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Revision 1.178 by root, Sat Sep 13 18:25:50 2008 UTC vs.
Revision 1.212 by root, Mon Nov 3 15:13:53 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
…		…
294	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
295	function.	299	function.
296		300
297	Note that this function is I<not> thread-safe, so if you want to use it	301	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	302	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	303	as loops cannot be shared easily between threads anyway).
300		304
301	The default loop is the only loop that can handle C<ev_signal> and	305	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	306	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	307	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
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.
372		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		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
377	like O(total_fds) where n is the total number of fds (or the highest fd),	388	like O(total_fds) where n is the total number of fds (or the highest fd),
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).
379	of shortcomings, such as silently dropping events in some hard-to-detect	390
380	cases and requiring a system call per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	392	of the more advanced event mechanisms: mere annoyances include silently
		393	dropping file descriptors, requiring a system call per change per file
		394	descriptor (and unnecessary guessing of parameters), problems with dup and
		395	so on. The biggest issue is fork races, however - if a program forks then
		396	I<both> parent and child process have to recreate the epoll set, which can
		397	take considerable time (one syscall per file descriptor) and is of course
		398	hard to detect.
		399
		400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		401	of course I<doesn't>, and epoll just loves to report events for totally
		402	I<different> file descriptors (even already closed ones, so one cannot
		403	even remove them from the set) than registered in the set (especially
		404	on SMP systems). Libev tries to counter these spurious notifications by
		405	employing an additional generation counter and comparing that against the
		406	events to filter out spurious ones, recreating the set when required.
382		407
383	While stopping, setting and starting an I/O watcher in the same iteration	408	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	409	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	410	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
388		413	file descriptors.
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		414
393	Best performance from this backend is achieved by not unregistering all	415	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.	416	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	417	i.e. keep at least one watcher active per fd at all times. Stopping and
		418	starting a watcher (without re-setting it) also usually doesn't cause
		419	extra overhead. A fork can both result in spurious notifications as well
		420	as in libev having to destroy and recreate the epoll object, which can
		421	take considerable time and thus should be avoided.
396		422
397	While nominally embeddable in other event loops, this feature is broken in	423	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	424	all kernel versions tested so far.
		425
		426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		427	C<EVBACKEND_POLL>.
399		428
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		430
402	Kqueue deserves special mention, as at the time of this writing, it	431	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	432	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	433	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	434	it's completely useless). Unlike epoll, however, whose brokenness
		435	is by design, these kqueue bugs can (and eventually will) be fixed
		436	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	437	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	439	system like NetBSD.
409		440
410	You still can embed kqueue into a normal poll or select backend and use it	441	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	442	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		444
414	It scales in the same way as the epoll backend, but the interface to the	445	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	446	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	447	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	448	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	449	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		451	cases
420		452
421	This backend usually performs well under most conditions.	453	This backend usually performs well under most conditions.
422		454
423	While nominally embeddable in other event loops, this doesn't work	455	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	456	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	457	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	458	(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	459	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	460	using it only for sockets.
		461
		462	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		463	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		464	C<NOTE_EOF>.
429		465
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	466	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		467
432	This is not implemented yet (and might never be, unless you send me an	468	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	469	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	482	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	483	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	484	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	485	might perform better.
450		486
451	On the positive side, ignoring the spurious readiness notifications, this	487	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	488	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	489	in all tests and is fully embeddable, which is a rare feat among the
		490	OS-specific backends (I vastly prefer correctness over speed hacks).
		491
		492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		493	C<EVBACKEND_POLL>.
454		494
455	=item C<EVBACKEND_ALL>	495	=item C<EVBACKEND_ALL>
456		496
457	Try all backends (even potentially broken ones that wouldn't be tried	497	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	498	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		504
465	If one or more of these are or'ed into the flags value, then only these	505	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	506	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.	507	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		508
469	The most typical usage is like this:	509	Example: This is the most typical usage.
470		510
471	if (!ev_default_loop (0))	511	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		513
474	Restrict libev to the select and poll backends, and do not allow	514	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	515	environment settings to be taken into account:
476		516
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		518
479	Use whatever libev has to offer, but make sure that kqueue is used if	519	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	520	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):	521	private event loop and only if you know the OS supports your types of
		522	fds):
482		523
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		525
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	526	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		527
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	548	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	549	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	550	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	551	for example).
511		552
512	Note that certain global state, such as signal state, will not be freed by	553	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	554	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	555	as signal and child watchers) would need to be stopped manually.
515		556
516	In general it is not advisable to call this function except in the	557	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	558	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	559	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	560	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		585
545	=item ev_loop_fork (loop)	586	=item ev_loop_fork (loop)
546		587
547	Like C<ev_default_fork>, but acts on an event loop created by	588	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	589	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.	590	after fork that you want to re-use in the child, and how you do this is
		591	entirely your own problem.
550		592
551	=item int ev_is_default_loop (loop)	593	=item int ev_is_default_loop (loop)
552		594
553	Returns true when the given loop actually is the default loop, false otherwise.	595	Returns true when the given loop is, in fact, the default loop, and false
		596	otherwise.
554		597
555	=item unsigned int ev_loop_count (loop)	598	=item unsigned int ev_loop_count (loop)
556		599
557	Returns the count of loop iterations for the loop, which is identical to	600	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	601	the number of times libev did poll for new events. It starts at C<0> and
…		…
596	If the flags argument is specified as C<0>, it will not return until	639	If the flags argument is specified as C<0>, it will not return until
597	either no event watchers are active anymore or C<ev_unloop> was called.	640	either no event watchers are active anymore or C<ev_unloop> was called.
598		641
599	Please note that an explicit C<ev_unloop> is usually better than	642	Please note that an explicit C<ev_unloop> is usually better than
600	relying on all watchers to be stopped when deciding when a program has	643	relying on all watchers to be stopped when deciding when a program has
601	finished (especially in interactive programs), but having a program that	644	finished (especially in interactive programs), but having a program
602	automatically loops as long as it has to and no longer by virtue of	645	that automatically loops as long as it has to and no longer by virtue
603	relying on its watchers stopping correctly is a thing of beauty.	646	of relying on its watchers stopping correctly, that is truly a thing of
		647	beauty.
604		648
605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	649	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
606	those events and any outstanding ones, but will not block your process in	650	those events and any already outstanding ones, but will not block your
607	case there are no events and will return after one iteration of the loop.	651	process in case there are no events and will return after one iteration of
		652	the loop.
608		653
609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	654	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
610	necessary) and will handle those and any outstanding ones. It will block	655	necessary) and will handle those and any already outstanding ones. It
611	your process until at least one new event arrives, and will return after	656	will block your process until at least one new event arrives (which could
612	one iteration of the loop. This is useful if you are waiting for some	657	be an event internal to libev itself, so there is no guarantee that a
613	external event in conjunction with something not expressible using other	658	user-registered callback will be called), and will return after one
		659	iteration of the loop.
		660
		661	This is useful if you are waiting for some external event in conjunction
		662	with something not expressible using other libev watchers (i.e. "roll your
614	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	663	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
615	usually a better approach for this kind of thing.	664	usually a better approach for this kind of thing.
616		665
617	Here are the gory details of what C<ev_loop> does:	666	Here are the gory details of what C<ev_loop> does:
618		667
619	- Before the first iteration, call any pending watchers.	668	- Before the first iteration, call any pending watchers.
…		…
629	any active watchers at all will result in not sleeping).	678	any active watchers at all will result in not sleeping).
630	- Sleep if the I/O and timer collect interval say so.	679	- Sleep if the I/O and timer collect interval say so.
631	- Block the process, waiting for any events.	680	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	681	- Queue all outstanding I/O (fd) events.
633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	682	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
634	- Queue all outstanding timers.	683	- Queue all expired timers.
635	- Queue all outstanding periodics.	684	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	685	- Unless any events are pending now, queue all idle watchers.
637	- Queue all check watchers.	686	- Queue all check watchers.
638	- Call all queued watchers in reverse order (i.e. check watchers first).	687	- Call all queued watchers in reverse order (i.e. check watchers first).
639	Signals and child watchers are implemented as I/O watchers, and will	688	Signals and child watchers are implemented as I/O watchers, and will
640	be handled here by queueing them when their watcher gets executed.	689	be handled here by queueing them when their watcher gets executed.
…		…
657	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	706	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
658	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
659		708
660	This "unloop state" will be cleared when entering C<ev_loop> again.	709	This "unloop state" will be cleared when entering C<ev_loop> again.
661		710
		711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		712
662	=item ev_ref (loop)	713	=item ev_ref (loop)
663		714
664	=item ev_unref (loop)	715	=item ev_unref (loop)
665		716
666	Ref/unref can be used to add or remove a reference count on the event	717	Ref/unref can be used to add or remove a reference count on the event
667	loop: Every watcher keeps one reference, and as long as the reference	718	loop: Every watcher keeps one reference, and as long as the reference
668	count is nonzero, C<ev_loop> will not return on its own. If you have	719	count is nonzero, C<ev_loop> will not return on its own.
		720
669	a watcher you never unregister that should not keep C<ev_loop> from	721	If you have a watcher you never unregister that should not keep C<ev_loop>
670	returning, ev_unref() after starting, and ev_ref() before stopping it. For	722	from returning, call ev_unref() after starting, and ev_ref() before
		723	stopping it.
		724
671	example, libev itself uses this for its internal signal pipe: It is not	725	As an example, libev itself uses this for its internal signal pipe: It is
672	visible to the libev user and should not keep C<ev_loop> from exiting if	726	not visible to the libev user and should not keep C<ev_loop> from exiting
673	no event watchers registered by it are active. It is also an excellent	727	if no event watchers registered by it are active. It is also an excellent
674	way to do this for generic recurring timers or from within third-party	728	way to do this for generic recurring timers or from within third-party
675	libraries. Just remember to I<unref after start> and I<ref before stop>	729	libraries. Just remember to I<unref after start> and I<ref before stop>
676	(but only if the watcher wasn't active before, or was active before,	730	(but only if the watcher wasn't active before, or was active before,
677	respectively).	731	respectively).
678		732
679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
680	running when nothing else is active.	734	running when nothing else is active.
681		735
682	struct ev_signal exitsig;	736	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	737	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	738	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	739	evf_unref (loop);
686		740
687	Example: For some weird reason, unregister the above signal handler again.	741	Example: For some weird reason, unregister the above signal handler again.
…		…
701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	755	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
702	allows libev to delay invocation of I/O and timer/periodic callbacks	756	allows libev to delay invocation of I/O and timer/periodic callbacks
703	to increase efficiency of loop iterations (or to increase power-saving	757	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	758	opportunities).
705		759
706	The background is that sometimes your program runs just fast enough to	760	The idea is that sometimes your program runs just fast enough to handle
707	handle one (or very few) event(s) per loop iteration. While this makes	761	one (or very few) event(s) per loop iteration. While this makes the
708	the program responsive, it also wastes a lot of CPU time to poll for new	762	program responsive, it also wastes a lot of CPU time to poll for new
709	events, especially with backends like C<select ()> which have a high	763	events, especially with backends like C<select ()> which have a high
710	overhead for the actual polling but can deliver many events at once.	764	overhead for the actual polling but can deliver many events at once.
711		765
712	By setting a higher I<io collect interval> you allow libev to spend more	766	By setting a higher I<io collect interval> you allow libev to spend more
713	time collecting I/O events, so you can handle more events per iteration,	767	time collecting I/O events, so you can handle more events per iteration,
…		…
715	C<ev_timer>) will be not affected. Setting this to a non-null value will	769	C<ev_timer>) will be not affected. Setting this to a non-null value will
716	introduce an additional C<ev_sleep ()> call into most loop iterations.	770	introduce an additional C<ev_sleep ()> call into most loop iterations.
717		771
718	Likewise, by setting a higher I<timeout collect interval> you allow libev	772	Likewise, by setting a higher I<timeout collect interval> you allow libev
719	to spend more time collecting timeouts, at the expense of increased	773	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	774	latency/jitter/inexactness (the watcher callback will be called
721	will not be affected. Setting this to a non-null value will not introduce	775	later). C<ev_io> watchers will not be affected. Setting this to a non-null
722	any overhead in libev.	776	value will not introduce any overhead in libev.
723		777
724	Many (busy) programs can usually benefit by setting the I/O collect	778	Many (busy) programs can usually benefit by setting the I/O collect
725	interval to a value near C<0.1> or so, which is often enough for	779	interval to a value near C<0.1> or so, which is often enough for
726	interactive servers (of course not for games), likewise for timeouts. It	780	interactive servers (of course not for games), likewise for timeouts. It
727	usually doesn't make much sense to set it to a lower value than C<0.01>,	781	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
735	they fire on, say, one-second boundaries only.	789	they fire on, say, one-second boundaries only.
736		790
737	=item ev_loop_verify (loop)	791	=item ev_loop_verify (loop)
738		792
739	This function only does something when C<EV_VERIFY> support has been	793	This function only does something when C<EV_VERIFY> support has been
740	compiled in. It tries to go through all internal structures and checks	794	compiled in, which is the default for non-minimal builds. It tries to go
741	them for validity. If anything is found to be inconsistent, it will print	795	through all internal structures and checks them for validity. If anything
742	an error message to standard error and call C<abort ()>.	796	is found to be inconsistent, it will print an error message to standard
		797	error and call C<abort ()>.
743		798
744	This can be used to catch bugs inside libev itself: under normal	799	This can be used to catch bugs inside libev itself: under normal
745	circumstances, this function will never abort as of course libev keeps its	800	circumstances, this function will never abort as of course libev keeps its
746	data structures consistent.	801	data structures consistent.
747		802
748	=back	803	=back
749		804
750		805
751	=head1 ANATOMY OF A WATCHER	806	=head1 ANATOMY OF A WATCHER
752		807
		808	In the following description, uppercase C<TYPE> in names stands for the
		809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		810	watchers and C<ev_io_start> for I/O watchers.
		811
753	A watcher is a structure that you create and register to record your	812	A watcher is a structure that you create and register to record your
754	interest in some event. For instance, if you want to wait for STDIN to	813	interest in some event. For instance, if you want to wait for STDIN to
755	become readable, you would create an C<ev_io> watcher for that:	814	become readable, you would create an C<ev_io> watcher for that:
756		815
757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
758	{	817	{
759	ev_io_stop (w);	818	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	819	ev_unloop (loop, EVUNLOOP_ALL);
761	}	820	}
762		821
763	struct ev_loop *loop = ev_default_loop (0);	822	struct ev_loop *loop = ev_default_loop (0);
		823
764	struct ev_io stdin_watcher;	824	ev_io stdin_watcher;
		825
765	ev_init (&stdin_watcher, my_cb);	826	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	828	ev_io_start (loop, &stdin_watcher);
		829
768	ev_loop (loop, 0);	830	ev_loop (loop, 0);
769		831
770	As you can see, you are responsible for allocating the memory for your	832	As you can see, you are responsible for allocating the memory for your
771	watcher structures (and it is usually a bad idea to do this on the stack,	833	watcher structures (and it is I<usually> a bad idea to do this on the
772	although this can sometimes be quite valid).	834	stack).
		835
		836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
773		838
774	Each watcher structure must be initialised by a call to C<ev_init	839	Each watcher structure must be initialised by a call to C<ev_init
775	(watcher *, callback)>, which expects a callback to be provided. This	840	(watcher *, callback)>, which expects a callback to be provided. This
776	callback gets invoked each time the event occurs (or, in the case of I/O	841	callback gets invoked each time the event occurs (or, in the case of I/O
777	watchers, each time the event loop detects that the file descriptor given	842	watchers, each time the event loop detects that the file descriptor given
778	is readable and/or writable).	843	is readable and/or writable).
779		844
780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	845	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
781	with arguments specific to this watcher type. There is also a macro	846	macro to configure it, with arguments specific to the watcher type. There
782	to combine initialisation and setting in one call: C<< ev_<type>_init	847	is also a macro to combine initialisation and setting in one call: C<<
783	(watcher *, callback, ...) >>.	848	ev_TYPE_init (watcher *, callback, ...) >>.
784		849
785	To make the watcher actually watch out for events, you have to start it	850	To make the watcher actually watch out for events, you have to start it
786	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	851	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
787	*) >>), and you can stop watching for events at any time by calling the	852	*) >>), and you can stop watching for events at any time by calling the
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	853	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		854
790	As long as your watcher is active (has been started but not stopped) you	855	As long as your watcher is active (has been started but not stopped) you
791	must not touch the values stored in it. Most specifically you must never	856	must not touch the values stored in it. Most specifically you must never
792	reinitialise it or call its C<set> macro.	857	reinitialise it or call its C<ev_TYPE_set> macro.
793		858
794	Each and every callback receives the event loop pointer as first, the	859	Each and every callback receives the event loop pointer as first, the
795	registered watcher structure as second, and a bitset of received events as	860	registered watcher structure as second, and a bitset of received events as
796	third argument.	861	third argument.
797		862
…		…
860	=item C<EV_ERROR>	925	=item C<EV_ERROR>
861		926
862	An unspecified error has occurred, the watcher has been stopped. This might	927	An unspecified error has occurred, the watcher has been stopped. This might
863	happen because the watcher could not be properly started because libev	928	happen because the watcher could not be properly started because libev
864	ran out of memory, a file descriptor was found to be closed or any other	929	ran out of memory, a file descriptor was found to be closed or any other
		930	problem. Libev considers these application bugs.
		931
865	problem. You best act on it by reporting the problem and somehow coping	932	You best act on it by reporting the problem and somehow coping with the
866	with the watcher being stopped.	933	watcher being stopped. Note that well-written programs should not receive
		934	an error ever, so when your watcher receives it, this usually indicates a
		935	bug in your program.
867		936
868	Libev will usually signal a few "dummy" events together with an error,	937	Libev will usually signal a few "dummy" events together with an error, for
869	for example it might indicate that a fd is readable or writable, and if	938	example it might indicate that a fd is readable or writable, and if your
870	your callbacks is well-written it can just attempt the operation and cope	939	callbacks is well-written it can just attempt the operation and cope with
871	with the error from read() or write(). This will not work in multi-threaded	940	the error from read() or write(). This will not work in multi-threaded
872	programs, though, so beware.	941	programs, though, as the fd could already be closed and reused for another
		942	thing, so beware.
873		943
874	=back	944	=back
875		945
876	=head2 GENERIC WATCHER FUNCTIONS	946	=head2 GENERIC WATCHER FUNCTIONS
877
878	In the following description, C<TYPE> stands for the watcher type,
879	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
880		947
881	=over 4	948	=over 4
882		949
883	=item C<ev_init> (ev_TYPE *watcher, callback)	950	=item C<ev_init> (ev_TYPE *watcher, callback)
884		951
…		…
890	which rolls both calls into one.	957	which rolls both calls into one.
891		958
892	You can reinitialise a watcher at any time as long as it has been stopped	959	You can reinitialise a watcher at any time as long as it has been stopped
893	(or never started) and there are no pending events outstanding.	960	(or never started) and there are no pending events outstanding.
894		961
895	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	962	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
896	int revents)>.	963	int revents)>.
		964
		965	Example: Initialise an C<ev_io> watcher in two steps.
		966
		967	ev_io w;
		968	ev_init (&w, my_cb);
		969	ev_io_set (&w, STDIN_FILENO, EV_READ);
897		970
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	971	=item C<ev_TYPE_set> (ev_TYPE *, [args])
899		972
900	This macro initialises the type-specific parts of a watcher. You need to	973	This macro initialises the type-specific parts of a watcher. You need to
901	call C<ev_init> at least once before you call this macro, but you can	974	call C<ev_init> at least once before you call this macro, but you can
…		…
904	difference to the C<ev_init> macro).	977	difference to the C<ev_init> macro).
905		978
906	Although some watcher types do not have type-specific arguments	979	Although some watcher types do not have type-specific arguments
907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	980	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
908		981
		982	See C<ev_init>, above, for an example.
		983
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	984	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		985
911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	986	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
912	calls into a single call. This is the most convenient method to initialise	987	calls into a single call. This is the most convenient method to initialise
913	a watcher. The same limitations apply, of course.	988	a watcher. The same limitations apply, of course.
914		989
		990	Example: Initialise and set an C<ev_io> watcher in one step.
		991
		992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		993
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
916		995
917	Starts (activates) the given watcher. Only active watchers will receive	996	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	997	events. If the watcher is already active nothing will happen.
919		998
		999	Example: Start the C<ev_io> watcher that is being abused as example in this
		1000	whole section.
		1001
		1002	ev_io_start (EV_DEFAULT_UC, &w);
		1003
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
921		1005
922	Stops the given watcher again (if active) and clears the pending	1006	Stops the given watcher if active, and clears the pending status (whether
		1007	the watcher was active or not).
		1008
923	status. It is possible that stopped watchers are pending (for example,	1009	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	1010	non-repeating timers are being stopped when they become pending - but
925	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1011	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
926	you want to free or reuse the memory used by the watcher it is therefore a	1012	pending. If you want to free or reuse the memory used by the watcher it is
927	good idea to always call its C<ev_TYPE_stop> function.	1013	therefore a good idea to always call its C<ev_TYPE_stop> function.
928		1014
929	=item bool ev_is_active (ev_TYPE *watcher)	1015	=item bool ev_is_active (ev_TYPE *watcher)
930		1016
931	Returns a true value iff the watcher is active (i.e. it has been started	1017	Returns a true value iff the watcher is active (i.e. it has been started
932	and not yet been stopped). As long as a watcher is active you must not modify	1018	and not yet been stopped). As long as a watcher is active you must not modify
…		…
974	The default priority used by watchers when no priority has been set is	1060	The default priority used by watchers when no priority has been set is
975	always C<0>, which is supposed to not be too high and not be too low :).	1061	always C<0>, which is supposed to not be too high and not be too low :).
976		1062
977	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1063	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
978	fine, as long as you do not mind that the priority value you query might	1064	fine, as long as you do not mind that the priority value you query might
979	or might not have been adjusted to be within valid range.	1065	or might not have been clamped to the valid range.
980		1066
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1068
983	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1069	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
984	C<loop> nor C<revents> need to be valid as long as the watcher callback	1070	C<loop> nor C<revents> need to be valid as long as the watcher callback
985	can deal with that fact.	1071	can deal with that fact, as both are simply passed through to the
		1072	callback.
986		1073
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1074	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1075
989	If the watcher is pending, this function returns clears its pending status	1076	If the watcher is pending, this function clears its pending status and
990	and returns its C<revents> bitset (as if its callback was invoked). If the	1077	returns its C<revents> bitset (as if its callback was invoked). If the
991	watcher isn't pending it does nothing and returns C<0>.	1078	watcher isn't pending it does nothing and returns C<0>.
992		1079
		1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1081	callback to be invoked, which can be accomplished with this function.
		1082
993	=back	1083	=back
994		1084
995		1085
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1087
998	Each watcher has, by default, a member C<void *data> that you can change	1088	Each watcher has, by default, a member C<void *data> that you can change
999	and read at any time, libev will completely ignore it. This can be used	1089	and read at any time: libev will completely ignore it. This can be used
1000	to associate arbitrary data with your watcher. If you need more data and	1090	to associate arbitrary data with your watcher. If you need more data and
1001	don't want to allocate memory and store a pointer to it in that data	1091	don't want to allocate memory and store a pointer to it in that data
1002	member, you can also "subclass" the watcher type and provide your own	1092	member, you can also "subclass" the watcher type and provide your own
1003	data:	1093	data:
1004		1094
1005	struct my_io	1095	struct my_io
1006	{	1096	{
1007	struct ev_io io;	1097	ev_io io;
1008	int otherfd;	1098	int otherfd;
1009	void *somedata;	1099	void *somedata;
1010	struct whatever *mostinteresting;	1100	struct whatever *mostinteresting;
1011	};	1101	};
1012		1102
…		…
1015	ev_io_init (&w.io, my_cb, fd, EV_READ);	1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
1016		1106
1017	And since your callback will be called with a pointer to the watcher, you	1107	And since your callback will be called with a pointer to the watcher, you
1018	can cast it back to your own type:	1108	can cast it back to your own type:
1019		1109
1020	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1021	{	1111	{
1022	struct my_io *w = (struct my_io *)w_;	1112	struct my_io *w = (struct my_io *)w_;
1023	...	1113	...
1024	}	1114	}
1025		1115
…		…
1036	ev_timer t2;	1126	ev_timer t2;
1037	}	1127	}
1038		1128
1039	In this case getting the pointer to C<my_biggy> is a bit more	1129	In this case getting the pointer to C<my_biggy> is a bit more
1040	complicated: Either you store the address of your C<my_biggy> struct	1130	complicated: Either you store the address of your C<my_biggy> struct
1041	in the C<data> member of the watcher, or you need to use some pointer	1131	in the C<data> member of the watcher (for woozies), or you need to use
1042	arithmetic using C<offsetof> inside your watchers:	1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1133	programmers):
1043		1134
1044	#include <stddef.h>	1135	#include <stddef.h>
1045		1136
1046	static void	1137	static void
1047	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
1048	{	1139	{
1049	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
1050	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
1051	}	1142	}
1052		1143
1053	static void	1144	static void
1054	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
1055	{	1146	{
1056	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
1057	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
1058	}	1149	}
1059		1150
…		…
1087	In general you can register as many read and/or write event watchers per	1178	In general you can register as many read and/or write event watchers per
1088	fd as you want (as long as you don't confuse yourself). Setting all file	1179	fd as you want (as long as you don't confuse yourself). Setting all file
1089	descriptors to non-blocking mode is also usually a good idea (but not	1180	descriptors to non-blocking mode is also usually a good idea (but not
1090	required if you know what you are doing).	1181	required if you know what you are doing).
1091		1182
1092	If you must do this, then force the use of a known-to-be-good backend	1183	If you cannot use non-blocking mode, then force the use of a
1093	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1184	known-to-be-good backend (at the time of this writing, this includes only
1094	C<EVBACKEND_POLL>).	1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1095		1186
1096	Another thing you have to watch out for is that it is quite easy to	1187	Another thing you have to watch out for is that it is quite easy to
1097	receive "spurious" readiness notifications, that is your callback might	1188	receive "spurious" readiness notifications, that is your callback might
1098	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1189	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1099	because there is no data. Not only are some backends known to create a	1190	because there is no data. Not only are some backends known to create a
1100	lot of those (for example Solaris ports), it is very easy to get into	1191	lot of those (for example Solaris ports), it is very easy to get into
1101	this situation even with a relatively standard program structure. Thus	1192	this situation even with a relatively standard program structure. Thus
1102	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1193	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1103	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1194	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1104		1195
1105	If you cannot run the fd in non-blocking mode (for example you should not	1196	If you cannot run the fd in non-blocking mode (for example you should
1106	play around with an Xlib connection), then you have to separately re-test	1197	not play around with an Xlib connection), then you have to separately
1107	whether a file descriptor is really ready with a known-to-be good interface	1198	re-test whether a file descriptor is really ready with a known-to-be good
1108	such as poll (fortunately in our Xlib example, Xlib already does this on	1199	interface such as poll (fortunately in our Xlib example, Xlib already
1109	its own, so its quite safe to use).	1200	does this on its own, so its quite safe to use). Some people additionally
		1201	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1202	indefinitely.
		1203
		1204	But really, best use non-blocking mode.
1110		1205
1111	=head3 The special problem of disappearing file descriptors	1206	=head3 The special problem of disappearing file descriptors
1112		1207
1113	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1208	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1114	descriptor (either by calling C<close> explicitly or by any other means,	1209	descriptor (either due to calling C<close> explicitly or any other means,
1115	such as C<dup>). The reason is that you register interest in some file	1210	such as C<dup2>). The reason is that you register interest in some file
1116	descriptor, but when it goes away, the operating system will silently drop	1211	descriptor, but when it goes away, the operating system will silently drop
1117	this interest. If another file descriptor with the same number then is	1212	this interest. If another file descriptor with the same number then is
1118	registered with libev, there is no efficient way to see that this is, in	1213	registered with libev, there is no efficient way to see that this is, in
1119	fact, a different file descriptor.	1214	fact, a different file descriptor.
1120		1215
…		…
1151	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1152	C<EVBACKEND_POLL>.	1247	C<EVBACKEND_POLL>.
1153		1248
1154	=head3 The special problem of SIGPIPE	1249	=head3 The special problem of SIGPIPE
1155		1250
1156	While not really specific to libev, it is easy to forget about SIGPIPE:	1251	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1157	when writing to a pipe whose other end has been closed, your program gets	1252	when writing to a pipe whose other end has been closed, your program gets
1158	send a SIGPIPE, which, by default, aborts your program. For most programs	1253	sent a SIGPIPE, which, by default, aborts your program. For most programs
1159	this is sensible behaviour, for daemons, this is usually undesirable.	1254	this is sensible behaviour, for daemons, this is usually undesirable.
1160		1255
1161	So when you encounter spurious, unexplained daemon exits, make sure you	1256	So when you encounter spurious, unexplained daemon exits, make sure you
1162	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1257	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1163	somewhere, as that would have given you a big clue).	1258	somewhere, as that would have given you a big clue).
…		…
1170	=item ev_io_init (ev_io *, callback, int fd, int events)	1265	=item ev_io_init (ev_io *, callback, int fd, int events)
1171		1266
1172	=item ev_io_set (ev_io *, int fd, int events)	1267	=item ev_io_set (ev_io *, int fd, int events)
1173		1268
1174	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1269	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1175	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1270	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1176	C<EV_READ | EV_WRITE> to receive the given events.	1271	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1177		1272
1178	=item int fd [read-only]	1273	=item int fd [read-only]
1179		1274
1180	The file descriptor being watched.	1275	The file descriptor being watched.
1181		1276
…		…
1190	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1285	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1191	readable, but only once. Since it is likely line-buffered, you could	1286	readable, but only once. Since it is likely line-buffered, you could
1192	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1193		1288
1194	static void	1289	static void
1195	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1290	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1196	{	1291	{
1197	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1198	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1293	.. read from stdin here (or from w->fd) and handle any I/O errors
1199	}	1294	}
1200		1295
1201	...	1296	...
1202	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1203	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1204	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1205	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1206	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1207		1302
1208		1303
…		…
1211	Timer watchers are simple relative timers that generate an event after a	1306	Timer watchers are simple relative timers that generate an event after a
1212	given time, and optionally repeating in regular intervals after that.	1307	given time, and optionally repeating in regular intervals after that.
1213		1308
1214	The timers are based on real time, that is, if you register an event that	1309	The timers are based on real time, that is, if you register an event that
1215	times out after an hour and you reset your system clock to January last	1310	times out after an hour and you reset your system clock to January last
1216	year, it will still time out after (roughly) and hour. "Roughly" because	1311	year, it will still time out after (roughly) one hour. "Roughly" because
1217	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1218	monotonic clock option helps a lot here).	1313	monotonic clock option helps a lot here).
1219		1314
1220	The callback is guaranteed to be invoked only after its timeout has passed,	1315	The callback is guaranteed to be invoked only I<after> its timeout has
1221	but if multiple timers become ready during the same loop iteration then	1316	passed, but if multiple timers become ready during the same loop iteration
1222	order of execution is undefined.	1317	then order of execution is undefined.
		1318
		1319	=head3 Be smart about timeouts
		1320
		1321	Many real-world problems involve some kind of timeout, usually for error
		1322	recovery. A typical example is an HTTP request - if the other side hangs,
		1323	you want to raise some error after a while.
		1324
		1325	What follows are some ways to handle this problem, from obvious and
		1326	inefficient to smart and efficient.
		1327
		1328	In the following, a 60 second activity timeout is assumed - a timeout that
		1329	gets reset to 60 seconds each time there is activity (e.g. each time some
		1330	data or other life sign was received).
		1331
		1332	=over 4
		1333
		1334	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1335
		1336	This is the most obvious, but not the most simple way: In the beginning,
		1337	start the watcher:
		1338
		1339	ev_timer_init (timer, callback, 60., 0.);
		1340	ev_timer_start (loop, timer);
		1341
		1342	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1343	and start it again:
		1344
		1345	ev_timer_stop (loop, timer);
		1346	ev_timer_set (timer, 60., 0.);
		1347	ev_timer_start (loop, timer);
		1348
		1349	This is relatively simple to implement, but means that each time there is
		1350	some activity, libev will first have to remove the timer from its internal
		1351	data structure and then add it again. Libev tries to be fast, but it's
		1352	still not a constant-time operation.
		1353
		1354	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1355
		1356	This is the easiest way, and involves using C<ev_timer_again> instead of
		1357	C<ev_timer_start>.
		1358
		1359	To implement this, configure an C<ev_timer> with a C<repeat> value
		1360	of C<60> and then call C<ev_timer_again> at start and each time you
		1361	successfully read or write some data. If you go into an idle state where
		1362	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1363	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1364
		1365	That means you can ignore both the C<ev_timer_start> function and the
		1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1367	member and C<ev_timer_again>.
		1368
		1369	At start:
		1370
		1371	ev_timer_init (timer, callback);
		1372	timer->repeat = 60.;
		1373	ev_timer_again (loop, timer);
		1374
		1375	Each time there is some activity:
		1376
		1377	ev_timer_again (loop, timer);
		1378
		1379	It is even possible to change the time-out on the fly, regardless of
		1380	whether the watcher is active or not:
		1381
		1382	timer->repeat = 30.;
		1383	ev_timer_again (loop, timer);
		1384
		1385	This is slightly more efficient then stopping/starting the timer each time
		1386	you want to modify its timeout value, as libev does not have to completely
		1387	remove and re-insert the timer from/into its internal data structure.
		1388
		1389	It is, however, even simpler than the "obvious" way to do it.
		1390
		1391	=item 3. Let the timer time out, but then re-arm it as required.
		1392
		1393	This method is more tricky, but usually most efficient: Most timeouts are
		1394	relatively long compared to the intervals between other activity - in
		1395	our example, within 60 seconds, there are usually many I/O events with
		1396	associated activity resets.
		1397
		1398	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1399	but remember the time of last activity, and check for a real timeout only
		1400	within the callback:
		1401
		1402	ev_tstamp last_activity; // time of last activity
		1403
		1404	static void
		1405	callback (EV_P_ ev_timer *w, int revents)
		1406	{
		1407	ev_tstamp now = ev_now (EV_A);
		1408	ev_tstamp timeout = last_activity + 60.;
		1409
		1410	// if last_activity + 60. is older than now, we did time out
		1411	if (timeout < now)
		1412	{
		1413	// timeout occured, take action
		1414	}
		1415	else
		1416	{
		1417	// callback was invoked, but there was some activity, re-arm
		1418	// the watcher to fire in last_activity + 60, which is
		1419	// guaranteed to be in the future, so "again" is positive:
		1420	w->again = timeout - now;
		1421	ev_timer_again (EV_A_ w);
		1422	}
		1423	}
		1424
		1425	To summarise the callback: first calculate the real timeout (defined
		1426	as "60 seconds after the last activity"), then check if that time has
		1427	been reached, which means something I<did>, in fact, time out. Otherwise
		1428	the callback was invoked too early (C<timeout> is in the future), so
		1429	re-schedule the timer to fire at that future time, to see if maybe we have
		1430	a timeout then.
		1431
		1432	Note how C<ev_timer_again> is used, taking advantage of the
		1433	C<ev_timer_again> optimisation when the timer is already running.
		1434
		1435	This scheme causes more callback invocations (about one every 60 seconds
		1436	minus half the average time between activity), but virtually no calls to
		1437	libev to change the timeout.
		1438
		1439	To start the timer, simply initialise the watcher and set C<last_activity>
		1440	to the current time (meaning we just have some activity :), then call the
		1441	callback, which will "do the right thing" and start the timer:
		1442
		1443	ev_timer_init (timer, callback);
		1444	last_activity = ev_now (loop);
		1445	callback (loop, timer, EV_TIMEOUT);
		1446
		1447	And when there is some activity, simply store the current time in
		1448	C<last_activity>, no libev calls at all:
		1449
		1450	last_actiivty = ev_now (loop);
		1451
		1452	This technique is slightly more complex, but in most cases where the
		1453	time-out is unlikely to be triggered, much more efficient.
		1454
		1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1456	callback :) - just change the timeout and invoke the callback, which will
		1457	fix things for you.
		1458
		1459	=item 4. Wee, just use a double-linked list for your timeouts.
		1460
		1461	If there is not one request, but many thousands (millions...), all
		1462	employing some kind of timeout with the same timeout value, then one can
		1463	do even better:
		1464
		1465	When starting the timeout, calculate the timeout value and put the timeout
		1466	at the I<end> of the list.
		1467
		1468	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1469	the list is expected to fire (for example, using the technique #3).
		1470
		1471	When there is some activity, remove the timer from the list, recalculate
		1472	the timeout, append it to the end of the list again, and make sure to
		1473	update the C<ev_timer> if it was taken from the beginning of the list.
		1474
		1475	This way, one can manage an unlimited number of timeouts in O(1) time for
		1476	starting, stopping and updating the timers, at the expense of a major
		1477	complication, and having to use a constant timeout. The constant timeout
		1478	ensures that the list stays sorted.
		1479
		1480	=back
		1481
		1482	So which method the best?
		1483
		1484	Method #2 is a simple no-brain-required solution that is adequate in most
		1485	situations. Method #3 requires a bit more thinking, but handles many cases
		1486	better, and isn't very complicated either. In most case, choosing either
		1487	one is fine, with #3 being better in typical situations.
		1488
		1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1490	rather complicated, but extremely efficient, something that really pays
		1491	off after the first million or so of active timers, i.e. it's usually
		1492	overkill :)
1223		1493
1224	=head3 The special problem of time updates	1494	=head3 The special problem of time updates
1225		1495
1226	Establishing the current time is a costly operation (it usually takes at	1496	Establishing the current time is a costly operation (it usually takes at
1227	least two system calls): EV therefore updates its idea of the current	1497	least two system calls): EV therefore updates its idea of the current
1228	time only before and after C<ev_loop> polls for new events, which causes	1498	time only before and after C<ev_loop> collects new events, which causes a
1229	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1230	lots of events.	1500	lots of events in one iteration.
1231		1501
1232	The relative timeouts are calculated relative to the C<ev_now ()>	1502	The relative timeouts are calculated relative to the C<ev_now ()>
1233	time. This is usually the right thing as this timestamp refers to the time	1503	time. This is usually the right thing as this timestamp refers to the time
1234	of the event triggering whatever timeout you are modifying/starting. If	1504	of the event triggering whatever timeout you are modifying/starting. If
1235	you suspect event processing to be delayed and you I<need> to base the	1505	you suspect event processing to be delayed and you I<need> to base the
…		…
1271	If the timer is started but non-repeating, stop it (as if it timed out).	1541	If the timer is started but non-repeating, stop it (as if it timed out).
1272		1542
1273	If the timer is repeating, either start it if necessary (with the	1543	If the timer is repeating, either start it if necessary (with the
1274	C<repeat> value), or reset the running timer to the C<repeat> value.	1544	C<repeat> value), or reset the running timer to the C<repeat> value.
1275		1545
1276	This sounds a bit complicated, but here is a useful and typical	1546	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1277	example: Imagine you have a TCP connection and you want a so-called idle	1547	usage example.
1278	timeout, that is, you want to be called when there have been, say, 60
1279	seconds of inactivity on the socket. The easiest way to do this is to
1280	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1281	C<ev_timer_again> each time you successfully read or write some data. If
1282	you go into an idle state where you do not expect data to travel on the
1283	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1284	automatically restart it if need be.
1285
1286	That means you can ignore the C<after> value and C<ev_timer_start>
1287	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1288
1289	ev_timer_init (timer, callback, 0., 5.);
1290	ev_timer_again (loop, timer);
1291	...
1292	timer->again = 17.;
1293	ev_timer_again (loop, timer);
1294	...
1295	timer->again = 10.;
1296	ev_timer_again (loop, timer);
1297
1298	This is more slightly efficient then stopping/starting the timer each time
1299	you want to modify its timeout value.
1300		1548
1301	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1302		1550
1303	The current C<repeat> value. Will be used each time the watcher times out	1551	The current C<repeat> value. Will be used each time the watcher times out
1304	or C<ev_timer_again> is called and determines the next timeout (if any),	1552	or C<ev_timer_again> is called, and determines the next timeout (if any),
1305	which is also when any modifications are taken into account.	1553	which is also when any modifications are taken into account.
1306		1554
1307	=back	1555	=back
1308		1556
1309	=head3 Examples	1557	=head3 Examples
1310		1558
1311	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1312		1560
1313	static void	1561	static void
1314	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1562	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1315	{	1563	{
1316	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1317	}	1565	}
1318		1566
1319	struct ev_timer mytimer;	1567	ev_timer mytimer;
1320	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1321	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1322		1570
1323	Example: Create a timeout timer that times out after 10 seconds of	1571	Example: Create a timeout timer that times out after 10 seconds of
1324	inactivity.	1572	inactivity.
1325		1573
1326	static void	1574	static void
1327	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1328	{	1576	{
1329	.. ten seconds without any activity	1577	.. ten seconds without any activity
1330	}	1578	}
1331		1579
1332	struct ev_timer mytimer;	1580	ev_timer mytimer;
1333	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1334	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1335	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1336		1584
1337	// and in some piece of code that gets executed on any "activity":	1585	// and in some piece of code that gets executed on any "activity":
…		…
1353	to trigger the event (unlike an C<ev_timer>, which would still trigger	1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1354	roughly 10 seconds later as it uses a relative timeout).	1602	roughly 10 seconds later as it uses a relative timeout).
1355		1603
1356	C<ev_periodic>s can also be used to implement vastly more complex timers,	1604	C<ev_periodic>s can also be used to implement vastly more complex timers,
1357	such as triggering an event on each "midnight, local time", or other	1605	such as triggering an event on each "midnight, local time", or other
1358	complicated, rules.	1606	complicated rules.
1359		1607
1360	As with timers, the callback is guaranteed to be invoked only when the	1608	As with timers, the callback is guaranteed to be invoked only when the
1361	time (C<at>) has passed, but if multiple periodic timers become ready	1609	time (C<at>) has passed, but if multiple periodic timers become ready
1362	during the same loop iteration then order of execution is undefined.	1610	during the same loop iteration, then order of execution is undefined.
1363		1611
1364	=head3 Watcher-Specific Functions and Data Members	1612	=head3 Watcher-Specific Functions and Data Members
1365		1613
1366	=over 4	1614	=over 4
1367		1615
1368	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1369		1617
1370	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1371		1619
1372	Lots of arguments, lets sort it out... There are basically three modes of	1620	Lots of arguments, lets sort it out... There are basically three modes of
1373	operation, and we will explain them from simplest to complex:	1621	operation, and we will explain them from simplest to most complex:
1374		1622
1375	=over 4	1623	=over 4
1376		1624
1377	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1378		1626
1379	In this configuration the watcher triggers an event after the wall clock	1627	In this configuration the watcher triggers an event after the wall clock
1380	time C<at> has passed and doesn't repeat. It will not adjust when a time	1628	time C<at> has passed. It will not repeat and will not adjust when a time
1381	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1629	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1382	run when the system time reaches or surpasses this time.	1630	only run when the system clock reaches or surpasses this time.
1383		1631
1384	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1385		1633
1386	In this mode the watcher will always be scheduled to time out at the next	1634	In this mode the watcher will always be scheduled to time out at the next
1387	C<at + N * interval> time (for some integer N, which can also be negative)	1635	C<at + N * interval> time (for some integer N, which can also be negative)
1388	and then repeat, regardless of any time jumps.	1636	and then repeat, regardless of any time jumps.
1389		1637
1390	This can be used to create timers that do not drift with respect to system	1638	This can be used to create timers that do not drift with respect to the
1391	time, for example, here is a C<ev_periodic> that triggers each hour, on	1639	system clock, for example, here is a C<ev_periodic> that triggers each
1392	the hour:	1640	hour, on the hour:
1393		1641
1394	ev_periodic_set (&periodic, 0., 3600., 0);	1642	ev_periodic_set (&periodic, 0., 3600., 0);
1395		1643
1396	This doesn't mean there will always be 3600 seconds in between triggers,	1644	This doesn't mean there will always be 3600 seconds in between triggers,
1397	but only that the callback will be called when the system time shows a	1645	but only that the callback will be called when the system time shows a
…		…
1423		1671
1424	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1672	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1425	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1426	only event loop modification you are allowed to do).	1674	only event loop modification you are allowed to do).
1427		1675
1428	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1429	*w, ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1430		1678
		1679	static ev_tstamp
1431	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1432	{	1681	{
1433	return now + 60.;	1682	return now + 60.;
1434	}	1683	}
1435		1684
1436	It must return the next time to trigger, based on the passed time value	1685	It must return the next time to trigger, based on the passed time value
…		…
1473		1722
1474	The current interval value. Can be modified any time, but changes only	1723	The current interval value. Can be modified any time, but changes only
1475	take effect when the periodic timer fires or C<ev_periodic_again> is being	1724	take effect when the periodic timer fires or C<ev_periodic_again> is being
1476	called.	1725	called.
1477		1726
1478	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1727	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1479		1728
1480	The current reschedule callback, or C<0>, if this functionality is	1729	The current reschedule callback, or C<0>, if this functionality is
1481	switched off. Can be changed any time, but changes only take effect when	1730	switched off. Can be changed any time, but changes only take effect when
1482	the periodic timer fires or C<ev_periodic_again> is being called.	1731	the periodic timer fires or C<ev_periodic_again> is being called.
1483		1732
1484	=back	1733	=back
1485		1734
1486	=head3 Examples	1735	=head3 Examples
1487		1736
1488	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1489	system clock is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1490	potentially a lot of jitter, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1491		1740
1492	static void	1741	static void
1493	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1494	{	1743	{
1495	... its now a full hour (UTC, or TAI or whatever your clock follows)	1744	... its now a full hour (UTC, or TAI or whatever your clock follows)
1496	}	1745	}
1497		1746
1498	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1499	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1500	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1501		1750
1502	Example: The same as above, but use a reschedule callback to do it:	1751	Example: The same as above, but use a reschedule callback to do it:
1503		1752
1504	#include <math.h>	1753	#include <math.h>
1505		1754
1506	static ev_tstamp	1755	static ev_tstamp
1507	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1508	{	1757	{
1509	return fmod (now, 3600.) + 3600.;	1758	return now + (3600. - fmod (now, 3600.));
1510	}	1759	}
1511		1760
1512	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1761	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1513		1762
1514	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1515		1764
1516	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1517	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1518	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1519	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1520		1769
1521		1770
…		…
1524	Signal watchers will trigger an event when the process receives a specific	1773	Signal watchers will trigger an event when the process receives a specific
1525	signal one or more times. Even though signals are very asynchronous, libev	1774	signal one or more times. Even though signals are very asynchronous, libev
1526	will try it's best to deliver signals synchronously, i.e. as part of the	1775	will try it's best to deliver signals synchronously, i.e. as part of the
1527	normal event processing, like any other event.	1776	normal event processing, like any other event.
1528		1777
		1778	If you want signals asynchronously, just use C<sigaction> as you would
		1779	do without libev and forget about sharing the signal. You can even use
		1780	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1781
1529	You can configure as many watchers as you like per signal. Only when the	1782	You can configure as many watchers as you like per signal. Only when the
1530	first watcher gets started will libev actually register a signal watcher	1783	first watcher gets started will libev actually register a signal handler
1531	with the kernel (thus it coexists with your own signal handlers as long	1784	with the kernel (thus it coexists with your own signal handlers as long as
1532	as you don't register any with libev). Similarly, when the last signal	1785	you don't register any with libev for the same signal). Similarly, when
1533	watcher for a signal is stopped libev will reset the signal handler to	1786	the last signal watcher for a signal is stopped, libev will reset the
1534	SIG_DFL (regardless of what it was set to before).	1787	signal handler to SIG_DFL (regardless of what it was set to before).
1535		1788
1536	If possible and supported, libev will install its handlers with	1789	If possible and supported, libev will install its handlers with
1537	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1538	interrupted. If you have a problem with system calls getting interrupted by	1791	interrupted. If you have a problem with system calls getting interrupted by
1539	signals you can block all signals in an C<ev_check> watcher and unblock	1792	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1556		1809
1557	=back	1810	=back
1558		1811
1559	=head3 Examples	1812	=head3 Examples
1560		1813
1561	Example: Try to exit cleanly on SIGINT and SIGTERM.	1814	Example: Try to exit cleanly on SIGINT.
1562		1815
1563	static void	1816	static void
1564	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1565	{	1818	{
1566	ev_unloop (loop, EVUNLOOP_ALL);	1819	ev_unloop (loop, EVUNLOOP_ALL);
1567	}	1820	}
1568		1821
1569	struct ev_signal signal_watcher;	1822	ev_signal signal_watcher;
1570	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1571	ev_signal_start (loop, &sigint_cb);	1824	ev_signal_start (loop, &signal_watcher);
1572		1825
1573		1826
1574	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
1575		1828
1576	Child watchers trigger when your process receives a SIGCHLD in response to	1829	Child watchers trigger when your process receives a SIGCHLD in response to
1577	some child status changes (most typically when a child of yours dies). It	1830	some child status changes (most typically when a child of yours dies or
1578	is permissible to install a child watcher I<after> the child has been	1831	exits). It is permissible to install a child watcher I<after> the child
1579	forked (which implies it might have already exited), as long as the event	1832	has been forked (which implies it might have already exited), as long
1580	loop isn't entered (or is continued from a watcher).	1833	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1834	forking and then immediately registering a watcher for the child is fine,
		1835	but forking and registering a watcher a few event loop iterations later is
		1836	not.
1581		1837
1582	Only the default event loop is capable of handling signals, and therefore	1838	Only the default event loop is capable of handling signals, and therefore
1583	you can only register child watchers in the default event loop.	1839	you can only register child watchers in the default event loop.
1584		1840
1585	=head3 Process Interaction	1841	=head3 Process Interaction
…		…
1646	its completion.	1902	its completion.
1647		1903
1648	ev_child cw;	1904	ev_child cw;
1649		1905
1650	static void	1906	static void
1651	child_cb (EV_P_ struct ev_child *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1652	{	1908	{
1653	ev_child_stop (EV_A_ w);	1909	ev_child_stop (EV_A_ w);
1654	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1910	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1655	}	1911	}
1656		1912
…		…
1671		1927
1672		1928
1673	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1674		1930
1675	This watches a file system path for attribute changes. That is, it calls	1931	This watches a file system path for attribute changes. That is, it calls
1676	C<stat> regularly (or when the OS says it changed) and sees if it changed	1932	C<stat> on that path in regular intervals (or when the OS says it changed)
1677	compared to the last time, invoking the callback if it did.	1933	and sees if it changed compared to the last time, invoking the callback if
		1934	it did.
1678		1935
1679	The path does not need to exist: changing from "path exists" to "path does	1936	The path does not need to exist: changing from "path exists" to "path does
1680	not exist" is a status change like any other. The condition "path does	1937	not exist" is a status change like any other. The condition "path does not
1681	not exist" is signified by the C<st_nlink> field being zero (which is	1938	exist" (or more correctly "path cannot be stat'ed") is signified by the
1682	otherwise always forced to be at least one) and all the other fields of	1939	C<st_nlink> field being zero (which is otherwise always forced to be at
1683	the stat buffer having unspecified contents.	1940	least one) and all the other fields of the stat buffer having unspecified
		1941	contents.
1684		1942
1685	The path I<should> be absolute and I<must not> end in a slash. If it is	1943	The path I<must not> end in a slash or contain special components such as
		1944	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1686	relative and your working directory changes, the behaviour is undefined.	1945	your working directory changes, then the behaviour is undefined.
1687		1946
1688	Since there is no standard to do this, the portable implementation simply	1947	Since there is no portable change notification interface available, the
1689	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1948	portable implementation simply calls C<stat(2)> regularly on the path
1690	can specify a recommended polling interval for this case. If you specify	1949	to see if it changed somehow. You can specify a recommended polling
1691	a polling interval of C<0> (highly recommended!) then a I<suitable,	1950	interval for this case. If you specify a polling interval of C<0> (highly
1692	unspecified default> value will be used (which you can expect to be around	1951	recommended!) then a I<suitable, unspecified default> value will be used
1693	five seconds, although this might change dynamically). Libev will also	1952	(which you can expect to be around five seconds, although this might
1694	impose a minimum interval which is currently around C<0.1>, but thats	1953	change dynamically). Libev will also impose a minimum interval which is
1695	usually overkill.	1954	currently around C<0.1>, but that's usually overkill.
1696		1955
1697	This watcher type is not meant for massive numbers of stat watchers,	1956	This watcher type is not meant for massive numbers of stat watchers,
1698	as even with OS-supported change notifications, this can be	1957	as even with OS-supported change notifications, this can be
1699	resource-intensive.	1958	resource-intensive.
1700		1959
1701	At the time of this writing, only the Linux inotify interface is	1960	At the time of this writing, the only OS-specific interface implemented
1702	implemented (implementing kqueue support is left as an exercise for the	1961	is the Linux inotify interface (implementing kqueue support is left as an
1703	reader, note, however, that the author sees no way of implementing ev_stat	1962	exercise for the reader. Note, however, that the author sees no way of
1704	semantics with kqueue). Inotify will be used to give hints only and should	1963	implementing C<ev_stat> semantics with kqueue, except as a hint).
1705	not change the semantics of C<ev_stat> watchers, which means that libev
1706	sometimes needs to fall back to regular polling again even with inotify,
1707	but changes are usually detected immediately, and if the file exists there
1708	will be no polling.
1709		1964
1710	=head3 ABI Issues (Largefile Support)	1965	=head3 ABI Issues (Largefile Support)
1711		1966
1712	Libev by default (unless the user overrides this) uses the default	1967	Libev by default (unless the user overrides this) uses the default
1713	compilation environment, which means that on systems with large file	1968	compilation environment, which means that on systems with large file
1714	support disabled by default, you get the 32 bit version of the stat	1969	support disabled by default, you get the 32 bit version of the stat
1715	structure. When using the library from programs that change the ABI to	1970	structure. When using the library from programs that change the ABI to
1716	use 64 bit file offsets the programs will fail. In that case you have to	1971	use 64 bit file offsets the programs will fail. In that case you have to
1717	compile libev with the same flags to get binary compatibility. This is	1972	compile libev with the same flags to get binary compatibility. This is
1718	obviously the case with any flags that change the ABI, but the problem is	1973	obviously the case with any flags that change the ABI, but the problem is
1719	most noticeably disabled with ev_stat and large file support.	1974	most noticeably displayed with ev_stat and large file support.
1720		1975
1721	The solution for this is to lobby your distribution maker to make large	1976	The solution for this is to lobby your distribution maker to make large
1722	file interfaces available by default (as e.g. FreeBSD does) and not	1977	file interfaces available by default (as e.g. FreeBSD does) and not
1723	optional. Libev cannot simply switch on large file support because it has	1978	optional. Libev cannot simply switch on large file support because it has
1724	to exchange stat structures with application programs compiled using the	1979	to exchange stat structures with application programs compiled using the
1725	default compilation environment.	1980	default compilation environment.
1726		1981
1727	=head3 Inotify	1982	=head3 Inotify and Kqueue
1728		1983
1729	When C<inotify (7)> support has been compiled into libev (generally only	1984	When C<inotify (7)> support has been compiled into libev and present at
1730	available on Linux) and present at runtime, it will be used to speed up	1985	runtime, it will be used to speed up change detection where possible. The
1731	change detection where possible. The inotify descriptor will be created lazily	1986	inotify descriptor will be created lazily when the first C<ev_stat>
1732	when the first C<ev_stat> watcher is being started.	1987	watcher is being started.
1733		1988
1734	Inotify presence does not change the semantics of C<ev_stat> watchers	1989	Inotify presence does not change the semantics of C<ev_stat> watchers
1735	except that changes might be detected earlier, and in some cases, to avoid	1990	except that changes might be detected earlier, and in some cases, to avoid
1736	making regular C<stat> calls. Even in the presence of inotify support	1991	making regular C<stat> calls. Even in the presence of inotify support
1737	there are many cases where libev has to resort to regular C<stat> polling.	1992	there are many cases where libev has to resort to regular C<stat> polling,
		1993	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1994	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1995	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		1996	xfs are fully working) libev usually gets away without polling.
1738		1997
1739	(There is no support for kqueue, as apparently it cannot be used to	1998	There is no support for kqueue, as apparently it cannot be used to
1740	implement this functionality, due to the requirement of having a file	1999	implement this functionality, due to the requirement of having a file
1741	descriptor open on the object at all times).	2000	descriptor open on the object at all times, and detecting renames, unlinks
		2001	etc. is difficult.
		2002
		2003	=head3 C<stat ()> is a synchronous operation
		2004
		2005	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2006	the process. The exception are C<ev_stat> watchers - those call C<stat
		2007	()>, which is a synchronous operation.
		2008
		2009	For local paths, this usually doesn't matter: unless the system is very
		2010	busy or the intervals between stat's are large, a stat call will be fast,
		2011	as the path data is suually in memory already (except when starting the
		2012	watcher).
		2013
		2014	For networked file systems, calling C<stat ()> can block an indefinite
		2015	time due to network issues, and even under good conditions, a stat call
		2016	often takes multiple milliseconds.
		2017
		2018	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2019	paths, although this is fully supported by libev.
1742		2020
1743	=head3 The special problem of stat time resolution	2021	=head3 The special problem of stat time resolution
1744		2022
1745	The C<stat ()> system call only supports full-second resolution portably, and	2023	The C<stat ()> system call only supports full-second resolution portably,
1746	even on systems where the resolution is higher, many file systems still	2024	and even on systems where the resolution is higher, most file systems
1747	only support whole seconds.	2025	still only support whole seconds.
1748		2026
1749	That means that, if the time is the only thing that changes, you can	2027	That means that, if the time is the only thing that changes, you can
1750	easily miss updates: on the first update, C<ev_stat> detects a change and	2028	easily miss updates: on the first update, C<ev_stat> detects a change and
1751	calls your callback, which does something. When there is another update	2029	calls your callback, which does something. When there is another update
1752	within the same second, C<ev_stat> will be unable to detect it as the stat	2030	within the same second, C<ev_stat> will be unable to detect unless the
1753	data does not change.	2031	stat data does change in other ways (e.g. file size).
1754		2032
1755	The solution to this is to delay acting on a change for slightly more	2033	The solution to this is to delay acting on a change for slightly more
1756	than a second (or till slightly after the next full second boundary), using	2034	than a second (or till slightly after the next full second boundary), using
1757	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2035	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1758	ev_timer_again (loop, w)>).	2036	ev_timer_again (loop, w)>).
…		…
1778	C<path>. The C<interval> is a hint on how quickly a change is expected to	2056	C<path>. The C<interval> is a hint on how quickly a change is expected to
1779	be detected and should normally be specified as C<0> to let libev choose	2057	be detected and should normally be specified as C<0> to let libev choose
1780	a suitable value. The memory pointed to by C<path> must point to the same	2058	a suitable value. The memory pointed to by C<path> must point to the same
1781	path for as long as the watcher is active.	2059	path for as long as the watcher is active.
1782		2060
1783	The callback will receive C<EV_STAT> when a change was detected, relative	2061	The callback will receive an C<EV_STAT> event when a change was detected,
1784	to the attributes at the time the watcher was started (or the last change	2062	relative to the attributes at the time the watcher was started (or the
1785	was detected).	2063	last change was detected).
1786		2064
1787	=item ev_stat_stat (loop, ev_stat *)	2065	=item ev_stat_stat (loop, ev_stat *)
1788		2066
1789	Updates the stat buffer immediately with new values. If you change the	2067	Updates the stat buffer immediately with new values. If you change the
1790	watched path in your callback, you could call this function to avoid	2068	watched path in your callback, you could call this function to avoid
…		…
1873		2151
1874		2152
1875	=head2 C<ev_idle> - when you've got nothing better to do...	2153	=head2 C<ev_idle> - when you've got nothing better to do...
1876		2154
1877	Idle watchers trigger events when no other events of the same or higher	2155	Idle watchers trigger events when no other events of the same or higher
1878	priority are pending (prepare, check and other idle watchers do not	2156	priority are pending (prepare, check and other idle watchers do not count
1879	count).	2157	as receiving "events").
1880		2158
1881	That is, as long as your process is busy handling sockets or timeouts	2159	That is, as long as your process is busy handling sockets or timeouts
1882	(or even signals, imagine) of the same or higher priority it will not be	2160	(or even signals, imagine) of the same or higher priority it will not be
1883	triggered. But when your process is idle (or only lower-priority watchers	2161	triggered. But when your process is idle (or only lower-priority watchers
1884	are pending), the idle watchers are being called once per event loop	2162	are pending), the idle watchers are being called once per event loop
…		…
1909		2187
1910	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2188	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1911	callback, free it. Also, use no error checking, as usual.	2189	callback, free it. Also, use no error checking, as usual.
1912		2190
1913	static void	2191	static void
1914	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2192	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1915	{	2193	{
1916	free (w);	2194	free (w);
1917	// now do something you wanted to do when the program has	2195	// now do something you wanted to do when the program has
1918	// no longer anything immediate to do.	2196	// no longer anything immediate to do.
1919	}	2197	}
1920		2198
1921	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2199	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1922	ev_idle_init (idle_watcher, idle_cb);	2200	ev_idle_init (idle_watcher, idle_cb);
1923	ev_idle_start (loop, idle_cb);	2201	ev_idle_start (loop, idle_cb);
1924		2202
1925		2203
1926	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2204	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1927		2205
1928	Prepare and check watchers are usually (but not always) used in tandem:	2206	Prepare and check watchers are usually (but not always) used in pairs:
1929	prepare watchers get invoked before the process blocks and check watchers	2207	prepare watchers get invoked before the process blocks and check watchers
1930	afterwards.	2208	afterwards.
1931		2209
1932	You I<must not> call C<ev_loop> or similar functions that enter	2210	You I<must not> call C<ev_loop> or similar functions that enter
1933	the current event loop from either C<ev_prepare> or C<ev_check>	2211	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1936	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2214	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1937	C<ev_check> so if you have one watcher of each kind they will always be	2215	C<ev_check> so if you have one watcher of each kind they will always be
1938	called in pairs bracketing the blocking call.	2216	called in pairs bracketing the blocking call.
1939		2217
1940	Their main purpose is to integrate other event mechanisms into libev and	2218	Their main purpose is to integrate other event mechanisms into libev and
1941	their use is somewhat advanced. This could be used, for example, to track	2219	their use is somewhat advanced. They could be used, for example, to track
1942	variable changes, implement your own watchers, integrate net-snmp or a	2220	variable changes, implement your own watchers, integrate net-snmp or a
1943	coroutine library and lots more. They are also occasionally useful if	2221	coroutine library and lots more. They are also occasionally useful if
1944	you cache some data and want to flush it before blocking (for example,	2222	you cache some data and want to flush it before blocking (for example,
1945	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2223	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1946	watcher).	2224	watcher).
1947		2225
1948	This is done by examining in each prepare call which file descriptors need	2226	This is done by examining in each prepare call which file descriptors
1949	to be watched by the other library, registering C<ev_io> watchers for	2227	need to be watched by the other library, registering C<ev_io> watchers
1950	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2228	for them and starting an C<ev_timer> watcher for any timeouts (many
1951	provide just this functionality). Then, in the check watcher you check for	2229	libraries provide exactly this functionality). Then, in the check watcher,
1952	any events that occurred (by checking the pending status of all watchers	2230	you check for any events that occurred (by checking the pending status
1953	and stopping them) and call back into the library. The I/O and timer	2231	of all watchers and stopping them) and call back into the library. The
1954	callbacks will never actually be called (but must be valid nevertheless,	2232	I/O and timer callbacks will never actually be called (but must be valid
1955	because you never know, you know?).	2233	nevertheless, because you never know, you know?).
1956		2234
1957	As another example, the Perl Coro module uses these hooks to integrate	2235	As another example, the Perl Coro module uses these hooks to integrate
1958	coroutines into libev programs, by yielding to other active coroutines	2236	coroutines into libev programs, by yielding to other active coroutines
1959	during each prepare and only letting the process block if no coroutines	2237	during each prepare and only letting the process block if no coroutines
1960	are ready to run (it's actually more complicated: it only runs coroutines	2238	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1963	loop from blocking if lower-priority coroutines are active, thus mapping	2241	loop from blocking if lower-priority coroutines are active, thus mapping
1964	low-priority coroutines to idle/background tasks).	2242	low-priority coroutines to idle/background tasks).
1965		2243
1966	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2244	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1967	priority, to ensure that they are being run before any other watchers	2245	priority, to ensure that they are being run before any other watchers
		2246	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2247
1968	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2248	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1969	too) should not activate ("feed") events into libev. While libev fully	2249	activate ("feed") events into libev. While libev fully supports this, they
1970	supports this, they might get executed before other C<ev_check> watchers	2250	might get executed before other C<ev_check> watchers did their job. As
1971	did their job. As C<ev_check> watchers are often used to embed other	2251	C<ev_check> watchers are often used to embed other (non-libev) event
1972	(non-libev) event loops those other event loops might be in an unusable	2252	loops those other event loops might be in an unusable state until their
1973	state until their C<ev_check> watcher ran (always remind yourself to	2253	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1974	coexist peacefully with others).	2254	others).
1975		2255
1976	=head3 Watcher-Specific Functions and Data Members	2256	=head3 Watcher-Specific Functions and Data Members
1977		2257
1978	=over 4	2258	=over 4
1979		2259
…		…
1981		2261
1982	=item ev_check_init (ev_check *, callback)	2262	=item ev_check_init (ev_check *, callback)
1983		2263
1984	Initialises and configures the prepare or check watcher - they have no	2264	Initialises and configures the prepare or check watcher - they have no
1985	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2265	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1986	macros, but using them is utterly, utterly and completely pointless.	2266	macros, but using them is utterly, utterly, utterly and completely
		2267	pointless.
1987		2268
1988	=back	2269	=back
1989		2270
1990	=head3 Examples	2271	=head3 Examples
1991		2272
…		…
2004		2285
2005	static ev_io iow [nfd];	2286	static ev_io iow [nfd];
2006	static ev_timer tw;	2287	static ev_timer tw;
2007		2288
2008	static void	2289	static void
2009	io_cb (ev_loop *loop, ev_io *w, int revents)	2290	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2010	{	2291	{
2011	}	2292	}
2012		2293
2013	// create io watchers for each fd and a timer before blocking	2294	// create io watchers for each fd and a timer before blocking
2014	static void	2295	static void
2015	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2296	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2016	{	2297	{
2017	int timeout = 3600000;	2298	int timeout = 3600000;
2018	struct pollfd fds [nfd];	2299	struct pollfd fds [nfd];
2019	// actual code will need to loop here and realloc etc.	2300	// actual code will need to loop here and realloc etc.
2020	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2301	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2035	}	2316	}
2036	}	2317	}
2037		2318
2038	// stop all watchers after blocking	2319	// stop all watchers after blocking
2039	static void	2320	static void
2040	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2321	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2041	{	2322	{
2042	ev_timer_stop (loop, &tw);	2323	ev_timer_stop (loop, &tw);
2043		2324
2044	for (int i = 0; i < nfd; ++i)	2325	for (int i = 0; i < nfd; ++i)
2045	{	2326	{
…		…
2084	}	2365	}
2085		2366
2086	// do not ever call adns_afterpoll	2367	// do not ever call adns_afterpoll
2087		2368
2088	Method 4: Do not use a prepare or check watcher because the module you	2369	Method 4: Do not use a prepare or check watcher because the module you
2089	want to embed is too inflexible to support it. Instead, you can override	2370	want to embed is not flexible enough to support it. Instead, you can
2090	their poll function. The drawback with this solution is that the main	2371	override their poll function. The drawback with this solution is that the
2091	loop is now no longer controllable by EV. The C<Glib::EV> module does	2372	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2092	this.	2373	this approach, effectively embedding EV as a client into the horrible
		2374	libglib event loop.
2093		2375
2094	static gint	2376	static gint
2095	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2377	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2096	{	2378	{
2097	int got_events = 0;	2379	int got_events = 0;
…		…
2128	prioritise I/O.	2410	prioritise I/O.
2129		2411
2130	As an example for a bug workaround, the kqueue backend might only support	2412	As an example for a bug workaround, the kqueue backend might only support
2131	sockets on some platform, so it is unusable as generic backend, but you	2413	sockets on some platform, so it is unusable as generic backend, but you
2132	still want to make use of it because you have many sockets and it scales	2414	still want to make use of it because you have many sockets and it scales
2133	so nicely. In this case, you would create a kqueue-based loop and embed it	2415	so nicely. In this case, you would create a kqueue-based loop and embed
2134	into your default loop (which might use e.g. poll). Overall operation will	2416	it into your default loop (which might use e.g. poll). Overall operation
2135	be a bit slower because first libev has to poll and then call kevent, but	2417	will be a bit slower because first libev has to call C<poll> and then
2136	at least you can use both at what they are best.	2418	C<kevent>, but at least you can use both mechanisms for what they are
		2419	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2137		2420
2138	As for prioritising I/O: rarely you have the case where some fds have	2421	As for prioritising I/O: under rare circumstances you have the case where
2139	to be watched and handled very quickly (with low latency), and even	2422	some fds have to be watched and handled very quickly (with low latency),
2140	priorities and idle watchers might have too much overhead. In this case	2423	and even priorities and idle watchers might have too much overhead. In
2141	you would put all the high priority stuff in one loop and all the rest in	2424	this case you would put all the high priority stuff in one loop and all
2142	a second one, and embed the second one in the first.	2425	the rest in a second one, and embed the second one in the first.
2143		2426
2144	As long as the watcher is active, the callback will be invoked every time	2427	As long as the watcher is active, the callback will be invoked every time
2145	there might be events pending in the embedded loop. The callback must then	2428	there might be events pending in the embedded loop. The callback must then
2146	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2429	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2147	their callbacks (you could also start an idle watcher to give the embedded	2430	their callbacks (you could also start an idle watcher to give the embedded
…		…
2155	interested in that.	2438	interested in that.
2156		2439
2157	Also, there have not currently been made special provisions for forking:	2440	Also, there have not currently been made special provisions for forking:
2158	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2441	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2159	but you will also have to stop and restart any C<ev_embed> watchers	2442	but you will also have to stop and restart any C<ev_embed> watchers
2160	yourself.	2443	yourself - but you can use a fork watcher to handle this automatically,
		2444	and future versions of libev might do just that.
2161		2445
2162	Unfortunately, not all backends are embeddable, only the ones returned by	2446	Unfortunately, not all backends are embeddable: only the ones returned by
2163	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2447	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2164	portable one.	2448	portable one.
2165		2449
2166	So when you want to use this feature you will always have to be prepared	2450	So when you want to use this feature you will always have to be prepared
2167	that you cannot get an embeddable loop. The recommended way to get around	2451	that you cannot get an embeddable loop. The recommended way to get around
2168	this is to have a separate variables for your embeddable loop, try to	2452	this is to have a separate variables for your embeddable loop, try to
2169	create it, and if that fails, use the normal loop for everything.	2453	create it, and if that fails, use the normal loop for everything.
		2454
		2455	=head3 C<ev_embed> and fork
		2456
		2457	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2458	automatically be applied to the embedded loop as well, so no special
		2459	fork handling is required in that case. When the watcher is not running,
		2460	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2461	as applicable.
2170		2462
2171	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
2172		2464
2173	=over 4	2465	=over 4
2174		2466
…		…
2202	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2494	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2203	used).	2495	used).
2204		2496
2205	struct ev_loop *loop_hi = ev_default_init (0);	2497	struct ev_loop *loop_hi = ev_default_init (0);
2206	struct ev_loop *loop_lo = 0;	2498	struct ev_loop *loop_lo = 0;
2207	struct ev_embed embed;	2499	ev_embed embed;
2208		2500
2209	// see if there is a chance of getting one that works	2501	// see if there is a chance of getting one that works
2210	// (remember that a flags value of 0 means autodetection)	2502	// (remember that a flags value of 0 means autodetection)
2211	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2503	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2212	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2504	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2226	kqueue implementation). Store the kqueue/socket-only event loop in	2518	kqueue implementation). Store the kqueue/socket-only event loop in
2227	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2519	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2228		2520
2229	struct ev_loop *loop = ev_default_init (0);	2521	struct ev_loop *loop = ev_default_init (0);
2230	struct ev_loop *loop_socket = 0;	2522	struct ev_loop *loop_socket = 0;
2231	struct ev_embed embed;	2523	ev_embed embed;
2232		2524
2233	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2525	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2234	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2526	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2235	{	2527	{
2236	ev_embed_init (&embed, 0, loop_socket);	2528	ev_embed_init (&embed, 0, loop_socket);
…		…
2292	is that the author does not know of a simple (or any) algorithm for a	2584	is that the author does not know of a simple (or any) algorithm for a
2293	multiple-writer-single-reader queue that works in all cases and doesn't	2585	multiple-writer-single-reader queue that works in all cases and doesn't
2294	need elaborate support such as pthreads.	2586	need elaborate support such as pthreads.
2295		2587
2296	That means that if you want to queue data, you have to provide your own	2588	That means that if you want to queue data, you have to provide your own
2297	queue. But at least I can tell you would implement locking around your	2589	queue. But at least I can tell you how to implement locking around your
2298	queue:	2590	queue:
2299		2591
2300	=over 4	2592	=over 4
2301		2593
2302	=item queueing from a signal handler context	2594	=item queueing from a signal handler context
2303		2595
2304	To implement race-free queueing, you simply add to the queue in the signal	2596	To implement race-free queueing, you simply add to the queue in the signal
2305	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2597	handler but you block the signal handler in the watcher callback. Here is
2306	some fictitious SIGUSR1 handler:	2598	an example that does that for some fictitious SIGUSR1 handler:
2307		2599
2308	static ev_async mysig;	2600	static ev_async mysig;
2309		2601
2310	static void	2602	static void
2311	sigusr1_handler (void)	2603	sigusr1_handler (void)
…		…
2377	=over 4	2669	=over 4
2378		2670
2379	=item ev_async_init (ev_async *, callback)	2671	=item ev_async_init (ev_async *, callback)
2380		2672
2381	Initialises and configures the async watcher - it has no parameters of any	2673	Initialises and configures the async watcher - it has no parameters of any
2382	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2674	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2383	believe me.	2675	trust me.
2384		2676
2385	=item ev_async_send (loop, ev_async *)	2677	=item ev_async_send (loop, ev_async *)
2386		2678
2387	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2679	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2388	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2680	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2389	C<ev_feed_event>, this call is safe to do in other threads, signal or	2681	C<ev_feed_event>, this call is safe to do from other threads, signal or
2390	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2682	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2391	section below on what exactly this means).	2683	section below on what exactly this means).
2392		2684
2393	This call incurs the overhead of a system call only once per loop iteration,	2685	This call incurs the overhead of a system call only once per loop iteration,
2394	so while the overhead might be noticeable, it doesn't apply to repeated	2686	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2418	=over 4	2710	=over 4
2419		2711
2420	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2712	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2421		2713
2422	This function combines a simple timer and an I/O watcher, calls your	2714	This function combines a simple timer and an I/O watcher, calls your
2423	callback on whichever event happens first and automatically stop both	2715	callback on whichever event happens first and automatically stops both
2424	watchers. This is useful if you want to wait for a single event on an fd	2716	watchers. This is useful if you want to wait for a single event on an fd
2425	or timeout without having to allocate/configure/start/stop/free one or	2717	or timeout without having to allocate/configure/start/stop/free one or
2426	more watchers yourself.	2718	more watchers yourself.
2427		2719
2428	If C<fd> is less than 0, then no I/O watcher will be started and events	2720	If C<fd> is less than 0, then no I/O watcher will be started and the
2429	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2721	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2430	C<events> set will be created and started.	2722	the given C<fd> and C<events> set will be created and started.
2431		2723
2432	If C<timeout> is less than 0, then no timeout watcher will be	2724	If C<timeout> is less than 0, then no timeout watcher will be
2433	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2725	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2434	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2726	repeat = 0) will be started. C<0> is a valid timeout.
2435	dubious value.
2436		2727
2437	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2728	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2438	passed an C<revents> set like normal event callbacks (a combination of	2729	passed an C<revents> set like normal event callbacks (a combination of
2439	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2730	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2440	value passed to C<ev_once>:	2731	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2732	a timeout and an io event at the same time - you probably should give io
		2733	events precedence.
		2734
		2735	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2441		2736
2442	static void stdin_ready (int revents, void *arg)	2737	static void stdin_ready (int revents, void *arg)
2443	{	2738	{
		2739	if (revents & EV_READ)
		2740	/* stdin might have data for us, joy! */;
2444	if (revents & EV_TIMEOUT)	2741	else if (revents & EV_TIMEOUT)
2445	/* doh, nothing entered */;	2742	/* doh, nothing entered */;
2446	else if (revents & EV_READ)
2447	/* stdin might have data for us, joy! */;
2448	}	2743	}
2449		2744
2450	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2745	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2451		2746
2452	=item ev_feed_event (ev_loop *, watcher *, int revents)	2747	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2453		2748
2454	Feeds the given event set into the event loop, as if the specified event	2749	Feeds the given event set into the event loop, as if the specified event
2455	had happened for the specified watcher (which must be a pointer to an	2750	had happened for the specified watcher (which must be a pointer to an
2456	initialised but not necessarily started event watcher).	2751	initialised but not necessarily started event watcher).
2457		2752
2458	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2753	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2459		2754
2460	Feed an event on the given fd, as if a file descriptor backend detected	2755	Feed an event on the given fd, as if a file descriptor backend detected
2461	the given events it.	2756	the given events it.
2462		2757
2463	=item ev_feed_signal_event (ev_loop *loop, int signum)	2758	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2464		2759
2465	Feed an event as if the given signal occurred (C<loop> must be the default	2760	Feed an event as if the given signal occurred (C<loop> must be the default
2466	loop!).	2761	loop!).
2467		2762
2468	=back	2763	=back
…		…
2600		2895
2601	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2896	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2602		2897
2603	See the method-C<set> above for more details.	2898	See the method-C<set> above for more details.
2604		2899
2605	Example:	2900	Example: Use a plain function as callback.
2606		2901
2607	static void io_cb (ev::io &w, int revents) { }	2902	static void io_cb (ev::io &w, int revents) { }
2608	iow.set <io_cb> ();	2903	iow.set <io_cb> ();
2609		2904
2610	=item w->set (struct ev_loop *)	2905	=item w->set (struct ev_loop *)
…		…
2648	Example: Define a class with an IO and idle watcher, start one of them in	2943	Example: Define a class with an IO and idle watcher, start one of them in
2649	the constructor.	2944	the constructor.
2650		2945
2651	class myclass	2946	class myclass
2652	{	2947	{
2653	ev::io io; void io_cb (ev::io &w, int revents);	2948	ev::io io ; void io_cb (ev::io &w, int revents);
2654	ev:idle idle void idle_cb (ev::idle &w, int revents);	2949	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2655		2950
2656	myclass (int fd)	2951	myclass (int fd)
2657	{	2952	{
2658	io .set <myclass, &myclass::io_cb > (this);	2953	io .set <myclass, &myclass::io_cb > (this);
2659	idle.set <myclass, &myclass::idle_cb> (this);	2954	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2675	=item Perl	2970	=item Perl
2676		2971
2677	The EV module implements the full libev API and is actually used to test	2972	The EV module implements the full libev API and is actually used to test
2678	libev. EV is developed together with libev. Apart from the EV core module,	2973	libev. EV is developed together with libev. Apart from the EV core module,
2679	there are additional modules that implement libev-compatible interfaces	2974	there are additional modules that implement libev-compatible interfaces
2680	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2975	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2681	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2976	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2977	and C<EV::Glib>).
2682		2978
2683	It can be found and installed via CPAN, its homepage is at	2979	It can be found and installed via CPAN, its homepage is at
2684	L<http://software.schmorp.de/pkg/EV>.	2980	L<http://software.schmorp.de/pkg/EV>.
2685		2981
2686	=item Python	2982	=item Python
…		…
2702	=item D	2998	=item D
2703		2999
2704	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3000	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2705	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3001	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2706		3002
		3003	=item Ocaml
		3004
		3005	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3006	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3007
2707	=back	3008	=back
2708		3009
2709		3010
2710	=head1 MACRO MAGIC	3011	=head1 MACRO MAGIC
2711		3012
…		…
2811		3112
2812	#define EV_STANDALONE 1	3113	#define EV_STANDALONE 1
2813	#include "ev.h"	3114	#include "ev.h"
2814		3115
2815	Both header files and implementation files can be compiled with a C++	3116	Both header files and implementation files can be compiled with a C++
2816	compiler (at least, thats a stated goal, and breakage will be treated	3117	compiler (at least, that's a stated goal, and breakage will be treated
2817	as a bug).	3118	as a bug).
2818		3119
2819	You need the following files in your source tree, or in a directory	3120	You need the following files in your source tree, or in a directory
2820	in your include path (e.g. in libev/ when using -Ilibev):	3121	in your include path (e.g. in libev/ when using -Ilibev):
2821		3122
…		…
2865		3166
2866	=head2 PREPROCESSOR SYMBOLS/MACROS	3167	=head2 PREPROCESSOR SYMBOLS/MACROS
2867		3168
2868	Libev can be configured via a variety of preprocessor symbols you have to	3169	Libev can be configured via a variety of preprocessor symbols you have to
2869	define before including any of its files. The default in the absence of	3170	define before including any of its files. The default in the absence of
2870	autoconf is noted for every option.	3171	autoconf is documented for every option.
2871		3172
2872	=over 4	3173	=over 4
2873		3174
2874	=item EV_STANDALONE	3175	=item EV_STANDALONE
2875		3176
…		…
3045	When doing priority-based operations, libev usually has to linearly search	3346	When doing priority-based operations, libev usually has to linearly search
3046	all the priorities, so having many of them (hundreds) uses a lot of space	3347	all the priorities, so having many of them (hundreds) uses a lot of space
3047	and time, so using the defaults of five priorities (-2 .. +2) is usually	3348	and time, so using the defaults of five priorities (-2 .. +2) is usually
3048	fine.	3349	fine.
3049		3350
3050	If your embedding application does not need any priorities, defining these both to	3351	If your embedding application does not need any priorities, defining these
3051	C<0> will save some memory and CPU.	3352	both to C<0> will save some memory and CPU.
3052		3353
3053	=item EV_PERIODIC_ENABLE	3354	=item EV_PERIODIC_ENABLE
3054		3355
3055	If undefined or defined to be C<1>, then periodic timers are supported. If	3356	If undefined or defined to be C<1>, then periodic timers are supported. If
3056	defined to be C<0>, then they are not. Disabling them saves a few kB of	3357	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3063	code.	3364	code.
3064		3365
3065	=item EV_EMBED_ENABLE	3366	=item EV_EMBED_ENABLE
3066		3367
3067	If undefined or defined to be C<1>, then embed watchers are supported. If	3368	If undefined or defined to be C<1>, then embed watchers are supported. If
3068	defined to be C<0>, then they are not.	3369	defined to be C<0>, then they are not. Embed watchers rely on most other
		3370	watcher types, which therefore must not be disabled.
3069		3371
3070	=item EV_STAT_ENABLE	3372	=item EV_STAT_ENABLE
3071		3373
3072	If undefined or defined to be C<1>, then stat watchers are supported. If	3374	If undefined or defined to be C<1>, then stat watchers are supported. If
3073	defined to be C<0>, then they are not.	3375	defined to be C<0>, then they are not.
…		…
3105	two).	3407	two).
3106		3408
3107	=item EV_USE_4HEAP	3409	=item EV_USE_4HEAP
3108		3410
3109	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3411	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3110	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3412	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3111	to C<1>. The 4-heap uses more complicated (longer) code but has	3413	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3112	noticeably faster performance with many (thousands) of watchers.	3414	faster performance with many (thousands) of watchers.
3113		3415
3114	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3416	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3115	(disabled).	3417	(disabled).
3116		3418
3117	=item EV_HEAP_CACHE_AT	3419	=item EV_HEAP_CACHE_AT
3118		3420
3119	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3421	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3120	timer and periodics heap, libev can cache the timestamp (I<at>) within	3422	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3121	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3423	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3122	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3424	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3123	but avoids random read accesses on heap changes. This improves performance	3425	but avoids random read accesses on heap changes. This improves performance
3124	noticeably with with many (hundreds) of watchers.	3426	noticeably with many (hundreds) of watchers.
3125		3427
3126	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3428	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3127	(disabled).	3429	(disabled).
3128		3430
3129	=item EV_VERIFY	3431	=item EV_VERIFY
…		…
3135	called once per loop, which can slow down libev. If set to C<3>, then the	3437	called once per loop, which can slow down libev. If set to C<3>, then the
3136	verification code will be called very frequently, which will slow down	3438	verification code will be called very frequently, which will slow down
3137	libev considerably.	3439	libev considerably.
3138		3440
3139	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3441	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3140	C<0.>	3442	C<0>.
3141		3443
3142	=item EV_COMMON	3444	=item EV_COMMON
3143		3445
3144	By default, all watchers have a C<void *data> member. By redefining	3446	By default, all watchers have a C<void *data> member. By redefining
3145	this macro to a something else you can include more and other types of	3447	this macro to a something else you can include more and other types of
…		…
3162	and the way callbacks are invoked and set. Must expand to a struct member	3464	and the way callbacks are invoked and set. Must expand to a struct member
3163	definition and a statement, respectively. See the F<ev.h> header file for	3465	definition and a statement, respectively. See the F<ev.h> header file for
3164	their default definitions. One possible use for overriding these is to	3466	their default definitions. One possible use for overriding these is to
3165	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3467	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3166	method calls instead of plain function calls in C++.	3468	method calls instead of plain function calls in C++.
		3469
		3470	=back
3167		3471
3168	=head2 EXPORTED API SYMBOLS	3472	=head2 EXPORTED API SYMBOLS
3169		3473
3170	If you need to re-export the API (e.g. via a DLL) and you need a list of	3474	If you need to re-export the API (e.g. via a DLL) and you need a list of
3171	exported symbols, you can use the provided F<Symbol.*> files which list	3475	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3218	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3522	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3219		3523
3220	#include "ev_cpp.h"	3524	#include "ev_cpp.h"
3221	#include "ev.c"	3525	#include "ev.c"
3222		3526
		3527	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3223		3528
3224	=head1 THREADS AND COROUTINES	3529	=head2 THREADS AND COROUTINES
3225		3530
3226	=head2 THREADS	3531	=head3 THREADS
3227		3532
3228	Libev itself is completely thread-safe, but it uses no locking. This	3533	All libev functions are reentrant and thread-safe unless explicitly
		3534	documented otherwise, but libev implements no locking itself. This means
3229	means that you can use as many loops as you want in parallel, as long as	3535	that you can use as many loops as you want in parallel, as long as there
3230	only one thread ever calls into one libev function with the same loop	3536	are no concurrent calls into any libev function with the same loop
3231	parameter.	3537	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3538	of course): libev guarantees that different event loops share no data
		3539	structures that need any locking.
3232		3540
3233	Or put differently: calls with different loop parameters can be done in	3541	Or to put it differently: calls with different loop parameters can be done
3234	parallel from multiple threads, calls with the same loop parameter must be	3542	concurrently from multiple threads, calls with the same loop parameter
3235	done serially (but can be done from different threads, as long as only one	3543	must be done serially (but can be done from different threads, as long as
3236	thread ever is inside a call at any point in time, e.g. by using a mutex	3544	only one thread ever is inside a call at any point in time, e.g. by using
3237	per loop).	3545	a mutex per loop).
		3546
		3547	Specifically to support threads (and signal handlers), libev implements
		3548	so-called C<ev_async> watchers, which allow some limited form of
		3549	concurrency on the same event loop, namely waking it up "from the
		3550	outside".
3238		3551
3239	If you want to know which design (one loop, locking, or multiple loops	3552	If you want to know which design (one loop, locking, or multiple loops
3240	without or something else still) is best for your problem, then I cannot	3553	without or something else still) is best for your problem, then I cannot
3241	help you. I can give some generic advice however:	3554	help you, but here is some generic advice:
3242		3555
3243	=over 4	3556	=over 4
3244		3557
3245	=item * most applications have a main thread: use the default libev loop	3558	=item * most applications have a main thread: use the default libev loop
3246	in that thread, or create a separate thread running only the default loop.	3559	in that thread, or create a separate thread running only the default loop.
…		…
3258		3571
3259	Choosing a model is hard - look around, learn, know that usually you can do	3572	Choosing a model is hard - look around, learn, know that usually you can do
3260	better than you currently do :-)	3573	better than you currently do :-)
3261		3574
3262	=item * often you need to talk to some other thread which blocks in the	3575	=item * often you need to talk to some other thread which blocks in the
		3576	event loop.
		3577
3263	event loop - C<ev_async> watchers can be used to wake them up from other	3578	C<ev_async> watchers can be used to wake them up from other threads safely
3264	threads safely (or from signal contexts...).	3579	(or from signal contexts...).
		3580
		3581	An example use would be to communicate signals or other events that only
		3582	work in the default loop by registering the signal watcher with the
		3583	default loop and triggering an C<ev_async> watcher from the default loop
		3584	watcher callback into the event loop interested in the signal.
3265		3585
3266	=back	3586	=back
3267		3587
3268	=head2 COROUTINES	3588	=head3 COROUTINES
3269		3589
3270	Libev is much more accommodating to coroutines ("cooperative threads"):	3590	Libev is very accommodating to coroutines ("cooperative threads"):
3271	libev fully supports nesting calls to it's functions from different	3591	libev fully supports nesting calls to its functions from different
3272	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3592	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3273	different coroutines and switch freely between both coroutines running the	3593	different coroutines, and switch freely between both coroutines running the
3274	loop, as long as you don't confuse yourself). The only exception is that	3594	loop, as long as you don't confuse yourself). The only exception is that
3275	you must not do this from C<ev_periodic> reschedule callbacks.	3595	you must not do this from C<ev_periodic> reschedule callbacks.
3276		3596
3277	Care has been invested into making sure that libev does not keep local	3597	Care has been taken to ensure that libev does not keep local state inside
3278	state inside C<ev_loop>, and other calls do not usually allow coroutine	3598	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3279	switches.	3599	they do not call any callbacks.
3280		3600
		3601	=head2 COMPILER WARNINGS
3281		3602
3282	=head1 COMPLEXITIES	3603	Depending on your compiler and compiler settings, you might get no or a
		3604	lot of warnings when compiling libev code. Some people are apparently
		3605	scared by this.
3283		3606
3284	In this section the complexities of (many of) the algorithms used inside	3607	However, these are unavoidable for many reasons. For one, each compiler
3285	libev will be explained. For complexity discussions about backends see the	3608	has different warnings, and each user has different tastes regarding
3286	documentation for C<ev_default_init>.	3609	warning options. "Warn-free" code therefore cannot be a goal except when
		3610	targeting a specific compiler and compiler-version.
3287		3611
3288	All of the following are about amortised time: If an array needs to be	3612	Another reason is that some compiler warnings require elaborate
3289	extended, libev needs to realloc and move the whole array, but this	3613	workarounds, or other changes to the code that make it less clear and less
3290	happens asymptotically never with higher number of elements, so O(1) might	3614	maintainable.
3291	mean it might do a lengthy realloc operation in rare cases, but on average
3292	it is much faster and asymptotically approaches constant time.
3293		3615
3294	=over 4	3616	And of course, some compiler warnings are just plain stupid, or simply
		3617	wrong (because they don't actually warn about the condition their message
		3618	seems to warn about). For example, certain older gcc versions had some
		3619	warnings that resulted an extreme number of false positives. These have
		3620	been fixed, but some people still insist on making code warn-free with
		3621	such buggy versions.
3295		3622
3296	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3623	While libev is written to generate as few warnings as possible,
		3624	"warn-free" code is not a goal, and it is recommended not to build libev
		3625	with any compiler warnings enabled unless you are prepared to cope with
		3626	them (e.g. by ignoring them). Remember that warnings are just that:
		3627	warnings, not errors, or proof of bugs.
3297		3628
3298	This means that, when you have a watcher that triggers in one hour and
3299	there are 100 watchers that would trigger before that then inserting will
3300	have to skip roughly seven (C<ld 100>) of these watchers.
3301		3629
3302	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3630	=head2 VALGRIND
3303		3631
3304	That means that changing a timer costs less than removing/adding them	3632	Valgrind has a special section here because it is a popular tool that is
3305	as only the relative motion in the event queue has to be paid for.	3633	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3306		3634
3307	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3635	If you think you found a bug (memory leak, uninitialised data access etc.)
		3636	in libev, then check twice: If valgrind reports something like:
3308		3637
3309	These just add the watcher into an array or at the head of a list.	3638	==2274== definitely lost: 0 bytes in 0 blocks.
		3639	==2274== possibly lost: 0 bytes in 0 blocks.
		3640	==2274== still reachable: 256 bytes in 1 blocks.
3310		3641
3311	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3642	Then there is no memory leak, just as memory accounted to global variables
		3643	is not a memleak - the memory is still being referenced, and didn't leak.
3312		3644
3313	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3645	Similarly, under some circumstances, valgrind might report kernel bugs
		3646	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3647	although an acceptable workaround has been found here), or it might be
		3648	confused.
3314		3649
3315	These watchers are stored in lists then need to be walked to find the	3650	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3316	correct watcher to remove. The lists are usually short (you don't usually	3651	make it into some kind of religion.
3317	have many watchers waiting for the same fd or signal).
3318		3652
3319	=item Finding the next timer in each loop iteration: O(1)	3653	If you are unsure about something, feel free to contact the mailing list
		3654	with the full valgrind report and an explanation on why you think this
		3655	is a bug in libev (best check the archives, too :). However, don't be
		3656	annoyed when you get a brisk "this is no bug" answer and take the chance
		3657	of learning how to interpret valgrind properly.
3320		3658
3321	By virtue of using a binary or 4-heap, the next timer is always found at a	3659	If you need, for some reason, empty reports from valgrind for your project
3322	fixed position in the storage array.	3660	I suggest using suppression lists.
3323		3661
3324	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3325		3662
3326	A change means an I/O watcher gets started or stopped, which requires	3663	=head1 PORTABILITY NOTES
3327	libev to recalculate its status (and possibly tell the kernel, depending
3328	on backend and whether C<ev_io_set> was used).
3329		3664
3330	=item Activating one watcher (putting it into the pending state): O(1)
3331
3332	=item Priority handling: O(number_of_priorities)
3333
3334	Priorities are implemented by allocating some space for each
3335	priority. When doing priority-based operations, libev usually has to
3336	linearly search all the priorities, but starting/stopping and activating
3337	watchers becomes O(1) w.r.t. priority handling.
3338
3339	=item Sending an ev_async: O(1)
3340
3341	=item Processing ev_async_send: O(number_of_async_watchers)
3342
3343	=item Processing signals: O(max_signal_number)
3344
3345	Sending involves a system call I<iff> there were no other C<ev_async_send>
3346	calls in the current loop iteration. Checking for async and signal events
3347	involves iterating over all running async watchers or all signal numbers.
3348
3349	=back
3350
3351
3352	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3665	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3353		3666
3354	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3667	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3355	requires, and its I/O model is fundamentally incompatible with the POSIX	3668	requires, and its I/O model is fundamentally incompatible with the POSIX
3356	model. Libev still offers limited functionality on this platform in	3669	model. Libev still offers limited functionality on this platform in
3357	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3670	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3368		3681
3369	Not a libev limitation but worth mentioning: windows apparently doesn't	3682	Not a libev limitation but worth mentioning: windows apparently doesn't
3370	accept large writes: instead of resulting in a partial write, windows will	3683	accept large writes: instead of resulting in a partial write, windows will
3371	either accept everything or return C<ENOBUFS> if the buffer is too large,	3684	either accept everything or return C<ENOBUFS> if the buffer is too large,
3372	so make sure you only write small amounts into your sockets (less than a	3685	so make sure you only write small amounts into your sockets (less than a
3373	megabyte seems safe, but thsi apparently depends on the amount of memory	3686	megabyte seems safe, but this apparently depends on the amount of memory
3374	available).	3687	available).
3375		3688
3376	Due to the many, low, and arbitrary limits on the win32 platform and	3689	Due to the many, low, and arbitrary limits on the win32 platform and
3377	the abysmal performance of winsockets, using a large number of sockets	3690	the abysmal performance of winsockets, using a large number of sockets
3378	is not recommended (and not reasonable). If your program needs to use	3691	is not recommended (and not reasonable). If your program needs to use
…		…
3389	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3702	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3390		3703
3391	#include "ev.h"	3704	#include "ev.h"
3392		3705
3393	And compile the following F<evwrap.c> file into your project (make sure	3706	And compile the following F<evwrap.c> file into your project (make sure
3394	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3707	you do I<not> compile the F<ev.c> or any other embedded source files!):
3395		3708
3396	#include "evwrap.h"	3709	#include "evwrap.h"
3397	#include "ev.c"	3710	#include "ev.c"
3398		3711
3399	=over 4	3712	=over 4
…		…
3444	wrap all I/O functions and provide your own fd management, but the cost of	3757	wrap all I/O functions and provide your own fd management, but the cost of
3445	calling select (O(n²)) will likely make this unworkable.	3758	calling select (O(n²)) will likely make this unworkable.
3446		3759
3447	=back	3760	=back
3448		3761
3449
3450	=head1 PORTABILITY REQUIREMENTS	3762	=head2 PORTABILITY REQUIREMENTS
3451		3763
3452	In addition to a working ISO-C implementation, libev relies on a few	3764	In addition to a working ISO-C implementation and of course the
3453	additional extensions:	3765	backend-specific APIs, libev relies on a few additional extensions:
3454		3766
3455	=over 4	3767	=over 4
3456		3768
3457	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3769	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3458	calling conventions regardless of C<ev_watcher_type *>.	3770	calling conventions regardless of C<ev_watcher_type *>.
…		…
3464	calls them using an C<ev_watcher *> internally.	3776	calls them using an C<ev_watcher *> internally.
3465		3777
3466	=item C<sig_atomic_t volatile> must be thread-atomic as well	3778	=item C<sig_atomic_t volatile> must be thread-atomic as well
3467		3779
3468	The type C<sig_atomic_t volatile> (or whatever is defined as	3780	The type C<sig_atomic_t volatile> (or whatever is defined as
3469	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3781	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3470	threads. This is not part of the specification for C<sig_atomic_t>, but is	3782	threads. This is not part of the specification for C<sig_atomic_t>, but is
3471	believed to be sufficiently portable.	3783	believed to be sufficiently portable.
3472		3784
3473	=item C<sigprocmask> must work in a threaded environment	3785	=item C<sigprocmask> must work in a threaded environment
3474		3786
…		…
3483	except the initial one, and run the default loop in the initial thread as	3795	except the initial one, and run the default loop in the initial thread as
3484	well.	3796	well.
3485		3797
3486	=item C<long> must be large enough for common memory allocation sizes	3798	=item C<long> must be large enough for common memory allocation sizes
3487		3799
3488	To improve portability and simplify using libev, libev uses C<long>	3800	To improve portability and simplify its API, libev uses C<long> internally
3489	internally instead of C<size_t> when allocating its data structures. On	3801	instead of C<size_t> when allocating its data structures. On non-POSIX
3490	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3802	systems (Microsoft...) this might be unexpectedly low, but is still at
3491	is still at least 31 bits everywhere, which is enough for hundreds of	3803	least 31 bits everywhere, which is enough for hundreds of millions of
3492	millions of watchers.	3804	watchers.
3493		3805
3494	=item C<double> must hold a time value in seconds with enough accuracy	3806	=item C<double> must hold a time value in seconds with enough accuracy
3495		3807
3496	The type C<double> is used to represent timestamps. It is required to	3808	The type C<double> is used to represent timestamps. It is required to
3497	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3809	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3501	=back	3813	=back
3502		3814
3503	If you know of other additional requirements drop me a note.	3815	If you know of other additional requirements drop me a note.
3504		3816
3505		3817
3506	=head1 COMPILER WARNINGS	3818	=head1 ALGORITHMIC COMPLEXITIES
3507		3819
3508	Depending on your compiler and compiler settings, you might get no or a	3820	In this section the complexities of (many of) the algorithms used inside
3509	lot of warnings when compiling libev code. Some people are apparently	3821	libev will be documented. For complexity discussions about backends see
3510	scared by this.	3822	the documentation for C<ev_default_init>.
3511		3823
3512	However, these are unavoidable for many reasons. For one, each compiler	3824	All of the following are about amortised time: If an array needs to be
3513	has different warnings, and each user has different tastes regarding	3825	extended, libev needs to realloc and move the whole array, but this
3514	warning options. "Warn-free" code therefore cannot be a goal except when	3826	happens asymptotically rarer with higher number of elements, so O(1) might
3515	targeting a specific compiler and compiler-version.	3827	mean that libev does a lengthy realloc operation in rare cases, but on
		3828	average it is much faster and asymptotically approaches constant time.
3516		3829
3517	Another reason is that some compiler warnings require elaborate	3830	=over 4
3518	workarounds, or other changes to the code that make it less clear and less
3519	maintainable.
3520		3831
3521	And of course, some compiler warnings are just plain stupid, or simply	3832	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3522	wrong (because they don't actually warn about the condition their message
3523	seems to warn about).
3524		3833
3525	While libev is written to generate as few warnings as possible,	3834	This means that, when you have a watcher that triggers in one hour and
3526	"warn-free" code is not a goal, and it is recommended not to build libev	3835	there are 100 watchers that would trigger before that, then inserting will
3527	with any compiler warnings enabled unless you are prepared to cope with	3836	have to skip roughly seven (C<ld 100>) of these watchers.
3528	them (e.g. by ignoring them). Remember that warnings are just that:
3529	warnings, not errors, or proof of bugs.
3530		3837
		3838	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3531		3839
3532	=head1 VALGRIND	3840	That means that changing a timer costs less than removing/adding them,
		3841	as only the relative motion in the event queue has to be paid for.
3533		3842
3534	Valgrind has a special section here because it is a popular tool that is	3843	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3535	highly useful, but valgrind reports are very hard to interpret.
3536		3844
3537	If you think you found a bug (memory leak, uninitialised data access etc.)	3845	These just add the watcher into an array or at the head of a list.
3538	in libev, then check twice: If valgrind reports something like:
3539		3846
3540	==2274== definitely lost: 0 bytes in 0 blocks.	3847	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3541	==2274== possibly lost: 0 bytes in 0 blocks.
3542	==2274== still reachable: 256 bytes in 1 blocks.
3543		3848
3544	Then there is no memory leak. Similarly, under some circumstances,	3849	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3545	valgrind might report kernel bugs as if it were a bug in libev, or it
3546	might be confused (it is a very good tool, but only a tool).
3547		3850
3548	If you are unsure about something, feel free to contact the mailing list	3851	These watchers are stored in lists, so they need to be walked to find the
3549	with the full valgrind report and an explanation on why you think this is	3852	correct watcher to remove. The lists are usually short (you don't usually
3550	a bug in libev. However, don't be annoyed when you get a brisk "this is	3853	have many watchers waiting for the same fd or signal: one is typical, two
3551	no bug" answer and take the chance of learning how to interpret valgrind	3854	is rare).
3552	properly.
3553		3855
3554	If you need, for some reason, empty reports from valgrind for your project	3856	=item Finding the next timer in each loop iteration: O(1)
3555	I suggest using suppression lists.	3857
		3858	By virtue of using a binary or 4-heap, the next timer is always found at a
		3859	fixed position in the storage array.
		3860
		3861	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3862
		3863	A change means an I/O watcher gets started or stopped, which requires
		3864	libev to recalculate its status (and possibly tell the kernel, depending
		3865	on backend and whether C<ev_io_set> was used).
		3866
		3867	=item Activating one watcher (putting it into the pending state): O(1)
		3868
		3869	=item Priority handling: O(number_of_priorities)
		3870
		3871	Priorities are implemented by allocating some space for each
		3872	priority. When doing priority-based operations, libev usually has to
		3873	linearly search all the priorities, but starting/stopping and activating
		3874	watchers becomes O(1) with respect to priority handling.
		3875
		3876	=item Sending an ev_async: O(1)
		3877
		3878	=item Processing ev_async_send: O(number_of_async_watchers)
		3879
		3880	=item Processing signals: O(max_signal_number)
		3881
		3882	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3883	calls in the current loop iteration. Checking for async and signal events
		3884	involves iterating over all running async watchers or all signal numbers.
		3885
		3886	=back
3556		3887
3557		3888
3558	=head1 AUTHOR	3889	=head1 AUTHOR
3559		3890
3560	Marc Lehmann <libev@schmorp.de>.	3891	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3561		3892

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