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Revision 1.163 by root, Sat May 31 23:19:23 2008 UTC vs.
Revision 1.191 by root, Tue Sep 30 19:45:23 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_<type>
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
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_ struct 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);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
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_ struct 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	struct 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);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
…		…
178	not a problem.	178	not a problem.
179		179
180	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	181	version.
182		182
183	assert (("libev version mismatch",	183	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
186		186
187	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
188		188
189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
190	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
192	a description of the set values.	192	a description of the set values.
193		193
194	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
195	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
196		196
197	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
199		199
200	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
201		201
202	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
203	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	362	readiness notifications you get per iteration.
363		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
		367
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		369
366	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
372		379
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		381
375	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
…		…
389	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.	398	(or space) is available.
392		399
393	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
396		405
397	While nominally embeddable in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	407	all kernel versions tested so far.
399		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		413
402	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
404	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
405	it's completely useless). For this reason it's not being "auto-detected"	417	completely useless). For this reason it's not being "auto-detected" unless
406	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
408	system like NetBSD.
409		420
410	You still can embed kqueue into a normal poll or select backend and use it	421	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	422	only for sockets (after having made sure that sockets work with kqueue on
412	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
413		424
414	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	427	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	429	two event changes per incident. Support for C<fork ()> is very bad and it
419	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
420		431
421	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
422		433
423	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	435	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	436	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	437	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
429		444
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		446
432	This is not implemented yet (and might never be, unless you send me an	447	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	461	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	462	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	464	might perform better.
450		465
451	On the positive side, ignoring the spurious readiness notifications, this	466	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
454		473
455	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
456		475
457	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		483
465	If one or more of these are or'ed into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		487
469	The most typical usage is like this:	488	Example: This is the most typical usage.
470		489
471	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		492
474	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	494	environment settings to be taken into account:
476		495
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		497
479	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
482		502
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		504
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		506
487	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
488	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
…		…
493	libev with threads is indeed to create one loop per thread, and using the	513	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.	514	default loop in the "main" or "initial" thread.
495		515
496	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
497		517
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	519	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
501		521
502	=item ev_default_destroy ()	522	=item ev_default_destroy ()
503		523
504	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
505	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
…		…
544		564
545	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
546		566
547	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
550		571
551	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
552		573
553	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
554		576
555	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
556		578
557	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
573	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
577		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
578	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
579		613
580	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
582	events.	616	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
586		620
587	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
592		627
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
596		632
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
601	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
604		644
605	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
606		646
607	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	662	- Queue all expired timers.
622	- Queue all outstanding periodics.	663	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	665	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	674	anymore.
634		675
635	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
638	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
639		680
640	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
641		682
642	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
…		…
650		691
651	=item ev_unref (loop)	692	=item ev_unref (loop)
652		693
653	Ref/unref can be used to add or remove a reference count on the event	694	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	695	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	696	count is nonzero, C<ev_loop> will not return on its own.
		697
656	a watcher you never unregister that should not keep C<ev_loop> from	698	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	699	from returning, call ev_unref() after starting, and ev_ref() before
		700	stopping it.
		701
658	example, libev itself uses this for its internal signal pipe: It is not	702	As an example, libev itself uses this for its internal signal pipe: It is
659	visible to the libev user and should not keep C<ev_loop> from exiting if	703	not visible to the libev user and should not keep C<ev_loop> from exiting
660	no event watchers registered by it are active. It is also an excellent	704	if no event watchers registered by it are active. It is also an excellent
661	way to do this for generic recurring timers or from within third-party	705	way to do this for generic recurring timers or from within third-party
662	libraries. Just remember to I<unref after start> and I<ref before stop>	706	libraries. Just remember to I<unref after start> and I<ref before stop>
663	(but only if the watcher wasn't active before, or was active before,	707	(but only if the watcher wasn't active before, or was active before,
664	respectively).	708	respectively).
665		709
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	711	running when nothing else is active.
668		712
669	struct ev_signal exitsig;	713	struct ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	714	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	715	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	716	evf_unref (loop);
673		717
674	Example: For some weird reason, unregister the above signal handler again.	718	Example: For some weird reason, unregister the above signal handler again.
675		719
676	ev_ref (loop);	720	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	721	ev_signal_stop (loop, &exitsig);
678		722
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	723	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		724
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		726
683	These advanced functions influence the time that libev will spend waiting	727	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	728	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	729	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		730	latency.
686		731
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	732	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	733	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	734	to increase efficiency of loop iterations (or to increase power-saving
		735	opportunities).
690		736
691	The background is that sometimes your program runs just fast enough to	737	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	738	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	739	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	740	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	741	overhead for the actual polling but can deliver many events at once.
696		742
697	By setting a higher I<io collect interval> you allow libev to spend more	743	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	744	time collecting I/O events, so you can handle more events per iteration,
…		…
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	746	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	747	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		748
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	749	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	750	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	751	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	752	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	753	value will not introduce any overhead in libev.
708		754
709	Many (busy) programs can usually benefit by setting the I/O collect	755	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	756	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	757	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	758	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	759	as this approaches the timing granularity of most systems.
714		760
		761	Setting the I<timeout collect interval> can improve the opportunity for
		762	saving power, as the program will "bundle" timer callback invocations that
		763	are "near" in time together, by delaying some, thus reducing the number of
		764	times the process sleeps and wakes up again. Another useful technique to
		765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		766	they fire on, say, one-second boundaries only.
		767
715	=item ev_loop_verify (loop)	768	=item ev_loop_verify (loop)
716		769
717	This function only does something when C<EV_VERIFY> support has been	770	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	771	compiled in. which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	772	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	773	is found to be inconsistent, it will print an error message to standard
		774	error and call C<abort ()>.
721		775
722	This can be used to catch bugs inside libev itself: under normal	776	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	777	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	778	data structures consistent.
725		779
…		…
730		784
731	A watcher is a structure that you create and register to record your	785	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	786	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	787	become readable, you would create an C<ev_io> watcher for that:
734		788
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
736	{	790	{
737	ev_io_stop (w);	791	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	792	ev_unloop (loop, EVUNLOOP_ALL);
739	}	793	}
740		794
741	struct ev_loop *loop = ev_default_loop (0);	795	struct ev_loop *loop = ev_default_loop (0);
742	struct ev_io stdin_watcher;	796	struct ev_io stdin_watcher;
743	ev_init (&stdin_watcher, my_cb);	797	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	799	ev_io_start (loop, &stdin_watcher);
746	ev_loop (loop, 0);	800	ev_loop (loop, 0);
747		801
748	As you can see, you are responsible for allocating the memory for your	802	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	803	watcher structures (and it is usually a bad idea to do this on the stack,
750	although this can sometimes be quite valid).	804	although this can sometimes be quite valid).
751		805
…		…
841	happen because the watcher could not be properly started because libev	895	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	896	ran out of memory, a file descriptor was found to be closed or any other
843	problem. You best act on it by reporting the problem and somehow coping	897	problem. You best act on it by reporting the problem and somehow coping
844	with the watcher being stopped.	898	with the watcher being stopped.
845		899
846	Libev will usually signal a few "dummy" events together with an error,	900	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	901	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	902	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	903	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	904	programs, though, as the fd could already be closed and reused for another
		905	thing, so beware.
851		906
852	=back	907	=back
853		908
854	=head2 GENERIC WATCHER FUNCTIONS	909	=head2 GENERIC WATCHER FUNCTIONS
855		910
…		…
871	(or never started) and there are no pending events outstanding.	926	(or never started) and there are no pending events outstanding.
872		927
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	929	int revents)>.
875		930
		931	Example: Initialise an C<ev_io> watcher in two steps.
		932
		933	ev_io w;
		934	ev_init (&w, my_cb);
		935	ev_io_set (&w, STDIN_FILENO, EV_READ);
		936
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	937	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		938
878	This macro initialises the type-specific parts of a watcher. You need to	939	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	940	call C<ev_init> at least once before you call this macro, but you can
880	call C<ev_TYPE_set> any number of times. You must not, however, call this	941	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
882	difference to the C<ev_init> macro).	943	difference to the C<ev_init> macro).
883		944
884	Although some watcher types do not have type-specific arguments	945	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	946	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		947
		948	See C<ev_init>, above, for an example.
		949
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	950	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		951
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	952	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	953	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	954	a watcher. The same limitations apply, of course.
892		955
		956	Example: Initialise and set an C<ev_io> watcher in one step.
		957
		958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		959
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		961
895	Starts (activates) the given watcher. Only active watchers will receive	962	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	963	events. If the watcher is already active nothing will happen.
		964
		965	Example: Start the C<ev_io> watcher that is being abused as example in this
		966	whole section.
		967
		968	ev_io_start (EV_DEFAULT_UC, &w);
897		969
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		971
900	Stops the given watcher again (if active) and clears the pending	972	Stops the given watcher again (if active) and clears the pending
901	status. It is possible that stopped watchers are pending (for example,	973	status. It is possible that stopped watchers are pending (for example,
…		…
958		1030
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1032
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1034	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1035	can deal with that fact, as both are simply passed through to the
		1036	callback.
964		1037
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1038	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1039
967	If the watcher is pending, this function returns clears its pending status	1040	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1041	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1042	watcher isn't pending it does nothing and returns C<0>.
970		1043
		1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1045	callback to be invoked, which can be accomplished with this function.
		1046
971	=back	1047	=back
972		1048
973		1049
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1051
976	Each watcher has, by default, a member C<void *data> that you can change	1052	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1053	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1054	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1055	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1056	member, you can also "subclass" the watcher type and provide your own
981	data:	1057	data:
982		1058
983	struct my_io	1059	struct my_io
984	{	1060	{
985	struct ev_io io;	1061	struct ev_io io;
986	int otherfd;	1062	int otherfd;
987	void *somedata;	1063	void *somedata;
988	struct whatever *mostinteresting;	1064	struct whatever *mostinteresting;
989	}	1065	};
		1066
		1067	...
		1068	struct my_io w;
		1069	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1070
991	And since your callback will be called with a pointer to the watcher, you	1071	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1072	can cast it back to your own type:
993		1073
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
995	{	1075	{
996	struct my_io *w = (struct my_io *)w_;	1076	struct my_io *w = (struct my_io *)w_;
997	...	1077	...
998	}	1078	}
999		1079
1000	More interesting and less C-conformant ways of casting your callback type	1080	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1081	instead have been omitted.
1002		1082
1003	Another common scenario is having some data structure with multiple	1083	Another common scenario is to use some data structure with multiple
1004	watchers:	1084	embedded watchers:
1005		1085
1006	struct my_biggy	1086	struct my_biggy
1007	{	1087	{
1008	int some_data;	1088	int some_data;
1009	ev_timer t1;	1089	ev_timer t1;
1010	ev_timer t2;	1090	ev_timer t2;
1011	}	1091	}
1012		1092
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1093	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1094	complicated: Either you store the address of your C<my_biggy> struct
		1095	in the C<data> member of the watcher (for woozies), or you need to use
		1096	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1097	programmers):
1015		1098
1016	#include <stddef.h>	1099	#include <stddef.h>
1017		1100
1018	static void	1101	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1102	t1_cb (EV_P_ struct ev_timer *w, int revents)
1020	{	1103	{
1021	struct my_biggy big = (struct my_biggy *	1104	struct my_biggy big = (struct my_biggy *
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1105	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1106	}
1024		1107
1025	static void	1108	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1109	t2_cb (EV_P_ struct ev_timer *w, int revents)
1027	{	1110	{
1028	struct my_biggy big = (struct my_biggy *	1111	struct my_biggy big = (struct my_biggy *
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1112	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1113	}
1031		1114
1032		1115
1033	=head1 WATCHER TYPES	1116	=head1 WATCHER TYPES
1034		1117
1035	This section describes each watcher in detail, but will not repeat	1118	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1142	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1143	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1144	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1145	required if you know what you are doing).
1063		1146
1064	If you must do this, then force the use of a known-to-be-good backend	1147	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1148	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1150
1068	Another thing you have to watch out for is that it is quite easy to	1151	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1152	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1154	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1155	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1156	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1157	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1158	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1159
1077	If you cannot run the fd in non-blocking mode (for example you should not	1160	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1161	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1162	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1163	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1164	does this on its own, so its quite safe to use). Some people additionally
		1165	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1166	indefinitely.
		1167
		1168	But really, best use non-blocking mode.
1082		1169
1083	=head3 The special problem of disappearing file descriptors	1170	=head3 The special problem of disappearing file descriptors
1084		1171
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1172	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1173	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1174	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1175	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1176	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1177	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1178	fact, a different file descriptor.
1092		1179
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1210	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1211	C<EVBACKEND_POLL>.
1125		1212
1126	=head3 The special problem of SIGPIPE	1213	=head3 The special problem of SIGPIPE
1127		1214
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1215	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1216	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1217	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1218	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1219
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1220	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1222	somewhere, as that would have given you a big clue).
1137		1223
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1229	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1230
1145	=item ev_io_set (ev_io *, int fd, int events)	1231	=item ev_io_set (ev_io *, int fd, int events)
1146		1232
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1233	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1234	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1235	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1236
1151	=item int fd [read-only]	1237	=item int fd [read-only]
1152		1238
1153	The file descriptor being watched.	1239	The file descriptor being watched.
1154		1240
…		…
1162		1248
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1250	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1251	attempt to read a whole line in the callback.
1166		1252
1167	static void	1253	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1169	{	1255	{
1170	ev_io_stop (loop, w);	1256	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1257	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1258	}
1173		1259
1174	...	1260	...
1175	struct ev_loop *loop = ev_default_init (0);	1261	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1262	struct ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1264	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1265	ev_loop (loop, 0);
1180		1266
1181		1267
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1268	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1269
1184	Timer watchers are simple relative timers that generate an event after a	1270	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1271	given time, and optionally repeating in regular intervals after that.
1186		1272
1187	The timers are based on real time, that is, if you register an event that	1273	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1274	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1275	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1277	monotonic clock option helps a lot here).
		1278
		1279	The callback is guaranteed to be invoked only I<after> its timeout has
		1280	passed, but if multiple timers become ready during the same loop iteration
		1281	then order of execution is undefined.
		1282
		1283	=head3 The special problem of time updates
		1284
		1285	Establishing the current time is a costly operation (it usually takes at
		1286	least two system calls): EV therefore updates its idea of the current
		1287	time only before and after C<ev_loop> collects new events, which causes a
		1288	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1289	lots of events in one iteration.
1192		1290
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1291	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1292	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1293	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1294	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1295	timeout on the current time, use something like this to adjust for this:
1198		1296
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1297	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1298
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1299	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1301	()>.
1204		1302
1205	=head3 Watcher-Specific Functions and Data Members	1303	=head3 Watcher-Specific Functions and Data Members
1206		1304
1207	=over 4	1305	=over 4
1208		1306
…		…
1257	ev_timer_again (loop, timer);	1355	ev_timer_again (loop, timer);
1258		1356
1259	This is more slightly efficient then stopping/starting the timer each time	1357	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.	1358	you want to modify its timeout value.
1261		1359
		1360	Note, however, that it is often even more efficient to remember the
		1361	time of the last activity and let the timer time-out naturally. In the
		1362	callback, you then check whether the time-out is real, or, if there was
		1363	some activity, you reschedule the watcher to time-out in "last_activity +
		1364	timeout - ev_now ()" seconds.
		1365
1262	=item ev_tstamp repeat [read-write]	1366	=item ev_tstamp repeat [read-write]
1263		1367
1264	The current C<repeat> value. Will be used each time the watcher times out	1368	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1369	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1370	which is also when any modifications are taken into account.
1267		1371
1268	=back	1372	=back
1269		1373
1270	=head3 Examples	1374	=head3 Examples
1271		1375
1272	Example: Create a timer that fires after 60 seconds.	1376	Example: Create a timer that fires after 60 seconds.
1273		1377
1274	static void	1378	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1276	{	1380	{
1277	.. one minute over, w is actually stopped right here	1381	.. one minute over, w is actually stopped right here
1278	}	1382	}
1279		1383
1280	struct ev_timer mytimer;	1384	struct ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1386	ev_timer_start (loop, &mytimer);
1283		1387
1284	Example: Create a timeout timer that times out after 10 seconds of	1388	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1389	inactivity.
1286		1390
1287	static void	1391	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1289	{	1393	{
1290	.. ten seconds without any activity	1394	.. ten seconds without any activity
1291	}	1395	}
1292		1396
1293	struct ev_timer mytimer;	1397	struct ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1399	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1400	ev_loop (loop, 0);
1297		1401
1298	// and in some piece of code that gets executed on any "activity":	1402	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	1403	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	1404	ev_timer_again (&mytimer);
1301		1405
1302		1406
1303	=head2 C<ev_periodic> - to cron or not to cron?	1407	=head2 C<ev_periodic> - to cron or not to cron?
1304		1408
1305	Periodic watchers are also timers of a kind, but they are very versatile	1409	Periodic watchers are also timers of a kind, but they are very versatile
…		…
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger	1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).	1419	roughly 10 seconds later as it uses a relative timeout).
1316		1420
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1421	C<ev_periodic>s can also be used to implement vastly more complex timers,
1318	such as triggering an event on each "midnight, local time", or other	1422	such as triggering an event on each "midnight, local time", or other
1319	complicated, rules.	1423	complicated rules.
1320		1424
1321	As with timers, the callback is guaranteed to be invoked only when the	1425	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1426	time (C<at>) has passed, but if multiple periodic timers become ready
1323	during the same loop iteration then order of execution is undefined.	1427	during the same loop iteration, then order of execution is undefined.
1324		1428
1325	=head3 Watcher-Specific Functions and Data Members	1429	=head3 Watcher-Specific Functions and Data Members
1326		1430
1327	=over 4	1431	=over 4
1328		1432
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1330		1434
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1332		1436
1333	Lots of arguments, lets sort it out... There are basically three modes of	1437	Lots of arguments, lets sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1438	operation, and we will explain them from simplest to most complex:
1335		1439
1336	=over 4	1440	=over 4
1337		1441
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1339		1443
1340	In this configuration the watcher triggers an event after the wall clock	1444	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1445	time C<at> has passed. It will not repeat and will not adjust when a time
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1343	run when the system time reaches or surpasses this time.	1447	only run when the system clock reaches or surpasses this time.
1344		1448
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1346		1450
1347	In this mode the watcher will always be scheduled to time out at the next	1451	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1452	C<at + N * interval> time (for some integer N, which can also be negative)
1349	and then repeat, regardless of any time jumps.	1453	and then repeat, regardless of any time jumps.
1350		1454
1351	This can be used to create timers that do not drift with respect to system	1455	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1456	system clock, for example, here is a C<ev_periodic> that triggers each
1353	the hour:	1457	hour, on the hour:
1354		1458
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1459	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1460
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1461	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1462	but only that the callback will be called when the system time shows a
…		…
1445	=back	1549	=back
1446		1550
1447	=head3 Examples	1551	=head3 Examples
1448		1552
1449	Example: Call a callback every hour, or, more precisely, whenever the	1553	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1554	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1555	potentially a lot of jitter, but good long-term stability.
1452		1556
1453	static void	1557	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1455	{	1559	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1560	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1561	}
1458		1562
1459	struct ev_periodic hourly_tick;	1563	struct ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1565	ev_periodic_start (loop, &hourly_tick);
1462		1566
1463	Example: The same as above, but use a reschedule callback to do it:	1567	Example: The same as above, but use a reschedule callback to do it:
1464		1568
1465	#include <math.h>	1569	#include <math.h>
1466		1570
1467	static ev_tstamp	1571	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1469	{	1573	{
1470	return fmod (now, 3600.) + 3600.;	1574	return now + (3600. - fmod (now, 3600.));
1471	}	1575	}
1472		1576
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1578
1475	Example: Call a callback every hour, starting now:	1579	Example: Call a callback every hour, starting now:
1476		1580
1477	struct ev_periodic hourly_tick;	1581	struct ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1582	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1583	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1584	ev_periodic_start (loop, &hourly_tick);
1481		1585
1482		1586
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	1587	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		1588
1485	Signal watchers will trigger an event when the process receives a specific	1589	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	1590	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	1591	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1592	normal event processing, like any other event.
1489		1593
		1594	If you want signals asynchronously, just use C<sigaction> as you would
		1595	do without libev and forget about sharing the signal. You can even use
		1596	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1597
1490	You can configure as many watchers as you like per signal. Only when the	1598	You can configure as many watchers as you like per signal. Only when the
1491	first watcher gets started will libev actually register a signal watcher	1599	first watcher gets started will libev actually register a signal handler
1492	with the kernel (thus it coexists with your own signal handlers as long	1600	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	1601	you don't register any with libev for the same signal). Similarly, when
1494	watcher for a signal is stopped libev will reset the signal handler to	1602	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1603	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1604
1497	If possible and supported, libev will install its handlers with	1605	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1499	interrupted. If you have a problem with system calls getting interrupted by	1607	interrupted. If you have a problem with system calls getting interrupted by
1500	signals you can block all signals in an C<ev_check> watcher and unblock	1608	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1625
1518	=back	1626	=back
1519		1627
1520	=head3 Examples	1628	=head3 Examples
1521		1629
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1630	Example: Try to exit cleanly on SIGINT.
1523		1631
1524	static void	1632	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1526	{	1634	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1635	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1636	}
1529		1637
1530	struct ev_signal signal_watcher;	1638	struct ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1640	ev_signal_start (loop, &signal_watcher);
1533		1641
1534		1642
1535	=head2 C<ev_child> - watch out for process status changes	1643	=head2 C<ev_child> - watch out for process status changes
1536		1644
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1645	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	1646	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	1647	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	1648	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	1649	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1650	forking and then immediately registering a watcher for the child is fine,
		1651	but forking and registering a watcher a few event loop iterations later is
		1652	not.
1542		1653
1543	Only the default event loop is capable of handling signals, and therefore	1654	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	1655	you can only register child watchers in the default event loop.
1545		1656
1546	=head3 Process Interaction	1657	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	1670	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	1671	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	1672	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	1673	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	1674	that, so other libev users can use C<ev_child> watchers freely.
		1675
		1676	=head3 Stopping the Child Watcher
		1677
		1678	Currently, the child watcher never gets stopped, even when the
		1679	child terminates, so normally one needs to stop the watcher in the
		1680	callback. Future versions of libev might stop the watcher automatically
		1681	when a child exit is detected.
1564		1682
1565	=head3 Watcher-Specific Functions and Data Members	1683	=head3 Watcher-Specific Functions and Data Members
1566		1684
1567	=over 4	1685	=over 4
1568		1686
…		…
1597	=head3 Examples	1715	=head3 Examples
1598		1716
1599	Example: C<fork()> a new process and install a child handler to wait for	1717	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	1718	its completion.
1601		1719
1602	ev_child cw;	1720	ev_child cw;
1603		1721
1604	static void	1722	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	1723	child_cb (EV_P_ struct ev_child *w, int revents)
1606	{	1724	{
1607	ev_child_stop (EV_A_ w);	1725	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	1727	}
1610		1728
1611	pid_t pid = fork ();	1729	pid_t pid = fork ();
1612		1730
1613	if (pid < 0)	1731	if (pid < 0)
1614	// error	1732	// error
1615	else if (pid == 0)	1733	else if (pid == 0)
1616	{	1734	{
1617	// the forked child executes here	1735	// the forked child executes here
1618	exit (1);	1736	exit (1);
1619	}	1737	}
1620	else	1738	else
1621	{	1739	{
1622	ev_child_init (&cw, child_cb, pid, 0);	1740	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	1741	ev_child_start (EV_DEFAULT_ &cw);
1624	}	1742	}
1625		1743
1626		1744
1627	=head2 C<ev_stat> - did the file attributes just change?	1745	=head2 C<ev_stat> - did the file attributes just change?
1628		1746
1629	This watches a file system path for attribute changes. That is, it calls	1747	This watches a file system path for attribute changes. That is, it calls
…		…
1637	the stat buffer having unspecified contents.	1755	the stat buffer having unspecified contents.
1638		1756
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	1757	The path I<should> be absolute and I<must not> end in a slash. If it is
1640	relative and your working directory changes, the behaviour is undefined.	1758	relative and your working directory changes, the behaviour is undefined.
1641		1759
1642	Since there is no standard to do this, the portable implementation simply	1760	Since there is no standard kernel interface to do this, the portable
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1761	implementation simply calls C<stat (2)> regularly on the path to see if
1644	can specify a recommended polling interval for this case. If you specify	1762	it changed somehow. You can specify a recommended polling interval for
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	1763	this case. If you specify a polling interval of C<0> (highly recommended!)
1646	unspecified default> value will be used (which you can expect to be around	1764	then a I<suitable, unspecified default> value will be used (which
1647	five seconds, although this might change dynamically). Libev will also	1765	you can expect to be around five seconds, although this might change
1648	impose a minimum interval which is currently around C<0.1>, but thats	1766	dynamically). Libev will also impose a minimum interval which is currently
1649	usually overkill.	1767	around C<0.1>, but thats usually overkill.
1650		1768
1651	This watcher type is not meant for massive numbers of stat watchers,	1769	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	1770	as even with OS-supported change notifications, this can be
1653	resource-intensive.	1771	resource-intensive.
1654		1772
1655	At the time of this writing, only the Linux inotify interface is	1773	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	1774	is the Linux inotify interface (implementing kqueue support is left as
1657	reader, note, however, that the author sees no way of implementing ev_stat	1775	an exercise for the reader. Note, however, that the author sees no way
1658	semantics with kqueue). Inotify will be used to give hints only and should	1776	of implementing C<ev_stat> semantics with kqueue).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		1777
1664	=head3 ABI Issues (Largefile Support)	1778	=head3 ABI Issues (Largefile Support)
1665		1779
1666	Libev by default (unless the user overrides this) uses the default	1780	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	1781	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	1782	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	1783	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	1784	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	1785	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	1786	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	1787	most noticeably disabled with ev_stat and large file support.
1674		1788
1675	=head3 Inotify	1789	The solution for this is to lobby your distribution maker to make large
		1790	file interfaces available by default (as e.g. FreeBSD does) and not
		1791	optional. Libev cannot simply switch on large file support because it has
		1792	to exchange stat structures with application programs compiled using the
		1793	default compilation environment.
		1794
		1795	=head3 Inotify and Kqueue
1676		1796
1677	When C<inotify (7)> support has been compiled into libev (generally only	1797	When C<inotify (7)> support has been compiled into libev (generally only
1678	available on Linux) and present at runtime, it will be used to speed up	1798	available with Linux) and present at runtime, it will be used to speed up
1679	change detection where possible. The inotify descriptor will be created lazily	1799	change detection where possible. The inotify descriptor will be created lazily
1680	when the first C<ev_stat> watcher is being started.	1800	when the first C<ev_stat> watcher is being started.
1681		1801
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	1802	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	1803	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	1804	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	1805	there are many cases where libev has to resort to regular C<stat> polling,
		1806	but as long as the path exists, libev usually gets away without polling.
1686		1807
1687	(There is no support for kqueue, as apparently it cannot be used to	1808	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	1809	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	1810	descriptor open on the object at all times, and detecting renames, unlinks
		1811	etc. is difficult.
1690		1812
1691	=head3 The special problem of stat time resolution	1813	=head3 The special problem of stat time resolution
1692		1814
1693	The C<stat ()> system call only supports full-second resolution portably, and	1815	The C<stat ()> system call only supports full-second resolution portably, and
1694	even on systems where the resolution is higher, many file systems still	1816	even on systems where the resolution is higher, most file systems still
1695	only support whole seconds.	1817	only support whole seconds.
1696		1818
1697	That means that, if the time is the only thing that changes, you can	1819	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	1820	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	1821	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	1822	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	1823	stat data does change in other ways (e.g. file size).
1702		1824
1703	The solution to this is to delay acting on a change for slightly more	1825	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	1826	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1827	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	1828	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	1848	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	1849	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	1850	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	1851	path for as long as the watcher is active.
1730		1852
1731	The callback will receive C<EV_STAT> when a change was detected, relative	1853	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	1854	relative to the attributes at the time the watcher was started (or the
1733	was detected).	1855	last change was detected).
1734		1856
1735	=item ev_stat_stat (loop, ev_stat *)	1857	=item ev_stat_stat (loop, ev_stat *)
1736		1858
1737	Updates the stat buffer immediately with new values. If you change the	1859	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	1860	watched path in your callback, you could call this function to avoid
…		…
1767		1889
1768	=head3 Examples	1890	=head3 Examples
1769		1891
1770	Example: Watch C</etc/passwd> for attribute changes.	1892	Example: Watch C</etc/passwd> for attribute changes.
1771		1893
1772	static void	1894	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1895	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	1896	{
1775	/* /etc/passwd changed in some way */	1897	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	1898	if (w->attr.st_nlink)
1777	{	1899	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1900	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1901	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1902	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	1903	}
1782	else	1904	else
1783	/* you shalt not abuse printf for puts */	1905	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	1906	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	1907	"if this is windows, they already arrived\n");
1786	}	1908	}
1787		1909
1788	...	1910	...
1789	ev_stat passwd;	1911	ev_stat passwd;
1790		1912
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1913	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	1914	ev_stat_start (loop, &passwd);
1793		1915
1794	Example: Like above, but additionally use a one-second delay so we do not	1916	Example: Like above, but additionally use a one-second delay so we do not
1795	miss updates (however, frequent updates will delay processing, too, so	1917	miss updates (however, frequent updates will delay processing, too, so
1796	one might do the work both on C<ev_stat> callback invocation I<and> on	1918	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	1919	C<ev_timer> callback invocation).
1798		1920
1799	static ev_stat passwd;	1921	static ev_stat passwd;
1800	static ev_timer timer;	1922	static ev_timer timer;
1801		1923
1802	static void	1924	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	1925	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	1926	{
1805	ev_timer_stop (EV_A_ w);	1927	ev_timer_stop (EV_A_ w);
1806		1928
1807	/* now it's one second after the most recent passwd change */	1929	/* now it's one second after the most recent passwd change */
1808	}	1930	}
1809		1931
1810	static void	1932	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	1933	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	1934	{
1813	/* reset the one-second timer */	1935	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	1936	ev_timer_again (EV_A_ &timer);
1815	}	1937	}
1816		1938
1817	...	1939	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1940	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	1941	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	1942	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		1943
1822		1944
1823	=head2 C<ev_idle> - when you've got nothing better to do...	1945	=head2 C<ev_idle> - when you've got nothing better to do...
1824		1946
1825	Idle watchers trigger events when no other events of the same or higher	1947	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	1948	priority are pending (prepare, check and other idle watchers do not count
1827	count).	1949	as receiving "events").
1828		1950
1829	That is, as long as your process is busy handling sockets or timeouts	1951	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	1952	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	1953	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	1954	are pending), the idle watchers are being called once per event loop
…		…
1856	=head3 Examples	1978	=head3 Examples
1857		1979
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	1981	callback, free it. Also, use no error checking, as usual.
1860		1982
1861	static void	1983	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1863	{	1985	{
1864	free (w);	1986	free (w);
1865	// now do something you wanted to do when the program has	1987	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	1988	// no longer anything immediate to do.
1867	}	1989	}
1868		1990
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	1992	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	1993	ev_idle_start (loop, idle_cb);
1872		1994
1873		1995
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		1997
1876	Prepare and check watchers are usually (but not always) used in tandem:	1998	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	1999	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2000	afterwards.
1879		2001
1880	You I<must not> call C<ev_loop> or similar functions that enter	2002	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2003	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2006	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2007	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2008	called in pairs bracketing the blocking call.
1887		2009
1888	Their main purpose is to integrate other event mechanisms into libev and	2010	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2011	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2012	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2013	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2014	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2015	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2016	watcher).
1895		2017
1896	This is done by examining in each prepare call which file descriptors need	2018	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2019	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2020	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2021	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2022	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2023	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2024	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2025	nevertheless, because you never know, you know?).
1904		2026
1905	As another example, the Perl Coro module uses these hooks to integrate	2027	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2028	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2029	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2030	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2033	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2034	low-priority coroutines to idle/background tasks).
1913		2035
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2036	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2037	priority, to ensure that they are being run before any other watchers
		2038	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2039
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2041	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2042	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2043	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2044	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2046	others).
1923		2047
1924	=head3 Watcher-Specific Functions and Data Members	2048	=head3 Watcher-Specific Functions and Data Members
1925		2049
1926	=over 4	2050	=over 4
1927		2051
…		…
1929		2053
1930	=item ev_check_init (ev_check *, callback)	2054	=item ev_check_init (ev_check *, callback)
1931		2055
1932	Initialises and configures the prepare or check watcher - they have no	2056	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2057	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2058	macros, but using them is utterly, utterly, utterly and completely
		2059	pointless.
1935		2060
1936	=back	2061	=back
1937		2062
1938	=head3 Examples	2063	=head3 Examples
1939		2064
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2073	and in a check watcher, destroy them and call into libadns. What follows
1949	is pseudo-code only of course. This requires you to either use a low	2074	is pseudo-code only of course. This requires you to either use a low
1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2075	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1951	the callbacks for the IO/timeout watchers might not have been called yet.	2076	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2077
1953	static ev_io iow [nfd];	2078	static ev_io iow [nfd];
1954	static ev_timer tw;	2079	static ev_timer tw;
1955		2080
1956	static void	2081	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2082	io_cb (ev_loop *loop, ev_io *w, int revents)
1958	{	2083	{
1959	}	2084	}
1960		2085
1961	// create io watchers for each fd and a timer before blocking	2086	// create io watchers for each fd and a timer before blocking
1962	static void	2087	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1964	{	2089	{
1965	int timeout = 3600000;	2090	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2091	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2092	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2094
1970	/* the callback is illegal, but won't be called as we stop during check */	2095	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2096	ev_timer_init (&tw, 0, timeout * 1e-3);
1972	ev_timer_start (loop, &tw);	2097	ev_timer_start (loop, &tw);
1973		2098
1974	// create one ev_io per pollfd	2099	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2100	for (int i = 0; i < nfd; ++i)
1976	{	2101	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2102	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2103	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2104	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2105
1981	fds [i].revents = 0;	2106	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2107	ev_io_start (loop, iow + i);
1983	}	2108	}
1984	}	2109	}
1985		2110
1986	// stop all watchers after blocking	2111	// stop all watchers after blocking
1987	static void	2112	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1989	{	2114	{
1990	ev_timer_stop (loop, &tw);	2115	ev_timer_stop (loop, &tw);
1991		2116
1992	for (int i = 0; i < nfd; ++i)	2117	for (int i = 0; i < nfd; ++i)
1993	{	2118	{
1994	// set the relevant poll flags	2119	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2120	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2121	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2122	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2123	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2124	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2125
2001	// now stop the watcher	2126	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2127	ev_io_stop (loop, iow + i);
2003	}	2128	}
2004		2129
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2130	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2131	}
2007		2132
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2133	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
2009	in the prepare watcher and would dispose of the check watcher.	2134	in the prepare watcher and would dispose of the check watcher.
2010		2135
2011	Method 3: If the module to be embedded supports explicit event	2136	Method 3: If the module to be embedded supports explicit event
2012	notification (libadns does), you can also make use of the actual watcher	2137	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2138	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2139
2015	static void	2140	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2141	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2142	{
2018	adns_state ads = (adns_state)w->data;	2143	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2144	update_now (EV_A);
2020		2145
2021	adns_processtimeouts (ads, &tv_now);	2146	adns_processtimeouts (ads, &tv_now);
2022	}	2147	}
2023		2148
2024	static void	2149	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2150	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2151	{
2027	adns_state ads = (adns_state)w->data;	2152	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2153	update_now (EV_A);
2029		2154
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2155	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2156	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2157	}
2033		2158
2034	// do not ever call adns_afterpoll	2159	// do not ever call adns_afterpoll
2035		2160
2036	Method 4: Do not use a prepare or check watcher because the module you	2161	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2162	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2163	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2164	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2165	this approach, effectively embedding EV as a client into the horrible
		2166	libglib event loop.
2041		2167
2042	static gint	2168	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2169	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2170	{
2045	int got_events = 0;	2171	int got_events = 0;
2046		2172
2047	for (n = 0; n < nfds; ++n)	2173	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2174	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2175
2050	if (timeout >= 0)	2176	if (timeout >= 0)
2051	// create/start timer	2177	// create/start timer
2052		2178
2053	// poll	2179	// poll
2054	ev_loop (EV_A_ 0);	2180	ev_loop (EV_A_ 0);
2055		2181
2056	// stop timer again	2182	// stop timer again
2057	if (timeout >= 0)	2183	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2184	ev_timer_stop (EV_A_ &to);
2059		2185
2060	// stop io watchers again - their callbacks should have set	2186	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	2187	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	2188	ev_io_stop (EV_A_ iow [n]);
2063		2189
2064	return got_events;	2190	return got_events;
2065	}	2191	}
2066		2192
2067		2193
2068	=head2 C<ev_embed> - when one backend isn't enough...	2194	=head2 C<ev_embed> - when one backend isn't enough...
2069		2195
2070	This is a rather advanced watcher type that lets you embed one event loop	2196	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	2202	prioritise I/O.
2077		2203
2078	As an example for a bug workaround, the kqueue backend might only support	2204	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2205	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2206	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2207	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2208	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2209	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2210	C<kevent>, but at least you can use both mechanisms for what they are
		2211	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2212
2086	As for prioritising I/O: rarely you have the case where some fds have	2213	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2214	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2215	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2216	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2217	the rest in a second one, and embed the second one in the first.
2091		2218
2092	As long as the watcher is active, the callback will be invoked every time	2219	As long as the watcher is active, the callback will be invoked every time
2093	there might be events pending in the embedded loop. The callback must then	2220	there might be events pending in the embedded loop. The callback must then
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2095	their callbacks (you could also start an idle watcher to give the embedded	2222	their callbacks (you could also start an idle watcher to give the embedded
…		…
2103	interested in that.	2230	interested in that.
2104		2231
2105	Also, there have not currently been made special provisions for forking:	2232	Also, there have not currently been made special provisions for forking:
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2107	but you will also have to stop and restart any C<ev_embed> watchers	2234	but you will also have to stop and restart any C<ev_embed> watchers
2108	yourself.	2235	yourself - but you can use a fork watcher to handle this automatically,
		2236	and future versions of libev might do just that.
2109		2237
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2238	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2240	portable one.
2113		2241
2114	So when you want to use this feature you will always have to be prepared	2242	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2243	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2244	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2245	create it, and if that fails, use the normal loop for everything.
		2246
		2247	=head3 C<ev_embed> and fork
		2248
		2249	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2250	automatically be applied to the embedded loop as well, so no special
		2251	fork handling is required in that case. When the watcher is not running,
		2252	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2253	as applicable.
2118		2254
2119	=head3 Watcher-Specific Functions and Data Members	2255	=head3 Watcher-Specific Functions and Data Members
2120		2256
2121	=over 4	2257	=over 4
2122		2258
…		…
2148	event loop. If that is not possible, use the default loop. The default	2284	event loop. If that is not possible, use the default loop. The default
2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in	2285	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2287	used).
2152		2288
2153	struct ev_loop *loop_hi = ev_default_init (0);	2289	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2290	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2291	struct ev_embed embed;
2156		2292
2157	// see if there is a chance of getting one that works	2293	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2294	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	2297	: 0;
2162		2298
2163	// if we got one, then embed it, otherwise default to loop_hi	2299	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	2300	if (loop_lo)
2165	{	2301	{
2166	ev_embed_init (&embed, 0, loop_lo);	2302	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	2303	ev_embed_start (loop_hi, &embed);
2168	}	2304	}
2169	else	2305	else
2170	loop_lo = loop_hi;	2306	loop_lo = loop_hi;
2171		2307
2172	Example: Check if kqueue is available but not recommended and create	2308	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	2309	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2310	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2312
2177	struct ev_loop *loop = ev_default_init (0);	2313	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2314	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2315	struct ev_embed embed;
2180		2316
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2319	{
2184	ev_embed_init (&embed, 0, loop_socket);	2320	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	2321	ev_embed_start (loop, &embed);
2186	}	2322	}
2187		2323
2188	if (!loop_socket)	2324	if (!loop_socket)
2189	loop_socket = loop;	2325	loop_socket = loop;
2190		2326
2191	// now use loop_socket for all sockets, and loop for everything else	2327	// now use loop_socket for all sockets, and loop for everything else
2192		2328
2193		2329
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2330	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		2331
2196	Fork watchers are called when a C<fork ()> was detected (usually because	2332	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2376	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2377	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2378	need elaborate support such as pthreads.
2243		2379
2244	That means that if you want to queue data, you have to provide your own	2380	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2381	queue. But at least I can tell you how to implement locking around your
2246	queue:	2382	queue:
2247		2383
2248	=over 4	2384	=over 4
2249		2385
2250	=item queueing from a signal handler context	2386	=item queueing from a signal handler context
2251		2387
2252	To implement race-free queueing, you simply add to the queue in the signal	2388	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2389	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2390	an example that does that for some fictitious SIGUSR1 handler:
2255		2391
2256	static ev_async mysig;	2392	static ev_async mysig;
2257		2393
2258	static void	2394	static void
2259	sigusr1_handler (void)	2395	sigusr1_handler (void)
…		…
2326		2462
2327	=item ev_async_init (ev_async *, callback)	2463	=item ev_async_init (ev_async *, callback)
2328		2464
2329	Initialises and configures the async watcher - it has no parameters of any	2465	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2331	believe me.	2467	trust me.
2332		2468
2333	=item ev_async_send (loop, ev_async *)	2469	=item ev_async_send (loop, ev_async *)
2334		2470
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	2473	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2475	section below on what exactly this means).
2340		2476
2341	This call incurs the overhead of a system call only once per loop iteration,	2477	This call incurs the overhead of a system call only once per loop iteration,
2342	so while the overhead might be noticeable, it doesn't apply to repeated	2478	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2521	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	2522	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2524	value passed to C<ev_once>:
2389		2525
2390	static void stdin_ready (int revents, void *arg)	2526	static void stdin_ready (int revents, void *arg)
2391	{	2527	{
2392	if (revents & EV_TIMEOUT)	2528	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;	2529	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	2530	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	2531	/* stdin might have data for us, joy! */;
2396	}	2532	}
2397		2533
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2535
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2536	=item ev_feed_event (ev_loop *, watcher *, int revents)
2401		2537
2402	Feeds the given event set into the event loop, as if the specified event	2538	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an	2539	had happened for the specified watcher (which must be a pointer to an
…		…
2452	you to use some convenience methods to start/stop watchers and also change	2588	you to use some convenience methods to start/stop watchers and also change
2453	the callback model to a model using method callbacks on objects.	2589	the callback model to a model using method callbacks on objects.
2454		2590
2455	To use it,	2591	To use it,
2456		2592
2457	#include <ev++.h>	2593	#include <ev++.h>
2458		2594
2459	This automatically includes F<ev.h> and puts all of its definitions (many	2595	This automatically includes F<ev.h> and puts all of its definitions (many
2460	of them macros) into the global namespace. All C++ specific things are	2596	of them macros) into the global namespace. All C++ specific things are
2461	put into the C<ev> namespace. It should support all the same embedding	2597	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2598	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	2665	your compiler is good :), then the method will be fully inlined into the
2530	thunking function, making it as fast as a direct C callback.	2666	thunking function, making it as fast as a direct C callback.
2531		2667
2532	Example: simple class declaration and watcher initialisation	2668	Example: simple class declaration and watcher initialisation
2533		2669
2534	struct myclass	2670	struct myclass
2535	{	2671	{
2536	void io_cb (ev::io &w, int revents) { }	2672	void io_cb (ev::io &w, int revents) { }
2537	}	2673	}
2538		2674
2539	myclass obj;	2675	myclass obj;
2540	ev::io iow;	2676	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	2677	iow.set <myclass, &myclass::io_cb> (&obj);
2542		2678
2543	=item w->set<function> (void *data = 0)	2679	=item w->set<function> (void *data = 0)
2544		2680
2545	Also sets a callback, but uses a static method or plain function as	2681	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	2682	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		2684
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2685	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		2686
2551	See the method-C<set> above for more details.	2687	See the method-C<set> above for more details.
2552		2688
2553	Example:	2689	Example: Use a plain function as callback.
2554		2690
2555	static void io_cb (ev::io &w, int revents) { }	2691	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	2692	iow.set <io_cb> ();
2557		2693
2558	=item w->set (struct ev_loop *)	2694	=item w->set (struct ev_loop *)
2559		2695
2560	Associates a different C<struct ev_loop> with this watcher. You can only	2696	Associates a different C<struct ev_loop> with this watcher. You can only
2561	do this when the watcher is inactive (and not pending either).	2697	do this when the watcher is inactive (and not pending either).
…		…
2594	=back	2730	=back
2595		2731
2596	Example: Define a class with an IO and idle watcher, start one of them in	2732	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	2733	the constructor.
2598		2734
2599	class myclass	2735	class myclass
2600	{	2736	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	2737	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	2738	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		2739
2604	myclass (int fd)	2740	myclass (int fd)
2605	{	2741	{
2606	io .set <myclass, &myclass::io_cb > (this);	2742	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	2743	idle.set <myclass, &myclass::idle_cb> (this);
2608		2744
2609	io.start (fd, ev::READ);	2745	io.start (fd, ev::READ);
2610	}	2746	}
2611	};	2747	};
2612		2748
2613		2749
2614	=head1 OTHER LANGUAGE BINDINGS	2750	=head1 OTHER LANGUAGE BINDINGS
2615		2751
2616	Libev does not offer other language bindings itself, but bindings for a	2752	Libev does not offer other language bindings itself, but bindings for a
…		…
2623	=item Perl	2759	=item Perl
2624		2760
2625	The EV module implements the full libev API and is actually used to test	2761	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	2762	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	2763	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2764	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2765	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2766	and C<EV::Glib>).
2630		2767
2631	It can be found and installed via CPAN, its homepage is found at	2768	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	2769	L<http://software.schmorp.de/pkg/EV>.
		2770
		2771	=item Python
		2772
		2773	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2774	seems to be quite complete and well-documented. Note, however, that the
		2775	patch they require for libev is outright dangerous as it breaks the ABI
		2776	for everybody else, and therefore, should never be applied in an installed
		2777	libev (if python requires an incompatible ABI then it needs to embed
		2778	libev).
2633		2779
2634	=item Ruby	2780	=item Ruby
2635		2781
2636	Tony Arcieri has written a ruby extension that offers access to a subset	2782	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds file handle abstractions, asynchronous DNS and	2783	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
2639	L<http://rev.rubyforge.org/>.	2785	L<http://rev.rubyforge.org/>.
2640		2786
2641	=item D	2787	=item D
2642		2788
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2645		2791
2646	=back	2792	=back
2647		2793
2648		2794
2649	=head1 MACRO MAGIC	2795	=head1 MACRO MAGIC
…		…
2661		2807
2662	This provides the loop I<argument> for functions, if one is required ("ev	2808	This provides the loop I<argument> for functions, if one is required ("ev
2663	loop argument"). The C<EV_A> form is used when this is the sole argument,	2809	loop argument"). The C<EV_A> form is used when this is the sole argument,
2664	C<EV_A_> is used when other arguments are following. Example:	2810	C<EV_A_> is used when other arguments are following. Example:
2665		2811
2666	ev_unref (EV_A);	2812	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	2813	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	2814	ev_loop (EV_A_ 0);
2669		2815
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2816	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	2817	which is often provided by the following macro.
2672		2818
2673	=item C<EV_P>, C<EV_P_>	2819	=item C<EV_P>, C<EV_P_>
2674		2820
2675	This provides the loop I<parameter> for functions, if one is required ("ev	2821	This provides the loop I<parameter> for functions, if one is required ("ev
2676	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2822	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2677	C<EV_P_> is used when other parameters are following. Example:	2823	C<EV_P_> is used when other parameters are following. Example:
2678		2824
2679	// this is how ev_unref is being declared	2825	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	2826	static void ev_unref (EV_P);
2681		2827
2682	// this is how you can declare your typical callback	2828	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	2829	static void cb (EV_P_ ev_timer *w, int revents)
2684		2830
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2831	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	2832	suitable for use with C<EV_A>.
2687		2833
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2834	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		2850
2705	Example: Declare and initialise a check watcher, utilising the above	2851	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	2852	macros so it will work regardless of whether multiple loops are supported
2707	or not.	2853	or not.
2708		2854
2709	static void	2855	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	2856	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	2857	{
2712	ev_check_stop (EV_A_ w);	2858	ev_check_stop (EV_A_ w);
2713	}	2859	}
2714		2860
2715	ev_check check;	2861	ev_check check;
2716	ev_check_init (&check, check_cb);	2862	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	2863	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	2864	ev_loop (EV_DEFAULT_ 0);
2719		2865
2720	=head1 EMBEDDING	2866	=head1 EMBEDDING
2721		2867
2722	Libev can (and often is) directly embedded into host	2868	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	2869	applications. Examples of applications that embed it include the Deliantra
…		…
2737	=head3 CORE EVENT LOOP	2883	=head3 CORE EVENT LOOP
2738		2884
2739	To include only the libev core (all the C<ev_*> functions), with manual	2885	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	2886	configuration (no autoconf):
2741		2887
2742	#define EV_STANDALONE 1	2888	#define EV_STANDALONE 1
2743	#include "ev.c"	2889	#include "ev.c"
2744		2890
2745	This will automatically include F<ev.h>, too, and should be done in a	2891	This will automatically include F<ev.h>, too, and should be done in a
2746	single C source file only to provide the function implementations. To use	2892	single C source file only to provide the function implementations. To use
2747	it, do the same for F<ev.h> in all files wishing to use this API (best	2893	it, do the same for F<ev.h> in all files wishing to use this API (best
2748	done by writing a wrapper around F<ev.h> that you can include instead and	2894	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	2895	where you can put other configuration options):
2750		2896
2751	#define EV_STANDALONE 1	2897	#define EV_STANDALONE 1
2752	#include "ev.h"	2898	#include "ev.h"
2753		2899
2754	Both header files and implementation files can be compiled with a C++	2900	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	2901	compiler (at least, thats a stated goal, and breakage will be treated
2756	as a bug).	2902	as a bug).
2757		2903
2758	You need the following files in your source tree, or in a directory	2904	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	2905	in your include path (e.g. in libev/ when using -Ilibev):
2760		2906
2761	ev.h	2907	ev.h
2762	ev.c	2908	ev.c
2763	ev_vars.h	2909	ev_vars.h
2764	ev_wrap.h	2910	ev_wrap.h
2765		2911
2766	ev_win32.c required on win32 platforms only	2912	ev_win32.c required on win32 platforms only
2767		2913
2768	ev_select.c only when select backend is enabled (which is enabled by default)	2914	ev_select.c only when select backend is enabled (which is enabled by default)
2769	ev_poll.c only when poll backend is enabled (disabled by default)	2915	ev_poll.c only when poll backend is enabled (disabled by default)
2770	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2916	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2771	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2917	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2772	ev_port.c only when the solaris port backend is enabled (disabled by default)	2918	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		2919
2774	F<ev.c> includes the backend files directly when enabled, so you only need	2920	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	2921	to compile this single file.
2776		2922
2777	=head3 LIBEVENT COMPATIBILITY API	2923	=head3 LIBEVENT COMPATIBILITY API
2778		2924
2779	To include the libevent compatibility API, also include:	2925	To include the libevent compatibility API, also include:
2780		2926
2781	#include "event.c"	2927	#include "event.c"
2782		2928
2783	in the file including F<ev.c>, and:	2929	in the file including F<ev.c>, and:
2784		2930
2785	#include "event.h"	2931	#include "event.h"
2786		2932
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	2933	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		2934
2789	You need the following additional files for this:	2935	You need the following additional files for this:
2790		2936
2791	event.h	2937	event.h
2792	event.c	2938	event.c
2793		2939
2794	=head3 AUTOCONF SUPPORT	2940	=head3 AUTOCONF SUPPORT
2795		2941
2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in	2942	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2797	whatever way you want, you can also C<m4_include([libev.m4])> in your	2943	whatever way you want, you can also C<m4_include([libev.m4])> in your
2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2944	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	2945	include F<config.h> and configure itself accordingly.
2800		2946
2801	For this of course you need the m4 file:	2947	For this of course you need the m4 file:
2802		2948
2803	libev.m4	2949	libev.m4
2804		2950
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	2951	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		2952
2807	Libev can be configured via a variety of preprocessor symbols you have to	2953	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absence of	2954	define before including any of its files. The default in the absence of
2809	autoconf is noted for every option.	2955	autoconf is documented for every option.
2810		2956
2811	=over 4	2957	=over 4
2812		2958
2813	=item EV_STANDALONE	2959	=item EV_STANDALONE
2814		2960
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3130	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	3131	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	3132	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3133	fine.
2988		3134
2989	If your embedding application does not need any priorities, defining these both to	3135	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3136	both to C<0> will save some memory and CPU.
2991		3137
2992	=item EV_PERIODIC_ENABLE	3138	=item EV_PERIODIC_ENABLE
2993		3139
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3140	If undefined or defined to be C<1>, then periodic timers are supported. If
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	3141	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3002	code.	3148	code.
3003		3149
3004	=item EV_EMBED_ENABLE	3150	=item EV_EMBED_ENABLE
3005		3151
3006	If undefined or defined to be C<1>, then embed watchers are supported. If	3152	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.	3153	defined to be C<0>, then they are not. Embed watchers rely on most other
		3154	watcher types, which therefore must not be disabled.
3008		3155
3009	=item EV_STAT_ENABLE	3156	=item EV_STAT_ENABLE
3010		3157
3011	If undefined or defined to be C<1>, then stat watchers are supported. If	3158	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.	3159	defined to be C<0>, then they are not.
…		…
3044	two).	3191	two).
3045		3192
3046	=item EV_USE_4HEAP	3193	=item EV_USE_4HEAP
3047		3194
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3196	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	3197	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	3198	faster performance with many (thousands) of watchers.
3052		3199
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3200	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3054	(disabled).	3201	(disabled).
3055		3202
3056	=item EV_HEAP_CACHE_AT	3203	=item EV_HEAP_CACHE_AT
3057		3204
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3205	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	3206	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3207	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3208	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	3209	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	3210	noticeably with many (hundreds) of watchers.
3064		3211
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3066	(disabled).	3213	(disabled).
3067		3214
3068	=item EV_VERIFY	3215	=item EV_VERIFY
…		…
3074	called once per loop, which can slow down libev. If set to C<3>, then the	3221	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	3222	verification code will be called very frequently, which will slow down
3076	libev considerably.	3223	libev considerably.
3077		3224
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3225	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3079	C<0.>	3226	C<0>.
3080		3227
3081	=item EV_COMMON	3228	=item EV_COMMON
3082		3229
3083	By default, all watchers have a C<void *data> member. By redefining	3230	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	3231	this macro to a something else you can include more and other types of
3085	members. You have to define it each time you include one of the files,	3232	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	3233	though, and it must be identical each time.
3087		3234
3088	For example, the perl EV module uses something like this:	3235	For example, the perl EV module uses something like this:
3089		3236
3090	#define EV_COMMON \	3237	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	3238	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	3239	SV *cb_sv, *fh /* note no trailing ";" */
3093		3240
3094	=item EV_CB_DECLARE (type)	3241	=item EV_CB_DECLARE (type)
3095		3242
3096	=item EV_CB_INVOKE (watcher, revents)	3243	=item EV_CB_INVOKE (watcher, revents)
3097		3244
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	3249	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	3250	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3251	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	3252	method calls instead of plain function calls in C++.
3106		3253
		3254	=back
		3255
3107	=head2 EXPORTED API SYMBOLS	3256	=head2 EXPORTED API SYMBOLS
3108		3257
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	3258	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	3259	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	3260	all public symbols, one per line:
3112		3261
3113	Symbols.ev for libev proper	3262	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	3263	Symbols.event for the libevent emulation
3115		3264
3116	This can also be used to rename all public symbols to avoid clashes with	3265	This can also be used to rename all public symbols to avoid clashes with
3117	multiple versions of libev linked together (which is obviously bad in	3266	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvenient to avoid this).	3267	itself, but sometimes it is inconvenient to avoid this).
3119		3268
…		…
3140	file.	3289	file.
3141		3290
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3291	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3143	that everybody includes and which overrides some configure choices:	3292	that everybody includes and which overrides some configure choices:
3144		3293
3145	#define EV_MINIMAL 1	3294	#define EV_MINIMAL 1
3146	#define EV_USE_POLL 0	3295	#define EV_USE_POLL 0
3147	#define EV_MULTIPLICITY 0	3296	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	3297	#define EV_PERIODIC_ENABLE 0
3149	#define EV_STAT_ENABLE 0	3298	#define EV_STAT_ENABLE 0
3150	#define EV_FORK_ENABLE 0	3299	#define EV_FORK_ENABLE 0
3151	#define EV_CONFIG_H <config.h>	3300	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0	3301	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0	3302	#define EV_MAXPRI 0
3154		3303
3155	#include "ev++.h"	3304	#include "ev++.h"
3156		3305
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3306	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		3307
3159	#include "ev_cpp.h"	3308	#include "ev_cpp.h"
3160	#include "ev.c"	3309	#include "ev.c"
3161		3310
		3311	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		3312
3163	=head1 THREADS AND COROUTINES	3313	=head2 THREADS AND COROUTINES
3164		3314
3165	=head2 THREADS	3315	=head3 THREADS
3166		3316
3167	Libev itself is completely thread-safe, but it uses no locking. This	3317	All libev functions are reentrant and thread-safe unless explicitly
		3318	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	3319	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	3320	are no concurrent calls into any libev function with the same loop
3170	parameter.	3321	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3322	of course): libev guarantees that different event loops share no data
		3323	structures that need any locking.
3171		3324
3172	Or put differently: calls with different loop parameters can be done in	3325	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	3326	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	3327	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	3328	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	3329	a mutex per loop).
3177		3330
3178	If you want to know which design is best for your problem, then I cannot	3331	Specifically to support threads (and signal handlers), libev implements
		3332	so-called C<ev_async> watchers, which allow some limited form of
		3333	concurrency on the same event loop, namely waking it up "from the
		3334	outside".
		3335
		3336	If you want to know which design (one loop, locking, or multiple loops
		3337	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	3338	help you, but here is some generic advice:
3180		3339
3181	=over 4	3340	=over 4
3182		3341
3183	=item * most applications have a main thread: use the default libev loop	3342	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a separate thread running only the default loop.	3343	in that thread, or create a separate thread running only the default loop.
…		…
3196		3355
3197	Choosing a model is hard - look around, learn, know that usually you can do	3356	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	3357	better than you currently do :-)
3199		3358
3200	=item * often you need to talk to some other thread which blocks in the	3359	=item * often you need to talk to some other thread which blocks in the
		3360	event loop.
		3361
3201	event loop - C<ev_async> watchers can be used to wake them up from other	3362	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	3363	(or from signal contexts...).
		3364
		3365	An example use would be to communicate signals or other events that only
		3366	work in the default loop by registering the signal watcher with the
		3367	default loop and triggering an C<ev_async> watcher from the default loop
		3368	watcher callback into the event loop interested in the signal.
3203		3369
3204	=back	3370	=back
3205		3371
3206	=head2 COROUTINES	3372	=head3 COROUTINES
3207		3373
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	3374	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	3375	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3376	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	3377	different coroutines, and switch freely between both coroutines running the
3212	loop, as long as you don't confuse yourself). The only exception is that	3378	loop, as long as you don't confuse yourself). The only exception is that
3213	you must not do this from C<ev_periodic> reschedule callbacks.	3379	you must not do this from C<ev_periodic> reschedule callbacks.
3214		3380
3215	Care has been invested into making sure that libev does not keep local	3381	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	3382	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	3383	they do not clal any callbacks.
3218		3384
		3385	=head2 COMPILER WARNINGS
3219		3386
3220	=head1 COMPLEXITIES	3387	Depending on your compiler and compiler settings, you might get no or a
		3388	lot of warnings when compiling libev code. Some people are apparently
		3389	scared by this.
3221		3390
3222	In this section the complexities of (many of) the algorithms used inside	3391	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	3392	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	3393	warning options. "Warn-free" code therefore cannot be a goal except when
		3394	targeting a specific compiler and compiler-version.
3225		3395
3226	All of the following are about amortised time: If an array needs to be	3396	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	3397	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	3398	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		3399
3232	=over 4	3400	And of course, some compiler warnings are just plain stupid, or simply
		3401	wrong (because they don't actually warn about the condition their message
		3402	seems to warn about). For example, certain older gcc versions had some
		3403	warnings that resulted an extreme number of false positives. These have
		3404	been fixed, but some people still insist on making code warn-free with
		3405	such buggy versions.
3233		3406
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3407	While libev is written to generate as few warnings as possible,
		3408	"warn-free" code is not a goal, and it is recommended not to build libev
		3409	with any compiler warnings enabled unless you are prepared to cope with
		3410	them (e.g. by ignoring them). Remember that warnings are just that:
		3411	warnings, not errors, or proof of bugs.
3235		3412
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		3413
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3414	=head2 VALGRIND
3241		3415
3242	That means that changing a timer costs less than removing/adding them	3416	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	3417	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		3418
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3419	If you think you found a bug (memory leak, uninitialised data access etc.)
		3420	in libev, then check twice: If valgrind reports something like:
3246		3421
3247	These just add the watcher into an array or at the head of a list.	3422	==2274== definitely lost: 0 bytes in 0 blocks.
		3423	==2274== possibly lost: 0 bytes in 0 blocks.
		3424	==2274== still reachable: 256 bytes in 1 blocks.
3248		3425
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3426	Then there is no memory leak, just as memory accounted to global variables
		3427	is not a memleak - the memory is still being refernced, and didn't leak.
3250		3428
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3429	Similarly, under some circumstances, valgrind might report kernel bugs
		3430	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3431	although an acceptable workaround has been found here), or it might be
		3432	confused.
3252		3433
3253	These watchers are stored in lists then need to be walked to find the	3434	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	3435	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		3436
3257	=item Finding the next timer in each loop iteration: O(1)	3437	If you are unsure about something, feel free to contact the mailing list
		3438	with the full valgrind report and an explanation on why you think this
		3439	is a bug in libev (best check the archives, too :). However, don't be
		3440	annoyed when you get a brisk "this is no bug" answer and take the chance
		3441	of learning how to interpret valgrind properly.
3258		3442
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	3443	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	3444	I suggest using suppression lists.
3261		3445
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		3446
3264	A change means an I/O watcher gets started or stopped, which requires	3447	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and whether C<ev_io_set> was used).
3267		3448
3268	=item Activating one watcher (putting it into the pending state): O(1)
3269
3270	=item Priority handling: O(number_of_priorities)
3271
3272	Priorities are implemented by allocating some space for each
3273	priority. When doing priority-based operations, libev usually has to
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276
3277	=item Sending an ev_async: O(1)
3278
3279	=item Processing ev_async_send: O(number_of_async_watchers)
3280
3281	=item Processing signals: O(max_signal_number)
3282
3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
3284	calls in the current loop iteration. Checking for async and signal events
3285	involves iterating over all running async watchers or all signal numbers.
3286
3287	=back
3288
3289
3290	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3449	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3291		3450
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3451	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	3452	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	3453	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3454	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3306		3465
3307	Not a libev limitation but worth mentioning: windows apparently doesn't	3466	Not a libev limitation but worth mentioning: windows apparently doesn't
3308	accept large writes: instead of resulting in a partial write, windows will	3467	accept large writes: instead of resulting in a partial write, windows will
3309	either accept everything or return C<ENOBUFS> if the buffer is too large,	3468	either accept everything or return C<ENOBUFS> if the buffer is too large,
3310	so make sure you only write small amounts into your sockets (less than a	3469	so make sure you only write small amounts into your sockets (less than a
3311	megabyte seems safe, but thsi apparently depends on the amount of memory	3470	megabyte seems safe, but this apparently depends on the amount of memory
3312	available).	3471	available).
3313		3472
3314	Due to the many, low, and arbitrary limits on the win32 platform and	3473	Due to the many, low, and arbitrary limits on the win32 platform and
3315	the abysmal performance of winsockets, using a large number of sockets	3474	the abysmal performance of winsockets, using a large number of sockets
3316	is not recommended (and not reasonable). If your program needs to use	3475	is not recommended (and not reasonable). If your program needs to use
3317	more than a hundred or so sockets, then likely it needs to use a totally	3476	more than a hundred or so sockets, then likely it needs to use a totally
3318	different implementation for windows, as libev offers the POSIX readiness	3477	different implementation for windows, as libev offers the POSIX readiness
3319	notification model, which cannot be implemented efficiently on windows	3478	notification model, which cannot be implemented efficiently on windows
3320	(Microsoft monopoly games).	3479	(Microsoft monopoly games).
3321		3480
		3481	A typical way to use libev under windows is to embed it (see the embedding
		3482	section for details) and use the following F<evwrap.h> header file instead
		3483	of F<ev.h>:
		3484
		3485	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3486	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3487
		3488	#include "ev.h"
		3489
		3490	And compile the following F<evwrap.c> file into your project (make sure
		3491	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3492
		3493	#include "evwrap.h"
		3494	#include "ev.c"
		3495
3322	=over 4	3496	=over 4
3323		3497
3324	=item The winsocket select function	3498	=item The winsocket select function
3325		3499
3326	The winsocket C<select> function doesn't follow POSIX in that it	3500	The winsocket C<select> function doesn't follow POSIX in that it
3327	requires socket I<handles> and not socket I<file descriptors> (it is	3501	requires socket I<handles> and not socket I<file descriptors> (it is
3328	also extremely buggy). This makes select very inefficient, and also	3502	also extremely buggy). This makes select very inefficient, and also
3329	requires a mapping from file descriptors to socket handles. See the	3503	requires a mapping from file descriptors to socket handles (the Microsoft
		3504	C runtime provides the function C<_open_osfhandle> for this). See the
3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	3505	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	3506	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3332		3507
3333	The configuration for a "naked" win32 using the Microsoft runtime	3508	The configuration for a "naked" win32 using the Microsoft runtime
3334	libraries and raw winsocket select is:	3509	libraries and raw winsocket select is:
3335		3510
3336	#define EV_USE_SELECT 1	3511	#define EV_USE_SELECT 1
3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3512	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3338		3513
3339	Note that winsockets handling of fd sets is O(n), so you can easily get a	3514	Note that winsockets handling of fd sets is O(n), so you can easily get a
3340	complexity in the O(n²) range when using win32.	3515	complexity in the O(n²) range when using win32.
3341		3516
3342	=item Limited number of file descriptors	3517	=item Limited number of file descriptors
…		…
3366	wrap all I/O functions and provide your own fd management, but the cost of	3541	wrap all I/O functions and provide your own fd management, but the cost of
3367	calling select (O(n²)) will likely make this unworkable.	3542	calling select (O(n²)) will likely make this unworkable.
3368		3543
3369	=back	3544	=back
3370		3545
3371
3372	=head1 PORTABILITY REQUIREMENTS	3546	=head2 PORTABILITY REQUIREMENTS
3373		3547
3374	In addition to a working ISO-C implementation, libev relies on a few	3548	In addition to a working ISO-C implementation and of course the
3375	additional extensions:	3549	backend-specific APIs, libev relies on a few additional extensions:
3376		3550
3377	=over 4	3551	=over 4
3378		3552
		3553	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3554	calling conventions regardless of C<ev_watcher_type *>.
		3555
		3556	Libev assumes not only that all watcher pointers have the same internal
		3557	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3558	assumes that the same (machine) code can be used to call any watcher
		3559	callback: The watcher callbacks have different type signatures, but libev
		3560	calls them using an C<ev_watcher *> internally.
		3561
3379	=item C<sig_atomic_t volatile> must be thread-atomic as well	3562	=item C<sig_atomic_t volatile> must be thread-atomic as well
3380		3563
3381	The type C<sig_atomic_t volatile> (or whatever is defined as	3564	The type C<sig_atomic_t volatile> (or whatever is defined as
3382	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3565	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3383	threads. This is not part of the specification for C<sig_atomic_t>, but is	3566	threads. This is not part of the specification for C<sig_atomic_t>, but is
3384	believed to be sufficiently portable.	3567	believed to be sufficiently portable.
3385		3568
3386	=item C<sigprocmask> must work in a threaded environment	3569	=item C<sigprocmask> must work in a threaded environment
3387		3570
…		…
3396	except the initial one, and run the default loop in the initial thread as	3579	except the initial one, and run the default loop in the initial thread as
3397	well.	3580	well.
3398		3581
3399	=item C<long> must be large enough for common memory allocation sizes	3582	=item C<long> must be large enough for common memory allocation sizes
3400		3583
3401	To improve portability and simplify using libev, libev uses C<long>	3584	To improve portability and simplify its API, libev uses C<long> internally
3402	internally instead of C<size_t> when allocating its data structures. On	3585	instead of C<size_t> when allocating its data structures. On non-POSIX
3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3586	systems (Microsoft...) this might be unexpectedly low, but is still at
3404	is still at least 31 bits everywhere, which is enough for hundreds of	3587	least 31 bits everywhere, which is enough for hundreds of millions of
3405	millions of watchers.	3588	watchers.
3406		3589
3407	=item C<double> must hold a time value in seconds with enough accuracy	3590	=item C<double> must hold a time value in seconds with enough accuracy
3408		3591
3409	The type C<double> is used to represent timestamps. It is required to	3592	The type C<double> is used to represent timestamps. It is required to
3410	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3593	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3414	=back	3597	=back
3415		3598
3416	If you know of other additional requirements drop me a note.	3599	If you know of other additional requirements drop me a note.
3417		3600
3418		3601
3419	=head1 COMPILER WARNINGS	3602	=head1 ALGORITHMIC COMPLEXITIES
3420		3603
3421	Depending on your compiler and compiler settings, you might get no or a	3604	In this section the complexities of (many of) the algorithms used inside
3422	lot of warnings when compiling libev code. Some people are apparently	3605	libev will be documented. For complexity discussions about backends see
3423	scared by this.	3606	the documentation for C<ev_default_init>.
3424		3607
3425	However, these are unavoidable for many reasons. For one, each compiler	3608	All of the following are about amortised time: If an array needs to be
3426	has different warnings, and each user has different tastes regarding	3609	extended, libev needs to realloc and move the whole array, but this
3427	warning options. "Warn-free" code therefore cannot be a goal except when	3610	happens asymptotically rarer with higher number of elements, so O(1) might
3428	targeting a specific compiler and compiler-version.	3611	mean that libev does a lengthy realloc operation in rare cases, but on
		3612	average it is much faster and asymptotically approaches constant time.
3429		3613
3430	Another reason is that some compiler warnings require elaborate	3614	=over 4
3431	workarounds, or other changes to the code that make it less clear and less
3432	maintainable.
3433		3615
3434	And of course, some compiler warnings are just plain stupid, or simply	3616	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3435	wrong (because they don't actually warn about the condition their message
3436	seems to warn about).
3437		3617
3438	While libev is written to generate as few warnings as possible,	3618	This means that, when you have a watcher that triggers in one hour and
3439	"warn-free" code is not a goal, and it is recommended not to build libev	3619	there are 100 watchers that would trigger before that, then inserting will
3440	with any compiler warnings enabled unless you are prepared to cope with	3620	have to skip roughly seven (C<ld 100>) of these watchers.
3441	them (e.g. by ignoring them). Remember that warnings are just that:
3442	warnings, not errors, or proof of bugs.
3443		3621
		3622	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3444		3623
3445	=head1 VALGRIND	3624	That means that changing a timer costs less than removing/adding them,
		3625	as only the relative motion in the event queue has to be paid for.
3446		3626
3447	Valgrind has a special section here because it is a popular tool that is	3627	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3448	highly useful, but valgrind reports are very hard to interpret.
3449		3628
3450	If you think you found a bug (memory leak, uninitialised data access etc.)	3629	These just add the watcher into an array or at the head of a list.
3451	in libev, then check twice: If valgrind reports something like:
3452		3630
3453	==2274== definitely lost: 0 bytes in 0 blocks.	3631	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3454	==2274== possibly lost: 0 bytes in 0 blocks.
3455	==2274== still reachable: 256 bytes in 1 blocks.
3456		3632
3457	Then there is no memory leak. Similarly, under some circumstances,	3633	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3458	valgrind might report kernel bugs as if it were a bug in libev, or it
3459	might be confused (it is a very good tool, but only a tool).
3460		3634
3461	If you are unsure about something, feel free to contact the mailing list	3635	These watchers are stored in lists, so they need to be walked to find the
3462	with the full valgrind report and an explanation on why you think this is	3636	correct watcher to remove. The lists are usually short (you don't usually
3463	a bug in libev. However, don't be annoyed when you get a brisk "this is	3637	have many watchers waiting for the same fd or signal: one is typical, two
3464	no bug" answer and take the chance of learning how to interpret valgrind	3638	is rare).
3465	properly.
3466		3639
3467	If you need, for some reason, empty reports from valgrind for your project	3640	=item Finding the next timer in each loop iteration: O(1)
3468	I suggest using suppression lists.	3641
		3642	By virtue of using a binary or 4-heap, the next timer is always found at a
		3643	fixed position in the storage array.
		3644
		3645	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3646
		3647	A change means an I/O watcher gets started or stopped, which requires
		3648	libev to recalculate its status (and possibly tell the kernel, depending
		3649	on backend and whether C<ev_io_set> was used).
		3650
		3651	=item Activating one watcher (putting it into the pending state): O(1)
		3652
		3653	=item Priority handling: O(number_of_priorities)
		3654
		3655	Priorities are implemented by allocating some space for each
		3656	priority. When doing priority-based operations, libev usually has to
		3657	linearly search all the priorities, but starting/stopping and activating
		3658	watchers becomes O(1) with respect to priority handling.
		3659
		3660	=item Sending an ev_async: O(1)
		3661
		3662	=item Processing ev_async_send: O(number_of_async_watchers)
		3663
		3664	=item Processing signals: O(max_signal_number)
		3665
		3666	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3667	calls in the current loop iteration. Checking for async and signal events
		3668	involves iterating over all running async watchers or all signal numbers.
		3669
		3670	=back
3469		3671
3470		3672
3471	=head1 AUTHOR	3673	=head1 AUTHOR
3472		3674
3473	Marc Lehmann <libev@schmorp.de>.	3675	Marc Lehmann <libev@schmorp.de>.

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