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

Comparing libev/ev.pod (file contents):
Revision 1.59 by root, Wed Nov 28 17:32:24 2007 UTC vs.
Revision 1.105 by root, Sun Dec 23 03:50:10 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.
…		…
266	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
267	override the flags completely if it is found in the environment. This is	282	override the flags completely if it is found in the environment. This is
268	useful to try out specific backends to test their performance, or to work	283	useful to try out specific backends to test their performance, or to work
269	around bugs.	284	around bugs.
270		285
		286	=item C<EVFLAG_FORKCHECK>
		287
		288	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		289	a fork, you can also make libev check for a fork in each iteration by
		290	enabling this flag.
		291
		292	This works by calling C<getpid ()> on every iteration of the loop,
		293	and thus this might slow down your event loop if you do a lot of loop
		294	iterations and little real work, but is usually not noticeable (on my
		295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		296	without a syscall and thus I<very> fast, but my Linux system also has
		297	C<pthread_atfork> which is even faster).
		298
		299	The big advantage of this flag is that you can forget about fork (and
		300	forget about forgetting to tell libev about forking) when you use this
		301	flag.
		302
		303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		304	environment variable.
		305
271	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
272		307
273	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
274	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,
275	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
276	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
277	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.
278		320
279	=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)
280		322
281	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
282	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
283	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
284	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.
285		329
286	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
287		331
288	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,
289	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
290	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),
291	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.
292		339
293	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
294	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
295	(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
296	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
297	well if you register events for both fds.	344	very well if you register events for both fds.
298		345
299	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
300	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
301	(or space) is available.	348	(or space) is available.
302		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
303	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
304		358
305	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
306	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
307	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
308	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
309	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
310	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.
311		370
312	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
313	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
314	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
315	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
316	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.
317		386
318	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
319		388
320	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.
321		393
322	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
323		395
324	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,
325	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)).
326		398
327	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
328	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
329	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.
330		407
331	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
332		409
333	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
334	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
335	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
336		415
337	=back	416	=back
338		417
339	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
340	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
…		…
375	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
376	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
377	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
378	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
379	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
380	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
381	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>).
382		470
383	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
384		472
385	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
386	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
410		498
411	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
412	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
413	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.
414		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
415	=item unsigned int ev_backend (loop)	513	=item unsigned int ev_backend (loop)
416		514
417	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
418	use.	516	use.
419		517
…		…
421		519
422	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
423	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
424	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
425	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
426	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
427		525
428	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
429		527
430	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
431	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
…		…
452	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
453	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
454		552
455	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
456		554
		555	- Before the first iteration, call any pending watchers.
457	* If there are no active watchers (reference count is zero), return.	556	* If there are no active watchers (reference count is zero), return.
458	- Queue prepare watchers and then call all outstanding watchers.	557	- Queue all prepare watchers and then call all outstanding watchers.
459	- If we have been forked, recreate the kernel state.	558	- If we have been forked, recreate the kernel state.
460	- Update the kernel state with all outstanding changes.	559	- Update the kernel state with all outstanding changes.
461	- Update the "event loop time".	560	- Update the "event loop time".
462	- Calculate for how long to block.	561	- Calculate for how long to block.
463	- Block the process, waiting for any events.	562	- Block the process, waiting for any events.
…		…
514	Example: For some weird reason, unregister the above signal handler again.	613	Example: For some weird reason, unregister the above signal handler again.
515		614
516	ev_ref (loop);	615	ev_ref (loop);
517	ev_signal_stop (loop, &exitsig);	616	ev_signal_stop (loop, &exitsig);
518		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
519	=back	654	=back
520		655
521		656
522	=head1 ANATOMY OF A WATCHER	657	=head1 ANATOMY OF A WATCHER
523		658
…		…
702	=item bool ev_is_pending (ev_TYPE *watcher)	837	=item bool ev_is_pending (ev_TYPE *watcher)
703		838
704	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
705	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
706	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
707	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
708	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).
709		845
710	=item callback ev_cb (ev_TYPE *watcher)	846	=item callback ev_cb (ev_TYPE *watcher)
711		847
712	Returns the callback currently set on the watcher.	848	Returns the callback currently set on the watcher.
713		849
714	=item ev_cb_set (ev_TYPE *watcher, callback)	850	=item ev_cb_set (ev_TYPE *watcher, callback)
715		851
716	Change the callback. You can change the callback at virtually any time	852	Change the callback. You can change the callback at virtually any time
717	(modulo threads).	853	(modulo threads).
		854
		855	=item ev_set_priority (ev_TYPE *watcher, priority)
		856
		857	=item int ev_priority (ev_TYPE *watcher)
		858
		859	Set and query the priority of the watcher. The priority is a small
		860	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		861	(default: C<-2>). Pending watchers with higher priority will be invoked
		862	before watchers with lower priority, but priority will not keep watchers
		863	from being executed (except for C<ev_idle> watchers).
		864
		865	This means that priorities are I<only> used for ordering callback
		866	invocation after new events have been received. This is useful, for
		867	example, to reduce latency after idling, or more often, to bind two
		868	watchers on the same event and make sure one is called first.
		869
		870	If you need to suppress invocation when higher priority events are pending
		871	you need to look at C<ev_idle> watchers, which provide this functionality.
		872
		873	You I<must not> change the priority of a watcher as long as it is active or
		874	pending.
		875
		876	The default priority used by watchers when no priority has been set is
		877	always C<0>, which is supposed to not be too high and not be too low :).
		878
		879	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		880	fine, as long as you do not mind that the priority value you query might
		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>.
718		894
719	=back	895	=back
720		896
721		897
722	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
828	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1004	it is best to always use non-blocking I/O: An extra C<read>(2) returning
829	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1005	C<EAGAIN> is far preferable to a program hanging until some data arrives.
830		1006
831	If you cannot run the fd in non-blocking mode (for example you should not	1007	If you cannot run the fd in non-blocking mode (for example you should not
832	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
833	wether 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
834	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
835	its own, so its quite safe to use).	1011	its own, so its quite safe to use).
		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
836		1058
837	=over 4	1059	=over 4
838		1060
839	=item ev_io_init (ev_io *, callback, int fd, int events)	1061	=item ev_io_init (ev_io *, callback, int fd, int events)
840		1062
…		…
894		1116
895	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,
896	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
897	order of execution is undefined.	1119	order of execution is undefined.
898		1120
		1121	=head3 Watcher-Specific Functions and Data Members
		1122
899	=over 4	1123	=over 4
900		1124
901	=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)
902		1126
903	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1127	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
916	=item ev_timer_again (loop)	1140	=item ev_timer_again (loop)
917		1141
918	This will act as if the timer timed out and restart it again if it is	1142	This will act as if the timer timed out and restart it again if it is
919	repeating. The exact semantics are:	1143	repeating. The exact semantics are:
920		1144
		1145	If the timer is pending, its pending status is cleared.
		1146
921	If the timer is started but nonrepeating, stop it.	1147	If the timer is started but nonrepeating, stop it (as if it timed out).
922		1148
923	If the timer is repeating, either start it if necessary (with the repeat	1149	If the timer is repeating, either start it if necessary (with the
924	value), or reset the running timer to the repeat value.	1150	C<repeat> value), or reset the running timer to the C<repeat> value.
925		1151
926	This sounds a bit complicated, but here is a useful and typical	1152	This sounds a bit complicated, but here is a useful and typical
927	example: Imagine you have a tcp connection and you want a so-called	1153	example: Imagine you have a tcp connection and you want a so-called idle
928	idle timeout, that is, you want to be called when there have been,	1154	timeout, that is, you want to be called when there have been, say, 60
929	say, 60 seconds of inactivity on the socket. The easiest way to do	1155	seconds of inactivity on the socket. The easiest way to do this is to
930	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1156	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
931	C<ev_timer_again> each time you successfully read or write some data. If	1157	C<ev_timer_again> each time you successfully read or write some data. If
932	you go into an idle state where you do not expect data to travel on the	1158	you go into an idle state where you do not expect data to travel on the
933	socket, you can stop the timer, and again will automatically restart it if	1159	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
934	need be.	1160	automatically restart it if need be.
935		1161
936	You can also ignore the C<after> value and C<ev_timer_start> altogether	1162	That means you can ignore the C<after> value and C<ev_timer_start>
937	and only ever use the C<repeat> value:	1163	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
938		1164
939	ev_timer_init (timer, callback, 0., 5.);	1165	ev_timer_init (timer, callback, 0., 5.);
940	ev_timer_again (loop, timer);	1166	ev_timer_again (loop, timer);
941	...	1167	...
942	timer->again = 17.;	1168	timer->again = 17.;
943	ev_timer_again (loop, timer);	1169	ev_timer_again (loop, timer);
944	...	1170	...
945	timer->again = 10.;	1171	timer->again = 10.;
946	ev_timer_again (loop, timer);	1172	ev_timer_again (loop, timer);
947		1173
948	This is more efficient then stopping/starting the timer eahc time you want	1174	This is more slightly efficient then stopping/starting the timer each time
949	to modify its timeout value.	1175	you want to modify its timeout value.
950		1176
951	=item ev_tstamp repeat [read-write]	1177	=item ev_tstamp repeat [read-write]
952		1178
953	The current C<repeat> value. Will be used each time the watcher times out	1179	The current C<repeat> value. Will be used each time the watcher times out
954	or C<ev_timer_again> is called and determines the next timeout (if any),	1180	or C<ev_timer_again> is called and determines the next timeout (if any),
…		…
996	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
997	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
998	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 ()
999	+ 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
1000	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
1001	roughly 10 seconds later and of course not if you reset your system time	1227	roughly 10 seconds later).
1002	again).
1003		1228
1004	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
1005	triggering an event on eahc midnight, local time.	1230	triggering an event on each midnight, local time or other, complicated,
		1231	rules.
1006		1232
1007	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
1008	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
1009	during the same loop iteration then order of execution is undefined.	1235	during the same loop iteration then order of execution is undefined.
1010		1236
		1237	=head3 Watcher-Specific Functions and Data Members
		1238
1011	=over 4	1239	=over 4
1012		1240
1013	=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)
1014		1242
1015	=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)
…		…
1017	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
1018	operation, and we will explain them from simplest to complex:	1246	operation, and we will explain them from simplest to complex:
1019		1247
1020	=over 4	1248	=over 4
1021		1249
1022	=item * absolute timer (interval = reschedule_cb = 0)	1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1023		1251
1024	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
1025	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,
1026	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
1027	system time reaches or surpasses this time.	1255	system time reaches or surpasses this time.
1028		1256
1029	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1030		1258
1031	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
1032	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)
1033	of any time jumps.	1261	and then repeat, regardless of any time jumps.
1034		1262
1035	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
1036	time:	1264	time:
1037		1265
1038	ev_periodic_set (&periodic, 0., 3600., 0);	1266	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1044		1272
1045	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
1046	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
1047	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.
1048		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
1049	=item * manual reschedule mode (reschedule_cb = callback)	1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1050		1282
1051	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
1052	ignored. Instead, each time the periodic watcher gets scheduled, the	1284	ignored. Instead, each time the periodic watcher gets scheduled, the
1053	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
1054	current time as second argument.	1286	current time as second argument.
1055		1287
1056	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,
1057	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,
1058	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
1059	starting a prepare watcher).	1291	starting an C<ev_prepare> watcher, which is legal).
1060		1292
1061	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,
1062	ev_tstamp now)>, e.g.:	1294	ev_tstamp now)>, e.g.:
1063		1295
1064	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)
…		…
1087	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
1088	when you changed some parameters or the reschedule callback would return	1320	when you changed some parameters or the reschedule callback would return
1089	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
1090	program when the crontabs have changed).	1322	program when the crontabs have changed).
1091		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
1092	=item ev_tstamp interval [read-write]	1332	=item ev_tstamp interval [read-write]
1093		1333
1094	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
1095	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
1096	called.	1336	called.
…		…
1098	=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]
1099		1339
1100	The current reschedule callback, or C<0>, if this functionality is	1340	The current reschedule callback, or C<0>, if this functionality is
1101	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
1102	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.
1103		1348
1104	=back	1349	=back
1105		1350
1106	Example: Call a callback every hour, or, more precisely, whenever the	1351	Example: Call a callback every hour, or, more precisely, whenever the
1107	system clock is divisible by 3600. The callback invocation times have	1352	system clock is divisible by 3600. The callback invocation times have
…		…
1149	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
1150	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
1151	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
1152	SIG_DFL (regardless of what it was set to before).	1397	SIG_DFL (regardless of what it was set to before).
1153		1398
		1399	=head3 Watcher-Specific Functions and Data Members
		1400
1154	=over 4	1401	=over 4
1155		1402
1156	=item ev_signal_init (ev_signal *, callback, int signum)	1403	=item ev_signal_init (ev_signal *, callback, int signum)
1157		1404
1158	=item ev_signal_set (ev_signal *, int signum)	1405	=item ev_signal_set (ev_signal *, int signum)
…		…
1169		1416
1170	=head2 C<ev_child> - watch out for process status changes	1417	=head2 C<ev_child> - watch out for process status changes
1171		1418
1172	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
1173	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
1174		1423
1175	=over 4	1424	=over 4
1176		1425
1177	=item ev_child_init (ev_child *, callback, int pid)	1426	=item ev_child_init (ev_child *, callback, int pid)
1178		1427
…		…
1222	The path does not need to exist: changing from "path exists" to "path does	1471	The path does not need to exist: changing from "path exists" to "path does
1223	not exist" is a status change like any other. The condition "path does	1472	not exist" is a status change like any other. The condition "path does
1224	not exist" is signified by the C<st_nlink> field being zero (which is	1473	not exist" is signified by the C<st_nlink> field being zero (which is
1225	otherwise always forced to be at least one) and all the other fields of	1474	otherwise always forced to be at least one) and all the other fields of
1226	the stat buffer having unspecified contents.	1475	the stat buffer having unspecified contents.
		1476
		1477	The path I<should> be absolute and I<must not> end in a slash. If it is
		1478	relative and your working directory changes, the behaviour is undefined.
1227		1479
1228	Since there is no standard to do this, the portable implementation simply	1480	Since there is no standard to do this, the portable implementation simply
1229	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1481	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1230	can specify a recommended polling interval for this case. If you specify	1482	can specify a recommended polling interval for this case. If you specify
1231	a polling interval of C<0> (highly recommended!) then a I<suitable,	1483	a polling interval of C<0> (highly recommended!) then a I<suitable,
…		…
1243	reader). Inotify will be used to give hints only and should not change the	1495	reader). Inotify will be used to give hints only and should not change the
1244	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
1245	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
1246	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
1247	polling.	1499	polling.
		1500
		1501	=head3 Watcher-Specific Functions and Data Members
1248		1502
1249	=over 4	1503	=over 4
1250		1504
1251	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1505	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1252		1506
…		…
1316	ev_stat_start (loop, &passwd);	1570	ev_stat_start (loop, &passwd);
1317		1571
1318		1572
1319	=head2 C<ev_idle> - when you've got nothing better to do...	1573	=head2 C<ev_idle> - when you've got nothing better to do...
1320		1574
1321	Idle watchers trigger events when there are no other events are pending	1575	Idle watchers trigger events when no other events of the same or higher
1322	(prepare, check and other idle watchers do not count). That is, as long	1576	priority are pending (prepare, check and other idle watchers do not
1323	as your process is busy handling sockets or timeouts (or even signals,	1577	count).
1324	imagine) it will not be triggered. But when your process is idle all idle	1578
1325	watchers are being called again and again, once per event loop iteration -	1579	That is, as long as your process is busy handling sockets or timeouts
		1580	(or even signals, imagine) of the same or higher priority it will not be
		1581	triggered. But when your process is idle (or only lower-priority watchers
		1582	are pending), the idle watchers are being called once per event loop
1326	until stopped, that is, or your process receives more events and becomes	1583	iteration - until stopped, that is, or your process receives more events
1327	busy.	1584	and becomes busy again with higher priority stuff.
1328		1585
1329	The most noteworthy effect is that as long as any idle watchers are	1586	The most noteworthy effect is that as long as any idle watchers are
1330	active, the process will not block when waiting for new events.	1587	active, the process will not block when waiting for new events.
1331		1588
1332	Apart from keeping your process non-blocking (which is a useful	1589	Apart from keeping your process non-blocking (which is a useful
1333	effect on its own sometimes), idle watchers are a good place to do	1590	effect on its own sometimes), idle watchers are a good place to do
1334	"pseudo-background processing", or delay processing stuff to after the	1591	"pseudo-background processing", or delay processing stuff to after the
1335	event loop has handled all outstanding events.	1592	event loop has handled all outstanding events.
		1593
		1594	=head3 Watcher-Specific Functions and Data Members
1336		1595
1337	=over 4	1596	=over 4
1338		1597
1339	=item ev_idle_init (ev_signal *, callback)	1598	=item ev_idle_init (ev_signal *, callback)
1340		1599
…		…
1398	with priority higher than or equal to the event loop and one coroutine	1657	with priority higher than or equal to the event loop and one coroutine
1399	of lower priority, but only once, using idle watchers to keep the event	1658	of lower priority, but only once, using idle watchers to keep the event
1400	loop from blocking if lower-priority coroutines are active, thus mapping	1659	loop from blocking if lower-priority coroutines are active, thus mapping
1401	low-priority coroutines to idle/background tasks).	1660	low-priority coroutines to idle/background tasks).
1402		1661
		1662	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1663	priority, to ensure that they are being run before any other watchers
		1664	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1665	too) should not activate ("feed") events into libev. While libev fully
		1666	supports this, they will be called before other C<ev_check> watchers
		1667	did their job. As C<ev_check> watchers are often used to embed other
		1668	(non-libev) event loops those other event loops might be in an unusable
		1669	state until their C<ev_check> watcher ran (always remind yourself to
		1670	coexist peacefully with others).
		1671
		1672	=head3 Watcher-Specific Functions and Data Members
		1673
1403	=over 4	1674	=over 4
1404		1675
1405	=item ev_prepare_init (ev_prepare *, callback)	1676	=item ev_prepare_init (ev_prepare *, callback)
1406		1677
1407	=item ev_check_init (ev_check *, callback)	1678	=item ev_check_init (ev_check *, callback)
…		…
1410	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1681	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1411	macros, but using them is utterly, utterly and completely pointless.	1682	macros, but using them is utterly, utterly and completely pointless.
1412		1683
1413	=back	1684	=back
1414		1685
1415	Example: To include a library such as adns, you would add IO watchers	1686	There are a number of principal ways to embed other event loops or modules
1416	and a timeout watcher in a prepare handler, as required by libadns, and	1687	into libev. Here are some ideas on how to include libadns into libev
		1688	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1689	use for an actually working example. Another Perl module named C<EV::Glib>
		1690	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1691	into the Glib event loop).
		1692
		1693	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1417	in a check watcher, destroy them and call into libadns. What follows is	1694	and in a check watcher, destroy them and call into libadns. What follows
1418	pseudo-code only of course:	1695	is pseudo-code only of course. This requires you to either use a low
		1696	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1697	the callbacks for the IO/timeout watchers might not have been called yet.
1419		1698
1420	static ev_io iow [nfd];	1699	static ev_io iow [nfd];
1421	static ev_timer tw;	1700	static ev_timer tw;
1422		1701
1423	static void	1702	static void
1424	io_cb (ev_loop loop, ev_io w, int revents)	1703	io_cb (ev_loop loop, ev_io w, int revents)
1425	{	1704	{
1426	// set the relevant poll flags
1427	// could also call adns_processreadable etc. here
1428	struct pollfd fd = (struct pollfd )w->data;
1429	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1430	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1431	}	1705	}
1432		1706
1433	// create io watchers for each fd and a timer before blocking	1707	// create io watchers for each fd and a timer before blocking
1434	static void	1708	static void
1435	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1709	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1436	{	1710	{
1437	int timeout = 3600000;truct pollfd fds [nfd];	1711	int timeout = 3600000;
		1712	struct pollfd fds [nfd];
1438	// actual code will need to loop here and realloc etc.	1713	// actual code will need to loop here and realloc etc.
1439	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1714	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1440		1715
1441	/* the callback is illegal, but won't be called as we stop during check */	1716	/* the callback is illegal, but won't be called as we stop during check */
1442	ev_timer_init (&tw, 0, timeout * 1e-3);	1717	ev_timer_init (&tw, 0, timeout * 1e-3);
1443	ev_timer_start (loop, &tw);	1718	ev_timer_start (loop, &tw);
1444		1719
1445	// create on ev_io per pollfd	1720	// create one ev_io per pollfd
1446	for (int i = 0; i < nfd; ++i)	1721	for (int i = 0; i < nfd; ++i)
1447	{	1722	{
1448	ev_io_init (iow + i, io_cb, fds [i].fd,	1723	ev_io_init (iow + i, io_cb, fds [i].fd,
1449	((fds [i].events & POLLIN ? EV_READ : 0)	1724	((fds [i].events & POLLIN ? EV_READ : 0)
1450	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1725	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1451		1726
1452	fds [i].revents = 0;	1727	fds [i].revents = 0;
1453	iow [i].data = fds + i;
1454	ev_io_start (loop, iow + i);	1728	ev_io_start (loop, iow + i);
1455	}	1729	}
1456	}	1730	}
1457		1731
1458	// stop all watchers after blocking	1732	// stop all watchers after blocking
…		…
1460	adns_check_cb (ev_loop loop, ev_check w, int revents)	1734	adns_check_cb (ev_loop loop, ev_check w, int revents)
1461	{	1735	{
1462	ev_timer_stop (loop, &tw);	1736	ev_timer_stop (loop, &tw);
1463		1737
1464	for (int i = 0; i < nfd; ++i)	1738	for (int i = 0; i < nfd; ++i)
		1739	{
		1740	// set the relevant poll flags
		1741	// could also call adns_processreadable etc. here
		1742	struct pollfd *fd = fds + i;
		1743	int revents = ev_clear_pending (iow + i);
		1744	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1745	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1746
		1747	// now stop the watcher
1465	ev_io_stop (loop, iow + i);	1748	ev_io_stop (loop, iow + i);
		1749	}
1466		1750
1467	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1751	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1752	}
		1753
		1754	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1755	in the prepare watcher and would dispose of the check watcher.
		1756
		1757	Method 3: If the module to be embedded supports explicit event
		1758	notification (adns does), you can also make use of the actual watcher
		1759	callbacks, and only destroy/create the watchers in the prepare watcher.
		1760
		1761	static void
		1762	timer_cb (EV_P_ ev_timer *w, int revents)
		1763	{
		1764	adns_state ads = (adns_state)w->data;
		1765	update_now (EV_A);
		1766
		1767	adns_processtimeouts (ads, &tv_now);
		1768	}
		1769
		1770	static void
		1771	io_cb (EV_P_ ev_io *w, int revents)
		1772	{
		1773	adns_state ads = (adns_state)w->data;
		1774	update_now (EV_A);
		1775
		1776	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1777	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1778	}
		1779
		1780	// do not ever call adns_afterpoll
		1781
		1782	Method 4: Do not use a prepare or check watcher because the module you
		1783	want to embed is too inflexible to support it. Instead, youc na override
		1784	their poll function. The drawback with this solution is that the main
		1785	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1786	this.
		1787
		1788	static gint
		1789	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1790	{
		1791	int got_events = 0;
		1792
		1793	for (n = 0; n < nfds; ++n)
		1794	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1795
		1796	if (timeout >= 0)
		1797	// create/start timer
		1798
		1799	// poll
		1800	ev_loop (EV_A_ 0);
		1801
		1802	// stop timer again
		1803	if (timeout >= 0)
		1804	ev_timer_stop (EV_A_ &to);
		1805
		1806	// stop io watchers again - their callbacks should have set
		1807	for (n = 0; n < nfds; ++n)
		1808	ev_io_stop (EV_A_ iow [n]);
		1809
		1810	return got_events;
1468	}	1811	}
1469		1812
1470		1813
1471	=head2 C<ev_embed> - when one backend isn't enough...	1814	=head2 C<ev_embed> - when one backend isn't enough...
1472		1815
…		…
1536	ev_embed_start (loop_hi, &embed);	1879	ev_embed_start (loop_hi, &embed);
1537	}	1880	}
1538	else	1881	else
1539	loop_lo = loop_hi;	1882	loop_lo = loop_hi;
1540		1883
		1884	=head3 Watcher-Specific Functions and Data Members
		1885
1541	=over 4	1886	=over 4
1542		1887
1543	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1888	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1544		1889
1545	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1890	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
…		…
1554		1899
1555	Make a single, non-blocking sweep over the embedded loop. This works	1900	Make a single, non-blocking sweep over the embedded loop. This works
1556	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1901	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1557	apropriate way for embedded loops.	1902	apropriate way for embedded loops.
1558		1903
1559	=item struct ev_loop *loop [read-only]	1904	=item struct ev_loop *other [read-only]
1560		1905
1561	The embedded event loop.	1906	The embedded event loop.
1562		1907
1563	=back	1908	=back
1564		1909
…		…
1571	event loop blocks next and before C<ev_check> watchers are being called,	1916	event loop blocks next and before C<ev_check> watchers are being called,
1572	and only in the child after the fork. If whoever good citizen calling	1917	and only in the child after the fork. If whoever good citizen calling
1573	C<ev_default_fork> cheats and calls it in the wrong process, the fork	1918	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1574	handlers will be invoked, too, of course.	1919	handlers will be invoked, too, of course.
1575		1920
		1921	=head3 Watcher-Specific Functions and Data Members
		1922
1576	=over 4	1923	=over 4
1577		1924
1578	=item ev_fork_init (ev_signal *, callback)	1925	=item ev_fork_init (ev_signal *, callback)
1579		1926
1580	Initialises and configures the fork watcher - it has no parameters of any	1927	Initialises and configures the fork watcher - it has no parameters of any
…		…
1676		2023
1677	To use it,	2024	To use it,
1678		2025
1679	#include <ev++.h>	2026	#include <ev++.h>
1680		2027
1681	(it is not installed by default). This automatically includes F<ev.h>	2028	This automatically includes F<ev.h> and puts all of its definitions (many
1682	and puts all of its definitions (many of them macros) into the global	2029	of them macros) into the global namespace. All C++ specific things are
1683	namespace. All C++ specific things are put into the C<ev> namespace.	2030	put into the C<ev> namespace. It should support all the same embedding
		2031	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1684		2032
1685	It should support all the same embedding options as F<ev.h>, most notably	2033	Care has been taken to keep the overhead low. The only data member the C++
1686	C<EV_MULTIPLICITY>.	2034	classes add (compared to plain C-style watchers) is the event loop pointer
		2035	that the watcher is associated with (or no additional members at all if
		2036	you disable C<EV_MULTIPLICITY> when embedding libev).
		2037
		2038	Currently, functions, and static and non-static member functions can be
		2039	used as callbacks. Other types should be easy to add as long as they only
		2040	need one additional pointer for context. If you need support for other
		2041	types of functors please contact the author (preferably after implementing
		2042	it).
1687		2043
1688	Here is a list of things available in the C<ev> namespace:	2044	Here is a list of things available in the C<ev> namespace:
1689		2045
1690	=over 4	2046	=over 4
1691		2047
…		…
1707		2063
1708	All of those classes have these methods:	2064	All of those classes have these methods:
1709		2065
1710	=over 4	2066	=over 4
1711		2067
1712	=item ev::TYPE::TYPE (object , object::method )	2068	=item ev::TYPE::TYPE ()
1713		2069
1714	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	2070	=item ev::TYPE::TYPE (struct ev_loop *)
1715		2071
1716	=item ev::TYPE::~TYPE	2072	=item ev::TYPE::~TYPE
1717		2073
1718	The constructor takes a pointer to an object and a method pointer to	2074	The constructor (optionally) takes an event loop to associate the watcher
1719	the event handler callback to call in this class. The constructor calls	2075	with. If it is omitted, it will use C<EV_DEFAULT>.
1720	C<ev_init> for you, which means you have to call the C<set> method	2076
1721	before starting it. If you do not specify a loop then the constructor	2077	The constructor calls C<ev_init> for you, which means you have to call the
1722	automatically associates the default loop with this watcher.	2078	C<set> method before starting it.
		2079
		2080	It will not set a callback, however: You have to call the templated C<set>
		2081	method to set a callback before you can start the watcher.
		2082
		2083	(The reason why you have to use a method is a limitation in C++ which does
		2084	not allow explicit template arguments for constructors).
1723		2085
1724	The destructor automatically stops the watcher if it is active.	2086	The destructor automatically stops the watcher if it is active.
		2087
		2088	=item w->set<class, &class::method> (object *)
		2089
		2090	This method sets the callback method to call. The method has to have a
		2091	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2092	first argument and the C<revents> as second. The object must be given as
		2093	parameter and is stored in the C<data> member of the watcher.
		2094
		2095	This method synthesizes efficient thunking code to call your method from
		2096	the C callback that libev requires. If your compiler can inline your
		2097	callback (i.e. it is visible to it at the place of the C<set> call and
		2098	your compiler is good :), then the method will be fully inlined into the
		2099	thunking function, making it as fast as a direct C callback.
		2100
		2101	Example: simple class declaration and watcher initialisation
		2102
		2103	struct myclass
		2104	{
		2105	void io_cb (ev::io &w, int revents) { }
		2106	}
		2107
		2108	myclass obj;
		2109	ev::io iow;
		2110	iow.set <myclass, &myclass::io_cb> (&obj);
		2111
		2112	=item w->set<function> (void *data = 0)
		2113
		2114	Also sets a callback, but uses a static method or plain function as
		2115	callback. The optional C<data> argument will be stored in the watcher's
		2116	C<data> member and is free for you to use.
		2117
		2118	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2119
		2120	See the method-C<set> above for more details.
		2121
		2122	Example:
		2123
		2124	static void io_cb (ev::io &w, int revents) { }
		2125	iow.set <io_cb> ();
1725		2126
1726	=item w->set (struct ev_loop *)	2127	=item w->set (struct ev_loop *)
1727		2128
1728	Associates a different C<struct ev_loop> with this watcher. You can only	2129	Associates a different C<struct ev_loop> with this watcher. You can only
1729	do this when the watcher is inactive (and not pending either).	2130	do this when the watcher is inactive (and not pending either).
1730		2131
1731	=item w->set ([args])	2132	=item w->set ([args])
1732		2133
1733	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2134	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1734	called at least once. Unlike the C counterpart, an active watcher gets	2135	called at least once. Unlike the C counterpart, an active watcher gets
1735	automatically stopped and restarted.	2136	automatically stopped and restarted when reconfiguring it with this
		2137	method.
1736		2138
1737	=item w->start ()	2139	=item w->start ()
1738		2140
1739	Starts the watcher. Note that there is no C<loop> argument as the	2141	Starts the watcher. Note that there is no C<loop> argument, as the
1740	constructor already takes the loop.	2142	constructor already stores the event loop.
1741		2143
1742	=item w->stop ()	2144	=item w->stop ()
1743		2145
1744	Stops the watcher if it is active. Again, no C<loop> argument.	2146	Stops the watcher if it is active. Again, no C<loop> argument.
1745		2147
1746	=item w->again () C<ev::timer>, C<ev::periodic> only	2148	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1747		2149
1748	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2150	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1749	C<ev_TYPE_again> function.	2151	C<ev_TYPE_again> function.
1750		2152
1751	=item w->sweep () C<ev::embed> only	2153	=item w->sweep () (C<ev::embed> only)
1752		2154
1753	Invokes C<ev_embed_sweep>.	2155	Invokes C<ev_embed_sweep>.
1754		2156
1755	=item w->update () C<ev::stat> only	2157	=item w->update () (C<ev::stat> only)
1756		2158
1757	Invokes C<ev_stat_stat>.	2159	Invokes C<ev_stat_stat>.
1758		2160
1759	=back	2161	=back
1760		2162
…		…
1770		2172
1771	myclass ();	2173	myclass ();
1772	}	2174	}
1773		2175
1774	myclass::myclass (int fd)	2176	myclass::myclass (int fd)
1775	: io (this, &myclass::io_cb),
1776	idle (this, &myclass::idle_cb)
1777	{	2177	{
		2178	io .set <myclass, &myclass::io_cb > (this);
		2179	idle.set <myclass, &myclass::idle_cb> (this);
		2180
1778	io.start (fd, ev::READ);	2181	io.start (fd, ev::READ);
1779	}	2182	}
1780		2183
1781		2184
1782	=head1 MACRO MAGIC	2185	=head1 MACRO MAGIC
1783		2186
1784	Libev can be compiled with a variety of options, the most fundemantal is	2187	Libev can be compiled with a variety of options, the most fundamantal
1785	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2188	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1786	callbacks have an initial C<struct ev_loop *> argument.	2189	functions and callbacks have an initial C<struct ev_loop *> argument.
1787		2190
1788	To make it easier to write programs that cope with either variant, the	2191	To make it easier to write programs that cope with either variant, the
1789	following macros are defined:	2192	following macros are defined:
1790		2193
1791	=over 4	2194	=over 4
…		…
1823	Similar to the other two macros, this gives you the value of the default	2226	Similar to the other two macros, this gives you the value of the default
1824	loop, if multiple loops are supported ("ev loop default").	2227	loop, if multiple loops are supported ("ev loop default").
1825		2228
1826	=back	2229	=back
1827		2230
1828	Example: Declare and initialise a check watcher, working regardless of	2231	Example: Declare and initialise a check watcher, utilising the above
1829	wether multiple loops are supported or not.	2232	macros so it will work regardless of whether multiple loops are supported
		2233	or not.
1830		2234
1831	static void	2235	static void
1832	check_cb (EV_P_ ev_timer *w, int revents)	2236	check_cb (EV_P_ ev_timer *w, int revents)
1833	{	2237	{
1834	ev_check_stop (EV_A_ w);	2238	ev_check_stop (EV_A_ w);
…		…
1837	ev_check check;	2241	ev_check check;
1838	ev_check_init (&check, check_cb);	2242	ev_check_init (&check, check_cb);
1839	ev_check_start (EV_DEFAULT_ &check);	2243	ev_check_start (EV_DEFAULT_ &check);
1840	ev_loop (EV_DEFAULT_ 0);	2244	ev_loop (EV_DEFAULT_ 0);
1841		2245
1842
1843	=head1 EMBEDDING	2246	=head1 EMBEDDING
1844		2247
1845	Libev can (and often is) directly embedded into host	2248	Libev can (and often is) directly embedded into host
1846	applications. Examples of applications that embed it include the Deliantra	2249	applications. Examples of applications that embed it include the Deliantra
1847	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2250	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1848	and rxvt-unicode.	2251	and rxvt-unicode.
1849		2252
1850	The goal is to enable you to just copy the neecssary files into your	2253	The goal is to enable you to just copy the necessary files into your
1851	source directory without having to change even a single line in them, so	2254	source directory without having to change even a single line in them, so
1852	you can easily upgrade by simply copying (or having a checked-out copy of	2255	you can easily upgrade by simply copying (or having a checked-out copy of
1853	libev somewhere in your source tree).	2256	libev somewhere in your source tree).
1854		2257
1855	=head2 FILESETS	2258	=head2 FILESETS
…		…
1886	ev_vars.h	2289	ev_vars.h
1887	ev_wrap.h	2290	ev_wrap.h
1888		2291
1889	ev_win32.c required on win32 platforms only	2292	ev_win32.c required on win32 platforms only
1890		2293
1891	ev_select.c only when select backend is enabled (which is by default)	2294	ev_select.c only when select backend is enabled (which is enabled by default)
1892	ev_poll.c only when poll backend is enabled (disabled by default)	2295	ev_poll.c only when poll backend is enabled (disabled by default)
1893	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2296	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1894	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2297	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1895	ev_port.c only when the solaris port backend is enabled (disabled by default)	2298	ev_port.c only when the solaris port backend is enabled (disabled by default)
1896		2299
…		…
1945		2348
1946	If defined to be C<1>, libev will try to detect the availability of the	2349	If defined to be C<1>, libev will try to detect the availability of the
1947	monotonic clock option at both compiletime and runtime. Otherwise no use	2350	monotonic clock option at both compiletime and runtime. Otherwise no use
1948	of the monotonic clock option will be attempted. If you enable this, you	2351	of the monotonic clock option will be attempted. If you enable this, you
1949	usually have to link against librt or something similar. Enabling it when	2352	usually have to link against librt or something similar. Enabling it when
1950	the functionality isn't available is safe, though, althoguh you have	2353	the functionality isn't available is safe, though, although you have
1951	to make sure you link against any libraries where the C<clock_gettime>	2354	to make sure you link against any libraries where the C<clock_gettime>
1952	function is hiding in (often F<-lrt>).	2355	function is hiding in (often F<-lrt>).
1953		2356
1954	=item EV_USE_REALTIME	2357	=item EV_USE_REALTIME
1955		2358
1956	If defined to be C<1>, libev will try to detect the availability of the	2359	If defined to be C<1>, libev will try to detect the availability of the
1957	realtime clock option at compiletime (and assume its availability at	2360	realtime clock option at compiletime (and assume its availability at
1958	runtime if successful). Otherwise no use of the realtime clock option will	2361	runtime if successful). Otherwise no use of the realtime clock option will
1959	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2362	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1960	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2363	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1961	in the description of C<EV_USE_MONOTONIC>, though.	2364	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2365
		2366	=item EV_USE_NANOSLEEP
		2367
		2368	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2369	and will use it for delays. Otherwise it will use C<select ()>.
1962		2370
1963	=item EV_USE_SELECT	2371	=item EV_USE_SELECT
1964		2372
1965	If undefined or defined to be C<1>, libev will compile in support for the	2373	If undefined or defined to be C<1>, libev will compile in support for the
1966	C<select>(2) backend. No attempt at autodetection will be done: if no	2374	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2059	will have the C<struct ev_loop *> as first argument, and you can create	2467	will have the C<struct ev_loop *> as first argument, and you can create
2060	additional independent event loops. Otherwise there will be no support	2468	additional independent event loops. Otherwise there will be no support
2061	for multiple event loops and there is no first event loop pointer	2469	for multiple event loops and there is no first event loop pointer
2062	argument. Instead, all functions act on the single default loop.	2470	argument. Instead, all functions act on the single default loop.
2063		2471
		2472	=item EV_MINPRI
		2473
		2474	=item EV_MAXPRI
		2475
		2476	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2477	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2478	provide for more priorities by overriding those symbols (usually defined
		2479	to be C<-2> and C<2>, respectively).
		2480
		2481	When doing priority-based operations, libev usually has to linearly search
		2482	all the priorities, so having many of them (hundreds) uses a lot of space
		2483	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2484	fine.
		2485
		2486	If your embedding app does not need any priorities, defining these both to
		2487	C<0> will save some memory and cpu.
		2488
2064	=item EV_PERIODIC_ENABLE	2489	=item EV_PERIODIC_ENABLE
2065		2490
2066	If undefined or defined to be C<1>, then periodic timers are supported. If	2491	If undefined or defined to be C<1>, then periodic timers are supported. If
		2492	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2493	code.
		2494
		2495	=item EV_IDLE_ENABLE
		2496
		2497	If undefined or defined to be C<1>, then idle watchers are supported. If
2067	defined to be C<0>, then they are not. Disabling them saves a few kB of	2498	defined to be C<0>, then they are not. Disabling them saves a few kB of
2068	code.	2499	code.
2069		2500
2070	=item EV_EMBED_ENABLE	2501	=item EV_EMBED_ENABLE
2071		2502
…		…
2095	than enough. If you need to manage thousands of children you might want to	2526	than enough. If you need to manage thousands of children you might want to
2096	increase this value (I<must> be a power of two).	2527	increase this value (I<must> be a power of two).
2097		2528
2098	=item EV_INOTIFY_HASHSIZE	2529	=item EV_INOTIFY_HASHSIZE
2099		2530
2100	C<ev_staz> watchers use a small hash table to distribute workload by	2531	C<ev_stat> watchers use a small hash table to distribute workload by
2101	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2532	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2102	usually more than enough. If you need to manage thousands of C<ev_stat>	2533	usually more than enough. If you need to manage thousands of C<ev_stat>
2103	watchers you might want to increase this value (I<must> be a power of	2534	watchers you might want to increase this value (I<must> be a power of
2104	two).	2535	two).
2105		2536
…		…
2122		2553
2123	=item ev_set_cb (ev, cb)	2554	=item ev_set_cb (ev, cb)
2124		2555
2125	Can be used to change the callback member declaration in each watcher,	2556	Can be used to change the callback member declaration in each watcher,
2126	and the way callbacks are invoked and set. Must expand to a struct member	2557	and the way callbacks are invoked and set. Must expand to a struct member
2127	definition and a statement, respectively. See the F<ev.v> header file for	2558	definition and a statement, respectively. See the F<ev.h> header file for
2128	their default definitions. One possible use for overriding these is to	2559	their default definitions. One possible use for overriding these is to
2129	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2560	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2130	method calls instead of plain function calls in C++.	2561	method calls instead of plain function calls in C++.
		2562
		2563	=head2 EXPORTED API SYMBOLS
		2564
		2565	If you need to re-export the API (e.g. via a dll) and you need a list of
		2566	exported symbols, you can use the provided F<Symbol.*> files which list
		2567	all public symbols, one per line:
		2568
		2569	Symbols.ev for libev proper
		2570	Symbols.event for the libevent emulation
		2571
		2572	This can also be used to rename all public symbols to avoid clashes with
		2573	multiple versions of libev linked together (which is obviously bad in
		2574	itself, but sometimes it is inconvinient to avoid this).
		2575
		2576	A sed command like this will create wrapper C<#define>'s that you need to
		2577	include before including F<ev.h>:
		2578
		2579	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2580
		2581	This would create a file F<wrap.h> which essentially looks like this:
		2582
		2583	#define ev_backend myprefix_ev_backend
		2584	#define ev_check_start myprefix_ev_check_start
		2585	#define ev_check_stop myprefix_ev_check_stop
		2586	...
2131		2587
2132	=head2 EXAMPLES	2588	=head2 EXAMPLES
2133		2589
2134	For a real-world example of a program the includes libev	2590	For a real-world example of a program the includes libev
2135	verbatim, you can have a look at the EV perl module	2591	verbatim, you can have a look at the EV perl module
…		…
2138	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2594	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2139	will be compiled. It is pretty complex because it provides its own header	2595	will be compiled. It is pretty complex because it provides its own header
2140	file.	2596	file.
2141		2597
2142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2598	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2143	that everybody includes and which overrides some autoconf choices:	2599	that everybody includes and which overrides some configure choices:
2144		2600
		2601	#define EV_MINIMAL 1
2145	#define EV_USE_POLL 0	2602	#define EV_USE_POLL 0
2146	#define EV_MULTIPLICITY 0	2603	#define EV_MULTIPLICITY 0
2147	#define EV_PERIODICS 0	2604	#define EV_PERIODIC_ENABLE 0
		2605	#define EV_STAT_ENABLE 0
		2606	#define EV_FORK_ENABLE 0
2148	#define EV_CONFIG_H <config.h>	2607	#define EV_CONFIG_H <config.h>
		2608	#define EV_MINPRI 0
		2609	#define EV_MAXPRI 0
2149		2610
2150	#include "ev++.h"	2611	#include "ev++.h"
2151		2612
2152	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2613	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2153		2614
…		…
2159		2620
2160	In this section the complexities of (many of) the algorithms used inside	2621	In this section the complexities of (many of) the algorithms used inside
2161	libev will be explained. For complexity discussions about backends see the	2622	libev will be explained. For complexity discussions about backends see the
2162	documentation for C<ev_default_init>.	2623	documentation for C<ev_default_init>.
2163		2624
		2625	All of the following are about amortised time: If an array needs to be
		2626	extended, libev needs to realloc and move the whole array, but this
		2627	happens asymptotically never with higher number of elements, so O(1) might
		2628	mean it might do a lengthy realloc operation in rare cases, but on average
		2629	it is much faster and asymptotically approaches constant time.
		2630
2164	=over 4	2631	=over 4
2165		2632
2166	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2633	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2167		2634
		2635	This means that, when you have a watcher that triggers in one hour and
		2636	there are 100 watchers that would trigger before that then inserting will
		2637	have to skip those 100 watchers.
		2638
2168	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2639	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2169		2640
		2641	That means that for changing a timer costs less than removing/adding them
		2642	as only the relative motion in the event queue has to be paid for.
		2643
2170	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2644	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2171		2645
		2646	These just add the watcher into an array or at the head of a list.
2172	=item Stopping check/prepare/idle watchers: O(1)	2647	=item Stopping check/prepare/idle watchers: O(1)
2173		2648
2174	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2649	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2175		2650
		2651	These watchers are stored in lists then need to be walked to find the
		2652	correct watcher to remove. The lists are usually short (you don't usually
		2653	have many watchers waiting for the same fd or signal).
		2654
2176	=item Finding the next timer per loop iteration: O(1)	2655	=item Finding the next timer per loop iteration: O(1)
2177		2656
2178	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2179		2658
		2659	A change means an I/O watcher gets started or stopped, which requires
		2660	libev to recalculate its status (and possibly tell the kernel).
		2661
2180	=item Activating one watcher: O(1)	2662	=item Activating one watcher: O(1)
2181		2663
		2664	=item Priority handling: O(number_of_priorities)
		2665
		2666	Priorities are implemented by allocating some space for each
		2667	priority. When doing priority-based operations, libev usually has to
		2668	linearly search all the priorities.
		2669
2182	=back	2670	=back
2183		2671
2184		2672
2185	=head1 AUTHOR	2673	=head1 AUTHOR
2186		2674

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Comparing libev/ev.pod (file contents): Revision 1.59 by root, Wed Nov 28 17:32:24 2007 UTC vs. Revision 1.105 by root, Sun Dec 23 03:50:10 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.59 by root, Wed Nov 28 17:32:24 2007 UTC vs.
Revision 1.105 by root, Sun Dec 23 03:50:10 2007 UTC