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Revision 1.162 by root, Mon May 26 03:54:40 2008 UTC vs.
Revision 1.205 by root, Mon Oct 27 12:20:32 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.
372		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		385
375	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	388	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	389	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	390
380	cases and requiring a system call per fd change, no fork support and bad	391	The epoll syscalls are the most misdesigned of the more advanced
381	support for dup.	392	event mechanisms: probelsm include silently dropping events in some
		393	hard-to-detect cases, requiring a system call per fd change, no fork
		394	support, problems with dup and so on.
		395
		396	Epoll is also notoriously buggy - embedding epoll fds should work, but
		397	of course doesn't, and epoll just loves to report events for totally
		398	I<different> file descriptors (even already closed ones, so one cannot
		399	even remove them from the set) than registered in the set (especially
		400	on SMP systems). Libev tries to counter these spurious notifications by
		401	employing an additional generation counter and comparing that against the
		402	events to filter out spurious ones.
382		403
383	While stopping, setting and starting an I/O watcher in the same iteration	404	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	405	will result in some caching, there is still a system call per such incident
385	(because the fd could point to a different file description now), so its	406	(because the fd could point to a different file description now), so its
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	407	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
387	very well if you register events for both fds.	408	very well if you register events for both fds.
388		409
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392
393	Best performance from this backend is achieved by not unregistering all	410	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.	411	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	412	i.e. keep at least one watcher active per fd at all times. Stopping and
		413	starting a watcher (without re-setting it) also usually doesn't cause
		414	extra overhead.
396		415
397	While nominally embeddable in other event loops, this feature is broken in	416	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	417	all kernel versions tested so far.
399		418
		419	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		420	C<EVBACKEND_POLL>.
		421
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	422	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		423
402	Kqueue deserves special mention, as at the time of this writing, it	424	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	425	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	426	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"	427	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	428	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)	429	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
408	system like NetBSD.
409		430
410	You still can embed kqueue into a normal poll or select backend and use it	431	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	432	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.	433	the target platform). See C<ev_embed> watchers for more info.
413		434
414	It scales in the same way as the epoll backend, but the interface to the	435	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	436	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	437	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	438	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	439	two event changes per incident. Support for C<fork ()> is very bad and it
419	drops fds silently in similarly hard-to-detect cases.	440	drops fds silently in similarly hard-to-detect cases.
420		441
421	This backend usually performs well under most conditions.	442	This backend usually performs well under most conditions.
422		443
423	While nominally embeddable in other event loops, this doesn't work	444	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	445	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	446	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	447	(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	448	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	449	using it only for sockets.
		450
		451	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		452	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		453	C<NOTE_EOF>.
429		454
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	455	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		456
432	This is not implemented yet (and might never be, unless you send me an	457	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	458	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	471	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	472	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	473	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	474	might perform better.
450		475
451	On the positive side, ignoring the spurious readiness notifications, this	476	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	477	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	478	in all tests and is fully embeddable, which is a rare feat among the
		479	OS-specific backends.
		480
		481	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		482	C<EVBACKEND_POLL>.
454		483
455	=item C<EVBACKEND_ALL>	484	=item C<EVBACKEND_ALL>
456		485
457	Try all backends (even potentially broken ones that wouldn't be tried	486	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	487	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		493
465	If one or more of these are or'ed into the flags value, then only these	494	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	495	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.	496	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		497
469	The most typical usage is like this:	498	Example: This is the most typical usage.
470		499
471	if (!ev_default_loop (0))	500	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	501	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		502
474	Restrict libev to the select and poll backends, and do not allow	503	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	504	environment settings to be taken into account:
476		505
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	506	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		507
479	Use whatever libev has to offer, but make sure that kqueue is used if	508	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	509	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):	510	private event loop and only if you know the OS supports your types of
		511	fds):
482		512
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	513	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		514
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	515	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		516
487	Similar to C<ev_default_loop>, but always creates a new event loop that is	517	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	518	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	523	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.	524	default loop in the "main" or "initial" thread.
495		525
496	Example: Try to create a event loop that uses epoll and nothing else.	526	Example: Try to create a event loop that uses epoll and nothing else.
497		527
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	528	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	529	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	530	fatal ("no epoll found here, maybe it hides under your chair");
501		531
502	=item ev_default_destroy ()	532	=item ev_default_destroy ()
503		533
504	Destroys the default loop again (frees all memory and kernel state	534	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	535	etc.). None of the active event watchers will be stopped in the normal
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	537	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	538	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	539	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	540	for example).
511		541
512	Note that certain global state, such as signal state, will not be freed by	542	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	543	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	544	as signal and child watchers) would need to be stopped manually.
515		545
516	In general it is not advisable to call this function except in the	546	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	547	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	548	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	549	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		574
545	=item ev_loop_fork (loop)	575	=item ev_loop_fork (loop)
546		576
547	Like C<ev_default_fork>, but acts on an event loop created by	577	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	578	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.	579	after fork that you want to re-use in the child, and how you do this is
		580	entirely your own problem.
550		581
551	=item int ev_is_default_loop (loop)	582	=item int ev_is_default_loop (loop)
552		583
553	Returns true when the given loop actually is the default loop, false otherwise.	584	Returns true when the given loop is, in fact, the default loop, and false
		585	otherwise.
554		586
555	=item unsigned int ev_loop_count (loop)	587	=item unsigned int ev_loop_count (loop)
556		588
557	Returns the count of loop iterations for the loop, which is identical to	589	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	590	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	605	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	606	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	607	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).	608	event occurring (or more correctly, libev finding out about it).
577		609
		610	=item ev_now_update (loop)
		611
		612	Establishes the current time by querying the kernel, updating the time
		613	returned by C<ev_now ()> in the progress. This is a costly operation and
		614	is usually done automatically within C<ev_loop ()>.
		615
		616	This function is rarely useful, but when some event callback runs for a
		617	very long time without entering the event loop, updating libev's idea of
		618	the current time is a good idea.
		619
		620	See also "The special problem of time updates" in the C<ev_timer> section.
		621
578	=item ev_loop (loop, int flags)	622	=item ev_loop (loop, int flags)
579		623
580	Finally, this is it, the event handler. This function usually is called	624	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	625	after you initialised all your watchers and you want to start handling
582	events.	626	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	628	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.	629	either no event watchers are active anymore or C<ev_unloop> was called.
586		630
587	Please note that an explicit C<ev_unloop> is usually better than	631	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	632	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	633	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	634	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.	635	of relying on its watchers stopping correctly, that is truly a thing of
		636	beauty.
592		637
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	638	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	639	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.	640	process in case there are no events and will return after one iteration of
		641	the loop.
596		642
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	643	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	644	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	645	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	646	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	647	user-registered callback will be called), and will return after one
		648	iteration of the loop.
		649
		650	This is useful if you are waiting for some external event in conjunction
		651	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	652	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.	653	usually a better approach for this kind of thing.
604		654
605	Here are the gory details of what C<ev_loop> does:	655	Here are the gory details of what C<ev_loop> does:
606		656
607	- Before the first iteration, call any pending watchers.	657	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	658	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	659	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	660	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	661	- If we have been forked, detach and recreate the kernel state
		662	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	663	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	664	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	665	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	666	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	667	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	668	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	669	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	670	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	671	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	672	- Queue all expired timers.
622	- Queue all outstanding periodics.	673	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	674	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	675	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	676	- 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	677	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	678	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	679	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	684	anymore.
634		685
635	... queue jobs here, make sure they register event watchers as long	686	... 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..)	687	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	688	ev_loop (my_loop, 0);
638	... jobs done. yeah!	689	... jobs done or somebody called unloop. yeah!
639		690
640	=item ev_unloop (loop, how)	691	=item ev_unloop (loop, how)
641		692
642	Can be used to make a call to C<ev_loop> return early (but only after it	693	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	694	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	695	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.	696	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		697
647	This "unloop state" will be cleared when entering C<ev_loop> again.	698	This "unloop state" will be cleared when entering C<ev_loop> again.
648		699
		700	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		701
649	=item ev_ref (loop)	702	=item ev_ref (loop)
650		703
651	=item ev_unref (loop)	704	=item ev_unref (loop)
652		705
653	Ref/unref can be used to add or remove a reference count on the event	706	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	707	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	708	count is nonzero, C<ev_loop> will not return on its own.
		709
656	a watcher you never unregister that should not keep C<ev_loop> from	710	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	711	from returning, call ev_unref() after starting, and ev_ref() before
		712	stopping it.
		713
658	example, libev itself uses this for its internal signal pipe: It is not	714	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	715	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	716	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	717	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>	718	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,	719	(but only if the watcher wasn't active before, or was active before,
664	respectively).	720	respectively).
665		721
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	722	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	723	running when nothing else is active.
668		724
669	struct ev_signal exitsig;	725	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	726	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	727	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	728	evf_unref (loop);
673		729
674	Example: For some weird reason, unregister the above signal handler again.	730	Example: For some weird reason, unregister the above signal handler again.
675		731
676	ev_ref (loop);	732	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	733	ev_signal_stop (loop, &exitsig);
678		734
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	735	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		736
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	737	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		738
683	These advanced functions influence the time that libev will spend waiting	739	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	740	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.	741	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		742	latency.
686		743
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	744	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	745	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	746	to increase efficiency of loop iterations (or to increase power-saving
		747	opportunities).
690		748
691	The background is that sometimes your program runs just fast enough to	749	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	750	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	751	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	752	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	753	overhead for the actual polling but can deliver many events at once.
696		754
697	By setting a higher I<io collect interval> you allow libev to spend more	755	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,	756	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	758	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.	759	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		760
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	761	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	762	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	763	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	764	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	765	value will not introduce any overhead in libev.
708		766
709	Many (busy) programs can usually benefit by setting the I/O collect	767	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	768	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	769	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>,	770	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.	771	as this approaches the timing granularity of most systems.
714		772
		773	Setting the I<timeout collect interval> can improve the opportunity for
		774	saving power, as the program will "bundle" timer callback invocations that
		775	are "near" in time together, by delaying some, thus reducing the number of
		776	times the process sleeps and wakes up again. Another useful technique to
		777	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		778	they fire on, say, one-second boundaries only.
		779
715	=item ev_loop_verify (loop)	780	=item ev_loop_verify (loop)
716		781
717	This function only does something when C<EV_VERIFY> support has been	782	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	783	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	784	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	785	is found to be inconsistent, it will print an error message to standard
		786	error and call C<abort ()>.
721		787
722	This can be used to catch bugs inside libev itself: under normal	788	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	789	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	790	data structures consistent.
725		791
726	=back	792	=back
727		793
728		794
729	=head1 ANATOMY OF A WATCHER	795	=head1 ANATOMY OF A WATCHER
730		796
		797	In the following description, uppercase C<TYPE> in names stands for the
		798	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		799	watchers and C<ev_io_start> for I/O watchers.
		800
731	A watcher is a structure that you create and register to record your	801	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	802	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:	803	become readable, you would create an C<ev_io> watcher for that:
734		804
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	805	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	806	{
737	ev_io_stop (w);	807	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	808	ev_unloop (loop, EVUNLOOP_ALL);
739	}	809	}
740		810
741	struct ev_loop *loop = ev_default_loop (0);	811	struct ev_loop *loop = ev_default_loop (0);
		812
742	struct ev_io stdin_watcher;	813	ev_io stdin_watcher;
		814
743	ev_init (&stdin_watcher, my_cb);	815	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	816	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	817	ev_io_start (loop, &stdin_watcher);
		818
746	ev_loop (loop, 0);	819	ev_loop (loop, 0);
747		820
748	As you can see, you are responsible for allocating the memory for your	821	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,	822	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	823	stack).
		824
		825	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		826	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		827
752	Each watcher structure must be initialised by a call to C<ev_init	828	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	829	(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	830	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	831	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	832	is readable and/or writable).
757		833
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	834	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	835	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	836	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	837	ev_TYPE_init (watcher *, callback, ...) >>.
762		838
763	To make the watcher actually watch out for events, you have to start it	839	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	840	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	841	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	842	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		843
768	As long as your watcher is active (has been started but not stopped) you	844	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	845	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	846	reinitialise it or call its C<ev_TYPE_set> macro.
771		847
772	Each and every callback receives the event loop pointer as first, the	848	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	849	registered watcher structure as second, and a bitset of received events as
774	third argument.	850	third argument.
775		851
…		…
838	=item C<EV_ERROR>	914	=item C<EV_ERROR>
839		915
840	An unspecified error has occurred, the watcher has been stopped. This might	916	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	917	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	918	ran out of memory, a file descriptor was found to be closed or any other
		919	problem. Libev considers these application bugs.
		920
843	problem. You best act on it by reporting the problem and somehow coping	921	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	922	watcher being stopped. Note that well-written programs should not receive
		923	an error ever, so when your watcher receives it, this usually indicates a
		924	bug in your program.
845		925
846	Libev will usually signal a few "dummy" events together with an error,	926	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	927	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	928	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	929	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	930	programs, though, as the fd could already be closed and reused for another
		931	thing, so beware.
851		932
852	=back	933	=back
853		934
854	=head2 GENERIC WATCHER FUNCTIONS	935	=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		936
859	=over 4	937	=over 4
860		938
861	=item C<ev_init> (ev_TYPE *watcher, callback)	939	=item C<ev_init> (ev_TYPE *watcher, callback)
862		940
…		…
868	which rolls both calls into one.	946	which rolls both calls into one.
869		947
870	You can reinitialise a watcher at any time as long as it has been stopped	948	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.	949	(or never started) and there are no pending events outstanding.
872		950
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	951	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	952	int revents)>.
		953
		954	Example: Initialise an C<ev_io> watcher in two steps.
		955
		956	ev_io w;
		957	ev_init (&w, my_cb);
		958	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		959
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	960	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		961
878	This macro initialises the type-specific parts of a watcher. You need to	962	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	963	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	966	difference to the C<ev_init> macro).
883		967
884	Although some watcher types do not have type-specific arguments	968	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.	969	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		970
		971	See C<ev_init>, above, for an example.
		972
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	973	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		974
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	975	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	976	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	977	a watcher. The same limitations apply, of course.
892		978
		979	Example: Initialise and set an C<ev_io> watcher in one step.
		980
		981	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		982
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	983	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		984
895	Starts (activates) the given watcher. Only active watchers will receive	985	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	986	events. If the watcher is already active nothing will happen.
897		987
		988	Example: Start the C<ev_io> watcher that is being abused as example in this
		989	whole section.
		990
		991	ev_io_start (EV_DEFAULT_UC, &w);
		992
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	993	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		994
900	Stops the given watcher again (if active) and clears the pending	995	Stops the given watcher if active, and clears the pending status (whether
		996	the watcher was active or not).
		997
901	status. It is possible that stopped watchers are pending (for example,	998	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	999	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	1000	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	1001	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.	1002	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1003
907	=item bool ev_is_active (ev_TYPE *watcher)	1004	=item bool ev_is_active (ev_TYPE *watcher)
908		1005
909	Returns a true value iff the watcher is active (i.e. it has been started	1006	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	1007	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	1049	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 :).	1050	always C<0>, which is supposed to not be too high and not be too low :).
954		1051
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1052	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	1053	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.	1054	or might not have been clamped to the valid range.
958		1055
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1056	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1057
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1058	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	1059	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1060	can deal with that fact, as both are simply passed through to the
		1061	callback.
964		1062
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1063	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1064
967	If the watcher is pending, this function returns clears its pending status	1065	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	1066	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>.	1067	watcher isn't pending it does nothing and returns C<0>.
970		1068
		1069	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1070	callback to be invoked, which can be accomplished with this function.
		1071
971	=back	1072	=back
972		1073
973		1074
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1075	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1076
976	Each watcher has, by default, a member C<void *data> that you can change	1077	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	1078	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	1079	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	1080	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	1081	member, you can also "subclass" the watcher type and provide your own
981	data:	1082	data:
982		1083
983	struct my_io	1084	struct my_io
984	{	1085	{
985	struct ev_io io;	1086	ev_io io;
986	int otherfd;	1087	int otherfd;
987	void *somedata;	1088	void *somedata;
988	struct whatever *mostinteresting;	1089	struct whatever *mostinteresting;
989	}	1090	};
		1091
		1092	...
		1093	struct my_io w;
		1094	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1095
991	And since your callback will be called with a pointer to the watcher, you	1096	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1097	can cast it back to your own type:
993		1098
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1099	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1100	{
996	struct my_io *w = (struct my_io *)w_;	1101	struct my_io *w = (struct my_io *)w_;
997	...	1102	...
998	}	1103	}
999		1104
1000	More interesting and less C-conformant ways of casting your callback type	1105	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1106	instead have been omitted.
1002		1107
1003	Another common scenario is having some data structure with multiple	1108	Another common scenario is to use some data structure with multiple
1004	watchers:	1109	embedded watchers:
1005		1110
1006	struct my_biggy	1111	struct my_biggy
1007	{	1112	{
1008	int some_data;	1113	int some_data;
1009	ev_timer t1;	1114	ev_timer t1;
1010	ev_timer t2;	1115	ev_timer t2;
1011	}	1116	}
1012		1117
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1118	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1119	complicated: Either you store the address of your C<my_biggy> struct
		1120	in the C<data> member of the watcher (for woozies), or you need to use
		1121	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1122	programmers):
1015		1123
1016	#include <stddef.h>	1124	#include <stddef.h>
1017		1125
1018	static void	1126	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1127	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1128	{
1021	struct my_biggy big = (struct my_biggy *	1129	struct my_biggy big = (struct my_biggy *
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1130	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1131	}
1024		1132
1025	static void	1133	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1134	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1135	{
1028	struct my_biggy big = (struct my_biggy *	1136	struct my_biggy big = (struct my_biggy *
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1137	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1138	}
1031		1139
1032		1140
1033	=head1 WATCHER TYPES	1141	=head1 WATCHER TYPES
1034		1142
1035	This section describes each watcher in detail, but will not repeat	1143	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	1167	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	1168	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	1169	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1170	required if you know what you are doing).
1063		1171
1064	If you must do this, then force the use of a known-to-be-good backend	1172	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	1173	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1174	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1175
1068	Another thing you have to watch out for is that it is quite easy to	1176	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	1177	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	1178	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	1179	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	1180	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	1181	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	1182	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.	1183	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1184
1077	If you cannot run the fd in non-blocking mode (for example you should not	1185	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	1186	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	1187	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	1188	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1189	does this on its own, so its quite safe to use). Some people additionally
		1190	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1191	indefinitely.
		1192
		1193	But really, best use non-blocking mode.
1082		1194
1083	=head3 The special problem of disappearing file descriptors	1195	=head3 The special problem of disappearing file descriptors
1084		1196
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1197	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,	1198	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	1199	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	1200	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	1201	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	1202	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1203	fact, a different file descriptor.
1092		1204
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1235	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1236	C<EVBACKEND_POLL>.
1125		1237
1126	=head3 The special problem of SIGPIPE	1238	=head3 The special problem of SIGPIPE
1127		1239
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1240	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	1241	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	1242	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1243	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1244
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1245	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	1246	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).	1247	somewhere, as that would have given you a big clue).
1137		1248
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1254	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1255
1145	=item ev_io_set (ev_io *, int fd, int events)	1256	=item ev_io_set (ev_io *, int fd, int events)
1146		1257
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1258	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	1259	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.	1260	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1261
1151	=item int fd [read-only]	1262	=item int fd [read-only]
1152		1263
1153	The file descriptor being watched.	1264	The file descriptor being watched.
1154		1265
…		…
1162		1273
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1274	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	1275	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1276	attempt to read a whole line in the callback.
1166		1277
1167	static void	1278	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1279	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1280	{
1170	ev_io_stop (loop, w);	1281	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1282	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1283	}
1173		1284
1174	...	1285	...
1175	struct ev_loop *loop = ev_default_init (0);	1286	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1287	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1288	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1289	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1290	ev_loop (loop, 0);
1180		1291
1181		1292
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1293	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1294
1184	Timer watchers are simple relative timers that generate an event after a	1295	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1296	given time, and optionally repeating in regular intervals after that.
1186		1297
1187	The timers are based on real time, that is, if you register an event that	1298	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	1299	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	1300	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1301	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1302	monotonic clock option helps a lot here).
		1303
		1304	The callback is guaranteed to be invoked only I<after> its timeout has
		1305	passed, but if multiple timers become ready during the same loop iteration
		1306	then order of execution is undefined.
		1307
		1308	=head3 Be smart about timeouts
		1309
		1310	Many real-world problems involve some kind of timeout, usually for error
		1311	recovery. A typical example is an HTTP request - if the other side hangs,
		1312	you want to raise some error after a while.
		1313
		1314	What follows are some ways to handle this problem, from obvious and
		1315	inefficient to smart and efficient.
		1316
		1317	In the following, a 60 second activity timeout is assumed - a timeout that
		1318	gets reset to 60 seconds each time there is activity (e.g. each time some
		1319	data or other life sign was received).
		1320
		1321	=over 4
		1322
		1323	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1324
		1325	This is the most obvious, but not the most simple way: In the beginning,
		1326	start the watcher:
		1327
		1328	ev_timer_init (timer, callback, 60., 0.);
		1329	ev_timer_start (loop, timer);
		1330
		1331	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1332	and start it again:
		1333
		1334	ev_timer_stop (loop, timer);
		1335	ev_timer_set (timer, 60., 0.);
		1336	ev_timer_start (loop, timer);
		1337
		1338	This is relatively simple to implement, but means that each time there is
		1339	some activity, libev will first have to remove the timer from its internal
		1340	data structure and then add it again. Libev tries to be fast, but it's
		1341	still not a constant-time operation.
		1342
		1343	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1344
		1345	This is the easiest way, and involves using C<ev_timer_again> instead of
		1346	C<ev_timer_start>.
		1347
		1348	To implement this, configure an C<ev_timer> with a C<repeat> value
		1349	of C<60> and then call C<ev_timer_again> at start and each time you
		1350	successfully read or write some data. If you go into an idle state where
		1351	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1352	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1353
		1354	That means you can ignore both the C<ev_timer_start> function and the
		1355	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1356	member and C<ev_timer_again>.
		1357
		1358	At start:
		1359
		1360	ev_timer_init (timer, callback);
		1361	timer->repeat = 60.;
		1362	ev_timer_again (loop, timer);
		1363
		1364	Each time there is some activity:
		1365
		1366	ev_timer_again (loop, timer);
		1367
		1368	It is even possible to change the time-out on the fly, regardless of
		1369	whether the watcher is active or not:
		1370
		1371	timer->repeat = 30.;
		1372	ev_timer_again (loop, timer);
		1373
		1374	This is slightly more efficient then stopping/starting the timer each time
		1375	you want to modify its timeout value, as libev does not have to completely
		1376	remove and re-insert the timer from/into its internal data structure.
		1377
		1378	It is, however, even simpler than the "obvious" way to do it.
		1379
		1380	=item 3. Let the timer time out, but then re-arm it as required.
		1381
		1382	This method is more tricky, but usually most efficient: Most timeouts are
		1383	relatively long compared to the intervals between other activity - in
		1384	our example, within 60 seconds, there are usually many I/O events with
		1385	associated activity resets.
		1386
		1387	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1388	but remember the time of last activity, and check for a real timeout only
		1389	within the callback:
		1390
		1391	ev_tstamp last_activity; // time of last activity
		1392
		1393	static void
		1394	callback (EV_P_ ev_timer *w, int revents)
		1395	{
		1396	ev_tstamp now = ev_now (EV_A);
		1397	ev_tstamp timeout = last_activity + 60.;
		1398
		1399	// if last_activity + 60. is older than now, we did time out
		1400	if (timeout < now)
		1401	{
		1402	// timeout occured, take action
		1403	}
		1404	else
		1405	{
		1406	// callback was invoked, but there was some activity, re-arm
		1407	// the watcher to fire in last_activity + 60, which is
		1408	// guaranteed to be in the future, so "again" is positive:
		1409	w->again = timeout - now;
		1410	ev_timer_again (EV_A_ w);
		1411	}
		1412	}
		1413
		1414	To summarise the callback: first calculate the real timeout (defined
		1415	as "60 seconds after the last activity"), then check if that time has
		1416	been reached, which means something I<did>, in fact, time out. Otherwise
		1417	the callback was invoked too early (C<timeout> is in the future), so
		1418	re-schedule the timer to fire at that future time, to see if maybe we have
		1419	a timeout then.
		1420
		1421	Note how C<ev_timer_again> is used, taking advantage of the
		1422	C<ev_timer_again> optimisation when the timer is already running.
		1423
		1424	This scheme causes more callback invocations (about one every 60 seconds
		1425	minus half the average time between activity), but virtually no calls to
		1426	libev to change the timeout.
		1427
		1428	To start the timer, simply initialise the watcher and set C<last_activity>
		1429	to the current time (meaning we just have some activity :), then call the
		1430	callback, which will "do the right thing" and start the timer:
		1431
		1432	ev_timer_init (timer, callback);
		1433	last_activity = ev_now (loop);
		1434	callback (loop, timer, EV_TIMEOUT);
		1435
		1436	And when there is some activity, simply store the current time in
		1437	C<last_activity>, no libev calls at all:
		1438
		1439	last_actiivty = ev_now (loop);
		1440
		1441	This technique is slightly more complex, but in most cases where the
		1442	time-out is unlikely to be triggered, much more efficient.
		1443
		1444	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1445	callback :) - just change the timeout and invoke the callback, which will
		1446	fix things for you.
		1447
		1448	=item 4. Wee, just use a double-linked list for your timeouts.
		1449
		1450	If there is not one request, but many thousands (millions...), all
		1451	employing some kind of timeout with the same timeout value, then one can
		1452	do even better:
		1453
		1454	When starting the timeout, calculate the timeout value and put the timeout
		1455	at the I<end> of the list.
		1456
		1457	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1458	the list is expected to fire (for example, using the technique #3).
		1459
		1460	When there is some activity, remove the timer from the list, recalculate
		1461	the timeout, append it to the end of the list again, and make sure to
		1462	update the C<ev_timer> if it was taken from the beginning of the list.
		1463
		1464	This way, one can manage an unlimited number of timeouts in O(1) time for
		1465	starting, stopping and updating the timers, at the expense of a major
		1466	complication, and having to use a constant timeout. The constant timeout
		1467	ensures that the list stays sorted.
		1468
		1469	=back
		1470
		1471	So which method the best?
		1472
		1473	Method #2 is a simple no-brain-required solution that is adequate in most
		1474	situations. Method #3 requires a bit more thinking, but handles many cases
		1475	better, and isn't very complicated either. In most case, choosing either
		1476	one is fine, with #3 being better in typical situations.
		1477
		1478	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1479	rather complicated, but extremely efficient, something that really pays
		1480	off after the first million or so of active timers, i.e. it's usually
		1481	overkill :)
		1482
		1483	=head3 The special problem of time updates
		1484
		1485	Establishing the current time is a costly operation (it usually takes at
		1486	least two system calls): EV therefore updates its idea of the current
		1487	time only before and after C<ev_loop> collects new events, which causes a
		1488	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1489	lots of events in one iteration.
1192		1490
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1491	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	1492	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	1493	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	1494	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:	1495	timeout on the current time, use something like this to adjust for this:
1198		1496
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1497	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1498
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1499	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	1500	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1501	()>.
1204		1502
1205	=head3 Watcher-Specific Functions and Data Members	1503	=head3 Watcher-Specific Functions and Data Members
1206		1504
1207	=over 4	1505	=over 4
1208		1506
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1530	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1531
1234	If the timer is repeating, either start it if necessary (with the	1532	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.	1533	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1534
1237	This sounds a bit complicated, but here is a useful and typical	1535	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	1536	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		1537
1262	=item ev_tstamp repeat [read-write]	1538	=item ev_tstamp repeat [read-write]
1263		1539
1264	The current C<repeat> value. Will be used each time the watcher times out	1540	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),	1541	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.	1542	which is also when any modifications are taken into account.
1267		1543
1268	=back	1544	=back
1269		1545
1270	=head3 Examples	1546	=head3 Examples
1271		1547
1272	Example: Create a timer that fires after 60 seconds.	1548	Example: Create a timer that fires after 60 seconds.
1273		1549
1274	static void	1550	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1551	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1552	{
1277	.. one minute over, w is actually stopped right here	1553	.. one minute over, w is actually stopped right here
1278	}	1554	}
1279		1555
1280	struct ev_timer mytimer;	1556	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1557	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1558	ev_timer_start (loop, &mytimer);
1283		1559
1284	Example: Create a timeout timer that times out after 10 seconds of	1560	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1561	inactivity.
1286		1562
1287	static void	1563	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1564	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1565	{
1290	.. ten seconds without any activity	1566	.. ten seconds without any activity
1291	}	1567	}
1292		1568
1293	struct ev_timer mytimer;	1569	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1570	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1571	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1572	ev_loop (loop, 0);
1297		1573
1298	// and in some piece of code that gets executed on any "activity":	1574	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	1575	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	1576	ev_timer_again (&mytimer);
1301		1577
1302		1578
1303	=head2 C<ev_periodic> - to cron or not to cron?	1579	=head2 C<ev_periodic> - to cron or not to cron?
1304		1580
1305	Periodic watchers are also timers of a kind, but they are very versatile	1581	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	1590	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).	1591	roughly 10 seconds later as it uses a relative timeout).
1316		1592
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1593	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	1594	such as triggering an event on each "midnight, local time", or other
1319	complicated, rules.	1595	complicated rules.
1320		1596
1321	As with timers, the callback is guaranteed to be invoked only when the	1597	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	1598	time (C<at>) has passed, but if multiple periodic timers become ready
1323	during the same loop iteration then order of execution is undefined.	1599	during the same loop iteration, then order of execution is undefined.
1324		1600
1325	=head3 Watcher-Specific Functions and Data Members	1601	=head3 Watcher-Specific Functions and Data Members
1326		1602
1327	=over 4	1603	=over 4
1328		1604
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1605	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1330		1606
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1607	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1332		1608
1333	Lots of arguments, lets sort it out... There are basically three modes of	1609	Lots of arguments, lets sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1610	operation, and we will explain them from simplest to most complex:
1335		1611
1336	=over 4	1612	=over 4
1337		1613
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1614	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1339		1615
1340	In this configuration the watcher triggers an event after the wall clock	1616	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	1617	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	1618	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.	1619	only run when the system clock reaches or surpasses this time.
1344		1620
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1621	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1346		1622
1347	In this mode the watcher will always be scheduled to time out at the next	1623	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)	1624	C<at + N * interval> time (for some integer N, which can also be negative)
1349	and then repeat, regardless of any time jumps.	1625	and then repeat, regardless of any time jumps.
1350		1626
1351	This can be used to create timers that do not drift with respect to system	1627	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	1628	system clock, for example, here is a C<ev_periodic> that triggers each
1353	the hour:	1629	hour, on the hour:
1354		1630
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1631	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1632
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1633	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	1634	but only that the callback will be called when the system time shows a
…		…
1384		1660
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1661	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	1662	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1663	only event loop modification you are allowed to do).
1388		1664
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1665	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1666	*w, ev_tstamp now)>, e.g.:
1391		1667
		1668	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1669	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1670	{
1394	return now + 60.;	1671	return now + 60.;
1395	}	1672	}
1396		1673
1397	It must return the next time to trigger, based on the passed time value	1674	It must return the next time to trigger, based on the passed time value
…		…
1434		1711
1435	The current interval value. Can be modified any time, but changes only	1712	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	1713	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1714	called.
1438		1715
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1716	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1717
1441	The current reschedule callback, or C<0>, if this functionality is	1718	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	1719	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.	1720	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1721
1445	=back	1722	=back
1446		1723
1447	=head3 Examples	1724	=head3 Examples
1448		1725
1449	Example: Call a callback every hour, or, more precisely, whenever the	1726	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1727	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1728	potentially a lot of jitter, but good long-term stability.
1452		1729
1453	static void	1730	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1731	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1732	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1733	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1734	}
1458		1735
1459	struct ev_periodic hourly_tick;	1736	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1737	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1738	ev_periodic_start (loop, &hourly_tick);
1462		1739
1463	Example: The same as above, but use a reschedule callback to do it:	1740	Example: The same as above, but use a reschedule callback to do it:
1464		1741
1465	#include <math.h>	1742	#include <math.h>
1466		1743
1467	static ev_tstamp	1744	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1745	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	1746	{
1470	return fmod (now, 3600.) + 3600.;	1747	return now + (3600. - fmod (now, 3600.));
1471	}	1748	}
1472		1749
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1750	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1751
1475	Example: Call a callback every hour, starting now:	1752	Example: Call a callback every hour, starting now:
1476		1753
1477	struct ev_periodic hourly_tick;	1754	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1755	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1756	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1757	ev_periodic_start (loop, &hourly_tick);
1481		1758
1482		1759
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	1760	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		1761
1485	Signal watchers will trigger an event when the process receives a specific	1762	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	1763	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	1764	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1765	normal event processing, like any other event.
1489		1766
		1767	If you want signals asynchronously, just use C<sigaction> as you would
		1768	do without libev and forget about sharing the signal. You can even use
		1769	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1770
1490	You can configure as many watchers as you like per signal. Only when the	1771	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	1772	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	1773	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	1774	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	1775	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1776	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1777
1497	If possible and supported, libev will install its handlers with	1778	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1779	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	1780	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	1781	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1798
1518	=back	1799	=back
1519		1800
1520	=head3 Examples	1801	=head3 Examples
1521		1802
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1803	Example: Try to exit cleanly on SIGINT.
1523		1804
1524	static void	1805	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1806	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	1807	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1808	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1809	}
1529		1810
1530	struct ev_signal signal_watcher;	1811	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1812	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1813	ev_signal_start (loop, &signal_watcher);
1533		1814
1534		1815
1535	=head2 C<ev_child> - watch out for process status changes	1816	=head2 C<ev_child> - watch out for process status changes
1536		1817
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1818	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	1819	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	1820	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	1821	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	1822	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1823	forking and then immediately registering a watcher for the child is fine,
		1824	but forking and registering a watcher a few event loop iterations later is
		1825	not.
1542		1826
1543	Only the default event loop is capable of handling signals, and therefore	1827	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	1828	you can only register child watchers in the default event loop.
1545		1829
1546	=head3 Process Interaction	1830	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	1843	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	1844	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	1845	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	1846	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.	1847	that, so other libev users can use C<ev_child> watchers freely.
		1848
		1849	=head3 Stopping the Child Watcher
		1850
		1851	Currently, the child watcher never gets stopped, even when the
		1852	child terminates, so normally one needs to stop the watcher in the
		1853	callback. Future versions of libev might stop the watcher automatically
		1854	when a child exit is detected.
1564		1855
1565	=head3 Watcher-Specific Functions and Data Members	1856	=head3 Watcher-Specific Functions and Data Members
1566		1857
1567	=over 4	1858	=over 4
1568		1859
…		…
1597	=head3 Examples	1888	=head3 Examples
1598		1889
1599	Example: C<fork()> a new process and install a child handler to wait for	1890	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	1891	its completion.
1601		1892
1602	ev_child cw;	1893	ev_child cw;
1603		1894
1604	static void	1895	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	1896	child_cb (EV_P_ ev_child *w, int revents)
1606	{	1897	{
1607	ev_child_stop (EV_A_ w);	1898	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1899	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	1900	}
1610		1901
1611	pid_t pid = fork ();	1902	pid_t pid = fork ();
1612		1903
1613	if (pid < 0)	1904	if (pid < 0)
1614	// error	1905	// error
1615	else if (pid == 0)	1906	else if (pid == 0)
1616	{	1907	{
1617	// the forked child executes here	1908	// the forked child executes here
1618	exit (1);	1909	exit (1);
1619	}	1910	}
1620	else	1911	else
1621	{	1912	{
1622	ev_child_init (&cw, child_cb, pid, 0);	1913	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	1914	ev_child_start (EV_DEFAULT_ &cw);
1624	}	1915	}
1625		1916
1626		1917
1627	=head2 C<ev_stat> - did the file attributes just change?	1918	=head2 C<ev_stat> - did the file attributes just change?
1628		1919
1629	This watches a file system path for attribute changes. That is, it calls	1920	This watches a file system path for attribute changes. That is, it calls
…		…
1637	the stat buffer having unspecified contents.	1928	the stat buffer having unspecified contents.
1638		1929
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	1930	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.	1931	relative and your working directory changes, the behaviour is undefined.
1641		1932
1642	Since there is no standard to do this, the portable implementation simply	1933	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	1934	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	1935	it changed somehow. You can specify a recommended polling interval for
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	1936	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	1937	then a I<suitable, unspecified default> value will be used (which
1647	five seconds, although this might change dynamically). Libev will also	1938	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	1939	dynamically). Libev will also impose a minimum interval which is currently
1649	usually overkill.	1940	around C<0.1>, but thats usually overkill.
1650		1941
1651	This watcher type is not meant for massive numbers of stat watchers,	1942	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	1943	as even with OS-supported change notifications, this can be
1653	resource-intensive.	1944	resource-intensive.
1654		1945
1655	At the time of this writing, only the Linux inotify interface is	1946	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	1947	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	1948	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	1949	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		1950
1664	=head3 ABI Issues (Largefile Support)	1951	=head3 ABI Issues (Largefile Support)
1665		1952
1666	Libev by default (unless the user overrides this) uses the default	1953	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	1954	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	1955	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	1956	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	1957	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	1958	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	1959	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	1960	most noticeably disabled with ev_stat and large file support.
1674		1961
1675	=head3 Inotify	1962	The solution for this is to lobby your distribution maker to make large
		1963	file interfaces available by default (as e.g. FreeBSD does) and not
		1964	optional. Libev cannot simply switch on large file support because it has
		1965	to exchange stat structures with application programs compiled using the
		1966	default compilation environment.
1676		1967
		1968	=head3 Inotify and Kqueue
		1969
1677	When C<inotify (7)> support has been compiled into libev (generally only	1970	When C<inotify (7)> support has been compiled into libev (generally
		1971	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	1972	implementations) and present at runtime, it will be used to speed up
1679	change detection where possible. The inotify descriptor will be created lazily	1973	change detection where possible. The inotify descriptor will be created
1680	when the first C<ev_stat> watcher is being started.	1974	lazily when the first C<ev_stat> watcher is being started.
1681		1975
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	1976	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	1977	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	1978	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.	1979	there are many cases where libev has to resort to regular C<stat> polling,
		1980	but as long as the path exists, libev usually gets away without polling.
1686		1981
1687	(There is no support for kqueue, as apparently it cannot be used to	1982	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	1983	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	1984	descriptor open on the object at all times, and detecting renames, unlinks
		1985	etc. is difficult.
1690		1986
1691	=head3 The special problem of stat time resolution	1987	=head3 The special problem of stat time resolution
1692		1988
1693	The C<stat ()> system call only supports full-second resolution portably, and	1989	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	1990	even on systems where the resolution is higher, most file systems still
1695	only support whole seconds.	1991	only support whole seconds.
1696		1992
1697	That means that, if the time is the only thing that changes, you can	1993	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	1994	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	1995	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	1996	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	1997	stat data does change in other ways (e.g. file size).
1702		1998
1703	The solution to this is to delay acting on a change for slightly more	1999	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	2000	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);	2001	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2002	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2022	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	2023	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	2024	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.	2025	path for as long as the watcher is active.
1730		2026
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2027	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	2028	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2029	last change was detected).
1734		2030
1735	=item ev_stat_stat (loop, ev_stat *)	2031	=item ev_stat_stat (loop, ev_stat *)
1736		2032
1737	Updates the stat buffer immediately with new values. If you change the	2033	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	2034	watched path in your callback, you could call this function to avoid
…		…
1767		2063
1768	=head3 Examples	2064	=head3 Examples
1769		2065
1770	Example: Watch C</etc/passwd> for attribute changes.	2066	Example: Watch C</etc/passwd> for attribute changes.
1771		2067
1772	static void	2068	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2069	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	2070	{
1775	/* /etc/passwd changed in some way */	2071	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	2072	if (w->attr.st_nlink)
1777	{	2073	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2074	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2075	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2076	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	2077	}
1782	else	2078	else
1783	/* you shalt not abuse printf for puts */	2079	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	2080	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	2081	"if this is windows, they already arrived\n");
1786	}	2082	}
1787		2083
1788	...	2084	...
1789	ev_stat passwd;	2085	ev_stat passwd;
1790		2086
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2087	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	2088	ev_stat_start (loop, &passwd);
1793		2089
1794	Example: Like above, but additionally use a one-second delay so we do not	2090	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	2091	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	2092	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	2093	C<ev_timer> callback invocation).
1798		2094
1799	static ev_stat passwd;	2095	static ev_stat passwd;
1800	static ev_timer timer;	2096	static ev_timer timer;
1801		2097
1802	static void	2098	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	2099	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	2100	{
1805	ev_timer_stop (EV_A_ w);	2101	ev_timer_stop (EV_A_ w);
1806		2102
1807	/* now it's one second after the most recent passwd change */	2103	/* now it's one second after the most recent passwd change */
1808	}	2104	}
1809		2105
1810	static void	2106	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	2107	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	2108	{
1813	/* reset the one-second timer */	2109	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	2110	ev_timer_again (EV_A_ &timer);
1815	}	2111	}
1816		2112
1817	...	2113	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2114	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	2115	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	2116	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		2117
1822		2118
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2119	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2120
1825	Idle watchers trigger events when no other events of the same or higher	2121	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	2122	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2123	as receiving "events").
1828		2124
1829	That is, as long as your process is busy handling sockets or timeouts	2125	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	2126	(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	2127	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	2128	are pending), the idle watchers are being called once per event loop
…		…
1856	=head3 Examples	2152	=head3 Examples
1857		2153
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2154	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2155	callback, free it. Also, use no error checking, as usual.
1860		2156
1861	static void	2157	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2158	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2159	{
1864	free (w);	2160	free (w);
1865	// now do something you wanted to do when the program has	2161	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2162	// no longer anything immediate to do.
1867	}	2163	}
1868		2164
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2165	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2166	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2167	ev_idle_start (loop, idle_cb);
1872		2168
1873		2169
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2170	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2171
1876	Prepare and check watchers are usually (but not always) used in tandem:	2172	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2173	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2174	afterwards.
1879		2175
1880	You I<must not> call C<ev_loop> or similar functions that enter	2176	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>	2177	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,	2180	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	2181	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2182	called in pairs bracketing the blocking call.
1887		2183
1888	Their main purpose is to integrate other event mechanisms into libev and	2184	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	2185	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	2186	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2187	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,	2188	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>	2189	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2190	watcher).
1895		2191
1896	This is done by examining in each prepare call which file descriptors need	2192	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	2193	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	2194	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	2195	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2196	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	2197	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,	2198	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2199	nevertheless, because you never know, you know?).
1904		2200
1905	As another example, the Perl Coro module uses these hooks to integrate	2201	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2202	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2203	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	2204	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	2207	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2208	low-priority coroutines to idle/background tasks).
1913		2209
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2210	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	2211	priority, to ensure that they are being run before any other watchers
		2212	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2213
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2214	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	2215	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2216	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	2217	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	2218	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	2219	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2220	others).
1923		2221
1924	=head3 Watcher-Specific Functions and Data Members	2222	=head3 Watcher-Specific Functions and Data Members
1925		2223
1926	=over 4	2224	=over 4
1927		2225
…		…
1929		2227
1930	=item ev_check_init (ev_check *, callback)	2228	=item ev_check_init (ev_check *, callback)
1931		2229
1932	Initialises and configures the prepare or check watcher - they have no	2230	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>	2231	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.	2232	macros, but using them is utterly, utterly, utterly and completely
		2233	pointless.
1935		2234
1936	=back	2235	=back
1937		2236
1938	=head3 Examples	2237	=head3 Examples
1939		2238
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2247	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	2248	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	2249	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.	2250	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2251
1953	static ev_io iow [nfd];	2252	static ev_io iow [nfd];
1954	static ev_timer tw;	2253	static ev_timer tw;
1955		2254
1956	static void	2255	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2256	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2257	{
1959	}	2258	}
1960		2259
1961	// create io watchers for each fd and a timer before blocking	2260	// create io watchers for each fd and a timer before blocking
1962	static void	2261	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2262	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2263	{
1965	int timeout = 3600000;	2264	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2265	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2266	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2267	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2268
1970	/* the callback is illegal, but won't be called as we stop during check */	2269	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2270	ev_timer_init (&tw, 0, timeout * 1e-3);
1972	ev_timer_start (loop, &tw);	2271	ev_timer_start (loop, &tw);
1973		2272
1974	// create one ev_io per pollfd	2273	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2274	for (int i = 0; i < nfd; ++i)
1976	{	2275	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2276	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2277	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2278	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2279
1981	fds [i].revents = 0;	2280	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2281	ev_io_start (loop, iow + i);
1983	}	2282	}
1984	}	2283	}
1985		2284
1986	// stop all watchers after blocking	2285	// stop all watchers after blocking
1987	static void	2286	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2287	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2288	{
1990	ev_timer_stop (loop, &tw);	2289	ev_timer_stop (loop, &tw);
1991		2290
1992	for (int i = 0; i < nfd; ++i)	2291	for (int i = 0; i < nfd; ++i)
1993	{	2292	{
1994	// set the relevant poll flags	2293	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2294	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2295	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2296	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2297	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2298	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2299
2001	// now stop the watcher	2300	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2301	ev_io_stop (loop, iow + i);
2003	}	2302	}
2004		2303
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2304	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2305	}
2007		2306
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2307	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.	2308	in the prepare watcher and would dispose of the check watcher.
2010		2309
2011	Method 3: If the module to be embedded supports explicit event	2310	Method 3: If the module to be embedded supports explicit event
2012	notification (libadns does), you can also make use of the actual watcher	2311	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2312	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2313
2015	static void	2314	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2315	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2316	{
2018	adns_state ads = (adns_state)w->data;	2317	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2318	update_now (EV_A);
2020		2319
2021	adns_processtimeouts (ads, &tv_now);	2320	adns_processtimeouts (ads, &tv_now);
2022	}	2321	}
2023		2322
2024	static void	2323	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2324	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2325	{
2027	adns_state ads = (adns_state)w->data;	2326	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2327	update_now (EV_A);
2029		2328
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2329	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2330	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2331	}
2033		2332
2034	// do not ever call adns_afterpoll	2333	// do not ever call adns_afterpoll
2035		2334
2036	Method 4: Do not use a prepare or check watcher because the module you	2335	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	2336	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	2337	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	2338	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2339	this approach, effectively embedding EV as a client into the horrible
		2340	libglib event loop.
2041		2341
2042	static gint	2342	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2343	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2344	{
2045	int got_events = 0;	2345	int got_events = 0;
2046		2346
2047	for (n = 0; n < nfds; ++n)	2347	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2348	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2349
2050	if (timeout >= 0)	2350	if (timeout >= 0)
2051	// create/start timer	2351	// create/start timer
2052		2352
2053	// poll	2353	// poll
2054	ev_loop (EV_A_ 0);	2354	ev_loop (EV_A_ 0);
2055		2355
2056	// stop timer again	2356	// stop timer again
2057	if (timeout >= 0)	2357	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2358	ev_timer_stop (EV_A_ &to);
2059		2359
2060	// stop io watchers again - their callbacks should have set	2360	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	2361	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	2362	ev_io_stop (EV_A_ iow [n]);
2063		2363
2064	return got_events;	2364	return got_events;
2065	}	2365	}
2066		2366
2067		2367
2068	=head2 C<ev_embed> - when one backend isn't enough...	2368	=head2 C<ev_embed> - when one backend isn't enough...
2069		2369
2070	This is a rather advanced watcher type that lets you embed one event loop	2370	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	2376	prioritise I/O.
2077		2377
2078	As an example for a bug workaround, the kqueue backend might only support	2378	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	2379	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	2380	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	2381	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	2382	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	2383	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.	2384	C<kevent>, but at least you can use both mechanisms for what they are
		2385	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2386
2086	As for prioritising I/O: rarely you have the case where some fds have	2387	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	2388	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	2389	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	2390	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.	2391	the rest in a second one, and embed the second one in the first.
2091		2392
2092	As long as the watcher is active, the callback will be invoked every time	2393	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	2394	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	2395	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	2396	their callbacks (you could also start an idle watcher to give the embedded
…		…
2103	interested in that.	2404	interested in that.
2104		2405
2105	Also, there have not currently been made special provisions for forking:	2406	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,	2407	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	2408	but you will also have to stop and restart any C<ev_embed> watchers
2108	yourself.	2409	yourself - but you can use a fork watcher to handle this automatically,
		2410	and future versions of libev might do just that.
2109		2411
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2412	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2413	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2414	portable one.
2113		2415
2114	So when you want to use this feature you will always have to be prepared	2416	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	2417	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	2418	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.	2419	create it, and if that fails, use the normal loop for everything.
		2420
		2421	=head3 C<ev_embed> and fork
		2422
		2423	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2424	automatically be applied to the embedded loop as well, so no special
		2425	fork handling is required in that case. When the watcher is not running,
		2426	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2427	as applicable.
2118		2428
2119	=head3 Watcher-Specific Functions and Data Members	2429	=head3 Watcher-Specific Functions and Data Members
2120		2430
2121	=over 4	2431	=over 4
2122		2432
…		…
2148	event loop. If that is not possible, use the default loop. The default	2458	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	2459	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	2460	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2461	used).
2152		2462
2153	struct ev_loop *loop_hi = ev_default_init (0);	2463	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2464	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2465	ev_embed embed;
2156		2466
2157	// see if there is a chance of getting one that works	2467	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2468	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2469	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2470	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	2471	: 0;
2162		2472
2163	// if we got one, then embed it, otherwise default to loop_hi	2473	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	2474	if (loop_lo)
2165	{	2475	{
2166	ev_embed_init (&embed, 0, loop_lo);	2476	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	2477	ev_embed_start (loop_hi, &embed);
2168	}	2478	}
2169	else	2479	else
2170	loop_lo = loop_hi;	2480	loop_lo = loop_hi;
2171		2481
2172	Example: Check if kqueue is available but not recommended and create	2482	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	2483	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2484	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2485	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2486
2177	struct ev_loop *loop = ev_default_init (0);	2487	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2488	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2489	ev_embed embed;
2180		2490
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2491	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2492	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2493	{
2184	ev_embed_init (&embed, 0, loop_socket);	2494	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	2495	ev_embed_start (loop, &embed);
2186	}	2496	}
2187		2497
2188	if (!loop_socket)	2498	if (!loop_socket)
2189	loop_socket = loop;	2499	loop_socket = loop;
2190		2500
2191	// now use loop_socket for all sockets, and loop for everything else	2501	// now use loop_socket for all sockets, and loop for everything else
2192		2502
2193		2503
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2504	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		2505
2196	Fork watchers are called when a C<fork ()> was detected (usually because	2506	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	2550	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	2551	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2552	need elaborate support such as pthreads.
2243		2553
2244	That means that if you want to queue data, you have to provide your own	2554	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	2555	queue. But at least I can tell you how to implement locking around your
2246	queue:	2556	queue:
2247		2557
2248	=over 4	2558	=over 4
2249		2559
2250	=item queueing from a signal handler context	2560	=item queueing from a signal handler context
2251		2561
2252	To implement race-free queueing, you simply add to the queue in the signal	2562	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	2563	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2564	an example that does that for some fictitious SIGUSR1 handler:
2255		2565
2256	static ev_async mysig;	2566	static ev_async mysig;
2257		2567
2258	static void	2568	static void
2259	sigusr1_handler (void)	2569	sigusr1_handler (void)
…		…
2326		2636
2327	=item ev_async_init (ev_async *, callback)	2637	=item ev_async_init (ev_async *, callback)
2328		2638
2329	Initialises and configures the async watcher - it has no parameters of any	2639	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,	2640	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2331	believe me.	2641	trust me.
2332		2642
2333	=item ev_async_send (loop, ev_async *)	2643	=item ev_async_send (loop, ev_async *)
2334		2644
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2645	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	2646	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	2647	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	2648	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2649	section below on what exactly this means).
2340		2650
2341	This call incurs the overhead of a system call only once per loop iteration,	2651	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	2652	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2366	=over 4	2676	=over 4
2367		2677
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2678	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		2679
2370	This function combines a simple timer and an I/O watcher, calls your	2680	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	2681	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	2682	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	2683	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	2684	more watchers yourself.
2375		2685
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	2686	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	2687	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	2688	the given C<fd> and C<events> set will be created and started.
2379		2689
2380	If C<timeout> is less than 0, then no timeout watcher will be	2690	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	2691	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	2692	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		2693
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2694	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	2695	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>	2696	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2697	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2698	a timeout and an io event at the same time - you probably should give io
		2699	events precedence.
2389		2700
		2701	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2702
2390	static void stdin_ready (int revents, void *arg)	2703	static void stdin_ready (int revents, void *arg)
2391	{	2704	{
2392	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	2705	if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	2706	/* stdin might have data for us, joy! */;
		2707	else if (revents & EV_TIMEOUT)
		2708	/* doh, nothing entered */;
2396	}	2709	}
2397		2710
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2711	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2712
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2713	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		2714
2402	Feeds the given event set into the event loop, as if the specified event	2715	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	2716	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	2717	initialised but not necessarily started event watcher).
2405		2718
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2719	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		2720
2408	Feed an event on the given fd, as if a file descriptor backend detected	2721	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	2722	the given events it.
2410		2723
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	2724	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		2725
2413	Feed an event as if the given signal occurred (C<loop> must be the default	2726	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	2727	loop!).
2415		2728
2416	=back	2729	=back
…		…
2452	you to use some convenience methods to start/stop watchers and also change	2765	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.	2766	the callback model to a model using method callbacks on objects.
2454		2767
2455	To use it,	2768	To use it,
2456		2769
2457	#include <ev++.h>	2770	#include <ev++.h>
2458		2771
2459	This automatically includes F<ev.h> and puts all of its definitions (many	2772	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	2773	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	2774	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2775	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	2842	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.	2843	thunking function, making it as fast as a direct C callback.
2531		2844
2532	Example: simple class declaration and watcher initialisation	2845	Example: simple class declaration and watcher initialisation
2533		2846
2534	struct myclass	2847	struct myclass
2535	{	2848	{
2536	void io_cb (ev::io &w, int revents) { }	2849	void io_cb (ev::io &w, int revents) { }
2537	}	2850	}
2538		2851
2539	myclass obj;	2852	myclass obj;
2540	ev::io iow;	2853	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	2854	iow.set <myclass, &myclass::io_cb> (&obj);
2542		2855
2543	=item w->set<function> (void *data = 0)	2856	=item w->set<function> (void *data = 0)
2544		2857
2545	Also sets a callback, but uses a static method or plain function as	2858	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	2859	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		2861
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2862	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		2863
2551	See the method-C<set> above for more details.	2864	See the method-C<set> above for more details.
2552		2865
2553	Example:	2866	Example: Use a plain function as callback.
2554		2867
2555	static void io_cb (ev::io &w, int revents) { }	2868	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	2869	iow.set <io_cb> ();
2557		2870
2558	=item w->set (struct ev_loop *)	2871	=item w->set (struct ev_loop *)
2559		2872
2560	Associates a different C<struct ev_loop> with this watcher. You can only	2873	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).	2874	do this when the watcher is inactive (and not pending either).
…		…
2594	=back	2907	=back
2595		2908
2596	Example: Define a class with an IO and idle watcher, start one of them in	2909	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	2910	the constructor.
2598		2911
2599	class myclass	2912	class myclass
2600	{	2913	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	2914	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	2915	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		2916
2604	myclass (int fd)	2917	myclass (int fd)
2605	{	2918	{
2606	io .set <myclass, &myclass::io_cb > (this);	2919	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	2920	idle.set <myclass, &myclass::idle_cb> (this);
2608		2921
2609	io.start (fd, ev::READ);	2922	io.start (fd, ev::READ);
2610	}	2923	}
2611	};	2924	};
2612		2925
2613		2926
2614	=head1 OTHER LANGUAGE BINDINGS	2927	=head1 OTHER LANGUAGE BINDINGS
2615		2928
2616	Libev does not offer other language bindings itself, but bindings for a	2929	Libev does not offer other language bindings itself, but bindings for a
…		…
2623	=item Perl	2936	=item Perl
2624		2937
2625	The EV module implements the full libev API and is actually used to test	2938	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,	2939	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	2940	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	2941	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>).	2942	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2943	and C<EV::Glib>).
2630		2944
2631	It can be found and installed via CPAN, its homepage is found at	2945	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	2946	L<http://software.schmorp.de/pkg/EV>.
		2947
		2948	=item Python
		2949
		2950	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2951	seems to be quite complete and well-documented. Note, however, that the
		2952	patch they require for libev is outright dangerous as it breaks the ABI
		2953	for everybody else, and therefore, should never be applied in an installed
		2954	libev (if python requires an incompatible ABI then it needs to embed
		2955	libev).
2633		2956
2634	=item Ruby	2957	=item Ruby
2635		2958
2636	Tony Arcieri has written a ruby extension that offers access to a subset	2959	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	2960	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
2639	L<http://rev.rubyforge.org/>.	2962	L<http://rev.rubyforge.org/>.
2640		2963
2641	=item D	2964	=item D
2642		2965
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2966	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>.	2967	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2968
		2969	=item Ocaml
		2970
		2971	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2972	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2645		2973
2646	=back	2974	=back
2647		2975
2648		2976
2649	=head1 MACRO MAGIC	2977	=head1 MACRO MAGIC
…		…
2661		2989
2662	This provides the loop I<argument> for functions, if one is required ("ev	2990	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,	2991	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:	2992	C<EV_A_> is used when other arguments are following. Example:
2665		2993
2666	ev_unref (EV_A);	2994	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	2995	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	2996	ev_loop (EV_A_ 0);
2669		2997
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2998	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	2999	which is often provided by the following macro.
2672		3000
2673	=item C<EV_P>, C<EV_P_>	3001	=item C<EV_P>, C<EV_P_>
2674		3002
2675	This provides the loop I<parameter> for functions, if one is required ("ev	3003	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,	3004	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:	3005	C<EV_P_> is used when other parameters are following. Example:
2678		3006
2679	// this is how ev_unref is being declared	3007	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	3008	static void ev_unref (EV_P);
2681		3009
2682	// this is how you can declare your typical callback	3010	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	3011	static void cb (EV_P_ ev_timer *w, int revents)
2684		3012
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3013	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	3014	suitable for use with C<EV_A>.
2687		3015
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3016	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		3032
2705	Example: Declare and initialise a check watcher, utilising the above	3033	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	3034	macros so it will work regardless of whether multiple loops are supported
2707	or not.	3035	or not.
2708		3036
2709	static void	3037	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	3038	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	3039	{
2712	ev_check_stop (EV_A_ w);	3040	ev_check_stop (EV_A_ w);
2713	}	3041	}
2714		3042
2715	ev_check check;	3043	ev_check check;
2716	ev_check_init (&check, check_cb);	3044	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	3045	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	3046	ev_loop (EV_DEFAULT_ 0);
2719		3047
2720	=head1 EMBEDDING	3048	=head1 EMBEDDING
2721		3049
2722	Libev can (and often is) directly embedded into host	3050	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	3051	applications. Examples of applications that embed it include the Deliantra
…		…
2737	=head3 CORE EVENT LOOP	3065	=head3 CORE EVENT LOOP
2738		3066
2739	To include only the libev core (all the C<ev_*> functions), with manual	3067	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	3068	configuration (no autoconf):
2741		3069
2742	#define EV_STANDALONE 1	3070	#define EV_STANDALONE 1
2743	#include "ev.c"	3071	#include "ev.c"
2744		3072
2745	This will automatically include F<ev.h>, too, and should be done in a	3073	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	3074	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	3075	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	3076	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	3077	where you can put other configuration options):
2750		3078
2751	#define EV_STANDALONE 1	3079	#define EV_STANDALONE 1
2752	#include "ev.h"	3080	#include "ev.h"
2753		3081
2754	Both header files and implementation files can be compiled with a C++	3082	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	3083	compiler (at least, thats a stated goal, and breakage will be treated
2756	as a bug).	3084	as a bug).
2757		3085
2758	You need the following files in your source tree, or in a directory	3086	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):	3087	in your include path (e.g. in libev/ when using -Ilibev):
2760		3088
2761	ev.h	3089	ev.h
2762	ev.c	3090	ev.c
2763	ev_vars.h	3091	ev_vars.h
2764	ev_wrap.h	3092	ev_wrap.h
2765		3093
2766	ev_win32.c required on win32 platforms only	3094	ev_win32.c required on win32 platforms only
2767		3095
2768	ev_select.c only when select backend is enabled (which is enabled by default)	3096	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)	3097	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)	3098	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)	3099	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)	3100	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		3101
2774	F<ev.c> includes the backend files directly when enabled, so you only need	3102	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	3103	to compile this single file.
2776		3104
2777	=head3 LIBEVENT COMPATIBILITY API	3105	=head3 LIBEVENT COMPATIBILITY API
2778		3106
2779	To include the libevent compatibility API, also include:	3107	To include the libevent compatibility API, also include:
2780		3108
2781	#include "event.c"	3109	#include "event.c"
2782		3110
2783	in the file including F<ev.c>, and:	3111	in the file including F<ev.c>, and:
2784		3112
2785	#include "event.h"	3113	#include "event.h"
2786		3114
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	3115	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		3116
2789	You need the following additional files for this:	3117	You need the following additional files for this:
2790		3118
2791	event.h	3119	event.h
2792	event.c	3120	event.c
2793		3121
2794	=head3 AUTOCONF SUPPORT	3122	=head3 AUTOCONF SUPPORT
2795		3123
2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in	3124	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	3125	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	3126	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	3127	include F<config.h> and configure itself accordingly.
2800		3128
2801	For this of course you need the m4 file:	3129	For this of course you need the m4 file:
2802		3130
2803	libev.m4	3131	libev.m4
2804		3132
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3133	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3134
2807	Libev can be configured via a variety of preprocessor symbols you have to	3135	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	3136	define before including any of its files. The default in the absence of
2809	autoconf is noted for every option.	3137	autoconf is documented for every option.
2810		3138
2811	=over 4	3139	=over 4
2812		3140
2813	=item EV_STANDALONE	3141	=item EV_STANDALONE
2814		3142
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3312	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	3313	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	3314	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3315	fine.
2988		3316
2989	If your embedding application does not need any priorities, defining these both to	3317	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3318	both to C<0> will save some memory and CPU.
2991		3319
2992	=item EV_PERIODIC_ENABLE	3320	=item EV_PERIODIC_ENABLE
2993		3321
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3322	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	3323	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3002	code.	3330	code.
3003		3331
3004	=item EV_EMBED_ENABLE	3332	=item EV_EMBED_ENABLE
3005		3333
3006	If undefined or defined to be C<1>, then embed watchers are supported. If	3334	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.	3335	defined to be C<0>, then they are not. Embed watchers rely on most other
		3336	watcher types, which therefore must not be disabled.
3008		3337
3009	=item EV_STAT_ENABLE	3338	=item EV_STAT_ENABLE
3010		3339
3011	If undefined or defined to be C<1>, then stat watchers are supported. If	3340	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.	3341	defined to be C<0>, then they are not.
…		…
3044	two).	3373	two).
3045		3374
3046	=item EV_USE_4HEAP	3375	=item EV_USE_4HEAP
3047		3376
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3377	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	3378	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	3379	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	3380	faster performance with many (thousands) of watchers.
3052		3381
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3382	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3054	(disabled).	3383	(disabled).
3055		3384
3056	=item EV_HEAP_CACHE_AT	3385	=item EV_HEAP_CACHE_AT
3057		3386
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3387	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	3388	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>),	3389	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,	3390	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	3391	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	3392	noticeably with many (hundreds) of watchers.
3064		3393
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3394	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3066	(disabled).	3395	(disabled).
3067		3396
3068	=item EV_VERIFY	3397	=item EV_VERIFY
…		…
3074	called once per loop, which can slow down libev. If set to C<3>, then the	3403	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	3404	verification code will be called very frequently, which will slow down
3076	libev considerably.	3405	libev considerably.
3077		3406
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3407	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3079	C<0.>	3408	C<0>.
3080		3409
3081	=item EV_COMMON	3410	=item EV_COMMON
3082		3411
3083	By default, all watchers have a C<void *data> member. By redefining	3412	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	3413	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,	3414	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	3415	though, and it must be identical each time.
3087		3416
3088	For example, the perl EV module uses something like this:	3417	For example, the perl EV module uses something like this:
3089		3418
3090	#define EV_COMMON \	3419	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	3420	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	3421	SV *cb_sv, *fh /* note no trailing ";" */
3093		3422
3094	=item EV_CB_DECLARE (type)	3423	=item EV_CB_DECLARE (type)
3095		3424
3096	=item EV_CB_INVOKE (watcher, revents)	3425	=item EV_CB_INVOKE (watcher, revents)
3097		3426
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	3431	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	3432	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	3433	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++.	3434	method calls instead of plain function calls in C++.
3106		3435
		3436	=back
		3437
3107	=head2 EXPORTED API SYMBOLS	3438	=head2 EXPORTED API SYMBOLS
3108		3439
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	3440	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	3441	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	3442	all public symbols, one per line:
3112		3443
3113	Symbols.ev for libev proper	3444	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	3445	Symbols.event for the libevent emulation
3115		3446
3116	This can also be used to rename all public symbols to avoid clashes with	3447	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	3448	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvenient to avoid this).	3449	itself, but sometimes it is inconvenient to avoid this).
3119		3450
…		…
3140	file.	3471	file.
3141		3472
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3473	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:	3474	that everybody includes and which overrides some configure choices:
3144		3475
3145	#define EV_MINIMAL 1	3476	#define EV_MINIMAL 1
3146	#define EV_USE_POLL 0	3477	#define EV_USE_POLL 0
3147	#define EV_MULTIPLICITY 0	3478	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	3479	#define EV_PERIODIC_ENABLE 0
3149	#define EV_STAT_ENABLE 0	3480	#define EV_STAT_ENABLE 0
3150	#define EV_FORK_ENABLE 0	3481	#define EV_FORK_ENABLE 0
3151	#define EV_CONFIG_H <config.h>	3482	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0	3483	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0	3484	#define EV_MAXPRI 0
3154		3485
3155	#include "ev++.h"	3486	#include "ev++.h"
3156		3487
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3488	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		3489
3159	#include "ev_cpp.h"	3490	#include "ev_cpp.h"
3160	#include "ev.c"	3491	#include "ev.c"
3161		3492
		3493	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		3494
3163	=head1 THREADS AND COROUTINES	3495	=head2 THREADS AND COROUTINES
3164		3496
3165	=head2 THREADS	3497	=head3 THREADS
3166		3498
3167	Libev itself is completely thread-safe, but it uses no locking. This	3499	All libev functions are reentrant and thread-safe unless explicitly
		3500	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	3501	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	3502	are no concurrent calls into any libev function with the same loop
3170	parameter.	3503	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3504	of course): libev guarantees that different event loops share no data
		3505	structures that need any locking.
3171		3506
3172	Or put differently: calls with different loop parameters can be done in	3507	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	3508	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	3509	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	3510	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	3511	a mutex per loop).
3177		3512
3178	If you want to know which design is best for your problem, then I cannot	3513	Specifically to support threads (and signal handlers), libev implements
		3514	so-called C<ev_async> watchers, which allow some limited form of
		3515	concurrency on the same event loop, namely waking it up "from the
		3516	outside".
		3517
		3518	If you want to know which design (one loop, locking, or multiple loops
		3519	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	3520	help you, but here is some generic advice:
3180		3521
3181	=over 4	3522	=over 4
3182		3523
3183	=item * most applications have a main thread: use the default libev loop	3524	=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.	3525	in that thread, or create a separate thread running only the default loop.
…		…
3196		3537
3197	Choosing a model is hard - look around, learn, know that usually you can do	3538	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	3539	better than you currently do :-)
3199		3540
3200	=item * often you need to talk to some other thread which blocks in the	3541	=item * often you need to talk to some other thread which blocks in the
		3542	event loop.
		3543
3201	event loop - C<ev_async> watchers can be used to wake them up from other	3544	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	3545	(or from signal contexts...).
		3546
		3547	An example use would be to communicate signals or other events that only
		3548	work in the default loop by registering the signal watcher with the
		3549	default loop and triggering an C<ev_async> watcher from the default loop
		3550	watcher callback into the event loop interested in the signal.
3203		3551
3204	=back	3552	=back
3205		3553
3206	=head2 COROUTINES	3554	=head3 COROUTINES
3207		3555
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	3556	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	3557	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	3558	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	3559	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	3560	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.	3561	you must not do this from C<ev_periodic> reschedule callbacks.
3214		3562
3215	Care has been invested into making sure that libev does not keep local	3563	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	3564	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	3565	they do not clal any callbacks.
3218		3566
		3567	=head2 COMPILER WARNINGS
3219		3568
3220	=head1 COMPLEXITIES	3569	Depending on your compiler and compiler settings, you might get no or a
		3570	lot of warnings when compiling libev code. Some people are apparently
		3571	scared by this.
3221		3572
3222	In this section the complexities of (many of) the algorithms used inside	3573	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	3574	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	3575	warning options. "Warn-free" code therefore cannot be a goal except when
		3576	targeting a specific compiler and compiler-version.
3225		3577
3226	All of the following are about amortised time: If an array needs to be	3578	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	3579	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	3580	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		3581
3232	=over 4	3582	And of course, some compiler warnings are just plain stupid, or simply
		3583	wrong (because they don't actually warn about the condition their message
		3584	seems to warn about). For example, certain older gcc versions had some
		3585	warnings that resulted an extreme number of false positives. These have
		3586	been fixed, but some people still insist on making code warn-free with
		3587	such buggy versions.
3233		3588
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3589	While libev is written to generate as few warnings as possible,
		3590	"warn-free" code is not a goal, and it is recommended not to build libev
		3591	with any compiler warnings enabled unless you are prepared to cope with
		3592	them (e.g. by ignoring them). Remember that warnings are just that:
		3593	warnings, not errors, or proof of bugs.
3235		3594
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		3595
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3596	=head2 VALGRIND
3241		3597
3242	That means that changing a timer costs less than removing/adding them	3598	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.	3599	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		3600
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3601	If you think you found a bug (memory leak, uninitialised data access etc.)
		3602	in libev, then check twice: If valgrind reports something like:
3246		3603
3247	These just add the watcher into an array or at the head of a list.	3604	==2274== definitely lost: 0 bytes in 0 blocks.
		3605	==2274== possibly lost: 0 bytes in 0 blocks.
		3606	==2274== still reachable: 256 bytes in 1 blocks.
3248		3607
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3608	Then there is no memory leak, just as memory accounted to global variables
		3609	is not a memleak - the memory is still being refernced, and didn't leak.
3250		3610
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3611	Similarly, under some circumstances, valgrind might report kernel bugs
		3612	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3613	although an acceptable workaround has been found here), or it might be
		3614	confused.
3252		3615
3253	These watchers are stored in lists then need to be walked to find the	3616	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	3617	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		3618
3257	=item Finding the next timer in each loop iteration: O(1)	3619	If you are unsure about something, feel free to contact the mailing list
		3620	with the full valgrind report and an explanation on why you think this
		3621	is a bug in libev (best check the archives, too :). However, don't be
		3622	annoyed when you get a brisk "this is no bug" answer and take the chance
		3623	of learning how to interpret valgrind properly.
3258		3624
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	3625	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	3626	I suggest using suppression lists.
3261		3627
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		3628
3264	A change means an I/O watcher gets started or stopped, which requires	3629	=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		3630
3268	=item Activating one watcher (putting it into the pending state): O(1)	3631	=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		3632
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3633	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	3634	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	3635	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3636	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3306		3647
3307	Not a libev limitation but worth mentioning: windows apparently doesn't	3648	Not a libev limitation but worth mentioning: windows apparently doesn't
3308	accept large writes: instead of resulting in a partial write, windows will	3649	accept large writes: instead of resulting in a partial write, windows will
3309	either accept everything or return C<ENOBUFS> if the buffer is too large,	3650	either accept everything or return C<ENOBUFS> if the buffer is too large,
3310	so make sure you only write small amounts into your sockets (less than a	3651	so make sure you only write small amounts into your sockets (less than a
3311	megabyte seems safe, but thsi apparently depends on the amount of memory	3652	megabyte seems safe, but this apparently depends on the amount of memory
3312	available).	3653	available).
3313		3654
3314	Due to the many, low, and arbitrary limits on the win32 platform and	3655	Due to the many, low, and arbitrary limits on the win32 platform and
3315	the abysmal performance of winsockets, using a large number of sockets	3656	the abysmal performance of winsockets, using a large number of sockets
3316	is not recommended (and not reasonable). If your program needs to use	3657	is not recommended (and not reasonable). If your program needs to use
3317	more than a hundred or so sockets, then likely it needs to use a totally	3658	more than a hundred or so sockets, then likely it needs to use a totally
3318	different implementation for windows, as libev offers the POSIX readiness	3659	different implementation for windows, as libev offers the POSIX readiness
3319	notification model, which cannot be implemented efficiently on windows	3660	notification model, which cannot be implemented efficiently on windows
3320	(Microsoft monopoly games).	3661	(Microsoft monopoly games).
3321		3662
		3663	A typical way to use libev under windows is to embed it (see the embedding
		3664	section for details) and use the following F<evwrap.h> header file instead
		3665	of F<ev.h>:
		3666
		3667	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3668	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3669
		3670	#include "ev.h"
		3671
		3672	And compile the following F<evwrap.c> file into your project (make sure
		3673	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3674
		3675	#include "evwrap.h"
		3676	#include "ev.c"
		3677
3322	=over 4	3678	=over 4
3323		3679
3324	=item The winsocket select function	3680	=item The winsocket select function
3325		3681
3326	The winsocket C<select> function doesn't follow POSIX in that it	3682	The winsocket C<select> function doesn't follow POSIX in that it
3327	requires socket I<handles> and not socket I<file descriptors> (it is	3683	requires socket I<handles> and not socket I<file descriptors> (it is
3328	also extremely buggy). This makes select very inefficient, and also	3684	also extremely buggy). This makes select very inefficient, and also
3329	requires a mapping from file descriptors to socket handles. See the	3685	requires a mapping from file descriptors to socket handles (the Microsoft
		3686	C runtime provides the function C<_open_osfhandle> for this). See the
3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	3687	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	3688	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3332		3689
3333	The configuration for a "naked" win32 using the Microsoft runtime	3690	The configuration for a "naked" win32 using the Microsoft runtime
3334	libraries and raw winsocket select is:	3691	libraries and raw winsocket select is:
3335		3692
3336	#define EV_USE_SELECT 1	3693	#define EV_USE_SELECT 1
3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3694	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3338		3695
3339	Note that winsockets handling of fd sets is O(n), so you can easily get a	3696	Note that winsockets handling of fd sets is O(n), so you can easily get a
3340	complexity in the O(n²) range when using win32.	3697	complexity in the O(n²) range when using win32.
3341		3698
3342	=item Limited number of file descriptors	3699	=item Limited number of file descriptors
…		…
3366	wrap all I/O functions and provide your own fd management, but the cost of	3723	wrap all I/O functions and provide your own fd management, but the cost of
3367	calling select (O(n²)) will likely make this unworkable.	3724	calling select (O(n²)) will likely make this unworkable.
3368		3725
3369	=back	3726	=back
3370		3727
3371
3372	=head1 PORTABILITY REQUIREMENTS	3728	=head2 PORTABILITY REQUIREMENTS
3373		3729
3374	In addition to a working ISO-C implementation, libev relies on a few	3730	In addition to a working ISO-C implementation and of course the
3375	additional extensions:	3731	backend-specific APIs, libev relies on a few additional extensions:
3376		3732
3377	=over 4	3733	=over 4
3378		3734
		3735	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3736	calling conventions regardless of C<ev_watcher_type *>.
		3737
		3738	Libev assumes not only that all watcher pointers have the same internal
		3739	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3740	assumes that the same (machine) code can be used to call any watcher
		3741	callback: The watcher callbacks have different type signatures, but libev
		3742	calls them using an C<ev_watcher *> internally.
		3743
3379	=item C<sig_atomic_t volatile> must be thread-atomic as well	3744	=item C<sig_atomic_t volatile> must be thread-atomic as well
3380		3745
3381	The type C<sig_atomic_t volatile> (or whatever is defined as	3746	The type C<sig_atomic_t volatile> (or whatever is defined as
3382	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3747	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3383	threads. This is not part of the specification for C<sig_atomic_t>, but is	3748	threads. This is not part of the specification for C<sig_atomic_t>, but is
3384	believed to be sufficiently portable.	3749	believed to be sufficiently portable.
3385		3750
3386	=item C<sigprocmask> must work in a threaded environment	3751	=item C<sigprocmask> must work in a threaded environment
3387		3752
…		…
3396	except the initial one, and run the default loop in the initial thread as	3761	except the initial one, and run the default loop in the initial thread as
3397	well.	3762	well.
3398		3763
3399	=item C<long> must be large enough for common memory allocation sizes	3764	=item C<long> must be large enough for common memory allocation sizes
3400		3765
3401	To improve portability and simplify using libev, libev uses C<long>	3766	To improve portability and simplify its API, libev uses C<long> internally
3402	internally instead of C<size_t> when allocating its data structures. On	3767	instead of C<size_t> when allocating its data structures. On non-POSIX
3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3768	systems (Microsoft...) this might be unexpectedly low, but is still at
3404	is still at least 31 bits everywhere, which is enough for hundreds of	3769	least 31 bits everywhere, which is enough for hundreds of millions of
3405	millions of watchers.	3770	watchers.
3406		3771
3407	=item C<double> must hold a time value in seconds with enough accuracy	3772	=item C<double> must hold a time value in seconds with enough accuracy
3408		3773
3409	The type C<double> is used to represent timestamps. It is required to	3774	The type C<double> is used to represent timestamps. It is required to
3410	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3775	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3414	=back	3779	=back
3415		3780
3416	If you know of other additional requirements drop me a note.	3781	If you know of other additional requirements drop me a note.
3417		3782
3418		3783
3419	=head1 COMPILER WARNINGS	3784	=head1 ALGORITHMIC COMPLEXITIES
3420		3785
3421	Depending on your compiler and compiler settings, you might get no or a	3786	In this section the complexities of (many of) the algorithms used inside
3422	lot of warnings when compiling libev code. Some people are apparently	3787	libev will be documented. For complexity discussions about backends see
3423	scared by this.	3788	the documentation for C<ev_default_init>.
3424		3789
3425	However, these are unavoidable for many reasons. For one, each compiler	3790	All of the following are about amortised time: If an array needs to be
3426	has different warnings, and each user has different tastes regarding	3791	extended, libev needs to realloc and move the whole array, but this
3427	warning options. "Warn-free" code therefore cannot be a goal except when	3792	happens asymptotically rarer with higher number of elements, so O(1) might
3428	targeting a specific compiler and compiler-version.	3793	mean that libev does a lengthy realloc operation in rare cases, but on
		3794	average it is much faster and asymptotically approaches constant time.
3429		3795
3430	Another reason is that some compiler warnings require elaborate	3796	=over 4
3431	workarounds, or other changes to the code that make it less clear and less
3432	maintainable.
3433		3797
3434	And of course, some compiler warnings are just plain stupid, or simply	3798	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3435	wrong (because they don't actually warn about the condition their message
3436	seems to warn about).
3437		3799
3438	While libev is written to generate as few warnings as possible,	3800	This means that, when you have a watcher that triggers in one hour and
3439	"warn-free" code is not a goal, and it is recommended not to build libev	3801	there are 100 watchers that would trigger before that, then inserting will
3440	with any compiler warnings enabled unless you are prepared to cope with	3802	have to skip roughly seven (C<ld 100>) of these watchers.
3441	them (e.g. by ignoring them). Remember that warnings are just that:
3442	warnings, not errors, or proof of bugs.
3443		3803
		3804	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3444		3805
3445	=head1 VALGRIND	3806	That means that changing a timer costs less than removing/adding them,
		3807	as only the relative motion in the event queue has to be paid for.
3446		3808
3447	Valgrind has a special section here because it is a popular tool that is	3809	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3448	highly useful, but valgrind reports are very hard to interpret.
3449		3810
3450	If you think you found a bug (memory leak, uninitialised data access etc.)	3811	These just add the watcher into an array or at the head of a list.
3451	in libev, then check twice: If valgrind reports something like:
3452		3812
3453	==2274== definitely lost: 0 bytes in 0 blocks.	3813	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3454	==2274== possibly lost: 0 bytes in 0 blocks.
3455	==2274== still reachable: 256 bytes in 1 blocks.
3456		3814
3457	Then there is no memory leak. Similarly, under some circumstances,	3815	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3458	valgrind might report kernel bugs as if it were a bug in libev, or it
3459	might be confused (it is a very good tool, but only a tool).
3460		3816
3461	If you are unsure about something, feel free to contact the mailing list	3817	These watchers are stored in lists, so they need to be walked to find the
3462	with the full valgrind report and an explanation on why you think this is	3818	correct watcher to remove. The lists are usually short (you don't usually
3463	a bug in libev. However, don't be annoyed when you get a brisk "this is	3819	have many watchers waiting for the same fd or signal: one is typical, two
3464	no bug" answer and take the chance of learning how to interpret valgrind	3820	is rare).
3465	properly.
3466		3821
3467	If you need, for some reason, empty reports from valgrind for your project	3822	=item Finding the next timer in each loop iteration: O(1)
3468	I suggest using suppression lists.	3823
		3824	By virtue of using a binary or 4-heap, the next timer is always found at a
		3825	fixed position in the storage array.
		3826
		3827	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3828
		3829	A change means an I/O watcher gets started or stopped, which requires
		3830	libev to recalculate its status (and possibly tell the kernel, depending
		3831	on backend and whether C<ev_io_set> was used).
		3832
		3833	=item Activating one watcher (putting it into the pending state): O(1)
		3834
		3835	=item Priority handling: O(number_of_priorities)
		3836
		3837	Priorities are implemented by allocating some space for each
		3838	priority. When doing priority-based operations, libev usually has to
		3839	linearly search all the priorities, but starting/stopping and activating
		3840	watchers becomes O(1) with respect to priority handling.
		3841
		3842	=item Sending an ev_async: O(1)
		3843
		3844	=item Processing ev_async_send: O(number_of_async_watchers)
		3845
		3846	=item Processing signals: O(max_signal_number)
		3847
		3848	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3849	calls in the current loop iteration. Checking for async and signal events
		3850	involves iterating over all running async watchers or all signal numbers.
		3851
		3852	=back
3469		3853
3470		3854
3471	=head1 AUTHOR	3855	=head1 AUTHOR
3472		3856
3473	Marc Lehmann <libev@schmorp.de>.	3857	Marc Lehmann <libev@schmorp.de>.

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