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Revision 1.177 by root, Mon Sep 8 17:27:42 2008 UTC vs.
Revision 1.210 by root, Thu Oct 30 08:09:30 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	};
		1102
		1103	...
		1104	struct my_io w;
		1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
1012		1106
1013	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
1014	can cast it back to your own type:	1108	can cast it back to your own type:
1015		1109
1016	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)
1017	{	1111	{
1018	struct my_io *w = (struct my_io *)w_;	1112	struct my_io *w = (struct my_io *)w_;
1019	...	1113	...
1020	}	1114	}
1021		1115
1022	More interesting and less C-conformant ways of casting your callback type	1116	More interesting and less C-conformant ways of casting your callback type
1023	instead have been omitted.	1117	instead have been omitted.
1024		1118
1025	Another common scenario is having some data structure with multiple	1119	Another common scenario is to use some data structure with multiple
1026	watchers:	1120	embedded watchers:
1027		1121
1028	struct my_biggy	1122	struct my_biggy
1029	{	1123	{
1030	int some_data;	1124	int some_data;
1031	ev_timer t1;	1125	ev_timer t1;
1032	ev_timer t2;	1126	ev_timer t2;
1033	}	1127	}
1034		1128
1035	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1129	In this case getting the pointer to C<my_biggy> is a bit more
1036	you need to use C<offsetof>:	1130	complicated: Either you store the address of your C<my_biggy> struct
		1131	in the C<data> member of the watcher (for woozies), or you need to use
		1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1133	programmers):
1037		1134
1038	#include <stddef.h>	1135	#include <stddef.h>
1039		1136
1040	static void	1137	static void
1041	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
1042	{	1139	{
1043	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
1044	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
1045	}	1142	}
1046		1143
1047	static void	1144	static void
1048	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
1049	{	1146	{
1050	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
1051	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
1052	}	1149	}
1053		1150
…		…
1081	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
1082	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
1083	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
1084	required if you know what you are doing).	1181	required if you know what you are doing).
1085		1182
1086	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
1087	(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
1088	C<EVBACKEND_POLL>).	1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1089		1186
1090	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
1091	receive "spurious" readiness notifications, that is your callback might	1188	receive "spurious" readiness notifications, that is your callback might
1092	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
1093	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
1094	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
1095	this situation even with a relatively standard program structure. Thus	1192	this situation even with a relatively standard program structure. Thus
1096	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
1097	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.
1098		1195
1099	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
1100	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
1101	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
1102	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
1103	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.
1104		1205
1105	=head3 The special problem of disappearing file descriptors	1206	=head3 The special problem of disappearing file descriptors
1106		1207
1107	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
1108	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,
1109	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
1110	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
1111	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
1112	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
1113	fact, a different file descriptor.	1214	fact, a different file descriptor.
1114		1215
…		…
1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1146	C<EVBACKEND_POLL>.	1247	C<EVBACKEND_POLL>.
1147		1248
1148	=head3 The special problem of SIGPIPE	1249	=head3 The special problem of SIGPIPE
1149		1250
1150	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>:
1151	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
1152	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
1153	this is sensible behaviour, for daemons, this is usually undesirable.	1254	this is sensible behaviour, for daemons, this is usually undesirable.
1154		1255
1155	So when you encounter spurious, unexplained daemon exits, make sure you	1256	So when you encounter spurious, unexplained daemon exits, make sure you
1156	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
1157	somewhere, as that would have given you a big clue).	1258	somewhere, as that would have given you a big clue).
…		…
1164	=item ev_io_init (ev_io *, callback, int fd, int events)	1265	=item ev_io_init (ev_io *, callback, int fd, int events)
1165		1266
1166	=item ev_io_set (ev_io *, int fd, int events)	1267	=item ev_io_set (ev_io *, int fd, int events)
1167		1268
1168	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
1169	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
1170	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.
1171		1272
1172	=item int fd [read-only]	1273	=item int fd [read-only]
1173		1274
1174	The file descriptor being watched.	1275	The file descriptor being watched.
1175		1276
…		…
1184	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
1185	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
1186	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1187		1288
1188	static void	1289	static void
1189	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)
1190	{	1291	{
1191	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1192	.. 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
1193	}	1294	}
1194		1295
1195	...	1296	...
1196	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1197	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1198	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);
1199	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1200	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1201		1302
1202		1303
…		…
1205	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
1206	given time, and optionally repeating in regular intervals after that.	1307	given time, and optionally repeating in regular intervals after that.
1207		1308
1208	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
1209	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
1210	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
1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1212	monotonic clock option helps a lot here).	1313	monotonic clock option helps a lot here).
1213		1314
1214	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
1215	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
1216	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 :)
1217		1493
1218	=head3 The special problem of time updates	1494	=head3 The special problem of time updates
1219		1495
1220	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
1221	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
1222	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
1223	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
1224	lots of events.	1500	lots of events in one iteration.
1225		1501
1226	The relative timeouts are calculated relative to the C<ev_now ()>	1502	The relative timeouts are calculated relative to the C<ev_now ()>
1227	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
1228	of the event triggering whatever timeout you are modifying/starting. If	1504	of the event triggering whatever timeout you are modifying/starting. If
1229	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
…		…
1265	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).
1266		1542
1267	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
1268	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.
1269		1545
1270	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
1271	example: Imagine you have a TCP connection and you want a so-called idle	1547	usage example.
1272	timeout, that is, you want to be called when there have been, say, 60
1273	seconds of inactivity on the socket. The easiest way to do this is to
1274	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1275	C<ev_timer_again> each time you successfully read or write some data. If
1276	you go into an idle state where you do not expect data to travel on the
1277	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1278	automatically restart it if need be.
1279
1280	That means you can ignore the C<after> value and C<ev_timer_start>
1281	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1282
1283	ev_timer_init (timer, callback, 0., 5.);
1284	ev_timer_again (loop, timer);
1285	...
1286	timer->again = 17.;
1287	ev_timer_again (loop, timer);
1288	...
1289	timer->again = 10.;
1290	ev_timer_again (loop, timer);
1291
1292	This is more slightly efficient then stopping/starting the timer each time
1293	you want to modify its timeout value.
1294		1548
1295	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1296		1550
1297	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
1298	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),
1299	which is also when any modifications are taken into account.	1553	which is also when any modifications are taken into account.
1300		1554
1301	=back	1555	=back
1302		1556
1303	=head3 Examples	1557	=head3 Examples
1304		1558
1305	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1306		1560
1307	static void	1561	static void
1308	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)
1309	{	1563	{
1310	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1311	}	1565	}
1312		1566
1313	struct ev_timer mytimer;	1567	ev_timer mytimer;
1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1315	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1316		1570
1317	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
1318	inactivity.	1572	inactivity.
1319		1573
1320	static void	1574	static void
1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1322	{	1576	{
1323	.. ten seconds without any activity	1577	.. ten seconds without any activity
1324	}	1578	}
1325		1579
1326	struct ev_timer mytimer;	1580	ev_timer mytimer;
1327	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 */
1328	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1329	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1330		1584
1331	// 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":
…		…
1347	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
1348	roughly 10 seconds later as it uses a relative timeout).	1602	roughly 10 seconds later as it uses a relative timeout).
1349		1603
1350	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,
1351	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
1352	complicated, rules.	1606	complicated rules.
1353		1607
1354	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
1355	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
1356	during the same loop iteration then order of execution is undefined.	1610	during the same loop iteration, then order of execution is undefined.
1357		1611
1358	=head3 Watcher-Specific Functions and Data Members	1612	=head3 Watcher-Specific Functions and Data Members
1359		1613
1360	=over 4	1614	=over 4
1361		1615
1362	=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)
1363		1617
1364	=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)
1365		1619
1366	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
1367	operation, and we will explain them from simplest to complex:	1621	operation, and we will explain them from simplest to most complex:
1368		1622
1369	=over 4	1623	=over 4
1370		1624
1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1372		1626
1373	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
1374	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
1375	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
1376	run when the system time reaches or surpasses this time.	1630	only run when the system clock reaches or surpasses this time.
1377		1631
1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1379		1633
1380	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
1381	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)
1382	and then repeat, regardless of any time jumps.	1636	and then repeat, regardless of any time jumps.
1383		1637
1384	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
1385	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
1386	the hour:	1640	hour, on the hour:
1387		1641
1388	ev_periodic_set (&periodic, 0., 3600., 0);	1642	ev_periodic_set (&periodic, 0., 3600., 0);
1389		1643
1390	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,
1391	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
…		…
1417		1671
1418	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
1419	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
1420	only event loop modification you are allowed to do).	1674	only event loop modification you are allowed to do).
1421		1675
1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1423	*w, ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1424		1678
		1679	static ev_tstamp
1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1426	{	1681	{
1427	return now + 60.;	1682	return now + 60.;
1428	}	1683	}
1429		1684
1430	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
…		…
1467		1722
1468	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
1469	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
1470	called.	1725	called.
1471		1726
1472	=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]
1473		1728
1474	The current reschedule callback, or C<0>, if this functionality is	1729	The current reschedule callback, or C<0>, if this functionality is
1475	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
1476	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.
1477		1732
1478	=back	1733	=back
1479		1734
1480	=head3 Examples	1735	=head3 Examples
1481		1736
1482	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1483	system clock is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1484	potentially a lot of jitter, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1485		1740
1486	static void	1741	static void
1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1488	{	1743	{
1489	... 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)
1490	}	1745	}
1491		1746
1492	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1494	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1495		1750
1496	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:
1497		1752
1498	#include <math.h>	1753	#include <math.h>
1499		1754
1500	static ev_tstamp	1755	static ev_tstamp
1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1502	{	1757	{
1503	return fmod (now, 3600.) + 3600.;	1758	return now + (3600. - fmod (now, 3600.));
1504	}	1759	}
1505		1760
1506	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);
1507		1762
1508	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1509		1764
1510	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1511	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1512	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1513	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1514		1769
1515		1770
…		…
1518	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
1519	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
1520	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
1521	normal event processing, like any other event.	1776	normal event processing, like any other event.
1522		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
1523	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
1524	first watcher gets started will libev actually register a signal watcher	1783	first watcher gets started will libev actually register a signal handler
1525	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
1526	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
1527	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
1528	SIG_DFL (regardless of what it was set to before).	1787	signal handler to SIG_DFL (regardless of what it was set to before).
1529		1788
1530	If possible and supported, libev will install its handlers with	1789	If possible and supported, libev will install its handlers with
1531	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
1532	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
1533	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
…		…
1550		1809
1551	=back	1810	=back
1552		1811
1553	=head3 Examples	1812	=head3 Examples
1554		1813
1555	Example: Try to exit cleanly on SIGINT and SIGTERM.	1814	Example: Try to exit cleanly on SIGINT.
1556		1815
1557	static void	1816	static void
1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1559	{	1818	{
1560	ev_unloop (loop, EVUNLOOP_ALL);	1819	ev_unloop (loop, EVUNLOOP_ALL);
1561	}	1820	}
1562		1821
1563	struct ev_signal signal_watcher;	1822	ev_signal signal_watcher;
1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1565	ev_signal_start (loop, &sigint_cb);	1824	ev_signal_start (loop, &signal_watcher);
1566		1825
1567		1826
1568	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
1569		1828
1570	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
1571	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
1572	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
1573	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
1574	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.
1575		1837
1576	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
1577	you can only register child watchers in the default event loop.	1839	you can only register child watchers in the default event loop.
1578		1840
1579	=head3 Process Interaction	1841	=head3 Process Interaction
…		…
1640	its completion.	1902	its completion.
1641		1903
1642	ev_child cw;	1904	ev_child cw;
1643		1905
1644	static void	1906	static void
1645	child_cb (EV_P_ struct ev_child *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1646	{	1908	{
1647	ev_child_stop (EV_A_ w);	1909	ev_child_stop (EV_A_ w);
1648	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);
1649	}	1911	}
1650		1912
…		…
1665		1927
1666		1928
1667	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1668		1930
1669	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
1670	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)
1671	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.
1672		1935
1673	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
1674	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
1675	not exist" is signified by the C<st_nlink> field being zero (which is	1938	not exist" is signified by the C<st_nlink> field being zero (which is
1676	otherwise always forced to be at least one) and all the other fields of	1939	otherwise always forced to be at least one) and all the other fields of
1677	the stat buffer having unspecified contents.	1940	the stat buffer having unspecified contents.
1678		1941
1679	The path I<should> be absolute and I<must not> end in a slash. If it is	1942	The path I<must not> end in a slash or contain special components such as
		1943	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1680	relative and your working directory changes, the behaviour is undefined.	1944	your working directory changes, then the behaviour is undefined.
1681		1945
1682	Since there is no standard to do this, the portable implementation simply	1946	Since there is no portable change notification interface available, the
1683	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1947	portable implementation simply calls C<stat(2)> regularly on the path
1684	can specify a recommended polling interval for this case. If you specify	1948	to see if it changed somehow. You can specify a recommended polling
1685	a polling interval of C<0> (highly recommended!) then a I<suitable,	1949	interval for this case. If you specify a polling interval of C<0> (highly
1686	unspecified default> value will be used (which you can expect to be around	1950	recommended!) then a I<suitable, unspecified default> value will be used
1687	five seconds, although this might change dynamically). Libev will also	1951	(which you can expect to be around five seconds, although this might
1688	impose a minimum interval which is currently around C<0.1>, but thats	1952	change dynamically). Libev will also impose a minimum interval which is
1689	usually overkill.	1953	currently around C<0.1>, but that's usually overkill.
1690		1954
1691	This watcher type is not meant for massive numbers of stat watchers,	1955	This watcher type is not meant for massive numbers of stat watchers,
1692	as even with OS-supported change notifications, this can be	1956	as even with OS-supported change notifications, this can be
1693	resource-intensive.	1957	resource-intensive.
1694		1958
1695	At the time of this writing, only the Linux inotify interface is	1959	At the time of this writing, the only OS-specific interface implemented
1696	implemented (implementing kqueue support is left as an exercise for the	1960	is the Linux inotify interface (implementing kqueue support is left as
1697	reader, note, however, that the author sees no way of implementing ev_stat	1961	an exercise for the reader. Note, however, that the author sees no way
1698	semantics with kqueue). Inotify will be used to give hints only and should	1962	of implementing C<ev_stat> semantics with kqueue).
1699	not change the semantics of C<ev_stat> watchers, which means that libev
1700	sometimes needs to fall back to regular polling again even with inotify,
1701	but changes are usually detected immediately, and if the file exists there
1702	will be no polling.
1703		1963
1704	=head3 ABI Issues (Largefile Support)	1964	=head3 ABI Issues (Largefile Support)
1705		1965
1706	Libev by default (unless the user overrides this) uses the default	1966	Libev by default (unless the user overrides this) uses the default
1707	compilation environment, which means that on systems with large file	1967	compilation environment, which means that on systems with large file
1708	support disabled by default, you get the 32 bit version of the stat	1968	support disabled by default, you get the 32 bit version of the stat
1709	structure. When using the library from programs that change the ABI to	1969	structure. When using the library from programs that change the ABI to
1710	use 64 bit file offsets the programs will fail. In that case you have to	1970	use 64 bit file offsets the programs will fail. In that case you have to
1711	compile libev with the same flags to get binary compatibility. This is	1971	compile libev with the same flags to get binary compatibility. This is
1712	obviously the case with any flags that change the ABI, but the problem is	1972	obviously the case with any flags that change the ABI, but the problem is
1713	most noticeably disabled with ev_stat and large file support.	1973	most noticeably displayed with ev_stat and large file support.
1714		1974
1715	The solution for this is to lobby your distribution maker to make large	1975	The solution for this is to lobby your distribution maker to make large
1716	file interfaces available by default (as e.g. FreeBSD does) and not	1976	file interfaces available by default (as e.g. FreeBSD does) and not
1717	optional. Libev cannot simply switch on large file support because it has	1977	optional. Libev cannot simply switch on large file support because it has
1718	to exchange stat structures with application programs compiled using the	1978	to exchange stat structures with application programs compiled using the
1719	default compilation environment.	1979	default compilation environment.
1720		1980
1721	=head3 Inotify	1981	=head3 Inotify and Kqueue
1722		1982
1723	When C<inotify (7)> support has been compiled into libev (generally only	1983	When C<inotify (7)> support has been compiled into libev (generally
		1984	only available with Linux 2.6.25 or above due to bugs in earlier
1724	available on Linux) and present at runtime, it will be used to speed up	1985	implementations) and present at runtime, it will be used to speed up
1725	change detection where possible. The inotify descriptor will be created lazily	1986	change detection where possible. The inotify descriptor will be created
1726	when the first C<ev_stat> watcher is being started.	1987	lazily when the first C<ev_stat> watcher is being started.
1727		1988
1728	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
1729	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
1730	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
1731	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 the path exists, libev usually gets away without polling.
1732		1994
1733	(There is no support for kqueue, as apparently it cannot be used to	1995	There is no support for kqueue, as apparently it cannot be used to
1734	implement this functionality, due to the requirement of having a file	1996	implement this functionality, due to the requirement of having a file
1735	descriptor open on the object at all times).	1997	descriptor open on the object at all times, and detecting renames, unlinks
		1998	etc. is difficult.
1736		1999
1737	=head3 The special problem of stat time resolution	2000	=head3 The special problem of stat time resolution
1738		2001
1739	The C<stat ()> system call only supports full-second resolution portably, and	2002	The C<stat ()> system call only supports full-second resolution portably,
1740	even on systems where the resolution is higher, many file systems still	2003	and even on systems where the resolution is higher, most file systems
1741	only support whole seconds.	2004	still only support whole seconds.
1742		2005
1743	That means that, if the time is the only thing that changes, you can	2006	That means that, if the time is the only thing that changes, you can
1744	easily miss updates: on the first update, C<ev_stat> detects a change and	2007	easily miss updates: on the first update, C<ev_stat> detects a change and
1745	calls your callback, which does something. When there is another update	2008	calls your callback, which does something. When there is another update
1746	within the same second, C<ev_stat> will be unable to detect it as the stat	2009	within the same second, C<ev_stat> will be unable to detect unless the
1747	data does not change.	2010	stat data does change in other ways (e.g. file size).
1748		2011
1749	The solution to this is to delay acting on a change for slightly more	2012	The solution to this is to delay acting on a change for slightly more
1750	than a second (or till slightly after the next full second boundary), using	2013	than a second (or till slightly after the next full second boundary), using
1751	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2014	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1752	ev_timer_again (loop, w)>).	2015	ev_timer_again (loop, w)>).
…		…
1772	C<path>. The C<interval> is a hint on how quickly a change is expected to	2035	C<path>. The C<interval> is a hint on how quickly a change is expected to
1773	be detected and should normally be specified as C<0> to let libev choose	2036	be detected and should normally be specified as C<0> to let libev choose
1774	a suitable value. The memory pointed to by C<path> must point to the same	2037	a suitable value. The memory pointed to by C<path> must point to the same
1775	path for as long as the watcher is active.	2038	path for as long as the watcher is active.
1776		2039
1777	The callback will receive C<EV_STAT> when a change was detected, relative	2040	The callback will receive an C<EV_STAT> event when a change was detected,
1778	to the attributes at the time the watcher was started (or the last change	2041	relative to the attributes at the time the watcher was started (or the
1779	was detected).	2042	last change was detected).
1780		2043
1781	=item ev_stat_stat (loop, ev_stat *)	2044	=item ev_stat_stat (loop, ev_stat *)
1782		2045
1783	Updates the stat buffer immediately with new values. If you change the	2046	Updates the stat buffer immediately with new values. If you change the
1784	watched path in your callback, you could call this function to avoid	2047	watched path in your callback, you could call this function to avoid
…		…
1867		2130
1868		2131
1869	=head2 C<ev_idle> - when you've got nothing better to do...	2132	=head2 C<ev_idle> - when you've got nothing better to do...
1870		2133
1871	Idle watchers trigger events when no other events of the same or higher	2134	Idle watchers trigger events when no other events of the same or higher
1872	priority are pending (prepare, check and other idle watchers do not	2135	priority are pending (prepare, check and other idle watchers do not count
1873	count).	2136	as receiving "events").
1874		2137
1875	That is, as long as your process is busy handling sockets or timeouts	2138	That is, as long as your process is busy handling sockets or timeouts
1876	(or even signals, imagine) of the same or higher priority it will not be	2139	(or even signals, imagine) of the same or higher priority it will not be
1877	triggered. But when your process is idle (or only lower-priority watchers	2140	triggered. But when your process is idle (or only lower-priority watchers
1878	are pending), the idle watchers are being called once per event loop	2141	are pending), the idle watchers are being called once per event loop
…		…
1903		2166
1904	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2167	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1905	callback, free it. Also, use no error checking, as usual.	2168	callback, free it. Also, use no error checking, as usual.
1906		2169
1907	static void	2170	static void
1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2171	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1909	{	2172	{
1910	free (w);	2173	free (w);
1911	// now do something you wanted to do when the program has	2174	// now do something you wanted to do when the program has
1912	// no longer anything immediate to do.	2175	// no longer anything immediate to do.
1913	}	2176	}
1914		2177
1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2178	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1916	ev_idle_init (idle_watcher, idle_cb);	2179	ev_idle_init (idle_watcher, idle_cb);
1917	ev_idle_start (loop, idle_cb);	2180	ev_idle_start (loop, idle_cb);
1918		2181
1919		2182
1920	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2183	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1921		2184
1922	Prepare and check watchers are usually (but not always) used in tandem:	2185	Prepare and check watchers are usually (but not always) used in pairs:
1923	prepare watchers get invoked before the process blocks and check watchers	2186	prepare watchers get invoked before the process blocks and check watchers
1924	afterwards.	2187	afterwards.
1925		2188
1926	You I<must not> call C<ev_loop> or similar functions that enter	2189	You I<must not> call C<ev_loop> or similar functions that enter
1927	the current event loop from either C<ev_prepare> or C<ev_check>	2190	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1930	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2193	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1931	C<ev_check> so if you have one watcher of each kind they will always be	2194	C<ev_check> so if you have one watcher of each kind they will always be
1932	called in pairs bracketing the blocking call.	2195	called in pairs bracketing the blocking call.
1933		2196
1934	Their main purpose is to integrate other event mechanisms into libev and	2197	Their main purpose is to integrate other event mechanisms into libev and
1935	their use is somewhat advanced. This could be used, for example, to track	2198	their use is somewhat advanced. They could be used, for example, to track
1936	variable changes, implement your own watchers, integrate net-snmp or a	2199	variable changes, implement your own watchers, integrate net-snmp or a
1937	coroutine library and lots more. They are also occasionally useful if	2200	coroutine library and lots more. They are also occasionally useful if
1938	you cache some data and want to flush it before blocking (for example,	2201	you cache some data and want to flush it before blocking (for example,
1939	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2202	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1940	watcher).	2203	watcher).
1941		2204
1942	This is done by examining in each prepare call which file descriptors need	2205	This is done by examining in each prepare call which file descriptors
1943	to be watched by the other library, registering C<ev_io> watchers for	2206	need to be watched by the other library, registering C<ev_io> watchers
1944	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2207	for them and starting an C<ev_timer> watcher for any timeouts (many
1945	provide just this functionality). Then, in the check watcher you check for	2208	libraries provide exactly this functionality). Then, in the check watcher,
1946	any events that occurred (by checking the pending status of all watchers	2209	you check for any events that occurred (by checking the pending status
1947	and stopping them) and call back into the library. The I/O and timer	2210	of all watchers and stopping them) and call back into the library. The
1948	callbacks will never actually be called (but must be valid nevertheless,	2211	I/O and timer callbacks will never actually be called (but must be valid
1949	because you never know, you know?).	2212	nevertheless, because you never know, you know?).
1950		2213
1951	As another example, the Perl Coro module uses these hooks to integrate	2214	As another example, the Perl Coro module uses these hooks to integrate
1952	coroutines into libev programs, by yielding to other active coroutines	2215	coroutines into libev programs, by yielding to other active coroutines
1953	during each prepare and only letting the process block if no coroutines	2216	during each prepare and only letting the process block if no coroutines
1954	are ready to run (it's actually more complicated: it only runs coroutines	2217	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1957	loop from blocking if lower-priority coroutines are active, thus mapping	2220	loop from blocking if lower-priority coroutines are active, thus mapping
1958	low-priority coroutines to idle/background tasks).	2221	low-priority coroutines to idle/background tasks).
1959		2222
1960	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2223	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1961	priority, to ensure that they are being run before any other watchers	2224	priority, to ensure that they are being run before any other watchers
		2225	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2226
1962	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2227	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1963	too) should not activate ("feed") events into libev. While libev fully	2228	activate ("feed") events into libev. While libev fully supports this, they
1964	supports this, they might get executed before other C<ev_check> watchers	2229	might get executed before other C<ev_check> watchers did their job. As
1965	did their job. As C<ev_check> watchers are often used to embed other	2230	C<ev_check> watchers are often used to embed other (non-libev) event
1966	(non-libev) event loops those other event loops might be in an unusable	2231	loops those other event loops might be in an unusable state until their
1967	state until their C<ev_check> watcher ran (always remind yourself to	2232	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1968	coexist peacefully with others).	2233	others).
1969		2234
1970	=head3 Watcher-Specific Functions and Data Members	2235	=head3 Watcher-Specific Functions and Data Members
1971		2236
1972	=over 4	2237	=over 4
1973		2238
…		…
1975		2240
1976	=item ev_check_init (ev_check *, callback)	2241	=item ev_check_init (ev_check *, callback)
1977		2242
1978	Initialises and configures the prepare or check watcher - they have no	2243	Initialises and configures the prepare or check watcher - they have no
1979	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2244	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1980	macros, but using them is utterly, utterly and completely pointless.	2245	macros, but using them is utterly, utterly, utterly and completely
		2246	pointless.
1981		2247
1982	=back	2248	=back
1983		2249
1984	=head3 Examples	2250	=head3 Examples
1985		2251
…		…
1998		2264
1999	static ev_io iow [nfd];	2265	static ev_io iow [nfd];
2000	static ev_timer tw;	2266	static ev_timer tw;
2001		2267
2002	static void	2268	static void
2003	io_cb (ev_loop *loop, ev_io *w, int revents)	2269	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2004	{	2270	{
2005	}	2271	}
2006		2272
2007	// create io watchers for each fd and a timer before blocking	2273	// create io watchers for each fd and a timer before blocking
2008	static void	2274	static void
2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2275	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2010	{	2276	{
2011	int timeout = 3600000;	2277	int timeout = 3600000;
2012	struct pollfd fds [nfd];	2278	struct pollfd fds [nfd];
2013	// actual code will need to loop here and realloc etc.	2279	// actual code will need to loop here and realloc etc.
2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2280	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2029	}	2295	}
2030	}	2296	}
2031		2297
2032	// stop all watchers after blocking	2298	// stop all watchers after blocking
2033	static void	2299	static void
2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2300	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2035	{	2301	{
2036	ev_timer_stop (loop, &tw);	2302	ev_timer_stop (loop, &tw);
2037		2303
2038	for (int i = 0; i < nfd; ++i)	2304	for (int i = 0; i < nfd; ++i)
2039	{	2305	{
…		…
2078	}	2344	}
2079		2345
2080	// do not ever call adns_afterpoll	2346	// do not ever call adns_afterpoll
2081		2347
2082	Method 4: Do not use a prepare or check watcher because the module you	2348	Method 4: Do not use a prepare or check watcher because the module you
2083	want to embed is too inflexible to support it. Instead, you can override	2349	want to embed is not flexible enough to support it. Instead, you can
2084	their poll function. The drawback with this solution is that the main	2350	override their poll function. The drawback with this solution is that the
2085	loop is now no longer controllable by EV. The C<Glib::EV> module does	2351	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2086	this.	2352	this approach, effectively embedding EV as a client into the horrible
		2353	libglib event loop.
2087		2354
2088	static gint	2355	static gint
2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2356	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2090	{	2357	{
2091	int got_events = 0;	2358	int got_events = 0;
…		…
2122	prioritise I/O.	2389	prioritise I/O.
2123		2390
2124	As an example for a bug workaround, the kqueue backend might only support	2391	As an example for a bug workaround, the kqueue backend might only support
2125	sockets on some platform, so it is unusable as generic backend, but you	2392	sockets on some platform, so it is unusable as generic backend, but you
2126	still want to make use of it because you have many sockets and it scales	2393	still want to make use of it because you have many sockets and it scales
2127	so nicely. In this case, you would create a kqueue-based loop and embed it	2394	so nicely. In this case, you would create a kqueue-based loop and embed
2128	into your default loop (which might use e.g. poll). Overall operation will	2395	it into your default loop (which might use e.g. poll). Overall operation
2129	be a bit slower because first libev has to poll and then call kevent, but	2396	will be a bit slower because first libev has to call C<poll> and then
2130	at least you can use both at what they are best.	2397	C<kevent>, but at least you can use both mechanisms for what they are
		2398	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2131		2399
2132	As for prioritising I/O: rarely you have the case where some fds have	2400	As for prioritising I/O: under rare circumstances you have the case where
2133	to be watched and handled very quickly (with low latency), and even	2401	some fds have to be watched and handled very quickly (with low latency),
2134	priorities and idle watchers might have too much overhead. In this case	2402	and even priorities and idle watchers might have too much overhead. In
2135	you would put all the high priority stuff in one loop and all the rest in	2403	this case you would put all the high priority stuff in one loop and all
2136	a second one, and embed the second one in the first.	2404	the rest in a second one, and embed the second one in the first.
2137		2405
2138	As long as the watcher is active, the callback will be invoked every time	2406	As long as the watcher is active, the callback will be invoked every time
2139	there might be events pending in the embedded loop. The callback must then	2407	there might be events pending in the embedded loop. The callback must then
2140	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2408	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2141	their callbacks (you could also start an idle watcher to give the embedded	2409	their callbacks (you could also start an idle watcher to give the embedded
…		…
2149	interested in that.	2417	interested in that.
2150		2418
2151	Also, there have not currently been made special provisions for forking:	2419	Also, there have not currently been made special provisions for forking:
2152	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2420	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2153	but you will also have to stop and restart any C<ev_embed> watchers	2421	but you will also have to stop and restart any C<ev_embed> watchers
2154	yourself.	2422	yourself - but you can use a fork watcher to handle this automatically,
		2423	and future versions of libev might do just that.
2155		2424
2156	Unfortunately, not all backends are embeddable, only the ones returned by	2425	Unfortunately, not all backends are embeddable: only the ones returned by
2157	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2426	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2158	portable one.	2427	portable one.
2159		2428
2160	So when you want to use this feature you will always have to be prepared	2429	So when you want to use this feature you will always have to be prepared
2161	that you cannot get an embeddable loop. The recommended way to get around	2430	that you cannot get an embeddable loop. The recommended way to get around
2162	this is to have a separate variables for your embeddable loop, try to	2431	this is to have a separate variables for your embeddable loop, try to
2163	create it, and if that fails, use the normal loop for everything.	2432	create it, and if that fails, use the normal loop for everything.
		2433
		2434	=head3 C<ev_embed> and fork
		2435
		2436	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2437	automatically be applied to the embedded loop as well, so no special
		2438	fork handling is required in that case. When the watcher is not running,
		2439	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2440	as applicable.
2164		2441
2165	=head3 Watcher-Specific Functions and Data Members	2442	=head3 Watcher-Specific Functions and Data Members
2166		2443
2167	=over 4	2444	=over 4
2168		2445
…		…
2196	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2473	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2197	used).	2474	used).
2198		2475
2199	struct ev_loop *loop_hi = ev_default_init (0);	2476	struct ev_loop *loop_hi = ev_default_init (0);
2200	struct ev_loop *loop_lo = 0;	2477	struct ev_loop *loop_lo = 0;
2201	struct ev_embed embed;	2478	ev_embed embed;
2202		2479
2203	// see if there is a chance of getting one that works	2480	// see if there is a chance of getting one that works
2204	// (remember that a flags value of 0 means autodetection)	2481	// (remember that a flags value of 0 means autodetection)
2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2482	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2483	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2220	kqueue implementation). Store the kqueue/socket-only event loop in	2497	kqueue implementation). Store the kqueue/socket-only event loop in
2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2498	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2222		2499
2223	struct ev_loop *loop = ev_default_init (0);	2500	struct ev_loop *loop = ev_default_init (0);
2224	struct ev_loop *loop_socket = 0;	2501	struct ev_loop *loop_socket = 0;
2225	struct ev_embed embed;	2502	ev_embed embed;
2226		2503
2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2504	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2505	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2229	{	2506	{
2230	ev_embed_init (&embed, 0, loop_socket);	2507	ev_embed_init (&embed, 0, loop_socket);
…		…
2286	is that the author does not know of a simple (or any) algorithm for a	2563	is that the author does not know of a simple (or any) algorithm for a
2287	multiple-writer-single-reader queue that works in all cases and doesn't	2564	multiple-writer-single-reader queue that works in all cases and doesn't
2288	need elaborate support such as pthreads.	2565	need elaborate support such as pthreads.
2289		2566
2290	That means that if you want to queue data, you have to provide your own	2567	That means that if you want to queue data, you have to provide your own
2291	queue. But at least I can tell you would implement locking around your	2568	queue. But at least I can tell you how to implement locking around your
2292	queue:	2569	queue:
2293		2570
2294	=over 4	2571	=over 4
2295		2572
2296	=item queueing from a signal handler context	2573	=item queueing from a signal handler context
2297		2574
2298	To implement race-free queueing, you simply add to the queue in the signal	2575	To implement race-free queueing, you simply add to the queue in the signal
2299	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2576	handler but you block the signal handler in the watcher callback. Here is
2300	some fictitious SIGUSR1 handler:	2577	an example that does that for some fictitious SIGUSR1 handler:
2301		2578
2302	static ev_async mysig;	2579	static ev_async mysig;
2303		2580
2304	static void	2581	static void
2305	sigusr1_handler (void)	2582	sigusr1_handler (void)
…		…
2371	=over 4	2648	=over 4
2372		2649
2373	=item ev_async_init (ev_async *, callback)	2650	=item ev_async_init (ev_async *, callback)
2374		2651
2375	Initialises and configures the async watcher - it has no parameters of any	2652	Initialises and configures the async watcher - it has no parameters of any
2376	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2653	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2377	believe me.	2654	trust me.
2378		2655
2379	=item ev_async_send (loop, ev_async *)	2656	=item ev_async_send (loop, ev_async *)
2380		2657
2381	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2658	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2382	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2659	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2383	C<ev_feed_event>, this call is safe to do in other threads, signal or	2660	C<ev_feed_event>, this call is safe to do from other threads, signal or
2384	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2661	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2385	section below on what exactly this means).	2662	section below on what exactly this means).
2386		2663
2387	This call incurs the overhead of a system call only once per loop iteration,	2664	This call incurs the overhead of a system call only once per loop iteration,
2388	so while the overhead might be noticeable, it doesn't apply to repeated	2665	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2412	=over 4	2689	=over 4
2413		2690
2414	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2691	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2415		2692
2416	This function combines a simple timer and an I/O watcher, calls your	2693	This function combines a simple timer and an I/O watcher, calls your
2417	callback on whichever event happens first and automatically stop both	2694	callback on whichever event happens first and automatically stops both
2418	watchers. This is useful if you want to wait for a single event on an fd	2695	watchers. This is useful if you want to wait for a single event on an fd
2419	or timeout without having to allocate/configure/start/stop/free one or	2696	or timeout without having to allocate/configure/start/stop/free one or
2420	more watchers yourself.	2697	more watchers yourself.
2421		2698
2422	If C<fd> is less than 0, then no I/O watcher will be started and events	2699	If C<fd> is less than 0, then no I/O watcher will be started and the
2423	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2700	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2424	C<events> set will be created and started.	2701	the given C<fd> and C<events> set will be created and started.
2425		2702
2426	If C<timeout> is less than 0, then no timeout watcher will be	2703	If C<timeout> is less than 0, then no timeout watcher will be
2427	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2704	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2428	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2705	repeat = 0) will be started. C<0> is a valid timeout.
2429	dubious value.
2430		2706
2431	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2707	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2432	passed an C<revents> set like normal event callbacks (a combination of	2708	passed an C<revents> set like normal event callbacks (a combination of
2433	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2709	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2434	value passed to C<ev_once>:	2710	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2711	a timeout and an io event at the same time - you probably should give io
		2712	events precedence.
		2713
		2714	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2435		2715
2436	static void stdin_ready (int revents, void *arg)	2716	static void stdin_ready (int revents, void *arg)
2437	{	2717	{
		2718	if (revents & EV_READ)
		2719	/* stdin might have data for us, joy! */;
2438	if (revents & EV_TIMEOUT)	2720	else if (revents & EV_TIMEOUT)
2439	/* doh, nothing entered */;	2721	/* doh, nothing entered */;
2440	else if (revents & EV_READ)
2441	/* stdin might have data for us, joy! */;
2442	}	2722	}
2443		2723
2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2724	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2445		2725
2446	=item ev_feed_event (ev_loop *, watcher *, int revents)	2726	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2447		2727
2448	Feeds the given event set into the event loop, as if the specified event	2728	Feeds the given event set into the event loop, as if the specified event
2449	had happened for the specified watcher (which must be a pointer to an	2729	had happened for the specified watcher (which must be a pointer to an
2450	initialised but not necessarily started event watcher).	2730	initialised but not necessarily started event watcher).
2451		2731
2452	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2732	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2453		2733
2454	Feed an event on the given fd, as if a file descriptor backend detected	2734	Feed an event on the given fd, as if a file descriptor backend detected
2455	the given events it.	2735	the given events it.
2456		2736
2457	=item ev_feed_signal_event (ev_loop *loop, int signum)	2737	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2458		2738
2459	Feed an event as if the given signal occurred (C<loop> must be the default	2739	Feed an event as if the given signal occurred (C<loop> must be the default
2460	loop!).	2740	loop!).
2461		2741
2462	=back	2742	=back
…		…
2594		2874
2595	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2875	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2596		2876
2597	See the method-C<set> above for more details.	2877	See the method-C<set> above for more details.
2598		2878
2599	Example:	2879	Example: Use a plain function as callback.
2600		2880
2601	static void io_cb (ev::io &w, int revents) { }	2881	static void io_cb (ev::io &w, int revents) { }
2602	iow.set <io_cb> ();	2882	iow.set <io_cb> ();
2603		2883
2604	=item w->set (struct ev_loop *)	2884	=item w->set (struct ev_loop *)
…		…
2642	Example: Define a class with an IO and idle watcher, start one of them in	2922	Example: Define a class with an IO and idle watcher, start one of them in
2643	the constructor.	2923	the constructor.
2644		2924
2645	class myclass	2925	class myclass
2646	{	2926	{
2647	ev::io io; void io_cb (ev::io &w, int revents);	2927	ev::io io ; void io_cb (ev::io &w, int revents);
2648	ev:idle idle void idle_cb (ev::idle &w, int revents);	2928	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2649		2929
2650	myclass (int fd)	2930	myclass (int fd)
2651	{	2931	{
2652	io .set <myclass, &myclass::io_cb > (this);	2932	io .set <myclass, &myclass::io_cb > (this);
2653	idle.set <myclass, &myclass::idle_cb> (this);	2933	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2669	=item Perl	2949	=item Perl
2670		2950
2671	The EV module implements the full libev API and is actually used to test	2951	The EV module implements the full libev API and is actually used to test
2672	libev. EV is developed together with libev. Apart from the EV core module,	2952	libev. EV is developed together with libev. Apart from the EV core module,
2673	there are additional modules that implement libev-compatible interfaces	2953	there are additional modules that implement libev-compatible interfaces
2674	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2954	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2675	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2955	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2956	and C<EV::Glib>).
2676		2957
2677	It can be found and installed via CPAN, its homepage is at	2958	It can be found and installed via CPAN, its homepage is at
2678	L<http://software.schmorp.de/pkg/EV>.	2959	L<http://software.schmorp.de/pkg/EV>.
2679		2960
2680	=item Python	2961	=item Python
…		…
2696	=item D	2977	=item D
2697		2978
2698	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2979	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2699	be found at L<http://proj.llucax.com.ar/wiki/evd>.	2980	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2700		2981
		2982	=item Ocaml
		2983
		2984	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2985	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2986
2701	=back	2987	=back
2702		2988
2703		2989
2704	=head1 MACRO MAGIC	2990	=head1 MACRO MAGIC
2705		2991
…		…
2805		3091
2806	#define EV_STANDALONE 1	3092	#define EV_STANDALONE 1
2807	#include "ev.h"	3093	#include "ev.h"
2808		3094
2809	Both header files and implementation files can be compiled with a C++	3095	Both header files and implementation files can be compiled with a C++
2810	compiler (at least, thats a stated goal, and breakage will be treated	3096	compiler (at least, that's a stated goal, and breakage will be treated
2811	as a bug).	3097	as a bug).
2812		3098
2813	You need the following files in your source tree, or in a directory	3099	You need the following files in your source tree, or in a directory
2814	in your include path (e.g. in libev/ when using -Ilibev):	3100	in your include path (e.g. in libev/ when using -Ilibev):
2815		3101
…		…
2859		3145
2860	=head2 PREPROCESSOR SYMBOLS/MACROS	3146	=head2 PREPROCESSOR SYMBOLS/MACROS
2861		3147
2862	Libev can be configured via a variety of preprocessor symbols you have to	3148	Libev can be configured via a variety of preprocessor symbols you have to
2863	define before including any of its files. The default in the absence of	3149	define before including any of its files. The default in the absence of
2864	autoconf is noted for every option.	3150	autoconf is documented for every option.
2865		3151
2866	=over 4	3152	=over 4
2867		3153
2868	=item EV_STANDALONE	3154	=item EV_STANDALONE
2869		3155
…		…
3039	When doing priority-based operations, libev usually has to linearly search	3325	When doing priority-based operations, libev usually has to linearly search
3040	all the priorities, so having many of them (hundreds) uses a lot of space	3326	all the priorities, so having many of them (hundreds) uses a lot of space
3041	and time, so using the defaults of five priorities (-2 .. +2) is usually	3327	and time, so using the defaults of five priorities (-2 .. +2) is usually
3042	fine.	3328	fine.
3043		3329
3044	If your embedding application does not need any priorities, defining these both to	3330	If your embedding application does not need any priorities, defining these
3045	C<0> will save some memory and CPU.	3331	both to C<0> will save some memory and CPU.
3046		3332
3047	=item EV_PERIODIC_ENABLE	3333	=item EV_PERIODIC_ENABLE
3048		3334
3049	If undefined or defined to be C<1>, then periodic timers are supported. If	3335	If undefined or defined to be C<1>, then periodic timers are supported. If
3050	defined to be C<0>, then they are not. Disabling them saves a few kB of	3336	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3057	code.	3343	code.
3058		3344
3059	=item EV_EMBED_ENABLE	3345	=item EV_EMBED_ENABLE
3060		3346
3061	If undefined or defined to be C<1>, then embed watchers are supported. If	3347	If undefined or defined to be C<1>, then embed watchers are supported. If
3062	defined to be C<0>, then they are not.	3348	defined to be C<0>, then they are not. Embed watchers rely on most other
		3349	watcher types, which therefore must not be disabled.
3063		3350
3064	=item EV_STAT_ENABLE	3351	=item EV_STAT_ENABLE
3065		3352
3066	If undefined or defined to be C<1>, then stat watchers are supported. If	3353	If undefined or defined to be C<1>, then stat watchers are supported. If
3067	defined to be C<0>, then they are not.	3354	defined to be C<0>, then they are not.
…		…
3099	two).	3386	two).
3100		3387
3101	=item EV_USE_4HEAP	3388	=item EV_USE_4HEAP
3102		3389
3103	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3390	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3104	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3391	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3105	to C<1>. The 4-heap uses more complicated (longer) code but has	3392	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3106	noticeably faster performance with many (thousands) of watchers.	3393	faster performance with many (thousands) of watchers.
3107		3394
3108	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3395	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3109	(disabled).	3396	(disabled).
3110		3397
3111	=item EV_HEAP_CACHE_AT	3398	=item EV_HEAP_CACHE_AT
3112		3399
3113	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3400	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3114	timer and periodics heap, libev can cache the timestamp (I<at>) within	3401	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3115	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3402	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3116	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3403	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3117	but avoids random read accesses on heap changes. This improves performance	3404	but avoids random read accesses on heap changes. This improves performance
3118	noticeably with with many (hundreds) of watchers.	3405	noticeably with many (hundreds) of watchers.
3119		3406
3120	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3407	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3121	(disabled).	3408	(disabled).
3122		3409
3123	=item EV_VERIFY	3410	=item EV_VERIFY
…		…
3129	called once per loop, which can slow down libev. If set to C<3>, then the	3416	called once per loop, which can slow down libev. If set to C<3>, then the
3130	verification code will be called very frequently, which will slow down	3417	verification code will be called very frequently, which will slow down
3131	libev considerably.	3418	libev considerably.
3132		3419
3133	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3420	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3134	C<0.>	3421	C<0>.
3135		3422
3136	=item EV_COMMON	3423	=item EV_COMMON
3137		3424
3138	By default, all watchers have a C<void *data> member. By redefining	3425	By default, all watchers have a C<void *data> member. By redefining
3139	this macro to a something else you can include more and other types of	3426	this macro to a something else you can include more and other types of
…		…
3156	and the way callbacks are invoked and set. Must expand to a struct member	3443	and the way callbacks are invoked and set. Must expand to a struct member
3157	definition and a statement, respectively. See the F<ev.h> header file for	3444	definition and a statement, respectively. See the F<ev.h> header file for
3158	their default definitions. One possible use for overriding these is to	3445	their default definitions. One possible use for overriding these is to
3159	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3446	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3160	method calls instead of plain function calls in C++.	3447	method calls instead of plain function calls in C++.
		3448
		3449	=back
3161		3450
3162	=head2 EXPORTED API SYMBOLS	3451	=head2 EXPORTED API SYMBOLS
3163		3452
3164	If you need to re-export the API (e.g. via a DLL) and you need a list of	3453	If you need to re-export the API (e.g. via a DLL) and you need a list of
3165	exported symbols, you can use the provided F<Symbol.*> files which list	3454	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3212	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3501	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3213		3502
3214	#include "ev_cpp.h"	3503	#include "ev_cpp.h"
3215	#include "ev.c"	3504	#include "ev.c"
3216		3505
		3506	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3217		3507
3218	=head1 THREADS AND COROUTINES	3508	=head2 THREADS AND COROUTINES
3219		3509
3220	=head2 THREADS	3510	=head3 THREADS
3221		3511
3222	Libev itself is completely thread-safe, but it uses no locking. This	3512	All libev functions are reentrant and thread-safe unless explicitly
		3513	documented otherwise, but libev implements no locking itself. This means
3223	means that you can use as many loops as you want in parallel, as long as	3514	that you can use as many loops as you want in parallel, as long as there
3224	only one thread ever calls into one libev function with the same loop	3515	are no concurrent calls into any libev function with the same loop
3225	parameter.	3516	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3517	of course): libev guarantees that different event loops share no data
		3518	structures that need any locking.
3226		3519
3227	Or put differently: calls with different loop parameters can be done in	3520	Or to put it differently: calls with different loop parameters can be done
3228	parallel from multiple threads, calls with the same loop parameter must be	3521	concurrently from multiple threads, calls with the same loop parameter
3229	done serially (but can be done from different threads, as long as only one	3522	must be done serially (but can be done from different threads, as long as
3230	thread ever is inside a call at any point in time, e.g. by using a mutex	3523	only one thread ever is inside a call at any point in time, e.g. by using
3231	per loop).	3524	a mutex per loop).
		3525
		3526	Specifically to support threads (and signal handlers), libev implements
		3527	so-called C<ev_async> watchers, which allow some limited form of
		3528	concurrency on the same event loop, namely waking it up "from the
		3529	outside".
3232		3530
3233	If you want to know which design (one loop, locking, or multiple loops	3531	If you want to know which design (one loop, locking, or multiple loops
3234	without or something else still) is best for your problem, then I cannot	3532	without or something else still) is best for your problem, then I cannot
3235	help you. I can give some generic advice however:	3533	help you, but here is some generic advice:
3236		3534
3237	=over 4	3535	=over 4
3238		3536
3239	=item * most applications have a main thread: use the default libev loop	3537	=item * most applications have a main thread: use the default libev loop
3240	in that thread, or create a separate thread running only the default loop.	3538	in that thread, or create a separate thread running only the default loop.
…		…
3252		3550
3253	Choosing a model is hard - look around, learn, know that usually you can do	3551	Choosing a model is hard - look around, learn, know that usually you can do
3254	better than you currently do :-)	3552	better than you currently do :-)
3255		3553
3256	=item * often you need to talk to some other thread which blocks in the	3554	=item * often you need to talk to some other thread which blocks in the
		3555	event loop.
		3556
3257	event loop - C<ev_async> watchers can be used to wake them up from other	3557	C<ev_async> watchers can be used to wake them up from other threads safely
3258	threads safely (or from signal contexts...).	3558	(or from signal contexts...).
		3559
		3560	An example use would be to communicate signals or other events that only
		3561	work in the default loop by registering the signal watcher with the
		3562	default loop and triggering an C<ev_async> watcher from the default loop
		3563	watcher callback into the event loop interested in the signal.
3259		3564
3260	=back	3565	=back
3261		3566
3262	=head2 COROUTINES	3567	=head3 COROUTINES
3263		3568
3264	Libev is much more accommodating to coroutines ("cooperative threads"):	3569	Libev is very accommodating to coroutines ("cooperative threads"):
3265	libev fully supports nesting calls to it's functions from different	3570	libev fully supports nesting calls to its functions from different
3266	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3571	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3267	different coroutines and switch freely between both coroutines running the	3572	different coroutines, and switch freely between both coroutines running the
3268	loop, as long as you don't confuse yourself). The only exception is that	3573	loop, as long as you don't confuse yourself). The only exception is that
3269	you must not do this from C<ev_periodic> reschedule callbacks.	3574	you must not do this from C<ev_periodic> reschedule callbacks.
3270		3575
3271	Care has been invested into making sure that libev does not keep local	3576	Care has been taken to ensure that libev does not keep local state inside
3272	state inside C<ev_loop>, and other calls do not usually allow coroutine	3577	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3273	switches.	3578	they do not call any callbacks.
3274		3579
		3580	=head2 COMPILER WARNINGS
3275		3581
3276	=head1 COMPLEXITIES	3582	Depending on your compiler and compiler settings, you might get no or a
		3583	lot of warnings when compiling libev code. Some people are apparently
		3584	scared by this.
3277		3585
3278	In this section the complexities of (many of) the algorithms used inside	3586	However, these are unavoidable for many reasons. For one, each compiler
3279	libev will be explained. For complexity discussions about backends see the	3587	has different warnings, and each user has different tastes regarding
3280	documentation for C<ev_default_init>.	3588	warning options. "Warn-free" code therefore cannot be a goal except when
		3589	targeting a specific compiler and compiler-version.
3281		3590
3282	All of the following are about amortised time: If an array needs to be	3591	Another reason is that some compiler warnings require elaborate
3283	extended, libev needs to realloc and move the whole array, but this	3592	workarounds, or other changes to the code that make it less clear and less
3284	happens asymptotically never with higher number of elements, so O(1) might	3593	maintainable.
3285	mean it might do a lengthy realloc operation in rare cases, but on average
3286	it is much faster and asymptotically approaches constant time.
3287		3594
3288	=over 4	3595	And of course, some compiler warnings are just plain stupid, or simply
		3596	wrong (because they don't actually warn about the condition their message
		3597	seems to warn about). For example, certain older gcc versions had some
		3598	warnings that resulted an extreme number of false positives. These have
		3599	been fixed, but some people still insist on making code warn-free with
		3600	such buggy versions.
3289		3601
3290	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3602	While libev is written to generate as few warnings as possible,
		3603	"warn-free" code is not a goal, and it is recommended not to build libev
		3604	with any compiler warnings enabled unless you are prepared to cope with
		3605	them (e.g. by ignoring them). Remember that warnings are just that:
		3606	warnings, not errors, or proof of bugs.
3291		3607
3292	This means that, when you have a watcher that triggers in one hour and
3293	there are 100 watchers that would trigger before that then inserting will
3294	have to skip roughly seven (C<ld 100>) of these watchers.
3295		3608
3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3609	=head2 VALGRIND
3297		3610
3298	That means that changing a timer costs less than removing/adding them	3611	Valgrind has a special section here because it is a popular tool that is
3299	as only the relative motion in the event queue has to be paid for.	3612	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3300		3613
3301	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3614	If you think you found a bug (memory leak, uninitialised data access etc.)
		3615	in libev, then check twice: If valgrind reports something like:
3302		3616
3303	These just add the watcher into an array or at the head of a list.	3617	==2274== definitely lost: 0 bytes in 0 blocks.
		3618	==2274== possibly lost: 0 bytes in 0 blocks.
		3619	==2274== still reachable: 256 bytes in 1 blocks.
3304		3620
3305	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3621	Then there is no memory leak, just as memory accounted to global variables
		3622	is not a memleak - the memory is still being referenced, and didn't leak.
3306		3623
3307	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3624	Similarly, under some circumstances, valgrind might report kernel bugs
		3625	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3626	although an acceptable workaround has been found here), or it might be
		3627	confused.
3308		3628
3309	These watchers are stored in lists then need to be walked to find the	3629	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3310	correct watcher to remove. The lists are usually short (you don't usually	3630	make it into some kind of religion.
3311	have many watchers waiting for the same fd or signal).
3312		3631
3313	=item Finding the next timer in each loop iteration: O(1)	3632	If you are unsure about something, feel free to contact the mailing list
		3633	with the full valgrind report and an explanation on why you think this
		3634	is a bug in libev (best check the archives, too :). However, don't be
		3635	annoyed when you get a brisk "this is no bug" answer and take the chance
		3636	of learning how to interpret valgrind properly.
3314		3637
3315	By virtue of using a binary or 4-heap, the next timer is always found at a	3638	If you need, for some reason, empty reports from valgrind for your project
3316	fixed position in the storage array.	3639	I suggest using suppression lists.
3317		3640
3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3319		3641
3320	A change means an I/O watcher gets started or stopped, which requires	3642	=head1 PORTABILITY NOTES
3321	libev to recalculate its status (and possibly tell the kernel, depending
3322	on backend and whether C<ev_io_set> was used).
3323		3643
3324	=item Activating one watcher (putting it into the pending state): O(1)
3325
3326	=item Priority handling: O(number_of_priorities)
3327
3328	Priorities are implemented by allocating some space for each
3329	priority. When doing priority-based operations, libev usually has to
3330	linearly search all the priorities, but starting/stopping and activating
3331	watchers becomes O(1) w.r.t. priority handling.
3332
3333	=item Sending an ev_async: O(1)
3334
3335	=item Processing ev_async_send: O(number_of_async_watchers)
3336
3337	=item Processing signals: O(max_signal_number)
3338
3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
3340	calls in the current loop iteration. Checking for async and signal events
3341	involves iterating over all running async watchers or all signal numbers.
3342
3343	=back
3344
3345
3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3644	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3347		3645
3348	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3646	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3349	requires, and its I/O model is fundamentally incompatible with the POSIX	3647	requires, and its I/O model is fundamentally incompatible with the POSIX
3350	model. Libev still offers limited functionality on this platform in	3648	model. Libev still offers limited functionality on this platform in
3351	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3649	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3362		3660
3363	Not a libev limitation but worth mentioning: windows apparently doesn't	3661	Not a libev limitation but worth mentioning: windows apparently doesn't
3364	accept large writes: instead of resulting in a partial write, windows will	3662	accept large writes: instead of resulting in a partial write, windows will
3365	either accept everything or return C<ENOBUFS> if the buffer is too large,	3663	either accept everything or return C<ENOBUFS> if the buffer is too large,
3366	so make sure you only write small amounts into your sockets (less than a	3664	so make sure you only write small amounts into your sockets (less than a
3367	megabyte seems safe, but thsi apparently depends on the amount of memory	3665	megabyte seems safe, but this apparently depends on the amount of memory
3368	available).	3666	available).
3369		3667
3370	Due to the many, low, and arbitrary limits on the win32 platform and	3668	Due to the many, low, and arbitrary limits on the win32 platform and
3371	the abysmal performance of winsockets, using a large number of sockets	3669	the abysmal performance of winsockets, using a large number of sockets
3372	is not recommended (and not reasonable). If your program needs to use	3670	is not recommended (and not reasonable). If your program needs to use
…		…
3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3681	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3384		3682
3385	#include "ev.h"	3683	#include "ev.h"
3386		3684
3387	And compile the following F<evwrap.c> file into your project (make sure	3685	And compile the following F<evwrap.c> file into your project (make sure
3388	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3686	you do I<not> compile the F<ev.c> or any other embedded source files!):
3389		3687
3390	#include "evwrap.h"	3688	#include "evwrap.h"
3391	#include "ev.c"	3689	#include "ev.c"
3392		3690
3393	=over 4	3691	=over 4
…		…
3438	wrap all I/O functions and provide your own fd management, but the cost of	3736	wrap all I/O functions and provide your own fd management, but the cost of
3439	calling select (O(n²)) will likely make this unworkable.	3737	calling select (O(n²)) will likely make this unworkable.
3440		3738
3441	=back	3739	=back
3442		3740
3443
3444	=head1 PORTABILITY REQUIREMENTS	3741	=head2 PORTABILITY REQUIREMENTS
3445		3742
3446	In addition to a working ISO-C implementation, libev relies on a few	3743	In addition to a working ISO-C implementation and of course the
3447	additional extensions:	3744	backend-specific APIs, libev relies on a few additional extensions:
3448		3745
3449	=over 4	3746	=over 4
3450		3747
3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3748	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3452	calling conventions regardless of C<ev_watcher_type *>.	3749	calling conventions regardless of C<ev_watcher_type *>.
…		…
3458	calls them using an C<ev_watcher *> internally.	3755	calls them using an C<ev_watcher *> internally.
3459		3756
3460	=item C<sig_atomic_t volatile> must be thread-atomic as well	3757	=item C<sig_atomic_t volatile> must be thread-atomic as well
3461		3758
3462	The type C<sig_atomic_t volatile> (or whatever is defined as	3759	The type C<sig_atomic_t volatile> (or whatever is defined as
3463	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3760	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3464	threads. This is not part of the specification for C<sig_atomic_t>, but is	3761	threads. This is not part of the specification for C<sig_atomic_t>, but is
3465	believed to be sufficiently portable.	3762	believed to be sufficiently portable.
3466		3763
3467	=item C<sigprocmask> must work in a threaded environment	3764	=item C<sigprocmask> must work in a threaded environment
3468		3765
…		…
3477	except the initial one, and run the default loop in the initial thread as	3774	except the initial one, and run the default loop in the initial thread as
3478	well.	3775	well.
3479		3776
3480	=item C<long> must be large enough for common memory allocation sizes	3777	=item C<long> must be large enough for common memory allocation sizes
3481		3778
3482	To improve portability and simplify using libev, libev uses C<long>	3779	To improve portability and simplify its API, libev uses C<long> internally
3483	internally instead of C<size_t> when allocating its data structures. On	3780	instead of C<size_t> when allocating its data structures. On non-POSIX
3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3781	systems (Microsoft...) this might be unexpectedly low, but is still at
3485	is still at least 31 bits everywhere, which is enough for hundreds of	3782	least 31 bits everywhere, which is enough for hundreds of millions of
3486	millions of watchers.	3783	watchers.
3487		3784
3488	=item C<double> must hold a time value in seconds with enough accuracy	3785	=item C<double> must hold a time value in seconds with enough accuracy
3489		3786
3490	The type C<double> is used to represent timestamps. It is required to	3787	The type C<double> is used to represent timestamps. It is required to
3491	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3788	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3495	=back	3792	=back
3496		3793
3497	If you know of other additional requirements drop me a note.	3794	If you know of other additional requirements drop me a note.
3498		3795
3499		3796
3500	=head1 COMPILER WARNINGS	3797	=head1 ALGORITHMIC COMPLEXITIES
3501		3798
3502	Depending on your compiler and compiler settings, you might get no or a	3799	In this section the complexities of (many of) the algorithms used inside
3503	lot of warnings when compiling libev code. Some people are apparently	3800	libev will be documented. For complexity discussions about backends see
3504	scared by this.	3801	the documentation for C<ev_default_init>.
3505		3802
3506	However, these are unavoidable for many reasons. For one, each compiler	3803	All of the following are about amortised time: If an array needs to be
3507	has different warnings, and each user has different tastes regarding	3804	extended, libev needs to realloc and move the whole array, but this
3508	warning options. "Warn-free" code therefore cannot be a goal except when	3805	happens asymptotically rarer with higher number of elements, so O(1) might
3509	targeting a specific compiler and compiler-version.	3806	mean that libev does a lengthy realloc operation in rare cases, but on
		3807	average it is much faster and asymptotically approaches constant time.
3510		3808
3511	Another reason is that some compiler warnings require elaborate	3809	=over 4
3512	workarounds, or other changes to the code that make it less clear and less
3513	maintainable.
3514		3810
3515	And of course, some compiler warnings are just plain stupid, or simply	3811	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3516	wrong (because they don't actually warn about the condition their message
3517	seems to warn about).
3518		3812
3519	While libev is written to generate as few warnings as possible,	3813	This means that, when you have a watcher that triggers in one hour and
3520	"warn-free" code is not a goal, and it is recommended not to build libev	3814	there are 100 watchers that would trigger before that, then inserting will
3521	with any compiler warnings enabled unless you are prepared to cope with	3815	have to skip roughly seven (C<ld 100>) of these watchers.
3522	them (e.g. by ignoring them). Remember that warnings are just that:
3523	warnings, not errors, or proof of bugs.
3524		3816
		3817	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3525		3818
3526	=head1 VALGRIND	3819	That means that changing a timer costs less than removing/adding them,
		3820	as only the relative motion in the event queue has to be paid for.
3527		3821
3528	Valgrind has a special section here because it is a popular tool that is	3822	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3529	highly useful, but valgrind reports are very hard to interpret.
3530		3823
3531	If you think you found a bug (memory leak, uninitialised data access etc.)	3824	These just add the watcher into an array or at the head of a list.
3532	in libev, then check twice: If valgrind reports something like:
3533		3825
3534	==2274== definitely lost: 0 bytes in 0 blocks.	3826	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3535	==2274== possibly lost: 0 bytes in 0 blocks.
3536	==2274== still reachable: 256 bytes in 1 blocks.
3537		3827
3538	Then there is no memory leak. Similarly, under some circumstances,	3828	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3539	valgrind might report kernel bugs as if it were a bug in libev, or it
3540	might be confused (it is a very good tool, but only a tool).
3541		3829
3542	If you are unsure about something, feel free to contact the mailing list	3830	These watchers are stored in lists, so they need to be walked to find the
3543	with the full valgrind report and an explanation on why you think this is	3831	correct watcher to remove. The lists are usually short (you don't usually
3544	a bug in libev. However, don't be annoyed when you get a brisk "this is	3832	have many watchers waiting for the same fd or signal: one is typical, two
3545	no bug" answer and take the chance of learning how to interpret valgrind	3833	is rare).
3546	properly.
3547		3834
3548	If you need, for some reason, empty reports from valgrind for your project	3835	=item Finding the next timer in each loop iteration: O(1)
3549	I suggest using suppression lists.	3836
		3837	By virtue of using a binary or 4-heap, the next timer is always found at a
		3838	fixed position in the storage array.
		3839
		3840	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3841
		3842	A change means an I/O watcher gets started or stopped, which requires
		3843	libev to recalculate its status (and possibly tell the kernel, depending
		3844	on backend and whether C<ev_io_set> was used).
		3845
		3846	=item Activating one watcher (putting it into the pending state): O(1)
		3847
		3848	=item Priority handling: O(number_of_priorities)
		3849
		3850	Priorities are implemented by allocating some space for each
		3851	priority. When doing priority-based operations, libev usually has to
		3852	linearly search all the priorities, but starting/stopping and activating
		3853	watchers becomes O(1) with respect to priority handling.
		3854
		3855	=item Sending an ev_async: O(1)
		3856
		3857	=item Processing ev_async_send: O(number_of_async_watchers)
		3858
		3859	=item Processing signals: O(max_signal_number)
		3860
		3861	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3862	calls in the current loop iteration. Checking for async and signal events
		3863	involves iterating over all running async watchers or all signal numbers.
		3864
		3865	=back
3550		3866
3551		3867
3552	=head1 AUTHOR	3868	=head1 AUTHOR
3553		3869
3554	Marc Lehmann <libev@schmorp.de>.	3870	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3555		3871

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