ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.46 by root, Mon Nov 26 10:20:43 2007 UTC vs.
Revision 1.111 by root, Tue Dec 25 18:01:20 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
		555	- Before the first iteration, call any pending watchers.
409	* If there are no active watchers (reference count is zero), return.	556	* If there are no active watchers (reference count is zero), return.
410	- Queue prepare watchers and then call all outstanding watchers.	557	- Queue all prepare watchers and then call all outstanding watchers.
411	- If we have been forked, recreate the kernel state.	558	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	559	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	560	- Update the "event loop time".
414	- Calculate for how long to block.	561	- Calculate for how long to block.
415	- Block the process, waiting for any events.	562	- Block the process, waiting for any events.
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	570	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	571	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	573	were used, return, otherwise continue with step *.
427		574
428	Example: queue some jobs and then loop until no events are outsanding	575	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	576	anymore.
430		577
431	... queue jobs here, make sure they register event watchers as long	578	... 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..)	579	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	580	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	600	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	601	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	602	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>.	603	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		604
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	606	running when nothing else is active.
460		607
461	struct dv_signal exitsig;	608	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	609	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	610	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	611	evf_unref (loop);
465		612
466	Example: for some weird reason, unregister the above signal handler again.	613	Example: For some weird reason, unregister the above signal handler again.
467		614
468	ev_ref (myloop);	615	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	616	ev_signal_stop (loop, &exitsig);
		617
		618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		619
		620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		621
		622	These advanced functions influence the time that libev will spend waiting
		623	for events. Both are by default C<0>, meaning that libev will try to
		624	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		625
		626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		627	allows libev to delay invocation of I/O and timer/periodic callbacks to
		628	increase efficiency of loop iterations.
		629
		630	The background is that sometimes your program runs just fast enough to
		631	handle one (or very few) event(s) per loop iteration. While this makes
		632	the program responsive, it also wastes a lot of CPU time to poll for new
		633	events, especially with backends like C<select ()> which have a high
		634	overhead for the actual polling but can deliver many events at once.
		635
		636	By setting a higher I<io collect interval> you allow libev to spend more
		637	time collecting I/O events, so you can handle more events per iteration,
		638	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		639	C<ev_timer>) will be not affected. Setting this to a non-null value will
		640	introduce an additional C<ev_sleep ()> call into most loop iterations.
		641
		642	Likewise, by setting a higher I<timeout collect interval> you allow libev
		643	to spend more time collecting timeouts, at the expense of increased
		644	latency (the watcher callback will be called later). C<ev_io> watchers
		645	will not be affected. Setting this to a non-null value will not introduce
		646	any overhead in libev.
		647
		648	Many (busy) programs can usually benefit by setting the io collect
		649	interval to a value near C<0.1> or so, which is often enough for
		650	interactive servers (of course not for games), likewise for timeouts. It
		651	usually doesn't make much sense to set it to a lower value than C<0.01>,
		652	as this approsaches the timing granularity of most systems.
470		653
471	=back	654	=back
472		655
473		656
474	=head1 ANATOMY OF A WATCHER	657	=head1 ANATOMY OF A WATCHER
…		…
544	The signal specified in the C<ev_signal> watcher has been received by a thread.	727	The signal specified in the C<ev_signal> watcher has been received by a thread.
545		728
546	=item C<EV_CHILD>	729	=item C<EV_CHILD>
547		730
548	The pid specified in the C<ev_child> watcher has received a status change.	731	The pid specified in the C<ev_child> watcher has received a status change.
		732
		733	=item C<EV_STAT>
		734
		735	The path specified in the C<ev_stat> watcher changed its attributes somehow.
549		736
550	=item C<EV_IDLE>	737	=item C<EV_IDLE>
551		738
552	The C<ev_idle> watcher has determined that you have nothing better to do.	739	The C<ev_idle> watcher has determined that you have nothing better to do.
553		740
…		…
561	received events. Callbacks of both watcher types can start and stop as	748	received events. Callbacks of both watcher types can start and stop as
562	many watchers as they want, and all of them will be taken into account	749	many watchers as they want, and all of them will be taken into account
563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	750	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
564	C<ev_loop> from blocking).	751	C<ev_loop> from blocking).
565		752
		753	=item C<EV_EMBED>
		754
		755	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		756
		757	=item C<EV_FORK>
		758
		759	The event loop has been resumed in the child process after fork (see
		760	C<ev_fork>).
		761
566	=item C<EV_ERROR>	762	=item C<EV_ERROR>
567		763
568	An unspecified error has occured, the watcher has been stopped. This might	764	An unspecified error has occured, the watcher has been stopped. This might
569	happen because the watcher could not be properly started because libev	765	happen because the watcher could not be properly started because libev
570	ran out of memory, a file descriptor was found to be closed or any other	766	ran out of memory, a file descriptor was found to be closed or any other
…		…
641	=item bool ev_is_pending (ev_TYPE *watcher)	837	=item bool ev_is_pending (ev_TYPE *watcher)
642		838
643	Returns a true value iff the watcher is pending, (i.e. it has outstanding	839	Returns a true value iff the watcher is pending, (i.e. it has outstanding
644	events but its callback has not yet been invoked). As long as a watcher	840	events but its callback has not yet been invoked). As long as a watcher
645	is pending (but not active) you must not call an init function on it (but	841	is pending (but not active) you must not call an init function on it (but
646	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	842	C<ev_TYPE_set> is safe), you must not change its priority, and you must
647	libev (e.g. you cnanot C<free ()> it).	843	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		844	it).
648		845
649	=item callback = ev_cb (ev_TYPE *watcher)	846	=item callback ev_cb (ev_TYPE *watcher)
650		847
651	Returns the callback currently set on the watcher.	848	Returns the callback currently set on the watcher.
652		849
653	=item ev_cb_set (ev_TYPE *watcher, callback)	850	=item ev_cb_set (ev_TYPE *watcher, callback)
654		851
655	Change the callback. You can change the callback at virtually any time	852	Change the callback. You can change the callback at virtually any time
656	(modulo threads).	853	(modulo threads).
		854
		855	=item ev_set_priority (ev_TYPE *watcher, priority)
		856
		857	=item int ev_priority (ev_TYPE *watcher)
		858
		859	Set and query the priority of the watcher. The priority is a small
		860	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		861	(default: C<-2>). Pending watchers with higher priority will be invoked
		862	before watchers with lower priority, but priority will not keep watchers
		863	from being executed (except for C<ev_idle> watchers).
		864
		865	This means that priorities are I<only> used for ordering callback
		866	invocation after new events have been received. This is useful, for
		867	example, to reduce latency after idling, or more often, to bind two
		868	watchers on the same event and make sure one is called first.
		869
		870	If you need to suppress invocation when higher priority events are pending
		871	you need to look at C<ev_idle> watchers, which provide this functionality.
		872
		873	You I<must not> change the priority of a watcher as long as it is active or
		874	pending.
		875
		876	The default priority used by watchers when no priority has been set is
		877	always C<0>, which is supposed to not be too high and not be too low :).
		878
		879	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		880	fine, as long as you do not mind that the priority value you query might
		881	or might not have been adjusted to be within valid range.
		882
		883	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		884
		885	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		886	C<loop> nor C<revents> need to be valid as long as the watcher callback
		887	can deal with that fact.
		888
		889	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		890
		891	If the watcher is pending, this function returns clears its pending status
		892	and returns its C<revents> bitset (as if its callback was invoked). If the
		893	watcher isn't pending it does nothing and returns C<0>.
657		894
658	=back	895	=back
659		896
660		897
661	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
682	{	919	{
683	struct my_io *w = (struct my_io *)w_;	920	struct my_io *w = (struct my_io *)w_;
684	...	921	...
685	}	922	}
686		923
687	More interesting and less C-conformant ways of catsing your callback type	924	More interesting and less C-conformant ways of casting your callback type
688	have been omitted....	925	instead have been omitted.
		926
		927	Another common scenario is having some data structure with multiple
		928	watchers:
		929
		930	struct my_biggy
		931	{
		932	int some_data;
		933	ev_timer t1;
		934	ev_timer t2;
		935	}
		936
		937	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		938	you need to use C<offsetof>:
		939
		940	#include <stddef.h>
		941
		942	static void
		943	t1_cb (EV_P_ struct ev_timer *w, int revents)
		944	{
		945	struct my_biggy big = (struct my_biggy *
		946	(((char *)w) - offsetof (struct my_biggy, t1));
		947	}
		948
		949	static void
		950	t2_cb (EV_P_ struct ev_timer *w, int revents)
		951	{
		952	struct my_biggy big = (struct my_biggy *
		953	(((char *)w) - offsetof (struct my_biggy, t2));
		954	}
689		955
690		956
691	=head1 WATCHER TYPES	957	=head1 WATCHER TYPES
692		958
693	This section describes each watcher in detail, but will not repeat	959	This section describes each watcher in detail, but will not repeat
694	information given in the last section.	960	information given in the last section. Any initialisation/set macros,
		961	functions and members specific to the watcher type are explained.
		962
		963	Members are additionally marked with either I<[read-only]>, meaning that,
		964	while the watcher is active, you can look at the member and expect some
		965	sensible content, but you must not modify it (you can modify it while the
		966	watcher is stopped to your hearts content), or I<[read-write]>, which
		967	means you can expect it to have some sensible content while the watcher
		968	is active, but you can also modify it. Modifying it may not do something
		969	sensible or take immediate effect (or do anything at all), but libev will
		970	not crash or malfunction in any way.
695		971
696		972
697	=head2 C<ev_io> - is this file descriptor readable or writable?	973	=head2 C<ev_io> - is this file descriptor readable or writable?
698		974
699	I/O watchers check whether a file descriptor is readable or writable	975	I/O watchers check whether a file descriptor is readable or writable
…		…
706		982
707	In general you can register as many read and/or write event watchers per	983	In general you can register as many read and/or write event watchers per
708	fd as you want (as long as you don't confuse yourself). Setting all file	984	fd as you want (as long as you don't confuse yourself). Setting all file
709	descriptors to non-blocking mode is also usually a good idea (but not	985	descriptors to non-blocking mode is also usually a good idea (but not
710	required if you know what you are doing).	986	required if you know what you are doing).
711
712	You have to be careful with dup'ed file descriptors, though. Some backends
713	(the linux epoll backend is a notable example) cannot handle dup'ed file
714	descriptors correctly if you register interest in two or more fds pointing
715	to the same underlying file/socket/etc. description (that is, they share
716	the same underlying "file open").
717		987
718	If you must do this, then force the use of a known-to-be-good backend	988	If you must do this, then force the use of a known-to-be-good backend
719	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	989	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
720	C<EVBACKEND_POLL>).	990	C<EVBACKEND_POLL>).
721		991
…		…
728	it is best to always use non-blocking I/O: An extra C<read>(2) returning	998	it is best to always use non-blocking I/O: An extra C<read>(2) returning
729	C<EAGAIN> is far preferable to a program hanging until some data arrives.	999	C<EAGAIN> is far preferable to a program hanging until some data arrives.
730		1000
731	If you cannot run the fd in non-blocking mode (for example you should not	1001	If you cannot run the fd in non-blocking mode (for example you should not
732	play around with an Xlib connection), then you have to seperately re-test	1002	play around with an Xlib connection), then you have to seperately re-test
733	wether a file descriptor is really ready with a known-to-be good interface	1003	whether a file descriptor is really ready with a known-to-be good interface
734	such as poll (fortunately in our Xlib example, Xlib already does this on	1004	such as poll (fortunately in our Xlib example, Xlib already does this on
735	its own, so its quite safe to use).	1005	its own, so its quite safe to use).
		1006
		1007	=head3 The special problem of disappearing file descriptors
		1008
		1009	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1010	descriptor (either by calling C<close> explicitly or by any other means,
		1011	such as C<dup>). The reason is that you register interest in some file
		1012	descriptor, but when it goes away, the operating system will silently drop
		1013	this interest. If another file descriptor with the same number then is
		1014	registered with libev, there is no efficient way to see that this is, in
		1015	fact, a different file descriptor.
		1016
		1017	To avoid having to explicitly tell libev about such cases, libev follows
		1018	the following policy: Each time C<ev_io_set> is being called, libev
		1019	will assume that this is potentially a new file descriptor, otherwise
		1020	it is assumed that the file descriptor stays the same. That means that
		1021	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1022	descriptor even if the file descriptor number itself did not change.
		1023
		1024	This is how one would do it normally anyway, the important point is that
		1025	the libev application should not optimise around libev but should leave
		1026	optimisations to libev.
		1027
		1028	=head3 The special problem of dup'ed file descriptors
		1029
		1030	Some backends (e.g. epoll), cannot register events for file descriptors,
		1031	but only events for the underlying file descriptions. That means when you
		1032	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1033	events for them, only one file descriptor might actually receive events.
		1034
		1035	There is no workaround possible except not registering events
		1036	for potentially C<dup ()>'ed file descriptors, or to resort to
		1037	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1038
		1039	=head3 The special problem of fork
		1040
		1041	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1042	useless behaviour. Libev fully supports fork, but needs to be told about
		1043	it in the child.
		1044
		1045	To support fork in your programs, you either have to call
		1046	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1047	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1048	C<EVBACKEND_POLL>.
		1049
		1050
		1051	=head3 Watcher-Specific Functions
736		1052
737	=over 4	1053	=over 4
738		1054
739	=item ev_io_init (ev_io *, callback, int fd, int events)	1055	=item ev_io_init (ev_io *, callback, int fd, int events)
740		1056
…		…
742		1058
743	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1059	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
744	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1060	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
745	C<EV_READ | EV_WRITE> to receive the given events.	1061	C<EV_READ | EV_WRITE> to receive the given events.
746		1062
		1063	=item int fd [read-only]
		1064
		1065	The file descriptor being watched.
		1066
		1067	=item int events [read-only]
		1068
		1069	The events being watched.
		1070
747	=back	1071	=back
748		1072
		1073	=head3 Examples
		1074
749	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1075	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
750	readable, but only once. Since it is likely line-buffered, you could	1076	readable, but only once. Since it is likely line-buffered, you could
751	attempt to read a whole line in the callback:	1077	attempt to read a whole line in the callback.
752		1078
753	static void	1079	static void
754	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1080	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
755	{	1081	{
756	ev_io_stop (loop, w);	1082	ev_io_stop (loop, w);
…		…
786		1112
787	The callback is guarenteed to be invoked only when its timeout has passed,	1113	The callback is guarenteed to be invoked only when its timeout has passed,
788	but if multiple timers become ready during the same loop iteration then	1114	but if multiple timers become ready during the same loop iteration then
789	order of execution is undefined.	1115	order of execution is undefined.
790		1116
		1117	=head3 Watcher-Specific Functions and Data Members
		1118
791	=over 4	1119	=over 4
792		1120
793	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1121	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
794		1122
795	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1123	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
808	=item ev_timer_again (loop)	1136	=item ev_timer_again (loop)
809		1137
810	This will act as if the timer timed out and restart it again if it is	1138	This will act as if the timer timed out and restart it again if it is
811	repeating. The exact semantics are:	1139	repeating. The exact semantics are:
812		1140
		1141	If the timer is pending, its pending status is cleared.
		1142
813	If the timer is started but nonrepeating, stop it.	1143	If the timer is started but nonrepeating, stop it (as if it timed out).
814		1144
815	If the timer is repeating, either start it if necessary (with the repeat	1145	If the timer is repeating, either start it if necessary (with the
816	value), or reset the running timer to the repeat value.	1146	C<repeat> value), or reset the running timer to the C<repeat> value.
817		1147
818	This sounds a bit complicated, but here is a useful and typical	1148	This sounds a bit complicated, but here is a useful and typical
819	example: Imagine you have a tcp connection and you want a so-called idle	1149	example: Imagine you have a tcp connection and you want a so-called idle
820	timeout, that is, you want to be called when there have been, say, 60	1150	timeout, that is, you want to be called when there have been, say, 60
821	seconds of inactivity on the socket. The easiest way to do this is to	1151	seconds of inactivity on the socket. The easiest way to do this is to
822	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1152	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
823	time you successfully read or write some data. If you go into an idle	1153	C<ev_timer_again> each time you successfully read or write some data. If
824	state where you do not expect data to travel on the socket, you can stop	1154	you go into an idle state where you do not expect data to travel on the
825	the timer, and again will automatically restart it if need be.	1155	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1156	automatically restart it if need be.
		1157
		1158	That means you can ignore the C<after> value and C<ev_timer_start>
		1159	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1160
		1161	ev_timer_init (timer, callback, 0., 5.);
		1162	ev_timer_again (loop, timer);
		1163	...
		1164	timer->again = 17.;
		1165	ev_timer_again (loop, timer);
		1166	...
		1167	timer->again = 10.;
		1168	ev_timer_again (loop, timer);
		1169
		1170	This is more slightly efficient then stopping/starting the timer each time
		1171	you want to modify its timeout value.
		1172
		1173	=item ev_tstamp repeat [read-write]
		1174
		1175	The current C<repeat> value. Will be used each time the watcher times out
		1176	or C<ev_timer_again> is called and determines the next timeout (if any),
		1177	which is also when any modifications are taken into account.
826		1178
827	=back	1179	=back
828		1180
		1181	=head3 Examples
		1182
829	Example: create a timer that fires after 60 seconds.	1183	Example: Create a timer that fires after 60 seconds.
830		1184
831	static void	1185	static void
832	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1186	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
833	{	1187	{
834	.. one minute over, w is actually stopped right here	1188	.. one minute over, w is actually stopped right here
…		…
836		1190
837	struct ev_timer mytimer;	1191	struct ev_timer mytimer;
838	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1192	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
839	ev_timer_start (loop, &mytimer);	1193	ev_timer_start (loop, &mytimer);
840		1194
841	Example: create a timeout timer that times out after 10 seconds of	1195	Example: Create a timeout timer that times out after 10 seconds of
842	inactivity.	1196	inactivity.
843		1197
844	static void	1198	static void
845	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1199	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
846	{	1200	{
…		…
866	but on wallclock time (absolute time). You can tell a periodic watcher	1220	but on wallclock time (absolute time). You can tell a periodic watcher
867	to trigger "at" some specific point in time. For example, if you tell a	1221	to trigger "at" some specific point in time. For example, if you tell a
868	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1222	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
869	+ 10.>) and then reset your system clock to the last year, then it will	1223	+ 10.>) and then reset your system clock to the last year, then it will
870	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1224	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
871	roughly 10 seconds later and of course not if you reset your system time	1225	roughly 10 seconds later).
872	again).
873		1226
874	They can also be used to implement vastly more complex timers, such as	1227	They can also be used to implement vastly more complex timers, such as
875	triggering an event on eahc midnight, local time.	1228	triggering an event on each midnight, local time or other, complicated,
		1229	rules.
876		1230
877	As with timers, the callback is guarenteed to be invoked only when the	1231	As with timers, the callback is guarenteed to be invoked only when the
878	time (C<at>) has been passed, but if multiple periodic timers become ready	1232	time (C<at>) has been passed, but if multiple periodic timers become ready
879	during the same loop iteration then order of execution is undefined.	1233	during the same loop iteration then order of execution is undefined.
880		1234
		1235	=head3 Watcher-Specific Functions and Data Members
		1236
881	=over 4	1237	=over 4
882		1238
883	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1239	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
884		1240
885	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1241	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
887	Lots of arguments, lets sort it out... There are basically three modes of	1243	Lots of arguments, lets sort it out... There are basically three modes of
888	operation, and we will explain them from simplest to complex:	1244	operation, and we will explain them from simplest to complex:
889		1245
890	=over 4	1246	=over 4
891		1247
892	=item * absolute timer (interval = reschedule_cb = 0)	1248	=item * absolute timer (at = time, interval = reschedule_cb = 0)
893		1249
894	In this configuration the watcher triggers an event at the wallclock time	1250	In this configuration the watcher triggers an event at the wallclock time
895	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1251	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
896	that is, if it is to be run at January 1st 2011 then it will run when the	1252	that is, if it is to be run at January 1st 2011 then it will run when the
897	system time reaches or surpasses this time.	1253	system time reaches or surpasses this time.
898		1254
899	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1255	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
900		1256
901	In this mode the watcher will always be scheduled to time out at the next	1257	In this mode the watcher will always be scheduled to time out at the next
902	C<at + N * interval> time (for some integer N) and then repeat, regardless	1258	C<at + N * interval> time (for some integer N, which can also be negative)
903	of any time jumps.	1259	and then repeat, regardless of any time jumps.
904		1260
905	This can be used to create timers that do not drift with respect to system	1261	This can be used to create timers that do not drift with respect to system
906	time:	1262	time:
907		1263
908	ev_periodic_set (&periodic, 0., 3600., 0);	1264	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
914		1270
915	Another way to think about it (for the mathematically inclined) is that	1271	Another way to think about it (for the mathematically inclined) is that
916	C<ev_periodic> will try to run the callback in this mode at the next possible	1272	C<ev_periodic> will try to run the callback in this mode at the next possible
917	time where C<time = at (mod interval)>, regardless of any time jumps.	1273	time where C<time = at (mod interval)>, regardless of any time jumps.
918		1274
		1275	For numerical stability it is preferable that the C<at> value is near
		1276	C<ev_now ()> (the current time), but there is no range requirement for
		1277	this value.
		1278
919	=item * manual reschedule mode (reschedule_cb = callback)	1279	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
920		1280
921	In this mode the values for C<interval> and C<at> are both being	1281	In this mode the values for C<interval> and C<at> are both being
922	ignored. Instead, each time the periodic watcher gets scheduled, the	1282	ignored. Instead, each time the periodic watcher gets scheduled, the
923	reschedule callback will be called with the watcher as first, and the	1283	reschedule callback will be called with the watcher as first, and the
924	current time as second argument.	1284	current time as second argument.
925		1285
926	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1286	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
927	ever, or make any event loop modifications>. If you need to stop it,	1287	ever, or make any event loop modifications>. If you need to stop it,
928	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1288	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
929	starting a prepare watcher).	1289	starting an C<ev_prepare> watcher, which is legal).
930		1290
931	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1291	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
932	ev_tstamp now)>, e.g.:	1292	ev_tstamp now)>, e.g.:
933		1293
934	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1294	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
957	Simply stops and restarts the periodic watcher again. This is only useful	1317	Simply stops and restarts the periodic watcher again. This is only useful
958	when you changed some parameters or the reschedule callback would return	1318	when you changed some parameters or the reschedule callback would return
959	a different time than the last time it was called (e.g. in a crond like	1319	a different time than the last time it was called (e.g. in a crond like
960	program when the crontabs have changed).	1320	program when the crontabs have changed).
961		1321
		1322	=item ev_tstamp offset [read-write]
		1323
		1324	When repeating, this contains the offset value, otherwise this is the
		1325	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1326
		1327	Can be modified any time, but changes only take effect when the periodic
		1328	timer fires or C<ev_periodic_again> is being called.
		1329
		1330	=item ev_tstamp interval [read-write]
		1331
		1332	The current interval value. Can be modified any time, but changes only
		1333	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1334	called.
		1335
		1336	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1337
		1338	The current reschedule callback, or C<0>, if this functionality is
		1339	switched off. Can be changed any time, but changes only take effect when
		1340	the periodic timer fires or C<ev_periodic_again> is being called.
		1341
		1342	=item ev_tstamp at [read-only]
		1343
		1344	When active, contains the absolute time that the watcher is supposed to
		1345	trigger next.
		1346
962	=back	1347	=back
963		1348
		1349	=head3 Examples
		1350
964	Example: call a callback every hour, or, more precisely, whenever the	1351	Example: Call a callback every hour, or, more precisely, whenever the
965	system clock is divisible by 3600. The callback invocation times have	1352	system clock is divisible by 3600. The callback invocation times have
966	potentially a lot of jittering, but good long-term stability.	1353	potentially a lot of jittering, but good long-term stability.
967		1354
968	static void	1355	static void
969	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1356	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
973		1360
974	struct ev_periodic hourly_tick;	1361	struct ev_periodic hourly_tick;
975	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1362	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
976	ev_periodic_start (loop, &hourly_tick);	1363	ev_periodic_start (loop, &hourly_tick);
977		1364
978	Example: the same as above, but use a reschedule callback to do it:	1365	Example: The same as above, but use a reschedule callback to do it:
979		1366
980	#include <math.h>	1367	#include <math.h>
981		1368
982	static ev_tstamp	1369	static ev_tstamp
983	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1370	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
985	return fmod (now, 3600.) + 3600.;	1372	return fmod (now, 3600.) + 3600.;
986	}	1373	}
987		1374
988	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1375	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
989		1376
990	Example: call a callback every hour, starting now:	1377	Example: Call a callback every hour, starting now:
991		1378
992	struct ev_periodic hourly_tick;	1379	struct ev_periodic hourly_tick;
993	ev_periodic_init (&hourly_tick, clock_cb,	1380	ev_periodic_init (&hourly_tick, clock_cb,
994	fmod (ev_now (loop), 3600.), 3600., 0);	1381	fmod (ev_now (loop), 3600.), 3600., 0);
995	ev_periodic_start (loop, &hourly_tick);	1382	ev_periodic_start (loop, &hourly_tick);
…		…
1007	with the kernel (thus it coexists with your own signal handlers as long	1394	with the kernel (thus it coexists with your own signal handlers as long
1008	as you don't register any with libev). Similarly, when the last signal	1395	as you don't register any with libev). Similarly, when the last signal
1009	watcher for a signal is stopped libev will reset the signal handler to	1396	watcher for a signal is stopped libev will reset the signal handler to
1010	SIG_DFL (regardless of what it was set to before).	1397	SIG_DFL (regardless of what it was set to before).
1011		1398
		1399	=head3 Watcher-Specific Functions and Data Members
		1400
1012	=over 4	1401	=over 4
1013		1402
1014	=item ev_signal_init (ev_signal *, callback, int signum)	1403	=item ev_signal_init (ev_signal *, callback, int signum)
1015		1404
1016	=item ev_signal_set (ev_signal *, int signum)	1405	=item ev_signal_set (ev_signal *, int signum)
1017		1406
1018	Configures the watcher to trigger on the given signal number (usually one	1407	Configures the watcher to trigger on the given signal number (usually one
1019	of the C<SIGxxx> constants).	1408	of the C<SIGxxx> constants).
1020		1409
		1410	=item int signum [read-only]
		1411
		1412	The signal the watcher watches out for.
		1413
1021	=back	1414	=back
1022		1415
1023		1416
1024	=head2 C<ev_child> - watch out for process status changes	1417	=head2 C<ev_child> - watch out for process status changes
1025		1418
1026	Child watchers trigger when your process receives a SIGCHLD in response to	1419	Child watchers trigger when your process receives a SIGCHLD in response to
1027	some child status changes (most typically when a child of yours dies).	1420	some child status changes (most typically when a child of yours dies).
		1421
		1422	=head3 Watcher-Specific Functions and Data Members
1028		1423
1029	=over 4	1424	=over 4
1030		1425
1031	=item ev_child_init (ev_child *, callback, int pid)	1426	=item ev_child_init (ev_child *, callback, int pid)
1032		1427
…		…
1037	at the C<rstatus> member of the C<ev_child> watcher structure to see	1432	at the C<rstatus> member of the C<ev_child> watcher structure to see
1038	the status word (use the macros from C<sys/wait.h> and see your systems	1433	the status word (use the macros from C<sys/wait.h> and see your systems
1039	C<waitpid> documentation). The C<rpid> member contains the pid of the	1434	C<waitpid> documentation). The C<rpid> member contains the pid of the
1040	process causing the status change.	1435	process causing the status change.
1041		1436
		1437	=item int pid [read-only]
		1438
		1439	The process id this watcher watches out for, or C<0>, meaning any process id.
		1440
		1441	=item int rpid [read-write]
		1442
		1443	The process id that detected a status change.
		1444
		1445	=item int rstatus [read-write]
		1446
		1447	The process exit/trace status caused by C<rpid> (see your systems
		1448	C<waitpid> and C<sys/wait.h> documentation for details).
		1449
1042	=back	1450	=back
1043		1451
		1452	=head3 Examples
		1453
1044	Example: try to exit cleanly on SIGINT and SIGTERM.	1454	Example: Try to exit cleanly on SIGINT and SIGTERM.
1045		1455
1046	static void	1456	static void
1047	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1457	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1048	{	1458	{
1049	ev_unloop (loop, EVUNLOOP_ALL);	1459	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1052	struct ev_signal signal_watcher;	1462	struct ev_signal signal_watcher;
1053	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1463	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1054	ev_signal_start (loop, &sigint_cb);	1464	ev_signal_start (loop, &sigint_cb);
1055		1465
1056		1466
		1467	=head2 C<ev_stat> - did the file attributes just change?
		1468
		1469	This watches a filesystem path for attribute changes. That is, it calls
		1470	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1471	compared to the last time, invoking the callback if it did.
		1472
		1473	The path does not need to exist: changing from "path exists" to "path does
		1474	not exist" is a status change like any other. The condition "path does
		1475	not exist" is signified by the C<st_nlink> field being zero (which is
		1476	otherwise always forced to be at least one) and all the other fields of
		1477	the stat buffer having unspecified contents.
		1478
		1479	The path I<should> be absolute and I<must not> end in a slash. If it is
		1480	relative and your working directory changes, the behaviour is undefined.
		1481
		1482	Since there is no standard to do this, the portable implementation simply
		1483	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1484	can specify a recommended polling interval for this case. If you specify
		1485	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1486	unspecified default> value will be used (which you can expect to be around
		1487	five seconds, although this might change dynamically). Libev will also
		1488	impose a minimum interval which is currently around C<0.1>, but thats
		1489	usually overkill.
		1490
		1491	This watcher type is not meant for massive numbers of stat watchers,
		1492	as even with OS-supported change notifications, this can be
		1493	resource-intensive.
		1494
		1495	At the time of this writing, only the Linux inotify interface is
		1496	implemented (implementing kqueue support is left as an exercise for the
		1497	reader). Inotify will be used to give hints only and should not change the
		1498	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1499	to fall back to regular polling again even with inotify, but changes are
		1500	usually detected immediately, and if the file exists there will be no
		1501	polling.
		1502
		1503	=head3 Inotify
		1504
		1505	When C<inotify (7)> support has been compiled into libev (generally only
		1506	available on Linux) and present at runtime, it will be used to speed up
		1507	change detection where possible. The inotify descriptor will be created lazily
		1508	when the first C<ev_stat> watcher is being started.
		1509
		1510	Inotify presense does not change the semantics of C<ev_stat> watchers
		1511	except that changes might be detected earlier, and in some cases, to avoid
		1512	making regular C<stat> calls. Even in the presense of inotify support
		1513	there are many cases where libev has to resort to regular C<stat> polling.
		1514
		1515	(There is no support for kqueue, as apparently it cannot be used to
		1516	implement this functionality, due to the requirement of having a file
		1517	descriptor open on the object at all times).
		1518
		1519	=head3 The special problem of stat time resolution
		1520
		1521	The C<stat ()> syscall only supports full-second resolution portably, and
		1522	even on systems where the resolution is higher, many filesystems still
		1523	only support whole seconds.
		1524
		1525	That means that, if the time is the only thing that changes, you might
		1526	miss updates: on the first update, C<ev_stat> detects a change and calls
		1527	your callback, which does something. When there is another update within
		1528	the same second, C<ev_stat> will be unable to detect it.
		1529
		1530	The solution to this is to delay acting on a change for a second (or till
		1531	the next second boundary), using a roughly one-second delay C<ev_timer>
		1532	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1533	is added to work around small timing inconsistencies of some operating
		1534	systems.
		1535
		1536	=head3 Watcher-Specific Functions and Data Members
		1537
		1538	=over 4
		1539
		1540	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1541
		1542	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1543
		1544	Configures the watcher to wait for status changes of the given
		1545	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1546	be detected and should normally be specified as C<0> to let libev choose
		1547	a suitable value. The memory pointed to by C<path> must point to the same
		1548	path for as long as the watcher is active.
		1549
		1550	The callback will be receive C<EV_STAT> when a change was detected,
		1551	relative to the attributes at the time the watcher was started (or the
		1552	last change was detected).
		1553
		1554	=item ev_stat_stat (ev_stat *)
		1555
		1556	Updates the stat buffer immediately with new values. If you change the
		1557	watched path in your callback, you could call this fucntion to avoid
		1558	detecting this change (while introducing a race condition). Can also be
		1559	useful simply to find out the new values.
		1560
		1561	=item ev_statdata attr [read-only]
		1562
		1563	The most-recently detected attributes of the file. Although the type is of
		1564	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1565	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1566	was some error while C<stat>ing the file.
		1567
		1568	=item ev_statdata prev [read-only]
		1569
		1570	The previous attributes of the file. The callback gets invoked whenever
		1571	C<prev> != C<attr>.
		1572
		1573	=item ev_tstamp interval [read-only]
		1574
		1575	The specified interval.
		1576
		1577	=item const char *path [read-only]
		1578
		1579	The filesystem path that is being watched.
		1580
		1581	=back
		1582
		1583	=head3 Examples
		1584
		1585	Example: Watch C</etc/passwd> for attribute changes.
		1586
		1587	static void
		1588	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1589	{
		1590	/* /etc/passwd changed in some way */
		1591	if (w->attr.st_nlink)
		1592	{
		1593	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1594	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1595	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1596	}
		1597	else
		1598	/* you shalt not abuse printf for puts */
		1599	puts ("wow, /etc/passwd is not there, expect problems. "
		1600	"if this is windows, they already arrived\n");
		1601	}
		1602
		1603	...
		1604	ev_stat passwd;
		1605
		1606	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1607	ev_stat_start (loop, &passwd);
		1608
		1609	Example: Like above, but additionally use a one-second delay so we do not
		1610	miss updates (however, frequent updates will delay processing, too, so
		1611	one might do the work both on C<ev_stat> callback invocation I<and> on
		1612	C<ev_timer> callback invocation).
		1613
		1614	static ev_stat passwd;
		1615	static ev_timer timer;
		1616
		1617	static void
		1618	timer_cb (EV_P_ ev_timer *w, int revents)
		1619	{
		1620	ev_timer_stop (EV_A_ w);
		1621
		1622	/* now it's one second after the most recent passwd change */
		1623	}
		1624
		1625	static void
		1626	stat_cb (EV_P_ ev_stat *w, int revents)
		1627	{
		1628	/* reset the one-second timer */
		1629	ev_timer_again (EV_A_ &timer);
		1630	}
		1631
		1632	...
		1633	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1634	ev_stat_start (loop, &passwd);
		1635	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1636
		1637
1057	=head2 C<ev_idle> - when you've got nothing better to do...	1638	=head2 C<ev_idle> - when you've got nothing better to do...
1058		1639
1059	Idle watchers trigger events when there are no other events are pending	1640	Idle watchers trigger events when no other events of the same or higher
1060	(prepare, check and other idle watchers do not count). That is, as long	1641	priority are pending (prepare, check and other idle watchers do not
1061	as your process is busy handling sockets or timeouts (or even signals,	1642	count).
1062	imagine) it will not be triggered. But when your process is idle all idle	1643
1063	watchers are being called again and again, once per event loop iteration -	1644	That is, as long as your process is busy handling sockets or timeouts
		1645	(or even signals, imagine) of the same or higher priority it will not be
		1646	triggered. But when your process is idle (or only lower-priority watchers
		1647	are pending), the idle watchers are being called once per event loop
1064	until stopped, that is, or your process receives more events and becomes	1648	iteration - until stopped, that is, or your process receives more events
1065	busy.	1649	and becomes busy again with higher priority stuff.
1066		1650
1067	The most noteworthy effect is that as long as any idle watchers are	1651	The most noteworthy effect is that as long as any idle watchers are
1068	active, the process will not block when waiting for new events.	1652	active, the process will not block when waiting for new events.
1069		1653
1070	Apart from keeping your process non-blocking (which is a useful	1654	Apart from keeping your process non-blocking (which is a useful
1071	effect on its own sometimes), idle watchers are a good place to do	1655	effect on its own sometimes), idle watchers are a good place to do
1072	"pseudo-background processing", or delay processing stuff to after the	1656	"pseudo-background processing", or delay processing stuff to after the
1073	event loop has handled all outstanding events.	1657	event loop has handled all outstanding events.
1074		1658
		1659	=head3 Watcher-Specific Functions and Data Members
		1660
1075	=over 4	1661	=over 4
1076		1662
1077	=item ev_idle_init (ev_signal *, callback)	1663	=item ev_idle_init (ev_signal *, callback)
1078		1664
1079	Initialises and configures the idle watcher - it has no parameters of any	1665	Initialises and configures the idle watcher - it has no parameters of any
1080	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1666	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1081	believe me.	1667	believe me.
1082		1668
1083	=back	1669	=back
1084		1670
		1671	=head3 Examples
		1672
1085	Example: dynamically allocate an C<ev_idle>, start it, and in the	1673	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1086	callback, free it. Alos, use no error checking, as usual.	1674	callback, free it. Also, use no error checking, as usual.
1087		1675
1088	static void	1676	static void
1089	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1677	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1090	{	1678	{
1091	free (w);	1679	free (w);
…		…
1136	with priority higher than or equal to the event loop and one coroutine	1724	with priority higher than or equal to the event loop and one coroutine
1137	of lower priority, but only once, using idle watchers to keep the event	1725	of lower priority, but only once, using idle watchers to keep the event
1138	loop from blocking if lower-priority coroutines are active, thus mapping	1726	loop from blocking if lower-priority coroutines are active, thus mapping
1139	low-priority coroutines to idle/background tasks).	1727	low-priority coroutines to idle/background tasks).
1140		1728
		1729	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1730	priority, to ensure that they are being run before any other watchers
		1731	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1732	too) should not activate ("feed") events into libev. While libev fully
		1733	supports this, they will be called before other C<ev_check> watchers
		1734	did their job. As C<ev_check> watchers are often used to embed other
		1735	(non-libev) event loops those other event loops might be in an unusable
		1736	state until their C<ev_check> watcher ran (always remind yourself to
		1737	coexist peacefully with others).
		1738
		1739	=head3 Watcher-Specific Functions and Data Members
		1740
1141	=over 4	1741	=over 4
1142		1742
1143	=item ev_prepare_init (ev_prepare *, callback)	1743	=item ev_prepare_init (ev_prepare *, callback)
1144		1744
1145	=item ev_check_init (ev_check *, callback)	1745	=item ev_check_init (ev_check *, callback)
…		…
1148	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1748	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1149	macros, but using them is utterly, utterly and completely pointless.	1749	macros, but using them is utterly, utterly and completely pointless.
1150		1750
1151	=back	1751	=back
1152		1752
1153	Example: To include a library such as adns, you would add IO watchers	1753	=head3 Examples
1154	and a timeout watcher in a prepare handler, as required by libadns, and	1754
		1755	There are a number of principal ways to embed other event loops or modules
		1756	into libev. Here are some ideas on how to include libadns into libev
		1757	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1758	use for an actually working example. Another Perl module named C<EV::Glib>
		1759	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1760	into the Glib event loop).
		1761
		1762	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1155	in a check watcher, destroy them and call into libadns. What follows is	1763	and in a check watcher, destroy them and call into libadns. What follows
1156	pseudo-code only of course:	1764	is pseudo-code only of course. This requires you to either use a low
		1765	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1766	the callbacks for the IO/timeout watchers might not have been called yet.
1157		1767
1158	static ev_io iow [nfd];	1768	static ev_io iow [nfd];
1159	static ev_timer tw;	1769	static ev_timer tw;
1160		1770
1161	static void	1771	static void
1162	io_cb (ev_loop *loop, ev_io *w, int revents)	1772	io_cb (ev_loop *loop, ev_io *w, int revents)
1163	{	1773	{
1164	// set the relevant poll flags
1165	// could also call adns_processreadable etc. here
1166	struct pollfd *fd = (struct pollfd *)w->data;
1167	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1168	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1169	}	1774	}
1170		1775
1171	// create io watchers for each fd and a timer before blocking	1776	// create io watchers for each fd and a timer before blocking
1172	static void	1777	static void
1173	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1778	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1174	{	1779	{
1175	int timeout = 3600000;truct pollfd fds [nfd];	1780	int timeout = 3600000;
		1781	struct pollfd fds [nfd];
1176	// actual code will need to loop here and realloc etc.	1782	// actual code will need to loop here and realloc etc.
1177	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1783	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1178		1784
1179	/* the callback is illegal, but won't be called as we stop during check */	1785	/* the callback is illegal, but won't be called as we stop during check */
1180	ev_timer_init (&tw, 0, timeout * 1e-3);	1786	ev_timer_init (&tw, 0, timeout * 1e-3);
1181	ev_timer_start (loop, &tw);	1787	ev_timer_start (loop, &tw);
1182		1788
1183	// create on ev_io per pollfd	1789	// create one ev_io per pollfd
1184	for (int i = 0; i < nfd; ++i)	1790	for (int i = 0; i < nfd; ++i)
1185	{	1791	{
1186	ev_io_init (iow + i, io_cb, fds [i].fd,	1792	ev_io_init (iow + i, io_cb, fds [i].fd,
1187	((fds [i].events & POLLIN ? EV_READ : 0)	1793	((fds [i].events & POLLIN ? EV_READ : 0)
1188	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1794	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1189		1795
1190	fds [i].revents = 0;	1796	fds [i].revents = 0;
1191	iow [i].data = fds + i;
1192	ev_io_start (loop, iow + i);	1797	ev_io_start (loop, iow + i);
1193	}	1798	}
1194	}	1799	}
1195		1800
1196	// stop all watchers after blocking	1801	// stop all watchers after blocking
…		…
1198	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1803	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1199	{	1804	{
1200	ev_timer_stop (loop, &tw);	1805	ev_timer_stop (loop, &tw);
1201		1806
1202	for (int i = 0; i < nfd; ++i)	1807	for (int i = 0; i < nfd; ++i)
		1808	{
		1809	// set the relevant poll flags
		1810	// could also call adns_processreadable etc. here
		1811	struct pollfd *fd = fds + i;
		1812	int revents = ev_clear_pending (iow + i);
		1813	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1814	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1815
		1816	// now stop the watcher
1203	ev_io_stop (loop, iow + i);	1817	ev_io_stop (loop, iow + i);
		1818	}
1204		1819
1205	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1820	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1821	}
		1822
		1823	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1824	in the prepare watcher and would dispose of the check watcher.
		1825
		1826	Method 3: If the module to be embedded supports explicit event
		1827	notification (adns does), you can also make use of the actual watcher
		1828	callbacks, and only destroy/create the watchers in the prepare watcher.
		1829
		1830	static void
		1831	timer_cb (EV_P_ ev_timer *w, int revents)
		1832	{
		1833	adns_state ads = (adns_state)w->data;
		1834	update_now (EV_A);
		1835
		1836	adns_processtimeouts (ads, &tv_now);
		1837	}
		1838
		1839	static void
		1840	io_cb (EV_P_ ev_io *w, int revents)
		1841	{
		1842	adns_state ads = (adns_state)w->data;
		1843	update_now (EV_A);
		1844
		1845	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1846	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1847	}
		1848
		1849	// do not ever call adns_afterpoll
		1850
		1851	Method 4: Do not use a prepare or check watcher because the module you
		1852	want to embed is too inflexible to support it. Instead, youc na override
		1853	their poll function. The drawback with this solution is that the main
		1854	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1855	this.
		1856
		1857	static gint
		1858	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1859	{
		1860	int got_events = 0;
		1861
		1862	for (n = 0; n < nfds; ++n)
		1863	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1864
		1865	if (timeout >= 0)
		1866	// create/start timer
		1867
		1868	// poll
		1869	ev_loop (EV_A_ 0);
		1870
		1871	// stop timer again
		1872	if (timeout >= 0)
		1873	ev_timer_stop (EV_A_ &to);
		1874
		1875	// stop io watchers again - their callbacks should have set
		1876	for (n = 0; n < nfds; ++n)
		1877	ev_io_stop (EV_A_ iow [n]);
		1878
		1879	return got_events;
1206	}	1880	}
1207		1881
1208		1882
1209	=head2 C<ev_embed> - when one backend isn't enough...	1883	=head2 C<ev_embed> - when one backend isn't enough...
1210		1884
…		…
1253	portable one.	1927	portable one.
1254		1928
1255	So when you want to use this feature you will always have to be prepared	1929	So when you want to use this feature you will always have to be prepared
1256	that you cannot get an embeddable loop. The recommended way to get around	1930	that you cannot get an embeddable loop. The recommended way to get around
1257	this is to have a separate variables for your embeddable loop, try to	1931	this is to have a separate variables for your embeddable loop, try to
1258	create it, and if that fails, use the normal loop for everything:	1932	create it, and if that fails, use the normal loop for everything.
		1933
		1934	=head3 Watcher-Specific Functions and Data Members
		1935
		1936	=over 4
		1937
		1938	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1939
		1940	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1941
		1942	Configures the watcher to embed the given loop, which must be
		1943	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1944	invoked automatically, otherwise it is the responsibility of the callback
		1945	to invoke it (it will continue to be called until the sweep has been done,
		1946	if you do not want thta, you need to temporarily stop the embed watcher).
		1947
		1948	=item ev_embed_sweep (loop, ev_embed *)
		1949
		1950	Make a single, non-blocking sweep over the embedded loop. This works
		1951	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1952	apropriate way for embedded loops.
		1953
		1954	=item struct ev_loop *other [read-only]
		1955
		1956	The embedded event loop.
		1957
		1958	=back
		1959
		1960	=head3 Examples
		1961
		1962	Example: Try to get an embeddable event loop and embed it into the default
		1963	event loop. If that is not possible, use the default loop. The default
		1964	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1965	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1966	used).
1259		1967
1260	struct ev_loop *loop_hi = ev_default_init (0);	1968	struct ev_loop *loop_hi = ev_default_init (0);
1261	struct ev_loop *loop_lo = 0;	1969	struct ev_loop *loop_lo = 0;
1262	struct ev_embed embed;	1970	struct ev_embed embed;
1263		1971
…		…
1274	ev_embed_start (loop_hi, &embed);	1982	ev_embed_start (loop_hi, &embed);
1275	}	1983	}
1276	else	1984	else
1277	loop_lo = loop_hi;	1985	loop_lo = loop_hi;
1278		1986
		1987	Example: Check if kqueue is available but not recommended and create
		1988	a kqueue backend for use with sockets (which usually work with any
		1989	kqueue implementation). Store the kqueue/socket-only event loop in
		1990	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		1991
		1992	struct ev_loop *loop = ev_default_init (0);
		1993	struct ev_loop *loop_socket = 0;
		1994	struct ev_embed embed;
		1995
		1996	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		1997	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		1998	{
		1999	ev_embed_init (&embed, 0, loop_socket);
		2000	ev_embed_start (loop, &embed);
		2001	}
		2002
		2003	if (!loop_socket)
		2004	loop_socket = loop;
		2005
		2006	// now use loop_socket for all sockets, and loop for everything else
		2007
		2008
		2009	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2010
		2011	Fork watchers are called when a C<fork ()> was detected (usually because
		2012	whoever is a good citizen cared to tell libev about it by calling
		2013	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2014	event loop blocks next and before C<ev_check> watchers are being called,
		2015	and only in the child after the fork. If whoever good citizen calling
		2016	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2017	handlers will be invoked, too, of course.
		2018
		2019	=head3 Watcher-Specific Functions and Data Members
		2020
1279	=over 4	2021	=over 4
1280		2022
1281	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2023	=item ev_fork_init (ev_signal *, callback)
1282		2024
1283	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2025	Initialises and configures the fork watcher - it has no parameters of any
1284		2026	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1285	Configures the watcher to embed the given loop, which must be	2027	believe me.
1286	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1287	invoked automatically, otherwise it is the responsibility of the callback
1288	to invoke it (it will continue to be called until the sweep has been done,
1289	if you do not want thta, you need to temporarily stop the embed watcher).
1290
1291	=item ev_embed_sweep (loop, ev_embed *)
1292
1293	Make a single, non-blocking sweep over the embedded loop. This works
1294	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1295	apropriate way for embedded loops.
1296		2028
1297	=back	2029	=back
1298		2030
1299		2031
1300	=head1 OTHER FUNCTIONS	2032	=head1 OTHER FUNCTIONS
…		…
1389		2121
1390	To use it,	2122	To use it,
1391		2123
1392	#include <ev++.h>	2124	#include <ev++.h>
1393		2125
1394	(it is not installed by default). This automatically includes F<ev.h>	2126	This automatically includes F<ev.h> and puts all of its definitions (many
1395	and puts all of its definitions (many of them macros) into the global	2127	of them macros) into the global namespace. All C++ specific things are
1396	namespace. All C++ specific things are put into the C<ev> namespace.	2128	put into the C<ev> namespace. It should support all the same embedding
		2129	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1397		2130
1398	It should support all the same embedding options as F<ev.h>, most notably	2131	Care has been taken to keep the overhead low. The only data member the C++
1399	C<EV_MULTIPLICITY>.	2132	classes add (compared to plain C-style watchers) is the event loop pointer
		2133	that the watcher is associated with (or no additional members at all if
		2134	you disable C<EV_MULTIPLICITY> when embedding libev).
		2135
		2136	Currently, functions, and static and non-static member functions can be
		2137	used as callbacks. Other types should be easy to add as long as they only
		2138	need one additional pointer for context. If you need support for other
		2139	types of functors please contact the author (preferably after implementing
		2140	it).
1400		2141
1401	Here is a list of things available in the C<ev> namespace:	2142	Here is a list of things available in the C<ev> namespace:
1402		2143
1403	=over 4	2144	=over 4
1404		2145
…		…
1420		2161
1421	All of those classes have these methods:	2162	All of those classes have these methods:
1422		2163
1423	=over 4	2164	=over 4
1424		2165
1425	=item ev::TYPE::TYPE (object *, object::method *)	2166	=item ev::TYPE::TYPE ()
1426		2167
1427	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2168	=item ev::TYPE::TYPE (struct ev_loop *)
1428		2169
1429	=item ev::TYPE::~TYPE	2170	=item ev::TYPE::~TYPE
1430		2171
1431	The constructor takes a pointer to an object and a method pointer to	2172	The constructor (optionally) takes an event loop to associate the watcher
1432	the event handler callback to call in this class. The constructor calls	2173	with. If it is omitted, it will use C<EV_DEFAULT>.
1433	C<ev_init> for you, which means you have to call the C<set> method	2174
1434	before starting it. If you do not specify a loop then the constructor	2175	The constructor calls C<ev_init> for you, which means you have to call the
1435	automatically associates the default loop with this watcher.	2176	C<set> method before starting it.
		2177
		2178	It will not set a callback, however: You have to call the templated C<set>
		2179	method to set a callback before you can start the watcher.
		2180
		2181	(The reason why you have to use a method is a limitation in C++ which does
		2182	not allow explicit template arguments for constructors).
1436		2183
1437	The destructor automatically stops the watcher if it is active.	2184	The destructor automatically stops the watcher if it is active.
		2185
		2186	=item w->set<class, &class::method> (object *)
		2187
		2188	This method sets the callback method to call. The method has to have a
		2189	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2190	first argument and the C<revents> as second. The object must be given as
		2191	parameter and is stored in the C<data> member of the watcher.
		2192
		2193	This method synthesizes efficient thunking code to call your method from
		2194	the C callback that libev requires. If your compiler can inline your
		2195	callback (i.e. it is visible to it at the place of the C<set> call and
		2196	your compiler is good :), then the method will be fully inlined into the
		2197	thunking function, making it as fast as a direct C callback.
		2198
		2199	Example: simple class declaration and watcher initialisation
		2200
		2201	struct myclass
		2202	{
		2203	void io_cb (ev::io &w, int revents) { }
		2204	}
		2205
		2206	myclass obj;
		2207	ev::io iow;
		2208	iow.set <myclass, &myclass::io_cb> (&obj);
		2209
		2210	=item w->set<function> (void *data = 0)
		2211
		2212	Also sets a callback, but uses a static method or plain function as
		2213	callback. The optional C<data> argument will be stored in the watcher's
		2214	C<data> member and is free for you to use.
		2215
		2216	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2217
		2218	See the method-C<set> above for more details.
		2219
		2220	Example:
		2221
		2222	static void io_cb (ev::io &w, int revents) { }
		2223	iow.set <io_cb> ();
1438		2224
1439	=item w->set (struct ev_loop *)	2225	=item w->set (struct ev_loop *)
1440		2226
1441	Associates a different C<struct ev_loop> with this watcher. You can only	2227	Associates a different C<struct ev_loop> with this watcher. You can only
1442	do this when the watcher is inactive (and not pending either).	2228	do this when the watcher is inactive (and not pending either).
1443		2229
1444	=item w->set ([args])	2230	=item w->set ([args])
1445		2231
1446	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2232	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1447	called at least once. Unlike the C counterpart, an active watcher gets	2233	called at least once. Unlike the C counterpart, an active watcher gets
1448	automatically stopped and restarted.	2234	automatically stopped and restarted when reconfiguring it with this
		2235	method.
1449		2236
1450	=item w->start ()	2237	=item w->start ()
1451		2238
1452	Starts the watcher. Note that there is no C<loop> argument as the	2239	Starts the watcher. Note that there is no C<loop> argument, as the
1453	constructor already takes the loop.	2240	constructor already stores the event loop.
1454		2241
1455	=item w->stop ()	2242	=item w->stop ()
1456		2243
1457	Stops the watcher if it is active. Again, no C<loop> argument.	2244	Stops the watcher if it is active. Again, no C<loop> argument.
1458		2245
1459	=item w->again () C<ev::timer>, C<ev::periodic> only	2246	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1460		2247
1461	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2248	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1462	C<ev_TYPE_again> function.	2249	C<ev_TYPE_again> function.
1463		2250
1464	=item w->sweep () C<ev::embed> only	2251	=item w->sweep () (C<ev::embed> only)
1465		2252
1466	Invokes C<ev_embed_sweep>.	2253	Invokes C<ev_embed_sweep>.
		2254
		2255	=item w->update () (C<ev::stat> only)
		2256
		2257	Invokes C<ev_stat_stat>.
1467		2258
1468	=back	2259	=back
1469		2260
1470	=back	2261	=back
1471		2262
…		…
1479		2270
1480	myclass ();	2271	myclass ();
1481	}	2272	}
1482		2273
1483	myclass::myclass (int fd)	2274	myclass::myclass (int fd)
1484	: io (this, &myclass::io_cb),
1485	idle (this, &myclass::idle_cb)
1486	{	2275	{
		2276	io .set <myclass, &myclass::io_cb > (this);
		2277	idle.set <myclass, &myclass::idle_cb> (this);
		2278
1487	io.start (fd, ev::READ);	2279	io.start (fd, ev::READ);
1488	}	2280	}
		2281
		2282
		2283	=head1 MACRO MAGIC
		2284
		2285	Libev can be compiled with a variety of options, the most fundamantal
		2286	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2287	functions and callbacks have an initial C<struct ev_loop *> argument.
		2288
		2289	To make it easier to write programs that cope with either variant, the
		2290	following macros are defined:
		2291
		2292	=over 4
		2293
		2294	=item C<EV_A>, C<EV_A_>
		2295
		2296	This provides the loop I<argument> for functions, if one is required ("ev
		2297	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2298	C<EV_A_> is used when other arguments are following. Example:
		2299
		2300	ev_unref (EV_A);
		2301	ev_timer_add (EV_A_ watcher);
		2302	ev_loop (EV_A_ 0);
		2303
		2304	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2305	which is often provided by the following macro.
		2306
		2307	=item C<EV_P>, C<EV_P_>
		2308
		2309	This provides the loop I<parameter> for functions, if one is required ("ev
		2310	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2311	C<EV_P_> is used when other parameters are following. Example:
		2312
		2313	// this is how ev_unref is being declared
		2314	static void ev_unref (EV_P);
		2315
		2316	// this is how you can declare your typical callback
		2317	static void cb (EV_P_ ev_timer *w, int revents)
		2318
		2319	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2320	suitable for use with C<EV_A>.
		2321
		2322	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2323
		2324	Similar to the other two macros, this gives you the value of the default
		2325	loop, if multiple loops are supported ("ev loop default").
		2326
		2327	=back
		2328
		2329	Example: Declare and initialise a check watcher, utilising the above
		2330	macros so it will work regardless of whether multiple loops are supported
		2331	or not.
		2332
		2333	static void
		2334	check_cb (EV_P_ ev_timer *w, int revents)
		2335	{
		2336	ev_check_stop (EV_A_ w);
		2337	}
		2338
		2339	ev_check check;
		2340	ev_check_init (&check, check_cb);
		2341	ev_check_start (EV_DEFAULT_ &check);
		2342	ev_loop (EV_DEFAULT_ 0);
1489		2343
1490	=head1 EMBEDDING	2344	=head1 EMBEDDING
1491		2345
1492	Libev can (and often is) directly embedded into host	2346	Libev can (and often is) directly embedded into host
1493	applications. Examples of applications that embed it include the Deliantra	2347	applications. Examples of applications that embed it include the Deliantra
1494	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2348	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1495	and rxvt-unicode.	2349	and rxvt-unicode.
1496		2350
1497	The goal is to enable you to just copy the neecssary files into your	2351	The goal is to enable you to just copy the necessary files into your
1498	source directory without having to change even a single line in them, so	2352	source directory without having to change even a single line in them, so
1499	you can easily upgrade by simply copying (or having a checked-out copy of	2353	you can easily upgrade by simply copying (or having a checked-out copy of
1500	libev somewhere in your source tree).	2354	libev somewhere in your source tree).
1501		2355
1502	=head2 FILESETS	2356	=head2 FILESETS
…		…
1533	ev_vars.h	2387	ev_vars.h
1534	ev_wrap.h	2388	ev_wrap.h
1535		2389
1536	ev_win32.c required on win32 platforms only	2390	ev_win32.c required on win32 platforms only
1537		2391
1538	ev_select.c only when select backend is enabled (which is by default)	2392	ev_select.c only when select backend is enabled (which is enabled by default)
1539	ev_poll.c only when poll backend is enabled (disabled by default)	2393	ev_poll.c only when poll backend is enabled (disabled by default)
1540	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2394	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1541	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2395	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1542	ev_port.c only when the solaris port backend is enabled (disabled by default)	2396	ev_port.c only when the solaris port backend is enabled (disabled by default)
1543		2397
…		…
1592		2446
1593	If defined to be C<1>, libev will try to detect the availability of the	2447	If defined to be C<1>, libev will try to detect the availability of the
1594	monotonic clock option at both compiletime and runtime. Otherwise no use	2448	monotonic clock option at both compiletime and runtime. Otherwise no use
1595	of the monotonic clock option will be attempted. If you enable this, you	2449	of the monotonic clock option will be attempted. If you enable this, you
1596	usually have to link against librt or something similar. Enabling it when	2450	usually have to link against librt or something similar. Enabling it when
1597	the functionality isn't available is safe, though, althoguh you have	2451	the functionality isn't available is safe, though, although you have
1598	to make sure you link against any libraries where the C<clock_gettime>	2452	to make sure you link against any libraries where the C<clock_gettime>
1599	function is hiding in (often F<-lrt>).	2453	function is hiding in (often F<-lrt>).
1600		2454
1601	=item EV_USE_REALTIME	2455	=item EV_USE_REALTIME
1602		2456
1603	If defined to be C<1>, libev will try to detect the availability of the	2457	If defined to be C<1>, libev will try to detect the availability of the
1604	realtime clock option at compiletime (and assume its availability at	2458	realtime clock option at compiletime (and assume its availability at
1605	runtime if successful). Otherwise no use of the realtime clock option will	2459	runtime if successful). Otherwise no use of the realtime clock option will
1606	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2460	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1607	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2461	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1608	in the description of C<EV_USE_MONOTONIC>, though.	2462	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2463
		2464	=item EV_USE_NANOSLEEP
		2465
		2466	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2467	and will use it for delays. Otherwise it will use C<select ()>.
1609		2468
1610	=item EV_USE_SELECT	2469	=item EV_USE_SELECT
1611		2470
1612	If undefined or defined to be C<1>, libev will compile in support for the	2471	If undefined or defined to be C<1>, libev will compile in support for the
1613	C<select>(2) backend. No attempt at autodetection will be done: if no	2472	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1668		2527
1669	=item EV_USE_DEVPOLL	2528	=item EV_USE_DEVPOLL
1670		2529
1671	reserved for future expansion, works like the USE symbols above.	2530	reserved for future expansion, works like the USE symbols above.
1672		2531
		2532	=item EV_USE_INOTIFY
		2533
		2534	If defined to be C<1>, libev will compile in support for the Linux inotify
		2535	interface to speed up C<ev_stat> watchers. Its actual availability will
		2536	be detected at runtime.
		2537
1673	=item EV_H	2538	=item EV_H
1674		2539
1675	The name of the F<ev.h> header file used to include it. The default if	2540	The name of the F<ev.h> header file used to include it. The default if
1676	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2541	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
1677	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2542	virtually rename the F<ev.h> header file in case of conflicts.
1678		2543
1679	=item EV_CONFIG_H	2544	=item EV_CONFIG_H
1680		2545
1681	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2546	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1682	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2547	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1683	C<EV_H>, above.	2548	C<EV_H>, above.
1684		2549
1685	=item EV_EVENT_H	2550	=item EV_EVENT_H
1686		2551
1687	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2552	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1688	of how the F<event.h> header can be found.	2553	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
1689		2554
1690	=item EV_PROTOTYPES	2555	=item EV_PROTOTYPES
1691		2556
1692	If defined to be C<0>, then F<ev.h> will not define any function	2557	If defined to be C<0>, then F<ev.h> will not define any function
1693	prototypes, but still define all the structs and other symbols. This is	2558	prototypes, but still define all the structs and other symbols. This is
…		…
1700	will have the C<struct ev_loop *> as first argument, and you can create	2565	will have the C<struct ev_loop *> as first argument, and you can create
1701	additional independent event loops. Otherwise there will be no support	2566	additional independent event loops. Otherwise there will be no support
1702	for multiple event loops and there is no first event loop pointer	2567	for multiple event loops and there is no first event loop pointer
1703	argument. Instead, all functions act on the single default loop.	2568	argument. Instead, all functions act on the single default loop.
1704		2569
		2570	=item EV_MINPRI
		2571
		2572	=item EV_MAXPRI
		2573
		2574	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2575	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2576	provide for more priorities by overriding those symbols (usually defined
		2577	to be C<-2> and C<2>, respectively).
		2578
		2579	When doing priority-based operations, libev usually has to linearly search
		2580	all the priorities, so having many of them (hundreds) uses a lot of space
		2581	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2582	fine.
		2583
		2584	If your embedding app does not need any priorities, defining these both to
		2585	C<0> will save some memory and cpu.
		2586
1705	=item EV_PERIODICS	2587	=item EV_PERIODIC_ENABLE
1706		2588
1707	If undefined or defined to be C<1>, then periodic timers are supported,	2589	If undefined or defined to be C<1>, then periodic timers are supported. If
1708	otherwise not. This saves a few kb of code.	2590	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2591	code.
		2592
		2593	=item EV_IDLE_ENABLE
		2594
		2595	If undefined or defined to be C<1>, then idle watchers are supported. If
		2596	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2597	code.
		2598
		2599	=item EV_EMBED_ENABLE
		2600
		2601	If undefined or defined to be C<1>, then embed watchers are supported. If
		2602	defined to be C<0>, then they are not.
		2603
		2604	=item EV_STAT_ENABLE
		2605
		2606	If undefined or defined to be C<1>, then stat watchers are supported. If
		2607	defined to be C<0>, then they are not.
		2608
		2609	=item EV_FORK_ENABLE
		2610
		2611	If undefined or defined to be C<1>, then fork watchers are supported. If
		2612	defined to be C<0>, then they are not.
		2613
		2614	=item EV_MINIMAL
		2615
		2616	If you need to shave off some kilobytes of code at the expense of some
		2617	speed, define this symbol to C<1>. Currently only used for gcc to override
		2618	some inlining decisions, saves roughly 30% codesize of amd64.
		2619
		2620	=item EV_PID_HASHSIZE
		2621
		2622	C<ev_child> watchers use a small hash table to distribute workload by
		2623	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2624	than enough. If you need to manage thousands of children you might want to
		2625	increase this value (I<must> be a power of two).
		2626
		2627	=item EV_INOTIFY_HASHSIZE
		2628
		2629	C<ev_stat> watchers use a small hash table to distribute workload by
		2630	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2631	usually more than enough. If you need to manage thousands of C<ev_stat>
		2632	watchers you might want to increase this value (I<must> be a power of
		2633	two).
1709		2634
1710	=item EV_COMMON	2635	=item EV_COMMON
1711		2636
1712	By default, all watchers have a C<void *data> member. By redefining	2637	By default, all watchers have a C<void *data> member. By redefining
1713	this macro to a something else you can include more and other types of	2638	this macro to a something else you can include more and other types of
…		…
1726		2651
1727	=item ev_set_cb (ev, cb)	2652	=item ev_set_cb (ev, cb)
1728		2653
1729	Can be used to change the callback member declaration in each watcher,	2654	Can be used to change the callback member declaration in each watcher,
1730	and the way callbacks are invoked and set. Must expand to a struct member	2655	and the way callbacks are invoked and set. Must expand to a struct member
1731	definition and a statement, respectively. See the F<ev.v> header file for	2656	definition and a statement, respectively. See the F<ev.h> header file for
1732	their default definitions. One possible use for overriding these is to	2657	their default definitions. One possible use for overriding these is to
1733	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2658	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1734	method calls instead of plain function calls in C++.	2659	method calls instead of plain function calls in C++.
		2660
		2661	=head2 EXPORTED API SYMBOLS
		2662
		2663	If you need to re-export the API (e.g. via a dll) and you need a list of
		2664	exported symbols, you can use the provided F<Symbol.*> files which list
		2665	all public symbols, one per line:
		2666
		2667	Symbols.ev for libev proper
		2668	Symbols.event for the libevent emulation
		2669
		2670	This can also be used to rename all public symbols to avoid clashes with
		2671	multiple versions of libev linked together (which is obviously bad in
		2672	itself, but sometimes it is inconvinient to avoid this).
		2673
		2674	A sed command like this will create wrapper C<#define>'s that you need to
		2675	include before including F<ev.h>:
		2676
		2677	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2678
		2679	This would create a file F<wrap.h> which essentially looks like this:
		2680
		2681	#define ev_backend myprefix_ev_backend
		2682	#define ev_check_start myprefix_ev_check_start
		2683	#define ev_check_stop myprefix_ev_check_stop
		2684	...
1735		2685
1736	=head2 EXAMPLES	2686	=head2 EXAMPLES
1737		2687
1738	For a real-world example of a program the includes libev	2688	For a real-world example of a program the includes libev
1739	verbatim, you can have a look at the EV perl module	2689	verbatim, you can have a look at the EV perl module
…		…
1742	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2692	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1743	will be compiled. It is pretty complex because it provides its own header	2693	will be compiled. It is pretty complex because it provides its own header
1744	file.	2694	file.
1745		2695
1746	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2696	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1747	that everybody includes and which overrides some autoconf choices:	2697	that everybody includes and which overrides some configure choices:
1748		2698
		2699	#define EV_MINIMAL 1
1749	#define EV_USE_POLL 0	2700	#define EV_USE_POLL 0
1750	#define EV_MULTIPLICITY 0	2701	#define EV_MULTIPLICITY 0
1751	#define EV_PERIODICS 0	2702	#define EV_PERIODIC_ENABLE 0
		2703	#define EV_STAT_ENABLE 0
		2704	#define EV_FORK_ENABLE 0
1752	#define EV_CONFIG_H <config.h>	2705	#define EV_CONFIG_H <config.h>
		2706	#define EV_MINPRI 0
		2707	#define EV_MAXPRI 0
1753		2708
1754	#include "ev++.h"	2709	#include "ev++.h"
1755		2710
1756	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2711	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1757		2712
…		…
1763		2718
1764	In this section the complexities of (many of) the algorithms used inside	2719	In this section the complexities of (many of) the algorithms used inside
1765	libev will be explained. For complexity discussions about backends see the	2720	libev will be explained. For complexity discussions about backends see the
1766	documentation for C<ev_default_init>.	2721	documentation for C<ev_default_init>.
1767		2722
		2723	All of the following are about amortised time: If an array needs to be
		2724	extended, libev needs to realloc and move the whole array, but this
		2725	happens asymptotically never with higher number of elements, so O(1) might
		2726	mean it might do a lengthy realloc operation in rare cases, but on average
		2727	it is much faster and asymptotically approaches constant time.
		2728
1768	=over 4	2729	=over 4
1769		2730
1770	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2731	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
1771		2732
		2733	This means that, when you have a watcher that triggers in one hour and
		2734	there are 100 watchers that would trigger before that then inserting will
		2735	have to skip roughly seven (C<ld 100>) of these watchers.
		2736
1772	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2737	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2738
		2739	That means that changing a timer costs less than removing/adding them
		2740	as only the relative motion in the event queue has to be paid for.
1773		2741
1774	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2742	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
1775		2743
		2744	These just add the watcher into an array or at the head of a list.
		2745
1776	=item Stopping check/prepare/idle watchers: O(1)	2746	=item Stopping check/prepare/idle watchers: O(1)
1777		2747
1778	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2748	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
1779		2749
		2750	These watchers are stored in lists then need to be walked to find the
		2751	correct watcher to remove. The lists are usually short (you don't usually
		2752	have many watchers waiting for the same fd or signal).
		2753
1780	=item Finding the next timer per loop iteration: O(1)	2754	=item Finding the next timer in each loop iteration: O(1)
		2755
		2756	By virtue of using a binary heap, the next timer is always found at the
		2757	beginning of the storage array.
1781		2758
1782	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2759	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
1783		2760
1784	=item Activating one watcher: O(1)	2761	A change means an I/O watcher gets started or stopped, which requires
		2762	libev to recalculate its status (and possibly tell the kernel, depending
		2763	on backend and wether C<ev_io_set> was used).
		2764
		2765	=item Activating one watcher (putting it into the pending state): O(1)
		2766
		2767	=item Priority handling: O(number_of_priorities)
		2768
		2769	Priorities are implemented by allocating some space for each
		2770	priority. When doing priority-based operations, libev usually has to
		2771	linearly search all the priorities, but starting/stopping and activating
		2772	watchers becomes O(1) w.r.t. prioritiy handling.
1785		2773
1786	=back	2774	=back
1787		2775
1788		2776
1789	=head1 AUTHOR	2777	=head1 AUTHOR

Diff Legend

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