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Revision 1.168 by root, Mon Jun 9 14:31:36 2008 UTC vs.
Revision 1.196 by root, Tue Oct 21 20:04:14 2008 UTC

…		…
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
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	359	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	360	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	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	362	readiness notifications you get per iteration.
363		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
		367
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		369
366	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	371	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	372	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,	373	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	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
372		379
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		381
375	For few fds, this backend is a bit little slower than poll and select,	382	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	383	but it scales phenomenally better. While poll and select usually scale
…		…
389	Please note that epoll sometimes generates spurious notifications, so you	396	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	397	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.	398	(or space) is available.
392		399
393	Best performance from this backend is achieved by not unregistering all	400	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.	401	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
396		405
397	While nominally embeddable in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	407	all kernel versions tested so far.
399		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		413
402	Kqueue deserves special mention, as at the time of this writing, it	414	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	415	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	416	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"	417	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	418	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)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
408	system like NetBSD.
409		420
410	You still can embed kqueue into a normal poll or select backend and use it	421	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	422	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.	423	the target platform). See C<ev_embed> watchers for more info.
413		424
414	It scales in the same way as the epoll backend, but the interface to the	425	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	426	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	427	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	428	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	429	two event changes per incident. Support for C<fork ()> is very bad and it
419	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
420		431
421	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
422		433
423	While nominally embeddable in other event loops, this doesn't work	434	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	435	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	436	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	437	(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	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
429		444
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		446
432	This is not implemented yet (and might never be, unless you send me an	447	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	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	461	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	462	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	464	might perform better.
450		465
451	On the positive side, ignoring the spurious readiness notifications, this	466	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
454		473
455	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
456		475
457	Try all backends (even potentially broken ones that wouldn't be tried	476	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	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		483
465	If one or more of these are or'ed into the flags value, then only these	484	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	485	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.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		487
469	The most typical usage is like this:	488	Example: This is the most typical usage.
470		489
471	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		492
474	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	494	environment settings to be taken into account:
476		495
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		497
479	Use whatever libev has to offer, but make sure that kqueue is used if	498	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	499	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):	500	private event loop and only if you know the OS supports your types of
		501	fds):
482		502
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		504
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		506
…		…
544		564
545	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
546		566
547	Like C<ev_default_fork>, but acts on an event loop created by	567	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	568	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.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
550		571
551	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
552		573
553	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
554		576
555	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
556		578
557	Returns the count of loop iterations for the loop, which is identical to	579	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	580	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	595	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	596	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	597	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).	598	event occurring (or more correctly, libev finding out about it).
577		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
578	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
579		613
580	Finally, this is it, the event handler. This function usually is called	614	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	615	after you initialised all your watchers and you want to start handling
582	events.	616	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	618	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.	619	either no event watchers are active anymore or C<ev_unloop> was called.
586		620
587	Please note that an explicit C<ev_unloop> is usually better than	621	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	622	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	624	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.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
592		627
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	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	629	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.	630	process in case there are no events and will return after one iteration of
		631	the loop.
596		632
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	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	634	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	635	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	636	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	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	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	642	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.	643	usually a better approach for this kind of thing.
604		644
605	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
606		646
607	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	662	- Queue all expired timers.
622	- Queue all outstanding periodics.	663	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	665	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	674	anymore.
634		675
635	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
638	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
639		680
640	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
641		682
642	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		687
647	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
648		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
649	=item ev_ref (loop)	692	=item ev_ref (loop)
650		693
651	=item ev_unref (loop)	694	=item ev_unref (loop)
652		695
653	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
656	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
658	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
659	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
660	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
661	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
662	libraries. Just remember to I<unref after start> and I<ref before stop>	708	libraries. Just remember to I<unref after start> and I<ref before stop>
663	(but only if the watcher wasn't active before, or was active before,	709	(but only if the watcher wasn't active before, or was active before,
664	respectively).	710	respectively).
665		711
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		726
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		728
683	These advanced functions influence the time that libev will spend waiting	729	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	730	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
686		733
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	735	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
690		738
691	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	741	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
696		744
697	By setting a higher I<io collect interval> you allow libev to spend more	745	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		750
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	755	value will not introduce any overhead in libev.
708		756
709	Many (busy) programs can usually benefit by setting the I/O collect	757	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	758	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	760	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	761	as this approaches the timing granularity of most systems.
714		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
715	=item ev_loop_verify (loop)	770	=item ev_loop_verify (loop)
716		771
717	This function only does something when C<EV_VERIFY> support has been	772	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	773	compiled in. which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	774	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
721		777
722	This can be used to catch bugs inside libev itself: under normal	778	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	779	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	780	data structures consistent.
725		781
…		…
841	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
843	problem. You best act on it by reporting the problem and somehow coping	899	problem. You best act on it by reporting the problem and somehow coping
844	with the watcher being stopped.	900	with the watcher being stopped.
845		901
846	Libev will usually signal a few "dummy" events together with an error,	902	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	903	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	904	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	905	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	906	programs, though, as the fd could already be closed and reused for another
		907	thing, so beware.
851		908
852	=back	909	=back
853		910
854	=head2 GENERIC WATCHER FUNCTIONS	911	=head2 GENERIC WATCHER FUNCTIONS
855		912
…		…
871	(or never started) and there are no pending events outstanding.	928	(or never started) and there are no pending events outstanding.
872		929
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	931	int revents)>.
875		932
		933	Example: Initialise an C<ev_io> watcher in two steps.
		934
		935	ev_io w;
		936	ev_init (&w, my_cb);
		937	ev_io_set (&w, STDIN_FILENO, EV_READ);
		938
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	939	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		940
878	This macro initialises the type-specific parts of a watcher. You need to	941	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	942	call C<ev_init> at least once before you call this macro, but you can
880	call C<ev_TYPE_set> any number of times. You must not, however, call this	943	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
882	difference to the C<ev_init> macro).	945	difference to the C<ev_init> macro).
883		946
884	Although some watcher types do not have type-specific arguments	947	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	948	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		949
		950	See C<ev_init>, above, for an example.
		951
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	952	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		953
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	954	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	955	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	956	a watcher. The same limitations apply, of course.
892		957
		958	Example: Initialise and set an C<ev_io> watcher in one step.
		959
		960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		961
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		963
895	Starts (activates) the given watcher. Only active watchers will receive	964	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	965	events. If the watcher is already active nothing will happen.
897		966
		967	Example: Start the C<ev_io> watcher that is being abused as example in this
		968	whole section.
		969
		970	ev_io_start (EV_DEFAULT_UC, &w);
		971
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		973
900	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher if active, and clears the pending status (whether
		975	the watcher was active or not).
		976
901	status. It is possible that stopped watchers are pending (for example,	977	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	978	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	979	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	980	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	981	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		982
907	=item bool ev_is_active (ev_TYPE *watcher)	983	=item bool ev_is_active (ev_TYPE *watcher)
908		984
909	Returns a true value iff the watcher is active (i.e. it has been started	985	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	986	and not yet been stopped). As long as a watcher is active you must not modify
…		…
958		1034
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1035	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1036
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1037	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1038	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1039	can deal with that fact, as both are simply passed through to the
		1040	callback.
964		1041
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1042	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1043
967	If the watcher is pending, this function returns clears its pending status	1044	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1045	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1046	watcher isn't pending it does nothing and returns C<0>.
970		1047
		1048	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1049	callback to be invoked, which can be accomplished with this function.
		1050
971	=back	1051	=back
972		1052
973		1053
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1054	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1055
976	Each watcher has, by default, a member C<void *data> that you can change	1056	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1057	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1058	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1059	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1060	member, you can also "subclass" the watcher type and provide your own
981	data:	1061	data:
982		1062
…		…
984	{	1064	{
985	struct ev_io io;	1065	struct ev_io io;
986	int otherfd;	1066	int otherfd;
987	void *somedata;	1067	void *somedata;
988	struct whatever *mostinteresting;	1068	struct whatever *mostinteresting;
989	}	1069	};
		1070
		1071	...
		1072	struct my_io w;
		1073	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1074
991	And since your callback will be called with a pointer to the watcher, you	1075	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1076	can cast it back to your own type:
993		1077
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1078	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
…		…
998	}	1082	}
999		1083
1000	More interesting and less C-conformant ways of casting your callback type	1084	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1085	instead have been omitted.
1002		1086
1003	Another common scenario is having some data structure with multiple	1087	Another common scenario is to use some data structure with multiple
1004	watchers:	1088	embedded watchers:
1005		1089
1006	struct my_biggy	1090	struct my_biggy
1007	{	1091	{
1008	int some_data;	1092	int some_data;
1009	ev_timer t1;	1093	ev_timer t1;
1010	ev_timer t2;	1094	ev_timer t2;
1011	}	1095	}
1012		1096
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1097	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1098	complicated: Either you store the address of your C<my_biggy> struct
		1099	in the C<data> member of the watcher (for woozies), or you need to use
		1100	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1101	programmers):
1015		1102
1016	#include <stddef.h>	1103	#include <stddef.h>
1017		1104
1018	static void	1105	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1106	t1_cb (EV_P_ struct ev_timer *w, int revents)
…		…
1059	In general you can register as many read and/or write event watchers per	1146	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1147	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1148	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1149	required if you know what you are doing).
1063		1150
1064	If you must do this, then force the use of a known-to-be-good backend	1151	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1152	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1153	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1154
1068	Another thing you have to watch out for is that it is quite easy to	1155	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1156	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1157	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1158	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1159	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1160	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1161	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1162	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1163
1077	If you cannot run the fd in non-blocking mode (for example you should not	1164	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1165	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1166	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1167	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1168	does this on its own, so its quite safe to use). Some people additionally
		1169	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1170	indefinitely.
		1171
		1172	But really, best use non-blocking mode.
1082		1173
1083	=head3 The special problem of disappearing file descriptors	1174	=head3 The special problem of disappearing file descriptors
1084		1175
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1176	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1177	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1178	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1179	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1180	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1181	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1182	fact, a different file descriptor.
1092		1183
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1214	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1215	C<EVBACKEND_POLL>.
1125		1216
1126	=head3 The special problem of SIGPIPE	1217	=head3 The special problem of SIGPIPE
1127		1218
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1219	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1220	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1221	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1222	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1223
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1224	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1225	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1226	somewhere, as that would have given you a big clue).
1137		1227
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1233	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1234
1145	=item ev_io_set (ev_io *, int fd, int events)	1235	=item ev_io_set (ev_io *, int fd, int events)
1146		1236
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1237	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1238	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1239	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1240
1151	=item int fd [read-only]	1241	=item int fd [read-only]
1152		1242
1153	The file descriptor being watched.	1243	The file descriptor being watched.
1154		1244
…		…
1166		1256
1167	static void	1257	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1258	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1169	{	1259	{
1170	ev_io_stop (loop, w);	1260	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1261	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1262	}
1173		1263
1174	...	1264	...
1175	struct ev_loop *loop = ev_default_init (0);	1265	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1266	struct ev_io stdin_readable;
…		…
1184	Timer watchers are simple relative timers that generate an event after a	1274	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1275	given time, and optionally repeating in regular intervals after that.
1186		1276
1187	The timers are based on real time, that is, if you register an event that	1277	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1278	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1279	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1280	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1281	monotonic clock option helps a lot here).
		1282
		1283	The callback is guaranteed to be invoked only I<after> its timeout has
		1284	passed, but if multiple timers become ready during the same loop iteration
		1285	then order of execution is undefined.
		1286
		1287	=head3 The special problem of time updates
		1288
		1289	Establishing the current time is a costly operation (it usually takes at
		1290	least two system calls): EV therefore updates its idea of the current
		1291	time only before and after C<ev_loop> collects new events, which causes a
		1292	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1293	lots of events in one iteration.
1192		1294
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1295	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1296	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1297	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1298	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1299	timeout on the current time, use something like this to adjust for this:
1198		1300
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1301	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1302
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1303	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1304	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1305	()>.
1204		1306
1205	=head3 Watcher-Specific Functions and Data Members	1307	=head3 Watcher-Specific Functions and Data Members
1206		1308
1207	=over 4	1309	=over 4
1208		1310
…		…
1257	ev_timer_again (loop, timer);	1359	ev_timer_again (loop, timer);
1258		1360
1259	This is more slightly efficient then stopping/starting the timer each time	1361	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.	1362	you want to modify its timeout value.
1261		1363
		1364	Note, however, that it is often even more efficient to remember the
		1365	time of the last activity and let the timer time-out naturally. In the
		1366	callback, you then check whether the time-out is real, or, if there was
		1367	some activity, you reschedule the watcher to time-out in "last_activity +
		1368	timeout - ev_now ()" seconds.
		1369
1262	=item ev_tstamp repeat [read-write]	1370	=item ev_tstamp repeat [read-write]
1263		1371
1264	The current C<repeat> value. Will be used each time the watcher times out	1372	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1373	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1374	which is also when any modifications are taken into account.
1267		1375
1268	=back	1376	=back
1269		1377
1270	=head3 Examples	1378	=head3 Examples
…		…
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger	1422	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).	1423	roughly 10 seconds later as it uses a relative timeout).
1316		1424
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1425	C<ev_periodic>s can also be used to implement vastly more complex timers,
1318	such as triggering an event on each "midnight, local time", or other	1426	such as triggering an event on each "midnight, local time", or other
1319	complicated, rules.	1427	complicated rules.
1320		1428
1321	As with timers, the callback is guaranteed to be invoked only when the	1429	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1430	time (C<at>) has passed, but if multiple periodic timers become ready
1323	during the same loop iteration then order of execution is undefined.	1431	during the same loop iteration, then order of execution is undefined.
1324		1432
1325	=head3 Watcher-Specific Functions and Data Members	1433	=head3 Watcher-Specific Functions and Data Members
1326		1434
1327	=over 4	1435	=over 4
1328		1436
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1437	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1330		1438
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1439	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1332		1440
1333	Lots of arguments, lets sort it out... There are basically three modes of	1441	Lots of arguments, lets sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1442	operation, and we will explain them from simplest to most complex:
1335		1443
1336	=over 4	1444	=over 4
1337		1445
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1446	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1339		1447
1340	In this configuration the watcher triggers an event after the wall clock	1448	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1449	time C<at> has passed. It will not repeat and will not adjust when a time
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1450	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1343	run when the system time reaches or surpasses this time.	1451	only run when the system clock reaches or surpasses this time.
1344		1452
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1453	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1346		1454
1347	In this mode the watcher will always be scheduled to time out at the next	1455	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1456	C<at + N * interval> time (for some integer N, which can also be negative)
1349	and then repeat, regardless of any time jumps.	1457	and then repeat, regardless of any time jumps.
1350		1458
1351	This can be used to create timers that do not drift with respect to system	1459	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1460	system clock, for example, here is a C<ev_periodic> that triggers each
1353	the hour:	1461	hour, on the hour:
1354		1462
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1463	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1464
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1465	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1466	but only that the callback will be called when the system time shows a
…		…
1445	=back	1553	=back
1446		1554
1447	=head3 Examples	1555	=head3 Examples
1448		1556
1449	Example: Call a callback every hour, or, more precisely, whenever the	1557	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1558	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1559	potentially a lot of jitter, but good long-term stability.
1452		1560
1453	static void	1561	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1562	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1455	{	1563	{
…		…
1465	#include <math.h>	1573	#include <math.h>
1466		1574
1467	static ev_tstamp	1575	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1576	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1469	{	1577	{
1470	return fmod (now, 3600.) + 3600.;	1578	return now + (3600. - fmod (now, 3600.));
1471	}	1579	}
1472		1580
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1581	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1582
1475	Example: Call a callback every hour, starting now:	1583	Example: Call a callback every hour, starting now:
…		…
1485	Signal watchers will trigger an event when the process receives a specific	1593	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	1594	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	1595	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1596	normal event processing, like any other event.
1489		1597
		1598	If you want signals asynchronously, just use C<sigaction> as you would
		1599	do without libev and forget about sharing the signal. You can even use
		1600	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1601
1490	You can configure as many watchers as you like per signal. Only when the	1602	You can configure as many watchers as you like per signal. Only when the
1491	first watcher gets started will libev actually register a signal watcher	1603	first watcher gets started will libev actually register a signal handler
1492	with the kernel (thus it coexists with your own signal handlers as long	1604	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	1605	you don't register any with libev for the same signal). Similarly, when
1494	watcher for a signal is stopped libev will reset the signal handler to	1606	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1607	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1608
1497	If possible and supported, libev will install its handlers with	1609	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1610	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1499	interrupted. If you have a problem with system calls getting interrupted by	1611	interrupted. If you have a problem with system calls getting interrupted by
1500	signals you can block all signals in an C<ev_check> watcher and unblock	1612	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1629
1518	=back	1630	=back
1519		1631
1520	=head3 Examples	1632	=head3 Examples
1521		1633
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1634	Example: Try to exit cleanly on SIGINT.
1523		1635
1524	static void	1636	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1637	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1526	{	1638	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1639	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1640	}
1529		1641
1530	struct ev_signal signal_watcher;	1642	struct ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1644	ev_signal_start (loop, &signal_watcher);
1533		1645
1534		1646
1535	=head2 C<ev_child> - watch out for process status changes	1647	=head2 C<ev_child> - watch out for process status changes
1536		1648
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1649	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	1650	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	1651	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	1652	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	1653	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1654	forking and then immediately registering a watcher for the child is fine,
		1655	but forking and registering a watcher a few event loop iterations later is
		1656	not.
1542		1657
1543	Only the default event loop is capable of handling signals, and therefore	1658	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	1659	you can only register child watchers in the default event loop.
1545		1660
1546	=head3 Process Interaction	1661	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	1674	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	1675	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	1676	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	1677	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	1678	that, so other libev users can use C<ev_child> watchers freely.
		1679
		1680	=head3 Stopping the Child Watcher
		1681
		1682	Currently, the child watcher never gets stopped, even when the
		1683	child terminates, so normally one needs to stop the watcher in the
		1684	callback. Future versions of libev might stop the watcher automatically
		1685	when a child exit is detected.
1564		1686
1565	=head3 Watcher-Specific Functions and Data Members	1687	=head3 Watcher-Specific Functions and Data Members
1566		1688
1567	=over 4	1689	=over 4
1568		1690
…		…
1637	the stat buffer having unspecified contents.	1759	the stat buffer having unspecified contents.
1638		1760
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	1761	The path I<should> be absolute and I<must not> end in a slash. If it is
1640	relative and your working directory changes, the behaviour is undefined.	1762	relative and your working directory changes, the behaviour is undefined.
1641		1763
1642	Since there is no standard to do this, the portable implementation simply	1764	Since there is no standard kernel interface to do this, the portable
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1765	implementation simply calls C<stat (2)> regularly on the path to see if
1644	can specify a recommended polling interval for this case. If you specify	1766	it changed somehow. You can specify a recommended polling interval for
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	1767	this case. If you specify a polling interval of C<0> (highly recommended!)
1646	unspecified default> value will be used (which you can expect to be around	1768	then a I<suitable, unspecified default> value will be used (which
1647	five seconds, although this might change dynamically). Libev will also	1769	you can expect to be around five seconds, although this might change
1648	impose a minimum interval which is currently around C<0.1>, but thats	1770	dynamically). Libev will also impose a minimum interval which is currently
1649	usually overkill.	1771	around C<0.1>, but thats usually overkill.
1650		1772
1651	This watcher type is not meant for massive numbers of stat watchers,	1773	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	1774	as even with OS-supported change notifications, this can be
1653	resource-intensive.	1775	resource-intensive.
1654		1776
1655	At the time of this writing, only the Linux inotify interface is	1777	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	1778	is the Linux inotify interface (implementing kqueue support is left as
1657	reader, note, however, that the author sees no way of implementing ev_stat	1779	an exercise for the reader. Note, however, that the author sees no way
1658	semantics with kqueue). Inotify will be used to give hints only and should	1780	of implementing C<ev_stat> semantics with kqueue).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		1781
1664	=head3 ABI Issues (Largefile Support)	1782	=head3 ABI Issues (Largefile Support)
1665		1783
1666	Libev by default (unless the user overrides this) uses the default	1784	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	1785	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	1786	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	1787	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	1788	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	1789	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	1790	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	1791	most noticeably disabled with ev_stat and large file support.
1674		1792
1675	=head3 Inotify	1793	The solution for this is to lobby your distribution maker to make large
		1794	file interfaces available by default (as e.g. FreeBSD does) and not
		1795	optional. Libev cannot simply switch on large file support because it has
		1796	to exchange stat structures with application programs compiled using the
		1797	default compilation environment.
1676		1798
		1799	=head3 Inotify and Kqueue
		1800
1677	When C<inotify (7)> support has been compiled into libev (generally only	1801	When C<inotify (7)> support has been compiled into libev (generally
		1802	only available with Linux 2.6.25 or above due to bugs in earlier
1678	available on Linux) and present at runtime, it will be used to speed up	1803	implementations) and present at runtime, it will be used to speed up
1679	change detection where possible. The inotify descriptor will be created lazily	1804	change detection where possible. The inotify descriptor will be created
1680	when the first C<ev_stat> watcher is being started.	1805	lazily when the first C<ev_stat> watcher is being started.
1681		1806
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	1807	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	1808	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	1809	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	1810	there are many cases where libev has to resort to regular C<stat> polling,
		1811	but as long as the path exists, libev usually gets away without polling.
1686		1812
1687	(There is no support for kqueue, as apparently it cannot be used to	1813	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	1814	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	1815	descriptor open on the object at all times, and detecting renames, unlinks
		1816	etc. is difficult.
1690		1817
1691	=head3 The special problem of stat time resolution	1818	=head3 The special problem of stat time resolution
1692		1819
1693	The C<stat ()> system call only supports full-second resolution portably, and	1820	The C<stat ()> system call only supports full-second resolution portably, and
1694	even on systems where the resolution is higher, many file systems still	1821	even on systems where the resolution is higher, most file systems still
1695	only support whole seconds.	1822	only support whole seconds.
1696		1823
1697	That means that, if the time is the only thing that changes, you can	1824	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	1825	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	1826	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	1827	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	1828	stat data does change in other ways (e.g. file size).
1702		1829
1703	The solution to this is to delay acting on a change for slightly more	1830	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	1831	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1832	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	1833	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	1853	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	1854	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	1855	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	1856	path for as long as the watcher is active.
1730		1857
1731	The callback will receive C<EV_STAT> when a change was detected, relative	1858	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	1859	relative to the attributes at the time the watcher was started (or the
1733	was detected).	1860	last change was detected).
1734		1861
1735	=item ev_stat_stat (loop, ev_stat *)	1862	=item ev_stat_stat (loop, ev_stat *)
1736		1863
1737	Updates the stat buffer immediately with new values. If you change the	1864	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	1865	watched path in your callback, you could call this function to avoid
…		…
1821		1948
1822		1949
1823	=head2 C<ev_idle> - when you've got nothing better to do...	1950	=head2 C<ev_idle> - when you've got nothing better to do...
1824		1951
1825	Idle watchers trigger events when no other events of the same or higher	1952	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	1953	priority are pending (prepare, check and other idle watchers do not count
1827	count).	1954	as receiving "events").
1828		1955
1829	That is, as long as your process is busy handling sockets or timeouts	1956	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	1957	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	1958	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	1959	are pending), the idle watchers are being called once per event loop
…		…
1871	ev_idle_start (loop, idle_cb);	1998	ev_idle_start (loop, idle_cb);
1872		1999
1873		2000
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2001	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2002
1876	Prepare and check watchers are usually (but not always) used in tandem:	2003	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2004	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2005	afterwards.
1879		2006
1880	You I<must not> call C<ev_loop> or similar functions that enter	2007	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2008	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2011	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2012	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2013	called in pairs bracketing the blocking call.
1887		2014
1888	Their main purpose is to integrate other event mechanisms into libev and	2015	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2016	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2017	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2018	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2019	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2020	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2021	watcher).
1895		2022
1896	This is done by examining in each prepare call which file descriptors need	2023	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2024	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2025	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2026	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2027	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2028	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2029	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2030	nevertheless, because you never know, you know?).
1904		2031
1905	As another example, the Perl Coro module uses these hooks to integrate	2032	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2033	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2034	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2035	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2038	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2039	low-priority coroutines to idle/background tasks).
1913		2040
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2041	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2042	priority, to ensure that they are being run before any other watchers
		2043	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2044
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2045	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2046	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2047	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2048	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2049	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2050	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2051	others).
1923		2052
1924	=head3 Watcher-Specific Functions and Data Members	2053	=head3 Watcher-Specific Functions and Data Members
1925		2054
1926	=over 4	2055	=over 4
1927		2056
…		…
1929		2058
1930	=item ev_check_init (ev_check *, callback)	2059	=item ev_check_init (ev_check *, callback)
1931		2060
1932	Initialises and configures the prepare or check watcher - they have no	2061	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2062	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2063	macros, but using them is utterly, utterly, utterly and completely
		2064	pointless.
1935		2065
1936	=back	2066	=back
1937		2067
1938	=head3 Examples	2068	=head3 Examples
1939		2069
…		…
2032	}	2162	}
2033		2163
2034	// do not ever call adns_afterpoll	2164	// do not ever call adns_afterpoll
2035		2165
2036	Method 4: Do not use a prepare or check watcher because the module you	2166	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2167	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2168	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2169	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2170	this approach, effectively embedding EV as a client into the horrible
		2171	libglib event loop.
2041		2172
2042	static gint	2173	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2174	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2175	{
2045	int got_events = 0;	2176	int got_events = 0;
…		…
2076	prioritise I/O.	2207	prioritise I/O.
2077		2208
2078	As an example for a bug workaround, the kqueue backend might only support	2209	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2210	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2211	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2212	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2213	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2214	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2215	C<kevent>, but at least you can use both mechanisms for what they are
		2216	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2217
2086	As for prioritising I/O: rarely you have the case where some fds have	2218	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2219	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2220	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2221	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2222	the rest in a second one, and embed the second one in the first.
2091		2223
2092	As long as the watcher is active, the callback will be invoked every time	2224	As long as the watcher is active, the callback will be invoked every time
2093	there might be events pending in the embedded loop. The callback must then	2225	there might be events pending in the embedded loop. The callback must then
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2226	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2095	their callbacks (you could also start an idle watcher to give the embedded	2227	their callbacks (you could also start an idle watcher to give the embedded
…		…
2103	interested in that.	2235	interested in that.
2104		2236
2105	Also, there have not currently been made special provisions for forking:	2237	Also, there have not currently been made special provisions for forking:
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2238	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2107	but you will also have to stop and restart any C<ev_embed> watchers	2239	but you will also have to stop and restart any C<ev_embed> watchers
2108	yourself.	2240	yourself - but you can use a fork watcher to handle this automatically,
		2241	and future versions of libev might do just that.
2109		2242
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2243	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2244	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2245	portable one.
2113		2246
2114	So when you want to use this feature you will always have to be prepared	2247	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2248	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2249	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2250	create it, and if that fails, use the normal loop for everything.
		2251
		2252	=head3 C<ev_embed> and fork
		2253
		2254	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2255	automatically be applied to the embedded loop as well, so no special
		2256	fork handling is required in that case. When the watcher is not running,
		2257	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2258	as applicable.
2118		2259
2119	=head3 Watcher-Specific Functions and Data Members	2260	=head3 Watcher-Specific Functions and Data Members
2120		2261
2121	=over 4	2262	=over 4
2122		2263
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2381	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2382	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2383	need elaborate support such as pthreads.
2243		2384
2244	That means that if you want to queue data, you have to provide your own	2385	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2386	queue. But at least I can tell you how to implement locking around your
2246	queue:	2387	queue:
2247		2388
2248	=over 4	2389	=over 4
2249		2390
2250	=item queueing from a signal handler context	2391	=item queueing from a signal handler context
2251		2392
2252	To implement race-free queueing, you simply add to the queue in the signal	2393	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2394	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2395	an example that does that for some fictitious SIGUSR1 handler:
2255		2396
2256	static ev_async mysig;	2397	static ev_async mysig;
2257		2398
2258	static void	2399	static void
2259	sigusr1_handler (void)	2400	sigusr1_handler (void)
…		…
2326		2467
2327	=item ev_async_init (ev_async *, callback)	2468	=item ev_async_init (ev_async *, callback)
2328		2469
2329	Initialises and configures the async watcher - it has no parameters of any	2470	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2471	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2331	believe me.	2472	trust me.
2332		2473
2333	=item ev_async_send (loop, ev_async *)	2474	=item ev_async_send (loop, ev_async *)
2334		2475
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2476	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2477	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	2478	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2479	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2480	section below on what exactly this means).
2340		2481
2341	This call incurs the overhead of a system call only once per loop iteration,	2482	This call incurs the overhead of a system call only once per loop iteration,
2342	so while the overhead might be noticeable, it doesn't apply to repeated	2483	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2366	=over 4	2507	=over 4
2367		2508
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2509	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		2510
2370	This function combines a simple timer and an I/O watcher, calls your	2511	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	2512	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	2513	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	2514	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	2515	more watchers yourself.
2375		2516
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	2517	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2518	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	2519	the given C<fd> and C<events> set will be created and started.
2379		2520
2380	If C<timeout> is less than 0, then no timeout watcher will be	2521	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2522	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2523	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		2524
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2525	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	2526	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2527	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2528	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2529	a timeout and an io event at the same time - you probably should give io
		2530	events precedence.
		2531
		2532	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2389		2533
2390	static void stdin_ready (int revents, void *arg)	2534	static void stdin_ready (int revents, void *arg)
2391	{	2535	{
		2536	if (revents & EV_READ)
		2537	/* stdin might have data for us, joy! */;
2392	if (revents & EV_TIMEOUT)	2538	else if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;	2539	/* doh, nothing entered */;
2394	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;
2396	}	2540	}
2397		2541
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2542	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2543
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2544	=item ev_feed_event (ev_loop *, watcher *, int revents)
…		…
2548		2692
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2693	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		2694
2551	See the method-C<set> above for more details.	2695	See the method-C<set> above for more details.
2552		2696
2553	Example:	2697	Example: Use a plain function as callback.
2554		2698
2555	static void io_cb (ev::io &w, int revents) { }	2699	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	2700	iow.set <io_cb> ();
2557		2701
2558	=item w->set (struct ev_loop *)	2702	=item w->set (struct ev_loop *)
…		…
2596	Example: Define a class with an IO and idle watcher, start one of them in	2740	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	2741	the constructor.
2598		2742
2599	class myclass	2743	class myclass
2600	{	2744	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	2745	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	2746	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		2747
2604	myclass (int fd)	2748	myclass (int fd)
2605	{	2749	{
2606	io .set <myclass, &myclass::io_cb > (this);	2750	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	2751	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2623	=item Perl	2767	=item Perl
2624		2768
2625	The EV module implements the full libev API and is actually used to test	2769	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	2770	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	2771	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2772	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2773	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2774	and C<EV::Glib>).
2630		2775
2631	It can be found and installed via CPAN, its homepage is at	2776	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	2777	L<http://software.schmorp.de/pkg/EV>.
2633		2778
2634	=item Python	2779	=item Python
…		…
2648	L<http://rev.rubyforge.org/>.	2793	L<http://rev.rubyforge.org/>.
2649		2794
2650	=item D	2795	=item D
2651		2796
2652	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2797	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2653	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2798	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2654		2799
2655	=back	2800	=back
2656		2801
2657		2802
2658	=head1 MACRO MAGIC	2803	=head1 MACRO MAGIC
…		…
2813		2958
2814	=head2 PREPROCESSOR SYMBOLS/MACROS	2959	=head2 PREPROCESSOR SYMBOLS/MACROS
2815		2960
2816	Libev can be configured via a variety of preprocessor symbols you have to	2961	Libev can be configured via a variety of preprocessor symbols you have to
2817	define before including any of its files. The default in the absence of	2962	define before including any of its files. The default in the absence of
2818	autoconf is noted for every option.	2963	autoconf is documented for every option.
2819		2964
2820	=over 4	2965	=over 4
2821		2966
2822	=item EV_STANDALONE	2967	=item EV_STANDALONE
2823		2968
…		…
2993	When doing priority-based operations, libev usually has to linearly search	3138	When doing priority-based operations, libev usually has to linearly search
2994	all the priorities, so having many of them (hundreds) uses a lot of space	3139	all the priorities, so having many of them (hundreds) uses a lot of space
2995	and time, so using the defaults of five priorities (-2 .. +2) is usually	3140	and time, so using the defaults of five priorities (-2 .. +2) is usually
2996	fine.	3141	fine.
2997		3142
2998	If your embedding application does not need any priorities, defining these both to	3143	If your embedding application does not need any priorities, defining these
2999	C<0> will save some memory and CPU.	3144	both to C<0> will save some memory and CPU.
3000		3145
3001	=item EV_PERIODIC_ENABLE	3146	=item EV_PERIODIC_ENABLE
3002		3147
3003	If undefined or defined to be C<1>, then periodic timers are supported. If	3148	If undefined or defined to be C<1>, then periodic timers are supported. If
3004	defined to be C<0>, then they are not. Disabling them saves a few kB of	3149	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3011	code.	3156	code.
3012		3157
3013	=item EV_EMBED_ENABLE	3158	=item EV_EMBED_ENABLE
3014		3159
3015	If undefined or defined to be C<1>, then embed watchers are supported. If	3160	If undefined or defined to be C<1>, then embed watchers are supported. If
3016	defined to be C<0>, then they are not.	3161	defined to be C<0>, then they are not. Embed watchers rely on most other
		3162	watcher types, which therefore must not be disabled.
3017		3163
3018	=item EV_STAT_ENABLE	3164	=item EV_STAT_ENABLE
3019		3165
3020	If undefined or defined to be C<1>, then stat watchers are supported. If	3166	If undefined or defined to be C<1>, then stat watchers are supported. If
3021	defined to be C<0>, then they are not.	3167	defined to be C<0>, then they are not.
…		…
3053	two).	3199	two).
3054		3200
3055	=item EV_USE_4HEAP	3201	=item EV_USE_4HEAP
3056		3202
3057	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3203	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3058	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3204	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3059	to C<1>. The 4-heap uses more complicated (longer) code but has	3205	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3060	noticeably faster performance with many (thousands) of watchers.	3206	faster performance with many (thousands) of watchers.
3061		3207
3062	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3208	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3063	(disabled).	3209	(disabled).
3064		3210
3065	=item EV_HEAP_CACHE_AT	3211	=item EV_HEAP_CACHE_AT
3066		3212
3067	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3213	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3068	timer and periodics heap, libev can cache the timestamp (I<at>) within	3214	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3069	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3215	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3070	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3216	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3071	but avoids random read accesses on heap changes. This improves performance	3217	but avoids random read accesses on heap changes. This improves performance
3072	noticeably with with many (hundreds) of watchers.	3218	noticeably with many (hundreds) of watchers.
3073		3219
3074	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3220	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3075	(disabled).	3221	(disabled).
3076		3222
3077	=item EV_VERIFY	3223	=item EV_VERIFY
…		…
3083	called once per loop, which can slow down libev. If set to C<3>, then the	3229	called once per loop, which can slow down libev. If set to C<3>, then the
3084	verification code will be called very frequently, which will slow down	3230	verification code will be called very frequently, which will slow down
3085	libev considerably.	3231	libev considerably.
3086		3232
3087	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3233	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3088	C<0.>	3234	C<0>.
3089		3235
3090	=item EV_COMMON	3236	=item EV_COMMON
3091		3237
3092	By default, all watchers have a C<void *data> member. By redefining	3238	By default, all watchers have a C<void *data> member. By redefining
3093	this macro to a something else you can include more and other types of	3239	this macro to a something else you can include more and other types of
…		…
3110	and the way callbacks are invoked and set. Must expand to a struct member	3256	and the way callbacks are invoked and set. Must expand to a struct member
3111	definition and a statement, respectively. See the F<ev.h> header file for	3257	definition and a statement, respectively. See the F<ev.h> header file for
3112	their default definitions. One possible use for overriding these is to	3258	their default definitions. One possible use for overriding these is to
3113	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3259	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3114	method calls instead of plain function calls in C++.	3260	method calls instead of plain function calls in C++.
		3261
		3262	=back
3115		3263
3116	=head2 EXPORTED API SYMBOLS	3264	=head2 EXPORTED API SYMBOLS
3117		3265
3118	If you need to re-export the API (e.g. via a DLL) and you need a list of	3266	If you need to re-export the API (e.g. via a DLL) and you need a list of
3119	exported symbols, you can use the provided F<Symbol.*> files which list	3267	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3166	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3314	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3167		3315
3168	#include "ev_cpp.h"	3316	#include "ev_cpp.h"
3169	#include "ev.c"	3317	#include "ev.c"
3170		3318
		3319	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3171		3320
3172	=head1 THREADS AND COROUTINES	3321	=head2 THREADS AND COROUTINES
3173		3322
3174	=head2 THREADS	3323	=head3 THREADS
3175		3324
3176	Libev itself is completely thread-safe, but it uses no locking. This	3325	All libev functions are reentrant and thread-safe unless explicitly
		3326	documented otherwise, but libev implements no locking itself. This means
3177	means that you can use as many loops as you want in parallel, as long as	3327	that you can use as many loops as you want in parallel, as long as there
3178	only one thread ever calls into one libev function with the same loop	3328	are no concurrent calls into any libev function with the same loop
3179	parameter.	3329	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3330	of course): libev guarantees that different event loops share no data
		3331	structures that need any locking.
3180		3332
3181	Or put differently: calls with different loop parameters can be done in	3333	Or to put it differently: calls with different loop parameters can be done
3182	parallel from multiple threads, calls with the same loop parameter must be	3334	concurrently from multiple threads, calls with the same loop parameter
3183	done serially (but can be done from different threads, as long as only one	3335	must be done serially (but can be done from different threads, as long as
3184	thread ever is inside a call at any point in time, e.g. by using a mutex	3336	only one thread ever is inside a call at any point in time, e.g. by using
3185	per loop).	3337	a mutex per loop).
3186		3338
3187	If you want to know which design is best for your problem, then I cannot	3339	Specifically to support threads (and signal handlers), libev implements
		3340	so-called C<ev_async> watchers, which allow some limited form of
		3341	concurrency on the same event loop, namely waking it up "from the
		3342	outside".
		3343
		3344	If you want to know which design (one loop, locking, or multiple loops
		3345	without or something else still) is best for your problem, then I cannot
3188	help you but by giving some generic advice:	3346	help you, but here is some generic advice:
3189		3347
3190	=over 4	3348	=over 4
3191		3349
3192	=item * most applications have a main thread: use the default libev loop	3350	=item * most applications have a main thread: use the default libev loop
3193	in that thread, or create a separate thread running only the default loop.	3351	in that thread, or create a separate thread running only the default loop.
…		…
3205		3363
3206	Choosing a model is hard - look around, learn, know that usually you can do	3364	Choosing a model is hard - look around, learn, know that usually you can do
3207	better than you currently do :-)	3365	better than you currently do :-)
3208		3366
3209	=item * often you need to talk to some other thread which blocks in the	3367	=item * often you need to talk to some other thread which blocks in the
		3368	event loop.
		3369
3210	event loop - C<ev_async> watchers can be used to wake them up from other	3370	C<ev_async> watchers can be used to wake them up from other threads safely
3211	threads safely (or from signal contexts...).	3371	(or from signal contexts...).
		3372
		3373	An example use would be to communicate signals or other events that only
		3374	work in the default loop by registering the signal watcher with the
		3375	default loop and triggering an C<ev_async> watcher from the default loop
		3376	watcher callback into the event loop interested in the signal.
3212		3377
3213	=back	3378	=back
3214		3379
3215	=head2 COROUTINES	3380	=head3 COROUTINES
3216		3381
3217	Libev is much more accommodating to coroutines ("cooperative threads"):	3382	Libev is very accommodating to coroutines ("cooperative threads"):
3218	libev fully supports nesting calls to it's functions from different	3383	libev fully supports nesting calls to its functions from different
3219	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3384	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3220	different coroutines and switch freely between both coroutines running the	3385	different coroutines, and switch freely between both coroutines running the
3221	loop, as long as you don't confuse yourself). The only exception is that	3386	loop, as long as you don't confuse yourself). The only exception is that
3222	you must not do this from C<ev_periodic> reschedule callbacks.	3387	you must not do this from C<ev_periodic> reschedule callbacks.
3223		3388
3224	Care has been invested into making sure that libev does not keep local	3389	Care has been taken to ensure that libev does not keep local state inside
3225	state inside C<ev_loop>, and other calls do not usually allow coroutine	3390	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3226	switches.	3391	they do not clal any callbacks.
3227		3392
		3393	=head2 COMPILER WARNINGS
3228		3394
3229	=head1 COMPLEXITIES	3395	Depending on your compiler and compiler settings, you might get no or a
		3396	lot of warnings when compiling libev code. Some people are apparently
		3397	scared by this.
3230		3398
3231	In this section the complexities of (many of) the algorithms used inside	3399	However, these are unavoidable for many reasons. For one, each compiler
3232	libev will be explained. For complexity discussions about backends see the	3400	has different warnings, and each user has different tastes regarding
3233	documentation for C<ev_default_init>.	3401	warning options. "Warn-free" code therefore cannot be a goal except when
		3402	targeting a specific compiler and compiler-version.
3234		3403
3235	All of the following are about amortised time: If an array needs to be	3404	Another reason is that some compiler warnings require elaborate
3236	extended, libev needs to realloc and move the whole array, but this	3405	workarounds, or other changes to the code that make it less clear and less
3237	happens asymptotically never with higher number of elements, so O(1) might	3406	maintainable.
3238	mean it might do a lengthy realloc operation in rare cases, but on average
3239	it is much faster and asymptotically approaches constant time.
3240		3407
3241	=over 4	3408	And of course, some compiler warnings are just plain stupid, or simply
		3409	wrong (because they don't actually warn about the condition their message
		3410	seems to warn about). For example, certain older gcc versions had some
		3411	warnings that resulted an extreme number of false positives. These have
		3412	been fixed, but some people still insist on making code warn-free with
		3413	such buggy versions.
3242		3414
3243	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3415	While libev is written to generate as few warnings as possible,
		3416	"warn-free" code is not a goal, and it is recommended not to build libev
		3417	with any compiler warnings enabled unless you are prepared to cope with
		3418	them (e.g. by ignoring them). Remember that warnings are just that:
		3419	warnings, not errors, or proof of bugs.
3244		3420
3245	This means that, when you have a watcher that triggers in one hour and
3246	there are 100 watchers that would trigger before that then inserting will
3247	have to skip roughly seven (C<ld 100>) of these watchers.
3248		3421
3249	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3422	=head2 VALGRIND
3250		3423
3251	That means that changing a timer costs less than removing/adding them	3424	Valgrind has a special section here because it is a popular tool that is
3252	as only the relative motion in the event queue has to be paid for.	3425	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3253		3426
3254	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3427	If you think you found a bug (memory leak, uninitialised data access etc.)
		3428	in libev, then check twice: If valgrind reports something like:
3255		3429
3256	These just add the watcher into an array or at the head of a list.	3430	==2274== definitely lost: 0 bytes in 0 blocks.
		3431	==2274== possibly lost: 0 bytes in 0 blocks.
		3432	==2274== still reachable: 256 bytes in 1 blocks.
3257		3433
3258	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3434	Then there is no memory leak, just as memory accounted to global variables
		3435	is not a memleak - the memory is still being refernced, and didn't leak.
3259		3436
3260	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3437	Similarly, under some circumstances, valgrind might report kernel bugs
		3438	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3439	although an acceptable workaround has been found here), or it might be
		3440	confused.
3261		3441
3262	These watchers are stored in lists then need to be walked to find the	3442	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3263	correct watcher to remove. The lists are usually short (you don't usually	3443	make it into some kind of religion.
3264	have many watchers waiting for the same fd or signal).
3265		3444
3266	=item Finding the next timer in each loop iteration: O(1)	3445	If you are unsure about something, feel free to contact the mailing list
		3446	with the full valgrind report and an explanation on why you think this
		3447	is a bug in libev (best check the archives, too :). However, don't be
		3448	annoyed when you get a brisk "this is no bug" answer and take the chance
		3449	of learning how to interpret valgrind properly.
3267		3450
3268	By virtue of using a binary or 4-heap, the next timer is always found at a	3451	If you need, for some reason, empty reports from valgrind for your project
3269	fixed position in the storage array.	3452	I suggest using suppression lists.
3270		3453
3271	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3272		3454
3273	A change means an I/O watcher gets started or stopped, which requires	3455	=head1 PORTABILITY NOTES
3274	libev to recalculate its status (and possibly tell the kernel, depending
3275	on backend and whether C<ev_io_set> was used).
3276		3456
3277	=item Activating one watcher (putting it into the pending state): O(1)
3278
3279	=item Priority handling: O(number_of_priorities)
3280
3281	Priorities are implemented by allocating some space for each
3282	priority. When doing priority-based operations, libev usually has to
3283	linearly search all the priorities, but starting/stopping and activating
3284	watchers becomes O(1) w.r.t. priority handling.
3285
3286	=item Sending an ev_async: O(1)
3287
3288	=item Processing ev_async_send: O(number_of_async_watchers)
3289
3290	=item Processing signals: O(max_signal_number)
3291
3292	Sending involves a system call I<iff> there were no other C<ev_async_send>
3293	calls in the current loop iteration. Checking for async and signal events
3294	involves iterating over all running async watchers or all signal numbers.
3295
3296	=back
3297
3298
3299	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3457	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3300		3458
3301	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3459	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3302	requires, and its I/O model is fundamentally incompatible with the POSIX	3460	requires, and its I/O model is fundamentally incompatible with the POSIX
3303	model. Libev still offers limited functionality on this platform in	3461	model. Libev still offers limited functionality on this platform in
3304	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3462	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3315		3473
3316	Not a libev limitation but worth mentioning: windows apparently doesn't	3474	Not a libev limitation but worth mentioning: windows apparently doesn't
3317	accept large writes: instead of resulting in a partial write, windows will	3475	accept large writes: instead of resulting in a partial write, windows will
3318	either accept everything or return C<ENOBUFS> if the buffer is too large,	3476	either accept everything or return C<ENOBUFS> if the buffer is too large,
3319	so make sure you only write small amounts into your sockets (less than a	3477	so make sure you only write small amounts into your sockets (less than a
3320	megabyte seems safe, but thsi apparently depends on the amount of memory	3478	megabyte seems safe, but this apparently depends on the amount of memory
3321	available).	3479	available).
3322		3480
3323	Due to the many, low, and arbitrary limits on the win32 platform and	3481	Due to the many, low, and arbitrary limits on the win32 platform and
3324	the abysmal performance of winsockets, using a large number of sockets	3482	the abysmal performance of winsockets, using a large number of sockets
3325	is not recommended (and not reasonable). If your program needs to use	3483	is not recommended (and not reasonable). If your program needs to use
…		…
3336	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3494	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3337		3495
3338	#include "ev.h"	3496	#include "ev.h"
3339		3497
3340	And compile the following F<evwrap.c> file into your project (make sure	3498	And compile the following F<evwrap.c> file into your project (make sure
3341	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3499	you do I<not> compile the F<ev.c> or any other embedded source files!):
3342		3500
3343	#include "evwrap.h"	3501	#include "evwrap.h"
3344	#include "ev.c"	3502	#include "ev.c"
3345		3503
3346	=over 4	3504	=over 4
…		…
3391	wrap all I/O functions and provide your own fd management, but the cost of	3549	wrap all I/O functions and provide your own fd management, but the cost of
3392	calling select (O(n²)) will likely make this unworkable.	3550	calling select (O(n²)) will likely make this unworkable.
3393		3551
3394	=back	3552	=back
3395		3553
3396
3397	=head1 PORTABILITY REQUIREMENTS	3554	=head2 PORTABILITY REQUIREMENTS
3398		3555
3399	In addition to a working ISO-C implementation, libev relies on a few	3556	In addition to a working ISO-C implementation and of course the
3400	additional extensions:	3557	backend-specific APIs, libev relies on a few additional extensions:
3401		3558
3402	=over 4	3559	=over 4
3403		3560
3404	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3561	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3405	calling conventions regardless of C<ev_watcher_type *>.	3562	calling conventions regardless of C<ev_watcher_type *>.
…		…
3411	calls them using an C<ev_watcher *> internally.	3568	calls them using an C<ev_watcher *> internally.
3412		3569
3413	=item C<sig_atomic_t volatile> must be thread-atomic as well	3570	=item C<sig_atomic_t volatile> must be thread-atomic as well
3414		3571
3415	The type C<sig_atomic_t volatile> (or whatever is defined as	3572	The type C<sig_atomic_t volatile> (or whatever is defined as
3416	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3573	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3417	threads. This is not part of the specification for C<sig_atomic_t>, but is	3574	threads. This is not part of the specification for C<sig_atomic_t>, but is
3418	believed to be sufficiently portable.	3575	believed to be sufficiently portable.
3419		3576
3420	=item C<sigprocmask> must work in a threaded environment	3577	=item C<sigprocmask> must work in a threaded environment
3421		3578
…		…
3430	except the initial one, and run the default loop in the initial thread as	3587	except the initial one, and run the default loop in the initial thread as
3431	well.	3588	well.
3432		3589
3433	=item C<long> must be large enough for common memory allocation sizes	3590	=item C<long> must be large enough for common memory allocation sizes
3434		3591
3435	To improve portability and simplify using libev, libev uses C<long>	3592	To improve portability and simplify its API, libev uses C<long> internally
3436	internally instead of C<size_t> when allocating its data structures. On	3593	instead of C<size_t> when allocating its data structures. On non-POSIX
3437	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3594	systems (Microsoft...) this might be unexpectedly low, but is still at
3438	is still at least 31 bits everywhere, which is enough for hundreds of	3595	least 31 bits everywhere, which is enough for hundreds of millions of
3439	millions of watchers.	3596	watchers.
3440		3597
3441	=item C<double> must hold a time value in seconds with enough accuracy	3598	=item C<double> must hold a time value in seconds with enough accuracy
3442		3599
3443	The type C<double> is used to represent timestamps. It is required to	3600	The type C<double> is used to represent timestamps. It is required to
3444	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3601	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3448	=back	3605	=back
3449		3606
3450	If you know of other additional requirements drop me a note.	3607	If you know of other additional requirements drop me a note.
3451		3608
3452		3609
3453	=head1 COMPILER WARNINGS	3610	=head1 ALGORITHMIC COMPLEXITIES
3454		3611
3455	Depending on your compiler and compiler settings, you might get no or a	3612	In this section the complexities of (many of) the algorithms used inside
3456	lot of warnings when compiling libev code. Some people are apparently	3613	libev will be documented. For complexity discussions about backends see
3457	scared by this.	3614	the documentation for C<ev_default_init>.
3458		3615
3459	However, these are unavoidable for many reasons. For one, each compiler	3616	All of the following are about amortised time: If an array needs to be
3460	has different warnings, and each user has different tastes regarding	3617	extended, libev needs to realloc and move the whole array, but this
3461	warning options. "Warn-free" code therefore cannot be a goal except when	3618	happens asymptotically rarer with higher number of elements, so O(1) might
3462	targeting a specific compiler and compiler-version.	3619	mean that libev does a lengthy realloc operation in rare cases, but on
		3620	average it is much faster and asymptotically approaches constant time.
3463		3621
3464	Another reason is that some compiler warnings require elaborate	3622	=over 4
3465	workarounds, or other changes to the code that make it less clear and less
3466	maintainable.
3467		3623
3468	And of course, some compiler warnings are just plain stupid, or simply	3624	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3469	wrong (because they don't actually warn about the condition their message
3470	seems to warn about).
3471		3625
3472	While libev is written to generate as few warnings as possible,	3626	This means that, when you have a watcher that triggers in one hour and
3473	"warn-free" code is not a goal, and it is recommended not to build libev	3627	there are 100 watchers that would trigger before that, then inserting will
3474	with any compiler warnings enabled unless you are prepared to cope with	3628	have to skip roughly seven (C<ld 100>) of these watchers.
3475	them (e.g. by ignoring them). Remember that warnings are just that:
3476	warnings, not errors, or proof of bugs.
3477		3629
		3630	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3478		3631
3479	=head1 VALGRIND	3632	That means that changing a timer costs less than removing/adding them,
		3633	as only the relative motion in the event queue has to be paid for.
3480		3634
3481	Valgrind has a special section here because it is a popular tool that is	3635	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3482	highly useful, but valgrind reports are very hard to interpret.
3483		3636
3484	If you think you found a bug (memory leak, uninitialised data access etc.)	3637	These just add the watcher into an array or at the head of a list.
3485	in libev, then check twice: If valgrind reports something like:
3486		3638
3487	==2274== definitely lost: 0 bytes in 0 blocks.	3639	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3488	==2274== possibly lost: 0 bytes in 0 blocks.
3489	==2274== still reachable: 256 bytes in 1 blocks.
3490		3640
3491	Then there is no memory leak. Similarly, under some circumstances,	3641	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3492	valgrind might report kernel bugs as if it were a bug in libev, or it
3493	might be confused (it is a very good tool, but only a tool).
3494		3642
3495	If you are unsure about something, feel free to contact the mailing list	3643	These watchers are stored in lists, so they need to be walked to find the
3496	with the full valgrind report and an explanation on why you think this is	3644	correct watcher to remove. The lists are usually short (you don't usually
3497	a bug in libev. However, don't be annoyed when you get a brisk "this is	3645	have many watchers waiting for the same fd or signal: one is typical, two
3498	no bug" answer and take the chance of learning how to interpret valgrind	3646	is rare).
3499	properly.
3500		3647
3501	If you need, for some reason, empty reports from valgrind for your project	3648	=item Finding the next timer in each loop iteration: O(1)
3502	I suggest using suppression lists.	3649
		3650	By virtue of using a binary or 4-heap, the next timer is always found at a
		3651	fixed position in the storage array.
		3652
		3653	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3654
		3655	A change means an I/O watcher gets started or stopped, which requires
		3656	libev to recalculate its status (and possibly tell the kernel, depending
		3657	on backend and whether C<ev_io_set> was used).
		3658
		3659	=item Activating one watcher (putting it into the pending state): O(1)
		3660
		3661	=item Priority handling: O(number_of_priorities)
		3662
		3663	Priorities are implemented by allocating some space for each
		3664	priority. When doing priority-based operations, libev usually has to
		3665	linearly search all the priorities, but starting/stopping and activating
		3666	watchers becomes O(1) with respect to priority handling.
		3667
		3668	=item Sending an ev_async: O(1)
		3669
		3670	=item Processing ev_async_send: O(number_of_async_watchers)
		3671
		3672	=item Processing signals: O(max_signal_number)
		3673
		3674	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3675	calls in the current loop iteration. Checking for async and signal events
		3676	involves iterating over all running async watchers or all signal numbers.
		3677
		3678	=back
3503		3679
3504		3680
3505	=head1 AUTHOR	3681	=head1 AUTHOR
3506		3682
3507	Marc Lehmann <libev@schmorp.de>.	3683	Marc Lehmann <libev@schmorp.de>.

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