ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.49 by root, Tue Nov 27 08:20:42 2007 UTC vs.
Revision 1.116 by root, Mon Dec 31 01:34:09 2007 UTC

…		…
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);
…		…
437		589
438	Can be used to make a call to C<ev_loop> return early (but only after it	590	Can be used to make a call to C<ev_loop> return early (but only after it
439	has processed all outstanding events). The C<how> argument must be either	591	has processed all outstanding events). The C<how> argument must be either
440	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	592	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
441	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	593	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		594
		595	This "unloop state" will be cleared when entering C<ev_loop> again.
442		596
443	=item ev_ref (loop)	597	=item ev_ref (loop)
444		598
445	=item ev_unref (loop)	599	=item ev_unref (loop)
446		600
…		…
451	returning, ev_unref() after starting, and ev_ref() before stopping it. For	605	returning, ev_unref() after starting, and ev_ref() before stopping it. For
452	example, libev itself uses this for its internal signal pipe: It is not	606	example, libev itself uses this for its internal signal pipe: It is not
453	visible to the libev user and should not keep C<ev_loop> from exiting if	607	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	608	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	609	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>.	610	libraries. Just remember to I<unref after start> and I<ref before stop>
		611	(but only if the watcher wasn't active before, or was active before,
		612	respectively).
457		613
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	614	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	615	running when nothing else is active.
460		616
461	struct dv_signal exitsig;	617	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	618	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	619	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	620	evf_unref (loop);
465		621
466	Example: for some weird reason, unregister the above signal handler again.	622	Example: For some weird reason, unregister the above signal handler again.
467		623
468	ev_ref (myloop);	624	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	625	ev_signal_stop (loop, &exitsig);
		626
		627	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		628
		629	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		630
		631	These advanced functions influence the time that libev will spend waiting
		632	for events. Both are by default C<0>, meaning that libev will try to
		633	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		634
		635	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		636	allows libev to delay invocation of I/O and timer/periodic callbacks to
		637	increase efficiency of loop iterations.
		638
		639	The background is that sometimes your program runs just fast enough to
		640	handle one (or very few) event(s) per loop iteration. While this makes
		641	the program responsive, it also wastes a lot of CPU time to poll for new
		642	events, especially with backends like C<select ()> which have a high
		643	overhead for the actual polling but can deliver many events at once.
		644
		645	By setting a higher I<io collect interval> you allow libev to spend more
		646	time collecting I/O events, so you can handle more events per iteration,
		647	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		648	C<ev_timer>) will be not affected. Setting this to a non-null value will
		649	introduce an additional C<ev_sleep ()> call into most loop iterations.
		650
		651	Likewise, by setting a higher I<timeout collect interval> you allow libev
		652	to spend more time collecting timeouts, at the expense of increased
		653	latency (the watcher callback will be called later). C<ev_io> watchers
		654	will not be affected. Setting this to a non-null value will not introduce
		655	any overhead in libev.
		656
		657	Many (busy) programs can usually benefit by setting the io collect
		658	interval to a value near C<0.1> or so, which is often enough for
		659	interactive servers (of course not for games), likewise for timeouts. It
		660	usually doesn't make much sense to set it to a lower value than C<0.01>,
		661	as this approsaches the timing granularity of most systems.
470		662
471	=back	663	=back
472		664
473		665
474	=head1 ANATOMY OF A WATCHER	666	=head1 ANATOMY OF A WATCHER
…		…
565	received events. Callbacks of both watcher types can start and stop as	757	received events. Callbacks of both watcher types can start and stop as
566	many watchers as they want, and all of them will be taken into account	758	many watchers as they want, and all of them will be taken into account
567	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	759	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
568	C<ev_loop> from blocking).	760	C<ev_loop> from blocking).
569		761
		762	=item C<EV_EMBED>
		763
		764	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		765
		766	=item C<EV_FORK>
		767
		768	The event loop has been resumed in the child process after fork (see
		769	C<ev_fork>).
		770
570	=item C<EV_ERROR>	771	=item C<EV_ERROR>
571		772
572	An unspecified error has occured, the watcher has been stopped. This might	773	An unspecified error has occured, the watcher has been stopped. This might
573	happen because the watcher could not be properly started because libev	774	happen because the watcher could not be properly started because libev
574	ran out of memory, a file descriptor was found to be closed or any other	775	ran out of memory, a file descriptor was found to be closed or any other
…		…
645	=item bool ev_is_pending (ev_TYPE *watcher)	846	=item bool ev_is_pending (ev_TYPE *watcher)
646		847
647	Returns a true value iff the watcher is pending, (i.e. it has outstanding	848	Returns a true value iff the watcher is pending, (i.e. it has outstanding
648	events but its callback has not yet been invoked). As long as a watcher	849	events but its callback has not yet been invoked). As long as a watcher
649	is pending (but not active) you must not call an init function on it (but	850	is pending (but not active) you must not call an init function on it (but
650	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	851	C<ev_TYPE_set> is safe), you must not change its priority, and you must
651	libev (e.g. you cnanot C<free ()> it).	852	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		853	it).
652		854
653	=item callback = ev_cb (ev_TYPE *watcher)	855	=item callback ev_cb (ev_TYPE *watcher)
654		856
655	Returns the callback currently set on the watcher.	857	Returns the callback currently set on the watcher.
656		858
657	=item ev_cb_set (ev_TYPE *watcher, callback)	859	=item ev_cb_set (ev_TYPE *watcher, callback)
658		860
659	Change the callback. You can change the callback at virtually any time	861	Change the callback. You can change the callback at virtually any time
660	(modulo threads).	862	(modulo threads).
		863
		864	=item ev_set_priority (ev_TYPE *watcher, priority)
		865
		866	=item int ev_priority (ev_TYPE *watcher)
		867
		868	Set and query the priority of the watcher. The priority is a small
		869	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		870	(default: C<-2>). Pending watchers with higher priority will be invoked
		871	before watchers with lower priority, but priority will not keep watchers
		872	from being executed (except for C<ev_idle> watchers).
		873
		874	This means that priorities are I<only> used for ordering callback
		875	invocation after new events have been received. This is useful, for
		876	example, to reduce latency after idling, or more often, to bind two
		877	watchers on the same event and make sure one is called first.
		878
		879	If you need to suppress invocation when higher priority events are pending
		880	you need to look at C<ev_idle> watchers, which provide this functionality.
		881
		882	You I<must not> change the priority of a watcher as long as it is active or
		883	pending.
		884
		885	The default priority used by watchers when no priority has been set is
		886	always C<0>, which is supposed to not be too high and not be too low :).
		887
		888	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		889	fine, as long as you do not mind that the priority value you query might
		890	or might not have been adjusted to be within valid range.
		891
		892	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		893
		894	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		895	C<loop> nor C<revents> need to be valid as long as the watcher callback
		896	can deal with that fact.
		897
		898	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		899
		900	If the watcher is pending, this function returns clears its pending status
		901	and returns its C<revents> bitset (as if its callback was invoked). If the
		902	watcher isn't pending it does nothing and returns C<0>.
661		903
662	=back	904	=back
663		905
664		906
665	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	907	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
686	{	928	{
687	struct my_io *w = (struct my_io *)w_;	929	struct my_io *w = (struct my_io *)w_;
688	...	930	...
689	}	931	}
690		932
691	More interesting and less C-conformant ways of catsing your callback type	933	More interesting and less C-conformant ways of casting your callback type
692	have been omitted....	934	instead have been omitted.
		935
		936	Another common scenario is having some data structure with multiple
		937	watchers:
		938
		939	struct my_biggy
		940	{
		941	int some_data;
		942	ev_timer t1;
		943	ev_timer t2;
		944	}
		945
		946	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		947	you need to use C<offsetof>:
		948
		949	#include <stddef.h>
		950
		951	static void
		952	t1_cb (EV_P_ struct ev_timer *w, int revents)
		953	{
		954	struct my_biggy big = (struct my_biggy *
		955	(((char *)w) - offsetof (struct my_biggy, t1));
		956	}
		957
		958	static void
		959	t2_cb (EV_P_ struct ev_timer *w, int revents)
		960	{
		961	struct my_biggy big = (struct my_biggy *
		962	(((char *)w) - offsetof (struct my_biggy, t2));
		963	}
693		964
694		965
695	=head1 WATCHER TYPES	966	=head1 WATCHER TYPES
696		967
697	This section describes each watcher in detail, but will not repeat	968	This section describes each watcher in detail, but will not repeat
…		…
721	In general you can register as many read and/or write event watchers per	992	In general you can register as many read and/or write event watchers per
722	fd as you want (as long as you don't confuse yourself). Setting all file	993	fd as you want (as long as you don't confuse yourself). Setting all file
723	descriptors to non-blocking mode is also usually a good idea (but not	994	descriptors to non-blocking mode is also usually a good idea (but not
724	required if you know what you are doing).	995	required if you know what you are doing).
725		996
726	You have to be careful with dup'ed file descriptors, though. Some backends
727	(the linux epoll backend is a notable example) cannot handle dup'ed file
728	descriptors correctly if you register interest in two or more fds pointing
729	to the same underlying file/socket/etc. description (that is, they share
730	the same underlying "file open").
731
732	If you must do this, then force the use of a known-to-be-good backend	997	If you must do this, then force the use of a known-to-be-good backend
733	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	998	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
734	C<EVBACKEND_POLL>).	999	C<EVBACKEND_POLL>).
735		1000
736	Another thing you have to watch out for is that it is quite easy to	1001	Another thing you have to watch out for is that it is quite easy to
…		…
742	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1007	it is best to always use non-blocking I/O: An extra C<read>(2) returning
743	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1008	C<EAGAIN> is far preferable to a program hanging until some data arrives.
744		1009
745	If you cannot run the fd in non-blocking mode (for example you should not	1010	If you cannot run the fd in non-blocking mode (for example you should not
746	play around with an Xlib connection), then you have to seperately re-test	1011	play around with an Xlib connection), then you have to seperately re-test
747	wether a file descriptor is really ready with a known-to-be good interface	1012	whether a file descriptor is really ready with a known-to-be good interface
748	such as poll (fortunately in our Xlib example, Xlib already does this on	1013	such as poll (fortunately in our Xlib example, Xlib already does this on
749	its own, so its quite safe to use).	1014	its own, so its quite safe to use).
		1015
		1016	=head3 The special problem of disappearing file descriptors
		1017
		1018	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1019	descriptor (either by calling C<close> explicitly or by any other means,
		1020	such as C<dup>). The reason is that you register interest in some file
		1021	descriptor, but when it goes away, the operating system will silently drop
		1022	this interest. If another file descriptor with the same number then is
		1023	registered with libev, there is no efficient way to see that this is, in
		1024	fact, a different file descriptor.
		1025
		1026	To avoid having to explicitly tell libev about such cases, libev follows
		1027	the following policy: Each time C<ev_io_set> is being called, libev
		1028	will assume that this is potentially a new file descriptor, otherwise
		1029	it is assumed that the file descriptor stays the same. That means that
		1030	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1031	descriptor even if the file descriptor number itself did not change.
		1032
		1033	This is how one would do it normally anyway, the important point is that
		1034	the libev application should not optimise around libev but should leave
		1035	optimisations to libev.
		1036
		1037	=head3 The special problem of dup'ed file descriptors
		1038
		1039	Some backends (e.g. epoll), cannot register events for file descriptors,
		1040	but only events for the underlying file descriptions. That means when you
		1041	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1042	events for them, only one file descriptor might actually receive events.
		1043
		1044	There is no workaround possible except not registering events
		1045	for potentially C<dup ()>'ed file descriptors, or to resort to
		1046	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1047
		1048	=head3 The special problem of fork
		1049
		1050	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1051	useless behaviour. Libev fully supports fork, but needs to be told about
		1052	it in the child.
		1053
		1054	To support fork in your programs, you either have to call
		1055	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1056	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1057	C<EVBACKEND_POLL>.
		1058
		1059
		1060	=head3 Watcher-Specific Functions
750		1061
751	=over 4	1062	=over 4
752		1063
753	=item ev_io_init (ev_io *, callback, int fd, int events)	1064	=item ev_io_init (ev_io *, callback, int fd, int events)
754		1065
…		…
766		1077
767	The events being watched.	1078	The events being watched.
768		1079
769	=back	1080	=back
770		1081
		1082	=head3 Examples
		1083
771	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1084	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
772	readable, but only once. Since it is likely line-buffered, you could	1085	readable, but only once. Since it is likely line-buffered, you could
773	attempt to read a whole line in the callback:	1086	attempt to read a whole line in the callback.
774		1087
775	static void	1088	static void
776	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1089	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
777	{	1090	{
778	ev_io_stop (loop, w);	1091	ev_io_stop (loop, w);
…		…
808		1121
809	The callback is guarenteed to be invoked only when its timeout has passed,	1122	The callback is guarenteed to be invoked only when its timeout has passed,
810	but if multiple timers become ready during the same loop iteration then	1123	but if multiple timers become ready during the same loop iteration then
811	order of execution is undefined.	1124	order of execution is undefined.
812		1125
		1126	=head3 Watcher-Specific Functions and Data Members
		1127
813	=over 4	1128	=over 4
814		1129
815	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1130	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
816		1131
817	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1132	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
830	=item ev_timer_again (loop)	1145	=item ev_timer_again (loop)
831		1146
832	This will act as if the timer timed out and restart it again if it is	1147	This will act as if the timer timed out and restart it again if it is
833	repeating. The exact semantics are:	1148	repeating. The exact semantics are:
834		1149
		1150	If the timer is pending, its pending status is cleared.
		1151
835	If the timer is started but nonrepeating, stop it.	1152	If the timer is started but nonrepeating, stop it (as if it timed out).
836		1153
837	If the timer is repeating, either start it if necessary (with the repeat	1154	If the timer is repeating, either start it if necessary (with the
838	value), or reset the running timer to the repeat value.	1155	C<repeat> value), or reset the running timer to the C<repeat> value.
839		1156
840	This sounds a bit complicated, but here is a useful and typical	1157	This sounds a bit complicated, but here is a useful and typical
841	example: Imagine you have a tcp connection and you want a so-called	1158	example: Imagine you have a tcp connection and you want a so-called idle
842	idle timeout, that is, you want to be called when there have been,	1159	timeout, that is, you want to be called when there have been, say, 60
843	say, 60 seconds of inactivity on the socket. The easiest way to do	1160	seconds of inactivity on the socket. The easiest way to do this is to
844	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1161	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
845	C<ev_timer_again> each time you successfully read or write some data. If	1162	C<ev_timer_again> each time you successfully read or write some data. If
846	you go into an idle state where you do not expect data to travel on the	1163	you go into an idle state where you do not expect data to travel on the
847	socket, you can stop the timer, and again will automatically restart it if	1164	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
848	need be.	1165	automatically restart it if need be.
849		1166
850	You can also ignore the C<after> value and C<ev_timer_start> altogether	1167	That means you can ignore the C<after> value and C<ev_timer_start>
851	and only ever use the C<repeat> value:	1168	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
852		1169
853	ev_timer_init (timer, callback, 0., 5.);	1170	ev_timer_init (timer, callback, 0., 5.);
854	ev_timer_again (loop, timer);	1171	ev_timer_again (loop, timer);
855	...	1172	...
856	timer->again = 17.;	1173	timer->again = 17.;
857	ev_timer_again (loop, timer);	1174	ev_timer_again (loop, timer);
858	...	1175	...
859	timer->again = 10.;	1176	timer->again = 10.;
860	ev_timer_again (loop, timer);	1177	ev_timer_again (loop, timer);
861		1178
862	This is more efficient then stopping/starting the timer eahc time you want	1179	This is more slightly efficient then stopping/starting the timer each time
863	to modify its timeout value.	1180	you want to modify its timeout value.
864		1181
865	=item ev_tstamp repeat [read-write]	1182	=item ev_tstamp repeat [read-write]
866		1183
867	The current C<repeat> value. Will be used each time the watcher times out	1184	The current C<repeat> value. Will be used each time the watcher times out
868	or C<ev_timer_again> is called and determines the next timeout (if any),	1185	or C<ev_timer_again> is called and determines the next timeout (if any),
869	which is also when any modifications are taken into account.	1186	which is also when any modifications are taken into account.
870		1187
871	=back	1188	=back
872		1189
		1190	=head3 Examples
		1191
873	Example: create a timer that fires after 60 seconds.	1192	Example: Create a timer that fires after 60 seconds.
874		1193
875	static void	1194	static void
876	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1195	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
877	{	1196	{
878	.. one minute over, w is actually stopped right here	1197	.. one minute over, w is actually stopped right here
…		…
880		1199
881	struct ev_timer mytimer;	1200	struct ev_timer mytimer;
882	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1201	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
883	ev_timer_start (loop, &mytimer);	1202	ev_timer_start (loop, &mytimer);
884		1203
885	Example: create a timeout timer that times out after 10 seconds of	1204	Example: Create a timeout timer that times out after 10 seconds of
886	inactivity.	1205	inactivity.
887		1206
888	static void	1207	static void
889	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1208	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
890	{	1209	{
…		…
910	but on wallclock time (absolute time). You can tell a periodic watcher	1229	but on wallclock time (absolute time). You can tell a periodic watcher
911	to trigger "at" some specific point in time. For example, if you tell a	1230	to trigger "at" some specific point in time. For example, if you tell a
912	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1231	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
913	+ 10.>) and then reset your system clock to the last year, then it will	1232	+ 10.>) and then reset your system clock to the last year, then it will
914	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1233	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
915	roughly 10 seconds later and of course not if you reset your system time	1234	roughly 10 seconds later).
916	again).
917		1235
918	They can also be used to implement vastly more complex timers, such as	1236	They can also be used to implement vastly more complex timers, such as
919	triggering an event on eahc midnight, local time.	1237	triggering an event on each midnight, local time or other, complicated,
		1238	rules.
920		1239
921	As with timers, the callback is guarenteed to be invoked only when the	1240	As with timers, the callback is guarenteed to be invoked only when the
922	time (C<at>) has been passed, but if multiple periodic timers become ready	1241	time (C<at>) has been passed, but if multiple periodic timers become ready
923	during the same loop iteration then order of execution is undefined.	1242	during the same loop iteration then order of execution is undefined.
924		1243
		1244	=head3 Watcher-Specific Functions and Data Members
		1245
925	=over 4	1246	=over 4
926		1247
927	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1248	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
928		1249
929	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1250	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
931	Lots of arguments, lets sort it out... There are basically three modes of	1252	Lots of arguments, lets sort it out... There are basically three modes of
932	operation, and we will explain them from simplest to complex:	1253	operation, and we will explain them from simplest to complex:
933		1254
934	=over 4	1255	=over 4
935		1256
936	=item * absolute timer (interval = reschedule_cb = 0)	1257	=item * absolute timer (at = time, interval = reschedule_cb = 0)
937		1258
938	In this configuration the watcher triggers an event at the wallclock time	1259	In this configuration the watcher triggers an event at the wallclock time
939	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1260	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
940	that is, if it is to be run at January 1st 2011 then it will run when the	1261	that is, if it is to be run at January 1st 2011 then it will run when the
941	system time reaches or surpasses this time.	1262	system time reaches or surpasses this time.
942		1263
943	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1264	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
944		1265
945	In this mode the watcher will always be scheduled to time out at the next	1266	In this mode the watcher will always be scheduled to time out at the next
946	C<at + N * interval> time (for some integer N) and then repeat, regardless	1267	C<at + N * interval> time (for some integer N, which can also be negative)
947	of any time jumps.	1268	and then repeat, regardless of any time jumps.
948		1269
949	This can be used to create timers that do not drift with respect to system	1270	This can be used to create timers that do not drift with respect to system
950	time:	1271	time:
951		1272
952	ev_periodic_set (&periodic, 0., 3600., 0);	1273	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
958		1279
959	Another way to think about it (for the mathematically inclined) is that	1280	Another way to think about it (for the mathematically inclined) is that
960	C<ev_periodic> will try to run the callback in this mode at the next possible	1281	C<ev_periodic> will try to run the callback in this mode at the next possible
961	time where C<time = at (mod interval)>, regardless of any time jumps.	1282	time where C<time = at (mod interval)>, regardless of any time jumps.
962		1283
		1284	For numerical stability it is preferable that the C<at> value is near
		1285	C<ev_now ()> (the current time), but there is no range requirement for
		1286	this value.
		1287
963	=item * manual reschedule mode (reschedule_cb = callback)	1288	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
964		1289
965	In this mode the values for C<interval> and C<at> are both being	1290	In this mode the values for C<interval> and C<at> are both being
966	ignored. Instead, each time the periodic watcher gets scheduled, the	1291	ignored. Instead, each time the periodic watcher gets scheduled, the
967	reschedule callback will be called with the watcher as first, and the	1292	reschedule callback will be called with the watcher as first, and the
968	current time as second argument.	1293	current time as second argument.
969		1294
970	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1295	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
971	ever, or make any event loop modifications>. If you need to stop it,	1296	ever, or make any event loop modifications>. If you need to stop it,
972	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1297	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
973	starting a prepare watcher).	1298	starting an C<ev_prepare> watcher, which is legal).
974		1299
975	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1300	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
976	ev_tstamp now)>, e.g.:	1301	ev_tstamp now)>, e.g.:
977		1302
978	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1303	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1001	Simply stops and restarts the periodic watcher again. This is only useful	1326	Simply stops and restarts the periodic watcher again. This is only useful
1002	when you changed some parameters or the reschedule callback would return	1327	when you changed some parameters or the reschedule callback would return
1003	a different time than the last time it was called (e.g. in a crond like	1328	a different time than the last time it was called (e.g. in a crond like
1004	program when the crontabs have changed).	1329	program when the crontabs have changed).
1005		1330
		1331	=item ev_tstamp offset [read-write]
		1332
		1333	When repeating, this contains the offset value, otherwise this is the
		1334	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1335
		1336	Can be modified any time, but changes only take effect when the periodic
		1337	timer fires or C<ev_periodic_again> is being called.
		1338
1006	=item ev_tstamp interval [read-write]	1339	=item ev_tstamp interval [read-write]
1007		1340
1008	The current interval value. Can be modified any time, but changes only	1341	The current interval value. Can be modified any time, but changes only
1009	take effect when the periodic timer fires or C<ev_periodic_again> is being	1342	take effect when the periodic timer fires or C<ev_periodic_again> is being
1010	called.	1343	called.
…		…
1013		1346
1014	The current reschedule callback, or C<0>, if this functionality is	1347	The current reschedule callback, or C<0>, if this functionality is
1015	switched off. Can be changed any time, but changes only take effect when	1348	switched off. Can be changed any time, but changes only take effect when
1016	the periodic timer fires or C<ev_periodic_again> is being called.	1349	the periodic timer fires or C<ev_periodic_again> is being called.
1017		1350
		1351	=item ev_tstamp at [read-only]
		1352
		1353	When active, contains the absolute time that the watcher is supposed to
		1354	trigger next.
		1355
1018	=back	1356	=back
1019		1357
		1358	=head3 Examples
		1359
1020	Example: call a callback every hour, or, more precisely, whenever the	1360	Example: Call a callback every hour, or, more precisely, whenever the
1021	system clock is divisible by 3600. The callback invocation times have	1361	system clock is divisible by 3600. The callback invocation times have
1022	potentially a lot of jittering, but good long-term stability.	1362	potentially a lot of jittering, but good long-term stability.
1023		1363
1024	static void	1364	static void
1025	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1365	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
1029		1369
1030	struct ev_periodic hourly_tick;	1370	struct ev_periodic hourly_tick;
1031	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1371	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1032	ev_periodic_start (loop, &hourly_tick);	1372	ev_periodic_start (loop, &hourly_tick);
1033		1373
1034	Example: the same as above, but use a reschedule callback to do it:	1374	Example: The same as above, but use a reschedule callback to do it:
1035		1375
1036	#include <math.h>	1376	#include <math.h>
1037		1377
1038	static ev_tstamp	1378	static ev_tstamp
1039	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1379	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
1041	return fmod (now, 3600.) + 3600.;	1381	return fmod (now, 3600.) + 3600.;
1042	}	1382	}
1043		1383
1044	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1384	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1045		1385
1046	Example: call a callback every hour, starting now:	1386	Example: Call a callback every hour, starting now:
1047		1387
1048	struct ev_periodic hourly_tick;	1388	struct ev_periodic hourly_tick;
1049	ev_periodic_init (&hourly_tick, clock_cb,	1389	ev_periodic_init (&hourly_tick, clock_cb,
1050	fmod (ev_now (loop), 3600.), 3600., 0);	1390	fmod (ev_now (loop), 3600.), 3600., 0);
1051	ev_periodic_start (loop, &hourly_tick);	1391	ev_periodic_start (loop, &hourly_tick);
…		…
1063	with the kernel (thus it coexists with your own signal handlers as long	1403	with the kernel (thus it coexists with your own signal handlers as long
1064	as you don't register any with libev). Similarly, when the last signal	1404	as you don't register any with libev). Similarly, when the last signal
1065	watcher for a signal is stopped libev will reset the signal handler to	1405	watcher for a signal is stopped libev will reset the signal handler to
1066	SIG_DFL (regardless of what it was set to before).	1406	SIG_DFL (regardless of what it was set to before).
1067		1407
		1408	=head3 Watcher-Specific Functions and Data Members
		1409
1068	=over 4	1410	=over 4
1069		1411
1070	=item ev_signal_init (ev_signal *, callback, int signum)	1412	=item ev_signal_init (ev_signal *, callback, int signum)
1071		1413
1072	=item ev_signal_set (ev_signal *, int signum)	1414	=item ev_signal_set (ev_signal *, int signum)
…		…
1083		1425
1084	=head2 C<ev_child> - watch out for process status changes	1426	=head2 C<ev_child> - watch out for process status changes
1085		1427
1086	Child watchers trigger when your process receives a SIGCHLD in response to	1428	Child watchers trigger when your process receives a SIGCHLD in response to
1087	some child status changes (most typically when a child of yours dies).	1429	some child status changes (most typically when a child of yours dies).
		1430
		1431	=head3 Watcher-Specific Functions and Data Members
1088		1432
1089	=over 4	1433	=over 4
1090		1434
1091	=item ev_child_init (ev_child *, callback, int pid)	1435	=item ev_child_init (ev_child *, callback, int pid)
1092		1436
…		…
1112	The process exit/trace status caused by C<rpid> (see your systems	1456	The process exit/trace status caused by C<rpid> (see your systems
1113	C<waitpid> and C<sys/wait.h> documentation for details).	1457	C<waitpid> and C<sys/wait.h> documentation for details).
1114		1458
1115	=back	1459	=back
1116		1460
		1461	=head3 Examples
		1462
1117	Example: try to exit cleanly on SIGINT and SIGTERM.	1463	Example: Try to exit cleanly on SIGINT and SIGTERM.
1118		1464
1119	static void	1465	static void
1120	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1466	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1121	{	1467	{
1122	ev_unloop (loop, EVUNLOOP_ALL);	1468	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1137	not exist" is a status change like any other. The condition "path does	1483	not exist" is a status change like any other. The condition "path does
1138	not exist" is signified by the C<st_nlink> field being zero (which is	1484	not exist" is signified by the C<st_nlink> field being zero (which is
1139	otherwise always forced to be at least one) and all the other fields of	1485	otherwise always forced to be at least one) and all the other fields of
1140	the stat buffer having unspecified contents.	1486	the stat buffer having unspecified contents.
1141		1487
		1488	The path I<should> be absolute and I<must not> end in a slash. If it is
		1489	relative and your working directory changes, the behaviour is undefined.
		1490
1142	Since there is no standard to do this, the portable implementation simply	1491	Since there is no standard to do this, the portable implementation simply
1143	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1492	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1144	can specify a recommended polling interval for this case. If you specify	1493	can specify a recommended polling interval for this case. If you specify
1145	a polling interval of C<0> (highly recommended!) then a I<suitable,	1494	a polling interval of C<0> (highly recommended!) then a I<suitable,
1146	unspecified default> value will be used (which you can expect to be around	1495	unspecified default> value will be used (which you can expect to be around
1147	five seconds, although this might change dynamically). Libev will also	1496	five seconds, although this might change dynamically). Libev will also
1148	impose a minimum interval which is currently around C<0.1>, but thats	1497	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1150		1499
1151	This watcher type is not meant for massive numbers of stat watchers,	1500	This watcher type is not meant for massive numbers of stat watchers,
1152	as even with OS-supported change notifications, this can be	1501	as even with OS-supported change notifications, this can be
1153	resource-intensive.	1502	resource-intensive.
1154		1503
1155	At the time of this writing, no specific OS backends are implemented, but	1504	At the time of this writing, only the Linux inotify interface is
1156	if demand increases, at least a kqueue and inotify backend will be added.	1505	implemented (implementing kqueue support is left as an exercise for the
		1506	reader). Inotify will be used to give hints only and should not change the
		1507	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1508	to fall back to regular polling again even with inotify, but changes are
		1509	usually detected immediately, and if the file exists there will be no
		1510	polling.
		1511
		1512	=head3 Inotify
		1513
		1514	When C<inotify (7)> support has been compiled into libev (generally only
		1515	available on Linux) and present at runtime, it will be used to speed up
		1516	change detection where possible. The inotify descriptor will be created lazily
		1517	when the first C<ev_stat> watcher is being started.
		1518
		1519	Inotify presense does not change the semantics of C<ev_stat> watchers
		1520	except that changes might be detected earlier, and in some cases, to avoid
		1521	making regular C<stat> calls. Even in the presense of inotify support
		1522	there are many cases where libev has to resort to regular C<stat> polling.
		1523
		1524	(There is no support for kqueue, as apparently it cannot be used to
		1525	implement this functionality, due to the requirement of having a file
		1526	descriptor open on the object at all times).
		1527
		1528	=head3 The special problem of stat time resolution
		1529
		1530	The C<stat ()> syscall only supports full-second resolution portably, and
		1531	even on systems where the resolution is higher, many filesystems still
		1532	only support whole seconds.
		1533
		1534	That means that, if the time is the only thing that changes, you might
		1535	miss updates: on the first update, C<ev_stat> detects a change and calls
		1536	your callback, which does something. When there is another update within
		1537	the same second, C<ev_stat> will be unable to detect it.
		1538
		1539	The solution to this is to delay acting on a change for a second (or till
		1540	the next second boundary), using a roughly one-second delay C<ev_timer>
		1541	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1542	is added to work around small timing inconsistencies of some operating
		1543	systems.
		1544
		1545	=head3 Watcher-Specific Functions and Data Members
1157		1546
1158	=over 4	1547	=over 4
1159		1548
1160	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1549	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1161		1550
…		…
1197	=item const char *path [read-only]	1586	=item const char *path [read-only]
1198		1587
1199	The filesystem path that is being watched.	1588	The filesystem path that is being watched.
1200		1589
1201	=back	1590	=back
		1591
		1592	=head3 Examples
1202		1593
1203	Example: Watch C</etc/passwd> for attribute changes.	1594	Example: Watch C</etc/passwd> for attribute changes.
1204		1595
1205	static void	1596	static void
1206	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1597	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1219	}	1610	}
1220		1611
1221	...	1612	...
1222	ev_stat passwd;	1613	ev_stat passwd;
1223		1614
1224	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1615	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1225	ev_stat_start (loop, &passwd);	1616	ev_stat_start (loop, &passwd);
1226		1617
		1618	Example: Like above, but additionally use a one-second delay so we do not
		1619	miss updates (however, frequent updates will delay processing, too, so
		1620	one might do the work both on C<ev_stat> callback invocation I<and> on
		1621	C<ev_timer> callback invocation).
		1622
		1623	static ev_stat passwd;
		1624	static ev_timer timer;
		1625
		1626	static void
		1627	timer_cb (EV_P_ ev_timer *w, int revents)
		1628	{
		1629	ev_timer_stop (EV_A_ w);
		1630
		1631	/* now it's one second after the most recent passwd change */
		1632	}
		1633
		1634	static void
		1635	stat_cb (EV_P_ ev_stat *w, int revents)
		1636	{
		1637	/* reset the one-second timer */
		1638	ev_timer_again (EV_A_ &timer);
		1639	}
		1640
		1641	...
		1642	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1643	ev_stat_start (loop, &passwd);
		1644	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1645
1227		1646
1228	=head2 C<ev_idle> - when you've got nothing better to do...	1647	=head2 C<ev_idle> - when you've got nothing better to do...
1229		1648
1230	Idle watchers trigger events when there are no other events are pending	1649	Idle watchers trigger events when no other events of the same or higher
1231	(prepare, check and other idle watchers do not count). That is, as long	1650	priority are pending (prepare, check and other idle watchers do not
1232	as your process is busy handling sockets or timeouts (or even signals,	1651	count).
1233	imagine) it will not be triggered. But when your process is idle all idle	1652
1234	watchers are being called again and again, once per event loop iteration -	1653	That is, as long as your process is busy handling sockets or timeouts
		1654	(or even signals, imagine) of the same or higher priority it will not be
		1655	triggered. But when your process is idle (or only lower-priority watchers
		1656	are pending), the idle watchers are being called once per event loop
1235	until stopped, that is, or your process receives more events and becomes	1657	iteration - until stopped, that is, or your process receives more events
1236	busy.	1658	and becomes busy again with higher priority stuff.
1237		1659
1238	The most noteworthy effect is that as long as any idle watchers are	1660	The most noteworthy effect is that as long as any idle watchers are
1239	active, the process will not block when waiting for new events.	1661	active, the process will not block when waiting for new events.
1240		1662
1241	Apart from keeping your process non-blocking (which is a useful	1663	Apart from keeping your process non-blocking (which is a useful
1242	effect on its own sometimes), idle watchers are a good place to do	1664	effect on its own sometimes), idle watchers are a good place to do
1243	"pseudo-background processing", or delay processing stuff to after the	1665	"pseudo-background processing", or delay processing stuff to after the
1244	event loop has handled all outstanding events.	1666	event loop has handled all outstanding events.
1245		1667
		1668	=head3 Watcher-Specific Functions and Data Members
		1669
1246	=over 4	1670	=over 4
1247		1671
1248	=item ev_idle_init (ev_signal *, callback)	1672	=item ev_idle_init (ev_signal *, callback)
1249		1673
1250	Initialises and configures the idle watcher - it has no parameters of any	1674	Initialises and configures the idle watcher - it has no parameters of any
1251	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1675	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1252	believe me.	1676	believe me.
1253		1677
1254	=back	1678	=back
1255		1679
		1680	=head3 Examples
		1681
1256	Example: dynamically allocate an C<ev_idle>, start it, and in the	1682	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1257	callback, free it. Alos, use no error checking, as usual.	1683	callback, free it. Also, use no error checking, as usual.
1258		1684
1259	static void	1685	static void
1260	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1686	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1261	{	1687	{
1262	free (w);	1688	free (w);
…		…
1307	with priority higher than or equal to the event loop and one coroutine	1733	with priority higher than or equal to the event loop and one coroutine
1308	of lower priority, but only once, using idle watchers to keep the event	1734	of lower priority, but only once, using idle watchers to keep the event
1309	loop from blocking if lower-priority coroutines are active, thus mapping	1735	loop from blocking if lower-priority coroutines are active, thus mapping
1310	low-priority coroutines to idle/background tasks).	1736	low-priority coroutines to idle/background tasks).
1311		1737
		1738	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1739	priority, to ensure that they are being run before any other watchers
		1740	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1741	too) should not activate ("feed") events into libev. While libev fully
		1742	supports this, they will be called before other C<ev_check> watchers
		1743	did their job. As C<ev_check> watchers are often used to embed other
		1744	(non-libev) event loops those other event loops might be in an unusable
		1745	state until their C<ev_check> watcher ran (always remind yourself to
		1746	coexist peacefully with others).
		1747
		1748	=head3 Watcher-Specific Functions and Data Members
		1749
1312	=over 4	1750	=over 4
1313		1751
1314	=item ev_prepare_init (ev_prepare *, callback)	1752	=item ev_prepare_init (ev_prepare *, callback)
1315		1753
1316	=item ev_check_init (ev_check *, callback)	1754	=item ev_check_init (ev_check *, callback)
…		…
1319	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1757	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1320	macros, but using them is utterly, utterly and completely pointless.	1758	macros, but using them is utterly, utterly and completely pointless.
1321		1759
1322	=back	1760	=back
1323		1761
1324	Example: To include a library such as adns, you would add IO watchers	1762	=head3 Examples
1325	and a timeout watcher in a prepare handler, as required by libadns, and	1763
		1764	There are a number of principal ways to embed other event loops or modules
		1765	into libev. Here are some ideas on how to include libadns into libev
		1766	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1767	use for an actually working example. Another Perl module named C<EV::Glib>
		1768	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1769	into the Glib event loop).
		1770
		1771	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1326	in a check watcher, destroy them and call into libadns. What follows is	1772	and in a check watcher, destroy them and call into libadns. What follows
1327	pseudo-code only of course:	1773	is pseudo-code only of course. This requires you to either use a low
		1774	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1775	the callbacks for the IO/timeout watchers might not have been called yet.
1328		1776
1329	static ev_io iow [nfd];	1777	static ev_io iow [nfd];
1330	static ev_timer tw;	1778	static ev_timer tw;
1331		1779
1332	static void	1780	static void
1333	io_cb (ev_loop *loop, ev_io *w, int revents)	1781	io_cb (ev_loop *loop, ev_io *w, int revents)
1334	{	1782	{
1335	// set the relevant poll flags
1336	// could also call adns_processreadable etc. here
1337	struct pollfd *fd = (struct pollfd *)w->data;
1338	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1339	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1340	}	1783	}
1341		1784
1342	// create io watchers for each fd and a timer before blocking	1785	// create io watchers for each fd and a timer before blocking
1343	static void	1786	static void
1344	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1787	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1345	{	1788	{
1346	int timeout = 3600000;truct pollfd fds [nfd];	1789	int timeout = 3600000;
		1790	struct pollfd fds [nfd];
1347	// actual code will need to loop here and realloc etc.	1791	// actual code will need to loop here and realloc etc.
1348	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1792	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1349		1793
1350	/* the callback is illegal, but won't be called as we stop during check */	1794	/* the callback is illegal, but won't be called as we stop during check */
1351	ev_timer_init (&tw, 0, timeout * 1e-3);	1795	ev_timer_init (&tw, 0, timeout * 1e-3);
1352	ev_timer_start (loop, &tw);	1796	ev_timer_start (loop, &tw);
1353		1797
1354	// create on ev_io per pollfd	1798	// create one ev_io per pollfd
1355	for (int i = 0; i < nfd; ++i)	1799	for (int i = 0; i < nfd; ++i)
1356	{	1800	{
1357	ev_io_init (iow + i, io_cb, fds [i].fd,	1801	ev_io_init (iow + i, io_cb, fds [i].fd,
1358	((fds [i].events & POLLIN ? EV_READ : 0)	1802	((fds [i].events & POLLIN ? EV_READ : 0)
1359	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1803	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1360		1804
1361	fds [i].revents = 0;	1805	fds [i].revents = 0;
1362	iow [i].data = fds + i;
1363	ev_io_start (loop, iow + i);	1806	ev_io_start (loop, iow + i);
1364	}	1807	}
1365	}	1808	}
1366		1809
1367	// stop all watchers after blocking	1810	// stop all watchers after blocking
…		…
1369	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1812	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1370	{	1813	{
1371	ev_timer_stop (loop, &tw);	1814	ev_timer_stop (loop, &tw);
1372		1815
1373	for (int i = 0; i < nfd; ++i)	1816	for (int i = 0; i < nfd; ++i)
		1817	{
		1818	// set the relevant poll flags
		1819	// could also call adns_processreadable etc. here
		1820	struct pollfd *fd = fds + i;
		1821	int revents = ev_clear_pending (iow + i);
		1822	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1823	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1824
		1825	// now stop the watcher
1374	ev_io_stop (loop, iow + i);	1826	ev_io_stop (loop, iow + i);
		1827	}
1375		1828
1376	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1829	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1830	}
		1831
		1832	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1833	in the prepare watcher and would dispose of the check watcher.
		1834
		1835	Method 3: If the module to be embedded supports explicit event
		1836	notification (adns does), you can also make use of the actual watcher
		1837	callbacks, and only destroy/create the watchers in the prepare watcher.
		1838
		1839	static void
		1840	timer_cb (EV_P_ ev_timer *w, int revents)
		1841	{
		1842	adns_state ads = (adns_state)w->data;
		1843	update_now (EV_A);
		1844
		1845	adns_processtimeouts (ads, &tv_now);
		1846	}
		1847
		1848	static void
		1849	io_cb (EV_P_ ev_io *w, int revents)
		1850	{
		1851	adns_state ads = (adns_state)w->data;
		1852	update_now (EV_A);
		1853
		1854	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1855	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1856	}
		1857
		1858	// do not ever call adns_afterpoll
		1859
		1860	Method 4: Do not use a prepare or check watcher because the module you
		1861	want to embed is too inflexible to support it. Instead, youc na override
		1862	their poll function. The drawback with this solution is that the main
		1863	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1864	this.
		1865
		1866	static gint
		1867	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1868	{
		1869	int got_events = 0;
		1870
		1871	for (n = 0; n < nfds; ++n)
		1872	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1873
		1874	if (timeout >= 0)
		1875	// create/start timer
		1876
		1877	// poll
		1878	ev_loop (EV_A_ 0);
		1879
		1880	// stop timer again
		1881	if (timeout >= 0)
		1882	ev_timer_stop (EV_A_ &to);
		1883
		1884	// stop io watchers again - their callbacks should have set
		1885	for (n = 0; n < nfds; ++n)
		1886	ev_io_stop (EV_A_ iow [n]);
		1887
		1888	return got_events;
1377	}	1889	}
1378		1890
1379		1891
1380	=head2 C<ev_embed> - when one backend isn't enough...	1892	=head2 C<ev_embed> - when one backend isn't enough...
1381		1893
…		…
1424	portable one.	1936	portable one.
1425		1937
1426	So when you want to use this feature you will always have to be prepared	1938	So when you want to use this feature you will always have to be prepared
1427	that you cannot get an embeddable loop. The recommended way to get around	1939	that you cannot get an embeddable loop. The recommended way to get around
1428	this is to have a separate variables for your embeddable loop, try to	1940	this is to have a separate variables for your embeddable loop, try to
1429	create it, and if that fails, use the normal loop for everything:	1941	create it, and if that fails, use the normal loop for everything.
		1942
		1943	=head3 Watcher-Specific Functions and Data Members
		1944
		1945	=over 4
		1946
		1947	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1948
		1949	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1950
		1951	Configures the watcher to embed the given loop, which must be
		1952	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1953	invoked automatically, otherwise it is the responsibility of the callback
		1954	to invoke it (it will continue to be called until the sweep has been done,
		1955	if you do not want thta, you need to temporarily stop the embed watcher).
		1956
		1957	=item ev_embed_sweep (loop, ev_embed *)
		1958
		1959	Make a single, non-blocking sweep over the embedded loop. This works
		1960	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1961	apropriate way for embedded loops.
		1962
		1963	=item struct ev_loop *other [read-only]
		1964
		1965	The embedded event loop.
		1966
		1967	=back
		1968
		1969	=head3 Examples
		1970
		1971	Example: Try to get an embeddable event loop and embed it into the default
		1972	event loop. If that is not possible, use the default loop. The default
		1973	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1974	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1975	used).
1430		1976
1431	struct ev_loop *loop_hi = ev_default_init (0);	1977	struct ev_loop *loop_hi = ev_default_init (0);
1432	struct ev_loop *loop_lo = 0;	1978	struct ev_loop *loop_lo = 0;
1433	struct ev_embed embed;	1979	struct ev_embed embed;
1434		1980
…		…
1445	ev_embed_start (loop_hi, &embed);	1991	ev_embed_start (loop_hi, &embed);
1446	}	1992	}
1447	else	1993	else
1448	loop_lo = loop_hi;	1994	loop_lo = loop_hi;
1449		1995
		1996	Example: Check if kqueue is available but not recommended and create
		1997	a kqueue backend for use with sockets (which usually work with any
		1998	kqueue implementation). Store the kqueue/socket-only event loop in
		1999	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2000
		2001	struct ev_loop *loop = ev_default_init (0);
		2002	struct ev_loop *loop_socket = 0;
		2003	struct ev_embed embed;
		2004
		2005	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2006	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2007	{
		2008	ev_embed_init (&embed, 0, loop_socket);
		2009	ev_embed_start (loop, &embed);
		2010	}
		2011
		2012	if (!loop_socket)
		2013	loop_socket = loop;
		2014
		2015	// now use loop_socket for all sockets, and loop for everything else
		2016
		2017
		2018	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2019
		2020	Fork watchers are called when a C<fork ()> was detected (usually because
		2021	whoever is a good citizen cared to tell libev about it by calling
		2022	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2023	event loop blocks next and before C<ev_check> watchers are being called,
		2024	and only in the child after the fork. If whoever good citizen calling
		2025	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2026	handlers will be invoked, too, of course.
		2027
		2028	=head3 Watcher-Specific Functions and Data Members
		2029
1450	=over 4	2030	=over 4
1451		2031
1452	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2032	=item ev_fork_init (ev_signal *, callback)
1453		2033
1454	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2034	Initialises and configures the fork watcher - it has no parameters of any
1455		2035	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1456	Configures the watcher to embed the given loop, which must be	2036	believe me.
1457	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1458	invoked automatically, otherwise it is the responsibility of the callback
1459	to invoke it (it will continue to be called until the sweep has been done,
1460	if you do not want thta, you need to temporarily stop the embed watcher).
1461
1462	=item ev_embed_sweep (loop, ev_embed *)
1463
1464	Make a single, non-blocking sweep over the embedded loop. This works
1465	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1466	apropriate way for embedded loops.
1467
1468	=item struct ev_loop *loop [read-only]
1469
1470	The embedded event loop.
1471		2037
1472	=back	2038	=back
1473		2039
1474		2040
1475	=head1 OTHER FUNCTIONS	2041	=head1 OTHER FUNCTIONS
…		…
1564		2130
1565	To use it,	2131	To use it,
1566		2132
1567	#include <ev++.h>	2133	#include <ev++.h>
1568		2134
1569	(it is not installed by default). This automatically includes F<ev.h>	2135	This automatically includes F<ev.h> and puts all of its definitions (many
1570	and puts all of its definitions (many of them macros) into the global	2136	of them macros) into the global namespace. All C++ specific things are
1571	namespace. All C++ specific things are put into the C<ev> namespace.	2137	put into the C<ev> namespace. It should support all the same embedding
		2138	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1572		2139
1573	It should support all the same embedding options as F<ev.h>, most notably	2140	Care has been taken to keep the overhead low. The only data member the C++
1574	C<EV_MULTIPLICITY>.	2141	classes add (compared to plain C-style watchers) is the event loop pointer
		2142	that the watcher is associated with (or no additional members at all if
		2143	you disable C<EV_MULTIPLICITY> when embedding libev).
		2144
		2145	Currently, functions, and static and non-static member functions can be
		2146	used as callbacks. Other types should be easy to add as long as they only
		2147	need one additional pointer for context. If you need support for other
		2148	types of functors please contact the author (preferably after implementing
		2149	it).
1575		2150
1576	Here is a list of things available in the C<ev> namespace:	2151	Here is a list of things available in the C<ev> namespace:
1577		2152
1578	=over 4	2153	=over 4
1579		2154
…		…
1595		2170
1596	All of those classes have these methods:	2171	All of those classes have these methods:
1597		2172
1598	=over 4	2173	=over 4
1599		2174
1600	=item ev::TYPE::TYPE (object *, object::method *)	2175	=item ev::TYPE::TYPE ()
1601		2176
1602	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2177	=item ev::TYPE::TYPE (struct ev_loop *)
1603		2178
1604	=item ev::TYPE::~TYPE	2179	=item ev::TYPE::~TYPE
1605		2180
1606	The constructor takes a pointer to an object and a method pointer to	2181	The constructor (optionally) takes an event loop to associate the watcher
1607	the event handler callback to call in this class. The constructor calls	2182	with. If it is omitted, it will use C<EV_DEFAULT>.
1608	C<ev_init> for you, which means you have to call the C<set> method	2183
1609	before starting it. If you do not specify a loop then the constructor	2184	The constructor calls C<ev_init> for you, which means you have to call the
1610	automatically associates the default loop with this watcher.	2185	C<set> method before starting it.
		2186
		2187	It will not set a callback, however: You have to call the templated C<set>
		2188	method to set a callback before you can start the watcher.
		2189
		2190	(The reason why you have to use a method is a limitation in C++ which does
		2191	not allow explicit template arguments for constructors).
1611		2192
1612	The destructor automatically stops the watcher if it is active.	2193	The destructor automatically stops the watcher if it is active.
		2194
		2195	=item w->set<class, &class::method> (object *)
		2196
		2197	This method sets the callback method to call. The method has to have a
		2198	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2199	first argument and the C<revents> as second. The object must be given as
		2200	parameter and is stored in the C<data> member of the watcher.
		2201
		2202	This method synthesizes efficient thunking code to call your method from
		2203	the C callback that libev requires. If your compiler can inline your
		2204	callback (i.e. it is visible to it at the place of the C<set> call and
		2205	your compiler is good :), then the method will be fully inlined into the
		2206	thunking function, making it as fast as a direct C callback.
		2207
		2208	Example: simple class declaration and watcher initialisation
		2209
		2210	struct myclass
		2211	{
		2212	void io_cb (ev::io &w, int revents) { }
		2213	}
		2214
		2215	myclass obj;
		2216	ev::io iow;
		2217	iow.set <myclass, &myclass::io_cb> (&obj);
		2218
		2219	=item w->set<function> (void *data = 0)
		2220
		2221	Also sets a callback, but uses a static method or plain function as
		2222	callback. The optional C<data> argument will be stored in the watcher's
		2223	C<data> member and is free for you to use.
		2224
		2225	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2226
		2227	See the method-C<set> above for more details.
		2228
		2229	Example:
		2230
		2231	static void io_cb (ev::io &w, int revents) { }
		2232	iow.set <io_cb> ();
1613		2233
1614	=item w->set (struct ev_loop *)	2234	=item w->set (struct ev_loop *)
1615		2235
1616	Associates a different C<struct ev_loop> with this watcher. You can only	2236	Associates a different C<struct ev_loop> with this watcher. You can only
1617	do this when the watcher is inactive (and not pending either).	2237	do this when the watcher is inactive (and not pending either).
1618		2238
1619	=item w->set ([args])	2239	=item w->set ([args])
1620		2240
1621	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2241	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1622	called at least once. Unlike the C counterpart, an active watcher gets	2242	called at least once. Unlike the C counterpart, an active watcher gets
1623	automatically stopped and restarted.	2243	automatically stopped and restarted when reconfiguring it with this
		2244	method.
1624		2245
1625	=item w->start ()	2246	=item w->start ()
1626		2247
1627	Starts the watcher. Note that there is no C<loop> argument as the	2248	Starts the watcher. Note that there is no C<loop> argument, as the
1628	constructor already takes the loop.	2249	constructor already stores the event loop.
1629		2250
1630	=item w->stop ()	2251	=item w->stop ()
1631		2252
1632	Stops the watcher if it is active. Again, no C<loop> argument.	2253	Stops the watcher if it is active. Again, no C<loop> argument.
1633		2254
1634	=item w->again () C<ev::timer>, C<ev::periodic> only	2255	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1635		2256
1636	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2257	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1637	C<ev_TYPE_again> function.	2258	C<ev_TYPE_again> function.
1638		2259
1639	=item w->sweep () C<ev::embed> only	2260	=item w->sweep () (C<ev::embed> only)
1640		2261
1641	Invokes C<ev_embed_sweep>.	2262	Invokes C<ev_embed_sweep>.
1642		2263
1643	=item w->update () C<ev::stat> only	2264	=item w->update () (C<ev::stat> only)
1644		2265
1645	Invokes C<ev_stat_stat>.	2266	Invokes C<ev_stat_stat>.
1646		2267
1647	=back	2268	=back
1648		2269
…		…
1658		2279
1659	myclass ();	2280	myclass ();
1660	}	2281	}
1661		2282
1662	myclass::myclass (int fd)	2283	myclass::myclass (int fd)
1663	: io (this, &myclass::io_cb),
1664	idle (this, &myclass::idle_cb)
1665	{	2284	{
		2285	io .set <myclass, &myclass::io_cb > (this);
		2286	idle.set <myclass, &myclass::idle_cb> (this);
		2287
1666	io.start (fd, ev::READ);	2288	io.start (fd, ev::READ);
1667	}	2289	}
		2290
		2291
		2292	=head1 MACRO MAGIC
		2293
		2294	Libev can be compiled with a variety of options, the most fundamantal
		2295	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2296	functions and callbacks have an initial C<struct ev_loop *> argument.
		2297
		2298	To make it easier to write programs that cope with either variant, the
		2299	following macros are defined:
		2300
		2301	=over 4
		2302
		2303	=item C<EV_A>, C<EV_A_>
		2304
		2305	This provides the loop I<argument> for functions, if one is required ("ev
		2306	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2307	C<EV_A_> is used when other arguments are following. Example:
		2308
		2309	ev_unref (EV_A);
		2310	ev_timer_add (EV_A_ watcher);
		2311	ev_loop (EV_A_ 0);
		2312
		2313	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2314	which is often provided by the following macro.
		2315
		2316	=item C<EV_P>, C<EV_P_>
		2317
		2318	This provides the loop I<parameter> for functions, if one is required ("ev
		2319	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2320	C<EV_P_> is used when other parameters are following. Example:
		2321
		2322	// this is how ev_unref is being declared
		2323	static void ev_unref (EV_P);
		2324
		2325	// this is how you can declare your typical callback
		2326	static void cb (EV_P_ ev_timer *w, int revents)
		2327
		2328	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2329	suitable for use with C<EV_A>.
		2330
		2331	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2332
		2333	Similar to the other two macros, this gives you the value of the default
		2334	loop, if multiple loops are supported ("ev loop default").
		2335
		2336	=back
		2337
		2338	Example: Declare and initialise a check watcher, utilising the above
		2339	macros so it will work regardless of whether multiple loops are supported
		2340	or not.
		2341
		2342	static void
		2343	check_cb (EV_P_ ev_timer *w, int revents)
		2344	{
		2345	ev_check_stop (EV_A_ w);
		2346	}
		2347
		2348	ev_check check;
		2349	ev_check_init (&check, check_cb);
		2350	ev_check_start (EV_DEFAULT_ &check);
		2351	ev_loop (EV_DEFAULT_ 0);
1668		2352
1669	=head1 EMBEDDING	2353	=head1 EMBEDDING
1670		2354
1671	Libev can (and often is) directly embedded into host	2355	Libev can (and often is) directly embedded into host
1672	applications. Examples of applications that embed it include the Deliantra	2356	applications. Examples of applications that embed it include the Deliantra
1673	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2357	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1674	and rxvt-unicode.	2358	and rxvt-unicode.
1675		2359
1676	The goal is to enable you to just copy the neecssary files into your	2360	The goal is to enable you to just copy the necessary files into your
1677	source directory without having to change even a single line in them, so	2361	source directory without having to change even a single line in them, so
1678	you can easily upgrade by simply copying (or having a checked-out copy of	2362	you can easily upgrade by simply copying (or having a checked-out copy of
1679	libev somewhere in your source tree).	2363	libev somewhere in your source tree).
1680		2364
1681	=head2 FILESETS	2365	=head2 FILESETS
…		…
1712	ev_vars.h	2396	ev_vars.h
1713	ev_wrap.h	2397	ev_wrap.h
1714		2398
1715	ev_win32.c required on win32 platforms only	2399	ev_win32.c required on win32 platforms only
1716		2400
1717	ev_select.c only when select backend is enabled (which is by default)	2401	ev_select.c only when select backend is enabled (which is enabled by default)
1718	ev_poll.c only when poll backend is enabled (disabled by default)	2402	ev_poll.c only when poll backend is enabled (disabled by default)
1719	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2403	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1720	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2404	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1721	ev_port.c only when the solaris port backend is enabled (disabled by default)	2405	ev_port.c only when the solaris port backend is enabled (disabled by default)
1722		2406
…		…
1771		2455
1772	If defined to be C<1>, libev will try to detect the availability of the	2456	If defined to be C<1>, libev will try to detect the availability of the
1773	monotonic clock option at both compiletime and runtime. Otherwise no use	2457	monotonic clock option at both compiletime and runtime. Otherwise no use
1774	of the monotonic clock option will be attempted. If you enable this, you	2458	of the monotonic clock option will be attempted. If you enable this, you
1775	usually have to link against librt or something similar. Enabling it when	2459	usually have to link against librt or something similar. Enabling it when
1776	the functionality isn't available is safe, though, althoguh you have	2460	the functionality isn't available is safe, though, although you have
1777	to make sure you link against any libraries where the C<clock_gettime>	2461	to make sure you link against any libraries where the C<clock_gettime>
1778	function is hiding in (often F<-lrt>).	2462	function is hiding in (often F<-lrt>).
1779		2463
1780	=item EV_USE_REALTIME	2464	=item EV_USE_REALTIME
1781		2465
1782	If defined to be C<1>, libev will try to detect the availability of the	2466	If defined to be C<1>, libev will try to detect the availability of the
1783	realtime clock option at compiletime (and assume its availability at	2467	realtime clock option at compiletime (and assume its availability at
1784	runtime if successful). Otherwise no use of the realtime clock option will	2468	runtime if successful). Otherwise no use of the realtime clock option will
1785	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2469	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1786	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2470	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1787	in the description of C<EV_USE_MONOTONIC>, though.	2471	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2472
		2473	=item EV_USE_NANOSLEEP
		2474
		2475	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2476	and will use it for delays. Otherwise it will use C<select ()>.
1788		2477
1789	=item EV_USE_SELECT	2478	=item EV_USE_SELECT
1790		2479
1791	If undefined or defined to be C<1>, libev will compile in support for the	2480	If undefined or defined to be C<1>, libev will compile in support for the
1792	C<select>(2) backend. No attempt at autodetection will be done: if no	2481	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1810	wants osf handles on win32 (this is the case when the select to	2499	wants osf handles on win32 (this is the case when the select to
1811	be used is the winsock select). This means that it will call	2500	be used is the winsock select). This means that it will call
1812	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2501	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1813	it is assumed that all these functions actually work on fds, even	2502	it is assumed that all these functions actually work on fds, even
1814	on win32. Should not be defined on non-win32 platforms.	2503	on win32. Should not be defined on non-win32 platforms.
		2504
		2505	=item EV_FD_TO_WIN32_HANDLE
		2506
		2507	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2508	file descriptors to socket handles. When not defining this symbol (the
		2509	default), then libev will call C<_get_osfhandle>, which is usually
		2510	correct. In some cases, programs use their own file descriptor management,
		2511	in which case they can provide this function to map fds to socket handles.
1815		2512
1816	=item EV_USE_POLL	2513	=item EV_USE_POLL
1817		2514
1818	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2515	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1819	backend. Otherwise it will be enabled on non-win32 platforms. It	2516	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
1847		2544
1848	=item EV_USE_DEVPOLL	2545	=item EV_USE_DEVPOLL
1849		2546
1850	reserved for future expansion, works like the USE symbols above.	2547	reserved for future expansion, works like the USE symbols above.
1851		2548
		2549	=item EV_USE_INOTIFY
		2550
		2551	If defined to be C<1>, libev will compile in support for the Linux inotify
		2552	interface to speed up C<ev_stat> watchers. Its actual availability will
		2553	be detected at runtime.
		2554
1852	=item EV_H	2555	=item EV_H
1853		2556
1854	The name of the F<ev.h> header file used to include it. The default if	2557	The name of the F<ev.h> header file used to include it. The default if
1855	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2558	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
1856	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2559	virtually rename the F<ev.h> header file in case of conflicts.
1857		2560
1858	=item EV_CONFIG_H	2561	=item EV_CONFIG_H
1859		2562
1860	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2563	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1861	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2564	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1862	C<EV_H>, above.	2565	C<EV_H>, above.
1863		2566
1864	=item EV_EVENT_H	2567	=item EV_EVENT_H
1865		2568
1866	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2569	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1867	of how the F<event.h> header can be found.	2570	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
1868		2571
1869	=item EV_PROTOTYPES	2572	=item EV_PROTOTYPES
1870		2573
1871	If defined to be C<0>, then F<ev.h> will not define any function	2574	If defined to be C<0>, then F<ev.h> will not define any function
1872	prototypes, but still define all the structs and other symbols. This is	2575	prototypes, but still define all the structs and other symbols. This is
…		…
1879	will have the C<struct ev_loop *> as first argument, and you can create	2582	will have the C<struct ev_loop *> as first argument, and you can create
1880	additional independent event loops. Otherwise there will be no support	2583	additional independent event loops. Otherwise there will be no support
1881	for multiple event loops and there is no first event loop pointer	2584	for multiple event loops and there is no first event loop pointer
1882	argument. Instead, all functions act on the single default loop.	2585	argument. Instead, all functions act on the single default loop.
1883		2586
		2587	=item EV_MINPRI
		2588
		2589	=item EV_MAXPRI
		2590
		2591	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2592	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2593	provide for more priorities by overriding those symbols (usually defined
		2594	to be C<-2> and C<2>, respectively).
		2595
		2596	When doing priority-based operations, libev usually has to linearly search
		2597	all the priorities, so having many of them (hundreds) uses a lot of space
		2598	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2599	fine.
		2600
		2601	If your embedding app does not need any priorities, defining these both to
		2602	C<0> will save some memory and cpu.
		2603
1884	=item EV_PERIODIC_ENABLE	2604	=item EV_PERIODIC_ENABLE
1885		2605
1886	If undefined or defined to be C<1>, then periodic timers are supported. If	2606	If undefined or defined to be C<1>, then periodic timers are supported. If
1887	defined to be C<0>, then they are not. Disabling them saves a few kB of	2607	defined to be C<0>, then they are not. Disabling them saves a few kB of
1888	code.	2608	code.
1889		2609
		2610	=item EV_IDLE_ENABLE
		2611
		2612	If undefined or defined to be C<1>, then idle watchers are supported. If
		2613	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2614	code.
		2615
1890	=item EV_EMBED_ENABLE	2616	=item EV_EMBED_ENABLE
1891		2617
1892	If undefined or defined to be C<1>, then embed watchers are supported. If	2618	If undefined or defined to be C<1>, then embed watchers are supported. If
1893	defined to be C<0>, then they are not.	2619	defined to be C<0>, then they are not.
1894		2620
1895	=item EV_STAT_ENABLE	2621	=item EV_STAT_ENABLE
1896		2622
1897	If undefined or defined to be C<1>, then stat watchers are supported. If	2623	If undefined or defined to be C<1>, then stat watchers are supported. If
		2624	defined to be C<0>, then they are not.
		2625
		2626	=item EV_FORK_ENABLE
		2627
		2628	If undefined or defined to be C<1>, then fork watchers are supported. If
1898	defined to be C<0>, then they are not.	2629	defined to be C<0>, then they are not.
1899		2630
1900	=item EV_MINIMAL	2631	=item EV_MINIMAL
1901		2632
1902	If you need to shave off some kilobytes of code at the expense of some	2633	If you need to shave off some kilobytes of code at the expense of some
1903	speed, define this symbol to C<1>. Currently only used for gcc to override	2634	speed, define this symbol to C<1>. Currently only used for gcc to override
1904	some inlining decisions, saves roughly 30% codesize of amd64.	2635	some inlining decisions, saves roughly 30% codesize of amd64.
		2636
		2637	=item EV_PID_HASHSIZE
		2638
		2639	C<ev_child> watchers use a small hash table to distribute workload by
		2640	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2641	than enough. If you need to manage thousands of children you might want to
		2642	increase this value (I<must> be a power of two).
		2643
		2644	=item EV_INOTIFY_HASHSIZE
		2645
		2646	C<ev_stat> watchers use a small hash table to distribute workload by
		2647	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2648	usually more than enough. If you need to manage thousands of C<ev_stat>
		2649	watchers you might want to increase this value (I<must> be a power of
		2650	two).
1905		2651
1906	=item EV_COMMON	2652	=item EV_COMMON
1907		2653
1908	By default, all watchers have a C<void *data> member. By redefining	2654	By default, all watchers have a C<void *data> member. By redefining
1909	this macro to a something else you can include more and other types of	2655	this macro to a something else you can include more and other types of
…		…
1922		2668
1923	=item ev_set_cb (ev, cb)	2669	=item ev_set_cb (ev, cb)
1924		2670
1925	Can be used to change the callback member declaration in each watcher,	2671	Can be used to change the callback member declaration in each watcher,
1926	and the way callbacks are invoked and set. Must expand to a struct member	2672	and the way callbacks are invoked and set. Must expand to a struct member
1927	definition and a statement, respectively. See the F<ev.v> header file for	2673	definition and a statement, respectively. See the F<ev.h> header file for
1928	their default definitions. One possible use for overriding these is to	2674	their default definitions. One possible use for overriding these is to
1929	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2675	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1930	method calls instead of plain function calls in C++.	2676	method calls instead of plain function calls in C++.
		2677
		2678	=head2 EXPORTED API SYMBOLS
		2679
		2680	If you need to re-export the API (e.g. via a dll) and you need a list of
		2681	exported symbols, you can use the provided F<Symbol.*> files which list
		2682	all public symbols, one per line:
		2683
		2684	Symbols.ev for libev proper
		2685	Symbols.event for the libevent emulation
		2686
		2687	This can also be used to rename all public symbols to avoid clashes with
		2688	multiple versions of libev linked together (which is obviously bad in
		2689	itself, but sometimes it is inconvinient to avoid this).
		2690
		2691	A sed command like this will create wrapper C<#define>'s that you need to
		2692	include before including F<ev.h>:
		2693
		2694	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2695
		2696	This would create a file F<wrap.h> which essentially looks like this:
		2697
		2698	#define ev_backend myprefix_ev_backend
		2699	#define ev_check_start myprefix_ev_check_start
		2700	#define ev_check_stop myprefix_ev_check_stop
		2701	...
1931		2702
1932	=head2 EXAMPLES	2703	=head2 EXAMPLES
1933		2704
1934	For a real-world example of a program the includes libev	2705	For a real-world example of a program the includes libev
1935	verbatim, you can have a look at the EV perl module	2706	verbatim, you can have a look at the EV perl module
…		…
1938	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2709	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1939	will be compiled. It is pretty complex because it provides its own header	2710	will be compiled. It is pretty complex because it provides its own header
1940	file.	2711	file.
1941		2712
1942	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2713	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1943	that everybody includes and which overrides some autoconf choices:	2714	that everybody includes and which overrides some configure choices:
1944		2715
		2716	#define EV_MINIMAL 1
1945	#define EV_USE_POLL 0	2717	#define EV_USE_POLL 0
1946	#define EV_MULTIPLICITY 0	2718	#define EV_MULTIPLICITY 0
1947	#define EV_PERIODICS 0	2719	#define EV_PERIODIC_ENABLE 0
		2720	#define EV_STAT_ENABLE 0
		2721	#define EV_FORK_ENABLE 0
1948	#define EV_CONFIG_H <config.h>	2722	#define EV_CONFIG_H <config.h>
		2723	#define EV_MINPRI 0
		2724	#define EV_MAXPRI 0
1949		2725
1950	#include "ev++.h"	2726	#include "ev++.h"
1951		2727
1952	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2728	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1953		2729
…		…
1959		2735
1960	In this section the complexities of (many of) the algorithms used inside	2736	In this section the complexities of (many of) the algorithms used inside
1961	libev will be explained. For complexity discussions about backends see the	2737	libev will be explained. For complexity discussions about backends see the
1962	documentation for C<ev_default_init>.	2738	documentation for C<ev_default_init>.
1963		2739
		2740	All of the following are about amortised time: If an array needs to be
		2741	extended, libev needs to realloc and move the whole array, but this
		2742	happens asymptotically never with higher number of elements, so O(1) might
		2743	mean it might do a lengthy realloc operation in rare cases, but on average
		2744	it is much faster and asymptotically approaches constant time.
		2745
1964	=over 4	2746	=over 4
1965		2747
1966	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2748	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
1967		2749
		2750	This means that, when you have a watcher that triggers in one hour and
		2751	there are 100 watchers that would trigger before that then inserting will
		2752	have to skip roughly seven (C<ld 100>) of these watchers.
		2753
1968	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2754	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2755
		2756	That means that changing a timer costs less than removing/adding them
		2757	as only the relative motion in the event queue has to be paid for.
1969		2758
1970	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2759	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
1971		2760
		2761	These just add the watcher into an array or at the head of a list.
		2762
1972	=item Stopping check/prepare/idle watchers: O(1)	2763	=item Stopping check/prepare/idle watchers: O(1)
1973		2764
1974	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2765	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
1975		2766
		2767	These watchers are stored in lists then need to be walked to find the
		2768	correct watcher to remove. The lists are usually short (you don't usually
		2769	have many watchers waiting for the same fd or signal).
		2770
1976	=item Finding the next timer per loop iteration: O(1)	2771	=item Finding the next timer in each loop iteration: O(1)
		2772
		2773	By virtue of using a binary heap, the next timer is always found at the
		2774	beginning of the storage array.
1977		2775
1978	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2776	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
1979		2777
1980	=item Activating one watcher: O(1)	2778	A change means an I/O watcher gets started or stopped, which requires
		2779	libev to recalculate its status (and possibly tell the kernel, depending
		2780	on backend and wether C<ev_io_set> was used).
		2781
		2782	=item Activating one watcher (putting it into the pending state): O(1)
		2783
		2784	=item Priority handling: O(number_of_priorities)
		2785
		2786	Priorities are implemented by allocating some space for each
		2787	priority. When doing priority-based operations, libev usually has to
		2788	linearly search all the priorities, but starting/stopping and activating
		2789	watchers becomes O(1) w.r.t. prioritiy handling.
1981		2790
1982	=back	2791	=back
1983		2792
1984		2793
		2794	=head1 Win32 platform limitations and workarounds
		2795
		2796	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2797	requires, and its I/O model is fundamentally incompatible with the POSIX
		2798	model. Libev still offers limited functionality on this platform in
		2799	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2800	descriptors. This only applies when using Win32 natively, not when using
		2801	e.g. cygwin.
		2802
		2803	There is no supported compilation method available on windows except
		2804	embedding it into other applications.
		2805
		2806	Due to the many, low, and arbitrary limits on the win32 platform and the
		2807	abysmal performance of winsockets, using a large number of sockets is not
		2808	recommended (and not reasonable). If your program needs to use more than
		2809	a hundred or so sockets, then likely it needs to use a totally different
		2810	implementation for windows, as libev offers the POSIX model, which cannot
		2811	be implemented efficiently on windows (microsoft monopoly games).
		2812
		2813	=over 4
		2814
		2815	=item The winsocket select function
		2816
		2817	The winsocket C<select> function doesn't follow POSIX in that it requires
		2818	socket I<handles> and not socket I<file descriptors>. This makes select
		2819	very inefficient, and also requires a mapping from file descriptors
		2820	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2821	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2822	symbols for more info.
		2823
		2824	The configuration for a "naked" win32 using the microsoft runtime
		2825	libraries and raw winsocket select is:
		2826
		2827	#define EV_USE_SELECT 1
		2828	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2829
		2830	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2831	complexity in the O(n²) range when using win32.
		2832
		2833	=item Limited number of file descriptors
		2834
		2835	Windows has numerous arbitrary (and low) limits on things. Early versions
		2836	of winsocket's select only supported waiting for a max. of C<64> handles
		2837	(probably owning to the fact that all windows kernels can only wait for
		2838	C<64> things at the same time internally; microsoft recommends spawning a
		2839	chain of threads and wait for 63 handles and the previous thread in each).
		2840
		2841	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2842	to some high number (e.g. C<2048>) before compiling the winsocket select
		2843	call (which might be in libev or elsewhere, for example, perl does its own
		2844	select emulation on windows).
		2845
		2846	Another limit is the number of file descriptors in the microsoft runtime
		2847	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2848	or something like this inside microsoft). You can increase this by calling
		2849	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2850	arbitrary limit), but is broken in many versions of the microsoft runtime
		2851	libraries.
		2852
		2853	This might get you to about C<512> or C<2048> sockets (depending on
		2854	windows version and/or the phase of the moon). To get more, you need to
		2855	wrap all I/O functions and provide your own fd management, but the cost of
		2856	calling select (O(n²)) will likely make this unworkable.
		2857
		2858	=back
		2859
		2860
1985	=head1 AUTHOR	2861	=head1 AUTHOR
1986		2862
1987	Marc Lehmann <libev@schmorp.de>.	2863	Marc Lehmann <libev@schmorp.de>.
1988		2864

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines