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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 reading from a pipe whose other end has been closed, your program	1418	when writing to a pipe whose other end has been closed, your program gets
1140	gets send a SIGPIPE, which, by default, aborts your program. For most	1419	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	programs this is sensible behaviour, for daemons, this is usually	1420	this is sensible behaviour, for daemons, this is usually undesirable.
1142	undesirable.
1143		1421
1144	So when you encounter spurious, unexplained daemon exits, make sure you	1422	So when you encounter spurious, unexplained daemon exits, make sure you
1145	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
1146	somewhere, as that would have given you a big clue).	1424	somewhere, as that would have given you a big clue).
1147		1425
…		…
1153	=item ev_io_init (ev_io *, callback, int fd, int events)	1431	=item ev_io_init (ev_io *, callback, int fd, int events)
1154		1432
1155	=item ev_io_set (ev_io *, int fd, int events)	1433	=item ev_io_set (ev_io *, int fd, int events)
1156		1434
1157	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
1158	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
1159	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.
1160		1438
1161	=item int fd [read-only]	1439	=item int fd [read-only]
1162		1440
1163	The file descriptor being watched.	1441	The file descriptor being watched.
1164		1442
…		…
1173	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
1174	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
1175	attempt to read a whole line in the callback.	1453	attempt to read a whole line in the callback.
1176		1454
1177	static void	1455	static void
1178	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)
1179	{	1457	{
1180	ev_io_stop (loop, w);	1458	ev_io_stop (loop, w);
1181	.. 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
1182	}	1460	}
1183		1461
1184	...	1462	...
1185	struct ev_loop *loop = ev_default_init (0);	1463	struct ev_loop *loop = ev_default_init (0);
1186	struct ev_io stdin_readable;	1464	ev_io stdin_readable;
1187	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);
1188	ev_io_start (loop, &stdin_readable);	1466	ev_io_start (loop, &stdin_readable);
1189	ev_loop (loop, 0);	1467	ev_loop (loop, 0);
1190		1468
1191		1469
…		…
1194	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
1195	given time, and optionally repeating in regular intervals after that.	1473	given time, and optionally repeating in regular intervals after that.
1196		1474
1197	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
1198	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
1199	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
1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1478	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1201	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.
1202		1670
1203	The relative timeouts are calculated relative to the C<ev_now ()>	1671	The relative timeouts are calculated relative to the C<ev_now ()>
1204	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
1205	of the event triggering whatever timeout you are modifying/starting. If	1673	of the event triggering whatever timeout you are modifying/starting. If
1206	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
1207	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:
1208		1676
1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1677	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1210		1678
1211	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
1212	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
1213	order of execution is undefined.	1681	()>.
1214		1682
1215	=head3 Watcher-Specific Functions and Data Members	1683	=head3 Watcher-Specific Functions and Data Members
1216		1684
1217	=over 4	1685	=over 4
1218		1686
…		…
1242	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).
1243		1711
1244	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
1245	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.
1246		1714
1247	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
1248	example: Imagine you have a TCP connection and you want a so-called idle	1716	usage example.
1249	timeout, that is, you want to be called when there have been, say, 60
1250	seconds of inactivity on the socket. The easiest way to do this is to
1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1252	C<ev_timer_again> each time you successfully read or write some data. If
1253	you go into an idle state where you do not expect data to travel on the
1254	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1255	automatically restart it if need be.
1256
1257	That means you can ignore the C<after> value and C<ev_timer_start>
1258	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1259
1260	ev_timer_init (timer, callback, 0., 5.);
1261	ev_timer_again (loop, timer);
1262	...
1263	timer->again = 17.;
1264	ev_timer_again (loop, timer);
1265	...
1266	timer->again = 10.;
1267	ev_timer_again (loop, timer);
1268
1269	This is more slightly efficient then stopping/starting the timer each time
1270	you want to modify its timeout value.
1271		1717
1272	=item ev_tstamp repeat [read-write]	1718	=item ev_tstamp repeat [read-write]
1273		1719
1274	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
1275	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),
1276	which is also when any modifications are taken into account.	1722	which is also when any modifications are taken into account.
1277		1723
1278	=back	1724	=back
1279		1725
1280	=head3 Examples	1726	=head3 Examples
1281		1727
1282	Example: Create a timer that fires after 60 seconds.	1728	Example: Create a timer that fires after 60 seconds.
1283		1729
1284	static void	1730	static void
1285	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)
1286	{	1732	{
1287	.. one minute over, w is actually stopped right here	1733	.. one minute over, w is actually stopped right here
1288	}	1734	}
1289		1735
1290	struct ev_timer mytimer;	1736	ev_timer mytimer;
1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1737	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1292	ev_timer_start (loop, &mytimer);	1738	ev_timer_start (loop, &mytimer);
1293		1739
1294	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
1295	inactivity.	1741	inactivity.
1296		1742
1297	static void	1743	static void
1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1744	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1299	{	1745	{
1300	.. ten seconds without any activity	1746	.. ten seconds without any activity
1301	}	1747	}
1302		1748
1303	struct ev_timer mytimer;	1749	ev_timer mytimer;
1304	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 */
1305	ev_timer_again (&mytimer); /* start timer */	1751	ev_timer_again (&mytimer); /* start timer */
1306	ev_loop (loop, 0);	1752	ev_loop (loop, 0);
1307		1753
1308	// 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":
…		…
1313	=head2 C<ev_periodic> - to cron or not to cron?	1759	=head2 C<ev_periodic> - to cron or not to cron?
1314		1760
1315	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
1316	(and unfortunately a bit complex).	1762	(and unfortunately a bit complex).
1317		1763
1318	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
1319	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
1320	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
1321	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
1322	+ 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
1323	clock to January of the previous year, then it will take more than year	1769	wrist-watch).
1324	to trigger the event (unlike an C<ev_timer>, which would still trigger
1325	roughly 10 seconds later as it uses a relative timeout).
1326		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
1327	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
1328	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
1329	complicated, rules.	1781	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1782	those cannot react to time jumps.
1330		1783
1331	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
1332	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
1333	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).
1334		1789
1335	=head3 Watcher-Specific Functions and Data Members	1790	=head3 Watcher-Specific Functions and Data Members
1336		1791
1337	=over 4	1792	=over 4
1338		1793
1339	=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)
1340		1795
1341	=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)
1342		1797
1343	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
1344	operation, and we will explain them from simplest to complex:	1799	operation, and we will explain them from simplest to most complex:
1345		1800
1346	=over 4	1801	=over 4
1347		1802
1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1803	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1349		1804
1350	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
1351	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
1352	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
1353	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.
1354		1810
1355	=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)
1356		1812
1357	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
1358	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
1359	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.
1360		1817
1361	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
1362	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
1363	the hour:	1820	hour, on the hour (with respect to UTC):
1364		1821
1365	ev_periodic_set (&periodic, 0., 3600., 0);	1822	ev_periodic_set (&periodic, 0., 3600., 0);
1366		1823
1367	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,
1368	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
1369	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
1370	by 3600.	1827	by 3600.
1371		1828
1372	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
1373	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
1374	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.
1375		1832
1376	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
1377	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
1378	this value, and in fact is often specified as zero.	1835	this value, and in fact is often specified as zero.
1379		1836
1380	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
1381	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
1382	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
1383	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).
1384		1841
1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1842	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1386		1843
1387	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
1388	ignored. Instead, each time the periodic watcher gets scheduled, the	1845	ignored. Instead, each time the periodic watcher gets scheduled, the
1389	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
1390	current time as second argument.	1847	current time as second argument.
1391		1848
1392	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,
1393	ever, or make ANY event loop modifications whatsoever>.	1850	or make ANY other event loop modifications whatsoever, unless explicitly
		1851	allowed by documentation here>.
1394		1852
1395	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
1396	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
1397	only event loop modification you are allowed to do).	1855	only event loop modification you are allowed to do).
1398		1856
1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1857	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1400	*w, ev_tstamp now)>, e.g.:	1858	*w, ev_tstamp now)>, e.g.:
1401		1859
		1860	static ev_tstamp
1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1861	my_rescheduler (ev_periodic *w, ev_tstamp now)
1403	{	1862	{
1404	return now + 60.;	1863	return now + 60.;
1405	}	1864	}
1406		1865
1407	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
…		…
1427	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
1428	program when the crontabs have changed).	1887	program when the crontabs have changed).
1429		1888
1430	=item ev_tstamp ev_periodic_at (ev_periodic *)	1889	=item ev_tstamp ev_periodic_at (ev_periodic *)
1431		1890
1432	When active, returns the absolute time that the watcher is supposed to	1891	When active, returns the absolute time that the watcher is supposed
1433	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.
1434		1895
1435	=item ev_tstamp offset [read-write]	1896	=item ev_tstamp offset [read-write]
1436		1897
1437	When repeating, this contains the offset value, otherwise this is the	1898	When repeating, this contains the offset value, otherwise this is the
1438	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).
1439		1901
1440	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
1441	timer fires or C<ev_periodic_again> is being called.	1903	timer fires or C<ev_periodic_again> is being called.
1442		1904
1443	=item ev_tstamp interval [read-write]	1905	=item ev_tstamp interval [read-write]
1444		1906
1445	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
1446	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
1447	called.	1909	called.
1448		1910
1449	=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]
1450		1912
1451	The current reschedule callback, or C<0>, if this functionality is	1913	The current reschedule callback, or C<0>, if this functionality is
1452	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
1453	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.
1454		1916
1455	=back	1917	=back
1456		1918
1457	=head3 Examples	1919	=head3 Examples
1458		1920
1459	Example: Call a callback every hour, or, more precisely, whenever the	1921	Example: Call a callback every hour, or, more precisely, whenever the
1460	system clock is divisible by 3600. The callback invocation times have	1922	system time is divisible by 3600. The callback invocation times have
1461	potentially a lot of jitter, but good long-term stability.	1923	potentially a lot of jitter, but good long-term stability.
1462		1924
1463	static void	1925	static void
1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1926	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1465	{	1927	{
1466	... 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)
1467	}	1929	}
1468		1930
1469	struct ev_periodic hourly_tick;	1931	ev_periodic hourly_tick;
1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1932	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1471	ev_periodic_start (loop, &hourly_tick);	1933	ev_periodic_start (loop, &hourly_tick);
1472		1934
1473	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:
1474		1936
1475	#include <math.h>	1937	#include <math.h>
1476		1938
1477	static ev_tstamp	1939	static ev_tstamp
1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1940	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1479	{	1941	{
1480	return fmod (now, 3600.) + 3600.;	1942	return now + (3600. - fmod (now, 3600.));
1481	}	1943	}
1482		1944
1483	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);
1484		1946
1485	Example: Call a callback every hour, starting now:	1947	Example: Call a callback every hour, starting now:
1486		1948
1487	struct ev_periodic hourly_tick;	1949	ev_periodic hourly_tick;
1488	ev_periodic_init (&hourly_tick, clock_cb,	1950	ev_periodic_init (&hourly_tick, clock_cb,
1489	fmod (ev_now (loop), 3600.), 3600., 0);	1951	fmod (ev_now (loop), 3600.), 3600., 0);
1490	ev_periodic_start (loop, &hourly_tick);	1952	ev_periodic_start (loop, &hourly_tick);
1491		1953
1492		1954
…		…
1495	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
1496	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
1497	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
1498	normal event processing, like any other event.	1960	normal event processing, like any other event.
1499		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
1500	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
1501	first watcher gets started will libev actually register a signal watcher	1967	first watcher gets started will libev actually register a signal handler
1502	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
1503	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
1504	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
1505	SIG_DFL (regardless of what it was set to before).	1971	signal handler to SIG_DFL (regardless of what it was set to before).
1506		1972
1507	If possible and supported, libev will install its handlers with	1973	If possible and supported, libev will install its handlers with
1508	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
1509	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
1510	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
…		…
1527		1993
1528	=back	1994	=back
1529		1995
1530	=head3 Examples	1996	=head3 Examples
1531		1997
1532	Example: Try to exit cleanly on SIGINT and SIGTERM.	1998	Example: Try to exit cleanly on SIGINT.
1533		1999
1534	static void	2000	static void
1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2001	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1536	{	2002	{
1537	ev_unloop (loop, EVUNLOOP_ALL);	2003	ev_unloop (loop, EVUNLOOP_ALL);
1538	}	2004	}
1539		2005
1540	struct ev_signal signal_watcher;	2006	ev_signal signal_watcher;
1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2007	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1542	ev_signal_start (loop, &sigint_cb);	2008	ev_signal_start (loop, &signal_watcher);
1543		2009
1544		2010
1545	=head2 C<ev_child> - watch out for process status changes	2011	=head2 C<ev_child> - watch out for process status changes
1546		2012
1547	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
1548	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
1549	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
1550	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
1551	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.
1552		2021
1553	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
1554	you can only register child watchers in the default event loop.	2023	you can only register child watchers in the default event loop.
1555		2024
1556	=head3 Process Interaction	2025	=head3 Process Interaction
…		…
1569	handler, you can override it easily by installing your own handler for	2038	handler, you can override it easily by installing your own handler for
1570	C<SIGCHLD> after initialising the default loop, and making sure the	2039	C<SIGCHLD> after initialising the default loop, and making sure the
1571	default loop never gets destroyed. You are encouraged, however, to use an	2040	default loop never gets destroyed. You are encouraged, however, to use an
1572	event-based approach to child reaping and thus use libev's support for	2041	event-based approach to child reaping and thus use libev's support for
1573	that, so other libev users can use C<ev_child> watchers freely.	2042	that, so other libev users can use C<ev_child> watchers freely.
		2043
		2044	=head3 Stopping the Child Watcher
		2045
		2046	Currently, the child watcher never gets stopped, even when the
		2047	child terminates, so normally one needs to stop the watcher in the
		2048	callback. Future versions of libev might stop the watcher automatically
		2049	when a child exit is detected.
1574		2050
1575	=head3 Watcher-Specific Functions and Data Members	2051	=head3 Watcher-Specific Functions and Data Members
1576		2052
1577	=over 4	2053	=over 4
1578		2054
…		…
1610	its completion.	2086	its completion.
1611		2087
1612	ev_child cw;	2088	ev_child cw;
1613		2089
1614	static void	2090	static void
1615	child_cb (EV_P_ struct ev_child *w, int revents)	2091	child_cb (EV_P_ ev_child *w, int revents)
1616	{	2092	{
1617	ev_child_stop (EV_A_ w);	2093	ev_child_stop (EV_A_ w);
1618	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);
1619	}	2095	}
1620		2096
…		…
1635		2111
1636		2112
1637	=head2 C<ev_stat> - did the file attributes just change?	2113	=head2 C<ev_stat> - did the file attributes just change?
1638		2114
1639	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
1640	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)
1641	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.
1642		2119
1643	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
1644	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
1645	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
1646	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
1647	the stat buffer having unspecified contents.	2124	least one) and all the other fields of the stat buffer having unspecified
		2125	contents.
1648		2126
1649	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
1650	relative and your working directory changes, the behaviour is undefined.	2129	your working directory changes, then the behaviour is undefined.
1651		2130
1652	Since there is no standard to do this, the portable implementation simply	2131	Since there is no portable change notification interface available, the
1653	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
1654	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
1655	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
1656	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
1657	five seconds, although this might change dynamically). Libev will also	2136	(which you can expect to be around five seconds, although this might
1658	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
1659	usually overkill.	2138	currently around C<0.1>, but that's usually overkill.
1660		2139
1661	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,
1662	as even with OS-supported change notifications, this can be	2141	as even with OS-supported change notifications, this can be
1663	resource-intensive.	2142	resource-intensive.
1664		2143
1665	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
1666	implemented (implementing kqueue support is left as an exercise for the	2145	is the Linux inotify interface (implementing kqueue support is left as an
1667	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
1668	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).
1669	not change the semantics of C<ev_stat> watchers, which means that libev
1670	sometimes needs to fall back to regular polling again even with inotify,
1671	but changes are usually detected immediately, and if the file exists there
1672	will be no polling.
1673		2148
1674	=head3 ABI Issues (Largefile Support)	2149	=head3 ABI Issues (Largefile Support)
1675		2150
1676	Libev by default (unless the user overrides this) uses the default	2151	Libev by default (unless the user overrides this) uses the default
1677	compilation environment, which means that on systems with large file	2152	compilation environment, which means that on systems with large file
1678	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
1679	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
1680	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
1681	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
1682	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
1683	most noticeably disabled with ev_stat and large file support.	2158	most noticeably displayed with ev_stat and large file support.
1684		2159
1685	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
1686	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
1687	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
1688	to exchange stat structures with application programs compiled using the	2163	to exchange stat structures with application programs compiled using the
1689	default compilation environment.	2164	default compilation environment.
1690		2165
1691	=head3 Inotify	2166	=head3 Inotify and Kqueue
1692		2167
1693	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
1694	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
1695	change detection where possible. The inotify descriptor will be created lazily	2170	inotify descriptor will be created lazily when the first C<ev_stat>
1696	when the first C<ev_stat> watcher is being started.	2171	watcher is being started.
1697		2172
1698	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
1699	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
1700	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
1701	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.
1702		2181
1703	(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
1704	implement this functionality, due to the requirement of having a file	2183	implement this functionality, due to the requirement of having a file
1705	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.
1706		2204
1707	=head3 The special problem of stat time resolution	2205	=head3 The special problem of stat time resolution
1708		2206
1709	The C<stat ()> system call only supports full-second resolution portably, and	2207	The C<stat ()> system call only supports full-second resolution portably,
1710	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
1711	only support whole seconds.	2209	still only support whole seconds.
1712		2210
1713	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
1714	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
1715	calls your callback, which does something. When there is another update	2213	calls your callback, which does something. When there is another update
1716	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
1717	data does not change.	2215	stat data does change in other ways (e.g. file size).
1718		2216
1719	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
1720	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
1721	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);
1722	ev_timer_again (loop, w)>).	2220	ev_timer_again (loop, w)>).
…		…
1742	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
1743	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
1744	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
1745	path for as long as the watcher is active.	2243	path for as long as the watcher is active.
1746		2244
1747	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,
1748	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
1749	was detected).	2247	last change was detected).
1750		2248
1751	=item ev_stat_stat (loop, ev_stat *)	2249	=item ev_stat_stat (loop, ev_stat *)
1752		2250
1753	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
1754	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
…		…
1837		2335
1838		2336
1839	=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...
1840		2338
1841	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
1842	priority are pending (prepare, check and other idle watchers do not	2340	priority are pending (prepare, check and other idle watchers do not count
1843	count).	2341	as receiving "events").
1844		2342
1845	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
1846	(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
1847	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
1848	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
…		…
1859		2357
1860	=head3 Watcher-Specific Functions and Data Members	2358	=head3 Watcher-Specific Functions and Data Members
1861		2359
1862	=over 4	2360	=over 4
1863		2361
1864	=item ev_idle_init (ev_signal *, callback)	2362	=item ev_idle_init (ev_idle *, callback)
1865		2363
1866	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
1867	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,
1868	believe me.	2366	believe me.
1869		2367
…		…
1873		2371
1874	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
1875	callback, free it. Also, use no error checking, as usual.	2373	callback, free it. Also, use no error checking, as usual.
1876		2374
1877	static void	2375	static void
1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2376	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1879	{	2377	{
1880	free (w);	2378	free (w);
1881	// now do something you wanted to do when the program has	2379	// now do something you wanted to do when the program has
1882	// no longer anything immediate to do.	2380	// no longer anything immediate to do.
1883	}	2381	}
1884		2382
1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2383	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1886	ev_idle_init (idle_watcher, idle_cb);	2384	ev_idle_init (idle_watcher, idle_cb);
1887	ev_idle_start (loop, idle_cb);	2385	ev_idle_start (loop, idle_watcher);
1888		2386
1889		2387
1890	=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!
1891		2389
1892	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:
1893	prepare watchers get invoked before the process blocks and check watchers	2391	prepare watchers get invoked before the process blocks and check watchers
1894	afterwards.	2392	afterwards.
1895		2393
1896	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
1897	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>
…		…
1900	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,
1901	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
1902	called in pairs bracketing the blocking call.	2400	called in pairs bracketing the blocking call.
1903		2401
1904	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
1905	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
1906	variable changes, implement your own watchers, integrate net-snmp or a	2404	variable changes, implement your own watchers, integrate net-snmp or a
1907	coroutine library and lots more. They are also occasionally useful if	2405	coroutine library and lots more. They are also occasionally useful if
1908	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,
1909	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>
1910	watcher).	2408	watcher).
1911		2409
1912	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
1913	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
1914	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
1915	provide just this functionality). Then, in the check watcher you check for	2413	libraries provide exactly this functionality). Then, in the check watcher,
1916	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
1917	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
1918	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
1919	because you never know, you know?).	2417	nevertheless, because you never know, you know?).
1920		2418
1921	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
1922	coroutines into libev programs, by yielding to other active coroutines	2420	coroutines into libev programs, by yielding to other active coroutines
1923	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
1924	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
…		…
1927	loop from blocking if lower-priority coroutines are active, thus mapping	2425	loop from blocking if lower-priority coroutines are active, thus mapping
1928	low-priority coroutines to idle/background tasks).	2426	low-priority coroutines to idle/background tasks).
1929		2427
1930	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>)
1931	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
1932	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
1933	too) should not activate ("feed") events into libev. While libev fully	2433	activate ("feed") events into libev. While libev fully supports this, they
1934	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
1935	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
1936	(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
1937	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
1938	coexist peacefully with others).	2438	others).
1939		2439
1940	=head3 Watcher-Specific Functions and Data Members	2440	=head3 Watcher-Specific Functions and Data Members
1941		2441
1942	=over 4	2442	=over 4
1943		2443
…		…
1945		2445
1946	=item ev_check_init (ev_check *, callback)	2446	=item ev_check_init (ev_check *, callback)
1947		2447
1948	Initialises and configures the prepare or check watcher - they have no	2448	Initialises and configures the prepare or check watcher - they have no
1949	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>
1950	macros, but using them is utterly, utterly and completely pointless.	2450	macros, but using them is utterly, utterly, utterly and completely
		2451	pointless.
1951		2452
1952	=back	2453	=back
1953		2454
1954	=head3 Examples	2455	=head3 Examples
1955		2456
…		…
1968		2469
1969	static ev_io iow [nfd];	2470	static ev_io iow [nfd];
1970	static ev_timer tw;	2471	static ev_timer tw;
1971		2472
1972	static void	2473	static void
1973	io_cb (ev_loop *loop, ev_io *w, int revents)	2474	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1974	{	2475	{
1975	}	2476	}
1976		2477
1977	// create io watchers for each fd and a timer before blocking	2478	// create io watchers for each fd and a timer before blocking
1978	static void	2479	static void
1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2480	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1980	{	2481	{
1981	int timeout = 3600000;	2482	int timeout = 3600000;
1982	struct pollfd fds [nfd];	2483	struct pollfd fds [nfd];
1983	// actual code will need to loop here and realloc etc.	2484	// actual code will need to loop here and realloc etc.
1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2485	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1985		2486
1986	/* 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 */
1987	ev_timer_init (&tw, 0, timeout * 1e-3);	2488	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1988	ev_timer_start (loop, &tw);	2489	ev_timer_start (loop, &tw);
1989		2490
1990	// create one ev_io per pollfd	2491	// create one ev_io per pollfd
1991	for (int i = 0; i < nfd; ++i)	2492	for (int i = 0; i < nfd; ++i)
1992	{	2493	{
…		…
1999	}	2500	}
2000	}	2501	}
2001		2502
2002	// stop all watchers after blocking	2503	// stop all watchers after blocking
2003	static void	2504	static void
2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2505	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2005	{	2506	{
2006	ev_timer_stop (loop, &tw);	2507	ev_timer_stop (loop, &tw);
2007		2508
2008	for (int i = 0; i < nfd; ++i)	2509	for (int i = 0; i < nfd; ++i)
2009	{	2510	{
…		…
2048	}	2549	}
2049		2550
2050	// do not ever call adns_afterpoll	2551	// do not ever call adns_afterpoll
2051		2552
2052	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
2053	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
2054	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
2055	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
2056	this.	2557	this approach, effectively embedding EV as a client into the horrible
		2558	libglib event loop.
2057		2559
2058	static gint	2560	static gint
2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2561	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2060	{	2562	{
2061	int got_events = 0;	2563	int got_events = 0;
…		…
2092	prioritise I/O.	2594	prioritise I/O.
2093		2595
2094	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
2095	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
2096	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
2097	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
2098	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
2099	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
2100	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 :)
2101		2604
2102	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
2103	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),
2104	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
2105	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
2106	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.
2107		2610
2108	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
2109	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
2110	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
2111	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
2112	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
2113	to C<0>, in which case the embed watcher will automatically execute the	2616	to give the embedded loop strictly lower priority for example).
2114	embedded loop sweep.
2115		2617
2116	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
2117	callback will be invoked whenever some events have been handled. You can	2619	will automatically execute the embedded loop sweep whenever necessary.
2118	set the callback to C<0> to avoid having to specify one if you are not
2119	interested in that.
2120		2620
2121	Also, there have not currently been made special provisions for forking:	2621	Fork detection will be handled transparently while the C<ev_embed> watcher
2122	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
2123	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
2124	yourself.	2624	C<ev_loop_fork> on the embedded loop.
2125		2625
2126	Unfortunately, not all backends are embeddable, only the ones returned by	2626	Unfortunately, not all backends are embeddable: only the ones returned by
2127	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2627	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2128	portable one.	2628	portable one.
2129		2629
2130	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
2131	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
2132	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
2133	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.
2134		2642
2135	=head3 Watcher-Specific Functions and Data Members	2643	=head3 Watcher-Specific Functions and Data Members
2136		2644
2137	=over 4	2645	=over 4
2138		2646
…		…
2166	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
2167	used).	2675	used).
2168		2676
2169	struct ev_loop *loop_hi = ev_default_init (0);	2677	struct ev_loop *loop_hi = ev_default_init (0);
2170	struct ev_loop *loop_lo = 0;	2678	struct ev_loop *loop_lo = 0;
2171	struct ev_embed embed;	2679	ev_embed embed;
2172		2680
2173	// see if there is a chance of getting one that works	2681	// see if there is a chance of getting one that works
2174	// (remember that a flags value of 0 means autodetection)	2682	// (remember that a flags value of 0 means autodetection)
2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2683	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2684	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2190	kqueue implementation). Store the kqueue/socket-only event loop in	2698	kqueue implementation). Store the kqueue/socket-only event loop in
2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2699	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2192		2700
2193	struct ev_loop *loop = ev_default_init (0);	2701	struct ev_loop *loop = ev_default_init (0);
2194	struct ev_loop *loop_socket = 0;	2702	struct ev_loop *loop_socket = 0;
2195	struct ev_embed embed;	2703	ev_embed embed;
2196		2704
2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2705	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2706	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2199	{	2707	{
2200	ev_embed_init (&embed, 0, loop_socket);	2708	ev_embed_init (&embed, 0, loop_socket);
…		…
2215	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,
2216	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
2217	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
2218	handlers will be invoked, too, of course.	2726	handlers will be invoked, too, of course.
2219		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
2220	=head3 Watcher-Specific Functions and Data Members	2761	=head3 Watcher-Specific Functions and Data Members
2221		2762
2222	=over 4	2763	=over 4
2223		2764
2224	=item ev_fork_init (ev_signal *, callback)	2765	=item ev_fork_init (ev_signal *, callback)
…		…
2256	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
2257	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
2258	need elaborate support such as pthreads.	2799	need elaborate support such as pthreads.
2259		2800
2260	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
2261	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
2262	queue:	2803	queue:
2263		2804
2264	=over 4	2805	=over 4
2265		2806
2266	=item queueing from a signal handler context	2807	=item queueing from a signal handler context
2267		2808
2268	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
2269	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
2270	some fictitious SIGUSR1 handler:	2811	an example that does that for some fictitious SIGUSR1 handler:
2271		2812
2272	static ev_async mysig;	2813	static ev_async mysig;
2273		2814
2274	static void	2815	static void
2275	sigusr1_handler (void)	2816	sigusr1_handler (void)
…		…
2341	=over 4	2882	=over 4
2342		2883
2343	=item ev_async_init (ev_async *, callback)	2884	=item ev_async_init (ev_async *, callback)
2344		2885
2345	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
2346	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,
2347	believe me.	2888	trust me.
2348		2889
2349	=item ev_async_send (loop, ev_async *)	2890	=item ev_async_send (loop, ev_async *)
2350		2891
2351	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
2352	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
2353	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
2354	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
2355	section below on what exactly this means).	2896	section below on what exactly this means).
2356		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
2357	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
2358	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
2359	calls to C<ev_async_send>.	2905	repeated calls to C<ev_async_send> for the same event loop.
2360		2906
2361	=item bool = ev_async_pending (ev_async *)	2907	=item bool = ev_async_pending (ev_async *)
2362		2908
2363	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
2364	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
…		…
2367	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
2368	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,
2369	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
2370	quickly check whether invoking the loop might be a good idea.	2916	quickly check whether invoking the loop might be a good idea.
2371		2917
2372	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,
2373	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.
2374		2922
2375	=back	2923	=back
2376		2924
2377		2925
2378	=head1 OTHER FUNCTIONS	2926	=head1 OTHER FUNCTIONS
…		…
2382	=over 4	2930	=over 4
2383		2931
2384	=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)
2385		2933
2386	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
2387	callback on whichever event happens first and automatically stop both	2935	callback on whichever event happens first and automatically stops both
2388	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
2389	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
2390	more watchers yourself.	2938	more watchers yourself.
2391		2939
2392	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
2393	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
2394	C<events> set will be created and started.	2942	the given C<fd> and C<events> set will be created and started.
2395		2943
2396	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
2397	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
2398	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.
2399	dubious value.
2400		2947
2401	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
2402	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
2403	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>
2404	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.
2405		2956
2406	static void stdin_ready (int revents, void *arg)	2957	static void stdin_ready (int revents, void *arg)
2407	{	2958	{
		2959	if (revents & EV_READ)
		2960	/* stdin might have data for us, joy! */;
2408	if (revents & EV_TIMEOUT)	2961	else if (revents & EV_TIMEOUT)
2409	/* doh, nothing entered */;	2962	/* doh, nothing entered */;
2410	else if (revents & EV_READ)
2411	/* stdin might have data for us, joy! */;
2412	}	2963	}
2413		2964
2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2965	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2415		2966
2416	=item ev_feed_event (ev_loop *, watcher *, int revents)	2967	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2417		2968
2418	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
2419	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
2420	initialised but not necessarily started event watcher).	2971	initialised but not necessarily started event watcher).
2421		2972
2422	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2973	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2423		2974
2424	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
2425	the given events it.	2976	the given events it.
2426		2977
2427	=item ev_feed_signal_event (ev_loop *loop, int signum)	2978	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2428		2979
2429	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
2430	loop!).	2981	loop!).
2431		2982
2432	=back	2983	=back
…		…
2554		3105
2555	myclass obj;	3106	myclass obj;
2556	ev::io iow;	3107	ev::io iow;
2557	iow.set <myclass, &myclass::io_cb> (&obj);	3108	iow.set <myclass, &myclass::io_cb> (&obj);
2558		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
2559	=item w->set<function> (void *data = 0)	3140	=item w->set<function> (void *data = 0)
2560		3141
2561	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
2562	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
2563	C<data> member and is free for you to use.	3144	C<data> member and is free for you to use.
2564		3145
2565	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)>.
2566		3147
2567	See the method-C<set> above for more details.	3148	See the method-C<set> above for more details.
2568		3149
2569	Example:	3150	Example: Use a plain function as callback.
2570		3151
2571	static void io_cb (ev::io &w, int revents) { }	3152	static void io_cb (ev::io &w, int revents) { }
2572	iow.set <io_cb> ();	3153	iow.set <io_cb> ();
2573		3154
2574	=item w->set (struct ev_loop *)	3155	=item w->set (struct ev_loop *)
…		…
2612	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
2613	the constructor.	3194	the constructor.
2614		3195
2615	class myclass	3196	class myclass
2616	{	3197	{
2617	ev::io io; void io_cb (ev::io &w, int revents);	3198	ev::io io ; void io_cb (ev::io &w, int revents);
2618	ev:idle idle void idle_cb (ev::idle &w, int revents);	3199	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2619		3200
2620	myclass (int fd)	3201	myclass (int fd)
2621	{	3202	{
2622	io .set <myclass, &myclass::io_cb > (this);	3203	io .set <myclass, &myclass::io_cb > (this);
2623	idle.set <myclass, &myclass::idle_cb> (this);	3204	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2639	=item Perl	3220	=item Perl
2640		3221
2641	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
2642	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,
2643	there are additional modules that implement libev-compatible interfaces	3224	there are additional modules that implement libev-compatible interfaces
2644	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),
2645	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>).
2646		3228
2647	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
2648	L<http://software.schmorp.de/pkg/EV>.	3230	L<http://software.schmorp.de/pkg/EV>.
2649		3231
2650	=item Python	3232	=item Python
2651		3233
2652	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
2653	seems to be quite complete and well-documented. Note, however, that the	3235	seems to be quite complete and well-documented.
2654	patch they require for libev is outright dangerous as it breaks the ABI
2655	for everybody else, and therefore, should never be applied in an installed
2656	libev (if python requires an incompatible ABI then it needs to embed
2657	libev).
2658		3236
2659	=item Ruby	3237	=item Ruby
2660		3238
2661	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
2662	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
2663	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
2664	L<http://rev.rubyforge.org/>.	3242	L<http://rev.rubyforge.org/>.
2665		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
2666	=item D	3252	=item D
2667		3253
2668	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
2669	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/>.
2670		3261
2671	=back	3262	=back
2672		3263
2673		3264
2674	=head1 MACRO MAGIC	3265	=head1 MACRO MAGIC
…		…
2775		3366
2776	#define EV_STANDALONE 1	3367	#define EV_STANDALONE 1
2777	#include "ev.h"	3368	#include "ev.h"
2778		3369
2779	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++
2780	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
2781	as a bug).	3372	as a bug).
2782		3373
2783	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
2784	in your include path (e.g. in libev/ when using -Ilibev):	3375	in your include path (e.g. in libev/ when using -Ilibev):
2785		3376
…		…
2829		3420
2830	=head2 PREPROCESSOR SYMBOLS/MACROS	3421	=head2 PREPROCESSOR SYMBOLS/MACROS
2831		3422
2832	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
2833	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
2834	autoconf is noted for every option.	3425	autoconf is documented for every option.
2835		3426
2836	=over 4	3427	=over 4
2837		3428
2838	=item EV_STANDALONE	3429	=item EV_STANDALONE
2839		3430
…		…
2841	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
2842	implementations for some libevent functions (such as logging, which is not	3433	implementations for some libevent functions (such as logging, which is not
2843	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
2844	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.
2845		3436
		3437	In stanbdalone mode, libev will still try to automatically deduce the
		3438	configuration, but has to be more conservative.
		3439
2846	=item EV_USE_MONOTONIC	3440	=item EV_USE_MONOTONIC
2847		3441
2848	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
2849	monotonic clock option at both compile time and runtime. Otherwise no use	3443	monotonic clock option at both compile time and runtime. Otherwise no
2850	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,
2851	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
2852	the functionality isn't available is safe, though, although you have	3446	when the functionality isn't available is safe, though, although you have
2853	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>
2854	function is hiding in (often F<-lrt>).	3448	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2855		3449
2856	=item EV_USE_REALTIME	3450	=item EV_USE_REALTIME
2857		3451
2858	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
2859	real-time clock option at compile time (and assume its availability at	3453	real-time clock option at compile time (and assume its availability
2860	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
2861	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3455	option will be attempted. This effectively replaces C<gettimeofday>
2862	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3456	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2863	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>).
2864		3471
2865	=item EV_USE_NANOSLEEP	3472	=item EV_USE_NANOSLEEP
2866		3473
2867	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
2868	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 ()>.
…		…
2884		3491
2885	=item EV_SELECT_USE_FD_SET	3492	=item EV_SELECT_USE_FD_SET
2886		3493
2887	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>
2888	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
2889	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
2890	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
2891	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
2892	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,
2893	influence the size of the C<fd_set> used.	3500	configures the maximum size of the C<fd_set>.
2894		3501
2895	=item EV_SELECT_IS_WINSOCKET	3502	=item EV_SELECT_IS_WINSOCKET
2896		3503
2897	When defined to C<1>, the select backend will assume that	3504	When defined to C<1>, the select backend will assume that
2898	select/socket/connect etc. don't understand file descriptors but	3505	select/socket/connect etc. don't understand file descriptors but
…		…
3009	When doing priority-based operations, libev usually has to linearly search	3616	When doing priority-based operations, libev usually has to linearly search
3010	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
3011	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
3012	fine.	3619	fine.
3013		3620
3014	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
3015	C<0> will save some memory and CPU.	3622	both to C<0> will save some memory and CPU.
3016		3623
3017	=item EV_PERIODIC_ENABLE	3624	=item EV_PERIODIC_ENABLE
3018		3625
3019	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
3020	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
…		…
3027	code.	3634	code.
3028		3635
3029	=item EV_EMBED_ENABLE	3636	=item EV_EMBED_ENABLE
3030		3637
3031	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
3032	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.
3033		3641
3034	=item EV_STAT_ENABLE	3642	=item EV_STAT_ENABLE
3035		3643
3036	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
3037	defined to be C<0>, then they are not.	3645	defined to be C<0>, then they are not.
…		…
3069	two).	3677	two).
3070		3678
3071	=item EV_USE_4HEAP	3679	=item EV_USE_4HEAP
3072		3680
3073	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
3074	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
3075	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
3076	noticeably faster performance with many (thousands) of watchers.	3684	faster performance with many (thousands) of watchers.
3077		3685
3078	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>
3079	(disabled).	3687	(disabled).
3080		3688
3081	=item EV_HEAP_CACHE_AT	3689	=item EV_HEAP_CACHE_AT
3082		3690
3083	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
3084	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
3085	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>),
3086	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,
3087	but avoids random read accesses on heap changes. This improves performance	3695	but avoids random read accesses on heap changes. This improves performance
3088	noticeably with with many (hundreds) of watchers.	3696	noticeably with many (hundreds) of watchers.
3089		3697
3090	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>
3091	(disabled).	3699	(disabled).
3092		3700
3093	=item EV_VERIFY	3701	=item EV_VERIFY
…		…
3099	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
3100	verification code will be called very frequently, which will slow down	3708	verification code will be called very frequently, which will slow down
3101	libev considerably.	3709	libev considerably.
3102		3710
3103	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
3104	C<0.>	3712	C<0>.
3105		3713
3106	=item EV_COMMON	3714	=item EV_COMMON
3107		3715
3108	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
3109	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
…		…
3126	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
3127	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
3128	their default definitions. One possible use for overriding these is to	3736	their default definitions. One possible use for overriding these is to
3129	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
3130	method calls instead of plain function calls in C++.	3738	method calls instead of plain function calls in C++.
		3739
		3740	=back
3131		3741
3132	=head2 EXPORTED API SYMBOLS	3742	=head2 EXPORTED API SYMBOLS
3133		3743
3134	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
3135	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
…		…
3182	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:
3183		3793
3184	#include "ev_cpp.h"	3794	#include "ev_cpp.h"
3185	#include "ev.c"	3795	#include "ev.c"
3186		3796
		3797	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3187		3798
3188	=head1 THREADS AND COROUTINES	3799	=head2 THREADS AND COROUTINES
3189		3800
3190	=head2 THREADS	3801	=head3 THREADS
3191		3802
3192	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
3193	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
3194	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
3195	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.
3196		3810
3197	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
3198	parallel from multiple threads, calls with the same loop parameter must be	3812	concurrently from multiple threads, calls with the same loop parameter
3199	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
3200	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
3201	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".
3202		3821
3203	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
3204	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
3205	help you. I can give some generic advice however:	3824	help you, but here is some generic advice:
3206		3825
3207	=over 4	3826	=over 4
3208		3827
3209	=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
3210	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.
…		…
3222		3841
3223	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
3224	better than you currently do :-)	3843	better than you currently do :-)
3225		3844
3226	=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
3227	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
3228	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.
3229		3855
3230	=back	3856	=back
3231		3857
3232	=head2 COROUTINES	3858	=head3 COROUTINES
3233		3859
3234	Libev is much more accommodating to coroutines ("cooperative threads"):	3860	Libev is very accommodating to coroutines ("cooperative threads"):
3235	libev fully supports nesting calls to it's functions from different	3861	libev fully supports nesting calls to its functions from different
3236	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
3237	different coroutines and switch freely between both coroutines running the	3863	different coroutines, and switch freely between both coroutines running the
3238	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
3239	you must not do this from C<ev_periodic> reschedule callbacks.	3865	you must not do this from C<ev_periodic> reschedule callbacks.
3240		3866
3241	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
3242	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
3243	switches.	3869	they do not call any callbacks.
3244		3870
		3871	=head2 COMPILER WARNINGS
3245		3872
3246	=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.
3247		3876
3248	In this section the complexities of (many of) the algorithms used inside	3877	However, these are unavoidable for many reasons. For one, each compiler
3249	libev will be explained. For complexity discussions about backends see the	3878	has different warnings, and each user has different tastes regarding
3250	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.
3251		3881
3252	All of the following are about amortised time: If an array needs to be	3882	Another reason is that some compiler warnings require elaborate
3253	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
3254	happens asymptotically never with higher number of elements, so O(1) might	3884	maintainable.
3255	mean it might do a lengthy realloc operation in rare cases, but on average
3256	it is much faster and asymptotically approaches constant time.
3257		3885
3258	=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.
3259		3892
3260	=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.
3261		3898
3262	This means that, when you have a watcher that triggers in one hour and
3263	there are 100 watchers that would trigger before that then inserting will
3264	have to skip roughly seven (C<ld 100>) of these watchers.
3265		3899
3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3900	=head2 VALGRIND
3267		3901
3268	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
3269	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.
3270		3904
3271	=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:
3272		3907
3273	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.
3274		3911
3275	=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.
3276		3914
3277	=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.
3278		3919
3279	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
3280	correct watcher to remove. The lists are usually short (you don't usually	3921	make it into some kind of religion.
3281	have many watchers waiting for the same fd or signal).
3282		3922
3283	=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.
3284		3928
3285	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
3286	fixed position in the storage array.	3930	I suggest using suppression lists.
3287		3931
3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3289		3932
3290	A change means an I/O watcher gets started or stopped, which requires	3933	=head1 PORTABILITY NOTES
3291	libev to recalculate its status (and possibly tell the kernel, depending
3292	on backend and whether C<ev_io_set> was used).
3293		3934
3294	=item Activating one watcher (putting it into the pending state): O(1)
3295
3296	=item Priority handling: O(number_of_priorities)
3297
3298	Priorities are implemented by allocating some space for each
3299	priority. When doing priority-based operations, libev usually has to
3300	linearly search all the priorities, but starting/stopping and activating
3301	watchers becomes O(1) w.r.t. priority handling.
3302
3303	=item Sending an ev_async: O(1)
3304
3305	=item Processing ev_async_send: O(number_of_async_watchers)
3306
3307	=item Processing signals: O(max_signal_number)
3308
3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
3310	calls in the current loop iteration. Checking for async and signal events
3311	involves iterating over all running async watchers or all signal numbers.
3312
3313	=back
3314
3315
3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3935	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3317		3936
3318	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
3319	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
3320	model. Libev still offers limited functionality on this platform in	3939	model. Libev still offers limited functionality on this platform in
3321	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
…		…
3328	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).
3329		3948
3330	There is no supported compilation method available on windows except	3949	There is no supported compilation method available on windows except
3331	embedding it into other applications.	3950	embedding it into other applications.
3332		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
3333	Not a libev limitation but worth mentioning: windows apparently doesn't	3955	Not a libev limitation but worth mentioning: windows apparently doesn't
3334	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
3335	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,
3336	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
3337	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
3338	available).	3960	available).
3339		3961
3340	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
3341	the abysmal performance of winsockets, using a large number of sockets	3963	the abysmal performance of winsockets, using a large number of sockets
3342	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
3343	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
3344	different implementation for windows, as libev offers the POSIX readiness	3966	different implementation for windows, as libev offers the POSIX readiness
3345	notification model, which cannot be implemented efficiently on windows	3967	notification model, which cannot be implemented efficiently on windows
3346	(Microsoft monopoly games).	3968	(due to Microsoft monopoly games).
3347		3969
3348	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
3349	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
3350	of F<ev.h>:	3972	of F<ev.h>:
3351		3973
…		…
3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3975	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3354		3976
3355	#include "ev.h"	3977	#include "ev.h"
3356		3978
3357	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
3358	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!):
3359		3981
3360	#include "evwrap.h"	3982	#include "evwrap.h"
3361	#include "ev.c"	3983	#include "ev.c"
3362		3984
3363	=over 4	3985	=over 4
…		…
3387		4009
3388	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
3389	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
3390	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
3391	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
3392	previous thread in each. Great).	4014	previous thread in each. Sounds great!).
3393		4015
3394	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>
3395	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
3396	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
3397	select emulation on windows).	4019	other interpreters do their own select emulation on windows).
3398		4020
3399	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
3400	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>
3401	or something like this inside Microsoft). You can increase this by calling	4023	fetish or something like this inside Microsoft). You can increase this
3402	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4024	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3403	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
3404	libraries.
3405
3406	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
3407	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,
3408	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
3409	calling select (O(n²)) will likely make this unworkable.	4029	the cost of calling select (O(n²)) will likely make this unworkable.
3410		4030
3411	=back	4031	=back
3412		4032
3413
3414	=head1 PORTABILITY REQUIREMENTS	4033	=head2 PORTABILITY REQUIREMENTS
3415		4034
3416	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
3417	additional extensions:	4036	backend-specific APIs, libev relies on a few additional extensions:
3418		4037
3419	=over 4	4038	=over 4
3420		4039
3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4040	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3422	calling conventions regardless of C<ev_watcher_type *>.	4041	calling conventions regardless of C<ev_watcher_type *>.
…		…
3428	calls them using an C<ev_watcher *> internally.	4047	calls them using an C<ev_watcher *> internally.
3429		4048
3430	=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
3431		4050
3432	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
3433	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
3434	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
3435	believed to be sufficiently portable.	4054	believed to be sufficiently portable.
3436		4055
3437	=item C<sigprocmask> must work in a threaded environment	4056	=item C<sigprocmask> must work in a threaded environment
3438		4057
…		…
3447	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
3448	well.	4067	well.
3449		4068
3450	=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
3451		4070
3452	To improve portability and simplify using libev, libev uses C<long>	4071	To improve portability and simplify its API, libev uses C<long> internally
3453	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
3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4073	systems (Microsoft...) this might be unexpectedly low, but is still at
3455	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
3456	millions of watchers.	4075	watchers.
3457		4076
3458	=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
3459		4078
3460	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
3461	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
3462	enough for at least into the year 4000. This requirement is fulfilled by	4081	enough for at least into the year 4000. This requirement is fulfilled by
3463	implementations implementing IEEE 754 (basically all existing ones).	4082	implementations implementing IEEE 754, which is basically all existing
		4083	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4084	2200.
3464		4085
3465	=back	4086	=back
3466		4087
3467	If you know of other additional requirements drop me a note.	4088	If you know of other additional requirements drop me a note.
3468		4089
3469		4090
3470	=head1 COMPILER WARNINGS	4091	=head1 ALGORITHMIC COMPLEXITIES
3471		4092
3472	Depending on your compiler and compiler settings, you might get no or a	4093	In this section the complexities of (many of) the algorithms used inside
3473	lot of warnings when compiling libev code. Some people are apparently	4094	libev will be documented. For complexity discussions about backends see
3474	scared by this.	4095	the documentation for C<ev_default_init>.
3475		4096
3476	However, these are unavoidable for many reasons. For one, each compiler	4097	All of the following are about amortised time: If an array needs to be
3477	has different warnings, and each user has different tastes regarding	4098	extended, libev needs to realloc and move the whole array, but this
3478	warning options. "Warn-free" code therefore cannot be a goal except when	4099	happens asymptotically rarer with higher number of elements, so O(1) might
3479	targeting a specific compiler and compiler-version.	4100	mean that libev does a lengthy realloc operation in rare cases, but on
		4101	average it is much faster and asymptotically approaches constant time.
3480		4102
3481	Another reason is that some compiler warnings require elaborate	4103	=over 4
3482	workarounds, or other changes to the code that make it less clear and less
3483	maintainable.
3484		4104
3485	And of course, some compiler warnings are just plain stupid, or simply	4105	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3486	wrong (because they don't actually warn about the condition their message
3487	seems to warn about).
3488		4106
3489	While libev is written to generate as few warnings as possible,	4107	This means that, when you have a watcher that triggers in one hour and
3490	"warn-free" code is not a goal, and it is recommended not to build libev	4108	there are 100 watchers that would trigger before that, then inserting will
3491	with any compiler warnings enabled unless you are prepared to cope with	4109	have to skip roughly seven (C<ld 100>) of these watchers.
3492	them (e.g. by ignoring them). Remember that warnings are just that:
3493	warnings, not errors, or proof of bugs.
3494		4110
		4111	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3495		4112
3496	=head1 VALGRIND	4113	That means that changing a timer costs less than removing/adding them,
		4114	as only the relative motion in the event queue has to be paid for.
3497		4115
3498	Valgrind has a special section here because it is a popular tool that is	4116	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3499	highly useful, but valgrind reports are very hard to interpret.
3500		4117
3501	If you think you found a bug (memory leak, uninitialised data access etc.)	4118	These just add the watcher into an array or at the head of a list.
3502	in libev, then check twice: If valgrind reports something like:
3503		4119
3504	==2274== definitely lost: 0 bytes in 0 blocks.	4120	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3505	==2274== possibly lost: 0 bytes in 0 blocks.
3506	==2274== still reachable: 256 bytes in 1 blocks.
3507		4121
3508	Then there is no memory leak. Similarly, under some circumstances,	4122	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3509	valgrind might report kernel bugs as if it were a bug in libev, or it
3510	might be confused (it is a very good tool, but only a tool).
3511		4123
3512	If you are unsure about something, feel free to contact the mailing list	4124	These watchers are stored in lists, so they need to be walked to find the
3513	with the full valgrind report and an explanation on why you think this is	4125	correct watcher to remove. The lists are usually short (you don't usually
3514	a bug in libev. However, don't be annoyed when you get a brisk "this is	4126	have many watchers waiting for the same fd or signal: one is typical, two
3515	no bug" answer and take the chance of learning how to interpret valgrind	4127	is rare).
3516	properly.
3517		4128
3518	If you need, for some reason, empty reports from valgrind for your project	4129	=item Finding the next timer in each loop iteration: O(1)
3519	I suggest using suppression lists.
3520		4130
		4131	By virtue of using a binary or 4-heap, the next timer is always found at a
		4132	fixed position in the storage array.
		4133
		4134	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4135
		4136	A change means an I/O watcher gets started or stopped, which requires
		4137	libev to recalculate its status (and possibly tell the kernel, depending
		4138	on backend and whether C<ev_io_set> was used).
		4139
		4140	=item Activating one watcher (putting it into the pending state): O(1)
		4141
		4142	=item Priority handling: O(number_of_priorities)
		4143
		4144	Priorities are implemented by allocating some space for each
		4145	priority. When doing priority-based operations, libev usually has to
		4146	linearly search all the priorities, but starting/stopping and activating
		4147	watchers becomes O(1) with respect to priority handling.
		4148
		4149	=item Sending an ev_async: O(1)
		4150
		4151	=item Processing ev_async_send: O(number_of_async_watchers)
		4152
		4153	=item Processing signals: O(max_signal_number)
		4154
		4155	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4156	calls in the current loop iteration. Checking for async and signal events
		4157	involves iterating over all running async watchers or all signal numbers.
		4158
		4159	=back
		4160
		4161
		4162	=head1 GLOSSARY
		4163
		4164	=over 4
		4165
		4166	=item active
		4167
		4168	A watcher is active as long as it has been started (has been attached to
		4169	an event loop) but not yet stopped (disassociated from the event loop).
		4170
		4171	=item application
		4172
		4173	In this document, an application is whatever is using libev.
		4174
		4175	=item callback
		4176
		4177	The address of a function that is called when some event has been
		4178	detected. Callbacks are being passed the event loop, the watcher that
		4179	received the event, and the actual event bitset.
		4180
		4181	=item callback invocation
		4182
		4183	The act of calling the callback associated with a watcher.
		4184
		4185	=item event
		4186
		4187	A change of state of some external event, such as data now being available
		4188	for reading on a file descriptor, time having passed or simply not having
		4189	any other events happening anymore.
		4190
		4191	In libev, events are represented as single bits (such as C<EV_READ> or
		4192	C<EV_TIMEOUT>).
		4193
		4194	=item event library
		4195
		4196	A software package implementing an event model and loop.
		4197
		4198	=item event loop
		4199
		4200	An entity that handles and processes external events and converts them
		4201	into callback invocations.
		4202
		4203	=item event model
		4204
		4205	The model used to describe how an event loop handles and processes
		4206	watchers and events.
		4207
		4208	=item pending
		4209
		4210	A watcher is pending as soon as the corresponding event has been detected,
		4211	and stops being pending as soon as the watcher will be invoked or its
		4212	pending status is explicitly cleared by the application.
		4213
		4214	A watcher can be pending, but not active. Stopping a watcher also clears
		4215	its pending status.
		4216
		4217	=item real time
		4218
		4219	The physical time that is observed. It is apparently strictly monotonic :)
		4220
		4221	=item wall-clock time
		4222
		4223	The time and date as shown on clocks. Unlike real time, it can actually
		4224	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4225	clock.
		4226
		4227	=item watcher
		4228
		4229	A data structure that describes interest in certain events. Watchers need
		4230	to be started (attached to an event loop) before they can receive events.
		4231
		4232	=item watcher invocation
		4233
		4234	The act of calling the callback associated with a watcher.
		4235
		4236	=back
3521		4237
3522	=head1 AUTHOR	4238	=head1 AUTHOR
3523		4239
3524	Marc Lehmann <libev@schmorp.de>.	4240	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3525		4241

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