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Revision 1.175 by root, Mon Sep 8 16:36:14 2008 UTC vs.
Revision 1.194 by root, Mon Oct 20 16:08:36 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.
…		…
617	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	662	- Queue all expired timers.
623	- Queue all outstanding periodics.	663	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	665	- Queue all check watchers.
626	- 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).
627	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
628	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
…		…
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		687
648	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.
649		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
650	=item ev_ref (loop)	692	=item ev_ref (loop)
651		693
652	=item ev_unref (loop)	694	=item ev_unref (loop)
653		695
654	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
655	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
656	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
657	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>
658	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
659	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
660	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
661	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
662	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
663	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>
664	(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,
665	respectively).	710	respectively).
666		711
…		…
689	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>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	735	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	736	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	737	opportunities).
693		738
694	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
695	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
696	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
697	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
698	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.
699		744
700	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
701	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,
…		…
703	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
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
705		750
706	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
707	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
709	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
710	any overhead in libev.	755	value will not introduce any overhead in libev.
711		756
712	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
713	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
714	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	760	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
723	they fire on, say, one-second boundaries only.	768	they fire on, say, one-second boundaries only.
724		769
725	=item ev_loop_verify (loop)	770	=item ev_loop_verify (loop)
726		771
727	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
728	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
729	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
730	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 ()>.
731		777
732	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
733	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
734	data structures consistent.	780	data structures consistent.
735		781
…		…
851	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
853	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
854	with the watcher being stopped.	900	with the watcher being stopped.
855		901
856	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
857	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
858	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
859	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
860	programs, though, so beware.	906	programs, though, as the fd could already be closed and reused for another
		907	thing, so beware.
861		908
862	=back	909	=back
863		910
864	=head2 GENERIC WATCHER FUNCTIONS	911	=head2 GENERIC WATCHER FUNCTIONS
865		912
…		…
881	(or never started) and there are no pending events outstanding.	928	(or never started) and there are no pending events outstanding.
882		929
883	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,
884	int revents)>.	931	int revents)>.
885		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
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	939	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		940
888	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
889	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
890	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
…		…
892	difference to the C<ev_init> macro).	945	difference to the C<ev_init> macro).
893		946
894	Although some watcher types do not have type-specific arguments	947	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	948	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		949
		950	See C<ev_init>, above, for an example.
		951
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	952	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		953
899	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
900	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
901	a watcher. The same limitations apply, of course.	956	a watcher. The same limitations apply, of course.
902		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
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		963
905	Starts (activates) the given watcher. Only active watchers will receive	964	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	965	events. If the watcher is already active nothing will happen.
		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);
907		971
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		973
910	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher again (if active) and clears the pending
911	status. It is possible that stopped watchers are pending (for example,	975	status. It is possible that stopped watchers are pending (for example,
…		…
968		1032
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1034
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1036	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1037	can deal with that fact, as both are simply passed through to the
		1038	callback.
974		1039
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1040	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1041
977	If the watcher is pending, this function returns clears its pending status	1042	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1043	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1044	watcher isn't pending it does nothing and returns C<0>.
980		1045
		1046	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1047	callback to be invoked, which can be accomplished with this function.
		1048
981	=back	1049	=back
982		1050
983		1051
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1052	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1053
986	Each watcher has, by default, a member C<void *data> that you can change	1054	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1055	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1056	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1057	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1058	member, you can also "subclass" the watcher type and provide your own
991	data:	1059	data:
992		1060
…		…
994	{	1062	{
995	struct ev_io io;	1063	struct ev_io io;
996	int otherfd;	1064	int otherfd;
997	void *somedata;	1065	void *somedata;
998	struct whatever *mostinteresting;	1066	struct whatever *mostinteresting;
999	}	1067	};
		1068
		1069	...
		1070	struct my_io w;
		1071	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1072
1001	And since your callback will be called with a pointer to the watcher, you	1073	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1074	can cast it back to your own type:
1003		1075
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1076	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
…		…
1008	}	1080	}
1009		1081
1010	More interesting and less C-conformant ways of casting your callback type	1082	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1083	instead have been omitted.
1012		1084
1013	Another common scenario is having some data structure with multiple	1085	Another common scenario is to use some data structure with multiple
1014	watchers:	1086	embedded watchers:
1015		1087
1016	struct my_biggy	1088	struct my_biggy
1017	{	1089	{
1018	int some_data;	1090	int some_data;
1019	ev_timer t1;	1091	ev_timer t1;
1020	ev_timer t2;	1092	ev_timer t2;
1021	}	1093	}
1022		1094
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1095	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1096	complicated: Either you store the address of your C<my_biggy> struct
		1097	in the C<data> member of the watcher (for woozies), or you need to use
		1098	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1099	programmers):
1025		1100
1026	#include <stddef.h>	1101	#include <stddef.h>
1027		1102
1028	static void	1103	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1104	t1_cb (EV_P_ struct ev_timer *w, int revents)
…		…
1069	In general you can register as many read and/or write event watchers per	1144	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1145	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1146	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1147	required if you know what you are doing).
1073		1148
1074	If you must do this, then force the use of a known-to-be-good backend	1149	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1150	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1151	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1077		1152
1078	Another thing you have to watch out for is that it is quite easy to	1153	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1154	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1155	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1156	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1157	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1158	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1159	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1160	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1161
1087	If you cannot run the fd in non-blocking mode (for example you should not	1162	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1163	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1164	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1165	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1166	does this on its own, so its quite safe to use). Some people additionally
		1167	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1168	indefinitely.
		1169
		1170	But really, best use non-blocking mode.
1092		1171
1093	=head3 The special problem of disappearing file descriptors	1172	=head3 The special problem of disappearing file descriptors
1094		1173
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1174	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1175	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1176	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1177	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1178	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1179	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1180	fact, a different file descriptor.
1102		1181
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1212	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1213	C<EVBACKEND_POLL>.
1135		1214
1136	=head3 The special problem of SIGPIPE	1215	=head3 The special problem of SIGPIPE
1137		1216
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1217	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when writing to a pipe whose other end has been closed, your program gets	1218	when writing to a pipe whose other end has been closed, your program gets
1140	send a SIGPIPE, which, by default, aborts your program. For most programs	1219	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	this is sensible behaviour, for daemons, this is usually undesirable.	1220	this is sensible behaviour, for daemons, this is usually undesirable.
1142		1221
1143	So when you encounter spurious, unexplained daemon exits, make sure you	1222	So when you encounter spurious, unexplained daemon exits, make sure you
1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1223	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1145	somewhere, as that would have given you a big clue).	1224	somewhere, as that would have given you a big clue).
…		…
1152	=item ev_io_init (ev_io *, callback, int fd, int events)	1231	=item ev_io_init (ev_io *, callback, int fd, int events)
1153		1232
1154	=item ev_io_set (ev_io *, int fd, int events)	1233	=item ev_io_set (ev_io *, int fd, int events)
1155		1234
1156	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1235	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1157	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1236	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1158	C<EV_READ | EV_WRITE> to receive the given events.	1237	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1159		1238
1160	=item int fd [read-only]	1239	=item int fd [read-only]
1161		1240
1162	The file descriptor being watched.	1241	The file descriptor being watched.
1163		1242
…		…
1175		1254
1176	static void	1255	static void
1177	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1256	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1178	{	1257	{
1179	ev_io_stop (loop, w);	1258	ev_io_stop (loop, w);
1180	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1259	.. read from stdin here (or from w->fd) and handle any I/O errors
1181	}	1260	}
1182		1261
1183	...	1262	...
1184	struct ev_loop *loop = ev_default_init (0);	1263	struct ev_loop *loop = ev_default_init (0);
1185	struct ev_io stdin_readable;	1264	struct ev_io stdin_readable;
…		…
1193	Timer watchers are simple relative timers that generate an event after a	1272	Timer watchers are simple relative timers that generate an event after a
1194	given time, and optionally repeating in regular intervals after that.	1273	given time, and optionally repeating in regular intervals after that.
1195		1274
1196	The timers are based on real time, that is, if you register an event that	1275	The timers are based on real time, that is, if you register an event that
1197	times out after an hour and you reset your system clock to January last	1276	times out after an hour and you reset your system clock to January last
1198	year, it will still time out after (roughly) and hour. "Roughly" because	1277	year, it will still time out after (roughly) one hour. "Roughly" because
1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1200	monotonic clock option helps a lot here).	1279	monotonic clock option helps a lot here).
1201		1280
1202	The callback is guaranteed to be invoked only after its timeout has passed,	1281	The callback is guaranteed to be invoked only I<after> its timeout has
1203	but if multiple timers become ready during the same loop iteration then	1282	passed, but if multiple timers become ready during the same loop iteration
1204	order of execution is undefined.	1283	then order of execution is undefined.
1205		1284
1206	=head3 The special problem of time updates	1285	=head3 The special problem of time updates
1207		1286
1208	Requesting the current time is a costly operation (it usually takes at	1287	Establishing the current time is a costly operation (it usually takes at
1209	least two syscalls): EV therefore updates it's idea of the current time	1288	least two system calls): EV therefore updates its idea of the current
1210	only before and after C<ev_loop> polls for new events, which causes the	1289	time only before and after C<ev_loop> collects new events, which causes a
1211	difference between C<ev_now ()> and C<ev_time ()>.	1290	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1291	lots of events in one iteration.
1212		1292
1213	The relative timeouts are calculated relative to the C<ev_now ()>	1293	The relative timeouts are calculated relative to the C<ev_now ()>
1214	time. This is usually the right thing as this timestamp refers to the time	1294	time. This is usually the right thing as this timestamp refers to the time
1215	of the event triggering whatever timeout you are modifying/starting. If	1295	of the event triggering whatever timeout you are modifying/starting. If
1216	you suspect event processing to be delayed and you I<need> to base the	1296	you suspect event processing to be delayed and you I<need> to base the
1217	timeout on the current time, use something like this to adjust for this:	1297	timeout on the current time, use something like this to adjust for this:
1218		1298
1219	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1299	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		1300
		1301	If the event loop is suspended for a long time, you can also force an
		1302	update of the time returned by C<ev_now ()> by calling C<ev_now_update
		1303	()>.
1220		1304
1221	=head3 Watcher-Specific Functions and Data Members	1305	=head3 Watcher-Specific Functions and Data Members
1222		1306
1223	=over 4	1307	=over 4
1224		1308
…		…
1273	ev_timer_again (loop, timer);	1357	ev_timer_again (loop, timer);
1274		1358
1275	This is more slightly efficient then stopping/starting the timer each time	1359	This is more slightly efficient then stopping/starting the timer each time
1276	you want to modify its timeout value.	1360	you want to modify its timeout value.
1277		1361
		1362	Note, however, that it is often even more efficient to remember the
		1363	time of the last activity and let the timer time-out naturally. In the
		1364	callback, you then check whether the time-out is real, or, if there was
		1365	some activity, you reschedule the watcher to time-out in "last_activity +
		1366	timeout - ev_now ()" seconds.
		1367
1278	=item ev_tstamp repeat [read-write]	1368	=item ev_tstamp repeat [read-write]
1279		1369
1280	The current C<repeat> value. Will be used each time the watcher times out	1370	The current C<repeat> value. Will be used each time the watcher times out
1281	or C<ev_timer_again> is called and determines the next timeout (if any),	1371	or C<ev_timer_again> is called, and determines the next timeout (if any),
1282	which is also when any modifications are taken into account.	1372	which is also when any modifications are taken into account.
1283		1373
1284	=back	1374	=back
1285		1375
1286	=head3 Examples	1376	=head3 Examples
…		…
1330	to trigger the event (unlike an C<ev_timer>, which would still trigger	1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1331	roughly 10 seconds later as it uses a relative timeout).	1421	roughly 10 seconds later as it uses a relative timeout).
1332		1422
1333	C<ev_periodic>s can also be used to implement vastly more complex timers,	1423	C<ev_periodic>s can also be used to implement vastly more complex timers,
1334	such as triggering an event on each "midnight, local time", or other	1424	such as triggering an event on each "midnight, local time", or other
1335	complicated, rules.	1425	complicated rules.
1336		1426
1337	As with timers, the callback is guaranteed to be invoked only when the	1427	As with timers, the callback is guaranteed to be invoked only when the
1338	time (C<at>) has passed, but if multiple periodic timers become ready	1428	time (C<at>) has passed, but if multiple periodic timers become ready
1339	during the same loop iteration then order of execution is undefined.	1429	during the same loop iteration, then order of execution is undefined.
1340		1430
1341	=head3 Watcher-Specific Functions and Data Members	1431	=head3 Watcher-Specific Functions and Data Members
1342		1432
1343	=over 4	1433	=over 4
1344		1434
1345	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1346		1436
1347	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1348		1438
1349	Lots of arguments, lets sort it out... There are basically three modes of	1439	Lots of arguments, lets sort it out... There are basically three modes of
1350	operation, and we will explain them from simplest to complex:	1440	operation, and we will explain them from simplest to most complex:
1351		1441
1352	=over 4	1442	=over 4
1353		1443
1354	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1355		1445
1356	In this configuration the watcher triggers an event after the wall clock	1446	In this configuration the watcher triggers an event after the wall clock
1357	time C<at> has passed and doesn't repeat. It will not adjust when a time	1447	time C<at> has passed. It will not repeat and will not adjust when a time
1358	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1448	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1359	run when the system time reaches or surpasses this time.	1449	only run when the system clock reaches or surpasses this time.
1360		1450
1361	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1362		1452
1363	In this mode the watcher will always be scheduled to time out at the next	1453	In this mode the watcher will always be scheduled to time out at the next
1364	C<at + N * interval> time (for some integer N, which can also be negative)	1454	C<at + N * interval> time (for some integer N, which can also be negative)
1365	and then repeat, regardless of any time jumps.	1455	and then repeat, regardless of any time jumps.
1366		1456
1367	This can be used to create timers that do not drift with respect to system	1457	This can be used to create timers that do not drift with respect to the
1368	time, for example, here is a C<ev_periodic> that triggers each hour, on	1458	system clock, for example, here is a C<ev_periodic> that triggers each
1369	the hour:	1459	hour, on the hour:
1370		1460
1371	ev_periodic_set (&periodic, 0., 3600., 0);	1461	ev_periodic_set (&periodic, 0., 3600., 0);
1372		1462
1373	This doesn't mean there will always be 3600 seconds in between triggers,	1463	This doesn't mean there will always be 3600 seconds in between triggers,
1374	but only that the callback will be called when the system time shows a	1464	but only that the callback will be called when the system time shows a
…		…
1461	=back	1551	=back
1462		1552
1463	=head3 Examples	1553	=head3 Examples
1464		1554
1465	Example: Call a callback every hour, or, more precisely, whenever the	1555	Example: Call a callback every hour, or, more precisely, whenever the
1466	system clock is divisible by 3600. The callback invocation times have	1556	system time is divisible by 3600. The callback invocation times have
1467	potentially a lot of jitter, but good long-term stability.	1557	potentially a lot of jitter, but good long-term stability.
1468		1558
1469	static void	1559	static void
1470	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1560	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1471	{	1561	{
…		…
1481	#include <math.h>	1571	#include <math.h>
1482		1572
1483	static ev_tstamp	1573	static ev_tstamp
1484	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1485	{	1575	{
1486	return fmod (now, 3600.) + 3600.;	1576	return now + (3600. - fmod (now, 3600.));
1487	}	1577	}
1488		1578
1489	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1490		1580
1491	Example: Call a callback every hour, starting now:	1581	Example: Call a callback every hour, starting now:
…		…
1501	Signal watchers will trigger an event when the process receives a specific	1591	Signal watchers will trigger an event when the process receives a specific
1502	signal one or more times. Even though signals are very asynchronous, libev	1592	signal one or more times. Even though signals are very asynchronous, libev
1503	will try it's best to deliver signals synchronously, i.e. as part of the	1593	will try it's best to deliver signals synchronously, i.e. as part of the
1504	normal event processing, like any other event.	1594	normal event processing, like any other event.
1505		1595
		1596	If you want signals asynchronously, just use C<sigaction> as you would
		1597	do without libev and forget about sharing the signal. You can even use
		1598	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1599
1506	You can configure as many watchers as you like per signal. Only when the	1600	You can configure as many watchers as you like per signal. Only when the
1507	first watcher gets started will libev actually register a signal watcher	1601	first watcher gets started will libev actually register a signal handler
1508	with the kernel (thus it coexists with your own signal handlers as long	1602	with the kernel (thus it coexists with your own signal handlers as long as
1509	as you don't register any with libev). Similarly, when the last signal	1603	you don't register any with libev for the same signal). Similarly, when
1510	watcher for a signal is stopped libev will reset the signal handler to	1604	the last signal watcher for a signal is stopped, libev will reset the
1511	SIG_DFL (regardless of what it was set to before).	1605	signal handler to SIG_DFL (regardless of what it was set to before).
1512		1606
1513	If possible and supported, libev will install its handlers with	1607	If possible and supported, libev will install its handlers with
1514	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1608	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1515	interrupted. If you have a problem with system calls getting interrupted by	1609	interrupted. If you have a problem with system calls getting interrupted by
1516	signals you can block all signals in an C<ev_check> watcher and unblock	1610	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1533		1627
1534	=back	1628	=back
1535		1629
1536	=head3 Examples	1630	=head3 Examples
1537		1631
1538	Example: Try to exit cleanly on SIGINT and SIGTERM.	1632	Example: Try to exit cleanly on SIGINT.
1539		1633
1540	static void	1634	static void
1541	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1635	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1542	{	1636	{
1543	ev_unloop (loop, EVUNLOOP_ALL);	1637	ev_unloop (loop, EVUNLOOP_ALL);
1544	}	1638	}
1545		1639
1546	struct ev_signal signal_watcher;	1640	struct ev_signal signal_watcher;
1547	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1548	ev_signal_start (loop, &sigint_cb);	1642	ev_signal_start (loop, &signal_watcher);
1549		1643
1550		1644
1551	=head2 C<ev_child> - watch out for process status changes	1645	=head2 C<ev_child> - watch out for process status changes
1552		1646
1553	Child watchers trigger when your process receives a SIGCHLD in response to	1647	Child watchers trigger when your process receives a SIGCHLD in response to
1554	some child status changes (most typically when a child of yours dies). It	1648	some child status changes (most typically when a child of yours dies or
1555	is permissible to install a child watcher I<after> the child has been	1649	exits). It is permissible to install a child watcher I<after> the child
1556	forked (which implies it might have already exited), as long as the event	1650	has been forked (which implies it might have already exited), as long
1557	loop isn't entered (or is continued from a watcher).	1651	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1652	forking and then immediately registering a watcher for the child is fine,
		1653	but forking and registering a watcher a few event loop iterations later is
		1654	not.
1558		1655
1559	Only the default event loop is capable of handling signals, and therefore	1656	Only the default event loop is capable of handling signals, and therefore
1560	you can only register child watchers in the default event loop.	1657	you can only register child watchers in the default event loop.
1561		1658
1562	=head3 Process Interaction	1659	=head3 Process Interaction
…		…
1660	the stat buffer having unspecified contents.	1757	the stat buffer having unspecified contents.
1661		1758
1662	The path I<should> be absolute and I<must not> end in a slash. If it is	1759	The path I<should> be absolute and I<must not> end in a slash. If it is
1663	relative and your working directory changes, the behaviour is undefined.	1760	relative and your working directory changes, the behaviour is undefined.
1664		1761
1665	Since there is no standard to do this, the portable implementation simply	1762	Since there is no standard kernel interface to do this, the portable
1666	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1763	implementation simply calls C<stat (2)> regularly on the path to see if
1667	can specify a recommended polling interval for this case. If you specify	1764	it changed somehow. You can specify a recommended polling interval for
1668	a polling interval of C<0> (highly recommended!) then a I<suitable,	1765	this case. If you specify a polling interval of C<0> (highly recommended!)
1669	unspecified default> value will be used (which you can expect to be around	1766	then a I<suitable, unspecified default> value will be used (which
1670	five seconds, although this might change dynamically). Libev will also	1767	you can expect to be around five seconds, although this might change
1671	impose a minimum interval which is currently around C<0.1>, but thats	1768	dynamically). Libev will also impose a minimum interval which is currently
1672	usually overkill.	1769	around C<0.1>, but thats usually overkill.
1673		1770
1674	This watcher type is not meant for massive numbers of stat watchers,	1771	This watcher type is not meant for massive numbers of stat watchers,
1675	as even with OS-supported change notifications, this can be	1772	as even with OS-supported change notifications, this can be
1676	resource-intensive.	1773	resource-intensive.
1677		1774
1678	At the time of this writing, only the Linux inotify interface is	1775	At the time of this writing, the only OS-specific interface implemented
1679	implemented (implementing kqueue support is left as an exercise for the	1776	is the Linux inotify interface (implementing kqueue support is left as
1680	reader, note, however, that the author sees no way of implementing ev_stat	1777	an exercise for the reader. Note, however, that the author sees no way
1681	semantics with kqueue). Inotify will be used to give hints only and should	1778	of implementing C<ev_stat> semantics with kqueue).
1682	not change the semantics of C<ev_stat> watchers, which means that libev
1683	sometimes needs to fall back to regular polling again even with inotify,
1684	but changes are usually detected immediately, and if the file exists there
1685	will be no polling.
1686		1779
1687	=head3 ABI Issues (Largefile Support)	1780	=head3 ABI Issues (Largefile Support)
1688		1781
1689	Libev by default (unless the user overrides this) uses the default	1782	Libev by default (unless the user overrides this) uses the default
1690	compilation environment, which means that on systems with large file	1783	compilation environment, which means that on systems with large file
…		…
1699	file interfaces available by default (as e.g. FreeBSD does) and not	1792	file interfaces available by default (as e.g. FreeBSD does) and not
1700	optional. Libev cannot simply switch on large file support because it has	1793	optional. Libev cannot simply switch on large file support because it has
1701	to exchange stat structures with application programs compiled using the	1794	to exchange stat structures with application programs compiled using the
1702	default compilation environment.	1795	default compilation environment.
1703		1796
1704	=head3 Inotify	1797	=head3 Inotify and Kqueue
1705		1798
1706	When C<inotify (7)> support has been compiled into libev (generally only	1799	When C<inotify (7)> support has been compiled into libev (generally only
1707	available on Linux) and present at runtime, it will be used to speed up	1800	available with Linux) and present at runtime, it will be used to speed up
1708	change detection where possible. The inotify descriptor will be created lazily	1801	change detection where possible. The inotify descriptor will be created lazily
1709	when the first C<ev_stat> watcher is being started.	1802	when the first C<ev_stat> watcher is being started.
1710		1803
1711	Inotify presence does not change the semantics of C<ev_stat> watchers	1804	Inotify presence does not change the semantics of C<ev_stat> watchers
1712	except that changes might be detected earlier, and in some cases, to avoid	1805	except that changes might be detected earlier, and in some cases, to avoid
1713	making regular C<stat> calls. Even in the presence of inotify support	1806	making regular C<stat> calls. Even in the presence of inotify support
1714	there are many cases where libev has to resort to regular C<stat> polling.	1807	there are many cases where libev has to resort to regular C<stat> polling,
		1808	but as long as the path exists, libev usually gets away without polling.
1715		1809
1716	(There is no support for kqueue, as apparently it cannot be used to	1810	There is no support for kqueue, as apparently it cannot be used to
1717	implement this functionality, due to the requirement of having a file	1811	implement this functionality, due to the requirement of having a file
1718	descriptor open on the object at all times).	1812	descriptor open on the object at all times, and detecting renames, unlinks
		1813	etc. is difficult.
1719		1814
1720	=head3 The special problem of stat time resolution	1815	=head3 The special problem of stat time resolution
1721		1816
1722	The C<stat ()> system call only supports full-second resolution portably, and	1817	The C<stat ()> system call only supports full-second resolution portably, and
1723	even on systems where the resolution is higher, many file systems still	1818	even on systems where the resolution is higher, most file systems still
1724	only support whole seconds.	1819	only support whole seconds.
1725		1820
1726	That means that, if the time is the only thing that changes, you can	1821	That means that, if the time is the only thing that changes, you can
1727	easily miss updates: on the first update, C<ev_stat> detects a change and	1822	easily miss updates: on the first update, C<ev_stat> detects a change and
1728	calls your callback, which does something. When there is another update	1823	calls your callback, which does something. When there is another update
1729	within the same second, C<ev_stat> will be unable to detect it as the stat	1824	within the same second, C<ev_stat> will be unable to detect unless the
1730	data does not change.	1825	stat data does change in other ways (e.g. file size).
1731		1826
1732	The solution to this is to delay acting on a change for slightly more	1827	The solution to this is to delay acting on a change for slightly more
1733	than a second (or till slightly after the next full second boundary), using	1828	than a second (or till slightly after the next full second boundary), using
1734	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1829	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1735	ev_timer_again (loop, w)>).	1830	ev_timer_again (loop, w)>).
…		…
1755	C<path>. The C<interval> is a hint on how quickly a change is expected to	1850	C<path>. The C<interval> is a hint on how quickly a change is expected to
1756	be detected and should normally be specified as C<0> to let libev choose	1851	be detected and should normally be specified as C<0> to let libev choose
1757	a suitable value. The memory pointed to by C<path> must point to the same	1852	a suitable value. The memory pointed to by C<path> must point to the same
1758	path for as long as the watcher is active.	1853	path for as long as the watcher is active.
1759		1854
1760	The callback will receive C<EV_STAT> when a change was detected, relative	1855	The callback will receive an C<EV_STAT> event when a change was detected,
1761	to the attributes at the time the watcher was started (or the last change	1856	relative to the attributes at the time the watcher was started (or the
1762	was detected).	1857	last change was detected).
1763		1858
1764	=item ev_stat_stat (loop, ev_stat *)	1859	=item ev_stat_stat (loop, ev_stat *)
1765		1860
1766	Updates the stat buffer immediately with new values. If you change the	1861	Updates the stat buffer immediately with new values. If you change the
1767	watched path in your callback, you could call this function to avoid	1862	watched path in your callback, you could call this function to avoid
…		…
1850		1945
1851		1946
1852	=head2 C<ev_idle> - when you've got nothing better to do...	1947	=head2 C<ev_idle> - when you've got nothing better to do...
1853		1948
1854	Idle watchers trigger events when no other events of the same or higher	1949	Idle watchers trigger events when no other events of the same or higher
1855	priority are pending (prepare, check and other idle watchers do not	1950	priority are pending (prepare, check and other idle watchers do not count
1856	count).	1951	as receiving "events").
1857		1952
1858	That is, as long as your process is busy handling sockets or timeouts	1953	That is, as long as your process is busy handling sockets or timeouts
1859	(or even signals, imagine) of the same or higher priority it will not be	1954	(or even signals, imagine) of the same or higher priority it will not be
1860	triggered. But when your process is idle (or only lower-priority watchers	1955	triggered. But when your process is idle (or only lower-priority watchers
1861	are pending), the idle watchers are being called once per event loop	1956	are pending), the idle watchers are being called once per event loop
…		…
1900	ev_idle_start (loop, idle_cb);	1995	ev_idle_start (loop, idle_cb);
1901		1996
1902		1997
1903	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1904		1999
1905	Prepare and check watchers are usually (but not always) used in tandem:	2000	Prepare and check watchers are usually (but not always) used in pairs:
1906	prepare watchers get invoked before the process blocks and check watchers	2001	prepare watchers get invoked before the process blocks and check watchers
1907	afterwards.	2002	afterwards.
1908		2003
1909	You I<must not> call C<ev_loop> or similar functions that enter	2004	You I<must not> call C<ev_loop> or similar functions that enter
1910	the current event loop from either C<ev_prepare> or C<ev_check>	2005	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1913	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2008	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1914	C<ev_check> so if you have one watcher of each kind they will always be	2009	C<ev_check> so if you have one watcher of each kind they will always be
1915	called in pairs bracketing the blocking call.	2010	called in pairs bracketing the blocking call.
1916		2011
1917	Their main purpose is to integrate other event mechanisms into libev and	2012	Their main purpose is to integrate other event mechanisms into libev and
1918	their use is somewhat advanced. This could be used, for example, to track	2013	their use is somewhat advanced. They could be used, for example, to track
1919	variable changes, implement your own watchers, integrate net-snmp or a	2014	variable changes, implement your own watchers, integrate net-snmp or a
1920	coroutine library and lots more. They are also occasionally useful if	2015	coroutine library and lots more. They are also occasionally useful if
1921	you cache some data and want to flush it before blocking (for example,	2016	you cache some data and want to flush it before blocking (for example,
1922	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2017	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1923	watcher).	2018	watcher).
1924		2019
1925	This is done by examining in each prepare call which file descriptors need	2020	This is done by examining in each prepare call which file descriptors
1926	to be watched by the other library, registering C<ev_io> watchers for	2021	need to be watched by the other library, registering C<ev_io> watchers
1927	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2022	for them and starting an C<ev_timer> watcher for any timeouts (many
1928	provide just this functionality). Then, in the check watcher you check for	2023	libraries provide exactly this functionality). Then, in the check watcher,
1929	any events that occurred (by checking the pending status of all watchers	2024	you check for any events that occurred (by checking the pending status
1930	and stopping them) and call back into the library. The I/O and timer	2025	of all watchers and stopping them) and call back into the library. The
1931	callbacks will never actually be called (but must be valid nevertheless,	2026	I/O and timer callbacks will never actually be called (but must be valid
1932	because you never know, you know?).	2027	nevertheless, because you never know, you know?).
1933		2028
1934	As another example, the Perl Coro module uses these hooks to integrate	2029	As another example, the Perl Coro module uses these hooks to integrate
1935	coroutines into libev programs, by yielding to other active coroutines	2030	coroutines into libev programs, by yielding to other active coroutines
1936	during each prepare and only letting the process block if no coroutines	2031	during each prepare and only letting the process block if no coroutines
1937	are ready to run (it's actually more complicated: it only runs coroutines	2032	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1940	loop from blocking if lower-priority coroutines are active, thus mapping	2035	loop from blocking if lower-priority coroutines are active, thus mapping
1941	low-priority coroutines to idle/background tasks).	2036	low-priority coroutines to idle/background tasks).
1942		2037
1943	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2038	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1944	priority, to ensure that they are being run before any other watchers	2039	priority, to ensure that they are being run before any other watchers
		2040	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2041
1945	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2042	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1946	too) should not activate ("feed") events into libev. While libev fully	2043	activate ("feed") events into libev. While libev fully supports this, they
1947	supports this, they might get executed before other C<ev_check> watchers	2044	might get executed before other C<ev_check> watchers did their job. As
1948	did their job. As C<ev_check> watchers are often used to embed other	2045	C<ev_check> watchers are often used to embed other (non-libev) event
1949	(non-libev) event loops those other event loops might be in an unusable	2046	loops those other event loops might be in an unusable state until their
1950	state until their C<ev_check> watcher ran (always remind yourself to	2047	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1951	coexist peacefully with others).	2048	others).
1952		2049
1953	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1954		2051
1955	=over 4	2052	=over 4
1956		2053
…		…
1958		2055
1959	=item ev_check_init (ev_check *, callback)	2056	=item ev_check_init (ev_check *, callback)
1960		2057
1961	Initialises and configures the prepare or check watcher - they have no	2058	Initialises and configures the prepare or check watcher - they have no
1962	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2059	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1963	macros, but using them is utterly, utterly and completely pointless.	2060	macros, but using them is utterly, utterly, utterly and completely
		2061	pointless.
1964		2062
1965	=back	2063	=back
1966		2064
1967	=head3 Examples	2065	=head3 Examples
1968		2066
…		…
2061	}	2159	}
2062		2160
2063	// do not ever call adns_afterpoll	2161	// do not ever call adns_afterpoll
2064		2162
2065	Method 4: Do not use a prepare or check watcher because the module you	2163	Method 4: Do not use a prepare or check watcher because the module you
2066	want to embed is too inflexible to support it. Instead, you can override	2164	want to embed is not flexible enough to support it. Instead, you can
2067	their poll function. The drawback with this solution is that the main	2165	override their poll function. The drawback with this solution is that the
2068	loop is now no longer controllable by EV. The C<Glib::EV> module does	2166	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2069	this.	2167	this approach, effectively embedding EV as a client into the horrible
		2168	libglib event loop.
2070		2169
2071	static gint	2170	static gint
2072	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2171	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2073	{	2172	{
2074	int got_events = 0;	2173	int got_events = 0;
…		…
2105	prioritise I/O.	2204	prioritise I/O.
2106		2205
2107	As an example for a bug workaround, the kqueue backend might only support	2206	As an example for a bug workaround, the kqueue backend might only support
2108	sockets on some platform, so it is unusable as generic backend, but you	2207	sockets on some platform, so it is unusable as generic backend, but you
2109	still want to make use of it because you have many sockets and it scales	2208	still want to make use of it because you have many sockets and it scales
2110	so nicely. In this case, you would create a kqueue-based loop and embed it	2209	so nicely. In this case, you would create a kqueue-based loop and embed
2111	into your default loop (which might use e.g. poll). Overall operation will	2210	it into your default loop (which might use e.g. poll). Overall operation
2112	be a bit slower because first libev has to poll and then call kevent, but	2211	will be a bit slower because first libev has to call C<poll> and then
2113	at least you can use both at what they are best.	2212	C<kevent>, but at least you can use both mechanisms for what they are
		2213	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2114		2214
2115	As for prioritising I/O: rarely you have the case where some fds have	2215	As for prioritising I/O: under rare circumstances you have the case where
2116	to be watched and handled very quickly (with low latency), and even	2216	some fds have to be watched and handled very quickly (with low latency),
2117	priorities and idle watchers might have too much overhead. In this case	2217	and even priorities and idle watchers might have too much overhead. In
2118	you would put all the high priority stuff in one loop and all the rest in	2218	this case you would put all the high priority stuff in one loop and all
2119	a second one, and embed the second one in the first.	2219	the rest in a second one, and embed the second one in the first.
2120		2220
2121	As long as the watcher is active, the callback will be invoked every time	2221	As long as the watcher is active, the callback will be invoked every time
2122	there might be events pending in the embedded loop. The callback must then	2222	there might be events pending in the embedded loop. The callback must then
2123	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2124	their callbacks (you could also start an idle watcher to give the embedded	2224	their callbacks (you could also start an idle watcher to give the embedded
…		…
2132	interested in that.	2232	interested in that.
2133		2233
2134	Also, there have not currently been made special provisions for forking:	2234	Also, there have not currently been made special provisions for forking:
2135	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2136	but you will also have to stop and restart any C<ev_embed> watchers	2236	but you will also have to stop and restart any C<ev_embed> watchers
2137	yourself.	2237	yourself - but you can use a fork watcher to handle this automatically,
		2238	and future versions of libev might do just that.
2138		2239
2139	Unfortunately, not all backends are embeddable, only the ones returned by	2240	Unfortunately, not all backends are embeddable: only the ones returned by
2140	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2141	portable one.	2242	portable one.
2142		2243
2143	So when you want to use this feature you will always have to be prepared	2244	So when you want to use this feature you will always have to be prepared
2144	that you cannot get an embeddable loop. The recommended way to get around	2245	that you cannot get an embeddable loop. The recommended way to get around
2145	this is to have a separate variables for your embeddable loop, try to	2246	this is to have a separate variables for your embeddable loop, try to
2146	create it, and if that fails, use the normal loop for everything.	2247	create it, and if that fails, use the normal loop for everything.
		2248
		2249	=head3 C<ev_embed> and fork
		2250
		2251	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2252	automatically be applied to the embedded loop as well, so no special
		2253	fork handling is required in that case. When the watcher is not running,
		2254	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2255	as applicable.
2147		2256
2148	=head3 Watcher-Specific Functions and Data Members	2257	=head3 Watcher-Specific Functions and Data Members
2149		2258
2150	=over 4	2259	=over 4
2151		2260
…		…
2269	is that the author does not know of a simple (or any) algorithm for a	2378	is that the author does not know of a simple (or any) algorithm for a
2270	multiple-writer-single-reader queue that works in all cases and doesn't	2379	multiple-writer-single-reader queue that works in all cases and doesn't
2271	need elaborate support such as pthreads.	2380	need elaborate support such as pthreads.
2272		2381
2273	That means that if you want to queue data, you have to provide your own	2382	That means that if you want to queue data, you have to provide your own
2274	queue. But at least I can tell you would implement locking around your	2383	queue. But at least I can tell you how to implement locking around your
2275	queue:	2384	queue:
2276		2385
2277	=over 4	2386	=over 4
2278		2387
2279	=item queueing from a signal handler context	2388	=item queueing from a signal handler context
2280		2389
2281	To implement race-free queueing, you simply add to the queue in the signal	2390	To implement race-free queueing, you simply add to the queue in the signal
2282	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2391	handler but you block the signal handler in the watcher callback. Here is
2283	some fictitious SIGUSR1 handler:	2392	an example that does that for some fictitious SIGUSR1 handler:
2284		2393
2285	static ev_async mysig;	2394	static ev_async mysig;
2286		2395
2287	static void	2396	static void
2288	sigusr1_handler (void)	2397	sigusr1_handler (void)
…		…
2355		2464
2356	=item ev_async_init (ev_async *, callback)	2465	=item ev_async_init (ev_async *, callback)
2357		2466
2358	Initialises and configures the async watcher - it has no parameters of any	2467	Initialises and configures the async watcher - it has no parameters of any
2359	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2360	believe me.	2469	trust me.
2361		2470
2362	=item ev_async_send (loop, ev_async *)	2471	=item ev_async_send (loop, ev_async *)
2363		2472
2364	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2365	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2366	C<ev_feed_event>, this call is safe to do in other threads, signal or	2475	C<ev_feed_event>, this call is safe to do from other threads, signal or
2367	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2368	section below on what exactly this means).	2477	section below on what exactly this means).
2369		2478
2370	This call incurs the overhead of a system call only once per loop iteration,	2479	This call incurs the overhead of a system call only once per loop iteration,
2371	so while the overhead might be noticeable, it doesn't apply to repeated	2480	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2395	=over 4	2504	=over 4
2396		2505
2397	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2506	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2398		2507
2399	This function combines a simple timer and an I/O watcher, calls your	2508	This function combines a simple timer and an I/O watcher, calls your
2400	callback on whichever event happens first and automatically stop both	2509	callback on whichever event happens first and automatically stops both
2401	watchers. This is useful if you want to wait for a single event on an fd	2510	watchers. This is useful if you want to wait for a single event on an fd
2402	or timeout without having to allocate/configure/start/stop/free one or	2511	or timeout without having to allocate/configure/start/stop/free one or
2403	more watchers yourself.	2512	more watchers yourself.
2404		2513
2405	If C<fd> is less than 0, then no I/O watcher will be started and events	2514	If C<fd> is less than 0, then no I/O watcher will be started and the
2406	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2515	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2407	C<events> set will be created and started.	2516	the given C<fd> and C<events> set will be created and started.
2408		2517
2409	If C<timeout> is less than 0, then no timeout watcher will be	2518	If C<timeout> is less than 0, then no timeout watcher will be
2410	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2519	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2411	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2520	repeat = 0) will be started. C<0> is a valid timeout.
2412	dubious value.
2413		2521
2414	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2522	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2415	passed an C<revents> set like normal event callbacks (a combination of	2523	passed an C<revents> set like normal event callbacks (a combination of
2416	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2524	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2417	value passed to C<ev_once>:	2525	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2526	a timeout and an io event at the same time - you probably should give io
		2527	events precedence.
		2528
		2529	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2418		2530
2419	static void stdin_ready (int revents, void *arg)	2531	static void stdin_ready (int revents, void *arg)
2420	{	2532	{
		2533	if (revents & EV_READ)
		2534	/* stdin might have data for us, joy! */;
2421	if (revents & EV_TIMEOUT)	2535	else if (revents & EV_TIMEOUT)
2422	/* doh, nothing entered */;	2536	/* doh, nothing entered */;
2423	else if (revents & EV_READ)
2424	/* stdin might have data for us, joy! */;
2425	}	2537	}
2426		2538
2427	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2428		2540
2429	=item ev_feed_event (ev_loop *, watcher *, int revents)	2541	=item ev_feed_event (ev_loop *, watcher *, int revents)
…		…
2577		2689
2578	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2690	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2579		2691
2580	See the method-C<set> above for more details.	2692	See the method-C<set> above for more details.
2581		2693
2582	Example:	2694	Example: Use a plain function as callback.
2583		2695
2584	static void io_cb (ev::io &w, int revents) { }	2696	static void io_cb (ev::io &w, int revents) { }
2585	iow.set <io_cb> ();	2697	iow.set <io_cb> ();
2586		2698
2587	=item w->set (struct ev_loop *)	2699	=item w->set (struct ev_loop *)
…		…
2625	Example: Define a class with an IO and idle watcher, start one of them in	2737	Example: Define a class with an IO and idle watcher, start one of them in
2626	the constructor.	2738	the constructor.
2627		2739
2628	class myclass	2740	class myclass
2629	{	2741	{
2630	ev::io io; void io_cb (ev::io &w, int revents);	2742	ev::io io ; void io_cb (ev::io &w, int revents);
2631	ev:idle idle void idle_cb (ev::idle &w, int revents);	2743	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2632		2744
2633	myclass (int fd)	2745	myclass (int fd)
2634	{	2746	{
2635	io .set <myclass, &myclass::io_cb > (this);	2747	io .set <myclass, &myclass::io_cb > (this);
2636	idle.set <myclass, &myclass::idle_cb> (this);	2748	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2652	=item Perl	2764	=item Perl
2653		2765
2654	The EV module implements the full libev API and is actually used to test	2766	The EV module implements the full libev API and is actually used to test
2655	libev. EV is developed together with libev. Apart from the EV core module,	2767	libev. EV is developed together with libev. Apart from the EV core module,
2656	there are additional modules that implement libev-compatible interfaces	2768	there are additional modules that implement libev-compatible interfaces
2657	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2769	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2658	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2770	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2771	and C<EV::Glib>).
2659		2772
2660	It can be found and installed via CPAN, its homepage is at	2773	It can be found and installed via CPAN, its homepage is at
2661	L<http://software.schmorp.de/pkg/EV>.	2774	L<http://software.schmorp.de/pkg/EV>.
2662		2775
2663	=item Python	2776	=item Python
…		…
2842		2955
2843	=head2 PREPROCESSOR SYMBOLS/MACROS	2956	=head2 PREPROCESSOR SYMBOLS/MACROS
2844		2957
2845	Libev can be configured via a variety of preprocessor symbols you have to	2958	Libev can be configured via a variety of preprocessor symbols you have to
2846	define before including any of its files. The default in the absence of	2959	define before including any of its files. The default in the absence of
2847	autoconf is noted for every option.	2960	autoconf is documented for every option.
2848		2961
2849	=over 4	2962	=over 4
2850		2963
2851	=item EV_STANDALONE	2964	=item EV_STANDALONE
2852		2965
…		…
3022	When doing priority-based operations, libev usually has to linearly search	3135	When doing priority-based operations, libev usually has to linearly search
3023	all the priorities, so having many of them (hundreds) uses a lot of space	3136	all the priorities, so having many of them (hundreds) uses a lot of space
3024	and time, so using the defaults of five priorities (-2 .. +2) is usually	3137	and time, so using the defaults of five priorities (-2 .. +2) is usually
3025	fine.	3138	fine.
3026		3139
3027	If your embedding application does not need any priorities, defining these both to	3140	If your embedding application does not need any priorities, defining these
3028	C<0> will save some memory and CPU.	3141	both to C<0> will save some memory and CPU.
3029		3142
3030	=item EV_PERIODIC_ENABLE	3143	=item EV_PERIODIC_ENABLE
3031		3144
3032	If undefined or defined to be C<1>, then periodic timers are supported. If	3145	If undefined or defined to be C<1>, then periodic timers are supported. If
3033	defined to be C<0>, then they are not. Disabling them saves a few kB of	3146	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3040	code.	3153	code.
3041		3154
3042	=item EV_EMBED_ENABLE	3155	=item EV_EMBED_ENABLE
3043		3156
3044	If undefined or defined to be C<1>, then embed watchers are supported. If	3157	If undefined or defined to be C<1>, then embed watchers are supported. If
3045	defined to be C<0>, then they are not.	3158	defined to be C<0>, then they are not. Embed watchers rely on most other
		3159	watcher types, which therefore must not be disabled.
3046		3160
3047	=item EV_STAT_ENABLE	3161	=item EV_STAT_ENABLE
3048		3162
3049	If undefined or defined to be C<1>, then stat watchers are supported. If	3163	If undefined or defined to be C<1>, then stat watchers are supported. If
3050	defined to be C<0>, then they are not.	3164	defined to be C<0>, then they are not.
…		…
3082	two).	3196	two).
3083		3197
3084	=item EV_USE_4HEAP	3198	=item EV_USE_4HEAP
3085		3199
3086	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3200	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3087	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3201	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3088	to C<1>. The 4-heap uses more complicated (longer) code but has	3202	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3089	noticeably faster performance with many (thousands) of watchers.	3203	faster performance with many (thousands) of watchers.
3090		3204
3091	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3205	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3092	(disabled).	3206	(disabled).
3093		3207
3094	=item EV_HEAP_CACHE_AT	3208	=item EV_HEAP_CACHE_AT
3095		3209
3096	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3210	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3097	timer and periodics heap, libev can cache the timestamp (I<at>) within	3211	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3098	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3212	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3099	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3213	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3100	but avoids random read accesses on heap changes. This improves performance	3214	but avoids random read accesses on heap changes. This improves performance
3101	noticeably with with many (hundreds) of watchers.	3215	noticeably with many (hundreds) of watchers.
3102		3216
3103	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3217	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3104	(disabled).	3218	(disabled).
3105		3219
3106	=item EV_VERIFY	3220	=item EV_VERIFY
…		…
3112	called once per loop, which can slow down libev. If set to C<3>, then the	3226	called once per loop, which can slow down libev. If set to C<3>, then the
3113	verification code will be called very frequently, which will slow down	3227	verification code will be called very frequently, which will slow down
3114	libev considerably.	3228	libev considerably.
3115		3229
3116	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3230	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3117	C<0.>	3231	C<0>.
3118		3232
3119	=item EV_COMMON	3233	=item EV_COMMON
3120		3234
3121	By default, all watchers have a C<void *data> member. By redefining	3235	By default, all watchers have a C<void *data> member. By redefining
3122	this macro to a something else you can include more and other types of	3236	this macro to a something else you can include more and other types of
…		…
3139	and the way callbacks are invoked and set. Must expand to a struct member	3253	and the way callbacks are invoked and set. Must expand to a struct member
3140	definition and a statement, respectively. See the F<ev.h> header file for	3254	definition and a statement, respectively. See the F<ev.h> header file for
3141	their default definitions. One possible use for overriding these is to	3255	their default definitions. One possible use for overriding these is to
3142	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3256	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3143	method calls instead of plain function calls in C++.	3257	method calls instead of plain function calls in C++.
		3258
		3259	=back
3144		3260
3145	=head2 EXPORTED API SYMBOLS	3261	=head2 EXPORTED API SYMBOLS
3146		3262
3147	If you need to re-export the API (e.g. via a DLL) and you need a list of	3263	If you need to re-export the API (e.g. via a DLL) and you need a list of
3148	exported symbols, you can use the provided F<Symbol.*> files which list	3264	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3195	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3311	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3196		3312
3197	#include "ev_cpp.h"	3313	#include "ev_cpp.h"
3198	#include "ev.c"	3314	#include "ev.c"
3199		3315
		3316	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3200		3317
3201	=head1 THREADS AND COROUTINES	3318	=head2 THREADS AND COROUTINES
3202		3319
3203	=head2 THREADS	3320	=head3 THREADS
3204		3321
3205	Libev itself is completely thread-safe, but it uses no locking. This	3322	All libev functions are reentrant and thread-safe unless explicitly
		3323	documented otherwise, but libev implements no locking itself. This means
3206	means that you can use as many loops as you want in parallel, as long as	3324	that you can use as many loops as you want in parallel, as long as there
3207	only one thread ever calls into one libev function with the same loop	3325	are no concurrent calls into any libev function with the same loop
3208	parameter.	3326	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3327	of course): libev guarantees that different event loops share no data
		3328	structures that need any locking.
3209		3329
3210	Or put differently: calls with different loop parameters can be done in	3330	Or to put it differently: calls with different loop parameters can be done
3211	parallel from multiple threads, calls with the same loop parameter must be	3331	concurrently from multiple threads, calls with the same loop parameter
3212	done serially (but can be done from different threads, as long as only one	3332	must be done serially (but can be done from different threads, as long as
3213	thread ever is inside a call at any point in time, e.g. by using a mutex	3333	only one thread ever is inside a call at any point in time, e.g. by using
3214	per loop).	3334	a mutex per loop).
		3335
		3336	Specifically to support threads (and signal handlers), libev implements
		3337	so-called C<ev_async> watchers, which allow some limited form of
		3338	concurrency on the same event loop, namely waking it up "from the
		3339	outside".
3215		3340
3216	If you want to know which design (one loop, locking, or multiple loops	3341	If you want to know which design (one loop, locking, or multiple loops
3217	without or something else still) is best for your problem, then I cannot	3342	without or something else still) is best for your problem, then I cannot
3218	help you. I can give some generic advice however:	3343	help you, but here is some generic advice:
3219		3344
3220	=over 4	3345	=over 4
3221		3346
3222	=item * most applications have a main thread: use the default libev loop	3347	=item * most applications have a main thread: use the default libev loop
3223	in that thread, or create a separate thread running only the default loop.	3348	in that thread, or create a separate thread running only the default loop.
…		…
3235		3360
3236	Choosing a model is hard - look around, learn, know that usually you can do	3361	Choosing a model is hard - look around, learn, know that usually you can do
3237	better than you currently do :-)	3362	better than you currently do :-)
3238		3363
3239	=item * often you need to talk to some other thread which blocks in the	3364	=item * often you need to talk to some other thread which blocks in the
		3365	event loop.
		3366
3240	event loop - C<ev_async> watchers can be used to wake them up from other	3367	C<ev_async> watchers can be used to wake them up from other threads safely
3241	threads safely (or from signal contexts...).	3368	(or from signal contexts...).
		3369
		3370	An example use would be to communicate signals or other events that only
		3371	work in the default loop by registering the signal watcher with the
		3372	default loop and triggering an C<ev_async> watcher from the default loop
		3373	watcher callback into the event loop interested in the signal.
3242		3374
3243	=back	3375	=back
3244		3376
3245	=head2 COROUTINES	3377	=head3 COROUTINES
3246		3378
3247	Libev is much more accommodating to coroutines ("cooperative threads"):	3379	Libev is very accommodating to coroutines ("cooperative threads"):
3248	libev fully supports nesting calls to it's functions from different	3380	libev fully supports nesting calls to its functions from different
3249	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3381	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3250	different coroutines and switch freely between both coroutines running the	3382	different coroutines, and switch freely between both coroutines running the
3251	loop, as long as you don't confuse yourself). The only exception is that	3383	loop, as long as you don't confuse yourself). The only exception is that
3252	you must not do this from C<ev_periodic> reschedule callbacks.	3384	you must not do this from C<ev_periodic> reschedule callbacks.
3253		3385
3254	Care has been invested into making sure that libev does not keep local	3386	Care has been taken to ensure that libev does not keep local state inside
3255	state inside C<ev_loop>, and other calls do not usually allow coroutine	3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3256	switches.	3388	they do not clal any callbacks.
3257		3389
		3390	=head2 COMPILER WARNINGS
3258		3391
3259	=head1 COMPLEXITIES	3392	Depending on your compiler and compiler settings, you might get no or a
		3393	lot of warnings when compiling libev code. Some people are apparently
		3394	scared by this.
3260		3395
3261	In this section the complexities of (many of) the algorithms used inside	3396	However, these are unavoidable for many reasons. For one, each compiler
3262	libev will be explained. For complexity discussions about backends see the	3397	has different warnings, and each user has different tastes regarding
3263	documentation for C<ev_default_init>.	3398	warning options. "Warn-free" code therefore cannot be a goal except when
		3399	targeting a specific compiler and compiler-version.
3264		3400
3265	All of the following are about amortised time: If an array needs to be	3401	Another reason is that some compiler warnings require elaborate
3266	extended, libev needs to realloc and move the whole array, but this	3402	workarounds, or other changes to the code that make it less clear and less
3267	happens asymptotically never with higher number of elements, so O(1) might	3403	maintainable.
3268	mean it might do a lengthy realloc operation in rare cases, but on average
3269	it is much faster and asymptotically approaches constant time.
3270		3404
3271	=over 4	3405	And of course, some compiler warnings are just plain stupid, or simply
		3406	wrong (because they don't actually warn about the condition their message
		3407	seems to warn about). For example, certain older gcc versions had some
		3408	warnings that resulted an extreme number of false positives. These have
		3409	been fixed, but some people still insist on making code warn-free with
		3410	such buggy versions.
3272		3411
3273	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3412	While libev is written to generate as few warnings as possible,
		3413	"warn-free" code is not a goal, and it is recommended not to build libev
		3414	with any compiler warnings enabled unless you are prepared to cope with
		3415	them (e.g. by ignoring them). Remember that warnings are just that:
		3416	warnings, not errors, or proof of bugs.
3274		3417
3275	This means that, when you have a watcher that triggers in one hour and
3276	there are 100 watchers that would trigger before that then inserting will
3277	have to skip roughly seven (C<ld 100>) of these watchers.
3278		3418
3279	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3419	=head2 VALGRIND
3280		3420
3281	That means that changing a timer costs less than removing/adding them	3421	Valgrind has a special section here because it is a popular tool that is
3282	as only the relative motion in the event queue has to be paid for.	3422	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3283		3423
3284	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3424	If you think you found a bug (memory leak, uninitialised data access etc.)
		3425	in libev, then check twice: If valgrind reports something like:
3285		3426
3286	These just add the watcher into an array or at the head of a list.	3427	==2274== definitely lost: 0 bytes in 0 blocks.
		3428	==2274== possibly lost: 0 bytes in 0 blocks.
		3429	==2274== still reachable: 256 bytes in 1 blocks.
3287		3430
3288	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3431	Then there is no memory leak, just as memory accounted to global variables
		3432	is not a memleak - the memory is still being refernced, and didn't leak.
3289		3433
3290	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3434	Similarly, under some circumstances, valgrind might report kernel bugs
		3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3436	although an acceptable workaround has been found here), or it might be
		3437	confused.
3291		3438
3292	These watchers are stored in lists then need to be walked to find the	3439	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3293	correct watcher to remove. The lists are usually short (you don't usually	3440	make it into some kind of religion.
3294	have many watchers waiting for the same fd or signal).
3295		3441
3296	=item Finding the next timer in each loop iteration: O(1)	3442	If you are unsure about something, feel free to contact the mailing list
		3443	with the full valgrind report and an explanation on why you think this
		3444	is a bug in libev (best check the archives, too :). However, don't be
		3445	annoyed when you get a brisk "this is no bug" answer and take the chance
		3446	of learning how to interpret valgrind properly.
3297		3447
3298	By virtue of using a binary or 4-heap, the next timer is always found at a	3448	If you need, for some reason, empty reports from valgrind for your project
3299	fixed position in the storage array.	3449	I suggest using suppression lists.
3300		3450
3301	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3302		3451
3303	A change means an I/O watcher gets started or stopped, which requires	3452	=head1 PORTABILITY NOTES
3304	libev to recalculate its status (and possibly tell the kernel, depending
3305	on backend and whether C<ev_io_set> was used).
3306		3453
3307	=item Activating one watcher (putting it into the pending state): O(1)
3308
3309	=item Priority handling: O(number_of_priorities)
3310
3311	Priorities are implemented by allocating some space for each
3312	priority. When doing priority-based operations, libev usually has to
3313	linearly search all the priorities, but starting/stopping and activating
3314	watchers becomes O(1) w.r.t. priority handling.
3315
3316	=item Sending an ev_async: O(1)
3317
3318	=item Processing ev_async_send: O(number_of_async_watchers)
3319
3320	=item Processing signals: O(max_signal_number)
3321
3322	Sending involves a system call I<iff> there were no other C<ev_async_send>
3323	calls in the current loop iteration. Checking for async and signal events
3324	involves iterating over all running async watchers or all signal numbers.
3325
3326	=back
3327
3328
3329	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3454	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3330		3455
3331	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3332	requires, and its I/O model is fundamentally incompatible with the POSIX	3457	requires, and its I/O model is fundamentally incompatible with the POSIX
3333	model. Libev still offers limited functionality on this platform in	3458	model. Libev still offers limited functionality on this platform in
3334	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3345		3470
3346	Not a libev limitation but worth mentioning: windows apparently doesn't	3471	Not a libev limitation but worth mentioning: windows apparently doesn't
3347	accept large writes: instead of resulting in a partial write, windows will	3472	accept large writes: instead of resulting in a partial write, windows will
3348	either accept everything or return C<ENOBUFS> if the buffer is too large,	3473	either accept everything or return C<ENOBUFS> if the buffer is too large,
3349	so make sure you only write small amounts into your sockets (less than a	3474	so make sure you only write small amounts into your sockets (less than a
3350	megabyte seems safe, but thsi apparently depends on the amount of memory	3475	megabyte seems safe, but this apparently depends on the amount of memory
3351	available).	3476	available).
3352		3477
3353	Due to the many, low, and arbitrary limits on the win32 platform and	3478	Due to the many, low, and arbitrary limits on the win32 platform and
3354	the abysmal performance of winsockets, using a large number of sockets	3479	the abysmal performance of winsockets, using a large number of sockets
3355	is not recommended (and not reasonable). If your program needs to use	3480	is not recommended (and not reasonable). If your program needs to use
…		…
3366	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3491	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3367		3492
3368	#include "ev.h"	3493	#include "ev.h"
3369		3494
3370	And compile the following F<evwrap.c> file into your project (make sure	3495	And compile the following F<evwrap.c> file into your project (make sure
3371	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3496	you do I<not> compile the F<ev.c> or any other embedded source files!):
3372		3497
3373	#include "evwrap.h"	3498	#include "evwrap.h"
3374	#include "ev.c"	3499	#include "ev.c"
3375		3500
3376	=over 4	3501	=over 4
…		…
3421	wrap all I/O functions and provide your own fd management, but the cost of	3546	wrap all I/O functions and provide your own fd management, but the cost of
3422	calling select (O(n²)) will likely make this unworkable.	3547	calling select (O(n²)) will likely make this unworkable.
3423		3548
3424	=back	3549	=back
3425		3550
3426
3427	=head1 PORTABILITY REQUIREMENTS	3551	=head2 PORTABILITY REQUIREMENTS
3428		3552
3429	In addition to a working ISO-C implementation, libev relies on a few	3553	In addition to a working ISO-C implementation and of course the
3430	additional extensions:	3554	backend-specific APIs, libev relies on a few additional extensions:
3431		3555
3432	=over 4	3556	=over 4
3433		3557
3434	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3558	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3435	calling conventions regardless of C<ev_watcher_type *>.	3559	calling conventions regardless of C<ev_watcher_type *>.
…		…
3441	calls them using an C<ev_watcher *> internally.	3565	calls them using an C<ev_watcher *> internally.
3442		3566
3443	=item C<sig_atomic_t volatile> must be thread-atomic as well	3567	=item C<sig_atomic_t volatile> must be thread-atomic as well
3444		3568
3445	The type C<sig_atomic_t volatile> (or whatever is defined as	3569	The type C<sig_atomic_t volatile> (or whatever is defined as
3446	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3570	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3447	threads. This is not part of the specification for C<sig_atomic_t>, but is	3571	threads. This is not part of the specification for C<sig_atomic_t>, but is
3448	believed to be sufficiently portable.	3572	believed to be sufficiently portable.
3449		3573
3450	=item C<sigprocmask> must work in a threaded environment	3574	=item C<sigprocmask> must work in a threaded environment
3451		3575
…		…
3460	except the initial one, and run the default loop in the initial thread as	3584	except the initial one, and run the default loop in the initial thread as
3461	well.	3585	well.
3462		3586
3463	=item C<long> must be large enough for common memory allocation sizes	3587	=item C<long> must be large enough for common memory allocation sizes
3464		3588
3465	To improve portability and simplify using libev, libev uses C<long>	3589	To improve portability and simplify its API, libev uses C<long> internally
3466	internally instead of C<size_t> when allocating its data structures. On	3590	instead of C<size_t> when allocating its data structures. On non-POSIX
3467	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3591	systems (Microsoft...) this might be unexpectedly low, but is still at
3468	is still at least 31 bits everywhere, which is enough for hundreds of	3592	least 31 bits everywhere, which is enough for hundreds of millions of
3469	millions of watchers.	3593	watchers.
3470		3594
3471	=item C<double> must hold a time value in seconds with enough accuracy	3595	=item C<double> must hold a time value in seconds with enough accuracy
3472		3596
3473	The type C<double> is used to represent timestamps. It is required to	3597	The type C<double> is used to represent timestamps. It is required to
3474	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3598	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3478	=back	3602	=back
3479		3603
3480	If you know of other additional requirements drop me a note.	3604	If you know of other additional requirements drop me a note.
3481		3605
3482		3606
3483	=head1 COMPILER WARNINGS	3607	=head1 ALGORITHMIC COMPLEXITIES
3484		3608
3485	Depending on your compiler and compiler settings, you might get no or a	3609	In this section the complexities of (many of) the algorithms used inside
3486	lot of warnings when compiling libev code. Some people are apparently	3610	libev will be documented. For complexity discussions about backends see
3487	scared by this.	3611	the documentation for C<ev_default_init>.
3488		3612
3489	However, these are unavoidable for many reasons. For one, each compiler	3613	All of the following are about amortised time: If an array needs to be
3490	has different warnings, and each user has different tastes regarding	3614	extended, libev needs to realloc and move the whole array, but this
3491	warning options. "Warn-free" code therefore cannot be a goal except when	3615	happens asymptotically rarer with higher number of elements, so O(1) might
3492	targeting a specific compiler and compiler-version.	3616	mean that libev does a lengthy realloc operation in rare cases, but on
		3617	average it is much faster and asymptotically approaches constant time.
3493		3618
3494	Another reason is that some compiler warnings require elaborate	3619	=over 4
3495	workarounds, or other changes to the code that make it less clear and less
3496	maintainable.
3497		3620
3498	And of course, some compiler warnings are just plain stupid, or simply	3621	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3499	wrong (because they don't actually warn about the condition their message
3500	seems to warn about).
3501		3622
3502	While libev is written to generate as few warnings as possible,	3623	This means that, when you have a watcher that triggers in one hour and
3503	"warn-free" code is not a goal, and it is recommended not to build libev	3624	there are 100 watchers that would trigger before that, then inserting will
3504	with any compiler warnings enabled unless you are prepared to cope with	3625	have to skip roughly seven (C<ld 100>) of these watchers.
3505	them (e.g. by ignoring them). Remember that warnings are just that:
3506	warnings, not errors, or proof of bugs.
3507		3626
		3627	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3508		3628
3509	=head1 VALGRIND	3629	That means that changing a timer costs less than removing/adding them,
		3630	as only the relative motion in the event queue has to be paid for.
3510		3631
3511	Valgrind has a special section here because it is a popular tool that is	3632	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3512	highly useful, but valgrind reports are very hard to interpret.
3513		3633
3514	If you think you found a bug (memory leak, uninitialised data access etc.)	3634	These just add the watcher into an array or at the head of a list.
3515	in libev, then check twice: If valgrind reports something like:
3516		3635
3517	==2274== definitely lost: 0 bytes in 0 blocks.	3636	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3518	==2274== possibly lost: 0 bytes in 0 blocks.
3519	==2274== still reachable: 256 bytes in 1 blocks.
3520		3637
3521	Then there is no memory leak. Similarly, under some circumstances,	3638	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3522	valgrind might report kernel bugs as if it were a bug in libev, or it
3523	might be confused (it is a very good tool, but only a tool).
3524		3639
3525	If you are unsure about something, feel free to contact the mailing list	3640	These watchers are stored in lists, so they need to be walked to find the
3526	with the full valgrind report and an explanation on why you think this is	3641	correct watcher to remove. The lists are usually short (you don't usually
3527	a bug in libev. However, don't be annoyed when you get a brisk "this is	3642	have many watchers waiting for the same fd or signal: one is typical, two
3528	no bug" answer and take the chance of learning how to interpret valgrind	3643	is rare).
3529	properly.
3530		3644
3531	If you need, for some reason, empty reports from valgrind for your project	3645	=item Finding the next timer in each loop iteration: O(1)
3532	I suggest using suppression lists.	3646
		3647	By virtue of using a binary or 4-heap, the next timer is always found at a
		3648	fixed position in the storage array.
		3649
		3650	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3651
		3652	A change means an I/O watcher gets started or stopped, which requires
		3653	libev to recalculate its status (and possibly tell the kernel, depending
		3654	on backend and whether C<ev_io_set> was used).
		3655
		3656	=item Activating one watcher (putting it into the pending state): O(1)
		3657
		3658	=item Priority handling: O(number_of_priorities)
		3659
		3660	Priorities are implemented by allocating some space for each
		3661	priority. When doing priority-based operations, libev usually has to
		3662	linearly search all the priorities, but starting/stopping and activating
		3663	watchers becomes O(1) with respect to priority handling.
		3664
		3665	=item Sending an ev_async: O(1)
		3666
		3667	=item Processing ev_async_send: O(number_of_async_watchers)
		3668
		3669	=item Processing signals: O(max_signal_number)
		3670
		3671	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3672	calls in the current loop iteration. Checking for async and signal events
		3673	involves iterating over all running async watchers or all signal numbers.
		3674
		3675	=back
3533		3676
3534		3677
3535	=head1 AUTHOR	3678	=head1 AUTHOR
3536		3679
3537	Marc Lehmann <libev@schmorp.de>.	3680	Marc Lehmann <libev@schmorp.de>.

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