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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	#include <ev.h>	11	#include <ev.h>
12		12
13	ev_io stdin_watcher;	13	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
…		…
53	The newest version of this document is also available as a html-formatted	53	The newest version of this document is also available as a html-formatted
54	web page you might find easier to navigate when reading it for the first	54	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	55	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		56
57	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	59	these event sources and provide your program with events.
60		60
61	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	68	watcher.
69		69
70	=head1 FEATURES	70	=head2 FEATURES
71		71
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		82
83	It also is quite fast (see this	83	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	85	for example).
86		86
87	=head1 CONVENTIONS	87	=head2 CONVENTIONS
88		88
89	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
90	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
91	various configuration options please have a look at B<EMBED> section in	91	various configuration options please have a look at B<EMBED> section in
92	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
93	loops, then all functions taking an initial argument of name C<loop>	93	loops, then all functions taking an initial argument of name C<loop>
94	(which is always of type C<struct ev_loop *>) will not have this argument.	94	(which is always of type C<struct ev_loop *>) will not have this argument.
95		95
96	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
97		97
98	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
104		106
105	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
106		108
107	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
108	library in any way.	110	library in any way.
…		…
113		115
114	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	118	you actually want to know.
117		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
118	=item int ev_version_major ()	126	=item int ev_version_major ()
119		127
120	=item int ev_version_minor ()	128	=item int ev_version_minor ()
121		129
122	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	134	version of the library your program was compiled against.
127		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
128	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	142	not a problem.
132		143
133	Example: Make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
134	version.	145	version.
…		…
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		307
297	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
298	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
299	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
302		320
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		322
305	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
309		329
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		331
312	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	334	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
		336	of shortcomings, such as silently dropping events in some hard-to-detect
		337	cases and rewiring a syscall per fd change, no fork support and bad
		338	support for dup.
316		339
317	While stopping and starting an I/O watcher in the same iteration will	340	While stopping, setting and starting an I/O watcher in the same iteration
318	result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
319	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
320	best to avoid that. Also, dup()ed file descriptors might not work very	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	344	very well if you register events for both fds.
322		345
323	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
324	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	348	(or space) is available.
326		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		358
329	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
330	was broken on all BSDs except NetBSD (usually it doesn't work with	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
331	anything but sockets and pipes, except on Darwin, where of course its	361	with anything but sockets and pipes, except on Darwin, where of course
332	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
333	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
334	C<EVBACKEND_KQUEUE>).	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		365	system like NetBSD.
		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
335		370
336	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	372	kernel is more efficient (which says nothing about its actual speed, of
338	course). While starting and stopping an I/O watcher does not cause an	373	course). While stopping, setting and starting an I/O watcher does never
339	extra syscall as with epoll, it still adds up to four event changes per	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	375	two event changes per incident, support for C<fork ()> is very bad and it
		376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
341		386
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		388
344	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
345		393
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		395
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
350		398
351	Please note that solaris ports can result in a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
352	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
354		407
355	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
356		409
357	Try all backends (even potentially broken ones that wouldn't be tried	410	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
360		415
361	=back	416	=back
362		417
363	If one or more of these are ored into the flags value, then only these	418	If one or more of these are ored into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	419	backends will be tried (in the reverse order as given here). If none are
…		…
399	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	455	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	456	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
403	calling this function, or cope with the fact afterwards (which is usually	458	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	459	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	460	for example).
		461
		462	Note that certain global state, such as signal state, will not be freed by
		463	this function, and related watchers (such as signal and child watchers)
		464	would need to be stopped manually.
		465
		466	In general it is not advisable to call this function except in the
		467	rare occasion where you really need to free e.g. the signal handling
		468	pipe fds. If you need dynamically allocated loops it is better to use
		469	C<ev_loop_new> and C<ev_loop_destroy>).
406		470
407	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
408		472
409	Like C<ev_default_destroy>, but destroys an event loop created by an	473	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
455		519
456	Returns the current "event loop time", which is the time the event loop	520	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	522	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	523	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
461		525
462	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
463		527
464	Finally, this is it, the event handler. This function usually is called	528	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	529	after you initialised all your watchers and you want to start handling
…		…
486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
488		552
489	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
490		554
491	* If there are no active watchers (reference count is zero), return.	555	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	556	* If EVFLAG_FORKCHECK was used, check for a fork.
		557	- If a fork was detected, queue and call all fork watchers.
		558	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	559	- If we have been forked, recreate the kernel state.
494	- Update the kernel state with all outstanding changes.	560	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	561	- Update the "event loop time".
496	- Calculate for how long to block.	562	- Calculate for how long to sleep or block, if at all
		563	(active idle watchers, EVLOOP_NONBLOCK or not having
		564	any active watchers at all will result in not sleeping).
		565	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	566	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	567	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	568	- Update the "event loop time" and do time jump handling.
500	- Queue all outstanding timers.	569	- Queue all outstanding timers.
501	- Queue all outstanding periodics.	570	- Queue all outstanding periodics.
502	- If no events are pending now, queue all idle watchers.	571	- If no events are pending now, queue all idle watchers.
503	- Queue all check watchers.	572	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	573	- Call all queued watchers in reverse order (i.e. check watchers first).
505	Signals and child watchers are implemented as I/O watchers, and will	574	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	575	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	576	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	577	were used, or there are no active watchers, return, otherwise
		578	continue with step *.
509		579
510	Example: Queue some jobs and then loop until no events are outsanding	580	Example: Queue some jobs and then loop until no events are outstanding
511	anymore.	581	anymore.
512		582
513	... queue jobs here, make sure they register event watchers as long	583	... queue jobs here, make sure they register event watchers as long
514	... 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..)
515	ev_loop (my_loop, 0);	585	ev_loop (my_loop, 0);
…		…
519		589
520	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
521	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
522	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
523	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.
524		596
525	=item ev_ref (loop)	597	=item ev_ref (loop)
526		598
527	=item ev_unref (loop)	599	=item ev_unref (loop)
528		600
…		…
533	returning, ev_unref() after starting, and ev_ref() before stopping it. For	605	returning, ev_unref() after starting, and ev_ref() before stopping it. For
534	example, libev itself uses this for its internal signal pipe: It is not	606	example, libev itself uses this for its internal signal pipe: It is not
535	visible to the libev user and should not keep C<ev_loop> from exiting if	607	visible to the libev user and should not keep C<ev_loop> from exiting if
536	no event watchers registered by it are active. It is also an excellent	608	no event watchers registered by it are active. It is also an excellent
537	way to do this for generic recurring timers or from within third-party	609	way to do this for generic recurring timers or from within third-party
538	libraries. Just remember to I<unref after start> and I<ref before stop>.	610	libraries. Just remember to I<unref after start> and I<ref before stop>
		611	(but only if the watcher wasn't active before, or was active before,
		612	respectively).
539		613
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	614	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	615	running when nothing else is active.
542		616
543	struct ev_signal exitsig;	617	struct ev_signal exitsig;
…		…
547		621
548	Example: For some weird reason, unregister the above signal handler again.	622	Example: For some weird reason, unregister the above signal handler again.
549		623
550	ev_ref (loop);	624	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	625	ev_signal_stop (loop, &exitsig);
		626
		627	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		628
		629	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		630
		631	These advanced functions influence the time that libev will spend waiting
		632	for events. Both are by default C<0>, meaning that libev will try to
		633	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		634
		635	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		636	allows libev to delay invocation of I/O and timer/periodic callbacks to
		637	increase efficiency of loop iterations.
		638
		639	The background is that sometimes your program runs just fast enough to
		640	handle one (or very few) event(s) per loop iteration. While this makes
		641	the program responsive, it also wastes a lot of CPU time to poll for new
		642	events, especially with backends like C<select ()> which have a high
		643	overhead for the actual polling but can deliver many events at once.
		644
		645	By setting a higher I<io collect interval> you allow libev to spend more
		646	time collecting I/O events, so you can handle more events per iteration,
		647	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		648	C<ev_timer>) will be not affected. Setting this to a non-null value will
		649	introduce an additional C<ev_sleep ()> call into most loop iterations.
		650
		651	Likewise, by setting a higher I<timeout collect interval> you allow libev
		652	to spend more time collecting timeouts, at the expense of increased
		653	latency (the watcher callback will be called later). C<ev_io> watchers
		654	will not be affected. Setting this to a non-null value will not introduce
		655	any overhead in libev.
		656
		657	Many (busy) programs can usually benefit by setting the io collect
		658	interval to a value near C<0.1> or so, which is often enough for
		659	interactive servers (of course not for games), likewise for timeouts. It
		660	usually doesn't make much sense to set it to a lower value than C<0.01>,
		661	as this approsaches the timing granularity of most systems.
552		662
553	=back	663	=back
554		664
555		665
556	=head1 ANATOMY OF A WATCHER	666	=head1 ANATOMY OF A WATCHER
…		…
736	=item bool ev_is_pending (ev_TYPE *watcher)	846	=item bool ev_is_pending (ev_TYPE *watcher)
737		847
738	Returns a true value iff the watcher is pending, (i.e. it has outstanding	848	Returns a true value iff the watcher is pending, (i.e. it has outstanding
739	events but its callback has not yet been invoked). As long as a watcher	849	events but its callback has not yet been invoked). As long as a watcher
740	is pending (but not active) you must not call an init function on it (but	850	is pending (but not active) you must not call an init function on it (but
741	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	851	C<ev_TYPE_set> is safe), you must not change its priority, and you must
742	libev (e.g. you cnanot C<free ()> it).	852	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		853	it).
743		854
744	=item callback ev_cb (ev_TYPE *watcher)	855	=item callback ev_cb (ev_TYPE *watcher)
745		856
746	Returns the callback currently set on the watcher.	857	Returns the callback currently set on the watcher.
747		858
…		…
766	watchers on the same event and make sure one is called first.	877	watchers on the same event and make sure one is called first.
767		878
768	If you need to suppress invocation when higher priority events are pending	879	If you need to suppress invocation when higher priority events are pending
769	you need to look at C<ev_idle> watchers, which provide this functionality.	880	you need to look at C<ev_idle> watchers, which provide this functionality.
770		881
		882	You I<must not> change the priority of a watcher as long as it is active or
		883	pending.
		884
771	The default priority used by watchers when no priority has been set is	885	The default priority used by watchers when no priority has been set is
772	always C<0>, which is supposed to not be too high and not be too low :).	886	always C<0>, which is supposed to not be too high and not be too low :).
773		887
774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	888	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
775	fine, as long as you do not mind that the priority value you query might	889	fine, as long as you do not mind that the priority value you query might
776	or might not have been adjusted to be within valid range.	890	or might not have been adjusted to be within valid range.
		891
		892	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		893
		894	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		895	C<loop> nor C<revents> need to be valid as long as the watcher callback
		896	can deal with that fact.
		897
		898	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		899
		900	If the watcher is pending, this function returns clears its pending status
		901	and returns its C<revents> bitset (as if its callback was invoked). If the
		902	watcher isn't pending it does nothing and returns C<0>.
777		903
778	=back	904	=back
779		905
780		906
781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	907	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
866	In general you can register as many read and/or write event watchers per	992	In general you can register as many read and/or write event watchers per
867	fd as you want (as long as you don't confuse yourself). Setting all file	993	fd as you want (as long as you don't confuse yourself). Setting all file
868	descriptors to non-blocking mode is also usually a good idea (but not	994	descriptors to non-blocking mode is also usually a good idea (but not
869	required if you know what you are doing).	995	required if you know what you are doing).
870		996
871	You have to be careful with dup'ed file descriptors, though. Some backends
872	(the linux epoll backend is a notable example) cannot handle dup'ed file
873	descriptors correctly if you register interest in two or more fds pointing
874	to the same underlying file/socket/etc. description (that is, they share
875	the same underlying "file open").
876
877	If you must do this, then force the use of a known-to-be-good backend	997	If you must do this, then force the use of a known-to-be-good backend
878	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	998	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
879	C<EVBACKEND_POLL>).	999	C<EVBACKEND_POLL>).
880		1000
881	Another thing you have to watch out for is that it is quite easy to	1001	Another thing you have to watch out for is that it is quite easy to
…		…
891	play around with an Xlib connection), then you have to seperately re-test	1011	play around with an Xlib connection), then you have to seperately re-test
892	whether a file descriptor is really ready with a known-to-be good interface	1012	whether a file descriptor is really ready with a known-to-be good interface
893	such as poll (fortunately in our Xlib example, Xlib already does this on	1013	such as poll (fortunately in our Xlib example, Xlib already does this on
894	its own, so its quite safe to use).	1014	its own, so its quite safe to use).
895		1015
		1016	=head3 The special problem of disappearing file descriptors
		1017
		1018	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1019	descriptor (either by calling C<close> explicitly or by any other means,
		1020	such as C<dup>). The reason is that you register interest in some file
		1021	descriptor, but when it goes away, the operating system will silently drop
		1022	this interest. If another file descriptor with the same number then is
		1023	registered with libev, there is no efficient way to see that this is, in
		1024	fact, a different file descriptor.
		1025
		1026	To avoid having to explicitly tell libev about such cases, libev follows
		1027	the following policy: Each time C<ev_io_set> is being called, libev
		1028	will assume that this is potentially a new file descriptor, otherwise
		1029	it is assumed that the file descriptor stays the same. That means that
		1030	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1031	descriptor even if the file descriptor number itself did not change.
		1032
		1033	This is how one would do it normally anyway, the important point is that
		1034	the libev application should not optimise around libev but should leave
		1035	optimisations to libev.
		1036
		1037	=head3 The special problem of dup'ed file descriptors
		1038
		1039	Some backends (e.g. epoll), cannot register events for file descriptors,
		1040	but only events for the underlying file descriptions. That means when you
		1041	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1042	events for them, only one file descriptor might actually receive events.
		1043
		1044	There is no workaround possible except not registering events
		1045	for potentially C<dup ()>'ed file descriptors, or to resort to
		1046	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1047
		1048	=head3 The special problem of fork
		1049
		1050	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1051	useless behaviour. Libev fully supports fork, but needs to be told about
		1052	it in the child.
		1053
		1054	To support fork in your programs, you either have to call
		1055	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1056	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1057	C<EVBACKEND_POLL>.
		1058
		1059
		1060	=head3 Watcher-Specific Functions
		1061
896	=over 4	1062	=over 4
897		1063
898	=item ev_io_init (ev_io *, callback, int fd, int events)	1064	=item ev_io_init (ev_io *, callback, int fd, int events)
899		1065
900	=item ev_io_set (ev_io *, int fd, int events)	1066	=item ev_io_set (ev_io *, int fd, int events)
…		…
910	=item int events [read-only]	1076	=item int events [read-only]
911		1077
912	The events being watched.	1078	The events being watched.
913		1079
914	=back	1080	=back
		1081
		1082	=head3 Examples
915		1083
916	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1084	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
917	readable, but only once. Since it is likely line-buffered, you could	1085	readable, but only once. Since it is likely line-buffered, you could
918	attempt to read a whole line in the callback.	1086	attempt to read a whole line in the callback.
919		1087
…		…
952	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1120	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
953		1121
954	The callback is guarenteed to be invoked only when its timeout has passed,	1122	The callback is guarenteed to be invoked only when its timeout has passed,
955	but if multiple timers become ready during the same loop iteration then	1123	but if multiple timers become ready during the same loop iteration then
956	order of execution is undefined.	1124	order of execution is undefined.
		1125
		1126	=head3 Watcher-Specific Functions and Data Members
957		1127
958	=over 4	1128	=over 4
959		1129
960	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1130	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
961		1131
…		…
1015	or C<ev_timer_again> is called and determines the next timeout (if any),	1185	or C<ev_timer_again> is called and determines the next timeout (if any),
1016	which is also when any modifications are taken into account.	1186	which is also when any modifications are taken into account.
1017		1187
1018	=back	1188	=back
1019		1189
		1190	=head3 Examples
		1191
1020	Example: Create a timer that fires after 60 seconds.	1192	Example: Create a timer that fires after 60 seconds.
1021		1193
1022	static void	1194	static void
1023	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1195	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1024	{	1196	{
…		…
1057	but on wallclock time (absolute time). You can tell a periodic watcher	1229	but on wallclock time (absolute time). You can tell a periodic watcher
1058	to trigger "at" some specific point in time. For example, if you tell a	1230	to trigger "at" some specific point in time. For example, if you tell a
1059	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1231	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1060	+ 10.>) and then reset your system clock to the last year, then it will	1232	+ 10.>) and then reset your system clock to the last year, then it will
1061	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1233	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1062	roughly 10 seconds later and of course not if you reset your system time	1234	roughly 10 seconds later).
1063	again).
1064		1235
1065	They can also be used to implement vastly more complex timers, such as	1236	They can also be used to implement vastly more complex timers, such as
1066	triggering an event on eahc midnight, local time.	1237	triggering an event on each midnight, local time or other, complicated,
		1238	rules.
1067		1239
1068	As with timers, the callback is guarenteed to be invoked only when the	1240	As with timers, the callback is guarenteed to be invoked only when the
1069	time (C<at>) has been passed, but if multiple periodic timers become ready	1241	time (C<at>) has been passed, but if multiple periodic timers become ready
1070	during the same loop iteration then order of execution is undefined.	1242	during the same loop iteration then order of execution is undefined.
1071		1243
		1244	=head3 Watcher-Specific Functions and Data Members
		1245
1072	=over 4	1246	=over 4
1073		1247
1074	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1248	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1075		1249
1076	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1250	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1078	Lots of arguments, lets sort it out... There are basically three modes of	1252	Lots of arguments, lets sort it out... There are basically three modes of
1079	operation, and we will explain them from simplest to complex:	1253	operation, and we will explain them from simplest to complex:
1080		1254
1081	=over 4	1255	=over 4
1082		1256
1083	=item * absolute timer (interval = reschedule_cb = 0)	1257	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1084		1258
1085	In this configuration the watcher triggers an event at the wallclock time	1259	In this configuration the watcher triggers an event at the wallclock time
1086	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1260	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1087	that is, if it is to be run at January 1st 2011 then it will run when the	1261	that is, if it is to be run at January 1st 2011 then it will run when the
1088	system time reaches or surpasses this time.	1262	system time reaches or surpasses this time.
1089		1263
1090	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1264	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1091		1265
1092	In this mode the watcher will always be scheduled to time out at the next	1266	In this mode the watcher will always be scheduled to time out at the next
1093	C<at + N * interval> time (for some integer N) and then repeat, regardless	1267	C<at + N * interval> time (for some integer N, which can also be negative)
1094	of any time jumps.	1268	and then repeat, regardless of any time jumps.
1095		1269
1096	This can be used to create timers that do not drift with respect to system	1270	This can be used to create timers that do not drift with respect to system
1097	time:	1271	time:
1098		1272
1099	ev_periodic_set (&periodic, 0., 3600., 0);	1273	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1105		1279
1106	Another way to think about it (for the mathematically inclined) is that	1280	Another way to think about it (for the mathematically inclined) is that
1107	C<ev_periodic> will try to run the callback in this mode at the next possible	1281	C<ev_periodic> will try to run the callback in this mode at the next possible
1108	time where C<time = at (mod interval)>, regardless of any time jumps.	1282	time where C<time = at (mod interval)>, regardless of any time jumps.
1109		1283
		1284	For numerical stability it is preferable that the C<at> value is near
		1285	C<ev_now ()> (the current time), but there is no range requirement for
		1286	this value.
		1287
1110	=item * manual reschedule mode (reschedule_cb = callback)	1288	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1111		1289
1112	In this mode the values for C<interval> and C<at> are both being	1290	In this mode the values for C<interval> and C<at> are both being
1113	ignored. Instead, each time the periodic watcher gets scheduled, the	1291	ignored. Instead, each time the periodic watcher gets scheduled, the
1114	reschedule callback will be called with the watcher as first, and the	1292	reschedule callback will be called with the watcher as first, and the
1115	current time as second argument.	1293	current time as second argument.
1116		1294
1117	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1295	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1118	ever, or make any event loop modifications>. If you need to stop it,	1296	ever, or make any event loop modifications>. If you need to stop it,
1119	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1297	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1120	starting a prepare watcher).	1298	starting an C<ev_prepare> watcher, which is legal).
1121		1299
1122	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1300	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1123	ev_tstamp now)>, e.g.:	1301	ev_tstamp now)>, e.g.:
1124		1302
1125	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1303	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1148	Simply stops and restarts the periodic watcher again. This is only useful	1326	Simply stops and restarts the periodic watcher again. This is only useful
1149	when you changed some parameters or the reschedule callback would return	1327	when you changed some parameters or the reschedule callback would return
1150	a different time than the last time it was called (e.g. in a crond like	1328	a different time than the last time it was called (e.g. in a crond like
1151	program when the crontabs have changed).	1329	program when the crontabs have changed).
1152		1330
		1331	=item ev_tstamp offset [read-write]
		1332
		1333	When repeating, this contains the offset value, otherwise this is the
		1334	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1335
		1336	Can be modified any time, but changes only take effect when the periodic
		1337	timer fires or C<ev_periodic_again> is being called.
		1338
1153	=item ev_tstamp interval [read-write]	1339	=item ev_tstamp interval [read-write]
1154		1340
1155	The current interval value. Can be modified any time, but changes only	1341	The current interval value. Can be modified any time, but changes only
1156	take effect when the periodic timer fires or C<ev_periodic_again> is being	1342	take effect when the periodic timer fires or C<ev_periodic_again> is being
1157	called.	1343	called.
…		…
1160		1346
1161	The current reschedule callback, or C<0>, if this functionality is	1347	The current reschedule callback, or C<0>, if this functionality is
1162	switched off. Can be changed any time, but changes only take effect when	1348	switched off. Can be changed any time, but changes only take effect when
1163	the periodic timer fires or C<ev_periodic_again> is being called.	1349	the periodic timer fires or C<ev_periodic_again> is being called.
1164		1350
		1351	=item ev_tstamp at [read-only]
		1352
		1353	When active, contains the absolute time that the watcher is supposed to
		1354	trigger next.
		1355
1165	=back	1356	=back
		1357
		1358	=head3 Examples
1166		1359
1167	Example: Call a callback every hour, or, more precisely, whenever the	1360	Example: Call a callback every hour, or, more precisely, whenever the
1168	system clock is divisible by 3600. The callback invocation times have	1361	system clock is divisible by 3600. The callback invocation times have
1169	potentially a lot of jittering, but good long-term stability.	1362	potentially a lot of jittering, but good long-term stability.
1170		1363
…		…
1210	with the kernel (thus it coexists with your own signal handlers as long	1403	with the kernel (thus it coexists with your own signal handlers as long
1211	as you don't register any with libev). Similarly, when the last signal	1404	as you don't register any with libev). Similarly, when the last signal
1212	watcher for a signal is stopped libev will reset the signal handler to	1405	watcher for a signal is stopped libev will reset the signal handler to
1213	SIG_DFL (regardless of what it was set to before).	1406	SIG_DFL (regardless of what it was set to before).
1214		1407
		1408	=head3 Watcher-Specific Functions and Data Members
		1409
1215	=over 4	1410	=over 4
1216		1411
1217	=item ev_signal_init (ev_signal *, callback, int signum)	1412	=item ev_signal_init (ev_signal *, callback, int signum)
1218		1413
1219	=item ev_signal_set (ev_signal *, int signum)	1414	=item ev_signal_set (ev_signal *, int signum)
…		…
1230		1425
1231	=head2 C<ev_child> - watch out for process status changes	1426	=head2 C<ev_child> - watch out for process status changes
1232		1427
1233	Child watchers trigger when your process receives a SIGCHLD in response to	1428	Child watchers trigger when your process receives a SIGCHLD in response to
1234	some child status changes (most typically when a child of yours dies).	1429	some child status changes (most typically when a child of yours dies).
		1430
		1431	=head3 Watcher-Specific Functions and Data Members
1235		1432
1236	=over 4	1433	=over 4
1237		1434
1238	=item ev_child_init (ev_child *, callback, int pid)	1435	=item ev_child_init (ev_child *, callback, int pid)
1239		1436
…		…
1258		1455
1259	The process exit/trace status caused by C<rpid> (see your systems	1456	The process exit/trace status caused by C<rpid> (see your systems
1260	C<waitpid> and C<sys/wait.h> documentation for details).	1457	C<waitpid> and C<sys/wait.h> documentation for details).
1261		1458
1262	=back	1459	=back
		1460
		1461	=head3 Examples
1263		1462
1264	Example: Try to exit cleanly on SIGINT and SIGTERM.	1463	Example: Try to exit cleanly on SIGINT and SIGTERM.
1265		1464
1266	static void	1465	static void
1267	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1466	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
…		…
1308	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1507	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1309	to fall back to regular polling again even with inotify, but changes are	1508	to fall back to regular polling again even with inotify, but changes are
1310	usually detected immediately, and if the file exists there will be no	1509	usually detected immediately, and if the file exists there will be no
1311	polling.	1510	polling.
1312		1511
		1512	=head3 Inotify
		1513
		1514	When C<inotify (7)> support has been compiled into libev (generally only
		1515	available on Linux) and present at runtime, it will be used to speed up
		1516	change detection where possible. The inotify descriptor will be created lazily
		1517	when the first C<ev_stat> watcher is being started.
		1518
		1519	Inotify presense does not change the semantics of C<ev_stat> watchers
		1520	except that changes might be detected earlier, and in some cases, to avoid
		1521	making regular C<stat> calls. Even in the presense of inotify support
		1522	there are many cases where libev has to resort to regular C<stat> polling.
		1523
		1524	(There is no support for kqueue, as apparently it cannot be used to
		1525	implement this functionality, due to the requirement of having a file
		1526	descriptor open on the object at all times).
		1527
		1528	=head3 The special problem of stat time resolution
		1529
		1530	The C<stat ()> syscall only supports full-second resolution portably, and
		1531	even on systems where the resolution is higher, many filesystems still
		1532	only support whole seconds.
		1533
		1534	That means that, if the time is the only thing that changes, you might
		1535	miss updates: on the first update, C<ev_stat> detects a change and calls
		1536	your callback, which does something. When there is another update within
		1537	the same second, C<ev_stat> will be unable to detect it.
		1538
		1539	The solution to this is to delay acting on a change for a second (or till
		1540	the next second boundary), using a roughly one-second delay C<ev_timer>
		1541	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1542	is added to work around small timing inconsistencies of some operating
		1543	systems.
		1544
		1545	=head3 Watcher-Specific Functions and Data Members
		1546
1313	=over 4	1547	=over 4
1314		1548
1315	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1549	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1316		1550
1317	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1551	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1352	=item const char *path [read-only]	1586	=item const char *path [read-only]
1353		1587
1354	The filesystem path that is being watched.	1588	The filesystem path that is being watched.
1355		1589
1356	=back	1590	=back
		1591
		1592	=head3 Examples
1357		1593
1358	Example: Watch C</etc/passwd> for attribute changes.	1594	Example: Watch C</etc/passwd> for attribute changes.
1359		1595
1360	static void	1596	static void
1361	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1597	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1374	}	1610	}
1375		1611
1376	...	1612	...
1377	ev_stat passwd;	1613	ev_stat passwd;
1378		1614
1379	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1615	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1380	ev_stat_start (loop, &passwd);	1616	ev_stat_start (loop, &passwd);
		1617
		1618	Example: Like above, but additionally use a one-second delay so we do not
		1619	miss updates (however, frequent updates will delay processing, too, so
		1620	one might do the work both on C<ev_stat> callback invocation I<and> on
		1621	C<ev_timer> callback invocation).
		1622
		1623	static ev_stat passwd;
		1624	static ev_timer timer;
		1625
		1626	static void
		1627	timer_cb (EV_P_ ev_timer *w, int revents)
		1628	{
		1629	ev_timer_stop (EV_A_ w);
		1630
		1631	/* now it's one second after the most recent passwd change */
		1632	}
		1633
		1634	static void
		1635	stat_cb (EV_P_ ev_stat *w, int revents)
		1636	{
		1637	/* reset the one-second timer */
		1638	ev_timer_again (EV_A_ &timer);
		1639	}
		1640
		1641	...
		1642	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1643	ev_stat_start (loop, &passwd);
		1644	ev_timer_init (&timer, timer_cb, 0., 1.01);
1381		1645
1382		1646
1383	=head2 C<ev_idle> - when you've got nothing better to do...	1647	=head2 C<ev_idle> - when you've got nothing better to do...
1384		1648
1385	Idle watchers trigger events when no other events of the same or higher	1649	Idle watchers trigger events when no other events of the same or higher
…		…
1399	Apart from keeping your process non-blocking (which is a useful	1663	Apart from keeping your process non-blocking (which is a useful
1400	effect on its own sometimes), idle watchers are a good place to do	1664	effect on its own sometimes), idle watchers are a good place to do
1401	"pseudo-background processing", or delay processing stuff to after the	1665	"pseudo-background processing", or delay processing stuff to after the
1402	event loop has handled all outstanding events.	1666	event loop has handled all outstanding events.
1403		1667
		1668	=head3 Watcher-Specific Functions and Data Members
		1669
1404	=over 4	1670	=over 4
1405		1671
1406	=item ev_idle_init (ev_signal *, callback)	1672	=item ev_idle_init (ev_signal *, callback)
1407		1673
1408	Initialises and configures the idle watcher - it has no parameters of any	1674	Initialises and configures the idle watcher - it has no parameters of any
1409	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1675	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1410	believe me.	1676	believe me.
1411		1677
1412	=back	1678	=back
		1679
		1680	=head3 Examples
1413		1681
1414	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1682	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1415	callback, free it. Also, use no error checking, as usual.	1683	callback, free it. Also, use no error checking, as usual.
1416		1684
1417	static void	1685	static void
…		…
1465	with priority higher than or equal to the event loop and one coroutine	1733	with priority higher than or equal to the event loop and one coroutine
1466	of lower priority, but only once, using idle watchers to keep the event	1734	of lower priority, but only once, using idle watchers to keep the event
1467	loop from blocking if lower-priority coroutines are active, thus mapping	1735	loop from blocking if lower-priority coroutines are active, thus mapping
1468	low-priority coroutines to idle/background tasks).	1736	low-priority coroutines to idle/background tasks).
1469		1737
		1738	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1739	priority, to ensure that they are being run before any other watchers
		1740	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1741	too) should not activate ("feed") events into libev. While libev fully
		1742	supports this, they will be called before other C<ev_check> watchers
		1743	did their job. As C<ev_check> watchers are often used to embed other
		1744	(non-libev) event loops those other event loops might be in an unusable
		1745	state until their C<ev_check> watcher ran (always remind yourself to
		1746	coexist peacefully with others).
		1747
		1748	=head3 Watcher-Specific Functions and Data Members
		1749
1470	=over 4	1750	=over 4
1471		1751
1472	=item ev_prepare_init (ev_prepare *, callback)	1752	=item ev_prepare_init (ev_prepare *, callback)
1473		1753
1474	=item ev_check_init (ev_check *, callback)	1754	=item ev_check_init (ev_check *, callback)
…		…
1477	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1757	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1478	macros, but using them is utterly, utterly and completely pointless.	1758	macros, but using them is utterly, utterly and completely pointless.
1479		1759
1480	=back	1760	=back
1481		1761
1482	Example: To include a library such as adns, you would add IO watchers	1762	=head3 Examples
1483	and a timeout watcher in a prepare handler, as required by libadns, and	1763
		1764	There are a number of principal ways to embed other event loops or modules
		1765	into libev. Here are some ideas on how to include libadns into libev
		1766	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1767	use for an actually working example. Another Perl module named C<EV::Glib>
		1768	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1769	into the Glib event loop).
		1770
		1771	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1484	in a check watcher, destroy them and call into libadns. What follows is	1772	and in a check watcher, destroy them and call into libadns. What follows
1485	pseudo-code only of course:	1773	is pseudo-code only of course. This requires you to either use a low
		1774	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1775	the callbacks for the IO/timeout watchers might not have been called yet.
1486		1776
1487	static ev_io iow [nfd];	1777	static ev_io iow [nfd];
1488	static ev_timer tw;	1778	static ev_timer tw;
1489		1779
1490	static void	1780	static void
1491	io_cb (ev_loop *loop, ev_io *w, int revents)	1781	io_cb (ev_loop *loop, ev_io *w, int revents)
1492	{	1782	{
1493	// set the relevant poll flags
1494	// could also call adns_processreadable etc. here
1495	struct pollfd *fd = (struct pollfd *)w->data;
1496	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1497	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1498	}	1783	}
1499		1784
1500	// create io watchers for each fd and a timer before blocking	1785	// create io watchers for each fd and a timer before blocking
1501	static void	1786	static void
1502	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1787	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
…		…
1508		1793
1509	/* the callback is illegal, but won't be called as we stop during check */	1794	/* the callback is illegal, but won't be called as we stop during check */
1510	ev_timer_init (&tw, 0, timeout * 1e-3);	1795	ev_timer_init (&tw, 0, timeout * 1e-3);
1511	ev_timer_start (loop, &tw);	1796	ev_timer_start (loop, &tw);
1512		1797
1513	// create on ev_io per pollfd	1798	// create one ev_io per pollfd
1514	for (int i = 0; i < nfd; ++i)	1799	for (int i = 0; i < nfd; ++i)
1515	{	1800	{
1516	ev_io_init (iow + i, io_cb, fds [i].fd,	1801	ev_io_init (iow + i, io_cb, fds [i].fd,
1517	((fds [i].events & POLLIN ? EV_READ : 0)	1802	((fds [i].events & POLLIN ? EV_READ : 0)
1518	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1803	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1519		1804
1520	fds [i].revents = 0;	1805	fds [i].revents = 0;
1521	iow [i].data = fds + i;
1522	ev_io_start (loop, iow + i);	1806	ev_io_start (loop, iow + i);
1523	}	1807	}
1524	}	1808	}
1525		1809
1526	// stop all watchers after blocking	1810	// stop all watchers after blocking
…		…
1528	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1812	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1529	{	1813	{
1530	ev_timer_stop (loop, &tw);	1814	ev_timer_stop (loop, &tw);
1531		1815
1532	for (int i = 0; i < nfd; ++i)	1816	for (int i = 0; i < nfd; ++i)
		1817	{
		1818	// set the relevant poll flags
		1819	// could also call adns_processreadable etc. here
		1820	struct pollfd *fd = fds + i;
		1821	int revents = ev_clear_pending (iow + i);
		1822	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1823	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1824
		1825	// now stop the watcher
1533	ev_io_stop (loop, iow + i);	1826	ev_io_stop (loop, iow + i);
		1827	}
1534		1828
1535	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1829	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1830	}
		1831
		1832	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1833	in the prepare watcher and would dispose of the check watcher.
		1834
		1835	Method 3: If the module to be embedded supports explicit event
		1836	notification (adns does), you can also make use of the actual watcher
		1837	callbacks, and only destroy/create the watchers in the prepare watcher.
		1838
		1839	static void
		1840	timer_cb (EV_P_ ev_timer *w, int revents)
		1841	{
		1842	adns_state ads = (adns_state)w->data;
		1843	update_now (EV_A);
		1844
		1845	adns_processtimeouts (ads, &tv_now);
		1846	}
		1847
		1848	static void
		1849	io_cb (EV_P_ ev_io *w, int revents)
		1850	{
		1851	adns_state ads = (adns_state)w->data;
		1852	update_now (EV_A);
		1853
		1854	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1855	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1856	}
		1857
		1858	// do not ever call adns_afterpoll
		1859
		1860	Method 4: Do not use a prepare or check watcher because the module you
		1861	want to embed is too inflexible to support it. Instead, youc na override
		1862	their poll function. The drawback with this solution is that the main
		1863	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1864	this.
		1865
		1866	static gint
		1867	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1868	{
		1869	int got_events = 0;
		1870
		1871	for (n = 0; n < nfds; ++n)
		1872	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1873
		1874	if (timeout >= 0)
		1875	// create/start timer
		1876
		1877	// poll
		1878	ev_loop (EV_A_ 0);
		1879
		1880	// stop timer again
		1881	if (timeout >= 0)
		1882	ev_timer_stop (EV_A_ &to);
		1883
		1884	// stop io watchers again - their callbacks should have set
		1885	for (n = 0; n < nfds; ++n)
		1886	ev_io_stop (EV_A_ iow [n]);
		1887
		1888	return got_events;
1536	}	1889	}
1537		1890
1538		1891
1539	=head2 C<ev_embed> - when one backend isn't enough...	1892	=head2 C<ev_embed> - when one backend isn't enough...
1540		1893
…		…
1583	portable one.	1936	portable one.
1584		1937
1585	So when you want to use this feature you will always have to be prepared	1938	So when you want to use this feature you will always have to be prepared
1586	that you cannot get an embeddable loop. The recommended way to get around	1939	that you cannot get an embeddable loop. The recommended way to get around
1587	this is to have a separate variables for your embeddable loop, try to	1940	this is to have a separate variables for your embeddable loop, try to
1588	create it, and if that fails, use the normal loop for everything:	1941	create it, and if that fails, use the normal loop for everything.
		1942
		1943	=head3 Watcher-Specific Functions and Data Members
		1944
		1945	=over 4
		1946
		1947	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1948
		1949	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1950
		1951	Configures the watcher to embed the given loop, which must be
		1952	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1953	invoked automatically, otherwise it is the responsibility of the callback
		1954	to invoke it (it will continue to be called until the sweep has been done,
		1955	if you do not want thta, you need to temporarily stop the embed watcher).
		1956
		1957	=item ev_embed_sweep (loop, ev_embed *)
		1958
		1959	Make a single, non-blocking sweep over the embedded loop. This works
		1960	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1961	apropriate way for embedded loops.
		1962
		1963	=item struct ev_loop *other [read-only]
		1964
		1965	The embedded event loop.
		1966
		1967	=back
		1968
		1969	=head3 Examples
		1970
		1971	Example: Try to get an embeddable event loop and embed it into the default
		1972	event loop. If that is not possible, use the default loop. The default
		1973	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1974	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1975	used).
1589		1976
1590	struct ev_loop *loop_hi = ev_default_init (0);	1977	struct ev_loop *loop_hi = ev_default_init (0);
1591	struct ev_loop *loop_lo = 0;	1978	struct ev_loop *loop_lo = 0;
1592	struct ev_embed embed;	1979	struct ev_embed embed;
1593		1980
…		…
1604	ev_embed_start (loop_hi, &embed);	1991	ev_embed_start (loop_hi, &embed);
1605	}	1992	}
1606	else	1993	else
1607	loop_lo = loop_hi;	1994	loop_lo = loop_hi;
1608		1995
1609	=over 4	1996	Example: Check if kqueue is available but not recommended and create
		1997	a kqueue backend for use with sockets (which usually work with any
		1998	kqueue implementation). Store the kqueue/socket-only event loop in
		1999	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1610		2000
1611	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2001	struct ev_loop *loop = ev_default_init (0);
		2002	struct ev_loop *loop_socket = 0;
		2003	struct ev_embed embed;
		2004
		2005	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2006	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2007	{
		2008	ev_embed_init (&embed, 0, loop_socket);
		2009	ev_embed_start (loop, &embed);
		2010	}
1612		2011
1613	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2012	if (!loop_socket)
		2013	loop_socket = loop;
1614		2014
1615	Configures the watcher to embed the given loop, which must be	2015	// now use loop_socket for all sockets, and loop for everything else
1616	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1617	invoked automatically, otherwise it is the responsibility of the callback
1618	to invoke it (it will continue to be called until the sweep has been done,
1619	if you do not want thta, you need to temporarily stop the embed watcher).
1620
1621	=item ev_embed_sweep (loop, ev_embed *)
1622
1623	Make a single, non-blocking sweep over the embedded loop. This works
1624	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1625	apropriate way for embedded loops.
1626
1627	=item struct ev_loop *loop [read-only]
1628
1629	The embedded event loop.
1630
1631	=back
1632		2016
1633		2017
1634	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2018	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1635		2019
1636	Fork watchers are called when a C<fork ()> was detected (usually because	2020	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1639	event loop blocks next and before C<ev_check> watchers are being called,	2023	event loop blocks next and before C<ev_check> watchers are being called,
1640	and only in the child after the fork. If whoever good citizen calling	2024	and only in the child after the fork. If whoever good citizen calling
1641	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2025	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1642	handlers will be invoked, too, of course.	2026	handlers will be invoked, too, of course.
1643		2027
		2028	=head3 Watcher-Specific Functions and Data Members
		2029
1644	=over 4	2030	=over 4
1645		2031
1646	=item ev_fork_init (ev_signal *, callback)	2032	=item ev_fork_init (ev_signal *, callback)
1647		2033
1648	Initialises and configures the fork watcher - it has no parameters of any	2034	Initialises and configures the fork watcher - it has no parameters of any
…		…
1744		2130
1745	To use it,	2131	To use it,
1746		2132
1747	#include <ev++.h>	2133	#include <ev++.h>
1748		2134
1749	(it is not installed by default). This automatically includes F<ev.h>	2135	This automatically includes F<ev.h> and puts all of its definitions (many
1750	and puts all of its definitions (many of them macros) into the global	2136	of them macros) into the global namespace. All C++ specific things are
1751	namespace. All C++ specific things are put into the C<ev> namespace.	2137	put into the C<ev> namespace. It should support all the same embedding
		2138	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1752		2139
1753	It should support all the same embedding options as F<ev.h>, most notably	2140	Care has been taken to keep the overhead low. The only data member the C++
1754	C<EV_MULTIPLICITY>.	2141	classes add (compared to plain C-style watchers) is the event loop pointer
		2142	that the watcher is associated with (or no additional members at all if
		2143	you disable C<EV_MULTIPLICITY> when embedding libev).
		2144
		2145	Currently, functions, and static and non-static member functions can be
		2146	used as callbacks. Other types should be easy to add as long as they only
		2147	need one additional pointer for context. If you need support for other
		2148	types of functors please contact the author (preferably after implementing
		2149	it).
1755		2150
1756	Here is a list of things available in the C<ev> namespace:	2151	Here is a list of things available in the C<ev> namespace:
1757		2152
1758	=over 4	2153	=over 4
1759		2154
…		…
1775		2170
1776	All of those classes have these methods:	2171	All of those classes have these methods:
1777		2172
1778	=over 4	2173	=over 4
1779		2174
1780	=item ev::TYPE::TYPE (object *, object::method *)	2175	=item ev::TYPE::TYPE ()
1781		2176
1782	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2177	=item ev::TYPE::TYPE (struct ev_loop *)
1783		2178
1784	=item ev::TYPE::~TYPE	2179	=item ev::TYPE::~TYPE
1785		2180
1786	The constructor takes a pointer to an object and a method pointer to	2181	The constructor (optionally) takes an event loop to associate the watcher
1787	the event handler callback to call in this class. The constructor calls	2182	with. If it is omitted, it will use C<EV_DEFAULT>.
1788	C<ev_init> for you, which means you have to call the C<set> method	2183
1789	before starting it. If you do not specify a loop then the constructor	2184	The constructor calls C<ev_init> for you, which means you have to call the
1790	automatically associates the default loop with this watcher.	2185	C<set> method before starting it.
		2186
		2187	It will not set a callback, however: You have to call the templated C<set>
		2188	method to set a callback before you can start the watcher.
		2189
		2190	(The reason why you have to use a method is a limitation in C++ which does
		2191	not allow explicit template arguments for constructors).
1791		2192
1792	The destructor automatically stops the watcher if it is active.	2193	The destructor automatically stops the watcher if it is active.
		2194
		2195	=item w->set<class, &class::method> (object *)
		2196
		2197	This method sets the callback method to call. The method has to have a
		2198	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2199	first argument and the C<revents> as second. The object must be given as
		2200	parameter and is stored in the C<data> member of the watcher.
		2201
		2202	This method synthesizes efficient thunking code to call your method from
		2203	the C callback that libev requires. If your compiler can inline your
		2204	callback (i.e. it is visible to it at the place of the C<set> call and
		2205	your compiler is good :), then the method will be fully inlined into the
		2206	thunking function, making it as fast as a direct C callback.
		2207
		2208	Example: simple class declaration and watcher initialisation
		2209
		2210	struct myclass
		2211	{
		2212	void io_cb (ev::io &w, int revents) { }
		2213	}
		2214
		2215	myclass obj;
		2216	ev::io iow;
		2217	iow.set <myclass, &myclass::io_cb> (&obj);
		2218
		2219	=item w->set<function> (void *data = 0)
		2220
		2221	Also sets a callback, but uses a static method or plain function as
		2222	callback. The optional C<data> argument will be stored in the watcher's
		2223	C<data> member and is free for you to use.
		2224
		2225	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2226
		2227	See the method-C<set> above for more details.
		2228
		2229	Example:
		2230
		2231	static void io_cb (ev::io &w, int revents) { }
		2232	iow.set <io_cb> ();
1793		2233
1794	=item w->set (struct ev_loop *)	2234	=item w->set (struct ev_loop *)
1795		2235
1796	Associates a different C<struct ev_loop> with this watcher. You can only	2236	Associates a different C<struct ev_loop> with this watcher. You can only
1797	do this when the watcher is inactive (and not pending either).	2237	do this when the watcher is inactive (and not pending either).
1798		2238
1799	=item w->set ([args])	2239	=item w->set ([args])
1800		2240
1801	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2241	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1802	called at least once. Unlike the C counterpart, an active watcher gets	2242	called at least once. Unlike the C counterpart, an active watcher gets
1803	automatically stopped and restarted.	2243	automatically stopped and restarted when reconfiguring it with this
		2244	method.
1804		2245
1805	=item w->start ()	2246	=item w->start ()
1806		2247
1807	Starts the watcher. Note that there is no C<loop> argument as the	2248	Starts the watcher. Note that there is no C<loop> argument, as the
1808	constructor already takes the loop.	2249	constructor already stores the event loop.
1809		2250
1810	=item w->stop ()	2251	=item w->stop ()
1811		2252
1812	Stops the watcher if it is active. Again, no C<loop> argument.	2253	Stops the watcher if it is active. Again, no C<loop> argument.
1813		2254
1814	=item w->again () C<ev::timer>, C<ev::periodic> only	2255	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1815		2256
1816	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2257	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1817	C<ev_TYPE_again> function.	2258	C<ev_TYPE_again> function.
1818		2259
1819	=item w->sweep () C<ev::embed> only	2260	=item w->sweep () (C<ev::embed> only)
1820		2261
1821	Invokes C<ev_embed_sweep>.	2262	Invokes C<ev_embed_sweep>.
1822		2263
1823	=item w->update () C<ev::stat> only	2264	=item w->update () (C<ev::stat> only)
1824		2265
1825	Invokes C<ev_stat_stat>.	2266	Invokes C<ev_stat_stat>.
1826		2267
1827	=back	2268	=back
1828		2269
…		…
1838		2279
1839	myclass ();	2280	myclass ();
1840	}	2281	}
1841		2282
1842	myclass::myclass (int fd)	2283	myclass::myclass (int fd)
1843	: io (this, &myclass::io_cb),
1844	idle (this, &myclass::idle_cb)
1845	{	2284	{
		2285	io .set <myclass, &myclass::io_cb > (this);
		2286	idle.set <myclass, &myclass::idle_cb> (this);
		2287
1846	io.start (fd, ev::READ);	2288	io.start (fd, ev::READ);
1847	}	2289	}
1848		2290
1849		2291
1850	=head1 MACRO MAGIC	2292	=head1 MACRO MAGIC
1851		2293
1852	Libev can be compiled with a variety of options, the most fundemantal is	2294	Libev can be compiled with a variety of options, the most fundamantal
1853	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2295	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1854	callbacks have an initial C<struct ev_loop *> argument.	2296	functions and callbacks have an initial C<struct ev_loop *> argument.
1855		2297
1856	To make it easier to write programs that cope with either variant, the	2298	To make it easier to write programs that cope with either variant, the
1857	following macros are defined:	2299	following macros are defined:
1858		2300
1859	=over 4	2301	=over 4
…		…
1913	Libev can (and often is) directly embedded into host	2355	Libev can (and often is) directly embedded into host
1914	applications. Examples of applications that embed it include the Deliantra	2356	applications. Examples of applications that embed it include the Deliantra
1915	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2357	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1916	and rxvt-unicode.	2358	and rxvt-unicode.
1917		2359
1918	The goal is to enable you to just copy the neecssary files into your	2360	The goal is to enable you to just copy the necessary files into your
1919	source directory without having to change even a single line in them, so	2361	source directory without having to change even a single line in them, so
1920	you can easily upgrade by simply copying (or having a checked-out copy of	2362	you can easily upgrade by simply copying (or having a checked-out copy of
1921	libev somewhere in your source tree).	2363	libev somewhere in your source tree).
1922		2364
1923	=head2 FILESETS	2365	=head2 FILESETS
…		…
2013		2455
2014	If defined to be C<1>, libev will try to detect the availability of the	2456	If defined to be C<1>, libev will try to detect the availability of the
2015	monotonic clock option at both compiletime and runtime. Otherwise no use	2457	monotonic clock option at both compiletime and runtime. Otherwise no use
2016	of the monotonic clock option will be attempted. If you enable this, you	2458	of the monotonic clock option will be attempted. If you enable this, you
2017	usually have to link against librt or something similar. Enabling it when	2459	usually have to link against librt or something similar. Enabling it when
2018	the functionality isn't available is safe, though, althoguh you have	2460	the functionality isn't available is safe, though, although you have
2019	to make sure you link against any libraries where the C<clock_gettime>	2461	to make sure you link against any libraries where the C<clock_gettime>
2020	function is hiding in (often F<-lrt>).	2462	function is hiding in (often F<-lrt>).
2021		2463
2022	=item EV_USE_REALTIME	2464	=item EV_USE_REALTIME
2023		2465
2024	If defined to be C<1>, libev will try to detect the availability of the	2466	If defined to be C<1>, libev will try to detect the availability of the
2025	realtime clock option at compiletime (and assume its availability at	2467	realtime clock option at compiletime (and assume its availability at
2026	runtime if successful). Otherwise no use of the realtime clock option will	2468	runtime if successful). Otherwise no use of the realtime clock option will
2027	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2469	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2028	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2470	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2029	in the description of C<EV_USE_MONOTONIC>, though.	2471	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2472
		2473	=item EV_USE_NANOSLEEP
		2474
		2475	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2476	and will use it for delays. Otherwise it will use C<select ()>.
2030		2477
2031	=item EV_USE_SELECT	2478	=item EV_USE_SELECT
2032		2479
2033	If undefined or defined to be C<1>, libev will compile in support for the	2480	If undefined or defined to be C<1>, libev will compile in support for the
2034	C<select>(2) backend. No attempt at autodetection will be done: if no	2481	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2052	wants osf handles on win32 (this is the case when the select to	2499	wants osf handles on win32 (this is the case when the select to
2053	be used is the winsock select). This means that it will call	2500	be used is the winsock select). This means that it will call
2054	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2501	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2055	it is assumed that all these functions actually work on fds, even	2502	it is assumed that all these functions actually work on fds, even
2056	on win32. Should not be defined on non-win32 platforms.	2503	on win32. Should not be defined on non-win32 platforms.
		2504
		2505	=item EV_FD_TO_WIN32_HANDLE
		2506
		2507	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2508	file descriptors to socket handles. When not defining this symbol (the
		2509	default), then libev will call C<_get_osfhandle>, which is usually
		2510	correct. In some cases, programs use their own file descriptor management,
		2511	in which case they can provide this function to map fds to socket handles.
2057		2512
2058	=item EV_USE_POLL	2513	=item EV_USE_POLL
2059		2514
2060	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2515	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2061	backend. Otherwise it will be enabled on non-win32 platforms. It	2516	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2098	be detected at runtime.	2553	be detected at runtime.
2099		2554
2100	=item EV_H	2555	=item EV_H
2101		2556
2102	The name of the F<ev.h> header file used to include it. The default if	2557	The name of the F<ev.h> header file used to include it. The default if
2103	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2558	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2104	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2559	virtually rename the F<ev.h> header file in case of conflicts.
2105		2560
2106	=item EV_CONFIG_H	2561	=item EV_CONFIG_H
2107		2562
2108	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2563	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2109	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2564	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2110	C<EV_H>, above.	2565	C<EV_H>, above.
2111		2566
2112	=item EV_EVENT_H	2567	=item EV_EVENT_H
2113		2568
2114	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2569	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2115	of how the F<event.h> header can be found.	2570	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2116		2571
2117	=item EV_PROTOTYPES	2572	=item EV_PROTOTYPES
2118		2573
2119	If defined to be C<0>, then F<ev.h> will not define any function	2574	If defined to be C<0>, then F<ev.h> will not define any function
2120	prototypes, but still define all the structs and other symbols. This is	2575	prototypes, but still define all the structs and other symbols. This is
…		…
2186	than enough. If you need to manage thousands of children you might want to	2641	than enough. If you need to manage thousands of children you might want to
2187	increase this value (I<must> be a power of two).	2642	increase this value (I<must> be a power of two).
2188		2643
2189	=item EV_INOTIFY_HASHSIZE	2644	=item EV_INOTIFY_HASHSIZE
2190		2645
2191	C<ev_staz> watchers use a small hash table to distribute workload by	2646	C<ev_stat> watchers use a small hash table to distribute workload by
2192	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2647	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2193	usually more than enough. If you need to manage thousands of C<ev_stat>	2648	usually more than enough. If you need to manage thousands of C<ev_stat>
2194	watchers you might want to increase this value (I<must> be a power of	2649	watchers you might want to increase this value (I<must> be a power of
2195	two).	2650	two).
2196		2651
…		…
2213		2668
2214	=item ev_set_cb (ev, cb)	2669	=item ev_set_cb (ev, cb)
2215		2670
2216	Can be used to change the callback member declaration in each watcher,	2671	Can be used to change the callback member declaration in each watcher,
2217	and the way callbacks are invoked and set. Must expand to a struct member	2672	and the way callbacks are invoked and set. Must expand to a struct member
2218	definition and a statement, respectively. See the F<ev.v> header file for	2673	definition and a statement, respectively. See the F<ev.h> header file for
2219	their default definitions. One possible use for overriding these is to	2674	their default definitions. One possible use for overriding these is to
2220	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2675	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2221	method calls instead of plain function calls in C++.	2676	method calls instead of plain function calls in C++.
		2677
		2678	=head2 EXPORTED API SYMBOLS
		2679
		2680	If you need to re-export the API (e.g. via a dll) and you need a list of
		2681	exported symbols, you can use the provided F<Symbol.*> files which list
		2682	all public symbols, one per line:
		2683
		2684	Symbols.ev for libev proper
		2685	Symbols.event for the libevent emulation
		2686
		2687	This can also be used to rename all public symbols to avoid clashes with
		2688	multiple versions of libev linked together (which is obviously bad in
		2689	itself, but sometimes it is inconvinient to avoid this).
		2690
		2691	A sed command like this will create wrapper C<#define>'s that you need to
		2692	include before including F<ev.h>:
		2693
		2694	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2695
		2696	This would create a file F<wrap.h> which essentially looks like this:
		2697
		2698	#define ev_backend myprefix_ev_backend
		2699	#define ev_check_start myprefix_ev_check_start
		2700	#define ev_check_stop myprefix_ev_check_stop
		2701	...
2222		2702
2223	=head2 EXAMPLES	2703	=head2 EXAMPLES
2224		2704
2225	For a real-world example of a program the includes libev	2705	For a real-world example of a program the includes libev
2226	verbatim, you can have a look at the EV perl module	2706	verbatim, you can have a look at the EV perl module
…		…
2255		2735
2256	In this section the complexities of (many of) the algorithms used inside	2736	In this section the complexities of (many of) the algorithms used inside
2257	libev will be explained. For complexity discussions about backends see the	2737	libev will be explained. For complexity discussions about backends see the
2258	documentation for C<ev_default_init>.	2738	documentation for C<ev_default_init>.
2259		2739
		2740	All of the following are about amortised time: If an array needs to be
		2741	extended, libev needs to realloc and move the whole array, but this
		2742	happens asymptotically never with higher number of elements, so O(1) might
		2743	mean it might do a lengthy realloc operation in rare cases, but on average
		2744	it is much faster and asymptotically approaches constant time.
		2745
2260	=over 4	2746	=over 4
2261		2747
2262	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2748	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2263		2749
2264	This means that, when you have a watcher that triggers in one hour and	2750	This means that, when you have a watcher that triggers in one hour and
2265	there are 100 watchers that would trigger before that then inserting will	2751	there are 100 watchers that would trigger before that then inserting will
2266	have to skip those 100 watchers.	2752	have to skip roughly seven (C<ld 100>) of these watchers.
2267		2753
2268	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2754	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2269		2755
2270	That means that for changing a timer costs less than removing/adding them	2756	That means that changing a timer costs less than removing/adding them
2271	as only the relative motion in the event queue has to be paid for.	2757	as only the relative motion in the event queue has to be paid for.
2272		2758
2273	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2759	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2274		2760
2275	These just add the watcher into an array or at the head of a list. If	2761	These just add the watcher into an array or at the head of a list.
2276	the array needs to be extended libev needs to realloc and move the whole
2277	array, but this happen asymptotically less and less with more watchers,
2278	thus amortised O(1).
2279		2762
2280	=item Stopping check/prepare/idle watchers: O(1)	2763	=item Stopping check/prepare/idle watchers: O(1)
2281		2764
2282	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2765	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2283		2766
2284	These watchers are stored in lists then need to be walked to find the	2767	These watchers are stored in lists then need to be walked to find the
2285	correct watcher to remove. The lists are usually short (you don't usually	2768	correct watcher to remove. The lists are usually short (you don't usually
2286	have many watchers waiting for the same fd or signal).	2769	have many watchers waiting for the same fd or signal).
2287		2770
2288	=item Finding the next timer per loop iteration: O(1)	2771	=item Finding the next timer in each loop iteration: O(1)
		2772
		2773	By virtue of using a binary heap, the next timer is always found at the
		2774	beginning of the storage array.
2289		2775
2290	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2776	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2291		2777
2292	A change means an I/O watcher gets started or stopped, which requires	2778	A change means an I/O watcher gets started or stopped, which requires
2293	libev to recalculate its status (and possibly tell the kernel).	2779	libev to recalculate its status (and possibly tell the kernel, depending
		2780	on backend and wether C<ev_io_set> was used).
2294		2781
2295	=item Activating one watcher: O(1)	2782	=item Activating one watcher (putting it into the pending state): O(1)
2296		2783
2297	=item Priority handling: O(number_of_priorities)	2784	=item Priority handling: O(number_of_priorities)
2298		2785
2299	Priorities are implemented by allocating some space for each	2786	Priorities are implemented by allocating some space for each
2300	priority. When doing priority-based operations, libev usually has to	2787	priority. When doing priority-based operations, libev usually has to
2301	linearly search all the priorities.	2788	linearly search all the priorities, but starting/stopping and activating
		2789	watchers becomes O(1) w.r.t. prioritiy handling.
2302		2790
2303	=back	2791	=back
2304		2792
2305		2793
		2794	=head1 Win32 platform limitations and workarounds
		2795
		2796	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2797	requires, and its I/O model is fundamentally incompatible with the POSIX
		2798	model. Libev still offers limited functionality on this platform in
		2799	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2800	descriptors. This only applies when using Win32 natively, not when using
		2801	e.g. cygwin.
		2802
		2803	There is no supported compilation method available on windows except
		2804	embedding it into other applications.
		2805
		2806	Due to the many, low, and arbitrary limits on the win32 platform and the
		2807	abysmal performance of winsockets, using a large number of sockets is not
		2808	recommended (and not reasonable). If your program needs to use more than
		2809	a hundred or so sockets, then likely it needs to use a totally different
		2810	implementation for windows, as libev offers the POSIX model, which cannot
		2811	be implemented efficiently on windows (microsoft monopoly games).
		2812
		2813	=over 4
		2814
		2815	=item The winsocket select function
		2816
		2817	The winsocket C<select> function doesn't follow POSIX in that it requires
		2818	socket I<handles> and not socket I<file descriptors>. This makes select
		2819	very inefficient, and also requires a mapping from file descriptors
		2820	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2821	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2822	symbols for more info.
		2823
		2824	The configuration for a "naked" win32 using the microsoft runtime
		2825	libraries and raw winsocket select is:
		2826
		2827	#define EV_USE_SELECT 1
		2828	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2829
		2830	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2831	complexity in the O(n²) range when using win32.
		2832
		2833	=item Limited number of file descriptors
		2834
		2835	Windows has numerous arbitrary (and low) limits on things. Early versions
		2836	of winsocket's select only supported waiting for a max. of C<64> handles
		2837	(probably owning to the fact that all windows kernels can only wait for
		2838	C<64> things at the same time internally; microsoft recommends spawning a
		2839	chain of threads and wait for 63 handles and the previous thread in each).
		2840
		2841	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2842	to some high number (e.g. C<2048>) before compiling the winsocket select
		2843	call (which might be in libev or elsewhere, for example, perl does its own
		2844	select emulation on windows).
		2845
		2846	Another limit is the number of file descriptors in the microsoft runtime
		2847	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2848	or something like this inside microsoft). You can increase this by calling
		2849	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2850	arbitrary limit), but is broken in many versions of the microsoft runtime
		2851	libraries.
		2852
		2853	This might get you to about C<512> or C<2048> sockets (depending on
		2854	windows version and/or the phase of the moon). To get more, you need to
		2855	wrap all I/O functions and provide your own fd management, but the cost of
		2856	calling select (O(n²)) will likely make this unworkable.
		2857
		2858	=back
		2859
		2860
2306	=head1 AUTHOR	2861	=head1 AUTHOR
2307		2862
2308	Marc Lehmann <libev@schmorp.de>.	2863	Marc Lehmann <libev@schmorp.de>.
2309		2864

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