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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>), the Linux C<inotify> interface	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
78		82
79	It also is quite fast (see this	83	It also is quite fast (see this
80	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
81	for example).	85	for example).
82		86
83	=head1 CONVENTIONS	87	=head2 CONVENTIONS
84		88
85	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
86	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
87	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
88	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
89	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>
90	(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.
91		95
92	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
93		97
94	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	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
97	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
98	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
99	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.
100		106
101	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
102		108
103	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
104	library in any way.	110	library in any way.
…		…
109		115
110	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
111	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
112	you actually want to know.	118	you actually want to know.
113		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
114	=item int ev_version_major ()	126	=item int ev_version_major ()
115		127
116	=item int ev_version_minor ()	128	=item int ev_version_minor ()
117		129
118	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
119	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
120	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
121	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
122	version of the library your program was compiled against.	134	version of the library your program was compiled against.
123		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
124	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,
125	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
126	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
127	not a problem.	142	not a problem.
128		143
129	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
130	version.	145	version.
…		…
291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
292		307
293	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
294	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,
295	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
296	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
297	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.
298		320
299	=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)
300		322
301	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
302	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
303	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
304	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.
305		329
306	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
307		331
308	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,
309	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
310	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),
311	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.
312		339
313	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
314	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
315	(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
316	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
317	well if you register events for both fds.	344	very well if you register events for both fds.
318		345
319	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
320	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
321	(or space) is available.	348	(or space) is available.
322		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
323	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
324		358
325	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
326	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
327	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
328	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
329	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
330	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.
331		370
332	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
333	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
334	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
335	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
336	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.
337		386
338	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
339		388
340	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.
341		393
342	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
343		395
344	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,
345	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)).
346		398
347	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
348	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
349	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.
350		407
351	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
352		409
353	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
354	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
355	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
356		415
357	=back	416	=back
358		417
359	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
360	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
…		…
395	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
396	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
397	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
398	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
399	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
400	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
401	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>).
402		470
403	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
404		472
405	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
406	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
451		519
452	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
453	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
454	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
455	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
456	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
457		525
458	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
459		527
460	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
461	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
…		…
482	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
483	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
484		552
485	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
486		554
487	* If there are no active watchers (reference count is zero), return.	555	- Before the first iteration, call any pending watchers.
488	- 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.
489	- If we have been forked, recreate the kernel state.	559	- If we have been forked, recreate the kernel state.
490	- Update the kernel state with all outstanding changes.	560	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	561	- Update the "event loop time".
492	- 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.
493	- Block the process, waiting for any events.	566	- Block the process, waiting for any events.
494	- Queue all outstanding I/O (fd) events.	567	- Queue all outstanding I/O (fd) events.
495	- Update the "event loop time" and do time jump handling.	568	- Update the "event loop time" and do time jump handling.
496	- Queue all outstanding timers.	569	- Queue all outstanding timers.
497	- Queue all outstanding periodics.	570	- Queue all outstanding periodics.
498	- If no events are pending now, queue all idle watchers.	571	- If no events are pending now, queue all idle watchers.
499	- Queue all check watchers.	572	- Queue all check watchers.
500	- 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).
501	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
502	be handled here by queueing them when their watcher gets executed.	575	be handled here by queueing them when their watcher gets executed.
503	- 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
504	were used, return, otherwise continue with step *.	577	were used, or there are no active watchers, return, otherwise
		578	continue with step *.
505		579
506	Example: Queue some jobs and then loop until no events are outsanding	580	Example: Queue some jobs and then loop until no events are outstanding
507	anymore.	581	anymore.
508		582
509	... queue jobs here, make sure they register event watchers as long	583	... queue jobs here, make sure they register event watchers as long
510	... as they still have work to do (even an idle watcher will do..)	584	... as they still have work to do (even an idle watcher will do..)
511	ev_loop (my_loop, 0);	585	ev_loop (my_loop, 0);
…		…
515		589
516	Can be used to make a call to C<ev_loop> return early (but only after it	590	Can be used to make a call to C<ev_loop> return early (but only after it
517	has processed all outstanding events). The C<how> argument must be either	591	has processed all outstanding events). The C<how> argument must be either
518	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	592	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
519	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	593	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		594
		595	This "unloop state" will be cleared when entering C<ev_loop> again.
520		596
521	=item ev_ref (loop)	597	=item ev_ref (loop)
522		598
523	=item ev_unref (loop)	599	=item ev_unref (loop)
524		600
…		…
544	Example: For some weird reason, unregister the above signal handler again.	620	Example: For some weird reason, unregister the above signal handler again.
545		621
546	ev_ref (loop);	622	ev_ref (loop);
547	ev_signal_stop (loop, &exitsig);	623	ev_signal_stop (loop, &exitsig);
548		624
		625	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		626
		627	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		628
		629	These advanced functions influence the time that libev will spend waiting
		630	for events. Both are by default C<0>, meaning that libev will try to
		631	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		632
		633	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		634	allows libev to delay invocation of I/O and timer/periodic callbacks to
		635	increase efficiency of loop iterations.
		636
		637	The background is that sometimes your program runs just fast enough to
		638	handle one (or very few) event(s) per loop iteration. While this makes
		639	the program responsive, it also wastes a lot of CPU time to poll for new
		640	events, especially with backends like C<select ()> which have a high
		641	overhead for the actual polling but can deliver many events at once.
		642
		643	By setting a higher I<io collect interval> you allow libev to spend more
		644	time collecting I/O events, so you can handle more events per iteration,
		645	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		646	C<ev_timer>) will be not affected. Setting this to a non-null value will
		647	introduce an additional C<ev_sleep ()> call into most loop iterations.
		648
		649	Likewise, by setting a higher I<timeout collect interval> you allow libev
		650	to spend more time collecting timeouts, at the expense of increased
		651	latency (the watcher callback will be called later). C<ev_io> watchers
		652	will not be affected. Setting this to a non-null value will not introduce
		653	any overhead in libev.
		654
		655	Many (busy) programs can usually benefit by setting the io collect
		656	interval to a value near C<0.1> or so, which is often enough for
		657	interactive servers (of course not for games), likewise for timeouts. It
		658	usually doesn't make much sense to set it to a lower value than C<0.01>,
		659	as this approsaches the timing granularity of most systems.
		660
549	=back	661	=back
550		662
551		663
552	=head1 ANATOMY OF A WATCHER	664	=head1 ANATOMY OF A WATCHER
553		665
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	844	=item bool ev_is_pending (ev_TYPE *watcher)
733		845
734	Returns a true value iff the watcher is pending, (i.e. it has outstanding	846	Returns a true value iff the watcher is pending, (i.e. it has outstanding
735	events but its callback has not yet been invoked). As long as a watcher	847	events but its callback has not yet been invoked). As long as a watcher
736	is pending (but not active) you must not call an init function on it (but	848	is pending (but not active) you must not call an init function on it (but
737	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	849	C<ev_TYPE_set> is safe), you must not change its priority, and you must
738	libev (e.g. you cnanot C<free ()> it).	850	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		851	it).
739		852
740	=item callback ev_cb (ev_TYPE *watcher)	853	=item callback ev_cb (ev_TYPE *watcher)
741		854
742	Returns the callback currently set on the watcher.	855	Returns the callback currently set on the watcher.
743		856
744	=item ev_cb_set (ev_TYPE *watcher, callback)	857	=item ev_cb_set (ev_TYPE *watcher, callback)
745		858
746	Change the callback. You can change the callback at virtually any time	859	Change the callback. You can change the callback at virtually any time
747	(modulo threads).	860	(modulo threads).
		861
		862	=item ev_set_priority (ev_TYPE *watcher, priority)
		863
		864	=item int ev_priority (ev_TYPE *watcher)
		865
		866	Set and query the priority of the watcher. The priority is a small
		867	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		868	(default: C<-2>). Pending watchers with higher priority will be invoked
		869	before watchers with lower priority, but priority will not keep watchers
		870	from being executed (except for C<ev_idle> watchers).
		871
		872	This means that priorities are I<only> used for ordering callback
		873	invocation after new events have been received. This is useful, for
		874	example, to reduce latency after idling, or more often, to bind two
		875	watchers on the same event and make sure one is called first.
		876
		877	If you need to suppress invocation when higher priority events are pending
		878	you need to look at C<ev_idle> watchers, which provide this functionality.
		879
		880	You I<must not> change the priority of a watcher as long as it is active or
		881	pending.
		882
		883	The default priority used by watchers when no priority has been set is
		884	always C<0>, which is supposed to not be too high and not be too low :).
		885
		886	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		887	fine, as long as you do not mind that the priority value you query might
		888	or might not have been adjusted to be within valid range.
		889
		890	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		891
		892	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		893	C<loop> nor C<revents> need to be valid as long as the watcher callback
		894	can deal with that fact.
		895
		896	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		897
		898	If the watcher is pending, this function returns clears its pending status
		899	and returns its C<revents> bitset (as if its callback was invoked). If the
		900	watcher isn't pending it does nothing and returns C<0>.
748		901
749	=back	902	=back
750		903
751		904
752	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	905	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
837	In general you can register as many read and/or write event watchers per	990	In general you can register as many read and/or write event watchers per
838	fd as you want (as long as you don't confuse yourself). Setting all file	991	fd as you want (as long as you don't confuse yourself). Setting all file
839	descriptors to non-blocking mode is also usually a good idea (but not	992	descriptors to non-blocking mode is also usually a good idea (but not
840	required if you know what you are doing).	993	required if you know what you are doing).
841		994
842	You have to be careful with dup'ed file descriptors, though. Some backends
843	(the linux epoll backend is a notable example) cannot handle dup'ed file
844	descriptors correctly if you register interest in two or more fds pointing
845	to the same underlying file/socket/etc. description (that is, they share
846	the same underlying "file open").
847
848	If you must do this, then force the use of a known-to-be-good backend	995	If you must do this, then force the use of a known-to-be-good backend
849	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	996	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
850	C<EVBACKEND_POLL>).	997	C<EVBACKEND_POLL>).
851		998
852	Another thing you have to watch out for is that it is quite easy to	999	Another thing you have to watch out for is that it is quite easy to
…		…
858	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1005	it is best to always use non-blocking I/O: An extra C<read>(2) returning
859	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1006	C<EAGAIN> is far preferable to a program hanging until some data arrives.
860		1007
861	If you cannot run the fd in non-blocking mode (for example you should not	1008	If you cannot run the fd in non-blocking mode (for example you should not
862	play around with an Xlib connection), then you have to seperately re-test	1009	play around with an Xlib connection), then you have to seperately re-test
863	wether a file descriptor is really ready with a known-to-be good interface	1010	whether a file descriptor is really ready with a known-to-be good interface
864	such as poll (fortunately in our Xlib example, Xlib already does this on	1011	such as poll (fortunately in our Xlib example, Xlib already does this on
865	its own, so its quite safe to use).	1012	its own, so its quite safe to use).
		1013
		1014	=head3 The special problem of disappearing file descriptors
		1015
		1016	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1017	descriptor (either by calling C<close> explicitly or by any other means,
		1018	such as C<dup>). The reason is that you register interest in some file
		1019	descriptor, but when it goes away, the operating system will silently drop
		1020	this interest. If another file descriptor with the same number then is
		1021	registered with libev, there is no efficient way to see that this is, in
		1022	fact, a different file descriptor.
		1023
		1024	To avoid having to explicitly tell libev about such cases, libev follows
		1025	the following policy: Each time C<ev_io_set> is being called, libev
		1026	will assume that this is potentially a new file descriptor, otherwise
		1027	it is assumed that the file descriptor stays the same. That means that
		1028	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1029	descriptor even if the file descriptor number itself did not change.
		1030
		1031	This is how one would do it normally anyway, the important point is that
		1032	the libev application should not optimise around libev but should leave
		1033	optimisations to libev.
		1034
		1035	=head3 The special problem of dup'ed file descriptors
		1036
		1037	Some backends (e.g. epoll), cannot register events for file descriptors,
		1038	but only events for the underlying file descriptions. That means when you
		1039	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1040	events for them, only one file descriptor might actually receive events.
		1041
		1042	There is no workaround possible except not registering events
		1043	for potentially C<dup ()>'ed file descriptors, or to resort to
		1044	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1045
		1046	=head3 The special problem of fork
		1047
		1048	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1049	useless behaviour. Libev fully supports fork, but needs to be told about
		1050	it in the child.
		1051
		1052	To support fork in your programs, you either have to call
		1053	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1054	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1055	C<EVBACKEND_POLL>.
		1056
		1057
		1058	=head3 Watcher-Specific Functions
866		1059
867	=over 4	1060	=over 4
868		1061
869	=item ev_io_init (ev_io *, callback, int fd, int events)	1062	=item ev_io_init (ev_io *, callback, int fd, int events)
870		1063
…		…
881	=item int events [read-only]	1074	=item int events [read-only]
882		1075
883	The events being watched.	1076	The events being watched.
884		1077
885	=back	1078	=back
		1079
		1080	=head3 Examples
886		1081
887	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1082	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
888	readable, but only once. Since it is likely line-buffered, you could	1083	readable, but only once. Since it is likely line-buffered, you could
889	attempt to read a whole line in the callback.	1084	attempt to read a whole line in the callback.
890		1085
…		…
923	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1118	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
924		1119
925	The callback is guarenteed to be invoked only when its timeout has passed,	1120	The callback is guarenteed to be invoked only when its timeout has passed,
926	but if multiple timers become ready during the same loop iteration then	1121	but if multiple timers become ready during the same loop iteration then
927	order of execution is undefined.	1122	order of execution is undefined.
		1123
		1124	=head3 Watcher-Specific Functions and Data Members
928		1125
929	=over 4	1126	=over 4
930		1127
931	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1128	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
932		1129
…		…
986	or C<ev_timer_again> is called and determines the next timeout (if any),	1183	or C<ev_timer_again> is called and determines the next timeout (if any),
987	which is also when any modifications are taken into account.	1184	which is also when any modifications are taken into account.
988		1185
989	=back	1186	=back
990		1187
		1188	=head3 Examples
		1189
991	Example: Create a timer that fires after 60 seconds.	1190	Example: Create a timer that fires after 60 seconds.
992		1191
993	static void	1192	static void
994	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1193	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
995	{	1194	{
…		…
1028	but on wallclock time (absolute time). You can tell a periodic watcher	1227	but on wallclock time (absolute time). You can tell a periodic watcher
1029	to trigger "at" some specific point in time. For example, if you tell a	1228	to trigger "at" some specific point in time. For example, if you tell a
1030	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1229	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1031	+ 10.>) and then reset your system clock to the last year, then it will	1230	+ 10.>) and then reset your system clock to the last year, then it will
1032	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1231	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1033	roughly 10 seconds later and of course not if you reset your system time	1232	roughly 10 seconds later).
1034	again).
1035		1233
1036	They can also be used to implement vastly more complex timers, such as	1234	They can also be used to implement vastly more complex timers, such as
1037	triggering an event on eahc midnight, local time.	1235	triggering an event on each midnight, local time or other, complicated,
		1236	rules.
1038		1237
1039	As with timers, the callback is guarenteed to be invoked only when the	1238	As with timers, the callback is guarenteed to be invoked only when the
1040	time (C<at>) has been passed, but if multiple periodic timers become ready	1239	time (C<at>) has been passed, but if multiple periodic timers become ready
1041	during the same loop iteration then order of execution is undefined.	1240	during the same loop iteration then order of execution is undefined.
1042		1241
		1242	=head3 Watcher-Specific Functions and Data Members
		1243
1043	=over 4	1244	=over 4
1044		1245
1045	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1246	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1046		1247
1047	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1248	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1049	Lots of arguments, lets sort it out... There are basically three modes of	1250	Lots of arguments, lets sort it out... There are basically three modes of
1050	operation, and we will explain them from simplest to complex:	1251	operation, and we will explain them from simplest to complex:
1051		1252
1052	=over 4	1253	=over 4
1053		1254
1054	=item * absolute timer (interval = reschedule_cb = 0)	1255	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1055		1256
1056	In this configuration the watcher triggers an event at the wallclock time	1257	In this configuration the watcher triggers an event at the wallclock time
1057	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1258	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1058	that is, if it is to be run at January 1st 2011 then it will run when the	1259	that is, if it is to be run at January 1st 2011 then it will run when the
1059	system time reaches or surpasses this time.	1260	system time reaches or surpasses this time.
1060		1261
1061	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1262	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1062		1263
1063	In this mode the watcher will always be scheduled to time out at the next	1264	In this mode the watcher will always be scheduled to time out at the next
1064	C<at + N * interval> time (for some integer N) and then repeat, regardless	1265	C<at + N * interval> time (for some integer N, which can also be negative)
1065	of any time jumps.	1266	and then repeat, regardless of any time jumps.
1066		1267
1067	This can be used to create timers that do not drift with respect to system	1268	This can be used to create timers that do not drift with respect to system
1068	time:	1269	time:
1069		1270
1070	ev_periodic_set (&periodic, 0., 3600., 0);	1271	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1076		1277
1077	Another way to think about it (for the mathematically inclined) is that	1278	Another way to think about it (for the mathematically inclined) is that
1078	C<ev_periodic> will try to run the callback in this mode at the next possible	1279	C<ev_periodic> will try to run the callback in this mode at the next possible
1079	time where C<time = at (mod interval)>, regardless of any time jumps.	1280	time where C<time = at (mod interval)>, regardless of any time jumps.
1080		1281
		1282	For numerical stability it is preferable that the C<at> value is near
		1283	C<ev_now ()> (the current time), but there is no range requirement for
		1284	this value.
		1285
1081	=item * manual reschedule mode (reschedule_cb = callback)	1286	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1082		1287
1083	In this mode the values for C<interval> and C<at> are both being	1288	In this mode the values for C<interval> and C<at> are both being
1084	ignored. Instead, each time the periodic watcher gets scheduled, the	1289	ignored. Instead, each time the periodic watcher gets scheduled, the
1085	reschedule callback will be called with the watcher as first, and the	1290	reschedule callback will be called with the watcher as first, and the
1086	current time as second argument.	1291	current time as second argument.
1087		1292
1088	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1293	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1089	ever, or make any event loop modifications>. If you need to stop it,	1294	ever, or make any event loop modifications>. If you need to stop it,
1090	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1295	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1091	starting a prepare watcher).	1296	starting an C<ev_prepare> watcher, which is legal).
1092		1297
1093	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1298	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1094	ev_tstamp now)>, e.g.:	1299	ev_tstamp now)>, e.g.:
1095		1300
1096	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1301	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1119	Simply stops and restarts the periodic watcher again. This is only useful	1324	Simply stops and restarts the periodic watcher again. This is only useful
1120	when you changed some parameters or the reschedule callback would return	1325	when you changed some parameters or the reschedule callback would return
1121	a different time than the last time it was called (e.g. in a crond like	1326	a different time than the last time it was called (e.g. in a crond like
1122	program when the crontabs have changed).	1327	program when the crontabs have changed).
1123		1328
		1329	=item ev_tstamp offset [read-write]
		1330
		1331	When repeating, this contains the offset value, otherwise this is the
		1332	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1333
		1334	Can be modified any time, but changes only take effect when the periodic
		1335	timer fires or C<ev_periodic_again> is being called.
		1336
1124	=item ev_tstamp interval [read-write]	1337	=item ev_tstamp interval [read-write]
1125		1338
1126	The current interval value. Can be modified any time, but changes only	1339	The current interval value. Can be modified any time, but changes only
1127	take effect when the periodic timer fires or C<ev_periodic_again> is being	1340	take effect when the periodic timer fires or C<ev_periodic_again> is being
1128	called.	1341	called.
…		…
1131		1344
1132	The current reschedule callback, or C<0>, if this functionality is	1345	The current reschedule callback, or C<0>, if this functionality is
1133	switched off. Can be changed any time, but changes only take effect when	1346	switched off. Can be changed any time, but changes only take effect when
1134	the periodic timer fires or C<ev_periodic_again> is being called.	1347	the periodic timer fires or C<ev_periodic_again> is being called.
1135		1348
		1349	=item ev_tstamp at [read-only]
		1350
		1351	When active, contains the absolute time that the watcher is supposed to
		1352	trigger next.
		1353
1136	=back	1354	=back
		1355
		1356	=head3 Examples
1137		1357
1138	Example: Call a callback every hour, or, more precisely, whenever the	1358	Example: Call a callback every hour, or, more precisely, whenever the
1139	system clock is divisible by 3600. The callback invocation times have	1359	system clock is divisible by 3600. The callback invocation times have
1140	potentially a lot of jittering, but good long-term stability.	1360	potentially a lot of jittering, but good long-term stability.
1141		1361
…		…
1181	with the kernel (thus it coexists with your own signal handlers as long	1401	with the kernel (thus it coexists with your own signal handlers as long
1182	as you don't register any with libev). Similarly, when the last signal	1402	as you don't register any with libev). Similarly, when the last signal
1183	watcher for a signal is stopped libev will reset the signal handler to	1403	watcher for a signal is stopped libev will reset the signal handler to
1184	SIG_DFL (regardless of what it was set to before).	1404	SIG_DFL (regardless of what it was set to before).
1185		1405
		1406	=head3 Watcher-Specific Functions and Data Members
		1407
1186	=over 4	1408	=over 4
1187		1409
1188	=item ev_signal_init (ev_signal *, callback, int signum)	1410	=item ev_signal_init (ev_signal *, callback, int signum)
1189		1411
1190	=item ev_signal_set (ev_signal *, int signum)	1412	=item ev_signal_set (ev_signal *, int signum)
…		…
1201		1423
1202	=head2 C<ev_child> - watch out for process status changes	1424	=head2 C<ev_child> - watch out for process status changes
1203		1425
1204	Child watchers trigger when your process receives a SIGCHLD in response to	1426	Child watchers trigger when your process receives a SIGCHLD in response to
1205	some child status changes (most typically when a child of yours dies).	1427	some child status changes (most typically when a child of yours dies).
		1428
		1429	=head3 Watcher-Specific Functions and Data Members
1206		1430
1207	=over 4	1431	=over 4
1208		1432
1209	=item ev_child_init (ev_child *, callback, int pid)	1433	=item ev_child_init (ev_child *, callback, int pid)
1210		1434
…		…
1229		1453
1230	The process exit/trace status caused by C<rpid> (see your systems	1454	The process exit/trace status caused by C<rpid> (see your systems
1231	C<waitpid> and C<sys/wait.h> documentation for details).	1455	C<waitpid> and C<sys/wait.h> documentation for details).
1232		1456
1233	=back	1457	=back
		1458
		1459	=head3 Examples
1234		1460
1235	Example: Try to exit cleanly on SIGINT and SIGTERM.	1461	Example: Try to exit cleanly on SIGINT and SIGTERM.
1236		1462
1237	static void	1463	static void
1238	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1464	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
…		…
1279	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1505	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1280	to fall back to regular polling again even with inotify, but changes are	1506	to fall back to regular polling again even with inotify, but changes are
1281	usually detected immediately, and if the file exists there will be no	1507	usually detected immediately, and if the file exists there will be no
1282	polling.	1508	polling.
1283		1509
		1510	=head3 Inotify
		1511
		1512	When C<inotify (7)> support has been compiled into libev (generally only
		1513	available on Linux) and present at runtime, it will be used to speed up
		1514	change detection where possible. The inotify descriptor will be created lazily
		1515	when the first C<ev_stat> watcher is being started.
		1516
		1517	Inotify presense does not change the semantics of C<ev_stat> watchers
		1518	except that changes might be detected earlier, and in some cases, to avoid
		1519	making regular C<stat> calls. Even in the presense of inotify support
		1520	there are many cases where libev has to resort to regular C<stat> polling.
		1521
		1522	(There is no support for kqueue, as apparently it cannot be used to
		1523	implement this functionality, due to the requirement of having a file
		1524	descriptor open on the object at all times).
		1525
		1526	=head3 The special problem of stat time resolution
		1527
		1528	The C<stat ()> syscall only supports full-second resolution portably, and
		1529	even on systems where the resolution is higher, many filesystems still
		1530	only support whole seconds.
		1531
		1532	That means that, if the time is the only thing that changes, you might
		1533	miss updates: on the first update, C<ev_stat> detects a change and calls
		1534	your callback, which does something. When there is another update within
		1535	the same second, C<ev_stat> will be unable to detect it.
		1536
		1537	The solution to this is to delay acting on a change for a second (or till
		1538	the next second boundary), using a roughly one-second delay C<ev_timer>
		1539	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1540	is added to work around small timing inconsistencies of some operating
		1541	systems.
		1542
		1543	=head3 Watcher-Specific Functions and Data Members
		1544
1284	=over 4	1545	=over 4
1285		1546
1286	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1547	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1287		1548
1288	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1549	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1323	=item const char *path [read-only]	1584	=item const char *path [read-only]
1324		1585
1325	The filesystem path that is being watched.	1586	The filesystem path that is being watched.
1326		1587
1327	=back	1588	=back
		1589
		1590	=head3 Examples
1328		1591
1329	Example: Watch C</etc/passwd> for attribute changes.	1592	Example: Watch C</etc/passwd> for attribute changes.
1330		1593
1331	static void	1594	static void
1332	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1595	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1345	}	1608	}
1346		1609
1347	...	1610	...
1348	ev_stat passwd;	1611	ev_stat passwd;
1349		1612
1350	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1613	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1351	ev_stat_start (loop, &passwd);	1614	ev_stat_start (loop, &passwd);
1352		1615
		1616	Example: Like above, but additionally use a one-second delay so we do not
		1617	miss updates (however, frequent updates will delay processing, too, so
		1618	one might do the work both on C<ev_stat> callback invocation I<and> on
		1619	C<ev_timer> callback invocation).
		1620
		1621	static ev_stat passwd;
		1622	static ev_timer timer;
		1623
		1624	static void
		1625	timer_cb (EV_P_ ev_timer *w, int revents)
		1626	{
		1627	ev_timer_stop (EV_A_ w);
		1628
		1629	/* now it's one second after the most recent passwd change */
		1630	}
		1631
		1632	static void
		1633	stat_cb (EV_P_ ev_stat *w, int revents)
		1634	{
		1635	/* reset the one-second timer */
		1636	ev_timer_again (EV_A_ &timer);
		1637	}
		1638
		1639	...
		1640	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1641	ev_stat_start (loop, &passwd);
		1642	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1643
1353		1644
1354	=head2 C<ev_idle> - when you've got nothing better to do...	1645	=head2 C<ev_idle> - when you've got nothing better to do...
1355		1646
1356	Idle watchers trigger events when there are no other events are pending	1647	Idle watchers trigger events when no other events of the same or higher
1357	(prepare, check and other idle watchers do not count). That is, as long	1648	priority are pending (prepare, check and other idle watchers do not
1358	as your process is busy handling sockets or timeouts (or even signals,	1649	count).
1359	imagine) it will not be triggered. But when your process is idle all idle	1650
1360	watchers are being called again and again, once per event loop iteration -	1651	That is, as long as your process is busy handling sockets or timeouts
		1652	(or even signals, imagine) of the same or higher priority it will not be
		1653	triggered. But when your process is idle (or only lower-priority watchers
		1654	are pending), the idle watchers are being called once per event loop
1361	until stopped, that is, or your process receives more events and becomes	1655	iteration - until stopped, that is, or your process receives more events
1362	busy.	1656	and becomes busy again with higher priority stuff.
1363		1657
1364	The most noteworthy effect is that as long as any idle watchers are	1658	The most noteworthy effect is that as long as any idle watchers are
1365	active, the process will not block when waiting for new events.	1659	active, the process will not block when waiting for new events.
1366		1660
1367	Apart from keeping your process non-blocking (which is a useful	1661	Apart from keeping your process non-blocking (which is a useful
1368	effect on its own sometimes), idle watchers are a good place to do	1662	effect on its own sometimes), idle watchers are a good place to do
1369	"pseudo-background processing", or delay processing stuff to after the	1663	"pseudo-background processing", or delay processing stuff to after the
1370	event loop has handled all outstanding events.	1664	event loop has handled all outstanding events.
1371		1665
		1666	=head3 Watcher-Specific Functions and Data Members
		1667
1372	=over 4	1668	=over 4
1373		1669
1374	=item ev_idle_init (ev_signal *, callback)	1670	=item ev_idle_init (ev_signal *, callback)
1375		1671
1376	Initialises and configures the idle watcher - it has no parameters of any	1672	Initialises and configures the idle watcher - it has no parameters of any
1377	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1673	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1378	believe me.	1674	believe me.
1379		1675
1380	=back	1676	=back
		1677
		1678	=head3 Examples
1381		1679
1382	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1680	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1383	callback, free it. Also, use no error checking, as usual.	1681	callback, free it. Also, use no error checking, as usual.
1384		1682
1385	static void	1683	static void
…		…
1433	with priority higher than or equal to the event loop and one coroutine	1731	with priority higher than or equal to the event loop and one coroutine
1434	of lower priority, but only once, using idle watchers to keep the event	1732	of lower priority, but only once, using idle watchers to keep the event
1435	loop from blocking if lower-priority coroutines are active, thus mapping	1733	loop from blocking if lower-priority coroutines are active, thus mapping
1436	low-priority coroutines to idle/background tasks).	1734	low-priority coroutines to idle/background tasks).
1437		1735
		1736	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1737	priority, to ensure that they are being run before any other watchers
		1738	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1739	too) should not activate ("feed") events into libev. While libev fully
		1740	supports this, they will be called before other C<ev_check> watchers
		1741	did their job. As C<ev_check> watchers are often used to embed other
		1742	(non-libev) event loops those other event loops might be in an unusable
		1743	state until their C<ev_check> watcher ran (always remind yourself to
		1744	coexist peacefully with others).
		1745
		1746	=head3 Watcher-Specific Functions and Data Members
		1747
1438	=over 4	1748	=over 4
1439		1749
1440	=item ev_prepare_init (ev_prepare *, callback)	1750	=item ev_prepare_init (ev_prepare *, callback)
1441		1751
1442	=item ev_check_init (ev_check *, callback)	1752	=item ev_check_init (ev_check *, callback)
…		…
1445	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1755	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1446	macros, but using them is utterly, utterly and completely pointless.	1756	macros, but using them is utterly, utterly and completely pointless.
1447		1757
1448	=back	1758	=back
1449		1759
1450	Example: To include a library such as adns, you would add IO watchers	1760	=head3 Examples
1451	and a timeout watcher in a prepare handler, as required by libadns, and	1761
		1762	There are a number of principal ways to embed other event loops or modules
		1763	into libev. Here are some ideas on how to include libadns into libev
		1764	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1765	use for an actually working example. Another Perl module named C<EV::Glib>
		1766	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1767	into the Glib event loop).
		1768
		1769	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1452	in a check watcher, destroy them and call into libadns. What follows is	1770	and in a check watcher, destroy them and call into libadns. What follows
1453	pseudo-code only of course:	1771	is pseudo-code only of course. This requires you to either use a low
		1772	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1773	the callbacks for the IO/timeout watchers might not have been called yet.
1454		1774
1455	static ev_io iow [nfd];	1775	static ev_io iow [nfd];
1456	static ev_timer tw;	1776	static ev_timer tw;
1457		1777
1458	static void	1778	static void
1459	io_cb (ev_loop *loop, ev_io *w, int revents)	1779	io_cb (ev_loop *loop, ev_io *w, int revents)
1460	{	1780	{
1461	// set the relevant poll flags
1462	// could also call adns_processreadable etc. here
1463	struct pollfd *fd = (struct pollfd *)w->data;
1464	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1465	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1466	}	1781	}
1467		1782
1468	// create io watchers for each fd and a timer before blocking	1783	// create io watchers for each fd and a timer before blocking
1469	static void	1784	static void
1470	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1785	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
…		…
1476		1791
1477	/* the callback is illegal, but won't be called as we stop during check */	1792	/* the callback is illegal, but won't be called as we stop during check */
1478	ev_timer_init (&tw, 0, timeout * 1e-3);	1793	ev_timer_init (&tw, 0, timeout * 1e-3);
1479	ev_timer_start (loop, &tw);	1794	ev_timer_start (loop, &tw);
1480		1795
1481	// create on ev_io per pollfd	1796	// create one ev_io per pollfd
1482	for (int i = 0; i < nfd; ++i)	1797	for (int i = 0; i < nfd; ++i)
1483	{	1798	{
1484	ev_io_init (iow + i, io_cb, fds [i].fd,	1799	ev_io_init (iow + i, io_cb, fds [i].fd,
1485	((fds [i].events & POLLIN ? EV_READ : 0)	1800	((fds [i].events & POLLIN ? EV_READ : 0)
1486	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1801	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1487		1802
1488	fds [i].revents = 0;	1803	fds [i].revents = 0;
1489	iow [i].data = fds + i;
1490	ev_io_start (loop, iow + i);	1804	ev_io_start (loop, iow + i);
1491	}	1805	}
1492	}	1806	}
1493		1807
1494	// stop all watchers after blocking	1808	// stop all watchers after blocking
…		…
1496	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1810	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1497	{	1811	{
1498	ev_timer_stop (loop, &tw);	1812	ev_timer_stop (loop, &tw);
1499		1813
1500	for (int i = 0; i < nfd; ++i)	1814	for (int i = 0; i < nfd; ++i)
		1815	{
		1816	// set the relevant poll flags
		1817	// could also call adns_processreadable etc. here
		1818	struct pollfd *fd = fds + i;
		1819	int revents = ev_clear_pending (iow + i);
		1820	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1821	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1822
		1823	// now stop the watcher
1501	ev_io_stop (loop, iow + i);	1824	ev_io_stop (loop, iow + i);
		1825	}
1502		1826
1503	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1827	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1828	}
		1829
		1830	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1831	in the prepare watcher and would dispose of the check watcher.
		1832
		1833	Method 3: If the module to be embedded supports explicit event
		1834	notification (adns does), you can also make use of the actual watcher
		1835	callbacks, and only destroy/create the watchers in the prepare watcher.
		1836
		1837	static void
		1838	timer_cb (EV_P_ ev_timer *w, int revents)
		1839	{
		1840	adns_state ads = (adns_state)w->data;
		1841	update_now (EV_A);
		1842
		1843	adns_processtimeouts (ads, &tv_now);
		1844	}
		1845
		1846	static void
		1847	io_cb (EV_P_ ev_io *w, int revents)
		1848	{
		1849	adns_state ads = (adns_state)w->data;
		1850	update_now (EV_A);
		1851
		1852	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1853	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1854	}
		1855
		1856	// do not ever call adns_afterpoll
		1857
		1858	Method 4: Do not use a prepare or check watcher because the module you
		1859	want to embed is too inflexible to support it. Instead, youc na override
		1860	their poll function. The drawback with this solution is that the main
		1861	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1862	this.
		1863
		1864	static gint
		1865	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1866	{
		1867	int got_events = 0;
		1868
		1869	for (n = 0; n < nfds; ++n)
		1870	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1871
		1872	if (timeout >= 0)
		1873	// create/start timer
		1874
		1875	// poll
		1876	ev_loop (EV_A_ 0);
		1877
		1878	// stop timer again
		1879	if (timeout >= 0)
		1880	ev_timer_stop (EV_A_ &to);
		1881
		1882	// stop io watchers again - their callbacks should have set
		1883	for (n = 0; n < nfds; ++n)
		1884	ev_io_stop (EV_A_ iow [n]);
		1885
		1886	return got_events;
1504	}	1887	}
1505		1888
1506		1889
1507	=head2 C<ev_embed> - when one backend isn't enough...	1890	=head2 C<ev_embed> - when one backend isn't enough...
1508		1891
…		…
1551	portable one.	1934	portable one.
1552		1935
1553	So when you want to use this feature you will always have to be prepared	1936	So when you want to use this feature you will always have to be prepared
1554	that you cannot get an embeddable loop. The recommended way to get around	1937	that you cannot get an embeddable loop. The recommended way to get around
1555	this is to have a separate variables for your embeddable loop, try to	1938	this is to have a separate variables for your embeddable loop, try to
1556	create it, and if that fails, use the normal loop for everything:	1939	create it, and if that fails, use the normal loop for everything.
		1940
		1941	=head3 Watcher-Specific Functions and Data Members
		1942
		1943	=over 4
		1944
		1945	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1946
		1947	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1948
		1949	Configures the watcher to embed the given loop, which must be
		1950	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1951	invoked automatically, otherwise it is the responsibility of the callback
		1952	to invoke it (it will continue to be called until the sweep has been done,
		1953	if you do not want thta, you need to temporarily stop the embed watcher).
		1954
		1955	=item ev_embed_sweep (loop, ev_embed *)
		1956
		1957	Make a single, non-blocking sweep over the embedded loop. This works
		1958	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1959	apropriate way for embedded loops.
		1960
		1961	=item struct ev_loop *other [read-only]
		1962
		1963	The embedded event loop.
		1964
		1965	=back
		1966
		1967	=head3 Examples
		1968
		1969	Example: Try to get an embeddable event loop and embed it into the default
		1970	event loop. If that is not possible, use the default loop. The default
		1971	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1972	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1973	used).
1557		1974
1558	struct ev_loop *loop_hi = ev_default_init (0);	1975	struct ev_loop *loop_hi = ev_default_init (0);
1559	struct ev_loop *loop_lo = 0;	1976	struct ev_loop *loop_lo = 0;
1560	struct ev_embed embed;	1977	struct ev_embed embed;
1561		1978
…		…
1572	ev_embed_start (loop_hi, &embed);	1989	ev_embed_start (loop_hi, &embed);
1573	}	1990	}
1574	else	1991	else
1575	loop_lo = loop_hi;	1992	loop_lo = loop_hi;
1576		1993
1577	=over 4	1994	Example: Check if kqueue is available but not recommended and create
		1995	a kqueue backend for use with sockets (which usually work with any
		1996	kqueue implementation). Store the kqueue/socket-only event loop in
		1997	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1578		1998
1579	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	1999	struct ev_loop *loop = ev_default_init (0);
		2000	struct ev_loop *loop_socket = 0;
		2001	struct ev_embed embed;
		2002
		2003	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2004	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2005	{
		2006	ev_embed_init (&embed, 0, loop_socket);
		2007	ev_embed_start (loop, &embed);
		2008	}
1580		2009
1581	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2010	if (!loop_socket)
		2011	loop_socket = loop;
1582		2012
1583	Configures the watcher to embed the given loop, which must be	2013	// now use loop_socket for all sockets, and loop for everything else
1584	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1585	invoked automatically, otherwise it is the responsibility of the callback
1586	to invoke it (it will continue to be called until the sweep has been done,
1587	if you do not want thta, you need to temporarily stop the embed watcher).
1588
1589	=item ev_embed_sweep (loop, ev_embed *)
1590
1591	Make a single, non-blocking sweep over the embedded loop. This works
1592	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1593	apropriate way for embedded loops.
1594
1595	=item struct ev_loop *loop [read-only]
1596
1597	The embedded event loop.
1598
1599	=back
1600		2014
1601		2015
1602	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2016	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1603		2017
1604	Fork watchers are called when a C<fork ()> was detected (usually because	2018	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1607	event loop blocks next and before C<ev_check> watchers are being called,	2021	event loop blocks next and before C<ev_check> watchers are being called,
1608	and only in the child after the fork. If whoever good citizen calling	2022	and only in the child after the fork. If whoever good citizen calling
1609	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2023	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1610	handlers will be invoked, too, of course.	2024	handlers will be invoked, too, of course.
1611		2025
		2026	=head3 Watcher-Specific Functions and Data Members
		2027
1612	=over 4	2028	=over 4
1613		2029
1614	=item ev_fork_init (ev_signal *, callback)	2030	=item ev_fork_init (ev_signal *, callback)
1615		2031
1616	Initialises and configures the fork watcher - it has no parameters of any	2032	Initialises and configures the fork watcher - it has no parameters of any
…		…
1712		2128
1713	To use it,	2129	To use it,
1714		2130
1715	#include <ev++.h>	2131	#include <ev++.h>
1716		2132
1717	(it is not installed by default). This automatically includes F<ev.h>	2133	This automatically includes F<ev.h> and puts all of its definitions (many
1718	and puts all of its definitions (many of them macros) into the global	2134	of them macros) into the global namespace. All C++ specific things are
1719	namespace. All C++ specific things are put into the C<ev> namespace.	2135	put into the C<ev> namespace. It should support all the same embedding
		2136	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1720		2137
1721	It should support all the same embedding options as F<ev.h>, most notably	2138	Care has been taken to keep the overhead low. The only data member the C++
1722	C<EV_MULTIPLICITY>.	2139	classes add (compared to plain C-style watchers) is the event loop pointer
		2140	that the watcher is associated with (or no additional members at all if
		2141	you disable C<EV_MULTIPLICITY> when embedding libev).
		2142
		2143	Currently, functions, and static and non-static member functions can be
		2144	used as callbacks. Other types should be easy to add as long as they only
		2145	need one additional pointer for context. If you need support for other
		2146	types of functors please contact the author (preferably after implementing
		2147	it).
1723		2148
1724	Here is a list of things available in the C<ev> namespace:	2149	Here is a list of things available in the C<ev> namespace:
1725		2150
1726	=over 4	2151	=over 4
1727		2152
…		…
1743		2168
1744	All of those classes have these methods:	2169	All of those classes have these methods:
1745		2170
1746	=over 4	2171	=over 4
1747		2172
1748	=item ev::TYPE::TYPE (object *, object::method *)	2173	=item ev::TYPE::TYPE ()
1749		2174
1750	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2175	=item ev::TYPE::TYPE (struct ev_loop *)
1751		2176
1752	=item ev::TYPE::~TYPE	2177	=item ev::TYPE::~TYPE
1753		2178
1754	The constructor takes a pointer to an object and a method pointer to	2179	The constructor (optionally) takes an event loop to associate the watcher
1755	the event handler callback to call in this class. The constructor calls	2180	with. If it is omitted, it will use C<EV_DEFAULT>.
1756	C<ev_init> for you, which means you have to call the C<set> method	2181
1757	before starting it. If you do not specify a loop then the constructor	2182	The constructor calls C<ev_init> for you, which means you have to call the
1758	automatically associates the default loop with this watcher.	2183	C<set> method before starting it.
		2184
		2185	It will not set a callback, however: You have to call the templated C<set>
		2186	method to set a callback before you can start the watcher.
		2187
		2188	(The reason why you have to use a method is a limitation in C++ which does
		2189	not allow explicit template arguments for constructors).
1759		2190
1760	The destructor automatically stops the watcher if it is active.	2191	The destructor automatically stops the watcher if it is active.
		2192
		2193	=item w->set<class, &class::method> (object *)
		2194
		2195	This method sets the callback method to call. The method has to have a
		2196	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2197	first argument and the C<revents> as second. The object must be given as
		2198	parameter and is stored in the C<data> member of the watcher.
		2199
		2200	This method synthesizes efficient thunking code to call your method from
		2201	the C callback that libev requires. If your compiler can inline your
		2202	callback (i.e. it is visible to it at the place of the C<set> call and
		2203	your compiler is good :), then the method will be fully inlined into the
		2204	thunking function, making it as fast as a direct C callback.
		2205
		2206	Example: simple class declaration and watcher initialisation
		2207
		2208	struct myclass
		2209	{
		2210	void io_cb (ev::io &w, int revents) { }
		2211	}
		2212
		2213	myclass obj;
		2214	ev::io iow;
		2215	iow.set <myclass, &myclass::io_cb> (&obj);
		2216
		2217	=item w->set<function> (void *data = 0)
		2218
		2219	Also sets a callback, but uses a static method or plain function as
		2220	callback. The optional C<data> argument will be stored in the watcher's
		2221	C<data> member and is free for you to use.
		2222
		2223	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2224
		2225	See the method-C<set> above for more details.
		2226
		2227	Example:
		2228
		2229	static void io_cb (ev::io &w, int revents) { }
		2230	iow.set <io_cb> ();
1761		2231
1762	=item w->set (struct ev_loop *)	2232	=item w->set (struct ev_loop *)
1763		2233
1764	Associates a different C<struct ev_loop> with this watcher. You can only	2234	Associates a different C<struct ev_loop> with this watcher. You can only
1765	do this when the watcher is inactive (and not pending either).	2235	do this when the watcher is inactive (and not pending either).
1766		2236
1767	=item w->set ([args])	2237	=item w->set ([args])
1768		2238
1769	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2239	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1770	called at least once. Unlike the C counterpart, an active watcher gets	2240	called at least once. Unlike the C counterpart, an active watcher gets
1771	automatically stopped and restarted.	2241	automatically stopped and restarted when reconfiguring it with this
		2242	method.
1772		2243
1773	=item w->start ()	2244	=item w->start ()
1774		2245
1775	Starts the watcher. Note that there is no C<loop> argument as the	2246	Starts the watcher. Note that there is no C<loop> argument, as the
1776	constructor already takes the loop.	2247	constructor already stores the event loop.
1777		2248
1778	=item w->stop ()	2249	=item w->stop ()
1779		2250
1780	Stops the watcher if it is active. Again, no C<loop> argument.	2251	Stops the watcher if it is active. Again, no C<loop> argument.
1781		2252
1782	=item w->again () C<ev::timer>, C<ev::periodic> only	2253	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1783		2254
1784	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2255	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1785	C<ev_TYPE_again> function.	2256	C<ev_TYPE_again> function.
1786		2257
1787	=item w->sweep () C<ev::embed> only	2258	=item w->sweep () (C<ev::embed> only)
1788		2259
1789	Invokes C<ev_embed_sweep>.	2260	Invokes C<ev_embed_sweep>.
1790		2261
1791	=item w->update () C<ev::stat> only	2262	=item w->update () (C<ev::stat> only)
1792		2263
1793	Invokes C<ev_stat_stat>.	2264	Invokes C<ev_stat_stat>.
1794		2265
1795	=back	2266	=back
1796		2267
…		…
1806		2277
1807	myclass ();	2278	myclass ();
1808	}	2279	}
1809		2280
1810	myclass::myclass (int fd)	2281	myclass::myclass (int fd)
1811	: io (this, &myclass::io_cb),
1812	idle (this, &myclass::idle_cb)
1813	{	2282	{
		2283	io .set <myclass, &myclass::io_cb > (this);
		2284	idle.set <myclass, &myclass::idle_cb> (this);
		2285
1814	io.start (fd, ev::READ);	2286	io.start (fd, ev::READ);
1815	}	2287	}
1816		2288
1817		2289
1818	=head1 MACRO MAGIC	2290	=head1 MACRO MAGIC
1819		2291
1820	Libev can be compiled with a variety of options, the most fundemantal is	2292	Libev can be compiled with a variety of options, the most fundamantal
1821	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2293	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1822	callbacks have an initial C<struct ev_loop *> argument.	2294	functions and callbacks have an initial C<struct ev_loop *> argument.
1823		2295
1824	To make it easier to write programs that cope with either variant, the	2296	To make it easier to write programs that cope with either variant, the
1825	following macros are defined:	2297	following macros are defined:
1826		2298
1827	=over 4	2299	=over 4
…		…
1860	loop, if multiple loops are supported ("ev loop default").	2332	loop, if multiple loops are supported ("ev loop default").
1861		2333
1862	=back	2334	=back
1863		2335
1864	Example: Declare and initialise a check watcher, utilising the above	2336	Example: Declare and initialise a check watcher, utilising the above
1865	macros so it will work regardless of wether multiple loops are supported	2337	macros so it will work regardless of whether multiple loops are supported
1866	or not.	2338	or not.
1867		2339
1868	static void	2340	static void
1869	check_cb (EV_P_ ev_timer *w, int revents)	2341	check_cb (EV_P_ ev_timer *w, int revents)
1870	{	2342	{
…		…
1881	Libev can (and often is) directly embedded into host	2353	Libev can (and often is) directly embedded into host
1882	applications. Examples of applications that embed it include the Deliantra	2354	applications. Examples of applications that embed it include the Deliantra
1883	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2355	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1884	and rxvt-unicode.	2356	and rxvt-unicode.
1885		2357
1886	The goal is to enable you to just copy the neecssary files into your	2358	The goal is to enable you to just copy the necessary files into your
1887	source directory without having to change even a single line in them, so	2359	source directory without having to change even a single line in them, so
1888	you can easily upgrade by simply copying (or having a checked-out copy of	2360	you can easily upgrade by simply copying (or having a checked-out copy of
1889	libev somewhere in your source tree).	2361	libev somewhere in your source tree).
1890		2362
1891	=head2 FILESETS	2363	=head2 FILESETS
…		…
1981		2453
1982	If defined to be C<1>, libev will try to detect the availability of the	2454	If defined to be C<1>, libev will try to detect the availability of the
1983	monotonic clock option at both compiletime and runtime. Otherwise no use	2455	monotonic clock option at both compiletime and runtime. Otherwise no use
1984	of the monotonic clock option will be attempted. If you enable this, you	2456	of the monotonic clock option will be attempted. If you enable this, you
1985	usually have to link against librt or something similar. Enabling it when	2457	usually have to link against librt or something similar. Enabling it when
1986	the functionality isn't available is safe, though, althoguh you have	2458	the functionality isn't available is safe, though, although you have
1987	to make sure you link against any libraries where the C<clock_gettime>	2459	to make sure you link against any libraries where the C<clock_gettime>
1988	function is hiding in (often F<-lrt>).	2460	function is hiding in (often F<-lrt>).
1989		2461
1990	=item EV_USE_REALTIME	2462	=item EV_USE_REALTIME
1991		2463
1992	If defined to be C<1>, libev will try to detect the availability of the	2464	If defined to be C<1>, libev will try to detect the availability of the
1993	realtime clock option at compiletime (and assume its availability at	2465	realtime clock option at compiletime (and assume its availability at
1994	runtime if successful). Otherwise no use of the realtime clock option will	2466	runtime if successful). Otherwise no use of the realtime clock option will
1995	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2467	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1996	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2468	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1997	in the description of C<EV_USE_MONOTONIC>, though.	2469	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2470
		2471	=item EV_USE_NANOSLEEP
		2472
		2473	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2474	and will use it for delays. Otherwise it will use C<select ()>.
1998		2475
1999	=item EV_USE_SELECT	2476	=item EV_USE_SELECT
2000		2477
2001	If undefined or defined to be C<1>, libev will compile in support for the	2478	If undefined or defined to be C<1>, libev will compile in support for the
2002	C<select>(2) backend. No attempt at autodetection will be done: if no	2479	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2020	wants osf handles on win32 (this is the case when the select to	2497	wants osf handles on win32 (this is the case when the select to
2021	be used is the winsock select). This means that it will call	2498	be used is the winsock select). This means that it will call
2022	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2499	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2023	it is assumed that all these functions actually work on fds, even	2500	it is assumed that all these functions actually work on fds, even
2024	on win32. Should not be defined on non-win32 platforms.	2501	on win32. Should not be defined on non-win32 platforms.
		2502
		2503	=item EV_FD_TO_WIN32_HANDLE
		2504
		2505	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2506	file descriptors to socket handles. When not defining this symbol (the
		2507	default), then libev will call C<_get_osfhandle>, which is usually
		2508	correct. In some cases, programs use their own file descriptor management,
		2509	in which case they can provide this function to map fds to socket handles.
2025		2510
2026	=item EV_USE_POLL	2511	=item EV_USE_POLL
2027		2512
2028	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2513	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2029	backend. Otherwise it will be enabled on non-win32 platforms. It	2514	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2066	be detected at runtime.	2551	be detected at runtime.
2067		2552
2068	=item EV_H	2553	=item EV_H
2069		2554
2070	The name of the F<ev.h> header file used to include it. The default if	2555	The name of the F<ev.h> header file used to include it. The default if
2071	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2556	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2072	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2557	virtually rename the F<ev.h> header file in case of conflicts.
2073		2558
2074	=item EV_CONFIG_H	2559	=item EV_CONFIG_H
2075		2560
2076	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2561	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2077	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2562	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2078	C<EV_H>, above.	2563	C<EV_H>, above.
2079		2564
2080	=item EV_EVENT_H	2565	=item EV_EVENT_H
2081		2566
2082	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2567	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2083	of how the F<event.h> header can be found.	2568	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2084		2569
2085	=item EV_PROTOTYPES	2570	=item EV_PROTOTYPES
2086		2571
2087	If defined to be C<0>, then F<ev.h> will not define any function	2572	If defined to be C<0>, then F<ev.h> will not define any function
2088	prototypes, but still define all the structs and other symbols. This is	2573	prototypes, but still define all the structs and other symbols. This is
…		…
2095	will have the C<struct ev_loop *> as first argument, and you can create	2580	will have the C<struct ev_loop *> as first argument, and you can create
2096	additional independent event loops. Otherwise there will be no support	2581	additional independent event loops. Otherwise there will be no support
2097	for multiple event loops and there is no first event loop pointer	2582	for multiple event loops and there is no first event loop pointer
2098	argument. Instead, all functions act on the single default loop.	2583	argument. Instead, all functions act on the single default loop.
2099		2584
		2585	=item EV_MINPRI
		2586
		2587	=item EV_MAXPRI
		2588
		2589	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2590	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2591	provide for more priorities by overriding those symbols (usually defined
		2592	to be C<-2> and C<2>, respectively).
		2593
		2594	When doing priority-based operations, libev usually has to linearly search
		2595	all the priorities, so having many of them (hundreds) uses a lot of space
		2596	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2597	fine.
		2598
		2599	If your embedding app does not need any priorities, defining these both to
		2600	C<0> will save some memory and cpu.
		2601
2100	=item EV_PERIODIC_ENABLE	2602	=item EV_PERIODIC_ENABLE
2101		2603
2102	If undefined or defined to be C<1>, then periodic timers are supported. If	2604	If undefined or defined to be C<1>, then periodic timers are supported. If
		2605	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2606	code.
		2607
		2608	=item EV_IDLE_ENABLE
		2609
		2610	If undefined or defined to be C<1>, then idle watchers are supported. If
2103	defined to be C<0>, then they are not. Disabling them saves a few kB of	2611	defined to be C<0>, then they are not. Disabling them saves a few kB of
2104	code.	2612	code.
2105		2613
2106	=item EV_EMBED_ENABLE	2614	=item EV_EMBED_ENABLE
2107		2615
…		…
2131	than enough. If you need to manage thousands of children you might want to	2639	than enough. If you need to manage thousands of children you might want to
2132	increase this value (I<must> be a power of two).	2640	increase this value (I<must> be a power of two).
2133		2641
2134	=item EV_INOTIFY_HASHSIZE	2642	=item EV_INOTIFY_HASHSIZE
2135		2643
2136	C<ev_staz> watchers use a small hash table to distribute workload by	2644	C<ev_stat> watchers use a small hash table to distribute workload by
2137	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2645	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2138	usually more than enough. If you need to manage thousands of C<ev_stat>	2646	usually more than enough. If you need to manage thousands of C<ev_stat>
2139	watchers you might want to increase this value (I<must> be a power of	2647	watchers you might want to increase this value (I<must> be a power of
2140	two).	2648	two).
2141		2649
…		…
2158		2666
2159	=item ev_set_cb (ev, cb)	2667	=item ev_set_cb (ev, cb)
2160		2668
2161	Can be used to change the callback member declaration in each watcher,	2669	Can be used to change the callback member declaration in each watcher,
2162	and the way callbacks are invoked and set. Must expand to a struct member	2670	and the way callbacks are invoked and set. Must expand to a struct member
2163	definition and a statement, respectively. See the F<ev.v> header file for	2671	definition and a statement, respectively. See the F<ev.h> header file for
2164	their default definitions. One possible use for overriding these is to	2672	their default definitions. One possible use for overriding these is to
2165	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2673	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2166	method calls instead of plain function calls in C++.	2674	method calls instead of plain function calls in C++.
		2675
		2676	=head2 EXPORTED API SYMBOLS
		2677
		2678	If you need to re-export the API (e.g. via a dll) and you need a list of
		2679	exported symbols, you can use the provided F<Symbol.*> files which list
		2680	all public symbols, one per line:
		2681
		2682	Symbols.ev for libev proper
		2683	Symbols.event for the libevent emulation
		2684
		2685	This can also be used to rename all public symbols to avoid clashes with
		2686	multiple versions of libev linked together (which is obviously bad in
		2687	itself, but sometimes it is inconvinient to avoid this).
		2688
		2689	A sed command like this will create wrapper C<#define>'s that you need to
		2690	include before including F<ev.h>:
		2691
		2692	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2693
		2694	This would create a file F<wrap.h> which essentially looks like this:
		2695
		2696	#define ev_backend myprefix_ev_backend
		2697	#define ev_check_start myprefix_ev_check_start
		2698	#define ev_check_stop myprefix_ev_check_stop
		2699	...
2167		2700
2168	=head2 EXAMPLES	2701	=head2 EXAMPLES
2169		2702
2170	For a real-world example of a program the includes libev	2703	For a real-world example of a program the includes libev
2171	verbatim, you can have a look at the EV perl module	2704	verbatim, you can have a look at the EV perl module
…		…
2200		2733
2201	In this section the complexities of (many of) the algorithms used inside	2734	In this section the complexities of (many of) the algorithms used inside
2202	libev will be explained. For complexity discussions about backends see the	2735	libev will be explained. For complexity discussions about backends see the
2203	documentation for C<ev_default_init>.	2736	documentation for C<ev_default_init>.
2204		2737
		2738	All of the following are about amortised time: If an array needs to be
		2739	extended, libev needs to realloc and move the whole array, but this
		2740	happens asymptotically never with higher number of elements, so O(1) might
		2741	mean it might do a lengthy realloc operation in rare cases, but on average
		2742	it is much faster and asymptotically approaches constant time.
		2743
2205	=over 4	2744	=over 4
2206		2745
2207	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2746	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2208		2747
		2748	This means that, when you have a watcher that triggers in one hour and
		2749	there are 100 watchers that would trigger before that then inserting will
		2750	have to skip roughly seven (C<ld 100>) of these watchers.
		2751
2209	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2752	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2753
		2754	That means that changing a timer costs less than removing/adding them
		2755	as only the relative motion in the event queue has to be paid for.
2210		2756
2211	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2757	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2212		2758
		2759	These just add the watcher into an array or at the head of a list.
		2760
2213	=item Stopping check/prepare/idle watchers: O(1)	2761	=item Stopping check/prepare/idle watchers: O(1)
2214		2762
2215	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2763	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2216		2764
		2765	These watchers are stored in lists then need to be walked to find the
		2766	correct watcher to remove. The lists are usually short (you don't usually
		2767	have many watchers waiting for the same fd or signal).
		2768
2217	=item Finding the next timer per loop iteration: O(1)	2769	=item Finding the next timer in each loop iteration: O(1)
		2770
		2771	By virtue of using a binary heap, the next timer is always found at the
		2772	beginning of the storage array.
2218		2773
2219	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2774	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2220		2775
2221	=item Activating one watcher: O(1)	2776	A change means an I/O watcher gets started or stopped, which requires
		2777	libev to recalculate its status (and possibly tell the kernel, depending
		2778	on backend and wether C<ev_io_set> was used).
		2779
		2780	=item Activating one watcher (putting it into the pending state): O(1)
		2781
		2782	=item Priority handling: O(number_of_priorities)
		2783
		2784	Priorities are implemented by allocating some space for each
		2785	priority. When doing priority-based operations, libev usually has to
		2786	linearly search all the priorities, but starting/stopping and activating
		2787	watchers becomes O(1) w.r.t. prioritiy handling.
2222		2788
2223	=back	2789	=back
2224		2790
2225		2791
		2792	=head1 Win32 platform limitations and workarounds
		2793
		2794	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2795	requires, and its I/O model is fundamentally incompatible with the POSIX
		2796	model. Libev still offers limited functionality on this platform in
		2797	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2798	descriptors. This only applies when using Win32 natively, not when using
		2799	e.g. cygwin.
		2800
		2801	There is no supported compilation method available on windows except
		2802	embedding it into other applications.
		2803
		2804	Due to the many, low, and arbitrary limits on the win32 platform and the
		2805	abysmal performance of winsockets, using a large number of sockets is not
		2806	recommended (and not reasonable). If your program needs to use more than
		2807	a hundred or so sockets, then likely it needs to use a totally different
		2808	implementation for windows, as libev offers the POSIX model, which cannot
		2809	be implemented efficiently on windows (microsoft monopoly games).
		2810
		2811	=over 4
		2812
		2813	=item The winsocket select function
		2814
		2815	The winsocket C<select> function doesn't follow POSIX in that it requires
		2816	socket I<handles> and not socket I<file descriptors>. This makes select
		2817	very inefficient, and also requires a mapping from file descriptors
		2818	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2819	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2820	symbols for more info.
		2821
		2822	The configuration for a "naked" win32 using the microsoft runtime
		2823	libraries and raw winsocket select is:
		2824
		2825	#define EV_USE_SELECT 1
		2826	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2827
		2828	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2829	complexity in the O(n²) range when using win32.
		2830
		2831	=item Limited number of file descriptors
		2832
		2833	Windows has numerous arbitrary (and low) limits on things. Early versions
		2834	of winsocket's select only supported waiting for a max. of C<64> handles
		2835	(probably owning to the fact that all windows kernels can only wait for
		2836	C<64> things at the same time internally; microsoft recommends spawning a
		2837	chain of threads and wait for 63 handles and the previous thread in each).
		2838
		2839	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2840	to some high number (e.g. C<2048>) before compiling the winsocket select
		2841	call (which might be in libev or elsewhere, for example, perl does its own
		2842	select emulation on windows).
		2843
		2844	Another limit is the number of file descriptors in the microsoft runtime
		2845	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2846	or something like this inside microsoft). You can increase this by calling
		2847	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2848	arbitrary limit), but is broken in many versions of the microsoft runtime
		2849	libraries.
		2850
		2851	This might get you to about C<512> or C<2048> sockets (depending on
		2852	windows version and/or the phase of the moon). To get more, you need to
		2853	wrap all I/O functions and provide your own fd management, but the cost of
		2854	calling select (O(n²)) will likely make this unworkable.
		2855
		2856	=back
		2857
		2858
2226	=head1 AUTHOR	2859	=head1 AUTHOR
2227		2860
2228	Marc Lehmann <libev@schmorp.de>.	2861	Marc Lehmann <libev@schmorp.de>.
2229		2862

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