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Revision 1.136 by root, Thu Mar 13 13:06:16 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	// a single header file is required
		12	#include <ev.h>
		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
		16	ev_io stdin_watcher;
		17	ev_timer timeout_watcher;
		18
		19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
		21	static void
		22	stdin_cb (EV_P_ struct ev_io *w, int revents)
		23	{
		24	puts ("stdin ready");
		25	// for one-shot events, one must manually stop the watcher
		26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
		31	}
		32
		33	// another callback, this time for a time-out
		34	static void
		35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		36	{
		37	puts ("timeout");
		38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
		40	}
		41
		42	int
		43	main (void)
		44	{
		45	// use the default event loop unless you have special needs
		46	struct ev_loop *loop = ev_default_loop (0);
		47
		48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
		50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		51	ev_io_start (loop, &stdin_watcher);
		52
		53	// initialise a timer watcher, then start it
		54	// simple non-repeating 5.5 second timeout
		55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		56	ev_timer_start (loop, &timeout_watcher);
		57
		58	// now wait for events to arrive
		59	ev_loop (loop, 0);
		60
		61	// unloop was called, so exit
		62	return 0;
		63	}
		64
9	=head1 DESCRIPTION	65	=head1 DESCRIPTION
10		66
		67	The newest version of this document is also available as an html-formatted
		68	web page you might find easier to navigate when reading it for the first
		69	time: L<http://cvs.schmorp.de/libev/ev.html>.
		70
11	Libev is an event loop: you register interest in certain events (such as a	71	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	72	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	73	these event sources and provide your program with events.
14		74
15	To do this, it must take more or less complete control over your process	75	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	76	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
19	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
20	watchers>, which are relatively small C structures you initialise with the	80	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	81	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	82	watcher.
23		83
24	=head1 FEATURES	84	=head2 FEATURES
25		85
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	90	with customised rescheduling (C<ev_periodic>), synchronous signals
		91	(C<ev_signal>), process status change events (C<ev_child>), and event
		92	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		94	file watchers (C<ev_stat>) and even limited support for fork events
		95	(C<ev_fork>).
		96
		97	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	99	for example).
33		100
34	=head1 CONVENTIONS	101	=head2 CONVENTIONS
35		102
36	Libev is very configurable. In this manual the default configuration	103	Libev is very configurable. In this manual the default (and most common)
37	will be described, which supports multiple event loops. For more info	104	configuration will be described, which supports multiple event loops. For
38	about various configuration options please have a look at the file	105	more info about various configuration options please have a look at
39	F<README.embed> in the libev distribution. If libev was configured without	106	B<EMBED> section in this manual. If libev was configured without support
40	support for multiple event loops, then all functions taking an initial	107	for multiple event loops, then all functions taking an initial argument of
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
42	will not have this argument.	109	this argument.
43		110
44	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
45		112
46	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	115	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	116	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	117	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	118	it, you should treat it as some floatingpoint value. Unlike the name
52		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
53		121
54	=head1 GLOBAL FUNCTIONS	122	=head1 GLOBAL FUNCTIONS
55		123
56	These functions can be called anytime, even before initialising the	124	These functions can be called anytime, even before initialising the
57	library in any way.	125	library in any way.
…		…
62		130
63	Returns the current time as libev would use it. Please note that the	131	Returns the current time as libev would use it. Please note that the
64	C<ev_now> function is usually faster and also often returns the timestamp	132	C<ev_now> function is usually faster and also often returns the timestamp
65	you actually want to know.	133	you actually want to know.
66		134
		135	=item ev_sleep (ev_tstamp interval)
		136
		137	Sleep for the given interval: The current thread will be blocked until
		138	either it is interrupted or the given time interval has passed. Basically
		139	this is a subsecond-resolution C<sleep ()>.
		140
67	=item int ev_version_major ()	141	=item int ev_version_major ()
68		142
69	=item int ev_version_minor ()	143	=item int ev_version_minor ()
70		144
71	You can find out the major and minor version numbers of the library	145	You can find out the major and minor ABI version numbers of the library
72	you linked against by calling the functions C<ev_version_major> and	146	you linked against by calling the functions C<ev_version_major> and
73	C<ev_version_minor>. If you want, you can compare against the global	147	C<ev_version_minor>. If you want, you can compare against the global
74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	148	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
75	version of the library your program was compiled against.	149	version of the library your program was compiled against.
76		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
77	Usually, it's a good idea to terminate if the major versions mismatch,	154	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	156	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	157	not a problem.
81		158
82	Example: make sure we haven't accidentally been linked against the wrong	159	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	160	version.
84		161
85	assert (("libev version mismatch",	162	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	163	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	164	&& ev_version_minor () >= EV_VERSION_MINOR));
88		165
…		…
118		195
119	See the description of C<ev_embed> watchers for more info.	196	See the description of C<ev_embed> watchers for more info.
120		197
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		199
123	Sets the allocation function to use (the prototype is similar to the	200	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	201	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	202	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	203	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	204	potentially destructive action. The default is your system realloc
		205	function.
128		206
129	You could override this function in high-availability programs to, say,	207	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	208	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	209	or even to sleep a while and retry until some memory is available.
132		210
133	Example: replace the libev allocator with one that waits a bit and then	211	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	212	retries).
135		213
136	static void *	214	static void *
137	persistent_realloc (void *ptr, long size)	215	persistent_realloc (void *ptr, size_t size)
138	{	216	{
139	for (;;)	217	for (;;)
140	{	218	{
141	void *newptr = realloc (ptr, size);	219	void *newptr = realloc (ptr, size);
142		220
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	236	callback is set, then libev will expect it to remedy the sitution, no
159	matter what, when it returns. That is, libev will generally retry the	237	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	238	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	239	(such as abort).
162		240
163	Example: do the same thing as libev does internally:	241	Example: This is basically the same thing that libev does internally, too.
164		242
165	static void	243	static void
166	fatal_error (const char *msg)	244	fatal_error (const char *msg)
167	{	245	{
168	perror (msg);	246	perror (msg);
…		…
197	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
198		276
199	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
200	function.	278	function.
201		279
		280	The default loop is the only loop that can handle C<ev_signal> and
		281	C<ev_child> watchers, and to do this, it always registers a handler
		282	for C<SIGCHLD>. If this is a problem for your app you can either
		283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		285	C<ev_default_init>.
		286
202	The flags argument can be used to specify special behaviour or specific	287	The flags argument can be used to specify special behaviour or specific
203	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
204		289
205	The following flags are supported:	290	The following flags are supported:
206		291
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	304	override the flags completely if it is found in the environment. This is
220	useful to try out specific backends to test their performance, or to work	305	useful to try out specific backends to test their performance, or to work
221	around bugs.	306	around bugs.
222		307
		308	=item C<EVFLAG_FORKCHECK>
		309
		310	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		311	a fork, you can also make libev check for a fork in each iteration by
		312	enabling this flag.
		313
		314	This works by calling C<getpid ()> on every iteration of the loop,
		315	and thus this might slow down your event loop if you do a lot of loop
		316	iterations and little real work, but is usually not noticeable (on my
		317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		318	without a syscall and thus I<very> fast, but my GNU/Linux system also has
		319	C<pthread_atfork> which is even faster).
		320
		321	The big advantage of this flag is that you can forget about fork (and
		322	forget about forgetting to tell libev about forking) when you use this
		323	flag.
		324
		325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		326	environment variable.
		327
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		329
225	This is your standard select(2) backend. Not I<completely> standard, as	330	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	331	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	332	but if that fails, expect a fairly low limit on the number of fds when
228	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	333	using this backend. It doesn't scale too well (O(highest_fd)), but its
229	the fastest backend for a low number of fds.	334	usually the fastest backend for a low number of (low-numbered :) fds.
		335
		336	To get good performance out of this backend you need a high amount of
		337	parallelity (most of the file descriptors should be busy). If you are
		338	writing a server, you should C<accept ()> in a loop to accept as many
		339	connections as possible during one iteration. You might also want to have
		340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		341	readyness notifications you get per iteration.
230		342
231	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
232		344
233	And this is your standard poll(2) backend. It's more complicated than	345	And this is your standard poll(2) backend. It's more complicated
234	select, but handles sparse fds better and has no artificial limit on the	346	than select, but handles sparse fds better and has no artificial
235	number of fds you can use (except it will slow down considerably with a	347	limit on the number of fds you can use (except it will slow down
236	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	348	considerably with a lot of inactive fds). It scales similarly to select,
		349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		350	performance tips.
237		351
238	=item C<EVBACKEND_EPOLL> (value 4, Linux)	352	=item C<EVBACKEND_EPOLL> (value 4, Linux)
239		353
240	For few fds, this backend is a bit little slower than poll and select,	354	For few fds, this backend is a bit little slower than poll and select,
241	but it scales phenomenally better. While poll and select usually scale like	355	but it scales phenomenally better. While poll and select usually scale
242	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	356	like O(total_fds) where n is the total number of fds (or the highest fd),
243	either O(1) or O(active_fds).	357	epoll scales either O(1) or O(active_fds). The epoll design has a number
		358	of shortcomings, such as silently dropping events in some hard-to-detect
		359	cases and rewiring a syscall per fd change, no fork support and bad
		360	support for dup.
244		361
245	While stopping and starting an I/O watcher in the same iteration will	362	While stopping, setting and starting an I/O watcher in the same iteration
246	result in some caching, there is still a syscall per such incident	363	will result in some caching, there is still a syscall per such incident
247	(because the fd could point to a different file description now), so its	364	(because the fd could point to a different file description now), so its
248	best to avoid that. Also, dup()ed file descriptors might not work very	365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
249	well if you register events for both fds.	366	very well if you register events for both fds.
250		367
251	Please note that epoll sometimes generates spurious notifications, so you	368	Please note that epoll sometimes generates spurious notifications, so you
252	need to use non-blocking I/O or other means to avoid blocking when no data	369	need to use non-blocking I/O or other means to avoid blocking when no data
253	(or space) is available.	370	(or space) is available.
254		371
		372	Best performance from this backend is achieved by not unregistering all
		373	watchers for a file descriptor until it has been closed, if possible, i.e.
		374	keep at least one watcher active per fd at all times.
		375
		376	While nominally embeddeble in other event loops, this feature is broken in
		377	all kernel versions tested so far.
		378
255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256		380
257	Kqueue deserves special mention, as at the time of this writing, it	381	Kqueue deserves special mention, as at the time of this writing, it
258	was broken on all BSDs except NetBSD (usually it doesn't work with	382	was broken on all BSDs except NetBSD (usually it doesn't work reliably
259	anything but sockets and pipes, except on Darwin, where of course its	383	with anything but sockets and pipes, except on Darwin, where of course
260	completely useless). For this reason its not being "autodetected"	384	it's completely useless). For this reason it's not being "autodetected"
261	unless you explicitly specify it explicitly in the flags (i.e. using	385	unless you explicitly specify it explicitly in the flags (i.e. using
262	C<EVBACKEND_KQUEUE>).	386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		387	system like NetBSD.
		388
		389	You still can embed kqueue into a normal poll or select backend and use it
		390	only for sockets (after having made sure that sockets work with kqueue on
		391	the target platform). See C<ev_embed> watchers for more info.
263		392
264	It scales in the same way as the epoll backend, but the interface to the	393	It scales in the same way as the epoll backend, but the interface to the
265	kernel is more efficient (which says nothing about its actual speed, of	394	kernel is more efficient (which says nothing about its actual speed, of
266	course). While starting and stopping an I/O watcher does not cause an	395	course). While stopping, setting and starting an I/O watcher does never
267	extra syscall as with epoll, it still adds up to four event changes per	396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
268	incident, so its best to avoid that.	397	two event changes per incident, support for C<fork ()> is very bad and it
		398	drops fds silently in similarly hard-to-detect cases.
		399
		400	This backend usually performs well under most conditions.
		401
		402	While nominally embeddable in other event loops, this doesn't work
		403	everywhere, so you might need to test for this. And since it is broken
		404	almost everywhere, you should only use it when you have a lot of sockets
		405	(for which it usually works), by embedding it into another event loop
		406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		407	sockets.
269		408
270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271		410
272	This is not implemented yet (and might never be).	411	This is not implemented yet (and might never be, unless you send me an
		412	implementation). According to reports, C</dev/poll> only supports sockets
		413	and is not embeddable, which would limit the usefulness of this backend
		414	immensely.
273		415
274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275		417
276	This uses the Solaris 10 port mechanism. As with everything on Solaris,	418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
277	it's really slow, but it still scales very well (O(active_fds)).	419	it's really slow, but it still scales very well (O(active_fds)).
278		420
279	Please note that solaris ports can result in a lot of spurious	421	Please note that solaris event ports can deliver a lot of spurious
280	notifications, so you need to use non-blocking I/O or other means to avoid	422	notifications, so you need to use non-blocking I/O or other means to avoid
281	blocking when no data (or space) is available.	423	blocking when no data (or space) is available.
		424
		425	While this backend scales well, it requires one system call per active
		426	file descriptor per loop iteration. For small and medium numbers of file
		427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		428	might perform better.
		429
		430	On the positive side, ignoring the spurious readyness notifications, this
		431	backend actually performed to specification in all tests and is fully
		432	embeddable, which is a rare feat among the OS-specific backends.
282		433
283	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
284		435
285	Try all backends (even potentially broken ones that wouldn't be tried	436	Try all backends (even potentially broken ones that wouldn't be tried
286	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
288		439
		440	It is definitely not recommended to use this flag.
		441
289	=back	442	=back
290		443
291	If one or more of these are ored into the flags value, then only these	444	If one or more of these are ored into the flags value, then only these
292	backends will be tried (in the reverse order as given here). If none are	445	backends will be tried (in the reverse order as listed here). If none are
293	specified, most compiled-in backend will be tried, usually in reverse	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
294	order of their flag values :)
295		447
296	The most typical usage is like this:	448	The most typical usage is like this:
297		449
298	if (!ev_default_loop (0))	450	if (!ev_default_loop (0))
299	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	466	Similar to C<ev_default_loop>, but always creates a new event loop that is
315	always distinct from the default loop. Unlike the default loop, it cannot	467	always distinct from the default loop. Unlike the default loop, it cannot
316	handle signal and child watchers, and attempts to do so will be greeted by	468	handle signal and child watchers, and attempts to do so will be greeted by
317	undefined behaviour (or a failed assertion if assertions are enabled).	469	undefined behaviour (or a failed assertion if assertions are enabled).
318		470
319	Example: try to create a event loop that uses epoll and nothing else.	471	Example: Try to create a event loop that uses epoll and nothing else.
320		472
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	474	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	475	fatal ("no epoll found here, maybe it hides under your chair");
324		476
…		…
327	Destroys the default loop again (frees all memory and kernel state	479	Destroys the default loop again (frees all memory and kernel state
328	etc.). None of the active event watchers will be stopped in the normal	480	etc.). None of the active event watchers will be stopped in the normal
329	sense, so e.g. C<ev_is_active> might still return true. It is your	481	sense, so e.g. C<ev_is_active> might still return true. It is your
330	responsibility to either stop all watchers cleanly yoursef I<before>	482	responsibility to either stop all watchers cleanly yoursef I<before>
331	calling this function, or cope with the fact afterwards (which is usually	483	calling this function, or cope with the fact afterwards (which is usually
332	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	484	the easiest thing, you can just ignore the watchers and/or C<free ()> them
333	for example).	485	for example).
		486
		487	Note that certain global state, such as signal state, will not be freed by
		488	this function, and related watchers (such as signal and child watchers)
		489	would need to be stopped manually.
		490
		491	In general it is not advisable to call this function except in the
		492	rare occasion where you really need to free e.g. the signal handling
		493	pipe fds. If you need dynamically allocated loops it is better to use
		494	C<ev_loop_new> and C<ev_loop_destroy>).
334		495
335	=item ev_loop_destroy (loop)	496	=item ev_loop_destroy (loop)
336		497
337	Like C<ev_default_destroy>, but destroys an event loop created by an	498	Like C<ev_default_destroy>, but destroys an event loop created by an
338	earlier call to C<ev_loop_new>.	499	earlier call to C<ev_loop_new>.
339		500
340	=item ev_default_fork ()	501	=item ev_default_fork ()
341		502
		503	This function sets a flag that causes subsequent C<ev_loop> iterations
342	This function reinitialises the kernel state for backends that have	504	to reinitialise the kernel state for backends that have one. Despite the
343	one. Despite the name, you can call it anytime, but it makes most sense	505	name, you can call it anytime, but it makes most sense after forking, in
344	after forking, in either the parent or child process (or both, but that	506	the child process (or both child and parent, but that again makes little
345	again makes little sense).	507	sense). You I<must> call it in the child before using any of the libev
		508	functions, and it will only take effect at the next C<ev_loop> iteration.
346		509
347	You I<must> call this function in the child process after forking if and	510	On the other hand, you only need to call this function in the child
348	only if you want to use the event library in both processes. If you just	511	process if and only if you want to use the event library in the child. If
349	fork+exec, you don't have to call it.	512	you just fork+exec, you don't have to call it at all.
350		513
351	The function itself is quite fast and it's usually not a problem to call	514	The function itself is quite fast and it's usually not a problem to call
352	it just in case after a fork. To make this easy, the function will fit in	515	it just in case after a fork. To make this easy, the function will fit in
353	quite nicely into a call to C<pthread_atfork>:	516	quite nicely into a call to C<pthread_atfork>:
354		517
355	pthread_atfork (0, 0, ev_default_fork);	518	pthread_atfork (0, 0, ev_default_fork);
356		519
357	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
358	without calling this function, so if you force one of those backends you
359	do not need to care.
360
361	=item ev_loop_fork (loop)	520	=item ev_loop_fork (loop)
362		521
363	Like C<ev_default_fork>, but acts on an event loop created by	522	Like C<ev_default_fork>, but acts on an event loop created by
364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	523	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
365	after fork, and how you do this is entirely your own problem.	524	after fork, and how you do this is entirely your own problem.
		525
		526	=item int ev_is_default_loop (loop)
		527
		528	Returns true when the given loop actually is the default loop, false otherwise.
		529
		530	=item unsigned int ev_loop_count (loop)
		531
		532	Returns the count of loop iterations for the loop, which is identical to
		533	the number of times libev did poll for new events. It starts at C<0> and
		534	happily wraps around with enough iterations.
		535
		536	This value can sometimes be useful as a generation counter of sorts (it
		537	"ticks" the number of loop iterations), as it roughly corresponds with
		538	C<ev_prepare> and C<ev_check> calls.
366		539
367	=item unsigned int ev_backend (loop)	540	=item unsigned int ev_backend (loop)
368		541
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	542	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	543	use.
…		…
373		546
374	Returns the current "event loop time", which is the time the event loop	547	Returns the current "event loop time", which is the time the event loop
375	received events and started processing them. This timestamp does not	548	received events and started processing them. This timestamp does not
376	change as long as callbacks are being processed, and this is also the base	549	change as long as callbacks are being processed, and this is also the base
377	time used for relative timers. You can treat it as the timestamp of the	550	time used for relative timers. You can treat it as the timestamp of the
378	event occuring (or more correctly, libev finding out about it).	551	event occurring (or more correctly, libev finding out about it).
379		552
380	=item ev_loop (loop, int flags)	553	=item ev_loop (loop, int flags)
381		554
382	Finally, this is it, the event handler. This function usually is called	555	Finally, this is it, the event handler. This function usually is called
383	after you initialised all your watchers and you want to start handling	556	after you initialised all your watchers and you want to start handling
…		…
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	577	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	578	usually a better approach for this kind of thing.
406		579
407	Here are the gory details of what C<ev_loop> does:	580	Here are the gory details of what C<ev_loop> does:
408		581
409	* If there are no active watchers (reference count is zero), return.	582	- Before the first iteration, call any pending watchers.
410	- Queue prepare watchers and then call all outstanding watchers.	583	* If EVFLAG_FORKCHECK was used, check for a fork.
		584	- If a fork was detected, queue and call all fork watchers.
		585	- Queue and call all prepare watchers.
411	- If we have been forked, recreate the kernel state.	586	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	587	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	588	- Update the "event loop time".
414	- Calculate for how long to block.	589	- Calculate for how long to sleep or block, if at all
		590	(active idle watchers, EVLOOP_NONBLOCK or not having
		591	any active watchers at all will result in not sleeping).
		592	- Sleep if the I/O and timer collect interval say so.
415	- Block the process, waiting for any events.	593	- Block the process, waiting for any events.
416	- Queue all outstanding I/O (fd) events.	594	- Queue all outstanding I/O (fd) events.
417	- Update the "event loop time" and do time jump handling.	595	- Update the "event loop time" and do time jump handling.
418	- Queue all outstanding timers.	596	- Queue all outstanding timers.
419	- Queue all outstanding periodics.	597	- Queue all outstanding periodics.
420	- If no events are pending now, queue all idle watchers.	598	- If no events are pending now, queue all idle watchers.
421	- Queue all check watchers.	599	- Queue all check watchers.
422	- Call all queued watchers in reverse order (i.e. check watchers first).	600	- Call all queued watchers in reverse order (i.e. check watchers first).
423	Signals and child watchers are implemented as I/O watchers, and will	601	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	602	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	604	were used, or there are no active watchers, return, otherwise
		605	continue with step *.
427		606
428	Example: queue some jobs and then loop until no events are outsanding	607	Example: Queue some jobs and then loop until no events are outstanding
429	anymore.	608	anymore.
430		609
431	... queue jobs here, make sure they register event watchers as long	610	... queue jobs here, make sure they register event watchers as long
432	... as they still have work to do (even an idle watcher will do..)	611	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	612	ev_loop (my_loop, 0);
…		…
437		616
438	Can be used to make a call to C<ev_loop> return early (but only after it	617	Can be used to make a call to C<ev_loop> return early (but only after it
439	has processed all outstanding events). The C<how> argument must be either	618	has processed all outstanding events). The C<how> argument must be either
440	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	619	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
441	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	620	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		621
		622	This "unloop state" will be cleared when entering C<ev_loop> again.
442		623
443	=item ev_ref (loop)	624	=item ev_ref (loop)
444		625
445	=item ev_unref (loop)	626	=item ev_unref (loop)
446		627
…		…
451	returning, ev_unref() after starting, and ev_ref() before stopping it. For	632	returning, ev_unref() after starting, and ev_ref() before stopping it. For
452	example, libev itself uses this for its internal signal pipe: It is not	633	example, libev itself uses this for its internal signal pipe: It is not
453	visible to the libev user and should not keep C<ev_loop> from exiting if	634	visible to the libev user and should not keep C<ev_loop> from exiting if
454	no event watchers registered by it are active. It is also an excellent	635	no event watchers registered by it are active. It is also an excellent
455	way to do this for generic recurring timers or from within third-party	636	way to do this for generic recurring timers or from within third-party
456	libraries. Just remember to I<unref after start> and I<ref before stop>.	637	libraries. Just remember to I<unref after start> and I<ref before stop>
		638	(but only if the watcher wasn't active before, or was active before,
		639	respectively).
457		640
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	642	running when nothing else is active.
460		643
461	struct dv_signal exitsig;	644	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	645	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	646	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	647	evf_unref (loop);
465		648
466	Example: for some weird reason, unregister the above signal handler again.	649	Example: For some weird reason, unregister the above signal handler again.
467		650
468	ev_ref (myloop);	651	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	652	ev_signal_stop (loop, &exitsig);
		653
		654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		655
		656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		657
		658	These advanced functions influence the time that libev will spend waiting
		659	for events. Both are by default C<0>, meaning that libev will try to
		660	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		661
		662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		663	allows libev to delay invocation of I/O and timer/periodic callbacks to
		664	increase efficiency of loop iterations.
		665
		666	The background is that sometimes your program runs just fast enough to
		667	handle one (or very few) event(s) per loop iteration. While this makes
		668	the program responsive, it also wastes a lot of CPU time to poll for new
		669	events, especially with backends like C<select ()> which have a high
		670	overhead for the actual polling but can deliver many events at once.
		671
		672	By setting a higher I<io collect interval> you allow libev to spend more
		673	time collecting I/O events, so you can handle more events per iteration,
		674	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		675	C<ev_timer>) will be not affected. Setting this to a non-null value will
		676	introduce an additional C<ev_sleep ()> call into most loop iterations.
		677
		678	Likewise, by setting a higher I<timeout collect interval> you allow libev
		679	to spend more time collecting timeouts, at the expense of increased
		680	latency (the watcher callback will be called later). C<ev_io> watchers
		681	will not be affected. Setting this to a non-null value will not introduce
		682	any overhead in libev.
		683
		684	Many (busy) programs can usually benefit by setting the io collect
		685	interval to a value near C<0.1> or so, which is often enough for
		686	interactive servers (of course not for games), likewise for timeouts. It
		687	usually doesn't make much sense to set it to a lower value than C<0.01>,
		688	as this approsaches the timing granularity of most systems.
470		689
471	=back	690	=back
472		691
473		692
474	=head1 ANATOMY OF A WATCHER	693	=head1 ANATOMY OF A WATCHER
…		…
544	The signal specified in the C<ev_signal> watcher has been received by a thread.	763	The signal specified in the C<ev_signal> watcher has been received by a thread.
545		764
546	=item C<EV_CHILD>	765	=item C<EV_CHILD>
547		766
548	The pid specified in the C<ev_child> watcher has received a status change.	767	The pid specified in the C<ev_child> watcher has received a status change.
		768
		769	=item C<EV_STAT>
		770
		771	The path specified in the C<ev_stat> watcher changed its attributes somehow.
549		772
550	=item C<EV_IDLE>	773	=item C<EV_IDLE>
551		774
552	The C<ev_idle> watcher has determined that you have nothing better to do.	775	The C<ev_idle> watcher has determined that you have nothing better to do.
553		776
…		…
561	received events. Callbacks of both watcher types can start and stop as	784	received events. Callbacks of both watcher types can start and stop as
562	many watchers as they want, and all of them will be taken into account	785	many watchers as they want, and all of them will be taken into account
563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	786	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
564	C<ev_loop> from blocking).	787	C<ev_loop> from blocking).
565		788
		789	=item C<EV_EMBED>
		790
		791	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		792
		793	=item C<EV_FORK>
		794
		795	The event loop has been resumed in the child process after fork (see
		796	C<ev_fork>).
		797
		798	=item C<EV_ASYNC>
		799
		800	The given async watcher has been asynchronously notified (see C<ev_async>).
		801
566	=item C<EV_ERROR>	802	=item C<EV_ERROR>
567		803
568	An unspecified error has occured, the watcher has been stopped. This might	804	An unspecified error has occured, the watcher has been stopped. This might
569	happen because the watcher could not be properly started because libev	805	happen because the watcher could not be properly started because libev
570	ran out of memory, a file descriptor was found to be closed or any other	806	ran out of memory, a file descriptor was found to be closed or any other
…		…
641	=item bool ev_is_pending (ev_TYPE *watcher)	877	=item bool ev_is_pending (ev_TYPE *watcher)
642		878
643	Returns a true value iff the watcher is pending, (i.e. it has outstanding	879	Returns a true value iff the watcher is pending, (i.e. it has outstanding
644	events but its callback has not yet been invoked). As long as a watcher	880	events but its callback has not yet been invoked). As long as a watcher
645	is pending (but not active) you must not call an init function on it (but	881	is pending (but not active) you must not call an init function on it (but
646	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	882	C<ev_TYPE_set> is safe), you must not change its priority, and you must
647	libev (e.g. you cnanot C<free ()> it).	883	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		884	it).
648		885
649	=item callback = ev_cb (ev_TYPE *watcher)	886	=item callback ev_cb (ev_TYPE *watcher)
650		887
651	Returns the callback currently set on the watcher.	888	Returns the callback currently set on the watcher.
652		889
653	=item ev_cb_set (ev_TYPE *watcher, callback)	890	=item ev_cb_set (ev_TYPE *watcher, callback)
654		891
655	Change the callback. You can change the callback at virtually any time	892	Change the callback. You can change the callback at virtually any time
656	(modulo threads).	893	(modulo threads).
		894
		895	=item ev_set_priority (ev_TYPE *watcher, priority)
		896
		897	=item int ev_priority (ev_TYPE *watcher)
		898
		899	Set and query the priority of the watcher. The priority is a small
		900	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		901	(default: C<-2>). Pending watchers with higher priority will be invoked
		902	before watchers with lower priority, but priority will not keep watchers
		903	from being executed (except for C<ev_idle> watchers).
		904
		905	This means that priorities are I<only> used for ordering callback
		906	invocation after new events have been received. This is useful, for
		907	example, to reduce latency after idling, or more often, to bind two
		908	watchers on the same event and make sure one is called first.
		909
		910	If you need to suppress invocation when higher priority events are pending
		911	you need to look at C<ev_idle> watchers, which provide this functionality.
		912
		913	You I<must not> change the priority of a watcher as long as it is active or
		914	pending.
		915
		916	The default priority used by watchers when no priority has been set is
		917	always C<0>, which is supposed to not be too high and not be too low :).
		918
		919	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		920	fine, as long as you do not mind that the priority value you query might
		921	or might not have been adjusted to be within valid range.
		922
		923	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		924
		925	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		926	C<loop> nor C<revents> need to be valid as long as the watcher callback
		927	can deal with that fact.
		928
		929	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		930
		931	If the watcher is pending, this function returns clears its pending status
		932	and returns its C<revents> bitset (as if its callback was invoked). If the
		933	watcher isn't pending it does nothing and returns C<0>.
657		934
658	=back	935	=back
659		936
660		937
661	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	938	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
682	{	959	{
683	struct my_io *w = (struct my_io *)w_;	960	struct my_io *w = (struct my_io *)w_;
684	...	961	...
685	}	962	}
686		963
687	More interesting and less C-conformant ways of catsing your callback type	964	More interesting and less C-conformant ways of casting your callback type
688	have been omitted....	965	instead have been omitted.
		966
		967	Another common scenario is having some data structure with multiple
		968	watchers:
		969
		970	struct my_biggy
		971	{
		972	int some_data;
		973	ev_timer t1;
		974	ev_timer t2;
		975	}
		976
		977	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		978	you need to use C<offsetof>:
		979
		980	#include <stddef.h>
		981
		982	static void
		983	t1_cb (EV_P_ struct ev_timer *w, int revents)
		984	{
		985	struct my_biggy big = (struct my_biggy *
		986	(((char *)w) - offsetof (struct my_biggy, t1));
		987	}
		988
		989	static void
		990	t2_cb (EV_P_ struct ev_timer *w, int revents)
		991	{
		992	struct my_biggy big = (struct my_biggy *
		993	(((char *)w) - offsetof (struct my_biggy, t2));
		994	}
689		995
690		996
691	=head1 WATCHER TYPES	997	=head1 WATCHER TYPES
692		998
693	This section describes each watcher in detail, but will not repeat	999	This section describes each watcher in detail, but will not repeat
694	information given in the last section.	1000	information given in the last section. Any initialisation/set macros,
		1001	functions and members specific to the watcher type are explained.
		1002
		1003	Members are additionally marked with either I<[read-only]>, meaning that,
		1004	while the watcher is active, you can look at the member and expect some
		1005	sensible content, but you must not modify it (you can modify it while the
		1006	watcher is stopped to your hearts content), or I<[read-write]>, which
		1007	means you can expect it to have some sensible content while the watcher
		1008	is active, but you can also modify it. Modifying it may not do something
		1009	sensible or take immediate effect (or do anything at all), but libev will
		1010	not crash or malfunction in any way.
695		1011
696		1012
697	=head2 C<ev_io> - is this file descriptor readable or writable?	1013	=head2 C<ev_io> - is this file descriptor readable or writable?
698		1014
699	I/O watchers check whether a file descriptor is readable or writable	1015	I/O watchers check whether a file descriptor is readable or writable
…		…
706		1022
707	In general you can register as many read and/or write event watchers per	1023	In general you can register as many read and/or write event watchers per
708	fd as you want (as long as you don't confuse yourself). Setting all file	1024	fd as you want (as long as you don't confuse yourself). Setting all file
709	descriptors to non-blocking mode is also usually a good idea (but not	1025	descriptors to non-blocking mode is also usually a good idea (but not
710	required if you know what you are doing).	1026	required if you know what you are doing).
711
712	You have to be careful with dup'ed file descriptors, though. Some backends
713	(the linux epoll backend is a notable example) cannot handle dup'ed file
714	descriptors correctly if you register interest in two or more fds pointing
715	to the same underlying file/socket/etc. description (that is, they share
716	the same underlying "file open").
717		1027
718	If you must do this, then force the use of a known-to-be-good backend	1028	If you must do this, then force the use of a known-to-be-good backend
719	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
720	C<EVBACKEND_POLL>).	1030	C<EVBACKEND_POLL>).
721		1031
…		…
728	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1038	it is best to always use non-blocking I/O: An extra C<read>(2) returning
729	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1039	C<EAGAIN> is far preferable to a program hanging until some data arrives.
730		1040
731	If you cannot run the fd in non-blocking mode (for example you should not	1041	If you cannot run the fd in non-blocking mode (for example you should not
732	play around with an Xlib connection), then you have to seperately re-test	1042	play around with an Xlib connection), then you have to seperately re-test
733	wether a file descriptor is really ready with a known-to-be good interface	1043	whether a file descriptor is really ready with a known-to-be good interface
734	such as poll (fortunately in our Xlib example, Xlib already does this on	1044	such as poll (fortunately in our Xlib example, Xlib already does this on
735	its own, so its quite safe to use).	1045	its own, so its quite safe to use).
		1046
		1047	=head3 The special problem of disappearing file descriptors
		1048
		1049	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1050	descriptor (either by calling C<close> explicitly or by any other means,
		1051	such as C<dup>). The reason is that you register interest in some file
		1052	descriptor, but when it goes away, the operating system will silently drop
		1053	this interest. If another file descriptor with the same number then is
		1054	registered with libev, there is no efficient way to see that this is, in
		1055	fact, a different file descriptor.
		1056
		1057	To avoid having to explicitly tell libev about such cases, libev follows
		1058	the following policy: Each time C<ev_io_set> is being called, libev
		1059	will assume that this is potentially a new file descriptor, otherwise
		1060	it is assumed that the file descriptor stays the same. That means that
		1061	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1062	descriptor even if the file descriptor number itself did not change.
		1063
		1064	This is how one would do it normally anyway, the important point is that
		1065	the libev application should not optimise around libev but should leave
		1066	optimisations to libev.
		1067
		1068	=head3 The special problem of dup'ed file descriptors
		1069
		1070	Some backends (e.g. epoll), cannot register events for file descriptors,
		1071	but only events for the underlying file descriptions. That means when you
		1072	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1073	events for them, only one file descriptor might actually receive events.
		1074
		1075	There is no workaround possible except not registering events
		1076	for potentially C<dup ()>'ed file descriptors, or to resort to
		1077	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1078
		1079	=head3 The special problem of fork
		1080
		1081	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1082	useless behaviour. Libev fully supports fork, but needs to be told about
		1083	it in the child.
		1084
		1085	To support fork in your programs, you either have to call
		1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1088	C<EVBACKEND_POLL>.
		1089
		1090
		1091	=head3 Watcher-Specific Functions
736		1092
737	=over 4	1093	=over 4
738		1094
739	=item ev_io_init (ev_io *, callback, int fd, int events)	1095	=item ev_io_init (ev_io *, callback, int fd, int events)
740		1096
…		…
742		1098
743	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1099	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
744	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1100	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
745	C<EV_READ | EV_WRITE> to receive the given events.	1101	C<EV_READ | EV_WRITE> to receive the given events.
746		1102
		1103	=item int fd [read-only]
		1104
		1105	The file descriptor being watched.
		1106
		1107	=item int events [read-only]
		1108
		1109	The events being watched.
		1110
747	=back	1111	=back
748		1112
		1113	=head3 Examples
		1114
749	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1115	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
750	readable, but only once. Since it is likely line-buffered, you could	1116	readable, but only once. Since it is likely line-buffered, you could
751	attempt to read a whole line in the callback:	1117	attempt to read a whole line in the callback.
752		1118
753	static void	1119	static void
754	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1120	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
755	{	1121	{
756	ev_io_stop (loop, w);	1122	ev_io_stop (loop, w);
…		…
786		1152
787	The callback is guarenteed to be invoked only when its timeout has passed,	1153	The callback is guarenteed to be invoked only when its timeout has passed,
788	but if multiple timers become ready during the same loop iteration then	1154	but if multiple timers become ready during the same loop iteration then
789	order of execution is undefined.	1155	order of execution is undefined.
790		1156
		1157	=head3 Watcher-Specific Functions and Data Members
		1158
791	=over 4	1159	=over 4
792		1160
793	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1161	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
794		1162
795	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1163	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
803	configure a timer to trigger every 10 seconds, then it will trigger at	1171	configure a timer to trigger every 10 seconds, then it will trigger at
804	exactly 10 second intervals. If, however, your program cannot keep up with	1172	exactly 10 second intervals. If, however, your program cannot keep up with
805	the timer (because it takes longer than those 10 seconds to do stuff) the	1173	the timer (because it takes longer than those 10 seconds to do stuff) the
806	timer will not fire more than once per event loop iteration.	1174	timer will not fire more than once per event loop iteration.
807		1175
808	=item ev_timer_again (loop)	1176	=item ev_timer_again (loop, ev_timer *)
809		1177
810	This will act as if the timer timed out and restart it again if it is	1178	This will act as if the timer timed out and restart it again if it is
811	repeating. The exact semantics are:	1179	repeating. The exact semantics are:
812		1180
		1181	If the timer is pending, its pending status is cleared.
		1182
813	If the timer is started but nonrepeating, stop it.	1183	If the timer is started but nonrepeating, stop it (as if it timed out).
814		1184
815	If the timer is repeating, either start it if necessary (with the repeat	1185	If the timer is repeating, either start it if necessary (with the
816	value), or reset the running timer to the repeat value.	1186	C<repeat> value), or reset the running timer to the C<repeat> value.
817		1187
818	This sounds a bit complicated, but here is a useful and typical	1188	This sounds a bit complicated, but here is a useful and typical
819	example: Imagine you have a tcp connection and you want a so-called idle	1189	example: Imagine you have a tcp connection and you want a so-called idle
820	timeout, that is, you want to be called when there have been, say, 60	1190	timeout, that is, you want to be called when there have been, say, 60
821	seconds of inactivity on the socket. The easiest way to do this is to	1191	seconds of inactivity on the socket. The easiest way to do this is to
822	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1192	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
823	time you successfully read or write some data. If you go into an idle	1193	C<ev_timer_again> each time you successfully read or write some data. If
824	state where you do not expect data to travel on the socket, you can stop	1194	you go into an idle state where you do not expect data to travel on the
825	the timer, and again will automatically restart it if need be.	1195	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1196	automatically restart it if need be.
		1197
		1198	That means you can ignore the C<after> value and C<ev_timer_start>
		1199	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1200
		1201	ev_timer_init (timer, callback, 0., 5.);
		1202	ev_timer_again (loop, timer);
		1203	...
		1204	timer->again = 17.;
		1205	ev_timer_again (loop, timer);
		1206	...
		1207	timer->again = 10.;
		1208	ev_timer_again (loop, timer);
		1209
		1210	This is more slightly efficient then stopping/starting the timer each time
		1211	you want to modify its timeout value.
		1212
		1213	=item ev_tstamp repeat [read-write]
		1214
		1215	The current C<repeat> value. Will be used each time the watcher times out
		1216	or C<ev_timer_again> is called and determines the next timeout (if any),
		1217	which is also when any modifications are taken into account.
826		1218
827	=back	1219	=back
828		1220
		1221	=head3 Examples
		1222
829	Example: create a timer that fires after 60 seconds.	1223	Example: Create a timer that fires after 60 seconds.
830		1224
831	static void	1225	static void
832	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1226	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
833	{	1227	{
834	.. one minute over, w is actually stopped right here	1228	.. one minute over, w is actually stopped right here
…		…
836		1230
837	struct ev_timer mytimer;	1231	struct ev_timer mytimer;
838	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1232	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
839	ev_timer_start (loop, &mytimer);	1233	ev_timer_start (loop, &mytimer);
840		1234
841	Example: create a timeout timer that times out after 10 seconds of	1235	Example: Create a timeout timer that times out after 10 seconds of
842	inactivity.	1236	inactivity.
843		1237
844	static void	1238	static void
845	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1239	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
846	{	1240	{
…		…
866	but on wallclock time (absolute time). You can tell a periodic watcher	1260	but on wallclock time (absolute time). You can tell a periodic watcher
867	to trigger "at" some specific point in time. For example, if you tell a	1261	to trigger "at" some specific point in time. For example, if you tell a
868	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1262	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
869	+ 10.>) and then reset your system clock to the last year, then it will	1263	+ 10.>) and then reset your system clock to the last year, then it will
870	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1264	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
871	roughly 10 seconds later and of course not if you reset your system time	1265	roughly 10 seconds later).
872	again).
873		1266
874	They can also be used to implement vastly more complex timers, such as	1267	They can also be used to implement vastly more complex timers, such as
875	triggering an event on eahc midnight, local time.	1268	triggering an event on each midnight, local time or other, complicated,
		1269	rules.
876		1270
877	As with timers, the callback is guarenteed to be invoked only when the	1271	As with timers, the callback is guarenteed to be invoked only when the
878	time (C<at>) has been passed, but if multiple periodic timers become ready	1272	time (C<at>) has been passed, but if multiple periodic timers become ready
879	during the same loop iteration then order of execution is undefined.	1273	during the same loop iteration then order of execution is undefined.
880		1274
		1275	=head3 Watcher-Specific Functions and Data Members
		1276
881	=over 4	1277	=over 4
882		1278
883	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1279	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
884		1280
885	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1281	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
887	Lots of arguments, lets sort it out... There are basically three modes of	1283	Lots of arguments, lets sort it out... There are basically three modes of
888	operation, and we will explain them from simplest to complex:	1284	operation, and we will explain them from simplest to complex:
889		1285
890	=over 4	1286	=over 4
891		1287
892	=item * absolute timer (interval = reschedule_cb = 0)	1288	=item * absolute timer (at = time, interval = reschedule_cb = 0)
893		1289
894	In this configuration the watcher triggers an event at the wallclock time	1290	In this configuration the watcher triggers an event at the wallclock time
895	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1291	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
896	that is, if it is to be run at January 1st 2011 then it will run when the	1292	that is, if it is to be run at January 1st 2011 then it will run when the
897	system time reaches or surpasses this time.	1293	system time reaches or surpasses this time.
898		1294
899	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
900		1296
901	In this mode the watcher will always be scheduled to time out at the next	1297	In this mode the watcher will always be scheduled to time out at the next
902	C<at + N * interval> time (for some integer N) and then repeat, regardless	1298	C<at + N * interval> time (for some integer N, which can also be negative)
903	of any time jumps.	1299	and then repeat, regardless of any time jumps.
904		1300
905	This can be used to create timers that do not drift with respect to system	1301	This can be used to create timers that do not drift with respect to system
906	time:	1302	time:
907		1303
908	ev_periodic_set (&periodic, 0., 3600., 0);	1304	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
914		1310
915	Another way to think about it (for the mathematically inclined) is that	1311	Another way to think about it (for the mathematically inclined) is that
916	C<ev_periodic> will try to run the callback in this mode at the next possible	1312	C<ev_periodic> will try to run the callback in this mode at the next possible
917	time where C<time = at (mod interval)>, regardless of any time jumps.	1313	time where C<time = at (mod interval)>, regardless of any time jumps.
918		1314
		1315	For numerical stability it is preferable that the C<at> value is near
		1316	C<ev_now ()> (the current time), but there is no range requirement for
		1317	this value.
		1318
919	=item * manual reschedule mode (reschedule_cb = callback)	1319	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
920		1320
921	In this mode the values for C<interval> and C<at> are both being	1321	In this mode the values for C<interval> and C<at> are both being
922	ignored. Instead, each time the periodic watcher gets scheduled, the	1322	ignored. Instead, each time the periodic watcher gets scheduled, the
923	reschedule callback will be called with the watcher as first, and the	1323	reschedule callback will be called with the watcher as first, and the
924	current time as second argument.	1324	current time as second argument.
925		1325
926	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1326	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
927	ever, or make any event loop modifications>. If you need to stop it,	1327	ever, or make any event loop modifications>. If you need to stop it,
928	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1328	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
929	starting a prepare watcher).	1329	starting an C<ev_prepare> watcher, which is legal).
930		1330
931	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1331	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
932	ev_tstamp now)>, e.g.:	1332	ev_tstamp now)>, e.g.:
933		1333
934	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1334	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
957	Simply stops and restarts the periodic watcher again. This is only useful	1357	Simply stops and restarts the periodic watcher again. This is only useful
958	when you changed some parameters or the reschedule callback would return	1358	when you changed some parameters or the reschedule callback would return
959	a different time than the last time it was called (e.g. in a crond like	1359	a different time than the last time it was called (e.g. in a crond like
960	program when the crontabs have changed).	1360	program when the crontabs have changed).
961		1361
		1362	=item ev_tstamp offset [read-write]
		1363
		1364	When repeating, this contains the offset value, otherwise this is the
		1365	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1366
		1367	Can be modified any time, but changes only take effect when the periodic
		1368	timer fires or C<ev_periodic_again> is being called.
		1369
		1370	=item ev_tstamp interval [read-write]
		1371
		1372	The current interval value. Can be modified any time, but changes only
		1373	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1374	called.
		1375
		1376	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1377
		1378	The current reschedule callback, or C<0>, if this functionality is
		1379	switched off. Can be changed any time, but changes only take effect when
		1380	the periodic timer fires or C<ev_periodic_again> is being called.
		1381
		1382	=item ev_tstamp at [read-only]
		1383
		1384	When active, contains the absolute time that the watcher is supposed to
		1385	trigger next.
		1386
962	=back	1387	=back
963		1388
		1389	=head3 Examples
		1390
964	Example: call a callback every hour, or, more precisely, whenever the	1391	Example: Call a callback every hour, or, more precisely, whenever the
965	system clock is divisible by 3600. The callback invocation times have	1392	system clock is divisible by 3600. The callback invocation times have
966	potentially a lot of jittering, but good long-term stability.	1393	potentially a lot of jittering, but good long-term stability.
967		1394
968	static void	1395	static void
969	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1396	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
973		1400
974	struct ev_periodic hourly_tick;	1401	struct ev_periodic hourly_tick;
975	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1402	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
976	ev_periodic_start (loop, &hourly_tick);	1403	ev_periodic_start (loop, &hourly_tick);
977		1404
978	Example: the same as above, but use a reschedule callback to do it:	1405	Example: The same as above, but use a reschedule callback to do it:
979		1406
980	#include <math.h>	1407	#include <math.h>
981		1408
982	static ev_tstamp	1409	static ev_tstamp
983	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1410	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
985	return fmod (now, 3600.) + 3600.;	1412	return fmod (now, 3600.) + 3600.;
986	}	1413	}
987		1414
988	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
989		1416
990	Example: call a callback every hour, starting now:	1417	Example: Call a callback every hour, starting now:
991		1418
992	struct ev_periodic hourly_tick;	1419	struct ev_periodic hourly_tick;
993	ev_periodic_init (&hourly_tick, clock_cb,	1420	ev_periodic_init (&hourly_tick, clock_cb,
994	fmod (ev_now (loop), 3600.), 3600., 0);	1421	fmod (ev_now (loop), 3600.), 3600., 0);
995	ev_periodic_start (loop, &hourly_tick);	1422	ev_periodic_start (loop, &hourly_tick);
…		…
1007	with the kernel (thus it coexists with your own signal handlers as long	1434	with the kernel (thus it coexists with your own signal handlers as long
1008	as you don't register any with libev). Similarly, when the last signal	1435	as you don't register any with libev). Similarly, when the last signal
1009	watcher for a signal is stopped libev will reset the signal handler to	1436	watcher for a signal is stopped libev will reset the signal handler to
1010	SIG_DFL (regardless of what it was set to before).	1437	SIG_DFL (regardless of what it was set to before).
1011		1438
		1439	If possible and supported, libev will install its handlers with
		1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1441	interrupted. If you have a problem with syscalls getting interrupted by
		1442	signals you can block all signals in an C<ev_check> watcher and unblock
		1443	them in an C<ev_prepare> watcher.
		1444
		1445	=head3 Watcher-Specific Functions and Data Members
		1446
1012	=over 4	1447	=over 4
1013		1448
1014	=item ev_signal_init (ev_signal *, callback, int signum)	1449	=item ev_signal_init (ev_signal *, callback, int signum)
1015		1450
1016	=item ev_signal_set (ev_signal *, int signum)	1451	=item ev_signal_set (ev_signal *, int signum)
1017		1452
1018	Configures the watcher to trigger on the given signal number (usually one	1453	Configures the watcher to trigger on the given signal number (usually one
1019	of the C<SIGxxx> constants).	1454	of the C<SIGxxx> constants).
1020		1455
		1456	=item int signum [read-only]
		1457
		1458	The signal the watcher watches out for.
		1459
1021	=back	1460	=back
1022		1461
		1462	=head3 Examples
		1463
		1464	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1465
		1466	static void
		1467	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1468	{
		1469	ev_unloop (loop, EVUNLOOP_ALL);
		1470	}
		1471
		1472	struct ev_signal signal_watcher;
		1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1474	ev_signal_start (loop, &sigint_cb);
		1475
1023		1476
1024	=head2 C<ev_child> - watch out for process status changes	1477	=head2 C<ev_child> - watch out for process status changes
1025		1478
1026	Child watchers trigger when your process receives a SIGCHLD in response to	1479	Child watchers trigger when your process receives a SIGCHLD in response to
1027	some child status changes (most typically when a child of yours dies).	1480	some child status changes (most typically when a child of yours dies). It
		1481	is permissible to install a child watcher I<after> the child has been
		1482	forked (which implies it might have already exited), as long as the event
		1483	loop isn't entered (or is continued from a watcher).
		1484
		1485	Only the default event loop is capable of handling signals, and therefore
		1486	you can only rgeister child watchers in the default event loop.
		1487
		1488	=head3 Process Interaction
		1489
		1490	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1491	initialised. This is necessary to guarantee proper behaviour even if
		1492	the first child watcher is started after the child exits. The occurance
		1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1494	synchronously as part of the event loop processing. Libev always reaps all
		1495	children, even ones not watched.
		1496
		1497	=head3 Overriding the Built-In Processing
		1498
		1499	Libev offers no special support for overriding the built-in child
		1500	processing, but if your application collides with libev's default child
		1501	handler, you can override it easily by installing your own handler for
		1502	C<SIGCHLD> after initialising the default loop, and making sure the
		1503	default loop never gets destroyed. You are encouraged, however, to use an
		1504	event-based approach to child reaping and thus use libev's support for
		1505	that, so other libev users can use C<ev_child> watchers freely.
		1506
		1507	=head3 Watcher-Specific Functions and Data Members
1028		1508
1029	=over 4	1509	=over 4
1030		1510
1031	=item ev_child_init (ev_child *, callback, int pid)	1511	=item ev_child_init (ev_child *, callback, int pid, int trace)
1032		1512
1033	=item ev_child_set (ev_child *, int pid)	1513	=item ev_child_set (ev_child *, int pid, int trace)
1034		1514
1035	Configures the watcher to wait for status changes of process C<pid> (or	1515	Configures the watcher to wait for status changes of process C<pid> (or
1036	I<any> process if C<pid> is specified as C<0>). The callback can look	1516	I<any> process if C<pid> is specified as C<0>). The callback can look
1037	at the C<rstatus> member of the C<ev_child> watcher structure to see	1517	at the C<rstatus> member of the C<ev_child> watcher structure to see
1038	the status word (use the macros from C<sys/wait.h> and see your systems	1518	the status word (use the macros from C<sys/wait.h> and see your systems
1039	C<waitpid> documentation). The C<rpid> member contains the pid of the	1519	C<waitpid> documentation). The C<rpid> member contains the pid of the
1040	process causing the status change.	1520	process causing the status change. C<trace> must be either C<0> (only
		1521	activate the watcher when the process terminates) or C<1> (additionally
		1522	activate the watcher when the process is stopped or continued).
		1523
		1524	=item int pid [read-only]
		1525
		1526	The process id this watcher watches out for, or C<0>, meaning any process id.
		1527
		1528	=item int rpid [read-write]
		1529
		1530	The process id that detected a status change.
		1531
		1532	=item int rstatus [read-write]
		1533
		1534	The process exit/trace status caused by C<rpid> (see your systems
		1535	C<waitpid> and C<sys/wait.h> documentation for details).
1041		1536
1042	=back	1537	=back
1043		1538
1044	Example: try to exit cleanly on SIGINT and SIGTERM.	1539	=head3 Examples
		1540
		1541	Example: C<fork()> a new process and install a child handler to wait for
		1542	its completion.
		1543
		1544	ev_child cw;
1045		1545
1046	static void	1546	static void
1047	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1547	child_cb (EV_P_ struct ev_child *w, int revents)
1048	{	1548	{
1049	ev_unloop (loop, EVUNLOOP_ALL);	1549	ev_child_stop (EV_A_ w);
		1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1050	}	1551	}
1051		1552
1052	struct ev_signal signal_watcher;	1553	pid_t pid = fork ();
1053	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1554
1054	ev_signal_start (loop, &sigint_cb);	1555	if (pid < 0)
		1556	// error
		1557	else if (pid == 0)
		1558	{
		1559	// the forked child executes here
		1560	exit (1);
		1561	}
		1562	else
		1563	{
		1564	ev_child_init (&cw, child_cb, pid, 0);
		1565	ev_child_start (EV_DEFAULT_ &cw);
		1566	}
		1567
		1568
		1569	=head2 C<ev_stat> - did the file attributes just change?
		1570
		1571	This watches a filesystem path for attribute changes. That is, it calls
		1572	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1573	compared to the last time, invoking the callback if it did.
		1574
		1575	The path does not need to exist: changing from "path exists" to "path does
		1576	not exist" is a status change like any other. The condition "path does
		1577	not exist" is signified by the C<st_nlink> field being zero (which is
		1578	otherwise always forced to be at least one) and all the other fields of
		1579	the stat buffer having unspecified contents.
		1580
		1581	The path I<should> be absolute and I<must not> end in a slash. If it is
		1582	relative and your working directory changes, the behaviour is undefined.
		1583
		1584	Since there is no standard to do this, the portable implementation simply
		1585	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1586	can specify a recommended polling interval for this case. If you specify
		1587	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1588	unspecified default> value will be used (which you can expect to be around
		1589	five seconds, although this might change dynamically). Libev will also
		1590	impose a minimum interval which is currently around C<0.1>, but thats
		1591	usually overkill.
		1592
		1593	This watcher type is not meant for massive numbers of stat watchers,
		1594	as even with OS-supported change notifications, this can be
		1595	resource-intensive.
		1596
		1597	At the time of this writing, only the Linux inotify interface is
		1598	implemented (implementing kqueue support is left as an exercise for the
		1599	reader). Inotify will be used to give hints only and should not change the
		1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1601	to fall back to regular polling again even with inotify, but changes are
		1602	usually detected immediately, and if the file exists there will be no
		1603	polling.
		1604
		1605	=head3 Inotify
		1606
		1607	When C<inotify (7)> support has been compiled into libev (generally only
		1608	available on Linux) and present at runtime, it will be used to speed up
		1609	change detection where possible. The inotify descriptor will be created lazily
		1610	when the first C<ev_stat> watcher is being started.
		1611
		1612	Inotify presense does not change the semantics of C<ev_stat> watchers
		1613	except that changes might be detected earlier, and in some cases, to avoid
		1614	making regular C<stat> calls. Even in the presense of inotify support
		1615	there are many cases where libev has to resort to regular C<stat> polling.
		1616
		1617	(There is no support for kqueue, as apparently it cannot be used to
		1618	implement this functionality, due to the requirement of having a file
		1619	descriptor open on the object at all times).
		1620
		1621	=head3 The special problem of stat time resolution
		1622
		1623	The C<stat ()> syscall only supports full-second resolution portably, and
		1624	even on systems where the resolution is higher, many filesystems still
		1625	only support whole seconds.
		1626
		1627	That means that, if the time is the only thing that changes, you might
		1628	miss updates: on the first update, C<ev_stat> detects a change and calls
		1629	your callback, which does something. When there is another update within
		1630	the same second, C<ev_stat> will be unable to detect it.
		1631
		1632	The solution to this is to delay acting on a change for a second (or till
		1633	the next second boundary), using a roughly one-second delay C<ev_timer>
		1634	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1635	is added to work around small timing inconsistencies of some operating
		1636	systems.
		1637
		1638	=head3 Watcher-Specific Functions and Data Members
		1639
		1640	=over 4
		1641
		1642	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1643
		1644	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1645
		1646	Configures the watcher to wait for status changes of the given
		1647	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1648	be detected and should normally be specified as C<0> to let libev choose
		1649	a suitable value. The memory pointed to by C<path> must point to the same
		1650	path for as long as the watcher is active.
		1651
		1652	The callback will be receive C<EV_STAT> when a change was detected,
		1653	relative to the attributes at the time the watcher was started (or the
		1654	last change was detected).
		1655
		1656	=item ev_stat_stat (loop, ev_stat *)
		1657
		1658	Updates the stat buffer immediately with new values. If you change the
		1659	watched path in your callback, you could call this fucntion to avoid
		1660	detecting this change (while introducing a race condition). Can also be
		1661	useful simply to find out the new values.
		1662
		1663	=item ev_statdata attr [read-only]
		1664
		1665	The most-recently detected attributes of the file. Although the type is of
		1666	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1667	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1668	was some error while C<stat>ing the file.
		1669
		1670	=item ev_statdata prev [read-only]
		1671
		1672	The previous attributes of the file. The callback gets invoked whenever
		1673	C<prev> != C<attr>.
		1674
		1675	=item ev_tstamp interval [read-only]
		1676
		1677	The specified interval.
		1678
		1679	=item const char *path [read-only]
		1680
		1681	The filesystem path that is being watched.
		1682
		1683	=back
		1684
		1685	=head3 Examples
		1686
		1687	Example: Watch C</etc/passwd> for attribute changes.
		1688
		1689	static void
		1690	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1691	{
		1692	/* /etc/passwd changed in some way */
		1693	if (w->attr.st_nlink)
		1694	{
		1695	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1696	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1697	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1698	}
		1699	else
		1700	/* you shalt not abuse printf for puts */
		1701	puts ("wow, /etc/passwd is not there, expect problems. "
		1702	"if this is windows, they already arrived\n");
		1703	}
		1704
		1705	...
		1706	ev_stat passwd;
		1707
		1708	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1709	ev_stat_start (loop, &passwd);
		1710
		1711	Example: Like above, but additionally use a one-second delay so we do not
		1712	miss updates (however, frequent updates will delay processing, too, so
		1713	one might do the work both on C<ev_stat> callback invocation I<and> on
		1714	C<ev_timer> callback invocation).
		1715
		1716	static ev_stat passwd;
		1717	static ev_timer timer;
		1718
		1719	static void
		1720	timer_cb (EV_P_ ev_timer *w, int revents)
		1721	{
		1722	ev_timer_stop (EV_A_ w);
		1723
		1724	/* now it's one second after the most recent passwd change */
		1725	}
		1726
		1727	static void
		1728	stat_cb (EV_P_ ev_stat *w, int revents)
		1729	{
		1730	/* reset the one-second timer */
		1731	ev_timer_again (EV_A_ &timer);
		1732	}
		1733
		1734	...
		1735	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1736	ev_stat_start (loop, &passwd);
		1737	ev_timer_init (&timer, timer_cb, 0., 1.01);
1055		1738
1056		1739
1057	=head2 C<ev_idle> - when you've got nothing better to do...	1740	=head2 C<ev_idle> - when you've got nothing better to do...
1058		1741
1059	Idle watchers trigger events when there are no other events are pending	1742	Idle watchers trigger events when no other events of the same or higher
1060	(prepare, check and other idle watchers do not count). That is, as long	1743	priority are pending (prepare, check and other idle watchers do not
1061	as your process is busy handling sockets or timeouts (or even signals,	1744	count).
1062	imagine) it will not be triggered. But when your process is idle all idle	1745
1063	watchers are being called again and again, once per event loop iteration -	1746	That is, as long as your process is busy handling sockets or timeouts
		1747	(or even signals, imagine) of the same or higher priority it will not be
		1748	triggered. But when your process is idle (or only lower-priority watchers
		1749	are pending), the idle watchers are being called once per event loop
1064	until stopped, that is, or your process receives more events and becomes	1750	iteration - until stopped, that is, or your process receives more events
1065	busy.	1751	and becomes busy again with higher priority stuff.
1066		1752
1067	The most noteworthy effect is that as long as any idle watchers are	1753	The most noteworthy effect is that as long as any idle watchers are
1068	active, the process will not block when waiting for new events.	1754	active, the process will not block when waiting for new events.
1069		1755
1070	Apart from keeping your process non-blocking (which is a useful	1756	Apart from keeping your process non-blocking (which is a useful
1071	effect on its own sometimes), idle watchers are a good place to do	1757	effect on its own sometimes), idle watchers are a good place to do
1072	"pseudo-background processing", or delay processing stuff to after the	1758	"pseudo-background processing", or delay processing stuff to after the
1073	event loop has handled all outstanding events.	1759	event loop has handled all outstanding events.
1074		1760
		1761	=head3 Watcher-Specific Functions and Data Members
		1762
1075	=over 4	1763	=over 4
1076		1764
1077	=item ev_idle_init (ev_signal *, callback)	1765	=item ev_idle_init (ev_signal *, callback)
1078		1766
1079	Initialises and configures the idle watcher - it has no parameters of any	1767	Initialises and configures the idle watcher - it has no parameters of any
1080	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1768	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1081	believe me.	1769	believe me.
1082		1770
1083	=back	1771	=back
1084		1772
		1773	=head3 Examples
		1774
1085	Example: dynamically allocate an C<ev_idle>, start it, and in the	1775	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1086	callback, free it. Alos, use no error checking, as usual.	1776	callback, free it. Also, use no error checking, as usual.
1087		1777
1088	static void	1778	static void
1089	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1779	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1090	{	1780	{
1091	free (w);	1781	free (w);
1092	// now do something you wanted to do when the program has	1782	// now do something you wanted to do when the program has
1093	// no longer asnything immediate to do.	1783	// no longer anything immediate to do.
1094	}	1784	}
1095		1785
1096	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1786	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1097	ev_idle_init (idle_watcher, idle_cb);	1787	ev_idle_init (idle_watcher, idle_cb);
1098	ev_idle_start (loop, idle_cb);	1788	ev_idle_start (loop, idle_cb);
…		…
1102		1792
1103	Prepare and check watchers are usually (but not always) used in tandem:	1793	Prepare and check watchers are usually (but not always) used in tandem:
1104	prepare watchers get invoked before the process blocks and check watchers	1794	prepare watchers get invoked before the process blocks and check watchers
1105	afterwards.	1795	afterwards.
1106		1796
		1797	You I<must not> call C<ev_loop> or similar functions that enter
		1798	the current event loop from either C<ev_prepare> or C<ev_check>
		1799	watchers. Other loops than the current one are fine, however. The
		1800	rationale behind this is that you do not need to check for recursion in
		1801	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1802	C<ev_check> so if you have one watcher of each kind they will always be
		1803	called in pairs bracketing the blocking call.
		1804
1107	Their main purpose is to integrate other event mechanisms into libev and	1805	Their main purpose is to integrate other event mechanisms into libev and
1108	their use is somewhat advanced. This could be used, for example, to track	1806	their use is somewhat advanced. This could be used, for example, to track
1109	variable changes, implement your own watchers, integrate net-snmp or a	1807	variable changes, implement your own watchers, integrate net-snmp or a
1110	coroutine library and lots more.	1808	coroutine library and lots more. They are also occasionally useful if
		1809	you cache some data and want to flush it before blocking (for example,
		1810	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1811	watcher).
1111		1812
1112	This is done by examining in each prepare call which file descriptors need	1813	This is done by examining in each prepare call which file descriptors need
1113	to be watched by the other library, registering C<ev_io> watchers for	1814	to be watched by the other library, registering C<ev_io> watchers for
1114	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1815	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1115	provide just this functionality). Then, in the check watcher you check for	1816	provide just this functionality). Then, in the check watcher you check for
…		…
1125	with priority higher than or equal to the event loop and one coroutine	1826	with priority higher than or equal to the event loop and one coroutine
1126	of lower priority, but only once, using idle watchers to keep the event	1827	of lower priority, but only once, using idle watchers to keep the event
1127	loop from blocking if lower-priority coroutines are active, thus mapping	1828	loop from blocking if lower-priority coroutines are active, thus mapping
1128	low-priority coroutines to idle/background tasks).	1829	low-priority coroutines to idle/background tasks).
1129		1830
		1831	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1832	priority, to ensure that they are being run before any other watchers
		1833	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1834	too) should not activate ("feed") events into libev. While libev fully
		1835	supports this, they will be called before other C<ev_check> watchers
		1836	did their job. As C<ev_check> watchers are often used to embed other
		1837	(non-libev) event loops those other event loops might be in an unusable
		1838	state until their C<ev_check> watcher ran (always remind yourself to
		1839	coexist peacefully with others).
		1840
		1841	=head3 Watcher-Specific Functions and Data Members
		1842
1130	=over 4	1843	=over 4
1131		1844
1132	=item ev_prepare_init (ev_prepare *, callback)	1845	=item ev_prepare_init (ev_prepare *, callback)
1133		1846
1134	=item ev_check_init (ev_check *, callback)	1847	=item ev_check_init (ev_check *, callback)
…		…
1137	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1850	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1138	macros, but using them is utterly, utterly and completely pointless.	1851	macros, but using them is utterly, utterly and completely pointless.
1139		1852
1140	=back	1853	=back
1141		1854
1142	Example: *TODO*.	1855	=head3 Examples
		1856
		1857	There are a number of principal ways to embed other event loops or modules
		1858	into libev. Here are some ideas on how to include libadns into libev
		1859	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1860	use for an actually working example. Another Perl module named C<EV::Glib>
		1861	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1862	into the Glib event loop).
		1863
		1864	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1865	and in a check watcher, destroy them and call into libadns. What follows
		1866	is pseudo-code only of course. This requires you to either use a low
		1867	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1868	the callbacks for the IO/timeout watchers might not have been called yet.
		1869
		1870	static ev_io iow [nfd];
		1871	static ev_timer tw;
		1872
		1873	static void
		1874	io_cb (ev_loop *loop, ev_io *w, int revents)
		1875	{
		1876	}
		1877
		1878	// create io watchers for each fd and a timer before blocking
		1879	static void
		1880	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1881	{
		1882	int timeout = 3600000;
		1883	struct pollfd fds [nfd];
		1884	// actual code will need to loop here and realloc etc.
		1885	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1886
		1887	/* the callback is illegal, but won't be called as we stop during check */
		1888	ev_timer_init (&tw, 0, timeout * 1e-3);
		1889	ev_timer_start (loop, &tw);
		1890
		1891	// create one ev_io per pollfd
		1892	for (int i = 0; i < nfd; ++i)
		1893	{
		1894	ev_io_init (iow + i, io_cb, fds [i].fd,
		1895	((fds [i].events & POLLIN ? EV_READ : 0)
		1896	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1897
		1898	fds [i].revents = 0;
		1899	ev_io_start (loop, iow + i);
		1900	}
		1901	}
		1902
		1903	// stop all watchers after blocking
		1904	static void
		1905	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1906	{
		1907	ev_timer_stop (loop, &tw);
		1908
		1909	for (int i = 0; i < nfd; ++i)
		1910	{
		1911	// set the relevant poll flags
		1912	// could also call adns_processreadable etc. here
		1913	struct pollfd *fd = fds + i;
		1914	int revents = ev_clear_pending (iow + i);
		1915	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1916	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1917
		1918	// now stop the watcher
		1919	ev_io_stop (loop, iow + i);
		1920	}
		1921
		1922	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1923	}
		1924
		1925	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1926	in the prepare watcher and would dispose of the check watcher.
		1927
		1928	Method 3: If the module to be embedded supports explicit event
		1929	notification (adns does), you can also make use of the actual watcher
		1930	callbacks, and only destroy/create the watchers in the prepare watcher.
		1931
		1932	static void
		1933	timer_cb (EV_P_ ev_timer *w, int revents)
		1934	{
		1935	adns_state ads = (adns_state)w->data;
		1936	update_now (EV_A);
		1937
		1938	adns_processtimeouts (ads, &tv_now);
		1939	}
		1940
		1941	static void
		1942	io_cb (EV_P_ ev_io *w, int revents)
		1943	{
		1944	adns_state ads = (adns_state)w->data;
		1945	update_now (EV_A);
		1946
		1947	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1948	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1949	}
		1950
		1951	// do not ever call adns_afterpoll
		1952
		1953	Method 4: Do not use a prepare or check watcher because the module you
		1954	want to embed is too inflexible to support it. Instead, youc na override
		1955	their poll function. The drawback with this solution is that the main
		1956	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1957	this.
		1958
		1959	static gint
		1960	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1961	{
		1962	int got_events = 0;
		1963
		1964	for (n = 0; n < nfds; ++n)
		1965	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1966
		1967	if (timeout >= 0)
		1968	// create/start timer
		1969
		1970	// poll
		1971	ev_loop (EV_A_ 0);
		1972
		1973	// stop timer again
		1974	if (timeout >= 0)
		1975	ev_timer_stop (EV_A_ &to);
		1976
		1977	// stop io watchers again - their callbacks should have set
		1978	for (n = 0; n < nfds; ++n)
		1979	ev_io_stop (EV_A_ iow [n]);
		1980
		1981	return got_events;
		1982	}
1143		1983
1144		1984
1145	=head2 C<ev_embed> - when one backend isn't enough...	1985	=head2 C<ev_embed> - when one backend isn't enough...
1146		1986
1147	This is a rather advanced watcher type that lets you embed one event loop	1987	This is a rather advanced watcher type that lets you embed one event loop
…		…
1189	portable one.	2029	portable one.
1190		2030
1191	So when you want to use this feature you will always have to be prepared	2031	So when you want to use this feature you will always have to be prepared
1192	that you cannot get an embeddable loop. The recommended way to get around	2032	that you cannot get an embeddable loop. The recommended way to get around
1193	this is to have a separate variables for your embeddable loop, try to	2033	this is to have a separate variables for your embeddable loop, try to
1194	create it, and if that fails, use the normal loop for everything:	2034	create it, and if that fails, use the normal loop for everything.
		2035
		2036	=head3 Watcher-Specific Functions and Data Members
		2037
		2038	=over 4
		2039
		2040	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2041
		2042	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2043
		2044	Configures the watcher to embed the given loop, which must be
		2045	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2046	invoked automatically, otherwise it is the responsibility of the callback
		2047	to invoke it (it will continue to be called until the sweep has been done,
		2048	if you do not want thta, you need to temporarily stop the embed watcher).
		2049
		2050	=item ev_embed_sweep (loop, ev_embed *)
		2051
		2052	Make a single, non-blocking sweep over the embedded loop. This works
		2053	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2054	apropriate way for embedded loops.
		2055
		2056	=item struct ev_loop *other [read-only]
		2057
		2058	The embedded event loop.
		2059
		2060	=back
		2061
		2062	=head3 Examples
		2063
		2064	Example: Try to get an embeddable event loop and embed it into the default
		2065	event loop. If that is not possible, use the default loop. The default
		2066	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2067	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2068	used).
1195		2069
1196	struct ev_loop *loop_hi = ev_default_init (0);	2070	struct ev_loop *loop_hi = ev_default_init (0);
1197	struct ev_loop *loop_lo = 0;	2071	struct ev_loop *loop_lo = 0;
1198	struct ev_embed embed;	2072	struct ev_embed embed;
1199		2073
…		…
1210	ev_embed_start (loop_hi, &embed);	2084	ev_embed_start (loop_hi, &embed);
1211	}	2085	}
1212	else	2086	else
1213	loop_lo = loop_hi;	2087	loop_lo = loop_hi;
1214		2088
		2089	Example: Check if kqueue is available but not recommended and create
		2090	a kqueue backend for use with sockets (which usually work with any
		2091	kqueue implementation). Store the kqueue/socket-only event loop in
		2092	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2093
		2094	struct ev_loop *loop = ev_default_init (0);
		2095	struct ev_loop *loop_socket = 0;
		2096	struct ev_embed embed;
		2097
		2098	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2099	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2100	{
		2101	ev_embed_init (&embed, 0, loop_socket);
		2102	ev_embed_start (loop, &embed);
		2103	}
		2104
		2105	if (!loop_socket)
		2106	loop_socket = loop;
		2107
		2108	// now use loop_socket for all sockets, and loop for everything else
		2109
		2110
		2111	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2112
		2113	Fork watchers are called when a C<fork ()> was detected (usually because
		2114	whoever is a good citizen cared to tell libev about it by calling
		2115	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2116	event loop blocks next and before C<ev_check> watchers are being called,
		2117	and only in the child after the fork. If whoever good citizen calling
		2118	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2119	handlers will be invoked, too, of course.
		2120
		2121	=head3 Watcher-Specific Functions and Data Members
		2122
1215	=over 4	2123	=over 4
1216		2124
1217	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2125	=item ev_fork_init (ev_signal *, callback)
1218		2126
1219	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2127	Initialises and configures the fork watcher - it has no parameters of any
		2128	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2129	believe me.
1220		2130
1221	Configures the watcher to embed the given loop, which must be	2131	=back
1222	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1223	invoked automatically, otherwise it is the responsibility of the callback
1224	to invoke it (it will continue to be called until the sweep has been done,
1225	if you do not want thta, you need to temporarily stop the embed watcher).
1226		2132
1227	=item ev_embed_sweep (loop, ev_embed *)
1228		2133
1229	Make a single, non-blocking sweep over the embedded loop. This works	2134	=head2 C<ev_async> - how to wake up another event loop
1230	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2135
1231	apropriate way for embedded loops.	2136	In general, you cannot use an C<ev_loop> from multiple threads or other
		2137	asynchronous sources such as signal handlers (as opposed to multiple event
		2138	loops - those are of course safe to use in different threads).
		2139
		2140	Sometimes, however, you need to wake up another event loop you do not
		2141	control, for example because it belongs to another thread. This is what
		2142	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2143	can signal it by calling C<ev_async_send>, which is thread- and signal
		2144	safe.
		2145
		2146	This functionality is very similar to C<ev_signal> watchers, as signals,
		2147	too, are asynchronous in nature, and signals, too, will be compressed
		2148	(i.e. the number of callback invocations may be less than the number of
		2149	C<ev_async_sent> calls).
		2150
		2151	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2152	just the default loop.
		2153
		2154	=head3 Queueing
		2155
		2156	C<ev_async> does not support queueing of data in any way. The reason
		2157	is that the author does not know of a simple (or any) algorithm for a
		2158	multiple-writer-single-reader queue that works in all cases and doesn't
		2159	need elaborate support such as pthreads.
		2160
		2161	That means that if you want to queue data, you have to provide your own
		2162	queue. But at least I can tell you would implement locking around your
		2163	queue:
		2164
		2165	=over 4
		2166
		2167	=item queueing from a signal handler context
		2168
		2169	To implement race-free queueing, you simply add to the queue in the signal
		2170	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2171	some fictitiuous SIGUSR1 handler:
		2172
		2173	static ev_async mysig;
		2174
		2175	static void
		2176	sigusr1_handler (void)
		2177	{
		2178	sometype data;
		2179
		2180	// no locking etc.
		2181	queue_put (data);
		2182	ev_async_send (EV_DEFAULT_ &mysig);
		2183	}
		2184
		2185	static void
		2186	mysig_cb (EV_P_ ev_async *w, int revents)
		2187	{
		2188	sometype data;
		2189	sigset_t block, prev;
		2190
		2191	sigemptyset (&block);
		2192	sigaddset (&block, SIGUSR1);
		2193	sigprocmask (SIG_BLOCK, &block, &prev);
		2194
		2195	while (queue_get (&data))
		2196	process (data);
		2197
		2198	if (sigismember (&prev, SIGUSR1)
		2199	sigprocmask (SIG_UNBLOCK, &block, 0);
		2200	}
		2201
		2202	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2203	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2204	either...).
		2205
		2206	=item queueing from a thread context
		2207
		2208	The strategy for threads is different, as you cannot (easily) block
		2209	threads but you can easily preempt them, so to queue safely you need to
		2210	employ a traditional mutex lock, such as in this pthread example:
		2211
		2212	static ev_async mysig;
		2213	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2214
		2215	static void
		2216	otherthread (void)
		2217	{
		2218	// only need to lock the actual queueing operation
		2219	pthread_mutex_lock (&mymutex);
		2220	queue_put (data);
		2221	pthread_mutex_unlock (&mymutex);
		2222
		2223	ev_async_send (EV_DEFAULT_ &mysig);
		2224	}
		2225
		2226	static void
		2227	mysig_cb (EV_P_ ev_async *w, int revents)
		2228	{
		2229	pthread_mutex_lock (&mymutex);
		2230
		2231	while (queue_get (&data))
		2232	process (data);
		2233
		2234	pthread_mutex_unlock (&mymutex);
		2235	}
		2236
		2237	=back
		2238
		2239
		2240	=head3 Watcher-Specific Functions and Data Members
		2241
		2242	=over 4
		2243
		2244	=item ev_async_init (ev_async *, callback)
		2245
		2246	Initialises and configures the async watcher - it has no parameters of any
		2247	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2248	believe me.
		2249
		2250	=item ev_async_send (loop, ev_async *)
		2251
		2252	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2253	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2254	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2255	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2256	section below on what exactly this means).
		2257
		2258	This call incurs the overhead of a syscall only once per loop iteration,
		2259	so while the overhead might be noticable, it doesn't apply to repeated
		2260	calls to C<ev_async_send>.
1232		2261
1233	=back	2262	=back
1234		2263
1235		2264
1236	=head1 OTHER FUNCTIONS	2265	=head1 OTHER FUNCTIONS
…		…
1325		2354
1326	To use it,	2355	To use it,
1327		2356
1328	#include <ev++.h>	2357	#include <ev++.h>
1329		2358
1330	(it is not installed by default). This automatically includes F<ev.h>	2359	This automatically includes F<ev.h> and puts all of its definitions (many
1331	and puts all of its definitions (many of them macros) into the global	2360	of them macros) into the global namespace. All C++ specific things are
1332	namespace. All C++ specific things are put into the C<ev> namespace.	2361	put into the C<ev> namespace. It should support all the same embedding
		2362	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1333		2363
1334	It should support all the same embedding options as F<ev.h>, most notably	2364	Care has been taken to keep the overhead low. The only data member the C++
1335	C<EV_MULTIPLICITY>.	2365	classes add (compared to plain C-style watchers) is the event loop pointer
		2366	that the watcher is associated with (or no additional members at all if
		2367	you disable C<EV_MULTIPLICITY> when embedding libev).
		2368
		2369	Currently, functions, and static and non-static member functions can be
		2370	used as callbacks. Other types should be easy to add as long as they only
		2371	need one additional pointer for context. If you need support for other
		2372	types of functors please contact the author (preferably after implementing
		2373	it).
1336		2374
1337	Here is a list of things available in the C<ev> namespace:	2375	Here is a list of things available in the C<ev> namespace:
1338		2376
1339	=over 4	2377	=over 4
1340		2378
…		…
1356		2394
1357	All of those classes have these methods:	2395	All of those classes have these methods:
1358		2396
1359	=over 4	2397	=over 4
1360		2398
1361	=item ev::TYPE::TYPE (object *, object::method *)	2399	=item ev::TYPE::TYPE ()
1362		2400
1363	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2401	=item ev::TYPE::TYPE (struct ev_loop *)
1364		2402
1365	=item ev::TYPE::~TYPE	2403	=item ev::TYPE::~TYPE
1366		2404
1367	The constructor takes a pointer to an object and a method pointer to	2405	The constructor (optionally) takes an event loop to associate the watcher
1368	the event handler callback to call in this class. The constructor calls	2406	with. If it is omitted, it will use C<EV_DEFAULT>.
1369	C<ev_init> for you, which means you have to call the C<set> method	2407
1370	before starting it. If you do not specify a loop then the constructor	2408	The constructor calls C<ev_init> for you, which means you have to call the
1371	automatically associates the default loop with this watcher.	2409	C<set> method before starting it.
		2410
		2411	It will not set a callback, however: You have to call the templated C<set>
		2412	method to set a callback before you can start the watcher.
		2413
		2414	(The reason why you have to use a method is a limitation in C++ which does
		2415	not allow explicit template arguments for constructors).
1372		2416
1373	The destructor automatically stops the watcher if it is active.	2417	The destructor automatically stops the watcher if it is active.
		2418
		2419	=item w->set<class, &class::method> (object *)
		2420
		2421	This method sets the callback method to call. The method has to have a
		2422	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2423	first argument and the C<revents> as second. The object must be given as
		2424	parameter and is stored in the C<data> member of the watcher.
		2425
		2426	This method synthesizes efficient thunking code to call your method from
		2427	the C callback that libev requires. If your compiler can inline your
		2428	callback (i.e. it is visible to it at the place of the C<set> call and
		2429	your compiler is good :), then the method will be fully inlined into the
		2430	thunking function, making it as fast as a direct C callback.
		2431
		2432	Example: simple class declaration and watcher initialisation
		2433
		2434	struct myclass
		2435	{
		2436	void io_cb (ev::io &w, int revents) { }
		2437	}
		2438
		2439	myclass obj;
		2440	ev::io iow;
		2441	iow.set <myclass, &myclass::io_cb> (&obj);
		2442
		2443	=item w->set<function> (void *data = 0)
		2444
		2445	Also sets a callback, but uses a static method or plain function as
		2446	callback. The optional C<data> argument will be stored in the watcher's
		2447	C<data> member and is free for you to use.
		2448
		2449	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2450
		2451	See the method-C<set> above for more details.
		2452
		2453	Example:
		2454
		2455	static void io_cb (ev::io &w, int revents) { }
		2456	iow.set <io_cb> ();
1374		2457
1375	=item w->set (struct ev_loop *)	2458	=item w->set (struct ev_loop *)
1376		2459
1377	Associates a different C<struct ev_loop> with this watcher. You can only	2460	Associates a different C<struct ev_loop> with this watcher. You can only
1378	do this when the watcher is inactive (and not pending either).	2461	do this when the watcher is inactive (and not pending either).
1379		2462
1380	=item w->set ([args])	2463	=item w->set ([args])
1381		2464
1382	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2465	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1383	called at least once. Unlike the C counterpart, an active watcher gets	2466	called at least once. Unlike the C counterpart, an active watcher gets
1384	automatically stopped and restarted.	2467	automatically stopped and restarted when reconfiguring it with this
		2468	method.
1385		2469
1386	=item w->start ()	2470	=item w->start ()
1387		2471
1388	Starts the watcher. Note that there is no C<loop> argument as the	2472	Starts the watcher. Note that there is no C<loop> argument, as the
1389	constructor already takes the loop.	2473	constructor already stores the event loop.
1390		2474
1391	=item w->stop ()	2475	=item w->stop ()
1392		2476
1393	Stops the watcher if it is active. Again, no C<loop> argument.	2477	Stops the watcher if it is active. Again, no C<loop> argument.
1394		2478
1395	=item w->again () C<ev::timer>, C<ev::periodic> only	2479	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1396		2480
1397	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2481	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1398	C<ev_TYPE_again> function.	2482	C<ev_TYPE_again> function.
1399		2483
1400	=item w->sweep () C<ev::embed> only	2484	=item w->sweep () (C<ev::embed> only)
1401		2485
1402	Invokes C<ev_embed_sweep>.	2486	Invokes C<ev_embed_sweep>.
		2487
		2488	=item w->update () (C<ev::stat> only)
		2489
		2490	Invokes C<ev_stat_stat>.
1403		2491
1404	=back	2492	=back
1405		2493
1406	=back	2494	=back
1407		2495
1408	Example: Define a class with an IO and idle watcher, start one of them in	2496	Example: Define a class with an IO and idle watcher, start one of them in
1409	the constructor.	2497	the constructor.
1410		2498
1411	class myclass	2499	class myclass
1412	{	2500	{
1413	ev_io io; void io_cb (ev::io &w, int revents);	2501	ev::io io; void io_cb (ev::io &w, int revents);
1414	ev_idle idle void idle_cb (ev::idle &w, int revents);	2502	ev:idle idle void idle_cb (ev::idle &w, int revents);
1415		2503
1416	myclass ();	2504	myclass (int fd)
		2505	{
		2506	io .set <myclass, &myclass::io_cb > (this);
		2507	idle.set <myclass, &myclass::idle_cb> (this);
		2508
		2509	io.start (fd, ev::READ);
		2510	}
		2511	};
		2512
		2513
		2514	=head1 OTHER LANGUAGE BINDINGS
		2515
		2516	Libev does not offer other language bindings itself, but bindings for a
		2517	numbe rof languages exist in the form of third-party packages. If you know
		2518	any interesting language binding in addition to the ones listed here, drop
		2519	me a note.
		2520
		2521	=over 4
		2522
		2523	=item Perl
		2524
		2525	The EV module implements the full libev API and is actually used to test
		2526	libev. EV is developed together with libev. Apart from the EV core module,
		2527	there are additional modules that implement libev-compatible interfaces
		2528	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2529	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2530
		2531	It can be found and installed via CPAN, its homepage is found at
		2532	L<http://software.schmorp.de/pkg/EV>.
		2533
		2534	=item Ruby
		2535
		2536	Tony Arcieri has written a ruby extension that offers access to a subset
		2537	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2538	more on top of it. It can be found via gem servers. Its homepage is at
		2539	L<http://rev.rubyforge.org/>.
		2540
		2541	=item D
		2542
		2543	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2544	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2545
		2546	=back
		2547
		2548
		2549	=head1 MACRO MAGIC
		2550
		2551	Libev can be compiled with a variety of options, the most fundamantal
		2552	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2553	functions and callbacks have an initial C<struct ev_loop *> argument.
		2554
		2555	To make it easier to write programs that cope with either variant, the
		2556	following macros are defined:
		2557
		2558	=over 4
		2559
		2560	=item C<EV_A>, C<EV_A_>
		2561
		2562	This provides the loop I<argument> for functions, if one is required ("ev
		2563	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2564	C<EV_A_> is used when other arguments are following. Example:
		2565
		2566	ev_unref (EV_A);
		2567	ev_timer_add (EV_A_ watcher);
		2568	ev_loop (EV_A_ 0);
		2569
		2570	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2571	which is often provided by the following macro.
		2572
		2573	=item C<EV_P>, C<EV_P_>
		2574
		2575	This provides the loop I<parameter> for functions, if one is required ("ev
		2576	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2577	C<EV_P_> is used when other parameters are following. Example:
		2578
		2579	// this is how ev_unref is being declared
		2580	static void ev_unref (EV_P);
		2581
		2582	// this is how you can declare your typical callback
		2583	static void cb (EV_P_ ev_timer *w, int revents)
		2584
		2585	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2586	suitable for use with C<EV_A>.
		2587
		2588	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2589
		2590	Similar to the other two macros, this gives you the value of the default
		2591	loop, if multiple loops are supported ("ev loop default").
		2592
		2593	=back
		2594
		2595	Example: Declare and initialise a check watcher, utilising the above
		2596	macros so it will work regardless of whether multiple loops are supported
		2597	or not.
		2598
		2599	static void
		2600	check_cb (EV_P_ ev_timer *w, int revents)
		2601	{
		2602	ev_check_stop (EV_A_ w);
1417	}	2603	}
1418		2604
1419	myclass::myclass (int fd)	2605	ev_check check;
1420	: io (this, &myclass::io_cb),	2606	ev_check_init (&check, check_cb);
1421	idle (this, &myclass::idle_cb)	2607	ev_check_start (EV_DEFAULT_ &check);
1422	{	2608	ev_loop (EV_DEFAULT_ 0);
1423	io.start (fd, ev::READ);
1424	}
1425		2609
1426	=head1 EMBEDDING	2610	=head1 EMBEDDING
1427		2611
1428	Libev can (and often is) directly embedded into host	2612	Libev can (and often is) directly embedded into host
1429	applications. Examples of applications that embed it include the Deliantra	2613	applications. Examples of applications that embed it include the Deliantra
1430	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2614	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1431	and rxvt-unicode.	2615	and rxvt-unicode.
1432		2616
1433	The goal is to enable you to just copy the neecssary files into your	2617	The goal is to enable you to just copy the necessary files into your
1434	source directory without having to change even a single line in them, so	2618	source directory without having to change even a single line in them, so
1435	you can easily upgrade by simply copying (or having a checked-out copy of	2619	you can easily upgrade by simply copying (or having a checked-out copy of
1436	libev somewhere in your source tree).	2620	libev somewhere in your source tree).
1437		2621
1438	=head2 FILESETS	2622	=head2 FILESETS
…		…
1469	ev_vars.h	2653	ev_vars.h
1470	ev_wrap.h	2654	ev_wrap.h
1471		2655
1472	ev_win32.c required on win32 platforms only	2656	ev_win32.c required on win32 platforms only
1473		2657
1474	ev_select.c only when select backend is enabled (which is is by default)	2658	ev_select.c only when select backend is enabled (which is enabled by default)
1475	ev_poll.c only when poll backend is enabled (disabled by default)	2659	ev_poll.c only when poll backend is enabled (disabled by default)
1476	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2660	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1477	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2661	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1478	ev_port.c only when the solaris port backend is enabled (disabled by default)	2662	ev_port.c only when the solaris port backend is enabled (disabled by default)
1479		2663
1480	F<ev.c> includes the backend files directly when enabled, so you only need	2664	F<ev.c> includes the backend files directly when enabled, so you only need
1481	to compile a single file.	2665	to compile this single file.
1482		2666
1483	=head3 LIBEVENT COMPATIBILITY API	2667	=head3 LIBEVENT COMPATIBILITY API
1484		2668
1485	To include the libevent compatibility API, also include:	2669	To include the libevent compatibility API, also include:
1486		2670
…		…
1499		2683
1500	=head3 AUTOCONF SUPPORT	2684	=head3 AUTOCONF SUPPORT
1501		2685
1502	Instead of using C<EV_STANDALONE=1> and providing your config in	2686	Instead of using C<EV_STANDALONE=1> and providing your config in
1503	whatever way you want, you can also C<m4_include([libev.m4])> in your	2687	whatever way you want, you can also C<m4_include([libev.m4])> in your
1504	F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include	2688	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1505	F<config.h> and configure itself accordingly.	2689	include F<config.h> and configure itself accordingly.
1506		2690
1507	For this of course you need the m4 file:	2691	For this of course you need the m4 file:
1508		2692
1509	libev.m4	2693	libev.m4
1510		2694
…		…
1528		2712
1529	If defined to be C<1>, libev will try to detect the availability of the	2713	If defined to be C<1>, libev will try to detect the availability of the
1530	monotonic clock option at both compiletime and runtime. Otherwise no use	2714	monotonic clock option at both compiletime and runtime. Otherwise no use
1531	of the monotonic clock option will be attempted. If you enable this, you	2715	of the monotonic clock option will be attempted. If you enable this, you
1532	usually have to link against librt or something similar. Enabling it when	2716	usually have to link against librt or something similar. Enabling it when
1533	the functionality isn't available is safe, though, althoguh you have	2717	the functionality isn't available is safe, though, although you have
1534	to make sure you link against any libraries where the C<clock_gettime>	2718	to make sure you link against any libraries where the C<clock_gettime>
1535	function is hiding in (often F<-lrt>).	2719	function is hiding in (often F<-lrt>).
1536		2720
1537	=item EV_USE_REALTIME	2721	=item EV_USE_REALTIME
1538		2722
1539	If defined to be C<1>, libev will try to detect the availability of the	2723	If defined to be C<1>, libev will try to detect the availability of the
1540	realtime clock option at compiletime (and assume its availability at	2724	realtime clock option at compiletime (and assume its availability at
1541	runtime if successful). Otherwise no use of the realtime clock option will	2725	runtime if successful). Otherwise no use of the realtime clock option will
1542	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2726	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1543	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2727	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1544	in the description of C<EV_USE_MONOTONIC>, though.	2728	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2729
		2730	=item EV_USE_NANOSLEEP
		2731
		2732	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2733	and will use it for delays. Otherwise it will use C<select ()>.
1545		2734
1546	=item EV_USE_SELECT	2735	=item EV_USE_SELECT
1547		2736
1548	If undefined or defined to be C<1>, libev will compile in support for the	2737	If undefined or defined to be C<1>, libev will compile in support for the
1549	C<select>(2) backend. No attempt at autodetection will be done: if no	2738	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1567	wants osf handles on win32 (this is the case when the select to	2756	wants osf handles on win32 (this is the case when the select to
1568	be used is the winsock select). This means that it will call	2757	be used is the winsock select). This means that it will call
1569	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2758	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1570	it is assumed that all these functions actually work on fds, even	2759	it is assumed that all these functions actually work on fds, even
1571	on win32. Should not be defined on non-win32 platforms.	2760	on win32. Should not be defined on non-win32 platforms.
		2761
		2762	=item EV_FD_TO_WIN32_HANDLE
		2763
		2764	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2765	file descriptors to socket handles. When not defining this symbol (the
		2766	default), then libev will call C<_get_osfhandle>, which is usually
		2767	correct. In some cases, programs use their own file descriptor management,
		2768	in which case they can provide this function to map fds to socket handles.
1572		2769
1573	=item EV_USE_POLL	2770	=item EV_USE_POLL
1574		2771
1575	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2772	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1576	backend. Otherwise it will be enabled on non-win32 platforms. It	2773	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
1604		2801
1605	=item EV_USE_DEVPOLL	2802	=item EV_USE_DEVPOLL
1606		2803
1607	reserved for future expansion, works like the USE symbols above.	2804	reserved for future expansion, works like the USE symbols above.
1608		2805
		2806	=item EV_USE_INOTIFY
		2807
		2808	If defined to be C<1>, libev will compile in support for the Linux inotify
		2809	interface to speed up C<ev_stat> watchers. Its actual availability will
		2810	be detected at runtime.
		2811
		2812	=item EV_ATOMIC_T
		2813
		2814	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2815	access is atomic with respect to other threads or signal contexts. No such
		2816	type is easily found in the C language, so you can provide your own type
		2817	that you know is safe for your purposes. It is used both for signal handler "locking"
		2818	as well as for signal and thread safety in C<ev_async> watchers.
		2819
		2820	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2821	(from F<signal.h>), which is usually good enough on most platforms.
		2822
1609	=item EV_H	2823	=item EV_H
1610		2824
1611	The name of the F<ev.h> header file used to include it. The default if	2825	The name of the F<ev.h> header file used to include it. The default if
1612	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2826	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
1613	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2827	used to virtually rename the F<ev.h> header file in case of conflicts.
1614		2828
1615	=item EV_CONFIG_H	2829	=item EV_CONFIG_H
1616		2830
1617	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2831	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1618	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2832	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1619	C<EV_H>, above.	2833	C<EV_H>, above.
1620		2834
1621	=item EV_EVENT_H	2835	=item EV_EVENT_H
1622		2836
1623	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2837	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1624	of how the F<event.h> header can be found.	2838	of how the F<event.h> header can be found, the default is C<"event.h">.
1625		2839
1626	=item EV_PROTOTYPES	2840	=item EV_PROTOTYPES
1627		2841
1628	If defined to be C<0>, then F<ev.h> will not define any function	2842	If defined to be C<0>, then F<ev.h> will not define any function
1629	prototypes, but still define all the structs and other symbols. This is	2843	prototypes, but still define all the structs and other symbols. This is
…		…
1636	will have the C<struct ev_loop *> as first argument, and you can create	2850	will have the C<struct ev_loop *> as first argument, and you can create
1637	additional independent event loops. Otherwise there will be no support	2851	additional independent event loops. Otherwise there will be no support
1638	for multiple event loops and there is no first event loop pointer	2852	for multiple event loops and there is no first event loop pointer
1639	argument. Instead, all functions act on the single default loop.	2853	argument. Instead, all functions act on the single default loop.
1640		2854
		2855	=item EV_MINPRI
		2856
		2857	=item EV_MAXPRI
		2858
		2859	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2860	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2861	provide for more priorities by overriding those symbols (usually defined
		2862	to be C<-2> and C<2>, respectively).
		2863
		2864	When doing priority-based operations, libev usually has to linearly search
		2865	all the priorities, so having many of them (hundreds) uses a lot of space
		2866	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2867	fine.
		2868
		2869	If your embedding app does not need any priorities, defining these both to
		2870	C<0> will save some memory and cpu.
		2871
1641	=item EV_PERIODICS	2872	=item EV_PERIODIC_ENABLE
1642		2873
1643	If undefined or defined to be C<1>, then periodic timers are supported,	2874	If undefined or defined to be C<1>, then periodic timers are supported. If
1644	otherwise not. This saves a few kb of code.	2875	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2876	code.
		2877
		2878	=item EV_IDLE_ENABLE
		2879
		2880	If undefined or defined to be C<1>, then idle watchers are supported. If
		2881	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2882	code.
		2883
		2884	=item EV_EMBED_ENABLE
		2885
		2886	If undefined or defined to be C<1>, then embed watchers are supported. If
		2887	defined to be C<0>, then they are not.
		2888
		2889	=item EV_STAT_ENABLE
		2890
		2891	If undefined or defined to be C<1>, then stat watchers are supported. If
		2892	defined to be C<0>, then they are not.
		2893
		2894	=item EV_FORK_ENABLE
		2895
		2896	If undefined or defined to be C<1>, then fork watchers are supported. If
		2897	defined to be C<0>, then they are not.
		2898
		2899	=item EV_ASYNC_ENABLE
		2900
		2901	If undefined or defined to be C<1>, then async watchers are supported. If
		2902	defined to be C<0>, then they are not.
		2903
		2904	=item EV_MINIMAL
		2905
		2906	If you need to shave off some kilobytes of code at the expense of some
		2907	speed, define this symbol to C<1>. Currently only used for gcc to override
		2908	some inlining decisions, saves roughly 30% codesize of amd64.
		2909
		2910	=item EV_PID_HASHSIZE
		2911
		2912	C<ev_child> watchers use a small hash table to distribute workload by
		2913	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2914	than enough. If you need to manage thousands of children you might want to
		2915	increase this value (I<must> be a power of two).
		2916
		2917	=item EV_INOTIFY_HASHSIZE
		2918
		2919	C<ev_stat> watchers use a small hash table to distribute workload by
		2920	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2921	usually more than enough. If you need to manage thousands of C<ev_stat>
		2922	watchers you might want to increase this value (I<must> be a power of
		2923	two).
1645		2924
1646	=item EV_COMMON	2925	=item EV_COMMON
1647		2926
1648	By default, all watchers have a C<void *data> member. By redefining	2927	By default, all watchers have a C<void *data> member. By redefining
1649	this macro to a something else you can include more and other types of	2928	this macro to a something else you can include more and other types of
…		…
1654		2933
1655	#define EV_COMMON \	2934	#define EV_COMMON \
1656	SV *self; /* contains this struct */ \	2935	SV *self; /* contains this struct */ \
1657	SV *cb_sv, *fh /* note no trailing ";" */	2936	SV *cb_sv, *fh /* note no trailing ";" */
1658		2937
1659	=item EV_CB_DECLARE(type)	2938	=item EV_CB_DECLARE (type)
1660		2939
1661	=item EV_CB_INVOKE(watcher,revents)	2940	=item EV_CB_INVOKE (watcher, revents)
1662		2941
1663	=item ev_set_cb(ev,cb)	2942	=item ev_set_cb (ev, cb)
1664		2943
1665	Can be used to change the callback member declaration in each watcher,	2944	Can be used to change the callback member declaration in each watcher,
1666	and the way callbacks are invoked and set. Must expand to a struct member	2945	and the way callbacks are invoked and set. Must expand to a struct member
1667	definition and a statement, respectively. See the F<ev.v> header file for	2946	definition and a statement, respectively. See the F<ev.h> header file for
1668	their default definitions. One possible use for overriding these is to	2947	their default definitions. One possible use for overriding these is to
1669	avoid the ev_loop pointer as first argument in all cases, or to use method	2948	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1670	calls instead of plain function calls in C++.	2949	method calls instead of plain function calls in C++.
		2950
		2951	=head2 EXPORTED API SYMBOLS
		2952
		2953	If you need to re-export the API (e.g. via a dll) and you need a list of
		2954	exported symbols, you can use the provided F<Symbol.*> files which list
		2955	all public symbols, one per line:
		2956
		2957	Symbols.ev for libev proper
		2958	Symbols.event for the libevent emulation
		2959
		2960	This can also be used to rename all public symbols to avoid clashes with
		2961	multiple versions of libev linked together (which is obviously bad in
		2962	itself, but sometimes it is inconvinient to avoid this).
		2963
		2964	A sed command like this will create wrapper C<#define>'s that you need to
		2965	include before including F<ev.h>:
		2966
		2967	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2968
		2969	This would create a file F<wrap.h> which essentially looks like this:
		2970
		2971	#define ev_backend myprefix_ev_backend
		2972	#define ev_check_start myprefix_ev_check_start
		2973	#define ev_check_stop myprefix_ev_check_stop
		2974	...
1671		2975
1672	=head2 EXAMPLES	2976	=head2 EXAMPLES
1673		2977
1674	For a real-world example of a program the includes libev	2978	For a real-world example of a program the includes libev
1675	verbatim, you can have a look at the EV perl module	2979	verbatim, you can have a look at the EV perl module
…		…
1678	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2982	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1679	will be compiled. It is pretty complex because it provides its own header	2983	will be compiled. It is pretty complex because it provides its own header
1680	file.	2984	file.
1681		2985
1682	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2986	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1683	that everybody includes and which overrides some autoconf choices:	2987	that everybody includes and which overrides some configure choices:
1684		2988
		2989	#define EV_MINIMAL 1
1685	#define EV_USE_POLL 0	2990	#define EV_USE_POLL 0
1686	#define EV_MULTIPLICITY 0	2991	#define EV_MULTIPLICITY 0
1687	#define EV_PERIODICS 0	2992	#define EV_PERIODIC_ENABLE 0
		2993	#define EV_STAT_ENABLE 0
		2994	#define EV_FORK_ENABLE 0
1688	#define EV_CONFIG_H <config.h>	2995	#define EV_CONFIG_H <config.h>
		2996	#define EV_MINPRI 0
		2997	#define EV_MAXPRI 0
1689		2998
1690	#include "ev++.h"	2999	#include "ev++.h"
1691		3000
1692	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3001	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1693		3002
1694	#include "ev_cpp.h"	3003	#include "ev_cpp.h"
1695	#include "ev.c"	3004	#include "ev.c"
1696		3005
		3006
		3007	=head1 COMPLEXITIES
		3008
		3009	In this section the complexities of (many of) the algorithms used inside
		3010	libev will be explained. For complexity discussions about backends see the
		3011	documentation for C<ev_default_init>.
		3012
		3013	All of the following are about amortised time: If an array needs to be
		3014	extended, libev needs to realloc and move the whole array, but this
		3015	happens asymptotically never with higher number of elements, so O(1) might
		3016	mean it might do a lengthy realloc operation in rare cases, but on average
		3017	it is much faster and asymptotically approaches constant time.
		3018
		3019	=over 4
		3020
		3021	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3022
		3023	This means that, when you have a watcher that triggers in one hour and
		3024	there are 100 watchers that would trigger before that then inserting will
		3025	have to skip roughly seven (C<ld 100>) of these watchers.
		3026
		3027	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3028
		3029	That means that changing a timer costs less than removing/adding them
		3030	as only the relative motion in the event queue has to be paid for.
		3031
		3032	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3033
		3034	These just add the watcher into an array or at the head of a list.
		3035
		3036	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3037
		3038	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3039
		3040	These watchers are stored in lists then need to be walked to find the
		3041	correct watcher to remove. The lists are usually short (you don't usually
		3042	have many watchers waiting for the same fd or signal).
		3043
		3044	=item Finding the next timer in each loop iteration: O(1)
		3045
		3046	By virtue of using a binary heap, the next timer is always found at the
		3047	beginning of the storage array.
		3048
		3049	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3050
		3051	A change means an I/O watcher gets started or stopped, which requires
		3052	libev to recalculate its status (and possibly tell the kernel, depending
		3053	on backend and wether C<ev_io_set> was used).
		3054
		3055	=item Activating one watcher (putting it into the pending state): O(1)
		3056
		3057	=item Priority handling: O(number_of_priorities)
		3058
		3059	Priorities are implemented by allocating some space for each
		3060	priority. When doing priority-based operations, libev usually has to
		3061	linearly search all the priorities, but starting/stopping and activating
		3062	watchers becomes O(1) w.r.t. priority handling.
		3063
		3064	=item Sending an ev_async: O(1)
		3065
		3066	=item Processing ev_async_send: O(number_of_async_watchers)
		3067
		3068	=item Processing signals: O(max_signal_number)
		3069
		3070	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3071	calls in the current loop iteration. Checking for async and signal events
		3072	involves iterating over all running async watchers or all signal numbers.
		3073
		3074	=back
		3075
		3076
		3077	=head1 Win32 platform limitations and workarounds
		3078
		3079	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3080	requires, and its I/O model is fundamentally incompatible with the POSIX
		3081	model. Libev still offers limited functionality on this platform in
		3082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3083	descriptors. This only applies when using Win32 natively, not when using
		3084	e.g. cygwin.
		3085
		3086	There is no supported compilation method available on windows except
		3087	embedding it into other applications.
		3088
		3089	Due to the many, low, and arbitrary limits on the win32 platform and the
		3090	abysmal performance of winsockets, using a large number of sockets is not
		3091	recommended (and not reasonable). If your program needs to use more than
		3092	a hundred or so sockets, then likely it needs to use a totally different
		3093	implementation for windows, as libev offers the POSIX model, which cannot
		3094	be implemented efficiently on windows (microsoft monopoly games).
		3095
		3096	=over 4
		3097
		3098	=item The winsocket select function
		3099
		3100	The winsocket C<select> function doesn't follow POSIX in that it requires
		3101	socket I<handles> and not socket I<file descriptors>. This makes select
		3102	very inefficient, and also requires a mapping from file descriptors
		3103	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3104	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3105	symbols for more info.
		3106
		3107	The configuration for a "naked" win32 using the microsoft runtime
		3108	libraries and raw winsocket select is:
		3109
		3110	#define EV_USE_SELECT 1
		3111	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3112
		3113	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3114	complexity in the O(n²) range when using win32.
		3115
		3116	=item Limited number of file descriptors
		3117
		3118	Windows has numerous arbitrary (and low) limits on things. Early versions
		3119	of winsocket's select only supported waiting for a max. of C<64> handles
		3120	(probably owning to the fact that all windows kernels can only wait for
		3121	C<64> things at the same time internally; microsoft recommends spawning a
		3122	chain of threads and wait for 63 handles and the previous thread in each).
		3123
		3124	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3125	to some high number (e.g. C<2048>) before compiling the winsocket select
		3126	call (which might be in libev or elsewhere, for example, perl does its own
		3127	select emulation on windows).
		3128
		3129	Another limit is the number of file descriptors in the microsoft runtime
		3130	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3131	or something like this inside microsoft). You can increase this by calling
		3132	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3133	arbitrary limit), but is broken in many versions of the microsoft runtime
		3134	libraries.
		3135
		3136	This might get you to about C<512> or C<2048> sockets (depending on
		3137	windows version and/or the phase of the moon). To get more, you need to
		3138	wrap all I/O functions and provide your own fd management, but the cost of
		3139	calling select (O(n²)) will likely make this unworkable.
		3140
		3141	=back
		3142
		3143
1697	=head1 AUTHOR	3144	=head1 AUTHOR
1698		3145
1699	Marc Lehmann <libev@schmorp.de>.	3146	Marc Lehmann <libev@schmorp.de>.
1700		3147

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