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

Comparing libev/ev.pod (file contents):
Revision 1.69 by root, Fri Dec 7 19:15:39 2007 UTC vs.
Revision 1.108 by root, Mon Dec 24 10:39:21 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;
…		…
53	The newest version of this document is also available as a html-formatted	53	The newest version of this document is also available as a html-formatted
54	web page you might find easier to navigate when reading it for the first	54	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	55	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		56
57	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	59	these event sources and provide your program with events.
60		60
61	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	68	watcher.
69		69
70	=head1 FEATURES	70	=head2 FEATURES
71		71
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		82
83	It also is quite fast (see this	83	It also is quite fast (see this
84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	85	for example).
86		86
87	=head1 CONVENTIONS	87	=head2 CONVENTIONS
88		88
89	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
90	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
91	various configuration options please have a look at B<EMBED> section in	91	various configuration options please have a look at B<EMBED> section in
92	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
93	loops, then all functions taking an initial argument of name C<loop>	93	loops, then all functions taking an initial argument of name C<loop>
94	(which is always of type C<struct ev_loop *>) will not have this argument.	94	(which is always of type C<struct ev_loop *>) will not have this argument.
95		95
96	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
97		97
98	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
104		106
105	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
106		108
107	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
108	library in any way.	110	library in any way.
…		…
113		115
114	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	118	you actually want to know.
117		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
118	=item int ev_version_major ()	126	=item int ev_version_major ()
119		127
120	=item int ev_version_minor ()	128	=item int ev_version_minor ()
121		129
122	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	134	version of the library your program was compiled against.
127		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
128	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	142	not a problem.
132		143
133	Example: Make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
134	version.	145	version.
…		…
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		307
297	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
298	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
299	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
302		320
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		322
305	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
309		329
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		331
312	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	334	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
		336	of shortcomings, such as silently dropping events in some hard-to-detect
		337	cases and rewiring a syscall per fd change, no fork support and bad
		338	support for dup.
316		339
317	While stopping and starting an I/O watcher in the same iteration will	340	While stopping, setting and starting an I/O watcher in the same iteration
318	result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
319	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
320	best to avoid that. Also, dup()ed file descriptors might not work very	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	344	very well if you register events for both fds.
322		345
323	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
324	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	348	(or space) is available.
326		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		358
329	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
330	was broken on all BSDs except NetBSD (usually it doesn't work with	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
331	anything but sockets and pipes, except on Darwin, where of course its	361	with anything but sockets and pipes, except on Darwin, where of course
332	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
333	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
334	C<EVBACKEND_KQUEUE>).	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		365	system like NetBSD.
		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
335		370
336	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	372	kernel is more efficient (which says nothing about its actual speed, of
338	course). While starting and stopping an I/O watcher does not cause an	373	course). While stopping, setting and starting an I/O watcher does never
339	extra syscall as with epoll, it still adds up to four event changes per	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	375	two event changes per incident, support for C<fork ()> is very bad and it
		376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
341		386
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		388
344	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
345		393
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		395
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
350		398
351	Please note that solaris ports can result in a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
352	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
354		407
355	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
356		409
357	Try all backends (even potentially broken ones that wouldn't be tried	410	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
360		415
361	=back	416	=back
362		417
363	If one or more of these are ored into the flags value, then only these	418	If one or more of these are ored into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	419	backends will be tried (in the reverse order as given here). If none are
…		…
399	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	455	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	456	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
403	calling this function, or cope with the fact afterwards (which is usually	458	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	459	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	460	for example).
		461
		462	Note that certain global state, such as signal state, will not be freed by
		463	this function, and related watchers (such as signal and child watchers)
		464	would need to be stopped manually.
		465
		466	In general it is not advisable to call this function except in the
		467	rare occasion where you really need to free e.g. the signal handling
		468	pipe fds. If you need dynamically allocated loops it is better to use
		469	C<ev_loop_new> and C<ev_loop_destroy>).
406		470
407	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
408		472
409	Like C<ev_default_destroy>, but destroys an event loop created by an	473	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
455		519
456	Returns the current "event loop time", which is the time the event loop	520	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	522	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	523	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
461		525
462	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
463		527
464	Finally, this is it, the event handler. This function usually is called	528	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	529	after you initialised all your watchers and you want to start handling
…		…
486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
488		552
489	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
490		554
		555	- Before the first iteration, call any pending watchers.
491	* If there are no active watchers (reference count is zero), return.	556	* If there are no active watchers (reference count is zero), return.
492	- Queue prepare watchers and then call all outstanding watchers.	557	- Queue all prepare watchers and then call all outstanding watchers.
493	- If we have been forked, recreate the kernel state.	558	- If we have been forked, recreate the kernel state.
494	- Update the kernel state with all outstanding changes.	559	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	560	- Update the "event loop time".
496	- Calculate for how long to block.	561	- Calculate for how long to block.
497	- Block the process, waiting for any events.	562	- Block the process, waiting for any events.
…		…
548	Example: For some weird reason, unregister the above signal handler again.	613	Example: For some weird reason, unregister the above signal handler again.
549		614
550	ev_ref (loop);	615	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	616	ev_signal_stop (loop, &exitsig);
552		617
		618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		619
		620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		621
		622	These advanced functions influence the time that libev will spend waiting
		623	for events. Both are by default C<0>, meaning that libev will try to
		624	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		625
		626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		627	allows libev to delay invocation of I/O and timer/periodic callbacks to
		628	increase efficiency of loop iterations.
		629
		630	The background is that sometimes your program runs just fast enough to
		631	handle one (or very few) event(s) per loop iteration. While this makes
		632	the program responsive, it also wastes a lot of CPU time to poll for new
		633	events, especially with backends like C<select ()> which have a high
		634	overhead for the actual polling but can deliver many events at once.
		635
		636	By setting a higher I<io collect interval> you allow libev to spend more
		637	time collecting I/O events, so you can handle more events per iteration,
		638	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		639	C<ev_timer>) will be not affected. Setting this to a non-null value will
		640	introduce an additional C<ev_sleep ()> call into most loop iterations.
		641
		642	Likewise, by setting a higher I<timeout collect interval> you allow libev
		643	to spend more time collecting timeouts, at the expense of increased
		644	latency (the watcher callback will be called later). C<ev_io> watchers
		645	will not be affected. Setting this to a non-null value will not introduce
		646	any overhead in libev.
		647
		648	Many (busy) programs can usually benefit by setting the io collect
		649	interval to a value near C<0.1> or so, which is often enough for
		650	interactive servers (of course not for games), likewise for timeouts. It
		651	usually doesn't make much sense to set it to a lower value than C<0.01>,
		652	as this approsaches the timing granularity of most systems.
		653
553	=back	654	=back
554		655
555		656
556	=head1 ANATOMY OF A WATCHER	657	=head1 ANATOMY OF A WATCHER
557		658
…		…
736	=item bool ev_is_pending (ev_TYPE *watcher)	837	=item bool ev_is_pending (ev_TYPE *watcher)
737		838
738	Returns a true value iff the watcher is pending, (i.e. it has outstanding	839	Returns a true value iff the watcher is pending, (i.e. it has outstanding
739	events but its callback has not yet been invoked). As long as a watcher	840	events but its callback has not yet been invoked). As long as a watcher
740	is pending (but not active) you must not call an init function on it (but	841	is pending (but not active) you must not call an init function on it (but
741	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	842	C<ev_TYPE_set> is safe), you must not change its priority, and you must
742	libev (e.g. you cnanot C<free ()> it).	843	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		844	it).
743		845
744	=item callback ev_cb (ev_TYPE *watcher)	846	=item callback ev_cb (ev_TYPE *watcher)
745		847
746	Returns the callback currently set on the watcher.	848	Returns the callback currently set on the watcher.
747		849
…		…
766	watchers on the same event and make sure one is called first.	868	watchers on the same event and make sure one is called first.
767		869
768	If you need to suppress invocation when higher priority events are pending	870	If you need to suppress invocation when higher priority events are pending
769	you need to look at C<ev_idle> watchers, which provide this functionality.	871	you need to look at C<ev_idle> watchers, which provide this functionality.
770		872
		873	You I<must not> change the priority of a watcher as long as it is active or
		874	pending.
		875
771	The default priority used by watchers when no priority has been set is	876	The default priority used by watchers when no priority has been set is
772	always C<0>, which is supposed to not be too high and not be too low :).	877	always C<0>, which is supposed to not be too high and not be too low :).
773		878
774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	879	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
775	fine, as long as you do not mind that the priority value you query might	880	fine, as long as you do not mind that the priority value you query might
776	or might not have been adjusted to be within valid range.	881	or might not have been adjusted to be within valid range.
		882
		883	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		884
		885	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		886	C<loop> nor C<revents> need to be valid as long as the watcher callback
		887	can deal with that fact.
		888
		889	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		890
		891	If the watcher is pending, this function returns clears its pending status
		892	and returns its C<revents> bitset (as if its callback was invoked). If the
		893	watcher isn't pending it does nothing and returns C<0>.
777		894
778	=back	895	=back
779		896
780		897
781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
891	play around with an Xlib connection), then you have to seperately re-test	1008	play around with an Xlib connection), then you have to seperately re-test
892	whether a file descriptor is really ready with a known-to-be good interface	1009	whether a file descriptor is really ready with a known-to-be good interface
893	such as poll (fortunately in our Xlib example, Xlib already does this on	1010	such as poll (fortunately in our Xlib example, Xlib already does this on
894	its own, so its quite safe to use).	1011	its own, so its quite safe to use).
895		1012
		1013	=head3 The special problem of disappearing file descriptors
		1014
		1015	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1016	descriptor (either by calling C<close> explicitly or by any other means,
		1017	such as C<dup>). The reason is that you register interest in some file
		1018	descriptor, but when it goes away, the operating system will silently drop
		1019	this interest. If another file descriptor with the same number then is
		1020	registered with libev, there is no efficient way to see that this is, in
		1021	fact, a different file descriptor.
		1022
		1023	To avoid having to explicitly tell libev about such cases, libev follows
		1024	the following policy: Each time C<ev_io_set> is being called, libev
		1025	will assume that this is potentially a new file descriptor, otherwise
		1026	it is assumed that the file descriptor stays the same. That means that
		1027	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1028	descriptor even if the file descriptor number itself did not change.
		1029
		1030	This is how one would do it normally anyway, the important point is that
		1031	the libev application should not optimise around libev but should leave
		1032	optimisations to libev.
		1033
		1034	=head3 The special problem of dup'ed file descriptors
		1035
		1036	Some backends (e.g. epoll), cannot register events for file descriptors,
		1037	but only events for the underlying file descriptions. That means when you
		1038	have C<dup ()>'ed file descriptors and register events for them, only one
		1039	file descriptor might actually receive events.
		1040
		1041	There is no workaround possible except not registering events
		1042	for potentially C<dup ()>'ed file descriptors, or to resort to
		1043	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1044
		1045	=head3 The special problem of fork
		1046
		1047	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1048	useless behaviour. Libev fully supports fork, but needs to be told about
		1049	it in the child.
		1050
		1051	To support fork in your programs, you either have to call
		1052	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1053	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1054	C<EVBACKEND_POLL>.
		1055
		1056
		1057	=head3 Watcher-Specific Functions
		1058
896	=over 4	1059	=over 4
897		1060
898	=item ev_io_init (ev_io *, callback, int fd, int events)	1061	=item ev_io_init (ev_io *, callback, int fd, int events)
899		1062
900	=item ev_io_set (ev_io *, int fd, int events)	1063	=item ev_io_set (ev_io *, int fd, int events)
…		…
952	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1115	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
953		1116
954	The callback is guarenteed to be invoked only when its timeout has passed,	1117	The callback is guarenteed to be invoked only when its timeout has passed,
955	but if multiple timers become ready during the same loop iteration then	1118	but if multiple timers become ready during the same loop iteration then
956	order of execution is undefined.	1119	order of execution is undefined.
		1120
		1121	=head3 Watcher-Specific Functions and Data Members
957		1122
958	=over 4	1123	=over 4
959		1124
960	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1125	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
961		1126
…		…
1057	but on wallclock time (absolute time). You can tell a periodic watcher	1222	but on wallclock time (absolute time). You can tell a periodic watcher
1058	to trigger "at" some specific point in time. For example, if you tell a	1223	to trigger "at" some specific point in time. For example, if you tell a
1059	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1224	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1060	+ 10.>) and then reset your system clock to the last year, then it will	1225	+ 10.>) and then reset your system clock to the last year, then it will
1061	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1226	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1062	roughly 10 seconds later and of course not if you reset your system time	1227	roughly 10 seconds later).
1063	again).
1064		1228
1065	They can also be used to implement vastly more complex timers, such as	1229	They can also be used to implement vastly more complex timers, such as
1066	triggering an event on eahc midnight, local time.	1230	triggering an event on each midnight, local time or other, complicated,
		1231	rules.
1067		1232
1068	As with timers, the callback is guarenteed to be invoked only when the	1233	As with timers, the callback is guarenteed to be invoked only when the
1069	time (C<at>) has been passed, but if multiple periodic timers become ready	1234	time (C<at>) has been passed, but if multiple periodic timers become ready
1070	during the same loop iteration then order of execution is undefined.	1235	during the same loop iteration then order of execution is undefined.
1071		1236
		1237	=head3 Watcher-Specific Functions and Data Members
		1238
1072	=over 4	1239	=over 4
1073		1240
1074	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1241	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1075		1242
1076	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1243	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1078	Lots of arguments, lets sort it out... There are basically three modes of	1245	Lots of arguments, lets sort it out... There are basically three modes of
1079	operation, and we will explain them from simplest to complex:	1246	operation, and we will explain them from simplest to complex:
1080		1247
1081	=over 4	1248	=over 4
1082		1249
1083	=item * absolute timer (interval = reschedule_cb = 0)	1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1084		1251
1085	In this configuration the watcher triggers an event at the wallclock time	1252	In this configuration the watcher triggers an event at the wallclock time
1086	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1253	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1087	that is, if it is to be run at January 1st 2011 then it will run when the	1254	that is, if it is to be run at January 1st 2011 then it will run when the
1088	system time reaches or surpasses this time.	1255	system time reaches or surpasses this time.
1089		1256
1090	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1091		1258
1092	In this mode the watcher will always be scheduled to time out at the next	1259	In this mode the watcher will always be scheduled to time out at the next
1093	C<at + N * interval> time (for some integer N) and then repeat, regardless	1260	C<at + N * interval> time (for some integer N, which can also be negative)
1094	of any time jumps.	1261	and then repeat, regardless of any time jumps.
1095		1262
1096	This can be used to create timers that do not drift with respect to system	1263	This can be used to create timers that do not drift with respect to system
1097	time:	1264	time:
1098		1265
1099	ev_periodic_set (&periodic, 0., 3600., 0);	1266	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1105		1272
1106	Another way to think about it (for the mathematically inclined) is that	1273	Another way to think about it (for the mathematically inclined) is that
1107	C<ev_periodic> will try to run the callback in this mode at the next possible	1274	C<ev_periodic> will try to run the callback in this mode at the next possible
1108	time where C<time = at (mod interval)>, regardless of any time jumps.	1275	time where C<time = at (mod interval)>, regardless of any time jumps.
1109		1276
		1277	For numerical stability it is preferable that the C<at> value is near
		1278	C<ev_now ()> (the current time), but there is no range requirement for
		1279	this value.
		1280
1110	=item * manual reschedule mode (reschedule_cb = callback)	1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1111		1282
1112	In this mode the values for C<interval> and C<at> are both being	1283	In this mode the values for C<interval> and C<at> are both being
1113	ignored. Instead, each time the periodic watcher gets scheduled, the	1284	ignored. Instead, each time the periodic watcher gets scheduled, the
1114	reschedule callback will be called with the watcher as first, and the	1285	reschedule callback will be called with the watcher as first, and the
1115	current time as second argument.	1286	current time as second argument.
1116		1287
1117	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1288	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1118	ever, or make any event loop modifications>. If you need to stop it,	1289	ever, or make any event loop modifications>. If you need to stop it,
1119	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1290	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1120	starting a prepare watcher).	1291	starting an C<ev_prepare> watcher, which is legal).
1121		1292
1122	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1293	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1123	ev_tstamp now)>, e.g.:	1294	ev_tstamp now)>, e.g.:
1124		1295
1125	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1296	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1148	Simply stops and restarts the periodic watcher again. This is only useful	1319	Simply stops and restarts the periodic watcher again. This is only useful
1149	when you changed some parameters or the reschedule callback would return	1320	when you changed some parameters or the reschedule callback would return
1150	a different time than the last time it was called (e.g. in a crond like	1321	a different time than the last time it was called (e.g. in a crond like
1151	program when the crontabs have changed).	1322	program when the crontabs have changed).
1152		1323
		1324	=item ev_tstamp offset [read-write]
		1325
		1326	When repeating, this contains the offset value, otherwise this is the
		1327	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1328
		1329	Can be modified any time, but changes only take effect when the periodic
		1330	timer fires or C<ev_periodic_again> is being called.
		1331
1153	=item ev_tstamp interval [read-write]	1332	=item ev_tstamp interval [read-write]
1154		1333
1155	The current interval value. Can be modified any time, but changes only	1334	The current interval value. Can be modified any time, but changes only
1156	take effect when the periodic timer fires or C<ev_periodic_again> is being	1335	take effect when the periodic timer fires or C<ev_periodic_again> is being
1157	called.	1336	called.
…		…
1159	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1338	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
1160		1339
1161	The current reschedule callback, or C<0>, if this functionality is	1340	The current reschedule callback, or C<0>, if this functionality is
1162	switched off. Can be changed any time, but changes only take effect when	1341	switched off. Can be changed any time, but changes only take effect when
1163	the periodic timer fires or C<ev_periodic_again> is being called.	1342	the periodic timer fires or C<ev_periodic_again> is being called.
		1343
		1344	=item ev_tstamp at [read-only]
		1345
		1346	When active, contains the absolute time that the watcher is supposed to
		1347	trigger next.
1164		1348
1165	=back	1349	=back
1166		1350
1167	Example: Call a callback every hour, or, more precisely, whenever the	1351	Example: Call a callback every hour, or, more precisely, whenever the
1168	system clock is divisible by 3600. The callback invocation times have	1352	system clock is divisible by 3600. The callback invocation times have
…		…
1210	with the kernel (thus it coexists with your own signal handlers as long	1394	with the kernel (thus it coexists with your own signal handlers as long
1211	as you don't register any with libev). Similarly, when the last signal	1395	as you don't register any with libev). Similarly, when the last signal
1212	watcher for a signal is stopped libev will reset the signal handler to	1396	watcher for a signal is stopped libev will reset the signal handler to
1213	SIG_DFL (regardless of what it was set to before).	1397	SIG_DFL (regardless of what it was set to before).
1214		1398
		1399	=head3 Watcher-Specific Functions and Data Members
		1400
1215	=over 4	1401	=over 4
1216		1402
1217	=item ev_signal_init (ev_signal *, callback, int signum)	1403	=item ev_signal_init (ev_signal *, callback, int signum)
1218		1404
1219	=item ev_signal_set (ev_signal *, int signum)	1405	=item ev_signal_set (ev_signal *, int signum)
…		…
1230		1416
1231	=head2 C<ev_child> - watch out for process status changes	1417	=head2 C<ev_child> - watch out for process status changes
1232		1418
1233	Child watchers trigger when your process receives a SIGCHLD in response to	1419	Child watchers trigger when your process receives a SIGCHLD in response to
1234	some child status changes (most typically when a child of yours dies).	1420	some child status changes (most typically when a child of yours dies).
		1421
		1422	=head3 Watcher-Specific Functions and Data Members
1235		1423
1236	=over 4	1424	=over 4
1237		1425
1238	=item ev_child_init (ev_child *, callback, int pid)	1426	=item ev_child_init (ev_child *, callback, int pid)
1239		1427
…		…
1308	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1496	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1309	to fall back to regular polling again even with inotify, but changes are	1497	to fall back to regular polling again even with inotify, but changes are
1310	usually detected immediately, and if the file exists there will be no	1498	usually detected immediately, and if the file exists there will be no
1311	polling.	1499	polling.
1312		1500
		1501	=head3 Inotify
		1502
		1503	When C<inotify (7)> support has been compiled into libev (generally only
		1504	available on Linux) and present at runtime, it will be used to speed up
		1505	change detection where possible. The inotify descriptor will be created lazily
		1506	when the first C<ev_stat> watcher is being started.
		1507
		1508	Inotify presense does not change the semantics of C<ev_stat> watchers
		1509	except that changes might be detected earlier, and in some cases, to avoid
		1510	making regular C<stat> calls. Even in the presense of inotify support
		1511	there are many cases where libev has to resort to regular C<stat> polling.
		1512
		1513	(There is no support for kqueue, as apparently it cannot be used to
		1514	implement this functionality, due to the requirement of having a file
		1515	descriptor open on the object at all times).
		1516
		1517	=head3 The special problem of stat time resolution
		1518
		1519	The C<stat ()> syscall only supports full-second resolution portably, and
		1520	even on systems where the resolution is higher, many filesystems still
		1521	only support whole seconds.
		1522
		1523	That means that, if the time is the only thing that changes, you might
		1524	miss updates: on the first update, C<ev_stat> detects a change and calls
		1525	your callback, which does something. When there is another update within
		1526	the same second, C<ev_stat> will be unable to detect it.
		1527
		1528	The solution to this is to delay acting on a change for a second (or till
		1529	the next second boundary), using a roughly one-second delay C<ev_timer>
		1530	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1531	is added to work around small timing inconsistencies of some operating
		1532	systems.
		1533
		1534	=head3 Watcher-Specific Functions and Data Members
		1535
1313	=over 4	1536	=over 4
1314		1537
1315	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1538	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1316		1539
1317	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)	1540	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
…		…
1352	=item const char *path [read-only]	1575	=item const char *path [read-only]
1353		1576
1354	The filesystem path that is being watched.	1577	The filesystem path that is being watched.
1355		1578
1356	=back	1579	=back
		1580
		1581	=head3 Examples
1357		1582
1358	Example: Watch C</etc/passwd> for attribute changes.	1583	Example: Watch C</etc/passwd> for attribute changes.
1359		1584
1360	static void	1585	static void
1361	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1586	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1374	}	1599	}
1375		1600
1376	...	1601	...
1377	ev_stat passwd;	1602	ev_stat passwd;
1378		1603
1379	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1604	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1380	ev_stat_start (loop, &passwd);	1605	ev_stat_start (loop, &passwd);
		1606
		1607	Example: Like above, but additionally use a one-second delay so we do not
		1608	miss updates (however, frequent updates will delay processing, too, so
		1609	one might do the work both on C<ev_stat> callback invocation I<and> on
		1610	C<ev_timer> callback invocation).
		1611
		1612	static ev_stat passwd;
		1613	static ev_timer timer;
		1614
		1615	static void
		1616	timer_cb (EV_P_ ev_timer *w, int revents)
		1617	{
		1618	ev_timer_stop (EV_A_ w);
		1619
		1620	/* now it's one second after the most recent passwd change */
		1621	}
		1622
		1623	static void
		1624	stat_cb (EV_P_ ev_stat *w, int revents)
		1625	{
		1626	/* reset the one-second timer */
		1627	ev_timer_again (EV_A_ &timer);
		1628	}
		1629
		1630	...
		1631	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1632	ev_stat_start (loop, &passwd);
		1633	ev_timer_init (&timer, timer_cb, 0., 1.01);
1381		1634
1382		1635
1383	=head2 C<ev_idle> - when you've got nothing better to do...	1636	=head2 C<ev_idle> - when you've got nothing better to do...
1384		1637
1385	Idle watchers trigger events when no other events of the same or higher	1638	Idle watchers trigger events when no other events of the same or higher
…		…
1398		1651
1399	Apart from keeping your process non-blocking (which is a useful	1652	Apart from keeping your process non-blocking (which is a useful
1400	effect on its own sometimes), idle watchers are a good place to do	1653	effect on its own sometimes), idle watchers are a good place to do
1401	"pseudo-background processing", or delay processing stuff to after the	1654	"pseudo-background processing", or delay processing stuff to after the
1402	event loop has handled all outstanding events.	1655	event loop has handled all outstanding events.
		1656
		1657	=head3 Watcher-Specific Functions and Data Members
1403		1658
1404	=over 4	1659	=over 4
1405		1660
1406	=item ev_idle_init (ev_signal *, callback)	1661	=item ev_idle_init (ev_signal *, callback)
1407		1662
…		…
1465	with priority higher than or equal to the event loop and one coroutine	1720	with priority higher than or equal to the event loop and one coroutine
1466	of lower priority, but only once, using idle watchers to keep the event	1721	of lower priority, but only once, using idle watchers to keep the event
1467	loop from blocking if lower-priority coroutines are active, thus mapping	1722	loop from blocking if lower-priority coroutines are active, thus mapping
1468	low-priority coroutines to idle/background tasks).	1723	low-priority coroutines to idle/background tasks).
1469		1724
		1725	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1726	priority, to ensure that they are being run before any other watchers
		1727	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1728	too) should not activate ("feed") events into libev. While libev fully
		1729	supports this, they will be called before other C<ev_check> watchers
		1730	did their job. As C<ev_check> watchers are often used to embed other
		1731	(non-libev) event loops those other event loops might be in an unusable
		1732	state until their C<ev_check> watcher ran (always remind yourself to
		1733	coexist peacefully with others).
		1734
		1735	=head3 Watcher-Specific Functions and Data Members
		1736
1470	=over 4	1737	=over 4
1471		1738
1472	=item ev_prepare_init (ev_prepare *, callback)	1739	=item ev_prepare_init (ev_prepare *, callback)
1473		1740
1474	=item ev_check_init (ev_check *, callback)	1741	=item ev_check_init (ev_check *, callback)
…		…
1477	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1744	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1478	macros, but using them is utterly, utterly and completely pointless.	1745	macros, but using them is utterly, utterly and completely pointless.
1479		1746
1480	=back	1747	=back
1481		1748
1482	Example: To include a library such as adns, you would add IO watchers	1749	There are a number of principal ways to embed other event loops or modules
1483	and a timeout watcher in a prepare handler, as required by libadns, and	1750	into libev. Here are some ideas on how to include libadns into libev
		1751	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1752	use for an actually working example. Another Perl module named C<EV::Glib>
		1753	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1754	into the Glib event loop).
		1755
		1756	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1484	in a check watcher, destroy them and call into libadns. What follows is	1757	and in a check watcher, destroy them and call into libadns. What follows
1485	pseudo-code only of course:	1758	is pseudo-code only of course. This requires you to either use a low
		1759	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1760	the callbacks for the IO/timeout watchers might not have been called yet.
1486		1761
1487	static ev_io iow [nfd];	1762	static ev_io iow [nfd];
1488	static ev_timer tw;	1763	static ev_timer tw;
1489		1764
1490	static void	1765	static void
1491	io_cb (ev_loop loop, ev_io w, int revents)	1766	io_cb (ev_loop loop, ev_io w, int revents)
1492	{	1767	{
1493	// set the relevant poll flags
1494	// could also call adns_processreadable etc. here
1495	struct pollfd fd = (struct pollfd )w->data;
1496	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1497	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1498	}	1768	}
1499		1769
1500	// create io watchers for each fd and a timer before blocking	1770	// create io watchers for each fd and a timer before blocking
1501	static void	1771	static void
1502	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1772	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1508		1778
1509	/* the callback is illegal, but won't be called as we stop during check */	1779	/* the callback is illegal, but won't be called as we stop during check */
1510	ev_timer_init (&tw, 0, timeout * 1e-3);	1780	ev_timer_init (&tw, 0, timeout * 1e-3);
1511	ev_timer_start (loop, &tw);	1781	ev_timer_start (loop, &tw);
1512		1782
1513	// create on ev_io per pollfd	1783	// create one ev_io per pollfd
1514	for (int i = 0; i < nfd; ++i)	1784	for (int i = 0; i < nfd; ++i)
1515	{	1785	{
1516	ev_io_init (iow + i, io_cb, fds [i].fd,	1786	ev_io_init (iow + i, io_cb, fds [i].fd,
1517	((fds [i].events & POLLIN ? EV_READ : 0)	1787	((fds [i].events & POLLIN ? EV_READ : 0)
1518	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1788	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1519		1789
1520	fds [i].revents = 0;	1790	fds [i].revents = 0;
1521	iow [i].data = fds + i;
1522	ev_io_start (loop, iow + i);	1791	ev_io_start (loop, iow + i);
1523	}	1792	}
1524	}	1793	}
1525		1794
1526	// stop all watchers after blocking	1795	// stop all watchers after blocking
…		…
1528	adns_check_cb (ev_loop loop, ev_check w, int revents)	1797	adns_check_cb (ev_loop loop, ev_check w, int revents)
1529	{	1798	{
1530	ev_timer_stop (loop, &tw);	1799	ev_timer_stop (loop, &tw);
1531		1800
1532	for (int i = 0; i < nfd; ++i)	1801	for (int i = 0; i < nfd; ++i)
		1802	{
		1803	// set the relevant poll flags
		1804	// could also call adns_processreadable etc. here
		1805	struct pollfd *fd = fds + i;
		1806	int revents = ev_clear_pending (iow + i);
		1807	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1808	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1809
		1810	// now stop the watcher
1533	ev_io_stop (loop, iow + i);	1811	ev_io_stop (loop, iow + i);
		1812	}
1534		1813
1535	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1814	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1815	}
		1816
		1817	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1818	in the prepare watcher and would dispose of the check watcher.
		1819
		1820	Method 3: If the module to be embedded supports explicit event
		1821	notification (adns does), you can also make use of the actual watcher
		1822	callbacks, and only destroy/create the watchers in the prepare watcher.
		1823
		1824	static void
		1825	timer_cb (EV_P_ ev_timer *w, int revents)
		1826	{
		1827	adns_state ads = (adns_state)w->data;
		1828	update_now (EV_A);
		1829
		1830	adns_processtimeouts (ads, &tv_now);
		1831	}
		1832
		1833	static void
		1834	io_cb (EV_P_ ev_io *w, int revents)
		1835	{
		1836	adns_state ads = (adns_state)w->data;
		1837	update_now (EV_A);
		1838
		1839	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1840	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1841	}
		1842
		1843	// do not ever call adns_afterpoll
		1844
		1845	Method 4: Do not use a prepare or check watcher because the module you
		1846	want to embed is too inflexible to support it. Instead, youc na override
		1847	their poll function. The drawback with this solution is that the main
		1848	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1849	this.
		1850
		1851	static gint
		1852	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1853	{
		1854	int got_events = 0;
		1855
		1856	for (n = 0; n < nfds; ++n)
		1857	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1858
		1859	if (timeout >= 0)
		1860	// create/start timer
		1861
		1862	// poll
		1863	ev_loop (EV_A_ 0);
		1864
		1865	// stop timer again
		1866	if (timeout >= 0)
		1867	ev_timer_stop (EV_A_ &to);
		1868
		1869	// stop io watchers again - their callbacks should have set
		1870	for (n = 0; n < nfds; ++n)
		1871	ev_io_stop (EV_A_ iow [n]);
		1872
		1873	return got_events;
1536	}	1874	}
1537		1875
1538		1876
1539	=head2 C<ev_embed> - when one backend isn't enough...	1877	=head2 C<ev_embed> - when one backend isn't enough...
1540		1878
…		…
1604	ev_embed_start (loop_hi, &embed);	1942	ev_embed_start (loop_hi, &embed);
1605	}	1943	}
1606	else	1944	else
1607	loop_lo = loop_hi;	1945	loop_lo = loop_hi;
1608		1946
		1947	=head3 Watcher-Specific Functions and Data Members
		1948
1609	=over 4	1949	=over 4
1610		1950
1611	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1951	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1612		1952
1613	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1953	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
…		…
1622		1962
1623	Make a single, non-blocking sweep over the embedded loop. This works	1963	Make a single, non-blocking sweep over the embedded loop. This works
1624	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1964	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1625	apropriate way for embedded loops.	1965	apropriate way for embedded loops.
1626		1966
1627	=item struct ev_loop *loop [read-only]	1967	=item struct ev_loop *other [read-only]
1628		1968
1629	The embedded event loop.	1969	The embedded event loop.
1630		1970
1631	=back	1971	=back
1632		1972
…		…
1639	event loop blocks next and before C<ev_check> watchers are being called,	1979	event loop blocks next and before C<ev_check> watchers are being called,
1640	and only in the child after the fork. If whoever good citizen calling	1980	and only in the child after the fork. If whoever good citizen calling
1641	C<ev_default_fork> cheats and calls it in the wrong process, the fork	1981	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1642	handlers will be invoked, too, of course.	1982	handlers will be invoked, too, of course.
1643		1983
		1984	=head3 Watcher-Specific Functions and Data Members
		1985
1644	=over 4	1986	=over 4
1645		1987
1646	=item ev_fork_init (ev_signal *, callback)	1988	=item ev_fork_init (ev_signal *, callback)
1647		1989
1648	Initialises and configures the fork watcher - it has no parameters of any	1990	Initialises and configures the fork watcher - it has no parameters of any
…		…
1744		2086
1745	To use it,	2087	To use it,
1746		2088
1747	#include <ev++.h>	2089	#include <ev++.h>
1748		2090
1749	(it is not installed by default). This automatically includes F<ev.h>	2091	This automatically includes F<ev.h> and puts all of its definitions (many
1750	and puts all of its definitions (many of them macros) into the global	2092	of them macros) into the global namespace. All C++ specific things are
1751	namespace. All C++ specific things are put into the C<ev> namespace.	2093	put into the C<ev> namespace. It should support all the same embedding
		2094	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1752		2095
1753	It should support all the same embedding options as F<ev.h>, most notably	2096	Care has been taken to keep the overhead low. The only data member the C++
1754	C<EV_MULTIPLICITY>.	2097	classes add (compared to plain C-style watchers) is the event loop pointer
		2098	that the watcher is associated with (or no additional members at all if
		2099	you disable C<EV_MULTIPLICITY> when embedding libev).
		2100
		2101	Currently, functions, and static and non-static member functions can be
		2102	used as callbacks. Other types should be easy to add as long as they only
		2103	need one additional pointer for context. If you need support for other
		2104	types of functors please contact the author (preferably after implementing
		2105	it).
1755		2106
1756	Here is a list of things available in the C<ev> namespace:	2107	Here is a list of things available in the C<ev> namespace:
1757		2108
1758	=over 4	2109	=over 4
1759		2110
…		…
1775		2126
1776	All of those classes have these methods:	2127	All of those classes have these methods:
1777		2128
1778	=over 4	2129	=over 4
1779		2130
1780	=item ev::TYPE::TYPE (object , object::method )	2131	=item ev::TYPE::TYPE ()
1781		2132
1782	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	2133	=item ev::TYPE::TYPE (struct ev_loop *)
1783		2134
1784	=item ev::TYPE::~TYPE	2135	=item ev::TYPE::~TYPE
1785		2136
1786	The constructor takes a pointer to an object and a method pointer to	2137	The constructor (optionally) takes an event loop to associate the watcher
1787	the event handler callback to call in this class. The constructor calls	2138	with. If it is omitted, it will use C<EV_DEFAULT>.
1788	C<ev_init> for you, which means you have to call the C<set> method	2139
1789	before starting it. If you do not specify a loop then the constructor	2140	The constructor calls C<ev_init> for you, which means you have to call the
1790	automatically associates the default loop with this watcher.	2141	C<set> method before starting it.
		2142
		2143	It will not set a callback, however: You have to call the templated C<set>
		2144	method to set a callback before you can start the watcher.
		2145
		2146	(The reason why you have to use a method is a limitation in C++ which does
		2147	not allow explicit template arguments for constructors).
1791		2148
1792	The destructor automatically stops the watcher if it is active.	2149	The destructor automatically stops the watcher if it is active.
		2150
		2151	=item w->set<class, &class::method> (object *)
		2152
		2153	This method sets the callback method to call. The method has to have a
		2154	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2155	first argument and the C<revents> as second. The object must be given as
		2156	parameter and is stored in the C<data> member of the watcher.
		2157
		2158	This method synthesizes efficient thunking code to call your method from
		2159	the C callback that libev requires. If your compiler can inline your
		2160	callback (i.e. it is visible to it at the place of the C<set> call and
		2161	your compiler is good :), then the method will be fully inlined into the
		2162	thunking function, making it as fast as a direct C callback.
		2163
		2164	Example: simple class declaration and watcher initialisation
		2165
		2166	struct myclass
		2167	{
		2168	void io_cb (ev::io &w, int revents) { }
		2169	}
		2170
		2171	myclass obj;
		2172	ev::io iow;
		2173	iow.set <myclass, &myclass::io_cb> (&obj);
		2174
		2175	=item w->set<function> (void *data = 0)
		2176
		2177	Also sets a callback, but uses a static method or plain function as
		2178	callback. The optional C<data> argument will be stored in the watcher's
		2179	C<data> member and is free for you to use.
		2180
		2181	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2182
		2183	See the method-C<set> above for more details.
		2184
		2185	Example:
		2186
		2187	static void io_cb (ev::io &w, int revents) { }
		2188	iow.set <io_cb> ();
1793		2189
1794	=item w->set (struct ev_loop *)	2190	=item w->set (struct ev_loop *)
1795		2191
1796	Associates a different C<struct ev_loop> with this watcher. You can only	2192	Associates a different C<struct ev_loop> with this watcher. You can only
1797	do this when the watcher is inactive (and not pending either).	2193	do this when the watcher is inactive (and not pending either).
1798		2194
1799	=item w->set ([args])	2195	=item w->set ([args])
1800		2196
1801	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2197	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1802	called at least once. Unlike the C counterpart, an active watcher gets	2198	called at least once. Unlike the C counterpart, an active watcher gets
1803	automatically stopped and restarted.	2199	automatically stopped and restarted when reconfiguring it with this
		2200	method.
1804		2201
1805	=item w->start ()	2202	=item w->start ()
1806		2203
1807	Starts the watcher. Note that there is no C<loop> argument as the	2204	Starts the watcher. Note that there is no C<loop> argument, as the
1808	constructor already takes the loop.	2205	constructor already stores the event loop.
1809		2206
1810	=item w->stop ()	2207	=item w->stop ()
1811		2208
1812	Stops the watcher if it is active. Again, no C<loop> argument.	2209	Stops the watcher if it is active. Again, no C<loop> argument.
1813		2210
1814	=item w->again () C<ev::timer>, C<ev::periodic> only	2211	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1815		2212
1816	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2213	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1817	C<ev_TYPE_again> function.	2214	C<ev_TYPE_again> function.
1818		2215
1819	=item w->sweep () C<ev::embed> only	2216	=item w->sweep () (C<ev::embed> only)
1820		2217
1821	Invokes C<ev_embed_sweep>.	2218	Invokes C<ev_embed_sweep>.
1822		2219
1823	=item w->update () C<ev::stat> only	2220	=item w->update () (C<ev::stat> only)
1824		2221
1825	Invokes C<ev_stat_stat>.	2222	Invokes C<ev_stat_stat>.
1826		2223
1827	=back	2224	=back
1828		2225
…		…
1838		2235
1839	myclass ();	2236	myclass ();
1840	}	2237	}
1841		2238
1842	myclass::myclass (int fd)	2239	myclass::myclass (int fd)
1843	: io (this, &myclass::io_cb),
1844	idle (this, &myclass::idle_cb)
1845	{	2240	{
		2241	io .set <myclass, &myclass::io_cb > (this);
		2242	idle.set <myclass, &myclass::idle_cb> (this);
		2243
1846	io.start (fd, ev::READ);	2244	io.start (fd, ev::READ);
1847	}	2245	}
1848		2246
1849		2247
1850	=head1 MACRO MAGIC	2248	=head1 MACRO MAGIC
1851		2249
1852	Libev can be compiled with a variety of options, the most fundemantal is	2250	Libev can be compiled with a variety of options, the most fundamantal
1853	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2251	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1854	callbacks have an initial C<struct ev_loop *> argument.	2252	functions and callbacks have an initial C<struct ev_loop *> argument.
1855		2253
1856	To make it easier to write programs that cope with either variant, the	2254	To make it easier to write programs that cope with either variant, the
1857	following macros are defined:	2255	following macros are defined:
1858		2256
1859	=over 4	2257	=over 4
…		…
1913	Libev can (and often is) directly embedded into host	2311	Libev can (and often is) directly embedded into host
1914	applications. Examples of applications that embed it include the Deliantra	2312	applications. Examples of applications that embed it include the Deliantra
1915	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2313	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1916	and rxvt-unicode.	2314	and rxvt-unicode.
1917		2315
1918	The goal is to enable you to just copy the neecssary files into your	2316	The goal is to enable you to just copy the necessary files into your
1919	source directory without having to change even a single line in them, so	2317	source directory without having to change even a single line in them, so
1920	you can easily upgrade by simply copying (or having a checked-out copy of	2318	you can easily upgrade by simply copying (or having a checked-out copy of
1921	libev somewhere in your source tree).	2319	libev somewhere in your source tree).
1922		2320
1923	=head2 FILESETS	2321	=head2 FILESETS
…		…
2013		2411
2014	If defined to be C<1>, libev will try to detect the availability of the	2412	If defined to be C<1>, libev will try to detect the availability of the
2015	monotonic clock option at both compiletime and runtime. Otherwise no use	2413	monotonic clock option at both compiletime and runtime. Otherwise no use
2016	of the monotonic clock option will be attempted. If you enable this, you	2414	of the monotonic clock option will be attempted. If you enable this, you
2017	usually have to link against librt or something similar. Enabling it when	2415	usually have to link against librt or something similar. Enabling it when
2018	the functionality isn't available is safe, though, althoguh you have	2416	the functionality isn't available is safe, though, although you have
2019	to make sure you link against any libraries where the C<clock_gettime>	2417	to make sure you link against any libraries where the C<clock_gettime>
2020	function is hiding in (often F<-lrt>).	2418	function is hiding in (often F<-lrt>).
2021		2419
2022	=item EV_USE_REALTIME	2420	=item EV_USE_REALTIME
2023		2421
2024	If defined to be C<1>, libev will try to detect the availability of the	2422	If defined to be C<1>, libev will try to detect the availability of the
2025	realtime clock option at compiletime (and assume its availability at	2423	realtime clock option at compiletime (and assume its availability at
2026	runtime if successful). Otherwise no use of the realtime clock option will	2424	runtime if successful). Otherwise no use of the realtime clock option will
2027	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2425	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2028	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2426	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2029	in the description of C<EV_USE_MONOTONIC>, though.	2427	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2428
		2429	=item EV_USE_NANOSLEEP
		2430
		2431	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2432	and will use it for delays. Otherwise it will use C<select ()>.
2030		2433
2031	=item EV_USE_SELECT	2434	=item EV_USE_SELECT
2032		2435
2033	If undefined or defined to be C<1>, libev will compile in support for the	2436	If undefined or defined to be C<1>, libev will compile in support for the
2034	C<select>(2) backend. No attempt at autodetection will be done: if no	2437	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2186	than enough. If you need to manage thousands of children you might want to	2589	than enough. If you need to manage thousands of children you might want to
2187	increase this value (I<must> be a power of two).	2590	increase this value (I<must> be a power of two).
2188		2591
2189	=item EV_INOTIFY_HASHSIZE	2592	=item EV_INOTIFY_HASHSIZE
2190		2593
2191	C<ev_staz> watchers use a small hash table to distribute workload by	2594	C<ev_stat> watchers use a small hash table to distribute workload by
2192	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2595	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2193	usually more than enough. If you need to manage thousands of C<ev_stat>	2596	usually more than enough. If you need to manage thousands of C<ev_stat>
2194	watchers you might want to increase this value (I<must> be a power of	2597	watchers you might want to increase this value (I<must> be a power of
2195	two).	2598	two).
2196		2599
…		…
2213		2616
2214	=item ev_set_cb (ev, cb)	2617	=item ev_set_cb (ev, cb)
2215		2618
2216	Can be used to change the callback member declaration in each watcher,	2619	Can be used to change the callback member declaration in each watcher,
2217	and the way callbacks are invoked and set. Must expand to a struct member	2620	and the way callbacks are invoked and set. Must expand to a struct member
2218	definition and a statement, respectively. See the F<ev.v> header file for	2621	definition and a statement, respectively. See the F<ev.h> header file for
2219	their default definitions. One possible use for overriding these is to	2622	their default definitions. One possible use for overriding these is to
2220	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2623	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2221	method calls instead of plain function calls in C++.	2624	method calls instead of plain function calls in C++.
		2625
		2626	=head2 EXPORTED API SYMBOLS
		2627
		2628	If you need to re-export the API (e.g. via a dll) and you need a list of
		2629	exported symbols, you can use the provided F<Symbol.*> files which list
		2630	all public symbols, one per line:
		2631
		2632	Symbols.ev for libev proper
		2633	Symbols.event for the libevent emulation
		2634
		2635	This can also be used to rename all public symbols to avoid clashes with
		2636	multiple versions of libev linked together (which is obviously bad in
		2637	itself, but sometimes it is inconvinient to avoid this).
		2638
		2639	A sed command like this will create wrapper C<#define>'s that you need to
		2640	include before including F<ev.h>:
		2641
		2642	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2643
		2644	This would create a file F<wrap.h> which essentially looks like this:
		2645
		2646	#define ev_backend myprefix_ev_backend
		2647	#define ev_check_start myprefix_ev_check_start
		2648	#define ev_check_stop myprefix_ev_check_stop
		2649	...
2222		2650
2223	=head2 EXAMPLES	2651	=head2 EXAMPLES
2224		2652
2225	For a real-world example of a program the includes libev	2653	For a real-world example of a program the includes libev
2226	verbatim, you can have a look at the EV perl module	2654	verbatim, you can have a look at the EV perl module
…		…
2255		2683
2256	In this section the complexities of (many of) the algorithms used inside	2684	In this section the complexities of (many of) the algorithms used inside
2257	libev will be explained. For complexity discussions about backends see the	2685	libev will be explained. For complexity discussions about backends see the
2258	documentation for C<ev_default_init>.	2686	documentation for C<ev_default_init>.
2259		2687
		2688	All of the following are about amortised time: If an array needs to be
		2689	extended, libev needs to realloc and move the whole array, but this
		2690	happens asymptotically never with higher number of elements, so O(1) might
		2691	mean it might do a lengthy realloc operation in rare cases, but on average
		2692	it is much faster and asymptotically approaches constant time.
		2693
2260	=over 4	2694	=over 4
2261		2695
2262	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2696	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2263		2697
2264	This means that, when you have a watcher that triggers in one hour and	2698	This means that, when you have a watcher that triggers in one hour and
2265	there are 100 watchers that would trigger before that then inserting will	2699	there are 100 watchers that would trigger before that then inserting will
2266	have to skip those 100 watchers.	2700	have to skip roughly seven (C<ld 100>) of these watchers.
2267		2701
2268	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2702	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2269		2703
2270	That means that for changing a timer costs less than removing/adding them	2704	That means that changing a timer costs less than removing/adding them
2271	as only the relative motion in the event queue has to be paid for.	2705	as only the relative motion in the event queue has to be paid for.
2272		2706
2273	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2707	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2274		2708
2275	These just add the watcher into an array or at the head of a list. If	2709	These just add the watcher into an array or at the head of a list.
2276	the array needs to be extended libev needs to realloc and move the whole
2277	array, but this happen asymptotically less and less with more watchers,
2278	thus amortised O(1).
2279		2710
2280	=item Stopping check/prepare/idle watchers: O(1)	2711	=item Stopping check/prepare/idle watchers: O(1)
2281		2712
2282	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2713	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2283		2714
2284	These watchers are stored in lists then need to be walked to find the	2715	These watchers are stored in lists then need to be walked to find the
2285	correct watcher to remove. The lists are usually short (you don't usually	2716	correct watcher to remove. The lists are usually short (you don't usually
2286	have many watchers waiting for the same fd or signal).	2717	have many watchers waiting for the same fd or signal).
2287		2718
2288	=item Finding the next timer per loop iteration: O(1)	2719	=item Finding the next timer in each loop iteration: O(1)
		2720
		2721	By virtue of using a binary heap, the next timer is always found at the
		2722	beginning of the storage array.
2289		2723
2290	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2724	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2291		2725
2292	A change means an I/O watcher gets started or stopped, which requires	2726	A change means an I/O watcher gets started or stopped, which requires
2293	libev to recalculate its status (and possibly tell the kernel).	2727	libev to recalculate its status (and possibly tell the kernel, depending
		2728	on backend and wether C<ev_io_set> was used).
2294		2729
2295	=item Activating one watcher: O(1)	2730	=item Activating one watcher (putting it into the pending state): O(1)
2296		2731
2297	=item Priority handling: O(number_of_priorities)	2732	=item Priority handling: O(number_of_priorities)
2298		2733
2299	Priorities are implemented by allocating some space for each	2734	Priorities are implemented by allocating some space for each
2300	priority. When doing priority-based operations, libev usually has to	2735	priority. When doing priority-based operations, libev usually has to
2301	linearly search all the priorities.	2736	linearly search all the priorities, but starting/stopping and activating
		2737	watchers becomes O(1) w.r.t. prioritiy handling.
2302		2738
2303	=back	2739	=back
2304		2740
2305		2741
2306	=head1 AUTHOR	2742	=head1 AUTHOR

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Comparing libev/ev.pod (file contents): Revision 1.69 by root, Fri Dec 7 19:15:39 2007 UTC vs. Revision 1.108 by root, Mon Dec 24 10:39:21 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.69 by root, Fri Dec 7 19:15:39 2007 UTC vs.
Revision 1.108 by root, Mon Dec 24 10:39:21 2007 UTC