
2745	This will automatically include F<ev.h>, too, and should be done in a	3528	This will automatically include F<ev.h>, too, and should be done in a
2746	single C source file only to provide the function implementations. To use	3529	single C source file only to provide the function implementations. To use
2747	it, do the same for F<ev.h> in all files wishing to use this API (best	3530	it, do the same for F<ev.h> in all files wishing to use this API (best
2748	done by writing a wrapper around F<ev.h> that you can include instead and	3531	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	3532	where you can put other configuration options):
2750		3533
2751	#define EV_STANDALONE 1	3534	#define EV_STANDALONE 1
2752	#include "ev.h"	3535	#include "ev.h"
2753		3536
2754	Both header files and implementation files can be compiled with a C++	3537	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	3538	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	3539	as a bug).
2757		3540
2758	You need the following files in your source tree, or in a directory	3541	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	3542	in your include path (e.g. in libev/ when using -Ilibev):
2760		3543
2761	ev.h	3544	ev.h
2762	ev.c	3545	ev.c
2763	ev_vars.h	3546	ev_vars.h
2764	ev_wrap.h	3547	ev_wrap.h
2765		3548
2766	ev_win32.c required on win32 platforms only	3549	ev_win32.c required on win32 platforms only
2767		3550
2768	ev_select.c only when select backend is enabled (which is enabled by default)	3551	ev_select.c only when select backend is enabled (which is enabled by default)
2769	ev_poll.c only when poll backend is enabled (disabled by default)	3552	ev_poll.c only when poll backend is enabled (disabled by default)
2770	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3553	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2771	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3554	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2772	ev_port.c only when the solaris port backend is enabled (disabled by default)	3555	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		3556
2774	F<ev.c> includes the backend files directly when enabled, so you only need	3557	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	3558	to compile this single file.
2776		3559
2777	=head3 LIBEVENT COMPATIBILITY API	3560	=head3 LIBEVENT COMPATIBILITY API
2778		3561
2779	To include the libevent compatibility API, also include:	3562	To include the libevent compatibility API, also include:
2780		3563
2781	#include "event.c"	3564	#include "event.c"
2782		3565
2783	in the file including F<ev.c>, and:	3566	in the file including F<ev.c>, and:
2784		3567
2785	#include "event.h"	3568	#include "event.h"
2786		3569
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	3570	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		3571
2789	You need the following additional files for this:	3572	You need the following additional files for this:
2790		3573
2791	event.h	3574	event.h
2792	event.c	3575	event.c
2793		3576
2794	=head3 AUTOCONF SUPPORT	3577	=head3 AUTOCONF SUPPORT
2795		3578
2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in	3579	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2797	whatever way you want, you can also C<m4_include([libev.m4])> in your	3580	whatever way you want, you can also C<m4_include([libev.m4])> in your
2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3581	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	3582	include F<config.h> and configure itself accordingly.
2800		3583
2801	For this of course you need the m4 file:	3584	For this of course you need the m4 file:
2802		3585
2803	libev.m4	3586	libev.m4
2804		3587
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3588	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3589
2807	Libev can be configured via a variety of preprocessor symbols you have to	3590	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absence of	3591	define before including any of its files. The default in the absence of
2809	autoconf is noted for every option.	3592	autoconf is documented for every option.
2810		3593
2811	=over 4	3594	=over 4
2812		3595
2813	=item EV_STANDALONE	3596	=item EV_STANDALONE
2814		3597
…		…
2816	keeps libev from including F<config.h>, and it also defines dummy	3599	keeps libev from including F<config.h>, and it also defines dummy
2817	implementations for some libevent functions (such as logging, which is not	3600	implementations for some libevent functions (such as logging, which is not
2818	supported). It will also not define any of the structs usually found in	3601	supported). It will also not define any of the structs usually found in
2819	F<event.h> that are not directly supported by the libev core alone.	3602	F<event.h> that are not directly supported by the libev core alone.
2820		3603
		3604	In standalone mode, libev will still try to automatically deduce the
		3605	configuration, but has to be more conservative.
		3606
2821	=item EV_USE_MONOTONIC	3607	=item EV_USE_MONOTONIC
2822		3608
2823	If defined to be C<1>, libev will try to detect the availability of the	3609	If defined to be C<1>, libev will try to detect the availability of the
2824	monotonic clock option at both compile time and runtime. Otherwise no use	3610	monotonic clock option at both compile time and runtime. Otherwise no
2825	of the monotonic clock option will be attempted. If you enable this, you	3611	use of the monotonic clock option will be attempted. If you enable this,
2826	usually have to link against librt or something similar. Enabling it when	3612	you usually have to link against librt or something similar. Enabling it
2827	the functionality isn't available is safe, though, although you have	3613	when the functionality isn't available is safe, though, although you have
2828	to make sure you link against any libraries where the C<clock_gettime>	3614	to make sure you link against any libraries where the C<clock_gettime>
2829	function is hiding in (often F<-lrt>).	3615	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2830		3616
2831	=item EV_USE_REALTIME	3617	=item EV_USE_REALTIME
2832		3618
2833	If defined to be C<1>, libev will try to detect the availability of the	3619	If defined to be C<1>, libev will try to detect the availability of the
2834	real-time clock option at compile time (and assume its availability at	3620	real-time clock option at compile time (and assume its availability
2835	runtime if successful). Otherwise no use of the real-time clock option will	3621	at runtime if successful). Otherwise no use of the real-time clock
2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3622	option will be attempted. This effectively replaces C<gettimeofday>
2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3623	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3624	correctness. See the note about libraries in the description of
		3625	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3626	C<EV_USE_CLOCK_SYSCALL>.
		3627
		3628	=item EV_USE_CLOCK_SYSCALL
		3629
		3630	If defined to be C<1>, libev will try to use a direct syscall instead
		3631	of calling the system-provided C<clock_gettime> function. This option
		3632	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3633	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3634	programs needlessly. Using a direct syscall is slightly slower (in
		3635	theory), because no optimised vdso implementation can be used, but avoids
		3636	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3637	higher, as it simplifies linking (no need for C<-lrt>).
2839		3638
2840	=item EV_USE_NANOSLEEP	3639	=item EV_USE_NANOSLEEP
2841		3640
2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3641	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2843	and will use it for delays. Otherwise it will use C<select ()>.	3642	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2859		3658
2860	=item EV_SELECT_USE_FD_SET	3659	=item EV_SELECT_USE_FD_SET
2861		3660
2862	If defined to C<1>, then the select backend will use the system C<fd_set>	3661	If defined to C<1>, then the select backend will use the system C<fd_set>
2863	structure. This is useful if libev doesn't compile due to a missing	3662	structure. This is useful if libev doesn't compile due to a missing
2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3663	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2865	exotic systems. This usually limits the range of file descriptors to some	3664	on exotic systems. This usually limits the range of file descriptors to
2866	low limit such as 1024 or might have other limitations (winsocket only	3665	some low limit such as 1024 or might have other limitations (winsocket
2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3666	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2868	influence the size of the C<fd_set> used.	3667	configures the maximum size of the C<fd_set>.
2869		3668
2870	=item EV_SELECT_IS_WINSOCKET	3669	=item EV_SELECT_IS_WINSOCKET
2871		3670
2872	When defined to C<1>, the select backend will assume that	3671	When defined to C<1>, the select backend will assume that
2873	select/socket/connect etc. don't understand file descriptors but	3672	select/socket/connect etc. don't understand file descriptors but
…		…
2875	be used is the winsock select). This means that it will call	3674	be used is the winsock select). This means that it will call
2876	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3675	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2877	it is assumed that all these functions actually work on fds, even	3676	it is assumed that all these functions actually work on fds, even
2878	on win32. Should not be defined on non-win32 platforms.	3677	on win32. Should not be defined on non-win32 platforms.
2879		3678
2880	=item EV_FD_TO_WIN32_HANDLE	3679	=item EV_FD_TO_WIN32_HANDLE(fd)
2881		3680
2882	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3681	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2883	file descriptors to socket handles. When not defining this symbol (the	3682	file descriptors to socket handles. When not defining this symbol (the
2884	default), then libev will call C<_get_osfhandle>, which is usually	3683	default), then libev will call C<_get_osfhandle>, which is usually
2885	correct. In some cases, programs use their own file descriptor management,	3684	correct. In some cases, programs use their own file descriptor management,
2886	in which case they can provide this function to map fds to socket handles.	3685	in which case they can provide this function to map fds to socket handles.
		3686
		3687	=item EV_WIN32_HANDLE_TO_FD(handle)
		3688
		3689	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3690	using the standard C<_open_osfhandle> function. For programs implementing
		3691	their own fd to handle mapping, overwriting this function makes it easier
		3692	to do so. This can be done by defining this macro to an appropriate value.
		3693
		3694	=item EV_WIN32_CLOSE_FD(fd)
		3695
		3696	If programs implement their own fd to handle mapping on win32, then this
		3697	macro can be used to override the C<close> function, useful to unregister
		3698	file descriptors again. Note that the replacement function has to close
		3699	the underlying OS handle.
2887		3700
2888	=item EV_USE_POLL	3701	=item EV_USE_POLL
2889		3702
2890	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3703	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2891	backend. Otherwise it will be enabled on non-win32 platforms. It	3704	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3797	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	3798	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	3799	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3800	fine.
2988		3801
2989	If your embedding application does not need any priorities, defining these both to	3802	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3803	both to C<0> will save some memory and CPU.
2991		3804
2992	=item EV_PERIODIC_ENABLE	3805	=item EV_PERIODIC_ENABLE
2993		3806
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3807	If undefined or defined to be C<1>, then periodic timers are supported. If
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	3808	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3002	code.	3815	code.
3003		3816
3004	=item EV_EMBED_ENABLE	3817	=item EV_EMBED_ENABLE
3005		3818
3006	If undefined or defined to be C<1>, then embed watchers are supported. If	3819	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.	3820	defined to be C<0>, then they are not. Embed watchers rely on most other
		3821	watcher types, which therefore must not be disabled.
3008		3822
3009	=item EV_STAT_ENABLE	3823	=item EV_STAT_ENABLE
3010		3824
3011	If undefined or defined to be C<1>, then stat watchers are supported. If	3825	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.	3826	defined to be C<0>, then they are not.
…		…
3022	defined to be C<0>, then they are not.	3836	defined to be C<0>, then they are not.
3023		3837
3024	=item EV_MINIMAL	3838	=item EV_MINIMAL
3025		3839
3026	If you need to shave off some kilobytes of code at the expense of some	3840	If you need to shave off some kilobytes of code at the expense of some
3027	speed, define this symbol to C<1>. Currently this is used to override some	3841	speed (but with the full API), define this symbol to C<1>. Currently this
3028	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3842	is used to override some inlining decisions, saves roughly 30% code size
3029	much smaller 2-heap for timer management over the default 4-heap.	3843	on amd64. It also selects a much smaller 2-heap for timer management over
		3844	the default 4-heap.
		3845
		3846	You can save even more by disabling watcher types you do not need
		3847	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3848	(C<-DNDEBUG>) will usually reduce code size a lot.
		3849
		3850	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3851	provide a bare-bones event library. See C<ev.h> for details on what parts
		3852	of the API are still available, and do not complain if this subset changes
		3853	over time.
		3854
		3855	=item EV_NSIG
		3856
		3857	The highest supported signal number, +1 (or, the number of
		3858	signals): Normally, libev tries to deduce the maximum number of signals
		3859	automatically, but sometimes this fails, in which case it can be
		3860	specified. Also, using a lower number than detected (C<32> should be
		3861	good for about any system in existance) can save some memory, as libev
		3862	statically allocates some 12-24 bytes per signal number.
3030		3863
3031	=item EV_PID_HASHSIZE	3864	=item EV_PID_HASHSIZE
3032		3865
3033	C<ev_child> watchers use a small hash table to distribute workload by	3866	C<ev_child> watchers use a small hash table to distribute workload by
3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3867	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3044	two).	3877	two).
3045		3878
3046	=item EV_USE_4HEAP	3879	=item EV_USE_4HEAP
3047		3880
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3881	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3882	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	3883	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	3884	faster performance with many (thousands) of watchers.
3052		3885
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3886	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3054	(disabled).	3887	(disabled).
3055		3888
3056	=item EV_HEAP_CACHE_AT	3889	=item EV_HEAP_CACHE_AT
3057		3890
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3891	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	3892	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3893	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3894	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	3895	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	3896	noticeably with many (hundreds) of watchers.
3064		3897
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3898	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3066	(disabled).	3899	(disabled).
3067		3900
3068	=item EV_VERIFY	3901	=item EV_VERIFY
…		…
3074	called once per loop, which can slow down libev. If set to C<3>, then the	3907	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	3908	verification code will be called very frequently, which will slow down
3076	libev considerably.	3909	libev considerably.
3077		3910
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3911	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3079	C<0.>	3912	C<0>.
3080		3913
3081	=item EV_COMMON	3914	=item EV_COMMON
3082		3915
3083	By default, all watchers have a C<void *data> member. By redefining	3916	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	3917	this macro to a something else you can include more and other types of
3085	members. You have to define it each time you include one of the files,	3918	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	3919	though, and it must be identical each time.
3087		3920
3088	For example, the perl EV module uses something like this:	3921	For example, the perl EV module uses something like this:
3089		3922
3090	#define EV_COMMON \	3923	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	3924	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	3925	SV *cb_sv, *fh /* note no trailing ";" */
3093		3926
3094	=item EV_CB_DECLARE (type)	3927	=item EV_CB_DECLARE (type)
3095		3928
3096	=item EV_CB_INVOKE (watcher, revents)	3929	=item EV_CB_INVOKE (watcher, revents)
3097		3930
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	3935	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	3936	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3937	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	3938	method calls instead of plain function calls in C++.
3106		3939
		3940	=back
		3941
3107	=head2 EXPORTED API SYMBOLS	3942	=head2 EXPORTED API SYMBOLS
3108		3943
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	3944	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	3945	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	3946	all public symbols, one per line:
3112		3947
3113	Symbols.ev for libev proper	3948	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	3949	Symbols.event for the libevent emulation
3115		3950
3116	This can also be used to rename all public symbols to avoid clashes with	3951	This can also be used to rename all public symbols to avoid clashes with
3117	multiple versions of libev linked together (which is obviously bad in	3952	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvenient to avoid this).	3953	itself, but sometimes it is inconvenient to avoid this).
3119		3954
…		…
3140	file.	3975	file.
3141		3976
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3977	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3143	that everybody includes and which overrides some configure choices:	3978	that everybody includes and which overrides some configure choices:
3144		3979
3145	#define EV_MINIMAL 1	3980	#define EV_MINIMAL 1
3146	#define EV_USE_POLL 0	3981	#define EV_USE_POLL 0
3147	#define EV_MULTIPLICITY 0	3982	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	3983	#define EV_PERIODIC_ENABLE 0
3149	#define EV_STAT_ENABLE 0	3984	#define EV_STAT_ENABLE 0
3150	#define EV_FORK_ENABLE 0	3985	#define EV_FORK_ENABLE 0
3151	#define EV_CONFIG_H <config.h>	3986	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0	3987	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0	3988	#define EV_MAXPRI 0
3154		3989
3155	#include "ev++.h"	3990	#include "ev++.h"
3156		3991
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3992	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		3993
3159	#include "ev_cpp.h"	3994	#include "ev_cpp.h"
3160	#include "ev.c"	3995	#include "ev.c"
3161		3996
		3997	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		3998
3163	=head1 THREADS AND COROUTINES	3999	=head2 THREADS AND COROUTINES
3164		4000
3165	=head2 THREADS	4001	=head3 THREADS
3166		4002
3167	Libev itself is completely thread-safe, but it uses no locking. This	4003	All libev functions are reentrant and thread-safe unless explicitly
		4004	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	4005	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	4006	are no concurrent calls into any libev function with the same loop
3170	parameter.	4007	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4008	of course): libev guarantees that different event loops share no data
		4009	structures that need any locking.
3171		4010
3172	Or put differently: calls with different loop parameters can be done in	4011	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	4012	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	4013	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	4014	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	4015	a mutex per loop).
3177		4016
3178	If you want to know which design is best for your problem, then I cannot	4017	Specifically to support threads (and signal handlers), libev implements
		4018	so-called C<ev_async> watchers, which allow some limited form of
		4019	concurrency on the same event loop, namely waking it up "from the
		4020	outside".
		4021
		4022	If you want to know which design (one loop, locking, or multiple loops
		4023	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	4024	help you, but here is some generic advice:
3180		4025
3181	=over 4	4026	=over 4
3182		4027
3183	=item * most applications have a main thread: use the default libev loop	4028	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a separate thread running only the default loop.	4029	in that thread, or create a separate thread running only the default loop.
…		…
3196		4041
3197	Choosing a model is hard - look around, learn, know that usually you can do	4042	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	4043	better than you currently do :-)
3199		4044
3200	=item * often you need to talk to some other thread which blocks in the	4045	=item * often you need to talk to some other thread which blocks in the
		4046	event loop.
		4047
3201	event loop - C<ev_async> watchers can be used to wake them up from other	4048	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	4049	(or from signal contexts...).
		4050
		4051	An example use would be to communicate signals or other events that only
		4052	work in the default loop by registering the signal watcher with the
		4053	default loop and triggering an C<ev_async> watcher from the default loop
		4054	watcher callback into the event loop interested in the signal.
3203		4055
3204	=back	4056	=back
3205		4057
		4058	=head4 THREAD LOCKING EXAMPLE
		4059
		4060	Here is a fictitious example of how to run an event loop in a different
		4061	thread than where callbacks are being invoked and watchers are
		4062	created/added/removed.
		4063
		4064	For a real-world example, see the C<EV::Loop::Async> perl module,
		4065	which uses exactly this technique (which is suited for many high-level
		4066	languages).
		4067
		4068	The example uses a pthread mutex to protect the loop data, a condition
		4069	variable to wait for callback invocations, an async watcher to notify the
		4070	event loop thread and an unspecified mechanism to wake up the main thread.
		4071
		4072	First, you need to associate some data with the event loop:
		4073
		4074	typedef struct {
		4075	mutex_t lock; /* global loop lock */
		4076	ev_async async_w;
		4077	thread_t tid;
		4078	cond_t invoke_cv;
		4079	} userdata;
		4080
		4081	void prepare_loop (EV_P)
		4082	{
		4083	// for simplicity, we use a static userdata struct.
		4084	static userdata u;
		4085
		4086	ev_async_init (&u->async_w, async_cb);
		4087	ev_async_start (EV_A_ &u->async_w);
		4088
		4089	pthread_mutex_init (&u->lock, 0);
		4090	pthread_cond_init (&u->invoke_cv, 0);
		4091
		4092	// now associate this with the loop
		4093	ev_set_userdata (EV_A_ u);
		4094	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4095	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4096
		4097	// then create the thread running ev_loop
		4098	pthread_create (&u->tid, 0, l_run, EV_A);
		4099	}
		4100
		4101	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4102	solely to wake up the event loop so it takes notice of any new watchers
		4103	that might have been added:
		4104
		4105	static void
		4106	async_cb (EV_P_ ev_async *w, int revents)
		4107	{
		4108	// just used for the side effects
		4109	}
		4110
		4111	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4112	protecting the loop data, respectively.
		4113
		4114	static void
		4115	l_release (EV_P)
		4116	{
		4117	userdata *u = ev_userdata (EV_A);
		4118	pthread_mutex_unlock (&u->lock);
		4119	}
		4120
		4121	static void
		4122	l_acquire (EV_P)
		4123	{
		4124	userdata *u = ev_userdata (EV_A);
		4125	pthread_mutex_lock (&u->lock);
		4126	}
		4127
		4128	The event loop thread first acquires the mutex, and then jumps straight
		4129	into C<ev_loop>:
		4130
		4131	void *
		4132	l_run (void *thr_arg)
		4133	{
		4134	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4135
		4136	l_acquire (EV_A);
		4137	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4138	ev_loop (EV_A_ 0);
		4139	l_release (EV_A);
		4140
		4141	return 0;
		4142	}
		4143
		4144	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4145	signal the main thread via some unspecified mechanism (signals? pipe
		4146	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4147	have been called (in a while loop because a) spurious wakeups are possible
		4148	and b) skipping inter-thread-communication when there are no pending
		4149	watchers is very beneficial):
		4150
		4151	static void
		4152	l_invoke (EV_P)
		4153	{
		4154	userdata *u = ev_userdata (EV_A);
		4155
		4156	while (ev_pending_count (EV_A))
		4157	{
		4158	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4159	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4160	}
		4161	}
		4162
		4163	Now, whenever the main thread gets told to invoke pending watchers, it
		4164	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4165	thread to continue:
		4166
		4167	static void
		4168	real_invoke_pending (EV_P)
		4169	{
		4170	userdata *u = ev_userdata (EV_A);
		4171
		4172	pthread_mutex_lock (&u->lock);
		4173	ev_invoke_pending (EV_A);
		4174	pthread_cond_signal (&u->invoke_cv);
		4175	pthread_mutex_unlock (&u->lock);
		4176	}
		4177
		4178	Whenever you want to start/stop a watcher or do other modifications to an
		4179	event loop, you will now have to lock:
		4180
		4181	ev_timer timeout_watcher;
		4182	userdata *u = ev_userdata (EV_A);
		4183
		4184	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4185
		4186	pthread_mutex_lock (&u->lock);
		4187	ev_timer_start (EV_A_ &timeout_watcher);
		4188	ev_async_send (EV_A_ &u->async_w);
		4189	pthread_mutex_unlock (&u->lock);
		4190
		4191	Note that sending the C<ev_async> watcher is required because otherwise
		4192	an event loop currently blocking in the kernel will have no knowledge
		4193	about the newly added timer. By waking up the loop it will pick up any new
		4194	watchers in the next event loop iteration.
		4195
3206	=head2 COROUTINES	4196	=head3 COROUTINES
3207		4197
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	4198	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	4199	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4200	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	4201	different coroutines, and switch freely between both coroutines running
3212	loop, as long as you don't confuse yourself). The only exception is that	4202	the loop, as long as you don't confuse yourself). The only exception is
3213	you must not do this from C<ev_periodic> reschedule callbacks.	4203	that you must not do this from C<ev_periodic> reschedule callbacks.
3214		4204
3215	Care has been invested into making sure that libev does not keep local	4205	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	4206	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	4207	they do not call any callbacks.
3218		4208
		4209	=head2 COMPILER WARNINGS
3219		4210
3220	=head1 COMPLEXITIES	4211	Depending on your compiler and compiler settings, you might get no or a
		4212	lot of warnings when compiling libev code. Some people are apparently
		4213	scared by this.
3221		4214
3222	In this section the complexities of (many of) the algorithms used inside	4215	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	4216	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	4217	warning options. "Warn-free" code therefore cannot be a goal except when
		4218	targeting a specific compiler and compiler-version.
3225		4219
3226	All of the following are about amortised time: If an array needs to be	4220	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	4221	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	4222	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		4223
3232	=over 4	4224	And of course, some compiler warnings are just plain stupid, or simply
		4225	wrong (because they don't actually warn about the condition their message
		4226	seems to warn about). For example, certain older gcc versions had some
		4227	warnings that resulted an extreme number of false positives. These have
		4228	been fixed, but some people still insist on making code warn-free with
		4229	such buggy versions.
3233		4230
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4231	While libev is written to generate as few warnings as possible,
		4232	"warn-free" code is not a goal, and it is recommended not to build libev
		4233	with any compiler warnings enabled unless you are prepared to cope with
		4234	them (e.g. by ignoring them). Remember that warnings are just that:
		4235	warnings, not errors, or proof of bugs.
3235		4236
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		4237
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4238	=head2 VALGRIND
3241		4239
3242	That means that changing a timer costs less than removing/adding them	4240	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	4241	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		4242
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4243	If you think you found a bug (memory leak, uninitialised data access etc.)
		4244	in libev, then check twice: If valgrind reports something like:
3246		4245
3247	These just add the watcher into an array or at the head of a list.	4246	==2274== definitely lost: 0 bytes in 0 blocks.
		4247	==2274== possibly lost: 0 bytes in 0 blocks.
		4248	==2274== still reachable: 256 bytes in 1 blocks.
3248		4249
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4250	Then there is no memory leak, just as memory accounted to global variables
		4251	is not a memleak - the memory is still being referenced, and didn't leak.
3250		4252
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4253	Similarly, under some circumstances, valgrind might report kernel bugs
		4254	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4255	although an acceptable workaround has been found here), or it might be
		4256	confused.
3252		4257
3253	These watchers are stored in lists then need to be walked to find the	4258	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	4259	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		4260
3257	=item Finding the next timer in each loop iteration: O(1)	4261	If you are unsure about something, feel free to contact the mailing list
		4262	with the full valgrind report and an explanation on why you think this
		4263	is a bug in libev (best check the archives, too :). However, don't be
		4264	annoyed when you get a brisk "this is no bug" answer and take the chance
		4265	of learning how to interpret valgrind properly.
3258		4266
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	4267	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	4268	I suggest using suppression lists.
3261		4269
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		4270
3264	A change means an I/O watcher gets started or stopped, which requires	4271	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and whether C<ev_io_set> was used).
3267		4272
3268	=item Activating one watcher (putting it into the pending state): O(1)	4273	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3269
3270	=item Priority handling: O(number_of_priorities)
3271
3272	Priorities are implemented by allocating some space for each
3273	priority. When doing priority-based operations, libev usually has to
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276
3277	=item Sending an ev_async: O(1)
3278
3279	=item Processing ev_async_send: O(number_of_async_watchers)
3280
3281	=item Processing signals: O(max_signal_number)
3282
3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
3284	calls in the current loop iteration. Checking for async and signal events
3285	involves iterating over all running async watchers or all signal numbers.
3286
3287	=back
3288
3289
3290	=head1 Win32 platform limitations and workarounds
3291		4274
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4275	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	4276	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	4277	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4278	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3302	way (note also that glib is the slowest event library known to man).	4285	way (note also that glib is the slowest event library known to man).
3303		4286
3304	There is no supported compilation method available on windows except	4287	There is no supported compilation method available on windows except
3305	embedding it into other applications.	4288	embedding it into other applications.
3306		4289
		4290	Sensible signal handling is officially unsupported by Microsoft - libev
		4291	tries its best, but under most conditions, signals will simply not work.
		4292
		4293	Not a libev limitation but worth mentioning: windows apparently doesn't
		4294	accept large writes: instead of resulting in a partial write, windows will
		4295	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4296	so make sure you only write small amounts into your sockets (less than a
		4297	megabyte seems safe, but this apparently depends on the amount of memory
		4298	available).
		4299
3307	Due to the many, low, and arbitrary limits on the win32 platform and	4300	Due to the many, low, and arbitrary limits on the win32 platform and
3308	the abysmal performance of winsockets, using a large number of sockets	4301	the abysmal performance of winsockets, using a large number of sockets
3309	is not recommended (and not reasonable). If your program needs to use	4302	is not recommended (and not reasonable). If your program needs to use
3310	more than a hundred or so sockets, then likely it needs to use a totally	4303	more than a hundred or so sockets, then likely it needs to use a totally
3311	different implementation for windows, as libev offers the POSIX readiness	4304	different implementation for windows, as libev offers the POSIX readiness
3312	notification model, which cannot be implemented efficiently on windows	4305	notification model, which cannot be implemented efficiently on windows
3313	(Microsoft monopoly games).	4306	(due to Microsoft monopoly games).
		4307
		4308	A typical way to use libev under windows is to embed it (see the embedding
		4309	section for details) and use the following F<evwrap.h> header file instead
		4310	of F<ev.h>:
		4311
		4312	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4313	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4314
		4315	#include "ev.h"
		4316
		4317	And compile the following F<evwrap.c> file into your project (make sure
		4318	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4319
		4320	#include "evwrap.h"
		4321	#include "ev.c"
3314		4322
3315	=over 4	4323	=over 4
3316		4324
3317	=item The winsocket select function	4325	=item The winsocket select function
3318		4326
3319	The winsocket C<select> function doesn't follow POSIX in that it	4327	The winsocket C<select> function doesn't follow POSIX in that it
3320	requires socket I<handles> and not socket I<file descriptors> (it is	4328	requires socket I<handles> and not socket I<file descriptors> (it is
3321	also extremely buggy). This makes select very inefficient, and also	4329	also extremely buggy). This makes select very inefficient, and also
3322	requires a mapping from file descriptors to socket handles. See the	4330	requires a mapping from file descriptors to socket handles (the Microsoft
		4331	C runtime provides the function C<_open_osfhandle> for this). See the
3323	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	4332	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3324	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	4333	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3325		4334
3326	The configuration for a "naked" win32 using the Microsoft runtime	4335	The configuration for a "naked" win32 using the Microsoft runtime
3327	libraries and raw winsocket select is:	4336	libraries and raw winsocket select is:
3328		4337
3329	#define EV_USE_SELECT 1	4338	#define EV_USE_SELECT 1
3330	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4339	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3331		4340
3332	Note that winsockets handling of fd sets is O(n), so you can easily get a	4341	Note that winsockets handling of fd sets is O(n), so you can easily get a
3333	complexity in the O(n²) range when using win32.	4342	complexity in the O(n²) range when using win32.
3334		4343
3335	=item Limited number of file descriptors	4344	=item Limited number of file descriptors
…		…
3338		4347
3339	Early versions of winsocket's select only supported waiting for a maximum	4348	Early versions of winsocket's select only supported waiting for a maximum
3340	of C<64> handles (probably owning to the fact that all windows kernels	4349	of C<64> handles (probably owning to the fact that all windows kernels
3341	can only wait for C<64> things at the same time internally; Microsoft	4350	can only wait for C<64> things at the same time internally; Microsoft
3342	recommends spawning a chain of threads and wait for 63 handles and the	4351	recommends spawning a chain of threads and wait for 63 handles and the
3343	previous thread in each. Great).	4352	previous thread in each. Sounds great!).
3344		4353
3345	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4354	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3346	to some high number (e.g. C<2048>) before compiling the winsocket select	4355	to some high number (e.g. C<2048>) before compiling the winsocket select
3347	call (which might be in libev or elsewhere, for example, perl does its own	4356	call (which might be in libev or elsewhere, for example, perl and many
3348	select emulation on windows).	4357	other interpreters do their own select emulation on windows).
3349		4358
3350	Another limit is the number of file descriptors in the Microsoft runtime	4359	Another limit is the number of file descriptors in the Microsoft runtime
3351	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4360	libraries, which by default is C<64> (there must be a hidden I<64>
3352	or something like this inside Microsoft). You can increase this by calling	4361	fetish or something like this inside Microsoft). You can increase this
3353	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4362	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3354	arbitrary limit), but is broken in many versions of the Microsoft runtime	4363	(another arbitrary limit), but is broken in many versions of the Microsoft
3355	libraries.
3356
3357	This might get you to about C<512> or C<2048> sockets (depending on	4364	runtime libraries. This might get you to about C<512> or C<2048> sockets
3358	windows version and/or the phase of the moon). To get more, you need to	4365	(depending on windows version and/or the phase of the moon). To get more,
3359	wrap all I/O functions and provide your own fd management, but the cost of	4366	you need to wrap all I/O functions and provide your own fd management, but
3360	calling select (O(n²)) will likely make this unworkable.	4367	the cost of calling select (O(n²)) will likely make this unworkable.
3361		4368
3362	=back	4369	=back
3363		4370
3364
3365	=head1 PORTABILITY REQUIREMENTS	4371	=head2 PORTABILITY REQUIREMENTS
3366		4372
3367	In addition to a working ISO-C implementation, libev relies on a few	4373	In addition to a working ISO-C implementation and of course the
3368	additional extensions:	4374	backend-specific APIs, libev relies on a few additional extensions:
3369		4375
3370	=over 4	4376	=over 4
3371		4377
		4378	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4379	calling conventions regardless of C<ev_watcher_type *>.
		4380
		4381	Libev assumes not only that all watcher pointers have the same internal
		4382	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4383	assumes that the same (machine) code can be used to call any watcher
		4384	callback: The watcher callbacks have different type signatures, but libev
		4385	calls them using an C<ev_watcher *> internally.
		4386
3372	=item C<sig_atomic_t volatile> must be thread-atomic as well	4387	=item C<sig_atomic_t volatile> must be thread-atomic as well
3373		4388
3374	The type C<sig_atomic_t volatile> (or whatever is defined as	4389	The type C<sig_atomic_t volatile> (or whatever is defined as
3375	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4390	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3376	threads. This is not part of the specification for C<sig_atomic_t>, but is	4391	threads. This is not part of the specification for C<sig_atomic_t>, but is
3377	believed to be sufficiently portable.	4392	believed to be sufficiently portable.
3378		4393
3379	=item C<sigprocmask> must work in a threaded environment	4394	=item C<sigprocmask> must work in a threaded environment
3380		4395
…		…
3389	except the initial one, and run the default loop in the initial thread as	4404	except the initial one, and run the default loop in the initial thread as
3390	well.	4405	well.
3391		4406
3392	=item C<long> must be large enough for common memory allocation sizes	4407	=item C<long> must be large enough for common memory allocation sizes
3393		4408
3394	To improve portability and simplify using libev, libev uses C<long>	4409	To improve portability and simplify its API, libev uses C<long> internally
3395	internally instead of C<size_t> when allocating its data structures. On	4410	instead of C<size_t> when allocating its data structures. On non-POSIX
3396	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4411	systems (Microsoft...) this might be unexpectedly low, but is still at
3397	is still at least 31 bits everywhere, which is enough for hundreds of	4412	least 31 bits everywhere, which is enough for hundreds of millions of
3398	millions of watchers.	4413	watchers.
3399		4414
3400	=item C<double> must hold a time value in seconds with enough accuracy	4415	=item C<double> must hold a time value in seconds with enough accuracy
3401		4416
3402	The type C<double> is used to represent timestamps. It is required to	4417	The type C<double> is used to represent timestamps. It is required to
3403	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4418	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3404	enough for at least into the year 4000. This requirement is fulfilled by	4419	enough for at least into the year 4000. This requirement is fulfilled by
3405	implementations implementing IEEE 754 (basically all existing ones).	4420	implementations implementing IEEE 754, which is basically all existing
		4421	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4422	2200.
3406		4423
3407	=back	4424	=back
3408		4425
3409	If you know of other additional requirements drop me a note.	4426	If you know of other additional requirements drop me a note.
3410		4427
3411		4428
3412	=head1 COMPILER WARNINGS	4429	=head1 ALGORITHMIC COMPLEXITIES
3413		4430
3414	Depending on your compiler and compiler settings, you might get no or a	4431	In this section the complexities of (many of) the algorithms used inside
3415	lot of warnings when compiling libev code. Some people are apparently	4432	libev will be documented. For complexity discussions about backends see
3416	scared by this.	4433	the documentation for C<ev_default_init>.
3417		4434
3418	However, these are unavoidable for many reasons. For one, each compiler	4435	All of the following are about amortised time: If an array needs to be
3419	has different warnings, and each user has different tastes regarding	4436	extended, libev needs to realloc and move the whole array, but this
3420	warning options. "Warn-free" code therefore cannot be a goal except when	4437	happens asymptotically rarer with higher number of elements, so O(1) might
3421	targeting a specific compiler and compiler-version.	4438	mean that libev does a lengthy realloc operation in rare cases, but on
		4439	average it is much faster and asymptotically approaches constant time.
3422		4440
3423	Another reason is that some compiler warnings require elaborate	4441	=over 4
3424	workarounds, or other changes to the code that make it less clear and less
3425	maintainable.
3426		4442
3427	And of course, some compiler warnings are just plain stupid, or simply	4443	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3428	wrong (because they don't actually warn about the condition their message
3429	seems to warn about).
3430		4444
3431	While libev is written to generate as few warnings as possible,	4445	This means that, when you have a watcher that triggers in one hour and
3432	"warn-free" code is not a goal, and it is recommended not to build libev	4446	there are 100 watchers that would trigger before that, then inserting will
3433	with any compiler warnings enabled unless you are prepared to cope with	4447	have to skip roughly seven (C<ld 100>) of these watchers.
3434	them (e.g. by ignoring them). Remember that warnings are just that:
3435	warnings, not errors, or proof of bugs.
3436		4448
		4449	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3437		4450
3438	=head1 VALGRIND	4451	That means that changing a timer costs less than removing/adding them,
		4452	as only the relative motion in the event queue has to be paid for.
3439		4453
3440	Valgrind has a special section here because it is a popular tool that is	4454	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3441	highly useful, but valgrind reports are very hard to interpret.
3442		4455
3443	If you think you found a bug (memory leak, uninitialised data access etc.)	4456	These just add the watcher into an array or at the head of a list.
3444	in libev, then check twice: If valgrind reports something like:
3445		4457
3446	==2274== definitely lost: 0 bytes in 0 blocks.	4458	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3447	==2274== possibly lost: 0 bytes in 0 blocks.
3448	==2274== still reachable: 256 bytes in 1 blocks.
3449		4459
3450	Then there is no memory leak. Similarly, under some circumstances,	4460	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3451	valgrind might report kernel bugs as if it were a bug in libev, or it
3452	might be confused (it is a very good tool, but only a tool).
3453		4461
3454	If you are unsure about something, feel free to contact the mailing list	4462	These watchers are stored in lists, so they need to be walked to find the
3455	with the full valgrind report and an explanation on why you think this is	4463	correct watcher to remove. The lists are usually short (you don't usually
3456	a bug in libev. However, don't be annoyed when you get a brisk "this is	4464	have many watchers waiting for the same fd or signal: one is typical, two
3457	no bug" answer and take the chance of learning how to interpret valgrind	4465	is rare).
3458	properly.
3459		4466
3460	If you need, for some reason, empty reports from valgrind for your project	4467	=item Finding the next timer in each loop iteration: O(1)
3461	I suggest using suppression lists.
3462		4468
		4469	By virtue of using a binary or 4-heap, the next timer is always found at a
		4470	fixed position in the storage array.
		4471
		4472	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4473
		4474	A change means an I/O watcher gets started or stopped, which requires
		4475	libev to recalculate its status (and possibly tell the kernel, depending
		4476	on backend and whether C<ev_io_set> was used).
		4477
		4478	=item Activating one watcher (putting it into the pending state): O(1)
		4479
		4480	=item Priority handling: O(number_of_priorities)
		4481
		4482	Priorities are implemented by allocating some space for each
		4483	priority. When doing priority-based operations, libev usually has to
		4484	linearly search all the priorities, but starting/stopping and activating
		4485	watchers becomes O(1) with respect to priority handling.
		4486
		4487	=item Sending an ev_async: O(1)
		4488
		4489	=item Processing ev_async_send: O(number_of_async_watchers)
		4490
		4491	=item Processing signals: O(max_signal_number)
		4492
		4493	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4494	calls in the current loop iteration. Checking for async and signal events
		4495	involves iterating over all running async watchers or all signal numbers.
		4496
		4497	=back
		4498
		4499
		4500	=head1 GLOSSARY
		4501
		4502	=over 4
		4503
		4504	=item active
		4505
		4506	A watcher is active as long as it has been started (has been attached to
		4507	an event loop) but not yet stopped (disassociated from the event loop).
		4508
		4509	=item application
		4510
		4511	In this document, an application is whatever is using libev.
		4512
		4513	=item callback
		4514
		4515	The address of a function that is called when some event has been
		4516	detected. Callbacks are being passed the event loop, the watcher that
		4517	received the event, and the actual event bitset.
		4518
		4519	=item callback invocation
		4520
		4521	The act of calling the callback associated with a watcher.
		4522
		4523	=item event
		4524
		4525	A change of state of some external event, such as data now being available
		4526	for reading on a file descriptor, time having passed or simply not having
		4527	any other events happening anymore.
		4528
		4529	In libev, events are represented as single bits (such as C<EV_READ> or
		4530	C<EV_TIMEOUT>).
		4531
		4532	=item event library
		4533
		4534	A software package implementing an event model and loop.
		4535
		4536	=item event loop
		4537
		4538	An entity that handles and processes external events and converts them
		4539	into callback invocations.
		4540
		4541	=item event model
		4542
		4543	The model used to describe how an event loop handles and processes
		4544	watchers and events.
		4545
		4546	=item pending
		4547
		4548	A watcher is pending as soon as the corresponding event has been detected,
		4549	and stops being pending as soon as the watcher will be invoked or its
		4550	pending status is explicitly cleared by the application.
		4551
		4552	A watcher can be pending, but not active. Stopping a watcher also clears
		4553	its pending status.
		4554
		4555	=item real time
		4556
		4557	The physical time that is observed. It is apparently strictly monotonic :)
		4558
		4559	=item wall-clock time
		4560
		4561	The time and date as shown on clocks. Unlike real time, it can actually
		4562	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4563	clock.
		4564
		4565	=item watcher
		4566
		4567	A data structure that describes interest in certain events. Watchers need
		4568	to be started (attached to an event loop) before they can receive events.
		4569
		4570	=item watcher invocation
		4571
		4572	The act of calling the callback associated with a watcher.
		4573
		4574	=back
3463		4575
3464	=head1 AUTHOR	4576	=head1 AUTHOR
3465		4577
3466	Marc Lehmann <libev@schmorp.de>.	4578	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3467		4579

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