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Revision 1.172 by root, Wed Aug 6 07:01:25 2008 UTC vs.
Revision 1.206 by root, Tue Oct 28 12:31:38 2008 UTC

…		…
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	363	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	364	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	366	readiness notifications you get per iteration.
363		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
		371
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		373
366	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	375	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	376	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	377	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	379	performance tips.
372		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		385
375	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	388	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	389	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	390
380	cases and requiring a system call per fd change, no fork support and bad	391	The epoll syscalls are the most misdesigned of the more advanced event
381	support for dup.	392	mechanisms: problems include silently dropping fds, requiring a system
		393	call per change per fd (and unnecessary guessing of parameters), problems
		394	with dup and so on. The biggest issue is fork races, however - if a
		395	program forks then I<both> parent and child process have to recreate the
		396	epoll set, which can take considerable time (one syscall per fd) and is of
		397	course hard to detect.
		398
		399	Epoll is also notoriously buggy - embedding epoll fds should work, but
		400	of course doesn't, and epoll just loves to report events for totally
		401	I<different> file descriptors (even already closed ones, so one cannot
		402	even remove them from the set) than registered in the set (especially
		403	on SMP systems). Libev tries to counter these spurious notifications by
		404	employing an additional generation counter and comparing that against the
		405	events to filter out spurious ones.
382		406
383	While stopping, setting and starting an I/O watcher in the same iteration	407	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	408	will result in some caching, there is still a system call per such incident
385	(because the fd could point to a different file description now), so its	409	(because the fd could point to a different file description now), so its
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	410	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
387	very well if you register events for both fds.	411	very well if you register events for both fds.
388		412
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392
393	Best performance from this backend is achieved by not unregistering all	413	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	414	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	415	i.e. keep at least one watcher active per fd at all times. Stopping and
		416	starting a watcher (without re-setting it) also usually doesn't cause
		417	extra overhead. A fork can both result in spurious notifications as well
		418	as in libev having to destroy and recreate the epoll object, which can
		419	take considerable time and thus should be avoided.
396		420
397	While nominally embeddable in other event loops, this feature is broken in	421	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	422	all kernel versions tested so far.
399		423
		424	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		425	C<EVBACKEND_POLL>.
		426
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	427	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		428
402	Kqueue deserves special mention, as at the time of this writing, it	429	Kqueue deserves special mention, as at the time of this writing, it was
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	430	broken on all BSDs except NetBSD (usually it doesn't work reliably with
404	with anything but sockets and pipes, except on Darwin, where of course	431	anything but sockets and pipes, except on Darwin, where of course it's
405	it's completely useless). For this reason it's not being "auto-detected"	432	completely useless). For this reason it's not being "auto-detected" unless
406	unless you explicitly specify it explicitly in the flags (i.e. using	433	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	434	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
408	system like NetBSD.
409		435
410	You still can embed kqueue into a normal poll or select backend and use it	436	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	437	only for sockets (after having made sure that sockets work with kqueue on
412	the target platform). See C<ev_embed> watchers for more info.	438	the target platform). See C<ev_embed> watchers for more info.
413		439
414	It scales in the same way as the epoll backend, but the interface to the	440	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	441	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	442	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	443	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	444	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	445	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		446	cases
420		447
421	This backend usually performs well under most conditions.	448	This backend usually performs well under most conditions.
422		449
423	While nominally embeddable in other event loops, this doesn't work	450	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	451	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	452	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	453	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	454	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	455	using it only for sockets.
		456
		457	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		458	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		459	C<NOTE_EOF>.
429		460
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	461	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		462
432	This is not implemented yet (and might never be, unless you send me an	463	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	464	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	477	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	478	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	479	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	480	might perform better.
450		481
451	On the positive side, ignoring the spurious readiness notifications, this	482	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	483	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	484	in all tests and is fully embeddable, which is a rare feat among the
		485	OS-specific backends (I vastly prefer correctness over speed hacks).
		486
		487	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		488	C<EVBACKEND_POLL>.
454		489
455	=item C<EVBACKEND_ALL>	490	=item C<EVBACKEND_ALL>
456		491
457	Try all backends (even potentially broken ones that wouldn't be tried	492	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	493	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		499
465	If one or more of these are or'ed into the flags value, then only these	500	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	501	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	502	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		503
469	The most typical usage is like this:	504	Example: This is the most typical usage.
470		505
471	if (!ev_default_loop (0))	506	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	507	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		508
474	Restrict libev to the select and poll backends, and do not allow	509	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	510	environment settings to be taken into account:
476		511
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	512	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		513
479	Use whatever libev has to offer, but make sure that kqueue is used if	514	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	515	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	516	private event loop and only if you know the OS supports your types of
		517	fds):
482		518
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	519	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		520
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	521	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		522
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	543	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	544	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	545	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	546	for example).
511		547
512	Note that certain global state, such as signal state, will not be freed by	548	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	549	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	550	as signal and child watchers) would need to be stopped manually.
515		551
516	In general it is not advisable to call this function except in the	552	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	553	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	554	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	555	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		580
545	=item ev_loop_fork (loop)	581	=item ev_loop_fork (loop)
546		582
547	Like C<ev_default_fork>, but acts on an event loop created by	583	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	584	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	585	after fork that you want to re-use in the child, and how you do this is
		586	entirely your own problem.
550		587
551	=item int ev_is_default_loop (loop)	588	=item int ev_is_default_loop (loop)
552		589
553	Returns true when the given loop actually is the default loop, false otherwise.	590	Returns true when the given loop is, in fact, the default loop, and false
		591	otherwise.
554		592
555	=item unsigned int ev_loop_count (loop)	593	=item unsigned int ev_loop_count (loop)
556		594
557	Returns the count of loop iterations for the loop, which is identical to	595	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	596	the number of times libev did poll for new events. It starts at C<0> and
…		…
573	received events and started processing them. This timestamp does not	611	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	612	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	613	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	614	event occurring (or more correctly, libev finding out about it).
577		615
		616	=item ev_now_update (loop)
		617
		618	Establishes the current time by querying the kernel, updating the time
		619	returned by C<ev_now ()> in the progress. This is a costly operation and
		620	is usually done automatically within C<ev_loop ()>.
		621
		622	This function is rarely useful, but when some event callback runs for a
		623	very long time without entering the event loop, updating libev's idea of
		624	the current time is a good idea.
		625
		626	See also "The special problem of time updates" in the C<ev_timer> section.
		627
578	=item ev_loop (loop, int flags)	628	=item ev_loop (loop, int flags)
579		629
580	Finally, this is it, the event handler. This function usually is called	630	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	631	after you initialised all your watchers and you want to start handling
582	events.	632	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	634	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	635	either no event watchers are active anymore or C<ev_unloop> was called.
586		636
587	Please note that an explicit C<ev_unloop> is usually better than	637	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	638	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	639	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	640	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	641	of relying on its watchers stopping correctly, that is truly a thing of
		642	beauty.
592		643
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	644	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	645	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	646	process in case there are no events and will return after one iteration of
		647	the loop.
596		648
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	649	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	650	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	651	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	652	be an event internal to libev itself, so there is no guarentee that a
601	external event in conjunction with something not expressible using other	653	user-registered callback will be called), and will return after one
		654	iteration of the loop.
		655
		656	This is useful if you are waiting for some external event in conjunction
		657	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	658	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	659	usually a better approach for this kind of thing.
604		660
605	Here are the gory details of what C<ev_loop> does:	661	Here are the gory details of what C<ev_loop> does:
606		662
607	- Before the first iteration, call any pending watchers.	663	- Before the first iteration, call any pending watchers.
…		…
617	any active watchers at all will result in not sleeping).	673	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	674	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	675	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	676	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	677	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	678	- Queue all expired timers.
623	- Queue all outstanding periodics.	679	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	680	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	681	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	682	- Call all queued watchers in reverse order (i.e. check watchers first).
627	Signals and child watchers are implemented as I/O watchers, and will	683	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	684	be handled here by queueing them when their watcher gets executed.
…		…
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	701	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	702	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		703
648	This "unloop state" will be cleared when entering C<ev_loop> again.	704	This "unloop state" will be cleared when entering C<ev_loop> again.
649		705
		706	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		707
650	=item ev_ref (loop)	708	=item ev_ref (loop)
651		709
652	=item ev_unref (loop)	710	=item ev_unref (loop)
653		711
654	Ref/unref can be used to add or remove a reference count on the event	712	Ref/unref can be used to add or remove a reference count on the event
655	loop: Every watcher keeps one reference, and as long as the reference	713	loop: Every watcher keeps one reference, and as long as the reference
656	count is nonzero, C<ev_loop> will not return on its own. If you have	714	count is nonzero, C<ev_loop> will not return on its own.
		715
657	a watcher you never unregister that should not keep C<ev_loop> from	716	If you have a watcher you never unregister that should not keep C<ev_loop>
658	returning, ev_unref() after starting, and ev_ref() before stopping it. For	717	from returning, call ev_unref() after starting, and ev_ref() before
		718	stopping it.
		719
659	example, libev itself uses this for its internal signal pipe: It is not	720	As an example, libev itself uses this for its internal signal pipe: It is
660	visible to the libev user and should not keep C<ev_loop> from exiting if	721	not visible to the libev user and should not keep C<ev_loop> from exiting
661	no event watchers registered by it are active. It is also an excellent	722	if no event watchers registered by it are active. It is also an excellent
662	way to do this for generic recurring timers or from within third-party	723	way to do this for generic recurring timers or from within third-party
663	libraries. Just remember to I<unref after start> and I<ref before stop>	724	libraries. Just remember to I<unref after start> and I<ref before stop>
664	(but only if the watcher wasn't active before, or was active before,	725	(but only if the watcher wasn't active before, or was active before,
665	respectively).	726	respectively).
666		727
667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	728	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
668	running when nothing else is active.	729	running when nothing else is active.
669		730
670	struct ev_signal exitsig;	731	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	732	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	733	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	734	evf_unref (loop);
674		735
675	Example: For some weird reason, unregister the above signal handler again.	736	Example: For some weird reason, unregister the above signal handler again.
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	750	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	751	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	752	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	753	opportunities).
693		754
694	The background is that sometimes your program runs just fast enough to	755	The idea is that sometimes your program runs just fast enough to handle
695	handle one (or very few) event(s) per loop iteration. While this makes	756	one (or very few) event(s) per loop iteration. While this makes the
696	the program responsive, it also wastes a lot of CPU time to poll for new	757	program responsive, it also wastes a lot of CPU time to poll for new
697	events, especially with backends like C<select ()> which have a high	758	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	759	overhead for the actual polling but can deliver many events at once.
699		760
700	By setting a higher I<io collect interval> you allow libev to spend more	761	By setting a higher I<io collect interval> you allow libev to spend more
701	time collecting I/O events, so you can handle more events per iteration,	762	time collecting I/O events, so you can handle more events per iteration,
…		…
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	764	C<ev_timer>) will be not affected. Setting this to a non-null value will
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	765	introduce an additional C<ev_sleep ()> call into most loop iterations.
705		766
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	767	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	768	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	769	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	770	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	771	value will not introduce any overhead in libev.
711		772
712	Many (busy) programs can usually benefit by setting the I/O collect	773	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	774	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	775	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	776	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
723	they fire on, say, one-second boundaries only.	784	they fire on, say, one-second boundaries only.
724		785
725	=item ev_loop_verify (loop)	786	=item ev_loop_verify (loop)
726		787
727	This function only does something when C<EV_VERIFY> support has been	788	This function only does something when C<EV_VERIFY> support has been
728	compiled in. It tries to go through all internal structures and checks	789	compiled in, which is the default for non-minimal builds. It tries to go
729	them for validity. If anything is found to be inconsistent, it will print	790	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	791	is found to be inconsistent, it will print an error message to standard
		792	error and call C<abort ()>.
731		793
732	This can be used to catch bugs inside libev itself: under normal	794	This can be used to catch bugs inside libev itself: under normal
733	circumstances, this function will never abort as of course libev keeps its	795	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	796	data structures consistent.
735		797
736	=back	798	=back
737		799
738		800
739	=head1 ANATOMY OF A WATCHER	801	=head1 ANATOMY OF A WATCHER
740		802
		803	In the following description, uppercase C<TYPE> in names stands for the
		804	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		805	watchers and C<ev_io_start> for I/O watchers.
		806
741	A watcher is a structure that you create and register to record your	807	A watcher is a structure that you create and register to record your
742	interest in some event. For instance, if you want to wait for STDIN to	808	interest in some event. For instance, if you want to wait for STDIN to
743	become readable, you would create an C<ev_io> watcher for that:	809	become readable, you would create an C<ev_io> watcher for that:
744		810
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	811	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	812	{
747	ev_io_stop (w);	813	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	814	ev_unloop (loop, EVUNLOOP_ALL);
749	}	815	}
750		816
751	struct ev_loop *loop = ev_default_loop (0);	817	struct ev_loop *loop = ev_default_loop (0);
		818
752	struct ev_io stdin_watcher;	819	ev_io stdin_watcher;
		820
753	ev_init (&stdin_watcher, my_cb);	821	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	822	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	823	ev_io_start (loop, &stdin_watcher);
		824
756	ev_loop (loop, 0);	825	ev_loop (loop, 0);
757		826
758	As you can see, you are responsible for allocating the memory for your	827	As you can see, you are responsible for allocating the memory for your
759	watcher structures (and it is usually a bad idea to do this on the stack,	828	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	829	stack).
		830
		831	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		832	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
761		833
762	Each watcher structure must be initialised by a call to C<ev_init	834	Each watcher structure must be initialised by a call to C<ev_init
763	(watcher *, callback)>, which expects a callback to be provided. This	835	(watcher *, callback)>, which expects a callback to be provided. This
764	callback gets invoked each time the event occurs (or, in the case of I/O	836	callback gets invoked each time the event occurs (or, in the case of I/O
765	watchers, each time the event loop detects that the file descriptor given	837	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	838	is readable and/or writable).
767		839
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	840	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
769	with arguments specific to this watcher type. There is also a macro	841	macro to configure it, with arguments specific to the watcher type. There
770	to combine initialisation and setting in one call: C<< ev_<type>_init	842	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	843	ev_TYPE_init (watcher *, callback, ...) >>.
772		844
773	To make the watcher actually watch out for events, you have to start it	845	To make the watcher actually watch out for events, you have to start it
774	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	846	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
775	*) >>), and you can stop watching for events at any time by calling the	847	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	848	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		849
778	As long as your watcher is active (has been started but not stopped) you	850	As long as your watcher is active (has been started but not stopped) you
779	must not touch the values stored in it. Most specifically you must never	851	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	852	reinitialise it or call its C<ev_TYPE_set> macro.
781		853
782	Each and every callback receives the event loop pointer as first, the	854	Each and every callback receives the event loop pointer as first, the
783	registered watcher structure as second, and a bitset of received events as	855	registered watcher structure as second, and a bitset of received events as
784	third argument.	856	third argument.
785		857
…		…
848	=item C<EV_ERROR>	920	=item C<EV_ERROR>
849		921
850	An unspecified error has occurred, the watcher has been stopped. This might	922	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	923	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	924	ran out of memory, a file descriptor was found to be closed or any other
		925	problem. Libev considers these application bugs.
		926
853	problem. You best act on it by reporting the problem and somehow coping	927	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	928	watcher being stopped. Note that well-written programs should not receive
		929	an error ever, so when your watcher receives it, this usually indicates a
		930	bug in your program.
855		931
856	Libev will usually signal a few "dummy" events together with an error,	932	Libev will usually signal a few "dummy" events together with an error, for
857	for example it might indicate that a fd is readable or writable, and if	933	example it might indicate that a fd is readable or writable, and if your
858	your callbacks is well-written it can just attempt the operation and cope	934	callbacks is well-written it can just attempt the operation and cope with
859	with the error from read() or write(). This will not work in multi-threaded	935	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	936	programs, though, as the fd could already be closed and reused for another
		937	thing, so beware.
861		938
862	=back	939	=back
863		940
864	=head2 GENERIC WATCHER FUNCTIONS	941	=head2 GENERIC WATCHER FUNCTIONS
865
866	In the following description, C<TYPE> stands for the watcher type,
867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
868		942
869	=over 4	943	=over 4
870		944
871	=item C<ev_init> (ev_TYPE *watcher, callback)	945	=item C<ev_init> (ev_TYPE *watcher, callback)
872		946
…		…
878	which rolls both calls into one.	952	which rolls both calls into one.
879		953
880	You can reinitialise a watcher at any time as long as it has been stopped	954	You can reinitialise a watcher at any time as long as it has been stopped
881	(or never started) and there are no pending events outstanding.	955	(or never started) and there are no pending events outstanding.
882		956
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	957	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	958	int revents)>.
		959
		960	Example: Initialise an C<ev_io> watcher in two steps.
		961
		962	ev_io w;
		963	ev_init (&w, my_cb);
		964	ev_io_set (&w, STDIN_FILENO, EV_READ);
885		965
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	966	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		967
888	This macro initialises the type-specific parts of a watcher. You need to	968	This macro initialises the type-specific parts of a watcher. You need to
889	call C<ev_init> at least once before you call this macro, but you can	969	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	972	difference to the C<ev_init> macro).
893		973
894	Although some watcher types do not have type-specific arguments	974	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	975	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		976
		977	See C<ev_init>, above, for an example.
		978
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	979	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		980
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	981	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
900	calls into a single call. This is the most convenient method to initialise	982	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	983	a watcher. The same limitations apply, of course.
902		984
		985	Example: Initialise and set an C<ev_io> watcher in one step.
		986
		987	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		988
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	989	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		990
905	Starts (activates) the given watcher. Only active watchers will receive	991	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	992	events. If the watcher is already active nothing will happen.
907		993
		994	Example: Start the C<ev_io> watcher that is being abused as example in this
		995	whole section.
		996
		997	ev_io_start (EV_DEFAULT_UC, &w);
		998
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	999	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1000
910	Stops the given watcher again (if active) and clears the pending	1001	Stops the given watcher if active, and clears the pending status (whether
		1002	the watcher was active or not).
		1003
911	status. It is possible that stopped watchers are pending (for example,	1004	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1005	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1006	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	1007	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	1008	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1009
917	=item bool ev_is_active (ev_TYPE *watcher)	1010	=item bool ev_is_active (ev_TYPE *watcher)
918		1011
919	Returns a true value iff the watcher is active (i.e. it has been started	1012	Returns a true value iff the watcher is active (i.e. it has been started
920	and not yet been stopped). As long as a watcher is active you must not modify	1013	and not yet been stopped). As long as a watcher is active you must not modify
…		…
962	The default priority used by watchers when no priority has been set is	1055	The default priority used by watchers when no priority has been set is
963	always C<0>, which is supposed to not be too high and not be too low :).	1056	always C<0>, which is supposed to not be too high and not be too low :).
964		1057
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1058	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
966	fine, as long as you do not mind that the priority value you query might	1059	fine, as long as you do not mind that the priority value you query might
967	or might not have been adjusted to be within valid range.	1060	or might not have been clamped to the valid range.
968		1061
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1062	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1063
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1064	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1065	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1066	can deal with that fact, as both are simply passed through to the
		1067	callback.
974		1068
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1069	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1070
977	If the watcher is pending, this function returns clears its pending status	1071	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1072	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1073	watcher isn't pending it does nothing and returns C<0>.
980		1074
		1075	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1076	callback to be invoked, which can be accomplished with this function.
		1077
981	=back	1078	=back
982		1079
983		1080
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1081	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1082
986	Each watcher has, by default, a member C<void *data> that you can change	1083	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1084	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1085	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1086	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1087	member, you can also "subclass" the watcher type and provide your own
991	data:	1088	data:
992		1089
993	struct my_io	1090	struct my_io
994	{	1091	{
995	struct ev_io io;	1092	ev_io io;
996	int otherfd;	1093	int otherfd;
997	void *somedata;	1094	void *somedata;
998	struct whatever *mostinteresting;	1095	struct whatever *mostinteresting;
999	}	1096	};
		1097
		1098	...
		1099	struct my_io w;
		1100	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1101
1001	And since your callback will be called with a pointer to the watcher, you	1102	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1103	can cast it back to your own type:
1003		1104
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1105	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1106	{
1006	struct my_io *w = (struct my_io *)w_;	1107	struct my_io *w = (struct my_io *)w_;
1007	...	1108	...
1008	}	1109	}
1009		1110
1010	More interesting and less C-conformant ways of casting your callback type	1111	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1112	instead have been omitted.
1012		1113
1013	Another common scenario is having some data structure with multiple	1114	Another common scenario is to use some data structure with multiple
1014	watchers:	1115	embedded watchers:
1015		1116
1016	struct my_biggy	1117	struct my_biggy
1017	{	1118	{
1018	int some_data;	1119	int some_data;
1019	ev_timer t1;	1120	ev_timer t1;
1020	ev_timer t2;	1121	ev_timer t2;
1021	}	1122	}
1022		1123
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1124	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1125	complicated: Either you store the address of your C<my_biggy> struct
		1126	in the C<data> member of the watcher (for woozies), or you need to use
		1127	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1128	programmers):
1025		1129
1026	#include <stddef.h>	1130	#include <stddef.h>
1027		1131
1028	static void	1132	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1133	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1134	{
1031	struct my_biggy big = (struct my_biggy *	1135	struct my_biggy big = (struct my_biggy *
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1136	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1137	}
1034		1138
1035	static void	1139	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1140	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1141	{
1038	struct my_biggy big = (struct my_biggy *	1142	struct my_biggy big = (struct my_biggy *
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1143	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1144	}
1041		1145
…		…
1069	In general you can register as many read and/or write event watchers per	1173	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1174	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1175	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1176	required if you know what you are doing).
1073		1177
1074	If you must do this, then force the use of a known-to-be-good backend	1178	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1179	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1180	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1077		1181
1078	Another thing you have to watch out for is that it is quite easy to	1182	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1183	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1184	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1185	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1186	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1187	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1188	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1189	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1190
1087	If you cannot run the fd in non-blocking mode (for example you should not	1191	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1192	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1193	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1194	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1195	does this on its own, so its quite safe to use). Some people additionally
		1196	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1197	indefinitely.
		1198
		1199	But really, best use non-blocking mode.
1092		1200
1093	=head3 The special problem of disappearing file descriptors	1201	=head3 The special problem of disappearing file descriptors
1094		1202
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1203	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1204	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1205	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1206	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1207	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1208	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1209	fact, a different file descriptor.
1102		1210
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1241	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1242	C<EVBACKEND_POLL>.
1135		1243
1136	=head3 The special problem of SIGPIPE	1244	=head3 The special problem of SIGPIPE
1137		1245
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1246	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when reading from a pipe whose other end has been closed, your program	1247	when writing to a pipe whose other end has been closed, your program gets
1140	gets send a SIGPIPE, which, by default, aborts your program. For most	1248	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	programs this is sensible behaviour, for daemons, this is usually	1249	this is sensible behaviour, for daemons, this is usually undesirable.
1142	undesirable.
1143		1250
1144	So when you encounter spurious, unexplained daemon exits, make sure you	1251	So when you encounter spurious, unexplained daemon exits, make sure you
1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1252	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1146	somewhere, as that would have given you a big clue).	1253	somewhere, as that would have given you a big clue).
1147		1254
…		…
1153	=item ev_io_init (ev_io *, callback, int fd, int events)	1260	=item ev_io_init (ev_io *, callback, int fd, int events)
1154		1261
1155	=item ev_io_set (ev_io *, int fd, int events)	1262	=item ev_io_set (ev_io *, int fd, int events)
1156		1263
1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1264	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1265	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1159	C<EV_READ | EV_WRITE> to receive the given events.	1266	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1160		1267
1161	=item int fd [read-only]	1268	=item int fd [read-only]
1162		1269
1163	The file descriptor being watched.	1270	The file descriptor being watched.
1164		1271
…		…
1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1280	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1174	readable, but only once. Since it is likely line-buffered, you could	1281	readable, but only once. Since it is likely line-buffered, you could
1175	attempt to read a whole line in the callback.	1282	attempt to read a whole line in the callback.
1176		1283
1177	static void	1284	static void
1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1285	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1179	{	1286	{
1180	ev_io_stop (loop, w);	1287	ev_io_stop (loop, w);
1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1288	.. read from stdin here (or from w->fd) and handle any I/O errors
1182	}	1289	}
1183		1290
1184	...	1291	...
1185	struct ev_loop *loop = ev_default_init (0);	1292	struct ev_loop *loop = ev_default_init (0);
1186	struct ev_io stdin_readable;	1293	ev_io stdin_readable;
1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1294	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1188	ev_io_start (loop, &stdin_readable);	1295	ev_io_start (loop, &stdin_readable);
1189	ev_loop (loop, 0);	1296	ev_loop (loop, 0);
1190		1297
1191		1298
…		…
1194	Timer watchers are simple relative timers that generate an event after a	1301	Timer watchers are simple relative timers that generate an event after a
1195	given time, and optionally repeating in regular intervals after that.	1302	given time, and optionally repeating in regular intervals after that.
1196		1303
1197	The timers are based on real time, that is, if you register an event that	1304	The timers are based on real time, that is, if you register an event that
1198	times out after an hour and you reset your system clock to January last	1305	times out after an hour and you reset your system clock to January last
1199	year, it will still time out after (roughly) and hour. "Roughly" because	1306	year, it will still time out after (roughly) one hour. "Roughly" because
1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1307	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1201	monotonic clock option helps a lot here).	1308	monotonic clock option helps a lot here).
		1309
		1310	The callback is guaranteed to be invoked only I<after> its timeout has
		1311	passed, but if multiple timers become ready during the same loop iteration
		1312	then order of execution is undefined.
		1313
		1314	=head3 Be smart about timeouts
		1315
		1316	Many real-world problems involve some kind of timeout, usually for error
		1317	recovery. A typical example is an HTTP request - if the other side hangs,
		1318	you want to raise some error after a while.
		1319
		1320	What follows are some ways to handle this problem, from obvious and
		1321	inefficient to smart and efficient.
		1322
		1323	In the following, a 60 second activity timeout is assumed - a timeout that
		1324	gets reset to 60 seconds each time there is activity (e.g. each time some
		1325	data or other life sign was received).
		1326
		1327	=over 4
		1328
		1329	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1330
		1331	This is the most obvious, but not the most simple way: In the beginning,
		1332	start the watcher:
		1333
		1334	ev_timer_init (timer, callback, 60., 0.);
		1335	ev_timer_start (loop, timer);
		1336
		1337	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1338	and start it again:
		1339
		1340	ev_timer_stop (loop, timer);
		1341	ev_timer_set (timer, 60., 0.);
		1342	ev_timer_start (loop, timer);
		1343
		1344	This is relatively simple to implement, but means that each time there is
		1345	some activity, libev will first have to remove the timer from its internal
		1346	data structure and then add it again. Libev tries to be fast, but it's
		1347	still not a constant-time operation.
		1348
		1349	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1350
		1351	This is the easiest way, and involves using C<ev_timer_again> instead of
		1352	C<ev_timer_start>.
		1353
		1354	To implement this, configure an C<ev_timer> with a C<repeat> value
		1355	of C<60> and then call C<ev_timer_again> at start and each time you
		1356	successfully read or write some data. If you go into an idle state where
		1357	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1358	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1359
		1360	That means you can ignore both the C<ev_timer_start> function and the
		1361	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1362	member and C<ev_timer_again>.
		1363
		1364	At start:
		1365
		1366	ev_timer_init (timer, callback);
		1367	timer->repeat = 60.;
		1368	ev_timer_again (loop, timer);
		1369
		1370	Each time there is some activity:
		1371
		1372	ev_timer_again (loop, timer);
		1373
		1374	It is even possible to change the time-out on the fly, regardless of
		1375	whether the watcher is active or not:
		1376
		1377	timer->repeat = 30.;
		1378	ev_timer_again (loop, timer);
		1379
		1380	This is slightly more efficient then stopping/starting the timer each time
		1381	you want to modify its timeout value, as libev does not have to completely
		1382	remove and re-insert the timer from/into its internal data structure.
		1383
		1384	It is, however, even simpler than the "obvious" way to do it.
		1385
		1386	=item 3. Let the timer time out, but then re-arm it as required.
		1387
		1388	This method is more tricky, but usually most efficient: Most timeouts are
		1389	relatively long compared to the intervals between other activity - in
		1390	our example, within 60 seconds, there are usually many I/O events with
		1391	associated activity resets.
		1392
		1393	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1394	but remember the time of last activity, and check for a real timeout only
		1395	within the callback:
		1396
		1397	ev_tstamp last_activity; // time of last activity
		1398
		1399	static void
		1400	callback (EV_P_ ev_timer *w, int revents)
		1401	{
		1402	ev_tstamp now = ev_now (EV_A);
		1403	ev_tstamp timeout = last_activity + 60.;
		1404
		1405	// if last_activity + 60. is older than now, we did time out
		1406	if (timeout < now)
		1407	{
		1408	// timeout occured, take action
		1409	}
		1410	else
		1411	{
		1412	// callback was invoked, but there was some activity, re-arm
		1413	// the watcher to fire in last_activity + 60, which is
		1414	// guaranteed to be in the future, so "again" is positive:
		1415	w->again = timeout - now;
		1416	ev_timer_again (EV_A_ w);
		1417	}
		1418	}
		1419
		1420	To summarise the callback: first calculate the real timeout (defined
		1421	as "60 seconds after the last activity"), then check if that time has
		1422	been reached, which means something I<did>, in fact, time out. Otherwise
		1423	the callback was invoked too early (C<timeout> is in the future), so
		1424	re-schedule the timer to fire at that future time, to see if maybe we have
		1425	a timeout then.
		1426
		1427	Note how C<ev_timer_again> is used, taking advantage of the
		1428	C<ev_timer_again> optimisation when the timer is already running.
		1429
		1430	This scheme causes more callback invocations (about one every 60 seconds
		1431	minus half the average time between activity), but virtually no calls to
		1432	libev to change the timeout.
		1433
		1434	To start the timer, simply initialise the watcher and set C<last_activity>
		1435	to the current time (meaning we just have some activity :), then call the
		1436	callback, which will "do the right thing" and start the timer:
		1437
		1438	ev_timer_init (timer, callback);
		1439	last_activity = ev_now (loop);
		1440	callback (loop, timer, EV_TIMEOUT);
		1441
		1442	And when there is some activity, simply store the current time in
		1443	C<last_activity>, no libev calls at all:
		1444
		1445	last_actiivty = ev_now (loop);
		1446
		1447	This technique is slightly more complex, but in most cases where the
		1448	time-out is unlikely to be triggered, much more efficient.
		1449
		1450	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1451	callback :) - just change the timeout and invoke the callback, which will
		1452	fix things for you.
		1453
		1454	=item 4. Wee, just use a double-linked list for your timeouts.
		1455
		1456	If there is not one request, but many thousands (millions...), all
		1457	employing some kind of timeout with the same timeout value, then one can
		1458	do even better:
		1459
		1460	When starting the timeout, calculate the timeout value and put the timeout
		1461	at the I<end> of the list.
		1462
		1463	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1464	the list is expected to fire (for example, using the technique #3).
		1465
		1466	When there is some activity, remove the timer from the list, recalculate
		1467	the timeout, append it to the end of the list again, and make sure to
		1468	update the C<ev_timer> if it was taken from the beginning of the list.
		1469
		1470	This way, one can manage an unlimited number of timeouts in O(1) time for
		1471	starting, stopping and updating the timers, at the expense of a major
		1472	complication, and having to use a constant timeout. The constant timeout
		1473	ensures that the list stays sorted.
		1474
		1475	=back
		1476
		1477	So which method the best?
		1478
		1479	Method #2 is a simple no-brain-required solution that is adequate in most
		1480	situations. Method #3 requires a bit more thinking, but handles many cases
		1481	better, and isn't very complicated either. In most case, choosing either
		1482	one is fine, with #3 being better in typical situations.
		1483
		1484	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1485	rather complicated, but extremely efficient, something that really pays
		1486	off after the first million or so of active timers, i.e. it's usually
		1487	overkill :)
		1488
		1489	=head3 The special problem of time updates
		1490
		1491	Establishing the current time is a costly operation (it usually takes at
		1492	least two system calls): EV therefore updates its idea of the current
		1493	time only before and after C<ev_loop> collects new events, which causes a
		1494	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1495	lots of events in one iteration.
1202		1496
1203	The relative timeouts are calculated relative to the C<ev_now ()>	1497	The relative timeouts are calculated relative to the C<ev_now ()>
1204	time. This is usually the right thing as this timestamp refers to the time	1498	time. This is usually the right thing as this timestamp refers to the time
1205	of the event triggering whatever timeout you are modifying/starting. If	1499	of the event triggering whatever timeout you are modifying/starting. If
1206	you suspect event processing to be delayed and you I<need> to base the timeout	1500	you suspect event processing to be delayed and you I<need> to base the
1207	on the current time, use something like this to adjust for this:	1501	timeout on the current time, use something like this to adjust for this:
1208		1502
1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1503	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1210		1504
1211	The callback is guaranteed to be invoked only after its timeout has passed,	1505	If the event loop is suspended for a long time, you can also force an
1212	but if multiple timers become ready during the same loop iteration then	1506	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1213	order of execution is undefined.	1507	()>.
1214		1508
1215	=head3 Watcher-Specific Functions and Data Members	1509	=head3 Watcher-Specific Functions and Data Members
1216		1510
1217	=over 4	1511	=over 4
1218		1512
…		…
1242	If the timer is started but non-repeating, stop it (as if it timed out).	1536	If the timer is started but non-repeating, stop it (as if it timed out).
1243		1537
1244	If the timer is repeating, either start it if necessary (with the	1538	If the timer is repeating, either start it if necessary (with the
1245	C<repeat> value), or reset the running timer to the C<repeat> value.	1539	C<repeat> value), or reset the running timer to the C<repeat> value.
1246		1540
1247	This sounds a bit complicated, but here is a useful and typical	1541	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1248	example: Imagine you have a TCP connection and you want a so-called idle	1542	usage example.
1249	timeout, that is, you want to be called when there have been, say, 60
1250	seconds of inactivity on the socket. The easiest way to do this is to
1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1252	C<ev_timer_again> each time you successfully read or write some data. If
1253	you go into an idle state where you do not expect data to travel on the
1254	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1255	automatically restart it if need be.
1256
1257	That means you can ignore the C<after> value and C<ev_timer_start>
1258	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1259
1260	ev_timer_init (timer, callback, 0., 5.);
1261	ev_timer_again (loop, timer);
1262	...
1263	timer->again = 17.;
1264	ev_timer_again (loop, timer);
1265	...
1266	timer->again = 10.;
1267	ev_timer_again (loop, timer);
1268
1269	This is more slightly efficient then stopping/starting the timer each time
1270	you want to modify its timeout value.
1271		1543
1272	=item ev_tstamp repeat [read-write]	1544	=item ev_tstamp repeat [read-write]
1273		1545
1274	The current C<repeat> value. Will be used each time the watcher times out	1546	The current C<repeat> value. Will be used each time the watcher times out
1275	or C<ev_timer_again> is called and determines the next timeout (if any),	1547	or C<ev_timer_again> is called, and determines the next timeout (if any),
1276	which is also when any modifications are taken into account.	1548	which is also when any modifications are taken into account.
1277		1549
1278	=back	1550	=back
1279		1551
1280	=head3 Examples	1552	=head3 Examples
1281		1553
1282	Example: Create a timer that fires after 60 seconds.	1554	Example: Create a timer that fires after 60 seconds.
1283		1555
1284	static void	1556	static void
1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1557	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1286	{	1558	{
1287	.. one minute over, w is actually stopped right here	1559	.. one minute over, w is actually stopped right here
1288	}	1560	}
1289		1561
1290	struct ev_timer mytimer;	1562	ev_timer mytimer;
1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1563	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1292	ev_timer_start (loop, &mytimer);	1564	ev_timer_start (loop, &mytimer);
1293		1565
1294	Example: Create a timeout timer that times out after 10 seconds of	1566	Example: Create a timeout timer that times out after 10 seconds of
1295	inactivity.	1567	inactivity.
1296		1568
1297	static void	1569	static void
1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1570	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1299	{	1571	{
1300	.. ten seconds without any activity	1572	.. ten seconds without any activity
1301	}	1573	}
1302		1574
1303	struct ev_timer mytimer;	1575	ev_timer mytimer;
1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1576	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1305	ev_timer_again (&mytimer); /* start timer */	1577	ev_timer_again (&mytimer); /* start timer */
1306	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1307		1579
1308	// and in some piece of code that gets executed on any "activity":	1580	// and in some piece of code that gets executed on any "activity":
…		…
1324	to trigger the event (unlike an C<ev_timer>, which would still trigger	1596	to trigger the event (unlike an C<ev_timer>, which would still trigger
1325	roughly 10 seconds later as it uses a relative timeout).	1597	roughly 10 seconds later as it uses a relative timeout).
1326		1598
1327	C<ev_periodic>s can also be used to implement vastly more complex timers,	1599	C<ev_periodic>s can also be used to implement vastly more complex timers,
1328	such as triggering an event on each "midnight, local time", or other	1600	such as triggering an event on each "midnight, local time", or other
1329	complicated, rules.	1601	complicated rules.
1330		1602
1331	As with timers, the callback is guaranteed to be invoked only when the	1603	As with timers, the callback is guaranteed to be invoked only when the
1332	time (C<at>) has passed, but if multiple periodic timers become ready	1604	time (C<at>) has passed, but if multiple periodic timers become ready
1333	during the same loop iteration then order of execution is undefined.	1605	during the same loop iteration, then order of execution is undefined.
1334		1606
1335	=head3 Watcher-Specific Functions and Data Members	1607	=head3 Watcher-Specific Functions and Data Members
1336		1608
1337	=over 4	1609	=over 4
1338		1610
1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1611	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1340		1612
1341	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1613	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1342		1614
1343	Lots of arguments, lets sort it out... There are basically three modes of	1615	Lots of arguments, lets sort it out... There are basically three modes of
1344	operation, and we will explain them from simplest to complex:	1616	operation, and we will explain them from simplest to most complex:
1345		1617
1346	=over 4	1618	=over 4
1347		1619
1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1620	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1349		1621
1350	In this configuration the watcher triggers an event after the wall clock	1622	In this configuration the watcher triggers an event after the wall clock
1351	time C<at> has passed and doesn't repeat. It will not adjust when a time	1623	time C<at> has passed. It will not repeat and will not adjust when a time
1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1624	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1353	run when the system time reaches or surpasses this time.	1625	only run when the system clock reaches or surpasses this time.
1354		1626
1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1627	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1356		1628
1357	In this mode the watcher will always be scheduled to time out at the next	1629	In this mode the watcher will always be scheduled to time out at the next
1358	C<at + N * interval> time (for some integer N, which can also be negative)	1630	C<at + N * interval> time (for some integer N, which can also be negative)
1359	and then repeat, regardless of any time jumps.	1631	and then repeat, regardless of any time jumps.
1360		1632
1361	This can be used to create timers that do not drift with respect to system	1633	This can be used to create timers that do not drift with respect to the
1362	time, for example, here is a C<ev_periodic> that triggers each hour, on	1634	system clock, for example, here is a C<ev_periodic> that triggers each
1363	the hour:	1635	hour, on the hour:
1364		1636
1365	ev_periodic_set (&periodic, 0., 3600., 0);	1637	ev_periodic_set (&periodic, 0., 3600., 0);
1366		1638
1367	This doesn't mean there will always be 3600 seconds in between triggers,	1639	This doesn't mean there will always be 3600 seconds in between triggers,
1368	but only that the callback will be called when the system time shows a	1640	but only that the callback will be called when the system time shows a
…		…
1394		1666
1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1667	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1668	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1397	only event loop modification you are allowed to do).	1669	only event loop modification you are allowed to do).
1398		1670
1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1671	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1400	*w, ev_tstamp now)>, e.g.:	1672	*w, ev_tstamp now)>, e.g.:
1401		1673
		1674	static ev_tstamp
1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1675	my_rescheduler (ev_periodic *w, ev_tstamp now)
1403	{	1676	{
1404	return now + 60.;	1677	return now + 60.;
1405	}	1678	}
1406		1679
1407	It must return the next time to trigger, based on the passed time value	1680	It must return the next time to trigger, based on the passed time value
…		…
1444		1717
1445	The current interval value. Can be modified any time, but changes only	1718	The current interval value. Can be modified any time, but changes only
1446	take effect when the periodic timer fires or C<ev_periodic_again> is being	1719	take effect when the periodic timer fires or C<ev_periodic_again> is being
1447	called.	1720	called.
1448		1721
1449	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1722	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1450		1723
1451	The current reschedule callback, or C<0>, if this functionality is	1724	The current reschedule callback, or C<0>, if this functionality is
1452	switched off. Can be changed any time, but changes only take effect when	1725	switched off. Can be changed any time, but changes only take effect when
1453	the periodic timer fires or C<ev_periodic_again> is being called.	1726	the periodic timer fires or C<ev_periodic_again> is being called.
1454		1727
1455	=back	1728	=back
1456		1729
1457	=head3 Examples	1730	=head3 Examples
1458		1731
1459	Example: Call a callback every hour, or, more precisely, whenever the	1732	Example: Call a callback every hour, or, more precisely, whenever the
1460	system clock is divisible by 3600. The callback invocation times have	1733	system time is divisible by 3600. The callback invocation times have
1461	potentially a lot of jitter, but good long-term stability.	1734	potentially a lot of jitter, but good long-term stability.
1462		1735
1463	static void	1736	static void
1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1737	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1465	{	1738	{
1466	... its now a full hour (UTC, or TAI or whatever your clock follows)	1739	... its now a full hour (UTC, or TAI or whatever your clock follows)
1467	}	1740	}
1468		1741
1469	struct ev_periodic hourly_tick;	1742	ev_periodic hourly_tick;
1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1743	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1471	ev_periodic_start (loop, &hourly_tick);	1744	ev_periodic_start (loop, &hourly_tick);
1472		1745
1473	Example: The same as above, but use a reschedule callback to do it:	1746	Example: The same as above, but use a reschedule callback to do it:
1474		1747
1475	#include <math.h>	1748	#include <math.h>
1476		1749
1477	static ev_tstamp	1750	static ev_tstamp
1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1751	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1479	{	1752	{
1480	return fmod (now, 3600.) + 3600.;	1753	return now + (3600. - fmod (now, 3600.));
1481	}	1754	}
1482		1755
1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1756	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1484		1757
1485	Example: Call a callback every hour, starting now:	1758	Example: Call a callback every hour, starting now:
1486		1759
1487	struct ev_periodic hourly_tick;	1760	ev_periodic hourly_tick;
1488	ev_periodic_init (&hourly_tick, clock_cb,	1761	ev_periodic_init (&hourly_tick, clock_cb,
1489	fmod (ev_now (loop), 3600.), 3600., 0);	1762	fmod (ev_now (loop), 3600.), 3600., 0);
1490	ev_periodic_start (loop, &hourly_tick);	1763	ev_periodic_start (loop, &hourly_tick);
1491		1764
1492		1765
…		…
1495	Signal watchers will trigger an event when the process receives a specific	1768	Signal watchers will trigger an event when the process receives a specific
1496	signal one or more times. Even though signals are very asynchronous, libev	1769	signal one or more times. Even though signals are very asynchronous, libev
1497	will try it's best to deliver signals synchronously, i.e. as part of the	1770	will try it's best to deliver signals synchronously, i.e. as part of the
1498	normal event processing, like any other event.	1771	normal event processing, like any other event.
1499		1772
		1773	If you want signals asynchronously, just use C<sigaction> as you would
		1774	do without libev and forget about sharing the signal. You can even use
		1775	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1776
1500	You can configure as many watchers as you like per signal. Only when the	1777	You can configure as many watchers as you like per signal. Only when the
1501	first watcher gets started will libev actually register a signal watcher	1778	first watcher gets started will libev actually register a signal handler
1502	with the kernel (thus it coexists with your own signal handlers as long	1779	with the kernel (thus it coexists with your own signal handlers as long as
1503	as you don't register any with libev). Similarly, when the last signal	1780	you don't register any with libev for the same signal). Similarly, when
1504	watcher for a signal is stopped libev will reset the signal handler to	1781	the last signal watcher for a signal is stopped, libev will reset the
1505	SIG_DFL (regardless of what it was set to before).	1782	signal handler to SIG_DFL (regardless of what it was set to before).
1506		1783
1507	If possible and supported, libev will install its handlers with	1784	If possible and supported, libev will install its handlers with
1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1785	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1509	interrupted. If you have a problem with system calls getting interrupted by	1786	interrupted. If you have a problem with system calls getting interrupted by
1510	signals you can block all signals in an C<ev_check> watcher and unblock	1787	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1527		1804
1528	=back	1805	=back
1529		1806
1530	=head3 Examples	1807	=head3 Examples
1531		1808
1532	Example: Try to exit cleanly on SIGINT and SIGTERM.	1809	Example: Try to exit cleanly on SIGINT.
1533		1810
1534	static void	1811	static void
1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1812	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1536	{	1813	{
1537	ev_unloop (loop, EVUNLOOP_ALL);	1814	ev_unloop (loop, EVUNLOOP_ALL);
1538	}	1815	}
1539		1816
1540	struct ev_signal signal_watcher;	1817	ev_signal signal_watcher;
1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1818	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1542	ev_signal_start (loop, &sigint_cb);	1819	ev_signal_start (loop, &signal_watcher);
1543		1820
1544		1821
1545	=head2 C<ev_child> - watch out for process status changes	1822	=head2 C<ev_child> - watch out for process status changes
1546		1823
1547	Child watchers trigger when your process receives a SIGCHLD in response to	1824	Child watchers trigger when your process receives a SIGCHLD in response to
1548	some child status changes (most typically when a child of yours dies). It	1825	some child status changes (most typically when a child of yours dies or
1549	is permissible to install a child watcher I<after> the child has been	1826	exits). It is permissible to install a child watcher I<after> the child
1550	forked (which implies it might have already exited), as long as the event	1827	has been forked (which implies it might have already exited), as long
1551	loop isn't entered (or is continued from a watcher).	1828	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1829	forking and then immediately registering a watcher for the child is fine,
		1830	but forking and registering a watcher a few event loop iterations later is
		1831	not.
1552		1832
1553	Only the default event loop is capable of handling signals, and therefore	1833	Only the default event loop is capable of handling signals, and therefore
1554	you can only register child watchers in the default event loop.	1834	you can only register child watchers in the default event loop.
1555		1835
1556	=head3 Process Interaction	1836	=head3 Process Interaction
…		…
1569	handler, you can override it easily by installing your own handler for	1849	handler, you can override it easily by installing your own handler for
1570	C<SIGCHLD> after initialising the default loop, and making sure the	1850	C<SIGCHLD> after initialising the default loop, and making sure the
1571	default loop never gets destroyed. You are encouraged, however, to use an	1851	default loop never gets destroyed. You are encouraged, however, to use an
1572	event-based approach to child reaping and thus use libev's support for	1852	event-based approach to child reaping and thus use libev's support for
1573	that, so other libev users can use C<ev_child> watchers freely.	1853	that, so other libev users can use C<ev_child> watchers freely.
		1854
		1855	=head3 Stopping the Child Watcher
		1856
		1857	Currently, the child watcher never gets stopped, even when the
		1858	child terminates, so normally one needs to stop the watcher in the
		1859	callback. Future versions of libev might stop the watcher automatically
		1860	when a child exit is detected.
1574		1861
1575	=head3 Watcher-Specific Functions and Data Members	1862	=head3 Watcher-Specific Functions and Data Members
1576		1863
1577	=over 4	1864	=over 4
1578		1865
…		…
1610	its completion.	1897	its completion.
1611		1898
1612	ev_child cw;	1899	ev_child cw;
1613		1900
1614	static void	1901	static void
1615	child_cb (EV_P_ struct ev_child *w, int revents)	1902	child_cb (EV_P_ ev_child *w, int revents)
1616	{	1903	{
1617	ev_child_stop (EV_A_ w);	1904	ev_child_stop (EV_A_ w);
1618	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1905	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1619	}	1906	}
1620		1907
…		…
1647	the stat buffer having unspecified contents.	1934	the stat buffer having unspecified contents.
1648		1935
1649	The path I<should> be absolute and I<must not> end in a slash. If it is	1936	The path I<should> be absolute and I<must not> end in a slash. If it is
1650	relative and your working directory changes, the behaviour is undefined.	1937	relative and your working directory changes, the behaviour is undefined.
1651		1938
1652	Since there is no standard to do this, the portable implementation simply	1939	Since there is no standard kernel interface to do this, the portable
1653	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1940	implementation simply calls C<stat (2)> regularly on the path to see if
1654	can specify a recommended polling interval for this case. If you specify	1941	it changed somehow. You can specify a recommended polling interval for
1655	a polling interval of C<0> (highly recommended!) then a I<suitable,	1942	this case. If you specify a polling interval of C<0> (highly recommended!)
1656	unspecified default> value will be used (which you can expect to be around	1943	then a I<suitable, unspecified default> value will be used (which
1657	five seconds, although this might change dynamically). Libev will also	1944	you can expect to be around five seconds, although this might change
1658	impose a minimum interval which is currently around C<0.1>, but thats	1945	dynamically). Libev will also impose a minimum interval which is currently
1659	usually overkill.	1946	around C<0.1>, but thats usually overkill.
1660		1947
1661	This watcher type is not meant for massive numbers of stat watchers,	1948	This watcher type is not meant for massive numbers of stat watchers,
1662	as even with OS-supported change notifications, this can be	1949	as even with OS-supported change notifications, this can be
1663	resource-intensive.	1950	resource-intensive.
1664		1951
1665	At the time of this writing, only the Linux inotify interface is	1952	At the time of this writing, the only OS-specific interface implemented
1666	implemented (implementing kqueue support is left as an exercise for the	1953	is the Linux inotify interface (implementing kqueue support is left as
1667	reader, note, however, that the author sees no way of implementing ev_stat	1954	an exercise for the reader. Note, however, that the author sees no way
1668	semantics with kqueue). Inotify will be used to give hints only and should	1955	of implementing C<ev_stat> semantics with kqueue).
1669	not change the semantics of C<ev_stat> watchers, which means that libev
1670	sometimes needs to fall back to regular polling again even with inotify,
1671	but changes are usually detected immediately, and if the file exists there
1672	will be no polling.
1673		1956
1674	=head3 ABI Issues (Largefile Support)	1957	=head3 ABI Issues (Largefile Support)
1675		1958
1676	Libev by default (unless the user overrides this) uses the default	1959	Libev by default (unless the user overrides this) uses the default
1677	compilation environment, which means that on systems with large file	1960	compilation environment, which means that on systems with large file
…		…
1686	file interfaces available by default (as e.g. FreeBSD does) and not	1969	file interfaces available by default (as e.g. FreeBSD does) and not
1687	optional. Libev cannot simply switch on large file support because it has	1970	optional. Libev cannot simply switch on large file support because it has
1688	to exchange stat structures with application programs compiled using the	1971	to exchange stat structures with application programs compiled using the
1689	default compilation environment.	1972	default compilation environment.
1690		1973
1691	=head3 Inotify	1974	=head3 Inotify and Kqueue
1692		1975
1693	When C<inotify (7)> support has been compiled into libev (generally only	1976	When C<inotify (7)> support has been compiled into libev (generally
		1977	only available with Linux 2.6.25 or above due to bugs in earlier
1694	available on Linux) and present at runtime, it will be used to speed up	1978	implementations) and present at runtime, it will be used to speed up
1695	change detection where possible. The inotify descriptor will be created lazily	1979	change detection where possible. The inotify descriptor will be created
1696	when the first C<ev_stat> watcher is being started.	1980	lazily when the first C<ev_stat> watcher is being started.
1697		1981
1698	Inotify presence does not change the semantics of C<ev_stat> watchers	1982	Inotify presence does not change the semantics of C<ev_stat> watchers
1699	except that changes might be detected earlier, and in some cases, to avoid	1983	except that changes might be detected earlier, and in some cases, to avoid
1700	making regular C<stat> calls. Even in the presence of inotify support	1984	making regular C<stat> calls. Even in the presence of inotify support
1701	there are many cases where libev has to resort to regular C<stat> polling.	1985	there are many cases where libev has to resort to regular C<stat> polling,
		1986	but as long as the path exists, libev usually gets away without polling.
1702		1987
1703	(There is no support for kqueue, as apparently it cannot be used to	1988	There is no support for kqueue, as apparently it cannot be used to
1704	implement this functionality, due to the requirement of having a file	1989	implement this functionality, due to the requirement of having a file
1705	descriptor open on the object at all times).	1990	descriptor open on the object at all times, and detecting renames, unlinks
		1991	etc. is difficult.
1706		1992
1707	=head3 The special problem of stat time resolution	1993	=head3 The special problem of stat time resolution
1708		1994
1709	The C<stat ()> system call only supports full-second resolution portably, and	1995	The C<stat ()> system call only supports full-second resolution portably, and
1710	even on systems where the resolution is higher, many file systems still	1996	even on systems where the resolution is higher, most file systems still
1711	only support whole seconds.	1997	only support whole seconds.
1712		1998
1713	That means that, if the time is the only thing that changes, you can	1999	That means that, if the time is the only thing that changes, you can
1714	easily miss updates: on the first update, C<ev_stat> detects a change and	2000	easily miss updates: on the first update, C<ev_stat> detects a change and
1715	calls your callback, which does something. When there is another update	2001	calls your callback, which does something. When there is another update
1716	within the same second, C<ev_stat> will be unable to detect it as the stat	2002	within the same second, C<ev_stat> will be unable to detect unless the
1717	data does not change.	2003	stat data does change in other ways (e.g. file size).
1718		2004
1719	The solution to this is to delay acting on a change for slightly more	2005	The solution to this is to delay acting on a change for slightly more
1720	than a second (or till slightly after the next full second boundary), using	2006	than a second (or till slightly after the next full second boundary), using
1721	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2007	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1722	ev_timer_again (loop, w)>).	2008	ev_timer_again (loop, w)>).
…		…
1742	C<path>. The C<interval> is a hint on how quickly a change is expected to	2028	C<path>. The C<interval> is a hint on how quickly a change is expected to
1743	be detected and should normally be specified as C<0> to let libev choose	2029	be detected and should normally be specified as C<0> to let libev choose
1744	a suitable value. The memory pointed to by C<path> must point to the same	2030	a suitable value. The memory pointed to by C<path> must point to the same
1745	path for as long as the watcher is active.	2031	path for as long as the watcher is active.
1746		2032
1747	The callback will receive C<EV_STAT> when a change was detected, relative	2033	The callback will receive an C<EV_STAT> event when a change was detected,
1748	to the attributes at the time the watcher was started (or the last change	2034	relative to the attributes at the time the watcher was started (or the
1749	was detected).	2035	last change was detected).
1750		2036
1751	=item ev_stat_stat (loop, ev_stat *)	2037	=item ev_stat_stat (loop, ev_stat *)
1752		2038
1753	Updates the stat buffer immediately with new values. If you change the	2039	Updates the stat buffer immediately with new values. If you change the
1754	watched path in your callback, you could call this function to avoid	2040	watched path in your callback, you could call this function to avoid
…		…
1837		2123
1838		2124
1839	=head2 C<ev_idle> - when you've got nothing better to do...	2125	=head2 C<ev_idle> - when you've got nothing better to do...
1840		2126
1841	Idle watchers trigger events when no other events of the same or higher	2127	Idle watchers trigger events when no other events of the same or higher
1842	priority are pending (prepare, check and other idle watchers do not	2128	priority are pending (prepare, check and other idle watchers do not count
1843	count).	2129	as receiving "events").
1844		2130
1845	That is, as long as your process is busy handling sockets or timeouts	2131	That is, as long as your process is busy handling sockets or timeouts
1846	(or even signals, imagine) of the same or higher priority it will not be	2132	(or even signals, imagine) of the same or higher priority it will not be
1847	triggered. But when your process is idle (or only lower-priority watchers	2133	triggered. But when your process is idle (or only lower-priority watchers
1848	are pending), the idle watchers are being called once per event loop	2134	are pending), the idle watchers are being called once per event loop
…		…
1873		2159
1874	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2160	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1875	callback, free it. Also, use no error checking, as usual.	2161	callback, free it. Also, use no error checking, as usual.
1876		2162
1877	static void	2163	static void
1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2164	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1879	{	2165	{
1880	free (w);	2166	free (w);
1881	// now do something you wanted to do when the program has	2167	// now do something you wanted to do when the program has
1882	// no longer anything immediate to do.	2168	// no longer anything immediate to do.
1883	}	2169	}
1884		2170
1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2171	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1886	ev_idle_init (idle_watcher, idle_cb);	2172	ev_idle_init (idle_watcher, idle_cb);
1887	ev_idle_start (loop, idle_cb);	2173	ev_idle_start (loop, idle_cb);
1888		2174
1889		2175
1890	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2176	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1891		2177
1892	Prepare and check watchers are usually (but not always) used in tandem:	2178	Prepare and check watchers are usually (but not always) used in pairs:
1893	prepare watchers get invoked before the process blocks and check watchers	2179	prepare watchers get invoked before the process blocks and check watchers
1894	afterwards.	2180	afterwards.
1895		2181
1896	You I<must not> call C<ev_loop> or similar functions that enter	2182	You I<must not> call C<ev_loop> or similar functions that enter
1897	the current event loop from either C<ev_prepare> or C<ev_check>	2183	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1900	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2186	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1901	C<ev_check> so if you have one watcher of each kind they will always be	2187	C<ev_check> so if you have one watcher of each kind they will always be
1902	called in pairs bracketing the blocking call.	2188	called in pairs bracketing the blocking call.
1903		2189
1904	Their main purpose is to integrate other event mechanisms into libev and	2190	Their main purpose is to integrate other event mechanisms into libev and
1905	their use is somewhat advanced. This could be used, for example, to track	2191	their use is somewhat advanced. They could be used, for example, to track
1906	variable changes, implement your own watchers, integrate net-snmp or a	2192	variable changes, implement your own watchers, integrate net-snmp or a
1907	coroutine library and lots more. They are also occasionally useful if	2193	coroutine library and lots more. They are also occasionally useful if
1908	you cache some data and want to flush it before blocking (for example,	2194	you cache some data and want to flush it before blocking (for example,
1909	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2195	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1910	watcher).	2196	watcher).
1911		2197
1912	This is done by examining in each prepare call which file descriptors need	2198	This is done by examining in each prepare call which file descriptors
1913	to be watched by the other library, registering C<ev_io> watchers for	2199	need to be watched by the other library, registering C<ev_io> watchers
1914	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2200	for them and starting an C<ev_timer> watcher for any timeouts (many
1915	provide just this functionality). Then, in the check watcher you check for	2201	libraries provide exactly this functionality). Then, in the check watcher,
1916	any events that occurred (by checking the pending status of all watchers	2202	you check for any events that occurred (by checking the pending status
1917	and stopping them) and call back into the library. The I/O and timer	2203	of all watchers and stopping them) and call back into the library. The
1918	callbacks will never actually be called (but must be valid nevertheless,	2204	I/O and timer callbacks will never actually be called (but must be valid
1919	because you never know, you know?).	2205	nevertheless, because you never know, you know?).
1920		2206
1921	As another example, the Perl Coro module uses these hooks to integrate	2207	As another example, the Perl Coro module uses these hooks to integrate
1922	coroutines into libev programs, by yielding to other active coroutines	2208	coroutines into libev programs, by yielding to other active coroutines
1923	during each prepare and only letting the process block if no coroutines	2209	during each prepare and only letting the process block if no coroutines
1924	are ready to run (it's actually more complicated: it only runs coroutines	2210	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1927	loop from blocking if lower-priority coroutines are active, thus mapping	2213	loop from blocking if lower-priority coroutines are active, thus mapping
1928	low-priority coroutines to idle/background tasks).	2214	low-priority coroutines to idle/background tasks).
1929		2215
1930	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2216	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1931	priority, to ensure that they are being run before any other watchers	2217	priority, to ensure that they are being run before any other watchers
		2218	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2219
1932	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2220	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1933	too) should not activate ("feed") events into libev. While libev fully	2221	activate ("feed") events into libev. While libev fully supports this, they
1934	supports this, they might get executed before other C<ev_check> watchers	2222	might get executed before other C<ev_check> watchers did their job. As
1935	did their job. As C<ev_check> watchers are often used to embed other	2223	C<ev_check> watchers are often used to embed other (non-libev) event
1936	(non-libev) event loops those other event loops might be in an unusable	2224	loops those other event loops might be in an unusable state until their
1937	state until their C<ev_check> watcher ran (always remind yourself to	2225	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1938	coexist peacefully with others).	2226	others).
1939		2227
1940	=head3 Watcher-Specific Functions and Data Members	2228	=head3 Watcher-Specific Functions and Data Members
1941		2229
1942	=over 4	2230	=over 4
1943		2231
…		…
1945		2233
1946	=item ev_check_init (ev_check *, callback)	2234	=item ev_check_init (ev_check *, callback)
1947		2235
1948	Initialises and configures the prepare or check watcher - they have no	2236	Initialises and configures the prepare or check watcher - they have no
1949	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2237	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1950	macros, but using them is utterly, utterly and completely pointless.	2238	macros, but using them is utterly, utterly, utterly and completely
		2239	pointless.
1951		2240
1952	=back	2241	=back
1953		2242
1954	=head3 Examples	2243	=head3 Examples
1955		2244
…		…
1968		2257
1969	static ev_io iow [nfd];	2258	static ev_io iow [nfd];
1970	static ev_timer tw;	2259	static ev_timer tw;
1971		2260
1972	static void	2261	static void
1973	io_cb (ev_loop *loop, ev_io *w, int revents)	2262	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1974	{	2263	{
1975	}	2264	}
1976		2265
1977	// create io watchers for each fd and a timer before blocking	2266	// create io watchers for each fd and a timer before blocking
1978	static void	2267	static void
1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2268	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1980	{	2269	{
1981	int timeout = 3600000;	2270	int timeout = 3600000;
1982	struct pollfd fds [nfd];	2271	struct pollfd fds [nfd];
1983	// actual code will need to loop here and realloc etc.	2272	// actual code will need to loop here and realloc etc.
1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2273	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
1999	}	2288	}
2000	}	2289	}
2001		2290
2002	// stop all watchers after blocking	2291	// stop all watchers after blocking
2003	static void	2292	static void
2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2293	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2005	{	2294	{
2006	ev_timer_stop (loop, &tw);	2295	ev_timer_stop (loop, &tw);
2007		2296
2008	for (int i = 0; i < nfd; ++i)	2297	for (int i = 0; i < nfd; ++i)
2009	{	2298	{
…		…
2048	}	2337	}
2049		2338
2050	// do not ever call adns_afterpoll	2339	// do not ever call adns_afterpoll
2051		2340
2052	Method 4: Do not use a prepare or check watcher because the module you	2341	Method 4: Do not use a prepare or check watcher because the module you
2053	want to embed is too inflexible to support it. Instead, you can override	2342	want to embed is not flexible enough to support it. Instead, you can
2054	their poll function. The drawback with this solution is that the main	2343	override their poll function. The drawback with this solution is that the
2055	loop is now no longer controllable by EV. The C<Glib::EV> module does	2344	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2056	this.	2345	this approach, effectively embedding EV as a client into the horrible
		2346	libglib event loop.
2057		2347
2058	static gint	2348	static gint
2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2349	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2060	{	2350	{
2061	int got_events = 0;	2351	int got_events = 0;
…		…
2092	prioritise I/O.	2382	prioritise I/O.
2093		2383
2094	As an example for a bug workaround, the kqueue backend might only support	2384	As an example for a bug workaround, the kqueue backend might only support
2095	sockets on some platform, so it is unusable as generic backend, but you	2385	sockets on some platform, so it is unusable as generic backend, but you
2096	still want to make use of it because you have many sockets and it scales	2386	still want to make use of it because you have many sockets and it scales
2097	so nicely. In this case, you would create a kqueue-based loop and embed it	2387	so nicely. In this case, you would create a kqueue-based loop and embed
2098	into your default loop (which might use e.g. poll). Overall operation will	2388	it into your default loop (which might use e.g. poll). Overall operation
2099	be a bit slower because first libev has to poll and then call kevent, but	2389	will be a bit slower because first libev has to call C<poll> and then
2100	at least you can use both at what they are best.	2390	C<kevent>, but at least you can use both mechanisms for what they are
		2391	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2101		2392
2102	As for prioritising I/O: rarely you have the case where some fds have	2393	As for prioritising I/O: under rare circumstances you have the case where
2103	to be watched and handled very quickly (with low latency), and even	2394	some fds have to be watched and handled very quickly (with low latency),
2104	priorities and idle watchers might have too much overhead. In this case	2395	and even priorities and idle watchers might have too much overhead. In
2105	you would put all the high priority stuff in one loop and all the rest in	2396	this case you would put all the high priority stuff in one loop and all
2106	a second one, and embed the second one in the first.	2397	the rest in a second one, and embed the second one in the first.
2107		2398
2108	As long as the watcher is active, the callback will be invoked every time	2399	As long as the watcher is active, the callback will be invoked every time
2109	there might be events pending in the embedded loop. The callback must then	2400	there might be events pending in the embedded loop. The callback must then
2110	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2401	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2111	their callbacks (you could also start an idle watcher to give the embedded	2402	their callbacks (you could also start an idle watcher to give the embedded
…		…
2119	interested in that.	2410	interested in that.
2120		2411
2121	Also, there have not currently been made special provisions for forking:	2412	Also, there have not currently been made special provisions for forking:
2122	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2413	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2123	but you will also have to stop and restart any C<ev_embed> watchers	2414	but you will also have to stop and restart any C<ev_embed> watchers
2124	yourself.	2415	yourself - but you can use a fork watcher to handle this automatically,
		2416	and future versions of libev might do just that.
2125		2417
2126	Unfortunately, not all backends are embeddable, only the ones returned by	2418	Unfortunately, not all backends are embeddable: only the ones returned by
2127	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2419	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2128	portable one.	2420	portable one.
2129		2421
2130	So when you want to use this feature you will always have to be prepared	2422	So when you want to use this feature you will always have to be prepared
2131	that you cannot get an embeddable loop. The recommended way to get around	2423	that you cannot get an embeddable loop. The recommended way to get around
2132	this is to have a separate variables for your embeddable loop, try to	2424	this is to have a separate variables for your embeddable loop, try to
2133	create it, and if that fails, use the normal loop for everything.	2425	create it, and if that fails, use the normal loop for everything.
		2426
		2427	=head3 C<ev_embed> and fork
		2428
		2429	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2430	automatically be applied to the embedded loop as well, so no special
		2431	fork handling is required in that case. When the watcher is not running,
		2432	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2433	as applicable.
2134		2434
2135	=head3 Watcher-Specific Functions and Data Members	2435	=head3 Watcher-Specific Functions and Data Members
2136		2436
2137	=over 4	2437	=over 4
2138		2438
…		…
2166	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2466	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2167	used).	2467	used).
2168		2468
2169	struct ev_loop *loop_hi = ev_default_init (0);	2469	struct ev_loop *loop_hi = ev_default_init (0);
2170	struct ev_loop *loop_lo = 0;	2470	struct ev_loop *loop_lo = 0;
2171	struct ev_embed embed;	2471	ev_embed embed;
2172		2472
2173	// see if there is a chance of getting one that works	2473	// see if there is a chance of getting one that works
2174	// (remember that a flags value of 0 means autodetection)	2474	// (remember that a flags value of 0 means autodetection)
2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2475	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2476	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2190	kqueue implementation). Store the kqueue/socket-only event loop in	2490	kqueue implementation). Store the kqueue/socket-only event loop in
2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2491	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2192		2492
2193	struct ev_loop *loop = ev_default_init (0);	2493	struct ev_loop *loop = ev_default_init (0);
2194	struct ev_loop *loop_socket = 0;	2494	struct ev_loop *loop_socket = 0;
2195	struct ev_embed embed;	2495	ev_embed embed;
2196		2496
2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2497	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2498	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2199	{	2499	{
2200	ev_embed_init (&embed, 0, loop_socket);	2500	ev_embed_init (&embed, 0, loop_socket);
…		…
2256	is that the author does not know of a simple (or any) algorithm for a	2556	is that the author does not know of a simple (or any) algorithm for a
2257	multiple-writer-single-reader queue that works in all cases and doesn't	2557	multiple-writer-single-reader queue that works in all cases and doesn't
2258	need elaborate support such as pthreads.	2558	need elaborate support such as pthreads.
2259		2559
2260	That means that if you want to queue data, you have to provide your own	2560	That means that if you want to queue data, you have to provide your own
2261	queue. But at least I can tell you would implement locking around your	2561	queue. But at least I can tell you how to implement locking around your
2262	queue:	2562	queue:
2263		2563
2264	=over 4	2564	=over 4
2265		2565
2266	=item queueing from a signal handler context	2566	=item queueing from a signal handler context
2267		2567
2268	To implement race-free queueing, you simply add to the queue in the signal	2568	To implement race-free queueing, you simply add to the queue in the signal
2269	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2569	handler but you block the signal handler in the watcher callback. Here is
2270	some fictitious SIGUSR1 handler:	2570	an example that does that for some fictitious SIGUSR1 handler:
2271		2571
2272	static ev_async mysig;	2572	static ev_async mysig;
2273		2573
2274	static void	2574	static void
2275	sigusr1_handler (void)	2575	sigusr1_handler (void)
…		…
2342		2642
2343	=item ev_async_init (ev_async *, callback)	2643	=item ev_async_init (ev_async *, callback)
2344		2644
2345	Initialises and configures the async watcher - it has no parameters of any	2645	Initialises and configures the async watcher - it has no parameters of any
2346	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2646	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2347	believe me.	2647	trust me.
2348		2648
2349	=item ev_async_send (loop, ev_async *)	2649	=item ev_async_send (loop, ev_async *)
2350		2650
2351	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2651	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2352	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2652	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2353	C<ev_feed_event>, this call is safe to do in other threads, signal or	2653	C<ev_feed_event>, this call is safe to do from other threads, signal or
2354	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2654	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2355	section below on what exactly this means).	2655	section below on what exactly this means).
2356		2656
2357	This call incurs the overhead of a system call only once per loop iteration,	2657	This call incurs the overhead of a system call only once per loop iteration,
2358	so while the overhead might be noticeable, it doesn't apply to repeated	2658	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2382	=over 4	2682	=over 4
2383		2683
2384	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2684	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2385		2685
2386	This function combines a simple timer and an I/O watcher, calls your	2686	This function combines a simple timer and an I/O watcher, calls your
2387	callback on whichever event happens first and automatically stop both	2687	callback on whichever event happens first and automatically stops both
2388	watchers. This is useful if you want to wait for a single event on an fd	2688	watchers. This is useful if you want to wait for a single event on an fd
2389	or timeout without having to allocate/configure/start/stop/free one or	2689	or timeout without having to allocate/configure/start/stop/free one or
2390	more watchers yourself.	2690	more watchers yourself.
2391		2691
2392	If C<fd> is less than 0, then no I/O watcher will be started and events	2692	If C<fd> is less than 0, then no I/O watcher will be started and the
2393	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2693	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2394	C<events> set will be created and started.	2694	the given C<fd> and C<events> set will be created and started.
2395		2695
2396	If C<timeout> is less than 0, then no timeout watcher will be	2696	If C<timeout> is less than 0, then no timeout watcher will be
2397	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2697	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2398	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2698	repeat = 0) will be started. C<0> is a valid timeout.
2399	dubious value.
2400		2699
2401	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2700	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2402	passed an C<revents> set like normal event callbacks (a combination of	2701	passed an C<revents> set like normal event callbacks (a combination of
2403	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2702	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2404	value passed to C<ev_once>:	2703	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2704	a timeout and an io event at the same time - you probably should give io
		2705	events precedence.
		2706
		2707	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2405		2708
2406	static void stdin_ready (int revents, void *arg)	2709	static void stdin_ready (int revents, void *arg)
2407	{	2710	{
		2711	if (revents & EV_READ)
		2712	/* stdin might have data for us, joy! */;
2408	if (revents & EV_TIMEOUT)	2713	else if (revents & EV_TIMEOUT)
2409	/* doh, nothing entered */;	2714	/* doh, nothing entered */;
2410	else if (revents & EV_READ)
2411	/* stdin might have data for us, joy! */;
2412	}	2715	}
2413		2716
2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2717	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2415		2718
2416	=item ev_feed_event (ev_loop *, watcher *, int revents)	2719	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2417		2720
2418	Feeds the given event set into the event loop, as if the specified event	2721	Feeds the given event set into the event loop, as if the specified event
2419	had happened for the specified watcher (which must be a pointer to an	2722	had happened for the specified watcher (which must be a pointer to an
2420	initialised but not necessarily started event watcher).	2723	initialised but not necessarily started event watcher).
2421		2724
2422	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2725	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2423		2726
2424	Feed an event on the given fd, as if a file descriptor backend detected	2727	Feed an event on the given fd, as if a file descriptor backend detected
2425	the given events it.	2728	the given events it.
2426		2729
2427	=item ev_feed_signal_event (ev_loop *loop, int signum)	2730	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2428		2731
2429	Feed an event as if the given signal occurred (C<loop> must be the default	2732	Feed an event as if the given signal occurred (C<loop> must be the default
2430	loop!).	2733	loop!).
2431		2734
2432	=back	2735	=back
…		…
2564		2867
2565	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2868	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2566		2869
2567	See the method-C<set> above for more details.	2870	See the method-C<set> above for more details.
2568		2871
2569	Example:	2872	Example: Use a plain function as callback.
2570		2873
2571	static void io_cb (ev::io &w, int revents) { }	2874	static void io_cb (ev::io &w, int revents) { }
2572	iow.set <io_cb> ();	2875	iow.set <io_cb> ();
2573		2876
2574	=item w->set (struct ev_loop *)	2877	=item w->set (struct ev_loop *)
…		…
2612	Example: Define a class with an IO and idle watcher, start one of them in	2915	Example: Define a class with an IO and idle watcher, start one of them in
2613	the constructor.	2916	the constructor.
2614		2917
2615	class myclass	2918	class myclass
2616	{	2919	{
2617	ev::io io; void io_cb (ev::io &w, int revents);	2920	ev::io io ; void io_cb (ev::io &w, int revents);
2618	ev:idle idle void idle_cb (ev::idle &w, int revents);	2921	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2619		2922
2620	myclass (int fd)	2923	myclass (int fd)
2621	{	2924	{
2622	io .set <myclass, &myclass::io_cb > (this);	2925	io .set <myclass, &myclass::io_cb > (this);
2623	idle.set <myclass, &myclass::idle_cb> (this);	2926	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2639	=item Perl	2942	=item Perl
2640		2943
2641	The EV module implements the full libev API and is actually used to test	2944	The EV module implements the full libev API and is actually used to test
2642	libev. EV is developed together with libev. Apart from the EV core module,	2945	libev. EV is developed together with libev. Apart from the EV core module,
2643	there are additional modules that implement libev-compatible interfaces	2946	there are additional modules that implement libev-compatible interfaces
2644	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2947	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2645	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2948	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2949	and C<EV::Glib>).
2646		2950
2647	It can be found and installed via CPAN, its homepage is at	2951	It can be found and installed via CPAN, its homepage is at
2648	L<http://software.schmorp.de/pkg/EV>.	2952	L<http://software.schmorp.de/pkg/EV>.
2649		2953
2650	=item Python	2954	=item Python
…		…
2666	=item D	2970	=item D
2667		2971
2668	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2972	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2669	be found at L<http://proj.llucax.com.ar/wiki/evd>.	2973	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2670		2974
		2975	=item Ocaml
		2976
		2977	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2978	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2979
2671	=back	2980	=back
2672		2981
2673		2982
2674	=head1 MACRO MAGIC	2983	=head1 MACRO MAGIC
2675		2984
…		…
2829		3138
2830	=head2 PREPROCESSOR SYMBOLS/MACROS	3139	=head2 PREPROCESSOR SYMBOLS/MACROS
2831		3140
2832	Libev can be configured via a variety of preprocessor symbols you have to	3141	Libev can be configured via a variety of preprocessor symbols you have to
2833	define before including any of its files. The default in the absence of	3142	define before including any of its files. The default in the absence of
2834	autoconf is noted for every option.	3143	autoconf is documented for every option.
2835		3144
2836	=over 4	3145	=over 4
2837		3146
2838	=item EV_STANDALONE	3147	=item EV_STANDALONE
2839		3148
…		…
3009	When doing priority-based operations, libev usually has to linearly search	3318	When doing priority-based operations, libev usually has to linearly search
3010	all the priorities, so having many of them (hundreds) uses a lot of space	3319	all the priorities, so having many of them (hundreds) uses a lot of space
3011	and time, so using the defaults of five priorities (-2 .. +2) is usually	3320	and time, so using the defaults of five priorities (-2 .. +2) is usually
3012	fine.	3321	fine.
3013		3322
3014	If your embedding application does not need any priorities, defining these both to	3323	If your embedding application does not need any priorities, defining these
3015	C<0> will save some memory and CPU.	3324	both to C<0> will save some memory and CPU.
3016		3325
3017	=item EV_PERIODIC_ENABLE	3326	=item EV_PERIODIC_ENABLE
3018		3327
3019	If undefined or defined to be C<1>, then periodic timers are supported. If	3328	If undefined or defined to be C<1>, then periodic timers are supported. If
3020	defined to be C<0>, then they are not. Disabling them saves a few kB of	3329	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3027	code.	3336	code.
3028		3337
3029	=item EV_EMBED_ENABLE	3338	=item EV_EMBED_ENABLE
3030		3339
3031	If undefined or defined to be C<1>, then embed watchers are supported. If	3340	If undefined or defined to be C<1>, then embed watchers are supported. If
3032	defined to be C<0>, then they are not.	3341	defined to be C<0>, then they are not. Embed watchers rely on most other
		3342	watcher types, which therefore must not be disabled.
3033		3343
3034	=item EV_STAT_ENABLE	3344	=item EV_STAT_ENABLE
3035		3345
3036	If undefined or defined to be C<1>, then stat watchers are supported. If	3346	If undefined or defined to be C<1>, then stat watchers are supported. If
3037	defined to be C<0>, then they are not.	3347	defined to be C<0>, then they are not.
…		…
3069	two).	3379	two).
3070		3380
3071	=item EV_USE_4HEAP	3381	=item EV_USE_4HEAP
3072		3382
3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3383	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3074	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3384	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3075	to C<1>. The 4-heap uses more complicated (longer) code but has	3385	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3076	noticeably faster performance with many (thousands) of watchers.	3386	faster performance with many (thousands) of watchers.
3077		3387
3078	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3079	(disabled).	3389	(disabled).
3080		3390
3081	=item EV_HEAP_CACHE_AT	3391	=item EV_HEAP_CACHE_AT
3082		3392
3083	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3084	timer and periodics heap, libev can cache the timestamp (I<at>) within	3394	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3085	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3395	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3086	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3396	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3087	but avoids random read accesses on heap changes. This improves performance	3397	but avoids random read accesses on heap changes. This improves performance
3088	noticeably with with many (hundreds) of watchers.	3398	noticeably with many (hundreds) of watchers.
3089		3399
3090	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3400	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3091	(disabled).	3401	(disabled).
3092		3402
3093	=item EV_VERIFY	3403	=item EV_VERIFY
…		…
3099	called once per loop, which can slow down libev. If set to C<3>, then the	3409	called once per loop, which can slow down libev. If set to C<3>, then the
3100	verification code will be called very frequently, which will slow down	3410	verification code will be called very frequently, which will slow down
3101	libev considerably.	3411	libev considerably.
3102		3412
3103	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3413	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3104	C<0.>	3414	C<0>.
3105		3415
3106	=item EV_COMMON	3416	=item EV_COMMON
3107		3417
3108	By default, all watchers have a C<void *data> member. By redefining	3418	By default, all watchers have a C<void *data> member. By redefining
3109	this macro to a something else you can include more and other types of	3419	this macro to a something else you can include more and other types of
…		…
3126	and the way callbacks are invoked and set. Must expand to a struct member	3436	and the way callbacks are invoked and set. Must expand to a struct member
3127	definition and a statement, respectively. See the F<ev.h> header file for	3437	definition and a statement, respectively. See the F<ev.h> header file for
3128	their default definitions. One possible use for overriding these is to	3438	their default definitions. One possible use for overriding these is to
3129	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3439	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3130	method calls instead of plain function calls in C++.	3440	method calls instead of plain function calls in C++.
		3441
		3442	=back
3131		3443
3132	=head2 EXPORTED API SYMBOLS	3444	=head2 EXPORTED API SYMBOLS
3133		3445
3134	If you need to re-export the API (e.g. via a DLL) and you need a list of	3446	If you need to re-export the API (e.g. via a DLL) and you need a list of
3135	exported symbols, you can use the provided F<Symbol.*> files which list	3447	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3182	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3494	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3183		3495
3184	#include "ev_cpp.h"	3496	#include "ev_cpp.h"
3185	#include "ev.c"	3497	#include "ev.c"
3186		3498
		3499	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3187		3500
3188	=head1 THREADS AND COROUTINES	3501	=head2 THREADS AND COROUTINES
3189		3502
3190	=head2 THREADS	3503	=head3 THREADS
3191		3504
3192	Libev itself is completely thread-safe, but it uses no locking. This	3505	All libev functions are reentrant and thread-safe unless explicitly
		3506	documented otherwise, but libev implements no locking itself. This means
3193	means that you can use as many loops as you want in parallel, as long as	3507	that you can use as many loops as you want in parallel, as long as there
3194	only one thread ever calls into one libev function with the same loop	3508	are no concurrent calls into any libev function with the same loop
3195	parameter.	3509	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3510	of course): libev guarantees that different event loops share no data
		3511	structures that need any locking.
3196		3512
3197	Or put differently: calls with different loop parameters can be done in	3513	Or to put it differently: calls with different loop parameters can be done
3198	parallel from multiple threads, calls with the same loop parameter must be	3514	concurrently from multiple threads, calls with the same loop parameter
3199	done serially (but can be done from different threads, as long as only one	3515	must be done serially (but can be done from different threads, as long as
3200	thread ever is inside a call at any point in time, e.g. by using a mutex	3516	only one thread ever is inside a call at any point in time, e.g. by using
3201	per loop).	3517	a mutex per loop).
		3518
		3519	Specifically to support threads (and signal handlers), libev implements
		3520	so-called C<ev_async> watchers, which allow some limited form of
		3521	concurrency on the same event loop, namely waking it up "from the
		3522	outside".
3202		3523
3203	If you want to know which design (one loop, locking, or multiple loops	3524	If you want to know which design (one loop, locking, or multiple loops
3204	without or something else still) is best for your problem, then I cannot	3525	without or something else still) is best for your problem, then I cannot
3205	help you. I can give some generic advice however:	3526	help you, but here is some generic advice:
3206		3527
3207	=over 4	3528	=over 4
3208		3529
3209	=item * most applications have a main thread: use the default libev loop	3530	=item * most applications have a main thread: use the default libev loop
3210	in that thread, or create a separate thread running only the default loop.	3531	in that thread, or create a separate thread running only the default loop.
…		…
3222		3543
3223	Choosing a model is hard - look around, learn, know that usually you can do	3544	Choosing a model is hard - look around, learn, know that usually you can do
3224	better than you currently do :-)	3545	better than you currently do :-)
3225		3546
3226	=item * often you need to talk to some other thread which blocks in the	3547	=item * often you need to talk to some other thread which blocks in the
		3548	event loop.
		3549
3227	event loop - C<ev_async> watchers can be used to wake them up from other	3550	C<ev_async> watchers can be used to wake them up from other threads safely
3228	threads safely (or from signal contexts...).	3551	(or from signal contexts...).
		3552
		3553	An example use would be to communicate signals or other events that only
		3554	work in the default loop by registering the signal watcher with the
		3555	default loop and triggering an C<ev_async> watcher from the default loop
		3556	watcher callback into the event loop interested in the signal.
3229		3557
3230	=back	3558	=back
3231		3559
3232	=head2 COROUTINES	3560	=head3 COROUTINES
3233		3561
3234	Libev is much more accommodating to coroutines ("cooperative threads"):	3562	Libev is very accommodating to coroutines ("cooperative threads"):
3235	libev fully supports nesting calls to it's functions from different	3563	libev fully supports nesting calls to its functions from different
3236	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3564	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3237	different coroutines and switch freely between both coroutines running the	3565	different coroutines, and switch freely between both coroutines running the
3238	loop, as long as you don't confuse yourself). The only exception is that	3566	loop, as long as you don't confuse yourself). The only exception is that
3239	you must not do this from C<ev_periodic> reschedule callbacks.	3567	you must not do this from C<ev_periodic> reschedule callbacks.
3240		3568
3241	Care has been invested into making sure that libev does not keep local	3569	Care has been taken to ensure that libev does not keep local state inside
3242	state inside C<ev_loop>, and other calls do not usually allow coroutine	3570	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3243	switches.	3571	they do not clal any callbacks.
3244		3572
		3573	=head2 COMPILER WARNINGS
3245		3574
3246	=head1 COMPLEXITIES	3575	Depending on your compiler and compiler settings, you might get no or a
		3576	lot of warnings when compiling libev code. Some people are apparently
		3577	scared by this.
3247		3578
3248	In this section the complexities of (many of) the algorithms used inside	3579	However, these are unavoidable for many reasons. For one, each compiler
3249	libev will be explained. For complexity discussions about backends see the	3580	has different warnings, and each user has different tastes regarding
3250	documentation for C<ev_default_init>.	3581	warning options. "Warn-free" code therefore cannot be a goal except when
		3582	targeting a specific compiler and compiler-version.
3251		3583
3252	All of the following are about amortised time: If an array needs to be	3584	Another reason is that some compiler warnings require elaborate
3253	extended, libev needs to realloc and move the whole array, but this	3585	workarounds, or other changes to the code that make it less clear and less
3254	happens asymptotically never with higher number of elements, so O(1) might	3586	maintainable.
3255	mean it might do a lengthy realloc operation in rare cases, but on average
3256	it is much faster and asymptotically approaches constant time.
3257		3587
3258	=over 4	3588	And of course, some compiler warnings are just plain stupid, or simply
		3589	wrong (because they don't actually warn about the condition their message
		3590	seems to warn about). For example, certain older gcc versions had some
		3591	warnings that resulted an extreme number of false positives. These have
		3592	been fixed, but some people still insist on making code warn-free with
		3593	such buggy versions.
3259		3594
3260	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3595	While libev is written to generate as few warnings as possible,
		3596	"warn-free" code is not a goal, and it is recommended not to build libev
		3597	with any compiler warnings enabled unless you are prepared to cope with
		3598	them (e.g. by ignoring them). Remember that warnings are just that:
		3599	warnings, not errors, or proof of bugs.
3261		3600
3262	This means that, when you have a watcher that triggers in one hour and
3263	there are 100 watchers that would trigger before that then inserting will
3264	have to skip roughly seven (C<ld 100>) of these watchers.
3265		3601
3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3602	=head2 VALGRIND
3267		3603
3268	That means that changing a timer costs less than removing/adding them	3604	Valgrind has a special section here because it is a popular tool that is
3269	as only the relative motion in the event queue has to be paid for.	3605	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3270		3606
3271	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3607	If you think you found a bug (memory leak, uninitialised data access etc.)
		3608	in libev, then check twice: If valgrind reports something like:
3272		3609
3273	These just add the watcher into an array or at the head of a list.	3610	==2274== definitely lost: 0 bytes in 0 blocks.
		3611	==2274== possibly lost: 0 bytes in 0 blocks.
		3612	==2274== still reachable: 256 bytes in 1 blocks.
3274		3613
3275	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3614	Then there is no memory leak, just as memory accounted to global variables
		3615	is not a memleak - the memory is still being refernced, and didn't leak.
3276		3616
3277	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3617	Similarly, under some circumstances, valgrind might report kernel bugs
		3618	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3619	although an acceptable workaround has been found here), or it might be
		3620	confused.
3278		3621
3279	These watchers are stored in lists then need to be walked to find the	3622	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3280	correct watcher to remove. The lists are usually short (you don't usually	3623	make it into some kind of religion.
3281	have many watchers waiting for the same fd or signal).
3282		3624
3283	=item Finding the next timer in each loop iteration: O(1)	3625	If you are unsure about something, feel free to contact the mailing list
		3626	with the full valgrind report and an explanation on why you think this
		3627	is a bug in libev (best check the archives, too :). However, don't be
		3628	annoyed when you get a brisk "this is no bug" answer and take the chance
		3629	of learning how to interpret valgrind properly.
3284		3630
3285	By virtue of using a binary or 4-heap, the next timer is always found at a	3631	If you need, for some reason, empty reports from valgrind for your project
3286	fixed position in the storage array.	3632	I suggest using suppression lists.
3287		3633
3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3289		3634
3290	A change means an I/O watcher gets started or stopped, which requires	3635	=head1 PORTABILITY NOTES
3291	libev to recalculate its status (and possibly tell the kernel, depending
3292	on backend and whether C<ev_io_set> was used).
3293		3636
3294	=item Activating one watcher (putting it into the pending state): O(1)
3295
3296	=item Priority handling: O(number_of_priorities)
3297
3298	Priorities are implemented by allocating some space for each
3299	priority. When doing priority-based operations, libev usually has to
3300	linearly search all the priorities, but starting/stopping and activating
3301	watchers becomes O(1) w.r.t. priority handling.
3302
3303	=item Sending an ev_async: O(1)
3304
3305	=item Processing ev_async_send: O(number_of_async_watchers)
3306
3307	=item Processing signals: O(max_signal_number)
3308
3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
3310	calls in the current loop iteration. Checking for async and signal events
3311	involves iterating over all running async watchers or all signal numbers.
3312
3313	=back
3314
3315
3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3637	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3317		3638
3318	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3639	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3319	requires, and its I/O model is fundamentally incompatible with the POSIX	3640	requires, and its I/O model is fundamentally incompatible with the POSIX
3320	model. Libev still offers limited functionality on this platform in	3641	model. Libev still offers limited functionality on this platform in
3321	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3642	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3332		3653
3333	Not a libev limitation but worth mentioning: windows apparently doesn't	3654	Not a libev limitation but worth mentioning: windows apparently doesn't
3334	accept large writes: instead of resulting in a partial write, windows will	3655	accept large writes: instead of resulting in a partial write, windows will
3335	either accept everything or return C<ENOBUFS> if the buffer is too large,	3656	either accept everything or return C<ENOBUFS> if the buffer is too large,
3336	so make sure you only write small amounts into your sockets (less than a	3657	so make sure you only write small amounts into your sockets (less than a
3337	megabyte seems safe, but thsi apparently depends on the amount of memory	3658	megabyte seems safe, but this apparently depends on the amount of memory
3338	available).	3659	available).
3339		3660
3340	Due to the many, low, and arbitrary limits on the win32 platform and	3661	Due to the many, low, and arbitrary limits on the win32 platform and
3341	the abysmal performance of winsockets, using a large number of sockets	3662	the abysmal performance of winsockets, using a large number of sockets
3342	is not recommended (and not reasonable). If your program needs to use	3663	is not recommended (and not reasonable). If your program needs to use
…		…
3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3674	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3354		3675
3355	#include "ev.h"	3676	#include "ev.h"
3356		3677
3357	And compile the following F<evwrap.c> file into your project (make sure	3678	And compile the following F<evwrap.c> file into your project (make sure
3358	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3679	you do I<not> compile the F<ev.c> or any other embedded source files!):
3359		3680
3360	#include "evwrap.h"	3681	#include "evwrap.h"
3361	#include "ev.c"	3682	#include "ev.c"
3362		3683
3363	=over 4	3684	=over 4
…		…
3408	wrap all I/O functions and provide your own fd management, but the cost of	3729	wrap all I/O functions and provide your own fd management, but the cost of
3409	calling select (O(n²)) will likely make this unworkable.	3730	calling select (O(n²)) will likely make this unworkable.
3410		3731
3411	=back	3732	=back
3412		3733
3413
3414	=head1 PORTABILITY REQUIREMENTS	3734	=head2 PORTABILITY REQUIREMENTS
3415		3735
3416	In addition to a working ISO-C implementation, libev relies on a few	3736	In addition to a working ISO-C implementation and of course the
3417	additional extensions:	3737	backend-specific APIs, libev relies on a few additional extensions:
3418		3738
3419	=over 4	3739	=over 4
3420		3740
3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3741	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3422	calling conventions regardless of C<ev_watcher_type *>.	3742	calling conventions regardless of C<ev_watcher_type *>.
…		…
3428	calls them using an C<ev_watcher *> internally.	3748	calls them using an C<ev_watcher *> internally.
3429		3749
3430	=item C<sig_atomic_t volatile> must be thread-atomic as well	3750	=item C<sig_atomic_t volatile> must be thread-atomic as well
3431		3751
3432	The type C<sig_atomic_t volatile> (or whatever is defined as	3752	The type C<sig_atomic_t volatile> (or whatever is defined as
3433	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3753	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3434	threads. This is not part of the specification for C<sig_atomic_t>, but is	3754	threads. This is not part of the specification for C<sig_atomic_t>, but is
3435	believed to be sufficiently portable.	3755	believed to be sufficiently portable.
3436		3756
3437	=item C<sigprocmask> must work in a threaded environment	3757	=item C<sigprocmask> must work in a threaded environment
3438		3758
…		…
3447	except the initial one, and run the default loop in the initial thread as	3767	except the initial one, and run the default loop in the initial thread as
3448	well.	3768	well.
3449		3769
3450	=item C<long> must be large enough for common memory allocation sizes	3770	=item C<long> must be large enough for common memory allocation sizes
3451		3771
3452	To improve portability and simplify using libev, libev uses C<long>	3772	To improve portability and simplify its API, libev uses C<long> internally
3453	internally instead of C<size_t> when allocating its data structures. On	3773	instead of C<size_t> when allocating its data structures. On non-POSIX
3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3774	systems (Microsoft...) this might be unexpectedly low, but is still at
3455	is still at least 31 bits everywhere, which is enough for hundreds of	3775	least 31 bits everywhere, which is enough for hundreds of millions of
3456	millions of watchers.	3776	watchers.
3457		3777
3458	=item C<double> must hold a time value in seconds with enough accuracy	3778	=item C<double> must hold a time value in seconds with enough accuracy
3459		3779
3460	The type C<double> is used to represent timestamps. It is required to	3780	The type C<double> is used to represent timestamps. It is required to
3461	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3781	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3465	=back	3785	=back
3466		3786
3467	If you know of other additional requirements drop me a note.	3787	If you know of other additional requirements drop me a note.
3468		3788
3469		3789
3470	=head1 COMPILER WARNINGS	3790	=head1 ALGORITHMIC COMPLEXITIES
3471		3791
3472	Depending on your compiler and compiler settings, you might get no or a	3792	In this section the complexities of (many of) the algorithms used inside
3473	lot of warnings when compiling libev code. Some people are apparently	3793	libev will be documented. For complexity discussions about backends see
3474	scared by this.	3794	the documentation for C<ev_default_init>.
3475		3795
3476	However, these are unavoidable for many reasons. For one, each compiler	3796	All of the following are about amortised time: If an array needs to be
3477	has different warnings, and each user has different tastes regarding	3797	extended, libev needs to realloc and move the whole array, but this
3478	warning options. "Warn-free" code therefore cannot be a goal except when	3798	happens asymptotically rarer with higher number of elements, so O(1) might
3479	targeting a specific compiler and compiler-version.	3799	mean that libev does a lengthy realloc operation in rare cases, but on
		3800	average it is much faster and asymptotically approaches constant time.
3480		3801
3481	Another reason is that some compiler warnings require elaborate	3802	=over 4
3482	workarounds, or other changes to the code that make it less clear and less
3483	maintainable.
3484		3803
3485	And of course, some compiler warnings are just plain stupid, or simply	3804	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3486	wrong (because they don't actually warn about the condition their message
3487	seems to warn about).
3488		3805
3489	While libev is written to generate as few warnings as possible,	3806	This means that, when you have a watcher that triggers in one hour and
3490	"warn-free" code is not a goal, and it is recommended not to build libev	3807	there are 100 watchers that would trigger before that, then inserting will
3491	with any compiler warnings enabled unless you are prepared to cope with	3808	have to skip roughly seven (C<ld 100>) of these watchers.
3492	them (e.g. by ignoring them). Remember that warnings are just that:
3493	warnings, not errors, or proof of bugs.
3494		3809
		3810	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3495		3811
3496	=head1 VALGRIND	3812	That means that changing a timer costs less than removing/adding them,
		3813	as only the relative motion in the event queue has to be paid for.
3497		3814
3498	Valgrind has a special section here because it is a popular tool that is	3815	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3499	highly useful, but valgrind reports are very hard to interpret.
3500		3816
3501	If you think you found a bug (memory leak, uninitialised data access etc.)	3817	These just add the watcher into an array or at the head of a list.
3502	in libev, then check twice: If valgrind reports something like:
3503		3818
3504	==2274== definitely lost: 0 bytes in 0 blocks.	3819	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3505	==2274== possibly lost: 0 bytes in 0 blocks.
3506	==2274== still reachable: 256 bytes in 1 blocks.
3507		3820
3508	Then there is no memory leak. Similarly, under some circumstances,	3821	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3509	valgrind might report kernel bugs as if it were a bug in libev, or it
3510	might be confused (it is a very good tool, but only a tool).
3511		3822
3512	If you are unsure about something, feel free to contact the mailing list	3823	These watchers are stored in lists, so they need to be walked to find the
3513	with the full valgrind report and an explanation on why you think this is	3824	correct watcher to remove. The lists are usually short (you don't usually
3514	a bug in libev. However, don't be annoyed when you get a brisk "this is	3825	have many watchers waiting for the same fd or signal: one is typical, two
3515	no bug" answer and take the chance of learning how to interpret valgrind	3826	is rare).
3516	properly.
3517		3827
3518	If you need, for some reason, empty reports from valgrind for your project	3828	=item Finding the next timer in each loop iteration: O(1)
3519	I suggest using suppression lists.	3829
		3830	By virtue of using a binary or 4-heap, the next timer is always found at a
		3831	fixed position in the storage array.
		3832
		3833	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3834
		3835	A change means an I/O watcher gets started or stopped, which requires
		3836	libev to recalculate its status (and possibly tell the kernel, depending
		3837	on backend and whether C<ev_io_set> was used).
		3838
		3839	=item Activating one watcher (putting it into the pending state): O(1)
		3840
		3841	=item Priority handling: O(number_of_priorities)
		3842
		3843	Priorities are implemented by allocating some space for each
		3844	priority. When doing priority-based operations, libev usually has to
		3845	linearly search all the priorities, but starting/stopping and activating
		3846	watchers becomes O(1) with respect to priority handling.
		3847
		3848	=item Sending an ev_async: O(1)
		3849
		3850	=item Processing ev_async_send: O(number_of_async_watchers)
		3851
		3852	=item Processing signals: O(max_signal_number)
		3853
		3854	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3855	calls in the current loop iteration. Checking for async and signal events
		3856	involves iterating over all running async watchers or all signal numbers.
		3857
		3858	=back
3520		3859
3521		3860
3522	=head1 AUTHOR	3861	=head1 AUTHOR
3523		3862
3524	Marc Lehmann <libev@schmorp.de>.	3863	Marc Lehmann <libev@schmorp.de>.

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