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…		…
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	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	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	121	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	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	229	recommended ones.
216		230
217	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
218		232
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		234
221	Sets the allocation function to use (the prototype is similar - the	235	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	236	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	237	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	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	264	}
251		265
252	...	266	...
253	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
254		268
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		270
257	Set the callback function to call on a retryable system call error (such	271	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	272	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	273	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	274	callback is set, then libev will expect it to remedy the situation, no
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	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	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	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,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	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	320	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	321	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	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	377	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	378	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	380	readiness notifications you get per iteration.
363		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
		385
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	386	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		387
366	And this is your standard poll(2) backend. It's more complicated	388	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	390	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	391	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	393	performance tips.
372		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		399
375	For few fds, this backend is a bit little slower than poll and select,	400	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	404
380	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
382		421
383	While stopping, setting and starting an I/O watcher in the same iteration	422	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	423	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
388		427	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		428
393	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	430	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
396		440
397	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	442	all kernel versions tested so far.
		443
		444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		445	C<EVBACKEND_POLL>.
399		446
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		448
402	Kqueue deserves special mention, as at the time of this writing, it	449	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	451	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	457	system like NetBSD.
409		458
410	You still can embed kqueue into a normal poll or select backend and use it	459	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	460	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		462
414	It scales in the same way as the epoll backend, but the interface to the	463	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	464	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	465	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	467	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
420		470
421	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
422		472
423	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
		479
		480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		482	C<NOTE_EOF>.
429		483
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		485
432	This is not implemented yet (and might never be, unless you send me an	486	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	500	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	501	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	503	might perform better.
450		504
451	On the positive side, ignoring the spurious readiness notifications, this	505	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
454		512
455	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
456		514
457	Try all backends (even potentially broken ones that wouldn't be tried	515	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		522
465	If one or more of these are or'ed into the flags value, then only these	523	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	524	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		526
469	The most typical usage is like this:	527	Example: This is the most typical usage.
470		528
471	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		531
474	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	533	environment settings to be taken into account:
476		534
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		536
479	Use whatever libev has to offer, but make sure that kqueue is used if	537	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	539	private event loop and only if you know the OS supports your types of
		540	fds):
482		541
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		543
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		545
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	567	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	569	for example).
511		570
512	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
515		574
516	In general it is not advisable to call this function except in the	575	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	576	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	577	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		603
545	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
546		605
547	Like C<ev_default_fork>, but acts on an event loop created by	606	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
550		610
551	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
552		612
553	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
554		615
555	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
556		617
557	Returns the count of loop iterations for the loop, which is identical to	618	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	619	the number of times libev did poll for new events. It starts at C<0> and
…		…
585	very long time without entering the event loop, updating libev's idea of	646	very long time without entering the event loop, updating libev's idea of
586	the current time is a good idea.	647	the current time is a good idea.
587		648
588	See also "The special problem of time updates" in the C<ev_timer> section.	649	See also "The special problem of time updates" in the C<ev_timer> section.
589		650
		651	=item ev_suspend (loop)
		652
		653	=item ev_resume (loop)
		654
		655	These two functions suspend and resume a loop, for use when the loop is
		656	not used for a while and timeouts should not be processed.
		657
		658	A typical use case would be an interactive program such as a game: When
		659	the user presses C<^Z> to suspend the game and resumes it an hour later it
		660	would be best to handle timeouts as if no time had actually passed while
		661	the program was suspended. This can be achieved by calling C<ev_suspend>
		662	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		663	C<ev_resume> directly afterwards to resume timer processing.
		664
		665	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		666	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		667	will be rescheduled (that is, they will lose any events that would have
		668	occured while suspended).
		669
		670	After calling C<ev_suspend> you B<must not> call I<any> function on the
		671	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		672	without a previous call to C<ev_suspend>.
		673
		674	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		675	event loop time (see C<ev_now_update>).
		676
590	=item ev_loop (loop, int flags)	677	=item ev_loop (loop, int flags)
591		678
592	Finally, this is it, the event handler. This function usually is called	679	Finally, this is it, the event handler. This function usually is called
593	after you initialised all your watchers and you want to start handling	680	after you initialised all your watchers and you want to start handling
594	events.	681	events.
…		…
596	If the flags argument is specified as C<0>, it will not return until	683	If the flags argument is specified as C<0>, it will not return until
597	either no event watchers are active anymore or C<ev_unloop> was called.	684	either no event watchers are active anymore or C<ev_unloop> was called.
598		685
599	Please note that an explicit C<ev_unloop> is usually better than	686	Please note that an explicit C<ev_unloop> is usually better than
600	relying on all watchers to be stopped when deciding when a program has	687	relying on all watchers to be stopped when deciding when a program has
601	finished (especially in interactive programs), but having a program that	688	finished (especially in interactive programs), but having a program
602	automatically loops as long as it has to and no longer by virtue of	689	that automatically loops as long as it has to and no longer by virtue
603	relying on its watchers stopping correctly is a thing of beauty.	690	of relying on its watchers stopping correctly, that is truly a thing of
		691	beauty.
604		692
605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	693	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
606	those events and any outstanding ones, but will not block your process in	694	those events and any already outstanding ones, but will not block your
607	case there are no events and will return after one iteration of the loop.	695	process in case there are no events and will return after one iteration of
		696	the loop.
608		697
609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	698	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
610	necessary) and will handle those and any outstanding ones. It will block	699	necessary) and will handle those and any already outstanding ones. It
611	your process until at least one new event arrives, and will return after	700	will block your process until at least one new event arrives (which could
612	one iteration of the loop. This is useful if you are waiting for some	701	be an event internal to libev itself, so there is no guarantee that a
613	external event in conjunction with something not expressible using other	702	user-registered callback will be called), and will return after one
		703	iteration of the loop.
		704
		705	This is useful if you are waiting for some external event in conjunction
		706	with something not expressible using other libev watchers (i.e. "roll your
614	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	707	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
615	usually a better approach for this kind of thing.	708	usually a better approach for this kind of thing.
616		709
617	Here are the gory details of what C<ev_loop> does:	710	Here are the gory details of what C<ev_loop> does:
618		711
619	- Before the first iteration, call any pending watchers.	712	- Before the first iteration, call any pending watchers.
…		…
629	any active watchers at all will result in not sleeping).	722	any active watchers at all will result in not sleeping).
630	- Sleep if the I/O and timer collect interval say so.	723	- Sleep if the I/O and timer collect interval say so.
631	- Block the process, waiting for any events.	724	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	725	- Queue all outstanding I/O (fd) events.
633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	726	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
634	- Queue all outstanding timers.	727	- Queue all expired timers.
635	- Queue all outstanding periodics.	728	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	729	- Unless any events are pending now, queue all idle watchers.
637	- Queue all check watchers.	730	- Queue all check watchers.
638	- Call all queued watchers in reverse order (i.e. check watchers first).	731	- Call all queued watchers in reverse order (i.e. check watchers first).
639	Signals and child watchers are implemented as I/O watchers, and will	732	Signals and child watchers are implemented as I/O watchers, and will
640	be handled here by queueing them when their watcher gets executed.	733	be handled here by queueing them when their watcher gets executed.
…		…
657	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	750	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
658	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	751	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
659		752
660	This "unloop state" will be cleared when entering C<ev_loop> again.	753	This "unloop state" will be cleared when entering C<ev_loop> again.
661		754
		755	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		756
662	=item ev_ref (loop)	757	=item ev_ref (loop)
663		758
664	=item ev_unref (loop)	759	=item ev_unref (loop)
665		760
666	Ref/unref can be used to add or remove a reference count on the event	761	Ref/unref can be used to add or remove a reference count on the event
667	loop: Every watcher keeps one reference, and as long as the reference	762	loop: Every watcher keeps one reference, and as long as the reference
668	count is nonzero, C<ev_loop> will not return on its own. If you have	763	count is nonzero, C<ev_loop> will not return on its own.
		764
669	a watcher you never unregister that should not keep C<ev_loop> from	765	If you have a watcher you never unregister that should not keep C<ev_loop>
670	returning, ev_unref() after starting, and ev_ref() before stopping it. For	766	from returning, call ev_unref() after starting, and ev_ref() before
		767	stopping it.
		768
671	example, libev itself uses this for its internal signal pipe: It is not	769	As an example, libev itself uses this for its internal signal pipe: It
672	visible to the libev user and should not keep C<ev_loop> from exiting if	770	is not visible to the libev user and should not keep C<ev_loop> from
673	no event watchers registered by it are active. It is also an excellent	771	exiting if no event watchers registered by it are active. It is also an
674	way to do this for generic recurring timers or from within third-party	772	excellent way to do this for generic recurring timers or from within
675	libraries. Just remember to I<unref after start> and I<ref before stop>	773	third-party libraries. Just remember to I<unref after start> and I<ref
676	(but only if the watcher wasn't active before, or was active before,	774	before stop> (but only if the watcher wasn't active before, or was active
677	respectively).	775	before, respectively. Note also that libev might stop watchers itself
		776	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		777	in the callback).
678		778
679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	779	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
680	running when nothing else is active.	780	running when nothing else is active.
681		781
682	struct ev_signal exitsig;	782	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	783	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	784	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	785	evf_unref (loop);
686		786
687	Example: For some weird reason, unregister the above signal handler again.	787	Example: For some weird reason, unregister the above signal handler again.
…		…
701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	801	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
702	allows libev to delay invocation of I/O and timer/periodic callbacks	802	allows libev to delay invocation of I/O and timer/periodic callbacks
703	to increase efficiency of loop iterations (or to increase power-saving	803	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	804	opportunities).
705		805
706	The background is that sometimes your program runs just fast enough to	806	The idea is that sometimes your program runs just fast enough to handle
707	handle one (or very few) event(s) per loop iteration. While this makes	807	one (or very few) event(s) per loop iteration. While this makes the
708	the program responsive, it also wastes a lot of CPU time to poll for new	808	program responsive, it also wastes a lot of CPU time to poll for new
709	events, especially with backends like C<select ()> which have a high	809	events, especially with backends like C<select ()> which have a high
710	overhead for the actual polling but can deliver many events at once.	810	overhead for the actual polling but can deliver many events at once.
711		811
712	By setting a higher I<io collect interval> you allow libev to spend more	812	By setting a higher I<io collect interval> you allow libev to spend more
713	time collecting I/O events, so you can handle more events per iteration,	813	time collecting I/O events, so you can handle more events per iteration,
…		…
715	C<ev_timer>) will be not affected. Setting this to a non-null value will	815	C<ev_timer>) will be not affected. Setting this to a non-null value will
716	introduce an additional C<ev_sleep ()> call into most loop iterations.	816	introduce an additional C<ev_sleep ()> call into most loop iterations.
717		817
718	Likewise, by setting a higher I<timeout collect interval> you allow libev	818	Likewise, by setting a higher I<timeout collect interval> you allow libev
719	to spend more time collecting timeouts, at the expense of increased	819	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	820	latency/jitter/inexactness (the watcher callback will be called
721	will not be affected. Setting this to a non-null value will not introduce	821	later). C<ev_io> watchers will not be affected. Setting this to a non-null
722	any overhead in libev.	822	value will not introduce any overhead in libev.
723		823
724	Many (busy) programs can usually benefit by setting the I/O collect	824	Many (busy) programs can usually benefit by setting the I/O collect
725	interval to a value near C<0.1> or so, which is often enough for	825	interval to a value near C<0.1> or so, which is often enough for
726	interactive servers (of course not for games), likewise for timeouts. It	826	interactive servers (of course not for games), likewise for timeouts. It
727	usually doesn't make much sense to set it to a lower value than C<0.01>,	827	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
735	they fire on, say, one-second boundaries only.	835	they fire on, say, one-second boundaries only.
736		836
737	=item ev_loop_verify (loop)	837	=item ev_loop_verify (loop)
738		838
739	This function only does something when C<EV_VERIFY> support has been	839	This function only does something when C<EV_VERIFY> support has been
740	compiled in. It tries to go through all internal structures and checks	840	compiled in, which is the default for non-minimal builds. It tries to go
741	them for validity. If anything is found to be inconsistent, it will print	841	through all internal structures and checks them for validity. If anything
742	an error message to standard error and call C<abort ()>.	842	is found to be inconsistent, it will print an error message to standard
		843	error and call C<abort ()>.
743		844
744	This can be used to catch bugs inside libev itself: under normal	845	This can be used to catch bugs inside libev itself: under normal
745	circumstances, this function will never abort as of course libev keeps its	846	circumstances, this function will never abort as of course libev keeps its
746	data structures consistent.	847	data structures consistent.
747		848
748	=back	849	=back
749		850
750		851
751	=head1 ANATOMY OF A WATCHER	852	=head1 ANATOMY OF A WATCHER
752		853
		854	In the following description, uppercase C<TYPE> in names stands for the
		855	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		856	watchers and C<ev_io_start> for I/O watchers.
		857
753	A watcher is a structure that you create and register to record your	858	A watcher is a structure that you create and register to record your
754	interest in some event. For instance, if you want to wait for STDIN to	859	interest in some event. For instance, if you want to wait for STDIN to
755	become readable, you would create an C<ev_io> watcher for that:	860	become readable, you would create an C<ev_io> watcher for that:
756		861
757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	862	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
758	{	863	{
759	ev_io_stop (w);	864	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	865	ev_unloop (loop, EVUNLOOP_ALL);
761	}	866	}
762		867
763	struct ev_loop *loop = ev_default_loop (0);	868	struct ev_loop *loop = ev_default_loop (0);
		869
764	struct ev_io stdin_watcher;	870	ev_io stdin_watcher;
		871
765	ev_init (&stdin_watcher, my_cb);	872	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	873	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	874	ev_io_start (loop, &stdin_watcher);
		875
768	ev_loop (loop, 0);	876	ev_loop (loop, 0);
769		877
770	As you can see, you are responsible for allocating the memory for your	878	As you can see, you are responsible for allocating the memory for your
771	watcher structures (and it is usually a bad idea to do this on the stack,	879	watcher structures (and it is I<usually> a bad idea to do this on the
772	although this can sometimes be quite valid).	880	stack).
		881
		882	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		883	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
773		884
774	Each watcher structure must be initialised by a call to C<ev_init	885	Each watcher structure must be initialised by a call to C<ev_init
775	(watcher *, callback)>, which expects a callback to be provided. This	886	(watcher *, callback)>, which expects a callback to be provided. This
776	callback gets invoked each time the event occurs (or, in the case of I/O	887	callback gets invoked each time the event occurs (or, in the case of I/O
777	watchers, each time the event loop detects that the file descriptor given	888	watchers, each time the event loop detects that the file descriptor given
778	is readable and/or writable).	889	is readable and/or writable).
779		890
780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	891	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
781	with arguments specific to this watcher type. There is also a macro	892	macro to configure it, with arguments specific to the watcher type. There
782	to combine initialisation and setting in one call: C<< ev_<type>_init	893	is also a macro to combine initialisation and setting in one call: C<<
783	(watcher *, callback, ...) >>.	894	ev_TYPE_init (watcher *, callback, ...) >>.
784		895
785	To make the watcher actually watch out for events, you have to start it	896	To make the watcher actually watch out for events, you have to start it
786	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	897	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
787	*) >>), and you can stop watching for events at any time by calling the	898	*) >>), and you can stop watching for events at any time by calling the
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	899	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		900
790	As long as your watcher is active (has been started but not stopped) you	901	As long as your watcher is active (has been started but not stopped) you
791	must not touch the values stored in it. Most specifically you must never	902	must not touch the values stored in it. Most specifically you must never
792	reinitialise it or call its C<set> macro.	903	reinitialise it or call its C<ev_TYPE_set> macro.
793		904
794	Each and every callback receives the event loop pointer as first, the	905	Each and every callback receives the event loop pointer as first, the
795	registered watcher structure as second, and a bitset of received events as	906	registered watcher structure as second, and a bitset of received events as
796	third argument.	907	third argument.
797		908
…		…
855		966
856	=item C<EV_ASYNC>	967	=item C<EV_ASYNC>
857		968
858	The given async watcher has been asynchronously notified (see C<ev_async>).	969	The given async watcher has been asynchronously notified (see C<ev_async>).
859		970
		971	=item C<EV_CUSTOM>
		972
		973	Not ever sent (or otherwise used) by libev itself, but can be freely used
		974	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		975
860	=item C<EV_ERROR>	976	=item C<EV_ERROR>
861		977
862	An unspecified error has occurred, the watcher has been stopped. This might	978	An unspecified error has occurred, the watcher has been stopped. This might
863	happen because the watcher could not be properly started because libev	979	happen because the watcher could not be properly started because libev
864	ran out of memory, a file descriptor was found to be closed or any other	980	ran out of memory, a file descriptor was found to be closed or any other
		981	problem. Libev considers these application bugs.
		982
865	problem. You best act on it by reporting the problem and somehow coping	983	You best act on it by reporting the problem and somehow coping with the
866	with the watcher being stopped.	984	watcher being stopped. Note that well-written programs should not receive
		985	an error ever, so when your watcher receives it, this usually indicates a
		986	bug in your program.
867		987
868	Libev will usually signal a few "dummy" events together with an error,	988	Libev will usually signal a few "dummy" events together with an error, for
869	for example it might indicate that a fd is readable or writable, and if	989	example it might indicate that a fd is readable or writable, and if your
870	your callbacks is well-written it can just attempt the operation and cope	990	callbacks is well-written it can just attempt the operation and cope with
871	with the error from read() or write(). This will not work in multi-threaded	991	the error from read() or write(). This will not work in multi-threaded
872	programs, though, so beware.	992	programs, though, as the fd could already be closed and reused for another
		993	thing, so beware.
873		994
874	=back	995	=back
875		996
876	=head2 GENERIC WATCHER FUNCTIONS	997	=head2 GENERIC WATCHER FUNCTIONS
877
878	In the following description, C<TYPE> stands for the watcher type,
879	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
880		998
881	=over 4	999	=over 4
882		1000
883	=item C<ev_init> (ev_TYPE *watcher, callback)	1001	=item C<ev_init> (ev_TYPE *watcher, callback)
884		1002
…		…
890	which rolls both calls into one.	1008	which rolls both calls into one.
891		1009
892	You can reinitialise a watcher at any time as long as it has been stopped	1010	You can reinitialise a watcher at any time as long as it has been stopped
893	(or never started) and there are no pending events outstanding.	1011	(or never started) and there are no pending events outstanding.
894		1012
895	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1013	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
896	int revents)>.	1014	int revents)>.
		1015
		1016	Example: Initialise an C<ev_io> watcher in two steps.
		1017
		1018	ev_io w;
		1019	ev_init (&w, my_cb);
		1020	ev_io_set (&w, STDIN_FILENO, EV_READ);
897		1021
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1022	=item C<ev_TYPE_set> (ev_TYPE *, [args])
899		1023
900	This macro initialises the type-specific parts of a watcher. You need to	1024	This macro initialises the type-specific parts of a watcher. You need to
901	call C<ev_init> at least once before you call this macro, but you can	1025	call C<ev_init> at least once before you call this macro, but you can
…		…
904	difference to the C<ev_init> macro).	1028	difference to the C<ev_init> macro).
905		1029
906	Although some watcher types do not have type-specific arguments	1030	Although some watcher types do not have type-specific arguments
907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1031	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
908		1032
		1033	See C<ev_init>, above, for an example.
		1034
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1035	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		1036
911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1037	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
912	calls into a single call. This is the most convenient method to initialise	1038	calls into a single call. This is the most convenient method to initialise
913	a watcher. The same limitations apply, of course.	1039	a watcher. The same limitations apply, of course.
914		1040
		1041	Example: Initialise and set an C<ev_io> watcher in one step.
		1042
		1043	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1044
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1045	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
916		1046
917	Starts (activates) the given watcher. Only active watchers will receive	1047	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	1048	events. If the watcher is already active nothing will happen.
919		1049
		1050	Example: Start the C<ev_io> watcher that is being abused as example in this
		1051	whole section.
		1052
		1053	ev_io_start (EV_DEFAULT_UC, &w);
		1054
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1055	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
921		1056
922	Stops the given watcher again (if active) and clears the pending	1057	Stops the given watcher if active, and clears the pending status (whether
		1058	the watcher was active or not).
		1059
923	status. It is possible that stopped watchers are pending (for example,	1060	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	1061	non-repeating timers are being stopped when they become pending - but
925	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1062	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
926	you want to free or reuse the memory used by the watcher it is therefore a	1063	pending. If you want to free or reuse the memory used by the watcher it is
927	good idea to always call its C<ev_TYPE_stop> function.	1064	therefore a good idea to always call its C<ev_TYPE_stop> function.
928		1065
929	=item bool ev_is_active (ev_TYPE *watcher)	1066	=item bool ev_is_active (ev_TYPE *watcher)
930		1067
931	Returns a true value iff the watcher is active (i.e. it has been started	1068	Returns a true value iff the watcher is active (i.e. it has been started
932	and not yet been stopped). As long as a watcher is active you must not modify	1069	and not yet been stopped). As long as a watcher is active you must not modify
…		…
958	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1095	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
959	(default: C<-2>). Pending watchers with higher priority will be invoked	1096	(default: C<-2>). Pending watchers with higher priority will be invoked
960	before watchers with lower priority, but priority will not keep watchers	1097	before watchers with lower priority, but priority will not keep watchers
961	from being executed (except for C<ev_idle> watchers).	1098	from being executed (except for C<ev_idle> watchers).
962		1099
963	This means that priorities are I<only> used for ordering callback
964	invocation after new events have been received. This is useful, for
965	example, to reduce latency after idling, or more often, to bind two
966	watchers on the same event and make sure one is called first.
967
968	If you need to suppress invocation when higher priority events are pending	1100	If you need to suppress invocation when higher priority events are pending
969	you need to look at C<ev_idle> watchers, which provide this functionality.	1101	you need to look at C<ev_idle> watchers, which provide this functionality.
970		1102
971	You I<must not> change the priority of a watcher as long as it is active or	1103	You I<must not> change the priority of a watcher as long as it is active or
972	pending.	1104	pending.
973		1105
		1106	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1107	fine, as long as you do not mind that the priority value you query might
		1108	or might not have been clamped to the valid range.
		1109
974	The default priority used by watchers when no priority has been set is	1110	The default priority used by watchers when no priority has been set is
975	always C<0>, which is supposed to not be too high and not be too low :).	1111	always C<0>, which is supposed to not be too high and not be too low :).
976		1112
977	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1113	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
978	fine, as long as you do not mind that the priority value you query might	1114	priorities.
979	or might not have been adjusted to be within valid range.
980		1115
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1116	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1117
983	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1118	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
984	C<loop> nor C<revents> need to be valid as long as the watcher callback	1119	C<loop> nor C<revents> need to be valid as long as the watcher callback
985	can deal with that fact.	1120	can deal with that fact, as both are simply passed through to the
		1121	callback.
986		1122
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1123	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1124
989	If the watcher is pending, this function returns clears its pending status	1125	If the watcher is pending, this function clears its pending status and
990	and returns its C<revents> bitset (as if its callback was invoked). If the	1126	returns its C<revents> bitset (as if its callback was invoked). If the
991	watcher isn't pending it does nothing and returns C<0>.	1127	watcher isn't pending it does nothing and returns C<0>.
992		1128
		1129	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1130	callback to be invoked, which can be accomplished with this function.
		1131
993	=back	1132	=back
994		1133
995		1134
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1135	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1136
998	Each watcher has, by default, a member C<void *data> that you can change	1137	Each watcher has, by default, a member C<void *data> that you can change
999	and read at any time, libev will completely ignore it. This can be used	1138	and read at any time: libev will completely ignore it. This can be used
1000	to associate arbitrary data with your watcher. If you need more data and	1139	to associate arbitrary data with your watcher. If you need more data and
1001	don't want to allocate memory and store a pointer to it in that data	1140	don't want to allocate memory and store a pointer to it in that data
1002	member, you can also "subclass" the watcher type and provide your own	1141	member, you can also "subclass" the watcher type and provide your own
1003	data:	1142	data:
1004		1143
1005	struct my_io	1144	struct my_io
1006	{	1145	{
1007	struct ev_io io;	1146	ev_io io;
1008	int otherfd;	1147	int otherfd;
1009	void *somedata;	1148	void *somedata;
1010	struct whatever *mostinteresting;	1149	struct whatever *mostinteresting;
1011	}	1150	};
		1151
		1152	...
		1153	struct my_io w;
		1154	ev_io_init (&w.io, my_cb, fd, EV_READ);
1012		1155
1013	And since your callback will be called with a pointer to the watcher, you	1156	And since your callback will be called with a pointer to the watcher, you
1014	can cast it back to your own type:	1157	can cast it back to your own type:
1015		1158
1016	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1159	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1017	{	1160	{
1018	struct my_io *w = (struct my_io *)w_;	1161	struct my_io *w = (struct my_io *)w_;
1019	...	1162	...
1020	}	1163	}
1021		1164
1022	More interesting and less C-conformant ways of casting your callback type	1165	More interesting and less C-conformant ways of casting your callback type
1023	instead have been omitted.	1166	instead have been omitted.
1024		1167
1025	Another common scenario is having some data structure with multiple	1168	Another common scenario is to use some data structure with multiple
1026	watchers:	1169	embedded watchers:
1027		1170
1028	struct my_biggy	1171	struct my_biggy
1029	{	1172	{
1030	int some_data;	1173	int some_data;
1031	ev_timer t1;	1174	ev_timer t1;
1032	ev_timer t2;	1175	ev_timer t2;
1033	}	1176	}
1034		1177
1035	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1178	In this case getting the pointer to C<my_biggy> is a bit more
1036	you need to use C<offsetof>:	1179	complicated: Either you store the address of your C<my_biggy> struct
		1180	in the C<data> member of the watcher (for woozies), or you need to use
		1181	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1182	programmers):
1037		1183
1038	#include <stddef.h>	1184	#include <stddef.h>
1039		1185
1040	static void	1186	static void
1041	t1_cb (EV_P_ struct ev_timer *w, int revents)	1187	t1_cb (EV_P_ ev_timer *w, int revents)
1042	{	1188	{
1043	struct my_biggy big = (struct my_biggy *	1189	struct my_biggy big = (struct my_biggy *
1044	(((char *)w) - offsetof (struct my_biggy, t1));	1190	(((char *)w) - offsetof (struct my_biggy, t1));
1045	}	1191	}
1046		1192
1047	static void	1193	static void
1048	t2_cb (EV_P_ struct ev_timer *w, int revents)	1194	t2_cb (EV_P_ ev_timer *w, int revents)
1049	{	1195	{
1050	struct my_biggy big = (struct my_biggy *	1196	struct my_biggy big = (struct my_biggy *
1051	(((char *)w) - offsetof (struct my_biggy, t2));	1197	(((char *)w) - offsetof (struct my_biggy, t2));
1052	}	1198	}
		1199
		1200	=head2 WATCHER PRIORITY MODELS
		1201
		1202	Many event loops support I<watcher priorities>, which are usually small
		1203	integers that influence the ordering of event callback invocation
		1204	between watchers in some way, all else being equal.
		1205
		1206	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1207	description for the more technical details such as the actual priority
		1208	range.
		1209
		1210	There are two common ways how these these priorities are being interpreted
		1211	by event loops:
		1212
		1213	In the more common lock-out model, higher priorities "lock out" invocation
		1214	of lower priority watchers, which means as long as higher priority
		1215	watchers receive events, lower priority watchers are not being invoked.
		1216
		1217	The less common only-for-ordering model uses priorities solely to order
		1218	callback invocation within a single event loop iteration: Higher priority
		1219	watchers are invoked before lower priority ones, but they all get invoked
		1220	before polling for new events.
		1221
		1222	Libev uses the second (only-for-ordering) model for all its watchers
		1223	except for idle watchers (which use the lock-out model).
		1224
		1225	The rationale behind this is that implementing the lock-out model for
		1226	watchers is not well supported by most kernel interfaces, and most event
		1227	libraries will just poll for the same events again and again as long as
		1228	their callbacks have not been executed, which is very inefficient in the
		1229	common case of one high-priority watcher locking out a mass of lower
		1230	priority ones.
		1231
		1232	Static (ordering) priorities are most useful when you have two or more
		1233	watchers handling the same resource: a typical usage example is having an
		1234	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1235	timeouts. Under load, data might be received while the program handles
		1236	other jobs, but since timers normally get invoked first, the timeout
		1237	handler will be executed before checking for data. In that case, giving
		1238	the timer a lower priority than the I/O watcher ensures that I/O will be
		1239	handled first even under adverse conditions (which is usually, but not
		1240	always, what you want).
		1241
		1242	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1243	will only be executed when no same or higher priority watchers have
		1244	received events, they can be used to implement the "lock-out" model when
		1245	required.
		1246
		1247	For example, to emulate how many other event libraries handle priorities,
		1248	you can associate an C<ev_idle> watcher to each such watcher, and in
		1249	the normal watcher callback, you just start the idle watcher. The real
		1250	processing is done in the idle watcher callback. This causes libev to
		1251	continously poll and process kernel event data for the watcher, but when
		1252	the lock-out case is known to be rare (which in turn is rare :), this is
		1253	workable.
		1254
		1255	Usually, however, the lock-out model implemented that way will perform
		1256	miserably under the type of load it was designed to handle. In that case,
		1257	it might be preferable to stop the real watcher before starting the
		1258	idle watcher, so the kernel will not have to process the event in case
		1259	the actual processing will be delayed for considerable time.
		1260
		1261	Here is an example of an I/O watcher that should run at a strictly lower
		1262	priority than the default, and which should only process data when no
		1263	other events are pending:
		1264
		1265	ev_idle idle; // actual processing watcher
		1266	ev_io io; // actual event watcher
		1267
		1268	static void
		1269	io_cb (EV_P_ ev_io *w, int revents)
		1270	{
		1271	// stop the I/O watcher, we received the event, but
		1272	// are not yet ready to handle it.
		1273	ev_io_stop (EV_A_ w);
		1274
		1275	// start the idle watcher to ahndle the actual event.
		1276	// it will not be executed as long as other watchers
		1277	// with the default priority are receiving events.
		1278	ev_idle_start (EV_A_ &idle);
		1279	}
		1280
		1281	static void
		1282	idle-cb (EV_P_ ev_idle *w, int revents)
		1283	{
		1284	// actual processing
		1285	read (STDIN_FILENO, ...);
		1286
		1287	// have to start the I/O watcher again, as
		1288	// we have handled the event
		1289	ev_io_start (EV_P_ &io);
		1290	}
		1291
		1292	// initialisation
		1293	ev_idle_init (&idle, idle_cb);
		1294	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1295	ev_io_start (EV_DEFAULT_ &io);
		1296
		1297	In the "real" world, it might also be beneficial to start a timer, so that
		1298	low-priority connections can not be locked out forever under load. This
		1299	enables your program to keep a lower latency for important connections
		1300	during short periods of high load, while not completely locking out less
		1301	important ones.
1053		1302
1054		1303
1055	=head1 WATCHER TYPES	1304	=head1 WATCHER TYPES
1056		1305
1057	This section describes each watcher in detail, but will not repeat	1306	This section describes each watcher in detail, but will not repeat
…		…
1081	In general you can register as many read and/or write event watchers per	1330	In general you can register as many read and/or write event watchers per
1082	fd as you want (as long as you don't confuse yourself). Setting all file	1331	fd as you want (as long as you don't confuse yourself). Setting all file
1083	descriptors to non-blocking mode is also usually a good idea (but not	1332	descriptors to non-blocking mode is also usually a good idea (but not
1084	required if you know what you are doing).	1333	required if you know what you are doing).
1085		1334
1086	If you must do this, then force the use of a known-to-be-good backend	1335	If you cannot use non-blocking mode, then force the use of a
1087	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1336	known-to-be-good backend (at the time of this writing, this includes only
1088	C<EVBACKEND_POLL>).	1337	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1089		1338
1090	Another thing you have to watch out for is that it is quite easy to	1339	Another thing you have to watch out for is that it is quite easy to
1091	receive "spurious" readiness notifications, that is your callback might	1340	receive "spurious" readiness notifications, that is your callback might
1092	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1341	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1093	because there is no data. Not only are some backends known to create a	1342	because there is no data. Not only are some backends known to create a
1094	lot of those (for example Solaris ports), it is very easy to get into	1343	lot of those (for example Solaris ports), it is very easy to get into
1095	this situation even with a relatively standard program structure. Thus	1344	this situation even with a relatively standard program structure. Thus
1096	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1345	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1097	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1346	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1098		1347
1099	If you cannot run the fd in non-blocking mode (for example you should not	1348	If you cannot run the fd in non-blocking mode (for example you should
1100	play around with an Xlib connection), then you have to separately re-test	1349	not play around with an Xlib connection), then you have to separately
1101	whether a file descriptor is really ready with a known-to-be good interface	1350	re-test whether a file descriptor is really ready with a known-to-be good
1102	such as poll (fortunately in our Xlib example, Xlib already does this on	1351	interface such as poll (fortunately in our Xlib example, Xlib already
1103	its own, so its quite safe to use).	1352	does this on its own, so its quite safe to use). Some people additionally
		1353	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1354	indefinitely.
		1355
		1356	But really, best use non-blocking mode.
1104		1357
1105	=head3 The special problem of disappearing file descriptors	1358	=head3 The special problem of disappearing file descriptors
1106		1359
1107	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1360	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1108	descriptor (either by calling C<close> explicitly or by any other means,	1361	descriptor (either due to calling C<close> explicitly or any other means,
1109	such as C<dup>). The reason is that you register interest in some file	1362	such as C<dup2>). The reason is that you register interest in some file
1110	descriptor, but when it goes away, the operating system will silently drop	1363	descriptor, but when it goes away, the operating system will silently drop
1111	this interest. If another file descriptor with the same number then is	1364	this interest. If another file descriptor with the same number then is
1112	registered with libev, there is no efficient way to see that this is, in	1365	registered with libev, there is no efficient way to see that this is, in
1113	fact, a different file descriptor.	1366	fact, a different file descriptor.
1114		1367
…		…
1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1398	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1146	C<EVBACKEND_POLL>.	1399	C<EVBACKEND_POLL>.
1147		1400
1148	=head3 The special problem of SIGPIPE	1401	=head3 The special problem of SIGPIPE
1149		1402
1150	While not really specific to libev, it is easy to forget about SIGPIPE:	1403	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1151	when writing to a pipe whose other end has been closed, your program gets	1404	when writing to a pipe whose other end has been closed, your program gets
1152	send a SIGPIPE, which, by default, aborts your program. For most programs	1405	sent a SIGPIPE, which, by default, aborts your program. For most programs
1153	this is sensible behaviour, for daemons, this is usually undesirable.	1406	this is sensible behaviour, for daemons, this is usually undesirable.
1154		1407
1155	So when you encounter spurious, unexplained daemon exits, make sure you	1408	So when you encounter spurious, unexplained daemon exits, make sure you
1156	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1409	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1157	somewhere, as that would have given you a big clue).	1410	somewhere, as that would have given you a big clue).
…		…
1164	=item ev_io_init (ev_io *, callback, int fd, int events)	1417	=item ev_io_init (ev_io *, callback, int fd, int events)
1165		1418
1166	=item ev_io_set (ev_io *, int fd, int events)	1419	=item ev_io_set (ev_io *, int fd, int events)
1167		1420
1168	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1421	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1169	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1422	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1170	C<EV_READ | EV_WRITE> to receive the given events.	1423	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1171		1424
1172	=item int fd [read-only]	1425	=item int fd [read-only]
1173		1426
1174	The file descriptor being watched.	1427	The file descriptor being watched.
1175		1428
…		…
1184	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1437	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1185	readable, but only once. Since it is likely line-buffered, you could	1438	readable, but only once. Since it is likely line-buffered, you could
1186	attempt to read a whole line in the callback.	1439	attempt to read a whole line in the callback.
1187		1440
1188	static void	1441	static void
1189	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1442	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1190	{	1443	{
1191	ev_io_stop (loop, w);	1444	ev_io_stop (loop, w);
1192	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1445	.. read from stdin here (or from w->fd) and handle any I/O errors
1193	}	1446	}
1194		1447
1195	...	1448	...
1196	struct ev_loop *loop = ev_default_init (0);	1449	struct ev_loop *loop = ev_default_init (0);
1197	struct ev_io stdin_readable;	1450	ev_io stdin_readable;
1198	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1451	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1199	ev_io_start (loop, &stdin_readable);	1452	ev_io_start (loop, &stdin_readable);
1200	ev_loop (loop, 0);	1453	ev_loop (loop, 0);
1201		1454
1202		1455
…		…
1205	Timer watchers are simple relative timers that generate an event after a	1458	Timer watchers are simple relative timers that generate an event after a
1206	given time, and optionally repeating in regular intervals after that.	1459	given time, and optionally repeating in regular intervals after that.
1207		1460
1208	The timers are based on real time, that is, if you register an event that	1461	The timers are based on real time, that is, if you register an event that
1209	times out after an hour and you reset your system clock to January last	1462	times out after an hour and you reset your system clock to January last
1210	year, it will still time out after (roughly) and hour. "Roughly" because	1463	year, it will still time out after (roughly) one hour. "Roughly" because
1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1464	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1212	monotonic clock option helps a lot here).	1465	monotonic clock option helps a lot here).
1213		1466
1214	The callback is guaranteed to be invoked only after its timeout has passed,	1467	The callback is guaranteed to be invoked only I<after> its timeout has
1215	but if multiple timers become ready during the same loop iteration then	1468	passed. If multiple timers become ready during the same loop iteration
1216	order of execution is undefined.	1469	then the ones with earlier time-out values are invoked before ones with
		1470	later time-out values (but this is no longer true when a callback calls
		1471	C<ev_loop> recursively).
		1472
		1473	=head3 Be smart about timeouts
		1474
		1475	Many real-world problems involve some kind of timeout, usually for error
		1476	recovery. A typical example is an HTTP request - if the other side hangs,
		1477	you want to raise some error after a while.
		1478
		1479	What follows are some ways to handle this problem, from obvious and
		1480	inefficient to smart and efficient.
		1481
		1482	In the following, a 60 second activity timeout is assumed - a timeout that
		1483	gets reset to 60 seconds each time there is activity (e.g. each time some
		1484	data or other life sign was received).
		1485
		1486	=over 4
		1487
		1488	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1489
		1490	This is the most obvious, but not the most simple way: In the beginning,
		1491	start the watcher:
		1492
		1493	ev_timer_init (timer, callback, 60., 0.);
		1494	ev_timer_start (loop, timer);
		1495
		1496	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1497	and start it again:
		1498
		1499	ev_timer_stop (loop, timer);
		1500	ev_timer_set (timer, 60., 0.);
		1501	ev_timer_start (loop, timer);
		1502
		1503	This is relatively simple to implement, but means that each time there is
		1504	some activity, libev will first have to remove the timer from its internal
		1505	data structure and then add it again. Libev tries to be fast, but it's
		1506	still not a constant-time operation.
		1507
		1508	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1509
		1510	This is the easiest way, and involves using C<ev_timer_again> instead of
		1511	C<ev_timer_start>.
		1512
		1513	To implement this, configure an C<ev_timer> with a C<repeat> value
		1514	of C<60> and then call C<ev_timer_again> at start and each time you
		1515	successfully read or write some data. If you go into an idle state where
		1516	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1517	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1518
		1519	That means you can ignore both the C<ev_timer_start> function and the
		1520	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1521	member and C<ev_timer_again>.
		1522
		1523	At start:
		1524
		1525	ev_timer_init (timer, callback);
		1526	timer->repeat = 60.;
		1527	ev_timer_again (loop, timer);
		1528
		1529	Each time there is some activity:
		1530
		1531	ev_timer_again (loop, timer);
		1532
		1533	It is even possible to change the time-out on the fly, regardless of
		1534	whether the watcher is active or not:
		1535
		1536	timer->repeat = 30.;
		1537	ev_timer_again (loop, timer);
		1538
		1539	This is slightly more efficient then stopping/starting the timer each time
		1540	you want to modify its timeout value, as libev does not have to completely
		1541	remove and re-insert the timer from/into its internal data structure.
		1542
		1543	It is, however, even simpler than the "obvious" way to do it.
		1544
		1545	=item 3. Let the timer time out, but then re-arm it as required.
		1546
		1547	This method is more tricky, but usually most efficient: Most timeouts are
		1548	relatively long compared to the intervals between other activity - in
		1549	our example, within 60 seconds, there are usually many I/O events with
		1550	associated activity resets.
		1551
		1552	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1553	but remember the time of last activity, and check for a real timeout only
		1554	within the callback:
		1555
		1556	ev_tstamp last_activity; // time of last activity
		1557
		1558	static void
		1559	callback (EV_P_ ev_timer *w, int revents)
		1560	{
		1561	ev_tstamp now = ev_now (EV_A);
		1562	ev_tstamp timeout = last_activity + 60.;
		1563
		1564	// if last_activity + 60. is older than now, we did time out
		1565	if (timeout < now)
		1566	{
		1567	// timeout occured, take action
		1568	}
		1569	else
		1570	{
		1571	// callback was invoked, but there was some activity, re-arm
		1572	// the watcher to fire in last_activity + 60, which is
		1573	// guaranteed to be in the future, so "again" is positive:
		1574	w->repeat = timeout - now;
		1575	ev_timer_again (EV_A_ w);
		1576	}
		1577	}
		1578
		1579	To summarise the callback: first calculate the real timeout (defined
		1580	as "60 seconds after the last activity"), then check if that time has
		1581	been reached, which means something I<did>, in fact, time out. Otherwise
		1582	the callback was invoked too early (C<timeout> is in the future), so
		1583	re-schedule the timer to fire at that future time, to see if maybe we have
		1584	a timeout then.
		1585
		1586	Note how C<ev_timer_again> is used, taking advantage of the
		1587	C<ev_timer_again> optimisation when the timer is already running.
		1588
		1589	This scheme causes more callback invocations (about one every 60 seconds
		1590	minus half the average time between activity), but virtually no calls to
		1591	libev to change the timeout.
		1592
		1593	To start the timer, simply initialise the watcher and set C<last_activity>
		1594	to the current time (meaning we just have some activity :), then call the
		1595	callback, which will "do the right thing" and start the timer:
		1596
		1597	ev_timer_init (timer, callback);
		1598	last_activity = ev_now (loop);
		1599	callback (loop, timer, EV_TIMEOUT);
		1600
		1601	And when there is some activity, simply store the current time in
		1602	C<last_activity>, no libev calls at all:
		1603
		1604	last_actiivty = ev_now (loop);
		1605
		1606	This technique is slightly more complex, but in most cases where the
		1607	time-out is unlikely to be triggered, much more efficient.
		1608
		1609	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1610	callback :) - just change the timeout and invoke the callback, which will
		1611	fix things for you.
		1612
		1613	=item 4. Wee, just use a double-linked list for your timeouts.
		1614
		1615	If there is not one request, but many thousands (millions...), all
		1616	employing some kind of timeout with the same timeout value, then one can
		1617	do even better:
		1618
		1619	When starting the timeout, calculate the timeout value and put the timeout
		1620	at the I<end> of the list.
		1621
		1622	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1623	the list is expected to fire (for example, using the technique #3).
		1624
		1625	When there is some activity, remove the timer from the list, recalculate
		1626	the timeout, append it to the end of the list again, and make sure to
		1627	update the C<ev_timer> if it was taken from the beginning of the list.
		1628
		1629	This way, one can manage an unlimited number of timeouts in O(1) time for
		1630	starting, stopping and updating the timers, at the expense of a major
		1631	complication, and having to use a constant timeout. The constant timeout
		1632	ensures that the list stays sorted.
		1633
		1634	=back
		1635
		1636	So which method the best?
		1637
		1638	Method #2 is a simple no-brain-required solution that is adequate in most
		1639	situations. Method #3 requires a bit more thinking, but handles many cases
		1640	better, and isn't very complicated either. In most case, choosing either
		1641	one is fine, with #3 being better in typical situations.
		1642
		1643	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1644	rather complicated, but extremely efficient, something that really pays
		1645	off after the first million or so of active timers, i.e. it's usually
		1646	overkill :)
1217		1647
1218	=head3 The special problem of time updates	1648	=head3 The special problem of time updates
1219		1649
1220	Establishing the current time is a costly operation (it usually takes at	1650	Establishing the current time is a costly operation (it usually takes at
1221	least two system calls): EV therefore updates its idea of the current	1651	least two system calls): EV therefore updates its idea of the current
1222	time only before and after C<ev_loop> polls for new events, which causes	1652	time only before and after C<ev_loop> collects new events, which causes a
1223	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1653	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1224	lots of events.	1654	lots of events in one iteration.
1225		1655
1226	The relative timeouts are calculated relative to the C<ev_now ()>	1656	The relative timeouts are calculated relative to the C<ev_now ()>
1227	time. This is usually the right thing as this timestamp refers to the time	1657	time. This is usually the right thing as this timestamp refers to the time
1228	of the event triggering whatever timeout you are modifying/starting. If	1658	of the event triggering whatever timeout you are modifying/starting. If
1229	you suspect event processing to be delayed and you I<need> to base the	1659	you suspect event processing to be delayed and you I<need> to base the
…		…
1265	If the timer is started but non-repeating, stop it (as if it timed out).	1695	If the timer is started but non-repeating, stop it (as if it timed out).
1266		1696
1267	If the timer is repeating, either start it if necessary (with the	1697	If the timer is repeating, either start it if necessary (with the
1268	C<repeat> value), or reset the running timer to the C<repeat> value.	1698	C<repeat> value), or reset the running timer to the C<repeat> value.
1269		1699
1270	This sounds a bit complicated, but here is a useful and typical	1700	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1271	example: Imagine you have a TCP connection and you want a so-called idle	1701	usage example.
1272	timeout, that is, you want to be called when there have been, say, 60
1273	seconds of inactivity on the socket. The easiest way to do this is to
1274	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1275	C<ev_timer_again> each time you successfully read or write some data. If
1276	you go into an idle state where you do not expect data to travel on the
1277	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1278	automatically restart it if need be.
1279
1280	That means you can ignore the C<after> value and C<ev_timer_start>
1281	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1282
1283	ev_timer_init (timer, callback, 0., 5.);
1284	ev_timer_again (loop, timer);
1285	...
1286	timer->again = 17.;
1287	ev_timer_again (loop, timer);
1288	...
1289	timer->again = 10.;
1290	ev_timer_again (loop, timer);
1291
1292	This is more slightly efficient then stopping/starting the timer each time
1293	you want to modify its timeout value.
1294		1702
1295	=item ev_tstamp repeat [read-write]	1703	=item ev_tstamp repeat [read-write]
1296		1704
1297	The current C<repeat> value. Will be used each time the watcher times out	1705	The current C<repeat> value. Will be used each time the watcher times out
1298	or C<ev_timer_again> is called and determines the next timeout (if any),	1706	or C<ev_timer_again> is called, and determines the next timeout (if any),
1299	which is also when any modifications are taken into account.	1707	which is also when any modifications are taken into account.
1300		1708
1301	=back	1709	=back
1302		1710
1303	=head3 Examples	1711	=head3 Examples
1304		1712
1305	Example: Create a timer that fires after 60 seconds.	1713	Example: Create a timer that fires after 60 seconds.
1306		1714
1307	static void	1715	static void
1308	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1716	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1309	{	1717	{
1310	.. one minute over, w is actually stopped right here	1718	.. one minute over, w is actually stopped right here
1311	}	1719	}
1312		1720
1313	struct ev_timer mytimer;	1721	ev_timer mytimer;
1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1722	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1315	ev_timer_start (loop, &mytimer);	1723	ev_timer_start (loop, &mytimer);
1316		1724
1317	Example: Create a timeout timer that times out after 10 seconds of	1725	Example: Create a timeout timer that times out after 10 seconds of
1318	inactivity.	1726	inactivity.
1319		1727
1320	static void	1728	static void
1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1729	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1322	{	1730	{
1323	.. ten seconds without any activity	1731	.. ten seconds without any activity
1324	}	1732	}
1325		1733
1326	struct ev_timer mytimer;	1734	ev_timer mytimer;
1327	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1735	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1328	ev_timer_again (&mytimer); /* start timer */	1736	ev_timer_again (&mytimer); /* start timer */
1329	ev_loop (loop, 0);	1737	ev_loop (loop, 0);
1330		1738
1331	// and in some piece of code that gets executed on any "activity":	1739	// and in some piece of code that gets executed on any "activity":
…		…
1336	=head2 C<ev_periodic> - to cron or not to cron?	1744	=head2 C<ev_periodic> - to cron or not to cron?
1337		1745
1338	Periodic watchers are also timers of a kind, but they are very versatile	1746	Periodic watchers are also timers of a kind, but they are very versatile
1339	(and unfortunately a bit complex).	1747	(and unfortunately a bit complex).
1340		1748
1341	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1749	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1342	but on wall clock time (absolute time). You can tell a periodic watcher	1750	relative time, the physical time that passes) but on wall clock time
1343	to trigger after some specific point in time. For example, if you tell a	1751	(absolute time, the thing you can read on your calender or clock). The
1344	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1752	difference is that wall clock time can run faster or slower than real
1345	+ 10.>, that is, an absolute time not a delay) and then reset your system	1753	time, and time jumps are not uncommon (e.g. when you adjust your
1346	clock to January of the previous year, then it will take more than year	1754	wrist-watch).
1347	to trigger the event (unlike an C<ev_timer>, which would still trigger
1348	roughly 10 seconds later as it uses a relative timeout).
1349		1755
		1756	You can tell a periodic watcher to trigger after some specific point
		1757	in time: for example, if you tell a periodic watcher to trigger "in 10
		1758	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1759	not a delay) and then reset your system clock to January of the previous
		1760	year, then it will take a year or more to trigger the event (unlike an
		1761	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1762	it, as it uses a relative timeout).
		1763
1350	C<ev_periodic>s can also be used to implement vastly more complex timers,	1764	C<ev_periodic> watchers can also be used to implement vastly more complex
1351	such as triggering an event on each "midnight, local time", or other	1765	timers, such as triggering an event on each "midnight, local time", or
1352	complicated, rules.	1766	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1767	those cannot react to time jumps.
1353		1768
1354	As with timers, the callback is guaranteed to be invoked only when the	1769	As with timers, the callback is guaranteed to be invoked only when the
1355	time (C<at>) has passed, but if multiple periodic timers become ready	1770	point in time where it is supposed to trigger has passed. If multiple
1356	during the same loop iteration then order of execution is undefined.	1771	timers become ready during the same loop iteration then the ones with
		1772	earlier time-out values are invoked before ones with later time-out values
		1773	(but this is no longer true when a callback calls C<ev_loop> recursively).
1357		1774
1358	=head3 Watcher-Specific Functions and Data Members	1775	=head3 Watcher-Specific Functions and Data Members
1359		1776
1360	=over 4	1777	=over 4
1361		1778
1362	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1779	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1363		1780
1364	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1781	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1365		1782
1366	Lots of arguments, lets sort it out... There are basically three modes of	1783	Lots of arguments, let's sort it out... There are basically three modes of
1367	operation, and we will explain them from simplest to complex:	1784	operation, and we will explain them from simplest to most complex:
1368		1785
1369	=over 4	1786	=over 4
1370		1787
1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1788	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1372		1789
1373	In this configuration the watcher triggers an event after the wall clock	1790	In this configuration the watcher triggers an event after the wall clock
1374	time C<at> has passed and doesn't repeat. It will not adjust when a time	1791	time C<offset> has passed. It will not repeat and will not adjust when a
1375	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1792	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1376	run when the system time reaches or surpasses this time.	1793	will be stopped and invoked when the system clock reaches or surpasses
		1794	this point in time.
1377		1795
1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1796	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1379		1797
1380	In this mode the watcher will always be scheduled to time out at the next	1798	In this mode the watcher will always be scheduled to time out at the next
1381	C<at + N * interval> time (for some integer N, which can also be negative)	1799	C<offset + N * interval> time (for some integer N, which can also be
1382	and then repeat, regardless of any time jumps.	1800	negative) and then repeat, regardless of any time jumps. The C<offset>
		1801	argument is merely an offset into the C<interval> periods.
1383		1802
1384	This can be used to create timers that do not drift with respect to system	1803	This can be used to create timers that do not drift with respect to the
1385	time, for example, here is a C<ev_periodic> that triggers each hour, on	1804	system clock, for example, here is an C<ev_periodic> that triggers each
1386	the hour:	1805	hour, on the hour (with respect to UTC):
1387		1806
1388	ev_periodic_set (&periodic, 0., 3600., 0);	1807	ev_periodic_set (&periodic, 0., 3600., 0);
1389		1808
1390	This doesn't mean there will always be 3600 seconds in between triggers,	1809	This doesn't mean there will always be 3600 seconds in between triggers,
1391	but only that the callback will be called when the system time shows a	1810	but only that the callback will be called when the system time shows a
1392	full hour (UTC), or more correctly, when the system time is evenly divisible	1811	full hour (UTC), or more correctly, when the system time is evenly divisible
1393	by 3600.	1812	by 3600.
1394		1813
1395	Another way to think about it (for the mathematically inclined) is that	1814	Another way to think about it (for the mathematically inclined) is that
1396	C<ev_periodic> will try to run the callback in this mode at the next possible	1815	C<ev_periodic> will try to run the callback in this mode at the next possible
1397	time where C<time = at (mod interval)>, regardless of any time jumps.	1816	time where C<time = offset (mod interval)>, regardless of any time jumps.
1398		1817
1399	For numerical stability it is preferable that the C<at> value is near	1818	For numerical stability it is preferable that the C<offset> value is near
1400	C<ev_now ()> (the current time), but there is no range requirement for	1819	C<ev_now ()> (the current time), but there is no range requirement for
1401	this value, and in fact is often specified as zero.	1820	this value, and in fact is often specified as zero.
1402		1821
1403	Note also that there is an upper limit to how often a timer can fire (CPU	1822	Note also that there is an upper limit to how often a timer can fire (CPU
1404	speed for example), so if C<interval> is very small then timing stability	1823	speed for example), so if C<interval> is very small then timing stability
1405	will of course deteriorate. Libev itself tries to be exact to be about one	1824	will of course deteriorate. Libev itself tries to be exact to be about one
1406	millisecond (if the OS supports it and the machine is fast enough).	1825	millisecond (if the OS supports it and the machine is fast enough).
1407		1826
1408	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1827	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1409		1828
1410	In this mode the values for C<interval> and C<at> are both being	1829	In this mode the values for C<interval> and C<offset> are both being
1411	ignored. Instead, each time the periodic watcher gets scheduled, the	1830	ignored. Instead, each time the periodic watcher gets scheduled, the
1412	reschedule callback will be called with the watcher as first, and the	1831	reschedule callback will be called with the watcher as first, and the
1413	current time as second argument.	1832	current time as second argument.
1414		1833
1415	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1834	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1416	ever, or make ANY event loop modifications whatsoever>.	1835	or make ANY other event loop modifications whatsoever, unless explicitly
		1836	allowed by documentation here>.
1417		1837
1418	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1838	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1419	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1839	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1420	only event loop modification you are allowed to do).	1840	only event loop modification you are allowed to do).
1421		1841
1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1842	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1423	*w, ev_tstamp now)>, e.g.:	1843	*w, ev_tstamp now)>, e.g.:
1424		1844
		1845	static ev_tstamp
1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1846	my_rescheduler (ev_periodic *w, ev_tstamp now)
1426	{	1847	{
1427	return now + 60.;	1848	return now + 60.;
1428	}	1849	}
1429		1850
1430	It must return the next time to trigger, based on the passed time value	1851	It must return the next time to trigger, based on the passed time value
…		…
1450	a different time than the last time it was called (e.g. in a crond like	1871	a different time than the last time it was called (e.g. in a crond like
1451	program when the crontabs have changed).	1872	program when the crontabs have changed).
1452		1873
1453	=item ev_tstamp ev_periodic_at (ev_periodic *)	1874	=item ev_tstamp ev_periodic_at (ev_periodic *)
1454		1875
1455	When active, returns the absolute time that the watcher is supposed to	1876	When active, returns the absolute time that the watcher is supposed
1456	trigger next.	1877	to trigger next. This is not the same as the C<offset> argument to
		1878	C<ev_periodic_set>, but indeed works even in interval and manual
		1879	rescheduling modes.
1457		1880
1458	=item ev_tstamp offset [read-write]	1881	=item ev_tstamp offset [read-write]
1459		1882
1460	When repeating, this contains the offset value, otherwise this is the	1883	When repeating, this contains the offset value, otherwise this is the
1461	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1884	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1885	although libev might modify this value for better numerical stability).
1462		1886
1463	Can be modified any time, but changes only take effect when the periodic	1887	Can be modified any time, but changes only take effect when the periodic
1464	timer fires or C<ev_periodic_again> is being called.	1888	timer fires or C<ev_periodic_again> is being called.
1465		1889
1466	=item ev_tstamp interval [read-write]	1890	=item ev_tstamp interval [read-write]
1467		1891
1468	The current interval value. Can be modified any time, but changes only	1892	The current interval value. Can be modified any time, but changes only
1469	take effect when the periodic timer fires or C<ev_periodic_again> is being	1893	take effect when the periodic timer fires or C<ev_periodic_again> is being
1470	called.	1894	called.
1471		1895
1472	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1896	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1473		1897
1474	The current reschedule callback, or C<0>, if this functionality is	1898	The current reschedule callback, or C<0>, if this functionality is
1475	switched off. Can be changed any time, but changes only take effect when	1899	switched off. Can be changed any time, but changes only take effect when
1476	the periodic timer fires or C<ev_periodic_again> is being called.	1900	the periodic timer fires or C<ev_periodic_again> is being called.
1477		1901
1478	=back	1902	=back
1479		1903
1480	=head3 Examples	1904	=head3 Examples
1481		1905
1482	Example: Call a callback every hour, or, more precisely, whenever the	1906	Example: Call a callback every hour, or, more precisely, whenever the
1483	system clock is divisible by 3600. The callback invocation times have	1907	system time is divisible by 3600. The callback invocation times have
1484	potentially a lot of jitter, but good long-term stability.	1908	potentially a lot of jitter, but good long-term stability.
1485		1909
1486	static void	1910	static void
1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1911	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1488	{	1912	{
1489	... its now a full hour (UTC, or TAI or whatever your clock follows)	1913	... its now a full hour (UTC, or TAI or whatever your clock follows)
1490	}	1914	}
1491		1915
1492	struct ev_periodic hourly_tick;	1916	ev_periodic hourly_tick;
1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1917	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1494	ev_periodic_start (loop, &hourly_tick);	1918	ev_periodic_start (loop, &hourly_tick);
1495		1919
1496	Example: The same as above, but use a reschedule callback to do it:	1920	Example: The same as above, but use a reschedule callback to do it:
1497		1921
1498	#include <math.h>	1922	#include <math.h>
1499		1923
1500	static ev_tstamp	1924	static ev_tstamp
1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1925	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1502	{	1926	{
1503	return fmod (now, 3600.) + 3600.;	1927	return now + (3600. - fmod (now, 3600.));
1504	}	1928	}
1505		1929
1506	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1930	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1507		1931
1508	Example: Call a callback every hour, starting now:	1932	Example: Call a callback every hour, starting now:
1509		1933
1510	struct ev_periodic hourly_tick;	1934	ev_periodic hourly_tick;
1511	ev_periodic_init (&hourly_tick, clock_cb,	1935	ev_periodic_init (&hourly_tick, clock_cb,
1512	fmod (ev_now (loop), 3600.), 3600., 0);	1936	fmod (ev_now (loop), 3600.), 3600., 0);
1513	ev_periodic_start (loop, &hourly_tick);	1937	ev_periodic_start (loop, &hourly_tick);
1514		1938
1515		1939
…		…
1518	Signal watchers will trigger an event when the process receives a specific	1942	Signal watchers will trigger an event when the process receives a specific
1519	signal one or more times. Even though signals are very asynchronous, libev	1943	signal one or more times. Even though signals are very asynchronous, libev
1520	will try it's best to deliver signals synchronously, i.e. as part of the	1944	will try it's best to deliver signals synchronously, i.e. as part of the
1521	normal event processing, like any other event.	1945	normal event processing, like any other event.
1522		1946
		1947	If you want signals asynchronously, just use C<sigaction> as you would
		1948	do without libev and forget about sharing the signal. You can even use
		1949	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1950
1523	You can configure as many watchers as you like per signal. Only when the	1951	You can configure as many watchers as you like per signal. Only when the
1524	first watcher gets started will libev actually register a signal watcher	1952	first watcher gets started will libev actually register a signal handler
1525	with the kernel (thus it coexists with your own signal handlers as long	1953	with the kernel (thus it coexists with your own signal handlers as long as
1526	as you don't register any with libev). Similarly, when the last signal	1954	you don't register any with libev for the same signal). Similarly, when
1527	watcher for a signal is stopped libev will reset the signal handler to	1955	the last signal watcher for a signal is stopped, libev will reset the
1528	SIG_DFL (regardless of what it was set to before).	1956	signal handler to SIG_DFL (regardless of what it was set to before).
1529		1957
1530	If possible and supported, libev will install its handlers with	1958	If possible and supported, libev will install its handlers with
1531	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1959	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1532	interrupted. If you have a problem with system calls getting interrupted by	1960	interrupted. If you have a problem with system calls getting interrupted by
1533	signals you can block all signals in an C<ev_check> watcher and unblock	1961	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1550		1978
1551	=back	1979	=back
1552		1980
1553	=head3 Examples	1981	=head3 Examples
1554		1982
1555	Example: Try to exit cleanly on SIGINT and SIGTERM.	1983	Example: Try to exit cleanly on SIGINT.
1556		1984
1557	static void	1985	static void
1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1986	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1559	{	1987	{
1560	ev_unloop (loop, EVUNLOOP_ALL);	1988	ev_unloop (loop, EVUNLOOP_ALL);
1561	}	1989	}
1562		1990
1563	struct ev_signal signal_watcher;	1991	ev_signal signal_watcher;
1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1992	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1565	ev_signal_start (loop, &sigint_cb);	1993	ev_signal_start (loop, &signal_watcher);
1566		1994
1567		1995
1568	=head2 C<ev_child> - watch out for process status changes	1996	=head2 C<ev_child> - watch out for process status changes
1569		1997
1570	Child watchers trigger when your process receives a SIGCHLD in response to	1998	Child watchers trigger when your process receives a SIGCHLD in response to
1571	some child status changes (most typically when a child of yours dies). It	1999	some child status changes (most typically when a child of yours dies or
1572	is permissible to install a child watcher I<after> the child has been	2000	exits). It is permissible to install a child watcher I<after> the child
1573	forked (which implies it might have already exited), as long as the event	2001	has been forked (which implies it might have already exited), as long
1574	loop isn't entered (or is continued from a watcher).	2002	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2003	forking and then immediately registering a watcher for the child is fine,
		2004	but forking and registering a watcher a few event loop iterations later is
		2005	not.
1575		2006
1576	Only the default event loop is capable of handling signals, and therefore	2007	Only the default event loop is capable of handling signals, and therefore
1577	you can only register child watchers in the default event loop.	2008	you can only register child watchers in the default event loop.
1578		2009
1579	=head3 Process Interaction	2010	=head3 Process Interaction
…		…
1640	its completion.	2071	its completion.
1641		2072
1642	ev_child cw;	2073	ev_child cw;
1643		2074
1644	static void	2075	static void
1645	child_cb (EV_P_ struct ev_child *w, int revents)	2076	child_cb (EV_P_ ev_child *w, int revents)
1646	{	2077	{
1647	ev_child_stop (EV_A_ w);	2078	ev_child_stop (EV_A_ w);
1648	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2079	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1649	}	2080	}
1650		2081
…		…
1665		2096
1666		2097
1667	=head2 C<ev_stat> - did the file attributes just change?	2098	=head2 C<ev_stat> - did the file attributes just change?
1668		2099
1669	This watches a file system path for attribute changes. That is, it calls	2100	This watches a file system path for attribute changes. That is, it calls
1670	C<stat> regularly (or when the OS says it changed) and sees if it changed	2101	C<stat> on that path in regular intervals (or when the OS says it changed)
1671	compared to the last time, invoking the callback if it did.	2102	and sees if it changed compared to the last time, invoking the callback if
		2103	it did.
1672		2104
1673	The path does not need to exist: changing from "path exists" to "path does	2105	The path does not need to exist: changing from "path exists" to "path does
1674	not exist" is a status change like any other. The condition "path does	2106	not exist" is a status change like any other. The condition "path does not
1675	not exist" is signified by the C<st_nlink> field being zero (which is	2107	exist" (or more correctly "path cannot be stat'ed") is signified by the
1676	otherwise always forced to be at least one) and all the other fields of	2108	C<st_nlink> field being zero (which is otherwise always forced to be at
1677	the stat buffer having unspecified contents.	2109	least one) and all the other fields of the stat buffer having unspecified
		2110	contents.
1678		2111
1679	The path I<should> be absolute and I<must not> end in a slash. If it is	2112	The path I<must not> end in a slash or contain special components such as
		2113	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1680	relative and your working directory changes, the behaviour is undefined.	2114	your working directory changes, then the behaviour is undefined.
1681		2115
1682	Since there is no standard to do this, the portable implementation simply	2116	Since there is no portable change notification interface available, the
1683	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2117	portable implementation simply calls C<stat(2)> regularly on the path
1684	can specify a recommended polling interval for this case. If you specify	2118	to see if it changed somehow. You can specify a recommended polling
1685	a polling interval of C<0> (highly recommended!) then a I<suitable,	2119	interval for this case. If you specify a polling interval of C<0> (highly
1686	unspecified default> value will be used (which you can expect to be around	2120	recommended!) then a I<suitable, unspecified default> value will be used
1687	five seconds, although this might change dynamically). Libev will also	2121	(which you can expect to be around five seconds, although this might
1688	impose a minimum interval which is currently around C<0.1>, but thats	2122	change dynamically). Libev will also impose a minimum interval which is
1689	usually overkill.	2123	currently around C<0.1>, but that's usually overkill.
1690		2124
1691	This watcher type is not meant for massive numbers of stat watchers,	2125	This watcher type is not meant for massive numbers of stat watchers,
1692	as even with OS-supported change notifications, this can be	2126	as even with OS-supported change notifications, this can be
1693	resource-intensive.	2127	resource-intensive.
1694		2128
1695	At the time of this writing, only the Linux inotify interface is	2129	At the time of this writing, the only OS-specific interface implemented
1696	implemented (implementing kqueue support is left as an exercise for the	2130	is the Linux inotify interface (implementing kqueue support is left as an
1697	reader, note, however, that the author sees no way of implementing ev_stat	2131	exercise for the reader. Note, however, that the author sees no way of
1698	semantics with kqueue). Inotify will be used to give hints only and should	2132	implementing C<ev_stat> semantics with kqueue, except as a hint).
1699	not change the semantics of C<ev_stat> watchers, which means that libev
1700	sometimes needs to fall back to regular polling again even with inotify,
1701	but changes are usually detected immediately, and if the file exists there
1702	will be no polling.
1703		2133
1704	=head3 ABI Issues (Largefile Support)	2134	=head3 ABI Issues (Largefile Support)
1705		2135
1706	Libev by default (unless the user overrides this) uses the default	2136	Libev by default (unless the user overrides this) uses the default
1707	compilation environment, which means that on systems with large file	2137	compilation environment, which means that on systems with large file
1708	support disabled by default, you get the 32 bit version of the stat	2138	support disabled by default, you get the 32 bit version of the stat
1709	structure. When using the library from programs that change the ABI to	2139	structure. When using the library from programs that change the ABI to
1710	use 64 bit file offsets the programs will fail. In that case you have to	2140	use 64 bit file offsets the programs will fail. In that case you have to
1711	compile libev with the same flags to get binary compatibility. This is	2141	compile libev with the same flags to get binary compatibility. This is
1712	obviously the case with any flags that change the ABI, but the problem is	2142	obviously the case with any flags that change the ABI, but the problem is
1713	most noticeably disabled with ev_stat and large file support.	2143	most noticeably displayed with ev_stat and large file support.
1714		2144
1715	The solution for this is to lobby your distribution maker to make large	2145	The solution for this is to lobby your distribution maker to make large
1716	file interfaces available by default (as e.g. FreeBSD does) and not	2146	file interfaces available by default (as e.g. FreeBSD does) and not
1717	optional. Libev cannot simply switch on large file support because it has	2147	optional. Libev cannot simply switch on large file support because it has
1718	to exchange stat structures with application programs compiled using the	2148	to exchange stat structures with application programs compiled using the
1719	default compilation environment.	2149	default compilation environment.
1720		2150
1721	=head3 Inotify	2151	=head3 Inotify and Kqueue
1722		2152
1723	When C<inotify (7)> support has been compiled into libev (generally only	2153	When C<inotify (7)> support has been compiled into libev and present at
1724	available on Linux) and present at runtime, it will be used to speed up	2154	runtime, it will be used to speed up change detection where possible. The
1725	change detection where possible. The inotify descriptor will be created lazily	2155	inotify descriptor will be created lazily when the first C<ev_stat>
1726	when the first C<ev_stat> watcher is being started.	2156	watcher is being started.
1727		2157
1728	Inotify presence does not change the semantics of C<ev_stat> watchers	2158	Inotify presence does not change the semantics of C<ev_stat> watchers
1729	except that changes might be detected earlier, and in some cases, to avoid	2159	except that changes might be detected earlier, and in some cases, to avoid
1730	making regular C<stat> calls. Even in the presence of inotify support	2160	making regular C<stat> calls. Even in the presence of inotify support
1731	there are many cases where libev has to resort to regular C<stat> polling.	2161	there are many cases where libev has to resort to regular C<stat> polling,
		2162	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2163	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2164	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2165	xfs are fully working) libev usually gets away without polling.
1732		2166
1733	(There is no support for kqueue, as apparently it cannot be used to	2167	There is no support for kqueue, as apparently it cannot be used to
1734	implement this functionality, due to the requirement of having a file	2168	implement this functionality, due to the requirement of having a file
1735	descriptor open on the object at all times).	2169	descriptor open on the object at all times, and detecting renames, unlinks
		2170	etc. is difficult.
		2171
		2172	=head3 C<stat ()> is a synchronous operation
		2173
		2174	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2175	the process. The exception are C<ev_stat> watchers - those call C<stat
		2176	()>, which is a synchronous operation.
		2177
		2178	For local paths, this usually doesn't matter: unless the system is very
		2179	busy or the intervals between stat's are large, a stat call will be fast,
		2180	as the path data is usually in memory already (except when starting the
		2181	watcher).
		2182
		2183	For networked file systems, calling C<stat ()> can block an indefinite
		2184	time due to network issues, and even under good conditions, a stat call
		2185	often takes multiple milliseconds.
		2186
		2187	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2188	paths, although this is fully supported by libev.
1736		2189
1737	=head3 The special problem of stat time resolution	2190	=head3 The special problem of stat time resolution
1738		2191
1739	The C<stat ()> system call only supports full-second resolution portably, and	2192	The C<stat ()> system call only supports full-second resolution portably,
1740	even on systems where the resolution is higher, many file systems still	2193	and even on systems where the resolution is higher, most file systems
1741	only support whole seconds.	2194	still only support whole seconds.
1742		2195
1743	That means that, if the time is the only thing that changes, you can	2196	That means that, if the time is the only thing that changes, you can
1744	easily miss updates: on the first update, C<ev_stat> detects a change and	2197	easily miss updates: on the first update, C<ev_stat> detects a change and
1745	calls your callback, which does something. When there is another update	2198	calls your callback, which does something. When there is another update
1746	within the same second, C<ev_stat> will be unable to detect it as the stat	2199	within the same second, C<ev_stat> will be unable to detect unless the
1747	data does not change.	2200	stat data does change in other ways (e.g. file size).
1748		2201
1749	The solution to this is to delay acting on a change for slightly more	2202	The solution to this is to delay acting on a change for slightly more
1750	than a second (or till slightly after the next full second boundary), using	2203	than a second (or till slightly after the next full second boundary), using
1751	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2204	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1752	ev_timer_again (loop, w)>).	2205	ev_timer_again (loop, w)>).
…		…
1772	C<path>. The C<interval> is a hint on how quickly a change is expected to	2225	C<path>. The C<interval> is a hint on how quickly a change is expected to
1773	be detected and should normally be specified as C<0> to let libev choose	2226	be detected and should normally be specified as C<0> to let libev choose
1774	a suitable value. The memory pointed to by C<path> must point to the same	2227	a suitable value. The memory pointed to by C<path> must point to the same
1775	path for as long as the watcher is active.	2228	path for as long as the watcher is active.
1776		2229
1777	The callback will receive C<EV_STAT> when a change was detected, relative	2230	The callback will receive an C<EV_STAT> event when a change was detected,
1778	to the attributes at the time the watcher was started (or the last change	2231	relative to the attributes at the time the watcher was started (or the
1779	was detected).	2232	last change was detected).
1780		2233
1781	=item ev_stat_stat (loop, ev_stat *)	2234	=item ev_stat_stat (loop, ev_stat *)
1782		2235
1783	Updates the stat buffer immediately with new values. If you change the	2236	Updates the stat buffer immediately with new values. If you change the
1784	watched path in your callback, you could call this function to avoid	2237	watched path in your callback, you could call this function to avoid
…		…
1867		2320
1868		2321
1869	=head2 C<ev_idle> - when you've got nothing better to do...	2322	=head2 C<ev_idle> - when you've got nothing better to do...
1870		2323
1871	Idle watchers trigger events when no other events of the same or higher	2324	Idle watchers trigger events when no other events of the same or higher
1872	priority are pending (prepare, check and other idle watchers do not	2325	priority are pending (prepare, check and other idle watchers do not count
1873	count).	2326	as receiving "events").
1874		2327
1875	That is, as long as your process is busy handling sockets or timeouts	2328	That is, as long as your process is busy handling sockets or timeouts
1876	(or even signals, imagine) of the same or higher priority it will not be	2329	(or even signals, imagine) of the same or higher priority it will not be
1877	triggered. But when your process is idle (or only lower-priority watchers	2330	triggered. But when your process is idle (or only lower-priority watchers
1878	are pending), the idle watchers are being called once per event loop	2331	are pending), the idle watchers are being called once per event loop
…		…
1889		2342
1890	=head3 Watcher-Specific Functions and Data Members	2343	=head3 Watcher-Specific Functions and Data Members
1891		2344
1892	=over 4	2345	=over 4
1893		2346
1894	=item ev_idle_init (ev_signal *, callback)	2347	=item ev_idle_init (ev_idle *, callback)
1895		2348
1896	Initialises and configures the idle watcher - it has no parameters of any	2349	Initialises and configures the idle watcher - it has no parameters of any
1897	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2350	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1898	believe me.	2351	believe me.
1899		2352
…		…
1903		2356
1904	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2357	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1905	callback, free it. Also, use no error checking, as usual.	2358	callback, free it. Also, use no error checking, as usual.
1906		2359
1907	static void	2360	static void
1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2361	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1909	{	2362	{
1910	free (w);	2363	free (w);
1911	// now do something you wanted to do when the program has	2364	// now do something you wanted to do when the program has
1912	// no longer anything immediate to do.	2365	// no longer anything immediate to do.
1913	}	2366	}
1914		2367
1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2368	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1916	ev_idle_init (idle_watcher, idle_cb);	2369	ev_idle_init (idle_watcher, idle_cb);
1917	ev_idle_start (loop, idle_cb);	2370	ev_idle_start (loop, idle_cb);
1918		2371
1919		2372
1920	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2373	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1921		2374
1922	Prepare and check watchers are usually (but not always) used in tandem:	2375	Prepare and check watchers are usually (but not always) used in pairs:
1923	prepare watchers get invoked before the process blocks and check watchers	2376	prepare watchers get invoked before the process blocks and check watchers
1924	afterwards.	2377	afterwards.
1925		2378
1926	You I<must not> call C<ev_loop> or similar functions that enter	2379	You I<must not> call C<ev_loop> or similar functions that enter
1927	the current event loop from either C<ev_prepare> or C<ev_check>	2380	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1930	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2383	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1931	C<ev_check> so if you have one watcher of each kind they will always be	2384	C<ev_check> so if you have one watcher of each kind they will always be
1932	called in pairs bracketing the blocking call.	2385	called in pairs bracketing the blocking call.
1933		2386
1934	Their main purpose is to integrate other event mechanisms into libev and	2387	Their main purpose is to integrate other event mechanisms into libev and
1935	their use is somewhat advanced. This could be used, for example, to track	2388	their use is somewhat advanced. They could be used, for example, to track
1936	variable changes, implement your own watchers, integrate net-snmp or a	2389	variable changes, implement your own watchers, integrate net-snmp or a
1937	coroutine library and lots more. They are also occasionally useful if	2390	coroutine library and lots more. They are also occasionally useful if
1938	you cache some data and want to flush it before blocking (for example,	2391	you cache some data and want to flush it before blocking (for example,
1939	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2392	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1940	watcher).	2393	watcher).
1941		2394
1942	This is done by examining in each prepare call which file descriptors need	2395	This is done by examining in each prepare call which file descriptors
1943	to be watched by the other library, registering C<ev_io> watchers for	2396	need to be watched by the other library, registering C<ev_io> watchers
1944	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2397	for them and starting an C<ev_timer> watcher for any timeouts (many
1945	provide just this functionality). Then, in the check watcher you check for	2398	libraries provide exactly this functionality). Then, in the check watcher,
1946	any events that occurred (by checking the pending status of all watchers	2399	you check for any events that occurred (by checking the pending status
1947	and stopping them) and call back into the library. The I/O and timer	2400	of all watchers and stopping them) and call back into the library. The
1948	callbacks will never actually be called (but must be valid nevertheless,	2401	I/O and timer callbacks will never actually be called (but must be valid
1949	because you never know, you know?).	2402	nevertheless, because you never know, you know?).
1950		2403
1951	As another example, the Perl Coro module uses these hooks to integrate	2404	As another example, the Perl Coro module uses these hooks to integrate
1952	coroutines into libev programs, by yielding to other active coroutines	2405	coroutines into libev programs, by yielding to other active coroutines
1953	during each prepare and only letting the process block if no coroutines	2406	during each prepare and only letting the process block if no coroutines
1954	are ready to run (it's actually more complicated: it only runs coroutines	2407	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1957	loop from blocking if lower-priority coroutines are active, thus mapping	2410	loop from blocking if lower-priority coroutines are active, thus mapping
1958	low-priority coroutines to idle/background tasks).	2411	low-priority coroutines to idle/background tasks).
1959		2412
1960	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2413	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1961	priority, to ensure that they are being run before any other watchers	2414	priority, to ensure that they are being run before any other watchers
		2415	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2416
1962	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2417	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1963	too) should not activate ("feed") events into libev. While libev fully	2418	activate ("feed") events into libev. While libev fully supports this, they
1964	supports this, they might get executed before other C<ev_check> watchers	2419	might get executed before other C<ev_check> watchers did their job. As
1965	did their job. As C<ev_check> watchers are often used to embed other	2420	C<ev_check> watchers are often used to embed other (non-libev) event
1966	(non-libev) event loops those other event loops might be in an unusable	2421	loops those other event loops might be in an unusable state until their
1967	state until their C<ev_check> watcher ran (always remind yourself to	2422	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1968	coexist peacefully with others).	2423	others).
1969		2424
1970	=head3 Watcher-Specific Functions and Data Members	2425	=head3 Watcher-Specific Functions and Data Members
1971		2426
1972	=over 4	2427	=over 4
1973		2428
…		…
1975		2430
1976	=item ev_check_init (ev_check *, callback)	2431	=item ev_check_init (ev_check *, callback)
1977		2432
1978	Initialises and configures the prepare or check watcher - they have no	2433	Initialises and configures the prepare or check watcher - they have no
1979	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2434	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1980	macros, but using them is utterly, utterly and completely pointless.	2435	macros, but using them is utterly, utterly, utterly and completely
		2436	pointless.
1981		2437
1982	=back	2438	=back
1983		2439
1984	=head3 Examples	2440	=head3 Examples
1985		2441
…		…
1998		2454
1999	static ev_io iow [nfd];	2455	static ev_io iow [nfd];
2000	static ev_timer tw;	2456	static ev_timer tw;
2001		2457
2002	static void	2458	static void
2003	io_cb (ev_loop *loop, ev_io *w, int revents)	2459	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2004	{	2460	{
2005	}	2461	}
2006		2462
2007	// create io watchers for each fd and a timer before blocking	2463	// create io watchers for each fd and a timer before blocking
2008	static void	2464	static void
2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2465	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2010	{	2466	{
2011	int timeout = 3600000;	2467	int timeout = 3600000;
2012	struct pollfd fds [nfd];	2468	struct pollfd fds [nfd];
2013	// actual code will need to loop here and realloc etc.	2469	// actual code will need to loop here and realloc etc.
2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2470	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2029	}	2485	}
2030	}	2486	}
2031		2487
2032	// stop all watchers after blocking	2488	// stop all watchers after blocking
2033	static void	2489	static void
2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2490	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2035	{	2491	{
2036	ev_timer_stop (loop, &tw);	2492	ev_timer_stop (loop, &tw);
2037		2493
2038	for (int i = 0; i < nfd; ++i)	2494	for (int i = 0; i < nfd; ++i)
2039	{	2495	{
…		…
2078	}	2534	}
2079		2535
2080	// do not ever call adns_afterpoll	2536	// do not ever call adns_afterpoll
2081		2537
2082	Method 4: Do not use a prepare or check watcher because the module you	2538	Method 4: Do not use a prepare or check watcher because the module you
2083	want to embed is too inflexible to support it. Instead, you can override	2539	want to embed is not flexible enough to support it. Instead, you can
2084	their poll function. The drawback with this solution is that the main	2540	override their poll function. The drawback with this solution is that the
2085	loop is now no longer controllable by EV. The C<Glib::EV> module does	2541	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2086	this.	2542	this approach, effectively embedding EV as a client into the horrible
		2543	libglib event loop.
2087		2544
2088	static gint	2545	static gint
2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2546	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2090	{	2547	{
2091	int got_events = 0;	2548	int got_events = 0;
…		…
2122	prioritise I/O.	2579	prioritise I/O.
2123		2580
2124	As an example for a bug workaround, the kqueue backend might only support	2581	As an example for a bug workaround, the kqueue backend might only support
2125	sockets on some platform, so it is unusable as generic backend, but you	2582	sockets on some platform, so it is unusable as generic backend, but you
2126	still want to make use of it because you have many sockets and it scales	2583	still want to make use of it because you have many sockets and it scales
2127	so nicely. In this case, you would create a kqueue-based loop and embed it	2584	so nicely. In this case, you would create a kqueue-based loop and embed
2128	into your default loop (which might use e.g. poll). Overall operation will	2585	it into your default loop (which might use e.g. poll). Overall operation
2129	be a bit slower because first libev has to poll and then call kevent, but	2586	will be a bit slower because first libev has to call C<poll> and then
2130	at least you can use both at what they are best.	2587	C<kevent>, but at least you can use both mechanisms for what they are
		2588	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2131		2589
2132	As for prioritising I/O: rarely you have the case where some fds have	2590	As for prioritising I/O: under rare circumstances you have the case where
2133	to be watched and handled very quickly (with low latency), and even	2591	some fds have to be watched and handled very quickly (with low latency),
2134	priorities and idle watchers might have too much overhead. In this case	2592	and even priorities and idle watchers might have too much overhead. In
2135	you would put all the high priority stuff in one loop and all the rest in	2593	this case you would put all the high priority stuff in one loop and all
2136	a second one, and embed the second one in the first.	2594	the rest in a second one, and embed the second one in the first.
2137		2595
2138	As long as the watcher is active, the callback will be invoked every time	2596	As long as the watcher is active, the callback will be invoked every
2139	there might be events pending in the embedded loop. The callback must then	2597	time there might be events pending in the embedded loop. The callback
2140	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2598	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2141	their callbacks (you could also start an idle watcher to give the embedded	2599	sweep and invoke their callbacks (the callback doesn't need to invoke the
2142	loop strictly lower priority for example). You can also set the callback	2600	C<ev_embed_sweep> function directly, it could also start an idle watcher
2143	to C<0>, in which case the embed watcher will automatically execute the	2601	to give the embedded loop strictly lower priority for example).
2144	embedded loop sweep.
2145		2602
2146	As long as the watcher is started it will automatically handle events. The	2603	You can also set the callback to C<0>, in which case the embed watcher
2147	callback will be invoked whenever some events have been handled. You can	2604	will automatically execute the embedded loop sweep whenever necessary.
2148	set the callback to C<0> to avoid having to specify one if you are not
2149	interested in that.
2150		2605
2151	Also, there have not currently been made special provisions for forking:	2606	Fork detection will be handled transparently while the C<ev_embed> watcher
2152	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2607	is active, i.e., the embedded loop will automatically be forked when the
2153	but you will also have to stop and restart any C<ev_embed> watchers	2608	embedding loop forks. In other cases, the user is responsible for calling
2154	yourself.	2609	C<ev_loop_fork> on the embedded loop.
2155		2610
2156	Unfortunately, not all backends are embeddable, only the ones returned by	2611	Unfortunately, not all backends are embeddable: only the ones returned by
2157	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2612	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2158	portable one.	2613	portable one.
2159		2614
2160	So when you want to use this feature you will always have to be prepared	2615	So when you want to use this feature you will always have to be prepared
2161	that you cannot get an embeddable loop. The recommended way to get around	2616	that you cannot get an embeddable loop. The recommended way to get around
2162	this is to have a separate variables for your embeddable loop, try to	2617	this is to have a separate variables for your embeddable loop, try to
2163	create it, and if that fails, use the normal loop for everything.	2618	create it, and if that fails, use the normal loop for everything.
		2619
		2620	=head3 C<ev_embed> and fork
		2621
		2622	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2623	automatically be applied to the embedded loop as well, so no special
		2624	fork handling is required in that case. When the watcher is not running,
		2625	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2626	as applicable.
2164		2627
2165	=head3 Watcher-Specific Functions and Data Members	2628	=head3 Watcher-Specific Functions and Data Members
2166		2629
2167	=over 4	2630	=over 4
2168		2631
…		…
2196	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2659	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2197	used).	2660	used).
2198		2661
2199	struct ev_loop *loop_hi = ev_default_init (0);	2662	struct ev_loop *loop_hi = ev_default_init (0);
2200	struct ev_loop *loop_lo = 0;	2663	struct ev_loop *loop_lo = 0;
2201	struct ev_embed embed;	2664	ev_embed embed;
2202		2665
2203	// see if there is a chance of getting one that works	2666	// see if there is a chance of getting one that works
2204	// (remember that a flags value of 0 means autodetection)	2667	// (remember that a flags value of 0 means autodetection)
2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2668	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2669	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2220	kqueue implementation). Store the kqueue/socket-only event loop in	2683	kqueue implementation). Store the kqueue/socket-only event loop in
2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2684	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2222		2685
2223	struct ev_loop *loop = ev_default_init (0);	2686	struct ev_loop *loop = ev_default_init (0);
2224	struct ev_loop *loop_socket = 0;	2687	struct ev_loop *loop_socket = 0;
2225	struct ev_embed embed;	2688	ev_embed embed;
2226		2689
2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2690	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2691	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2229	{	2692	{
2230	ev_embed_init (&embed, 0, loop_socket);	2693	ev_embed_init (&embed, 0, loop_socket);
…		…
2286	is that the author does not know of a simple (or any) algorithm for a	2749	is that the author does not know of a simple (or any) algorithm for a
2287	multiple-writer-single-reader queue that works in all cases and doesn't	2750	multiple-writer-single-reader queue that works in all cases and doesn't
2288	need elaborate support such as pthreads.	2751	need elaborate support such as pthreads.
2289		2752
2290	That means that if you want to queue data, you have to provide your own	2753	That means that if you want to queue data, you have to provide your own
2291	queue. But at least I can tell you would implement locking around your	2754	queue. But at least I can tell you how to implement locking around your
2292	queue:	2755	queue:
2293		2756
2294	=over 4	2757	=over 4
2295		2758
2296	=item queueing from a signal handler context	2759	=item queueing from a signal handler context
2297		2760
2298	To implement race-free queueing, you simply add to the queue in the signal	2761	To implement race-free queueing, you simply add to the queue in the signal
2299	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2762	handler but you block the signal handler in the watcher callback. Here is
2300	some fictitious SIGUSR1 handler:	2763	an example that does that for some fictitious SIGUSR1 handler:
2301		2764
2302	static ev_async mysig;	2765	static ev_async mysig;
2303		2766
2304	static void	2767	static void
2305	sigusr1_handler (void)	2768	sigusr1_handler (void)
…		…
2371	=over 4	2834	=over 4
2372		2835
2373	=item ev_async_init (ev_async *, callback)	2836	=item ev_async_init (ev_async *, callback)
2374		2837
2375	Initialises and configures the async watcher - it has no parameters of any	2838	Initialises and configures the async watcher - it has no parameters of any
2376	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2839	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2377	believe me.	2840	trust me.
2378		2841
2379	=item ev_async_send (loop, ev_async *)	2842	=item ev_async_send (loop, ev_async *)
2380		2843
2381	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2844	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2382	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2845	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2383	C<ev_feed_event>, this call is safe to do in other threads, signal or	2846	C<ev_feed_event>, this call is safe to do from other threads, signal or
2384	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2847	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2385	section below on what exactly this means).	2848	section below on what exactly this means).
2386		2849
		2850	Note that, as with other watchers in libev, multiple events might get
		2851	compressed into a single callback invocation (another way to look at this
		2852	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2853	reset when the event loop detects that).
		2854
2387	This call incurs the overhead of a system call only once per loop iteration,	2855	This call incurs the overhead of a system call only once per event loop
2388	so while the overhead might be noticeable, it doesn't apply to repeated	2856	iteration, so while the overhead might be noticeable, it doesn't apply to
2389	calls to C<ev_async_send>.	2857	repeated calls to C<ev_async_send> for the same event loop.
2390		2858
2391	=item bool = ev_async_pending (ev_async *)	2859	=item bool = ev_async_pending (ev_async *)
2392		2860
2393	Returns a non-zero value when C<ev_async_send> has been called on the	2861	Returns a non-zero value when C<ev_async_send> has been called on the
2394	watcher but the event has not yet been processed (or even noted) by the	2862	watcher but the event has not yet been processed (or even noted) by the
…		…
2397	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2865	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2398	the loop iterates next and checks for the watcher to have become active,	2866	the loop iterates next and checks for the watcher to have become active,
2399	it will reset the flag again. C<ev_async_pending> can be used to very	2867	it will reset the flag again. C<ev_async_pending> can be used to very
2400	quickly check whether invoking the loop might be a good idea.	2868	quickly check whether invoking the loop might be a good idea.
2401		2869
2402	Not that this does I<not> check whether the watcher itself is pending, only	2870	Not that this does I<not> check whether the watcher itself is pending,
2403	whether it has been requested to make this watcher pending.	2871	only whether it has been requested to make this watcher pending: there
		2872	is a time window between the event loop checking and resetting the async
		2873	notification, and the callback being invoked.
2404		2874
2405	=back	2875	=back
2406		2876
2407		2877
2408	=head1 OTHER FUNCTIONS	2878	=head1 OTHER FUNCTIONS
…		…
2412	=over 4	2882	=over 4
2413		2883
2414	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2884	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2415		2885
2416	This function combines a simple timer and an I/O watcher, calls your	2886	This function combines a simple timer and an I/O watcher, calls your
2417	callback on whichever event happens first and automatically stop both	2887	callback on whichever event happens first and automatically stops both
2418	watchers. This is useful if you want to wait for a single event on an fd	2888	watchers. This is useful if you want to wait for a single event on an fd
2419	or timeout without having to allocate/configure/start/stop/free one or	2889	or timeout without having to allocate/configure/start/stop/free one or
2420	more watchers yourself.	2890	more watchers yourself.
2421		2891
2422	If C<fd> is less than 0, then no I/O watcher will be started and events	2892	If C<fd> is less than 0, then no I/O watcher will be started and the
2423	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2893	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2424	C<events> set will be created and started.	2894	the given C<fd> and C<events> set will be created and started.
2425		2895
2426	If C<timeout> is less than 0, then no timeout watcher will be	2896	If C<timeout> is less than 0, then no timeout watcher will be
2427	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2897	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2428	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2898	repeat = 0) will be started. C<0> is a valid timeout.
2429	dubious value.
2430		2899
2431	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2900	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2432	passed an C<revents> set like normal event callbacks (a combination of	2901	passed an C<revents> set like normal event callbacks (a combination of
2433	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2902	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2434	value passed to C<ev_once>:	2903	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2904	a timeout and an io event at the same time - you probably should give io
		2905	events precedence.
		2906
		2907	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2435		2908
2436	static void stdin_ready (int revents, void *arg)	2909	static void stdin_ready (int revents, void *arg)
2437	{	2910	{
		2911	if (revents & EV_READ)
		2912	/* stdin might have data for us, joy! */;
2438	if (revents & EV_TIMEOUT)	2913	else if (revents & EV_TIMEOUT)
2439	/* doh, nothing entered */;	2914	/* doh, nothing entered */;
2440	else if (revents & EV_READ)
2441	/* stdin might have data for us, joy! */;
2442	}	2915	}
2443		2916
2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2917	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2445		2918
2446	=item ev_feed_event (ev_loop *, watcher *, int revents)	2919	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2447		2920
2448	Feeds the given event set into the event loop, as if the specified event	2921	Feeds the given event set into the event loop, as if the specified event
2449	had happened for the specified watcher (which must be a pointer to an	2922	had happened for the specified watcher (which must be a pointer to an
2450	initialised but not necessarily started event watcher).	2923	initialised but not necessarily started event watcher).
2451		2924
2452	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2925	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2453		2926
2454	Feed an event on the given fd, as if a file descriptor backend detected	2927	Feed an event on the given fd, as if a file descriptor backend detected
2455	the given events it.	2928	the given events it.
2456		2929
2457	=item ev_feed_signal_event (ev_loop *loop, int signum)	2930	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2458		2931
2459	Feed an event as if the given signal occurred (C<loop> must be the default	2932	Feed an event as if the given signal occurred (C<loop> must be the default
2460	loop!).	2933	loop!).
2461		2934
2462	=back	2935	=back
…		…
2584		3057
2585	myclass obj;	3058	myclass obj;
2586	ev::io iow;	3059	ev::io iow;
2587	iow.set <myclass, &myclass::io_cb> (&obj);	3060	iow.set <myclass, &myclass::io_cb> (&obj);
2588		3061
		3062	=item w->set (object *)
		3063
		3064	This is an B<experimental> feature that might go away in a future version.
		3065
		3066	This is a variation of a method callback - leaving out the method to call
		3067	will default the method to C<operator ()>, which makes it possible to use
		3068	functor objects without having to manually specify the C<operator ()> all
		3069	the time. Incidentally, you can then also leave out the template argument
		3070	list.
		3071
		3072	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3073	int revents)>.
		3074
		3075	See the method-C<set> above for more details.
		3076
		3077	Example: use a functor object as callback.
		3078
		3079	struct myfunctor
		3080	{
		3081	void operator() (ev::io &w, int revents)
		3082	{
		3083	...
		3084	}
		3085	}
		3086
		3087	myfunctor f;
		3088
		3089	ev::io w;
		3090	w.set (&f);
		3091
2589	=item w->set<function> (void *data = 0)	3092	=item w->set<function> (void *data = 0)
2590		3093
2591	Also sets a callback, but uses a static method or plain function as	3094	Also sets a callback, but uses a static method or plain function as
2592	callback. The optional C<data> argument will be stored in the watcher's	3095	callback. The optional C<data> argument will be stored in the watcher's
2593	C<data> member and is free for you to use.	3096	C<data> member and is free for you to use.
2594		3097
2595	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3098	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2596		3099
2597	See the method-C<set> above for more details.	3100	See the method-C<set> above for more details.
2598		3101
2599	Example:	3102	Example: Use a plain function as callback.
2600		3103
2601	static void io_cb (ev::io &w, int revents) { }	3104	static void io_cb (ev::io &w, int revents) { }
2602	iow.set <io_cb> ();	3105	iow.set <io_cb> ();
2603		3106
2604	=item w->set (struct ev_loop *)	3107	=item w->set (struct ev_loop *)
…		…
2642	Example: Define a class with an IO and idle watcher, start one of them in	3145	Example: Define a class with an IO and idle watcher, start one of them in
2643	the constructor.	3146	the constructor.
2644		3147
2645	class myclass	3148	class myclass
2646	{	3149	{
2647	ev::io io; void io_cb (ev::io &w, int revents);	3150	ev::io io ; void io_cb (ev::io &w, int revents);
2648	ev:idle idle void idle_cb (ev::idle &w, int revents);	3151	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2649		3152
2650	myclass (int fd)	3153	myclass (int fd)
2651	{	3154	{
2652	io .set <myclass, &myclass::io_cb > (this);	3155	io .set <myclass, &myclass::io_cb > (this);
2653	idle.set <myclass, &myclass::idle_cb> (this);	3156	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2669	=item Perl	3172	=item Perl
2670		3173
2671	The EV module implements the full libev API and is actually used to test	3174	The EV module implements the full libev API and is actually used to test
2672	libev. EV is developed together with libev. Apart from the EV core module,	3175	libev. EV is developed together with libev. Apart from the EV core module,
2673	there are additional modules that implement libev-compatible interfaces	3176	there are additional modules that implement libev-compatible interfaces
2674	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3177	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2675	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3178	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3179	and C<EV::Glib>).
2676		3180
2677	It can be found and installed via CPAN, its homepage is at	3181	It can be found and installed via CPAN, its homepage is at
2678	L<http://software.schmorp.de/pkg/EV>.	3182	L<http://software.schmorp.de/pkg/EV>.
2679		3183
2680	=item Python	3184	=item Python
2681		3185
2682	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3186	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2683	seems to be quite complete and well-documented. Note, however, that the	3187	seems to be quite complete and well-documented.
2684	patch they require for libev is outright dangerous as it breaks the ABI
2685	for everybody else, and therefore, should never be applied in an installed
2686	libev (if python requires an incompatible ABI then it needs to embed
2687	libev).
2688		3188
2689	=item Ruby	3189	=item Ruby
2690		3190
2691	Tony Arcieri has written a ruby extension that offers access to a subset	3191	Tony Arcieri has written a ruby extension that offers access to a subset
2692	of the libev API and adds file handle abstractions, asynchronous DNS and	3192	of the libev API and adds file handle abstractions, asynchronous DNS and
2693	more on top of it. It can be found via gem servers. Its homepage is at	3193	more on top of it. It can be found via gem servers. Its homepage is at
2694	L<http://rev.rubyforge.org/>.	3194	L<http://rev.rubyforge.org/>.
2695		3195
		3196	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3197	makes rev work even on mingw.
		3198
		3199	=item Haskell
		3200
		3201	A haskell binding to libev is available at
		3202	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3203
2696	=item D	3204	=item D
2697		3205
2698	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3206	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2699	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3207	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3208
		3209	=item Ocaml
		3210
		3211	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3212	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2700		3213
2701	=back	3214	=back
2702		3215
2703		3216
2704	=head1 MACRO MAGIC	3217	=head1 MACRO MAGIC
…		…
2805		3318
2806	#define EV_STANDALONE 1	3319	#define EV_STANDALONE 1
2807	#include "ev.h"	3320	#include "ev.h"
2808		3321
2809	Both header files and implementation files can be compiled with a C++	3322	Both header files and implementation files can be compiled with a C++
2810	compiler (at least, thats a stated goal, and breakage will be treated	3323	compiler (at least, that's a stated goal, and breakage will be treated
2811	as a bug).	3324	as a bug).
2812		3325
2813	You need the following files in your source tree, or in a directory	3326	You need the following files in your source tree, or in a directory
2814	in your include path (e.g. in libev/ when using -Ilibev):	3327	in your include path (e.g. in libev/ when using -Ilibev):
2815		3328
…		…
2859		3372
2860	=head2 PREPROCESSOR SYMBOLS/MACROS	3373	=head2 PREPROCESSOR SYMBOLS/MACROS
2861		3374
2862	Libev can be configured via a variety of preprocessor symbols you have to	3375	Libev can be configured via a variety of preprocessor symbols you have to
2863	define before including any of its files. The default in the absence of	3376	define before including any of its files. The default in the absence of
2864	autoconf is noted for every option.	3377	autoconf is documented for every option.
2865		3378
2866	=over 4	3379	=over 4
2867		3380
2868	=item EV_STANDALONE	3381	=item EV_STANDALONE
2869		3382
…		…
2871	keeps libev from including F<config.h>, and it also defines dummy	3384	keeps libev from including F<config.h>, and it also defines dummy
2872	implementations for some libevent functions (such as logging, which is not	3385	implementations for some libevent functions (such as logging, which is not
2873	supported). It will also not define any of the structs usually found in	3386	supported). It will also not define any of the structs usually found in
2874	F<event.h> that are not directly supported by the libev core alone.	3387	F<event.h> that are not directly supported by the libev core alone.
2875		3388
		3389	In stanbdalone mode, libev will still try to automatically deduce the
		3390	configuration, but has to be more conservative.
		3391
2876	=item EV_USE_MONOTONIC	3392	=item EV_USE_MONOTONIC
2877		3393
2878	If defined to be C<1>, libev will try to detect the availability of the	3394	If defined to be C<1>, libev will try to detect the availability of the
2879	monotonic clock option at both compile time and runtime. Otherwise no use	3395	monotonic clock option at both compile time and runtime. Otherwise no
2880	of the monotonic clock option will be attempted. If you enable this, you	3396	use of the monotonic clock option will be attempted. If you enable this,
2881	usually have to link against librt or something similar. Enabling it when	3397	you usually have to link against librt or something similar. Enabling it
2882	the functionality isn't available is safe, though, although you have	3398	when the functionality isn't available is safe, though, although you have
2883	to make sure you link against any libraries where the C<clock_gettime>	3399	to make sure you link against any libraries where the C<clock_gettime>
2884	function is hiding in (often F<-lrt>).	3400	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2885		3401
2886	=item EV_USE_REALTIME	3402	=item EV_USE_REALTIME
2887		3403
2888	If defined to be C<1>, libev will try to detect the availability of the	3404	If defined to be C<1>, libev will try to detect the availability of the
2889	real-time clock option at compile time (and assume its availability at	3405	real-time clock option at compile time (and assume its availability
2890	runtime if successful). Otherwise no use of the real-time clock option will	3406	at runtime if successful). Otherwise no use of the real-time clock
2891	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3407	option will be attempted. This effectively replaces C<gettimeofday>
2892	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3408	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2893	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3409	correctness. See the note about libraries in the description of
		3410	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3411	C<EV_USE_CLOCK_SYSCALL>.
		3412
		3413	=item EV_USE_CLOCK_SYSCALL
		3414
		3415	If defined to be C<1>, libev will try to use a direct syscall instead
		3416	of calling the system-provided C<clock_gettime> function. This option
		3417	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3418	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3419	programs needlessly. Using a direct syscall is slightly slower (in
		3420	theory), because no optimised vdso implementation can be used, but avoids
		3421	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3422	higher, as it simplifies linking (no need for C<-lrt>).
2894		3423
2895	=item EV_USE_NANOSLEEP	3424	=item EV_USE_NANOSLEEP
2896		3425
2897	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3426	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2898	and will use it for delays. Otherwise it will use C<select ()>.	3427	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2914		3443
2915	=item EV_SELECT_USE_FD_SET	3444	=item EV_SELECT_USE_FD_SET
2916		3445
2917	If defined to C<1>, then the select backend will use the system C<fd_set>	3446	If defined to C<1>, then the select backend will use the system C<fd_set>
2918	structure. This is useful if libev doesn't compile due to a missing	3447	structure. This is useful if libev doesn't compile due to a missing
2919	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3448	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2920	exotic systems. This usually limits the range of file descriptors to some	3449	on exotic systems. This usually limits the range of file descriptors to
2921	low limit such as 1024 or might have other limitations (winsocket only	3450	some low limit such as 1024 or might have other limitations (winsocket
2922	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3451	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2923	influence the size of the C<fd_set> used.	3452	configures the maximum size of the C<fd_set>.
2924		3453
2925	=item EV_SELECT_IS_WINSOCKET	3454	=item EV_SELECT_IS_WINSOCKET
2926		3455
2927	When defined to C<1>, the select backend will assume that	3456	When defined to C<1>, the select backend will assume that
2928	select/socket/connect etc. don't understand file descriptors but	3457	select/socket/connect etc. don't understand file descriptors but
…		…
3039	When doing priority-based operations, libev usually has to linearly search	3568	When doing priority-based operations, libev usually has to linearly search
3040	all the priorities, so having many of them (hundreds) uses a lot of space	3569	all the priorities, so having many of them (hundreds) uses a lot of space
3041	and time, so using the defaults of five priorities (-2 .. +2) is usually	3570	and time, so using the defaults of five priorities (-2 .. +2) is usually
3042	fine.	3571	fine.
3043		3572
3044	If your embedding application does not need any priorities, defining these both to	3573	If your embedding application does not need any priorities, defining these
3045	C<0> will save some memory and CPU.	3574	both to C<0> will save some memory and CPU.
3046		3575
3047	=item EV_PERIODIC_ENABLE	3576	=item EV_PERIODIC_ENABLE
3048		3577
3049	If undefined or defined to be C<1>, then periodic timers are supported. If	3578	If undefined or defined to be C<1>, then periodic timers are supported. If
3050	defined to be C<0>, then they are not. Disabling them saves a few kB of	3579	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3057	code.	3586	code.
3058		3587
3059	=item EV_EMBED_ENABLE	3588	=item EV_EMBED_ENABLE
3060		3589
3061	If undefined or defined to be C<1>, then embed watchers are supported. If	3590	If undefined or defined to be C<1>, then embed watchers are supported. If
3062	defined to be C<0>, then they are not.	3591	defined to be C<0>, then they are not. Embed watchers rely on most other
		3592	watcher types, which therefore must not be disabled.
3063		3593
3064	=item EV_STAT_ENABLE	3594	=item EV_STAT_ENABLE
3065		3595
3066	If undefined or defined to be C<1>, then stat watchers are supported. If	3596	If undefined or defined to be C<1>, then stat watchers are supported. If
3067	defined to be C<0>, then they are not.	3597	defined to be C<0>, then they are not.
…		…
3099	two).	3629	two).
3100		3630
3101	=item EV_USE_4HEAP	3631	=item EV_USE_4HEAP
3102		3632
3103	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3633	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3104	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3634	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3105	to C<1>. The 4-heap uses more complicated (longer) code but has	3635	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3106	noticeably faster performance with many (thousands) of watchers.	3636	faster performance with many (thousands) of watchers.
3107		3637
3108	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3638	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3109	(disabled).	3639	(disabled).
3110		3640
3111	=item EV_HEAP_CACHE_AT	3641	=item EV_HEAP_CACHE_AT
3112		3642
3113	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3643	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3114	timer and periodics heap, libev can cache the timestamp (I<at>) within	3644	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3115	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3645	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3116	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3646	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3117	but avoids random read accesses on heap changes. This improves performance	3647	but avoids random read accesses on heap changes. This improves performance
3118	noticeably with with many (hundreds) of watchers.	3648	noticeably with many (hundreds) of watchers.
3119		3649
3120	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3650	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3121	(disabled).	3651	(disabled).
3122		3652
3123	=item EV_VERIFY	3653	=item EV_VERIFY
…		…
3129	called once per loop, which can slow down libev. If set to C<3>, then the	3659	called once per loop, which can slow down libev. If set to C<3>, then the
3130	verification code will be called very frequently, which will slow down	3660	verification code will be called very frequently, which will slow down
3131	libev considerably.	3661	libev considerably.
3132		3662
3133	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3663	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3134	C<0.>	3664	C<0>.
3135		3665
3136	=item EV_COMMON	3666	=item EV_COMMON
3137		3667
3138	By default, all watchers have a C<void *data> member. By redefining	3668	By default, all watchers have a C<void *data> member. By redefining
3139	this macro to a something else you can include more and other types of	3669	this macro to a something else you can include more and other types of
…		…
3156	and the way callbacks are invoked and set. Must expand to a struct member	3686	and the way callbacks are invoked and set. Must expand to a struct member
3157	definition and a statement, respectively. See the F<ev.h> header file for	3687	definition and a statement, respectively. See the F<ev.h> header file for
3158	their default definitions. One possible use for overriding these is to	3688	their default definitions. One possible use for overriding these is to
3159	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3689	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3160	method calls instead of plain function calls in C++.	3690	method calls instead of plain function calls in C++.
		3691
		3692	=back
3161		3693
3162	=head2 EXPORTED API SYMBOLS	3694	=head2 EXPORTED API SYMBOLS
3163		3695
3164	If you need to re-export the API (e.g. via a DLL) and you need a list of	3696	If you need to re-export the API (e.g. via a DLL) and you need a list of
3165	exported symbols, you can use the provided F<Symbol.*> files which list	3697	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3212	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3744	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3213		3745
3214	#include "ev_cpp.h"	3746	#include "ev_cpp.h"
3215	#include "ev.c"	3747	#include "ev.c"
3216		3748
		3749	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3217		3750
3218	=head1 THREADS AND COROUTINES	3751	=head2 THREADS AND COROUTINES
3219		3752
3220	=head2 THREADS	3753	=head3 THREADS
3221		3754
3222	Libev itself is completely thread-safe, but it uses no locking. This	3755	All libev functions are reentrant and thread-safe unless explicitly
		3756	documented otherwise, but libev implements no locking itself. This means
3223	means that you can use as many loops as you want in parallel, as long as	3757	that you can use as many loops as you want in parallel, as long as there
3224	only one thread ever calls into one libev function with the same loop	3758	are no concurrent calls into any libev function with the same loop
3225	parameter.	3759	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3760	of course): libev guarantees that different event loops share no data
		3761	structures that need any locking.
3226		3762
3227	Or put differently: calls with different loop parameters can be done in	3763	Or to put it differently: calls with different loop parameters can be done
3228	parallel from multiple threads, calls with the same loop parameter must be	3764	concurrently from multiple threads, calls with the same loop parameter
3229	done serially (but can be done from different threads, as long as only one	3765	must be done serially (but can be done from different threads, as long as
3230	thread ever is inside a call at any point in time, e.g. by using a mutex	3766	only one thread ever is inside a call at any point in time, e.g. by using
3231	per loop).	3767	a mutex per loop).
		3768
		3769	Specifically to support threads (and signal handlers), libev implements
		3770	so-called C<ev_async> watchers, which allow some limited form of
		3771	concurrency on the same event loop, namely waking it up "from the
		3772	outside".
3232		3773
3233	If you want to know which design (one loop, locking, or multiple loops	3774	If you want to know which design (one loop, locking, or multiple loops
3234	without or something else still) is best for your problem, then I cannot	3775	without or something else still) is best for your problem, then I cannot
3235	help you. I can give some generic advice however:	3776	help you, but here is some generic advice:
3236		3777
3237	=over 4	3778	=over 4
3238		3779
3239	=item * most applications have a main thread: use the default libev loop	3780	=item * most applications have a main thread: use the default libev loop
3240	in that thread, or create a separate thread running only the default loop.	3781	in that thread, or create a separate thread running only the default loop.
…		…
3252		3793
3253	Choosing a model is hard - look around, learn, know that usually you can do	3794	Choosing a model is hard - look around, learn, know that usually you can do
3254	better than you currently do :-)	3795	better than you currently do :-)
3255		3796
3256	=item * often you need to talk to some other thread which blocks in the	3797	=item * often you need to talk to some other thread which blocks in the
		3798	event loop.
		3799
3257	event loop - C<ev_async> watchers can be used to wake them up from other	3800	C<ev_async> watchers can be used to wake them up from other threads safely
3258	threads safely (or from signal contexts...).	3801	(or from signal contexts...).
		3802
		3803	An example use would be to communicate signals or other events that only
		3804	work in the default loop by registering the signal watcher with the
		3805	default loop and triggering an C<ev_async> watcher from the default loop
		3806	watcher callback into the event loop interested in the signal.
3259		3807
3260	=back	3808	=back
3261		3809
3262	=head2 COROUTINES	3810	=head3 COROUTINES
3263		3811
3264	Libev is much more accommodating to coroutines ("cooperative threads"):	3812	Libev is very accommodating to coroutines ("cooperative threads"):
3265	libev fully supports nesting calls to it's functions from different	3813	libev fully supports nesting calls to its functions from different
3266	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3814	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3267	different coroutines and switch freely between both coroutines running the	3815	different coroutines, and switch freely between both coroutines running the
3268	loop, as long as you don't confuse yourself). The only exception is that	3816	loop, as long as you don't confuse yourself). The only exception is that
3269	you must not do this from C<ev_periodic> reschedule callbacks.	3817	you must not do this from C<ev_periodic> reschedule callbacks.
3270		3818
3271	Care has been invested into making sure that libev does not keep local	3819	Care has been taken to ensure that libev does not keep local state inside
3272	state inside C<ev_loop>, and other calls do not usually allow coroutine	3820	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3273	switches.	3821	they do not call any callbacks.
3274		3822
		3823	=head2 COMPILER WARNINGS
3275		3824
3276	=head1 COMPLEXITIES	3825	Depending on your compiler and compiler settings, you might get no or a
		3826	lot of warnings when compiling libev code. Some people are apparently
		3827	scared by this.
3277		3828
3278	In this section the complexities of (many of) the algorithms used inside	3829	However, these are unavoidable for many reasons. For one, each compiler
3279	libev will be explained. For complexity discussions about backends see the	3830	has different warnings, and each user has different tastes regarding
3280	documentation for C<ev_default_init>.	3831	warning options. "Warn-free" code therefore cannot be a goal except when
		3832	targeting a specific compiler and compiler-version.
3281		3833
3282	All of the following are about amortised time: If an array needs to be	3834	Another reason is that some compiler warnings require elaborate
3283	extended, libev needs to realloc and move the whole array, but this	3835	workarounds, or other changes to the code that make it less clear and less
3284	happens asymptotically never with higher number of elements, so O(1) might	3836	maintainable.
3285	mean it might do a lengthy realloc operation in rare cases, but on average
3286	it is much faster and asymptotically approaches constant time.
3287		3837
3288	=over 4	3838	And of course, some compiler warnings are just plain stupid, or simply
		3839	wrong (because they don't actually warn about the condition their message
		3840	seems to warn about). For example, certain older gcc versions had some
		3841	warnings that resulted an extreme number of false positives. These have
		3842	been fixed, but some people still insist on making code warn-free with
		3843	such buggy versions.
3289		3844
3290	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3845	While libev is written to generate as few warnings as possible,
		3846	"warn-free" code is not a goal, and it is recommended not to build libev
		3847	with any compiler warnings enabled unless you are prepared to cope with
		3848	them (e.g. by ignoring them). Remember that warnings are just that:
		3849	warnings, not errors, or proof of bugs.
3291		3850
3292	This means that, when you have a watcher that triggers in one hour and
3293	there are 100 watchers that would trigger before that then inserting will
3294	have to skip roughly seven (C<ld 100>) of these watchers.
3295		3851
3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3852	=head2 VALGRIND
3297		3853
3298	That means that changing a timer costs less than removing/adding them	3854	Valgrind has a special section here because it is a popular tool that is
3299	as only the relative motion in the event queue has to be paid for.	3855	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3300		3856
3301	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3857	If you think you found a bug (memory leak, uninitialised data access etc.)
		3858	in libev, then check twice: If valgrind reports something like:
3302		3859
3303	These just add the watcher into an array or at the head of a list.	3860	==2274== definitely lost: 0 bytes in 0 blocks.
		3861	==2274== possibly lost: 0 bytes in 0 blocks.
		3862	==2274== still reachable: 256 bytes in 1 blocks.
3304		3863
3305	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3864	Then there is no memory leak, just as memory accounted to global variables
		3865	is not a memleak - the memory is still being referenced, and didn't leak.
3306		3866
3307	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3867	Similarly, under some circumstances, valgrind might report kernel bugs
		3868	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3869	although an acceptable workaround has been found here), or it might be
		3870	confused.
3308		3871
3309	These watchers are stored in lists then need to be walked to find the	3872	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3310	correct watcher to remove. The lists are usually short (you don't usually	3873	make it into some kind of religion.
3311	have many watchers waiting for the same fd or signal).
3312		3874
3313	=item Finding the next timer in each loop iteration: O(1)	3875	If you are unsure about something, feel free to contact the mailing list
		3876	with the full valgrind report and an explanation on why you think this
		3877	is a bug in libev (best check the archives, too :). However, don't be
		3878	annoyed when you get a brisk "this is no bug" answer and take the chance
		3879	of learning how to interpret valgrind properly.
3314		3880
3315	By virtue of using a binary or 4-heap, the next timer is always found at a	3881	If you need, for some reason, empty reports from valgrind for your project
3316	fixed position in the storage array.	3882	I suggest using suppression lists.
3317		3883
3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3319		3884
3320	A change means an I/O watcher gets started or stopped, which requires	3885	=head1 PORTABILITY NOTES
3321	libev to recalculate its status (and possibly tell the kernel, depending
3322	on backend and whether C<ev_io_set> was used).
3323		3886
3324	=item Activating one watcher (putting it into the pending state): O(1)
3325
3326	=item Priority handling: O(number_of_priorities)
3327
3328	Priorities are implemented by allocating some space for each
3329	priority. When doing priority-based operations, libev usually has to
3330	linearly search all the priorities, but starting/stopping and activating
3331	watchers becomes O(1) w.r.t. priority handling.
3332
3333	=item Sending an ev_async: O(1)
3334
3335	=item Processing ev_async_send: O(number_of_async_watchers)
3336
3337	=item Processing signals: O(max_signal_number)
3338
3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
3340	calls in the current loop iteration. Checking for async and signal events
3341	involves iterating over all running async watchers or all signal numbers.
3342
3343	=back
3344
3345
3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3887	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3347		3888
3348	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3889	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3349	requires, and its I/O model is fundamentally incompatible with the POSIX	3890	requires, and its I/O model is fundamentally incompatible with the POSIX
3350	model. Libev still offers limited functionality on this platform in	3891	model. Libev still offers limited functionality on this platform in
3351	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3892	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3362		3903
3363	Not a libev limitation but worth mentioning: windows apparently doesn't	3904	Not a libev limitation but worth mentioning: windows apparently doesn't
3364	accept large writes: instead of resulting in a partial write, windows will	3905	accept large writes: instead of resulting in a partial write, windows will
3365	either accept everything or return C<ENOBUFS> if the buffer is too large,	3906	either accept everything or return C<ENOBUFS> if the buffer is too large,
3366	so make sure you only write small amounts into your sockets (less than a	3907	so make sure you only write small amounts into your sockets (less than a
3367	megabyte seems safe, but thsi apparently depends on the amount of memory	3908	megabyte seems safe, but this apparently depends on the amount of memory
3368	available).	3909	available).
3369		3910
3370	Due to the many, low, and arbitrary limits on the win32 platform and	3911	Due to the many, low, and arbitrary limits on the win32 platform and
3371	the abysmal performance of winsockets, using a large number of sockets	3912	the abysmal performance of winsockets, using a large number of sockets
3372	is not recommended (and not reasonable). If your program needs to use	3913	is not recommended (and not reasonable). If your program needs to use
…		…
3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3924	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3384		3925
3385	#include "ev.h"	3926	#include "ev.h"
3386		3927
3387	And compile the following F<evwrap.c> file into your project (make sure	3928	And compile the following F<evwrap.c> file into your project (make sure
3388	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3929	you do I<not> compile the F<ev.c> or any other embedded source files!):
3389		3930
3390	#include "evwrap.h"	3931	#include "evwrap.h"
3391	#include "ev.c"	3932	#include "ev.c"
3392		3933
3393	=over 4	3934	=over 4
…		…
3438	wrap all I/O functions and provide your own fd management, but the cost of	3979	wrap all I/O functions and provide your own fd management, but the cost of
3439	calling select (O(n²)) will likely make this unworkable.	3980	calling select (O(n²)) will likely make this unworkable.
3440		3981
3441	=back	3982	=back
3442		3983
3443
3444	=head1 PORTABILITY REQUIREMENTS	3984	=head2 PORTABILITY REQUIREMENTS
3445		3985
3446	In addition to a working ISO-C implementation, libev relies on a few	3986	In addition to a working ISO-C implementation and of course the
3447	additional extensions:	3987	backend-specific APIs, libev relies on a few additional extensions:
3448		3988
3449	=over 4	3989	=over 4
3450		3990
3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3991	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3452	calling conventions regardless of C<ev_watcher_type *>.	3992	calling conventions regardless of C<ev_watcher_type *>.
…		…
3458	calls them using an C<ev_watcher *> internally.	3998	calls them using an C<ev_watcher *> internally.
3459		3999
3460	=item C<sig_atomic_t volatile> must be thread-atomic as well	4000	=item C<sig_atomic_t volatile> must be thread-atomic as well
3461		4001
3462	The type C<sig_atomic_t volatile> (or whatever is defined as	4002	The type C<sig_atomic_t volatile> (or whatever is defined as
3463	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4003	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3464	threads. This is not part of the specification for C<sig_atomic_t>, but is	4004	threads. This is not part of the specification for C<sig_atomic_t>, but is
3465	believed to be sufficiently portable.	4005	believed to be sufficiently portable.
3466		4006
3467	=item C<sigprocmask> must work in a threaded environment	4007	=item C<sigprocmask> must work in a threaded environment
3468		4008
…		…
3477	except the initial one, and run the default loop in the initial thread as	4017	except the initial one, and run the default loop in the initial thread as
3478	well.	4018	well.
3479		4019
3480	=item C<long> must be large enough for common memory allocation sizes	4020	=item C<long> must be large enough for common memory allocation sizes
3481		4021
3482	To improve portability and simplify using libev, libev uses C<long>	4022	To improve portability and simplify its API, libev uses C<long> internally
3483	internally instead of C<size_t> when allocating its data structures. On	4023	instead of C<size_t> when allocating its data structures. On non-POSIX
3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4024	systems (Microsoft...) this might be unexpectedly low, but is still at
3485	is still at least 31 bits everywhere, which is enough for hundreds of	4025	least 31 bits everywhere, which is enough for hundreds of millions of
3486	millions of watchers.	4026	watchers.
3487		4027
3488	=item C<double> must hold a time value in seconds with enough accuracy	4028	=item C<double> must hold a time value in seconds with enough accuracy
3489		4029
3490	The type C<double> is used to represent timestamps. It is required to	4030	The type C<double> is used to represent timestamps. It is required to
3491	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4031	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3495	=back	4035	=back
3496		4036
3497	If you know of other additional requirements drop me a note.	4037	If you know of other additional requirements drop me a note.
3498		4038
3499		4039
3500	=head1 COMPILER WARNINGS	4040	=head1 ALGORITHMIC COMPLEXITIES
3501		4041
3502	Depending on your compiler and compiler settings, you might get no or a	4042	In this section the complexities of (many of) the algorithms used inside
3503	lot of warnings when compiling libev code. Some people are apparently	4043	libev will be documented. For complexity discussions about backends see
3504	scared by this.	4044	the documentation for C<ev_default_init>.
3505		4045
3506	However, these are unavoidable for many reasons. For one, each compiler	4046	All of the following are about amortised time: If an array needs to be
3507	has different warnings, and each user has different tastes regarding	4047	extended, libev needs to realloc and move the whole array, but this
3508	warning options. "Warn-free" code therefore cannot be a goal except when	4048	happens asymptotically rarer with higher number of elements, so O(1) might
3509	targeting a specific compiler and compiler-version.	4049	mean that libev does a lengthy realloc operation in rare cases, but on
		4050	average it is much faster and asymptotically approaches constant time.
3510		4051
3511	Another reason is that some compiler warnings require elaborate	4052	=over 4
3512	workarounds, or other changes to the code that make it less clear and less
3513	maintainable.
3514		4053
3515	And of course, some compiler warnings are just plain stupid, or simply	4054	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3516	wrong (because they don't actually warn about the condition their message
3517	seems to warn about).
3518		4055
3519	While libev is written to generate as few warnings as possible,	4056	This means that, when you have a watcher that triggers in one hour and
3520	"warn-free" code is not a goal, and it is recommended not to build libev	4057	there are 100 watchers that would trigger before that, then inserting will
3521	with any compiler warnings enabled unless you are prepared to cope with	4058	have to skip roughly seven (C<ld 100>) of these watchers.
3522	them (e.g. by ignoring them). Remember that warnings are just that:
3523	warnings, not errors, or proof of bugs.
3524		4059
		4060	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3525		4061
3526	=head1 VALGRIND	4062	That means that changing a timer costs less than removing/adding them,
		4063	as only the relative motion in the event queue has to be paid for.
3527		4064
3528	Valgrind has a special section here because it is a popular tool that is	4065	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3529	highly useful, but valgrind reports are very hard to interpret.
3530		4066
3531	If you think you found a bug (memory leak, uninitialised data access etc.)	4067	These just add the watcher into an array or at the head of a list.
3532	in libev, then check twice: If valgrind reports something like:
3533		4068
3534	==2274== definitely lost: 0 bytes in 0 blocks.	4069	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3535	==2274== possibly lost: 0 bytes in 0 blocks.
3536	==2274== still reachable: 256 bytes in 1 blocks.
3537		4070
3538	Then there is no memory leak. Similarly, under some circumstances,	4071	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3539	valgrind might report kernel bugs as if it were a bug in libev, or it
3540	might be confused (it is a very good tool, but only a tool).
3541		4072
3542	If you are unsure about something, feel free to contact the mailing list	4073	These watchers are stored in lists, so they need to be walked to find the
3543	with the full valgrind report and an explanation on why you think this is	4074	correct watcher to remove. The lists are usually short (you don't usually
3544	a bug in libev. However, don't be annoyed when you get a brisk "this is	4075	have many watchers waiting for the same fd or signal: one is typical, two
3545	no bug" answer and take the chance of learning how to interpret valgrind	4076	is rare).
3546	properly.
3547		4077
3548	If you need, for some reason, empty reports from valgrind for your project	4078	=item Finding the next timer in each loop iteration: O(1)
3549	I suggest using suppression lists.
3550		4079
		4080	By virtue of using a binary or 4-heap, the next timer is always found at a
		4081	fixed position in the storage array.
		4082
		4083	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4084
		4085	A change means an I/O watcher gets started or stopped, which requires
		4086	libev to recalculate its status (and possibly tell the kernel, depending
		4087	on backend and whether C<ev_io_set> was used).
		4088
		4089	=item Activating one watcher (putting it into the pending state): O(1)
		4090
		4091	=item Priority handling: O(number_of_priorities)
		4092
		4093	Priorities are implemented by allocating some space for each
		4094	priority. When doing priority-based operations, libev usually has to
		4095	linearly search all the priorities, but starting/stopping and activating
		4096	watchers becomes O(1) with respect to priority handling.
		4097
		4098	=item Sending an ev_async: O(1)
		4099
		4100	=item Processing ev_async_send: O(number_of_async_watchers)
		4101
		4102	=item Processing signals: O(max_signal_number)
		4103
		4104	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4105	calls in the current loop iteration. Checking for async and signal events
		4106	involves iterating over all running async watchers or all signal numbers.
		4107
		4108	=back
		4109
		4110
		4111	=head1 GLOSSARY
		4112
		4113	=over 4
		4114
		4115	=item active
		4116
		4117	A watcher is active as long as it has been started (has been attached to
		4118	an event loop) but not yet stopped (disassociated from the event loop).
		4119
		4120	=item application
		4121
		4122	In this document, an application is whatever is using libev.
		4123
		4124	=item callback
		4125
		4126	The address of a function that is called when some event has been
		4127	detected. Callbacks are being passed the event loop, the watcher that
		4128	received the event, and the actual event bitset.
		4129
		4130	=item callback invocation
		4131
		4132	The act of calling the callback associated with a watcher.
		4133
		4134	=item event
		4135
		4136	A change of state of some external event, such as data now being available
		4137	for reading on a file descriptor, time having passed or simply not having
		4138	any other events happening anymore.
		4139
		4140	In libev, events are represented as single bits (such as C<EV_READ> or
		4141	C<EV_TIMEOUT>).
		4142
		4143	=item event library
		4144
		4145	A software package implementing an event model and loop.
		4146
		4147	=item event loop
		4148
		4149	An entity that handles and processes external events and converts them
		4150	into callback invocations.
		4151
		4152	=item event model
		4153
		4154	The model used to describe how an event loop handles and processes
		4155	watchers and events.
		4156
		4157	=item pending
		4158
		4159	A watcher is pending as soon as the corresponding event has been detected,
		4160	and stops being pending as soon as the watcher will be invoked or its
		4161	pending status is explicitly cleared by the application.
		4162
		4163	A watcher can be pending, but not active. Stopping a watcher also clears
		4164	its pending status.
		4165
		4166	=item real time
		4167
		4168	The physical time that is observed. It is apparently strictly monotonic :)
		4169
		4170	=item wall-clock time
		4171
		4172	The time and date as shown on clocks. Unlike real time, it can actually
		4173	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4174	clock.
		4175
		4176	=item watcher
		4177
		4178	A data structure that describes interest in certain events. Watchers need
		4179	to be started (attached to an event loop) before they can receive events.
		4180
		4181	=item watcher invocation
		4182
		4183	The act of calling the callback associated with a watcher.
		4184
		4185	=back
3551		4186
3552	=head1 AUTHOR	4187	=head1 AUTHOR
3553		4188
3554	Marc Lehmann <libev@schmorp.de>.	4189	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3555		4190

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