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Revision 1.166 by root, Tue Jun 3 03:48:10 2008 UTC vs.
Revision 1.204 by root, Mon Oct 27 11:08:29 2008 UTC

…		…
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_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	363	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	364	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	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	366	readiness notifications you get per iteration.
363		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
		371
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		373
366	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	375	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	376	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,	377	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	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	379	performance tips.
		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
372		383
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		385
375	For few fds, this backend is a bit little slower than poll and select,	386	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	387	but it scales phenomenally better. While poll and select usually scale
…		…
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	389	epoll scales either O(1) or O(active_fds). The epoll design has a number
379	of shortcomings, such as silently dropping events in some hard-to-detect	390	of shortcomings, such as silently dropping events in some hard-to-detect
380	cases and requiring a system call per fd change, no fork support and bad	391	cases and requiring a system call per fd change, no fork support and bad
381	support for dup.	392	support for dup.
382		393
		394	Epoll is also notoriously buggy - embedding epoll fds should work, but
		395	of course doesn't, and epoll just loves to report events for totally
		396	I<different> file descriptors (even already closed ones) than registered
		397	in the set (especially on SMP systems). Libev tries to counter these
		398	spurious notifications by employing an additional generation counter and
		399	comparing that against the events to filter out spurious ones.
		400
383	While stopping, setting and starting an I/O watcher in the same iteration	401	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	402	will result in some caching, there is still a system call per such incident
385	(because the fd could point to a different file description now), so its	403	(because the fd could point to a different file description now), so its
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	404	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
387	very well if you register events for both fds.	405	very well if you register events for both fds.
388		406
389	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
391	(or space) is available.
392
393	Best performance from this backend is achieved by not unregistering all	407	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.	408	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	409	i.e. keep at least one watcher active per fd at all times. Stopping and
		410	starting a watcher (without re-setting it) also usually doesn't cause
		411	extra overhead.
396		412
397	While nominally embeddable in other event loops, this feature is broken in	413	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	414	all kernel versions tested so far.
399		415
		416	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		417	C<EVBACKEND_POLL>.
		418
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	419	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		420
402	Kqueue deserves special mention, as at the time of this writing, it	421	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	422	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	423	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"	424	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	425	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)	426	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
408	system like NetBSD.
409		427
410	You still can embed kqueue into a normal poll or select backend and use it	428	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	429	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.	430	the target platform). See C<ev_embed> watchers for more info.
413		431
414	It scales in the same way as the epoll backend, but the interface to the	432	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	433	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	434	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	435	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	436	two event changes per incident. Support for C<fork ()> is very bad and it
419	drops fds silently in similarly hard-to-detect cases.	437	drops fds silently in similarly hard-to-detect cases.
420		438
421	This backend usually performs well under most conditions.	439	This backend usually performs well under most conditions.
422		440
423	While nominally embeddable in other event loops, this doesn't work	441	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	442	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	443	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	444	(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	445	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	446	using it only for sockets.
		447
		448	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		449	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		450	C<NOTE_EOF>.
429		451
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	452	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		453
432	This is not implemented yet (and might never be, unless you send me an	454	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	455	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	468	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	469	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	470	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	471	might perform better.
450		472
451	On the positive side, ignoring the spurious readiness notifications, this	473	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	474	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	475	in all tests and is fully embeddable, which is a rare feat among the
		476	OS-specific backends.
		477
		478	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		479	C<EVBACKEND_POLL>.
454		480
455	=item C<EVBACKEND_ALL>	481	=item C<EVBACKEND_ALL>
456		482
457	Try all backends (even potentially broken ones that wouldn't be tried	483	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	484	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		490
465	If one or more of these are or'ed into the flags value, then only these	491	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	492	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.	493	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		494
469	The most typical usage is like this:	495	Example: This is the most typical usage.
470		496
471	if (!ev_default_loop (0))	497	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	498	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		499
474	Restrict libev to the select and poll backends, and do not allow	500	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	501	environment settings to be taken into account:
476		502
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	503	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		504
479	Use whatever libev has to offer, but make sure that kqueue is used if	505	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	506	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):	507	private event loop and only if you know the OS supports your types of
		508	fds):
482		509
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	510	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		511
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	512	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		513
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	534	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	535	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	536	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	537	for example).
511		538
512	Note that certain global state, such as signal state, will not be freed by	539	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	540	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	541	as signal and child watchers) would need to be stopped manually.
515		542
516	In general it is not advisable to call this function except in the	543	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	544	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	545	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	546	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		571
545	=item ev_loop_fork (loop)	572	=item ev_loop_fork (loop)
546		573
547	Like C<ev_default_fork>, but acts on an event loop created by	574	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	575	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.	576	after fork that you want to re-use in the child, and how you do this is
		577	entirely your own problem.
550		578
551	=item int ev_is_default_loop (loop)	579	=item int ev_is_default_loop (loop)
552		580
553	Returns true when the given loop actually is the default loop, false otherwise.	581	Returns true when the given loop is, in fact, the default loop, and false
		582	otherwise.
554		583
555	=item unsigned int ev_loop_count (loop)	584	=item unsigned int ev_loop_count (loop)
556		585
557	Returns the count of loop iterations for the loop, which is identical to	586	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	587	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	602	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	603	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	604	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).	605	event occurring (or more correctly, libev finding out about it).
577		606
		607	=item ev_now_update (loop)
		608
		609	Establishes the current time by querying the kernel, updating the time
		610	returned by C<ev_now ()> in the progress. This is a costly operation and
		611	is usually done automatically within C<ev_loop ()>.
		612
		613	This function is rarely useful, but when some event callback runs for a
		614	very long time without entering the event loop, updating libev's idea of
		615	the current time is a good idea.
		616
		617	See also "The special problem of time updates" in the C<ev_timer> section.
		618
578	=item ev_loop (loop, int flags)	619	=item ev_loop (loop, int flags)
579		620
580	Finally, this is it, the event handler. This function usually is called	621	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	622	after you initialised all your watchers and you want to start handling
582	events.	623	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	625	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.	626	either no event watchers are active anymore or C<ev_unloop> was called.
586		627
587	Please note that an explicit C<ev_unloop> is usually better than	628	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	629	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	630	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	631	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.	632	of relying on its watchers stopping correctly, that is truly a thing of
		633	beauty.
592		634
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	635	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	636	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.	637	process in case there are no events and will return after one iteration of
		638	the loop.
596		639
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	640	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	641	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	642	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	643	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	644	user-registered callback will be called), and will return after one
		645	iteration of the loop.
		646
		647	This is useful if you are waiting for some external event in conjunction
		648	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	649	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.	650	usually a better approach for this kind of thing.
604		651
605	Here are the gory details of what C<ev_loop> does:	652	Here are the gory details of what C<ev_loop> does:
606		653
607	- Before the first iteration, call any pending watchers.	654	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	655	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	656	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	657	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	658	- If we have been forked, detach and recreate the kernel state
		659	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	660	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	661	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	662	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	663	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	664	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	665	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	666	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	667	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	668	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	669	- Queue all expired timers.
622	- Queue all outstanding periodics.	670	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	671	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	672	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	673	- 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	674	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	675	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	676	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	681	anymore.
634		682
635	... queue jobs here, make sure they register event watchers as long	683	... 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..)	684	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	685	ev_loop (my_loop, 0);
638	... jobs done. yeah!	686	... jobs done or somebody called unloop. yeah!
639		687
640	=item ev_unloop (loop, how)	688	=item ev_unloop (loop, how)
641		689
642	Can be used to make a call to C<ev_loop> return early (but only after it	690	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	691	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	692	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	693	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		694
647	This "unloop state" will be cleared when entering C<ev_loop> again.	695	This "unloop state" will be cleared when entering C<ev_loop> again.
648		696
		697	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		698
649	=item ev_ref (loop)	699	=item ev_ref (loop)
650		700
651	=item ev_unref (loop)	701	=item ev_unref (loop)
652		702
653	Ref/unref can be used to add or remove a reference count on the event	703	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	704	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	705	count is nonzero, C<ev_loop> will not return on its own.
		706
656	a watcher you never unregister that should not keep C<ev_loop> from	707	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	708	from returning, call ev_unref() after starting, and ev_ref() before
		709	stopping it.
		710
658	example, libev itself uses this for its internal signal pipe: It is not	711	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	712	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	713	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	714	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>	715	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,	716	(but only if the watcher wasn't active before, or was active before,
664	respectively).	717	respectively).
665		718
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	719	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	720	running when nothing else is active.
668		721
669	struct ev_signal exitsig;	722	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	723	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	724	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	725	evf_unref (loop);
673		726
674	Example: For some weird reason, unregister the above signal handler again.	727	Example: For some weird reason, unregister the above signal handler again.
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	732	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		733
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	734	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		735
683	These advanced functions influence the time that libev will spend waiting	736	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	737	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.	738	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		739	latency.
686		740
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	741	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	742	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	743	to increase efficiency of loop iterations (or to increase power-saving
		744	opportunities).
690		745
691	The background is that sometimes your program runs just fast enough to	746	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	747	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	748	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	749	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	750	overhead for the actual polling but can deliver many events at once.
696		751
697	By setting a higher I<io collect interval> you allow libev to spend more	752	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,	753	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	755	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.	756	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		757
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	758	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	759	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	760	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	761	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	762	value will not introduce any overhead in libev.
708		763
709	Many (busy) programs can usually benefit by setting the I/O collect	764	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	765	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	766	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>,	767	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.	768	as this approaches the timing granularity of most systems.
714		769
		770	Setting the I<timeout collect interval> can improve the opportunity for
		771	saving power, as the program will "bundle" timer callback invocations that
		772	are "near" in time together, by delaying some, thus reducing the number of
		773	times the process sleeps and wakes up again. Another useful technique to
		774	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		775	they fire on, say, one-second boundaries only.
		776
715	=item ev_loop_verify (loop)	777	=item ev_loop_verify (loop)
716		778
717	This function only does something when C<EV_VERIFY> support has been	779	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	780	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	781	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	782	is found to be inconsistent, it will print an error message to standard
		783	error and call C<abort ()>.
721		784
722	This can be used to catch bugs inside libev itself: under normal	785	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	786	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	787	data structures consistent.
725		788
726	=back	789	=back
727		790
728		791
729	=head1 ANATOMY OF A WATCHER	792	=head1 ANATOMY OF A WATCHER
730		793
		794	In the following description, uppercase C<TYPE> in names stands for the
		795	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		796	watchers and C<ev_io_start> for I/O watchers.
		797
731	A watcher is a structure that you create and register to record your	798	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	799	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:	800	become readable, you would create an C<ev_io> watcher for that:
734		801
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	802	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	803	{
737	ev_io_stop (w);	804	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	805	ev_unloop (loop, EVUNLOOP_ALL);
739	}	806	}
740		807
741	struct ev_loop *loop = ev_default_loop (0);	808	struct ev_loop *loop = ev_default_loop (0);
		809
742	struct ev_io stdin_watcher;	810	ev_io stdin_watcher;
		811
743	ev_init (&stdin_watcher, my_cb);	812	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	813	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	814	ev_io_start (loop, &stdin_watcher);
		815
746	ev_loop (loop, 0);	816	ev_loop (loop, 0);
747		817
748	As you can see, you are responsible for allocating the memory for your	818	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,	819	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	820	stack).
		821
		822	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		823	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		824
752	Each watcher structure must be initialised by a call to C<ev_init	825	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	826	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	827	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	828	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	829	is readable and/or writable).
757		830
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	831	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	832	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	833	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	834	ev_TYPE_init (watcher *, callback, ...) >>.
762		835
763	To make the watcher actually watch out for events, you have to start it	836	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	837	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	838	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	839	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		840
768	As long as your watcher is active (has been started but not stopped) you	841	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	842	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	843	reinitialise it or call its C<ev_TYPE_set> macro.
771		844
772	Each and every callback receives the event loop pointer as first, the	845	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	846	registered watcher structure as second, and a bitset of received events as
774	third argument.	847	third argument.
775		848
…		…
838	=item C<EV_ERROR>	911	=item C<EV_ERROR>
839		912
840	An unspecified error has occurred, the watcher has been stopped. This might	913	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	914	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	915	ran out of memory, a file descriptor was found to be closed or any other
		916	problem. Libev considers these application bugs.
		917
843	problem. You best act on it by reporting the problem and somehow coping	918	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	919	watcher being stopped. Note that well-written programs should not receive
		920	an error ever, so when your watcher receives it, this usually indicates a
		921	bug in your program.
845		922
846	Libev will usually signal a few "dummy" events together with an error,	923	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	924	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	925	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	926	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	927	programs, though, as the fd could already be closed and reused for another
		928	thing, so beware.
851		929
852	=back	930	=back
853		931
854	=head2 GENERIC WATCHER FUNCTIONS	932	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		933
859	=over 4	934	=over 4
860		935
861	=item C<ev_init> (ev_TYPE *watcher, callback)	936	=item C<ev_init> (ev_TYPE *watcher, callback)
862		937
…		…
868	which rolls both calls into one.	943	which rolls both calls into one.
869		944
870	You can reinitialise a watcher at any time as long as it has been stopped	945	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	946	(or never started) and there are no pending events outstanding.
872		947
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	948	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	949	int revents)>.
		950
		951	Example: Initialise an C<ev_io> watcher in two steps.
		952
		953	ev_io w;
		954	ev_init (&w, my_cb);
		955	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		956
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	957	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		958
878	This macro initialises the type-specific parts of a watcher. You need to	959	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	960	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	963	difference to the C<ev_init> macro).
883		964
884	Although some watcher types do not have type-specific arguments	965	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.	966	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		967
		968	See C<ev_init>, above, for an example.
		969
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	970	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		971
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	972	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	973	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	974	a watcher. The same limitations apply, of course.
892		975
		976	Example: Initialise and set an C<ev_io> watcher in one step.
		977
		978	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		979
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	980	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		981
895	Starts (activates) the given watcher. Only active watchers will receive	982	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	983	events. If the watcher is already active nothing will happen.
897		984
		985	Example: Start the C<ev_io> watcher that is being abused as example in this
		986	whole section.
		987
		988	ev_io_start (EV_DEFAULT_UC, &w);
		989
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	990	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		991
900	Stops the given watcher again (if active) and clears the pending	992	Stops the given watcher if active, and clears the pending status (whether
		993	the watcher was active or not).
		994
901	status. It is possible that stopped watchers are pending (for example,	995	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	996	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	997	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	998	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	999	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1000
907	=item bool ev_is_active (ev_TYPE *watcher)	1001	=item bool ev_is_active (ev_TYPE *watcher)
908		1002
909	Returns a true value iff the watcher is active (i.e. it has been started	1003	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1004	and not yet been stopped). As long as a watcher is active you must not modify
…		…
952	The default priority used by watchers when no priority has been set is	1046	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1047	always C<0>, which is supposed to not be too high and not be too low :).
954		1048
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1049	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
956	fine, as long as you do not mind that the priority value you query might	1050	fine, as long as you do not mind that the priority value you query might
957	or might not have been adjusted to be within valid range.	1051	or might not have been clamped to the valid range.
958		1052
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1053	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1054
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1055	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	1056	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1057	can deal with that fact, as both are simply passed through to the
		1058	callback.
964		1059
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1060	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1061
967	If the watcher is pending, this function returns clears its pending status	1062	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	1063	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>.	1064	watcher isn't pending it does nothing and returns C<0>.
970		1065
		1066	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1067	callback to be invoked, which can be accomplished with this function.
		1068
971	=back	1069	=back
972		1070
973		1071
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1072	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1073
976	Each watcher has, by default, a member C<void *data> that you can change	1074	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	1075	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	1076	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	1077	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	1078	member, you can also "subclass" the watcher type and provide your own
981	data:	1079	data:
982		1080
983	struct my_io	1081	struct my_io
984	{	1082	{
985	struct ev_io io;	1083	ev_io io;
986	int otherfd;	1084	int otherfd;
987	void *somedata;	1085	void *somedata;
988	struct whatever *mostinteresting;	1086	struct whatever *mostinteresting;
989	}	1087	};
		1088
		1089	...
		1090	struct my_io w;
		1091	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1092
991	And since your callback will be called with a pointer to the watcher, you	1093	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1094	can cast it back to your own type:
993		1095
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1096	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1097	{
996	struct my_io *w = (struct my_io *)w_;	1098	struct my_io *w = (struct my_io *)w_;
997	...	1099	...
998	}	1100	}
999		1101
1000	More interesting and less C-conformant ways of casting your callback type	1102	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1103	instead have been omitted.
1002		1104
1003	Another common scenario is having some data structure with multiple	1105	Another common scenario is to use some data structure with multiple
1004	watchers:	1106	embedded watchers:
1005		1107
1006	struct my_biggy	1108	struct my_biggy
1007	{	1109	{
1008	int some_data;	1110	int some_data;
1009	ev_timer t1;	1111	ev_timer t1;
1010	ev_timer t2;	1112	ev_timer t2;
1011	}	1113	}
1012		1114
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1115	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1116	complicated: Either you store the address of your C<my_biggy> struct
		1117	in the C<data> member of the watcher (for woozies), or you need to use
		1118	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1119	programmers):
1015		1120
1016	#include <stddef.h>	1121	#include <stddef.h>
1017		1122
1018	static void	1123	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1124	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1125	{
1021	struct my_biggy big = (struct my_biggy *	1126	struct my_biggy big = (struct my_biggy *
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1127	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1128	}
1024		1129
1025	static void	1130	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1131	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1132	{
1028	struct my_biggy big = (struct my_biggy *	1133	struct my_biggy big = (struct my_biggy *
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1134	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1135	}
1031		1136
…		…
1059	In general you can register as many read and/or write event watchers per	1164	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	1165	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	1166	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1167	required if you know what you are doing).
1063		1168
1064	If you must do this, then force the use of a known-to-be-good backend	1169	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	1170	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1171	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1172
1068	Another thing you have to watch out for is that it is quite easy to	1173	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	1174	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	1175	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	1176	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	1177	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	1178	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	1179	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.	1180	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1181
1077	If you cannot run the fd in non-blocking mode (for example you should not	1182	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	1183	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	1184	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	1185	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1186	does this on its own, so its quite safe to use). Some people additionally
		1187	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1188	indefinitely.
		1189
		1190	But really, best use non-blocking mode.
1082		1191
1083	=head3 The special problem of disappearing file descriptors	1192	=head3 The special problem of disappearing file descriptors
1084		1193
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1194	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,	1195	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	1196	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	1197	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	1198	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	1199	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1200	fact, a different file descriptor.
1092		1201
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1232	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1233	C<EVBACKEND_POLL>.
1125		1234
1126	=head3 The special problem of SIGPIPE	1235	=head3 The special problem of SIGPIPE
1127		1236
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1237	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	1238	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	1239	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1240	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1241
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1242	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	1243	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).	1244	somewhere, as that would have given you a big clue).
1137		1245
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1251	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1252
1145	=item ev_io_set (ev_io *, int fd, int events)	1253	=item ev_io_set (ev_io *, int fd, int events)
1146		1254
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1255	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	1256	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.	1257	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1258
1151	=item int fd [read-only]	1259	=item int fd [read-only]
1152		1260
1153	The file descriptor being watched.	1261	The file descriptor being watched.
1154		1262
…		…
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1271	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	1272	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1273	attempt to read a whole line in the callback.
1166		1274
1167	static void	1275	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1276	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1277	{
1170	ev_io_stop (loop, w);	1278	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1279	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1280	}
1173		1281
1174	...	1282	...
1175	struct ev_loop *loop = ev_default_init (0);	1283	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1284	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1285	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1286	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1287	ev_loop (loop, 0);
1180		1288
1181		1289
…		…
1184	Timer watchers are simple relative timers that generate an event after a	1292	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1293	given time, and optionally repeating in regular intervals after that.
1186		1294
1187	The timers are based on real time, that is, if you register an event that	1295	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	1296	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	1297	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1298	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1299	monotonic clock option helps a lot here).
		1300
		1301	The callback is guaranteed to be invoked only I<after> its timeout has
		1302	passed, but if multiple timers become ready during the same loop iteration
		1303	then order of execution is undefined.
		1304
		1305	=head3 Be smart about timeouts
		1306
		1307	Many real-world problems involve some kind of timeout, usually for error
		1308	recovery. A typical example is an HTTP request - if the other side hangs,
		1309	you want to raise some error after a while.
		1310
		1311	What follows are some ways to handle this problem, from obvious and
		1312	inefficient to smart and efficient.
		1313
		1314	In the following, a 60 second activity timeout is assumed - a timeout that
		1315	gets reset to 60 seconds each time there is activity (e.g. each time some
		1316	data or other life sign was received).
		1317
		1318	=over 4
		1319
		1320	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1321
		1322	This is the most obvious, but not the most simple way: In the beginning,
		1323	start the watcher:
		1324
		1325	ev_timer_init (timer, callback, 60., 0.);
		1326	ev_timer_start (loop, timer);
		1327
		1328	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1329	and start it again:
		1330
		1331	ev_timer_stop (loop, timer);
		1332	ev_timer_set (timer, 60., 0.);
		1333	ev_timer_start (loop, timer);
		1334
		1335	This is relatively simple to implement, but means that each time there is
		1336	some activity, libev will first have to remove the timer from its internal
		1337	data structure and then add it again. Libev tries to be fast, but it's
		1338	still not a constant-time operation.
		1339
		1340	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1341
		1342	This is the easiest way, and involves using C<ev_timer_again> instead of
		1343	C<ev_timer_start>.
		1344
		1345	To implement this, configure an C<ev_timer> with a C<repeat> value
		1346	of C<60> and then call C<ev_timer_again> at start and each time you
		1347	successfully read or write some data. If you go into an idle state where
		1348	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1349	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1350
		1351	That means you can ignore both the C<ev_timer_start> function and the
		1352	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1353	member and C<ev_timer_again>.
		1354
		1355	At start:
		1356
		1357	ev_timer_init (timer, callback);
		1358	timer->repeat = 60.;
		1359	ev_timer_again (loop, timer);
		1360
		1361	Each time there is some activity:
		1362
		1363	ev_timer_again (loop, timer);
		1364
		1365	It is even possible to change the time-out on the fly, regardless of
		1366	whether the watcher is active or not:
		1367
		1368	timer->repeat = 30.;
		1369	ev_timer_again (loop, timer);
		1370
		1371	This is slightly more efficient then stopping/starting the timer each time
		1372	you want to modify its timeout value, as libev does not have to completely
		1373	remove and re-insert the timer from/into its internal data structure.
		1374
		1375	It is, however, even simpler than the "obvious" way to do it.
		1376
		1377	=item 3. Let the timer time out, but then re-arm it as required.
		1378
		1379	This method is more tricky, but usually most efficient: Most timeouts are
		1380	relatively long compared to the intervals between other activity - in
		1381	our example, within 60 seconds, there are usually many I/O events with
		1382	associated activity resets.
		1383
		1384	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1385	but remember the time of last activity, and check for a real timeout only
		1386	within the callback:
		1387
		1388	ev_tstamp last_activity; // time of last activity
		1389
		1390	static void
		1391	callback (EV_P_ ev_timer *w, int revents)
		1392	{
		1393	ev_tstamp now = ev_now (EV_A);
		1394	ev_tstamp timeout = last_activity + 60.;
		1395
		1396	// if last_activity + 60. is older than now, we did time out
		1397	if (timeout < now)
		1398	{
		1399	// timeout occured, take action
		1400	}
		1401	else
		1402	{
		1403	// callback was invoked, but there was some activity, re-arm
		1404	// the watcher to fire in last_activity + 60, which is
		1405	// guaranteed to be in the future, so "again" is positive:
		1406	w->again = timeout - now;
		1407	ev_timer_again (EV_A_ w);
		1408	}
		1409	}
		1410
		1411	To summarise the callback: first calculate the real timeout (defined
		1412	as "60 seconds after the last activity"), then check if that time has
		1413	been reached, which means something I<did>, in fact, time out. Otherwise
		1414	the callback was invoked too early (C<timeout> is in the future), so
		1415	re-schedule the timer to fire at that future time, to see if maybe we have
		1416	a timeout then.
		1417
		1418	Note how C<ev_timer_again> is used, taking advantage of the
		1419	C<ev_timer_again> optimisation when the timer is already running.
		1420
		1421	This scheme causes more callback invocations (about one every 60 seconds
		1422	minus half the average time between activity), but virtually no calls to
		1423	libev to change the timeout.
		1424
		1425	To start the timer, simply initialise the watcher and set C<last_activity>
		1426	to the current time (meaning we just have some activity :), then call the
		1427	callback, which will "do the right thing" and start the timer:
		1428
		1429	ev_timer_init (timer, callback);
		1430	last_activity = ev_now (loop);
		1431	callback (loop, timer, EV_TIMEOUT);
		1432
		1433	And when there is some activity, simply store the current time in
		1434	C<last_activity>, no libev calls at all:
		1435
		1436	last_actiivty = ev_now (loop);
		1437
		1438	This technique is slightly more complex, but in most cases where the
		1439	time-out is unlikely to be triggered, much more efficient.
		1440
		1441	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1442	callback :) - just change the timeout and invoke the callback, which will
		1443	fix things for you.
		1444
		1445	=item 4. Wee, just use a double-linked list for your timeouts.
		1446
		1447	If there is not one request, but many thousands (millions...), all
		1448	employing some kind of timeout with the same timeout value, then one can
		1449	do even better:
		1450
		1451	When starting the timeout, calculate the timeout value and put the timeout
		1452	at the I<end> of the list.
		1453
		1454	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1455	the list is expected to fire (for example, using the technique #3).
		1456
		1457	When there is some activity, remove the timer from the list, recalculate
		1458	the timeout, append it to the end of the list again, and make sure to
		1459	update the C<ev_timer> if it was taken from the beginning of the list.
		1460
		1461	This way, one can manage an unlimited number of timeouts in O(1) time for
		1462	starting, stopping and updating the timers, at the expense of a major
		1463	complication, and having to use a constant timeout. The constant timeout
		1464	ensures that the list stays sorted.
		1465
		1466	=back
		1467
		1468	So which method the best?
		1469
		1470	Method #2 is a simple no-brain-required solution that is adequate in most
		1471	situations. Method #3 requires a bit more thinking, but handles many cases
		1472	better, and isn't very complicated either. In most case, choosing either
		1473	one is fine, with #3 being better in typical situations.
		1474
		1475	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1476	rather complicated, but extremely efficient, something that really pays
		1477	off after the first million or so of active timers, i.e. it's usually
		1478	overkill :)
		1479
		1480	=head3 The special problem of time updates
		1481
		1482	Establishing the current time is a costly operation (it usually takes at
		1483	least two system calls): EV therefore updates its idea of the current
		1484	time only before and after C<ev_loop> collects new events, which causes a
		1485	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1486	lots of events in one iteration.
1192		1487
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1488	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	1489	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	1490	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	1491	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:	1492	timeout on the current time, use something like this to adjust for this:
1198		1493
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1494	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1495
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1496	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	1497	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1498	()>.
1204		1499
1205	=head3 Watcher-Specific Functions and Data Members	1500	=head3 Watcher-Specific Functions and Data Members
1206		1501
1207	=over 4	1502	=over 4
1208		1503
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1527	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1528
1234	If the timer is repeating, either start it if necessary (with the	1529	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1530	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1531
1237	This sounds a bit complicated, but here is a useful and typical	1532	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1533	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246
1247	That means you can ignore the C<after> value and C<ev_timer_start>
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249
1250	ev_timer_init (timer, callback, 0., 5.);
1251	ev_timer_again (loop, timer);
1252	...
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258
1259	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.
1261		1534
1262	=item ev_tstamp repeat [read-write]	1535	=item ev_tstamp repeat [read-write]
1263		1536
1264	The current C<repeat> value. Will be used each time the watcher times out	1537	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),	1538	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.	1539	which is also when any modifications are taken into account.
1267		1540
1268	=back	1541	=back
1269		1542
1270	=head3 Examples	1543	=head3 Examples
1271		1544
1272	Example: Create a timer that fires after 60 seconds.	1545	Example: Create a timer that fires after 60 seconds.
1273		1546
1274	static void	1547	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1548	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1549	{
1277	.. one minute over, w is actually stopped right here	1550	.. one minute over, w is actually stopped right here
1278	}	1551	}
1279		1552
1280	struct ev_timer mytimer;	1553	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1554	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1555	ev_timer_start (loop, &mytimer);
1283		1556
1284	Example: Create a timeout timer that times out after 10 seconds of	1557	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1558	inactivity.
1286		1559
1287	static void	1560	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1561	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1562	{
1290	.. ten seconds without any activity	1563	.. ten seconds without any activity
1291	}	1564	}
1292		1565
1293	struct ev_timer mytimer;	1566	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1567	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1568	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1569	ev_loop (loop, 0);
1297		1570
1298	// and in some piece of code that gets executed on any "activity":	1571	// and in some piece of code that gets executed on any "activity":
…		…
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger	1587	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).	1588	roughly 10 seconds later as it uses a relative timeout).
1316		1589
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1590	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	1591	such as triggering an event on each "midnight, local time", or other
1319	complicated, rules.	1592	complicated rules.
1320		1593
1321	As with timers, the callback is guaranteed to be invoked only when the	1594	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	1595	time (C<at>) has passed, but if multiple periodic timers become ready
1323	during the same loop iteration then order of execution is undefined.	1596	during the same loop iteration, then order of execution is undefined.
1324		1597
1325	=head3 Watcher-Specific Functions and Data Members	1598	=head3 Watcher-Specific Functions and Data Members
1326		1599
1327	=over 4	1600	=over 4
1328		1601
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1602	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1330		1603
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1604	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1332		1605
1333	Lots of arguments, lets sort it out... There are basically three modes of	1606	Lots of arguments, lets sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1607	operation, and we will explain them from simplest to most complex:
1335		1608
1336	=over 4	1609	=over 4
1337		1610
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1611	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1339		1612
1340	In this configuration the watcher triggers an event after the wall clock	1613	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	1614	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	1615	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.	1616	only run when the system clock reaches or surpasses this time.
1344		1617
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1618	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1346		1619
1347	In this mode the watcher will always be scheduled to time out at the next	1620	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)	1621	C<at + N * interval> time (for some integer N, which can also be negative)
1349	and then repeat, regardless of any time jumps.	1622	and then repeat, regardless of any time jumps.
1350		1623
1351	This can be used to create timers that do not drift with respect to system	1624	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	1625	system clock, for example, here is a C<ev_periodic> that triggers each
1353	the hour:	1626	hour, on the hour:
1354		1627
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1628	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1629
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1630	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	1631	but only that the callback will be called when the system time shows a
…		…
1384		1657
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1658	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1659	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1660	only event loop modification you are allowed to do).
1388		1661
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1662	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1663	*w, ev_tstamp now)>, e.g.:
1391		1664
		1665	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1666	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1667	{
1394	return now + 60.;	1668	return now + 60.;
1395	}	1669	}
1396		1670
1397	It must return the next time to trigger, based on the passed time value	1671	It must return the next time to trigger, based on the passed time value
…		…
1434		1708
1435	The current interval value. Can be modified any time, but changes only	1709	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	1710	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1711	called.
1438		1712
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1713	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1714
1441	The current reschedule callback, or C<0>, if this functionality is	1715	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	1716	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	1717	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1718
1445	=back	1719	=back
1446		1720
1447	=head3 Examples	1721	=head3 Examples
1448		1722
1449	Example: Call a callback every hour, or, more precisely, whenever the	1723	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1724	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1725	potentially a lot of jitter, but good long-term stability.
1452		1726
1453	static void	1727	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1728	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1729	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1730	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1731	}
1458		1732
1459	struct ev_periodic hourly_tick;	1733	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1734	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1735	ev_periodic_start (loop, &hourly_tick);
1462		1736
1463	Example: The same as above, but use a reschedule callback to do it:	1737	Example: The same as above, but use a reschedule callback to do it:
1464		1738
1465	#include <math.h>	1739	#include <math.h>
1466		1740
1467	static ev_tstamp	1741	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1742	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	1743	{
1470	return fmod (now, 3600.) + 3600.;	1744	return now + (3600. - fmod (now, 3600.));
1471	}	1745	}
1472		1746
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1747	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1748
1475	Example: Call a callback every hour, starting now:	1749	Example: Call a callback every hour, starting now:
1476		1750
1477	struct ev_periodic hourly_tick;	1751	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1752	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1753	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1754	ev_periodic_start (loop, &hourly_tick);
1481		1755
1482		1756
…		…
1485	Signal watchers will trigger an event when the process receives a specific	1759	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	1760	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	1761	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1762	normal event processing, like any other event.
1489		1763
		1764	If you want signals asynchronously, just use C<sigaction> as you would
		1765	do without libev and forget about sharing the signal. You can even use
		1766	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1767
1490	You can configure as many watchers as you like per signal. Only when the	1768	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	1769	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	1770	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	1771	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	1772	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1773	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1774
1497	If possible and supported, libev will install its handlers with	1775	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1776	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	1777	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	1778	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1795
1518	=back	1796	=back
1519		1797
1520	=head3 Examples	1798	=head3 Examples
1521		1799
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1800	Example: Try to exit cleanly on SIGINT.
1523		1801
1524	static void	1802	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1803	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	1804	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1805	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1806	}
1529		1807
1530	struct ev_signal signal_watcher;	1808	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1809	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1810	ev_signal_start (loop, &signal_watcher);
1533		1811
1534		1812
1535	=head2 C<ev_child> - watch out for process status changes	1813	=head2 C<ev_child> - watch out for process status changes
1536		1814
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1815	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	1816	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	1817	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	1818	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	1819	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1820	forking and then immediately registering a watcher for the child is fine,
		1821	but forking and registering a watcher a few event loop iterations later is
		1822	not.
1542		1823
1543	Only the default event loop is capable of handling signals, and therefore	1824	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	1825	you can only register child watchers in the default event loop.
1545		1826
1546	=head3 Process Interaction	1827	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	1840	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	1841	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	1842	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	1843	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.	1844	that, so other libev users can use C<ev_child> watchers freely.
		1845
		1846	=head3 Stopping the Child Watcher
		1847
		1848	Currently, the child watcher never gets stopped, even when the
		1849	child terminates, so normally one needs to stop the watcher in the
		1850	callback. Future versions of libev might stop the watcher automatically
		1851	when a child exit is detected.
1564		1852
1565	=head3 Watcher-Specific Functions and Data Members	1853	=head3 Watcher-Specific Functions and Data Members
1566		1854
1567	=over 4	1855	=over 4
1568		1856
…		…
1600	its completion.	1888	its completion.
1601		1889
1602	ev_child cw;	1890	ev_child cw;
1603		1891
1604	static void	1892	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	1893	child_cb (EV_P_ ev_child *w, int revents)
1606	{	1894	{
1607	ev_child_stop (EV_A_ w);	1895	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1896	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	1897	}
1610		1898
…		…
1637	the stat buffer having unspecified contents.	1925	the stat buffer having unspecified contents.
1638		1926
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	1927	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.	1928	relative and your working directory changes, the behaviour is undefined.
1641		1929
1642	Since there is no standard to do this, the portable implementation simply	1930	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	1931	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	1932	it changed somehow. You can specify a recommended polling interval for
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	1933	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	1934	then a I<suitable, unspecified default> value will be used (which
1647	five seconds, although this might change dynamically). Libev will also	1935	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	1936	dynamically). Libev will also impose a minimum interval which is currently
1649	usually overkill.	1937	around C<0.1>, but thats usually overkill.
1650		1938
1651	This watcher type is not meant for massive numbers of stat watchers,	1939	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	1940	as even with OS-supported change notifications, this can be
1653	resource-intensive.	1941	resource-intensive.
1654		1942
1655	At the time of this writing, only the Linux inotify interface is	1943	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	1944	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	1945	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	1946	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		1947
1664	=head3 ABI Issues (Largefile Support)	1948	=head3 ABI Issues (Largefile Support)
1665		1949
1666	Libev by default (unless the user overrides this) uses the default	1950	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	1951	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	1952	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	1953	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	1954	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	1955	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	1956	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	1957	most noticeably disabled with ev_stat and large file support.
1674		1958
1675	=head3 Inotify	1959	The solution for this is to lobby your distribution maker to make large
		1960	file interfaces available by default (as e.g. FreeBSD does) and not
		1961	optional. Libev cannot simply switch on large file support because it has
		1962	to exchange stat structures with application programs compiled using the
		1963	default compilation environment.
1676		1964
		1965	=head3 Inotify and Kqueue
		1966
1677	When C<inotify (7)> support has been compiled into libev (generally only	1967	When C<inotify (7)> support has been compiled into libev (generally
		1968	only available with Linux 2.6.25 or above due to bugs in earlier
1678	available on Linux) and present at runtime, it will be used to speed up	1969	implementations) and present at runtime, it will be used to speed up
1679	change detection where possible. The inotify descriptor will be created lazily	1970	change detection where possible. The inotify descriptor will be created
1680	when the first C<ev_stat> watcher is being started.	1971	lazily when the first C<ev_stat> watcher is being started.
1681		1972
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	1973	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	1974	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	1975	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.	1976	there are many cases where libev has to resort to regular C<stat> polling,
		1977	but as long as the path exists, libev usually gets away without polling.
1686		1978
1687	(There is no support for kqueue, as apparently it cannot be used to	1979	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	1980	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	1981	descriptor open on the object at all times, and detecting renames, unlinks
		1982	etc. is difficult.
1690		1983
1691	=head3 The special problem of stat time resolution	1984	=head3 The special problem of stat time resolution
1692		1985
1693	The C<stat ()> system call only supports full-second resolution portably, and	1986	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	1987	even on systems where the resolution is higher, most file systems still
1695	only support whole seconds.	1988	only support whole seconds.
1696		1989
1697	That means that, if the time is the only thing that changes, you can	1990	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	1991	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	1992	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	1993	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	1994	stat data does change in other ways (e.g. file size).
1702		1995
1703	The solution to this is to delay acting on a change for slightly more	1996	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	1997	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);	1998	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	1999	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2019	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	2020	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	2021	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.	2022	path for as long as the watcher is active.
1730		2023
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2024	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	2025	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2026	last change was detected).
1734		2027
1735	=item ev_stat_stat (loop, ev_stat *)	2028	=item ev_stat_stat (loop, ev_stat *)
1736		2029
1737	Updates the stat buffer immediately with new values. If you change the	2030	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	2031	watched path in your callback, you could call this function to avoid
…		…
1821		2114
1822		2115
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2116	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2117
1825	Idle watchers trigger events when no other events of the same or higher	2118	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	2119	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2120	as receiving "events").
1828		2121
1829	That is, as long as your process is busy handling sockets or timeouts	2122	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	2123	(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	2124	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	2125	are pending), the idle watchers are being called once per event loop
…		…
1857		2150
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2151	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2152	callback, free it. Also, use no error checking, as usual.
1860		2153
1861	static void	2154	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2155	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2156	{
1864	free (w);	2157	free (w);
1865	// now do something you wanted to do when the program has	2158	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2159	// no longer anything immediate to do.
1867	}	2160	}
1868		2161
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2162	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2163	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2164	ev_idle_start (loop, idle_cb);
1872		2165
1873		2166
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2167	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2168
1876	Prepare and check watchers are usually (but not always) used in tandem:	2169	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2170	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2171	afterwards.
1879		2172
1880	You I<must not> call C<ev_loop> or similar functions that enter	2173	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>	2174	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,	2177	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	2178	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2179	called in pairs bracketing the blocking call.
1887		2180
1888	Their main purpose is to integrate other event mechanisms into libev and	2181	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	2182	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	2183	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2184	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,	2185	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>	2186	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2187	watcher).
1895		2188
1896	This is done by examining in each prepare call which file descriptors need	2189	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	2190	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	2191	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	2192	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2193	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	2194	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,	2195	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2196	nevertheless, because you never know, you know?).
1904		2197
1905	As another example, the Perl Coro module uses these hooks to integrate	2198	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2199	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2200	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	2201	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	2204	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2205	low-priority coroutines to idle/background tasks).
1913		2206
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2207	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	2208	priority, to ensure that they are being run before any other watchers
		2209	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2210
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2211	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	2212	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2213	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	2214	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	2215	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	2216	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2217	others).
1923		2218
1924	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
1925		2220
1926	=over 4	2221	=over 4
1927		2222
…		…
1929		2224
1930	=item ev_check_init (ev_check *, callback)	2225	=item ev_check_init (ev_check *, callback)
1931		2226
1932	Initialises and configures the prepare or check watcher - they have no	2227	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>	2228	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.	2229	macros, but using them is utterly, utterly, utterly and completely
		2230	pointless.
1935		2231
1936	=back	2232	=back
1937		2233
1938	=head3 Examples	2234	=head3 Examples
1939		2235
…		…
1952		2248
1953	static ev_io iow [nfd];	2249	static ev_io iow [nfd];
1954	static ev_timer tw;	2250	static ev_timer tw;
1955		2251
1956	static void	2252	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2253	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2254	{
1959	}	2255	}
1960		2256
1961	// create io watchers for each fd and a timer before blocking	2257	// create io watchers for each fd and a timer before blocking
1962	static void	2258	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2259	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2260	{
1965	int timeout = 3600000;	2261	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2262	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2263	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2264	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
1983	}	2279	}
1984	}	2280	}
1985		2281
1986	// stop all watchers after blocking	2282	// stop all watchers after blocking
1987	static void	2283	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2284	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2285	{
1990	ev_timer_stop (loop, &tw);	2286	ev_timer_stop (loop, &tw);
1991		2287
1992	for (int i = 0; i < nfd; ++i)	2288	for (int i = 0; i < nfd; ++i)
1993	{	2289	{
…		…
2032	}	2328	}
2033		2329
2034	// do not ever call adns_afterpoll	2330	// do not ever call adns_afterpoll
2035		2331
2036	Method 4: Do not use a prepare or check watcher because the module you	2332	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	2333	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	2334	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	2335	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2336	this approach, effectively embedding EV as a client into the horrible
		2337	libglib event loop.
2041		2338
2042	static gint	2339	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2340	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2341	{
2045	int got_events = 0;	2342	int got_events = 0;
…		…
2076	prioritise I/O.	2373	prioritise I/O.
2077		2374
2078	As an example for a bug workaround, the kqueue backend might only support	2375	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	2376	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	2377	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	2378	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	2379	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	2380	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.	2381	C<kevent>, but at least you can use both mechanisms for what they are
		2382	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2383
2086	As for prioritising I/O: rarely you have the case where some fds have	2384	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	2385	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	2386	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	2387	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.	2388	the rest in a second one, and embed the second one in the first.
2091		2389
2092	As long as the watcher is active, the callback will be invoked every time	2390	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	2391	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	2392	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	2393	their callbacks (you could also start an idle watcher to give the embedded
…		…
2103	interested in that.	2401	interested in that.
2104		2402
2105	Also, there have not currently been made special provisions for forking:	2403	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,	2404	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	2405	but you will also have to stop and restart any C<ev_embed> watchers
2108	yourself.	2406	yourself - but you can use a fork watcher to handle this automatically,
		2407	and future versions of libev might do just that.
2109		2408
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2409	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2410	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2411	portable one.
2113		2412
2114	So when you want to use this feature you will always have to be prepared	2413	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	2414	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	2415	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.	2416	create it, and if that fails, use the normal loop for everything.
		2417
		2418	=head3 C<ev_embed> and fork
		2419
		2420	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2421	automatically be applied to the embedded loop as well, so no special
		2422	fork handling is required in that case. When the watcher is not running,
		2423	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2424	as applicable.
2118		2425
2119	=head3 Watcher-Specific Functions and Data Members	2426	=head3 Watcher-Specific Functions and Data Members
2120		2427
2121	=over 4	2428	=over 4
2122		2429
…		…
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2457	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2458	used).
2152		2459
2153	struct ev_loop *loop_hi = ev_default_init (0);	2460	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2461	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2462	ev_embed embed;
2156		2463
2157	// see if there is a chance of getting one that works	2464	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2465	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2466	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2467	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2481	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2482	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2483
2177	struct ev_loop *loop = ev_default_init (0);	2484	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2485	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2486	ev_embed embed;
2180		2487
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2488	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2489	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2490	{
2184	ev_embed_init (&embed, 0, loop_socket);	2491	ev_embed_init (&embed, 0, loop_socket);
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2547	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	2548	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2549	need elaborate support such as pthreads.
2243		2550
2244	That means that if you want to queue data, you have to provide your own	2551	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	2552	queue. But at least I can tell you how to implement locking around your
2246	queue:	2553	queue:
2247		2554
2248	=over 4	2555	=over 4
2249		2556
2250	=item queueing from a signal handler context	2557	=item queueing from a signal handler context
2251		2558
2252	To implement race-free queueing, you simply add to the queue in the signal	2559	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	2560	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2561	an example that does that for some fictitious SIGUSR1 handler:
2255		2562
2256	static ev_async mysig;	2563	static ev_async mysig;
2257		2564
2258	static void	2565	static void
2259	sigusr1_handler (void)	2566	sigusr1_handler (void)
…		…
2326		2633
2327	=item ev_async_init (ev_async *, callback)	2634	=item ev_async_init (ev_async *, callback)
2328		2635
2329	Initialises and configures the async watcher - it has no parameters of any	2636	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,	2637	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2331	believe me.	2638	trust me.
2332		2639
2333	=item ev_async_send (loop, ev_async *)	2640	=item ev_async_send (loop, ev_async *)
2334		2641
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2642	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	2643	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	2644	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	2645	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2646	section below on what exactly this means).
2340		2647
2341	This call incurs the overhead of a system call only once per loop iteration,	2648	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	2649	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2366	=over 4	2673	=over 4
2367		2674
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2675	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		2676
2370	This function combines a simple timer and an I/O watcher, calls your	2677	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	2678	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	2679	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	2680	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	2681	more watchers yourself.
2375		2682
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	2683	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2684	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	2685	the given C<fd> and C<events> set will be created and started.
2379		2686
2380	If C<timeout> is less than 0, then no timeout watcher will be	2687	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2688	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2689	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		2690
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2691	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	2692	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>	2693	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2694	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2695	a timeout and an io event at the same time - you probably should give io
		2696	events precedence.
		2697
		2698	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2389		2699
2390	static void stdin_ready (int revents, void *arg)	2700	static void stdin_ready (int revents, void *arg)
2391	{	2701	{
		2702	if (revents & EV_READ)
		2703	/* stdin might have data for us, joy! */;
2392	if (revents & EV_TIMEOUT)	2704	else if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;	2705	/* doh, nothing entered */;
2394	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;
2396	}	2706	}
2397		2707
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2708	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2709
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2710	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		2711
2402	Feeds the given event set into the event loop, as if the specified event	2712	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	2713	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	2714	initialised but not necessarily started event watcher).
2405		2715
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2716	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		2717
2408	Feed an event on the given fd, as if a file descriptor backend detected	2718	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	2719	the given events it.
2410		2720
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	2721	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		2722
2413	Feed an event as if the given signal occurred (C<loop> must be the default	2723	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	2724	loop!).
2415		2725
2416	=back	2726	=back
…		…
2548		2858
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2859	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		2860
2551	See the method-C<set> above for more details.	2861	See the method-C<set> above for more details.
2552		2862
2553	Example:	2863	Example: Use a plain function as callback.
2554		2864
2555	static void io_cb (ev::io &w, int revents) { }	2865	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	2866	iow.set <io_cb> ();
2557		2867
2558	=item w->set (struct ev_loop *)	2868	=item w->set (struct ev_loop *)
…		…
2596	Example: Define a class with an IO and idle watcher, start one of them in	2906	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	2907	the constructor.
2598		2908
2599	class myclass	2909	class myclass
2600	{	2910	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	2911	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	2912	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		2913
2604	myclass (int fd)	2914	myclass (int fd)
2605	{	2915	{
2606	io .set <myclass, &myclass::io_cb > (this);	2916	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	2917	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2623	=item Perl	2933	=item Perl
2624		2934
2625	The EV module implements the full libev API and is actually used to test	2935	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,	2936	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	2937	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	2938	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>).	2939	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2940	and C<EV::Glib>).
2630		2941
2631	It can be found and installed via CPAN, its homepage is at	2942	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	2943	L<http://software.schmorp.de/pkg/EV>.
2633		2944
2634	=item Python	2945	=item Python
…		…
2648	L<http://rev.rubyforge.org/>.	2959	L<http://rev.rubyforge.org/>.
2649		2960
2650	=item D	2961	=item D
2651		2962
2652	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2963	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2653	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2964	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2965
		2966	=item Ocaml
		2967
		2968	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2969	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2654		2970
2655	=back	2971	=back
2656		2972
2657		2973
2658	=head1 MACRO MAGIC	2974	=head1 MACRO MAGIC
…		…
2813		3129
2814	=head2 PREPROCESSOR SYMBOLS/MACROS	3130	=head2 PREPROCESSOR SYMBOLS/MACROS
2815		3131
2816	Libev can be configured via a variety of preprocessor symbols you have to	3132	Libev can be configured via a variety of preprocessor symbols you have to
2817	define before including any of its files. The default in the absence of	3133	define before including any of its files. The default in the absence of
2818	autoconf is noted for every option.	3134	autoconf is documented for every option.
2819		3135
2820	=over 4	3136	=over 4
2821		3137
2822	=item EV_STANDALONE	3138	=item EV_STANDALONE
2823		3139
…		…
2993	When doing priority-based operations, libev usually has to linearly search	3309	When doing priority-based operations, libev usually has to linearly search
2994	all the priorities, so having many of them (hundreds) uses a lot of space	3310	all the priorities, so having many of them (hundreds) uses a lot of space
2995	and time, so using the defaults of five priorities (-2 .. +2) is usually	3311	and time, so using the defaults of five priorities (-2 .. +2) is usually
2996	fine.	3312	fine.
2997		3313
2998	If your embedding application does not need any priorities, defining these both to	3314	If your embedding application does not need any priorities, defining these
2999	C<0> will save some memory and CPU.	3315	both to C<0> will save some memory and CPU.
3000		3316
3001	=item EV_PERIODIC_ENABLE	3317	=item EV_PERIODIC_ENABLE
3002		3318
3003	If undefined or defined to be C<1>, then periodic timers are supported. If	3319	If undefined or defined to be C<1>, then periodic timers are supported. If
3004	defined to be C<0>, then they are not. Disabling them saves a few kB of	3320	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3011	code.	3327	code.
3012		3328
3013	=item EV_EMBED_ENABLE	3329	=item EV_EMBED_ENABLE
3014		3330
3015	If undefined or defined to be C<1>, then embed watchers are supported. If	3331	If undefined or defined to be C<1>, then embed watchers are supported. If
3016	defined to be C<0>, then they are not.	3332	defined to be C<0>, then they are not. Embed watchers rely on most other
		3333	watcher types, which therefore must not be disabled.
3017		3334
3018	=item EV_STAT_ENABLE	3335	=item EV_STAT_ENABLE
3019		3336
3020	If undefined or defined to be C<1>, then stat watchers are supported. If	3337	If undefined or defined to be C<1>, then stat watchers are supported. If
3021	defined to be C<0>, then they are not.	3338	defined to be C<0>, then they are not.
…		…
3053	two).	3370	two).
3054		3371
3055	=item EV_USE_4HEAP	3372	=item EV_USE_4HEAP
3056		3373
3057	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3374	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3058	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3375	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3059	to C<1>. The 4-heap uses more complicated (longer) code but has	3376	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3060	noticeably faster performance with many (thousands) of watchers.	3377	faster performance with many (thousands) of watchers.
3061		3378
3062	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3379	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3063	(disabled).	3380	(disabled).
3064		3381
3065	=item EV_HEAP_CACHE_AT	3382	=item EV_HEAP_CACHE_AT
3066		3383
3067	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3384	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3068	timer and periodics heap, libev can cache the timestamp (I<at>) within	3385	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3069	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3386	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3070	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3387	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3071	but avoids random read accesses on heap changes. This improves performance	3388	but avoids random read accesses on heap changes. This improves performance
3072	noticeably with with many (hundreds) of watchers.	3389	noticeably with many (hundreds) of watchers.
3073		3390
3074	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3391	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3075	(disabled).	3392	(disabled).
3076		3393
3077	=item EV_VERIFY	3394	=item EV_VERIFY
…		…
3083	called once per loop, which can slow down libev. If set to C<3>, then the	3400	called once per loop, which can slow down libev. If set to C<3>, then the
3084	verification code will be called very frequently, which will slow down	3401	verification code will be called very frequently, which will slow down
3085	libev considerably.	3402	libev considerably.
3086		3403
3087	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3404	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3088	C<0.>	3405	C<0>.
3089		3406
3090	=item EV_COMMON	3407	=item EV_COMMON
3091		3408
3092	By default, all watchers have a C<void *data> member. By redefining	3409	By default, all watchers have a C<void *data> member. By redefining
3093	this macro to a something else you can include more and other types of	3410	this macro to a something else you can include more and other types of
…		…
3110	and the way callbacks are invoked and set. Must expand to a struct member	3427	and the way callbacks are invoked and set. Must expand to a struct member
3111	definition and a statement, respectively. See the F<ev.h> header file for	3428	definition and a statement, respectively. See the F<ev.h> header file for
3112	their default definitions. One possible use for overriding these is to	3429	their default definitions. One possible use for overriding these is to
3113	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3430	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3114	method calls instead of plain function calls in C++.	3431	method calls instead of plain function calls in C++.
		3432
		3433	=back
3115		3434
3116	=head2 EXPORTED API SYMBOLS	3435	=head2 EXPORTED API SYMBOLS
3117		3436
3118	If you need to re-export the API (e.g. via a DLL) and you need a list of	3437	If you need to re-export the API (e.g. via a DLL) and you need a list of
3119	exported symbols, you can use the provided F<Symbol.*> files which list	3438	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3166	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3485	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3167		3486
3168	#include "ev_cpp.h"	3487	#include "ev_cpp.h"
3169	#include "ev.c"	3488	#include "ev.c"
3170		3489
		3490	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3171		3491
3172	=head1 THREADS AND COROUTINES	3492	=head2 THREADS AND COROUTINES
3173		3493
3174	=head2 THREADS	3494	=head3 THREADS
3175		3495
3176	Libev itself is completely thread-safe, but it uses no locking. This	3496	All libev functions are reentrant and thread-safe unless explicitly
		3497	documented otherwise, but libev implements no locking itself. This means
3177	means that you can use as many loops as you want in parallel, as long as	3498	that you can use as many loops as you want in parallel, as long as there
3178	only one thread ever calls into one libev function with the same loop	3499	are no concurrent calls into any libev function with the same loop
3179	parameter.	3500	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3501	of course): libev guarantees that different event loops share no data
		3502	structures that need any locking.
3180		3503
3181	Or put differently: calls with different loop parameters can be done in	3504	Or to put it differently: calls with different loop parameters can be done
3182	parallel from multiple threads, calls with the same loop parameter must be	3505	concurrently from multiple threads, calls with the same loop parameter
3183	done serially (but can be done from different threads, as long as only one	3506	must be done serially (but can be done from different threads, as long as
3184	thread ever is inside a call at any point in time, e.g. by using a mutex	3507	only one thread ever is inside a call at any point in time, e.g. by using
3185	per loop).	3508	a mutex per loop).
3186		3509
3187	If you want to know which design is best for your problem, then I cannot	3510	Specifically to support threads (and signal handlers), libev implements
		3511	so-called C<ev_async> watchers, which allow some limited form of
		3512	concurrency on the same event loop, namely waking it up "from the
		3513	outside".
		3514
		3515	If you want to know which design (one loop, locking, or multiple loops
		3516	without or something else still) is best for your problem, then I cannot
3188	help you but by giving some generic advice:	3517	help you, but here is some generic advice:
3189		3518
3190	=over 4	3519	=over 4
3191		3520
3192	=item * most applications have a main thread: use the default libev loop	3521	=item * most applications have a main thread: use the default libev loop
3193	in that thread, or create a separate thread running only the default loop.	3522	in that thread, or create a separate thread running only the default loop.
…		…
3205		3534
3206	Choosing a model is hard - look around, learn, know that usually you can do	3535	Choosing a model is hard - look around, learn, know that usually you can do
3207	better than you currently do :-)	3536	better than you currently do :-)
3208		3537
3209	=item * often you need to talk to some other thread which blocks in the	3538	=item * often you need to talk to some other thread which blocks in the
		3539	event loop.
		3540
3210	event loop - C<ev_async> watchers can be used to wake them up from other	3541	C<ev_async> watchers can be used to wake them up from other threads safely
3211	threads safely (or from signal contexts...).	3542	(or from signal contexts...).
		3543
		3544	An example use would be to communicate signals or other events that only
		3545	work in the default loop by registering the signal watcher with the
		3546	default loop and triggering an C<ev_async> watcher from the default loop
		3547	watcher callback into the event loop interested in the signal.
3212		3548
3213	=back	3549	=back
3214		3550
3215	=head2 COROUTINES	3551	=head3 COROUTINES
3216		3552
3217	Libev is much more accommodating to coroutines ("cooperative threads"):	3553	Libev is very accommodating to coroutines ("cooperative threads"):
3218	libev fully supports nesting calls to it's functions from different	3554	libev fully supports nesting calls to its functions from different
3219	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3555	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3220	different coroutines and switch freely between both coroutines running the	3556	different coroutines, and switch freely between both coroutines running the
3221	loop, as long as you don't confuse yourself). The only exception is that	3557	loop, as long as you don't confuse yourself). The only exception is that
3222	you must not do this from C<ev_periodic> reschedule callbacks.	3558	you must not do this from C<ev_periodic> reschedule callbacks.
3223		3559
3224	Care has been invested into making sure that libev does not keep local	3560	Care has been taken to ensure that libev does not keep local state inside
3225	state inside C<ev_loop>, and other calls do not usually allow coroutine	3561	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3226	switches.	3562	they do not clal any callbacks.
3227		3563
		3564	=head2 COMPILER WARNINGS
3228		3565
3229	=head1 COMPLEXITIES	3566	Depending on your compiler and compiler settings, you might get no or a
		3567	lot of warnings when compiling libev code. Some people are apparently
		3568	scared by this.
3230		3569
3231	In this section the complexities of (many of) the algorithms used inside	3570	However, these are unavoidable for many reasons. For one, each compiler
3232	libev will be explained. For complexity discussions about backends see the	3571	has different warnings, and each user has different tastes regarding
3233	documentation for C<ev_default_init>.	3572	warning options. "Warn-free" code therefore cannot be a goal except when
		3573	targeting a specific compiler and compiler-version.
3234		3574
3235	All of the following are about amortised time: If an array needs to be	3575	Another reason is that some compiler warnings require elaborate
3236	extended, libev needs to realloc and move the whole array, but this	3576	workarounds, or other changes to the code that make it less clear and less
3237	happens asymptotically never with higher number of elements, so O(1) might	3577	maintainable.
3238	mean it might do a lengthy realloc operation in rare cases, but on average
3239	it is much faster and asymptotically approaches constant time.
3240		3578
3241	=over 4	3579	And of course, some compiler warnings are just plain stupid, or simply
		3580	wrong (because they don't actually warn about the condition their message
		3581	seems to warn about). For example, certain older gcc versions had some
		3582	warnings that resulted an extreme number of false positives. These have
		3583	been fixed, but some people still insist on making code warn-free with
		3584	such buggy versions.
3242		3585
3243	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3586	While libev is written to generate as few warnings as possible,
		3587	"warn-free" code is not a goal, and it is recommended not to build libev
		3588	with any compiler warnings enabled unless you are prepared to cope with
		3589	them (e.g. by ignoring them). Remember that warnings are just that:
		3590	warnings, not errors, or proof of bugs.
3244		3591
3245	This means that, when you have a watcher that triggers in one hour and
3246	there are 100 watchers that would trigger before that then inserting will
3247	have to skip roughly seven (C<ld 100>) of these watchers.
3248		3592
3249	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3593	=head2 VALGRIND
3250		3594
3251	That means that changing a timer costs less than removing/adding them	3595	Valgrind has a special section here because it is a popular tool that is
3252	as only the relative motion in the event queue has to be paid for.	3596	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3253		3597
3254	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3598	If you think you found a bug (memory leak, uninitialised data access etc.)
		3599	in libev, then check twice: If valgrind reports something like:
3255		3600
3256	These just add the watcher into an array or at the head of a list.	3601	==2274== definitely lost: 0 bytes in 0 blocks.
		3602	==2274== possibly lost: 0 bytes in 0 blocks.
		3603	==2274== still reachable: 256 bytes in 1 blocks.
3257		3604
3258	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3605	Then there is no memory leak, just as memory accounted to global variables
		3606	is not a memleak - the memory is still being refernced, and didn't leak.
3259		3607
3260	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3608	Similarly, under some circumstances, valgrind might report kernel bugs
		3609	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3610	although an acceptable workaround has been found here), or it might be
		3611	confused.
3261		3612
3262	These watchers are stored in lists then need to be walked to find the	3613	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3263	correct watcher to remove. The lists are usually short (you don't usually	3614	make it into some kind of religion.
3264	have many watchers waiting for the same fd or signal).
3265		3615
3266	=item Finding the next timer in each loop iteration: O(1)	3616	If you are unsure about something, feel free to contact the mailing list
		3617	with the full valgrind report and an explanation on why you think this
		3618	is a bug in libev (best check the archives, too :). However, don't be
		3619	annoyed when you get a brisk "this is no bug" answer and take the chance
		3620	of learning how to interpret valgrind properly.
3267		3621
3268	By virtue of using a binary or 4-heap, the next timer is always found at a	3622	If you need, for some reason, empty reports from valgrind for your project
3269	fixed position in the storage array.	3623	I suggest using suppression lists.
3270		3624
3271	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3272		3625
3273	A change means an I/O watcher gets started or stopped, which requires	3626	=head1 PORTABILITY NOTES
3274	libev to recalculate its status (and possibly tell the kernel, depending
3275	on backend and whether C<ev_io_set> was used).
3276		3627
3277	=item Activating one watcher (putting it into the pending state): O(1)
3278
3279	=item Priority handling: O(number_of_priorities)
3280
3281	Priorities are implemented by allocating some space for each
3282	priority. When doing priority-based operations, libev usually has to
3283	linearly search all the priorities, but starting/stopping and activating
3284	watchers becomes O(1) w.r.t. priority handling.
3285
3286	=item Sending an ev_async: O(1)
3287
3288	=item Processing ev_async_send: O(number_of_async_watchers)
3289
3290	=item Processing signals: O(max_signal_number)
3291
3292	Sending involves a system call I<iff> there were no other C<ev_async_send>
3293	calls in the current loop iteration. Checking for async and signal events
3294	involves iterating over all running async watchers or all signal numbers.
3295
3296	=back
3297
3298
3299	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3628	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3300		3629
3301	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3630	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3302	requires, and its I/O model is fundamentally incompatible with the POSIX	3631	requires, and its I/O model is fundamentally incompatible with the POSIX
3303	model. Libev still offers limited functionality on this platform in	3632	model. Libev still offers limited functionality on this platform in
3304	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3633	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3315		3644
3316	Not a libev limitation but worth mentioning: windows apparently doesn't	3645	Not a libev limitation but worth mentioning: windows apparently doesn't
3317	accept large writes: instead of resulting in a partial write, windows will	3646	accept large writes: instead of resulting in a partial write, windows will
3318	either accept everything or return C<ENOBUFS> if the buffer is too large,	3647	either accept everything or return C<ENOBUFS> if the buffer is too large,
3319	so make sure you only write small amounts into your sockets (less than a	3648	so make sure you only write small amounts into your sockets (less than a
3320	megabyte seems safe, but thsi apparently depends on the amount of memory	3649	megabyte seems safe, but this apparently depends on the amount of memory
3321	available).	3650	available).
3322		3651
3323	Due to the many, low, and arbitrary limits on the win32 platform and	3652	Due to the many, low, and arbitrary limits on the win32 platform and
3324	the abysmal performance of winsockets, using a large number of sockets	3653	the abysmal performance of winsockets, using a large number of sockets
3325	is not recommended (and not reasonable). If your program needs to use	3654	is not recommended (and not reasonable). If your program needs to use
3326	more than a hundred or so sockets, then likely it needs to use a totally	3655	more than a hundred or so sockets, then likely it needs to use a totally
3327	different implementation for windows, as libev offers the POSIX readiness	3656	different implementation for windows, as libev offers the POSIX readiness
3328	notification model, which cannot be implemented efficiently on windows	3657	notification model, which cannot be implemented efficiently on windows
3329	(Microsoft monopoly games).	3658	(Microsoft monopoly games).
3330		3659
		3660	A typical way to use libev under windows is to embed it (see the embedding
		3661	section for details) and use the following F<evwrap.h> header file instead
		3662	of F<ev.h>:
		3663
		3664	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3665	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3666
		3667	#include "ev.h"
		3668
		3669	And compile the following F<evwrap.c> file into your project (make sure
		3670	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3671
		3672	#include "evwrap.h"
		3673	#include "ev.c"
		3674
3331	=over 4	3675	=over 4
3332		3676
3333	=item The winsocket select function	3677	=item The winsocket select function
3334		3678
3335	The winsocket C<select> function doesn't follow POSIX in that it	3679	The winsocket C<select> function doesn't follow POSIX in that it
3336	requires socket I<handles> and not socket I<file descriptors> (it is	3680	requires socket I<handles> and not socket I<file descriptors> (it is
3337	also extremely buggy). This makes select very inefficient, and also	3681	also extremely buggy). This makes select very inefficient, and also
3338	requires a mapping from file descriptors to socket handles. See the	3682	requires a mapping from file descriptors to socket handles (the Microsoft
		3683	C runtime provides the function C<_open_osfhandle> for this). See the
3339	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	3684	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3340	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	3685	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3341		3686
3342	The configuration for a "naked" win32 using the Microsoft runtime	3687	The configuration for a "naked" win32 using the Microsoft runtime
3343	libraries and raw winsocket select is:	3688	libraries and raw winsocket select is:
…		…
3375	wrap all I/O functions and provide your own fd management, but the cost of	3720	wrap all I/O functions and provide your own fd management, but the cost of
3376	calling select (O(n²)) will likely make this unworkable.	3721	calling select (O(n²)) will likely make this unworkable.
3377		3722
3378	=back	3723	=back
3379		3724
3380
3381	=head1 PORTABILITY REQUIREMENTS	3725	=head2 PORTABILITY REQUIREMENTS
3382		3726
3383	In addition to a working ISO-C implementation, libev relies on a few	3727	In addition to a working ISO-C implementation and of course the
3384	additional extensions:	3728	backend-specific APIs, libev relies on a few additional extensions:
3385		3729
3386	=over 4	3730	=over 4
3387		3731
3388	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3732	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3389	calling conventions regardless of C<ev_watcher_type *>.	3733	calling conventions regardless of C<ev_watcher_type *>.
…		…
3395	calls them using an C<ev_watcher *> internally.	3739	calls them using an C<ev_watcher *> internally.
3396		3740
3397	=item C<sig_atomic_t volatile> must be thread-atomic as well	3741	=item C<sig_atomic_t volatile> must be thread-atomic as well
3398		3742
3399	The type C<sig_atomic_t volatile> (or whatever is defined as	3743	The type C<sig_atomic_t volatile> (or whatever is defined as
3400	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3744	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3401	threads. This is not part of the specification for C<sig_atomic_t>, but is	3745	threads. This is not part of the specification for C<sig_atomic_t>, but is
3402	believed to be sufficiently portable.	3746	believed to be sufficiently portable.
3403		3747
3404	=item C<sigprocmask> must work in a threaded environment	3748	=item C<sigprocmask> must work in a threaded environment
3405		3749
…		…
3414	except the initial one, and run the default loop in the initial thread as	3758	except the initial one, and run the default loop in the initial thread as
3415	well.	3759	well.
3416		3760
3417	=item C<long> must be large enough for common memory allocation sizes	3761	=item C<long> must be large enough for common memory allocation sizes
3418		3762
3419	To improve portability and simplify using libev, libev uses C<long>	3763	To improve portability and simplify its API, libev uses C<long> internally
3420	internally instead of C<size_t> when allocating its data structures. On	3764	instead of C<size_t> when allocating its data structures. On non-POSIX
3421	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3765	systems (Microsoft...) this might be unexpectedly low, but is still at
3422	is still at least 31 bits everywhere, which is enough for hundreds of	3766	least 31 bits everywhere, which is enough for hundreds of millions of
3423	millions of watchers.	3767	watchers.
3424		3768
3425	=item C<double> must hold a time value in seconds with enough accuracy	3769	=item C<double> must hold a time value in seconds with enough accuracy
3426		3770
3427	The type C<double> is used to represent timestamps. It is required to	3771	The type C<double> is used to represent timestamps. It is required to
3428	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3772	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3432	=back	3776	=back
3433		3777
3434	If you know of other additional requirements drop me a note.	3778	If you know of other additional requirements drop me a note.
3435		3779
3436		3780
3437	=head1 COMPILER WARNINGS	3781	=head1 ALGORITHMIC COMPLEXITIES
3438		3782
3439	Depending on your compiler and compiler settings, you might get no or a	3783	In this section the complexities of (many of) the algorithms used inside
3440	lot of warnings when compiling libev code. Some people are apparently	3784	libev will be documented. For complexity discussions about backends see
3441	scared by this.	3785	the documentation for C<ev_default_init>.
3442		3786
3443	However, these are unavoidable for many reasons. For one, each compiler	3787	All of the following are about amortised time: If an array needs to be
3444	has different warnings, and each user has different tastes regarding	3788	extended, libev needs to realloc and move the whole array, but this
3445	warning options. "Warn-free" code therefore cannot be a goal except when	3789	happens asymptotically rarer with higher number of elements, so O(1) might
3446	targeting a specific compiler and compiler-version.	3790	mean that libev does a lengthy realloc operation in rare cases, but on
		3791	average it is much faster and asymptotically approaches constant time.
3447		3792
3448	Another reason is that some compiler warnings require elaborate	3793	=over 4
3449	workarounds, or other changes to the code that make it less clear and less
3450	maintainable.
3451		3794
3452	And of course, some compiler warnings are just plain stupid, or simply	3795	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3453	wrong (because they don't actually warn about the condition their message
3454	seems to warn about).
3455		3796
3456	While libev is written to generate as few warnings as possible,	3797	This means that, when you have a watcher that triggers in one hour and
3457	"warn-free" code is not a goal, and it is recommended not to build libev	3798	there are 100 watchers that would trigger before that, then inserting will
3458	with any compiler warnings enabled unless you are prepared to cope with	3799	have to skip roughly seven (C<ld 100>) of these watchers.
3459	them (e.g. by ignoring them). Remember that warnings are just that:
3460	warnings, not errors, or proof of bugs.
3461		3800
		3801	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3462		3802
3463	=head1 VALGRIND	3803	That means that changing a timer costs less than removing/adding them,
		3804	as only the relative motion in the event queue has to be paid for.
3464		3805
3465	Valgrind has a special section here because it is a popular tool that is	3806	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3466	highly useful, but valgrind reports are very hard to interpret.
3467		3807
3468	If you think you found a bug (memory leak, uninitialised data access etc.)	3808	These just add the watcher into an array or at the head of a list.
3469	in libev, then check twice: If valgrind reports something like:
3470		3809
3471	==2274== definitely lost: 0 bytes in 0 blocks.	3810	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3472	==2274== possibly lost: 0 bytes in 0 blocks.
3473	==2274== still reachable: 256 bytes in 1 blocks.
3474		3811
3475	Then there is no memory leak. Similarly, under some circumstances,	3812	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3476	valgrind might report kernel bugs as if it were a bug in libev, or it
3477	might be confused (it is a very good tool, but only a tool).
3478		3813
3479	If you are unsure about something, feel free to contact the mailing list	3814	These watchers are stored in lists, so they need to be walked to find the
3480	with the full valgrind report and an explanation on why you think this is	3815	correct watcher to remove. The lists are usually short (you don't usually
3481	a bug in libev. However, don't be annoyed when you get a brisk "this is	3816	have many watchers waiting for the same fd or signal: one is typical, two
3482	no bug" answer and take the chance of learning how to interpret valgrind	3817	is rare).
3483	properly.
3484		3818
3485	If you need, for some reason, empty reports from valgrind for your project	3819	=item Finding the next timer in each loop iteration: O(1)
3486	I suggest using suppression lists.	3820
		3821	By virtue of using a binary or 4-heap, the next timer is always found at a
		3822	fixed position in the storage array.
		3823
		3824	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3825
		3826	A change means an I/O watcher gets started or stopped, which requires
		3827	libev to recalculate its status (and possibly tell the kernel, depending
		3828	on backend and whether C<ev_io_set> was used).
		3829
		3830	=item Activating one watcher (putting it into the pending state): O(1)
		3831
		3832	=item Priority handling: O(number_of_priorities)
		3833
		3834	Priorities are implemented by allocating some space for each
		3835	priority. When doing priority-based operations, libev usually has to
		3836	linearly search all the priorities, but starting/stopping and activating
		3837	watchers becomes O(1) with respect to priority handling.
		3838
		3839	=item Sending an ev_async: O(1)
		3840
		3841	=item Processing ev_async_send: O(number_of_async_watchers)
		3842
		3843	=item Processing signals: O(max_signal_number)
		3844
		3845	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3846	calls in the current loop iteration. Checking for async and signal events
		3847	involves iterating over all running async watchers or all signal numbers.
		3848
		3849	=back
3487		3850
3488		3851
3489	=head1 AUTHOR	3852	=head1 AUTHOR
3490		3853
3491	Marc Lehmann <libev@schmorp.de>.	3854	Marc Lehmann <libev@schmorp.de>.

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