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

Comparing libev/ev.pod (file contents):
Revision 1.68 by root, Fri Dec 7 18:09:43 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.
…		…
291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
292		307
293	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
294	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
295	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
296	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
297	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
298		320
299	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
300		322
301	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
302	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
303	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
304	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
305		329
306	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
307		331
308	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
309	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
310	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	334	like O(total_fds) where n is the total number of fds (or the highest fd),
311	either O(1) or O(active_fds).	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
		336	of shortcomings, such as silently dropping events in some hard-to-detect
		337	cases and rewiring a syscall per fd change, no fork support and bad
		338	support for dup.
312		339
313	While stopping and starting an I/O watcher in the same iteration will	340	While stopping, setting and starting an I/O watcher in the same iteration
314	result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
315	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
316	best to avoid that. Also, dup()ed file descriptors might not work very	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
317	well if you register events for both fds.	344	very well if you register events for both fds.
318		345
319	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
320	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
321	(or space) is available.	348	(or space) is available.
322		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
323	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
324		358
325	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
326	was broken on all BSDs except NetBSD (usually it doesn't work with	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
327	anything but sockets and pipes, except on Darwin, where of course its	361	with anything but sockets and pipes, except on Darwin, where of course
328	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
329	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
330	C<EVBACKEND_KQUEUE>).	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		365	system like NetBSD.
		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
331		370
332	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
333	kernel is more efficient (which says nothing about its actual speed, of	372	kernel is more efficient (which says nothing about its actual speed, of
334	course). While starting and stopping an I/O watcher does not cause an	373	course). While stopping, setting and starting an I/O watcher does never
335	extra syscall as with epoll, it still adds up to four event changes per	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
336	incident, so its best to avoid that.	375	two event changes per incident, support for C<fork ()> is very bad and it
		376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
337		386
338	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
339		388
340	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
341		393
342	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
343		395
344	This uses the Solaris 10 port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
345	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
346		398
347	Please note that solaris ports can result in a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
348	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
349	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
350		407
351	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
352		409
353	Try all backends (even potentially broken ones that wouldn't be tried	410	Try all backends (even potentially broken ones that wouldn't be tried
354	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
355	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
356		415
357	=back	416	=back
358		417
359	If one or more of these are ored into the flags value, then only these	418	If one or more of these are ored into the flags value, then only these
360	backends will be tried (in the reverse order as given here). If none are	419	backends will be tried (in the reverse order as given here). If none are
…		…
395	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
396	etc.). None of the active event watchers will be stopped in the normal	455	etc.). None of the active event watchers will be stopped in the normal
397	sense, so e.g. C<ev_is_active> might still return true. It is your	456	sense, so e.g. C<ev_is_active> might still return true. It is your
398	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
399	calling this function, or cope with the fact afterwards (which is usually	458	calling this function, or cope with the fact afterwards (which is usually
400	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	459	the easiest thing, you can just ignore the watchers and/or C<free ()> them
401	for example).	460	for example).
		461
		462	Note that certain global state, such as signal state, will not be freed by
		463	this function, and related watchers (such as signal and child watchers)
		464	would need to be stopped manually.
		465
		466	In general it is not advisable to call this function except in the
		467	rare occasion where you really need to free e.g. the signal handling
		468	pipe fds. If you need dynamically allocated loops it is better to use
		469	C<ev_loop_new> and C<ev_loop_destroy>).
402		470
403	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
404		472
405	Like C<ev_default_destroy>, but destroys an event loop created by an	473	Like C<ev_default_destroy>, but destroys an event loop created by an
406	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
451		519
452	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
453	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
454	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
455	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
456	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
457		525
458	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
459		527
460	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
461	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
…		…
482	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
483	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
484		552
485	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
486		554
		555	- Before the first iteration, call any pending watchers.
487	* If there are no active watchers (reference count is zero), return.	556	* If there are no active watchers (reference count is zero), return.
488	- Queue prepare watchers and then call all outstanding watchers.	557	- Queue all prepare watchers and then call all outstanding watchers.
489	- If we have been forked, recreate the kernel state.	558	- If we have been forked, recreate the kernel state.
490	- Update the kernel state with all outstanding changes.	559	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	560	- Update the "event loop time".
492	- Calculate for how long to block.	561	- Calculate for how long to block.
493	- Block the process, waiting for any events.	562	- Block the process, waiting for any events.
…		…
544	Example: For some weird reason, unregister the above signal handler again.	613	Example: For some weird reason, unregister the above signal handler again.
545		614
546	ev_ref (loop);	615	ev_ref (loop);
547	ev_signal_stop (loop, &exitsig);	616	ev_signal_stop (loop, &exitsig);
548		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
549	=back	654	=back
550		655
551		656
552	=head1 ANATOMY OF A WATCHER	657	=head1 ANATOMY OF A WATCHER
553		658
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	837	=item bool ev_is_pending (ev_TYPE *watcher)
733		838
734	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
735	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
736	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
737	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
738	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).
739		845
740	=item callback ev_cb (ev_TYPE *watcher)	846	=item callback ev_cb (ev_TYPE *watcher)
741		847
742	Returns the callback currently set on the watcher.	848	Returns the callback currently set on the watcher.
743		849
…		…
762	watchers on the same event and make sure one is called first.	868	watchers on the same event and make sure one is called first.
763		869
764	If you need to suppress invocation when higher priority events are pending	870	If you need to suppress invocation when higher priority events are pending
765	you need to look at C<ev_idle> watchers, which provide this functionality.	871	you need to look at C<ev_idle> watchers, which provide this functionality.
766		872
		873	You I<must not> change the priority of a watcher as long as it is active or
		874	pending.
		875
767	The default priority used by watchers when no priority has been set is	876	The default priority used by watchers when no priority has been set is
768	always C<0>, which is supposed to not be too high and not be too low :).	877	always C<0>, which is supposed to not be too high and not be too low :).
769		878
770	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	879	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
771	fine, as long as you do not mind that the priority value you query might	880	fine, as long as you do not mind that the priority value you query might
772	or might not have been adjusted to be within valid range.	881	or might not have been adjusted to be within valid range.
		882
		883	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		884
		885	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		886	C<loop> nor C<revents> need to be valid as long as the watcher callback
		887	can deal with that fact.
		888
		889	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		890
		891	If the watcher is pending, this function returns clears its pending status
		892	and returns its C<revents> bitset (as if its callback was invoked). If the
		893	watcher isn't pending it does nothing and returns C<0>.
773		894
774	=back	895	=back
775		896
776		897
777	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
887	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
888	whether a file descriptor is really ready with a known-to-be good interface	1009	whether a file descriptor is really ready with a known-to-be good interface
889	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
890	its own, so its quite safe to use).	1011	its own, so its quite safe to use).
891		1012
		1013	=head3 The special problem of disappearing file descriptors
		1014
		1015	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1016	descriptor (either by calling C<close> explicitly or by any other means,
		1017	such as C<dup>). The reason is that you register interest in some file
		1018	descriptor, but when it goes away, the operating system will silently drop
		1019	this interest. If another file descriptor with the same number then is
		1020	registered with libev, there is no efficient way to see that this is, in
		1021	fact, a different file descriptor.
		1022
		1023	To avoid having to explicitly tell libev about such cases, libev follows
		1024	the following policy: Each time C<ev_io_set> is being called, libev
		1025	will assume that this is potentially a new file descriptor, otherwise
		1026	it is assumed that the file descriptor stays the same. That means that
		1027	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1028	descriptor even if the file descriptor number itself did not change.
		1029
		1030	This is how one would do it normally anyway, the important point is that
		1031	the libev application should not optimise around libev but should leave
		1032	optimisations to libev.
		1033
		1034	=head3 The special problem of dup'ed file descriptors
		1035
		1036	Some backends (e.g. epoll), cannot register events for file descriptors,
		1037	but only events for the underlying file descriptions. That means when you
		1038	have C<dup ()>'ed file descriptors and register events for them, only one
		1039	file descriptor might actually receive events.
		1040
		1041	There is no workaround possible except not registering events
		1042	for potentially C<dup ()>'ed file descriptors, or to resort to
		1043	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1044
		1045	=head3 The special problem of fork
		1046
		1047	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1048	useless behaviour. Libev fully supports fork, but needs to be told about
		1049	it in the child.
		1050
		1051	To support fork in your programs, you either have to call
		1052	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1053	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1054	C<EVBACKEND_POLL>.
		1055
		1056
		1057	=head3 Watcher-Specific Functions
		1058
892	=over 4	1059	=over 4
893		1060
894	=item ev_io_init (ev_io *, callback, int fd, int events)	1061	=item ev_io_init (ev_io *, callback, int fd, int events)
895		1062
896	=item ev_io_set (ev_io *, int fd, int events)	1063	=item ev_io_set (ev_io *, int fd, int events)
…		…
948	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1115	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
949		1116
950	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,
951	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
952	order of execution is undefined.	1119	order of execution is undefined.
		1120
		1121	=head3 Watcher-Specific Functions and Data Members
953		1122
954	=over 4	1123	=over 4
955		1124
956	=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)
957		1126
…		…
1053	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
1054	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
1055	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 ()
1056	+ 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
1057	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
1058	roughly 10 seconds later and of course not if you reset your system time	1227	roughly 10 seconds later).
1059	again).
1060		1228
1061	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
1062	triggering an event on eahc midnight, local time.	1230	triggering an event on each midnight, local time or other, complicated,
		1231	rules.
1063		1232
1064	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
1065	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
1066	during the same loop iteration then order of execution is undefined.	1235	during the same loop iteration then order of execution is undefined.
1067		1236
		1237	=head3 Watcher-Specific Functions and Data Members
		1238
1068	=over 4	1239	=over 4
1069		1240
1070	=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)
1071		1242
1072	=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)
…		…
1074	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
1075	operation, and we will explain them from simplest to complex:	1246	operation, and we will explain them from simplest to complex:
1076		1247
1077	=over 4	1248	=over 4
1078		1249
1079	=item * absolute timer (interval = reschedule_cb = 0)	1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1080		1251
1081	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
1082	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,
1083	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
1084	system time reaches or surpasses this time.	1255	system time reaches or surpasses this time.
1085		1256
1086	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1087		1258
1088	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
1089	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)
1090	of any time jumps.	1261	and then repeat, regardless of any time jumps.
1091		1262
1092	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
1093	time:	1264	time:
1094		1265
1095	ev_periodic_set (&periodic, 0., 3600., 0);	1266	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1101		1272
1102	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
1103	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
1104	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.
1105		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
1106	=item * manual reschedule mode (reschedule_cb = callback)	1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1107		1282
1108	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
1109	ignored. Instead, each time the periodic watcher gets scheduled, the	1284	ignored. Instead, each time the periodic watcher gets scheduled, the
1110	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
1111	current time as second argument.	1286	current time as second argument.
1112		1287
1113	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,
1114	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,
1115	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
1116	starting a prepare watcher).	1291	starting an C<ev_prepare> watcher, which is legal).
1117		1292
1118	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,
1119	ev_tstamp now)>, e.g.:	1294	ev_tstamp now)>, e.g.:
1120		1295
1121	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)
…		…
1144	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
1145	when you changed some parameters or the reschedule callback would return	1320	when you changed some parameters or the reschedule callback would return
1146	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
1147	program when the crontabs have changed).	1322	program when the crontabs have changed).
1148		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
1149	=item ev_tstamp interval [read-write]	1332	=item ev_tstamp interval [read-write]
1150		1333
1151	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
1152	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
1153	called.	1336	called.
…		…
1155	=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]
1156		1339
1157	The current reschedule callback, or C<0>, if this functionality is	1340	The current reschedule callback, or C<0>, if this functionality is
1158	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
1159	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.
1160		1348
1161	=back	1349	=back
1162		1350
1163	Example: Call a callback every hour, or, more precisely, whenever the	1351	Example: Call a callback every hour, or, more precisely, whenever the
1164	system clock is divisible by 3600. The callback invocation times have	1352	system clock is divisible by 3600. The callback invocation times have
…		…
1206	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
1207	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
1208	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
1209	SIG_DFL (regardless of what it was set to before).	1397	SIG_DFL (regardless of what it was set to before).
1210		1398
		1399	=head3 Watcher-Specific Functions and Data Members
		1400
1211	=over 4	1401	=over 4
1212		1402
1213	=item ev_signal_init (ev_signal *, callback, int signum)	1403	=item ev_signal_init (ev_signal *, callback, int signum)
1214		1404
1215	=item ev_signal_set (ev_signal *, int signum)	1405	=item ev_signal_set (ev_signal *, int signum)
…		…
1226		1416
1227	=head2 C<ev_child> - watch out for process status changes	1417	=head2 C<ev_child> - watch out for process status changes
1228		1418
1229	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
1230	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
1231		1423
1232	=over 4	1424	=over 4
1233		1425
1234	=item ev_child_init (ev_child *, callback, int pid)	1426	=item ev_child_init (ev_child *, callback, int pid)
1235		1427
…		…
1303	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
1304	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
1305	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
1306	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
1307	polling.	1499	polling.
		1500
		1501	=head3 Watcher-Specific Functions and Data Members
1308		1502
1309	=over 4	1503	=over 4
1310		1504
1311	=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)
1312		1506
…		…
1395	Apart from keeping your process non-blocking (which is a useful	1589	Apart from keeping your process non-blocking (which is a useful
1396	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
1397	"pseudo-background processing", or delay processing stuff to after the	1591	"pseudo-background processing", or delay processing stuff to after the
1398	event loop has handled all outstanding events.	1592	event loop has handled all outstanding events.
1399		1593
		1594	=head3 Watcher-Specific Functions and Data Members
		1595
1400	=over 4	1596	=over 4
1401		1597
1402	=item ev_idle_init (ev_signal *, callback)	1598	=item ev_idle_init (ev_signal *, callback)
1403		1599
1404	Initialises and configures the idle watcher - it has no parameters of any	1600	Initialises and configures the idle watcher - it has no parameters of any
…		…
1461	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
1462	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
1463	loop from blocking if lower-priority coroutines are active, thus mapping	1659	loop from blocking if lower-priority coroutines are active, thus mapping
1464	low-priority coroutines to idle/background tasks).	1660	low-priority coroutines to idle/background tasks).
1465		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
1466	=over 4	1674	=over 4
1467		1675
1468	=item ev_prepare_init (ev_prepare *, callback)	1676	=item ev_prepare_init (ev_prepare *, callback)
1469		1677
1470	=item ev_check_init (ev_check *, callback)	1678	=item ev_check_init (ev_check *, callback)
…		…
1473	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>
1474	macros, but using them is utterly, utterly and completely pointless.	1682	macros, but using them is utterly, utterly and completely pointless.
1475		1683
1476	=back	1684	=back
1477		1685
1478	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
1479	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,
1480	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
1481	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.
1482		1698
1483	static ev_io iow [nfd];	1699	static ev_io iow [nfd];
1484	static ev_timer tw;	1700	static ev_timer tw;
1485		1701
1486	static void	1702	static void
1487	io_cb (ev_loop loop, ev_io w, int revents)	1703	io_cb (ev_loop loop, ev_io w, int revents)
1488	{	1704	{
1489	// set the relevant poll flags
1490	// could also call adns_processreadable etc. here
1491	struct pollfd fd = (struct pollfd )w->data;
1492	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1493	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1494	}	1705	}
1495		1706
1496	// create io watchers for each fd and a timer before blocking	1707	// create io watchers for each fd and a timer before blocking
1497	static void	1708	static void
1498	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1709	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1504		1715
1505	/* 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 */
1506	ev_timer_init (&tw, 0, timeout * 1e-3);	1717	ev_timer_init (&tw, 0, timeout * 1e-3);
1507	ev_timer_start (loop, &tw);	1718	ev_timer_start (loop, &tw);
1508		1719
1509	// create on ev_io per pollfd	1720	// create one ev_io per pollfd
1510	for (int i = 0; i < nfd; ++i)	1721	for (int i = 0; i < nfd; ++i)
1511	{	1722	{
1512	ev_io_init (iow + i, io_cb, fds [i].fd,	1723	ev_io_init (iow + i, io_cb, fds [i].fd,
1513	((fds [i].events & POLLIN ? EV_READ : 0)	1724	((fds [i].events & POLLIN ? EV_READ : 0)
1514	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1725	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1515		1726
1516	fds [i].revents = 0;	1727	fds [i].revents = 0;
1517	iow [i].data = fds + i;
1518	ev_io_start (loop, iow + i);	1728	ev_io_start (loop, iow + i);
1519	}	1729	}
1520	}	1730	}
1521		1731
1522	// stop all watchers after blocking	1732	// stop all watchers after blocking
…		…
1524	adns_check_cb (ev_loop loop, ev_check w, int revents)	1734	adns_check_cb (ev_loop loop, ev_check w, int revents)
1525	{	1735	{
1526	ev_timer_stop (loop, &tw);	1736	ev_timer_stop (loop, &tw);
1527		1737
1528	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
1529	ev_io_stop (loop, iow + i);	1748	ev_io_stop (loop, iow + i);
		1749	}
1530		1750
1531	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;
1532	}	1811	}
1533		1812
1534		1813
1535	=head2 C<ev_embed> - when one backend isn't enough...	1814	=head2 C<ev_embed> - when one backend isn't enough...
1536		1815
…		…
1600	ev_embed_start (loop_hi, &embed);	1879	ev_embed_start (loop_hi, &embed);
1601	}	1880	}
1602	else	1881	else
1603	loop_lo = loop_hi;	1882	loop_lo = loop_hi;
1604		1883
		1884	=head3 Watcher-Specific Functions and Data Members
		1885
1605	=over 4	1886	=over 4
1606		1887
1607	=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)
1608		1889
1609	=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)
…		…
1618		1899
1619	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
1620	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
1621	apropriate way for embedded loops.	1902	apropriate way for embedded loops.
1622		1903
1623	=item struct ev_loop *loop [read-only]	1904	=item struct ev_loop *other [read-only]
1624		1905
1625	The embedded event loop.	1906	The embedded event loop.
1626		1907
1627	=back	1908	=back
1628		1909
…		…
1635	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,
1636	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
1637	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
1638	handlers will be invoked, too, of course.	1919	handlers will be invoked, too, of course.
1639		1920
		1921	=head3 Watcher-Specific Functions and Data Members
		1922
1640	=over 4	1923	=over 4
1641		1924
1642	=item ev_fork_init (ev_signal *, callback)	1925	=item ev_fork_init (ev_signal *, callback)
1643		1926
1644	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
…		…
1740		2023
1741	To use it,	2024	To use it,
1742		2025
1743	#include <ev++.h>	2026	#include <ev++.h>
1744		2027
1745	(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
1746	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
1747	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>.
1748		2032
1749	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++
1750	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).
1751		2043
1752	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:
1753		2045
1754	=over 4	2046	=over 4
1755		2047
…		…
1771		2063
1772	All of those classes have these methods:	2064	All of those classes have these methods:
1773		2065
1774	=over 4	2066	=over 4
1775		2067
1776	=item ev::TYPE::TYPE (object , object::method )	2068	=item ev::TYPE::TYPE ()
1777		2069
1778	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	2070	=item ev::TYPE::TYPE (struct ev_loop *)
1779		2071
1780	=item ev::TYPE::~TYPE	2072	=item ev::TYPE::~TYPE
1781		2073
1782	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
1783	the event handler callback to call in this class. The constructor calls	2075	with. If it is omitted, it will use C<EV_DEFAULT>.
1784	C<ev_init> for you, which means you have to call the C<set> method	2076
1785	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
1786	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).
1787		2085
1788	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> ();
1789		2126
1790	=item w->set (struct ev_loop *)	2127	=item w->set (struct ev_loop *)
1791		2128
1792	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
1793	do this when the watcher is inactive (and not pending either).	2130	do this when the watcher is inactive (and not pending either).
1794		2131
1795	=item w->set ([args])	2132	=item w->set ([args])
1796		2133
1797	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
1798	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
1799	automatically stopped and restarted.	2136	automatically stopped and restarted when reconfiguring it with this
		2137	method.
1800		2138
1801	=item w->start ()	2139	=item w->start ()
1802		2140
1803	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
1804	constructor already takes the loop.	2142	constructor already stores the event loop.
1805		2143
1806	=item w->stop ()	2144	=item w->stop ()
1807		2145
1808	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.
1809		2147
1810	=item w->again () C<ev::timer>, C<ev::periodic> only	2148	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1811		2149
1812	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
1813	C<ev_TYPE_again> function.	2151	C<ev_TYPE_again> function.
1814		2152
1815	=item w->sweep () C<ev::embed> only	2153	=item w->sweep () (C<ev::embed> only)
1816		2154
1817	Invokes C<ev_embed_sweep>.	2155	Invokes C<ev_embed_sweep>.
1818		2156
1819	=item w->update () C<ev::stat> only	2157	=item w->update () (C<ev::stat> only)
1820		2158
1821	Invokes C<ev_stat_stat>.	2159	Invokes C<ev_stat_stat>.
1822		2160
1823	=back	2161	=back
1824		2162
…		…
1834		2172
1835	myclass ();	2173	myclass ();
1836	}	2174	}
1837		2175
1838	myclass::myclass (int fd)	2176	myclass::myclass (int fd)
1839	: io (this, &myclass::io_cb),
1840	idle (this, &myclass::idle_cb)
1841	{	2177	{
		2178	io .set <myclass, &myclass::io_cb > (this);
		2179	idle.set <myclass, &myclass::idle_cb> (this);
		2180
1842	io.start (fd, ev::READ);	2181	io.start (fd, ev::READ);
1843	}	2182	}
1844		2183
1845		2184
1846	=head1 MACRO MAGIC	2185	=head1 MACRO MAGIC
1847		2186
1848	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
1849	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2188	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1850	callbacks have an initial C<struct ev_loop *> argument.	2189	functions and callbacks have an initial C<struct ev_loop *> argument.
1851		2190
1852	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
1853	following macros are defined:	2192	following macros are defined:
1854		2193
1855	=over 4	2194	=over 4
…		…
1909	Libev can (and often is) directly embedded into host	2248	Libev can (and often is) directly embedded into host
1910	applications. Examples of applications that embed it include the Deliantra	2249	applications. Examples of applications that embed it include the Deliantra
1911	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)
1912	and rxvt-unicode.	2251	and rxvt-unicode.
1913		2252
1914	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
1915	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
1916	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
1917	libev somewhere in your source tree).	2256	libev somewhere in your source tree).
1918		2257
1919	=head2 FILESETS	2258	=head2 FILESETS
…		…
2009		2348
2010	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
2011	monotonic clock option at both compiletime and runtime. Otherwise no use	2350	monotonic clock option at both compiletime and runtime. Otherwise no use
2012	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
2013	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
2014	the functionality isn't available is safe, though, althoguh you have	2353	the functionality isn't available is safe, though, although you have
2015	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>
2016	function is hiding in (often F<-lrt>).	2355	function is hiding in (often F<-lrt>).
2017		2356
2018	=item EV_USE_REALTIME	2357	=item EV_USE_REALTIME
2019		2358
2020	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
2021	realtime clock option at compiletime (and assume its availability at	2360	realtime clock option at compiletime (and assume its availability at
2022	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
2023	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2362	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2024	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2363	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2025	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 ()>.
2026		2370
2027	=item EV_USE_SELECT	2371	=item EV_USE_SELECT
2028		2372
2029	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
2030	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
…		…
2123	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
2124	additional independent event loops. Otherwise there will be no support	2468	additional independent event loops. Otherwise there will be no support
2125	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
2126	argument. Instead, all functions act on the single default loop.	2470	argument. Instead, all functions act on the single default loop.
2127		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
2128	=item EV_PERIODIC_ENABLE	2489	=item EV_PERIODIC_ENABLE
2129		2490
2130	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
2131	defined to be C<0>, then they are not. Disabling them saves a few kB of	2492	defined to be C<0>, then they are not. Disabling them saves a few kB of
2132	code.	2493	code.
…		…
2165	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
2166	increase this value (I<must> be a power of two).	2527	increase this value (I<must> be a power of two).
2167		2528
2168	=item EV_INOTIFY_HASHSIZE	2529	=item EV_INOTIFY_HASHSIZE
2169		2530
2170	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
2171	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>),
2172	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>
2173	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
2174	two).	2535	two).
2175		2536
…		…
2192		2553
2193	=item ev_set_cb (ev, cb)	2554	=item ev_set_cb (ev, cb)
2194		2555
2195	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,
2196	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
2197	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
2198	their default definitions. One possible use for overriding these is to	2559	their default definitions. One possible use for overriding these is to
2199	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
2200	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	...
2201		2587
2202	=head2 EXAMPLES	2588	=head2 EXAMPLES
2203		2589
2204	For a real-world example of a program the includes libev	2590	For a real-world example of a program the includes libev
2205	verbatim, you can have a look at the EV perl module	2591	verbatim, you can have a look at the EV perl module
…		…
2234		2620
2235	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
2236	libev will be explained. For complexity discussions about backends see the	2622	libev will be explained. For complexity discussions about backends see the
2237	documentation for C<ev_default_init>.	2623	documentation for C<ev_default_init>.
2238		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
2239	=over 4	2631	=over 4
2240		2632
2241	=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)
2242		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
2243	=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)
2244		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
2245	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2644	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2246		2645
		2646	These just add the watcher into an array or at the head of a list.
2247	=item Stopping check/prepare/idle watchers: O(1)	2647	=item Stopping check/prepare/idle watchers: O(1)
2248		2648
2249	=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))
2250		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
2251	=item Finding the next timer per loop iteration: O(1)	2655	=item Finding the next timer per loop iteration: O(1)
2252		2656
2253	=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)
2254		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
2255	=item Activating one watcher: O(1)	2662	=item Activating one watcher: O(1)
2256		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
2257	=back	2670	=back
2258		2671
2259		2672
2260	=head1 AUTHOR	2673	=head1 AUTHOR
2261		2674

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Comparing libev/ev.pod (file contents): Revision 1.68 by root, Fri Dec 7 18:09:43 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 1.68 by root, Fri Dec 7 18:09:43 2007 UTC vs.
Revision 1.105 by root, Sun Dec 23 03:50:10 2007 UTC