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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;
…		…
53	The newest version of this document is also available as a html-formatted	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	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>.	55	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		56
57	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
58	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
59	these event sources and provide your program with events.	59	these event sources and provide your program with events.
60		60
61	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
62	(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
63	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
65	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
66	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
67	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
68	watcher.	68	watcher.
69		69
70	=head1 FEATURES	70	=head2 FEATURES
71		71
72	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
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	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	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		82
83	It also is quite fast (see this	83	It also is quite fast (see this
84	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
85	for example).	85	for example).
86		86
87	=head1 CONVENTIONS	87	=head2 CONVENTIONS
88		88
89	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
90	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
91	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
92	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
93	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>
94	(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.
95		95
96	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
97		97
98	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	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
101	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
102	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
103	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.
104		106
105	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
106		108
107	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
108	library in any way.	110	library in any way.
…		…
113		115
114	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
115	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
116	you actually want to know.	118	you actually want to know.
117		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
118	=item int ev_version_major ()	126	=item int ev_version_major ()
119		127
120	=item int ev_version_minor ()	128	=item int ev_version_minor ()
121		129
122	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
123	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
124	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
125	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
126	version of the library your program was compiled against.	134	version of the library your program was compiled against.
127		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
128	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,
129	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
130	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
131	not a problem.	142	not a problem.
132		143
133	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
134	version.	145	version.
…		…
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		307
297	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
298	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,
299	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
300	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
301	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.
302		320
303	=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)
304		322
305	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
306	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
307	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
308	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.
309		329
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		331
312	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,
313	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
314	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),
315	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.
316		339
317	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
318	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
319	(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
320	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
321	well if you register events for both fds.	344	very well if you register events for both fds.
322		345
323	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
324	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
325	(or space) is available.	348	(or space) is available.
326		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
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		358
329	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
330	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
331	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
332	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
333	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
334	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.
335		370
336	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
337	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
338	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
339	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
340	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.
341		386
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		388
344	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.
345		393
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		395
348	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,
349	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)).
350		398
351	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
352	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
353	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.
354		407
355	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
356		409
357	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
358	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
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
360		415
361	=back	416	=back
362		417
363	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
364	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
…		…
399	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
400	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
401	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
402	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
403	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
404	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
405	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>).
406		470
407	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
408		472
409	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
410	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
455		519
456	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
457	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
458	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
459	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
460	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
461		525
462	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
463		527
464	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
465	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
…		…
486	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
487	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
488		552
489	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
490		554
491	* If there are no active watchers (reference count is zero), return.	555	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	556	* If EVFLAG_FORKCHECK was used, check for a fork.
		557	- If a fork was detected, queue and call all fork watchers.
		558	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	559	- If we have been forked, recreate the kernel state.
494	- Update the kernel state with all outstanding changes.	560	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	561	- Update the "event loop time".
496	- Calculate for how long to block.	562	- Calculate for how long to sleep or block, if at all
		563	(active idle watchers, EVLOOP_NONBLOCK or not having
		564	any active watchers at all will result in not sleeping).
		565	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	566	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	567	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	568	- Update the "event loop time" and do time jump handling.
500	- Queue all outstanding timers.	569	- Queue all outstanding timers.
501	- Queue all outstanding periodics.	570	- Queue all outstanding periodics.
502	- If no events are pending now, queue all idle watchers.	571	- If no events are pending now, queue all idle watchers.
503	- Queue all check watchers.	572	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	573	- Call all queued watchers in reverse order (i.e. check watchers first).
505	Signals and child watchers are implemented as I/O watchers, and will	574	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	575	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	576	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	577	were used, or there are no active watchers, return, otherwise
		578	continue with step *.
509		579
510	Example: Queue some jobs and then loop until no events are outsanding	580	Example: Queue some jobs and then loop until no events are outsanding
511	anymore.	581	anymore.
512		582
513	... queue jobs here, make sure they register event watchers as long	583	... queue jobs here, make sure they register event watchers as long
…		…
548	Example: For some weird reason, unregister the above signal handler again.	618	Example: For some weird reason, unregister the above signal handler again.
549		619
550	ev_ref (loop);	620	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	621	ev_signal_stop (loop, &exitsig);
552		622
		623	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		624
		625	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		626
		627	These advanced functions influence the time that libev will spend waiting
		628	for events. Both are by default C<0>, meaning that libev will try to
		629	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		630
		631	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		632	allows libev to delay invocation of I/O and timer/periodic callbacks to
		633	increase efficiency of loop iterations.
		634
		635	The background is that sometimes your program runs just fast enough to
		636	handle one (or very few) event(s) per loop iteration. While this makes
		637	the program responsive, it also wastes a lot of CPU time to poll for new
		638	events, especially with backends like C<select ()> which have a high
		639	overhead for the actual polling but can deliver many events at once.
		640
		641	By setting a higher I<io collect interval> you allow libev to spend more
		642	time collecting I/O events, so you can handle more events per iteration,
		643	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		644	C<ev_timer>) will be not affected. Setting this to a non-null value will
		645	introduce an additional C<ev_sleep ()> call into most loop iterations.
		646
		647	Likewise, by setting a higher I<timeout collect interval> you allow libev
		648	to spend more time collecting timeouts, at the expense of increased
		649	latency (the watcher callback will be called later). C<ev_io> watchers
		650	will not be affected. Setting this to a non-null value will not introduce
		651	any overhead in libev.
		652
		653	Many (busy) programs can usually benefit by setting the io collect
		654	interval to a value near C<0.1> or so, which is often enough for
		655	interactive servers (of course not for games), likewise for timeouts. It
		656	usually doesn't make much sense to set it to a lower value than C<0.01>,
		657	as this approsaches the timing granularity of most systems.
		658
553	=back	659	=back
554		660
555		661
556	=head1 ANATOMY OF A WATCHER	662	=head1 ANATOMY OF A WATCHER
557		663
…		…
736	=item bool ev_is_pending (ev_TYPE *watcher)	842	=item bool ev_is_pending (ev_TYPE *watcher)
737		843
738	Returns a true value iff the watcher is pending, (i.e. it has outstanding	844	Returns a true value iff the watcher is pending, (i.e. it has outstanding
739	events but its callback has not yet been invoked). As long as a watcher	845	events but its callback has not yet been invoked). As long as a watcher
740	is pending (but not active) you must not call an init function on it (but	846	is pending (but not active) you must not call an init function on it (but
741	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	847	C<ev_TYPE_set> is safe), you must not change its priority, and you must
742	libev (e.g. you cnanot C<free ()> it).	848	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		849	it).
743		850
744	=item callback ev_cb (ev_TYPE *watcher)	851	=item callback ev_cb (ev_TYPE *watcher)
745		852
746	Returns the callback currently set on the watcher.	853	Returns the callback currently set on the watcher.
747		854
…		…
766	watchers on the same event and make sure one is called first.	873	watchers on the same event and make sure one is called first.
767		874
768	If you need to suppress invocation when higher priority events are pending	875	If you need to suppress invocation when higher priority events are pending
769	you need to look at C<ev_idle> watchers, which provide this functionality.	876	you need to look at C<ev_idle> watchers, which provide this functionality.
770		877
		878	You I<must not> change the priority of a watcher as long as it is active or
		879	pending.
		880
771	The default priority used by watchers when no priority has been set is	881	The default priority used by watchers when no priority has been set is
772	always C<0>, which is supposed to not be too high and not be too low :).	882	always C<0>, which is supposed to not be too high and not be too low :).
773		883
774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	884	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
775	fine, as long as you do not mind that the priority value you query might	885	fine, as long as you do not mind that the priority value you query might
776	or might not have been adjusted to be within valid range.	886	or might not have been adjusted to be within valid range.
		887
		888	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		889
		890	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		891	C<loop> nor C<revents> need to be valid as long as the watcher callback
		892	can deal with that fact.
		893
		894	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		895
		896	If the watcher is pending, this function returns clears its pending status
		897	and returns its C<revents> bitset (as if its callback was invoked). If the
		898	watcher isn't pending it does nothing and returns C<0>.
777		899
778	=back	900	=back
779		901
780		902
781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	903	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
866	In general you can register as many read and/or write event watchers per	988	In general you can register as many read and/or write event watchers per
867	fd as you want (as long as you don't confuse yourself). Setting all file	989	fd as you want (as long as you don't confuse yourself). Setting all file
868	descriptors to non-blocking mode is also usually a good idea (but not	990	descriptors to non-blocking mode is also usually a good idea (but not
869	required if you know what you are doing).	991	required if you know what you are doing).
870		992
871	You have to be careful with dup'ed file descriptors, though. Some backends
872	(the linux epoll backend is a notable example) cannot handle dup'ed file
873	descriptors correctly if you register interest in two or more fds pointing
874	to the same underlying file/socket/etc. description (that is, they share
875	the same underlying "file open").
876
877	If you must do this, then force the use of a known-to-be-good backend	993	If you must do this, then force the use of a known-to-be-good backend
878	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	994	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
879	C<EVBACKEND_POLL>).	995	C<EVBACKEND_POLL>).
880		996
881	Another thing you have to watch out for is that it is quite easy to	997	Another thing you have to watch out for is that it is quite easy to
…		…
891	play around with an Xlib connection), then you have to seperately re-test	1007	play around with an Xlib connection), then you have to seperately re-test
892	whether a file descriptor is really ready with a known-to-be good interface	1008	whether a file descriptor is really ready with a known-to-be good interface
893	such as poll (fortunately in our Xlib example, Xlib already does this on	1009	such as poll (fortunately in our Xlib example, Xlib already does this on
894	its own, so its quite safe to use).	1010	its own, so its quite safe to use).
895		1011
		1012	=head3 The special problem of disappearing file descriptors
		1013
		1014	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1015	descriptor (either by calling C<close> explicitly or by any other means,
		1016	such as C<dup>). The reason is that you register interest in some file
		1017	descriptor, but when it goes away, the operating system will silently drop
		1018	this interest. If another file descriptor with the same number then is
		1019	registered with libev, there is no efficient way to see that this is, in
		1020	fact, a different file descriptor.
		1021
		1022	To avoid having to explicitly tell libev about such cases, libev follows
		1023	the following policy: Each time C<ev_io_set> is being called, libev
		1024	will assume that this is potentially a new file descriptor, otherwise
		1025	it is assumed that the file descriptor stays the same. That means that
		1026	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1027	descriptor even if the file descriptor number itself did not change.
		1028
		1029	This is how one would do it normally anyway, the important point is that
		1030	the libev application should not optimise around libev but should leave
		1031	optimisations to libev.
		1032
		1033	=head3 The special problem of dup'ed file descriptors
		1034
		1035	Some backends (e.g. epoll), cannot register events for file descriptors,
		1036	but only events for the underlying file descriptions. That means when you
		1037	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1038	events for them, only one file descriptor might actually receive events.
		1039
		1040	There is no workaround possible except not registering events
		1041	for potentially C<dup ()>'ed file descriptors, or to resort to
		1042	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1043
		1044	=head3 The special problem of fork
		1045
		1046	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1047	useless behaviour. Libev fully supports fork, but needs to be told about
		1048	it in the child.
		1049
		1050	To support fork in your programs, you either have to call
		1051	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1052	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1053	C<EVBACKEND_POLL>.
		1054
		1055
		1056	=head3 Watcher-Specific Functions
		1057
896	=over 4	1058	=over 4
897		1059
898	=item ev_io_init (ev_io *, callback, int fd, int events)	1060	=item ev_io_init (ev_io *, callback, int fd, int events)
899		1061
900	=item ev_io_set (ev_io *, int fd, int events)	1062	=item ev_io_set (ev_io *, int fd, int events)
…		…
910	=item int events [read-only]	1072	=item int events [read-only]
911		1073
912	The events being watched.	1074	The events being watched.
913		1075
914	=back	1076	=back
		1077
		1078	=head3 Examples
915		1079
916	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1080	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
917	readable, but only once. Since it is likely line-buffered, you could	1081	readable, but only once. Since it is likely line-buffered, you could
918	attempt to read a whole line in the callback.	1082	attempt to read a whole line in the callback.
919		1083
…		…
952	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1116	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
953		1117
954	The callback is guarenteed to be invoked only when its timeout has passed,	1118	The callback is guarenteed to be invoked only when its timeout has passed,
955	but if multiple timers become ready during the same loop iteration then	1119	but if multiple timers become ready during the same loop iteration then
956	order of execution is undefined.	1120	order of execution is undefined.
		1121
		1122	=head3 Watcher-Specific Functions and Data Members
957		1123
958	=over 4	1124	=over 4
959		1125
960	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1126	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
961		1127
…		…
1015	or C<ev_timer_again> is called and determines the next timeout (if any),	1181	or C<ev_timer_again> is called and determines the next timeout (if any),
1016	which is also when any modifications are taken into account.	1182	which is also when any modifications are taken into account.
1017		1183
1018	=back	1184	=back
1019		1185
		1186	=head3 Examples
		1187
1020	Example: Create a timer that fires after 60 seconds.	1188	Example: Create a timer that fires after 60 seconds.
1021		1189
1022	static void	1190	static void
1023	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1191	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1024	{	1192	{
…		…
1057	but on wallclock time (absolute time). You can tell a periodic watcher	1225	but on wallclock time (absolute time). You can tell a periodic watcher
1058	to trigger "at" some specific point in time. For example, if you tell a	1226	to trigger "at" some specific point in time. For example, if you tell a
1059	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1227	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1060	+ 10.>) and then reset your system clock to the last year, then it will	1228	+ 10.>) and then reset your system clock to the last year, then it will
1061	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1229	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1062	roughly 10 seconds later and of course not if you reset your system time	1230	roughly 10 seconds later).
1063	again).
1064		1231
1065	They can also be used to implement vastly more complex timers, such as	1232	They can also be used to implement vastly more complex timers, such as
1066	triggering an event on eahc midnight, local time.	1233	triggering an event on each midnight, local time or other, complicated,
		1234	rules.
1067		1235
1068	As with timers, the callback is guarenteed to be invoked only when the	1236	As with timers, the callback is guarenteed to be invoked only when the
1069	time (C<at>) has been passed, but if multiple periodic timers become ready	1237	time (C<at>) has been passed, but if multiple periodic timers become ready
1070	during the same loop iteration then order of execution is undefined.	1238	during the same loop iteration then order of execution is undefined.
1071		1239
		1240	=head3 Watcher-Specific Functions and Data Members
		1241
1072	=over 4	1242	=over 4
1073		1243
1074	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1244	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1075		1245
1076	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1246	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1078	Lots of arguments, lets sort it out... There are basically three modes of	1248	Lots of arguments, lets sort it out... There are basically three modes of
1079	operation, and we will explain them from simplest to complex:	1249	operation, and we will explain them from simplest to complex:
1080		1250
1081	=over 4	1251	=over 4
1082		1252
1083	=item * absolute timer (interval = reschedule_cb = 0)	1253	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1084		1254
1085	In this configuration the watcher triggers an event at the wallclock time	1255	In this configuration the watcher triggers an event at the wallclock time
1086	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1256	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1087	that is, if it is to be run at January 1st 2011 then it will run when the	1257	that is, if it is to be run at January 1st 2011 then it will run when the
1088	system time reaches or surpasses this time.	1258	system time reaches or surpasses this time.
1089		1259
1090	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1260	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1091		1261
1092	In this mode the watcher will always be scheduled to time out at the next	1262	In this mode the watcher will always be scheduled to time out at the next
1093	C<at + N * interval> time (for some integer N) and then repeat, regardless	1263	C<at + N * interval> time (for some integer N, which can also be negative)
1094	of any time jumps.	1264	and then repeat, regardless of any time jumps.
1095		1265
1096	This can be used to create timers that do not drift with respect to system	1266	This can be used to create timers that do not drift with respect to system
1097	time:	1267	time:
1098		1268
1099	ev_periodic_set (&periodic, 0., 3600., 0);	1269	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1105		1275
1106	Another way to think about it (for the mathematically inclined) is that	1276	Another way to think about it (for the mathematically inclined) is that
1107	C<ev_periodic> will try to run the callback in this mode at the next possible	1277	C<ev_periodic> will try to run the callback in this mode at the next possible
1108	time where C<time = at (mod interval)>, regardless of any time jumps.	1278	time where C<time = at (mod interval)>, regardless of any time jumps.
1109		1279
		1280	For numerical stability it is preferable that the C<at> value is near
		1281	C<ev_now ()> (the current time), but there is no range requirement for
		1282	this value.
		1283
1110	=item * manual reschedule mode (reschedule_cb = callback)	1284	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1111		1285
1112	In this mode the values for C<interval> and C<at> are both being	1286	In this mode the values for C<interval> and C<at> are both being
1113	ignored. Instead, each time the periodic watcher gets scheduled, the	1287	ignored. Instead, each time the periodic watcher gets scheduled, the
1114	reschedule callback will be called with the watcher as first, and the	1288	reschedule callback will be called with the watcher as first, and the
1115	current time as second argument.	1289	current time as second argument.
1116		1290
1117	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1291	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1118	ever, or make any event loop modifications>. If you need to stop it,	1292	ever, or make any event loop modifications>. If you need to stop it,
1119	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1293	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1120	starting a prepare watcher).	1294	starting an C<ev_prepare> watcher, which is legal).
1121		1295
1122	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1296	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1123	ev_tstamp now)>, e.g.:	1297	ev_tstamp now)>, e.g.:
1124		1298
1125	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1299	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1148	Simply stops and restarts the periodic watcher again. This is only useful	1322	Simply stops and restarts the periodic watcher again. This is only useful
1149	when you changed some parameters or the reschedule callback would return	1323	when you changed some parameters or the reschedule callback would return
1150	a different time than the last time it was called (e.g. in a crond like	1324	a different time than the last time it was called (e.g. in a crond like
1151	program when the crontabs have changed).	1325	program when the crontabs have changed).
1152		1326
		1327	=item ev_tstamp offset [read-write]
		1328
		1329	When repeating, this contains the offset value, otherwise this is the
		1330	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1331
		1332	Can be modified any time, but changes only take effect when the periodic
		1333	timer fires or C<ev_periodic_again> is being called.
		1334
1153	=item ev_tstamp interval [read-write]	1335	=item ev_tstamp interval [read-write]
1154		1336
1155	The current interval value. Can be modified any time, but changes only	1337	The current interval value. Can be modified any time, but changes only
1156	take effect when the periodic timer fires or C<ev_periodic_again> is being	1338	take effect when the periodic timer fires or C<ev_periodic_again> is being
1157	called.	1339	called.
…		…
1160		1342
1161	The current reschedule callback, or C<0>, if this functionality is	1343	The current reschedule callback, or C<0>, if this functionality is
1162	switched off. Can be changed any time, but changes only take effect when	1344	switched off. Can be changed any time, but changes only take effect when
1163	the periodic timer fires or C<ev_periodic_again> is being called.	1345	the periodic timer fires or C<ev_periodic_again> is being called.
1164		1346
		1347	=item ev_tstamp at [read-only]
		1348
		1349	When active, contains the absolute time that the watcher is supposed to
		1350	trigger next.
		1351
1165	=back	1352	=back
		1353
		1354	=head3 Examples
1166		1355
1167	Example: Call a callback every hour, or, more precisely, whenever the	1356	Example: Call a callback every hour, or, more precisely, whenever the
1168	system clock is divisible by 3600. The callback invocation times have	1357	system clock is divisible by 3600. The callback invocation times have
1169	potentially a lot of jittering, but good long-term stability.	1358	potentially a lot of jittering, but good long-term stability.
1170		1359
…		…
1210	with the kernel (thus it coexists with your own signal handlers as long	1399	with the kernel (thus it coexists with your own signal handlers as long
1211	as you don't register any with libev). Similarly, when the last signal	1400	as you don't register any with libev). Similarly, when the last signal
1212	watcher for a signal is stopped libev will reset the signal handler to	1401	watcher for a signal is stopped libev will reset the signal handler to
1213	SIG_DFL (regardless of what it was set to before).	1402	SIG_DFL (regardless of what it was set to before).
1214		1403
		1404	=head3 Watcher-Specific Functions and Data Members
		1405
1215	=over 4	1406	=over 4
1216		1407
1217	=item ev_signal_init (ev_signal *, callback, int signum)	1408	=item ev_signal_init (ev_signal *, callback, int signum)
1218		1409
1219	=item ev_signal_set (ev_signal *, int signum)	1410	=item ev_signal_set (ev_signal *, int signum)
…		…
1230		1421
1231	=head2 C<ev_child> - watch out for process status changes	1422	=head2 C<ev_child> - watch out for process status changes
1232		1423
1233	Child watchers trigger when your process receives a SIGCHLD in response to	1424	Child watchers trigger when your process receives a SIGCHLD in response to
1234	some child status changes (most typically when a child of yours dies).	1425	some child status changes (most typically when a child of yours dies).
		1426
		1427	=head3 Watcher-Specific Functions and Data Members
1235		1428
1236	=over 4	1429	=over 4
1237		1430
1238	=item ev_child_init (ev_child *, callback, int pid)	1431	=item ev_child_init (ev_child *, callback, int pid)
1239		1432
…		…
1258		1451
1259	The process exit/trace status caused by C<rpid> (see your systems	1452	The process exit/trace status caused by C<rpid> (see your systems
1260	C<waitpid> and C<sys/wait.h> documentation for details).	1453	C<waitpid> and C<sys/wait.h> documentation for details).
1261		1454
1262	=back	1455	=back
		1456
		1457	=head3 Examples
1263		1458
1264	Example: Try to exit cleanly on SIGINT and SIGTERM.	1459	Example: Try to exit cleanly on SIGINT and SIGTERM.
1265		1460
1266	static void	1461	static void
1267	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1462	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
…		…
1308	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1503	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1309	to fall back to regular polling again even with inotify, but changes are	1504	to fall back to regular polling again even with inotify, but changes are
1310	usually detected immediately, and if the file exists there will be no	1505	usually detected immediately, and if the file exists there will be no
1311	polling.	1506	polling.
1312		1507
		1508	=head3 Inotify
		1509
		1510	When C<inotify (7)> support has been compiled into libev (generally only
		1511	available on Linux) and present at runtime, it will be used to speed up
		1512	change detection where possible. The inotify descriptor will be created lazily
		1513	when the first C<ev_stat> watcher is being started.
		1514
		1515	Inotify presense does not change the semantics of C<ev_stat> watchers
		1516	except that changes might be detected earlier, and in some cases, to avoid
		1517	making regular C<stat> calls. Even in the presense of inotify support
		1518	there are many cases where libev has to resort to regular C<stat> polling.
		1519
		1520	(There is no support for kqueue, as apparently it cannot be used to
		1521	implement this functionality, due to the requirement of having a file
		1522	descriptor open on the object at all times).
		1523
		1524	=head3 The special problem of stat time resolution
		1525
		1526	The C<stat ()> syscall only supports full-second resolution portably, and
		1527	even on systems where the resolution is higher, many filesystems still
		1528	only support whole seconds.
		1529
		1530	That means that, if the time is the only thing that changes, you might
		1531	miss updates: on the first update, C<ev_stat> detects a change and calls
		1532	your callback, which does something. When there is another update within
		1533	the same second, C<ev_stat> will be unable to detect it.
		1534
		1535	The solution to this is to delay acting on a change for a second (or till
		1536	the next second boundary), using a roughly one-second delay C<ev_timer>
		1537	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1538	is added to work around small timing inconsistencies of some operating
		1539	systems.
		1540
		1541	=head3 Watcher-Specific Functions and Data Members
		1542
1313	=over 4	1543	=over 4
1314		1544
1315	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1545	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1316		1546
1317	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1547	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1352	=item const char *path [read-only]	1582	=item const char *path [read-only]
1353		1583
1354	The filesystem path that is being watched.	1584	The filesystem path that is being watched.
1355		1585
1356	=back	1586	=back
		1587
		1588	=head3 Examples
1357		1589
1358	Example: Watch C</etc/passwd> for attribute changes.	1590	Example: Watch C</etc/passwd> for attribute changes.
1359		1591
1360	static void	1592	static void
1361	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1593	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1374	}	1606	}
1375		1607
1376	...	1608	...
1377	ev_stat passwd;	1609	ev_stat passwd;
1378		1610
1379	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1611	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1380	ev_stat_start (loop, &passwd);	1612	ev_stat_start (loop, &passwd);
		1613
		1614	Example: Like above, but additionally use a one-second delay so we do not
		1615	miss updates (however, frequent updates will delay processing, too, so
		1616	one might do the work both on C<ev_stat> callback invocation I<and> on
		1617	C<ev_timer> callback invocation).
		1618
		1619	static ev_stat passwd;
		1620	static ev_timer timer;
		1621
		1622	static void
		1623	timer_cb (EV_P_ ev_timer *w, int revents)
		1624	{
		1625	ev_timer_stop (EV_A_ w);
		1626
		1627	/* now it's one second after the most recent passwd change */
		1628	}
		1629
		1630	static void
		1631	stat_cb (EV_P_ ev_stat *w, int revents)
		1632	{
		1633	/* reset the one-second timer */
		1634	ev_timer_again (EV_A_ &timer);
		1635	}
		1636
		1637	...
		1638	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1639	ev_stat_start (loop, &passwd);
		1640	ev_timer_init (&timer, timer_cb, 0., 1.01);
1381		1641
1382		1642
1383	=head2 C<ev_idle> - when you've got nothing better to do...	1643	=head2 C<ev_idle> - when you've got nothing better to do...
1384		1644
1385	Idle watchers trigger events when no other events of the same or higher	1645	Idle watchers trigger events when no other events of the same or higher
…		…
1399	Apart from keeping your process non-blocking (which is a useful	1659	Apart from keeping your process non-blocking (which is a useful
1400	effect on its own sometimes), idle watchers are a good place to do	1660	effect on its own sometimes), idle watchers are a good place to do
1401	"pseudo-background processing", or delay processing stuff to after the	1661	"pseudo-background processing", or delay processing stuff to after the
1402	event loop has handled all outstanding events.	1662	event loop has handled all outstanding events.
1403		1663
		1664	=head3 Watcher-Specific Functions and Data Members
		1665
1404	=over 4	1666	=over 4
1405		1667
1406	=item ev_idle_init (ev_signal *, callback)	1668	=item ev_idle_init (ev_signal *, callback)
1407		1669
1408	Initialises and configures the idle watcher - it has no parameters of any	1670	Initialises and configures the idle watcher - it has no parameters of any
1409	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1671	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1410	believe me.	1672	believe me.
1411		1673
1412	=back	1674	=back
		1675
		1676	=head3 Examples
1413		1677
1414	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1678	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1415	callback, free it. Also, use no error checking, as usual.	1679	callback, free it. Also, use no error checking, as usual.
1416		1680
1417	static void	1681	static void
…		…
1465	with priority higher than or equal to the event loop and one coroutine	1729	with priority higher than or equal to the event loop and one coroutine
1466	of lower priority, but only once, using idle watchers to keep the event	1730	of lower priority, but only once, using idle watchers to keep the event
1467	loop from blocking if lower-priority coroutines are active, thus mapping	1731	loop from blocking if lower-priority coroutines are active, thus mapping
1468	low-priority coroutines to idle/background tasks).	1732	low-priority coroutines to idle/background tasks).
1469		1733
		1734	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1735	priority, to ensure that they are being run before any other watchers
		1736	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1737	too) should not activate ("feed") events into libev. While libev fully
		1738	supports this, they will be called before other C<ev_check> watchers
		1739	did their job. As C<ev_check> watchers are often used to embed other
		1740	(non-libev) event loops those other event loops might be in an unusable
		1741	state until their C<ev_check> watcher ran (always remind yourself to
		1742	coexist peacefully with others).
		1743
		1744	=head3 Watcher-Specific Functions and Data Members
		1745
1470	=over 4	1746	=over 4
1471		1747
1472	=item ev_prepare_init (ev_prepare *, callback)	1748	=item ev_prepare_init (ev_prepare *, callback)
1473		1749
1474	=item ev_check_init (ev_check *, callback)	1750	=item ev_check_init (ev_check *, callback)
…		…
1477	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1753	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1478	macros, but using them is utterly, utterly and completely pointless.	1754	macros, but using them is utterly, utterly and completely pointless.
1479		1755
1480	=back	1756	=back
1481		1757
1482	Example: To include a library such as adns, you would add IO watchers	1758	=head3 Examples
1483	and a timeout watcher in a prepare handler, as required by libadns, and	1759
		1760	There are a number of principal ways to embed other event loops or modules
		1761	into libev. Here are some ideas on how to include libadns into libev
		1762	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1763	use for an actually working example. Another Perl module named C<EV::Glib>
		1764	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1765	into the Glib event loop).
		1766
		1767	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1484	in a check watcher, destroy them and call into libadns. What follows is	1768	and in a check watcher, destroy them and call into libadns. What follows
1485	pseudo-code only of course:	1769	is pseudo-code only of course. This requires you to either use a low
		1770	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1771	the callbacks for the IO/timeout watchers might not have been called yet.
1486		1772
1487	static ev_io iow [nfd];	1773	static ev_io iow [nfd];
1488	static ev_timer tw;	1774	static ev_timer tw;
1489		1775
1490	static void	1776	static void
1491	io_cb (ev_loop *loop, ev_io *w, int revents)	1777	io_cb (ev_loop *loop, ev_io *w, int revents)
1492	{	1778	{
1493	// set the relevant poll flags
1494	// could also call adns_processreadable etc. here
1495	struct pollfd *fd = (struct pollfd *)w->data;
1496	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1497	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1498	}	1779	}
1499		1780
1500	// create io watchers for each fd and a timer before blocking	1781	// create io watchers for each fd and a timer before blocking
1501	static void	1782	static void
1502	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1783	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
…		…
1508		1789
1509	/* the callback is illegal, but won't be called as we stop during check */	1790	/* the callback is illegal, but won't be called as we stop during check */
1510	ev_timer_init (&tw, 0, timeout * 1e-3);	1791	ev_timer_init (&tw, 0, timeout * 1e-3);
1511	ev_timer_start (loop, &tw);	1792	ev_timer_start (loop, &tw);
1512		1793
1513	// create on ev_io per pollfd	1794	// create one ev_io per pollfd
1514	for (int i = 0; i < nfd; ++i)	1795	for (int i = 0; i < nfd; ++i)
1515	{	1796	{
1516	ev_io_init (iow + i, io_cb, fds [i].fd,	1797	ev_io_init (iow + i, io_cb, fds [i].fd,
1517	((fds [i].events & POLLIN ? EV_READ : 0)	1798	((fds [i].events & POLLIN ? EV_READ : 0)
1518	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1799	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1519		1800
1520	fds [i].revents = 0;	1801	fds [i].revents = 0;
1521	iow [i].data = fds + i;
1522	ev_io_start (loop, iow + i);	1802	ev_io_start (loop, iow + i);
1523	}	1803	}
1524	}	1804	}
1525		1805
1526	// stop all watchers after blocking	1806	// stop all watchers after blocking
…		…
1528	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1808	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1529	{	1809	{
1530	ev_timer_stop (loop, &tw);	1810	ev_timer_stop (loop, &tw);
1531		1811
1532	for (int i = 0; i < nfd; ++i)	1812	for (int i = 0; i < nfd; ++i)
		1813	{
		1814	// set the relevant poll flags
		1815	// could also call adns_processreadable etc. here
		1816	struct pollfd *fd = fds + i;
		1817	int revents = ev_clear_pending (iow + i);
		1818	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1819	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1820
		1821	// now stop the watcher
1533	ev_io_stop (loop, iow + i);	1822	ev_io_stop (loop, iow + i);
		1823	}
1534		1824
1535	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1825	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1826	}
		1827
		1828	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1829	in the prepare watcher and would dispose of the check watcher.
		1830
		1831	Method 3: If the module to be embedded supports explicit event
		1832	notification (adns does), you can also make use of the actual watcher
		1833	callbacks, and only destroy/create the watchers in the prepare watcher.
		1834
		1835	static void
		1836	timer_cb (EV_P_ ev_timer *w, int revents)
		1837	{
		1838	adns_state ads = (adns_state)w->data;
		1839	update_now (EV_A);
		1840
		1841	adns_processtimeouts (ads, &tv_now);
		1842	}
		1843
		1844	static void
		1845	io_cb (EV_P_ ev_io *w, int revents)
		1846	{
		1847	adns_state ads = (adns_state)w->data;
		1848	update_now (EV_A);
		1849
		1850	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1851	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1852	}
		1853
		1854	// do not ever call adns_afterpoll
		1855
		1856	Method 4: Do not use a prepare or check watcher because the module you
		1857	want to embed is too inflexible to support it. Instead, youc na override
		1858	their poll function. The drawback with this solution is that the main
		1859	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1860	this.
		1861
		1862	static gint
		1863	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1864	{
		1865	int got_events = 0;
		1866
		1867	for (n = 0; n < nfds; ++n)
		1868	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1869
		1870	if (timeout >= 0)
		1871	// create/start timer
		1872
		1873	// poll
		1874	ev_loop (EV_A_ 0);
		1875
		1876	// stop timer again
		1877	if (timeout >= 0)
		1878	ev_timer_stop (EV_A_ &to);
		1879
		1880	// stop io watchers again - their callbacks should have set
		1881	for (n = 0; n < nfds; ++n)
		1882	ev_io_stop (EV_A_ iow [n]);
		1883
		1884	return got_events;
1536	}	1885	}
1537		1886
1538		1887
1539	=head2 C<ev_embed> - when one backend isn't enough...	1888	=head2 C<ev_embed> - when one backend isn't enough...
1540		1889
…		…
1583	portable one.	1932	portable one.
1584		1933
1585	So when you want to use this feature you will always have to be prepared	1934	So when you want to use this feature you will always have to be prepared
1586	that you cannot get an embeddable loop. The recommended way to get around	1935	that you cannot get an embeddable loop. The recommended way to get around
1587	this is to have a separate variables for your embeddable loop, try to	1936	this is to have a separate variables for your embeddable loop, try to
1588	create it, and if that fails, use the normal loop for everything:	1937	create it, and if that fails, use the normal loop for everything.
		1938
		1939	=head3 Watcher-Specific Functions and Data Members
		1940
		1941	=over 4
		1942
		1943	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1944
		1945	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1946
		1947	Configures the watcher to embed the given loop, which must be
		1948	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1949	invoked automatically, otherwise it is the responsibility of the callback
		1950	to invoke it (it will continue to be called until the sweep has been done,
		1951	if you do not want thta, you need to temporarily stop the embed watcher).
		1952
		1953	=item ev_embed_sweep (loop, ev_embed *)
		1954
		1955	Make a single, non-blocking sweep over the embedded loop. This works
		1956	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1957	apropriate way for embedded loops.
		1958
		1959	=item struct ev_loop *other [read-only]
		1960
		1961	The embedded event loop.
		1962
		1963	=back
		1964
		1965	=head3 Examples
		1966
		1967	Example: Try to get an embeddable event loop and embed it into the default
		1968	event loop. If that is not possible, use the default loop. The default
		1969	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1970	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1971	used).
1589		1972
1590	struct ev_loop *loop_hi = ev_default_init (0);	1973	struct ev_loop *loop_hi = ev_default_init (0);
1591	struct ev_loop *loop_lo = 0;	1974	struct ev_loop *loop_lo = 0;
1592	struct ev_embed embed;	1975	struct ev_embed embed;
1593		1976
…		…
1604	ev_embed_start (loop_hi, &embed);	1987	ev_embed_start (loop_hi, &embed);
1605	}	1988	}
1606	else	1989	else
1607	loop_lo = loop_hi;	1990	loop_lo = loop_hi;
1608		1991
1609	=over 4	1992	Example: Check if kqueue is available but not recommended and create
		1993	a kqueue backend for use with sockets (which usually work with any
		1994	kqueue implementation). Store the kqueue/socket-only event loop in
		1995	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1610		1996
1611	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	1997	struct ev_loop *loop = ev_default_init (0);
		1998	struct ev_loop *loop_socket = 0;
		1999	struct ev_embed embed;
		2000
		2001	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2002	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2003	{
		2004	ev_embed_init (&embed, 0, loop_socket);
		2005	ev_embed_start (loop, &embed);
		2006	}
1612		2007
1613	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2008	if (!loop_socket)
		2009	loop_socket = loop;
1614		2010
1615	Configures the watcher to embed the given loop, which must be	2011	// now use loop_socket for all sockets, and loop for everything else
1616	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1617	invoked automatically, otherwise it is the responsibility of the callback
1618	to invoke it (it will continue to be called until the sweep has been done,
1619	if you do not want thta, you need to temporarily stop the embed watcher).
1620
1621	=item ev_embed_sweep (loop, ev_embed *)
1622
1623	Make a single, non-blocking sweep over the embedded loop. This works
1624	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1625	apropriate way for embedded loops.
1626
1627	=item struct ev_loop *loop [read-only]
1628
1629	The embedded event loop.
1630
1631	=back
1632		2012
1633		2013
1634	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2014	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1635		2015
1636	Fork watchers are called when a C<fork ()> was detected (usually because	2016	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1639	event loop blocks next and before C<ev_check> watchers are being called,	2019	event loop blocks next and before C<ev_check> watchers are being called,
1640	and only in the child after the fork. If whoever good citizen calling	2020	and only in the child after the fork. If whoever good citizen calling
1641	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2021	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1642	handlers will be invoked, too, of course.	2022	handlers will be invoked, too, of course.
1643		2023
		2024	=head3 Watcher-Specific Functions and Data Members
		2025
1644	=over 4	2026	=over 4
1645		2027
1646	=item ev_fork_init (ev_signal *, callback)	2028	=item ev_fork_init (ev_signal *, callback)
1647		2029
1648	Initialises and configures the fork watcher - it has no parameters of any	2030	Initialises and configures the fork watcher - it has no parameters of any
…		…
1744		2126
1745	To use it,	2127	To use it,
1746		2128
1747	#include <ev++.h>	2129	#include <ev++.h>
1748		2130
1749	(it is not installed by default). This automatically includes F<ev.h>	2131	This automatically includes F<ev.h> and puts all of its definitions (many
1750	and puts all of its definitions (many of them macros) into the global	2132	of them macros) into the global namespace. All C++ specific things are
1751	namespace. All C++ specific things are put into the C<ev> namespace.	2133	put into the C<ev> namespace. It should support all the same embedding
		2134	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1752		2135
1753	It should support all the same embedding options as F<ev.h>, most notably	2136	Care has been taken to keep the overhead low. The only data member the C++
1754	C<EV_MULTIPLICITY>.	2137	classes add (compared to plain C-style watchers) is the event loop pointer
		2138	that the watcher is associated with (or no additional members at all if
		2139	you disable C<EV_MULTIPLICITY> when embedding libev).
		2140
		2141	Currently, functions, and static and non-static member functions can be
		2142	used as callbacks. Other types should be easy to add as long as they only
		2143	need one additional pointer for context. If you need support for other
		2144	types of functors please contact the author (preferably after implementing
		2145	it).
1755		2146
1756	Here is a list of things available in the C<ev> namespace:	2147	Here is a list of things available in the C<ev> namespace:
1757		2148
1758	=over 4	2149	=over 4
1759		2150
…		…
1775		2166
1776	All of those classes have these methods:	2167	All of those classes have these methods:
1777		2168
1778	=over 4	2169	=over 4
1779		2170
1780	=item ev::TYPE::TYPE (object *, object::method *)	2171	=item ev::TYPE::TYPE ()
1781		2172
1782	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2173	=item ev::TYPE::TYPE (struct ev_loop *)
1783		2174
1784	=item ev::TYPE::~TYPE	2175	=item ev::TYPE::~TYPE
1785		2176
1786	The constructor takes a pointer to an object and a method pointer to	2177	The constructor (optionally) takes an event loop to associate the watcher
1787	the event handler callback to call in this class. The constructor calls	2178	with. If it is omitted, it will use C<EV_DEFAULT>.
1788	C<ev_init> for you, which means you have to call the C<set> method	2179
1789	before starting it. If you do not specify a loop then the constructor	2180	The constructor calls C<ev_init> for you, which means you have to call the
1790	automatically associates the default loop with this watcher.	2181	C<set> method before starting it.
		2182
		2183	It will not set a callback, however: You have to call the templated C<set>
		2184	method to set a callback before you can start the watcher.
		2185
		2186	(The reason why you have to use a method is a limitation in C++ which does
		2187	not allow explicit template arguments for constructors).
1791		2188
1792	The destructor automatically stops the watcher if it is active.	2189	The destructor automatically stops the watcher if it is active.
		2190
		2191	=item w->set<class, &class::method> (object *)
		2192
		2193	This method sets the callback method to call. The method has to have a
		2194	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2195	first argument and the C<revents> as second. The object must be given as
		2196	parameter and is stored in the C<data> member of the watcher.
		2197
		2198	This method synthesizes efficient thunking code to call your method from
		2199	the C callback that libev requires. If your compiler can inline your
		2200	callback (i.e. it is visible to it at the place of the C<set> call and
		2201	your compiler is good :), then the method will be fully inlined into the
		2202	thunking function, making it as fast as a direct C callback.
		2203
		2204	Example: simple class declaration and watcher initialisation
		2205
		2206	struct myclass
		2207	{
		2208	void io_cb (ev::io &w, int revents) { }
		2209	}
		2210
		2211	myclass obj;
		2212	ev::io iow;
		2213	iow.set <myclass, &myclass::io_cb> (&obj);
		2214
		2215	=item w->set<function> (void *data = 0)
		2216
		2217	Also sets a callback, but uses a static method or plain function as
		2218	callback. The optional C<data> argument will be stored in the watcher's
		2219	C<data> member and is free for you to use.
		2220
		2221	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2222
		2223	See the method-C<set> above for more details.
		2224
		2225	Example:
		2226
		2227	static void io_cb (ev::io &w, int revents) { }
		2228	iow.set <io_cb> ();
1793		2229
1794	=item w->set (struct ev_loop *)	2230	=item w->set (struct ev_loop *)
1795		2231
1796	Associates a different C<struct ev_loop> with this watcher. You can only	2232	Associates a different C<struct ev_loop> with this watcher. You can only
1797	do this when the watcher is inactive (and not pending either).	2233	do this when the watcher is inactive (and not pending either).
1798		2234
1799	=item w->set ([args])	2235	=item w->set ([args])
1800		2236
1801	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2237	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1802	called at least once. Unlike the C counterpart, an active watcher gets	2238	called at least once. Unlike the C counterpart, an active watcher gets
1803	automatically stopped and restarted.	2239	automatically stopped and restarted when reconfiguring it with this
		2240	method.
1804		2241
1805	=item w->start ()	2242	=item w->start ()
1806		2243
1807	Starts the watcher. Note that there is no C<loop> argument as the	2244	Starts the watcher. Note that there is no C<loop> argument, as the
1808	constructor already takes the loop.	2245	constructor already stores the event loop.
1809		2246
1810	=item w->stop ()	2247	=item w->stop ()
1811		2248
1812	Stops the watcher if it is active. Again, no C<loop> argument.	2249	Stops the watcher if it is active. Again, no C<loop> argument.
1813		2250
1814	=item w->again () C<ev::timer>, C<ev::periodic> only	2251	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1815		2252
1816	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2253	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1817	C<ev_TYPE_again> function.	2254	C<ev_TYPE_again> function.
1818		2255
1819	=item w->sweep () C<ev::embed> only	2256	=item w->sweep () (C<ev::embed> only)
1820		2257
1821	Invokes C<ev_embed_sweep>.	2258	Invokes C<ev_embed_sweep>.
1822		2259
1823	=item w->update () C<ev::stat> only	2260	=item w->update () (C<ev::stat> only)
1824		2261
1825	Invokes C<ev_stat_stat>.	2262	Invokes C<ev_stat_stat>.
1826		2263
1827	=back	2264	=back
1828		2265
…		…
1838		2275
1839	myclass ();	2276	myclass ();
1840	}	2277	}
1841		2278
1842	myclass::myclass (int fd)	2279	myclass::myclass (int fd)
1843	: io (this, &myclass::io_cb),
1844	idle (this, &myclass::idle_cb)
1845	{	2280	{
		2281	io .set <myclass, &myclass::io_cb > (this);
		2282	idle.set <myclass, &myclass::idle_cb> (this);
		2283
1846	io.start (fd, ev::READ);	2284	io.start (fd, ev::READ);
1847	}	2285	}
1848		2286
1849		2287
1850	=head1 MACRO MAGIC	2288	=head1 MACRO MAGIC
1851		2289
1852	Libev can be compiled with a variety of options, the most fundemantal is	2290	Libev can be compiled with a variety of options, the most fundamantal
1853	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2291	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1854	callbacks have an initial C<struct ev_loop *> argument.	2292	functions and callbacks have an initial C<struct ev_loop *> argument.
1855		2293
1856	To make it easier to write programs that cope with either variant, the	2294	To make it easier to write programs that cope with either variant, the
1857	following macros are defined:	2295	following macros are defined:
1858		2296
1859	=over 4	2297	=over 4
…		…
1913	Libev can (and often is) directly embedded into host	2351	Libev can (and often is) directly embedded into host
1914	applications. Examples of applications that embed it include the Deliantra	2352	applications. Examples of applications that embed it include the Deliantra
1915	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2353	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1916	and rxvt-unicode.	2354	and rxvt-unicode.
1917		2355
1918	The goal is to enable you to just copy the neecssary files into your	2356	The goal is to enable you to just copy the necessary files into your
1919	source directory without having to change even a single line in them, so	2357	source directory without having to change even a single line in them, so
1920	you can easily upgrade by simply copying (or having a checked-out copy of	2358	you can easily upgrade by simply copying (or having a checked-out copy of
1921	libev somewhere in your source tree).	2359	libev somewhere in your source tree).
1922		2360
1923	=head2 FILESETS	2361	=head2 FILESETS
…		…
2013		2451
2014	If defined to be C<1>, libev will try to detect the availability of the	2452	If defined to be C<1>, libev will try to detect the availability of the
2015	monotonic clock option at both compiletime and runtime. Otherwise no use	2453	monotonic clock option at both compiletime and runtime. Otherwise no use
2016	of the monotonic clock option will be attempted. If you enable this, you	2454	of the monotonic clock option will be attempted. If you enable this, you
2017	usually have to link against librt or something similar. Enabling it when	2455	usually have to link against librt or something similar. Enabling it when
2018	the functionality isn't available is safe, though, althoguh you have	2456	the functionality isn't available is safe, though, although you have
2019	to make sure you link against any libraries where the C<clock_gettime>	2457	to make sure you link against any libraries where the C<clock_gettime>
2020	function is hiding in (often F<-lrt>).	2458	function is hiding in (often F<-lrt>).
2021		2459
2022	=item EV_USE_REALTIME	2460	=item EV_USE_REALTIME
2023		2461
2024	If defined to be C<1>, libev will try to detect the availability of the	2462	If defined to be C<1>, libev will try to detect the availability of the
2025	realtime clock option at compiletime (and assume its availability at	2463	realtime clock option at compiletime (and assume its availability at
2026	runtime if successful). Otherwise no use of the realtime clock option will	2464	runtime if successful). Otherwise no use of the realtime clock option will
2027	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2465	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2028	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2466	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2029	in the description of C<EV_USE_MONOTONIC>, though.	2467	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2468
		2469	=item EV_USE_NANOSLEEP
		2470
		2471	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2472	and will use it for delays. Otherwise it will use C<select ()>.
2030		2473
2031	=item EV_USE_SELECT	2474	=item EV_USE_SELECT
2032		2475
2033	If undefined or defined to be C<1>, libev will compile in support for the	2476	If undefined or defined to be C<1>, libev will compile in support for the
2034	C<select>(2) backend. No attempt at autodetection will be done: if no	2477	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2052	wants osf handles on win32 (this is the case when the select to	2495	wants osf handles on win32 (this is the case when the select to
2053	be used is the winsock select). This means that it will call	2496	be used is the winsock select). This means that it will call
2054	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2497	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2055	it is assumed that all these functions actually work on fds, even	2498	it is assumed that all these functions actually work on fds, even
2056	on win32. Should not be defined on non-win32 platforms.	2499	on win32. Should not be defined on non-win32 platforms.
		2500
		2501	=item EV_FD_TO_WIN32_HANDLE
		2502
		2503	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2504	file descriptors to socket handles. When not defining this symbol (the
		2505	default), then libev will call C<_get_osfhandle>, which is usually
		2506	correct. In some cases, programs use their own file descriptor management,
		2507	in which case they can provide this function to map fds to socket handles.
2057		2508
2058	=item EV_USE_POLL	2509	=item EV_USE_POLL
2059		2510
2060	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2511	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2061	backend. Otherwise it will be enabled on non-win32 platforms. It	2512	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2098	be detected at runtime.	2549	be detected at runtime.
2099		2550
2100	=item EV_H	2551	=item EV_H
2101		2552
2102	The name of the F<ev.h> header file used to include it. The default if	2553	The name of the F<ev.h> header file used to include it. The default if
2103	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2554	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2104	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2555	virtually rename the F<ev.h> header file in case of conflicts.
2105		2556
2106	=item EV_CONFIG_H	2557	=item EV_CONFIG_H
2107		2558
2108	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2559	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2109	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2560	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2110	C<EV_H>, above.	2561	C<EV_H>, above.
2111		2562
2112	=item EV_EVENT_H	2563	=item EV_EVENT_H
2113		2564
2114	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2565	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2115	of how the F<event.h> header can be found.	2566	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2116		2567
2117	=item EV_PROTOTYPES	2568	=item EV_PROTOTYPES
2118		2569
2119	If defined to be C<0>, then F<ev.h> will not define any function	2570	If defined to be C<0>, then F<ev.h> will not define any function
2120	prototypes, but still define all the structs and other symbols. This is	2571	prototypes, but still define all the structs and other symbols. This is
…		…
2186	than enough. If you need to manage thousands of children you might want to	2637	than enough. If you need to manage thousands of children you might want to
2187	increase this value (I<must> be a power of two).	2638	increase this value (I<must> be a power of two).
2188		2639
2189	=item EV_INOTIFY_HASHSIZE	2640	=item EV_INOTIFY_HASHSIZE
2190		2641
2191	C<ev_staz> watchers use a small hash table to distribute workload by	2642	C<ev_stat> watchers use a small hash table to distribute workload by
2192	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2643	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2193	usually more than enough. If you need to manage thousands of C<ev_stat>	2644	usually more than enough. If you need to manage thousands of C<ev_stat>
2194	watchers you might want to increase this value (I<must> be a power of	2645	watchers you might want to increase this value (I<must> be a power of
2195	two).	2646	two).
2196		2647
…		…
2213		2664
2214	=item ev_set_cb (ev, cb)	2665	=item ev_set_cb (ev, cb)
2215		2666
2216	Can be used to change the callback member declaration in each watcher,	2667	Can be used to change the callback member declaration in each watcher,
2217	and the way callbacks are invoked and set. Must expand to a struct member	2668	and the way callbacks are invoked and set. Must expand to a struct member
2218	definition and a statement, respectively. See the F<ev.v> header file for	2669	definition and a statement, respectively. See the F<ev.h> header file for
2219	their default definitions. One possible use for overriding these is to	2670	their default definitions. One possible use for overriding these is to
2220	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2671	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2221	method calls instead of plain function calls in C++.	2672	method calls instead of plain function calls in C++.
		2673
		2674	=head2 EXPORTED API SYMBOLS
		2675
		2676	If you need to re-export the API (e.g. via a dll) and you need a list of
		2677	exported symbols, you can use the provided F<Symbol.*> files which list
		2678	all public symbols, one per line:
		2679
		2680	Symbols.ev for libev proper
		2681	Symbols.event for the libevent emulation
		2682
		2683	This can also be used to rename all public symbols to avoid clashes with
		2684	multiple versions of libev linked together (which is obviously bad in
		2685	itself, but sometimes it is inconvinient to avoid this).
		2686
		2687	A sed command like this will create wrapper C<#define>'s that you need to
		2688	include before including F<ev.h>:
		2689
		2690	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2691
		2692	This would create a file F<wrap.h> which essentially looks like this:
		2693
		2694	#define ev_backend myprefix_ev_backend
		2695	#define ev_check_start myprefix_ev_check_start
		2696	#define ev_check_stop myprefix_ev_check_stop
		2697	...
2222		2698
2223	=head2 EXAMPLES	2699	=head2 EXAMPLES
2224		2700
2225	For a real-world example of a program the includes libev	2701	For a real-world example of a program the includes libev
2226	verbatim, you can have a look at the EV perl module	2702	verbatim, you can have a look at the EV perl module
…		…
2267		2743
2268	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2744	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2269		2745
2270	This means that, when you have a watcher that triggers in one hour and	2746	This means that, when you have a watcher that triggers in one hour and
2271	there are 100 watchers that would trigger before that then inserting will	2747	there are 100 watchers that would trigger before that then inserting will
2272	have to skip those 100 watchers.	2748	have to skip roughly seven (C<ld 100>) of these watchers.
2273		2749
2274	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2750	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2275		2751
2276	That means that for changing a timer costs less than removing/adding them	2752	That means that changing a timer costs less than removing/adding them
2277	as only the relative motion in the event queue has to be paid for.	2753	as only the relative motion in the event queue has to be paid for.
2278		2754
2279	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2755	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2280		2756
2281	These just add the watcher into an array or at the head of a list.	2757	These just add the watcher into an array or at the head of a list.
		2758
2282	=item Stopping check/prepare/idle watchers: O(1)	2759	=item Stopping check/prepare/idle watchers: O(1)
2283		2760
2284	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2761	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2285		2762
2286	These watchers are stored in lists then need to be walked to find the	2763	These watchers are stored in lists then need to be walked to find the
2287	correct watcher to remove. The lists are usually short (you don't usually	2764	correct watcher to remove. The lists are usually short (you don't usually
2288	have many watchers waiting for the same fd or signal).	2765	have many watchers waiting for the same fd or signal).
2289		2766
2290	=item Finding the next timer per loop iteration: O(1)	2767	=item Finding the next timer in each loop iteration: O(1)
		2768
		2769	By virtue of using a binary heap, the next timer is always found at the
		2770	beginning of the storage array.
2291		2771
2292	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2772	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2293		2773
2294	A change means an I/O watcher gets started or stopped, which requires	2774	A change means an I/O watcher gets started or stopped, which requires
2295	libev to recalculate its status (and possibly tell the kernel).	2775	libev to recalculate its status (and possibly tell the kernel, depending
		2776	on backend and wether C<ev_io_set> was used).
2296		2777
2297	=item Activating one watcher: O(1)	2778	=item Activating one watcher (putting it into the pending state): O(1)
2298		2779
2299	=item Priority handling: O(number_of_priorities)	2780	=item Priority handling: O(number_of_priorities)
2300		2781
2301	Priorities are implemented by allocating some space for each	2782	Priorities are implemented by allocating some space for each
2302	priority. When doing priority-based operations, libev usually has to	2783	priority. When doing priority-based operations, libev usually has to
2303	linearly search all the priorities.	2784	linearly search all the priorities, but starting/stopping and activating
		2785	watchers becomes O(1) w.r.t. prioritiy handling.
2304		2786
2305	=back	2787	=back
2306		2788
2307		2789
		2790	=head1 Win32 platform limitations and workarounds
		2791
		2792	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2793	requires, and its I/O model is fundamentally incompatible with the POSIX
		2794	model. Libev still offers limited functionality on this platform in
		2795	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2796	descriptors. This only applies when using Win32 natively, not when using
		2797	e.g. cygwin.
		2798
		2799	There is no supported compilation method available on windows except
		2800	embedding it into other applications.
		2801
		2802	Due to the many, low, and arbitrary limits on the win32 platform and the
		2803	abysmal performance of winsockets, using a large number of sockets is not
		2804	recommended (and not reasonable). If your program needs to use more than
		2805	a hundred or so sockets, then likely it needs to use a totally different
		2806	implementation for windows, as libev offers the POSIX model, which cannot
		2807	be implemented efficiently on windows (microsoft monopoly games).
		2808
		2809	=over 4
		2810
		2811	=item The winsocket select function
		2812
		2813	The winsocket C<select> function doesn't follow POSIX in that it requires
		2814	socket I<handles> and not socket I<file descriptors>. This makes select
		2815	very inefficient, and also requires a mapping from file descriptors
		2816	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2817	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2818	symbols for more info.
		2819
		2820	The configuration for a "naked" win32 using the microsoft runtime
		2821	libraries and raw winsocket select is:
		2822
		2823	#define EV_USE_SELECT 1
		2824	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2825
		2826	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2827	complexity in the O(n²) range when using win32.
		2828
		2829	=item Limited number of file descriptors
		2830
		2831	Windows has numerous arbitrary (and low) limits on things. Early versions
		2832	of winsocket's select only supported waiting for a max. of C<64> handles
		2833	(probably owning to the fact that all windows kernels can only wait for
		2834	C<64> things at the same time internally; microsoft recommends spawning a
		2835	chain of threads and wait for 63 handles and the previous thread in each).
		2836
		2837	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2838	to some high number (e.g. C<2048>) before compiling the winsocket select
		2839	call (which might be in libev or elsewhere, for example, perl does its own
		2840	select emulation on windows).
		2841
		2842	Another limit is the number of file descriptors in the microsoft runtime
		2843	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2844	or something like this inside microsoft). You can increase this by calling
		2845	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2846	arbitrary limit), but is broken in many versions of the microsoft runtime
		2847	libraries.
		2848
		2849	This might get you to about C<512> or C<2048> sockets (depending on
		2850	windows version and/or the phase of the moon). To get more, you need to
		2851	wrap all I/O functions and provide your own fd management, but the cost of
		2852	calling select (O(n²)) will likely make this unworkable.
		2853
		2854	=back
		2855
		2856
2308	=head1 AUTHOR	2857	=head1 AUTHOR
2309		2858
2310	Marc Lehmann <libev@schmorp.de>.	2859	Marc Lehmann <libev@schmorp.de>.
2311		2860

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