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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
…		…
573	received events and started processing them. This timestamp does not	634	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	635	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	636	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	637	event occurring (or more correctly, libev finding out about it).
577		638
		639	=item ev_now_update (loop)
		640
		641	Establishes the current time by querying the kernel, updating the time
		642	returned by C<ev_now ()> in the progress. This is a costly operation and
		643	is usually done automatically within C<ev_loop ()>.
		644
		645	This function is rarely useful, but when some event callback runs for a
		646	very long time without entering the event loop, updating libev's idea of
		647	the current time is a good idea.
		648
		649	See also L<The special problem of time updates> in the C<ev_timer> section.
		650
		651	=item ev_suspend (loop)
		652
		653	=item ev_resume (loop)
		654
		655	These two functions suspend and resume a loop, for use when the loop is
		656	not used for a while and timeouts should not be processed.
		657
		658	A typical use case would be an interactive program such as a game: When
		659	the user presses C<^Z> to suspend the game and resumes it an hour later it
		660	would be best to handle timeouts as if no time had actually passed while
		661	the program was suspended. This can be achieved by calling C<ev_suspend>
		662	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		663	C<ev_resume> directly afterwards to resume timer processing.
		664
		665	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		666	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		667	will be rescheduled (that is, they will lose any events that would have
		668	occured while suspended).
		669
		670	After calling C<ev_suspend> you B<must not> call I<any> function on the
		671	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		672	without a previous call to C<ev_suspend>.
		673
		674	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		675	event loop time (see C<ev_now_update>).
		676
578	=item ev_loop (loop, int flags)	677	=item ev_loop (loop, int flags)
579		678
580	Finally, this is it, the event handler. This function usually is called	679	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	680	after you initialised all your watchers and you want to start handling
582	events.	681	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	683	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	684	either no event watchers are active anymore or C<ev_unloop> was called.
586		685
587	Please note that an explicit C<ev_unloop> is usually better than	686	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	687	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	688	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	689	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	690	of relying on its watchers stopping correctly, that is truly a thing of
		691	beauty.
592		692
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	693	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	694	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	695	process in case there are no events and will return after one iteration of
		696	the loop.
596		697
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	698	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	699	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	700	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	701	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	702	user-registered callback will be called), and will return after one
		703	iteration of the loop.
		704
		705	This is useful if you are waiting for some external event in conjunction
		706	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	707	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	708	usually a better approach for this kind of thing.
604		709
605	Here are the gory details of what C<ev_loop> does:	710	Here are the gory details of what C<ev_loop> does:
606		711
607	- Before the first iteration, call any pending watchers.	712	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	713	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	714	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	715	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	716	- If we have been forked, detach and recreate the kernel state
		717	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	718	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	719	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	720	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	721	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	722	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	723	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	724	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	725	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	726	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	727	- Queue all expired timers.
622	- Queue all outstanding periodics.	728	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	729	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	730	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	731	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	732	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	733	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	734	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	739	anymore.
634		740
635	... queue jobs here, make sure they register event watchers as long	741	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	742	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	743	ev_loop (my_loop, 0);
638	... jobs done. yeah!	744	... jobs done or somebody called unloop. yeah!
639		745
640	=item ev_unloop (loop, how)	746	=item ev_unloop (loop, how)
641		747
642	Can be used to make a call to C<ev_loop> return early (but only after it	748	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	749	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	750	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	751	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		752
647	This "unloop state" will be cleared when entering C<ev_loop> again.	753	This "unloop state" will be cleared when entering C<ev_loop> again.
648		754
		755	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		756
649	=item ev_ref (loop)	757	=item ev_ref (loop)
650		758
651	=item ev_unref (loop)	759	=item ev_unref (loop)
652		760
653	Ref/unref can be used to add or remove a reference count on the event	761	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	762	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	763	count is nonzero, C<ev_loop> will not return on its own.
		764
656	a watcher you never unregister that should not keep C<ev_loop> from	765	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	766	from returning, call ev_unref() after starting, and ev_ref() before
		767	stopping it.
		768
658	example, libev itself uses this for its internal signal pipe: It is not	769	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	770	is not visible to the libev user and should not keep C<ev_loop> from
660	no event watchers registered by it are active. It is also an excellent	771	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	772	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	773	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	774	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	775	before, respectively. Note also that libev might stop watchers itself
		776	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		777	in the callback).
665		778
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	779	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	780	running when nothing else is active.
668		781
669	struct ev_signal exitsig;	782	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	783	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	784	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	785	evf_unref (loop);
673		786
674	Example: For some weird reason, unregister the above signal handler again.	787	Example: For some weird reason, unregister the above signal handler again.
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	792	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		793
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	794	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		795
683	These advanced functions influence the time that libev will spend waiting	796	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	797	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	798	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		799	latency.
686		800
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	801	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	802	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	803	to increase efficiency of loop iterations (or to increase power-saving
		804	opportunities).
690		805
691	The background is that sometimes your program runs just fast enough to	806	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	807	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	808	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	809	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	810	overhead for the actual polling but can deliver many events at once.
696		811
697	By setting a higher I<io collect interval> you allow libev to spend more	812	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	813	time collecting I/O events, so you can handle more events per iteration,
…		…
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	815	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	816	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		817
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	818	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	819	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	820	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	821	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	822	value will not introduce any overhead in libev.
708		823
709	Many (busy) programs can usually benefit by setting the I/O collect	824	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	825	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	826	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	827	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	828	as this approaches the timing granularity of most systems.
714		829
		830	Setting the I<timeout collect interval> can improve the opportunity for
		831	saving power, as the program will "bundle" timer callback invocations that
		832	are "near" in time together, by delaying some, thus reducing the number of
		833	times the process sleeps and wakes up again. Another useful technique to
		834	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		835	they fire on, say, one-second boundaries only.
		836
715	=item ev_loop_verify (loop)	837	=item ev_loop_verify (loop)
716		838
717	This function only does something when C<EV_VERIFY> support has been	839	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	840	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	841	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	842	is found to be inconsistent, it will print an error message to standard
		843	error and call C<abort ()>.
721		844
722	This can be used to catch bugs inside libev itself: under normal	845	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	846	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	847	data structures consistent.
725		848
726	=back	849	=back
727		850
728		851
729	=head1 ANATOMY OF A WATCHER	852	=head1 ANATOMY OF A WATCHER
730		853
		854	In the following description, uppercase C<TYPE> in names stands for the
		855	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		856	watchers and C<ev_io_start> for I/O watchers.
		857
731	A watcher is a structure that you create and register to record your	858	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	859	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	860	become readable, you would create an C<ev_io> watcher for that:
734		861
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	862	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	863	{
737	ev_io_stop (w);	864	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	865	ev_unloop (loop, EVUNLOOP_ALL);
739	}	866	}
740		867
741	struct ev_loop *loop = ev_default_loop (0);	868	struct ev_loop *loop = ev_default_loop (0);
		869
742	struct ev_io stdin_watcher;	870	ev_io stdin_watcher;
		871
743	ev_init (&stdin_watcher, my_cb);	872	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	873	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	874	ev_io_start (loop, &stdin_watcher);
		875
746	ev_loop (loop, 0);	876	ev_loop (loop, 0);
747		877
748	As you can see, you are responsible for allocating the memory for your	878	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	879	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	880	stack).
		881
		882	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		883	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		884
752	Each watcher structure must be initialised by a call to C<ev_init	885	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	886	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	887	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	888	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	889	is readable and/or writable).
757		890
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	891	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	892	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	893	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	894	ev_TYPE_init (watcher *, callback, ...) >>.
762		895
763	To make the watcher actually watch out for events, you have to start it	896	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	897	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	898	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	899	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		900
768	As long as your watcher is active (has been started but not stopped) you	901	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	902	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	903	reinitialise it or call its C<ev_TYPE_set> macro.
771		904
772	Each and every callback receives the event loop pointer as first, the	905	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	906	registered watcher structure as second, and a bitset of received events as
774	third argument.	907	third argument.
775		908
…		…
833		966
834	=item C<EV_ASYNC>	967	=item C<EV_ASYNC>
835		968
836	The given async watcher has been asynchronously notified (see C<ev_async>).	969	The given async watcher has been asynchronously notified (see C<ev_async>).
837		970
		971	=item C<EV_CUSTOM>
		972
		973	Not ever sent (or otherwise used) by libev itself, but can be freely used
		974	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		975
838	=item C<EV_ERROR>	976	=item C<EV_ERROR>
839		977
840	An unspecified error has occurred, the watcher has been stopped. This might	978	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	979	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	980	ran out of memory, a file descriptor was found to be closed or any other
		981	problem. Libev considers these application bugs.
		982
843	problem. You best act on it by reporting the problem and somehow coping	983	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	984	watcher being stopped. Note that well-written programs should not receive
		985	an error ever, so when your watcher receives it, this usually indicates a
		986	bug in your program.
845		987
846	Libev will usually signal a few "dummy" events together with an error,	988	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	989	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	990	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	991	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	992	programs, though, as the fd could already be closed and reused for another
		993	thing, so beware.
851		994
852	=back	995	=back
853		996
854	=head2 GENERIC WATCHER FUNCTIONS	997	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		998
859	=over 4	999	=over 4
860		1000
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1001	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1002
…		…
868	which rolls both calls into one.	1008	which rolls both calls into one.
869		1009
870	You can reinitialise a watcher at any time as long as it has been stopped	1010	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1011	(or never started) and there are no pending events outstanding.
872		1012
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1013	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1014	int revents)>.
		1015
		1016	Example: Initialise an C<ev_io> watcher in two steps.
		1017
		1018	ev_io w;
		1019	ev_init (&w, my_cb);
		1020	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		1021
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1022	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		1023
878	This macro initialises the type-specific parts of a watcher. You need to	1024	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1025	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	1028	difference to the C<ev_init> macro).
883		1029
884	Although some watcher types do not have type-specific arguments	1030	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1031	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1032
		1033	See C<ev_init>, above, for an example.
		1034
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1035	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1036
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1037	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1038	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1039	a watcher. The same limitations apply, of course.
892		1040
		1041	Example: Initialise and set an C<ev_io> watcher in one step.
		1042
		1043	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1044
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1045	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		1046
895	Starts (activates) the given watcher. Only active watchers will receive	1047	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1048	events. If the watcher is already active nothing will happen.
897		1049
		1050	Example: Start the C<ev_io> watcher that is being abused as example in this
		1051	whole section.
		1052
		1053	ev_io_start (EV_DEFAULT_UC, &w);
		1054
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1055	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		1056
900	Stops the given watcher again (if active) and clears the pending	1057	Stops the given watcher if active, and clears the pending status (whether
		1058	the watcher was active or not).
		1059
901	status. It is possible that stopped watchers are pending (for example,	1060	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1061	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1062	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1063	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1064	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1065
907	=item bool ev_is_active (ev_TYPE *watcher)	1066	=item bool ev_is_active (ev_TYPE *watcher)
908		1067
909	Returns a true value iff the watcher is active (i.e. it has been started	1068	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1069	and not yet been stopped). As long as a watcher is active you must not modify
…		…
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1095	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1096	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1097	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1098	from being executed (except for C<ev_idle> watchers).
940		1099
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1100	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1101	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1102
949	You I<must not> change the priority of a watcher as long as it is active or	1103	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1104	pending.
951		1105
		1106	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1107	fine, as long as you do not mind that the priority value you query might
		1108	or might not have been clamped to the valid range.
		1109
952	The default priority used by watchers when no priority has been set is	1110	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1111	always C<0>, which is supposed to not be too high and not be too low :).
954		1112
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1113	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1114	priorities.
957	or might not have been adjusted to be within valid range.
958		1115
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1116	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1117
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1118	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1119	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1120	can deal with that fact, as both are simply passed through to the
		1121	callback.
964		1122
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1123	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1124
967	If the watcher is pending, this function returns clears its pending status	1125	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1126	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1127	watcher isn't pending it does nothing and returns C<0>.
970		1128
		1129	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1130	callback to be invoked, which can be accomplished with this function.
		1131
971	=back	1132	=back
972		1133
973		1134
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1135	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1136
976	Each watcher has, by default, a member C<void *data> that you can change	1137	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1138	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1139	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1140	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1141	member, you can also "subclass" the watcher type and provide your own
981	data:	1142	data:
982		1143
983	struct my_io	1144	struct my_io
984	{	1145	{
985	struct ev_io io;	1146	ev_io io;
986	int otherfd;	1147	int otherfd;
987	void *somedata;	1148	void *somedata;
988	struct whatever *mostinteresting;	1149	struct whatever *mostinteresting;
989	}	1150	};
		1151
		1152	...
		1153	struct my_io w;
		1154	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1155
991	And since your callback will be called with a pointer to the watcher, you	1156	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1157	can cast it back to your own type:
993		1158
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1159	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1160	{
996	struct my_io *w = (struct my_io *)w_;	1161	struct my_io *w = (struct my_io *)w_;
997	...	1162	...
998	}	1163	}
999		1164
1000	More interesting and less C-conformant ways of casting your callback type	1165	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1166	instead have been omitted.
1002		1167
1003	Another common scenario is having some data structure with multiple	1168	Another common scenario is to use some data structure with multiple
1004	watchers:	1169	embedded watchers:
1005		1170
1006	struct my_biggy	1171	struct my_biggy
1007	{	1172	{
1008	int some_data;	1173	int some_data;
1009	ev_timer t1;	1174	ev_timer t1;
1010	ev_timer t2;	1175	ev_timer t2;
1011	}	1176	}
1012		1177
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1178	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1179	complicated: Either you store the address of your C<my_biggy> struct
		1180	in the C<data> member of the watcher (for woozies), or you need to use
		1181	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1182	programmers):
1015		1183
1016	#include <stddef.h>	1184	#include <stddef.h>
1017		1185
1018	static void	1186	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1187	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1188	{
1021	struct my_biggy big = (struct my_biggy *	1189	struct my_biggy big = (struct my_biggy *
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1190	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1191	}
1024		1192
1025	static void	1193	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1194	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1195	{
1028	struct my_biggy big = (struct my_biggy *	1196	struct my_biggy big = (struct my_biggy *
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1197	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1198	}
		1199
		1200	=head2 WATCHER PRIORITY MODELS
		1201
		1202	Many event loops support I<watcher priorities>, which are usually small
		1203	integers that influence the ordering of event callback invocation
		1204	between watchers in some way, all else being equal.
		1205
		1206	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1207	description for the more technical details such as the actual priority
		1208	range.
		1209
		1210	There are two common ways how these these priorities are being interpreted
		1211	by event loops:
		1212
		1213	In the more common lock-out model, higher priorities "lock out" invocation
		1214	of lower priority watchers, which means as long as higher priority
		1215	watchers receive events, lower priority watchers are not being invoked.
		1216
		1217	The less common only-for-ordering model uses priorities solely to order
		1218	callback invocation within a single event loop iteration: Higher priority
		1219	watchers are invoked before lower priority ones, but they all get invoked
		1220	before polling for new events.
		1221
		1222	Libev uses the second (only-for-ordering) model for all its watchers
		1223	except for idle watchers (which use the lock-out model).
		1224
		1225	The rationale behind this is that implementing the lock-out model for
		1226	watchers is not well supported by most kernel interfaces, and most event
		1227	libraries will just poll for the same events again and again as long as
		1228	their callbacks have not been executed, which is very inefficient in the
		1229	common case of one high-priority watcher locking out a mass of lower
		1230	priority ones.
		1231
		1232	Static (ordering) priorities are most useful when you have two or more
		1233	watchers handling the same resource: a typical usage example is having an
		1234	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1235	timeouts. Under load, data might be received while the program handles
		1236	other jobs, but since timers normally get invoked first, the timeout
		1237	handler will be executed before checking for data. In that case, giving
		1238	the timer a lower priority than the I/O watcher ensures that I/O will be
		1239	handled first even under adverse conditions (which is usually, but not
		1240	always, what you want).
		1241
		1242	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1243	will only be executed when no same or higher priority watchers have
		1244	received events, they can be used to implement the "lock-out" model when
		1245	required.
		1246
		1247	For example, to emulate how many other event libraries handle priorities,
		1248	you can associate an C<ev_idle> watcher to each such watcher, and in
		1249	the normal watcher callback, you just start the idle watcher. The real
		1250	processing is done in the idle watcher callback. This causes libev to
		1251	continously poll and process kernel event data for the watcher, but when
		1252	the lock-out case is known to be rare (which in turn is rare :), this is
		1253	workable.
		1254
		1255	Usually, however, the lock-out model implemented that way will perform
		1256	miserably under the type of load it was designed to handle. In that case,
		1257	it might be preferable to stop the real watcher before starting the
		1258	idle watcher, so the kernel will not have to process the event in case
		1259	the actual processing will be delayed for considerable time.
		1260
		1261	Here is an example of an I/O watcher that should run at a strictly lower
		1262	priority than the default, and which should only process data when no
		1263	other events are pending:
		1264
		1265	ev_idle idle; // actual processing watcher
		1266	ev_io io; // actual event watcher
		1267
		1268	static void
		1269	io_cb (EV_P_ ev_io *w, int revents)
		1270	{
		1271	// stop the I/O watcher, we received the event, but
		1272	// are not yet ready to handle it.
		1273	ev_io_stop (EV_A_ w);
		1274
		1275	// start the idle watcher to ahndle the actual event.
		1276	// it will not be executed as long as other watchers
		1277	// with the default priority are receiving events.
		1278	ev_idle_start (EV_A_ &idle);
		1279	}
		1280
		1281	static void
		1282	idle-cb (EV_P_ ev_idle *w, int revents)
		1283	{
		1284	// actual processing
		1285	read (STDIN_FILENO, ...);
		1286
		1287	// have to start the I/O watcher again, as
		1288	// we have handled the event
		1289	ev_io_start (EV_P_ &io);
		1290	}
		1291
		1292	// initialisation
		1293	ev_idle_init (&idle, idle_cb);
		1294	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1295	ev_io_start (EV_DEFAULT_ &io);
		1296
		1297	In the "real" world, it might also be beneficial to start a timer, so that
		1298	low-priority connections can not be locked out forever under load. This
		1299	enables your program to keep a lower latency for important connections
		1300	during short periods of high load, while not completely locking out less
		1301	important ones.
1031		1302
1032		1303
1033	=head1 WATCHER TYPES	1304	=head1 WATCHER TYPES
1034		1305
1035	This section describes each watcher in detail, but will not repeat	1306	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1330	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1331	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1332	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1333	required if you know what you are doing).
1063		1334
1064	If you must do this, then force the use of a known-to-be-good backend	1335	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1336	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1337	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1338
1068	Another thing you have to watch out for is that it is quite easy to	1339	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1340	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1341	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1342	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1343	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1344	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1345	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1346	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1347
1077	If you cannot run the fd in non-blocking mode (for example you should not	1348	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1349	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1350	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1351	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1352	does this on its own, so its quite safe to use). Some people additionally
		1353	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1354	indefinitely.
		1355
		1356	But really, best use non-blocking mode.
1082		1357
1083	=head3 The special problem of disappearing file descriptors	1358	=head3 The special problem of disappearing file descriptors
1084		1359
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1360	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1361	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1362	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1363	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1364	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1365	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1366	fact, a different file descriptor.
1092		1367
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1398	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1399	C<EVBACKEND_POLL>.
1125		1400
1126	=head3 The special problem of SIGPIPE	1401	=head3 The special problem of SIGPIPE
1127		1402
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1403	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1404	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1405	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1406	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1407
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1408	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1409	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1410	somewhere, as that would have given you a big clue).
1137		1411
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1417	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1418
1145	=item ev_io_set (ev_io *, int fd, int events)	1419	=item ev_io_set (ev_io *, int fd, int events)
1146		1420
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1421	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1422	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1423	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1424
1151	=item int fd [read-only]	1425	=item int fd [read-only]
1152		1426
1153	The file descriptor being watched.	1427	The file descriptor being watched.
1154		1428
…		…
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1437	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1438	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1439	attempt to read a whole line in the callback.
1166		1440
1167	static void	1441	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1442	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1443	{
1170	ev_io_stop (loop, w);	1444	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1445	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1446	}
1173		1447
1174	...	1448	...
1175	struct ev_loop *loop = ev_default_init (0);	1449	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1450	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1451	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1452	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1453	ev_loop (loop, 0);
1180		1454
1181		1455
…		…
1184	Timer watchers are simple relative timers that generate an event after a	1458	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1459	given time, and optionally repeating in regular intervals after that.
1186		1460
1187	The timers are based on real time, that is, if you register an event that	1461	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1462	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1463	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1464	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1465	monotonic clock option helps a lot here).
		1466
		1467	The callback is guaranteed to be invoked only I<after> its timeout has
		1468	passed. If multiple timers become ready during the same loop iteration
		1469	then the ones with earlier time-out values are invoked before ones with
		1470	later time-out values (but this is no longer true when a callback calls
		1471	C<ev_loop> recursively).
		1472
		1473	=head3 Be smart about timeouts
		1474
		1475	Many real-world problems involve some kind of timeout, usually for error
		1476	recovery. A typical example is an HTTP request - if the other side hangs,
		1477	you want to raise some error after a while.
		1478
		1479	What follows are some ways to handle this problem, from obvious and
		1480	inefficient to smart and efficient.
		1481
		1482	In the following, a 60 second activity timeout is assumed - a timeout that
		1483	gets reset to 60 seconds each time there is activity (e.g. each time some
		1484	data or other life sign was received).
		1485
		1486	=over 4
		1487
		1488	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1489
		1490	This is the most obvious, but not the most simple way: In the beginning,
		1491	start the watcher:
		1492
		1493	ev_timer_init (timer, callback, 60., 0.);
		1494	ev_timer_start (loop, timer);
		1495
		1496	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1497	and start it again:
		1498
		1499	ev_timer_stop (loop, timer);
		1500	ev_timer_set (timer, 60., 0.);
		1501	ev_timer_start (loop, timer);
		1502
		1503	This is relatively simple to implement, but means that each time there is
		1504	some activity, libev will first have to remove the timer from its internal
		1505	data structure and then add it again. Libev tries to be fast, but it's
		1506	still not a constant-time operation.
		1507
		1508	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1509
		1510	This is the easiest way, and involves using C<ev_timer_again> instead of
		1511	C<ev_timer_start>.
		1512
		1513	To implement this, configure an C<ev_timer> with a C<repeat> value
		1514	of C<60> and then call C<ev_timer_again> at start and each time you
		1515	successfully read or write some data. If you go into an idle state where
		1516	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1517	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1518
		1519	That means you can ignore both the C<ev_timer_start> function and the
		1520	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1521	member and C<ev_timer_again>.
		1522
		1523	At start:
		1524
		1525	ev_timer_init (timer, callback);
		1526	timer->repeat = 60.;
		1527	ev_timer_again (loop, timer);
		1528
		1529	Each time there is some activity:
		1530
		1531	ev_timer_again (loop, timer);
		1532
		1533	It is even possible to change the time-out on the fly, regardless of
		1534	whether the watcher is active or not:
		1535
		1536	timer->repeat = 30.;
		1537	ev_timer_again (loop, timer);
		1538
		1539	This is slightly more efficient then stopping/starting the timer each time
		1540	you want to modify its timeout value, as libev does not have to completely
		1541	remove and re-insert the timer from/into its internal data structure.
		1542
		1543	It is, however, even simpler than the "obvious" way to do it.
		1544
		1545	=item 3. Let the timer time out, but then re-arm it as required.
		1546
		1547	This method is more tricky, but usually most efficient: Most timeouts are
		1548	relatively long compared to the intervals between other activity - in
		1549	our example, within 60 seconds, there are usually many I/O events with
		1550	associated activity resets.
		1551
		1552	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1553	but remember the time of last activity, and check for a real timeout only
		1554	within the callback:
		1555
		1556	ev_tstamp last_activity; // time of last activity
		1557
		1558	static void
		1559	callback (EV_P_ ev_timer *w, int revents)
		1560	{
		1561	ev_tstamp now = ev_now (EV_A);
		1562	ev_tstamp timeout = last_activity + 60.;
		1563
		1564	// if last_activity + 60. is older than now, we did time out
		1565	if (timeout < now)
		1566	{
		1567	// timeout occured, take action
		1568	}
		1569	else
		1570	{
		1571	// callback was invoked, but there was some activity, re-arm
		1572	// the watcher to fire in last_activity + 60, which is
		1573	// guaranteed to be in the future, so "again" is positive:
		1574	w->repeat = timeout - now;
		1575	ev_timer_again (EV_A_ w);
		1576	}
		1577	}
		1578
		1579	To summarise the callback: first calculate the real timeout (defined
		1580	as "60 seconds after the last activity"), then check if that time has
		1581	been reached, which means something I<did>, in fact, time out. Otherwise
		1582	the callback was invoked too early (C<timeout> is in the future), so
		1583	re-schedule the timer to fire at that future time, to see if maybe we have
		1584	a timeout then.
		1585
		1586	Note how C<ev_timer_again> is used, taking advantage of the
		1587	C<ev_timer_again> optimisation when the timer is already running.
		1588
		1589	This scheme causes more callback invocations (about one every 60 seconds
		1590	minus half the average time between activity), but virtually no calls to
		1591	libev to change the timeout.
		1592
		1593	To start the timer, simply initialise the watcher and set C<last_activity>
		1594	to the current time (meaning we just have some activity :), then call the
		1595	callback, which will "do the right thing" and start the timer:
		1596
		1597	ev_timer_init (timer, callback);
		1598	last_activity = ev_now (loop);
		1599	callback (loop, timer, EV_TIMEOUT);
		1600
		1601	And when there is some activity, simply store the current time in
		1602	C<last_activity>, no libev calls at all:
		1603
		1604	last_actiivty = ev_now (loop);
		1605
		1606	This technique is slightly more complex, but in most cases where the
		1607	time-out is unlikely to be triggered, much more efficient.
		1608
		1609	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1610	callback :) - just change the timeout and invoke the callback, which will
		1611	fix things for you.
		1612
		1613	=item 4. Wee, just use a double-linked list for your timeouts.
		1614
		1615	If there is not one request, but many thousands (millions...), all
		1616	employing some kind of timeout with the same timeout value, then one can
		1617	do even better:
		1618
		1619	When starting the timeout, calculate the timeout value and put the timeout
		1620	at the I<end> of the list.
		1621
		1622	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1623	the list is expected to fire (for example, using the technique #3).
		1624
		1625	When there is some activity, remove the timer from the list, recalculate
		1626	the timeout, append it to the end of the list again, and make sure to
		1627	update the C<ev_timer> if it was taken from the beginning of the list.
		1628
		1629	This way, one can manage an unlimited number of timeouts in O(1) time for
		1630	starting, stopping and updating the timers, at the expense of a major
		1631	complication, and having to use a constant timeout. The constant timeout
		1632	ensures that the list stays sorted.
		1633
		1634	=back
		1635
		1636	So which method the best?
		1637
		1638	Method #2 is a simple no-brain-required solution that is adequate in most
		1639	situations. Method #3 requires a bit more thinking, but handles many cases
		1640	better, and isn't very complicated either. In most case, choosing either
		1641	one is fine, with #3 being better in typical situations.
		1642
		1643	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1644	rather complicated, but extremely efficient, something that really pays
		1645	off after the first million or so of active timers, i.e. it's usually
		1646	overkill :)
		1647
		1648	=head3 The special problem of time updates
		1649
		1650	Establishing the current time is a costly operation (it usually takes at
		1651	least two system calls): EV therefore updates its idea of the current
		1652	time only before and after C<ev_loop> collects new events, which causes a
		1653	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1654	lots of events in one iteration.
1192		1655
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1656	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1657	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1658	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1659	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1660	timeout on the current time, use something like this to adjust for this:
1198		1661
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1662	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1663
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1664	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1665	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1666	()>.
1204		1667
1205	=head3 Watcher-Specific Functions and Data Members	1668	=head3 Watcher-Specific Functions and Data Members
1206		1669
1207	=over 4	1670	=over 4
1208		1671
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1695	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1696
1234	If the timer is repeating, either start it if necessary (with the	1697	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1698	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1699
1237	This sounds a bit complicated, but here is a useful and typical	1700	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1701	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246
1247	That means you can ignore the C<after> value and C<ev_timer_start>
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249
1250	ev_timer_init (timer, callback, 0., 5.);
1251	ev_timer_again (loop, timer);
1252	...
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258
1259	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.
1261		1702
1262	=item ev_tstamp repeat [read-write]	1703	=item ev_tstamp repeat [read-write]
1263		1704
1264	The current C<repeat> value. Will be used each time the watcher times out	1705	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1706	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1707	which is also when any modifications are taken into account.
1267		1708
1268	=back	1709	=back
1269		1710
1270	=head3 Examples	1711	=head3 Examples
1271		1712
1272	Example: Create a timer that fires after 60 seconds.	1713	Example: Create a timer that fires after 60 seconds.
1273		1714
1274	static void	1715	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1716	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1717	{
1277	.. one minute over, w is actually stopped right here	1718	.. one minute over, w is actually stopped right here
1278	}	1719	}
1279		1720
1280	struct ev_timer mytimer;	1721	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1722	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1723	ev_timer_start (loop, &mytimer);
1283		1724
1284	Example: Create a timeout timer that times out after 10 seconds of	1725	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1726	inactivity.
1286		1727
1287	static void	1728	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1729	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1730	{
1290	.. ten seconds without any activity	1731	.. ten seconds without any activity
1291	}	1732	}
1292		1733
1293	struct ev_timer mytimer;	1734	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1735	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1736	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1737	ev_loop (loop, 0);
1297		1738
1298	// and in some piece of code that gets executed on any "activity":	1739	// and in some piece of code that gets executed on any "activity":
…		…
1303	=head2 C<ev_periodic> - to cron or not to cron?	1744	=head2 C<ev_periodic> - to cron or not to cron?
1304		1745
1305	Periodic watchers are also timers of a kind, but they are very versatile	1746	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	1747	(and unfortunately a bit complex).
1307		1748
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1749	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	1750	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	1751	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1752	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	1753	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	1754	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		1755
		1756	You can tell a periodic watcher to trigger after some specific point
		1757	in time: for example, if you tell a periodic watcher to trigger "in 10
		1758	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1759	not a delay) and then reset your system clock to January of the previous
		1760	year, then it will take a year or more to trigger the event (unlike an
		1761	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1762	it, as it uses a relative timeout).
		1763
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1764	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	1765	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	1766	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1767	those cannot react to time jumps.
1320		1768
1321	As with timers, the callback is guaranteed to be invoked only when the	1769	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1770	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	1771	timers become ready during the same loop iteration then the ones with
		1772	earlier time-out values are invoked before ones with later time-out values
		1773	(but this is no longer true when a callback calls C<ev_loop> recursively).
1324		1774
1325	=head3 Watcher-Specific Functions and Data Members	1775	=head3 Watcher-Specific Functions and Data Members
1326		1776
1327	=over 4	1777	=over 4
1328		1778
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1779	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		1780
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1781	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		1782
1333	Lots of arguments, lets sort it out... There are basically three modes of	1783	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1784	operation, and we will explain them from simplest to most complex:
1335		1785
1336	=over 4	1786	=over 4
1337		1787
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1788	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		1789
1340	In this configuration the watcher triggers an event after the wall clock	1790	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1791	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1792	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	1793	will be stopped and invoked when the system clock reaches or surpasses
		1794	this point in time.
1344		1795
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1796	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		1797
1347	In this mode the watcher will always be scheduled to time out at the next	1798	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1799	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	1800	negative) and then repeat, regardless of any time jumps. The C<offset>
		1801	argument is merely an offset into the C<interval> periods.
1350		1802
1351	This can be used to create timers that do not drift with respect to system	1803	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1804	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	1805	hour, on the hour (with respect to UTC):
1354		1806
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1807	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1808
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1809	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1810	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	1811	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	1812	by 3600.
1361		1813
1362	Another way to think about it (for the mathematically inclined) is that	1814	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	1815	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	1816	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		1817
1366	For numerical stability it is preferable that the C<at> value is near	1818	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	1819	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	1820	this value, and in fact is often specified as zero.
1369		1821
1370	Note also that there is an upper limit to how often a timer can fire (CPU	1822	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	1823	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	1824	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	1825	millisecond (if the OS supports it and the machine is fast enough).
1374		1826
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1827	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		1828
1377	In this mode the values for C<interval> and C<at> are both being	1829	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	1830	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	1831	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	1832	current time as second argument.
1381		1833
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1834	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	1835	or make ANY other event loop modifications whatsoever, unless explicitly
		1836	allowed by documentation here>.
1384		1837
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1838	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1839	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1840	only event loop modification you are allowed to do).
1388		1841
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1842	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1843	*w, ev_tstamp now)>, e.g.:
1391		1844
		1845	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1846	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1847	{
1394	return now + 60.;	1848	return now + 60.;
1395	}	1849	}
1396		1850
1397	It must return the next time to trigger, based on the passed time value	1851	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	1871	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	1872	program when the crontabs have changed).
1419		1873
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	1874	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		1875
1422	When active, returns the absolute time that the watcher is supposed to	1876	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	1877	to trigger next. This is not the same as the C<offset> argument to
		1878	C<ev_periodic_set>, but indeed works even in interval and manual
		1879	rescheduling modes.
1424		1880
1425	=item ev_tstamp offset [read-write]	1881	=item ev_tstamp offset [read-write]
1426		1882
1427	When repeating, this contains the offset value, otherwise this is the	1883	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1884	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1885	although libev might modify this value for better numerical stability).
1429		1886
1430	Can be modified any time, but changes only take effect when the periodic	1887	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	1888	timer fires or C<ev_periodic_again> is being called.
1432		1889
1433	=item ev_tstamp interval [read-write]	1890	=item ev_tstamp interval [read-write]
1434		1891
1435	The current interval value. Can be modified any time, but changes only	1892	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	1893	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1894	called.
1438		1895
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1896	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1897
1441	The current reschedule callback, or C<0>, if this functionality is	1898	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	1899	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	1900	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1901
1445	=back	1902	=back
1446		1903
1447	=head3 Examples	1904	=head3 Examples
1448		1905
1449	Example: Call a callback every hour, or, more precisely, whenever the	1906	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1907	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1908	potentially a lot of jitter, but good long-term stability.
1452		1909
1453	static void	1910	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1911	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1912	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1913	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1914	}
1458		1915
1459	struct ev_periodic hourly_tick;	1916	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1917	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1918	ev_periodic_start (loop, &hourly_tick);
1462		1919
1463	Example: The same as above, but use a reschedule callback to do it:	1920	Example: The same as above, but use a reschedule callback to do it:
1464		1921
1465	#include <math.h>	1922	#include <math.h>
1466		1923
1467	static ev_tstamp	1924	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1925	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	1926	{
1470	return fmod (now, 3600.) + 3600.;	1927	return now + (3600. - fmod (now, 3600.));
1471	}	1928	}
1472		1929
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1930	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1931
1475	Example: Call a callback every hour, starting now:	1932	Example: Call a callback every hour, starting now:
1476		1933
1477	struct ev_periodic hourly_tick;	1934	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1935	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1936	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1937	ev_periodic_start (loop, &hourly_tick);
1481		1938
1482		1939
…		…
1485	Signal watchers will trigger an event when the process receives a specific	1942	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	1943	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	1944	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1945	normal event processing, like any other event.
1489		1946
		1947	If you want signals asynchronously, just use C<sigaction> as you would
		1948	do without libev and forget about sharing the signal. You can even use
		1949	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1950
1490	You can configure as many watchers as you like per signal. Only when the	1951	You can configure as many watchers as you like per signal. Only when the
1491	first watcher gets started will libev actually register a signal watcher	1952	first watcher gets started will libev actually register a signal handler
1492	with the kernel (thus it coexists with your own signal handlers as long	1953	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	1954	you don't register any with libev for the same signal). Similarly, when
1494	watcher for a signal is stopped libev will reset the signal handler to	1955	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1956	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1957
1497	If possible and supported, libev will install its handlers with	1958	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1959	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1499	interrupted. If you have a problem with system calls getting interrupted by	1960	interrupted. If you have a problem with system calls getting interrupted by
1500	signals you can block all signals in an C<ev_check> watcher and unblock	1961	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1978
1518	=back	1979	=back
1519		1980
1520	=head3 Examples	1981	=head3 Examples
1521		1982
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1983	Example: Try to exit cleanly on SIGINT.
1523		1984
1524	static void	1985	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1986	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	1987	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1988	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1989	}
1529		1990
1530	struct ev_signal signal_watcher;	1991	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1992	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1993	ev_signal_start (loop, &signal_watcher);
1533		1994
1534		1995
1535	=head2 C<ev_child> - watch out for process status changes	1996	=head2 C<ev_child> - watch out for process status changes
1536		1997
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1998	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	1999	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2000	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2001	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2002	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2003	forking and then immediately registering a watcher for the child is fine,
		2004	but forking and registering a watcher a few event loop iterations later is
		2005	not.
1542		2006
1543	Only the default event loop is capable of handling signals, and therefore	2007	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2008	you can only register child watchers in the default event loop.
1545		2009
1546	=head3 Process Interaction	2010	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	2023	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2024	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2025	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2026	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2027	that, so other libev users can use C<ev_child> watchers freely.
		2028
		2029	=head3 Stopping the Child Watcher
		2030
		2031	Currently, the child watcher never gets stopped, even when the
		2032	child terminates, so normally one needs to stop the watcher in the
		2033	callback. Future versions of libev might stop the watcher automatically
		2034	when a child exit is detected.
1564		2035
1565	=head3 Watcher-Specific Functions and Data Members	2036	=head3 Watcher-Specific Functions and Data Members
1566		2037
1567	=over 4	2038	=over 4
1568		2039
…		…
1600	its completion.	2071	its completion.
1601		2072
1602	ev_child cw;	2073	ev_child cw;
1603		2074
1604	static void	2075	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2076	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2077	{
1607	ev_child_stop (EV_A_ w);	2078	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2079	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2080	}
1610		2081
…		…
1625		2096
1626		2097
1627	=head2 C<ev_stat> - did the file attributes just change?	2098	=head2 C<ev_stat> - did the file attributes just change?
1628		2099
1629	This watches a file system path for attribute changes. That is, it calls	2100	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2101	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2102	and sees if it changed compared to the last time, invoking the callback if
		2103	it did.
1632		2104
1633	The path does not need to exist: changing from "path exists" to "path does	2105	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2106	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2107	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2108	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2109	least one) and all the other fields of the stat buffer having unspecified
		2110	contents.
1638		2111
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2112	The path I<must not> end in a slash or contain special components such as
		2113	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2114	your working directory changes, then the behaviour is undefined.
1641		2115
1642	Since there is no standard to do this, the portable implementation simply	2116	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2117	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2118	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2119	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2120	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2121	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2122	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2123	currently around C<0.1>, but that's usually overkill.
1650		2124
1651	This watcher type is not meant for massive numbers of stat watchers,	2125	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2126	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2127	resource-intensive.
1654		2128
1655	At the time of this writing, only the Linux inotify interface is	2129	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2130	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2131	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2132	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2133
1664	=head3 ABI Issues (Largefile Support)	2134	=head3 ABI Issues (Largefile Support)
1665		2135
1666	Libev by default (unless the user overrides this) uses the default	2136	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2137	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2138	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2139	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2140	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2141	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2142	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2143	most noticeably displayed with ev_stat and large file support.
1674		2144
1675	=head3 Inotify	2145	The solution for this is to lobby your distribution maker to make large
		2146	file interfaces available by default (as e.g. FreeBSD does) and not
		2147	optional. Libev cannot simply switch on large file support because it has
		2148	to exchange stat structures with application programs compiled using the
		2149	default compilation environment.
1676		2150
		2151	=head3 Inotify and Kqueue
		2152
1677	When C<inotify (7)> support has been compiled into libev (generally only	2153	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2154	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2155	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2156	watcher is being started.
1681		2157
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2158	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2159	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2160	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2161	there are many cases where libev has to resort to regular C<stat> polling,
		2162	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2163	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2164	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2165	xfs are fully working) libev usually gets away without polling.
1686		2166
1687	(There is no support for kqueue, as apparently it cannot be used to	2167	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2168	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2169	descriptor open on the object at all times, and detecting renames, unlinks
		2170	etc. is difficult.
		2171
		2172	=head3 C<stat ()> is a synchronous operation
		2173
		2174	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2175	the process. The exception are C<ev_stat> watchers - those call C<stat
		2176	()>, which is a synchronous operation.
		2177
		2178	For local paths, this usually doesn't matter: unless the system is very
		2179	busy or the intervals between stat's are large, a stat call will be fast,
		2180	as the path data is usually in memory already (except when starting the
		2181	watcher).
		2182
		2183	For networked file systems, calling C<stat ()> can block an indefinite
		2184	time due to network issues, and even under good conditions, a stat call
		2185	often takes multiple milliseconds.
		2186
		2187	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2188	paths, although this is fully supported by libev.
1690		2189
1691	=head3 The special problem of stat time resolution	2190	=head3 The special problem of stat time resolution
1692		2191
1693	The C<stat ()> system call only supports full-second resolution portably, and	2192	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2193	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2194	still only support whole seconds.
1696		2195
1697	That means that, if the time is the only thing that changes, you can	2196	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2197	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2198	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2199	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2200	stat data does change in other ways (e.g. file size).
1702		2201
1703	The solution to this is to delay acting on a change for slightly more	2202	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2203	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2204	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2205	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2225	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2226	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2227	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2228	path for as long as the watcher is active.
1730		2229
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2230	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2231	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2232	last change was detected).
1734		2233
1735	=item ev_stat_stat (loop, ev_stat *)	2234	=item ev_stat_stat (loop, ev_stat *)
1736		2235
1737	Updates the stat buffer immediately with new values. If you change the	2236	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2237	watched path in your callback, you could call this function to avoid
…		…
1821		2320
1822		2321
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2322	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2323
1825	Idle watchers trigger events when no other events of the same or higher	2324	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2325	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2326	as receiving "events").
1828		2327
1829	That is, as long as your process is busy handling sockets or timeouts	2328	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2329	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2330	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2331	are pending), the idle watchers are being called once per event loop
…		…
1843		2342
1844	=head3 Watcher-Specific Functions and Data Members	2343	=head3 Watcher-Specific Functions and Data Members
1845		2344
1846	=over 4	2345	=over 4
1847		2346
1848	=item ev_idle_init (ev_signal *, callback)	2347	=item ev_idle_init (ev_idle *, callback)
1849		2348
1850	Initialises and configures the idle watcher - it has no parameters of any	2349	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2350	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2351	believe me.
1853		2352
…		…
1857		2356
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2357	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2358	callback, free it. Also, use no error checking, as usual.
1860		2359
1861	static void	2360	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2361	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2362	{
1864	free (w);	2363	free (w);
1865	// now do something you wanted to do when the program has	2364	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2365	// no longer anything immediate to do.
1867	}	2366	}
1868		2367
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2368	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2369	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2370	ev_idle_start (loop, idle_cb);
1872		2371
1873		2372
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2373	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2374
1876	Prepare and check watchers are usually (but not always) used in tandem:	2375	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2376	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2377	afterwards.
1879		2378
1880	You I<must not> call C<ev_loop> or similar functions that enter	2379	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2380	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2383	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2384	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2385	called in pairs bracketing the blocking call.
1887		2386
1888	Their main purpose is to integrate other event mechanisms into libev and	2387	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2388	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2389	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2390	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2391	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2392	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2393	watcher).
1895		2394
1896	This is done by examining in each prepare call which file descriptors need	2395	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2396	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2397	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2398	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2399	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2400	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2401	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2402	nevertheless, because you never know, you know?).
1904		2403
1905	As another example, the Perl Coro module uses these hooks to integrate	2404	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2405	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2406	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2407	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2410	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2411	low-priority coroutines to idle/background tasks).
1913		2412
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2413	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2414	priority, to ensure that they are being run before any other watchers
		2415	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2416
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2417	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2418	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2419	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2420	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2421	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2422	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2423	others).
1923		2424
1924	=head3 Watcher-Specific Functions and Data Members	2425	=head3 Watcher-Specific Functions and Data Members
1925		2426
1926	=over 4	2427	=over 4
1927		2428
…		…
1929		2430
1930	=item ev_check_init (ev_check *, callback)	2431	=item ev_check_init (ev_check *, callback)
1931		2432
1932	Initialises and configures the prepare or check watcher - they have no	2433	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2434	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2435	macros, but using them is utterly, utterly, utterly and completely
		2436	pointless.
1935		2437
1936	=back	2438	=back
1937		2439
1938	=head3 Examples	2440	=head3 Examples
1939		2441
…		…
1952		2454
1953	static ev_io iow [nfd];	2455	static ev_io iow [nfd];
1954	static ev_timer tw;	2456	static ev_timer tw;
1955		2457
1956	static void	2458	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2459	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2460	{
1959	}	2461	}
1960		2462
1961	// create io watchers for each fd and a timer before blocking	2463	// create io watchers for each fd and a timer before blocking
1962	static void	2464	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2465	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2466	{
1965	int timeout = 3600000;	2467	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2468	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2469	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2470	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
1983	}	2485	}
1984	}	2486	}
1985		2487
1986	// stop all watchers after blocking	2488	// stop all watchers after blocking
1987	static void	2489	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2490	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2491	{
1990	ev_timer_stop (loop, &tw);	2492	ev_timer_stop (loop, &tw);
1991		2493
1992	for (int i = 0; i < nfd; ++i)	2494	for (int i = 0; i < nfd; ++i)
1993	{	2495	{
…		…
2032	}	2534	}
2033		2535
2034	// do not ever call adns_afterpoll	2536	// do not ever call adns_afterpoll
2035		2537
2036	Method 4: Do not use a prepare or check watcher because the module you	2538	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2539	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2540	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2541	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2542	this approach, effectively embedding EV as a client into the horrible
		2543	libglib event loop.
2041		2544
2042	static gint	2545	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2546	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2547	{
2045	int got_events = 0;	2548	int got_events = 0;
…		…
2076	prioritise I/O.	2579	prioritise I/O.
2077		2580
2078	As an example for a bug workaround, the kqueue backend might only support	2581	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2582	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2583	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2584	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2585	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2586	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2587	C<kevent>, but at least you can use both mechanisms for what they are
		2588	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2589
2086	As for prioritising I/O: rarely you have the case where some fds have	2590	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2591	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2592	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2593	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2594	the rest in a second one, and embed the second one in the first.
2091		2595
2092	As long as the watcher is active, the callback will be invoked every time	2596	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2597	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2598	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2599	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2600	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2601	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2602
2100	As long as the watcher is started it will automatically handle events. The	2603	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2604	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2605
2105	Also, there have not currently been made special provisions for forking:	2606	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2607	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2608	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2609	C<ev_loop_fork> on the embedded loop.
2109		2610
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2611	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2612	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2613	portable one.
2113		2614
2114	So when you want to use this feature you will always have to be prepared	2615	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2616	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2617	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2618	create it, and if that fails, use the normal loop for everything.
		2619
		2620	=head3 C<ev_embed> and fork
		2621
		2622	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2623	automatically be applied to the embedded loop as well, so no special
		2624	fork handling is required in that case. When the watcher is not running,
		2625	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2626	as applicable.
2118		2627
2119	=head3 Watcher-Specific Functions and Data Members	2628	=head3 Watcher-Specific Functions and Data Members
2120		2629
2121	=over 4	2630	=over 4
2122		2631
…		…
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2659	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2660	used).
2152		2661
2153	struct ev_loop *loop_hi = ev_default_init (0);	2662	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2663	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2664	ev_embed embed;
2156		2665
2157	// see if there is a chance of getting one that works	2666	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2667	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2668	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2669	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2683	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2684	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2685
2177	struct ev_loop *loop = ev_default_init (0);	2686	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2687	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2688	ev_embed embed;
2180		2689
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2690	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2691	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2692	{
2184	ev_embed_init (&embed, 0, loop_socket);	2693	ev_embed_init (&embed, 0, loop_socket);
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	2708	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	2709	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2710	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	2711	handlers will be invoked, too, of course.
2203		2712
		2713	=head3 The special problem of life after fork - how is it possible?
		2714
		2715	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2716	up/change the process environment, followed by a call to C<exec()>. This
		2717	sequence should be handled by libev without any problems.
		2718
		2719	This changes when the application actually wants to do event handling
		2720	in the child, or both parent in child, in effect "continuing" after the
		2721	fork.
		2722
		2723	The default mode of operation (for libev, with application help to detect
		2724	forks) is to duplicate all the state in the child, as would be expected
		2725	when I<either> the parent I<or> the child process continues.
		2726
		2727	When both processes want to continue using libev, then this is usually the
		2728	wrong result. In that case, usually one process (typically the parent) is
		2729	supposed to continue with all watchers in place as before, while the other
		2730	process typically wants to start fresh, i.e. without any active watchers.
		2731
		2732	The cleanest and most efficient way to achieve that with libev is to
		2733	simply create a new event loop, which of course will be "empty", and
		2734	use that for new watchers. This has the advantage of not touching more
		2735	memory than necessary, and thus avoiding the copy-on-write, and the
		2736	disadvantage of having to use multiple event loops (which do not support
		2737	signal watchers).
		2738
		2739	When this is not possible, or you want to use the default loop for
		2740	other reasons, then in the process that wants to start "fresh", call
		2741	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2742	the default loop will "orphan" (not stop) all registered watchers, so you
		2743	have to be careful not to execute code that modifies those watchers. Note
		2744	also that in that case, you have to re-register any signal watchers.
		2745
2204	=head3 Watcher-Specific Functions and Data Members	2746	=head3 Watcher-Specific Functions and Data Members
2205		2747
2206	=over 4	2748	=over 4
2207		2749
2208	=item ev_fork_init (ev_signal *, callback)	2750	=item ev_fork_init (ev_signal *, callback)
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2782	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2783	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2784	need elaborate support such as pthreads.
2243		2785
2244	That means that if you want to queue data, you have to provide your own	2786	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2787	queue. But at least I can tell you how to implement locking around your
2246	queue:	2788	queue:
2247		2789
2248	=over 4	2790	=over 4
2249		2791
2250	=item queueing from a signal handler context	2792	=item queueing from a signal handler context
2251		2793
2252	To implement race-free queueing, you simply add to the queue in the signal	2794	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2795	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2796	an example that does that for some fictitious SIGUSR1 handler:
2255		2797
2256	static ev_async mysig;	2798	static ev_async mysig;
2257		2799
2258	static void	2800	static void
2259	sigusr1_handler (void)	2801	sigusr1_handler (void)
…		…
2325	=over 4	2867	=over 4
2326		2868
2327	=item ev_async_init (ev_async *, callback)	2869	=item ev_async_init (ev_async *, callback)
2328		2870
2329	Initialises and configures the async watcher - it has no parameters of any	2871	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2872	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	2873	trust me.
2332		2874
2333	=item ev_async_send (loop, ev_async *)	2875	=item ev_async_send (loop, ev_async *)
2334		2876
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2877	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2878	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	2879	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2880	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2881	section below on what exactly this means).
2340		2882
		2883	Note that, as with other watchers in libev, multiple events might get
		2884	compressed into a single callback invocation (another way to look at this
		2885	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2886	reset when the event loop detects that).
		2887
2341	This call incurs the overhead of a system call only once per loop iteration,	2888	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	2889	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	2890	repeated calls to C<ev_async_send> for the same event loop.
2344		2891
2345	=item bool = ev_async_pending (ev_async *)	2892	=item bool = ev_async_pending (ev_async *)
2346		2893
2347	Returns a non-zero value when C<ev_async_send> has been called on the	2894	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	2895	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2898	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	2899	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	2900	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	2901	quickly check whether invoking the loop might be a good idea.
2355		2902
2356	Not that this does I<not> check whether the watcher itself is pending, only	2903	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	2904	only whether it has been requested to make this watcher pending: there
		2905	is a time window between the event loop checking and resetting the async
		2906	notification, and the callback being invoked.
2358		2907
2359	=back	2908	=back
2360		2909
2361		2910
2362	=head1 OTHER FUNCTIONS	2911	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	2915	=over 4
2367		2916
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2917	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		2918
2370	This function combines a simple timer and an I/O watcher, calls your	2919	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	2920	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	2921	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	2922	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	2923	more watchers yourself.
2375		2924
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	2925	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2926	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	2927	the given C<fd> and C<events> set will be created and started.
2379		2928
2380	If C<timeout> is less than 0, then no timeout watcher will be	2929	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2930	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2931	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		2932
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2933	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	2934	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2935	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2936	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2937	a timeout and an io event at the same time - you probably should give io
		2938	events precedence.
		2939
		2940	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2389		2941
2390	static void stdin_ready (int revents, void *arg)	2942	static void stdin_ready (int revents, void *arg)
2391	{	2943	{
		2944	if (revents & EV_READ)
		2945	/* stdin might have data for us, joy! */;
2392	if (revents & EV_TIMEOUT)	2946	else if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;	2947	/* doh, nothing entered */;
2394	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;
2396	}	2948	}
2397		2949
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2950	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2951
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2952	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		2953
2402	Feeds the given event set into the event loop, as if the specified event	2954	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an	2955	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	2956	initialised but not necessarily started event watcher).
2405		2957
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2958	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		2959
2408	Feed an event on the given fd, as if a file descriptor backend detected	2960	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	2961	the given events it.
2410		2962
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	2963	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		2964
2413	Feed an event as if the given signal occurred (C<loop> must be the default	2965	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	2966	loop!).
2415		2967
2416	=back	2968	=back
…		…
2538		3090
2539	myclass obj;	3091	myclass obj;
2540	ev::io iow;	3092	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3093	iow.set <myclass, &myclass::io_cb> (&obj);
2542		3094
		3095	=item w->set (object *)
		3096
		3097	This is an B<experimental> feature that might go away in a future version.
		3098
		3099	This is a variation of a method callback - leaving out the method to call
		3100	will default the method to C<operator ()>, which makes it possible to use
		3101	functor objects without having to manually specify the C<operator ()> all
		3102	the time. Incidentally, you can then also leave out the template argument
		3103	list.
		3104
		3105	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3106	int revents)>.
		3107
		3108	See the method-C<set> above for more details.
		3109
		3110	Example: use a functor object as callback.
		3111
		3112	struct myfunctor
		3113	{
		3114	void operator() (ev::io &w, int revents)
		3115	{
		3116	...
		3117	}
		3118	}
		3119
		3120	myfunctor f;
		3121
		3122	ev::io w;
		3123	w.set (&f);
		3124
2543	=item w->set<function> (void *data = 0)	3125	=item w->set<function> (void *data = 0)
2544		3126
2545	Also sets a callback, but uses a static method or plain function as	3127	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3128	callback. The optional C<data> argument will be stored in the watcher's
2547	C<data> member and is free for you to use.	3129	C<data> member and is free for you to use.
2548		3130
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3131	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3132
2551	See the method-C<set> above for more details.	3133	See the method-C<set> above for more details.
2552		3134
2553	Example:	3135	Example: Use a plain function as callback.
2554		3136
2555	static void io_cb (ev::io &w, int revents) { }	3137	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3138	iow.set <io_cb> ();
2557		3139
2558	=item w->set (struct ev_loop *)	3140	=item w->set (struct ev_loop *)
…		…
2596	Example: Define a class with an IO and idle watcher, start one of them in	3178	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	3179	the constructor.
2598		3180
2599	class myclass	3181	class myclass
2600	{	3182	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3183	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3184	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3185
2604	myclass (int fd)	3186	myclass (int fd)
2605	{	3187	{
2606	io .set <myclass, &myclass::io_cb > (this);	3188	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3189	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2623	=item Perl	3205	=item Perl
2624		3206
2625	The EV module implements the full libev API and is actually used to test	3207	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3208	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3209	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3210	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3211	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3212	and C<EV::Glib>).
2630		3213
2631	It can be found and installed via CPAN, its homepage is found at	3214	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3215	L<http://software.schmorp.de/pkg/EV>.
		3216
		3217	=item Python
		3218
		3219	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3220	seems to be quite complete and well-documented.
2633		3221
2634	=item Ruby	3222	=item Ruby
2635		3223
2636	Tony Arcieri has written a ruby extension that offers access to a subset	3224	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds file handle abstractions, asynchronous DNS and	3225	of the libev API and adds file handle abstractions, asynchronous DNS and
2638	more on top of it. It can be found via gem servers. Its homepage is at	3226	more on top of it. It can be found via gem servers. Its homepage is at
2639	L<http://rev.rubyforge.org/>.	3227	L<http://rev.rubyforge.org/>.
2640		3228
		3229	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3230	makes rev work even on mingw.
		3231
		3232	=item Haskell
		3233
		3234	A haskell binding to libev is available at
		3235	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3236
2641	=item D	3237	=item D
2642		3238
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3239	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3240	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3241
		3242	=item Ocaml
		3243
		3244	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3245	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2645		3246
2646	=back	3247	=back
2647		3248
2648		3249
2649	=head1 MACRO MAGIC	3250	=head1 MACRO MAGIC
…		…
2750		3351
2751	#define EV_STANDALONE 1	3352	#define EV_STANDALONE 1
2752	#include "ev.h"	3353	#include "ev.h"
2753		3354
2754	Both header files and implementation files can be compiled with a C++	3355	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	3356	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	3357	as a bug).
2757		3358
2758	You need the following files in your source tree, or in a directory	3359	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	3360	in your include path (e.g. in libev/ when using -Ilibev):
2760		3361
…		…
2804		3405
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3406	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3407
2807	Libev can be configured via a variety of preprocessor symbols you have to	3408	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absence of	3409	define before including any of its files. The default in the absence of
2809	autoconf is noted for every option.	3410	autoconf is documented for every option.
2810		3411
2811	=over 4	3412	=over 4
2812		3413
2813	=item EV_STANDALONE	3414	=item EV_STANDALONE
2814		3415
…		…
2816	keeps libev from including F<config.h>, and it also defines dummy	3417	keeps libev from including F<config.h>, and it also defines dummy
2817	implementations for some libevent functions (such as logging, which is not	3418	implementations for some libevent functions (such as logging, which is not
2818	supported). It will also not define any of the structs usually found in	3419	supported). It will also not define any of the structs usually found in
2819	F<event.h> that are not directly supported by the libev core alone.	3420	F<event.h> that are not directly supported by the libev core alone.
2820		3421
		3422	In stanbdalone mode, libev will still try to automatically deduce the
		3423	configuration, but has to be more conservative.
		3424
2821	=item EV_USE_MONOTONIC	3425	=item EV_USE_MONOTONIC
2822		3426
2823	If defined to be C<1>, libev will try to detect the availability of the	3427	If defined to be C<1>, libev will try to detect the availability of the
2824	monotonic clock option at both compile time and runtime. Otherwise no use	3428	monotonic clock option at both compile time and runtime. Otherwise no
2825	of the monotonic clock option will be attempted. If you enable this, you	3429	use of the monotonic clock option will be attempted. If you enable this,
2826	usually have to link against librt or something similar. Enabling it when	3430	you usually have to link against librt or something similar. Enabling it
2827	the functionality isn't available is safe, though, although you have	3431	when the functionality isn't available is safe, though, although you have
2828	to make sure you link against any libraries where the C<clock_gettime>	3432	to make sure you link against any libraries where the C<clock_gettime>
2829	function is hiding in (often F<-lrt>).	3433	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2830		3434
2831	=item EV_USE_REALTIME	3435	=item EV_USE_REALTIME
2832		3436
2833	If defined to be C<1>, libev will try to detect the availability of the	3437	If defined to be C<1>, libev will try to detect the availability of the
2834	real-time clock option at compile time (and assume its availability at	3438	real-time clock option at compile time (and assume its availability
2835	runtime if successful). Otherwise no use of the real-time clock option will	3439	at runtime if successful). Otherwise no use of the real-time clock
2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3440	option will be attempted. This effectively replaces C<gettimeofday>
2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3441	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3442	correctness. See the note about libraries in the description of
		3443	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3444	C<EV_USE_CLOCK_SYSCALL>.
		3445
		3446	=item EV_USE_CLOCK_SYSCALL
		3447
		3448	If defined to be C<1>, libev will try to use a direct syscall instead
		3449	of calling the system-provided C<clock_gettime> function. This option
		3450	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3451	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3452	programs needlessly. Using a direct syscall is slightly slower (in
		3453	theory), because no optimised vdso implementation can be used, but avoids
		3454	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3455	higher, as it simplifies linking (no need for C<-lrt>).
2839		3456
2840	=item EV_USE_NANOSLEEP	3457	=item EV_USE_NANOSLEEP
2841		3458
2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3459	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2843	and will use it for delays. Otherwise it will use C<select ()>.	3460	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2859		3476
2860	=item EV_SELECT_USE_FD_SET	3477	=item EV_SELECT_USE_FD_SET
2861		3478
2862	If defined to C<1>, then the select backend will use the system C<fd_set>	3479	If defined to C<1>, then the select backend will use the system C<fd_set>
2863	structure. This is useful if libev doesn't compile due to a missing	3480	structure. This is useful if libev doesn't compile due to a missing
2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3481	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2865	exotic systems. This usually limits the range of file descriptors to some	3482	on exotic systems. This usually limits the range of file descriptors to
2866	low limit such as 1024 or might have other limitations (winsocket only	3483	some low limit such as 1024 or might have other limitations (winsocket
2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3484	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2868	influence the size of the C<fd_set> used.	3485	configures the maximum size of the C<fd_set>.
2869		3486
2870	=item EV_SELECT_IS_WINSOCKET	3487	=item EV_SELECT_IS_WINSOCKET
2871		3488
2872	When defined to C<1>, the select backend will assume that	3489	When defined to C<1>, the select backend will assume that
2873	select/socket/connect etc. don't understand file descriptors but	3490	select/socket/connect etc. don't understand file descriptors but
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3601	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	3602	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	3603	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3604	fine.
2988		3605
2989	If your embedding application does not need any priorities, defining these both to	3606	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3607	both to C<0> will save some memory and CPU.
2991		3608
2992	=item EV_PERIODIC_ENABLE	3609	=item EV_PERIODIC_ENABLE
2993		3610
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3611	If undefined or defined to be C<1>, then periodic timers are supported. If
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	3612	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3002	code.	3619	code.
3003		3620
3004	=item EV_EMBED_ENABLE	3621	=item EV_EMBED_ENABLE
3005		3622
3006	If undefined or defined to be C<1>, then embed watchers are supported. If	3623	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.	3624	defined to be C<0>, then they are not. Embed watchers rely on most other
		3625	watcher types, which therefore must not be disabled.
3008		3626
3009	=item EV_STAT_ENABLE	3627	=item EV_STAT_ENABLE
3010		3628
3011	If undefined or defined to be C<1>, then stat watchers are supported. If	3629	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.	3630	defined to be C<0>, then they are not.
…		…
3044	two).	3662	two).
3045		3663
3046	=item EV_USE_4HEAP	3664	=item EV_USE_4HEAP
3047		3665
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3666	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3667	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	3668	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	3669	faster performance with many (thousands) of watchers.
3052		3670
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3671	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3054	(disabled).	3672	(disabled).
3055		3673
3056	=item EV_HEAP_CACHE_AT	3674	=item EV_HEAP_CACHE_AT
3057		3675
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3676	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	3677	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3678	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3679	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	3680	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	3681	noticeably with many (hundreds) of watchers.
3064		3682
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3683	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3066	(disabled).	3684	(disabled).
3067		3685
3068	=item EV_VERIFY	3686	=item EV_VERIFY
…		…
3074	called once per loop, which can slow down libev. If set to C<3>, then the	3692	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	3693	verification code will be called very frequently, which will slow down
3076	libev considerably.	3694	libev considerably.
3077		3695
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3696	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3079	C<0.>	3697	C<0>.
3080		3698
3081	=item EV_COMMON	3699	=item EV_COMMON
3082		3700
3083	By default, all watchers have a C<void *data> member. By redefining	3701	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	3702	this macro to a something else you can include more and other types of
…		…
3101	and the way callbacks are invoked and set. Must expand to a struct member	3719	and the way callbacks are invoked and set. Must expand to a struct member
3102	definition and a statement, respectively. See the F<ev.h> header file for	3720	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	3721	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3722	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	3723	method calls instead of plain function calls in C++.
		3724
		3725	=back
3106		3726
3107	=head2 EXPORTED API SYMBOLS	3727	=head2 EXPORTED API SYMBOLS
3108		3728
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	3729	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	3730	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3777	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		3778
3159	#include "ev_cpp.h"	3779	#include "ev_cpp.h"
3160	#include "ev.c"	3780	#include "ev.c"
3161		3781
		3782	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		3783
3163	=head1 THREADS AND COROUTINES	3784	=head2 THREADS AND COROUTINES
3164		3785
3165	=head2 THREADS	3786	=head3 THREADS
3166		3787
3167	Libev itself is completely thread-safe, but it uses no locking. This	3788	All libev functions are reentrant and thread-safe unless explicitly
		3789	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	3790	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	3791	are no concurrent calls into any libev function with the same loop
3170	parameter.	3792	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3793	of course): libev guarantees that different event loops share no data
		3794	structures that need any locking.
3171		3795
3172	Or put differently: calls with different loop parameters can be done in	3796	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	3797	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	3798	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	3799	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	3800	a mutex per loop).
3177		3801
3178	If you want to know which design is best for your problem, then I cannot	3802	Specifically to support threads (and signal handlers), libev implements
		3803	so-called C<ev_async> watchers, which allow some limited form of
		3804	concurrency on the same event loop, namely waking it up "from the
		3805	outside".
		3806
		3807	If you want to know which design (one loop, locking, or multiple loops
		3808	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	3809	help you, but here is some generic advice:
3180		3810
3181	=over 4	3811	=over 4
3182		3812
3183	=item * most applications have a main thread: use the default libev loop	3813	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a separate thread running only the default loop.	3814	in that thread, or create a separate thread running only the default loop.
…		…
3196		3826
3197	Choosing a model is hard - look around, learn, know that usually you can do	3827	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	3828	better than you currently do :-)
3199		3829
3200	=item * often you need to talk to some other thread which blocks in the	3830	=item * often you need to talk to some other thread which blocks in the
		3831	event loop.
		3832
3201	event loop - C<ev_async> watchers can be used to wake them up from other	3833	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	3834	(or from signal contexts...).
		3835
		3836	An example use would be to communicate signals or other events that only
		3837	work in the default loop by registering the signal watcher with the
		3838	default loop and triggering an C<ev_async> watcher from the default loop
		3839	watcher callback into the event loop interested in the signal.
3203		3840
3204	=back	3841	=back
3205		3842
3206	=head2 COROUTINES	3843	=head3 COROUTINES
3207		3844
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	3845	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	3846	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3847	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	3848	different coroutines, and switch freely between both coroutines running the
3212	loop, as long as you don't confuse yourself). The only exception is that	3849	loop, as long as you don't confuse yourself). The only exception is that
3213	you must not do this from C<ev_periodic> reschedule callbacks.	3850	you must not do this from C<ev_periodic> reschedule callbacks.
3214		3851
3215	Care has been invested into making sure that libev does not keep local	3852	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	3853	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	3854	they do not call any callbacks.
3218		3855
		3856	=head2 COMPILER WARNINGS
3219		3857
3220	=head1 COMPLEXITIES	3858	Depending on your compiler and compiler settings, you might get no or a
		3859	lot of warnings when compiling libev code. Some people are apparently
		3860	scared by this.
3221		3861
3222	In this section the complexities of (many of) the algorithms used inside	3862	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	3863	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	3864	warning options. "Warn-free" code therefore cannot be a goal except when
		3865	targeting a specific compiler and compiler-version.
3225		3866
3226	All of the following are about amortised time: If an array needs to be	3867	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	3868	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	3869	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		3870
3232	=over 4	3871	And of course, some compiler warnings are just plain stupid, or simply
		3872	wrong (because they don't actually warn about the condition their message
		3873	seems to warn about). For example, certain older gcc versions had some
		3874	warnings that resulted an extreme number of false positives. These have
		3875	been fixed, but some people still insist on making code warn-free with
		3876	such buggy versions.
3233		3877
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3878	While libev is written to generate as few warnings as possible,
		3879	"warn-free" code is not a goal, and it is recommended not to build libev
		3880	with any compiler warnings enabled unless you are prepared to cope with
		3881	them (e.g. by ignoring them). Remember that warnings are just that:
		3882	warnings, not errors, or proof of bugs.
3235		3883
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		3884
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3885	=head2 VALGRIND
3241		3886
3242	That means that changing a timer costs less than removing/adding them	3887	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	3888	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		3889
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3890	If you think you found a bug (memory leak, uninitialised data access etc.)
		3891	in libev, then check twice: If valgrind reports something like:
3246		3892
3247	These just add the watcher into an array or at the head of a list.	3893	==2274== definitely lost: 0 bytes in 0 blocks.
		3894	==2274== possibly lost: 0 bytes in 0 blocks.
		3895	==2274== still reachable: 256 bytes in 1 blocks.
3248		3896
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3897	Then there is no memory leak, just as memory accounted to global variables
		3898	is not a memleak - the memory is still being referenced, and didn't leak.
3250		3899
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3900	Similarly, under some circumstances, valgrind might report kernel bugs
		3901	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3902	although an acceptable workaround has been found here), or it might be
		3903	confused.
3252		3904
3253	These watchers are stored in lists then need to be walked to find the	3905	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	3906	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		3907
3257	=item Finding the next timer in each loop iteration: O(1)	3908	If you are unsure about something, feel free to contact the mailing list
		3909	with the full valgrind report and an explanation on why you think this
		3910	is a bug in libev (best check the archives, too :). However, don't be
		3911	annoyed when you get a brisk "this is no bug" answer and take the chance
		3912	of learning how to interpret valgrind properly.
3258		3913
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	3914	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	3915	I suggest using suppression lists.
3261		3916
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		3917
3264	A change means an I/O watcher gets started or stopped, which requires	3918	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and whether C<ev_io_set> was used).
3267		3919
3268	=item Activating one watcher (putting it into the pending state): O(1)
3269
3270	=item Priority handling: O(number_of_priorities)
3271
3272	Priorities are implemented by allocating some space for each
3273	priority. When doing priority-based operations, libev usually has to
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276
3277	=item Sending an ev_async: O(1)
3278
3279	=item Processing ev_async_send: O(number_of_async_watchers)
3280
3281	=item Processing signals: O(max_signal_number)
3282
3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
3284	calls in the current loop iteration. Checking for async and signal events
3285	involves iterating over all running async watchers or all signal numbers.
3286
3287	=back
3288
3289
3290	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3920	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3291		3921
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3922	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	3923	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	3924	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3925	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3306		3936
3307	Not a libev limitation but worth mentioning: windows apparently doesn't	3937	Not a libev limitation but worth mentioning: windows apparently doesn't
3308	accept large writes: instead of resulting in a partial write, windows will	3938	accept large writes: instead of resulting in a partial write, windows will
3309	either accept everything or return C<ENOBUFS> if the buffer is too large,	3939	either accept everything or return C<ENOBUFS> if the buffer is too large,
3310	so make sure you only write small amounts into your sockets (less than a	3940	so make sure you only write small amounts into your sockets (less than a
3311	megabyte seems safe, but thsi apparently depends on the amount of memory	3941	megabyte seems safe, but this apparently depends on the amount of memory
3312	available).	3942	available).
3313		3943
3314	Due to the many, low, and arbitrary limits on the win32 platform and	3944	Due to the many, low, and arbitrary limits on the win32 platform and
3315	the abysmal performance of winsockets, using a large number of sockets	3945	the abysmal performance of winsockets, using a large number of sockets
3316	is not recommended (and not reasonable). If your program needs to use	3946	is not recommended (and not reasonable). If your program needs to use
3317	more than a hundred or so sockets, then likely it needs to use a totally	3947	more than a hundred or so sockets, then likely it needs to use a totally
3318	different implementation for windows, as libev offers the POSIX readiness	3948	different implementation for windows, as libev offers the POSIX readiness
3319	notification model, which cannot be implemented efficiently on windows	3949	notification model, which cannot be implemented efficiently on windows
3320	(Microsoft monopoly games).	3950	(Microsoft monopoly games).
3321		3951
		3952	A typical way to use libev under windows is to embed it (see the embedding
		3953	section for details) and use the following F<evwrap.h> header file instead
		3954	of F<ev.h>:
		3955
		3956	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3957	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3958
		3959	#include "ev.h"
		3960
		3961	And compile the following F<evwrap.c> file into your project (make sure
		3962	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3963
		3964	#include "evwrap.h"
		3965	#include "ev.c"
		3966
3322	=over 4	3967	=over 4
3323		3968
3324	=item The winsocket select function	3969	=item The winsocket select function
3325		3970
3326	The winsocket C<select> function doesn't follow POSIX in that it	3971	The winsocket C<select> function doesn't follow POSIX in that it
3327	requires socket I<handles> and not socket I<file descriptors> (it is	3972	requires socket I<handles> and not socket I<file descriptors> (it is
3328	also extremely buggy). This makes select very inefficient, and also	3973	also extremely buggy). This makes select very inefficient, and also
3329	requires a mapping from file descriptors to socket handles. See the	3974	requires a mapping from file descriptors to socket handles (the Microsoft
		3975	C runtime provides the function C<_open_osfhandle> for this). See the
3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	3976	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	3977	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3332		3978
3333	The configuration for a "naked" win32 using the Microsoft runtime	3979	The configuration for a "naked" win32 using the Microsoft runtime
3334	libraries and raw winsocket select is:	3980	libraries and raw winsocket select is:
…		…
3366	wrap all I/O functions and provide your own fd management, but the cost of	4012	wrap all I/O functions and provide your own fd management, but the cost of
3367	calling select (O(n²)) will likely make this unworkable.	4013	calling select (O(n²)) will likely make this unworkable.
3368		4014
3369	=back	4015	=back
3370		4016
3371
3372	=head1 PORTABILITY REQUIREMENTS	4017	=head2 PORTABILITY REQUIREMENTS
3373		4018
3374	In addition to a working ISO-C implementation, libev relies on a few	4019	In addition to a working ISO-C implementation and of course the
3375	additional extensions:	4020	backend-specific APIs, libev relies on a few additional extensions:
3376		4021
3377	=over 4	4022	=over 4
3378		4023
		4024	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4025	calling conventions regardless of C<ev_watcher_type *>.
		4026
		4027	Libev assumes not only that all watcher pointers have the same internal
		4028	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4029	assumes that the same (machine) code can be used to call any watcher
		4030	callback: The watcher callbacks have different type signatures, but libev
		4031	calls them using an C<ev_watcher *> internally.
		4032
3379	=item C<sig_atomic_t volatile> must be thread-atomic as well	4033	=item C<sig_atomic_t volatile> must be thread-atomic as well
3380		4034
3381	The type C<sig_atomic_t volatile> (or whatever is defined as	4035	The type C<sig_atomic_t volatile> (or whatever is defined as
3382	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4036	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3383	threads. This is not part of the specification for C<sig_atomic_t>, but is	4037	threads. This is not part of the specification for C<sig_atomic_t>, but is
3384	believed to be sufficiently portable.	4038	believed to be sufficiently portable.
3385		4039
3386	=item C<sigprocmask> must work in a threaded environment	4040	=item C<sigprocmask> must work in a threaded environment
3387		4041
…		…
3396	except the initial one, and run the default loop in the initial thread as	4050	except the initial one, and run the default loop in the initial thread as
3397	well.	4051	well.
3398		4052
3399	=item C<long> must be large enough for common memory allocation sizes	4053	=item C<long> must be large enough for common memory allocation sizes
3400		4054
3401	To improve portability and simplify using libev, libev uses C<long>	4055	To improve portability and simplify its API, libev uses C<long> internally
3402	internally instead of C<size_t> when allocating its data structures. On	4056	instead of C<size_t> when allocating its data structures. On non-POSIX
3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4057	systems (Microsoft...) this might be unexpectedly low, but is still at
3404	is still at least 31 bits everywhere, which is enough for hundreds of	4058	least 31 bits everywhere, which is enough for hundreds of millions of
3405	millions of watchers.	4059	watchers.
3406		4060
3407	=item C<double> must hold a time value in seconds with enough accuracy	4061	=item C<double> must hold a time value in seconds with enough accuracy
3408		4062
3409	The type C<double> is used to represent timestamps. It is required to	4063	The type C<double> is used to represent timestamps. It is required to
3410	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4064	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3414	=back	4068	=back
3415		4069
3416	If you know of other additional requirements drop me a note.	4070	If you know of other additional requirements drop me a note.
3417		4071
3418		4072
3419	=head1 COMPILER WARNINGS	4073	=head1 ALGORITHMIC COMPLEXITIES
3420		4074
3421	Depending on your compiler and compiler settings, you might get no or a	4075	In this section the complexities of (many of) the algorithms used inside
3422	lot of warnings when compiling libev code. Some people are apparently	4076	libev will be documented. For complexity discussions about backends see
3423	scared by this.	4077	the documentation for C<ev_default_init>.
3424		4078
3425	However, these are unavoidable for many reasons. For one, each compiler	4079	All of the following are about amortised time: If an array needs to be
3426	has different warnings, and each user has different tastes regarding	4080	extended, libev needs to realloc and move the whole array, but this
3427	warning options. "Warn-free" code therefore cannot be a goal except when	4081	happens asymptotically rarer with higher number of elements, so O(1) might
3428	targeting a specific compiler and compiler-version.	4082	mean that libev does a lengthy realloc operation in rare cases, but on
		4083	average it is much faster and asymptotically approaches constant time.
3429		4084
3430	Another reason is that some compiler warnings require elaborate	4085	=over 4
3431	workarounds, or other changes to the code that make it less clear and less
3432	maintainable.
3433		4086
3434	And of course, some compiler warnings are just plain stupid, or simply	4087	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3435	wrong (because they don't actually warn about the condition their message
3436	seems to warn about).
3437		4088
3438	While libev is written to generate as few warnings as possible,	4089	This means that, when you have a watcher that triggers in one hour and
3439	"warn-free" code is not a goal, and it is recommended not to build libev	4090	there are 100 watchers that would trigger before that, then inserting will
3440	with any compiler warnings enabled unless you are prepared to cope with	4091	have to skip roughly seven (C<ld 100>) of these watchers.
3441	them (e.g. by ignoring them). Remember that warnings are just that:
3442	warnings, not errors, or proof of bugs.
3443		4092
		4093	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3444		4094
3445	=head1 VALGRIND	4095	That means that changing a timer costs less than removing/adding them,
		4096	as only the relative motion in the event queue has to be paid for.
3446		4097
3447	Valgrind has a special section here because it is a popular tool that is	4098	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3448	highly useful, but valgrind reports are very hard to interpret.
3449		4099
3450	If you think you found a bug (memory leak, uninitialised data access etc.)	4100	These just add the watcher into an array or at the head of a list.
3451	in libev, then check twice: If valgrind reports something like:
3452		4101
3453	==2274== definitely lost: 0 bytes in 0 blocks.	4102	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3454	==2274== possibly lost: 0 bytes in 0 blocks.
3455	==2274== still reachable: 256 bytes in 1 blocks.
3456		4103
3457	Then there is no memory leak. Similarly, under some circumstances,	4104	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3458	valgrind might report kernel bugs as if it were a bug in libev, or it
3459	might be confused (it is a very good tool, but only a tool).
3460		4105
3461	If you are unsure about something, feel free to contact the mailing list	4106	These watchers are stored in lists, so they need to be walked to find the
3462	with the full valgrind report and an explanation on why you think this is	4107	correct watcher to remove. The lists are usually short (you don't usually
3463	a bug in libev. However, don't be annoyed when you get a brisk "this is	4108	have many watchers waiting for the same fd or signal: one is typical, two
3464	no bug" answer and take the chance of learning how to interpret valgrind	4109	is rare).
3465	properly.
3466		4110
3467	If you need, for some reason, empty reports from valgrind for your project	4111	=item Finding the next timer in each loop iteration: O(1)
3468	I suggest using suppression lists.
3469		4112
		4113	By virtue of using a binary or 4-heap, the next timer is always found at a
		4114	fixed position in the storage array.
		4115
		4116	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4117
		4118	A change means an I/O watcher gets started or stopped, which requires
		4119	libev to recalculate its status (and possibly tell the kernel, depending
		4120	on backend and whether C<ev_io_set> was used).
		4121
		4122	=item Activating one watcher (putting it into the pending state): O(1)
		4123
		4124	=item Priority handling: O(number_of_priorities)
		4125
		4126	Priorities are implemented by allocating some space for each
		4127	priority. When doing priority-based operations, libev usually has to
		4128	linearly search all the priorities, but starting/stopping and activating
		4129	watchers becomes O(1) with respect to priority handling.
		4130
		4131	=item Sending an ev_async: O(1)
		4132
		4133	=item Processing ev_async_send: O(number_of_async_watchers)
		4134
		4135	=item Processing signals: O(max_signal_number)
		4136
		4137	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4138	calls in the current loop iteration. Checking for async and signal events
		4139	involves iterating over all running async watchers or all signal numbers.
		4140
		4141	=back
		4142
		4143
		4144	=head1 GLOSSARY
		4145
		4146	=over 4
		4147
		4148	=item active
		4149
		4150	A watcher is active as long as it has been started (has been attached to
		4151	an event loop) but not yet stopped (disassociated from the event loop).
		4152
		4153	=item application
		4154
		4155	In this document, an application is whatever is using libev.
		4156
		4157	=item callback
		4158
		4159	The address of a function that is called when some event has been
		4160	detected. Callbacks are being passed the event loop, the watcher that
		4161	received the event, and the actual event bitset.
		4162
		4163	=item callback invocation
		4164
		4165	The act of calling the callback associated with a watcher.
		4166
		4167	=item event
		4168
		4169	A change of state of some external event, such as data now being available
		4170	for reading on a file descriptor, time having passed or simply not having
		4171	any other events happening anymore.
		4172
		4173	In libev, events are represented as single bits (such as C<EV_READ> or
		4174	C<EV_TIMEOUT>).
		4175
		4176	=item event library
		4177
		4178	A software package implementing an event model and loop.
		4179
		4180	=item event loop
		4181
		4182	An entity that handles and processes external events and converts them
		4183	into callback invocations.
		4184
		4185	=item event model
		4186
		4187	The model used to describe how an event loop handles and processes
		4188	watchers and events.
		4189
		4190	=item pending
		4191
		4192	A watcher is pending as soon as the corresponding event has been detected,
		4193	and stops being pending as soon as the watcher will be invoked or its
		4194	pending status is explicitly cleared by the application.
		4195
		4196	A watcher can be pending, but not active. Stopping a watcher also clears
		4197	its pending status.
		4198
		4199	=item real time
		4200
		4201	The physical time that is observed. It is apparently strictly monotonic :)
		4202
		4203	=item wall-clock time
		4204
		4205	The time and date as shown on clocks. Unlike real time, it can actually
		4206	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4207	clock.
		4208
		4209	=item watcher
		4210
		4211	A data structure that describes interest in certain events. Watchers need
		4212	to be started (attached to an event loop) before they can receive events.
		4213
		4214	=item watcher invocation
		4215
		4216	The act of calling the callback associated with a watcher.
		4217
		4218	=back
3470		4219
3471	=head1 AUTHOR	4220	=head1 AUTHOR
3472		4221
3473	Marc Lehmann <libev@schmorp.de>.	4222	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3474		4223

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