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Revision 1.136 by root, Thu Mar 13 13:06:16 2008 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
		19	// all watcher callbacks have a similar signature
16	/* called when data readable on stdin */	20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	118	it, you should treat it as some floatingpoint value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
104		121
105	=head1 GLOBAL FUNCTIONS	122	=head1 GLOBAL FUNCTIONS
106		123
107	These functions can be called anytime, even before initialising the	124	These functions can be called anytime, even before initialising the
108	library in any way.	125	library in any way.
…		…
113		130
114	Returns the current time as libev would use it. Please note that the	131	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	132	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	133	you actually want to know.
117		134
		135	=item ev_sleep (ev_tstamp interval)
		136
		137	Sleep for the given interval: The current thread will be blocked until
		138	either it is interrupted or the given time interval has passed. Basically
		139	this is a subsecond-resolution C<sleep ()>.
		140
118	=item int ev_version_major ()	141	=item int ev_version_major ()
119		142
120	=item int ev_version_minor ()	143	=item int ev_version_minor ()
121		144
122	You can find out the major and minor version numbers of the library	145	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	146	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	147	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	148	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	149	version of the library your program was compiled against.
127		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
128	Usually, it's a good idea to terminate if the major versions mismatch,	154	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	156	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	157	not a problem.
132		158
133	Example: Make sure we haven't accidentally been linked against the wrong	159	Example: Make sure we haven't accidentally been linked against the wrong
134	version.	160	version.
…		…
249	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
250		276
251	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
252	function.	278	function.
253		279
		280	The default loop is the only loop that can handle C<ev_signal> and
		281	C<ev_child> watchers, and to do this, it always registers a handler
		282	for C<SIGCHLD>. If this is a problem for your app you can either
		283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		285	C<ev_default_init>.
		286
254	The flags argument can be used to specify special behaviour or specific	287	The flags argument can be used to specify special behaviour or specific
255	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
256		289
257	The following flags are supported:	290	The following flags are supported:
258		291
…		…
279	enabling this flag.	312	enabling this flag.
280		313
281	This works by calling C<getpid ()> on every iteration of the loop,	314	This works by calling C<getpid ()> on every iteration of the loop,
282	and thus this might slow down your event loop if you do a lot of loop	315	and thus this might slow down your event loop if you do a lot of loop
283	iterations and little real work, but is usually not noticeable (on my	316	iterations and little real work, but is usually not noticeable (on my
284	Linux system for example, C<getpid> is actually a simple 5-insn sequence	317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
285	without a syscall and thus I<very> fast, but my Linux system also has	318	without a syscall and thus I<very> fast, but my GNU/Linux system also has
286	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
287		320
288	The big advantage of this flag is that you can forget about fork (and	321	The big advantage of this flag is that you can forget about fork (and
289	forget about forgetting to tell libev about forking) when you use this	322	forget about forgetting to tell libev about forking) when you use this
290	flag.	323	flag.
…		…
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		329
297	This is your standard select(2) backend. Not I<completely> standard, as	330	This is your standard select(2) backend. Not I<completely> standard, as
298	libev tries to roll its own fd_set with no limits on the number of fds,	331	libev tries to roll its own fd_set with no limits on the number of fds,
299	but if that fails, expect a fairly low limit on the number of fds when	332	but if that fails, expect a fairly low limit on the number of fds when
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	333	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	334	usually the fastest backend for a low number of (low-numbered :) fds.
		335
		336	To get good performance out of this backend you need a high amount of
		337	parallelity (most of the file descriptors should be busy). If you are
		338	writing a server, you should C<accept ()> in a loop to accept as many
		339	connections as possible during one iteration. You might also want to have
		340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		341	readyness notifications you get per iteration.
302		342
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		344
305	And this is your standard poll(2) backend. It's more complicated than	345	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	346	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	347	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	348	considerably with a lot of inactive fds). It scales similarly to select,
		349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		350	performance tips.
309		351
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	352	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		353
312	For few fds, this backend is a bit little slower than poll and select,	354	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	355	but it scales phenomenally better. While poll and select usually scale
314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	356	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	357	epoll scales either O(1) or O(active_fds). The epoll design has a number
		358	of shortcomings, such as silently dropping events in some hard-to-detect
		359	cases and rewiring a syscall per fd change, no fork support and bad
		360	support for dup.
316		361
317	While stopping and starting an I/O watcher in the same iteration will	362	While stopping, setting and starting an I/O watcher in the same iteration
318	result in some caching, there is still a syscall per such incident	363	will result in some caching, there is still a syscall per such incident
319	(because the fd could point to a different file description now), so its	364	(because the fd could point to a different file description now), so its
320	best to avoid that. Also, dup()ed file descriptors might not work very	365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	366	very well if you register events for both fds.
322		367
323	Please note that epoll sometimes generates spurious notifications, so you	368	Please note that epoll sometimes generates spurious notifications, so you
324	need to use non-blocking I/O or other means to avoid blocking when no data	369	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	370	(or space) is available.
326		371
		372	Best performance from this backend is achieved by not unregistering all
		373	watchers for a file descriptor until it has been closed, if possible, i.e.
		374	keep at least one watcher active per fd at all times.
		375
		376	While nominally embeddeble in other event loops, this feature is broken in
		377	all kernel versions tested so far.
		378
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		380
329	Kqueue deserves special mention, as at the time of this writing, it	381	Kqueue deserves special mention, as at the time of this writing, it
330	was broken on all BSDs except NetBSD (usually it doesn't work with	382	was broken on all BSDs except NetBSD (usually it doesn't work reliably
331	anything but sockets and pipes, except on Darwin, where of course its	383	with anything but sockets and pipes, except on Darwin, where of course
332	completely useless). For this reason its not being "autodetected"	384	it's completely useless). For this reason it's not being "autodetected"
333	unless you explicitly specify it explicitly in the flags (i.e. using	385	unless you explicitly specify it explicitly in the flags (i.e. using
334	C<EVBACKEND_KQUEUE>).	386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		387	system like NetBSD.
		388
		389	You still can embed kqueue into a normal poll or select backend and use it
		390	only for sockets (after having made sure that sockets work with kqueue on
		391	the target platform). See C<ev_embed> watchers for more info.
335		392
336	It scales in the same way as the epoll backend, but the interface to the	393	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	394	kernel is more efficient (which says nothing about its actual speed, of
338	course). While starting and stopping an I/O watcher does not cause an	395	course). While stopping, setting and starting an I/O watcher does never
339	extra syscall as with epoll, it still adds up to four event changes per	396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	397	two event changes per incident, support for C<fork ()> is very bad and it
		398	drops fds silently in similarly hard-to-detect cases.
		399
		400	This backend usually performs well under most conditions.
		401
		402	While nominally embeddable in other event loops, this doesn't work
		403	everywhere, so you might need to test for this. And since it is broken
		404	almost everywhere, you should only use it when you have a lot of sockets
		405	(for which it usually works), by embedding it into another event loop
		406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		407	sockets.
341		408
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		410
344	This is not implemented yet (and might never be).	411	This is not implemented yet (and might never be, unless you send me an
		412	implementation). According to reports, C</dev/poll> only supports sockets
		413	and is not embeddable, which would limit the usefulness of this backend
		414	immensely.
345		415
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		417
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349	it's really slow, but it still scales very well (O(active_fds)).	419	it's really slow, but it still scales very well (O(active_fds)).
350		420
351	Please note that solaris ports can result in a lot of spurious	421	Please note that solaris event ports can deliver a lot of spurious
352	notifications, so you need to use non-blocking I/O or other means to avoid	422	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	423	blocking when no data (or space) is available.
		424
		425	While this backend scales well, it requires one system call per active
		426	file descriptor per loop iteration. For small and medium numbers of file
		427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		428	might perform better.
		429
		430	On the positive side, ignoring the spurious readyness notifications, this
		431	backend actually performed to specification in all tests and is fully
		432	embeddable, which is a rare feat among the OS-specific backends.
354		433
355	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
356		435
357	Try all backends (even potentially broken ones that wouldn't be tried	436	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		439
		440	It is definitely not recommended to use this flag.
		441
361	=back	442	=back
362		443
363	If one or more of these are ored into the flags value, then only these	444	If one or more of these are ored into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	445	backends will be tried (in the reverse order as listed here). If none are
365	specified, most compiled-in backend will be tried, usually in reverse	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		447
368	The most typical usage is like this:	448	The most typical usage is like this:
369		449
370	if (!ev_default_loop (0))	450	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
399	Destroys the default loop again (frees all memory and kernel state	479	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	480	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	481	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	482	responsibility to either stop all watchers cleanly yoursef I<before>
403	calling this function, or cope with the fact afterwards (which is usually	483	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	484	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	485	for example).
		486
		487	Note that certain global state, such as signal state, will not be freed by
		488	this function, and related watchers (such as signal and child watchers)
		489	would need to be stopped manually.
		490
		491	In general it is not advisable to call this function except in the
		492	rare occasion where you really need to free e.g. the signal handling
		493	pipe fds. If you need dynamically allocated loops it is better to use
		494	C<ev_loop_new> and C<ev_loop_destroy>).
406		495
407	=item ev_loop_destroy (loop)	496	=item ev_loop_destroy (loop)
408		497
409	Like C<ev_default_destroy>, but destroys an event loop created by an	498	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	499	earlier call to C<ev_loop_new>.
411		500
412	=item ev_default_fork ()	501	=item ev_default_fork ()
413		502
		503	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	504	to reinitialise the kernel state for backends that have one. Despite the
415	one. Despite the name, you can call it anytime, but it makes most sense	505	name, you can call it anytime, but it makes most sense after forking, in
416	after forking, in either the parent or child process (or both, but that	506	the child process (or both child and parent, but that again makes little
417	again makes little sense).	507	sense). You I<must> call it in the child before using any of the libev
		508	functions, and it will only take effect at the next C<ev_loop> iteration.
418		509
419	You I<must> call this function in the child process after forking if and	510	On the other hand, you only need to call this function in the child
420	only if you want to use the event library in both processes. If you just	511	process if and only if you want to use the event library in the child. If
421	fork+exec, you don't have to call it.	512	you just fork+exec, you don't have to call it at all.
422		513
423	The function itself is quite fast and it's usually not a problem to call	514	The function itself is quite fast and it's usually not a problem to call
424	it just in case after a fork. To make this easy, the function will fit in	515	it just in case after a fork. To make this easy, the function will fit in
425	quite nicely into a call to C<pthread_atfork>:	516	quite nicely into a call to C<pthread_atfork>:
426		517
427	pthread_atfork (0, 0, ev_default_fork);	518	pthread_atfork (0, 0, ev_default_fork);
428		519
429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
430	without calling this function, so if you force one of those backends you
431	do not need to care.
432
433	=item ev_loop_fork (loop)	520	=item ev_loop_fork (loop)
434		521
435	Like C<ev_default_fork>, but acts on an event loop created by	522	Like C<ev_default_fork>, but acts on an event loop created by
436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	523	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
437	after fork, and how you do this is entirely your own problem.	524	after fork, and how you do this is entirely your own problem.
		525
		526	=item int ev_is_default_loop (loop)
		527
		528	Returns true when the given loop actually is the default loop, false otherwise.
438		529
439	=item unsigned int ev_loop_count (loop)	530	=item unsigned int ev_loop_count (loop)
440		531
441	Returns the count of loop iterations for the loop, which is identical to	532	Returns the count of loop iterations for the loop, which is identical to
442	the number of times libev did poll for new events. It starts at C<0> and	533	the number of times libev did poll for new events. It starts at C<0> and
…		…
455		546
456	Returns the current "event loop time", which is the time the event loop	547	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	548	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	549	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	550	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	551	event occurring (or more correctly, libev finding out about it).
461		552
462	=item ev_loop (loop, int flags)	553	=item ev_loop (loop, int flags)
463		554
464	Finally, this is it, the event handler. This function usually is called	555	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	556	after you initialised all your watchers and you want to start handling
…		…
486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	577	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	578	usually a better approach for this kind of thing.
488		579
489	Here are the gory details of what C<ev_loop> does:	580	Here are the gory details of what C<ev_loop> does:
490		581
491	* If there are no active watchers (reference count is zero), return.	582	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	583	* If EVFLAG_FORKCHECK was used, check for a fork.
		584	- If a fork was detected, queue and call all fork watchers.
		585	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	586	- If we have been forked, recreate the kernel state.
494	- Update the kernel state with all outstanding changes.	587	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	588	- Update the "event loop time".
496	- Calculate for how long to block.	589	- Calculate for how long to sleep or block, if at all
		590	(active idle watchers, EVLOOP_NONBLOCK or not having
		591	any active watchers at all will result in not sleeping).
		592	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	593	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	594	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	595	- Update the "event loop time" and do time jump handling.
500	- Queue all outstanding timers.	596	- Queue all outstanding timers.
501	- Queue all outstanding periodics.	597	- Queue all outstanding periodics.
502	- If no events are pending now, queue all idle watchers.	598	- If no events are pending now, queue all idle watchers.
503	- Queue all check watchers.	599	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	600	- Call all queued watchers in reverse order (i.e. check watchers first).
505	Signals and child watchers are implemented as I/O watchers, and will	601	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	602	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	604	were used, or there are no active watchers, return, otherwise
		605	continue with step *.
509		606
510	Example: Queue some jobs and then loop until no events are outsanding	607	Example: Queue some jobs and then loop until no events are outstanding
511	anymore.	608	anymore.
512		609
513	... queue jobs here, make sure they register event watchers as long	610	... queue jobs here, make sure they register event watchers as long
514	... as they still have work to do (even an idle watcher will do..)	611	... as they still have work to do (even an idle watcher will do..)
515	ev_loop (my_loop, 0);	612	ev_loop (my_loop, 0);
…		…
519		616
520	Can be used to make a call to C<ev_loop> return early (but only after it	617	Can be used to make a call to C<ev_loop> return early (but only after it
521	has processed all outstanding events). The C<how> argument must be either	618	has processed all outstanding events). The C<how> argument must be either
522	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	619	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
523	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	620	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		621
		622	This "unloop state" will be cleared when entering C<ev_loop> again.
524		623
525	=item ev_ref (loop)	624	=item ev_ref (loop)
526		625
527	=item ev_unref (loop)	626	=item ev_unref (loop)
528		627
…		…
533	returning, ev_unref() after starting, and ev_ref() before stopping it. For	632	returning, ev_unref() after starting, and ev_ref() before stopping it. For
534	example, libev itself uses this for its internal signal pipe: It is not	633	example, libev itself uses this for its internal signal pipe: It is not
535	visible to the libev user and should not keep C<ev_loop> from exiting if	634	visible to the libev user and should not keep C<ev_loop> from exiting if
536	no event watchers registered by it are active. It is also an excellent	635	no event watchers registered by it are active. It is also an excellent
537	way to do this for generic recurring timers or from within third-party	636	way to do this for generic recurring timers or from within third-party
538	libraries. Just remember to I<unref after start> and I<ref before stop>.	637	libraries. Just remember to I<unref after start> and I<ref before stop>
		638	(but only if the watcher wasn't active before, or was active before,
		639	respectively).
539		640
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	642	running when nothing else is active.
542		643
543	struct ev_signal exitsig;	644	struct ev_signal exitsig;
…		…
547		648
548	Example: For some weird reason, unregister the above signal handler again.	649	Example: For some weird reason, unregister the above signal handler again.
549		650
550	ev_ref (loop);	651	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	652	ev_signal_stop (loop, &exitsig);
		653
		654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		655
		656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		657
		658	These advanced functions influence the time that libev will spend waiting
		659	for events. Both are by default C<0>, meaning that libev will try to
		660	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		661
		662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		663	allows libev to delay invocation of I/O and timer/periodic callbacks to
		664	increase efficiency of loop iterations.
		665
		666	The background is that sometimes your program runs just fast enough to
		667	handle one (or very few) event(s) per loop iteration. While this makes
		668	the program responsive, it also wastes a lot of CPU time to poll for new
		669	events, especially with backends like C<select ()> which have a high
		670	overhead for the actual polling but can deliver many events at once.
		671
		672	By setting a higher I<io collect interval> you allow libev to spend more
		673	time collecting I/O events, so you can handle more events per iteration,
		674	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		675	C<ev_timer>) will be not affected. Setting this to a non-null value will
		676	introduce an additional C<ev_sleep ()> call into most loop iterations.
		677
		678	Likewise, by setting a higher I<timeout collect interval> you allow libev
		679	to spend more time collecting timeouts, at the expense of increased
		680	latency (the watcher callback will be called later). C<ev_io> watchers
		681	will not be affected. Setting this to a non-null value will not introduce
		682	any overhead in libev.
		683
		684	Many (busy) programs can usually benefit by setting the io collect
		685	interval to a value near C<0.1> or so, which is often enough for
		686	interactive servers (of course not for games), likewise for timeouts. It
		687	usually doesn't make much sense to set it to a lower value than C<0.01>,
		688	as this approsaches the timing granularity of most systems.
552		689
553	=back	690	=back
554		691
555		692
556	=head1 ANATOMY OF A WATCHER	693	=head1 ANATOMY OF A WATCHER
…		…
656	=item C<EV_FORK>	793	=item C<EV_FORK>
657		794
658	The event loop has been resumed in the child process after fork (see	795	The event loop has been resumed in the child process after fork (see
659	C<ev_fork>).	796	C<ev_fork>).
660		797
		798	=item C<EV_ASYNC>
		799
		800	The given async watcher has been asynchronously notified (see C<ev_async>).
		801
661	=item C<EV_ERROR>	802	=item C<EV_ERROR>
662		803
663	An unspecified error has occured, the watcher has been stopped. This might	804	An unspecified error has occured, the watcher has been stopped. This might
664	happen because the watcher could not be properly started because libev	805	happen because the watcher could not be properly started because libev
665	ran out of memory, a file descriptor was found to be closed or any other	806	ran out of memory, a file descriptor was found to be closed or any other
…		…
736	=item bool ev_is_pending (ev_TYPE *watcher)	877	=item bool ev_is_pending (ev_TYPE *watcher)
737		878
738	Returns a true value iff the watcher is pending, (i.e. it has outstanding	879	Returns a true value iff the watcher is pending, (i.e. it has outstanding
739	events but its callback has not yet been invoked). As long as a watcher	880	events but its callback has not yet been invoked). As long as a watcher
740	is pending (but not active) you must not call an init function on it (but	881	is pending (but not active) you must not call an init function on it (but
741	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	882	C<ev_TYPE_set> is safe), you must not change its priority, and you must
742	libev (e.g. you cnanot C<free ()> it).	883	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		884	it).
743		885
744	=item callback ev_cb (ev_TYPE *watcher)	886	=item callback ev_cb (ev_TYPE *watcher)
745		887
746	Returns the callback currently set on the watcher.	888	Returns the callback currently set on the watcher.
747		889
…		…
766	watchers on the same event and make sure one is called first.	908	watchers on the same event and make sure one is called first.
767		909
768	If you need to suppress invocation when higher priority events are pending	910	If you need to suppress invocation when higher priority events are pending
769	you need to look at C<ev_idle> watchers, which provide this functionality.	911	you need to look at C<ev_idle> watchers, which provide this functionality.
770		912
		913	You I<must not> change the priority of a watcher as long as it is active or
		914	pending.
		915
771	The default priority used by watchers when no priority has been set is	916	The default priority used by watchers when no priority has been set is
772	always C<0>, which is supposed to not be too high and not be too low :).	917	always C<0>, which is supposed to not be too high and not be too low :).
773		918
774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	919	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
775	fine, as long as you do not mind that the priority value you query might	920	fine, as long as you do not mind that the priority value you query might
776	or might not have been adjusted to be within valid range.	921	or might not have been adjusted to be within valid range.
		922
		923	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		924
		925	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		926	C<loop> nor C<revents> need to be valid as long as the watcher callback
		927	can deal with that fact.
		928
		929	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		930
		931	If the watcher is pending, this function returns clears its pending status
		932	and returns its C<revents> bitset (as if its callback was invoked). If the
		933	watcher isn't pending it does nothing and returns C<0>.
777		934
778	=back	935	=back
779		936
780		937
781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	938	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
866	In general you can register as many read and/or write event watchers per	1023	In general you can register as many read and/or write event watchers per
867	fd as you want (as long as you don't confuse yourself). Setting all file	1024	fd as you want (as long as you don't confuse yourself). Setting all file
868	descriptors to non-blocking mode is also usually a good idea (but not	1025	descriptors to non-blocking mode is also usually a good idea (but not
869	required if you know what you are doing).	1026	required if you know what you are doing).
870		1027
871	You have to be careful with dup'ed file descriptors, though. Some backends
872	(the linux epoll backend is a notable example) cannot handle dup'ed file
873	descriptors correctly if you register interest in two or more fds pointing
874	to the same underlying file/socket/etc. description (that is, they share
875	the same underlying "file open").
876
877	If you must do this, then force the use of a known-to-be-good backend	1028	If you must do this, then force the use of a known-to-be-good backend
878	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
879	C<EVBACKEND_POLL>).	1030	C<EVBACKEND_POLL>).
880		1031
881	Another thing you have to watch out for is that it is quite easy to	1032	Another thing you have to watch out for is that it is quite easy to
…		…
891	play around with an Xlib connection), then you have to seperately re-test	1042	play around with an Xlib connection), then you have to seperately re-test
892	whether a file descriptor is really ready with a known-to-be good interface	1043	whether a file descriptor is really ready with a known-to-be good interface
893	such as poll (fortunately in our Xlib example, Xlib already does this on	1044	such as poll (fortunately in our Xlib example, Xlib already does this on
894	its own, so its quite safe to use).	1045	its own, so its quite safe to use).
895		1046
		1047	=head3 The special problem of disappearing file descriptors
		1048
		1049	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1050	descriptor (either by calling C<close> explicitly or by any other means,
		1051	such as C<dup>). The reason is that you register interest in some file
		1052	descriptor, but when it goes away, the operating system will silently drop
		1053	this interest. If another file descriptor with the same number then is
		1054	registered with libev, there is no efficient way to see that this is, in
		1055	fact, a different file descriptor.
		1056
		1057	To avoid having to explicitly tell libev about such cases, libev follows
		1058	the following policy: Each time C<ev_io_set> is being called, libev
		1059	will assume that this is potentially a new file descriptor, otherwise
		1060	it is assumed that the file descriptor stays the same. That means that
		1061	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1062	descriptor even if the file descriptor number itself did not change.
		1063
		1064	This is how one would do it normally anyway, the important point is that
		1065	the libev application should not optimise around libev but should leave
		1066	optimisations to libev.
		1067
		1068	=head3 The special problem of dup'ed file descriptors
		1069
		1070	Some backends (e.g. epoll), cannot register events for file descriptors,
		1071	but only events for the underlying file descriptions. That means when you
		1072	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1073	events for them, only one file descriptor might actually receive events.
		1074
		1075	There is no workaround possible except not registering events
		1076	for potentially C<dup ()>'ed file descriptors, or to resort to
		1077	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1078
		1079	=head3 The special problem of fork
		1080
		1081	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1082	useless behaviour. Libev fully supports fork, but needs to be told about
		1083	it in the child.
		1084
		1085	To support fork in your programs, you either have to call
		1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1088	C<EVBACKEND_POLL>.
		1089
		1090
		1091	=head3 Watcher-Specific Functions
		1092
896	=over 4	1093	=over 4
897		1094
898	=item ev_io_init (ev_io *, callback, int fd, int events)	1095	=item ev_io_init (ev_io *, callback, int fd, int events)
899		1096
900	=item ev_io_set (ev_io *, int fd, int events)	1097	=item ev_io_set (ev_io *, int fd, int events)
…		…
910	=item int events [read-only]	1107	=item int events [read-only]
911		1108
912	The events being watched.	1109	The events being watched.
913		1110
914	=back	1111	=back
		1112
		1113	=head3 Examples
915		1114
916	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1115	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
917	readable, but only once. Since it is likely line-buffered, you could	1116	readable, but only once. Since it is likely line-buffered, you could
918	attempt to read a whole line in the callback.	1117	attempt to read a whole line in the callback.
919		1118
…		…
953		1152
954	The callback is guarenteed to be invoked only when its timeout has passed,	1153	The callback is guarenteed to be invoked only when its timeout has passed,
955	but if multiple timers become ready during the same loop iteration then	1154	but if multiple timers become ready during the same loop iteration then
956	order of execution is undefined.	1155	order of execution is undefined.
957		1156
		1157	=head3 Watcher-Specific Functions and Data Members
		1158
958	=over 4	1159	=over 4
959		1160
960	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1161	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
961		1162
962	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1163	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
970	configure a timer to trigger every 10 seconds, then it will trigger at	1171	configure a timer to trigger every 10 seconds, then it will trigger at
971	exactly 10 second intervals. If, however, your program cannot keep up with	1172	exactly 10 second intervals. If, however, your program cannot keep up with
972	the timer (because it takes longer than those 10 seconds to do stuff) the	1173	the timer (because it takes longer than those 10 seconds to do stuff) the
973	timer will not fire more than once per event loop iteration.	1174	timer will not fire more than once per event loop iteration.
974		1175
975	=item ev_timer_again (loop)	1176	=item ev_timer_again (loop, ev_timer *)
976		1177
977	This will act as if the timer timed out and restart it again if it is	1178	This will act as if the timer timed out and restart it again if it is
978	repeating. The exact semantics are:	1179	repeating. The exact semantics are:
979		1180
980	If the timer is pending, its pending status is cleared.	1181	If the timer is pending, its pending status is cleared.
…		…
1015	or C<ev_timer_again> is called and determines the next timeout (if any),	1216	or C<ev_timer_again> is called and determines the next timeout (if any),
1016	which is also when any modifications are taken into account.	1217	which is also when any modifications are taken into account.
1017		1218
1018	=back	1219	=back
1019		1220
		1221	=head3 Examples
		1222
1020	Example: Create a timer that fires after 60 seconds.	1223	Example: Create a timer that fires after 60 seconds.
1021		1224
1022	static void	1225	static void
1023	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1226	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1024	{	1227	{
…		…
1057	but on wallclock time (absolute time). You can tell a periodic watcher	1260	but on wallclock time (absolute time). You can tell a periodic watcher
1058	to trigger "at" some specific point in time. For example, if you tell a	1261	to trigger "at" some specific point in time. For example, if you tell a
1059	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1262	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1060	+ 10.>) and then reset your system clock to the last year, then it will	1263	+ 10.>) and then reset your system clock to the last year, then it will
1061	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1264	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1062	roughly 10 seconds later and of course not if you reset your system time	1265	roughly 10 seconds later).
1063	again).
1064		1266
1065	They can also be used to implement vastly more complex timers, such as	1267	They can also be used to implement vastly more complex timers, such as
1066	triggering an event on eahc midnight, local time.	1268	triggering an event on each midnight, local time or other, complicated,
		1269	rules.
1067		1270
1068	As with timers, the callback is guarenteed to be invoked only when the	1271	As with timers, the callback is guarenteed to be invoked only when the
1069	time (C<at>) has been passed, but if multiple periodic timers become ready	1272	time (C<at>) has been passed, but if multiple periodic timers become ready
1070	during the same loop iteration then order of execution is undefined.	1273	during the same loop iteration then order of execution is undefined.
1071		1274
		1275	=head3 Watcher-Specific Functions and Data Members
		1276
1072	=over 4	1277	=over 4
1073		1278
1074	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1279	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1075		1280
1076	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1281	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1078	Lots of arguments, lets sort it out... There are basically three modes of	1283	Lots of arguments, lets sort it out... There are basically three modes of
1079	operation, and we will explain them from simplest to complex:	1284	operation, and we will explain them from simplest to complex:
1080		1285
1081	=over 4	1286	=over 4
1082		1287
1083	=item * absolute timer (interval = reschedule_cb = 0)	1288	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1084		1289
1085	In this configuration the watcher triggers an event at the wallclock time	1290	In this configuration the watcher triggers an event at the wallclock time
1086	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1291	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1087	that is, if it is to be run at January 1st 2011 then it will run when the	1292	that is, if it is to be run at January 1st 2011 then it will run when the
1088	system time reaches or surpasses this time.	1293	system time reaches or surpasses this time.
1089		1294
1090	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1091		1296
1092	In this mode the watcher will always be scheduled to time out at the next	1297	In this mode the watcher will always be scheduled to time out at the next
1093	C<at + N * interval> time (for some integer N) and then repeat, regardless	1298	C<at + N * interval> time (for some integer N, which can also be negative)
1094	of any time jumps.	1299	and then repeat, regardless of any time jumps.
1095		1300
1096	This can be used to create timers that do not drift with respect to system	1301	This can be used to create timers that do not drift with respect to system
1097	time:	1302	time:
1098		1303
1099	ev_periodic_set (&periodic, 0., 3600., 0);	1304	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1105		1310
1106	Another way to think about it (for the mathematically inclined) is that	1311	Another way to think about it (for the mathematically inclined) is that
1107	C<ev_periodic> will try to run the callback in this mode at the next possible	1312	C<ev_periodic> will try to run the callback in this mode at the next possible
1108	time where C<time = at (mod interval)>, regardless of any time jumps.	1313	time where C<time = at (mod interval)>, regardless of any time jumps.
1109		1314
		1315	For numerical stability it is preferable that the C<at> value is near
		1316	C<ev_now ()> (the current time), but there is no range requirement for
		1317	this value.
		1318
1110	=item * manual reschedule mode (reschedule_cb = callback)	1319	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1111		1320
1112	In this mode the values for C<interval> and C<at> are both being	1321	In this mode the values for C<interval> and C<at> are both being
1113	ignored. Instead, each time the periodic watcher gets scheduled, the	1322	ignored. Instead, each time the periodic watcher gets scheduled, the
1114	reschedule callback will be called with the watcher as first, and the	1323	reschedule callback will be called with the watcher as first, and the
1115	current time as second argument.	1324	current time as second argument.
1116		1325
1117	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1326	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1118	ever, or make any event loop modifications>. If you need to stop it,	1327	ever, or make any event loop modifications>. If you need to stop it,
1119	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1328	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1120	starting a prepare watcher).	1329	starting an C<ev_prepare> watcher, which is legal).
1121		1330
1122	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1331	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1123	ev_tstamp now)>, e.g.:	1332	ev_tstamp now)>, e.g.:
1124		1333
1125	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1334	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1148	Simply stops and restarts the periodic watcher again. This is only useful	1357	Simply stops and restarts the periodic watcher again. This is only useful
1149	when you changed some parameters or the reschedule callback would return	1358	when you changed some parameters or the reschedule callback would return
1150	a different time than the last time it was called (e.g. in a crond like	1359	a different time than the last time it was called (e.g. in a crond like
1151	program when the crontabs have changed).	1360	program when the crontabs have changed).
1152		1361
		1362	=item ev_tstamp offset [read-write]
		1363
		1364	When repeating, this contains the offset value, otherwise this is the
		1365	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1366
		1367	Can be modified any time, but changes only take effect when the periodic
		1368	timer fires or C<ev_periodic_again> is being called.
		1369
1153	=item ev_tstamp interval [read-write]	1370	=item ev_tstamp interval [read-write]
1154		1371
1155	The current interval value. Can be modified any time, but changes only	1372	The current interval value. Can be modified any time, but changes only
1156	take effect when the periodic timer fires or C<ev_periodic_again> is being	1373	take effect when the periodic timer fires or C<ev_periodic_again> is being
1157	called.	1374	called.
…		…
1160		1377
1161	The current reschedule callback, or C<0>, if this functionality is	1378	The current reschedule callback, or C<0>, if this functionality is
1162	switched off. Can be changed any time, but changes only take effect when	1379	switched off. Can be changed any time, but changes only take effect when
1163	the periodic timer fires or C<ev_periodic_again> is being called.	1380	the periodic timer fires or C<ev_periodic_again> is being called.
1164		1381
		1382	=item ev_tstamp at [read-only]
		1383
		1384	When active, contains the absolute time that the watcher is supposed to
		1385	trigger next.
		1386
1165	=back	1387	=back
		1388
		1389	=head3 Examples
1166		1390
1167	Example: Call a callback every hour, or, more precisely, whenever the	1391	Example: Call a callback every hour, or, more precisely, whenever the
1168	system clock is divisible by 3600. The callback invocation times have	1392	system clock is divisible by 3600. The callback invocation times have
1169	potentially a lot of jittering, but good long-term stability.	1393	potentially a lot of jittering, but good long-term stability.
1170		1394
…		…
1210	with the kernel (thus it coexists with your own signal handlers as long	1434	with the kernel (thus it coexists with your own signal handlers as long
1211	as you don't register any with libev). Similarly, when the last signal	1435	as you don't register any with libev). Similarly, when the last signal
1212	watcher for a signal is stopped libev will reset the signal handler to	1436	watcher for a signal is stopped libev will reset the signal handler to
1213	SIG_DFL (regardless of what it was set to before).	1437	SIG_DFL (regardless of what it was set to before).
1214		1438
		1439	If possible and supported, libev will install its handlers with
		1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1441	interrupted. If you have a problem with syscalls getting interrupted by
		1442	signals you can block all signals in an C<ev_check> watcher and unblock
		1443	them in an C<ev_prepare> watcher.
		1444
		1445	=head3 Watcher-Specific Functions and Data Members
		1446
1215	=over 4	1447	=over 4
1216		1448
1217	=item ev_signal_init (ev_signal *, callback, int signum)	1449	=item ev_signal_init (ev_signal *, callback, int signum)
1218		1450
1219	=item ev_signal_set (ev_signal *, int signum)	1451	=item ev_signal_set (ev_signal *, int signum)
…		…
1225		1457
1226	The signal the watcher watches out for.	1458	The signal the watcher watches out for.
1227		1459
1228	=back	1460	=back
1229		1461
		1462	=head3 Examples
		1463
		1464	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1465
		1466	static void
		1467	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1468	{
		1469	ev_unloop (loop, EVUNLOOP_ALL);
		1470	}
		1471
		1472	struct ev_signal signal_watcher;
		1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1474	ev_signal_start (loop, &sigint_cb);
		1475
1230		1476
1231	=head2 C<ev_child> - watch out for process status changes	1477	=head2 C<ev_child> - watch out for process status changes
1232		1478
1233	Child watchers trigger when your process receives a SIGCHLD in response to	1479	Child watchers trigger when your process receives a SIGCHLD in response to
1234	some child status changes (most typically when a child of yours dies).	1480	some child status changes (most typically when a child of yours dies). It
		1481	is permissible to install a child watcher I<after> the child has been
		1482	forked (which implies it might have already exited), as long as the event
		1483	loop isn't entered (or is continued from a watcher).
		1484
		1485	Only the default event loop is capable of handling signals, and therefore
		1486	you can only rgeister child watchers in the default event loop.
		1487
		1488	=head3 Process Interaction
		1489
		1490	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1491	initialised. This is necessary to guarantee proper behaviour even if
		1492	the first child watcher is started after the child exits. The occurance
		1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1494	synchronously as part of the event loop processing. Libev always reaps all
		1495	children, even ones not watched.
		1496
		1497	=head3 Overriding the Built-In Processing
		1498
		1499	Libev offers no special support for overriding the built-in child
		1500	processing, but if your application collides with libev's default child
		1501	handler, you can override it easily by installing your own handler for
		1502	C<SIGCHLD> after initialising the default loop, and making sure the
		1503	default loop never gets destroyed. You are encouraged, however, to use an
		1504	event-based approach to child reaping and thus use libev's support for
		1505	that, so other libev users can use C<ev_child> watchers freely.
		1506
		1507	=head3 Watcher-Specific Functions and Data Members
1235		1508
1236	=over 4	1509	=over 4
1237		1510
1238	=item ev_child_init (ev_child *, callback, int pid)	1511	=item ev_child_init (ev_child *, callback, int pid, int trace)
1239		1512
1240	=item ev_child_set (ev_child *, int pid)	1513	=item ev_child_set (ev_child *, int pid, int trace)
1241		1514
1242	Configures the watcher to wait for status changes of process C<pid> (or	1515	Configures the watcher to wait for status changes of process C<pid> (or
1243	I<any> process if C<pid> is specified as C<0>). The callback can look	1516	I<any> process if C<pid> is specified as C<0>). The callback can look
1244	at the C<rstatus> member of the C<ev_child> watcher structure to see	1517	at the C<rstatus> member of the C<ev_child> watcher structure to see
1245	the status word (use the macros from C<sys/wait.h> and see your systems	1518	the status word (use the macros from C<sys/wait.h> and see your systems
1246	C<waitpid> documentation). The C<rpid> member contains the pid of the	1519	C<waitpid> documentation). The C<rpid> member contains the pid of the
1247	process causing the status change.	1520	process causing the status change. C<trace> must be either C<0> (only
		1521	activate the watcher when the process terminates) or C<1> (additionally
		1522	activate the watcher when the process is stopped or continued).
1248		1523
1249	=item int pid [read-only]	1524	=item int pid [read-only]
1250		1525
1251	The process id this watcher watches out for, or C<0>, meaning any process id.	1526	The process id this watcher watches out for, or C<0>, meaning any process id.
1252		1527
…		…
1259	The process exit/trace status caused by C<rpid> (see your systems	1534	The process exit/trace status caused by C<rpid> (see your systems
1260	C<waitpid> and C<sys/wait.h> documentation for details).	1535	C<waitpid> and C<sys/wait.h> documentation for details).
1261		1536
1262	=back	1537	=back
1263		1538
1264	Example: Try to exit cleanly on SIGINT and SIGTERM.	1539	=head3 Examples
		1540
		1541	Example: C<fork()> a new process and install a child handler to wait for
		1542	its completion.
		1543
		1544	ev_child cw;
1265		1545
1266	static void	1546	static void
1267	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1547	child_cb (EV_P_ struct ev_child *w, int revents)
1268	{	1548	{
1269	ev_unloop (loop, EVUNLOOP_ALL);	1549	ev_child_stop (EV_A_ w);
		1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1270	}	1551	}
1271		1552
1272	struct ev_signal signal_watcher;	1553	pid_t pid = fork ();
1273	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1554
1274	ev_signal_start (loop, &sigint_cb);	1555	if (pid < 0)
		1556	// error
		1557	else if (pid == 0)
		1558	{
		1559	// the forked child executes here
		1560	exit (1);
		1561	}
		1562	else
		1563	{
		1564	ev_child_init (&cw, child_cb, pid, 0);
		1565	ev_child_start (EV_DEFAULT_ &cw);
		1566	}
1275		1567
1276		1568
1277	=head2 C<ev_stat> - did the file attributes just change?	1569	=head2 C<ev_stat> - did the file attributes just change?
1278		1570
1279	This watches a filesystem path for attribute changes. That is, it calls	1571	This watches a filesystem path for attribute changes. That is, it calls
…		…
1308	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1309	to fall back to regular polling again even with inotify, but changes are	1601	to fall back to regular polling again even with inotify, but changes are
1310	usually detected immediately, and if the file exists there will be no	1602	usually detected immediately, and if the file exists there will be no
1311	polling.	1603	polling.
1312		1604
		1605	=head3 Inotify
		1606
		1607	When C<inotify (7)> support has been compiled into libev (generally only
		1608	available on Linux) and present at runtime, it will be used to speed up
		1609	change detection where possible. The inotify descriptor will be created lazily
		1610	when the first C<ev_stat> watcher is being started.
		1611
		1612	Inotify presense does not change the semantics of C<ev_stat> watchers
		1613	except that changes might be detected earlier, and in some cases, to avoid
		1614	making regular C<stat> calls. Even in the presense of inotify support
		1615	there are many cases where libev has to resort to regular C<stat> polling.
		1616
		1617	(There is no support for kqueue, as apparently it cannot be used to
		1618	implement this functionality, due to the requirement of having a file
		1619	descriptor open on the object at all times).
		1620
		1621	=head3 The special problem of stat time resolution
		1622
		1623	The C<stat ()> syscall only supports full-second resolution portably, and
		1624	even on systems where the resolution is higher, many filesystems still
		1625	only support whole seconds.
		1626
		1627	That means that, if the time is the only thing that changes, you might
		1628	miss updates: on the first update, C<ev_stat> detects a change and calls
		1629	your callback, which does something. When there is another update within
		1630	the same second, C<ev_stat> will be unable to detect it.
		1631
		1632	The solution to this is to delay acting on a change for a second (or till
		1633	the next second boundary), using a roughly one-second delay C<ev_timer>
		1634	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1635	is added to work around small timing inconsistencies of some operating
		1636	systems.
		1637
		1638	=head3 Watcher-Specific Functions and Data Members
		1639
1313	=over 4	1640	=over 4
1314		1641
1315	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1642	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1316		1643
1317	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1644	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1324		1651
1325	The callback will be receive C<EV_STAT> when a change was detected,	1652	The callback will be receive C<EV_STAT> when a change was detected,
1326	relative to the attributes at the time the watcher was started (or the	1653	relative to the attributes at the time the watcher was started (or the
1327	last change was detected).	1654	last change was detected).
1328		1655
1329	=item ev_stat_stat (ev_stat *)	1656	=item ev_stat_stat (loop, ev_stat *)
1330		1657
1331	Updates the stat buffer immediately with new values. If you change the	1658	Updates the stat buffer immediately with new values. If you change the
1332	watched path in your callback, you could call this fucntion to avoid	1659	watched path in your callback, you could call this fucntion to avoid
1333	detecting this change (while introducing a race condition). Can also be	1660	detecting this change (while introducing a race condition). Can also be
1334	useful simply to find out the new values.	1661	useful simply to find out the new values.
…		…
1352	=item const char *path [read-only]	1679	=item const char *path [read-only]
1353		1680
1354	The filesystem path that is being watched.	1681	The filesystem path that is being watched.
1355		1682
1356	=back	1683	=back
		1684
		1685	=head3 Examples
1357		1686
1358	Example: Watch C</etc/passwd> for attribute changes.	1687	Example: Watch C</etc/passwd> for attribute changes.
1359		1688
1360	static void	1689	static void
1361	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1690	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1374	}	1703	}
1375		1704
1376	...	1705	...
1377	ev_stat passwd;	1706	ev_stat passwd;
1378		1707
1379	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1708	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1380	ev_stat_start (loop, &passwd);	1709	ev_stat_start (loop, &passwd);
		1710
		1711	Example: Like above, but additionally use a one-second delay so we do not
		1712	miss updates (however, frequent updates will delay processing, too, so
		1713	one might do the work both on C<ev_stat> callback invocation I<and> on
		1714	C<ev_timer> callback invocation).
		1715
		1716	static ev_stat passwd;
		1717	static ev_timer timer;
		1718
		1719	static void
		1720	timer_cb (EV_P_ ev_timer *w, int revents)
		1721	{
		1722	ev_timer_stop (EV_A_ w);
		1723
		1724	/* now it's one second after the most recent passwd change */
		1725	}
		1726
		1727	static void
		1728	stat_cb (EV_P_ ev_stat *w, int revents)
		1729	{
		1730	/* reset the one-second timer */
		1731	ev_timer_again (EV_A_ &timer);
		1732	}
		1733
		1734	...
		1735	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1736	ev_stat_start (loop, &passwd);
		1737	ev_timer_init (&timer, timer_cb, 0., 1.01);
1381		1738
1382		1739
1383	=head2 C<ev_idle> - when you've got nothing better to do...	1740	=head2 C<ev_idle> - when you've got nothing better to do...
1384		1741
1385	Idle watchers trigger events when no other events of the same or higher	1742	Idle watchers trigger events when no other events of the same or higher
…		…
1399	Apart from keeping your process non-blocking (which is a useful	1756	Apart from keeping your process non-blocking (which is a useful
1400	effect on its own sometimes), idle watchers are a good place to do	1757	effect on its own sometimes), idle watchers are a good place to do
1401	"pseudo-background processing", or delay processing stuff to after the	1758	"pseudo-background processing", or delay processing stuff to after the
1402	event loop has handled all outstanding events.	1759	event loop has handled all outstanding events.
1403		1760
		1761	=head3 Watcher-Specific Functions and Data Members
		1762
1404	=over 4	1763	=over 4
1405		1764
1406	=item ev_idle_init (ev_signal *, callback)	1765	=item ev_idle_init (ev_signal *, callback)
1407		1766
1408	Initialises and configures the idle watcher - it has no parameters of any	1767	Initialises and configures the idle watcher - it has no parameters of any
1409	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1768	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1410	believe me.	1769	believe me.
1411		1770
1412	=back	1771	=back
		1772
		1773	=head3 Examples
1413		1774
1414	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1775	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1415	callback, free it. Also, use no error checking, as usual.	1776	callback, free it. Also, use no error checking, as usual.
1416		1777
1417	static void	1778	static void
1418	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1779	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1419	{	1780	{
1420	free (w);	1781	free (w);
1421	// now do something you wanted to do when the program has	1782	// now do something you wanted to do when the program has
1422	// no longer asnything immediate to do.	1783	// no longer anything immediate to do.
1423	}	1784	}
1424		1785
1425	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1786	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1426	ev_idle_init (idle_watcher, idle_cb);	1787	ev_idle_init (idle_watcher, idle_cb);
1427	ev_idle_start (loop, idle_cb);	1788	ev_idle_start (loop, idle_cb);
…		…
1465	with priority higher than or equal to the event loop and one coroutine	1826	with priority higher than or equal to the event loop and one coroutine
1466	of lower priority, but only once, using idle watchers to keep the event	1827	of lower priority, but only once, using idle watchers to keep the event
1467	loop from blocking if lower-priority coroutines are active, thus mapping	1828	loop from blocking if lower-priority coroutines are active, thus mapping
1468	low-priority coroutines to idle/background tasks).	1829	low-priority coroutines to idle/background tasks).
1469		1830
		1831	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1832	priority, to ensure that they are being run before any other watchers
		1833	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1834	too) should not activate ("feed") events into libev. While libev fully
		1835	supports this, they will be called before other C<ev_check> watchers
		1836	did their job. As C<ev_check> watchers are often used to embed other
		1837	(non-libev) event loops those other event loops might be in an unusable
		1838	state until their C<ev_check> watcher ran (always remind yourself to
		1839	coexist peacefully with others).
		1840
		1841	=head3 Watcher-Specific Functions and Data Members
		1842
1470	=over 4	1843	=over 4
1471		1844
1472	=item ev_prepare_init (ev_prepare *, callback)	1845	=item ev_prepare_init (ev_prepare *, callback)
1473		1846
1474	=item ev_check_init (ev_check *, callback)	1847	=item ev_check_init (ev_check *, callback)
…		…
1477	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1850	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1478	macros, but using them is utterly, utterly and completely pointless.	1851	macros, but using them is utterly, utterly and completely pointless.
1479		1852
1480	=back	1853	=back
1481		1854
1482	Example: To include a library such as adns, you would add IO watchers	1855	=head3 Examples
1483	and a timeout watcher in a prepare handler, as required by libadns, and	1856
		1857	There are a number of principal ways to embed other event loops or modules
		1858	into libev. Here are some ideas on how to include libadns into libev
		1859	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1860	use for an actually working example. Another Perl module named C<EV::Glib>
		1861	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1862	into the Glib event loop).
		1863
		1864	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1484	in a check watcher, destroy them and call into libadns. What follows is	1865	and in a check watcher, destroy them and call into libadns. What follows
1485	pseudo-code only of course:	1866	is pseudo-code only of course. This requires you to either use a low
		1867	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1868	the callbacks for the IO/timeout watchers might not have been called yet.
1486		1869
1487	static ev_io iow [nfd];	1870	static ev_io iow [nfd];
1488	static ev_timer tw;	1871	static ev_timer tw;
1489		1872
1490	static void	1873	static void
1491	io_cb (ev_loop *loop, ev_io *w, int revents)	1874	io_cb (ev_loop *loop, ev_io *w, int revents)
1492	{	1875	{
1493	// set the relevant poll flags
1494	// could also call adns_processreadable etc. here
1495	struct pollfd *fd = (struct pollfd *)w->data;
1496	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1497	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1498	}	1876	}
1499		1877
1500	// create io watchers for each fd and a timer before blocking	1878	// create io watchers for each fd and a timer before blocking
1501	static void	1879	static void
1502	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1880	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
…		…
1508		1886
1509	/* the callback is illegal, but won't be called as we stop during check */	1887	/* the callback is illegal, but won't be called as we stop during check */
1510	ev_timer_init (&tw, 0, timeout * 1e-3);	1888	ev_timer_init (&tw, 0, timeout * 1e-3);
1511	ev_timer_start (loop, &tw);	1889	ev_timer_start (loop, &tw);
1512		1890
1513	// create on ev_io per pollfd	1891	// create one ev_io per pollfd
1514	for (int i = 0; i < nfd; ++i)	1892	for (int i = 0; i < nfd; ++i)
1515	{	1893	{
1516	ev_io_init (iow + i, io_cb, fds [i].fd,	1894	ev_io_init (iow + i, io_cb, fds [i].fd,
1517	((fds [i].events & POLLIN ? EV_READ : 0)	1895	((fds [i].events & POLLIN ? EV_READ : 0)
1518	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1896	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1519		1897
1520	fds [i].revents = 0;	1898	fds [i].revents = 0;
1521	iow [i].data = fds + i;
1522	ev_io_start (loop, iow + i);	1899	ev_io_start (loop, iow + i);
1523	}	1900	}
1524	}	1901	}
1525		1902
1526	// stop all watchers after blocking	1903	// stop all watchers after blocking
…		…
1528	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1905	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1529	{	1906	{
1530	ev_timer_stop (loop, &tw);	1907	ev_timer_stop (loop, &tw);
1531		1908
1532	for (int i = 0; i < nfd; ++i)	1909	for (int i = 0; i < nfd; ++i)
		1910	{
		1911	// set the relevant poll flags
		1912	// could also call adns_processreadable etc. here
		1913	struct pollfd *fd = fds + i;
		1914	int revents = ev_clear_pending (iow + i);
		1915	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1916	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1917
		1918	// now stop the watcher
1533	ev_io_stop (loop, iow + i);	1919	ev_io_stop (loop, iow + i);
		1920	}
1534		1921
1535	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1922	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1923	}
		1924
		1925	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1926	in the prepare watcher and would dispose of the check watcher.
		1927
		1928	Method 3: If the module to be embedded supports explicit event
		1929	notification (adns does), you can also make use of the actual watcher
		1930	callbacks, and only destroy/create the watchers in the prepare watcher.
		1931
		1932	static void
		1933	timer_cb (EV_P_ ev_timer *w, int revents)
		1934	{
		1935	adns_state ads = (adns_state)w->data;
		1936	update_now (EV_A);
		1937
		1938	adns_processtimeouts (ads, &tv_now);
		1939	}
		1940
		1941	static void
		1942	io_cb (EV_P_ ev_io *w, int revents)
		1943	{
		1944	adns_state ads = (adns_state)w->data;
		1945	update_now (EV_A);
		1946
		1947	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1948	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1949	}
		1950
		1951	// do not ever call adns_afterpoll
		1952
		1953	Method 4: Do not use a prepare or check watcher because the module you
		1954	want to embed is too inflexible to support it. Instead, youc na override
		1955	their poll function. The drawback with this solution is that the main
		1956	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1957	this.
		1958
		1959	static gint
		1960	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1961	{
		1962	int got_events = 0;
		1963
		1964	for (n = 0; n < nfds; ++n)
		1965	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1966
		1967	if (timeout >= 0)
		1968	// create/start timer
		1969
		1970	// poll
		1971	ev_loop (EV_A_ 0);
		1972
		1973	// stop timer again
		1974	if (timeout >= 0)
		1975	ev_timer_stop (EV_A_ &to);
		1976
		1977	// stop io watchers again - their callbacks should have set
		1978	for (n = 0; n < nfds; ++n)
		1979	ev_io_stop (EV_A_ iow [n]);
		1980
		1981	return got_events;
1536	}	1982	}
1537		1983
1538		1984
1539	=head2 C<ev_embed> - when one backend isn't enough...	1985	=head2 C<ev_embed> - when one backend isn't enough...
1540		1986
…		…
1583	portable one.	2029	portable one.
1584		2030
1585	So when you want to use this feature you will always have to be prepared	2031	So when you want to use this feature you will always have to be prepared
1586	that you cannot get an embeddable loop. The recommended way to get around	2032	that you cannot get an embeddable loop. The recommended way to get around
1587	this is to have a separate variables for your embeddable loop, try to	2033	this is to have a separate variables for your embeddable loop, try to
1588	create it, and if that fails, use the normal loop for everything:	2034	create it, and if that fails, use the normal loop for everything.
		2035
		2036	=head3 Watcher-Specific Functions and Data Members
		2037
		2038	=over 4
		2039
		2040	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2041
		2042	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2043
		2044	Configures the watcher to embed the given loop, which must be
		2045	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2046	invoked automatically, otherwise it is the responsibility of the callback
		2047	to invoke it (it will continue to be called until the sweep has been done,
		2048	if you do not want thta, you need to temporarily stop the embed watcher).
		2049
		2050	=item ev_embed_sweep (loop, ev_embed *)
		2051
		2052	Make a single, non-blocking sweep over the embedded loop. This works
		2053	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2054	apropriate way for embedded loops.
		2055
		2056	=item struct ev_loop *other [read-only]
		2057
		2058	The embedded event loop.
		2059
		2060	=back
		2061
		2062	=head3 Examples
		2063
		2064	Example: Try to get an embeddable event loop and embed it into the default
		2065	event loop. If that is not possible, use the default loop. The default
		2066	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2067	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2068	used).
1589		2069
1590	struct ev_loop *loop_hi = ev_default_init (0);	2070	struct ev_loop *loop_hi = ev_default_init (0);
1591	struct ev_loop *loop_lo = 0;	2071	struct ev_loop *loop_lo = 0;
1592	struct ev_embed embed;	2072	struct ev_embed embed;
1593		2073
…		…
1604	ev_embed_start (loop_hi, &embed);	2084	ev_embed_start (loop_hi, &embed);
1605	}	2085	}
1606	else	2086	else
1607	loop_lo = loop_hi;	2087	loop_lo = loop_hi;
1608		2088
1609	=over 4	2089	Example: Check if kqueue is available but not recommended and create
		2090	a kqueue backend for use with sockets (which usually work with any
		2091	kqueue implementation). Store the kqueue/socket-only event loop in
		2092	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1610		2093
1611	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2094	struct ev_loop *loop = ev_default_init (0);
		2095	struct ev_loop *loop_socket = 0;
		2096	struct ev_embed embed;
		2097
		2098	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2099	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2100	{
		2101	ev_embed_init (&embed, 0, loop_socket);
		2102	ev_embed_start (loop, &embed);
		2103	}
1612		2104
1613	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2105	if (!loop_socket)
		2106	loop_socket = loop;
1614		2107
1615	Configures the watcher to embed the given loop, which must be	2108	// now use loop_socket for all sockets, and loop for everything else
1616	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1617	invoked automatically, otherwise it is the responsibility of the callback
1618	to invoke it (it will continue to be called until the sweep has been done,
1619	if you do not want thta, you need to temporarily stop the embed watcher).
1620
1621	=item ev_embed_sweep (loop, ev_embed *)
1622
1623	Make a single, non-blocking sweep over the embedded loop. This works
1624	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1625	apropriate way for embedded loops.
1626
1627	=item struct ev_loop *loop [read-only]
1628
1629	The embedded event loop.
1630
1631	=back
1632		2109
1633		2110
1634	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2111	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1635		2112
1636	Fork watchers are called when a C<fork ()> was detected (usually because	2113	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1639	event loop blocks next and before C<ev_check> watchers are being called,	2116	event loop blocks next and before C<ev_check> watchers are being called,
1640	and only in the child after the fork. If whoever good citizen calling	2117	and only in the child after the fork. If whoever good citizen calling
1641	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2118	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1642	handlers will be invoked, too, of course.	2119	handlers will be invoked, too, of course.
1643		2120
		2121	=head3 Watcher-Specific Functions and Data Members
		2122
1644	=over 4	2123	=over 4
1645		2124
1646	=item ev_fork_init (ev_signal *, callback)	2125	=item ev_fork_init (ev_signal *, callback)
1647		2126
1648	Initialises and configures the fork watcher - it has no parameters of any	2127	Initialises and configures the fork watcher - it has no parameters of any
1649	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2128	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1650	believe me.	2129	believe me.
		2130
		2131	=back
		2132
		2133
		2134	=head2 C<ev_async> - how to wake up another event loop
		2135
		2136	In general, you cannot use an C<ev_loop> from multiple threads or other
		2137	asynchronous sources such as signal handlers (as opposed to multiple event
		2138	loops - those are of course safe to use in different threads).
		2139
		2140	Sometimes, however, you need to wake up another event loop you do not
		2141	control, for example because it belongs to another thread. This is what
		2142	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2143	can signal it by calling C<ev_async_send>, which is thread- and signal
		2144	safe.
		2145
		2146	This functionality is very similar to C<ev_signal> watchers, as signals,
		2147	too, are asynchronous in nature, and signals, too, will be compressed
		2148	(i.e. the number of callback invocations may be less than the number of
		2149	C<ev_async_sent> calls).
		2150
		2151	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2152	just the default loop.
		2153
		2154	=head3 Queueing
		2155
		2156	C<ev_async> does not support queueing of data in any way. The reason
		2157	is that the author does not know of a simple (or any) algorithm for a
		2158	multiple-writer-single-reader queue that works in all cases and doesn't
		2159	need elaborate support such as pthreads.
		2160
		2161	That means that if you want to queue data, you have to provide your own
		2162	queue. But at least I can tell you would implement locking around your
		2163	queue:
		2164
		2165	=over 4
		2166
		2167	=item queueing from a signal handler context
		2168
		2169	To implement race-free queueing, you simply add to the queue in the signal
		2170	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2171	some fictitiuous SIGUSR1 handler:
		2172
		2173	static ev_async mysig;
		2174
		2175	static void
		2176	sigusr1_handler (void)
		2177	{
		2178	sometype data;
		2179
		2180	// no locking etc.
		2181	queue_put (data);
		2182	ev_async_send (EV_DEFAULT_ &mysig);
		2183	}
		2184
		2185	static void
		2186	mysig_cb (EV_P_ ev_async *w, int revents)
		2187	{
		2188	sometype data;
		2189	sigset_t block, prev;
		2190
		2191	sigemptyset (&block);
		2192	sigaddset (&block, SIGUSR1);
		2193	sigprocmask (SIG_BLOCK, &block, &prev);
		2194
		2195	while (queue_get (&data))
		2196	process (data);
		2197
		2198	if (sigismember (&prev, SIGUSR1)
		2199	sigprocmask (SIG_UNBLOCK, &block, 0);
		2200	}
		2201
		2202	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2203	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2204	either...).
		2205
		2206	=item queueing from a thread context
		2207
		2208	The strategy for threads is different, as you cannot (easily) block
		2209	threads but you can easily preempt them, so to queue safely you need to
		2210	employ a traditional mutex lock, such as in this pthread example:
		2211
		2212	static ev_async mysig;
		2213	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2214
		2215	static void
		2216	otherthread (void)
		2217	{
		2218	// only need to lock the actual queueing operation
		2219	pthread_mutex_lock (&mymutex);
		2220	queue_put (data);
		2221	pthread_mutex_unlock (&mymutex);
		2222
		2223	ev_async_send (EV_DEFAULT_ &mysig);
		2224	}
		2225
		2226	static void
		2227	mysig_cb (EV_P_ ev_async *w, int revents)
		2228	{
		2229	pthread_mutex_lock (&mymutex);
		2230
		2231	while (queue_get (&data))
		2232	process (data);
		2233
		2234	pthread_mutex_unlock (&mymutex);
		2235	}
		2236
		2237	=back
		2238
		2239
		2240	=head3 Watcher-Specific Functions and Data Members
		2241
		2242	=over 4
		2243
		2244	=item ev_async_init (ev_async *, callback)
		2245
		2246	Initialises and configures the async watcher - it has no parameters of any
		2247	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2248	believe me.
		2249
		2250	=item ev_async_send (loop, ev_async *)
		2251
		2252	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2253	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2254	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2255	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2256	section below on what exactly this means).
		2257
		2258	This call incurs the overhead of a syscall only once per loop iteration,
		2259	so while the overhead might be noticable, it doesn't apply to repeated
		2260	calls to C<ev_async_send>.
1651		2261
1652	=back	2262	=back
1653		2263
1654		2264
1655	=head1 OTHER FUNCTIONS	2265	=head1 OTHER FUNCTIONS
…		…
1744		2354
1745	To use it,	2355	To use it,
1746		2356
1747	#include <ev++.h>	2357	#include <ev++.h>
1748		2358
1749	(it is not installed by default). This automatically includes F<ev.h>	2359	This automatically includes F<ev.h> and puts all of its definitions (many
1750	and puts all of its definitions (many of them macros) into the global	2360	of them macros) into the global namespace. All C++ specific things are
1751	namespace. All C++ specific things are put into the C<ev> namespace.	2361	put into the C<ev> namespace. It should support all the same embedding
		2362	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1752		2363
1753	It should support all the same embedding options as F<ev.h>, most notably	2364	Care has been taken to keep the overhead low. The only data member the C++
1754	C<EV_MULTIPLICITY>.	2365	classes add (compared to plain C-style watchers) is the event loop pointer
		2366	that the watcher is associated with (or no additional members at all if
		2367	you disable C<EV_MULTIPLICITY> when embedding libev).
		2368
		2369	Currently, functions, and static and non-static member functions can be
		2370	used as callbacks. Other types should be easy to add as long as they only
		2371	need one additional pointer for context. If you need support for other
		2372	types of functors please contact the author (preferably after implementing
		2373	it).
1755		2374
1756	Here is a list of things available in the C<ev> namespace:	2375	Here is a list of things available in the C<ev> namespace:
1757		2376
1758	=over 4	2377	=over 4
1759		2378
…		…
1775		2394
1776	All of those classes have these methods:	2395	All of those classes have these methods:
1777		2396
1778	=over 4	2397	=over 4
1779		2398
1780	=item ev::TYPE::TYPE (object *, object::method *)	2399	=item ev::TYPE::TYPE ()
1781		2400
1782	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2401	=item ev::TYPE::TYPE (struct ev_loop *)
1783		2402
1784	=item ev::TYPE::~TYPE	2403	=item ev::TYPE::~TYPE
1785		2404
1786	The constructor takes a pointer to an object and a method pointer to	2405	The constructor (optionally) takes an event loop to associate the watcher
1787	the event handler callback to call in this class. The constructor calls	2406	with. If it is omitted, it will use C<EV_DEFAULT>.
1788	C<ev_init> for you, which means you have to call the C<set> method	2407
1789	before starting it. If you do not specify a loop then the constructor	2408	The constructor calls C<ev_init> for you, which means you have to call the
1790	automatically associates the default loop with this watcher.	2409	C<set> method before starting it.
		2410
		2411	It will not set a callback, however: You have to call the templated C<set>
		2412	method to set a callback before you can start the watcher.
		2413
		2414	(The reason why you have to use a method is a limitation in C++ which does
		2415	not allow explicit template arguments for constructors).
1791		2416
1792	The destructor automatically stops the watcher if it is active.	2417	The destructor automatically stops the watcher if it is active.
		2418
		2419	=item w->set<class, &class::method> (object *)
		2420
		2421	This method sets the callback method to call. The method has to have a
		2422	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2423	first argument and the C<revents> as second. The object must be given as
		2424	parameter and is stored in the C<data> member of the watcher.
		2425
		2426	This method synthesizes efficient thunking code to call your method from
		2427	the C callback that libev requires. If your compiler can inline your
		2428	callback (i.e. it is visible to it at the place of the C<set> call and
		2429	your compiler is good :), then the method will be fully inlined into the
		2430	thunking function, making it as fast as a direct C callback.
		2431
		2432	Example: simple class declaration and watcher initialisation
		2433
		2434	struct myclass
		2435	{
		2436	void io_cb (ev::io &w, int revents) { }
		2437	}
		2438
		2439	myclass obj;
		2440	ev::io iow;
		2441	iow.set <myclass, &myclass::io_cb> (&obj);
		2442
		2443	=item w->set<function> (void *data = 0)
		2444
		2445	Also sets a callback, but uses a static method or plain function as
		2446	callback. The optional C<data> argument will be stored in the watcher's
		2447	C<data> member and is free for you to use.
		2448
		2449	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2450
		2451	See the method-C<set> above for more details.
		2452
		2453	Example:
		2454
		2455	static void io_cb (ev::io &w, int revents) { }
		2456	iow.set <io_cb> ();
1793		2457
1794	=item w->set (struct ev_loop *)	2458	=item w->set (struct ev_loop *)
1795		2459
1796	Associates a different C<struct ev_loop> with this watcher. You can only	2460	Associates a different C<struct ev_loop> with this watcher. You can only
1797	do this when the watcher is inactive (and not pending either).	2461	do this when the watcher is inactive (and not pending either).
1798		2462
1799	=item w->set ([args])	2463	=item w->set ([args])
1800		2464
1801	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2465	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1802	called at least once. Unlike the C counterpart, an active watcher gets	2466	called at least once. Unlike the C counterpart, an active watcher gets
1803	automatically stopped and restarted.	2467	automatically stopped and restarted when reconfiguring it with this
		2468	method.
1804		2469
1805	=item w->start ()	2470	=item w->start ()
1806		2471
1807	Starts the watcher. Note that there is no C<loop> argument as the	2472	Starts the watcher. Note that there is no C<loop> argument, as the
1808	constructor already takes the loop.	2473	constructor already stores the event loop.
1809		2474
1810	=item w->stop ()	2475	=item w->stop ()
1811		2476
1812	Stops the watcher if it is active. Again, no C<loop> argument.	2477	Stops the watcher if it is active. Again, no C<loop> argument.
1813		2478
1814	=item w->again () C<ev::timer>, C<ev::periodic> only	2479	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1815		2480
1816	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2481	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1817	C<ev_TYPE_again> function.	2482	C<ev_TYPE_again> function.
1818		2483
1819	=item w->sweep () C<ev::embed> only	2484	=item w->sweep () (C<ev::embed> only)
1820		2485
1821	Invokes C<ev_embed_sweep>.	2486	Invokes C<ev_embed_sweep>.
1822		2487
1823	=item w->update () C<ev::stat> only	2488	=item w->update () (C<ev::stat> only)
1824		2489
1825	Invokes C<ev_stat_stat>.	2490	Invokes C<ev_stat_stat>.
1826		2491
1827	=back	2492	=back
1828		2493
…		…
1831	Example: Define a class with an IO and idle watcher, start one of them in	2496	Example: Define a class with an IO and idle watcher, start one of them in
1832	the constructor.	2497	the constructor.
1833		2498
1834	class myclass	2499	class myclass
1835	{	2500	{
1836	ev_io io; void io_cb (ev::io &w, int revents);	2501	ev::io io; void io_cb (ev::io &w, int revents);
1837	ev_idle idle void idle_cb (ev::idle &w, int revents);	2502	ev:idle idle void idle_cb (ev::idle &w, int revents);
1838		2503
1839	myclass ();	2504	myclass (int fd)
1840	}
1841
1842	myclass::myclass (int fd)
1843	: io (this, &myclass::io_cb),
1844	idle (this, &myclass::idle_cb)
1845	{	2505	{
		2506	io .set <myclass, &myclass::io_cb > (this);
		2507	idle.set <myclass, &myclass::idle_cb> (this);
		2508
1846	io.start (fd, ev::READ);	2509	io.start (fd, ev::READ);
		2510	}
1847	}	2511	};
		2512
		2513
		2514	=head1 OTHER LANGUAGE BINDINGS
		2515
		2516	Libev does not offer other language bindings itself, but bindings for a
		2517	numbe rof languages exist in the form of third-party packages. If you know
		2518	any interesting language binding in addition to the ones listed here, drop
		2519	me a note.
		2520
		2521	=over 4
		2522
		2523	=item Perl
		2524
		2525	The EV module implements the full libev API and is actually used to test
		2526	libev. EV is developed together with libev. Apart from the EV core module,
		2527	there are additional modules that implement libev-compatible interfaces
		2528	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2529	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2530
		2531	It can be found and installed via CPAN, its homepage is found at
		2532	L<http://software.schmorp.de/pkg/EV>.
		2533
		2534	=item Ruby
		2535
		2536	Tony Arcieri has written a ruby extension that offers access to a subset
		2537	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2538	more on top of it. It can be found via gem servers. Its homepage is at
		2539	L<http://rev.rubyforge.org/>.
		2540
		2541	=item D
		2542
		2543	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2544	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2545
		2546	=back
1848		2547
1849		2548
1850	=head1 MACRO MAGIC	2549	=head1 MACRO MAGIC
1851		2550
1852	Libev can be compiled with a variety of options, the most fundemantal is	2551	Libev can be compiled with a variety of options, the most fundamantal
1853	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2552	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1854	callbacks have an initial C<struct ev_loop *> argument.	2553	functions and callbacks have an initial C<struct ev_loop *> argument.
1855		2554
1856	To make it easier to write programs that cope with either variant, the	2555	To make it easier to write programs that cope with either variant, the
1857	following macros are defined:	2556	following macros are defined:
1858		2557
1859	=over 4	2558	=over 4
…		…
1913	Libev can (and often is) directly embedded into host	2612	Libev can (and often is) directly embedded into host
1914	applications. Examples of applications that embed it include the Deliantra	2613	applications. Examples of applications that embed it include the Deliantra
1915	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2614	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1916	and rxvt-unicode.	2615	and rxvt-unicode.
1917		2616
1918	The goal is to enable you to just copy the neecssary files into your	2617	The goal is to enable you to just copy the necessary files into your
1919	source directory without having to change even a single line in them, so	2618	source directory without having to change even a single line in them, so
1920	you can easily upgrade by simply copying (or having a checked-out copy of	2619	you can easily upgrade by simply copying (or having a checked-out copy of
1921	libev somewhere in your source tree).	2620	libev somewhere in your source tree).
1922		2621
1923	=head2 FILESETS	2622	=head2 FILESETS
…		…
2013		2712
2014	If defined to be C<1>, libev will try to detect the availability of the	2713	If defined to be C<1>, libev will try to detect the availability of the
2015	monotonic clock option at both compiletime and runtime. Otherwise no use	2714	monotonic clock option at both compiletime and runtime. Otherwise no use
2016	of the monotonic clock option will be attempted. If you enable this, you	2715	of the monotonic clock option will be attempted. If you enable this, you
2017	usually have to link against librt or something similar. Enabling it when	2716	usually have to link against librt or something similar. Enabling it when
2018	the functionality isn't available is safe, though, althoguh you have	2717	the functionality isn't available is safe, though, although you have
2019	to make sure you link against any libraries where the C<clock_gettime>	2718	to make sure you link against any libraries where the C<clock_gettime>
2020	function is hiding in (often F<-lrt>).	2719	function is hiding in (often F<-lrt>).
2021		2720
2022	=item EV_USE_REALTIME	2721	=item EV_USE_REALTIME
2023		2722
2024	If defined to be C<1>, libev will try to detect the availability of the	2723	If defined to be C<1>, libev will try to detect the availability of the
2025	realtime clock option at compiletime (and assume its availability at	2724	realtime clock option at compiletime (and assume its availability at
2026	runtime if successful). Otherwise no use of the realtime clock option will	2725	runtime if successful). Otherwise no use of the realtime clock option will
2027	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2726	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2028	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2727	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2029	in the description of C<EV_USE_MONOTONIC>, though.	2728	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2729
		2730	=item EV_USE_NANOSLEEP
		2731
		2732	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2733	and will use it for delays. Otherwise it will use C<select ()>.
2030		2734
2031	=item EV_USE_SELECT	2735	=item EV_USE_SELECT
2032		2736
2033	If undefined or defined to be C<1>, libev will compile in support for the	2737	If undefined or defined to be C<1>, libev will compile in support for the
2034	C<select>(2) backend. No attempt at autodetection will be done: if no	2738	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2052	wants osf handles on win32 (this is the case when the select to	2756	wants osf handles on win32 (this is the case when the select to
2053	be used is the winsock select). This means that it will call	2757	be used is the winsock select). This means that it will call
2054	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2758	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2055	it is assumed that all these functions actually work on fds, even	2759	it is assumed that all these functions actually work on fds, even
2056	on win32. Should not be defined on non-win32 platforms.	2760	on win32. Should not be defined on non-win32 platforms.
		2761
		2762	=item EV_FD_TO_WIN32_HANDLE
		2763
		2764	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2765	file descriptors to socket handles. When not defining this symbol (the
		2766	default), then libev will call C<_get_osfhandle>, which is usually
		2767	correct. In some cases, programs use their own file descriptor management,
		2768	in which case they can provide this function to map fds to socket handles.
2057		2769
2058	=item EV_USE_POLL	2770	=item EV_USE_POLL
2059		2771
2060	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2772	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2061	backend. Otherwise it will be enabled on non-win32 platforms. It	2773	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2095		2807
2096	If defined to be C<1>, libev will compile in support for the Linux inotify	2808	If defined to be C<1>, libev will compile in support for the Linux inotify
2097	interface to speed up C<ev_stat> watchers. Its actual availability will	2809	interface to speed up C<ev_stat> watchers. Its actual availability will
2098	be detected at runtime.	2810	be detected at runtime.
2099		2811
		2812	=item EV_ATOMIC_T
		2813
		2814	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2815	access is atomic with respect to other threads or signal contexts. No such
		2816	type is easily found in the C language, so you can provide your own type
		2817	that you know is safe for your purposes. It is used both for signal handler "locking"
		2818	as well as for signal and thread safety in C<ev_async> watchers.
		2819
		2820	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2821	(from F<signal.h>), which is usually good enough on most platforms.
		2822
2100	=item EV_H	2823	=item EV_H
2101		2824
2102	The name of the F<ev.h> header file used to include it. The default if	2825	The name of the F<ev.h> header file used to include it. The default if
2103	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2826	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2104	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2827	used to virtually rename the F<ev.h> header file in case of conflicts.
2105		2828
2106	=item EV_CONFIG_H	2829	=item EV_CONFIG_H
2107		2830
2108	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2831	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2109	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2832	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2110	C<EV_H>, above.	2833	C<EV_H>, above.
2111		2834
2112	=item EV_EVENT_H	2835	=item EV_EVENT_H
2113		2836
2114	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2837	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2115	of how the F<event.h> header can be found.	2838	of how the F<event.h> header can be found, the default is C<"event.h">.
2116		2839
2117	=item EV_PROTOTYPES	2840	=item EV_PROTOTYPES
2118		2841
2119	If defined to be C<0>, then F<ev.h> will not define any function	2842	If defined to be C<0>, then F<ev.h> will not define any function
2120	prototypes, but still define all the structs and other symbols. This is	2843	prototypes, but still define all the structs and other symbols. This is
…		…
2171	=item EV_FORK_ENABLE	2894	=item EV_FORK_ENABLE
2172		2895
2173	If undefined or defined to be C<1>, then fork watchers are supported. If	2896	If undefined or defined to be C<1>, then fork watchers are supported. If
2174	defined to be C<0>, then they are not.	2897	defined to be C<0>, then they are not.
2175		2898
		2899	=item EV_ASYNC_ENABLE
		2900
		2901	If undefined or defined to be C<1>, then async watchers are supported. If
		2902	defined to be C<0>, then they are not.
		2903
2176	=item EV_MINIMAL	2904	=item EV_MINIMAL
2177		2905
2178	If you need to shave off some kilobytes of code at the expense of some	2906	If you need to shave off some kilobytes of code at the expense of some
2179	speed, define this symbol to C<1>. Currently only used for gcc to override	2907	speed, define this symbol to C<1>. Currently only used for gcc to override
2180	some inlining decisions, saves roughly 30% codesize of amd64.	2908	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2186	than enough. If you need to manage thousands of children you might want to	2914	than enough. If you need to manage thousands of children you might want to
2187	increase this value (I<must> be a power of two).	2915	increase this value (I<must> be a power of two).
2188		2916
2189	=item EV_INOTIFY_HASHSIZE	2917	=item EV_INOTIFY_HASHSIZE
2190		2918
2191	C<ev_staz> watchers use a small hash table to distribute workload by	2919	C<ev_stat> watchers use a small hash table to distribute workload by
2192	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2920	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2193	usually more than enough. If you need to manage thousands of C<ev_stat>	2921	usually more than enough. If you need to manage thousands of C<ev_stat>
2194	watchers you might want to increase this value (I<must> be a power of	2922	watchers you might want to increase this value (I<must> be a power of
2195	two).	2923	two).
2196		2924
…		…
2213		2941
2214	=item ev_set_cb (ev, cb)	2942	=item ev_set_cb (ev, cb)
2215		2943
2216	Can be used to change the callback member declaration in each watcher,	2944	Can be used to change the callback member declaration in each watcher,
2217	and the way callbacks are invoked and set. Must expand to a struct member	2945	and the way callbacks are invoked and set. Must expand to a struct member
2218	definition and a statement, respectively. See the F<ev.v> header file for	2946	definition and a statement, respectively. See the F<ev.h> header file for
2219	their default definitions. One possible use for overriding these is to	2947	their default definitions. One possible use for overriding these is to
2220	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2948	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2221	method calls instead of plain function calls in C++.	2949	method calls instead of plain function calls in C++.
		2950
		2951	=head2 EXPORTED API SYMBOLS
		2952
		2953	If you need to re-export the API (e.g. via a dll) and you need a list of
		2954	exported symbols, you can use the provided F<Symbol.*> files which list
		2955	all public symbols, one per line:
		2956
		2957	Symbols.ev for libev proper
		2958	Symbols.event for the libevent emulation
		2959
		2960	This can also be used to rename all public symbols to avoid clashes with
		2961	multiple versions of libev linked together (which is obviously bad in
		2962	itself, but sometimes it is inconvinient to avoid this).
		2963
		2964	A sed command like this will create wrapper C<#define>'s that you need to
		2965	include before including F<ev.h>:
		2966
		2967	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2968
		2969	This would create a file F<wrap.h> which essentially looks like this:
		2970
		2971	#define ev_backend myprefix_ev_backend
		2972	#define ev_check_start myprefix_ev_check_start
		2973	#define ev_check_stop myprefix_ev_check_stop
		2974	...
2222		2975
2223	=head2 EXAMPLES	2976	=head2 EXAMPLES
2224		2977
2225	For a real-world example of a program the includes libev	2978	For a real-world example of a program the includes libev
2226	verbatim, you can have a look at the EV perl module	2979	verbatim, you can have a look at the EV perl module
…		…
2255		3008
2256	In this section the complexities of (many of) the algorithms used inside	3009	In this section the complexities of (many of) the algorithms used inside
2257	libev will be explained. For complexity discussions about backends see the	3010	libev will be explained. For complexity discussions about backends see the
2258	documentation for C<ev_default_init>.	3011	documentation for C<ev_default_init>.
2259		3012
		3013	All of the following are about amortised time: If an array needs to be
		3014	extended, libev needs to realloc and move the whole array, but this
		3015	happens asymptotically never with higher number of elements, so O(1) might
		3016	mean it might do a lengthy realloc operation in rare cases, but on average
		3017	it is much faster and asymptotically approaches constant time.
		3018
2260	=over 4	3019	=over 4
2261		3020
2262	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3021	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2263		3022
2264	This means that, when you have a watcher that triggers in one hour and	3023	This means that, when you have a watcher that triggers in one hour and
2265	there are 100 watchers that would trigger before that then inserting will	3024	there are 100 watchers that would trigger before that then inserting will
2266	have to skip those 100 watchers.	3025	have to skip roughly seven (C<ld 100>) of these watchers.
2267		3026
2268	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3027	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2269		3028
2270	That means that for changing a timer costs less than removing/adding them	3029	That means that changing a timer costs less than removing/adding them
2271	as only the relative motion in the event queue has to be paid for.	3030	as only the relative motion in the event queue has to be paid for.
2272		3031
2273	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3032	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2274		3033
2275	These just add the watcher into an array or at the head of a list. If	3034	These just add the watcher into an array or at the head of a list.
2276	the array needs to be extended libev needs to realloc and move the whole
2277	array, but this happen asymptotically less and less with more watchers,
2278	thus amortised O(1).
2279		3035
2280	=item Stopping check/prepare/idle watchers: O(1)	3036	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2281		3037
2282	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3038	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2283		3039
2284	These watchers are stored in lists then need to be walked to find the	3040	These watchers are stored in lists then need to be walked to find the
2285	correct watcher to remove. The lists are usually short (you don't usually	3041	correct watcher to remove. The lists are usually short (you don't usually
2286	have many watchers waiting for the same fd or signal).	3042	have many watchers waiting for the same fd or signal).
2287		3043
2288	=item Finding the next timer per loop iteration: O(1)	3044	=item Finding the next timer in each loop iteration: O(1)
		3045
		3046	By virtue of using a binary heap, the next timer is always found at the
		3047	beginning of the storage array.
2289		3048
2290	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3049	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2291		3050
2292	A change means an I/O watcher gets started or stopped, which requires	3051	A change means an I/O watcher gets started or stopped, which requires
2293	libev to recalculate its status (and possibly tell the kernel).	3052	libev to recalculate its status (and possibly tell the kernel, depending
		3053	on backend and wether C<ev_io_set> was used).
2294		3054
2295	=item Activating one watcher: O(1)	3055	=item Activating one watcher (putting it into the pending state): O(1)
2296		3056
2297	=item Priority handling: O(number_of_priorities)	3057	=item Priority handling: O(number_of_priorities)
2298		3058
2299	Priorities are implemented by allocating some space for each	3059	Priorities are implemented by allocating some space for each
2300	priority. When doing priority-based operations, libev usually has to	3060	priority. When doing priority-based operations, libev usually has to
2301	linearly search all the priorities.	3061	linearly search all the priorities, but starting/stopping and activating
		3062	watchers becomes O(1) w.r.t. priority handling.
		3063
		3064	=item Sending an ev_async: O(1)
		3065
		3066	=item Processing ev_async_send: O(number_of_async_watchers)
		3067
		3068	=item Processing signals: O(max_signal_number)
		3069
		3070	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3071	calls in the current loop iteration. Checking for async and signal events
		3072	involves iterating over all running async watchers or all signal numbers.
2302		3073
2303	=back	3074	=back
2304		3075
2305		3076
		3077	=head1 Win32 platform limitations and workarounds
		3078
		3079	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3080	requires, and its I/O model is fundamentally incompatible with the POSIX
		3081	model. Libev still offers limited functionality on this platform in
		3082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3083	descriptors. This only applies when using Win32 natively, not when using
		3084	e.g. cygwin.
		3085
		3086	There is no supported compilation method available on windows except
		3087	embedding it into other applications.
		3088
		3089	Due to the many, low, and arbitrary limits on the win32 platform and the
		3090	abysmal performance of winsockets, using a large number of sockets is not
		3091	recommended (and not reasonable). If your program needs to use more than
		3092	a hundred or so sockets, then likely it needs to use a totally different
		3093	implementation for windows, as libev offers the POSIX model, which cannot
		3094	be implemented efficiently on windows (microsoft monopoly games).
		3095
		3096	=over 4
		3097
		3098	=item The winsocket select function
		3099
		3100	The winsocket C<select> function doesn't follow POSIX in that it requires
		3101	socket I<handles> and not socket I<file descriptors>. This makes select
		3102	very inefficient, and also requires a mapping from file descriptors
		3103	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3104	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3105	symbols for more info.
		3106
		3107	The configuration for a "naked" win32 using the microsoft runtime
		3108	libraries and raw winsocket select is:
		3109
		3110	#define EV_USE_SELECT 1
		3111	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3112
		3113	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3114	complexity in the O(n²) range when using win32.
		3115
		3116	=item Limited number of file descriptors
		3117
		3118	Windows has numerous arbitrary (and low) limits on things. Early versions
		3119	of winsocket's select only supported waiting for a max. of C<64> handles
		3120	(probably owning to the fact that all windows kernels can only wait for
		3121	C<64> things at the same time internally; microsoft recommends spawning a
		3122	chain of threads and wait for 63 handles and the previous thread in each).
		3123
		3124	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3125	to some high number (e.g. C<2048>) before compiling the winsocket select
		3126	call (which might be in libev or elsewhere, for example, perl does its own
		3127	select emulation on windows).
		3128
		3129	Another limit is the number of file descriptors in the microsoft runtime
		3130	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3131	or something like this inside microsoft). You can increase this by calling
		3132	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3133	arbitrary limit), but is broken in many versions of the microsoft runtime
		3134	libraries.
		3135
		3136	This might get you to about C<512> or C<2048> sockets (depending on
		3137	windows version and/or the phase of the moon). To get more, you need to
		3138	wrap all I/O functions and provide your own fd management, but the cost of
		3139	calling select (O(n²)) will likely make this unworkable.
		3140
		3141	=back
		3142
		3143
2306	=head1 AUTHOR	3144	=head1 AUTHOR
2307		3145
2308	Marc Lehmann <libev@schmorp.de>.	3146	Marc Lehmann <libev@schmorp.de>.
2309		3147

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