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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
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
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
559	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
560		621
561	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
564		637
565	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
566		639
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	641	use.
…		…
583		656
584	This function is rarely useful, but when some event callback runs for a	657	This function is rarely useful, but when some event callback runs for a
585	very long time without entering the event loop, updating libev's idea of	658	very long time without entering the event loop, updating libev's idea of
586	the current time is a good idea.	659	the current time is a good idea.
587		660
588	See also "The special problem of time updates" in the C<ev_timer> section.	661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
589		688
590	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
591		690
592	Finally, this is it, the event handler. This function usually is called	691	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	692	after you initialised all your watchers and you want to start handling
…		…
596	If the flags argument is specified as C<0>, it will not return until	695	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.	696	either no event watchers are active anymore or C<ev_unloop> was called.
598		697
599	Please note that an explicit C<ev_unloop> is usually better than	698	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	699	relying on all watchers to be stopped when deciding when a program has
601	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
602	automatically loops as long as it has to and no longer by virtue of	701	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.	702	of relying on its watchers stopping correctly, that is truly a thing of
		703	beauty.
604		704
605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	705	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	706	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.	707	process in case there are no events and will return after one iteration of
		708	the loop.
608		709
609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	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	711	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	712	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	713	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	714	user-registered callback will be called), and will return after one
		715	iteration of the loop.
		716
		717	This is useful if you are waiting for some external event in conjunction
		718	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	719	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.	720	usually a better approach for this kind of thing.
616		721
617	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
618		723
619	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
…		…
629	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
630	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
631	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
634	- Queue all outstanding timers.	739	- Queue all expired timers.
635	- Queue all outstanding periodics.	740	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
637	- Queue all check watchers.	742	- Queue all check watchers.
638	- Call all queued watchers in reverse order (i.e. check watchers first).	743	- 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	744	Signals and child watchers are implemented as I/O watchers, and will
640	be handled here by queueing them when their watcher gets executed.	745	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	762	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.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
659		764
660	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
661		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
662	=item ev_ref (loop)	769	=item ev_ref (loop)
663		770
664	=item ev_unref (loop)	771	=item ev_unref (loop)
665		772
666	Ref/unref can be used to add or remove a reference count on the event	773	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	774	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	775	count is nonzero, C<ev_loop> will not return on its own.
		776
669	a watcher you never unregister that should not keep C<ev_loop> from	777	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	778	from returning, call ev_unref() after starting, and ev_ref() before
		779	stopping it.
		780
671	example, libev itself uses this for its internal signal pipe: It is not	781	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	782	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	783	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	784	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>	785	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,	786	before stop> (but only if the watcher wasn't active before, or was active
677	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
678		790
679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
680	running when nothing else is active.	792	running when nothing else is active.
681		793
682	struct ev_signal exitsig;	794	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	797	evf_unref (loop);
686		798
687	Example: For some weird reason, unregister the above signal handler again.	799	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>)	813	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	814	allows libev to delay invocation of I/O and timer/periodic callbacks
703	to increase efficiency of loop iterations (or to increase power-saving	815	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	816	opportunities).
705		817
706	The background is that sometimes your program runs just fast enough to	818	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	819	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	820	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	821	events, especially with backends like C<select ()> which have a high
710	overhead for the actual polling but can deliver many events at once.	822	overhead for the actual polling but can deliver many events at once.
711		823
712	By setting a higher I<io collect interval> you allow libev to spend more	824	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,	825	time collecting I/O events, so you can handle more events per iteration,
714	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
715	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	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.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
717		831
718	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
719	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
721	will not be affected. Setting this to a non-null value will not introduce	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
722	any overhead in libev.	836	value will not introduce any overhead in libev.
723		837
724	Many (busy) programs can usually benefit by setting the I/O collect	838	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	839	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	840	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>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
728	as this approaches the timing granularity of most systems.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
729		847
730	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
731	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
732	are "near" in time together, by delaying some, thus reducing the number of	850	are "near" in time together, by delaying some, thus reducing the number of
733	times the process sleeps and wakes up again. Another useful technique to	851	times the process sleeps and wakes up again. Another useful technique to
734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
735	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
736		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
737	=item ev_loop_verify (loop)	861	=item ev_loop_verify (loop)
738		862
739	This function only does something when C<EV_VERIFY> support has been	863	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	864	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	865	through all internal structures and checks them for validity. If anything
742	an error message to standard error and call C<abort ()>.	866	is found to be inconsistent, it will print an error message to standard
		867	error and call C<abort ()>.
743		868
744	This can be used to catch bugs inside libev itself: under normal	869	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	870	circumstances, this function will never abort as of course libev keeps its
746	data structures consistent.	871	data structures consistent.
747		872
748	=back	873	=back
749		874
750		875
751	=head1 ANATOMY OF A WATCHER	876	=head1 ANATOMY OF A WATCHER
752		877
		878	In the following description, uppercase C<TYPE> in names stands for the
		879	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		880	watchers and C<ev_io_start> for I/O watchers.
		881
753	A watcher is a structure that you create and register to record your	882	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	883	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:	884	become readable, you would create an C<ev_io> watcher for that:
756		885
757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	886	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
758	{	887	{
759	ev_io_stop (w);	888	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	889	ev_unloop (loop, EVUNLOOP_ALL);
761	}	890	}
762		891
763	struct ev_loop *loop = ev_default_loop (0);	892	struct ev_loop *loop = ev_default_loop (0);
		893
764	struct ev_io stdin_watcher;	894	ev_io stdin_watcher;
		895
765	ev_init (&stdin_watcher, my_cb);	896	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	898	ev_io_start (loop, &stdin_watcher);
		899
768	ev_loop (loop, 0);	900	ev_loop (loop, 0);
769		901
770	As you can see, you are responsible for allocating the memory for your	902	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,	903	watcher structures (and it is I<usually> a bad idea to do this on the
772	although this can sometimes be quite valid).	904	stack).
		905
		906	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		907	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
773		908
774	Each watcher structure must be initialised by a call to C<ev_init	909	Each watcher structure must be initialised by a call to C<ev_init
775	(watcher *, callback)>, which expects a callback to be provided. This	910	(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	911	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	912	watchers, each time the event loop detects that the file descriptor given
778	is readable and/or writable).	913	is readable and/or writable).
779		914
780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	915	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	916	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	917	is also a macro to combine initialisation and setting in one call: C<<
783	(watcher *, callback, ...) >>.	918	ev_TYPE_init (watcher *, callback, ...) >>.
784		919
785	To make the watcher actually watch out for events, you have to start it	920	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	921	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	922	*) >>), and you can stop watching for events at any time by calling the
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	923	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		924
790	As long as your watcher is active (has been started but not stopped) you	925	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	926	must not touch the values stored in it. Most specifically you must never
792	reinitialise it or call its C<set> macro.	927	reinitialise it or call its C<ev_TYPE_set> macro.
793		928
794	Each and every callback receives the event loop pointer as first, the	929	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	930	registered watcher structure as second, and a bitset of received events as
796	third argument.	931	third argument.
797		932
…		…
855		990
856	=item C<EV_ASYNC>	991	=item C<EV_ASYNC>
857		992
858	The given async watcher has been asynchronously notified (see C<ev_async>).	993	The given async watcher has been asynchronously notified (see C<ev_async>).
859		994
		995	=item C<EV_CUSTOM>
		996
		997	Not ever sent (or otherwise used) by libev itself, but can be freely used
		998	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		999
860	=item C<EV_ERROR>	1000	=item C<EV_ERROR>
861		1001
862	An unspecified error has occurred, the watcher has been stopped. This might	1002	An unspecified error has occurred, the watcher has been stopped. This might
863	happen because the watcher could not be properly started because libev	1003	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	1004	ran out of memory, a file descriptor was found to be closed or any other
		1005	problem. Libev considers these application bugs.
		1006
865	problem. You best act on it by reporting the problem and somehow coping	1007	You best act on it by reporting the problem and somehow coping with the
866	with the watcher being stopped.	1008	watcher being stopped. Note that well-written programs should not receive
		1009	an error ever, so when your watcher receives it, this usually indicates a
		1010	bug in your program.
867		1011
868	Libev will usually signal a few "dummy" events together with an error,	1012	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	1013	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	1014	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	1015	the error from read() or write(). This will not work in multi-threaded
872	programs, though, so beware.	1016	programs, though, as the fd could already be closed and reused for another
		1017	thing, so beware.
873		1018
874	=back	1019	=back
875		1020
876	=head2 GENERIC WATCHER FUNCTIONS	1021	=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		1022
881	=over 4	1023	=over 4
882		1024
883	=item C<ev_init> (ev_TYPE *watcher, callback)	1025	=item C<ev_init> (ev_TYPE *watcher, callback)
884		1026
…		…
890	which rolls both calls into one.	1032	which rolls both calls into one.
891		1033
892	You can reinitialise a watcher at any time as long as it has been stopped	1034	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.	1035	(or never started) and there are no pending events outstanding.
894		1036
895	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1037	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
896	int revents)>.	1038	int revents)>.
		1039
		1040	Example: Initialise an C<ev_io> watcher in two steps.
		1041
		1042	ev_io w;
		1043	ev_init (&w, my_cb);
		1044	ev_io_set (&w, STDIN_FILENO, EV_READ);
897		1045
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])
899		1047
900	This macro initialises the type-specific parts of a watcher. You need to	1048	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	1049	call C<ev_init> at least once before you call this macro, but you can
…		…
904	difference to the C<ev_init> macro).	1052	difference to the C<ev_init> macro).
905		1053
906	Although some watcher types do not have type-specific arguments	1054	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.	1055	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
908		1056
		1057	See C<ev_init>, above, for an example.
		1058
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1059	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		1060
911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1061	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	1062	calls into a single call. This is the most convenient method to initialise
913	a watcher. The same limitations apply, of course.	1063	a watcher. The same limitations apply, of course.
914		1064
		1065	Example: Initialise and set an C<ev_io> watcher in one step.
		1066
		1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1068
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
916		1070
917	Starts (activates) the given watcher. Only active watchers will receive	1071	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	1072	events. If the watcher is already active nothing will happen.
919		1073
		1074	Example: Start the C<ev_io> watcher that is being abused as example in this
		1075	whole section.
		1076
		1077	ev_io_start (EV_DEFAULT_UC, &w);
		1078
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
921		1080
922	Stops the given watcher again (if active) and clears the pending	1081	Stops the given watcher if active, and clears the pending status (whether
		1082	the watcher was active or not).
		1083
923	status. It is possible that stopped watchers are pending (for example,	1084	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	1085	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	1086	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	1087	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.	1088	therefore a good idea to always call its C<ev_TYPE_stop> function.
928		1089
929	=item bool ev_is_active (ev_TYPE *watcher)	1090	=item bool ev_is_active (ev_TYPE *watcher)
930		1091
931	Returns a true value iff the watcher is active (i.e. it has been started	1092	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	1093	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>	1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
959	(default: C<-2>). Pending watchers with higher priority will be invoked	1120	(default: C<-2>). Pending watchers with higher priority will be invoked
960	before watchers with lower priority, but priority will not keep watchers	1121	before watchers with lower priority, but priority will not keep watchers
961	from being executed (except for C<ev_idle> watchers).	1122	from being executed (except for C<ev_idle> watchers).
962		1123
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	1124	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.	1125	you need to look at C<ev_idle> watchers, which provide this functionality.
970		1126
971	You I<must not> change the priority of a watcher as long as it is active or	1127	You I<must not> change the priority of a watcher as long as it is active or
972	pending.	1128	pending.
973		1129
		1130	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1131	fine, as long as you do not mind that the priority value you query might
		1132	or might not have been clamped to the valid range.
		1133
974	The default priority used by watchers when no priority has been set is	1134	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 :).	1135	always C<0>, which is supposed to not be too high and not be too low :).
976		1136
977	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1137	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	1138	priorities.
979	or might not have been adjusted to be within valid range.
980		1139
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1141
983	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1142	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	1143	C<loop> nor C<revents> need to be valid as long as the watcher callback
985	can deal with that fact.	1144	can deal with that fact, as both are simply passed through to the
		1145	callback.
986		1146
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1147	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1148
989	If the watcher is pending, this function returns clears its pending status	1149	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	1150	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>.	1151	watcher isn't pending it does nothing and returns C<0>.
992		1152
		1153	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1154	callback to be invoked, which can be accomplished with this function.
		1155
993	=back	1156	=back
994		1157
995		1158
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1160
998	Each watcher has, by default, a member C<void *data> that you can change	1161	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	1162	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	1163	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	1164	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	1165	member, you can also "subclass" the watcher type and provide your own
1003	data:	1166	data:
1004		1167
1005	struct my_io	1168	struct my_io
1006	{	1169	{
1007	struct ev_io io;	1170	ev_io io;
1008	int otherfd;	1171	int otherfd;
1009	void *somedata;	1172	void *somedata;
1010	struct whatever *mostinteresting;	1173	struct whatever *mostinteresting;
1011	}	1174	};
		1175
		1176	...
		1177	struct my_io w;
		1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
1012		1179
1013	And since your callback will be called with a pointer to the watcher, you	1180	And since your callback will be called with a pointer to the watcher, you
1014	can cast it back to your own type:	1181	can cast it back to your own type:
1015		1182
1016	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1017	{	1184	{
1018	struct my_io *w = (struct my_io *)w_;	1185	struct my_io *w = (struct my_io *)w_;
1019	...	1186	...
1020	}	1187	}
1021		1188
1022	More interesting and less C-conformant ways of casting your callback type	1189	More interesting and less C-conformant ways of casting your callback type
1023	instead have been omitted.	1190	instead have been omitted.
1024		1191
1025	Another common scenario is having some data structure with multiple	1192	Another common scenario is to use some data structure with multiple
1026	watchers:	1193	embedded watchers:
1027		1194
1028	struct my_biggy	1195	struct my_biggy
1029	{	1196	{
1030	int some_data;	1197	int some_data;
1031	ev_timer t1;	1198	ev_timer t1;
1032	ev_timer t2;	1199	ev_timer t2;
1033	}	1200	}
1034		1201
1035	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1202	In this case getting the pointer to C<my_biggy> is a bit more
1036	you need to use C<offsetof>:	1203	complicated: Either you store the address of your C<my_biggy> struct
		1204	in the C<data> member of the watcher (for woozies), or you need to use
		1205	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1206	programmers):
1037		1207
1038	#include <stddef.h>	1208	#include <stddef.h>
1039		1209
1040	static void	1210	static void
1041	t1_cb (EV_P_ struct ev_timer *w, int revents)	1211	t1_cb (EV_P_ ev_timer *w, int revents)
1042	{	1212	{
1043	struct my_biggy big = (struct my_biggy *	1213	struct my_biggy big = (struct my_biggy *)
1044	(((char *)w) - offsetof (struct my_biggy, t1));	1214	(((char *)w) - offsetof (struct my_biggy, t1));
1045	}	1215	}
1046		1216
1047	static void	1217	static void
1048	t2_cb (EV_P_ struct ev_timer *w, int revents)	1218	t2_cb (EV_P_ ev_timer *w, int revents)
1049	{	1219	{
1050	struct my_biggy big = (struct my_biggy *	1220	struct my_biggy big = (struct my_biggy *)
1051	(((char *)w) - offsetof (struct my_biggy, t2));	1221	(((char *)w) - offsetof (struct my_biggy, t2));
1052	}	1222	}
		1223
		1224	=head2 WATCHER PRIORITY MODELS
		1225
		1226	Many event loops support I<watcher priorities>, which are usually small
		1227	integers that influence the ordering of event callback invocation
		1228	between watchers in some way, all else being equal.
		1229
		1230	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1231	description for the more technical details such as the actual priority
		1232	range.
		1233
		1234	There are two common ways how these these priorities are being interpreted
		1235	by event loops:
		1236
		1237	In the more common lock-out model, higher priorities "lock out" invocation
		1238	of lower priority watchers, which means as long as higher priority
		1239	watchers receive events, lower priority watchers are not being invoked.
		1240
		1241	The less common only-for-ordering model uses priorities solely to order
		1242	callback invocation within a single event loop iteration: Higher priority
		1243	watchers are invoked before lower priority ones, but they all get invoked
		1244	before polling for new events.
		1245
		1246	Libev uses the second (only-for-ordering) model for all its watchers
		1247	except for idle watchers (which use the lock-out model).
		1248
		1249	The rationale behind this is that implementing the lock-out model for
		1250	watchers is not well supported by most kernel interfaces, and most event
		1251	libraries will just poll for the same events again and again as long as
		1252	their callbacks have not been executed, which is very inefficient in the
		1253	common case of one high-priority watcher locking out a mass of lower
		1254	priority ones.
		1255
		1256	Static (ordering) priorities are most useful when you have two or more
		1257	watchers handling the same resource: a typical usage example is having an
		1258	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1259	timeouts. Under load, data might be received while the program handles
		1260	other jobs, but since timers normally get invoked first, the timeout
		1261	handler will be executed before checking for data. In that case, giving
		1262	the timer a lower priority than the I/O watcher ensures that I/O will be
		1263	handled first even under adverse conditions (which is usually, but not
		1264	always, what you want).
		1265
		1266	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1267	will only be executed when no same or higher priority watchers have
		1268	received events, they can be used to implement the "lock-out" model when
		1269	required.
		1270
		1271	For example, to emulate how many other event libraries handle priorities,
		1272	you can associate an C<ev_idle> watcher to each such watcher, and in
		1273	the normal watcher callback, you just start the idle watcher. The real
		1274	processing is done in the idle watcher callback. This causes libev to
		1275	continously poll and process kernel event data for the watcher, but when
		1276	the lock-out case is known to be rare (which in turn is rare :), this is
		1277	workable.
		1278
		1279	Usually, however, the lock-out model implemented that way will perform
		1280	miserably under the type of load it was designed to handle. In that case,
		1281	it might be preferable to stop the real watcher before starting the
		1282	idle watcher, so the kernel will not have to process the event in case
		1283	the actual processing will be delayed for considerable time.
		1284
		1285	Here is an example of an I/O watcher that should run at a strictly lower
		1286	priority than the default, and which should only process data when no
		1287	other events are pending:
		1288
		1289	ev_idle idle; // actual processing watcher
		1290	ev_io io; // actual event watcher
		1291
		1292	static void
		1293	io_cb (EV_P_ ev_io *w, int revents)
		1294	{
		1295	// stop the I/O watcher, we received the event, but
		1296	// are not yet ready to handle it.
		1297	ev_io_stop (EV_A_ w);
		1298
		1299	// start the idle watcher to ahndle the actual event.
		1300	// it will not be executed as long as other watchers
		1301	// with the default priority are receiving events.
		1302	ev_idle_start (EV_A_ &idle);
		1303	}
		1304
		1305	static void
		1306	idle_cb (EV_P_ ev_idle *w, int revents)
		1307	{
		1308	// actual processing
		1309	read (STDIN_FILENO, ...);
		1310
		1311	// have to start the I/O watcher again, as
		1312	// we have handled the event
		1313	ev_io_start (EV_P_ &io);
		1314	}
		1315
		1316	// initialisation
		1317	ev_idle_init (&idle, idle_cb);
		1318	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1319	ev_io_start (EV_DEFAULT_ &io);
		1320
		1321	In the "real" world, it might also be beneficial to start a timer, so that
		1322	low-priority connections can not be locked out forever under load. This
		1323	enables your program to keep a lower latency for important connections
		1324	during short periods of high load, while not completely locking out less
		1325	important ones.
1053		1326
1054		1327
1055	=head1 WATCHER TYPES	1328	=head1 WATCHER TYPES
1056		1329
1057	This section describes each watcher in detail, but will not repeat	1330	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	1354	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	1355	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	1356	descriptors to non-blocking mode is also usually a good idea (but not
1084	required if you know what you are doing).	1357	required if you know what you are doing).
1085		1358
1086	If you must do this, then force the use of a known-to-be-good backend	1359	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	1360	known-to-be-good backend (at the time of this writing, this includes only
1088	C<EVBACKEND_POLL>).	1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1362	descriptors for which non-blocking operation makes no sense (such as
		1363	files) - libev doesn't guarentee any specific behaviour in that case.
1089		1364
1090	Another thing you have to watch out for is that it is quite easy to	1365	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	1366	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	1367	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	1368	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	1369	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	1370	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	1371	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.	1372	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1098		1373
1099	If you cannot run the fd in non-blocking mode (for example you should not	1374	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	1375	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	1376	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	1377	interface such as poll (fortunately in our Xlib example, Xlib already
1103	its own, so its quite safe to use).	1378	does this on its own, so its quite safe to use). Some people additionally
		1379	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1380	indefinitely.
		1381
		1382	But really, best use non-blocking mode.
1104		1383
1105	=head3 The special problem of disappearing file descriptors	1384	=head3 The special problem of disappearing file descriptors
1106		1385
1107	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1386	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,	1387	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	1388	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	1389	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	1390	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	1391	registered with libev, there is no efficient way to see that this is, in
1113	fact, a different file descriptor.	1392	fact, a different file descriptor.
1114		1393
…		…
1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1424	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1146	C<EVBACKEND_POLL>.	1425	C<EVBACKEND_POLL>.
1147		1426
1148	=head3 The special problem of SIGPIPE	1427	=head3 The special problem of SIGPIPE
1149		1428
1150	While not really specific to libev, it is easy to forget about SIGPIPE:	1429	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	1430	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	1431	sent a SIGPIPE, which, by default, aborts your program. For most programs
1153	this is sensible behaviour, for daemons, this is usually undesirable.	1432	this is sensible behaviour, for daemons, this is usually undesirable.
1154		1433
1155	So when you encounter spurious, unexplained daemon exits, make sure you	1434	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	1435	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).	1436	somewhere, as that would have given you a big clue).
…		…
1164	=item ev_io_init (ev_io *, callback, int fd, int events)	1443	=item ev_io_init (ev_io *, callback, int fd, int events)
1165		1444
1166	=item ev_io_set (ev_io *, int fd, int events)	1445	=item ev_io_set (ev_io *, int fd, int events)
1167		1446
1168	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1447	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	1448	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.	1449	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1171		1450
1172	=item int fd [read-only]	1451	=item int fd [read-only]
1173		1452
1174	The file descriptor being watched.	1453	The file descriptor being watched.
1175		1454
…		…
1184	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1463	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	1464	readable, but only once. Since it is likely line-buffered, you could
1186	attempt to read a whole line in the callback.	1465	attempt to read a whole line in the callback.
1187		1466
1188	static void	1467	static void
1189	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1468	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1190	{	1469	{
1191	ev_io_stop (loop, w);	1470	ev_io_stop (loop, w);
1192	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1471	.. read from stdin here (or from w->fd) and handle any I/O errors
1193	}	1472	}
1194		1473
1195	...	1474	...
1196	struct ev_loop *loop = ev_default_init (0);	1475	struct ev_loop *loop = ev_default_init (0);
1197	struct ev_io stdin_readable;	1476	ev_io stdin_readable;
1198	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1199	ev_io_start (loop, &stdin_readable);	1478	ev_io_start (loop, &stdin_readable);
1200	ev_loop (loop, 0);	1479	ev_loop (loop, 0);
1201		1480
1202		1481
…		…
1205	Timer watchers are simple relative timers that generate an event after a	1484	Timer watchers are simple relative timers that generate an event after a
1206	given time, and optionally repeating in regular intervals after that.	1485	given time, and optionally repeating in regular intervals after that.
1207		1486
1208	The timers are based on real time, that is, if you register an event that	1487	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	1488	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	1489	year, it will still time out after (roughly) one hour. "Roughly" because
1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1212	monotonic clock option helps a lot here).	1491	monotonic clock option helps a lot here).
1213		1492
1214	The callback is guaranteed to be invoked only after its timeout has passed,	1493	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	1494	passed (not I<at>, so on systems with very low-resolution clocks this
1216	order of execution is undefined.	1495	might introduce a small delay). If multiple timers become ready during the
		1496	same loop iteration then the ones with earlier time-out values are invoked
		1497	before ones of the same priority with later time-out values (but this is
		1498	no longer true when a callback calls C<ev_loop> recursively).
		1499
		1500	=head3 Be smart about timeouts
		1501
		1502	Many real-world problems involve some kind of timeout, usually for error
		1503	recovery. A typical example is an HTTP request - if the other side hangs,
		1504	you want to raise some error after a while.
		1505
		1506	What follows are some ways to handle this problem, from obvious and
		1507	inefficient to smart and efficient.
		1508
		1509	In the following, a 60 second activity timeout is assumed - a timeout that
		1510	gets reset to 60 seconds each time there is activity (e.g. each time some
		1511	data or other life sign was received).
		1512
		1513	=over 4
		1514
		1515	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1516
		1517	This is the most obvious, but not the most simple way: In the beginning,
		1518	start the watcher:
		1519
		1520	ev_timer_init (timer, callback, 60., 0.);
		1521	ev_timer_start (loop, timer);
		1522
		1523	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1524	and start it again:
		1525
		1526	ev_timer_stop (loop, timer);
		1527	ev_timer_set (timer, 60., 0.);
		1528	ev_timer_start (loop, timer);
		1529
		1530	This is relatively simple to implement, but means that each time there is
		1531	some activity, libev will first have to remove the timer from its internal
		1532	data structure and then add it again. Libev tries to be fast, but it's
		1533	still not a constant-time operation.
		1534
		1535	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1536
		1537	This is the easiest way, and involves using C<ev_timer_again> instead of
		1538	C<ev_timer_start>.
		1539
		1540	To implement this, configure an C<ev_timer> with a C<repeat> value
		1541	of C<60> and then call C<ev_timer_again> at start and each time you
		1542	successfully read or write some data. If you go into an idle state where
		1543	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1544	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1545
		1546	That means you can ignore both the C<ev_timer_start> function and the
		1547	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1548	member and C<ev_timer_again>.
		1549
		1550	At start:
		1551
		1552	ev_init (timer, callback);
		1553	timer->repeat = 60.;
		1554	ev_timer_again (loop, timer);
		1555
		1556	Each time there is some activity:
		1557
		1558	ev_timer_again (loop, timer);
		1559
		1560	It is even possible to change the time-out on the fly, regardless of
		1561	whether the watcher is active or not:
		1562
		1563	timer->repeat = 30.;
		1564	ev_timer_again (loop, timer);
		1565
		1566	This is slightly more efficient then stopping/starting the timer each time
		1567	you want to modify its timeout value, as libev does not have to completely
		1568	remove and re-insert the timer from/into its internal data structure.
		1569
		1570	It is, however, even simpler than the "obvious" way to do it.
		1571
		1572	=item 3. Let the timer time out, but then re-arm it as required.
		1573
		1574	This method is more tricky, but usually most efficient: Most timeouts are
		1575	relatively long compared to the intervals between other activity - in
		1576	our example, within 60 seconds, there are usually many I/O events with
		1577	associated activity resets.
		1578
		1579	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1580	but remember the time of last activity, and check for a real timeout only
		1581	within the callback:
		1582
		1583	ev_tstamp last_activity; // time of last activity
		1584
		1585	static void
		1586	callback (EV_P_ ev_timer *w, int revents)
		1587	{
		1588	ev_tstamp now = ev_now (EV_A);
		1589	ev_tstamp timeout = last_activity + 60.;
		1590
		1591	// if last_activity + 60. is older than now, we did time out
		1592	if (timeout < now)
		1593	{
		1594	// timeout occured, take action
		1595	}
		1596	else
		1597	{
		1598	// callback was invoked, but there was some activity, re-arm
		1599	// the watcher to fire in last_activity + 60, which is
		1600	// guaranteed to be in the future, so "again" is positive:
		1601	w->repeat = timeout - now;
		1602	ev_timer_again (EV_A_ w);
		1603	}
		1604	}
		1605
		1606	To summarise the callback: first calculate the real timeout (defined
		1607	as "60 seconds after the last activity"), then check if that time has
		1608	been reached, which means something I<did>, in fact, time out. Otherwise
		1609	the callback was invoked too early (C<timeout> is in the future), so
		1610	re-schedule the timer to fire at that future time, to see if maybe we have
		1611	a timeout then.
		1612
		1613	Note how C<ev_timer_again> is used, taking advantage of the
		1614	C<ev_timer_again> optimisation when the timer is already running.
		1615
		1616	This scheme causes more callback invocations (about one every 60 seconds
		1617	minus half the average time between activity), but virtually no calls to
		1618	libev to change the timeout.
		1619
		1620	To start the timer, simply initialise the watcher and set C<last_activity>
		1621	to the current time (meaning we just have some activity :), then call the
		1622	callback, which will "do the right thing" and start the timer:
		1623
		1624	ev_init (timer, callback);
		1625	last_activity = ev_now (loop);
		1626	callback (loop, timer, EV_TIMEOUT);
		1627
		1628	And when there is some activity, simply store the current time in
		1629	C<last_activity>, no libev calls at all:
		1630
		1631	last_actiivty = ev_now (loop);
		1632
		1633	This technique is slightly more complex, but in most cases where the
		1634	time-out is unlikely to be triggered, much more efficient.
		1635
		1636	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1637	callback :) - just change the timeout and invoke the callback, which will
		1638	fix things for you.
		1639
		1640	=item 4. Wee, just use a double-linked list for your timeouts.
		1641
		1642	If there is not one request, but many thousands (millions...), all
		1643	employing some kind of timeout with the same timeout value, then one can
		1644	do even better:
		1645
		1646	When starting the timeout, calculate the timeout value and put the timeout
		1647	at the I<end> of the list.
		1648
		1649	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1650	the list is expected to fire (for example, using the technique #3).
		1651
		1652	When there is some activity, remove the timer from the list, recalculate
		1653	the timeout, append it to the end of the list again, and make sure to
		1654	update the C<ev_timer> if it was taken from the beginning of the list.
		1655
		1656	This way, one can manage an unlimited number of timeouts in O(1) time for
		1657	starting, stopping and updating the timers, at the expense of a major
		1658	complication, and having to use a constant timeout. The constant timeout
		1659	ensures that the list stays sorted.
		1660
		1661	=back
		1662
		1663	So which method the best?
		1664
		1665	Method #2 is a simple no-brain-required solution that is adequate in most
		1666	situations. Method #3 requires a bit more thinking, but handles many cases
		1667	better, and isn't very complicated either. In most case, choosing either
		1668	one is fine, with #3 being better in typical situations.
		1669
		1670	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1671	rather complicated, but extremely efficient, something that really pays
		1672	off after the first million or so of active timers, i.e. it's usually
		1673	overkill :)
1217		1674
1218	=head3 The special problem of time updates	1675	=head3 The special problem of time updates
1219		1676
1220	Establishing the current time is a costly operation (it usually takes at	1677	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	1678	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	1679	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	1680	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1224	lots of events.	1681	lots of events in one iteration.
1225		1682
1226	The relative timeouts are calculated relative to the C<ev_now ()>	1683	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	1684	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	1685	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	1686	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).	1722	If the timer is started but non-repeating, stop it (as if it timed out).
1266		1723
1267	If the timer is repeating, either start it if necessary (with the	1724	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.	1725	C<repeat> value), or reset the running timer to the C<repeat> value.
1269		1726
1270	This sounds a bit complicated, but here is a useful and typical	1727	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	1728	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		1729
1295	=item ev_tstamp repeat [read-write]	1730	=item ev_tstamp repeat [read-write]
1296		1731
1297	The current C<repeat> value. Will be used each time the watcher times out	1732	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),	1733	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.	1734	which is also when any modifications are taken into account.
1300		1735
1301	=back	1736	=back
1302		1737
1303	=head3 Examples	1738	=head3 Examples
1304		1739
1305	Example: Create a timer that fires after 60 seconds.	1740	Example: Create a timer that fires after 60 seconds.
1306		1741
1307	static void	1742	static void
1308	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1743	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1309	{	1744	{
1310	.. one minute over, w is actually stopped right here	1745	.. one minute over, w is actually stopped right here
1311	}	1746	}
1312		1747
1313	struct ev_timer mytimer;	1748	ev_timer mytimer;
1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1749	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1315	ev_timer_start (loop, &mytimer);	1750	ev_timer_start (loop, &mytimer);
1316		1751
1317	Example: Create a timeout timer that times out after 10 seconds of	1752	Example: Create a timeout timer that times out after 10 seconds of
1318	inactivity.	1753	inactivity.
1319		1754
1320	static void	1755	static void
1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1756	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1322	{	1757	{
1323	.. ten seconds without any activity	1758	.. ten seconds without any activity
1324	}	1759	}
1325		1760
1326	struct ev_timer mytimer;	1761	ev_timer mytimer;
1327	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1328	ev_timer_again (&mytimer); /* start timer */	1763	ev_timer_again (&mytimer); /* start timer */
1329	ev_loop (loop, 0);	1764	ev_loop (loop, 0);
1330		1765
1331	// and in some piece of code that gets executed on any "activity":	1766	// and in some piece of code that gets executed on any "activity":
…		…
1336	=head2 C<ev_periodic> - to cron or not to cron?	1771	=head2 C<ev_periodic> - to cron or not to cron?
1337		1772
1338	Periodic watchers are also timers of a kind, but they are very versatile	1773	Periodic watchers are also timers of a kind, but they are very versatile
1339	(and unfortunately a bit complex).	1774	(and unfortunately a bit complex).
1340		1775
1341	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1776	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	1777	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	1778	(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 ()	1779	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	1780	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	1781	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		1782
		1783	You can tell a periodic watcher to trigger after some specific point
		1784	in time: for example, if you tell a periodic watcher to trigger "in 10
		1785	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1786	not a delay) and then reset your system clock to January of the previous
		1787	year, then it will take a year or more to trigger the event (unlike an
		1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1789	it, as it uses a relative timeout).
		1790
1350	C<ev_periodic>s can also be used to implement vastly more complex timers,	1791	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	1792	timers, such as triggering an event on each "midnight, local time", or
1352	complicated, rules.	1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1794	those cannot react to time jumps.
1353		1795
1354	As with timers, the callback is guaranteed to be invoked only when the	1796	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	1797	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.	1798	timers become ready during the same loop iteration then the ones with
		1799	earlier time-out values are invoked before ones with later time-out values
		1800	(but this is no longer true when a callback calls C<ev_loop> recursively).
1357		1801
1358	=head3 Watcher-Specific Functions and Data Members	1802	=head3 Watcher-Specific Functions and Data Members
1359		1803
1360	=over 4	1804	=over 4
1361		1805
1362	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1806	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1363		1807
1364	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1808	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1365		1809
1366	Lots of arguments, lets sort it out... There are basically three modes of	1810	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:	1811	operation, and we will explain them from simplest to most complex:
1368		1812
1369	=over 4	1813	=over 4
1370		1814
1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1815	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1372		1816
1373	In this configuration the watcher triggers an event after the wall clock	1817	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	1818	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	1819	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.	1820	will be stopped and invoked when the system clock reaches or surpasses
		1821	this point in time.
1377		1822
1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1823	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1379		1824
1380	In this mode the watcher will always be scheduled to time out at the next	1825	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)	1826	C<offset + N * interval> time (for some integer N, which can also be
1382	and then repeat, regardless of any time jumps.	1827	negative) and then repeat, regardless of any time jumps. The C<offset>
		1828	argument is merely an offset into the C<interval> periods.
1383		1829
1384	This can be used to create timers that do not drift with respect to system	1830	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	1831	system clock, for example, here is an C<ev_periodic> that triggers each
1386	the hour:	1832	hour, on the hour (with respect to UTC):
1387		1833
1388	ev_periodic_set (&periodic, 0., 3600., 0);	1834	ev_periodic_set (&periodic, 0., 3600., 0);
1389		1835
1390	This doesn't mean there will always be 3600 seconds in between triggers,	1836	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	1837	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	1838	full hour (UTC), or more correctly, when the system time is evenly divisible
1393	by 3600.	1839	by 3600.
1394		1840
1395	Another way to think about it (for the mathematically inclined) is that	1841	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	1842	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.	1843	time where C<time = offset (mod interval)>, regardless of any time jumps.
1398		1844
1399	For numerical stability it is preferable that the C<at> value is near	1845	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	1846	C<ev_now ()> (the current time), but there is no range requirement for
1401	this value, and in fact is often specified as zero.	1847	this value, and in fact is often specified as zero.
1402		1848
1403	Note also that there is an upper limit to how often a timer can fire (CPU	1849	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	1850	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	1851	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).	1852	millisecond (if the OS supports it and the machine is fast enough).
1407		1853
1408	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1854	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1409		1855
1410	In this mode the values for C<interval> and C<at> are both being	1856	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	1857	ignored. Instead, each time the periodic watcher gets scheduled, the
1412	reschedule callback will be called with the watcher as first, and the	1858	reschedule callback will be called with the watcher as first, and the
1413	current time as second argument.	1859	current time as second argument.
1414		1860
1415	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1861	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1416	ever, or make ANY event loop modifications whatsoever>.	1862	or make ANY other event loop modifications whatsoever, unless explicitly
		1863	allowed by documentation here>.
1417		1864
1418	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1865	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	1866	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1420	only event loop modification you are allowed to do).	1867	only event loop modification you are allowed to do).
1421		1868
1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1869	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1423	*w, ev_tstamp now)>, e.g.:	1870	*w, ev_tstamp now)>, e.g.:
1424		1871
		1872	static ev_tstamp
1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1873	my_rescheduler (ev_periodic *w, ev_tstamp now)
1426	{	1874	{
1427	return now + 60.;	1875	return now + 60.;
1428	}	1876	}
1429		1877
1430	It must return the next time to trigger, based on the passed time value	1878	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	1898	a different time than the last time it was called (e.g. in a crond like
1451	program when the crontabs have changed).	1899	program when the crontabs have changed).
1452		1900
1453	=item ev_tstamp ev_periodic_at (ev_periodic *)	1901	=item ev_tstamp ev_periodic_at (ev_periodic *)
1454		1902
1455	When active, returns the absolute time that the watcher is supposed to	1903	When active, returns the absolute time that the watcher is supposed
1456	trigger next.	1904	to trigger next. This is not the same as the C<offset> argument to
		1905	C<ev_periodic_set>, but indeed works even in interval and manual
		1906	rescheduling modes.
1457		1907
1458	=item ev_tstamp offset [read-write]	1908	=item ev_tstamp offset [read-write]
1459		1909
1460	When repeating, this contains the offset value, otherwise this is the	1910	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>).	1911	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1912	although libev might modify this value for better numerical stability).
1462		1913
1463	Can be modified any time, but changes only take effect when the periodic	1914	Can be modified any time, but changes only take effect when the periodic
1464	timer fires or C<ev_periodic_again> is being called.	1915	timer fires or C<ev_periodic_again> is being called.
1465		1916
1466	=item ev_tstamp interval [read-write]	1917	=item ev_tstamp interval [read-write]
1467		1918
1468	The current interval value. Can be modified any time, but changes only	1919	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	1920	take effect when the periodic timer fires or C<ev_periodic_again> is being
1470	called.	1921	called.
1471		1922
1472	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1923	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1473		1924
1474	The current reschedule callback, or C<0>, if this functionality is	1925	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	1926	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.	1927	the periodic timer fires or C<ev_periodic_again> is being called.
1477		1928
1478	=back	1929	=back
1479		1930
1480	=head3 Examples	1931	=head3 Examples
1481		1932
1482	Example: Call a callback every hour, or, more precisely, whenever the	1933	Example: Call a callback every hour, or, more precisely, whenever the
1483	system clock is divisible by 3600. The callback invocation times have	1934	system time is divisible by 3600. The callback invocation times have
1484	potentially a lot of jitter, but good long-term stability.	1935	potentially a lot of jitter, but good long-term stability.
1485		1936
1486	static void	1937	static void
1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1488	{	1939	{
1489	... its now a full hour (UTC, or TAI or whatever your clock follows)	1940	... its now a full hour (UTC, or TAI or whatever your clock follows)
1490	}	1941	}
1491		1942
1492	struct ev_periodic hourly_tick;	1943	ev_periodic hourly_tick;
1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1944	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1494	ev_periodic_start (loop, &hourly_tick);	1945	ev_periodic_start (loop, &hourly_tick);
1495		1946
1496	Example: The same as above, but use a reschedule callback to do it:	1947	Example: The same as above, but use a reschedule callback to do it:
1497		1948
1498	#include <math.h>	1949	#include <math.h>
1499		1950
1500	static ev_tstamp	1951	static ev_tstamp
1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1952	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1502	{	1953	{
1503	return fmod (now, 3600.) + 3600.;	1954	return now + (3600. - fmod (now, 3600.));
1504	}	1955	}
1505		1956
1506	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1957	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1507		1958
1508	Example: Call a callback every hour, starting now:	1959	Example: Call a callback every hour, starting now:
1509		1960
1510	struct ev_periodic hourly_tick;	1961	ev_periodic hourly_tick;
1511	ev_periodic_init (&hourly_tick, clock_cb,	1962	ev_periodic_init (&hourly_tick, clock_cb,
1512	fmod (ev_now (loop), 3600.), 3600., 0);	1963	fmod (ev_now (loop), 3600.), 3600., 0);
1513	ev_periodic_start (loop, &hourly_tick);	1964	ev_periodic_start (loop, &hourly_tick);
1514		1965
1515		1966
…		…
1518	Signal watchers will trigger an event when the process receives a specific	1969	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	1970	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	1971	will try it's best to deliver signals synchronously, i.e. as part of the
1521	normal event processing, like any other event.	1972	normal event processing, like any other event.
1522		1973
		1974	If you want signals asynchronously, just use C<sigaction> as you would
		1975	do without libev and forget about sharing the signal. You can even use
		1976	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1977
1523	You can configure as many watchers as you like per signal. Only when the	1978	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	1979	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	1980	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	1981	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	1982	the last signal watcher for a signal is stopped, libev will reset the
1528	SIG_DFL (regardless of what it was set to before).	1983	signal handler to SIG_DFL (regardless of what it was set to before).
1529		1984
1530	If possible and supported, libev will install its handlers with	1985	If possible and supported, libev will install its handlers with
1531	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1986	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	1987	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	1988	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1550		2005
1551	=back	2006	=back
1552		2007
1553	=head3 Examples	2008	=head3 Examples
1554		2009
1555	Example: Try to exit cleanly on SIGINT and SIGTERM.	2010	Example: Try to exit cleanly on SIGINT.
1556		2011
1557	static void	2012	static void
1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1559	{	2014	{
1560	ev_unloop (loop, EVUNLOOP_ALL);	2015	ev_unloop (loop, EVUNLOOP_ALL);
1561	}	2016	}
1562		2017
1563	struct ev_signal signal_watcher;	2018	ev_signal signal_watcher;
1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1565	ev_signal_start (loop, &sigint_cb);	2020	ev_signal_start (loop, &signal_watcher);
1566		2021
1567		2022
1568	=head2 C<ev_child> - watch out for process status changes	2023	=head2 C<ev_child> - watch out for process status changes
1569		2024
1570	Child watchers trigger when your process receives a SIGCHLD in response to	2025	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	2026	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	2027	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	2028	has been forked (which implies it might have already exited), as long
1574	loop isn't entered (or is continued from a watcher).	2029	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2030	forking and then immediately registering a watcher for the child is fine,
		2031	but forking and registering a watcher a few event loop iterations later or
		2032	in the next callback invocation is not.
1575		2033
1576	Only the default event loop is capable of handling signals, and therefore	2034	Only the default event loop is capable of handling signals, and therefore
1577	you can only register child watchers in the default event loop.	2035	you can only register child watchers in the default event loop.
		2036
		2037	Due to some design glitches inside libev, child watchers will always be
		2038	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2039	libev)
1578		2040
1579	=head3 Process Interaction	2041	=head3 Process Interaction
1580		2042
1581	Libev grabs C<SIGCHLD> as soon as the default event loop is	2043	Libev grabs C<SIGCHLD> as soon as the default event loop is
1582	initialised. This is necessary to guarantee proper behaviour even if	2044	initialised. This is necessary to guarantee proper behaviour even if
…		…
1640	its completion.	2102	its completion.
1641		2103
1642	ev_child cw;	2104	ev_child cw;
1643		2105
1644	static void	2106	static void
1645	child_cb (EV_P_ struct ev_child *w, int revents)	2107	child_cb (EV_P_ ev_child *w, int revents)
1646	{	2108	{
1647	ev_child_stop (EV_A_ w);	2109	ev_child_stop (EV_A_ w);
1648	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2110	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1649	}	2111	}
1650		2112
…		…
1665		2127
1666		2128
1667	=head2 C<ev_stat> - did the file attributes just change?	2129	=head2 C<ev_stat> - did the file attributes just change?
1668		2130
1669	This watches a file system path for attribute changes. That is, it calls	2131	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	2132	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.	2133	and sees if it changed compared to the last time, invoking the callback if
		2134	it did.
1672		2135
1673	The path does not need to exist: changing from "path exists" to "path does	2136	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	2137	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	2138	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	2139	C<st_nlink> field being zero (which is otherwise always forced to be at
1677	the stat buffer having unspecified contents.	2140	least one) and all the other fields of the stat buffer having unspecified
		2141	contents.
1678		2142
1679	The path I<should> be absolute and I<must not> end in a slash. If it is	2143	The path I<must not> end in a slash or contain special components such as
		2144	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.	2145	your working directory changes, then the behaviour is undefined.
1681		2146
1682	Since there is no standard to do this, the portable implementation simply	2147	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	2148	portable implementation simply calls C<stat(2)> regularly on the path
1684	can specify a recommended polling interval for this case. If you specify	2149	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,	2150	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	2151	recommended!) then a I<suitable, unspecified default> value will be used
1687	five seconds, although this might change dynamically). Libev will also	2152	(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	2153	change dynamically). Libev will also impose a minimum interval which is
1689	usually overkill.	2154	currently around C<0.1>, but that's usually overkill.
1690		2155
1691	This watcher type is not meant for massive numbers of stat watchers,	2156	This watcher type is not meant for massive numbers of stat watchers,
1692	as even with OS-supported change notifications, this can be	2157	as even with OS-supported change notifications, this can be
1693	resource-intensive.	2158	resource-intensive.
1694		2159
1695	At the time of this writing, only the Linux inotify interface is	2160	At the time of this writing, the only OS-specific interface implemented
1696	implemented (implementing kqueue support is left as an exercise for the	2161	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	2162	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	2163	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		2164
1704	=head3 ABI Issues (Largefile Support)	2165	=head3 ABI Issues (Largefile Support)
1705		2166
1706	Libev by default (unless the user overrides this) uses the default	2167	Libev by default (unless the user overrides this) uses the default
1707	compilation environment, which means that on systems with large file	2168	compilation environment, which means that on systems with large file
1708	support disabled by default, you get the 32 bit version of the stat	2169	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	2170	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	2171	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	2172	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	2173	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.	2174	most noticeably displayed with ev_stat and large file support.
1714		2175
1715	The solution for this is to lobby your distribution maker to make large	2176	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	2177	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	2178	optional. Libev cannot simply switch on large file support because it has
1718	to exchange stat structures with application programs compiled using the	2179	to exchange stat structures with application programs compiled using the
1719	default compilation environment.	2180	default compilation environment.
1720		2181
1721	=head3 Inotify	2182	=head3 Inotify and Kqueue
1722		2183
1723	When C<inotify (7)> support has been compiled into libev (generally only	2184	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	2185	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	2186	inotify descriptor will be created lazily when the first C<ev_stat>
1726	when the first C<ev_stat> watcher is being started.	2187	watcher is being started.
1727		2188
1728	Inotify presence does not change the semantics of C<ev_stat> watchers	2189	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	2190	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	2191	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.	2192	there are many cases where libev has to resort to regular C<stat> polling,
		2193	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2194	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2195	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2196	xfs are fully working) libev usually gets away without polling.
1732		2197
1733	(There is no support for kqueue, as apparently it cannot be used to	2198	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	2199	implement this functionality, due to the requirement of having a file
1735	descriptor open on the object at all times).	2200	descriptor open on the object at all times, and detecting renames, unlinks
		2201	etc. is difficult.
		2202
		2203	=head3 C<stat ()> is a synchronous operation
		2204
		2205	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2206	the process. The exception are C<ev_stat> watchers - those call C<stat
		2207	()>, which is a synchronous operation.
		2208
		2209	For local paths, this usually doesn't matter: unless the system is very
		2210	busy or the intervals between stat's are large, a stat call will be fast,
		2211	as the path data is usually in memory already (except when starting the
		2212	watcher).
		2213
		2214	For networked file systems, calling C<stat ()> can block an indefinite
		2215	time due to network issues, and even under good conditions, a stat call
		2216	often takes multiple milliseconds.
		2217
		2218	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2219	paths, although this is fully supported by libev.
1736		2220
1737	=head3 The special problem of stat time resolution	2221	=head3 The special problem of stat time resolution
1738		2222
1739	The C<stat ()> system call only supports full-second resolution portably, and	2223	The C<stat ()> system call only supports full-second resolution portably,
1740	even on systems where the resolution is higher, many file systems still	2224	and even on systems where the resolution is higher, most file systems
1741	only support whole seconds.	2225	still only support whole seconds.
1742		2226
1743	That means that, if the time is the only thing that changes, you can	2227	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	2228	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	2229	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	2230	within the same second, C<ev_stat> will be unable to detect unless the
1747	data does not change.	2231	stat data does change in other ways (e.g. file size).
1748		2232
1749	The solution to this is to delay acting on a change for slightly more	2233	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	2234	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);	2235	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1752	ev_timer_again (loop, w)>).	2236	ev_timer_again (loop, w)>).
…		…
1772	C<path>. The C<interval> is a hint on how quickly a change is expected to	2256	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	2257	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	2258	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.	2259	path for as long as the watcher is active.
1776		2260
1777	The callback will receive C<EV_STAT> when a change was detected, relative	2261	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	2262	relative to the attributes at the time the watcher was started (or the
1779	was detected).	2263	last change was detected).
1780		2264
1781	=item ev_stat_stat (loop, ev_stat *)	2265	=item ev_stat_stat (loop, ev_stat *)
1782		2266
1783	Updates the stat buffer immediately with new values. If you change the	2267	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	2268	watched path in your callback, you could call this function to avoid
…		…
1867		2351
1868		2352
1869	=head2 C<ev_idle> - when you've got nothing better to do...	2353	=head2 C<ev_idle> - when you've got nothing better to do...
1870		2354
1871	Idle watchers trigger events when no other events of the same or higher	2355	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	2356	priority are pending (prepare, check and other idle watchers do not count
1873	count).	2357	as receiving "events").
1874		2358
1875	That is, as long as your process is busy handling sockets or timeouts	2359	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	2360	(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	2361	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	2362	are pending), the idle watchers are being called once per event loop
…		…
1889		2373
1890	=head3 Watcher-Specific Functions and Data Members	2374	=head3 Watcher-Specific Functions and Data Members
1891		2375
1892	=over 4	2376	=over 4
1893		2377
1894	=item ev_idle_init (ev_signal *, callback)	2378	=item ev_idle_init (ev_idle *, callback)
1895		2379
1896	Initialises and configures the idle watcher - it has no parameters of any	2380	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,	2381	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1898	believe me.	2382	believe me.
1899		2383
…		…
1903		2387
1904	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2388	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1905	callback, free it. Also, use no error checking, as usual.	2389	callback, free it. Also, use no error checking, as usual.
1906		2390
1907	static void	2391	static void
1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2392	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1909	{	2393	{
1910	free (w);	2394	free (w);
1911	// now do something you wanted to do when the program has	2395	// now do something you wanted to do when the program has
1912	// no longer anything immediate to do.	2396	// no longer anything immediate to do.
1913	}	2397	}
1914		2398
1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2399	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1916	ev_idle_init (idle_watcher, idle_cb);	2400	ev_idle_init (idle_watcher, idle_cb);
1917	ev_idle_start (loop, idle_cb);	2401	ev_idle_start (loop, idle_watcher);
1918		2402
1919		2403
1920	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2404	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1921		2405
1922	Prepare and check watchers are usually (but not always) used in tandem:	2406	Prepare and check watchers are usually (but not always) used in pairs:
1923	prepare watchers get invoked before the process blocks and check watchers	2407	prepare watchers get invoked before the process blocks and check watchers
1924	afterwards.	2408	afterwards.
1925		2409
1926	You I<must not> call C<ev_loop> or similar functions that enter	2410	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>	2411	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,	2414	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	2415	C<ev_check> so if you have one watcher of each kind they will always be
1932	called in pairs bracketing the blocking call.	2416	called in pairs bracketing the blocking call.
1933		2417
1934	Their main purpose is to integrate other event mechanisms into libev and	2418	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	2419	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	2420	variable changes, implement your own watchers, integrate net-snmp or a
1937	coroutine library and lots more. They are also occasionally useful if	2421	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,	2422	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>	2423	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1940	watcher).	2424	watcher).
1941		2425
1942	This is done by examining in each prepare call which file descriptors need	2426	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	2427	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	2428	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	2429	libraries provide exactly this functionality). Then, in the check watcher,
1946	any events that occurred (by checking the pending status of all watchers	2430	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	2431	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,	2432	I/O and timer callbacks will never actually be called (but must be valid
1949	because you never know, you know?).	2433	nevertheless, because you never know, you know?).
1950		2434
1951	As another example, the Perl Coro module uses these hooks to integrate	2435	As another example, the Perl Coro module uses these hooks to integrate
1952	coroutines into libev programs, by yielding to other active coroutines	2436	coroutines into libev programs, by yielding to other active coroutines
1953	during each prepare and only letting the process block if no coroutines	2437	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	2438	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	2441	loop from blocking if lower-priority coroutines are active, thus mapping
1958	low-priority coroutines to idle/background tasks).	2442	low-priority coroutines to idle/background tasks).
1959		2443
1960	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2444	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	2445	priority, to ensure that they are being run before any other watchers
		2446	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2447
1962	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2448	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	2449	activate ("feed") events into libev. While libev fully supports this, they
1964	supports this, they might get executed before other C<ev_check> watchers	2450	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	2451	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	2452	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	2453	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1968	coexist peacefully with others).	2454	others).
1969		2455
1970	=head3 Watcher-Specific Functions and Data Members	2456	=head3 Watcher-Specific Functions and Data Members
1971		2457
1972	=over 4	2458	=over 4
1973		2459
…		…
1975		2461
1976	=item ev_check_init (ev_check *, callback)	2462	=item ev_check_init (ev_check *, callback)
1977		2463
1978	Initialises and configures the prepare or check watcher - they have no	2464	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>	2465	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.	2466	macros, but using them is utterly, utterly, utterly and completely
		2467	pointless.
1981		2468
1982	=back	2469	=back
1983		2470
1984	=head3 Examples	2471	=head3 Examples
1985		2472
…		…
1998		2485
1999	static ev_io iow [nfd];	2486	static ev_io iow [nfd];
2000	static ev_timer tw;	2487	static ev_timer tw;
2001		2488
2002	static void	2489	static void
2003	io_cb (ev_loop *loop, ev_io *w, int revents)	2490	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2004	{	2491	{
2005	}	2492	}
2006		2493
2007	// create io watchers for each fd and a timer before blocking	2494	// create io watchers for each fd and a timer before blocking
2008	static void	2495	static void
2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2496	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2010	{	2497	{
2011	int timeout = 3600000;	2498	int timeout = 3600000;
2012	struct pollfd fds [nfd];	2499	struct pollfd fds [nfd];
2013	// actual code will need to loop here and realloc etc.	2500	// actual code will need to loop here and realloc etc.
2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2501	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2015		2502
2016	/* the callback is illegal, but won't be called as we stop during check */	2503	/* the callback is illegal, but won't be called as we stop during check */
2017	ev_timer_init (&tw, 0, timeout * 1e-3);	2504	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2018	ev_timer_start (loop, &tw);	2505	ev_timer_start (loop, &tw);
2019		2506
2020	// create one ev_io per pollfd	2507	// create one ev_io per pollfd
2021	for (int i = 0; i < nfd; ++i)	2508	for (int i = 0; i < nfd; ++i)
2022	{	2509	{
…		…
2029	}	2516	}
2030	}	2517	}
2031		2518
2032	// stop all watchers after blocking	2519	// stop all watchers after blocking
2033	static void	2520	static void
2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2521	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2035	{	2522	{
2036	ev_timer_stop (loop, &tw);	2523	ev_timer_stop (loop, &tw);
2037		2524
2038	for (int i = 0; i < nfd; ++i)	2525	for (int i = 0; i < nfd; ++i)
2039	{	2526	{
…		…
2078	}	2565	}
2079		2566
2080	// do not ever call adns_afterpoll	2567	// do not ever call adns_afterpoll
2081		2568
2082	Method 4: Do not use a prepare or check watcher because the module you	2569	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	2570	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	2571	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	2572	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2086	this.	2573	this approach, effectively embedding EV as a client into the horrible
		2574	libglib event loop.
2087		2575
2088	static gint	2576	static gint
2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2577	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2090	{	2578	{
2091	int got_events = 0;	2579	int got_events = 0;
…		…
2122	prioritise I/O.	2610	prioritise I/O.
2123		2611
2124	As an example for a bug workaround, the kqueue backend might only support	2612	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	2613	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	2614	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	2615	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	2616	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	2617	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.	2618	C<kevent>, but at least you can use both mechanisms for what they are
		2619	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2131		2620
2132	As for prioritising I/O: rarely you have the case where some fds have	2621	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	2622	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	2623	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	2624	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.	2625	the rest in a second one, and embed the second one in the first.
2137		2626
2138	As long as the watcher is active, the callback will be invoked every time	2627	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	2628	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	2629	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	2630	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	2631	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	2632	to give the embedded loop strictly lower priority for example).
2144	embedded loop sweep.
2145		2633
2146	As long as the watcher is started it will automatically handle events. The	2634	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	2635	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		2636
2151	Also, there have not currently been made special provisions for forking:	2637	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,	2638	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	2639	embedding loop forks. In other cases, the user is responsible for calling
2154	yourself.	2640	C<ev_loop_fork> on the embedded loop.
2155		2641
2156	Unfortunately, not all backends are embeddable, only the ones returned by	2642	Unfortunately, not all backends are embeddable: only the ones returned by
2157	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2643	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2158	portable one.	2644	portable one.
2159		2645
2160	So when you want to use this feature you will always have to be prepared	2646	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	2647	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	2648	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.	2649	create it, and if that fails, use the normal loop for everything.
		2650
		2651	=head3 C<ev_embed> and fork
		2652
		2653	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2654	automatically be applied to the embedded loop as well, so no special
		2655	fork handling is required in that case. When the watcher is not running,
		2656	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2657	as applicable.
2164		2658
2165	=head3 Watcher-Specific Functions and Data Members	2659	=head3 Watcher-Specific Functions and Data Members
2166		2660
2167	=over 4	2661	=over 4
2168		2662
…		…
2196	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2690	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2197	used).	2691	used).
2198		2692
2199	struct ev_loop *loop_hi = ev_default_init (0);	2693	struct ev_loop *loop_hi = ev_default_init (0);
2200	struct ev_loop *loop_lo = 0;	2694	struct ev_loop *loop_lo = 0;
2201	struct ev_embed embed;	2695	ev_embed embed;
2202		2696
2203	// see if there is a chance of getting one that works	2697	// see if there is a chance of getting one that works
2204	// (remember that a flags value of 0 means autodetection)	2698	// (remember that a flags value of 0 means autodetection)
2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2699	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2700	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2220	kqueue implementation). Store the kqueue/socket-only event loop in	2714	kqueue implementation). Store the kqueue/socket-only event loop in
2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2715	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2222		2716
2223	struct ev_loop *loop = ev_default_init (0);	2717	struct ev_loop *loop = ev_default_init (0);
2224	struct ev_loop *loop_socket = 0;	2718	struct ev_loop *loop_socket = 0;
2225	struct ev_embed embed;	2719	ev_embed embed;
2226		2720
2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2721	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2722	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2229	{	2723	{
2230	ev_embed_init (&embed, 0, loop_socket);	2724	ev_embed_init (&embed, 0, loop_socket);
…		…
2245	event loop blocks next and before C<ev_check> watchers are being called,	2739	event loop blocks next and before C<ev_check> watchers are being called,
2246	and only in the child after the fork. If whoever good citizen calling	2740	and only in the child after the fork. If whoever good citizen calling
2247	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2741	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2248	handlers will be invoked, too, of course.	2742	handlers will be invoked, too, of course.
2249		2743
		2744	=head3 The special problem of life after fork - how is it possible?
		2745
		2746	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2747	up/change the process environment, followed by a call to C<exec()>. This
		2748	sequence should be handled by libev without any problems.
		2749
		2750	This changes when the application actually wants to do event handling
		2751	in the child, or both parent in child, in effect "continuing" after the
		2752	fork.
		2753
		2754	The default mode of operation (for libev, with application help to detect
		2755	forks) is to duplicate all the state in the child, as would be expected
		2756	when I<either> the parent I<or> the child process continues.
		2757
		2758	When both processes want to continue using libev, then this is usually the
		2759	wrong result. In that case, usually one process (typically the parent) is
		2760	supposed to continue with all watchers in place as before, while the other
		2761	process typically wants to start fresh, i.e. without any active watchers.
		2762
		2763	The cleanest and most efficient way to achieve that with libev is to
		2764	simply create a new event loop, which of course will be "empty", and
		2765	use that for new watchers. This has the advantage of not touching more
		2766	memory than necessary, and thus avoiding the copy-on-write, and the
		2767	disadvantage of having to use multiple event loops (which do not support
		2768	signal watchers).
		2769
		2770	When this is not possible, or you want to use the default loop for
		2771	other reasons, then in the process that wants to start "fresh", call
		2772	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2773	the default loop will "orphan" (not stop) all registered watchers, so you
		2774	have to be careful not to execute code that modifies those watchers. Note
		2775	also that in that case, you have to re-register any signal watchers.
		2776
2250	=head3 Watcher-Specific Functions and Data Members	2777	=head3 Watcher-Specific Functions and Data Members
2251		2778
2252	=over 4	2779	=over 4
2253		2780
2254	=item ev_fork_init (ev_signal *, callback)	2781	=item ev_fork_init (ev_signal *, callback)
…		…
2286	is that the author does not know of a simple (or any) algorithm for a	2813	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	2814	multiple-writer-single-reader queue that works in all cases and doesn't
2288	need elaborate support such as pthreads.	2815	need elaborate support such as pthreads.
2289		2816
2290	That means that if you want to queue data, you have to provide your own	2817	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	2818	queue. But at least I can tell you how to implement locking around your
2292	queue:	2819	queue:
2293		2820
2294	=over 4	2821	=over 4
2295		2822
2296	=item queueing from a signal handler context	2823	=item queueing from a signal handler context
2297		2824
2298	To implement race-free queueing, you simply add to the queue in the signal	2825	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	2826	handler but you block the signal handler in the watcher callback. Here is
2300	some fictitious SIGUSR1 handler:	2827	an example that does that for some fictitious SIGUSR1 handler:
2301		2828
2302	static ev_async mysig;	2829	static ev_async mysig;
2303		2830
2304	static void	2831	static void
2305	sigusr1_handler (void)	2832	sigusr1_handler (void)
…		…
2371	=over 4	2898	=over 4
2372		2899
2373	=item ev_async_init (ev_async *, callback)	2900	=item ev_async_init (ev_async *, callback)
2374		2901
2375	Initialises and configures the async watcher - it has no parameters of any	2902	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,	2903	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2377	believe me.	2904	trust me.
2378		2905
2379	=item ev_async_send (loop, ev_async *)	2906	=item ev_async_send (loop, ev_async *)
2380		2907
2381	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2908	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	2909	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	2910	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	2911	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2385	section below on what exactly this means).	2912	section below on what exactly this means).
2386		2913
		2914	Note that, as with other watchers in libev, multiple events might get
		2915	compressed into a single callback invocation (another way to look at this
		2916	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2917	reset when the event loop detects that).
		2918
2387	This call incurs the overhead of a system call only once per loop iteration,	2919	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	2920	iteration, so while the overhead might be noticeable, it doesn't apply to
2389	calls to C<ev_async_send>.	2921	repeated calls to C<ev_async_send> for the same event loop.
2390		2922
2391	=item bool = ev_async_pending (ev_async *)	2923	=item bool = ev_async_pending (ev_async *)
2392		2924
2393	Returns a non-zero value when C<ev_async_send> has been called on the	2925	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	2926	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	2929	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,	2930	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	2931	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.	2932	quickly check whether invoking the loop might be a good idea.
2401		2933
2402	Not that this does I<not> check whether the watcher itself is pending, only	2934	Not that this does I<not> check whether the watcher itself is pending,
2403	whether it has been requested to make this watcher pending.	2935	only whether it has been requested to make this watcher pending: there
		2936	is a time window between the event loop checking and resetting the async
		2937	notification, and the callback being invoked.
2404		2938
2405	=back	2939	=back
2406		2940
2407		2941
2408	=head1 OTHER FUNCTIONS	2942	=head1 OTHER FUNCTIONS
…		…
2412	=over 4	2946	=over 4
2413		2947
2414	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2948	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2415		2949
2416	This function combines a simple timer and an I/O watcher, calls your	2950	This function combines a simple timer and an I/O watcher, calls your
2417	callback on whichever event happens first and automatically stop both	2951	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	2952	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	2953	or timeout without having to allocate/configure/start/stop/free one or
2420	more watchers yourself.	2954	more watchers yourself.
2421		2955
2422	If C<fd> is less than 0, then no I/O watcher will be started and events	2956	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	2957	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2424	C<events> set will be created and started.	2958	the given C<fd> and C<events> set will be created and started.
2425		2959
2426	If C<timeout> is less than 0, then no timeout watcher will be	2960	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	2961	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	2962	repeat = 0) will be started. C<0> is a valid timeout.
2429	dubious value.
2430		2963
2431	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2964	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	2965	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>	2966	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2434	value passed to C<ev_once>:	2967	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2968	a timeout and an io event at the same time - you probably should give io
		2969	events precedence.
		2970
		2971	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2435		2972
2436	static void stdin_ready (int revents, void *arg)	2973	static void stdin_ready (int revents, void *arg)
2437	{	2974	{
		2975	if (revents & EV_READ)
		2976	/* stdin might have data for us, joy! */;
2438	if (revents & EV_TIMEOUT)	2977	else if (revents & EV_TIMEOUT)
2439	/* doh, nothing entered */;	2978	/* doh, nothing entered */;
2440	else if (revents & EV_READ)
2441	/* stdin might have data for us, joy! */;
2442	}	2979	}
2443		2980
2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2981	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2445		2982
2446	=item ev_feed_event (ev_loop *, watcher *, int revents)	2983	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2447		2984
2448	Feeds the given event set into the event loop, as if the specified event	2985	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	2986	had happened for the specified watcher (which must be a pointer to an
2450	initialised but not necessarily started event watcher).	2987	initialised but not necessarily started event watcher).
2451		2988
2452	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2989	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2453		2990
2454	Feed an event on the given fd, as if a file descriptor backend detected	2991	Feed an event on the given fd, as if a file descriptor backend detected
2455	the given events it.	2992	the given events it.
2456		2993
2457	=item ev_feed_signal_event (ev_loop *loop, int signum)	2994	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2458		2995
2459	Feed an event as if the given signal occurred (C<loop> must be the default	2996	Feed an event as if the given signal occurred (C<loop> must be the default
2460	loop!).	2997	loop!).
2461		2998
2462	=back	2999	=back
…		…
2584		3121
2585	myclass obj;	3122	myclass obj;
2586	ev::io iow;	3123	ev::io iow;
2587	iow.set <myclass, &myclass::io_cb> (&obj);	3124	iow.set <myclass, &myclass::io_cb> (&obj);
2588		3125
		3126	=item w->set (object *)
		3127
		3128	This is an B<experimental> feature that might go away in a future version.
		3129
		3130	This is a variation of a method callback - leaving out the method to call
		3131	will default the method to C<operator ()>, which makes it possible to use
		3132	functor objects without having to manually specify the C<operator ()> all
		3133	the time. Incidentally, you can then also leave out the template argument
		3134	list.
		3135
		3136	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3137	int revents)>.
		3138
		3139	See the method-C<set> above for more details.
		3140
		3141	Example: use a functor object as callback.
		3142
		3143	struct myfunctor
		3144	{
		3145	void operator() (ev::io &w, int revents)
		3146	{
		3147	...
		3148	}
		3149	}
		3150
		3151	myfunctor f;
		3152
		3153	ev::io w;
		3154	w.set (&f);
		3155
2589	=item w->set<function> (void *data = 0)	3156	=item w->set<function> (void *data = 0)
2590		3157
2591	Also sets a callback, but uses a static method or plain function as	3158	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	3159	callback. The optional C<data> argument will be stored in the watcher's
2593	C<data> member and is free for you to use.	3160	C<data> member and is free for you to use.
2594		3161
2595	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3162	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2596		3163
2597	See the method-C<set> above for more details.	3164	See the method-C<set> above for more details.
2598		3165
2599	Example:	3166	Example: Use a plain function as callback.
2600		3167
2601	static void io_cb (ev::io &w, int revents) { }	3168	static void io_cb (ev::io &w, int revents) { }
2602	iow.set <io_cb> ();	3169	iow.set <io_cb> ();
2603		3170
2604	=item w->set (struct ev_loop *)	3171	=item w->set (struct ev_loop *)
…		…
2642	Example: Define a class with an IO and idle watcher, start one of them in	3209	Example: Define a class with an IO and idle watcher, start one of them in
2643	the constructor.	3210	the constructor.
2644		3211
2645	class myclass	3212	class myclass
2646	{	3213	{
2647	ev::io io; void io_cb (ev::io &w, int revents);	3214	ev::io io ; void io_cb (ev::io &w, int revents);
2648	ev:idle idle void idle_cb (ev::idle &w, int revents);	3215	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2649		3216
2650	myclass (int fd)	3217	myclass (int fd)
2651	{	3218	{
2652	io .set <myclass, &myclass::io_cb > (this);	3219	io .set <myclass, &myclass::io_cb > (this);
2653	idle.set <myclass, &myclass::idle_cb> (this);	3220	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2669	=item Perl	3236	=item Perl
2670		3237
2671	The EV module implements the full libev API and is actually used to test	3238	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,	3239	libev. EV is developed together with libev. Apart from the EV core module,
2673	there are additional modules that implement libev-compatible interfaces	3240	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	3241	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>).	3242	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3243	and C<EV::Glib>).
2676		3244
2677	It can be found and installed via CPAN, its homepage is at	3245	It can be found and installed via CPAN, its homepage is at
2678	L<http://software.schmorp.de/pkg/EV>.	3246	L<http://software.schmorp.de/pkg/EV>.
2679		3247
2680	=item Python	3248	=item Python
2681		3249
2682	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3250	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	3251	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		3252
2689	=item Ruby	3253	=item Ruby
2690		3254
2691	Tony Arcieri has written a ruby extension that offers access to a subset	3255	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	3256	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	3257	more on top of it. It can be found via gem servers. Its homepage is at
2694	L<http://rev.rubyforge.org/>.	3258	L<http://rev.rubyforge.org/>.
2695		3259
		3260	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3261	makes rev work even on mingw.
		3262
		3263	=item Haskell
		3264
		3265	A haskell binding to libev is available at
		3266	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3267
2696	=item D	3268	=item D
2697		3269
2698	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3270	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>.	3271	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3272
		3273	=item Ocaml
		3274
		3275	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3276	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2700		3277
2701	=back	3278	=back
2702		3279
2703		3280
2704	=head1 MACRO MAGIC	3281	=head1 MACRO MAGIC
…		…
2805		3382
2806	#define EV_STANDALONE 1	3383	#define EV_STANDALONE 1
2807	#include "ev.h"	3384	#include "ev.h"
2808		3385
2809	Both header files and implementation files can be compiled with a C++	3386	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	3387	compiler (at least, that's a stated goal, and breakage will be treated
2811	as a bug).	3388	as a bug).
2812		3389
2813	You need the following files in your source tree, or in a directory	3390	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):	3391	in your include path (e.g. in libev/ when using -Ilibev):
2815		3392
…		…
2859		3436
2860	=head2 PREPROCESSOR SYMBOLS/MACROS	3437	=head2 PREPROCESSOR SYMBOLS/MACROS
2861		3438
2862	Libev can be configured via a variety of preprocessor symbols you have to	3439	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	3440	define before including any of its files. The default in the absence of
2864	autoconf is noted for every option.	3441	autoconf is documented for every option.
2865		3442
2866	=over 4	3443	=over 4
2867		3444
2868	=item EV_STANDALONE	3445	=item EV_STANDALONE
2869		3446
…		…
2871	keeps libev from including F<config.h>, and it also defines dummy	3448	keeps libev from including F<config.h>, and it also defines dummy
2872	implementations for some libevent functions (such as logging, which is not	3449	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	3450	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.	3451	F<event.h> that are not directly supported by the libev core alone.
2875		3452
		3453	In stanbdalone mode, libev will still try to automatically deduce the
		3454	configuration, but has to be more conservative.
		3455
2876	=item EV_USE_MONOTONIC	3456	=item EV_USE_MONOTONIC
2877		3457
2878	If defined to be C<1>, libev will try to detect the availability of the	3458	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	3459	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	3460	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	3461	you usually have to link against librt or something similar. Enabling it
2882	the functionality isn't available is safe, though, although you have	3462	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>	3463	to make sure you link against any libraries where the C<clock_gettime>
2884	function is hiding in (often F<-lrt>).	3464	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2885		3465
2886	=item EV_USE_REALTIME	3466	=item EV_USE_REALTIME
2887		3467
2888	If defined to be C<1>, libev will try to detect the availability of the	3468	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	3469	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	3470	at runtime if successful). Otherwise no use of the real-time clock
2891	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3471	option will be attempted. This effectively replaces C<gettimeofday>
2892	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3472	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2893	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3473	correctness. See the note about libraries in the description of
		3474	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3475	C<EV_USE_CLOCK_SYSCALL>.
		3476
		3477	=item EV_USE_CLOCK_SYSCALL
		3478
		3479	If defined to be C<1>, libev will try to use a direct syscall instead
		3480	of calling the system-provided C<clock_gettime> function. This option
		3481	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3482	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3483	programs needlessly. Using a direct syscall is slightly slower (in
		3484	theory), because no optimised vdso implementation can be used, but avoids
		3485	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3486	higher, as it simplifies linking (no need for C<-lrt>).
2894		3487
2895	=item EV_USE_NANOSLEEP	3488	=item EV_USE_NANOSLEEP
2896		3489
2897	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3490	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 ()>.	3491	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2914		3507
2915	=item EV_SELECT_USE_FD_SET	3508	=item EV_SELECT_USE_FD_SET
2916		3509
2917	If defined to C<1>, then the select backend will use the system C<fd_set>	3510	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	3511	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	3512	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	3513	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	3514	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	3515	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2923	influence the size of the C<fd_set> used.	3516	configures the maximum size of the C<fd_set>.
2924		3517
2925	=item EV_SELECT_IS_WINSOCKET	3518	=item EV_SELECT_IS_WINSOCKET
2926		3519
2927	When defined to C<1>, the select backend will assume that	3520	When defined to C<1>, the select backend will assume that
2928	select/socket/connect etc. don't understand file descriptors but	3521	select/socket/connect etc. don't understand file descriptors but
…		…
3039	When doing priority-based operations, libev usually has to linearly search	3632	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	3633	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	3634	and time, so using the defaults of five priorities (-2 .. +2) is usually
3042	fine.	3635	fine.
3043		3636
3044	If your embedding application does not need any priorities, defining these both to	3637	If your embedding application does not need any priorities, defining these
3045	C<0> will save some memory and CPU.	3638	both to C<0> will save some memory and CPU.
3046		3639
3047	=item EV_PERIODIC_ENABLE	3640	=item EV_PERIODIC_ENABLE
3048		3641
3049	If undefined or defined to be C<1>, then periodic timers are supported. If	3642	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	3643	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3057	code.	3650	code.
3058		3651
3059	=item EV_EMBED_ENABLE	3652	=item EV_EMBED_ENABLE
3060		3653
3061	If undefined or defined to be C<1>, then embed watchers are supported. If	3654	If undefined or defined to be C<1>, then embed watchers are supported. If
3062	defined to be C<0>, then they are not.	3655	defined to be C<0>, then they are not. Embed watchers rely on most other
		3656	watcher types, which therefore must not be disabled.
3063		3657
3064	=item EV_STAT_ENABLE	3658	=item EV_STAT_ENABLE
3065		3659
3066	If undefined or defined to be C<1>, then stat watchers are supported. If	3660	If undefined or defined to be C<1>, then stat watchers are supported. If
3067	defined to be C<0>, then they are not.	3661	defined to be C<0>, then they are not.
…		…
3099	two).	3693	two).
3100		3694
3101	=item EV_USE_4HEAP	3695	=item EV_USE_4HEAP
3102		3696
3103	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3697	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	3698	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	3699	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3106	noticeably faster performance with many (thousands) of watchers.	3700	faster performance with many (thousands) of watchers.
3107		3701
3108	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3702	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3109	(disabled).	3703	(disabled).
3110		3704
3111	=item EV_HEAP_CACHE_AT	3705	=item EV_HEAP_CACHE_AT
3112		3706
3113	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3707	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	3708	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>),	3709	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,	3710	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	3711	but avoids random read accesses on heap changes. This improves performance
3118	noticeably with with many (hundreds) of watchers.	3712	noticeably with many (hundreds) of watchers.
3119		3713
3120	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3714	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3121	(disabled).	3715	(disabled).
3122		3716
3123	=item EV_VERIFY	3717	=item EV_VERIFY
…		…
3129	called once per loop, which can slow down libev. If set to C<3>, then the	3723	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	3724	verification code will be called very frequently, which will slow down
3131	libev considerably.	3725	libev considerably.
3132		3726
3133	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3727	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3134	C<0.>	3728	C<0>.
3135		3729
3136	=item EV_COMMON	3730	=item EV_COMMON
3137		3731
3138	By default, all watchers have a C<void *data> member. By redefining	3732	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	3733	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	3750	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	3751	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	3752	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	3753	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++.	3754	method calls instead of plain function calls in C++.
		3755
		3756	=back
3161		3757
3162	=head2 EXPORTED API SYMBOLS	3758	=head2 EXPORTED API SYMBOLS
3163		3759
3164	If you need to re-export the API (e.g. via a DLL) and you need a list of	3760	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	3761	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:	3808	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3213		3809
3214	#include "ev_cpp.h"	3810	#include "ev_cpp.h"
3215	#include "ev.c"	3811	#include "ev.c"
3216		3812
		3813	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3217		3814
3218	=head1 THREADS AND COROUTINES	3815	=head2 THREADS AND COROUTINES
3219		3816
3220	=head2 THREADS	3817	=head3 THREADS
3221		3818
3222	Libev itself is completely thread-safe, but it uses no locking. This	3819	All libev functions are reentrant and thread-safe unless explicitly
		3820	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	3821	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	3822	are no concurrent calls into any libev function with the same loop
3225	parameter.	3823	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3824	of course): libev guarantees that different event loops share no data
		3825	structures that need any locking.
3226		3826
3227	Or put differently: calls with different loop parameters can be done in	3827	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	3828	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	3829	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	3830	only one thread ever is inside a call at any point in time, e.g. by using
3231	per loop).	3831	a mutex per loop).
		3832
		3833	Specifically to support threads (and signal handlers), libev implements
		3834	so-called C<ev_async> watchers, which allow some limited form of
		3835	concurrency on the same event loop, namely waking it up "from the
		3836	outside".
3232		3837
3233	If you want to know which design (one loop, locking, or multiple loops	3838	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	3839	without or something else still) is best for your problem, then I cannot
3235	help you. I can give some generic advice however:	3840	help you, but here is some generic advice:
3236		3841
3237	=over 4	3842	=over 4
3238		3843
3239	=item * most applications have a main thread: use the default libev loop	3844	=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.	3845	in that thread, or create a separate thread running only the default loop.
…		…
3252		3857
3253	Choosing a model is hard - look around, learn, know that usually you can do	3858	Choosing a model is hard - look around, learn, know that usually you can do
3254	better than you currently do :-)	3859	better than you currently do :-)
3255		3860
3256	=item * often you need to talk to some other thread which blocks in the	3861	=item * often you need to talk to some other thread which blocks in the
		3862	event loop.
		3863
3257	event loop - C<ev_async> watchers can be used to wake them up from other	3864	C<ev_async> watchers can be used to wake them up from other threads safely
3258	threads safely (or from signal contexts...).	3865	(or from signal contexts...).
		3866
		3867	An example use would be to communicate signals or other events that only
		3868	work in the default loop by registering the signal watcher with the
		3869	default loop and triggering an C<ev_async> watcher from the default loop
		3870	watcher callback into the event loop interested in the signal.
3259		3871
3260	=back	3872	=back
3261		3873
3262	=head2 COROUTINES	3874	=head3 COROUTINES
3263		3875
3264	Libev is much more accommodating to coroutines ("cooperative threads"):	3876	Libev is very accommodating to coroutines ("cooperative threads"):
3265	libev fully supports nesting calls to it's functions from different	3877	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	3878	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	3879	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	3880	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.	3881	you must not do this from C<ev_periodic> reschedule callbacks.
3270		3882
3271	Care has been invested into making sure that libev does not keep local	3883	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	3884	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3273	switches.	3885	they do not call any callbacks.
3274		3886
		3887	=head2 COMPILER WARNINGS
3275		3888
3276	=head1 COMPLEXITIES	3889	Depending on your compiler and compiler settings, you might get no or a
		3890	lot of warnings when compiling libev code. Some people are apparently
		3891	scared by this.
3277		3892
3278	In this section the complexities of (many of) the algorithms used inside	3893	However, these are unavoidable for many reasons. For one, each compiler
3279	libev will be explained. For complexity discussions about backends see the	3894	has different warnings, and each user has different tastes regarding
3280	documentation for C<ev_default_init>.	3895	warning options. "Warn-free" code therefore cannot be a goal except when
		3896	targeting a specific compiler and compiler-version.
3281		3897
3282	All of the following are about amortised time: If an array needs to be	3898	Another reason is that some compiler warnings require elaborate
3283	extended, libev needs to realloc and move the whole array, but this	3899	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	3900	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		3901
3288	=over 4	3902	And of course, some compiler warnings are just plain stupid, or simply
		3903	wrong (because they don't actually warn about the condition their message
		3904	seems to warn about). For example, certain older gcc versions had some
		3905	warnings that resulted an extreme number of false positives. These have
		3906	been fixed, but some people still insist on making code warn-free with
		3907	such buggy versions.
3289		3908
3290	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3909	While libev is written to generate as few warnings as possible,
		3910	"warn-free" code is not a goal, and it is recommended not to build libev
		3911	with any compiler warnings enabled unless you are prepared to cope with
		3912	them (e.g. by ignoring them). Remember that warnings are just that:
		3913	warnings, not errors, or proof of bugs.
3291		3914
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		3915
3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3916	=head2 VALGRIND
3297		3917
3298	That means that changing a timer costs less than removing/adding them	3918	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.	3919	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3300		3920
3301	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3921	If you think you found a bug (memory leak, uninitialised data access etc.)
		3922	in libev, then check twice: If valgrind reports something like:
3302		3923
3303	These just add the watcher into an array or at the head of a list.	3924	==2274== definitely lost: 0 bytes in 0 blocks.
		3925	==2274== possibly lost: 0 bytes in 0 blocks.
		3926	==2274== still reachable: 256 bytes in 1 blocks.
3304		3927
3305	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3928	Then there is no memory leak, just as memory accounted to global variables
		3929	is not a memleak - the memory is still being referenced, and didn't leak.
3306		3930
3307	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3931	Similarly, under some circumstances, valgrind might report kernel bugs
		3932	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3933	although an acceptable workaround has been found here), or it might be
		3934	confused.
3308		3935
3309	These watchers are stored in lists then need to be walked to find the	3936	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	3937	make it into some kind of religion.
3311	have many watchers waiting for the same fd or signal).
3312		3938
3313	=item Finding the next timer in each loop iteration: O(1)	3939	If you are unsure about something, feel free to contact the mailing list
		3940	with the full valgrind report and an explanation on why you think this
		3941	is a bug in libev (best check the archives, too :). However, don't be
		3942	annoyed when you get a brisk "this is no bug" answer and take the chance
		3943	of learning how to interpret valgrind properly.
3314		3944
3315	By virtue of using a binary or 4-heap, the next timer is always found at a	3945	If you need, for some reason, empty reports from valgrind for your project
3316	fixed position in the storage array.	3946	I suggest using suppression lists.
3317		3947
3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3319		3948
3320	A change means an I/O watcher gets started or stopped, which requires	3949	=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		3950
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	3951	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3347		3952
3348	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3953	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	3954	requires, and its I/O model is fundamentally incompatible with the POSIX
3350	model. Libev still offers limited functionality on this platform in	3955	model. Libev still offers limited functionality on this platform in
3351	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3956	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3358	way (note also that glib is the slowest event library known to man).	3963	way (note also that glib is the slowest event library known to man).
3359		3964
3360	There is no supported compilation method available on windows except	3965	There is no supported compilation method available on windows except
3361	embedding it into other applications.	3966	embedding it into other applications.
3362		3967
		3968	Sensible signal handling is officially unsupported by Microsoft - libev
		3969	tries its best, but under most conditions, signals will simply not work.
		3970
3363	Not a libev limitation but worth mentioning: windows apparently doesn't	3971	Not a libev limitation but worth mentioning: windows apparently doesn't
3364	accept large writes: instead of resulting in a partial write, windows will	3972	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,	3973	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	3974	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	3975	megabyte seems safe, but this apparently depends on the amount of memory
3368	available).	3976	available).
3369		3977
3370	Due to the many, low, and arbitrary limits on the win32 platform and	3978	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	3979	the abysmal performance of winsockets, using a large number of sockets
3372	is not recommended (and not reasonable). If your program needs to use	3980	is not recommended (and not reasonable). If your program needs to use
3373	more than a hundred or so sockets, then likely it needs to use a totally	3981	more than a hundred or so sockets, then likely it needs to use a totally
3374	different implementation for windows, as libev offers the POSIX readiness	3982	different implementation for windows, as libev offers the POSIX readiness
3375	notification model, which cannot be implemented efficiently on windows	3983	notification model, which cannot be implemented efficiently on windows
3376	(Microsoft monopoly games).	3984	(due to Microsoft monopoly games).
3377		3985
3378	A typical way to use libev under windows is to embed it (see the embedding	3986	A typical way to use libev under windows is to embed it (see the embedding
3379	section for details) and use the following F<evwrap.h> header file instead	3987	section for details) and use the following F<evwrap.h> header file instead
3380	of F<ev.h>:	3988	of F<ev.h>:
3381		3989
…		…
3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3991	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3384		3992
3385	#include "ev.h"	3993	#include "ev.h"
3386		3994
3387	And compile the following F<evwrap.c> file into your project (make sure	3995	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!):	3996	you do I<not> compile the F<ev.c> or any other embedded source files!):
3389		3997
3390	#include "evwrap.h"	3998	#include "evwrap.h"
3391	#include "ev.c"	3999	#include "ev.c"
3392		4000
3393	=over 4	4001	=over 4
…		…
3417		4025
3418	Early versions of winsocket's select only supported waiting for a maximum	4026	Early versions of winsocket's select only supported waiting for a maximum
3419	of C<64> handles (probably owning to the fact that all windows kernels	4027	of C<64> handles (probably owning to the fact that all windows kernels
3420	can only wait for C<64> things at the same time internally; Microsoft	4028	can only wait for C<64> things at the same time internally; Microsoft
3421	recommends spawning a chain of threads and wait for 63 handles and the	4029	recommends spawning a chain of threads and wait for 63 handles and the
3422	previous thread in each. Great).	4030	previous thread in each. Sounds great!).
3423		4031
3424	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4032	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3425	to some high number (e.g. C<2048>) before compiling the winsocket select	4033	to some high number (e.g. C<2048>) before compiling the winsocket select
3426	call (which might be in libev or elsewhere, for example, perl does its own	4034	call (which might be in libev or elsewhere, for example, perl and many
3427	select emulation on windows).	4035	other interpreters do their own select emulation on windows).
3428		4036
3429	Another limit is the number of file descriptors in the Microsoft runtime	4037	Another limit is the number of file descriptors in the Microsoft runtime
3430	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4038	libraries, which by default is C<64> (there must be a hidden I<64>
3431	or something like this inside Microsoft). You can increase this by calling	4039	fetish or something like this inside Microsoft). You can increase this
3432	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4040	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3433	arbitrary limit), but is broken in many versions of the Microsoft runtime	4041	(another arbitrary limit), but is broken in many versions of the Microsoft
3434	libraries.
3435
3436	This might get you to about C<512> or C<2048> sockets (depending on	4042	runtime libraries. This might get you to about C<512> or C<2048> sockets
3437	windows version and/or the phase of the moon). To get more, you need to	4043	(depending on windows version and/or the phase of the moon). To get more,
3438	wrap all I/O functions and provide your own fd management, but the cost of	4044	you need to wrap all I/O functions and provide your own fd management, but
3439	calling select (O(n²)) will likely make this unworkable.	4045	the cost of calling select (O(n²)) will likely make this unworkable.
3440		4046
3441	=back	4047	=back
3442		4048
3443
3444	=head1 PORTABILITY REQUIREMENTS	4049	=head2 PORTABILITY REQUIREMENTS
3445		4050
3446	In addition to a working ISO-C implementation, libev relies on a few	4051	In addition to a working ISO-C implementation and of course the
3447	additional extensions:	4052	backend-specific APIs, libev relies on a few additional extensions:
3448		4053
3449	=over 4	4054	=over 4
3450		4055
3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4056	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3452	calling conventions regardless of C<ev_watcher_type *>.	4057	calling conventions regardless of C<ev_watcher_type *>.
…		…
3458	calls them using an C<ev_watcher *> internally.	4063	calls them using an C<ev_watcher *> internally.
3459		4064
3460	=item C<sig_atomic_t volatile> must be thread-atomic as well	4065	=item C<sig_atomic_t volatile> must be thread-atomic as well
3461		4066
3462	The type C<sig_atomic_t volatile> (or whatever is defined as	4067	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	4068	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	4069	threads. This is not part of the specification for C<sig_atomic_t>, but is
3465	believed to be sufficiently portable.	4070	believed to be sufficiently portable.
3466		4071
3467	=item C<sigprocmask> must work in a threaded environment	4072	=item C<sigprocmask> must work in a threaded environment
3468		4073
…		…
3477	except the initial one, and run the default loop in the initial thread as	4082	except the initial one, and run the default loop in the initial thread as
3478	well.	4083	well.
3479		4084
3480	=item C<long> must be large enough for common memory allocation sizes	4085	=item C<long> must be large enough for common memory allocation sizes
3481		4086
3482	To improve portability and simplify using libev, libev uses C<long>	4087	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	4088	instead of C<size_t> when allocating its data structures. On non-POSIX
3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4089	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	4090	least 31 bits everywhere, which is enough for hundreds of millions of
3486	millions of watchers.	4091	watchers.
3487		4092
3488	=item C<double> must hold a time value in seconds with enough accuracy	4093	=item C<double> must hold a time value in seconds with enough accuracy
3489		4094
3490	The type C<double> is used to represent timestamps. It is required to	4095	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	4096	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3492	enough for at least into the year 4000. This requirement is fulfilled by	4097	enough for at least into the year 4000. This requirement is fulfilled by
3493	implementations implementing IEEE 754 (basically all existing ones).	4098	implementations implementing IEEE 754, which is basically all existing
		4099	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4100	2200.
3494		4101
3495	=back	4102	=back
3496		4103
3497	If you know of other additional requirements drop me a note.	4104	If you know of other additional requirements drop me a note.
3498		4105
3499		4106
3500	=head1 COMPILER WARNINGS	4107	=head1 ALGORITHMIC COMPLEXITIES
3501		4108
3502	Depending on your compiler and compiler settings, you might get no or a	4109	In this section the complexities of (many of) the algorithms used inside
3503	lot of warnings when compiling libev code. Some people are apparently	4110	libev will be documented. For complexity discussions about backends see
3504	scared by this.	4111	the documentation for C<ev_default_init>.
3505		4112
3506	However, these are unavoidable for many reasons. For one, each compiler	4113	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	4114	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	4115	happens asymptotically rarer with higher number of elements, so O(1) might
3509	targeting a specific compiler and compiler-version.	4116	mean that libev does a lengthy realloc operation in rare cases, but on
		4117	average it is much faster and asymptotically approaches constant time.
3510		4118
3511	Another reason is that some compiler warnings require elaborate	4119	=over 4
3512	workarounds, or other changes to the code that make it less clear and less
3513	maintainable.
3514		4120
3515	And of course, some compiler warnings are just plain stupid, or simply	4121	=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		4122
3519	While libev is written to generate as few warnings as possible,	4123	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	4124	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	4125	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		4126
		4127	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3525		4128
3526	=head1 VALGRIND	4129	That means that changing a timer costs less than removing/adding them,
		4130	as only the relative motion in the event queue has to be paid for.
3527		4131
3528	Valgrind has a special section here because it is a popular tool that is	4132	=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		4133
3531	If you think you found a bug (memory leak, uninitialised data access etc.)	4134	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		4135
3534	==2274== definitely lost: 0 bytes in 0 blocks.	4136	=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		4137
3538	Then there is no memory leak. Similarly, under some circumstances,	4138	=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		4139
3542	If you are unsure about something, feel free to contact the mailing list	4140	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	4141	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	4142	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	4143	is rare).
3546	properly.
3547		4144
3548	If you need, for some reason, empty reports from valgrind for your project	4145	=item Finding the next timer in each loop iteration: O(1)
3549	I suggest using suppression lists.
3550		4146
		4147	By virtue of using a binary or 4-heap, the next timer is always found at a
		4148	fixed position in the storage array.
		4149
		4150	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4151
		4152	A change means an I/O watcher gets started or stopped, which requires
		4153	libev to recalculate its status (and possibly tell the kernel, depending
		4154	on backend and whether C<ev_io_set> was used).
		4155
		4156	=item Activating one watcher (putting it into the pending state): O(1)
		4157
		4158	=item Priority handling: O(number_of_priorities)
		4159
		4160	Priorities are implemented by allocating some space for each
		4161	priority. When doing priority-based operations, libev usually has to
		4162	linearly search all the priorities, but starting/stopping and activating
		4163	watchers becomes O(1) with respect to priority handling.
		4164
		4165	=item Sending an ev_async: O(1)
		4166
		4167	=item Processing ev_async_send: O(number_of_async_watchers)
		4168
		4169	=item Processing signals: O(max_signal_number)
		4170
		4171	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4172	calls in the current loop iteration. Checking for async and signal events
		4173	involves iterating over all running async watchers or all signal numbers.
		4174
		4175	=back
		4176
		4177
		4178	=head1 GLOSSARY
		4179
		4180	=over 4
		4181
		4182	=item active
		4183
		4184	A watcher is active as long as it has been started (has been attached to
		4185	an event loop) but not yet stopped (disassociated from the event loop).
		4186
		4187	=item application
		4188
		4189	In this document, an application is whatever is using libev.
		4190
		4191	=item callback
		4192
		4193	The address of a function that is called when some event has been
		4194	detected. Callbacks are being passed the event loop, the watcher that
		4195	received the event, and the actual event bitset.
		4196
		4197	=item callback invocation
		4198
		4199	The act of calling the callback associated with a watcher.
		4200
		4201	=item event
		4202
		4203	A change of state of some external event, such as data now being available
		4204	for reading on a file descriptor, time having passed or simply not having
		4205	any other events happening anymore.
		4206
		4207	In libev, events are represented as single bits (such as C<EV_READ> or
		4208	C<EV_TIMEOUT>).
		4209
		4210	=item event library
		4211
		4212	A software package implementing an event model and loop.
		4213
		4214	=item event loop
		4215
		4216	An entity that handles and processes external events and converts them
		4217	into callback invocations.
		4218
		4219	=item event model
		4220
		4221	The model used to describe how an event loop handles and processes
		4222	watchers and events.
		4223
		4224	=item pending
		4225
		4226	A watcher is pending as soon as the corresponding event has been detected,
		4227	and stops being pending as soon as the watcher will be invoked or its
		4228	pending status is explicitly cleared by the application.
		4229
		4230	A watcher can be pending, but not active. Stopping a watcher also clears
		4231	its pending status.
		4232
		4233	=item real time
		4234
		4235	The physical time that is observed. It is apparently strictly monotonic :)
		4236
		4237	=item wall-clock time
		4238
		4239	The time and date as shown on clocks. Unlike real time, it can actually
		4240	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4241	clock.
		4242
		4243	=item watcher
		4244
		4245	A data structure that describes interest in certain events. Watchers need
		4246	to be started (attached to an event loop) before they can receive events.
		4247
		4248	=item watcher invocation
		4249
		4250	The act of calling the callback associated with a watcher.
		4251
		4252	=back
3551		4253
3552	=head1 AUTHOR	4254	=head1 AUTHOR
3553		4255
3554	Marc Lehmann <libev@schmorp.de>.	4256	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3555		4257

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