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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	#include <ev.h>	11	#include <ev.h>
12		12
13	ev_io stdin_watcher;	13	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
…		…
48	return 0;	48	return 0;
49	}	49	}
50		50
51	=head1 DESCRIPTION	51	=head1 DESCRIPTION
52		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
53	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
54	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
55	these event sources and provide your program with events.	59	these event sources and provide your program with events.
56		60
57	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
58	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
59	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
61	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
62	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
63	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
64	watcher.	68	watcher.
65		69
66	=head1 FEATURES	70	=head2 FEATURES
67		71
68	Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
69	bsd-specific C<kqueue> and the solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	for file descriptor events (C<ev_io>), relative timers (C<ev_timer>),	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
		75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
71	absolute timers with customised rescheduling (C<ev_periodic>), synchronous	76	with customised rescheduling (C<ev_periodic>), synchronous signals
72	signals (C<ev_signal>), process status change events (C<ev_child>), and	77	(C<ev_signal>), process status change events (C<ev_child>), and event
73	event watchers dealing with the event loop mechanism itself (C<ev_idle>,	78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
74	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
75	file watchers (C<ev_stat>) and even limited support for fork events	80	file watchers (C<ev_stat>) and even limited support for fork events
76	(C<ev_fork>).	81	(C<ev_fork>).
77		82
78	It also is quite fast (see this	83	It also is quite fast (see this
79	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
80	for example).	85	for example).
81		86
82	=head1 CONVENTIONS	87	=head2 CONVENTIONS
83		88
84	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
85	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
86	various configuration options please have a look at B<EMBED> section in	91	various configuration options please have a look at B<EMBED> section in
87	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
88	loops, then all functions taking an initial argument of name C<loop>	93	loops, then all functions taking an initial argument of name C<loop>
89	(which is always of type C<struct ev_loop *>) will not have this argument.	94	(which is always of type C<struct ev_loop *>) will not have this argument.
90		95
91	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
92		97
93	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
94	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
95	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
96	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
97	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
98	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
99		106
100	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
101		108
102	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
103	library in any way.	110	library in any way.
…		…
108		115
109	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
110	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
111	you actually want to know.	118	you actually want to know.
112		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
113	=item int ev_version_major ()	126	=item int ev_version_major ()
114		127
115	=item int ev_version_minor ()	128	=item int ev_version_minor ()
116		129
117	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
118	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
119	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
120	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
121	version of the library your program was compiled against.	134	version of the library your program was compiled against.
122		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
123	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
124	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
125	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
126	not a problem.	142	not a problem.
127		143
128	Example: Make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
129	version.	145	version.
…		…
162	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
163	recommended ones.	179	recommended ones.
164		180
165	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
166		182
167	=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
168		184
169	Sets the allocation function to use (the prototype and semantics are	185	Sets the allocation function to use (the prototype is similar - the
170	identical to the realloc C function). It is used to allocate and free	186	semantics is identical - to the realloc C function). It is used to
171	memory (no surprises here). If it returns zero when memory needs to be	187	allocate and free memory (no surprises here). If it returns zero when
172	allocated, the library might abort or take some potentially destructive	188	memory needs to be allocated, the library might abort or take some
173	action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
174		191
175	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
176	free some memory if it cannot allocate memory, to use a special allocator,	193	free some memory if it cannot allocate memory, to use a special allocator,
177	or even to sleep a while and retry until some memory is available.	194	or even to sleep a while and retry until some memory is available.
178		195
…		…
264	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
265	override the flags completely if it is found in the environment. This is	282	override the flags completely if it is found in the environment. This is
266	useful to try out specific backends to test their performance, or to work	283	useful to try out specific backends to test their performance, or to work
267	around bugs.	284	around bugs.
268		285
		286	=item C<EVFLAG_FORKCHECK>
		287
		288	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		289	a fork, you can also make libev check for a fork in each iteration by
		290	enabling this flag.
		291
		292	This works by calling C<getpid ()> on every iteration of the loop,
		293	and thus this might slow down your event loop if you do a lot of loop
		294	iterations and little real work, but is usually not noticeable (on my
		295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		296	without a syscall and thus I<very> fast, but my Linux system also has
		297	C<pthread_atfork> which is even faster).
		298
		299	The big advantage of this flag is that you can forget about fork (and
		300	forget about forgetting to tell libev about forking) when you use this
		301	flag.
		302
		303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		304	environment variable.
		305
269	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
270		307
271	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
272	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
273	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
274	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
275	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
276		320
277	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
278		322
279	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
280	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
281	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
282	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
283		329
284	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
285		331
286	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
287	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
288	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	334	like O(total_fds) where n is the total number of fds (or the highest fd),
289	either O(1) or O(active_fds).	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
		336	of shortcomings, such as silently dropping events in some hard-to-detect
		337	cases and rewiring a syscall per fd change, no fork support and bad
		338	support for dup.
290		339
291	While stopping and starting an I/O watcher in the same iteration will	340	While stopping, setting and starting an I/O watcher in the same iteration
292	result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
293	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
294	best to avoid that. Also, dup()ed file descriptors might not work very	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
295	well if you register events for both fds.	344	very well if you register events for both fds.
296		345
297	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
298	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
299	(or space) is available.	348	(or space) is available.
300		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
301	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
302		358
303	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
304	was broken on all BSDs except NetBSD (usually it doesn't work with	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
305	anything but sockets and pipes, except on Darwin, where of course its	361	with anything but sockets and pipes, except on Darwin, where of course
306	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
307	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
308	C<EVBACKEND_KQUEUE>).	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		365	system like NetBSD.
		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
309		370
310	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
311	kernel is more efficient (which says nothing about its actual speed, of	372	kernel is more efficient (which says nothing about its actual speed, of
312	course). While starting and stopping an I/O watcher does not cause an	373	course). While stopping, setting and starting an I/O watcher does never
313	extra syscall as with epoll, it still adds up to four event changes per	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
314	incident, so its best to avoid that.	375	two event changes per incident, support for C<fork ()> is very bad and it
		376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
315		386
316	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
317		388
318	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
319		393
320	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
321		395
322	This uses the Solaris 10 port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
323	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
324		398
325	Please note that solaris ports can result in a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
326	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
327	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
328		407
329	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
330		409
331	Try all backends (even potentially broken ones that wouldn't be tried	410	Try all backends (even potentially broken ones that wouldn't be tried
332	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
333	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
334		415
335	=back	416	=back
336		417
337	If one or more of these are ored into the flags value, then only these	418	If one or more of these are ored into the flags value, then only these
338	backends will be tried (in the reverse order as given here). If none are	419	backends will be tried (in the reverse order as given here). If none are
…		…
373	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
374	etc.). None of the active event watchers will be stopped in the normal	455	etc.). None of the active event watchers will be stopped in the normal
375	sense, so e.g. C<ev_is_active> might still return true. It is your	456	sense, so e.g. C<ev_is_active> might still return true. It is your
376	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
377	calling this function, or cope with the fact afterwards (which is usually	458	calling this function, or cope with the fact afterwards (which is usually
378	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	459	the easiest thing, you can just ignore the watchers and/or C<free ()> them
379	for example).	460	for example).
		461
		462	Note that certain global state, such as signal state, will not be freed by
		463	this function, and related watchers (such as signal and child watchers)
		464	would need to be stopped manually.
		465
		466	In general it is not advisable to call this function except in the
		467	rare occasion where you really need to free e.g. the signal handling
		468	pipe fds. If you need dynamically allocated loops it is better to use
		469	C<ev_loop_new> and C<ev_loop_destroy>).
380		470
381	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
382		472
383	Like C<ev_default_destroy>, but destroys an event loop created by an	473	Like C<ev_default_destroy>, but destroys an event loop created by an
384	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
408		498
409	Like C<ev_default_fork>, but acts on an event loop created by	499	Like C<ev_default_fork>, but acts on an event loop created by
410	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
411	after fork, and how you do this is entirely your own problem.	501	after fork, and how you do this is entirely your own problem.
412		502
		503	=item unsigned int ev_loop_count (loop)
		504
		505	Returns the count of loop iterations for the loop, which is identical to
		506	the number of times libev did poll for new events. It starts at C<0> and
		507	happily wraps around with enough iterations.
		508
		509	This value can sometimes be useful as a generation counter of sorts (it
		510	"ticks" the number of loop iterations), as it roughly corresponds with
		511	C<ev_prepare> and C<ev_check> calls.
		512
413	=item unsigned int ev_backend (loop)	513	=item unsigned int ev_backend (loop)
414		514
415	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	515	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
416	use.	516	use.
417		517
…		…
419		519
420	Returns the current "event loop time", which is the time the event loop	520	Returns the current "event loop time", which is the time the event loop
421	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
422	change as long as callbacks are being processed, and this is also the base	522	change as long as callbacks are being processed, and this is also the base
423	time used for relative timers. You can treat it as the timestamp of the	523	time used for relative timers. You can treat it as the timestamp of the
424	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
425		525
426	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
427		527
428	Finally, this is it, the event handler. This function usually is called	528	Finally, this is it, the event handler. This function usually is called
429	after you initialised all your watchers and you want to start handling	529	after you initialised all your watchers and you want to start handling
…		…
450	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
451	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
452		552
453	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
454		554
		555	- Before the first iteration, call any pending watchers.
455	* If there are no active watchers (reference count is zero), return.	556	* If there are no active watchers (reference count is zero), return.
456	- Queue prepare watchers and then call all outstanding watchers.	557	- Queue all prepare watchers and then call all outstanding watchers.
457	- If we have been forked, recreate the kernel state.	558	- If we have been forked, recreate the kernel state.
458	- Update the kernel state with all outstanding changes.	559	- Update the kernel state with all outstanding changes.
459	- Update the "event loop time".	560	- Update the "event loop time".
460	- Calculate for how long to block.	561	- Calculate for how long to block.
461	- Block the process, waiting for any events.	562	- Block the process, waiting for any events.
…		…
512	Example: For some weird reason, unregister the above signal handler again.	613	Example: For some weird reason, unregister the above signal handler again.
513		614
514	ev_ref (loop);	615	ev_ref (loop);
515	ev_signal_stop (loop, &exitsig);	616	ev_signal_stop (loop, &exitsig);
516		617
		618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		619
		620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		621
		622	These advanced functions influence the time that libev will spend waiting
		623	for events. Both are by default C<0>, meaning that libev will try to
		624	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		625
		626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		627	allows libev to delay invocation of I/O and timer/periodic callbacks to
		628	increase efficiency of loop iterations.
		629
		630	The background is that sometimes your program runs just fast enough to
		631	handle one (or very few) event(s) per loop iteration. While this makes
		632	the program responsive, it also wastes a lot of CPU time to poll for new
		633	events, especially with backends like C<select ()> which have a high
		634	overhead for the actual polling but can deliver many events at once.
		635
		636	By setting a higher I<io collect interval> you allow libev to spend more
		637	time collecting I/O events, so you can handle more events per iteration,
		638	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		639	C<ev_timer>) will be not affected. Setting this to a non-null value will
		640	introduce an additional C<ev_sleep ()> call into most loop iterations.
		641
		642	Likewise, by setting a higher I<timeout collect interval> you allow libev
		643	to spend more time collecting timeouts, at the expense of increased
		644	latency (the watcher callback will be called later). C<ev_io> watchers
		645	will not be affected. Setting this to a non-null value will not introduce
		646	any overhead in libev.
		647
		648	Many (busy) programs can usually benefit by setting the io collect
		649	interval to a value near C<0.1> or so, which is often enough for
		650	interactive servers (of course not for games), likewise for timeouts. It
		651	usually doesn't make much sense to set it to a lower value than C<0.01>,
		652	as this approsaches the timing granularity of most systems.
		653
517	=back	654	=back
518		655
519		656
520	=head1 ANATOMY OF A WATCHER	657	=head1 ANATOMY OF A WATCHER
521		658
…		…
700	=item bool ev_is_pending (ev_TYPE *watcher)	837	=item bool ev_is_pending (ev_TYPE *watcher)
701		838
702	Returns a true value iff the watcher is pending, (i.e. it has outstanding	839	Returns a true value iff the watcher is pending, (i.e. it has outstanding
703	events but its callback has not yet been invoked). As long as a watcher	840	events but its callback has not yet been invoked). As long as a watcher
704	is pending (but not active) you must not call an init function on it (but	841	is pending (but not active) you must not call an init function on it (but
705	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	842	C<ev_TYPE_set> is safe), you must not change its priority, and you must
706	libev (e.g. you cnanot C<free ()> it).	843	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		844	it).
707		845
708	=item callback = ev_cb (ev_TYPE *watcher)	846	=item callback ev_cb (ev_TYPE *watcher)
709		847
710	Returns the callback currently set on the watcher.	848	Returns the callback currently set on the watcher.
711		849
712	=item ev_cb_set (ev_TYPE *watcher, callback)	850	=item ev_cb_set (ev_TYPE *watcher, callback)
713		851
714	Change the callback. You can change the callback at virtually any time	852	Change the callback. You can change the callback at virtually any time
715	(modulo threads).	853	(modulo threads).
		854
		855	=item ev_set_priority (ev_TYPE *watcher, priority)
		856
		857	=item int ev_priority (ev_TYPE *watcher)
		858
		859	Set and query the priority of the watcher. The priority is a small
		860	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		861	(default: C<-2>). Pending watchers with higher priority will be invoked
		862	before watchers with lower priority, but priority will not keep watchers
		863	from being executed (except for C<ev_idle> watchers).
		864
		865	This means that priorities are I<only> used for ordering callback
		866	invocation after new events have been received. This is useful, for
		867	example, to reduce latency after idling, or more often, to bind two
		868	watchers on the same event and make sure one is called first.
		869
		870	If you need to suppress invocation when higher priority events are pending
		871	you need to look at C<ev_idle> watchers, which provide this functionality.
		872
		873	You I<must not> change the priority of a watcher as long as it is active or
		874	pending.
		875
		876	The default priority used by watchers when no priority has been set is
		877	always C<0>, which is supposed to not be too high and not be too low :).
		878
		879	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		880	fine, as long as you do not mind that the priority value you query might
		881	or might not have been adjusted to be within valid range.
		882
		883	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		884
		885	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		886	C<loop> nor C<revents> need to be valid as long as the watcher callback
		887	can deal with that fact.
		888
		889	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		890
		891	If the watcher is pending, this function returns clears its pending status
		892	and returns its C<revents> bitset (as if its callback was invoked). If the
		893	watcher isn't pending it does nothing and returns C<0>.
716		894
717	=back	895	=back
718		896
719		897
720	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
741	{	919	{
742	struct my_io *w = (struct my_io *)w_;	920	struct my_io *w = (struct my_io *)w_;
743	...	921	...
744	}	922	}
745		923
746	More interesting and less C-conformant ways of catsing your callback type	924	More interesting and less C-conformant ways of casting your callback type
747	have been omitted....	925	instead have been omitted.
		926
		927	Another common scenario is having some data structure with multiple
		928	watchers:
		929
		930	struct my_biggy
		931	{
		932	int some_data;
		933	ev_timer t1;
		934	ev_timer t2;
		935	}
		936
		937	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		938	you need to use C<offsetof>:
		939
		940	#include <stddef.h>
		941
		942	static void
		943	t1_cb (EV_P_ struct ev_timer *w, int revents)
		944	{
		945	struct my_biggy big = (struct my_biggy *
		946	(((char *)w) - offsetof (struct my_biggy, t1));
		947	}
		948
		949	static void
		950	t2_cb (EV_P_ struct ev_timer *w, int revents)
		951	{
		952	struct my_biggy big = (struct my_biggy *
		953	(((char *)w) - offsetof (struct my_biggy, t2));
		954	}
748		955
749		956
750	=head1 WATCHER TYPES	957	=head1 WATCHER TYPES
751		958
752	This section describes each watcher in detail, but will not repeat	959	This section describes each watcher in detail, but will not repeat
…		…
797	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1004	it is best to always use non-blocking I/O: An extra C<read>(2) returning
798	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1005	C<EAGAIN> is far preferable to a program hanging until some data arrives.
799		1006
800	If you cannot run the fd in non-blocking mode (for example you should not	1007	If you cannot run the fd in non-blocking mode (for example you should not
801	play around with an Xlib connection), then you have to seperately re-test	1008	play around with an Xlib connection), then you have to seperately re-test
802	wether a file descriptor is really ready with a known-to-be good interface	1009	whether a file descriptor is really ready with a known-to-be good interface
803	such as poll (fortunately in our Xlib example, Xlib already does this on	1010	such as poll (fortunately in our Xlib example, Xlib already does this on
804	its own, so its quite safe to use).	1011	its own, so its quite safe to use).
		1012
		1013	=head3 The special problem of disappearing file descriptors
		1014
		1015	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1016	descriptor (either by calling C<close> explicitly or by any other means,
		1017	such as C<dup>). The reason is that you register interest in some file
		1018	descriptor, but when it goes away, the operating system will silently drop
		1019	this interest. If another file descriptor with the same number then is
		1020	registered with libev, there is no efficient way to see that this is, in
		1021	fact, a different file descriptor.
		1022
		1023	To avoid having to explicitly tell libev about such cases, libev follows
		1024	the following policy: Each time C<ev_io_set> is being called, libev
		1025	will assume that this is potentially a new file descriptor, otherwise
		1026	it is assumed that the file descriptor stays the same. That means that
		1027	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1028	descriptor even if the file descriptor number itself did not change.
		1029
		1030	This is how one would do it normally anyway, the important point is that
		1031	the libev application should not optimise around libev but should leave
		1032	optimisations to libev.
		1033
		1034	=head3 The special problem of dup'ed file descriptors
		1035
		1036	Some backends (e.g. epoll), cannot register events for file descriptors,
		1037	but only events for the underlying file descriptions. That means when you
		1038	have C<dup ()>'ed file descriptors and register events for them, only one
		1039	file descriptor might actually receive events.
		1040
		1041	There is no workaround possible except not registering events
		1042	for potentially C<dup ()>'ed file descriptors, or to resort to
		1043	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1044
		1045	=head3 The special problem of fork
		1046
		1047	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1048	useless behaviour. Libev fully supports fork, but needs to be told about
		1049	it in the child.
		1050
		1051	To support fork in your programs, you either have to call
		1052	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1053	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1054	C<EVBACKEND_POLL>.
		1055
		1056
		1057	=head3 Watcher-Specific Functions
805		1058
806	=over 4	1059	=over 4
807		1060
808	=item ev_io_init (ev_io *, callback, int fd, int events)	1061	=item ev_io_init (ev_io *, callback, int fd, int events)
809		1062
…		…
863		1116
864	The callback is guarenteed to be invoked only when its timeout has passed,	1117	The callback is guarenteed to be invoked only when its timeout has passed,
865	but if multiple timers become ready during the same loop iteration then	1118	but if multiple timers become ready during the same loop iteration then
866	order of execution is undefined.	1119	order of execution is undefined.
867		1120
		1121	=head3 Watcher-Specific Functions and Data Members
		1122
868	=over 4	1123	=over 4
869		1124
870	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1125	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
871		1126
872	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1127	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
885	=item ev_timer_again (loop)	1140	=item ev_timer_again (loop)
886		1141
887	This will act as if the timer timed out and restart it again if it is	1142	This will act as if the timer timed out and restart it again if it is
888	repeating. The exact semantics are:	1143	repeating. The exact semantics are:
889		1144
		1145	If the timer is pending, its pending status is cleared.
		1146
890	If the timer is started but nonrepeating, stop it.	1147	If the timer is started but nonrepeating, stop it (as if it timed out).
891		1148
892	If the timer is repeating, either start it if necessary (with the repeat	1149	If the timer is repeating, either start it if necessary (with the
893	value), or reset the running timer to the repeat value.	1150	C<repeat> value), or reset the running timer to the C<repeat> value.
894		1151
895	This sounds a bit complicated, but here is a useful and typical	1152	This sounds a bit complicated, but here is a useful and typical
896	example: Imagine you have a tcp connection and you want a so-called	1153	example: Imagine you have a tcp connection and you want a so-called idle
897	idle timeout, that is, you want to be called when there have been,	1154	timeout, that is, you want to be called when there have been, say, 60
898	say, 60 seconds of inactivity on the socket. The easiest way to do	1155	seconds of inactivity on the socket. The easiest way to do this is to
899	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1156	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
900	C<ev_timer_again> each time you successfully read or write some data. If	1157	C<ev_timer_again> each time you successfully read or write some data. If
901	you go into an idle state where you do not expect data to travel on the	1158	you go into an idle state where you do not expect data to travel on the
902	socket, you can stop the timer, and again will automatically restart it if	1159	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
903	need be.	1160	automatically restart it if need be.
904		1161
905	You can also ignore the C<after> value and C<ev_timer_start> altogether	1162	That means you can ignore the C<after> value and C<ev_timer_start>
906	and only ever use the C<repeat> value:	1163	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
907		1164
908	ev_timer_init (timer, callback, 0., 5.);	1165	ev_timer_init (timer, callback, 0., 5.);
909	ev_timer_again (loop, timer);	1166	ev_timer_again (loop, timer);
910	...	1167	...
911	timer->again = 17.;	1168	timer->again = 17.;
912	ev_timer_again (loop, timer);	1169	ev_timer_again (loop, timer);
913	...	1170	...
914	timer->again = 10.;	1171	timer->again = 10.;
915	ev_timer_again (loop, timer);	1172	ev_timer_again (loop, timer);
916		1173
917	This is more efficient then stopping/starting the timer eahc time you want	1174	This is more slightly efficient then stopping/starting the timer each time
918	to modify its timeout value.	1175	you want to modify its timeout value.
919		1176
920	=item ev_tstamp repeat [read-write]	1177	=item ev_tstamp repeat [read-write]
921		1178
922	The current C<repeat> value. Will be used each time the watcher times out	1179	The current C<repeat> value. Will be used each time the watcher times out
923	or C<ev_timer_again> is called and determines the next timeout (if any),	1180	or C<ev_timer_again> is called and determines the next timeout (if any),
…		…
965	but on wallclock time (absolute time). You can tell a periodic watcher	1222	but on wallclock time (absolute time). You can tell a periodic watcher
966	to trigger "at" some specific point in time. For example, if you tell a	1223	to trigger "at" some specific point in time. For example, if you tell a
967	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1224	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
968	+ 10.>) and then reset your system clock to the last year, then it will	1225	+ 10.>) and then reset your system clock to the last year, then it will
969	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1226	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
970	roughly 10 seconds later and of course not if you reset your system time	1227	roughly 10 seconds later).
971	again).
972		1228
973	They can also be used to implement vastly more complex timers, such as	1229	They can also be used to implement vastly more complex timers, such as
974	triggering an event on eahc midnight, local time.	1230	triggering an event on each midnight, local time or other, complicated,
		1231	rules.
975		1232
976	As with timers, the callback is guarenteed to be invoked only when the	1233	As with timers, the callback is guarenteed to be invoked only when the
977	time (C<at>) has been passed, but if multiple periodic timers become ready	1234	time (C<at>) has been passed, but if multiple periodic timers become ready
978	during the same loop iteration then order of execution is undefined.	1235	during the same loop iteration then order of execution is undefined.
979		1236
		1237	=head3 Watcher-Specific Functions and Data Members
		1238
980	=over 4	1239	=over 4
981		1240
982	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1241	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
983		1242
984	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1243	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
986	Lots of arguments, lets sort it out... There are basically three modes of	1245	Lots of arguments, lets sort it out... There are basically three modes of
987	operation, and we will explain them from simplest to complex:	1246	operation, and we will explain them from simplest to complex:
988		1247
989	=over 4	1248	=over 4
990		1249
991	=item * absolute timer (interval = reschedule_cb = 0)	1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)
992		1251
993	In this configuration the watcher triggers an event at the wallclock time	1252	In this configuration the watcher triggers an event at the wallclock time
994	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1253	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
995	that is, if it is to be run at January 1st 2011 then it will run when the	1254	that is, if it is to be run at January 1st 2011 then it will run when the
996	system time reaches or surpasses this time.	1255	system time reaches or surpasses this time.
997		1256
998	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
999		1258
1000	In this mode the watcher will always be scheduled to time out at the next	1259	In this mode the watcher will always be scheduled to time out at the next
1001	C<at + N * interval> time (for some integer N) and then repeat, regardless	1260	C<at + N * interval> time (for some integer N, which can also be negative)
1002	of any time jumps.	1261	and then repeat, regardless of any time jumps.
1003		1262
1004	This can be used to create timers that do not drift with respect to system	1263	This can be used to create timers that do not drift with respect to system
1005	time:	1264	time:
1006		1265
1007	ev_periodic_set (&periodic, 0., 3600., 0);	1266	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1013		1272
1014	Another way to think about it (for the mathematically inclined) is that	1273	Another way to think about it (for the mathematically inclined) is that
1015	C<ev_periodic> will try to run the callback in this mode at the next possible	1274	C<ev_periodic> will try to run the callback in this mode at the next possible
1016	time where C<time = at (mod interval)>, regardless of any time jumps.	1275	time where C<time = at (mod interval)>, regardless of any time jumps.
1017		1276
		1277	For numerical stability it is preferable that the C<at> value is near
		1278	C<ev_now ()> (the current time), but there is no range requirement for
		1279	this value.
		1280
1018	=item * manual reschedule mode (reschedule_cb = callback)	1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1019		1282
1020	In this mode the values for C<interval> and C<at> are both being	1283	In this mode the values for C<interval> and C<at> are both being
1021	ignored. Instead, each time the periodic watcher gets scheduled, the	1284	ignored. Instead, each time the periodic watcher gets scheduled, the
1022	reschedule callback will be called with the watcher as first, and the	1285	reschedule callback will be called with the watcher as first, and the
1023	current time as second argument.	1286	current time as second argument.
1024		1287
1025	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1288	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1026	ever, or make any event loop modifications>. If you need to stop it,	1289	ever, or make any event loop modifications>. If you need to stop it,
1027	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1290	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1028	starting a prepare watcher).	1291	starting an C<ev_prepare> watcher, which is legal).
1029		1292
1030	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1293	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1031	ev_tstamp now)>, e.g.:	1294	ev_tstamp now)>, e.g.:
1032		1295
1033	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1296	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1056	Simply stops and restarts the periodic watcher again. This is only useful	1319	Simply stops and restarts the periodic watcher again. This is only useful
1057	when you changed some parameters or the reschedule callback would return	1320	when you changed some parameters or the reschedule callback would return
1058	a different time than the last time it was called (e.g. in a crond like	1321	a different time than the last time it was called (e.g. in a crond like
1059	program when the crontabs have changed).	1322	program when the crontabs have changed).
1060		1323
		1324	=item ev_tstamp offset [read-write]
		1325
		1326	When repeating, this contains the offset value, otherwise this is the
		1327	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1328
		1329	Can be modified any time, but changes only take effect when the periodic
		1330	timer fires or C<ev_periodic_again> is being called.
		1331
1061	=item ev_tstamp interval [read-write]	1332	=item ev_tstamp interval [read-write]
1062		1333
1063	The current interval value. Can be modified any time, but changes only	1334	The current interval value. Can be modified any time, but changes only
1064	take effect when the periodic timer fires or C<ev_periodic_again> is being	1335	take effect when the periodic timer fires or C<ev_periodic_again> is being
1065	called.	1336	called.
…		…
1067	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1338	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
1068		1339
1069	The current reschedule callback, or C<0>, if this functionality is	1340	The current reschedule callback, or C<0>, if this functionality is
1070	switched off. Can be changed any time, but changes only take effect when	1341	switched off. Can be changed any time, but changes only take effect when
1071	the periodic timer fires or C<ev_periodic_again> is being called.	1342	the periodic timer fires or C<ev_periodic_again> is being called.
		1343
		1344	=item ev_tstamp at [read-only]
		1345
		1346	When active, contains the absolute time that the watcher is supposed to
		1347	trigger next.
1072		1348
1073	=back	1349	=back
1074		1350
1075	Example: Call a callback every hour, or, more precisely, whenever the	1351	Example: Call a callback every hour, or, more precisely, whenever the
1076	system clock is divisible by 3600. The callback invocation times have	1352	system clock is divisible by 3600. The callback invocation times have
…		…
1118	with the kernel (thus it coexists with your own signal handlers as long	1394	with the kernel (thus it coexists with your own signal handlers as long
1119	as you don't register any with libev). Similarly, when the last signal	1395	as you don't register any with libev). Similarly, when the last signal
1120	watcher for a signal is stopped libev will reset the signal handler to	1396	watcher for a signal is stopped libev will reset the signal handler to
1121	SIG_DFL (regardless of what it was set to before).	1397	SIG_DFL (regardless of what it was set to before).
1122		1398
		1399	=head3 Watcher-Specific Functions and Data Members
		1400
1123	=over 4	1401	=over 4
1124		1402
1125	=item ev_signal_init (ev_signal *, callback, int signum)	1403	=item ev_signal_init (ev_signal *, callback, int signum)
1126		1404
1127	=item ev_signal_set (ev_signal *, int signum)	1405	=item ev_signal_set (ev_signal *, int signum)
…		…
1138		1416
1139	=head2 C<ev_child> - watch out for process status changes	1417	=head2 C<ev_child> - watch out for process status changes
1140		1418
1141	Child watchers trigger when your process receives a SIGCHLD in response to	1419	Child watchers trigger when your process receives a SIGCHLD in response to
1142	some child status changes (most typically when a child of yours dies).	1420	some child status changes (most typically when a child of yours dies).
		1421
		1422	=head3 Watcher-Specific Functions and Data Members
1143		1423
1144	=over 4	1424	=over 4
1145		1425
1146	=item ev_child_init (ev_child *, callback, int pid)	1426	=item ev_child_init (ev_child *, callback, int pid)
1147		1427
…		…
1192	not exist" is a status change like any other. The condition "path does	1472	not exist" is a status change like any other. The condition "path does
1193	not exist" is signified by the C<st_nlink> field being zero (which is	1473	not exist" is signified by the C<st_nlink> field being zero (which is
1194	otherwise always forced to be at least one) and all the other fields of	1474	otherwise always forced to be at least one) and all the other fields of
1195	the stat buffer having unspecified contents.	1475	the stat buffer having unspecified contents.
1196		1476
		1477	The path I<should> be absolute and I<must not> end in a slash. If it is
		1478	relative and your working directory changes, the behaviour is undefined.
		1479
1197	Since there is no standard to do this, the portable implementation simply	1480	Since there is no standard to do this, the portable implementation simply
1198	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1481	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1199	can specify a recommended polling interval for this case. If you specify	1482	can specify a recommended polling interval for this case. If you specify
1200	a polling interval of C<0> (highly recommended!) then a I<suitable,	1483	a polling interval of C<0> (highly recommended!) then a I<suitable,
1201	unspecified default> value will be used (which you can expect to be around	1484	unspecified default> value will be used (which you can expect to be around
1202	five seconds, although this might change dynamically). Libev will also	1485	five seconds, although this might change dynamically). Libev will also
1203	impose a minimum interval which is currently around C<0.1>, but thats	1486	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1205		1488
1206	This watcher type is not meant for massive numbers of stat watchers,	1489	This watcher type is not meant for massive numbers of stat watchers,
1207	as even with OS-supported change notifications, this can be	1490	as even with OS-supported change notifications, this can be
1208	resource-intensive.	1491	resource-intensive.
1209		1492
1210	At the time of this writing, no specific OS backends are implemented, but	1493	At the time of this writing, only the Linux inotify interface is
1211	if demand increases, at least a kqueue and inotify backend will be added.	1494	implemented (implementing kqueue support is left as an exercise for the
		1495	reader). Inotify will be used to give hints only and should not change the
		1496	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1497	to fall back to regular polling again even with inotify, but changes are
		1498	usually detected immediately, and if the file exists there will be no
		1499	polling.
		1500
		1501	=head3 The special problem of stat time resolution
		1502
		1503	The C<stat ()> syscall only supports full-second resolution portably, and
		1504	even on systems where the resolution is higher, many filesystems still
		1505	only support whole seconds.
		1506
		1507	That means that, if the time is the only thing that changes, you might
		1508	miss updates: on the first update, C<ev_stat> detects a change and calls
		1509	your callback, which does something. When there is another update within
		1510	the same second, C<ev_stat> will be unable to detect it.
		1511
		1512	The solution to this is to delay acting on a change for a second (or till
		1513	the next second boundary), using a roughly one-second delay C<ev_timer>
		1514	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1515	is added to work around small timing inconsistencies of some operating
		1516	systems.
		1517
		1518	=head3 Watcher-Specific Functions and Data Members
1212		1519
1213	=over 4	1520	=over 4
1214		1521
1215	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1522	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1216		1523
…		…
1274	}	1581	}
1275		1582
1276	...	1583	...
1277	ev_stat passwd;	1584	ev_stat passwd;
1278		1585
1279	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1586	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1280	ev_stat_start (loop, &passwd);	1587	ev_stat_start (loop, &passwd);
1281		1588
		1589	Example: Like above, but additionally use a one-second delay so we do not
		1590	miss updates (however, frequent updates will delay processing, too, so
		1591	one might do the work both on C<ev_stat> callback invocation I<and> on
		1592	C<ev_timer> callback invocation).
		1593
		1594	static ev_stat passwd;
		1595	static ev_timer timer;
		1596
		1597	static void
		1598	timer_cb (EV_P_ ev_timer *w, int revents)
		1599	{
		1600	ev_timer_stop (EV_A_ w);
		1601
		1602	/* now it's one second after the most recent passwd change */
		1603	}
		1604
		1605	static void
		1606	stat_cb (EV_P_ ev_stat *w, int revents)
		1607	{
		1608	/* reset the one-second timer */
		1609	ev_timer_again (EV_A_ &timer);
		1610	}
		1611
		1612	...
		1613	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1614	ev_stat_start (loop, &passwd);
		1615	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1616
1282		1617
1283	=head2 C<ev_idle> - when you've got nothing better to do...	1618	=head2 C<ev_idle> - when you've got nothing better to do...
1284		1619
1285	Idle watchers trigger events when there are no other events are pending	1620	Idle watchers trigger events when no other events of the same or higher
1286	(prepare, check and other idle watchers do not count). That is, as long	1621	priority are pending (prepare, check and other idle watchers do not
1287	as your process is busy handling sockets or timeouts (or even signals,	1622	count).
1288	imagine) it will not be triggered. But when your process is idle all idle	1623
1289	watchers are being called again and again, once per event loop iteration -	1624	That is, as long as your process is busy handling sockets or timeouts
		1625	(or even signals, imagine) of the same or higher priority it will not be
		1626	triggered. But when your process is idle (or only lower-priority watchers
		1627	are pending), the idle watchers are being called once per event loop
1290	until stopped, that is, or your process receives more events and becomes	1628	iteration - until stopped, that is, or your process receives more events
1291	busy.	1629	and becomes busy again with higher priority stuff.
1292		1630
1293	The most noteworthy effect is that as long as any idle watchers are	1631	The most noteworthy effect is that as long as any idle watchers are
1294	active, the process will not block when waiting for new events.	1632	active, the process will not block when waiting for new events.
1295		1633
1296	Apart from keeping your process non-blocking (which is a useful	1634	Apart from keeping your process non-blocking (which is a useful
1297	effect on its own sometimes), idle watchers are a good place to do	1635	effect on its own sometimes), idle watchers are a good place to do
1298	"pseudo-background processing", or delay processing stuff to after the	1636	"pseudo-background processing", or delay processing stuff to after the
1299	event loop has handled all outstanding events.	1637	event loop has handled all outstanding events.
		1638
		1639	=head3 Watcher-Specific Functions and Data Members
1300		1640
1301	=over 4	1641	=over 4
1302		1642
1303	=item ev_idle_init (ev_signal *, callback)	1643	=item ev_idle_init (ev_signal *, callback)
1304		1644
…		…
1362	with priority higher than or equal to the event loop and one coroutine	1702	with priority higher than or equal to the event loop and one coroutine
1363	of lower priority, but only once, using idle watchers to keep the event	1703	of lower priority, but only once, using idle watchers to keep the event
1364	loop from blocking if lower-priority coroutines are active, thus mapping	1704	loop from blocking if lower-priority coroutines are active, thus mapping
1365	low-priority coroutines to idle/background tasks).	1705	low-priority coroutines to idle/background tasks).
1366		1706
		1707	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1708	priority, to ensure that they are being run before any other watchers
		1709	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1710	too) should not activate ("feed") events into libev. While libev fully
		1711	supports this, they will be called before other C<ev_check> watchers
		1712	did their job. As C<ev_check> watchers are often used to embed other
		1713	(non-libev) event loops those other event loops might be in an unusable
		1714	state until their C<ev_check> watcher ran (always remind yourself to
		1715	coexist peacefully with others).
		1716
		1717	=head3 Watcher-Specific Functions and Data Members
		1718
1367	=over 4	1719	=over 4
1368		1720
1369	=item ev_prepare_init (ev_prepare *, callback)	1721	=item ev_prepare_init (ev_prepare *, callback)
1370		1722
1371	=item ev_check_init (ev_check *, callback)	1723	=item ev_check_init (ev_check *, callback)
…		…
1374	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1726	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1375	macros, but using them is utterly, utterly and completely pointless.	1727	macros, but using them is utterly, utterly and completely pointless.
1376		1728
1377	=back	1729	=back
1378		1730
1379	Example: To include a library such as adns, you would add IO watchers	1731	There are a number of principal ways to embed other event loops or modules
1380	and a timeout watcher in a prepare handler, as required by libadns, and	1732	into libev. Here are some ideas on how to include libadns into libev
		1733	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1734	use for an actually working example. Another Perl module named C<EV::Glib>
		1735	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1736	into the Glib event loop).
		1737
		1738	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1381	in a check watcher, destroy them and call into libadns. What follows is	1739	and in a check watcher, destroy them and call into libadns. What follows
1382	pseudo-code only of course:	1740	is pseudo-code only of course. This requires you to either use a low
		1741	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1742	the callbacks for the IO/timeout watchers might not have been called yet.
1383		1743
1384	static ev_io iow [nfd];	1744	static ev_io iow [nfd];
1385	static ev_timer tw;	1745	static ev_timer tw;
1386		1746
1387	static void	1747	static void
1388	io_cb (ev_loop *loop, ev_io *w, int revents)	1748	io_cb (ev_loop *loop, ev_io *w, int revents)
1389	{	1749	{
1390	// set the relevant poll flags
1391	// could also call adns_processreadable etc. here
1392	struct pollfd *fd = (struct pollfd *)w->data;
1393	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1394	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1395	}	1750	}
1396		1751
1397	// create io watchers for each fd and a timer before blocking	1752	// create io watchers for each fd and a timer before blocking
1398	static void	1753	static void
1399	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1754	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1400	{	1755	{
1401	int timeout = 3600000;truct pollfd fds [nfd];	1756	int timeout = 3600000;
		1757	struct pollfd fds [nfd];
1402	// actual code will need to loop here and realloc etc.	1758	// actual code will need to loop here and realloc etc.
1403	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1759	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1404		1760
1405	/* the callback is illegal, but won't be called as we stop during check */	1761	/* the callback is illegal, but won't be called as we stop during check */
1406	ev_timer_init (&tw, 0, timeout * 1e-3);	1762	ev_timer_init (&tw, 0, timeout * 1e-3);
1407	ev_timer_start (loop, &tw);	1763	ev_timer_start (loop, &tw);
1408		1764
1409	// create on ev_io per pollfd	1765	// create one ev_io per pollfd
1410	for (int i = 0; i < nfd; ++i)	1766	for (int i = 0; i < nfd; ++i)
1411	{	1767	{
1412	ev_io_init (iow + i, io_cb, fds [i].fd,	1768	ev_io_init (iow + i, io_cb, fds [i].fd,
1413	((fds [i].events & POLLIN ? EV_READ : 0)	1769	((fds [i].events & POLLIN ? EV_READ : 0)
1414	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1770	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1415		1771
1416	fds [i].revents = 0;	1772	fds [i].revents = 0;
1417	iow [i].data = fds + i;
1418	ev_io_start (loop, iow + i);	1773	ev_io_start (loop, iow + i);
1419	}	1774	}
1420	}	1775	}
1421		1776
1422	// stop all watchers after blocking	1777	// stop all watchers after blocking
…		…
1424	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1779	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1425	{	1780	{
1426	ev_timer_stop (loop, &tw);	1781	ev_timer_stop (loop, &tw);
1427		1782
1428	for (int i = 0; i < nfd; ++i)	1783	for (int i = 0; i < nfd; ++i)
		1784	{
		1785	// set the relevant poll flags
		1786	// could also call adns_processreadable etc. here
		1787	struct pollfd *fd = fds + i;
		1788	int revents = ev_clear_pending (iow + i);
		1789	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1790	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1791
		1792	// now stop the watcher
1429	ev_io_stop (loop, iow + i);	1793	ev_io_stop (loop, iow + i);
		1794	}
1430		1795
1431	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1796	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1797	}
		1798
		1799	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1800	in the prepare watcher and would dispose of the check watcher.
		1801
		1802	Method 3: If the module to be embedded supports explicit event
		1803	notification (adns does), you can also make use of the actual watcher
		1804	callbacks, and only destroy/create the watchers in the prepare watcher.
		1805
		1806	static void
		1807	timer_cb (EV_P_ ev_timer *w, int revents)
		1808	{
		1809	adns_state ads = (adns_state)w->data;
		1810	update_now (EV_A);
		1811
		1812	adns_processtimeouts (ads, &tv_now);
		1813	}
		1814
		1815	static void
		1816	io_cb (EV_P_ ev_io *w, int revents)
		1817	{
		1818	adns_state ads = (adns_state)w->data;
		1819	update_now (EV_A);
		1820
		1821	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1822	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1823	}
		1824
		1825	// do not ever call adns_afterpoll
		1826
		1827	Method 4: Do not use a prepare or check watcher because the module you
		1828	want to embed is too inflexible to support it. Instead, youc na override
		1829	their poll function. The drawback with this solution is that the main
		1830	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1831	this.
		1832
		1833	static gint
		1834	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1835	{
		1836	int got_events = 0;
		1837
		1838	for (n = 0; n < nfds; ++n)
		1839	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1840
		1841	if (timeout >= 0)
		1842	// create/start timer
		1843
		1844	// poll
		1845	ev_loop (EV_A_ 0);
		1846
		1847	// stop timer again
		1848	if (timeout >= 0)
		1849	ev_timer_stop (EV_A_ &to);
		1850
		1851	// stop io watchers again - their callbacks should have set
		1852	for (n = 0; n < nfds; ++n)
		1853	ev_io_stop (EV_A_ iow [n]);
		1854
		1855	return got_events;
1432	}	1856	}
1433		1857
1434		1858
1435	=head2 C<ev_embed> - when one backend isn't enough...	1859	=head2 C<ev_embed> - when one backend isn't enough...
1436		1860
…		…
1500	ev_embed_start (loop_hi, &embed);	1924	ev_embed_start (loop_hi, &embed);
1501	}	1925	}
1502	else	1926	else
1503	loop_lo = loop_hi;	1927	loop_lo = loop_hi;
1504		1928
		1929	=head3 Watcher-Specific Functions and Data Members
		1930
1505	=over 4	1931	=over 4
1506		1932
1507	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	1933	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1508		1934
1509	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	1935	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1518		1944
1519	Make a single, non-blocking sweep over the embedded loop. This works	1945	Make a single, non-blocking sweep over the embedded loop. This works
1520	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1946	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1521	apropriate way for embedded loops.	1947	apropriate way for embedded loops.
1522		1948
1523	=item struct ev_loop *loop [read-only]	1949	=item struct ev_loop *other [read-only]
1524		1950
1525	The embedded event loop.	1951	The embedded event loop.
1526		1952
1527	=back	1953	=back
1528		1954
…		…
1535	event loop blocks next and before C<ev_check> watchers are being called,	1961	event loop blocks next and before C<ev_check> watchers are being called,
1536	and only in the child after the fork. If whoever good citizen calling	1962	and only in the child after the fork. If whoever good citizen calling
1537	C<ev_default_fork> cheats and calls it in the wrong process, the fork	1963	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1538	handlers will be invoked, too, of course.	1964	handlers will be invoked, too, of course.
1539		1965
		1966	=head3 Watcher-Specific Functions and Data Members
		1967
1540	=over 4	1968	=over 4
1541		1969
1542	=item ev_fork_init (ev_signal *, callback)	1970	=item ev_fork_init (ev_signal *, callback)
1543		1971
1544	Initialises and configures the fork watcher - it has no parameters of any	1972	Initialises and configures the fork watcher - it has no parameters of any
…		…
1640		2068
1641	To use it,	2069	To use it,
1642		2070
1643	#include <ev++.h>	2071	#include <ev++.h>
1644		2072
1645	(it is not installed by default). This automatically includes F<ev.h>	2073	This automatically includes F<ev.h> and puts all of its definitions (many
1646	and puts all of its definitions (many of them macros) into the global	2074	of them macros) into the global namespace. All C++ specific things are
1647	namespace. All C++ specific things are put into the C<ev> namespace.	2075	put into the C<ev> namespace. It should support all the same embedding
		2076	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1648		2077
1649	It should support all the same embedding options as F<ev.h>, most notably	2078	Care has been taken to keep the overhead low. The only data member the C++
1650	C<EV_MULTIPLICITY>.	2079	classes add (compared to plain C-style watchers) is the event loop pointer
		2080	that the watcher is associated with (or no additional members at all if
		2081	you disable C<EV_MULTIPLICITY> when embedding libev).
		2082
		2083	Currently, functions, and static and non-static member functions can be
		2084	used as callbacks. Other types should be easy to add as long as they only
		2085	need one additional pointer for context. If you need support for other
		2086	types of functors please contact the author (preferably after implementing
		2087	it).
1651		2088
1652	Here is a list of things available in the C<ev> namespace:	2089	Here is a list of things available in the C<ev> namespace:
1653		2090
1654	=over 4	2091	=over 4
1655		2092
…		…
1671		2108
1672	All of those classes have these methods:	2109	All of those classes have these methods:
1673		2110
1674	=over 4	2111	=over 4
1675		2112
1676	=item ev::TYPE::TYPE (object *, object::method *)	2113	=item ev::TYPE::TYPE ()
1677		2114
1678	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2115	=item ev::TYPE::TYPE (struct ev_loop *)
1679		2116
1680	=item ev::TYPE::~TYPE	2117	=item ev::TYPE::~TYPE
1681		2118
1682	The constructor takes a pointer to an object and a method pointer to	2119	The constructor (optionally) takes an event loop to associate the watcher
1683	the event handler callback to call in this class. The constructor calls	2120	with. If it is omitted, it will use C<EV_DEFAULT>.
1684	C<ev_init> for you, which means you have to call the C<set> method	2121
1685	before starting it. If you do not specify a loop then the constructor	2122	The constructor calls C<ev_init> for you, which means you have to call the
1686	automatically associates the default loop with this watcher.	2123	C<set> method before starting it.
		2124
		2125	It will not set a callback, however: You have to call the templated C<set>
		2126	method to set a callback before you can start the watcher.
		2127
		2128	(The reason why you have to use a method is a limitation in C++ which does
		2129	not allow explicit template arguments for constructors).
1687		2130
1688	The destructor automatically stops the watcher if it is active.	2131	The destructor automatically stops the watcher if it is active.
		2132
		2133	=item w->set<class, &class::method> (object *)
		2134
		2135	This method sets the callback method to call. The method has to have a
		2136	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2137	first argument and the C<revents> as second. The object must be given as
		2138	parameter and is stored in the C<data> member of the watcher.
		2139
		2140	This method synthesizes efficient thunking code to call your method from
		2141	the C callback that libev requires. If your compiler can inline your
		2142	callback (i.e. it is visible to it at the place of the C<set> call and
		2143	your compiler is good :), then the method will be fully inlined into the
		2144	thunking function, making it as fast as a direct C callback.
		2145
		2146	Example: simple class declaration and watcher initialisation
		2147
		2148	struct myclass
		2149	{
		2150	void io_cb (ev::io &w, int revents) { }
		2151	}
		2152
		2153	myclass obj;
		2154	ev::io iow;
		2155	iow.set <myclass, &myclass::io_cb> (&obj);
		2156
		2157	=item w->set<function> (void *data = 0)
		2158
		2159	Also sets a callback, but uses a static method or plain function as
		2160	callback. The optional C<data> argument will be stored in the watcher's
		2161	C<data> member and is free for you to use.
		2162
		2163	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2164
		2165	See the method-C<set> above for more details.
		2166
		2167	Example:
		2168
		2169	static void io_cb (ev::io &w, int revents) { }
		2170	iow.set <io_cb> ();
1689		2171
1690	=item w->set (struct ev_loop *)	2172	=item w->set (struct ev_loop *)
1691		2173
1692	Associates a different C<struct ev_loop> with this watcher. You can only	2174	Associates a different C<struct ev_loop> with this watcher. You can only
1693	do this when the watcher is inactive (and not pending either).	2175	do this when the watcher is inactive (and not pending either).
1694		2176
1695	=item w->set ([args])	2177	=item w->set ([args])
1696		2178
1697	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2179	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1698	called at least once. Unlike the C counterpart, an active watcher gets	2180	called at least once. Unlike the C counterpart, an active watcher gets
1699	automatically stopped and restarted.	2181	automatically stopped and restarted when reconfiguring it with this
		2182	method.
1700		2183
1701	=item w->start ()	2184	=item w->start ()
1702		2185
1703	Starts the watcher. Note that there is no C<loop> argument as the	2186	Starts the watcher. Note that there is no C<loop> argument, as the
1704	constructor already takes the loop.	2187	constructor already stores the event loop.
1705		2188
1706	=item w->stop ()	2189	=item w->stop ()
1707		2190
1708	Stops the watcher if it is active. Again, no C<loop> argument.	2191	Stops the watcher if it is active. Again, no C<loop> argument.
1709		2192
1710	=item w->again () C<ev::timer>, C<ev::periodic> only	2193	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1711		2194
1712	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2195	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1713	C<ev_TYPE_again> function.	2196	C<ev_TYPE_again> function.
1714		2197
1715	=item w->sweep () C<ev::embed> only	2198	=item w->sweep () (C<ev::embed> only)
1716		2199
1717	Invokes C<ev_embed_sweep>.	2200	Invokes C<ev_embed_sweep>.
1718		2201
1719	=item w->update () C<ev::stat> only	2202	=item w->update () (C<ev::stat> only)
1720		2203
1721	Invokes C<ev_stat_stat>.	2204	Invokes C<ev_stat_stat>.
1722		2205
1723	=back	2206	=back
1724		2207
…		…
1734		2217
1735	myclass ();	2218	myclass ();
1736	}	2219	}
1737		2220
1738	myclass::myclass (int fd)	2221	myclass::myclass (int fd)
1739	: io (this, &myclass::io_cb),
1740	idle (this, &myclass::idle_cb)
1741	{	2222	{
		2223	io .set <myclass, &myclass::io_cb > (this);
		2224	idle.set <myclass, &myclass::idle_cb> (this);
		2225
1742	io.start (fd, ev::READ);	2226	io.start (fd, ev::READ);
1743	}	2227	}
1744		2228
1745		2229
1746	=head1 MACRO MAGIC	2230	=head1 MACRO MAGIC
1747		2231
1748	Libev can be compiled with a variety of options, the most fundemantal is	2232	Libev can be compiled with a variety of options, the most fundamantal
1749	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2233	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1750	callbacks have an initial C<struct ev_loop *> argument.	2234	functions and callbacks have an initial C<struct ev_loop *> argument.
1751		2235
1752	To make it easier to write programs that cope with either variant, the	2236	To make it easier to write programs that cope with either variant, the
1753	following macros are defined:	2237	following macros are defined:
1754		2238
1755	=over 4	2239	=over 4
…		…
1787	Similar to the other two macros, this gives you the value of the default	2271	Similar to the other two macros, this gives you the value of the default
1788	loop, if multiple loops are supported ("ev loop default").	2272	loop, if multiple loops are supported ("ev loop default").
1789		2273
1790	=back	2274	=back
1791		2275
1792	Example: Declare and initialise a check watcher, working regardless of	2276	Example: Declare and initialise a check watcher, utilising the above
1793	wether multiple loops are supported or not.	2277	macros so it will work regardless of whether multiple loops are supported
		2278	or not.
1794		2279
1795	static void	2280	static void
1796	check_cb (EV_P_ ev_timer *w, int revents)	2281	check_cb (EV_P_ ev_timer *w, int revents)
1797	{	2282	{
1798	ev_check_stop (EV_A_ w);	2283	ev_check_stop (EV_A_ w);
…		…
1801	ev_check check;	2286	ev_check check;
1802	ev_check_init (&check, check_cb);	2287	ev_check_init (&check, check_cb);
1803	ev_check_start (EV_DEFAULT_ &check);	2288	ev_check_start (EV_DEFAULT_ &check);
1804	ev_loop (EV_DEFAULT_ 0);	2289	ev_loop (EV_DEFAULT_ 0);
1805		2290
1806
1807	=head1 EMBEDDING	2291	=head1 EMBEDDING
1808		2292
1809	Libev can (and often is) directly embedded into host	2293	Libev can (and often is) directly embedded into host
1810	applications. Examples of applications that embed it include the Deliantra	2294	applications. Examples of applications that embed it include the Deliantra
1811	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2295	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1812	and rxvt-unicode.	2296	and rxvt-unicode.
1813		2297
1814	The goal is to enable you to just copy the neecssary files into your	2298	The goal is to enable you to just copy the necessary files into your
1815	source directory without having to change even a single line in them, so	2299	source directory without having to change even a single line in them, so
1816	you can easily upgrade by simply copying (or having a checked-out copy of	2300	you can easily upgrade by simply copying (or having a checked-out copy of
1817	libev somewhere in your source tree).	2301	libev somewhere in your source tree).
1818		2302
1819	=head2 FILESETS	2303	=head2 FILESETS
…		…
1850	ev_vars.h	2334	ev_vars.h
1851	ev_wrap.h	2335	ev_wrap.h
1852		2336
1853	ev_win32.c required on win32 platforms only	2337	ev_win32.c required on win32 platforms only
1854		2338
1855	ev_select.c only when select backend is enabled (which is by default)	2339	ev_select.c only when select backend is enabled (which is enabled by default)
1856	ev_poll.c only when poll backend is enabled (disabled by default)	2340	ev_poll.c only when poll backend is enabled (disabled by default)
1857	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2341	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1858	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2342	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1859	ev_port.c only when the solaris port backend is enabled (disabled by default)	2343	ev_port.c only when the solaris port backend is enabled (disabled by default)
1860		2344
…		…
1909		2393
1910	If defined to be C<1>, libev will try to detect the availability of the	2394	If defined to be C<1>, libev will try to detect the availability of the
1911	monotonic clock option at both compiletime and runtime. Otherwise no use	2395	monotonic clock option at both compiletime and runtime. Otherwise no use
1912	of the monotonic clock option will be attempted. If you enable this, you	2396	of the monotonic clock option will be attempted. If you enable this, you
1913	usually have to link against librt or something similar. Enabling it when	2397	usually have to link against librt or something similar. Enabling it when
1914	the functionality isn't available is safe, though, althoguh you have	2398	the functionality isn't available is safe, though, although you have
1915	to make sure you link against any libraries where the C<clock_gettime>	2399	to make sure you link against any libraries where the C<clock_gettime>
1916	function is hiding in (often F<-lrt>).	2400	function is hiding in (often F<-lrt>).
1917		2401
1918	=item EV_USE_REALTIME	2402	=item EV_USE_REALTIME
1919		2403
1920	If defined to be C<1>, libev will try to detect the availability of the	2404	If defined to be C<1>, libev will try to detect the availability of the
1921	realtime clock option at compiletime (and assume its availability at	2405	realtime clock option at compiletime (and assume its availability at
1922	runtime if successful). Otherwise no use of the realtime clock option will	2406	runtime if successful). Otherwise no use of the realtime clock option will
1923	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2407	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1924	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2408	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1925	in the description of C<EV_USE_MONOTONIC>, though.	2409	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2410
		2411	=item EV_USE_NANOSLEEP
		2412
		2413	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2414	and will use it for delays. Otherwise it will use C<select ()>.
1926		2415
1927	=item EV_USE_SELECT	2416	=item EV_USE_SELECT
1928		2417
1929	If undefined or defined to be C<1>, libev will compile in support for the	2418	If undefined or defined to be C<1>, libev will compile in support for the
1930	C<select>(2) backend. No attempt at autodetection will be done: if no	2419	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1985		2474
1986	=item EV_USE_DEVPOLL	2475	=item EV_USE_DEVPOLL
1987		2476
1988	reserved for future expansion, works like the USE symbols above.	2477	reserved for future expansion, works like the USE symbols above.
1989		2478
		2479	=item EV_USE_INOTIFY
		2480
		2481	If defined to be C<1>, libev will compile in support for the Linux inotify
		2482	interface to speed up C<ev_stat> watchers. Its actual availability will
		2483	be detected at runtime.
		2484
1990	=item EV_H	2485	=item EV_H
1991		2486
1992	The name of the F<ev.h> header file used to include it. The default if	2487	The name of the F<ev.h> header file used to include it. The default if
1993	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2488	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
1994	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2489	can be used to virtually rename the F<ev.h> header file in case of conflicts.
…		…
2017	will have the C<struct ev_loop *> as first argument, and you can create	2512	will have the C<struct ev_loop *> as first argument, and you can create
2018	additional independent event loops. Otherwise there will be no support	2513	additional independent event loops. Otherwise there will be no support
2019	for multiple event loops and there is no first event loop pointer	2514	for multiple event loops and there is no first event loop pointer
2020	argument. Instead, all functions act on the single default loop.	2515	argument. Instead, all functions act on the single default loop.
2021		2516
		2517	=item EV_MINPRI
		2518
		2519	=item EV_MAXPRI
		2520
		2521	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2522	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2523	provide for more priorities by overriding those symbols (usually defined
		2524	to be C<-2> and C<2>, respectively).
		2525
		2526	When doing priority-based operations, libev usually has to linearly search
		2527	all the priorities, so having many of them (hundreds) uses a lot of space
		2528	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2529	fine.
		2530
		2531	If your embedding app does not need any priorities, defining these both to
		2532	C<0> will save some memory and cpu.
		2533
2022	=item EV_PERIODIC_ENABLE	2534	=item EV_PERIODIC_ENABLE
2023		2535
2024	If undefined or defined to be C<1>, then periodic timers are supported. If	2536	If undefined or defined to be C<1>, then periodic timers are supported. If
2025	defined to be C<0>, then they are not. Disabling them saves a few kB of	2537	defined to be C<0>, then they are not. Disabling them saves a few kB of
2026	code.	2538	code.
2027		2539
		2540	=item EV_IDLE_ENABLE
		2541
		2542	If undefined or defined to be C<1>, then idle watchers are supported. If
		2543	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2544	code.
		2545
2028	=item EV_EMBED_ENABLE	2546	=item EV_EMBED_ENABLE
2029		2547
2030	If undefined or defined to be C<1>, then embed watchers are supported. If	2548	If undefined or defined to be C<1>, then embed watchers are supported. If
2031	defined to be C<0>, then they are not.	2549	defined to be C<0>, then they are not.
2032		2550
…		…
2049	=item EV_PID_HASHSIZE	2567	=item EV_PID_HASHSIZE
2050		2568
2051	C<ev_child> watchers use a small hash table to distribute workload by	2569	C<ev_child> watchers use a small hash table to distribute workload by
2052	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	2570	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2053	than enough. If you need to manage thousands of children you might want to	2571	than enough. If you need to manage thousands of children you might want to
2054	increase this value.	2572	increase this value (I<must> be a power of two).
		2573
		2574	=item EV_INOTIFY_HASHSIZE
		2575
		2576	C<ev_stat> watchers use a small hash table to distribute workload by
		2577	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2578	usually more than enough. If you need to manage thousands of C<ev_stat>
		2579	watchers you might want to increase this value (I<must> be a power of
		2580	two).
2055		2581
2056	=item EV_COMMON	2582	=item EV_COMMON
2057		2583
2058	By default, all watchers have a C<void *data> member. By redefining	2584	By default, all watchers have a C<void *data> member. By redefining
2059	this macro to a something else you can include more and other types of	2585	this macro to a something else you can include more and other types of
…		…
2072		2598
2073	=item ev_set_cb (ev, cb)	2599	=item ev_set_cb (ev, cb)
2074		2600
2075	Can be used to change the callback member declaration in each watcher,	2601	Can be used to change the callback member declaration in each watcher,
2076	and the way callbacks are invoked and set. Must expand to a struct member	2602	and the way callbacks are invoked and set. Must expand to a struct member
2077	definition and a statement, respectively. See the F<ev.v> header file for	2603	definition and a statement, respectively. See the F<ev.h> header file for
2078	their default definitions. One possible use for overriding these is to	2604	their default definitions. One possible use for overriding these is to
2079	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2605	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2080	method calls instead of plain function calls in C++.	2606	method calls instead of plain function calls in C++.
		2607
		2608	=head2 EXPORTED API SYMBOLS
		2609
		2610	If you need to re-export the API (e.g. via a dll) and you need a list of
		2611	exported symbols, you can use the provided F<Symbol.*> files which list
		2612	all public symbols, one per line:
		2613
		2614	Symbols.ev for libev proper
		2615	Symbols.event for the libevent emulation
		2616
		2617	This can also be used to rename all public symbols to avoid clashes with
		2618	multiple versions of libev linked together (which is obviously bad in
		2619	itself, but sometimes it is inconvinient to avoid this).
		2620
		2621	A sed command like this will create wrapper C<#define>'s that you need to
		2622	include before including F<ev.h>:
		2623
		2624	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2625
		2626	This would create a file F<wrap.h> which essentially looks like this:
		2627
		2628	#define ev_backend myprefix_ev_backend
		2629	#define ev_check_start myprefix_ev_check_start
		2630	#define ev_check_stop myprefix_ev_check_stop
		2631	...
2081		2632
2082	=head2 EXAMPLES	2633	=head2 EXAMPLES
2083		2634
2084	For a real-world example of a program the includes libev	2635	For a real-world example of a program the includes libev
2085	verbatim, you can have a look at the EV perl module	2636	verbatim, you can have a look at the EV perl module
…		…
2088	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2639	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2089	will be compiled. It is pretty complex because it provides its own header	2640	will be compiled. It is pretty complex because it provides its own header
2090	file.	2641	file.
2091		2642
2092	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2643	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2093	that everybody includes and which overrides some autoconf choices:	2644	that everybody includes and which overrides some configure choices:
2094		2645
		2646	#define EV_MINIMAL 1
2095	#define EV_USE_POLL 0	2647	#define EV_USE_POLL 0
2096	#define EV_MULTIPLICITY 0	2648	#define EV_MULTIPLICITY 0
2097	#define EV_PERIODICS 0	2649	#define EV_PERIODIC_ENABLE 0
		2650	#define EV_STAT_ENABLE 0
		2651	#define EV_FORK_ENABLE 0
2098	#define EV_CONFIG_H <config.h>	2652	#define EV_CONFIG_H <config.h>
		2653	#define EV_MINPRI 0
		2654	#define EV_MAXPRI 0
2099		2655
2100	#include "ev++.h"	2656	#include "ev++.h"
2101		2657
2102	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2658	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2103		2659
…		…
2109		2665
2110	In this section the complexities of (many of) the algorithms used inside	2666	In this section the complexities of (many of) the algorithms used inside
2111	libev will be explained. For complexity discussions about backends see the	2667	libev will be explained. For complexity discussions about backends see the
2112	documentation for C<ev_default_init>.	2668	documentation for C<ev_default_init>.
2113		2669
		2670	All of the following are about amortised time: If an array needs to be
		2671	extended, libev needs to realloc and move the whole array, but this
		2672	happens asymptotically never with higher number of elements, so O(1) might
		2673	mean it might do a lengthy realloc operation in rare cases, but on average
		2674	it is much faster and asymptotically approaches constant time.
		2675
2114	=over 4	2676	=over 4
2115		2677
2116	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2678	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2117		2679
		2680	This means that, when you have a watcher that triggers in one hour and
		2681	there are 100 watchers that would trigger before that then inserting will
		2682	have to skip roughly seven (C<ld 100>) of these watchers.
		2683
2118	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2684	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2685
		2686	That means that changing a timer costs less than removing/adding them
		2687	as only the relative motion in the event queue has to be paid for.
2119		2688
2120	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2689	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2121		2690
		2691	These just add the watcher into an array or at the head of a list.
		2692
2122	=item Stopping check/prepare/idle watchers: O(1)	2693	=item Stopping check/prepare/idle watchers: O(1)
2123		2694
2124	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2695	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2125		2696
		2697	These watchers are stored in lists then need to be walked to find the
		2698	correct watcher to remove. The lists are usually short (you don't usually
		2699	have many watchers waiting for the same fd or signal).
		2700
2126	=item Finding the next timer per loop iteration: O(1)	2701	=item Finding the next timer in each loop iteration: O(1)
		2702
		2703	By virtue of using a binary heap, the next timer is always found at the
		2704	beginning of the storage array.
2127		2705
2128	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2706	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2129		2707
2130	=item Activating one watcher: O(1)	2708	A change means an I/O watcher gets started or stopped, which requires
		2709	libev to recalculate its status (and possibly tell the kernel, depending
		2710	on backend and wether C<ev_io_set> was used).
		2711
		2712	=item Activating one watcher (putting it into the pending state): O(1)
		2713
		2714	=item Priority handling: O(number_of_priorities)
		2715
		2716	Priorities are implemented by allocating some space for each
		2717	priority. When doing priority-based operations, libev usually has to
		2718	linearly search all the priorities, but starting/stopping and activating
		2719	watchers becomes O(1) w.r.t. prioritiy handling.
2131		2720
2132	=back	2721	=back
2133		2722
2134		2723
2135	=head1 AUTHOR	2724	=head1 AUTHOR

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