ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.51 by root, Tue Nov 27 19:23:31 2007 UTC vs.
Revision 1.117 by root, Wed Jan 9 04:15:39 2008 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
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
52		106
53	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
54		108
55	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
56	library in any way.	110	library in any way.
…		…
61		115
62	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
63	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
64	you actually want to know.	118	you actually want to know.
65		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
66	=item int ev_version_major ()	126	=item int ev_version_major ()
67		127
68	=item int ev_version_minor ()	128	=item int ev_version_minor ()
69		129
70	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
71	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
72	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
73	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
74	version of the library your program was compiled against.	134	version of the library your program was compiled against.
75		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
76	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,
77	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
78	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
79	not a problem.	142	not a problem.
80		143
81	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
82	version:	145	version.
83		146
84	assert (("libev version mismatch",	147	assert (("libev version mismatch",
85	ev_version_major () == EV_VERSION_MAJOR	148	ev_version_major () == EV_VERSION_MAJOR
86	&& ev_version_minor () >= EV_VERSION_MINOR));	149	&& ev_version_minor () >= EV_VERSION_MINOR));
87		150
…		…
117		180
118	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
119		182
120	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
121		184
122	Sets the allocation function to use (the prototype is similar to the	185	Sets the allocation function to use (the prototype is similar - the
123	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
124	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
125	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
126	destructive action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
127		191
128	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
129	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,
130	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.
131		195
132	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
133	retries: better than mine).	197	retries).
134		198
135	static void *	199	static void *
136	persistent_realloc (void *ptr, long size)	200	persistent_realloc (void *ptr, size_t size)
137	{	201	{
138	for (;;)	202	for (;;)
139	{	203	{
140	void *newptr = realloc (ptr, size);	204	void *newptr = realloc (ptr, size);
141		205
…		…
157	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
158	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
159	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
160	(such as abort).	224	(such as abort).
161		225
162	Example: do the same thing as libev does internally:	226	Example: This is basically the same thing that libev does internally, too.
163		227
164	static void	228	static void
165	fatal_error (const char *msg)	229	fatal_error (const char *msg)
166	{	230	{
167	perror (msg);	231	perror (msg);
…		…
217	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
218	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
219	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
220	around bugs.	284	around bugs.
221		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
222	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
223		307
224	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
225	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,
226	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
227	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
228	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.
229		320
230	=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)
231		322
232	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
233	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
234	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
235	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.
236		329
237	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
238		331
239	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,
240	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
241	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),
242	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.
243		339
244	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
245	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
246	(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
247	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
248	well if you register events for both fds.	344	very well if you register events for both fds.
249		345
250	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
251	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
252	(or space) is available.	348	(or space) is available.
253		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
254	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
255		358
256	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
257	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
258	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
259	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
260	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
261	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.
262		370
263	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
264	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
265	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
266	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
267	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.
268		386
269	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
270		388
271	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.
272		393
273	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
274		395
275	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,
276	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)).
277		398
278	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
279	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
280	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.
		407
		408	On the positive side, ignoring the spurious readyness notifications, this
		409	backend actually performed to specification in all tests and is fully
		410	embeddable, which is a rare feat among the OS-specific backends.
281		411
282	=item C<EVBACKEND_ALL>	412	=item C<EVBACKEND_ALL>
283		413
284	Try all backends (even potentially broken ones that wouldn't be tried	414	Try all backends (even potentially broken ones that wouldn't be tried
285	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	415	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
286	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	416	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
287		417
		418	It is definitely not recommended to use this flag.
		419
288	=back	420	=back
289		421
290	If one or more of these are ored into the flags value, then only these	422	If one or more of these are ored into the flags value, then only these
291	backends will be tried (in the reverse order as given here). If none are	423	backends will be tried (in the reverse order as listed here). If none are
292	specified, most compiled-in backend will be tried, usually in reverse	424	specified, all backends in C<ev_recommended_backends ()> will be tried.
293	order of their flag values :)
294		425
295	The most typical usage is like this:	426	The most typical usage is like this:
296		427
297	if (!ev_default_loop (0))	428	if (!ev_default_loop (0))
298	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	429	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
313	Similar to C<ev_default_loop>, but always creates a new event loop that is	444	Similar to C<ev_default_loop>, but always creates a new event loop that is
314	always distinct from the default loop. Unlike the default loop, it cannot	445	always distinct from the default loop. Unlike the default loop, it cannot
315	handle signal and child watchers, and attempts to do so will be greeted by	446	handle signal and child watchers, and attempts to do so will be greeted by
316	undefined behaviour (or a failed assertion if assertions are enabled).	447	undefined behaviour (or a failed assertion if assertions are enabled).
317		448
318	Example: try to create a event loop that uses epoll and nothing else.	449	Example: Try to create a event loop that uses epoll and nothing else.
319		450
320	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	451	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
321	if (!epoller)	452	if (!epoller)
322	fatal ("no epoll found here, maybe it hides under your chair");	453	fatal ("no epoll found here, maybe it hides under your chair");
323		454
…		…
326	Destroys the default loop again (frees all memory and kernel state	457	Destroys the default loop again (frees all memory and kernel state
327	etc.). None of the active event watchers will be stopped in the normal	458	etc.). None of the active event watchers will be stopped in the normal
328	sense, so e.g. C<ev_is_active> might still return true. It is your	459	sense, so e.g. C<ev_is_active> might still return true. It is your
329	responsibility to either stop all watchers cleanly yoursef I<before>	460	responsibility to either stop all watchers cleanly yoursef I<before>
330	calling this function, or cope with the fact afterwards (which is usually	461	calling this function, or cope with the fact afterwards (which is usually
331	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	462	the easiest thing, you can just ignore the watchers and/or C<free ()> them
332	for example).	463	for example).
		464
		465	Note that certain global state, such as signal state, will not be freed by
		466	this function, and related watchers (such as signal and child watchers)
		467	would need to be stopped manually.
		468
		469	In general it is not advisable to call this function except in the
		470	rare occasion where you really need to free e.g. the signal handling
		471	pipe fds. If you need dynamically allocated loops it is better to use
		472	C<ev_loop_new> and C<ev_loop_destroy>).
333		473
334	=item ev_loop_destroy (loop)	474	=item ev_loop_destroy (loop)
335		475
336	Like C<ev_default_destroy>, but destroys an event loop created by an	476	Like C<ev_default_destroy>, but destroys an event loop created by an
337	earlier call to C<ev_loop_new>.	477	earlier call to C<ev_loop_new>.
…		…
361		501
362	Like C<ev_default_fork>, but acts on an event loop created by	502	Like C<ev_default_fork>, but acts on an event loop created by
363	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	503	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
364	after fork, and how you do this is entirely your own problem.	504	after fork, and how you do this is entirely your own problem.
365		505
		506	=item unsigned int ev_loop_count (loop)
		507
		508	Returns the count of loop iterations for the loop, which is identical to
		509	the number of times libev did poll for new events. It starts at C<0> and
		510	happily wraps around with enough iterations.
		511
		512	This value can sometimes be useful as a generation counter of sorts (it
		513	"ticks" the number of loop iterations), as it roughly corresponds with
		514	C<ev_prepare> and C<ev_check> calls.
		515
366	=item unsigned int ev_backend (loop)	516	=item unsigned int ev_backend (loop)
367		517
368	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	518	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
369	use.	519	use.
370		520
…		…
372		522
373	Returns the current "event loop time", which is the time the event loop	523	Returns the current "event loop time", which is the time the event loop
374	received events and started processing them. This timestamp does not	524	received events and started processing them. This timestamp does not
375	change as long as callbacks are being processed, and this is also the base	525	change as long as callbacks are being processed, and this is also the base
376	time used for relative timers. You can treat it as the timestamp of the	526	time used for relative timers. You can treat it as the timestamp of the
377	event occuring (or more correctly, libev finding out about it).	527	event occurring (or more correctly, libev finding out about it).
378		528
379	=item ev_loop (loop, int flags)	529	=item ev_loop (loop, int flags)
380		530
381	Finally, this is it, the event handler. This function usually is called	531	Finally, this is it, the event handler. This function usually is called
382	after you initialised all your watchers and you want to start handling	532	after you initialised all your watchers and you want to start handling
…		…
403	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	553	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
404	usually a better approach for this kind of thing.	554	usually a better approach for this kind of thing.
405		555
406	Here are the gory details of what C<ev_loop> does:	556	Here are the gory details of what C<ev_loop> does:
407		557
408	* If there are no active watchers (reference count is zero), return.	558	- Before the first iteration, call any pending watchers.
409	- Queue prepare watchers and then call all outstanding watchers.	559	* If EVFLAG_FORKCHECK was used, check for a fork.
		560	- If a fork was detected, queue and call all fork watchers.
		561	- Queue and call all prepare watchers.
410	- If we have been forked, recreate the kernel state.	562	- If we have been forked, recreate the kernel state.
411	- Update the kernel state with all outstanding changes.	563	- Update the kernel state with all outstanding changes.
412	- Update the "event loop time".	564	- Update the "event loop time".
413	- Calculate for how long to block.	565	- Calculate for how long to sleep or block, if at all
		566	(active idle watchers, EVLOOP_NONBLOCK or not having
		567	any active watchers at all will result in not sleeping).
		568	- Sleep if the I/O and timer collect interval say so.
414	- Block the process, waiting for any events.	569	- Block the process, waiting for any events.
415	- Queue all outstanding I/O (fd) events.	570	- Queue all outstanding I/O (fd) events.
416	- Update the "event loop time" and do time jump handling.	571	- Update the "event loop time" and do time jump handling.
417	- Queue all outstanding timers.	572	- Queue all outstanding timers.
418	- Queue all outstanding periodics.	573	- Queue all outstanding periodics.
419	- If no events are pending now, queue all idle watchers.	574	- If no events are pending now, queue all idle watchers.
420	- Queue all check watchers.	575	- Queue all check watchers.
421	- Call all queued watchers in reverse order (i.e. check watchers first).	576	- Call all queued watchers in reverse order (i.e. check watchers first).
422	Signals and child watchers are implemented as I/O watchers, and will	577	Signals and child watchers are implemented as I/O watchers, and will
423	be handled here by queueing them when their watcher gets executed.	578	be handled here by queueing them when their watcher gets executed.
424	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	579	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
425	were used, return, otherwise continue with step *.	580	were used, or there are no active watchers, return, otherwise
		581	continue with step *.
426		582
427	Example: queue some jobs and then loop until no events are outsanding	583	Example: Queue some jobs and then loop until no events are outstanding
428	anymore.	584	anymore.
429		585
430	... queue jobs here, make sure they register event watchers as long	586	... queue jobs here, make sure they register event watchers as long
431	... as they still have work to do (even an idle watcher will do..)	587	... as they still have work to do (even an idle watcher will do..)
432	ev_loop (my_loop, 0);	588	ev_loop (my_loop, 0);
…		…
436		592
437	Can be used to make a call to C<ev_loop> return early (but only after it	593	Can be used to make a call to C<ev_loop> return early (but only after it
438	has processed all outstanding events). The C<how> argument must be either	594	has processed all outstanding events). The C<how> argument must be either
439	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	595	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
440	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	596	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		597
		598	This "unloop state" will be cleared when entering C<ev_loop> again.
441		599
442	=item ev_ref (loop)	600	=item ev_ref (loop)
443		601
444	=item ev_unref (loop)	602	=item ev_unref (loop)
445		603
…		…
450	returning, ev_unref() after starting, and ev_ref() before stopping it. For	608	returning, ev_unref() after starting, and ev_ref() before stopping it. For
451	example, libev itself uses this for its internal signal pipe: It is not	609	example, libev itself uses this for its internal signal pipe: It is not
452	visible to the libev user and should not keep C<ev_loop> from exiting if	610	visible to the libev user and should not keep C<ev_loop> from exiting if
453	no event watchers registered by it are active. It is also an excellent	611	no event watchers registered by it are active. It is also an excellent
454	way to do this for generic recurring timers or from within third-party	612	way to do this for generic recurring timers or from within third-party
455	libraries. Just remember to I<unref after start> and I<ref before stop>.	613	libraries. Just remember to I<unref after start> and I<ref before stop>
		614	(but only if the watcher wasn't active before, or was active before,
		615	respectively).
456		616
457	Example: create a signal watcher, but keep it from keeping C<ev_loop>	617	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
458	running when nothing else is active.	618	running when nothing else is active.
459		619
460	struct dv_signal exitsig;	620	struct ev_signal exitsig;
461	ev_signal_init (&exitsig, sig_cb, SIGINT);	621	ev_signal_init (&exitsig, sig_cb, SIGINT);
462	ev_signal_start (myloop, &exitsig);	622	ev_signal_start (loop, &exitsig);
463	evf_unref (myloop);	623	evf_unref (loop);
464		624
465	Example: for some weird reason, unregister the above signal handler again.	625	Example: For some weird reason, unregister the above signal handler again.
466		626
467	ev_ref (myloop);	627	ev_ref (loop);
468	ev_signal_stop (myloop, &exitsig);	628	ev_signal_stop (loop, &exitsig);
		629
		630	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		631
		632	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		633
		634	These advanced functions influence the time that libev will spend waiting
		635	for events. Both are by default C<0>, meaning that libev will try to
		636	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		637
		638	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		639	allows libev to delay invocation of I/O and timer/periodic callbacks to
		640	increase efficiency of loop iterations.
		641
		642	The background is that sometimes your program runs just fast enough to
		643	handle one (or very few) event(s) per loop iteration. While this makes
		644	the program responsive, it also wastes a lot of CPU time to poll for new
		645	events, especially with backends like C<select ()> which have a high
		646	overhead for the actual polling but can deliver many events at once.
		647
		648	By setting a higher I<io collect interval> you allow libev to spend more
		649	time collecting I/O events, so you can handle more events per iteration,
		650	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		651	C<ev_timer>) will be not affected. Setting this to a non-null value will
		652	introduce an additional C<ev_sleep ()> call into most loop iterations.
		653
		654	Likewise, by setting a higher I<timeout collect interval> you allow libev
		655	to spend more time collecting timeouts, at the expense of increased
		656	latency (the watcher callback will be called later). C<ev_io> watchers
		657	will not be affected. Setting this to a non-null value will not introduce
		658	any overhead in libev.
		659
		660	Many (busy) programs can usually benefit by setting the io collect
		661	interval to a value near C<0.1> or so, which is often enough for
		662	interactive servers (of course not for games), likewise for timeouts. It
		663	usually doesn't make much sense to set it to a lower value than C<0.01>,
		664	as this approsaches the timing granularity of most systems.
469		665
470	=back	666	=back
471		667
472		668
473	=head1 ANATOMY OF A WATCHER	669	=head1 ANATOMY OF A WATCHER
…		…
653	=item bool ev_is_pending (ev_TYPE *watcher)	849	=item bool ev_is_pending (ev_TYPE *watcher)
654		850
655	Returns a true value iff the watcher is pending, (i.e. it has outstanding	851	Returns a true value iff the watcher is pending, (i.e. it has outstanding
656	events but its callback has not yet been invoked). As long as a watcher	852	events but its callback has not yet been invoked). As long as a watcher
657	is pending (but not active) you must not call an init function on it (but	853	is pending (but not active) you must not call an init function on it (but
658	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	854	C<ev_TYPE_set> is safe), you must not change its priority, and you must
659	libev (e.g. you cnanot C<free ()> it).	855	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		856	it).
660		857
661	=item callback = ev_cb (ev_TYPE *watcher)	858	=item callback ev_cb (ev_TYPE *watcher)
662		859
663	Returns the callback currently set on the watcher.	860	Returns the callback currently set on the watcher.
664		861
665	=item ev_cb_set (ev_TYPE *watcher, callback)	862	=item ev_cb_set (ev_TYPE *watcher, callback)
666		863
667	Change the callback. You can change the callback at virtually any time	864	Change the callback. You can change the callback at virtually any time
668	(modulo threads).	865	(modulo threads).
		866
		867	=item ev_set_priority (ev_TYPE *watcher, priority)
		868
		869	=item int ev_priority (ev_TYPE *watcher)
		870
		871	Set and query the priority of the watcher. The priority is a small
		872	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		873	(default: C<-2>). Pending watchers with higher priority will be invoked
		874	before watchers with lower priority, but priority will not keep watchers
		875	from being executed (except for C<ev_idle> watchers).
		876
		877	This means that priorities are I<only> used for ordering callback
		878	invocation after new events have been received. This is useful, for
		879	example, to reduce latency after idling, or more often, to bind two
		880	watchers on the same event and make sure one is called first.
		881
		882	If you need to suppress invocation when higher priority events are pending
		883	you need to look at C<ev_idle> watchers, which provide this functionality.
		884
		885	You I<must not> change the priority of a watcher as long as it is active or
		886	pending.
		887
		888	The default priority used by watchers when no priority has been set is
		889	always C<0>, which is supposed to not be too high and not be too low :).
		890
		891	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		892	fine, as long as you do not mind that the priority value you query might
		893	or might not have been adjusted to be within valid range.
		894
		895	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		896
		897	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		898	C<loop> nor C<revents> need to be valid as long as the watcher callback
		899	can deal with that fact.
		900
		901	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		902
		903	If the watcher is pending, this function returns clears its pending status
		904	and returns its C<revents> bitset (as if its callback was invoked). If the
		905	watcher isn't pending it does nothing and returns C<0>.
669		906
670	=back	907	=back
671		908
672		909
673	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	910	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
694	{	931	{
695	struct my_io *w = (struct my_io *)w_;	932	struct my_io *w = (struct my_io *)w_;
696	...	933	...
697	}	934	}
698		935
699	More interesting and less C-conformant ways of catsing your callback type	936	More interesting and less C-conformant ways of casting your callback type
700	have been omitted....	937	instead have been omitted.
		938
		939	Another common scenario is having some data structure with multiple
		940	watchers:
		941
		942	struct my_biggy
		943	{
		944	int some_data;
		945	ev_timer t1;
		946	ev_timer t2;
		947	}
		948
		949	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		950	you need to use C<offsetof>:
		951
		952	#include <stddef.h>
		953
		954	static void
		955	t1_cb (EV_P_ struct ev_timer *w, int revents)
		956	{
		957	struct my_biggy big = (struct my_biggy *
		958	(((char *)w) - offsetof (struct my_biggy, t1));
		959	}
		960
		961	static void
		962	t2_cb (EV_P_ struct ev_timer *w, int revents)
		963	{
		964	struct my_biggy big = (struct my_biggy *
		965	(((char *)w) - offsetof (struct my_biggy, t2));
		966	}
701		967
702		968
703	=head1 WATCHER TYPES	969	=head1 WATCHER TYPES
704		970
705	This section describes each watcher in detail, but will not repeat	971	This section describes each watcher in detail, but will not repeat
…		…
729	In general you can register as many read and/or write event watchers per	995	In general you can register as many read and/or write event watchers per
730	fd as you want (as long as you don't confuse yourself). Setting all file	996	fd as you want (as long as you don't confuse yourself). Setting all file
731	descriptors to non-blocking mode is also usually a good idea (but not	997	descriptors to non-blocking mode is also usually a good idea (but not
732	required if you know what you are doing).	998	required if you know what you are doing).
733		999
734	You have to be careful with dup'ed file descriptors, though. Some backends
735	(the linux epoll backend is a notable example) cannot handle dup'ed file
736	descriptors correctly if you register interest in two or more fds pointing
737	to the same underlying file/socket/etc. description (that is, they share
738	the same underlying "file open").
739
740	If you must do this, then force the use of a known-to-be-good backend	1000	If you must do this, then force the use of a known-to-be-good backend
741	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1001	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
742	C<EVBACKEND_POLL>).	1002	C<EVBACKEND_POLL>).
743		1003
744	Another thing you have to watch out for is that it is quite easy to	1004	Another thing you have to watch out for is that it is quite easy to
…		…
750	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1010	it is best to always use non-blocking I/O: An extra C<read>(2) returning
751	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1011	C<EAGAIN> is far preferable to a program hanging until some data arrives.
752		1012
753	If you cannot run the fd in non-blocking mode (for example you should not	1013	If you cannot run the fd in non-blocking mode (for example you should not
754	play around with an Xlib connection), then you have to seperately re-test	1014	play around with an Xlib connection), then you have to seperately re-test
755	wether a file descriptor is really ready with a known-to-be good interface	1015	whether a file descriptor is really ready with a known-to-be good interface
756	such as poll (fortunately in our Xlib example, Xlib already does this on	1016	such as poll (fortunately in our Xlib example, Xlib already does this on
757	its own, so its quite safe to use).	1017	its own, so its quite safe to use).
		1018
		1019	=head3 The special problem of disappearing file descriptors
		1020
		1021	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1022	descriptor (either by calling C<close> explicitly or by any other means,
		1023	such as C<dup>). The reason is that you register interest in some file
		1024	descriptor, but when it goes away, the operating system will silently drop
		1025	this interest. If another file descriptor with the same number then is
		1026	registered with libev, there is no efficient way to see that this is, in
		1027	fact, a different file descriptor.
		1028
		1029	To avoid having to explicitly tell libev about such cases, libev follows
		1030	the following policy: Each time C<ev_io_set> is being called, libev
		1031	will assume that this is potentially a new file descriptor, otherwise
		1032	it is assumed that the file descriptor stays the same. That means that
		1033	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1034	descriptor even if the file descriptor number itself did not change.
		1035
		1036	This is how one would do it normally anyway, the important point is that
		1037	the libev application should not optimise around libev but should leave
		1038	optimisations to libev.
		1039
		1040	=head3 The special problem of dup'ed file descriptors
		1041
		1042	Some backends (e.g. epoll), cannot register events for file descriptors,
		1043	but only events for the underlying file descriptions. That means when you
		1044	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1045	events for them, only one file descriptor might actually receive events.
		1046
		1047	There is no workaround possible except not registering events
		1048	for potentially C<dup ()>'ed file descriptors, or to resort to
		1049	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1050
		1051	=head3 The special problem of fork
		1052
		1053	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1054	useless behaviour. Libev fully supports fork, but needs to be told about
		1055	it in the child.
		1056
		1057	To support fork in your programs, you either have to call
		1058	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1059	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1060	C<EVBACKEND_POLL>.
		1061
		1062
		1063	=head3 Watcher-Specific Functions
758		1064
759	=over 4	1065	=over 4
760		1066
761	=item ev_io_init (ev_io *, callback, int fd, int events)	1067	=item ev_io_init (ev_io *, callback, int fd, int events)
762		1068
…		…
774		1080
775	The events being watched.	1081	The events being watched.
776		1082
777	=back	1083	=back
778		1084
		1085	=head3 Examples
		1086
779	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1087	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
780	readable, but only once. Since it is likely line-buffered, you could	1088	readable, but only once. Since it is likely line-buffered, you could
781	attempt to read a whole line in the callback:	1089	attempt to read a whole line in the callback.
782		1090
783	static void	1091	static void
784	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1092	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
785	{	1093	{
786	ev_io_stop (loop, w);	1094	ev_io_stop (loop, w);
…		…
816		1124
817	The callback is guarenteed to be invoked only when its timeout has passed,	1125	The callback is guarenteed to be invoked only when its timeout has passed,
818	but if multiple timers become ready during the same loop iteration then	1126	but if multiple timers become ready during the same loop iteration then
819	order of execution is undefined.	1127	order of execution is undefined.
820		1128
		1129	=head3 Watcher-Specific Functions and Data Members
		1130
821	=over 4	1131	=over 4
822		1132
823	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1133	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
824		1134
825	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1135	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
838	=item ev_timer_again (loop)	1148	=item ev_timer_again (loop)
839		1149
840	This will act as if the timer timed out and restart it again if it is	1150	This will act as if the timer timed out and restart it again if it is
841	repeating. The exact semantics are:	1151	repeating. The exact semantics are:
842		1152
		1153	If the timer is pending, its pending status is cleared.
		1154
843	If the timer is started but nonrepeating, stop it.	1155	If the timer is started but nonrepeating, stop it (as if it timed out).
844		1156
845	If the timer is repeating, either start it if necessary (with the repeat	1157	If the timer is repeating, either start it if necessary (with the
846	value), or reset the running timer to the repeat value.	1158	C<repeat> value), or reset the running timer to the C<repeat> value.
847		1159
848	This sounds a bit complicated, but here is a useful and typical	1160	This sounds a bit complicated, but here is a useful and typical
849	example: Imagine you have a tcp connection and you want a so-called	1161	example: Imagine you have a tcp connection and you want a so-called idle
850	idle timeout, that is, you want to be called when there have been,	1162	timeout, that is, you want to be called when there have been, say, 60
851	say, 60 seconds of inactivity on the socket. The easiest way to do	1163	seconds of inactivity on the socket. The easiest way to do this is to
852	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1164	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
853	C<ev_timer_again> each time you successfully read or write some data. If	1165	C<ev_timer_again> each time you successfully read or write some data. If
854	you go into an idle state where you do not expect data to travel on the	1166	you go into an idle state where you do not expect data to travel on the
855	socket, you can stop the timer, and again will automatically restart it if	1167	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
856	need be.	1168	automatically restart it if need be.
857		1169
858	You can also ignore the C<after> value and C<ev_timer_start> altogether	1170	That means you can ignore the C<after> value and C<ev_timer_start>
859	and only ever use the C<repeat> value:	1171	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
860		1172
861	ev_timer_init (timer, callback, 0., 5.);	1173	ev_timer_init (timer, callback, 0., 5.);
862	ev_timer_again (loop, timer);	1174	ev_timer_again (loop, timer);
863	...	1175	...
864	timer->again = 17.;	1176	timer->again = 17.;
865	ev_timer_again (loop, timer);	1177	ev_timer_again (loop, timer);
866	...	1178	...
867	timer->again = 10.;	1179	timer->again = 10.;
868	ev_timer_again (loop, timer);	1180	ev_timer_again (loop, timer);
869		1181
870	This is more efficient then stopping/starting the timer eahc time you want	1182	This is more slightly efficient then stopping/starting the timer each time
871	to modify its timeout value.	1183	you want to modify its timeout value.
872		1184
873	=item ev_tstamp repeat [read-write]	1185	=item ev_tstamp repeat [read-write]
874		1186
875	The current C<repeat> value. Will be used each time the watcher times out	1187	The current C<repeat> value. Will be used each time the watcher times out
876	or C<ev_timer_again> is called and determines the next timeout (if any),	1188	or C<ev_timer_again> is called and determines the next timeout (if any),
877	which is also when any modifications are taken into account.	1189	which is also when any modifications are taken into account.
878		1190
879	=back	1191	=back
880		1192
		1193	=head3 Examples
		1194
881	Example: create a timer that fires after 60 seconds.	1195	Example: Create a timer that fires after 60 seconds.
882		1196
883	static void	1197	static void
884	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1198	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
885	{	1199	{
886	.. one minute over, w is actually stopped right here	1200	.. one minute over, w is actually stopped right here
…		…
888		1202
889	struct ev_timer mytimer;	1203	struct ev_timer mytimer;
890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1204	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
891	ev_timer_start (loop, &mytimer);	1205	ev_timer_start (loop, &mytimer);
892		1206
893	Example: create a timeout timer that times out after 10 seconds of	1207	Example: Create a timeout timer that times out after 10 seconds of
894	inactivity.	1208	inactivity.
895		1209
896	static void	1210	static void
897	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1211	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
898	{	1212	{
…		…
918	but on wallclock time (absolute time). You can tell a periodic watcher	1232	but on wallclock time (absolute time). You can tell a periodic watcher
919	to trigger "at" some specific point in time. For example, if you tell a	1233	to trigger "at" some specific point in time. For example, if you tell a
920	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1234	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
921	+ 10.>) and then reset your system clock to the last year, then it will	1235	+ 10.>) and then reset your system clock to the last year, then it will
922	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1236	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
923	roughly 10 seconds later and of course not if you reset your system time	1237	roughly 10 seconds later).
924	again).
925		1238
926	They can also be used to implement vastly more complex timers, such as	1239	They can also be used to implement vastly more complex timers, such as
927	triggering an event on eahc midnight, local time.	1240	triggering an event on each midnight, local time or other, complicated,
		1241	rules.
928		1242
929	As with timers, the callback is guarenteed to be invoked only when the	1243	As with timers, the callback is guarenteed to be invoked only when the
930	time (C<at>) has been passed, but if multiple periodic timers become ready	1244	time (C<at>) has been passed, but if multiple periodic timers become ready
931	during the same loop iteration then order of execution is undefined.	1245	during the same loop iteration then order of execution is undefined.
932		1246
		1247	=head3 Watcher-Specific Functions and Data Members
		1248
933	=over 4	1249	=over 4
934		1250
935	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1251	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
936		1252
937	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1253	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
939	Lots of arguments, lets sort it out... There are basically three modes of	1255	Lots of arguments, lets sort it out... There are basically three modes of
940	operation, and we will explain them from simplest to complex:	1256	operation, and we will explain them from simplest to complex:
941		1257
942	=over 4	1258	=over 4
943		1259
944	=item * absolute timer (interval = reschedule_cb = 0)	1260	=item * absolute timer (at = time, interval = reschedule_cb = 0)
945		1261
946	In this configuration the watcher triggers an event at the wallclock time	1262	In this configuration the watcher triggers an event at the wallclock time
947	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1263	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
948	that is, if it is to be run at January 1st 2011 then it will run when the	1264	that is, if it is to be run at January 1st 2011 then it will run when the
949	system time reaches or surpasses this time.	1265	system time reaches or surpasses this time.
950		1266
951	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1267	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
952		1268
953	In this mode the watcher will always be scheduled to time out at the next	1269	In this mode the watcher will always be scheduled to time out at the next
954	C<at + N * interval> time (for some integer N) and then repeat, regardless	1270	C<at + N * interval> time (for some integer N, which can also be negative)
955	of any time jumps.	1271	and then repeat, regardless of any time jumps.
956		1272
957	This can be used to create timers that do not drift with respect to system	1273	This can be used to create timers that do not drift with respect to system
958	time:	1274	time:
959		1275
960	ev_periodic_set (&periodic, 0., 3600., 0);	1276	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
966		1282
967	Another way to think about it (for the mathematically inclined) is that	1283	Another way to think about it (for the mathematically inclined) is that
968	C<ev_periodic> will try to run the callback in this mode at the next possible	1284	C<ev_periodic> will try to run the callback in this mode at the next possible
969	time where C<time = at (mod interval)>, regardless of any time jumps.	1285	time where C<time = at (mod interval)>, regardless of any time jumps.
970		1286
		1287	For numerical stability it is preferable that the C<at> value is near
		1288	C<ev_now ()> (the current time), but there is no range requirement for
		1289	this value.
		1290
971	=item * manual reschedule mode (reschedule_cb = callback)	1291	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
972		1292
973	In this mode the values for C<interval> and C<at> are both being	1293	In this mode the values for C<interval> and C<at> are both being
974	ignored. Instead, each time the periodic watcher gets scheduled, the	1294	ignored. Instead, each time the periodic watcher gets scheduled, the
975	reschedule callback will be called with the watcher as first, and the	1295	reschedule callback will be called with the watcher as first, and the
976	current time as second argument.	1296	current time as second argument.
977		1297
978	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1298	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
979	ever, or make any event loop modifications>. If you need to stop it,	1299	ever, or make any event loop modifications>. If you need to stop it,
980	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1300	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
981	starting a prepare watcher).	1301	starting an C<ev_prepare> watcher, which is legal).
982		1302
983	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1303	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
984	ev_tstamp now)>, e.g.:	1304	ev_tstamp now)>, e.g.:
985		1305
986	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1306	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1009	Simply stops and restarts the periodic watcher again. This is only useful	1329	Simply stops and restarts the periodic watcher again. This is only useful
1010	when you changed some parameters or the reschedule callback would return	1330	when you changed some parameters or the reschedule callback would return
1011	a different time than the last time it was called (e.g. in a crond like	1331	a different time than the last time it was called (e.g. in a crond like
1012	program when the crontabs have changed).	1332	program when the crontabs have changed).
1013		1333
		1334	=item ev_tstamp offset [read-write]
		1335
		1336	When repeating, this contains the offset value, otherwise this is the
		1337	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1338
		1339	Can be modified any time, but changes only take effect when the periodic
		1340	timer fires or C<ev_periodic_again> is being called.
		1341
1014	=item ev_tstamp interval [read-write]	1342	=item ev_tstamp interval [read-write]
1015		1343
1016	The current interval value. Can be modified any time, but changes only	1344	The current interval value. Can be modified any time, but changes only
1017	take effect when the periodic timer fires or C<ev_periodic_again> is being	1345	take effect when the periodic timer fires or C<ev_periodic_again> is being
1018	called.	1346	called.
…		…
1021		1349
1022	The current reschedule callback, or C<0>, if this functionality is	1350	The current reschedule callback, or C<0>, if this functionality is
1023	switched off. Can be changed any time, but changes only take effect when	1351	switched off. Can be changed any time, but changes only take effect when
1024	the periodic timer fires or C<ev_periodic_again> is being called.	1352	the periodic timer fires or C<ev_periodic_again> is being called.
1025		1353
		1354	=item ev_tstamp at [read-only]
		1355
		1356	When active, contains the absolute time that the watcher is supposed to
		1357	trigger next.
		1358
1026	=back	1359	=back
1027		1360
		1361	=head3 Examples
		1362
1028	Example: call a callback every hour, or, more precisely, whenever the	1363	Example: Call a callback every hour, or, more precisely, whenever the
1029	system clock is divisible by 3600. The callback invocation times have	1364	system clock is divisible by 3600. The callback invocation times have
1030	potentially a lot of jittering, but good long-term stability.	1365	potentially a lot of jittering, but good long-term stability.
1031		1366
1032	static void	1367	static void
1033	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1368	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
1037		1372
1038	struct ev_periodic hourly_tick;	1373	struct ev_periodic hourly_tick;
1039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1374	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1040	ev_periodic_start (loop, &hourly_tick);	1375	ev_periodic_start (loop, &hourly_tick);
1041		1376
1042	Example: the same as above, but use a reschedule callback to do it:	1377	Example: The same as above, but use a reschedule callback to do it:
1043		1378
1044	#include <math.h>	1379	#include <math.h>
1045		1380
1046	static ev_tstamp	1381	static ev_tstamp
1047	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1382	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
1049	return fmod (now, 3600.) + 3600.;	1384	return fmod (now, 3600.) + 3600.;
1050	}	1385	}
1051		1386
1052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1387	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1053		1388
1054	Example: call a callback every hour, starting now:	1389	Example: Call a callback every hour, starting now:
1055		1390
1056	struct ev_periodic hourly_tick;	1391	struct ev_periodic hourly_tick;
1057	ev_periodic_init (&hourly_tick, clock_cb,	1392	ev_periodic_init (&hourly_tick, clock_cb,
1058	fmod (ev_now (loop), 3600.), 3600., 0);	1393	fmod (ev_now (loop), 3600.), 3600., 0);
1059	ev_periodic_start (loop, &hourly_tick);	1394	ev_periodic_start (loop, &hourly_tick);
…		…
1071	with the kernel (thus it coexists with your own signal handlers as long	1406	with the kernel (thus it coexists with your own signal handlers as long
1072	as you don't register any with libev). Similarly, when the last signal	1407	as you don't register any with libev). Similarly, when the last signal
1073	watcher for a signal is stopped libev will reset the signal handler to	1408	watcher for a signal is stopped libev will reset the signal handler to
1074	SIG_DFL (regardless of what it was set to before).	1409	SIG_DFL (regardless of what it was set to before).
1075		1410
		1411	=head3 Watcher-Specific Functions and Data Members
		1412
1076	=over 4	1413	=over 4
1077		1414
1078	=item ev_signal_init (ev_signal *, callback, int signum)	1415	=item ev_signal_init (ev_signal *, callback, int signum)
1079		1416
1080	=item ev_signal_set (ev_signal *, int signum)	1417	=item ev_signal_set (ev_signal *, int signum)
…		…
1091		1428
1092	=head2 C<ev_child> - watch out for process status changes	1429	=head2 C<ev_child> - watch out for process status changes
1093		1430
1094	Child watchers trigger when your process receives a SIGCHLD in response to	1431	Child watchers trigger when your process receives a SIGCHLD in response to
1095	some child status changes (most typically when a child of yours dies).	1432	some child status changes (most typically when a child of yours dies).
		1433
		1434	=head3 Watcher-Specific Functions and Data Members
1096		1435
1097	=over 4	1436	=over 4
1098		1437
1099	=item ev_child_init (ev_child *, callback, int pid)	1438	=item ev_child_init (ev_child *, callback, int pid)
1100		1439
…		…
1120	The process exit/trace status caused by C<rpid> (see your systems	1459	The process exit/trace status caused by C<rpid> (see your systems
1121	C<waitpid> and C<sys/wait.h> documentation for details).	1460	C<waitpid> and C<sys/wait.h> documentation for details).
1122		1461
1123	=back	1462	=back
1124		1463
		1464	=head3 Examples
		1465
1125	Example: try to exit cleanly on SIGINT and SIGTERM.	1466	Example: Try to exit cleanly on SIGINT and SIGTERM.
1126		1467
1127	static void	1468	static void
1128	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1469	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1129	{	1470	{
1130	ev_unloop (loop, EVUNLOOP_ALL);	1471	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1145	not exist" is a status change like any other. The condition "path does	1486	not exist" is a status change like any other. The condition "path does
1146	not exist" is signified by the C<st_nlink> field being zero (which is	1487	not exist" is signified by the C<st_nlink> field being zero (which is
1147	otherwise always forced to be at least one) and all the other fields of	1488	otherwise always forced to be at least one) and all the other fields of
1148	the stat buffer having unspecified contents.	1489	the stat buffer having unspecified contents.
1149		1490
		1491	The path I<should> be absolute and I<must not> end in a slash. If it is
		1492	relative and your working directory changes, the behaviour is undefined.
		1493
1150	Since there is no standard to do this, the portable implementation simply	1494	Since there is no standard to do this, the portable implementation simply
1151	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1495	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1152	can specify a recommended polling interval for this case. If you specify	1496	can specify a recommended polling interval for this case. If you specify
1153	a polling interval of C<0> (highly recommended!) then a I<suitable,	1497	a polling interval of C<0> (highly recommended!) then a I<suitable,
1154	unspecified default> value will be used (which you can expect to be around	1498	unspecified default> value will be used (which you can expect to be around
1155	five seconds, although this might change dynamically). Libev will also	1499	five seconds, although this might change dynamically). Libev will also
1156	impose a minimum interval which is currently around C<0.1>, but thats	1500	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1158		1502
1159	This watcher type is not meant for massive numbers of stat watchers,	1503	This watcher type is not meant for massive numbers of stat watchers,
1160	as even with OS-supported change notifications, this can be	1504	as even with OS-supported change notifications, this can be
1161	resource-intensive.	1505	resource-intensive.
1162		1506
1163	At the time of this writing, no specific OS backends are implemented, but	1507	At the time of this writing, only the Linux inotify interface is
1164	if demand increases, at least a kqueue and inotify backend will be added.	1508	implemented (implementing kqueue support is left as an exercise for the
		1509	reader). Inotify will be used to give hints only and should not change the
		1510	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1511	to fall back to regular polling again even with inotify, but changes are
		1512	usually detected immediately, and if the file exists there will be no
		1513	polling.
		1514
		1515	=head3 Inotify
		1516
		1517	When C<inotify (7)> support has been compiled into libev (generally only
		1518	available on Linux) and present at runtime, it will be used to speed up
		1519	change detection where possible. The inotify descriptor will be created lazily
		1520	when the first C<ev_stat> watcher is being started.
		1521
		1522	Inotify presense does not change the semantics of C<ev_stat> watchers
		1523	except that changes might be detected earlier, and in some cases, to avoid
		1524	making regular C<stat> calls. Even in the presense of inotify support
		1525	there are many cases where libev has to resort to regular C<stat> polling.
		1526
		1527	(There is no support for kqueue, as apparently it cannot be used to
		1528	implement this functionality, due to the requirement of having a file
		1529	descriptor open on the object at all times).
		1530
		1531	=head3 The special problem of stat time resolution
		1532
		1533	The C<stat ()> syscall only supports full-second resolution portably, and
		1534	even on systems where the resolution is higher, many filesystems still
		1535	only support whole seconds.
		1536
		1537	That means that, if the time is the only thing that changes, you might
		1538	miss updates: on the first update, C<ev_stat> detects a change and calls
		1539	your callback, which does something. When there is another update within
		1540	the same second, C<ev_stat> will be unable to detect it.
		1541
		1542	The solution to this is to delay acting on a change for a second (or till
		1543	the next second boundary), using a roughly one-second delay C<ev_timer>
		1544	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1545	is added to work around small timing inconsistencies of some operating
		1546	systems.
		1547
		1548	=head3 Watcher-Specific Functions and Data Members
1165		1549
1166	=over 4	1550	=over 4
1167		1551
1168	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1552	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1169		1553
…		…
1205	=item const char *path [read-only]	1589	=item const char *path [read-only]
1206		1590
1207	The filesystem path that is being watched.	1591	The filesystem path that is being watched.
1208		1592
1209	=back	1593	=back
		1594
		1595	=head3 Examples
1210		1596
1211	Example: Watch C</etc/passwd> for attribute changes.	1597	Example: Watch C</etc/passwd> for attribute changes.
1212		1598
1213	static void	1599	static void
1214	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1600	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1227	}	1613	}
1228		1614
1229	...	1615	...
1230	ev_stat passwd;	1616	ev_stat passwd;
1231		1617
1232	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1618	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1233	ev_stat_start (loop, &passwd);	1619	ev_stat_start (loop, &passwd);
1234		1620
		1621	Example: Like above, but additionally use a one-second delay so we do not
		1622	miss updates (however, frequent updates will delay processing, too, so
		1623	one might do the work both on C<ev_stat> callback invocation I<and> on
		1624	C<ev_timer> callback invocation).
		1625
		1626	static ev_stat passwd;
		1627	static ev_timer timer;
		1628
		1629	static void
		1630	timer_cb (EV_P_ ev_timer *w, int revents)
		1631	{
		1632	ev_timer_stop (EV_A_ w);
		1633
		1634	/* now it's one second after the most recent passwd change */
		1635	}
		1636
		1637	static void
		1638	stat_cb (EV_P_ ev_stat *w, int revents)
		1639	{
		1640	/* reset the one-second timer */
		1641	ev_timer_again (EV_A_ &timer);
		1642	}
		1643
		1644	...
		1645	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1646	ev_stat_start (loop, &passwd);
		1647	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1648
1235		1649
1236	=head2 C<ev_idle> - when you've got nothing better to do...	1650	=head2 C<ev_idle> - when you've got nothing better to do...
1237		1651
1238	Idle watchers trigger events when there are no other events are pending	1652	Idle watchers trigger events when no other events of the same or higher
1239	(prepare, check and other idle watchers do not count). That is, as long	1653	priority are pending (prepare, check and other idle watchers do not
1240	as your process is busy handling sockets or timeouts (or even signals,	1654	count).
1241	imagine) it will not be triggered. But when your process is idle all idle	1655
1242	watchers are being called again and again, once per event loop iteration -	1656	That is, as long as your process is busy handling sockets or timeouts
		1657	(or even signals, imagine) of the same or higher priority it will not be
		1658	triggered. But when your process is idle (or only lower-priority watchers
		1659	are pending), the idle watchers are being called once per event loop
1243	until stopped, that is, or your process receives more events and becomes	1660	iteration - until stopped, that is, or your process receives more events
1244	busy.	1661	and becomes busy again with higher priority stuff.
1245		1662
1246	The most noteworthy effect is that as long as any idle watchers are	1663	The most noteworthy effect is that as long as any idle watchers are
1247	active, the process will not block when waiting for new events.	1664	active, the process will not block when waiting for new events.
1248		1665
1249	Apart from keeping your process non-blocking (which is a useful	1666	Apart from keeping your process non-blocking (which is a useful
1250	effect on its own sometimes), idle watchers are a good place to do	1667	effect on its own sometimes), idle watchers are a good place to do
1251	"pseudo-background processing", or delay processing stuff to after the	1668	"pseudo-background processing", or delay processing stuff to after the
1252	event loop has handled all outstanding events.	1669	event loop has handled all outstanding events.
1253		1670
		1671	=head3 Watcher-Specific Functions and Data Members
		1672
1254	=over 4	1673	=over 4
1255		1674
1256	=item ev_idle_init (ev_signal *, callback)	1675	=item ev_idle_init (ev_signal *, callback)
1257		1676
1258	Initialises and configures the idle watcher - it has no parameters of any	1677	Initialises and configures the idle watcher - it has no parameters of any
1259	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1678	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1260	believe me.	1679	believe me.
1261		1680
1262	=back	1681	=back
1263		1682
		1683	=head3 Examples
		1684
1264	Example: dynamically allocate an C<ev_idle>, start it, and in the	1685	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1265	callback, free it. Alos, use no error checking, as usual.	1686	callback, free it. Also, use no error checking, as usual.
1266		1687
1267	static void	1688	static void
1268	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1689	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1269	{	1690	{
1270	free (w);	1691	free (w);
…		…
1315	with priority higher than or equal to the event loop and one coroutine	1736	with priority higher than or equal to the event loop and one coroutine
1316	of lower priority, but only once, using idle watchers to keep the event	1737	of lower priority, but only once, using idle watchers to keep the event
1317	loop from blocking if lower-priority coroutines are active, thus mapping	1738	loop from blocking if lower-priority coroutines are active, thus mapping
1318	low-priority coroutines to idle/background tasks).	1739	low-priority coroutines to idle/background tasks).
1319		1740
		1741	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1742	priority, to ensure that they are being run before any other watchers
		1743	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1744	too) should not activate ("feed") events into libev. While libev fully
		1745	supports this, they will be called before other C<ev_check> watchers
		1746	did their job. As C<ev_check> watchers are often used to embed other
		1747	(non-libev) event loops those other event loops might be in an unusable
		1748	state until their C<ev_check> watcher ran (always remind yourself to
		1749	coexist peacefully with others).
		1750
		1751	=head3 Watcher-Specific Functions and Data Members
		1752
1320	=over 4	1753	=over 4
1321		1754
1322	=item ev_prepare_init (ev_prepare *, callback)	1755	=item ev_prepare_init (ev_prepare *, callback)
1323		1756
1324	=item ev_check_init (ev_check *, callback)	1757	=item ev_check_init (ev_check *, callback)
…		…
1327	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1760	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1328	macros, but using them is utterly, utterly and completely pointless.	1761	macros, but using them is utterly, utterly and completely pointless.
1329		1762
1330	=back	1763	=back
1331		1764
1332	Example: To include a library such as adns, you would add IO watchers	1765	=head3 Examples
1333	and a timeout watcher in a prepare handler, as required by libadns, and	1766
		1767	There are a number of principal ways to embed other event loops or modules
		1768	into libev. Here are some ideas on how to include libadns into libev
		1769	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1770	use for an actually working example. Another Perl module named C<EV::Glib>
		1771	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1772	into the Glib event loop).
		1773
		1774	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1334	in a check watcher, destroy them and call into libadns. What follows is	1775	and in a check watcher, destroy them and call into libadns. What follows
1335	pseudo-code only of course:	1776	is pseudo-code only of course. This requires you to either use a low
		1777	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1778	the callbacks for the IO/timeout watchers might not have been called yet.
1336		1779
1337	static ev_io iow [nfd];	1780	static ev_io iow [nfd];
1338	static ev_timer tw;	1781	static ev_timer tw;
1339		1782
1340	static void	1783	static void
1341	io_cb (ev_loop *loop, ev_io *w, int revents)	1784	io_cb (ev_loop *loop, ev_io *w, int revents)
1342	{	1785	{
1343	// set the relevant poll flags
1344	// could also call adns_processreadable etc. here
1345	struct pollfd *fd = (struct pollfd *)w->data;
1346	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1347	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1348	}	1786	}
1349		1787
1350	// create io watchers for each fd and a timer before blocking	1788	// create io watchers for each fd and a timer before blocking
1351	static void	1789	static void
1352	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1790	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1353	{	1791	{
1354	int timeout = 3600000;truct pollfd fds [nfd];	1792	int timeout = 3600000;
		1793	struct pollfd fds [nfd];
1355	// actual code will need to loop here and realloc etc.	1794	// actual code will need to loop here and realloc etc.
1356	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1795	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1357		1796
1358	/* the callback is illegal, but won't be called as we stop during check */	1797	/* the callback is illegal, but won't be called as we stop during check */
1359	ev_timer_init (&tw, 0, timeout * 1e-3);	1798	ev_timer_init (&tw, 0, timeout * 1e-3);
1360	ev_timer_start (loop, &tw);	1799	ev_timer_start (loop, &tw);
1361		1800
1362	// create on ev_io per pollfd	1801	// create one ev_io per pollfd
1363	for (int i = 0; i < nfd; ++i)	1802	for (int i = 0; i < nfd; ++i)
1364	{	1803	{
1365	ev_io_init (iow + i, io_cb, fds [i].fd,	1804	ev_io_init (iow + i, io_cb, fds [i].fd,
1366	((fds [i].events & POLLIN ? EV_READ : 0)	1805	((fds [i].events & POLLIN ? EV_READ : 0)
1367	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1806	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1368		1807
1369	fds [i].revents = 0;	1808	fds [i].revents = 0;
1370	iow [i].data = fds + i;
1371	ev_io_start (loop, iow + i);	1809	ev_io_start (loop, iow + i);
1372	}	1810	}
1373	}	1811	}
1374		1812
1375	// stop all watchers after blocking	1813	// stop all watchers after blocking
…		…
1377	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1815	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1378	{	1816	{
1379	ev_timer_stop (loop, &tw);	1817	ev_timer_stop (loop, &tw);
1380		1818
1381	for (int i = 0; i < nfd; ++i)	1819	for (int i = 0; i < nfd; ++i)
		1820	{
		1821	// set the relevant poll flags
		1822	// could also call adns_processreadable etc. here
		1823	struct pollfd *fd = fds + i;
		1824	int revents = ev_clear_pending (iow + i);
		1825	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1826	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1827
		1828	// now stop the watcher
1382	ev_io_stop (loop, iow + i);	1829	ev_io_stop (loop, iow + i);
		1830	}
1383		1831
1384	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1832	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1833	}
		1834
		1835	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1836	in the prepare watcher and would dispose of the check watcher.
		1837
		1838	Method 3: If the module to be embedded supports explicit event
		1839	notification (adns does), you can also make use of the actual watcher
		1840	callbacks, and only destroy/create the watchers in the prepare watcher.
		1841
		1842	static void
		1843	timer_cb (EV_P_ ev_timer *w, int revents)
		1844	{
		1845	adns_state ads = (adns_state)w->data;
		1846	update_now (EV_A);
		1847
		1848	adns_processtimeouts (ads, &tv_now);
		1849	}
		1850
		1851	static void
		1852	io_cb (EV_P_ ev_io *w, int revents)
		1853	{
		1854	adns_state ads = (adns_state)w->data;
		1855	update_now (EV_A);
		1856
		1857	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1858	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1859	}
		1860
		1861	// do not ever call adns_afterpoll
		1862
		1863	Method 4: Do not use a prepare or check watcher because the module you
		1864	want to embed is too inflexible to support it. Instead, youc na override
		1865	their poll function. The drawback with this solution is that the main
		1866	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1867	this.
		1868
		1869	static gint
		1870	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1871	{
		1872	int got_events = 0;
		1873
		1874	for (n = 0; n < nfds; ++n)
		1875	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1876
		1877	if (timeout >= 0)
		1878	// create/start timer
		1879
		1880	// poll
		1881	ev_loop (EV_A_ 0);
		1882
		1883	// stop timer again
		1884	if (timeout >= 0)
		1885	ev_timer_stop (EV_A_ &to);
		1886
		1887	// stop io watchers again - their callbacks should have set
		1888	for (n = 0; n < nfds; ++n)
		1889	ev_io_stop (EV_A_ iow [n]);
		1890
		1891	return got_events;
1385	}	1892	}
1386		1893
1387		1894
1388	=head2 C<ev_embed> - when one backend isn't enough...	1895	=head2 C<ev_embed> - when one backend isn't enough...
1389		1896
…		…
1432	portable one.	1939	portable one.
1433		1940
1434	So when you want to use this feature you will always have to be prepared	1941	So when you want to use this feature you will always have to be prepared
1435	that you cannot get an embeddable loop. The recommended way to get around	1942	that you cannot get an embeddable loop. The recommended way to get around
1436	this is to have a separate variables for your embeddable loop, try to	1943	this is to have a separate variables for your embeddable loop, try to
1437	create it, and if that fails, use the normal loop for everything:	1944	create it, and if that fails, use the normal loop for everything.
		1945
		1946	=head3 Watcher-Specific Functions and Data Members
		1947
		1948	=over 4
		1949
		1950	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1951
		1952	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1953
		1954	Configures the watcher to embed the given loop, which must be
		1955	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1956	invoked automatically, otherwise it is the responsibility of the callback
		1957	to invoke it (it will continue to be called until the sweep has been done,
		1958	if you do not want thta, you need to temporarily stop the embed watcher).
		1959
		1960	=item ev_embed_sweep (loop, ev_embed *)
		1961
		1962	Make a single, non-blocking sweep over the embedded loop. This works
		1963	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1964	apropriate way for embedded loops.
		1965
		1966	=item struct ev_loop *other [read-only]
		1967
		1968	The embedded event loop.
		1969
		1970	=back
		1971
		1972	=head3 Examples
		1973
		1974	Example: Try to get an embeddable event loop and embed it into the default
		1975	event loop. If that is not possible, use the default loop. The default
		1976	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1977	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1978	used).
1438		1979
1439	struct ev_loop *loop_hi = ev_default_init (0);	1980	struct ev_loop *loop_hi = ev_default_init (0);
1440	struct ev_loop *loop_lo = 0;	1981	struct ev_loop *loop_lo = 0;
1441	struct ev_embed embed;	1982	struct ev_embed embed;
1442		1983
…		…
1453	ev_embed_start (loop_hi, &embed);	1994	ev_embed_start (loop_hi, &embed);
1454	}	1995	}
1455	else	1996	else
1456	loop_lo = loop_hi;	1997	loop_lo = loop_hi;
1457		1998
1458	=over 4	1999	Example: Check if kqueue is available but not recommended and create
		2000	a kqueue backend for use with sockets (which usually work with any
		2001	kqueue implementation). Store the kqueue/socket-only event loop in
		2002	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1459		2003
1460	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2004	struct ev_loop *loop = ev_default_init (0);
		2005	struct ev_loop *loop_socket = 0;
		2006	struct ev_embed embed;
		2007
		2008	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2009	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2010	{
		2011	ev_embed_init (&embed, 0, loop_socket);
		2012	ev_embed_start (loop, &embed);
		2013	}
1461		2014
1462	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2015	if (!loop_socket)
		2016	loop_socket = loop;
1463		2017
1464	Configures the watcher to embed the given loop, which must be	2018	// now use loop_socket for all sockets, and loop for everything else
1465	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1466	invoked automatically, otherwise it is the responsibility of the callback
1467	to invoke it (it will continue to be called until the sweep has been done,
1468	if you do not want thta, you need to temporarily stop the embed watcher).
1469
1470	=item ev_embed_sweep (loop, ev_embed *)
1471
1472	Make a single, non-blocking sweep over the embedded loop. This works
1473	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1474	apropriate way for embedded loops.
1475
1476	=item struct ev_loop *loop [read-only]
1477
1478	The embedded event loop.
1479
1480	=back
1481		2019
1482		2020
1483	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2021	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1484		2022
1485	Fork watchers are called when a C<fork ()> was detected (usually because	2023	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1488	event loop blocks next and before C<ev_check> watchers are being called,	2026	event loop blocks next and before C<ev_check> watchers are being called,
1489	and only in the child after the fork. If whoever good citizen calling	2027	and only in the child after the fork. If whoever good citizen calling
1490	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2028	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1491	handlers will be invoked, too, of course.	2029	handlers will be invoked, too, of course.
1492		2030
		2031	=head3 Watcher-Specific Functions and Data Members
		2032
1493	=over 4	2033	=over 4
1494		2034
1495	=item ev_fork_init (ev_signal *, callback)	2035	=item ev_fork_init (ev_signal *, callback)
1496		2036
1497	Initialises and configures the fork watcher - it has no parameters of any	2037	Initialises and configures the fork watcher - it has no parameters of any
…		…
1593		2133
1594	To use it,	2134	To use it,
1595		2135
1596	#include <ev++.h>	2136	#include <ev++.h>
1597		2137
1598	(it is not installed by default). This automatically includes F<ev.h>	2138	This automatically includes F<ev.h> and puts all of its definitions (many
1599	and puts all of its definitions (many of them macros) into the global	2139	of them macros) into the global namespace. All C++ specific things are
1600	namespace. All C++ specific things are put into the C<ev> namespace.	2140	put into the C<ev> namespace. It should support all the same embedding
		2141	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1601		2142
1602	It should support all the same embedding options as F<ev.h>, most notably	2143	Care has been taken to keep the overhead low. The only data member the C++
1603	C<EV_MULTIPLICITY>.	2144	classes add (compared to plain C-style watchers) is the event loop pointer
		2145	that the watcher is associated with (or no additional members at all if
		2146	you disable C<EV_MULTIPLICITY> when embedding libev).
		2147
		2148	Currently, functions, and static and non-static member functions can be
		2149	used as callbacks. Other types should be easy to add as long as they only
		2150	need one additional pointer for context. If you need support for other
		2151	types of functors please contact the author (preferably after implementing
		2152	it).
1604		2153
1605	Here is a list of things available in the C<ev> namespace:	2154	Here is a list of things available in the C<ev> namespace:
1606		2155
1607	=over 4	2156	=over 4
1608		2157
…		…
1624		2173
1625	All of those classes have these methods:	2174	All of those classes have these methods:
1626		2175
1627	=over 4	2176	=over 4
1628		2177
1629	=item ev::TYPE::TYPE (object *, object::method *)	2178	=item ev::TYPE::TYPE ()
1630		2179
1631	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2180	=item ev::TYPE::TYPE (struct ev_loop *)
1632		2181
1633	=item ev::TYPE::~TYPE	2182	=item ev::TYPE::~TYPE
1634		2183
1635	The constructor takes a pointer to an object and a method pointer to	2184	The constructor (optionally) takes an event loop to associate the watcher
1636	the event handler callback to call in this class. The constructor calls	2185	with. If it is omitted, it will use C<EV_DEFAULT>.
1637	C<ev_init> for you, which means you have to call the C<set> method	2186
1638	before starting it. If you do not specify a loop then the constructor	2187	The constructor calls C<ev_init> for you, which means you have to call the
1639	automatically associates the default loop with this watcher.	2188	C<set> method before starting it.
		2189
		2190	It will not set a callback, however: You have to call the templated C<set>
		2191	method to set a callback before you can start the watcher.
		2192
		2193	(The reason why you have to use a method is a limitation in C++ which does
		2194	not allow explicit template arguments for constructors).
1640		2195
1641	The destructor automatically stops the watcher if it is active.	2196	The destructor automatically stops the watcher if it is active.
		2197
		2198	=item w->set<class, &class::method> (object *)
		2199
		2200	This method sets the callback method to call. The method has to have a
		2201	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2202	first argument and the C<revents> as second. The object must be given as
		2203	parameter and is stored in the C<data> member of the watcher.
		2204
		2205	This method synthesizes efficient thunking code to call your method from
		2206	the C callback that libev requires. If your compiler can inline your
		2207	callback (i.e. it is visible to it at the place of the C<set> call and
		2208	your compiler is good :), then the method will be fully inlined into the
		2209	thunking function, making it as fast as a direct C callback.
		2210
		2211	Example: simple class declaration and watcher initialisation
		2212
		2213	struct myclass
		2214	{
		2215	void io_cb (ev::io &w, int revents) { }
		2216	}
		2217
		2218	myclass obj;
		2219	ev::io iow;
		2220	iow.set <myclass, &myclass::io_cb> (&obj);
		2221
		2222	=item w->set<function> (void *data = 0)
		2223
		2224	Also sets a callback, but uses a static method or plain function as
		2225	callback. The optional C<data> argument will be stored in the watcher's
		2226	C<data> member and is free for you to use.
		2227
		2228	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2229
		2230	See the method-C<set> above for more details.
		2231
		2232	Example:
		2233
		2234	static void io_cb (ev::io &w, int revents) { }
		2235	iow.set <io_cb> ();
1642		2236
1643	=item w->set (struct ev_loop *)	2237	=item w->set (struct ev_loop *)
1644		2238
1645	Associates a different C<struct ev_loop> with this watcher. You can only	2239	Associates a different C<struct ev_loop> with this watcher. You can only
1646	do this when the watcher is inactive (and not pending either).	2240	do this when the watcher is inactive (and not pending either).
1647		2241
1648	=item w->set ([args])	2242	=item w->set ([args])
1649		2243
1650	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2244	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1651	called at least once. Unlike the C counterpart, an active watcher gets	2245	called at least once. Unlike the C counterpart, an active watcher gets
1652	automatically stopped and restarted.	2246	automatically stopped and restarted when reconfiguring it with this
		2247	method.
1653		2248
1654	=item w->start ()	2249	=item w->start ()
1655		2250
1656	Starts the watcher. Note that there is no C<loop> argument as the	2251	Starts the watcher. Note that there is no C<loop> argument, as the
1657	constructor already takes the loop.	2252	constructor already stores the event loop.
1658		2253
1659	=item w->stop ()	2254	=item w->stop ()
1660		2255
1661	Stops the watcher if it is active. Again, no C<loop> argument.	2256	Stops the watcher if it is active. Again, no C<loop> argument.
1662		2257
1663	=item w->again () C<ev::timer>, C<ev::periodic> only	2258	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1664		2259
1665	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2260	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1666	C<ev_TYPE_again> function.	2261	C<ev_TYPE_again> function.
1667		2262
1668	=item w->sweep () C<ev::embed> only	2263	=item w->sweep () (C<ev::embed> only)
1669		2264
1670	Invokes C<ev_embed_sweep>.	2265	Invokes C<ev_embed_sweep>.
1671		2266
1672	=item w->update () C<ev::stat> only	2267	=item w->update () (C<ev::stat> only)
1673		2268
1674	Invokes C<ev_stat_stat>.	2269	Invokes C<ev_stat_stat>.
1675		2270
1676	=back	2271	=back
1677		2272
…		…
1687		2282
1688	myclass ();	2283	myclass ();
1689	}	2284	}
1690		2285
1691	myclass::myclass (int fd)	2286	myclass::myclass (int fd)
1692	: io (this, &myclass::io_cb),
1693	idle (this, &myclass::idle_cb)
1694	{	2287	{
		2288	io .set <myclass, &myclass::io_cb > (this);
		2289	idle.set <myclass, &myclass::idle_cb> (this);
		2290
1695	io.start (fd, ev::READ);	2291	io.start (fd, ev::READ);
1696	}	2292	}
1697		2293
1698		2294
1699	=head1 MACRO MAGIC	2295	=head1 MACRO MAGIC
1700		2296
1701	Libev can be compiled with a variety of options, the most fundemantal is	2297	Libev can be compiled with a variety of options, the most fundamantal
1702	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2298	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1703	callbacks have an initial C<struct ev_loop *> argument.	2299	functions and callbacks have an initial C<struct ev_loop *> argument.
1704		2300
1705	To make it easier to write programs that cope with either variant, the	2301	To make it easier to write programs that cope with either variant, the
1706	following macros are defined:	2302	following macros are defined:
1707		2303
1708	=over 4	2304	=over 4
…		…
1740	Similar to the other two macros, this gives you the value of the default	2336	Similar to the other two macros, this gives you the value of the default
1741	loop, if multiple loops are supported ("ev loop default").	2337	loop, if multiple loops are supported ("ev loop default").
1742		2338
1743	=back	2339	=back
1744		2340
1745	Example: Declare and initialise a check watcher, working regardless of	2341	Example: Declare and initialise a check watcher, utilising the above
1746	wether multiple loops are supported or not.	2342	macros so it will work regardless of whether multiple loops are supported
		2343	or not.
1747		2344
1748	static void	2345	static void
1749	check_cb (EV_P_ ev_timer *w, int revents)	2346	check_cb (EV_P_ ev_timer *w, int revents)
1750	{	2347	{
1751	ev_check_stop (EV_A_ w);	2348	ev_check_stop (EV_A_ w);
…		…
1754	ev_check check;	2351	ev_check check;
1755	ev_check_init (&check, check_cb);	2352	ev_check_init (&check, check_cb);
1756	ev_check_start (EV_DEFAULT_ &check);	2353	ev_check_start (EV_DEFAULT_ &check);
1757	ev_loop (EV_DEFAULT_ 0);	2354	ev_loop (EV_DEFAULT_ 0);
1758		2355
1759
1760	=head1 EMBEDDING	2356	=head1 EMBEDDING
1761		2357
1762	Libev can (and often is) directly embedded into host	2358	Libev can (and often is) directly embedded into host
1763	applications. Examples of applications that embed it include the Deliantra	2359	applications. Examples of applications that embed it include the Deliantra
1764	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2360	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1765	and rxvt-unicode.	2361	and rxvt-unicode.
1766		2362
1767	The goal is to enable you to just copy the neecssary files into your	2363	The goal is to enable you to just copy the necessary files into your
1768	source directory without having to change even a single line in them, so	2364	source directory without having to change even a single line in them, so
1769	you can easily upgrade by simply copying (or having a checked-out copy of	2365	you can easily upgrade by simply copying (or having a checked-out copy of
1770	libev somewhere in your source tree).	2366	libev somewhere in your source tree).
1771		2367
1772	=head2 FILESETS	2368	=head2 FILESETS
…		…
1803	ev_vars.h	2399	ev_vars.h
1804	ev_wrap.h	2400	ev_wrap.h
1805		2401
1806	ev_win32.c required on win32 platforms only	2402	ev_win32.c required on win32 platforms only
1807		2403
1808	ev_select.c only when select backend is enabled (which is by default)	2404	ev_select.c only when select backend is enabled (which is enabled by default)
1809	ev_poll.c only when poll backend is enabled (disabled by default)	2405	ev_poll.c only when poll backend is enabled (disabled by default)
1810	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2406	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1811	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2407	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1812	ev_port.c only when the solaris port backend is enabled (disabled by default)	2408	ev_port.c only when the solaris port backend is enabled (disabled by default)
1813		2409
…		…
1862		2458
1863	If defined to be C<1>, libev will try to detect the availability of the	2459	If defined to be C<1>, libev will try to detect the availability of the
1864	monotonic clock option at both compiletime and runtime. Otherwise no use	2460	monotonic clock option at both compiletime and runtime. Otherwise no use
1865	of the monotonic clock option will be attempted. If you enable this, you	2461	of the monotonic clock option will be attempted. If you enable this, you
1866	usually have to link against librt or something similar. Enabling it when	2462	usually have to link against librt or something similar. Enabling it when
1867	the functionality isn't available is safe, though, althoguh you have	2463	the functionality isn't available is safe, though, although you have
1868	to make sure you link against any libraries where the C<clock_gettime>	2464	to make sure you link against any libraries where the C<clock_gettime>
1869	function is hiding in (often F<-lrt>).	2465	function is hiding in (often F<-lrt>).
1870		2466
1871	=item EV_USE_REALTIME	2467	=item EV_USE_REALTIME
1872		2468
1873	If defined to be C<1>, libev will try to detect the availability of the	2469	If defined to be C<1>, libev will try to detect the availability of the
1874	realtime clock option at compiletime (and assume its availability at	2470	realtime clock option at compiletime (and assume its availability at
1875	runtime if successful). Otherwise no use of the realtime clock option will	2471	runtime if successful). Otherwise no use of the realtime clock option will
1876	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2472	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1877	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2473	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1878	in the description of C<EV_USE_MONOTONIC>, though.	2474	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2475
		2476	=item EV_USE_NANOSLEEP
		2477
		2478	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2479	and will use it for delays. Otherwise it will use C<select ()>.
1879		2480
1880	=item EV_USE_SELECT	2481	=item EV_USE_SELECT
1881		2482
1882	If undefined or defined to be C<1>, libev will compile in support for the	2483	If undefined or defined to be C<1>, libev will compile in support for the
1883	C<select>(2) backend. No attempt at autodetection will be done: if no	2484	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1901	wants osf handles on win32 (this is the case when the select to	2502	wants osf handles on win32 (this is the case when the select to
1902	be used is the winsock select). This means that it will call	2503	be used is the winsock select). This means that it will call
1903	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2504	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1904	it is assumed that all these functions actually work on fds, even	2505	it is assumed that all these functions actually work on fds, even
1905	on win32. Should not be defined on non-win32 platforms.	2506	on win32. Should not be defined on non-win32 platforms.
		2507
		2508	=item EV_FD_TO_WIN32_HANDLE
		2509
		2510	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2511	file descriptors to socket handles. When not defining this symbol (the
		2512	default), then libev will call C<_get_osfhandle>, which is usually
		2513	correct. In some cases, programs use their own file descriptor management,
		2514	in which case they can provide this function to map fds to socket handles.
1906		2515
1907	=item EV_USE_POLL	2516	=item EV_USE_POLL
1908		2517
1909	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2518	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1910	backend. Otherwise it will be enabled on non-win32 platforms. It	2519	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
1938		2547
1939	=item EV_USE_DEVPOLL	2548	=item EV_USE_DEVPOLL
1940		2549
1941	reserved for future expansion, works like the USE symbols above.	2550	reserved for future expansion, works like the USE symbols above.
1942		2551
		2552	=item EV_USE_INOTIFY
		2553
		2554	If defined to be C<1>, libev will compile in support for the Linux inotify
		2555	interface to speed up C<ev_stat> watchers. Its actual availability will
		2556	be detected at runtime.
		2557
1943	=item EV_H	2558	=item EV_H
1944		2559
1945	The name of the F<ev.h> header file used to include it. The default if	2560	The name of the F<ev.h> header file used to include it. The default if
1946	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2561	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
1947	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2562	virtually rename the F<ev.h> header file in case of conflicts.
1948		2563
1949	=item EV_CONFIG_H	2564	=item EV_CONFIG_H
1950		2565
1951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2566	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2567	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1953	C<EV_H>, above.	2568	C<EV_H>, above.
1954		2569
1955	=item EV_EVENT_H	2570	=item EV_EVENT_H
1956		2571
1957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2572	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1958	of how the F<event.h> header can be found.	2573	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
1959		2574
1960	=item EV_PROTOTYPES	2575	=item EV_PROTOTYPES
1961		2576
1962	If defined to be C<0>, then F<ev.h> will not define any function	2577	If defined to be C<0>, then F<ev.h> will not define any function
1963	prototypes, but still define all the structs and other symbols. This is	2578	prototypes, but still define all the structs and other symbols. This is
…		…
1970	will have the C<struct ev_loop *> as first argument, and you can create	2585	will have the C<struct ev_loop *> as first argument, and you can create
1971	additional independent event loops. Otherwise there will be no support	2586	additional independent event loops. Otherwise there will be no support
1972	for multiple event loops and there is no first event loop pointer	2587	for multiple event loops and there is no first event loop pointer
1973	argument. Instead, all functions act on the single default loop.	2588	argument. Instead, all functions act on the single default loop.
1974		2589
		2590	=item EV_MINPRI
		2591
		2592	=item EV_MAXPRI
		2593
		2594	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2595	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2596	provide for more priorities by overriding those symbols (usually defined
		2597	to be C<-2> and C<2>, respectively).
		2598
		2599	When doing priority-based operations, libev usually has to linearly search
		2600	all the priorities, so having many of them (hundreds) uses a lot of space
		2601	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2602	fine.
		2603
		2604	If your embedding app does not need any priorities, defining these both to
		2605	C<0> will save some memory and cpu.
		2606
1975	=item EV_PERIODIC_ENABLE	2607	=item EV_PERIODIC_ENABLE
1976		2608
1977	If undefined or defined to be C<1>, then periodic timers are supported. If	2609	If undefined or defined to be C<1>, then periodic timers are supported. If
1978	defined to be C<0>, then they are not. Disabling them saves a few kB of	2610	defined to be C<0>, then they are not. Disabling them saves a few kB of
1979	code.	2611	code.
1980		2612
		2613	=item EV_IDLE_ENABLE
		2614
		2615	If undefined or defined to be C<1>, then idle watchers are supported. If
		2616	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2617	code.
		2618
1981	=item EV_EMBED_ENABLE	2619	=item EV_EMBED_ENABLE
1982		2620
1983	If undefined or defined to be C<1>, then embed watchers are supported. If	2621	If undefined or defined to be C<1>, then embed watchers are supported. If
1984	defined to be C<0>, then they are not.	2622	defined to be C<0>, then they are not.
1985		2623
…		…
2002	=item EV_PID_HASHSIZE	2640	=item EV_PID_HASHSIZE
2003		2641
2004	C<ev_child> watchers use a small hash table to distribute workload by	2642	C<ev_child> watchers use a small hash table to distribute workload by
2005	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	2643	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2006	than enough. If you need to manage thousands of children you might want to	2644	than enough. If you need to manage thousands of children you might want to
2007	increase this value.	2645	increase this value (I<must> be a power of two).
		2646
		2647	=item EV_INOTIFY_HASHSIZE
		2648
		2649	C<ev_stat> watchers use a small hash table to distribute workload by
		2650	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2651	usually more than enough. If you need to manage thousands of C<ev_stat>
		2652	watchers you might want to increase this value (I<must> be a power of
		2653	two).
2008		2654
2009	=item EV_COMMON	2655	=item EV_COMMON
2010		2656
2011	By default, all watchers have a C<void *data> member. By redefining	2657	By default, all watchers have a C<void *data> member. By redefining
2012	this macro to a something else you can include more and other types of	2658	this macro to a something else you can include more and other types of
…		…
2025		2671
2026	=item ev_set_cb (ev, cb)	2672	=item ev_set_cb (ev, cb)
2027		2673
2028	Can be used to change the callback member declaration in each watcher,	2674	Can be used to change the callback member declaration in each watcher,
2029	and the way callbacks are invoked and set. Must expand to a struct member	2675	and the way callbacks are invoked and set. Must expand to a struct member
2030	definition and a statement, respectively. See the F<ev.v> header file for	2676	definition and a statement, respectively. See the F<ev.h> header file for
2031	their default definitions. One possible use for overriding these is to	2677	their default definitions. One possible use for overriding these is to
2032	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2678	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2033	method calls instead of plain function calls in C++.	2679	method calls instead of plain function calls in C++.
		2680
		2681	=head2 EXPORTED API SYMBOLS
		2682
		2683	If you need to re-export the API (e.g. via a dll) and you need a list of
		2684	exported symbols, you can use the provided F<Symbol.*> files which list
		2685	all public symbols, one per line:
		2686
		2687	Symbols.ev for libev proper
		2688	Symbols.event for the libevent emulation
		2689
		2690	This can also be used to rename all public symbols to avoid clashes with
		2691	multiple versions of libev linked together (which is obviously bad in
		2692	itself, but sometimes it is inconvinient to avoid this).
		2693
		2694	A sed command like this will create wrapper C<#define>'s that you need to
		2695	include before including F<ev.h>:
		2696
		2697	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2698
		2699	This would create a file F<wrap.h> which essentially looks like this:
		2700
		2701	#define ev_backend myprefix_ev_backend
		2702	#define ev_check_start myprefix_ev_check_start
		2703	#define ev_check_stop myprefix_ev_check_stop
		2704	...
2034		2705
2035	=head2 EXAMPLES	2706	=head2 EXAMPLES
2036		2707
2037	For a real-world example of a program the includes libev	2708	For a real-world example of a program the includes libev
2038	verbatim, you can have a look at the EV perl module	2709	verbatim, you can have a look at the EV perl module
…		…
2041	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2712	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2042	will be compiled. It is pretty complex because it provides its own header	2713	will be compiled. It is pretty complex because it provides its own header
2043	file.	2714	file.
2044		2715
2045	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2716	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2046	that everybody includes and which overrides some autoconf choices:	2717	that everybody includes and which overrides some configure choices:
2047		2718
		2719	#define EV_MINIMAL 1
2048	#define EV_USE_POLL 0	2720	#define EV_USE_POLL 0
2049	#define EV_MULTIPLICITY 0	2721	#define EV_MULTIPLICITY 0
2050	#define EV_PERIODICS 0	2722	#define EV_PERIODIC_ENABLE 0
		2723	#define EV_STAT_ENABLE 0
		2724	#define EV_FORK_ENABLE 0
2051	#define EV_CONFIG_H <config.h>	2725	#define EV_CONFIG_H <config.h>
		2726	#define EV_MINPRI 0
		2727	#define EV_MAXPRI 0
2052		2728
2053	#include "ev++.h"	2729	#include "ev++.h"
2054		2730
2055	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2731	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2056		2732
…		…
2062		2738
2063	In this section the complexities of (many of) the algorithms used inside	2739	In this section the complexities of (many of) the algorithms used inside
2064	libev will be explained. For complexity discussions about backends see the	2740	libev will be explained. For complexity discussions about backends see the
2065	documentation for C<ev_default_init>.	2741	documentation for C<ev_default_init>.
2066		2742
		2743	All of the following are about amortised time: If an array needs to be
		2744	extended, libev needs to realloc and move the whole array, but this
		2745	happens asymptotically never with higher number of elements, so O(1) might
		2746	mean it might do a lengthy realloc operation in rare cases, but on average
		2747	it is much faster and asymptotically approaches constant time.
		2748
2067	=over 4	2749	=over 4
2068		2750
2069	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2751	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2070		2752
		2753	This means that, when you have a watcher that triggers in one hour and
		2754	there are 100 watchers that would trigger before that then inserting will
		2755	have to skip roughly seven (C<ld 100>) of these watchers.
		2756
2071	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2757	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2758
		2759	That means that changing a timer costs less than removing/adding them
		2760	as only the relative motion in the event queue has to be paid for.
2072		2761
2073	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2762	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2074		2763
		2764	These just add the watcher into an array or at the head of a list.
		2765
2075	=item Stopping check/prepare/idle watchers: O(1)	2766	=item Stopping check/prepare/idle watchers: O(1)
2076		2767
2077	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2768	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2078		2769
		2770	These watchers are stored in lists then need to be walked to find the
		2771	correct watcher to remove. The lists are usually short (you don't usually
		2772	have many watchers waiting for the same fd or signal).
		2773
2079	=item Finding the next timer per loop iteration: O(1)	2774	=item Finding the next timer in each loop iteration: O(1)
		2775
		2776	By virtue of using a binary heap, the next timer is always found at the
		2777	beginning of the storage array.
2080		2778
2081	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2779	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2082		2780
2083	=item Activating one watcher: O(1)	2781	A change means an I/O watcher gets started or stopped, which requires
		2782	libev to recalculate its status (and possibly tell the kernel, depending
		2783	on backend and wether C<ev_io_set> was used).
		2784
		2785	=item Activating one watcher (putting it into the pending state): O(1)
		2786
		2787	=item Priority handling: O(number_of_priorities)
		2788
		2789	Priorities are implemented by allocating some space for each
		2790	priority. When doing priority-based operations, libev usually has to
		2791	linearly search all the priorities, but starting/stopping and activating
		2792	watchers becomes O(1) w.r.t. prioritiy handling.
2084		2793
2085	=back	2794	=back
2086		2795
2087		2796
		2797	=head1 Win32 platform limitations and workarounds
		2798
		2799	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2800	requires, and its I/O model is fundamentally incompatible with the POSIX
		2801	model. Libev still offers limited functionality on this platform in
		2802	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2803	descriptors. This only applies when using Win32 natively, not when using
		2804	e.g. cygwin.
		2805
		2806	There is no supported compilation method available on windows except
		2807	embedding it into other applications.
		2808
		2809	Due to the many, low, and arbitrary limits on the win32 platform and the
		2810	abysmal performance of winsockets, using a large number of sockets is not
		2811	recommended (and not reasonable). If your program needs to use more than
		2812	a hundred or so sockets, then likely it needs to use a totally different
		2813	implementation for windows, as libev offers the POSIX model, which cannot
		2814	be implemented efficiently on windows (microsoft monopoly games).
		2815
		2816	=over 4
		2817
		2818	=item The winsocket select function
		2819
		2820	The winsocket C<select> function doesn't follow POSIX in that it requires
		2821	socket I<handles> and not socket I<file descriptors>. This makes select
		2822	very inefficient, and also requires a mapping from file descriptors
		2823	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2824	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2825	symbols for more info.
		2826
		2827	The configuration for a "naked" win32 using the microsoft runtime
		2828	libraries and raw winsocket select is:
		2829
		2830	#define EV_USE_SELECT 1
		2831	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2832
		2833	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2834	complexity in the O(n²) range when using win32.
		2835
		2836	=item Limited number of file descriptors
		2837
		2838	Windows has numerous arbitrary (and low) limits on things. Early versions
		2839	of winsocket's select only supported waiting for a max. of C<64> handles
		2840	(probably owning to the fact that all windows kernels can only wait for
		2841	C<64> things at the same time internally; microsoft recommends spawning a
		2842	chain of threads and wait for 63 handles and the previous thread in each).
		2843
		2844	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2845	to some high number (e.g. C<2048>) before compiling the winsocket select
		2846	call (which might be in libev or elsewhere, for example, perl does its own
		2847	select emulation on windows).
		2848
		2849	Another limit is the number of file descriptors in the microsoft runtime
		2850	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2851	or something like this inside microsoft). You can increase this by calling
		2852	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2853	arbitrary limit), but is broken in many versions of the microsoft runtime
		2854	libraries.
		2855
		2856	This might get you to about C<512> or C<2048> sockets (depending on
		2857	windows version and/or the phase of the moon). To get more, you need to
		2858	wrap all I/O functions and provide your own fd management, but the cost of
		2859	calling select (O(n²)) will likely make this unworkable.
		2860
		2861	=back
		2862
		2863
2088	=head1 AUTHOR	2864	=head1 AUTHOR
2089		2865
2090	Marc Lehmann <libev@schmorp.de>.	2866	Marc Lehmann <libev@schmorp.de>.
2091		2867

Diff Legend

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