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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head2 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
15	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
19	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
20	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head2 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head2 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
52		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
53		106
54	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
55		108
56	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
57	library in any way.	110	library in any way.
…		…
62		115
63	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
64	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
65	you actually want to know.	118	you actually want to know.
66		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
67	=item int ev_version_major ()	126	=item int ev_version_major ()
68		127
69	=item int ev_version_minor ()	128	=item int ev_version_minor ()
70		129
71	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
72	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
73	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
75	version of the library your program was compiled against.	134	version of the library your program was compiled against.
76		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
77	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	142	not a problem.
81		143
82	Example: make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	145	version.
84		146
85	assert (("libev version mismatch",	147	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	148	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	149	&& ev_version_minor () >= EV_VERSION_MINOR));
88		150
…		…
118		180
119	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
120		182
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		184
123	Sets the allocation function to use (the prototype is similar to the	185	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	186	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	187	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	188	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
128		191
129	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	193	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	194	or even to sleep a while and retry until some memory is available.
132		195
133	Example: replace the libev allocator with one that waits a bit and then	196	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	197	retries).
135		198
136	static void *	199	static void *
137	persistent_realloc (void *ptr, long size)	200	persistent_realloc (void *ptr, size_t size)
138	{	201	{
139	for (;;)	202	for (;;)
140	{	203	{
141	void *newptr = realloc (ptr, size);	204	void *newptr = realloc (ptr, size);
142		205
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	221	callback is set, then libev will expect it to remedy the sitution, no
159	matter what, when it returns. That is, libev will generally retry the	222	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	223	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	224	(such as abort).
162		225
163	Example: do the same thing as libev does internally:	226	Example: This is basically the same thing that libev does internally, too.
164		227
165	static void	228	static void
166	fatal_error (const char *msg)	229	fatal_error (const char *msg)
167	{	230	{
168	perror (msg);	231	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	282	override the flags completely if it is found in the environment. This is
220	useful to try out specific backends to test their performance, or to work	283	useful to try out specific backends to test their performance, or to work
221	around bugs.	284	around bugs.
222		285
		286	=item C<EVFLAG_FORKCHECK>
		287
		288	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		289	a fork, you can also make libev check for a fork in each iteration by
		290	enabling this flag.
		291
		292	This works by calling C<getpid ()> on every iteration of the loop,
		293	and thus this might slow down your event loop if you do a lot of loop
		294	iterations and little real work, but is usually not noticeable (on my
		295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		296	without a syscall and thus I<very> fast, but my Linux system also has
		297	C<pthread_atfork> which is even faster).
		298
		299	The big advantage of this flag is that you can forget about fork (and
		300	forget about forgetting to tell libev about forking) when you use this
		301	flag.
		302
		303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		304	environment variable.
		305
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		307
225	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
228	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
229	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
230		320
231	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
232		322
233	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
234	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
235	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
236	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
237		329
238	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
239		331
240	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
241	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
242	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	334	like O(total_fds) where n is the total number of fds (or the highest fd),
243	either O(1) or O(active_fds).	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
		336	of shortcomings, such as silently dropping events in some hard-to-detect
		337	cases and rewiring a syscall per fd change, no fork support and bad
		338	support for dup.
244		339
245	While stopping and starting an I/O watcher in the same iteration will	340	While stopping, setting and starting an I/O watcher in the same iteration
246	result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
247	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
248	best to avoid that. Also, dup()ed file descriptors might not work very	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
249	well if you register events for both fds.	344	very well if you register events for both fds.
250		345
251	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
252	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
253	(or space) is available.	348	(or space) is available.
254		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256		358
257	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
258	was broken on all BSDs except NetBSD (usually it doesn't work with	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
259	anything but sockets and pipes, except on Darwin, where of course its	361	with anything but sockets and pipes, except on Darwin, where of course
260	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
261	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
262	C<EVBACKEND_KQUEUE>).	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		365	system like NetBSD.
		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
263		370
264	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
265	kernel is more efficient (which says nothing about its actual speed, of	372	kernel is more efficient (which says nothing about its actual speed, of
266	course). While starting and stopping an I/O watcher does not cause an	373	course). While stopping, setting and starting an I/O watcher does never
267	extra syscall as with epoll, it still adds up to four event changes per	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
268	incident, so its best to avoid that.	375	two event changes per incident, support for C<fork ()> is very bad and it
		376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
269		386
270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271		388
272	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
273		393
274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275		395
276	This uses the Solaris 10 port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
277	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
278		398
279	Please note that solaris ports can result in a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
280	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
281	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
282		407
283	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
284		409
285	Try all backends (even potentially broken ones that wouldn't be tried	410	Try all backends (even potentially broken ones that wouldn't be tried
286	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
288		415
289	=back	416	=back
290		417
291	If one or more of these are ored into the flags value, then only these	418	If one or more of these are ored into the flags value, then only these
292	backends will be tried (in the reverse order as given here). If none are	419	backends will be tried (in the reverse order as given here). If none are
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	441	Similar to C<ev_default_loop>, but always creates a new event loop that is
315	always distinct from the default loop. Unlike the default loop, it cannot	442	always distinct from the default loop. Unlike the default loop, it cannot
316	handle signal and child watchers, and attempts to do so will be greeted by	443	handle signal and child watchers, and attempts to do so will be greeted by
317	undefined behaviour (or a failed assertion if assertions are enabled).	444	undefined behaviour (or a failed assertion if assertions are enabled).
318		445
319	Example: try to create a event loop that uses epoll and nothing else.	446	Example: Try to create a event loop that uses epoll and nothing else.
320		447
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	449	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	450	fatal ("no epoll found here, maybe it hides under your chair");
324		451
…		…
327	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
328	etc.). None of the active event watchers will be stopped in the normal	455	etc.). None of the active event watchers will be stopped in the normal
329	sense, so e.g. C<ev_is_active> might still return true. It is your	456	sense, so e.g. C<ev_is_active> might still return true. It is your
330	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
331	calling this function, or cope with the fact afterwards (which is usually	458	calling this function, or cope with the fact afterwards (which is usually
332	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	459	the easiest thing, you can just ignore the watchers and/or C<free ()> them
333	for example).	460	for example).
		461
		462	Note that certain global state, such as signal state, will not be freed by
		463	this function, and related watchers (such as signal and child watchers)
		464	would need to be stopped manually.
		465
		466	In general it is not advisable to call this function except in the
		467	rare occasion where you really need to free e.g. the signal handling
		468	pipe fds. If you need dynamically allocated loops it is better to use
		469	C<ev_loop_new> and C<ev_loop_destroy>).
334		470
335	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
336		472
337	Like C<ev_default_destroy>, but destroys an event loop created by an	473	Like C<ev_default_destroy>, but destroys an event loop created by an
338	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
362		498
363	Like C<ev_default_fork>, but acts on an event loop created by	499	Like C<ev_default_fork>, but acts on an event loop created by
364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
365	after fork, and how you do this is entirely your own problem.	501	after fork, and how you do this is entirely your own problem.
366		502
		503	=item unsigned int ev_loop_count (loop)
		504
		505	Returns the count of loop iterations for the loop, which is identical to
		506	the number of times libev did poll for new events. It starts at C<0> and
		507	happily wraps around with enough iterations.
		508
		509	This value can sometimes be useful as a generation counter of sorts (it
		510	"ticks" the number of loop iterations), as it roughly corresponds with
		511	C<ev_prepare> and C<ev_check> calls.
		512
367	=item unsigned int ev_backend (loop)	513	=item unsigned int ev_backend (loop)
368		514
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	515	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	516	use.
371		517
…		…
373		519
374	Returns the current "event loop time", which is the time the event loop	520	Returns the current "event loop time", which is the time the event loop
375	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
376	change as long as callbacks are being processed, and this is also the base	522	change as long as callbacks are being processed, and this is also the base
377	time used for relative timers. You can treat it as the timestamp of the	523	time used for relative timers. You can treat it as the timestamp of the
378	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
379		525
380	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
381		527
382	Finally, this is it, the event handler. This function usually is called	528	Finally, this is it, the event handler. This function usually is called
383	after you initialised all your watchers and you want to start handling	529	after you initialised all your watchers and you want to start handling
…		…
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
406		552
407	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
408		554
409	* If there are no active watchers (reference count is zero), return.	555	- Before the first iteration, call any pending watchers.
410	- Queue prepare watchers and then call all outstanding watchers.	556	* If EVFLAG_FORKCHECK was used, check for a fork.
		557	- If a fork was detected, queue and call all fork watchers.
		558	- Queue and call all prepare watchers.
411	- If we have been forked, recreate the kernel state.	559	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	560	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	561	- Update the "event loop time".
414	- Calculate for how long to block.	562	- Calculate for how long to sleep or block, if at all
		563	(active idle watchers, EVLOOP_NONBLOCK or not having
		564	any active watchers at all will result in not sleeping).
		565	- Sleep if the I/O and timer collect interval say so.
415	- Block the process, waiting for any events.	566	- Block the process, waiting for any events.
416	- Queue all outstanding I/O (fd) events.	567	- Queue all outstanding I/O (fd) events.
417	- Update the "event loop time" and do time jump handling.	568	- Update the "event loop time" and do time jump handling.
418	- Queue all outstanding timers.	569	- Queue all outstanding timers.
419	- Queue all outstanding periodics.	570	- Queue all outstanding periodics.
420	- If no events are pending now, queue all idle watchers.	571	- If no events are pending now, queue all idle watchers.
421	- Queue all check watchers.	572	- Queue all check watchers.
422	- Call all queued watchers in reverse order (i.e. check watchers first).	573	- Call all queued watchers in reverse order (i.e. check watchers first).
423	Signals and child watchers are implemented as I/O watchers, and will	574	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	575	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	576	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	577	were used, or there are no active watchers, return, otherwise
		578	continue with step *.
427		579
428	Example: queue some jobs and then loop until no events are outsanding	580	Example: Queue some jobs and then loop until no events are outstanding
429	anymore.	581	anymore.
430		582
431	... queue jobs here, make sure they register event watchers as long	583	... queue jobs here, make sure they register event watchers as long
432	... as they still have work to do (even an idle watcher will do..)	584	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	585	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	605	visible to the libev user and should not keep C<ev_loop> from exiting if
454	no event watchers registered by it are active. It is also an excellent	606	no event watchers registered by it are active. It is also an excellent
455	way to do this for generic recurring timers or from within third-party	607	way to do this for generic recurring timers or from within third-party
456	libraries. Just remember to I<unref after start> and I<ref before stop>.	608	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		609
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	610	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	611	running when nothing else is active.
460		612
461	struct dv_signal exitsig;	613	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	614	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	615	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	616	evf_unref (loop);
465		617
466	Example: for some weird reason, unregister the above signal handler again.	618	Example: For some weird reason, unregister the above signal handler again.
467		619
468	ev_ref (myloop);	620	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	621	ev_signal_stop (loop, &exitsig);
		622
		623	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		624
		625	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		626
		627	These advanced functions influence the time that libev will spend waiting
		628	for events. Both are by default C<0>, meaning that libev will try to
		629	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		630
		631	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		632	allows libev to delay invocation of I/O and timer/periodic callbacks to
		633	increase efficiency of loop iterations.
		634
		635	The background is that sometimes your program runs just fast enough to
		636	handle one (or very few) event(s) per loop iteration. While this makes
		637	the program responsive, it also wastes a lot of CPU time to poll for new
		638	events, especially with backends like C<select ()> which have a high
		639	overhead for the actual polling but can deliver many events at once.
		640
		641	By setting a higher I<io collect interval> you allow libev to spend more
		642	time collecting I/O events, so you can handle more events per iteration,
		643	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		644	C<ev_timer>) will be not affected. Setting this to a non-null value will
		645	introduce an additional C<ev_sleep ()> call into most loop iterations.
		646
		647	Likewise, by setting a higher I<timeout collect interval> you allow libev
		648	to spend more time collecting timeouts, at the expense of increased
		649	latency (the watcher callback will be called later). C<ev_io> watchers
		650	will not be affected. Setting this to a non-null value will not introduce
		651	any overhead in libev.
		652
		653	Many (busy) programs can usually benefit by setting the io collect
		654	interval to a value near C<0.1> or so, which is often enough for
		655	interactive servers (of course not for games), likewise for timeouts. It
		656	usually doesn't make much sense to set it to a lower value than C<0.01>,
		657	as this approsaches the timing granularity of most systems.
470		658
471	=back	659	=back
472		660
473		661
474	=head1 ANATOMY OF A WATCHER	662	=head1 ANATOMY OF A WATCHER
…		…
544	The signal specified in the C<ev_signal> watcher has been received by a thread.	732	The signal specified in the C<ev_signal> watcher has been received by a thread.
545		733
546	=item C<EV_CHILD>	734	=item C<EV_CHILD>
547		735
548	The pid specified in the C<ev_child> watcher has received a status change.	736	The pid specified in the C<ev_child> watcher has received a status change.
		737
		738	=item C<EV_STAT>
		739
		740	The path specified in the C<ev_stat> watcher changed its attributes somehow.
549		741
550	=item C<EV_IDLE>	742	=item C<EV_IDLE>
551		743
552	The C<ev_idle> watcher has determined that you have nothing better to do.	744	The C<ev_idle> watcher has determined that you have nothing better to do.
553		745
…		…
561	received events. Callbacks of both watcher types can start and stop as	753	received events. Callbacks of both watcher types can start and stop as
562	many watchers as they want, and all of them will be taken into account	754	many watchers as they want, and all of them will be taken into account
563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	755	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
564	C<ev_loop> from blocking).	756	C<ev_loop> from blocking).
565		757
		758	=item C<EV_EMBED>
		759
		760	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		761
		762	=item C<EV_FORK>
		763
		764	The event loop has been resumed in the child process after fork (see
		765	C<ev_fork>).
		766
566	=item C<EV_ERROR>	767	=item C<EV_ERROR>
567		768
568	An unspecified error has occured, the watcher has been stopped. This might	769	An unspecified error has occured, the watcher has been stopped. This might
569	happen because the watcher could not be properly started because libev	770	happen because the watcher could not be properly started because libev
570	ran out of memory, a file descriptor was found to be closed or any other	771	ran out of memory, a file descriptor was found to be closed or any other
…		…
641	=item bool ev_is_pending (ev_TYPE *watcher)	842	=item bool ev_is_pending (ev_TYPE *watcher)
642		843
643	Returns a true value iff the watcher is pending, (i.e. it has outstanding	844	Returns a true value iff the watcher is pending, (i.e. it has outstanding
644	events but its callback has not yet been invoked). As long as a watcher	845	events but its callback has not yet been invoked). As long as a watcher
645	is pending (but not active) you must not call an init function on it (but	846	is pending (but not active) you must not call an init function on it (but
646	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	847	C<ev_TYPE_set> is safe), you must not change its priority, and you must
647	libev (e.g. you cnanot C<free ()> it).	848	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		849	it).
648		850
649	=item callback = ev_cb (ev_TYPE *watcher)	851	=item callback ev_cb (ev_TYPE *watcher)
650		852
651	Returns the callback currently set on the watcher.	853	Returns the callback currently set on the watcher.
652		854
653	=item ev_cb_set (ev_TYPE *watcher, callback)	855	=item ev_cb_set (ev_TYPE *watcher, callback)
654		856
655	Change the callback. You can change the callback at virtually any time	857	Change the callback. You can change the callback at virtually any time
656	(modulo threads).	858	(modulo threads).
		859
		860	=item ev_set_priority (ev_TYPE *watcher, priority)
		861
		862	=item int ev_priority (ev_TYPE *watcher)
		863
		864	Set and query the priority of the watcher. The priority is a small
		865	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		866	(default: C<-2>). Pending watchers with higher priority will be invoked
		867	before watchers with lower priority, but priority will not keep watchers
		868	from being executed (except for C<ev_idle> watchers).
		869
		870	This means that priorities are I<only> used for ordering callback
		871	invocation after new events have been received. This is useful, for
		872	example, to reduce latency after idling, or more often, to bind two
		873	watchers on the same event and make sure one is called first.
		874
		875	If you need to suppress invocation when higher priority events are pending
		876	you need to look at C<ev_idle> watchers, which provide this functionality.
		877
		878	You I<must not> change the priority of a watcher as long as it is active or
		879	pending.
		880
		881	The default priority used by watchers when no priority has been set is
		882	always C<0>, which is supposed to not be too high and not be too low :).
		883
		884	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		885	fine, as long as you do not mind that the priority value you query might
		886	or might not have been adjusted to be within valid range.
		887
		888	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		889
		890	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		891	C<loop> nor C<revents> need to be valid as long as the watcher callback
		892	can deal with that fact.
		893
		894	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		895
		896	If the watcher is pending, this function returns clears its pending status
		897	and returns its C<revents> bitset (as if its callback was invoked). If the
		898	watcher isn't pending it does nothing and returns C<0>.
657		899
658	=back	900	=back
659		901
660		902
661	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	903	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
682	{	924	{
683	struct my_io *w = (struct my_io *)w_;	925	struct my_io *w = (struct my_io *)w_;
684	...	926	...
685	}	927	}
686		928
687	More interesting and less C-conformant ways of catsing your callback type	929	More interesting and less C-conformant ways of casting your callback type
688	have been omitted....	930	instead have been omitted.
		931
		932	Another common scenario is having some data structure with multiple
		933	watchers:
		934
		935	struct my_biggy
		936	{
		937	int some_data;
		938	ev_timer t1;
		939	ev_timer t2;
		940	}
		941
		942	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		943	you need to use C<offsetof>:
		944
		945	#include <stddef.h>
		946
		947	static void
		948	t1_cb (EV_P_ struct ev_timer *w, int revents)
		949	{
		950	struct my_biggy big = (struct my_biggy *
		951	(((char *)w) - offsetof (struct my_biggy, t1));
		952	}
		953
		954	static void
		955	t2_cb (EV_P_ struct ev_timer *w, int revents)
		956	{
		957	struct my_biggy big = (struct my_biggy *
		958	(((char *)w) - offsetof (struct my_biggy, t2));
		959	}
689		960
690		961
691	=head1 WATCHER TYPES	962	=head1 WATCHER TYPES
692		963
693	This section describes each watcher in detail, but will not repeat	964	This section describes each watcher in detail, but will not repeat
694	information given in the last section.	965	information given in the last section. Any initialisation/set macros,
		966	functions and members specific to the watcher type are explained.
		967
		968	Members are additionally marked with either I<[read-only]>, meaning that,
		969	while the watcher is active, you can look at the member and expect some
		970	sensible content, but you must not modify it (you can modify it while the
		971	watcher is stopped to your hearts content), or I<[read-write]>, which
		972	means you can expect it to have some sensible content while the watcher
		973	is active, but you can also modify it. Modifying it may not do something
		974	sensible or take immediate effect (or do anything at all), but libev will
		975	not crash or malfunction in any way.
695		976
696		977
697	=head2 C<ev_io> - is this file descriptor readable or writable?	978	=head2 C<ev_io> - is this file descriptor readable or writable?
698		979
699	I/O watchers check whether a file descriptor is readable or writable	980	I/O watchers check whether a file descriptor is readable or writable
…		…
706		987
707	In general you can register as many read and/or write event watchers per	988	In general you can register as many read and/or write event watchers per
708	fd as you want (as long as you don't confuse yourself). Setting all file	989	fd as you want (as long as you don't confuse yourself). Setting all file
709	descriptors to non-blocking mode is also usually a good idea (but not	990	descriptors to non-blocking mode is also usually a good idea (but not
710	required if you know what you are doing).	991	required if you know what you are doing).
711
712	You have to be careful with dup'ed file descriptors, though. Some backends
713	(the linux epoll backend is a notable example) cannot handle dup'ed file
714	descriptors correctly if you register interest in two or more fds pointing
715	to the same underlying file/socket/etc. description (that is, they share
716	the same underlying "file open").
717		992
718	If you must do this, then force the use of a known-to-be-good backend	993	If you must do this, then force the use of a known-to-be-good backend
719	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	994	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
720	C<EVBACKEND_POLL>).	995	C<EVBACKEND_POLL>).
721		996
…		…
728	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1003	it is best to always use non-blocking I/O: An extra C<read>(2) returning
729	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1004	C<EAGAIN> is far preferable to a program hanging until some data arrives.
730		1005
731	If you cannot run the fd in non-blocking mode (for example you should not	1006	If you cannot run the fd in non-blocking mode (for example you should not
732	play around with an Xlib connection), then you have to seperately re-test	1007	play around with an Xlib connection), then you have to seperately re-test
733	wether a file descriptor is really ready with a known-to-be good interface	1008	whether a file descriptor is really ready with a known-to-be good interface
734	such as poll (fortunately in our Xlib example, Xlib already does this on	1009	such as poll (fortunately in our Xlib example, Xlib already does this on
735	its own, so its quite safe to use).	1010	its own, so its quite safe to use).
		1011
		1012	=head3 The special problem of disappearing file descriptors
		1013
		1014	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1015	descriptor (either by calling C<close> explicitly or by any other means,
		1016	such as C<dup>). The reason is that you register interest in some file
		1017	descriptor, but when it goes away, the operating system will silently drop
		1018	this interest. If another file descriptor with the same number then is
		1019	registered with libev, there is no efficient way to see that this is, in
		1020	fact, a different file descriptor.
		1021
		1022	To avoid having to explicitly tell libev about such cases, libev follows
		1023	the following policy: Each time C<ev_io_set> is being called, libev
		1024	will assume that this is potentially a new file descriptor, otherwise
		1025	it is assumed that the file descriptor stays the same. That means that
		1026	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1027	descriptor even if the file descriptor number itself did not change.
		1028
		1029	This is how one would do it normally anyway, the important point is that
		1030	the libev application should not optimise around libev but should leave
		1031	optimisations to libev.
		1032
		1033	=head3 The special problem of dup'ed file descriptors
		1034
		1035	Some backends (e.g. epoll), cannot register events for file descriptors,
		1036	but only events for the underlying file descriptions. That means when you
		1037	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1038	events for them, only one file descriptor might actually receive events.
		1039
		1040	There is no workaround possible except not registering events
		1041	for potentially C<dup ()>'ed file descriptors, or to resort to
		1042	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1043
		1044	=head3 The special problem of fork
		1045
		1046	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1047	useless behaviour. Libev fully supports fork, but needs to be told about
		1048	it in the child.
		1049
		1050	To support fork in your programs, you either have to call
		1051	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1052	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1053	C<EVBACKEND_POLL>.
		1054
		1055
		1056	=head3 Watcher-Specific Functions
736		1057
737	=over 4	1058	=over 4
738		1059
739	=item ev_io_init (ev_io *, callback, int fd, int events)	1060	=item ev_io_init (ev_io *, callback, int fd, int events)
740		1061
…		…
742		1063
743	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1064	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
744	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1065	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
745	C<EV_READ | EV_WRITE> to receive the given events.	1066	C<EV_READ | EV_WRITE> to receive the given events.
746		1067
		1068	=item int fd [read-only]
		1069
		1070	The file descriptor being watched.
		1071
		1072	=item int events [read-only]
		1073
		1074	The events being watched.
		1075
747	=back	1076	=back
748		1077
		1078	=head3 Examples
		1079
749	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1080	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
750	readable, but only once. Since it is likely line-buffered, you could	1081	readable, but only once. Since it is likely line-buffered, you could
751	attempt to read a whole line in the callback:	1082	attempt to read a whole line in the callback.
752		1083
753	static void	1084	static void
754	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1085	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
755	{	1086	{
756	ev_io_stop (loop, w);	1087	ev_io_stop (loop, w);
…		…
786		1117
787	The callback is guarenteed to be invoked only when its timeout has passed,	1118	The callback is guarenteed to be invoked only when its timeout has passed,
788	but if multiple timers become ready during the same loop iteration then	1119	but if multiple timers become ready during the same loop iteration then
789	order of execution is undefined.	1120	order of execution is undefined.
790		1121
		1122	=head3 Watcher-Specific Functions and Data Members
		1123
791	=over 4	1124	=over 4
792		1125
793	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1126	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
794		1127
795	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1128	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
808	=item ev_timer_again (loop)	1141	=item ev_timer_again (loop)
809		1142
810	This will act as if the timer timed out and restart it again if it is	1143	This will act as if the timer timed out and restart it again if it is
811	repeating. The exact semantics are:	1144	repeating. The exact semantics are:
812		1145
		1146	If the timer is pending, its pending status is cleared.
		1147
813	If the timer is started but nonrepeating, stop it.	1148	If the timer is started but nonrepeating, stop it (as if it timed out).
814		1149
815	If the timer is repeating, either start it if necessary (with the repeat	1150	If the timer is repeating, either start it if necessary (with the
816	value), or reset the running timer to the repeat value.	1151	C<repeat> value), or reset the running timer to the C<repeat> value.
817		1152
818	This sounds a bit complicated, but here is a useful and typical	1153	This sounds a bit complicated, but here is a useful and typical
819	example: Imagine you have a tcp connection and you want a so-called idle	1154	example: Imagine you have a tcp connection and you want a so-called idle
820	timeout, that is, you want to be called when there have been, say, 60	1155	timeout, that is, you want to be called when there have been, say, 60
821	seconds of inactivity on the socket. The easiest way to do this is to	1156	seconds of inactivity on the socket. The easiest way to do this is to
822	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1157	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
823	time you successfully read or write some data. If you go into an idle	1158	C<ev_timer_again> each time you successfully read or write some data. If
824	state where you do not expect data to travel on the socket, you can stop	1159	you go into an idle state where you do not expect data to travel on the
825	the timer, and again will automatically restart it if need be.	1160	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1161	automatically restart it if need be.
		1162
		1163	That means you can ignore the C<after> value and C<ev_timer_start>
		1164	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1165
		1166	ev_timer_init (timer, callback, 0., 5.);
		1167	ev_timer_again (loop, timer);
		1168	...
		1169	timer->again = 17.;
		1170	ev_timer_again (loop, timer);
		1171	...
		1172	timer->again = 10.;
		1173	ev_timer_again (loop, timer);
		1174
		1175	This is more slightly efficient then stopping/starting the timer each time
		1176	you want to modify its timeout value.
		1177
		1178	=item ev_tstamp repeat [read-write]
		1179
		1180	The current C<repeat> value. Will be used each time the watcher times out
		1181	or C<ev_timer_again> is called and determines the next timeout (if any),
		1182	which is also when any modifications are taken into account.
826		1183
827	=back	1184	=back
828		1185
		1186	=head3 Examples
		1187
829	Example: create a timer that fires after 60 seconds.	1188	Example: Create a timer that fires after 60 seconds.
830		1189
831	static void	1190	static void
832	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1191	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
833	{	1192	{
834	.. one minute over, w is actually stopped right here	1193	.. one minute over, w is actually stopped right here
…		…
836		1195
837	struct ev_timer mytimer;	1196	struct ev_timer mytimer;
838	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1197	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
839	ev_timer_start (loop, &mytimer);	1198	ev_timer_start (loop, &mytimer);
840		1199
841	Example: create a timeout timer that times out after 10 seconds of	1200	Example: Create a timeout timer that times out after 10 seconds of
842	inactivity.	1201	inactivity.
843		1202
844	static void	1203	static void
845	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1204	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
846	{	1205	{
…		…
866	but on wallclock time (absolute time). You can tell a periodic watcher	1225	but on wallclock time (absolute time). You can tell a periodic watcher
867	to trigger "at" some specific point in time. For example, if you tell a	1226	to trigger "at" some specific point in time. For example, if you tell a
868	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1227	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
869	+ 10.>) and then reset your system clock to the last year, then it will	1228	+ 10.>) and then reset your system clock to the last year, then it will
870	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1229	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
871	roughly 10 seconds later and of course not if you reset your system time	1230	roughly 10 seconds later).
872	again).
873		1231
874	They can also be used to implement vastly more complex timers, such as	1232	They can also be used to implement vastly more complex timers, such as
875	triggering an event on eahc midnight, local time.	1233	triggering an event on each midnight, local time or other, complicated,
		1234	rules.
876		1235
877	As with timers, the callback is guarenteed to be invoked only when the	1236	As with timers, the callback is guarenteed to be invoked only when the
878	time (C<at>) has been passed, but if multiple periodic timers become ready	1237	time (C<at>) has been passed, but if multiple periodic timers become ready
879	during the same loop iteration then order of execution is undefined.	1238	during the same loop iteration then order of execution is undefined.
880		1239
		1240	=head3 Watcher-Specific Functions and Data Members
		1241
881	=over 4	1242	=over 4
882		1243
883	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1244	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
884		1245
885	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1246	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
887	Lots of arguments, lets sort it out... There are basically three modes of	1248	Lots of arguments, lets sort it out... There are basically three modes of
888	operation, and we will explain them from simplest to complex:	1249	operation, and we will explain them from simplest to complex:
889		1250
890	=over 4	1251	=over 4
891		1252
892	=item * absolute timer (interval = reschedule_cb = 0)	1253	=item * absolute timer (at = time, interval = reschedule_cb = 0)
893		1254
894	In this configuration the watcher triggers an event at the wallclock time	1255	In this configuration the watcher triggers an event at the wallclock time
895	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1256	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
896	that is, if it is to be run at January 1st 2011 then it will run when the	1257	that is, if it is to be run at January 1st 2011 then it will run when the
897	system time reaches or surpasses this time.	1258	system time reaches or surpasses this time.
898		1259
899	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1260	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
900		1261
901	In this mode the watcher will always be scheduled to time out at the next	1262	In this mode the watcher will always be scheduled to time out at the next
902	C<at + N * interval> time (for some integer N) and then repeat, regardless	1263	C<at + N * interval> time (for some integer N, which can also be negative)
903	of any time jumps.	1264	and then repeat, regardless of any time jumps.
904		1265
905	This can be used to create timers that do not drift with respect to system	1266	This can be used to create timers that do not drift with respect to system
906	time:	1267	time:
907		1268
908	ev_periodic_set (&periodic, 0., 3600., 0);	1269	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
914		1275
915	Another way to think about it (for the mathematically inclined) is that	1276	Another way to think about it (for the mathematically inclined) is that
916	C<ev_periodic> will try to run the callback in this mode at the next possible	1277	C<ev_periodic> will try to run the callback in this mode at the next possible
917	time where C<time = at (mod interval)>, regardless of any time jumps.	1278	time where C<time = at (mod interval)>, regardless of any time jumps.
918		1279
		1280	For numerical stability it is preferable that the C<at> value is near
		1281	C<ev_now ()> (the current time), but there is no range requirement for
		1282	this value.
		1283
919	=item * manual reschedule mode (reschedule_cb = callback)	1284	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
920		1285
921	In this mode the values for C<interval> and C<at> are both being	1286	In this mode the values for C<interval> and C<at> are both being
922	ignored. Instead, each time the periodic watcher gets scheduled, the	1287	ignored. Instead, each time the periodic watcher gets scheduled, the
923	reschedule callback will be called with the watcher as first, and the	1288	reschedule callback will be called with the watcher as first, and the
924	current time as second argument.	1289	current time as second argument.
925		1290
926	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1291	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
927	ever, or make any event loop modifications>. If you need to stop it,	1292	ever, or make any event loop modifications>. If you need to stop it,
928	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1293	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
929	starting a prepare watcher).	1294	starting an C<ev_prepare> watcher, which is legal).
930		1295
931	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1296	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
932	ev_tstamp now)>, e.g.:	1297	ev_tstamp now)>, e.g.:
933		1298
934	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1299	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
957	Simply stops and restarts the periodic watcher again. This is only useful	1322	Simply stops and restarts the periodic watcher again. This is only useful
958	when you changed some parameters or the reschedule callback would return	1323	when you changed some parameters or the reschedule callback would return
959	a different time than the last time it was called (e.g. in a crond like	1324	a different time than the last time it was called (e.g. in a crond like
960	program when the crontabs have changed).	1325	program when the crontabs have changed).
961		1326
		1327	=item ev_tstamp offset [read-write]
		1328
		1329	When repeating, this contains the offset value, otherwise this is the
		1330	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1331
		1332	Can be modified any time, but changes only take effect when the periodic
		1333	timer fires or C<ev_periodic_again> is being called.
		1334
		1335	=item ev_tstamp interval [read-write]
		1336
		1337	The current interval value. Can be modified any time, but changes only
		1338	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1339	called.
		1340
		1341	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1342
		1343	The current reschedule callback, or C<0>, if this functionality is
		1344	switched off. Can be changed any time, but changes only take effect when
		1345	the periodic timer fires or C<ev_periodic_again> is being called.
		1346
		1347	=item ev_tstamp at [read-only]
		1348
		1349	When active, contains the absolute time that the watcher is supposed to
		1350	trigger next.
		1351
962	=back	1352	=back
963		1353
		1354	=head3 Examples
		1355
964	Example: call a callback every hour, or, more precisely, whenever the	1356	Example: Call a callback every hour, or, more precisely, whenever the
965	system clock is divisible by 3600. The callback invocation times have	1357	system clock is divisible by 3600. The callback invocation times have
966	potentially a lot of jittering, but good long-term stability.	1358	potentially a lot of jittering, but good long-term stability.
967		1359
968	static void	1360	static void
969	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1361	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
973		1365
974	struct ev_periodic hourly_tick;	1366	struct ev_periodic hourly_tick;
975	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1367	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
976	ev_periodic_start (loop, &hourly_tick);	1368	ev_periodic_start (loop, &hourly_tick);
977		1369
978	Example: the same as above, but use a reschedule callback to do it:	1370	Example: The same as above, but use a reschedule callback to do it:
979		1371
980	#include <math.h>	1372	#include <math.h>
981		1373
982	static ev_tstamp	1374	static ev_tstamp
983	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1375	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
985	return fmod (now, 3600.) + 3600.;	1377	return fmod (now, 3600.) + 3600.;
986	}	1378	}
987		1379
988	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1380	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
989		1381
990	Example: call a callback every hour, starting now:	1382	Example: Call a callback every hour, starting now:
991		1383
992	struct ev_periodic hourly_tick;	1384	struct ev_periodic hourly_tick;
993	ev_periodic_init (&hourly_tick, clock_cb,	1385	ev_periodic_init (&hourly_tick, clock_cb,
994	fmod (ev_now (loop), 3600.), 3600., 0);	1386	fmod (ev_now (loop), 3600.), 3600., 0);
995	ev_periodic_start (loop, &hourly_tick);	1387	ev_periodic_start (loop, &hourly_tick);
…		…
1007	with the kernel (thus it coexists with your own signal handlers as long	1399	with the kernel (thus it coexists with your own signal handlers as long
1008	as you don't register any with libev). Similarly, when the last signal	1400	as you don't register any with libev). Similarly, when the last signal
1009	watcher for a signal is stopped libev will reset the signal handler to	1401	watcher for a signal is stopped libev will reset the signal handler to
1010	SIG_DFL (regardless of what it was set to before).	1402	SIG_DFL (regardless of what it was set to before).
1011		1403
		1404	=head3 Watcher-Specific Functions and Data Members
		1405
1012	=over 4	1406	=over 4
1013		1407
1014	=item ev_signal_init (ev_signal *, callback, int signum)	1408	=item ev_signal_init (ev_signal *, callback, int signum)
1015		1409
1016	=item ev_signal_set (ev_signal *, int signum)	1410	=item ev_signal_set (ev_signal *, int signum)
1017		1411
1018	Configures the watcher to trigger on the given signal number (usually one	1412	Configures the watcher to trigger on the given signal number (usually one
1019	of the C<SIGxxx> constants).	1413	of the C<SIGxxx> constants).
1020		1414
		1415	=item int signum [read-only]
		1416
		1417	The signal the watcher watches out for.
		1418
1021	=back	1419	=back
1022		1420
1023		1421
1024	=head2 C<ev_child> - watch out for process status changes	1422	=head2 C<ev_child> - watch out for process status changes
1025		1423
1026	Child watchers trigger when your process receives a SIGCHLD in response to	1424	Child watchers trigger when your process receives a SIGCHLD in response to
1027	some child status changes (most typically when a child of yours dies).	1425	some child status changes (most typically when a child of yours dies).
		1426
		1427	=head3 Watcher-Specific Functions and Data Members
1028		1428
1029	=over 4	1429	=over 4
1030		1430
1031	=item ev_child_init (ev_child *, callback, int pid)	1431	=item ev_child_init (ev_child *, callback, int pid)
1032		1432
…		…
1037	at the C<rstatus> member of the C<ev_child> watcher structure to see	1437	at the C<rstatus> member of the C<ev_child> watcher structure to see
1038	the status word (use the macros from C<sys/wait.h> and see your systems	1438	the status word (use the macros from C<sys/wait.h> and see your systems
1039	C<waitpid> documentation). The C<rpid> member contains the pid of the	1439	C<waitpid> documentation). The C<rpid> member contains the pid of the
1040	process causing the status change.	1440	process causing the status change.
1041		1441
		1442	=item int pid [read-only]
		1443
		1444	The process id this watcher watches out for, or C<0>, meaning any process id.
		1445
		1446	=item int rpid [read-write]
		1447
		1448	The process id that detected a status change.
		1449
		1450	=item int rstatus [read-write]
		1451
		1452	The process exit/trace status caused by C<rpid> (see your systems
		1453	C<waitpid> and C<sys/wait.h> documentation for details).
		1454
1042	=back	1455	=back
1043		1456
		1457	=head3 Examples
		1458
1044	Example: try to exit cleanly on SIGINT and SIGTERM.	1459	Example: Try to exit cleanly on SIGINT and SIGTERM.
1045		1460
1046	static void	1461	static void
1047	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1462	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1048	{	1463	{
1049	ev_unloop (loop, EVUNLOOP_ALL);	1464	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1052	struct ev_signal signal_watcher;	1467	struct ev_signal signal_watcher;
1053	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1468	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1054	ev_signal_start (loop, &sigint_cb);	1469	ev_signal_start (loop, &sigint_cb);
1055		1470
1056		1471
		1472	=head2 C<ev_stat> - did the file attributes just change?
		1473
		1474	This watches a filesystem path for attribute changes. That is, it calls
		1475	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1476	compared to the last time, invoking the callback if it did.
		1477
		1478	The path does not need to exist: changing from "path exists" to "path does
		1479	not exist" is a status change like any other. The condition "path does
		1480	not exist" is signified by the C<st_nlink> field being zero (which is
		1481	otherwise always forced to be at least one) and all the other fields of
		1482	the stat buffer having unspecified contents.
		1483
		1484	The path I<should> be absolute and I<must not> end in a slash. If it is
		1485	relative and your working directory changes, the behaviour is undefined.
		1486
		1487	Since there is no standard to do this, the portable implementation simply
		1488	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1489	can specify a recommended polling interval for this case. If you specify
		1490	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1491	unspecified default> value will be used (which you can expect to be around
		1492	five seconds, although this might change dynamically). Libev will also
		1493	impose a minimum interval which is currently around C<0.1>, but thats
		1494	usually overkill.
		1495
		1496	This watcher type is not meant for massive numbers of stat watchers,
		1497	as even with OS-supported change notifications, this can be
		1498	resource-intensive.
		1499
		1500	At the time of this writing, only the Linux inotify interface is
		1501	implemented (implementing kqueue support is left as an exercise for the
		1502	reader). Inotify will be used to give hints only and should not change the
		1503	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1504	to fall back to regular polling again even with inotify, but changes are
		1505	usually detected immediately, and if the file exists there will be no
		1506	polling.
		1507
		1508	=head3 Inotify
		1509
		1510	When C<inotify (7)> support has been compiled into libev (generally only
		1511	available on Linux) and present at runtime, it will be used to speed up
		1512	change detection where possible. The inotify descriptor will be created lazily
		1513	when the first C<ev_stat> watcher is being started.
		1514
		1515	Inotify presense does not change the semantics of C<ev_stat> watchers
		1516	except that changes might be detected earlier, and in some cases, to avoid
		1517	making regular C<stat> calls. Even in the presense of inotify support
		1518	there are many cases where libev has to resort to regular C<stat> polling.
		1519
		1520	(There is no support for kqueue, as apparently it cannot be used to
		1521	implement this functionality, due to the requirement of having a file
		1522	descriptor open on the object at all times).
		1523
		1524	=head3 The special problem of stat time resolution
		1525
		1526	The C<stat ()> syscall only supports full-second resolution portably, and
		1527	even on systems where the resolution is higher, many filesystems still
		1528	only support whole seconds.
		1529
		1530	That means that, if the time is the only thing that changes, you might
		1531	miss updates: on the first update, C<ev_stat> detects a change and calls
		1532	your callback, which does something. When there is another update within
		1533	the same second, C<ev_stat> will be unable to detect it.
		1534
		1535	The solution to this is to delay acting on a change for a second (or till
		1536	the next second boundary), using a roughly one-second delay C<ev_timer>
		1537	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1538	is added to work around small timing inconsistencies of some operating
		1539	systems.
		1540
		1541	=head3 Watcher-Specific Functions and Data Members
		1542
		1543	=over 4
		1544
		1545	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1546
		1547	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1548
		1549	Configures the watcher to wait for status changes of the given
		1550	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1551	be detected and should normally be specified as C<0> to let libev choose
		1552	a suitable value. The memory pointed to by C<path> must point to the same
		1553	path for as long as the watcher is active.
		1554
		1555	The callback will be receive C<EV_STAT> when a change was detected,
		1556	relative to the attributes at the time the watcher was started (or the
		1557	last change was detected).
		1558
		1559	=item ev_stat_stat (ev_stat *)
		1560
		1561	Updates the stat buffer immediately with new values. If you change the
		1562	watched path in your callback, you could call this fucntion to avoid
		1563	detecting this change (while introducing a race condition). Can also be
		1564	useful simply to find out the new values.
		1565
		1566	=item ev_statdata attr [read-only]
		1567
		1568	The most-recently detected attributes of the file. Although the type is of
		1569	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1570	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1571	was some error while C<stat>ing the file.
		1572
		1573	=item ev_statdata prev [read-only]
		1574
		1575	The previous attributes of the file. The callback gets invoked whenever
		1576	C<prev> != C<attr>.
		1577
		1578	=item ev_tstamp interval [read-only]
		1579
		1580	The specified interval.
		1581
		1582	=item const char *path [read-only]
		1583
		1584	The filesystem path that is being watched.
		1585
		1586	=back
		1587
		1588	=head3 Examples
		1589
		1590	Example: Watch C</etc/passwd> for attribute changes.
		1591
		1592	static void
		1593	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1594	{
		1595	/* /etc/passwd changed in some way */
		1596	if (w->attr.st_nlink)
		1597	{
		1598	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1599	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1600	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1601	}
		1602	else
		1603	/* you shalt not abuse printf for puts */
		1604	puts ("wow, /etc/passwd is not there, expect problems. "
		1605	"if this is windows, they already arrived\n");
		1606	}
		1607
		1608	...
		1609	ev_stat passwd;
		1610
		1611	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1612	ev_stat_start (loop, &passwd);
		1613
		1614	Example: Like above, but additionally use a one-second delay so we do not
		1615	miss updates (however, frequent updates will delay processing, too, so
		1616	one might do the work both on C<ev_stat> callback invocation I<and> on
		1617	C<ev_timer> callback invocation).
		1618
		1619	static ev_stat passwd;
		1620	static ev_timer timer;
		1621
		1622	static void
		1623	timer_cb (EV_P_ ev_timer *w, int revents)
		1624	{
		1625	ev_timer_stop (EV_A_ w);
		1626
		1627	/* now it's one second after the most recent passwd change */
		1628	}
		1629
		1630	static void
		1631	stat_cb (EV_P_ ev_stat *w, int revents)
		1632	{
		1633	/* reset the one-second timer */
		1634	ev_timer_again (EV_A_ &timer);
		1635	}
		1636
		1637	...
		1638	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1639	ev_stat_start (loop, &passwd);
		1640	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1641
		1642
1057	=head2 C<ev_idle> - when you've got nothing better to do...	1643	=head2 C<ev_idle> - when you've got nothing better to do...
1058		1644
1059	Idle watchers trigger events when there are no other events are pending	1645	Idle watchers trigger events when no other events of the same or higher
1060	(prepare, check and other idle watchers do not count). That is, as long	1646	priority are pending (prepare, check and other idle watchers do not
1061	as your process is busy handling sockets or timeouts (or even signals,	1647	count).
1062	imagine) it will not be triggered. But when your process is idle all idle	1648
1063	watchers are being called again and again, once per event loop iteration -	1649	That is, as long as your process is busy handling sockets or timeouts
		1650	(or even signals, imagine) of the same or higher priority it will not be
		1651	triggered. But when your process is idle (or only lower-priority watchers
		1652	are pending), the idle watchers are being called once per event loop
1064	until stopped, that is, or your process receives more events and becomes	1653	iteration - until stopped, that is, or your process receives more events
1065	busy.	1654	and becomes busy again with higher priority stuff.
1066		1655
1067	The most noteworthy effect is that as long as any idle watchers are	1656	The most noteworthy effect is that as long as any idle watchers are
1068	active, the process will not block when waiting for new events.	1657	active, the process will not block when waiting for new events.
1069		1658
1070	Apart from keeping your process non-blocking (which is a useful	1659	Apart from keeping your process non-blocking (which is a useful
1071	effect on its own sometimes), idle watchers are a good place to do	1660	effect on its own sometimes), idle watchers are a good place to do
1072	"pseudo-background processing", or delay processing stuff to after the	1661	"pseudo-background processing", or delay processing stuff to after the
1073	event loop has handled all outstanding events.	1662	event loop has handled all outstanding events.
1074		1663
		1664	=head3 Watcher-Specific Functions and Data Members
		1665
1075	=over 4	1666	=over 4
1076		1667
1077	=item ev_idle_init (ev_signal *, callback)	1668	=item ev_idle_init (ev_signal *, callback)
1078		1669
1079	Initialises and configures the idle watcher - it has no parameters of any	1670	Initialises and configures the idle watcher - it has no parameters of any
1080	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1671	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1081	believe me.	1672	believe me.
1082		1673
1083	=back	1674	=back
1084		1675
		1676	=head3 Examples
		1677
1085	Example: dynamically allocate an C<ev_idle>, start it, and in the	1678	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1086	callback, free it. Alos, use no error checking, as usual.	1679	callback, free it. Also, use no error checking, as usual.
1087		1680
1088	static void	1681	static void
1089	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1682	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1090	{	1683	{
1091	free (w);	1684	free (w);
…		…
1102		1695
1103	Prepare and check watchers are usually (but not always) used in tandem:	1696	Prepare and check watchers are usually (but not always) used in tandem:
1104	prepare watchers get invoked before the process blocks and check watchers	1697	prepare watchers get invoked before the process blocks and check watchers
1105	afterwards.	1698	afterwards.
1106		1699
		1700	You I<must not> call C<ev_loop> or similar functions that enter
		1701	the current event loop from either C<ev_prepare> or C<ev_check>
		1702	watchers. Other loops than the current one are fine, however. The
		1703	rationale behind this is that you do not need to check for recursion in
		1704	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1705	C<ev_check> so if you have one watcher of each kind they will always be
		1706	called in pairs bracketing the blocking call.
		1707
1107	Their main purpose is to integrate other event mechanisms into libev and	1708	Their main purpose is to integrate other event mechanisms into libev and
1108	their use is somewhat advanced. This could be used, for example, to track	1709	their use is somewhat advanced. This could be used, for example, to track
1109	variable changes, implement your own watchers, integrate net-snmp or a	1710	variable changes, implement your own watchers, integrate net-snmp or a
1110	coroutine library and lots more.	1711	coroutine library and lots more. They are also occasionally useful if
		1712	you cache some data and want to flush it before blocking (for example,
		1713	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1714	watcher).
1111		1715
1112	This is done by examining in each prepare call which file descriptors need	1716	This is done by examining in each prepare call which file descriptors need
1113	to be watched by the other library, registering C<ev_io> watchers for	1717	to be watched by the other library, registering C<ev_io> watchers for
1114	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1718	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1115	provide just this functionality). Then, in the check watcher you check for	1719	provide just this functionality). Then, in the check watcher you check for
…		…
1125	with priority higher than or equal to the event loop and one coroutine	1729	with priority higher than or equal to the event loop and one coroutine
1126	of lower priority, but only once, using idle watchers to keep the event	1730	of lower priority, but only once, using idle watchers to keep the event
1127	loop from blocking if lower-priority coroutines are active, thus mapping	1731	loop from blocking if lower-priority coroutines are active, thus mapping
1128	low-priority coroutines to idle/background tasks).	1732	low-priority coroutines to idle/background tasks).
1129		1733
		1734	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1735	priority, to ensure that they are being run before any other watchers
		1736	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1737	too) should not activate ("feed") events into libev. While libev fully
		1738	supports this, they will be called before other C<ev_check> watchers
		1739	did their job. As C<ev_check> watchers are often used to embed other
		1740	(non-libev) event loops those other event loops might be in an unusable
		1741	state until their C<ev_check> watcher ran (always remind yourself to
		1742	coexist peacefully with others).
		1743
		1744	=head3 Watcher-Specific Functions and Data Members
		1745
1130	=over 4	1746	=over 4
1131		1747
1132	=item ev_prepare_init (ev_prepare *, callback)	1748	=item ev_prepare_init (ev_prepare *, callback)
1133		1749
1134	=item ev_check_init (ev_check *, callback)	1750	=item ev_check_init (ev_check *, callback)
…		…
1137	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1753	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1138	macros, but using them is utterly, utterly and completely pointless.	1754	macros, but using them is utterly, utterly and completely pointless.
1139		1755
1140	=back	1756	=back
1141		1757
1142	Example: *TODO*.	1758	=head3 Examples
		1759
		1760	There are a number of principal ways to embed other event loops or modules
		1761	into libev. Here are some ideas on how to include libadns into libev
		1762	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1763	use for an actually working example. Another Perl module named C<EV::Glib>
		1764	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1765	into the Glib event loop).
		1766
		1767	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1768	and in a check watcher, destroy them and call into libadns. What follows
		1769	is pseudo-code only of course. This requires you to either use a low
		1770	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1771	the callbacks for the IO/timeout watchers might not have been called yet.
		1772
		1773	static ev_io iow [nfd];
		1774	static ev_timer tw;
		1775
		1776	static void
		1777	io_cb (ev_loop *loop, ev_io *w, int revents)
		1778	{
		1779	}
		1780
		1781	// create io watchers for each fd and a timer before blocking
		1782	static void
		1783	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1784	{
		1785	int timeout = 3600000;
		1786	struct pollfd fds [nfd];
		1787	// actual code will need to loop here and realloc etc.
		1788	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1789
		1790	/* the callback is illegal, but won't be called as we stop during check */
		1791	ev_timer_init (&tw, 0, timeout * 1e-3);
		1792	ev_timer_start (loop, &tw);
		1793
		1794	// create one ev_io per pollfd
		1795	for (int i = 0; i < nfd; ++i)
		1796	{
		1797	ev_io_init (iow + i, io_cb, fds [i].fd,
		1798	((fds [i].events & POLLIN ? EV_READ : 0)
		1799	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1800
		1801	fds [i].revents = 0;
		1802	ev_io_start (loop, iow + i);
		1803	}
		1804	}
		1805
		1806	// stop all watchers after blocking
		1807	static void
		1808	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1809	{
		1810	ev_timer_stop (loop, &tw);
		1811
		1812	for (int i = 0; i < nfd; ++i)
		1813	{
		1814	// set the relevant poll flags
		1815	// could also call adns_processreadable etc. here
		1816	struct pollfd *fd = fds + i;
		1817	int revents = ev_clear_pending (iow + i);
		1818	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1819	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1820
		1821	// now stop the watcher
		1822	ev_io_stop (loop, iow + i);
		1823	}
		1824
		1825	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1826	}
		1827
		1828	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1829	in the prepare watcher and would dispose of the check watcher.
		1830
		1831	Method 3: If the module to be embedded supports explicit event
		1832	notification (adns does), you can also make use of the actual watcher
		1833	callbacks, and only destroy/create the watchers in the prepare watcher.
		1834
		1835	static void
		1836	timer_cb (EV_P_ ev_timer *w, int revents)
		1837	{
		1838	adns_state ads = (adns_state)w->data;
		1839	update_now (EV_A);
		1840
		1841	adns_processtimeouts (ads, &tv_now);
		1842	}
		1843
		1844	static void
		1845	io_cb (EV_P_ ev_io *w, int revents)
		1846	{
		1847	adns_state ads = (adns_state)w->data;
		1848	update_now (EV_A);
		1849
		1850	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1851	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1852	}
		1853
		1854	// do not ever call adns_afterpoll
		1855
		1856	Method 4: Do not use a prepare or check watcher because the module you
		1857	want to embed is too inflexible to support it. Instead, youc na override
		1858	their poll function. The drawback with this solution is that the main
		1859	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1860	this.
		1861
		1862	static gint
		1863	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1864	{
		1865	int got_events = 0;
		1866
		1867	for (n = 0; n < nfds; ++n)
		1868	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1869
		1870	if (timeout >= 0)
		1871	// create/start timer
		1872
		1873	// poll
		1874	ev_loop (EV_A_ 0);
		1875
		1876	// stop timer again
		1877	if (timeout >= 0)
		1878	ev_timer_stop (EV_A_ &to);
		1879
		1880	// stop io watchers again - their callbacks should have set
		1881	for (n = 0; n < nfds; ++n)
		1882	ev_io_stop (EV_A_ iow [n]);
		1883
		1884	return got_events;
		1885	}
1143		1886
1144		1887
1145	=head2 C<ev_embed> - when one backend isn't enough...	1888	=head2 C<ev_embed> - when one backend isn't enough...
1146		1889
1147	This is a rather advanced watcher type that lets you embed one event loop	1890	This is a rather advanced watcher type that lets you embed one event loop
…		…
1189	portable one.	1932	portable one.
1190		1933
1191	So when you want to use this feature you will always have to be prepared	1934	So when you want to use this feature you will always have to be prepared
1192	that you cannot get an embeddable loop. The recommended way to get around	1935	that you cannot get an embeddable loop. The recommended way to get around
1193	this is to have a separate variables for your embeddable loop, try to	1936	this is to have a separate variables for your embeddable loop, try to
1194	create it, and if that fails, use the normal loop for everything:	1937	create it, and if that fails, use the normal loop for everything.
		1938
		1939	=head3 Watcher-Specific Functions and Data Members
		1940
		1941	=over 4
		1942
		1943	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1944
		1945	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1946
		1947	Configures the watcher to embed the given loop, which must be
		1948	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1949	invoked automatically, otherwise it is the responsibility of the callback
		1950	to invoke it (it will continue to be called until the sweep has been done,
		1951	if you do not want thta, you need to temporarily stop the embed watcher).
		1952
		1953	=item ev_embed_sweep (loop, ev_embed *)
		1954
		1955	Make a single, non-blocking sweep over the embedded loop. This works
		1956	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1957	apropriate way for embedded loops.
		1958
		1959	=item struct ev_loop *other [read-only]
		1960
		1961	The embedded event loop.
		1962
		1963	=back
		1964
		1965	=head3 Examples
		1966
		1967	Example: Try to get an embeddable event loop and embed it into the default
		1968	event loop. If that is not possible, use the default loop. The default
		1969	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1970	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1971	used).
1195		1972
1196	struct ev_loop *loop_hi = ev_default_init (0);	1973	struct ev_loop *loop_hi = ev_default_init (0);
1197	struct ev_loop *loop_lo = 0;	1974	struct ev_loop *loop_lo = 0;
1198	struct ev_embed embed;	1975	struct ev_embed embed;
1199		1976
…		…
1210	ev_embed_start (loop_hi, &embed);	1987	ev_embed_start (loop_hi, &embed);
1211	}	1988	}
1212	else	1989	else
1213	loop_lo = loop_hi;	1990	loop_lo = loop_hi;
1214		1991
		1992	Example: Check if kqueue is available but not recommended and create
		1993	a kqueue backend for use with sockets (which usually work with any
		1994	kqueue implementation). Store the kqueue/socket-only event loop in
		1995	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		1996
		1997	struct ev_loop *loop = ev_default_init (0);
		1998	struct ev_loop *loop_socket = 0;
		1999	struct ev_embed embed;
		2000
		2001	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2002	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2003	{
		2004	ev_embed_init (&embed, 0, loop_socket);
		2005	ev_embed_start (loop, &embed);
		2006	}
		2007
		2008	if (!loop_socket)
		2009	loop_socket = loop;
		2010
		2011	// now use loop_socket for all sockets, and loop for everything else
		2012
		2013
		2014	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2015
		2016	Fork watchers are called when a C<fork ()> was detected (usually because
		2017	whoever is a good citizen cared to tell libev about it by calling
		2018	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2019	event loop blocks next and before C<ev_check> watchers are being called,
		2020	and only in the child after the fork. If whoever good citizen calling
		2021	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2022	handlers will be invoked, too, of course.
		2023
		2024	=head3 Watcher-Specific Functions and Data Members
		2025
1215	=over 4	2026	=over 4
1216		2027
1217	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2028	=item ev_fork_init (ev_signal *, callback)
1218		2029
1219	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2030	Initialises and configures the fork watcher - it has no parameters of any
1220		2031	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1221	Configures the watcher to embed the given loop, which must be	2032	believe me.
1222	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1223	invoked automatically, otherwise it is the responsibility of the callback
1224	to invoke it (it will continue to be called until the sweep has been done,
1225	if you do not want thta, you need to temporarily stop the embed watcher).
1226
1227	=item ev_embed_sweep (loop, ev_embed *)
1228
1229	Make a single, non-blocking sweep over the embedded loop. This works
1230	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1231	apropriate way for embedded loops.
1232		2033
1233	=back	2034	=back
1234		2035
1235		2036
1236	=head1 OTHER FUNCTIONS	2037	=head1 OTHER FUNCTIONS
…		…
1325		2126
1326	To use it,	2127	To use it,
1327		2128
1328	#include <ev++.h>	2129	#include <ev++.h>
1329		2130
1330	(it is not installed by default). This automatically includes F<ev.h>	2131	This automatically includes F<ev.h> and puts all of its definitions (many
1331	and puts all of its definitions (many of them macros) into the global	2132	of them macros) into the global namespace. All C++ specific things are
1332	namespace. All C++ specific things are put into the C<ev> namespace.	2133	put into the C<ev> namespace. It should support all the same embedding
		2134	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1333		2135
1334	It should support all the same embedding options as F<ev.h>, most notably	2136	Care has been taken to keep the overhead low. The only data member the C++
1335	C<EV_MULTIPLICITY>.	2137	classes add (compared to plain C-style watchers) is the event loop pointer
		2138	that the watcher is associated with (or no additional members at all if
		2139	you disable C<EV_MULTIPLICITY> when embedding libev).
		2140
		2141	Currently, functions, and static and non-static member functions can be
		2142	used as callbacks. Other types should be easy to add as long as they only
		2143	need one additional pointer for context. If you need support for other
		2144	types of functors please contact the author (preferably after implementing
		2145	it).
1336		2146
1337	Here is a list of things available in the C<ev> namespace:	2147	Here is a list of things available in the C<ev> namespace:
1338		2148
1339	=over 4	2149	=over 4
1340		2150
…		…
1356		2166
1357	All of those classes have these methods:	2167	All of those classes have these methods:
1358		2168
1359	=over 4	2169	=over 4
1360		2170
1361	=item ev::TYPE::TYPE (object *, object::method *)	2171	=item ev::TYPE::TYPE ()
1362		2172
1363	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2173	=item ev::TYPE::TYPE (struct ev_loop *)
1364		2174
1365	=item ev::TYPE::~TYPE	2175	=item ev::TYPE::~TYPE
1366		2176
1367	The constructor takes a pointer to an object and a method pointer to	2177	The constructor (optionally) takes an event loop to associate the watcher
1368	the event handler callback to call in this class. The constructor calls	2178	with. If it is omitted, it will use C<EV_DEFAULT>.
1369	C<ev_init> for you, which means you have to call the C<set> method	2179
1370	before starting it. If you do not specify a loop then the constructor	2180	The constructor calls C<ev_init> for you, which means you have to call the
1371	automatically associates the default loop with this watcher.	2181	C<set> method before starting it.
		2182
		2183	It will not set a callback, however: You have to call the templated C<set>
		2184	method to set a callback before you can start the watcher.
		2185
		2186	(The reason why you have to use a method is a limitation in C++ which does
		2187	not allow explicit template arguments for constructors).
1372		2188
1373	The destructor automatically stops the watcher if it is active.	2189	The destructor automatically stops the watcher if it is active.
		2190
		2191	=item w->set<class, &class::method> (object *)
		2192
		2193	This method sets the callback method to call. The method has to have a
		2194	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2195	first argument and the C<revents> as second. The object must be given as
		2196	parameter and is stored in the C<data> member of the watcher.
		2197
		2198	This method synthesizes efficient thunking code to call your method from
		2199	the C callback that libev requires. If your compiler can inline your
		2200	callback (i.e. it is visible to it at the place of the C<set> call and
		2201	your compiler is good :), then the method will be fully inlined into the
		2202	thunking function, making it as fast as a direct C callback.
		2203
		2204	Example: simple class declaration and watcher initialisation
		2205
		2206	struct myclass
		2207	{
		2208	void io_cb (ev::io &w, int revents) { }
		2209	}
		2210
		2211	myclass obj;
		2212	ev::io iow;
		2213	iow.set <myclass, &myclass::io_cb> (&obj);
		2214
		2215	=item w->set<function> (void *data = 0)
		2216
		2217	Also sets a callback, but uses a static method or plain function as
		2218	callback. The optional C<data> argument will be stored in the watcher's
		2219	C<data> member and is free for you to use.
		2220
		2221	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2222
		2223	See the method-C<set> above for more details.
		2224
		2225	Example:
		2226
		2227	static void io_cb (ev::io &w, int revents) { }
		2228	iow.set <io_cb> ();
1374		2229
1375	=item w->set (struct ev_loop *)	2230	=item w->set (struct ev_loop *)
1376		2231
1377	Associates a different C<struct ev_loop> with this watcher. You can only	2232	Associates a different C<struct ev_loop> with this watcher. You can only
1378	do this when the watcher is inactive (and not pending either).	2233	do this when the watcher is inactive (and not pending either).
1379		2234
1380	=item w->set ([args])	2235	=item w->set ([args])
1381		2236
1382	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2237	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1383	called at least once. Unlike the C counterpart, an active watcher gets	2238	called at least once. Unlike the C counterpart, an active watcher gets
1384	automatically stopped and restarted.	2239	automatically stopped and restarted when reconfiguring it with this
		2240	method.
1385		2241
1386	=item w->start ()	2242	=item w->start ()
1387		2243
1388	Starts the watcher. Note that there is no C<loop> argument as the	2244	Starts the watcher. Note that there is no C<loop> argument, as the
1389	constructor already takes the loop.	2245	constructor already stores the event loop.
1390		2246
1391	=item w->stop ()	2247	=item w->stop ()
1392		2248
1393	Stops the watcher if it is active. Again, no C<loop> argument.	2249	Stops the watcher if it is active. Again, no C<loop> argument.
1394		2250
1395	=item w->again () C<ev::timer>, C<ev::periodic> only	2251	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1396		2252
1397	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2253	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1398	C<ev_TYPE_again> function.	2254	C<ev_TYPE_again> function.
1399		2255
1400	=item w->sweep () C<ev::embed> only	2256	=item w->sweep () (C<ev::embed> only)
1401		2257
1402	Invokes C<ev_embed_sweep>.	2258	Invokes C<ev_embed_sweep>.
		2259
		2260	=item w->update () (C<ev::stat> only)
		2261
		2262	Invokes C<ev_stat_stat>.
1403		2263
1404	=back	2264	=back
1405		2265
1406	=back	2266	=back
1407		2267
…		…
1415		2275
1416	myclass ();	2276	myclass ();
1417	}	2277	}
1418		2278
1419	myclass::myclass (int fd)	2279	myclass::myclass (int fd)
1420	: io (this, &myclass::io_cb),
1421	idle (this, &myclass::idle_cb)
1422	{	2280	{
		2281	io .set <myclass, &myclass::io_cb > (this);
		2282	idle.set <myclass, &myclass::idle_cb> (this);
		2283
1423	io.start (fd, ev::READ);	2284	io.start (fd, ev::READ);
1424	}	2285	}
		2286
		2287
		2288	=head1 MACRO MAGIC
		2289
		2290	Libev can be compiled with a variety of options, the most fundamantal
		2291	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2292	functions and callbacks have an initial C<struct ev_loop *> argument.
		2293
		2294	To make it easier to write programs that cope with either variant, the
		2295	following macros are defined:
		2296
		2297	=over 4
		2298
		2299	=item C<EV_A>, C<EV_A_>
		2300
		2301	This provides the loop I<argument> for functions, if one is required ("ev
		2302	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2303	C<EV_A_> is used when other arguments are following. Example:
		2304
		2305	ev_unref (EV_A);
		2306	ev_timer_add (EV_A_ watcher);
		2307	ev_loop (EV_A_ 0);
		2308
		2309	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2310	which is often provided by the following macro.
		2311
		2312	=item C<EV_P>, C<EV_P_>
		2313
		2314	This provides the loop I<parameter> for functions, if one is required ("ev
		2315	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2316	C<EV_P_> is used when other parameters are following. Example:
		2317
		2318	// this is how ev_unref is being declared
		2319	static void ev_unref (EV_P);
		2320
		2321	// this is how you can declare your typical callback
		2322	static void cb (EV_P_ ev_timer *w, int revents)
		2323
		2324	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2325	suitable for use with C<EV_A>.
		2326
		2327	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2328
		2329	Similar to the other two macros, this gives you the value of the default
		2330	loop, if multiple loops are supported ("ev loop default").
		2331
		2332	=back
		2333
		2334	Example: Declare and initialise a check watcher, utilising the above
		2335	macros so it will work regardless of whether multiple loops are supported
		2336	or not.
		2337
		2338	static void
		2339	check_cb (EV_P_ ev_timer *w, int revents)
		2340	{
		2341	ev_check_stop (EV_A_ w);
		2342	}
		2343
		2344	ev_check check;
		2345	ev_check_init (&check, check_cb);
		2346	ev_check_start (EV_DEFAULT_ &check);
		2347	ev_loop (EV_DEFAULT_ 0);
1425		2348
1426	=head1 EMBEDDING	2349	=head1 EMBEDDING
1427		2350
1428	Libev can (and often is) directly embedded into host	2351	Libev can (and often is) directly embedded into host
1429	applications. Examples of applications that embed it include the Deliantra	2352	applications. Examples of applications that embed it include the Deliantra
1430	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2353	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1431	and rxvt-unicode.	2354	and rxvt-unicode.
1432		2355
1433	The goal is to enable you to just copy the neecssary files into your	2356	The goal is to enable you to just copy the necessary files into your
1434	source directory without having to change even a single line in them, so	2357	source directory without having to change even a single line in them, so
1435	you can easily upgrade by simply copying (or having a checked-out copy of	2358	you can easily upgrade by simply copying (or having a checked-out copy of
1436	libev somewhere in your source tree).	2359	libev somewhere in your source tree).
1437		2360
1438	=head2 FILESETS	2361	=head2 FILESETS
…		…
1469	ev_vars.h	2392	ev_vars.h
1470	ev_wrap.h	2393	ev_wrap.h
1471		2394
1472	ev_win32.c required on win32 platforms only	2395	ev_win32.c required on win32 platforms only
1473		2396
1474	ev_select.c only when select backend is enabled (which is by default)	2397	ev_select.c only when select backend is enabled (which is enabled by default)
1475	ev_poll.c only when poll backend is enabled (disabled by default)	2398	ev_poll.c only when poll backend is enabled (disabled by default)
1476	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2399	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1477	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2400	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1478	ev_port.c only when the solaris port backend is enabled (disabled by default)	2401	ev_port.c only when the solaris port backend is enabled (disabled by default)
1479		2402
…		…
1528		2451
1529	If defined to be C<1>, libev will try to detect the availability of the	2452	If defined to be C<1>, libev will try to detect the availability of the
1530	monotonic clock option at both compiletime and runtime. Otherwise no use	2453	monotonic clock option at both compiletime and runtime. Otherwise no use
1531	of the monotonic clock option will be attempted. If you enable this, you	2454	of the monotonic clock option will be attempted. If you enable this, you
1532	usually have to link against librt or something similar. Enabling it when	2455	usually have to link against librt or something similar. Enabling it when
1533	the functionality isn't available is safe, though, althoguh you have	2456	the functionality isn't available is safe, though, although you have
1534	to make sure you link against any libraries where the C<clock_gettime>	2457	to make sure you link against any libraries where the C<clock_gettime>
1535	function is hiding in (often F<-lrt>).	2458	function is hiding in (often F<-lrt>).
1536		2459
1537	=item EV_USE_REALTIME	2460	=item EV_USE_REALTIME
1538		2461
1539	If defined to be C<1>, libev will try to detect the availability of the	2462	If defined to be C<1>, libev will try to detect the availability of the
1540	realtime clock option at compiletime (and assume its availability at	2463	realtime clock option at compiletime (and assume its availability at
1541	runtime if successful). Otherwise no use of the realtime clock option will	2464	runtime if successful). Otherwise no use of the realtime clock option will
1542	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2465	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1543	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2466	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1544	in the description of C<EV_USE_MONOTONIC>, though.	2467	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2468
		2469	=item EV_USE_NANOSLEEP
		2470
		2471	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2472	and will use it for delays. Otherwise it will use C<select ()>.
1545		2473
1546	=item EV_USE_SELECT	2474	=item EV_USE_SELECT
1547		2475
1548	If undefined or defined to be C<1>, libev will compile in support for the	2476	If undefined or defined to be C<1>, libev will compile in support for the
1549	C<select>(2) backend. No attempt at autodetection will be done: if no	2477	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1567	wants osf handles on win32 (this is the case when the select to	2495	wants osf handles on win32 (this is the case when the select to
1568	be used is the winsock select). This means that it will call	2496	be used is the winsock select). This means that it will call
1569	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2497	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1570	it is assumed that all these functions actually work on fds, even	2498	it is assumed that all these functions actually work on fds, even
1571	on win32. Should not be defined on non-win32 platforms.	2499	on win32. Should not be defined on non-win32 platforms.
		2500
		2501	=item EV_FD_TO_WIN32_HANDLE
		2502
		2503	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2504	file descriptors to socket handles. When not defining this symbol (the
		2505	default), then libev will call C<_get_osfhandle>, which is usually
		2506	correct. In some cases, programs use their own file descriptor management,
		2507	in which case they can provide this function to map fds to socket handles.
1572		2508
1573	=item EV_USE_POLL	2509	=item EV_USE_POLL
1574		2510
1575	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2511	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1576	backend. Otherwise it will be enabled on non-win32 platforms. It	2512	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
1604		2540
1605	=item EV_USE_DEVPOLL	2541	=item EV_USE_DEVPOLL
1606		2542
1607	reserved for future expansion, works like the USE symbols above.	2543	reserved for future expansion, works like the USE symbols above.
1608		2544
		2545	=item EV_USE_INOTIFY
		2546
		2547	If defined to be C<1>, libev will compile in support for the Linux inotify
		2548	interface to speed up C<ev_stat> watchers. Its actual availability will
		2549	be detected at runtime.
		2550
1609	=item EV_H	2551	=item EV_H
1610		2552
1611	The name of the F<ev.h> header file used to include it. The default if	2553	The name of the F<ev.h> header file used to include it. The default if
1612	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2554	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
1613	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2555	virtually rename the F<ev.h> header file in case of conflicts.
1614		2556
1615	=item EV_CONFIG_H	2557	=item EV_CONFIG_H
1616		2558
1617	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2559	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1618	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2560	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1619	C<EV_H>, above.	2561	C<EV_H>, above.
1620		2562
1621	=item EV_EVENT_H	2563	=item EV_EVENT_H
1622		2564
1623	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2565	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1624	of how the F<event.h> header can be found.	2566	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
1625		2567
1626	=item EV_PROTOTYPES	2568	=item EV_PROTOTYPES
1627		2569
1628	If defined to be C<0>, then F<ev.h> will not define any function	2570	If defined to be C<0>, then F<ev.h> will not define any function
1629	prototypes, but still define all the structs and other symbols. This is	2571	prototypes, but still define all the structs and other symbols. This is
…		…
1636	will have the C<struct ev_loop *> as first argument, and you can create	2578	will have the C<struct ev_loop *> as first argument, and you can create
1637	additional independent event loops. Otherwise there will be no support	2579	additional independent event loops. Otherwise there will be no support
1638	for multiple event loops and there is no first event loop pointer	2580	for multiple event loops and there is no first event loop pointer
1639	argument. Instead, all functions act on the single default loop.	2581	argument. Instead, all functions act on the single default loop.
1640		2582
		2583	=item EV_MINPRI
		2584
		2585	=item EV_MAXPRI
		2586
		2587	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2588	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2589	provide for more priorities by overriding those symbols (usually defined
		2590	to be C<-2> and C<2>, respectively).
		2591
		2592	When doing priority-based operations, libev usually has to linearly search
		2593	all the priorities, so having many of them (hundreds) uses a lot of space
		2594	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2595	fine.
		2596
		2597	If your embedding app does not need any priorities, defining these both to
		2598	C<0> will save some memory and cpu.
		2599
1641	=item EV_PERIODICS	2600	=item EV_PERIODIC_ENABLE
1642		2601
1643	If undefined or defined to be C<1>, then periodic timers are supported,	2602	If undefined or defined to be C<1>, then periodic timers are supported. If
1644	otherwise not. This saves a few kb of code.	2603	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2604	code.
		2605
		2606	=item EV_IDLE_ENABLE
		2607
		2608	If undefined or defined to be C<1>, then idle watchers are supported. If
		2609	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2610	code.
		2611
		2612	=item EV_EMBED_ENABLE
		2613
		2614	If undefined or defined to be C<1>, then embed watchers are supported. If
		2615	defined to be C<0>, then they are not.
		2616
		2617	=item EV_STAT_ENABLE
		2618
		2619	If undefined or defined to be C<1>, then stat watchers are supported. If
		2620	defined to be C<0>, then they are not.
		2621
		2622	=item EV_FORK_ENABLE
		2623
		2624	If undefined or defined to be C<1>, then fork watchers are supported. If
		2625	defined to be C<0>, then they are not.
		2626
		2627	=item EV_MINIMAL
		2628
		2629	If you need to shave off some kilobytes of code at the expense of some
		2630	speed, define this symbol to C<1>. Currently only used for gcc to override
		2631	some inlining decisions, saves roughly 30% codesize of amd64.
		2632
		2633	=item EV_PID_HASHSIZE
		2634
		2635	C<ev_child> watchers use a small hash table to distribute workload by
		2636	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2637	than enough. If you need to manage thousands of children you might want to
		2638	increase this value (I<must> be a power of two).
		2639
		2640	=item EV_INOTIFY_HASHSIZE
		2641
		2642	C<ev_stat> watchers use a small hash table to distribute workload by
		2643	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2644	usually more than enough. If you need to manage thousands of C<ev_stat>
		2645	watchers you might want to increase this value (I<must> be a power of
		2646	two).
1645		2647
1646	=item EV_COMMON	2648	=item EV_COMMON
1647		2649
1648	By default, all watchers have a C<void *data> member. By redefining	2650	By default, all watchers have a C<void *data> member. By redefining
1649	this macro to a something else you can include more and other types of	2651	this macro to a something else you can include more and other types of
…		…
1654		2656
1655	#define EV_COMMON \	2657	#define EV_COMMON \
1656	SV *self; /* contains this struct */ \	2658	SV *self; /* contains this struct */ \
1657	SV *cb_sv, *fh /* note no trailing ";" */	2659	SV *cb_sv, *fh /* note no trailing ";" */
1658		2660
1659	=item EV_CB_DECLARE(type)	2661	=item EV_CB_DECLARE (type)
1660		2662
1661	=item EV_CB_INVOKE(watcher,revents)	2663	=item EV_CB_INVOKE (watcher, revents)
1662		2664
1663	=item ev_set_cb(ev,cb)	2665	=item ev_set_cb (ev, cb)
1664		2666
1665	Can be used to change the callback member declaration in each watcher,	2667	Can be used to change the callback member declaration in each watcher,
1666	and the way callbacks are invoked and set. Must expand to a struct member	2668	and the way callbacks are invoked and set. Must expand to a struct member
1667	definition and a statement, respectively. See the F<ev.v> header file for	2669	definition and a statement, respectively. See the F<ev.h> header file for
1668	their default definitions. One possible use for overriding these is to	2670	their default definitions. One possible use for overriding these is to
1669	avoid the ev_loop pointer as first argument in all cases, or to use method	2671	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1670	calls instead of plain function calls in C++.	2672	method calls instead of plain function calls in C++.
		2673
		2674	=head2 EXPORTED API SYMBOLS
		2675
		2676	If you need to re-export the API (e.g. via a dll) and you need a list of
		2677	exported symbols, you can use the provided F<Symbol.*> files which list
		2678	all public symbols, one per line:
		2679
		2680	Symbols.ev for libev proper
		2681	Symbols.event for the libevent emulation
		2682
		2683	This can also be used to rename all public symbols to avoid clashes with
		2684	multiple versions of libev linked together (which is obviously bad in
		2685	itself, but sometimes it is inconvinient to avoid this).
		2686
		2687	A sed command like this will create wrapper C<#define>'s that you need to
		2688	include before including F<ev.h>:
		2689
		2690	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2691
		2692	This would create a file F<wrap.h> which essentially looks like this:
		2693
		2694	#define ev_backend myprefix_ev_backend
		2695	#define ev_check_start myprefix_ev_check_start
		2696	#define ev_check_stop myprefix_ev_check_stop
		2697	...
1671		2698
1672	=head2 EXAMPLES	2699	=head2 EXAMPLES
1673		2700
1674	For a real-world example of a program the includes libev	2701	For a real-world example of a program the includes libev
1675	verbatim, you can have a look at the EV perl module	2702	verbatim, you can have a look at the EV perl module
…		…
1678	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2705	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1679	will be compiled. It is pretty complex because it provides its own header	2706	will be compiled. It is pretty complex because it provides its own header
1680	file.	2707	file.
1681		2708
1682	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2709	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1683	that everybody includes and which overrides some autoconf choices:	2710	that everybody includes and which overrides some configure choices:
1684		2711
		2712	#define EV_MINIMAL 1
1685	#define EV_USE_POLL 0	2713	#define EV_USE_POLL 0
1686	#define EV_MULTIPLICITY 0	2714	#define EV_MULTIPLICITY 0
1687	#define EV_PERIODICS 0	2715	#define EV_PERIODIC_ENABLE 0
		2716	#define EV_STAT_ENABLE 0
		2717	#define EV_FORK_ENABLE 0
1688	#define EV_CONFIG_H <config.h>	2718	#define EV_CONFIG_H <config.h>
		2719	#define EV_MINPRI 0
		2720	#define EV_MAXPRI 0
1689		2721
1690	#include "ev++.h"	2722	#include "ev++.h"
1691		2723
1692	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2724	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1693		2725
1694	#include "ev_cpp.h"	2726	#include "ev_cpp.h"
1695	#include "ev.c"	2727	#include "ev.c"
1696		2728
		2729
		2730	=head1 COMPLEXITIES
		2731
		2732	In this section the complexities of (many of) the algorithms used inside
		2733	libev will be explained. For complexity discussions about backends see the
		2734	documentation for C<ev_default_init>.
		2735
		2736	All of the following are about amortised time: If an array needs to be
		2737	extended, libev needs to realloc and move the whole array, but this
		2738	happens asymptotically never with higher number of elements, so O(1) might
		2739	mean it might do a lengthy realloc operation in rare cases, but on average
		2740	it is much faster and asymptotically approaches constant time.
		2741
		2742	=over 4
		2743
		2744	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2745
		2746	This means that, when you have a watcher that triggers in one hour and
		2747	there are 100 watchers that would trigger before that then inserting will
		2748	have to skip roughly seven (C<ld 100>) of these watchers.
		2749
		2750	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2751
		2752	That means that changing a timer costs less than removing/adding them
		2753	as only the relative motion in the event queue has to be paid for.
		2754
		2755	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2756
		2757	These just add the watcher into an array or at the head of a list.
		2758
		2759	=item Stopping check/prepare/idle watchers: O(1)
		2760
		2761	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2762
		2763	These watchers are stored in lists then need to be walked to find the
		2764	correct watcher to remove. The lists are usually short (you don't usually
		2765	have many watchers waiting for the same fd or signal).
		2766
		2767	=item Finding the next timer in each loop iteration: O(1)
		2768
		2769	By virtue of using a binary heap, the next timer is always found at the
		2770	beginning of the storage array.
		2771
		2772	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2773
		2774	A change means an I/O watcher gets started or stopped, which requires
		2775	libev to recalculate its status (and possibly tell the kernel, depending
		2776	on backend and wether C<ev_io_set> was used).
		2777
		2778	=item Activating one watcher (putting it into the pending state): O(1)
		2779
		2780	=item Priority handling: O(number_of_priorities)
		2781
		2782	Priorities are implemented by allocating some space for each
		2783	priority. When doing priority-based operations, libev usually has to
		2784	linearly search all the priorities, but starting/stopping and activating
		2785	watchers becomes O(1) w.r.t. prioritiy handling.
		2786
		2787	=back
		2788
		2789
		2790	=head1 Win32 platform limitations and workarounds
		2791
		2792	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2793	requires, and its I/O model is fundamentally incompatible with the POSIX
		2794	model. Libev still offers limited functionality on this platform in
		2795	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2796	descriptors. This only applies when using Win32 natively, not when using
		2797	e.g. cygwin.
		2798
		2799	There is no supported compilation method available on windows except
		2800	embedding it into other applications.
		2801
		2802	Due to the many, low, and arbitrary limits on the win32 platform and the
		2803	abysmal performance of winsockets, using a large number of sockets is not
		2804	recommended (and not reasonable). If your program needs to use more than
		2805	a hundred or so sockets, then likely it needs to use a totally different
		2806	implementation for windows, as libev offers the POSIX model, which cannot
		2807	be implemented efficiently on windows (microsoft monopoly games).
		2808
		2809	=over 4
		2810
		2811	=item The winsocket select function
		2812
		2813	The winsocket C<select> function doesn't follow POSIX in that it requires
		2814	socket I<handles> and not socket I<file descriptors>. This makes select
		2815	very inefficient, and also requires a mapping from file descriptors
		2816	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2817	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2818	symbols for more info.
		2819
		2820	The configuration for a "naked" win32 using the microsoft runtime
		2821	libraries and raw winsocket select is:
		2822
		2823	#define EV_USE_SELECT 1
		2824	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2825
		2826	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2827	complexity in the O(n²) range when using win32.
		2828
		2829	=item Limited number of file descriptors
		2830
		2831	Windows has numerous arbitrary (and low) limits on things. Early versions
		2832	of winsocket's select only supported waiting for a max. of C<64> handles
		2833	(probably owning to the fact that all windows kernels can only wait for
		2834	C<64> things at the same time internally; microsoft recommends spawning a
		2835	chain of threads and wait for 63 handles and the previous thread in each).
		2836
		2837	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2838	to some high number (e.g. C<2048>) before compiling the winsocket select
		2839	call (which might be in libev or elsewhere, for example, perl does its own
		2840	select emulation on windows).
		2841
		2842	Another limit is the number of file descriptors in the microsoft runtime
		2843	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2844	or something like this inside microsoft). You can increase this by calling
		2845	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2846	arbitrary limit), but is broken in many versions of the microsoft runtime
		2847	libraries.
		2848
		2849	This might get you to about C<512> or C<2048> sockets (depending on
		2850	windows version and/or the phase of the moon). To get more, you need to
		2851	wrap all I/O functions and provide your own fd management, but the cost of
		2852	calling select (O(n²)) will likely make this unworkable.
		2853
		2854	=back
		2855
		2856
1697	=head1 AUTHOR	2857	=head1 AUTHOR
1698		2858
1699	Marc Lehmann <libev@schmorp.de>.	2859	Marc Lehmann <libev@schmorp.de>.
1700		2860

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