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Revision 1.161 by root, Sat May 24 03:08:03 2008 UTC vs.
Revision 1.202 by root, Fri Oct 24 08:30:01 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ 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);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
…		…
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
…		…
178	not a problem.	178	not a problem.
179		179
180	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	181	version.
182		182
183	assert (("libev version mismatch",	183	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
186		186
187	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
188		188
189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
190	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
192	a description of the set values.	192	a description of the set values.
193		193
194	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
195	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
196		196
197	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
199		199
200	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
201		201
202	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
203	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	363	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	364	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	366	readiness notifications you get per iteration.
363		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
		371
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		373
366	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	375	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	376	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	377	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	379	performance tips.
		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
372		383
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		385
375	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
…		…
389	Please note that epoll sometimes generates spurious notifications, so you	400	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data	401	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.	402	(or space) is available.
392		403
393	Best performance from this backend is achieved by not unregistering all	404	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	405	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	406	i.e. keep at least one watcher active per fd at all times. Stopping and
		407	starting a watcher (without re-setting it) also usually doesn't cause
		408	extra overhead.
396		409
397	While nominally embeddable in other event loops, this feature is broken in	410	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	411	all kernel versions tested so far.
399		412
		413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		414	C<EVBACKEND_POLL>.
		415
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		417
402	Kqueue deserves special mention, as at the time of this writing, it	418	Kqueue deserves special mention, as at the time of this writing, it was
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	419	broken on all BSDs except NetBSD (usually it doesn't work reliably with
404	with anything but sockets and pipes, except on Darwin, where of course	420	anything but sockets and pipes, except on Darwin, where of course it's
405	it's completely useless). For this reason it's not being "auto-detected"	421	completely useless). For this reason it's not being "auto-detected" unless
406	unless you explicitly specify it explicitly in the flags (i.e. using	422	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	423	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
408	system like NetBSD.
409		424
410	You still can embed kqueue into a normal poll or select backend and use it	425	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	426	only for sockets (after having made sure that sockets work with kqueue on
412	the target platform). See C<ev_embed> watchers for more info.	427	the target platform). See C<ev_embed> watchers for more info.
413		428
414	It scales in the same way as the epoll backend, but the interface to the	429	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	430	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	431	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	432	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	433	two event changes per incident. Support for C<fork ()> is very bad and it
419	drops fds silently in similarly hard-to-detect cases.	434	drops fds silently in similarly hard-to-detect cases.
420		435
421	This backend usually performs well under most conditions.	436	This backend usually performs well under most conditions.
422		437
423	While nominally embeddable in other event loops, this doesn't work	438	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	439	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	440	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	441	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	443	using it only for sockets.
		444
		445	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		446	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		447	C<NOTE_EOF>.
429		448
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	449	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		450
432	This is not implemented yet (and might never be, unless you send me an	451	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	452	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	465	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	466	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	467	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	468	might perform better.
450		469
451	On the positive side, ignoring the spurious readiness notifications, this	470	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	471	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	472	in all tests and is fully embeddable, which is a rare feat among the
		473	OS-specific backends.
		474
		475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		476	C<EVBACKEND_POLL>.
454		477
455	=item C<EVBACKEND_ALL>	478	=item C<EVBACKEND_ALL>
456		479
457	Try all backends (even potentially broken ones that wouldn't be tried	480	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	481	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		487
465	If one or more of these are or'ed into the flags value, then only these	488	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	489	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	490	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		491
469	The most typical usage is like this:	492	Example: This is the most typical usage.
470		493
471	if (!ev_default_loop (0))	494	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		496
474	Restrict libev to the select and poll backends, and do not allow	497	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	498	environment settings to be taken into account:
476		499
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	500	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		501
479	Use whatever libev has to offer, but make sure that kqueue is used if	502	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	503	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	504	private event loop and only if you know the OS supports your types of
		505	fds):
482		506
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		508
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	509	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		510
487	Similar to C<ev_default_loop>, but always creates a new event loop that is	511	Similar to C<ev_default_loop>, but always creates a new event loop that is
488	always distinct from the default loop. Unlike the default loop, it cannot	512	always distinct from the default loop. Unlike the default loop, it cannot
…		…
493	libev with threads is indeed to create one loop per thread, and using the	517	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.	518	default loop in the "main" or "initial" thread.
495		519
496	Example: Try to create a event loop that uses epoll and nothing else.	520	Example: Try to create a event loop that uses epoll and nothing else.
497		521
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	522	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	523	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	524	fatal ("no epoll found here, maybe it hides under your chair");
501		525
502	=item ev_default_destroy ()	526	=item ev_default_destroy ()
503		527
504	Destroys the default loop again (frees all memory and kernel state	528	Destroys the default loop again (frees all memory and kernel state
505	etc.). None of the active event watchers will be stopped in the normal	529	etc.). None of the active event watchers will be stopped in the normal
…		…
544		568
545	=item ev_loop_fork (loop)	569	=item ev_loop_fork (loop)
546		570
547	Like C<ev_default_fork>, but acts on an event loop created by	571	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	572	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	573	after fork that you want to re-use in the child, and how you do this is
		574	entirely your own problem.
550		575
551	=item int ev_is_default_loop (loop)	576	=item int ev_is_default_loop (loop)
552		577
553	Returns true when the given loop actually is the default loop, false otherwise.	578	Returns true when the given loop is, in fact, the default loop, and false
		579	otherwise.
554		580
555	=item unsigned int ev_loop_count (loop)	581	=item unsigned int ev_loop_count (loop)
556		582
557	Returns the count of loop iterations for the loop, which is identical to	583	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	584	the number of times libev did poll for new events. It starts at C<0> and
…		…
573	received events and started processing them. This timestamp does not	599	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	600	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	601	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	602	event occurring (or more correctly, libev finding out about it).
577		603
		604	=item ev_now_update (loop)
		605
		606	Establishes the current time by querying the kernel, updating the time
		607	returned by C<ev_now ()> in the progress. This is a costly operation and
		608	is usually done automatically within C<ev_loop ()>.
		609
		610	This function is rarely useful, but when some event callback runs for a
		611	very long time without entering the event loop, updating libev's idea of
		612	the current time is a good idea.
		613
		614	See also "The special problem of time updates" in the C<ev_timer> section.
		615
578	=item ev_loop (loop, int flags)	616	=item ev_loop (loop, int flags)
579		617
580	Finally, this is it, the event handler. This function usually is called	618	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	619	after you initialised all your watchers and you want to start handling
582	events.	620	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	622	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	623	either no event watchers are active anymore or C<ev_unloop> was called.
586		624
587	Please note that an explicit C<ev_unloop> is usually better than	625	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	626	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	627	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	628	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	629	of relying on its watchers stopping correctly, that is truly a thing of
		630	beauty.
592		631
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	632	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	633	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	634	process in case there are no events and will return after one iteration of
		635	the loop.
596		636
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	637	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	638	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	639	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	640	be an event internal to libev itself, so there is no guarentee that a
601	external event in conjunction with something not expressible using other	641	user-registered callback will be called), and will return after one
		642	iteration of the loop.
		643
		644	This is useful if you are waiting for some external event in conjunction
		645	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	646	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	647	usually a better approach for this kind of thing.
604		648
605	Here are the gory details of what C<ev_loop> does:	649	Here are the gory details of what C<ev_loop> does:
606		650
607	- Before the first iteration, call any pending watchers.	651	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	652	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	653	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	654	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	655	- If we have been forked, detach and recreate the kernel state
		656	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	657	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	658	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	659	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	660	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	661	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	662	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	663	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	664	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	665	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	666	- Queue all expired timers.
622	- Queue all outstanding periodics.	667	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	668	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	669	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	670	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	671	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	672	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	673	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	678	anymore.
634		679
635	... queue jobs here, make sure they register event watchers as long	680	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	681	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	682	ev_loop (my_loop, 0);
638	... jobs done. yeah!	683	... jobs done or somebody called unloop. yeah!
639		684
640	=item ev_unloop (loop, how)	685	=item ev_unloop (loop, how)
641		686
642	Can be used to make a call to C<ev_loop> return early (but only after it	687	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	688	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	689	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	690	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		691
647	This "unloop state" will be cleared when entering C<ev_loop> again.	692	This "unloop state" will be cleared when entering C<ev_loop> again.
648		693
		694	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		695
649	=item ev_ref (loop)	696	=item ev_ref (loop)
650		697
651	=item ev_unref (loop)	698	=item ev_unref (loop)
652		699
653	Ref/unref can be used to add or remove a reference count on the event	700	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	701	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	702	count is nonzero, C<ev_loop> will not return on its own.
		703
656	a watcher you never unregister that should not keep C<ev_loop> from	704	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	705	from returning, call ev_unref() after starting, and ev_ref() before
		706	stopping it.
		707
658	example, libev itself uses this for its internal signal pipe: It is not	708	As an example, libev itself uses this for its internal signal pipe: It is
659	visible to the libev user and should not keep C<ev_loop> from exiting if	709	not visible to the libev user and should not keep C<ev_loop> from exiting
660	no event watchers registered by it are active. It is also an excellent	710	if no event watchers registered by it are active. It is also an excellent
661	way to do this for generic recurring timers or from within third-party	711	way to do this for generic recurring timers or from within third-party
662	libraries. Just remember to I<unref after start> and I<ref before stop>	712	libraries. Just remember to I<unref after start> and I<ref before stop>
663	(but only if the watcher wasn't active before, or was active before,	713	(but only if the watcher wasn't active before, or was active before,
664	respectively).	714	respectively).
665		715
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	717	running when nothing else is active.
668		718
669	struct ev_signal exitsig;	719	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	720	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	721	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	722	evf_unref (loop);
673		723
674	Example: For some weird reason, unregister the above signal handler again.	724	Example: For some weird reason, unregister the above signal handler again.
675		725
676	ev_ref (loop);	726	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	727	ev_signal_stop (loop, &exitsig);
678		728
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	729	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		730
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	731	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		732
683	These advanced functions influence the time that libev will spend waiting	733	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	734	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	735	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		736	latency.
686		737
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	738	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	739	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	740	to increase efficiency of loop iterations (or to increase power-saving
		741	opportunities).
690		742
691	The background is that sometimes your program runs just fast enough to	743	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	744	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	745	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	746	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	747	overhead for the actual polling but can deliver many events at once.
696		748
697	By setting a higher I<io collect interval> you allow libev to spend more	749	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	750	time collecting I/O events, so you can handle more events per iteration,
…		…
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	752	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	753	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		754
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	755	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	756	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	757	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	758	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	759	value will not introduce any overhead in libev.
708		760
709	Many (busy) programs can usually benefit by setting the I/O collect	761	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	762	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	763	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	764	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	765	as this approaches the timing granularity of most systems.
714		766
		767	Setting the I<timeout collect interval> can improve the opportunity for
		768	saving power, as the program will "bundle" timer callback invocations that
		769	are "near" in time together, by delaying some, thus reducing the number of
		770	times the process sleeps and wakes up again. Another useful technique to
		771	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		772	they fire on, say, one-second boundaries only.
		773
715	=item ev_loop_verify (loop)	774	=item ev_loop_verify (loop)
716		775
717	This function only does something when C<EV_VERIFY> support has been	776	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	777	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	778	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	779	is found to be inconsistent, it will print an error message to standard
		780	error and call C<abort ()>.
721		781
722	This can be used to catch bugs inside libev itself: under normal	782	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	783	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	784	data structures consistent.
725		785
726	=back	786	=back
727		787
728		788
729	=head1 ANATOMY OF A WATCHER	789	=head1 ANATOMY OF A WATCHER
730		790
		791	In the following description, uppercase C<TYPE> in names stands for the
		792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		793	watchers and C<ev_io_start> for I/O watchers.
		794
731	A watcher is a structure that you create and register to record your	795	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	796	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	797	become readable, you would create an C<ev_io> watcher for that:
734		798
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	799	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	800	{
737	ev_io_stop (w);	801	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	802	ev_unloop (loop, EVUNLOOP_ALL);
739	}	803	}
740		804
741	struct ev_loop *loop = ev_default_loop (0);	805	struct ev_loop *loop = ev_default_loop (0);
		806
742	struct ev_io stdin_watcher;	807	ev_io stdin_watcher;
		808
743	ev_init (&stdin_watcher, my_cb);	809	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	811	ev_io_start (loop, &stdin_watcher);
		812
746	ev_loop (loop, 0);	813	ev_loop (loop, 0);
747		814
748	As you can see, you are responsible for allocating the memory for your	815	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	816	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	817	stack).
		818
		819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		821
752	Each watcher structure must be initialised by a call to C<ev_init	822	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	823	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	824	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	825	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	826	is readable and/or writable).
757		827
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	828	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	829	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	830	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	831	ev_TYPE_init (watcher *, callback, ...) >>.
762		832
763	To make the watcher actually watch out for events, you have to start it	833	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	834	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	835	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	836	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		837
768	As long as your watcher is active (has been started but not stopped) you	838	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	839	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	840	reinitialise it or call its C<ev_TYPE_set> macro.
771		841
772	Each and every callback receives the event loop pointer as first, the	842	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	843	registered watcher structure as second, and a bitset of received events as
774	third argument.	844	third argument.
775		845
…		…
838	=item C<EV_ERROR>	908	=item C<EV_ERROR>
839		909
840	An unspecified error has occurred, the watcher has been stopped. This might	910	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	911	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	912	ran out of memory, a file descriptor was found to be closed or any other
		913	problem. Libev considers these application bugs.
		914
843	problem. You best act on it by reporting the problem and somehow coping	915	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	916	watcher being stopped. Note that well-written programs should not receive
		917	an error ever, so when your watcher receives it, this usually indicates a
		918	bug in your program.
845		919
846	Libev will usually signal a few "dummy" events together with an error,	920	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	921	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	922	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	923	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	924	programs, though, as the fd could already be closed and reused for another
		925	thing, so beware.
851		926
852	=back	927	=back
853		928
854	=head2 GENERIC WATCHER FUNCTIONS	929	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		930
859	=over 4	931	=over 4
860		932
861	=item C<ev_init> (ev_TYPE *watcher, callback)	933	=item C<ev_init> (ev_TYPE *watcher, callback)
862		934
…		…
868	which rolls both calls into one.	940	which rolls both calls into one.
869		941
870	You can reinitialise a watcher at any time as long as it has been stopped	942	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	943	(or never started) and there are no pending events outstanding.
872		944
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	945	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	946	int revents)>.
		947
		948	Example: Initialise an C<ev_io> watcher in two steps.
		949
		950	ev_io w;
		951	ev_init (&w, my_cb);
		952	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		953
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	954	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		955
878	This macro initialises the type-specific parts of a watcher. You need to	956	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	957	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	960	difference to the C<ev_init> macro).
883		961
884	Although some watcher types do not have type-specific arguments	962	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	963	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		964
		965	See C<ev_init>, above, for an example.
		966
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	967	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		968
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	969	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	970	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	971	a watcher. The same limitations apply, of course.
892		972
		973	Example: Initialise and set an C<ev_io> watcher in one step.
		974
		975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		976
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		978
895	Starts (activates) the given watcher. Only active watchers will receive	979	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	980	events. If the watcher is already active nothing will happen.
897		981
		982	Example: Start the C<ev_io> watcher that is being abused as example in this
		983	whole section.
		984
		985	ev_io_start (EV_DEFAULT_UC, &w);
		986
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		988
900	Stops the given watcher again (if active) and clears the pending	989	Stops the given watcher if active, and clears the pending status (whether
		990	the watcher was active or not).
		991
901	status. It is possible that stopped watchers are pending (for example,	992	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	993	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	994	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	995	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	996	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		997
907	=item bool ev_is_active (ev_TYPE *watcher)	998	=item bool ev_is_active (ev_TYPE *watcher)
908		999
909	Returns a true value iff the watcher is active (i.e. it has been started	1000	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1001	and not yet been stopped). As long as a watcher is active you must not modify
…		…
952	The default priority used by watchers when no priority has been set is	1043	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1044	always C<0>, which is supposed to not be too high and not be too low :).
954		1045
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
956	fine, as long as you do not mind that the priority value you query might	1047	fine, as long as you do not mind that the priority value you query might
957	or might not have been adjusted to be within valid range.	1048	or might not have been clamped to the valid range.
958		1049
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1051
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1053	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1054	can deal with that fact, as both are simply passed through to the
		1055	callback.
964		1056
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1057	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1058
967	If the watcher is pending, this function returns clears its pending status	1059	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1060	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1061	watcher isn't pending it does nothing and returns C<0>.
970		1062
		1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1064	callback to be invoked, which can be accomplished with this function.
		1065
971	=back	1066	=back
972		1067
973		1068
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1070
976	Each watcher has, by default, a member C<void *data> that you can change	1071	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1072	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1073	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1074	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1075	member, you can also "subclass" the watcher type and provide your own
981	data:	1076	data:
982		1077
983	struct my_io	1078	struct my_io
984	{	1079	{
985	struct ev_io io;	1080	ev_io io;
986	int otherfd;	1081	int otherfd;
987	void *somedata;	1082	void *somedata;
988	struct whatever *mostinteresting;	1083	struct whatever *mostinteresting;
989	}	1084	};
		1085
		1086	...
		1087	struct my_io w;
		1088	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1089
991	And since your callback will be called with a pointer to the watcher, you	1090	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1091	can cast it back to your own type:
993		1092
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1093	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1094	{
996	struct my_io *w = (struct my_io *)w_;	1095	struct my_io *w = (struct my_io *)w_;
997	...	1096	...
998	}	1097	}
999		1098
1000	More interesting and less C-conformant ways of casting your callback type	1099	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1100	instead have been omitted.
1002		1101
1003	Another common scenario is having some data structure with multiple	1102	Another common scenario is to use some data structure with multiple
1004	watchers:	1103	embedded watchers:
1005		1104
1006	struct my_biggy	1105	struct my_biggy
1007	{	1106	{
1008	int some_data;	1107	int some_data;
1009	ev_timer t1;	1108	ev_timer t1;
1010	ev_timer t2;	1109	ev_timer t2;
1011	}	1110	}
1012		1111
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1112	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1113	complicated: Either you store the address of your C<my_biggy> struct
		1114	in the C<data> member of the watcher (for woozies), or you need to use
		1115	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1116	programmers):
1015		1117
1016	#include <stddef.h>	1118	#include <stddef.h>
1017		1119
1018	static void	1120	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1121	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1122	{
1021	struct my_biggy big = (struct my_biggy *	1123	struct my_biggy big = (struct my_biggy *
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1124	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1125	}
1024		1126
1025	static void	1127	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1128	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1129	{
1028	struct my_biggy big = (struct my_biggy *	1130	struct my_biggy big = (struct my_biggy *
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1131	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1132	}
1031		1133
1032		1134
1033	=head1 WATCHER TYPES	1135	=head1 WATCHER TYPES
1034		1136
1035	This section describes each watcher in detail, but will not repeat	1137	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1161	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1162	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1163	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1164	required if you know what you are doing).
1063		1165
1064	If you must do this, then force the use of a known-to-be-good backend	1166	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1167	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1169
1068	Another thing you have to watch out for is that it is quite easy to	1170	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1171	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1172	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1173	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1174	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1175	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1176	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1177	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1178
1077	If you cannot run the fd in non-blocking mode (for example you should not	1179	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1180	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1181	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1182	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1183	does this on its own, so its quite safe to use). Some people additionally
		1184	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1185	indefinitely.
		1186
		1187	But really, best use non-blocking mode.
1082		1188
1083	=head3 The special problem of disappearing file descriptors	1189	=head3 The special problem of disappearing file descriptors
1084		1190
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1191	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1192	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1193	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1194	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1195	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1196	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1197	fact, a different file descriptor.
1092		1198
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1229	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1230	C<EVBACKEND_POLL>.
1125		1231
1126	=head3 The special problem of SIGPIPE	1232	=head3 The special problem of SIGPIPE
1127		1233
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1234	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1235	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1236	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1237	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1238
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1239	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1240	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1241	somewhere, as that would have given you a big clue).
1137		1242
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1248	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1249
1145	=item ev_io_set (ev_io *, int fd, int events)	1250	=item ev_io_set (ev_io *, int fd, int events)
1146		1251
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1252	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1253	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1254	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1255
1151	=item int fd [read-only]	1256	=item int fd [read-only]
1152		1257
1153	The file descriptor being watched.	1258	The file descriptor being watched.
1154		1259
…		…
1162		1267
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1268	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1269	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1270	attempt to read a whole line in the callback.
1166		1271
1167	static void	1272	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1273	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1274	{
1170	ev_io_stop (loop, w);	1275	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1276	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1277	}
1173		1278
1174	...	1279	...
1175	struct ev_loop *loop = ev_default_init (0);	1280	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1281	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1283	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1284	ev_loop (loop, 0);
1180		1285
1181		1286
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1287	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1288
1184	Timer watchers are simple relative timers that generate an event after a	1289	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1290	given time, and optionally repeating in regular intervals after that.
1186		1291
1187	The timers are based on real time, that is, if you register an event that	1292	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1293	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1294	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1296	monotonic clock option helps a lot here).
		1297
		1298	The callback is guaranteed to be invoked only I<after> its timeout has
		1299	passed, but if multiple timers become ready during the same loop iteration
		1300	then order of execution is undefined.
		1301
		1302	=head3 Be smart about timeouts
		1303
		1304	Many real-world problems involve some kind of timeout, usually for error
		1305	recovery. A typical example is an HTTP request - if the other side hangs,
		1306	you want to raise some error after a while.
		1307
		1308	What follows are some ways to handle this problem, from obvious and
		1309	inefficient to smart and efficient.
		1310
		1311	In the following, a 60 second activity timeout is assumed - a timeout that
		1312	gets reset to 60 seconds each time there is activity (e.g. each time some
		1313	data or other life sign was received).
		1314
		1315	=over 4
		1316
		1317	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1318
		1319	This is the most obvious, but not the most simple way: In the beginning,
		1320	start the watcher:
		1321
		1322	ev_timer_init (timer, callback, 60., 0.);
		1323	ev_timer_start (loop, timer);
		1324
		1325	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1326	and start it again:
		1327
		1328	ev_timer_stop (loop, timer);
		1329	ev_timer_set (timer, 60., 0.);
		1330	ev_timer_start (loop, timer);
		1331
		1332	This is relatively simple to implement, but means that each time there is
		1333	some activity, libev will first have to remove the timer from its internal
		1334	data structure and then add it again. Libev tries to be fast, but it's
		1335	still not a constant-time operation.
		1336
		1337	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1338
		1339	This is the easiest way, and involves using C<ev_timer_again> instead of
		1340	C<ev_timer_start>.
		1341
		1342	To implement this, configure an C<ev_timer> with a C<repeat> value
		1343	of C<60> and then call C<ev_timer_again> at start and each time you
		1344	successfully read or write some data. If you go into an idle state where
		1345	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1346	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1347
		1348	That means you can ignore both the C<ev_timer_start> function and the
		1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1350	member and C<ev_timer_again>.
		1351
		1352	At start:
		1353
		1354	ev_timer_init (timer, callback);
		1355	timer->repeat = 60.;
		1356	ev_timer_again (loop, timer);
		1357
		1358	Each time there is some activity:
		1359
		1360	ev_timer_again (loop, timer);
		1361
		1362	It is even possible to change the time-out on the fly, regardless of
		1363	whether the watcher is active or not:
		1364
		1365	timer->repeat = 30.;
		1366	ev_timer_again (loop, timer);
		1367
		1368	This is slightly more efficient then stopping/starting the timer each time
		1369	you want to modify its timeout value, as libev does not have to completely
		1370	remove and re-insert the timer from/into its internal data structure.
		1371
		1372	It is, however, even simpler than the "obvious" way to do it.
		1373
		1374	=item 3. Let the timer time out, but then re-arm it as required.
		1375
		1376	This method is more tricky, but usually most efficient: Most timeouts are
		1377	relatively long compared to the intervals between other activity - in
		1378	our example, within 60 seconds, there are usually many I/O events with
		1379	associated activity resets.
		1380
		1381	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1382	but remember the time of last activity, and check for a real timeout only
		1383	within the callback:
		1384
		1385	ev_tstamp last_activity; // time of last activity
		1386
		1387	static void
		1388	callback (EV_P_ ev_timer *w, int revents)
		1389	{
		1390	ev_tstamp now = ev_now (EV_A);
		1391	ev_tstamp timeout = last_activity + 60.;
		1392
		1393	// if last_activity + 60. is older than now, we did time out
		1394	if (timeout < now)
		1395	{
		1396	// timeout occured, take action
		1397	}
		1398	else
		1399	{
		1400	// callback was invoked, but there was some activity, re-arm
		1401	// the watcher to fire in last_activity + 60, which is
		1402	// guaranteed to be in the future, so "again" is positive:
		1403	w->again = timeout - now;
		1404	ev_timer_again (EV_A_ w);
		1405	}
		1406	}
		1407
		1408	To summarise the callback: first calculate the real timeout (defined
		1409	as "60 seconds after the last activity"), then check if that time has
		1410	been reached, which means something I<did>, in fact, time out. Otherwise
		1411	the callback was invoked too early (C<timeout> is in the future), so
		1412	re-schedule the timer to fire at that future time, to see if maybe we have
		1413	a timeout then.
		1414
		1415	Note how C<ev_timer_again> is used, taking advantage of the
		1416	C<ev_timer_again> optimisation when the timer is already running.
		1417
		1418	This scheme causes more callback invocations (about one every 60 seconds
		1419	minus half the average time between activity), but virtually no calls to
		1420	libev to change the timeout.
		1421
		1422	To start the timer, simply initialise the watcher and set C<last_activity>
		1423	to the current time (meaning we just have some activity :), then call the
		1424	callback, which will "do the right thing" and start the timer:
		1425
		1426	ev_timer_init (timer, callback);
		1427	last_activity = ev_now (loop);
		1428	callback (loop, timer, EV_TIMEOUT);
		1429
		1430	And when there is some activity, simply store the current time in
		1431	C<last_activity>, no libev calls at all:
		1432
		1433	last_actiivty = ev_now (loop);
		1434
		1435	This technique is slightly more complex, but in most cases where the
		1436	time-out is unlikely to be triggered, much more efficient.
		1437
		1438	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1439	callback :) - just change the timeout and invoke the callback, which will
		1440	fix things for you.
		1441
		1442	=item 4. Wee, just use a double-linked list for your timeouts.
		1443
		1444	If there is not one request, but many thousands (millions...), all
		1445	employing some kind of timeout with the same timeout value, then one can
		1446	do even better:
		1447
		1448	When starting the timeout, calculate the timeout value and put the timeout
		1449	at the I<end> of the list.
		1450
		1451	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1452	the list is expected to fire (for example, using the technique #3).
		1453
		1454	When there is some activity, remove the timer from the list, recalculate
		1455	the timeout, append it to the end of the list again, and make sure to
		1456	update the C<ev_timer> if it was taken from the beginning of the list.
		1457
		1458	This way, one can manage an unlimited number of timeouts in O(1) time for
		1459	starting, stopping and updating the timers, at the expense of a major
		1460	complication, and having to use a constant timeout. The constant timeout
		1461	ensures that the list stays sorted.
		1462
		1463	=back
		1464
		1465	So which method the best?
		1466
		1467	Method #2 is a simple no-brain-required solution that is adequate in most
		1468	situations. Method #3 requires a bit more thinking, but handles many cases
		1469	better, and isn't very complicated either. In most case, choosing either
		1470	one is fine, with #3 being better in typical situations.
		1471
		1472	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1473	rather complicated, but extremely efficient, something that really pays
		1474	off after the first million or so of active timers, i.e. it's usually
		1475	overkill :)
		1476
		1477	=head3 The special problem of time updates
		1478
		1479	Establishing the current time is a costly operation (it usually takes at
		1480	least two system calls): EV therefore updates its idea of the current
		1481	time only before and after C<ev_loop> collects new events, which causes a
		1482	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1483	lots of events in one iteration.
1192		1484
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1485	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1486	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1487	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1488	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1489	timeout on the current time, use something like this to adjust for this:
1198		1490
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1491	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1492
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1493	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1494	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1495	()>.
1204		1496
1205	=head3 Watcher-Specific Functions and Data Members	1497	=head3 Watcher-Specific Functions and Data Members
1206		1498
1207	=over 4	1499	=over 4
1208		1500
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1524	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1525
1234	If the timer is repeating, either start it if necessary (with the	1526	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1527	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1528
1237	This sounds a bit complicated, but here is a useful and typical	1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1530	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246
1247	That means you can ignore the C<after> value and C<ev_timer_start>
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249
1250	ev_timer_init (timer, callback, 0., 5.);
1251	ev_timer_again (loop, timer);
1252	...
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258
1259	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.
1261		1531
1262	=item ev_tstamp repeat [read-write]	1532	=item ev_tstamp repeat [read-write]
1263		1533
1264	The current C<repeat> value. Will be used each time the watcher times out	1534	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1535	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1536	which is also when any modifications are taken into account.
1267		1537
1268	=back	1538	=back
1269		1539
1270	=head3 Examples	1540	=head3 Examples
1271		1541
1272	Example: Create a timer that fires after 60 seconds.	1542	Example: Create a timer that fires after 60 seconds.
1273		1543
1274	static void	1544	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1545	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1546	{
1277	.. one minute over, w is actually stopped right here	1547	.. one minute over, w is actually stopped right here
1278	}	1548	}
1279		1549
1280	struct ev_timer mytimer;	1550	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1551	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1552	ev_timer_start (loop, &mytimer);
1283		1553
1284	Example: Create a timeout timer that times out after 10 seconds of	1554	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1555	inactivity.
1286		1556
1287	static void	1557	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1558	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1559	{
1290	.. ten seconds without any activity	1560	.. ten seconds without any activity
1291	}	1561	}
1292		1562
1293	struct ev_timer mytimer;	1563	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1565	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1566	ev_loop (loop, 0);
1297		1567
1298	// and in some piece of code that gets executed on any "activity":	1568	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	1569	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	1570	ev_timer_again (&mytimer);
1301		1571
1302		1572
1303	=head2 C<ev_periodic> - to cron or not to cron?	1573	=head2 C<ev_periodic> - to cron or not to cron?
1304		1574
1305	Periodic watchers are also timers of a kind, but they are very versatile	1575	Periodic watchers are also timers of a kind, but they are very versatile
…		…
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger	1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).	1585	roughly 10 seconds later as it uses a relative timeout).
1316		1586
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1587	C<ev_periodic>s can also be used to implement vastly more complex timers,
1318	such as triggering an event on each "midnight, local time", or other	1588	such as triggering an event on each "midnight, local time", or other
1319	complicated, rules.	1589	complicated rules.
1320		1590
1321	As with timers, the callback is guaranteed to be invoked only when the	1591	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1592	time (C<at>) has passed, but if multiple periodic timers become ready
1323	during the same loop iteration then order of execution is undefined.	1593	during the same loop iteration, then order of execution is undefined.
1324		1594
1325	=head3 Watcher-Specific Functions and Data Members	1595	=head3 Watcher-Specific Functions and Data Members
1326		1596
1327	=over 4	1597	=over 4
1328		1598
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1330		1600
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1332		1602
1333	Lots of arguments, lets sort it out... There are basically three modes of	1603	Lots of arguments, lets sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1604	operation, and we will explain them from simplest to most complex:
1335		1605
1336	=over 4	1606	=over 4
1337		1607
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1339		1609
1340	In this configuration the watcher triggers an event after the wall clock	1610	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1611	time C<at> has passed. It will not repeat and will not adjust when a time
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1612	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1343	run when the system time reaches or surpasses this time.	1613	only run when the system clock reaches or surpasses this time.
1344		1614
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1346		1616
1347	In this mode the watcher will always be scheduled to time out at the next	1617	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1618	C<at + N * interval> time (for some integer N, which can also be negative)
1349	and then repeat, regardless of any time jumps.	1619	and then repeat, regardless of any time jumps.
1350		1620
1351	This can be used to create timers that do not drift with respect to system	1621	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1622	system clock, for example, here is a C<ev_periodic> that triggers each
1353	the hour:	1623	hour, on the hour:
1354		1624
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1625	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1626
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1627	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1628	but only that the callback will be called when the system time shows a
…		…
1384		1654
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1657	only event loop modification you are allowed to do).
1388		1658
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1659	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1660	*w, ev_tstamp now)>, e.g.:
1391		1661
		1662	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1663	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1664	{
1394	return now + 60.;	1665	return now + 60.;
1395	}	1666	}
1396		1667
1397	It must return the next time to trigger, based on the passed time value	1668	It must return the next time to trigger, based on the passed time value
…		…
1434		1705
1435	The current interval value. Can be modified any time, but changes only	1706	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	1707	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1708	called.
1438		1709
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1710	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1711
1441	The current reschedule callback, or C<0>, if this functionality is	1712	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	1713	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	1714	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1715
1445	=back	1716	=back
1446		1717
1447	=head3 Examples	1718	=head3 Examples
1448		1719
1449	Example: Call a callback every hour, or, more precisely, whenever the	1720	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1721	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1722	potentially a lot of jitter, but good long-term stability.
1452		1723
1453	static void	1724	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1725	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1726	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1727	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1728	}
1458		1729
1459	struct ev_periodic hourly_tick;	1730	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1731	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1732	ev_periodic_start (loop, &hourly_tick);
1462		1733
1463	Example: The same as above, but use a reschedule callback to do it:	1734	Example: The same as above, but use a reschedule callback to do it:
1464		1735
1465	#include <math.h>	1736	#include <math.h>
1466		1737
1467	static ev_tstamp	1738	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1739	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	1740	{
1470	return fmod (now, 3600.) + 3600.;	1741	return now + (3600. - fmod (now, 3600.));
1471	}	1742	}
1472		1743
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1744	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1745
1475	Example: Call a callback every hour, starting now:	1746	Example: Call a callback every hour, starting now:
1476		1747
1477	struct ev_periodic hourly_tick;	1748	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1749	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1750	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1751	ev_periodic_start (loop, &hourly_tick);
1481		1752
1482		1753
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	1754	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		1755
1485	Signal watchers will trigger an event when the process receives a specific	1756	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	1757	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	1758	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1759	normal event processing, like any other event.
1489		1760
		1761	If you want signals asynchronously, just use C<sigaction> as you would
		1762	do without libev and forget about sharing the signal. You can even use
		1763	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1764
1490	You can configure as many watchers as you like per signal. Only when the	1765	You can configure as many watchers as you like per signal. Only when the
1491	first watcher gets started will libev actually register a signal watcher	1766	first watcher gets started will libev actually register a signal handler
1492	with the kernel (thus it coexists with your own signal handlers as long	1767	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	1768	you don't register any with libev for the same signal). Similarly, when
1494	watcher for a signal is stopped libev will reset the signal handler to	1769	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1770	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1771
1497	If possible and supported, libev will install its handlers with	1772	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1499	interrupted. If you have a problem with system calls getting interrupted by	1774	interrupted. If you have a problem with system calls getting interrupted by
1500	signals you can block all signals in an C<ev_check> watcher and unblock	1775	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1792
1518	=back	1793	=back
1519		1794
1520	=head3 Examples	1795	=head3 Examples
1521		1796
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1797	Example: Try to exit cleanly on SIGINT.
1523		1798
1524	static void	1799	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1800	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	1801	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1802	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1803	}
1529		1804
1530	struct ev_signal signal_watcher;	1805	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1807	ev_signal_start (loop, &signal_watcher);
1533		1808
1534		1809
1535	=head2 C<ev_child> - watch out for process status changes	1810	=head2 C<ev_child> - watch out for process status changes
1536		1811
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1812	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	1813	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	1814	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	1815	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	1816	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1817	forking and then immediately registering a watcher for the child is fine,
		1818	but forking and registering a watcher a few event loop iterations later is
		1819	not.
1542		1820
1543	Only the default event loop is capable of handling signals, and therefore	1821	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	1822	you can only register child watchers in the default event loop.
1545		1823
1546	=head3 Process Interaction	1824	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	1837	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	1838	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	1839	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	1840	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	1841	that, so other libev users can use C<ev_child> watchers freely.
		1842
		1843	=head3 Stopping the Child Watcher
		1844
		1845	Currently, the child watcher never gets stopped, even when the
		1846	child terminates, so normally one needs to stop the watcher in the
		1847	callback. Future versions of libev might stop the watcher automatically
		1848	when a child exit is detected.
1564		1849
1565	=head3 Watcher-Specific Functions and Data Members	1850	=head3 Watcher-Specific Functions and Data Members
1566		1851
1567	=over 4	1852	=over 4
1568		1853
…		…
1597	=head3 Examples	1882	=head3 Examples
1598		1883
1599	Example: C<fork()> a new process and install a child handler to wait for	1884	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	1885	its completion.
1601		1886
1602	ev_child cw;	1887	ev_child cw;
1603		1888
1604	static void	1889	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	1890	child_cb (EV_P_ ev_child *w, int revents)
1606	{	1891	{
1607	ev_child_stop (EV_A_ w);	1892	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1893	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	1894	}
1610		1895
1611	pid_t pid = fork ();	1896	pid_t pid = fork ();
1612		1897
1613	if (pid < 0)	1898	if (pid < 0)
1614	// error	1899	// error
1615	else if (pid == 0)	1900	else if (pid == 0)
1616	{	1901	{
1617	// the forked child executes here	1902	// the forked child executes here
1618	exit (1);	1903	exit (1);
1619	}	1904	}
1620	else	1905	else
1621	{	1906	{
1622	ev_child_init (&cw, child_cb, pid, 0);	1907	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	1908	ev_child_start (EV_DEFAULT_ &cw);
1624	}	1909	}
1625		1910
1626		1911
1627	=head2 C<ev_stat> - did the file attributes just change?	1912	=head2 C<ev_stat> - did the file attributes just change?
1628		1913
1629	This watches a file system path for attribute changes. That is, it calls	1914	This watches a file system path for attribute changes. That is, it calls
…		…
1637	the stat buffer having unspecified contents.	1922	the stat buffer having unspecified contents.
1638		1923
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	1924	The path I<should> be absolute and I<must not> end in a slash. If it is
1640	relative and your working directory changes, the behaviour is undefined.	1925	relative and your working directory changes, the behaviour is undefined.
1641		1926
1642	Since there is no standard to do this, the portable implementation simply	1927	Since there is no standard kernel interface to do this, the portable
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1928	implementation simply calls C<stat (2)> regularly on the path to see if
1644	can specify a recommended polling interval for this case. If you specify	1929	it changed somehow. You can specify a recommended polling interval for
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	1930	this case. If you specify a polling interval of C<0> (highly recommended!)
1646	unspecified default> value will be used (which you can expect to be around	1931	then a I<suitable, unspecified default> value will be used (which
1647	five seconds, although this might change dynamically). Libev will also	1932	you can expect to be around five seconds, although this might change
1648	impose a minimum interval which is currently around C<0.1>, but thats	1933	dynamically). Libev will also impose a minimum interval which is currently
1649	usually overkill.	1934	around C<0.1>, but thats usually overkill.
1650		1935
1651	This watcher type is not meant for massive numbers of stat watchers,	1936	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	1937	as even with OS-supported change notifications, this can be
1653	resource-intensive.	1938	resource-intensive.
1654		1939
1655	At the time of this writing, only the Linux inotify interface is	1940	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	1941	is the Linux inotify interface (implementing kqueue support is left as
1657	reader, note, however, that the author sees no way of implementing ev_stat	1942	an exercise for the reader. Note, however, that the author sees no way
1658	semantics with kqueue). Inotify will be used to give hints only and should	1943	of implementing C<ev_stat> semantics with kqueue).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		1944
1664	=head3 ABI Issues (Largefile Support)	1945	=head3 ABI Issues (Largefile Support)
1665		1946
1666	Libev by default (unless the user overrides this) uses the default	1947	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	1948	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	1949	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	1950	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	1951	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	1952	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	1953	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	1954	most noticeably disabled with ev_stat and large file support.
1674		1955
1675	=head3 Inotify	1956	The solution for this is to lobby your distribution maker to make large
		1957	file interfaces available by default (as e.g. FreeBSD does) and not
		1958	optional. Libev cannot simply switch on large file support because it has
		1959	to exchange stat structures with application programs compiled using the
		1960	default compilation environment.
1676		1961
		1962	=head3 Inotify and Kqueue
		1963
1677	When C<inotify (7)> support has been compiled into libev (generally only	1964	When C<inotify (7)> support has been compiled into libev (generally
		1965	only available with Linux 2.6.25 or above due to bugs in earlier
1678	available on Linux) and present at runtime, it will be used to speed up	1966	implementations) and present at runtime, it will be used to speed up
1679	change detection where possible. The inotify descriptor will be created lazily	1967	change detection where possible. The inotify descriptor will be created
1680	when the first C<ev_stat> watcher is being started.	1968	lazily when the first C<ev_stat> watcher is being started.
1681		1969
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	1970	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	1971	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	1972	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	1973	there are many cases where libev has to resort to regular C<stat> polling,
		1974	but as long as the path exists, libev usually gets away without polling.
1686		1975
1687	(There is no support for kqueue, as apparently it cannot be used to	1976	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	1977	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	1978	descriptor open on the object at all times, and detecting renames, unlinks
		1979	etc. is difficult.
1690		1980
1691	=head3 The special problem of stat time resolution	1981	=head3 The special problem of stat time resolution
1692		1982
1693	The C<stat ()> system call only supports full-second resolution portably, and	1983	The C<stat ()> system call only supports full-second resolution portably, and
1694	even on systems where the resolution is higher, many file systems still	1984	even on systems where the resolution is higher, most file systems still
1695	only support whole seconds.	1985	only support whole seconds.
1696		1986
1697	That means that, if the time is the only thing that changes, you can	1987	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	1988	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	1989	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	1990	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	1991	stat data does change in other ways (e.g. file size).
1702		1992
1703	The solution to this is to delay acting on a change for slightly more	1993	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	1994	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1995	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	1996	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2016	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2017	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2018	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2019	path for as long as the watcher is active.
1730		2020
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2021	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2022	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2023	last change was detected).
1734		2024
1735	=item ev_stat_stat (loop, ev_stat *)	2025	=item ev_stat_stat (loop, ev_stat *)
1736		2026
1737	Updates the stat buffer immediately with new values. If you change the	2027	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2028	watched path in your callback, you could call this function to avoid
…		…
1767		2057
1768	=head3 Examples	2058	=head3 Examples
1769		2059
1770	Example: Watch C</etc/passwd> for attribute changes.	2060	Example: Watch C</etc/passwd> for attribute changes.
1771		2061
1772	static void	2062	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2063	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	2064	{
1775	/* /etc/passwd changed in some way */	2065	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	2066	if (w->attr.st_nlink)
1777	{	2067	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2068	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2069	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2070	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	2071	}
1782	else	2072	else
1783	/* you shalt not abuse printf for puts */	2073	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	2074	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	2075	"if this is windows, they already arrived\n");
1786	}	2076	}
1787		2077
1788	...	2078	...
1789	ev_stat passwd;	2079	ev_stat passwd;
1790		2080
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2081	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	2082	ev_stat_start (loop, &passwd);
1793		2083
1794	Example: Like above, but additionally use a one-second delay so we do not	2084	Example: Like above, but additionally use a one-second delay so we do not
1795	miss updates (however, frequent updates will delay processing, too, so	2085	miss updates (however, frequent updates will delay processing, too, so
1796	one might do the work both on C<ev_stat> callback invocation I<and> on	2086	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	2087	C<ev_timer> callback invocation).
1798		2088
1799	static ev_stat passwd;	2089	static ev_stat passwd;
1800	static ev_timer timer;	2090	static ev_timer timer;
1801		2091
1802	static void	2092	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	2093	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	2094	{
1805	ev_timer_stop (EV_A_ w);	2095	ev_timer_stop (EV_A_ w);
1806		2096
1807	/* now it's one second after the most recent passwd change */	2097	/* now it's one second after the most recent passwd change */
1808	}	2098	}
1809		2099
1810	static void	2100	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	2101	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	2102	{
1813	/* reset the one-second timer */	2103	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	2104	ev_timer_again (EV_A_ &timer);
1815	}	2105	}
1816		2106
1817	...	2107	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2108	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	2109	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	2110	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		2111
1822		2112
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2113	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2114
1825	Idle watchers trigger events when no other events of the same or higher	2115	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2116	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2117	as receiving "events").
1828		2118
1829	That is, as long as your process is busy handling sockets or timeouts	2119	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2120	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2121	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2122	are pending), the idle watchers are being called once per event loop
…		…
1856	=head3 Examples	2146	=head3 Examples
1857		2147
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2148	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2149	callback, free it. Also, use no error checking, as usual.
1860		2150
1861	static void	2151	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2152	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2153	{
1864	free (w);	2154	free (w);
1865	// now do something you wanted to do when the program has	2155	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2156	// no longer anything immediate to do.
1867	}	2157	}
1868		2158
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2160	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2161	ev_idle_start (loop, idle_cb);
1872		2162
1873		2163
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2165
1876	Prepare and check watchers are usually (but not always) used in tandem:	2166	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2167	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2168	afterwards.
1879		2169
1880	You I<must not> call C<ev_loop> or similar functions that enter	2170	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2171	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2174	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2175	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2176	called in pairs bracketing the blocking call.
1887		2177
1888	Their main purpose is to integrate other event mechanisms into libev and	2178	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2179	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2180	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2181	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2182	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2183	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2184	watcher).
1895		2185
1896	This is done by examining in each prepare call which file descriptors need	2186	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2187	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2188	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2189	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2190	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2191	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2192	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2193	nevertheless, because you never know, you know?).
1904		2194
1905	As another example, the Perl Coro module uses these hooks to integrate	2195	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2196	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2197	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2198	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2201	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2202	low-priority coroutines to idle/background tasks).
1913		2203
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2204	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2205	priority, to ensure that they are being run before any other watchers
		2206	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2207
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2208	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2209	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2210	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2211	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2212	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2213	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2214	others).
1923		2215
1924	=head3 Watcher-Specific Functions and Data Members	2216	=head3 Watcher-Specific Functions and Data Members
1925		2217
1926	=over 4	2218	=over 4
1927		2219
…		…
1929		2221
1930	=item ev_check_init (ev_check *, callback)	2222	=item ev_check_init (ev_check *, callback)
1931		2223
1932	Initialises and configures the prepare or check watcher - they have no	2224	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2225	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2226	macros, but using them is utterly, utterly, utterly and completely
		2227	pointless.
1935		2228
1936	=back	2229	=back
1937		2230
1938	=head3 Examples	2231	=head3 Examples
1939		2232
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2241	and in a check watcher, destroy them and call into libadns. What follows
1949	is pseudo-code only of course. This requires you to either use a low	2242	is pseudo-code only of course. This requires you to either use a low
1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2243	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1951	the callbacks for the IO/timeout watchers might not have been called yet.	2244	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2245
1953	static ev_io iow [nfd];	2246	static ev_io iow [nfd];
1954	static ev_timer tw;	2247	static ev_timer tw;
1955		2248
1956	static void	2249	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2250	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2251	{
1959	}	2252	}
1960		2253
1961	// create io watchers for each fd and a timer before blocking	2254	// create io watchers for each fd and a timer before blocking
1962	static void	2255	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2256	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2257	{
1965	int timeout = 3600000;	2258	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2259	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2260	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2262
1970	/* the callback is illegal, but won't be called as we stop during check */	2263	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2264	ev_timer_init (&tw, 0, timeout * 1e-3);
1972	ev_timer_start (loop, &tw);	2265	ev_timer_start (loop, &tw);
1973		2266
1974	// create one ev_io per pollfd	2267	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2268	for (int i = 0; i < nfd; ++i)
1976	{	2269	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2270	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2271	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2272	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2273
1981	fds [i].revents = 0;	2274	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2275	ev_io_start (loop, iow + i);
1983	}	2276	}
1984	}	2277	}
1985		2278
1986	// stop all watchers after blocking	2279	// stop all watchers after blocking
1987	static void	2280	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2281	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2282	{
1990	ev_timer_stop (loop, &tw);	2283	ev_timer_stop (loop, &tw);
1991		2284
1992	for (int i = 0; i < nfd; ++i)	2285	for (int i = 0; i < nfd; ++i)
1993	{	2286	{
1994	// set the relevant poll flags	2287	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2288	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2289	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2290	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2291	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2292	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2293
2001	// now stop the watcher	2294	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2295	ev_io_stop (loop, iow + i);
2003	}	2296	}
2004		2297
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2298	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2299	}
2007		2300
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2301	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
2009	in the prepare watcher and would dispose of the check watcher.	2302	in the prepare watcher and would dispose of the check watcher.
2010		2303
2011	Method 3: If the module to be embedded supports explicit event	2304	Method 3: If the module to be embedded supports explicit event
2012	notification (libadns does), you can also make use of the actual watcher	2305	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2306	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2307
2015	static void	2308	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2309	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2310	{
2018	adns_state ads = (adns_state)w->data;	2311	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2312	update_now (EV_A);
2020		2313
2021	adns_processtimeouts (ads, &tv_now);	2314	adns_processtimeouts (ads, &tv_now);
2022	}	2315	}
2023		2316
2024	static void	2317	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2318	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2319	{
2027	adns_state ads = (adns_state)w->data;	2320	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2321	update_now (EV_A);
2029		2322
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2323	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2324	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2325	}
2033		2326
2034	// do not ever call adns_afterpoll	2327	// do not ever call adns_afterpoll
2035		2328
2036	Method 4: Do not use a prepare or check watcher because the module you	2329	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2330	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2331	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2332	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2333	this approach, effectively embedding EV as a client into the horrible
		2334	libglib event loop.
2041		2335
2042	static gint	2336	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2337	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2338	{
2045	int got_events = 0;	2339	int got_events = 0;
2046		2340
2047	for (n = 0; n < nfds; ++n)	2341	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2342	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2343
2050	if (timeout >= 0)	2344	if (timeout >= 0)
2051	// create/start timer	2345	// create/start timer
2052		2346
2053	// poll	2347	// poll
2054	ev_loop (EV_A_ 0);	2348	ev_loop (EV_A_ 0);
2055		2349
2056	// stop timer again	2350	// stop timer again
2057	if (timeout >= 0)	2351	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2352	ev_timer_stop (EV_A_ &to);
2059		2353
2060	// stop io watchers again - their callbacks should have set	2354	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	2355	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	2356	ev_io_stop (EV_A_ iow [n]);
2063		2357
2064	return got_events;	2358	return got_events;
2065	}	2359	}
2066		2360
2067		2361
2068	=head2 C<ev_embed> - when one backend isn't enough...	2362	=head2 C<ev_embed> - when one backend isn't enough...
2069		2363
2070	This is a rather advanced watcher type that lets you embed one event loop	2364	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	2370	prioritise I/O.
2077		2371
2078	As an example for a bug workaround, the kqueue backend might only support	2372	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2373	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2374	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2375	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2376	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2377	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2378	C<kevent>, but at least you can use both mechanisms for what they are
		2379	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2380
2086	As for prioritising I/O: rarely you have the case where some fds have	2381	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2382	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2383	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2384	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2385	the rest in a second one, and embed the second one in the first.
2091		2386
2092	As long as the watcher is active, the callback will be invoked every time	2387	As long as the watcher is active, the callback will be invoked every time
2093	there might be events pending in the embedded loop. The callback must then	2388	there might be events pending in the embedded loop. The callback must then
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2095	their callbacks (you could also start an idle watcher to give the embedded	2390	their callbacks (you could also start an idle watcher to give the embedded
…		…
2103	interested in that.	2398	interested in that.
2104		2399
2105	Also, there have not currently been made special provisions for forking:	2400	Also, there have not currently been made special provisions for forking:
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2107	but you will also have to stop and restart any C<ev_embed> watchers	2402	but you will also have to stop and restart any C<ev_embed> watchers
2108	yourself.	2403	yourself - but you can use a fork watcher to handle this automatically,
		2404	and future versions of libev might do just that.
2109		2405
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2406	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2408	portable one.
2113		2409
2114	So when you want to use this feature you will always have to be prepared	2410	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2411	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2412	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2413	create it, and if that fails, use the normal loop for everything.
		2414
		2415	=head3 C<ev_embed> and fork
		2416
		2417	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2418	automatically be applied to the embedded loop as well, so no special
		2419	fork handling is required in that case. When the watcher is not running,
		2420	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2421	as applicable.
2118		2422
2119	=head3 Watcher-Specific Functions and Data Members	2423	=head3 Watcher-Specific Functions and Data Members
2120		2424
2121	=over 4	2425	=over 4
2122		2426
…		…
2148	event loop. If that is not possible, use the default loop. The default	2452	event loop. If that is not possible, use the default loop. The default
2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in	2453	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2454	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2455	used).
2152		2456
2153	struct ev_loop *loop_hi = ev_default_init (0);	2457	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2458	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2459	ev_embed embed;
2156		2460
2157	// see if there is a chance of getting one that works	2461	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2462	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2463	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2464	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	2465	: 0;
2162		2466
2163	// if we got one, then embed it, otherwise default to loop_hi	2467	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	2468	if (loop_lo)
2165	{	2469	{
2166	ev_embed_init (&embed, 0, loop_lo);	2470	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	2471	ev_embed_start (loop_hi, &embed);
2168	}	2472	}
2169	else	2473	else
2170	loop_lo = loop_hi;	2474	loop_lo = loop_hi;
2171		2475
2172	Example: Check if kqueue is available but not recommended and create	2476	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	2477	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2478	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2479	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2480
2177	struct ev_loop *loop = ev_default_init (0);	2481	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2482	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2483	ev_embed embed;
2180		2484
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2485	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2486	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2487	{
2184	ev_embed_init (&embed, 0, loop_socket);	2488	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	2489	ev_embed_start (loop, &embed);
2186	}	2490	}
2187		2491
2188	if (!loop_socket)	2492	if (!loop_socket)
2189	loop_socket = loop;	2493	loop_socket = loop;
2190		2494
2191	// now use loop_socket for all sockets, and loop for everything else	2495	// now use loop_socket for all sockets, and loop for everything else
2192		2496
2193		2497
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2498	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		2499
2196	Fork watchers are called when a C<fork ()> was detected (usually because	2500	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2544	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2545	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2546	need elaborate support such as pthreads.
2243		2547
2244	That means that if you want to queue data, you have to provide your own	2548	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2549	queue. But at least I can tell you how to implement locking around your
2246	queue:	2550	queue:
2247		2551
2248	=over 4	2552	=over 4
2249		2553
2250	=item queueing from a signal handler context	2554	=item queueing from a signal handler context
2251		2555
2252	To implement race-free queueing, you simply add to the queue in the signal	2556	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2557	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2558	an example that does that for some fictitious SIGUSR1 handler:
2255		2559
2256	static ev_async mysig;	2560	static ev_async mysig;
2257		2561
2258	static void	2562	static void
2259	sigusr1_handler (void)	2563	sigusr1_handler (void)
…		…
2326		2630
2327	=item ev_async_init (ev_async *, callback)	2631	=item ev_async_init (ev_async *, callback)
2328		2632
2329	Initialises and configures the async watcher - it has no parameters of any	2633	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2331	believe me.	2635	trust me.
2332		2636
2333	=item ev_async_send (loop, ev_async *)	2637	=item ev_async_send (loop, ev_async *)
2334		2638
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	2641	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2643	section below on what exactly this means).
2340		2644
2341	This call incurs the overhead of a system call only once per loop iteration,	2645	This call incurs the overhead of a system call only once per loop iteration,
2342	so while the overhead might be noticeable, it doesn't apply to repeated	2646	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2366	=over 4	2670	=over 4
2367		2671
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2672	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		2673
2370	This function combines a simple timer and an I/O watcher, calls your	2674	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	2675	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	2676	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	2677	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	2678	more watchers yourself.
2375		2679
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	2680	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2681	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	2682	the given C<fd> and C<events> set will be created and started.
2379		2683
2380	If C<timeout> is less than 0, then no timeout watcher will be	2684	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2685	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2686	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		2687
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2688	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	2689	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2691	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2692	a timeout and an io event at the same time - you probably should give io
		2693	events precedence.
2389		2694
		2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2696
2390	static void stdin_ready (int revents, void *arg)	2697	static void stdin_ready (int revents, void *arg)
2391	{	2698	{
2392	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	2699	if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	2700	/* stdin might have data for us, joy! */;
		2701	else if (revents & EV_TIMEOUT)
		2702	/* doh, nothing entered */;
2396	}	2703	}
2397		2704
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2706
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2707	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		2708
2402	Feeds the given event set into the event loop, as if the specified event	2709	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an	2710	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	2711	initialised but not necessarily started event watcher).
2405		2712
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		2714
2408	Feed an event on the given fd, as if a file descriptor backend detected	2715	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	2716	the given events it.
2410		2717
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		2719
2413	Feed an event as if the given signal occurred (C<loop> must be the default	2720	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	2721	loop!).
2415		2722
2416	=back	2723	=back
…		…
2452	you to use some convenience methods to start/stop watchers and also change	2759	you to use some convenience methods to start/stop watchers and also change
2453	the callback model to a model using method callbacks on objects.	2760	the callback model to a model using method callbacks on objects.
2454		2761
2455	To use it,	2762	To use it,
2456		2763
2457	#include <ev++.h>	2764	#include <ev++.h>
2458		2765
2459	This automatically includes F<ev.h> and puts all of its definitions (many	2766	This automatically includes F<ev.h> and puts all of its definitions (many
2460	of them macros) into the global namespace. All C++ specific things are	2767	of them macros) into the global namespace. All C++ specific things are
2461	put into the C<ev> namespace. It should support all the same embedding	2768	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2769	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	2836	your compiler is good :), then the method will be fully inlined into the
2530	thunking function, making it as fast as a direct C callback.	2837	thunking function, making it as fast as a direct C callback.
2531		2838
2532	Example: simple class declaration and watcher initialisation	2839	Example: simple class declaration and watcher initialisation
2533		2840
2534	struct myclass	2841	struct myclass
2535	{	2842	{
2536	void io_cb (ev::io &w, int revents) { }	2843	void io_cb (ev::io &w, int revents) { }
2537	}	2844	}
2538		2845
2539	myclass obj;	2846	myclass obj;
2540	ev::io iow;	2847	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	2848	iow.set <myclass, &myclass::io_cb> (&obj);
2542		2849
2543	=item w->set<function> (void *data = 0)	2850	=item w->set<function> (void *data = 0)
2544		2851
2545	Also sets a callback, but uses a static method or plain function as	2852	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	2853	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		2855
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2856	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		2857
2551	See the method-C<set> above for more details.	2858	See the method-C<set> above for more details.
2552		2859
2553	Example:	2860	Example: Use a plain function as callback.
2554		2861
2555	static void io_cb (ev::io &w, int revents) { }	2862	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	2863	iow.set <io_cb> ();
2557		2864
2558	=item w->set (struct ev_loop *)	2865	=item w->set (struct ev_loop *)
2559		2866
2560	Associates a different C<struct ev_loop> with this watcher. You can only	2867	Associates a different C<struct ev_loop> with this watcher. You can only
2561	do this when the watcher is inactive (and not pending either).	2868	do this when the watcher is inactive (and not pending either).
…		…
2594	=back	2901	=back
2595		2902
2596	Example: Define a class with an IO and idle watcher, start one of them in	2903	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	2904	the constructor.
2598		2905
2599	class myclass	2906	class myclass
2600	{	2907	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	2908	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		2910
2604	myclass (int fd)	2911	myclass (int fd)
2605	{	2912	{
2606	io .set <myclass, &myclass::io_cb > (this);	2913	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	2914	idle.set <myclass, &myclass::idle_cb> (this);
2608		2915
2609	io.start (fd, ev::READ);	2916	io.start (fd, ev::READ);
2610	}	2917	}
2611	};	2918	};
2612		2919
2613		2920
2614	=head1 OTHER LANGUAGE BINDINGS	2921	=head1 OTHER LANGUAGE BINDINGS
2615		2922
2616	Libev does not offer other language bindings itself, but bindings for a	2923	Libev does not offer other language bindings itself, but bindings for a
…		…
2623	=item Perl	2930	=item Perl
2624		2931
2625	The EV module implements the full libev API and is actually used to test	2932	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	2933	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	2934	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2935	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2936	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2937	and C<EV::Glib>).
2630		2938
2631	It can be found and installed via CPAN, its homepage is found at	2939	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	2940	L<http://software.schmorp.de/pkg/EV>.
		2941
		2942	=item Python
		2943
		2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2945	seems to be quite complete and well-documented. Note, however, that the
		2946	patch they require for libev is outright dangerous as it breaks the ABI
		2947	for everybody else, and therefore, should never be applied in an installed
		2948	libev (if python requires an incompatible ABI then it needs to embed
		2949	libev).
2633		2950
2634	=item Ruby	2951	=item Ruby
2635		2952
2636	Tony Arcieri has written a ruby extension that offers access to a subset	2953	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds file handle abstractions, asynchronous DNS and	2954	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
2639	L<http://rev.rubyforge.org/>.	2956	L<http://rev.rubyforge.org/>.
2640		2957
2641	=item D	2958	=item D
2642		2959
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2962
		2963	=item Ocaml
		2964
		2965	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2966	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2645		2967
2646	=back	2968	=back
2647		2969
2648		2970
2649	=head1 MACRO MAGIC	2971	=head1 MACRO MAGIC
…		…
2661		2983
2662	This provides the loop I<argument> for functions, if one is required ("ev	2984	This provides the loop I<argument> for functions, if one is required ("ev
2663	loop argument"). The C<EV_A> form is used when this is the sole argument,	2985	loop argument"). The C<EV_A> form is used when this is the sole argument,
2664	C<EV_A_> is used when other arguments are following. Example:	2986	C<EV_A_> is used when other arguments are following. Example:
2665		2987
2666	ev_unref (EV_A);	2988	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	2989	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	2990	ev_loop (EV_A_ 0);
2669		2991
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2992	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	2993	which is often provided by the following macro.
2672		2994
2673	=item C<EV_P>, C<EV_P_>	2995	=item C<EV_P>, C<EV_P_>
2674		2996
2675	This provides the loop I<parameter> for functions, if one is required ("ev	2997	This provides the loop I<parameter> for functions, if one is required ("ev
2676	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2998	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2677	C<EV_P_> is used when other parameters are following. Example:	2999	C<EV_P_> is used when other parameters are following. Example:
2678		3000
2679	// this is how ev_unref is being declared	3001	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	3002	static void ev_unref (EV_P);
2681		3003
2682	// this is how you can declare your typical callback	3004	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	3005	static void cb (EV_P_ ev_timer *w, int revents)
2684		3006
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3007	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	3008	suitable for use with C<EV_A>.
2687		3009
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3010	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		3026
2705	Example: Declare and initialise a check watcher, utilising the above	3027	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	3028	macros so it will work regardless of whether multiple loops are supported
2707	or not.	3029	or not.
2708		3030
2709	static void	3031	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	3032	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	3033	{
2712	ev_check_stop (EV_A_ w);	3034	ev_check_stop (EV_A_ w);
2713	}	3035	}
2714		3036
2715	ev_check check;	3037	ev_check check;
2716	ev_check_init (&check, check_cb);	3038	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	3039	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	3040	ev_loop (EV_DEFAULT_ 0);
2719		3041
2720	=head1 EMBEDDING	3042	=head1 EMBEDDING
2721		3043
2722	Libev can (and often is) directly embedded into host	3044	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	3045	applications. Examples of applications that embed it include the Deliantra
…		…
2737	=head3 CORE EVENT LOOP	3059	=head3 CORE EVENT LOOP
2738		3060
2739	To include only the libev core (all the C<ev_*> functions), with manual	3061	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	3062	configuration (no autoconf):
2741		3063
2742	#define EV_STANDALONE 1	3064	#define EV_STANDALONE 1
2743	#include "ev.c"	3065	#include "ev.c"
2744		3066
2745	This will automatically include F<ev.h>, too, and should be done in a	3067	This will automatically include F<ev.h>, too, and should be done in a
2746	single C source file only to provide the function implementations. To use	3068	single C source file only to provide the function implementations. To use
2747	it, do the same for F<ev.h> in all files wishing to use this API (best	3069	it, do the same for F<ev.h> in all files wishing to use this API (best
2748	done by writing a wrapper around F<ev.h> that you can include instead and	3070	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	3071	where you can put other configuration options):
2750		3072
2751	#define EV_STANDALONE 1	3073	#define EV_STANDALONE 1
2752	#include "ev.h"	3074	#include "ev.h"
2753		3075
2754	Both header files and implementation files can be compiled with a C++	3076	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	3077	compiler (at least, thats a stated goal, and breakage will be treated
2756	as a bug).	3078	as a bug).
2757		3079
2758	You need the following files in your source tree, or in a directory	3080	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	3081	in your include path (e.g. in libev/ when using -Ilibev):
2760		3082
2761	ev.h	3083	ev.h
2762	ev.c	3084	ev.c
2763	ev_vars.h	3085	ev_vars.h
2764	ev_wrap.h	3086	ev_wrap.h
2765		3087
2766	ev_win32.c required on win32 platforms only	3088	ev_win32.c required on win32 platforms only
2767		3089
2768	ev_select.c only when select backend is enabled (which is enabled by default)	3090	ev_select.c only when select backend is enabled (which is enabled by default)
2769	ev_poll.c only when poll backend is enabled (disabled by default)	3091	ev_poll.c only when poll backend is enabled (disabled by default)
2770	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3092	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2771	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3093	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2772	ev_port.c only when the solaris port backend is enabled (disabled by default)	3094	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		3095
2774	F<ev.c> includes the backend files directly when enabled, so you only need	3096	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	3097	to compile this single file.
2776		3098
2777	=head3 LIBEVENT COMPATIBILITY API	3099	=head3 LIBEVENT COMPATIBILITY API
2778		3100
2779	To include the libevent compatibility API, also include:	3101	To include the libevent compatibility API, also include:
2780		3102
2781	#include "event.c"	3103	#include "event.c"
2782		3104
2783	in the file including F<ev.c>, and:	3105	in the file including F<ev.c>, and:
2784		3106
2785	#include "event.h"	3107	#include "event.h"
2786		3108
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	3109	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		3110
2789	You need the following additional files for this:	3111	You need the following additional files for this:
2790		3112
2791	event.h	3113	event.h
2792	event.c	3114	event.c
2793		3115
2794	=head3 AUTOCONF SUPPORT	3116	=head3 AUTOCONF SUPPORT
2795		3117
2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in	3118	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2797	whatever way you want, you can also C<m4_include([libev.m4])> in your	3119	whatever way you want, you can also C<m4_include([libev.m4])> in your
2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3120	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	3121	include F<config.h> and configure itself accordingly.
2800		3122
2801	For this of course you need the m4 file:	3123	For this of course you need the m4 file:
2802		3124
2803	libev.m4	3125	libev.m4
2804		3126
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3127	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3128
2807	Libev can be configured via a variety of preprocessor symbols you have to	3129	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absence of	3130	define before including any of its files. The default in the absence of
2809	autoconf is noted for every option.	3131	autoconf is documented for every option.
2810		3132
2811	=over 4	3133	=over 4
2812		3134
2813	=item EV_STANDALONE	3135	=item EV_STANDALONE
2814		3136
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3306	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	3307	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	3308	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3309	fine.
2988		3310
2989	If your embedding application does not need any priorities, defining these both to	3311	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3312	both to C<0> will save some memory and CPU.
2991		3313
2992	=item EV_PERIODIC_ENABLE	3314	=item EV_PERIODIC_ENABLE
2993		3315
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3316	If undefined or defined to be C<1>, then periodic timers are supported. If
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	3317	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3002	code.	3324	code.
3003		3325
3004	=item EV_EMBED_ENABLE	3326	=item EV_EMBED_ENABLE
3005		3327
3006	If undefined or defined to be C<1>, then embed watchers are supported. If	3328	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.	3329	defined to be C<0>, then they are not. Embed watchers rely on most other
		3330	watcher types, which therefore must not be disabled.
3008		3331
3009	=item EV_STAT_ENABLE	3332	=item EV_STAT_ENABLE
3010		3333
3011	If undefined or defined to be C<1>, then stat watchers are supported. If	3334	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.	3335	defined to be C<0>, then they are not.
…		…
3044	two).	3367	two).
3045		3368
3046	=item EV_USE_4HEAP	3369	=item EV_USE_4HEAP
3047		3370
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3371	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3372	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	3373	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	3374	faster performance with many (thousands) of watchers.
3052		3375
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3376	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3054	(disabled).	3377	(disabled).
3055		3378
3056	=item EV_HEAP_CACHE_AT	3379	=item EV_HEAP_CACHE_AT
3057		3380
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3381	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	3382	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3383	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3384	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	3385	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	3386	noticeably with many (hundreds) of watchers.
3064		3387
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3066	(disabled).	3389	(disabled).
3067		3390
3068	=item EV_VERIFY	3391	=item EV_VERIFY
…		…
3074	called once per loop, which can slow down libev. If set to C<3>, then the	3397	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	3398	verification code will be called very frequently, which will slow down
3076	libev considerably.	3399	libev considerably.
3077		3400
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3401	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3079	C<0.>	3402	C<0>.
3080		3403
3081	=item EV_COMMON	3404	=item EV_COMMON
3082		3405
3083	By default, all watchers have a C<void *data> member. By redefining	3406	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	3407	this macro to a something else you can include more and other types of
3085	members. You have to define it each time you include one of the files,	3408	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	3409	though, and it must be identical each time.
3087		3410
3088	For example, the perl EV module uses something like this:	3411	For example, the perl EV module uses something like this:
3089		3412
3090	#define EV_COMMON \	3413	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	3414	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	3415	SV *cb_sv, *fh /* note no trailing ";" */
3093		3416
3094	=item EV_CB_DECLARE (type)	3417	=item EV_CB_DECLARE (type)
3095		3418
3096	=item EV_CB_INVOKE (watcher, revents)	3419	=item EV_CB_INVOKE (watcher, revents)
3097		3420
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	3425	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	3426	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3427	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	3428	method calls instead of plain function calls in C++.
3106		3429
		3430	=back
		3431
3107	=head2 EXPORTED API SYMBOLS	3432	=head2 EXPORTED API SYMBOLS
3108		3433
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	3434	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	3435	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	3436	all public symbols, one per line:
3112		3437
3113	Symbols.ev for libev proper	3438	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	3439	Symbols.event for the libevent emulation
3115		3440
3116	This can also be used to rename all public symbols to avoid clashes with	3441	This can also be used to rename all public symbols to avoid clashes with
3117	multiple versions of libev linked together (which is obviously bad in	3442	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvenient to avoid this).	3443	itself, but sometimes it is inconvenient to avoid this).
3119		3444
…		…
3140	file.	3465	file.
3141		3466
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3467	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3143	that everybody includes and which overrides some configure choices:	3468	that everybody includes and which overrides some configure choices:
3144		3469
3145	#define EV_MINIMAL 1	3470	#define EV_MINIMAL 1
3146	#define EV_USE_POLL 0	3471	#define EV_USE_POLL 0
3147	#define EV_MULTIPLICITY 0	3472	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	3473	#define EV_PERIODIC_ENABLE 0
3149	#define EV_STAT_ENABLE 0	3474	#define EV_STAT_ENABLE 0
3150	#define EV_FORK_ENABLE 0	3475	#define EV_FORK_ENABLE 0
3151	#define EV_CONFIG_H <config.h>	3476	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0	3477	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0	3478	#define EV_MAXPRI 0
3154		3479
3155	#include "ev++.h"	3480	#include "ev++.h"
3156		3481
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3482	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		3483
3159	#include "ev_cpp.h"	3484	#include "ev_cpp.h"
3160	#include "ev.c"	3485	#include "ev.c"
3161		3486
		3487	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		3488
3163	=head1 THREADS AND COROUTINES	3489	=head2 THREADS AND COROUTINES
3164		3490
3165	=head2 THREADS	3491	=head3 THREADS
3166		3492
3167	Libev itself is completely thread-safe, but it uses no locking. This	3493	All libev functions are reentrant and thread-safe unless explicitly
		3494	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	3495	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	3496	are no concurrent calls into any libev function with the same loop
3170	parameter.	3497	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3498	of course): libev guarantees that different event loops share no data
		3499	structures that need any locking.
3171		3500
3172	Or put differently: calls with different loop parameters can be done in	3501	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	3502	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	3503	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	3504	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	3505	a mutex per loop).
3177		3506
3178	If you want to know which design is best for your problem, then I cannot	3507	Specifically to support threads (and signal handlers), libev implements
		3508	so-called C<ev_async> watchers, which allow some limited form of
		3509	concurrency on the same event loop, namely waking it up "from the
		3510	outside".
		3511
		3512	If you want to know which design (one loop, locking, or multiple loops
		3513	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	3514	help you, but here is some generic advice:
3180		3515
3181	=over 4	3516	=over 4
3182		3517
3183	=item * most applications have a main thread: use the default libev loop	3518	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a separate thread running only the default loop.	3519	in that thread, or create a separate thread running only the default loop.
…		…
3196		3531
3197	Choosing a model is hard - look around, learn, know that usually you can do	3532	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	3533	better than you currently do :-)
3199		3534
3200	=item * often you need to talk to some other thread which blocks in the	3535	=item * often you need to talk to some other thread which blocks in the
		3536	event loop.
		3537
3201	event loop - C<ev_async> watchers can be used to wake them up from other	3538	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	3539	(or from signal contexts...).
		3540
		3541	An example use would be to communicate signals or other events that only
		3542	work in the default loop by registering the signal watcher with the
		3543	default loop and triggering an C<ev_async> watcher from the default loop
		3544	watcher callback into the event loop interested in the signal.
3203		3545
3204	=back	3546	=back
3205		3547
3206	=head2 COROUTINES	3548	=head3 COROUTINES
3207		3549
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	3550	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	3551	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3552	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	3553	different coroutines, and switch freely between both coroutines running the
3212	loop, as long as you don't confuse yourself). The only exception is that	3554	loop, as long as you don't confuse yourself). The only exception is that
3213	you must not do this from C<ev_periodic> reschedule callbacks.	3555	you must not do this from C<ev_periodic> reschedule callbacks.
3214		3556
3215	Care has been invested into making sure that libev does not keep local	3557	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	3559	they do not clal any callbacks.
3218		3560
		3561	=head2 COMPILER WARNINGS
3219		3562
3220	=head1 COMPLEXITIES	3563	Depending on your compiler and compiler settings, you might get no or a
		3564	lot of warnings when compiling libev code. Some people are apparently
		3565	scared by this.
3221		3566
3222	In this section the complexities of (many of) the algorithms used inside	3567	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	3568	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	3569	warning options. "Warn-free" code therefore cannot be a goal except when
		3570	targeting a specific compiler and compiler-version.
3225		3571
3226	All of the following are about amortised time: If an array needs to be	3572	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	3573	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	3574	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		3575
3232	=over 4	3576	And of course, some compiler warnings are just plain stupid, or simply
		3577	wrong (because they don't actually warn about the condition their message
		3578	seems to warn about). For example, certain older gcc versions had some
		3579	warnings that resulted an extreme number of false positives. These have
		3580	been fixed, but some people still insist on making code warn-free with
		3581	such buggy versions.
3233		3582
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3583	While libev is written to generate as few warnings as possible,
		3584	"warn-free" code is not a goal, and it is recommended not to build libev
		3585	with any compiler warnings enabled unless you are prepared to cope with
		3586	them (e.g. by ignoring them). Remember that warnings are just that:
		3587	warnings, not errors, or proof of bugs.
3235		3588
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		3589
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3590	=head2 VALGRIND
3241		3591
3242	That means that changing a timer costs less than removing/adding them	3592	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	3593	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		3594
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3595	If you think you found a bug (memory leak, uninitialised data access etc.)
		3596	in libev, then check twice: If valgrind reports something like:
3246		3597
3247	These just add the watcher into an array or at the head of a list.	3598	==2274== definitely lost: 0 bytes in 0 blocks.
		3599	==2274== possibly lost: 0 bytes in 0 blocks.
		3600	==2274== still reachable: 256 bytes in 1 blocks.
3248		3601
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3602	Then there is no memory leak, just as memory accounted to global variables
		3603	is not a memleak - the memory is still being refernced, and didn't leak.
3250		3604
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3605	Similarly, under some circumstances, valgrind might report kernel bugs
		3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3607	although an acceptable workaround has been found here), or it might be
		3608	confused.
3252		3609
3253	These watchers are stored in lists then need to be walked to find the	3610	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	3611	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		3612
3257	=item Finding the next timer in each loop iteration: O(1)	3613	If you are unsure about something, feel free to contact the mailing list
		3614	with the full valgrind report and an explanation on why you think this
		3615	is a bug in libev (best check the archives, too :). However, don't be
		3616	annoyed when you get a brisk "this is no bug" answer and take the chance
		3617	of learning how to interpret valgrind properly.
3258		3618
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	3619	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	3620	I suggest using suppression lists.
3261		3621
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		3622
3264	A change means an I/O watcher gets started or stopped, which requires	3623	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and whether C<ev_io_set> was used).
3267		3624
3268	=item Activating one watcher (putting it into the pending state): O(1)	3625	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3269
3270	=item Priority handling: O(number_of_priorities)
3271
3272	Priorities are implemented by allocating some space for each
3273	priority. When doing priority-based operations, libev usually has to
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276
3277	=item Sending an ev_async: O(1)
3278
3279	=item Processing ev_async_send: O(number_of_async_watchers)
3280
3281	=item Processing signals: O(max_signal_number)
3282
3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
3284	calls in the current loop iteration. Checking for async and signal events
3285	involves iterating over all running async watchers or all signal numbers.
3286
3287	=back
3288
3289
3290	=head1 Win32 platform limitations and workarounds
3291		3626
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3627	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	3628	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	3629	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3630	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3301	things, then note that glib does exactly that for you in a very portable	3636	things, then note that glib does exactly that for you in a very portable
3302	way (note also that glib is the slowest event library known to man).	3637	way (note also that glib is the slowest event library known to man).
3303		3638
3304	There is no supported compilation method available on windows except	3639	There is no supported compilation method available on windows except
3305	embedding it into other applications.	3640	embedding it into other applications.
		3641
		3642	Not a libev limitation but worth mentioning: windows apparently doesn't
		3643	accept large writes: instead of resulting in a partial write, windows will
		3644	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3645	so make sure you only write small amounts into your sockets (less than a
		3646	megabyte seems safe, but this apparently depends on the amount of memory
		3647	available).
3306		3648
3307	Due to the many, low, and arbitrary limits on the win32 platform and	3649	Due to the many, low, and arbitrary limits on the win32 platform and
3308	the abysmal performance of winsockets, using a large number of sockets	3650	the abysmal performance of winsockets, using a large number of sockets
3309	is not recommended (and not reasonable). If your program needs to use	3651	is not recommended (and not reasonable). If your program needs to use
3310	more than a hundred or so sockets, then likely it needs to use a totally	3652	more than a hundred or so sockets, then likely it needs to use a totally
3311	different implementation for windows, as libev offers the POSIX readiness	3653	different implementation for windows, as libev offers the POSIX readiness
3312	notification model, which cannot be implemented efficiently on windows	3654	notification model, which cannot be implemented efficiently on windows
3313	(Microsoft monopoly games).	3655	(Microsoft monopoly games).
3314		3656
		3657	A typical way to use libev under windows is to embed it (see the embedding
		3658	section for details) and use the following F<evwrap.h> header file instead
		3659	of F<ev.h>:
		3660
		3661	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3662	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3663
		3664	#include "ev.h"
		3665
		3666	And compile the following F<evwrap.c> file into your project (make sure
		3667	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3668
		3669	#include "evwrap.h"
		3670	#include "ev.c"
		3671
3315	=over 4	3672	=over 4
3316		3673
3317	=item The winsocket select function	3674	=item The winsocket select function
3318		3675
3319	The winsocket C<select> function doesn't follow POSIX in that it	3676	The winsocket C<select> function doesn't follow POSIX in that it
3320	requires socket I<handles> and not socket I<file descriptors> (it is	3677	requires socket I<handles> and not socket I<file descriptors> (it is
3321	also extremely buggy). This makes select very inefficient, and also	3678	also extremely buggy). This makes select very inefficient, and also
3322	requires a mapping from file descriptors to socket handles. See the	3679	requires a mapping from file descriptors to socket handles (the Microsoft
		3680	C runtime provides the function C<_open_osfhandle> for this). See the
3323	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	3681	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3324	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	3682	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3325		3683
3326	The configuration for a "naked" win32 using the Microsoft runtime	3684	The configuration for a "naked" win32 using the Microsoft runtime
3327	libraries and raw winsocket select is:	3685	libraries and raw winsocket select is:
3328		3686
3329	#define EV_USE_SELECT 1	3687	#define EV_USE_SELECT 1
3330	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3688	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3331		3689
3332	Note that winsockets handling of fd sets is O(n), so you can easily get a	3690	Note that winsockets handling of fd sets is O(n), so you can easily get a
3333	complexity in the O(n²) range when using win32.	3691	complexity in the O(n²) range when using win32.
3334		3692
3335	=item Limited number of file descriptors	3693	=item Limited number of file descriptors
…		…
3359	wrap all I/O functions and provide your own fd management, but the cost of	3717	wrap all I/O functions and provide your own fd management, but the cost of
3360	calling select (O(n²)) will likely make this unworkable.	3718	calling select (O(n²)) will likely make this unworkable.
3361		3719
3362	=back	3720	=back
3363		3721
3364
3365	=head1 PORTABILITY REQUIREMENTS	3722	=head2 PORTABILITY REQUIREMENTS
3366		3723
3367	In addition to a working ISO-C implementation, libev relies on a few	3724	In addition to a working ISO-C implementation and of course the
3368	additional extensions:	3725	backend-specific APIs, libev relies on a few additional extensions:
3369		3726
3370	=over 4	3727	=over 4
3371		3728
		3729	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3730	calling conventions regardless of C<ev_watcher_type *>.
		3731
		3732	Libev assumes not only that all watcher pointers have the same internal
		3733	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3734	assumes that the same (machine) code can be used to call any watcher
		3735	callback: The watcher callbacks have different type signatures, but libev
		3736	calls them using an C<ev_watcher *> internally.
		3737
3372	=item C<sig_atomic_t volatile> must be thread-atomic as well	3738	=item C<sig_atomic_t volatile> must be thread-atomic as well
3373		3739
3374	The type C<sig_atomic_t volatile> (or whatever is defined as	3740	The type C<sig_atomic_t volatile> (or whatever is defined as
3375	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3741	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3376	threads. This is not part of the specification for C<sig_atomic_t>, but is	3742	threads. This is not part of the specification for C<sig_atomic_t>, but is
3377	believed to be sufficiently portable.	3743	believed to be sufficiently portable.
3378		3744
3379	=item C<sigprocmask> must work in a threaded environment	3745	=item C<sigprocmask> must work in a threaded environment
3380		3746
…		…
3389	except the initial one, and run the default loop in the initial thread as	3755	except the initial one, and run the default loop in the initial thread as
3390	well.	3756	well.
3391		3757
3392	=item C<long> must be large enough for common memory allocation sizes	3758	=item C<long> must be large enough for common memory allocation sizes
3393		3759
3394	To improve portability and simplify using libev, libev uses C<long>	3760	To improve portability and simplify its API, libev uses C<long> internally
3395	internally instead of C<size_t> when allocating its data structures. On	3761	instead of C<size_t> when allocating its data structures. On non-POSIX
3396	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3762	systems (Microsoft...) this might be unexpectedly low, but is still at
3397	is still at least 31 bits everywhere, which is enough for hundreds of	3763	least 31 bits everywhere, which is enough for hundreds of millions of
3398	millions of watchers.	3764	watchers.
3399		3765
3400	=item C<double> must hold a time value in seconds with enough accuracy	3766	=item C<double> must hold a time value in seconds with enough accuracy
3401		3767
3402	The type C<double> is used to represent timestamps. It is required to	3768	The type C<double> is used to represent timestamps. It is required to
3403	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3769	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3407	=back	3773	=back
3408		3774
3409	If you know of other additional requirements drop me a note.	3775	If you know of other additional requirements drop me a note.
3410		3776
3411		3777
3412	=head1 COMPILER WARNINGS	3778	=head1 ALGORITHMIC COMPLEXITIES
3413		3779
3414	Depending on your compiler and compiler settings, you might get no or a	3780	In this section the complexities of (many of) the algorithms used inside
3415	lot of warnings when compiling libev code. Some people are apparently	3781	libev will be documented. For complexity discussions about backends see
3416	scared by this.	3782	the documentation for C<ev_default_init>.
3417		3783
3418	However, these are unavoidable for many reasons. For one, each compiler	3784	All of the following are about amortised time: If an array needs to be
3419	has different warnings, and each user has different tastes regarding	3785	extended, libev needs to realloc and move the whole array, but this
3420	warning options. "Warn-free" code therefore cannot be a goal except when	3786	happens asymptotically rarer with higher number of elements, so O(1) might
3421	targeting a specific compiler and compiler-version.	3787	mean that libev does a lengthy realloc operation in rare cases, but on
		3788	average it is much faster and asymptotically approaches constant time.
3422		3789
3423	Another reason is that some compiler warnings require elaborate	3790	=over 4
3424	workarounds, or other changes to the code that make it less clear and less
3425	maintainable.
3426		3791
3427	And of course, some compiler warnings are just plain stupid, or simply	3792	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3428	wrong (because they don't actually warn about the condition their message
3429	seems to warn about).
3430		3793
3431	While libev is written to generate as few warnings as possible,	3794	This means that, when you have a watcher that triggers in one hour and
3432	"warn-free" code is not a goal, and it is recommended not to build libev	3795	there are 100 watchers that would trigger before that, then inserting will
3433	with any compiler warnings enabled unless you are prepared to cope with	3796	have to skip roughly seven (C<ld 100>) of these watchers.
3434	them (e.g. by ignoring them). Remember that warnings are just that:
3435	warnings, not errors, or proof of bugs.
3436		3797
		3798	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3437		3799
3438	=head1 VALGRIND	3800	That means that changing a timer costs less than removing/adding them,
		3801	as only the relative motion in the event queue has to be paid for.
3439		3802
3440	Valgrind has a special section here because it is a popular tool that is	3803	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3441	highly useful, but valgrind reports are very hard to interpret.
3442		3804
3443	If you think you found a bug (memory leak, uninitialised data access etc.)	3805	These just add the watcher into an array or at the head of a list.
3444	in libev, then check twice: If valgrind reports something like:
3445		3806
3446	==2274== definitely lost: 0 bytes in 0 blocks.	3807	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3447	==2274== possibly lost: 0 bytes in 0 blocks.
3448	==2274== still reachable: 256 bytes in 1 blocks.
3449		3808
3450	Then there is no memory leak. Similarly, under some circumstances,	3809	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3451	valgrind might report kernel bugs as if it were a bug in libev, or it
3452	might be confused (it is a very good tool, but only a tool).
3453		3810
3454	If you are unsure about something, feel free to contact the mailing list	3811	These watchers are stored in lists, so they need to be walked to find the
3455	with the full valgrind report and an explanation on why you think this is	3812	correct watcher to remove. The lists are usually short (you don't usually
3456	a bug in libev. However, don't be annoyed when you get a brisk "this is	3813	have many watchers waiting for the same fd or signal: one is typical, two
3457	no bug" answer and take the chance of learning how to interpret valgrind	3814	is rare).
3458	properly.
3459		3815
3460	If you need, for some reason, empty reports from valgrind for your project	3816	=item Finding the next timer in each loop iteration: O(1)
3461	I suggest using suppression lists.	3817
		3818	By virtue of using a binary or 4-heap, the next timer is always found at a
		3819	fixed position in the storage array.
		3820
		3821	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3822
		3823	A change means an I/O watcher gets started or stopped, which requires
		3824	libev to recalculate its status (and possibly tell the kernel, depending
		3825	on backend and whether C<ev_io_set> was used).
		3826
		3827	=item Activating one watcher (putting it into the pending state): O(1)
		3828
		3829	=item Priority handling: O(number_of_priorities)
		3830
		3831	Priorities are implemented by allocating some space for each
		3832	priority. When doing priority-based operations, libev usually has to
		3833	linearly search all the priorities, but starting/stopping and activating
		3834	watchers becomes O(1) with respect to priority handling.
		3835
		3836	=item Sending an ev_async: O(1)
		3837
		3838	=item Processing ev_async_send: O(number_of_async_watchers)
		3839
		3840	=item Processing signals: O(max_signal_number)
		3841
		3842	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3843	calls in the current loop iteration. Checking for async and signal events
		3844	involves iterating over all running async watchers or all signal numbers.
		3845
		3846	=back
3462		3847
3463		3848
3464	=head1 AUTHOR	3849	=head1 AUTHOR
3465		3850
3466	Marc Lehmann <libev@schmorp.de>.	3851	Marc Lehmann <libev@schmorp.de>.

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