ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.176 by root, Mon Sep 8 17:24:39 2008 UTC vs.
Revision 1.205 by root, Mon Oct 27 12:20:32 2008 UTC

…		…
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
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
…		…
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
…		…
596	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
597	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.
598		630
599	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
600	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
601	finished (especially in interactive programs), but having a program that	633	finished (especially in interactive programs), but having a program
602	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
603	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.
604		637
605	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
606	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
607	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.
608		642
609	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
610	necessary) and will handle those and any outstanding ones. It will block	644	necessary) and will handle those and any already outstanding ones. It
611	your process until at least one new event arrives, and will return after	645	will block your process until at least one new event arrives (which could
612	one iteration of the loop. This is useful if you are waiting for some	646	be an event internal to libev itself, so there is no guarentee that a
613	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
614	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
615	usually a better approach for this kind of thing.	653	usually a better approach for this kind of thing.
616		654
617	Here are the gory details of what C<ev_loop> does:	655	Here are the gory details of what C<ev_loop> does:
618		656
619	- Before the first iteration, call any pending watchers.	657	- Before the first iteration, call any pending watchers.
…		…
629	any active watchers at all will result in not sleeping).	667	any active watchers at all will result in not sleeping).
630	- Sleep if the I/O and timer collect interval say so.	668	- Sleep if the I/O and timer collect interval say so.
631	- Block the process, waiting for any events.	669	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	670	- Queue all outstanding I/O (fd) events.
633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	671	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
634	- Queue all outstanding timers.	672	- Queue all expired timers.
635	- Queue all outstanding periodics.	673	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	674	- Unless any events are pending now, queue all idle watchers.
637	- Queue all check watchers.	675	- Queue all check watchers.
638	- 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).
639	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
640	be handled here by queueing them when their watcher gets executed.	678	be handled here by queueing them when their watcher gets executed.
…		…
657	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	695	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
658	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	696	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
659		697
660	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.
661		699
		700	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		701
662	=item ev_ref (loop)	702	=item ev_ref (loop)
663		703
664	=item ev_unref (loop)	704	=item ev_unref (loop)
665		705
666	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
667	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
668	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
669	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>
670	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
671	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
672	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
673	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
674	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
675	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>
676	(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,
677	respectively).	720	respectively).
678		721
679	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>
680	running when nothing else is active.	723	running when nothing else is active.
681		724
682	struct ev_signal exitsig;	725	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	726	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	727	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	728	evf_unref (loop);
686		729
687	Example: For some weird reason, unregister the above signal handler again.	730	Example: For some weird reason, unregister the above signal handler again.
…		…
701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	744	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
702	allows libev to delay invocation of I/O and timer/periodic callbacks	745	allows libev to delay invocation of I/O and timer/periodic callbacks
703	to increase efficiency of loop iterations (or to increase power-saving	746	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	747	opportunities).
705		748
706	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
707	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
708	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
709	events, especially with backends like C<select ()> which have a high	752	events, especially with backends like C<select ()> which have a high
710	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.
711		754
712	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
713	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,
…		…
715	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
716	introduce an additional C<ev_sleep ()> call into most loop iterations.	759	introduce an additional C<ev_sleep ()> call into most loop iterations.
717		760
718	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
719	to spend more time collecting timeouts, at the expense of increased	762	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	763	latency/jitter/inexactness (the watcher callback will be called
721	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
722	any overhead in libev.	765	value will not introduce any overhead in libev.
723		766
724	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
725	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
726	interactive servers (of course not for games), likewise for timeouts. It	769	interactive servers (of course not for games), likewise for timeouts. It
727	usually doesn't make much sense to set it to a lower value than C<0.01>,	770	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
735	they fire on, say, one-second boundaries only.	778	they fire on, say, one-second boundaries only.
736		779
737	=item ev_loop_verify (loop)	780	=item ev_loop_verify (loop)
738		781
739	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
740	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
741	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
742	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 ()>.
743		787
744	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
745	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
746	data structures consistent.	790	data structures consistent.
747		791
748	=back	792	=back
749		793
750		794
751	=head1 ANATOMY OF A WATCHER	795	=head1 ANATOMY OF A WATCHER
752		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
753	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
754	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
755	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:
756		804
757	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)
758	{	806	{
759	ev_io_stop (w);	807	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	808	ev_unloop (loop, EVUNLOOP_ALL);
761	}	809	}
762		810
763	struct ev_loop *loop = ev_default_loop (0);	811	struct ev_loop *loop = ev_default_loop (0);
		812
764	struct ev_io stdin_watcher;	813	ev_io stdin_watcher;
		814
765	ev_init (&stdin_watcher, my_cb);	815	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	816	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	817	ev_io_start (loop, &stdin_watcher);
		818
768	ev_loop (loop, 0);	819	ev_loop (loop, 0);
769		820
770	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
771	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
772	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).
773		827
774	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
775	(watcher *, callback)>, which expects a callback to be provided. This	829	(watcher *, callback)>, which expects a callback to be provided. This
776	callback gets invoked each time the event occurs (or, in the case of I/O	830	callback gets invoked each time the event occurs (or, in the case of I/O
777	watchers, each time the event loop detects that the file descriptor given	831	watchers, each time the event loop detects that the file descriptor given
778	is readable and/or writable).	832	is readable and/or writable).
779		833
780	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 *, ...) >>
781	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
782	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<<
783	(watcher *, callback, ...) >>.	837	ev_TYPE_init (watcher *, callback, ...) >>.
784		838
785	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
786	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
787	*) >>), 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
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	842	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		843
790	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
791	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
792	reinitialise it or call its C<set> macro.	846	reinitialise it or call its C<ev_TYPE_set> macro.
793		847
794	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
795	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
796	third argument.	850	third argument.
797		851
…		…
860	=item C<EV_ERROR>	914	=item C<EV_ERROR>
861		915
862	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
863	happen because the watcher could not be properly started because libev	917	happen because the watcher could not be properly started because libev
864	ran out of memory, a file descriptor was found to be closed or any other	918	ran out of memory, a file descriptor was found to be closed or any other
		919	problem. Libev considers these application bugs.
		920
865	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
866	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.
867		925
868	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
869	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
870	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
871	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
872	programs, though, so beware.	930	programs, though, as the fd could already be closed and reused for another
		931	thing, so beware.
873		932
874	=back	933	=back
875		934
876	=head2 GENERIC WATCHER FUNCTIONS	935	=head2 GENERIC WATCHER FUNCTIONS
877
878	In the following description, C<TYPE> stands for the watcher type,
879	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
880		936
881	=over 4	937	=over 4
882		938
883	=item C<ev_init> (ev_TYPE *watcher, callback)	939	=item C<ev_init> (ev_TYPE *watcher, callback)
884		940
…		…
890	which rolls both calls into one.	946	which rolls both calls into one.
891		947
892	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
893	(or never started) and there are no pending events outstanding.	949	(or never started) and there are no pending events outstanding.
894		950
895	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,
896	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);
897		959
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	960	=item C<ev_TYPE_set> (ev_TYPE *, [args])
899		961
900	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
901	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
…		…
904	difference to the C<ev_init> macro).	966	difference to the C<ev_init> macro).
905		967
906	Although some watcher types do not have type-specific arguments	968	Although some watcher types do not have type-specific arguments
907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	969	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
908		970
		971	See C<ev_init>, above, for an example.
		972
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	973	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		974
911	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
912	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
913	a watcher. The same limitations apply, of course.	977	a watcher. The same limitations apply, of course.
914		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
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	983	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
916		984
917	Starts (activates) the given watcher. Only active watchers will receive	985	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	986	events. If the watcher is already active nothing will happen.
919		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
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	993	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
921		994
922	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
923	status. It is possible that stopped watchers are pending (for example,	998	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	999	non-repeating timers are being stopped when they become pending - but
925	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1000	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
926	you want to free or reuse the memory used by the watcher it is therefore a	1001	pending. If you want to free or reuse the memory used by the watcher it is
927	good idea to always call its C<ev_TYPE_stop> function.	1002	therefore a good idea to always call its C<ev_TYPE_stop> function.
928		1003
929	=item bool ev_is_active (ev_TYPE *watcher)	1004	=item bool ev_is_active (ev_TYPE *watcher)
930		1005
931	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
932	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
…		…
974	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
975	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 :).
976		1051
977	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
978	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
979	or might not have been adjusted to be within valid range.	1054	or might not have been clamped to the valid range.
980		1055
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1056	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1057
983	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
984	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
985	can deal with that fact.	1060	can deal with that fact, as both are simply passed through to the
		1061	callback.
986		1062
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1063	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1064
989	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
990	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
991	watcher isn't pending it does nothing and returns C<0>.	1067	watcher isn't pending it does nothing and returns C<0>.
992		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
993	=back	1072	=back
994		1073
995		1074
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1075	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1076
998	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
999	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
1000	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
1001	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
1002	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
1003	data:	1082	data:
1004		1083
1005	struct my_io	1084	struct my_io
1006	{	1085	{
1007	struct ev_io io;	1086	ev_io io;
1008	int otherfd;	1087	int otherfd;
1009	void *somedata;	1088	void *somedata;
1010	struct whatever *mostinteresting;	1089	struct whatever *mostinteresting;
1011	}	1090	};
		1091
		1092	...
		1093	struct my_io w;
		1094	ev_io_init (&w.io, my_cb, fd, EV_READ);
1012		1095
1013	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
1014	can cast it back to your own type:	1097	can cast it back to your own type:
1015		1098
1016	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)
1017	{	1100	{
1018	struct my_io *w = (struct my_io *)w_;	1101	struct my_io *w = (struct my_io *)w_;
1019	...	1102	...
1020	}	1103	}
1021		1104
1022	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
1023	instead have been omitted.	1106	instead have been omitted.
1024		1107
1025	Another common scenario is having some data structure with multiple	1108	Another common scenario is to use some data structure with multiple
1026	watchers:	1109	embedded watchers:
1027		1110
1028	struct my_biggy	1111	struct my_biggy
1029	{	1112	{
1030	int some_data;	1113	int some_data;
1031	ev_timer t1;	1114	ev_timer t1;
1032	ev_timer t2;	1115	ev_timer t2;
1033	}	1116	}
1034		1117
1035	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
1036	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):
1037		1123
1038	#include <stddef.h>	1124	#include <stddef.h>
1039		1125
1040	static void	1126	static void
1041	t1_cb (EV_P_ struct ev_timer *w, int revents)	1127	t1_cb (EV_P_ ev_timer *w, int revents)
1042	{	1128	{
1043	struct my_biggy big = (struct my_biggy *	1129	struct my_biggy big = (struct my_biggy *
1044	(((char *)w) - offsetof (struct my_biggy, t1));	1130	(((char *)w) - offsetof (struct my_biggy, t1));
1045	}	1131	}
1046		1132
1047	static void	1133	static void
1048	t2_cb (EV_P_ struct ev_timer *w, int revents)	1134	t2_cb (EV_P_ ev_timer *w, int revents)
1049	{	1135	{
1050	struct my_biggy big = (struct my_biggy *	1136	struct my_biggy big = (struct my_biggy *
1051	(((char *)w) - offsetof (struct my_biggy, t2));	1137	(((char *)w) - offsetof (struct my_biggy, t2));
1052	}	1138	}
1053		1139
…		…
1081	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
1082	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
1083	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
1084	required if you know what you are doing).	1170	required if you know what you are doing).
1085		1171
1086	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
1087	(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
1088	C<EVBACKEND_POLL>).	1174	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1089		1175
1090	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
1091	receive "spurious" readiness notifications, that is your callback might	1177	receive "spurious" readiness notifications, that is your callback might
1092	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1178	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1093	because there is no data. Not only are some backends known to create a	1179	because there is no data. Not only are some backends known to create a
1094	lot of those (for example Solaris ports), it is very easy to get into	1180	lot of those (for example Solaris ports), it is very easy to get into
1095	this situation even with a relatively standard program structure. Thus	1181	this situation even with a relatively standard program structure. Thus
1096	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1182	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1097	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1183	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1098		1184
1099	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
1100	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
1101	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
1102	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
1103	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.
1104		1194
1105	=head3 The special problem of disappearing file descriptors	1195	=head3 The special problem of disappearing file descriptors
1106		1196
1107	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
1108	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,
1109	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
1110	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
1111	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
1112	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
1113	fact, a different file descriptor.	1203	fact, a different file descriptor.
1114		1204
…		…
1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1235	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1146	C<EVBACKEND_POLL>.	1236	C<EVBACKEND_POLL>.
1147		1237
1148	=head3 The special problem of SIGPIPE	1238	=head3 The special problem of SIGPIPE
1149		1239
1150	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>:
1151	when writing to a pipe whose other end has been closed, your program gets	1241	when writing to a pipe whose other end has been closed, your program gets
1152	send a SIGPIPE, which, by default, aborts your program. For most programs	1242	sent a SIGPIPE, which, by default, aborts your program. For most programs
1153	this is sensible behaviour, for daemons, this is usually undesirable.	1243	this is sensible behaviour, for daemons, this is usually undesirable.
1154		1244
1155	So when you encounter spurious, unexplained daemon exits, make sure you	1245	So when you encounter spurious, unexplained daemon exits, make sure you
1156	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1246	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1157	somewhere, as that would have given you a big clue).	1247	somewhere, as that would have given you a big clue).
…		…
1164	=item ev_io_init (ev_io *, callback, int fd, int events)	1254	=item ev_io_init (ev_io *, callback, int fd, int events)
1165		1255
1166	=item ev_io_set (ev_io *, int fd, int events)	1256	=item ev_io_set (ev_io *, int fd, int events)
1167		1257
1168	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
1169	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
1170	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.
1171		1261
1172	=item int fd [read-only]	1262	=item int fd [read-only]
1173		1263
1174	The file descriptor being watched.	1264	The file descriptor being watched.
1175		1265
…		…
1184	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
1185	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
1186	attempt to read a whole line in the callback.	1276	attempt to read a whole line in the callback.
1187		1277
1188	static void	1278	static void
1189	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)
1190	{	1280	{
1191	ev_io_stop (loop, w);	1281	ev_io_stop (loop, w);
1192	.. 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
1193	}	1283	}
1194		1284
1195	...	1285	...
1196	struct ev_loop *loop = ev_default_init (0);	1286	struct ev_loop *loop = ev_default_init (0);
1197	struct ev_io stdin_readable;	1287	ev_io stdin_readable;
1198	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);
1199	ev_io_start (loop, &stdin_readable);	1289	ev_io_start (loop, &stdin_readable);
1200	ev_loop (loop, 0);	1290	ev_loop (loop, 0);
1201		1291
1202		1292
…		…
1205	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
1206	given time, and optionally repeating in regular intervals after that.	1296	given time, and optionally repeating in regular intervals after that.
1207		1297
1208	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
1209	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
1210	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
1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1301	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1212	monotonic clock option helps a lot here).	1302	monotonic clock option helps a lot here).
1213		1303
1214	The callback is guaranteed to be invoked only after its timeout has passed,	1304	The callback is guaranteed to be invoked only I<after> its timeout has
1215	but if multiple timers become ready during the same loop iteration then	1305	passed, but if multiple timers become ready during the same loop iteration
1216	order of execution is undefined.	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 :)
1217		1482
1218	=head3 The special problem of time updates	1483	=head3 The special problem of time updates
1219		1484
1220	Establishing the current time is a costly operation (it usually takes at	1485	Establishing the current time is a costly operation (it usually takes at
1221	least two system calls): EV therefore updates its idea of the current	1486	least two system calls): EV therefore updates its idea of the current
1222	time only before and after C<ev_loop> polls for new events, which causes	1487	time only before and after C<ev_loop> collects new events, which causes a
1223	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1488	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1224	lots of events.	1489	lots of events in one iteration.
1225		1490
1226	The relative timeouts are calculated relative to the C<ev_now ()>	1491	The relative timeouts are calculated relative to the C<ev_now ()>
1227	time. This is usually the right thing as this timestamp refers to the time	1492	time. This is usually the right thing as this timestamp refers to the time
1228	of the event triggering whatever timeout you are modifying/starting. If	1493	of the event triggering whatever timeout you are modifying/starting. If
1229	you suspect event processing to be delayed and you I<need> to base the	1494	you suspect event processing to be delayed and you I<need> to base the
1230	timeout 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:
1231		1496
1232	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1497	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1233		1498
1234	If the event loop is suspended for a long time, one can also force an	1499	If the event loop is suspended for a long time, you can also force an
1235	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1500	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1236	()>.	1501	()>.
1237		1502
1238	=head3 Watcher-Specific Functions and Data Members	1503	=head3 Watcher-Specific Functions and Data Members
1239		1504
…		…
1265	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).
1266		1531
1267	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
1268	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.
1269		1534
1270	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
1271	example: Imagine you have a TCP connection and you want a so-called idle	1536	usage example.
1272	timeout, that is, you want to be called when there have been, say, 60
1273	seconds of inactivity on the socket. The easiest way to do this is to
1274	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1275	C<ev_timer_again> each time you successfully read or write some data. If
1276	you go into an idle state where you do not expect data to travel on the
1277	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1278	automatically restart it if need be.
1279
1280	That means you can ignore the C<after> value and C<ev_timer_start>
1281	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1282
1283	ev_timer_init (timer, callback, 0., 5.);
1284	ev_timer_again (loop, timer);
1285	...
1286	timer->again = 17.;
1287	ev_timer_again (loop, timer);
1288	...
1289	timer->again = 10.;
1290	ev_timer_again (loop, timer);
1291
1292	This is more slightly efficient then stopping/starting the timer each time
1293	you want to modify its timeout value.
1294		1537
1295	=item ev_tstamp repeat [read-write]	1538	=item ev_tstamp repeat [read-write]
1296		1539
1297	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
1298	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),
1299	which is also when any modifications are taken into account.	1542	which is also when any modifications are taken into account.
1300		1543
1301	=back	1544	=back
1302		1545
1303	=head3 Examples	1546	=head3 Examples
1304		1547
1305	Example: Create a timer that fires after 60 seconds.	1548	Example: Create a timer that fires after 60 seconds.
1306		1549
1307	static void	1550	static void
1308	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)
1309	{	1552	{
1310	.. one minute over, w is actually stopped right here	1553	.. one minute over, w is actually stopped right here
1311	}	1554	}
1312		1555
1313	struct ev_timer mytimer;	1556	ev_timer mytimer;
1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1557	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1315	ev_timer_start (loop, &mytimer);	1558	ev_timer_start (loop, &mytimer);
1316		1559
1317	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
1318	inactivity.	1561	inactivity.
1319		1562
1320	static void	1563	static void
1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1564	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1322	{	1565	{
1323	.. ten seconds without any activity	1566	.. ten seconds without any activity
1324	}	1567	}
1325		1568
1326	struct ev_timer mytimer;	1569	ev_timer mytimer;
1327	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 */
1328	ev_timer_again (&mytimer); /* start timer */	1571	ev_timer_again (&mytimer); /* start timer */
1329	ev_loop (loop, 0);	1572	ev_loop (loop, 0);
1330		1573
1331	// 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":
…		…
1347	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
1348	roughly 10 seconds later as it uses a relative timeout).	1591	roughly 10 seconds later as it uses a relative timeout).
1349		1592
1350	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,
1351	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
1352	complicated, rules.	1595	complicated rules.
1353		1596
1354	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
1355	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
1356	during the same loop iteration then order of execution is undefined.	1599	during the same loop iteration, then order of execution is undefined.
1357		1600
1358	=head3 Watcher-Specific Functions and Data Members	1601	=head3 Watcher-Specific Functions and Data Members
1359		1602
1360	=over 4	1603	=over 4
1361		1604
1362	=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)
1363		1606
1364	=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)
1365		1608
1366	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
1367	operation, and we will explain them from simplest to complex:	1610	operation, and we will explain them from simplest to most complex:
1368		1611
1369	=over 4	1612	=over 4
1370		1613
1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1614	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1372		1615
1373	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
1374	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
1375	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
1376	run when the system time reaches or surpasses this time.	1619	only run when the system clock reaches or surpasses this time.
1377		1620
1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1621	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1379		1622
1380	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
1381	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)
1382	and then repeat, regardless of any time jumps.	1625	and then repeat, regardless of any time jumps.
1383		1626
1384	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
1385	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
1386	the hour:	1629	hour, on the hour:
1387		1630
1388	ev_periodic_set (&periodic, 0., 3600., 0);	1631	ev_periodic_set (&periodic, 0., 3600., 0);
1389		1632
1390	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,
1391	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
…		…
1417		1660
1418	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
1419	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
1420	only event loop modification you are allowed to do).	1663	only event loop modification you are allowed to do).
1421		1664
1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1665	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1423	*w, ev_tstamp now)>, e.g.:	1666	*w, ev_tstamp now)>, e.g.:
1424		1667
		1668	static ev_tstamp
1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1669	my_rescheduler (ev_periodic *w, ev_tstamp now)
1426	{	1670	{
1427	return now + 60.;	1671	return now + 60.;
1428	}	1672	}
1429		1673
1430	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
…		…
1467		1711
1468	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
1469	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
1470	called.	1714	called.
1471		1715
1472	=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]
1473		1717
1474	The current reschedule callback, or C<0>, if this functionality is	1718	The current reschedule callback, or C<0>, if this functionality is
1475	switched off. Can be changed any time, but changes only take effect when	1719	switched off. Can be changed any time, but changes only take effect when
1476	the periodic timer fires or C<ev_periodic_again> is being called.	1720	the periodic timer fires or C<ev_periodic_again> is being called.
1477		1721
1478	=back	1722	=back
1479		1723
1480	=head3 Examples	1724	=head3 Examples
1481		1725
1482	Example: Call a callback every hour, or, more precisely, whenever the	1726	Example: Call a callback every hour, or, more precisely, whenever the
1483	system clock is divisible by 3600. The callback invocation times have	1727	system time is divisible by 3600. The callback invocation times have
1484	potentially a lot of jitter, but good long-term stability.	1728	potentially a lot of jitter, but good long-term stability.
1485		1729
1486	static void	1730	static void
1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1731	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1488	{	1732	{
1489	... 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)
1490	}	1734	}
1491		1735
1492	struct ev_periodic hourly_tick;	1736	ev_periodic hourly_tick;
1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1737	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1494	ev_periodic_start (loop, &hourly_tick);	1738	ev_periodic_start (loop, &hourly_tick);
1495		1739
1496	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:
1497		1741
1498	#include <math.h>	1742	#include <math.h>
1499		1743
1500	static ev_tstamp	1744	static ev_tstamp
1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1745	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1502	{	1746	{
1503	return fmod (now, 3600.) + 3600.;	1747	return now + (3600. - fmod (now, 3600.));
1504	}	1748	}
1505		1749
1506	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);
1507		1751
1508	Example: Call a callback every hour, starting now:	1752	Example: Call a callback every hour, starting now:
1509		1753
1510	struct ev_periodic hourly_tick;	1754	ev_periodic hourly_tick;
1511	ev_periodic_init (&hourly_tick, clock_cb,	1755	ev_periodic_init (&hourly_tick, clock_cb,
1512	fmod (ev_now (loop), 3600.), 3600., 0);	1756	fmod (ev_now (loop), 3600.), 3600., 0);
1513	ev_periodic_start (loop, &hourly_tick);	1757	ev_periodic_start (loop, &hourly_tick);
1514		1758
1515		1759
…		…
1518	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
1519	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
1520	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
1521	normal event processing, like any other event.	1765	normal event processing, like any other event.
1522		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
1523	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
1524	first watcher gets started will libev actually register a signal watcher	1772	first watcher gets started will libev actually register a signal handler
1525	with the kernel (thus it coexists with your own signal handlers as long	1773	with the kernel (thus it coexists with your own signal handlers as long as
1526	as you don't register any with libev). Similarly, when the last signal	1774	you don't register any with libev for the same signal). Similarly, when
1527	watcher for a signal is stopped libev will reset the signal handler to	1775	the last signal watcher for a signal is stopped, libev will reset the
1528	SIG_DFL (regardless of what it was set to before).	1776	signal handler to SIG_DFL (regardless of what it was set to before).
1529		1777
1530	If possible and supported, libev will install its handlers with	1778	If possible and supported, libev will install its handlers with
1531	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
1532	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
1533	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
…		…
1550		1798
1551	=back	1799	=back
1552		1800
1553	=head3 Examples	1801	=head3 Examples
1554		1802
1555	Example: Try to exit cleanly on SIGINT and SIGTERM.	1803	Example: Try to exit cleanly on SIGINT.
1556		1804
1557	static void	1805	static void
1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1806	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1559	{	1807	{
1560	ev_unloop (loop, EVUNLOOP_ALL);	1808	ev_unloop (loop, EVUNLOOP_ALL);
1561	}	1809	}
1562		1810
1563	struct ev_signal signal_watcher;	1811	ev_signal signal_watcher;
1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1812	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1565	ev_signal_start (loop, &sigint_cb);	1813	ev_signal_start (loop, &signal_watcher);
1566		1814
1567		1815
1568	=head2 C<ev_child> - watch out for process status changes	1816	=head2 C<ev_child> - watch out for process status changes
1569		1817
1570	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
1571	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
1572	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
1573	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
1574	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.
1575		1826
1576	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
1577	you can only register child watchers in the default event loop.	1828	you can only register child watchers in the default event loop.
1578		1829
1579	=head3 Process Interaction	1830	=head3 Process Interaction
…		…
1640	its completion.	1891	its completion.
1641		1892
1642	ev_child cw;	1893	ev_child cw;
1643		1894
1644	static void	1895	static void
1645	child_cb (EV_P_ struct ev_child *w, int revents)	1896	child_cb (EV_P_ ev_child *w, int revents)
1646	{	1897	{
1647	ev_child_stop (EV_A_ w);	1898	ev_child_stop (EV_A_ w);
1648	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);
1649	}	1900	}
1650		1901
…		…
1677	the stat buffer having unspecified contents.	1928	the stat buffer having unspecified contents.
1678		1929
1679	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
1680	relative and your working directory changes, the behaviour is undefined.	1931	relative and your working directory changes, the behaviour is undefined.
1681		1932
1682	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
1683	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
1684	can specify a recommended polling interval for this case. If you specify	1935	it changed somehow. You can specify a recommended polling interval for
1685	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!)
1686	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
1687	five seconds, although this might change dynamically). Libev will also	1938	you can expect to be around five seconds, although this might change
1688	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
1689	usually overkill.	1940	around C<0.1>, but thats usually overkill.
1690		1941
1691	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,
1692	as even with OS-supported change notifications, this can be	1943	as even with OS-supported change notifications, this can be
1693	resource-intensive.	1944	resource-intensive.
1694		1945
1695	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
1696	implemented (implementing kqueue support is left as an exercise for the	1947	is the Linux inotify interface (implementing kqueue support is left as
1697	reader, note, however, that the author sees no way of implementing ev_stat	1948	an exercise for the reader. Note, however, that the author sees no way
1698	semantics with kqueue). Inotify will be used to give hints only and should	1949	of implementing C<ev_stat> semantics with kqueue).
1699	not change the semantics of C<ev_stat> watchers, which means that libev
1700	sometimes needs to fall back to regular polling again even with inotify,
1701	but changes are usually detected immediately, and if the file exists there
1702	will be no polling.
1703		1950
1704	=head3 ABI Issues (Largefile Support)	1951	=head3 ABI Issues (Largefile Support)
1705		1952
1706	Libev by default (unless the user overrides this) uses the default	1953	Libev by default (unless the user overrides this) uses the default
1707	compilation environment, which means that on systems with large file	1954	compilation environment, which means that on systems with large file
…		…
1716	file interfaces available by default (as e.g. FreeBSD does) and not	1963	file interfaces available by default (as e.g. FreeBSD does) and not
1717	optional. Libev cannot simply switch on large file support because it has	1964	optional. Libev cannot simply switch on large file support because it has
1718	to exchange stat structures with application programs compiled using the	1965	to exchange stat structures with application programs compiled using the
1719	default compilation environment.	1966	default compilation environment.
1720		1967
1721	=head3 Inotify	1968	=head3 Inotify and Kqueue
1722		1969
1723	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
1724	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
1725	change detection where possible. The inotify descriptor will be created lazily	1973	change detection where possible. The inotify descriptor will be created
1726	when the first C<ev_stat> watcher is being started.	1974	lazily when the first C<ev_stat> watcher is being started.
1727		1975
1728	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
1729	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
1730	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
1731	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.
1732		1981
1733	(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
1734	implement this functionality, due to the requirement of having a file	1983	implement this functionality, due to the requirement of having a file
1735	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.
1736		1986
1737	=head3 The special problem of stat time resolution	1987	=head3 The special problem of stat time resolution
1738		1988
1739	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
1740	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
1741	only support whole seconds.	1991	only support whole seconds.
1742		1992
1743	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
1744	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
1745	calls your callback, which does something. When there is another update	1995	calls your callback, which does something. When there is another update
1746	within the same second, C<ev_stat> will be unable to detect it as the stat	1996	within the same second, C<ev_stat> will be unable to detect unless the
1747	data does not change.	1997	stat data does change in other ways (e.g. file size).
1748		1998
1749	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
1750	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
1751	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);
1752	ev_timer_again (loop, w)>).	2002	ev_timer_again (loop, w)>).
…		…
1772	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
1773	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
1774	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
1775	path for as long as the watcher is active.	2025	path for as long as the watcher is active.
1776		2026
1777	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,
1778	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
1779	was detected).	2029	last change was detected).
1780		2030
1781	=item ev_stat_stat (loop, ev_stat *)	2031	=item ev_stat_stat (loop, ev_stat *)
1782		2032
1783	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
1784	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
…		…
1867		2117
1868		2118
1869	=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...
1870		2120
1871	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
1872	priority are pending (prepare, check and other idle watchers do not	2122	priority are pending (prepare, check and other idle watchers do not count
1873	count).	2123	as receiving "events").
1874		2124
1875	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
1876	(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
1877	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
1878	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
…		…
1903		2153
1904	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
1905	callback, free it. Also, use no error checking, as usual.	2155	callback, free it. Also, use no error checking, as usual.
1906		2156
1907	static void	2157	static void
1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2158	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1909	{	2159	{
1910	free (w);	2160	free (w);
1911	// now do something you wanted to do when the program has	2161	// now do something you wanted to do when the program has
1912	// no longer anything immediate to do.	2162	// no longer anything immediate to do.
1913	}	2163	}
1914		2164
1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2165	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1916	ev_idle_init (idle_watcher, idle_cb);	2166	ev_idle_init (idle_watcher, idle_cb);
1917	ev_idle_start (loop, idle_cb);	2167	ev_idle_start (loop, idle_cb);
1918		2168
1919		2169
1920	=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!
1921		2171
1922	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:
1923	prepare watchers get invoked before the process blocks and check watchers	2173	prepare watchers get invoked before the process blocks and check watchers
1924	afterwards.	2174	afterwards.
1925		2175
1926	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
1927	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>
…		…
1930	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,
1931	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
1932	called in pairs bracketing the blocking call.	2182	called in pairs bracketing the blocking call.
1933		2183
1934	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
1935	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
1936	variable changes, implement your own watchers, integrate net-snmp or a	2186	variable changes, implement your own watchers, integrate net-snmp or a
1937	coroutine library and lots more. They are also occasionally useful if	2187	coroutine library and lots more. They are also occasionally useful if
1938	you cache some data and want to flush it before blocking (for example,	2188	you cache some data and want to flush it before blocking (for example,
1939	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2189	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1940	watcher).	2190	watcher).
1941		2191
1942	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
1943	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
1944	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
1945	provide just this functionality). Then, in the check watcher you check for	2195	libraries provide exactly this functionality). Then, in the check watcher,
1946	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
1947	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
1948	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
1949	because you never know, you know?).	2199	nevertheless, because you never know, you know?).
1950		2200
1951	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
1952	coroutines into libev programs, by yielding to other active coroutines	2202	coroutines into libev programs, by yielding to other active coroutines
1953	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
1954	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
…		…
1957	loop from blocking if lower-priority coroutines are active, thus mapping	2207	loop from blocking if lower-priority coroutines are active, thus mapping
1958	low-priority coroutines to idle/background tasks).	2208	low-priority coroutines to idle/background tasks).
1959		2209
1960	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>)
1961	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
1962	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
1963	too) should not activate ("feed") events into libev. While libev fully	2215	activate ("feed") events into libev. While libev fully supports this, they
1964	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
1965	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
1966	(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
1967	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
1968	coexist peacefully with others).	2220	others).
1969		2221
1970	=head3 Watcher-Specific Functions and Data Members	2222	=head3 Watcher-Specific Functions and Data Members
1971		2223
1972	=over 4	2224	=over 4
1973		2225
…		…
1975		2227
1976	=item ev_check_init (ev_check *, callback)	2228	=item ev_check_init (ev_check *, callback)
1977		2229
1978	Initialises and configures the prepare or check watcher - they have no	2230	Initialises and configures the prepare or check watcher - they have no
1979	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2231	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1980	macros, but using them is utterly, utterly and completely pointless.	2232	macros, but using them is utterly, utterly, utterly and completely
		2233	pointless.
1981		2234
1982	=back	2235	=back
1983		2236
1984	=head3 Examples	2237	=head3 Examples
1985		2238
…		…
1998		2251
1999	static ev_io iow [nfd];	2252	static ev_io iow [nfd];
2000	static ev_timer tw;	2253	static ev_timer tw;
2001		2254
2002	static void	2255	static void
2003	io_cb (ev_loop *loop, ev_io *w, int revents)	2256	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2004	{	2257	{
2005	}	2258	}
2006		2259
2007	// create io watchers for each fd and a timer before blocking	2260	// create io watchers for each fd and a timer before blocking
2008	static void	2261	static void
2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2262	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2010	{	2263	{
2011	int timeout = 3600000;	2264	int timeout = 3600000;
2012	struct pollfd fds [nfd];	2265	struct pollfd fds [nfd];
2013	// actual code will need to loop here and realloc etc.	2266	// actual code will need to loop here and realloc etc.
2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2267	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2029	}	2282	}
2030	}	2283	}
2031		2284
2032	// stop all watchers after blocking	2285	// stop all watchers after blocking
2033	static void	2286	static void
2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2287	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2035	{	2288	{
2036	ev_timer_stop (loop, &tw);	2289	ev_timer_stop (loop, &tw);
2037		2290
2038	for (int i = 0; i < nfd; ++i)	2291	for (int i = 0; i < nfd; ++i)
2039	{	2292	{
…		…
2078	}	2331	}
2079		2332
2080	// do not ever call adns_afterpoll	2333	// do not ever call adns_afterpoll
2081		2334
2082	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
2083	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
2084	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
2085	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
2086	this.	2339	this approach, effectively embedding EV as a client into the horrible
		2340	libglib event loop.
2087		2341
2088	static gint	2342	static gint
2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2343	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2090	{	2344	{
2091	int got_events = 0;	2345	int got_events = 0;
…		…
2122	prioritise I/O.	2376	prioritise I/O.
2123		2377
2124	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
2125	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
2126	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
2127	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
2128	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
2129	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
2130	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 :)
2131		2386
2132	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
2133	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),
2134	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
2135	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
2136	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.
2137		2392
2138	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
2139	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
2140	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
2141	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
…		…
2149	interested in that.	2404	interested in that.
2150		2405
2151	Also, there have not currently been made special provisions for forking:	2406	Also, there have not currently been made special provisions for forking:
2152	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2407	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2153	but you will also have to stop and restart any C<ev_embed> watchers	2408	but you will also have to stop and restart any C<ev_embed> watchers
2154	yourself.	2409	yourself - but you can use a fork watcher to handle this automatically,
		2410	and future versions of libev might do just that.
2155		2411
2156	Unfortunately, not all backends are embeddable, only the ones returned by	2412	Unfortunately, not all backends are embeddable: only the ones returned by
2157	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2413	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2158	portable one.	2414	portable one.
2159		2415
2160	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
2161	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
2162	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
2163	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.
2164		2428
2165	=head3 Watcher-Specific Functions and Data Members	2429	=head3 Watcher-Specific Functions and Data Members
2166		2430
2167	=over 4	2431	=over 4
2168		2432
…		…
2196	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
2197	used).	2461	used).
2198		2462
2199	struct ev_loop *loop_hi = ev_default_init (0);	2463	struct ev_loop *loop_hi = ev_default_init (0);
2200	struct ev_loop *loop_lo = 0;	2464	struct ev_loop *loop_lo = 0;
2201	struct ev_embed embed;	2465	ev_embed embed;
2202		2466
2203	// see if there is a chance of getting one that works	2467	// see if there is a chance of getting one that works
2204	// (remember that a flags value of 0 means autodetection)	2468	// (remember that a flags value of 0 means autodetection)
2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2469	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2470	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2220	kqueue implementation). Store the kqueue/socket-only event loop in	2484	kqueue implementation). Store the kqueue/socket-only event loop in
2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2485	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2222		2486
2223	struct ev_loop *loop = ev_default_init (0);	2487	struct ev_loop *loop = ev_default_init (0);
2224	struct ev_loop *loop_socket = 0;	2488	struct ev_loop *loop_socket = 0;
2225	struct ev_embed embed;	2489	ev_embed embed;
2226		2490
2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2491	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2492	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2229	{	2493	{
2230	ev_embed_init (&embed, 0, loop_socket);	2494	ev_embed_init (&embed, 0, loop_socket);
…		…
2286	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
2287	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
2288	need elaborate support such as pthreads.	2552	need elaborate support such as pthreads.
2289		2553
2290	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
2291	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
2292	queue:	2556	queue:
2293		2557
2294	=over 4	2558	=over 4
2295		2559
2296	=item queueing from a signal handler context	2560	=item queueing from a signal handler context
2297		2561
2298	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
2299	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
2300	some fictitious SIGUSR1 handler:	2564	an example that does that for some fictitious SIGUSR1 handler:
2301		2565
2302	static ev_async mysig;	2566	static ev_async mysig;
2303		2567
2304	static void	2568	static void
2305	sigusr1_handler (void)	2569	sigusr1_handler (void)
…		…
2372		2636
2373	=item ev_async_init (ev_async *, callback)	2637	=item ev_async_init (ev_async *, callback)
2374		2638
2375	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
2376	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,
2377	believe me.	2641	trust me.
2378		2642
2379	=item ev_async_send (loop, ev_async *)	2643	=item ev_async_send (loop, ev_async *)
2380		2644
2381	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
2382	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
2383	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
2384	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
2385	section below on what exactly this means).	2649	section below on what exactly this means).
2386		2650
2387	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,
2388	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
…		…
2412	=over 4	2676	=over 4
2413		2677
2414	=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)
2415		2679
2416	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
2417	callback on whichever event happens first and automatically stop both	2681	callback on whichever event happens first and automatically stops both
2418	watchers. This is useful if you want to wait for a single event on an fd	2682	watchers. This is useful if you want to wait for a single event on an fd
2419	or timeout without having to allocate/configure/start/stop/free one or	2683	or timeout without having to allocate/configure/start/stop/free one or
2420	more watchers yourself.	2684	more watchers yourself.
2421		2685
2422	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
2423	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
2424	C<events> set will be created and started.	2688	the given C<fd> and C<events> set will be created and started.
2425		2689
2426	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
2427	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
2428	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.
2429	dubious value.
2430		2693
2431	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
2432	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
2433	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>
2434	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.
		2700
		2701	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2435		2702
2436	static void stdin_ready (int revents, void *arg)	2703	static void stdin_ready (int revents, void *arg)
2437	{	2704	{
		2705	if (revents & EV_READ)
		2706	/* stdin might have data for us, joy! */;
2438	if (revents & EV_TIMEOUT)	2707	else if (revents & EV_TIMEOUT)
2439	/* doh, nothing entered */;	2708	/* doh, nothing entered */;
2440	else if (revents & EV_READ)
2441	/* stdin might have data for us, joy! */;
2442	}	2709	}
2443		2710
2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2711	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2445		2712
2446	=item ev_feed_event (ev_loop *, watcher *, int revents)	2713	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2447		2714
2448	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
2449	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
2450	initialised but not necessarily started event watcher).	2717	initialised but not necessarily started event watcher).
2451		2718
2452	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2719	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2453		2720
2454	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
2455	the given events it.	2722	the given events it.
2456		2723
2457	=item ev_feed_signal_event (ev_loop *loop, int signum)	2724	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2458		2725
2459	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
2460	loop!).	2727	loop!).
2461		2728
2462	=back	2729	=back
…		…
2594		2861
2595	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)>.
2596		2863
2597	See the method-C<set> above for more details.	2864	See the method-C<set> above for more details.
2598		2865
2599	Example:	2866	Example: Use a plain function as callback.
2600		2867
2601	static void io_cb (ev::io &w, int revents) { }	2868	static void io_cb (ev::io &w, int revents) { }
2602	iow.set <io_cb> ();	2869	iow.set <io_cb> ();
2603		2870
2604	=item w->set (struct ev_loop *)	2871	=item w->set (struct ev_loop *)
…		…
2642	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
2643	the constructor.	2910	the constructor.
2644		2911
2645	class myclass	2912	class myclass
2646	{	2913	{
2647	ev::io io; void io_cb (ev::io &w, int revents);	2914	ev::io io ; void io_cb (ev::io &w, int revents);
2648	ev:idle idle void idle_cb (ev::idle &w, int revents);	2915	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2649		2916
2650	myclass (int fd)	2917	myclass (int fd)
2651	{	2918	{
2652	io .set <myclass, &myclass::io_cb > (this);	2919	io .set <myclass, &myclass::io_cb > (this);
2653	idle.set <myclass, &myclass::idle_cb> (this);	2920	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2669	=item Perl	2936	=item Perl
2670		2937
2671	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
2672	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,
2673	there are additional modules that implement libev-compatible interfaces	2940	there are additional modules that implement libev-compatible interfaces
2674	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2941	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2675	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2942	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2943	and C<EV::Glib>).
2676		2944
2677	It can be found and installed via CPAN, its homepage is at	2945	It can be found and installed via CPAN, its homepage is at
2678	L<http://software.schmorp.de/pkg/EV>.	2946	L<http://software.schmorp.de/pkg/EV>.
2679		2947
2680	=item Python	2948	=item Python
…		…
2696	=item D	2964	=item D
2697		2965
2698	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
2699	be found at L<http://proj.llucax.com.ar/wiki/evd>.	2967	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2700		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/>.
		2973
2701	=back	2974	=back
2702		2975
2703		2976
2704	=head1 MACRO MAGIC	2977	=head1 MACRO MAGIC
2705		2978
…		…
2859		3132
2860	=head2 PREPROCESSOR SYMBOLS/MACROS	3133	=head2 PREPROCESSOR SYMBOLS/MACROS
2861		3134
2862	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
2863	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
2864	autoconf is noted for every option.	3137	autoconf is documented for every option.
2865		3138
2866	=over 4	3139	=over 4
2867		3140
2868	=item EV_STANDALONE	3141	=item EV_STANDALONE
2869		3142
…		…
3039	When doing priority-based operations, libev usually has to linearly search	3312	When doing priority-based operations, libev usually has to linearly search
3040	all the priorities, so having many of them (hundreds) uses a lot of space	3313	all the priorities, so having many of them (hundreds) uses a lot of space
3041	and time, so using the defaults of five priorities (-2 .. +2) is usually	3314	and time, so using the defaults of five priorities (-2 .. +2) is usually
3042	fine.	3315	fine.
3043		3316
3044	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
3045	C<0> will save some memory and CPU.	3318	both to C<0> will save some memory and CPU.
3046		3319
3047	=item EV_PERIODIC_ENABLE	3320	=item EV_PERIODIC_ENABLE
3048		3321
3049	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
3050	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
…		…
3057	code.	3330	code.
3058		3331
3059	=item EV_EMBED_ENABLE	3332	=item EV_EMBED_ENABLE
3060		3333
3061	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
3062	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.
3063		3337
3064	=item EV_STAT_ENABLE	3338	=item EV_STAT_ENABLE
3065		3339
3066	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
3067	defined to be C<0>, then they are not.	3341	defined to be C<0>, then they are not.
…		…
3099	two).	3373	two).
3100		3374
3101	=item EV_USE_4HEAP	3375	=item EV_USE_4HEAP
3102		3376
3103	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
3104	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
3105	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
3106	noticeably faster performance with many (thousands) of watchers.	3380	faster performance with many (thousands) of watchers.
3107		3381
3108	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>
3109	(disabled).	3383	(disabled).
3110		3384
3111	=item EV_HEAP_CACHE_AT	3385	=item EV_HEAP_CACHE_AT
3112		3386
3113	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
3114	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
3115	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>),
3116	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,
3117	but avoids random read accesses on heap changes. This improves performance	3391	but avoids random read accesses on heap changes. This improves performance
3118	noticeably with with many (hundreds) of watchers.	3392	noticeably with many (hundreds) of watchers.
3119		3393
3120	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>
3121	(disabled).	3395	(disabled).
3122		3396
3123	=item EV_VERIFY	3397	=item EV_VERIFY
…		…
3129	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
3130	verification code will be called very frequently, which will slow down	3404	verification code will be called very frequently, which will slow down
3131	libev considerably.	3405	libev considerably.
3132		3406
3133	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
3134	C<0.>	3408	C<0>.
3135		3409
3136	=item EV_COMMON	3410	=item EV_COMMON
3137		3411
3138	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
3139	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
…		…
3156	and the way callbacks are invoked and set. Must expand to a struct member	3430	and the way callbacks are invoked and set. Must expand to a struct member
3157	definition and a statement, respectively. See the F<ev.h> header file for	3431	definition and a statement, respectively. See the F<ev.h> header file for
3158	their default definitions. One possible use for overriding these is to	3432	their default definitions. One possible use for overriding these is to
3159	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3433	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3160	method calls instead of plain function calls in C++.	3434	method calls instead of plain function calls in C++.
		3435
		3436	=back
3161		3437
3162	=head2 EXPORTED API SYMBOLS	3438	=head2 EXPORTED API SYMBOLS
3163		3439
3164	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
3165	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
…		…
3212	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:
3213		3489
3214	#include "ev_cpp.h"	3490	#include "ev_cpp.h"
3215	#include "ev.c"	3491	#include "ev.c"
3216		3492
		3493	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3217		3494
3218	=head1 THREADS AND COROUTINES	3495	=head2 THREADS AND COROUTINES
3219		3496
3220	=head2 THREADS	3497	=head3 THREADS
3221		3498
3222	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
3223	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
3224	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
3225	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.
3226		3506
3227	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
3228	parallel from multiple threads, calls with the same loop parameter must be	3508	concurrently from multiple threads, calls with the same loop parameter
3229	done serially (but can be done from different threads, as long as only one	3509	must be done serially (but can be done from different threads, as long as
3230	thread ever is inside a call at any point in time, e.g. by using a mutex	3510	only one thread ever is inside a call at any point in time, e.g. by using
3231	per loop).	3511	a mutex per loop).
		3512
		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".
3232		3517
3233	If you want to know which design (one loop, locking, or multiple loops	3518	If you want to know which design (one loop, locking, or multiple loops
3234	without or something else still) is best for your problem, then I cannot	3519	without or something else still) is best for your problem, then I cannot
3235	help you. I can give some generic advice however:	3520	help you, but here is some generic advice:
3236		3521
3237	=over 4	3522	=over 4
3238		3523
3239	=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
3240	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.
…		…
3252		3537
3253	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
3254	better than you currently do :-)	3539	better than you currently do :-)
3255		3540
3256	=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
3257	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
3258	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.
3259		3551
3260	=back	3552	=back
3261		3553
3262	=head2 COROUTINES	3554	=head3 COROUTINES
3263		3555
3264	Libev is much more accommodating to coroutines ("cooperative threads"):	3556	Libev is very accommodating to coroutines ("cooperative threads"):
3265	libev fully supports nesting calls to it's functions from different	3557	libev fully supports nesting calls to its functions from different
3266	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3558	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3267	different coroutines and switch freely between both coroutines running the	3559	different coroutines, and switch freely between both coroutines running the
3268	loop, as long as you don't confuse yourself). The only exception is that	3560	loop, as long as you don't confuse yourself). The only exception is that
3269	you must not do this from C<ev_periodic> reschedule callbacks.	3561	you must not do this from C<ev_periodic> reschedule callbacks.
3270		3562
3271	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
3272	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
3273	switches.	3565	they do not clal any callbacks.
3274		3566
		3567	=head2 COMPILER WARNINGS
3275		3568
3276	=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.
3277		3572
3278	In this section the complexities of (many of) the algorithms used inside	3573	However, these are unavoidable for many reasons. For one, each compiler
3279	libev will be explained. For complexity discussions about backends see the	3574	has different warnings, and each user has different tastes regarding
3280	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.
3281		3577
3282	All of the following are about amortised time: If an array needs to be	3578	Another reason is that some compiler warnings require elaborate
3283	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
3284	happens asymptotically never with higher number of elements, so O(1) might	3580	maintainable.
3285	mean it might do a lengthy realloc operation in rare cases, but on average
3286	it is much faster and asymptotically approaches constant time.
3287		3581
3288	=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.
3289		3588
3290	=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.
3291		3594
3292	This means that, when you have a watcher that triggers in one hour and
3293	there are 100 watchers that would trigger before that then inserting will
3294	have to skip roughly seven (C<ld 100>) of these watchers.
3295		3595
3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3596	=head2 VALGRIND
3297		3597
3298	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
3299	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.
3300		3600
3301	=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:
3302		3603
3303	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.
3304		3607
3305	=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.
3306		3610
3307	=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.
3308		3615
3309	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
3310	correct watcher to remove. The lists are usually short (you don't usually	3617	make it into some kind of religion.
3311	have many watchers waiting for the same fd or signal).
3312		3618
3313	=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.
3314		3624
3315	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
3316	fixed position in the storage array.	3626	I suggest using suppression lists.
3317		3627
3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3319		3628
3320	A change means an I/O watcher gets started or stopped, which requires	3629	=head1 PORTABILITY NOTES
3321	libev to recalculate its status (and possibly tell the kernel, depending
3322	on backend and whether C<ev_io_set> was used).
3323		3630
3324	=item Activating one watcher (putting it into the pending state): O(1)
3325
3326	=item Priority handling: O(number_of_priorities)
3327
3328	Priorities are implemented by allocating some space for each
3329	priority. When doing priority-based operations, libev usually has to
3330	linearly search all the priorities, but starting/stopping and activating
3331	watchers becomes O(1) w.r.t. priority handling.
3332
3333	=item Sending an ev_async: O(1)
3334
3335	=item Processing ev_async_send: O(number_of_async_watchers)
3336
3337	=item Processing signals: O(max_signal_number)
3338
3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
3340	calls in the current loop iteration. Checking for async and signal events
3341	involves iterating over all running async watchers or all signal numbers.
3342
3343	=back
3344
3345
3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3631	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3347		3632
3348	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
3349	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
3350	model. Libev still offers limited functionality on this platform in	3635	model. Libev still offers limited functionality on this platform in
3351	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
…		…
3362		3647
3363	Not a libev limitation but worth mentioning: windows apparently doesn't	3648	Not a libev limitation but worth mentioning: windows apparently doesn't
3364	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
3365	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,
3366	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
3367	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
3368	available).	3653	available).
3369		3654
3370	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
3371	the abysmal performance of winsockets, using a large number of sockets	3656	the abysmal performance of winsockets, using a large number of sockets
3372	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
…		…
3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3668	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3384		3669
3385	#include "ev.h"	3670	#include "ev.h"
3386		3671
3387	And compile the following F<evwrap.c> file into your project (make sure	3672	And compile the following F<evwrap.c> file into your project (make sure
3388	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3673	you do I<not> compile the F<ev.c> or any other embedded source files!):
3389		3674
3390	#include "evwrap.h"	3675	#include "evwrap.h"
3391	#include "ev.c"	3676	#include "ev.c"
3392		3677
3393	=over 4	3678	=over 4
…		…
3438	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
3439	calling select (O(n²)) will likely make this unworkable.	3724	calling select (O(n²)) will likely make this unworkable.
3440		3725
3441	=back	3726	=back
3442		3727
3443
3444	=head1 PORTABILITY REQUIREMENTS	3728	=head2 PORTABILITY REQUIREMENTS
3445		3729
3446	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
3447	additional extensions:	3731	backend-specific APIs, libev relies on a few additional extensions:
3448		3732
3449	=over 4	3733	=over 4
3450		3734
3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3735	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3452	calling conventions regardless of C<ev_watcher_type *>.	3736	calling conventions regardless of C<ev_watcher_type *>.
…		…
3458	calls them using an C<ev_watcher *> internally.	3742	calls them using an C<ev_watcher *> internally.
3459		3743
3460	=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
3461		3745
3462	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
3463	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
3464	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
3465	believed to be sufficiently portable.	3749	believed to be sufficiently portable.
3466		3750
3467	=item C<sigprocmask> must work in a threaded environment	3751	=item C<sigprocmask> must work in a threaded environment
3468		3752
…		…
3477	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
3478	well.	3762	well.
3479		3763
3480	=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
3481		3765
3482	To improve portability and simplify using libev, libev uses C<long>	3766	To improve portability and simplify its API, libev uses C<long> internally
3483	internally instead of C<size_t> when allocating its data structures. On	3767	instead of C<size_t> when allocating its data structures. On non-POSIX
3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3768	systems (Microsoft...) this might be unexpectedly low, but is still at
3485	is still at least 31 bits everywhere, which is enough for hundreds of	3769	least 31 bits everywhere, which is enough for hundreds of millions of
3486	millions of watchers.	3770	watchers.
3487		3771
3488	=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
3489		3773
3490	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
3491	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
…		…
3495	=back	3779	=back
3496		3780
3497	If you know of other additional requirements drop me a note.	3781	If you know of other additional requirements drop me a note.
3498		3782
3499		3783
3500	=head1 COMPILER WARNINGS	3784	=head1 ALGORITHMIC COMPLEXITIES
3501		3785
3502	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
3503	lot of warnings when compiling libev code. Some people are apparently	3787	libev will be documented. For complexity discussions about backends see
3504	scared by this.	3788	the documentation for C<ev_default_init>.
3505		3789
3506	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
3507	has different warnings, and each user has different tastes regarding	3791	extended, libev needs to realloc and move the whole array, but this
3508	warning options. "Warn-free" code therefore cannot be a goal except when	3792	happens asymptotically rarer with higher number of elements, so O(1) might
3509	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.
3510		3795
3511	Another reason is that some compiler warnings require elaborate	3796	=over 4
3512	workarounds, or other changes to the code that make it less clear and less
3513	maintainable.
3514		3797
3515	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)
3516	wrong (because they don't actually warn about the condition their message
3517	seems to warn about).
3518		3799
3519	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
3520	"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
3521	with any compiler warnings enabled unless you are prepared to cope with	3802	have to skip roughly seven (C<ld 100>) of these watchers.
3522	them (e.g. by ignoring them). Remember that warnings are just that:
3523	warnings, not errors, or proof of bugs.
3524		3803
		3804	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3525		3805
3526	=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.
3527		3808
3528	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)
3529	highly useful, but valgrind reports are very hard to interpret.
3530		3810
3531	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.
3532	in libev, then check twice: If valgrind reports something like:
3533		3812
3534	==2274== definitely lost: 0 bytes in 0 blocks.	3813	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3535	==2274== possibly lost: 0 bytes in 0 blocks.
3536	==2274== still reachable: 256 bytes in 1 blocks.
3537		3814
3538	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))
3539	valgrind might report kernel bugs as if it were a bug in libev, or it
3540	might be confused (it is a very good tool, but only a tool).
3541		3816
3542	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
3543	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
3544	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
3545	no bug" answer and take the chance of learning how to interpret valgrind	3820	is rare).
3546	properly.
3547		3821
3548	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)
3549	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
3550		3853
3551		3854
3552	=head1 AUTHOR	3855	=head1 AUTHOR
3553		3856
3554	Marc Lehmann <libev@schmorp.de>.	3857	Marc Lehmann <libev@schmorp.de>.

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines