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 1.130 by root, Wed Feb 6 18:34:24 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);
…		…
196	flags. If that is troubling you, check C<ev_backend ()> afterwards).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
197		261
198	If you don't know what event loop to use, use the one returned from this	262	If you don't know what event loop to use, use the one returned from this
199	function.	263	function.
200		264
		265	The default loop is the only loop that can handle C<ev_signal> and
		266	C<ev_child> watchers, and to do this, it always registers a handler
		267	for C<SIGCHLD>. If this is a problem for your app you can either
		268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		270	C<ev_default_init>.
		271
201	The flags argument can be used to specify special behaviour or specific	272	The flags argument can be used to specify special behaviour or specific
202	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	273	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
203		274
204	The following flags are supported:	275	The following flags are supported:
205		276
…		…
217	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
218	override the flags completely if it is found in the environment. This is	289	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	290	useful to try out specific backends to test their performance, or to work
220	around bugs.	291	around bugs.
221		292
		293	=item C<EVFLAG_FORKCHECK>
		294
		295	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		296	a fork, you can also make libev check for a fork in each iteration by
		297	enabling this flag.
		298
		299	This works by calling C<getpid ()> on every iteration of the loop,
		300	and thus this might slow down your event loop if you do a lot of loop
		301	iterations and little real work, but is usually not noticeable (on my
		302	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		303	without a syscall and thus I<very> fast, but my Linux system also has
		304	C<pthread_atfork> which is even faster).
		305
		306	The big advantage of this flag is that you can forget about fork (and
		307	forget about forgetting to tell libev about forking) when you use this
		308	flag.
		309
		310	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		311	environment variable.
		312
222	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
223		314
224	This is your standard select(2) backend. Not I<completely> standard, as	315	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,	316	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	317	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	318	using this backend. It doesn't scale too well (O(highest_fd)), but its
228	the fastest backend for a low number of fds.	319	usually the fastest backend for a low number of (low-numbered :) fds.
		320
		321	To get good performance out of this backend you need a high amount of
		322	parallelity (most of the file descriptors should be busy). If you are
		323	writing a server, you should C<accept ()> in a loop to accept as many
		324	connections as possible during one iteration. You might also want to have
		325	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		326	readyness notifications you get per iteration.
229		327
230	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	328	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
231		329
232	And this is your standard poll(2) backend. It's more complicated than	330	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	331	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	332	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).	333	considerably with a lot of inactive fds). It scales similarly to select,
		334	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		335	performance tips.
236		336
237	=item C<EVBACKEND_EPOLL> (value 4, Linux)	337	=item C<EVBACKEND_EPOLL> (value 4, Linux)
238		338
239	For few fds, this backend is a bit little slower than poll and select,	339	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	340	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	341	like O(total_fds) where n is the total number of fds (or the highest fd),
242	either O(1) or O(active_fds).	342	epoll scales either O(1) or O(active_fds). The epoll design has a number
		343	of shortcomings, such as silently dropping events in some hard-to-detect
		344	cases and rewiring a syscall per fd change, no fork support and bad
		345	support for dup.
243		346
244	While stopping and starting an I/O watcher in the same iteration will	347	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	348	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	349	(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	350	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
248	well if you register events for both fds.	351	very well if you register events for both fds.
249		352
250	Please note that epoll sometimes generates spurious notifications, so you	353	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	354	need to use non-blocking I/O or other means to avoid blocking when no data
252	(or space) is available.	355	(or space) is available.
253		356
		357	Best performance from this backend is achieved by not unregistering all
		358	watchers for a file descriptor until it has been closed, if possible, i.e.
		359	keep at least one watcher active per fd at all times.
		360
		361	While nominally embeddeble in other event loops, this feature is broken in
		362	all kernel versions tested so far.
		363
254	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
255		365
256	Kqueue deserves special mention, as at the time of this writing, it	366	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	367	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	368	with anything but sockets and pipes, except on Darwin, where of course
259	completely useless). For this reason its not being "autodetected"	369	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	370	unless you explicitly specify it explicitly in the flags (i.e. using
261	C<EVBACKEND_KQUEUE>).	371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		372	system like NetBSD.
		373
		374	You still can embed kqueue into a normal poll or select backend and use it
		375	only for sockets (after having made sure that sockets work with kqueue on
		376	the target platform). See C<ev_embed> watchers for more info.
262		377
263	It scales in the same way as the epoll backend, but the interface to the	378	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	379	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	380	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	381	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
267	incident, so its best to avoid that.	382	two event changes per incident, support for C<fork ()> is very bad and it
		383	drops fds silently in similarly hard-to-detect cases.
		384
		385	This backend usually performs well under most conditions.
		386
		387	While nominally embeddable in other event loops, this doesn't work
		388	everywhere, so you might need to test for this. And since it is broken
		389	almost everywhere, you should only use it when you have a lot of sockets
		390	(for which it usually works), by embedding it into another event loop
		391	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		392	sockets.
268		393
269	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
270		395
271	This is not implemented yet (and might never be).	396	This is not implemented yet (and might never be, unless you send me an
		397	implementation). According to reports, C</dev/poll> only supports sockets
		398	and is not embeddable, which would limit the usefulness of this backend
		399	immensely.
272		400
273	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
274		402
275	This uses the Solaris 10 port mechanism. As with everything on Solaris,	403	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)).	404	it's really slow, but it still scales very well (O(active_fds)).
277		405
278	Please note that solaris ports can result in a lot of spurious	406	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	407	notifications, so you need to use non-blocking I/O or other means to avoid
280	blocking when no data (or space) is available.	408	blocking when no data (or space) is available.
		409
		410	While this backend scales well, it requires one system call per active
		411	file descriptor per loop iteration. For small and medium numbers of file
		412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		413	might perform better.
		414
		415	On the positive side, ignoring the spurious readyness notifications, this
		416	backend actually performed to specification in all tests and is fully
		417	embeddable, which is a rare feat among the OS-specific backends.
281		418
282	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
283		420
284	Try all backends (even potentially broken ones that wouldn't be tried	421	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	422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
286	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
287		424
		425	It is definitely not recommended to use this flag.
		426
288	=back	427	=back
289		428
290	If one or more of these are ored into the flags value, then only these	429	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	430	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	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
293	order of their flag values :)
294		432
295	The most typical usage is like this:	433	The most typical usage is like this:
296		434
297	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
298	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	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	451	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	452	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	453	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).	454	undefined behaviour (or a failed assertion if assertions are enabled).
317		455
318	Example: try to create a event loop that uses epoll and nothing else.	456	Example: Try to create a event loop that uses epoll and nothing else.
319		457
320	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
321	if (!epoller)	459	if (!epoller)
322	fatal ("no epoll found here, maybe it hides under your chair");	460	fatal ("no epoll found here, maybe it hides under your chair");
323		461
…		…
326	Destroys the default loop again (frees all memory and kernel state	464	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	465	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	466	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>	467	responsibility to either stop all watchers cleanly yoursef I<before>
330	calling this function, or cope with the fact afterwards (which is usually	468	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	469	the easiest thing, you can just ignore the watchers and/or C<free ()> them
332	for example).	470	for example).
		471
		472	Note that certain global state, such as signal state, will not be freed by
		473	this function, and related watchers (such as signal and child watchers)
		474	would need to be stopped manually.
		475
		476	In general it is not advisable to call this function except in the
		477	rare occasion where you really need to free e.g. the signal handling
		478	pipe fds. If you need dynamically allocated loops it is better to use
		479	C<ev_loop_new> and C<ev_loop_destroy>).
333		480
334	=item ev_loop_destroy (loop)	481	=item ev_loop_destroy (loop)
335		482
336	Like C<ev_default_destroy>, but destroys an event loop created by an	483	Like C<ev_default_destroy>, but destroys an event loop created by an
337	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
338		485
339	=item ev_default_fork ()	486	=item ev_default_fork ()
340		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
341	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
342	one. Despite the name, you can call it anytime, but it makes most sense	490	name, you can call it anytime, but it makes most sense after forking, in
343	after forking, in either the parent or child process (or both, but that	491	the child process (or both child and parent, but that again makes little
344	again makes little sense).	492	sense). You I<must> call it in the child before using any of the libev
		493	functions, and it will only take effect at the next C<ev_loop> iteration.
345		494
346	You I<must> call this function in the child process after forking if and	495	On the other hand, you only need to call this function in the child
347	only if you want to use the event library in both processes. If you just	496	process if and only if you want to use the event library in the child. If
348	fork+exec, you don't have to call it.	497	you just fork+exec, you don't have to call it at all.
349		498
350	The function itself is quite fast and it's usually not a problem to call	499	The function itself is quite fast and it's usually not a problem to call
351	it just in case after a fork. To make this easy, the function will fit in	500	it just in case after a fork. To make this easy, the function will fit in
352	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
353		502
354	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
355		504
356	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
357	without calling this function, so if you force one of those backends you
358	do not need to care.
359
360	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
361		506
362	Like C<ev_default_fork>, but acts on an event loop created by	507	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	508	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.	509	after fork, and how you do this is entirely your own problem.
		510
		511	=item unsigned int ev_loop_count (loop)
		512
		513	Returns the count of loop iterations for the loop, which is identical to
		514	the number of times libev did poll for new events. It starts at C<0> and
		515	happily wraps around with enough iterations.
		516
		517	This value can sometimes be useful as a generation counter of sorts (it
		518	"ticks" the number of loop iterations), as it roughly corresponds with
		519	C<ev_prepare> and C<ev_check> calls.
365		520
366	=item unsigned int ev_backend (loop)	521	=item unsigned int ev_backend (loop)
367		522
368	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	523	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
369	use.	524	use.
…		…
372		527
373	Returns the current "event loop time", which is the time the event loop	528	Returns the current "event loop time", which is the time the event loop
374	received events and started processing them. This timestamp does not	529	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	530	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	531	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).	532	event occurring (or more correctly, libev finding out about it).
378		533
379	=item ev_loop (loop, int flags)	534	=item ev_loop (loop, int flags)
380		535
381	Finally, this is it, the event handler. This function usually is called	536	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	537	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	558	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
404	usually a better approach for this kind of thing.	559	usually a better approach for this kind of thing.
405		560
406	Here are the gory details of what C<ev_loop> does:	561	Here are the gory details of what C<ev_loop> does:
407		562
408	* If there are no active watchers (reference count is zero), return.	563	- Before the first iteration, call any pending watchers.
409	- Queue prepare watchers and then call all outstanding watchers.	564	* If EVFLAG_FORKCHECK was used, check for a fork.
		565	- If a fork was detected, queue and call all fork watchers.
		566	- Queue and call all prepare watchers.
410	- If we have been forked, recreate the kernel state.	567	- If we have been forked, recreate the kernel state.
411	- Update the kernel state with all outstanding changes.	568	- Update the kernel state with all outstanding changes.
412	- Update the "event loop time".	569	- Update the "event loop time".
413	- Calculate for how long to block.	570	- Calculate for how long to sleep or block, if at all
		571	(active idle watchers, EVLOOP_NONBLOCK or not having
		572	any active watchers at all will result in not sleeping).
		573	- Sleep if the I/O and timer collect interval say so.
414	- Block the process, waiting for any events.	574	- Block the process, waiting for any events.
415	- Queue all outstanding I/O (fd) events.	575	- Queue all outstanding I/O (fd) events.
416	- Update the "event loop time" and do time jump handling.	576	- Update the "event loop time" and do time jump handling.
417	- Queue all outstanding timers.	577	- Queue all outstanding timers.
418	- Queue all outstanding periodics.	578	- Queue all outstanding periodics.
419	- If no events are pending now, queue all idle watchers.	579	- If no events are pending now, queue all idle watchers.
420	- Queue all check watchers.	580	- Queue all check watchers.
421	- Call all queued watchers in reverse order (i.e. check watchers first).	581	- 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	582	Signals and child watchers are implemented as I/O watchers, and will
423	be handled here by queueing them when their watcher gets executed.	583	be handled here by queueing them when their watcher gets executed.
424	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	584	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
425	were used, return, otherwise continue with step *.	585	were used, or there are no active watchers, return, otherwise
		586	continue with step *.
426		587
427	Example: queue some jobs and then loop until no events are outsanding	588	Example: Queue some jobs and then loop until no events are outstanding
428	anymore.	589	anymore.
429		590
430	... queue jobs here, make sure they register event watchers as long	591	... 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..)	592	... as they still have work to do (even an idle watcher will do..)
432	ev_loop (my_loop, 0);	593	ev_loop (my_loop, 0);
…		…
436		597
437	Can be used to make a call to C<ev_loop> return early (but only after it	598	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	599	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	600	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.	601	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		602
		603	This "unloop state" will be cleared when entering C<ev_loop> again.
441		604
442	=item ev_ref (loop)	605	=item ev_ref (loop)
443		606
444	=item ev_unref (loop)	607	=item ev_unref (loop)
445		608
…		…
450	returning, ev_unref() after starting, and ev_ref() before stopping it. For	613	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	614	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	615	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	616	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	617	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>.	618	libraries. Just remember to I<unref after start> and I<ref before stop>
		619	(but only if the watcher wasn't active before, or was active before,
		620	respectively).
456		621
457	Example: create a signal watcher, but keep it from keeping C<ev_loop>	622	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
458	running when nothing else is active.	623	running when nothing else is active.
459		624
460	struct dv_signal exitsig;	625	struct ev_signal exitsig;
461	ev_signal_init (&exitsig, sig_cb, SIGINT);	626	ev_signal_init (&exitsig, sig_cb, SIGINT);
462	ev_signal_start (myloop, &exitsig);	627	ev_signal_start (loop, &exitsig);
463	evf_unref (myloop);	628	evf_unref (loop);
464		629
465	Example: for some weird reason, unregister the above signal handler again.	630	Example: For some weird reason, unregister the above signal handler again.
466		631
467	ev_ref (myloop);	632	ev_ref (loop);
468	ev_signal_stop (myloop, &exitsig);	633	ev_signal_stop (loop, &exitsig);
		634
		635	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		636
		637	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		638
		639	These advanced functions influence the time that libev will spend waiting
		640	for events. Both are by default C<0>, meaning that libev will try to
		641	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		642
		643	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		644	allows libev to delay invocation of I/O and timer/periodic callbacks to
		645	increase efficiency of loop iterations.
		646
		647	The background is that sometimes your program runs just fast enough to
		648	handle one (or very few) event(s) per loop iteration. While this makes
		649	the program responsive, it also wastes a lot of CPU time to poll for new
		650	events, especially with backends like C<select ()> which have a high
		651	overhead for the actual polling but can deliver many events at once.
		652
		653	By setting a higher I<io collect interval> you allow libev to spend more
		654	time collecting I/O events, so you can handle more events per iteration,
		655	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		656	C<ev_timer>) will be not affected. Setting this to a non-null value will
		657	introduce an additional C<ev_sleep ()> call into most loop iterations.
		658
		659	Likewise, by setting a higher I<timeout collect interval> you allow libev
		660	to spend more time collecting timeouts, at the expense of increased
		661	latency (the watcher callback will be called later). C<ev_io> watchers
		662	will not be affected. Setting this to a non-null value will not introduce
		663	any overhead in libev.
		664
		665	Many (busy) programs can usually benefit by setting the io collect
		666	interval to a value near C<0.1> or so, which is often enough for
		667	interactive servers (of course not for games), likewise for timeouts. It
		668	usually doesn't make much sense to set it to a lower value than C<0.01>,
		669	as this approsaches the timing granularity of most systems.
469		670
470	=back	671	=back
471		672
472		673
473	=head1 ANATOMY OF A WATCHER	674	=head1 ANATOMY OF A WATCHER
…		…
573	=item C<EV_FORK>	774	=item C<EV_FORK>
574		775
575	The event loop has been resumed in the child process after fork (see	776	The event loop has been resumed in the child process after fork (see
576	C<ev_fork>).	777	C<ev_fork>).
577		778
		779	=item C<EV_ASYNC>
		780
		781	The given async watcher has been asynchronously notified (see C<ev_async>).
		782
578	=item C<EV_ERROR>	783	=item C<EV_ERROR>
579		784
580	An unspecified error has occured, the watcher has been stopped. This might	785	An unspecified error has occured, the watcher has been stopped. This might
581	happen because the watcher could not be properly started because libev	786	happen because the watcher could not be properly started because libev
582	ran out of memory, a file descriptor was found to be closed or any other	787	ran out of memory, a file descriptor was found to be closed or any other
…		…
653	=item bool ev_is_pending (ev_TYPE *watcher)	858	=item bool ev_is_pending (ev_TYPE *watcher)
654		859
655	Returns a true value iff the watcher is pending, (i.e. it has outstanding	860	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	861	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	862	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	863	C<ev_TYPE_set> is safe), you must not change its priority, and you must
659	libev (e.g. you cnanot C<free ()> it).	864	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		865	it).
660		866
661	=item callback = ev_cb (ev_TYPE *watcher)	867	=item callback ev_cb (ev_TYPE *watcher)
662		868
663	Returns the callback currently set on the watcher.	869	Returns the callback currently set on the watcher.
664		870
665	=item ev_cb_set (ev_TYPE *watcher, callback)	871	=item ev_cb_set (ev_TYPE *watcher, callback)
666		872
667	Change the callback. You can change the callback at virtually any time	873	Change the callback. You can change the callback at virtually any time
668	(modulo threads).	874	(modulo threads).
		875
		876	=item ev_set_priority (ev_TYPE *watcher, priority)
		877
		878	=item int ev_priority (ev_TYPE *watcher)
		879
		880	Set and query the priority of the watcher. The priority is a small
		881	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		882	(default: C<-2>). Pending watchers with higher priority will be invoked
		883	before watchers with lower priority, but priority will not keep watchers
		884	from being executed (except for C<ev_idle> watchers).
		885
		886	This means that priorities are I<only> used for ordering callback
		887	invocation after new events have been received. This is useful, for
		888	example, to reduce latency after idling, or more often, to bind two
		889	watchers on the same event and make sure one is called first.
		890
		891	If you need to suppress invocation when higher priority events are pending
		892	you need to look at C<ev_idle> watchers, which provide this functionality.
		893
		894	You I<must not> change the priority of a watcher as long as it is active or
		895	pending.
		896
		897	The default priority used by watchers when no priority has been set is
		898	always C<0>, which is supposed to not be too high and not be too low :).
		899
		900	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		901	fine, as long as you do not mind that the priority value you query might
		902	or might not have been adjusted to be within valid range.
		903
		904	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		905
		906	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		907	C<loop> nor C<revents> need to be valid as long as the watcher callback
		908	can deal with that fact.
		909
		910	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		911
		912	If the watcher is pending, this function returns clears its pending status
		913	and returns its C<revents> bitset (as if its callback was invoked). If the
		914	watcher isn't pending it does nothing and returns C<0>.
669		915
670	=back	916	=back
671		917
672		918
673	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	919	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
694	{	940	{
695	struct my_io *w = (struct my_io *)w_;	941	struct my_io *w = (struct my_io *)w_;
696	...	942	...
697	}	943	}
698		944
699	More interesting and less C-conformant ways of catsing your callback type	945	More interesting and less C-conformant ways of casting your callback type
700	have been omitted....	946	instead have been omitted.
		947
		948	Another common scenario is having some data structure with multiple
		949	watchers:
		950
		951	struct my_biggy
		952	{
		953	int some_data;
		954	ev_timer t1;
		955	ev_timer t2;
		956	}
		957
		958	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		959	you need to use C<offsetof>:
		960
		961	#include <stddef.h>
		962
		963	static void
		964	t1_cb (EV_P_ struct ev_timer *w, int revents)
		965	{
		966	struct my_biggy big = (struct my_biggy *
		967	(((char *)w) - offsetof (struct my_biggy, t1));
		968	}
		969
		970	static void
		971	t2_cb (EV_P_ struct ev_timer *w, int revents)
		972	{
		973	struct my_biggy big = (struct my_biggy *
		974	(((char *)w) - offsetof (struct my_biggy, t2));
		975	}
701		976
702		977
703	=head1 WATCHER TYPES	978	=head1 WATCHER TYPES
704		979
705	This section describes each watcher in detail, but will not repeat	980	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	1004	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	1005	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	1006	descriptors to non-blocking mode is also usually a good idea (but not
732	required if you know what you are doing).	1007	required if you know what you are doing).
733		1008
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	1009	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	1010	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
742	C<EVBACKEND_POLL>).	1011	C<EVBACKEND_POLL>).
743		1012
744	Another thing you have to watch out for is that it is quite easy to	1013	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	1019	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.	1020	C<EAGAIN> is far preferable to a program hanging until some data arrives.
752		1021
753	If you cannot run the fd in non-blocking mode (for example you should not	1022	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	1023	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	1024	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	1025	such as poll (fortunately in our Xlib example, Xlib already does this on
757	its own, so its quite safe to use).	1026	its own, so its quite safe to use).
		1027
		1028	=head3 The special problem of disappearing file descriptors
		1029
		1030	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1031	descriptor (either by calling C<close> explicitly or by any other means,
		1032	such as C<dup>). The reason is that you register interest in some file
		1033	descriptor, but when it goes away, the operating system will silently drop
		1034	this interest. If another file descriptor with the same number then is
		1035	registered with libev, there is no efficient way to see that this is, in
		1036	fact, a different file descriptor.
		1037
		1038	To avoid having to explicitly tell libev about such cases, libev follows
		1039	the following policy: Each time C<ev_io_set> is being called, libev
		1040	will assume that this is potentially a new file descriptor, otherwise
		1041	it is assumed that the file descriptor stays the same. That means that
		1042	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1043	descriptor even if the file descriptor number itself did not change.
		1044
		1045	This is how one would do it normally anyway, the important point is that
		1046	the libev application should not optimise around libev but should leave
		1047	optimisations to libev.
		1048
		1049	=head3 The special problem of dup'ed file descriptors
		1050
		1051	Some backends (e.g. epoll), cannot register events for file descriptors,
		1052	but only events for the underlying file descriptions. That means when you
		1053	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1054	events for them, only one file descriptor might actually receive events.
		1055
		1056	There is no workaround possible except not registering events
		1057	for potentially C<dup ()>'ed file descriptors, or to resort to
		1058	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1059
		1060	=head3 The special problem of fork
		1061
		1062	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1063	useless behaviour. Libev fully supports fork, but needs to be told about
		1064	it in the child.
		1065
		1066	To support fork in your programs, you either have to call
		1067	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1068	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1069	C<EVBACKEND_POLL>.
		1070
		1071
		1072	=head3 Watcher-Specific Functions
758		1073
759	=over 4	1074	=over 4
760		1075
761	=item ev_io_init (ev_io *, callback, int fd, int events)	1076	=item ev_io_init (ev_io *, callback, int fd, int events)
762		1077
…		…
774		1089
775	The events being watched.	1090	The events being watched.
776		1091
777	=back	1092	=back
778		1093
		1094	=head3 Examples
		1095
779	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1096	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	1097	readable, but only once. Since it is likely line-buffered, you could
781	attempt to read a whole line in the callback:	1098	attempt to read a whole line in the callback.
782		1099
783	static void	1100	static void
784	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1101	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
785	{	1102	{
786	ev_io_stop (loop, w);	1103	ev_io_stop (loop, w);
…		…
816		1133
817	The callback is guarenteed to be invoked only when its timeout has passed,	1134	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	1135	but if multiple timers become ready during the same loop iteration then
819	order of execution is undefined.	1136	order of execution is undefined.
820		1137
		1138	=head3 Watcher-Specific Functions and Data Members
		1139
821	=over 4	1140	=over 4
822		1141
823	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1142	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
824		1143
825	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1144	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
838	=item ev_timer_again (loop)	1157	=item ev_timer_again (loop)
839		1158
840	This will act as if the timer timed out and restart it again if it is	1159	This will act as if the timer timed out and restart it again if it is
841	repeating. The exact semantics are:	1160	repeating. The exact semantics are:
842		1161
		1162	If the timer is pending, its pending status is cleared.
		1163
843	If the timer is started but nonrepeating, stop it.	1164	If the timer is started but nonrepeating, stop it (as if it timed out).
844		1165
845	If the timer is repeating, either start it if necessary (with the repeat	1166	If the timer is repeating, either start it if necessary (with the
846	value), or reset the running timer to the repeat value.	1167	C<repeat> value), or reset the running timer to the C<repeat> value.
847		1168
848	This sounds a bit complicated, but here is a useful and typical	1169	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	1170	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,	1171	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	1172	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	1173	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	1174	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	1175	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	1176	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
856	need be.	1177	automatically restart it if need be.
857		1178
858	You can also ignore the C<after> value and C<ev_timer_start> altogether	1179	That means you can ignore the C<after> value and C<ev_timer_start>
859	and only ever use the C<repeat> value:	1180	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
860		1181
861	ev_timer_init (timer, callback, 0., 5.);	1182	ev_timer_init (timer, callback, 0., 5.);
862	ev_timer_again (loop, timer);	1183	ev_timer_again (loop, timer);
863	...	1184	...
864	timer->again = 17.;	1185	timer->again = 17.;
865	ev_timer_again (loop, timer);	1186	ev_timer_again (loop, timer);
866	...	1187	...
867	timer->again = 10.;	1188	timer->again = 10.;
868	ev_timer_again (loop, timer);	1189	ev_timer_again (loop, timer);
869		1190
870	This is more efficient then stopping/starting the timer eahc time you want	1191	This is more slightly efficient then stopping/starting the timer each time
871	to modify its timeout value.	1192	you want to modify its timeout value.
872		1193
873	=item ev_tstamp repeat [read-write]	1194	=item ev_tstamp repeat [read-write]
874		1195
875	The current C<repeat> value. Will be used each time the watcher times out	1196	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),	1197	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.	1198	which is also when any modifications are taken into account.
878		1199
879	=back	1200	=back
880		1201
		1202	=head3 Examples
		1203
881	Example: create a timer that fires after 60 seconds.	1204	Example: Create a timer that fires after 60 seconds.
882		1205
883	static void	1206	static void
884	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1207	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
885	{	1208	{
886	.. one minute over, w is actually stopped right here	1209	.. one minute over, w is actually stopped right here
…		…
888		1211
889	struct ev_timer mytimer;	1212	struct ev_timer mytimer;
890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1213	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
891	ev_timer_start (loop, &mytimer);	1214	ev_timer_start (loop, &mytimer);
892		1215
893	Example: create a timeout timer that times out after 10 seconds of	1216	Example: Create a timeout timer that times out after 10 seconds of
894	inactivity.	1217	inactivity.
895		1218
896	static void	1219	static void
897	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1220	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
898	{	1221	{
…		…
918	but on wallclock time (absolute time). You can tell a periodic watcher	1241	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	1242	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 ()	1243	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	1244	+ 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	1245	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	1246	roughly 10 seconds later).
924	again).
925		1247
926	They can also be used to implement vastly more complex timers, such as	1248	They can also be used to implement vastly more complex timers, such as
927	triggering an event on eahc midnight, local time.	1249	triggering an event on each midnight, local time or other, complicated,
		1250	rules.
928		1251
929	As with timers, the callback is guarenteed to be invoked only when the	1252	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	1253	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.	1254	during the same loop iteration then order of execution is undefined.
932		1255
		1256	=head3 Watcher-Specific Functions and Data Members
		1257
933	=over 4	1258	=over 4
934		1259
935	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1260	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
936		1261
937	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1262	=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	1264	Lots of arguments, lets sort it out... There are basically three modes of
940	operation, and we will explain them from simplest to complex:	1265	operation, and we will explain them from simplest to complex:
941		1266
942	=over 4	1267	=over 4
943		1268
944	=item * absolute timer (interval = reschedule_cb = 0)	1269	=item * absolute timer (at = time, interval = reschedule_cb = 0)
945		1270
946	In this configuration the watcher triggers an event at the wallclock time	1271	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,	1272	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	1273	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.	1274	system time reaches or surpasses this time.
950		1275
951	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1276	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
952		1277
953	In this mode the watcher will always be scheduled to time out at the next	1278	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	1279	C<at + N * interval> time (for some integer N, which can also be negative)
955	of any time jumps.	1280	and then repeat, regardless of any time jumps.
956		1281
957	This can be used to create timers that do not drift with respect to system	1282	This can be used to create timers that do not drift with respect to system
958	time:	1283	time:
959		1284
960	ev_periodic_set (&periodic, 0., 3600., 0);	1285	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
966		1291
967	Another way to think about it (for the mathematically inclined) is that	1292	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	1293	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.	1294	time where C<time = at (mod interval)>, regardless of any time jumps.
970		1295
		1296	For numerical stability it is preferable that the C<at> value is near
		1297	C<ev_now ()> (the current time), but there is no range requirement for
		1298	this value.
		1299
971	=item * manual reschedule mode (reschedule_cb = callback)	1300	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
972		1301
973	In this mode the values for C<interval> and C<at> are both being	1302	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	1303	ignored. Instead, each time the periodic watcher gets scheduled, the
975	reschedule callback will be called with the watcher as first, and the	1304	reschedule callback will be called with the watcher as first, and the
976	current time as second argument.	1305	current time as second argument.
977		1306
978	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1307	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,	1308	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	1309	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
981	starting a prepare watcher).	1310	starting an C<ev_prepare> watcher, which is legal).
982		1311
983	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1312	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
984	ev_tstamp now)>, e.g.:	1313	ev_tstamp now)>, e.g.:
985		1314
986	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1315	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	1338	Simply stops and restarts the periodic watcher again. This is only useful
1010	when you changed some parameters or the reschedule callback would return	1339	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	1340	a different time than the last time it was called (e.g. in a crond like
1012	program when the crontabs have changed).	1341	program when the crontabs have changed).
1013		1342
		1343	=item ev_tstamp offset [read-write]
		1344
		1345	When repeating, this contains the offset value, otherwise this is the
		1346	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1347
		1348	Can be modified any time, but changes only take effect when the periodic
		1349	timer fires or C<ev_periodic_again> is being called.
		1350
1014	=item ev_tstamp interval [read-write]	1351	=item ev_tstamp interval [read-write]
1015		1352
1016	The current interval value. Can be modified any time, but changes only	1353	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	1354	take effect when the periodic timer fires or C<ev_periodic_again> is being
1018	called.	1355	called.
…		…
1021		1358
1022	The current reschedule callback, or C<0>, if this functionality is	1359	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	1360	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.	1361	the periodic timer fires or C<ev_periodic_again> is being called.
1025		1362
		1363	=item ev_tstamp at [read-only]
		1364
		1365	When active, contains the absolute time that the watcher is supposed to
		1366	trigger next.
		1367
1026	=back	1368	=back
1027		1369
		1370	=head3 Examples
		1371
1028	Example: call a callback every hour, or, more precisely, whenever the	1372	Example: Call a callback every hour, or, more precisely, whenever the
1029	system clock is divisible by 3600. The callback invocation times have	1373	system clock is divisible by 3600. The callback invocation times have
1030	potentially a lot of jittering, but good long-term stability.	1374	potentially a lot of jittering, but good long-term stability.
1031		1375
1032	static void	1376	static void
1033	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1377	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
1037		1381
1038	struct ev_periodic hourly_tick;	1382	struct ev_periodic hourly_tick;
1039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1383	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1040	ev_periodic_start (loop, &hourly_tick);	1384	ev_periodic_start (loop, &hourly_tick);
1041		1385
1042	Example: the same as above, but use a reschedule callback to do it:	1386	Example: The same as above, but use a reschedule callback to do it:
1043		1387
1044	#include <math.h>	1388	#include <math.h>
1045		1389
1046	static ev_tstamp	1390	static ev_tstamp
1047	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1391	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
1049	return fmod (now, 3600.) + 3600.;	1393	return fmod (now, 3600.) + 3600.;
1050	}	1394	}
1051		1395
1052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1396	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1053		1397
1054	Example: call a callback every hour, starting now:	1398	Example: Call a callback every hour, starting now:
1055		1399
1056	struct ev_periodic hourly_tick;	1400	struct ev_periodic hourly_tick;
1057	ev_periodic_init (&hourly_tick, clock_cb,	1401	ev_periodic_init (&hourly_tick, clock_cb,
1058	fmod (ev_now (loop), 3600.), 3600., 0);	1402	fmod (ev_now (loop), 3600.), 3600., 0);
1059	ev_periodic_start (loop, &hourly_tick);	1403	ev_periodic_start (loop, &hourly_tick);
…		…
1071	with the kernel (thus it coexists with your own signal handlers as long	1415	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	1416	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	1417	watcher for a signal is stopped libev will reset the signal handler to
1074	SIG_DFL (regardless of what it was set to before).	1418	SIG_DFL (regardless of what it was set to before).
1075		1419
		1420	=head3 Watcher-Specific Functions and Data Members
		1421
1076	=over 4	1422	=over 4
1077		1423
1078	=item ev_signal_init (ev_signal *, callback, int signum)	1424	=item ev_signal_init (ev_signal *, callback, int signum)
1079		1425
1080	=item ev_signal_set (ev_signal *, int signum)	1426	=item ev_signal_set (ev_signal *, int signum)
…		…
1092	=head2 C<ev_child> - watch out for process status changes	1438	=head2 C<ev_child> - watch out for process status changes
1093		1439
1094	Child watchers trigger when your process receives a SIGCHLD in response to	1440	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).	1441	some child status changes (most typically when a child of yours dies).
1096		1442
		1443	=head3 Watcher-Specific Functions and Data Members
		1444
1097	=over 4	1445	=over 4
1098		1446
1099	=item ev_child_init (ev_child *, callback, int pid)	1447	=item ev_child_init (ev_child *, callback, int pid, int trace)
1100		1448
1101	=item ev_child_set (ev_child *, int pid)	1449	=item ev_child_set (ev_child *, int pid, int trace)
1102		1450
1103	Configures the watcher to wait for status changes of process C<pid> (or	1451	Configures the watcher to wait for status changes of process C<pid> (or
1104	I<any> process if C<pid> is specified as C<0>). The callback can look	1452	I<any> process if C<pid> is specified as C<0>). The callback can look
1105	at the C<rstatus> member of the C<ev_child> watcher structure to see	1453	at the C<rstatus> member of the C<ev_child> watcher structure to see
1106	the status word (use the macros from C<sys/wait.h> and see your systems	1454	the status word (use the macros from C<sys/wait.h> and see your systems
1107	C<waitpid> documentation). The C<rpid> member contains the pid of the	1455	C<waitpid> documentation). The C<rpid> member contains the pid of the
1108	process causing the status change.	1456	process causing the status change. C<trace> must be either C<0> (only
		1457	activate the watcher when the process terminates) or C<1> (additionally
		1458	activate the watcher when the process is stopped or continued).
1109		1459
1110	=item int pid [read-only]	1460	=item int pid [read-only]
1111		1461
1112	The process id this watcher watches out for, or C<0>, meaning any process id.	1462	The process id this watcher watches out for, or C<0>, meaning any process id.
1113		1463
…		…
1120	The process exit/trace status caused by C<rpid> (see your systems	1470	The process exit/trace status caused by C<rpid> (see your systems
1121	C<waitpid> and C<sys/wait.h> documentation for details).	1471	C<waitpid> and C<sys/wait.h> documentation for details).
1122		1472
1123	=back	1473	=back
1124		1474
		1475	=head3 Examples
		1476
1125	Example: try to exit cleanly on SIGINT and SIGTERM.	1477	Example: Try to exit cleanly on SIGINT and SIGTERM.
1126		1478
1127	static void	1479	static void
1128	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1129	{	1481	{
1130	ev_unloop (loop, EVUNLOOP_ALL);	1482	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1145	not exist" is a status change like any other. The condition "path does	1497	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	1498	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	1499	otherwise always forced to be at least one) and all the other fields of
1148	the stat buffer having unspecified contents.	1500	the stat buffer having unspecified contents.
1149		1501
		1502	The path I<should> be absolute and I<must not> end in a slash. If it is
		1503	relative and your working directory changes, the behaviour is undefined.
		1504
1150	Since there is no standard to do this, the portable implementation simply	1505	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	1506	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	1507	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,	1508	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	1509	unspecified default> value will be used (which you can expect to be around
1155	five seconds, although this might change dynamically). Libev will also	1510	five seconds, although this might change dynamically). Libev will also
1156	impose a minimum interval which is currently around C<0.1>, but thats	1511	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1158		1513
1159	This watcher type is not meant for massive numbers of stat watchers,	1514	This watcher type is not meant for massive numbers of stat watchers,
1160	as even with OS-supported change notifications, this can be	1515	as even with OS-supported change notifications, this can be
1161	resource-intensive.	1516	resource-intensive.
1162		1517
1163	At the time of this writing, no specific OS backends are implemented, but	1518	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.	1519	implemented (implementing kqueue support is left as an exercise for the
		1520	reader). Inotify will be used to give hints only and should not change the
		1521	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1522	to fall back to regular polling again even with inotify, but changes are
		1523	usually detected immediately, and if the file exists there will be no
		1524	polling.
		1525
		1526	=head3 Inotify
		1527
		1528	When C<inotify (7)> support has been compiled into libev (generally only
		1529	available on Linux) and present at runtime, it will be used to speed up
		1530	change detection where possible. The inotify descriptor will be created lazily
		1531	when the first C<ev_stat> watcher is being started.
		1532
		1533	Inotify presense does not change the semantics of C<ev_stat> watchers
		1534	except that changes might be detected earlier, and in some cases, to avoid
		1535	making regular C<stat> calls. Even in the presense of inotify support
		1536	there are many cases where libev has to resort to regular C<stat> polling.
		1537
		1538	(There is no support for kqueue, as apparently it cannot be used to
		1539	implement this functionality, due to the requirement of having a file
		1540	descriptor open on the object at all times).
		1541
		1542	=head3 The special problem of stat time resolution
		1543
		1544	The C<stat ()> syscall only supports full-second resolution portably, and
		1545	even on systems where the resolution is higher, many filesystems still
		1546	only support whole seconds.
		1547
		1548	That means that, if the time is the only thing that changes, you might
		1549	miss updates: on the first update, C<ev_stat> detects a change and calls
		1550	your callback, which does something. When there is another update within
		1551	the same second, C<ev_stat> will be unable to detect it.
		1552
		1553	The solution to this is to delay acting on a change for a second (or till
		1554	the next second boundary), using a roughly one-second delay C<ev_timer>
		1555	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1556	is added to work around small timing inconsistencies of some operating
		1557	systems.
		1558
		1559	=head3 Watcher-Specific Functions and Data Members
1165		1560
1166	=over 4	1561	=over 4
1167		1562
1168	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1563	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1169		1564
…		…
1205	=item const char *path [read-only]	1600	=item const char *path [read-only]
1206		1601
1207	The filesystem path that is being watched.	1602	The filesystem path that is being watched.
1208		1603
1209	=back	1604	=back
		1605
		1606	=head3 Examples
1210		1607
1211	Example: Watch C</etc/passwd> for attribute changes.	1608	Example: Watch C</etc/passwd> for attribute changes.
1212		1609
1213	static void	1610	static void
1214	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1611	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1227	}	1624	}
1228		1625
1229	...	1626	...
1230	ev_stat passwd;	1627	ev_stat passwd;
1231		1628
1232	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1629	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1233	ev_stat_start (loop, &passwd);	1630	ev_stat_start (loop, &passwd);
1234		1631
		1632	Example: Like above, but additionally use a one-second delay so we do not
		1633	miss updates (however, frequent updates will delay processing, too, so
		1634	one might do the work both on C<ev_stat> callback invocation I<and> on
		1635	C<ev_timer> callback invocation).
		1636
		1637	static ev_stat passwd;
		1638	static ev_timer timer;
		1639
		1640	static void
		1641	timer_cb (EV_P_ ev_timer *w, int revents)
		1642	{
		1643	ev_timer_stop (EV_A_ w);
		1644
		1645	/* now it's one second after the most recent passwd change */
		1646	}
		1647
		1648	static void
		1649	stat_cb (EV_P_ ev_stat *w, int revents)
		1650	{
		1651	/* reset the one-second timer */
		1652	ev_timer_again (EV_A_ &timer);
		1653	}
		1654
		1655	...
		1656	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1657	ev_stat_start (loop, &passwd);
		1658	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1659
1235		1660
1236	=head2 C<ev_idle> - when you've got nothing better to do...	1661	=head2 C<ev_idle> - when you've got nothing better to do...
1237		1662
1238	Idle watchers trigger events when there are no other events are pending	1663	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	1664	priority are pending (prepare, check and other idle watchers do not
1240	as your process is busy handling sockets or timeouts (or even signals,	1665	count).
1241	imagine) it will not be triggered. But when your process is idle all idle	1666
1242	watchers are being called again and again, once per event loop iteration -	1667	That is, as long as your process is busy handling sockets or timeouts
		1668	(or even signals, imagine) of the same or higher priority it will not be
		1669	triggered. But when your process is idle (or only lower-priority watchers
		1670	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	1671	iteration - until stopped, that is, or your process receives more events
1244	busy.	1672	and becomes busy again with higher priority stuff.
1245		1673
1246	The most noteworthy effect is that as long as any idle watchers are	1674	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.	1675	active, the process will not block when waiting for new events.
1248		1676
1249	Apart from keeping your process non-blocking (which is a useful	1677	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	1678	effect on its own sometimes), idle watchers are a good place to do
1251	"pseudo-background processing", or delay processing stuff to after the	1679	"pseudo-background processing", or delay processing stuff to after the
1252	event loop has handled all outstanding events.	1680	event loop has handled all outstanding events.
1253		1681
		1682	=head3 Watcher-Specific Functions and Data Members
		1683
1254	=over 4	1684	=over 4
1255		1685
1256	=item ev_idle_init (ev_signal *, callback)	1686	=item ev_idle_init (ev_signal *, callback)
1257		1687
1258	Initialises and configures the idle watcher - it has no parameters of any	1688	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,	1689	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1260	believe me.	1690	believe me.
1261		1691
1262	=back	1692	=back
1263		1693
		1694	=head3 Examples
		1695
1264	Example: dynamically allocate an C<ev_idle>, start it, and in the	1696	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1265	callback, free it. Alos, use no error checking, as usual.	1697	callback, free it. Also, use no error checking, as usual.
1266		1698
1267	static void	1699	static void
1268	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1700	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1269	{	1701	{
1270	free (w);	1702	free (w);
1271	// now do something you wanted to do when the program has	1703	// now do something you wanted to do when the program has
1272	// no longer asnything immediate to do.	1704	// no longer anything immediate to do.
1273	}	1705	}
1274		1706
1275	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1707	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1276	ev_idle_init (idle_watcher, idle_cb);	1708	ev_idle_init (idle_watcher, idle_cb);
1277	ev_idle_start (loop, idle_cb);	1709	ev_idle_start (loop, idle_cb);
…		…
1315	with priority higher than or equal to the event loop and one coroutine	1747	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	1748	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	1749	loop from blocking if lower-priority coroutines are active, thus mapping
1318	low-priority coroutines to idle/background tasks).	1750	low-priority coroutines to idle/background tasks).
1319		1751
		1752	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1753	priority, to ensure that they are being run before any other watchers
		1754	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1755	too) should not activate ("feed") events into libev. While libev fully
		1756	supports this, they will be called before other C<ev_check> watchers
		1757	did their job. As C<ev_check> watchers are often used to embed other
		1758	(non-libev) event loops those other event loops might be in an unusable
		1759	state until their C<ev_check> watcher ran (always remind yourself to
		1760	coexist peacefully with others).
		1761
		1762	=head3 Watcher-Specific Functions and Data Members
		1763
1320	=over 4	1764	=over 4
1321		1765
1322	=item ev_prepare_init (ev_prepare *, callback)	1766	=item ev_prepare_init (ev_prepare *, callback)
1323		1767
1324	=item ev_check_init (ev_check *, callback)	1768	=item ev_check_init (ev_check *, callback)
…		…
1327	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1771	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.	1772	macros, but using them is utterly, utterly and completely pointless.
1329		1773
1330	=back	1774	=back
1331		1775
1332	Example: To include a library such as adns, you would add IO watchers	1776	=head3 Examples
1333	and a timeout watcher in a prepare handler, as required by libadns, and	1777
		1778	There are a number of principal ways to embed other event loops or modules
		1779	into libev. Here are some ideas on how to include libadns into libev
		1780	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1781	use for an actually working example. Another Perl module named C<EV::Glib>
		1782	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1783	into the Glib event loop).
		1784
		1785	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	1786	and in a check watcher, destroy them and call into libadns. What follows
1335	pseudo-code only of course:	1787	is pseudo-code only of course. This requires you to either use a low
		1788	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1789	the callbacks for the IO/timeout watchers might not have been called yet.
1336		1790
1337	static ev_io iow [nfd];	1791	static ev_io iow [nfd];
1338	static ev_timer tw;	1792	static ev_timer tw;
1339		1793
1340	static void	1794	static void
1341	io_cb (ev_loop *loop, ev_io *w, int revents)	1795	io_cb (ev_loop *loop, ev_io *w, int revents)
1342	{	1796	{
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	}	1797	}
1349		1798
1350	// create io watchers for each fd and a timer before blocking	1799	// create io watchers for each fd and a timer before blocking
1351	static void	1800	static void
1352	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1801	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1353	{	1802	{
1354	int timeout = 3600000;truct pollfd fds [nfd];	1803	int timeout = 3600000;
		1804	struct pollfd fds [nfd];
1355	// actual code will need to loop here and realloc etc.	1805	// actual code will need to loop here and realloc etc.
1356	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1806	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1357		1807
1358	/* the callback is illegal, but won't be called as we stop during check */	1808	/* the callback is illegal, but won't be called as we stop during check */
1359	ev_timer_init (&tw, 0, timeout * 1e-3);	1809	ev_timer_init (&tw, 0, timeout * 1e-3);
1360	ev_timer_start (loop, &tw);	1810	ev_timer_start (loop, &tw);
1361		1811
1362	// create on ev_io per pollfd	1812	// create one ev_io per pollfd
1363	for (int i = 0; i < nfd; ++i)	1813	for (int i = 0; i < nfd; ++i)
1364	{	1814	{
1365	ev_io_init (iow + i, io_cb, fds [i].fd,	1815	ev_io_init (iow + i, io_cb, fds [i].fd,
1366	((fds [i].events & POLLIN ? EV_READ : 0)	1816	((fds [i].events & POLLIN ? EV_READ : 0)
1367	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1817	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1368		1818
1369	fds [i].revents = 0;	1819	fds [i].revents = 0;
1370	iow [i].data = fds + i;
1371	ev_io_start (loop, iow + i);	1820	ev_io_start (loop, iow + i);
1372	}	1821	}
1373	}	1822	}
1374		1823
1375	// stop all watchers after blocking	1824	// stop all watchers after blocking
…		…
1377	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1826	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1378	{	1827	{
1379	ev_timer_stop (loop, &tw);	1828	ev_timer_stop (loop, &tw);
1380		1829
1381	for (int i = 0; i < nfd; ++i)	1830	for (int i = 0; i < nfd; ++i)
		1831	{
		1832	// set the relevant poll flags
		1833	// could also call adns_processreadable etc. here
		1834	struct pollfd *fd = fds + i;
		1835	int revents = ev_clear_pending (iow + i);
		1836	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1837	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1838
		1839	// now stop the watcher
1382	ev_io_stop (loop, iow + i);	1840	ev_io_stop (loop, iow + i);
		1841	}
1383		1842
1384	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1843	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1844	}
		1845
		1846	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1847	in the prepare watcher and would dispose of the check watcher.
		1848
		1849	Method 3: If the module to be embedded supports explicit event
		1850	notification (adns does), you can also make use of the actual watcher
		1851	callbacks, and only destroy/create the watchers in the prepare watcher.
		1852
		1853	static void
		1854	timer_cb (EV_P_ ev_timer *w, int revents)
		1855	{
		1856	adns_state ads = (adns_state)w->data;
		1857	update_now (EV_A);
		1858
		1859	adns_processtimeouts (ads, &tv_now);
		1860	}
		1861
		1862	static void
		1863	io_cb (EV_P_ ev_io *w, int revents)
		1864	{
		1865	adns_state ads = (adns_state)w->data;
		1866	update_now (EV_A);
		1867
		1868	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1869	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1870	}
		1871
		1872	// do not ever call adns_afterpoll
		1873
		1874	Method 4: Do not use a prepare or check watcher because the module you
		1875	want to embed is too inflexible to support it. Instead, youc na override
		1876	their poll function. The drawback with this solution is that the main
		1877	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1878	this.
		1879
		1880	static gint
		1881	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1882	{
		1883	int got_events = 0;
		1884
		1885	for (n = 0; n < nfds; ++n)
		1886	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1887
		1888	if (timeout >= 0)
		1889	// create/start timer
		1890
		1891	// poll
		1892	ev_loop (EV_A_ 0);
		1893
		1894	// stop timer again
		1895	if (timeout >= 0)
		1896	ev_timer_stop (EV_A_ &to);
		1897
		1898	// stop io watchers again - their callbacks should have set
		1899	for (n = 0; n < nfds; ++n)
		1900	ev_io_stop (EV_A_ iow [n]);
		1901
		1902	return got_events;
1385	}	1903	}
1386		1904
1387		1905
1388	=head2 C<ev_embed> - when one backend isn't enough...	1906	=head2 C<ev_embed> - when one backend isn't enough...
1389		1907
…		…
1432	portable one.	1950	portable one.
1433		1951
1434	So when you want to use this feature you will always have to be prepared	1952	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	1953	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	1954	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:	1955	create it, and if that fails, use the normal loop for everything.
		1956
		1957	=head3 Watcher-Specific Functions and Data Members
		1958
		1959	=over 4
		1960
		1961	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1962
		1963	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1964
		1965	Configures the watcher to embed the given loop, which must be
		1966	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1967	invoked automatically, otherwise it is the responsibility of the callback
		1968	to invoke it (it will continue to be called until the sweep has been done,
		1969	if you do not want thta, you need to temporarily stop the embed watcher).
		1970
		1971	=item ev_embed_sweep (loop, ev_embed *)
		1972
		1973	Make a single, non-blocking sweep over the embedded loop. This works
		1974	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1975	apropriate way for embedded loops.
		1976
		1977	=item struct ev_loop *other [read-only]
		1978
		1979	The embedded event loop.
		1980
		1981	=back
		1982
		1983	=head3 Examples
		1984
		1985	Example: Try to get an embeddable event loop and embed it into the default
		1986	event loop. If that is not possible, use the default loop. The default
		1987	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1988	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1989	used).
1438		1990
1439	struct ev_loop *loop_hi = ev_default_init (0);	1991	struct ev_loop *loop_hi = ev_default_init (0);
1440	struct ev_loop *loop_lo = 0;	1992	struct ev_loop *loop_lo = 0;
1441	struct ev_embed embed;	1993	struct ev_embed embed;
1442		1994
…		…
1453	ev_embed_start (loop_hi, &embed);	2005	ev_embed_start (loop_hi, &embed);
1454	}	2006	}
1455	else	2007	else
1456	loop_lo = loop_hi;	2008	loop_lo = loop_hi;
1457		2009
1458	=over 4	2010	Example: Check if kqueue is available but not recommended and create
		2011	a kqueue backend for use with sockets (which usually work with any
		2012	kqueue implementation). Store the kqueue/socket-only event loop in
		2013	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1459		2014
1460	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2015	struct ev_loop *loop = ev_default_init (0);
		2016	struct ev_loop *loop_socket = 0;
		2017	struct ev_embed embed;
		2018
		2019	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2020	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2021	{
		2022	ev_embed_init (&embed, 0, loop_socket);
		2023	ev_embed_start (loop, &embed);
		2024	}
1461		2025
1462	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2026	if (!loop_socket)
		2027	loop_socket = loop;
1463		2028
1464	Configures the watcher to embed the given loop, which must be	2029	// 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		2030
1482		2031
1483	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2032	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1484		2033
1485	Fork watchers are called when a C<fork ()> was detected (usually because	2034	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,	2037	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	2038	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	2039	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1491	handlers will be invoked, too, of course.	2040	handlers will be invoked, too, of course.
1492		2041
		2042	=head3 Watcher-Specific Functions and Data Members
		2043
1493	=over 4	2044	=over 4
1494		2045
1495	=item ev_fork_init (ev_signal *, callback)	2046	=item ev_fork_init (ev_signal *, callback)
1496		2047
1497	Initialises and configures the fork watcher - it has no parameters of any	2048	Initialises and configures the fork watcher - it has no parameters of any
1498	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2049	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1499	believe me.	2050	believe me.
		2051
		2052	=back
		2053
		2054
		2055	=head2 C<ev_async> - how to wake up another event loop
		2056
		2057	In general, you cannot use an C<ev_loop> from multiple threads or other
		2058	asynchronous sources such as signal handlers (as opposed to multiple event
		2059	loops - those are of course safe to use in different threads).
		2060
		2061	Sometimes, however, you need to wake up another event loop you do not
		2062	control, for example because it belongs to another thread. This is what
		2063	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2064	can signal it by calling C<ev_async_send>, which is thread- and signal
		2065	safe.
		2066
		2067	This functionality is very similar to C<ev_signal> watchers, as signals,
		2068	too, are asynchronous in nature, and signals, too, will be compressed
		2069	(i.e. the number of callback invocations may be less than the number of
		2070	C<ev_async_sent> calls).
		2071
		2072	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2073	just the default loop.
		2074
		2075	=head3 Queueing
		2076
		2077	C<ev_async> does not support queueing of data in any way. The reason
		2078	is that the author does not know of a simple (or any) algorithm for a
		2079	multiple-writer-single-reader queue that works in all cases and doesn't
		2080	need elaborate support such as pthreads.
		2081
		2082	That means that if you want to queue data, you have to provide your own
		2083	queue. But at least I can tell you would implement locking around your
		2084	queue:
		2085
		2086	=over 4
		2087
		2088	=item queueing from a signal handler context
		2089
		2090	To implement race-free queueing, you simply add to the queue in the signal
		2091	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2092	some fictitiuous SIGUSR1 handler:
		2093
		2094	static ev_async mysig;
		2095
		2096	static void
		2097	sigusr1_handler (void)
		2098	{
		2099	sometype data;
		2100
		2101	// no locking etc.
		2102	queue_put (data);
		2103	ev_async_send (DEFAULT_ &mysig);
		2104	}
		2105
		2106	static void
		2107	mysig_cb (EV_P_ ev_async *w, int revents)
		2108	{
		2109	sometype data;
		2110	sigset_t block, prev;
		2111
		2112	sigemptyset (&block);
		2113	sigaddset (&block, SIGUSR1);
		2114	sigprocmask (SIG_BLOCK, &block, &prev);
		2115
		2116	while (queue_get (&data))
		2117	process (data);
		2118
		2119	if (sigismember (&prev, SIGUSR1)
		2120	sigprocmask (SIG_UNBLOCK, &block, 0);
		2121	}
		2122
		2123	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2124	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2125	either...).
		2126
		2127	=item queueing from a thread context
		2128
		2129	The strategy for threads is different, as you cannot (easily) block
		2130	threads but you can easily preempt them, so to queue safely you need to
		2131	employ a traditional mutex lock, such as in this pthread example:
		2132
		2133	static ev_async mysig;
		2134	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2135
		2136	static void
		2137	otherthread (void)
		2138	{
		2139	// only need to lock the actual queueing operation
		2140	pthread_mutex_lock (&mymutex);
		2141	queue_put (data);
		2142	pthread_mutex_unlock (&mymutex);
		2143
		2144	ev_async_send (DEFAULT_ &mysig);
		2145	}
		2146
		2147	static void
		2148	mysig_cb (EV_P_ ev_async *w, int revents)
		2149	{
		2150	pthread_mutex_lock (&mymutex);
		2151
		2152	while (queue_get (&data))
		2153	process (data);
		2154
		2155	pthread_mutex_unlock (&mymutex);
		2156	}
		2157
		2158	=back
		2159
		2160
		2161	=head3 Watcher-Specific Functions and Data Members
		2162
		2163	=over 4
		2164
		2165	=item ev_async_init (ev_async *, callback)
		2166
		2167	Initialises and configures the async watcher - it has no parameters of any
		2168	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2169	believe me.
		2170
		2171	=item ev_async_send (loop, ev_async *)
		2172
		2173	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2174	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2175	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2176	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2177	section below on what exactly this means).
		2178
		2179	This call incurs the overhead of a syscall only once per loop iteration,
		2180	so while the overhead might be noticable, it doesn't apply to repeated
		2181	calls to C<ev_async_send>.
1500		2182
1501	=back	2183	=back
1502		2184
1503		2185
1504	=head1 OTHER FUNCTIONS	2186	=head1 OTHER FUNCTIONS
…		…
1593		2275
1594	To use it,	2276	To use it,
1595		2277
1596	#include <ev++.h>	2278	#include <ev++.h>
1597		2279
1598	(it is not installed by default). This automatically includes F<ev.h>	2280	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	2281	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.	2282	put into the C<ev> namespace. It should support all the same embedding
		2283	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1601		2284
1602	It should support all the same embedding options as F<ev.h>, most notably	2285	Care has been taken to keep the overhead low. The only data member the C++
1603	C<EV_MULTIPLICITY>.	2286	classes add (compared to plain C-style watchers) is the event loop pointer
		2287	that the watcher is associated with (or no additional members at all if
		2288	you disable C<EV_MULTIPLICITY> when embedding libev).
		2289
		2290	Currently, functions, and static and non-static member functions can be
		2291	used as callbacks. Other types should be easy to add as long as they only
		2292	need one additional pointer for context. If you need support for other
		2293	types of functors please contact the author (preferably after implementing
		2294	it).
1604		2295
1605	Here is a list of things available in the C<ev> namespace:	2296	Here is a list of things available in the C<ev> namespace:
1606		2297
1607	=over 4	2298	=over 4
1608		2299
…		…
1624		2315
1625	All of those classes have these methods:	2316	All of those classes have these methods:
1626		2317
1627	=over 4	2318	=over 4
1628		2319
1629	=item ev::TYPE::TYPE (object *, object::method *)	2320	=item ev::TYPE::TYPE ()
1630		2321
1631	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2322	=item ev::TYPE::TYPE (struct ev_loop *)
1632		2323
1633	=item ev::TYPE::~TYPE	2324	=item ev::TYPE::~TYPE
1634		2325
1635	The constructor takes a pointer to an object and a method pointer to	2326	The constructor (optionally) takes an event loop to associate the watcher
1636	the event handler callback to call in this class. The constructor calls	2327	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	2328
1638	before starting it. If you do not specify a loop then the constructor	2329	The constructor calls C<ev_init> for you, which means you have to call the
1639	automatically associates the default loop with this watcher.	2330	C<set> method before starting it.
		2331
		2332	It will not set a callback, however: You have to call the templated C<set>
		2333	method to set a callback before you can start the watcher.
		2334
		2335	(The reason why you have to use a method is a limitation in C++ which does
		2336	not allow explicit template arguments for constructors).
1640		2337
1641	The destructor automatically stops the watcher if it is active.	2338	The destructor automatically stops the watcher if it is active.
		2339
		2340	=item w->set<class, &class::method> (object *)
		2341
		2342	This method sets the callback method to call. The method has to have a
		2343	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2344	first argument and the C<revents> as second. The object must be given as
		2345	parameter and is stored in the C<data> member of the watcher.
		2346
		2347	This method synthesizes efficient thunking code to call your method from
		2348	the C callback that libev requires. If your compiler can inline your
		2349	callback (i.e. it is visible to it at the place of the C<set> call and
		2350	your compiler is good :), then the method will be fully inlined into the
		2351	thunking function, making it as fast as a direct C callback.
		2352
		2353	Example: simple class declaration and watcher initialisation
		2354
		2355	struct myclass
		2356	{
		2357	void io_cb (ev::io &w, int revents) { }
		2358	}
		2359
		2360	myclass obj;
		2361	ev::io iow;
		2362	iow.set <myclass, &myclass::io_cb> (&obj);
		2363
		2364	=item w->set<function> (void *data = 0)
		2365
		2366	Also sets a callback, but uses a static method or plain function as
		2367	callback. The optional C<data> argument will be stored in the watcher's
		2368	C<data> member and is free for you to use.
		2369
		2370	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2371
		2372	See the method-C<set> above for more details.
		2373
		2374	Example:
		2375
		2376	static void io_cb (ev::io &w, int revents) { }
		2377	iow.set <io_cb> ();
1642		2378
1643	=item w->set (struct ev_loop *)	2379	=item w->set (struct ev_loop *)
1644		2380
1645	Associates a different C<struct ev_loop> with this watcher. You can only	2381	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).	2382	do this when the watcher is inactive (and not pending either).
1647		2383
1648	=item w->set ([args])	2384	=item w->set ([args])
1649		2385
1650	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2386	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	2387	called at least once. Unlike the C counterpart, an active watcher gets
1652	automatically stopped and restarted.	2388	automatically stopped and restarted when reconfiguring it with this
		2389	method.
1653		2390
1654	=item w->start ()	2391	=item w->start ()
1655		2392
1656	Starts the watcher. Note that there is no C<loop> argument as the	2393	Starts the watcher. Note that there is no C<loop> argument, as the
1657	constructor already takes the loop.	2394	constructor already stores the event loop.
1658		2395
1659	=item w->stop ()	2396	=item w->stop ()
1660		2397
1661	Stops the watcher if it is active. Again, no C<loop> argument.	2398	Stops the watcher if it is active. Again, no C<loop> argument.
1662		2399
1663	=item w->again () C<ev::timer>, C<ev::periodic> only	2400	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1664		2401
1665	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2402	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1666	C<ev_TYPE_again> function.	2403	C<ev_TYPE_again> function.
1667		2404
1668	=item w->sweep () C<ev::embed> only	2405	=item w->sweep () (C<ev::embed> only)
1669		2406
1670	Invokes C<ev_embed_sweep>.	2407	Invokes C<ev_embed_sweep>.
1671		2408
1672	=item w->update () C<ev::stat> only	2409	=item w->update () (C<ev::stat> only)
1673		2410
1674	Invokes C<ev_stat_stat>.	2411	Invokes C<ev_stat_stat>.
1675		2412
1676	=back	2413	=back
1677		2414
…		…
1680	Example: Define a class with an IO and idle watcher, start one of them in	2417	Example: Define a class with an IO and idle watcher, start one of them in
1681	the constructor.	2418	the constructor.
1682		2419
1683	class myclass	2420	class myclass
1684	{	2421	{
1685	ev_io io; void io_cb (ev::io &w, int revents);	2422	ev::io io; void io_cb (ev::io &w, int revents);
1686	ev_idle idle void idle_cb (ev::idle &w, int revents);	2423	ev:idle idle void idle_cb (ev::idle &w, int revents);
1687		2424
1688	myclass ();	2425	myclass (int fd)
1689	}
1690
1691	myclass::myclass (int fd)
1692	: io (this, &myclass::io_cb),
1693	idle (this, &myclass::idle_cb)
1694	{	2426	{
		2427	io .set <myclass, &myclass::io_cb > (this);
		2428	idle.set <myclass, &myclass::idle_cb> (this);
		2429
1695	io.start (fd, ev::READ);	2430	io.start (fd, ev::READ);
		2431	}
1696	}	2432	};
1697		2433
1698		2434
1699	=head1 MACRO MAGIC	2435	=head1 MACRO MAGIC
1700		2436
1701	Libev can be compiled with a variety of options, the most fundemantal is	2437	Libev can be compiled with a variety of options, the most fundamantal
1702	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2438	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1703	callbacks have an initial C<struct ev_loop *> argument.	2439	functions and callbacks have an initial C<struct ev_loop *> argument.
1704		2440
1705	To make it easier to write programs that cope with either variant, the	2441	To make it easier to write programs that cope with either variant, the
1706	following macros are defined:	2442	following macros are defined:
1707		2443
1708	=over 4	2444	=over 4
…		…
1740	Similar to the other two macros, this gives you the value of the default	2476	Similar to the other two macros, this gives you the value of the default
1741	loop, if multiple loops are supported ("ev loop default").	2477	loop, if multiple loops are supported ("ev loop default").
1742		2478
1743	=back	2479	=back
1744		2480
1745	Example: Declare and initialise a check watcher, working regardless of	2481	Example: Declare and initialise a check watcher, utilising the above
1746	wether multiple loops are supported or not.	2482	macros so it will work regardless of whether multiple loops are supported
		2483	or not.
1747		2484
1748	static void	2485	static void
1749	check_cb (EV_P_ ev_timer *w, int revents)	2486	check_cb (EV_P_ ev_timer *w, int revents)
1750	{	2487	{
1751	ev_check_stop (EV_A_ w);	2488	ev_check_stop (EV_A_ w);
…		…
1754	ev_check check;	2491	ev_check check;
1755	ev_check_init (&check, check_cb);	2492	ev_check_init (&check, check_cb);
1756	ev_check_start (EV_DEFAULT_ &check);	2493	ev_check_start (EV_DEFAULT_ &check);
1757	ev_loop (EV_DEFAULT_ 0);	2494	ev_loop (EV_DEFAULT_ 0);
1758		2495
1759
1760	=head1 EMBEDDING	2496	=head1 EMBEDDING
1761		2497
1762	Libev can (and often is) directly embedded into host	2498	Libev can (and often is) directly embedded into host
1763	applications. Examples of applications that embed it include the Deliantra	2499	applications. Examples of applications that embed it include the Deliantra
1764	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2500	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1765	and rxvt-unicode.	2501	and rxvt-unicode.
1766		2502
1767	The goal is to enable you to just copy the neecssary files into your	2503	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	2504	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	2505	you can easily upgrade by simply copying (or having a checked-out copy of
1770	libev somewhere in your source tree).	2506	libev somewhere in your source tree).
1771		2507
1772	=head2 FILESETS	2508	=head2 FILESETS
…		…
1803	ev_vars.h	2539	ev_vars.h
1804	ev_wrap.h	2540	ev_wrap.h
1805		2541
1806	ev_win32.c required on win32 platforms only	2542	ev_win32.c required on win32 platforms only
1807		2543
1808	ev_select.c only when select backend is enabled (which is by default)	2544	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)	2545	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)	2546	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)	2547	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)	2548	ev_port.c only when the solaris port backend is enabled (disabled by default)
1813		2549
…		…
1862		2598
1863	If defined to be C<1>, libev will try to detect the availability of the	2599	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	2600	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	2601	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	2602	usually have to link against librt or something similar. Enabling it when
1867	the functionality isn't available is safe, though, althoguh you have	2603	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>	2604	to make sure you link against any libraries where the C<clock_gettime>
1869	function is hiding in (often F<-lrt>).	2605	function is hiding in (often F<-lrt>).
1870		2606
1871	=item EV_USE_REALTIME	2607	=item EV_USE_REALTIME
1872		2608
1873	If defined to be C<1>, libev will try to detect the availability of the	2609	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	2610	realtime clock option at compiletime (and assume its availability at
1875	runtime if successful). Otherwise no use of the realtime clock option will	2611	runtime if successful). Otherwise no use of the realtime clock option will
1876	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2612	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	2613	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1878	in the description of C<EV_USE_MONOTONIC>, though.	2614	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2615
		2616	=item EV_USE_NANOSLEEP
		2617
		2618	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2619	and will use it for delays. Otherwise it will use C<select ()>.
1879		2620
1880	=item EV_USE_SELECT	2621	=item EV_USE_SELECT
1881		2622
1882	If undefined or defined to be C<1>, libev will compile in support for the	2623	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	2624	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	2642	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	2643	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,	2644	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	2645	it is assumed that all these functions actually work on fds, even
1905	on win32. Should not be defined on non-win32 platforms.	2646	on win32. Should not be defined on non-win32 platforms.
		2647
		2648	=item EV_FD_TO_WIN32_HANDLE
		2649
		2650	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2651	file descriptors to socket handles. When not defining this symbol (the
		2652	default), then libev will call C<_get_osfhandle>, which is usually
		2653	correct. In some cases, programs use their own file descriptor management,
		2654	in which case they can provide this function to map fds to socket handles.
1906		2655
1907	=item EV_USE_POLL	2656	=item EV_USE_POLL
1908		2657
1909	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2658	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	2659	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
1938		2687
1939	=item EV_USE_DEVPOLL	2688	=item EV_USE_DEVPOLL
1940		2689
1941	reserved for future expansion, works like the USE symbols above.	2690	reserved for future expansion, works like the USE symbols above.
1942		2691
		2692	=item EV_USE_INOTIFY
		2693
		2694	If defined to be C<1>, libev will compile in support for the Linux inotify
		2695	interface to speed up C<ev_stat> watchers. Its actual availability will
		2696	be detected at runtime.
		2697
		2698	=item EV_ATOMIC_T
		2699
		2700	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2701	access is atomic with respect to other threads or signal contexts. No such
		2702	type is easily found in the C language, so you can provide your own type
		2703	that you know is safe for your purposes. It is used both for signal handler "locking"
		2704	as well as for signal and thread safety in C<ev_async> watchers.
		2705
		2706	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2707	(from F<signal.h>), which is usually good enough on most platforms.
		2708
1943	=item EV_H	2709	=item EV_H
1944		2710
1945	The name of the F<ev.h> header file used to include it. The default if	2711	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	2712	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
1947	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2713	used to virtually rename the F<ev.h> header file in case of conflicts.
1948		2714
1949	=item EV_CONFIG_H	2715	=item EV_CONFIG_H
1950		2716
1951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2717	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	2718	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1953	C<EV_H>, above.	2719	C<EV_H>, above.
1954		2720
1955	=item EV_EVENT_H	2721	=item EV_EVENT_H
1956		2722
1957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2723	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.	2724	of how the F<event.h> header can be found, the default is C<"event.h">.
1959		2725
1960	=item EV_PROTOTYPES	2726	=item EV_PROTOTYPES
1961		2727
1962	If defined to be C<0>, then F<ev.h> will not define any function	2728	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	2729	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	2736	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	2737	additional independent event loops. Otherwise there will be no support
1972	for multiple event loops and there is no first event loop pointer	2738	for multiple event loops and there is no first event loop pointer
1973	argument. Instead, all functions act on the single default loop.	2739	argument. Instead, all functions act on the single default loop.
1974		2740
		2741	=item EV_MINPRI
		2742
		2743	=item EV_MAXPRI
		2744
		2745	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2746	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2747	provide for more priorities by overriding those symbols (usually defined
		2748	to be C<-2> and C<2>, respectively).
		2749
		2750	When doing priority-based operations, libev usually has to linearly search
		2751	all the priorities, so having many of them (hundreds) uses a lot of space
		2752	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2753	fine.
		2754
		2755	If your embedding app does not need any priorities, defining these both to
		2756	C<0> will save some memory and cpu.
		2757
1975	=item EV_PERIODIC_ENABLE	2758	=item EV_PERIODIC_ENABLE
1976		2759
1977	If undefined or defined to be C<1>, then periodic timers are supported. If	2760	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	2761	defined to be C<0>, then they are not. Disabling them saves a few kB of
1979	code.	2762	code.
1980		2763
		2764	=item EV_IDLE_ENABLE
		2765
		2766	If undefined or defined to be C<1>, then idle watchers are supported. If
		2767	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2768	code.
		2769
1981	=item EV_EMBED_ENABLE	2770	=item EV_EMBED_ENABLE
1982		2771
1983	If undefined or defined to be C<1>, then embed watchers are supported. If	2772	If undefined or defined to be C<1>, then embed watchers are supported. If
1984	defined to be C<0>, then they are not.	2773	defined to be C<0>, then they are not.
1985		2774
…		…
1989	defined to be C<0>, then they are not.	2778	defined to be C<0>, then they are not.
1990		2779
1991	=item EV_FORK_ENABLE	2780	=item EV_FORK_ENABLE
1992		2781
1993	If undefined or defined to be C<1>, then fork watchers are supported. If	2782	If undefined or defined to be C<1>, then fork watchers are supported. If
		2783	defined to be C<0>, then they are not.
		2784
		2785	=item EV_ASYNC_ENABLE
		2786
		2787	If undefined or defined to be C<1>, then async watchers are supported. If
1994	defined to be C<0>, then they are not.	2788	defined to be C<0>, then they are not.
1995		2789
1996	=item EV_MINIMAL	2790	=item EV_MINIMAL
1997		2791
1998	If you need to shave off some kilobytes of code at the expense of some	2792	If you need to shave off some kilobytes of code at the expense of some
…		…
2002	=item EV_PID_HASHSIZE	2796	=item EV_PID_HASHSIZE
2003		2797
2004	C<ev_child> watchers use a small hash table to distribute workload by	2798	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	2799	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	2800	than enough. If you need to manage thousands of children you might want to
2007	increase this value.	2801	increase this value (I<must> be a power of two).
		2802
		2803	=item EV_INOTIFY_HASHSIZE
		2804
		2805	C<ev_stat> watchers use a small hash table to distribute workload by
		2806	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2807	usually more than enough. If you need to manage thousands of C<ev_stat>
		2808	watchers you might want to increase this value (I<must> be a power of
		2809	two).
2008		2810
2009	=item EV_COMMON	2811	=item EV_COMMON
2010		2812
2011	By default, all watchers have a C<void *data> member. By redefining	2813	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	2814	this macro to a something else you can include more and other types of
…		…
2025		2827
2026	=item ev_set_cb (ev, cb)	2828	=item ev_set_cb (ev, cb)
2027		2829
2028	Can be used to change the callback member declaration in each watcher,	2830	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	2831	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	2832	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	2833	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	2834	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++.	2835	method calls instead of plain function calls in C++.
		2836
		2837	=head2 EXPORTED API SYMBOLS
		2838
		2839	If you need to re-export the API (e.g. via a dll) and you need a list of
		2840	exported symbols, you can use the provided F<Symbol.*> files which list
		2841	all public symbols, one per line:
		2842
		2843	Symbols.ev for libev proper
		2844	Symbols.event for the libevent emulation
		2845
		2846	This can also be used to rename all public symbols to avoid clashes with
		2847	multiple versions of libev linked together (which is obviously bad in
		2848	itself, but sometimes it is inconvinient to avoid this).
		2849
		2850	A sed command like this will create wrapper C<#define>'s that you need to
		2851	include before including F<ev.h>:
		2852
		2853	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2854
		2855	This would create a file F<wrap.h> which essentially looks like this:
		2856
		2857	#define ev_backend myprefix_ev_backend
		2858	#define ev_check_start myprefix_ev_check_start
		2859	#define ev_check_stop myprefix_ev_check_stop
		2860	...
2034		2861
2035	=head2 EXAMPLES	2862	=head2 EXAMPLES
2036		2863
2037	For a real-world example of a program the includes libev	2864	For a real-world example of a program the includes libev
2038	verbatim, you can have a look at the EV perl module	2865	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	2868	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	2869	will be compiled. It is pretty complex because it provides its own header
2043	file.	2870	file.
2044		2871
2045	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2872	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:	2873	that everybody includes and which overrides some configure choices:
2047		2874
		2875	#define EV_MINIMAL 1
2048	#define EV_USE_POLL 0	2876	#define EV_USE_POLL 0
2049	#define EV_MULTIPLICITY 0	2877	#define EV_MULTIPLICITY 0
2050	#define EV_PERIODICS 0	2878	#define EV_PERIODIC_ENABLE 0
		2879	#define EV_STAT_ENABLE 0
		2880	#define EV_FORK_ENABLE 0
2051	#define EV_CONFIG_H <config.h>	2881	#define EV_CONFIG_H <config.h>
		2882	#define EV_MINPRI 0
		2883	#define EV_MAXPRI 0
2052		2884
2053	#include "ev++.h"	2885	#include "ev++.h"
2054		2886
2055	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2887	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2056		2888
…		…
2062		2894
2063	In this section the complexities of (many of) the algorithms used inside	2895	In this section the complexities of (many of) the algorithms used inside
2064	libev will be explained. For complexity discussions about backends see the	2896	libev will be explained. For complexity discussions about backends see the
2065	documentation for C<ev_default_init>.	2897	documentation for C<ev_default_init>.
2066		2898
		2899	All of the following are about amortised time: If an array needs to be
		2900	extended, libev needs to realloc and move the whole array, but this
		2901	happens asymptotically never with higher number of elements, so O(1) might
		2902	mean it might do a lengthy realloc operation in rare cases, but on average
		2903	it is much faster and asymptotically approaches constant time.
		2904
2067	=over 4	2905	=over 4
2068		2906
2069	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2907	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2070		2908
		2909	This means that, when you have a watcher that triggers in one hour and
		2910	there are 100 watchers that would trigger before that then inserting will
		2911	have to skip roughly seven (C<ld 100>) of these watchers.
		2912
2071	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2913	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2072		2914
		2915	That means that changing a timer costs less than removing/adding them
		2916	as only the relative motion in the event queue has to be paid for.
		2917
2073	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2918	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2074		2919
		2920	These just add the watcher into an array or at the head of a list.
		2921
2075	=item Stopping check/prepare/idle watchers: O(1)	2922	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2076		2923
2077	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2924	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2078		2925
		2926	These watchers are stored in lists then need to be walked to find the
		2927	correct watcher to remove. The lists are usually short (you don't usually
		2928	have many watchers waiting for the same fd or signal).
		2929
2079	=item Finding the next timer per loop iteration: O(1)	2930	=item Finding the next timer in each loop iteration: O(1)
		2931
		2932	By virtue of using a binary heap, the next timer is always found at the
		2933	beginning of the storage array.
2080		2934
2081	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2935	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2082		2936
2083	=item Activating one watcher: O(1)	2937	A change means an I/O watcher gets started or stopped, which requires
		2938	libev to recalculate its status (and possibly tell the kernel, depending
		2939	on backend and wether C<ev_io_set> was used).
		2940
		2941	=item Activating one watcher (putting it into the pending state): O(1)
		2942
		2943	=item Priority handling: O(number_of_priorities)
		2944
		2945	Priorities are implemented by allocating some space for each
		2946	priority. When doing priority-based operations, libev usually has to
		2947	linearly search all the priorities, but starting/stopping and activating
		2948	watchers becomes O(1) w.r.t. priority handling.
		2949
		2950	=item Sending an ev_async: O(1)
		2951
		2952	=item Processing ev_async_send: O(number_of_async_watchers)
		2953
		2954	=item Processing signals: O(max_signal_number)
		2955
		2956	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		2957	calls in the current loop iteration. Checking for async and signal events
		2958	involves iterating over all running async watchers or all signal numbers.
2084		2959
2085	=back	2960	=back
2086		2961
2087		2962
		2963	=head1 Win32 platform limitations and workarounds
		2964
		2965	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2966	requires, and its I/O model is fundamentally incompatible with the POSIX
		2967	model. Libev still offers limited functionality on this platform in
		2968	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2969	descriptors. This only applies when using Win32 natively, not when using
		2970	e.g. cygwin.
		2971
		2972	There is no supported compilation method available on windows except
		2973	embedding it into other applications.
		2974
		2975	Due to the many, low, and arbitrary limits on the win32 platform and the
		2976	abysmal performance of winsockets, using a large number of sockets is not
		2977	recommended (and not reasonable). If your program needs to use more than
		2978	a hundred or so sockets, then likely it needs to use a totally different
		2979	implementation for windows, as libev offers the POSIX model, which cannot
		2980	be implemented efficiently on windows (microsoft monopoly games).
		2981
		2982	=over 4
		2983
		2984	=item The winsocket select function
		2985
		2986	The winsocket C<select> function doesn't follow POSIX in that it requires
		2987	socket I<handles> and not socket I<file descriptors>. This makes select
		2988	very inefficient, and also requires a mapping from file descriptors
		2989	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2990	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2991	symbols for more info.
		2992
		2993	The configuration for a "naked" win32 using the microsoft runtime
		2994	libraries and raw winsocket select is:
		2995
		2996	#define EV_USE_SELECT 1
		2997	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2998
		2999	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3000	complexity in the O(n²) range when using win32.
		3001
		3002	=item Limited number of file descriptors
		3003
		3004	Windows has numerous arbitrary (and low) limits on things. Early versions
		3005	of winsocket's select only supported waiting for a max. of C<64> handles
		3006	(probably owning to the fact that all windows kernels can only wait for
		3007	C<64> things at the same time internally; microsoft recommends spawning a
		3008	chain of threads and wait for 63 handles and the previous thread in each).
		3009
		3010	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3011	to some high number (e.g. C<2048>) before compiling the winsocket select
		3012	call (which might be in libev or elsewhere, for example, perl does its own
		3013	select emulation on windows).
		3014
		3015	Another limit is the number of file descriptors in the microsoft runtime
		3016	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3017	or something like this inside microsoft). You can increase this by calling
		3018	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3019	arbitrary limit), but is broken in many versions of the microsoft runtime
		3020	libraries.
		3021
		3022	This might get you to about C<512> or C<2048> sockets (depending on
		3023	windows version and/or the phase of the moon). To get more, you need to
		3024	wrap all I/O functions and provide your own fd management, but the cost of
		3025	calling select (O(n²)) will likely make this unworkable.
		3026
		3027	=back
		3028
		3029
2088	=head1 AUTHOR	3030	=head1 AUTHOR
2089		3031
2090	Marc Lehmann <libev@schmorp.de>.	3032	Marc Lehmann <libev@schmorp.de>.
2091		3033

Diff Legend

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