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

Comparing libev/ev.pod (file contents):
Revision 1.61 by root, Thu Nov 29 12:21:05 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;
…		…
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
…		…
893	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1115	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
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.
		1120
		1121	=head3 Watcher-Specific Functions and Data Members
898		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
…		…
998	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
999	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
1000	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 ()
1001	+ 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
1002	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
1003	roughly 10 seconds later and of course not if you reset your system time	1227	roughly 10 seconds later).
1004	again).
1005		1228
1006	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
1007	triggering an event on eahc midnight, local time.	1230	triggering an event on each midnight, local time or other, complicated,
		1231	rules.
1008		1232
1009	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
1010	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
1011	during the same loop iteration then order of execution is undefined.	1235	during the same loop iteration then order of execution is undefined.
1012		1236
		1237	=head3 Watcher-Specific Functions and Data Members
		1238
1013	=over 4	1239	=over 4
1014		1240
1015	=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)
1016		1242
1017	=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)
…		…
1019	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
1020	operation, and we will explain them from simplest to complex:	1246	operation, and we will explain them from simplest to complex:
1021		1247
1022	=over 4	1248	=over 4
1023		1249
1024	=item * absolute timer (interval = reschedule_cb = 0)	1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1025		1251
1026	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
1027	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,
1028	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
1029	system time reaches or surpasses this time.	1255	system time reaches or surpasses this time.
1030		1256
1031	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1032		1258
1033	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
1034	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)
1035	of any time jumps.	1261	and then repeat, regardless of any time jumps.
1036		1262
1037	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
1038	time:	1264	time:
1039		1265
1040	ev_periodic_set (&periodic, 0., 3600., 0);	1266	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1046		1272
1047	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
1048	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
1049	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.
1050		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
1051	=item * manual reschedule mode (reschedule_cb = callback)	1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1052		1282
1053	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
1054	ignored. Instead, each time the periodic watcher gets scheduled, the	1284	ignored. Instead, each time the periodic watcher gets scheduled, the
1055	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
1056	current time as second argument.	1286	current time as second argument.
1057		1287
1058	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,
1059	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,
1060	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
1061	starting a prepare watcher).	1291	starting an C<ev_prepare> watcher, which is legal).
1062		1292
1063	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,
1064	ev_tstamp now)>, e.g.:	1294	ev_tstamp now)>, e.g.:
1065		1295
1066	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)
…		…
1089	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
1090	when you changed some parameters or the reschedule callback would return	1320	when you changed some parameters or the reschedule callback would return
1091	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
1092	program when the crontabs have changed).	1322	program when the crontabs have changed).
1093		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
1094	=item ev_tstamp interval [read-write]	1332	=item ev_tstamp interval [read-write]
1095		1333
1096	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
1097	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
1098	called.	1336	called.
…		…
1100	=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]
1101		1339
1102	The current reschedule callback, or C<0>, if this functionality is	1340	The current reschedule callback, or C<0>, if this functionality is
1103	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
1104	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.
1105		1348
1106	=back	1349	=back
1107		1350
1108	Example: Call a callback every hour, or, more precisely, whenever the	1351	Example: Call a callback every hour, or, more precisely, whenever the
1109	system clock is divisible by 3600. The callback invocation times have	1352	system clock is divisible by 3600. The callback invocation times have
…		…
1151	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
1152	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
1153	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
1154	SIG_DFL (regardless of what it was set to before).	1397	SIG_DFL (regardless of what it was set to before).
1155		1398
		1399	=head3 Watcher-Specific Functions and Data Members
		1400
1156	=over 4	1401	=over 4
1157		1402
1158	=item ev_signal_init (ev_signal *, callback, int signum)	1403	=item ev_signal_init (ev_signal *, callback, int signum)
1159		1404
1160	=item ev_signal_set (ev_signal *, int signum)	1405	=item ev_signal_set (ev_signal *, int signum)
…		…
1171		1416
1172	=head2 C<ev_child> - watch out for process status changes	1417	=head2 C<ev_child> - watch out for process status changes
1173		1418
1174	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
1175	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
1176		1423
1177	=over 4	1424	=over 4
1178		1425
1179	=item ev_child_init (ev_child *, callback, int pid)	1426	=item ev_child_init (ev_child *, callback, int pid)
1180		1427
…		…
1249	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
1250	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
1251	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
1252	polling.	1499	polling.
1253		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
1254	=over 4	1536	=over 4
1255		1537
1256	=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)
1257		1539
1258	=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)
…		…
1293	=item const char *path [read-only]	1575	=item const char *path [read-only]
1294		1576
1295	The filesystem path that is being watched.	1577	The filesystem path that is being watched.
1296		1578
1297	=back	1579	=back
		1580
		1581	=head3 Examples
1298		1582
1299	Example: Watch C</etc/passwd> for attribute changes.	1583	Example: Watch C</etc/passwd> for attribute changes.
1300		1584
1301	static void	1585	static void
1302	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1586	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1315	}	1599	}
1316		1600
1317	...	1601	...
1318	ev_stat passwd;	1602	ev_stat passwd;
1319		1603
1320	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1604	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1321	ev_stat_start (loop, &passwd);	1605	ev_stat_start (loop, &passwd);
1322		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);
		1634
1323		1635
1324	=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...
1325		1637
1326	Idle watchers trigger events when there are no other events are pending	1638	Idle watchers trigger events when no other events of the same or higher
1327	(prepare, check and other idle watchers do not count). That is, as long	1639	priority are pending (prepare, check and other idle watchers do not
1328	as your process is busy handling sockets or timeouts (or even signals,	1640	count).
1329	imagine) it will not be triggered. But when your process is idle all idle	1641
1330	watchers are being called again and again, once per event loop iteration -	1642	That is, as long as your process is busy handling sockets or timeouts
		1643	(or even signals, imagine) of the same or higher priority it will not be
		1644	triggered. But when your process is idle (or only lower-priority watchers
		1645	are pending), the idle watchers are being called once per event loop
1331	until stopped, that is, or your process receives more events and becomes	1646	iteration - until stopped, that is, or your process receives more events
1332	busy.	1647	and becomes busy again with higher priority stuff.
1333		1648
1334	The most noteworthy effect is that as long as any idle watchers are	1649	The most noteworthy effect is that as long as any idle watchers are
1335	active, the process will not block when waiting for new events.	1650	active, the process will not block when waiting for new events.
1336		1651
1337	Apart from keeping your process non-blocking (which is a useful	1652	Apart from keeping your process non-blocking (which is a useful
1338	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
1339	"pseudo-background processing", or delay processing stuff to after the	1654	"pseudo-background processing", or delay processing stuff to after the
1340	event loop has handled all outstanding events.	1655	event loop has handled all outstanding events.
		1656
		1657	=head3 Watcher-Specific Functions and Data Members
1341		1658
1342	=over 4	1659	=over 4
1343		1660
1344	=item ev_idle_init (ev_signal *, callback)	1661	=item ev_idle_init (ev_signal *, callback)
1345		1662
…		…
1403	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
1404	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
1405	loop from blocking if lower-priority coroutines are active, thus mapping	1722	loop from blocking if lower-priority coroutines are active, thus mapping
1406	low-priority coroutines to idle/background tasks).	1723	low-priority coroutines to idle/background tasks).
1407		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
1408	=over 4	1737	=over 4
1409		1738
1410	=item ev_prepare_init (ev_prepare *, callback)	1739	=item ev_prepare_init (ev_prepare *, callback)
1411		1740
1412	=item ev_check_init (ev_check *, callback)	1741	=item ev_check_init (ev_check *, callback)
…		…
1415	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>
1416	macros, but using them is utterly, utterly and completely pointless.	1745	macros, but using them is utterly, utterly and completely pointless.
1417		1746
1418	=back	1747	=back
1419		1748
1420	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
1421	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,
1422	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
1423	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.
1424		1761
1425	static ev_io iow [nfd];	1762	static ev_io iow [nfd];
1426	static ev_timer tw;	1763	static ev_timer tw;
1427		1764
1428	static void	1765	static void
1429	io_cb (ev_loop loop, ev_io w, int revents)	1766	io_cb (ev_loop loop, ev_io w, int revents)
1430	{	1767	{
1431	// set the relevant poll flags
1432	// could also call adns_processreadable etc. here
1433	struct pollfd fd = (struct pollfd )w->data;
1434	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1435	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1436	}	1768	}
1437		1769
1438	// create io watchers for each fd and a timer before blocking	1770	// create io watchers for each fd and a timer before blocking
1439	static void	1771	static void
1440	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1772	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1441	{	1773	{
1442	int timeout = 3600000;truct pollfd fds [nfd];	1774	int timeout = 3600000;
		1775	struct pollfd fds [nfd];
1443	// actual code will need to loop here and realloc etc.	1776	// actual code will need to loop here and realloc etc.
1444	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1777	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1445		1778
1446	/* 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 */
1447	ev_timer_init (&tw, 0, timeout * 1e-3);	1780	ev_timer_init (&tw, 0, timeout * 1e-3);
1448	ev_timer_start (loop, &tw);	1781	ev_timer_start (loop, &tw);
1449		1782
1450	// create on ev_io per pollfd	1783	// create one ev_io per pollfd
1451	for (int i = 0; i < nfd; ++i)	1784	for (int i = 0; i < nfd; ++i)
1452	{	1785	{
1453	ev_io_init (iow + i, io_cb, fds [i].fd,	1786	ev_io_init (iow + i, io_cb, fds [i].fd,
1454	((fds [i].events & POLLIN ? EV_READ : 0)	1787	((fds [i].events & POLLIN ? EV_READ : 0)
1455	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1788	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1456		1789
1457	fds [i].revents = 0;	1790	fds [i].revents = 0;
1458	iow [i].data = fds + i;
1459	ev_io_start (loop, iow + i);	1791	ev_io_start (loop, iow + i);
1460	}	1792	}
1461	}	1793	}
1462		1794
1463	// stop all watchers after blocking	1795	// stop all watchers after blocking
…		…
1465	adns_check_cb (ev_loop loop, ev_check w, int revents)	1797	adns_check_cb (ev_loop loop, ev_check w, int revents)
1466	{	1798	{
1467	ev_timer_stop (loop, &tw);	1799	ev_timer_stop (loop, &tw);
1468		1800
1469	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
1470	ev_io_stop (loop, iow + i);	1811	ev_io_stop (loop, iow + i);
		1812	}
1471		1813
1472	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;
1473	}	1874	}
1474		1875
1475		1876
1476	=head2 C<ev_embed> - when one backend isn't enough...	1877	=head2 C<ev_embed> - when one backend isn't enough...
1477		1878
…		…
1541	ev_embed_start (loop_hi, &embed);	1942	ev_embed_start (loop_hi, &embed);
1542	}	1943	}
1543	else	1944	else
1544	loop_lo = loop_hi;	1945	loop_lo = loop_hi;
1545		1946
		1947	=head3 Watcher-Specific Functions and Data Members
		1948
1546	=over 4	1949	=over 4
1547		1950
1548	=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)
1549		1952
1550	=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)
…		…
1559		1962
1560	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
1561	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
1562	apropriate way for embedded loops.	1965	apropriate way for embedded loops.
1563		1966
1564	=item struct ev_loop *loop [read-only]	1967	=item struct ev_loop *other [read-only]
1565		1968
1566	The embedded event loop.	1969	The embedded event loop.
1567		1970
1568	=back	1971	=back
1569		1972
…		…
1576	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,
1577	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
1578	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
1579	handlers will be invoked, too, of course.	1982	handlers will be invoked, too, of course.
1580		1983
		1984	=head3 Watcher-Specific Functions and Data Members
		1985
1581	=over 4	1986	=over 4
1582		1987
1583	=item ev_fork_init (ev_signal *, callback)	1988	=item ev_fork_init (ev_signal *, callback)
1584		1989
1585	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
…		…
1681		2086
1682	To use it,	2087	To use it,
1683		2088
1684	#include <ev++.h>	2089	#include <ev++.h>
1685		2090
1686	(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
1687	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
1688	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>.
1689		2095
1690	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++
1691	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).
1692		2106
1693	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:
1694		2108
1695	=over 4	2109	=over 4
1696		2110
…		…
1712		2126
1713	All of those classes have these methods:	2127	All of those classes have these methods:
1714		2128
1715	=over 4	2129	=over 4
1716		2130
1717	=item ev::TYPE::TYPE (object , object::method )	2131	=item ev::TYPE::TYPE ()
1718		2132
1719	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	2133	=item ev::TYPE::TYPE (struct ev_loop *)
1720		2134
1721	=item ev::TYPE::~TYPE	2135	=item ev::TYPE::~TYPE
1722		2136
1723	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
1724	the event handler callback to call in this class. The constructor calls	2138	with. If it is omitted, it will use C<EV_DEFAULT>.
1725	C<ev_init> for you, which means you have to call the C<set> method	2139
1726	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
1727	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).
1728		2148
1729	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> ();
1730		2189
1731	=item w->set (struct ev_loop *)	2190	=item w->set (struct ev_loop *)
1732		2191
1733	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
1734	do this when the watcher is inactive (and not pending either).	2193	do this when the watcher is inactive (and not pending either).
1735		2194
1736	=item w->set ([args])	2195	=item w->set ([args])
1737		2196
1738	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
1739	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
1740	automatically stopped and restarted.	2199	automatically stopped and restarted when reconfiguring it with this
		2200	method.
1741		2201
1742	=item w->start ()	2202	=item w->start ()
1743		2203
1744	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
1745	constructor already takes the loop.	2205	constructor already stores the event loop.
1746		2206
1747	=item w->stop ()	2207	=item w->stop ()
1748		2208
1749	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.
1750		2210
1751	=item w->again () C<ev::timer>, C<ev::periodic> only	2211	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1752		2212
1753	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
1754	C<ev_TYPE_again> function.	2214	C<ev_TYPE_again> function.
1755		2215
1756	=item w->sweep () C<ev::embed> only	2216	=item w->sweep () (C<ev::embed> only)
1757		2217
1758	Invokes C<ev_embed_sweep>.	2218	Invokes C<ev_embed_sweep>.
1759		2219
1760	=item w->update () C<ev::stat> only	2220	=item w->update () (C<ev::stat> only)
1761		2221
1762	Invokes C<ev_stat_stat>.	2222	Invokes C<ev_stat_stat>.
1763		2223
1764	=back	2224	=back
1765		2225
…		…
1775		2235
1776	myclass ();	2236	myclass ();
1777	}	2237	}
1778		2238
1779	myclass::myclass (int fd)	2239	myclass::myclass (int fd)
1780	: io (this, &myclass::io_cb),
1781	idle (this, &myclass::idle_cb)
1782	{	2240	{
		2241	io .set <myclass, &myclass::io_cb > (this);
		2242	idle.set <myclass, &myclass::idle_cb> (this);
		2243
1783	io.start (fd, ev::READ);	2244	io.start (fd, ev::READ);
1784	}	2245	}
1785		2246
1786		2247
1787	=head1 MACRO MAGIC	2248	=head1 MACRO MAGIC
1788		2249
1789	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
1790	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2251	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1791	callbacks have an initial C<struct ev_loop *> argument.	2252	functions and callbacks have an initial C<struct ev_loop *> argument.
1792		2253
1793	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
1794	following macros are defined:	2255	following macros are defined:
1795		2256
1796	=over 4	2257	=over 4
…		…
1828	Similar to the other two macros, this gives you the value of the default	2289	Similar to the other two macros, this gives you the value of the default
1829	loop, if multiple loops are supported ("ev loop default").	2290	loop, if multiple loops are supported ("ev loop default").
1830		2291
1831	=back	2292	=back
1832		2293
1833	Example: Declare and initialise a check watcher, working regardless of	2294	Example: Declare and initialise a check watcher, utilising the above
1834	wether multiple loops are supported or not.	2295	macros so it will work regardless of whether multiple loops are supported
		2296	or not.
1835		2297
1836	static void	2298	static void
1837	check_cb (EV_P_ ev_timer *w, int revents)	2299	check_cb (EV_P_ ev_timer *w, int revents)
1838	{	2300	{
1839	ev_check_stop (EV_A_ w);	2301	ev_check_stop (EV_A_ w);
…		…
1842	ev_check check;	2304	ev_check check;
1843	ev_check_init (&check, check_cb);	2305	ev_check_init (&check, check_cb);
1844	ev_check_start (EV_DEFAULT_ &check);	2306	ev_check_start (EV_DEFAULT_ &check);
1845	ev_loop (EV_DEFAULT_ 0);	2307	ev_loop (EV_DEFAULT_ 0);
1846		2308
1847
1848	=head1 EMBEDDING	2309	=head1 EMBEDDING
1849		2310
1850	Libev can (and often is) directly embedded into host	2311	Libev can (and often is) directly embedded into host
1851	applications. Examples of applications that embed it include the Deliantra	2312	applications. Examples of applications that embed it include the Deliantra
1852	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)
1853	and rxvt-unicode.	2314	and rxvt-unicode.
1854		2315
1855	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
1856	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
1857	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
1858	libev somewhere in your source tree).	2319	libev somewhere in your source tree).
1859		2320
1860	=head2 FILESETS	2321	=head2 FILESETS
…		…
1891	ev_vars.h	2352	ev_vars.h
1892	ev_wrap.h	2353	ev_wrap.h
1893		2354
1894	ev_win32.c required on win32 platforms only	2355	ev_win32.c required on win32 platforms only
1895		2356
1896	ev_select.c only when select backend is enabled (which is by default)	2357	ev_select.c only when select backend is enabled (which is enabled by default)
1897	ev_poll.c only when poll backend is enabled (disabled by default)	2358	ev_poll.c only when poll backend is enabled (disabled by default)
1898	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2359	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1899	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2360	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1900	ev_port.c only when the solaris port backend is enabled (disabled by default)	2361	ev_port.c only when the solaris port backend is enabled (disabled by default)
1901		2362
…		…
1950		2411
1951	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
1952	monotonic clock option at both compiletime and runtime. Otherwise no use	2413	monotonic clock option at both compiletime and runtime. Otherwise no use
1953	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
1954	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
1955	the functionality isn't available is safe, though, althoguh you have	2416	the functionality isn't available is safe, though, although you have
1956	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>
1957	function is hiding in (often F<-lrt>).	2418	function is hiding in (often F<-lrt>).
1958		2419
1959	=item EV_USE_REALTIME	2420	=item EV_USE_REALTIME
1960		2421
1961	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
1962	realtime clock option at compiletime (and assume its availability at	2423	realtime clock option at compiletime (and assume its availability at
1963	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
1964	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2425	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1965	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2426	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1966	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 ()>.
1967		2433
1968	=item EV_USE_SELECT	2434	=item EV_USE_SELECT
1969		2435
1970	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
1971	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
…		…
2064	will have the C<struct ev_loop *> as first argument, and you can create	2530	will have the C<struct ev_loop *> as first argument, and you can create
2065	additional independent event loops. Otherwise there will be no support	2531	additional independent event loops. Otherwise there will be no support
2066	for multiple event loops and there is no first event loop pointer	2532	for multiple event loops and there is no first event loop pointer
2067	argument. Instead, all functions act on the single default loop.	2533	argument. Instead, all functions act on the single default loop.
2068		2534
		2535	=item EV_MINPRI
		2536
		2537	=item EV_MAXPRI
		2538
		2539	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2540	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2541	provide for more priorities by overriding those symbols (usually defined
		2542	to be C<-2> and C<2>, respectively).
		2543
		2544	When doing priority-based operations, libev usually has to linearly search
		2545	all the priorities, so having many of them (hundreds) uses a lot of space
		2546	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2547	fine.
		2548
		2549	If your embedding app does not need any priorities, defining these both to
		2550	C<0> will save some memory and cpu.
		2551
2069	=item EV_PERIODIC_ENABLE	2552	=item EV_PERIODIC_ENABLE
2070		2553
2071	If undefined or defined to be C<1>, then periodic timers are supported. If	2554	If undefined or defined to be C<1>, then periodic timers are supported. If
		2555	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2556	code.
		2557
		2558	=item EV_IDLE_ENABLE
		2559
		2560	If undefined or defined to be C<1>, then idle watchers are supported. If
2072	defined to be C<0>, then they are not. Disabling them saves a few kB of	2561	defined to be C<0>, then they are not. Disabling them saves a few kB of
2073	code.	2562	code.
2074		2563
2075	=item EV_EMBED_ENABLE	2564	=item EV_EMBED_ENABLE
2076		2565
…		…
2100	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
2101	increase this value (I<must> be a power of two).	2590	increase this value (I<must> be a power of two).
2102		2591
2103	=item EV_INOTIFY_HASHSIZE	2592	=item EV_INOTIFY_HASHSIZE
2104		2593
2105	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
2106	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>),
2107	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>
2108	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
2109	two).	2598	two).
2110		2599
…		…
2127		2616
2128	=item ev_set_cb (ev, cb)	2617	=item ev_set_cb (ev, cb)
2129		2618
2130	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,
2131	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
2132	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
2133	their default definitions. One possible use for overriding these is to	2622	their default definitions. One possible use for overriding these is to
2134	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
2135	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	...
2136		2650
2137	=head2 EXAMPLES	2651	=head2 EXAMPLES
2138		2652
2139	For a real-world example of a program the includes libev	2653	For a real-world example of a program the includes libev
2140	verbatim, you can have a look at the EV perl module	2654	verbatim, you can have a look at the EV perl module
…		…
2143	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2657	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2144	will be compiled. It is pretty complex because it provides its own header	2658	will be compiled. It is pretty complex because it provides its own header
2145	file.	2659	file.
2146		2660
2147	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2661	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2148	that everybody includes and which overrides some autoconf choices:	2662	that everybody includes and which overrides some configure choices:
2149		2663
		2664	#define EV_MINIMAL 1
2150	#define EV_USE_POLL 0	2665	#define EV_USE_POLL 0
2151	#define EV_MULTIPLICITY 0	2666	#define EV_MULTIPLICITY 0
2152	#define EV_PERIODICS 0	2667	#define EV_PERIODIC_ENABLE 0
		2668	#define EV_STAT_ENABLE 0
		2669	#define EV_FORK_ENABLE 0
2153	#define EV_CONFIG_H <config.h>	2670	#define EV_CONFIG_H <config.h>
		2671	#define EV_MINPRI 0
		2672	#define EV_MAXPRI 0
2154		2673
2155	#include "ev++.h"	2674	#include "ev++.h"
2156		2675
2157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2676	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2158		2677
…		…
2164		2683
2165	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
2166	libev will be explained. For complexity discussions about backends see the	2685	libev will be explained. For complexity discussions about backends see the
2167	documentation for C<ev_default_init>.	2686	documentation for C<ev_default_init>.
2168		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
2169	=over 4	2694	=over 4
2170		2695
2171	=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)
2172		2697
		2698	This means that, when you have a watcher that triggers in one hour and
		2699	there are 100 watchers that would trigger before that then inserting will
		2700	have to skip roughly seven (C<ld 100>) of these watchers.
		2701
2173	=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)
		2703
		2704	That means that changing a timer costs less than removing/adding them
		2705	as only the relative motion in the event queue has to be paid for.
2174		2706
2175	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2707	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2176		2708
		2709	These just add the watcher into an array or at the head of a list.
		2710
2177	=item Stopping check/prepare/idle watchers: O(1)	2711	=item Stopping check/prepare/idle watchers: O(1)
2178		2712
2179	=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))
2180		2714
		2715	These watchers are stored in lists then need to be walked to find the
		2716	correct watcher to remove. The lists are usually short (you don't usually
		2717	have many watchers waiting for the same fd or signal).
		2718
2181	=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.
2182		2723
2183	=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)
2184		2725
2185	=item Activating one watcher: O(1)	2726	A change means an I/O watcher gets started or stopped, which requires
		2727	libev to recalculate its status (and possibly tell the kernel, depending
		2728	on backend and wether C<ev_io_set> was used).
		2729
		2730	=item Activating one watcher (putting it into the pending state): O(1)
		2731
		2732	=item Priority handling: O(number_of_priorities)
		2733
		2734	Priorities are implemented by allocating some space for each
		2735	priority. When doing priority-based operations, libev usually has to
		2736	linearly search all the priorities, but starting/stopping and activating
		2737	watchers becomes O(1) w.r.t. prioritiy handling.
2186		2738
2187	=back	2739	=back
2188		2740
2189		2741
2190	=head1 AUTHOR	2742	=head1 AUTHOR

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Comparing libev/ev.pod (file contents): Revision 1.61 by root, Thu Nov 29 12:21:05 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 1.61 by root, Thu Nov 29 12:21:05 2007 UTC vs.
Revision 1.108 by root, Mon Dec 24 10:39:21 2007 UTC