ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.176 by root, Mon Sep 8 17:24:39 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
…		…
596	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
597	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.
598		620
599	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
600	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
601	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
602	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
603	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.
604		627
605	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
606	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
607	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.
608		632
609	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
610	necessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
611	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
612	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
613	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
614	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
615	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
616		644
617	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
618		646
619	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
…		…
629	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
630	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
631	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
633	- 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.
634	- Queue all outstanding timers.	662	- Queue all expired timers.
635	- Queue all outstanding periodics.	663	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
637	- Queue all check watchers.	665	- Queue all check watchers.
638	- 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).
639	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
640	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
…		…
657	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
658	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.
659		687
660	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.
661		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
662	=item ev_ref (loop)	692	=item ev_ref (loop)
663		693
664	=item ev_unref (loop)	694	=item ev_unref (loop)
665		695
666	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
667	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
668	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
669	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>
670	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
671	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
672	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
673	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
674	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
675	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>
676	(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,
677	respectively).	710	respectively).
678		711
…		…
701	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>)
702	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
703	to increase efficiency of loop iterations (or to increase power-saving	736	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	737	opportunities).
705		738
706	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
707	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
708	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
709	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
710	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.
711		744
712	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
713	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,
…		…
715	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
716	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
717		750
718	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
719	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
721	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
722	any overhead in libev.	755	value will not introduce any overhead in libev.
723		756
724	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
725	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
726	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
727	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>,
…		…
735	they fire on, say, one-second boundaries only.	768	they fire on, say, one-second boundaries only.
736		769
737	=item ev_loop_verify (loop)	770	=item ev_loop_verify (loop)
738		771
739	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
740	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
741	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
742	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 ()>.
743		777
744	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
745	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
746	data structures consistent.	780	data structures consistent.
747		781
…		…
863	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
864	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
865	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
866	with the watcher being stopped.	900	with the watcher being stopped.
867		901
868	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
869	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
870	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
871	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
872	programs, though, so beware.	906	programs, though, as the fd could already be closed and reused for another
		907	thing, so beware.
873		908
874	=back	909	=back
875		910
876	=head2 GENERIC WATCHER FUNCTIONS	911	=head2 GENERIC WATCHER FUNCTIONS
877		912
…		…
893	(or never started) and there are no pending events outstanding.	928	(or never started) and there are no pending events outstanding.
894		929
895	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,
896	int revents)>.	931	int revents)>.
897		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
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	939	=item C<ev_TYPE_set> (ev_TYPE *, [args])
899		940
900	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
901	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
902	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
…		…
904	difference to the C<ev_init> macro).	945	difference to the C<ev_init> macro).
905		946
906	Although some watcher types do not have type-specific arguments	947	Although some watcher types do not have type-specific arguments
907	(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.
908		949
		950	See C<ev_init>, above, for an example.
		951
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	952	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		953
911	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
912	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
913	a watcher. The same limitations apply, of course.	956	a watcher. The same limitations apply, of course.
914		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
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
916		963
917	Starts (activates) the given watcher. Only active watchers will receive	964	Starts (activates) the given watcher. Only active watchers will receive
918	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);
919		971
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
921		973
922	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher again (if active) and clears the pending
923	status. It is possible that stopped watchers are pending (for example,	975	status. It is possible that stopped watchers are pending (for example,
…		…
980		1032
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1034
983	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
984	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
985	can deal with that fact.	1037	can deal with that fact, as both are simply passed through to the
		1038	callback.
986		1039
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1040	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1041
989	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
990	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
991	watcher isn't pending it does nothing and returns C<0>.	1044	watcher isn't pending it does nothing and returns C<0>.
992		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
993	=back	1049	=back
994		1050
995		1051
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1052	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1053
998	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
999	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
1000	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
1001	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
1002	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
1003	data:	1059	data:
1004		1060
…		…
1006	{	1062	{
1007	struct ev_io io;	1063	struct ev_io io;
1008	int otherfd;	1064	int otherfd;
1009	void *somedata;	1065	void *somedata;
1010	struct whatever *mostinteresting;	1066	struct whatever *mostinteresting;
1011	}	1067	};
		1068
		1069	...
		1070	struct my_io w;
		1071	ev_io_init (&w.io, my_cb, fd, EV_READ);
1012		1072
1013	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
1014	can cast it back to your own type:	1074	can cast it back to your own type:
1015		1075
1016	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)
…		…
1020	}	1080	}
1021		1081
1022	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
1023	instead have been omitted.	1083	instead have been omitted.
1024		1084
1025	Another common scenario is having some data structure with multiple	1085	Another common scenario is to use some data structure with multiple
1026	watchers:	1086	embedded watchers:
1027		1087
1028	struct my_biggy	1088	struct my_biggy
1029	{	1089	{
1030	int some_data;	1090	int some_data;
1031	ev_timer t1;	1091	ev_timer t1;
1032	ev_timer t2;	1092	ev_timer t2;
1033	}	1093	}
1034		1094
1035	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
1036	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):
1037		1100
1038	#include <stddef.h>	1101	#include <stddef.h>
1039		1102
1040	static void	1103	static void
1041	t1_cb (EV_P_ struct ev_timer *w, int revents)	1104	t1_cb (EV_P_ struct ev_timer *w, int revents)
…		…
1081	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
1082	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
1083	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
1084	required if you know what you are doing).	1147	required if you know what you are doing).
1085		1148
1086	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
1087	(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
1088	C<EVBACKEND_POLL>).	1151	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1089		1152
1090	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
1091	receive "spurious" readiness notifications, that is your callback might	1154	receive "spurious" readiness notifications, that is your callback might
1092	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
1093	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
1094	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
1095	this situation even with a relatively standard program structure. Thus	1158	this situation even with a relatively standard program structure. Thus
1096	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
1097	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.
1098		1161
1099	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
1100	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
1101	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
1102	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
1103	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.
1104		1171
1105	=head3 The special problem of disappearing file descriptors	1172	=head3 The special problem of disappearing file descriptors
1106		1173
1107	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
1108	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,
1109	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
1110	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
1111	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
1112	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
1113	fact, a different file descriptor.	1180	fact, a different file descriptor.
1114		1181
…		…
1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1212	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1146	C<EVBACKEND_POLL>.	1213	C<EVBACKEND_POLL>.
1147		1214
1148	=head3 The special problem of SIGPIPE	1215	=head3 The special problem of SIGPIPE
1149		1216
1150	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>:
1151	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
1152	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
1153	this is sensible behaviour, for daemons, this is usually undesirable.	1220	this is sensible behaviour, for daemons, this is usually undesirable.
1154		1221
1155	So when you encounter spurious, unexplained daemon exits, make sure you	1222	So when you encounter spurious, unexplained daemon exits, make sure you
1156	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
1157	somewhere, as that would have given you a big clue).	1224	somewhere, as that would have given you a big clue).
…		…
1164	=item ev_io_init (ev_io *, callback, int fd, int events)	1231	=item ev_io_init (ev_io *, callback, int fd, int events)
1165		1232
1166	=item ev_io_set (ev_io *, int fd, int events)	1233	=item ev_io_set (ev_io *, int fd, int events)
1167		1234
1168	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
1169	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
1170	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.
1171		1238
1172	=item int fd [read-only]	1239	=item int fd [read-only]
1173		1240
1174	The file descriptor being watched.	1241	The file descriptor being watched.
1175		1242
…		…
1187		1254
1188	static void	1255	static void
1189	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)
1190	{	1257	{
1191	ev_io_stop (loop, w);	1258	ev_io_stop (loop, w);
1192	.. 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
1193	}	1260	}
1194		1261
1195	...	1262	...
1196	struct ev_loop *loop = ev_default_init (0);	1263	struct ev_loop *loop = ev_default_init (0);
1197	struct ev_io stdin_readable;	1264	struct ev_io stdin_readable;
…		…
1205	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
1206	given time, and optionally repeating in regular intervals after that.	1273	given time, and optionally repeating in regular intervals after that.
1207		1274
1208	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
1209	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
1210	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
1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1212	monotonic clock option helps a lot here).	1279	monotonic clock option helps a lot here).
1213		1280
1214	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
1215	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
1216	order of execution is undefined.	1283	then order of execution is undefined.
1217		1284
1218	=head3 The special problem of time updates	1285	=head3 The special problem of time updates
1219		1286
1220	Establishing the current time is a costly operation (it usually takes at	1287	Establishing the current time is a costly operation (it usually takes at
1221	least two system calls): EV therefore updates its idea of the current	1288	least two system calls): EV therefore updates its idea of the current
1222	time only before and after C<ev_loop> polls for new events, which causes	1289	time only before and after C<ev_loop> collects new events, which causes a
1223	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1290	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1224	lots of events.	1291	lots of events in one iteration.
1225		1292
1226	The relative timeouts are calculated relative to the C<ev_now ()>	1293	The relative timeouts are calculated relative to the C<ev_now ()>
1227	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
1228	of the event triggering whatever timeout you are modifying/starting. If	1295	of the event triggering whatever timeout you are modifying/starting. If
1229	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
1230	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:
1231		1298
1232	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1299	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1233		1300
1234	If the event loop is suspended for a long time, one can also force an	1301	If the event loop is suspended for a long time, you can also force an
1235	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1302	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1236	()>.	1303	()>.
1237		1304
1238	=head3 Watcher-Specific Functions and Data Members	1305	=head3 Watcher-Specific Functions and Data Members
1239		1306
…		…
1290	ev_timer_again (loop, timer);	1357	ev_timer_again (loop, timer);
1291		1358
1292	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
1293	you want to modify its timeout value.	1360	you want to modify its timeout value.
1294		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
1295	=item ev_tstamp repeat [read-write]	1368	=item ev_tstamp repeat [read-write]
1296		1369
1297	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
1298	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),
1299	which is also when any modifications are taken into account.	1372	which is also when any modifications are taken into account.
1300		1373
1301	=back	1374	=back
1302		1375
1303	=head3 Examples	1376	=head3 Examples
…		…
1347	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
1348	roughly 10 seconds later as it uses a relative timeout).	1421	roughly 10 seconds later as it uses a relative timeout).
1349		1422
1350	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,
1351	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
1352	complicated, rules.	1425	complicated rules.
1353		1426
1354	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
1355	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
1356	during the same loop iteration then order of execution is undefined.	1429	during the same loop iteration, then order of execution is undefined.
1357		1430
1358	=head3 Watcher-Specific Functions and Data Members	1431	=head3 Watcher-Specific Functions and Data Members
1359		1432
1360	=over 4	1433	=over 4
1361		1434
1362	=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)
1363		1436
1364	=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)
1365		1438
1366	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
1367	operation, and we will explain them from simplest to complex:	1440	operation, and we will explain them from simplest to most complex:
1368		1441
1369	=over 4	1442	=over 4
1370		1443
1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1372		1445
1373	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
1374	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
1375	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
1376	run when the system time reaches or surpasses this time.	1449	only run when the system clock reaches or surpasses this time.
1377		1450
1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1379		1452
1380	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
1381	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)
1382	and then repeat, regardless of any time jumps.	1455	and then repeat, regardless of any time jumps.
1383		1456
1384	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
1385	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
1386	the hour:	1459	hour, on the hour:
1387		1460
1388	ev_periodic_set (&periodic, 0., 3600., 0);	1461	ev_periodic_set (&periodic, 0., 3600., 0);
1389		1462
1390	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,
1391	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
…		…
1478	=back	1551	=back
1479		1552
1480	=head3 Examples	1553	=head3 Examples
1481		1554
1482	Example: Call a callback every hour, or, more precisely, whenever the	1555	Example: Call a callback every hour, or, more precisely, whenever the
1483	system clock is divisible by 3600. The callback invocation times have	1556	system time is divisible by 3600. The callback invocation times have
1484	potentially a lot of jitter, but good long-term stability.	1557	potentially a lot of jitter, but good long-term stability.
1485		1558
1486	static void	1559	static void
1487	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)
1488	{	1561	{
…		…
1498	#include <math.h>	1571	#include <math.h>
1499		1572
1500	static ev_tstamp	1573	static ev_tstamp
1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1502	{	1575	{
1503	return fmod (now, 3600.) + 3600.;	1576	return now + (3600. - fmod (now, 3600.));
1504	}	1577	}
1505		1578
1506	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);
1507		1580
1508	Example: Call a callback every hour, starting now:	1581	Example: Call a callback every hour, starting now:
…		…
1518	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
1519	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
1520	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
1521	normal event processing, like any other event.	1594	normal event processing, like any other event.
1522		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
1523	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
1524	first watcher gets started will libev actually register a signal watcher	1601	first watcher gets started will libev actually register a signal handler
1525	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
1526	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
1527	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
1528	SIG_DFL (regardless of what it was set to before).	1605	signal handler to SIG_DFL (regardless of what it was set to before).
1529		1606
1530	If possible and supported, libev will install its handlers with	1607	If possible and supported, libev will install its handlers with
1531	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
1532	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
1533	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
…		…
1550		1627
1551	=back	1628	=back
1552		1629
1553	=head3 Examples	1630	=head3 Examples
1554		1631
1555	Example: Try to exit cleanly on SIGINT and SIGTERM.	1632	Example: Try to exit cleanly on SIGINT.
1556		1633
1557	static void	1634	static void
1558	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)
1559	{	1636	{
1560	ev_unloop (loop, EVUNLOOP_ALL);	1637	ev_unloop (loop, EVUNLOOP_ALL);
1561	}	1638	}
1562		1639
1563	struct ev_signal signal_watcher;	1640	struct ev_signal signal_watcher;
1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1565	ev_signal_start (loop, &sigint_cb);	1642	ev_signal_start (loop, &signal_watcher);
1566		1643
1567		1644
1568	=head2 C<ev_child> - watch out for process status changes	1645	=head2 C<ev_child> - watch out for process status changes
1569		1646
1570	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
1571	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
1572	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
1573	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
1574	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.
1575		1655
1576	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
1577	you can only register child watchers in the default event loop.	1657	you can only register child watchers in the default event loop.
1578		1658
1579	=head3 Process Interaction	1659	=head3 Process Interaction
…		…
1677	the stat buffer having unspecified contents.	1757	the stat buffer having unspecified contents.
1678		1758
1679	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
1680	relative and your working directory changes, the behaviour is undefined.	1760	relative and your working directory changes, the behaviour is undefined.
1681		1761
1682	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
1683	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
1684	can specify a recommended polling interval for this case. If you specify	1764	it changed somehow. You can specify a recommended polling interval for
1685	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!)
1686	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
1687	five seconds, although this might change dynamically). Libev will also	1767	you can expect to be around five seconds, although this might change
1688	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
1689	usually overkill.	1769	around C<0.1>, but thats usually overkill.
1690		1770
1691	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,
1692	as even with OS-supported change notifications, this can be	1772	as even with OS-supported change notifications, this can be
1693	resource-intensive.	1773	resource-intensive.
1694		1774
1695	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
1696	implemented (implementing kqueue support is left as an exercise for the	1776	is the Linux inotify interface (implementing kqueue support is left as
1697	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
1698	semantics with kqueue). Inotify will be used to give hints only and should	1778	of implementing C<ev_stat> semantics with kqueue).
1699	not change the semantics of C<ev_stat> watchers, which means that libev
1700	sometimes needs to fall back to regular polling again even with inotify,
1701	but changes are usually detected immediately, and if the file exists there
1702	will be no polling.
1703		1779
1704	=head3 ABI Issues (Largefile Support)	1780	=head3 ABI Issues (Largefile Support)
1705		1781
1706	Libev by default (unless the user overrides this) uses the default	1782	Libev by default (unless the user overrides this) uses the default
1707	compilation environment, which means that on systems with large file	1783	compilation environment, which means that on systems with large file
…		…
1716	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
1717	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
1718	to exchange stat structures with application programs compiled using the	1794	to exchange stat structures with application programs compiled using the
1719	default compilation environment.	1795	default compilation environment.
1720		1796
1721	=head3 Inotify	1797	=head3 Inotify and Kqueue
1722		1798
1723	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
1724	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
1725	change detection where possible. The inotify descriptor will be created lazily	1801	change detection where possible. The inotify descriptor will be created lazily
1726	when the first C<ev_stat> watcher is being started.	1802	when the first C<ev_stat> watcher is being started.
1727		1803
1728	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
1729	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
1730	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
1731	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.
1732		1809
1733	(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
1734	implement this functionality, due to the requirement of having a file	1811	implement this functionality, due to the requirement of having a file
1735	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.
1736		1814
1737	=head3 The special problem of stat time resolution	1815	=head3 The special problem of stat time resolution
1738		1816
1739	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
1740	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
1741	only support whole seconds.	1819	only support whole seconds.
1742		1820
1743	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
1744	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
1745	calls your callback, which does something. When there is another update	1823	calls your callback, which does something. When there is another update
1746	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
1747	data does not change.	1825	stat data does change in other ways (e.g. file size).
1748		1826
1749	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
1750	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
1751	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);
1752	ev_timer_again (loop, w)>).	1830	ev_timer_again (loop, w)>).
…		…
1772	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
1773	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
1774	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
1775	path for as long as the watcher is active.	1853	path for as long as the watcher is active.
1776		1854
1777	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,
1778	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
1779	was detected).	1857	last change was detected).
1780		1858
1781	=item ev_stat_stat (loop, ev_stat *)	1859	=item ev_stat_stat (loop, ev_stat *)
1782		1860
1783	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
1784	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
…		…
1867		1945
1868		1946
1869	=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...
1870		1948
1871	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
1872	priority are pending (prepare, check and other idle watchers do not	1950	priority are pending (prepare, check and other idle watchers do not count
1873	count).	1951	as receiving "events").
1874		1952
1875	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
1876	(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
1877	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
1878	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
…		…
1917	ev_idle_start (loop, idle_cb);	1995	ev_idle_start (loop, idle_cb);
1918		1996
1919		1997
1920	=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!
1921		1999
1922	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:
1923	prepare watchers get invoked before the process blocks and check watchers	2001	prepare watchers get invoked before the process blocks and check watchers
1924	afterwards.	2002	afterwards.
1925		2003
1926	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
1927	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>
…		…
1930	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,
1931	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
1932	called in pairs bracketing the blocking call.	2010	called in pairs bracketing the blocking call.
1933		2011
1934	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
1935	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
1936	variable changes, implement your own watchers, integrate net-snmp or a	2014	variable changes, implement your own watchers, integrate net-snmp or a
1937	coroutine library and lots more. They are also occasionally useful if	2015	coroutine library and lots more. They are also occasionally useful if
1938	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,
1939	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>
1940	watcher).	2018	watcher).
1941		2019
1942	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
1943	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
1944	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
1945	provide just this functionality). Then, in the check watcher you check for	2023	libraries provide exactly this functionality). Then, in the check watcher,
1946	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
1947	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
1948	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
1949	because you never know, you know?).	2027	nevertheless, because you never know, you know?).
1950		2028
1951	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
1952	coroutines into libev programs, by yielding to other active coroutines	2030	coroutines into libev programs, by yielding to other active coroutines
1953	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
1954	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
…		…
1957	loop from blocking if lower-priority coroutines are active, thus mapping	2035	loop from blocking if lower-priority coroutines are active, thus mapping
1958	low-priority coroutines to idle/background tasks).	2036	low-priority coroutines to idle/background tasks).
1959		2037
1960	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>)
1961	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
1962	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
1963	too) should not activate ("feed") events into libev. While libev fully	2043	activate ("feed") events into libev. While libev fully supports this, they
1964	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
1965	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
1966	(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
1967	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
1968	coexist peacefully with others).	2048	others).
1969		2049
1970	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1971		2051
1972	=over 4	2052	=over 4
1973		2053
…		…
1975		2055
1976	=item ev_check_init (ev_check *, callback)	2056	=item ev_check_init (ev_check *, callback)
1977		2057
1978	Initialises and configures the prepare or check watcher - they have no	2058	Initialises and configures the prepare or check watcher - they have no
1979	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>
1980	macros, but using them is utterly, utterly and completely pointless.	2060	macros, but using them is utterly, utterly, utterly and completely
		2061	pointless.
1981		2062
1982	=back	2063	=back
1983		2064
1984	=head3 Examples	2065	=head3 Examples
1985		2066
…		…
2078	}	2159	}
2079		2160
2080	// do not ever call adns_afterpoll	2161	// do not ever call adns_afterpoll
2081		2162
2082	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
2083	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
2084	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
2085	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
2086	this.	2167	this approach, effectively embedding EV as a client into the horrible
		2168	libglib event loop.
2087		2169
2088	static gint	2170	static gint
2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2171	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2090	{	2172	{
2091	int got_events = 0;	2173	int got_events = 0;
…		…
2122	prioritise I/O.	2204	prioritise I/O.
2123		2205
2124	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
2125	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
2126	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
2127	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
2128	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
2129	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
2130	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 :)
2131		2214
2132	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
2133	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),
2134	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
2135	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
2136	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.
2137		2220
2138	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
2139	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
2140	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
2141	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
…		…
2149	interested in that.	2232	interested in that.
2150		2233
2151	Also, there have not currently been made special provisions for forking:	2234	Also, there have not currently been made special provisions for forking:
2152	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,
2153	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
2154	yourself.	2237	yourself - but you can use a fork watcher to handle this automatically,
		2238	and future versions of libev might do just that.
2155		2239
2156	Unfortunately, not all backends are embeddable, only the ones returned by	2240	Unfortunately, not all backends are embeddable: only the ones returned by
2157	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2158	portable one.	2242	portable one.
2159		2243
2160	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
2161	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
2162	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
2163	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.
2164		2256
2165	=head3 Watcher-Specific Functions and Data Members	2257	=head3 Watcher-Specific Functions and Data Members
2166		2258
2167	=over 4	2259	=over 4
2168		2260
…		…
2286	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
2287	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
2288	need elaborate support such as pthreads.	2380	need elaborate support such as pthreads.
2289		2381
2290	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
2291	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
2292	queue:	2384	queue:
2293		2385
2294	=over 4	2386	=over 4
2295		2387
2296	=item queueing from a signal handler context	2388	=item queueing from a signal handler context
2297		2389
2298	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
2299	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
2300	some fictitious SIGUSR1 handler:	2392	an example that does that for some fictitious SIGUSR1 handler:
2301		2393
2302	static ev_async mysig;	2394	static ev_async mysig;
2303		2395
2304	static void	2396	static void
2305	sigusr1_handler (void)	2397	sigusr1_handler (void)
…		…
2372		2464
2373	=item ev_async_init (ev_async *, callback)	2465	=item ev_async_init (ev_async *, callback)
2374		2466
2375	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
2376	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,
2377	believe me.	2469	trust me.
2378		2470
2379	=item ev_async_send (loop, ev_async *)	2471	=item ev_async_send (loop, ev_async *)
2380		2472
2381	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
2382	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
2383	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
2384	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
2385	section below on what exactly this means).	2477	section below on what exactly this means).
2386		2478
2387	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,
2388	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
…		…
2412	=over 4	2504	=over 4
2413		2505
2414	=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)
2415		2507
2416	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
2417	callback on whichever event happens first and automatically stop both	2509	callback on whichever event happens first and automatically stops both
2418	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
2419	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
2420	more watchers yourself.	2512	more watchers yourself.
2421		2513
2422	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
2423	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
2424	C<events> set will be created and started.	2516	the given C<fd> and C<events> set will be created and started.
2425		2517
2426	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
2427	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
2428	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.
2429	dubious value.
2430		2521
2431	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
2432	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
2433	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>
2434	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.
2435		2530
2436	static void stdin_ready (int revents, void *arg)	2531	static void stdin_ready (int revents, void *arg)
2437	{	2532	{
		2533	if (revents & EV_READ)
		2534	/* stdin might have data for us, joy! */;
2438	if (revents & EV_TIMEOUT)	2535	else if (revents & EV_TIMEOUT)
2439	/* doh, nothing entered */;	2536	/* doh, nothing entered */;
2440	else if (revents & EV_READ)
2441	/* stdin might have data for us, joy! */;
2442	}	2537	}
2443		2538
2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2445		2540
2446	=item ev_feed_event (ev_loop *, watcher *, int revents)	2541	=item ev_feed_event (ev_loop *, watcher *, int revents)
…		…
2594		2689
2595	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)>.
2596		2691
2597	See the method-C<set> above for more details.	2692	See the method-C<set> above for more details.
2598		2693
2599	Example:	2694	Example: Use a plain function as callback.
2600		2695
2601	static void io_cb (ev::io &w, int revents) { }	2696	static void io_cb (ev::io &w, int revents) { }
2602	iow.set <io_cb> ();	2697	iow.set <io_cb> ();
2603		2698
2604	=item w->set (struct ev_loop *)	2699	=item w->set (struct ev_loop *)
…		…
2642	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
2643	the constructor.	2738	the constructor.
2644		2739
2645	class myclass	2740	class myclass
2646	{	2741	{
2647	ev::io io; void io_cb (ev::io &w, int revents);	2742	ev::io io ; void io_cb (ev::io &w, int revents);
2648	ev:idle idle void idle_cb (ev::idle &w, int revents);	2743	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2649		2744
2650	myclass (int fd)	2745	myclass (int fd)
2651	{	2746	{
2652	io .set <myclass, &myclass::io_cb > (this);	2747	io .set <myclass, &myclass::io_cb > (this);
2653	idle.set <myclass, &myclass::idle_cb> (this);	2748	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2669	=item Perl	2764	=item Perl
2670		2765
2671	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
2672	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,
2673	there are additional modules that implement libev-compatible interfaces	2768	there are additional modules that implement libev-compatible interfaces
2674	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),
2675	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>).
2676		2772
2677	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
2678	L<http://software.schmorp.de/pkg/EV>.	2774	L<http://software.schmorp.de/pkg/EV>.
2679		2775
2680	=item Python	2776	=item Python
…		…
2859		2955
2860	=head2 PREPROCESSOR SYMBOLS/MACROS	2956	=head2 PREPROCESSOR SYMBOLS/MACROS
2861		2957
2862	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
2863	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
2864	autoconf is noted for every option.	2960	autoconf is documented for every option.
2865		2961
2866	=over 4	2962	=over 4
2867		2963
2868	=item EV_STANDALONE	2964	=item EV_STANDALONE
2869		2965
…		…
3039	When doing priority-based operations, libev usually has to linearly search	3135	When doing priority-based operations, libev usually has to linearly search
3040	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
3041	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
3042	fine.	3138	fine.
3043		3139
3044	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
3045	C<0> will save some memory and CPU.	3141	both to C<0> will save some memory and CPU.
3046		3142
3047	=item EV_PERIODIC_ENABLE	3143	=item EV_PERIODIC_ENABLE
3048		3144
3049	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
3050	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
…		…
3057	code.	3153	code.
3058		3154
3059	=item EV_EMBED_ENABLE	3155	=item EV_EMBED_ENABLE
3060		3156
3061	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
3062	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.
3063		3160
3064	=item EV_STAT_ENABLE	3161	=item EV_STAT_ENABLE
3065		3162
3066	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
3067	defined to be C<0>, then they are not.	3164	defined to be C<0>, then they are not.
…		…
3099	two).	3196	two).
3100		3197
3101	=item EV_USE_4HEAP	3198	=item EV_USE_4HEAP
3102		3199
3103	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
3104	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
3105	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
3106	noticeably faster performance with many (thousands) of watchers.	3203	faster performance with many (thousands) of watchers.
3107		3204
3108	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>
3109	(disabled).	3206	(disabled).
3110		3207
3111	=item EV_HEAP_CACHE_AT	3208	=item EV_HEAP_CACHE_AT
3112		3209
3113	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
3114	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
3115	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>),
3116	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,
3117	but avoids random read accesses on heap changes. This improves performance	3214	but avoids random read accesses on heap changes. This improves performance
3118	noticeably with with many (hundreds) of watchers.	3215	noticeably with many (hundreds) of watchers.
3119		3216
3120	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>
3121	(disabled).	3218	(disabled).
3122		3219
3123	=item EV_VERIFY	3220	=item EV_VERIFY
…		…
3129	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
3130	verification code will be called very frequently, which will slow down	3227	verification code will be called very frequently, which will slow down
3131	libev considerably.	3228	libev considerably.
3132		3229
3133	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
3134	C<0.>	3231	C<0>.
3135		3232
3136	=item EV_COMMON	3233	=item EV_COMMON
3137		3234
3138	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
3139	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
…		…
3156	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
3157	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
3158	their default definitions. One possible use for overriding these is to	3255	their default definitions. One possible use for overriding these is to
3159	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
3160	method calls instead of plain function calls in C++.	3257	method calls instead of plain function calls in C++.
		3258
		3259	=back
3161		3260
3162	=head2 EXPORTED API SYMBOLS	3261	=head2 EXPORTED API SYMBOLS
3163		3262
3164	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
3165	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
…		…
3212	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:
3213		3312
3214	#include "ev_cpp.h"	3313	#include "ev_cpp.h"
3215	#include "ev.c"	3314	#include "ev.c"
3216		3315
		3316	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3217		3317
3218	=head1 THREADS AND COROUTINES	3318	=head2 THREADS AND COROUTINES
3219		3319
3220	=head2 THREADS	3320	=head3 THREADS
3221		3321
3222	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
3223	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
3224	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
3225	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.
3226		3329
3227	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
3228	parallel from multiple threads, calls with the same loop parameter must be	3331	concurrently from multiple threads, calls with the same loop parameter
3229	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
3230	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
3231	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".
3232		3340
3233	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
3234	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
3235	help you. I can give some generic advice however:	3343	help you, but here is some generic advice:
3236		3344
3237	=over 4	3345	=over 4
3238		3346
3239	=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
3240	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.
…		…
3252		3360
3253	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
3254	better than you currently do :-)	3362	better than you currently do :-)
3255		3363
3256	=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
3257	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
3258	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.
3259		3374
3260	=back	3375	=back
3261		3376
3262	=head2 COROUTINES	3377	=head3 COROUTINES
3263		3378
3264	Libev is much more accommodating to coroutines ("cooperative threads"):	3379	Libev is very accommodating to coroutines ("cooperative threads"):
3265	libev fully supports nesting calls to it's functions from different	3380	libev fully supports nesting calls to its functions from different
3266	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
3267	different coroutines and switch freely between both coroutines running the	3382	different coroutines, and switch freely between both coroutines running the
3268	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
3269	you must not do this from C<ev_periodic> reschedule callbacks.	3384	you must not do this from C<ev_periodic> reschedule callbacks.
3270		3385
3271	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
3272	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
3273	switches.	3388	they do not clal any callbacks.
3274		3389
		3390	=head2 COMPILER WARNINGS
3275		3391
3276	=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.
3277		3395
3278	In this section the complexities of (many of) the algorithms used inside	3396	However, these are unavoidable for many reasons. For one, each compiler
3279	libev will be explained. For complexity discussions about backends see the	3397	has different warnings, and each user has different tastes regarding
3280	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.
3281		3400
3282	All of the following are about amortised time: If an array needs to be	3401	Another reason is that some compiler warnings require elaborate
3283	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
3284	happens asymptotically never with higher number of elements, so O(1) might	3403	maintainable.
3285	mean it might do a lengthy realloc operation in rare cases, but on average
3286	it is much faster and asymptotically approaches constant time.
3287		3404
3288	=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.
3289		3411
3290	=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.
3291		3417
3292	This means that, when you have a watcher that triggers in one hour and
3293	there are 100 watchers that would trigger before that then inserting will
3294	have to skip roughly seven (C<ld 100>) of these watchers.
3295		3418
3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3419	=head2 VALGRIND
3297		3420
3298	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
3299	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.
3300		3423
3301	=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:
3302		3426
3303	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.
3304		3430
3305	=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.
3306		3433
3307	=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.
3308		3438
3309	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
3310	correct watcher to remove. The lists are usually short (you don't usually	3440	make it into some kind of religion.
3311	have many watchers waiting for the same fd or signal).
3312		3441
3313	=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.
3314		3447
3315	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
3316	fixed position in the storage array.	3449	I suggest using suppression lists.
3317		3450
3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3319		3451
3320	A change means an I/O watcher gets started or stopped, which requires	3452	=head1 PORTABILITY NOTES
3321	libev to recalculate its status (and possibly tell the kernel, depending
3322	on backend and whether C<ev_io_set> was used).
3323		3453
3324	=item Activating one watcher (putting it into the pending state): O(1)
3325
3326	=item Priority handling: O(number_of_priorities)
3327
3328	Priorities are implemented by allocating some space for each
3329	priority. When doing priority-based operations, libev usually has to
3330	linearly search all the priorities, but starting/stopping and activating
3331	watchers becomes O(1) w.r.t. priority handling.
3332
3333	=item Sending an ev_async: O(1)
3334
3335	=item Processing ev_async_send: O(number_of_async_watchers)
3336
3337	=item Processing signals: O(max_signal_number)
3338
3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
3340	calls in the current loop iteration. Checking for async and signal events
3341	involves iterating over all running async watchers or all signal numbers.
3342
3343	=back
3344
3345
3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3454	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3347		3455
3348	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
3349	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
3350	model. Libev still offers limited functionality on this platform in	3458	model. Libev still offers limited functionality on this platform in
3351	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
…		…
3362		3470
3363	Not a libev limitation but worth mentioning: windows apparently doesn't	3471	Not a libev limitation but worth mentioning: windows apparently doesn't
3364	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
3365	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,
3366	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
3367	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
3368	available).	3476	available).
3369		3477
3370	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
3371	the abysmal performance of winsockets, using a large number of sockets	3479	the abysmal performance of winsockets, using a large number of sockets
3372	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
…		…
3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3491	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3384		3492
3385	#include "ev.h"	3493	#include "ev.h"
3386		3494
3387	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
3388	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!):
3389		3497
3390	#include "evwrap.h"	3498	#include "evwrap.h"
3391	#include "ev.c"	3499	#include "ev.c"
3392		3500
3393	=over 4	3501	=over 4
…		…
3438	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
3439	calling select (O(n²)) will likely make this unworkable.	3547	calling select (O(n²)) will likely make this unworkable.
3440		3548
3441	=back	3549	=back
3442		3550
3443
3444	=head1 PORTABILITY REQUIREMENTS	3551	=head2 PORTABILITY REQUIREMENTS
3445		3552
3446	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
3447	additional extensions:	3554	backend-specific APIs, libev relies on a few additional extensions:
3448		3555
3449	=over 4	3556	=over 4
3450		3557
3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3558	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3452	calling conventions regardless of C<ev_watcher_type *>.	3559	calling conventions regardless of C<ev_watcher_type *>.
…		…
3458	calls them using an C<ev_watcher *> internally.	3565	calls them using an C<ev_watcher *> internally.
3459		3566
3460	=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
3461		3568
3462	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
3463	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
3464	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
3465	believed to be sufficiently portable.	3572	believed to be sufficiently portable.
3466		3573
3467	=item C<sigprocmask> must work in a threaded environment	3574	=item C<sigprocmask> must work in a threaded environment
3468		3575
…		…
3477	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
3478	well.	3585	well.
3479		3586
3480	=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
3481		3588
3482	To improve portability and simplify using libev, libev uses C<long>	3589	To improve portability and simplify its API, libev uses C<long> internally
3483	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
3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3591	systems (Microsoft...) this might be unexpectedly low, but is still at
3485	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
3486	millions of watchers.	3593	watchers.
3487		3594
3488	=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
3489		3596
3490	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
3491	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
…		…
3495	=back	3602	=back
3496		3603
3497	If you know of other additional requirements drop me a note.	3604	If you know of other additional requirements drop me a note.
3498		3605
3499		3606
3500	=head1 COMPILER WARNINGS	3607	=head1 ALGORITHMIC COMPLEXITIES
3501		3608
3502	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
3503	lot of warnings when compiling libev code. Some people are apparently	3610	libev will be documented. For complexity discussions about backends see
3504	scared by this.	3611	the documentation for C<ev_default_init>.
3505		3612
3506	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
3507	has different warnings, and each user has different tastes regarding	3614	extended, libev needs to realloc and move the whole array, but this
3508	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
3509	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.
3510		3618
3511	Another reason is that some compiler warnings require elaborate	3619	=over 4
3512	workarounds, or other changes to the code that make it less clear and less
3513	maintainable.
3514		3620
3515	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)
3516	wrong (because they don't actually warn about the condition their message
3517	seems to warn about).
3518		3622
3519	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
3520	"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
3521	with any compiler warnings enabled unless you are prepared to cope with	3625	have to skip roughly seven (C<ld 100>) of these watchers.
3522	them (e.g. by ignoring them). Remember that warnings are just that:
3523	warnings, not errors, or proof of bugs.
3524		3626
		3627	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3525		3628
3526	=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.
3527		3631
3528	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)
3529	highly useful, but valgrind reports are very hard to interpret.
3530		3633
3531	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.
3532	in libev, then check twice: If valgrind reports something like:
3533		3635
3534	==2274== definitely lost: 0 bytes in 0 blocks.	3636	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3535	==2274== possibly lost: 0 bytes in 0 blocks.
3536	==2274== still reachable: 256 bytes in 1 blocks.
3537		3637
3538	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))
3539	valgrind might report kernel bugs as if it were a bug in libev, or it
3540	might be confused (it is a very good tool, but only a tool).
3541		3639
3542	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
3543	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
3544	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
3545	no bug" answer and take the chance of learning how to interpret valgrind	3643	is rare).
3546	properly.
3547		3644
3548	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)
3549	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
3550		3676
3551		3677
3552	=head1 AUTHOR	3678	=head1 AUTHOR
3553		3679
3554	Marc Lehmann <libev@schmorp.de>.	3680	Marc Lehmann <libev@schmorp.de>.

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines