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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
		67	The newest version of this document is also available as an html-formatted
		68	web page you might find easier to navigate when reading it for the first
		69	time: L<http://cvs.schmorp.de/libev/ev.html>.
		70
53	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
54	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
55	these event sources and provide your program with events.	73	these event sources and provide your program with events.
56		74
57	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
58	(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
59	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
61	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
62	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
63	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
64	watcher.	82	watcher.
65		83
66	=head1 FEATURES	84	=head2 FEATURES
67		85
68	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
69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	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
71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
78		96
79	It also is quite fast (see this	97	It also is quite fast (see this
80	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
81	for example).	99	for example).
82		100
83	=head1 CONVENTIONS	101	=head2 CONVENTIONS
84		102
85	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
86	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
87	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
88	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
89	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
90	(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.
91		110
92	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
93		112
94	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	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
97	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
98	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
99	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.
100		121
101	=head1 GLOBAL FUNCTIONS	122	=head1 GLOBAL FUNCTIONS
102		123
103	These functions can be called anytime, even before initialising the	124	These functions can be called anytime, even before initialising the
104	library in any way.	125	library in any way.
…		…
109		130
110	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
111	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
112	you actually want to know.	133	you actually want to know.
113		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
114	=item int ev_version_major ()	141	=item int ev_version_major ()
115		142
116	=item int ev_version_minor ()	143	=item int ev_version_minor ()
117		144
118	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
119	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
120	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
121	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
122	version of the library your program was compiled against.	149	version of the library your program was compiled against.
123		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
124	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,
125	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
126	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
127	not a problem.	157	not a problem.
128		158
129	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
130	version.	160	version.
…		…
245	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
246		276
247	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
248	function.	278	function.
249		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
250	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
251	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>).
252		289
253	The following flags are supported:	290	The following flags are supported:
254		291
…		…
275	enabling this flag.	312	enabling this flag.
276		313
277	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,
278	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
279	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
280	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
281	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
282	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
283		320
284	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
285	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
286	flag.	323	flag.
…		…
291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
292		329
293	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
294	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,
295	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
296	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
297	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.
298		342
299	=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)
300		344
301	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
302	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
303	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
304	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.
305		351
306	=item C<EVBACKEND_EPOLL> (value 4, Linux)	352	=item C<EVBACKEND_EPOLL> (value 4, Linux)
307		353
308	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,
309	but it scales phenomenally better. While poll and select usually scale like	355	but it scales phenomenally better. While poll and select usually scale
310	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),
311	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.
312		361
313	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
314	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
315	(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
316	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
317	well if you register events for both fds.	366	very well if you register events for both fds.
318		367
319	Please note that epoll sometimes generates spurious notifications, so you	368	Please note that epoll sometimes generates spurious notifications, so you
320	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
321	(or space) is available.	370	(or space) is available.
322		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
323	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
324		380
325	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
326	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
327	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
328	completely useless). For this reason its not being "autodetected"	384	it's completely useless). For this reason it's not being "autodetected"
329	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
330	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.
331		392
332	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
333	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
334	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
335	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
336	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.
337		408
338	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
339		410
340	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.
341		415
342	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
343		417
344	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,
345	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)).
346		420
347	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
348	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
349	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.
350		433
351	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
352		435
353	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
354	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
355	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
356		439
		440	It is definitely not recommended to use this flag.
		441
357	=back	442	=back
358		443
359	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
360	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
361	specified, most compiled-in backend will be tried, usually in reverse	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
362	order of their flag values :)
363		447
364	The most typical usage is like this:	448	The most typical usage is like this:
365		449
366	if (!ev_default_loop (0))	450	if (!ev_default_loop (0))
367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
395	Destroys the default loop again (frees all memory and kernel state	479	Destroys the default loop again (frees all memory and kernel state
396	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
397	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
398	responsibility to either stop all watchers cleanly yoursef I<before>	482	responsibility to either stop all watchers cleanly yoursef I<before>
399	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
400	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
401	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>).
402		495
403	=item ev_loop_destroy (loop)	496	=item ev_loop_destroy (loop)
404		497
405	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
406	earlier call to C<ev_loop_new>.	499	earlier call to C<ev_loop_new>.
407		500
408	=item ev_default_fork ()	501	=item ev_default_fork ()
409		502
		503	This function sets a flag that causes subsequent C<ev_loop> iterations
410	This function reinitialises the kernel state for backends that have	504	to reinitialise the kernel state for backends that have one. Despite the
411	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
412	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
413	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.
414		509
415	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
416	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
417	fork+exec, you don't have to call it.	512	you just fork+exec, you don't have to call it at all.
418		513
419	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
420	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
421	quite nicely into a call to C<pthread_atfork>:	516	quite nicely into a call to C<pthread_atfork>:
422		517
423	pthread_atfork (0, 0, ev_default_fork);	518	pthread_atfork (0, 0, ev_default_fork);
424		519
425	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
426	without calling this function, so if you force one of those backends you
427	do not need to care.
428
429	=item ev_loop_fork (loop)	520	=item ev_loop_fork (loop)
430		521
431	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
432	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
433	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.
434		529
435	=item unsigned int ev_loop_count (loop)	530	=item unsigned int ev_loop_count (loop)
436		531
437	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
438	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
…		…
451		546
452	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
453	received events and started processing them. This timestamp does not	548	received events and started processing them. This timestamp does not
454	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
455	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
456	event occuring (or more correctly, libev finding out about it).	551	event occurring (or more correctly, libev finding out about it).
457		552
458	=item ev_loop (loop, int flags)	553	=item ev_loop (loop, int flags)
459		554
460	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
461	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
…		…
482	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
483	usually a better approach for this kind of thing.	578	usually a better approach for this kind of thing.
484		579
485	Here are the gory details of what C<ev_loop> does:	580	Here are the gory details of what C<ev_loop> does:
486		581
487	* If there are no active watchers (reference count is zero), return.	582	- Before the first iteration, call any pending watchers.
488	- 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.
489	- If we have been forked, recreate the kernel state.	586	- If we have been forked, recreate the kernel state.
490	- Update the kernel state with all outstanding changes.	587	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	588	- Update the "event loop time".
492	- 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.
493	- Block the process, waiting for any events.	593	- Block the process, waiting for any events.
494	- Queue all outstanding I/O (fd) events.	594	- Queue all outstanding I/O (fd) events.
495	- Update the "event loop time" and do time jump handling.	595	- Update the "event loop time" and do time jump handling.
496	- Queue all outstanding timers.	596	- Queue all outstanding timers.
497	- Queue all outstanding periodics.	597	- Queue all outstanding periodics.
498	- If no events are pending now, queue all idle watchers.	598	- If no events are pending now, queue all idle watchers.
499	- Queue all check watchers.	599	- Queue all check watchers.
500	- 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).
501	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
502	be handled here by queueing them when their watcher gets executed.	602	be handled here by queueing them when their watcher gets executed.
503	- 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
504	were used, return, otherwise continue with step *.	604	were used, or there are no active watchers, return, otherwise
		605	continue with step *.
505		606
506	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
507	anymore.	608	anymore.
508		609
509	... queue jobs here, make sure they register event watchers as long	610	... queue jobs here, make sure they register event watchers as long
510	... 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..)
511	ev_loop (my_loop, 0);	612	ev_loop (my_loop, 0);
…		…
515		616
516	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
517	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
518	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
519	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.
520		623
521	=item ev_ref (loop)	624	=item ev_ref (loop)
522		625
523	=item ev_unref (loop)	626	=item ev_unref (loop)
524		627
…		…
529	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
530	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
531	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
532	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
533	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
534	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).
535		640
536	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>
537	running when nothing else is active.	642	running when nothing else is active.
538		643
539	struct ev_signal exitsig;	644	struct ev_signal exitsig;
…		…
543		648
544	Example: For some weird reason, unregister the above signal handler again.	649	Example: For some weird reason, unregister the above signal handler again.
545		650
546	ev_ref (loop);	651	ev_ref (loop);
547	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.
548		689
549	=back	690	=back
550		691
551		692
552	=head1 ANATOMY OF A WATCHER	693	=head1 ANATOMY OF A WATCHER
…		…
652	=item C<EV_FORK>	793	=item C<EV_FORK>
653		794
654	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
655	C<ev_fork>).	796	C<ev_fork>).
656		797
		798	=item C<EV_ASYNC>
		799
		800	The given async watcher has been asynchronously notified (see C<ev_async>).
		801
657	=item C<EV_ERROR>	802	=item C<EV_ERROR>
658		803
659	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
660	happen because the watcher could not be properly started because libev	805	happen because the watcher could not be properly started because libev
661	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
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	877	=item bool ev_is_pending (ev_TYPE *watcher)
733		878
734	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
735	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
736	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
737	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
738	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).
739		885
740	=item callback ev_cb (ev_TYPE *watcher)	886	=item callback ev_cb (ev_TYPE *watcher)
741		887
742	Returns the callback currently set on the watcher.	888	Returns the callback currently set on the watcher.
743		889
…		…
762	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.
763		909
764	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
765	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.
766		912
		913	You I<must not> change the priority of a watcher as long as it is active or
		914	pending.
		915
767	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
768	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 :).
769		918
770	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
771	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
772	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>.
773		934
774	=back	935	=back
775		936
776		937
777	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	938	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
862	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
863	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
864	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
865	required if you know what you are doing).	1026	required if you know what you are doing).
866		1027
867	You have to be careful with dup'ed file descriptors, though. Some backends
868	(the linux epoll backend is a notable example) cannot handle dup'ed file
869	descriptors correctly if you register interest in two or more fds pointing
870	to the same underlying file/socket/etc. description (that is, they share
871	the same underlying "file open").
872
873	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
874	(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
875	C<EVBACKEND_POLL>).	1030	C<EVBACKEND_POLL>).
876		1031
877	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
…		…
883	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1038	it is best to always use non-blocking I/O: An extra C<read>(2) returning
884	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1039	C<EAGAIN> is far preferable to a program hanging until some data arrives.
885		1040
886	If you cannot run the fd in non-blocking mode (for example you should not	1041	If you cannot run the fd in non-blocking mode (for example you should not
887	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
888	wether 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
889	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
890	its own, so its quite safe to use).	1045	its own, so its quite safe to use).
		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
891		1092
892	=over 4	1093	=over 4
893		1094
894	=item ev_io_init (ev_io *, callback, int fd, int events)	1095	=item ev_io_init (ev_io *, callback, int fd, int events)
895		1096
…		…
906	=item int events [read-only]	1107	=item int events [read-only]
907		1108
908	The events being watched.	1109	The events being watched.
909		1110
910	=back	1111	=back
		1112
		1113	=head3 Examples
911		1114
912	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
913	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
914	attempt to read a whole line in the callback.	1117	attempt to read a whole line in the callback.
915		1118
…		…
949		1152
950	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,
951	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
952	order of execution is undefined.	1155	order of execution is undefined.
953		1156
		1157	=head3 Watcher-Specific Functions and Data Members
		1158
954	=over 4	1159	=over 4
955		1160
956	=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)
957		1162
958	=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)
…		…
966	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
967	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
968	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
969	timer will not fire more than once per event loop iteration.	1174	timer will not fire more than once per event loop iteration.
970		1175
971	=item ev_timer_again (loop)	1176	=item ev_timer_again (loop, ev_timer *)
972		1177
973	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
974	repeating. The exact semantics are:	1179	repeating. The exact semantics are:
975		1180
976	If the timer is pending, its pending status is cleared.	1181	If the timer is pending, its pending status is cleared.
…		…
1011	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),
1012	which is also when any modifications are taken into account.	1217	which is also when any modifications are taken into account.
1013		1218
1014	=back	1219	=back
1015		1220
		1221	=head3 Examples
		1222
1016	Example: Create a timer that fires after 60 seconds.	1223	Example: Create a timer that fires after 60 seconds.
1017		1224
1018	static void	1225	static void
1019	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)
1020	{	1227	{
…		…
1053	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
1054	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
1055	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 ()
1056	+ 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
1057	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
1058	roughly 10 seconds later and of course not if you reset your system time	1265	roughly 10 seconds later).
1059	again).
1060		1266
1061	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
1062	triggering an event on eahc midnight, local time.	1268	triggering an event on each midnight, local time or other, complicated,
		1269	rules.
1063		1270
1064	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
1065	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
1066	during the same loop iteration then order of execution is undefined.	1273	during the same loop iteration then order of execution is undefined.
1067		1274
		1275	=head3 Watcher-Specific Functions and Data Members
		1276
1068	=over 4	1277	=over 4
1069		1278
1070	=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)
1071		1280
1072	=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)
…		…
1074	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
1075	operation, and we will explain them from simplest to complex:	1284	operation, and we will explain them from simplest to complex:
1076		1285
1077	=over 4	1286	=over 4
1078		1287
1079	=item * absolute timer (interval = reschedule_cb = 0)	1288	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1080		1289
1081	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
1082	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,
1083	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
1084	system time reaches or surpasses this time.	1293	system time reaches or surpasses this time.
1085		1294
1086	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1087		1296
1088	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
1089	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)
1090	of any time jumps.	1299	and then repeat, regardless of any time jumps.
1091		1300
1092	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
1093	time:	1302	time:
1094		1303
1095	ev_periodic_set (&periodic, 0., 3600., 0);	1304	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1101		1310
1102	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
1103	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
1104	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.
1105		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
1106	=item * manual reschedule mode (reschedule_cb = callback)	1319	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1107		1320
1108	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
1109	ignored. Instead, each time the periodic watcher gets scheduled, the	1322	ignored. Instead, each time the periodic watcher gets scheduled, the
1110	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
1111	current time as second argument.	1324	current time as second argument.
1112		1325
1113	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,
1114	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,
1115	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
1116	starting a prepare watcher).	1329	starting an C<ev_prepare> watcher, which is legal).
1117		1330
1118	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,
1119	ev_tstamp now)>, e.g.:	1332	ev_tstamp now)>, e.g.:
1120		1333
1121	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)
…		…
1144	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
1145	when you changed some parameters or the reschedule callback would return	1358	when you changed some parameters or the reschedule callback would return
1146	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
1147	program when the crontabs have changed).	1360	program when the crontabs have changed).
1148		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
1149	=item ev_tstamp interval [read-write]	1370	=item ev_tstamp interval [read-write]
1150		1371
1151	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
1152	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
1153	called.	1374	called.
…		…
1156		1377
1157	The current reschedule callback, or C<0>, if this functionality is	1378	The current reschedule callback, or C<0>, if this functionality is
1158	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
1159	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.
1160		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
1161	=back	1387	=back
		1388
		1389	=head3 Examples
1162		1390
1163	Example: Call a callback every hour, or, more precisely, whenever the	1391	Example: Call a callback every hour, or, more precisely, whenever the
1164	system clock is divisible by 3600. The callback invocation times have	1392	system clock is divisible by 3600. The callback invocation times have
1165	potentially a lot of jittering, but good long-term stability.	1393	potentially a lot of jittering, but good long-term stability.
1166		1394
…		…
1206	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
1207	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
1208	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
1209	SIG_DFL (regardless of what it was set to before).	1437	SIG_DFL (regardless of what it was set to before).
1210		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
1211	=over 4	1447	=over 4
1212		1448
1213	=item ev_signal_init (ev_signal *, callback, int signum)	1449	=item ev_signal_init (ev_signal *, callback, int signum)
1214		1450
1215	=item ev_signal_set (ev_signal *, int signum)	1451	=item ev_signal_set (ev_signal *, int signum)
…		…
1221		1457
1222	The signal the watcher watches out for.	1458	The signal the watcher watches out for.
1223		1459
1224	=back	1460	=back
1225		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
1226		1476
1227	=head2 C<ev_child> - watch out for process status changes	1477	=head2 C<ev_child> - watch out for process status changes
1228		1478
1229	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
1230	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
1231		1508
1232	=over 4	1509	=over 4
1233		1510
1234	=item ev_child_init (ev_child *, callback, int pid)	1511	=item ev_child_init (ev_child *, callback, int pid, int trace)
1235		1512
1236	=item ev_child_set (ev_child *, int pid)	1513	=item ev_child_set (ev_child *, int pid, int trace)
1237		1514
1238	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
1239	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
1240	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
1241	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
1242	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
1243	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).
1244		1523
1245	=item int pid [read-only]	1524	=item int pid [read-only]
1246		1525
1247	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.
1248		1527
…		…
1255	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
1256	C<waitpid> and C<sys/wait.h> documentation for details).	1535	C<waitpid> and C<sys/wait.h> documentation for details).
1257		1536
1258	=back	1537	=back
1259		1538
1260	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;
1261		1545
1262	static void	1546	static void
1263	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1547	child_cb (EV_P_ struct ev_child *w, int revents)
1264	{	1548	{
1265	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);
1266	}	1551	}
1267		1552
1268	struct ev_signal signal_watcher;	1553	pid_t pid = fork ();
1269	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1554
1270	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	}
1271		1567
1272		1568
1273	=head2 C<ev_stat> - did the file attributes just change?	1569	=head2 C<ev_stat> - did the file attributes just change?
1274		1570
1275	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
…		…
1304	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
1305	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
1306	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
1307	polling.	1603	polling.
1308		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
1309	=over 4	1640	=over 4
1310		1641
1311	=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)
1312		1643
1313	=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)
…		…
1320		1651
1321	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,
1322	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
1323	last change was detected).	1654	last change was detected).
1324		1655
1325	=item ev_stat_stat (ev_stat *)	1656	=item ev_stat_stat (loop, ev_stat *)
1326		1657
1327	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
1328	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
1329	detecting this change (while introducing a race condition). Can also be	1660	detecting this change (while introducing a race condition). Can also be
1330	useful simply to find out the new values.	1661	useful simply to find out the new values.
…		…
1348	=item const char *path [read-only]	1679	=item const char *path [read-only]
1349		1680
1350	The filesystem path that is being watched.	1681	The filesystem path that is being watched.
1351		1682
1352	=back	1683	=back
		1684
		1685	=head3 Examples
1353		1686
1354	Example: Watch C</etc/passwd> for attribute changes.	1687	Example: Watch C</etc/passwd> for attribute changes.
1355		1688
1356	static void	1689	static void
1357	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1690	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1370	}	1703	}
1371		1704
1372	...	1705	...
1373	ev_stat passwd;	1706	ev_stat passwd;
1374		1707
1375	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1708	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1376	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);
1377		1738
1378		1739
1379	=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...
1380		1741
1381	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
…		…
1395	Apart from keeping your process non-blocking (which is a useful	1756	Apart from keeping your process non-blocking (which is a useful
1396	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
1397	"pseudo-background processing", or delay processing stuff to after the	1758	"pseudo-background processing", or delay processing stuff to after the
1398	event loop has handled all outstanding events.	1759	event loop has handled all outstanding events.
1399		1760
		1761	=head3 Watcher-Specific Functions and Data Members
		1762
1400	=over 4	1763	=over 4
1401		1764
1402	=item ev_idle_init (ev_signal *, callback)	1765	=item ev_idle_init (ev_signal *, callback)
1403		1766
1404	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
1405	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,
1406	believe me.	1769	believe me.
1407		1770
1408	=back	1771	=back
		1772
		1773	=head3 Examples
1409		1774
1410	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
1411	callback, free it. Also, use no error checking, as usual.	1776	callback, free it. Also, use no error checking, as usual.
1412		1777
1413	static void	1778	static void
1414	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)
1415	{	1780	{
1416	free (w);	1781	free (w);
1417	// now do something you wanted to do when the program has	1782	// now do something you wanted to do when the program has
1418	// no longer asnything immediate to do.	1783	// no longer anything immediate to do.
1419	}	1784	}
1420		1785
1421	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1786	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1422	ev_idle_init (idle_watcher, idle_cb);	1787	ev_idle_init (idle_watcher, idle_cb);
1423	ev_idle_start (loop, idle_cb);	1788	ev_idle_start (loop, idle_cb);
…		…
1461	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
1462	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
1463	loop from blocking if lower-priority coroutines are active, thus mapping	1828	loop from blocking if lower-priority coroutines are active, thus mapping
1464	low-priority coroutines to idle/background tasks).	1829	low-priority coroutines to idle/background tasks).
1465		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
1466	=over 4	1843	=over 4
1467		1844
1468	=item ev_prepare_init (ev_prepare *, callback)	1845	=item ev_prepare_init (ev_prepare *, callback)
1469		1846
1470	=item ev_check_init (ev_check *, callback)	1847	=item ev_check_init (ev_check *, callback)
…		…
1473	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>
1474	macros, but using them is utterly, utterly and completely pointless.	1851	macros, but using them is utterly, utterly and completely pointless.
1475		1852
1476	=back	1853	=back
1477		1854
1478	Example: To include a library such as adns, you would add IO watchers	1855	=head3 Examples
1479	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,
1480	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
1481	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.
1482		1869
1483	static ev_io iow [nfd];	1870	static ev_io iow [nfd];
1484	static ev_timer tw;	1871	static ev_timer tw;
1485		1872
1486	static void	1873	static void
1487	io_cb (ev_loop *loop, ev_io *w, int revents)	1874	io_cb (ev_loop *loop, ev_io *w, int revents)
1488	{	1875	{
1489	// set the relevant poll flags
1490	// could also call adns_processreadable etc. here
1491	struct pollfd *fd = (struct pollfd *)w->data;
1492	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1493	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1494	}	1876	}
1495		1877
1496	// create io watchers for each fd and a timer before blocking	1878	// create io watchers for each fd and a timer before blocking
1497	static void	1879	static void
1498	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1880	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
…		…
1504		1886
1505	/* 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 */
1506	ev_timer_init (&tw, 0, timeout * 1e-3);	1888	ev_timer_init (&tw, 0, timeout * 1e-3);
1507	ev_timer_start (loop, &tw);	1889	ev_timer_start (loop, &tw);
1508		1890
1509	// create on ev_io per pollfd	1891	// create one ev_io per pollfd
1510	for (int i = 0; i < nfd; ++i)	1892	for (int i = 0; i < nfd; ++i)
1511	{	1893	{
1512	ev_io_init (iow + i, io_cb, fds [i].fd,	1894	ev_io_init (iow + i, io_cb, fds [i].fd,
1513	((fds [i].events & POLLIN ? EV_READ : 0)	1895	((fds [i].events & POLLIN ? EV_READ : 0)
1514	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1896	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1515		1897
1516	fds [i].revents = 0;	1898	fds [i].revents = 0;
1517	iow [i].data = fds + i;
1518	ev_io_start (loop, iow + i);	1899	ev_io_start (loop, iow + i);
1519	}	1900	}
1520	}	1901	}
1521		1902
1522	// stop all watchers after blocking	1903	// stop all watchers after blocking
…		…
1524	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1905	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1525	{	1906	{
1526	ev_timer_stop (loop, &tw);	1907	ev_timer_stop (loop, &tw);
1527		1908
1528	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
1529	ev_io_stop (loop, iow + i);	1919	ev_io_stop (loop, iow + i);
		1920	}
1530		1921
1531	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;
1532	}	1982	}
1533		1983
1534		1984
1535	=head2 C<ev_embed> - when one backend isn't enough...	1985	=head2 C<ev_embed> - when one backend isn't enough...
1536		1986
…		…
1579	portable one.	2029	portable one.
1580		2030
1581	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
1582	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
1583	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
1584	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).
1585		2069
1586	struct ev_loop *loop_hi = ev_default_init (0);	2070	struct ev_loop *loop_hi = ev_default_init (0);
1587	struct ev_loop *loop_lo = 0;	2071	struct ev_loop *loop_lo = 0;
1588	struct ev_embed embed;	2072	struct ev_embed embed;
1589		2073
…		…
1600	ev_embed_start (loop_hi, &embed);	2084	ev_embed_start (loop_hi, &embed);
1601	}	2085	}
1602	else	2086	else
1603	loop_lo = loop_hi;	2087	loop_lo = loop_hi;
1604		2088
1605	=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).
1606		2093
1607	=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	}
1608		2104
1609	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2105	if (!loop_socket)
		2106	loop_socket = loop;
1610		2107
1611	Configures the watcher to embed the given loop, which must be	2108	// now use loop_socket for all sockets, and loop for everything else
1612	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1613	invoked automatically, otherwise it is the responsibility of the callback
1614	to invoke it (it will continue to be called until the sweep has been done,
1615	if you do not want thta, you need to temporarily stop the embed watcher).
1616
1617	=item ev_embed_sweep (loop, ev_embed *)
1618
1619	Make a single, non-blocking sweep over the embedded loop. This works
1620	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1621	apropriate way for embedded loops.
1622
1623	=item struct ev_loop *loop [read-only]
1624
1625	The embedded event loop.
1626
1627	=back
1628		2109
1629		2110
1630	=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
1631		2112
1632	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
…		…
1635	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,
1636	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
1637	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
1638	handlers will be invoked, too, of course.	2119	handlers will be invoked, too, of course.
1639		2120
		2121	=head3 Watcher-Specific Functions and Data Members
		2122
1640	=over 4	2123	=over 4
1641		2124
1642	=item ev_fork_init (ev_signal *, callback)	2125	=item ev_fork_init (ev_signal *, callback)
1643		2126
1644	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
1645	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,
1646	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>.
1647		2261
1648	=back	2262	=back
1649		2263
1650		2264
1651	=head1 OTHER FUNCTIONS	2265	=head1 OTHER FUNCTIONS
…		…
1740		2354
1741	To use it,	2355	To use it,
1742		2356
1743	#include <ev++.h>	2357	#include <ev++.h>
1744		2358
1745	(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
1746	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
1747	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>.
1748		2363
1749	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++
1750	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).
1751		2374
1752	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:
1753		2376
1754	=over 4	2377	=over 4
1755		2378
…		…
1771		2394
1772	All of those classes have these methods:	2395	All of those classes have these methods:
1773		2396
1774	=over 4	2397	=over 4
1775		2398
1776	=item ev::TYPE::TYPE (object *, object::method *)	2399	=item ev::TYPE::TYPE ()
1777		2400
1778	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2401	=item ev::TYPE::TYPE (struct ev_loop *)
1779		2402
1780	=item ev::TYPE::~TYPE	2403	=item ev::TYPE::~TYPE
1781		2404
1782	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
1783	the event handler callback to call in this class. The constructor calls	2406	with. If it is omitted, it will use C<EV_DEFAULT>.
1784	C<ev_init> for you, which means you have to call the C<set> method	2407
1785	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
1786	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).
1787		2416
1788	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> ();
1789		2457
1790	=item w->set (struct ev_loop *)	2458	=item w->set (struct ev_loop *)
1791		2459
1792	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
1793	do this when the watcher is inactive (and not pending either).	2461	do this when the watcher is inactive (and not pending either).
1794		2462
1795	=item w->set ([args])	2463	=item w->set ([args])
1796		2464
1797	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
1798	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
1799	automatically stopped and restarted.	2467	automatically stopped and restarted when reconfiguring it with this
		2468	method.
1800		2469
1801	=item w->start ()	2470	=item w->start ()
1802		2471
1803	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
1804	constructor already takes the loop.	2473	constructor already stores the event loop.
1805		2474
1806	=item w->stop ()	2475	=item w->stop ()
1807		2476
1808	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.
1809		2478
1810	=item w->again () C<ev::timer>, C<ev::periodic> only	2479	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1811		2480
1812	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
1813	C<ev_TYPE_again> function.	2482	C<ev_TYPE_again> function.
1814		2483
1815	=item w->sweep () C<ev::embed> only	2484	=item w->sweep () (C<ev::embed> only)
1816		2485
1817	Invokes C<ev_embed_sweep>.	2486	Invokes C<ev_embed_sweep>.
1818		2487
1819	=item w->update () C<ev::stat> only	2488	=item w->update () (C<ev::stat> only)
1820		2489
1821	Invokes C<ev_stat_stat>.	2490	Invokes C<ev_stat_stat>.
1822		2491
1823	=back	2492	=back
1824		2493
…		…
1827	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
1828	the constructor.	2497	the constructor.
1829		2498
1830	class myclass	2499	class myclass
1831	{	2500	{
1832	ev_io io; void io_cb (ev::io &w, int revents);	2501	ev::io io; void io_cb (ev::io &w, int revents);
1833	ev_idle idle void idle_cb (ev::idle &w, int revents);	2502	ev:idle idle void idle_cb (ev::idle &w, int revents);
1834		2503
1835	myclass ();	2504	myclass (int fd)
1836	}
1837
1838	myclass::myclass (int fd)
1839	: io (this, &myclass::io_cb),
1840	idle (this, &myclass::idle_cb)
1841	{	2505	{
		2506	io .set <myclass, &myclass::io_cb > (this);
		2507	idle.set <myclass, &myclass::idle_cb> (this);
		2508
1842	io.start (fd, ev::READ);	2509	io.start (fd, ev::READ);
		2510	}
1843	}	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
1844		2547
1845		2548
1846	=head1 MACRO MAGIC	2549	=head1 MACRO MAGIC
1847		2550
1848	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
1849	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2552	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1850	callbacks have an initial C<struct ev_loop *> argument.	2553	functions and callbacks have an initial C<struct ev_loop *> argument.
1851		2554
1852	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
1853	following macros are defined:	2556	following macros are defined:
1854		2557
1855	=over 4	2558	=over 4
…		…
1888	loop, if multiple loops are supported ("ev loop default").	2591	loop, if multiple loops are supported ("ev loop default").
1889		2592
1890	=back	2593	=back
1891		2594
1892	Example: Declare and initialise a check watcher, utilising the above	2595	Example: Declare and initialise a check watcher, utilising the above
1893	macros so it will work regardless of wether multiple loops are supported	2596	macros so it will work regardless of whether multiple loops are supported
1894	or not.	2597	or not.
1895		2598
1896	static void	2599	static void
1897	check_cb (EV_P_ ev_timer *w, int revents)	2600	check_cb (EV_P_ ev_timer *w, int revents)
1898	{	2601	{
…		…
1909	Libev can (and often is) directly embedded into host	2612	Libev can (and often is) directly embedded into host
1910	applications. Examples of applications that embed it include the Deliantra	2613	applications. Examples of applications that embed it include the Deliantra
1911	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)
1912	and rxvt-unicode.	2615	and rxvt-unicode.
1913		2616
1914	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
1915	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
1916	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
1917	libev somewhere in your source tree).	2620	libev somewhere in your source tree).
1918		2621
1919	=head2 FILESETS	2622	=head2 FILESETS
…		…
2009		2712
2010	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
2011	monotonic clock option at both compiletime and runtime. Otherwise no use	2714	monotonic clock option at both compiletime and runtime. Otherwise no use
2012	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
2013	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
2014	the functionality isn't available is safe, though, althoguh you have	2717	the functionality isn't available is safe, though, although you have
2015	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>
2016	function is hiding in (often F<-lrt>).	2719	function is hiding in (often F<-lrt>).
2017		2720
2018	=item EV_USE_REALTIME	2721	=item EV_USE_REALTIME
2019		2722
2020	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
2021	realtime clock option at compiletime (and assume its availability at	2724	realtime clock option at compiletime (and assume its availability at
2022	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
2023	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2726	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2024	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2727	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2025	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 ()>.
2026		2734
2027	=item EV_USE_SELECT	2735	=item EV_USE_SELECT
2028		2736
2029	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
2030	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
…		…
2048	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
2049	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
2050	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,
2051	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
2052	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.
2053		2769
2054	=item EV_USE_POLL	2770	=item EV_USE_POLL
2055		2771
2056	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)
2057	backend. Otherwise it will be enabled on non-win32 platforms. It	2773	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2091		2807
2092	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
2093	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
2094	be detected at runtime.	2810	be detected at runtime.
2095		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
2096	=item EV_H	2823	=item EV_H
2097		2824
2098	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
2099	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
2100	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.
2101		2828
2102	=item EV_CONFIG_H	2829	=item EV_CONFIG_H
2103		2830
2104	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
2105	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
2106	C<EV_H>, above.	2833	C<EV_H>, above.
2107		2834
2108	=item EV_EVENT_H	2835	=item EV_EVENT_H
2109		2836
2110	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
2111	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">.
2112		2839
2113	=item EV_PROTOTYPES	2840	=item EV_PROTOTYPES
2114		2841
2115	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
2116	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
…		…
2123	will have the C<struct ev_loop *> as first argument, and you can create	2850	will have the C<struct ev_loop *> as first argument, and you can create
2124	additional independent event loops. Otherwise there will be no support	2851	additional independent event loops. Otherwise there will be no support
2125	for multiple event loops and there is no first event loop pointer	2852	for multiple event loops and there is no first event loop pointer
2126	argument. Instead, all functions act on the single default loop.	2853	argument. Instead, all functions act on the single default loop.
2127		2854
		2855	=item EV_MINPRI
		2856
		2857	=item EV_MAXPRI
		2858
		2859	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2860	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2861	provide for more priorities by overriding those symbols (usually defined
		2862	to be C<-2> and C<2>, respectively).
		2863
		2864	When doing priority-based operations, libev usually has to linearly search
		2865	all the priorities, so having many of them (hundreds) uses a lot of space
		2866	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2867	fine.
		2868
		2869	If your embedding app does not need any priorities, defining these both to
		2870	C<0> will save some memory and cpu.
		2871
2128	=item EV_PERIODIC_ENABLE	2872	=item EV_PERIODIC_ENABLE
2129		2873
2130	If undefined or defined to be C<1>, then periodic timers are supported. If	2874	If undefined or defined to be C<1>, then periodic timers are supported. If
2131	defined to be C<0>, then they are not. Disabling them saves a few kB of	2875	defined to be C<0>, then they are not. Disabling them saves a few kB of
2132	code.	2876	code.
…		…
2148	defined to be C<0>, then they are not.	2892	defined to be C<0>, then they are not.
2149		2893
2150	=item EV_FORK_ENABLE	2894	=item EV_FORK_ENABLE
2151		2895
2152	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
		2897	defined to be C<0>, then they are not.
		2898
		2899	=item EV_ASYNC_ENABLE
		2900
		2901	If undefined or defined to be C<1>, then async watchers are supported. If
2153	defined to be C<0>, then they are not.	2902	defined to be C<0>, then they are not.
2154		2903
2155	=item EV_MINIMAL	2904	=item EV_MINIMAL
2156		2905
2157	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
…		…
2165	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
2166	increase this value (I<must> be a power of two).	2915	increase this value (I<must> be a power of two).
2167		2916
2168	=item EV_INOTIFY_HASHSIZE	2917	=item EV_INOTIFY_HASHSIZE
2169		2918
2170	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
2171	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>),
2172	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>
2173	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
2174	two).	2923	two).
2175		2924
…		…
2192		2941
2193	=item ev_set_cb (ev, cb)	2942	=item ev_set_cb (ev, cb)
2194		2943
2195	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,
2196	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
2197	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
2198	their default definitions. One possible use for overriding these is to	2947	their default definitions. One possible use for overriding these is to
2199	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
2200	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	...
2201		2975
2202	=head2 EXAMPLES	2976	=head2 EXAMPLES
2203		2977
2204	For a real-world example of a program the includes libev	2978	For a real-world example of a program the includes libev
2205	verbatim, you can have a look at the EV perl module	2979	verbatim, you can have a look at the EV perl module
…		…
2234		3008
2235	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
2236	libev will be explained. For complexity discussions about backends see the	3010	libev will be explained. For complexity discussions about backends see the
2237	documentation for C<ev_default_init>.	3011	documentation for C<ev_default_init>.
2238		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
2239	=over 4	3019	=over 4
2240		3020
2241	=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)
2242		3022
		3023	This means that, when you have a watcher that triggers in one hour and
		3024	there are 100 watchers that would trigger before that then inserting will
		3025	have to skip roughly seven (C<ld 100>) of these watchers.
		3026
2243	=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)
2244		3028
		3029	That means that changing a timer costs less than removing/adding them
		3030	as only the relative motion in the event queue has to be paid for.
		3031
2245	=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)
2246		3033
		3034	These just add the watcher into an array or at the head of a list.
		3035
2247	=item Stopping check/prepare/idle watchers: O(1)	3036	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2248		3037
2249	=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))
2250		3039
		3040	These watchers are stored in lists then need to be walked to find the
		3041	correct watcher to remove. The lists are usually short (you don't usually
		3042	have many watchers waiting for the same fd or signal).
		3043
2251	=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.
2252		3048
2253	=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)
2254		3050
2255	=item Activating one watcher: O(1)	3051	A change means an I/O watcher gets started or stopped, which requires
		3052	libev to recalculate its status (and possibly tell the kernel, depending
		3053	on backend and wether C<ev_io_set> was used).
		3054
		3055	=item Activating one watcher (putting it into the pending state): O(1)
		3056
		3057	=item Priority handling: O(number_of_priorities)
		3058
		3059	Priorities are implemented by allocating some space for each
		3060	priority. When doing priority-based operations, libev usually has to
		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.
2256		3073
2257	=back	3074	=back
2258		3075
2259		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
2260	=head1 AUTHOR	3144	=head1 AUTHOR
2261		3145
2262	Marc Lehmann <libev@schmorp.de>.	3146	Marc Lehmann <libev@schmorp.de>.
2263		3147

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