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…		…
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
487	* If there are no active watchers (reference count is zero), return.	555	- Before the first iteration, call any pending watchers.
488	- Queue prepare watchers and then call all outstanding watchers.	556	* If EVFLAG_FORKCHECK was used, check for a fork.
		557	- If a fork was detected, queue and call all fork watchers.
		558	- Queue and call all prepare watchers.
489	- If we have been forked, recreate the kernel state.	559	- If we have been forked, recreate the kernel state.
490	- Update the kernel state with all outstanding changes.	560	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	561	- Update the "event loop time".
492	- Calculate for how long to block.	562	- Calculate for how long to sleep or block, if at all
		563	(active idle watchers, EVLOOP_NONBLOCK or not having
		564	any active watchers at all will result in not sleeping).
		565	- Sleep if the I/O and timer collect interval say so.
493	- Block the process, waiting for any events.	566	- Block the process, waiting for any events.
494	- Queue all outstanding I/O (fd) events.	567	- Queue all outstanding I/O (fd) events.
495	- Update the "event loop time" and do time jump handling.	568	- Update the "event loop time" and do time jump handling.
496	- Queue all outstanding timers.	569	- Queue all outstanding timers.
497	- Queue all outstanding periodics.	570	- Queue all outstanding periodics.
498	- If no events are pending now, queue all idle watchers.	571	- If no events are pending now, queue all idle watchers.
499	- Queue all check watchers.	572	- Queue all check watchers.
500	- Call all queued watchers in reverse order (i.e. check watchers first).	573	- Call all queued watchers in reverse order (i.e. check watchers first).
501	Signals and child watchers are implemented as I/O watchers, and will	574	Signals and child watchers are implemented as I/O watchers, and will
502	be handled here by queueing them when their watcher gets executed.	575	be handled here by queueing them when their watcher gets executed.
503	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	576	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
504	were used, return, otherwise continue with step *.	577	were used, or there are no active watchers, return, otherwise
		578	continue with step *.
505		579
506	Example: Queue some jobs and then loop until no events are outsanding	580	Example: Queue some jobs and then loop until no events are outstanding
507	anymore.	581	anymore.
508		582
509	... queue jobs here, make sure they register event watchers as long	583	... queue jobs here, make sure they register event watchers as long
510	... as they still have work to do (even an idle watcher will do..)	584	... as they still have work to do (even an idle watcher will do..)
511	ev_loop (my_loop, 0);	585	ev_loop (my_loop, 0);
…		…
515		589
516	Can be used to make a call to C<ev_loop> return early (but only after it	590	Can be used to make a call to C<ev_loop> return early (but only after it
517	has processed all outstanding events). The C<how> argument must be either	591	has processed all outstanding events). The C<how> argument must be either
518	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	592	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
519	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	593	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		594
		595	This "unloop state" will be cleared when entering C<ev_loop> again.
520		596
521	=item ev_ref (loop)	597	=item ev_ref (loop)
522		598
523	=item ev_unref (loop)	599	=item ev_unref (loop)
524		600
…		…
529	returning, ev_unref() after starting, and ev_ref() before stopping it. For	605	returning, ev_unref() after starting, and ev_ref() before stopping it. For
530	example, libev itself uses this for its internal signal pipe: It is not	606	example, libev itself uses this for its internal signal pipe: It is not
531	visible to the libev user and should not keep C<ev_loop> from exiting if	607	visible to the libev user and should not keep C<ev_loop> from exiting if
532	no event watchers registered by it are active. It is also an excellent	608	no event watchers registered by it are active. It is also an excellent
533	way to do this for generic recurring timers or from within third-party	609	way to do this for generic recurring timers or from within third-party
534	libraries. Just remember to I<unref after start> and I<ref before stop>.	610	libraries. Just remember to I<unref after start> and I<ref before stop>
		611	(but only if the watcher wasn't active before, or was active before,
		612	respectively).
535		613
536	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	614	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
537	running when nothing else is active.	615	running when nothing else is active.
538		616
539	struct ev_signal exitsig;	617	struct ev_signal exitsig;
…		…
543		621
544	Example: For some weird reason, unregister the above signal handler again.	622	Example: For some weird reason, unregister the above signal handler again.
545		623
546	ev_ref (loop);	624	ev_ref (loop);
547	ev_signal_stop (loop, &exitsig);	625	ev_signal_stop (loop, &exitsig);
		626
		627	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		628
		629	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		630
		631	These advanced functions influence the time that libev will spend waiting
		632	for events. Both are by default C<0>, meaning that libev will try to
		633	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		634
		635	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		636	allows libev to delay invocation of I/O and timer/periodic callbacks to
		637	increase efficiency of loop iterations.
		638
		639	The background is that sometimes your program runs just fast enough to
		640	handle one (or very few) event(s) per loop iteration. While this makes
		641	the program responsive, it also wastes a lot of CPU time to poll for new
		642	events, especially with backends like C<select ()> which have a high
		643	overhead for the actual polling but can deliver many events at once.
		644
		645	By setting a higher I<io collect interval> you allow libev to spend more
		646	time collecting I/O events, so you can handle more events per iteration,
		647	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		648	C<ev_timer>) will be not affected. Setting this to a non-null value will
		649	introduce an additional C<ev_sleep ()> call into most loop iterations.
		650
		651	Likewise, by setting a higher I<timeout collect interval> you allow libev
		652	to spend more time collecting timeouts, at the expense of increased
		653	latency (the watcher callback will be called later). C<ev_io> watchers
		654	will not be affected. Setting this to a non-null value will not introduce
		655	any overhead in libev.
		656
		657	Many (busy) programs can usually benefit by setting the io collect
		658	interval to a value near C<0.1> or so, which is often enough for
		659	interactive servers (of course not for games), likewise for timeouts. It
		660	usually doesn't make much sense to set it to a lower value than C<0.01>,
		661	as this approsaches the timing granularity of most systems.
548		662
549	=back	663	=back
550		664
551		665
552	=head1 ANATOMY OF A WATCHER	666	=head1 ANATOMY OF A WATCHER
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	846	=item bool ev_is_pending (ev_TYPE *watcher)
733		847
734	Returns a true value iff the watcher is pending, (i.e. it has outstanding	848	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	849	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	850	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	851	C<ev_TYPE_set> is safe), you must not change its priority, and you must
738	libev (e.g. you cnanot C<free ()> it).	852	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		853	it).
739		854
740	=item callback ev_cb (ev_TYPE *watcher)	855	=item callback ev_cb (ev_TYPE *watcher)
741		856
742	Returns the callback currently set on the watcher.	857	Returns the callback currently set on the watcher.
743		858
…		…
762	watchers on the same event and make sure one is called first.	877	watchers on the same event and make sure one is called first.
763		878
764	If you need to suppress invocation when higher priority events are pending	879	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.	880	you need to look at C<ev_idle> watchers, which provide this functionality.
766		881
		882	You I<must not> change the priority of a watcher as long as it is active or
		883	pending.
		884
767	The default priority used by watchers when no priority has been set is	885	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 :).	886	always C<0>, which is supposed to not be too high and not be too low :).
769		887
770	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	888	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	889	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.	890	or might not have been adjusted to be within valid range.
		891
		892	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		893
		894	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		895	C<loop> nor C<revents> need to be valid as long as the watcher callback
		896	can deal with that fact.
		897
		898	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		899
		900	If the watcher is pending, this function returns clears its pending status
		901	and returns its C<revents> bitset (as if its callback was invoked). If the
		902	watcher isn't pending it does nothing and returns C<0>.
773		903
774	=back	904	=back
775		905
776		906
777	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	907	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
862	In general you can register as many read and/or write event watchers per	992	In general you can register as many read and/or write event watchers per
863	fd as you want (as long as you don't confuse yourself). Setting all file	993	fd as you want (as long as you don't confuse yourself). Setting all file
864	descriptors to non-blocking mode is also usually a good idea (but not	994	descriptors to non-blocking mode is also usually a good idea (but not
865	required if you know what you are doing).	995	required if you know what you are doing).
866		996
867	You have to be careful with dup'ed file descriptors, though. Some backends
868	(the linux epoll backend is a notable example) cannot handle dup'ed file
869	descriptors correctly if you register interest in two or more fds pointing
870	to the same underlying file/socket/etc. description (that is, they share
871	the same underlying "file open").
872
873	If you must do this, then force the use of a known-to-be-good backend	997	If you must do this, then force the use of a known-to-be-good backend
874	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	998	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
875	C<EVBACKEND_POLL>).	999	C<EVBACKEND_POLL>).
876		1000
877	Another thing you have to watch out for is that it is quite easy to	1001	Another thing you have to watch out for is that it is quite easy to
…		…
887	play around with an Xlib connection), then you have to seperately re-test	1011	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	1012	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	1013	such as poll (fortunately in our Xlib example, Xlib already does this on
890	its own, so its quite safe to use).	1014	its own, so its quite safe to use).
891		1015
		1016	=head3 The special problem of disappearing file descriptors
		1017
		1018	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1019	descriptor (either by calling C<close> explicitly or by any other means,
		1020	such as C<dup>). The reason is that you register interest in some file
		1021	descriptor, but when it goes away, the operating system will silently drop
		1022	this interest. If another file descriptor with the same number then is
		1023	registered with libev, there is no efficient way to see that this is, in
		1024	fact, a different file descriptor.
		1025
		1026	To avoid having to explicitly tell libev about such cases, libev follows
		1027	the following policy: Each time C<ev_io_set> is being called, libev
		1028	will assume that this is potentially a new file descriptor, otherwise
		1029	it is assumed that the file descriptor stays the same. That means that
		1030	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1031	descriptor even if the file descriptor number itself did not change.
		1032
		1033	This is how one would do it normally anyway, the important point is that
		1034	the libev application should not optimise around libev but should leave
		1035	optimisations to libev.
		1036
		1037	=head3 The special problem of dup'ed file descriptors
		1038
		1039	Some backends (e.g. epoll), cannot register events for file descriptors,
		1040	but only events for the underlying file descriptions. That means when you
		1041	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1042	events for them, only one file descriptor might actually receive events.
		1043
		1044	There is no workaround possible except not registering events
		1045	for potentially C<dup ()>'ed file descriptors, or to resort to
		1046	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1047
		1048	=head3 The special problem of fork
		1049
		1050	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1051	useless behaviour. Libev fully supports fork, but needs to be told about
		1052	it in the child.
		1053
		1054	To support fork in your programs, you either have to call
		1055	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1056	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1057	C<EVBACKEND_POLL>.
		1058
		1059
		1060	=head3 Watcher-Specific Functions
		1061
892	=over 4	1062	=over 4
893		1063
894	=item ev_io_init (ev_io *, callback, int fd, int events)	1064	=item ev_io_init (ev_io *, callback, int fd, int events)
895		1065
896	=item ev_io_set (ev_io *, int fd, int events)	1066	=item ev_io_set (ev_io *, int fd, int events)
…		…
906	=item int events [read-only]	1076	=item int events [read-only]
907		1077
908	The events being watched.	1078	The events being watched.
909		1079
910	=back	1080	=back
		1081
		1082	=head3 Examples
911		1083
912	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1084	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
913	readable, but only once. Since it is likely line-buffered, you could	1085	readable, but only once. Since it is likely line-buffered, you could
914	attempt to read a whole line in the callback.	1086	attempt to read a whole line in the callback.
915		1087
…		…
948	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1120	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
949		1121
950	The callback is guarenteed to be invoked only when its timeout has passed,	1122	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	1123	but if multiple timers become ready during the same loop iteration then
952	order of execution is undefined.	1124	order of execution is undefined.
		1125
		1126	=head3 Watcher-Specific Functions and Data Members
953		1127
954	=over 4	1128	=over 4
955		1129
956	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1130	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
957		1131
…		…
1011	or C<ev_timer_again> is called and determines the next timeout (if any),	1185	or C<ev_timer_again> is called and determines the next timeout (if any),
1012	which is also when any modifications are taken into account.	1186	which is also when any modifications are taken into account.
1013		1187
1014	=back	1188	=back
1015		1189
		1190	=head3 Examples
		1191
1016	Example: Create a timer that fires after 60 seconds.	1192	Example: Create a timer that fires after 60 seconds.
1017		1193
1018	static void	1194	static void
1019	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1195	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1020	{	1196	{
…		…
1053	but on wallclock time (absolute time). You can tell a periodic watcher	1229	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	1230	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 ()	1231	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	1232	+ 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	1233	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	1234	roughly 10 seconds later).
1059	again).
1060		1235
1061	They can also be used to implement vastly more complex timers, such as	1236	They can also be used to implement vastly more complex timers, such as
1062	triggering an event on eahc midnight, local time.	1237	triggering an event on each midnight, local time or other, complicated,
		1238	rules.
1063		1239
1064	As with timers, the callback is guarenteed to be invoked only when the	1240	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	1241	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.	1242	during the same loop iteration then order of execution is undefined.
1067		1243
		1244	=head3 Watcher-Specific Functions and Data Members
		1245
1068	=over 4	1246	=over 4
1069		1247
1070	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1248	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1071		1249
1072	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1250	=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	1252	Lots of arguments, lets sort it out... There are basically three modes of
1075	operation, and we will explain them from simplest to complex:	1253	operation, and we will explain them from simplest to complex:
1076		1254
1077	=over 4	1255	=over 4
1078		1256
1079	=item * absolute timer (interval = reschedule_cb = 0)	1257	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1080		1258
1081	In this configuration the watcher triggers an event at the wallclock time	1259	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,	1260	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	1261	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.	1262	system time reaches or surpasses this time.
1085		1263
1086	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1264	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1087		1265
1088	In this mode the watcher will always be scheduled to time out at the next	1266	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	1267	C<at + N * interval> time (for some integer N, which can also be negative)
1090	of any time jumps.	1268	and then repeat, regardless of any time jumps.
1091		1269
1092	This can be used to create timers that do not drift with respect to system	1270	This can be used to create timers that do not drift with respect to system
1093	time:	1271	time:
1094		1272
1095	ev_periodic_set (&periodic, 0., 3600., 0);	1273	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1101		1279
1102	Another way to think about it (for the mathematically inclined) is that	1280	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	1281	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.	1282	time where C<time = at (mod interval)>, regardless of any time jumps.
1105		1283
		1284	For numerical stability it is preferable that the C<at> value is near
		1285	C<ev_now ()> (the current time), but there is no range requirement for
		1286	this value.
		1287
1106	=item * manual reschedule mode (reschedule_cb = callback)	1288	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1107		1289
1108	In this mode the values for C<interval> and C<at> are both being	1290	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	1291	ignored. Instead, each time the periodic watcher gets scheduled, the
1110	reschedule callback will be called with the watcher as first, and the	1292	reschedule callback will be called with the watcher as first, and the
1111	current time as second argument.	1293	current time as second argument.
1112		1294
1113	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1295	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,	1296	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	1297	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1116	starting a prepare watcher).	1298	starting an C<ev_prepare> watcher, which is legal).
1117		1299
1118	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1300	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1119	ev_tstamp now)>, e.g.:	1301	ev_tstamp now)>, e.g.:
1120		1302
1121	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1303	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	1326	Simply stops and restarts the periodic watcher again. This is only useful
1145	when you changed some parameters or the reschedule callback would return	1327	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	1328	a different time than the last time it was called (e.g. in a crond like
1147	program when the crontabs have changed).	1329	program when the crontabs have changed).
1148		1330
		1331	=item ev_tstamp offset [read-write]
		1332
		1333	When repeating, this contains the offset value, otherwise this is the
		1334	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1335
		1336	Can be modified any time, but changes only take effect when the periodic
		1337	timer fires or C<ev_periodic_again> is being called.
		1338
1149	=item ev_tstamp interval [read-write]	1339	=item ev_tstamp interval [read-write]
1150		1340
1151	The current interval value. Can be modified any time, but changes only	1341	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	1342	take effect when the periodic timer fires or C<ev_periodic_again> is being
1153	called.	1343	called.
…		…
1156		1346
1157	The current reschedule callback, or C<0>, if this functionality is	1347	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	1348	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.	1349	the periodic timer fires or C<ev_periodic_again> is being called.
1160		1350
		1351	=item ev_tstamp at [read-only]
		1352
		1353	When active, contains the absolute time that the watcher is supposed to
		1354	trigger next.
		1355
1161	=back	1356	=back
		1357
		1358	=head3 Examples
1162		1359
1163	Example: Call a callback every hour, or, more precisely, whenever the	1360	Example: Call a callback every hour, or, more precisely, whenever the
1164	system clock is divisible by 3600. The callback invocation times have	1361	system clock is divisible by 3600. The callback invocation times have
1165	potentially a lot of jittering, but good long-term stability.	1362	potentially a lot of jittering, but good long-term stability.
1166		1363
…		…
1206	with the kernel (thus it coexists with your own signal handlers as long	1403	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	1404	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	1405	watcher for a signal is stopped libev will reset the signal handler to
1209	SIG_DFL (regardless of what it was set to before).	1406	SIG_DFL (regardless of what it was set to before).
1210		1407
		1408	=head3 Watcher-Specific Functions and Data Members
		1409
1211	=over 4	1410	=over 4
1212		1411
1213	=item ev_signal_init (ev_signal *, callback, int signum)	1412	=item ev_signal_init (ev_signal *, callback, int signum)
1214		1413
1215	=item ev_signal_set (ev_signal *, int signum)	1414	=item ev_signal_set (ev_signal *, int signum)
…		…
1226		1425
1227	=head2 C<ev_child> - watch out for process status changes	1426	=head2 C<ev_child> - watch out for process status changes
1228		1427
1229	Child watchers trigger when your process receives a SIGCHLD in response to	1428	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).	1429	some child status changes (most typically when a child of yours dies).
		1430
		1431	=head3 Watcher-Specific Functions and Data Members
1231		1432
1232	=over 4	1433	=over 4
1233		1434
1234	=item ev_child_init (ev_child *, callback, int pid)	1435	=item ev_child_init (ev_child *, callback, int pid)
1235		1436
…		…
1254		1455
1255	The process exit/trace status caused by C<rpid> (see your systems	1456	The process exit/trace status caused by C<rpid> (see your systems
1256	C<waitpid> and C<sys/wait.h> documentation for details).	1457	C<waitpid> and C<sys/wait.h> documentation for details).
1257		1458
1258	=back	1459	=back
		1460
		1461	=head3 Examples
1259		1462
1260	Example: Try to exit cleanly on SIGINT and SIGTERM.	1463	Example: Try to exit cleanly on SIGINT and SIGTERM.
1261		1464
1262	static void	1465	static void
1263	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1466	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
…		…
1304	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1507	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	1508	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	1509	usually detected immediately, and if the file exists there will be no
1307	polling.	1510	polling.
1308		1511
		1512	=head3 Inotify
		1513
		1514	When C<inotify (7)> support has been compiled into libev (generally only
		1515	available on Linux) and present at runtime, it will be used to speed up
		1516	change detection where possible. The inotify descriptor will be created lazily
		1517	when the first C<ev_stat> watcher is being started.
		1518
		1519	Inotify presense does not change the semantics of C<ev_stat> watchers
		1520	except that changes might be detected earlier, and in some cases, to avoid
		1521	making regular C<stat> calls. Even in the presense of inotify support
		1522	there are many cases where libev has to resort to regular C<stat> polling.
		1523
		1524	(There is no support for kqueue, as apparently it cannot be used to
		1525	implement this functionality, due to the requirement of having a file
		1526	descriptor open on the object at all times).
		1527
		1528	=head3 The special problem of stat time resolution
		1529
		1530	The C<stat ()> syscall only supports full-second resolution portably, and
		1531	even on systems where the resolution is higher, many filesystems still
		1532	only support whole seconds.
		1533
		1534	That means that, if the time is the only thing that changes, you might
		1535	miss updates: on the first update, C<ev_stat> detects a change and calls
		1536	your callback, which does something. When there is another update within
		1537	the same second, C<ev_stat> will be unable to detect it.
		1538
		1539	The solution to this is to delay acting on a change for a second (or till
		1540	the next second boundary), using a roughly one-second delay C<ev_timer>
		1541	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1542	is added to work around small timing inconsistencies of some operating
		1543	systems.
		1544
		1545	=head3 Watcher-Specific Functions and Data Members
		1546
1309	=over 4	1547	=over 4
1310		1548
1311	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1549	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1312		1550
1313	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1551	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1348	=item const char *path [read-only]	1586	=item const char *path [read-only]
1349		1587
1350	The filesystem path that is being watched.	1588	The filesystem path that is being watched.
1351		1589
1352	=back	1590	=back
		1591
		1592	=head3 Examples
1353		1593
1354	Example: Watch C</etc/passwd> for attribute changes.	1594	Example: Watch C</etc/passwd> for attribute changes.
1355		1595
1356	static void	1596	static void
1357	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1597	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1370	}	1610	}
1371		1611
1372	...	1612	...
1373	ev_stat passwd;	1613	ev_stat passwd;
1374		1614
1375	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1615	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1376	ev_stat_start (loop, &passwd);	1616	ev_stat_start (loop, &passwd);
		1617
		1618	Example: Like above, but additionally use a one-second delay so we do not
		1619	miss updates (however, frequent updates will delay processing, too, so
		1620	one might do the work both on C<ev_stat> callback invocation I<and> on
		1621	C<ev_timer> callback invocation).
		1622
		1623	static ev_stat passwd;
		1624	static ev_timer timer;
		1625
		1626	static void
		1627	timer_cb (EV_P_ ev_timer *w, int revents)
		1628	{
		1629	ev_timer_stop (EV_A_ w);
		1630
		1631	/* now it's one second after the most recent passwd change */
		1632	}
		1633
		1634	static void
		1635	stat_cb (EV_P_ ev_stat *w, int revents)
		1636	{
		1637	/* reset the one-second timer */
		1638	ev_timer_again (EV_A_ &timer);
		1639	}
		1640
		1641	...
		1642	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1643	ev_stat_start (loop, &passwd);
		1644	ev_timer_init (&timer, timer_cb, 0., 1.01);
1377		1645
1378		1646
1379	=head2 C<ev_idle> - when you've got nothing better to do...	1647	=head2 C<ev_idle> - when you've got nothing better to do...
1380		1648
1381	Idle watchers trigger events when no other events of the same or higher	1649	Idle watchers trigger events when no other events of the same or higher
…		…
1395	Apart from keeping your process non-blocking (which is a useful	1663	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	1664	effect on its own sometimes), idle watchers are a good place to do
1397	"pseudo-background processing", or delay processing stuff to after the	1665	"pseudo-background processing", or delay processing stuff to after the
1398	event loop has handled all outstanding events.	1666	event loop has handled all outstanding events.
1399		1667
		1668	=head3 Watcher-Specific Functions and Data Members
		1669
1400	=over 4	1670	=over 4
1401		1671
1402	=item ev_idle_init (ev_signal *, callback)	1672	=item ev_idle_init (ev_signal *, callback)
1403		1673
1404	Initialises and configures the idle watcher - it has no parameters of any	1674	Initialises and configures the idle watcher - it has no parameters of any
1405	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1675	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1406	believe me.	1676	believe me.
1407		1677
1408	=back	1678	=back
		1679
		1680	=head3 Examples
1409		1681
1410	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1682	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1411	callback, free it. Also, use no error checking, as usual.	1683	callback, free it. Also, use no error checking, as usual.
1412		1684
1413	static void	1685	static void
…		…
1461	with priority higher than or equal to the event loop and one coroutine	1733	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	1734	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	1735	loop from blocking if lower-priority coroutines are active, thus mapping
1464	low-priority coroutines to idle/background tasks).	1736	low-priority coroutines to idle/background tasks).
1465		1737
		1738	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1739	priority, to ensure that they are being run before any other watchers
		1740	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1741	too) should not activate ("feed") events into libev. While libev fully
		1742	supports this, they will be called before other C<ev_check> watchers
		1743	did their job. As C<ev_check> watchers are often used to embed other
		1744	(non-libev) event loops those other event loops might be in an unusable
		1745	state until their C<ev_check> watcher ran (always remind yourself to
		1746	coexist peacefully with others).
		1747
		1748	=head3 Watcher-Specific Functions and Data Members
		1749
1466	=over 4	1750	=over 4
1467		1751
1468	=item ev_prepare_init (ev_prepare *, callback)	1752	=item ev_prepare_init (ev_prepare *, callback)
1469		1753
1470	=item ev_check_init (ev_check *, callback)	1754	=item ev_check_init (ev_check *, callback)
…		…
1473	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1757	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.	1758	macros, but using them is utterly, utterly and completely pointless.
1475		1759
1476	=back	1760	=back
1477		1761
1478	Example: To include a library such as adns, you would add IO watchers	1762	=head3 Examples
1479	and a timeout watcher in a prepare handler, as required by libadns, and	1763
		1764	There are a number of principal ways to embed other event loops or modules
		1765	into libev. Here are some ideas on how to include libadns into libev
		1766	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1767	use for an actually working example. Another Perl module named C<EV::Glib>
		1768	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1769	into the Glib event loop).
		1770
		1771	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	1772	and in a check watcher, destroy them and call into libadns. What follows
1481	pseudo-code only of course:	1773	is pseudo-code only of course. This requires you to either use a low
		1774	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1775	the callbacks for the IO/timeout watchers might not have been called yet.
1482		1776
1483	static ev_io iow [nfd];	1777	static ev_io iow [nfd];
1484	static ev_timer tw;	1778	static ev_timer tw;
1485		1779
1486	static void	1780	static void
1487	io_cb (ev_loop *loop, ev_io *w, int revents)	1781	io_cb (ev_loop *loop, ev_io *w, int revents)
1488	{	1782	{
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	}	1783	}
1495		1784
1496	// create io watchers for each fd and a timer before blocking	1785	// create io watchers for each fd and a timer before blocking
1497	static void	1786	static void
1498	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1787	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
…		…
1504		1793
1505	/* the callback is illegal, but won't be called as we stop during check */	1794	/* the callback is illegal, but won't be called as we stop during check */
1506	ev_timer_init (&tw, 0, timeout * 1e-3);	1795	ev_timer_init (&tw, 0, timeout * 1e-3);
1507	ev_timer_start (loop, &tw);	1796	ev_timer_start (loop, &tw);
1508		1797
1509	// create on ev_io per pollfd	1798	// create one ev_io per pollfd
1510	for (int i = 0; i < nfd; ++i)	1799	for (int i = 0; i < nfd; ++i)
1511	{	1800	{
1512	ev_io_init (iow + i, io_cb, fds [i].fd,	1801	ev_io_init (iow + i, io_cb, fds [i].fd,
1513	((fds [i].events & POLLIN ? EV_READ : 0)	1802	((fds [i].events & POLLIN ? EV_READ : 0)
1514	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1803	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1515		1804
1516	fds [i].revents = 0;	1805	fds [i].revents = 0;
1517	iow [i].data = fds + i;
1518	ev_io_start (loop, iow + i);	1806	ev_io_start (loop, iow + i);
1519	}	1807	}
1520	}	1808	}
1521		1809
1522	// stop all watchers after blocking	1810	// stop all watchers after blocking
…		…
1524	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1812	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1525	{	1813	{
1526	ev_timer_stop (loop, &tw);	1814	ev_timer_stop (loop, &tw);
1527		1815
1528	for (int i = 0; i < nfd; ++i)	1816	for (int i = 0; i < nfd; ++i)
		1817	{
		1818	// set the relevant poll flags
		1819	// could also call adns_processreadable etc. here
		1820	struct pollfd *fd = fds + i;
		1821	int revents = ev_clear_pending (iow + i);
		1822	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1823	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1824
		1825	// now stop the watcher
1529	ev_io_stop (loop, iow + i);	1826	ev_io_stop (loop, iow + i);
		1827	}
1530		1828
1531	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1829	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1830	}
		1831
		1832	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1833	in the prepare watcher and would dispose of the check watcher.
		1834
		1835	Method 3: If the module to be embedded supports explicit event
		1836	notification (adns does), you can also make use of the actual watcher
		1837	callbacks, and only destroy/create the watchers in the prepare watcher.
		1838
		1839	static void
		1840	timer_cb (EV_P_ ev_timer *w, int revents)
		1841	{
		1842	adns_state ads = (adns_state)w->data;
		1843	update_now (EV_A);
		1844
		1845	adns_processtimeouts (ads, &tv_now);
		1846	}
		1847
		1848	static void
		1849	io_cb (EV_P_ ev_io *w, int revents)
		1850	{
		1851	adns_state ads = (adns_state)w->data;
		1852	update_now (EV_A);
		1853
		1854	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1855	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1856	}
		1857
		1858	// do not ever call adns_afterpoll
		1859
		1860	Method 4: Do not use a prepare or check watcher because the module you
		1861	want to embed is too inflexible to support it. Instead, youc na override
		1862	their poll function. The drawback with this solution is that the main
		1863	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1864	this.
		1865
		1866	static gint
		1867	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1868	{
		1869	int got_events = 0;
		1870
		1871	for (n = 0; n < nfds; ++n)
		1872	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1873
		1874	if (timeout >= 0)
		1875	// create/start timer
		1876
		1877	// poll
		1878	ev_loop (EV_A_ 0);
		1879
		1880	// stop timer again
		1881	if (timeout >= 0)
		1882	ev_timer_stop (EV_A_ &to);
		1883
		1884	// stop io watchers again - their callbacks should have set
		1885	for (n = 0; n < nfds; ++n)
		1886	ev_io_stop (EV_A_ iow [n]);
		1887
		1888	return got_events;
1532	}	1889	}
1533		1890
1534		1891
1535	=head2 C<ev_embed> - when one backend isn't enough...	1892	=head2 C<ev_embed> - when one backend isn't enough...
1536		1893
…		…
1579	portable one.	1936	portable one.
1580		1937
1581	So when you want to use this feature you will always have to be prepared	1938	So when you want to use this feature you will always have to be prepared
1582	that you cannot get an embeddable loop. The recommended way to get around	1939	that you cannot get an embeddable loop. The recommended way to get around
1583	this is to have a separate variables for your embeddable loop, try to	1940	this is to have a separate variables for your embeddable loop, try to
1584	create it, and if that fails, use the normal loop for everything:	1941	create it, and if that fails, use the normal loop for everything.
		1942
		1943	=head3 Watcher-Specific Functions and Data Members
		1944
		1945	=over 4
		1946
		1947	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1948
		1949	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1950
		1951	Configures the watcher to embed the given loop, which must be
		1952	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1953	invoked automatically, otherwise it is the responsibility of the callback
		1954	to invoke it (it will continue to be called until the sweep has been done,
		1955	if you do not want thta, you need to temporarily stop the embed watcher).
		1956
		1957	=item ev_embed_sweep (loop, ev_embed *)
		1958
		1959	Make a single, non-blocking sweep over the embedded loop. This works
		1960	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1961	apropriate way for embedded loops.
		1962
		1963	=item struct ev_loop *other [read-only]
		1964
		1965	The embedded event loop.
		1966
		1967	=back
		1968
		1969	=head3 Examples
		1970
		1971	Example: Try to get an embeddable event loop and embed it into the default
		1972	event loop. If that is not possible, use the default loop. The default
		1973	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1974	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1975	used).
1585		1976
1586	struct ev_loop *loop_hi = ev_default_init (0);	1977	struct ev_loop *loop_hi = ev_default_init (0);
1587	struct ev_loop *loop_lo = 0;	1978	struct ev_loop *loop_lo = 0;
1588	struct ev_embed embed;	1979	struct ev_embed embed;
1589		1980
…		…
1600	ev_embed_start (loop_hi, &embed);	1991	ev_embed_start (loop_hi, &embed);
1601	}	1992	}
1602	else	1993	else
1603	loop_lo = loop_hi;	1994	loop_lo = loop_hi;
1604		1995
1605	=over 4	1996	Example: Check if kqueue is available but not recommended and create
		1997	a kqueue backend for use with sockets (which usually work with any
		1998	kqueue implementation). Store the kqueue/socket-only event loop in
		1999	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1606		2000
1607	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2001	struct ev_loop *loop = ev_default_init (0);
		2002	struct ev_loop *loop_socket = 0;
		2003	struct ev_embed embed;
		2004
		2005	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2006	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2007	{
		2008	ev_embed_init (&embed, 0, loop_socket);
		2009	ev_embed_start (loop, &embed);
		2010	}
1608		2011
1609	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2012	if (!loop_socket)
		2013	loop_socket = loop;
1610		2014
1611	Configures the watcher to embed the given loop, which must be	2015	// now use loop_socket for all sockets, and loop for everything else
1612	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1613	invoked automatically, otherwise it is the responsibility of the callback
1614	to invoke it (it will continue to be called until the sweep has been done,
1615	if you do not want thta, you need to temporarily stop the embed watcher).
1616
1617	=item ev_embed_sweep (loop, ev_embed *)
1618
1619	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
1621	apropriate way for embedded loops.
1622
1623	=item struct ev_loop *loop [read-only]
1624
1625	The embedded event loop.
1626
1627	=back
1628		2016
1629		2017
1630	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2018	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1631		2019
1632	Fork watchers are called when a C<fork ()> was detected (usually because	2020	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1635	event loop blocks next and before C<ev_check> watchers are being called,	2023	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	2024	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	2025	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1638	handlers will be invoked, too, of course.	2026	handlers will be invoked, too, of course.
1639		2027
		2028	=head3 Watcher-Specific Functions and Data Members
		2029
1640	=over 4	2030	=over 4
1641		2031
1642	=item ev_fork_init (ev_signal *, callback)	2032	=item ev_fork_init (ev_signal *, callback)
1643		2033
1644	Initialises and configures the fork watcher - it has no parameters of any	2034	Initialises and configures the fork watcher - it has no parameters of any
…		…
1740		2130
1741	To use it,	2131	To use it,
1742		2132
1743	#include <ev++.h>	2133	#include <ev++.h>
1744		2134
1745	(it is not installed by default). This automatically includes F<ev.h>	2135	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	2136	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.	2137	put into the C<ev> namespace. It should support all the same embedding
		2138	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1748		2139
1749	It should support all the same embedding options as F<ev.h>, most notably	2140	Care has been taken to keep the overhead low. The only data member the C++
1750	C<EV_MULTIPLICITY>.	2141	classes add (compared to plain C-style watchers) is the event loop pointer
		2142	that the watcher is associated with (or no additional members at all if
		2143	you disable C<EV_MULTIPLICITY> when embedding libev).
		2144
		2145	Currently, functions, and static and non-static member functions can be
		2146	used as callbacks. Other types should be easy to add as long as they only
		2147	need one additional pointer for context. If you need support for other
		2148	types of functors please contact the author (preferably after implementing
		2149	it).
1751		2150
1752	Here is a list of things available in the C<ev> namespace:	2151	Here is a list of things available in the C<ev> namespace:
1753		2152
1754	=over 4	2153	=over 4
1755		2154
…		…
1771		2170
1772	All of those classes have these methods:	2171	All of those classes have these methods:
1773		2172
1774	=over 4	2173	=over 4
1775		2174
1776	=item ev::TYPE::TYPE (object *, object::method *)	2175	=item ev::TYPE::TYPE ()
1777		2176
1778	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2177	=item ev::TYPE::TYPE (struct ev_loop *)
1779		2178
1780	=item ev::TYPE::~TYPE	2179	=item ev::TYPE::~TYPE
1781		2180
1782	The constructor takes a pointer to an object and a method pointer to	2181	The constructor (optionally) takes an event loop to associate the watcher
1783	the event handler callback to call in this class. The constructor calls	2182	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	2183
1785	before starting it. If you do not specify a loop then the constructor	2184	The constructor calls C<ev_init> for you, which means you have to call the
1786	automatically associates the default loop with this watcher.	2185	C<set> method before starting it.
		2186
		2187	It will not set a callback, however: You have to call the templated C<set>
		2188	method to set a callback before you can start the watcher.
		2189
		2190	(The reason why you have to use a method is a limitation in C++ which does
		2191	not allow explicit template arguments for constructors).
1787		2192
1788	The destructor automatically stops the watcher if it is active.	2193	The destructor automatically stops the watcher if it is active.
		2194
		2195	=item w->set<class, &class::method> (object *)
		2196
		2197	This method sets the callback method to call. The method has to have a
		2198	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2199	first argument and the C<revents> as second. The object must be given as
		2200	parameter and is stored in the C<data> member of the watcher.
		2201
		2202	This method synthesizes efficient thunking code to call your method from
		2203	the C callback that libev requires. If your compiler can inline your
		2204	callback (i.e. it is visible to it at the place of the C<set> call and
		2205	your compiler is good :), then the method will be fully inlined into the
		2206	thunking function, making it as fast as a direct C callback.
		2207
		2208	Example: simple class declaration and watcher initialisation
		2209
		2210	struct myclass
		2211	{
		2212	void io_cb (ev::io &w, int revents) { }
		2213	}
		2214
		2215	myclass obj;
		2216	ev::io iow;
		2217	iow.set <myclass, &myclass::io_cb> (&obj);
		2218
		2219	=item w->set<function> (void *data = 0)
		2220
		2221	Also sets a callback, but uses a static method or plain function as
		2222	callback. The optional C<data> argument will be stored in the watcher's
		2223	C<data> member and is free for you to use.
		2224
		2225	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2226
		2227	See the method-C<set> above for more details.
		2228
		2229	Example:
		2230
		2231	static void io_cb (ev::io &w, int revents) { }
		2232	iow.set <io_cb> ();
1789		2233
1790	=item w->set (struct ev_loop *)	2234	=item w->set (struct ev_loop *)
1791		2235
1792	Associates a different C<struct ev_loop> with this watcher. You can only	2236	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).	2237	do this when the watcher is inactive (and not pending either).
1794		2238
1795	=item w->set ([args])	2239	=item w->set ([args])
1796		2240
1797	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2241	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	2242	called at least once. Unlike the C counterpart, an active watcher gets
1799	automatically stopped and restarted.	2243	automatically stopped and restarted when reconfiguring it with this
		2244	method.
1800		2245
1801	=item w->start ()	2246	=item w->start ()
1802		2247
1803	Starts the watcher. Note that there is no C<loop> argument as the	2248	Starts the watcher. Note that there is no C<loop> argument, as the
1804	constructor already takes the loop.	2249	constructor already stores the event loop.
1805		2250
1806	=item w->stop ()	2251	=item w->stop ()
1807		2252
1808	Stops the watcher if it is active. Again, no C<loop> argument.	2253	Stops the watcher if it is active. Again, no C<loop> argument.
1809		2254
1810	=item w->again () C<ev::timer>, C<ev::periodic> only	2255	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1811		2256
1812	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2257	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1813	C<ev_TYPE_again> function.	2258	C<ev_TYPE_again> function.
1814		2259
1815	=item w->sweep () C<ev::embed> only	2260	=item w->sweep () (C<ev::embed> only)
1816		2261
1817	Invokes C<ev_embed_sweep>.	2262	Invokes C<ev_embed_sweep>.
1818		2263
1819	=item w->update () C<ev::stat> only	2264	=item w->update () (C<ev::stat> only)
1820		2265
1821	Invokes C<ev_stat_stat>.	2266	Invokes C<ev_stat_stat>.
1822		2267
1823	=back	2268	=back
1824		2269
…		…
1834		2279
1835	myclass ();	2280	myclass ();
1836	}	2281	}
1837		2282
1838	myclass::myclass (int fd)	2283	myclass::myclass (int fd)
1839	: io (this, &myclass::io_cb),
1840	idle (this, &myclass::idle_cb)
1841	{	2284	{
		2285	io .set <myclass, &myclass::io_cb > (this);
		2286	idle.set <myclass, &myclass::idle_cb> (this);
		2287
1842	io.start (fd, ev::READ);	2288	io.start (fd, ev::READ);
1843	}	2289	}
1844		2290
1845		2291
1846	=head1 MACRO MAGIC	2292	=head1 MACRO MAGIC
1847		2293
1848	Libev can be compiled with a variety of options, the most fundemantal is	2294	Libev can be compiled with a variety of options, the most fundamantal
1849	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2295	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1850	callbacks have an initial C<struct ev_loop *> argument.	2296	functions and callbacks have an initial C<struct ev_loop *> argument.
1851		2297
1852	To make it easier to write programs that cope with either variant, the	2298	To make it easier to write programs that cope with either variant, the
1853	following macros are defined:	2299	following macros are defined:
1854		2300
1855	=over 4	2301	=over 4
…		…
1909	Libev can (and often is) directly embedded into host	2355	Libev can (and often is) directly embedded into host
1910	applications. Examples of applications that embed it include the Deliantra	2356	applications. Examples of applications that embed it include the Deliantra
1911	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2357	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1912	and rxvt-unicode.	2358	and rxvt-unicode.
1913		2359
1914	The goal is to enable you to just copy the neecssary files into your	2360	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	2361	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	2362	you can easily upgrade by simply copying (or having a checked-out copy of
1917	libev somewhere in your source tree).	2363	libev somewhere in your source tree).
1918		2364
1919	=head2 FILESETS	2365	=head2 FILESETS
…		…
2009		2455
2010	If defined to be C<1>, libev will try to detect the availability of the	2456	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	2457	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	2458	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	2459	usually have to link against librt or something similar. Enabling it when
2014	the functionality isn't available is safe, though, althoguh you have	2460	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>	2461	to make sure you link against any libraries where the C<clock_gettime>
2016	function is hiding in (often F<-lrt>).	2462	function is hiding in (often F<-lrt>).
2017		2463
2018	=item EV_USE_REALTIME	2464	=item EV_USE_REALTIME
2019		2465
2020	If defined to be C<1>, libev will try to detect the availability of the	2466	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	2467	realtime clock option at compiletime (and assume its availability at
2022	runtime if successful). Otherwise no use of the realtime clock option will	2468	runtime if successful). Otherwise no use of the realtime clock option will
2023	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2469	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	2470	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2025	in the description of C<EV_USE_MONOTONIC>, though.	2471	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2472
		2473	=item EV_USE_NANOSLEEP
		2474
		2475	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2476	and will use it for delays. Otherwise it will use C<select ()>.
2026		2477
2027	=item EV_USE_SELECT	2478	=item EV_USE_SELECT
2028		2479
2029	If undefined or defined to be C<1>, libev will compile in support for the	2480	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	2481	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2048	wants osf handles on win32 (this is the case when the select to	2499	wants osf handles on win32 (this is the case when the select to
2049	be used is the winsock select). This means that it will call	2500	be used is the winsock select). This means that it will call
2050	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2501	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2051	it is assumed that all these functions actually work on fds, even	2502	it is assumed that all these functions actually work on fds, even
2052	on win32. Should not be defined on non-win32 platforms.	2503	on win32. Should not be defined on non-win32 platforms.
		2504
		2505	=item EV_FD_TO_WIN32_HANDLE
		2506
		2507	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2508	file descriptors to socket handles. When not defining this symbol (the
		2509	default), then libev will call C<_get_osfhandle>, which is usually
		2510	correct. In some cases, programs use their own file descriptor management,
		2511	in which case they can provide this function to map fds to socket handles.
2053		2512
2054	=item EV_USE_POLL	2513	=item EV_USE_POLL
2055		2514
2056	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2515	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2057	backend. Otherwise it will be enabled on non-win32 platforms. It	2516	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2094	be detected at runtime.	2553	be detected at runtime.
2095		2554
2096	=item EV_H	2555	=item EV_H
2097		2556
2098	The name of the F<ev.h> header file used to include it. The default if	2557	The name of the F<ev.h> header file used to include it. The default if
2099	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2558	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2100	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2559	virtually rename the F<ev.h> header file in case of conflicts.
2101		2560
2102	=item EV_CONFIG_H	2561	=item EV_CONFIG_H
2103		2562
2104	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2563	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2105	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2564	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2106	C<EV_H>, above.	2565	C<EV_H>, above.
2107		2566
2108	=item EV_EVENT_H	2567	=item EV_EVENT_H
2109		2568
2110	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2569	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2111	of how the F<event.h> header can be found.	2570	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2112		2571
2113	=item EV_PROTOTYPES	2572	=item EV_PROTOTYPES
2114		2573
2115	If defined to be C<0>, then F<ev.h> will not define any function	2574	If defined to be C<0>, then F<ev.h> will not define any function
2116	prototypes, but still define all the structs and other symbols. This is	2575	prototypes, but still define all the structs and other symbols. This is
…		…
2123	will have the C<struct ev_loop *> as first argument, and you can create	2582	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	2583	additional independent event loops. Otherwise there will be no support
2125	for multiple event loops and there is no first event loop pointer	2584	for multiple event loops and there is no first event loop pointer
2126	argument. Instead, all functions act on the single default loop.	2585	argument. Instead, all functions act on the single default loop.
2127		2586
		2587	=item EV_MINPRI
		2588
		2589	=item EV_MAXPRI
		2590
		2591	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2592	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2593	provide for more priorities by overriding those symbols (usually defined
		2594	to be C<-2> and C<2>, respectively).
		2595
		2596	When doing priority-based operations, libev usually has to linearly search
		2597	all the priorities, so having many of them (hundreds) uses a lot of space
		2598	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2599	fine.
		2600
		2601	If your embedding app does not need any priorities, defining these both to
		2602	C<0> will save some memory and cpu.
		2603
2128	=item EV_PERIODIC_ENABLE	2604	=item EV_PERIODIC_ENABLE
2129		2605
2130	If undefined or defined to be C<1>, then periodic timers are supported. If	2606	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	2607	defined to be C<0>, then they are not. Disabling them saves a few kB of
2132	code.	2608	code.
…		…
2165	than enough. If you need to manage thousands of children you might want to	2641	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).	2642	increase this value (I<must> be a power of two).
2167		2643
2168	=item EV_INOTIFY_HASHSIZE	2644	=item EV_INOTIFY_HASHSIZE
2169		2645
2170	C<ev_staz> watchers use a small hash table to distribute workload by	2646	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>),	2647	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>	2648	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	2649	watchers you might want to increase this value (I<must> be a power of
2174	two).	2650	two).
2175		2651
…		…
2192		2668
2193	=item ev_set_cb (ev, cb)	2669	=item ev_set_cb (ev, cb)
2194		2670
2195	Can be used to change the callback member declaration in each watcher,	2671	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	2672	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	2673	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	2674	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	2675	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++.	2676	method calls instead of plain function calls in C++.
		2677
		2678	=head2 EXPORTED API SYMBOLS
		2679
		2680	If you need to re-export the API (e.g. via a dll) and you need a list of
		2681	exported symbols, you can use the provided F<Symbol.*> files which list
		2682	all public symbols, one per line:
		2683
		2684	Symbols.ev for libev proper
		2685	Symbols.event for the libevent emulation
		2686
		2687	This can also be used to rename all public symbols to avoid clashes with
		2688	multiple versions of libev linked together (which is obviously bad in
		2689	itself, but sometimes it is inconvinient to avoid this).
		2690
		2691	A sed command like this will create wrapper C<#define>'s that you need to
		2692	include before including F<ev.h>:
		2693
		2694	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2695
		2696	This would create a file F<wrap.h> which essentially looks like this:
		2697
		2698	#define ev_backend myprefix_ev_backend
		2699	#define ev_check_start myprefix_ev_check_start
		2700	#define ev_check_stop myprefix_ev_check_stop
		2701	...
2201		2702
2202	=head2 EXAMPLES	2703	=head2 EXAMPLES
2203		2704
2204	For a real-world example of a program the includes libev	2705	For a real-world example of a program the includes libev
2205	verbatim, you can have a look at the EV perl module	2706	verbatim, you can have a look at the EV perl module
…		…
2234		2735
2235	In this section the complexities of (many of) the algorithms used inside	2736	In this section the complexities of (many of) the algorithms used inside
2236	libev will be explained. For complexity discussions about backends see the	2737	libev will be explained. For complexity discussions about backends see the
2237	documentation for C<ev_default_init>.	2738	documentation for C<ev_default_init>.
2238		2739
		2740	All of the following are about amortised time: If an array needs to be
		2741	extended, libev needs to realloc and move the whole array, but this
		2742	happens asymptotically never with higher number of elements, so O(1) might
		2743	mean it might do a lengthy realloc operation in rare cases, but on average
		2744	it is much faster and asymptotically approaches constant time.
		2745
2239	=over 4	2746	=over 4
2240		2747
2241	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2748	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2242		2749
		2750	This means that, when you have a watcher that triggers in one hour and
		2751	there are 100 watchers that would trigger before that then inserting will
		2752	have to skip roughly seven (C<ld 100>) of these watchers.
		2753
2243	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2754	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2755
		2756	That means that changing a timer costs less than removing/adding them
		2757	as only the relative motion in the event queue has to be paid for.
2244		2758
2245	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2759	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2246		2760
		2761	These just add the watcher into an array or at the head of a list.
		2762
2247	=item Stopping check/prepare/idle watchers: O(1)	2763	=item Stopping check/prepare/idle watchers: O(1)
2248		2764
2249	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2765	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2250		2766
		2767	These watchers are stored in lists then need to be walked to find the
		2768	correct watcher to remove. The lists are usually short (you don't usually
		2769	have many watchers waiting for the same fd or signal).
		2770
2251	=item Finding the next timer per loop iteration: O(1)	2771	=item Finding the next timer in each loop iteration: O(1)
		2772
		2773	By virtue of using a binary heap, the next timer is always found at the
		2774	beginning of the storage array.
2252		2775
2253	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2776	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2254		2777
2255	=item Activating one watcher: O(1)	2778	A change means an I/O watcher gets started or stopped, which requires
		2779	libev to recalculate its status (and possibly tell the kernel, depending
		2780	on backend and wether C<ev_io_set> was used).
		2781
		2782	=item Activating one watcher (putting it into the pending state): O(1)
		2783
		2784	=item Priority handling: O(number_of_priorities)
		2785
		2786	Priorities are implemented by allocating some space for each
		2787	priority. When doing priority-based operations, libev usually has to
		2788	linearly search all the priorities, but starting/stopping and activating
		2789	watchers becomes O(1) w.r.t. prioritiy handling.
2256		2790
2257	=back	2791	=back
2258		2792
2259		2793
		2794	=head1 Win32 platform limitations and workarounds
		2795
		2796	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2797	requires, and its I/O model is fundamentally incompatible with the POSIX
		2798	model. Libev still offers limited functionality on this platform in
		2799	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2800	descriptors. This only applies when using Win32 natively, not when using
		2801	e.g. cygwin.
		2802
		2803	There is no supported compilation method available on windows except
		2804	embedding it into other applications.
		2805
		2806	Due to the many, low, and arbitrary limits on the win32 platform and the
		2807	abysmal performance of winsockets, using a large number of sockets is not
		2808	recommended (and not reasonable). If your program needs to use more than
		2809	a hundred or so sockets, then likely it needs to use a totally different
		2810	implementation for windows, as libev offers the POSIX model, which cannot
		2811	be implemented efficiently on windows (microsoft monopoly games).
		2812
		2813	=over 4
		2814
		2815	=item The winsocket select function
		2816
		2817	The winsocket C<select> function doesn't follow POSIX in that it requires
		2818	socket I<handles> and not socket I<file descriptors>. This makes select
		2819	very inefficient, and also requires a mapping from file descriptors
		2820	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2821	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2822	symbols for more info.
		2823
		2824	The configuration for a "naked" win32 using the microsoft runtime
		2825	libraries and raw winsocket select is:
		2826
		2827	#define EV_USE_SELECT 1
		2828	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2829
		2830	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2831	complexity in the O(n²) range when using win32.
		2832
		2833	=item Limited number of file descriptors
		2834
		2835	Windows has numerous arbitrary (and low) limits on things. Early versions
		2836	of winsocket's select only supported waiting for a max. of C<64> handles
		2837	(probably owning to the fact that all windows kernels can only wait for
		2838	C<64> things at the same time internally; microsoft recommends spawning a
		2839	chain of threads and wait for 63 handles and the previous thread in each).
		2840
		2841	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2842	to some high number (e.g. C<2048>) before compiling the winsocket select
		2843	call (which might be in libev or elsewhere, for example, perl does its own
		2844	select emulation on windows).
		2845
		2846	Another limit is the number of file descriptors in the microsoft runtime
		2847	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2848	or something like this inside microsoft). You can increase this by calling
		2849	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2850	arbitrary limit), but is broken in many versions of the microsoft runtime
		2851	libraries.
		2852
		2853	This might get you to about C<512> or C<2048> sockets (depending on
		2854	windows version and/or the phase of the moon). To get more, you need to
		2855	wrap all I/O functions and provide your own fd management, but the cost of
		2856	calling select (O(n²)) will likely make this unworkable.
		2857
		2858	=back
		2859
		2860
2260	=head1 AUTHOR	2861	=head1 AUTHOR
2261		2862
2262	Marc Lehmann <libev@schmorp.de>.	2863	Marc Lehmann <libev@schmorp.de>.
2263		2864

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