[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.62 by root, Thu Nov 29 17:28:13 2007 UTC vs.
Revision 1.113 by root, Mon Dec 31 01:30:53 2007 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	#include <ev.h>	11	#include <ev.h>
12		12
13	ev_io stdin_watcher;	13	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
…		…
48	return 0;	48	return 0;
49	}	49	}
50		50
51	=head1 DESCRIPTION	51	=head1 DESCRIPTION
52		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
53	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
54	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
55	these event sources and provide your program with events.	59	these event sources and provide your program with events.
56		60
57	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
58	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
59	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
61	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
62	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
63	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
64	watcher.	68	watcher.
65		69
66	=head1 FEATURES	70	=head2 FEATURES
67		71
68	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
78		82
79	It also is quite fast (see this	83	It also is quite fast (see this
80	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
81	for example).	85	for example).
82		86
83	=head1 CONVENTIONS	87	=head2 CONVENTIONS
84		88
85	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
86	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
87	various configuration options please have a look at B<EMBED> section in	91	various configuration options please have a look at B<EMBED> section in
88	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
89	loops, then all functions taking an initial argument of name C<loop>	93	loops, then all functions taking an initial argument of name C<loop>
90	(which is always of type C<struct ev_loop *>) will not have this argument.	94	(which is always of type C<struct ev_loop *>) will not have this argument.
91		95
92	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
93		97
94	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
97	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
98	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
99	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
100		106
101	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
102		108
103	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
104	library in any way.	110	library in any way.
…		…
109		115
110	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
111	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
112	you actually want to know.	118	you actually want to know.
113		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
114	=item int ev_version_major ()	126	=item int ev_version_major ()
115		127
116	=item int ev_version_minor ()	128	=item int ev_version_minor ()
117		129
118	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
119	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
120	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
121	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
122	version of the library your program was compiled against.	134	version of the library your program was compiled against.
123		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
124	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
125	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
126	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
127	not a problem.	142	not a problem.
128		143
129	Example: Make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
130	version.	145	version.
…		…
274	a fork, you can also make libev check for a fork in each iteration by	289	a fork, you can also make libev check for a fork in each iteration by
275	enabling this flag.	290	enabling this flag.
276		291
277	This works by calling C<getpid ()> on every iteration of the loop,	292	This works by calling C<getpid ()> on every iteration of the loop,
278	and thus this might slow down your event loop if you do a lot of loop	293	and thus this might slow down your event loop if you do a lot of loop
279	iterations and little real work, but is usually not noticable (on my	294	iterations and little real work, but is usually not noticeable (on my
280	Linux system for example, C<getpid> is actually a simple 5-insn sequence	295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
281	without a syscall and thus I<very> fast, but my Linux system also has	296	without a syscall and thus I<very> fast, but my Linux system also has
282	C<pthread_atfork> which is even faster).	297	C<pthread_atfork> which is even faster).
283		298
284	The big advantage of this flag is that you can forget about fork (and	299	The big advantage of this flag is that you can forget about fork (and
…		…
291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
292		307
293	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
294	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
295	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
296	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
297	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
298		320
299	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
300		322
301	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
302	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
303	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
304	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
305		329
306	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
307		331
308	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
309	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
310	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	334	like O(total_fds) where n is the total number of fds (or the highest fd),
311	either O(1) or O(active_fds).	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
		336	of shortcomings, such as silently dropping events in some hard-to-detect
		337	cases and rewiring a syscall per fd change, no fork support and bad
		338	support for dup.
312		339
313	While stopping and starting an I/O watcher in the same iteration will	340	While stopping, setting and starting an I/O watcher in the same iteration
314	result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
315	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
316	best to avoid that. Also, dup()ed file descriptors might not work very	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
317	well if you register events for both fds.	344	very well if you register events for both fds.
318		345
319	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
320	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
321	(or space) is available.	348	(or space) is available.
322		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
323	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
324		358
325	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
326	was broken on all BSDs except NetBSD (usually it doesn't work with	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
327	anything but sockets and pipes, except on Darwin, where of course its	361	with anything but sockets and pipes, except on Darwin, where of course
328	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
329	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
330	C<EVBACKEND_KQUEUE>).	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		365	system like NetBSD.
		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
331		370
332	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
333	kernel is more efficient (which says nothing about its actual speed, of	372	kernel is more efficient (which says nothing about its actual speed, of
334	course). While starting and stopping an I/O watcher does not cause an	373	course). While stopping, setting and starting an I/O watcher does never
335	extra syscall as with epoll, it still adds up to four event changes per	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
336	incident, so its best to avoid that.	375	two event changes per incident, support for C<fork ()> is very bad and it
		376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
337		386
338	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
339		388
340	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
341		393
342	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
343		395
344	This uses the Solaris 10 port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
345	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
346		398
347	Please note that solaris ports can result in a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
348	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
349	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
350		407
351	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
352		409
353	Try all backends (even potentially broken ones that wouldn't be tried	410	Try all backends (even potentially broken ones that wouldn't be tried
354	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
355	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
356		415
357	=back	416	=back
358		417
359	If one or more of these are ored into the flags value, then only these	418	If one or more of these are ored into the flags value, then only these
360	backends will be tried (in the reverse order as given here). If none are	419	backends will be tried (in the reverse order as given here). If none are
…		…
395	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
396	etc.). None of the active event watchers will be stopped in the normal	455	etc.). None of the active event watchers will be stopped in the normal
397	sense, so e.g. C<ev_is_active> might still return true. It is your	456	sense, so e.g. C<ev_is_active> might still return true. It is your
398	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
399	calling this function, or cope with the fact afterwards (which is usually	458	calling this function, or cope with the fact afterwards (which is usually
400	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	459	the easiest thing, you can just ignore the watchers and/or C<free ()> them
401	for example).	460	for example).
		461
		462	Note that certain global state, such as signal state, will not be freed by
		463	this function, and related watchers (such as signal and child watchers)
		464	would need to be stopped manually.
		465
		466	In general it is not advisable to call this function except in the
		467	rare occasion where you really need to free e.g. the signal handling
		468	pipe fds. If you need dynamically allocated loops it is better to use
		469	C<ev_loop_new> and C<ev_loop_destroy>).
402		470
403	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
404		472
405	Like C<ev_default_destroy>, but destroys an event loop created by an	473	Like C<ev_default_destroy>, but destroys an event loop created by an
406	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
430		498
431	Like C<ev_default_fork>, but acts on an event loop created by	499	Like C<ev_default_fork>, but acts on an event loop created by
432	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
433	after fork, and how you do this is entirely your own problem.	501	after fork, and how you do this is entirely your own problem.
434		502
		503	=item unsigned int ev_loop_count (loop)
		504
		505	Returns the count of loop iterations for the loop, which is identical to
		506	the number of times libev did poll for new events. It starts at C<0> and
		507	happily wraps around with enough iterations.
		508
		509	This value can sometimes be useful as a generation counter of sorts (it
		510	"ticks" the number of loop iterations), as it roughly corresponds with
		511	C<ev_prepare> and C<ev_check> calls.
		512
435	=item unsigned int ev_backend (loop)	513	=item unsigned int ev_backend (loop)
436		514
437	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	515	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
438	use.	516	use.
439		517
…		…
441		519
442	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
443	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
444	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
445	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
446	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
447		525
448	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
449		527
450	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
451	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
…		…
472	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
473	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
474		552
475	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
476		554
477	* If there are no active watchers (reference count is zero), return.	555	- Before the first iteration, call any pending watchers.
478	- 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.
479	- If we have been forked, recreate the kernel state.	559	- If we have been forked, recreate the kernel state.
480	- Update the kernel state with all outstanding changes.	560	- Update the kernel state with all outstanding changes.
481	- Update the "event loop time".	561	- Update the "event loop time".
482	- 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.
483	- Block the process, waiting for any events.	566	- Block the process, waiting for any events.
484	- Queue all outstanding I/O (fd) events.	567	- Queue all outstanding I/O (fd) events.
485	- Update the "event loop time" and do time jump handling.	568	- Update the "event loop time" and do time jump handling.
486	- Queue all outstanding timers.	569	- Queue all outstanding timers.
487	- Queue all outstanding periodics.	570	- Queue all outstanding periodics.
488	- If no events are pending now, queue all idle watchers.	571	- If no events are pending now, queue all idle watchers.
489	- Queue all check watchers.	572	- Queue all check watchers.
490	- 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).
491	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
492	be handled here by queueing them when their watcher gets executed.	575	be handled here by queueing them when their watcher gets executed.
493	- 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
494	were used, return, otherwise continue with step *.	577	were used, or there are no active watchers, return, otherwise
		578	continue with step *.
495		579
496	Example: Queue some jobs and then loop until no events are outsanding	580	Example: Queue some jobs and then loop until no events are outsanding
497	anymore.	581	anymore.
498		582
499	... queue jobs here, make sure they register event watchers as long	583	... queue jobs here, make sure they register event watchers as long
…		…
534	Example: For some weird reason, unregister the above signal handler again.	618	Example: For some weird reason, unregister the above signal handler again.
535		619
536	ev_ref (loop);	620	ev_ref (loop);
537	ev_signal_stop (loop, &exitsig);	621	ev_signal_stop (loop, &exitsig);
538		622
		623	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		624
		625	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		626
		627	These advanced functions influence the time that libev will spend waiting
		628	for events. Both are by default C<0>, meaning that libev will try to
		629	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		630
		631	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		632	allows libev to delay invocation of I/O and timer/periodic callbacks to
		633	increase efficiency of loop iterations.
		634
		635	The background is that sometimes your program runs just fast enough to
		636	handle one (or very few) event(s) per loop iteration. While this makes
		637	the program responsive, it also wastes a lot of CPU time to poll for new
		638	events, especially with backends like C<select ()> which have a high
		639	overhead for the actual polling but can deliver many events at once.
		640
		641	By setting a higher I<io collect interval> you allow libev to spend more
		642	time collecting I/O events, so you can handle more events per iteration,
		643	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		644	C<ev_timer>) will be not affected. Setting this to a non-null value will
		645	introduce an additional C<ev_sleep ()> call into most loop iterations.
		646
		647	Likewise, by setting a higher I<timeout collect interval> you allow libev
		648	to spend more time collecting timeouts, at the expense of increased
		649	latency (the watcher callback will be called later). C<ev_io> watchers
		650	will not be affected. Setting this to a non-null value will not introduce
		651	any overhead in libev.
		652
		653	Many (busy) programs can usually benefit by setting the io collect
		654	interval to a value near C<0.1> or so, which is often enough for
		655	interactive servers (of course not for games), likewise for timeouts. It
		656	usually doesn't make much sense to set it to a lower value than C<0.01>,
		657	as this approsaches the timing granularity of most systems.
		658
539	=back	659	=back
540		660
541		661
542	=head1 ANATOMY OF A WATCHER	662	=head1 ANATOMY OF A WATCHER
543		663
…		…
722	=item bool ev_is_pending (ev_TYPE *watcher)	842	=item bool ev_is_pending (ev_TYPE *watcher)
723		843
724	Returns a true value iff the watcher is pending, (i.e. it has outstanding	844	Returns a true value iff the watcher is pending, (i.e. it has outstanding
725	events but its callback has not yet been invoked). As long as a watcher	845	events but its callback has not yet been invoked). As long as a watcher
726	is pending (but not active) you must not call an init function on it (but	846	is pending (but not active) you must not call an init function on it (but
727	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	847	C<ev_TYPE_set> is safe), you must not change its priority, and you must
728	libev (e.g. you cnanot C<free ()> it).	848	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		849	it).
729		850
730	=item callback ev_cb (ev_TYPE *watcher)	851	=item callback ev_cb (ev_TYPE *watcher)
731		852
732	Returns the callback currently set on the watcher.	853	Returns the callback currently set on the watcher.
733		854
734	=item ev_cb_set (ev_TYPE *watcher, callback)	855	=item ev_cb_set (ev_TYPE *watcher, callback)
735		856
736	Change the callback. You can change the callback at virtually any time	857	Change the callback. You can change the callback at virtually any time
737	(modulo threads).	858	(modulo threads).
		859
		860	=item ev_set_priority (ev_TYPE *watcher, priority)
		861
		862	=item int ev_priority (ev_TYPE *watcher)
		863
		864	Set and query the priority of the watcher. The priority is a small
		865	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		866	(default: C<-2>). Pending watchers with higher priority will be invoked
		867	before watchers with lower priority, but priority will not keep watchers
		868	from being executed (except for C<ev_idle> watchers).
		869
		870	This means that priorities are I<only> used for ordering callback
		871	invocation after new events have been received. This is useful, for
		872	example, to reduce latency after idling, or more often, to bind two
		873	watchers on the same event and make sure one is called first.
		874
		875	If you need to suppress invocation when higher priority events are pending
		876	you need to look at C<ev_idle> watchers, which provide this functionality.
		877
		878	You I<must not> change the priority of a watcher as long as it is active or
		879	pending.
		880
		881	The default priority used by watchers when no priority has been set is
		882	always C<0>, which is supposed to not be too high and not be too low :).
		883
		884	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		885	fine, as long as you do not mind that the priority value you query might
		886	or might not have been adjusted to be within valid range.
		887
		888	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		889
		890	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		891	C<loop> nor C<revents> need to be valid as long as the watcher callback
		892	can deal with that fact.
		893
		894	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		895
		896	If the watcher is pending, this function returns clears its pending status
		897	and returns its C<revents> bitset (as if its callback was invoked). If the
		898	watcher isn't pending it does nothing and returns C<0>.
738		899
739	=back	900	=back
740		901
741		902
742	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	903	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
827	In general you can register as many read and/or write event watchers per	988	In general you can register as many read and/or write event watchers per
828	fd as you want (as long as you don't confuse yourself). Setting all file	989	fd as you want (as long as you don't confuse yourself). Setting all file
829	descriptors to non-blocking mode is also usually a good idea (but not	990	descriptors to non-blocking mode is also usually a good idea (but not
830	required if you know what you are doing).	991	required if you know what you are doing).
831		992
832	You have to be careful with dup'ed file descriptors, though. Some backends
833	(the linux epoll backend is a notable example) cannot handle dup'ed file
834	descriptors correctly if you register interest in two or more fds pointing
835	to the same underlying file/socket/etc. description (that is, they share
836	the same underlying "file open").
837
838	If you must do this, then force the use of a known-to-be-good backend	993	If you must do this, then force the use of a known-to-be-good backend
839	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	994	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
840	C<EVBACKEND_POLL>).	995	C<EVBACKEND_POLL>).
841		996
842	Another thing you have to watch out for is that it is quite easy to	997	Another thing you have to watch out for is that it is quite easy to
…		…
848	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1003	it is best to always use non-blocking I/O: An extra C<read>(2) returning
849	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1004	C<EAGAIN> is far preferable to a program hanging until some data arrives.
850		1005
851	If you cannot run the fd in non-blocking mode (for example you should not	1006	If you cannot run the fd in non-blocking mode (for example you should not
852	play around with an Xlib connection), then you have to seperately re-test	1007	play around with an Xlib connection), then you have to seperately re-test
853	wether a file descriptor is really ready with a known-to-be good interface	1008	whether a file descriptor is really ready with a known-to-be good interface
854	such as poll (fortunately in our Xlib example, Xlib already does this on	1009	such as poll (fortunately in our Xlib example, Xlib already does this on
855	its own, so its quite safe to use).	1010	its own, so its quite safe to use).
		1011
		1012	=head3 The special problem of disappearing file descriptors
		1013
		1014	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1015	descriptor (either by calling C<close> explicitly or by any other means,
		1016	such as C<dup>). The reason is that you register interest in some file
		1017	descriptor, but when it goes away, the operating system will silently drop
		1018	this interest. If another file descriptor with the same number then is
		1019	registered with libev, there is no efficient way to see that this is, in
		1020	fact, a different file descriptor.
		1021
		1022	To avoid having to explicitly tell libev about such cases, libev follows
		1023	the following policy: Each time C<ev_io_set> is being called, libev
		1024	will assume that this is potentially a new file descriptor, otherwise
		1025	it is assumed that the file descriptor stays the same. That means that
		1026	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1027	descriptor even if the file descriptor number itself did not change.
		1028
		1029	This is how one would do it normally anyway, the important point is that
		1030	the libev application should not optimise around libev but should leave
		1031	optimisations to libev.
		1032
		1033	=head3 The special problem of dup'ed file descriptors
		1034
		1035	Some backends (e.g. epoll), cannot register events for file descriptors,
		1036	but only events for the underlying file descriptions. That means when you
		1037	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1038	events for them, only one file descriptor might actually receive events.
		1039
		1040	There is no workaround possible except not registering events
		1041	for potentially C<dup ()>'ed file descriptors, or to resort to
		1042	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1043
		1044	=head3 The special problem of fork
		1045
		1046	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1047	useless behaviour. Libev fully supports fork, but needs to be told about
		1048	it in the child.
		1049
		1050	To support fork in your programs, you either have to call
		1051	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1052	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1053	C<EVBACKEND_POLL>.
		1054
		1055
		1056	=head3 Watcher-Specific Functions
856		1057
857	=over 4	1058	=over 4
858		1059
859	=item ev_io_init (ev_io *, callback, int fd, int events)	1060	=item ev_io_init (ev_io *, callback, int fd, int events)
860		1061
…		…
871	=item int events [read-only]	1072	=item int events [read-only]
872		1073
873	The events being watched.	1074	The events being watched.
874		1075
875	=back	1076	=back
		1077
		1078	=head3 Examples
876		1079
877	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1080	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
878	readable, but only once. Since it is likely line-buffered, you could	1081	readable, but only once. Since it is likely line-buffered, you could
879	attempt to read a whole line in the callback.	1082	attempt to read a whole line in the callback.
880		1083
…		…
913	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1116	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
914		1117
915	The callback is guarenteed to be invoked only when its timeout has passed,	1118	The callback is guarenteed to be invoked only when its timeout has passed,
916	but if multiple timers become ready during the same loop iteration then	1119	but if multiple timers become ready during the same loop iteration then
917	order of execution is undefined.	1120	order of execution is undefined.
		1121
		1122	=head3 Watcher-Specific Functions and Data Members
918		1123
919	=over 4	1124	=over 4
920		1125
921	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1126	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
922		1127
…		…
976	or C<ev_timer_again> is called and determines the next timeout (if any),	1181	or C<ev_timer_again> is called and determines the next timeout (if any),
977	which is also when any modifications are taken into account.	1182	which is also when any modifications are taken into account.
978		1183
979	=back	1184	=back
980		1185
		1186	=head3 Examples
		1187
981	Example: Create a timer that fires after 60 seconds.	1188	Example: Create a timer that fires after 60 seconds.
982		1189
983	static void	1190	static void
984	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1191	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
985	{	1192	{
…		…
1018	but on wallclock time (absolute time). You can tell a periodic watcher	1225	but on wallclock time (absolute time). You can tell a periodic watcher
1019	to trigger "at" some specific point in time. For example, if you tell a	1226	to trigger "at" some specific point in time. For example, if you tell a
1020	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1227	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1021	+ 10.>) and then reset your system clock to the last year, then it will	1228	+ 10.>) and then reset your system clock to the last year, then it will
1022	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1229	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1023	roughly 10 seconds later and of course not if you reset your system time	1230	roughly 10 seconds later).
1024	again).
1025		1231
1026	They can also be used to implement vastly more complex timers, such as	1232	They can also be used to implement vastly more complex timers, such as
1027	triggering an event on eahc midnight, local time.	1233	triggering an event on each midnight, local time or other, complicated,
		1234	rules.
1028		1235
1029	As with timers, the callback is guarenteed to be invoked only when the	1236	As with timers, the callback is guarenteed to be invoked only when the
1030	time (C<at>) has been passed, but if multiple periodic timers become ready	1237	time (C<at>) has been passed, but if multiple periodic timers become ready
1031	during the same loop iteration then order of execution is undefined.	1238	during the same loop iteration then order of execution is undefined.
1032		1239
		1240	=head3 Watcher-Specific Functions and Data Members
		1241
1033	=over 4	1242	=over 4
1034		1243
1035	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1244	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1036		1245
1037	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1246	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1039	Lots of arguments, lets sort it out... There are basically three modes of	1248	Lots of arguments, lets sort it out... There are basically three modes of
1040	operation, and we will explain them from simplest to complex:	1249	operation, and we will explain them from simplest to complex:
1041		1250
1042	=over 4	1251	=over 4
1043		1252
1044	=item * absolute timer (interval = reschedule_cb = 0)	1253	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1045		1254
1046	In this configuration the watcher triggers an event at the wallclock time	1255	In this configuration the watcher triggers an event at the wallclock time
1047	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1256	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1048	that is, if it is to be run at January 1st 2011 then it will run when the	1257	that is, if it is to be run at January 1st 2011 then it will run when the
1049	system time reaches or surpasses this time.	1258	system time reaches or surpasses this time.
1050		1259
1051	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1260	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1052		1261
1053	In this mode the watcher will always be scheduled to time out at the next	1262	In this mode the watcher will always be scheduled to time out at the next
1054	C<at + N * interval> time (for some integer N) and then repeat, regardless	1263	C<at + N * interval> time (for some integer N, which can also be negative)
1055	of any time jumps.	1264	and then repeat, regardless of any time jumps.
1056		1265
1057	This can be used to create timers that do not drift with respect to system	1266	This can be used to create timers that do not drift with respect to system
1058	time:	1267	time:
1059		1268
1060	ev_periodic_set (&periodic, 0., 3600., 0);	1269	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1066		1275
1067	Another way to think about it (for the mathematically inclined) is that	1276	Another way to think about it (for the mathematically inclined) is that
1068	C<ev_periodic> will try to run the callback in this mode at the next possible	1277	C<ev_periodic> will try to run the callback in this mode at the next possible
1069	time where C<time = at (mod interval)>, regardless of any time jumps.	1278	time where C<time = at (mod interval)>, regardless of any time jumps.
1070		1279
		1280	For numerical stability it is preferable that the C<at> value is near
		1281	C<ev_now ()> (the current time), but there is no range requirement for
		1282	this value.
		1283
1071	=item * manual reschedule mode (reschedule_cb = callback)	1284	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1072		1285
1073	In this mode the values for C<interval> and C<at> are both being	1286	In this mode the values for C<interval> and C<at> are both being
1074	ignored. Instead, each time the periodic watcher gets scheduled, the	1287	ignored. Instead, each time the periodic watcher gets scheduled, the
1075	reschedule callback will be called with the watcher as first, and the	1288	reschedule callback will be called with the watcher as first, and the
1076	current time as second argument.	1289	current time as second argument.
1077		1290
1078	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1291	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1079	ever, or make any event loop modifications>. If you need to stop it,	1292	ever, or make any event loop modifications>. If you need to stop it,
1080	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1293	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1081	starting a prepare watcher).	1294	starting an C<ev_prepare> watcher, which is legal).
1082		1295
1083	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1296	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1084	ev_tstamp now)>, e.g.:	1297	ev_tstamp now)>, e.g.:
1085		1298
1086	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1299	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1109	Simply stops and restarts the periodic watcher again. This is only useful	1322	Simply stops and restarts the periodic watcher again. This is only useful
1110	when you changed some parameters or the reschedule callback would return	1323	when you changed some parameters or the reschedule callback would return
1111	a different time than the last time it was called (e.g. in a crond like	1324	a different time than the last time it was called (e.g. in a crond like
1112	program when the crontabs have changed).	1325	program when the crontabs have changed).
1113		1326
		1327	=item ev_tstamp offset [read-write]
		1328
		1329	When repeating, this contains the offset value, otherwise this is the
		1330	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1331
		1332	Can be modified any time, but changes only take effect when the periodic
		1333	timer fires or C<ev_periodic_again> is being called.
		1334
1114	=item ev_tstamp interval [read-write]	1335	=item ev_tstamp interval [read-write]
1115		1336
1116	The current interval value. Can be modified any time, but changes only	1337	The current interval value. Can be modified any time, but changes only
1117	take effect when the periodic timer fires or C<ev_periodic_again> is being	1338	take effect when the periodic timer fires or C<ev_periodic_again> is being
1118	called.	1339	called.
…		…
1121		1342
1122	The current reschedule callback, or C<0>, if this functionality is	1343	The current reschedule callback, or C<0>, if this functionality is
1123	switched off. Can be changed any time, but changes only take effect when	1344	switched off. Can be changed any time, but changes only take effect when
1124	the periodic timer fires or C<ev_periodic_again> is being called.	1345	the periodic timer fires or C<ev_periodic_again> is being called.
1125		1346
		1347	=item ev_tstamp at [read-only]
		1348
		1349	When active, contains the absolute time that the watcher is supposed to
		1350	trigger next.
		1351
1126	=back	1352	=back
		1353
		1354	=head3 Examples
1127		1355
1128	Example: Call a callback every hour, or, more precisely, whenever the	1356	Example: Call a callback every hour, or, more precisely, whenever the
1129	system clock is divisible by 3600. The callback invocation times have	1357	system clock is divisible by 3600. The callback invocation times have
1130	potentially a lot of jittering, but good long-term stability.	1358	potentially a lot of jittering, but good long-term stability.
1131		1359
…		…
1171	with the kernel (thus it coexists with your own signal handlers as long	1399	with the kernel (thus it coexists with your own signal handlers as long
1172	as you don't register any with libev). Similarly, when the last signal	1400	as you don't register any with libev). Similarly, when the last signal
1173	watcher for a signal is stopped libev will reset the signal handler to	1401	watcher for a signal is stopped libev will reset the signal handler to
1174	SIG_DFL (regardless of what it was set to before).	1402	SIG_DFL (regardless of what it was set to before).
1175		1403
		1404	=head3 Watcher-Specific Functions and Data Members
		1405
1176	=over 4	1406	=over 4
1177		1407
1178	=item ev_signal_init (ev_signal *, callback, int signum)	1408	=item ev_signal_init (ev_signal *, callback, int signum)
1179		1409
1180	=item ev_signal_set (ev_signal *, int signum)	1410	=item ev_signal_set (ev_signal *, int signum)
…		…
1191		1421
1192	=head2 C<ev_child> - watch out for process status changes	1422	=head2 C<ev_child> - watch out for process status changes
1193		1423
1194	Child watchers trigger when your process receives a SIGCHLD in response to	1424	Child watchers trigger when your process receives a SIGCHLD in response to
1195	some child status changes (most typically when a child of yours dies).	1425	some child status changes (most typically when a child of yours dies).
		1426
		1427	=head3 Watcher-Specific Functions and Data Members
1196		1428
1197	=over 4	1429	=over 4
1198		1430
1199	=item ev_child_init (ev_child *, callback, int pid)	1431	=item ev_child_init (ev_child *, callback, int pid)
1200		1432
…		…
1219		1451
1220	The process exit/trace status caused by C<rpid> (see your systems	1452	The process exit/trace status caused by C<rpid> (see your systems
1221	C<waitpid> and C<sys/wait.h> documentation for details).	1453	C<waitpid> and C<sys/wait.h> documentation for details).
1222		1454
1223	=back	1455	=back
		1456
		1457	=head3 Examples
1224		1458
1225	Example: Try to exit cleanly on SIGINT and SIGTERM.	1459	Example: Try to exit cleanly on SIGINT and SIGTERM.
1226		1460
1227	static void	1461	static void
1228	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1462	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
…		…
1269	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1503	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1270	to fall back to regular polling again even with inotify, but changes are	1504	to fall back to regular polling again even with inotify, but changes are
1271	usually detected immediately, and if the file exists there will be no	1505	usually detected immediately, and if the file exists there will be no
1272	polling.	1506	polling.
1273		1507
		1508	=head3 Inotify
		1509
		1510	When C<inotify (7)> support has been compiled into libev (generally only
		1511	available on Linux) and present at runtime, it will be used to speed up
		1512	change detection where possible. The inotify descriptor will be created lazily
		1513	when the first C<ev_stat> watcher is being started.
		1514
		1515	Inotify presense does not change the semantics of C<ev_stat> watchers
		1516	except that changes might be detected earlier, and in some cases, to avoid
		1517	making regular C<stat> calls. Even in the presense of inotify support
		1518	there are many cases where libev has to resort to regular C<stat> polling.
		1519
		1520	(There is no support for kqueue, as apparently it cannot be used to
		1521	implement this functionality, due to the requirement of having a file
		1522	descriptor open on the object at all times).
		1523
		1524	=head3 The special problem of stat time resolution
		1525
		1526	The C<stat ()> syscall only supports full-second resolution portably, and
		1527	even on systems where the resolution is higher, many filesystems still
		1528	only support whole seconds.
		1529
		1530	That means that, if the time is the only thing that changes, you might
		1531	miss updates: on the first update, C<ev_stat> detects a change and calls
		1532	your callback, which does something. When there is another update within
		1533	the same second, C<ev_stat> will be unable to detect it.
		1534
		1535	The solution to this is to delay acting on a change for a second (or till
		1536	the next second boundary), using a roughly one-second delay C<ev_timer>
		1537	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1538	is added to work around small timing inconsistencies of some operating
		1539	systems.
		1540
		1541	=head3 Watcher-Specific Functions and Data Members
		1542
1274	=over 4	1543	=over 4
1275		1544
1276	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1545	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1277		1546
1278	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)	1547	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
…		…
1313	=item const char *path [read-only]	1582	=item const char *path [read-only]
1314		1583
1315	The filesystem path that is being watched.	1584	The filesystem path that is being watched.
1316		1585
1317	=back	1586	=back
		1587
		1588	=head3 Examples
1318		1589
1319	Example: Watch C</etc/passwd> for attribute changes.	1590	Example: Watch C</etc/passwd> for attribute changes.
1320		1591
1321	static void	1592	static void
1322	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1593	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1335	}	1606	}
1336		1607
1337	...	1608	...
1338	ev_stat passwd;	1609	ev_stat passwd;
1339		1610
1340	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1611	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1341	ev_stat_start (loop, &passwd);	1612	ev_stat_start (loop, &passwd);
1342		1613
		1614	Example: Like above, but additionally use a one-second delay so we do not
		1615	miss updates (however, frequent updates will delay processing, too, so
		1616	one might do the work both on C<ev_stat> callback invocation I<and> on
		1617	C<ev_timer> callback invocation).
		1618
		1619	static ev_stat passwd;
		1620	static ev_timer timer;
		1621
		1622	static void
		1623	timer_cb (EV_P_ ev_timer *w, int revents)
		1624	{
		1625	ev_timer_stop (EV_A_ w);
		1626
		1627	/* now it's one second after the most recent passwd change */
		1628	}
		1629
		1630	static void
		1631	stat_cb (EV_P_ ev_stat *w, int revents)
		1632	{
		1633	/* reset the one-second timer */
		1634	ev_timer_again (EV_A_ &timer);
		1635	}
		1636
		1637	...
		1638	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1639	ev_stat_start (loop, &passwd);
		1640	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1641
1343		1642
1344	=head2 C<ev_idle> - when you've got nothing better to do...	1643	=head2 C<ev_idle> - when you've got nothing better to do...
1345		1644
1346	Idle watchers trigger events when there are no other events are pending	1645	Idle watchers trigger events when no other events of the same or higher
1347	(prepare, check and other idle watchers do not count). That is, as long	1646	priority are pending (prepare, check and other idle watchers do not
1348	as your process is busy handling sockets or timeouts (or even signals,	1647	count).
1349	imagine) it will not be triggered. But when your process is idle all idle	1648
1350	watchers are being called again and again, once per event loop iteration -	1649	That is, as long as your process is busy handling sockets or timeouts
		1650	(or even signals, imagine) of the same or higher priority it will not be
		1651	triggered. But when your process is idle (or only lower-priority watchers
		1652	are pending), the idle watchers are being called once per event loop
1351	until stopped, that is, or your process receives more events and becomes	1653	iteration - until stopped, that is, or your process receives more events
1352	busy.	1654	and becomes busy again with higher priority stuff.
1353		1655
1354	The most noteworthy effect is that as long as any idle watchers are	1656	The most noteworthy effect is that as long as any idle watchers are
1355	active, the process will not block when waiting for new events.	1657	active, the process will not block when waiting for new events.
1356		1658
1357	Apart from keeping your process non-blocking (which is a useful	1659	Apart from keeping your process non-blocking (which is a useful
1358	effect on its own sometimes), idle watchers are a good place to do	1660	effect on its own sometimes), idle watchers are a good place to do
1359	"pseudo-background processing", or delay processing stuff to after the	1661	"pseudo-background processing", or delay processing stuff to after the
1360	event loop has handled all outstanding events.	1662	event loop has handled all outstanding events.
1361		1663
		1664	=head3 Watcher-Specific Functions and Data Members
		1665
1362	=over 4	1666	=over 4
1363		1667
1364	=item ev_idle_init (ev_signal *, callback)	1668	=item ev_idle_init (ev_signal *, callback)
1365		1669
1366	Initialises and configures the idle watcher - it has no parameters of any	1670	Initialises and configures the idle watcher - it has no parameters of any
1367	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1671	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1368	believe me.	1672	believe me.
1369		1673
1370	=back	1674	=back
		1675
		1676	=head3 Examples
1371		1677
1372	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1678	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1373	callback, free it. Also, use no error checking, as usual.	1679	callback, free it. Also, use no error checking, as usual.
1374		1680
1375	static void	1681	static void
…		…
1423	with priority higher than or equal to the event loop and one coroutine	1729	with priority higher than or equal to the event loop and one coroutine
1424	of lower priority, but only once, using idle watchers to keep the event	1730	of lower priority, but only once, using idle watchers to keep the event
1425	loop from blocking if lower-priority coroutines are active, thus mapping	1731	loop from blocking if lower-priority coroutines are active, thus mapping
1426	low-priority coroutines to idle/background tasks).	1732	low-priority coroutines to idle/background tasks).
1427		1733
		1734	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1735	priority, to ensure that they are being run before any other watchers
		1736	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1737	too) should not activate ("feed") events into libev. While libev fully
		1738	supports this, they will be called before other C<ev_check> watchers
		1739	did their job. As C<ev_check> watchers are often used to embed other
		1740	(non-libev) event loops those other event loops might be in an unusable
		1741	state until their C<ev_check> watcher ran (always remind yourself to
		1742	coexist peacefully with others).
		1743
		1744	=head3 Watcher-Specific Functions and Data Members
		1745
1428	=over 4	1746	=over 4
1429		1747
1430	=item ev_prepare_init (ev_prepare *, callback)	1748	=item ev_prepare_init (ev_prepare *, callback)
1431		1749
1432	=item ev_check_init (ev_check *, callback)	1750	=item ev_check_init (ev_check *, callback)
…		…
1435	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1753	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1436	macros, but using them is utterly, utterly and completely pointless.	1754	macros, but using them is utterly, utterly and completely pointless.
1437		1755
1438	=back	1756	=back
1439		1757
1440	Example: To include a library such as adns, you would add IO watchers	1758	=head3 Examples
1441	and a timeout watcher in a prepare handler, as required by libadns, and	1759
		1760	There are a number of principal ways to embed other event loops or modules
		1761	into libev. Here are some ideas on how to include libadns into libev
		1762	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1763	use for an actually working example. Another Perl module named C<EV::Glib>
		1764	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1765	into the Glib event loop).
		1766
		1767	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1442	in a check watcher, destroy them and call into libadns. What follows is	1768	and in a check watcher, destroy them and call into libadns. What follows
1443	pseudo-code only of course:	1769	is pseudo-code only of course. This requires you to either use a low
		1770	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1771	the callbacks for the IO/timeout watchers might not have been called yet.
1444		1772
1445	static ev_io iow [nfd];	1773	static ev_io iow [nfd];
1446	static ev_timer tw;	1774	static ev_timer tw;
1447		1775
1448	static void	1776	static void
1449	io_cb (ev_loop loop, ev_io w, int revents)	1777	io_cb (ev_loop loop, ev_io w, int revents)
1450	{	1778	{
1451	// set the relevant poll flags
1452	// could also call adns_processreadable etc. here
1453	struct pollfd fd = (struct pollfd )w->data;
1454	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1455	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1456	}	1779	}
1457		1780
1458	// create io watchers for each fd and a timer before blocking	1781	// create io watchers for each fd and a timer before blocking
1459	static void	1782	static void
1460	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1783	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1461	{	1784	{
1462	int timeout = 3600000;truct pollfd fds [nfd];	1785	int timeout = 3600000;
		1786	struct pollfd fds [nfd];
1463	// actual code will need to loop here and realloc etc.	1787	// actual code will need to loop here and realloc etc.
1464	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1788	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1465		1789
1466	/* the callback is illegal, but won't be called as we stop during check */	1790	/* the callback is illegal, but won't be called as we stop during check */
1467	ev_timer_init (&tw, 0, timeout * 1e-3);	1791	ev_timer_init (&tw, 0, timeout * 1e-3);
1468	ev_timer_start (loop, &tw);	1792	ev_timer_start (loop, &tw);
1469		1793
1470	// create on ev_io per pollfd	1794	// create one ev_io per pollfd
1471	for (int i = 0; i < nfd; ++i)	1795	for (int i = 0; i < nfd; ++i)
1472	{	1796	{
1473	ev_io_init (iow + i, io_cb, fds [i].fd,	1797	ev_io_init (iow + i, io_cb, fds [i].fd,
1474	((fds [i].events & POLLIN ? EV_READ : 0)	1798	((fds [i].events & POLLIN ? EV_READ : 0)
1475	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1799	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1476		1800
1477	fds [i].revents = 0;	1801	fds [i].revents = 0;
1478	iow [i].data = fds + i;
1479	ev_io_start (loop, iow + i);	1802	ev_io_start (loop, iow + i);
1480	}	1803	}
1481	}	1804	}
1482		1805
1483	// stop all watchers after blocking	1806	// stop all watchers after blocking
…		…
1485	adns_check_cb (ev_loop loop, ev_check w, int revents)	1808	adns_check_cb (ev_loop loop, ev_check w, int revents)
1486	{	1809	{
1487	ev_timer_stop (loop, &tw);	1810	ev_timer_stop (loop, &tw);
1488		1811
1489	for (int i = 0; i < nfd; ++i)	1812	for (int i = 0; i < nfd; ++i)
		1813	{
		1814	// set the relevant poll flags
		1815	// could also call adns_processreadable etc. here
		1816	struct pollfd *fd = fds + i;
		1817	int revents = ev_clear_pending (iow + i);
		1818	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1819	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1820
		1821	// now stop the watcher
1490	ev_io_stop (loop, iow + i);	1822	ev_io_stop (loop, iow + i);
		1823	}
1491		1824
1492	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1825	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1826	}
		1827
		1828	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1829	in the prepare watcher and would dispose of the check watcher.
		1830
		1831	Method 3: If the module to be embedded supports explicit event
		1832	notification (adns does), you can also make use of the actual watcher
		1833	callbacks, and only destroy/create the watchers in the prepare watcher.
		1834
		1835	static void
		1836	timer_cb (EV_P_ ev_timer *w, int revents)
		1837	{
		1838	adns_state ads = (adns_state)w->data;
		1839	update_now (EV_A);
		1840
		1841	adns_processtimeouts (ads, &tv_now);
		1842	}
		1843
		1844	static void
		1845	io_cb (EV_P_ ev_io *w, int revents)
		1846	{
		1847	adns_state ads = (adns_state)w->data;
		1848	update_now (EV_A);
		1849
		1850	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1851	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1852	}
		1853
		1854	// do not ever call adns_afterpoll
		1855
		1856	Method 4: Do not use a prepare or check watcher because the module you
		1857	want to embed is too inflexible to support it. Instead, youc na override
		1858	their poll function. The drawback with this solution is that the main
		1859	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1860	this.
		1861
		1862	static gint
		1863	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1864	{
		1865	int got_events = 0;
		1866
		1867	for (n = 0; n < nfds; ++n)
		1868	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1869
		1870	if (timeout >= 0)
		1871	// create/start timer
		1872
		1873	// poll
		1874	ev_loop (EV_A_ 0);
		1875
		1876	// stop timer again
		1877	if (timeout >= 0)
		1878	ev_timer_stop (EV_A_ &to);
		1879
		1880	// stop io watchers again - their callbacks should have set
		1881	for (n = 0; n < nfds; ++n)
		1882	ev_io_stop (EV_A_ iow [n]);
		1883
		1884	return got_events;
1493	}	1885	}
1494		1886
1495		1887
1496	=head2 C<ev_embed> - when one backend isn't enough...	1888	=head2 C<ev_embed> - when one backend isn't enough...
1497		1889
…		…
1540	portable one.	1932	portable one.
1541		1933
1542	So when you want to use this feature you will always have to be prepared	1934	So when you want to use this feature you will always have to be prepared
1543	that you cannot get an embeddable loop. The recommended way to get around	1935	that you cannot get an embeddable loop. The recommended way to get around
1544	this is to have a separate variables for your embeddable loop, try to	1936	this is to have a separate variables for your embeddable loop, try to
1545	create it, and if that fails, use the normal loop for everything:	1937	create it, and if that fails, use the normal loop for everything.
		1938
		1939	=head3 Watcher-Specific Functions and Data Members
		1940
		1941	=over 4
		1942
		1943	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1944
		1945	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1946
		1947	Configures the watcher to embed the given loop, which must be
		1948	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1949	invoked automatically, otherwise it is the responsibility of the callback
		1950	to invoke it (it will continue to be called until the sweep has been done,
		1951	if you do not want thta, you need to temporarily stop the embed watcher).
		1952
		1953	=item ev_embed_sweep (loop, ev_embed *)
		1954
		1955	Make a single, non-blocking sweep over the embedded loop. This works
		1956	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1957	apropriate way for embedded loops.
		1958
		1959	=item struct ev_loop *other [read-only]
		1960
		1961	The embedded event loop.
		1962
		1963	=back
		1964
		1965	=head3 Examples
		1966
		1967	Example: Try to get an embeddable event loop and embed it into the default
		1968	event loop. If that is not possible, use the default loop. The default
		1969	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1970	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1971	used).
1546		1972
1547	struct ev_loop *loop_hi = ev_default_init (0);	1973	struct ev_loop *loop_hi = ev_default_init (0);
1548	struct ev_loop *loop_lo = 0;	1974	struct ev_loop *loop_lo = 0;
1549	struct ev_embed embed;	1975	struct ev_embed embed;
1550		1976
…		…
1561	ev_embed_start (loop_hi, &embed);	1987	ev_embed_start (loop_hi, &embed);
1562	}	1988	}
1563	else	1989	else
1564	loop_lo = loop_hi;	1990	loop_lo = loop_hi;
1565		1991
1566	=over 4	1992	Example: Check if kqueue is available but not recommended and create
		1993	a kqueue backend for use with sockets (which usually work with any
		1994	kqueue implementation). Store the kqueue/socket-only event loop in
		1995	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1567		1996
1568	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1997	struct ev_loop *loop = ev_default_init (0);
		1998	struct ev_loop *loop_socket = 0;
		1999	struct ev_embed embed;
		2000
		2001	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2002	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2003	{
		2004	ev_embed_init (&embed, 0, loop_socket);
		2005	ev_embed_start (loop, &embed);
		2006	}
1569		2007
1570	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	2008	if (!loop_socket)
		2009	loop_socket = loop;
1571		2010
1572	Configures the watcher to embed the given loop, which must be	2011	// now use loop_socket for all sockets, and loop for everything else
1573	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1574	invoked automatically, otherwise it is the responsibility of the callback
1575	to invoke it (it will continue to be called until the sweep has been done,
1576	if you do not want thta, you need to temporarily stop the embed watcher).
1577
1578	=item ev_embed_sweep (loop, ev_embed *)
1579
1580	Make a single, non-blocking sweep over the embedded loop. This works
1581	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1582	apropriate way for embedded loops.
1583
1584	=item struct ev_loop *loop [read-only]
1585
1586	The embedded event loop.
1587
1588	=back
1589		2012
1590		2013
1591	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2014	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1592		2015
1593	Fork watchers are called when a C<fork ()> was detected (usually because	2016	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1596	event loop blocks next and before C<ev_check> watchers are being called,	2019	event loop blocks next and before C<ev_check> watchers are being called,
1597	and only in the child after the fork. If whoever good citizen calling	2020	and only in the child after the fork. If whoever good citizen calling
1598	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2021	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1599	handlers will be invoked, too, of course.	2022	handlers will be invoked, too, of course.
1600		2023
		2024	=head3 Watcher-Specific Functions and Data Members
		2025
1601	=over 4	2026	=over 4
1602		2027
1603	=item ev_fork_init (ev_signal *, callback)	2028	=item ev_fork_init (ev_signal *, callback)
1604		2029
1605	Initialises and configures the fork watcher - it has no parameters of any	2030	Initialises and configures the fork watcher - it has no parameters of any
…		…
1701		2126
1702	To use it,	2127	To use it,
1703		2128
1704	#include <ev++.h>	2129	#include <ev++.h>
1705		2130
1706	(it is not installed by default). This automatically includes F<ev.h>	2131	This automatically includes F<ev.h> and puts all of its definitions (many
1707	and puts all of its definitions (many of them macros) into the global	2132	of them macros) into the global namespace. All C++ specific things are
1708	namespace. All C++ specific things are put into the C<ev> namespace.	2133	put into the C<ev> namespace. It should support all the same embedding
		2134	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1709		2135
1710	It should support all the same embedding options as F<ev.h>, most notably	2136	Care has been taken to keep the overhead low. The only data member the C++
1711	C<EV_MULTIPLICITY>.	2137	classes add (compared to plain C-style watchers) is the event loop pointer
		2138	that the watcher is associated with (or no additional members at all if
		2139	you disable C<EV_MULTIPLICITY> when embedding libev).
		2140
		2141	Currently, functions, and static and non-static member functions can be
		2142	used as callbacks. Other types should be easy to add as long as they only
		2143	need one additional pointer for context. If you need support for other
		2144	types of functors please contact the author (preferably after implementing
		2145	it).
1712		2146
1713	Here is a list of things available in the C<ev> namespace:	2147	Here is a list of things available in the C<ev> namespace:
1714		2148
1715	=over 4	2149	=over 4
1716		2150
…		…
1732		2166
1733	All of those classes have these methods:	2167	All of those classes have these methods:
1734		2168
1735	=over 4	2169	=over 4
1736		2170
1737	=item ev::TYPE::TYPE (object , object::method )	2171	=item ev::TYPE::TYPE ()
1738		2172
1739	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	2173	=item ev::TYPE::TYPE (struct ev_loop *)
1740		2174
1741	=item ev::TYPE::~TYPE	2175	=item ev::TYPE::~TYPE
1742		2176
1743	The constructor takes a pointer to an object and a method pointer to	2177	The constructor (optionally) takes an event loop to associate the watcher
1744	the event handler callback to call in this class. The constructor calls	2178	with. If it is omitted, it will use C<EV_DEFAULT>.
1745	C<ev_init> for you, which means you have to call the C<set> method	2179
1746	before starting it. If you do not specify a loop then the constructor	2180	The constructor calls C<ev_init> for you, which means you have to call the
1747	automatically associates the default loop with this watcher.	2181	C<set> method before starting it.
		2182
		2183	It will not set a callback, however: You have to call the templated C<set>
		2184	method to set a callback before you can start the watcher.
		2185
		2186	(The reason why you have to use a method is a limitation in C++ which does
		2187	not allow explicit template arguments for constructors).
1748		2188
1749	The destructor automatically stops the watcher if it is active.	2189	The destructor automatically stops the watcher if it is active.
		2190
		2191	=item w->set<class, &class::method> (object *)
		2192
		2193	This method sets the callback method to call. The method has to have a
		2194	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2195	first argument and the C<revents> as second. The object must be given as
		2196	parameter and is stored in the C<data> member of the watcher.
		2197
		2198	This method synthesizes efficient thunking code to call your method from
		2199	the C callback that libev requires. If your compiler can inline your
		2200	callback (i.e. it is visible to it at the place of the C<set> call and
		2201	your compiler is good :), then the method will be fully inlined into the
		2202	thunking function, making it as fast as a direct C callback.
		2203
		2204	Example: simple class declaration and watcher initialisation
		2205
		2206	struct myclass
		2207	{
		2208	void io_cb (ev::io &w, int revents) { }
		2209	}
		2210
		2211	myclass obj;
		2212	ev::io iow;
		2213	iow.set <myclass, &myclass::io_cb> (&obj);
		2214
		2215	=item w->set<function> (void *data = 0)
		2216
		2217	Also sets a callback, but uses a static method or plain function as
		2218	callback. The optional C<data> argument will be stored in the watcher's
		2219	C<data> member and is free for you to use.
		2220
		2221	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2222
		2223	See the method-C<set> above for more details.
		2224
		2225	Example:
		2226
		2227	static void io_cb (ev::io &w, int revents) { }
		2228	iow.set <io_cb> ();
1750		2229
1751	=item w->set (struct ev_loop *)	2230	=item w->set (struct ev_loop *)
1752		2231
1753	Associates a different C<struct ev_loop> with this watcher. You can only	2232	Associates a different C<struct ev_loop> with this watcher. You can only
1754	do this when the watcher is inactive (and not pending either).	2233	do this when the watcher is inactive (and not pending either).
1755		2234
1756	=item w->set ([args])	2235	=item w->set ([args])
1757		2236
1758	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2237	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1759	called at least once. Unlike the C counterpart, an active watcher gets	2238	called at least once. Unlike the C counterpart, an active watcher gets
1760	automatically stopped and restarted.	2239	automatically stopped and restarted when reconfiguring it with this
		2240	method.
1761		2241
1762	=item w->start ()	2242	=item w->start ()
1763		2243
1764	Starts the watcher. Note that there is no C<loop> argument as the	2244	Starts the watcher. Note that there is no C<loop> argument, as the
1765	constructor already takes the loop.	2245	constructor already stores the event loop.
1766		2246
1767	=item w->stop ()	2247	=item w->stop ()
1768		2248
1769	Stops the watcher if it is active. Again, no C<loop> argument.	2249	Stops the watcher if it is active. Again, no C<loop> argument.
1770		2250
1771	=item w->again () C<ev::timer>, C<ev::periodic> only	2251	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1772		2252
1773	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2253	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1774	C<ev_TYPE_again> function.	2254	C<ev_TYPE_again> function.
1775		2255
1776	=item w->sweep () C<ev::embed> only	2256	=item w->sweep () (C<ev::embed> only)
1777		2257
1778	Invokes C<ev_embed_sweep>.	2258	Invokes C<ev_embed_sweep>.
1779		2259
1780	=item w->update () C<ev::stat> only	2260	=item w->update () (C<ev::stat> only)
1781		2261
1782	Invokes C<ev_stat_stat>.	2262	Invokes C<ev_stat_stat>.
1783		2263
1784	=back	2264	=back
1785		2265
…		…
1795		2275
1796	myclass ();	2276	myclass ();
1797	}	2277	}
1798		2278
1799	myclass::myclass (int fd)	2279	myclass::myclass (int fd)
1800	: io (this, &myclass::io_cb),
1801	idle (this, &myclass::idle_cb)
1802	{	2280	{
		2281	io .set <myclass, &myclass::io_cb > (this);
		2282	idle.set <myclass, &myclass::idle_cb> (this);
		2283
1803	io.start (fd, ev::READ);	2284	io.start (fd, ev::READ);
1804	}	2285	}
1805		2286
1806		2287
1807	=head1 MACRO MAGIC	2288	=head1 MACRO MAGIC
1808		2289
1809	Libev can be compiled with a variety of options, the most fundemantal is	2290	Libev can be compiled with a variety of options, the most fundamantal
1810	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2291	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1811	callbacks have an initial C<struct ev_loop *> argument.	2292	functions and callbacks have an initial C<struct ev_loop *> argument.
1812		2293
1813	To make it easier to write programs that cope with either variant, the	2294	To make it easier to write programs that cope with either variant, the
1814	following macros are defined:	2295	following macros are defined:
1815		2296
1816	=over 4	2297	=over 4
…		…
1848	Similar to the other two macros, this gives you the value of the default	2329	Similar to the other two macros, this gives you the value of the default
1849	loop, if multiple loops are supported ("ev loop default").	2330	loop, if multiple loops are supported ("ev loop default").
1850		2331
1851	=back	2332	=back
1852		2333
1853	Example: Declare and initialise a check watcher, working regardless of	2334	Example: Declare and initialise a check watcher, utilising the above
1854	wether multiple loops are supported or not.	2335	macros so it will work regardless of whether multiple loops are supported
		2336	or not.
1855		2337
1856	static void	2338	static void
1857	check_cb (EV_P_ ev_timer *w, int revents)	2339	check_cb (EV_P_ ev_timer *w, int revents)
1858	{	2340	{
1859	ev_check_stop (EV_A_ w);	2341	ev_check_stop (EV_A_ w);
…		…
1862	ev_check check;	2344	ev_check check;
1863	ev_check_init (&check, check_cb);	2345	ev_check_init (&check, check_cb);
1864	ev_check_start (EV_DEFAULT_ &check);	2346	ev_check_start (EV_DEFAULT_ &check);
1865	ev_loop (EV_DEFAULT_ 0);	2347	ev_loop (EV_DEFAULT_ 0);
1866		2348
1867
1868	=head1 EMBEDDING	2349	=head1 EMBEDDING
1869		2350
1870	Libev can (and often is) directly embedded into host	2351	Libev can (and often is) directly embedded into host
1871	applications. Examples of applications that embed it include the Deliantra	2352	applications. Examples of applications that embed it include the Deliantra
1872	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2353	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1873	and rxvt-unicode.	2354	and rxvt-unicode.
1874		2355
1875	The goal is to enable you to just copy the neecssary files into your	2356	The goal is to enable you to just copy the necessary files into your
1876	source directory without having to change even a single line in them, so	2357	source directory without having to change even a single line in them, so
1877	you can easily upgrade by simply copying (or having a checked-out copy of	2358	you can easily upgrade by simply copying (or having a checked-out copy of
1878	libev somewhere in your source tree).	2359	libev somewhere in your source tree).
1879		2360
1880	=head2 FILESETS	2361	=head2 FILESETS
…		…
1911	ev_vars.h	2392	ev_vars.h
1912	ev_wrap.h	2393	ev_wrap.h
1913		2394
1914	ev_win32.c required on win32 platforms only	2395	ev_win32.c required on win32 platforms only
1915		2396
1916	ev_select.c only when select backend is enabled (which is by default)	2397	ev_select.c only when select backend is enabled (which is enabled by default)
1917	ev_poll.c only when poll backend is enabled (disabled by default)	2398	ev_poll.c only when poll backend is enabled (disabled by default)
1918	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2399	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1919	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2400	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1920	ev_port.c only when the solaris port backend is enabled (disabled by default)	2401	ev_port.c only when the solaris port backend is enabled (disabled by default)
1921		2402
…		…
1970		2451
1971	If defined to be C<1>, libev will try to detect the availability of the	2452	If defined to be C<1>, libev will try to detect the availability of the
1972	monotonic clock option at both compiletime and runtime. Otherwise no use	2453	monotonic clock option at both compiletime and runtime. Otherwise no use
1973	of the monotonic clock option will be attempted. If you enable this, you	2454	of the monotonic clock option will be attempted. If you enable this, you
1974	usually have to link against librt or something similar. Enabling it when	2455	usually have to link against librt or something similar. Enabling it when
1975	the functionality isn't available is safe, though, althoguh you have	2456	the functionality isn't available is safe, though, although you have
1976	to make sure you link against any libraries where the C<clock_gettime>	2457	to make sure you link against any libraries where the C<clock_gettime>
1977	function is hiding in (often F<-lrt>).	2458	function is hiding in (often F<-lrt>).
1978		2459
1979	=item EV_USE_REALTIME	2460	=item EV_USE_REALTIME
1980		2461
1981	If defined to be C<1>, libev will try to detect the availability of the	2462	If defined to be C<1>, libev will try to detect the availability of the
1982	realtime clock option at compiletime (and assume its availability at	2463	realtime clock option at compiletime (and assume its availability at
1983	runtime if successful). Otherwise no use of the realtime clock option will	2464	runtime if successful). Otherwise no use of the realtime clock option will
1984	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2465	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1985	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2466	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1986	in the description of C<EV_USE_MONOTONIC>, though.	2467	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2468
		2469	=item EV_USE_NANOSLEEP
		2470
		2471	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2472	and will use it for delays. Otherwise it will use C<select ()>.
1987		2473
1988	=item EV_USE_SELECT	2474	=item EV_USE_SELECT
1989		2475
1990	If undefined or defined to be C<1>, libev will compile in support for the	2476	If undefined or defined to be C<1>, libev will compile in support for the
1991	C<select>(2) backend. No attempt at autodetection will be done: if no	2477	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2009	wants osf handles on win32 (this is the case when the select to	2495	wants osf handles on win32 (this is the case when the select to
2010	be used is the winsock select). This means that it will call	2496	be used is the winsock select). This means that it will call
2011	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2497	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2012	it is assumed that all these functions actually work on fds, even	2498	it is assumed that all these functions actually work on fds, even
2013	on win32. Should not be defined on non-win32 platforms.	2499	on win32. Should not be defined on non-win32 platforms.
		2500
		2501	=item EV_FD_TO_WIN32_HANDLE
		2502
		2503	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2504	file descriptors to socket handles. When not defining this symbol (the
		2505	default), then libev will call C<_get_osfhandle>, which is usually
		2506	correct. In some cases, programs use their own file descriptor management,
		2507	in which case they can provide this function to map fds to socket handles.
2014		2508
2015	=item EV_USE_POLL	2509	=item EV_USE_POLL
2016		2510
2017	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2511	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2018	backend. Otherwise it will be enabled on non-win32 platforms. It	2512	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2055	be detected at runtime.	2549	be detected at runtime.
2056		2550
2057	=item EV_H	2551	=item EV_H
2058		2552
2059	The name of the F<ev.h> header file used to include it. The default if	2553	The name of the F<ev.h> header file used to include it. The default if
2060	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2554	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2061	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2555	virtually rename the F<ev.h> header file in case of conflicts.
2062		2556
2063	=item EV_CONFIG_H	2557	=item EV_CONFIG_H
2064		2558
2065	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2559	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2066	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2560	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2067	C<EV_H>, above.	2561	C<EV_H>, above.
2068		2562
2069	=item EV_EVENT_H	2563	=item EV_EVENT_H
2070		2564
2071	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2565	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2072	of how the F<event.h> header can be found.	2566	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2073		2567
2074	=item EV_PROTOTYPES	2568	=item EV_PROTOTYPES
2075		2569
2076	If defined to be C<0>, then F<ev.h> will not define any function	2570	If defined to be C<0>, then F<ev.h> will not define any function
2077	prototypes, but still define all the structs and other symbols. This is	2571	prototypes, but still define all the structs and other symbols. This is
…		…
2084	will have the C<struct ev_loop *> as first argument, and you can create	2578	will have the C<struct ev_loop *> as first argument, and you can create
2085	additional independent event loops. Otherwise there will be no support	2579	additional independent event loops. Otherwise there will be no support
2086	for multiple event loops and there is no first event loop pointer	2580	for multiple event loops and there is no first event loop pointer
2087	argument. Instead, all functions act on the single default loop.	2581	argument. Instead, all functions act on the single default loop.
2088		2582
		2583	=item EV_MINPRI
		2584
		2585	=item EV_MAXPRI
		2586
		2587	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2588	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2589	provide for more priorities by overriding those symbols (usually defined
		2590	to be C<-2> and C<2>, respectively).
		2591
		2592	When doing priority-based operations, libev usually has to linearly search
		2593	all the priorities, so having many of them (hundreds) uses a lot of space
		2594	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2595	fine.
		2596
		2597	If your embedding app does not need any priorities, defining these both to
		2598	C<0> will save some memory and cpu.
		2599
2089	=item EV_PERIODIC_ENABLE	2600	=item EV_PERIODIC_ENABLE
2090		2601
2091	If undefined or defined to be C<1>, then periodic timers are supported. If	2602	If undefined or defined to be C<1>, then periodic timers are supported. If
		2603	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2604	code.
		2605
		2606	=item EV_IDLE_ENABLE
		2607
		2608	If undefined or defined to be C<1>, then idle watchers are supported. If
2092	defined to be C<0>, then they are not. Disabling them saves a few kB of	2609	defined to be C<0>, then they are not. Disabling them saves a few kB of
2093	code.	2610	code.
2094		2611
2095	=item EV_EMBED_ENABLE	2612	=item EV_EMBED_ENABLE
2096		2613
…		…
2120	than enough. If you need to manage thousands of children you might want to	2637	than enough. If you need to manage thousands of children you might want to
2121	increase this value (I<must> be a power of two).	2638	increase this value (I<must> be a power of two).
2122		2639
2123	=item EV_INOTIFY_HASHSIZE	2640	=item EV_INOTIFY_HASHSIZE
2124		2641
2125	C<ev_staz> watchers use a small hash table to distribute workload by	2642	C<ev_stat> watchers use a small hash table to distribute workload by
2126	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2643	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2127	usually more than enough. If you need to manage thousands of C<ev_stat>	2644	usually more than enough. If you need to manage thousands of C<ev_stat>
2128	watchers you might want to increase this value (I<must> be a power of	2645	watchers you might want to increase this value (I<must> be a power of
2129	two).	2646	two).
2130		2647
…		…
2147		2664
2148	=item ev_set_cb (ev, cb)	2665	=item ev_set_cb (ev, cb)
2149		2666
2150	Can be used to change the callback member declaration in each watcher,	2667	Can be used to change the callback member declaration in each watcher,
2151	and the way callbacks are invoked and set. Must expand to a struct member	2668	and the way callbacks are invoked and set. Must expand to a struct member
2152	definition and a statement, respectively. See the F<ev.v> header file for	2669	definition and a statement, respectively. See the F<ev.h> header file for
2153	their default definitions. One possible use for overriding these is to	2670	their default definitions. One possible use for overriding these is to
2154	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2671	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2155	method calls instead of plain function calls in C++.	2672	method calls instead of plain function calls in C++.
		2673
		2674	=head2 EXPORTED API SYMBOLS
		2675
		2676	If you need to re-export the API (e.g. via a dll) and you need a list of
		2677	exported symbols, you can use the provided F<Symbol.*> files which list
		2678	all public symbols, one per line:
		2679
		2680	Symbols.ev for libev proper
		2681	Symbols.event for the libevent emulation
		2682
		2683	This can also be used to rename all public symbols to avoid clashes with
		2684	multiple versions of libev linked together (which is obviously bad in
		2685	itself, but sometimes it is inconvinient to avoid this).
		2686
		2687	A sed command like this will create wrapper C<#define>'s that you need to
		2688	include before including F<ev.h>:
		2689
		2690	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2691
		2692	This would create a file F<wrap.h> which essentially looks like this:
		2693
		2694	#define ev_backend myprefix_ev_backend
		2695	#define ev_check_start myprefix_ev_check_start
		2696	#define ev_check_stop myprefix_ev_check_stop
		2697	...
2156		2698
2157	=head2 EXAMPLES	2699	=head2 EXAMPLES
2158		2700
2159	For a real-world example of a program the includes libev	2701	For a real-world example of a program the includes libev
2160	verbatim, you can have a look at the EV perl module	2702	verbatim, you can have a look at the EV perl module
…		…
2163	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2705	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2164	will be compiled. It is pretty complex because it provides its own header	2706	will be compiled. It is pretty complex because it provides its own header
2165	file.	2707	file.
2166		2708
2167	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2709	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2168	that everybody includes and which overrides some autoconf choices:	2710	that everybody includes and which overrides some configure choices:
2169		2711
		2712	#define EV_MINIMAL 1
2170	#define EV_USE_POLL 0	2713	#define EV_USE_POLL 0
2171	#define EV_MULTIPLICITY 0	2714	#define EV_MULTIPLICITY 0
2172	#define EV_PERIODICS 0	2715	#define EV_PERIODIC_ENABLE 0
		2716	#define EV_STAT_ENABLE 0
		2717	#define EV_FORK_ENABLE 0
2173	#define EV_CONFIG_H <config.h>	2718	#define EV_CONFIG_H <config.h>
		2719	#define EV_MINPRI 0
		2720	#define EV_MAXPRI 0
2174		2721
2175	#include "ev++.h"	2722	#include "ev++.h"
2176		2723
2177	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2724	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2178		2725
…		…
2184		2731
2185	In this section the complexities of (many of) the algorithms used inside	2732	In this section the complexities of (many of) the algorithms used inside
2186	libev will be explained. For complexity discussions about backends see the	2733	libev will be explained. For complexity discussions about backends see the
2187	documentation for C<ev_default_init>.	2734	documentation for C<ev_default_init>.
2188		2735
		2736	All of the following are about amortised time: If an array needs to be
		2737	extended, libev needs to realloc and move the whole array, but this
		2738	happens asymptotically never with higher number of elements, so O(1) might
		2739	mean it might do a lengthy realloc operation in rare cases, but on average
		2740	it is much faster and asymptotically approaches constant time.
		2741
2189	=over 4	2742	=over 4
2190		2743
2191	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2744	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2192		2745
		2746	This means that, when you have a watcher that triggers in one hour and
		2747	there are 100 watchers that would trigger before that then inserting will
		2748	have to skip roughly seven (C<ld 100>) of these watchers.
		2749
2193	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2750	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2751
		2752	That means that changing a timer costs less than removing/adding them
		2753	as only the relative motion in the event queue has to be paid for.
2194		2754
2195	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2755	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2196		2756
		2757	These just add the watcher into an array or at the head of a list.
		2758
2197	=item Stopping check/prepare/idle watchers: O(1)	2759	=item Stopping check/prepare/idle watchers: O(1)
2198		2760
2199	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2761	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2200		2762
		2763	These watchers are stored in lists then need to be walked to find the
		2764	correct watcher to remove. The lists are usually short (you don't usually
		2765	have many watchers waiting for the same fd or signal).
		2766
2201	=item Finding the next timer per loop iteration: O(1)	2767	=item Finding the next timer in each loop iteration: O(1)
		2768
		2769	By virtue of using a binary heap, the next timer is always found at the
		2770	beginning of the storage array.
2202		2771
2203	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2772	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2204		2773
2205	=item Activating one watcher: O(1)	2774	A change means an I/O watcher gets started or stopped, which requires
		2775	libev to recalculate its status (and possibly tell the kernel, depending
		2776	on backend and wether C<ev_io_set> was used).
		2777
		2778	=item Activating one watcher (putting it into the pending state): O(1)
		2779
		2780	=item Priority handling: O(number_of_priorities)
		2781
		2782	Priorities are implemented by allocating some space for each
		2783	priority. When doing priority-based operations, libev usually has to
		2784	linearly search all the priorities, but starting/stopping and activating
		2785	watchers becomes O(1) w.r.t. prioritiy handling.
2206		2786
2207	=back	2787	=back
2208		2788
2209		2789
		2790	=head1 Win32 platform limitations and workarounds
		2791
		2792	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2793	requires, and its I/O model is fundamentally incompatible with the POSIX
		2794	model. Libev still offers limited functionality on this platform in
		2795	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2796	descriptors. This only applies when using Win32 natively, not when using
		2797	e.g. cygwin.
		2798
		2799	There is no supported compilation method available on windows except
		2800	embedding it into other applications.
		2801
		2802	Due to the many, low, and arbitrary limits on the win32 platform and the
		2803	abysmal performance of winsockets, using a large number of sockets is not
		2804	recommended (and not reasonable). If your program needs to use more than
		2805	a hundred or so sockets, then likely it needs to use a totally different
		2806	implementation for windows, as libev offers the POSIX model, which cannot
		2807	be implemented efficiently on windows (microsoft monopoly games).
		2808
		2809	=over 4
		2810
		2811	=item The winsocket select function
		2812
		2813	The winsocket C<select> function doesn't follow POSIX in that it requires
		2814	socket I<handles> and not socket I<file descriptors>. This makes select
		2815	very inefficient, and also requires a mapping from file descriptors
		2816	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2817	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2818	symbols for more info.
		2819
		2820	The configuration for a "naked" win32 using the microsoft runtime
		2821	libraries and raw winsocket select is:
		2822
		2823	#define EV_USE_SELECT 1
		2824	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2825
		2826	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2827	complexity in the O(n²) range when using win32.
		2828
		2829	=item Limited number of file descriptors
		2830
		2831	Windows has numerous arbitrary (and low) limits on things. Early versions
		2832	of winsocket's select only supported waiting for a max. of C<64> handles
		2833	(probably owning to the fact that all windows kernels can only wait for
		2834	C<64> things at the same time internally; microsoft recommends spawning a
		2835	chain of threads and wait for 63 handles and the previous thread in each).
		2836
		2837	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2838	to some high number (e.g. C<2048>) before compiling the winsocket select
		2839	call (which might be in libev or elsewhere, for example, perl does its own
		2840	select emulation on windows).
		2841
		2842	Another limit is the number of file descriptors in the microsoft runtime
		2843	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2844	or something like this inside microsoft). You can increase this by calling
		2845	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2846	arbitrary limit), but is broken in many versions of the microsoft runtime
		2847	libraries.
		2848
		2849	This might get you to about C<512> or C<2048> sockets (depending on
		2850	windows version and/or the phase of the moon). To get more, you need to
		2851	wrap all I/O functions and provide your own fd management, but the cost of
		2852	calling select (O(n²)) will likely make this unworkable.
		2853
		2854	=back
		2855
		2856
2210	=head1 AUTHOR	2857	=head1 AUTHOR
2211		2858
2212	Marc Lehmann <libev@schmorp.de>.	2859	Marc Lehmann <libev@schmorp.de>.
2213		2860

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Comparing libev/ev.pod (file contents): Revision 1.62 by root, Thu Nov 29 17:28:13 2007 UTC vs. Revision 1.113 by root, Mon Dec 31 01:30:53 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.62 by root, Thu Nov 29 17:28:13 2007 UTC vs.
Revision 1.113 by root, Mon Dec 31 01:30:53 2007 UTC