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Revision 1.179 by root, Sat Sep 13 19:14:21 2008 UTC vs.
Revision 1.215 by root, Wed Nov 5 21:44:21 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
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		385
382	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,
383	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
384	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),
385	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).
386	of shortcomings, such as silently dropping events in some hard-to-detect	390
387	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
388	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.
389		407
390	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
391	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
392	(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
393	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
394	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
395		413	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		414
400	Best performance from this backend is achieved by not unregistering all	415	Best performance from this backend is achieved by not unregistering all
401	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,
402	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.
		422
		423	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		424	faster than epoll for maybe up to a hundred file descriptors, depending on
		425	the usage. So sad.
403		426
404	While nominally embeddable in other event loops, this feature is broken in	427	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	428	all kernel versions tested so far.
406		429
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	430	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	433	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		434
412	Kqueue deserves special mention, as at the time of this writing, it	435	Kqueue deserves special mention, as at the time of this writing, it
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	436	was broken on all BSDs except NetBSD (usually it doesn't work reliably
414	with anything but sockets and pipes, except on Darwin, where of course	437	with anything but sockets and pipes, except on Darwin, where of course
415	it's completely useless). For this reason it's not being "auto-detected"	438	it's completely useless). Unlike epoll, however, whose brokenness
		439	is by design, these kqueue bugs can (and eventually will) be fixed
		440	without API changes to existing programs. For this reason it's not being
416	unless you explicitly specify it explicitly in the flags (i.e. using	441	"auto-detected" unless you explicitly specify it in the flags (i.e. using
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	442	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	443	system like NetBSD.
419		444
420	You still can embed kqueue into a normal poll or select backend and use it	445	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	446	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		448
424	It scales in the same way as the epoll backend, but the interface to the	449	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	450	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	451	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	452	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	453	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	454	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		455	cases
430		456
431	This backend usually performs well under most conditions.	457	This backend usually performs well under most conditions.
432		458
433	While nominally embeddable in other event loops, this doesn't work	459	While nominally embeddable in other event loops, this doesn't work
434	everywhere, so you might need to test for this. And since it is broken	460	everywhere, so you might need to test for this. And since it is broken
435	almost everywhere, you should only use it when you have a lot of sockets	461	almost everywhere, you should only use it when you have a lot of sockets
436	(for which it usually works), by embedding it into another event loop	462	(for which it usually works), by embedding it into another event loop
437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	463	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
438	sockets.	464	using it only for sockets.
439		465
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	466	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	467	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	468	C<NOTE_EOF>.
443		469
…		…
460	While this backend scales well, it requires one system call per active	486	While this backend scales well, it requires one system call per active
461	file descriptor per loop iteration. For small and medium numbers of file	487	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	488	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	489	might perform better.
464		490
465	On the positive side, ignoring the spurious readiness notifications, this	491	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	492	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	493	in all tests and is fully embeddable, which is a rare feat among the
		494	OS-specific backends (I vastly prefer correctness over speed hacks).
468		495
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	496	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	497	C<EVBACKEND_POLL>.
471		498
472	=item C<EVBACKEND_ALL>	499	=item C<EVBACKEND_ALL>
…		…
481		508
482	If one or more of these are or'ed into the flags value, then only these	509	If one or more of these are or'ed into the flags value, then only these
483	backends will be tried (in the reverse order as listed here). If none are	510	backends will be tried (in the reverse order as listed here). If none are
484	specified, all backends in C<ev_recommended_backends ()> will be tried.	511	specified, all backends in C<ev_recommended_backends ()> will be tried.
485		512
486	The most typical usage is like this:	513	Example: This is the most typical usage.
487		514
488	if (!ev_default_loop (0))	515	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	516	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		517
491	Restrict libev to the select and poll backends, and do not allow	518	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	519	environment settings to be taken into account:
493		520
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	521	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		522
496	Use whatever libev has to offer, but make sure that kqueue is used if	523	Example: Use whatever libev has to offer, but make sure that kqueue is
497	available (warning, breaks stuff, best use only with your own private	524	used if available (warning, breaks stuff, best use only with your own
498	event loop and only if you know the OS supports your types of fds):	525	private event loop and only if you know the OS supports your types of
		526	fds):
499		527
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	528	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		529
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	530	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		531
…		…
524	responsibility to either stop all watchers cleanly yourself I<before>	552	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	553	calling this function, or cope with the fact afterwards (which is usually
526	the easiest thing, you can just ignore the watchers and/or C<free ()> them	554	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	555	for example).
528		556
529	Note that certain global state, such as signal state, will not be freed by	557	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	558	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	559	as signal and child watchers) would need to be stopped manually.
532		560
533	In general it is not advisable to call this function except in the	561	In general it is not advisable to call this function except in the
534	rare occasion where you really need to free e.g. the signal handling	562	rare occasion where you really need to free e.g. the signal handling
535	pipe fds. If you need dynamically allocated loops it is better to use	563	pipe fds. If you need dynamically allocated loops it is better to use
536	C<ev_loop_new> and C<ev_loop_destroy>).	564	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
561		589
562	=item ev_loop_fork (loop)	590	=item ev_loop_fork (loop)
563		591
564	Like C<ev_default_fork>, but acts on an event loop created by	592	Like C<ev_default_fork>, but acts on an event loop created by
565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	593	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
566	after fork, and how you do this is entirely your own problem.	594	after fork that you want to re-use in the child, and how you do this is
		595	entirely your own problem.
567		596
568	=item int ev_is_default_loop (loop)	597	=item int ev_is_default_loop (loop)
569		598
570	Returns true when the given loop actually is the default loop, false otherwise.	599	Returns true when the given loop is, in fact, the default loop, and false
		600	otherwise.
571		601
572	=item unsigned int ev_loop_count (loop)	602	=item unsigned int ev_loop_count (loop)
573		603
574	Returns the count of loop iterations for the loop, which is identical to	604	Returns the count of loop iterations for the loop, which is identical to
575	the number of times libev did poll for new events. It starts at C<0> and	605	the number of times libev did poll for new events. It starts at C<0> and
…		…
613	If the flags argument is specified as C<0>, it will not return until	643	If the flags argument is specified as C<0>, it will not return until
614	either no event watchers are active anymore or C<ev_unloop> was called.	644	either no event watchers are active anymore or C<ev_unloop> was called.
615		645
616	Please note that an explicit C<ev_unloop> is usually better than	646	Please note that an explicit C<ev_unloop> is usually better than
617	relying on all watchers to be stopped when deciding when a program has	647	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	648	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	649	that automatically loops as long as it has to and no longer by virtue
620	relying on its watchers stopping correctly is a thing of beauty.	650	of relying on its watchers stopping correctly, that is truly a thing of
		651	beauty.
621		652
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	653	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
623	those events and any outstanding ones, but will not block your process in	654	those events and any already outstanding ones, but will not block your
624	case there are no events and will return after one iteration of the loop.	655	process in case there are no events and will return after one iteration of
		656	the loop.
625		657
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	658	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
627	necessary) and will handle those and any outstanding ones. It will block	659	necessary) and will handle those and any already outstanding ones. It
628	your process until at least one new event arrives, and will return after	660	will block your process until at least one new event arrives (which could
629	one iteration of the loop. This is useful if you are waiting for some	661	be an event internal to libev itself, so there is no guarantee that a
630	external event in conjunction with something not expressible using other	662	user-registered callback will be called), and will return after one
		663	iteration of the loop.
		664
		665	This is useful if you are waiting for some external event in conjunction
		666	with something not expressible using other libev watchers (i.e. "roll your
631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	667	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
632	usually a better approach for this kind of thing.	668	usually a better approach for this kind of thing.
633		669
634	Here are the gory details of what C<ev_loop> does:	670	Here are the gory details of what C<ev_loop> does:
635		671
636	- Before the first iteration, call any pending watchers.	672	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	682	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	683	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	684	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	685	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	686	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	687	- Queue all expired timers.
652	- Queue all outstanding periodics.	688	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	689	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	690	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	691	- Call all queued watchers in reverse order (i.e. check watchers first).
656	Signals and child watchers are implemented as I/O watchers, and will	692	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	693	be handled here by queueing them when their watcher gets executed.
…		…
674	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	710	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
675	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	711	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		712
677	This "unloop state" will be cleared when entering C<ev_loop> again.	713	This "unloop state" will be cleared when entering C<ev_loop> again.
678		714
		715	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		716
679	=item ev_ref (loop)	717	=item ev_ref (loop)
680		718
681	=item ev_unref (loop)	719	=item ev_unref (loop)
682		720
683	Ref/unref can be used to add or remove a reference count on the event	721	Ref/unref can be used to add or remove a reference count on the event
684	loop: Every watcher keeps one reference, and as long as the reference	722	loop: Every watcher keeps one reference, and as long as the reference
685	count is nonzero, C<ev_loop> will not return on its own. If you have	723	count is nonzero, C<ev_loop> will not return on its own.
		724
686	a watcher you never unregister that should not keep C<ev_loop> from	725	If you have a watcher you never unregister that should not keep C<ev_loop>
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	726	from returning, call ev_unref() after starting, and ev_ref() before
		727	stopping it.
		728
688	example, libev itself uses this for its internal signal pipe: It is not	729	As an example, libev itself uses this for its internal signal pipe: It is
689	visible to the libev user and should not keep C<ev_loop> from exiting if	730	not visible to the libev user and should not keep C<ev_loop> from exiting
690	no event watchers registered by it are active. It is also an excellent	731	if no event watchers registered by it are active. It is also an excellent
691	way to do this for generic recurring timers or from within third-party	732	way to do this for generic recurring timers or from within third-party
692	libraries. Just remember to I<unref after start> and I<ref before stop>	733	libraries. Just remember to I<unref after start> and I<ref before stop>
693	(but only if the watcher wasn't active before, or was active before,	734	(but only if the watcher wasn't active before, or was active before,
694	respectively).	735	respectively).
695		736
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	737	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	738	running when nothing else is active.
698		739
699	struct ev_signal exitsig;	740	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	741	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	742	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	743	evf_unref (loop);
703		744
704	Example: For some weird reason, unregister the above signal handler again.	745	Example: For some weird reason, unregister the above signal handler again.
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	759	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
719	allows libev to delay invocation of I/O and timer/periodic callbacks	760	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	761	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	762	opportunities).
722		763
723	The background is that sometimes your program runs just fast enough to	764	The idea is that sometimes your program runs just fast enough to handle
724	handle one (or very few) event(s) per loop iteration. While this makes	765	one (or very few) event(s) per loop iteration. While this makes the
725	the program responsive, it also wastes a lot of CPU time to poll for new	766	program responsive, it also wastes a lot of CPU time to poll for new
726	events, especially with backends like C<select ()> which have a high	767	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	768	overhead for the actual polling but can deliver many events at once.
728		769
729	By setting a higher I<io collect interval> you allow libev to spend more	770	By setting a higher I<io collect interval> you allow libev to spend more
730	time collecting I/O events, so you can handle more events per iteration,	771	time collecting I/O events, so you can handle more events per iteration,
…		…
732	C<ev_timer>) will be not affected. Setting this to a non-null value will	773	C<ev_timer>) will be not affected. Setting this to a non-null value will
733	introduce an additional C<ev_sleep ()> call into most loop iterations.	774	introduce an additional C<ev_sleep ()> call into most loop iterations.
734		775
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	776	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	777	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	778	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	779	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	780	value will not introduce any overhead in libev.
740		781
741	Many (busy) programs can usually benefit by setting the I/O collect	782	Many (busy) programs can usually benefit by setting the I/O collect
742	interval to a value near C<0.1> or so, which is often enough for	783	interval to a value near C<0.1> or so, which is often enough for
743	interactive servers (of course not for games), likewise for timeouts. It	784	interactive servers (of course not for games), likewise for timeouts. It
744	usually doesn't make much sense to set it to a lower value than C<0.01>,	785	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
752	they fire on, say, one-second boundaries only.	793	they fire on, say, one-second boundaries only.
753		794
754	=item ev_loop_verify (loop)	795	=item ev_loop_verify (loop)
755		796
756	This function only does something when C<EV_VERIFY> support has been	797	This function only does something when C<EV_VERIFY> support has been
757	compiled in. It tries to go through all internal structures and checks	798	compiled in, which is the default for non-minimal builds. It tries to go
758	them for validity. If anything is found to be inconsistent, it will print	799	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	800	is found to be inconsistent, it will print an error message to standard
		801	error and call C<abort ()>.
760		802
761	This can be used to catch bugs inside libev itself: under normal	803	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	804	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	805	data structures consistent.
764		806
765	=back	807	=back
766		808
767		809
768	=head1 ANATOMY OF A WATCHER	810	=head1 ANATOMY OF A WATCHER
769		811
		812	In the following description, uppercase C<TYPE> in names stands for the
		813	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		814	watchers and C<ev_io_start> for I/O watchers.
		815
770	A watcher is a structure that you create and register to record your	816	A watcher is a structure that you create and register to record your
771	interest in some event. For instance, if you want to wait for STDIN to	817	interest in some event. For instance, if you want to wait for STDIN to
772	become readable, you would create an C<ev_io> watcher for that:	818	become readable, you would create an C<ev_io> watcher for that:
773		819
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	820	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	821	{
776	ev_io_stop (w);	822	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	823	ev_unloop (loop, EVUNLOOP_ALL);
778	}	824	}
779		825
780	struct ev_loop *loop = ev_default_loop (0);	826	struct ev_loop *loop = ev_default_loop (0);
		827
781	struct ev_io stdin_watcher;	828	ev_io stdin_watcher;
		829
782	ev_init (&stdin_watcher, my_cb);	830	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	831	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	832	ev_io_start (loop, &stdin_watcher);
		833
785	ev_loop (loop, 0);	834	ev_loop (loop, 0);
786		835
787	As you can see, you are responsible for allocating the memory for your	836	As you can see, you are responsible for allocating the memory for your
788	watcher structures (and it is usually a bad idea to do this on the stack,	837	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	838	stack).
		839
		840	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		841	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
790		842
791	Each watcher structure must be initialised by a call to C<ev_init	843	Each watcher structure must be initialised by a call to C<ev_init
792	(watcher *, callback)>, which expects a callback to be provided. This	844	(watcher *, callback)>, which expects a callback to be provided. This
793	callback gets invoked each time the event occurs (or, in the case of I/O	845	callback gets invoked each time the event occurs (or, in the case of I/O
794	watchers, each time the event loop detects that the file descriptor given	846	watchers, each time the event loop detects that the file descriptor given
795	is readable and/or writable).	847	is readable and/or writable).
796		848
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	849	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	850	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	851	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	852	ev_TYPE_init (watcher *, callback, ...) >>.
801		853
802	To make the watcher actually watch out for events, you have to start it	854	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	855	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	856	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	857	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		858
807	As long as your watcher is active (has been started but not stopped) you	859	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	860	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	861	reinitialise it or call its C<ev_TYPE_set> macro.
810		862
811	Each and every callback receives the event loop pointer as first, the	863	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	864	registered watcher structure as second, and a bitset of received events as
813	third argument.	865	third argument.
814		866
…		…
877	=item C<EV_ERROR>	929	=item C<EV_ERROR>
878		930
879	An unspecified error has occurred, the watcher has been stopped. This might	931	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	932	happen because the watcher could not be properly started because libev
881	ran out of memory, a file descriptor was found to be closed or any other	933	ran out of memory, a file descriptor was found to be closed or any other
		934	problem. Libev considers these application bugs.
		935
882	problem. You best act on it by reporting the problem and somehow coping	936	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	937	watcher being stopped. Note that well-written programs should not receive
		938	an error ever, so when your watcher receives it, this usually indicates a
		939	bug in your program.
884		940
885	Libev will usually signal a few "dummy" events together with an error,	941	Libev will usually signal a few "dummy" events together with an error, for
886	for example it might indicate that a fd is readable or writable, and if	942	example it might indicate that a fd is readable or writable, and if your
887	your callbacks is well-written it can just attempt the operation and cope	943	callbacks is well-written it can just attempt the operation and cope with
888	with the error from read() or write(). This will not work in multi-threaded	944	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	945	programs, though, as the fd could already be closed and reused for another
		946	thing, so beware.
890		947
891	=back	948	=back
892		949
893	=head2 GENERIC WATCHER FUNCTIONS	950	=head2 GENERIC WATCHER FUNCTIONS
894
895	In the following description, C<TYPE> stands for the watcher type,
896	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
897		951
898	=over 4	952	=over 4
899		953
900	=item C<ev_init> (ev_TYPE *watcher, callback)	954	=item C<ev_init> (ev_TYPE *watcher, callback)
901		955
…		…
907	which rolls both calls into one.	961	which rolls both calls into one.
908		962
909	You can reinitialise a watcher at any time as long as it has been stopped	963	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	964	(or never started) and there are no pending events outstanding.
911		965
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	966	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	967	int revents)>.
		968
		969	Example: Initialise an C<ev_io> watcher in two steps.
		970
		971	ev_io w;
		972	ev_init (&w, my_cb);
		973	ev_io_set (&w, STDIN_FILENO, EV_READ);
914		974
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	975	=item C<ev_TYPE_set> (ev_TYPE *, [args])
916		976
917	This macro initialises the type-specific parts of a watcher. You need to	977	This macro initialises the type-specific parts of a watcher. You need to
918	call C<ev_init> at least once before you call this macro, but you can	978	call C<ev_init> at least once before you call this macro, but you can
…		…
921	difference to the C<ev_init> macro).	981	difference to the C<ev_init> macro).
922		982
923	Although some watcher types do not have type-specific arguments	983	Although some watcher types do not have type-specific arguments
924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	984	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		985
		986	See C<ev_init>, above, for an example.
		987
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	988	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		989
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	990	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
929	calls into a single call. This is the most convenient method to initialise	991	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	992	a watcher. The same limitations apply, of course.
931		993
		994	Example: Initialise and set an C<ev_io> watcher in one step.
		995
		996	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		997
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	998	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
933		999
934	Starts (activates) the given watcher. Only active watchers will receive	1000	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1001	events. If the watcher is already active nothing will happen.
936		1002
		1003	Example: Start the C<ev_io> watcher that is being abused as example in this
		1004	whole section.
		1005
		1006	ev_io_start (EV_DEFAULT_UC, &w);
		1007
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1008	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
938		1009
939	Stops the given watcher again (if active) and clears the pending	1010	Stops the given watcher if active, and clears the pending status (whether
		1011	the watcher was active or not).
		1012
940	status. It is possible that stopped watchers are pending (for example,	1013	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1014	non-repeating timers are being stopped when they become pending - but
942	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1015	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
943	you want to free or reuse the memory used by the watcher it is therefore a	1016	pending. If you want to free or reuse the memory used by the watcher it is
944	good idea to always call its C<ev_TYPE_stop> function.	1017	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1018
946	=item bool ev_is_active (ev_TYPE *watcher)	1019	=item bool ev_is_active (ev_TYPE *watcher)
947		1020
948	Returns a true value iff the watcher is active (i.e. it has been started	1021	Returns a true value iff the watcher is active (i.e. it has been started
949	and not yet been stopped). As long as a watcher is active you must not modify	1022	and not yet been stopped). As long as a watcher is active you must not modify
…		…
991	The default priority used by watchers when no priority has been set is	1064	The default priority used by watchers when no priority has been set is
992	always C<0>, which is supposed to not be too high and not be too low :).	1065	always C<0>, which is supposed to not be too high and not be too low :).
993		1066
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1067	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
995	fine, as long as you do not mind that the priority value you query might	1068	fine, as long as you do not mind that the priority value you query might
996	or might not have been adjusted to be within valid range.	1069	or might not have been clamped to the valid range.
997		1070
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1071	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1072
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1073	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1001	C<loop> nor C<revents> need to be valid as long as the watcher callback	1074	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1075	can deal with that fact, as both are simply passed through to the
		1076	callback.
1003		1077
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1078	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1079
1006	If the watcher is pending, this function returns clears its pending status	1080	If the watcher is pending, this function clears its pending status and
1007	and returns its C<revents> bitset (as if its callback was invoked). If the	1081	returns its C<revents> bitset (as if its callback was invoked). If the
1008	watcher isn't pending it does nothing and returns C<0>.	1082	watcher isn't pending it does nothing and returns C<0>.
1009		1083
		1084	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1085	callback to be invoked, which can be accomplished with this function.
		1086
1010	=back	1087	=back
1011		1088
1012		1089
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1090	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1091
1015	Each watcher has, by default, a member C<void *data> that you can change	1092	Each watcher has, by default, a member C<void *data> that you can change
1016	and read at any time, libev will completely ignore it. This can be used	1093	and read at any time: libev will completely ignore it. This can be used
1017	to associate arbitrary data with your watcher. If you need more data and	1094	to associate arbitrary data with your watcher. If you need more data and
1018	don't want to allocate memory and store a pointer to it in that data	1095	don't want to allocate memory and store a pointer to it in that data
1019	member, you can also "subclass" the watcher type and provide your own	1096	member, you can also "subclass" the watcher type and provide your own
1020	data:	1097	data:
1021		1098
1022	struct my_io	1099	struct my_io
1023	{	1100	{
1024	struct ev_io io;	1101	ev_io io;
1025	int otherfd;	1102	int otherfd;
1026	void *somedata;	1103	void *somedata;
1027	struct whatever *mostinteresting;	1104	struct whatever *mostinteresting;
1028	};	1105	};
1029		1106
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1109	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1110
1034	And since your callback will be called with a pointer to the watcher, you	1111	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1112	can cast it back to your own type:
1036		1113
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1114	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1115	{
1039	struct my_io *w = (struct my_io *)w_;	1116	struct my_io *w = (struct my_io *)w_;
1040	...	1117	...
1041	}	1118	}
1042		1119
…		…
1053	ev_timer t2;	1130	ev_timer t2;
1054	}	1131	}
1055		1132
1056	In this case getting the pointer to C<my_biggy> is a bit more	1133	In this case getting the pointer to C<my_biggy> is a bit more
1057	complicated: Either you store the address of your C<my_biggy> struct	1134	complicated: Either you store the address of your C<my_biggy> struct
1058	in the C<data> member of the watcher, or you need to use some pointer	1135	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1136	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1137	programmers):
1060		1138
1061	#include <stddef.h>	1139	#include <stddef.h>
1062		1140
1063	static void	1141	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1142	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1143	{
1066	struct my_biggy big = (struct my_biggy *	1144	struct my_biggy big = (struct my_biggy *
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1145	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1146	}
1069		1147
1070	static void	1148	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1149	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1150	{
1073	struct my_biggy big = (struct my_biggy *	1151	struct my_biggy big = (struct my_biggy *
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1152	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1153	}
1076		1154
…		…
1104	In general you can register as many read and/or write event watchers per	1182	In general you can register as many read and/or write event watchers per
1105	fd as you want (as long as you don't confuse yourself). Setting all file	1183	fd as you want (as long as you don't confuse yourself). Setting all file
1106	descriptors to non-blocking mode is also usually a good idea (but not	1184	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1185	required if you know what you are doing).
1108		1186
1109	If you must do this, then force the use of a known-to-be-good backend	1187	If you cannot use non-blocking mode, then force the use of a
1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1188	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1189	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1112		1190
1113	Another thing you have to watch out for is that it is quite easy to	1191	Another thing you have to watch out for is that it is quite easy to
1114	receive "spurious" readiness notifications, that is your callback might	1192	receive "spurious" readiness notifications, that is your callback might
1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1193	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1116	because there is no data. Not only are some backends known to create a	1194	because there is no data. Not only are some backends known to create a
1117	lot of those (for example Solaris ports), it is very easy to get into	1195	lot of those (for example Solaris ports), it is very easy to get into
1118	this situation even with a relatively standard program structure. Thus	1196	this situation even with a relatively standard program structure. Thus
1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1197	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1198	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1199
1122	If you cannot run the fd in non-blocking mode (for example you should not	1200	If you cannot run the fd in non-blocking mode (for example you should
1123	play around with an Xlib connection), then you have to separately re-test	1201	not play around with an Xlib connection), then you have to separately
1124	whether a file descriptor is really ready with a known-to-be good interface	1202	re-test whether a file descriptor is really ready with a known-to-be good
1125	such as poll (fortunately in our Xlib example, Xlib already does this on	1203	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1204	does this on its own, so its quite safe to use). Some people additionally
		1205	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1206	indefinitely.
		1207
		1208	But really, best use non-blocking mode.
1127		1209
1128	=head3 The special problem of disappearing file descriptors	1210	=head3 The special problem of disappearing file descriptors
1129		1211
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1212	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1131	descriptor (either by calling C<close> explicitly or by any other means,	1213	descriptor (either due to calling C<close> explicitly or any other means,
1132	such as C<dup>). The reason is that you register interest in some file	1214	such as C<dup2>). The reason is that you register interest in some file
1133	descriptor, but when it goes away, the operating system will silently drop	1215	descriptor, but when it goes away, the operating system will silently drop
1134	this interest. If another file descriptor with the same number then is	1216	this interest. If another file descriptor with the same number then is
1135	registered with libev, there is no efficient way to see that this is, in	1217	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1218	fact, a different file descriptor.
1137		1219
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1250	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1251	C<EVBACKEND_POLL>.
1170		1252
1171	=head3 The special problem of SIGPIPE	1253	=head3 The special problem of SIGPIPE
1172		1254
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1255	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1174	when writing to a pipe whose other end has been closed, your program gets	1256	when writing to a pipe whose other end has been closed, your program gets
1175	send a SIGPIPE, which, by default, aborts your program. For most programs	1257	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1258	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1259
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1260	So when you encounter spurious, unexplained daemon exits, make sure you
1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1261	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1180	somewhere, as that would have given you a big clue).	1262	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1269	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1270
1189	=item ev_io_set (ev_io *, int fd, int events)	1271	=item ev_io_set (ev_io *, int fd, int events)
1190		1272
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1273	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1274	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1193	C<EV_READ | EV_WRITE> to receive the given events.	1275	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1276
1195	=item int fd [read-only]	1277	=item int fd [read-only]
1196		1278
1197	The file descriptor being watched.	1279	The file descriptor being watched.
1198		1280
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1289	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1208	readable, but only once. Since it is likely line-buffered, you could	1290	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1291	attempt to read a whole line in the callback.
1210		1292
1211	static void	1293	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1294	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1295	{
1214	ev_io_stop (loop, w);	1296	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1297	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1298	}
1217		1299
1218	...	1300	...
1219	struct ev_loop *loop = ev_default_init (0);	1301	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1302	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1303	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1304	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1305	ev_loop (loop, 0);
1224		1306
1225		1307
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1310	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1311	given time, and optionally repeating in regular intervals after that.
1230		1312
1231	The timers are based on real time, that is, if you register an event that	1313	The timers are based on real time, that is, if you register an event that
1232	times out after an hour and you reset your system clock to January last	1314	times out after an hour and you reset your system clock to January last
1233	year, it will still time out after (roughly) and hour. "Roughly" because	1315	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1316	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1317	monotonic clock option helps a lot here).
1236		1318
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1319	The callback is guaranteed to be invoked only I<after> its timeout has
1238	but if multiple timers become ready during the same loop iteration then	1320	passed, but if multiple timers become ready during the same loop iteration
1239	order of execution is undefined.	1321	then order of execution is undefined.
		1322
		1323	=head3 Be smart about timeouts
		1324
		1325	Many real-world problems involve some kind of timeout, usually for error
		1326	recovery. A typical example is an HTTP request - if the other side hangs,
		1327	you want to raise some error after a while.
		1328
		1329	What follows are some ways to handle this problem, from obvious and
		1330	inefficient to smart and efficient.
		1331
		1332	In the following, a 60 second activity timeout is assumed - a timeout that
		1333	gets reset to 60 seconds each time there is activity (e.g. each time some
		1334	data or other life sign was received).
		1335
		1336	=over 4
		1337
		1338	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1339
		1340	This is the most obvious, but not the most simple way: In the beginning,
		1341	start the watcher:
		1342
		1343	ev_timer_init (timer, callback, 60., 0.);
		1344	ev_timer_start (loop, timer);
		1345
		1346	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1347	and start it again:
		1348
		1349	ev_timer_stop (loop, timer);
		1350	ev_timer_set (timer, 60., 0.);
		1351	ev_timer_start (loop, timer);
		1352
		1353	This is relatively simple to implement, but means that each time there is
		1354	some activity, libev will first have to remove the timer from its internal
		1355	data structure and then add it again. Libev tries to be fast, but it's
		1356	still not a constant-time operation.
		1357
		1358	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1359
		1360	This is the easiest way, and involves using C<ev_timer_again> instead of
		1361	C<ev_timer_start>.
		1362
		1363	To implement this, configure an C<ev_timer> with a C<repeat> value
		1364	of C<60> and then call C<ev_timer_again> at start and each time you
		1365	successfully read or write some data. If you go into an idle state where
		1366	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1367	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1368
		1369	That means you can ignore both the C<ev_timer_start> function and the
		1370	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1371	member and C<ev_timer_again>.
		1372
		1373	At start:
		1374
		1375	ev_timer_init (timer, callback);
		1376	timer->repeat = 60.;
		1377	ev_timer_again (loop, timer);
		1378
		1379	Each time there is some activity:
		1380
		1381	ev_timer_again (loop, timer);
		1382
		1383	It is even possible to change the time-out on the fly, regardless of
		1384	whether the watcher is active or not:
		1385
		1386	timer->repeat = 30.;
		1387	ev_timer_again (loop, timer);
		1388
		1389	This is slightly more efficient then stopping/starting the timer each time
		1390	you want to modify its timeout value, as libev does not have to completely
		1391	remove and re-insert the timer from/into its internal data structure.
		1392
		1393	It is, however, even simpler than the "obvious" way to do it.
		1394
		1395	=item 3. Let the timer time out, but then re-arm it as required.
		1396
		1397	This method is more tricky, but usually most efficient: Most timeouts are
		1398	relatively long compared to the intervals between other activity - in
		1399	our example, within 60 seconds, there are usually many I/O events with
		1400	associated activity resets.
		1401
		1402	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1403	but remember the time of last activity, and check for a real timeout only
		1404	within the callback:
		1405
		1406	ev_tstamp last_activity; // time of last activity
		1407
		1408	static void
		1409	callback (EV_P_ ev_timer *w, int revents)
		1410	{
		1411	ev_tstamp now = ev_now (EV_A);
		1412	ev_tstamp timeout = last_activity + 60.;
		1413
		1414	// if last_activity + 60. is older than now, we did time out
		1415	if (timeout < now)
		1416	{
		1417	// timeout occured, take action
		1418	}
		1419	else
		1420	{
		1421	// callback was invoked, but there was some activity, re-arm
		1422	// the watcher to fire in last_activity + 60, which is
		1423	// guaranteed to be in the future, so "again" is positive:
		1424	w->again = timeout - now;
		1425	ev_timer_again (EV_A_ w);
		1426	}
		1427	}
		1428
		1429	To summarise the callback: first calculate the real timeout (defined
		1430	as "60 seconds after the last activity"), then check if that time has
		1431	been reached, which means something I<did>, in fact, time out. Otherwise
		1432	the callback was invoked too early (C<timeout> is in the future), so
		1433	re-schedule the timer to fire at that future time, to see if maybe we have
		1434	a timeout then.
		1435
		1436	Note how C<ev_timer_again> is used, taking advantage of the
		1437	C<ev_timer_again> optimisation when the timer is already running.
		1438
		1439	This scheme causes more callback invocations (about one every 60 seconds
		1440	minus half the average time between activity), but virtually no calls to
		1441	libev to change the timeout.
		1442
		1443	To start the timer, simply initialise the watcher and set C<last_activity>
		1444	to the current time (meaning we just have some activity :), then call the
		1445	callback, which will "do the right thing" and start the timer:
		1446
		1447	ev_timer_init (timer, callback);
		1448	last_activity = ev_now (loop);
		1449	callback (loop, timer, EV_TIMEOUT);
		1450
		1451	And when there is some activity, simply store the current time in
		1452	C<last_activity>, no libev calls at all:
		1453
		1454	last_actiivty = ev_now (loop);
		1455
		1456	This technique is slightly more complex, but in most cases where the
		1457	time-out is unlikely to be triggered, much more efficient.
		1458
		1459	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1460	callback :) - just change the timeout and invoke the callback, which will
		1461	fix things for you.
		1462
		1463	=item 4. Wee, just use a double-linked list for your timeouts.
		1464
		1465	If there is not one request, but many thousands (millions...), all
		1466	employing some kind of timeout with the same timeout value, then one can
		1467	do even better:
		1468
		1469	When starting the timeout, calculate the timeout value and put the timeout
		1470	at the I<end> of the list.
		1471
		1472	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1473	the list is expected to fire (for example, using the technique #3).
		1474
		1475	When there is some activity, remove the timer from the list, recalculate
		1476	the timeout, append it to the end of the list again, and make sure to
		1477	update the C<ev_timer> if it was taken from the beginning of the list.
		1478
		1479	This way, one can manage an unlimited number of timeouts in O(1) time for
		1480	starting, stopping and updating the timers, at the expense of a major
		1481	complication, and having to use a constant timeout. The constant timeout
		1482	ensures that the list stays sorted.
		1483
		1484	=back
		1485
		1486	So which method the best?
		1487
		1488	Method #2 is a simple no-brain-required solution that is adequate in most
		1489	situations. Method #3 requires a bit more thinking, but handles many cases
		1490	better, and isn't very complicated either. In most case, choosing either
		1491	one is fine, with #3 being better in typical situations.
		1492
		1493	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1494	rather complicated, but extremely efficient, something that really pays
		1495	off after the first million or so of active timers, i.e. it's usually
		1496	overkill :)
1240		1497
1241	=head3 The special problem of time updates	1498	=head3 The special problem of time updates
1242		1499
1243	Establishing the current time is a costly operation (it usually takes at	1500	Establishing the current time is a costly operation (it usually takes at
1244	least two system calls): EV therefore updates its idea of the current	1501	least two system calls): EV therefore updates its idea of the current
1245	time only before and after C<ev_loop> polls for new events, which causes	1502	time only before and after C<ev_loop> collects new events, which causes a
1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1503	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1504	lots of events in one iteration.
1248		1505
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1506	The relative timeouts are calculated relative to the C<ev_now ()>
1250	time. This is usually the right thing as this timestamp refers to the time	1507	time. This is usually the right thing as this timestamp refers to the time
1251	of the event triggering whatever timeout you are modifying/starting. If	1508	of the event triggering whatever timeout you are modifying/starting. If
1252	you suspect event processing to be delayed and you I<need> to base the	1509	you suspect event processing to be delayed and you I<need> to base the
…		…
1288	If the timer is started but non-repeating, stop it (as if it timed out).	1545	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1546
1290	If the timer is repeating, either start it if necessary (with the	1547	If the timer is repeating, either start it if necessary (with the
1291	C<repeat> value), or reset the running timer to the C<repeat> value.	1548	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1549
1293	This sounds a bit complicated, but here is a useful and typical	1550	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	1551	usage example.
1295	timeout, that is, you want to be called when there have been, say, 60
1296	seconds of inactivity on the socket. The easiest way to do this is to
1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1298	C<ev_timer_again> each time you successfully read or write some data. If
1299	you go into an idle state where you do not expect data to travel on the
1300	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1301	automatically restart it if need be.
1302
1303	That means you can ignore the C<after> value and C<ev_timer_start>
1304	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1305
1306	ev_timer_init (timer, callback, 0., 5.);
1307	ev_timer_again (loop, timer);
1308	...
1309	timer->again = 17.;
1310	ev_timer_again (loop, timer);
1311	...
1312	timer->again = 10.;
1313	ev_timer_again (loop, timer);
1314
1315	This is more slightly efficient then stopping/starting the timer each time
1316	you want to modify its timeout value.
1317		1552
1318	=item ev_tstamp repeat [read-write]	1553	=item ev_tstamp repeat [read-write]
1319		1554
1320	The current C<repeat> value. Will be used each time the watcher times out	1555	The current C<repeat> value. Will be used each time the watcher times out
1321	or C<ev_timer_again> is called and determines the next timeout (if any),	1556	or C<ev_timer_again> is called, and determines the next timeout (if any),
1322	which is also when any modifications are taken into account.	1557	which is also when any modifications are taken into account.
1323		1558
1324	=back	1559	=back
1325		1560
1326	=head3 Examples	1561	=head3 Examples
1327		1562
1328	Example: Create a timer that fires after 60 seconds.	1563	Example: Create a timer that fires after 60 seconds.
1329		1564
1330	static void	1565	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1566	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1567	{
1333	.. one minute over, w is actually stopped right here	1568	.. one minute over, w is actually stopped right here
1334	}	1569	}
1335		1570
1336	struct ev_timer mytimer;	1571	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1572	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1573	ev_timer_start (loop, &mytimer);
1339		1574
1340	Example: Create a timeout timer that times out after 10 seconds of	1575	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1576	inactivity.
1342		1577
1343	static void	1578	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1579	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1580	{
1346	.. ten seconds without any activity	1581	.. ten seconds without any activity
1347	}	1582	}
1348		1583
1349	struct ev_timer mytimer;	1584	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1585	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1586	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1587	ev_loop (loop, 0);
1353		1588
1354	// and in some piece of code that gets executed on any "activity":	1589	// and in some piece of code that gets executed on any "activity":
…		…
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger	1605	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).	1606	roughly 10 seconds later as it uses a relative timeout).
1372		1607
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1608	C<ev_periodic>s can also be used to implement vastly more complex timers,
1374	such as triggering an event on each "midnight, local time", or other	1609	such as triggering an event on each "midnight, local time", or other
1375	complicated, rules.	1610	complicated rules.
1376		1611
1377	As with timers, the callback is guaranteed to be invoked only when the	1612	As with timers, the callback is guaranteed to be invoked only when the
1378	time (C<at>) has passed, but if multiple periodic timers become ready	1613	time (C<at>) has passed, but if multiple periodic timers become ready
1379	during the same loop iteration then order of execution is undefined.	1614	during the same loop iteration, then order of execution is undefined.
1380		1615
1381	=head3 Watcher-Specific Functions and Data Members	1616	=head3 Watcher-Specific Functions and Data Members
1382		1617
1383	=over 4	1618	=over 4
1384		1619
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1620	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1386		1621
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1622	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1388		1623
1389	Lots of arguments, lets sort it out... There are basically three modes of	1624	Lots of arguments, lets sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	1625	operation, and we will explain them from simplest to most complex:
1391		1626
1392	=over 4	1627	=over 4
1393		1628
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1629	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1395		1630
1396	In this configuration the watcher triggers an event after the wall clock	1631	In this configuration the watcher triggers an event after the wall clock
1397	time C<at> has passed and doesn't repeat. It will not adjust when a time	1632	time C<at> has passed. It will not repeat and will not adjust when a time
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1633	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1399	run when the system time reaches or surpasses this time.	1634	only run when the system clock reaches or surpasses this time.
1400		1635
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1636	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1402		1637
1403	In this mode the watcher will always be scheduled to time out at the next	1638	In this mode the watcher will always be scheduled to time out at the next
1404	C<at + N * interval> time (for some integer N, which can also be negative)	1639	C<at + N * interval> time (for some integer N, which can also be negative)
1405	and then repeat, regardless of any time jumps.	1640	and then repeat, regardless of any time jumps.
1406		1641
1407	This can be used to create timers that do not drift with respect to system	1642	This can be used to create timers that do not drift with respect to the
1408	time, for example, here is a C<ev_periodic> that triggers each hour, on	1643	system clock, for example, here is a C<ev_periodic> that triggers each
1409	the hour:	1644	hour, on the hour:
1410		1645
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1646	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1647
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1648	This doesn't mean there will always be 3600 seconds in between triggers,
1414	but only that the callback will be called when the system time shows a	1649	but only that the callback will be called when the system time shows a
…		…
1440		1675
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1676	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1677	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	1678	only event loop modification you are allowed to do).
1444		1679
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1680	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	1681	*w, ev_tstamp now)>, e.g.:
1447		1682
		1683	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1684	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	1685	{
1450	return now + 60.;	1686	return now + 60.;
1451	}	1687	}
1452		1688
1453	It must return the next time to trigger, based on the passed time value	1689	It must return the next time to trigger, based on the passed time value
…		…
1490		1726
1491	The current interval value. Can be modified any time, but changes only	1727	The current interval value. Can be modified any time, but changes only
1492	take effect when the periodic timer fires or C<ev_periodic_again> is being	1728	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	1729	called.
1494		1730
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1731	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		1732
1497	The current reschedule callback, or C<0>, if this functionality is	1733	The current reschedule callback, or C<0>, if this functionality is
1498	switched off. Can be changed any time, but changes only take effect when	1734	switched off. Can be changed any time, but changes only take effect when
1499	the periodic timer fires or C<ev_periodic_again> is being called.	1735	the periodic timer fires or C<ev_periodic_again> is being called.
1500		1736
1501	=back	1737	=back
1502		1738
1503	=head3 Examples	1739	=head3 Examples
1504		1740
1505	Example: Call a callback every hour, or, more precisely, whenever the	1741	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	1742	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	1743	potentially a lot of jitter, but good long-term stability.
1508		1744
1509	static void	1745	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1746	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	1747	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	1748	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	1749	}
1514		1750
1515	struct ev_periodic hourly_tick;	1751	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1752	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	1753	ev_periodic_start (loop, &hourly_tick);
1518		1754
1519	Example: The same as above, but use a reschedule callback to do it:	1755	Example: The same as above, but use a reschedule callback to do it:
1520		1756
1521	#include <math.h>	1757	#include <math.h>
1522		1758
1523	static ev_tstamp	1759	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1760	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	1761	{
1526	return fmod (now, 3600.) + 3600.;	1762	return now + (3600. - fmod (now, 3600.));
1527	}	1763	}
1528		1764
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1765	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		1766
1531	Example: Call a callback every hour, starting now:	1767	Example: Call a callback every hour, starting now:
1532		1768
1533	struct ev_periodic hourly_tick;	1769	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	1770	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	1771	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	1772	ev_periodic_start (loop, &hourly_tick);
1537		1773
1538		1774
…		…
1541	Signal watchers will trigger an event when the process receives a specific	1777	Signal watchers will trigger an event when the process receives a specific
1542	signal one or more times. Even though signals are very asynchronous, libev	1778	signal one or more times. Even though signals are very asynchronous, libev
1543	will try it's best to deliver signals synchronously, i.e. as part of the	1779	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	1780	normal event processing, like any other event.
1545		1781
		1782	If you want signals asynchronously, just use C<sigaction> as you would
		1783	do without libev and forget about sharing the signal. You can even use
		1784	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1785
1546	You can configure as many watchers as you like per signal. Only when the	1786	You can configure as many watchers as you like per signal. Only when the
1547	first watcher gets started will libev actually register a signal watcher	1787	first watcher gets started will libev actually register a signal handler
1548	with the kernel (thus it coexists with your own signal handlers as long	1788	with the kernel (thus it coexists with your own signal handlers as long as
1549	as you don't register any with libev). Similarly, when the last signal	1789	you don't register any with libev for the same signal). Similarly, when
1550	watcher for a signal is stopped libev will reset the signal handler to	1790	the last signal watcher for a signal is stopped, libev will reset the
1551	SIG_DFL (regardless of what it was set to before).	1791	signal handler to SIG_DFL (regardless of what it was set to before).
1552		1792
1553	If possible and supported, libev will install its handlers with	1793	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1794	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1555	interrupted. If you have a problem with system calls getting interrupted by	1795	interrupted. If you have a problem with system calls getting interrupted by
1556	signals you can block all signals in an C<ev_check> watcher and unblock	1796	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1573		1813
1574	=back	1814	=back
1575		1815
1576	=head3 Examples	1816	=head3 Examples
1577		1817
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	1818	Example: Try to exit cleanly on SIGINT.
1579		1819
1580	static void	1820	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1821	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	1822	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	1823	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	1824	}
1585		1825
1586	struct ev_signal signal_watcher;	1826	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1827	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	1828	ev_signal_start (loop, &signal_watcher);
1589		1829
1590		1830
1591	=head2 C<ev_child> - watch out for process status changes	1831	=head2 C<ev_child> - watch out for process status changes
1592		1832
1593	Child watchers trigger when your process receives a SIGCHLD in response to	1833	Child watchers trigger when your process receives a SIGCHLD in response to
1594	some child status changes (most typically when a child of yours dies). It	1834	some child status changes (most typically when a child of yours dies or
1595	is permissible to install a child watcher I<after> the child has been	1835	exits). It is permissible to install a child watcher I<after> the child
1596	forked (which implies it might have already exited), as long as the event	1836	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	1837	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1838	forking and then immediately registering a watcher for the child is fine,
		1839	but forking and registering a watcher a few event loop iterations later is
		1840	not.
1598		1841
1599	Only the default event loop is capable of handling signals, and therefore	1842	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	1843	you can only register child watchers in the default event loop.
1601		1844
1602	=head3 Process Interaction	1845	=head3 Process Interaction
…		…
1663	its completion.	1906	its completion.
1664		1907
1665	ev_child cw;	1908	ev_child cw;
1666		1909
1667	static void	1910	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	1911	child_cb (EV_P_ ev_child *w, int revents)
1669	{	1912	{
1670	ev_child_stop (EV_A_ w);	1913	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1914	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	1915	}
1673		1916
…		…
1688		1931
1689		1932
1690	=head2 C<ev_stat> - did the file attributes just change?	1933	=head2 C<ev_stat> - did the file attributes just change?
1691		1934
1692	This watches a file system path for attribute changes. That is, it calls	1935	This watches a file system path for attribute changes. That is, it calls
1693	C<stat> regularly (or when the OS says it changed) and sees if it changed	1936	C<stat> on that path in regular intervals (or when the OS says it changed)
1694	compared to the last time, invoking the callback if it did.	1937	and sees if it changed compared to the last time, invoking the callback if
		1938	it did.
1695		1939
1696	The path does not need to exist: changing from "path exists" to "path does	1940	The path does not need to exist: changing from "path exists" to "path does
1697	not exist" is a status change like any other. The condition "path does	1941	not exist" is a status change like any other. The condition "path does not
1698	not exist" is signified by the C<st_nlink> field being zero (which is	1942	exist" (or more correctly "path cannot be stat'ed") is signified by the
1699	otherwise always forced to be at least one) and all the other fields of	1943	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	1944	least one) and all the other fields of the stat buffer having unspecified
		1945	contents.
1701		1946
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	1947	The path I<must not> end in a slash or contain special components such as
		1948	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1703	relative and your working directory changes, the behaviour is undefined.	1949	your working directory changes, then the behaviour is undefined.
1704		1950
1705	Since there is no standard to do this, the portable implementation simply	1951	Since there is no portable change notification interface available, the
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1952	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	1953	to see if it changed somehow. You can specify a recommended polling
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	1954	interval for this case. If you specify a polling interval of C<0> (highly
1709	unspecified default> value will be used (which you can expect to be around	1955	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	1956	(which you can expect to be around five seconds, although this might
1711	impose a minimum interval which is currently around C<0.1>, but thats	1957	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	1958	currently around C<0.1>, but that's usually overkill.
1713		1959
1714	This watcher type is not meant for massive numbers of stat watchers,	1960	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	1961	as even with OS-supported change notifications, this can be
1716	resource-intensive.	1962	resource-intensive.
1717		1963
1718	At the time of this writing, only the Linux inotify interface is	1964	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	1965	is the Linux inotify interface (implementing kqueue support is left as an
1720	reader, note, however, that the author sees no way of implementing ev_stat	1966	exercise for the reader. Note, however, that the author sees no way of
1721	semantics with kqueue). Inotify will be used to give hints only and should	1967	implementing C<ev_stat> semantics with kqueue, except as a hint).
1722	not change the semantics of C<ev_stat> watchers, which means that libev
1723	sometimes needs to fall back to regular polling again even with inotify,
1724	but changes are usually detected immediately, and if the file exists there
1725	will be no polling.
1726		1968
1727	=head3 ABI Issues (Largefile Support)	1969	=head3 ABI Issues (Largefile Support)
1728		1970
1729	Libev by default (unless the user overrides this) uses the default	1971	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	1972	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	1973	support disabled by default, you get the 32 bit version of the stat
1732	structure. When using the library from programs that change the ABI to	1974	structure. When using the library from programs that change the ABI to
1733	use 64 bit file offsets the programs will fail. In that case you have to	1975	use 64 bit file offsets the programs will fail. In that case you have to
1734	compile libev with the same flags to get binary compatibility. This is	1976	compile libev with the same flags to get binary compatibility. This is
1735	obviously the case with any flags that change the ABI, but the problem is	1977	obviously the case with any flags that change the ABI, but the problem is
1736	most noticeably disabled with ev_stat and large file support.	1978	most noticeably displayed with ev_stat and large file support.
1737		1979
1738	The solution for this is to lobby your distribution maker to make large	1980	The solution for this is to lobby your distribution maker to make large
1739	file interfaces available by default (as e.g. FreeBSD does) and not	1981	file interfaces available by default (as e.g. FreeBSD does) and not
1740	optional. Libev cannot simply switch on large file support because it has	1982	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	1983	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	1984	default compilation environment.
1743		1985
1744	=head3 Inotify	1986	=head3 Inotify and Kqueue
1745		1987
1746	When C<inotify (7)> support has been compiled into libev (generally only	1988	When C<inotify (7)> support has been compiled into libev and present at
1747	available on Linux) and present at runtime, it will be used to speed up	1989	runtime, it will be used to speed up change detection where possible. The
1748	change detection where possible. The inotify descriptor will be created lazily	1990	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	1991	watcher is being started.
1750		1992
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	1993	Inotify presence does not change the semantics of C<ev_stat> watchers
1752	except that changes might be detected earlier, and in some cases, to avoid	1994	except that changes might be detected earlier, and in some cases, to avoid
1753	making regular C<stat> calls. Even in the presence of inotify support	1995	making regular C<stat> calls. Even in the presence of inotify support
1754	there are many cases where libev has to resort to regular C<stat> polling.	1996	there are many cases where libev has to resort to regular C<stat> polling,
		1997	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1998	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1999	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2000	xfs are fully working) libev usually gets away without polling.
1755		2001
1756	(There is no support for kqueue, as apparently it cannot be used to	2002	There is no support for kqueue, as apparently it cannot be used to
1757	implement this functionality, due to the requirement of having a file	2003	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2004	descriptor open on the object at all times, and detecting renames, unlinks
		2005	etc. is difficult.
		2006
		2007	=head3 C<stat ()> is a synchronous operation
		2008
		2009	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2010	the process. The exception are C<ev_stat> watchers - those call C<stat
		2011	()>, which is a synchronous operation.
		2012
		2013	For local paths, this usually doesn't matter: unless the system is very
		2014	busy or the intervals between stat's are large, a stat call will be fast,
		2015	as the path data is suually in memory already (except when starting the
		2016	watcher).
		2017
		2018	For networked file systems, calling C<stat ()> can block an indefinite
		2019	time due to network issues, and even under good conditions, a stat call
		2020	often takes multiple milliseconds.
		2021
		2022	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2023	paths, although this is fully supported by libev.
1759		2024
1760	=head3 The special problem of stat time resolution	2025	=head3 The special problem of stat time resolution
1761		2026
1762	The C<stat ()> system call only supports full-second resolution portably, and	2027	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2028	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2029	still only support whole seconds.
1765		2030
1766	That means that, if the time is the only thing that changes, you can	2031	That means that, if the time is the only thing that changes, you can
1767	easily miss updates: on the first update, C<ev_stat> detects a change and	2032	easily miss updates: on the first update, C<ev_stat> detects a change and
1768	calls your callback, which does something. When there is another update	2033	calls your callback, which does something. When there is another update
1769	within the same second, C<ev_stat> will be unable to detect it as the stat	2034	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2035	stat data does change in other ways (e.g. file size).
1771		2036
1772	The solution to this is to delay acting on a change for slightly more	2037	The solution to this is to delay acting on a change for slightly more
1773	than a second (or till slightly after the next full second boundary), using	2038	than a second (or till slightly after the next full second boundary), using
1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2039	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2040	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2060	C<path>. The C<interval> is a hint on how quickly a change is expected to
1796	be detected and should normally be specified as C<0> to let libev choose	2061	be detected and should normally be specified as C<0> to let libev choose
1797	a suitable value. The memory pointed to by C<path> must point to the same	2062	a suitable value. The memory pointed to by C<path> must point to the same
1798	path for as long as the watcher is active.	2063	path for as long as the watcher is active.
1799		2064
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2065	The callback will receive an C<EV_STAT> event when a change was detected,
1801	to the attributes at the time the watcher was started (or the last change	2066	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2067	last change was detected).
1803		2068
1804	=item ev_stat_stat (loop, ev_stat *)	2069	=item ev_stat_stat (loop, ev_stat *)
1805		2070
1806	Updates the stat buffer immediately with new values. If you change the	2071	Updates the stat buffer immediately with new values. If you change the
1807	watched path in your callback, you could call this function to avoid	2072	watched path in your callback, you could call this function to avoid
…		…
1890		2155
1891		2156
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2157	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2158
1894	Idle watchers trigger events when no other events of the same or higher	2159	Idle watchers trigger events when no other events of the same or higher
1895	priority are pending (prepare, check and other idle watchers do not	2160	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2161	as receiving "events").
1897		2162
1898	That is, as long as your process is busy handling sockets or timeouts	2163	That is, as long as your process is busy handling sockets or timeouts
1899	(or even signals, imagine) of the same or higher priority it will not be	2164	(or even signals, imagine) of the same or higher priority it will not be
1900	triggered. But when your process is idle (or only lower-priority watchers	2165	triggered. But when your process is idle (or only lower-priority watchers
1901	are pending), the idle watchers are being called once per event loop	2166	are pending), the idle watchers are being called once per event loop
…		…
1926		2191
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2192	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2193	callback, free it. Also, use no error checking, as usual.
1929		2194
1930	static void	2195	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2196	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2197	{
1933	free (w);	2198	free (w);
1934	// now do something you wanted to do when the program has	2199	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2200	// no longer anything immediate to do.
1936	}	2201	}
1937		2202
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2203	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2204	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2205	ev_idle_start (loop, idle_cb);
1941		2206
1942		2207
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2208	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2209
1945	Prepare and check watchers are usually (but not always) used in tandem:	2210	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2211	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2212	afterwards.
1948		2213
1949	You I<must not> call C<ev_loop> or similar functions that enter	2214	You I<must not> call C<ev_loop> or similar functions that enter
1950	the current event loop from either C<ev_prepare> or C<ev_check>	2215	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1953	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2218	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1954	C<ev_check> so if you have one watcher of each kind they will always be	2219	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2220	called in pairs bracketing the blocking call.
1956		2221
1957	Their main purpose is to integrate other event mechanisms into libev and	2222	Their main purpose is to integrate other event mechanisms into libev and
1958	their use is somewhat advanced. This could be used, for example, to track	2223	their use is somewhat advanced. They could be used, for example, to track
1959	variable changes, implement your own watchers, integrate net-snmp or a	2224	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2225	coroutine library and lots more. They are also occasionally useful if
1961	you cache some data and want to flush it before blocking (for example,	2226	you cache some data and want to flush it before blocking (for example,
1962	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2227	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2228	watcher).
1964		2229
1965	This is done by examining in each prepare call which file descriptors need	2230	This is done by examining in each prepare call which file descriptors
1966	to be watched by the other library, registering C<ev_io> watchers for	2231	need to be watched by the other library, registering C<ev_io> watchers
1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2232	for them and starting an C<ev_timer> watcher for any timeouts (many
1968	provide just this functionality). Then, in the check watcher you check for	2233	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2234	you check for any events that occurred (by checking the pending status
1970	and stopping them) and call back into the library. The I/O and timer	2235	of all watchers and stopping them) and call back into the library. The
1971	callbacks will never actually be called (but must be valid nevertheless,	2236	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2237	nevertheless, because you never know, you know?).
1973		2238
1974	As another example, the Perl Coro module uses these hooks to integrate	2239	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2240	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2241	during each prepare and only letting the process block if no coroutines
1977	are ready to run (it's actually more complicated: it only runs coroutines	2242	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1980	loop from blocking if lower-priority coroutines are active, thus mapping	2245	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2246	low-priority coroutines to idle/background tasks).
1982		2247
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2248	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1984	priority, to ensure that they are being run before any other watchers	2249	priority, to ensure that they are being run before any other watchers
		2250	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2251
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2252	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1986	too) should not activate ("feed") events into libev. While libev fully	2253	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2254	might get executed before other C<ev_check> watchers did their job. As
1988	did their job. As C<ev_check> watchers are often used to embed other	2255	C<ev_check> watchers are often used to embed other (non-libev) event
1989	(non-libev) event loops those other event loops might be in an unusable	2256	loops those other event loops might be in an unusable state until their
1990	state until their C<ev_check> watcher ran (always remind yourself to	2257	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2258	others).
1992		2259
1993	=head3 Watcher-Specific Functions and Data Members	2260	=head3 Watcher-Specific Functions and Data Members
1994		2261
1995	=over 4	2262	=over 4
1996		2263
…		…
1998		2265
1999	=item ev_check_init (ev_check *, callback)	2266	=item ev_check_init (ev_check *, callback)
2000		2267
2001	Initialises and configures the prepare or check watcher - they have no	2268	Initialises and configures the prepare or check watcher - they have no
2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2269	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
2003	macros, but using them is utterly, utterly and completely pointless.	2270	macros, but using them is utterly, utterly, utterly and completely
		2271	pointless.
2004		2272
2005	=back	2273	=back
2006		2274
2007	=head3 Examples	2275	=head3 Examples
2008		2276
…		…
2021		2289
2022	static ev_io iow [nfd];	2290	static ev_io iow [nfd];
2023	static ev_timer tw;	2291	static ev_timer tw;
2024		2292
2025	static void	2293	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2294	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2295	{
2028	}	2296	}
2029		2297
2030	// create io watchers for each fd and a timer before blocking	2298	// create io watchers for each fd and a timer before blocking
2031	static void	2299	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2300	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2301	{
2034	int timeout = 3600000;	2302	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2303	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2304	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2305	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2052	}	2320	}
2053	}	2321	}
2054		2322
2055	// stop all watchers after blocking	2323	// stop all watchers after blocking
2056	static void	2324	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2325	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2326	{
2059	ev_timer_stop (loop, &tw);	2327	ev_timer_stop (loop, &tw);
2060		2328
2061	for (int i = 0; i < nfd; ++i)	2329	for (int i = 0; i < nfd; ++i)
2062	{	2330	{
…		…
2101	}	2369	}
2102		2370
2103	// do not ever call adns_afterpoll	2371	// do not ever call adns_afterpoll
2104		2372
2105	Method 4: Do not use a prepare or check watcher because the module you	2373	Method 4: Do not use a prepare or check watcher because the module you
2106	want to embed is too inflexible to support it. Instead, you can override	2374	want to embed is not flexible enough to support it. Instead, you can
2107	their poll function. The drawback with this solution is that the main	2375	override their poll function. The drawback with this solution is that the
2108	loop is now no longer controllable by EV. The C<Glib::EV> module does	2376	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2377	this approach, effectively embedding EV as a client into the horrible
		2378	libglib event loop.
2110		2379
2111	static gint	2380	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2381	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2382	{
2114	int got_events = 0;	2383	int got_events = 0;
…		…
2145	prioritise I/O.	2414	prioritise I/O.
2146		2415
2147	As an example for a bug workaround, the kqueue backend might only support	2416	As an example for a bug workaround, the kqueue backend might only support
2148	sockets on some platform, so it is unusable as generic backend, but you	2417	sockets on some platform, so it is unusable as generic backend, but you
2149	still want to make use of it because you have many sockets and it scales	2418	still want to make use of it because you have many sockets and it scales
2150	so nicely. In this case, you would create a kqueue-based loop and embed it	2419	so nicely. In this case, you would create a kqueue-based loop and embed
2151	into your default loop (which might use e.g. poll). Overall operation will	2420	it into your default loop (which might use e.g. poll). Overall operation
2152	be a bit slower because first libev has to poll and then call kevent, but	2421	will be a bit slower because first libev has to call C<poll> and then
2153	at least you can use both at what they are best.	2422	C<kevent>, but at least you can use both mechanisms for what they are
		2423	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2424
2155	As for prioritising I/O: rarely you have the case where some fds have	2425	As for prioritising I/O: under rare circumstances you have the case where
2156	to be watched and handled very quickly (with low latency), and even	2426	some fds have to be watched and handled very quickly (with low latency),
2157	priorities and idle watchers might have too much overhead. In this case	2427	and even priorities and idle watchers might have too much overhead. In
2158	you would put all the high priority stuff in one loop and all the rest in	2428	this case you would put all the high priority stuff in one loop and all
2159	a second one, and embed the second one in the first.	2429	the rest in a second one, and embed the second one in the first.
2160		2430
2161	As long as the watcher is active, the callback will be invoked every time	2431	As long as the watcher is active, the callback will be invoked every time
2162	there might be events pending in the embedded loop. The callback must then	2432	there might be events pending in the embedded loop. The callback must then
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2433	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2164	their callbacks (you could also start an idle watcher to give the embedded	2434	their callbacks (you could also start an idle watcher to give the embedded
…		…
2172	interested in that.	2442	interested in that.
2173		2443
2174	Also, there have not currently been made special provisions for forking:	2444	Also, there have not currently been made special provisions for forking:
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2445	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2176	but you will also have to stop and restart any C<ev_embed> watchers	2446	but you will also have to stop and restart any C<ev_embed> watchers
2177	yourself.	2447	yourself - but you can use a fork watcher to handle this automatically,
		2448	and future versions of libev might do just that.
2178		2449
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2450	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2451	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2452	portable one.
2182		2453
2183	So when you want to use this feature you will always have to be prepared	2454	So when you want to use this feature you will always have to be prepared
2184	that you cannot get an embeddable loop. The recommended way to get around	2455	that you cannot get an embeddable loop. The recommended way to get around
2185	this is to have a separate variables for your embeddable loop, try to	2456	this is to have a separate variables for your embeddable loop, try to
2186	create it, and if that fails, use the normal loop for everything.	2457	create it, and if that fails, use the normal loop for everything.
		2458
		2459	=head3 C<ev_embed> and fork
		2460
		2461	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2462	automatically be applied to the embedded loop as well, so no special
		2463	fork handling is required in that case. When the watcher is not running,
		2464	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2465	as applicable.
2187		2466
2188	=head3 Watcher-Specific Functions and Data Members	2467	=head3 Watcher-Specific Functions and Data Members
2189		2468
2190	=over 4	2469	=over 4
2191		2470
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2498	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2499	used).
2221		2500
2222	struct ev_loop *loop_hi = ev_default_init (0);	2501	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2502	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2503	ev_embed embed;
2225		2504
2226	// see if there is a chance of getting one that works	2505	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2506	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2507	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2508	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2522	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2523	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2524
2246	struct ev_loop *loop = ev_default_init (0);	2525	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2526	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2527	ev_embed embed;
2249		2528
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2529	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2530	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2531	{
2253	ev_embed_init (&embed, 0, loop_socket);	2532	ev_embed_init (&embed, 0, loop_socket);
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2588	is that the author does not know of a simple (or any) algorithm for a
2310	multiple-writer-single-reader queue that works in all cases and doesn't	2589	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2590	need elaborate support such as pthreads.
2312		2591
2313	That means that if you want to queue data, you have to provide your own	2592	That means that if you want to queue data, you have to provide your own
2314	queue. But at least I can tell you would implement locking around your	2593	queue. But at least I can tell you how to implement locking around your
2315	queue:	2594	queue:
2316		2595
2317	=over 4	2596	=over 4
2318		2597
2319	=item queueing from a signal handler context	2598	=item queueing from a signal handler context
2320		2599
2321	To implement race-free queueing, you simply add to the queue in the signal	2600	To implement race-free queueing, you simply add to the queue in the signal
2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2601	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2602	an example that does that for some fictitious SIGUSR1 handler:
2324		2603
2325	static ev_async mysig;	2604	static ev_async mysig;
2326		2605
2327	static void	2606	static void
2328	sigusr1_handler (void)	2607	sigusr1_handler (void)
…		…
2394	=over 4	2673	=over 4
2395		2674
2396	=item ev_async_init (ev_async *, callback)	2675	=item ev_async_init (ev_async *, callback)
2397		2676
2398	Initialises and configures the async watcher - it has no parameters of any	2677	Initialises and configures the async watcher - it has no parameters of any
2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2678	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	2679	trust me.
2401		2680
2402	=item ev_async_send (loop, ev_async *)	2681	=item ev_async_send (loop, ev_async *)
2403		2682
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2683	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2684	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2406	C<ev_feed_event>, this call is safe to do in other threads, signal or	2685	C<ev_feed_event>, this call is safe to do from other threads, signal or
2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2686	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	2687	section below on what exactly this means).
2409		2688
2410	This call incurs the overhead of a system call only once per loop iteration,	2689	This call incurs the overhead of a system call only once per loop iteration,
2411	so while the overhead might be noticeable, it doesn't apply to repeated	2690	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2435	=over 4	2714	=over 4
2436		2715
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2716	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		2717
2439	This function combines a simple timer and an I/O watcher, calls your	2718	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	2719	callback on whichever event happens first and automatically stops both
2441	watchers. This is useful if you want to wait for a single event on an fd	2720	watchers. This is useful if you want to wait for a single event on an fd
2442	or timeout without having to allocate/configure/start/stop/free one or	2721	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	2722	more watchers yourself.
2444		2723
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	2724	If C<fd> is less than 0, then no I/O watcher will be started and the
2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2725	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	2726	the given C<fd> and C<events> set will be created and started.
2448		2727
2449	If C<timeout> is less than 0, then no timeout watcher will be	2728	If C<timeout> is less than 0, then no timeout watcher will be
2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2729	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2730	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		2731
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2732	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2455	passed an C<revents> set like normal event callbacks (a combination of	2733	passed an C<revents> set like normal event callbacks (a combination of
2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2734	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	2735	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2736	a timeout and an io event at the same time - you probably should give io
		2737	events precedence.
		2738
		2739	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		2740
2459	static void stdin_ready (int revents, void *arg)	2741	static void stdin_ready (int revents, void *arg)
2460	{	2742	{
		2743	if (revents & EV_READ)
		2744	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	2745	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	2746	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	2747	}
2466		2748
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2749	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		2750
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)	2751	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2470		2752
2471	Feeds the given event set into the event loop, as if the specified event	2753	Feeds the given event set into the event loop, as if the specified event
2472	had happened for the specified watcher (which must be a pointer to an	2754	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).	2755	initialised but not necessarily started event watcher).
2474		2756
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2757	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		2758
2477	Feed an event on the given fd, as if a file descriptor backend detected	2759	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	2760	the given events it.
2479		2761
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	2762	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		2763
2482	Feed an event as if the given signal occurred (C<loop> must be the default	2764	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	2765	loop!).
2484		2766
2485	=back	2767	=back
…		…
2617		2899
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2900	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		2901
2620	See the method-C<set> above for more details.	2902	See the method-C<set> above for more details.
2621		2903
2622	Example:	2904	Example: Use a plain function as callback.
2623		2905
2624	static void io_cb (ev::io &w, int revents) { }	2906	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	2907	iow.set <io_cb> ();
2626		2908
2627	=item w->set (struct ev_loop *)	2909	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	2947	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	2948	the constructor.
2667		2949
2668	class myclass	2950	class myclass
2669	{	2951	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	2952	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	2953	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		2954
2673	myclass (int fd)	2955	myclass (int fd)
2674	{	2956	{
2675	io .set <myclass, &myclass::io_cb > (this);	2957	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	2958	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	2974	=item Perl
2693		2975
2694	The EV module implements the full libev API and is actually used to test	2976	The EV module implements the full libev API and is actually used to test
2695	libev. EV is developed together with libev. Apart from the EV core module,	2977	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	2978	there are additional modules that implement libev-compatible interfaces
2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2979	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2980	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2981	and C<EV::Glib>).
2699		2982
2700	It can be found and installed via CPAN, its homepage is at	2983	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	2984	L<http://software.schmorp.de/pkg/EV>.
2702		2985
2703	=item Python	2986	=item Python
…		…
2719	=item D	3002	=item D
2720		3003
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3004	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3005	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2723		3006
		3007	=item Ocaml
		3008
		3009	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3010	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3011
2724	=back	3012	=back
2725		3013
2726		3014
2727	=head1 MACRO MAGIC	3015	=head1 MACRO MAGIC
2728		3016
…		…
2828		3116
2829	#define EV_STANDALONE 1	3117	#define EV_STANDALONE 1
2830	#include "ev.h"	3118	#include "ev.h"
2831		3119
2832	Both header files and implementation files can be compiled with a C++	3120	Both header files and implementation files can be compiled with a C++
2833	compiler (at least, thats a stated goal, and breakage will be treated	3121	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3122	as a bug).
2835		3123
2836	You need the following files in your source tree, or in a directory	3124	You need the following files in your source tree, or in a directory
2837	in your include path (e.g. in libev/ when using -Ilibev):	3125	in your include path (e.g. in libev/ when using -Ilibev):
2838		3126
…		…
2882		3170
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3171	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3172
2885	Libev can be configured via a variety of preprocessor symbols you have to	3173	Libev can be configured via a variety of preprocessor symbols you have to
2886	define before including any of its files. The default in the absence of	3174	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3175	autoconf is documented for every option.
2888		3176
2889	=over 4	3177	=over 4
2890		3178
2891	=item EV_STANDALONE	3179	=item EV_STANDALONE
2892		3180
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3350	When doing priority-based operations, libev usually has to linearly search
3063	all the priorities, so having many of them (hundreds) uses a lot of space	3351	all the priorities, so having many of them (hundreds) uses a lot of space
3064	and time, so using the defaults of five priorities (-2 .. +2) is usually	3352	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3353	fine.
3066		3354
3067	If your embedding application does not need any priorities, defining these both to	3355	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3356	both to C<0> will save some memory and CPU.
3069		3357
3070	=item EV_PERIODIC_ENABLE	3358	=item EV_PERIODIC_ENABLE
3071		3359
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3360	If undefined or defined to be C<1>, then periodic timers are supported. If
3073	defined to be C<0>, then they are not. Disabling them saves a few kB of	3361	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3368	code.
3081		3369
3082	=item EV_EMBED_ENABLE	3370	=item EV_EMBED_ENABLE
3083		3371
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3372	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3373	defined to be C<0>, then they are not. Embed watchers rely on most other
		3374	watcher types, which therefore must not be disabled.
3086		3375
3087	=item EV_STAT_ENABLE	3376	=item EV_STAT_ENABLE
3088		3377
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3378	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3379	defined to be C<0>, then they are not.
…		…
3122	two).	3411	two).
3123		3412
3124	=item EV_USE_4HEAP	3413	=item EV_USE_4HEAP
3125		3414
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3415	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3416	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3128	to C<1>. The 4-heap uses more complicated (longer) code but has	3417	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3418	faster performance with many (thousands) of watchers.
3130		3419
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3420	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3132	(disabled).	3421	(disabled).
3133		3422
3134	=item EV_HEAP_CACHE_AT	3423	=item EV_HEAP_CACHE_AT
3135		3424
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3425	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3137	timer and periodics heap, libev can cache the timestamp (I<at>) within	3426	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3427	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3428	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3140	but avoids random read accesses on heap changes. This improves performance	3429	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3430	noticeably with many (hundreds) of watchers.
3142		3431
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3432	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3433	(disabled).
3145		3434
3146	=item EV_VERIFY	3435	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3441	called once per loop, which can slow down libev. If set to C<3>, then the
3153	verification code will be called very frequently, which will slow down	3442	verification code will be called very frequently, which will slow down
3154	libev considerably.	3443	libev considerably.
3155		3444
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3445	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3446	C<0>.
3158		3447
3159	=item EV_COMMON	3448	=item EV_COMMON
3160		3449
3161	By default, all watchers have a C<void *data> member. By redefining	3450	By default, all watchers have a C<void *data> member. By redefining
3162	this macro to a something else you can include more and other types of	3451	this macro to a something else you can include more and other types of
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	3468	and the way callbacks are invoked and set. Must expand to a struct member
3180	definition and a statement, respectively. See the F<ev.h> header file for	3469	definition and a statement, respectively. See the F<ev.h> header file for
3181	their default definitions. One possible use for overriding these is to	3470	their default definitions. One possible use for overriding these is to
3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3471	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3183	method calls instead of plain function calls in C++.	3472	method calls instead of plain function calls in C++.
		3473
		3474	=back
3184		3475
3185	=head2 EXPORTED API SYMBOLS	3476	=head2 EXPORTED API SYMBOLS
3186		3477
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3478	If you need to re-export the API (e.g. via a DLL) and you need a list of
3188	exported symbols, you can use the provided F<Symbol.*> files which list	3479	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3526	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		3527
3237	#include "ev_cpp.h"	3528	#include "ev_cpp.h"
3238	#include "ev.c"	3529	#include "ev.c"
3239		3530
		3531	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		3532
3241	=head1 THREADS AND COROUTINES	3533	=head2 THREADS AND COROUTINES
3242		3534
3243	=head2 THREADS	3535	=head3 THREADS
3244		3536
3245	Libev itself is completely thread-safe, but it uses no locking. This	3537	All libev functions are reentrant and thread-safe unless explicitly
		3538	documented otherwise, but libev implements no locking itself. This means
3246	means that you can use as many loops as you want in parallel, as long as	3539	that you can use as many loops as you want in parallel, as long as there
3247	only one thread ever calls into one libev function with the same loop	3540	are no concurrent calls into any libev function with the same loop
3248	parameter.	3541	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3542	of course): libev guarantees that different event loops share no data
		3543	structures that need any locking.
3249		3544
3250	Or put differently: calls with different loop parameters can be done in	3545	Or to put it differently: calls with different loop parameters can be done
3251	parallel from multiple threads, calls with the same loop parameter must be	3546	concurrently from multiple threads, calls with the same loop parameter
3252	done serially (but can be done from different threads, as long as only one	3547	must be done serially (but can be done from different threads, as long as
3253	thread ever is inside a call at any point in time, e.g. by using a mutex	3548	only one thread ever is inside a call at any point in time, e.g. by using
3254	per loop).	3549	a mutex per loop).
		3550
		3551	Specifically to support threads (and signal handlers), libev implements
		3552	so-called C<ev_async> watchers, which allow some limited form of
		3553	concurrency on the same event loop, namely waking it up "from the
		3554	outside".
3255		3555
3256	If you want to know which design (one loop, locking, or multiple loops	3556	If you want to know which design (one loop, locking, or multiple loops
3257	without or something else still) is best for your problem, then I cannot	3557	without or something else still) is best for your problem, then I cannot
3258	help you. I can give some generic advice however:	3558	help you, but here is some generic advice:
3259		3559
3260	=over 4	3560	=over 4
3261		3561
3262	=item * most applications have a main thread: use the default libev loop	3562	=item * most applications have a main thread: use the default libev loop
3263	in that thread, or create a separate thread running only the default loop.	3563	in that thread, or create a separate thread running only the default loop.
…		…
3275		3575
3276	Choosing a model is hard - look around, learn, know that usually you can do	3576	Choosing a model is hard - look around, learn, know that usually you can do
3277	better than you currently do :-)	3577	better than you currently do :-)
3278		3578
3279	=item * often you need to talk to some other thread which blocks in the	3579	=item * often you need to talk to some other thread which blocks in the
		3580	event loop.
		3581
3280	event loop - C<ev_async> watchers can be used to wake them up from other	3582	C<ev_async> watchers can be used to wake them up from other threads safely
3281	threads safely (or from signal contexts...).	3583	(or from signal contexts...).
		3584
		3585	An example use would be to communicate signals or other events that only
		3586	work in the default loop by registering the signal watcher with the
		3587	default loop and triggering an C<ev_async> watcher from the default loop
		3588	watcher callback into the event loop interested in the signal.
3282		3589
3283	=back	3590	=back
3284		3591
3285	=head2 COROUTINES	3592	=head3 COROUTINES
3286		3593
3287	Libev is much more accommodating to coroutines ("cooperative threads"):	3594	Libev is very accommodating to coroutines ("cooperative threads"):
3288	libev fully supports nesting calls to it's functions from different	3595	libev fully supports nesting calls to its functions from different
3289	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3596	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3290	different coroutines and switch freely between both coroutines running the	3597	different coroutines, and switch freely between both coroutines running the
3291	loop, as long as you don't confuse yourself). The only exception is that	3598	loop, as long as you don't confuse yourself). The only exception is that
3292	you must not do this from C<ev_periodic> reschedule callbacks.	3599	you must not do this from C<ev_periodic> reschedule callbacks.
3293		3600
3294	Care has been invested into making sure that libev does not keep local	3601	Care has been taken to ensure that libev does not keep local state inside
3295	state inside C<ev_loop>, and other calls do not usually allow coroutine	3602	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3296	switches.	3603	they do not call any callbacks.
3297		3604
		3605	=head2 COMPILER WARNINGS
3298		3606
3299	=head1 COMPLEXITIES	3607	Depending on your compiler and compiler settings, you might get no or a
		3608	lot of warnings when compiling libev code. Some people are apparently
		3609	scared by this.
3300		3610
3301	In this section the complexities of (many of) the algorithms used inside	3611	However, these are unavoidable for many reasons. For one, each compiler
3302	libev will be explained. For complexity discussions about backends see the	3612	has different warnings, and each user has different tastes regarding
3303	documentation for C<ev_default_init>.	3613	warning options. "Warn-free" code therefore cannot be a goal except when
		3614	targeting a specific compiler and compiler-version.
3304		3615
3305	All of the following are about amortised time: If an array needs to be	3616	Another reason is that some compiler warnings require elaborate
3306	extended, libev needs to realloc and move the whole array, but this	3617	workarounds, or other changes to the code that make it less clear and less
3307	happens asymptotically never with higher number of elements, so O(1) might	3618	maintainable.
3308	mean it might do a lengthy realloc operation in rare cases, but on average
3309	it is much faster and asymptotically approaches constant time.
3310		3619
3311	=over 4	3620	And of course, some compiler warnings are just plain stupid, or simply
		3621	wrong (because they don't actually warn about the condition their message
		3622	seems to warn about). For example, certain older gcc versions had some
		3623	warnings that resulted an extreme number of false positives. These have
		3624	been fixed, but some people still insist on making code warn-free with
		3625	such buggy versions.
3312		3626
3313	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3627	While libev is written to generate as few warnings as possible,
		3628	"warn-free" code is not a goal, and it is recommended not to build libev
		3629	with any compiler warnings enabled unless you are prepared to cope with
		3630	them (e.g. by ignoring them). Remember that warnings are just that:
		3631	warnings, not errors, or proof of bugs.
3314		3632
3315	This means that, when you have a watcher that triggers in one hour and
3316	there are 100 watchers that would trigger before that then inserting will
3317	have to skip roughly seven (C<ld 100>) of these watchers.
3318		3633
3319	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3634	=head2 VALGRIND
3320		3635
3321	That means that changing a timer costs less than removing/adding them	3636	Valgrind has a special section here because it is a popular tool that is
3322	as only the relative motion in the event queue has to be paid for.	3637	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3323		3638
3324	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3639	If you think you found a bug (memory leak, uninitialised data access etc.)
		3640	in libev, then check twice: If valgrind reports something like:
3325		3641
3326	These just add the watcher into an array or at the head of a list.	3642	==2274== definitely lost: 0 bytes in 0 blocks.
		3643	==2274== possibly lost: 0 bytes in 0 blocks.
		3644	==2274== still reachable: 256 bytes in 1 blocks.
3327		3645
3328	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3646	Then there is no memory leak, just as memory accounted to global variables
		3647	is not a memleak - the memory is still being referenced, and didn't leak.
3329		3648
3330	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3649	Similarly, under some circumstances, valgrind might report kernel bugs
		3650	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3651	although an acceptable workaround has been found here), or it might be
		3652	confused.
3331		3653
3332	These watchers are stored in lists then need to be walked to find the	3654	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3333	correct watcher to remove. The lists are usually short (you don't usually	3655	make it into some kind of religion.
3334	have many watchers waiting for the same fd or signal).
3335		3656
3336	=item Finding the next timer in each loop iteration: O(1)	3657	If you are unsure about something, feel free to contact the mailing list
		3658	with the full valgrind report and an explanation on why you think this
		3659	is a bug in libev (best check the archives, too :). However, don't be
		3660	annoyed when you get a brisk "this is no bug" answer and take the chance
		3661	of learning how to interpret valgrind properly.
3337		3662
3338	By virtue of using a binary or 4-heap, the next timer is always found at a	3663	If you need, for some reason, empty reports from valgrind for your project
3339	fixed position in the storage array.	3664	I suggest using suppression lists.
3340		3665
3341	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3342		3666
3343	A change means an I/O watcher gets started or stopped, which requires	3667	=head1 PORTABILITY NOTES
3344	libev to recalculate its status (and possibly tell the kernel, depending
3345	on backend and whether C<ev_io_set> was used).
3346		3668
3347	=item Activating one watcher (putting it into the pending state): O(1)
3348
3349	=item Priority handling: O(number_of_priorities)
3350
3351	Priorities are implemented by allocating some space for each
3352	priority. When doing priority-based operations, libev usually has to
3353	linearly search all the priorities, but starting/stopping and activating
3354	watchers becomes O(1) w.r.t. priority handling.
3355
3356	=item Sending an ev_async: O(1)
3357
3358	=item Processing ev_async_send: O(number_of_async_watchers)
3359
3360	=item Processing signals: O(max_signal_number)
3361
3362	Sending involves a system call I<iff> there were no other C<ev_async_send>
3363	calls in the current loop iteration. Checking for async and signal events
3364	involves iterating over all running async watchers or all signal numbers.
3365
3366	=back
3367
3368
3369	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3669	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3370		3670
3371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3671	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3372	requires, and its I/O model is fundamentally incompatible with the POSIX	3672	requires, and its I/O model is fundamentally incompatible with the POSIX
3373	model. Libev still offers limited functionality on this platform in	3673	model. Libev still offers limited functionality on this platform in
3374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3674	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3385		3685
3386	Not a libev limitation but worth mentioning: windows apparently doesn't	3686	Not a libev limitation but worth mentioning: windows apparently doesn't
3387	accept large writes: instead of resulting in a partial write, windows will	3687	accept large writes: instead of resulting in a partial write, windows will
3388	either accept everything or return C<ENOBUFS> if the buffer is too large,	3688	either accept everything or return C<ENOBUFS> if the buffer is too large,
3389	so make sure you only write small amounts into your sockets (less than a	3689	so make sure you only write small amounts into your sockets (less than a
3390	megabyte seems safe, but thsi apparently depends on the amount of memory	3690	megabyte seems safe, but this apparently depends on the amount of memory
3391	available).	3691	available).
3392		3692
3393	Due to the many, low, and arbitrary limits on the win32 platform and	3693	Due to the many, low, and arbitrary limits on the win32 platform and
3394	the abysmal performance of winsockets, using a large number of sockets	3694	the abysmal performance of winsockets, using a large number of sockets
3395	is not recommended (and not reasonable). If your program needs to use	3695	is not recommended (and not reasonable). If your program needs to use
…		…
3406	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3706	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3407		3707
3408	#include "ev.h"	3708	#include "ev.h"
3409		3709
3410	And compile the following F<evwrap.c> file into your project (make sure	3710	And compile the following F<evwrap.c> file into your project (make sure
3411	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3711	you do I<not> compile the F<ev.c> or any other embedded source files!):
3412		3712
3413	#include "evwrap.h"	3713	#include "evwrap.h"
3414	#include "ev.c"	3714	#include "ev.c"
3415		3715
3416	=over 4	3716	=over 4
…		…
3461	wrap all I/O functions and provide your own fd management, but the cost of	3761	wrap all I/O functions and provide your own fd management, but the cost of
3462	calling select (O(n²)) will likely make this unworkable.	3762	calling select (O(n²)) will likely make this unworkable.
3463		3763
3464	=back	3764	=back
3465		3765
3466
3467	=head1 PORTABILITY REQUIREMENTS	3766	=head2 PORTABILITY REQUIREMENTS
3468		3767
3469	In addition to a working ISO-C implementation, libev relies on a few	3768	In addition to a working ISO-C implementation and of course the
3470	additional extensions:	3769	backend-specific APIs, libev relies on a few additional extensions:
3471		3770
3472	=over 4	3771	=over 4
3473		3772
3474	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3773	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3475	calling conventions regardless of C<ev_watcher_type *>.	3774	calling conventions regardless of C<ev_watcher_type *>.
…		…
3481	calls them using an C<ev_watcher *> internally.	3780	calls them using an C<ev_watcher *> internally.
3482		3781
3483	=item C<sig_atomic_t volatile> must be thread-atomic as well	3782	=item C<sig_atomic_t volatile> must be thread-atomic as well
3484		3783
3485	The type C<sig_atomic_t volatile> (or whatever is defined as	3784	The type C<sig_atomic_t volatile> (or whatever is defined as
3486	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3785	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3487	threads. This is not part of the specification for C<sig_atomic_t>, but is	3786	threads. This is not part of the specification for C<sig_atomic_t>, but is
3488	believed to be sufficiently portable.	3787	believed to be sufficiently portable.
3489		3788
3490	=item C<sigprocmask> must work in a threaded environment	3789	=item C<sigprocmask> must work in a threaded environment
3491		3790
…		…
3500	except the initial one, and run the default loop in the initial thread as	3799	except the initial one, and run the default loop in the initial thread as
3501	well.	3800	well.
3502		3801
3503	=item C<long> must be large enough for common memory allocation sizes	3802	=item C<long> must be large enough for common memory allocation sizes
3504		3803
3505	To improve portability and simplify using libev, libev uses C<long>	3804	To improve portability and simplify its API, libev uses C<long> internally
3506	internally instead of C<size_t> when allocating its data structures. On	3805	instead of C<size_t> when allocating its data structures. On non-POSIX
3507	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3806	systems (Microsoft...) this might be unexpectedly low, but is still at
3508	is still at least 31 bits everywhere, which is enough for hundreds of	3807	least 31 bits everywhere, which is enough for hundreds of millions of
3509	millions of watchers.	3808	watchers.
3510		3809
3511	=item C<double> must hold a time value in seconds with enough accuracy	3810	=item C<double> must hold a time value in seconds with enough accuracy
3512		3811
3513	The type C<double> is used to represent timestamps. It is required to	3812	The type C<double> is used to represent timestamps. It is required to
3514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3813	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3518	=back	3817	=back
3519		3818
3520	If you know of other additional requirements drop me a note.	3819	If you know of other additional requirements drop me a note.
3521		3820
3522		3821
3523	=head1 COMPILER WARNINGS	3822	=head1 ALGORITHMIC COMPLEXITIES
3524		3823
3525	Depending on your compiler and compiler settings, you might get no or a	3824	In this section the complexities of (many of) the algorithms used inside
3526	lot of warnings when compiling libev code. Some people are apparently	3825	libev will be documented. For complexity discussions about backends see
3527	scared by this.	3826	the documentation for C<ev_default_init>.
3528		3827
3529	However, these are unavoidable for many reasons. For one, each compiler	3828	All of the following are about amortised time: If an array needs to be
3530	has different warnings, and each user has different tastes regarding	3829	extended, libev needs to realloc and move the whole array, but this
3531	warning options. "Warn-free" code therefore cannot be a goal except when	3830	happens asymptotically rarer with higher number of elements, so O(1) might
3532	targeting a specific compiler and compiler-version.	3831	mean that libev does a lengthy realloc operation in rare cases, but on
		3832	average it is much faster and asymptotically approaches constant time.
3533		3833
3534	Another reason is that some compiler warnings require elaborate	3834	=over 4
3535	workarounds, or other changes to the code that make it less clear and less
3536	maintainable.
3537		3835
3538	And of course, some compiler warnings are just plain stupid, or simply	3836	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3539	wrong (because they don't actually warn about the condition their message
3540	seems to warn about).
3541		3837
3542	While libev is written to generate as few warnings as possible,	3838	This means that, when you have a watcher that triggers in one hour and
3543	"warn-free" code is not a goal, and it is recommended not to build libev	3839	there are 100 watchers that would trigger before that, then inserting will
3544	with any compiler warnings enabled unless you are prepared to cope with	3840	have to skip roughly seven (C<ld 100>) of these watchers.
3545	them (e.g. by ignoring them). Remember that warnings are just that:
3546	warnings, not errors, or proof of bugs.
3547		3841
		3842	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3548		3843
3549	=head1 VALGRIND	3844	That means that changing a timer costs less than removing/adding them,
		3845	as only the relative motion in the event queue has to be paid for.
3550		3846
3551	Valgrind has a special section here because it is a popular tool that is	3847	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3552	highly useful, but valgrind reports are very hard to interpret.
3553		3848
3554	If you think you found a bug (memory leak, uninitialised data access etc.)	3849	These just add the watcher into an array or at the head of a list.
3555	in libev, then check twice: If valgrind reports something like:
3556		3850
3557	==2274== definitely lost: 0 bytes in 0 blocks.	3851	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3558	==2274== possibly lost: 0 bytes in 0 blocks.
3559	==2274== still reachable: 256 bytes in 1 blocks.
3560		3852
3561	Then there is no memory leak. Similarly, under some circumstances,	3853	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3562	valgrind might report kernel bugs as if it were a bug in libev, or it
3563	might be confused (it is a very good tool, but only a tool).
3564		3854
3565	If you are unsure about something, feel free to contact the mailing list	3855	These watchers are stored in lists, so they need to be walked to find the
3566	with the full valgrind report and an explanation on why you think this is	3856	correct watcher to remove. The lists are usually short (you don't usually
3567	a bug in libev. However, don't be annoyed when you get a brisk "this is	3857	have many watchers waiting for the same fd or signal: one is typical, two
3568	no bug" answer and take the chance of learning how to interpret valgrind	3858	is rare).
3569	properly.
3570		3859
3571	If you need, for some reason, empty reports from valgrind for your project	3860	=item Finding the next timer in each loop iteration: O(1)
3572	I suggest using suppression lists.	3861
		3862	By virtue of using a binary or 4-heap, the next timer is always found at a
		3863	fixed position in the storage array.
		3864
		3865	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3866
		3867	A change means an I/O watcher gets started or stopped, which requires
		3868	libev to recalculate its status (and possibly tell the kernel, depending
		3869	on backend and whether C<ev_io_set> was used).
		3870
		3871	=item Activating one watcher (putting it into the pending state): O(1)
		3872
		3873	=item Priority handling: O(number_of_priorities)
		3874
		3875	Priorities are implemented by allocating some space for each
		3876	priority. When doing priority-based operations, libev usually has to
		3877	linearly search all the priorities, but starting/stopping and activating
		3878	watchers becomes O(1) with respect to priority handling.
		3879
		3880	=item Sending an ev_async: O(1)
		3881
		3882	=item Processing ev_async_send: O(number_of_async_watchers)
		3883
		3884	=item Processing signals: O(max_signal_number)
		3885
		3886	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3887	calls in the current loop iteration. Checking for async and signal events
		3888	involves iterating over all running async watchers or all signal numbers.
		3889
		3890	=back
3573		3891
3574		3892
3575	=head1 AUTHOR	3893	=head1 AUTHOR
3576		3894
3577	Marc Lehmann <libev@schmorp.de>.	3895	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3578		3896

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