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Comparing libev/ev.pod (file contents):
Revision 1.175 by root, Mon Sep 8 16:36:14 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.
…		…
617	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	662	- Queue all expired timers.
623	- Queue all outstanding periodics.	663	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	665	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
627	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
…		…
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		687
648	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
649		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
650	=item ev_ref (loop)	692	=item ev_ref (loop)
651		693
652	=item ev_unref (loop)	694	=item ev_unref (loop)
653		695
654	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
655	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
656	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
657	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
658	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
659	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
660	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
661	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
662	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
663	libraries. Just remember to I<unref after start> and I<ref before stop>	708	libraries. Just remember to I<unref after start> and I<ref before stop>
664	(but only if the watcher wasn't active before, or was active before,	709	(but only if the watcher wasn't active before, or was active before,
665	respectively).	710	respectively).
666		711
667	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>
668	running when nothing else is active.	713	running when nothing else is active.
669		714
670	struct ev_signal exitsig;	715	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	718	evf_unref (loop);
674		719
675	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	735	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	736	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	737	opportunities).
693		738
694	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
695	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
696	the program responsive, it also wastes a lot of CPU time to poll for new	741	program responsive, it also wastes a lot of CPU time to poll for new
697	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
699		744
700	By setting a higher I<io collect interval> you allow libev to spend more	745	By setting a higher I<io collect interval> you allow libev to spend more
701	time collecting I/O events, so you can handle more events per iteration,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	C<ev_timer>) will be not affected. Setting this to a non-null value will
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
705		750
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	755	value will not introduce any overhead in libev.
711		756
712	Many (busy) programs can usually benefit by setting the I/O collect	757	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	758	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	760	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
723	they fire on, say, one-second boundaries only.	768	they fire on, say, one-second boundaries only.
724		769
725	=item ev_loop_verify (loop)	770	=item ev_loop_verify (loop)
726		771
727	This function only does something when C<EV_VERIFY> support has been	772	This function only does something when C<EV_VERIFY> support has been
728	compiled in. It tries to go through all internal structures and checks	773	compiled in. which is the default for non-minimal builds. It tries to go
729	them for validity. If anything is found to be inconsistent, it will print	774	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
731		777
732	This can be used to catch bugs inside libev itself: under normal	778	This can be used to catch bugs inside libev itself: under normal
733	circumstances, this function will never abort as of course libev keeps its	779	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	780	data structures consistent.
735		781
…		…
740		786
741	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
742	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
743	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:
744		790
745	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)
746	{	792	{
747	ev_io_stop (w);	793	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
749	}	795	}
750		796
751	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
752	struct ev_io stdin_watcher;	798	ev_io stdin_watcher;
753	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
756	ev_loop (loop, 0);	802	ev_loop (loop, 0);
757		803
…		…
848	=item C<EV_ERROR>	894	=item C<EV_ERROR>
849		895
850	An unspecified error has occurred, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
853	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
855		905
856	Libev will usually signal a few "dummy" events together with an error,	906	Libev will usually signal a few "dummy" events together with an error, for
857	for example it might indicate that a fd is readable or writable, and if	907	example it might indicate that a fd is readable or writable, and if your
858	your callbacks is well-written it can just attempt the operation and cope	908	callbacks is well-written it can just attempt the operation and cope with
859	with the error from read() or write(). This will not work in multi-threaded	909	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
861		912
862	=back	913	=back
863		914
864	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
865		916
…		…
878	which rolls both calls into one.	929	which rolls both calls into one.
879		930
880	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
881	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
882		933
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	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);
885		942
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		944
888	This macro initialises the type-specific parts of a watcher. You need to	945	This macro initialises the type-specific parts of a watcher. You need to
889	call C<ev_init> at least once before you call this macro, but you can	946	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
893		950
894	Although some watcher types do not have type-specific arguments	951	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		953
		954	See C<ev_init>, above, for an example.
		955
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		957
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
900	calls into a single call. This is the most convenient method to initialise	959	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
902		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		965
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		967
905	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
907		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		977
910	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
911	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		986
917	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
918		988
919	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
920	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
968		1038
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1040
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
974		1045
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1047
977	If the watcher is pending, this function returns clears its pending status	1048	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1049	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1050	watcher isn't pending it does nothing and returns C<0>.
980		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
981	=back	1055	=back
982		1056
983		1057
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1059
986	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
991	data:	1065	data:
992		1066
993	struct my_io	1067	struct my_io
994	{	1068	{
995	struct ev_io io;	1069	ev_io io;
996	int otherfd;	1070	int otherfd;
997	void *somedata;	1071	void *somedata;
998	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
999	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1078
1001	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1080	can cast it back to your own type:
1003		1081
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1083	{
1006	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
1007	...	1085	...
1008	}	1086	}
1009		1087
1010	More interesting and less C-conformant ways of casting your callback type	1088	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1089	instead have been omitted.
1012		1090
1013	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
1014	watchers:	1092	embedded watchers:
1015		1093
1016	struct my_biggy	1094	struct my_biggy
1017	{	1095	{
1018	int some_data;	1096	int some_data;
1019	ev_timer t1;	1097	ev_timer t1;
1020	ev_timer t2;	1098	ev_timer t2;
1021	}	1099	}
1022		1100
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1101	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
1025		1106
1026	#include <stddef.h>	1107	#include <stddef.h>
1027		1108
1028	static void	1109	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1111	{
1031	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1114	}
1034		1115
1035	static void	1116	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1118	{
1038	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1121	}
1041		1122
…		…
1069	In general you can register as many read and/or write event watchers per	1150	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1151	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1152	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1153	required if you know what you are doing).
1073		1154
1074	If you must do this, then force the use of a known-to-be-good backend	1155	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1156	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1077		1158
1078	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1167
1087	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1169	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
1092		1177
1093	=head3 The special problem of disappearing file descriptors	1178	=head3 The special problem of disappearing file descriptors
1094		1179
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1181	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1182	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1183	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1184	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1185	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1186	fact, a different file descriptor.
1102		1187
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1219	C<EVBACKEND_POLL>.
1135		1220
1136	=head3 The special problem of SIGPIPE	1221	=head3 The special problem of SIGPIPE
1137		1222
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when writing to a pipe whose other end has been closed, your program gets	1224	when writing to a pipe whose other end has been closed, your program gets
1140	send a SIGPIPE, which, by default, aborts your program. For most programs	1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	this is sensible behaviour, for daemons, this is usually undesirable.	1226	this is sensible behaviour, for daemons, this is usually undesirable.
1142		1227
1143	So when you encounter spurious, unexplained daemon exits, make sure you	1228	So when you encounter spurious, unexplained daemon exits, make sure you
1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1145	somewhere, as that would have given you a big clue).	1230	somewhere, as that would have given you a big clue).
…		…
1152	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
1153		1238
1154	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
1155		1240
1156	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
1157	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
1158	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.
1159		1244
1160	=item int fd [read-only]	1245	=item int fd [read-only]
1161		1246
1162	The file descriptor being watched.	1247	The file descriptor being watched.
1163		1248
…		…
1172	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
1173	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
1174	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
1175		1260
1176	static void	1261	static void
1177	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)
1178	{	1263	{
1179	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
1180	.. 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
1181	}	1266	}
1182		1267
1183	...	1268	...
1184	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
1185	struct ev_io stdin_readable;	1270	ev_io stdin_readable;
1186	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);
1187	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
1188	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
1189		1274
1190		1275
…		…
1193	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
1194	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
1195		1280
1196	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
1197	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
1198	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
1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1200	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
1201		1286
1202	The callback is guaranteed to be invoked only after its timeout has passed,	1287	The callback is guaranteed to be invoked only I<after> its timeout has
1203	but if multiple timers become ready during the same loop iteration then	1288	passed, but if multiple timers become ready during the same loop iteration
1204	order of execution is undefined.	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
1205		1418
1206	=head3 The special problem of time updates	1419	=head3 The special problem of time updates
1207		1420
1208	Requesting the current time is a costly operation (it usually takes at	1421	Establishing the current time is a costly operation (it usually takes at
1209	least two syscalls): EV therefore updates it's idea of the current time	1422	least two system calls): EV therefore updates its idea of the current
1210	only before and after C<ev_loop> polls for new events, which causes the	1423	time only before and after C<ev_loop> collects new events, which causes a
1211	difference between C<ev_now ()> and C<ev_time ()>.	1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1425	lots of events in one iteration.
1212		1426
1213	The relative timeouts are calculated relative to the C<ev_now ()>	1427	The relative timeouts are calculated relative to the C<ev_now ()>
1214	time. This is usually the right thing as this timestamp refers to the time	1428	time. This is usually the right thing as this timestamp refers to the time
1215	of the event triggering whatever timeout you are modifying/starting. If	1429	of the event triggering whatever timeout you are modifying/starting. If
1216	you suspect event processing to be delayed and you I<need> to base the	1430	you suspect event processing to be delayed and you I<need> to base the
1217	timeout on the current time, use something like this to adjust for this:	1431	timeout on the current time, use something like this to adjust for this:
1218		1432
1219	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1433	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1220		1434
		1435	If the event loop is suspended for a long time, you can also force an
		1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update
		1437	()>.
		1438
1221	=head3 Watcher-Specific Functions and Data Members	1439	=head3 Watcher-Specific Functions and Data Members
1222		1440
1223	=over 4	1441	=over 4
1224		1442
1225	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1248	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).
1249		1467
1250	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
1251	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.
1252		1470
1253	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
1254	example: Imagine you have a TCP connection and you want a so-called idle	1472	usage example.
1255	timeout, that is, you want to be called when there have been, say, 60
1256	seconds of inactivity on the socket. The easiest way to do this is to
1257	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1258	C<ev_timer_again> each time you successfully read or write some data. If
1259	you go into an idle state where you do not expect data to travel on the
1260	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1261	automatically restart it if need be.
1262
1263	That means you can ignore the C<after> value and C<ev_timer_start>
1264	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1265
1266	ev_timer_init (timer, callback, 0., 5.);
1267	ev_timer_again (loop, timer);
1268	...
1269	timer->again = 17.;
1270	ev_timer_again (loop, timer);
1271	...
1272	timer->again = 10.;
1273	ev_timer_again (loop, timer);
1274
1275	This is more slightly efficient then stopping/starting the timer each time
1276	you want to modify its timeout value.
1277		1473
1278	=item ev_tstamp repeat [read-write]	1474	=item ev_tstamp repeat [read-write]
1279		1475
1280	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
1281	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),
1282	which is also when any modifications are taken into account.	1478	which is also when any modifications are taken into account.
1283		1479
1284	=back	1480	=back
1285		1481
1286	=head3 Examples	1482	=head3 Examples
1287		1483
1288	Example: Create a timer that fires after 60 seconds.	1484	Example: Create a timer that fires after 60 seconds.
1289		1485
1290	static void	1486	static void
1291	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)
1292	{	1488	{
1293	.. one minute over, w is actually stopped right here	1489	.. one minute over, w is actually stopped right here
1294	}	1490	}
1295		1491
1296	struct ev_timer mytimer;	1492	ev_timer mytimer;
1297	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1493	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1298	ev_timer_start (loop, &mytimer);	1494	ev_timer_start (loop, &mytimer);
1299		1495
1300	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
1301	inactivity.	1497	inactivity.
1302		1498
1303	static void	1499	static void
1304	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1500	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1305	{	1501	{
1306	.. ten seconds without any activity	1502	.. ten seconds without any activity
1307	}	1503	}
1308		1504
1309	struct ev_timer mytimer;	1505	ev_timer mytimer;
1310	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 */
1311	ev_timer_again (&mytimer); /* start timer */	1507	ev_timer_again (&mytimer); /* start timer */
1312	ev_loop (loop, 0);	1508	ev_loop (loop, 0);
1313		1509
1314	// 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":
…		…
1330	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
1331	roughly 10 seconds later as it uses a relative timeout).	1527	roughly 10 seconds later as it uses a relative timeout).
1332		1528
1333	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,
1334	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
1335	complicated, rules.	1531	complicated rules.
1336		1532
1337	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
1338	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
1339	during the same loop iteration then order of execution is undefined.	1535	during the same loop iteration, then order of execution is undefined.
1340		1536
1341	=head3 Watcher-Specific Functions and Data Members	1537	=head3 Watcher-Specific Functions and Data Members
1342		1538
1343	=over 4	1539	=over 4
1344		1540
1345	=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)
1346		1542
1347	=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)
1348		1544
1349	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
1350	operation, and we will explain them from simplest to complex:	1546	operation, and we will explain them from simplest to most complex:
1351		1547
1352	=over 4	1548	=over 4
1353		1549
1354	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1355		1551
1356	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
1357	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
1358	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
1359	run when the system time reaches or surpasses this time.	1555	only run when the system clock reaches or surpasses this time.
1360		1556
1361	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1362		1558
1363	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
1364	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)
1365	and then repeat, regardless of any time jumps.	1561	and then repeat, regardless of any time jumps.
1366		1562
1367	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
1368	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
1369	the hour:	1565	hour, on the hour:
1370		1566
1371	ev_periodic_set (&periodic, 0., 3600., 0);	1567	ev_periodic_set (&periodic, 0., 3600., 0);
1372		1568
1373	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,
1374	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
…		…
1400		1596
1401	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
1402	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
1403	only event loop modification you are allowed to do).	1599	only event loop modification you are allowed to do).
1404		1600
1405	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1601	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1406	*w, ev_tstamp now)>, e.g.:	1602	*w, ev_tstamp now)>, e.g.:
1407		1603
		1604	static ev_tstamp
1408	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1605	my_rescheduler (ev_periodic *w, ev_tstamp now)
1409	{	1606	{
1410	return now + 60.;	1607	return now + 60.;
1411	}	1608	}
1412		1609
1413	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
…		…
1450		1647
1451	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
1452	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
1453	called.	1650	called.
1454		1651
1455	=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]
1456		1653
1457	The current reschedule callback, or C<0>, if this functionality is	1654	The current reschedule callback, or C<0>, if this functionality is
1458	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
1459	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.
1460		1657
1461	=back	1658	=back
1462		1659
1463	=head3 Examples	1660	=head3 Examples
1464		1661
1465	Example: Call a callback every hour, or, more precisely, whenever the	1662	Example: Call a callback every hour, or, more precisely, whenever the
1466	system clock is divisible by 3600. The callback invocation times have	1663	system time is divisible by 3600. The callback invocation times have
1467	potentially a lot of jitter, but good long-term stability.	1664	potentially a lot of jitter, but good long-term stability.
1468		1665
1469	static void	1666	static void
1470	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1471	{	1668	{
1472	... 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)
1473	}	1670	}
1474		1671
1475	struct ev_periodic hourly_tick;	1672	ev_periodic hourly_tick;
1476	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1673	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1477	ev_periodic_start (loop, &hourly_tick);	1674	ev_periodic_start (loop, &hourly_tick);
1478		1675
1479	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:
1480		1677
1481	#include <math.h>	1678	#include <math.h>
1482		1679
1483	static ev_tstamp	1680	static ev_tstamp
1484	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1681	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1485	{	1682	{
1486	return fmod (now, 3600.) + 3600.;	1683	return now + (3600. - fmod (now, 3600.));
1487	}	1684	}
1488		1685
1489	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);
1490		1687
1491	Example: Call a callback every hour, starting now:	1688	Example: Call a callback every hour, starting now:
1492		1689
1493	struct ev_periodic hourly_tick;	1690	ev_periodic hourly_tick;
1494	ev_periodic_init (&hourly_tick, clock_cb,	1691	ev_periodic_init (&hourly_tick, clock_cb,
1495	fmod (ev_now (loop), 3600.), 3600., 0);	1692	fmod (ev_now (loop), 3600.), 3600., 0);
1496	ev_periodic_start (loop, &hourly_tick);	1693	ev_periodic_start (loop, &hourly_tick);
1497		1694
1498		1695
…		…
1501	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
1502	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
1503	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
1504	normal event processing, like any other event.	1701	normal event processing, like any other event.
1505		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
1506	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
1507	first watcher gets started will libev actually register a signal watcher	1708	first watcher gets started will libev actually register a signal handler
1508	with the kernel (thus it coexists with your own signal handlers as long	1709	with the kernel (thus it coexists with your own signal handlers as long as
1509	as you don't register any with libev). Similarly, when the last signal	1710	you don't register any with libev for the same signal). Similarly, when
1510	watcher for a signal is stopped libev will reset the signal handler to	1711	the last signal watcher for a signal is stopped, libev will reset the
1511	SIG_DFL (regardless of what it was set to before).	1712	signal handler to SIG_DFL (regardless of what it was set to before).
1512		1713
1513	If possible and supported, libev will install its handlers with	1714	If possible and supported, libev will install its handlers with
1514	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
1515	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
1516	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
…		…
1533		1734
1534	=back	1735	=back
1535		1736
1536	=head3 Examples	1737	=head3 Examples
1537		1738
1538	Example: Try to exit cleanly on SIGINT and SIGTERM.	1739	Example: Try to exit cleanly on SIGINT.
1539		1740
1540	static void	1741	static void
1541	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1542	{	1743	{
1543	ev_unloop (loop, EVUNLOOP_ALL);	1744	ev_unloop (loop, EVUNLOOP_ALL);
1544	}	1745	}
1545		1746
1546	struct ev_signal signal_watcher;	1747	ev_signal signal_watcher;
1547	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1548	ev_signal_start (loop, &sigint_cb);	1749	ev_signal_start (loop, &signal_watcher);
1549		1750
1550		1751
1551	=head2 C<ev_child> - watch out for process status changes	1752	=head2 C<ev_child> - watch out for process status changes
1552		1753
1553	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
1554	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
1555	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
1556	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
1557	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.
1558		1762
1559	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
1560	you can only register child watchers in the default event loop.	1764	you can only register child watchers in the default event loop.
1561		1765
1562	=head3 Process Interaction	1766	=head3 Process Interaction
…		…
1623	its completion.	1827	its completion.
1624		1828
1625	ev_child cw;	1829	ev_child cw;
1626		1830
1627	static void	1831	static void
1628	child_cb (EV_P_ struct ev_child *w, int revents)	1832	child_cb (EV_P_ ev_child *w, int revents)
1629	{	1833	{
1630	ev_child_stop (EV_A_ w);	1834	ev_child_stop (EV_A_ w);
1631	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);
1632	}	1836	}
1633		1837
…		…
1660	the stat buffer having unspecified contents.	1864	the stat buffer having unspecified contents.
1661		1865
1662	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
1663	relative and your working directory changes, the behaviour is undefined.	1867	relative and your working directory changes, the behaviour is undefined.
1664		1868
1665	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
1666	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
1667	can specify a recommended polling interval for this case. If you specify	1871	it changed somehow. You can specify a recommended polling interval for
1668	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!)
1669	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
1670	five seconds, although this might change dynamically). Libev will also	1874	you can expect to be around five seconds, although this might change
1671	impose a minimum interval which is currently around C<0.1>, but thats	1875	dynamically). Libev will also impose a minimum interval which is currently
1672	usually overkill.	1876	around C<0.1>, but thats usually overkill.
1673		1877
1674	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,
1675	as even with OS-supported change notifications, this can be	1879	as even with OS-supported change notifications, this can be
1676	resource-intensive.	1880	resource-intensive.
1677		1881
1678	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
1679	implemented (implementing kqueue support is left as an exercise for the	1883	is the Linux inotify interface (implementing kqueue support is left as
1680	reader, note, however, that the author sees no way of implementing ev_stat	1884	an exercise for the reader. Note, however, that the author sees no way
1681	semantics with kqueue). Inotify will be used to give hints only and should	1885	of implementing C<ev_stat> semantics with kqueue).
1682	not change the semantics of C<ev_stat> watchers, which means that libev
1683	sometimes needs to fall back to regular polling again even with inotify,
1684	but changes are usually detected immediately, and if the file exists there
1685	will be no polling.
1686		1886
1687	=head3 ABI Issues (Largefile Support)	1887	=head3 ABI Issues (Largefile Support)
1688		1888
1689	Libev by default (unless the user overrides this) uses the default	1889	Libev by default (unless the user overrides this) uses the default
1690	compilation environment, which means that on systems with large file	1890	compilation environment, which means that on systems with large file
…		…
1699	file interfaces available by default (as e.g. FreeBSD does) and not	1899	file interfaces available by default (as e.g. FreeBSD does) and not
1700	optional. Libev cannot simply switch on large file support because it has	1900	optional. Libev cannot simply switch on large file support because it has
1701	to exchange stat structures with application programs compiled using the	1901	to exchange stat structures with application programs compiled using the
1702	default compilation environment.	1902	default compilation environment.
1703		1903
1704	=head3 Inotify	1904	=head3 Inotify and Kqueue
1705		1905
1706	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
1707	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
1708	change detection where possible. The inotify descriptor will be created lazily	1909	change detection where possible. The inotify descriptor will be created
1709	when the first C<ev_stat> watcher is being started.	1910	lazily when the first C<ev_stat> watcher is being started.
1710		1911
1711	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
1712	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
1713	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
1714	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.
1715		1917
1716	(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
1717	implement this functionality, due to the requirement of having a file	1919	implement this functionality, due to the requirement of having a file
1718	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.
1719		1922
1720	=head3 The special problem of stat time resolution	1923	=head3 The special problem of stat time resolution
1721		1924
1722	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
1723	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
1724	only support whole seconds.	1927	only support whole seconds.
1725		1928
1726	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
1727	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
1728	calls your callback, which does something. When there is another update	1931	calls your callback, which does something. When there is another update
1729	within the same second, C<ev_stat> will be unable to detect it as the stat	1932	within the same second, C<ev_stat> will be unable to detect unless the
1730	data does not change.	1933	stat data does change in other ways (e.g. file size).
1731		1934
1732	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
1733	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
1734	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);
1735	ev_timer_again (loop, w)>).	1938	ev_timer_again (loop, w)>).
…		…
1755	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
1756	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
1757	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
1758	path for as long as the watcher is active.	1961	path for as long as the watcher is active.
1759		1962
1760	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,
1761	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
1762	was detected).	1965	last change was detected).
1763		1966
1764	=item ev_stat_stat (loop, ev_stat *)	1967	=item ev_stat_stat (loop, ev_stat *)
1765		1968
1766	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
1767	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
…		…
1850		2053
1851		2054
1852	=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...
1853		2056
1854	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
1855	priority are pending (prepare, check and other idle watchers do not	2058	priority are pending (prepare, check and other idle watchers do not count
1856	count).	2059	as receiving "events").
1857		2060
1858	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
1859	(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
1860	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
1861	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
…		…
1886		2089
1887	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
1888	callback, free it. Also, use no error checking, as usual.	2091	callback, free it. Also, use no error checking, as usual.
1889		2092
1890	static void	2093	static void
1891	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2094	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1892	{	2095	{
1893	free (w);	2096	free (w);
1894	// now do something you wanted to do when the program has	2097	// now do something you wanted to do when the program has
1895	// no longer anything immediate to do.	2098	// no longer anything immediate to do.
1896	}	2099	}
1897		2100
1898	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1899	ev_idle_init (idle_watcher, idle_cb);	2102	ev_idle_init (idle_watcher, idle_cb);
1900	ev_idle_start (loop, idle_cb);	2103	ev_idle_start (loop, idle_cb);
1901		2104
1902		2105
1903	=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!
1904		2107
1905	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:
1906	prepare watchers get invoked before the process blocks and check watchers	2109	prepare watchers get invoked before the process blocks and check watchers
1907	afterwards.	2110	afterwards.
1908		2111
1909	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
1910	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>
…		…
1913	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,
1914	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
1915	called in pairs bracketing the blocking call.	2118	called in pairs bracketing the blocking call.
1916		2119
1917	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
1918	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
1919	variable changes, implement your own watchers, integrate net-snmp or a	2122	variable changes, implement your own watchers, integrate net-snmp or a
1920	coroutine library and lots more. They are also occasionally useful if	2123	coroutine library and lots more. They are also occasionally useful if
1921	you cache some data and want to flush it before blocking (for example,	2124	you cache some data and want to flush it before blocking (for example,
1922	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2125	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1923	watcher).	2126	watcher).
1924		2127
1925	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
1926	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
1927	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
1928	provide just this functionality). Then, in the check watcher you check for	2131	libraries provide exactly this functionality). Then, in the check watcher,
1929	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
1930	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
1931	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
1932	because you never know, you know?).	2135	nevertheless, because you never know, you know?).
1933		2136
1934	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
1935	coroutines into libev programs, by yielding to other active coroutines	2138	coroutines into libev programs, by yielding to other active coroutines
1936	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
1937	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
…		…
1940	loop from blocking if lower-priority coroutines are active, thus mapping	2143	loop from blocking if lower-priority coroutines are active, thus mapping
1941	low-priority coroutines to idle/background tasks).	2144	low-priority coroutines to idle/background tasks).
1942		2145
1943	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>)
1944	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
1945	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
1946	too) should not activate ("feed") events into libev. While libev fully	2151	activate ("feed") events into libev. While libev fully supports this, they
1947	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
1948	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
1949	(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
1950	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
1951	coexist peacefully with others).	2156	others).
1952		2157
1953	=head3 Watcher-Specific Functions and Data Members	2158	=head3 Watcher-Specific Functions and Data Members
1954		2159
1955	=over 4	2160	=over 4
1956		2161
…		…
1958		2163
1959	=item ev_check_init (ev_check *, callback)	2164	=item ev_check_init (ev_check *, callback)
1960		2165
1961	Initialises and configures the prepare or check watcher - they have no	2166	Initialises and configures the prepare or check watcher - they have no
1962	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2167	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1963	macros, but using them is utterly, utterly and completely pointless.	2168	macros, but using them is utterly, utterly, utterly and completely
		2169	pointless.
1964		2170
1965	=back	2171	=back
1966		2172
1967	=head3 Examples	2173	=head3 Examples
1968		2174
…		…
1981		2187
1982	static ev_io iow [nfd];	2188	static ev_io iow [nfd];
1983	static ev_timer tw;	2189	static ev_timer tw;
1984		2190
1985	static void	2191	static void
1986	io_cb (ev_loop *loop, ev_io *w, int revents)	2192	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1987	{	2193	{
1988	}	2194	}
1989		2195
1990	// create io watchers for each fd and a timer before blocking	2196	// create io watchers for each fd and a timer before blocking
1991	static void	2197	static void
1992	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2198	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1993	{	2199	{
1994	int timeout = 3600000;	2200	int timeout = 3600000;
1995	struct pollfd fds [nfd];	2201	struct pollfd fds [nfd];
1996	// actual code will need to loop here and realloc etc.	2202	// actual code will need to loop here and realloc etc.
1997	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2012	}	2218	}
2013	}	2219	}
2014		2220
2015	// stop all watchers after blocking	2221	// stop all watchers after blocking
2016	static void	2222	static void
2017	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2223	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2018	{	2224	{
2019	ev_timer_stop (loop, &tw);	2225	ev_timer_stop (loop, &tw);
2020		2226
2021	for (int i = 0; i < nfd; ++i)	2227	for (int i = 0; i < nfd; ++i)
2022	{	2228	{
…		…
2061	}	2267	}
2062		2268
2063	// do not ever call adns_afterpoll	2269	// do not ever call adns_afterpoll
2064		2270
2065	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
2066	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
2067	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
2068	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
2069	this.	2275	this approach, effectively embedding EV as a client into the horrible
		2276	libglib event loop.
2070		2277
2071	static gint	2278	static gint
2072	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2279	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2073	{	2280	{
2074	int got_events = 0;	2281	int got_events = 0;
…		…
2105	prioritise I/O.	2312	prioritise I/O.
2106		2313
2107	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
2108	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
2109	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
2110	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
2111	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
2112	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
2113	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 :)
2114		2322
2115	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
2116	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),
2117	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
2118	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
2119	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.
2120		2328
2121	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
2122	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
2123	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
2124	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
…		…
2132	interested in that.	2340	interested in that.
2133		2341
2134	Also, there have not currently been made special provisions for forking:	2342	Also, there have not currently been made special provisions for forking:
2135	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2136	but you will also have to stop and restart any C<ev_embed> watchers	2344	but you will also have to stop and restart any C<ev_embed> watchers
2137	yourself.	2345	yourself - but you can use a fork watcher to handle this automatically,
		2346	and future versions of libev might do just that.
2138		2347
2139	Unfortunately, not all backends are embeddable, only the ones returned by	2348	Unfortunately, not all backends are embeddable: only the ones returned by
2140	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2141	portable one.	2350	portable one.
2142		2351
2143	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
2144	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
2145	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
2146	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.
2147		2364
2148	=head3 Watcher-Specific Functions and Data Members	2365	=head3 Watcher-Specific Functions and Data Members
2149		2366
2150	=over 4	2367	=over 4
2151		2368
…		…
2179	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
2180	used).	2397	used).
2181		2398
2182	struct ev_loop *loop_hi = ev_default_init (0);	2399	struct ev_loop *loop_hi = ev_default_init (0);
2183	struct ev_loop *loop_lo = 0;	2400	struct ev_loop *loop_lo = 0;
2184	struct ev_embed embed;	2401	ev_embed embed;
2185		2402
2186	// see if there is a chance of getting one that works	2403	// see if there is a chance of getting one that works
2187	// (remember that a flags value of 0 means autodetection)	2404	// (remember that a flags value of 0 means autodetection)
2188	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2405	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2189	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2406	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2203	kqueue implementation). Store the kqueue/socket-only event loop in	2420	kqueue implementation). Store the kqueue/socket-only event loop in
2204	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2421	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2205		2422
2206	struct ev_loop *loop = ev_default_init (0);	2423	struct ev_loop *loop = ev_default_init (0);
2207	struct ev_loop *loop_socket = 0;	2424	struct ev_loop *loop_socket = 0;
2208	struct ev_embed embed;	2425	ev_embed embed;
2209		2426
2210	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2427	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2211	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2428	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2212	{	2429	{
2213	ev_embed_init (&embed, 0, loop_socket);	2430	ev_embed_init (&embed, 0, loop_socket);
…		…
2269	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
2270	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
2271	need elaborate support such as pthreads.	2488	need elaborate support such as pthreads.
2272		2489
2273	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
2274	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
2275	queue:	2492	queue:
2276		2493
2277	=over 4	2494	=over 4
2278		2495
2279	=item queueing from a signal handler context	2496	=item queueing from a signal handler context
2280		2497
2281	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
2282	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
2283	some fictitious SIGUSR1 handler:	2500	an example that does that for some fictitious SIGUSR1 handler:
2284		2501
2285	static ev_async mysig;	2502	static ev_async mysig;
2286		2503
2287	static void	2504	static void
2288	sigusr1_handler (void)	2505	sigusr1_handler (void)
…		…
2355		2572
2356	=item ev_async_init (ev_async *, callback)	2573	=item ev_async_init (ev_async *, callback)
2357		2574
2358	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
2359	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,
2360	believe me.	2577	trust me.
2361		2578
2362	=item ev_async_send (loop, ev_async *)	2579	=item ev_async_send (loop, ev_async *)
2363		2580
2364	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
2365	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
2366	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
2367	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
2368	section below on what exactly this means).	2585	section below on what exactly this means).
2369		2586
2370	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,
2371	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
…		…
2395	=over 4	2612	=over 4
2396		2613
2397	=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)
2398		2615
2399	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
2400	callback on whichever event happens first and automatically stop both	2617	callback on whichever event happens first and automatically stops both
2401	watchers. This is useful if you want to wait for a single event on an fd	2618	watchers. This is useful if you want to wait for a single event on an fd
2402	or timeout without having to allocate/configure/start/stop/free one or	2619	or timeout without having to allocate/configure/start/stop/free one or
2403	more watchers yourself.	2620	more watchers yourself.
2404		2621
2405	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
2406	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
2407	C<events> set will be created and started.	2624	the given C<fd> and C<events> set will be created and started.
2408		2625
2409	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
2410	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
2411	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.
2412	dubious value.
2413		2629
2414	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
2415	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
2416	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>
2417	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.
2418		2638
2419	static void stdin_ready (int revents, void *arg)	2639	static void stdin_ready (int revents, void *arg)
2420	{	2640	{
		2641	if (revents & EV_READ)
		2642	/* stdin might have data for us, joy! */;
2421	if (revents & EV_TIMEOUT)	2643	else if (revents & EV_TIMEOUT)
2422	/* doh, nothing entered */;	2644	/* doh, nothing entered */;
2423	else if (revents & EV_READ)
2424	/* stdin might have data for us, joy! */;
2425	}	2645	}
2426		2646
2427	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2428		2648
2429	=item ev_feed_event (ev_loop *, watcher *, int revents)	2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2430		2650
2431	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
2432	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
2433	initialised but not necessarily started event watcher).	2653	initialised but not necessarily started event watcher).
2434		2654
2435	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2436		2656
2437	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
2438	the given events it.	2658	the given events it.
2439		2659
2440	=item ev_feed_signal_event (ev_loop *loop, int signum)	2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2441		2661
2442	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
2443	loop!).	2663	loop!).
2444		2664
2445	=back	2665	=back
…		…
2577		2797
2578	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)>.
2579		2799
2580	See the method-C<set> above for more details.	2800	See the method-C<set> above for more details.
2581		2801
2582	Example:	2802	Example: Use a plain function as callback.
2583		2803
2584	static void io_cb (ev::io &w, int revents) { }	2804	static void io_cb (ev::io &w, int revents) { }
2585	iow.set <io_cb> ();	2805	iow.set <io_cb> ();
2586		2806
2587	=item w->set (struct ev_loop *)	2807	=item w->set (struct ev_loop *)
…		…
2625	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
2626	the constructor.	2846	the constructor.
2627		2847
2628	class myclass	2848	class myclass
2629	{	2849	{
2630	ev::io io; void io_cb (ev::io &w, int revents);	2850	ev::io io ; void io_cb (ev::io &w, int revents);
2631	ev:idle idle void idle_cb (ev::idle &w, int revents);	2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2632		2852
2633	myclass (int fd)	2853	myclass (int fd)
2634	{	2854	{
2635	io .set <myclass, &myclass::io_cb > (this);	2855	io .set <myclass, &myclass::io_cb > (this);
2636	idle.set <myclass, &myclass::idle_cb> (this);	2856	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2652	=item Perl	2872	=item Perl
2653		2873
2654	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
2655	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,
2656	there are additional modules that implement libev-compatible interfaces	2876	there are additional modules that implement libev-compatible interfaces
2657	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2877	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2658	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2878	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2879	and C<EV::Glib>).
2659		2880
2660	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
2661	L<http://software.schmorp.de/pkg/EV>.	2882	L<http://software.schmorp.de/pkg/EV>.
2662		2883
2663	=item Python	2884	=item Python
…		…
2842		3063
2843	=head2 PREPROCESSOR SYMBOLS/MACROS	3064	=head2 PREPROCESSOR SYMBOLS/MACROS
2844		3065
2845	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
2846	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
2847	autoconf is noted for every option.	3068	autoconf is documented for every option.
2848		3069
2849	=over 4	3070	=over 4
2850		3071
2851	=item EV_STANDALONE	3072	=item EV_STANDALONE
2852		3073
…		…
3022	When doing priority-based operations, libev usually has to linearly search	3243	When doing priority-based operations, libev usually has to linearly search
3023	all the priorities, so having many of them (hundreds) uses a lot of space	3244	all the priorities, so having many of them (hundreds) uses a lot of space
3024	and time, so using the defaults of five priorities (-2 .. +2) is usually	3245	and time, so using the defaults of five priorities (-2 .. +2) is usually
3025	fine.	3246	fine.
3026		3247
3027	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
3028	C<0> will save some memory and CPU.	3249	both to C<0> will save some memory and CPU.
3029		3250
3030	=item EV_PERIODIC_ENABLE	3251	=item EV_PERIODIC_ENABLE
3031		3252
3032	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
3033	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
…		…
3040	code.	3261	code.
3041		3262
3042	=item EV_EMBED_ENABLE	3263	=item EV_EMBED_ENABLE
3043		3264
3044	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
3045	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.
3046		3268
3047	=item EV_STAT_ENABLE	3269	=item EV_STAT_ENABLE
3048		3270
3049	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
3050	defined to be C<0>, then they are not.	3272	defined to be C<0>, then they are not.
…		…
3082	two).	3304	two).
3083		3305
3084	=item EV_USE_4HEAP	3306	=item EV_USE_4HEAP
3085		3307
3086	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
3087	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
3088	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
3089	noticeably faster performance with many (thousands) of watchers.	3311	faster performance with many (thousands) of watchers.
3090		3312
3091	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>
3092	(disabled).	3314	(disabled).
3093		3315
3094	=item EV_HEAP_CACHE_AT	3316	=item EV_HEAP_CACHE_AT
3095		3317
3096	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
3097	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
3098	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>),
3099	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,
3100	but avoids random read accesses on heap changes. This improves performance	3322	but avoids random read accesses on heap changes. This improves performance
3101	noticeably with with many (hundreds) of watchers.	3323	noticeably with many (hundreds) of watchers.
3102		3324
3103	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>
3104	(disabled).	3326	(disabled).
3105		3327
3106	=item EV_VERIFY	3328	=item EV_VERIFY
…		…
3112	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
3113	verification code will be called very frequently, which will slow down	3335	verification code will be called very frequently, which will slow down
3114	libev considerably.	3336	libev considerably.
3115		3337
3116	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
3117	C<0.>	3339	C<0>.
3118		3340
3119	=item EV_COMMON	3341	=item EV_COMMON
3120		3342
3121	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
3122	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
…		…
3139	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
3140	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
3141	their default definitions. One possible use for overriding these is to	3363	their default definitions. One possible use for overriding these is to
3142	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3364	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3143	method calls instead of plain function calls in C++.	3365	method calls instead of plain function calls in C++.
		3366
		3367	=back
3144		3368
3145	=head2 EXPORTED API SYMBOLS	3369	=head2 EXPORTED API SYMBOLS
3146		3370
3147	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
3148	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
…		…
3195	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:
3196		3420
3197	#include "ev_cpp.h"	3421	#include "ev_cpp.h"
3198	#include "ev.c"	3422	#include "ev.c"
3199		3423
		3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3200		3425
3201	=head1 THREADS AND COROUTINES	3426	=head2 THREADS AND COROUTINES
3202		3427
3203	=head2 THREADS	3428	=head3 THREADS
3204		3429
3205	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
3206	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
3207	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
3208	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.
3209		3437
3210	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
3211	parallel from multiple threads, calls with the same loop parameter must be	3439	concurrently from multiple threads, calls with the same loop parameter
3212	done serially (but can be done from different threads, as long as only one	3440	must be done serially (but can be done from different threads, as long as
3213	thread ever is inside a call at any point in time, e.g. by using a mutex	3441	only one thread ever is inside a call at any point in time, e.g. by using
3214	per loop).	3442	a mutex per loop).
		3443
		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".
3215		3448
3216	If you want to know which design (one loop, locking, or multiple loops	3449	If you want to know which design (one loop, locking, or multiple loops
3217	without or something else still) is best for your problem, then I cannot	3450	without or something else still) is best for your problem, then I cannot
3218	help you. I can give some generic advice however:	3451	help you, but here is some generic advice:
3219		3452
3220	=over 4	3453	=over 4
3221		3454
3222	=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
3223	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.
…		…
3235		3468
3236	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
3237	better than you currently do :-)	3470	better than you currently do :-)
3238		3471
3239	=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
3240	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
3241	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.
3242		3482
3243	=back	3483	=back
3244		3484
3245	=head2 COROUTINES	3485	=head3 COROUTINES
3246		3486
3247	Libev is much more accommodating to coroutines ("cooperative threads"):	3487	Libev is very accommodating to coroutines ("cooperative threads"):
3248	libev fully supports nesting calls to it's functions from different	3488	libev fully supports nesting calls to its functions from different
3249	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3250	different coroutines and switch freely between both coroutines running the	3490	different coroutines, and switch freely between both coroutines running the
3251	loop, as long as you don't confuse yourself). The only exception is that	3491	loop, as long as you don't confuse yourself). The only exception is that
3252	you must not do this from C<ev_periodic> reschedule callbacks.	3492	you must not do this from C<ev_periodic> reschedule callbacks.
3253		3493
3254	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
3255	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
3256	switches.	3496	they do not clal any callbacks.
3257		3497
		3498	=head2 COMPILER WARNINGS
3258		3499
3259	=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.
3260		3503
3261	In this section the complexities of (many of) the algorithms used inside	3504	However, these are unavoidable for many reasons. For one, each compiler
3262	libev will be explained. For complexity discussions about backends see the	3505	has different warnings, and each user has different tastes regarding
3263	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.
3264		3508
3265	All of the following are about amortised time: If an array needs to be	3509	Another reason is that some compiler warnings require elaborate
3266	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
3267	happens asymptotically never with higher number of elements, so O(1) might	3511	maintainable.
3268	mean it might do a lengthy realloc operation in rare cases, but on average
3269	it is much faster and asymptotically approaches constant time.
3270		3512
3271	=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.
3272		3519
3273	=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.
3274		3525
3275	This means that, when you have a watcher that triggers in one hour and
3276	there are 100 watchers that would trigger before that then inserting will
3277	have to skip roughly seven (C<ld 100>) of these watchers.
3278		3526
3279	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3527	=head2 VALGRIND
3280		3528
3281	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
3282	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.
3283		3531
3284	=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:
3285		3534
3286	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.
3287		3538
3288	=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.
3289		3541
3290	=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.
3291		3546
3292	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
3293	correct watcher to remove. The lists are usually short (you don't usually	3548	make it into some kind of religion.
3294	have many watchers waiting for the same fd or signal).
3295		3549
3296	=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.
3297		3555
3298	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
3299	fixed position in the storage array.	3557	I suggest using suppression lists.
3300		3558
3301	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3302		3559
3303	A change means an I/O watcher gets started or stopped, which requires	3560	=head1 PORTABILITY NOTES
3304	libev to recalculate its status (and possibly tell the kernel, depending
3305	on backend and whether C<ev_io_set> was used).
3306		3561
3307	=item Activating one watcher (putting it into the pending state): O(1)
3308
3309	=item Priority handling: O(number_of_priorities)
3310
3311	Priorities are implemented by allocating some space for each
3312	priority. When doing priority-based operations, libev usually has to
3313	linearly search all the priorities, but starting/stopping and activating
3314	watchers becomes O(1) w.r.t. priority handling.
3315
3316	=item Sending an ev_async: O(1)
3317
3318	=item Processing ev_async_send: O(number_of_async_watchers)
3319
3320	=item Processing signals: O(max_signal_number)
3321
3322	Sending involves a system call I<iff> there were no other C<ev_async_send>
3323	calls in the current loop iteration. Checking for async and signal events
3324	involves iterating over all running async watchers or all signal numbers.
3325
3326	=back
3327
3328
3329	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3330		3563
3331	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
3332	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
3333	model. Libev still offers limited functionality on this platform in	3566	model. Libev still offers limited functionality on this platform in
3334	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
…		…
3345		3578
3346	Not a libev limitation but worth mentioning: windows apparently doesn't	3579	Not a libev limitation but worth mentioning: windows apparently doesn't
3347	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
3348	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,
3349	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
3350	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
3351	available).	3584	available).
3352		3585
3353	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
3354	the abysmal performance of winsockets, using a large number of sockets	3587	the abysmal performance of winsockets, using a large number of sockets
3355	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
…		…
3366	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3599	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3367		3600
3368	#include "ev.h"	3601	#include "ev.h"
3369		3602
3370	And compile the following F<evwrap.c> file into your project (make sure	3603	And compile the following F<evwrap.c> file into your project (make sure
3371	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3604	you do I<not> compile the F<ev.c> or any other embedded source files!):
3372		3605
3373	#include "evwrap.h"	3606	#include "evwrap.h"
3374	#include "ev.c"	3607	#include "ev.c"
3375		3608
3376	=over 4	3609	=over 4
…		…
3421	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
3422	calling select (O(n²)) will likely make this unworkable.	3655	calling select (O(n²)) will likely make this unworkable.
3423		3656
3424	=back	3657	=back
3425		3658
3426
3427	=head1 PORTABILITY REQUIREMENTS	3659	=head2 PORTABILITY REQUIREMENTS
3428		3660
3429	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
3430	additional extensions:	3662	backend-specific APIs, libev relies on a few additional extensions:
3431		3663
3432	=over 4	3664	=over 4
3433		3665
3434	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3666	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3435	calling conventions regardless of C<ev_watcher_type *>.	3667	calling conventions regardless of C<ev_watcher_type *>.
…		…
3441	calls them using an C<ev_watcher *> internally.	3673	calls them using an C<ev_watcher *> internally.
3442		3674
3443	=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
3444		3676
3445	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
3446	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
3447	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
3448	believed to be sufficiently portable.	3680	believed to be sufficiently portable.
3449		3681
3450	=item C<sigprocmask> must work in a threaded environment	3682	=item C<sigprocmask> must work in a threaded environment
3451		3683
…		…
3460	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
3461	well.	3693	well.
3462		3694
3463	=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
3464		3696
3465	To improve portability and simplify using libev, libev uses C<long>	3697	To improve portability and simplify its API, libev uses C<long> internally
3466	internally instead of C<size_t> when allocating its data structures. On	3698	instead of C<size_t> when allocating its data structures. On non-POSIX
3467	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3699	systems (Microsoft...) this might be unexpectedly low, but is still at
3468	is still at least 31 bits everywhere, which is enough for hundreds of	3700	least 31 bits everywhere, which is enough for hundreds of millions of
3469	millions of watchers.	3701	watchers.
3470		3702
3471	=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
3472		3704
3473	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
3474	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
…		…
3478	=back	3710	=back
3479		3711
3480	If you know of other additional requirements drop me a note.	3712	If you know of other additional requirements drop me a note.
3481		3713
3482		3714
3483	=head1 COMPILER WARNINGS	3715	=head1 ALGORITHMIC COMPLEXITIES
3484		3716
3485	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
3486	lot of warnings when compiling libev code. Some people are apparently	3718	libev will be documented. For complexity discussions about backends see
3487	scared by this.	3719	the documentation for C<ev_default_init>.
3488		3720
3489	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
3490	has different warnings, and each user has different tastes regarding	3722	extended, libev needs to realloc and move the whole array, but this
3491	warning options. "Warn-free" code therefore cannot be a goal except when	3723	happens asymptotically rarer with higher number of elements, so O(1) might
3492	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.
3493		3726
3494	Another reason is that some compiler warnings require elaborate	3727	=over 4
3495	workarounds, or other changes to the code that make it less clear and less
3496	maintainable.
3497		3728
3498	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)
3499	wrong (because they don't actually warn about the condition their message
3500	seems to warn about).
3501		3730
3502	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
3503	"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
3504	with any compiler warnings enabled unless you are prepared to cope with	3733	have to skip roughly seven (C<ld 100>) of these watchers.
3505	them (e.g. by ignoring them). Remember that warnings are just that:
3506	warnings, not errors, or proof of bugs.
3507		3734
		3735	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3508		3736
3509	=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.
3510		3739
3511	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)
3512	highly useful, but valgrind reports are very hard to interpret.
3513		3741
3514	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.
3515	in libev, then check twice: If valgrind reports something like:
3516		3743
3517	==2274== definitely lost: 0 bytes in 0 blocks.	3744	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3518	==2274== possibly lost: 0 bytes in 0 blocks.
3519	==2274== still reachable: 256 bytes in 1 blocks.
3520		3745
3521	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))
3522	valgrind might report kernel bugs as if it were a bug in libev, or it
3523	might be confused (it is a very good tool, but only a tool).
3524		3747
3525	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
3526	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
3527	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
3528	no bug" answer and take the chance of learning how to interpret valgrind	3751	is rare).
3529	properly.
3530		3752
3531	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)
3532	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
3533		3784
3534		3785
3535	=head1 AUTHOR	3786	=head1 AUTHOR
3536		3787
3537	Marc Lehmann <libev@schmorp.de>.	3788	Marc Lehmann <libev@schmorp.de>.

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