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Revision 1.166 by root, Tue Jun 3 03:48:10 2008 UTC vs.
Revision 1.198 by root, Thu Oct 23 06:30:48 2008 UTC

…		…
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<ev_loop *>. The library knows two
282	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
283	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
284		284
285	=over 4	285	=over 4
286		286
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	362	readiness notifications you get per iteration.
363		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
		367
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		369
366	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
372		379
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		381
375	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
…		…
389	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.	398	(or space) is available.
392		399
393	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
396		405
397	While nominally embeddable in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	407	all kernel versions tested so far.
399		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		413
402	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
404	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
405	it's completely useless). For this reason it's not being "auto-detected"	417	completely useless). For this reason it's not being "auto-detected" unless
406	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
408	system like NetBSD.
409		420
410	You still can embed kqueue into a normal poll or select backend and use it	421	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	422	only for sockets (after having made sure that sockets work with kqueue on
412	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
413		424
414	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	427	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	429	two event changes per incident. Support for C<fork ()> is very bad and it
419	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
420		431
421	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
422		433
423	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	435	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	436	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	437	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
429		444
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		446
432	This is not implemented yet (and might never be, unless you send me an	447	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	461	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	462	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	464	might perform better.
450		465
451	On the positive side, ignoring the spurious readiness notifications, this	466	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
454		473
455	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
456		475
457	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		483
465	If one or more of these are or'ed into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		487
469	The most typical usage is like this:	488	Example: This is the most typical usage.
470		489
471	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		492
474	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	494	environment settings to be taken into account:
476		495
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		497
479	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
482		502
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		504
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		506
…		…
544		564
545	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
546		566
547	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
550		571
551	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
552		573
553	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
554		576
555	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
556		578
557	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
573	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
577		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
578	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
579		613
580	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
582	events.	616	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
586		620
587	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
592		627
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
596		632
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
601	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
604		644
605	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
606		646
607	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	662	- Queue all expired timers.
622	- Queue all outstanding periodics.	663	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	665	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	674	anymore.
634		675
635	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
638	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
639		680
640	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
641		682
642	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		687
647	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
648		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
649	=item ev_ref (loop)	692	=item ev_ref (loop)
650		693
651	=item ev_unref (loop)	694	=item ev_unref (loop)
652		695
653	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
656	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
658	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
659	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
660	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
661	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
662	libraries. Just remember to I<unref after start> and I<ref before stop>	708	libraries. Just remember to I<unref after start> and I<ref before stop>
663	(but only if the watcher wasn't active before, or was active before,	709	(but only if the watcher wasn't active before, or was active before,
664	respectively).	710	respectively).
665		711
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	713	running when nothing else is active.
668		714
669	struct ev_signal exitsig;	715	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	718	evf_unref (loop);
673		719
674	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		726
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		728
683	These advanced functions influence the time that libev will spend waiting	729	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	730	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
686		733
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	735	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
690		738
691	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	741	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
696		744
697	By setting a higher I<io collect interval> you allow libev to spend more	745	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		750
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	755	value will not introduce any overhead in libev.
708		756
709	Many (busy) programs can usually benefit by setting the I/O collect	757	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	758	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	760	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	761	as this approaches the timing granularity of most systems.
714		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
715	=item ev_loop_verify (loop)	770	=item ev_loop_verify (loop)
716		771
717	This function only does something when C<EV_VERIFY> support has been	772	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	773	compiled in. which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	774	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
721		777
722	This can be used to catch bugs inside libev itself: under normal	778	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	779	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	780	data structures consistent.
725		781
…		…
730		786
731	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
734		790
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	792	{
737	ev_io_stop (w);	793	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
739	}	795	}
740		796
741	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
742	struct ev_io stdin_watcher;	798	ev_io stdin_watcher;
743	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
746	ev_loop (loop, 0);	802	ev_loop (loop, 0);
747		803
…		…
838	=item C<EV_ERROR>	894	=item C<EV_ERROR>
839		895
840	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
841	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
843	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
844	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.
845		905
846	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
847	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
848	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
849	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
850	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
851		912
852	=back	913	=back
853		914
854	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
855		916
…		…
868	which rolls both calls into one.	929	which rolls both calls into one.
869		930
870	You can reinitialise a watcher at any time as long as it has been stopped	931	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
872		933
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	935	int revents)>.
		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);
875		942
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		944
878	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
879	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
…		…
882	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
883		950
884	Although some watcher types do not have type-specific arguments	951	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		953
		954	See C<ev_init>, above, for an example.
		955
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		957
889	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
890	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
891	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
892		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
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		967
895	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
897		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
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		977
900	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
901	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		986
907	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
908		988
909	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
910	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
…		…
958		1038
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1040
961	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
962	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
963	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
964		1045
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1047
967	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
968	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
969	watcher isn't pending it does nothing and returns C<0>.	1050	watcher isn't pending it does nothing and returns C<0>.
970		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
971	=back	1055	=back
972		1056
973		1057
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1059
976	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
977	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
978	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
979	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
980	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
981	data:	1065	data:
982		1066
983	struct my_io	1067	struct my_io
984	{	1068	{
985	struct ev_io io;	1069	ev_io io;
986	int otherfd;	1070	int otherfd;
987	void *somedata;	1071	void *somedata;
988	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
989	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1078
991	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
992	can cast it back to your own type:	1080	can cast it back to your own type:
993		1081
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1083	{
996	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
997	...	1085	...
998	}	1086	}
999		1087
1000	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
1001	instead have been omitted.	1089	instead have been omitted.
1002		1090
1003	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
1004	watchers:	1092	embedded watchers:
1005		1093
1006	struct my_biggy	1094	struct my_biggy
1007	{	1095	{
1008	int some_data;	1096	int some_data;
1009	ev_timer t1;	1097	ev_timer t1;
1010	ev_timer t2;	1098	ev_timer t2;
1011	}	1099	}
1012		1100
1013	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
1014	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):
1015		1106
1016	#include <stddef.h>	1107	#include <stddef.h>
1017		1108
1018	static void	1109	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1111	{
1021	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1114	}
1024		1115
1025	static void	1116	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1118	{
1028	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1121	}
1031		1122
…		…
1059	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
1060	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
1061	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
1062	required if you know what you are doing).	1153	required if you know what you are doing).
1063		1154
1064	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
1065	(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
1066	C<EVBACKEND_POLL>).	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1158
1068	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
1069	receive "spurious" readiness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1167
1077	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
1078	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
1079	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
1080	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
1081	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.
1082		1177
1083	=head3 The special problem of disappearing file descriptors	1178	=head3 The special problem of disappearing file descriptors
1084		1179
1085	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
1086	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,
1087	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
1088	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
1089	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
1090	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
1091	fact, a different file descriptor.	1186	fact, a different file descriptor.
1092		1187
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1219	C<EVBACKEND_POLL>.
1125		1220
1126	=head3 The special problem of SIGPIPE	1221	=head3 The special problem of SIGPIPE
1127		1222
1128	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>:
1129	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
1130	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
1131	programs this is sensible behaviour, for daemons, this is usually	1226	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1227
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1228	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1230	somewhere, as that would have given you a big clue).
1137		1231
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1238
1145	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
1146		1240
1147	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
1148	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
1149	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.
1150		1244
1151	=item int fd [read-only]	1245	=item int fd [read-only]
1152		1246
1153	The file descriptor being watched.	1247	The file descriptor being watched.
1154		1248
…		…
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
1166		1260
1167	static void	1261	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1263	{
1170	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
1171	.. 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
1172	}	1266	}
1173		1267
1174	...	1268	...
1175	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1270	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
1180		1274
1181		1275
…		…
1184	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
1185	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
1186		1280
1187	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
1188	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
1189	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
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	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 Be smart about timeouts
		1292
		1293	Many real-world problems invole some kind of time-out, usually for error
		1294	recovery. A typical example is an HTTP request - if the other side hangs,
		1295	you want to raise some error after a while.
		1296
		1297	Here are some ways on how to handle this problem, from simple and
		1298	inefficient to very efficient.
		1299
		1300	In the following examples a 60 second activity timeout is assumed - a
		1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")
		1302	was received.
		1303
		1304	=over 4
		1305
		1306	=item 1. Use a timer and stop, reinitialise, start it on activity.
		1307
		1308	This is the most obvious, but not the most simple way: In the beginning,
		1309	start the watcher:
		1310
		1311	ev_timer_init (timer, callback, 60., 0.);
		1312	ev_timer_start (loop, timer);
		1313
		1314	Then, each time there is some activity, C<ev_timer_stop> the timer,
		1315	initialise it again, and start it:
		1316
		1317	ev_timer_stop (loop, timer);
		1318	ev_timer_set (timer, 60., 0.);
		1319	ev_timer_start (loop, timer);
		1320
		1321	This is relatively simple to implement, but means that each time there
		1322	is some activity, libev will first have to remove the timer from it's
		1323	internal data strcuture and then add it again.
		1324
		1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1326
		1327	This is the easiest way, and involves using C<ev_timer_again> instead of
		1328	C<ev_timer_start>.
		1329
		1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and
		1331	then call C<ev_timer_again> at start and each time you successfully read
		1332	or write some data. If you go into an idle state where you do not expect
		1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and
		1334	C<ev_timer_again> will automatically restart it if need be.
		1335
		1336	That means you can ignore the C<after> value and C<ev_timer_start>
		1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.
		1338
		1339	At start:
		1340
		1341	ev_timer_init (timer, callback, 0., 60.);
		1342	ev_timer_again (loop, timer);
		1343
		1344	Each time you receive some data:
		1345
		1346	ev_timer_again (loop, timer);
		1347
		1348	It is even possible to change the time-out on the fly:
		1349
		1350	timer->repeat = 30.;
		1351	ev_timer_again (loop, timer);
		1352
		1353	This is slightly more efficient then stopping/starting the timer each time
		1354	you want to modify its timeout value, as libev does not have to completely
		1355	remove and re-insert the timer from/into it's internal data structure.
		1356
		1357	=item 3. Let the timer time out, but then re-arm it as required.
		1358
		1359	This method is more tricky, but usually most efficient: Most timeouts are
		1360	relatively long compared to the loop iteration time - in our example,
		1361	within 60 seconds, there are usually many I/O events with associated
		1362	activity resets.
		1363
		1364	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1365	but remember the time of last activity, and check for a real timeout only
		1366	within the callback:
		1367
		1368	ev_tstamp last_activity; // time of last activity
		1369
		1370	static void
		1371	callback (EV_P_ ev_timer *w, int revents)
		1372	{
		1373	ev_tstamp now = ev_now (EV_A);
		1374	ev_tstamp timeout = last_activity + 60.;
		1375
		1376	// if last_activity is older than now - timeout, we did time out
		1377	if (timeout < now)
		1378	{
		1379	// timeout occured, take action
		1380	}
		1381	else
		1382	{
		1383	// callback was invoked, but there was some activity, re-arm
		1384	// to fire in last_activity + 60.
		1385	w->again = timeout - now;
		1386	ev_timer_again (EV_A_ w);
		1387	}
		1388	}
		1389
		1390	To summarise the callback: first calculate the real time-out (defined as
		1391	"60 seconds after the last activity"), then check if that time has been
		1392	reached, which means there was a real timeout. Otherwise the callback was
		1393	invoked too early (timeout is in the future), so re-schedule the timer to
		1394	fire at that future time.
		1395
		1396	Note how C<ev_timer_again> is used, taking advantage of the
		1397	C<ev_timer_again> optimisation when the timer is already running.
		1398
		1399	This scheme causes more callback invocations (about one every 60 seconds),
		1400	but virtually no calls to libev to change the timeout.
		1401
		1402	To start the timer, simply intiialise the watcher and C<last_activity>,
		1403	then call the callback:
		1404
		1405	ev_timer_init (timer, callback);
		1406	last_activity = ev_now (loop);
		1407	callback (loop, timer, EV_TIMEOUT);
		1408
		1409	And when there is some activity, simply remember the time in
		1410	C<last_activity>:
		1411
		1412	last_actiivty = ev_now (loop);
		1413
		1414	This technique is slightly more complex, but in most cases where the
		1415	time-out is unlikely to be triggered, much more efficient.
		1416
		1417	=back
		1418
		1419	=head3 The special problem of time updates
		1420
		1421	Establishing the current time is a costly operation (it usually takes at
		1422	least two system calls): EV therefore updates its idea of the current
		1423	time only before and after C<ev_loop> collects new events, which causes a
		1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1425	lots of events in one iteration.
1192		1426
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1427	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1428	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1429	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1430	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1431	timeout on the current time, use something like this to adjust for this:
1198		1432
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1433	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1434
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1435	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1437	()>.
1204		1438
1205	=head3 Watcher-Specific Functions and Data Members	1439	=head3 Watcher-Specific Functions and Data Members
1206		1440
1207	=over 4	1441	=over 4
1208		1442
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1466	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1467
1234	If the timer is repeating, either start it if necessary (with the	1468	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1469	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1470
1237	This sounds a bit complicated, but here is a useful and typical	1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1472	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246
1247	That means you can ignore the C<after> value and C<ev_timer_start>
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249
1250	ev_timer_init (timer, callback, 0., 5.);
1251	ev_timer_again (loop, timer);
1252	...
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258
1259	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.
1261		1473
1262	=item ev_tstamp repeat [read-write]	1474	=item ev_tstamp repeat [read-write]
1263		1475
1264	The current C<repeat> value. Will be used each time the watcher times out	1476	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1477	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1478	which is also when any modifications are taken into account.
1267		1479
1268	=back	1480	=back
1269		1481
1270	=head3 Examples	1482	=head3 Examples
1271		1483
1272	Example: Create a timer that fires after 60 seconds.	1484	Example: Create a timer that fires after 60 seconds.
1273		1485
1274	static void	1486	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1487	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1488	{
1277	.. one minute over, w is actually stopped right here	1489	.. one minute over, w is actually stopped right here
1278	}	1490	}
1279		1491
1280	struct ev_timer mytimer;	1492	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1493	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1494	ev_timer_start (loop, &mytimer);
1283		1495
1284	Example: Create a timeout timer that times out after 10 seconds of	1496	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1497	inactivity.
1286		1498
1287	static void	1499	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1500	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1501	{
1290	.. ten seconds without any activity	1502	.. ten seconds without any activity
1291	}	1503	}
1292		1504
1293	struct ev_timer mytimer;	1505	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1507	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1508	ev_loop (loop, 0);
1297		1509
1298	// and in some piece of code that gets executed on any "activity":	1510	// and in some piece of code that gets executed on any "activity":
…		…
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger	1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).	1527	roughly 10 seconds later as it uses a relative timeout).
1316		1528
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1529	C<ev_periodic>s can also be used to implement vastly more complex timers,
1318	such as triggering an event on each "midnight, local time", or other	1530	such as triggering an event on each "midnight, local time", or other
1319	complicated, rules.	1531	complicated rules.
1320		1532
1321	As with timers, the callback is guaranteed to be invoked only when the	1533	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1534	time (C<at>) has passed, but if multiple periodic timers become ready
1323	during the same loop iteration then order of execution is undefined.	1535	during the same loop iteration, then order of execution is undefined.
1324		1536
1325	=head3 Watcher-Specific Functions and Data Members	1537	=head3 Watcher-Specific Functions and Data Members
1326		1538
1327	=over 4	1539	=over 4
1328		1540
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1330		1542
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1332		1544
1333	Lots of arguments, lets sort it out... There are basically three modes of	1545	Lots of arguments, lets sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1546	operation, and we will explain them from simplest to most complex:
1335		1547
1336	=over 4	1548	=over 4
1337		1549
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1339		1551
1340	In this configuration the watcher triggers an event after the wall clock	1552	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1553	time C<at> has passed. It will not repeat and will not adjust when a time
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1343	run when the system time reaches or surpasses this time.	1555	only run when the system clock reaches or surpasses this time.
1344		1556
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1346		1558
1347	In this mode the watcher will always be scheduled to time out at the next	1559	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1560	C<at + N * interval> time (for some integer N, which can also be negative)
1349	and then repeat, regardless of any time jumps.	1561	and then repeat, regardless of any time jumps.
1350		1562
1351	This can be used to create timers that do not drift with respect to system	1563	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1564	system clock, for example, here is a C<ev_periodic> that triggers each
1353	the hour:	1565	hour, on the hour:
1354		1566
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1567	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1568
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1569	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1570	but only that the callback will be called when the system time shows a
…		…
1384		1596
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1599	only event loop modification you are allowed to do).
1388		1600
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1601	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1602	*w, ev_tstamp now)>, e.g.:
1391		1603
		1604	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1605	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1606	{
1394	return now + 60.;	1607	return now + 60.;
1395	}	1608	}
1396		1609
1397	It must return the next time to trigger, based on the passed time value	1610	It must return the next time to trigger, based on the passed time value
…		…
1434		1647
1435	The current interval value. Can be modified any time, but changes only	1648	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	1649	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1650	called.
1438		1651
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1652	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1653
1441	The current reschedule callback, or C<0>, if this functionality is	1654	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	1655	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	1656	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1657
1445	=back	1658	=back
1446		1659
1447	=head3 Examples	1660	=head3 Examples
1448		1661
1449	Example: Call a callback every hour, or, more precisely, whenever the	1662	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1663	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1664	potentially a lot of jitter, but good long-term stability.
1452		1665
1453	static void	1666	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1668	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1669	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1670	}
1458		1671
1459	struct ev_periodic hourly_tick;	1672	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1673	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1674	ev_periodic_start (loop, &hourly_tick);
1462		1675
1463	Example: The same as above, but use a reschedule callback to do it:	1676	Example: The same as above, but use a reschedule callback to do it:
1464		1677
1465	#include <math.h>	1678	#include <math.h>
1466		1679
1467	static ev_tstamp	1680	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1681	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	1682	{
1470	return fmod (now, 3600.) + 3600.;	1683	return now + (3600. - fmod (now, 3600.));
1471	}	1684	}
1472		1685
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1686	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1687
1475	Example: Call a callback every hour, starting now:	1688	Example: Call a callback every hour, starting now:
1476		1689
1477	struct ev_periodic hourly_tick;	1690	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1691	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1692	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1693	ev_periodic_start (loop, &hourly_tick);
1481		1694
1482		1695
…		…
1485	Signal watchers will trigger an event when the process receives a specific	1698	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	1699	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	1700	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1701	normal event processing, like any other event.
1489		1702
		1703	If you want signals asynchronously, just use C<sigaction> as you would
		1704	do without libev and forget about sharing the signal. You can even use
		1705	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1706
1490	You can configure as many watchers as you like per signal. Only when the	1707	You can configure as many watchers as you like per signal. Only when the
1491	first watcher gets started will libev actually register a signal watcher	1708	first watcher gets started will libev actually register a signal handler
1492	with the kernel (thus it coexists with your own signal handlers as long	1709	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	1710	you don't register any with libev for the same signal). Similarly, when
1494	watcher for a signal is stopped libev will reset the signal handler to	1711	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1712	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1713
1497	If possible and supported, libev will install its handlers with	1714	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1499	interrupted. If you have a problem with system calls getting interrupted by	1716	interrupted. If you have a problem with system calls getting interrupted by
1500	signals you can block all signals in an C<ev_check> watcher and unblock	1717	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1734
1518	=back	1735	=back
1519		1736
1520	=head3 Examples	1737	=head3 Examples
1521		1738
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1739	Example: Try to exit cleanly on SIGINT.
1523		1740
1524	static void	1741	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	1743	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1744	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1745	}
1529		1746
1530	struct ev_signal signal_watcher;	1747	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1749	ev_signal_start (loop, &signal_watcher);
1533		1750
1534		1751
1535	=head2 C<ev_child> - watch out for process status changes	1752	=head2 C<ev_child> - watch out for process status changes
1536		1753
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1754	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	1755	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	1756	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	1757	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	1758	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1759	forking and then immediately registering a watcher for the child is fine,
		1760	but forking and registering a watcher a few event loop iterations later is
		1761	not.
1542		1762
1543	Only the default event loop is capable of handling signals, and therefore	1763	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	1764	you can only register child watchers in the default event loop.
1545		1765
1546	=head3 Process Interaction	1766	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	1779	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	1780	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	1781	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	1782	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	1783	that, so other libev users can use C<ev_child> watchers freely.
		1784
		1785	=head3 Stopping the Child Watcher
		1786
		1787	Currently, the child watcher never gets stopped, even when the
		1788	child terminates, so normally one needs to stop the watcher in the
		1789	callback. Future versions of libev might stop the watcher automatically
		1790	when a child exit is detected.
1564		1791
1565	=head3 Watcher-Specific Functions and Data Members	1792	=head3 Watcher-Specific Functions and Data Members
1566		1793
1567	=over 4	1794	=over 4
1568		1795
…		…
1600	its completion.	1827	its completion.
1601		1828
1602	ev_child cw;	1829	ev_child cw;
1603		1830
1604	static void	1831	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	1832	child_cb (EV_P_ ev_child *w, int revents)
1606	{	1833	{
1607	ev_child_stop (EV_A_ w);	1834	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1835	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	1836	}
1610		1837
…		…
1637	the stat buffer having unspecified contents.	1864	the stat buffer having unspecified contents.
1638		1865
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	1866	The path I<should> be absolute and I<must not> end in a slash. If it is
1640	relative and your working directory changes, the behaviour is undefined.	1867	relative and your working directory changes, the behaviour is undefined.
1641		1868
1642	Since there is no standard to do this, the portable implementation simply	1869	Since there is no standard kernel interface to do this, the portable
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1870	implementation simply calls C<stat (2)> regularly on the path to see if
1644	can specify a recommended polling interval for this case. If you specify	1871	it changed somehow. You can specify a recommended polling interval for
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	1872	this case. If you specify a polling interval of C<0> (highly recommended!)
1646	unspecified default> value will be used (which you can expect to be around	1873	then a I<suitable, unspecified default> value will be used (which
1647	five seconds, although this might change dynamically). Libev will also	1874	you can expect to be around five seconds, although this might change
1648	impose a minimum interval which is currently around C<0.1>, but thats	1875	dynamically). Libev will also impose a minimum interval which is currently
1649	usually overkill.	1876	around C<0.1>, but thats usually overkill.
1650		1877
1651	This watcher type is not meant for massive numbers of stat watchers,	1878	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	1879	as even with OS-supported change notifications, this can be
1653	resource-intensive.	1880	resource-intensive.
1654		1881
1655	At the time of this writing, only the Linux inotify interface is	1882	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	1883	is the Linux inotify interface (implementing kqueue support is left as
1657	reader, note, however, that the author sees no way of implementing ev_stat	1884	an exercise for the reader. Note, however, that the author sees no way
1658	semantics with kqueue). Inotify will be used to give hints only and should	1885	of implementing C<ev_stat> semantics with kqueue).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		1886
1664	=head3 ABI Issues (Largefile Support)	1887	=head3 ABI Issues (Largefile Support)
1665		1888
1666	Libev by default (unless the user overrides this) uses the default	1889	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	1890	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	1891	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	1892	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	1893	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	1894	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	1895	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	1896	most noticeably disabled with ev_stat and large file support.
1674		1897
1675	=head3 Inotify	1898	The solution for this is to lobby your distribution maker to make large
		1899	file interfaces available by default (as e.g. FreeBSD does) and not
		1900	optional. Libev cannot simply switch on large file support because it has
		1901	to exchange stat structures with application programs compiled using the
		1902	default compilation environment.
1676		1903
		1904	=head3 Inotify and Kqueue
		1905
1677	When C<inotify (7)> support has been compiled into libev (generally only	1906	When C<inotify (7)> support has been compiled into libev (generally
		1907	only available with Linux 2.6.25 or above due to bugs in earlier
1678	available on Linux) and present at runtime, it will be used to speed up	1908	implementations) and present at runtime, it will be used to speed up
1679	change detection where possible. The inotify descriptor will be created lazily	1909	change detection where possible. The inotify descriptor will be created
1680	when the first C<ev_stat> watcher is being started.	1910	lazily when the first C<ev_stat> watcher is being started.
1681		1911
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	1912	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	1913	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	1914	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	1915	there are many cases where libev has to resort to regular C<stat> polling,
		1916	but as long as the path exists, libev usually gets away without polling.
1686		1917
1687	(There is no support for kqueue, as apparently it cannot be used to	1918	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	1919	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	1920	descriptor open on the object at all times, and detecting renames, unlinks
		1921	etc. is difficult.
1690		1922
1691	=head3 The special problem of stat time resolution	1923	=head3 The special problem of stat time resolution
1692		1924
1693	The C<stat ()> system call only supports full-second resolution portably, and	1925	The C<stat ()> system call only supports full-second resolution portably, and
1694	even on systems where the resolution is higher, many file systems still	1926	even on systems where the resolution is higher, most file systems still
1695	only support whole seconds.	1927	only support whole seconds.
1696		1928
1697	That means that, if the time is the only thing that changes, you can	1929	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	1930	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	1931	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	1932	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	1933	stat data does change in other ways (e.g. file size).
1702		1934
1703	The solution to this is to delay acting on a change for slightly more	1935	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	1936	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1937	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	1938	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	1958	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	1959	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	1960	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	1961	path for as long as the watcher is active.
1730		1962
1731	The callback will receive C<EV_STAT> when a change was detected, relative	1963	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	1964	relative to the attributes at the time the watcher was started (or the
1733	was detected).	1965	last change was detected).
1734		1966
1735	=item ev_stat_stat (loop, ev_stat *)	1967	=item ev_stat_stat (loop, ev_stat *)
1736		1968
1737	Updates the stat buffer immediately with new values. If you change the	1969	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	1970	watched path in your callback, you could call this function to avoid
…		…
1821		2053
1822		2054
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2055	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2056
1825	Idle watchers trigger events when no other events of the same or higher	2057	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2058	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2059	as receiving "events").
1828		2060
1829	That is, as long as your process is busy handling sockets or timeouts	2061	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2062	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2063	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2064	are pending), the idle watchers are being called once per event loop
…		…
1857		2089
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2090	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2091	callback, free it. Also, use no error checking, as usual.
1860		2092
1861	static void	2093	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2094	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2095	{
1864	free (w);	2096	free (w);
1865	// now do something you wanted to do when the program has	2097	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2098	// no longer anything immediate to do.
1867	}	2099	}
1868		2100
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2102	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2103	ev_idle_start (loop, idle_cb);
1872		2104
1873		2105
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2107
1876	Prepare and check watchers are usually (but not always) used in tandem:	2108	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2109	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2110	afterwards.
1879		2111
1880	You I<must not> call C<ev_loop> or similar functions that enter	2112	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2113	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2117	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2118	called in pairs bracketing the blocking call.
1887		2119
1888	Their main purpose is to integrate other event mechanisms into libev and	2120	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2121	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2122	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2123	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2124	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2125	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2126	watcher).
1895		2127
1896	This is done by examining in each prepare call which file descriptors need	2128	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2129	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2130	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2131	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2132	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2133	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2134	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2135	nevertheless, because you never know, you know?).
1904		2136
1905	As another example, the Perl Coro module uses these hooks to integrate	2137	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2138	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2139	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2140	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2143	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2144	low-priority coroutines to idle/background tasks).
1913		2145
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2146	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2147	priority, to ensure that they are being run before any other watchers
		2148	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2149
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2150	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2151	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2152	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2153	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2154	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2155	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2156	others).
1923		2157
1924	=head3 Watcher-Specific Functions and Data Members	2158	=head3 Watcher-Specific Functions and Data Members
1925		2159
1926	=over 4	2160	=over 4
1927		2161
…		…
1929		2163
1930	=item ev_check_init (ev_check *, callback)	2164	=item ev_check_init (ev_check *, callback)
1931		2165
1932	Initialises and configures the prepare or check watcher - they have no	2166	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2167	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2168	macros, but using them is utterly, utterly, utterly and completely
		2169	pointless.
1935		2170
1936	=back	2171	=back
1937		2172
1938	=head3 Examples	2173	=head3 Examples
1939		2174
…		…
1952		2187
1953	static ev_io iow [nfd];	2188	static ev_io iow [nfd];
1954	static ev_timer tw;	2189	static ev_timer tw;
1955		2190
1956	static void	2191	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2192	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2193	{
1959	}	2194	}
1960		2195
1961	// create io watchers for each fd and a timer before blocking	2196	// create io watchers for each fd and a timer before blocking
1962	static void	2197	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2198	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2199	{
1965	int timeout = 3600000;	2200	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2201	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2202	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
1983	}	2218	}
1984	}	2219	}
1985		2220
1986	// stop all watchers after blocking	2221	// stop all watchers after blocking
1987	static void	2222	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2223	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2224	{
1990	ev_timer_stop (loop, &tw);	2225	ev_timer_stop (loop, &tw);
1991		2226
1992	for (int i = 0; i < nfd; ++i)	2227	for (int i = 0; i < nfd; ++i)
1993	{	2228	{
…		…
2032	}	2267	}
2033		2268
2034	// do not ever call adns_afterpoll	2269	// do not ever call adns_afterpoll
2035		2270
2036	Method 4: Do not use a prepare or check watcher because the module you	2271	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2272	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2273	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2274	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2275	this approach, effectively embedding EV as a client into the horrible
		2276	libglib event loop.
2041		2277
2042	static gint	2278	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2279	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2280	{
2045	int got_events = 0;	2281	int got_events = 0;
…		…
2076	prioritise I/O.	2312	prioritise I/O.
2077		2313
2078	As an example for a bug workaround, the kqueue backend might only support	2314	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2315	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2316	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2317	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2318	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2319	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2320	C<kevent>, but at least you can use both mechanisms for what they are
		2321	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2322
2086	As for prioritising I/O: rarely you have the case where some fds have	2323	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2324	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2325	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2326	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2327	the rest in a second one, and embed the second one in the first.
2091		2328
2092	As long as the watcher is active, the callback will be invoked every time	2329	As long as the watcher is active, the callback will be invoked every time
2093	there might be events pending in the embedded loop. The callback must then	2330	there might be events pending in the embedded loop. The callback must then
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2095	their callbacks (you could also start an idle watcher to give the embedded	2332	their callbacks (you could also start an idle watcher to give the embedded
…		…
2103	interested in that.	2340	interested in that.
2104		2341
2105	Also, there have not currently been made special provisions for forking:	2342	Also, there have not currently been made special provisions for forking:
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2107	but you will also have to stop and restart any C<ev_embed> watchers	2344	but you will also have to stop and restart any C<ev_embed> watchers
2108	yourself.	2345	yourself - but you can use a fork watcher to handle this automatically,
		2346	and future versions of libev might do just that.
2109		2347
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2348	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2350	portable one.
2113		2351
2114	So when you want to use this feature you will always have to be prepared	2352	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2353	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2354	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2355	create it, and if that fails, use the normal loop for everything.
		2356
		2357	=head3 C<ev_embed> and fork
		2358
		2359	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2360	automatically be applied to the embedded loop as well, so no special
		2361	fork handling is required in that case. When the watcher is not running,
		2362	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2363	as applicable.
2118		2364
2119	=head3 Watcher-Specific Functions and Data Members	2365	=head3 Watcher-Specific Functions and Data Members
2120		2366
2121	=over 4	2367	=over 4
2122		2368
…		…
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2396	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2397	used).
2152		2398
2153	struct ev_loop *loop_hi = ev_default_init (0);	2399	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2400	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2401	ev_embed embed;
2156		2402
2157	// see if there is a chance of getting one that works	2403	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2404	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2405	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2406	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2420	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2421	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2422
2177	struct ev_loop *loop = ev_default_init (0);	2423	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2424	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2425	ev_embed embed;
2180		2426
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2427	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2428	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2429	{
2184	ev_embed_init (&embed, 0, loop_socket);	2430	ev_embed_init (&embed, 0, loop_socket);
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2486	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2487	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2488	need elaborate support such as pthreads.
2243		2489
2244	That means that if you want to queue data, you have to provide your own	2490	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2491	queue. But at least I can tell you how to implement locking around your
2246	queue:	2492	queue:
2247		2493
2248	=over 4	2494	=over 4
2249		2495
2250	=item queueing from a signal handler context	2496	=item queueing from a signal handler context
2251		2497
2252	To implement race-free queueing, you simply add to the queue in the signal	2498	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2499	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2500	an example that does that for some fictitious SIGUSR1 handler:
2255		2501
2256	static ev_async mysig;	2502	static ev_async mysig;
2257		2503
2258	static void	2504	static void
2259	sigusr1_handler (void)	2505	sigusr1_handler (void)
…		…
2326		2572
2327	=item ev_async_init (ev_async *, callback)	2573	=item ev_async_init (ev_async *, callback)
2328		2574
2329	Initialises and configures the async watcher - it has no parameters of any	2575	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2331	believe me.	2577	trust me.
2332		2578
2333	=item ev_async_send (loop, ev_async *)	2579	=item ev_async_send (loop, ev_async *)
2334		2580
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	2583	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2585	section below on what exactly this means).
2340		2586
2341	This call incurs the overhead of a system call only once per loop iteration,	2587	This call incurs the overhead of a system call only once per loop iteration,
2342	so while the overhead might be noticeable, it doesn't apply to repeated	2588	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2366	=over 4	2612	=over 4
2367		2613
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2614	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		2615
2370	This function combines a simple timer and an I/O watcher, calls your	2616	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	2617	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	2618	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	2619	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	2620	more watchers yourself.
2375		2621
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	2622	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2623	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	2624	the given C<fd> and C<events> set will be created and started.
2379		2625
2380	If C<timeout> is less than 0, then no timeout watcher will be	2626	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2628	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		2629
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	2631	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2633	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2634	a timeout and an io event at the same time - you probably should give io
		2635	events precedence.
		2636
		2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2389		2638
2390	static void stdin_ready (int revents, void *arg)	2639	static void stdin_ready (int revents, void *arg)
2391	{	2640	{
		2641	if (revents & EV_READ)
		2642	/* stdin might have data for us, joy! */;
2392	if (revents & EV_TIMEOUT)	2643	else if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;	2644	/* doh, nothing entered */;
2394	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;
2396	}	2645	}
2397		2646
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2648
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		2650
2402	Feeds the given event set into the event loop, as if the specified event	2651	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an	2652	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	2653	initialised but not necessarily started event watcher).
2405		2654
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		2656
2408	Feed an event on the given fd, as if a file descriptor backend detected	2657	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	2658	the given events it.
2410		2659
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		2661
2413	Feed an event as if the given signal occurred (C<loop> must be the default	2662	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	2663	loop!).
2415		2664
2416	=back	2665	=back
…		…
2548		2797
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2798	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		2799
2551	See the method-C<set> above for more details.	2800	See the method-C<set> above for more details.
2552		2801
2553	Example:	2802	Example: Use a plain function as callback.
2554		2803
2555	static void io_cb (ev::io &w, int revents) { }	2804	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	2805	iow.set <io_cb> ();
2557		2806
2558	=item w->set (struct ev_loop *)	2807	=item w->set (struct ev_loop *)
…		…
2596	Example: Define a class with an IO and idle watcher, start one of them in	2845	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	2846	the constructor.
2598		2847
2599	class myclass	2848	class myclass
2600	{	2849	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	2850	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		2852
2604	myclass (int fd)	2853	myclass (int fd)
2605	{	2854	{
2606	io .set <myclass, &myclass::io_cb > (this);	2855	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	2856	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2623	=item Perl	2872	=item Perl
2624		2873
2625	The EV module implements the full libev API and is actually used to test	2874	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	2875	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	2876	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2877	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2878	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2879	and C<EV::Glib>).
2630		2880
2631	It can be found and installed via CPAN, its homepage is at	2881	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	2882	L<http://software.schmorp.de/pkg/EV>.
2633		2883
2634	=item Python	2884	=item Python
…		…
2648	L<http://rev.rubyforge.org/>.	2898	L<http://rev.rubyforge.org/>.
2649		2899
2650	=item D	2900	=item D
2651		2901
2652	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2653	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2654		2904
2655	=back	2905	=back
2656		2906
2657		2907
2658	=head1 MACRO MAGIC	2908	=head1 MACRO MAGIC
…		…
2813		3063
2814	=head2 PREPROCESSOR SYMBOLS/MACROS	3064	=head2 PREPROCESSOR SYMBOLS/MACROS
2815		3065
2816	Libev can be configured via a variety of preprocessor symbols you have to	3066	Libev can be configured via a variety of preprocessor symbols you have to
2817	define before including any of its files. The default in the absence of	3067	define before including any of its files. The default in the absence of
2818	autoconf is noted for every option.	3068	autoconf is documented for every option.
2819		3069
2820	=over 4	3070	=over 4
2821		3071
2822	=item EV_STANDALONE	3072	=item EV_STANDALONE
2823		3073
…		…
2993	When doing priority-based operations, libev usually has to linearly search	3243	When doing priority-based operations, libev usually has to linearly search
2994	all the priorities, so having many of them (hundreds) uses a lot of space	3244	all the priorities, so having many of them (hundreds) uses a lot of space
2995	and time, so using the defaults of five priorities (-2 .. +2) is usually	3245	and time, so using the defaults of five priorities (-2 .. +2) is usually
2996	fine.	3246	fine.
2997		3247
2998	If your embedding application does not need any priorities, defining these both to	3248	If your embedding application does not need any priorities, defining these
2999	C<0> will save some memory and CPU.	3249	both to C<0> will save some memory and CPU.
3000		3250
3001	=item EV_PERIODIC_ENABLE	3251	=item EV_PERIODIC_ENABLE
3002		3252
3003	If undefined or defined to be C<1>, then periodic timers are supported. If	3253	If undefined or defined to be C<1>, then periodic timers are supported. If
3004	defined to be C<0>, then they are not. Disabling them saves a few kB of	3254	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3011	code.	3261	code.
3012		3262
3013	=item EV_EMBED_ENABLE	3263	=item EV_EMBED_ENABLE
3014		3264
3015	If undefined or defined to be C<1>, then embed watchers are supported. If	3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3016	defined to be C<0>, then they are not.	3266	defined to be C<0>, then they are not. Embed watchers rely on most other
		3267	watcher types, which therefore must not be disabled.
3017		3268
3018	=item EV_STAT_ENABLE	3269	=item EV_STAT_ENABLE
3019		3270
3020	If undefined or defined to be C<1>, then stat watchers are supported. If	3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3021	defined to be C<0>, then they are not.	3272	defined to be C<0>, then they are not.
…		…
3053	two).	3304	two).
3054		3305
3055	=item EV_USE_4HEAP	3306	=item EV_USE_4HEAP
3056		3307
3057	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3058	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3059	to C<1>. The 4-heap uses more complicated (longer) code but has	3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3060	noticeably faster performance with many (thousands) of watchers.	3311	faster performance with many (thousands) of watchers.
3061		3312
3062	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3063	(disabled).	3314	(disabled).
3064		3315
3065	=item EV_HEAP_CACHE_AT	3316	=item EV_HEAP_CACHE_AT
3066		3317
3067	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3068	timer and periodics heap, libev can cache the timestamp (I<at>) within	3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3069	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3070	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3071	but avoids random read accesses on heap changes. This improves performance	3322	but avoids random read accesses on heap changes. This improves performance
3072	noticeably with with many (hundreds) of watchers.	3323	noticeably with many (hundreds) of watchers.
3073		3324
3074	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3075	(disabled).	3326	(disabled).
3076		3327
3077	=item EV_VERIFY	3328	=item EV_VERIFY
…		…
3083	called once per loop, which can slow down libev. If set to C<3>, then the	3334	called once per loop, which can slow down libev. If set to C<3>, then the
3084	verification code will be called very frequently, which will slow down	3335	verification code will be called very frequently, which will slow down
3085	libev considerably.	3336	libev considerably.
3086		3337
3087	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3088	C<0.>	3339	C<0>.
3089		3340
3090	=item EV_COMMON	3341	=item EV_COMMON
3091		3342
3092	By default, all watchers have a C<void *data> member. By redefining	3343	By default, all watchers have a C<void *data> member. By redefining
3093	this macro to a something else you can include more and other types of	3344	this macro to a something else you can include more and other types of
…		…
3110	and the way callbacks are invoked and set. Must expand to a struct member	3361	and the way callbacks are invoked and set. Must expand to a struct member
3111	definition and a statement, respectively. See the F<ev.h> header file for	3362	definition and a statement, respectively. See the F<ev.h> header file for
3112	their default definitions. One possible use for overriding these is to	3363	their default definitions. One possible use for overriding these is to
3113	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3364	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3114	method calls instead of plain function calls in C++.	3365	method calls instead of plain function calls in C++.
		3366
		3367	=back
3115		3368
3116	=head2 EXPORTED API SYMBOLS	3369	=head2 EXPORTED API SYMBOLS
3117		3370
3118	If you need to re-export the API (e.g. via a DLL) and you need a list of	3371	If you need to re-export the API (e.g. via a DLL) and you need a list of
3119	exported symbols, you can use the provided F<Symbol.*> files which list	3372	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3166	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3167		3420
3168	#include "ev_cpp.h"	3421	#include "ev_cpp.h"
3169	#include "ev.c"	3422	#include "ev.c"
3170		3423
		3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3171		3425
3172	=head1 THREADS AND COROUTINES	3426	=head2 THREADS AND COROUTINES
3173		3427
3174	=head2 THREADS	3428	=head3 THREADS
3175		3429
3176	Libev itself is completely thread-safe, but it uses no locking. This	3430	All libev functions are reentrant and thread-safe unless explicitly
		3431	documented otherwise, but libev implements no locking itself. This means
3177	means that you can use as many loops as you want in parallel, as long as	3432	that you can use as many loops as you want in parallel, as long as there
3178	only one thread ever calls into one libev function with the same loop	3433	are no concurrent calls into any libev function with the same loop
3179	parameter.	3434	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3435	of course): libev guarantees that different event loops share no data
		3436	structures that need any locking.
3180		3437
3181	Or put differently: calls with different loop parameters can be done in	3438	Or to put it differently: calls with different loop parameters can be done
3182	parallel from multiple threads, calls with the same loop parameter must be	3439	concurrently from multiple threads, calls with the same loop parameter
3183	done serially (but can be done from different threads, as long as only one	3440	must be done serially (but can be done from different threads, as long as
3184	thread ever is inside a call at any point in time, e.g. by using a mutex	3441	only one thread ever is inside a call at any point in time, e.g. by using
3185	per loop).	3442	a mutex per loop).
3186		3443
3187	If you want to know which design is best for your problem, then I cannot	3444	Specifically to support threads (and signal handlers), libev implements
		3445	so-called C<ev_async> watchers, which allow some limited form of
		3446	concurrency on the same event loop, namely waking it up "from the
		3447	outside".
		3448
		3449	If you want to know which design (one loop, locking, or multiple loops
		3450	without or something else still) is best for your problem, then I cannot
3188	help you but by giving some generic advice:	3451	help you, but here is some generic advice:
3189		3452
3190	=over 4	3453	=over 4
3191		3454
3192	=item * most applications have a main thread: use the default libev loop	3455	=item * most applications have a main thread: use the default libev loop
3193	in that thread, or create a separate thread running only the default loop.	3456	in that thread, or create a separate thread running only the default loop.
…		…
3205		3468
3206	Choosing a model is hard - look around, learn, know that usually you can do	3469	Choosing a model is hard - look around, learn, know that usually you can do
3207	better than you currently do :-)	3470	better than you currently do :-)
3208		3471
3209	=item * often you need to talk to some other thread which blocks in the	3472	=item * often you need to talk to some other thread which blocks in the
		3473	event loop.
		3474
3210	event loop - C<ev_async> watchers can be used to wake them up from other	3475	C<ev_async> watchers can be used to wake them up from other threads safely
3211	threads safely (or from signal contexts...).	3476	(or from signal contexts...).
		3477
		3478	An example use would be to communicate signals or other events that only
		3479	work in the default loop by registering the signal watcher with the
		3480	default loop and triggering an C<ev_async> watcher from the default loop
		3481	watcher callback into the event loop interested in the signal.
3212		3482
3213	=back	3483	=back
3214		3484
3215	=head2 COROUTINES	3485	=head3 COROUTINES
3216		3486
3217	Libev is much more accommodating to coroutines ("cooperative threads"):	3487	Libev is very accommodating to coroutines ("cooperative threads"):
3218	libev fully supports nesting calls to it's functions from different	3488	libev fully supports nesting calls to its functions from different
3219	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3220	different coroutines and switch freely between both coroutines running the	3490	different coroutines, and switch freely between both coroutines running the
3221	loop, as long as you don't confuse yourself). The only exception is that	3491	loop, as long as you don't confuse yourself). The only exception is that
3222	you must not do this from C<ev_periodic> reschedule callbacks.	3492	you must not do this from C<ev_periodic> reschedule callbacks.
3223		3493
3224	Care has been invested into making sure that libev does not keep local	3494	Care has been taken to ensure that libev does not keep local state inside
3225	state inside C<ev_loop>, and other calls do not usually allow coroutine	3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3226	switches.	3496	they do not clal any callbacks.
3227		3497
		3498	=head2 COMPILER WARNINGS
3228		3499
3229	=head1 COMPLEXITIES	3500	Depending on your compiler and compiler settings, you might get no or a
		3501	lot of warnings when compiling libev code. Some people are apparently
		3502	scared by this.
3230		3503
3231	In this section the complexities of (many of) the algorithms used inside	3504	However, these are unavoidable for many reasons. For one, each compiler
3232	libev will be explained. For complexity discussions about backends see the	3505	has different warnings, and each user has different tastes regarding
3233	documentation for C<ev_default_init>.	3506	warning options. "Warn-free" code therefore cannot be a goal except when
		3507	targeting a specific compiler and compiler-version.
3234		3508
3235	All of the following are about amortised time: If an array needs to be	3509	Another reason is that some compiler warnings require elaborate
3236	extended, libev needs to realloc and move the whole array, but this	3510	workarounds, or other changes to the code that make it less clear and less
3237	happens asymptotically never with higher number of elements, so O(1) might	3511	maintainable.
3238	mean it might do a lengthy realloc operation in rare cases, but on average
3239	it is much faster and asymptotically approaches constant time.
3240		3512
3241	=over 4	3513	And of course, some compiler warnings are just plain stupid, or simply
		3514	wrong (because they don't actually warn about the condition their message
		3515	seems to warn about). For example, certain older gcc versions had some
		3516	warnings that resulted an extreme number of false positives. These have
		3517	been fixed, but some people still insist on making code warn-free with
		3518	such buggy versions.
3242		3519
3243	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3520	While libev is written to generate as few warnings as possible,
		3521	"warn-free" code is not a goal, and it is recommended not to build libev
		3522	with any compiler warnings enabled unless you are prepared to cope with
		3523	them (e.g. by ignoring them). Remember that warnings are just that:
		3524	warnings, not errors, or proof of bugs.
3244		3525
3245	This means that, when you have a watcher that triggers in one hour and
3246	there are 100 watchers that would trigger before that then inserting will
3247	have to skip roughly seven (C<ld 100>) of these watchers.
3248		3526
3249	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3527	=head2 VALGRIND
3250		3528
3251	That means that changing a timer costs less than removing/adding them	3529	Valgrind has a special section here because it is a popular tool that is
3252	as only the relative motion in the event queue has to be paid for.	3530	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3253		3531
3254	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3532	If you think you found a bug (memory leak, uninitialised data access etc.)
		3533	in libev, then check twice: If valgrind reports something like:
3255		3534
3256	These just add the watcher into an array or at the head of a list.	3535	==2274== definitely lost: 0 bytes in 0 blocks.
		3536	==2274== possibly lost: 0 bytes in 0 blocks.
		3537	==2274== still reachable: 256 bytes in 1 blocks.
3257		3538
3258	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3539	Then there is no memory leak, just as memory accounted to global variables
		3540	is not a memleak - the memory is still being refernced, and didn't leak.
3259		3541
3260	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3542	Similarly, under some circumstances, valgrind might report kernel bugs
		3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3544	although an acceptable workaround has been found here), or it might be
		3545	confused.
3261		3546
3262	These watchers are stored in lists then need to be walked to find the	3547	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3263	correct watcher to remove. The lists are usually short (you don't usually	3548	make it into some kind of religion.
3264	have many watchers waiting for the same fd or signal).
3265		3549
3266	=item Finding the next timer in each loop iteration: O(1)	3550	If you are unsure about something, feel free to contact the mailing list
		3551	with the full valgrind report and an explanation on why you think this
		3552	is a bug in libev (best check the archives, too :). However, don't be
		3553	annoyed when you get a brisk "this is no bug" answer and take the chance
		3554	of learning how to interpret valgrind properly.
3267		3555
3268	By virtue of using a binary or 4-heap, the next timer is always found at a	3556	If you need, for some reason, empty reports from valgrind for your project
3269	fixed position in the storage array.	3557	I suggest using suppression lists.
3270		3558
3271	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3272		3559
3273	A change means an I/O watcher gets started or stopped, which requires	3560	=head1 PORTABILITY NOTES
3274	libev to recalculate its status (and possibly tell the kernel, depending
3275	on backend and whether C<ev_io_set> was used).
3276		3561
3277	=item Activating one watcher (putting it into the pending state): O(1)
3278
3279	=item Priority handling: O(number_of_priorities)
3280
3281	Priorities are implemented by allocating some space for each
3282	priority. When doing priority-based operations, libev usually has to
3283	linearly search all the priorities, but starting/stopping and activating
3284	watchers becomes O(1) w.r.t. priority handling.
3285
3286	=item Sending an ev_async: O(1)
3287
3288	=item Processing ev_async_send: O(number_of_async_watchers)
3289
3290	=item Processing signals: O(max_signal_number)
3291
3292	Sending involves a system call I<iff> there were no other C<ev_async_send>
3293	calls in the current loop iteration. Checking for async and signal events
3294	involves iterating over all running async watchers or all signal numbers.
3295
3296	=back
3297
3298
3299	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3300		3563
3301	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3302	requires, and its I/O model is fundamentally incompatible with the POSIX	3565	requires, and its I/O model is fundamentally incompatible with the POSIX
3303	model. Libev still offers limited functionality on this platform in	3566	model. Libev still offers limited functionality on this platform in
3304	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3315		3578
3316	Not a libev limitation but worth mentioning: windows apparently doesn't	3579	Not a libev limitation but worth mentioning: windows apparently doesn't
3317	accept large writes: instead of resulting in a partial write, windows will	3580	accept large writes: instead of resulting in a partial write, windows will
3318	either accept everything or return C<ENOBUFS> if the buffer is too large,	3581	either accept everything or return C<ENOBUFS> if the buffer is too large,
3319	so make sure you only write small amounts into your sockets (less than a	3582	so make sure you only write small amounts into your sockets (less than a
3320	megabyte seems safe, but thsi apparently depends on the amount of memory	3583	megabyte seems safe, but this apparently depends on the amount of memory
3321	available).	3584	available).
3322		3585
3323	Due to the many, low, and arbitrary limits on the win32 platform and	3586	Due to the many, low, and arbitrary limits on the win32 platform and
3324	the abysmal performance of winsockets, using a large number of sockets	3587	the abysmal performance of winsockets, using a large number of sockets
3325	is not recommended (and not reasonable). If your program needs to use	3588	is not recommended (and not reasonable). If your program needs to use
3326	more than a hundred or so sockets, then likely it needs to use a totally	3589	more than a hundred or so sockets, then likely it needs to use a totally
3327	different implementation for windows, as libev offers the POSIX readiness	3590	different implementation for windows, as libev offers the POSIX readiness
3328	notification model, which cannot be implemented efficiently on windows	3591	notification model, which cannot be implemented efficiently on windows
3329	(Microsoft monopoly games).	3592	(Microsoft monopoly games).
3330		3593
		3594	A typical way to use libev under windows is to embed it (see the embedding
		3595	section for details) and use the following F<evwrap.h> header file instead
		3596	of F<ev.h>:
		3597
		3598	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3599	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3600
		3601	#include "ev.h"
		3602
		3603	And compile the following F<evwrap.c> file into your project (make sure
		3604	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3605
		3606	#include "evwrap.h"
		3607	#include "ev.c"
		3608
3331	=over 4	3609	=over 4
3332		3610
3333	=item The winsocket select function	3611	=item The winsocket select function
3334		3612
3335	The winsocket C<select> function doesn't follow POSIX in that it	3613	The winsocket C<select> function doesn't follow POSIX in that it
3336	requires socket I<handles> and not socket I<file descriptors> (it is	3614	requires socket I<handles> and not socket I<file descriptors> (it is
3337	also extremely buggy). This makes select very inefficient, and also	3615	also extremely buggy). This makes select very inefficient, and also
3338	requires a mapping from file descriptors to socket handles. See the	3616	requires a mapping from file descriptors to socket handles (the Microsoft
		3617	C runtime provides the function C<_open_osfhandle> for this). See the
3339	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	3618	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3340	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	3619	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3341		3620
3342	The configuration for a "naked" win32 using the Microsoft runtime	3621	The configuration for a "naked" win32 using the Microsoft runtime
3343	libraries and raw winsocket select is:	3622	libraries and raw winsocket select is:
…		…
3375	wrap all I/O functions and provide your own fd management, but the cost of	3654	wrap all I/O functions and provide your own fd management, but the cost of
3376	calling select (O(n²)) will likely make this unworkable.	3655	calling select (O(n²)) will likely make this unworkable.
3377		3656
3378	=back	3657	=back
3379		3658
3380
3381	=head1 PORTABILITY REQUIREMENTS	3659	=head2 PORTABILITY REQUIREMENTS
3382		3660
3383	In addition to a working ISO-C implementation, libev relies on a few	3661	In addition to a working ISO-C implementation and of course the
3384	additional extensions:	3662	backend-specific APIs, libev relies on a few additional extensions:
3385		3663
3386	=over 4	3664	=over 4
3387		3665
3388	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3666	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3389	calling conventions regardless of C<ev_watcher_type *>.	3667	calling conventions regardless of C<ev_watcher_type *>.
…		…
3395	calls them using an C<ev_watcher *> internally.	3673	calls them using an C<ev_watcher *> internally.
3396		3674
3397	=item C<sig_atomic_t volatile> must be thread-atomic as well	3675	=item C<sig_atomic_t volatile> must be thread-atomic as well
3398		3676
3399	The type C<sig_atomic_t volatile> (or whatever is defined as	3677	The type C<sig_atomic_t volatile> (or whatever is defined as
3400	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3401	threads. This is not part of the specification for C<sig_atomic_t>, but is	3679	threads. This is not part of the specification for C<sig_atomic_t>, but is
3402	believed to be sufficiently portable.	3680	believed to be sufficiently portable.
3403		3681
3404	=item C<sigprocmask> must work in a threaded environment	3682	=item C<sigprocmask> must work in a threaded environment
3405		3683
…		…
3414	except the initial one, and run the default loop in the initial thread as	3692	except the initial one, and run the default loop in the initial thread as
3415	well.	3693	well.
3416		3694
3417	=item C<long> must be large enough for common memory allocation sizes	3695	=item C<long> must be large enough for common memory allocation sizes
3418		3696
3419	To improve portability and simplify using libev, libev uses C<long>	3697	To improve portability and simplify its API, libev uses C<long> internally
3420	internally instead of C<size_t> when allocating its data structures. On	3698	instead of C<size_t> when allocating its data structures. On non-POSIX
3421	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3699	systems (Microsoft...) this might be unexpectedly low, but is still at
3422	is still at least 31 bits everywhere, which is enough for hundreds of	3700	least 31 bits everywhere, which is enough for hundreds of millions of
3423	millions of watchers.	3701	watchers.
3424		3702
3425	=item C<double> must hold a time value in seconds with enough accuracy	3703	=item C<double> must hold a time value in seconds with enough accuracy
3426		3704
3427	The type C<double> is used to represent timestamps. It is required to	3705	The type C<double> is used to represent timestamps. It is required to
3428	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3432	=back	3710	=back
3433		3711
3434	If you know of other additional requirements drop me a note.	3712	If you know of other additional requirements drop me a note.
3435		3713
3436		3714
3437	=head1 COMPILER WARNINGS	3715	=head1 ALGORITHMIC COMPLEXITIES
3438		3716
3439	Depending on your compiler and compiler settings, you might get no or a	3717	In this section the complexities of (many of) the algorithms used inside
3440	lot of warnings when compiling libev code. Some people are apparently	3718	libev will be documented. For complexity discussions about backends see
3441	scared by this.	3719	the documentation for C<ev_default_init>.
3442		3720
3443	However, these are unavoidable for many reasons. For one, each compiler	3721	All of the following are about amortised time: If an array needs to be
3444	has different warnings, and each user has different tastes regarding	3722	extended, libev needs to realloc and move the whole array, but this
3445	warning options. "Warn-free" code therefore cannot be a goal except when	3723	happens asymptotically rarer with higher number of elements, so O(1) might
3446	targeting a specific compiler and compiler-version.	3724	mean that libev does a lengthy realloc operation in rare cases, but on
		3725	average it is much faster and asymptotically approaches constant time.
3447		3726
3448	Another reason is that some compiler warnings require elaborate	3727	=over 4
3449	workarounds, or other changes to the code that make it less clear and less
3450	maintainable.
3451		3728
3452	And of course, some compiler warnings are just plain stupid, or simply	3729	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3453	wrong (because they don't actually warn about the condition their message
3454	seems to warn about).
3455		3730
3456	While libev is written to generate as few warnings as possible,	3731	This means that, when you have a watcher that triggers in one hour and
3457	"warn-free" code is not a goal, and it is recommended not to build libev	3732	there are 100 watchers that would trigger before that, then inserting will
3458	with any compiler warnings enabled unless you are prepared to cope with	3733	have to skip roughly seven (C<ld 100>) of these watchers.
3459	them (e.g. by ignoring them). Remember that warnings are just that:
3460	warnings, not errors, or proof of bugs.
3461		3734
		3735	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3462		3736
3463	=head1 VALGRIND	3737	That means that changing a timer costs less than removing/adding them,
		3738	as only the relative motion in the event queue has to be paid for.
3464		3739
3465	Valgrind has a special section here because it is a popular tool that is	3740	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3466	highly useful, but valgrind reports are very hard to interpret.
3467		3741
3468	If you think you found a bug (memory leak, uninitialised data access etc.)	3742	These just add the watcher into an array or at the head of a list.
3469	in libev, then check twice: If valgrind reports something like:
3470		3743
3471	==2274== definitely lost: 0 bytes in 0 blocks.	3744	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3472	==2274== possibly lost: 0 bytes in 0 blocks.
3473	==2274== still reachable: 256 bytes in 1 blocks.
3474		3745
3475	Then there is no memory leak. Similarly, under some circumstances,	3746	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3476	valgrind might report kernel bugs as if it were a bug in libev, or it
3477	might be confused (it is a very good tool, but only a tool).
3478		3747
3479	If you are unsure about something, feel free to contact the mailing list	3748	These watchers are stored in lists, so they need to be walked to find the
3480	with the full valgrind report and an explanation on why you think this is	3749	correct watcher to remove. The lists are usually short (you don't usually
3481	a bug in libev. However, don't be annoyed when you get a brisk "this is	3750	have many watchers waiting for the same fd or signal: one is typical, two
3482	no bug" answer and take the chance of learning how to interpret valgrind	3751	is rare).
3483	properly.
3484		3752
3485	If you need, for some reason, empty reports from valgrind for your project	3753	=item Finding the next timer in each loop iteration: O(1)
3486	I suggest using suppression lists.	3754
		3755	By virtue of using a binary or 4-heap, the next timer is always found at a
		3756	fixed position in the storage array.
		3757
		3758	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3759
		3760	A change means an I/O watcher gets started or stopped, which requires
		3761	libev to recalculate its status (and possibly tell the kernel, depending
		3762	on backend and whether C<ev_io_set> was used).
		3763
		3764	=item Activating one watcher (putting it into the pending state): O(1)
		3765
		3766	=item Priority handling: O(number_of_priorities)
		3767
		3768	Priorities are implemented by allocating some space for each
		3769	priority. When doing priority-based operations, libev usually has to
		3770	linearly search all the priorities, but starting/stopping and activating
		3771	watchers becomes O(1) with respect to priority handling.
		3772
		3773	=item Sending an ev_async: O(1)
		3774
		3775	=item Processing ev_async_send: O(number_of_async_watchers)
		3776
		3777	=item Processing signals: O(max_signal_number)
		3778
		3779	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3780	calls in the current loop iteration. Checking for async and signal events
		3781	involves iterating over all running async watchers or all signal numbers.
		3782
		3783	=back
3487		3784
3488		3785
3489	=head1 AUTHOR	3786	=head1 AUTHOR
3490		3787
3491	Marc Lehmann <libev@schmorp.de>.	3788	Marc Lehmann <libev@schmorp.de>.

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