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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.
…		…
617	any active watchers at all will result in not sleeping).	722	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	723	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	724	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	725	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	726	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	727	- Queue all expired timers.
623	- Queue all outstanding periodics.	728	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	729	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	730	- Queue all check watchers.
626	- 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).
627	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
628	be handled here by queueing them when their watcher gets executed.	733	be handled here by queueing them when their watcher gets executed.
…		…
645	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
646	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.
647		752
648	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.
649		754
		755	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		756
650	=item ev_ref (loop)	757	=item ev_ref (loop)
651		758
652	=item ev_unref (loop)	759	=item ev_unref (loop)
653		760
654	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
655	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
656	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
657	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>
658	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
659	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
660	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
661	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
662	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
663	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
664	(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
665	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).
666		778
667	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>
668	running when nothing else is active.	780	running when nothing else is active.
669		781
670	struct ev_signal exitsig;	782	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	783	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	784	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	785	evf_unref (loop);
674		786
675	Example: For some weird reason, unregister the above signal handler again.	787	Example: For some weird reason, unregister the above signal handler again.
…		…
689	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>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	802	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	803	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	804	opportunities).
693		805
694	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
695	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
696	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
697	events, especially with backends like C<select ()> which have a high	809	events, especially with backends like C<select ()> which have a high
698	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.
699		811
700	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
701	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,
702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	814	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
703	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
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	816	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		817	sleep time ensures that libev will not poll for I/O events more often then
		818	once per this interval, on average.
705		819
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	820	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	821	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	822	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	823	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	824	value will not introduce any overhead in libev.
711		825
712	Many (busy) programs can usually benefit by setting the I/O collect	826	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	827	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	828	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	829	usually doesn't make much sense to set it to a lower value than C<0.01>,
716	as this approaches the timing granularity of most systems.	830	as this approaches the timing granularity of most systems. Note that if
		831	you do transactions with the outside world and you can't increase the
		832	parallelity, then this setting will limit your transaction rate (if you
		833	need to poll once per transaction and the I/O collect interval is 0.01,
		834	then you can't do more than 100 transations per second).
717		835
718	Setting the I<timeout collect interval> can improve the opportunity for	836	Setting the I<timeout collect interval> can improve the opportunity for
719	saving power, as the program will "bundle" timer callback invocations that	837	saving power, as the program will "bundle" timer callback invocations that
720	are "near" in time together, by delaying some, thus reducing the number of	838	are "near" in time together, by delaying some, thus reducing the number of
721	times the process sleeps and wakes up again. Another useful technique to	839	times the process sleeps and wakes up again. Another useful technique to
722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	840	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
723	they fire on, say, one-second boundaries only.	841	they fire on, say, one-second boundaries only.
724		842
		843	Example: we only need 0.1s timeout granularity, and we wish not to poll
		844	more often than 100 times per second:
		845
		846	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		847	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		848
725	=item ev_loop_verify (loop)	849	=item ev_loop_verify (loop)
726		850
727	This function only does something when C<EV_VERIFY> support has been	851	This function only does something when C<EV_VERIFY> support has been
728	compiled in. It tries to go through all internal structures and checks	852	compiled in, which is the default for non-minimal builds. It tries to go
729	them for validity. If anything is found to be inconsistent, it will print	853	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	854	is found to be inconsistent, it will print an error message to standard
		855	error and call C<abort ()>.
731		856
732	This can be used to catch bugs inside libev itself: under normal	857	This can be used to catch bugs inside libev itself: under normal
733	circumstances, this function will never abort as of course libev keeps its	858	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	859	data structures consistent.
735		860
736	=back	861	=back
737		862
738		863
739	=head1 ANATOMY OF A WATCHER	864	=head1 ANATOMY OF A WATCHER
740		865
		866	In the following description, uppercase C<TYPE> in names stands for the
		867	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		868	watchers and C<ev_io_start> for I/O watchers.
		869
741	A watcher is a structure that you create and register to record your	870	A watcher is a structure that you create and register to record your
742	interest in some event. For instance, if you want to wait for STDIN to	871	interest in some event. For instance, if you want to wait for STDIN to
743	become readable, you would create an C<ev_io> watcher for that:	872	become readable, you would create an C<ev_io> watcher for that:
744		873
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	874	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	875	{
747	ev_io_stop (w);	876	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	877	ev_unloop (loop, EVUNLOOP_ALL);
749	}	878	}
750		879
751	struct ev_loop *loop = ev_default_loop (0);	880	struct ev_loop *loop = ev_default_loop (0);
		881
752	struct ev_io stdin_watcher;	882	ev_io stdin_watcher;
		883
753	ev_init (&stdin_watcher, my_cb);	884	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	885	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	886	ev_io_start (loop, &stdin_watcher);
		887
756	ev_loop (loop, 0);	888	ev_loop (loop, 0);
757		889
758	As you can see, you are responsible for allocating the memory for your	890	As you can see, you are responsible for allocating the memory for your
759	watcher structures (and it is usually a bad idea to do this on the stack,	891	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	892	stack).
		893
		894	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		895	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
761		896
762	Each watcher structure must be initialised by a call to C<ev_init	897	Each watcher structure must be initialised by a call to C<ev_init
763	(watcher *, callback)>, which expects a callback to be provided. This	898	(watcher *, callback)>, which expects a callback to be provided. This
764	callback gets invoked each time the event occurs (or, in the case of I/O	899	callback gets invoked each time the event occurs (or, in the case of I/O
765	watchers, each time the event loop detects that the file descriptor given	900	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	901	is readable and/or writable).
767		902
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	903	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
769	with arguments specific to this watcher type. There is also a macro	904	macro to configure it, with arguments specific to the watcher type. There
770	to combine initialisation and setting in one call: C<< ev_<type>_init	905	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	906	ev_TYPE_init (watcher *, callback, ...) >>.
772		907
773	To make the watcher actually watch out for events, you have to start it	908	To make the watcher actually watch out for events, you have to start it
774	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	909	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
775	*) >>), and you can stop watching for events at any time by calling the	910	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	911	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		912
778	As long as your watcher is active (has been started but not stopped) you	913	As long as your watcher is active (has been started but not stopped) you
779	must not touch the values stored in it. Most specifically you must never	914	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	915	reinitialise it or call its C<ev_TYPE_set> macro.
781		916
782	Each and every callback receives the event loop pointer as first, the	917	Each and every callback receives the event loop pointer as first, the
783	registered watcher structure as second, and a bitset of received events as	918	registered watcher structure as second, and a bitset of received events as
784	third argument.	919	third argument.
785		920
…		…
843		978
844	=item C<EV_ASYNC>	979	=item C<EV_ASYNC>
845		980
846	The given async watcher has been asynchronously notified (see C<ev_async>).	981	The given async watcher has been asynchronously notified (see C<ev_async>).
847		982
		983	=item C<EV_CUSTOM>
		984
		985	Not ever sent (or otherwise used) by libev itself, but can be freely used
		986	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		987
848	=item C<EV_ERROR>	988	=item C<EV_ERROR>
849		989
850	An unspecified error has occurred, the watcher has been stopped. This might	990	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	991	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	992	ran out of memory, a file descriptor was found to be closed or any other
		993	problem. Libev considers these application bugs.
		994
853	problem. You best act on it by reporting the problem and somehow coping	995	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	996	watcher being stopped. Note that well-written programs should not receive
		997	an error ever, so when your watcher receives it, this usually indicates a
		998	bug in your program.
855		999
856	Libev will usually signal a few "dummy" events together with an error,	1000	Libev will usually signal a few "dummy" events together with an error, for
857	for example it might indicate that a fd is readable or writable, and if	1001	example it might indicate that a fd is readable or writable, and if your
858	your callbacks is well-written it can just attempt the operation and cope	1002	callbacks is well-written it can just attempt the operation and cope with
859	with the error from read() or write(). This will not work in multi-threaded	1003	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	1004	programs, though, as the fd could already be closed and reused for another
		1005	thing, so beware.
861		1006
862	=back	1007	=back
863		1008
864	=head2 GENERIC WATCHER FUNCTIONS	1009	=head2 GENERIC WATCHER FUNCTIONS
865
866	In the following description, C<TYPE> stands for the watcher type,
867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
868		1010
869	=over 4	1011	=over 4
870		1012
871	=item C<ev_init> (ev_TYPE *watcher, callback)	1013	=item C<ev_init> (ev_TYPE *watcher, callback)
872		1014
…		…
878	which rolls both calls into one.	1020	which rolls both calls into one.
879		1021
880	You can reinitialise a watcher at any time as long as it has been stopped	1022	You can reinitialise a watcher at any time as long as it has been stopped
881	(or never started) and there are no pending events outstanding.	1023	(or never started) and there are no pending events outstanding.
882		1024
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1025	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	1026	int revents)>.
		1027
		1028	Example: Initialise an C<ev_io> watcher in two steps.
		1029
		1030	ev_io w;
		1031	ev_init (&w, my_cb);
		1032	ev_io_set (&w, STDIN_FILENO, EV_READ);
885		1033
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1034	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		1035
888	This macro initialises the type-specific parts of a watcher. You need to	1036	This macro initialises the type-specific parts of a watcher. You need to
889	call C<ev_init> at least once before you call this macro, but you can	1037	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	1040	difference to the C<ev_init> macro).
893		1041
894	Although some watcher types do not have type-specific arguments	1042	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1043	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		1044
		1045	See C<ev_init>, above, for an example.
		1046
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1047	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		1048
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1049	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
900	calls into a single call. This is the most convenient method to initialise	1050	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	1051	a watcher. The same limitations apply, of course.
902		1052
		1053	Example: Initialise and set an C<ev_io> watcher in one step.
		1054
		1055	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1056
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1057	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1058
905	Starts (activates) the given watcher. Only active watchers will receive	1059	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1060	events. If the watcher is already active nothing will happen.
907		1061
		1062	Example: Start the C<ev_io> watcher that is being abused as example in this
		1063	whole section.
		1064
		1065	ev_io_start (EV_DEFAULT_UC, &w);
		1066
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1067	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1068
910	Stops the given watcher again (if active) and clears the pending	1069	Stops the given watcher if active, and clears the pending status (whether
		1070	the watcher was active or not).
		1071
911	status. It is possible that stopped watchers are pending (for example,	1072	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1073	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1074	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	1075	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	1076	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1077
917	=item bool ev_is_active (ev_TYPE *watcher)	1078	=item bool ev_is_active (ev_TYPE *watcher)
918		1079
919	Returns a true value iff the watcher is active (i.e. it has been started	1080	Returns a true value iff the watcher is active (i.e. it has been started
920	and not yet been stopped). As long as a watcher is active you must not modify	1081	and not yet been stopped). As long as a watcher is active you must not modify
…		…
946	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1107	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
947	(default: C<-2>). Pending watchers with higher priority will be invoked	1108	(default: C<-2>). Pending watchers with higher priority will be invoked
948	before watchers with lower priority, but priority will not keep watchers	1109	before watchers with lower priority, but priority will not keep watchers
949	from being executed (except for C<ev_idle> watchers).	1110	from being executed (except for C<ev_idle> watchers).
950		1111
951	This means that priorities are I<only> used for ordering callback
952	invocation after new events have been received. This is useful, for
953	example, to reduce latency after idling, or more often, to bind two
954	watchers on the same event and make sure one is called first.
955
956	If you need to suppress invocation when higher priority events are pending	1112	If you need to suppress invocation when higher priority events are pending
957	you need to look at C<ev_idle> watchers, which provide this functionality.	1113	you need to look at C<ev_idle> watchers, which provide this functionality.
958		1114
959	You I<must not> change the priority of a watcher as long as it is active or	1115	You I<must not> change the priority of a watcher as long as it is active or
960	pending.	1116	pending.
961		1117
		1118	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1119	fine, as long as you do not mind that the priority value you query might
		1120	or might not have been clamped to the valid range.
		1121
962	The default priority used by watchers when no priority has been set is	1122	The default priority used by watchers when no priority has been set is
963	always C<0>, which is supposed to not be too high and not be too low :).	1123	always C<0>, which is supposed to not be too high and not be too low :).
964		1124
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1125	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
966	fine, as long as you do not mind that the priority value you query might	1126	priorities.
967	or might not have been adjusted to be within valid range.
968		1127
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1128	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1129
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1130	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1131	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1132	can deal with that fact, as both are simply passed through to the
		1133	callback.
974		1134
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1135	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1136
977	If the watcher is pending, this function returns clears its pending status	1137	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1138	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1139	watcher isn't pending it does nothing and returns C<0>.
980		1140
		1141	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1142	callback to be invoked, which can be accomplished with this function.
		1143
981	=back	1144	=back
982		1145
983		1146
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1147	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1148
986	Each watcher has, by default, a member C<void *data> that you can change	1149	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1150	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1151	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1152	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1153	member, you can also "subclass" the watcher type and provide your own
991	data:	1154	data:
992		1155
993	struct my_io	1156	struct my_io
994	{	1157	{
995	struct ev_io io;	1158	ev_io io;
996	int otherfd;	1159	int otherfd;
997	void *somedata;	1160	void *somedata;
998	struct whatever *mostinteresting;	1161	struct whatever *mostinteresting;
999	}	1162	};
		1163
		1164	...
		1165	struct my_io w;
		1166	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1167
1001	And since your callback will be called with a pointer to the watcher, you	1168	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1169	can cast it back to your own type:
1003		1170
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1171	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1172	{
1006	struct my_io *w = (struct my_io *)w_;	1173	struct my_io *w = (struct my_io *)w_;
1007	...	1174	...
1008	}	1175	}
1009		1176
1010	More interesting and less C-conformant ways of casting your callback type	1177	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1178	instead have been omitted.
1012		1179
1013	Another common scenario is having some data structure with multiple	1180	Another common scenario is to use some data structure with multiple
1014	watchers:	1181	embedded watchers:
1015		1182
1016	struct my_biggy	1183	struct my_biggy
1017	{	1184	{
1018	int some_data;	1185	int some_data;
1019	ev_timer t1;	1186	ev_timer t1;
1020	ev_timer t2;	1187	ev_timer t2;
1021	}	1188	}
1022		1189
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1190	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1191	complicated: Either you store the address of your C<my_biggy> struct
		1192	in the C<data> member of the watcher (for woozies), or you need to use
		1193	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1194	programmers):
1025		1195
1026	#include <stddef.h>	1196	#include <stddef.h>
1027		1197
1028	static void	1198	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1199	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1200	{
1031	struct my_biggy big = (struct my_biggy *	1201	struct my_biggy big = (struct my_biggy *)
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1202	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1203	}
1034		1204
1035	static void	1205	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1206	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1207	{
1038	struct my_biggy big = (struct my_biggy *	1208	struct my_biggy big = (struct my_biggy *)
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1209	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1210	}
		1211
		1212	=head2 WATCHER PRIORITY MODELS
		1213
		1214	Many event loops support I<watcher priorities>, which are usually small
		1215	integers that influence the ordering of event callback invocation
		1216	between watchers in some way, all else being equal.
		1217
		1218	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1219	description for the more technical details such as the actual priority
		1220	range.
		1221
		1222	There are two common ways how these these priorities are being interpreted
		1223	by event loops:
		1224
		1225	In the more common lock-out model, higher priorities "lock out" invocation
		1226	of lower priority watchers, which means as long as higher priority
		1227	watchers receive events, lower priority watchers are not being invoked.
		1228
		1229	The less common only-for-ordering model uses priorities solely to order
		1230	callback invocation within a single event loop iteration: Higher priority
		1231	watchers are invoked before lower priority ones, but they all get invoked
		1232	before polling for new events.
		1233
		1234	Libev uses the second (only-for-ordering) model for all its watchers
		1235	except for idle watchers (which use the lock-out model).
		1236
		1237	The rationale behind this is that implementing the lock-out model for
		1238	watchers is not well supported by most kernel interfaces, and most event
		1239	libraries will just poll for the same events again and again as long as
		1240	their callbacks have not been executed, which is very inefficient in the
		1241	common case of one high-priority watcher locking out a mass of lower
		1242	priority ones.
		1243
		1244	Static (ordering) priorities are most useful when you have two or more
		1245	watchers handling the same resource: a typical usage example is having an
		1246	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1247	timeouts. Under load, data might be received while the program handles
		1248	other jobs, but since timers normally get invoked first, the timeout
		1249	handler will be executed before checking for data. In that case, giving
		1250	the timer a lower priority than the I/O watcher ensures that I/O will be
		1251	handled first even under adverse conditions (which is usually, but not
		1252	always, what you want).
		1253
		1254	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1255	will only be executed when no same or higher priority watchers have
		1256	received events, they can be used to implement the "lock-out" model when
		1257	required.
		1258
		1259	For example, to emulate how many other event libraries handle priorities,
		1260	you can associate an C<ev_idle> watcher to each such watcher, and in
		1261	the normal watcher callback, you just start the idle watcher. The real
		1262	processing is done in the idle watcher callback. This causes libev to
		1263	continously poll and process kernel event data for the watcher, but when
		1264	the lock-out case is known to be rare (which in turn is rare :), this is
		1265	workable.
		1266
		1267	Usually, however, the lock-out model implemented that way will perform
		1268	miserably under the type of load it was designed to handle. In that case,
		1269	it might be preferable to stop the real watcher before starting the
		1270	idle watcher, so the kernel will not have to process the event in case
		1271	the actual processing will be delayed for considerable time.
		1272
		1273	Here is an example of an I/O watcher that should run at a strictly lower
		1274	priority than the default, and which should only process data when no
		1275	other events are pending:
		1276
		1277	ev_idle idle; // actual processing watcher
		1278	ev_io io; // actual event watcher
		1279
		1280	static void
		1281	io_cb (EV_P_ ev_io *w, int revents)
		1282	{
		1283	// stop the I/O watcher, we received the event, but
		1284	// are not yet ready to handle it.
		1285	ev_io_stop (EV_A_ w);
		1286
		1287	// start the idle watcher to ahndle the actual event.
		1288	// it will not be executed as long as other watchers
		1289	// with the default priority are receiving events.
		1290	ev_idle_start (EV_A_ &idle);
		1291	}
		1292
		1293	static void
		1294	idle_cb (EV_P_ ev_idle *w, int revents)
		1295	{
		1296	// actual processing
		1297	read (STDIN_FILENO, ...);
		1298
		1299	// have to start the I/O watcher again, as
		1300	// we have handled the event
		1301	ev_io_start (EV_P_ &io);
		1302	}
		1303
		1304	// initialisation
		1305	ev_idle_init (&idle, idle_cb);
		1306	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1307	ev_io_start (EV_DEFAULT_ &io);
		1308
		1309	In the "real" world, it might also be beneficial to start a timer, so that
		1310	low-priority connections can not be locked out forever under load. This
		1311	enables your program to keep a lower latency for important connections
		1312	during short periods of high load, while not completely locking out less
		1313	important ones.
1041		1314
1042		1315
1043	=head1 WATCHER TYPES	1316	=head1 WATCHER TYPES
1044		1317
1045	This section describes each watcher in detail, but will not repeat	1318	This section describes each watcher in detail, but will not repeat
…		…
1069	In general you can register as many read and/or write event watchers per	1342	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1343	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1344	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1345	required if you know what you are doing).
1073		1346
1074	If you must do this, then force the use of a known-to-be-good backend	1347	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1348	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1349	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1350	descriptors for which non-blocking operation makes no sense (such as
		1351	files) - libev doesn't guarentee any specific behaviour in that case.
1077		1352
1078	Another thing you have to watch out for is that it is quite easy to	1353	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1354	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1355	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1356	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1357	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1358	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1359	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1360	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1361
1087	If you cannot run the fd in non-blocking mode (for example you should not	1362	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1363	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1364	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1365	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1366	does this on its own, so its quite safe to use). Some people additionally
		1367	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1368	indefinitely.
		1369
		1370	But really, best use non-blocking mode.
1092		1371
1093	=head3 The special problem of disappearing file descriptors	1372	=head3 The special problem of disappearing file descriptors
1094		1373
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1374	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1375	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1376	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1377	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1378	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1379	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1380	fact, a different file descriptor.
1102		1381
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1412	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1413	C<EVBACKEND_POLL>.
1135		1414
1136	=head3 The special problem of SIGPIPE	1415	=head3 The special problem of SIGPIPE
1137		1416
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1417	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when writing to a pipe whose other end has been closed, your program gets	1418	when writing to a pipe whose other end has been closed, your program gets
1140	send a SIGPIPE, which, by default, aborts your program. For most programs	1419	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	this is sensible behaviour, for daemons, this is usually undesirable.	1420	this is sensible behaviour, for daemons, this is usually undesirable.
1142		1421
1143	So when you encounter spurious, unexplained daemon exits, make sure you	1422	So when you encounter spurious, unexplained daemon exits, make sure you
1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1423	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1145	somewhere, as that would have given you a big clue).	1424	somewhere, as that would have given you a big clue).
…		…
1152	=item ev_io_init (ev_io *, callback, int fd, int events)	1431	=item ev_io_init (ev_io *, callback, int fd, int events)
1153		1432
1154	=item ev_io_set (ev_io *, int fd, int events)	1433	=item ev_io_set (ev_io *, int fd, int events)
1155		1434
1156	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1435	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1157	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1436	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1158	C<EV_READ | EV_WRITE> to receive the given events.	1437	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1159		1438
1160	=item int fd [read-only]	1439	=item int fd [read-only]
1161		1440
1162	The file descriptor being watched.	1441	The file descriptor being watched.
1163		1442
…		…
1172	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1451	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1173	readable, but only once. Since it is likely line-buffered, you could	1452	readable, but only once. Since it is likely line-buffered, you could
1174	attempt to read a whole line in the callback.	1453	attempt to read a whole line in the callback.
1175		1454
1176	static void	1455	static void
1177	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1456	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1178	{	1457	{
1179	ev_io_stop (loop, w);	1458	ev_io_stop (loop, w);
1180	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1459	.. read from stdin here (or from w->fd) and handle any I/O errors
1181	}	1460	}
1182		1461
1183	...	1462	...
1184	struct ev_loop *loop = ev_default_init (0);	1463	struct ev_loop *loop = ev_default_init (0);
1185	struct ev_io stdin_readable;	1464	ev_io stdin_readable;
1186	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1465	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1187	ev_io_start (loop, &stdin_readable);	1466	ev_io_start (loop, &stdin_readable);
1188	ev_loop (loop, 0);	1467	ev_loop (loop, 0);
1189		1468
1190		1469
…		…
1193	Timer watchers are simple relative timers that generate an event after a	1472	Timer watchers are simple relative timers that generate an event after a
1194	given time, and optionally repeating in regular intervals after that.	1473	given time, and optionally repeating in regular intervals after that.
1195		1474
1196	The timers are based on real time, that is, if you register an event that	1475	The timers are based on real time, that is, if you register an event that
1197	times out after an hour and you reset your system clock to January last	1476	times out after an hour and you reset your system clock to January last
1198	year, it will still time out after (roughly) and hour. "Roughly" because	1477	year, it will still time out after (roughly) one hour. "Roughly" because
1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1478	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1200	monotonic clock option helps a lot here).	1479	monotonic clock option helps a lot here).
		1480
		1481	The callback is guaranteed to be invoked only I<after> its timeout has
		1482	passed (not I<at>, so on systems with very low-resolution clocks this
		1483	might introduce a small delay). If multiple timers become ready during the
		1484	same loop iteration then the ones with earlier time-out values are invoked
		1485	before ones with later time-out values (but this is no longer true when a
		1486	callback calls C<ev_loop> recursively).
		1487
		1488	=head3 Be smart about timeouts
		1489
		1490	Many real-world problems involve some kind of timeout, usually for error
		1491	recovery. A typical example is an HTTP request - if the other side hangs,
		1492	you want to raise some error after a while.
		1493
		1494	What follows are some ways to handle this problem, from obvious and
		1495	inefficient to smart and efficient.
		1496
		1497	In the following, a 60 second activity timeout is assumed - a timeout that
		1498	gets reset to 60 seconds each time there is activity (e.g. each time some
		1499	data or other life sign was received).
		1500
		1501	=over 4
		1502
		1503	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1504
		1505	This is the most obvious, but not the most simple way: In the beginning,
		1506	start the watcher:
		1507
		1508	ev_timer_init (timer, callback, 60., 0.);
		1509	ev_timer_start (loop, timer);
		1510
		1511	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1512	and start it again:
		1513
		1514	ev_timer_stop (loop, timer);
		1515	ev_timer_set (timer, 60., 0.);
		1516	ev_timer_start (loop, timer);
		1517
		1518	This is relatively simple to implement, but means that each time there is
		1519	some activity, libev will first have to remove the timer from its internal
		1520	data structure and then add it again. Libev tries to be fast, but it's
		1521	still not a constant-time operation.
		1522
		1523	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1524
		1525	This is the easiest way, and involves using C<ev_timer_again> instead of
		1526	C<ev_timer_start>.
		1527
		1528	To implement this, configure an C<ev_timer> with a C<repeat> value
		1529	of C<60> and then call C<ev_timer_again> at start and each time you
		1530	successfully read or write some data. If you go into an idle state where
		1531	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1532	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1533
		1534	That means you can ignore both the C<ev_timer_start> function and the
		1535	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1536	member and C<ev_timer_again>.
		1537
		1538	At start:
		1539
		1540	ev_init (timer, callback);
		1541	timer->repeat = 60.;
		1542	ev_timer_again (loop, timer);
		1543
		1544	Each time there is some activity:
		1545
		1546	ev_timer_again (loop, timer);
		1547
		1548	It is even possible to change the time-out on the fly, regardless of
		1549	whether the watcher is active or not:
		1550
		1551	timer->repeat = 30.;
		1552	ev_timer_again (loop, timer);
		1553
		1554	This is slightly more efficient then stopping/starting the timer each time
		1555	you want to modify its timeout value, as libev does not have to completely
		1556	remove and re-insert the timer from/into its internal data structure.
		1557
		1558	It is, however, even simpler than the "obvious" way to do it.
		1559
		1560	=item 3. Let the timer time out, but then re-arm it as required.
		1561
		1562	This method is more tricky, but usually most efficient: Most timeouts are
		1563	relatively long compared to the intervals between other activity - in
		1564	our example, within 60 seconds, there are usually many I/O events with
		1565	associated activity resets.
		1566
		1567	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1568	but remember the time of last activity, and check for a real timeout only
		1569	within the callback:
		1570
		1571	ev_tstamp last_activity; // time of last activity
		1572
		1573	static void
		1574	callback (EV_P_ ev_timer *w, int revents)
		1575	{
		1576	ev_tstamp now = ev_now (EV_A);
		1577	ev_tstamp timeout = last_activity + 60.;
		1578
		1579	// if last_activity + 60. is older than now, we did time out
		1580	if (timeout < now)
		1581	{
		1582	// timeout occured, take action
		1583	}
		1584	else
		1585	{
		1586	// callback was invoked, but there was some activity, re-arm
		1587	// the watcher to fire in last_activity + 60, which is
		1588	// guaranteed to be in the future, so "again" is positive:
		1589	w->repeat = timeout - now;
		1590	ev_timer_again (EV_A_ w);
		1591	}
		1592	}
		1593
		1594	To summarise the callback: first calculate the real timeout (defined
		1595	as "60 seconds after the last activity"), then check if that time has
		1596	been reached, which means something I<did>, in fact, time out. Otherwise
		1597	the callback was invoked too early (C<timeout> is in the future), so
		1598	re-schedule the timer to fire at that future time, to see if maybe we have
		1599	a timeout then.
		1600
		1601	Note how C<ev_timer_again> is used, taking advantage of the
		1602	C<ev_timer_again> optimisation when the timer is already running.
		1603
		1604	This scheme causes more callback invocations (about one every 60 seconds
		1605	minus half the average time between activity), but virtually no calls to
		1606	libev to change the timeout.
		1607
		1608	To start the timer, simply initialise the watcher and set C<last_activity>
		1609	to the current time (meaning we just have some activity :), then call the
		1610	callback, which will "do the right thing" and start the timer:
		1611
		1612	ev_init (timer, callback);
		1613	last_activity = ev_now (loop);
		1614	callback (loop, timer, EV_TIMEOUT);
		1615
		1616	And when there is some activity, simply store the current time in
		1617	C<last_activity>, no libev calls at all:
		1618
		1619	last_actiivty = ev_now (loop);
		1620
		1621	This technique is slightly more complex, but in most cases where the
		1622	time-out is unlikely to be triggered, much more efficient.
		1623
		1624	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1625	callback :) - just change the timeout and invoke the callback, which will
		1626	fix things for you.
		1627
		1628	=item 4. Wee, just use a double-linked list for your timeouts.
		1629
		1630	If there is not one request, but many thousands (millions...), all
		1631	employing some kind of timeout with the same timeout value, then one can
		1632	do even better:
		1633
		1634	When starting the timeout, calculate the timeout value and put the timeout
		1635	at the I<end> of the list.
		1636
		1637	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1638	the list is expected to fire (for example, using the technique #3).
		1639
		1640	When there is some activity, remove the timer from the list, recalculate
		1641	the timeout, append it to the end of the list again, and make sure to
		1642	update the C<ev_timer> if it was taken from the beginning of the list.
		1643
		1644	This way, one can manage an unlimited number of timeouts in O(1) time for
		1645	starting, stopping and updating the timers, at the expense of a major
		1646	complication, and having to use a constant timeout. The constant timeout
		1647	ensures that the list stays sorted.
		1648
		1649	=back
		1650
		1651	So which method the best?
		1652
		1653	Method #2 is a simple no-brain-required solution that is adequate in most
		1654	situations. Method #3 requires a bit more thinking, but handles many cases
		1655	better, and isn't very complicated either. In most case, choosing either
		1656	one is fine, with #3 being better in typical situations.
		1657
		1658	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1659	rather complicated, but extremely efficient, something that really pays
		1660	off after the first million or so of active timers, i.e. it's usually
		1661	overkill :)
		1662
		1663	=head3 The special problem of time updates
		1664
		1665	Establishing the current time is a costly operation (it usually takes at
		1666	least two system calls): EV therefore updates its idea of the current
		1667	time only before and after C<ev_loop> collects new events, which causes a
		1668	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1669	lots of events in one iteration.
1201		1670
1202	The relative timeouts are calculated relative to the C<ev_now ()>	1671	The relative timeouts are calculated relative to the C<ev_now ()>
1203	time. This is usually the right thing as this timestamp refers to the time	1672	time. This is usually the right thing as this timestamp refers to the time
1204	of the event triggering whatever timeout you are modifying/starting. If	1673	of the event triggering whatever timeout you are modifying/starting. If
1205	you suspect event processing to be delayed and you I<need> to base the timeout	1674	you suspect event processing to be delayed and you I<need> to base the
1206	on the current time, use something like this to adjust for this:	1675	timeout on the current time, use something like this to adjust for this:
1207		1676
1208	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1677	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1209		1678
1210	The callback is guaranteed to be invoked only after its timeout has passed,	1679	If the event loop is suspended for a long time, you can also force an
1211	but if multiple timers become ready during the same loop iteration then	1680	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1212	order of execution is undefined.	1681	()>.
1213		1682
1214	=head3 Watcher-Specific Functions and Data Members	1683	=head3 Watcher-Specific Functions and Data Members
1215		1684
1216	=over 4	1685	=over 4
1217		1686
…		…
1241	If the timer is started but non-repeating, stop it (as if it timed out).	1710	If the timer is started but non-repeating, stop it (as if it timed out).
1242		1711
1243	If the timer is repeating, either start it if necessary (with the	1712	If the timer is repeating, either start it if necessary (with the
1244	C<repeat> value), or reset the running timer to the C<repeat> value.	1713	C<repeat> value), or reset the running timer to the C<repeat> value.
1245		1714
1246	This sounds a bit complicated, but here is a useful and typical	1715	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1247	example: Imagine you have a TCP connection and you want a so-called idle	1716	usage example.
1248	timeout, that is, you want to be called when there have been, say, 60
1249	seconds of inactivity on the socket. The easiest way to do this is to
1250	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1251	C<ev_timer_again> each time you successfully read or write some data. If
1252	you go into an idle state where you do not expect data to travel on the
1253	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1254	automatically restart it if need be.
1255
1256	That means you can ignore the C<after> value and C<ev_timer_start>
1257	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1258
1259	ev_timer_init (timer, callback, 0., 5.);
1260	ev_timer_again (loop, timer);
1261	...
1262	timer->again = 17.;
1263	ev_timer_again (loop, timer);
1264	...
1265	timer->again = 10.;
1266	ev_timer_again (loop, timer);
1267
1268	This is more slightly efficient then stopping/starting the timer each time
1269	you want to modify its timeout value.
1270		1717
1271	=item ev_tstamp repeat [read-write]	1718	=item ev_tstamp repeat [read-write]
1272		1719
1273	The current C<repeat> value. Will be used each time the watcher times out	1720	The current C<repeat> value. Will be used each time the watcher times out
1274	or C<ev_timer_again> is called and determines the next timeout (if any),	1721	or C<ev_timer_again> is called, and determines the next timeout (if any),
1275	which is also when any modifications are taken into account.	1722	which is also when any modifications are taken into account.
1276		1723
1277	=back	1724	=back
1278		1725
1279	=head3 Examples	1726	=head3 Examples
1280		1727
1281	Example: Create a timer that fires after 60 seconds.	1728	Example: Create a timer that fires after 60 seconds.
1282		1729
1283	static void	1730	static void
1284	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1731	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1285	{	1732	{
1286	.. one minute over, w is actually stopped right here	1733	.. one minute over, w is actually stopped right here
1287	}	1734	}
1288		1735
1289	struct ev_timer mytimer;	1736	ev_timer mytimer;
1290	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1737	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1291	ev_timer_start (loop, &mytimer);	1738	ev_timer_start (loop, &mytimer);
1292		1739
1293	Example: Create a timeout timer that times out after 10 seconds of	1740	Example: Create a timeout timer that times out after 10 seconds of
1294	inactivity.	1741	inactivity.
1295		1742
1296	static void	1743	static void
1297	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1744	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1298	{	1745	{
1299	.. ten seconds without any activity	1746	.. ten seconds without any activity
1300	}	1747	}
1301		1748
1302	struct ev_timer mytimer;	1749	ev_timer mytimer;
1303	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1750	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1304	ev_timer_again (&mytimer); /* start timer */	1751	ev_timer_again (&mytimer); /* start timer */
1305	ev_loop (loop, 0);	1752	ev_loop (loop, 0);
1306		1753
1307	// and in some piece of code that gets executed on any "activity":	1754	// and in some piece of code that gets executed on any "activity":
…		…
1312	=head2 C<ev_periodic> - to cron or not to cron?	1759	=head2 C<ev_periodic> - to cron or not to cron?
1313		1760
1314	Periodic watchers are also timers of a kind, but they are very versatile	1761	Periodic watchers are also timers of a kind, but they are very versatile
1315	(and unfortunately a bit complex).	1762	(and unfortunately a bit complex).
1316		1763
1317	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1764	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1318	but on wall clock time (absolute time). You can tell a periodic watcher	1765	relative time, the physical time that passes) but on wall clock time
1319	to trigger after some specific point in time. For example, if you tell a	1766	(absolute time, the thing you can read on your calender or clock). The
1320	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1767	difference is that wall clock time can run faster or slower than real
1321	+ 10.>, that is, an absolute time not a delay) and then reset your system	1768	time, and time jumps are not uncommon (e.g. when you adjust your
1322	clock to January of the previous year, then it will take more than year	1769	wrist-watch).
1323	to trigger the event (unlike an C<ev_timer>, which would still trigger
1324	roughly 10 seconds later as it uses a relative timeout).
1325		1770
		1771	You can tell a periodic watcher to trigger after some specific point
		1772	in time: for example, if you tell a periodic watcher to trigger "in 10
		1773	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1774	not a delay) and then reset your system clock to January of the previous
		1775	year, then it will take a year or more to trigger the event (unlike an
		1776	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1777	it, as it uses a relative timeout).
		1778
1326	C<ev_periodic>s can also be used to implement vastly more complex timers,	1779	C<ev_periodic> watchers can also be used to implement vastly more complex
1327	such as triggering an event on each "midnight, local time", or other	1780	timers, such as triggering an event on each "midnight, local time", or
1328	complicated, rules.	1781	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1782	those cannot react to time jumps.
1329		1783
1330	As with timers, the callback is guaranteed to be invoked only when the	1784	As with timers, the callback is guaranteed to be invoked only when the
1331	time (C<at>) has passed, but if multiple periodic timers become ready	1785	point in time where it is supposed to trigger has passed. If multiple
1332	during the same loop iteration then order of execution is undefined.	1786	timers become ready during the same loop iteration then the ones with
		1787	earlier time-out values are invoked before ones with later time-out values
		1788	(but this is no longer true when a callback calls C<ev_loop> recursively).
1333		1789
1334	=head3 Watcher-Specific Functions and Data Members	1790	=head3 Watcher-Specific Functions and Data Members
1335		1791
1336	=over 4	1792	=over 4
1337		1793
1338	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1794	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1339		1795
1340	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1796	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1341		1797
1342	Lots of arguments, lets sort it out... There are basically three modes of	1798	Lots of arguments, let's sort it out... There are basically three modes of
1343	operation, and we will explain them from simplest to complex:	1799	operation, and we will explain them from simplest to most complex:
1344		1800
1345	=over 4	1801	=over 4
1346		1802
1347	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1803	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1348		1804
1349	In this configuration the watcher triggers an event after the wall clock	1805	In this configuration the watcher triggers an event after the wall clock
1350	time C<at> has passed and doesn't repeat. It will not adjust when a time	1806	time C<offset> has passed. It will not repeat and will not adjust when a
1351	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1807	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1352	run when the system time reaches or surpasses this time.	1808	will be stopped and invoked when the system clock reaches or surpasses
		1809	this point in time.
1353		1810
1354	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1811	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1355		1812
1356	In this mode the watcher will always be scheduled to time out at the next	1813	In this mode the watcher will always be scheduled to time out at the next
1357	C<at + N * interval> time (for some integer N, which can also be negative)	1814	C<offset + N * interval> time (for some integer N, which can also be
1358	and then repeat, regardless of any time jumps.	1815	negative) and then repeat, regardless of any time jumps. The C<offset>
		1816	argument is merely an offset into the C<interval> periods.
1359		1817
1360	This can be used to create timers that do not drift with respect to system	1818	This can be used to create timers that do not drift with respect to the
1361	time, for example, here is a C<ev_periodic> that triggers each hour, on	1819	system clock, for example, here is an C<ev_periodic> that triggers each
1362	the hour:	1820	hour, on the hour (with respect to UTC):
1363		1821
1364	ev_periodic_set (&periodic, 0., 3600., 0);	1822	ev_periodic_set (&periodic, 0., 3600., 0);
1365		1823
1366	This doesn't mean there will always be 3600 seconds in between triggers,	1824	This doesn't mean there will always be 3600 seconds in between triggers,
1367	but only that the callback will be called when the system time shows a	1825	but only that the callback will be called when the system time shows a
1368	full hour (UTC), or more correctly, when the system time is evenly divisible	1826	full hour (UTC), or more correctly, when the system time is evenly divisible
1369	by 3600.	1827	by 3600.
1370		1828
1371	Another way to think about it (for the mathematically inclined) is that	1829	Another way to think about it (for the mathematically inclined) is that
1372	C<ev_periodic> will try to run the callback in this mode at the next possible	1830	C<ev_periodic> will try to run the callback in this mode at the next possible
1373	time where C<time = at (mod interval)>, regardless of any time jumps.	1831	time where C<time = offset (mod interval)>, regardless of any time jumps.
1374		1832
1375	For numerical stability it is preferable that the C<at> value is near	1833	For numerical stability it is preferable that the C<offset> value is near
1376	C<ev_now ()> (the current time), but there is no range requirement for	1834	C<ev_now ()> (the current time), but there is no range requirement for
1377	this value, and in fact is often specified as zero.	1835	this value, and in fact is often specified as zero.
1378		1836
1379	Note also that there is an upper limit to how often a timer can fire (CPU	1837	Note also that there is an upper limit to how often a timer can fire (CPU
1380	speed for example), so if C<interval> is very small then timing stability	1838	speed for example), so if C<interval> is very small then timing stability
1381	will of course deteriorate. Libev itself tries to be exact to be about one	1839	will of course deteriorate. Libev itself tries to be exact to be about one
1382	millisecond (if the OS supports it and the machine is fast enough).	1840	millisecond (if the OS supports it and the machine is fast enough).
1383		1841
1384	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1842	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1385		1843
1386	In this mode the values for C<interval> and C<at> are both being	1844	In this mode the values for C<interval> and C<offset> are both being
1387	ignored. Instead, each time the periodic watcher gets scheduled, the	1845	ignored. Instead, each time the periodic watcher gets scheduled, the
1388	reschedule callback will be called with the watcher as first, and the	1846	reschedule callback will be called with the watcher as first, and the
1389	current time as second argument.	1847	current time as second argument.
1390		1848
1391	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1849	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1392	ever, or make ANY event loop modifications whatsoever>.	1850	or make ANY other event loop modifications whatsoever, unless explicitly
		1851	allowed by documentation here>.
1393		1852
1394	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1853	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1395	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1854	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1396	only event loop modification you are allowed to do).	1855	only event loop modification you are allowed to do).
1397		1856
1398	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1857	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1399	*w, ev_tstamp now)>, e.g.:	1858	*w, ev_tstamp now)>, e.g.:
1400		1859
		1860	static ev_tstamp
1401	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1861	my_rescheduler (ev_periodic *w, ev_tstamp now)
1402	{	1862	{
1403	return now + 60.;	1863	return now + 60.;
1404	}	1864	}
1405		1865
1406	It must return the next time to trigger, based on the passed time value	1866	It must return the next time to trigger, based on the passed time value
…		…
1426	a different time than the last time it was called (e.g. in a crond like	1886	a different time than the last time it was called (e.g. in a crond like
1427	program when the crontabs have changed).	1887	program when the crontabs have changed).
1428		1888
1429	=item ev_tstamp ev_periodic_at (ev_periodic *)	1889	=item ev_tstamp ev_periodic_at (ev_periodic *)
1430		1890
1431	When active, returns the absolute time that the watcher is supposed to	1891	When active, returns the absolute time that the watcher is supposed
1432	trigger next.	1892	to trigger next. This is not the same as the C<offset> argument to
		1893	C<ev_periodic_set>, but indeed works even in interval and manual
		1894	rescheduling modes.
1433		1895
1434	=item ev_tstamp offset [read-write]	1896	=item ev_tstamp offset [read-write]
1435		1897
1436	When repeating, this contains the offset value, otherwise this is the	1898	When repeating, this contains the offset value, otherwise this is the
1437	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1899	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1900	although libev might modify this value for better numerical stability).
1438		1901
1439	Can be modified any time, but changes only take effect when the periodic	1902	Can be modified any time, but changes only take effect when the periodic
1440	timer fires or C<ev_periodic_again> is being called.	1903	timer fires or C<ev_periodic_again> is being called.
1441		1904
1442	=item ev_tstamp interval [read-write]	1905	=item ev_tstamp interval [read-write]
1443		1906
1444	The current interval value. Can be modified any time, but changes only	1907	The current interval value. Can be modified any time, but changes only
1445	take effect when the periodic timer fires or C<ev_periodic_again> is being	1908	take effect when the periodic timer fires or C<ev_periodic_again> is being
1446	called.	1909	called.
1447		1910
1448	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1911	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1449		1912
1450	The current reschedule callback, or C<0>, if this functionality is	1913	The current reschedule callback, or C<0>, if this functionality is
1451	switched off. Can be changed any time, but changes only take effect when	1914	switched off. Can be changed any time, but changes only take effect when
1452	the periodic timer fires or C<ev_periodic_again> is being called.	1915	the periodic timer fires or C<ev_periodic_again> is being called.
1453		1916
1454	=back	1917	=back
1455		1918
1456	=head3 Examples	1919	=head3 Examples
1457		1920
1458	Example: Call a callback every hour, or, more precisely, whenever the	1921	Example: Call a callback every hour, or, more precisely, whenever the
1459	system clock is divisible by 3600. The callback invocation times have	1922	system time is divisible by 3600. The callback invocation times have
1460	potentially a lot of jitter, but good long-term stability.	1923	potentially a lot of jitter, but good long-term stability.
1461		1924
1462	static void	1925	static void
1463	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1926	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1464	{	1927	{
1465	... its now a full hour (UTC, or TAI or whatever your clock follows)	1928	... its now a full hour (UTC, or TAI or whatever your clock follows)
1466	}	1929	}
1467		1930
1468	struct ev_periodic hourly_tick;	1931	ev_periodic hourly_tick;
1469	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1932	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1470	ev_periodic_start (loop, &hourly_tick);	1933	ev_periodic_start (loop, &hourly_tick);
1471		1934
1472	Example: The same as above, but use a reschedule callback to do it:	1935	Example: The same as above, but use a reschedule callback to do it:
1473		1936
1474	#include <math.h>	1937	#include <math.h>
1475		1938
1476	static ev_tstamp	1939	static ev_tstamp
1477	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1940	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1478	{	1941	{
1479	return fmod (now, 3600.) + 3600.;	1942	return now + (3600. - fmod (now, 3600.));
1480	}	1943	}
1481		1944
1482	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1945	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1483		1946
1484	Example: Call a callback every hour, starting now:	1947	Example: Call a callback every hour, starting now:
1485		1948
1486	struct ev_periodic hourly_tick;	1949	ev_periodic hourly_tick;
1487	ev_periodic_init (&hourly_tick, clock_cb,	1950	ev_periodic_init (&hourly_tick, clock_cb,
1488	fmod (ev_now (loop), 3600.), 3600., 0);	1951	fmod (ev_now (loop), 3600.), 3600., 0);
1489	ev_periodic_start (loop, &hourly_tick);	1952	ev_periodic_start (loop, &hourly_tick);
1490		1953
1491		1954
…		…
1494	Signal watchers will trigger an event when the process receives a specific	1957	Signal watchers will trigger an event when the process receives a specific
1495	signal one or more times. Even though signals are very asynchronous, libev	1958	signal one or more times. Even though signals are very asynchronous, libev
1496	will try it's best to deliver signals synchronously, i.e. as part of the	1959	will try it's best to deliver signals synchronously, i.e. as part of the
1497	normal event processing, like any other event.	1960	normal event processing, like any other event.
1498		1961
		1962	If you want signals asynchronously, just use C<sigaction> as you would
		1963	do without libev and forget about sharing the signal. You can even use
		1964	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1965
1499	You can configure as many watchers as you like per signal. Only when the	1966	You can configure as many watchers as you like per signal. Only when the
1500	first watcher gets started will libev actually register a signal watcher	1967	first watcher gets started will libev actually register a signal handler
1501	with the kernel (thus it coexists with your own signal handlers as long	1968	with the kernel (thus it coexists with your own signal handlers as long as
1502	as you don't register any with libev). Similarly, when the last signal	1969	you don't register any with libev for the same signal). Similarly, when
1503	watcher for a signal is stopped libev will reset the signal handler to	1970	the last signal watcher for a signal is stopped, libev will reset the
1504	SIG_DFL (regardless of what it was set to before).	1971	signal handler to SIG_DFL (regardless of what it was set to before).
1505		1972
1506	If possible and supported, libev will install its handlers with	1973	If possible and supported, libev will install its handlers with
1507	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1974	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1508	interrupted. If you have a problem with system calls getting interrupted by	1975	interrupted. If you have a problem with system calls getting interrupted by
1509	signals you can block all signals in an C<ev_check> watcher and unblock	1976	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1526		1993
1527	=back	1994	=back
1528		1995
1529	=head3 Examples	1996	=head3 Examples
1530		1997
1531	Example: Try to exit cleanly on SIGINT and SIGTERM.	1998	Example: Try to exit cleanly on SIGINT.
1532		1999
1533	static void	2000	static void
1534	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2001	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1535	{	2002	{
1536	ev_unloop (loop, EVUNLOOP_ALL);	2003	ev_unloop (loop, EVUNLOOP_ALL);
1537	}	2004	}
1538		2005
1539	struct ev_signal signal_watcher;	2006	ev_signal signal_watcher;
1540	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2007	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1541	ev_signal_start (loop, &sigint_cb);	2008	ev_signal_start (loop, &signal_watcher);
1542		2009
1543		2010
1544	=head2 C<ev_child> - watch out for process status changes	2011	=head2 C<ev_child> - watch out for process status changes
1545		2012
1546	Child watchers trigger when your process receives a SIGCHLD in response to	2013	Child watchers trigger when your process receives a SIGCHLD in response to
1547	some child status changes (most typically when a child of yours dies). It	2014	some child status changes (most typically when a child of yours dies or
1548	is permissible to install a child watcher I<after> the child has been	2015	exits). It is permissible to install a child watcher I<after> the child
1549	forked (which implies it might have already exited), as long as the event	2016	has been forked (which implies it might have already exited), as long
1550	loop isn't entered (or is continued from a watcher).	2017	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2018	forking and then immediately registering a watcher for the child is fine,
		2019	but forking and registering a watcher a few event loop iterations later or
		2020	in the next callback invocation is not.
1551		2021
1552	Only the default event loop is capable of handling signals, and therefore	2022	Only the default event loop is capable of handling signals, and therefore
1553	you can only register child watchers in the default event loop.	2023	you can only register child watchers in the default event loop.
1554		2024
1555	=head3 Process Interaction	2025	=head3 Process Interaction
…		…
1616	its completion.	2086	its completion.
1617		2087
1618	ev_child cw;	2088	ev_child cw;
1619		2089
1620	static void	2090	static void
1621	child_cb (EV_P_ struct ev_child *w, int revents)	2091	child_cb (EV_P_ ev_child *w, int revents)
1622	{	2092	{
1623	ev_child_stop (EV_A_ w);	2093	ev_child_stop (EV_A_ w);
1624	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2094	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1625	}	2095	}
1626		2096
…		…
1641		2111
1642		2112
1643	=head2 C<ev_stat> - did the file attributes just change?	2113	=head2 C<ev_stat> - did the file attributes just change?
1644		2114
1645	This watches a file system path for attribute changes. That is, it calls	2115	This watches a file system path for attribute changes. That is, it calls
1646	C<stat> regularly (or when the OS says it changed) and sees if it changed	2116	C<stat> on that path in regular intervals (or when the OS says it changed)
1647	compared to the last time, invoking the callback if it did.	2117	and sees if it changed compared to the last time, invoking the callback if
		2118	it did.
1648		2119
1649	The path does not need to exist: changing from "path exists" to "path does	2120	The path does not need to exist: changing from "path exists" to "path does
1650	not exist" is a status change like any other. The condition "path does	2121	not exist" is a status change like any other. The condition "path does not
1651	not exist" is signified by the C<st_nlink> field being zero (which is	2122	exist" (or more correctly "path cannot be stat'ed") is signified by the
1652	otherwise always forced to be at least one) and all the other fields of	2123	C<st_nlink> field being zero (which is otherwise always forced to be at
1653	the stat buffer having unspecified contents.	2124	least one) and all the other fields of the stat buffer having unspecified
		2125	contents.
1654		2126
1655	The path I<should> be absolute and I<must not> end in a slash. If it is	2127	The path I<must not> end in a slash or contain special components such as
		2128	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1656	relative and your working directory changes, the behaviour is undefined.	2129	your working directory changes, then the behaviour is undefined.
1657		2130
1658	Since there is no standard to do this, the portable implementation simply	2131	Since there is no portable change notification interface available, the
1659	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2132	portable implementation simply calls C<stat(2)> regularly on the path
1660	can specify a recommended polling interval for this case. If you specify	2133	to see if it changed somehow. You can specify a recommended polling
1661	a polling interval of C<0> (highly recommended!) then a I<suitable,	2134	interval for this case. If you specify a polling interval of C<0> (highly
1662	unspecified default> value will be used (which you can expect to be around	2135	recommended!) then a I<suitable, unspecified default> value will be used
1663	five seconds, although this might change dynamically). Libev will also	2136	(which you can expect to be around five seconds, although this might
1664	impose a minimum interval which is currently around C<0.1>, but thats	2137	change dynamically). Libev will also impose a minimum interval which is
1665	usually overkill.	2138	currently around C<0.1>, but that's usually overkill.
1666		2139
1667	This watcher type is not meant for massive numbers of stat watchers,	2140	This watcher type is not meant for massive numbers of stat watchers,
1668	as even with OS-supported change notifications, this can be	2141	as even with OS-supported change notifications, this can be
1669	resource-intensive.	2142	resource-intensive.
1670		2143
1671	At the time of this writing, only the Linux inotify interface is	2144	At the time of this writing, the only OS-specific interface implemented
1672	implemented (implementing kqueue support is left as an exercise for the	2145	is the Linux inotify interface (implementing kqueue support is left as an
1673	reader, note, however, that the author sees no way of implementing ev_stat	2146	exercise for the reader. Note, however, that the author sees no way of
1674	semantics with kqueue). Inotify will be used to give hints only and should	2147	implementing C<ev_stat> semantics with kqueue, except as a hint).
1675	not change the semantics of C<ev_stat> watchers, which means that libev
1676	sometimes needs to fall back to regular polling again even with inotify,
1677	but changes are usually detected immediately, and if the file exists there
1678	will be no polling.
1679		2148
1680	=head3 ABI Issues (Largefile Support)	2149	=head3 ABI Issues (Largefile Support)
1681		2150
1682	Libev by default (unless the user overrides this) uses the default	2151	Libev by default (unless the user overrides this) uses the default
1683	compilation environment, which means that on systems with large file	2152	compilation environment, which means that on systems with large file
1684	support disabled by default, you get the 32 bit version of the stat	2153	support disabled by default, you get the 32 bit version of the stat
1685	structure. When using the library from programs that change the ABI to	2154	structure. When using the library from programs that change the ABI to
1686	use 64 bit file offsets the programs will fail. In that case you have to	2155	use 64 bit file offsets the programs will fail. In that case you have to
1687	compile libev with the same flags to get binary compatibility. This is	2156	compile libev with the same flags to get binary compatibility. This is
1688	obviously the case with any flags that change the ABI, but the problem is	2157	obviously the case with any flags that change the ABI, but the problem is
1689	most noticeably disabled with ev_stat and large file support.	2158	most noticeably displayed with ev_stat and large file support.
1690		2159
1691	The solution for this is to lobby your distribution maker to make large	2160	The solution for this is to lobby your distribution maker to make large
1692	file interfaces available by default (as e.g. FreeBSD does) and not	2161	file interfaces available by default (as e.g. FreeBSD does) and not
1693	optional. Libev cannot simply switch on large file support because it has	2162	optional. Libev cannot simply switch on large file support because it has
1694	to exchange stat structures with application programs compiled using the	2163	to exchange stat structures with application programs compiled using the
1695	default compilation environment.	2164	default compilation environment.
1696		2165
1697	=head3 Inotify	2166	=head3 Inotify and Kqueue
1698		2167
1699	When C<inotify (7)> support has been compiled into libev (generally only	2168	When C<inotify (7)> support has been compiled into libev and present at
1700	available on Linux) and present at runtime, it will be used to speed up	2169	runtime, it will be used to speed up change detection where possible. The
1701	change detection where possible. The inotify descriptor will be created lazily	2170	inotify descriptor will be created lazily when the first C<ev_stat>
1702	when the first C<ev_stat> watcher is being started.	2171	watcher is being started.
1703		2172
1704	Inotify presence does not change the semantics of C<ev_stat> watchers	2173	Inotify presence does not change the semantics of C<ev_stat> watchers
1705	except that changes might be detected earlier, and in some cases, to avoid	2174	except that changes might be detected earlier, and in some cases, to avoid
1706	making regular C<stat> calls. Even in the presence of inotify support	2175	making regular C<stat> calls. Even in the presence of inotify support
1707	there are many cases where libev has to resort to regular C<stat> polling.	2176	there are many cases where libev has to resort to regular C<stat> polling,
		2177	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2178	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2179	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2180	xfs are fully working) libev usually gets away without polling.
1708		2181
1709	(There is no support for kqueue, as apparently it cannot be used to	2182	There is no support for kqueue, as apparently it cannot be used to
1710	implement this functionality, due to the requirement of having a file	2183	implement this functionality, due to the requirement of having a file
1711	descriptor open on the object at all times).	2184	descriptor open on the object at all times, and detecting renames, unlinks
		2185	etc. is difficult.
		2186
		2187	=head3 C<stat ()> is a synchronous operation
		2188
		2189	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2190	the process. The exception are C<ev_stat> watchers - those call C<stat
		2191	()>, which is a synchronous operation.
		2192
		2193	For local paths, this usually doesn't matter: unless the system is very
		2194	busy or the intervals between stat's are large, a stat call will be fast,
		2195	as the path data is usually in memory already (except when starting the
		2196	watcher).
		2197
		2198	For networked file systems, calling C<stat ()> can block an indefinite
		2199	time due to network issues, and even under good conditions, a stat call
		2200	often takes multiple milliseconds.
		2201
		2202	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2203	paths, although this is fully supported by libev.
1712		2204
1713	=head3 The special problem of stat time resolution	2205	=head3 The special problem of stat time resolution
1714		2206
1715	The C<stat ()> system call only supports full-second resolution portably, and	2207	The C<stat ()> system call only supports full-second resolution portably,
1716	even on systems where the resolution is higher, many file systems still	2208	and even on systems where the resolution is higher, most file systems
1717	only support whole seconds.	2209	still only support whole seconds.
1718		2210
1719	That means that, if the time is the only thing that changes, you can	2211	That means that, if the time is the only thing that changes, you can
1720	easily miss updates: on the first update, C<ev_stat> detects a change and	2212	easily miss updates: on the first update, C<ev_stat> detects a change and
1721	calls your callback, which does something. When there is another update	2213	calls your callback, which does something. When there is another update
1722	within the same second, C<ev_stat> will be unable to detect it as the stat	2214	within the same second, C<ev_stat> will be unable to detect unless the
1723	data does not change.	2215	stat data does change in other ways (e.g. file size).
1724		2216
1725	The solution to this is to delay acting on a change for slightly more	2217	The solution to this is to delay acting on a change for slightly more
1726	than a second (or till slightly after the next full second boundary), using	2218	than a second (or till slightly after the next full second boundary), using
1727	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2219	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1728	ev_timer_again (loop, w)>).	2220	ev_timer_again (loop, w)>).
…		…
1748	C<path>. The C<interval> is a hint on how quickly a change is expected to	2240	C<path>. The C<interval> is a hint on how quickly a change is expected to
1749	be detected and should normally be specified as C<0> to let libev choose	2241	be detected and should normally be specified as C<0> to let libev choose
1750	a suitable value. The memory pointed to by C<path> must point to the same	2242	a suitable value. The memory pointed to by C<path> must point to the same
1751	path for as long as the watcher is active.	2243	path for as long as the watcher is active.
1752		2244
1753	The callback will receive C<EV_STAT> when a change was detected, relative	2245	The callback will receive an C<EV_STAT> event when a change was detected,
1754	to the attributes at the time the watcher was started (or the last change	2246	relative to the attributes at the time the watcher was started (or the
1755	was detected).	2247	last change was detected).
1756		2248
1757	=item ev_stat_stat (loop, ev_stat *)	2249	=item ev_stat_stat (loop, ev_stat *)
1758		2250
1759	Updates the stat buffer immediately with new values. If you change the	2251	Updates the stat buffer immediately with new values. If you change the
1760	watched path in your callback, you could call this function to avoid	2252	watched path in your callback, you could call this function to avoid
…		…
1843		2335
1844		2336
1845	=head2 C<ev_idle> - when you've got nothing better to do...	2337	=head2 C<ev_idle> - when you've got nothing better to do...
1846		2338
1847	Idle watchers trigger events when no other events of the same or higher	2339	Idle watchers trigger events when no other events of the same or higher
1848	priority are pending (prepare, check and other idle watchers do not	2340	priority are pending (prepare, check and other idle watchers do not count
1849	count).	2341	as receiving "events").
1850		2342
1851	That is, as long as your process is busy handling sockets or timeouts	2343	That is, as long as your process is busy handling sockets or timeouts
1852	(or even signals, imagine) of the same or higher priority it will not be	2344	(or even signals, imagine) of the same or higher priority it will not be
1853	triggered. But when your process is idle (or only lower-priority watchers	2345	triggered. But when your process is idle (or only lower-priority watchers
1854	are pending), the idle watchers are being called once per event loop	2346	are pending), the idle watchers are being called once per event loop
…		…
1865		2357
1866	=head3 Watcher-Specific Functions and Data Members	2358	=head3 Watcher-Specific Functions and Data Members
1867		2359
1868	=over 4	2360	=over 4
1869		2361
1870	=item ev_idle_init (ev_signal *, callback)	2362	=item ev_idle_init (ev_idle *, callback)
1871		2363
1872	Initialises and configures the idle watcher - it has no parameters of any	2364	Initialises and configures the idle watcher - it has no parameters of any
1873	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2365	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1874	believe me.	2366	believe me.
1875		2367
…		…
1879		2371
1880	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2372	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1881	callback, free it. Also, use no error checking, as usual.	2373	callback, free it. Also, use no error checking, as usual.
1882		2374
1883	static void	2375	static void
1884	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2376	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1885	{	2377	{
1886	free (w);	2378	free (w);
1887	// now do something you wanted to do when the program has	2379	// now do something you wanted to do when the program has
1888	// no longer anything immediate to do.	2380	// no longer anything immediate to do.
1889	}	2381	}
1890		2382
1891	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2383	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1892	ev_idle_init (idle_watcher, idle_cb);	2384	ev_idle_init (idle_watcher, idle_cb);
1893	ev_idle_start (loop, idle_cb);	2385	ev_idle_start (loop, idle_watcher);
1894		2386
1895		2387
1896	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2388	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1897		2389
1898	Prepare and check watchers are usually (but not always) used in tandem:	2390	Prepare and check watchers are usually (but not always) used in pairs:
1899	prepare watchers get invoked before the process blocks and check watchers	2391	prepare watchers get invoked before the process blocks and check watchers
1900	afterwards.	2392	afterwards.
1901		2393
1902	You I<must not> call C<ev_loop> or similar functions that enter	2394	You I<must not> call C<ev_loop> or similar functions that enter
1903	the current event loop from either C<ev_prepare> or C<ev_check>	2395	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1906	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2398	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1907	C<ev_check> so if you have one watcher of each kind they will always be	2399	C<ev_check> so if you have one watcher of each kind they will always be
1908	called in pairs bracketing the blocking call.	2400	called in pairs bracketing the blocking call.
1909		2401
1910	Their main purpose is to integrate other event mechanisms into libev and	2402	Their main purpose is to integrate other event mechanisms into libev and
1911	their use is somewhat advanced. This could be used, for example, to track	2403	their use is somewhat advanced. They could be used, for example, to track
1912	variable changes, implement your own watchers, integrate net-snmp or a	2404	variable changes, implement your own watchers, integrate net-snmp or a
1913	coroutine library and lots more. They are also occasionally useful if	2405	coroutine library and lots more. They are also occasionally useful if
1914	you cache some data and want to flush it before blocking (for example,	2406	you cache some data and want to flush it before blocking (for example,
1915	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2407	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1916	watcher).	2408	watcher).
1917		2409
1918	This is done by examining in each prepare call which file descriptors need	2410	This is done by examining in each prepare call which file descriptors
1919	to be watched by the other library, registering C<ev_io> watchers for	2411	need to be watched by the other library, registering C<ev_io> watchers
1920	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2412	for them and starting an C<ev_timer> watcher for any timeouts (many
1921	provide just this functionality). Then, in the check watcher you check for	2413	libraries provide exactly this functionality). Then, in the check watcher,
1922	any events that occurred (by checking the pending status of all watchers	2414	you check for any events that occurred (by checking the pending status
1923	and stopping them) and call back into the library. The I/O and timer	2415	of all watchers and stopping them) and call back into the library. The
1924	callbacks will never actually be called (but must be valid nevertheless,	2416	I/O and timer callbacks will never actually be called (but must be valid
1925	because you never know, you know?).	2417	nevertheless, because you never know, you know?).
1926		2418
1927	As another example, the Perl Coro module uses these hooks to integrate	2419	As another example, the Perl Coro module uses these hooks to integrate
1928	coroutines into libev programs, by yielding to other active coroutines	2420	coroutines into libev programs, by yielding to other active coroutines
1929	during each prepare and only letting the process block if no coroutines	2421	during each prepare and only letting the process block if no coroutines
1930	are ready to run (it's actually more complicated: it only runs coroutines	2422	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1933	loop from blocking if lower-priority coroutines are active, thus mapping	2425	loop from blocking if lower-priority coroutines are active, thus mapping
1934	low-priority coroutines to idle/background tasks).	2426	low-priority coroutines to idle/background tasks).
1935		2427
1936	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2428	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1937	priority, to ensure that they are being run before any other watchers	2429	priority, to ensure that they are being run before any other watchers
		2430	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2431
1938	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2432	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1939	too) should not activate ("feed") events into libev. While libev fully	2433	activate ("feed") events into libev. While libev fully supports this, they
1940	supports this, they might get executed before other C<ev_check> watchers	2434	might get executed before other C<ev_check> watchers did their job. As
1941	did their job. As C<ev_check> watchers are often used to embed other	2435	C<ev_check> watchers are often used to embed other (non-libev) event
1942	(non-libev) event loops those other event loops might be in an unusable	2436	loops those other event loops might be in an unusable state until their
1943	state until their C<ev_check> watcher ran (always remind yourself to	2437	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1944	coexist peacefully with others).	2438	others).
1945		2439
1946	=head3 Watcher-Specific Functions and Data Members	2440	=head3 Watcher-Specific Functions and Data Members
1947		2441
1948	=over 4	2442	=over 4
1949		2443
…		…
1951		2445
1952	=item ev_check_init (ev_check *, callback)	2446	=item ev_check_init (ev_check *, callback)
1953		2447
1954	Initialises and configures the prepare or check watcher - they have no	2448	Initialises and configures the prepare or check watcher - they have no
1955	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2449	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1956	macros, but using them is utterly, utterly and completely pointless.	2450	macros, but using them is utterly, utterly, utterly and completely
		2451	pointless.
1957		2452
1958	=back	2453	=back
1959		2454
1960	=head3 Examples	2455	=head3 Examples
1961		2456
…		…
1974		2469
1975	static ev_io iow [nfd];	2470	static ev_io iow [nfd];
1976	static ev_timer tw;	2471	static ev_timer tw;
1977		2472
1978	static void	2473	static void
1979	io_cb (ev_loop *loop, ev_io *w, int revents)	2474	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1980	{	2475	{
1981	}	2476	}
1982		2477
1983	// create io watchers for each fd and a timer before blocking	2478	// create io watchers for each fd and a timer before blocking
1984	static void	2479	static void
1985	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2480	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1986	{	2481	{
1987	int timeout = 3600000;	2482	int timeout = 3600000;
1988	struct pollfd fds [nfd];	2483	struct pollfd fds [nfd];
1989	// actual code will need to loop here and realloc etc.	2484	// actual code will need to loop here and realloc etc.
1990	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2485	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1991		2486
1992	/* the callback is illegal, but won't be called as we stop during check */	2487	/* the callback is illegal, but won't be called as we stop during check */
1993	ev_timer_init (&tw, 0, timeout * 1e-3);	2488	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1994	ev_timer_start (loop, &tw);	2489	ev_timer_start (loop, &tw);
1995		2490
1996	// create one ev_io per pollfd	2491	// create one ev_io per pollfd
1997	for (int i = 0; i < nfd; ++i)	2492	for (int i = 0; i < nfd; ++i)
1998	{	2493	{
…		…
2005	}	2500	}
2006	}	2501	}
2007		2502
2008	// stop all watchers after blocking	2503	// stop all watchers after blocking
2009	static void	2504	static void
2010	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2505	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2011	{	2506	{
2012	ev_timer_stop (loop, &tw);	2507	ev_timer_stop (loop, &tw);
2013		2508
2014	for (int i = 0; i < nfd; ++i)	2509	for (int i = 0; i < nfd; ++i)
2015	{	2510	{
…		…
2054	}	2549	}
2055		2550
2056	// do not ever call adns_afterpoll	2551	// do not ever call adns_afterpoll
2057		2552
2058	Method 4: Do not use a prepare or check watcher because the module you	2553	Method 4: Do not use a prepare or check watcher because the module you
2059	want to embed is too inflexible to support it. Instead, you can override	2554	want to embed is not flexible enough to support it. Instead, you can
2060	their poll function. The drawback with this solution is that the main	2555	override their poll function. The drawback with this solution is that the
2061	loop is now no longer controllable by EV. The C<Glib::EV> module does	2556	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2062	this.	2557	this approach, effectively embedding EV as a client into the horrible
		2558	libglib event loop.
2063		2559
2064	static gint	2560	static gint
2065	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2561	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2066	{	2562	{
2067	int got_events = 0;	2563	int got_events = 0;
…		…
2098	prioritise I/O.	2594	prioritise I/O.
2099		2595
2100	As an example for a bug workaround, the kqueue backend might only support	2596	As an example for a bug workaround, the kqueue backend might only support
2101	sockets on some platform, so it is unusable as generic backend, but you	2597	sockets on some platform, so it is unusable as generic backend, but you
2102	still want to make use of it because you have many sockets and it scales	2598	still want to make use of it because you have many sockets and it scales
2103	so nicely. In this case, you would create a kqueue-based loop and embed it	2599	so nicely. In this case, you would create a kqueue-based loop and embed
2104	into your default loop (which might use e.g. poll). Overall operation will	2600	it into your default loop (which might use e.g. poll). Overall operation
2105	be a bit slower because first libev has to poll and then call kevent, but	2601	will be a bit slower because first libev has to call C<poll> and then
2106	at least you can use both at what they are best.	2602	C<kevent>, but at least you can use both mechanisms for what they are
		2603	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2107		2604
2108	As for prioritising I/O: rarely you have the case where some fds have	2605	As for prioritising I/O: under rare circumstances you have the case where
2109	to be watched and handled very quickly (with low latency), and even	2606	some fds have to be watched and handled very quickly (with low latency),
2110	priorities and idle watchers might have too much overhead. In this case	2607	and even priorities and idle watchers might have too much overhead. In
2111	you would put all the high priority stuff in one loop and all the rest in	2608	this case you would put all the high priority stuff in one loop and all
2112	a second one, and embed the second one in the first.	2609	the rest in a second one, and embed the second one in the first.
2113		2610
2114	As long as the watcher is active, the callback will be invoked every time	2611	As long as the watcher is active, the callback will be invoked every
2115	there might be events pending in the embedded loop. The callback must then	2612	time there might be events pending in the embedded loop. The callback
2116	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2613	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2117	their callbacks (you could also start an idle watcher to give the embedded	2614	sweep and invoke their callbacks (the callback doesn't need to invoke the
2118	loop strictly lower priority for example). You can also set the callback	2615	C<ev_embed_sweep> function directly, it could also start an idle watcher
2119	to C<0>, in which case the embed watcher will automatically execute the	2616	to give the embedded loop strictly lower priority for example).
2120	embedded loop sweep.
2121		2617
2122	As long as the watcher is started it will automatically handle events. The	2618	You can also set the callback to C<0>, in which case the embed watcher
2123	callback will be invoked whenever some events have been handled. You can	2619	will automatically execute the embedded loop sweep whenever necessary.
2124	set the callback to C<0> to avoid having to specify one if you are not
2125	interested in that.
2126		2620
2127	Also, there have not currently been made special provisions for forking:	2621	Fork detection will be handled transparently while the C<ev_embed> watcher
2128	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2622	is active, i.e., the embedded loop will automatically be forked when the
2129	but you will also have to stop and restart any C<ev_embed> watchers	2623	embedding loop forks. In other cases, the user is responsible for calling
2130	yourself.	2624	C<ev_loop_fork> on the embedded loop.
2131		2625
2132	Unfortunately, not all backends are embeddable, only the ones returned by	2626	Unfortunately, not all backends are embeddable: only the ones returned by
2133	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2627	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2134	portable one.	2628	portable one.
2135		2629
2136	So when you want to use this feature you will always have to be prepared	2630	So when you want to use this feature you will always have to be prepared
2137	that you cannot get an embeddable loop. The recommended way to get around	2631	that you cannot get an embeddable loop. The recommended way to get around
2138	this is to have a separate variables for your embeddable loop, try to	2632	this is to have a separate variables for your embeddable loop, try to
2139	create it, and if that fails, use the normal loop for everything.	2633	create it, and if that fails, use the normal loop for everything.
		2634
		2635	=head3 C<ev_embed> and fork
		2636
		2637	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2638	automatically be applied to the embedded loop as well, so no special
		2639	fork handling is required in that case. When the watcher is not running,
		2640	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2641	as applicable.
2140		2642
2141	=head3 Watcher-Specific Functions and Data Members	2643	=head3 Watcher-Specific Functions and Data Members
2142		2644
2143	=over 4	2645	=over 4
2144		2646
…		…
2172	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2674	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2173	used).	2675	used).
2174		2676
2175	struct ev_loop *loop_hi = ev_default_init (0);	2677	struct ev_loop *loop_hi = ev_default_init (0);
2176	struct ev_loop *loop_lo = 0;	2678	struct ev_loop *loop_lo = 0;
2177	struct ev_embed embed;	2679	ev_embed embed;
2178		2680
2179	// see if there is a chance of getting one that works	2681	// see if there is a chance of getting one that works
2180	// (remember that a flags value of 0 means autodetection)	2682	// (remember that a flags value of 0 means autodetection)
2181	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2683	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2182	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2684	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2196	kqueue implementation). Store the kqueue/socket-only event loop in	2698	kqueue implementation). Store the kqueue/socket-only event loop in
2197	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2699	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2198		2700
2199	struct ev_loop *loop = ev_default_init (0);	2701	struct ev_loop *loop = ev_default_init (0);
2200	struct ev_loop *loop_socket = 0;	2702	struct ev_loop *loop_socket = 0;
2201	struct ev_embed embed;	2703	ev_embed embed;
2202		2704
2203	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2705	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2204	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2706	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2205	{	2707	{
2206	ev_embed_init (&embed, 0, loop_socket);	2708	ev_embed_init (&embed, 0, loop_socket);
…		…
2221	event loop blocks next and before C<ev_check> watchers are being called,	2723	event loop blocks next and before C<ev_check> watchers are being called,
2222	and only in the child after the fork. If whoever good citizen calling	2724	and only in the child after the fork. If whoever good citizen calling
2223	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2725	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2224	handlers will be invoked, too, of course.	2726	handlers will be invoked, too, of course.
2225		2727
		2728	=head3 The special problem of life after fork - how is it possible?
		2729
		2730	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2731	up/change the process environment, followed by a call to C<exec()>. This
		2732	sequence should be handled by libev without any problems.
		2733
		2734	This changes when the application actually wants to do event handling
		2735	in the child, or both parent in child, in effect "continuing" after the
		2736	fork.
		2737
		2738	The default mode of operation (for libev, with application help to detect
		2739	forks) is to duplicate all the state in the child, as would be expected
		2740	when I<either> the parent I<or> the child process continues.
		2741
		2742	When both processes want to continue using libev, then this is usually the
		2743	wrong result. In that case, usually one process (typically the parent) is
		2744	supposed to continue with all watchers in place as before, while the other
		2745	process typically wants to start fresh, i.e. without any active watchers.
		2746
		2747	The cleanest and most efficient way to achieve that with libev is to
		2748	simply create a new event loop, which of course will be "empty", and
		2749	use that for new watchers. This has the advantage of not touching more
		2750	memory than necessary, and thus avoiding the copy-on-write, and the
		2751	disadvantage of having to use multiple event loops (which do not support
		2752	signal watchers).
		2753
		2754	When this is not possible, or you want to use the default loop for
		2755	other reasons, then in the process that wants to start "fresh", call
		2756	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2757	the default loop will "orphan" (not stop) all registered watchers, so you
		2758	have to be careful not to execute code that modifies those watchers. Note
		2759	also that in that case, you have to re-register any signal watchers.
		2760
2226	=head3 Watcher-Specific Functions and Data Members	2761	=head3 Watcher-Specific Functions and Data Members
2227		2762
2228	=over 4	2763	=over 4
2229		2764
2230	=item ev_fork_init (ev_signal *, callback)	2765	=item ev_fork_init (ev_signal *, callback)
…		…
2262	is that the author does not know of a simple (or any) algorithm for a	2797	is that the author does not know of a simple (or any) algorithm for a
2263	multiple-writer-single-reader queue that works in all cases and doesn't	2798	multiple-writer-single-reader queue that works in all cases and doesn't
2264	need elaborate support such as pthreads.	2799	need elaborate support such as pthreads.
2265		2800
2266	That means that if you want to queue data, you have to provide your own	2801	That means that if you want to queue data, you have to provide your own
2267	queue. But at least I can tell you would implement locking around your	2802	queue. But at least I can tell you how to implement locking around your
2268	queue:	2803	queue:
2269		2804
2270	=over 4	2805	=over 4
2271		2806
2272	=item queueing from a signal handler context	2807	=item queueing from a signal handler context
2273		2808
2274	To implement race-free queueing, you simply add to the queue in the signal	2809	To implement race-free queueing, you simply add to the queue in the signal
2275	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2810	handler but you block the signal handler in the watcher callback. Here is
2276	some fictitious SIGUSR1 handler:	2811	an example that does that for some fictitious SIGUSR1 handler:
2277		2812
2278	static ev_async mysig;	2813	static ev_async mysig;
2279		2814
2280	static void	2815	static void
2281	sigusr1_handler (void)	2816	sigusr1_handler (void)
…		…
2347	=over 4	2882	=over 4
2348		2883
2349	=item ev_async_init (ev_async *, callback)	2884	=item ev_async_init (ev_async *, callback)
2350		2885
2351	Initialises and configures the async watcher - it has no parameters of any	2886	Initialises and configures the async watcher - it has no parameters of any
2352	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2887	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2353	believe me.	2888	trust me.
2354		2889
2355	=item ev_async_send (loop, ev_async *)	2890	=item ev_async_send (loop, ev_async *)
2356		2891
2357	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2892	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2358	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2893	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2359	C<ev_feed_event>, this call is safe to do in other threads, signal or	2894	C<ev_feed_event>, this call is safe to do from other threads, signal or
2360	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2895	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2361	section below on what exactly this means).	2896	section below on what exactly this means).
2362		2897
		2898	Note that, as with other watchers in libev, multiple events might get
		2899	compressed into a single callback invocation (another way to look at this
		2900	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2901	reset when the event loop detects that).
		2902
2363	This call incurs the overhead of a system call only once per loop iteration,	2903	This call incurs the overhead of a system call only once per event loop
2364	so while the overhead might be noticeable, it doesn't apply to repeated	2904	iteration, so while the overhead might be noticeable, it doesn't apply to
2365	calls to C<ev_async_send>.	2905	repeated calls to C<ev_async_send> for the same event loop.
2366		2906
2367	=item bool = ev_async_pending (ev_async *)	2907	=item bool = ev_async_pending (ev_async *)
2368		2908
2369	Returns a non-zero value when C<ev_async_send> has been called on the	2909	Returns a non-zero value when C<ev_async_send> has been called on the
2370	watcher but the event has not yet been processed (or even noted) by the	2910	watcher but the event has not yet been processed (or even noted) by the
…		…
2373	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2913	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2374	the loop iterates next and checks for the watcher to have become active,	2914	the loop iterates next and checks for the watcher to have become active,
2375	it will reset the flag again. C<ev_async_pending> can be used to very	2915	it will reset the flag again. C<ev_async_pending> can be used to very
2376	quickly check whether invoking the loop might be a good idea.	2916	quickly check whether invoking the loop might be a good idea.
2377		2917
2378	Not that this does I<not> check whether the watcher itself is pending, only	2918	Not that this does I<not> check whether the watcher itself is pending,
2379	whether it has been requested to make this watcher pending.	2919	only whether it has been requested to make this watcher pending: there
		2920	is a time window between the event loop checking and resetting the async
		2921	notification, and the callback being invoked.
2380		2922
2381	=back	2923	=back
2382		2924
2383		2925
2384	=head1 OTHER FUNCTIONS	2926	=head1 OTHER FUNCTIONS
…		…
2388	=over 4	2930	=over 4
2389		2931
2390	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2932	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2391		2933
2392	This function combines a simple timer and an I/O watcher, calls your	2934	This function combines a simple timer and an I/O watcher, calls your
2393	callback on whichever event happens first and automatically stop both	2935	callback on whichever event happens first and automatically stops both
2394	watchers. This is useful if you want to wait for a single event on an fd	2936	watchers. This is useful if you want to wait for a single event on an fd
2395	or timeout without having to allocate/configure/start/stop/free one or	2937	or timeout without having to allocate/configure/start/stop/free one or
2396	more watchers yourself.	2938	more watchers yourself.
2397		2939
2398	If C<fd> is less than 0, then no I/O watcher will be started and events	2940	If C<fd> is less than 0, then no I/O watcher will be started and the
2399	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2941	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2400	C<events> set will be created and started.	2942	the given C<fd> and C<events> set will be created and started.
2401		2943
2402	If C<timeout> is less than 0, then no timeout watcher will be	2944	If C<timeout> is less than 0, then no timeout watcher will be
2403	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2945	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2404	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2946	repeat = 0) will be started. C<0> is a valid timeout.
2405	dubious value.
2406		2947
2407	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2948	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2408	passed an C<revents> set like normal event callbacks (a combination of	2949	passed an C<revents> set like normal event callbacks (a combination of
2409	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2950	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2410	value passed to C<ev_once>:	2951	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2952	a timeout and an io event at the same time - you probably should give io
		2953	events precedence.
		2954
		2955	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2411		2956
2412	static void stdin_ready (int revents, void *arg)	2957	static void stdin_ready (int revents, void *arg)
2413	{	2958	{
		2959	if (revents & EV_READ)
		2960	/* stdin might have data for us, joy! */;
2414	if (revents & EV_TIMEOUT)	2961	else if (revents & EV_TIMEOUT)
2415	/* doh, nothing entered */;	2962	/* doh, nothing entered */;
2416	else if (revents & EV_READ)
2417	/* stdin might have data for us, joy! */;
2418	}	2963	}
2419		2964
2420	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2965	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2421		2966
2422	=item ev_feed_event (ev_loop *, watcher *, int revents)	2967	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2423		2968
2424	Feeds the given event set into the event loop, as if the specified event	2969	Feeds the given event set into the event loop, as if the specified event
2425	had happened for the specified watcher (which must be a pointer to an	2970	had happened for the specified watcher (which must be a pointer to an
2426	initialised but not necessarily started event watcher).	2971	initialised but not necessarily started event watcher).
2427		2972
2428	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2973	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2429		2974
2430	Feed an event on the given fd, as if a file descriptor backend detected	2975	Feed an event on the given fd, as if a file descriptor backend detected
2431	the given events it.	2976	the given events it.
2432		2977
2433	=item ev_feed_signal_event (ev_loop *loop, int signum)	2978	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2434		2979
2435	Feed an event as if the given signal occurred (C<loop> must be the default	2980	Feed an event as if the given signal occurred (C<loop> must be the default
2436	loop!).	2981	loop!).
2437		2982
2438	=back	2983	=back
…		…
2560		3105
2561	myclass obj;	3106	myclass obj;
2562	ev::io iow;	3107	ev::io iow;
2563	iow.set <myclass, &myclass::io_cb> (&obj);	3108	iow.set <myclass, &myclass::io_cb> (&obj);
2564		3109
		3110	=item w->set (object *)
		3111
		3112	This is an B<experimental> feature that might go away in a future version.
		3113
		3114	This is a variation of a method callback - leaving out the method to call
		3115	will default the method to C<operator ()>, which makes it possible to use
		3116	functor objects without having to manually specify the C<operator ()> all
		3117	the time. Incidentally, you can then also leave out the template argument
		3118	list.
		3119
		3120	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3121	int revents)>.
		3122
		3123	See the method-C<set> above for more details.
		3124
		3125	Example: use a functor object as callback.
		3126
		3127	struct myfunctor
		3128	{
		3129	void operator() (ev::io &w, int revents)
		3130	{
		3131	...
		3132	}
		3133	}
		3134
		3135	myfunctor f;
		3136
		3137	ev::io w;
		3138	w.set (&f);
		3139
2565	=item w->set<function> (void *data = 0)	3140	=item w->set<function> (void *data = 0)
2566		3141
2567	Also sets a callback, but uses a static method or plain function as	3142	Also sets a callback, but uses a static method or plain function as
2568	callback. The optional C<data> argument will be stored in the watcher's	3143	callback. The optional C<data> argument will be stored in the watcher's
2569	C<data> member and is free for you to use.	3144	C<data> member and is free for you to use.
2570		3145
2571	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3146	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2572		3147
2573	See the method-C<set> above for more details.	3148	See the method-C<set> above for more details.
2574		3149
2575	Example:	3150	Example: Use a plain function as callback.
2576		3151
2577	static void io_cb (ev::io &w, int revents) { }	3152	static void io_cb (ev::io &w, int revents) { }
2578	iow.set <io_cb> ();	3153	iow.set <io_cb> ();
2579		3154
2580	=item w->set (struct ev_loop *)	3155	=item w->set (struct ev_loop *)
…		…
2618	Example: Define a class with an IO and idle watcher, start one of them in	3193	Example: Define a class with an IO and idle watcher, start one of them in
2619	the constructor.	3194	the constructor.
2620		3195
2621	class myclass	3196	class myclass
2622	{	3197	{
2623	ev::io io; void io_cb (ev::io &w, int revents);	3198	ev::io io ; void io_cb (ev::io &w, int revents);
2624	ev:idle idle void idle_cb (ev::idle &w, int revents);	3199	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2625		3200
2626	myclass (int fd)	3201	myclass (int fd)
2627	{	3202	{
2628	io .set <myclass, &myclass::io_cb > (this);	3203	io .set <myclass, &myclass::io_cb > (this);
2629	idle.set <myclass, &myclass::idle_cb> (this);	3204	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2645	=item Perl	3220	=item Perl
2646		3221
2647	The EV module implements the full libev API and is actually used to test	3222	The EV module implements the full libev API and is actually used to test
2648	libev. EV is developed together with libev. Apart from the EV core module,	3223	libev. EV is developed together with libev. Apart from the EV core module,
2649	there are additional modules that implement libev-compatible interfaces	3224	there are additional modules that implement libev-compatible interfaces
2650	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3225	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2651	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3226	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3227	and C<EV::Glib>).
2652		3228
2653	It can be found and installed via CPAN, its homepage is at	3229	It can be found and installed via CPAN, its homepage is at
2654	L<http://software.schmorp.de/pkg/EV>.	3230	L<http://software.schmorp.de/pkg/EV>.
2655		3231
2656	=item Python	3232	=item Python
2657		3233
2658	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3234	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2659	seems to be quite complete and well-documented. Note, however, that the	3235	seems to be quite complete and well-documented.
2660	patch they require for libev is outright dangerous as it breaks the ABI
2661	for everybody else, and therefore, should never be applied in an installed
2662	libev (if python requires an incompatible ABI then it needs to embed
2663	libev).
2664		3236
2665	=item Ruby	3237	=item Ruby
2666		3238
2667	Tony Arcieri has written a ruby extension that offers access to a subset	3239	Tony Arcieri has written a ruby extension that offers access to a subset
2668	of the libev API and adds file handle abstractions, asynchronous DNS and	3240	of the libev API and adds file handle abstractions, asynchronous DNS and
2669	more on top of it. It can be found via gem servers. Its homepage is at	3241	more on top of it. It can be found via gem servers. Its homepage is at
2670	L<http://rev.rubyforge.org/>.	3242	L<http://rev.rubyforge.org/>.
2671		3243
		3244	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3245	makes rev work even on mingw.
		3246
		3247	=item Haskell
		3248
		3249	A haskell binding to libev is available at
		3250	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3251
2672	=item D	3252	=item D
2673		3253
2674	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3254	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2675	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3255	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3256
		3257	=item Ocaml
		3258
		3259	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3260	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2676		3261
2677	=back	3262	=back
2678		3263
2679		3264
2680	=head1 MACRO MAGIC	3265	=head1 MACRO MAGIC
…		…
2781		3366
2782	#define EV_STANDALONE 1	3367	#define EV_STANDALONE 1
2783	#include "ev.h"	3368	#include "ev.h"
2784		3369
2785	Both header files and implementation files can be compiled with a C++	3370	Both header files and implementation files can be compiled with a C++
2786	compiler (at least, thats a stated goal, and breakage will be treated	3371	compiler (at least, that's a stated goal, and breakage will be treated
2787	as a bug).	3372	as a bug).
2788		3373
2789	You need the following files in your source tree, or in a directory	3374	You need the following files in your source tree, or in a directory
2790	in your include path (e.g. in libev/ when using -Ilibev):	3375	in your include path (e.g. in libev/ when using -Ilibev):
2791		3376
…		…
2835		3420
2836	=head2 PREPROCESSOR SYMBOLS/MACROS	3421	=head2 PREPROCESSOR SYMBOLS/MACROS
2837		3422
2838	Libev can be configured via a variety of preprocessor symbols you have to	3423	Libev can be configured via a variety of preprocessor symbols you have to
2839	define before including any of its files. The default in the absence of	3424	define before including any of its files. The default in the absence of
2840	autoconf is noted for every option.	3425	autoconf is documented for every option.
2841		3426
2842	=over 4	3427	=over 4
2843		3428
2844	=item EV_STANDALONE	3429	=item EV_STANDALONE
2845		3430
…		…
2847	keeps libev from including F<config.h>, and it also defines dummy	3432	keeps libev from including F<config.h>, and it also defines dummy
2848	implementations for some libevent functions (such as logging, which is not	3433	implementations for some libevent functions (such as logging, which is not
2849	supported). It will also not define any of the structs usually found in	3434	supported). It will also not define any of the structs usually found in
2850	F<event.h> that are not directly supported by the libev core alone.	3435	F<event.h> that are not directly supported by the libev core alone.
2851		3436
		3437	In stanbdalone mode, libev will still try to automatically deduce the
		3438	configuration, but has to be more conservative.
		3439
2852	=item EV_USE_MONOTONIC	3440	=item EV_USE_MONOTONIC
2853		3441
2854	If defined to be C<1>, libev will try to detect the availability of the	3442	If defined to be C<1>, libev will try to detect the availability of the
2855	monotonic clock option at both compile time and runtime. Otherwise no use	3443	monotonic clock option at both compile time and runtime. Otherwise no
2856	of the monotonic clock option will be attempted. If you enable this, you	3444	use of the monotonic clock option will be attempted. If you enable this,
2857	usually have to link against librt or something similar. Enabling it when	3445	you usually have to link against librt or something similar. Enabling it
2858	the functionality isn't available is safe, though, although you have	3446	when the functionality isn't available is safe, though, although you have
2859	to make sure you link against any libraries where the C<clock_gettime>	3447	to make sure you link against any libraries where the C<clock_gettime>
2860	function is hiding in (often F<-lrt>).	3448	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2861		3449
2862	=item EV_USE_REALTIME	3450	=item EV_USE_REALTIME
2863		3451
2864	If defined to be C<1>, libev will try to detect the availability of the	3452	If defined to be C<1>, libev will try to detect the availability of the
2865	real-time clock option at compile time (and assume its availability at	3453	real-time clock option at compile time (and assume its availability
2866	runtime if successful). Otherwise no use of the real-time clock option will	3454	at runtime if successful). Otherwise no use of the real-time clock
2867	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3455	option will be attempted. This effectively replaces C<gettimeofday>
2868	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3456	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2869	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3457	correctness. See the note about libraries in the description of
		3458	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3459	C<EV_USE_CLOCK_SYSCALL>.
		3460
		3461	=item EV_USE_CLOCK_SYSCALL
		3462
		3463	If defined to be C<1>, libev will try to use a direct syscall instead
		3464	of calling the system-provided C<clock_gettime> function. This option
		3465	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3466	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3467	programs needlessly. Using a direct syscall is slightly slower (in
		3468	theory), because no optimised vdso implementation can be used, but avoids
		3469	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3470	higher, as it simplifies linking (no need for C<-lrt>).
2870		3471
2871	=item EV_USE_NANOSLEEP	3472	=item EV_USE_NANOSLEEP
2872		3473
2873	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3474	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2874	and will use it for delays. Otherwise it will use C<select ()>.	3475	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2890		3491
2891	=item EV_SELECT_USE_FD_SET	3492	=item EV_SELECT_USE_FD_SET
2892		3493
2893	If defined to C<1>, then the select backend will use the system C<fd_set>	3494	If defined to C<1>, then the select backend will use the system C<fd_set>
2894	structure. This is useful if libev doesn't compile due to a missing	3495	structure. This is useful if libev doesn't compile due to a missing
2895	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3496	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2896	exotic systems. This usually limits the range of file descriptors to some	3497	on exotic systems. This usually limits the range of file descriptors to
2897	low limit such as 1024 or might have other limitations (winsocket only	3498	some low limit such as 1024 or might have other limitations (winsocket
2898	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3499	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2899	influence the size of the C<fd_set> used.	3500	configures the maximum size of the C<fd_set>.
2900		3501
2901	=item EV_SELECT_IS_WINSOCKET	3502	=item EV_SELECT_IS_WINSOCKET
2902		3503
2903	When defined to C<1>, the select backend will assume that	3504	When defined to C<1>, the select backend will assume that
2904	select/socket/connect etc. don't understand file descriptors but	3505	select/socket/connect etc. don't understand file descriptors but
…		…
3015	When doing priority-based operations, libev usually has to linearly search	3616	When doing priority-based operations, libev usually has to linearly search
3016	all the priorities, so having many of them (hundreds) uses a lot of space	3617	all the priorities, so having many of them (hundreds) uses a lot of space
3017	and time, so using the defaults of five priorities (-2 .. +2) is usually	3618	and time, so using the defaults of five priorities (-2 .. +2) is usually
3018	fine.	3619	fine.
3019		3620
3020	If your embedding application does not need any priorities, defining these both to	3621	If your embedding application does not need any priorities, defining these
3021	C<0> will save some memory and CPU.	3622	both to C<0> will save some memory and CPU.
3022		3623
3023	=item EV_PERIODIC_ENABLE	3624	=item EV_PERIODIC_ENABLE
3024		3625
3025	If undefined or defined to be C<1>, then periodic timers are supported. If	3626	If undefined or defined to be C<1>, then periodic timers are supported. If
3026	defined to be C<0>, then they are not. Disabling them saves a few kB of	3627	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3033	code.	3634	code.
3034		3635
3035	=item EV_EMBED_ENABLE	3636	=item EV_EMBED_ENABLE
3036		3637
3037	If undefined or defined to be C<1>, then embed watchers are supported. If	3638	If undefined or defined to be C<1>, then embed watchers are supported. If
3038	defined to be C<0>, then they are not.	3639	defined to be C<0>, then they are not. Embed watchers rely on most other
		3640	watcher types, which therefore must not be disabled.
3039		3641
3040	=item EV_STAT_ENABLE	3642	=item EV_STAT_ENABLE
3041		3643
3042	If undefined or defined to be C<1>, then stat watchers are supported. If	3644	If undefined or defined to be C<1>, then stat watchers are supported. If
3043	defined to be C<0>, then they are not.	3645	defined to be C<0>, then they are not.
…		…
3075	two).	3677	two).
3076		3678
3077	=item EV_USE_4HEAP	3679	=item EV_USE_4HEAP
3078		3680
3079	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3681	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3080	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3682	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3081	to C<1>. The 4-heap uses more complicated (longer) code but has	3683	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3082	noticeably faster performance with many (thousands) of watchers.	3684	faster performance with many (thousands) of watchers.
3083		3685
3084	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3686	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3085	(disabled).	3687	(disabled).
3086		3688
3087	=item EV_HEAP_CACHE_AT	3689	=item EV_HEAP_CACHE_AT
3088		3690
3089	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3691	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3090	timer and periodics heap, libev can cache the timestamp (I<at>) within	3692	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3091	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3693	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3092	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3694	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3093	but avoids random read accesses on heap changes. This improves performance	3695	but avoids random read accesses on heap changes. This improves performance
3094	noticeably with with many (hundreds) of watchers.	3696	noticeably with many (hundreds) of watchers.
3095		3697
3096	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3698	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3097	(disabled).	3699	(disabled).
3098		3700
3099	=item EV_VERIFY	3701	=item EV_VERIFY
…		…
3105	called once per loop, which can slow down libev. If set to C<3>, then the	3707	called once per loop, which can slow down libev. If set to C<3>, then the
3106	verification code will be called very frequently, which will slow down	3708	verification code will be called very frequently, which will slow down
3107	libev considerably.	3709	libev considerably.
3108		3710
3109	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3711	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3110	C<0.>	3712	C<0>.
3111		3713
3112	=item EV_COMMON	3714	=item EV_COMMON
3113		3715
3114	By default, all watchers have a C<void *data> member. By redefining	3716	By default, all watchers have a C<void *data> member. By redefining
3115	this macro to a something else you can include more and other types of	3717	this macro to a something else you can include more and other types of
…		…
3132	and the way callbacks are invoked and set. Must expand to a struct member	3734	and the way callbacks are invoked and set. Must expand to a struct member
3133	definition and a statement, respectively. See the F<ev.h> header file for	3735	definition and a statement, respectively. See the F<ev.h> header file for
3134	their default definitions. One possible use for overriding these is to	3736	their default definitions. One possible use for overriding these is to
3135	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3737	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3136	method calls instead of plain function calls in C++.	3738	method calls instead of plain function calls in C++.
		3739
		3740	=back
3137		3741
3138	=head2 EXPORTED API SYMBOLS	3742	=head2 EXPORTED API SYMBOLS
3139		3743
3140	If you need to re-export the API (e.g. via a DLL) and you need a list of	3744	If you need to re-export the API (e.g. via a DLL) and you need a list of
3141	exported symbols, you can use the provided F<Symbol.*> files which list	3745	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3188	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3792	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3189		3793
3190	#include "ev_cpp.h"	3794	#include "ev_cpp.h"
3191	#include "ev.c"	3795	#include "ev.c"
3192		3796
		3797	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3193		3798
3194	=head1 THREADS AND COROUTINES	3799	=head2 THREADS AND COROUTINES
3195		3800
3196	=head2 THREADS	3801	=head3 THREADS
3197		3802
3198	Libev itself is completely thread-safe, but it uses no locking. This	3803	All libev functions are reentrant and thread-safe unless explicitly
		3804	documented otherwise, but libev implements no locking itself. This means
3199	means that you can use as many loops as you want in parallel, as long as	3805	that you can use as many loops as you want in parallel, as long as there
3200	only one thread ever calls into one libev function with the same loop	3806	are no concurrent calls into any libev function with the same loop
3201	parameter.	3807	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3808	of course): libev guarantees that different event loops share no data
		3809	structures that need any locking.
3202		3810
3203	Or put differently: calls with different loop parameters can be done in	3811	Or to put it differently: calls with different loop parameters can be done
3204	parallel from multiple threads, calls with the same loop parameter must be	3812	concurrently from multiple threads, calls with the same loop parameter
3205	done serially (but can be done from different threads, as long as only one	3813	must be done serially (but can be done from different threads, as long as
3206	thread ever is inside a call at any point in time, e.g. by using a mutex	3814	only one thread ever is inside a call at any point in time, e.g. by using
3207	per loop).	3815	a mutex per loop).
		3816
		3817	Specifically to support threads (and signal handlers), libev implements
		3818	so-called C<ev_async> watchers, which allow some limited form of
		3819	concurrency on the same event loop, namely waking it up "from the
		3820	outside".
3208		3821
3209	If you want to know which design (one loop, locking, or multiple loops	3822	If you want to know which design (one loop, locking, or multiple loops
3210	without or something else still) is best for your problem, then I cannot	3823	without or something else still) is best for your problem, then I cannot
3211	help you. I can give some generic advice however:	3824	help you, but here is some generic advice:
3212		3825
3213	=over 4	3826	=over 4
3214		3827
3215	=item * most applications have a main thread: use the default libev loop	3828	=item * most applications have a main thread: use the default libev loop
3216	in that thread, or create a separate thread running only the default loop.	3829	in that thread, or create a separate thread running only the default loop.
…		…
3228		3841
3229	Choosing a model is hard - look around, learn, know that usually you can do	3842	Choosing a model is hard - look around, learn, know that usually you can do
3230	better than you currently do :-)	3843	better than you currently do :-)
3231		3844
3232	=item * often you need to talk to some other thread which blocks in the	3845	=item * often you need to talk to some other thread which blocks in the
		3846	event loop.
		3847
3233	event loop - C<ev_async> watchers can be used to wake them up from other	3848	C<ev_async> watchers can be used to wake them up from other threads safely
3234	threads safely (or from signal contexts...).	3849	(or from signal contexts...).
		3850
		3851	An example use would be to communicate signals or other events that only
		3852	work in the default loop by registering the signal watcher with the
		3853	default loop and triggering an C<ev_async> watcher from the default loop
		3854	watcher callback into the event loop interested in the signal.
3235		3855
3236	=back	3856	=back
3237		3857
3238	=head2 COROUTINES	3858	=head3 COROUTINES
3239		3859
3240	Libev is much more accommodating to coroutines ("cooperative threads"):	3860	Libev is very accommodating to coroutines ("cooperative threads"):
3241	libev fully supports nesting calls to it's functions from different	3861	libev fully supports nesting calls to its functions from different
3242	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3862	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3243	different coroutines and switch freely between both coroutines running the	3863	different coroutines, and switch freely between both coroutines running the
3244	loop, as long as you don't confuse yourself). The only exception is that	3864	loop, as long as you don't confuse yourself). The only exception is that
3245	you must not do this from C<ev_periodic> reschedule callbacks.	3865	you must not do this from C<ev_periodic> reschedule callbacks.
3246		3866
3247	Care has been invested into making sure that libev does not keep local	3867	Care has been taken to ensure that libev does not keep local state inside
3248	state inside C<ev_loop>, and other calls do not usually allow coroutine	3868	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3249	switches.	3869	they do not call any callbacks.
3250		3870
		3871	=head2 COMPILER WARNINGS
3251		3872
3252	=head1 COMPLEXITIES	3873	Depending on your compiler and compiler settings, you might get no or a
		3874	lot of warnings when compiling libev code. Some people are apparently
		3875	scared by this.
3253		3876
3254	In this section the complexities of (many of) the algorithms used inside	3877	However, these are unavoidable for many reasons. For one, each compiler
3255	libev will be explained. For complexity discussions about backends see the	3878	has different warnings, and each user has different tastes regarding
3256	documentation for C<ev_default_init>.	3879	warning options. "Warn-free" code therefore cannot be a goal except when
		3880	targeting a specific compiler and compiler-version.
3257		3881
3258	All of the following are about amortised time: If an array needs to be	3882	Another reason is that some compiler warnings require elaborate
3259	extended, libev needs to realloc and move the whole array, but this	3883	workarounds, or other changes to the code that make it less clear and less
3260	happens asymptotically never with higher number of elements, so O(1) might	3884	maintainable.
3261	mean it might do a lengthy realloc operation in rare cases, but on average
3262	it is much faster and asymptotically approaches constant time.
3263		3885
3264	=over 4	3886	And of course, some compiler warnings are just plain stupid, or simply
		3887	wrong (because they don't actually warn about the condition their message
		3888	seems to warn about). For example, certain older gcc versions had some
		3889	warnings that resulted an extreme number of false positives. These have
		3890	been fixed, but some people still insist on making code warn-free with
		3891	such buggy versions.
3265		3892
3266	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3893	While libev is written to generate as few warnings as possible,
		3894	"warn-free" code is not a goal, and it is recommended not to build libev
		3895	with any compiler warnings enabled unless you are prepared to cope with
		3896	them (e.g. by ignoring them). Remember that warnings are just that:
		3897	warnings, not errors, or proof of bugs.
3267		3898
3268	This means that, when you have a watcher that triggers in one hour and
3269	there are 100 watchers that would trigger before that then inserting will
3270	have to skip roughly seven (C<ld 100>) of these watchers.
3271		3899
3272	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3900	=head2 VALGRIND
3273		3901
3274	That means that changing a timer costs less than removing/adding them	3902	Valgrind has a special section here because it is a popular tool that is
3275	as only the relative motion in the event queue has to be paid for.	3903	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3276		3904
3277	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3905	If you think you found a bug (memory leak, uninitialised data access etc.)
		3906	in libev, then check twice: If valgrind reports something like:
3278		3907
3279	These just add the watcher into an array or at the head of a list.	3908	==2274== definitely lost: 0 bytes in 0 blocks.
		3909	==2274== possibly lost: 0 bytes in 0 blocks.
		3910	==2274== still reachable: 256 bytes in 1 blocks.
3280		3911
3281	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3912	Then there is no memory leak, just as memory accounted to global variables
		3913	is not a memleak - the memory is still being referenced, and didn't leak.
3282		3914
3283	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3915	Similarly, under some circumstances, valgrind might report kernel bugs
		3916	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3917	although an acceptable workaround has been found here), or it might be
		3918	confused.
3284		3919
3285	These watchers are stored in lists then need to be walked to find the	3920	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3286	correct watcher to remove. The lists are usually short (you don't usually	3921	make it into some kind of religion.
3287	have many watchers waiting for the same fd or signal).
3288		3922
3289	=item Finding the next timer in each loop iteration: O(1)	3923	If you are unsure about something, feel free to contact the mailing list
		3924	with the full valgrind report and an explanation on why you think this
		3925	is a bug in libev (best check the archives, too :). However, don't be
		3926	annoyed when you get a brisk "this is no bug" answer and take the chance
		3927	of learning how to interpret valgrind properly.
3290		3928
3291	By virtue of using a binary or 4-heap, the next timer is always found at a	3929	If you need, for some reason, empty reports from valgrind for your project
3292	fixed position in the storage array.	3930	I suggest using suppression lists.
3293		3931
3294	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3295		3932
3296	A change means an I/O watcher gets started or stopped, which requires	3933	=head1 PORTABILITY NOTES
3297	libev to recalculate its status (and possibly tell the kernel, depending
3298	on backend and whether C<ev_io_set> was used).
3299		3934
3300	=item Activating one watcher (putting it into the pending state): O(1)
3301
3302	=item Priority handling: O(number_of_priorities)
3303
3304	Priorities are implemented by allocating some space for each
3305	priority. When doing priority-based operations, libev usually has to
3306	linearly search all the priorities, but starting/stopping and activating
3307	watchers becomes O(1) w.r.t. priority handling.
3308
3309	=item Sending an ev_async: O(1)
3310
3311	=item Processing ev_async_send: O(number_of_async_watchers)
3312
3313	=item Processing signals: O(max_signal_number)
3314
3315	Sending involves a system call I<iff> there were no other C<ev_async_send>
3316	calls in the current loop iteration. Checking for async and signal events
3317	involves iterating over all running async watchers or all signal numbers.
3318
3319	=back
3320
3321
3322	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3935	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3323		3936
3324	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3937	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3325	requires, and its I/O model is fundamentally incompatible with the POSIX	3938	requires, and its I/O model is fundamentally incompatible with the POSIX
3326	model. Libev still offers limited functionality on this platform in	3939	model. Libev still offers limited functionality on this platform in
3327	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3940	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3334	way (note also that glib is the slowest event library known to man).	3947	way (note also that glib is the slowest event library known to man).
3335		3948
3336	There is no supported compilation method available on windows except	3949	There is no supported compilation method available on windows except
3337	embedding it into other applications.	3950	embedding it into other applications.
3338		3951
		3952	Sensible signal handling is officially unsupported by Microsoft - libev
		3953	tries its best, but under most conditions, signals will simply not work.
		3954
3339	Not a libev limitation but worth mentioning: windows apparently doesn't	3955	Not a libev limitation but worth mentioning: windows apparently doesn't
3340	accept large writes: instead of resulting in a partial write, windows will	3956	accept large writes: instead of resulting in a partial write, windows will
3341	either accept everything or return C<ENOBUFS> if the buffer is too large,	3957	either accept everything or return C<ENOBUFS> if the buffer is too large,
3342	so make sure you only write small amounts into your sockets (less than a	3958	so make sure you only write small amounts into your sockets (less than a
3343	megabyte seems safe, but thsi apparently depends on the amount of memory	3959	megabyte seems safe, but this apparently depends on the amount of memory
3344	available).	3960	available).
3345		3961
3346	Due to the many, low, and arbitrary limits on the win32 platform and	3962	Due to the many, low, and arbitrary limits on the win32 platform and
3347	the abysmal performance of winsockets, using a large number of sockets	3963	the abysmal performance of winsockets, using a large number of sockets
3348	is not recommended (and not reasonable). If your program needs to use	3964	is not recommended (and not reasonable). If your program needs to use
3349	more than a hundred or so sockets, then likely it needs to use a totally	3965	more than a hundred or so sockets, then likely it needs to use a totally
3350	different implementation for windows, as libev offers the POSIX readiness	3966	different implementation for windows, as libev offers the POSIX readiness
3351	notification model, which cannot be implemented efficiently on windows	3967	notification model, which cannot be implemented efficiently on windows
3352	(Microsoft monopoly games).	3968	(due to Microsoft monopoly games).
3353		3969
3354	A typical way to use libev under windows is to embed it (see the embedding	3970	A typical way to use libev under windows is to embed it (see the embedding
3355	section for details) and use the following F<evwrap.h> header file instead	3971	section for details) and use the following F<evwrap.h> header file instead
3356	of F<ev.h>:	3972	of F<ev.h>:
3357		3973
…		…
3359	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3975	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3360		3976
3361	#include "ev.h"	3977	#include "ev.h"
3362		3978
3363	And compile the following F<evwrap.c> file into your project (make sure	3979	And compile the following F<evwrap.c> file into your project (make sure
3364	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3980	you do I<not> compile the F<ev.c> or any other embedded source files!):
3365		3981
3366	#include "evwrap.h"	3982	#include "evwrap.h"
3367	#include "ev.c"	3983	#include "ev.c"
3368		3984
3369	=over 4	3985	=over 4
…		…
3393		4009
3394	Early versions of winsocket's select only supported waiting for a maximum	4010	Early versions of winsocket's select only supported waiting for a maximum
3395	of C<64> handles (probably owning to the fact that all windows kernels	4011	of C<64> handles (probably owning to the fact that all windows kernels
3396	can only wait for C<64> things at the same time internally; Microsoft	4012	can only wait for C<64> things at the same time internally; Microsoft
3397	recommends spawning a chain of threads and wait for 63 handles and the	4013	recommends spawning a chain of threads and wait for 63 handles and the
3398	previous thread in each. Great).	4014	previous thread in each. Sounds great!).
3399		4015
3400	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4016	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3401	to some high number (e.g. C<2048>) before compiling the winsocket select	4017	to some high number (e.g. C<2048>) before compiling the winsocket select
3402	call (which might be in libev or elsewhere, for example, perl does its own	4018	call (which might be in libev or elsewhere, for example, perl and many
3403	select emulation on windows).	4019	other interpreters do their own select emulation on windows).
3404		4020
3405	Another limit is the number of file descriptors in the Microsoft runtime	4021	Another limit is the number of file descriptors in the Microsoft runtime
3406	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4022	libraries, which by default is C<64> (there must be a hidden I<64>
3407	or something like this inside Microsoft). You can increase this by calling	4023	fetish or something like this inside Microsoft). You can increase this
3408	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4024	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3409	arbitrary limit), but is broken in many versions of the Microsoft runtime	4025	(another arbitrary limit), but is broken in many versions of the Microsoft
3410	libraries.
3411
3412	This might get you to about C<512> or C<2048> sockets (depending on	4026	runtime libraries. This might get you to about C<512> or C<2048> sockets
3413	windows version and/or the phase of the moon). To get more, you need to	4027	(depending on windows version and/or the phase of the moon). To get more,
3414	wrap all I/O functions and provide your own fd management, but the cost of	4028	you need to wrap all I/O functions and provide your own fd management, but
3415	calling select (O(n²)) will likely make this unworkable.	4029	the cost of calling select (O(n²)) will likely make this unworkable.
3416		4030
3417	=back	4031	=back
3418		4032
3419
3420	=head1 PORTABILITY REQUIREMENTS	4033	=head2 PORTABILITY REQUIREMENTS
3421		4034
3422	In addition to a working ISO-C implementation, libev relies on a few	4035	In addition to a working ISO-C implementation and of course the
3423	additional extensions:	4036	backend-specific APIs, libev relies on a few additional extensions:
3424		4037
3425	=over 4	4038	=over 4
3426		4039
3427	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4040	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3428	calling conventions regardless of C<ev_watcher_type *>.	4041	calling conventions regardless of C<ev_watcher_type *>.
…		…
3434	calls them using an C<ev_watcher *> internally.	4047	calls them using an C<ev_watcher *> internally.
3435		4048
3436	=item C<sig_atomic_t volatile> must be thread-atomic as well	4049	=item C<sig_atomic_t volatile> must be thread-atomic as well
3437		4050
3438	The type C<sig_atomic_t volatile> (or whatever is defined as	4051	The type C<sig_atomic_t volatile> (or whatever is defined as
3439	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4052	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3440	threads. This is not part of the specification for C<sig_atomic_t>, but is	4053	threads. This is not part of the specification for C<sig_atomic_t>, but is
3441	believed to be sufficiently portable.	4054	believed to be sufficiently portable.
3442		4055
3443	=item C<sigprocmask> must work in a threaded environment	4056	=item C<sigprocmask> must work in a threaded environment
3444		4057
…		…
3453	except the initial one, and run the default loop in the initial thread as	4066	except the initial one, and run the default loop in the initial thread as
3454	well.	4067	well.
3455		4068
3456	=item C<long> must be large enough for common memory allocation sizes	4069	=item C<long> must be large enough for common memory allocation sizes
3457		4070
3458	To improve portability and simplify using libev, libev uses C<long>	4071	To improve portability and simplify its API, libev uses C<long> internally
3459	internally instead of C<size_t> when allocating its data structures. On	4072	instead of C<size_t> when allocating its data structures. On non-POSIX
3460	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4073	systems (Microsoft...) this might be unexpectedly low, but is still at
3461	is still at least 31 bits everywhere, which is enough for hundreds of	4074	least 31 bits everywhere, which is enough for hundreds of millions of
3462	millions of watchers.	4075	watchers.
3463		4076
3464	=item C<double> must hold a time value in seconds with enough accuracy	4077	=item C<double> must hold a time value in seconds with enough accuracy
3465		4078
3466	The type C<double> is used to represent timestamps. It is required to	4079	The type C<double> is used to represent timestamps. It is required to
3467	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4080	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3471	=back	4084	=back
3472		4085
3473	If you know of other additional requirements drop me a note.	4086	If you know of other additional requirements drop me a note.
3474		4087
3475		4088
3476	=head1 COMPILER WARNINGS	4089	=head1 ALGORITHMIC COMPLEXITIES
3477		4090
3478	Depending on your compiler and compiler settings, you might get no or a	4091	In this section the complexities of (many of) the algorithms used inside
3479	lot of warnings when compiling libev code. Some people are apparently	4092	libev will be documented. For complexity discussions about backends see
3480	scared by this.	4093	the documentation for C<ev_default_init>.
3481		4094
3482	However, these are unavoidable for many reasons. For one, each compiler	4095	All of the following are about amortised time: If an array needs to be
3483	has different warnings, and each user has different tastes regarding	4096	extended, libev needs to realloc and move the whole array, but this
3484	warning options. "Warn-free" code therefore cannot be a goal except when	4097	happens asymptotically rarer with higher number of elements, so O(1) might
3485	targeting a specific compiler and compiler-version.	4098	mean that libev does a lengthy realloc operation in rare cases, but on
		4099	average it is much faster and asymptotically approaches constant time.
3486		4100
3487	Another reason is that some compiler warnings require elaborate	4101	=over 4
3488	workarounds, or other changes to the code that make it less clear and less
3489	maintainable.
3490		4102
3491	And of course, some compiler warnings are just plain stupid, or simply	4103	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3492	wrong (because they don't actually warn about the condition their message
3493	seems to warn about).
3494		4104
3495	While libev is written to generate as few warnings as possible,	4105	This means that, when you have a watcher that triggers in one hour and
3496	"warn-free" code is not a goal, and it is recommended not to build libev	4106	there are 100 watchers that would trigger before that, then inserting will
3497	with any compiler warnings enabled unless you are prepared to cope with	4107	have to skip roughly seven (C<ld 100>) of these watchers.
3498	them (e.g. by ignoring them). Remember that warnings are just that:
3499	warnings, not errors, or proof of bugs.
3500		4108
		4109	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3501		4110
3502	=head1 VALGRIND	4111	That means that changing a timer costs less than removing/adding them,
		4112	as only the relative motion in the event queue has to be paid for.
3503		4113
3504	Valgrind has a special section here because it is a popular tool that is	4114	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3505	highly useful, but valgrind reports are very hard to interpret.
3506		4115
3507	If you think you found a bug (memory leak, uninitialised data access etc.)	4116	These just add the watcher into an array or at the head of a list.
3508	in libev, then check twice: If valgrind reports something like:
3509		4117
3510	==2274== definitely lost: 0 bytes in 0 blocks.	4118	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3511	==2274== possibly lost: 0 bytes in 0 blocks.
3512	==2274== still reachable: 256 bytes in 1 blocks.
3513		4119
3514	Then there is no memory leak. Similarly, under some circumstances,	4120	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3515	valgrind might report kernel bugs as if it were a bug in libev, or it
3516	might be confused (it is a very good tool, but only a tool).
3517		4121
3518	If you are unsure about something, feel free to contact the mailing list	4122	These watchers are stored in lists, so they need to be walked to find the
3519	with the full valgrind report and an explanation on why you think this is	4123	correct watcher to remove. The lists are usually short (you don't usually
3520	a bug in libev. However, don't be annoyed when you get a brisk "this is	4124	have many watchers waiting for the same fd or signal: one is typical, two
3521	no bug" answer and take the chance of learning how to interpret valgrind	4125	is rare).
3522	properly.
3523		4126
3524	If you need, for some reason, empty reports from valgrind for your project	4127	=item Finding the next timer in each loop iteration: O(1)
3525	I suggest using suppression lists.
3526		4128
		4129	By virtue of using a binary or 4-heap, the next timer is always found at a
		4130	fixed position in the storage array.
		4131
		4132	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4133
		4134	A change means an I/O watcher gets started or stopped, which requires
		4135	libev to recalculate its status (and possibly tell the kernel, depending
		4136	on backend and whether C<ev_io_set> was used).
		4137
		4138	=item Activating one watcher (putting it into the pending state): O(1)
		4139
		4140	=item Priority handling: O(number_of_priorities)
		4141
		4142	Priorities are implemented by allocating some space for each
		4143	priority. When doing priority-based operations, libev usually has to
		4144	linearly search all the priorities, but starting/stopping and activating
		4145	watchers becomes O(1) with respect to priority handling.
		4146
		4147	=item Sending an ev_async: O(1)
		4148
		4149	=item Processing ev_async_send: O(number_of_async_watchers)
		4150
		4151	=item Processing signals: O(max_signal_number)
		4152
		4153	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4154	calls in the current loop iteration. Checking for async and signal events
		4155	involves iterating over all running async watchers or all signal numbers.
		4156
		4157	=back
		4158
		4159
		4160	=head1 GLOSSARY
		4161
		4162	=over 4
		4163
		4164	=item active
		4165
		4166	A watcher is active as long as it has been started (has been attached to
		4167	an event loop) but not yet stopped (disassociated from the event loop).
		4168
		4169	=item application
		4170
		4171	In this document, an application is whatever is using libev.
		4172
		4173	=item callback
		4174
		4175	The address of a function that is called when some event has been
		4176	detected. Callbacks are being passed the event loop, the watcher that
		4177	received the event, and the actual event bitset.
		4178
		4179	=item callback invocation
		4180
		4181	The act of calling the callback associated with a watcher.
		4182
		4183	=item event
		4184
		4185	A change of state of some external event, such as data now being available
		4186	for reading on a file descriptor, time having passed or simply not having
		4187	any other events happening anymore.
		4188
		4189	In libev, events are represented as single bits (such as C<EV_READ> or
		4190	C<EV_TIMEOUT>).
		4191
		4192	=item event library
		4193
		4194	A software package implementing an event model and loop.
		4195
		4196	=item event loop
		4197
		4198	An entity that handles and processes external events and converts them
		4199	into callback invocations.
		4200
		4201	=item event model
		4202
		4203	The model used to describe how an event loop handles and processes
		4204	watchers and events.
		4205
		4206	=item pending
		4207
		4208	A watcher is pending as soon as the corresponding event has been detected,
		4209	and stops being pending as soon as the watcher will be invoked or its
		4210	pending status is explicitly cleared by the application.
		4211
		4212	A watcher can be pending, but not active. Stopping a watcher also clears
		4213	its pending status.
		4214
		4215	=item real time
		4216
		4217	The physical time that is observed. It is apparently strictly monotonic :)
		4218
		4219	=item wall-clock time
		4220
		4221	The time and date as shown on clocks. Unlike real time, it can actually
		4222	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4223	clock.
		4224
		4225	=item watcher
		4226
		4227	A data structure that describes interest in certain events. Watchers need
		4228	to be started (attached to an event loop) before they can receive events.
		4229
		4230	=item watcher invocation
		4231
		4232	The act of calling the callback associated with a watcher.
		4233
		4234	=back
3527		4235
3528	=head1 AUTHOR	4236	=head1 AUTHOR
3529		4237
3530	Marc Lehmann <libev@schmorp.de>.	4238	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3531		4239

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