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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
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
578	=item ev_loop (loop, int flags)	639	=item ev_loop (loop, int flags)
579		640
580	Finally, this is it, the event handler. This function usually is called	641	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	642	after you initialised all your watchers and you want to start handling
582	events.	643	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	645	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.	646	either no event watchers are active anymore or C<ev_unloop> was called.
586		647
587	Please note that an explicit C<ev_unloop> is usually better than	648	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	649	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	650	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	651	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.	652	of relying on its watchers stopping correctly, that is truly a thing of
		653	beauty.
592		654
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	655	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	656	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.	657	process in case there are no events and will return after one iteration of
		658	the loop.
596		659
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	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	661	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	662	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	663	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	664	user-registered callback will be called), and will return after one
		665	iteration of the loop.
		666
		667	This is useful if you are waiting for some external event in conjunction
		668	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	669	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.	670	usually a better approach for this kind of thing.
604		671
605	Here are the gory details of what C<ev_loop> does:	672	Here are the gory details of what C<ev_loop> does:
606		673
607	- Before the first iteration, call any pending watchers.	674	- Before the first iteration, call any pending watchers.
…		…
617	any active watchers at all will result in not sleeping).	684	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	685	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	686	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	687	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	689	- Queue all expired timers.
623	- Queue all outstanding periodics.	690	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	691	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	692	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	693	- 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	694	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	695	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	712	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.	713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		714
648	This "unloop state" will be cleared when entering C<ev_loop> again.	715	This "unloop state" will be cleared when entering C<ev_loop> again.
649		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
650	=item ev_ref (loop)	719	=item ev_ref (loop)
651		720
652	=item ev_unref (loop)	721	=item ev_unref (loop)
653		722
654	Ref/unref can be used to add or remove a reference count on the event	723	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	724	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	725	count is nonzero, C<ev_loop> will not return on its own.
		726
657	a watcher you never unregister that should not keep C<ev_loop> from	727	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	728	from returning, call ev_unref() after starting, and ev_ref() before
		729	stopping it.
		730
659	example, libev itself uses this for its internal signal pipe: It is not	731	As an example, libev itself uses this for its internal signal pipe: It is
660	visible to the libev user and should not keep C<ev_loop> from exiting if	732	not visible to the libev user and should not keep C<ev_loop> from exiting
661	no event watchers registered by it are active. It is also an excellent	733	if no event watchers registered by it are active. It is also an excellent
662	way to do this for generic recurring timers or from within third-party	734	way to do this for generic recurring timers or from within third-party
663	libraries. Just remember to I<unref after start> and I<ref before stop>	735	libraries. Just remember to I<unref after start> and I<ref before stop>
664	(but only if the watcher wasn't active before, or was active before,	736	(but only if the watcher wasn't active before, or was active before,
665	respectively).	737	respectively).
666		738
667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
668	running when nothing else is active.	740	running when nothing else is active.
669		741
670	struct ev_signal exitsig;	742	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	743	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	744	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	745	evf_unref (loop);
674		746
675	Example: For some weird reason, unregister the above signal handler again.	747	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>)	761	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	762	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	763	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	764	opportunities).
693		765
694	The background is that sometimes your program runs just fast enough to	766	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	767	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	768	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	769	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	770	overhead for the actual polling but can deliver many events at once.
699		771
700	By setting a higher I<io collect interval> you allow libev to spend more	772	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,	773	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	775	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.	776	introduce an additional C<ev_sleep ()> call into most loop iterations.
705		777
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	778	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	779	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	780	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	781	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	782	value will not introduce any overhead in libev.
711		783
712	Many (busy) programs can usually benefit by setting the I/O collect	784	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	785	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	786	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>,	787	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.	795	they fire on, say, one-second boundaries only.
724		796
725	=item ev_loop_verify (loop)	797	=item ev_loop_verify (loop)
726		798
727	This function only does something when C<EV_VERIFY> support has been	799	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	800	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	801	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	802	is found to be inconsistent, it will print an error message to standard
		803	error and call C<abort ()>.
731		804
732	This can be used to catch bugs inside libev itself: under normal	805	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	806	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	807	data structures consistent.
735		808
736	=back	809	=back
737		810
738		811
739	=head1 ANATOMY OF A WATCHER	812	=head1 ANATOMY OF A WATCHER
740		813
		814	In the following description, uppercase C<TYPE> in names stands for the
		815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		816	watchers and C<ev_io_start> for I/O watchers.
		817
741	A watcher is a structure that you create and register to record your	818	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	819	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:	820	become readable, you would create an C<ev_io> watcher for that:
744		821
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	823	{
747	ev_io_stop (w);	824	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	825	ev_unloop (loop, EVUNLOOP_ALL);
749	}	826	}
750		827
751	struct ev_loop *loop = ev_default_loop (0);	828	struct ev_loop *loop = ev_default_loop (0);
		829
752	struct ev_io stdin_watcher;	830	ev_io stdin_watcher;
		831
753	ev_init (&stdin_watcher, my_cb);	832	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	834	ev_io_start (loop, &stdin_watcher);
		835
756	ev_loop (loop, 0);	836	ev_loop (loop, 0);
757		837
758	As you can see, you are responsible for allocating the memory for your	838	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,	839	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	840	stack).
		841
		842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
761		844
762	Each watcher structure must be initialised by a call to C<ev_init	845	Each watcher structure must be initialised by a call to C<ev_init
763	(watcher *, callback)>, which expects a callback to be provided. This	846	(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	847	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	848	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	849	is readable and/or writable).
767		850
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	851	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	852	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	853	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	854	ev_TYPE_init (watcher *, callback, ...) >>.
772		855
773	To make the watcher actually watch out for events, you have to start it	856	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	857	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	858	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		860
778	As long as your watcher is active (has been started but not stopped) you	861	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	862	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	863	reinitialise it or call its C<ev_TYPE_set> macro.
781		864
782	Each and every callback receives the event loop pointer as first, the	865	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	866	registered watcher structure as second, and a bitset of received events as
784	third argument.	867	third argument.
785		868
…		…
848	=item C<EV_ERROR>	931	=item C<EV_ERROR>
849		932
850	An unspecified error has occurred, the watcher has been stopped. This might	933	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	934	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	935	ran out of memory, a file descriptor was found to be closed or any other
		936	problem. Libev considers these application bugs.
		937
853	problem. You best act on it by reporting the problem and somehow coping	938	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	939	watcher being stopped. Note that well-written programs should not receive
		940	an error ever, so when your watcher receives it, this usually indicates a
		941	bug in your program.
855		942
856	Libev will usually signal a few "dummy" events together with an error,	943	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	944	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	945	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	946	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	947	programs, though, as the fd could already be closed and reused for another
		948	thing, so beware.
861		949
862	=back	950	=back
863		951
864	=head2 GENERIC WATCHER FUNCTIONS	952	=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		953
869	=over 4	954	=over 4
870		955
871	=item C<ev_init> (ev_TYPE *watcher, callback)	956	=item C<ev_init> (ev_TYPE *watcher, callback)
872		957
…		…
878	which rolls both calls into one.	963	which rolls both calls into one.
879		964
880	You can reinitialise a watcher at any time as long as it has been stopped	965	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.	966	(or never started) and there are no pending events outstanding.
882		967
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	968	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	969	int revents)>.
		970
		971	Example: Initialise an C<ev_io> watcher in two steps.
		972
		973	ev_io w;
		974	ev_init (&w, my_cb);
		975	ev_io_set (&w, STDIN_FILENO, EV_READ);
885		976
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	977	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		978
888	This macro initialises the type-specific parts of a watcher. You need to	979	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	980	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	983	difference to the C<ev_init> macro).
893		984
894	Although some watcher types do not have type-specific arguments	985	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.	986	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		987
		988	See C<ev_init>, above, for an example.
		989
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	990	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		991
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	992	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	993	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	994	a watcher. The same limitations apply, of course.
902		995
		996	Example: Initialise and set an C<ev_io> watcher in one step.
		997
		998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		999
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1001
905	Starts (activates) the given watcher. Only active watchers will receive	1002	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1003	events. If the watcher is already active nothing will happen.
907		1004
		1005	Example: Start the C<ev_io> watcher that is being abused as example in this
		1006	whole section.
		1007
		1008	ev_io_start (EV_DEFAULT_UC, &w);
		1009
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1011
910	Stops the given watcher again (if active) and clears the pending	1012	Stops the given watcher if active, and clears the pending status (whether
		1013	the watcher was active or not).
		1014
911	status. It is possible that stopped watchers are pending (for example,	1015	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1016	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	1017	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	1018	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.	1019	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1020
917	=item bool ev_is_active (ev_TYPE *watcher)	1021	=item bool ev_is_active (ev_TYPE *watcher)
918		1022
919	Returns a true value iff the watcher is active (i.e. it has been started	1023	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	1024	and not yet been stopped). As long as a watcher is active you must not modify
…		…
962	The default priority used by watchers when no priority has been set is	1066	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 :).	1067	always C<0>, which is supposed to not be too high and not be too low :).
964		1068
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
966	fine, as long as you do not mind that the priority value you query might	1070	fine, as long as you do not mind that the priority value you query might
967	or might not have been adjusted to be within valid range.	1071	or might not have been clamped to the valid range.
968		1072
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1074
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1075	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	1076	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1077	can deal with that fact, as both are simply passed through to the
		1078	callback.
974		1079
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1080	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1081
977	If the watcher is pending, this function returns clears its pending status	1082	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	1083	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>.	1084	watcher isn't pending it does nothing and returns C<0>.
980		1085
		1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1087	callback to be invoked, which can be accomplished with this function.
		1088
981	=back	1089	=back
982		1090
983		1091
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1093
986	Each watcher has, by default, a member C<void *data> that you can change	1094	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	1095	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	1096	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	1097	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	1098	member, you can also "subclass" the watcher type and provide your own
991	data:	1099	data:
992		1100
993	struct my_io	1101	struct my_io
994	{	1102	{
995	struct ev_io io;	1103	ev_io io;
996	int otherfd;	1104	int otherfd;
997	void *somedata;	1105	void *somedata;
998	struct whatever *mostinteresting;	1106	struct whatever *mostinteresting;
999	}	1107	};
		1108
		1109	...
		1110	struct my_io w;
		1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1112
1001	And since your callback will be called with a pointer to the watcher, you	1113	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1114	can cast it back to your own type:
1003		1115
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1117	{
1006	struct my_io *w = (struct my_io *)w_;	1118	struct my_io *w = (struct my_io *)w_;
1007	...	1119	...
1008	}	1120	}
1009		1121
1010	More interesting and less C-conformant ways of casting your callback type	1122	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1123	instead have been omitted.
1012		1124
1013	Another common scenario is having some data structure with multiple	1125	Another common scenario is to use some data structure with multiple
1014	watchers:	1126	embedded watchers:
1015		1127
1016	struct my_biggy	1128	struct my_biggy
1017	{	1129	{
1018	int some_data;	1130	int some_data;
1019	ev_timer t1;	1131	ev_timer t1;
1020	ev_timer t2;	1132	ev_timer t2;
1021	}	1133	}
1022		1134
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1135	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1136	complicated: Either you store the address of your C<my_biggy> struct
		1137	in the C<data> member of the watcher (for woozies), or you need to use
		1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1139	programmers):
1025		1140
1026	#include <stddef.h>	1141	#include <stddef.h>
1027		1142
1028	static void	1143	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1144	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1145	{
1031	struct my_biggy big = (struct my_biggy *	1146	struct my_biggy big = (struct my_biggy *
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1147	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1148	}
1034		1149
1035	static void	1150	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1151	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1152	{
1038	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1154	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1155	}
1041		1156
…		…
1069	In general you can register as many read and/or write event watchers per	1184	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	1185	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	1186	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1187	required if you know what you are doing).
1073		1188
1074	If you must do this, then force the use of a known-to-be-good backend	1189	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	1190	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1077		1192
1078	Another thing you have to watch out for is that it is quite easy to	1193	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	1194	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	1195	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	1196	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	1197	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	1198	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	1199	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.	1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1201
1087	If you cannot run the fd in non-blocking mode (for example you should not	1202	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	1203	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	1204	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	1205	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1206	does this on its own, so its quite safe to use). Some people additionally
		1207	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1208	indefinitely.
		1209
		1210	But really, best use non-blocking mode.
1092		1211
1093	=head3 The special problem of disappearing file descriptors	1212	=head3 The special problem of disappearing file descriptors
1094		1213
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1214	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,	1215	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	1216	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	1217	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	1218	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	1219	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1220	fact, a different file descriptor.
1102		1221
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1253	C<EVBACKEND_POLL>.
1135		1254
1136	=head3 The special problem of SIGPIPE	1255	=head3 The special problem of SIGPIPE
1137		1256
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when reading from a pipe whose other end has been closed, your program	1258	when writing to a pipe whose other end has been closed, your program gets
1140	gets send a SIGPIPE, which, by default, aborts your program. For most	1259	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	programs this is sensible behaviour, for daemons, this is usually	1260	this is sensible behaviour, for daemons, this is usually undesirable.
1142	undesirable.
1143		1261
1144	So when you encounter spurious, unexplained daemon exits, make sure you	1262	So when you encounter spurious, unexplained daemon exits, make sure you
1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1146	somewhere, as that would have given you a big clue).	1264	somewhere, as that would have given you a big clue).
1147		1265
…		…
1153	=item ev_io_init (ev_io *, callback, int fd, int events)	1271	=item ev_io_init (ev_io *, callback, int fd, int events)
1154		1272
1155	=item ev_io_set (ev_io *, int fd, int events)	1273	=item ev_io_set (ev_io *, int fd, int events)
1156		1274
1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1275	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1276	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1159	C<EV_READ | EV_WRITE> to receive the given events.	1277	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1160		1278
1161	=item int fd [read-only]	1279	=item int fd [read-only]
1162		1280
1163	The file descriptor being watched.	1281	The file descriptor being watched.
1164		1282
…		…
1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1291	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1174	readable, but only once. Since it is likely line-buffered, you could	1292	readable, but only once. Since it is likely line-buffered, you could
1175	attempt to read a whole line in the callback.	1293	attempt to read a whole line in the callback.
1176		1294
1177	static void	1295	static void
1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1296	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1179	{	1297	{
1180	ev_io_stop (loop, w);	1298	ev_io_stop (loop, w);
1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1299	.. read from stdin here (or from w->fd) and handle any I/O errors
1182	}	1300	}
1183		1301
1184	...	1302	...
1185	struct ev_loop *loop = ev_default_init (0);	1303	struct ev_loop *loop = ev_default_init (0);
1186	struct ev_io stdin_readable;	1304	ev_io stdin_readable;
1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1188	ev_io_start (loop, &stdin_readable);	1306	ev_io_start (loop, &stdin_readable);
1189	ev_loop (loop, 0);	1307	ev_loop (loop, 0);
1190		1308
1191		1309
…		…
1194	Timer watchers are simple relative timers that generate an event after a	1312	Timer watchers are simple relative timers that generate an event after a
1195	given time, and optionally repeating in regular intervals after that.	1313	given time, and optionally repeating in regular intervals after that.
1196		1314
1197	The timers are based on real time, that is, if you register an event that	1315	The timers are based on real time, that is, if you register an event that
1198	times out after an hour and you reset your system clock to January last	1316	times out after an hour and you reset your system clock to January last
1199	year, it will still time out after (roughly) and hour. "Roughly" because	1317	year, it will still time out after (roughly) one hour. "Roughly" because
1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1201	monotonic clock option helps a lot here).	1319	monotonic clock option helps a lot here).
		1320
		1321	The callback is guaranteed to be invoked only I<after> its timeout has
		1322	passed, but if multiple timers become ready during the same loop iteration
		1323	then order of execution is undefined.
		1324
		1325	=head3 Be smart about timeouts
		1326
		1327	Many real-world problems involve some kind of timeout, usually for error
		1328	recovery. A typical example is an HTTP request - if the other side hangs,
		1329	you want to raise some error after a while.
		1330
		1331	What follows are some ways to handle this problem, from obvious and
		1332	inefficient to smart and efficient.
		1333
		1334	In the following, a 60 second activity timeout is assumed - a timeout that
		1335	gets reset to 60 seconds each time there is activity (e.g. each time some
		1336	data or other life sign was received).
		1337
		1338	=over 4
		1339
		1340	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1341
		1342	This is the most obvious, but not the most simple way: In the beginning,
		1343	start the watcher:
		1344
		1345	ev_timer_init (timer, callback, 60., 0.);
		1346	ev_timer_start (loop, timer);
		1347
		1348	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1349	and start it again:
		1350
		1351	ev_timer_stop (loop, timer);
		1352	ev_timer_set (timer, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	This is relatively simple to implement, but means that each time there is
		1356	some activity, libev will first have to remove the timer from its internal
		1357	data structure and then add it again. Libev tries to be fast, but it's
		1358	still not a constant-time operation.
		1359
		1360	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1361
		1362	This is the easiest way, and involves using C<ev_timer_again> instead of
		1363	C<ev_timer_start>.
		1364
		1365	To implement this, configure an C<ev_timer> with a C<repeat> value
		1366	of C<60> and then call C<ev_timer_again> at start and each time you
		1367	successfully read or write some data. If you go into an idle state where
		1368	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1369	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1370
		1371	That means you can ignore both the C<ev_timer_start> function and the
		1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1373	member and C<ev_timer_again>.
		1374
		1375	At start:
		1376
		1377	ev_timer_init (timer, callback);
		1378	timer->repeat = 60.;
		1379	ev_timer_again (loop, timer);
		1380
		1381	Each time there is some activity:
		1382
		1383	ev_timer_again (loop, timer);
		1384
		1385	It is even possible to change the time-out on the fly, regardless of
		1386	whether the watcher is active or not:
		1387
		1388	timer->repeat = 30.;
		1389	ev_timer_again (loop, timer);
		1390
		1391	This is slightly more efficient then stopping/starting the timer each time
		1392	you want to modify its timeout value, as libev does not have to completely
		1393	remove and re-insert the timer from/into its internal data structure.
		1394
		1395	It is, however, even simpler than the "obvious" way to do it.
		1396
		1397	=item 3. Let the timer time out, but then re-arm it as required.
		1398
		1399	This method is more tricky, but usually most efficient: Most timeouts are
		1400	relatively long compared to the intervals between other activity - in
		1401	our example, within 60 seconds, there are usually many I/O events with
		1402	associated activity resets.
		1403
		1404	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1405	but remember the time of last activity, and check for a real timeout only
		1406	within the callback:
		1407
		1408	ev_tstamp last_activity; // time of last activity
		1409
		1410	static void
		1411	callback (EV_P_ ev_timer *w, int revents)
		1412	{
		1413	ev_tstamp now = ev_now (EV_A);
		1414	ev_tstamp timeout = last_activity + 60.;
		1415
		1416	// if last_activity + 60. is older than now, we did time out
		1417	if (timeout < now)
		1418	{
		1419	// timeout occured, take action
		1420	}
		1421	else
		1422	{
		1423	// callback was invoked, but there was some activity, re-arm
		1424	// the watcher to fire in last_activity + 60, which is
		1425	// guaranteed to be in the future, so "again" is positive:
		1426	w->repeat = timeout - now;
		1427	ev_timer_again (EV_A_ w);
		1428	}
		1429	}
		1430
		1431	To summarise the callback: first calculate the real timeout (defined
		1432	as "60 seconds after the last activity"), then check if that time has
		1433	been reached, which means something I<did>, in fact, time out. Otherwise
		1434	the callback was invoked too early (C<timeout> is in the future), so
		1435	re-schedule the timer to fire at that future time, to see if maybe we have
		1436	a timeout then.
		1437
		1438	Note how C<ev_timer_again> is used, taking advantage of the
		1439	C<ev_timer_again> optimisation when the timer is already running.
		1440
		1441	This scheme causes more callback invocations (about one every 60 seconds
		1442	minus half the average time between activity), but virtually no calls to
		1443	libev to change the timeout.
		1444
		1445	To start the timer, simply initialise the watcher and set C<last_activity>
		1446	to the current time (meaning we just have some activity :), then call the
		1447	callback, which will "do the right thing" and start the timer:
		1448
		1449	ev_timer_init (timer, callback);
		1450	last_activity = ev_now (loop);
		1451	callback (loop, timer, EV_TIMEOUT);
		1452
		1453	And when there is some activity, simply store the current time in
		1454	C<last_activity>, no libev calls at all:
		1455
		1456	last_actiivty = ev_now (loop);
		1457
		1458	This technique is slightly more complex, but in most cases where the
		1459	time-out is unlikely to be triggered, much more efficient.
		1460
		1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1462	callback :) - just change the timeout and invoke the callback, which will
		1463	fix things for you.
		1464
		1465	=item 4. Wee, just use a double-linked list for your timeouts.
		1466
		1467	If there is not one request, but many thousands (millions...), all
		1468	employing some kind of timeout with the same timeout value, then one can
		1469	do even better:
		1470
		1471	When starting the timeout, calculate the timeout value and put the timeout
		1472	at the I<end> of the list.
		1473
		1474	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1475	the list is expected to fire (for example, using the technique #3).
		1476
		1477	When there is some activity, remove the timer from the list, recalculate
		1478	the timeout, append it to the end of the list again, and make sure to
		1479	update the C<ev_timer> if it was taken from the beginning of the list.
		1480
		1481	This way, one can manage an unlimited number of timeouts in O(1) time for
		1482	starting, stopping and updating the timers, at the expense of a major
		1483	complication, and having to use a constant timeout. The constant timeout
		1484	ensures that the list stays sorted.
		1485
		1486	=back
		1487
		1488	So which method the best?
		1489
		1490	Method #2 is a simple no-brain-required solution that is adequate in most
		1491	situations. Method #3 requires a bit more thinking, but handles many cases
		1492	better, and isn't very complicated either. In most case, choosing either
		1493	one is fine, with #3 being better in typical situations.
		1494
		1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1496	rather complicated, but extremely efficient, something that really pays
		1497	off after the first million or so of active timers, i.e. it's usually
		1498	overkill :)
		1499
		1500	=head3 The special problem of time updates
		1501
		1502	Establishing the current time is a costly operation (it usually takes at
		1503	least two system calls): EV therefore updates its idea of the current
		1504	time only before and after C<ev_loop> collects new events, which causes a
		1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1506	lots of events in one iteration.
1202		1507
1203	The relative timeouts are calculated relative to the C<ev_now ()>	1508	The relative timeouts are calculated relative to the C<ev_now ()>
1204	time. This is usually the right thing as this timestamp refers to the time	1509	time. This is usually the right thing as this timestamp refers to the time
1205	of the event triggering whatever timeout you are modifying/starting. If	1510	of the event triggering whatever timeout you are modifying/starting. If
1206	you suspect event processing to be delayed and you I<need> to base the timeout	1511	you suspect event processing to be delayed and you I<need> to base the
1207	on the current time, use something like this to adjust for this:	1512	timeout on the current time, use something like this to adjust for this:
1208		1513
1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1210		1515
1211	The callback is guaranteed to be invoked only after its timeout has passed,	1516	If the event loop is suspended for a long time, you can also force an
1212	but if multiple timers become ready during the same loop iteration then	1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1213	order of execution is undefined.	1518	()>.
1214		1519
1215	=head3 Watcher-Specific Functions and Data Members	1520	=head3 Watcher-Specific Functions and Data Members
1216		1521
1217	=over 4	1522	=over 4
1218		1523
…		…
1242	If the timer is started but non-repeating, stop it (as if it timed out).	1547	If the timer is started but non-repeating, stop it (as if it timed out).
1243		1548
1244	If the timer is repeating, either start it if necessary (with the	1549	If the timer is repeating, either start it if necessary (with the
1245	C<repeat> value), or reset the running timer to the C<repeat> value.	1550	C<repeat> value), or reset the running timer to the C<repeat> value.
1246		1551
1247	This sounds a bit complicated, but here is a useful and typical	1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1248	example: Imagine you have a TCP connection and you want a so-called idle	1553	usage example.
1249	timeout, that is, you want to be called when there have been, say, 60
1250	seconds of inactivity on the socket. The easiest way to do this is to
1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1252	C<ev_timer_again> each time you successfully read or write some data. If
1253	you go into an idle state where you do not expect data to travel on the
1254	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1255	automatically restart it if need be.
1256
1257	That means you can ignore the C<after> value and C<ev_timer_start>
1258	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1259
1260	ev_timer_init (timer, callback, 0., 5.);
1261	ev_timer_again (loop, timer);
1262	...
1263	timer->again = 17.;
1264	ev_timer_again (loop, timer);
1265	...
1266	timer->again = 10.;
1267	ev_timer_again (loop, timer);
1268
1269	This is more slightly efficient then stopping/starting the timer each time
1270	you want to modify its timeout value.
1271		1554
1272	=item ev_tstamp repeat [read-write]	1555	=item ev_tstamp repeat [read-write]
1273		1556
1274	The current C<repeat> value. Will be used each time the watcher times out	1557	The current C<repeat> value. Will be used each time the watcher times out
1275	or C<ev_timer_again> is called and determines the next timeout (if any),	1558	or C<ev_timer_again> is called, and determines the next timeout (if any),
1276	which is also when any modifications are taken into account.	1559	which is also when any modifications are taken into account.
1277		1560
1278	=back	1561	=back
1279		1562
1280	=head3 Examples	1563	=head3 Examples
1281		1564
1282	Example: Create a timer that fires after 60 seconds.	1565	Example: Create a timer that fires after 60 seconds.
1283		1566
1284	static void	1567	static void
1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1568	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1286	{	1569	{
1287	.. one minute over, w is actually stopped right here	1570	.. one minute over, w is actually stopped right here
1288	}	1571	}
1289		1572
1290	struct ev_timer mytimer;	1573	ev_timer mytimer;
1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1574	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1292	ev_timer_start (loop, &mytimer);	1575	ev_timer_start (loop, &mytimer);
1293		1576
1294	Example: Create a timeout timer that times out after 10 seconds of	1577	Example: Create a timeout timer that times out after 10 seconds of
1295	inactivity.	1578	inactivity.
1296		1579
1297	static void	1580	static void
1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1581	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1299	{	1582	{
1300	.. ten seconds without any activity	1583	.. ten seconds without any activity
1301	}	1584	}
1302		1585
1303	struct ev_timer mytimer;	1586	ev_timer mytimer;
1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1305	ev_timer_again (&mytimer); /* start timer */	1588	ev_timer_again (&mytimer); /* start timer */
1306	ev_loop (loop, 0);	1589	ev_loop (loop, 0);
1307		1590
1308	// and in some piece of code that gets executed on any "activity":	1591	// and in some piece of code that gets executed on any "activity":
…		…
1313	=head2 C<ev_periodic> - to cron or not to cron?	1596	=head2 C<ev_periodic> - to cron or not to cron?
1314		1597
1315	Periodic watchers are also timers of a kind, but they are very versatile	1598	Periodic watchers are also timers of a kind, but they are very versatile
1316	(and unfortunately a bit complex).	1599	(and unfortunately a bit complex).
1317		1600
1318	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1601	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1319	but on wall clock time (absolute time). You can tell a periodic watcher	1602	relative time, the physical time that passes) but on wall clock time
1320	to trigger after some specific point in time. For example, if you tell a	1603	(absolute time, the thing you can read on your calender or clock). The
1321	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1604	difference is that wall clock time can run faster or slower than real
1322	+ 10.>, that is, an absolute time not a delay) and then reset your system	1605	time, and time jumps are not uncommon (e.g. when you adjust your
1323	clock to January of the previous year, then it will take more than year	1606	wrist-watch).
1324	to trigger the event (unlike an C<ev_timer>, which would still trigger
1325	roughly 10 seconds later as it uses a relative timeout).
1326		1607
		1608	You can tell a periodic watcher to trigger after some specific point
		1609	in time: for example, if you tell a periodic watcher to trigger "in 10
		1610	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1611	not a delay) and then reset your system clock to January of the previous
		1612	year, then it will take a year or more to trigger the event (unlike an
		1613	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1614	it, as it uses a relative timeout).
		1615
1327	C<ev_periodic>s can also be used to implement vastly more complex timers,	1616	C<ev_periodic> watchers can also be used to implement vastly more complex
1328	such as triggering an event on each "midnight, local time", or other	1617	timers, such as triggering an event on each "midnight, local time", or
1329	complicated, rules.	1618	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1619	those cannot react to time jumps.
1330		1620
1331	As with timers, the callback is guaranteed to be invoked only when the	1621	As with timers, the callback is guaranteed to be invoked only when the
1332	time (C<at>) has passed, but if multiple periodic timers become ready	1622	point in time where it is supposed to trigger has passed, but if multiple
1333	during the same loop iteration then order of execution is undefined.	1623	periodic timers become ready during the same loop iteration, then order of
		1624	execution is undefined.
1334		1625
1335	=head3 Watcher-Specific Functions and Data Members	1626	=head3 Watcher-Specific Functions and Data Members
1336		1627
1337	=over 4	1628	=over 4
1338		1629
1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1630	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1340		1631
1341	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1632	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1342		1633
1343	Lots of arguments, lets sort it out... There are basically three modes of	1634	Lots of arguments, let's sort it out... There are basically three modes of
1344	operation, and we will explain them from simplest to complex:	1635	operation, and we will explain them from simplest to most complex:
1345		1636
1346	=over 4	1637	=over 4
1347		1638
1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1639	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1349		1640
1350	In this configuration the watcher triggers an event after the wall clock	1641	In this configuration the watcher triggers an event after the wall clock
1351	time C<at> has passed and doesn't repeat. It will not adjust when a time	1642	time C<offset> has passed. It will not repeat and will not adjust when a
1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1643	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1353	run when the system time reaches or surpasses this time.	1644	will be stopped and invoked when the system clock reaches or surpasses
		1645	this point in time.
1354		1646
1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1647	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1356		1648
1357	In this mode the watcher will always be scheduled to time out at the next	1649	In this mode the watcher will always be scheduled to time out at the next
1358	C<at + N * interval> time (for some integer N, which can also be negative)	1650	C<offset + N * interval> time (for some integer N, which can also be
1359	and then repeat, regardless of any time jumps.	1651	negative) and then repeat, regardless of any time jumps. The C<offset>
		1652	argument is merely an offset into the C<interval> periods.
1360		1653
1361	This can be used to create timers that do not drift with respect to system	1654	This can be used to create timers that do not drift with respect to the
1362	time, for example, here is a C<ev_periodic> that triggers each hour, on	1655	system clock, for example, here is an C<ev_periodic> that triggers each
1363	the hour:	1656	hour, on the hour (with respect to UTC):
1364		1657
1365	ev_periodic_set (&periodic, 0., 3600., 0);	1658	ev_periodic_set (&periodic, 0., 3600., 0);
1366		1659
1367	This doesn't mean there will always be 3600 seconds in between triggers,	1660	This doesn't mean there will always be 3600 seconds in between triggers,
1368	but only that the callback will be called when the system time shows a	1661	but only that the callback will be called when the system time shows a
1369	full hour (UTC), or more correctly, when the system time is evenly divisible	1662	full hour (UTC), or more correctly, when the system time is evenly divisible
1370	by 3600.	1663	by 3600.
1371		1664
1372	Another way to think about it (for the mathematically inclined) is that	1665	Another way to think about it (for the mathematically inclined) is that
1373	C<ev_periodic> will try to run the callback in this mode at the next possible	1666	C<ev_periodic> will try to run the callback in this mode at the next possible
1374	time where C<time = at (mod interval)>, regardless of any time jumps.	1667	time where C<time = offset (mod interval)>, regardless of any time jumps.
1375		1668
1376	For numerical stability it is preferable that the C<at> value is near	1669	For numerical stability it is preferable that the C<offset> value is near
1377	C<ev_now ()> (the current time), but there is no range requirement for	1670	C<ev_now ()> (the current time), but there is no range requirement for
1378	this value, and in fact is often specified as zero.	1671	this value, and in fact is often specified as zero.
1379		1672
1380	Note also that there is an upper limit to how often a timer can fire (CPU	1673	Note also that there is an upper limit to how often a timer can fire (CPU
1381	speed for example), so if C<interval> is very small then timing stability	1674	speed for example), so if C<interval> is very small then timing stability
1382	will of course deteriorate. Libev itself tries to be exact to be about one	1675	will of course deteriorate. Libev itself tries to be exact to be about one
1383	millisecond (if the OS supports it and the machine is fast enough).	1676	millisecond (if the OS supports it and the machine is fast enough).
1384		1677
1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1678	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1386		1679
1387	In this mode the values for C<interval> and C<at> are both being	1680	In this mode the values for C<interval> and C<offset> are both being
1388	ignored. Instead, each time the periodic watcher gets scheduled, the	1681	ignored. Instead, each time the periodic watcher gets scheduled, the
1389	reschedule callback will be called with the watcher as first, and the	1682	reschedule callback will be called with the watcher as first, and the
1390	current time as second argument.	1683	current time as second argument.
1391		1684
1392	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1685	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1393	ever, or make ANY event loop modifications whatsoever>.	1686	or make ANY other event loop modifications whatsoever, unless explicitly
		1687	allowed by documentation here>.
1394		1688
1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1689	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1690	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1397	only event loop modification you are allowed to do).	1691	only event loop modification you are allowed to do).
1398		1692
1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1693	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1400	*w, ev_tstamp now)>, e.g.:	1694	*w, ev_tstamp now)>, e.g.:
1401		1695
		1696	static ev_tstamp
1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1697	my_rescheduler (ev_periodic *w, ev_tstamp now)
1403	{	1698	{
1404	return now + 60.;	1699	return now + 60.;
1405	}	1700	}
1406		1701
1407	It must return the next time to trigger, based on the passed time value	1702	It must return the next time to trigger, based on the passed time value
…		…
1427	a different time than the last time it was called (e.g. in a crond like	1722	a different time than the last time it was called (e.g. in a crond like
1428	program when the crontabs have changed).	1723	program when the crontabs have changed).
1429		1724
1430	=item ev_tstamp ev_periodic_at (ev_periodic *)	1725	=item ev_tstamp ev_periodic_at (ev_periodic *)
1431		1726
1432	When active, returns the absolute time that the watcher is supposed to	1727	When active, returns the absolute time that the watcher is supposed
1433	trigger next.	1728	to trigger next. This is not the same as the C<offset> argument to
		1729	C<ev_periodic_set>, but indeed works even in interval and manual
		1730	rescheduling modes.
1434		1731
1435	=item ev_tstamp offset [read-write]	1732	=item ev_tstamp offset [read-write]
1436		1733
1437	When repeating, this contains the offset value, otherwise this is the	1734	When repeating, this contains the offset value, otherwise this is the
1438	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1735	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1736	although libev might modify this value for better numerical stability).
1439		1737
1440	Can be modified any time, but changes only take effect when the periodic	1738	Can be modified any time, but changes only take effect when the periodic
1441	timer fires or C<ev_periodic_again> is being called.	1739	timer fires or C<ev_periodic_again> is being called.
1442		1740
1443	=item ev_tstamp interval [read-write]	1741	=item ev_tstamp interval [read-write]
1444		1742
1445	The current interval value. Can be modified any time, but changes only	1743	The current interval value. Can be modified any time, but changes only
1446	take effect when the periodic timer fires or C<ev_periodic_again> is being	1744	take effect when the periodic timer fires or C<ev_periodic_again> is being
1447	called.	1745	called.
1448		1746
1449	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1747	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1450		1748
1451	The current reschedule callback, or C<0>, if this functionality is	1749	The current reschedule callback, or C<0>, if this functionality is
1452	switched off. Can be changed any time, but changes only take effect when	1750	switched off. Can be changed any time, but changes only take effect when
1453	the periodic timer fires or C<ev_periodic_again> is being called.	1751	the periodic timer fires or C<ev_periodic_again> is being called.
1454		1752
1455	=back	1753	=back
1456		1754
1457	=head3 Examples	1755	=head3 Examples
1458		1756
1459	Example: Call a callback every hour, or, more precisely, whenever the	1757	Example: Call a callback every hour, or, more precisely, whenever the
1460	system clock is divisible by 3600. The callback invocation times have	1758	system time is divisible by 3600. The callback invocation times have
1461	potentially a lot of jitter, but good long-term stability.	1759	potentially a lot of jitter, but good long-term stability.
1462		1760
1463	static void	1761	static void
1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1762	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1465	{	1763	{
1466	... its now a full hour (UTC, or TAI or whatever your clock follows)	1764	... its now a full hour (UTC, or TAI or whatever your clock follows)
1467	}	1765	}
1468		1766
1469	struct ev_periodic hourly_tick;	1767	ev_periodic hourly_tick;
1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1768	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1471	ev_periodic_start (loop, &hourly_tick);	1769	ev_periodic_start (loop, &hourly_tick);
1472		1770
1473	Example: The same as above, but use a reschedule callback to do it:	1771	Example: The same as above, but use a reschedule callback to do it:
1474		1772
1475	#include <math.h>	1773	#include <math.h>
1476		1774
1477	static ev_tstamp	1775	static ev_tstamp
1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1776	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1479	{	1777	{
1480	return fmod (now, 3600.) + 3600.;	1778	return now + (3600. - fmod (now, 3600.));
1481	}	1779	}
1482		1780
1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1781	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1484		1782
1485	Example: Call a callback every hour, starting now:	1783	Example: Call a callback every hour, starting now:
1486		1784
1487	struct ev_periodic hourly_tick;	1785	ev_periodic hourly_tick;
1488	ev_periodic_init (&hourly_tick, clock_cb,	1786	ev_periodic_init (&hourly_tick, clock_cb,
1489	fmod (ev_now (loop), 3600.), 3600., 0);	1787	fmod (ev_now (loop), 3600.), 3600., 0);
1490	ev_periodic_start (loop, &hourly_tick);	1788	ev_periodic_start (loop, &hourly_tick);
1491		1789
1492		1790
…		…
1495	Signal watchers will trigger an event when the process receives a specific	1793	Signal watchers will trigger an event when the process receives a specific
1496	signal one or more times. Even though signals are very asynchronous, libev	1794	signal one or more times. Even though signals are very asynchronous, libev
1497	will try it's best to deliver signals synchronously, i.e. as part of the	1795	will try it's best to deliver signals synchronously, i.e. as part of the
1498	normal event processing, like any other event.	1796	normal event processing, like any other event.
1499		1797
		1798	If you want signals asynchronously, just use C<sigaction> as you would
		1799	do without libev and forget about sharing the signal. You can even use
		1800	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1801
1500	You can configure as many watchers as you like per signal. Only when the	1802	You can configure as many watchers as you like per signal. Only when the
1501	first watcher gets started will libev actually register a signal watcher	1803	first watcher gets started will libev actually register a signal handler
1502	with the kernel (thus it coexists with your own signal handlers as long	1804	with the kernel (thus it coexists with your own signal handlers as long as
1503	as you don't register any with libev). Similarly, when the last signal	1805	you don't register any with libev for the same signal). Similarly, when
1504	watcher for a signal is stopped libev will reset the signal handler to	1806	the last signal watcher for a signal is stopped, libev will reset the
1505	SIG_DFL (regardless of what it was set to before).	1807	signal handler to SIG_DFL (regardless of what it was set to before).
1506		1808
1507	If possible and supported, libev will install its handlers with	1809	If possible and supported, libev will install its handlers with
1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1810	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1509	interrupted. If you have a problem with system calls getting interrupted by	1811	interrupted. If you have a problem with system calls getting interrupted by
1510	signals you can block all signals in an C<ev_check> watcher and unblock	1812	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1527		1829
1528	=back	1830	=back
1529		1831
1530	=head3 Examples	1832	=head3 Examples
1531		1833
1532	Example: Try to exit cleanly on SIGINT and SIGTERM.	1834	Example: Try to exit cleanly on SIGINT.
1533		1835
1534	static void	1836	static void
1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1837	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1536	{	1838	{
1537	ev_unloop (loop, EVUNLOOP_ALL);	1839	ev_unloop (loop, EVUNLOOP_ALL);
1538	}	1840	}
1539		1841
1540	struct ev_signal signal_watcher;	1842	ev_signal signal_watcher;
1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1843	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1542	ev_signal_start (loop, &sigint_cb);	1844	ev_signal_start (loop, &signal_watcher);
1543		1845
1544		1846
1545	=head2 C<ev_child> - watch out for process status changes	1847	=head2 C<ev_child> - watch out for process status changes
1546		1848
1547	Child watchers trigger when your process receives a SIGCHLD in response to	1849	Child watchers trigger when your process receives a SIGCHLD in response to
1548	some child status changes (most typically when a child of yours dies). It	1850	some child status changes (most typically when a child of yours dies or
1549	is permissible to install a child watcher I<after> the child has been	1851	exits). It is permissible to install a child watcher I<after> the child
1550	forked (which implies it might have already exited), as long as the event	1852	has been forked (which implies it might have already exited), as long
1551	loop isn't entered (or is continued from a watcher).	1853	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1854	forking and then immediately registering a watcher for the child is fine,
		1855	but forking and registering a watcher a few event loop iterations later is
		1856	not.
1552		1857
1553	Only the default event loop is capable of handling signals, and therefore	1858	Only the default event loop is capable of handling signals, and therefore
1554	you can only register child watchers in the default event loop.	1859	you can only register child watchers in the default event loop.
1555		1860
1556	=head3 Process Interaction	1861	=head3 Process Interaction
…		…
1617	its completion.	1922	its completion.
1618		1923
1619	ev_child cw;	1924	ev_child cw;
1620		1925
1621	static void	1926	static void
1622	child_cb (EV_P_ struct ev_child *w, int revents)	1927	child_cb (EV_P_ ev_child *w, int revents)
1623	{	1928	{
1624	ev_child_stop (EV_A_ w);	1929	ev_child_stop (EV_A_ w);
1625	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1930	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1626	}	1931	}
1627		1932
…		…
1642		1947
1643		1948
1644	=head2 C<ev_stat> - did the file attributes just change?	1949	=head2 C<ev_stat> - did the file attributes just change?
1645		1950
1646	This watches a file system path for attribute changes. That is, it calls	1951	This watches a file system path for attribute changes. That is, it calls
1647	C<stat> regularly (or when the OS says it changed) and sees if it changed	1952	C<stat> on that path in regular intervals (or when the OS says it changed)
1648	compared to the last time, invoking the callback if it did.	1953	and sees if it changed compared to the last time, invoking the callback if
		1954	it did.
1649		1955
1650	The path does not need to exist: changing from "path exists" to "path does	1956	The path does not need to exist: changing from "path exists" to "path does
1651	not exist" is a status change like any other. The condition "path does	1957	not exist" is a status change like any other. The condition "path does not
1652	not exist" is signified by the C<st_nlink> field being zero (which is	1958	exist" (or more correctly "path cannot be stat'ed") is signified by the
1653	otherwise always forced to be at least one) and all the other fields of	1959	C<st_nlink> field being zero (which is otherwise always forced to be at
1654	the stat buffer having unspecified contents.	1960	least one) and all the other fields of the stat buffer having unspecified
		1961	contents.
1655		1962
1656	The path I<should> be absolute and I<must not> end in a slash. If it is	1963	The path I<must not> end in a slash or contain special components such as
		1964	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1657	relative and your working directory changes, the behaviour is undefined.	1965	your working directory changes, then the behaviour is undefined.
1658		1966
1659	Since there is no standard to do this, the portable implementation simply	1967	Since there is no portable change notification interface available, the
1660	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1968	portable implementation simply calls C<stat(2)> regularly on the path
1661	can specify a recommended polling interval for this case. If you specify	1969	to see if it changed somehow. You can specify a recommended polling
1662	a polling interval of C<0> (highly recommended!) then a I<suitable,	1970	interval for this case. If you specify a polling interval of C<0> (highly
1663	unspecified default> value will be used (which you can expect to be around	1971	recommended!) then a I<suitable, unspecified default> value will be used
1664	five seconds, although this might change dynamically). Libev will also	1972	(which you can expect to be around five seconds, although this might
1665	impose a minimum interval which is currently around C<0.1>, but thats	1973	change dynamically). Libev will also impose a minimum interval which is
1666	usually overkill.	1974	currently around C<0.1>, but that's usually overkill.
1667		1975
1668	This watcher type is not meant for massive numbers of stat watchers,	1976	This watcher type is not meant for massive numbers of stat watchers,
1669	as even with OS-supported change notifications, this can be	1977	as even with OS-supported change notifications, this can be
1670	resource-intensive.	1978	resource-intensive.
1671		1979
1672	At the time of this writing, only the Linux inotify interface is	1980	At the time of this writing, the only OS-specific interface implemented
1673	implemented (implementing kqueue support is left as an exercise for the	1981	is the Linux inotify interface (implementing kqueue support is left as an
1674	reader, note, however, that the author sees no way of implementing ev_stat	1982	exercise for the reader. Note, however, that the author sees no way of
1675	semantics with kqueue). Inotify will be used to give hints only and should	1983	implementing C<ev_stat> semantics with kqueue, except as a hint).
1676	not change the semantics of C<ev_stat> watchers, which means that libev
1677	sometimes needs to fall back to regular polling again even with inotify,
1678	but changes are usually detected immediately, and if the file exists there
1679	will be no polling.
1680		1984
1681	=head3 ABI Issues (Largefile Support)	1985	=head3 ABI Issues (Largefile Support)
1682		1986
1683	Libev by default (unless the user overrides this) uses the default	1987	Libev by default (unless the user overrides this) uses the default
1684	compilation environment, which means that on systems with large file	1988	compilation environment, which means that on systems with large file
1685	support disabled by default, you get the 32 bit version of the stat	1989	support disabled by default, you get the 32 bit version of the stat
1686	structure. When using the library from programs that change the ABI to	1990	structure. When using the library from programs that change the ABI to
1687	use 64 bit file offsets the programs will fail. In that case you have to	1991	use 64 bit file offsets the programs will fail. In that case you have to
1688	compile libev with the same flags to get binary compatibility. This is	1992	compile libev with the same flags to get binary compatibility. This is
1689	obviously the case with any flags that change the ABI, but the problem is	1993	obviously the case with any flags that change the ABI, but the problem is
1690	most noticeably disabled with ev_stat and large file support.	1994	most noticeably displayed with ev_stat and large file support.
1691		1995
1692	The solution for this is to lobby your distribution maker to make large	1996	The solution for this is to lobby your distribution maker to make large
1693	file interfaces available by default (as e.g. FreeBSD does) and not	1997	file interfaces available by default (as e.g. FreeBSD does) and not
1694	optional. Libev cannot simply switch on large file support because it has	1998	optional. Libev cannot simply switch on large file support because it has
1695	to exchange stat structures with application programs compiled using the	1999	to exchange stat structures with application programs compiled using the
1696	default compilation environment.	2000	default compilation environment.
1697		2001
1698	=head3 Inotify	2002	=head3 Inotify and Kqueue
1699		2003
1700	When C<inotify (7)> support has been compiled into libev (generally only	2004	When C<inotify (7)> support has been compiled into libev and present at
1701	available on Linux) and present at runtime, it will be used to speed up	2005	runtime, it will be used to speed up change detection where possible. The
1702	change detection where possible. The inotify descriptor will be created lazily	2006	inotify descriptor will be created lazily when the first C<ev_stat>
1703	when the first C<ev_stat> watcher is being started.	2007	watcher is being started.
1704		2008
1705	Inotify presence does not change the semantics of C<ev_stat> watchers	2009	Inotify presence does not change the semantics of C<ev_stat> watchers
1706	except that changes might be detected earlier, and in some cases, to avoid	2010	except that changes might be detected earlier, and in some cases, to avoid
1707	making regular C<stat> calls. Even in the presence of inotify support	2011	making regular C<stat> calls. Even in the presence of inotify support
1708	there are many cases where libev has to resort to regular C<stat> polling.	2012	there are many cases where libev has to resort to regular C<stat> polling,
		2013	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2014	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2015	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2016	xfs are fully working) libev usually gets away without polling.
1709		2017
1710	(There is no support for kqueue, as apparently it cannot be used to	2018	There is no support for kqueue, as apparently it cannot be used to
1711	implement this functionality, due to the requirement of having a file	2019	implement this functionality, due to the requirement of having a file
1712	descriptor open on the object at all times).	2020	descriptor open on the object at all times, and detecting renames, unlinks
		2021	etc. is difficult.
		2022
		2023	=head3 C<stat ()> is a synchronous operation
		2024
		2025	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2026	the process. The exception are C<ev_stat> watchers - those call C<stat
		2027	()>, which is a synchronous operation.
		2028
		2029	For local paths, this usually doesn't matter: unless the system is very
		2030	busy or the intervals between stat's are large, a stat call will be fast,
		2031	as the path data is usually in memory already (except when starting the
		2032	watcher).
		2033
		2034	For networked file systems, calling C<stat ()> can block an indefinite
		2035	time due to network issues, and even under good conditions, a stat call
		2036	often takes multiple milliseconds.
		2037
		2038	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2039	paths, although this is fully supported by libev.
1713		2040
1714	=head3 The special problem of stat time resolution	2041	=head3 The special problem of stat time resolution
1715		2042
1716	The C<stat ()> system call only supports full-second resolution portably, and	2043	The C<stat ()> system call only supports full-second resolution portably,
1717	even on systems where the resolution is higher, many file systems still	2044	and even on systems where the resolution is higher, most file systems
1718	only support whole seconds.	2045	still only support whole seconds.
1719		2046
1720	That means that, if the time is the only thing that changes, you can	2047	That means that, if the time is the only thing that changes, you can
1721	easily miss updates: on the first update, C<ev_stat> detects a change and	2048	easily miss updates: on the first update, C<ev_stat> detects a change and
1722	calls your callback, which does something. When there is another update	2049	calls your callback, which does something. When there is another update
1723	within the same second, C<ev_stat> will be unable to detect it as the stat	2050	within the same second, C<ev_stat> will be unable to detect unless the
1724	data does not change.	2051	stat data does change in other ways (e.g. file size).
1725		2052
1726	The solution to this is to delay acting on a change for slightly more	2053	The solution to this is to delay acting on a change for slightly more
1727	than a second (or till slightly after the next full second boundary), using	2054	than a second (or till slightly after the next full second boundary), using
1728	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2055	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1729	ev_timer_again (loop, w)>).	2056	ev_timer_again (loop, w)>).
…		…
1749	C<path>. The C<interval> is a hint on how quickly a change is expected to	2076	C<path>. The C<interval> is a hint on how quickly a change is expected to
1750	be detected and should normally be specified as C<0> to let libev choose	2077	be detected and should normally be specified as C<0> to let libev choose
1751	a suitable value. The memory pointed to by C<path> must point to the same	2078	a suitable value. The memory pointed to by C<path> must point to the same
1752	path for as long as the watcher is active.	2079	path for as long as the watcher is active.
1753		2080
1754	The callback will receive C<EV_STAT> when a change was detected, relative	2081	The callback will receive an C<EV_STAT> event when a change was detected,
1755	to the attributes at the time the watcher was started (or the last change	2082	relative to the attributes at the time the watcher was started (or the
1756	was detected).	2083	last change was detected).
1757		2084
1758	=item ev_stat_stat (loop, ev_stat *)	2085	=item ev_stat_stat (loop, ev_stat *)
1759		2086
1760	Updates the stat buffer immediately with new values. If you change the	2087	Updates the stat buffer immediately with new values. If you change the
1761	watched path in your callback, you could call this function to avoid	2088	watched path in your callback, you could call this function to avoid
…		…
1844		2171
1845		2172
1846	=head2 C<ev_idle> - when you've got nothing better to do...	2173	=head2 C<ev_idle> - when you've got nothing better to do...
1847		2174
1848	Idle watchers trigger events when no other events of the same or higher	2175	Idle watchers trigger events when no other events of the same or higher
1849	priority are pending (prepare, check and other idle watchers do not	2176	priority are pending (prepare, check and other idle watchers do not count
1850	count).	2177	as receiving "events").
1851		2178
1852	That is, as long as your process is busy handling sockets or timeouts	2179	That is, as long as your process is busy handling sockets or timeouts
1853	(or even signals, imagine) of the same or higher priority it will not be	2180	(or even signals, imagine) of the same or higher priority it will not be
1854	triggered. But when your process is idle (or only lower-priority watchers	2181	triggered. But when your process is idle (or only lower-priority watchers
1855	are pending), the idle watchers are being called once per event loop	2182	are pending), the idle watchers are being called once per event loop
…		…
1866		2193
1867	=head3 Watcher-Specific Functions and Data Members	2194	=head3 Watcher-Specific Functions and Data Members
1868		2195
1869	=over 4	2196	=over 4
1870		2197
1871	=item ev_idle_init (ev_signal *, callback)	2198	=item ev_idle_init (ev_idle *, callback)
1872		2199
1873	Initialises and configures the idle watcher - it has no parameters of any	2200	Initialises and configures the idle watcher - it has no parameters of any
1874	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2201	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1875	believe me.	2202	believe me.
1876		2203
…		…
1880		2207
1881	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2208	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1882	callback, free it. Also, use no error checking, as usual.	2209	callback, free it. Also, use no error checking, as usual.
1883		2210
1884	static void	2211	static void
1885	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2212	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1886	{	2213	{
1887	free (w);	2214	free (w);
1888	// now do something you wanted to do when the program has	2215	// now do something you wanted to do when the program has
1889	// no longer anything immediate to do.	2216	// no longer anything immediate to do.
1890	}	2217	}
1891		2218
1892	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2219	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1893	ev_idle_init (idle_watcher, idle_cb);	2220	ev_idle_init (idle_watcher, idle_cb);
1894	ev_idle_start (loop, idle_cb);	2221	ev_idle_start (loop, idle_cb);
1895		2222
1896		2223
1897	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2224	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1898		2225
1899	Prepare and check watchers are usually (but not always) used in tandem:	2226	Prepare and check watchers are usually (but not always) used in pairs:
1900	prepare watchers get invoked before the process blocks and check watchers	2227	prepare watchers get invoked before the process blocks and check watchers
1901	afterwards.	2228	afterwards.
1902		2229
1903	You I<must not> call C<ev_loop> or similar functions that enter	2230	You I<must not> call C<ev_loop> or similar functions that enter
1904	the current event loop from either C<ev_prepare> or C<ev_check>	2231	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1907	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2234	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1908	C<ev_check> so if you have one watcher of each kind they will always be	2235	C<ev_check> so if you have one watcher of each kind they will always be
1909	called in pairs bracketing the blocking call.	2236	called in pairs bracketing the blocking call.
1910		2237
1911	Their main purpose is to integrate other event mechanisms into libev and	2238	Their main purpose is to integrate other event mechanisms into libev and
1912	their use is somewhat advanced. This could be used, for example, to track	2239	their use is somewhat advanced. They could be used, for example, to track
1913	variable changes, implement your own watchers, integrate net-snmp or a	2240	variable changes, implement your own watchers, integrate net-snmp or a
1914	coroutine library and lots more. They are also occasionally useful if	2241	coroutine library and lots more. They are also occasionally useful if
1915	you cache some data and want to flush it before blocking (for example,	2242	you cache some data and want to flush it before blocking (for example,
1916	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2243	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1917	watcher).	2244	watcher).
1918		2245
1919	This is done by examining in each prepare call which file descriptors need	2246	This is done by examining in each prepare call which file descriptors
1920	to be watched by the other library, registering C<ev_io> watchers for	2247	need to be watched by the other library, registering C<ev_io> watchers
1921	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2248	for them and starting an C<ev_timer> watcher for any timeouts (many
1922	provide just this functionality). Then, in the check watcher you check for	2249	libraries provide exactly this functionality). Then, in the check watcher,
1923	any events that occurred (by checking the pending status of all watchers	2250	you check for any events that occurred (by checking the pending status
1924	and stopping them) and call back into the library. The I/O and timer	2251	of all watchers and stopping them) and call back into the library. The
1925	callbacks will never actually be called (but must be valid nevertheless,	2252	I/O and timer callbacks will never actually be called (but must be valid
1926	because you never know, you know?).	2253	nevertheless, because you never know, you know?).
1927		2254
1928	As another example, the Perl Coro module uses these hooks to integrate	2255	As another example, the Perl Coro module uses these hooks to integrate
1929	coroutines into libev programs, by yielding to other active coroutines	2256	coroutines into libev programs, by yielding to other active coroutines
1930	during each prepare and only letting the process block if no coroutines	2257	during each prepare and only letting the process block if no coroutines
1931	are ready to run (it's actually more complicated: it only runs coroutines	2258	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1934	loop from blocking if lower-priority coroutines are active, thus mapping	2261	loop from blocking if lower-priority coroutines are active, thus mapping
1935	low-priority coroutines to idle/background tasks).	2262	low-priority coroutines to idle/background tasks).
1936		2263
1937	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2264	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1938	priority, to ensure that they are being run before any other watchers	2265	priority, to ensure that they are being run before any other watchers
		2266	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2267
1939	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2268	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1940	too) should not activate ("feed") events into libev. While libev fully	2269	activate ("feed") events into libev. While libev fully supports this, they
1941	supports this, they might get executed before other C<ev_check> watchers	2270	might get executed before other C<ev_check> watchers did their job. As
1942	did their job. As C<ev_check> watchers are often used to embed other	2271	C<ev_check> watchers are often used to embed other (non-libev) event
1943	(non-libev) event loops those other event loops might be in an unusable	2272	loops those other event loops might be in an unusable state until their
1944	state until their C<ev_check> watcher ran (always remind yourself to	2273	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1945	coexist peacefully with others).	2274	others).
1946		2275
1947	=head3 Watcher-Specific Functions and Data Members	2276	=head3 Watcher-Specific Functions and Data Members
1948		2277
1949	=over 4	2278	=over 4
1950		2279
…		…
1952		2281
1953	=item ev_check_init (ev_check *, callback)	2282	=item ev_check_init (ev_check *, callback)
1954		2283
1955	Initialises and configures the prepare or check watcher - they have no	2284	Initialises and configures the prepare or check watcher - they have no
1956	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2285	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1957	macros, but using them is utterly, utterly and completely pointless.	2286	macros, but using them is utterly, utterly, utterly and completely
		2287	pointless.
1958		2288
1959	=back	2289	=back
1960		2290
1961	=head3 Examples	2291	=head3 Examples
1962		2292
…		…
1975		2305
1976	static ev_io iow [nfd];	2306	static ev_io iow [nfd];
1977	static ev_timer tw;	2307	static ev_timer tw;
1978		2308
1979	static void	2309	static void
1980	io_cb (ev_loop *loop, ev_io *w, int revents)	2310	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1981	{	2311	{
1982	}	2312	}
1983		2313
1984	// create io watchers for each fd and a timer before blocking	2314	// create io watchers for each fd and a timer before blocking
1985	static void	2315	static void
1986	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2316	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1987	{	2317	{
1988	int timeout = 3600000;	2318	int timeout = 3600000;
1989	struct pollfd fds [nfd];	2319	struct pollfd fds [nfd];
1990	// actual code will need to loop here and realloc etc.	2320	// actual code will need to loop here and realloc etc.
1991	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2321	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2006	}	2336	}
2007	}	2337	}
2008		2338
2009	// stop all watchers after blocking	2339	// stop all watchers after blocking
2010	static void	2340	static void
2011	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2341	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2012	{	2342	{
2013	ev_timer_stop (loop, &tw);	2343	ev_timer_stop (loop, &tw);
2014		2344
2015	for (int i = 0; i < nfd; ++i)	2345	for (int i = 0; i < nfd; ++i)
2016	{	2346	{
…		…
2055	}	2385	}
2056		2386
2057	// do not ever call adns_afterpoll	2387	// do not ever call adns_afterpoll
2058		2388
2059	Method 4: Do not use a prepare or check watcher because the module you	2389	Method 4: Do not use a prepare or check watcher because the module you
2060	want to embed is too inflexible to support it. Instead, you can override	2390	want to embed is not flexible enough to support it. Instead, you can
2061	their poll function. The drawback with this solution is that the main	2391	override their poll function. The drawback with this solution is that the
2062	loop is now no longer controllable by EV. The C<Glib::EV> module does	2392	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2063	this.	2393	this approach, effectively embedding EV as a client into the horrible
		2394	libglib event loop.
2064		2395
2065	static gint	2396	static gint
2066	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2397	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2067	{	2398	{
2068	int got_events = 0;	2399	int got_events = 0;
…		…
2099	prioritise I/O.	2430	prioritise I/O.
2100		2431
2101	As an example for a bug workaround, the kqueue backend might only support	2432	As an example for a bug workaround, the kqueue backend might only support
2102	sockets on some platform, so it is unusable as generic backend, but you	2433	sockets on some platform, so it is unusable as generic backend, but you
2103	still want to make use of it because you have many sockets and it scales	2434	still want to make use of it because you have many sockets and it scales
2104	so nicely. In this case, you would create a kqueue-based loop and embed it	2435	so nicely. In this case, you would create a kqueue-based loop and embed
2105	into your default loop (which might use e.g. poll). Overall operation will	2436	it into your default loop (which might use e.g. poll). Overall operation
2106	be a bit slower because first libev has to poll and then call kevent, but	2437	will be a bit slower because first libev has to call C<poll> and then
2107	at least you can use both at what they are best.	2438	C<kevent>, but at least you can use both mechanisms for what they are
		2439	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2108		2440
2109	As for prioritising I/O: rarely you have the case where some fds have	2441	As for prioritising I/O: under rare circumstances you have the case where
2110	to be watched and handled very quickly (with low latency), and even	2442	some fds have to be watched and handled very quickly (with low latency),
2111	priorities and idle watchers might have too much overhead. In this case	2443	and even priorities and idle watchers might have too much overhead. In
2112	you would put all the high priority stuff in one loop and all the rest in	2444	this case you would put all the high priority stuff in one loop and all
2113	a second one, and embed the second one in the first.	2445	the rest in a second one, and embed the second one in the first.
2114		2446
2115	As long as the watcher is active, the callback will be invoked every time	2447	As long as the watcher is active, the callback will be invoked every
2116	there might be events pending in the embedded loop. The callback must then	2448	time there might be events pending in the embedded loop. The callback
2117	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2449	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2118	their callbacks (you could also start an idle watcher to give the embedded	2450	sweep and invoke their callbacks (the callback doesn't need to invoke the
2119	loop strictly lower priority for example). You can also set the callback	2451	C<ev_embed_sweep> function directly, it could also start an idle watcher
2120	to C<0>, in which case the embed watcher will automatically execute the	2452	to give the embedded loop strictly lower priority for example).
2121	embedded loop sweep.
2122		2453
2123	As long as the watcher is started it will automatically handle events. The	2454	You can also set the callback to C<0>, in which case the embed watcher
2124	callback will be invoked whenever some events have been handled. You can	2455	will automatically execute the embedded loop sweep whenever necessary.
2125	set the callback to C<0> to avoid having to specify one if you are not
2126	interested in that.
2127		2456
2128	Also, there have not currently been made special provisions for forking:	2457	Fork detection will be handled transparently while the C<ev_embed> watcher
2129	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2458	is active, i.e., the embedded loop will automatically be forked when the
2130	but you will also have to stop and restart any C<ev_embed> watchers	2459	embedding loop forks. In other cases, the user is responsible for calling
2131	yourself.	2460	C<ev_loop_fork> on the embedded loop.
2132		2461
2133	Unfortunately, not all backends are embeddable, only the ones returned by	2462	Unfortunately, not all backends are embeddable: only the ones returned by
2134	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2463	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2135	portable one.	2464	portable one.
2136		2465
2137	So when you want to use this feature you will always have to be prepared	2466	So when you want to use this feature you will always have to be prepared
2138	that you cannot get an embeddable loop. The recommended way to get around	2467	that you cannot get an embeddable loop. The recommended way to get around
2139	this is to have a separate variables for your embeddable loop, try to	2468	this is to have a separate variables for your embeddable loop, try to
2140	create it, and if that fails, use the normal loop for everything.	2469	create it, and if that fails, use the normal loop for everything.
		2470
		2471	=head3 C<ev_embed> and fork
		2472
		2473	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2474	automatically be applied to the embedded loop as well, so no special
		2475	fork handling is required in that case. When the watcher is not running,
		2476	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2477	as applicable.
2141		2478
2142	=head3 Watcher-Specific Functions and Data Members	2479	=head3 Watcher-Specific Functions and Data Members
2143		2480
2144	=over 4	2481	=over 4
2145		2482
…		…
2173	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2510	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2174	used).	2511	used).
2175		2512
2176	struct ev_loop *loop_hi = ev_default_init (0);	2513	struct ev_loop *loop_hi = ev_default_init (0);
2177	struct ev_loop *loop_lo = 0;	2514	struct ev_loop *loop_lo = 0;
2178	struct ev_embed embed;	2515	ev_embed embed;
2179		2516
2180	// see if there is a chance of getting one that works	2517	// see if there is a chance of getting one that works
2181	// (remember that a flags value of 0 means autodetection)	2518	// (remember that a flags value of 0 means autodetection)
2182	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2519	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2183	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2520	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2197	kqueue implementation). Store the kqueue/socket-only event loop in	2534	kqueue implementation). Store the kqueue/socket-only event loop in
2198	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2535	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2199		2536
2200	struct ev_loop *loop = ev_default_init (0);	2537	struct ev_loop *loop = ev_default_init (0);
2201	struct ev_loop *loop_socket = 0;	2538	struct ev_loop *loop_socket = 0;
2202	struct ev_embed embed;	2539	ev_embed embed;
2203		2540
2204	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2541	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2205	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2542	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2206	{	2543	{
2207	ev_embed_init (&embed, 0, loop_socket);	2544	ev_embed_init (&embed, 0, loop_socket);
…		…
2263	is that the author does not know of a simple (or any) algorithm for a	2600	is that the author does not know of a simple (or any) algorithm for a
2264	multiple-writer-single-reader queue that works in all cases and doesn't	2601	multiple-writer-single-reader queue that works in all cases and doesn't
2265	need elaborate support such as pthreads.	2602	need elaborate support such as pthreads.
2266		2603
2267	That means that if you want to queue data, you have to provide your own	2604	That means that if you want to queue data, you have to provide your own
2268	queue. But at least I can tell you would implement locking around your	2605	queue. But at least I can tell you how to implement locking around your
2269	queue:	2606	queue:
2270		2607
2271	=over 4	2608	=over 4
2272		2609
2273	=item queueing from a signal handler context	2610	=item queueing from a signal handler context
2274		2611
2275	To implement race-free queueing, you simply add to the queue in the signal	2612	To implement race-free queueing, you simply add to the queue in the signal
2276	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2613	handler but you block the signal handler in the watcher callback. Here is
2277	some fictitious SIGUSR1 handler:	2614	an example that does that for some fictitious SIGUSR1 handler:
2278		2615
2279	static ev_async mysig;	2616	static ev_async mysig;
2280		2617
2281	static void	2618	static void
2282	sigusr1_handler (void)	2619	sigusr1_handler (void)
…		…
2348	=over 4	2685	=over 4
2349		2686
2350	=item ev_async_init (ev_async *, callback)	2687	=item ev_async_init (ev_async *, callback)
2351		2688
2352	Initialises and configures the async watcher - it has no parameters of any	2689	Initialises and configures the async watcher - it has no parameters of any
2353	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2690	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2354	believe me.	2691	trust me.
2355		2692
2356	=item ev_async_send (loop, ev_async *)	2693	=item ev_async_send (loop, ev_async *)
2357		2694
2358	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2695	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2359	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2696	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2360	C<ev_feed_event>, this call is safe to do in other threads, signal or	2697	C<ev_feed_event>, this call is safe to do from other threads, signal or
2361	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2698	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2362	section below on what exactly this means).	2699	section below on what exactly this means).
2363		2700
		2701	Note that, as with other watchers in libev, multiple events might get
		2702	compressed into a single callback invocation (another way to look at this
		2703	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2704	reset when the event loop detects that).
		2705
2364	This call incurs the overhead of a system call only once per loop iteration,	2706	This call incurs the overhead of a system call only once per event loop
2365	so while the overhead might be noticeable, it doesn't apply to repeated	2707	iteration, so while the overhead might be noticeable, it doesn't apply to
2366	calls to C<ev_async_send>.	2708	repeated calls to C<ev_async_send> for the same event loop.
2367		2709
2368	=item bool = ev_async_pending (ev_async *)	2710	=item bool = ev_async_pending (ev_async *)
2369		2711
2370	Returns a non-zero value when C<ev_async_send> has been called on the	2712	Returns a non-zero value when C<ev_async_send> has been called on the
2371	watcher but the event has not yet been processed (or even noted) by the	2713	watcher but the event has not yet been processed (or even noted) by the
…		…
2374	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2716	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2375	the loop iterates next and checks for the watcher to have become active,	2717	the loop iterates next and checks for the watcher to have become active,
2376	it will reset the flag again. C<ev_async_pending> can be used to very	2718	it will reset the flag again. C<ev_async_pending> can be used to very
2377	quickly check whether invoking the loop might be a good idea.	2719	quickly check whether invoking the loop might be a good idea.
2378		2720
2379	Not that this does I<not> check whether the watcher itself is pending, only	2721	Not that this does I<not> check whether the watcher itself is pending,
2380	whether it has been requested to make this watcher pending.	2722	only whether it has been requested to make this watcher pending: there
		2723	is a time window between the event loop checking and resetting the async
		2724	notification, and the callback being invoked.
2381		2725
2382	=back	2726	=back
2383		2727
2384		2728
2385	=head1 OTHER FUNCTIONS	2729	=head1 OTHER FUNCTIONS
…		…
2389	=over 4	2733	=over 4
2390		2734
2391	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2735	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2392		2736
2393	This function combines a simple timer and an I/O watcher, calls your	2737	This function combines a simple timer and an I/O watcher, calls your
2394	callback on whichever event happens first and automatically stop both	2738	callback on whichever event happens first and automatically stops both
2395	watchers. This is useful if you want to wait for a single event on an fd	2739	watchers. This is useful if you want to wait for a single event on an fd
2396	or timeout without having to allocate/configure/start/stop/free one or	2740	or timeout without having to allocate/configure/start/stop/free one or
2397	more watchers yourself.	2741	more watchers yourself.
2398		2742
2399	If C<fd> is less than 0, then no I/O watcher will be started and events	2743	If C<fd> is less than 0, then no I/O watcher will be started and the
2400	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2744	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2401	C<events> set will be created and started.	2745	the given C<fd> and C<events> set will be created and started.
2402		2746
2403	If C<timeout> is less than 0, then no timeout watcher will be	2747	If C<timeout> is less than 0, then no timeout watcher will be
2404	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2748	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2405	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2749	repeat = 0) will be started. C<0> is a valid timeout.
2406	dubious value.
2407		2750
2408	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2751	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2409	passed an C<revents> set like normal event callbacks (a combination of	2752	passed an C<revents> set like normal event callbacks (a combination of
2410	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2753	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2411	value passed to C<ev_once>:	2754	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2755	a timeout and an io event at the same time - you probably should give io
		2756	events precedence.
		2757
		2758	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2412		2759
2413	static void stdin_ready (int revents, void *arg)	2760	static void stdin_ready (int revents, void *arg)
2414	{	2761	{
		2762	if (revents & EV_READ)
		2763	/* stdin might have data for us, joy! */;
2415	if (revents & EV_TIMEOUT)	2764	else if (revents & EV_TIMEOUT)
2416	/* doh, nothing entered */;	2765	/* doh, nothing entered */;
2417	else if (revents & EV_READ)
2418	/* stdin might have data for us, joy! */;
2419	}	2766	}
2420		2767
2421	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2768	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2422		2769
2423	=item ev_feed_event (ev_loop *, watcher *, int revents)	2770	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2424		2771
2425	Feeds the given event set into the event loop, as if the specified event	2772	Feeds the given event set into the event loop, as if the specified event
2426	had happened for the specified watcher (which must be a pointer to an	2773	had happened for the specified watcher (which must be a pointer to an
2427	initialised but not necessarily started event watcher).	2774	initialised but not necessarily started event watcher).
2428		2775
2429	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2776	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2430		2777
2431	Feed an event on the given fd, as if a file descriptor backend detected	2778	Feed an event on the given fd, as if a file descriptor backend detected
2432	the given events it.	2779	the given events it.
2433		2780
2434	=item ev_feed_signal_event (ev_loop *loop, int signum)	2781	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2435		2782
2436	Feed an event as if the given signal occurred (C<loop> must be the default	2783	Feed an event as if the given signal occurred (C<loop> must be the default
2437	loop!).	2784	loop!).
2438		2785
2439	=back	2786	=back
…		…
2561		2908
2562	myclass obj;	2909	myclass obj;
2563	ev::io iow;	2910	ev::io iow;
2564	iow.set <myclass, &myclass::io_cb> (&obj);	2911	iow.set <myclass, &myclass::io_cb> (&obj);
2565		2912
		2913	=item w->set (object *)
		2914
		2915	This is an B<experimental> feature that might go away in a future version.
		2916
		2917	This is a variation of a method callback - leaving out the method to call
		2918	will default the method to C<operator ()>, which makes it possible to use
		2919	functor objects without having to manually specify the C<operator ()> all
		2920	the time. Incidentally, you can then also leave out the template argument
		2921	list.
		2922
		2923	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2924	int revents)>.
		2925
		2926	See the method-C<set> above for more details.
		2927
		2928	Example: use a functor object as callback.
		2929
		2930	struct myfunctor
		2931	{
		2932	void operator() (ev::io &w, int revents)
		2933	{
		2934	...
		2935	}
		2936	}
		2937
		2938	myfunctor f;
		2939
		2940	ev::io w;
		2941	w.set (&f);
		2942
2566	=item w->set<function> (void *data = 0)	2943	=item w->set<function> (void *data = 0)
2567		2944
2568	Also sets a callback, but uses a static method or plain function as	2945	Also sets a callback, but uses a static method or plain function as
2569	callback. The optional C<data> argument will be stored in the watcher's	2946	callback. The optional C<data> argument will be stored in the watcher's
2570	C<data> member and is free for you to use.	2947	C<data> member and is free for you to use.
2571		2948
2572	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2949	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2573		2950
2574	See the method-C<set> above for more details.	2951	See the method-C<set> above for more details.
2575		2952
2576	Example:	2953	Example: Use a plain function as callback.
2577		2954
2578	static void io_cb (ev::io &w, int revents) { }	2955	static void io_cb (ev::io &w, int revents) { }
2579	iow.set <io_cb> ();	2956	iow.set <io_cb> ();
2580		2957
2581	=item w->set (struct ev_loop *)	2958	=item w->set (struct ev_loop *)
…		…
2619	Example: Define a class with an IO and idle watcher, start one of them in	2996	Example: Define a class with an IO and idle watcher, start one of them in
2620	the constructor.	2997	the constructor.
2621		2998
2622	class myclass	2999	class myclass
2623	{	3000	{
2624	ev::io io; void io_cb (ev::io &w, int revents);	3001	ev::io io ; void io_cb (ev::io &w, int revents);
2625	ev:idle idle void idle_cb (ev::idle &w, int revents);	3002	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2626		3003
2627	myclass (int fd)	3004	myclass (int fd)
2628	{	3005	{
2629	io .set <myclass, &myclass::io_cb > (this);	3006	io .set <myclass, &myclass::io_cb > (this);
2630	idle.set <myclass, &myclass::idle_cb> (this);	3007	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2646	=item Perl	3023	=item Perl
2647		3024
2648	The EV module implements the full libev API and is actually used to test	3025	The EV module implements the full libev API and is actually used to test
2649	libev. EV is developed together with libev. Apart from the EV core module,	3026	libev. EV is developed together with libev. Apart from the EV core module,
2650	there are additional modules that implement libev-compatible interfaces	3027	there are additional modules that implement libev-compatible interfaces
2651	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3028	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2652	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3029	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3030	and C<EV::Glib>).
2653		3031
2654	It can be found and installed via CPAN, its homepage is at	3032	It can be found and installed via CPAN, its homepage is at
2655	L<http://software.schmorp.de/pkg/EV>.	3033	L<http://software.schmorp.de/pkg/EV>.
2656		3034
2657	=item Python	3035	=item Python
…		…
2668	Tony Arcieri has written a ruby extension that offers access to a subset	3046	Tony Arcieri has written a ruby extension that offers access to a subset
2669	of the libev API and adds file handle abstractions, asynchronous DNS and	3047	of the libev API and adds file handle abstractions, asynchronous DNS and
2670	more on top of it. It can be found via gem servers. Its homepage is at	3048	more on top of it. It can be found via gem servers. Its homepage is at
2671	L<http://rev.rubyforge.org/>.	3049	L<http://rev.rubyforge.org/>.
2672		3050
		3051	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3052	makes rev work even on mingw.
		3053
2673	=item D	3054	=item D
2674		3055
2675	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3056	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2676	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3057	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3058
		3059	=item Ocaml
		3060
		3061	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3062	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2677		3063
2678	=back	3064	=back
2679		3065
2680		3066
2681	=head1 MACRO MAGIC	3067	=head1 MACRO MAGIC
…		…
2782		3168
2783	#define EV_STANDALONE 1	3169	#define EV_STANDALONE 1
2784	#include "ev.h"	3170	#include "ev.h"
2785		3171
2786	Both header files and implementation files can be compiled with a C++	3172	Both header files and implementation files can be compiled with a C++
2787	compiler (at least, thats a stated goal, and breakage will be treated	3173	compiler (at least, that's a stated goal, and breakage will be treated
2788	as a bug).	3174	as a bug).
2789		3175
2790	You need the following files in your source tree, or in a directory	3176	You need the following files in your source tree, or in a directory
2791	in your include path (e.g. in libev/ when using -Ilibev):	3177	in your include path (e.g. in libev/ when using -Ilibev):
2792		3178
…		…
2836		3222
2837	=head2 PREPROCESSOR SYMBOLS/MACROS	3223	=head2 PREPROCESSOR SYMBOLS/MACROS
2838		3224
2839	Libev can be configured via a variety of preprocessor symbols you have to	3225	Libev can be configured via a variety of preprocessor symbols you have to
2840	define before including any of its files. The default in the absence of	3226	define before including any of its files. The default in the absence of
2841	autoconf is noted for every option.	3227	autoconf is documented for every option.
2842		3228
2843	=over 4	3229	=over 4
2844		3230
2845	=item EV_STANDALONE	3231	=item EV_STANDALONE
2846		3232
…		…
2848	keeps libev from including F<config.h>, and it also defines dummy	3234	keeps libev from including F<config.h>, and it also defines dummy
2849	implementations for some libevent functions (such as logging, which is not	3235	implementations for some libevent functions (such as logging, which is not
2850	supported). It will also not define any of the structs usually found in	3236	supported). It will also not define any of the structs usually found in
2851	F<event.h> that are not directly supported by the libev core alone.	3237	F<event.h> that are not directly supported by the libev core alone.
2852		3238
		3239	In stanbdalone mode, libev will still try to automatically deduce the
		3240	configuration, but has to be more conservative.
		3241
2853	=item EV_USE_MONOTONIC	3242	=item EV_USE_MONOTONIC
2854		3243
2855	If defined to be C<1>, libev will try to detect the availability of the	3244	If defined to be C<1>, libev will try to detect the availability of the
2856	monotonic clock option at both compile time and runtime. Otherwise no use	3245	monotonic clock option at both compile time and runtime. Otherwise no
2857	of the monotonic clock option will be attempted. If you enable this, you	3246	use of the monotonic clock option will be attempted. If you enable this,
2858	usually have to link against librt or something similar. Enabling it when	3247	you usually have to link against librt or something similar. Enabling it
2859	the functionality isn't available is safe, though, although you have	3248	when the functionality isn't available is safe, though, although you have
2860	to make sure you link against any libraries where the C<clock_gettime>	3249	to make sure you link against any libraries where the C<clock_gettime>
2861	function is hiding in (often F<-lrt>).	3250	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2862		3251
2863	=item EV_USE_REALTIME	3252	=item EV_USE_REALTIME
2864		3253
2865	If defined to be C<1>, libev will try to detect the availability of the	3254	If defined to be C<1>, libev will try to detect the availability of the
2866	real-time clock option at compile time (and assume its availability at	3255	real-time clock option at compile time (and assume its availability
2867	runtime if successful). Otherwise no use of the real-time clock option will	3256	at runtime if successful). Otherwise no use of the real-time clock
2868	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3257	option will be attempted. This effectively replaces C<gettimeofday>
2869	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3258	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2870	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3259	correctness. See the note about libraries in the description of
		3260	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3261	C<EV_USE_CLOCK_SYSCALL>.
		3262
		3263	=item EV_USE_CLOCK_SYSCALL
		3264
		3265	If defined to be C<1>, libev will try to use a direct syscall instead
		3266	of calling the system-provided C<clock_gettime> function. This option
		3267	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3268	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3269	programs needlessly. Using a direct syscall is slightly slower (in
		3270	theory), because no optimised vdso implementation can be used, but avoids
		3271	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3272	higher, as it simplifies linking (no need for C<-lrt>).
2871		3273
2872	=item EV_USE_NANOSLEEP	3274	=item EV_USE_NANOSLEEP
2873		3275
2874	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3276	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2875	and will use it for delays. Otherwise it will use C<select ()>.	3277	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2891		3293
2892	=item EV_SELECT_USE_FD_SET	3294	=item EV_SELECT_USE_FD_SET
2893		3295
2894	If defined to C<1>, then the select backend will use the system C<fd_set>	3296	If defined to C<1>, then the select backend will use the system C<fd_set>
2895	structure. This is useful if libev doesn't compile due to a missing	3297	structure. This is useful if libev doesn't compile due to a missing
2896	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3298	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2897	exotic systems. This usually limits the range of file descriptors to some	3299	on exotic systems. This usually limits the range of file descriptors to
2898	low limit such as 1024 or might have other limitations (winsocket only	3300	some low limit such as 1024 or might have other limitations (winsocket
2899	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3301	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2900	influence the size of the C<fd_set> used.	3302	configures the maximum size of the C<fd_set>.
2901		3303
2902	=item EV_SELECT_IS_WINSOCKET	3304	=item EV_SELECT_IS_WINSOCKET
2903		3305
2904	When defined to C<1>, the select backend will assume that	3306	When defined to C<1>, the select backend will assume that
2905	select/socket/connect etc. don't understand file descriptors but	3307	select/socket/connect etc. don't understand file descriptors but
…		…
3016	When doing priority-based operations, libev usually has to linearly search	3418	When doing priority-based operations, libev usually has to linearly search
3017	all the priorities, so having many of them (hundreds) uses a lot of space	3419	all the priorities, so having many of them (hundreds) uses a lot of space
3018	and time, so using the defaults of five priorities (-2 .. +2) is usually	3420	and time, so using the defaults of five priorities (-2 .. +2) is usually
3019	fine.	3421	fine.
3020		3422
3021	If your embedding application does not need any priorities, defining these both to	3423	If your embedding application does not need any priorities, defining these
3022	C<0> will save some memory and CPU.	3424	both to C<0> will save some memory and CPU.
3023		3425
3024	=item EV_PERIODIC_ENABLE	3426	=item EV_PERIODIC_ENABLE
3025		3427
3026	If undefined or defined to be C<1>, then periodic timers are supported. If	3428	If undefined or defined to be C<1>, then periodic timers are supported. If
3027	defined to be C<0>, then they are not. Disabling them saves a few kB of	3429	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3034	code.	3436	code.
3035		3437
3036	=item EV_EMBED_ENABLE	3438	=item EV_EMBED_ENABLE
3037		3439
3038	If undefined or defined to be C<1>, then embed watchers are supported. If	3440	If undefined or defined to be C<1>, then embed watchers are supported. If
3039	defined to be C<0>, then they are not.	3441	defined to be C<0>, then they are not. Embed watchers rely on most other
		3442	watcher types, which therefore must not be disabled.
3040		3443
3041	=item EV_STAT_ENABLE	3444	=item EV_STAT_ENABLE
3042		3445
3043	If undefined or defined to be C<1>, then stat watchers are supported. If	3446	If undefined or defined to be C<1>, then stat watchers are supported. If
3044	defined to be C<0>, then they are not.	3447	defined to be C<0>, then they are not.
…		…
3076	two).	3479	two).
3077		3480
3078	=item EV_USE_4HEAP	3481	=item EV_USE_4HEAP
3079		3482
3080	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3483	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3081	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3484	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3082	to C<1>. The 4-heap uses more complicated (longer) code but has	3485	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3083	noticeably faster performance with many (thousands) of watchers.	3486	faster performance with many (thousands) of watchers.
3084		3487
3085	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3488	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3086	(disabled).	3489	(disabled).
3087		3490
3088	=item EV_HEAP_CACHE_AT	3491	=item EV_HEAP_CACHE_AT
3089		3492
3090	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3493	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3091	timer and periodics heap, libev can cache the timestamp (I<at>) within	3494	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3092	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3495	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3093	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3496	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3094	but avoids random read accesses on heap changes. This improves performance	3497	but avoids random read accesses on heap changes. This improves performance
3095	noticeably with with many (hundreds) of watchers.	3498	noticeably with many (hundreds) of watchers.
3096		3499
3097	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3500	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3098	(disabled).	3501	(disabled).
3099		3502
3100	=item EV_VERIFY	3503	=item EV_VERIFY
…		…
3106	called once per loop, which can slow down libev. If set to C<3>, then the	3509	called once per loop, which can slow down libev. If set to C<3>, then the
3107	verification code will be called very frequently, which will slow down	3510	verification code will be called very frequently, which will slow down
3108	libev considerably.	3511	libev considerably.
3109		3512
3110	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3513	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3111	C<0.>	3514	C<0>.
3112		3515
3113	=item EV_COMMON	3516	=item EV_COMMON
3114		3517
3115	By default, all watchers have a C<void *data> member. By redefining	3518	By default, all watchers have a C<void *data> member. By redefining
3116	this macro to a something else you can include more and other types of	3519	this macro to a something else you can include more and other types of
…		…
3133	and the way callbacks are invoked and set. Must expand to a struct member	3536	and the way callbacks are invoked and set. Must expand to a struct member
3134	definition and a statement, respectively. See the F<ev.h> header file for	3537	definition and a statement, respectively. See the F<ev.h> header file for
3135	their default definitions. One possible use for overriding these is to	3538	their default definitions. One possible use for overriding these is to
3136	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3539	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3137	method calls instead of plain function calls in C++.	3540	method calls instead of plain function calls in C++.
		3541
		3542	=back
3138		3543
3139	=head2 EXPORTED API SYMBOLS	3544	=head2 EXPORTED API SYMBOLS
3140		3545
3141	If you need to re-export the API (e.g. via a DLL) and you need a list of	3546	If you need to re-export the API (e.g. via a DLL) and you need a list of
3142	exported symbols, you can use the provided F<Symbol.*> files which list	3547	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3189	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3594	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3190		3595
3191	#include "ev_cpp.h"	3596	#include "ev_cpp.h"
3192	#include "ev.c"	3597	#include "ev.c"
3193		3598
		3599	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3194		3600
3195	=head1 THREADS AND COROUTINES	3601	=head2 THREADS AND COROUTINES
3196		3602
3197	=head2 THREADS	3603	=head3 THREADS
3198		3604
3199	Libev itself is completely thread-safe, but it uses no locking. This	3605	All libev functions are reentrant and thread-safe unless explicitly
		3606	documented otherwise, but libev implements no locking itself. This means
3200	means that you can use as many loops as you want in parallel, as long as	3607	that you can use as many loops as you want in parallel, as long as there
3201	only one thread ever calls into one libev function with the same loop	3608	are no concurrent calls into any libev function with the same loop
3202	parameter.	3609	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3610	of course): libev guarantees that different event loops share no data
		3611	structures that need any locking.
3203		3612
3204	Or put differently: calls with different loop parameters can be done in	3613	Or to put it differently: calls with different loop parameters can be done
3205	parallel from multiple threads, calls with the same loop parameter must be	3614	concurrently from multiple threads, calls with the same loop parameter
3206	done serially (but can be done from different threads, as long as only one	3615	must be done serially (but can be done from different threads, as long as
3207	thread ever is inside a call at any point in time, e.g. by using a mutex	3616	only one thread ever is inside a call at any point in time, e.g. by using
3208	per loop).	3617	a mutex per loop).
		3618
		3619	Specifically to support threads (and signal handlers), libev implements
		3620	so-called C<ev_async> watchers, which allow some limited form of
		3621	concurrency on the same event loop, namely waking it up "from the
		3622	outside".
3209		3623
3210	If you want to know which design (one loop, locking, or multiple loops	3624	If you want to know which design (one loop, locking, or multiple loops
3211	without or something else still) is best for your problem, then I cannot	3625	without or something else still) is best for your problem, then I cannot
3212	help you. I can give some generic advice however:	3626	help you, but here is some generic advice:
3213		3627
3214	=over 4	3628	=over 4
3215		3629
3216	=item * most applications have a main thread: use the default libev loop	3630	=item * most applications have a main thread: use the default libev loop
3217	in that thread, or create a separate thread running only the default loop.	3631	in that thread, or create a separate thread running only the default loop.
…		…
3229		3643
3230	Choosing a model is hard - look around, learn, know that usually you can do	3644	Choosing a model is hard - look around, learn, know that usually you can do
3231	better than you currently do :-)	3645	better than you currently do :-)
3232		3646
3233	=item * often you need to talk to some other thread which blocks in the	3647	=item * often you need to talk to some other thread which blocks in the
		3648	event loop.
		3649
3234	event loop - C<ev_async> watchers can be used to wake them up from other	3650	C<ev_async> watchers can be used to wake them up from other threads safely
3235	threads safely (or from signal contexts...).	3651	(or from signal contexts...).
		3652
		3653	An example use would be to communicate signals or other events that only
		3654	work in the default loop by registering the signal watcher with the
		3655	default loop and triggering an C<ev_async> watcher from the default loop
		3656	watcher callback into the event loop interested in the signal.
3236		3657
3237	=back	3658	=back
3238		3659
3239	=head2 COROUTINES	3660	=head3 COROUTINES
3240		3661
3241	Libev is much more accommodating to coroutines ("cooperative threads"):	3662	Libev is very accommodating to coroutines ("cooperative threads"):
3242	libev fully supports nesting calls to it's functions from different	3663	libev fully supports nesting calls to its functions from different
3243	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3664	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3244	different coroutines and switch freely between both coroutines running the	3665	different coroutines, and switch freely between both coroutines running the
3245	loop, as long as you don't confuse yourself). The only exception is that	3666	loop, as long as you don't confuse yourself). The only exception is that
3246	you must not do this from C<ev_periodic> reschedule callbacks.	3667	you must not do this from C<ev_periodic> reschedule callbacks.
3247		3668
3248	Care has been invested into making sure that libev does not keep local	3669	Care has been taken to ensure that libev does not keep local state inside
3249	state inside C<ev_loop>, and other calls do not usually allow coroutine	3670	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3250	switches.	3671	they do not call any callbacks.
3251		3672
		3673	=head2 COMPILER WARNINGS
3252		3674
3253	=head1 COMPLEXITIES	3675	Depending on your compiler and compiler settings, you might get no or a
		3676	lot of warnings when compiling libev code. Some people are apparently
		3677	scared by this.
3254		3678
3255	In this section the complexities of (many of) the algorithms used inside	3679	However, these are unavoidable for many reasons. For one, each compiler
3256	libev will be explained. For complexity discussions about backends see the	3680	has different warnings, and each user has different tastes regarding
3257	documentation for C<ev_default_init>.	3681	warning options. "Warn-free" code therefore cannot be a goal except when
		3682	targeting a specific compiler and compiler-version.
3258		3683
3259	All of the following are about amortised time: If an array needs to be	3684	Another reason is that some compiler warnings require elaborate
3260	extended, libev needs to realloc and move the whole array, but this	3685	workarounds, or other changes to the code that make it less clear and less
3261	happens asymptotically never with higher number of elements, so O(1) might	3686	maintainable.
3262	mean it might do a lengthy realloc operation in rare cases, but on average
3263	it is much faster and asymptotically approaches constant time.
3264		3687
3265	=over 4	3688	And of course, some compiler warnings are just plain stupid, or simply
		3689	wrong (because they don't actually warn about the condition their message
		3690	seems to warn about). For example, certain older gcc versions had some
		3691	warnings that resulted an extreme number of false positives. These have
		3692	been fixed, but some people still insist on making code warn-free with
		3693	such buggy versions.
3266		3694
3267	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3695	While libev is written to generate as few warnings as possible,
		3696	"warn-free" code is not a goal, and it is recommended not to build libev
		3697	with any compiler warnings enabled unless you are prepared to cope with
		3698	them (e.g. by ignoring them). Remember that warnings are just that:
		3699	warnings, not errors, or proof of bugs.
3268		3700
3269	This means that, when you have a watcher that triggers in one hour and
3270	there are 100 watchers that would trigger before that then inserting will
3271	have to skip roughly seven (C<ld 100>) of these watchers.
3272		3701
3273	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3702	=head2 VALGRIND
3274		3703
3275	That means that changing a timer costs less than removing/adding them	3704	Valgrind has a special section here because it is a popular tool that is
3276	as only the relative motion in the event queue has to be paid for.	3705	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3277		3706
3278	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3707	If you think you found a bug (memory leak, uninitialised data access etc.)
		3708	in libev, then check twice: If valgrind reports something like:
3279		3709
3280	These just add the watcher into an array or at the head of a list.	3710	==2274== definitely lost: 0 bytes in 0 blocks.
		3711	==2274== possibly lost: 0 bytes in 0 blocks.
		3712	==2274== still reachable: 256 bytes in 1 blocks.
3281		3713
3282	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3714	Then there is no memory leak, just as memory accounted to global variables
		3715	is not a memleak - the memory is still being referenced, and didn't leak.
3283		3716
3284	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3717	Similarly, under some circumstances, valgrind might report kernel bugs
		3718	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3719	although an acceptable workaround has been found here), or it might be
		3720	confused.
3285		3721
3286	These watchers are stored in lists then need to be walked to find the	3722	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3287	correct watcher to remove. The lists are usually short (you don't usually	3723	make it into some kind of religion.
3288	have many watchers waiting for the same fd or signal).
3289		3724
3290	=item Finding the next timer in each loop iteration: O(1)	3725	If you are unsure about something, feel free to contact the mailing list
		3726	with the full valgrind report and an explanation on why you think this
		3727	is a bug in libev (best check the archives, too :). However, don't be
		3728	annoyed when you get a brisk "this is no bug" answer and take the chance
		3729	of learning how to interpret valgrind properly.
3291		3730
3292	By virtue of using a binary or 4-heap, the next timer is always found at a	3731	If you need, for some reason, empty reports from valgrind for your project
3293	fixed position in the storage array.	3732	I suggest using suppression lists.
3294		3733
3295	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3296		3734
3297	A change means an I/O watcher gets started or stopped, which requires	3735	=head1 PORTABILITY NOTES
3298	libev to recalculate its status (and possibly tell the kernel, depending
3299	on backend and whether C<ev_io_set> was used).
3300		3736
3301	=item Activating one watcher (putting it into the pending state): O(1)
3302
3303	=item Priority handling: O(number_of_priorities)
3304
3305	Priorities are implemented by allocating some space for each
3306	priority. When doing priority-based operations, libev usually has to
3307	linearly search all the priorities, but starting/stopping and activating
3308	watchers becomes O(1) w.r.t. priority handling.
3309
3310	=item Sending an ev_async: O(1)
3311
3312	=item Processing ev_async_send: O(number_of_async_watchers)
3313
3314	=item Processing signals: O(max_signal_number)
3315
3316	Sending involves a system call I<iff> there were no other C<ev_async_send>
3317	calls in the current loop iteration. Checking for async and signal events
3318	involves iterating over all running async watchers or all signal numbers.
3319
3320	=back
3321
3322
3323	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3737	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3324		3738
3325	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3739	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3326	requires, and its I/O model is fundamentally incompatible with the POSIX	3740	requires, and its I/O model is fundamentally incompatible with the POSIX
3327	model. Libev still offers limited functionality on this platform in	3741	model. Libev still offers limited functionality on this platform in
3328	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3742	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3339		3753
3340	Not a libev limitation but worth mentioning: windows apparently doesn't	3754	Not a libev limitation but worth mentioning: windows apparently doesn't
3341	accept large writes: instead of resulting in a partial write, windows will	3755	accept large writes: instead of resulting in a partial write, windows will
3342	either accept everything or return C<ENOBUFS> if the buffer is too large,	3756	either accept everything or return C<ENOBUFS> if the buffer is too large,
3343	so make sure you only write small amounts into your sockets (less than a	3757	so make sure you only write small amounts into your sockets (less than a
3344	megabyte seems safe, but thsi apparently depends on the amount of memory	3758	megabyte seems safe, but this apparently depends on the amount of memory
3345	available).	3759	available).
3346		3760
3347	Due to the many, low, and arbitrary limits on the win32 platform and	3761	Due to the many, low, and arbitrary limits on the win32 platform and
3348	the abysmal performance of winsockets, using a large number of sockets	3762	the abysmal performance of winsockets, using a large number of sockets
3349	is not recommended (and not reasonable). If your program needs to use	3763	is not recommended (and not reasonable). If your program needs to use
…		…
3360	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3774	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3361		3775
3362	#include "ev.h"	3776	#include "ev.h"
3363		3777
3364	And compile the following F<evwrap.c> file into your project (make sure	3778	And compile the following F<evwrap.c> file into your project (make sure
3365	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3779	you do I<not> compile the F<ev.c> or any other embedded source files!):
3366		3780
3367	#include "evwrap.h"	3781	#include "evwrap.h"
3368	#include "ev.c"	3782	#include "ev.c"
3369		3783
3370	=over 4	3784	=over 4
…		…
3415	wrap all I/O functions and provide your own fd management, but the cost of	3829	wrap all I/O functions and provide your own fd management, but the cost of
3416	calling select (O(n²)) will likely make this unworkable.	3830	calling select (O(n²)) will likely make this unworkable.
3417		3831
3418	=back	3832	=back
3419		3833
3420
3421	=head1 PORTABILITY REQUIREMENTS	3834	=head2 PORTABILITY REQUIREMENTS
3422		3835
3423	In addition to a working ISO-C implementation, libev relies on a few	3836	In addition to a working ISO-C implementation and of course the
3424	additional extensions:	3837	backend-specific APIs, libev relies on a few additional extensions:
3425		3838
3426	=over 4	3839	=over 4
3427		3840
3428	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3841	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3429	calling conventions regardless of C<ev_watcher_type *>.	3842	calling conventions regardless of C<ev_watcher_type *>.
…		…
3435	calls them using an C<ev_watcher *> internally.	3848	calls them using an C<ev_watcher *> internally.
3436		3849
3437	=item C<sig_atomic_t volatile> must be thread-atomic as well	3850	=item C<sig_atomic_t volatile> must be thread-atomic as well
3438		3851
3439	The type C<sig_atomic_t volatile> (or whatever is defined as	3852	The type C<sig_atomic_t volatile> (or whatever is defined as
3440	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3853	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3441	threads. This is not part of the specification for C<sig_atomic_t>, but is	3854	threads. This is not part of the specification for C<sig_atomic_t>, but is
3442	believed to be sufficiently portable.	3855	believed to be sufficiently portable.
3443		3856
3444	=item C<sigprocmask> must work in a threaded environment	3857	=item C<sigprocmask> must work in a threaded environment
3445		3858
…		…
3454	except the initial one, and run the default loop in the initial thread as	3867	except the initial one, and run the default loop in the initial thread as
3455	well.	3868	well.
3456		3869
3457	=item C<long> must be large enough for common memory allocation sizes	3870	=item C<long> must be large enough for common memory allocation sizes
3458		3871
3459	To improve portability and simplify using libev, libev uses C<long>	3872	To improve portability and simplify its API, libev uses C<long> internally
3460	internally instead of C<size_t> when allocating its data structures. On	3873	instead of C<size_t> when allocating its data structures. On non-POSIX
3461	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3874	systems (Microsoft...) this might be unexpectedly low, but is still at
3462	is still at least 31 bits everywhere, which is enough for hundreds of	3875	least 31 bits everywhere, which is enough for hundreds of millions of
3463	millions of watchers.	3876	watchers.
3464		3877
3465	=item C<double> must hold a time value in seconds with enough accuracy	3878	=item C<double> must hold a time value in seconds with enough accuracy
3466		3879
3467	The type C<double> is used to represent timestamps. It is required to	3880	The type C<double> is used to represent timestamps. It is required to
3468	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3881	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3472	=back	3885	=back
3473		3886
3474	If you know of other additional requirements drop me a note.	3887	If you know of other additional requirements drop me a note.
3475		3888
3476		3889
3477	=head1 COMPILER WARNINGS	3890	=head1 ALGORITHMIC COMPLEXITIES
3478		3891
3479	Depending on your compiler and compiler settings, you might get no or a	3892	In this section the complexities of (many of) the algorithms used inside
3480	lot of warnings when compiling libev code. Some people are apparently	3893	libev will be documented. For complexity discussions about backends see
3481	scared by this.	3894	the documentation for C<ev_default_init>.
3482		3895
3483	However, these are unavoidable for many reasons. For one, each compiler	3896	All of the following are about amortised time: If an array needs to be
3484	has different warnings, and each user has different tastes regarding	3897	extended, libev needs to realloc and move the whole array, but this
3485	warning options. "Warn-free" code therefore cannot be a goal except when	3898	happens asymptotically rarer with higher number of elements, so O(1) might
3486	targeting a specific compiler and compiler-version.	3899	mean that libev does a lengthy realloc operation in rare cases, but on
		3900	average it is much faster and asymptotically approaches constant time.
3487		3901
3488	Another reason is that some compiler warnings require elaborate	3902	=over 4
3489	workarounds, or other changes to the code that make it less clear and less
3490	maintainable.
3491		3903
3492	And of course, some compiler warnings are just plain stupid, or simply	3904	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3493	wrong (because they don't actually warn about the condition their message
3494	seems to warn about).
3495		3905
3496	While libev is written to generate as few warnings as possible,	3906	This means that, when you have a watcher that triggers in one hour and
3497	"warn-free" code is not a goal, and it is recommended not to build libev	3907	there are 100 watchers that would trigger before that, then inserting will
3498	with any compiler warnings enabled unless you are prepared to cope with	3908	have to skip roughly seven (C<ld 100>) of these watchers.
3499	them (e.g. by ignoring them). Remember that warnings are just that:
3500	warnings, not errors, or proof of bugs.
3501		3909
		3910	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3502		3911
3503	=head1 VALGRIND	3912	That means that changing a timer costs less than removing/adding them,
		3913	as only the relative motion in the event queue has to be paid for.
3504		3914
3505	Valgrind has a special section here because it is a popular tool that is	3915	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3506	highly useful, but valgrind reports are very hard to interpret.
3507		3916
3508	If you think you found a bug (memory leak, uninitialised data access etc.)	3917	These just add the watcher into an array or at the head of a list.
3509	in libev, then check twice: If valgrind reports something like:
3510		3918
3511	==2274== definitely lost: 0 bytes in 0 blocks.	3919	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3512	==2274== possibly lost: 0 bytes in 0 blocks.
3513	==2274== still reachable: 256 bytes in 1 blocks.
3514		3920
3515	Then there is no memory leak. Similarly, under some circumstances,	3921	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3516	valgrind might report kernel bugs as if it were a bug in libev, or it
3517	might be confused (it is a very good tool, but only a tool).
3518		3922
3519	If you are unsure about something, feel free to contact the mailing list	3923	These watchers are stored in lists, so they need to be walked to find the
3520	with the full valgrind report and an explanation on why you think this is	3924	correct watcher to remove. The lists are usually short (you don't usually
3521	a bug in libev. However, don't be annoyed when you get a brisk "this is	3925	have many watchers waiting for the same fd or signal: one is typical, two
3522	no bug" answer and take the chance of learning how to interpret valgrind	3926	is rare).
3523	properly.
3524		3927
3525	If you need, for some reason, empty reports from valgrind for your project	3928	=item Finding the next timer in each loop iteration: O(1)
3526	I suggest using suppression lists.	3929
		3930	By virtue of using a binary or 4-heap, the next timer is always found at a
		3931	fixed position in the storage array.
		3932
		3933	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3934
		3935	A change means an I/O watcher gets started or stopped, which requires
		3936	libev to recalculate its status (and possibly tell the kernel, depending
		3937	on backend and whether C<ev_io_set> was used).
		3938
		3939	=item Activating one watcher (putting it into the pending state): O(1)
		3940
		3941	=item Priority handling: O(number_of_priorities)
		3942
		3943	Priorities are implemented by allocating some space for each
		3944	priority. When doing priority-based operations, libev usually has to
		3945	linearly search all the priorities, but starting/stopping and activating
		3946	watchers becomes O(1) with respect to priority handling.
		3947
		3948	=item Sending an ev_async: O(1)
		3949
		3950	=item Processing ev_async_send: O(number_of_async_watchers)
		3951
		3952	=item Processing signals: O(max_signal_number)
		3953
		3954	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3955	calls in the current loop iteration. Checking for async and signal events
		3956	involves iterating over all running async watchers or all signal numbers.
		3957
		3958	=back
3527		3959
3528		3960
3529	=head1 AUTHOR	3961	=head1 AUTHOR
3530		3962
3531	Marc Lehmann <libev@schmorp.de>.	3963	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3532		3964

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