ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.171 by root, Tue Jul 8 09:49:15 2008 UTC vs.
Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC

…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	362	readiness notifications you get per iteration.
363		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
		367
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		369
366	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
372		379
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		381
375	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
…		…
389	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.	398	(or space) is available.
392		399
393	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
396		405
397	While nominally embeddable in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	407	all kernel versions tested so far.
399		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		413
402	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
404	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
405	it's completely useless). For this reason it's not being "auto-detected"	417	completely useless). For this reason it's not being "auto-detected" unless
406	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
408	system like NetBSD.
409		420
410	You still can embed kqueue into a normal poll or select backend and use it	421	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	422	only for sockets (after having made sure that sockets work with kqueue on
412	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
413		424
414	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	427	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	429	two event changes per incident. Support for C<fork ()> is very bad and it
419	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
420		431
421	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
422		433
423	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	435	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	436	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	437	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
429		444
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		446
432	This is not implemented yet (and might never be, unless you send me an	447	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	461	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	462	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	464	might perform better.
450		465
451	On the positive side, ignoring the spurious readiness notifications, this	466	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
454		473
455	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
456		475
457	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		483
465	If one or more of these are or'ed into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		487
469	The most typical usage is like this:	488	Example: This is the most typical usage.
470		489
471	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		492
474	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	494	environment settings to be taken into account:
476		495
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		497
479	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
482		502
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		504
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		506
…		…
544		564
545	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
546		566
547	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
550		571
551	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
552		573
553	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
554		576
555	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
556		578
557	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
573	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
577		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
578	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
579		613
580	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
582	events.	616	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
586		620
587	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
592		627
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
596		632
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
601	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
604		644
605	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
606		646
607	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
…		…
617	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	662	- Queue all expired timers.
623	- Queue all outstanding periodics.	663	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	665	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
627	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
…		…
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		687
648	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
649		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
650	=item ev_ref (loop)	692	=item ev_ref (loop)
651		693
652	=item ev_unref (loop)	694	=item ev_unref (loop)
653		695
654	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
655	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
656	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
657	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
658	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
659	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
660	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
661	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
662	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
663	libraries. Just remember to I<unref after start> and I<ref before stop>	708	libraries. Just remember to I<unref after start> and I<ref before stop>
664	(but only if the watcher wasn't active before, or was active before,	709	(but only if the watcher wasn't active before, or was active before,
665	respectively).	710	respectively).
666		711
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	735	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	736	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	737	opportunities).
693		738
694	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
695	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
696	the program responsive, it also wastes a lot of CPU time to poll for new	741	program responsive, it also wastes a lot of CPU time to poll for new
697	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
699		744
700	By setting a higher I<io collect interval> you allow libev to spend more	745	By setting a higher I<io collect interval> you allow libev to spend more
701	time collecting I/O events, so you can handle more events per iteration,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	C<ev_timer>) will be not affected. Setting this to a non-null value will
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
705		750
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	755	value will not introduce any overhead in libev.
711		756
712	Many (busy) programs can usually benefit by setting the I/O collect	757	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	758	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	760	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
723	they fire on, say, one-second boundaries only.	768	they fire on, say, one-second boundaries only.
724		769
725	=item ev_loop_verify (loop)	770	=item ev_loop_verify (loop)
726		771
727	This function only does something when C<EV_VERIFY> support has been	772	This function only does something when C<EV_VERIFY> support has been
728	compiled in. It tries to go through all internal structures and checks	773	compiled in. which is the default for non-minimal builds. It tries to go
729	them for validity. If anything is found to be inconsistent, it will print	774	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
731		777
732	This can be used to catch bugs inside libev itself: under normal	778	This can be used to catch bugs inside libev itself: under normal
733	circumstances, this function will never abort as of course libev keeps its	779	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	780	data structures consistent.
735		781
…		…
848	=item C<EV_ERROR>	894	=item C<EV_ERROR>
849		895
850	An unspecified error has occurred, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
853	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
855		905
856	Libev will usually signal a few "dummy" events together with an error,	906	Libev will usually signal a few "dummy" events together with an error, for
857	for example it might indicate that a fd is readable or writable, and if	907	example it might indicate that a fd is readable or writable, and if your
858	your callbacks is well-written it can just attempt the operation and cope	908	callbacks is well-written it can just attempt the operation and cope with
859	with the error from read() or write(). This will not work in multi-threaded	909	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
861		912
862	=back	913	=back
863		914
864	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
865		916
…		…
881	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
882		933
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	935	int revents)>.
885		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
		942
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		944
888	This macro initialises the type-specific parts of a watcher. You need to	945	This macro initialises the type-specific parts of a watcher. You need to
889	call C<ev_init> at least once before you call this macro, but you can	946	call C<ev_init> at least once before you call this macro, but you can
890	call C<ev_TYPE_set> any number of times. You must not, however, call this	947	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
892	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
893		950
894	Although some watcher types do not have type-specific arguments	951	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		953
		954	See C<ev_init>, above, for an example.
		955
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		957
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
900	calls into a single call. This is the most convenient method to initialise	959	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
902		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		965
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		967
905	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
907		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		977
910	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
911	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		986
917	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
918		988
919	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
920	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
968		1038
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1040
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
974		1045
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1047
977	If the watcher is pending, this function returns clears its pending status	1048	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1049	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1050	watcher isn't pending it does nothing and returns C<0>.
980		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
981	=back	1055	=back
982		1056
983		1057
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1059
986	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
991	data:	1065	data:
992		1066
…		…
994	{	1068	{
995	struct ev_io io;	1069	struct ev_io io;
996	int otherfd;	1070	int otherfd;
997	void *somedata;	1071	void *somedata;
998	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
999	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1078
1001	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1080	can cast it back to your own type:
1003		1081
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
…		…
1008	}	1086	}
1009		1087
1010	More interesting and less C-conformant ways of casting your callback type	1088	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1089	instead have been omitted.
1012		1090
1013	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
1014	watchers:	1092	embedded watchers:
1015		1093
1016	struct my_biggy	1094	struct my_biggy
1017	{	1095	{
1018	int some_data;	1096	int some_data;
1019	ev_timer t1;	1097	ev_timer t1;
1020	ev_timer t2;	1098	ev_timer t2;
1021	}	1099	}
1022		1100
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1101	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
1025		1106
1026	#include <stddef.h>	1107	#include <stddef.h>
1027		1108
1028	static void	1109	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ struct ev_timer *w, int revents)
…		…
1069	In general you can register as many read and/or write event watchers per	1150	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1151	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1152	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1153	required if you know what you are doing).
1073		1154
1074	If you must do this, then force the use of a known-to-be-good backend	1155	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1156	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1077		1158
1078	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1167
1087	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1169	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
1092		1177
1093	=head3 The special problem of disappearing file descriptors	1178	=head3 The special problem of disappearing file descriptors
1094		1179
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1181	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1182	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1183	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1184	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1185	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1186	fact, a different file descriptor.
1102		1187
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1219	C<EVBACKEND_POLL>.
1135		1220
1136	=head3 The special problem of SIGPIPE	1221	=head3 The special problem of SIGPIPE
1137		1222
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when reading from a pipe whose other end has been closed, your program	1224	when writing to a pipe whose other end has been closed, your program gets
1140	gets send a SIGPIPE, which, by default, aborts your program. For most	1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	programs this is sensible behaviour, for daemons, this is usually	1226	this is sensible behaviour, for daemons, this is usually undesirable.
1142	undesirable.
1143		1227
1144	So when you encounter spurious, unexplained daemon exits, make sure you	1228	So when you encounter spurious, unexplained daemon exits, make sure you
1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1146	somewhere, as that would have given you a big clue).	1230	somewhere, as that would have given you a big clue).
1147		1231
…		…
1153	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
1154		1238
1155	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
1156		1240
1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1242	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1159	C<EV_READ | EV_WRITE> to receive the given events.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1160		1244
1161	=item int fd [read-only]	1245	=item int fd [read-only]
1162		1246
1163	The file descriptor being watched.	1247	The file descriptor being watched.
1164		1248
…		…
1176		1260
1177	static void	1261	static void
1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1179	{	1263	{
1180	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
1182	}	1266	}
1183		1267
1184	...	1268	...
1185	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
1186	struct ev_io stdin_readable;	1270	struct ev_io stdin_readable;
…		…
1194	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
1195	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
1196		1280
1197	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
1198	times out after an hour and you reset your system clock to January last	1282	times out after an hour and you reset your system clock to January last
1199	year, it will still time out after (roughly) and hour. "Roughly" because	1283	year, it will still time out after (roughly) one hour. "Roughly" because
1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1201	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
		1286
		1287	The callback is guaranteed to be invoked only I<after> its timeout has
		1288	passed, but if multiple timers become ready during the same loop iteration
		1289	then order of execution is undefined.
		1290
		1291	=head3 The special problem of time updates
		1292
		1293	Establishing the current time is a costly operation (it usually takes at
		1294	least two system calls): EV therefore updates its idea of the current
		1295	time only before and after C<ev_loop> collects new events, which causes a
		1296	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1297	lots of events in one iteration.
1202		1298
1203	The relative timeouts are calculated relative to the C<ev_now ()>	1299	The relative timeouts are calculated relative to the C<ev_now ()>
1204	time. This is usually the right thing as this timestamp refers to the time	1300	time. This is usually the right thing as this timestamp refers to the time
1205	of the event triggering whatever timeout you are modifying/starting. If	1301	of the event triggering whatever timeout you are modifying/starting. If
1206	you suspect event processing to be delayed and you I<need> to base the timeout	1302	you suspect event processing to be delayed and you I<need> to base the
1207	on the current time, use something like this to adjust for this:	1303	timeout on the current time, use something like this to adjust for this:
1208		1304
1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1305	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1210		1306
1211	The callback is guaranteed to be invoked only after its timeout has passed,	1307	If the event loop is suspended for a long time, you can also force an
1212	but if multiple timers become ready during the same loop iteration then	1308	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1213	order of execution is undefined.	1309	()>.
1214		1310
1215	=head3 Watcher-Specific Functions and Data Members	1311	=head3 Watcher-Specific Functions and Data Members
1216		1312
1217	=over 4	1313	=over 4
1218		1314
…		…
1267	ev_timer_again (loop, timer);	1363	ev_timer_again (loop, timer);
1268		1364
1269	This is more slightly efficient then stopping/starting the timer each time	1365	This is more slightly efficient then stopping/starting the timer each time
1270	you want to modify its timeout value.	1366	you want to modify its timeout value.
1271		1367
		1368	Note, however, that it is often even more efficient to remember the
		1369	time of the last activity and let the timer time-out naturally. In the
		1370	callback, you then check whether the time-out is real, or, if there was
		1371	some activity, you reschedule the watcher to time-out in "last_activity +
		1372	timeout - ev_now ()" seconds.
		1373
1272	=item ev_tstamp repeat [read-write]	1374	=item ev_tstamp repeat [read-write]
1273		1375
1274	The current C<repeat> value. Will be used each time the watcher times out	1376	The current C<repeat> value. Will be used each time the watcher times out
1275	or C<ev_timer_again> is called and determines the next timeout (if any),	1377	or C<ev_timer_again> is called, and determines the next timeout (if any),
1276	which is also when any modifications are taken into account.	1378	which is also when any modifications are taken into account.
1277		1379
1278	=back	1380	=back
1279		1381
1280	=head3 Examples	1382	=head3 Examples
…		…
1324	to trigger the event (unlike an C<ev_timer>, which would still trigger	1426	to trigger the event (unlike an C<ev_timer>, which would still trigger
1325	roughly 10 seconds later as it uses a relative timeout).	1427	roughly 10 seconds later as it uses a relative timeout).
1326		1428
1327	C<ev_periodic>s can also be used to implement vastly more complex timers,	1429	C<ev_periodic>s can also be used to implement vastly more complex timers,
1328	such as triggering an event on each "midnight, local time", or other	1430	such as triggering an event on each "midnight, local time", or other
1329	complicated, rules.	1431	complicated rules.
1330		1432
1331	As with timers, the callback is guaranteed to be invoked only when the	1433	As with timers, the callback is guaranteed to be invoked only when the
1332	time (C<at>) has passed, but if multiple periodic timers become ready	1434	time (C<at>) has passed, but if multiple periodic timers become ready
1333	during the same loop iteration then order of execution is undefined.	1435	during the same loop iteration, then order of execution is undefined.
1334		1436
1335	=head3 Watcher-Specific Functions and Data Members	1437	=head3 Watcher-Specific Functions and Data Members
1336		1438
1337	=over 4	1439	=over 4
1338		1440
1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1441	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1340		1442
1341	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1443	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1342		1444
1343	Lots of arguments, lets sort it out... There are basically three modes of	1445	Lots of arguments, lets sort it out... There are basically three modes of
1344	operation, and we will explain them from simplest to complex:	1446	operation, and we will explain them from simplest to most complex:
1345		1447
1346	=over 4	1448	=over 4
1347		1449
1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1450	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1349		1451
1350	In this configuration the watcher triggers an event after the wall clock	1452	In this configuration the watcher triggers an event after the wall clock
1351	time C<at> has passed and doesn't repeat. It will not adjust when a time	1453	time C<at> has passed. It will not repeat and will not adjust when a time
1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1454	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1353	run when the system time reaches or surpasses this time.	1455	only run when the system clock reaches or surpasses this time.
1354		1456
1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1457	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1356		1458
1357	In this mode the watcher will always be scheduled to time out at the next	1459	In this mode the watcher will always be scheduled to time out at the next
1358	C<at + N * interval> time (for some integer N, which can also be negative)	1460	C<at + N * interval> time (for some integer N, which can also be negative)
1359	and then repeat, regardless of any time jumps.	1461	and then repeat, regardless of any time jumps.
1360		1462
1361	This can be used to create timers that do not drift with respect to system	1463	This can be used to create timers that do not drift with respect to the
1362	time, for example, here is a C<ev_periodic> that triggers each hour, on	1464	system clock, for example, here is a C<ev_periodic> that triggers each
1363	the hour:	1465	hour, on the hour:
1364		1466
1365	ev_periodic_set (&periodic, 0., 3600., 0);	1467	ev_periodic_set (&periodic, 0., 3600., 0);
1366		1468
1367	This doesn't mean there will always be 3600 seconds in between triggers,	1469	This doesn't mean there will always be 3600 seconds in between triggers,
1368	but only that the callback will be called when the system time shows a	1470	but only that the callback will be called when the system time shows a
…		…
1455	=back	1557	=back
1456		1558
1457	=head3 Examples	1559	=head3 Examples
1458		1560
1459	Example: Call a callback every hour, or, more precisely, whenever the	1561	Example: Call a callback every hour, or, more precisely, whenever the
1460	system clock is divisible by 3600. The callback invocation times have	1562	system time is divisible by 3600. The callback invocation times have
1461	potentially a lot of jitter, but good long-term stability.	1563	potentially a lot of jitter, but good long-term stability.
1462		1564
1463	static void	1565	static void
1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1566	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1465	{	1567	{
…		…
1475	#include <math.h>	1577	#include <math.h>
1476		1578
1477	static ev_tstamp	1579	static ev_tstamp
1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1580	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1479	{	1581	{
1480	return fmod (now, 3600.) + 3600.;	1582	return now + (3600. - fmod (now, 3600.));
1481	}	1583	}
1482		1584
1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1585	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1484		1586
1485	Example: Call a callback every hour, starting now:	1587	Example: Call a callback every hour, starting now:
…		…
1495	Signal watchers will trigger an event when the process receives a specific	1597	Signal watchers will trigger an event when the process receives a specific
1496	signal one or more times. Even though signals are very asynchronous, libev	1598	signal one or more times. Even though signals are very asynchronous, libev
1497	will try it's best to deliver signals synchronously, i.e. as part of the	1599	will try it's best to deliver signals synchronously, i.e. as part of the
1498	normal event processing, like any other event.	1600	normal event processing, like any other event.
1499		1601
		1602	If you want signals asynchronously, just use C<sigaction> as you would
		1603	do without libev and forget about sharing the signal. You can even use
		1604	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1605
1500	You can configure as many watchers as you like per signal. Only when the	1606	You can configure as many watchers as you like per signal. Only when the
1501	first watcher gets started will libev actually register a signal watcher	1607	first watcher gets started will libev actually register a signal handler
1502	with the kernel (thus it coexists with your own signal handlers as long	1608	with the kernel (thus it coexists with your own signal handlers as long as
1503	as you don't register any with libev). Similarly, when the last signal	1609	you don't register any with libev for the same signal). Similarly, when
1504	watcher for a signal is stopped libev will reset the signal handler to	1610	the last signal watcher for a signal is stopped, libev will reset the
1505	SIG_DFL (regardless of what it was set to before).	1611	signal handler to SIG_DFL (regardless of what it was set to before).
1506		1612
1507	If possible and supported, libev will install its handlers with	1613	If possible and supported, libev will install its handlers with
1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1614	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1509	interrupted. If you have a problem with system calls getting interrupted by	1615	interrupted. If you have a problem with system calls getting interrupted by
1510	signals you can block all signals in an C<ev_check> watcher and unblock	1616	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1527		1633
1528	=back	1634	=back
1529		1635
1530	=head3 Examples	1636	=head3 Examples
1531		1637
1532	Example: Try to exit cleanly on SIGINT and SIGTERM.	1638	Example: Try to exit cleanly on SIGINT.
1533		1639
1534	static void	1640	static void
1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1641	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1536	{	1642	{
1537	ev_unloop (loop, EVUNLOOP_ALL);	1643	ev_unloop (loop, EVUNLOOP_ALL);
1538	}	1644	}
1539		1645
1540	struct ev_signal signal_watcher;	1646	struct ev_signal signal_watcher;
1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1542	ev_signal_start (loop, &sigint_cb);	1648	ev_signal_start (loop, &signal_watcher);
1543		1649
1544		1650
1545	=head2 C<ev_child> - watch out for process status changes	1651	=head2 C<ev_child> - watch out for process status changes
1546		1652
1547	Child watchers trigger when your process receives a SIGCHLD in response to	1653	Child watchers trigger when your process receives a SIGCHLD in response to
1548	some child status changes (most typically when a child of yours dies). It	1654	some child status changes (most typically when a child of yours dies or
1549	is permissible to install a child watcher I<after> the child has been	1655	exits). It is permissible to install a child watcher I<after> the child
1550	forked (which implies it might have already exited), as long as the event	1656	has been forked (which implies it might have already exited), as long
1551	loop isn't entered (or is continued from a watcher).	1657	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1658	forking and then immediately registering a watcher for the child is fine,
		1659	but forking and registering a watcher a few event loop iterations later is
		1660	not.
1552		1661
1553	Only the default event loop is capable of handling signals, and therefore	1662	Only the default event loop is capable of handling signals, and therefore
1554	you can only register child watchers in the default event loop.	1663	you can only register child watchers in the default event loop.
1555		1664
1556	=head3 Process Interaction	1665	=head3 Process Interaction
…		…
1569	handler, you can override it easily by installing your own handler for	1678	handler, you can override it easily by installing your own handler for
1570	C<SIGCHLD> after initialising the default loop, and making sure the	1679	C<SIGCHLD> after initialising the default loop, and making sure the
1571	default loop never gets destroyed. You are encouraged, however, to use an	1680	default loop never gets destroyed. You are encouraged, however, to use an
1572	event-based approach to child reaping and thus use libev's support for	1681	event-based approach to child reaping and thus use libev's support for
1573	that, so other libev users can use C<ev_child> watchers freely.	1682	that, so other libev users can use C<ev_child> watchers freely.
		1683
		1684	=head3 Stopping the Child Watcher
		1685
		1686	Currently, the child watcher never gets stopped, even when the
		1687	child terminates, so normally one needs to stop the watcher in the
		1688	callback. Future versions of libev might stop the watcher automatically
		1689	when a child exit is detected.
1574		1690
1575	=head3 Watcher-Specific Functions and Data Members	1691	=head3 Watcher-Specific Functions and Data Members
1576		1692
1577	=over 4	1693	=over 4
1578		1694
…		…
1647	the stat buffer having unspecified contents.	1763	the stat buffer having unspecified contents.
1648		1764
1649	The path I<should> be absolute and I<must not> end in a slash. If it is	1765	The path I<should> be absolute and I<must not> end in a slash. If it is
1650	relative and your working directory changes, the behaviour is undefined.	1766	relative and your working directory changes, the behaviour is undefined.
1651		1767
1652	Since there is no standard to do this, the portable implementation simply	1768	Since there is no standard kernel interface to do this, the portable
1653	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1769	implementation simply calls C<stat (2)> regularly on the path to see if
1654	can specify a recommended polling interval for this case. If you specify	1770	it changed somehow. You can specify a recommended polling interval for
1655	a polling interval of C<0> (highly recommended!) then a I<suitable,	1771	this case. If you specify a polling interval of C<0> (highly recommended!)
1656	unspecified default> value will be used (which you can expect to be around	1772	then a I<suitable, unspecified default> value will be used (which
1657	five seconds, although this might change dynamically). Libev will also	1773	you can expect to be around five seconds, although this might change
1658	impose a minimum interval which is currently around C<0.1>, but thats	1774	dynamically). Libev will also impose a minimum interval which is currently
1659	usually overkill.	1775	around C<0.1>, but thats usually overkill.
1660		1776
1661	This watcher type is not meant for massive numbers of stat watchers,	1777	This watcher type is not meant for massive numbers of stat watchers,
1662	as even with OS-supported change notifications, this can be	1778	as even with OS-supported change notifications, this can be
1663	resource-intensive.	1779	resource-intensive.
1664		1780
1665	At the time of this writing, only the Linux inotify interface is	1781	At the time of this writing, the only OS-specific interface implemented
1666	implemented (implementing kqueue support is left as an exercise for the	1782	is the Linux inotify interface (implementing kqueue support is left as
1667	reader, note, however, that the author sees no way of implementing ev_stat	1783	an exercise for the reader. Note, however, that the author sees no way
1668	semantics with kqueue). Inotify will be used to give hints only and should	1784	of implementing C<ev_stat> semantics with kqueue).
1669	not change the semantics of C<ev_stat> watchers, which means that libev
1670	sometimes needs to fall back to regular polling again even with inotify,
1671	but changes are usually detected immediately, and if the file exists there
1672	will be no polling.
1673		1785
1674	=head3 ABI Issues (Largefile Support)	1786	=head3 ABI Issues (Largefile Support)
1675		1787
1676	Libev by default (unless the user overrides this) uses the default	1788	Libev by default (unless the user overrides this) uses the default
1677	compilation environment, which means that on systems with large file	1789	compilation environment, which means that on systems with large file
…		…
1686	file interfaces available by default (as e.g. FreeBSD does) and not	1798	file interfaces available by default (as e.g. FreeBSD does) and not
1687	optional. Libev cannot simply switch on large file support because it has	1799	optional. Libev cannot simply switch on large file support because it has
1688	to exchange stat structures with application programs compiled using the	1800	to exchange stat structures with application programs compiled using the
1689	default compilation environment.	1801	default compilation environment.
1690		1802
1691	=head3 Inotify	1803	=head3 Inotify and Kqueue
1692		1804
1693	When C<inotify (7)> support has been compiled into libev (generally only	1805	When C<inotify (7)> support has been compiled into libev (generally
		1806	only available with Linux 2.6.25 or above due to bugs in earlier
1694	available on Linux) and present at runtime, it will be used to speed up	1807	implementations) and present at runtime, it will be used to speed up
1695	change detection where possible. The inotify descriptor will be created lazily	1808	change detection where possible. The inotify descriptor will be created
1696	when the first C<ev_stat> watcher is being started.	1809	lazily when the first C<ev_stat> watcher is being started.
1697		1810
1698	Inotify presence does not change the semantics of C<ev_stat> watchers	1811	Inotify presence does not change the semantics of C<ev_stat> watchers
1699	except that changes might be detected earlier, and in some cases, to avoid	1812	except that changes might be detected earlier, and in some cases, to avoid
1700	making regular C<stat> calls. Even in the presence of inotify support	1813	making regular C<stat> calls. Even in the presence of inotify support
1701	there are many cases where libev has to resort to regular C<stat> polling.	1814	there are many cases where libev has to resort to regular C<stat> polling,
		1815	but as long as the path exists, libev usually gets away without polling.
1702		1816
1703	(There is no support for kqueue, as apparently it cannot be used to	1817	There is no support for kqueue, as apparently it cannot be used to
1704	implement this functionality, due to the requirement of having a file	1818	implement this functionality, due to the requirement of having a file
1705	descriptor open on the object at all times).	1819	descriptor open on the object at all times, and detecting renames, unlinks
		1820	etc. is difficult.
1706		1821
1707	=head3 The special problem of stat time resolution	1822	=head3 The special problem of stat time resolution
1708		1823
1709	The C<stat ()> system call only supports full-second resolution portably, and	1824	The C<stat ()> system call only supports full-second resolution portably, and
1710	even on systems where the resolution is higher, many file systems still	1825	even on systems where the resolution is higher, most file systems still
1711	only support whole seconds.	1826	only support whole seconds.
1712		1827
1713	That means that, if the time is the only thing that changes, you can	1828	That means that, if the time is the only thing that changes, you can
1714	easily miss updates: on the first update, C<ev_stat> detects a change and	1829	easily miss updates: on the first update, C<ev_stat> detects a change and
1715	calls your callback, which does something. When there is another update	1830	calls your callback, which does something. When there is another update
1716	within the same second, C<ev_stat> will be unable to detect it as the stat	1831	within the same second, C<ev_stat> will be unable to detect unless the
1717	data does not change.	1832	stat data does change in other ways (e.g. file size).
1718		1833
1719	The solution to this is to delay acting on a change for slightly more	1834	The solution to this is to delay acting on a change for slightly more
1720	than a second (or till slightly after the next full second boundary), using	1835	than a second (or till slightly after the next full second boundary), using
1721	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1836	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1722	ev_timer_again (loop, w)>).	1837	ev_timer_again (loop, w)>).
…		…
1742	C<path>. The C<interval> is a hint on how quickly a change is expected to	1857	C<path>. The C<interval> is a hint on how quickly a change is expected to
1743	be detected and should normally be specified as C<0> to let libev choose	1858	be detected and should normally be specified as C<0> to let libev choose
1744	a suitable value. The memory pointed to by C<path> must point to the same	1859	a suitable value. The memory pointed to by C<path> must point to the same
1745	path for as long as the watcher is active.	1860	path for as long as the watcher is active.
1746		1861
1747	The callback will receive C<EV_STAT> when a change was detected, relative	1862	The callback will receive an C<EV_STAT> event when a change was detected,
1748	to the attributes at the time the watcher was started (or the last change	1863	relative to the attributes at the time the watcher was started (or the
1749	was detected).	1864	last change was detected).
1750		1865
1751	=item ev_stat_stat (loop, ev_stat *)	1866	=item ev_stat_stat (loop, ev_stat *)
1752		1867
1753	Updates the stat buffer immediately with new values. If you change the	1868	Updates the stat buffer immediately with new values. If you change the
1754	watched path in your callback, you could call this function to avoid	1869	watched path in your callback, you could call this function to avoid
…		…
1837		1952
1838		1953
1839	=head2 C<ev_idle> - when you've got nothing better to do...	1954	=head2 C<ev_idle> - when you've got nothing better to do...
1840		1955
1841	Idle watchers trigger events when no other events of the same or higher	1956	Idle watchers trigger events when no other events of the same or higher
1842	priority are pending (prepare, check and other idle watchers do not	1957	priority are pending (prepare, check and other idle watchers do not count
1843	count).	1958	as receiving "events").
1844		1959
1845	That is, as long as your process is busy handling sockets or timeouts	1960	That is, as long as your process is busy handling sockets or timeouts
1846	(or even signals, imagine) of the same or higher priority it will not be	1961	(or even signals, imagine) of the same or higher priority it will not be
1847	triggered. But when your process is idle (or only lower-priority watchers	1962	triggered. But when your process is idle (or only lower-priority watchers
1848	are pending), the idle watchers are being called once per event loop	1963	are pending), the idle watchers are being called once per event loop
…		…
1887	ev_idle_start (loop, idle_cb);	2002	ev_idle_start (loop, idle_cb);
1888		2003
1889		2004
1890	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1891		2006
1892	Prepare and check watchers are usually (but not always) used in tandem:	2007	Prepare and check watchers are usually (but not always) used in pairs:
1893	prepare watchers get invoked before the process blocks and check watchers	2008	prepare watchers get invoked before the process blocks and check watchers
1894	afterwards.	2009	afterwards.
1895		2010
1896	You I<must not> call C<ev_loop> or similar functions that enter	2011	You I<must not> call C<ev_loop> or similar functions that enter
1897	the current event loop from either C<ev_prepare> or C<ev_check>	2012	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1900	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2015	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1901	C<ev_check> so if you have one watcher of each kind they will always be	2016	C<ev_check> so if you have one watcher of each kind they will always be
1902	called in pairs bracketing the blocking call.	2017	called in pairs bracketing the blocking call.
1903		2018
1904	Their main purpose is to integrate other event mechanisms into libev and	2019	Their main purpose is to integrate other event mechanisms into libev and
1905	their use is somewhat advanced. This could be used, for example, to track	2020	their use is somewhat advanced. They could be used, for example, to track
1906	variable changes, implement your own watchers, integrate net-snmp or a	2021	variable changes, implement your own watchers, integrate net-snmp or a
1907	coroutine library and lots more. They are also occasionally useful if	2022	coroutine library and lots more. They are also occasionally useful if
1908	you cache some data and want to flush it before blocking (for example,	2023	you cache some data and want to flush it before blocking (for example,
1909	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2024	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1910	watcher).	2025	watcher).
1911		2026
1912	This is done by examining in each prepare call which file descriptors need	2027	This is done by examining in each prepare call which file descriptors
1913	to be watched by the other library, registering C<ev_io> watchers for	2028	need to be watched by the other library, registering C<ev_io> watchers
1914	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2029	for them and starting an C<ev_timer> watcher for any timeouts (many
1915	provide just this functionality). Then, in the check watcher you check for	2030	libraries provide exactly this functionality). Then, in the check watcher,
1916	any events that occurred (by checking the pending status of all watchers	2031	you check for any events that occurred (by checking the pending status
1917	and stopping them) and call back into the library. The I/O and timer	2032	of all watchers and stopping them) and call back into the library. The
1918	callbacks will never actually be called (but must be valid nevertheless,	2033	I/O and timer callbacks will never actually be called (but must be valid
1919	because you never know, you know?).	2034	nevertheless, because you never know, you know?).
1920		2035
1921	As another example, the Perl Coro module uses these hooks to integrate	2036	As another example, the Perl Coro module uses these hooks to integrate
1922	coroutines into libev programs, by yielding to other active coroutines	2037	coroutines into libev programs, by yielding to other active coroutines
1923	during each prepare and only letting the process block if no coroutines	2038	during each prepare and only letting the process block if no coroutines
1924	are ready to run (it's actually more complicated: it only runs coroutines	2039	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1927	loop from blocking if lower-priority coroutines are active, thus mapping	2042	loop from blocking if lower-priority coroutines are active, thus mapping
1928	low-priority coroutines to idle/background tasks).	2043	low-priority coroutines to idle/background tasks).
1929		2044
1930	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2045	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1931	priority, to ensure that they are being run before any other watchers	2046	priority, to ensure that they are being run before any other watchers
		2047	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2048
1932	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2049	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1933	too) should not activate ("feed") events into libev. While libev fully	2050	activate ("feed") events into libev. While libev fully supports this, they
1934	supports this, they might get executed before other C<ev_check> watchers	2051	might get executed before other C<ev_check> watchers did their job. As
1935	did their job. As C<ev_check> watchers are often used to embed other	2052	C<ev_check> watchers are often used to embed other (non-libev) event
1936	(non-libev) event loops those other event loops might be in an unusable	2053	loops those other event loops might be in an unusable state until their
1937	state until their C<ev_check> watcher ran (always remind yourself to	2054	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1938	coexist peacefully with others).	2055	others).
1939		2056
1940	=head3 Watcher-Specific Functions and Data Members	2057	=head3 Watcher-Specific Functions and Data Members
1941		2058
1942	=over 4	2059	=over 4
1943		2060
…		…
1945		2062
1946	=item ev_check_init (ev_check *, callback)	2063	=item ev_check_init (ev_check *, callback)
1947		2064
1948	Initialises and configures the prepare or check watcher - they have no	2065	Initialises and configures the prepare or check watcher - they have no
1949	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2066	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1950	macros, but using them is utterly, utterly and completely pointless.	2067	macros, but using them is utterly, utterly, utterly and completely
		2068	pointless.
1951		2069
1952	=back	2070	=back
1953		2071
1954	=head3 Examples	2072	=head3 Examples
1955		2073
…		…
2048	}	2166	}
2049		2167
2050	// do not ever call adns_afterpoll	2168	// do not ever call adns_afterpoll
2051		2169
2052	Method 4: Do not use a prepare or check watcher because the module you	2170	Method 4: Do not use a prepare or check watcher because the module you
2053	want to embed is too inflexible to support it. Instead, you can override	2171	want to embed is not flexible enough to support it. Instead, you can
2054	their poll function. The drawback with this solution is that the main	2172	override their poll function. The drawback with this solution is that the
2055	loop is now no longer controllable by EV. The C<Glib::EV> module does	2173	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2056	this.	2174	this approach, effectively embedding EV as a client into the horrible
		2175	libglib event loop.
2057		2176
2058	static gint	2177	static gint
2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2178	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2060	{	2179	{
2061	int got_events = 0;	2180	int got_events = 0;
…		…
2092	prioritise I/O.	2211	prioritise I/O.
2093		2212
2094	As an example for a bug workaround, the kqueue backend might only support	2213	As an example for a bug workaround, the kqueue backend might only support
2095	sockets on some platform, so it is unusable as generic backend, but you	2214	sockets on some platform, so it is unusable as generic backend, but you
2096	still want to make use of it because you have many sockets and it scales	2215	still want to make use of it because you have many sockets and it scales
2097	so nicely. In this case, you would create a kqueue-based loop and embed it	2216	so nicely. In this case, you would create a kqueue-based loop and embed
2098	into your default loop (which might use e.g. poll). Overall operation will	2217	it into your default loop (which might use e.g. poll). Overall operation
2099	be a bit slower because first libev has to poll and then call kevent, but	2218	will be a bit slower because first libev has to call C<poll> and then
2100	at least you can use both at what they are best.	2219	C<kevent>, but at least you can use both mechanisms for what they are
		2220	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2101		2221
2102	As for prioritising I/O: rarely you have the case where some fds have	2222	As for prioritising I/O: under rare circumstances you have the case where
2103	to be watched and handled very quickly (with low latency), and even	2223	some fds have to be watched and handled very quickly (with low latency),
2104	priorities and idle watchers might have too much overhead. In this case	2224	and even priorities and idle watchers might have too much overhead. In
2105	you would put all the high priority stuff in one loop and all the rest in	2225	this case you would put all the high priority stuff in one loop and all
2106	a second one, and embed the second one in the first.	2226	the rest in a second one, and embed the second one in the first.
2107		2227
2108	As long as the watcher is active, the callback will be invoked every time	2228	As long as the watcher is active, the callback will be invoked every time
2109	there might be events pending in the embedded loop. The callback must then	2229	there might be events pending in the embedded loop. The callback must then
2110	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2230	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2111	their callbacks (you could also start an idle watcher to give the embedded	2231	their callbacks (you could also start an idle watcher to give the embedded
…		…
2119	interested in that.	2239	interested in that.
2120		2240
2121	Also, there have not currently been made special provisions for forking:	2241	Also, there have not currently been made special provisions for forking:
2122	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2242	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2123	but you will also have to stop and restart any C<ev_embed> watchers	2243	but you will also have to stop and restart any C<ev_embed> watchers
2124	yourself.	2244	yourself - but you can use a fork watcher to handle this automatically,
		2245	and future versions of libev might do just that.
2125		2246
2126	Unfortunately, not all backends are embeddable, only the ones returned by	2247	Unfortunately, not all backends are embeddable: only the ones returned by
2127	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2248	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2128	portable one.	2249	portable one.
2129		2250
2130	So when you want to use this feature you will always have to be prepared	2251	So when you want to use this feature you will always have to be prepared
2131	that you cannot get an embeddable loop. The recommended way to get around	2252	that you cannot get an embeddable loop. The recommended way to get around
2132	this is to have a separate variables for your embeddable loop, try to	2253	this is to have a separate variables for your embeddable loop, try to
2133	create it, and if that fails, use the normal loop for everything.	2254	create it, and if that fails, use the normal loop for everything.
		2255
		2256	=head3 C<ev_embed> and fork
		2257
		2258	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2259	automatically be applied to the embedded loop as well, so no special
		2260	fork handling is required in that case. When the watcher is not running,
		2261	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2262	as applicable.
2134		2263
2135	=head3 Watcher-Specific Functions and Data Members	2264	=head3 Watcher-Specific Functions and Data Members
2136		2265
2137	=over 4	2266	=over 4
2138		2267
…		…
2256	is that the author does not know of a simple (or any) algorithm for a	2385	is that the author does not know of a simple (or any) algorithm for a
2257	multiple-writer-single-reader queue that works in all cases and doesn't	2386	multiple-writer-single-reader queue that works in all cases and doesn't
2258	need elaborate support such as pthreads.	2387	need elaborate support such as pthreads.
2259		2388
2260	That means that if you want to queue data, you have to provide your own	2389	That means that if you want to queue data, you have to provide your own
2261	queue. But at least I can tell you would implement locking around your	2390	queue. But at least I can tell you how to implement locking around your
2262	queue:	2391	queue:
2263		2392
2264	=over 4	2393	=over 4
2265		2394
2266	=item queueing from a signal handler context	2395	=item queueing from a signal handler context
2267		2396
2268	To implement race-free queueing, you simply add to the queue in the signal	2397	To implement race-free queueing, you simply add to the queue in the signal
2269	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2398	handler but you block the signal handler in the watcher callback. Here is
2270	some fictitious SIGUSR1 handler:	2399	an example that does that for some fictitious SIGUSR1 handler:
2271		2400
2272	static ev_async mysig;	2401	static ev_async mysig;
2273		2402
2274	static void	2403	static void
2275	sigusr1_handler (void)	2404	sigusr1_handler (void)
…		…
2342		2471
2343	=item ev_async_init (ev_async *, callback)	2472	=item ev_async_init (ev_async *, callback)
2344		2473
2345	Initialises and configures the async watcher - it has no parameters of any	2474	Initialises and configures the async watcher - it has no parameters of any
2346	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2475	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2347	believe me.	2476	trust me.
2348		2477
2349	=item ev_async_send (loop, ev_async *)	2478	=item ev_async_send (loop, ev_async *)
2350		2479
2351	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2480	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2352	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2481	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2353	C<ev_feed_event>, this call is safe to do in other threads, signal or	2482	C<ev_feed_event>, this call is safe to do from other threads, signal or
2354	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2483	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2355	section below on what exactly this means).	2484	section below on what exactly this means).
2356		2485
2357	This call incurs the overhead of a system call only once per loop iteration,	2486	This call incurs the overhead of a system call only once per loop iteration,
2358	so while the overhead might be noticeable, it doesn't apply to repeated	2487	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2382	=over 4	2511	=over 4
2383		2512
2384	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2513	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2385		2514
2386	This function combines a simple timer and an I/O watcher, calls your	2515	This function combines a simple timer and an I/O watcher, calls your
2387	callback on whichever event happens first and automatically stop both	2516	callback on whichever event happens first and automatically stops both
2388	watchers. This is useful if you want to wait for a single event on an fd	2517	watchers. This is useful if you want to wait for a single event on an fd
2389	or timeout without having to allocate/configure/start/stop/free one or	2518	or timeout without having to allocate/configure/start/stop/free one or
2390	more watchers yourself.	2519	more watchers yourself.
2391		2520
2392	If C<fd> is less than 0, then no I/O watcher will be started and events	2521	If C<fd> is less than 0, then no I/O watcher will be started and the
2393	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2522	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2394	C<events> set will be created and started.	2523	the given C<fd> and C<events> set will be created and started.
2395		2524
2396	If C<timeout> is less than 0, then no timeout watcher will be	2525	If C<timeout> is less than 0, then no timeout watcher will be
2397	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2526	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2398	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2527	repeat = 0) will be started. C<0> is a valid timeout.
2399	dubious value.
2400		2528
2401	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2529	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2402	passed an C<revents> set like normal event callbacks (a combination of	2530	passed an C<revents> set like normal event callbacks (a combination of
2403	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2531	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2404	value passed to C<ev_once>:	2532	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2533	a timeout and an io event at the same time - you probably should give io
		2534	events precedence.
		2535
		2536	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2405		2537
2406	static void stdin_ready (int revents, void *arg)	2538	static void stdin_ready (int revents, void *arg)
2407	{	2539	{
		2540	if (revents & EV_READ)
		2541	/* stdin might have data for us, joy! */;
2408	if (revents & EV_TIMEOUT)	2542	else if (revents & EV_TIMEOUT)
2409	/* doh, nothing entered */;	2543	/* doh, nothing entered */;
2410	else if (revents & EV_READ)
2411	/* stdin might have data for us, joy! */;
2412	}	2544	}
2413		2545
2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2415		2547
2416	=item ev_feed_event (ev_loop *, watcher *, int revents)	2548	=item ev_feed_event (ev_loop *, watcher *, int revents)
…		…
2564		2696
2565	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2697	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2566		2698
2567	See the method-C<set> above for more details.	2699	See the method-C<set> above for more details.
2568		2700
2569	Example:	2701	Example: Use a plain function as callback.
2570		2702
2571	static void io_cb (ev::io &w, int revents) { }	2703	static void io_cb (ev::io &w, int revents) { }
2572	iow.set <io_cb> ();	2704	iow.set <io_cb> ();
2573		2705
2574	=item w->set (struct ev_loop *)	2706	=item w->set (struct ev_loop *)
…		…
2612	Example: Define a class with an IO and idle watcher, start one of them in	2744	Example: Define a class with an IO and idle watcher, start one of them in
2613	the constructor.	2745	the constructor.
2614		2746
2615	class myclass	2747	class myclass
2616	{	2748	{
2617	ev::io io; void io_cb (ev::io &w, int revents);	2749	ev::io io ; void io_cb (ev::io &w, int revents);
2618	ev:idle idle void idle_cb (ev::idle &w, int revents);	2750	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2619		2751
2620	myclass (int fd)	2752	myclass (int fd)
2621	{	2753	{
2622	io .set <myclass, &myclass::io_cb > (this);	2754	io .set <myclass, &myclass::io_cb > (this);
2623	idle.set <myclass, &myclass::idle_cb> (this);	2755	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2639	=item Perl	2771	=item Perl
2640		2772
2641	The EV module implements the full libev API and is actually used to test	2773	The EV module implements the full libev API and is actually used to test
2642	libev. EV is developed together with libev. Apart from the EV core module,	2774	libev. EV is developed together with libev. Apart from the EV core module,
2643	there are additional modules that implement libev-compatible interfaces	2775	there are additional modules that implement libev-compatible interfaces
2644	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2776	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2645	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2777	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2778	and C<EV::Glib>).
2646		2779
2647	It can be found and installed via CPAN, its homepage is at	2780	It can be found and installed via CPAN, its homepage is at
2648	L<http://software.schmorp.de/pkg/EV>.	2781	L<http://software.schmorp.de/pkg/EV>.
2649		2782
2650	=item Python	2783	=item Python
…		…
2664	L<http://rev.rubyforge.org/>.	2797	L<http://rev.rubyforge.org/>.
2665		2798
2666	=item D	2799	=item D
2667		2800
2668	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2801	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2669	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2802	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2670		2803
2671	=back	2804	=back
2672		2805
2673		2806
2674	=head1 MACRO MAGIC	2807	=head1 MACRO MAGIC
…		…
2829		2962
2830	=head2 PREPROCESSOR SYMBOLS/MACROS	2963	=head2 PREPROCESSOR SYMBOLS/MACROS
2831		2964
2832	Libev can be configured via a variety of preprocessor symbols you have to	2965	Libev can be configured via a variety of preprocessor symbols you have to
2833	define before including any of its files. The default in the absence of	2966	define before including any of its files. The default in the absence of
2834	autoconf is noted for every option.	2967	autoconf is documented for every option.
2835		2968
2836	=over 4	2969	=over 4
2837		2970
2838	=item EV_STANDALONE	2971	=item EV_STANDALONE
2839		2972
…		…
3009	When doing priority-based operations, libev usually has to linearly search	3142	When doing priority-based operations, libev usually has to linearly search
3010	all the priorities, so having many of them (hundreds) uses a lot of space	3143	all the priorities, so having many of them (hundreds) uses a lot of space
3011	and time, so using the defaults of five priorities (-2 .. +2) is usually	3144	and time, so using the defaults of five priorities (-2 .. +2) is usually
3012	fine.	3145	fine.
3013		3146
3014	If your embedding application does not need any priorities, defining these both to	3147	If your embedding application does not need any priorities, defining these
3015	C<0> will save some memory and CPU.	3148	both to C<0> will save some memory and CPU.
3016		3149
3017	=item EV_PERIODIC_ENABLE	3150	=item EV_PERIODIC_ENABLE
3018		3151
3019	If undefined or defined to be C<1>, then periodic timers are supported. If	3152	If undefined or defined to be C<1>, then periodic timers are supported. If
3020	defined to be C<0>, then they are not. Disabling them saves a few kB of	3153	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3027	code.	3160	code.
3028		3161
3029	=item EV_EMBED_ENABLE	3162	=item EV_EMBED_ENABLE
3030		3163
3031	If undefined or defined to be C<1>, then embed watchers are supported. If	3164	If undefined or defined to be C<1>, then embed watchers are supported. If
3032	defined to be C<0>, then they are not.	3165	defined to be C<0>, then they are not. Embed watchers rely on most other
		3166	watcher types, which therefore must not be disabled.
3033		3167
3034	=item EV_STAT_ENABLE	3168	=item EV_STAT_ENABLE
3035		3169
3036	If undefined or defined to be C<1>, then stat watchers are supported. If	3170	If undefined or defined to be C<1>, then stat watchers are supported. If
3037	defined to be C<0>, then they are not.	3171	defined to be C<0>, then they are not.
…		…
3069	two).	3203	two).
3070		3204
3071	=item EV_USE_4HEAP	3205	=item EV_USE_4HEAP
3072		3206
3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3207	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3074	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3208	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3075	to C<1>. The 4-heap uses more complicated (longer) code but has	3209	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3076	noticeably faster performance with many (thousands) of watchers.	3210	faster performance with many (thousands) of watchers.
3077		3211
3078	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3079	(disabled).	3213	(disabled).
3080		3214
3081	=item EV_HEAP_CACHE_AT	3215	=item EV_HEAP_CACHE_AT
3082		3216
3083	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3217	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3084	timer and periodics heap, libev can cache the timestamp (I<at>) within	3218	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3085	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3219	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3086	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3220	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3087	but avoids random read accesses on heap changes. This improves performance	3221	but avoids random read accesses on heap changes. This improves performance
3088	noticeably with with many (hundreds) of watchers.	3222	noticeably with many (hundreds) of watchers.
3089		3223
3090	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3224	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3091	(disabled).	3225	(disabled).
3092		3226
3093	=item EV_VERIFY	3227	=item EV_VERIFY
…		…
3099	called once per loop, which can slow down libev. If set to C<3>, then the	3233	called once per loop, which can slow down libev. If set to C<3>, then the
3100	verification code will be called very frequently, which will slow down	3234	verification code will be called very frequently, which will slow down
3101	libev considerably.	3235	libev considerably.
3102		3236
3103	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3237	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3104	C<0.>	3238	C<0>.
3105		3239
3106	=item EV_COMMON	3240	=item EV_COMMON
3107		3241
3108	By default, all watchers have a C<void *data> member. By redefining	3242	By default, all watchers have a C<void *data> member. By redefining
3109	this macro to a something else you can include more and other types of	3243	this macro to a something else you can include more and other types of
…		…
3126	and the way callbacks are invoked and set. Must expand to a struct member	3260	and the way callbacks are invoked and set. Must expand to a struct member
3127	definition and a statement, respectively. See the F<ev.h> header file for	3261	definition and a statement, respectively. See the F<ev.h> header file for
3128	their default definitions. One possible use for overriding these is to	3262	their default definitions. One possible use for overriding these is to
3129	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3263	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3130	method calls instead of plain function calls in C++.	3264	method calls instead of plain function calls in C++.
		3265
		3266	=back
3131		3267
3132	=head2 EXPORTED API SYMBOLS	3268	=head2 EXPORTED API SYMBOLS
3133		3269
3134	If you need to re-export the API (e.g. via a DLL) and you need a list of	3270	If you need to re-export the API (e.g. via a DLL) and you need a list of
3135	exported symbols, you can use the provided F<Symbol.*> files which list	3271	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3182	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3318	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3183		3319
3184	#include "ev_cpp.h"	3320	#include "ev_cpp.h"
3185	#include "ev.c"	3321	#include "ev.c"
3186		3322
		3323	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3187		3324
3188	=head1 THREADS AND COROUTINES	3325	=head2 THREADS AND COROUTINES
3189		3326
3190	=head2 THREADS	3327	=head3 THREADS
3191		3328
3192	Libev itself is completely thread-safe, but it uses no locking. This	3329	All libev functions are reentrant and thread-safe unless explicitly
		3330	documented otherwise, but libev implements no locking itself. This means
3193	means that you can use as many loops as you want in parallel, as long as	3331	that you can use as many loops as you want in parallel, as long as there
3194	only one thread ever calls into one libev function with the same loop	3332	are no concurrent calls into any libev function with the same loop
3195	parameter.	3333	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3334	of course): libev guarantees that different event loops share no data
		3335	structures that need any locking.
3196		3336
3197	Or put differently: calls with different loop parameters can be done in	3337	Or to put it differently: calls with different loop parameters can be done
3198	parallel from multiple threads, calls with the same loop parameter must be	3338	concurrently from multiple threads, calls with the same loop parameter
3199	done serially (but can be done from different threads, as long as only one	3339	must be done serially (but can be done from different threads, as long as
3200	thread ever is inside a call at any point in time, e.g. by using a mutex	3340	only one thread ever is inside a call at any point in time, e.g. by using
3201	per loop).	3341	a mutex per loop).
		3342
		3343	Specifically to support threads (and signal handlers), libev implements
		3344	so-called C<ev_async> watchers, which allow some limited form of
		3345	concurrency on the same event loop, namely waking it up "from the
		3346	outside".
3202		3347
3203	If you want to know which design (one loop, locking, or multiple loops	3348	If you want to know which design (one loop, locking, or multiple loops
3204	without or something else still) is best for your problem, then I cannot	3349	without or something else still) is best for your problem, then I cannot
3205	help you. I can give some generic advice however:	3350	help you, but here is some generic advice:
3206		3351
3207	=over 4	3352	=over 4
3208		3353
3209	=item * most applications have a main thread: use the default libev loop	3354	=item * most applications have a main thread: use the default libev loop
3210	in that thread, or create a separate thread running only the default loop.	3355	in that thread, or create a separate thread running only the default loop.
…		…
3222		3367
3223	Choosing a model is hard - look around, learn, know that usually you can do	3368	Choosing a model is hard - look around, learn, know that usually you can do
3224	better than you currently do :-)	3369	better than you currently do :-)
3225		3370
3226	=item * often you need to talk to some other thread which blocks in the	3371	=item * often you need to talk to some other thread which blocks in the
		3372	event loop.
		3373
3227	event loop - C<ev_async> watchers can be used to wake them up from other	3374	C<ev_async> watchers can be used to wake them up from other threads safely
3228	threads safely (or from signal contexts...).	3375	(or from signal contexts...).
		3376
		3377	An example use would be to communicate signals or other events that only
		3378	work in the default loop by registering the signal watcher with the
		3379	default loop and triggering an C<ev_async> watcher from the default loop
		3380	watcher callback into the event loop interested in the signal.
3229		3381
3230	=back	3382	=back
3231		3383
3232	=head2 COROUTINES	3384	=head3 COROUTINES
3233		3385
3234	Libev is much more accommodating to coroutines ("cooperative threads"):	3386	Libev is very accommodating to coroutines ("cooperative threads"):
3235	libev fully supports nesting calls to it's functions from different	3387	libev fully supports nesting calls to its functions from different
3236	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3388	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3237	different coroutines and switch freely between both coroutines running the	3389	different coroutines, and switch freely between both coroutines running the
3238	loop, as long as you don't confuse yourself). The only exception is that	3390	loop, as long as you don't confuse yourself). The only exception is that
3239	you must not do this from C<ev_periodic> reschedule callbacks.	3391	you must not do this from C<ev_periodic> reschedule callbacks.
3240		3392
3241	Care has been invested into making sure that libev does not keep local	3393	Care has been taken to ensure that libev does not keep local state inside
3242	state inside C<ev_loop>, and other calls do not usually allow coroutine	3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3243	switches.	3395	they do not clal any callbacks.
3244		3396
		3397	=head2 COMPILER WARNINGS
3245		3398
3246	=head1 COMPLEXITIES	3399	Depending on your compiler and compiler settings, you might get no or a
		3400	lot of warnings when compiling libev code. Some people are apparently
		3401	scared by this.
3247		3402
3248	In this section the complexities of (many of) the algorithms used inside	3403	However, these are unavoidable for many reasons. For one, each compiler
3249	libev will be explained. For complexity discussions about backends see the	3404	has different warnings, and each user has different tastes regarding
3250	documentation for C<ev_default_init>.	3405	warning options. "Warn-free" code therefore cannot be a goal except when
		3406	targeting a specific compiler and compiler-version.
3251		3407
3252	All of the following are about amortised time: If an array needs to be	3408	Another reason is that some compiler warnings require elaborate
3253	extended, libev needs to realloc and move the whole array, but this	3409	workarounds, or other changes to the code that make it less clear and less
3254	happens asymptotically never with higher number of elements, so O(1) might	3410	maintainable.
3255	mean it might do a lengthy realloc operation in rare cases, but on average
3256	it is much faster and asymptotically approaches constant time.
3257		3411
3258	=over 4	3412	And of course, some compiler warnings are just plain stupid, or simply
		3413	wrong (because they don't actually warn about the condition their message
		3414	seems to warn about). For example, certain older gcc versions had some
		3415	warnings that resulted an extreme number of false positives. These have
		3416	been fixed, but some people still insist on making code warn-free with
		3417	such buggy versions.
3259		3418
3260	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3419	While libev is written to generate as few warnings as possible,
		3420	"warn-free" code is not a goal, and it is recommended not to build libev
		3421	with any compiler warnings enabled unless you are prepared to cope with
		3422	them (e.g. by ignoring them). Remember that warnings are just that:
		3423	warnings, not errors, or proof of bugs.
3261		3424
3262	This means that, when you have a watcher that triggers in one hour and
3263	there are 100 watchers that would trigger before that then inserting will
3264	have to skip roughly seven (C<ld 100>) of these watchers.
3265		3425
3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3426	=head2 VALGRIND
3267		3427
3268	That means that changing a timer costs less than removing/adding them	3428	Valgrind has a special section here because it is a popular tool that is
3269	as only the relative motion in the event queue has to be paid for.	3429	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3270		3430
3271	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3431	If you think you found a bug (memory leak, uninitialised data access etc.)
		3432	in libev, then check twice: If valgrind reports something like:
3272		3433
3273	These just add the watcher into an array or at the head of a list.	3434	==2274== definitely lost: 0 bytes in 0 blocks.
		3435	==2274== possibly lost: 0 bytes in 0 blocks.
		3436	==2274== still reachable: 256 bytes in 1 blocks.
3274		3437
3275	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3438	Then there is no memory leak, just as memory accounted to global variables
		3439	is not a memleak - the memory is still being refernced, and didn't leak.
3276		3440
3277	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3441	Similarly, under some circumstances, valgrind might report kernel bugs
		3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3443	although an acceptable workaround has been found here), or it might be
		3444	confused.
3278		3445
3279	These watchers are stored in lists then need to be walked to find the	3446	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3280	correct watcher to remove. The lists are usually short (you don't usually	3447	make it into some kind of religion.
3281	have many watchers waiting for the same fd or signal).
3282		3448
3283	=item Finding the next timer in each loop iteration: O(1)	3449	If you are unsure about something, feel free to contact the mailing list
		3450	with the full valgrind report and an explanation on why you think this
		3451	is a bug in libev (best check the archives, too :). However, don't be
		3452	annoyed when you get a brisk "this is no bug" answer and take the chance
		3453	of learning how to interpret valgrind properly.
3284		3454
3285	By virtue of using a binary or 4-heap, the next timer is always found at a	3455	If you need, for some reason, empty reports from valgrind for your project
3286	fixed position in the storage array.	3456	I suggest using suppression lists.
3287		3457
3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3289		3458
3290	A change means an I/O watcher gets started or stopped, which requires	3459	=head1 PORTABILITY NOTES
3291	libev to recalculate its status (and possibly tell the kernel, depending
3292	on backend and whether C<ev_io_set> was used).
3293		3460
3294	=item Activating one watcher (putting it into the pending state): O(1)
3295
3296	=item Priority handling: O(number_of_priorities)
3297
3298	Priorities are implemented by allocating some space for each
3299	priority. When doing priority-based operations, libev usually has to
3300	linearly search all the priorities, but starting/stopping and activating
3301	watchers becomes O(1) w.r.t. priority handling.
3302
3303	=item Sending an ev_async: O(1)
3304
3305	=item Processing ev_async_send: O(number_of_async_watchers)
3306
3307	=item Processing signals: O(max_signal_number)
3308
3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
3310	calls in the current loop iteration. Checking for async and signal events
3311	involves iterating over all running async watchers or all signal numbers.
3312
3313	=back
3314
3315
3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3461	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3317		3462
3318	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3463	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3319	requires, and its I/O model is fundamentally incompatible with the POSIX	3464	requires, and its I/O model is fundamentally incompatible with the POSIX
3320	model. Libev still offers limited functionality on this platform in	3465	model. Libev still offers limited functionality on this platform in
3321	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3466	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3332		3477
3333	Not a libev limitation but worth mentioning: windows apparently doesn't	3478	Not a libev limitation but worth mentioning: windows apparently doesn't
3334	accept large writes: instead of resulting in a partial write, windows will	3479	accept large writes: instead of resulting in a partial write, windows will
3335	either accept everything or return C<ENOBUFS> if the buffer is too large,	3480	either accept everything or return C<ENOBUFS> if the buffer is too large,
3336	so make sure you only write small amounts into your sockets (less than a	3481	so make sure you only write small amounts into your sockets (less than a
3337	megabyte seems safe, but thsi apparently depends on the amount of memory	3482	megabyte seems safe, but this apparently depends on the amount of memory
3338	available).	3483	available).
3339		3484
3340	Due to the many, low, and arbitrary limits on the win32 platform and	3485	Due to the many, low, and arbitrary limits on the win32 platform and
3341	the abysmal performance of winsockets, using a large number of sockets	3486	the abysmal performance of winsockets, using a large number of sockets
3342	is not recommended (and not reasonable). If your program needs to use	3487	is not recommended (and not reasonable). If your program needs to use
…		…
3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3498	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3354		3499
3355	#include "ev.h"	3500	#include "ev.h"
3356		3501
3357	And compile the following F<evwrap.c> file into your project (make sure	3502	And compile the following F<evwrap.c> file into your project (make sure
3358	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3503	you do I<not> compile the F<ev.c> or any other embedded source files!):
3359		3504
3360	#include "evwrap.h"	3505	#include "evwrap.h"
3361	#include "ev.c"	3506	#include "ev.c"
3362		3507
3363	=over 4	3508	=over 4
…		…
3408	wrap all I/O functions and provide your own fd management, but the cost of	3553	wrap all I/O functions and provide your own fd management, but the cost of
3409	calling select (O(n²)) will likely make this unworkable.	3554	calling select (O(n²)) will likely make this unworkable.
3410		3555
3411	=back	3556	=back
3412		3557
3413
3414	=head1 PORTABILITY REQUIREMENTS	3558	=head2 PORTABILITY REQUIREMENTS
3415		3559
3416	In addition to a working ISO-C implementation, libev relies on a few	3560	In addition to a working ISO-C implementation and of course the
3417	additional extensions:	3561	backend-specific APIs, libev relies on a few additional extensions:
3418		3562
3419	=over 4	3563	=over 4
3420		3564
3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3565	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3422	calling conventions regardless of C<ev_watcher_type *>.	3566	calling conventions regardless of C<ev_watcher_type *>.
…		…
3428	calls them using an C<ev_watcher *> internally.	3572	calls them using an C<ev_watcher *> internally.
3429		3573
3430	=item C<sig_atomic_t volatile> must be thread-atomic as well	3574	=item C<sig_atomic_t volatile> must be thread-atomic as well
3431		3575
3432	The type C<sig_atomic_t volatile> (or whatever is defined as	3576	The type C<sig_atomic_t volatile> (or whatever is defined as
3433	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3577	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3434	threads. This is not part of the specification for C<sig_atomic_t>, but is	3578	threads. This is not part of the specification for C<sig_atomic_t>, but is
3435	believed to be sufficiently portable.	3579	believed to be sufficiently portable.
3436		3580
3437	=item C<sigprocmask> must work in a threaded environment	3581	=item C<sigprocmask> must work in a threaded environment
3438		3582
…		…
3447	except the initial one, and run the default loop in the initial thread as	3591	except the initial one, and run the default loop in the initial thread as
3448	well.	3592	well.
3449		3593
3450	=item C<long> must be large enough for common memory allocation sizes	3594	=item C<long> must be large enough for common memory allocation sizes
3451		3595
3452	To improve portability and simplify using libev, libev uses C<long>	3596	To improve portability and simplify its API, libev uses C<long> internally
3453	internally instead of C<size_t> when allocating its data structures. On	3597	instead of C<size_t> when allocating its data structures. On non-POSIX
3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3598	systems (Microsoft...) this might be unexpectedly low, but is still at
3455	is still at least 31 bits everywhere, which is enough for hundreds of	3599	least 31 bits everywhere, which is enough for hundreds of millions of
3456	millions of watchers.	3600	watchers.
3457		3601
3458	=item C<double> must hold a time value in seconds with enough accuracy	3602	=item C<double> must hold a time value in seconds with enough accuracy
3459		3603
3460	The type C<double> is used to represent timestamps. It is required to	3604	The type C<double> is used to represent timestamps. It is required to
3461	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3605	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3465	=back	3609	=back
3466		3610
3467	If you know of other additional requirements drop me a note.	3611	If you know of other additional requirements drop me a note.
3468		3612
3469		3613
3470	=head1 COMPILER WARNINGS	3614	=head1 ALGORITHMIC COMPLEXITIES
3471		3615
3472	Depending on your compiler and compiler settings, you might get no or a	3616	In this section the complexities of (many of) the algorithms used inside
3473	lot of warnings when compiling libev code. Some people are apparently	3617	libev will be documented. For complexity discussions about backends see
3474	scared by this.	3618	the documentation for C<ev_default_init>.
3475		3619
3476	However, these are unavoidable for many reasons. For one, each compiler	3620	All of the following are about amortised time: If an array needs to be
3477	has different warnings, and each user has different tastes regarding	3621	extended, libev needs to realloc and move the whole array, but this
3478	warning options. "Warn-free" code therefore cannot be a goal except when	3622	happens asymptotically rarer with higher number of elements, so O(1) might
3479	targeting a specific compiler and compiler-version.	3623	mean that libev does a lengthy realloc operation in rare cases, but on
		3624	average it is much faster and asymptotically approaches constant time.
3480		3625
3481	Another reason is that some compiler warnings require elaborate	3626	=over 4
3482	workarounds, or other changes to the code that make it less clear and less
3483	maintainable.
3484		3627
3485	And of course, some compiler warnings are just plain stupid, or simply	3628	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3486	wrong (because they don't actually warn about the condition their message
3487	seems to warn about).
3488		3629
3489	While libev is written to generate as few warnings as possible,	3630	This means that, when you have a watcher that triggers in one hour and
3490	"warn-free" code is not a goal, and it is recommended not to build libev	3631	there are 100 watchers that would trigger before that, then inserting will
3491	with any compiler warnings enabled unless you are prepared to cope with	3632	have to skip roughly seven (C<ld 100>) of these watchers.
3492	them (e.g. by ignoring them). Remember that warnings are just that:
3493	warnings, not errors, or proof of bugs.
3494		3633
		3634	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3495		3635
3496	=head1 VALGRIND	3636	That means that changing a timer costs less than removing/adding them,
		3637	as only the relative motion in the event queue has to be paid for.
3497		3638
3498	Valgrind has a special section here because it is a popular tool that is	3639	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3499	highly useful, but valgrind reports are very hard to interpret.
3500		3640
3501	If you think you found a bug (memory leak, uninitialised data access etc.)	3641	These just add the watcher into an array or at the head of a list.
3502	in libev, then check twice: If valgrind reports something like:
3503		3642
3504	==2274== definitely lost: 0 bytes in 0 blocks.	3643	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3505	==2274== possibly lost: 0 bytes in 0 blocks.
3506	==2274== still reachable: 256 bytes in 1 blocks.
3507		3644
3508	Then there is no memory leak. Similarly, under some circumstances,	3645	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3509	valgrind might report kernel bugs as if it were a bug in libev, or it
3510	might be confused (it is a very good tool, but only a tool).
3511		3646
3512	If you are unsure about something, feel free to contact the mailing list	3647	These watchers are stored in lists, so they need to be walked to find the
3513	with the full valgrind report and an explanation on why you think this is	3648	correct watcher to remove. The lists are usually short (you don't usually
3514	a bug in libev. However, don't be annoyed when you get a brisk "this is	3649	have many watchers waiting for the same fd or signal: one is typical, two
3515	no bug" answer and take the chance of learning how to interpret valgrind	3650	is rare).
3516	properly.
3517		3651
3518	If you need, for some reason, empty reports from valgrind for your project	3652	=item Finding the next timer in each loop iteration: O(1)
3519	I suggest using suppression lists.	3653
		3654	By virtue of using a binary or 4-heap, the next timer is always found at a
		3655	fixed position in the storage array.
		3656
		3657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3658
		3659	A change means an I/O watcher gets started or stopped, which requires
		3660	libev to recalculate its status (and possibly tell the kernel, depending
		3661	on backend and whether C<ev_io_set> was used).
		3662
		3663	=item Activating one watcher (putting it into the pending state): O(1)
		3664
		3665	=item Priority handling: O(number_of_priorities)
		3666
		3667	Priorities are implemented by allocating some space for each
		3668	priority. When doing priority-based operations, libev usually has to
		3669	linearly search all the priorities, but starting/stopping and activating
		3670	watchers becomes O(1) with respect to priority handling.
		3671
		3672	=item Sending an ev_async: O(1)
		3673
		3674	=item Processing ev_async_send: O(number_of_async_watchers)
		3675
		3676	=item Processing signals: O(max_signal_number)
		3677
		3678	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3679	calls in the current loop iteration. Checking for async and signal events
		3680	involves iterating over all running async watchers or all signal numbers.
		3681
		3682	=back
3520		3683
3521		3684
3522	=head1 AUTHOR	3685	=head1 AUTHOR
3523		3686
3524	Marc Lehmann <libev@schmorp.de>.	3687	Marc Lehmann <libev@schmorp.de>.

Diff Legend

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