ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.179 by root, Sat Sep 13 19:14:21 2008 UTC vs.
Revision 1.226 by root, Wed Mar 4 12:51:37 2009 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	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	109	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	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	217	recommended ones.
216		218
217	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
218		220
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		222
221	Sets the allocation function to use (the prototype is similar - the	223	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	224	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	225	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	226	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	252	}
251		253
252	...	254	...
253	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
254		256
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		258
257	Set the callback function to call on a retryable system call error (such	259	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	260	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	261	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	262	callback is set, then libev will expect it to remedy the situation, no
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	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	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		387
382	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	392
387	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
389		409
390	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	411	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
395		415	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		416
400	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible, i.e.	418	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
403		428
404	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	430	all kernel versions tested so far.
406		431
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		436
412	Kqueue deserves special mention, as at the time of this writing, it	437	Kqueue deserves special mention, as at the time of this writing, it
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
414	with anything but sockets and pipes, except on Darwin, where of course	439	with anything but sockets and pipes, except on Darwin, where of course
415	it's completely useless). For this reason it's not being "auto-detected"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	without API changes to existing programs. For this reason it's not being
416	unless you explicitly specify it explicitly in the flags (i.e. using	443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	445	system like NetBSD.
419		446
420	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		450
424	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
430		458
431	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
432		460
433	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
434	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
435	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
436	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
438	sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
439		467
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	470	C<NOTE_EOF>.
443		471
…		…
460	While this backend scales well, it requires one system call per active	488	While this backend scales well, it requires one system call per active
461	file descriptor per loop iteration. For small and medium numbers of file	489	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	491	might perform better.
464		492
465	On the positive side, ignoring the spurious readiness notifications, this	493	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
468		497
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	499	C<EVBACKEND_POLL>.
471		500
472	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
…		…
481		510
482	If one or more of these are or'ed into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
483	backends will be tried (in the reverse order as listed here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
484	specified, all backends in C<ev_recommended_backends ()> will be tried.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
485		514
486	The most typical usage is like this:	515	Example: This is the most typical usage.
487		516
488	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		519
491	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	521	environment settings to be taken into account:
493		522
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		524
496	Use whatever libev has to offer, but make sure that kqueue is used if	525	Example: Use whatever libev has to offer, but make sure that kqueue is
497	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
498	event loop and only if you know the OS supports your types of fds):	527	private event loop and only if you know the OS supports your types of
		528	fds):
499		529
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		531
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		533
…		…
524	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
526	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	557	for example).
528		558
529	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
532		562
533	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
534	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
535	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
536	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
561		591
562	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
563		593
564	Like C<ev_default_fork>, but acts on an event loop created by	594	Like C<ev_default_fork>, but acts on an event loop created by
565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
566	after fork, and how you do this is entirely your own problem.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
567		598
568	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
569		600
570	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
571		603
572	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
573		605
574	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
575	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
613	If the flags argument is specified as C<0>, it will not return until	645	If the flags argument is specified as C<0>, it will not return until
614	either no event watchers are active anymore or C<ev_unloop> was called.	646	either no event watchers are active anymore or C<ev_unloop> was called.
615		647
616	Please note that an explicit C<ev_unloop> is usually better than	648	Please note that an explicit C<ev_unloop> is usually better than
617	relying on all watchers to be stopped when deciding when a program has	649	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	650	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	651	that automatically loops as long as it has to and no longer by virtue
620	relying on its watchers stopping correctly is a thing of beauty.	652	of relying on its watchers stopping correctly, that is truly a thing of
		653	beauty.
621		654
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
623	those events and any outstanding ones, but will not block your process in	656	those events and any already outstanding ones, but will not block your
624	case there are no events and will return after one iteration of the loop.	657	process in case there are no events and will return after one iteration of
		658	the loop.
625		659
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
627	necessary) and will handle those and any outstanding ones. It will block	661	necessary) and will handle those and any already outstanding ones. It
628	your process until at least one new event arrives, and will return after	662	will block your process until at least one new event arrives (which could
629	one iteration of the loop. This is useful if you are waiting for some	663	be an event internal to libev itself, so there is no guarantee that a
630	external event in conjunction with something not expressible using other	664	user-registered callback will be called), and will return after one
		665	iteration of the loop.
		666
		667	This is useful if you are waiting for some external event in conjunction
		668	with something not expressible using other libev watchers (i.e. "roll your
631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
632	usually a better approach for this kind of thing.	670	usually a better approach for this kind of thing.
633		671
634	Here are the gory details of what C<ev_loop> does:	672	Here are the gory details of what C<ev_loop> does:
635		673
636	- Before the first iteration, call any pending watchers.	674	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	684	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	685	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	686	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	687	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	689	- Queue all expired timers.
652	- Queue all outstanding periodics.	690	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	691	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	692	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	693	- Call all queued watchers in reverse order (i.e. check watchers first).
656	Signals and child watchers are implemented as I/O watchers, and will	694	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	695	be handled here by queueing them when their watcher gets executed.
…		…
674	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
675	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		714
677	This "unloop state" will be cleared when entering C<ev_loop> again.	715	This "unloop state" will be cleared when entering C<ev_loop> again.
678		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
679	=item ev_ref (loop)	719	=item ev_ref (loop)
680		720
681	=item ev_unref (loop)	721	=item ev_unref (loop)
682		722
683	Ref/unref can be used to add or remove a reference count on the event	723	Ref/unref can be used to add or remove a reference count on the event
684	loop: Every watcher keeps one reference, and as long as the reference	724	loop: Every watcher keeps one reference, and as long as the reference
685	count is nonzero, C<ev_loop> will not return on its own. If you have	725	count is nonzero, C<ev_loop> will not return on its own.
		726
686	a watcher you never unregister that should not keep C<ev_loop> from	727	If you have a watcher you never unregister that should not keep C<ev_loop>
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	728	from returning, call ev_unref() after starting, and ev_ref() before
		729	stopping it.
		730
688	example, libev itself uses this for its internal signal pipe: It is not	731	As an example, libev itself uses this for its internal signal pipe: It is
689	visible to the libev user and should not keep C<ev_loop> from exiting if	732	not visible to the libev user and should not keep C<ev_loop> from exiting
690	no event watchers registered by it are active. It is also an excellent	733	if no event watchers registered by it are active. It is also an excellent
691	way to do this for generic recurring timers or from within third-party	734	way to do this for generic recurring timers or from within third-party
692	libraries. Just remember to I<unref after start> and I<ref before stop>	735	libraries. Just remember to I<unref after start> and I<ref before stop>
693	(but only if the watcher wasn't active before, or was active before,	736	(but only if the watcher wasn't active before, or was active before,
694	respectively).	737	respectively).
695		738
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	740	running when nothing else is active.
698		741
699	struct ev_signal exitsig;	742	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	743	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	744	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	745	evf_unref (loop);
703		746
704	Example: For some weird reason, unregister the above signal handler again.	747	Example: For some weird reason, unregister the above signal handler again.
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	761	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
719	allows libev to delay invocation of I/O and timer/periodic callbacks	762	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	763	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	764	opportunities).
722		765
723	The background is that sometimes your program runs just fast enough to	766	The idea is that sometimes your program runs just fast enough to handle
724	handle one (or very few) event(s) per loop iteration. While this makes	767	one (or very few) event(s) per loop iteration. While this makes the
725	the program responsive, it also wastes a lot of CPU time to poll for new	768	program responsive, it also wastes a lot of CPU time to poll for new
726	events, especially with backends like C<select ()> which have a high	769	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	770	overhead for the actual polling but can deliver many events at once.
728		771
729	By setting a higher I<io collect interval> you allow libev to spend more	772	By setting a higher I<io collect interval> you allow libev to spend more
730	time collecting I/O events, so you can handle more events per iteration,	773	time collecting I/O events, so you can handle more events per iteration,
…		…
732	C<ev_timer>) will be not affected. Setting this to a non-null value will	775	C<ev_timer>) will be not affected. Setting this to a non-null value will
733	introduce an additional C<ev_sleep ()> call into most loop iterations.	776	introduce an additional C<ev_sleep ()> call into most loop iterations.
734		777
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	778	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	779	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	780	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	781	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	782	value will not introduce any overhead in libev.
740		783
741	Many (busy) programs can usually benefit by setting the I/O collect	784	Many (busy) programs can usually benefit by setting the I/O collect
742	interval to a value near C<0.1> or so, which is often enough for	785	interval to a value near C<0.1> or so, which is often enough for
743	interactive servers (of course not for games), likewise for timeouts. It	786	interactive servers (of course not for games), likewise for timeouts. It
744	usually doesn't make much sense to set it to a lower value than C<0.01>,	787	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
752	they fire on, say, one-second boundaries only.	795	they fire on, say, one-second boundaries only.
753		796
754	=item ev_loop_verify (loop)	797	=item ev_loop_verify (loop)
755		798
756	This function only does something when C<EV_VERIFY> support has been	799	This function only does something when C<EV_VERIFY> support has been
757	compiled in. It tries to go through all internal structures and checks	800	compiled in, which is the default for non-minimal builds. It tries to go
758	them for validity. If anything is found to be inconsistent, it will print	801	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	802	is found to be inconsistent, it will print an error message to standard
		803	error and call C<abort ()>.
760		804
761	This can be used to catch bugs inside libev itself: under normal	805	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	806	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	807	data structures consistent.
764		808
765	=back	809	=back
766		810
767		811
768	=head1 ANATOMY OF A WATCHER	812	=head1 ANATOMY OF A WATCHER
769		813
		814	In the following description, uppercase C<TYPE> in names stands for the
		815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		816	watchers and C<ev_io_start> for I/O watchers.
		817
770	A watcher is a structure that you create and register to record your	818	A watcher is a structure that you create and register to record your
771	interest in some event. For instance, if you want to wait for STDIN to	819	interest in some event. For instance, if you want to wait for STDIN to
772	become readable, you would create an C<ev_io> watcher for that:	820	become readable, you would create an C<ev_io> watcher for that:
773		821
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	823	{
776	ev_io_stop (w);	824	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	825	ev_unloop (loop, EVUNLOOP_ALL);
778	}	826	}
779		827
780	struct ev_loop *loop = ev_default_loop (0);	828	struct ev_loop *loop = ev_default_loop (0);
		829
781	struct ev_io stdin_watcher;	830	ev_io stdin_watcher;
		831
782	ev_init (&stdin_watcher, my_cb);	832	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	834	ev_io_start (loop, &stdin_watcher);
		835
785	ev_loop (loop, 0);	836	ev_loop (loop, 0);
786		837
787	As you can see, you are responsible for allocating the memory for your	838	As you can see, you are responsible for allocating the memory for your
788	watcher structures (and it is usually a bad idea to do this on the stack,	839	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	840	stack).
		841
		842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
790		844
791	Each watcher structure must be initialised by a call to C<ev_init	845	Each watcher structure must be initialised by a call to C<ev_init
792	(watcher *, callback)>, which expects a callback to be provided. This	846	(watcher *, callback)>, which expects a callback to be provided. This
793	callback gets invoked each time the event occurs (or, in the case of I/O	847	callback gets invoked each time the event occurs (or, in the case of I/O
794	watchers, each time the event loop detects that the file descriptor given	848	watchers, each time the event loop detects that the file descriptor given
795	is readable and/or writable).	849	is readable and/or writable).
796		850
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	852	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	853	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	854	ev_TYPE_init (watcher *, callback, ...) >>.
801		855
802	To make the watcher actually watch out for events, you have to start it	856	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	857	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	858	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		860
807	As long as your watcher is active (has been started but not stopped) you	861	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	862	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	863	reinitialise it or call its C<ev_TYPE_set> macro.
810		864
811	Each and every callback receives the event loop pointer as first, the	865	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	866	registered watcher structure as second, and a bitset of received events as
813	third argument.	867	third argument.
814		868
…		…
877	=item C<EV_ERROR>	931	=item C<EV_ERROR>
878		932
879	An unspecified error has occurred, the watcher has been stopped. This might	933	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	934	happen because the watcher could not be properly started because libev
881	ran out of memory, a file descriptor was found to be closed or any other	935	ran out of memory, a file descriptor was found to be closed or any other
		936	problem. Libev considers these application bugs.
		937
882	problem. You best act on it by reporting the problem and somehow coping	938	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	939	watcher being stopped. Note that well-written programs should not receive
		940	an error ever, so when your watcher receives it, this usually indicates a
		941	bug in your program.
884		942
885	Libev will usually signal a few "dummy" events together with an error,	943	Libev will usually signal a few "dummy" events together with an error, for
886	for example it might indicate that a fd is readable or writable, and if	944	example it might indicate that a fd is readable or writable, and if your
887	your callbacks is well-written it can just attempt the operation and cope	945	callbacks is well-written it can just attempt the operation and cope with
888	with the error from read() or write(). This will not work in multi-threaded	946	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	947	programs, though, as the fd could already be closed and reused for another
		948	thing, so beware.
890		949
891	=back	950	=back
892		951
893	=head2 GENERIC WATCHER FUNCTIONS	952	=head2 GENERIC WATCHER FUNCTIONS
894
895	In the following description, C<TYPE> stands for the watcher type,
896	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
897		953
898	=over 4	954	=over 4
899		955
900	=item C<ev_init> (ev_TYPE *watcher, callback)	956	=item C<ev_init> (ev_TYPE *watcher, callback)
901		957
…		…
907	which rolls both calls into one.	963	which rolls both calls into one.
908		964
909	You can reinitialise a watcher at any time as long as it has been stopped	965	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	966	(or never started) and there are no pending events outstanding.
911		967
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	968	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	969	int revents)>.
		970
		971	Example: Initialise an C<ev_io> watcher in two steps.
		972
		973	ev_io w;
		974	ev_init (&w, my_cb);
		975	ev_io_set (&w, STDIN_FILENO, EV_READ);
914		976
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	977	=item C<ev_TYPE_set> (ev_TYPE *, [args])
916		978
917	This macro initialises the type-specific parts of a watcher. You need to	979	This macro initialises the type-specific parts of a watcher. You need to
918	call C<ev_init> at least once before you call this macro, but you can	980	call C<ev_init> at least once before you call this macro, but you can
…		…
921	difference to the C<ev_init> macro).	983	difference to the C<ev_init> macro).
922		984
923	Although some watcher types do not have type-specific arguments	985	Although some watcher types do not have type-specific arguments
924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	986	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		987
		988	See C<ev_init>, above, for an example.
		989
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	990	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		991
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	992	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
929	calls into a single call. This is the most convenient method to initialise	993	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	994	a watcher. The same limitations apply, of course.
931		995
		996	Example: Initialise and set an C<ev_io> watcher in one step.
		997
		998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		999
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
933		1001
934	Starts (activates) the given watcher. Only active watchers will receive	1002	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1003	events. If the watcher is already active nothing will happen.
936		1004
		1005	Example: Start the C<ev_io> watcher that is being abused as example in this
		1006	whole section.
		1007
		1008	ev_io_start (EV_DEFAULT_UC, &w);
		1009
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
938		1011
939	Stops the given watcher again (if active) and clears the pending	1012	Stops the given watcher if active, and clears the pending status (whether
		1013	the watcher was active or not).
		1014
940	status. It is possible that stopped watchers are pending (for example,	1015	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1016	non-repeating timers are being stopped when they become pending - but
942	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1017	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
943	you want to free or reuse the memory used by the watcher it is therefore a	1018	pending. If you want to free or reuse the memory used by the watcher it is
944	good idea to always call its C<ev_TYPE_stop> function.	1019	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1020
946	=item bool ev_is_active (ev_TYPE *watcher)	1021	=item bool ev_is_active (ev_TYPE *watcher)
947		1022
948	Returns a true value iff the watcher is active (i.e. it has been started	1023	Returns a true value iff the watcher is active (i.e. it has been started
949	and not yet been stopped). As long as a watcher is active you must not modify	1024	and not yet been stopped). As long as a watcher is active you must not modify
…		…
991	The default priority used by watchers when no priority has been set is	1066	The default priority used by watchers when no priority has been set is
992	always C<0>, which is supposed to not be too high and not be too low :).	1067	always C<0>, which is supposed to not be too high and not be too low :).
993		1068
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
995	fine, as long as you do not mind that the priority value you query might	1070	fine, as long as you do not mind that the priority value you query might
996	or might not have been adjusted to be within valid range.	1071	or might not have been clamped to the valid range.
997		1072
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1074
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1001	C<loop> nor C<revents> need to be valid as long as the watcher callback	1076	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1077	can deal with that fact, as both are simply passed through to the
		1078	callback.
1003		1079
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1080	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1081
1006	If the watcher is pending, this function returns clears its pending status	1082	If the watcher is pending, this function clears its pending status and
1007	and returns its C<revents> bitset (as if its callback was invoked). If the	1083	returns its C<revents> bitset (as if its callback was invoked). If the
1008	watcher isn't pending it does nothing and returns C<0>.	1084	watcher isn't pending it does nothing and returns C<0>.
1009		1085
		1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1087	callback to be invoked, which can be accomplished with this function.
		1088
1010	=back	1089	=back
1011		1090
1012		1091
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1093
1015	Each watcher has, by default, a member C<void *data> that you can change	1094	Each watcher has, by default, a member C<void *data> that you can change
1016	and read at any time, libev will completely ignore it. This can be used	1095	and read at any time: libev will completely ignore it. This can be used
1017	to associate arbitrary data with your watcher. If you need more data and	1096	to associate arbitrary data with your watcher. If you need more data and
1018	don't want to allocate memory and store a pointer to it in that data	1097	don't want to allocate memory and store a pointer to it in that data
1019	member, you can also "subclass" the watcher type and provide your own	1098	member, you can also "subclass" the watcher type and provide your own
1020	data:	1099	data:
1021		1100
1022	struct my_io	1101	struct my_io
1023	{	1102	{
1024	struct ev_io io;	1103	ev_io io;
1025	int otherfd;	1104	int otherfd;
1026	void *somedata;	1105	void *somedata;
1027	struct whatever *mostinteresting;	1106	struct whatever *mostinteresting;
1028	};	1107	};
1029		1108
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1112
1034	And since your callback will be called with a pointer to the watcher, you	1113	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1114	can cast it back to your own type:
1036		1115
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1117	{
1039	struct my_io *w = (struct my_io *)w_;	1118	struct my_io *w = (struct my_io *)w_;
1040	...	1119	...
1041	}	1120	}
1042		1121
…		…
1053	ev_timer t2;	1132	ev_timer t2;
1054	}	1133	}
1055		1134
1056	In this case getting the pointer to C<my_biggy> is a bit more	1135	In this case getting the pointer to C<my_biggy> is a bit more
1057	complicated: Either you store the address of your C<my_biggy> struct	1136	complicated: Either you store the address of your C<my_biggy> struct
1058	in the C<data> member of the watcher, or you need to use some pointer	1137	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1139	programmers):
1060		1140
1061	#include <stddef.h>	1141	#include <stddef.h>
1062		1142
1063	static void	1143	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1144	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1145	{
1066	struct my_biggy big = (struct my_biggy *	1146	struct my_biggy big = (struct my_biggy *
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1147	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1148	}
1069		1149
1070	static void	1150	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1151	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1152	{
1073	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1154	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1155	}
1076		1156
…		…
1104	In general you can register as many read and/or write event watchers per	1184	In general you can register as many read and/or write event watchers per
1105	fd as you want (as long as you don't confuse yourself). Setting all file	1185	fd as you want (as long as you don't confuse yourself). Setting all file
1106	descriptors to non-blocking mode is also usually a good idea (but not	1186	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1187	required if you know what you are doing).
1108		1188
1109	If you must do this, then force the use of a known-to-be-good backend	1189	If you cannot use non-blocking mode, then force the use of a
1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1190	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1112		1192
1113	Another thing you have to watch out for is that it is quite easy to	1193	Another thing you have to watch out for is that it is quite easy to
1114	receive "spurious" readiness notifications, that is your callback might	1194	receive "spurious" readiness notifications, that is your callback might
1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1116	because there is no data. Not only are some backends known to create a	1196	because there is no data. Not only are some backends known to create a
1117	lot of those (for example Solaris ports), it is very easy to get into	1197	lot of those (for example Solaris ports), it is very easy to get into
1118	this situation even with a relatively standard program structure. Thus	1198	this situation even with a relatively standard program structure. Thus
1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1201
1122	If you cannot run the fd in non-blocking mode (for example you should not	1202	If you cannot run the fd in non-blocking mode (for example you should
1123	play around with an Xlib connection), then you have to separately re-test	1203	not play around with an Xlib connection), then you have to separately
1124	whether a file descriptor is really ready with a known-to-be good interface	1204	re-test whether a file descriptor is really ready with a known-to-be good
1125	such as poll (fortunately in our Xlib example, Xlib already does this on	1205	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1206	does this on its own, so its quite safe to use). Some people additionally
		1207	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1208	indefinitely.
		1209
		1210	But really, best use non-blocking mode.
1127		1211
1128	=head3 The special problem of disappearing file descriptors	1212	=head3 The special problem of disappearing file descriptors
1129		1213
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1214	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1131	descriptor (either by calling C<close> explicitly or by any other means,	1215	descriptor (either due to calling C<close> explicitly or any other means,
1132	such as C<dup>). The reason is that you register interest in some file	1216	such as C<dup2>). The reason is that you register interest in some file
1133	descriptor, but when it goes away, the operating system will silently drop	1217	descriptor, but when it goes away, the operating system will silently drop
1134	this interest. If another file descriptor with the same number then is	1218	this interest. If another file descriptor with the same number then is
1135	registered with libev, there is no efficient way to see that this is, in	1219	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1220	fact, a different file descriptor.
1137		1221
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1253	C<EVBACKEND_POLL>.
1170		1254
1171	=head3 The special problem of SIGPIPE	1255	=head3 The special problem of SIGPIPE
1172		1256
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1174	when writing to a pipe whose other end has been closed, your program gets	1258	when writing to a pipe whose other end has been closed, your program gets
1175	send a SIGPIPE, which, by default, aborts your program. For most programs	1259	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1260	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1261
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1262	So when you encounter spurious, unexplained daemon exits, make sure you
1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1180	somewhere, as that would have given you a big clue).	1264	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1271	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1272
1189	=item ev_io_set (ev_io *, int fd, int events)	1273	=item ev_io_set (ev_io *, int fd, int events)
1190		1274
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1275	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1276	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1193	C<EV_READ | EV_WRITE> to receive the given events.	1277	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1278
1195	=item int fd [read-only]	1279	=item int fd [read-only]
1196		1280
1197	The file descriptor being watched.	1281	The file descriptor being watched.
1198		1282
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1291	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1208	readable, but only once. Since it is likely line-buffered, you could	1292	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1293	attempt to read a whole line in the callback.
1210		1294
1211	static void	1295	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1296	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1297	{
1214	ev_io_stop (loop, w);	1298	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1299	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1300	}
1217		1301
1218	...	1302	...
1219	struct ev_loop *loop = ev_default_init (0);	1303	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1304	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1306	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1307	ev_loop (loop, 0);
1224		1308
1225		1309
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1312	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1313	given time, and optionally repeating in regular intervals after that.
1230		1314
1231	The timers are based on real time, that is, if you register an event that	1315	The timers are based on real time, that is, if you register an event that
1232	times out after an hour and you reset your system clock to January last	1316	times out after an hour and you reset your system clock to January last
1233	year, it will still time out after (roughly) and hour. "Roughly" because	1317	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1319	monotonic clock option helps a lot here).
1236		1320
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1321	The callback is guaranteed to be invoked only I<after> its timeout has
1238	but if multiple timers become ready during the same loop iteration then	1322	passed, but if multiple timers become ready during the same loop iteration
1239	order of execution is undefined.	1323	then order of execution is undefined.
		1324
		1325	=head3 Be smart about timeouts
		1326
		1327	Many real-world problems involve some kind of timeout, usually for error
		1328	recovery. A typical example is an HTTP request - if the other side hangs,
		1329	you want to raise some error after a while.
		1330
		1331	What follows are some ways to handle this problem, from obvious and
		1332	inefficient to smart and efficient.
		1333
		1334	In the following, a 60 second activity timeout is assumed - a timeout that
		1335	gets reset to 60 seconds each time there is activity (e.g. each time some
		1336	data or other life sign was received).
		1337
		1338	=over 4
		1339
		1340	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1341
		1342	This is the most obvious, but not the most simple way: In the beginning,
		1343	start the watcher:
		1344
		1345	ev_timer_init (timer, callback, 60., 0.);
		1346	ev_timer_start (loop, timer);
		1347
		1348	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1349	and start it again:
		1350
		1351	ev_timer_stop (loop, timer);
		1352	ev_timer_set (timer, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	This is relatively simple to implement, but means that each time there is
		1356	some activity, libev will first have to remove the timer from its internal
		1357	data structure and then add it again. Libev tries to be fast, but it's
		1358	still not a constant-time operation.
		1359
		1360	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1361
		1362	This is the easiest way, and involves using C<ev_timer_again> instead of
		1363	C<ev_timer_start>.
		1364
		1365	To implement this, configure an C<ev_timer> with a C<repeat> value
		1366	of C<60> and then call C<ev_timer_again> at start and each time you
		1367	successfully read or write some data. If you go into an idle state where
		1368	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1369	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1370
		1371	That means you can ignore both the C<ev_timer_start> function and the
		1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1373	member and C<ev_timer_again>.
		1374
		1375	At start:
		1376
		1377	ev_timer_init (timer, callback);
		1378	timer->repeat = 60.;
		1379	ev_timer_again (loop, timer);
		1380
		1381	Each time there is some activity:
		1382
		1383	ev_timer_again (loop, timer);
		1384
		1385	It is even possible to change the time-out on the fly, regardless of
		1386	whether the watcher is active or not:
		1387
		1388	timer->repeat = 30.;
		1389	ev_timer_again (loop, timer);
		1390
		1391	This is slightly more efficient then stopping/starting the timer each time
		1392	you want to modify its timeout value, as libev does not have to completely
		1393	remove and re-insert the timer from/into its internal data structure.
		1394
		1395	It is, however, even simpler than the "obvious" way to do it.
		1396
		1397	=item 3. Let the timer time out, but then re-arm it as required.
		1398
		1399	This method is more tricky, but usually most efficient: Most timeouts are
		1400	relatively long compared to the intervals between other activity - in
		1401	our example, within 60 seconds, there are usually many I/O events with
		1402	associated activity resets.
		1403
		1404	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1405	but remember the time of last activity, and check for a real timeout only
		1406	within the callback:
		1407
		1408	ev_tstamp last_activity; // time of last activity
		1409
		1410	static void
		1411	callback (EV_P_ ev_timer *w, int revents)
		1412	{
		1413	ev_tstamp now = ev_now (EV_A);
		1414	ev_tstamp timeout = last_activity + 60.;
		1415
		1416	// if last_activity + 60. is older than now, we did time out
		1417	if (timeout < now)
		1418	{
		1419	// timeout occured, take action
		1420	}
		1421	else
		1422	{
		1423	// callback was invoked, but there was some activity, re-arm
		1424	// the watcher to fire in last_activity + 60, which is
		1425	// guaranteed to be in the future, so "again" is positive:
		1426	w->repeat = timeout - now;
		1427	ev_timer_again (EV_A_ w);
		1428	}
		1429	}
		1430
		1431	To summarise the callback: first calculate the real timeout (defined
		1432	as "60 seconds after the last activity"), then check if that time has
		1433	been reached, which means something I<did>, in fact, time out. Otherwise
		1434	the callback was invoked too early (C<timeout> is in the future), so
		1435	re-schedule the timer to fire at that future time, to see if maybe we have
		1436	a timeout then.
		1437
		1438	Note how C<ev_timer_again> is used, taking advantage of the
		1439	C<ev_timer_again> optimisation when the timer is already running.
		1440
		1441	This scheme causes more callback invocations (about one every 60 seconds
		1442	minus half the average time between activity), but virtually no calls to
		1443	libev to change the timeout.
		1444
		1445	To start the timer, simply initialise the watcher and set C<last_activity>
		1446	to the current time (meaning we just have some activity :), then call the
		1447	callback, which will "do the right thing" and start the timer:
		1448
		1449	ev_timer_init (timer, callback);
		1450	last_activity = ev_now (loop);
		1451	callback (loop, timer, EV_TIMEOUT);
		1452
		1453	And when there is some activity, simply store the current time in
		1454	C<last_activity>, no libev calls at all:
		1455
		1456	last_actiivty = ev_now (loop);
		1457
		1458	This technique is slightly more complex, but in most cases where the
		1459	time-out is unlikely to be triggered, much more efficient.
		1460
		1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1462	callback :) - just change the timeout and invoke the callback, which will
		1463	fix things for you.
		1464
		1465	=item 4. Wee, just use a double-linked list for your timeouts.
		1466
		1467	If there is not one request, but many thousands (millions...), all
		1468	employing some kind of timeout with the same timeout value, then one can
		1469	do even better:
		1470
		1471	When starting the timeout, calculate the timeout value and put the timeout
		1472	at the I<end> of the list.
		1473
		1474	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1475	the list is expected to fire (for example, using the technique #3).
		1476
		1477	When there is some activity, remove the timer from the list, recalculate
		1478	the timeout, append it to the end of the list again, and make sure to
		1479	update the C<ev_timer> if it was taken from the beginning of the list.
		1480
		1481	This way, one can manage an unlimited number of timeouts in O(1) time for
		1482	starting, stopping and updating the timers, at the expense of a major
		1483	complication, and having to use a constant timeout. The constant timeout
		1484	ensures that the list stays sorted.
		1485
		1486	=back
		1487
		1488	So which method the best?
		1489
		1490	Method #2 is a simple no-brain-required solution that is adequate in most
		1491	situations. Method #3 requires a bit more thinking, but handles many cases
		1492	better, and isn't very complicated either. In most case, choosing either
		1493	one is fine, with #3 being better in typical situations.
		1494
		1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1496	rather complicated, but extremely efficient, something that really pays
		1497	off after the first million or so of active timers, i.e. it's usually
		1498	overkill :)
1240		1499
1241	=head3 The special problem of time updates	1500	=head3 The special problem of time updates
1242		1501
1243	Establishing the current time is a costly operation (it usually takes at	1502	Establishing the current time is a costly operation (it usually takes at
1244	least two system calls): EV therefore updates its idea of the current	1503	least two system calls): EV therefore updates its idea of the current
1245	time only before and after C<ev_loop> polls for new events, which causes	1504	time only before and after C<ev_loop> collects new events, which causes a
1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1506	lots of events in one iteration.
1248		1507
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1508	The relative timeouts are calculated relative to the C<ev_now ()>
1250	time. This is usually the right thing as this timestamp refers to the time	1509	time. This is usually the right thing as this timestamp refers to the time
1251	of the event triggering whatever timeout you are modifying/starting. If	1510	of the event triggering whatever timeout you are modifying/starting. If
1252	you suspect event processing to be delayed and you I<need> to base the	1511	you suspect event processing to be delayed and you I<need> to base the
…		…
1288	If the timer is started but non-repeating, stop it (as if it timed out).	1547	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1548
1290	If the timer is repeating, either start it if necessary (with the	1549	If the timer is repeating, either start it if necessary (with the
1291	C<repeat> value), or reset the running timer to the C<repeat> value.	1550	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1551
1293	This sounds a bit complicated, but here is a useful and typical	1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	1553	usage example.
1295	timeout, that is, you want to be called when there have been, say, 60
1296	seconds of inactivity on the socket. The easiest way to do this is to
1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1298	C<ev_timer_again> each time you successfully read or write some data. If
1299	you go into an idle state where you do not expect data to travel on the
1300	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1301	automatically restart it if need be.
1302
1303	That means you can ignore the C<after> value and C<ev_timer_start>
1304	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1305
1306	ev_timer_init (timer, callback, 0., 5.);
1307	ev_timer_again (loop, timer);
1308	...
1309	timer->again = 17.;
1310	ev_timer_again (loop, timer);
1311	...
1312	timer->again = 10.;
1313	ev_timer_again (loop, timer);
1314
1315	This is more slightly efficient then stopping/starting the timer each time
1316	you want to modify its timeout value.
1317		1554
1318	=item ev_tstamp repeat [read-write]	1555	=item ev_tstamp repeat [read-write]
1319		1556
1320	The current C<repeat> value. Will be used each time the watcher times out	1557	The current C<repeat> value. Will be used each time the watcher times out
1321	or C<ev_timer_again> is called and determines the next timeout (if any),	1558	or C<ev_timer_again> is called, and determines the next timeout (if any),
1322	which is also when any modifications are taken into account.	1559	which is also when any modifications are taken into account.
1323		1560
1324	=back	1561	=back
1325		1562
1326	=head3 Examples	1563	=head3 Examples
1327		1564
1328	Example: Create a timer that fires after 60 seconds.	1565	Example: Create a timer that fires after 60 seconds.
1329		1566
1330	static void	1567	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1568	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1569	{
1333	.. one minute over, w is actually stopped right here	1570	.. one minute over, w is actually stopped right here
1334	}	1571	}
1335		1572
1336	struct ev_timer mytimer;	1573	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1574	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1575	ev_timer_start (loop, &mytimer);
1339		1576
1340	Example: Create a timeout timer that times out after 10 seconds of	1577	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1578	inactivity.
1342		1579
1343	static void	1580	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1581	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1582	{
1346	.. ten seconds without any activity	1583	.. ten seconds without any activity
1347	}	1584	}
1348		1585
1349	struct ev_timer mytimer;	1586	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1588	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1589	ev_loop (loop, 0);
1353		1590
1354	// and in some piece of code that gets executed on any "activity":	1591	// and in some piece of code that gets executed on any "activity":
…		…
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger	1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).	1608	roughly 10 seconds later as it uses a relative timeout).
1372		1609
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1610	C<ev_periodic>s can also be used to implement vastly more complex timers,
1374	such as triggering an event on each "midnight, local time", or other	1611	such as triggering an event on each "midnight, local time", or other
1375	complicated, rules.	1612	complicated rules.
1376		1613
1377	As with timers, the callback is guaranteed to be invoked only when the	1614	As with timers, the callback is guaranteed to be invoked only when the
1378	time (C<at>) has passed, but if multiple periodic timers become ready	1615	time (C<at>) has passed, but if multiple periodic timers become ready
1379	during the same loop iteration then order of execution is undefined.	1616	during the same loop iteration, then order of execution is undefined.
1380		1617
1381	=head3 Watcher-Specific Functions and Data Members	1618	=head3 Watcher-Specific Functions and Data Members
1382		1619
1383	=over 4	1620	=over 4
1384		1621
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1386		1623
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1624	=item ev_periodic_set (ev_periodic *, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1388		1625
1389	Lots of arguments, lets sort it out... There are basically three modes of	1626	Lots of arguments, lets sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	1627	operation, and we will explain them from simplest to most complex:
1391		1628
1392	=over 4	1629	=over 4
1393		1630
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1395		1632
1396	In this configuration the watcher triggers an event after the wall clock	1633	In this configuration the watcher triggers an event after the wall clock
1397	time C<at> has passed and doesn't repeat. It will not adjust when a time	1634	time C<at> has passed. It will not repeat and will not adjust when a time
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1399	run when the system time reaches or surpasses this time.	1636	only run when the system clock reaches or surpasses this time.
1400		1637
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1402		1639
1403	In this mode the watcher will always be scheduled to time out at the next	1640	In this mode the watcher will always be scheduled to time out at the next
1404	C<at + N * interval> time (for some integer N, which can also be negative)	1641	C<at + N * interval> time (for some integer N, which can also be negative)
1405	and then repeat, regardless of any time jumps.	1642	and then repeat, regardless of any time jumps.
1406		1643
1407	This can be used to create timers that do not drift with respect to system	1644	This can be used to create timers that do not drift with respect to the
1408	time, for example, here is a C<ev_periodic> that triggers each hour, on	1645	system clock, for example, here is a C<ev_periodic> that triggers each
1409	the hour:	1646	hour, on the hour:
1410		1647
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1648	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1649
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1650	This doesn't mean there will always be 3600 seconds in between triggers,
1414	but only that the callback will be called when the system time shows a	1651	but only that the callback will be called when the system time shows a
…		…
1434	ignored. Instead, each time the periodic watcher gets scheduled, the	1671	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	1672	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	1673	current time as second argument.
1437		1674
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1439	ever, or make ANY event loop modifications whatsoever>.	1676	ever, or make ANY other event loop modifications whatsoever>.
1440		1677
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	1680	only event loop modification you are allowed to do).
1444		1681
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1682	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	1683	*w, ev_tstamp now)>, e.g.:
1447		1684
		1685	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1686	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	1687	{
1450	return now + 60.;	1688	return now + 60.;
1451	}	1689	}
1452		1690
1453	It must return the next time to trigger, based on the passed time value	1691	It must return the next time to trigger, based on the passed time value
…		…
1490		1728
1491	The current interval value. Can be modified any time, but changes only	1729	The current interval value. Can be modified any time, but changes only
1492	take effect when the periodic timer fires or C<ev_periodic_again> is being	1730	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	1731	called.
1494		1732
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1733	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		1734
1497	The current reschedule callback, or C<0>, if this functionality is	1735	The current reschedule callback, or C<0>, if this functionality is
1498	switched off. Can be changed any time, but changes only take effect when	1736	switched off. Can be changed any time, but changes only take effect when
1499	the periodic timer fires or C<ev_periodic_again> is being called.	1737	the periodic timer fires or C<ev_periodic_again> is being called.
1500		1738
1501	=back	1739	=back
1502		1740
1503	=head3 Examples	1741	=head3 Examples
1504		1742
1505	Example: Call a callback every hour, or, more precisely, whenever the	1743	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	1744	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	1745	potentially a lot of jitter, but good long-term stability.
1508		1746
1509	static void	1747	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	1749	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	1750	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	1751	}
1514		1752
1515	struct ev_periodic hourly_tick;	1753	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1754	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	1755	ev_periodic_start (loop, &hourly_tick);
1518		1756
1519	Example: The same as above, but use a reschedule callback to do it:	1757	Example: The same as above, but use a reschedule callback to do it:
1520		1758
1521	#include <math.h>	1759	#include <math.h>
1522		1760
1523	static ev_tstamp	1761	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1762	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	1763	{
1526	return fmod (now, 3600.) + 3600.;	1764	return now + (3600. - fmod (now, 3600.));
1527	}	1765	}
1528		1766
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1767	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		1768
1531	Example: Call a callback every hour, starting now:	1769	Example: Call a callback every hour, starting now:
1532		1770
1533	struct ev_periodic hourly_tick;	1771	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	1772	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	1773	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	1774	ev_periodic_start (loop, &hourly_tick);
1537		1775
1538		1776
…		…
1541	Signal watchers will trigger an event when the process receives a specific	1779	Signal watchers will trigger an event when the process receives a specific
1542	signal one or more times. Even though signals are very asynchronous, libev	1780	signal one or more times. Even though signals are very asynchronous, libev
1543	will try it's best to deliver signals synchronously, i.e. as part of the	1781	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	1782	normal event processing, like any other event.
1545		1783
		1784	If you want signals asynchronously, just use C<sigaction> as you would
		1785	do without libev and forget about sharing the signal. You can even use
		1786	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1787
1546	You can configure as many watchers as you like per signal. Only when the	1788	You can configure as many watchers as you like per signal. Only when the
1547	first watcher gets started will libev actually register a signal watcher	1789	first watcher gets started will libev actually register a signal handler
1548	with the kernel (thus it coexists with your own signal handlers as long	1790	with the kernel (thus it coexists with your own signal handlers as long as
1549	as you don't register any with libev). Similarly, when the last signal	1791	you don't register any with libev for the same signal). Similarly, when
1550	watcher for a signal is stopped libev will reset the signal handler to	1792	the last signal watcher for a signal is stopped, libev will reset the
1551	SIG_DFL (regardless of what it was set to before).	1793	signal handler to SIG_DFL (regardless of what it was set to before).
1552		1794
1553	If possible and supported, libev will install its handlers with	1795	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1555	interrupted. If you have a problem with system calls getting interrupted by	1797	interrupted. If you have a problem with system calls getting interrupted by
1556	signals you can block all signals in an C<ev_check> watcher and unblock	1798	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1573		1815
1574	=back	1816	=back
1575		1817
1576	=head3 Examples	1818	=head3 Examples
1577		1819
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	1820	Example: Try to exit cleanly on SIGINT.
1579		1821
1580	static void	1822	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	1824	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	1825	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	1826	}
1585		1827
1586	struct ev_signal signal_watcher;	1828	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	1830	ev_signal_start (loop, &signal_watcher);
1589		1831
1590		1832
1591	=head2 C<ev_child> - watch out for process status changes	1833	=head2 C<ev_child> - watch out for process status changes
1592		1834
1593	Child watchers trigger when your process receives a SIGCHLD in response to	1835	Child watchers trigger when your process receives a SIGCHLD in response to
1594	some child status changes (most typically when a child of yours dies). It	1836	some child status changes (most typically when a child of yours dies or
1595	is permissible to install a child watcher I<after> the child has been	1837	exits). It is permissible to install a child watcher I<after> the child
1596	forked (which implies it might have already exited), as long as the event	1838	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	1839	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1840	forking and then immediately registering a watcher for the child is fine,
		1841	but forking and registering a watcher a few event loop iterations later is
		1842	not.
1598		1843
1599	Only the default event loop is capable of handling signals, and therefore	1844	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	1845	you can only register child watchers in the default event loop.
1601		1846
1602	=head3 Process Interaction	1847	=head3 Process Interaction
…		…
1663	its completion.	1908	its completion.
1664		1909
1665	ev_child cw;	1910	ev_child cw;
1666		1911
1667	static void	1912	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	1913	child_cb (EV_P_ ev_child *w, int revents)
1669	{	1914	{
1670	ev_child_stop (EV_A_ w);	1915	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1916	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	1917	}
1673		1918
…		…
1688		1933
1689		1934
1690	=head2 C<ev_stat> - did the file attributes just change?	1935	=head2 C<ev_stat> - did the file attributes just change?
1691		1936
1692	This watches a file system path for attribute changes. That is, it calls	1937	This watches a file system path for attribute changes. That is, it calls
1693	C<stat> regularly (or when the OS says it changed) and sees if it changed	1938	C<stat> on that path in regular intervals (or when the OS says it changed)
1694	compared to the last time, invoking the callback if it did.	1939	and sees if it changed compared to the last time, invoking the callback if
		1940	it did.
1695		1941
1696	The path does not need to exist: changing from "path exists" to "path does	1942	The path does not need to exist: changing from "path exists" to "path does
1697	not exist" is a status change like any other. The condition "path does	1943	not exist" is a status change like any other. The condition "path does not
1698	not exist" is signified by the C<st_nlink> field being zero (which is	1944	exist" (or more correctly "path cannot be stat'ed") is signified by the
1699	otherwise always forced to be at least one) and all the other fields of	1945	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	1946	least one) and all the other fields of the stat buffer having unspecified
		1947	contents.
1701		1948
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	1949	The path I<must not> end in a slash or contain special components such as
		1950	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1703	relative and your working directory changes, the behaviour is undefined.	1951	your working directory changes, then the behaviour is undefined.
1704		1952
1705	Since there is no standard to do this, the portable implementation simply	1953	Since there is no portable change notification interface available, the
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1954	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	1955	to see if it changed somehow. You can specify a recommended polling
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	1956	interval for this case. If you specify a polling interval of C<0> (highly
1709	unspecified default> value will be used (which you can expect to be around	1957	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	1958	(which you can expect to be around five seconds, although this might
1711	impose a minimum interval which is currently around C<0.1>, but thats	1959	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	1960	currently around C<0.1>, but that's usually overkill.
1713		1961
1714	This watcher type is not meant for massive numbers of stat watchers,	1962	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	1963	as even with OS-supported change notifications, this can be
1716	resource-intensive.	1964	resource-intensive.
1717		1965
1718	At the time of this writing, only the Linux inotify interface is	1966	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	1967	is the Linux inotify interface (implementing kqueue support is left as an
1720	reader, note, however, that the author sees no way of implementing ev_stat	1968	exercise for the reader. Note, however, that the author sees no way of
1721	semantics with kqueue). Inotify will be used to give hints only and should	1969	implementing C<ev_stat> semantics with kqueue, except as a hint).
1722	not change the semantics of C<ev_stat> watchers, which means that libev
1723	sometimes needs to fall back to regular polling again even with inotify,
1724	but changes are usually detected immediately, and if the file exists there
1725	will be no polling.
1726		1970
1727	=head3 ABI Issues (Largefile Support)	1971	=head3 ABI Issues (Largefile Support)
1728		1972
1729	Libev by default (unless the user overrides this) uses the default	1973	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	1974	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	1975	support disabled by default, you get the 32 bit version of the stat
1732	structure. When using the library from programs that change the ABI to	1976	structure. When using the library from programs that change the ABI to
1733	use 64 bit file offsets the programs will fail. In that case you have to	1977	use 64 bit file offsets the programs will fail. In that case you have to
1734	compile libev with the same flags to get binary compatibility. This is	1978	compile libev with the same flags to get binary compatibility. This is
1735	obviously the case with any flags that change the ABI, but the problem is	1979	obviously the case with any flags that change the ABI, but the problem is
1736	most noticeably disabled with ev_stat and large file support.	1980	most noticeably displayed with ev_stat and large file support.
1737		1981
1738	The solution for this is to lobby your distribution maker to make large	1982	The solution for this is to lobby your distribution maker to make large
1739	file interfaces available by default (as e.g. FreeBSD does) and not	1983	file interfaces available by default (as e.g. FreeBSD does) and not
1740	optional. Libev cannot simply switch on large file support because it has	1984	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	1985	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	1986	default compilation environment.
1743		1987
1744	=head3 Inotify	1988	=head3 Inotify and Kqueue
1745		1989
1746	When C<inotify (7)> support has been compiled into libev (generally only	1990	When C<inotify (7)> support has been compiled into libev and present at
1747	available on Linux) and present at runtime, it will be used to speed up	1991	runtime, it will be used to speed up change detection where possible. The
1748	change detection where possible. The inotify descriptor will be created lazily	1992	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	1993	watcher is being started.
1750		1994
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	1995	Inotify presence does not change the semantics of C<ev_stat> watchers
1752	except that changes might be detected earlier, and in some cases, to avoid	1996	except that changes might be detected earlier, and in some cases, to avoid
1753	making regular C<stat> calls. Even in the presence of inotify support	1997	making regular C<stat> calls. Even in the presence of inotify support
1754	there are many cases where libev has to resort to regular C<stat> polling.	1998	there are many cases where libev has to resort to regular C<stat> polling,
		1999	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2000	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2001	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2002	xfs are fully working) libev usually gets away without polling.
1755		2003
1756	(There is no support for kqueue, as apparently it cannot be used to	2004	There is no support for kqueue, as apparently it cannot be used to
1757	implement this functionality, due to the requirement of having a file	2005	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2006	descriptor open on the object at all times, and detecting renames, unlinks
		2007	etc. is difficult.
		2008
		2009	=head3 C<stat ()> is a synchronous operation
		2010
		2011	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2012	the process. The exception are C<ev_stat> watchers - those call C<stat
		2013	()>, which is a synchronous operation.
		2014
		2015	For local paths, this usually doesn't matter: unless the system is very
		2016	busy or the intervals between stat's are large, a stat call will be fast,
		2017	as the path data is usually in memory already (except when starting the
		2018	watcher).
		2019
		2020	For networked file systems, calling C<stat ()> can block an indefinite
		2021	time due to network issues, and even under good conditions, a stat call
		2022	often takes multiple milliseconds.
		2023
		2024	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2025	paths, although this is fully supported by libev.
1759		2026
1760	=head3 The special problem of stat time resolution	2027	=head3 The special problem of stat time resolution
1761		2028
1762	The C<stat ()> system call only supports full-second resolution portably, and	2029	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2030	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2031	still only support whole seconds.
1765		2032
1766	That means that, if the time is the only thing that changes, you can	2033	That means that, if the time is the only thing that changes, you can
1767	easily miss updates: on the first update, C<ev_stat> detects a change and	2034	easily miss updates: on the first update, C<ev_stat> detects a change and
1768	calls your callback, which does something. When there is another update	2035	calls your callback, which does something. When there is another update
1769	within the same second, C<ev_stat> will be unable to detect it as the stat	2036	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2037	stat data does change in other ways (e.g. file size).
1771		2038
1772	The solution to this is to delay acting on a change for slightly more	2039	The solution to this is to delay acting on a change for slightly more
1773	than a second (or till slightly after the next full second boundary), using	2040	than a second (or till slightly after the next full second boundary), using
1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2041	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2042	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2062	C<path>. The C<interval> is a hint on how quickly a change is expected to
1796	be detected and should normally be specified as C<0> to let libev choose	2063	be detected and should normally be specified as C<0> to let libev choose
1797	a suitable value. The memory pointed to by C<path> must point to the same	2064	a suitable value. The memory pointed to by C<path> must point to the same
1798	path for as long as the watcher is active.	2065	path for as long as the watcher is active.
1799		2066
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2067	The callback will receive an C<EV_STAT> event when a change was detected,
1801	to the attributes at the time the watcher was started (or the last change	2068	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2069	last change was detected).
1803		2070
1804	=item ev_stat_stat (loop, ev_stat *)	2071	=item ev_stat_stat (loop, ev_stat *)
1805		2072
1806	Updates the stat buffer immediately with new values. If you change the	2073	Updates the stat buffer immediately with new values. If you change the
1807	watched path in your callback, you could call this function to avoid	2074	watched path in your callback, you could call this function to avoid
…		…
1890		2157
1891		2158
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2159	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2160
1894	Idle watchers trigger events when no other events of the same or higher	2161	Idle watchers trigger events when no other events of the same or higher
1895	priority are pending (prepare, check and other idle watchers do not	2162	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2163	as receiving "events").
1897		2164
1898	That is, as long as your process is busy handling sockets or timeouts	2165	That is, as long as your process is busy handling sockets or timeouts
1899	(or even signals, imagine) of the same or higher priority it will not be	2166	(or even signals, imagine) of the same or higher priority it will not be
1900	triggered. But when your process is idle (or only lower-priority watchers	2167	triggered. But when your process is idle (or only lower-priority watchers
1901	are pending), the idle watchers are being called once per event loop	2168	are pending), the idle watchers are being called once per event loop
…		…
1912		2179
1913	=head3 Watcher-Specific Functions and Data Members	2180	=head3 Watcher-Specific Functions and Data Members
1914		2181
1915	=over 4	2182	=over 4
1916		2183
1917	=item ev_idle_init (ev_signal *, callback)	2184	=item ev_idle_init (ev_idle *, callback)
1918		2185
1919	Initialises and configures the idle watcher - it has no parameters of any	2186	Initialises and configures the idle watcher - it has no parameters of any
1920	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2187	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2188	believe me.
1922		2189
…		…
1926		2193
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2194	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2195	callback, free it. Also, use no error checking, as usual.
1929		2196
1930	static void	2197	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2199	{
1933	free (w);	2200	free (w);
1934	// now do something you wanted to do when the program has	2201	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2202	// no longer anything immediate to do.
1936	}	2203	}
1937		2204
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2206	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2207	ev_idle_start (loop, idle_cb);
1941		2208
1942		2209
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2211
1945	Prepare and check watchers are usually (but not always) used in tandem:	2212	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2213	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2214	afterwards.
1948		2215
1949	You I<must not> call C<ev_loop> or similar functions that enter	2216	You I<must not> call C<ev_loop> or similar functions that enter
1950	the current event loop from either C<ev_prepare> or C<ev_check>	2217	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1953	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1954	C<ev_check> so if you have one watcher of each kind they will always be	2221	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2222	called in pairs bracketing the blocking call.
1956		2223
1957	Their main purpose is to integrate other event mechanisms into libev and	2224	Their main purpose is to integrate other event mechanisms into libev and
1958	their use is somewhat advanced. This could be used, for example, to track	2225	their use is somewhat advanced. They could be used, for example, to track
1959	variable changes, implement your own watchers, integrate net-snmp or a	2226	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2227	coroutine library and lots more. They are also occasionally useful if
1961	you cache some data and want to flush it before blocking (for example,	2228	you cache some data and want to flush it before blocking (for example,
1962	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2229	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2230	watcher).
1964		2231
1965	This is done by examining in each prepare call which file descriptors need	2232	This is done by examining in each prepare call which file descriptors
1966	to be watched by the other library, registering C<ev_io> watchers for	2233	need to be watched by the other library, registering C<ev_io> watchers
1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2234	for them and starting an C<ev_timer> watcher for any timeouts (many
1968	provide just this functionality). Then, in the check watcher you check for	2235	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2236	you check for any events that occurred (by checking the pending status
1970	and stopping them) and call back into the library. The I/O and timer	2237	of all watchers and stopping them) and call back into the library. The
1971	callbacks will never actually be called (but must be valid nevertheless,	2238	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2239	nevertheless, because you never know, you know?).
1973		2240
1974	As another example, the Perl Coro module uses these hooks to integrate	2241	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2242	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2243	during each prepare and only letting the process block if no coroutines
1977	are ready to run (it's actually more complicated: it only runs coroutines	2244	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1980	loop from blocking if lower-priority coroutines are active, thus mapping	2247	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2248	low-priority coroutines to idle/background tasks).
1982		2249
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1984	priority, to ensure that they are being run before any other watchers	2251	priority, to ensure that they are being run before any other watchers
		2252	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2253
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1986	too) should not activate ("feed") events into libev. While libev fully	2255	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2256	might get executed before other C<ev_check> watchers did their job. As
1988	did their job. As C<ev_check> watchers are often used to embed other	2257	C<ev_check> watchers are often used to embed other (non-libev) event
1989	(non-libev) event loops those other event loops might be in an unusable	2258	loops those other event loops might be in an unusable state until their
1990	state until their C<ev_check> watcher ran (always remind yourself to	2259	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2260	others).
1992		2261
1993	=head3 Watcher-Specific Functions and Data Members	2262	=head3 Watcher-Specific Functions and Data Members
1994		2263
1995	=over 4	2264	=over 4
1996		2265
…		…
1998		2267
1999	=item ev_check_init (ev_check *, callback)	2268	=item ev_check_init (ev_check *, callback)
2000		2269
2001	Initialises and configures the prepare or check watcher - they have no	2270	Initialises and configures the prepare or check watcher - they have no
2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2271	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
2003	macros, but using them is utterly, utterly and completely pointless.	2272	macros, but using them is utterly, utterly, utterly and completely
		2273	pointless.
2004		2274
2005	=back	2275	=back
2006		2276
2007	=head3 Examples	2277	=head3 Examples
2008		2278
…		…
2021		2291
2022	static ev_io iow [nfd];	2292	static ev_io iow [nfd];
2023	static ev_timer tw;	2293	static ev_timer tw;
2024		2294
2025	static void	2295	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2296	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2297	{
2028	}	2298	}
2029		2299
2030	// create io watchers for each fd and a timer before blocking	2300	// create io watchers for each fd and a timer before blocking
2031	static void	2301	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2302	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2303	{
2034	int timeout = 3600000;	2304	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2305	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2306	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2052	}	2322	}
2053	}	2323	}
2054		2324
2055	// stop all watchers after blocking	2325	// stop all watchers after blocking
2056	static void	2326	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2327	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2328	{
2059	ev_timer_stop (loop, &tw);	2329	ev_timer_stop (loop, &tw);
2060		2330
2061	for (int i = 0; i < nfd; ++i)	2331	for (int i = 0; i < nfd; ++i)
2062	{	2332	{
…		…
2101	}	2371	}
2102		2372
2103	// do not ever call adns_afterpoll	2373	// do not ever call adns_afterpoll
2104		2374
2105	Method 4: Do not use a prepare or check watcher because the module you	2375	Method 4: Do not use a prepare or check watcher because the module you
2106	want to embed is too inflexible to support it. Instead, you can override	2376	want to embed is not flexible enough to support it. Instead, you can
2107	their poll function. The drawback with this solution is that the main	2377	override their poll function. The drawback with this solution is that the
2108	loop is now no longer controllable by EV. The C<Glib::EV> module does	2378	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2379	this approach, effectively embedding EV as a client into the horrible
		2380	libglib event loop.
2110		2381
2111	static gint	2382	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2383	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2384	{
2114	int got_events = 0;	2385	int got_events = 0;
…		…
2145	prioritise I/O.	2416	prioritise I/O.
2146		2417
2147	As an example for a bug workaround, the kqueue backend might only support	2418	As an example for a bug workaround, the kqueue backend might only support
2148	sockets on some platform, so it is unusable as generic backend, but you	2419	sockets on some platform, so it is unusable as generic backend, but you
2149	still want to make use of it because you have many sockets and it scales	2420	still want to make use of it because you have many sockets and it scales
2150	so nicely. In this case, you would create a kqueue-based loop and embed it	2421	so nicely. In this case, you would create a kqueue-based loop and embed
2151	into your default loop (which might use e.g. poll). Overall operation will	2422	it into your default loop (which might use e.g. poll). Overall operation
2152	be a bit slower because first libev has to poll and then call kevent, but	2423	will be a bit slower because first libev has to call C<poll> and then
2153	at least you can use both at what they are best.	2424	C<kevent>, but at least you can use both mechanisms for what they are
		2425	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2426
2155	As for prioritising I/O: rarely you have the case where some fds have	2427	As for prioritising I/O: under rare circumstances you have the case where
2156	to be watched and handled very quickly (with low latency), and even	2428	some fds have to be watched and handled very quickly (with low latency),
2157	priorities and idle watchers might have too much overhead. In this case	2429	and even priorities and idle watchers might have too much overhead. In
2158	you would put all the high priority stuff in one loop and all the rest in	2430	this case you would put all the high priority stuff in one loop and all
2159	a second one, and embed the second one in the first.	2431	the rest in a second one, and embed the second one in the first.
2160		2432
2161	As long as the watcher is active, the callback will be invoked every time	2433	As long as the watcher is active, the callback will be invoked every
2162	there might be events pending in the embedded loop. The callback must then	2434	time there might be events pending in the embedded loop. The callback
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2435	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2164	their callbacks (you could also start an idle watcher to give the embedded	2436	sweep and invoke their callbacks (the callback doesn't need to invoke the
2165	loop strictly lower priority for example). You can also set the callback	2437	C<ev_embed_sweep> function directly, it could also start an idle watcher
2166	to C<0>, in which case the embed watcher will automatically execute the	2438	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		2439
2169	As long as the watcher is started it will automatically handle events. The	2440	You can also set the callback to C<0>, in which case the embed watcher
2170	callback will be invoked whenever some events have been handled. You can	2441	will automatically execute the embedded loop sweep whenever necessary.
2171	set the callback to C<0> to avoid having to specify one if you are not
2172	interested in that.
2173		2442
2174	Also, there have not currently been made special provisions for forking:	2443	Fork detection will be handled transparently while the C<ev_embed> watcher
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2444	is active, i.e., the embedded loop will automatically be forked when the
2176	but you will also have to stop and restart any C<ev_embed> watchers	2445	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	2446	C<ev_loop_fork> on the embedded loop.
2178		2447
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2448	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2449	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2450	portable one.
2182		2451
2183	So when you want to use this feature you will always have to be prepared	2452	So when you want to use this feature you will always have to be prepared
2184	that you cannot get an embeddable loop. The recommended way to get around	2453	that you cannot get an embeddable loop. The recommended way to get around
2185	this is to have a separate variables for your embeddable loop, try to	2454	this is to have a separate variables for your embeddable loop, try to
2186	create it, and if that fails, use the normal loop for everything.	2455	create it, and if that fails, use the normal loop for everything.
		2456
		2457	=head3 C<ev_embed> and fork
		2458
		2459	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2460	automatically be applied to the embedded loop as well, so no special
		2461	fork handling is required in that case. When the watcher is not running,
		2462	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2463	as applicable.
2187		2464
2188	=head3 Watcher-Specific Functions and Data Members	2465	=head3 Watcher-Specific Functions and Data Members
2189		2466
2190	=over 4	2467	=over 4
2191		2468
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2496	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2497	used).
2221		2498
2222	struct ev_loop *loop_hi = ev_default_init (0);	2499	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2500	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2501	ev_embed embed;
2225		2502
2226	// see if there is a chance of getting one that works	2503	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2504	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2505	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2506	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2520	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2521	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2522
2246	struct ev_loop *loop = ev_default_init (0);	2523	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2524	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2525	ev_embed embed;
2249		2526
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2527	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2528	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2529	{
2253	ev_embed_init (&embed, 0, loop_socket);	2530	ev_embed_init (&embed, 0, loop_socket);
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2586	is that the author does not know of a simple (or any) algorithm for a
2310	multiple-writer-single-reader queue that works in all cases and doesn't	2587	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2588	need elaborate support such as pthreads.
2312		2589
2313	That means that if you want to queue data, you have to provide your own	2590	That means that if you want to queue data, you have to provide your own
2314	queue. But at least I can tell you would implement locking around your	2591	queue. But at least I can tell you how to implement locking around your
2315	queue:	2592	queue:
2316		2593
2317	=over 4	2594	=over 4
2318		2595
2319	=item queueing from a signal handler context	2596	=item queueing from a signal handler context
2320		2597
2321	To implement race-free queueing, you simply add to the queue in the signal	2598	To implement race-free queueing, you simply add to the queue in the signal
2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2599	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2600	an example that does that for some fictitious SIGUSR1 handler:
2324		2601
2325	static ev_async mysig;	2602	static ev_async mysig;
2326		2603
2327	static void	2604	static void
2328	sigusr1_handler (void)	2605	sigusr1_handler (void)
…		…
2394	=over 4	2671	=over 4
2395		2672
2396	=item ev_async_init (ev_async *, callback)	2673	=item ev_async_init (ev_async *, callback)
2397		2674
2398	Initialises and configures the async watcher - it has no parameters of any	2675	Initialises and configures the async watcher - it has no parameters of any
2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2676	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	2677	trust me.
2401		2678
2402	=item ev_async_send (loop, ev_async *)	2679	=item ev_async_send (loop, ev_async *)
2403		2680
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2406	C<ev_feed_event>, this call is safe to do in other threads, signal or	2683	C<ev_feed_event>, this call is safe to do from other threads, signal or
2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	2685	section below on what exactly this means).
2409		2686
2410	This call incurs the overhead of a system call only once per loop iteration,	2687	This call incurs the overhead of a system call only once per loop iteration,
2411	so while the overhead might be noticeable, it doesn't apply to repeated	2688	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2435	=over 4	2712	=over 4
2436		2713
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2714	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		2715
2439	This function combines a simple timer and an I/O watcher, calls your	2716	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	2717	callback on whichever event happens first and automatically stops both
2441	watchers. This is useful if you want to wait for a single event on an fd	2718	watchers. This is useful if you want to wait for a single event on an fd
2442	or timeout without having to allocate/configure/start/stop/free one or	2719	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	2720	more watchers yourself.
2444		2721
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	2722	If C<fd> is less than 0, then no I/O watcher will be started and the
2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2723	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	2724	the given C<fd> and C<events> set will be created and started.
2448		2725
2449	If C<timeout> is less than 0, then no timeout watcher will be	2726	If C<timeout> is less than 0, then no timeout watcher will be
2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2728	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		2729
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2455	passed an C<revents> set like normal event callbacks (a combination of	2731	passed an C<revents> set like normal event callbacks (a combination of
2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	2733	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2734	a timeout and an io event at the same time - you probably should give io
		2735	events precedence.
		2736
		2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		2738
2459	static void stdin_ready (int revents, void *arg)	2739	static void stdin_ready (int revents, void *arg)
2460	{	2740	{
		2741	if (revents & EV_READ)
		2742	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	2743	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	2744	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	2745	}
2466		2746
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		2748
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)	2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2470		2750
2471	Feeds the given event set into the event loop, as if the specified event	2751	Feeds the given event set into the event loop, as if the specified event
2472	had happened for the specified watcher (which must be a pointer to an	2752	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).	2753	initialised but not necessarily started event watcher).
2474		2754
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		2756
2477	Feed an event on the given fd, as if a file descriptor backend detected	2757	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	2758	the given events it.
2479		2759
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		2761
2482	Feed an event as if the given signal occurred (C<loop> must be the default	2762	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	2763	loop!).
2484		2764
2485	=back	2765	=back
…		…
2607		2887
2608	myclass obj;	2888	myclass obj;
2609	ev::io iow;	2889	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	2890	iow.set <myclass, &myclass::io_cb> (&obj);
2611		2891
		2892	=item w->set (object *)
		2893
		2894	This is an B<experimental> feature that might go away in a future version.
		2895
		2896	This is a variation of a method callback - leaving out the method to call
		2897	will default the method to C<operator ()>, which makes it possible to use
		2898	functor objects without having to manually specify the C<operator ()> all
		2899	the time. Incidentally, you can then also leave out the template argument
		2900	list.
		2901
		2902	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2903	int revents)>.
		2904
		2905	See the method-C<set> above for more details.
		2906
		2907	Example: use a functor object as callback.
		2908
		2909	struct myfunctor
		2910	{
		2911	void operator() (ev::io &w, int revents)
		2912	{
		2913	...
		2914	}
		2915	}
		2916
		2917	myfunctor f;
		2918
		2919	ev::io w;
		2920	w.set (&f);
		2921
2612	=item w->set<function> (void *data = 0)	2922	=item w->set<function> (void *data = 0)
2613		2923
2614	Also sets a callback, but uses a static method or plain function as	2924	Also sets a callback, but uses a static method or plain function as
2615	callback. The optional C<data> argument will be stored in the watcher's	2925	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	2926	C<data> member and is free for you to use.
2617		2927
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2928	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		2929
2620	See the method-C<set> above for more details.	2930	See the method-C<set> above for more details.
2621		2931
2622	Example:	2932	Example: Use a plain function as callback.
2623		2933
2624	static void io_cb (ev::io &w, int revents) { }	2934	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	2935	iow.set <io_cb> ();
2626		2936
2627	=item w->set (struct ev_loop *)	2937	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	2975	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	2976	the constructor.
2667		2977
2668	class myclass	2978	class myclass
2669	{	2979	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	2980	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		2982
2673	myclass (int fd)	2983	myclass (int fd)
2674	{	2984	{
2675	io .set <myclass, &myclass::io_cb > (this);	2985	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	2986	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	3002	=item Perl
2693		3003
2694	The EV module implements the full libev API and is actually used to test	3004	The EV module implements the full libev API and is actually used to test
2695	libev. EV is developed together with libev. Apart from the EV core module,	3005	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3006	there are additional modules that implement libev-compatible interfaces
2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3007	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3008	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3009	and C<EV::Glib>).
2699		3010
2700	It can be found and installed via CPAN, its homepage is at	3011	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3012	L<http://software.schmorp.de/pkg/EV>.
2702		3013
2703	=item Python	3014	=item Python
…		…
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3025	Tony Arcieri has written a ruby extension that offers access to a subset
2715	of the libev API and adds file handle abstractions, asynchronous DNS and	3026	of the libev API and adds file handle abstractions, asynchronous DNS and
2716	more on top of it. It can be found via gem servers. Its homepage is at	3027	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3028	L<http://rev.rubyforge.org/>.
2718		3029
		3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3031	makes rev work even on mingw.
		3032
2719	=item D	3033	=item D
2720		3034
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3037
		3038	=item Ocaml
		3039
		3040	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2723		3042
2724	=back	3043	=back
2725		3044
2726		3045
2727	=head1 MACRO MAGIC	3046	=head1 MACRO MAGIC
…		…
2828		3147
2829	#define EV_STANDALONE 1	3148	#define EV_STANDALONE 1
2830	#include "ev.h"	3149	#include "ev.h"
2831		3150
2832	Both header files and implementation files can be compiled with a C++	3151	Both header files and implementation files can be compiled with a C++
2833	compiler (at least, thats a stated goal, and breakage will be treated	3152	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3153	as a bug).
2835		3154
2836	You need the following files in your source tree, or in a directory	3155	You need the following files in your source tree, or in a directory
2837	in your include path (e.g. in libev/ when using -Ilibev):	3156	in your include path (e.g. in libev/ when using -Ilibev):
2838		3157
…		…
2882		3201
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3202	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3203
2885	Libev can be configured via a variety of preprocessor symbols you have to	3204	Libev can be configured via a variety of preprocessor symbols you have to
2886	define before including any of its files. The default in the absence of	3205	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3206	autoconf is documented for every option.
2888		3207
2889	=over 4	3208	=over 4
2890		3209
2891	=item EV_STANDALONE	3210	=item EV_STANDALONE
2892		3211
…		…
2894	keeps libev from including F<config.h>, and it also defines dummy	3213	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3214	implementations for some libevent functions (such as logging, which is not
2896	supported). It will also not define any of the structs usually found in	3215	supported). It will also not define any of the structs usually found in
2897	F<event.h> that are not directly supported by the libev core alone.	3216	F<event.h> that are not directly supported by the libev core alone.
2898		3217
		3218	In stanbdalone mode, libev will still try to automatically deduce the
		3219	configuration, but has to be more conservative.
		3220
2899	=item EV_USE_MONOTONIC	3221	=item EV_USE_MONOTONIC
2900		3222
2901	If defined to be C<1>, libev will try to detect the availability of the	3223	If defined to be C<1>, libev will try to detect the availability of the
2902	monotonic clock option at both compile time and runtime. Otherwise no use	3224	monotonic clock option at both compile time and runtime. Otherwise no
2903	of the monotonic clock option will be attempted. If you enable this, you	3225	use of the monotonic clock option will be attempted. If you enable this,
2904	usually have to link against librt or something similar. Enabling it when	3226	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3227	when the functionality isn't available is safe, though, although you have
2906	to make sure you link against any libraries where the C<clock_gettime>	3228	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3229	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3230
2909	=item EV_USE_REALTIME	3231	=item EV_USE_REALTIME
2910		3232
2911	If defined to be C<1>, libev will try to detect the availability of the	3233	If defined to be C<1>, libev will try to detect the availability of the
2912	real-time clock option at compile time (and assume its availability at	3234	real-time clock option at compile time (and assume its availability
2913	runtime if successful). Otherwise no use of the real-time clock option will	3235	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3236	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3237	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3238	correctness. See the note about libraries in the description of
		3239	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3240	C<EV_USE_CLOCK_SYSCALL>.
		3241
		3242	=item EV_USE_CLOCK_SYSCALL
		3243
		3244	If defined to be C<1>, libev will try to use a direct syscall instead
		3245	of calling the system-provided C<clock_gettime> function. This option
		3246	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3247	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3248	programs needlessly. Using a direct syscall is slightly slower (in
		3249	theory), because no optimised vdso implementation can be used, but avoids
		3250	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3251	higher, as it simplifies linking (no need for C<-lrt>).
2917		3252
2918	=item EV_USE_NANOSLEEP	3253	=item EV_USE_NANOSLEEP
2919		3254
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3255	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2921	and will use it for delays. Otherwise it will use C<select ()>.	3256	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		3272
2938	=item EV_SELECT_USE_FD_SET	3273	=item EV_SELECT_USE_FD_SET
2939		3274
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	3275	If defined to C<1>, then the select backend will use the system C<fd_set>
2941	structure. This is useful if libev doesn't compile due to a missing	3276	structure. This is useful if libev doesn't compile due to a missing
2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3277	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2943	exotic systems. This usually limits the range of file descriptors to some	3278	on exotic systems. This usually limits the range of file descriptors to
2944	low limit such as 1024 or might have other limitations (winsocket only	3279	some low limit such as 1024 or might have other limitations (winsocket
2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3280	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	3281	configures the maximum size of the C<fd_set>.
2947		3282
2948	=item EV_SELECT_IS_WINSOCKET	3283	=item EV_SELECT_IS_WINSOCKET
2949		3284
2950	When defined to C<1>, the select backend will assume that	3285	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	3286	select/socket/connect etc. don't understand file descriptors but
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3397	When doing priority-based operations, libev usually has to linearly search
3063	all the priorities, so having many of them (hundreds) uses a lot of space	3398	all the priorities, so having many of them (hundreds) uses a lot of space
3064	and time, so using the defaults of five priorities (-2 .. +2) is usually	3399	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3400	fine.
3066		3401
3067	If your embedding application does not need any priorities, defining these both to	3402	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3403	both to C<0> will save some memory and CPU.
3069		3404
3070	=item EV_PERIODIC_ENABLE	3405	=item EV_PERIODIC_ENABLE
3071		3406
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3407	If undefined or defined to be C<1>, then periodic timers are supported. If
3073	defined to be C<0>, then they are not. Disabling them saves a few kB of	3408	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3415	code.
3081		3416
3082	=item EV_EMBED_ENABLE	3417	=item EV_EMBED_ENABLE
3083		3418
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3419	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3420	defined to be C<0>, then they are not. Embed watchers rely on most other
		3421	watcher types, which therefore must not be disabled.
3086		3422
3087	=item EV_STAT_ENABLE	3423	=item EV_STAT_ENABLE
3088		3424
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3425	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3426	defined to be C<0>, then they are not.
…		…
3122	two).	3458	two).
3123		3459
3124	=item EV_USE_4HEAP	3460	=item EV_USE_4HEAP
3125		3461
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3462	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3463	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3128	to C<1>. The 4-heap uses more complicated (longer) code but has	3464	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3465	faster performance with many (thousands) of watchers.
3130		3466
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3467	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3132	(disabled).	3468	(disabled).
3133		3469
3134	=item EV_HEAP_CACHE_AT	3470	=item EV_HEAP_CACHE_AT
3135		3471
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3472	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3137	timer and periodics heap, libev can cache the timestamp (I<at>) within	3473	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3474	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3475	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3140	but avoids random read accesses on heap changes. This improves performance	3476	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3477	noticeably with many (hundreds) of watchers.
3142		3478
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3479	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3480	(disabled).
3145		3481
3146	=item EV_VERIFY	3482	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3488	called once per loop, which can slow down libev. If set to C<3>, then the
3153	verification code will be called very frequently, which will slow down	3489	verification code will be called very frequently, which will slow down
3154	libev considerably.	3490	libev considerably.
3155		3491
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3492	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3493	C<0>.
3158		3494
3159	=item EV_COMMON	3495	=item EV_COMMON
3160		3496
3161	By default, all watchers have a C<void *data> member. By redefining	3497	By default, all watchers have a C<void *data> member. By redefining
3162	this macro to a something else you can include more and other types of	3498	this macro to a something else you can include more and other types of
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	3515	and the way callbacks are invoked and set. Must expand to a struct member
3180	definition and a statement, respectively. See the F<ev.h> header file for	3516	definition and a statement, respectively. See the F<ev.h> header file for
3181	their default definitions. One possible use for overriding these is to	3517	their default definitions. One possible use for overriding these is to
3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3518	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3183	method calls instead of plain function calls in C++.	3519	method calls instead of plain function calls in C++.
		3520
		3521	=back
3184		3522
3185	=head2 EXPORTED API SYMBOLS	3523	=head2 EXPORTED API SYMBOLS
3186		3524
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3525	If you need to re-export the API (e.g. via a DLL) and you need a list of
3188	exported symbols, you can use the provided F<Symbol.*> files which list	3526	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		3574
3237	#include "ev_cpp.h"	3575	#include "ev_cpp.h"
3238	#include "ev.c"	3576	#include "ev.c"
3239		3577
		3578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		3579
3241	=head1 THREADS AND COROUTINES	3580	=head2 THREADS AND COROUTINES
3242		3581
3243	=head2 THREADS	3582	=head3 THREADS
3244		3583
3245	Libev itself is completely thread-safe, but it uses no locking. This	3584	All libev functions are reentrant and thread-safe unless explicitly
		3585	documented otherwise, but libev implements no locking itself. This means
3246	means that you can use as many loops as you want in parallel, as long as	3586	that you can use as many loops as you want in parallel, as long as there
3247	only one thread ever calls into one libev function with the same loop	3587	are no concurrent calls into any libev function with the same loop
3248	parameter.	3588	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3589	of course): libev guarantees that different event loops share no data
		3590	structures that need any locking.
3249		3591
3250	Or put differently: calls with different loop parameters can be done in	3592	Or to put it differently: calls with different loop parameters can be done
3251	parallel from multiple threads, calls with the same loop parameter must be	3593	concurrently from multiple threads, calls with the same loop parameter
3252	done serially (but can be done from different threads, as long as only one	3594	must be done serially (but can be done from different threads, as long as
3253	thread ever is inside a call at any point in time, e.g. by using a mutex	3595	only one thread ever is inside a call at any point in time, e.g. by using
3254	per loop).	3596	a mutex per loop).
		3597
		3598	Specifically to support threads (and signal handlers), libev implements
		3599	so-called C<ev_async> watchers, which allow some limited form of
		3600	concurrency on the same event loop, namely waking it up "from the
		3601	outside".
3255		3602
3256	If you want to know which design (one loop, locking, or multiple loops	3603	If you want to know which design (one loop, locking, or multiple loops
3257	without or something else still) is best for your problem, then I cannot	3604	without or something else still) is best for your problem, then I cannot
3258	help you. I can give some generic advice however:	3605	help you, but here is some generic advice:
3259		3606
3260	=over 4	3607	=over 4
3261		3608
3262	=item * most applications have a main thread: use the default libev loop	3609	=item * most applications have a main thread: use the default libev loop
3263	in that thread, or create a separate thread running only the default loop.	3610	in that thread, or create a separate thread running only the default loop.
…		…
3275		3622
3276	Choosing a model is hard - look around, learn, know that usually you can do	3623	Choosing a model is hard - look around, learn, know that usually you can do
3277	better than you currently do :-)	3624	better than you currently do :-)
3278		3625
3279	=item * often you need to talk to some other thread which blocks in the	3626	=item * often you need to talk to some other thread which blocks in the
		3627	event loop.
		3628
3280	event loop - C<ev_async> watchers can be used to wake them up from other	3629	C<ev_async> watchers can be used to wake them up from other threads safely
3281	threads safely (or from signal contexts...).	3630	(or from signal contexts...).
		3631
		3632	An example use would be to communicate signals or other events that only
		3633	work in the default loop by registering the signal watcher with the
		3634	default loop and triggering an C<ev_async> watcher from the default loop
		3635	watcher callback into the event loop interested in the signal.
3282		3636
3283	=back	3637	=back
3284		3638
3285	=head2 COROUTINES	3639	=head3 COROUTINES
3286		3640
3287	Libev is much more accommodating to coroutines ("cooperative threads"):	3641	Libev is very accommodating to coroutines ("cooperative threads"):
3288	libev fully supports nesting calls to it's functions from different	3642	libev fully supports nesting calls to its functions from different
3289	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3643	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3290	different coroutines and switch freely between both coroutines running the	3644	different coroutines, and switch freely between both coroutines running the
3291	loop, as long as you don't confuse yourself). The only exception is that	3645	loop, as long as you don't confuse yourself). The only exception is that
3292	you must not do this from C<ev_periodic> reschedule callbacks.	3646	you must not do this from C<ev_periodic> reschedule callbacks.
3293		3647
3294	Care has been invested into making sure that libev does not keep local	3648	Care has been taken to ensure that libev does not keep local state inside
3295	state inside C<ev_loop>, and other calls do not usually allow coroutine	3649	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3296	switches.	3650	they do not call any callbacks.
3297		3651
		3652	=head2 COMPILER WARNINGS
3298		3653
3299	=head1 COMPLEXITIES	3654	Depending on your compiler and compiler settings, you might get no or a
		3655	lot of warnings when compiling libev code. Some people are apparently
		3656	scared by this.
3300		3657
3301	In this section the complexities of (many of) the algorithms used inside	3658	However, these are unavoidable for many reasons. For one, each compiler
3302	libev will be explained. For complexity discussions about backends see the	3659	has different warnings, and each user has different tastes regarding
3303	documentation for C<ev_default_init>.	3660	warning options. "Warn-free" code therefore cannot be a goal except when
		3661	targeting a specific compiler and compiler-version.
3304		3662
3305	All of the following are about amortised time: If an array needs to be	3663	Another reason is that some compiler warnings require elaborate
3306	extended, libev needs to realloc and move the whole array, but this	3664	workarounds, or other changes to the code that make it less clear and less
3307	happens asymptotically never with higher number of elements, so O(1) might	3665	maintainable.
3308	mean it might do a lengthy realloc operation in rare cases, but on average
3309	it is much faster and asymptotically approaches constant time.
3310		3666
3311	=over 4	3667	And of course, some compiler warnings are just plain stupid, or simply
		3668	wrong (because they don't actually warn about the condition their message
		3669	seems to warn about). For example, certain older gcc versions had some
		3670	warnings that resulted an extreme number of false positives. These have
		3671	been fixed, but some people still insist on making code warn-free with
		3672	such buggy versions.
3312		3673
3313	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3674	While libev is written to generate as few warnings as possible,
		3675	"warn-free" code is not a goal, and it is recommended not to build libev
		3676	with any compiler warnings enabled unless you are prepared to cope with
		3677	them (e.g. by ignoring them). Remember that warnings are just that:
		3678	warnings, not errors, or proof of bugs.
3314		3679
3315	This means that, when you have a watcher that triggers in one hour and
3316	there are 100 watchers that would trigger before that then inserting will
3317	have to skip roughly seven (C<ld 100>) of these watchers.
3318		3680
3319	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3681	=head2 VALGRIND
3320		3682
3321	That means that changing a timer costs less than removing/adding them	3683	Valgrind has a special section here because it is a popular tool that is
3322	as only the relative motion in the event queue has to be paid for.	3684	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3323		3685
3324	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3686	If you think you found a bug (memory leak, uninitialised data access etc.)
		3687	in libev, then check twice: If valgrind reports something like:
3325		3688
3326	These just add the watcher into an array or at the head of a list.	3689	==2274== definitely lost: 0 bytes in 0 blocks.
		3690	==2274== possibly lost: 0 bytes in 0 blocks.
		3691	==2274== still reachable: 256 bytes in 1 blocks.
3327		3692
3328	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3693	Then there is no memory leak, just as memory accounted to global variables
		3694	is not a memleak - the memory is still being referenced, and didn't leak.
3329		3695
3330	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3696	Similarly, under some circumstances, valgrind might report kernel bugs
		3697	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3698	although an acceptable workaround has been found here), or it might be
		3699	confused.
3331		3700
3332	These watchers are stored in lists then need to be walked to find the	3701	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3333	correct watcher to remove. The lists are usually short (you don't usually	3702	make it into some kind of religion.
3334	have many watchers waiting for the same fd or signal).
3335		3703
3336	=item Finding the next timer in each loop iteration: O(1)	3704	If you are unsure about something, feel free to contact the mailing list
		3705	with the full valgrind report and an explanation on why you think this
		3706	is a bug in libev (best check the archives, too :). However, don't be
		3707	annoyed when you get a brisk "this is no bug" answer and take the chance
		3708	of learning how to interpret valgrind properly.
3337		3709
3338	By virtue of using a binary or 4-heap, the next timer is always found at a	3710	If you need, for some reason, empty reports from valgrind for your project
3339	fixed position in the storage array.	3711	I suggest using suppression lists.
3340		3712
3341	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3342		3713
3343	A change means an I/O watcher gets started or stopped, which requires	3714	=head1 PORTABILITY NOTES
3344	libev to recalculate its status (and possibly tell the kernel, depending
3345	on backend and whether C<ev_io_set> was used).
3346		3715
3347	=item Activating one watcher (putting it into the pending state): O(1)
3348
3349	=item Priority handling: O(number_of_priorities)
3350
3351	Priorities are implemented by allocating some space for each
3352	priority. When doing priority-based operations, libev usually has to
3353	linearly search all the priorities, but starting/stopping and activating
3354	watchers becomes O(1) w.r.t. priority handling.
3355
3356	=item Sending an ev_async: O(1)
3357
3358	=item Processing ev_async_send: O(number_of_async_watchers)
3359
3360	=item Processing signals: O(max_signal_number)
3361
3362	Sending involves a system call I<iff> there were no other C<ev_async_send>
3363	calls in the current loop iteration. Checking for async and signal events
3364	involves iterating over all running async watchers or all signal numbers.
3365
3366	=back
3367
3368
3369	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3716	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3370		3717
3371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3718	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3372	requires, and its I/O model is fundamentally incompatible with the POSIX	3719	requires, and its I/O model is fundamentally incompatible with the POSIX
3373	model. Libev still offers limited functionality on this platform in	3720	model. Libev still offers limited functionality on this platform in
3374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3721	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3385		3732
3386	Not a libev limitation but worth mentioning: windows apparently doesn't	3733	Not a libev limitation but worth mentioning: windows apparently doesn't
3387	accept large writes: instead of resulting in a partial write, windows will	3734	accept large writes: instead of resulting in a partial write, windows will
3388	either accept everything or return C<ENOBUFS> if the buffer is too large,	3735	either accept everything or return C<ENOBUFS> if the buffer is too large,
3389	so make sure you only write small amounts into your sockets (less than a	3736	so make sure you only write small amounts into your sockets (less than a
3390	megabyte seems safe, but thsi apparently depends on the amount of memory	3737	megabyte seems safe, but this apparently depends on the amount of memory
3391	available).	3738	available).
3392		3739
3393	Due to the many, low, and arbitrary limits on the win32 platform and	3740	Due to the many, low, and arbitrary limits on the win32 platform and
3394	the abysmal performance of winsockets, using a large number of sockets	3741	the abysmal performance of winsockets, using a large number of sockets
3395	is not recommended (and not reasonable). If your program needs to use	3742	is not recommended (and not reasonable). If your program needs to use
…		…
3406	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3753	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3407		3754
3408	#include "ev.h"	3755	#include "ev.h"
3409		3756
3410	And compile the following F<evwrap.c> file into your project (make sure	3757	And compile the following F<evwrap.c> file into your project (make sure
3411	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3758	you do I<not> compile the F<ev.c> or any other embedded source files!):
3412		3759
3413	#include "evwrap.h"	3760	#include "evwrap.h"
3414	#include "ev.c"	3761	#include "ev.c"
3415		3762
3416	=over 4	3763	=over 4
…		…
3461	wrap all I/O functions and provide your own fd management, but the cost of	3808	wrap all I/O functions and provide your own fd management, but the cost of
3462	calling select (O(n²)) will likely make this unworkable.	3809	calling select (O(n²)) will likely make this unworkable.
3463		3810
3464	=back	3811	=back
3465		3812
3466
3467	=head1 PORTABILITY REQUIREMENTS	3813	=head2 PORTABILITY REQUIREMENTS
3468		3814
3469	In addition to a working ISO-C implementation, libev relies on a few	3815	In addition to a working ISO-C implementation and of course the
3470	additional extensions:	3816	backend-specific APIs, libev relies on a few additional extensions:
3471		3817
3472	=over 4	3818	=over 4
3473		3819
3474	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3820	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3475	calling conventions regardless of C<ev_watcher_type *>.	3821	calling conventions regardless of C<ev_watcher_type *>.
…		…
3481	calls them using an C<ev_watcher *> internally.	3827	calls them using an C<ev_watcher *> internally.
3482		3828
3483	=item C<sig_atomic_t volatile> must be thread-atomic as well	3829	=item C<sig_atomic_t volatile> must be thread-atomic as well
3484		3830
3485	The type C<sig_atomic_t volatile> (or whatever is defined as	3831	The type C<sig_atomic_t volatile> (or whatever is defined as
3486	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3832	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3487	threads. This is not part of the specification for C<sig_atomic_t>, but is	3833	threads. This is not part of the specification for C<sig_atomic_t>, but is
3488	believed to be sufficiently portable.	3834	believed to be sufficiently portable.
3489		3835
3490	=item C<sigprocmask> must work in a threaded environment	3836	=item C<sigprocmask> must work in a threaded environment
3491		3837
…		…
3500	except the initial one, and run the default loop in the initial thread as	3846	except the initial one, and run the default loop in the initial thread as
3501	well.	3847	well.
3502		3848
3503	=item C<long> must be large enough for common memory allocation sizes	3849	=item C<long> must be large enough for common memory allocation sizes
3504		3850
3505	To improve portability and simplify using libev, libev uses C<long>	3851	To improve portability and simplify its API, libev uses C<long> internally
3506	internally instead of C<size_t> when allocating its data structures. On	3852	instead of C<size_t> when allocating its data structures. On non-POSIX
3507	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3853	systems (Microsoft...) this might be unexpectedly low, but is still at
3508	is still at least 31 bits everywhere, which is enough for hundreds of	3854	least 31 bits everywhere, which is enough for hundreds of millions of
3509	millions of watchers.	3855	watchers.
3510		3856
3511	=item C<double> must hold a time value in seconds with enough accuracy	3857	=item C<double> must hold a time value in seconds with enough accuracy
3512		3858
3513	The type C<double> is used to represent timestamps. It is required to	3859	The type C<double> is used to represent timestamps. It is required to
3514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3860	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3518	=back	3864	=back
3519		3865
3520	If you know of other additional requirements drop me a note.	3866	If you know of other additional requirements drop me a note.
3521		3867
3522		3868
3523	=head1 COMPILER WARNINGS	3869	=head1 ALGORITHMIC COMPLEXITIES
3524		3870
3525	Depending on your compiler and compiler settings, you might get no or a	3871	In this section the complexities of (many of) the algorithms used inside
3526	lot of warnings when compiling libev code. Some people are apparently	3872	libev will be documented. For complexity discussions about backends see
3527	scared by this.	3873	the documentation for C<ev_default_init>.
3528		3874
3529	However, these are unavoidable for many reasons. For one, each compiler	3875	All of the following are about amortised time: If an array needs to be
3530	has different warnings, and each user has different tastes regarding	3876	extended, libev needs to realloc and move the whole array, but this
3531	warning options. "Warn-free" code therefore cannot be a goal except when	3877	happens asymptotically rarer with higher number of elements, so O(1) might
3532	targeting a specific compiler and compiler-version.	3878	mean that libev does a lengthy realloc operation in rare cases, but on
		3879	average it is much faster and asymptotically approaches constant time.
3533		3880
3534	Another reason is that some compiler warnings require elaborate	3881	=over 4
3535	workarounds, or other changes to the code that make it less clear and less
3536	maintainable.
3537		3882
3538	And of course, some compiler warnings are just plain stupid, or simply	3883	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3539	wrong (because they don't actually warn about the condition their message
3540	seems to warn about).
3541		3884
3542	While libev is written to generate as few warnings as possible,	3885	This means that, when you have a watcher that triggers in one hour and
3543	"warn-free" code is not a goal, and it is recommended not to build libev	3886	there are 100 watchers that would trigger before that, then inserting will
3544	with any compiler warnings enabled unless you are prepared to cope with	3887	have to skip roughly seven (C<ld 100>) of these watchers.
3545	them (e.g. by ignoring them). Remember that warnings are just that:
3546	warnings, not errors, or proof of bugs.
3547		3888
		3889	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3548		3890
3549	=head1 VALGRIND	3891	That means that changing a timer costs less than removing/adding them,
		3892	as only the relative motion in the event queue has to be paid for.
3550		3893
3551	Valgrind has a special section here because it is a popular tool that is	3894	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3552	highly useful, but valgrind reports are very hard to interpret.
3553		3895
3554	If you think you found a bug (memory leak, uninitialised data access etc.)	3896	These just add the watcher into an array or at the head of a list.
3555	in libev, then check twice: If valgrind reports something like:
3556		3897
3557	==2274== definitely lost: 0 bytes in 0 blocks.	3898	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3558	==2274== possibly lost: 0 bytes in 0 blocks.
3559	==2274== still reachable: 256 bytes in 1 blocks.
3560		3899
3561	Then there is no memory leak. Similarly, under some circumstances,	3900	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3562	valgrind might report kernel bugs as if it were a bug in libev, or it
3563	might be confused (it is a very good tool, but only a tool).
3564		3901
3565	If you are unsure about something, feel free to contact the mailing list	3902	These watchers are stored in lists, so they need to be walked to find the
3566	with the full valgrind report and an explanation on why you think this is	3903	correct watcher to remove. The lists are usually short (you don't usually
3567	a bug in libev. However, don't be annoyed when you get a brisk "this is	3904	have many watchers waiting for the same fd or signal: one is typical, two
3568	no bug" answer and take the chance of learning how to interpret valgrind	3905	is rare).
3569	properly.
3570		3906
3571	If you need, for some reason, empty reports from valgrind for your project	3907	=item Finding the next timer in each loop iteration: O(1)
3572	I suggest using suppression lists.	3908
		3909	By virtue of using a binary or 4-heap, the next timer is always found at a
		3910	fixed position in the storage array.
		3911
		3912	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3913
		3914	A change means an I/O watcher gets started or stopped, which requires
		3915	libev to recalculate its status (and possibly tell the kernel, depending
		3916	on backend and whether C<ev_io_set> was used).
		3917
		3918	=item Activating one watcher (putting it into the pending state): O(1)
		3919
		3920	=item Priority handling: O(number_of_priorities)
		3921
		3922	Priorities are implemented by allocating some space for each
		3923	priority. When doing priority-based operations, libev usually has to
		3924	linearly search all the priorities, but starting/stopping and activating
		3925	watchers becomes O(1) with respect to priority handling.
		3926
		3927	=item Sending an ev_async: O(1)
		3928
		3929	=item Processing ev_async_send: O(number_of_async_watchers)
		3930
		3931	=item Processing signals: O(max_signal_number)
		3932
		3933	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3934	calls in the current loop iteration. Checking for async and signal events
		3935	involves iterating over all running async watchers or all signal numbers.
		3936
		3937	=back
3573		3938
3574		3939
3575	=head1 AUTHOR	3940	=head1 AUTHOR
3576		3941
3577	Marc Lehmann <libev@schmorp.de>.	3942	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3578		3943

Diff Legend

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