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Revision 1.175 by root, Mon Sep 8 16:36:14 2008 UTC vs.
Revision 1.234 by root, Thu Apr 16 07:49:23 2009 UTC

…		…
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	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	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	109	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	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	217	recommended ones.
216		218
217	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
218		220
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		222
221	Sets the allocation function to use (the prototype is similar - the	223	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	224	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	225	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	226	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	252	}
251		253
252	...	254	...
253	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
254		256
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		258
257	Set the callback function to call on a retryable system call error (such	259	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	260	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	261	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	262	callback is set, then libev will expect it to remedy the situation, no
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	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	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	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,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	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	308	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	309	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	310	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	365	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	366	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	367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	368	readiness notifications you get per iteration.
363		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
		373
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		375
366	And this is your standard poll(2) backend. It's more complicated	376	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	377	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	378	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,	379	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	380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	381	performance tips.
372		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		385
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		387
375	For few fds, this backend is a bit little slower than poll and select,	388	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	389	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),	390	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	391	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	392
380	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
382		409
383	While stopping, setting and starting an I/O watcher in the same iteration	410	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	411	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	412	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	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
388		415	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		416
393	Best performance from this backend is achieved by not unregistering all	417	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.	418	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
396		428
397	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
399		434
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		436
402	Kqueue deserves special mention, as at the time of this writing, it	437	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	438	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	439	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"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	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	443	"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)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	445	system like NetBSD.
409		446
410	You still can embed kqueue into a normal poll or select backend and use it	447	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	448	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		450
414	It scales in the same way as the epoll backend, but the interface to the	451	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	452	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	453	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	454	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	455	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
420		458
421	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
422		460
423	While nominally embeddable in other event loops, this doesn't work	461	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	462	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	463	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	464	(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	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
429		471
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		473
432	This is not implemented yet (and might never be, unless you send me an	474	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	475	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	488	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	489	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	491	might perform better.
450		492
451	On the positive side, ignoring the spurious readiness notifications, this	493	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
454		500
455	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
456		502
457	Try all backends (even potentially broken ones that wouldn't be tried	503	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	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		510
465	If one or more of these are or'ed into the flags value, then only these	511	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	512	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.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		514
469	The most typical usage is like this:	515	Example: This is the most typical usage.
470		516
471	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		519
474	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	521	environment settings to be taken into account:
476		522
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		524
479	Use whatever libev has to offer, but make sure that kqueue is used if	525	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	526	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):	527	private event loop and only if you know the OS supports your types of
		528	fds):
482		529
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		531
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		533
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	555	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	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	557	for example).
511		558
512	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
515		562
516	In general it is not advisable to call this function except in the	563	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	564	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	565	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		591
545	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
546		593
547	Like C<ev_default_fork>, but acts on an event loop created by	594	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	595	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.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
550		598
551	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
552		600
553	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
554		603
555	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
556		605
557	Returns the count of loop iterations for the loop, which is identical to	606	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	607	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	622	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	623	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	624	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).	625	event occurring (or more correctly, libev finding out about it).
577		626
		627	=item ev_now_update (loop)
		628
		629	Establishes the current time by querying the kernel, updating the time
		630	returned by C<ev_now ()> in the progress. This is a costly operation and
		631	is usually done automatically within C<ev_loop ()>.
		632
		633	This function is rarely useful, but when some event callback runs for a
		634	very long time without entering the event loop, updating libev's idea of
		635	the current time is a good idea.
		636
		637	See also "The special problem of time updates" in the C<ev_timer> section.
		638
		639	=item ev_suspend (loop)
		640
		641	=item ev_resume (loop)
		642
		643	These two functions suspend and resume a loop, for use when the loop is
		644	not used for a while and timeouts should not be processed.
		645
		646	A typical use case would be an interactive program such as a game: When
		647	the user presses C<^Z> to suspend the game and resumes it an hour later it
		648	would be best to handle timeouts as if no time had actually passed while
		649	the program was suspended. This can be achieved by calling C<ev_suspend>
		650	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		651	C<ev_resume> directly afterwards to resume timer processing.
		652
		653	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		655	will be rescheduled (that is, they will lose any events that would have
		656	occured while suspended).
		657
		658	After calling C<ev_suspend> you B<must not> call I<any> function on the
		659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		660	without a previous call to C<ev_suspend>.
		661
		662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		663	event loop time (see C<ev_now_update>).
		664
578	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
579		666
580	Finally, this is it, the event handler. This function usually is called	667	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	668	after you initialised all your watchers and you want to start handling
582	events.	669	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	671	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.	672	either no event watchers are active anymore or C<ev_unloop> was called.
586		673
587	Please note that an explicit C<ev_unloop> is usually better than	674	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	675	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	676	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	677	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.	678	of relying on its watchers stopping correctly, that is truly a thing of
		679	beauty.
592		680
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	681	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	682	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.	683	process in case there are no events and will return after one iteration of
		684	the loop.
596		685
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	686	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	687	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	688	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	689	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	690	user-registered callback will be called), and will return after one
		691	iteration of the loop.
		692
		693	This is useful if you are waiting for some external event in conjunction
		694	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	695	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.	696	usually a better approach for this kind of thing.
604		697
605	Here are the gory details of what C<ev_loop> does:	698	Here are the gory details of what C<ev_loop> does:
606		699
607	- Before the first iteration, call any pending watchers.	700	- Before the first iteration, call any pending watchers.
…		…
617	any active watchers at all will result in not sleeping).	710	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	711	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	712	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	713	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	715	- Queue all expired timers.
623	- Queue all outstanding periodics.	716	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	717	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	718	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	719	- 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	720	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	721	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	738	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.	739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		740
648	This "unloop state" will be cleared when entering C<ev_loop> again.	741	This "unloop state" will be cleared when entering C<ev_loop> again.
649		742
		743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		744
650	=item ev_ref (loop)	745	=item ev_ref (loop)
651		746
652	=item ev_unref (loop)	747	=item ev_unref (loop)
653		748
654	Ref/unref can be used to add or remove a reference count on the event	749	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	750	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	751	count is nonzero, C<ev_loop> will not return on its own.
		752
657	a watcher you never unregister that should not keep C<ev_loop> from	753	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	754	from returning, call ev_unref() after starting, and ev_ref() before
		755	stopping it.
		756
659	example, libev itself uses this for its internal signal pipe: It is not	757	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	758	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	759	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	760	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>	761	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,	762	before stop> (but only if the watcher wasn't active before, or was active
665	respectively).	763	before, respectively. Note also that libev might stop watchers itself
		764	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		765	in the callback).
666		766
667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
668	running when nothing else is active.	768	running when nothing else is active.
669		769
670	struct ev_signal exitsig;	770	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	771	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	772	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	773	evf_unref (loop);
674		774
675	Example: For some weird reason, unregister the above signal handler again.	775	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>)	789	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	790	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	791	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	792	opportunities).
693		793
694	The background is that sometimes your program runs just fast enough to	794	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	795	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	796	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	797	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	798	overhead for the actual polling but can deliver many events at once.
699		799
700	By setting a higher I<io collect interval> you allow libev to spend more	800	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,	801	time collecting I/O events, so you can handle more events per iteration,
…		…
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	803	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.	804	introduce an additional C<ev_sleep ()> call into most loop iterations.
705		805
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	806	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	807	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	808	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	809	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	810	value will not introduce any overhead in libev.
711		811
712	Many (busy) programs can usually benefit by setting the I/O collect	812	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	813	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	814	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>,	815	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
723	they fire on, say, one-second boundaries only.	823	they fire on, say, one-second boundaries only.
724		824
725	=item ev_loop_verify (loop)	825	=item ev_loop_verify (loop)
726		826
727	This function only does something when C<EV_VERIFY> support has been	827	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	828	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	829	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	830	is found to be inconsistent, it will print an error message to standard
		831	error and call C<abort ()>.
731		832
732	This can be used to catch bugs inside libev itself: under normal	833	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	834	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	835	data structures consistent.
735		836
736	=back	837	=back
737		838
738		839
739	=head1 ANATOMY OF A WATCHER	840	=head1 ANATOMY OF A WATCHER
740		841
		842	In the following description, uppercase C<TYPE> in names stands for the
		843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		844	watchers and C<ev_io_start> for I/O watchers.
		845
741	A watcher is a structure that you create and register to record your	846	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	847	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:	848	become readable, you would create an C<ev_io> watcher for that:
744		849
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	851	{
747	ev_io_stop (w);	852	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	853	ev_unloop (loop, EVUNLOOP_ALL);
749	}	854	}
750		855
751	struct ev_loop *loop = ev_default_loop (0);	856	struct ev_loop *loop = ev_default_loop (0);
		857
752	struct ev_io stdin_watcher;	858	ev_io stdin_watcher;
		859
753	ev_init (&stdin_watcher, my_cb);	860	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	862	ev_io_start (loop, &stdin_watcher);
		863
756	ev_loop (loop, 0);	864	ev_loop (loop, 0);
757		865
758	As you can see, you are responsible for allocating the memory for your	866	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,	867	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	868	stack).
		869
		870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
761		872
762	Each watcher structure must be initialised by a call to C<ev_init	873	Each watcher structure must be initialised by a call to C<ev_init
763	(watcher *, callback)>, which expects a callback to be provided. This	874	(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	875	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	876	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	877	is readable and/or writable).
767		878
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	879	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	880	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	881	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	882	ev_TYPE_init (watcher *, callback, ...) >>.
772		883
773	To make the watcher actually watch out for events, you have to start it	884	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	885	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	886	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	887	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		888
778	As long as your watcher is active (has been started but not stopped) you	889	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	890	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	891	reinitialise it or call its C<ev_TYPE_set> macro.
781		892
782	Each and every callback receives the event loop pointer as first, the	893	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	894	registered watcher structure as second, and a bitset of received events as
784	third argument.	895	third argument.
785		896
…		…
843		954
844	=item C<EV_ASYNC>	955	=item C<EV_ASYNC>
845		956
846	The given async watcher has been asynchronously notified (see C<ev_async>).	957	The given async watcher has been asynchronously notified (see C<ev_async>).
847		958
		959	=item C<EV_CUSTOM>
		960
		961	Not ever sent (or otherwise used) by libev itself, but can be freely used
		962	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		963
848	=item C<EV_ERROR>	964	=item C<EV_ERROR>
849		965
850	An unspecified error has occurred, the watcher has been stopped. This might	966	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	967	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	968	ran out of memory, a file descriptor was found to be closed or any other
		969	problem. Libev considers these application bugs.
		970
853	problem. You best act on it by reporting the problem and somehow coping	971	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	972	watcher being stopped. Note that well-written programs should not receive
		973	an error ever, so when your watcher receives it, this usually indicates a
		974	bug in your program.
855		975
856	Libev will usually signal a few "dummy" events together with an error,	976	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	977	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	978	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	979	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	980	programs, though, as the fd could already be closed and reused for another
		981	thing, so beware.
861		982
862	=back	983	=back
863		984
864	=head2 GENERIC WATCHER FUNCTIONS	985	=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		986
869	=over 4	987	=over 4
870		988
871	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
872		990
…		…
878	which rolls both calls into one.	996	which rolls both calls into one.
879		997
880	You can reinitialise a watcher at any time as long as it has been stopped	998	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.	999	(or never started) and there are no pending events outstanding.
882		1000
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1001	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	1002	int revents)>.
		1003
		1004	Example: Initialise an C<ev_io> watcher in two steps.
		1005
		1006	ev_io w;
		1007	ev_init (&w, my_cb);
		1008	ev_io_set (&w, STDIN_FILENO, EV_READ);
885		1009
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		1011
888	This macro initialises the type-specific parts of a watcher. You need to	1012	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	1013	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	1016	difference to the C<ev_init> macro).
893		1017
894	Although some watcher types do not have type-specific arguments	1018	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.	1019	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		1020
		1021	See C<ev_init>, above, for an example.
		1022
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1023	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		1024
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1025	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	1026	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	1027	a watcher. The same limitations apply, of course.
902		1028
		1029	Example: Initialise and set an C<ev_io> watcher in one step.
		1030
		1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1032
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1034
905	Starts (activates) the given watcher. Only active watchers will receive	1035	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1036	events. If the watcher is already active nothing will happen.
907		1037
		1038	Example: Start the C<ev_io> watcher that is being abused as example in this
		1039	whole section.
		1040
		1041	ev_io_start (EV_DEFAULT_UC, &w);
		1042
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1044
910	Stops the given watcher again (if active) and clears the pending	1045	Stops the given watcher if active, and clears the pending status (whether
		1046	the watcher was active or not).
		1047
911	status. It is possible that stopped watchers are pending (for example,	1048	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1049	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	1050	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	1051	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.	1052	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1053
917	=item bool ev_is_active (ev_TYPE *watcher)	1054	=item bool ev_is_active (ev_TYPE *watcher)
918		1055
919	Returns a true value iff the watcher is active (i.e. it has been started	1056	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	1057	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>	1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
947	(default: C<-2>). Pending watchers with higher priority will be invoked	1084	(default: C<-2>). Pending watchers with higher priority will be invoked
948	before watchers with lower priority, but priority will not keep watchers	1085	before watchers with lower priority, but priority will not keep watchers
949	from being executed (except for C<ev_idle> watchers).	1086	from being executed (except for C<ev_idle> watchers).
950		1087
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	1088	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.	1089	you need to look at C<ev_idle> watchers, which provide this functionality.
958		1090
959	You I<must not> change the priority of a watcher as long as it is active or	1091	You I<must not> change the priority of a watcher as long as it is active or
960	pending.	1092	pending.
961		1093
		1094	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1095	fine, as long as you do not mind that the priority value you query might
		1096	or might not have been clamped to the valid range.
		1097
962	The default priority used by watchers when no priority has been set is	1098	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 :).	1099	always C<0>, which is supposed to not be too high and not be too low :).
964		1100
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1101	See L<WATCHER PRIORITIES>, below, for a more thorough treatment of
966	fine, as long as you do not mind that the priority value you query might	1102	priorities.
967	or might not have been adjusted to be within valid range.
968		1103
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1104	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1105
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1106	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	1107	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1108	can deal with that fact, as both are simply passed through to the
		1109	callback.
974		1110
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1111	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1112
977	If the watcher is pending, this function returns clears its pending status	1113	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	1114	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>.	1115	watcher isn't pending it does nothing and returns C<0>.
980		1116
		1117	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1118	callback to be invoked, which can be accomplished with this function.
		1119
981	=back	1120	=back
982		1121
983		1122
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1123	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1124
986	Each watcher has, by default, a member C<void *data> that you can change	1125	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	1126	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	1127	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	1128	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	1129	member, you can also "subclass" the watcher type and provide your own
991	data:	1130	data:
992		1131
993	struct my_io	1132	struct my_io
994	{	1133	{
995	struct ev_io io;	1134	ev_io io;
996	int otherfd;	1135	int otherfd;
997	void *somedata;	1136	void *somedata;
998	struct whatever *mostinteresting;	1137	struct whatever *mostinteresting;
999	}	1138	};
		1139
		1140	...
		1141	struct my_io w;
		1142	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1143
1001	And since your callback will be called with a pointer to the watcher, you	1144	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1145	can cast it back to your own type:
1003		1146
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1147	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1148	{
1006	struct my_io *w = (struct my_io *)w_;	1149	struct my_io *w = (struct my_io *)w_;
1007	...	1150	...
1008	}	1151	}
1009		1152
1010	More interesting and less C-conformant ways of casting your callback type	1153	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1154	instead have been omitted.
1012		1155
1013	Another common scenario is having some data structure with multiple	1156	Another common scenario is to use some data structure with multiple
1014	watchers:	1157	embedded watchers:
1015		1158
1016	struct my_biggy	1159	struct my_biggy
1017	{	1160	{
1018	int some_data;	1161	int some_data;
1019	ev_timer t1;	1162	ev_timer t1;
1020	ev_timer t2;	1163	ev_timer t2;
1021	}	1164	}
1022		1165
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1166	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1167	complicated: Either you store the address of your C<my_biggy> struct
		1168	in the C<data> member of the watcher (for woozies), or you need to use
		1169	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1170	programmers):
1025		1171
1026	#include <stddef.h>	1172	#include <stddef.h>
1027		1173
1028	static void	1174	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1175	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1176	{
1031	struct my_biggy big = (struct my_biggy *	1177	struct my_biggy big = (struct my_biggy *
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1178	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1179	}
1034		1180
1035	static void	1181	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1182	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1183	{
1038	struct my_biggy big = (struct my_biggy *	1184	struct my_biggy big = (struct my_biggy *
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1185	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1186	}
		1187
		1188	=head2 WATCHER PRIORITY MODELS
		1189
		1190	Many event loops support I<watcher priorities>, which are usually small
		1191	integers that influence the ordering of event callback invocation
		1192	between watchers in some way, all else being equal.
		1193
		1194	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1195	description for the more technical details such as the actual priority
		1196	range.
		1197
		1198	There are two common ways how these these priorities are being interpreted
		1199	by event loops:
		1200
		1201	In the more common lock-out model, higher priorities "lock out" invocation
		1202	of lower priority watchers, which means as long as higher priority
		1203	watchers receive events, lower priority watchers are not being invoked.
		1204
		1205	The less common only-for-ordering model uses priorities solely to order
		1206	callback invocation within a single event loop iteration: Higher priority
		1207	watchers are invoked before lower priority ones, but they all get invoked
		1208	before polling for new events.
		1209
		1210	Libev uses the second (only-for-ordering) model for all its watchers
		1211	except for idle watchers (which use the lock-out model).
		1212
		1213	The rationale behind this is that implementing the lock-out model for
		1214	watchers is not well supported by most kernel interfaces, and most event
		1215	libraries will just poll for the same events again and again as long as
		1216	their callbacks have not been executed, which is very inefficient in the
		1217	common case of one high-priority watcher locking out a mass of lower
		1218	priority ones.
		1219
		1220	Static (ordering) priorities are most useful when you have two or more
		1221	watchers handling the same resource: a typical usage example is having an
		1222	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1223	timeouts. Under load, data might be received while the program handles
		1224	other jobs, but since timers normally get invoked first, the timeout
		1225	handler will be executed before checking for data. In that case, giving
		1226	the timer a lower priority than the I/O watcher ensures that I/O will be
		1227	handled first even under adverse conditions (which is usually, but not
		1228	always, what you want).
		1229
		1230	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1231	will only be executed when no same or higher priority watchers have
		1232	received events, they can be used to implement the "lock-out" model when
		1233	required.
		1234
		1235	For example, to emulate how many other event libraries handle priorities,
		1236	you can associate an C<ev_idle> watcher to each such watcher, and in
		1237	the normal watcher callback, you just start the idle watcher. The real
		1238	processing is done in the idle watcher callback. This causes libev to
		1239	continously poll and process kernel event data for the watcher, but when
		1240	the lock-out case is known to be rare (which in turn is rare :), this is
		1241	workable.
		1242
		1243	Usually, however, the lock-out model implemented that way will perform
		1244	miserably under the type of load it was designed to handle. In that case,
		1245	it might be preferable to stop the real watcher before starting the
		1246	idle watcher, so the kernel will not have to process the event in case
		1247	the actual processing will be delayed for considerable time.
		1248
		1249	Here is an example of an I/O watcher that should run at a strictly lower
		1250	priority than the default, and which should only process data when no
		1251	other events are pending:
		1252
		1253	ev_idle idle; // actual processing watcher
		1254	ev_io io; // actual event watcher
		1255
		1256	static void
		1257	io_cb (EV_P_ ev_io *w, int revents)
		1258	{
		1259	// stop the I/O watcher, we received the event, but
		1260	// are not yet ready to handle it.
		1261	ev_io_stop (EV_A_ w);
		1262
		1263	// start the idle watcher to ahndle the actual event.
		1264	// it will not be executed as long as other watchers
		1265	// with the default priority are receiving events.
		1266	ev_idle_start (EV_A_ &idle);
		1267	}
		1268
		1269	static void
		1270	idle-cb (EV_P_ ev_idle *w, int revents)
		1271	{
		1272	// actual processing
		1273	read (STDIN_FILENO, ...);
		1274
		1275	// have to start the I/O watcher again, as
		1276	// we have handled the event
		1277	ev_io_start (EV_P_ &io);
		1278	}
		1279
		1280	// initialisation
		1281	ev_idle_init (&idle, idle_cb);
		1282	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1283	ev_io_start (EV_DEFAULT_ &io);
		1284
		1285	In the "real" world, it might also be beneficial to start a timer, so that
		1286	low-priority connections can not be locked out forever under load. This
		1287	enables your program to keep a lower latency for important connections
		1288	during short periods of high load, while not completely locking out less
		1289	important ones.
1041		1290
1042		1291
1043	=head1 WATCHER TYPES	1292	=head1 WATCHER TYPES
1044		1293
1045	This section describes each watcher in detail, but will not repeat	1294	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	1318	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	1319	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	1320	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1321	required if you know what you are doing).
1073		1322
1074	If you must do this, then force the use of a known-to-be-good backend	1323	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	1324	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1325	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1077		1326
1078	Another thing you have to watch out for is that it is quite easy to	1327	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	1328	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	1329	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	1330	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	1331	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	1332	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	1333	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.	1334	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1335
1087	If you cannot run the fd in non-blocking mode (for example you should not	1336	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	1337	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	1338	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	1339	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1340	does this on its own, so its quite safe to use). Some people additionally
		1341	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1342	indefinitely.
		1343
		1344	But really, best use non-blocking mode.
1092		1345
1093	=head3 The special problem of disappearing file descriptors	1346	=head3 The special problem of disappearing file descriptors
1094		1347
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1348	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,	1349	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	1350	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	1351	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	1352	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	1353	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1354	fact, a different file descriptor.
1102		1355
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1386	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1387	C<EVBACKEND_POLL>.
1135		1388
1136	=head3 The special problem of SIGPIPE	1389	=head3 The special problem of SIGPIPE
1137		1390
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1391	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when writing to a pipe whose other end has been closed, your program gets	1392	when writing to a pipe whose other end has been closed, your program gets
1140	send a SIGPIPE, which, by default, aborts your program. For most programs	1393	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	this is sensible behaviour, for daemons, this is usually undesirable.	1394	this is sensible behaviour, for daemons, this is usually undesirable.
1142		1395
1143	So when you encounter spurious, unexplained daemon exits, make sure you	1396	So when you encounter spurious, unexplained daemon exits, make sure you
1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1397	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1145	somewhere, as that would have given you a big clue).	1398	somewhere, as that would have given you a big clue).
…		…
1152	=item ev_io_init (ev_io *, callback, int fd, int events)	1405	=item ev_io_init (ev_io *, callback, int fd, int events)
1153		1406
1154	=item ev_io_set (ev_io *, int fd, int events)	1407	=item ev_io_set (ev_io *, int fd, int events)
1155		1408
1156	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1409	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1157	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1410	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1158	C<EV_READ | EV_WRITE> to receive the given events.	1411	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1159		1412
1160	=item int fd [read-only]	1413	=item int fd [read-only]
1161		1414
1162	The file descriptor being watched.	1415	The file descriptor being watched.
1163		1416
…		…
1172	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1425	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1173	readable, but only once. Since it is likely line-buffered, you could	1426	readable, but only once. Since it is likely line-buffered, you could
1174	attempt to read a whole line in the callback.	1427	attempt to read a whole line in the callback.
1175		1428
1176	static void	1429	static void
1177	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1430	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1178	{	1431	{
1179	ev_io_stop (loop, w);	1432	ev_io_stop (loop, w);
1180	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1433	.. read from stdin here (or from w->fd) and handle any I/O errors
1181	}	1434	}
1182		1435
1183	...	1436	...
1184	struct ev_loop *loop = ev_default_init (0);	1437	struct ev_loop *loop = ev_default_init (0);
1185	struct ev_io stdin_readable;	1438	ev_io stdin_readable;
1186	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1439	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1187	ev_io_start (loop, &stdin_readable);	1440	ev_io_start (loop, &stdin_readable);
1188	ev_loop (loop, 0);	1441	ev_loop (loop, 0);
1189		1442
1190		1443
…		…
1193	Timer watchers are simple relative timers that generate an event after a	1446	Timer watchers are simple relative timers that generate an event after a
1194	given time, and optionally repeating in regular intervals after that.	1447	given time, and optionally repeating in regular intervals after that.
1195		1448
1196	The timers are based on real time, that is, if you register an event that	1449	The timers are based on real time, that is, if you register an event that
1197	times out after an hour and you reset your system clock to January last	1450	times out after an hour and you reset your system clock to January last
1198	year, it will still time out after (roughly) and hour. "Roughly" because	1451	year, it will still time out after (roughly) one hour. "Roughly" because
1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1452	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1200	monotonic clock option helps a lot here).	1453	monotonic clock option helps a lot here).
1201		1454
1202	The callback is guaranteed to be invoked only after its timeout has passed,	1455	The callback is guaranteed to be invoked only I<after> its timeout has
1203	but if multiple timers become ready during the same loop iteration then	1456	passed. If multiple timers become ready during the same loop iteration
1204	order of execution is undefined.	1457	then the ones with earlier time-out values are invoked before ones with
		1458	later time-out values (but this is no longer true when a callback calls
		1459	C<ev_loop> recursively).
		1460
		1461	=head3 Be smart about timeouts
		1462
		1463	Many real-world problems involve some kind of timeout, usually for error
		1464	recovery. A typical example is an HTTP request - if the other side hangs,
		1465	you want to raise some error after a while.
		1466
		1467	What follows are some ways to handle this problem, from obvious and
		1468	inefficient to smart and efficient.
		1469
		1470	In the following, a 60 second activity timeout is assumed - a timeout that
		1471	gets reset to 60 seconds each time there is activity (e.g. each time some
		1472	data or other life sign was received).
		1473
		1474	=over 4
		1475
		1476	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1477
		1478	This is the most obvious, but not the most simple way: In the beginning,
		1479	start the watcher:
		1480
		1481	ev_timer_init (timer, callback, 60., 0.);
		1482	ev_timer_start (loop, timer);
		1483
		1484	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1485	and start it again:
		1486
		1487	ev_timer_stop (loop, timer);
		1488	ev_timer_set (timer, 60., 0.);
		1489	ev_timer_start (loop, timer);
		1490
		1491	This is relatively simple to implement, but means that each time there is
		1492	some activity, libev will first have to remove the timer from its internal
		1493	data structure and then add it again. Libev tries to be fast, but it's
		1494	still not a constant-time operation.
		1495
		1496	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1497
		1498	This is the easiest way, and involves using C<ev_timer_again> instead of
		1499	C<ev_timer_start>.
		1500
		1501	To implement this, configure an C<ev_timer> with a C<repeat> value
		1502	of C<60> and then call C<ev_timer_again> at start and each time you
		1503	successfully read or write some data. If you go into an idle state where
		1504	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1505	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1506
		1507	That means you can ignore both the C<ev_timer_start> function and the
		1508	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1509	member and C<ev_timer_again>.
		1510
		1511	At start:
		1512
		1513	ev_timer_init (timer, callback);
		1514	timer->repeat = 60.;
		1515	ev_timer_again (loop, timer);
		1516
		1517	Each time there is some activity:
		1518
		1519	ev_timer_again (loop, timer);
		1520
		1521	It is even possible to change the time-out on the fly, regardless of
		1522	whether the watcher is active or not:
		1523
		1524	timer->repeat = 30.;
		1525	ev_timer_again (loop, timer);
		1526
		1527	This is slightly more efficient then stopping/starting the timer each time
		1528	you want to modify its timeout value, as libev does not have to completely
		1529	remove and re-insert the timer from/into its internal data structure.
		1530
		1531	It is, however, even simpler than the "obvious" way to do it.
		1532
		1533	=item 3. Let the timer time out, but then re-arm it as required.
		1534
		1535	This method is more tricky, but usually most efficient: Most timeouts are
		1536	relatively long compared to the intervals between other activity - in
		1537	our example, within 60 seconds, there are usually many I/O events with
		1538	associated activity resets.
		1539
		1540	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1541	but remember the time of last activity, and check for a real timeout only
		1542	within the callback:
		1543
		1544	ev_tstamp last_activity; // time of last activity
		1545
		1546	static void
		1547	callback (EV_P_ ev_timer *w, int revents)
		1548	{
		1549	ev_tstamp now = ev_now (EV_A);
		1550	ev_tstamp timeout = last_activity + 60.;
		1551
		1552	// if last_activity + 60. is older than now, we did time out
		1553	if (timeout < now)
		1554	{
		1555	// timeout occured, take action
		1556	}
		1557	else
		1558	{
		1559	// callback was invoked, but there was some activity, re-arm
		1560	// the watcher to fire in last_activity + 60, which is
		1561	// guaranteed to be in the future, so "again" is positive:
		1562	w->repeat = timeout - now;
		1563	ev_timer_again (EV_A_ w);
		1564	}
		1565	}
		1566
		1567	To summarise the callback: first calculate the real timeout (defined
		1568	as "60 seconds after the last activity"), then check if that time has
		1569	been reached, which means something I<did>, in fact, time out. Otherwise
		1570	the callback was invoked too early (C<timeout> is in the future), so
		1571	re-schedule the timer to fire at that future time, to see if maybe we have
		1572	a timeout then.
		1573
		1574	Note how C<ev_timer_again> is used, taking advantage of the
		1575	C<ev_timer_again> optimisation when the timer is already running.
		1576
		1577	This scheme causes more callback invocations (about one every 60 seconds
		1578	minus half the average time between activity), but virtually no calls to
		1579	libev to change the timeout.
		1580
		1581	To start the timer, simply initialise the watcher and set C<last_activity>
		1582	to the current time (meaning we just have some activity :), then call the
		1583	callback, which will "do the right thing" and start the timer:
		1584
		1585	ev_timer_init (timer, callback);
		1586	last_activity = ev_now (loop);
		1587	callback (loop, timer, EV_TIMEOUT);
		1588
		1589	And when there is some activity, simply store the current time in
		1590	C<last_activity>, no libev calls at all:
		1591
		1592	last_actiivty = ev_now (loop);
		1593
		1594	This technique is slightly more complex, but in most cases where the
		1595	time-out is unlikely to be triggered, much more efficient.
		1596
		1597	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1598	callback :) - just change the timeout and invoke the callback, which will
		1599	fix things for you.
		1600
		1601	=item 4. Wee, just use a double-linked list for your timeouts.
		1602
		1603	If there is not one request, but many thousands (millions...), all
		1604	employing some kind of timeout with the same timeout value, then one can
		1605	do even better:
		1606
		1607	When starting the timeout, calculate the timeout value and put the timeout
		1608	at the I<end> of the list.
		1609
		1610	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1611	the list is expected to fire (for example, using the technique #3).
		1612
		1613	When there is some activity, remove the timer from the list, recalculate
		1614	the timeout, append it to the end of the list again, and make sure to
		1615	update the C<ev_timer> if it was taken from the beginning of the list.
		1616
		1617	This way, one can manage an unlimited number of timeouts in O(1) time for
		1618	starting, stopping and updating the timers, at the expense of a major
		1619	complication, and having to use a constant timeout. The constant timeout
		1620	ensures that the list stays sorted.
		1621
		1622	=back
		1623
		1624	So which method the best?
		1625
		1626	Method #2 is a simple no-brain-required solution that is adequate in most
		1627	situations. Method #3 requires a bit more thinking, but handles many cases
		1628	better, and isn't very complicated either. In most case, choosing either
		1629	one is fine, with #3 being better in typical situations.
		1630
		1631	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1632	rather complicated, but extremely efficient, something that really pays
		1633	off after the first million or so of active timers, i.e. it's usually
		1634	overkill :)
1205		1635
1206	=head3 The special problem of time updates	1636	=head3 The special problem of time updates
1207		1637
1208	Requesting the current time is a costly operation (it usually takes at	1638	Establishing the current time is a costly operation (it usually takes at
1209	least two syscalls): EV therefore updates it's idea of the current time	1639	least two system calls): EV therefore updates its idea of the current
1210	only before and after C<ev_loop> polls for new events, which causes the	1640	time only before and after C<ev_loop> collects new events, which causes a
1211	difference between C<ev_now ()> and C<ev_time ()>.	1641	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1642	lots of events in one iteration.
1212		1643
1213	The relative timeouts are calculated relative to the C<ev_now ()>	1644	The relative timeouts are calculated relative to the C<ev_now ()>
1214	time. This is usually the right thing as this timestamp refers to the time	1645	time. This is usually the right thing as this timestamp refers to the time
1215	of the event triggering whatever timeout you are modifying/starting. If	1646	of the event triggering whatever timeout you are modifying/starting. If
1216	you suspect event processing to be delayed and you I<need> to base the	1647	you suspect event processing to be delayed and you I<need> to base the
1217	timeout on the current time, use something like this to adjust for this:	1648	timeout on the current time, use something like this to adjust for this:
1218		1649
1219	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1650	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1220		1651
		1652	If the event loop is suspended for a long time, you can also force an
		1653	update of the time returned by C<ev_now ()> by calling C<ev_now_update
		1654	()>.
		1655
1221	=head3 Watcher-Specific Functions and Data Members	1656	=head3 Watcher-Specific Functions and Data Members
1222		1657
1223	=over 4	1658	=over 4
1224		1659
1225	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1660	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1248	If the timer is started but non-repeating, stop it (as if it timed out).	1683	If the timer is started but non-repeating, stop it (as if it timed out).
1249		1684
1250	If the timer is repeating, either start it if necessary (with the	1685	If the timer is repeating, either start it if necessary (with the
1251	C<repeat> value), or reset the running timer to the C<repeat> value.	1686	C<repeat> value), or reset the running timer to the C<repeat> value.
1252		1687
1253	This sounds a bit complicated, but here is a useful and typical	1688	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1254	example: Imagine you have a TCP connection and you want a so-called idle	1689	usage example.
1255	timeout, that is, you want to be called when there have been, say, 60
1256	seconds of inactivity on the socket. The easiest way to do this is to
1257	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1258	C<ev_timer_again> each time you successfully read or write some data. If
1259	you go into an idle state where you do not expect data to travel on the
1260	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1261	automatically restart it if need be.
1262
1263	That means you can ignore the C<after> value and C<ev_timer_start>
1264	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1265
1266	ev_timer_init (timer, callback, 0., 5.);
1267	ev_timer_again (loop, timer);
1268	...
1269	timer->again = 17.;
1270	ev_timer_again (loop, timer);
1271	...
1272	timer->again = 10.;
1273	ev_timer_again (loop, timer);
1274
1275	This is more slightly efficient then stopping/starting the timer each time
1276	you want to modify its timeout value.
1277		1690
1278	=item ev_tstamp repeat [read-write]	1691	=item ev_tstamp repeat [read-write]
1279		1692
1280	The current C<repeat> value. Will be used each time the watcher times out	1693	The current C<repeat> value. Will be used each time the watcher times out
1281	or C<ev_timer_again> is called and determines the next timeout (if any),	1694	or C<ev_timer_again> is called, and determines the next timeout (if any),
1282	which is also when any modifications are taken into account.	1695	which is also when any modifications are taken into account.
1283		1696
1284	=back	1697	=back
1285		1698
1286	=head3 Examples	1699	=head3 Examples
1287		1700
1288	Example: Create a timer that fires after 60 seconds.	1701	Example: Create a timer that fires after 60 seconds.
1289		1702
1290	static void	1703	static void
1291	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1704	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1292	{	1705	{
1293	.. one minute over, w is actually stopped right here	1706	.. one minute over, w is actually stopped right here
1294	}	1707	}
1295		1708
1296	struct ev_timer mytimer;	1709	ev_timer mytimer;
1297	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1710	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1298	ev_timer_start (loop, &mytimer);	1711	ev_timer_start (loop, &mytimer);
1299		1712
1300	Example: Create a timeout timer that times out after 10 seconds of	1713	Example: Create a timeout timer that times out after 10 seconds of
1301	inactivity.	1714	inactivity.
1302		1715
1303	static void	1716	static void
1304	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1717	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1305	{	1718	{
1306	.. ten seconds without any activity	1719	.. ten seconds without any activity
1307	}	1720	}
1308		1721
1309	struct ev_timer mytimer;	1722	ev_timer mytimer;
1310	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1723	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1311	ev_timer_again (&mytimer); /* start timer */	1724	ev_timer_again (&mytimer); /* start timer */
1312	ev_loop (loop, 0);	1725	ev_loop (loop, 0);
1313		1726
1314	// and in some piece of code that gets executed on any "activity":	1727	// and in some piece of code that gets executed on any "activity":
…		…
1319	=head2 C<ev_periodic> - to cron or not to cron?	1732	=head2 C<ev_periodic> - to cron or not to cron?
1320		1733
1321	Periodic watchers are also timers of a kind, but they are very versatile	1734	Periodic watchers are also timers of a kind, but they are very versatile
1322	(and unfortunately a bit complex).	1735	(and unfortunately a bit complex).
1323		1736
1324	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1737	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1325	but on wall clock time (absolute time). You can tell a periodic watcher	1738	relative time, the physical time that passes) but on wall clock time
1326	to trigger after some specific point in time. For example, if you tell a	1739	(absolute time, the thing you can read on your calender or clock). The
1327	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1740	difference is that wall clock time can run faster or slower than real
1328	+ 10.>, that is, an absolute time not a delay) and then reset your system	1741	time, and time jumps are not uncommon (e.g. when you adjust your
1329	clock to January of the previous year, then it will take more than year	1742	wrist-watch).
1330	to trigger the event (unlike an C<ev_timer>, which would still trigger
1331	roughly 10 seconds later as it uses a relative timeout).
1332		1743
		1744	You can tell a periodic watcher to trigger after some specific point
		1745	in time: for example, if you tell a periodic watcher to trigger "in 10
		1746	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1747	not a delay) and then reset your system clock to January of the previous
		1748	year, then it will take a year or more to trigger the event (unlike an
		1749	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1750	it, as it uses a relative timeout).
		1751
1333	C<ev_periodic>s can also be used to implement vastly more complex timers,	1752	C<ev_periodic> watchers can also be used to implement vastly more complex
1334	such as triggering an event on each "midnight, local time", or other	1753	timers, such as triggering an event on each "midnight, local time", or
1335	complicated, rules.	1754	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1755	those cannot react to time jumps.
1336		1756
1337	As with timers, the callback is guaranteed to be invoked only when the	1757	As with timers, the callback is guaranteed to be invoked only when the
1338	time (C<at>) has passed, but if multiple periodic timers become ready	1758	point in time where it is supposed to trigger has passed. If multiple
1339	during the same loop iteration then order of execution is undefined.	1759	timers become ready during the same loop iteration then the ones with
		1760	earlier time-out values are invoked before ones with later time-out values
		1761	(but this is no longer true when a callback calls C<ev_loop> recursively).
1340		1762
1341	=head3 Watcher-Specific Functions and Data Members	1763	=head3 Watcher-Specific Functions and Data Members
1342		1764
1343	=over 4	1765	=over 4
1344		1766
1345	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1767	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1346		1768
1347	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1769	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1348		1770
1349	Lots of arguments, lets sort it out... There are basically three modes of	1771	Lots of arguments, let's sort it out... There are basically three modes of
1350	operation, and we will explain them from simplest to complex:	1772	operation, and we will explain them from simplest to most complex:
1351		1773
1352	=over 4	1774	=over 4
1353		1775
1354	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1776	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1355		1777
1356	In this configuration the watcher triggers an event after the wall clock	1778	In this configuration the watcher triggers an event after the wall clock
1357	time C<at> has passed and doesn't repeat. It will not adjust when a time	1779	time C<offset> has passed. It will not repeat and will not adjust when a
1358	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1780	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1359	run when the system time reaches or surpasses this time.	1781	will be stopped and invoked when the system clock reaches or surpasses
		1782	this point in time.
1360		1783
1361	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1784	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1362		1785
1363	In this mode the watcher will always be scheduled to time out at the next	1786	In this mode the watcher will always be scheduled to time out at the next
1364	C<at + N * interval> time (for some integer N, which can also be negative)	1787	C<offset + N * interval> time (for some integer N, which can also be
1365	and then repeat, regardless of any time jumps.	1788	negative) and then repeat, regardless of any time jumps. The C<offset>
		1789	argument is merely an offset into the C<interval> periods.
1366		1790
1367	This can be used to create timers that do not drift with respect to system	1791	This can be used to create timers that do not drift with respect to the
1368	time, for example, here is a C<ev_periodic> that triggers each hour, on	1792	system clock, for example, here is an C<ev_periodic> that triggers each
1369	the hour:	1793	hour, on the hour (with respect to UTC):
1370		1794
1371	ev_periodic_set (&periodic, 0., 3600., 0);	1795	ev_periodic_set (&periodic, 0., 3600., 0);
1372		1796
1373	This doesn't mean there will always be 3600 seconds in between triggers,	1797	This doesn't mean there will always be 3600 seconds in between triggers,
1374	but only that the callback will be called when the system time shows a	1798	but only that the callback will be called when the system time shows a
1375	full hour (UTC), or more correctly, when the system time is evenly divisible	1799	full hour (UTC), or more correctly, when the system time is evenly divisible
1376	by 3600.	1800	by 3600.
1377		1801
1378	Another way to think about it (for the mathematically inclined) is that	1802	Another way to think about it (for the mathematically inclined) is that
1379	C<ev_periodic> will try to run the callback in this mode at the next possible	1803	C<ev_periodic> will try to run the callback in this mode at the next possible
1380	time where C<time = at (mod interval)>, regardless of any time jumps.	1804	time where C<time = offset (mod interval)>, regardless of any time jumps.
1381		1805
1382	For numerical stability it is preferable that the C<at> value is near	1806	For numerical stability it is preferable that the C<offset> value is near
1383	C<ev_now ()> (the current time), but there is no range requirement for	1807	C<ev_now ()> (the current time), but there is no range requirement for
1384	this value, and in fact is often specified as zero.	1808	this value, and in fact is often specified as zero.
1385		1809
1386	Note also that there is an upper limit to how often a timer can fire (CPU	1810	Note also that there is an upper limit to how often a timer can fire (CPU
1387	speed for example), so if C<interval> is very small then timing stability	1811	speed for example), so if C<interval> is very small then timing stability
1388	will of course deteriorate. Libev itself tries to be exact to be about one	1812	will of course deteriorate. Libev itself tries to be exact to be about one
1389	millisecond (if the OS supports it and the machine is fast enough).	1813	millisecond (if the OS supports it and the machine is fast enough).
1390		1814
1391	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1815	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1392		1816
1393	In this mode the values for C<interval> and C<at> are both being	1817	In this mode the values for C<interval> and C<offset> are both being
1394	ignored. Instead, each time the periodic watcher gets scheduled, the	1818	ignored. Instead, each time the periodic watcher gets scheduled, the
1395	reschedule callback will be called with the watcher as first, and the	1819	reschedule callback will be called with the watcher as first, and the
1396	current time as second argument.	1820	current time as second argument.
1397		1821
1398	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1822	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1399	ever, or make ANY event loop modifications whatsoever>.	1823	or make ANY other event loop modifications whatsoever, unless explicitly
		1824	allowed by documentation here>.
1400		1825
1401	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1826	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1402	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1827	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1403	only event loop modification you are allowed to do).	1828	only event loop modification you are allowed to do).
1404		1829
1405	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1830	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1406	*w, ev_tstamp now)>, e.g.:	1831	*w, ev_tstamp now)>, e.g.:
1407		1832
		1833	static ev_tstamp
1408	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1834	my_rescheduler (ev_periodic *w, ev_tstamp now)
1409	{	1835	{
1410	return now + 60.;	1836	return now + 60.;
1411	}	1837	}
1412		1838
1413	It must return the next time to trigger, based on the passed time value	1839	It must return the next time to trigger, based on the passed time value
…		…
1433	a different time than the last time it was called (e.g. in a crond like	1859	a different time than the last time it was called (e.g. in a crond like
1434	program when the crontabs have changed).	1860	program when the crontabs have changed).
1435		1861
1436	=item ev_tstamp ev_periodic_at (ev_periodic *)	1862	=item ev_tstamp ev_periodic_at (ev_periodic *)
1437		1863
1438	When active, returns the absolute time that the watcher is supposed to	1864	When active, returns the absolute time that the watcher is supposed
1439	trigger next.	1865	to trigger next. This is not the same as the C<offset> argument to
		1866	C<ev_periodic_set>, but indeed works even in interval and manual
		1867	rescheduling modes.
1440		1868
1441	=item ev_tstamp offset [read-write]	1869	=item ev_tstamp offset [read-write]
1442		1870
1443	When repeating, this contains the offset value, otherwise this is the	1871	When repeating, this contains the offset value, otherwise this is the
1444	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1872	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1873	although libev might modify this value for better numerical stability).
1445		1874
1446	Can be modified any time, but changes only take effect when the periodic	1875	Can be modified any time, but changes only take effect when the periodic
1447	timer fires or C<ev_periodic_again> is being called.	1876	timer fires or C<ev_periodic_again> is being called.
1448		1877
1449	=item ev_tstamp interval [read-write]	1878	=item ev_tstamp interval [read-write]
1450		1879
1451	The current interval value. Can be modified any time, but changes only	1880	The current interval value. Can be modified any time, but changes only
1452	take effect when the periodic timer fires or C<ev_periodic_again> is being	1881	take effect when the periodic timer fires or C<ev_periodic_again> is being
1453	called.	1882	called.
1454		1883
1455	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1884	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1456		1885
1457	The current reschedule callback, or C<0>, if this functionality is	1886	The current reschedule callback, or C<0>, if this functionality is
1458	switched off. Can be changed any time, but changes only take effect when	1887	switched off. Can be changed any time, but changes only take effect when
1459	the periodic timer fires or C<ev_periodic_again> is being called.	1888	the periodic timer fires or C<ev_periodic_again> is being called.
1460		1889
1461	=back	1890	=back
1462		1891
1463	=head3 Examples	1892	=head3 Examples
1464		1893
1465	Example: Call a callback every hour, or, more precisely, whenever the	1894	Example: Call a callback every hour, or, more precisely, whenever the
1466	system clock is divisible by 3600. The callback invocation times have	1895	system time is divisible by 3600. The callback invocation times have
1467	potentially a lot of jitter, but good long-term stability.	1896	potentially a lot of jitter, but good long-term stability.
1468		1897
1469	static void	1898	static void
1470	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1899	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1471	{	1900	{
1472	... its now a full hour (UTC, or TAI or whatever your clock follows)	1901	... its now a full hour (UTC, or TAI or whatever your clock follows)
1473	}	1902	}
1474		1903
1475	struct ev_periodic hourly_tick;	1904	ev_periodic hourly_tick;
1476	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1905	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1477	ev_periodic_start (loop, &hourly_tick);	1906	ev_periodic_start (loop, &hourly_tick);
1478		1907
1479	Example: The same as above, but use a reschedule callback to do it:	1908	Example: The same as above, but use a reschedule callback to do it:
1480		1909
1481	#include <math.h>	1910	#include <math.h>
1482		1911
1483	static ev_tstamp	1912	static ev_tstamp
1484	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1913	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1485	{	1914	{
1486	return fmod (now, 3600.) + 3600.;	1915	return now + (3600. - fmod (now, 3600.));
1487	}	1916	}
1488		1917
1489	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1918	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1490		1919
1491	Example: Call a callback every hour, starting now:	1920	Example: Call a callback every hour, starting now:
1492		1921
1493	struct ev_periodic hourly_tick;	1922	ev_periodic hourly_tick;
1494	ev_periodic_init (&hourly_tick, clock_cb,	1923	ev_periodic_init (&hourly_tick, clock_cb,
1495	fmod (ev_now (loop), 3600.), 3600., 0);	1924	fmod (ev_now (loop), 3600.), 3600., 0);
1496	ev_periodic_start (loop, &hourly_tick);	1925	ev_periodic_start (loop, &hourly_tick);
1497		1926
1498		1927
…		…
1501	Signal watchers will trigger an event when the process receives a specific	1930	Signal watchers will trigger an event when the process receives a specific
1502	signal one or more times. Even though signals are very asynchronous, libev	1931	signal one or more times. Even though signals are very asynchronous, libev
1503	will try it's best to deliver signals synchronously, i.e. as part of the	1932	will try it's best to deliver signals synchronously, i.e. as part of the
1504	normal event processing, like any other event.	1933	normal event processing, like any other event.
1505		1934
		1935	If you want signals asynchronously, just use C<sigaction> as you would
		1936	do without libev and forget about sharing the signal. You can even use
		1937	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1938
1506	You can configure as many watchers as you like per signal. Only when the	1939	You can configure as many watchers as you like per signal. Only when the
1507	first watcher gets started will libev actually register a signal watcher	1940	first watcher gets started will libev actually register a signal handler
1508	with the kernel (thus it coexists with your own signal handlers as long	1941	with the kernel (thus it coexists with your own signal handlers as long as
1509	as you don't register any with libev). Similarly, when the last signal	1942	you don't register any with libev for the same signal). Similarly, when
1510	watcher for a signal is stopped libev will reset the signal handler to	1943	the last signal watcher for a signal is stopped, libev will reset the
1511	SIG_DFL (regardless of what it was set to before).	1944	signal handler to SIG_DFL (regardless of what it was set to before).
1512		1945
1513	If possible and supported, libev will install its handlers with	1946	If possible and supported, libev will install its handlers with
1514	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1947	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1515	interrupted. If you have a problem with system calls getting interrupted by	1948	interrupted. If you have a problem with system calls getting interrupted by
1516	signals you can block all signals in an C<ev_check> watcher and unblock	1949	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1533		1966
1534	=back	1967	=back
1535		1968
1536	=head3 Examples	1969	=head3 Examples
1537		1970
1538	Example: Try to exit cleanly on SIGINT and SIGTERM.	1971	Example: Try to exit cleanly on SIGINT.
1539		1972
1540	static void	1973	static void
1541	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1974	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1542	{	1975	{
1543	ev_unloop (loop, EVUNLOOP_ALL);	1976	ev_unloop (loop, EVUNLOOP_ALL);
1544	}	1977	}
1545		1978
1546	struct ev_signal signal_watcher;	1979	ev_signal signal_watcher;
1547	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1980	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1548	ev_signal_start (loop, &sigint_cb);	1981	ev_signal_start (loop, &signal_watcher);
1549		1982
1550		1983
1551	=head2 C<ev_child> - watch out for process status changes	1984	=head2 C<ev_child> - watch out for process status changes
1552		1985
1553	Child watchers trigger when your process receives a SIGCHLD in response to	1986	Child watchers trigger when your process receives a SIGCHLD in response to
1554	some child status changes (most typically when a child of yours dies). It	1987	some child status changes (most typically when a child of yours dies or
1555	is permissible to install a child watcher I<after> the child has been	1988	exits). It is permissible to install a child watcher I<after> the child
1556	forked (which implies it might have already exited), as long as the event	1989	has been forked (which implies it might have already exited), as long
1557	loop isn't entered (or is continued from a watcher).	1990	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1991	forking and then immediately registering a watcher for the child is fine,
		1992	but forking and registering a watcher a few event loop iterations later is
		1993	not.
1558		1994
1559	Only the default event loop is capable of handling signals, and therefore	1995	Only the default event loop is capable of handling signals, and therefore
1560	you can only register child watchers in the default event loop.	1996	you can only register child watchers in the default event loop.
1561		1997
1562	=head3 Process Interaction	1998	=head3 Process Interaction
…		…
1623	its completion.	2059	its completion.
1624		2060
1625	ev_child cw;	2061	ev_child cw;
1626		2062
1627	static void	2063	static void
1628	child_cb (EV_P_ struct ev_child *w, int revents)	2064	child_cb (EV_P_ ev_child *w, int revents)
1629	{	2065	{
1630	ev_child_stop (EV_A_ w);	2066	ev_child_stop (EV_A_ w);
1631	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2067	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1632	}	2068	}
1633		2069
…		…
1648		2084
1649		2085
1650	=head2 C<ev_stat> - did the file attributes just change?	2086	=head2 C<ev_stat> - did the file attributes just change?
1651		2087
1652	This watches a file system path for attribute changes. That is, it calls	2088	This watches a file system path for attribute changes. That is, it calls
1653	C<stat> regularly (or when the OS says it changed) and sees if it changed	2089	C<stat> on that path in regular intervals (or when the OS says it changed)
1654	compared to the last time, invoking the callback if it did.	2090	and sees if it changed compared to the last time, invoking the callback if
		2091	it did.
1655		2092
1656	The path does not need to exist: changing from "path exists" to "path does	2093	The path does not need to exist: changing from "path exists" to "path does
1657	not exist" is a status change like any other. The condition "path does	2094	not exist" is a status change like any other. The condition "path does not
1658	not exist" is signified by the C<st_nlink> field being zero (which is	2095	exist" (or more correctly "path cannot be stat'ed") is signified by the
1659	otherwise always forced to be at least one) and all the other fields of	2096	C<st_nlink> field being zero (which is otherwise always forced to be at
1660	the stat buffer having unspecified contents.	2097	least one) and all the other fields of the stat buffer having unspecified
		2098	contents.
1661		2099
1662	The path I<should> be absolute and I<must not> end in a slash. If it is	2100	The path I<must not> end in a slash or contain special components such as
		2101	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1663	relative and your working directory changes, the behaviour is undefined.	2102	your working directory changes, then the behaviour is undefined.
1664		2103
1665	Since there is no standard to do this, the portable implementation simply	2104	Since there is no portable change notification interface available, the
1666	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2105	portable implementation simply calls C<stat(2)> regularly on the path
1667	can specify a recommended polling interval for this case. If you specify	2106	to see if it changed somehow. You can specify a recommended polling
1668	a polling interval of C<0> (highly recommended!) then a I<suitable,	2107	interval for this case. If you specify a polling interval of C<0> (highly
1669	unspecified default> value will be used (which you can expect to be around	2108	recommended!) then a I<suitable, unspecified default> value will be used
1670	five seconds, although this might change dynamically). Libev will also	2109	(which you can expect to be around five seconds, although this might
1671	impose a minimum interval which is currently around C<0.1>, but thats	2110	change dynamically). Libev will also impose a minimum interval which is
1672	usually overkill.	2111	currently around C<0.1>, but that's usually overkill.
1673		2112
1674	This watcher type is not meant for massive numbers of stat watchers,	2113	This watcher type is not meant for massive numbers of stat watchers,
1675	as even with OS-supported change notifications, this can be	2114	as even with OS-supported change notifications, this can be
1676	resource-intensive.	2115	resource-intensive.
1677		2116
1678	At the time of this writing, only the Linux inotify interface is	2117	At the time of this writing, the only OS-specific interface implemented
1679	implemented (implementing kqueue support is left as an exercise for the	2118	is the Linux inotify interface (implementing kqueue support is left as an
1680	reader, note, however, that the author sees no way of implementing ev_stat	2119	exercise for the reader. Note, however, that the author sees no way of
1681	semantics with kqueue). Inotify will be used to give hints only and should	2120	implementing C<ev_stat> semantics with kqueue, except as a hint).
1682	not change the semantics of C<ev_stat> watchers, which means that libev
1683	sometimes needs to fall back to regular polling again even with inotify,
1684	but changes are usually detected immediately, and if the file exists there
1685	will be no polling.
1686		2121
1687	=head3 ABI Issues (Largefile Support)	2122	=head3 ABI Issues (Largefile Support)
1688		2123
1689	Libev by default (unless the user overrides this) uses the default	2124	Libev by default (unless the user overrides this) uses the default
1690	compilation environment, which means that on systems with large file	2125	compilation environment, which means that on systems with large file
1691	support disabled by default, you get the 32 bit version of the stat	2126	support disabled by default, you get the 32 bit version of the stat
1692	structure. When using the library from programs that change the ABI to	2127	structure. When using the library from programs that change the ABI to
1693	use 64 bit file offsets the programs will fail. In that case you have to	2128	use 64 bit file offsets the programs will fail. In that case you have to
1694	compile libev with the same flags to get binary compatibility. This is	2129	compile libev with the same flags to get binary compatibility. This is
1695	obviously the case with any flags that change the ABI, but the problem is	2130	obviously the case with any flags that change the ABI, but the problem is
1696	most noticeably disabled with ev_stat and large file support.	2131	most noticeably displayed with ev_stat and large file support.
1697		2132
1698	The solution for this is to lobby your distribution maker to make large	2133	The solution for this is to lobby your distribution maker to make large
1699	file interfaces available by default (as e.g. FreeBSD does) and not	2134	file interfaces available by default (as e.g. FreeBSD does) and not
1700	optional. Libev cannot simply switch on large file support because it has	2135	optional. Libev cannot simply switch on large file support because it has
1701	to exchange stat structures with application programs compiled using the	2136	to exchange stat structures with application programs compiled using the
1702	default compilation environment.	2137	default compilation environment.
1703		2138
1704	=head3 Inotify	2139	=head3 Inotify and Kqueue
1705		2140
1706	When C<inotify (7)> support has been compiled into libev (generally only	2141	When C<inotify (7)> support has been compiled into libev and present at
1707	available on Linux) and present at runtime, it will be used to speed up	2142	runtime, it will be used to speed up change detection where possible. The
1708	change detection where possible. The inotify descriptor will be created lazily	2143	inotify descriptor will be created lazily when the first C<ev_stat>
1709	when the first C<ev_stat> watcher is being started.	2144	watcher is being started.
1710		2145
1711	Inotify presence does not change the semantics of C<ev_stat> watchers	2146	Inotify presence does not change the semantics of C<ev_stat> watchers
1712	except that changes might be detected earlier, and in some cases, to avoid	2147	except that changes might be detected earlier, and in some cases, to avoid
1713	making regular C<stat> calls. Even in the presence of inotify support	2148	making regular C<stat> calls. Even in the presence of inotify support
1714	there are many cases where libev has to resort to regular C<stat> polling.	2149	there are many cases where libev has to resort to regular C<stat> polling,
		2150	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2151	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2152	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2153	xfs are fully working) libev usually gets away without polling.
1715		2154
1716	(There is no support for kqueue, as apparently it cannot be used to	2155	There is no support for kqueue, as apparently it cannot be used to
1717	implement this functionality, due to the requirement of having a file	2156	implement this functionality, due to the requirement of having a file
1718	descriptor open on the object at all times).	2157	descriptor open on the object at all times, and detecting renames, unlinks
		2158	etc. is difficult.
		2159
		2160	=head3 C<stat ()> is a synchronous operation
		2161
		2162	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2163	the process. The exception are C<ev_stat> watchers - those call C<stat
		2164	()>, which is a synchronous operation.
		2165
		2166	For local paths, this usually doesn't matter: unless the system is very
		2167	busy or the intervals between stat's are large, a stat call will be fast,
		2168	as the path data is usually in memory already (except when starting the
		2169	watcher).
		2170
		2171	For networked file systems, calling C<stat ()> can block an indefinite
		2172	time due to network issues, and even under good conditions, a stat call
		2173	often takes multiple milliseconds.
		2174
		2175	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2176	paths, although this is fully supported by libev.
1719		2177
1720	=head3 The special problem of stat time resolution	2178	=head3 The special problem of stat time resolution
1721		2179
1722	The C<stat ()> system call only supports full-second resolution portably, and	2180	The C<stat ()> system call only supports full-second resolution portably,
1723	even on systems where the resolution is higher, many file systems still	2181	and even on systems where the resolution is higher, most file systems
1724	only support whole seconds.	2182	still only support whole seconds.
1725		2183
1726	That means that, if the time is the only thing that changes, you can	2184	That means that, if the time is the only thing that changes, you can
1727	easily miss updates: on the first update, C<ev_stat> detects a change and	2185	easily miss updates: on the first update, C<ev_stat> detects a change and
1728	calls your callback, which does something. When there is another update	2186	calls your callback, which does something. When there is another update
1729	within the same second, C<ev_stat> will be unable to detect it as the stat	2187	within the same second, C<ev_stat> will be unable to detect unless the
1730	data does not change.	2188	stat data does change in other ways (e.g. file size).
1731		2189
1732	The solution to this is to delay acting on a change for slightly more	2190	The solution to this is to delay acting on a change for slightly more
1733	than a second (or till slightly after the next full second boundary), using	2191	than a second (or till slightly after the next full second boundary), using
1734	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2192	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1735	ev_timer_again (loop, w)>).	2193	ev_timer_again (loop, w)>).
…		…
1755	C<path>. The C<interval> is a hint on how quickly a change is expected to	2213	C<path>. The C<interval> is a hint on how quickly a change is expected to
1756	be detected and should normally be specified as C<0> to let libev choose	2214	be detected and should normally be specified as C<0> to let libev choose
1757	a suitable value. The memory pointed to by C<path> must point to the same	2215	a suitable value. The memory pointed to by C<path> must point to the same
1758	path for as long as the watcher is active.	2216	path for as long as the watcher is active.
1759		2217
1760	The callback will receive C<EV_STAT> when a change was detected, relative	2218	The callback will receive an C<EV_STAT> event when a change was detected,
1761	to the attributes at the time the watcher was started (or the last change	2219	relative to the attributes at the time the watcher was started (or the
1762	was detected).	2220	last change was detected).
1763		2221
1764	=item ev_stat_stat (loop, ev_stat *)	2222	=item ev_stat_stat (loop, ev_stat *)
1765		2223
1766	Updates the stat buffer immediately with new values. If you change the	2224	Updates the stat buffer immediately with new values. If you change the
1767	watched path in your callback, you could call this function to avoid	2225	watched path in your callback, you could call this function to avoid
…		…
1850		2308
1851		2309
1852	=head2 C<ev_idle> - when you've got nothing better to do...	2310	=head2 C<ev_idle> - when you've got nothing better to do...
1853		2311
1854	Idle watchers trigger events when no other events of the same or higher	2312	Idle watchers trigger events when no other events of the same or higher
1855	priority are pending (prepare, check and other idle watchers do not	2313	priority are pending (prepare, check and other idle watchers do not count
1856	count).	2314	as receiving "events").
1857		2315
1858	That is, as long as your process is busy handling sockets or timeouts	2316	That is, as long as your process is busy handling sockets or timeouts
1859	(or even signals, imagine) of the same or higher priority it will not be	2317	(or even signals, imagine) of the same or higher priority it will not be
1860	triggered. But when your process is idle (or only lower-priority watchers	2318	triggered. But when your process is idle (or only lower-priority watchers
1861	are pending), the idle watchers are being called once per event loop	2319	are pending), the idle watchers are being called once per event loop
…		…
1872		2330
1873	=head3 Watcher-Specific Functions and Data Members	2331	=head3 Watcher-Specific Functions and Data Members
1874		2332
1875	=over 4	2333	=over 4
1876		2334
1877	=item ev_idle_init (ev_signal *, callback)	2335	=item ev_idle_init (ev_idle *, callback)
1878		2336
1879	Initialises and configures the idle watcher - it has no parameters of any	2337	Initialises and configures the idle watcher - it has no parameters of any
1880	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2338	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1881	believe me.	2339	believe me.
1882		2340
…		…
1886		2344
1887	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2345	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1888	callback, free it. Also, use no error checking, as usual.	2346	callback, free it. Also, use no error checking, as usual.
1889		2347
1890	static void	2348	static void
1891	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2349	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1892	{	2350	{
1893	free (w);	2351	free (w);
1894	// now do something you wanted to do when the program has	2352	// now do something you wanted to do when the program has
1895	// no longer anything immediate to do.	2353	// no longer anything immediate to do.
1896	}	2354	}
1897		2355
1898	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2356	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1899	ev_idle_init (idle_watcher, idle_cb);	2357	ev_idle_init (idle_watcher, idle_cb);
1900	ev_idle_start (loop, idle_cb);	2358	ev_idle_start (loop, idle_cb);
1901		2359
1902		2360
1903	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2361	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1904		2362
1905	Prepare and check watchers are usually (but not always) used in tandem:	2363	Prepare and check watchers are usually (but not always) used in pairs:
1906	prepare watchers get invoked before the process blocks and check watchers	2364	prepare watchers get invoked before the process blocks and check watchers
1907	afterwards.	2365	afterwards.
1908		2366
1909	You I<must not> call C<ev_loop> or similar functions that enter	2367	You I<must not> call C<ev_loop> or similar functions that enter
1910	the current event loop from either C<ev_prepare> or C<ev_check>	2368	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1913	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2371	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1914	C<ev_check> so if you have one watcher of each kind they will always be	2372	C<ev_check> so if you have one watcher of each kind they will always be
1915	called in pairs bracketing the blocking call.	2373	called in pairs bracketing the blocking call.
1916		2374
1917	Their main purpose is to integrate other event mechanisms into libev and	2375	Their main purpose is to integrate other event mechanisms into libev and
1918	their use is somewhat advanced. This could be used, for example, to track	2376	their use is somewhat advanced. They could be used, for example, to track
1919	variable changes, implement your own watchers, integrate net-snmp or a	2377	variable changes, implement your own watchers, integrate net-snmp or a
1920	coroutine library and lots more. They are also occasionally useful if	2378	coroutine library and lots more. They are also occasionally useful if
1921	you cache some data and want to flush it before blocking (for example,	2379	you cache some data and want to flush it before blocking (for example,
1922	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2380	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1923	watcher).	2381	watcher).
1924		2382
1925	This is done by examining in each prepare call which file descriptors need	2383	This is done by examining in each prepare call which file descriptors
1926	to be watched by the other library, registering C<ev_io> watchers for	2384	need to be watched by the other library, registering C<ev_io> watchers
1927	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2385	for them and starting an C<ev_timer> watcher for any timeouts (many
1928	provide just this functionality). Then, in the check watcher you check for	2386	libraries provide exactly this functionality). Then, in the check watcher,
1929	any events that occurred (by checking the pending status of all watchers	2387	you check for any events that occurred (by checking the pending status
1930	and stopping them) and call back into the library. The I/O and timer	2388	of all watchers and stopping them) and call back into the library. The
1931	callbacks will never actually be called (but must be valid nevertheless,	2389	I/O and timer callbacks will never actually be called (but must be valid
1932	because you never know, you know?).	2390	nevertheless, because you never know, you know?).
1933		2391
1934	As another example, the Perl Coro module uses these hooks to integrate	2392	As another example, the Perl Coro module uses these hooks to integrate
1935	coroutines into libev programs, by yielding to other active coroutines	2393	coroutines into libev programs, by yielding to other active coroutines
1936	during each prepare and only letting the process block if no coroutines	2394	during each prepare and only letting the process block if no coroutines
1937	are ready to run (it's actually more complicated: it only runs coroutines	2395	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1940	loop from blocking if lower-priority coroutines are active, thus mapping	2398	loop from blocking if lower-priority coroutines are active, thus mapping
1941	low-priority coroutines to idle/background tasks).	2399	low-priority coroutines to idle/background tasks).
1942		2400
1943	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2401	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1944	priority, to ensure that they are being run before any other watchers	2402	priority, to ensure that they are being run before any other watchers
		2403	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2404
1945	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2405	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1946	too) should not activate ("feed") events into libev. While libev fully	2406	activate ("feed") events into libev. While libev fully supports this, they
1947	supports this, they might get executed before other C<ev_check> watchers	2407	might get executed before other C<ev_check> watchers did their job. As
1948	did their job. As C<ev_check> watchers are often used to embed other	2408	C<ev_check> watchers are often used to embed other (non-libev) event
1949	(non-libev) event loops those other event loops might be in an unusable	2409	loops those other event loops might be in an unusable state until their
1950	state until their C<ev_check> watcher ran (always remind yourself to	2410	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1951	coexist peacefully with others).	2411	others).
1952		2412
1953	=head3 Watcher-Specific Functions and Data Members	2413	=head3 Watcher-Specific Functions and Data Members
1954		2414
1955	=over 4	2415	=over 4
1956		2416
…		…
1958		2418
1959	=item ev_check_init (ev_check *, callback)	2419	=item ev_check_init (ev_check *, callback)
1960		2420
1961	Initialises and configures the prepare or check watcher - they have no	2421	Initialises and configures the prepare or check watcher - they have no
1962	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2422	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1963	macros, but using them is utterly, utterly and completely pointless.	2423	macros, but using them is utterly, utterly, utterly and completely
		2424	pointless.
1964		2425
1965	=back	2426	=back
1966		2427
1967	=head3 Examples	2428	=head3 Examples
1968		2429
…		…
1981		2442
1982	static ev_io iow [nfd];	2443	static ev_io iow [nfd];
1983	static ev_timer tw;	2444	static ev_timer tw;
1984		2445
1985	static void	2446	static void
1986	io_cb (ev_loop *loop, ev_io *w, int revents)	2447	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1987	{	2448	{
1988	}	2449	}
1989		2450
1990	// create io watchers for each fd and a timer before blocking	2451	// create io watchers for each fd and a timer before blocking
1991	static void	2452	static void
1992	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2453	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1993	{	2454	{
1994	int timeout = 3600000;	2455	int timeout = 3600000;
1995	struct pollfd fds [nfd];	2456	struct pollfd fds [nfd];
1996	// actual code will need to loop here and realloc etc.	2457	// actual code will need to loop here and realloc etc.
1997	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2458	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2012	}	2473	}
2013	}	2474	}
2014		2475
2015	// stop all watchers after blocking	2476	// stop all watchers after blocking
2016	static void	2477	static void
2017	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2478	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2018	{	2479	{
2019	ev_timer_stop (loop, &tw);	2480	ev_timer_stop (loop, &tw);
2020		2481
2021	for (int i = 0; i < nfd; ++i)	2482	for (int i = 0; i < nfd; ++i)
2022	{	2483	{
…		…
2061	}	2522	}
2062		2523
2063	// do not ever call adns_afterpoll	2524	// do not ever call adns_afterpoll
2064		2525
2065	Method 4: Do not use a prepare or check watcher because the module you	2526	Method 4: Do not use a prepare or check watcher because the module you
2066	want to embed is too inflexible to support it. Instead, you can override	2527	want to embed is not flexible enough to support it. Instead, you can
2067	their poll function. The drawback with this solution is that the main	2528	override their poll function. The drawback with this solution is that the
2068	loop is now no longer controllable by EV. The C<Glib::EV> module does	2529	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2069	this.	2530	this approach, effectively embedding EV as a client into the horrible
		2531	libglib event loop.
2070		2532
2071	static gint	2533	static gint
2072	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2534	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2073	{	2535	{
2074	int got_events = 0;	2536	int got_events = 0;
…		…
2105	prioritise I/O.	2567	prioritise I/O.
2106		2568
2107	As an example for a bug workaround, the kqueue backend might only support	2569	As an example for a bug workaround, the kqueue backend might only support
2108	sockets on some platform, so it is unusable as generic backend, but you	2570	sockets on some platform, so it is unusable as generic backend, but you
2109	still want to make use of it because you have many sockets and it scales	2571	still want to make use of it because you have many sockets and it scales
2110	so nicely. In this case, you would create a kqueue-based loop and embed it	2572	so nicely. In this case, you would create a kqueue-based loop and embed
2111	into your default loop (which might use e.g. poll). Overall operation will	2573	it into your default loop (which might use e.g. poll). Overall operation
2112	be a bit slower because first libev has to poll and then call kevent, but	2574	will be a bit slower because first libev has to call C<poll> and then
2113	at least you can use both at what they are best.	2575	C<kevent>, but at least you can use both mechanisms for what they are
		2576	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2114		2577
2115	As for prioritising I/O: rarely you have the case where some fds have	2578	As for prioritising I/O: under rare circumstances you have the case where
2116	to be watched and handled very quickly (with low latency), and even	2579	some fds have to be watched and handled very quickly (with low latency),
2117	priorities and idle watchers might have too much overhead. In this case	2580	and even priorities and idle watchers might have too much overhead. In
2118	you would put all the high priority stuff in one loop and all the rest in	2581	this case you would put all the high priority stuff in one loop and all
2119	a second one, and embed the second one in the first.	2582	the rest in a second one, and embed the second one in the first.
2120		2583
2121	As long as the watcher is active, the callback will be invoked every time	2584	As long as the watcher is active, the callback will be invoked every
2122	there might be events pending in the embedded loop. The callback must then	2585	time there might be events pending in the embedded loop. The callback
2123	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2586	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2124	their callbacks (you could also start an idle watcher to give the embedded	2587	sweep and invoke their callbacks (the callback doesn't need to invoke the
2125	loop strictly lower priority for example). You can also set the callback	2588	C<ev_embed_sweep> function directly, it could also start an idle watcher
2126	to C<0>, in which case the embed watcher will automatically execute the	2589	to give the embedded loop strictly lower priority for example).
2127	embedded loop sweep.
2128		2590
2129	As long as the watcher is started it will automatically handle events. The	2591	You can also set the callback to C<0>, in which case the embed watcher
2130	callback will be invoked whenever some events have been handled. You can	2592	will automatically execute the embedded loop sweep whenever necessary.
2131	set the callback to C<0> to avoid having to specify one if you are not
2132	interested in that.
2133		2593
2134	Also, there have not currently been made special provisions for forking:	2594	Fork detection will be handled transparently while the C<ev_embed> watcher
2135	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2595	is active, i.e., the embedded loop will automatically be forked when the
2136	but you will also have to stop and restart any C<ev_embed> watchers	2596	embedding loop forks. In other cases, the user is responsible for calling
2137	yourself.	2597	C<ev_loop_fork> on the embedded loop.
2138		2598
2139	Unfortunately, not all backends are embeddable, only the ones returned by	2599	Unfortunately, not all backends are embeddable: only the ones returned by
2140	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2600	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2141	portable one.	2601	portable one.
2142		2602
2143	So when you want to use this feature you will always have to be prepared	2603	So when you want to use this feature you will always have to be prepared
2144	that you cannot get an embeddable loop. The recommended way to get around	2604	that you cannot get an embeddable loop. The recommended way to get around
2145	this is to have a separate variables for your embeddable loop, try to	2605	this is to have a separate variables for your embeddable loop, try to
2146	create it, and if that fails, use the normal loop for everything.	2606	create it, and if that fails, use the normal loop for everything.
		2607
		2608	=head3 C<ev_embed> and fork
		2609
		2610	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2611	automatically be applied to the embedded loop as well, so no special
		2612	fork handling is required in that case. When the watcher is not running,
		2613	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2614	as applicable.
2147		2615
2148	=head3 Watcher-Specific Functions and Data Members	2616	=head3 Watcher-Specific Functions and Data Members
2149		2617
2150	=over 4	2618	=over 4
2151		2619
…		…
2179	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2647	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2180	used).	2648	used).
2181		2649
2182	struct ev_loop *loop_hi = ev_default_init (0);	2650	struct ev_loop *loop_hi = ev_default_init (0);
2183	struct ev_loop *loop_lo = 0;	2651	struct ev_loop *loop_lo = 0;
2184	struct ev_embed embed;	2652	ev_embed embed;
2185		2653
2186	// see if there is a chance of getting one that works	2654	// see if there is a chance of getting one that works
2187	// (remember that a flags value of 0 means autodetection)	2655	// (remember that a flags value of 0 means autodetection)
2188	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2656	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2189	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2657	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2203	kqueue implementation). Store the kqueue/socket-only event loop in	2671	kqueue implementation). Store the kqueue/socket-only event loop in
2204	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2672	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2205		2673
2206	struct ev_loop *loop = ev_default_init (0);	2674	struct ev_loop *loop = ev_default_init (0);
2207	struct ev_loop *loop_socket = 0;	2675	struct ev_loop *loop_socket = 0;
2208	struct ev_embed embed;	2676	ev_embed embed;
2209		2677
2210	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2678	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2211	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2679	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2212	{	2680	{
2213	ev_embed_init (&embed, 0, loop_socket);	2681	ev_embed_init (&embed, 0, loop_socket);
…		…
2269	is that the author does not know of a simple (or any) algorithm for a	2737	is that the author does not know of a simple (or any) algorithm for a
2270	multiple-writer-single-reader queue that works in all cases and doesn't	2738	multiple-writer-single-reader queue that works in all cases and doesn't
2271	need elaborate support such as pthreads.	2739	need elaborate support such as pthreads.
2272		2740
2273	That means that if you want to queue data, you have to provide your own	2741	That means that if you want to queue data, you have to provide your own
2274	queue. But at least I can tell you would implement locking around your	2742	queue. But at least I can tell you how to implement locking around your
2275	queue:	2743	queue:
2276		2744
2277	=over 4	2745	=over 4
2278		2746
2279	=item queueing from a signal handler context	2747	=item queueing from a signal handler context
2280		2748
2281	To implement race-free queueing, you simply add to the queue in the signal	2749	To implement race-free queueing, you simply add to the queue in the signal
2282	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2750	handler but you block the signal handler in the watcher callback. Here is
2283	some fictitious SIGUSR1 handler:	2751	an example that does that for some fictitious SIGUSR1 handler:
2284		2752
2285	static ev_async mysig;	2753	static ev_async mysig;
2286		2754
2287	static void	2755	static void
2288	sigusr1_handler (void)	2756	sigusr1_handler (void)
…		…
2354	=over 4	2822	=over 4
2355		2823
2356	=item ev_async_init (ev_async *, callback)	2824	=item ev_async_init (ev_async *, callback)
2357		2825
2358	Initialises and configures the async watcher - it has no parameters of any	2826	Initialises and configures the async watcher - it has no parameters of any
2359	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2827	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2360	believe me.	2828	trust me.
2361		2829
2362	=item ev_async_send (loop, ev_async *)	2830	=item ev_async_send (loop, ev_async *)
2363		2831
2364	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2832	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2365	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2833	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2366	C<ev_feed_event>, this call is safe to do in other threads, signal or	2834	C<ev_feed_event>, this call is safe to do from other threads, signal or
2367	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2835	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2368	section below on what exactly this means).	2836	section below on what exactly this means).
2369		2837
		2838	Note that, as with other watchers in libev, multiple events might get
		2839	compressed into a single callback invocation (another way to look at this
		2840	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2841	reset when the event loop detects that).
		2842
2370	This call incurs the overhead of a system call only once per loop iteration,	2843	This call incurs the overhead of a system call only once per event loop
2371	so while the overhead might be noticeable, it doesn't apply to repeated	2844	iteration, so while the overhead might be noticeable, it doesn't apply to
2372	calls to C<ev_async_send>.	2845	repeated calls to C<ev_async_send> for the same event loop.
2373		2846
2374	=item bool = ev_async_pending (ev_async *)	2847	=item bool = ev_async_pending (ev_async *)
2375		2848
2376	Returns a non-zero value when C<ev_async_send> has been called on the	2849	Returns a non-zero value when C<ev_async_send> has been called on the
2377	watcher but the event has not yet been processed (or even noted) by the	2850	watcher but the event has not yet been processed (or even noted) by the
…		…
2380	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2853	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2381	the loop iterates next and checks for the watcher to have become active,	2854	the loop iterates next and checks for the watcher to have become active,
2382	it will reset the flag again. C<ev_async_pending> can be used to very	2855	it will reset the flag again. C<ev_async_pending> can be used to very
2383	quickly check whether invoking the loop might be a good idea.	2856	quickly check whether invoking the loop might be a good idea.
2384		2857
2385	Not that this does I<not> check whether the watcher itself is pending, only	2858	Not that this does I<not> check whether the watcher itself is pending,
2386	whether it has been requested to make this watcher pending.	2859	only whether it has been requested to make this watcher pending: there
		2860	is a time window between the event loop checking and resetting the async
		2861	notification, and the callback being invoked.
2387		2862
2388	=back	2863	=back
2389		2864
2390		2865
2391	=head1 OTHER FUNCTIONS	2866	=head1 OTHER FUNCTIONS
…		…
2395	=over 4	2870	=over 4
2396		2871
2397	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2872	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2398		2873
2399	This function combines a simple timer and an I/O watcher, calls your	2874	This function combines a simple timer and an I/O watcher, calls your
2400	callback on whichever event happens first and automatically stop both	2875	callback on whichever event happens first and automatically stops both
2401	watchers. This is useful if you want to wait for a single event on an fd	2876	watchers. This is useful if you want to wait for a single event on an fd
2402	or timeout without having to allocate/configure/start/stop/free one or	2877	or timeout without having to allocate/configure/start/stop/free one or
2403	more watchers yourself.	2878	more watchers yourself.
2404		2879
2405	If C<fd> is less than 0, then no I/O watcher will be started and events	2880	If C<fd> is less than 0, then no I/O watcher will be started and the
2406	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2881	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2407	C<events> set will be created and started.	2882	the given C<fd> and C<events> set will be created and started.
2408		2883
2409	If C<timeout> is less than 0, then no timeout watcher will be	2884	If C<timeout> is less than 0, then no timeout watcher will be
2410	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2885	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2411	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2886	repeat = 0) will be started. C<0> is a valid timeout.
2412	dubious value.
2413		2887
2414	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2888	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2415	passed an C<revents> set like normal event callbacks (a combination of	2889	passed an C<revents> set like normal event callbacks (a combination of
2416	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2890	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2417	value passed to C<ev_once>:	2891	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2892	a timeout and an io event at the same time - you probably should give io
		2893	events precedence.
		2894
		2895	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2418		2896
2419	static void stdin_ready (int revents, void *arg)	2897	static void stdin_ready (int revents, void *arg)
2420	{	2898	{
		2899	if (revents & EV_READ)
		2900	/* stdin might have data for us, joy! */;
2421	if (revents & EV_TIMEOUT)	2901	else if (revents & EV_TIMEOUT)
2422	/* doh, nothing entered */;	2902	/* doh, nothing entered */;
2423	else if (revents & EV_READ)
2424	/* stdin might have data for us, joy! */;
2425	}	2903	}
2426		2904
2427	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2905	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2428		2906
2429	=item ev_feed_event (ev_loop *, watcher *, int revents)	2907	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2430		2908
2431	Feeds the given event set into the event loop, as if the specified event	2909	Feeds the given event set into the event loop, as if the specified event
2432	had happened for the specified watcher (which must be a pointer to an	2910	had happened for the specified watcher (which must be a pointer to an
2433	initialised but not necessarily started event watcher).	2911	initialised but not necessarily started event watcher).
2434		2912
2435	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2913	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2436		2914
2437	Feed an event on the given fd, as if a file descriptor backend detected	2915	Feed an event on the given fd, as if a file descriptor backend detected
2438	the given events it.	2916	the given events it.
2439		2917
2440	=item ev_feed_signal_event (ev_loop *loop, int signum)	2918	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2441		2919
2442	Feed an event as if the given signal occurred (C<loop> must be the default	2920	Feed an event as if the given signal occurred (C<loop> must be the default
2443	loop!).	2921	loop!).
2444		2922
2445	=back	2923	=back
…		…
2567		3045
2568	myclass obj;	3046	myclass obj;
2569	ev::io iow;	3047	ev::io iow;
2570	iow.set <myclass, &myclass::io_cb> (&obj);	3048	iow.set <myclass, &myclass::io_cb> (&obj);
2571		3049
		3050	=item w->set (object *)
		3051
		3052	This is an B<experimental> feature that might go away in a future version.
		3053
		3054	This is a variation of a method callback - leaving out the method to call
		3055	will default the method to C<operator ()>, which makes it possible to use
		3056	functor objects without having to manually specify the C<operator ()> all
		3057	the time. Incidentally, you can then also leave out the template argument
		3058	list.
		3059
		3060	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3061	int revents)>.
		3062
		3063	See the method-C<set> above for more details.
		3064
		3065	Example: use a functor object as callback.
		3066
		3067	struct myfunctor
		3068	{
		3069	void operator() (ev::io &w, int revents)
		3070	{
		3071	...
		3072	}
		3073	}
		3074
		3075	myfunctor f;
		3076
		3077	ev::io w;
		3078	w.set (&f);
		3079
2572	=item w->set<function> (void *data = 0)	3080	=item w->set<function> (void *data = 0)
2573		3081
2574	Also sets a callback, but uses a static method or plain function as	3082	Also sets a callback, but uses a static method or plain function as
2575	callback. The optional C<data> argument will be stored in the watcher's	3083	callback. The optional C<data> argument will be stored in the watcher's
2576	C<data> member and is free for you to use.	3084	C<data> member and is free for you to use.
2577		3085
2578	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3086	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2579		3087
2580	See the method-C<set> above for more details.	3088	See the method-C<set> above for more details.
2581		3089
2582	Example:	3090	Example: Use a plain function as callback.
2583		3091
2584	static void io_cb (ev::io &w, int revents) { }	3092	static void io_cb (ev::io &w, int revents) { }
2585	iow.set <io_cb> ();	3093	iow.set <io_cb> ();
2586		3094
2587	=item w->set (struct ev_loop *)	3095	=item w->set (struct ev_loop *)
…		…
2625	Example: Define a class with an IO and idle watcher, start one of them in	3133	Example: Define a class with an IO and idle watcher, start one of them in
2626	the constructor.	3134	the constructor.
2627		3135
2628	class myclass	3136	class myclass
2629	{	3137	{
2630	ev::io io; void io_cb (ev::io &w, int revents);	3138	ev::io io ; void io_cb (ev::io &w, int revents);
2631	ev:idle idle void idle_cb (ev::idle &w, int revents);	3139	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2632		3140
2633	myclass (int fd)	3141	myclass (int fd)
2634	{	3142	{
2635	io .set <myclass, &myclass::io_cb > (this);	3143	io .set <myclass, &myclass::io_cb > (this);
2636	idle.set <myclass, &myclass::idle_cb> (this);	3144	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2652	=item Perl	3160	=item Perl
2653		3161
2654	The EV module implements the full libev API and is actually used to test	3162	The EV module implements the full libev API and is actually used to test
2655	libev. EV is developed together with libev. Apart from the EV core module,	3163	libev. EV is developed together with libev. Apart from the EV core module,
2656	there are additional modules that implement libev-compatible interfaces	3164	there are additional modules that implement libev-compatible interfaces
2657	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3165	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2658	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3166	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3167	and C<EV::Glib>).
2659		3168
2660	It can be found and installed via CPAN, its homepage is at	3169	It can be found and installed via CPAN, its homepage is at
2661	L<http://software.schmorp.de/pkg/EV>.	3170	L<http://software.schmorp.de/pkg/EV>.
2662		3171
2663	=item Python	3172	=item Python
2664		3173
2665	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3174	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2666	seems to be quite complete and well-documented. Note, however, that the	3175	seems to be quite complete and well-documented.
2667	patch they require for libev is outright dangerous as it breaks the ABI
2668	for everybody else, and therefore, should never be applied in an installed
2669	libev (if python requires an incompatible ABI then it needs to embed
2670	libev).
2671		3176
2672	=item Ruby	3177	=item Ruby
2673		3178
2674	Tony Arcieri has written a ruby extension that offers access to a subset	3179	Tony Arcieri has written a ruby extension that offers access to a subset
2675	of the libev API and adds file handle abstractions, asynchronous DNS and	3180	of the libev API and adds file handle abstractions, asynchronous DNS and
2676	more on top of it. It can be found via gem servers. Its homepage is at	3181	more on top of it. It can be found via gem servers. Its homepage is at
2677	L<http://rev.rubyforge.org/>.	3182	L<http://rev.rubyforge.org/>.
2678		3183
		3184	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3185	makes rev work even on mingw.
		3186
		3187	=item Haskell
		3188
		3189	A haskell binding to libev is available at
		3190	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3191
2679	=item D	3192	=item D
2680		3193
2681	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3194	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2682	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3195	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3196
		3197	=item Ocaml
		3198
		3199	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3200	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2683		3201
2684	=back	3202	=back
2685		3203
2686		3204
2687	=head1 MACRO MAGIC	3205	=head1 MACRO MAGIC
…		…
2788		3306
2789	#define EV_STANDALONE 1	3307	#define EV_STANDALONE 1
2790	#include "ev.h"	3308	#include "ev.h"
2791		3309
2792	Both header files and implementation files can be compiled with a C++	3310	Both header files and implementation files can be compiled with a C++
2793	compiler (at least, thats a stated goal, and breakage will be treated	3311	compiler (at least, that's a stated goal, and breakage will be treated
2794	as a bug).	3312	as a bug).
2795		3313
2796	You need the following files in your source tree, or in a directory	3314	You need the following files in your source tree, or in a directory
2797	in your include path (e.g. in libev/ when using -Ilibev):	3315	in your include path (e.g. in libev/ when using -Ilibev):
2798		3316
…		…
2842		3360
2843	=head2 PREPROCESSOR SYMBOLS/MACROS	3361	=head2 PREPROCESSOR SYMBOLS/MACROS
2844		3362
2845	Libev can be configured via a variety of preprocessor symbols you have to	3363	Libev can be configured via a variety of preprocessor symbols you have to
2846	define before including any of its files. The default in the absence of	3364	define before including any of its files. The default in the absence of
2847	autoconf is noted for every option.	3365	autoconf is documented for every option.
2848		3366
2849	=over 4	3367	=over 4
2850		3368
2851	=item EV_STANDALONE	3369	=item EV_STANDALONE
2852		3370
…		…
2854	keeps libev from including F<config.h>, and it also defines dummy	3372	keeps libev from including F<config.h>, and it also defines dummy
2855	implementations for some libevent functions (such as logging, which is not	3373	implementations for some libevent functions (such as logging, which is not
2856	supported). It will also not define any of the structs usually found in	3374	supported). It will also not define any of the structs usually found in
2857	F<event.h> that are not directly supported by the libev core alone.	3375	F<event.h> that are not directly supported by the libev core alone.
2858		3376
		3377	In stanbdalone mode, libev will still try to automatically deduce the
		3378	configuration, but has to be more conservative.
		3379
2859	=item EV_USE_MONOTONIC	3380	=item EV_USE_MONOTONIC
2860		3381
2861	If defined to be C<1>, libev will try to detect the availability of the	3382	If defined to be C<1>, libev will try to detect the availability of the
2862	monotonic clock option at both compile time and runtime. Otherwise no use	3383	monotonic clock option at both compile time and runtime. Otherwise no
2863	of the monotonic clock option will be attempted. If you enable this, you	3384	use of the monotonic clock option will be attempted. If you enable this,
2864	usually have to link against librt or something similar. Enabling it when	3385	you usually have to link against librt or something similar. Enabling it
2865	the functionality isn't available is safe, though, although you have	3386	when the functionality isn't available is safe, though, although you have
2866	to make sure you link against any libraries where the C<clock_gettime>	3387	to make sure you link against any libraries where the C<clock_gettime>
2867	function is hiding in (often F<-lrt>).	3388	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2868		3389
2869	=item EV_USE_REALTIME	3390	=item EV_USE_REALTIME
2870		3391
2871	If defined to be C<1>, libev will try to detect the availability of the	3392	If defined to be C<1>, libev will try to detect the availability of the
2872	real-time clock option at compile time (and assume its availability at	3393	real-time clock option at compile time (and assume its availability
2873	runtime if successful). Otherwise no use of the real-time clock option will	3394	at runtime if successful). Otherwise no use of the real-time clock
2874	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3395	option will be attempted. This effectively replaces C<gettimeofday>
2875	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3396	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2876	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3397	correctness. See the note about libraries in the description of
		3398	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3399	C<EV_USE_CLOCK_SYSCALL>.
		3400
		3401	=item EV_USE_CLOCK_SYSCALL
		3402
		3403	If defined to be C<1>, libev will try to use a direct syscall instead
		3404	of calling the system-provided C<clock_gettime> function. This option
		3405	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3406	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3407	programs needlessly. Using a direct syscall is slightly slower (in
		3408	theory), because no optimised vdso implementation can be used, but avoids
		3409	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3410	higher, as it simplifies linking (no need for C<-lrt>).
2877		3411
2878	=item EV_USE_NANOSLEEP	3412	=item EV_USE_NANOSLEEP
2879		3413
2880	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3414	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2881	and will use it for delays. Otherwise it will use C<select ()>.	3415	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2897		3431
2898	=item EV_SELECT_USE_FD_SET	3432	=item EV_SELECT_USE_FD_SET
2899		3433
2900	If defined to C<1>, then the select backend will use the system C<fd_set>	3434	If defined to C<1>, then the select backend will use the system C<fd_set>
2901	structure. This is useful if libev doesn't compile due to a missing	3435	structure. This is useful if libev doesn't compile due to a missing
2902	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3436	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2903	exotic systems. This usually limits the range of file descriptors to some	3437	on exotic systems. This usually limits the range of file descriptors to
2904	low limit such as 1024 or might have other limitations (winsocket only	3438	some low limit such as 1024 or might have other limitations (winsocket
2905	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3439	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2906	influence the size of the C<fd_set> used.	3440	configures the maximum size of the C<fd_set>.
2907		3441
2908	=item EV_SELECT_IS_WINSOCKET	3442	=item EV_SELECT_IS_WINSOCKET
2909		3443
2910	When defined to C<1>, the select backend will assume that	3444	When defined to C<1>, the select backend will assume that
2911	select/socket/connect etc. don't understand file descriptors but	3445	select/socket/connect etc. don't understand file descriptors but
…		…
3022	When doing priority-based operations, libev usually has to linearly search	3556	When doing priority-based operations, libev usually has to linearly search
3023	all the priorities, so having many of them (hundreds) uses a lot of space	3557	all the priorities, so having many of them (hundreds) uses a lot of space
3024	and time, so using the defaults of five priorities (-2 .. +2) is usually	3558	and time, so using the defaults of five priorities (-2 .. +2) is usually
3025	fine.	3559	fine.
3026		3560
3027	If your embedding application does not need any priorities, defining these both to	3561	If your embedding application does not need any priorities, defining these
3028	C<0> will save some memory and CPU.	3562	both to C<0> will save some memory and CPU.
3029		3563
3030	=item EV_PERIODIC_ENABLE	3564	=item EV_PERIODIC_ENABLE
3031		3565
3032	If undefined or defined to be C<1>, then periodic timers are supported. If	3566	If undefined or defined to be C<1>, then periodic timers are supported. If
3033	defined to be C<0>, then they are not. Disabling them saves a few kB of	3567	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3040	code.	3574	code.
3041		3575
3042	=item EV_EMBED_ENABLE	3576	=item EV_EMBED_ENABLE
3043		3577
3044	If undefined or defined to be C<1>, then embed watchers are supported. If	3578	If undefined or defined to be C<1>, then embed watchers are supported. If
3045	defined to be C<0>, then they are not.	3579	defined to be C<0>, then they are not. Embed watchers rely on most other
		3580	watcher types, which therefore must not be disabled.
3046		3581
3047	=item EV_STAT_ENABLE	3582	=item EV_STAT_ENABLE
3048		3583
3049	If undefined or defined to be C<1>, then stat watchers are supported. If	3584	If undefined or defined to be C<1>, then stat watchers are supported. If
3050	defined to be C<0>, then they are not.	3585	defined to be C<0>, then they are not.
…		…
3082	two).	3617	two).
3083		3618
3084	=item EV_USE_4HEAP	3619	=item EV_USE_4HEAP
3085		3620
3086	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3621	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3087	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3622	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3088	to C<1>. The 4-heap uses more complicated (longer) code but has	3623	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3089	noticeably faster performance with many (thousands) of watchers.	3624	faster performance with many (thousands) of watchers.
3090		3625
3091	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3626	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3092	(disabled).	3627	(disabled).
3093		3628
3094	=item EV_HEAP_CACHE_AT	3629	=item EV_HEAP_CACHE_AT
3095		3630
3096	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3631	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3097	timer and periodics heap, libev can cache the timestamp (I<at>) within	3632	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3098	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3633	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3099	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3634	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3100	but avoids random read accesses on heap changes. This improves performance	3635	but avoids random read accesses on heap changes. This improves performance
3101	noticeably with with many (hundreds) of watchers.	3636	noticeably with many (hundreds) of watchers.
3102		3637
3103	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3638	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3104	(disabled).	3639	(disabled).
3105		3640
3106	=item EV_VERIFY	3641	=item EV_VERIFY
…		…
3112	called once per loop, which can slow down libev. If set to C<3>, then the	3647	called once per loop, which can slow down libev. If set to C<3>, then the
3113	verification code will be called very frequently, which will slow down	3648	verification code will be called very frequently, which will slow down
3114	libev considerably.	3649	libev considerably.
3115		3650
3116	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3651	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3117	C<0.>	3652	C<0>.
3118		3653
3119	=item EV_COMMON	3654	=item EV_COMMON
3120		3655
3121	By default, all watchers have a C<void *data> member. By redefining	3656	By default, all watchers have a C<void *data> member. By redefining
3122	this macro to a something else you can include more and other types of	3657	this macro to a something else you can include more and other types of
…		…
3139	and the way callbacks are invoked and set. Must expand to a struct member	3674	and the way callbacks are invoked and set. Must expand to a struct member
3140	definition and a statement, respectively. See the F<ev.h> header file for	3675	definition and a statement, respectively. See the F<ev.h> header file for
3141	their default definitions. One possible use for overriding these is to	3676	their default definitions. One possible use for overriding these is to
3142	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3677	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3143	method calls instead of plain function calls in C++.	3678	method calls instead of plain function calls in C++.
		3679
		3680	=back
3144		3681
3145	=head2 EXPORTED API SYMBOLS	3682	=head2 EXPORTED API SYMBOLS
3146		3683
3147	If you need to re-export the API (e.g. via a DLL) and you need a list of	3684	If you need to re-export the API (e.g. via a DLL) and you need a list of
3148	exported symbols, you can use the provided F<Symbol.*> files which list	3685	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3195	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3732	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3196		3733
3197	#include "ev_cpp.h"	3734	#include "ev_cpp.h"
3198	#include "ev.c"	3735	#include "ev.c"
3199		3736
		3737	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3200		3738
3201	=head1 THREADS AND COROUTINES	3739	=head2 THREADS AND COROUTINES
3202		3740
3203	=head2 THREADS	3741	=head3 THREADS
3204		3742
3205	Libev itself is completely thread-safe, but it uses no locking. This	3743	All libev functions are reentrant and thread-safe unless explicitly
		3744	documented otherwise, but libev implements no locking itself. This means
3206	means that you can use as many loops as you want in parallel, as long as	3745	that you can use as many loops as you want in parallel, as long as there
3207	only one thread ever calls into one libev function with the same loop	3746	are no concurrent calls into any libev function with the same loop
3208	parameter.	3747	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3748	of course): libev guarantees that different event loops share no data
		3749	structures that need any locking.
3209		3750
3210	Or put differently: calls with different loop parameters can be done in	3751	Or to put it differently: calls with different loop parameters can be done
3211	parallel from multiple threads, calls with the same loop parameter must be	3752	concurrently from multiple threads, calls with the same loop parameter
3212	done serially (but can be done from different threads, as long as only one	3753	must be done serially (but can be done from different threads, as long as
3213	thread ever is inside a call at any point in time, e.g. by using a mutex	3754	only one thread ever is inside a call at any point in time, e.g. by using
3214	per loop).	3755	a mutex per loop).
		3756
		3757	Specifically to support threads (and signal handlers), libev implements
		3758	so-called C<ev_async> watchers, which allow some limited form of
		3759	concurrency on the same event loop, namely waking it up "from the
		3760	outside".
3215		3761
3216	If you want to know which design (one loop, locking, or multiple loops	3762	If you want to know which design (one loop, locking, or multiple loops
3217	without or something else still) is best for your problem, then I cannot	3763	without or something else still) is best for your problem, then I cannot
3218	help you. I can give some generic advice however:	3764	help you, but here is some generic advice:
3219		3765
3220	=over 4	3766	=over 4
3221		3767
3222	=item * most applications have a main thread: use the default libev loop	3768	=item * most applications have a main thread: use the default libev loop
3223	in that thread, or create a separate thread running only the default loop.	3769	in that thread, or create a separate thread running only the default loop.
…		…
3235		3781
3236	Choosing a model is hard - look around, learn, know that usually you can do	3782	Choosing a model is hard - look around, learn, know that usually you can do
3237	better than you currently do :-)	3783	better than you currently do :-)
3238		3784
3239	=item * often you need to talk to some other thread which blocks in the	3785	=item * often you need to talk to some other thread which blocks in the
		3786	event loop.
		3787
3240	event loop - C<ev_async> watchers can be used to wake them up from other	3788	C<ev_async> watchers can be used to wake them up from other threads safely
3241	threads safely (or from signal contexts...).	3789	(or from signal contexts...).
		3790
		3791	An example use would be to communicate signals or other events that only
		3792	work in the default loop by registering the signal watcher with the
		3793	default loop and triggering an C<ev_async> watcher from the default loop
		3794	watcher callback into the event loop interested in the signal.
3242		3795
3243	=back	3796	=back
3244		3797
3245	=head2 COROUTINES	3798	=head3 COROUTINES
3246		3799
3247	Libev is much more accommodating to coroutines ("cooperative threads"):	3800	Libev is very accommodating to coroutines ("cooperative threads"):
3248	libev fully supports nesting calls to it's functions from different	3801	libev fully supports nesting calls to its functions from different
3249	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3802	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3250	different coroutines and switch freely between both coroutines running the	3803	different coroutines, and switch freely between both coroutines running the
3251	loop, as long as you don't confuse yourself). The only exception is that	3804	loop, as long as you don't confuse yourself). The only exception is that
3252	you must not do this from C<ev_periodic> reschedule callbacks.	3805	you must not do this from C<ev_periodic> reschedule callbacks.
3253		3806
3254	Care has been invested into making sure that libev does not keep local	3807	Care has been taken to ensure that libev does not keep local state inside
3255	state inside C<ev_loop>, and other calls do not usually allow coroutine	3808	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3256	switches.	3809	they do not call any callbacks.
3257		3810
		3811	=head2 COMPILER WARNINGS
3258		3812
3259	=head1 COMPLEXITIES	3813	Depending on your compiler and compiler settings, you might get no or a
		3814	lot of warnings when compiling libev code. Some people are apparently
		3815	scared by this.
3260		3816
3261	In this section the complexities of (many of) the algorithms used inside	3817	However, these are unavoidable for many reasons. For one, each compiler
3262	libev will be explained. For complexity discussions about backends see the	3818	has different warnings, and each user has different tastes regarding
3263	documentation for C<ev_default_init>.	3819	warning options. "Warn-free" code therefore cannot be a goal except when
		3820	targeting a specific compiler and compiler-version.
3264		3821
3265	All of the following are about amortised time: If an array needs to be	3822	Another reason is that some compiler warnings require elaborate
3266	extended, libev needs to realloc and move the whole array, but this	3823	workarounds, or other changes to the code that make it less clear and less
3267	happens asymptotically never with higher number of elements, so O(1) might	3824	maintainable.
3268	mean it might do a lengthy realloc operation in rare cases, but on average
3269	it is much faster and asymptotically approaches constant time.
3270		3825
3271	=over 4	3826	And of course, some compiler warnings are just plain stupid, or simply
		3827	wrong (because they don't actually warn about the condition their message
		3828	seems to warn about). For example, certain older gcc versions had some
		3829	warnings that resulted an extreme number of false positives. These have
		3830	been fixed, but some people still insist on making code warn-free with
		3831	such buggy versions.
3272		3832
3273	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3833	While libev is written to generate as few warnings as possible,
		3834	"warn-free" code is not a goal, and it is recommended not to build libev
		3835	with any compiler warnings enabled unless you are prepared to cope with
		3836	them (e.g. by ignoring them). Remember that warnings are just that:
		3837	warnings, not errors, or proof of bugs.
3274		3838
3275	This means that, when you have a watcher that triggers in one hour and
3276	there are 100 watchers that would trigger before that then inserting will
3277	have to skip roughly seven (C<ld 100>) of these watchers.
3278		3839
3279	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3840	=head2 VALGRIND
3280		3841
3281	That means that changing a timer costs less than removing/adding them	3842	Valgrind has a special section here because it is a popular tool that is
3282	as only the relative motion in the event queue has to be paid for.	3843	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3283		3844
3284	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3845	If you think you found a bug (memory leak, uninitialised data access etc.)
		3846	in libev, then check twice: If valgrind reports something like:
3285		3847
3286	These just add the watcher into an array or at the head of a list.	3848	==2274== definitely lost: 0 bytes in 0 blocks.
		3849	==2274== possibly lost: 0 bytes in 0 blocks.
		3850	==2274== still reachable: 256 bytes in 1 blocks.
3287		3851
3288	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3852	Then there is no memory leak, just as memory accounted to global variables
		3853	is not a memleak - the memory is still being referenced, and didn't leak.
3289		3854
3290	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3855	Similarly, under some circumstances, valgrind might report kernel bugs
		3856	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3857	although an acceptable workaround has been found here), or it might be
		3858	confused.
3291		3859
3292	These watchers are stored in lists then need to be walked to find the	3860	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3293	correct watcher to remove. The lists are usually short (you don't usually	3861	make it into some kind of religion.
3294	have many watchers waiting for the same fd or signal).
3295		3862
3296	=item Finding the next timer in each loop iteration: O(1)	3863	If you are unsure about something, feel free to contact the mailing list
		3864	with the full valgrind report and an explanation on why you think this
		3865	is a bug in libev (best check the archives, too :). However, don't be
		3866	annoyed when you get a brisk "this is no bug" answer and take the chance
		3867	of learning how to interpret valgrind properly.
3297		3868
3298	By virtue of using a binary or 4-heap, the next timer is always found at a	3869	If you need, for some reason, empty reports from valgrind for your project
3299	fixed position in the storage array.	3870	I suggest using suppression lists.
3300		3871
3301	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3302		3872
3303	A change means an I/O watcher gets started or stopped, which requires	3873	=head1 PORTABILITY NOTES
3304	libev to recalculate its status (and possibly tell the kernel, depending
3305	on backend and whether C<ev_io_set> was used).
3306		3874
3307	=item Activating one watcher (putting it into the pending state): O(1)
3308
3309	=item Priority handling: O(number_of_priorities)
3310
3311	Priorities are implemented by allocating some space for each
3312	priority. When doing priority-based operations, libev usually has to
3313	linearly search all the priorities, but starting/stopping and activating
3314	watchers becomes O(1) w.r.t. priority handling.
3315
3316	=item Sending an ev_async: O(1)
3317
3318	=item Processing ev_async_send: O(number_of_async_watchers)
3319
3320	=item Processing signals: O(max_signal_number)
3321
3322	Sending involves a system call I<iff> there were no other C<ev_async_send>
3323	calls in the current loop iteration. Checking for async and signal events
3324	involves iterating over all running async watchers or all signal numbers.
3325
3326	=back
3327
3328
3329	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3875	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3330		3876
3331	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3877	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3332	requires, and its I/O model is fundamentally incompatible with the POSIX	3878	requires, and its I/O model is fundamentally incompatible with the POSIX
3333	model. Libev still offers limited functionality on this platform in	3879	model. Libev still offers limited functionality on this platform in
3334	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3880	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3345		3891
3346	Not a libev limitation but worth mentioning: windows apparently doesn't	3892	Not a libev limitation but worth mentioning: windows apparently doesn't
3347	accept large writes: instead of resulting in a partial write, windows will	3893	accept large writes: instead of resulting in a partial write, windows will
3348	either accept everything or return C<ENOBUFS> if the buffer is too large,	3894	either accept everything or return C<ENOBUFS> if the buffer is too large,
3349	so make sure you only write small amounts into your sockets (less than a	3895	so make sure you only write small amounts into your sockets (less than a
3350	megabyte seems safe, but thsi apparently depends on the amount of memory	3896	megabyte seems safe, but this apparently depends on the amount of memory
3351	available).	3897	available).
3352		3898
3353	Due to the many, low, and arbitrary limits on the win32 platform and	3899	Due to the many, low, and arbitrary limits on the win32 platform and
3354	the abysmal performance of winsockets, using a large number of sockets	3900	the abysmal performance of winsockets, using a large number of sockets
3355	is not recommended (and not reasonable). If your program needs to use	3901	is not recommended (and not reasonable). If your program needs to use
…		…
3366	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3912	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3367		3913
3368	#include "ev.h"	3914	#include "ev.h"
3369		3915
3370	And compile the following F<evwrap.c> file into your project (make sure	3916	And compile the following F<evwrap.c> file into your project (make sure
3371	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3917	you do I<not> compile the F<ev.c> or any other embedded source files!):
3372		3918
3373	#include "evwrap.h"	3919	#include "evwrap.h"
3374	#include "ev.c"	3920	#include "ev.c"
3375		3921
3376	=over 4	3922	=over 4
…		…
3421	wrap all I/O functions and provide your own fd management, but the cost of	3967	wrap all I/O functions and provide your own fd management, but the cost of
3422	calling select (O(n²)) will likely make this unworkable.	3968	calling select (O(n²)) will likely make this unworkable.
3423		3969
3424	=back	3970	=back
3425		3971
3426
3427	=head1 PORTABILITY REQUIREMENTS	3972	=head2 PORTABILITY REQUIREMENTS
3428		3973
3429	In addition to a working ISO-C implementation, libev relies on a few	3974	In addition to a working ISO-C implementation and of course the
3430	additional extensions:	3975	backend-specific APIs, libev relies on a few additional extensions:
3431		3976
3432	=over 4	3977	=over 4
3433		3978
3434	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3979	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3435	calling conventions regardless of C<ev_watcher_type *>.	3980	calling conventions regardless of C<ev_watcher_type *>.
…		…
3441	calls them using an C<ev_watcher *> internally.	3986	calls them using an C<ev_watcher *> internally.
3442		3987
3443	=item C<sig_atomic_t volatile> must be thread-atomic as well	3988	=item C<sig_atomic_t volatile> must be thread-atomic as well
3444		3989
3445	The type C<sig_atomic_t volatile> (or whatever is defined as	3990	The type C<sig_atomic_t volatile> (or whatever is defined as
3446	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3991	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3447	threads. This is not part of the specification for C<sig_atomic_t>, but is	3992	threads. This is not part of the specification for C<sig_atomic_t>, but is
3448	believed to be sufficiently portable.	3993	believed to be sufficiently portable.
3449		3994
3450	=item C<sigprocmask> must work in a threaded environment	3995	=item C<sigprocmask> must work in a threaded environment
3451		3996
…		…
3460	except the initial one, and run the default loop in the initial thread as	4005	except the initial one, and run the default loop in the initial thread as
3461	well.	4006	well.
3462		4007
3463	=item C<long> must be large enough for common memory allocation sizes	4008	=item C<long> must be large enough for common memory allocation sizes
3464		4009
3465	To improve portability and simplify using libev, libev uses C<long>	4010	To improve portability and simplify its API, libev uses C<long> internally
3466	internally instead of C<size_t> when allocating its data structures. On	4011	instead of C<size_t> when allocating its data structures. On non-POSIX
3467	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4012	systems (Microsoft...) this might be unexpectedly low, but is still at
3468	is still at least 31 bits everywhere, which is enough for hundreds of	4013	least 31 bits everywhere, which is enough for hundreds of millions of
3469	millions of watchers.	4014	watchers.
3470		4015
3471	=item C<double> must hold a time value in seconds with enough accuracy	4016	=item C<double> must hold a time value in seconds with enough accuracy
3472		4017
3473	The type C<double> is used to represent timestamps. It is required to	4018	The type C<double> is used to represent timestamps. It is required to
3474	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4019	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3478	=back	4023	=back
3479		4024
3480	If you know of other additional requirements drop me a note.	4025	If you know of other additional requirements drop me a note.
3481		4026
3482		4027
3483	=head1 COMPILER WARNINGS	4028	=head1 ALGORITHMIC COMPLEXITIES
3484		4029
3485	Depending on your compiler and compiler settings, you might get no or a	4030	In this section the complexities of (many of) the algorithms used inside
3486	lot of warnings when compiling libev code. Some people are apparently	4031	libev will be documented. For complexity discussions about backends see
3487	scared by this.	4032	the documentation for C<ev_default_init>.
3488		4033
3489	However, these are unavoidable for many reasons. For one, each compiler	4034	All of the following are about amortised time: If an array needs to be
3490	has different warnings, and each user has different tastes regarding	4035	extended, libev needs to realloc and move the whole array, but this
3491	warning options. "Warn-free" code therefore cannot be a goal except when	4036	happens asymptotically rarer with higher number of elements, so O(1) might
3492	targeting a specific compiler and compiler-version.	4037	mean that libev does a lengthy realloc operation in rare cases, but on
		4038	average it is much faster and asymptotically approaches constant time.
3493		4039
3494	Another reason is that some compiler warnings require elaborate	4040	=over 4
3495	workarounds, or other changes to the code that make it less clear and less
3496	maintainable.
3497		4041
3498	And of course, some compiler warnings are just plain stupid, or simply	4042	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3499	wrong (because they don't actually warn about the condition their message
3500	seems to warn about).
3501		4043
3502	While libev is written to generate as few warnings as possible,	4044	This means that, when you have a watcher that triggers in one hour and
3503	"warn-free" code is not a goal, and it is recommended not to build libev	4045	there are 100 watchers that would trigger before that, then inserting will
3504	with any compiler warnings enabled unless you are prepared to cope with	4046	have to skip roughly seven (C<ld 100>) of these watchers.
3505	them (e.g. by ignoring them). Remember that warnings are just that:
3506	warnings, not errors, or proof of bugs.
3507		4047
		4048	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3508		4049
3509	=head1 VALGRIND	4050	That means that changing a timer costs less than removing/adding them,
		4051	as only the relative motion in the event queue has to be paid for.
3510		4052
3511	Valgrind has a special section here because it is a popular tool that is	4053	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3512	highly useful, but valgrind reports are very hard to interpret.
3513		4054
3514	If you think you found a bug (memory leak, uninitialised data access etc.)	4055	These just add the watcher into an array or at the head of a list.
3515	in libev, then check twice: If valgrind reports something like:
3516		4056
3517	==2274== definitely lost: 0 bytes in 0 blocks.	4057	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3518	==2274== possibly lost: 0 bytes in 0 blocks.
3519	==2274== still reachable: 256 bytes in 1 blocks.
3520		4058
3521	Then there is no memory leak. Similarly, under some circumstances,	4059	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3522	valgrind might report kernel bugs as if it were a bug in libev, or it
3523	might be confused (it is a very good tool, but only a tool).
3524		4060
3525	If you are unsure about something, feel free to contact the mailing list	4061	These watchers are stored in lists, so they need to be walked to find the
3526	with the full valgrind report and an explanation on why you think this is	4062	correct watcher to remove. The lists are usually short (you don't usually
3527	a bug in libev. However, don't be annoyed when you get a brisk "this is	4063	have many watchers waiting for the same fd or signal: one is typical, two
3528	no bug" answer and take the chance of learning how to interpret valgrind	4064	is rare).
3529	properly.
3530		4065
3531	If you need, for some reason, empty reports from valgrind for your project	4066	=item Finding the next timer in each loop iteration: O(1)
3532	I suggest using suppression lists.
3533		4067
		4068	By virtue of using a binary or 4-heap, the next timer is always found at a
		4069	fixed position in the storage array.
		4070
		4071	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4072
		4073	A change means an I/O watcher gets started or stopped, which requires
		4074	libev to recalculate its status (and possibly tell the kernel, depending
		4075	on backend and whether C<ev_io_set> was used).
		4076
		4077	=item Activating one watcher (putting it into the pending state): O(1)
		4078
		4079	=item Priority handling: O(number_of_priorities)
		4080
		4081	Priorities are implemented by allocating some space for each
		4082	priority. When doing priority-based operations, libev usually has to
		4083	linearly search all the priorities, but starting/stopping and activating
		4084	watchers becomes O(1) with respect to priority handling.
		4085
		4086	=item Sending an ev_async: O(1)
		4087
		4088	=item Processing ev_async_send: O(number_of_async_watchers)
		4089
		4090	=item Processing signals: O(max_signal_number)
		4091
		4092	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4093	calls in the current loop iteration. Checking for async and signal events
		4094	involves iterating over all running async watchers or all signal numbers.
		4095
		4096	=back
		4097
		4098
		4099	=head1 GLOSSARY
		4100
		4101	=over 4
		4102
		4103	=item active
		4104
		4105	A watcher is active as long as it has been started (has been attached to
		4106	an event loop) but not yet stopped (disassociated from the event loop).
		4107
		4108	=item application
		4109
		4110	In this document, an application is whatever is using libev.
		4111
		4112	=item callback
		4113
		4114	The address of a function that is called when some event has been
		4115	detected. Callbacks are being passed the event loop, the watcher that
		4116	received the event, and the actual event bitset.
		4117
		4118	=item callback invocation
		4119
		4120	The act of calling the callback associated with a watcher.
		4121
		4122	=item event
		4123
		4124	A change of state of some external event, such as data now being available
		4125	for reading on a file descriptor, time having passed or simply not having
		4126	any other events happening anymore.
		4127
		4128	In libev, events are represented as single bits (such as C<EV_READ> or
		4129	C<EV_TIMEOUT>).
		4130
		4131	=item event library
		4132
		4133	A software package implementing an event model and loop.
		4134
		4135	=item event loop
		4136
		4137	An entity that handles and processes external events and converts them
		4138	into callback invocations.
		4139
		4140	=item event model
		4141
		4142	The model used to describe how an event loop handles and processes
		4143	watchers and events.
		4144
		4145	=item pending
		4146
		4147	A watcher is pending as soon as the corresponding event has been detected,
		4148	and stops being pending as soon as the watcher will be invoked or its
		4149	pending status is explicitly cleared by the application.
		4150
		4151	A watcher can be pending, but not active. Stopping a watcher also clears
		4152	its pending status.
		4153
		4154	=item real time
		4155
		4156	The physical time that is observed. It is apparently strictly monotonic :)
		4157
		4158	=item wall-clock time
		4159
		4160	The time and date as shown on clocks. Unlike real time, it can actually
		4161	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4162	clock.
		4163
		4164	=item watcher
		4165
		4166	A data structure that describes interest in certain events. Watchers need
		4167	to be started (attached to an event loop) before they can receive events.
		4168
		4169	=item watcher invocation
		4170
		4171	The act of calling the callback associated with a watcher.
		4172
		4173	=back
3534		4174
3535	=head1 AUTHOR	4175	=head1 AUTHOR
3536		4176
3537	Marc Lehmann <libev@schmorp.de>.	4177	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3538		4178

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