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Revision 1.229 by root, Wed Apr 15 17:49:27 2009 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	217	recommended ones.
216		218
217	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
218		220
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		222
221	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	225	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	226	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	252	}
251		253
252	...	254	...
253	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
254		256
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		258
257	Set the callback function to call on a retryable system call error (such	259	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	262	callback is set, then libev will expect it to remedy the situation, no
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	365	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	366	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	368	readiness notifications you get per iteration.
363		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
		373
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		375
366	And this is your standard poll(2) backend. It's more complicated	376	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	377	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	378	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	379	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	381	performance tips.
372		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		385
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		387
375	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	392
380	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
382		409
383	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	411	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
388		415	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		416
393	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	418	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
396		428
397	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
399		434
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		436
402	Kqueue deserves special mention, as at the time of this writing, it	437	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	439	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	445	system like NetBSD.
409		446
410	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		450
414	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
420		458
421	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
422		460
423	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
429		471
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		473
432	This is not implemented yet (and might never be, unless you send me an	474	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	475	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	488	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	489	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	491	might perform better.
450		492
451	On the positive side, ignoring the spurious readiness notifications, this	493	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
454		500
455	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
456		502
457	Try all backends (even potentially broken ones that wouldn't be tried	503	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		510
465	If one or more of these are or'ed into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		514
469	The most typical usage is like this:	515	Example: This is the most typical usage.
470		516
471	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		519
474	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	521	environment settings to be taken into account:
476		522
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		524
479	Use whatever libev has to offer, but make sure that kqueue is used if	525	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	527	private event loop and only if you know the OS supports your types of
		528	fds):
482		529
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		531
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		533
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	557	for example).
511		558
512	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
515		562
516	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		591
545	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
546		593
547	Like C<ev_default_fork>, but acts on an event loop created by	594	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
550		598
551	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
552		600
553	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
554		603
555	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
556		605
557	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
596	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
597	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.
598		647
599	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
600	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
601	finished (especially in interactive programs), but having a program that	650	finished (especially in interactive programs), but having a program
602	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
603	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.
604		654
605	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
606	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
607	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.
608		659
609	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
610	necessary) and will handle those and any outstanding ones. It will block	661	necessary) and will handle those and any already outstanding ones. It
611	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
612	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
613	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
614	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
615	usually a better approach for this kind of thing.	670	usually a better approach for this kind of thing.
616		671
617	Here are the gory details of what C<ev_loop> does:	672	Here are the gory details of what C<ev_loop> does:
618		673
619	- Before the first iteration, call any pending watchers.	674	- Before the first iteration, call any pending watchers.
…		…
629	any active watchers at all will result in not sleeping).	684	any active watchers at all will result in not sleeping).
630	- Sleep if the I/O and timer collect interval say so.	685	- Sleep if the I/O and timer collect interval say so.
631	- Block the process, waiting for any events.	686	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	687	- Queue all outstanding I/O (fd) events.
633	- 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.
634	- Queue all outstanding timers.	689	- Queue all expired timers.
635	- Queue all outstanding periodics.	690	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	691	- Unless any events are pending now, queue all idle watchers.
637	- Queue all check watchers.	692	- Queue all check watchers.
638	- 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).
639	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
640	be handled here by queueing them when their watcher gets executed.	695	be handled here by queueing them when their watcher gets executed.
…		…
657	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
658	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.
659		714
660	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.
661		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
662	=item ev_ref (loop)	719	=item ev_ref (loop)
663		720
664	=item ev_unref (loop)	721	=item ev_unref (loop)
665		722
666	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
667	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
668	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
669	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>
670	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
671	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
672	visible to the libev user and should not keep C<ev_loop> from exiting if	732	is not visible to the libev user and should not keep C<ev_loop> from
673	no event watchers registered by it are active. It is also an excellent	733	exiting if no event watchers registered by it are active. It is also an
674	way to do this for generic recurring timers or from within third-party	734	excellent way to do this for generic recurring timers or from within
675	libraries. Just remember to I<unref after start> and I<ref before stop>	735	third-party libraries. Just remember to I<unref after start> and I<ref
676	(but only if the watcher wasn't active before, or was active before,	736	before stop> (but only if the watcher wasn't active before, or was active
677	respectively).	737	before, respectively. Note also that libev might stop watchers itself
		738	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		739	in the callback).
678		740
679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	741	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
680	running when nothing else is active.	742	running when nothing else is active.
681		743
682	struct ev_signal exitsig;	744	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	745	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	746	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	747	evf_unref (loop);
686		748
687	Example: For some weird reason, unregister the above signal handler again.	749	Example: For some weird reason, unregister the above signal handler again.
…		…
701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	763	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
702	allows libev to delay invocation of I/O and timer/periodic callbacks	764	allows libev to delay invocation of I/O and timer/periodic callbacks
703	to increase efficiency of loop iterations (or to increase power-saving	765	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	766	opportunities).
705		767
706	The background is that sometimes your program runs just fast enough to	768	The idea is that sometimes your program runs just fast enough to handle
707	handle one (or very few) event(s) per loop iteration. While this makes	769	one (or very few) event(s) per loop iteration. While this makes the
708	the program responsive, it also wastes a lot of CPU time to poll for new	770	program responsive, it also wastes a lot of CPU time to poll for new
709	events, especially with backends like C<select ()> which have a high	771	events, especially with backends like C<select ()> which have a high
710	overhead for the actual polling but can deliver many events at once.	772	overhead for the actual polling but can deliver many events at once.
711		773
712	By setting a higher I<io collect interval> you allow libev to spend more	774	By setting a higher I<io collect interval> you allow libev to spend more
713	time collecting I/O events, so you can handle more events per iteration,	775	time collecting I/O events, so you can handle more events per iteration,
…		…
715	C<ev_timer>) will be not affected. Setting this to a non-null value will	777	C<ev_timer>) will be not affected. Setting this to a non-null value will
716	introduce an additional C<ev_sleep ()> call into most loop iterations.	778	introduce an additional C<ev_sleep ()> call into most loop iterations.
717		779
718	Likewise, by setting a higher I<timeout collect interval> you allow libev	780	Likewise, by setting a higher I<timeout collect interval> you allow libev
719	to spend more time collecting timeouts, at the expense of increased	781	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	782	latency/jitter/inexactness (the watcher callback will be called
721	will not be affected. Setting this to a non-null value will not introduce	783	later). C<ev_io> watchers will not be affected. Setting this to a non-null
722	any overhead in libev.	784	value will not introduce any overhead in libev.
723		785
724	Many (busy) programs can usually benefit by setting the I/O collect	786	Many (busy) programs can usually benefit by setting the I/O collect
725	interval to a value near C<0.1> or so, which is often enough for	787	interval to a value near C<0.1> or so, which is often enough for
726	interactive servers (of course not for games), likewise for timeouts. It	788	interactive servers (of course not for games), likewise for timeouts. It
727	usually doesn't make much sense to set it to a lower value than C<0.01>,	789	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
735	they fire on, say, one-second boundaries only.	797	they fire on, say, one-second boundaries only.
736		798
737	=item ev_loop_verify (loop)	799	=item ev_loop_verify (loop)
738		800
739	This function only does something when C<EV_VERIFY> support has been	801	This function only does something when C<EV_VERIFY> support has been
740	compiled in. It tries to go through all internal structures and checks	802	compiled in, which is the default for non-minimal builds. It tries to go
741	them for validity. If anything is found to be inconsistent, it will print	803	through all internal structures and checks them for validity. If anything
742	an error message to standard error and call C<abort ()>.	804	is found to be inconsistent, it will print an error message to standard
		805	error and call C<abort ()>.
743		806
744	This can be used to catch bugs inside libev itself: under normal	807	This can be used to catch bugs inside libev itself: under normal
745	circumstances, this function will never abort as of course libev keeps its	808	circumstances, this function will never abort as of course libev keeps its
746	data structures consistent.	809	data structures consistent.
747		810
748	=back	811	=back
749		812
750		813
751	=head1 ANATOMY OF A WATCHER	814	=head1 ANATOMY OF A WATCHER
752		815
		816	In the following description, uppercase C<TYPE> in names stands for the
		817	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		818	watchers and C<ev_io_start> for I/O watchers.
		819
753	A watcher is a structure that you create and register to record your	820	A watcher is a structure that you create and register to record your
754	interest in some event. For instance, if you want to wait for STDIN to	821	interest in some event. For instance, if you want to wait for STDIN to
755	become readable, you would create an C<ev_io> watcher for that:	822	become readable, you would create an C<ev_io> watcher for that:
756		823
757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	824	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
758	{	825	{
759	ev_io_stop (w);	826	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	827	ev_unloop (loop, EVUNLOOP_ALL);
761	}	828	}
762		829
763	struct ev_loop *loop = ev_default_loop (0);	830	struct ev_loop *loop = ev_default_loop (0);
		831
764	struct ev_io stdin_watcher;	832	ev_io stdin_watcher;
		833
765	ev_init (&stdin_watcher, my_cb);	834	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	835	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	836	ev_io_start (loop, &stdin_watcher);
		837
768	ev_loop (loop, 0);	838	ev_loop (loop, 0);
769		839
770	As you can see, you are responsible for allocating the memory for your	840	As you can see, you are responsible for allocating the memory for your
771	watcher structures (and it is usually a bad idea to do this on the stack,	841	watcher structures (and it is I<usually> a bad idea to do this on the
772	although this can sometimes be quite valid).	842	stack).
		843
		844	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		845	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
773		846
774	Each watcher structure must be initialised by a call to C<ev_init	847	Each watcher structure must be initialised by a call to C<ev_init
775	(watcher *, callback)>, which expects a callback to be provided. This	848	(watcher *, callback)>, which expects a callback to be provided. This
776	callback gets invoked each time the event occurs (or, in the case of I/O	849	callback gets invoked each time the event occurs (or, in the case of I/O
777	watchers, each time the event loop detects that the file descriptor given	850	watchers, each time the event loop detects that the file descriptor given
778	is readable and/or writable).	851	is readable and/or writable).
779		852
780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	853	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
781	with arguments specific to this watcher type. There is also a macro	854	macro to configure it, with arguments specific to the watcher type. There
782	to combine initialisation and setting in one call: C<< ev_<type>_init	855	is also a macro to combine initialisation and setting in one call: C<<
783	(watcher *, callback, ...) >>.	856	ev_TYPE_init (watcher *, callback, ...) >>.
784		857
785	To make the watcher actually watch out for events, you have to start it	858	To make the watcher actually watch out for events, you have to start it
786	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	859	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
787	*) >>), and you can stop watching for events at any time by calling the	860	*) >>), and you can stop watching for events at any time by calling the
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	861	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		862
790	As long as your watcher is active (has been started but not stopped) you	863	As long as your watcher is active (has been started but not stopped) you
791	must not touch the values stored in it. Most specifically you must never	864	must not touch the values stored in it. Most specifically you must never
792	reinitialise it or call its C<set> macro.	865	reinitialise it or call its C<ev_TYPE_set> macro.
793		866
794	Each and every callback receives the event loop pointer as first, the	867	Each and every callback receives the event loop pointer as first, the
795	registered watcher structure as second, and a bitset of received events as	868	registered watcher structure as second, and a bitset of received events as
796	third argument.	869	third argument.
797		870
…		…
855		928
856	=item C<EV_ASYNC>	929	=item C<EV_ASYNC>
857		930
858	The given async watcher has been asynchronously notified (see C<ev_async>).	931	The given async watcher has been asynchronously notified (see C<ev_async>).
859		932
		933	=item C<EV_CUSTOM>
		934
		935	Not ever sent (or otherwise used) by libev itself, but can be freely used
		936	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		937
860	=item C<EV_ERROR>	938	=item C<EV_ERROR>
861		939
862	An unspecified error has occurred, the watcher has been stopped. This might	940	An unspecified error has occurred, the watcher has been stopped. This might
863	happen because the watcher could not be properly started because libev	941	happen because the watcher could not be properly started because libev
864	ran out of memory, a file descriptor was found to be closed or any other	942	ran out of memory, a file descriptor was found to be closed or any other
		943	problem. Libev considers these application bugs.
		944
865	problem. You best act on it by reporting the problem and somehow coping	945	You best act on it by reporting the problem and somehow coping with the
866	with the watcher being stopped.	946	watcher being stopped. Note that well-written programs should not receive
		947	an error ever, so when your watcher receives it, this usually indicates a
		948	bug in your program.
867		949
868	Libev will usually signal a few "dummy" events together with an error,	950	Libev will usually signal a few "dummy" events together with an error, for
869	for example it might indicate that a fd is readable or writable, and if	951	example it might indicate that a fd is readable or writable, and if your
870	your callbacks is well-written it can just attempt the operation and cope	952	callbacks is well-written it can just attempt the operation and cope with
871	with the error from read() or write(). This will not work in multi-threaded	953	the error from read() or write(). This will not work in multi-threaded
872	programs, though, so beware.	954	programs, though, as the fd could already be closed and reused for another
		955	thing, so beware.
873		956
874	=back	957	=back
875		958
876	=head2 GENERIC WATCHER FUNCTIONS	959	=head2 GENERIC WATCHER FUNCTIONS
877
878	In the following description, C<TYPE> stands for the watcher type,
879	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
880		960
881	=over 4	961	=over 4
882		962
883	=item C<ev_init> (ev_TYPE *watcher, callback)	963	=item C<ev_init> (ev_TYPE *watcher, callback)
884		964
…		…
890	which rolls both calls into one.	970	which rolls both calls into one.
891		971
892	You can reinitialise a watcher at any time as long as it has been stopped	972	You can reinitialise a watcher at any time as long as it has been stopped
893	(or never started) and there are no pending events outstanding.	973	(or never started) and there are no pending events outstanding.
894		974
895	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	975	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
896	int revents)>.	976	int revents)>.
		977
		978	Example: Initialise an C<ev_io> watcher in two steps.
		979
		980	ev_io w;
		981	ev_init (&w, my_cb);
		982	ev_io_set (&w, STDIN_FILENO, EV_READ);
897		983
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	984	=item C<ev_TYPE_set> (ev_TYPE *, [args])
899		985
900	This macro initialises the type-specific parts of a watcher. You need to	986	This macro initialises the type-specific parts of a watcher. You need to
901	call C<ev_init> at least once before you call this macro, but you can	987	call C<ev_init> at least once before you call this macro, but you can
…		…
904	difference to the C<ev_init> macro).	990	difference to the C<ev_init> macro).
905		991
906	Although some watcher types do not have type-specific arguments	992	Although some watcher types do not have type-specific arguments
907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	993	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
908		994
		995	See C<ev_init>, above, for an example.
		996
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	997	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		998
911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	999	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
912	calls into a single call. This is the most convenient method to initialise	1000	calls into a single call. This is the most convenient method to initialise
913	a watcher. The same limitations apply, of course.	1001	a watcher. The same limitations apply, of course.
914		1002
		1003	Example: Initialise and set an C<ev_io> watcher in one step.
		1004
		1005	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1006
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1007	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
916		1008
917	Starts (activates) the given watcher. Only active watchers will receive	1009	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	1010	events. If the watcher is already active nothing will happen.
919		1011
		1012	Example: Start the C<ev_io> watcher that is being abused as example in this
		1013	whole section.
		1014
		1015	ev_io_start (EV_DEFAULT_UC, &w);
		1016
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1017	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
921		1018
922	Stops the given watcher again (if active) and clears the pending	1019	Stops the given watcher if active, and clears the pending status (whether
		1020	the watcher was active or not).
		1021
923	status. It is possible that stopped watchers are pending (for example,	1022	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	1023	non-repeating timers are being stopped when they become pending - but
925	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1024	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
926	you want to free or reuse the memory used by the watcher it is therefore a	1025	pending. If you want to free or reuse the memory used by the watcher it is
927	good idea to always call its C<ev_TYPE_stop> function.	1026	therefore a good idea to always call its C<ev_TYPE_stop> function.
928		1027
929	=item bool ev_is_active (ev_TYPE *watcher)	1028	=item bool ev_is_active (ev_TYPE *watcher)
930		1029
931	Returns a true value iff the watcher is active (i.e. it has been started	1030	Returns a true value iff the watcher is active (i.e. it has been started
932	and not yet been stopped). As long as a watcher is active you must not modify	1031	and not yet been stopped). As long as a watcher is active you must not modify
…		…
974	The default priority used by watchers when no priority has been set is	1073	The default priority used by watchers when no priority has been set is
975	always C<0>, which is supposed to not be too high and not be too low :).	1074	always C<0>, which is supposed to not be too high and not be too low :).
976		1075
977	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1076	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
978	fine, as long as you do not mind that the priority value you query might	1077	fine, as long as you do not mind that the priority value you query might
979	or might not have been adjusted to be within valid range.	1078	or might not have been clamped to the valid range.
980		1079
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1080	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1081
983	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1082	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
984	C<loop> nor C<revents> need to be valid as long as the watcher callback	1083	C<loop> nor C<revents> need to be valid as long as the watcher callback
985	can deal with that fact.	1084	can deal with that fact, as both are simply passed through to the
		1085	callback.
986		1086
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1087	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1088
989	If the watcher is pending, this function returns clears its pending status	1089	If the watcher is pending, this function clears its pending status and
990	and returns its C<revents> bitset (as if its callback was invoked). If the	1090	returns its C<revents> bitset (as if its callback was invoked). If the
991	watcher isn't pending it does nothing and returns C<0>.	1091	watcher isn't pending it does nothing and returns C<0>.
992		1092
		1093	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1094	callback to be invoked, which can be accomplished with this function.
		1095
993	=back	1096	=back
994		1097
995		1098
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1099	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1100
998	Each watcher has, by default, a member C<void *data> that you can change	1101	Each watcher has, by default, a member C<void *data> that you can change
999	and read at any time, libev will completely ignore it. This can be used	1102	and read at any time: libev will completely ignore it. This can be used
1000	to associate arbitrary data with your watcher. If you need more data and	1103	to associate arbitrary data with your watcher. If you need more data and
1001	don't want to allocate memory and store a pointer to it in that data	1104	don't want to allocate memory and store a pointer to it in that data
1002	member, you can also "subclass" the watcher type and provide your own	1105	member, you can also "subclass" the watcher type and provide your own
1003	data:	1106	data:
1004		1107
1005	struct my_io	1108	struct my_io
1006	{	1109	{
1007	struct ev_io io;	1110	ev_io io;
1008	int otherfd;	1111	int otherfd;
1009	void *somedata;	1112	void *somedata;
1010	struct whatever *mostinteresting;	1113	struct whatever *mostinteresting;
1011	}	1114	};
		1115
		1116	...
		1117	struct my_io w;
		1118	ev_io_init (&w.io, my_cb, fd, EV_READ);
1012		1119
1013	And since your callback will be called with a pointer to the watcher, you	1120	And since your callback will be called with a pointer to the watcher, you
1014	can cast it back to your own type:	1121	can cast it back to your own type:
1015		1122
1016	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1123	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1017	{	1124	{
1018	struct my_io *w = (struct my_io *)w_;	1125	struct my_io *w = (struct my_io *)w_;
1019	...	1126	...
1020	}	1127	}
1021		1128
1022	More interesting and less C-conformant ways of casting your callback type	1129	More interesting and less C-conformant ways of casting your callback type
1023	instead have been omitted.	1130	instead have been omitted.
1024		1131
1025	Another common scenario is having some data structure with multiple	1132	Another common scenario is to use some data structure with multiple
1026	watchers:	1133	embedded watchers:
1027		1134
1028	struct my_biggy	1135	struct my_biggy
1029	{	1136	{
1030	int some_data;	1137	int some_data;
1031	ev_timer t1;	1138	ev_timer t1;
1032	ev_timer t2;	1139	ev_timer t2;
1033	}	1140	}
1034		1141
1035	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1142	In this case getting the pointer to C<my_biggy> is a bit more
1036	you need to use C<offsetof>:	1143	complicated: Either you store the address of your C<my_biggy> struct
		1144	in the C<data> member of the watcher (for woozies), or you need to use
		1145	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1146	programmers):
1037		1147
1038	#include <stddef.h>	1148	#include <stddef.h>
1039		1149
1040	static void	1150	static void
1041	t1_cb (EV_P_ struct ev_timer *w, int revents)	1151	t1_cb (EV_P_ ev_timer *w, int revents)
1042	{	1152	{
1043	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
1044	(((char *)w) - offsetof (struct my_biggy, t1));	1154	(((char *)w) - offsetof (struct my_biggy, t1));
1045	}	1155	}
1046		1156
1047	static void	1157	static void
1048	t2_cb (EV_P_ struct ev_timer *w, int revents)	1158	t2_cb (EV_P_ ev_timer *w, int revents)
1049	{	1159	{
1050	struct my_biggy big = (struct my_biggy *	1160	struct my_biggy big = (struct my_biggy *
1051	(((char *)w) - offsetof (struct my_biggy, t2));	1161	(((char *)w) - offsetof (struct my_biggy, t2));
1052	}	1162	}
1053		1163
…		…
1081	In general you can register as many read and/or write event watchers per	1191	In general you can register as many read and/or write event watchers per
1082	fd as you want (as long as you don't confuse yourself). Setting all file	1192	fd as you want (as long as you don't confuse yourself). Setting all file
1083	descriptors to non-blocking mode is also usually a good idea (but not	1193	descriptors to non-blocking mode is also usually a good idea (but not
1084	required if you know what you are doing).	1194	required if you know what you are doing).
1085		1195
1086	If you must do this, then force the use of a known-to-be-good backend	1196	If you cannot use non-blocking mode, then force the use of a
1087	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1197	known-to-be-good backend (at the time of this writing, this includes only
1088	C<EVBACKEND_POLL>).	1198	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1089		1199
1090	Another thing you have to watch out for is that it is quite easy to	1200	Another thing you have to watch out for is that it is quite easy to
1091	receive "spurious" readiness notifications, that is your callback might	1201	receive "spurious" readiness notifications, that is your callback might
1092	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1202	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1093	because there is no data. Not only are some backends known to create a	1203	because there is no data. Not only are some backends known to create a
1094	lot of those (for example Solaris ports), it is very easy to get into	1204	lot of those (for example Solaris ports), it is very easy to get into
1095	this situation even with a relatively standard program structure. Thus	1205	this situation even with a relatively standard program structure. Thus
1096	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1206	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1097	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1207	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1098		1208
1099	If you cannot run the fd in non-blocking mode (for example you should not	1209	If you cannot run the fd in non-blocking mode (for example you should
1100	play around with an Xlib connection), then you have to separately re-test	1210	not play around with an Xlib connection), then you have to separately
1101	whether a file descriptor is really ready with a known-to-be good interface	1211	re-test whether a file descriptor is really ready with a known-to-be good
1102	such as poll (fortunately in our Xlib example, Xlib already does this on	1212	interface such as poll (fortunately in our Xlib example, Xlib already
1103	its own, so its quite safe to use).	1213	does this on its own, so its quite safe to use). Some people additionally
		1214	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1215	indefinitely.
		1216
		1217	But really, best use non-blocking mode.
1104		1218
1105	=head3 The special problem of disappearing file descriptors	1219	=head3 The special problem of disappearing file descriptors
1106		1220
1107	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1221	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1108	descriptor (either by calling C<close> explicitly or by any other means,	1222	descriptor (either due to calling C<close> explicitly or any other means,
1109	such as C<dup>). The reason is that you register interest in some file	1223	such as C<dup2>). The reason is that you register interest in some file
1110	descriptor, but when it goes away, the operating system will silently drop	1224	descriptor, but when it goes away, the operating system will silently drop
1111	this interest. If another file descriptor with the same number then is	1225	this interest. If another file descriptor with the same number then is
1112	registered with libev, there is no efficient way to see that this is, in	1226	registered with libev, there is no efficient way to see that this is, in
1113	fact, a different file descriptor.	1227	fact, a different file descriptor.
1114		1228
…		…
1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1259	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1146	C<EVBACKEND_POLL>.	1260	C<EVBACKEND_POLL>.
1147		1261
1148	=head3 The special problem of SIGPIPE	1262	=head3 The special problem of SIGPIPE
1149		1263
1150	While not really specific to libev, it is easy to forget about SIGPIPE:	1264	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1151	when writing to a pipe whose other end has been closed, your program gets	1265	when writing to a pipe whose other end has been closed, your program gets
1152	send a SIGPIPE, which, by default, aborts your program. For most programs	1266	sent a SIGPIPE, which, by default, aborts your program. For most programs
1153	this is sensible behaviour, for daemons, this is usually undesirable.	1267	this is sensible behaviour, for daemons, this is usually undesirable.
1154		1268
1155	So when you encounter spurious, unexplained daemon exits, make sure you	1269	So when you encounter spurious, unexplained daemon exits, make sure you
1156	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1270	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1157	somewhere, as that would have given you a big clue).	1271	somewhere, as that would have given you a big clue).
…		…
1164	=item ev_io_init (ev_io *, callback, int fd, int events)	1278	=item ev_io_init (ev_io *, callback, int fd, int events)
1165		1279
1166	=item ev_io_set (ev_io *, int fd, int events)	1280	=item ev_io_set (ev_io *, int fd, int events)
1167		1281
1168	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1282	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1169	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1283	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1170	C<EV_READ | EV_WRITE> to receive the given events.	1284	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1171		1285
1172	=item int fd [read-only]	1286	=item int fd [read-only]
1173		1287
1174	The file descriptor being watched.	1288	The file descriptor being watched.
1175		1289
…		…
1184	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1298	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1185	readable, but only once. Since it is likely line-buffered, you could	1299	readable, but only once. Since it is likely line-buffered, you could
1186	attempt to read a whole line in the callback.	1300	attempt to read a whole line in the callback.
1187		1301
1188	static void	1302	static void
1189	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1303	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1190	{	1304	{
1191	ev_io_stop (loop, w);	1305	ev_io_stop (loop, w);
1192	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1306	.. read from stdin here (or from w->fd) and handle any I/O errors
1193	}	1307	}
1194		1308
1195	...	1309	...
1196	struct ev_loop *loop = ev_default_init (0);	1310	struct ev_loop *loop = ev_default_init (0);
1197	struct ev_io stdin_readable;	1311	ev_io stdin_readable;
1198	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1312	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1199	ev_io_start (loop, &stdin_readable);	1313	ev_io_start (loop, &stdin_readable);
1200	ev_loop (loop, 0);	1314	ev_loop (loop, 0);
1201		1315
1202		1316
…		…
1205	Timer watchers are simple relative timers that generate an event after a	1319	Timer watchers are simple relative timers that generate an event after a
1206	given time, and optionally repeating in regular intervals after that.	1320	given time, and optionally repeating in regular intervals after that.
1207		1321
1208	The timers are based on real time, that is, if you register an event that	1322	The timers are based on real time, that is, if you register an event that
1209	times out after an hour and you reset your system clock to January last	1323	times out after an hour and you reset your system clock to January last
1210	year, it will still time out after (roughly) and hour. "Roughly" because	1324	year, it will still time out after (roughly) one hour. "Roughly" because
1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1325	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1212	monotonic clock option helps a lot here).	1326	monotonic clock option helps a lot here).
1213		1327
1214	The callback is guaranteed to be invoked only after its timeout has passed,	1328	The callback is guaranteed to be invoked only I<after> its timeout has
1215	but if multiple timers become ready during the same loop iteration then	1329	passed, but if multiple timers become ready during the same loop iteration
1216	order of execution is undefined.	1330	then order of execution is undefined.
		1331
		1332	=head3 Be smart about timeouts
		1333
		1334	Many real-world problems involve some kind of timeout, usually for error
		1335	recovery. A typical example is an HTTP request - if the other side hangs,
		1336	you want to raise some error after a while.
		1337
		1338	What follows are some ways to handle this problem, from obvious and
		1339	inefficient to smart and efficient.
		1340
		1341	In the following, a 60 second activity timeout is assumed - a timeout that
		1342	gets reset to 60 seconds each time there is activity (e.g. each time some
		1343	data or other life sign was received).
		1344
		1345	=over 4
		1346
		1347	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1348
		1349	This is the most obvious, but not the most simple way: In the beginning,
		1350	start the watcher:
		1351
		1352	ev_timer_init (timer, callback, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1356	and start it again:
		1357
		1358	ev_timer_stop (loop, timer);
		1359	ev_timer_set (timer, 60., 0.);
		1360	ev_timer_start (loop, timer);
		1361
		1362	This is relatively simple to implement, but means that each time there is
		1363	some activity, libev will first have to remove the timer from its internal
		1364	data structure and then add it again. Libev tries to be fast, but it's
		1365	still not a constant-time operation.
		1366
		1367	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1368
		1369	This is the easiest way, and involves using C<ev_timer_again> instead of
		1370	C<ev_timer_start>.
		1371
		1372	To implement this, configure an C<ev_timer> with a C<repeat> value
		1373	of C<60> and then call C<ev_timer_again> at start and each time you
		1374	successfully read or write some data. If you go into an idle state where
		1375	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1376	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1377
		1378	That means you can ignore both the C<ev_timer_start> function and the
		1379	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1380	member and C<ev_timer_again>.
		1381
		1382	At start:
		1383
		1384	ev_timer_init (timer, callback);
		1385	timer->repeat = 60.;
		1386	ev_timer_again (loop, timer);
		1387
		1388	Each time there is some activity:
		1389
		1390	ev_timer_again (loop, timer);
		1391
		1392	It is even possible to change the time-out on the fly, regardless of
		1393	whether the watcher is active or not:
		1394
		1395	timer->repeat = 30.;
		1396	ev_timer_again (loop, timer);
		1397
		1398	This is slightly more efficient then stopping/starting the timer each time
		1399	you want to modify its timeout value, as libev does not have to completely
		1400	remove and re-insert the timer from/into its internal data structure.
		1401
		1402	It is, however, even simpler than the "obvious" way to do it.
		1403
		1404	=item 3. Let the timer time out, but then re-arm it as required.
		1405
		1406	This method is more tricky, but usually most efficient: Most timeouts are
		1407	relatively long compared to the intervals between other activity - in
		1408	our example, within 60 seconds, there are usually many I/O events with
		1409	associated activity resets.
		1410
		1411	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1412	but remember the time of last activity, and check for a real timeout only
		1413	within the callback:
		1414
		1415	ev_tstamp last_activity; // time of last activity
		1416
		1417	static void
		1418	callback (EV_P_ ev_timer *w, int revents)
		1419	{
		1420	ev_tstamp now = ev_now (EV_A);
		1421	ev_tstamp timeout = last_activity + 60.;
		1422
		1423	// if last_activity + 60. is older than now, we did time out
		1424	if (timeout < now)
		1425	{
		1426	// timeout occured, take action
		1427	}
		1428	else
		1429	{
		1430	// callback was invoked, but there was some activity, re-arm
		1431	// the watcher to fire in last_activity + 60, which is
		1432	// guaranteed to be in the future, so "again" is positive:
		1433	w->repeat = timeout - now;
		1434	ev_timer_again (EV_A_ w);
		1435	}
		1436	}
		1437
		1438	To summarise the callback: first calculate the real timeout (defined
		1439	as "60 seconds after the last activity"), then check if that time has
		1440	been reached, which means something I<did>, in fact, time out. Otherwise
		1441	the callback was invoked too early (C<timeout> is in the future), so
		1442	re-schedule the timer to fire at that future time, to see if maybe we have
		1443	a timeout then.
		1444
		1445	Note how C<ev_timer_again> is used, taking advantage of the
		1446	C<ev_timer_again> optimisation when the timer is already running.
		1447
		1448	This scheme causes more callback invocations (about one every 60 seconds
		1449	minus half the average time between activity), but virtually no calls to
		1450	libev to change the timeout.
		1451
		1452	To start the timer, simply initialise the watcher and set C<last_activity>
		1453	to the current time (meaning we just have some activity :), then call the
		1454	callback, which will "do the right thing" and start the timer:
		1455
		1456	ev_timer_init (timer, callback);
		1457	last_activity = ev_now (loop);
		1458	callback (loop, timer, EV_TIMEOUT);
		1459
		1460	And when there is some activity, simply store the current time in
		1461	C<last_activity>, no libev calls at all:
		1462
		1463	last_actiivty = ev_now (loop);
		1464
		1465	This technique is slightly more complex, but in most cases where the
		1466	time-out is unlikely to be triggered, much more efficient.
		1467
		1468	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1469	callback :) - just change the timeout and invoke the callback, which will
		1470	fix things for you.
		1471
		1472	=item 4. Wee, just use a double-linked list for your timeouts.
		1473
		1474	If there is not one request, but many thousands (millions...), all
		1475	employing some kind of timeout with the same timeout value, then one can
		1476	do even better:
		1477
		1478	When starting the timeout, calculate the timeout value and put the timeout
		1479	at the I<end> of the list.
		1480
		1481	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1482	the list is expected to fire (for example, using the technique #3).
		1483
		1484	When there is some activity, remove the timer from the list, recalculate
		1485	the timeout, append it to the end of the list again, and make sure to
		1486	update the C<ev_timer> if it was taken from the beginning of the list.
		1487
		1488	This way, one can manage an unlimited number of timeouts in O(1) time for
		1489	starting, stopping and updating the timers, at the expense of a major
		1490	complication, and having to use a constant timeout. The constant timeout
		1491	ensures that the list stays sorted.
		1492
		1493	=back
		1494
		1495	So which method the best?
		1496
		1497	Method #2 is a simple no-brain-required solution that is adequate in most
		1498	situations. Method #3 requires a bit more thinking, but handles many cases
		1499	better, and isn't very complicated either. In most case, choosing either
		1500	one is fine, with #3 being better in typical situations.
		1501
		1502	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1503	rather complicated, but extremely efficient, something that really pays
		1504	off after the first million or so of active timers, i.e. it's usually
		1505	overkill :)
1217		1506
1218	=head3 The special problem of time updates	1507	=head3 The special problem of time updates
1219		1508
1220	Establishing the current time is a costly operation (it usually takes at	1509	Establishing the current time is a costly operation (it usually takes at
1221	least two system calls): EV therefore updates its idea of the current	1510	least two system calls): EV therefore updates its idea of the current
1222	time only before and after C<ev_loop> polls for new events, which causes	1511	time only before and after C<ev_loop> collects new events, which causes a
1223	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1512	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1224	lots of events.	1513	lots of events in one iteration.
1225		1514
1226	The relative timeouts are calculated relative to the C<ev_now ()>	1515	The relative timeouts are calculated relative to the C<ev_now ()>
1227	time. This is usually the right thing as this timestamp refers to the time	1516	time. This is usually the right thing as this timestamp refers to the time
1228	of the event triggering whatever timeout you are modifying/starting. If	1517	of the event triggering whatever timeout you are modifying/starting. If
1229	you suspect event processing to be delayed and you I<need> to base the	1518	you suspect event processing to be delayed and you I<need> to base the
1230	timeout on the current time, use something like this to adjust for this:	1519	timeout on the current time, use something like this to adjust for this:
1231		1520
1232	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1521	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1233		1522
1234	If the event loop is suspended for a long time, one can also force an	1523	If the event loop is suspended for a long time, you can also force an
1235	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1524	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1236	()>.	1525	()>.
1237		1526
1238	=head3 Watcher-Specific Functions and Data Members	1527	=head3 Watcher-Specific Functions and Data Members
1239		1528
…		…
1265	If the timer is started but non-repeating, stop it (as if it timed out).	1554	If the timer is started but non-repeating, stop it (as if it timed out).
1266		1555
1267	If the timer is repeating, either start it if necessary (with the	1556	If the timer is repeating, either start it if necessary (with the
1268	C<repeat> value), or reset the running timer to the C<repeat> value.	1557	C<repeat> value), or reset the running timer to the C<repeat> value.
1269		1558
1270	This sounds a bit complicated, but here is a useful and typical	1559	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1271	example: Imagine you have a TCP connection and you want a so-called idle	1560	usage example.
1272	timeout, that is, you want to be called when there have been, say, 60
1273	seconds of inactivity on the socket. The easiest way to do this is to
1274	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1275	C<ev_timer_again> each time you successfully read or write some data. If
1276	you go into an idle state where you do not expect data to travel on the
1277	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1278	automatically restart it if need be.
1279
1280	That means you can ignore the C<after> value and C<ev_timer_start>
1281	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1282
1283	ev_timer_init (timer, callback, 0., 5.);
1284	ev_timer_again (loop, timer);
1285	...
1286	timer->again = 17.;
1287	ev_timer_again (loop, timer);
1288	...
1289	timer->again = 10.;
1290	ev_timer_again (loop, timer);
1291
1292	This is more slightly efficient then stopping/starting the timer each time
1293	you want to modify its timeout value.
1294		1561
1295	=item ev_tstamp repeat [read-write]	1562	=item ev_tstamp repeat [read-write]
1296		1563
1297	The current C<repeat> value. Will be used each time the watcher times out	1564	The current C<repeat> value. Will be used each time the watcher times out
1298	or C<ev_timer_again> is called and determines the next timeout (if any),	1565	or C<ev_timer_again> is called, and determines the next timeout (if any),
1299	which is also when any modifications are taken into account.	1566	which is also when any modifications are taken into account.
1300		1567
1301	=back	1568	=back
1302		1569
1303	=head3 Examples	1570	=head3 Examples
1304		1571
1305	Example: Create a timer that fires after 60 seconds.	1572	Example: Create a timer that fires after 60 seconds.
1306		1573
1307	static void	1574	static void
1308	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1309	{	1576	{
1310	.. one minute over, w is actually stopped right here	1577	.. one minute over, w is actually stopped right here
1311	}	1578	}
1312		1579
1313	struct ev_timer mytimer;	1580	ev_timer mytimer;
1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1581	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1315	ev_timer_start (loop, &mytimer);	1582	ev_timer_start (loop, &mytimer);
1316		1583
1317	Example: Create a timeout timer that times out after 10 seconds of	1584	Example: Create a timeout timer that times out after 10 seconds of
1318	inactivity.	1585	inactivity.
1319		1586
1320	static void	1587	static void
1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1588	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1322	{	1589	{
1323	.. ten seconds without any activity	1590	.. ten seconds without any activity
1324	}	1591	}
1325		1592
1326	struct ev_timer mytimer;	1593	ev_timer mytimer;
1327	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1594	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1328	ev_timer_again (&mytimer); /* start timer */	1595	ev_timer_again (&mytimer); /* start timer */
1329	ev_loop (loop, 0);	1596	ev_loop (loop, 0);
1330		1597
1331	// and in some piece of code that gets executed on any "activity":	1598	// and in some piece of code that gets executed on any "activity":
…		…
1336	=head2 C<ev_periodic> - to cron or not to cron?	1603	=head2 C<ev_periodic> - to cron or not to cron?
1337		1604
1338	Periodic watchers are also timers of a kind, but they are very versatile	1605	Periodic watchers are also timers of a kind, but they are very versatile
1339	(and unfortunately a bit complex).	1606	(and unfortunately a bit complex).
1340		1607
1341	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1608	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1342	but on wall clock time (absolute time). You can tell a periodic watcher	1609	relative time, the physical time that passes) but on wall clock time
1343	to trigger after some specific point in time. For example, if you tell a	1610	(absolute time, the thing you can read on your calender or clock). The
1344	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1611	difference is that wall clock time can run faster or slower than real
1345	+ 10.>, that is, an absolute time not a delay) and then reset your system	1612	time, and time jumps are not uncommon (e.g. when you adjust your
1346	clock to January of the previous year, then it will take more than year	1613	wrist-watch).
1347	to trigger the event (unlike an C<ev_timer>, which would still trigger
1348	roughly 10 seconds later as it uses a relative timeout).
1349		1614
		1615	You can tell a periodic watcher to trigger after some specific point
		1616	in time: for example, if you tell a periodic watcher to trigger "in 10
		1617	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1618	not a delay) and then reset your system clock to January of the previous
		1619	year, then it will take a year or more to trigger the event (unlike an
		1620	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1621	it, as it uses a relative timeout).
		1622
1350	C<ev_periodic>s can also be used to implement vastly more complex timers,	1623	C<ev_periodic> watchers can also be used to implement vastly more complex
1351	such as triggering an event on each "midnight, local time", or other	1624	timers, such as triggering an event on each "midnight, local time", or
1352	complicated, rules.	1625	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1626	those cannot react to time jumps.
1353		1627
1354	As with timers, the callback is guaranteed to be invoked only when the	1628	As with timers, the callback is guaranteed to be invoked only when the
1355	time (C<at>) has passed, but if multiple periodic timers become ready	1629	point in time where it is supposed to trigger has passed, but if multiple
1356	during the same loop iteration then order of execution is undefined.	1630	periodic timers become ready during the same loop iteration, then order of
		1631	execution is undefined.
1357		1632
1358	=head3 Watcher-Specific Functions and Data Members	1633	=head3 Watcher-Specific Functions and Data Members
1359		1634
1360	=over 4	1635	=over 4
1361		1636
1362	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1637	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1363		1638
1364	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1639	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1365		1640
1366	Lots of arguments, lets sort it out... There are basically three modes of	1641	Lots of arguments, let's sort it out... There are basically three modes of
1367	operation, and we will explain them from simplest to complex:	1642	operation, and we will explain them from simplest to most complex:
1368		1643
1369	=over 4	1644	=over 4
1370		1645
1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1646	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1372		1647
1373	In this configuration the watcher triggers an event after the wall clock	1648	In this configuration the watcher triggers an event after the wall clock
1374	time C<at> has passed and doesn't repeat. It will not adjust when a time	1649	time C<offset> has passed. It will not repeat and will not adjust when a
1375	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1650	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1376	run when the system time reaches or surpasses this time.	1651	will be stopped and invoked when the system clock reaches or surpasses
		1652	this point in time.
1377		1653
1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1654	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1379		1655
1380	In this mode the watcher will always be scheduled to time out at the next	1656	In this mode the watcher will always be scheduled to time out at the next
1381	C<at + N * interval> time (for some integer N, which can also be negative)	1657	C<offset + N * interval> time (for some integer N, which can also be
1382	and then repeat, regardless of any time jumps.	1658	negative) and then repeat, regardless of any time jumps. The C<offset>
		1659	argument is merely an offset into the C<interval> periods.
1383		1660
1384	This can be used to create timers that do not drift with respect to system	1661	This can be used to create timers that do not drift with respect to the
1385	time, for example, here is a C<ev_periodic> that triggers each hour, on	1662	system clock, for example, here is an C<ev_periodic> that triggers each
1386	the hour:	1663	hour, on the hour (with respect to UTC):
1387		1664
1388	ev_periodic_set (&periodic, 0., 3600., 0);	1665	ev_periodic_set (&periodic, 0., 3600., 0);
1389		1666
1390	This doesn't mean there will always be 3600 seconds in between triggers,	1667	This doesn't mean there will always be 3600 seconds in between triggers,
1391	but only that the callback will be called when the system time shows a	1668	but only that the callback will be called when the system time shows a
1392	full hour (UTC), or more correctly, when the system time is evenly divisible	1669	full hour (UTC), or more correctly, when the system time is evenly divisible
1393	by 3600.	1670	by 3600.
1394		1671
1395	Another way to think about it (for the mathematically inclined) is that	1672	Another way to think about it (for the mathematically inclined) is that
1396	C<ev_periodic> will try to run the callback in this mode at the next possible	1673	C<ev_periodic> will try to run the callback in this mode at the next possible
1397	time where C<time = at (mod interval)>, regardless of any time jumps.	1674	time where C<time = offset (mod interval)>, regardless of any time jumps.
1398		1675
1399	For numerical stability it is preferable that the C<at> value is near	1676	For numerical stability it is preferable that the C<offset> value is near
1400	C<ev_now ()> (the current time), but there is no range requirement for	1677	C<ev_now ()> (the current time), but there is no range requirement for
1401	this value, and in fact is often specified as zero.	1678	this value, and in fact is often specified as zero.
1402		1679
1403	Note also that there is an upper limit to how often a timer can fire (CPU	1680	Note also that there is an upper limit to how often a timer can fire (CPU
1404	speed for example), so if C<interval> is very small then timing stability	1681	speed for example), so if C<interval> is very small then timing stability
1405	will of course deteriorate. Libev itself tries to be exact to be about one	1682	will of course deteriorate. Libev itself tries to be exact to be about one
1406	millisecond (if the OS supports it and the machine is fast enough).	1683	millisecond (if the OS supports it and the machine is fast enough).
1407		1684
1408	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1685	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1409		1686
1410	In this mode the values for C<interval> and C<at> are both being	1687	In this mode the values for C<interval> and C<offset> are both being
1411	ignored. Instead, each time the periodic watcher gets scheduled, the	1688	ignored. Instead, each time the periodic watcher gets scheduled, the
1412	reschedule callback will be called with the watcher as first, and the	1689	reschedule callback will be called with the watcher as first, and the
1413	current time as second argument.	1690	current time as second argument.
1414		1691
1415	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1692	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1416	ever, or make ANY event loop modifications whatsoever>.	1693	or make ANY other event loop modifications whatsoever, unless explicitly
		1694	allowed by documentation here>.
1417		1695
1418	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1696	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1419	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1697	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1420	only event loop modification you are allowed to do).	1698	only event loop modification you are allowed to do).
1421		1699
1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1700	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1423	*w, ev_tstamp now)>, e.g.:	1701	*w, ev_tstamp now)>, e.g.:
1424		1702
		1703	static ev_tstamp
1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1704	my_rescheduler (ev_periodic *w, ev_tstamp now)
1426	{	1705	{
1427	return now + 60.;	1706	return now + 60.;
1428	}	1707	}
1429		1708
1430	It must return the next time to trigger, based on the passed time value	1709	It must return the next time to trigger, based on the passed time value
…		…
1450	a different time than the last time it was called (e.g. in a crond like	1729	a different time than the last time it was called (e.g. in a crond like
1451	program when the crontabs have changed).	1730	program when the crontabs have changed).
1452		1731
1453	=item ev_tstamp ev_periodic_at (ev_periodic *)	1732	=item ev_tstamp ev_periodic_at (ev_periodic *)
1454		1733
1455	When active, returns the absolute time that the watcher is supposed to	1734	When active, returns the absolute time that the watcher is supposed
1456	trigger next.	1735	to trigger next. This is not the same as the C<offset> argument to
		1736	C<ev_periodic_set>, but indeed works even in interval and manual
		1737	rescheduling modes.
1457		1738
1458	=item ev_tstamp offset [read-write]	1739	=item ev_tstamp offset [read-write]
1459		1740
1460	When repeating, this contains the offset value, otherwise this is the	1741	When repeating, this contains the offset value, otherwise this is the
1461	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1742	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1743	although libev might modify this value for better numerical stability).
1462		1744
1463	Can be modified any time, but changes only take effect when the periodic	1745	Can be modified any time, but changes only take effect when the periodic
1464	timer fires or C<ev_periodic_again> is being called.	1746	timer fires or C<ev_periodic_again> is being called.
1465		1747
1466	=item ev_tstamp interval [read-write]	1748	=item ev_tstamp interval [read-write]
1467		1749
1468	The current interval value. Can be modified any time, but changes only	1750	The current interval value. Can be modified any time, but changes only
1469	take effect when the periodic timer fires or C<ev_periodic_again> is being	1751	take effect when the periodic timer fires or C<ev_periodic_again> is being
1470	called.	1752	called.
1471		1753
1472	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1754	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1473		1755
1474	The current reschedule callback, or C<0>, if this functionality is	1756	The current reschedule callback, or C<0>, if this functionality is
1475	switched off. Can be changed any time, but changes only take effect when	1757	switched off. Can be changed any time, but changes only take effect when
1476	the periodic timer fires or C<ev_periodic_again> is being called.	1758	the periodic timer fires or C<ev_periodic_again> is being called.
1477		1759
1478	=back	1760	=back
1479		1761
1480	=head3 Examples	1762	=head3 Examples
1481		1763
1482	Example: Call a callback every hour, or, more precisely, whenever the	1764	Example: Call a callback every hour, or, more precisely, whenever the
1483	system clock is divisible by 3600. The callback invocation times have	1765	system time is divisible by 3600. The callback invocation times have
1484	potentially a lot of jitter, but good long-term stability.	1766	potentially a lot of jitter, but good long-term stability.
1485		1767
1486	static void	1768	static void
1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1769	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1488	{	1770	{
1489	... its now a full hour (UTC, or TAI or whatever your clock follows)	1771	... its now a full hour (UTC, or TAI or whatever your clock follows)
1490	}	1772	}
1491		1773
1492	struct ev_periodic hourly_tick;	1774	ev_periodic hourly_tick;
1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1775	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1494	ev_periodic_start (loop, &hourly_tick);	1776	ev_periodic_start (loop, &hourly_tick);
1495		1777
1496	Example: The same as above, but use a reschedule callback to do it:	1778	Example: The same as above, but use a reschedule callback to do it:
1497		1779
1498	#include <math.h>	1780	#include <math.h>
1499		1781
1500	static ev_tstamp	1782	static ev_tstamp
1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1783	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1502	{	1784	{
1503	return fmod (now, 3600.) + 3600.;	1785	return now + (3600. - fmod (now, 3600.));
1504	}	1786	}
1505		1787
1506	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1788	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1507		1789
1508	Example: Call a callback every hour, starting now:	1790	Example: Call a callback every hour, starting now:
1509		1791
1510	struct ev_periodic hourly_tick;	1792	ev_periodic hourly_tick;
1511	ev_periodic_init (&hourly_tick, clock_cb,	1793	ev_periodic_init (&hourly_tick, clock_cb,
1512	fmod (ev_now (loop), 3600.), 3600., 0);	1794	fmod (ev_now (loop), 3600.), 3600., 0);
1513	ev_periodic_start (loop, &hourly_tick);	1795	ev_periodic_start (loop, &hourly_tick);
1514		1796
1515		1797
…		…
1518	Signal watchers will trigger an event when the process receives a specific	1800	Signal watchers will trigger an event when the process receives a specific
1519	signal one or more times. Even though signals are very asynchronous, libev	1801	signal one or more times. Even though signals are very asynchronous, libev
1520	will try it's best to deliver signals synchronously, i.e. as part of the	1802	will try it's best to deliver signals synchronously, i.e. as part of the
1521	normal event processing, like any other event.	1803	normal event processing, like any other event.
1522		1804
		1805	If you want signals asynchronously, just use C<sigaction> as you would
		1806	do without libev and forget about sharing the signal. You can even use
		1807	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1808
1523	You can configure as many watchers as you like per signal. Only when the	1809	You can configure as many watchers as you like per signal. Only when the
1524	first watcher gets started will libev actually register a signal watcher	1810	first watcher gets started will libev actually register a signal handler
1525	with the kernel (thus it coexists with your own signal handlers as long	1811	with the kernel (thus it coexists with your own signal handlers as long as
1526	as you don't register any with libev). Similarly, when the last signal	1812	you don't register any with libev for the same signal). Similarly, when
1527	watcher for a signal is stopped libev will reset the signal handler to	1813	the last signal watcher for a signal is stopped, libev will reset the
1528	SIG_DFL (regardless of what it was set to before).	1814	signal handler to SIG_DFL (regardless of what it was set to before).
1529		1815
1530	If possible and supported, libev will install its handlers with	1816	If possible and supported, libev will install its handlers with
1531	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1817	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1532	interrupted. If you have a problem with system calls getting interrupted by	1818	interrupted. If you have a problem with system calls getting interrupted by
1533	signals you can block all signals in an C<ev_check> watcher and unblock	1819	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1550		1836
1551	=back	1837	=back
1552		1838
1553	=head3 Examples	1839	=head3 Examples
1554		1840
1555	Example: Try to exit cleanly on SIGINT and SIGTERM.	1841	Example: Try to exit cleanly on SIGINT.
1556		1842
1557	static void	1843	static void
1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1844	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1559	{	1845	{
1560	ev_unloop (loop, EVUNLOOP_ALL);	1846	ev_unloop (loop, EVUNLOOP_ALL);
1561	}	1847	}
1562		1848
1563	struct ev_signal signal_watcher;	1849	ev_signal signal_watcher;
1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1850	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1565	ev_signal_start (loop, &sigint_cb);	1851	ev_signal_start (loop, &signal_watcher);
1566		1852
1567		1853
1568	=head2 C<ev_child> - watch out for process status changes	1854	=head2 C<ev_child> - watch out for process status changes
1569		1855
1570	Child watchers trigger when your process receives a SIGCHLD in response to	1856	Child watchers trigger when your process receives a SIGCHLD in response to
1571	some child status changes (most typically when a child of yours dies). It	1857	some child status changes (most typically when a child of yours dies or
1572	is permissible to install a child watcher I<after> the child has been	1858	exits). It is permissible to install a child watcher I<after> the child
1573	forked (which implies it might have already exited), as long as the event	1859	has been forked (which implies it might have already exited), as long
1574	loop isn't entered (or is continued from a watcher).	1860	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1861	forking and then immediately registering a watcher for the child is fine,
		1862	but forking and registering a watcher a few event loop iterations later is
		1863	not.
1575		1864
1576	Only the default event loop is capable of handling signals, and therefore	1865	Only the default event loop is capable of handling signals, and therefore
1577	you can only register child watchers in the default event loop.	1866	you can only register child watchers in the default event loop.
1578		1867
1579	=head3 Process Interaction	1868	=head3 Process Interaction
…		…
1640	its completion.	1929	its completion.
1641		1930
1642	ev_child cw;	1931	ev_child cw;
1643		1932
1644	static void	1933	static void
1645	child_cb (EV_P_ struct ev_child *w, int revents)	1934	child_cb (EV_P_ ev_child *w, int revents)
1646	{	1935	{
1647	ev_child_stop (EV_A_ w);	1936	ev_child_stop (EV_A_ w);
1648	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1937	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1649	}	1938	}
1650		1939
…		…
1665		1954
1666		1955
1667	=head2 C<ev_stat> - did the file attributes just change?	1956	=head2 C<ev_stat> - did the file attributes just change?
1668		1957
1669	This watches a file system path for attribute changes. That is, it calls	1958	This watches a file system path for attribute changes. That is, it calls
1670	C<stat> regularly (or when the OS says it changed) and sees if it changed	1959	C<stat> on that path in regular intervals (or when the OS says it changed)
1671	compared to the last time, invoking the callback if it did.	1960	and sees if it changed compared to the last time, invoking the callback if
		1961	it did.
1672		1962
1673	The path does not need to exist: changing from "path exists" to "path does	1963	The path does not need to exist: changing from "path exists" to "path does
1674	not exist" is a status change like any other. The condition "path does	1964	not exist" is a status change like any other. The condition "path does not
1675	not exist" is signified by the C<st_nlink> field being zero (which is	1965	exist" (or more correctly "path cannot be stat'ed") is signified by the
1676	otherwise always forced to be at least one) and all the other fields of	1966	C<st_nlink> field being zero (which is otherwise always forced to be at
1677	the stat buffer having unspecified contents.	1967	least one) and all the other fields of the stat buffer having unspecified
		1968	contents.
1678		1969
1679	The path I<should> be absolute and I<must not> end in a slash. If it is	1970	The path I<must not> end in a slash or contain special components such as
		1971	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1680	relative and your working directory changes, the behaviour is undefined.	1972	your working directory changes, then the behaviour is undefined.
1681		1973
1682	Since there is no standard to do this, the portable implementation simply	1974	Since there is no portable change notification interface available, the
1683	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1975	portable implementation simply calls C<stat(2)> regularly on the path
1684	can specify a recommended polling interval for this case. If you specify	1976	to see if it changed somehow. You can specify a recommended polling
1685	a polling interval of C<0> (highly recommended!) then a I<suitable,	1977	interval for this case. If you specify a polling interval of C<0> (highly
1686	unspecified default> value will be used (which you can expect to be around	1978	recommended!) then a I<suitable, unspecified default> value will be used
1687	five seconds, although this might change dynamically). Libev will also	1979	(which you can expect to be around five seconds, although this might
1688	impose a minimum interval which is currently around C<0.1>, but thats	1980	change dynamically). Libev will also impose a minimum interval which is
1689	usually overkill.	1981	currently around C<0.1>, but that's usually overkill.
1690		1982
1691	This watcher type is not meant for massive numbers of stat watchers,	1983	This watcher type is not meant for massive numbers of stat watchers,
1692	as even with OS-supported change notifications, this can be	1984	as even with OS-supported change notifications, this can be
1693	resource-intensive.	1985	resource-intensive.
1694		1986
1695	At the time of this writing, only the Linux inotify interface is	1987	At the time of this writing, the only OS-specific interface implemented
1696	implemented (implementing kqueue support is left as an exercise for the	1988	is the Linux inotify interface (implementing kqueue support is left as an
1697	reader, note, however, that the author sees no way of implementing ev_stat	1989	exercise for the reader. Note, however, that the author sees no way of
1698	semantics with kqueue). Inotify will be used to give hints only and should	1990	implementing C<ev_stat> semantics with kqueue, except as a hint).
1699	not change the semantics of C<ev_stat> watchers, which means that libev
1700	sometimes needs to fall back to regular polling again even with inotify,
1701	but changes are usually detected immediately, and if the file exists there
1702	will be no polling.
1703		1991
1704	=head3 ABI Issues (Largefile Support)	1992	=head3 ABI Issues (Largefile Support)
1705		1993
1706	Libev by default (unless the user overrides this) uses the default	1994	Libev by default (unless the user overrides this) uses the default
1707	compilation environment, which means that on systems with large file	1995	compilation environment, which means that on systems with large file
1708	support disabled by default, you get the 32 bit version of the stat	1996	support disabled by default, you get the 32 bit version of the stat
1709	structure. When using the library from programs that change the ABI to	1997	structure. When using the library from programs that change the ABI to
1710	use 64 bit file offsets the programs will fail. In that case you have to	1998	use 64 bit file offsets the programs will fail. In that case you have to
1711	compile libev with the same flags to get binary compatibility. This is	1999	compile libev with the same flags to get binary compatibility. This is
1712	obviously the case with any flags that change the ABI, but the problem is	2000	obviously the case with any flags that change the ABI, but the problem is
1713	most noticeably disabled with ev_stat and large file support.	2001	most noticeably displayed with ev_stat and large file support.
1714		2002
1715	The solution for this is to lobby your distribution maker to make large	2003	The solution for this is to lobby your distribution maker to make large
1716	file interfaces available by default (as e.g. FreeBSD does) and not	2004	file interfaces available by default (as e.g. FreeBSD does) and not
1717	optional. Libev cannot simply switch on large file support because it has	2005	optional. Libev cannot simply switch on large file support because it has
1718	to exchange stat structures with application programs compiled using the	2006	to exchange stat structures with application programs compiled using the
1719	default compilation environment.	2007	default compilation environment.
1720		2008
1721	=head3 Inotify	2009	=head3 Inotify and Kqueue
1722		2010
1723	When C<inotify (7)> support has been compiled into libev (generally only	2011	When C<inotify (7)> support has been compiled into libev and present at
1724	available on Linux) and present at runtime, it will be used to speed up	2012	runtime, it will be used to speed up change detection where possible. The
1725	change detection where possible. The inotify descriptor will be created lazily	2013	inotify descriptor will be created lazily when the first C<ev_stat>
1726	when the first C<ev_stat> watcher is being started.	2014	watcher is being started.
1727		2015
1728	Inotify presence does not change the semantics of C<ev_stat> watchers	2016	Inotify presence does not change the semantics of C<ev_stat> watchers
1729	except that changes might be detected earlier, and in some cases, to avoid	2017	except that changes might be detected earlier, and in some cases, to avoid
1730	making regular C<stat> calls. Even in the presence of inotify support	2018	making regular C<stat> calls. Even in the presence of inotify support
1731	there are many cases where libev has to resort to regular C<stat> polling.	2019	there are many cases where libev has to resort to regular C<stat> polling,
		2020	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2021	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2022	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2023	xfs are fully working) libev usually gets away without polling.
1732		2024
1733	(There is no support for kqueue, as apparently it cannot be used to	2025	There is no support for kqueue, as apparently it cannot be used to
1734	implement this functionality, due to the requirement of having a file	2026	implement this functionality, due to the requirement of having a file
1735	descriptor open on the object at all times).	2027	descriptor open on the object at all times, and detecting renames, unlinks
		2028	etc. is difficult.
		2029
		2030	=head3 C<stat ()> is a synchronous operation
		2031
		2032	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2033	the process. The exception are C<ev_stat> watchers - those call C<stat
		2034	()>, which is a synchronous operation.
		2035
		2036	For local paths, this usually doesn't matter: unless the system is very
		2037	busy or the intervals between stat's are large, a stat call will be fast,
		2038	as the path data is usually in memory already (except when starting the
		2039	watcher).
		2040
		2041	For networked file systems, calling C<stat ()> can block an indefinite
		2042	time due to network issues, and even under good conditions, a stat call
		2043	often takes multiple milliseconds.
		2044
		2045	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2046	paths, although this is fully supported by libev.
1736		2047
1737	=head3 The special problem of stat time resolution	2048	=head3 The special problem of stat time resolution
1738		2049
1739	The C<stat ()> system call only supports full-second resolution portably, and	2050	The C<stat ()> system call only supports full-second resolution portably,
1740	even on systems where the resolution is higher, many file systems still	2051	and even on systems where the resolution is higher, most file systems
1741	only support whole seconds.	2052	still only support whole seconds.
1742		2053
1743	That means that, if the time is the only thing that changes, you can	2054	That means that, if the time is the only thing that changes, you can
1744	easily miss updates: on the first update, C<ev_stat> detects a change and	2055	easily miss updates: on the first update, C<ev_stat> detects a change and
1745	calls your callback, which does something. When there is another update	2056	calls your callback, which does something. When there is another update
1746	within the same second, C<ev_stat> will be unable to detect it as the stat	2057	within the same second, C<ev_stat> will be unable to detect unless the
1747	data does not change.	2058	stat data does change in other ways (e.g. file size).
1748		2059
1749	The solution to this is to delay acting on a change for slightly more	2060	The solution to this is to delay acting on a change for slightly more
1750	than a second (or till slightly after the next full second boundary), using	2061	than a second (or till slightly after the next full second boundary), using
1751	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2062	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1752	ev_timer_again (loop, w)>).	2063	ev_timer_again (loop, w)>).
…		…
1772	C<path>. The C<interval> is a hint on how quickly a change is expected to	2083	C<path>. The C<interval> is a hint on how quickly a change is expected to
1773	be detected and should normally be specified as C<0> to let libev choose	2084	be detected and should normally be specified as C<0> to let libev choose
1774	a suitable value. The memory pointed to by C<path> must point to the same	2085	a suitable value. The memory pointed to by C<path> must point to the same
1775	path for as long as the watcher is active.	2086	path for as long as the watcher is active.
1776		2087
1777	The callback will receive C<EV_STAT> when a change was detected, relative	2088	The callback will receive an C<EV_STAT> event when a change was detected,
1778	to the attributes at the time the watcher was started (or the last change	2089	relative to the attributes at the time the watcher was started (or the
1779	was detected).	2090	last change was detected).
1780		2091
1781	=item ev_stat_stat (loop, ev_stat *)	2092	=item ev_stat_stat (loop, ev_stat *)
1782		2093
1783	Updates the stat buffer immediately with new values. If you change the	2094	Updates the stat buffer immediately with new values. If you change the
1784	watched path in your callback, you could call this function to avoid	2095	watched path in your callback, you could call this function to avoid
…		…
1867		2178
1868		2179
1869	=head2 C<ev_idle> - when you've got nothing better to do...	2180	=head2 C<ev_idle> - when you've got nothing better to do...
1870		2181
1871	Idle watchers trigger events when no other events of the same or higher	2182	Idle watchers trigger events when no other events of the same or higher
1872	priority are pending (prepare, check and other idle watchers do not	2183	priority are pending (prepare, check and other idle watchers do not count
1873	count).	2184	as receiving "events").
1874		2185
1875	That is, as long as your process is busy handling sockets or timeouts	2186	That is, as long as your process is busy handling sockets or timeouts
1876	(or even signals, imagine) of the same or higher priority it will not be	2187	(or even signals, imagine) of the same or higher priority it will not be
1877	triggered. But when your process is idle (or only lower-priority watchers	2188	triggered. But when your process is idle (or only lower-priority watchers
1878	are pending), the idle watchers are being called once per event loop	2189	are pending), the idle watchers are being called once per event loop
…		…
1889		2200
1890	=head3 Watcher-Specific Functions and Data Members	2201	=head3 Watcher-Specific Functions and Data Members
1891		2202
1892	=over 4	2203	=over 4
1893		2204
1894	=item ev_idle_init (ev_signal *, callback)	2205	=item ev_idle_init (ev_idle *, callback)
1895		2206
1896	Initialises and configures the idle watcher - it has no parameters of any	2207	Initialises and configures the idle watcher - it has no parameters of any
1897	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2208	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1898	believe me.	2209	believe me.
1899		2210
…		…
1903		2214
1904	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2215	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1905	callback, free it. Also, use no error checking, as usual.	2216	callback, free it. Also, use no error checking, as usual.
1906		2217
1907	static void	2218	static void
1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2219	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1909	{	2220	{
1910	free (w);	2221	free (w);
1911	// now do something you wanted to do when the program has	2222	// now do something you wanted to do when the program has
1912	// no longer anything immediate to do.	2223	// no longer anything immediate to do.
1913	}	2224	}
1914		2225
1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2226	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1916	ev_idle_init (idle_watcher, idle_cb);	2227	ev_idle_init (idle_watcher, idle_cb);
1917	ev_idle_start (loop, idle_cb);	2228	ev_idle_start (loop, idle_cb);
1918		2229
1919		2230
1920	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2231	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1921		2232
1922	Prepare and check watchers are usually (but not always) used in tandem:	2233	Prepare and check watchers are usually (but not always) used in pairs:
1923	prepare watchers get invoked before the process blocks and check watchers	2234	prepare watchers get invoked before the process blocks and check watchers
1924	afterwards.	2235	afterwards.
1925		2236
1926	You I<must not> call C<ev_loop> or similar functions that enter	2237	You I<must not> call C<ev_loop> or similar functions that enter
1927	the current event loop from either C<ev_prepare> or C<ev_check>	2238	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1930	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2241	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1931	C<ev_check> so if you have one watcher of each kind they will always be	2242	C<ev_check> so if you have one watcher of each kind they will always be
1932	called in pairs bracketing the blocking call.	2243	called in pairs bracketing the blocking call.
1933		2244
1934	Their main purpose is to integrate other event mechanisms into libev and	2245	Their main purpose is to integrate other event mechanisms into libev and
1935	their use is somewhat advanced. This could be used, for example, to track	2246	their use is somewhat advanced. They could be used, for example, to track
1936	variable changes, implement your own watchers, integrate net-snmp or a	2247	variable changes, implement your own watchers, integrate net-snmp or a
1937	coroutine library and lots more. They are also occasionally useful if	2248	coroutine library and lots more. They are also occasionally useful if
1938	you cache some data and want to flush it before blocking (for example,	2249	you cache some data and want to flush it before blocking (for example,
1939	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2250	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1940	watcher).	2251	watcher).
1941		2252
1942	This is done by examining in each prepare call which file descriptors need	2253	This is done by examining in each prepare call which file descriptors
1943	to be watched by the other library, registering C<ev_io> watchers for	2254	need to be watched by the other library, registering C<ev_io> watchers
1944	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2255	for them and starting an C<ev_timer> watcher for any timeouts (many
1945	provide just this functionality). Then, in the check watcher you check for	2256	libraries provide exactly this functionality). Then, in the check watcher,
1946	any events that occurred (by checking the pending status of all watchers	2257	you check for any events that occurred (by checking the pending status
1947	and stopping them) and call back into the library. The I/O and timer	2258	of all watchers and stopping them) and call back into the library. The
1948	callbacks will never actually be called (but must be valid nevertheless,	2259	I/O and timer callbacks will never actually be called (but must be valid
1949	because you never know, you know?).	2260	nevertheless, because you never know, you know?).
1950		2261
1951	As another example, the Perl Coro module uses these hooks to integrate	2262	As another example, the Perl Coro module uses these hooks to integrate
1952	coroutines into libev programs, by yielding to other active coroutines	2263	coroutines into libev programs, by yielding to other active coroutines
1953	during each prepare and only letting the process block if no coroutines	2264	during each prepare and only letting the process block if no coroutines
1954	are ready to run (it's actually more complicated: it only runs coroutines	2265	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1957	loop from blocking if lower-priority coroutines are active, thus mapping	2268	loop from blocking if lower-priority coroutines are active, thus mapping
1958	low-priority coroutines to idle/background tasks).	2269	low-priority coroutines to idle/background tasks).
1959		2270
1960	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2271	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1961	priority, to ensure that they are being run before any other watchers	2272	priority, to ensure that they are being run before any other watchers
		2273	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2274
1962	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2275	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1963	too) should not activate ("feed") events into libev. While libev fully	2276	activate ("feed") events into libev. While libev fully supports this, they
1964	supports this, they might get executed before other C<ev_check> watchers	2277	might get executed before other C<ev_check> watchers did their job. As
1965	did their job. As C<ev_check> watchers are often used to embed other	2278	C<ev_check> watchers are often used to embed other (non-libev) event
1966	(non-libev) event loops those other event loops might be in an unusable	2279	loops those other event loops might be in an unusable state until their
1967	state until their C<ev_check> watcher ran (always remind yourself to	2280	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1968	coexist peacefully with others).	2281	others).
1969		2282
1970	=head3 Watcher-Specific Functions and Data Members	2283	=head3 Watcher-Specific Functions and Data Members
1971		2284
1972	=over 4	2285	=over 4
1973		2286
…		…
1975		2288
1976	=item ev_check_init (ev_check *, callback)	2289	=item ev_check_init (ev_check *, callback)
1977		2290
1978	Initialises and configures the prepare or check watcher - they have no	2291	Initialises and configures the prepare or check watcher - they have no
1979	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2292	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1980	macros, but using them is utterly, utterly and completely pointless.	2293	macros, but using them is utterly, utterly, utterly and completely
		2294	pointless.
1981		2295
1982	=back	2296	=back
1983		2297
1984	=head3 Examples	2298	=head3 Examples
1985		2299
…		…
1998		2312
1999	static ev_io iow [nfd];	2313	static ev_io iow [nfd];
2000	static ev_timer tw;	2314	static ev_timer tw;
2001		2315
2002	static void	2316	static void
2003	io_cb (ev_loop *loop, ev_io *w, int revents)	2317	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2004	{	2318	{
2005	}	2319	}
2006		2320
2007	// create io watchers for each fd and a timer before blocking	2321	// create io watchers for each fd and a timer before blocking
2008	static void	2322	static void
2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2323	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2010	{	2324	{
2011	int timeout = 3600000;	2325	int timeout = 3600000;
2012	struct pollfd fds [nfd];	2326	struct pollfd fds [nfd];
2013	// actual code will need to loop here and realloc etc.	2327	// actual code will need to loop here and realloc etc.
2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2328	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2029	}	2343	}
2030	}	2344	}
2031		2345
2032	// stop all watchers after blocking	2346	// stop all watchers after blocking
2033	static void	2347	static void
2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2348	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2035	{	2349	{
2036	ev_timer_stop (loop, &tw);	2350	ev_timer_stop (loop, &tw);
2037		2351
2038	for (int i = 0; i < nfd; ++i)	2352	for (int i = 0; i < nfd; ++i)
2039	{	2353	{
…		…
2078	}	2392	}
2079		2393
2080	// do not ever call adns_afterpoll	2394	// do not ever call adns_afterpoll
2081		2395
2082	Method 4: Do not use a prepare or check watcher because the module you	2396	Method 4: Do not use a prepare or check watcher because the module you
2083	want to embed is too inflexible to support it. Instead, you can override	2397	want to embed is not flexible enough to support it. Instead, you can
2084	their poll function. The drawback with this solution is that the main	2398	override their poll function. The drawback with this solution is that the
2085	loop is now no longer controllable by EV. The C<Glib::EV> module does	2399	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2086	this.	2400	this approach, effectively embedding EV as a client into the horrible
		2401	libglib event loop.
2087		2402
2088	static gint	2403	static gint
2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2404	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2090	{	2405	{
2091	int got_events = 0;	2406	int got_events = 0;
…		…
2122	prioritise I/O.	2437	prioritise I/O.
2123		2438
2124	As an example for a bug workaround, the kqueue backend might only support	2439	As an example for a bug workaround, the kqueue backend might only support
2125	sockets on some platform, so it is unusable as generic backend, but you	2440	sockets on some platform, so it is unusable as generic backend, but you
2126	still want to make use of it because you have many sockets and it scales	2441	still want to make use of it because you have many sockets and it scales
2127	so nicely. In this case, you would create a kqueue-based loop and embed it	2442	so nicely. In this case, you would create a kqueue-based loop and embed
2128	into your default loop (which might use e.g. poll). Overall operation will	2443	it into your default loop (which might use e.g. poll). Overall operation
2129	be a bit slower because first libev has to poll and then call kevent, but	2444	will be a bit slower because first libev has to call C<poll> and then
2130	at least you can use both at what they are best.	2445	C<kevent>, but at least you can use both mechanisms for what they are
		2446	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2131		2447
2132	As for prioritising I/O: rarely you have the case where some fds have	2448	As for prioritising I/O: under rare circumstances you have the case where
2133	to be watched and handled very quickly (with low latency), and even	2449	some fds have to be watched and handled very quickly (with low latency),
2134	priorities and idle watchers might have too much overhead. In this case	2450	and even priorities and idle watchers might have too much overhead. In
2135	you would put all the high priority stuff in one loop and all the rest in	2451	this case you would put all the high priority stuff in one loop and all
2136	a second one, and embed the second one in the first.	2452	the rest in a second one, and embed the second one in the first.
2137		2453
2138	As long as the watcher is active, the callback will be invoked every time	2454	As long as the watcher is active, the callback will be invoked every
2139	there might be events pending in the embedded loop. The callback must then	2455	time there might be events pending in the embedded loop. The callback
2140	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2456	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2141	their callbacks (you could also start an idle watcher to give the embedded	2457	sweep and invoke their callbacks (the callback doesn't need to invoke the
2142	loop strictly lower priority for example). You can also set the callback	2458	C<ev_embed_sweep> function directly, it could also start an idle watcher
2143	to C<0>, in which case the embed watcher will automatically execute the	2459	to give the embedded loop strictly lower priority for example).
2144	embedded loop sweep.
2145		2460
2146	As long as the watcher is started it will automatically handle events. The	2461	You can also set the callback to C<0>, in which case the embed watcher
2147	callback will be invoked whenever some events have been handled. You can	2462	will automatically execute the embedded loop sweep whenever necessary.
2148	set the callback to C<0> to avoid having to specify one if you are not
2149	interested in that.
2150		2463
2151	Also, there have not currently been made special provisions for forking:	2464	Fork detection will be handled transparently while the C<ev_embed> watcher
2152	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2465	is active, i.e., the embedded loop will automatically be forked when the
2153	but you will also have to stop and restart any C<ev_embed> watchers	2466	embedding loop forks. In other cases, the user is responsible for calling
2154	yourself.	2467	C<ev_loop_fork> on the embedded loop.
2155		2468
2156	Unfortunately, not all backends are embeddable, only the ones returned by	2469	Unfortunately, not all backends are embeddable: only the ones returned by
2157	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2470	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2158	portable one.	2471	portable one.
2159		2472
2160	So when you want to use this feature you will always have to be prepared	2473	So when you want to use this feature you will always have to be prepared
2161	that you cannot get an embeddable loop. The recommended way to get around	2474	that you cannot get an embeddable loop. The recommended way to get around
2162	this is to have a separate variables for your embeddable loop, try to	2475	this is to have a separate variables for your embeddable loop, try to
2163	create it, and if that fails, use the normal loop for everything.	2476	create it, and if that fails, use the normal loop for everything.
		2477
		2478	=head3 C<ev_embed> and fork
		2479
		2480	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2481	automatically be applied to the embedded loop as well, so no special
		2482	fork handling is required in that case. When the watcher is not running,
		2483	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2484	as applicable.
2164		2485
2165	=head3 Watcher-Specific Functions and Data Members	2486	=head3 Watcher-Specific Functions and Data Members
2166		2487
2167	=over 4	2488	=over 4
2168		2489
…		…
2196	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2517	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2197	used).	2518	used).
2198		2519
2199	struct ev_loop *loop_hi = ev_default_init (0);	2520	struct ev_loop *loop_hi = ev_default_init (0);
2200	struct ev_loop *loop_lo = 0;	2521	struct ev_loop *loop_lo = 0;
2201	struct ev_embed embed;	2522	ev_embed embed;
2202		2523
2203	// see if there is a chance of getting one that works	2524	// see if there is a chance of getting one that works
2204	// (remember that a flags value of 0 means autodetection)	2525	// (remember that a flags value of 0 means autodetection)
2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2526	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2527	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2220	kqueue implementation). Store the kqueue/socket-only event loop in	2541	kqueue implementation). Store the kqueue/socket-only event loop in
2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2542	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2222		2543
2223	struct ev_loop *loop = ev_default_init (0);	2544	struct ev_loop *loop = ev_default_init (0);
2224	struct ev_loop *loop_socket = 0;	2545	struct ev_loop *loop_socket = 0;
2225	struct ev_embed embed;	2546	ev_embed embed;
2226		2547
2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2548	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2549	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2229	{	2550	{
2230	ev_embed_init (&embed, 0, loop_socket);	2551	ev_embed_init (&embed, 0, loop_socket);
…		…
2286	is that the author does not know of a simple (or any) algorithm for a	2607	is that the author does not know of a simple (or any) algorithm for a
2287	multiple-writer-single-reader queue that works in all cases and doesn't	2608	multiple-writer-single-reader queue that works in all cases and doesn't
2288	need elaborate support such as pthreads.	2609	need elaborate support such as pthreads.
2289		2610
2290	That means that if you want to queue data, you have to provide your own	2611	That means that if you want to queue data, you have to provide your own
2291	queue. But at least I can tell you would implement locking around your	2612	queue. But at least I can tell you how to implement locking around your
2292	queue:	2613	queue:
2293		2614
2294	=over 4	2615	=over 4
2295		2616
2296	=item queueing from a signal handler context	2617	=item queueing from a signal handler context
2297		2618
2298	To implement race-free queueing, you simply add to the queue in the signal	2619	To implement race-free queueing, you simply add to the queue in the signal
2299	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2620	handler but you block the signal handler in the watcher callback. Here is
2300	some fictitious SIGUSR1 handler:	2621	an example that does that for some fictitious SIGUSR1 handler:
2301		2622
2302	static ev_async mysig;	2623	static ev_async mysig;
2303		2624
2304	static void	2625	static void
2305	sigusr1_handler (void)	2626	sigusr1_handler (void)
…		…
2371	=over 4	2692	=over 4
2372		2693
2373	=item ev_async_init (ev_async *, callback)	2694	=item ev_async_init (ev_async *, callback)
2374		2695
2375	Initialises and configures the async watcher - it has no parameters of any	2696	Initialises and configures the async watcher - it has no parameters of any
2376	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2697	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2377	believe me.	2698	trust me.
2378		2699
2379	=item ev_async_send (loop, ev_async *)	2700	=item ev_async_send (loop, ev_async *)
2380		2701
2381	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2702	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2382	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2703	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2383	C<ev_feed_event>, this call is safe to do in other threads, signal or	2704	C<ev_feed_event>, this call is safe to do from other threads, signal or
2384	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2705	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2385	section below on what exactly this means).	2706	section below on what exactly this means).
2386		2707
		2708	Note that, as with other watchers in libev, multiple events might get
		2709	compressed into a single callback invocation (another way to look at this
		2710	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2711	reset when the event loop detects that).
		2712
2387	This call incurs the overhead of a system call only once per loop iteration,	2713	This call incurs the overhead of a system call only once per event loop
2388	so while the overhead might be noticeable, it doesn't apply to repeated	2714	iteration, so while the overhead might be noticeable, it doesn't apply to
2389	calls to C<ev_async_send>.	2715	repeated calls to C<ev_async_send> for the same event loop.
2390		2716
2391	=item bool = ev_async_pending (ev_async *)	2717	=item bool = ev_async_pending (ev_async *)
2392		2718
2393	Returns a non-zero value when C<ev_async_send> has been called on the	2719	Returns a non-zero value when C<ev_async_send> has been called on the
2394	watcher but the event has not yet been processed (or even noted) by the	2720	watcher but the event has not yet been processed (or even noted) by the
…		…
2397	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2723	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2398	the loop iterates next and checks for the watcher to have become active,	2724	the loop iterates next and checks for the watcher to have become active,
2399	it will reset the flag again. C<ev_async_pending> can be used to very	2725	it will reset the flag again. C<ev_async_pending> can be used to very
2400	quickly check whether invoking the loop might be a good idea.	2726	quickly check whether invoking the loop might be a good idea.
2401		2727
2402	Not that this does I<not> check whether the watcher itself is pending, only	2728	Not that this does I<not> check whether the watcher itself is pending,
2403	whether it has been requested to make this watcher pending.	2729	only whether it has been requested to make this watcher pending: there
		2730	is a time window between the event loop checking and resetting the async
		2731	notification, and the callback being invoked.
2404		2732
2405	=back	2733	=back
2406		2734
2407		2735
2408	=head1 OTHER FUNCTIONS	2736	=head1 OTHER FUNCTIONS
…		…
2412	=over 4	2740	=over 4
2413		2741
2414	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2742	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2415		2743
2416	This function combines a simple timer and an I/O watcher, calls your	2744	This function combines a simple timer and an I/O watcher, calls your
2417	callback on whichever event happens first and automatically stop both	2745	callback on whichever event happens first and automatically stops both
2418	watchers. This is useful if you want to wait for a single event on an fd	2746	watchers. This is useful if you want to wait for a single event on an fd
2419	or timeout without having to allocate/configure/start/stop/free one or	2747	or timeout without having to allocate/configure/start/stop/free one or
2420	more watchers yourself.	2748	more watchers yourself.
2421		2749
2422	If C<fd> is less than 0, then no I/O watcher will be started and events	2750	If C<fd> is less than 0, then no I/O watcher will be started and the
2423	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2751	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2424	C<events> set will be created and started.	2752	the given C<fd> and C<events> set will be created and started.
2425		2753
2426	If C<timeout> is less than 0, then no timeout watcher will be	2754	If C<timeout> is less than 0, then no timeout watcher will be
2427	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2755	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2428	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2756	repeat = 0) will be started. C<0> is a valid timeout.
2429	dubious value.
2430		2757
2431	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2758	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2432	passed an C<revents> set like normal event callbacks (a combination of	2759	passed an C<revents> set like normal event callbacks (a combination of
2433	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2760	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2434	value passed to C<ev_once>:	2761	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2762	a timeout and an io event at the same time - you probably should give io
		2763	events precedence.
		2764
		2765	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2435		2766
2436	static void stdin_ready (int revents, void *arg)	2767	static void stdin_ready (int revents, void *arg)
2437	{	2768	{
		2769	if (revents & EV_READ)
		2770	/* stdin might have data for us, joy! */;
2438	if (revents & EV_TIMEOUT)	2771	else if (revents & EV_TIMEOUT)
2439	/* doh, nothing entered */;	2772	/* doh, nothing entered */;
2440	else if (revents & EV_READ)
2441	/* stdin might have data for us, joy! */;
2442	}	2773	}
2443		2774
2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2775	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2445		2776
2446	=item ev_feed_event (ev_loop *, watcher *, int revents)	2777	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2447		2778
2448	Feeds the given event set into the event loop, as if the specified event	2779	Feeds the given event set into the event loop, as if the specified event
2449	had happened for the specified watcher (which must be a pointer to an	2780	had happened for the specified watcher (which must be a pointer to an
2450	initialised but not necessarily started event watcher).	2781	initialised but not necessarily started event watcher).
2451		2782
2452	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2783	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2453		2784
2454	Feed an event on the given fd, as if a file descriptor backend detected	2785	Feed an event on the given fd, as if a file descriptor backend detected
2455	the given events it.	2786	the given events it.
2456		2787
2457	=item ev_feed_signal_event (ev_loop *loop, int signum)	2788	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2458		2789
2459	Feed an event as if the given signal occurred (C<loop> must be the default	2790	Feed an event as if the given signal occurred (C<loop> must be the default
2460	loop!).	2791	loop!).
2461		2792
2462	=back	2793	=back
…		…
2584		2915
2585	myclass obj;	2916	myclass obj;
2586	ev::io iow;	2917	ev::io iow;
2587	iow.set <myclass, &myclass::io_cb> (&obj);	2918	iow.set <myclass, &myclass::io_cb> (&obj);
2588		2919
		2920	=item w->set (object *)
		2921
		2922	This is an B<experimental> feature that might go away in a future version.
		2923
		2924	This is a variation of a method callback - leaving out the method to call
		2925	will default the method to C<operator ()>, which makes it possible to use
		2926	functor objects without having to manually specify the C<operator ()> all
		2927	the time. Incidentally, you can then also leave out the template argument
		2928	list.
		2929
		2930	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2931	int revents)>.
		2932
		2933	See the method-C<set> above for more details.
		2934
		2935	Example: use a functor object as callback.
		2936
		2937	struct myfunctor
		2938	{
		2939	void operator() (ev::io &w, int revents)
		2940	{
		2941	...
		2942	}
		2943	}
		2944
		2945	myfunctor f;
		2946
		2947	ev::io w;
		2948	w.set (&f);
		2949
2589	=item w->set<function> (void *data = 0)	2950	=item w->set<function> (void *data = 0)
2590		2951
2591	Also sets a callback, but uses a static method or plain function as	2952	Also sets a callback, but uses a static method or plain function as
2592	callback. The optional C<data> argument will be stored in the watcher's	2953	callback. The optional C<data> argument will be stored in the watcher's
2593	C<data> member and is free for you to use.	2954	C<data> member and is free for you to use.
2594		2955
2595	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2956	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2596		2957
2597	See the method-C<set> above for more details.	2958	See the method-C<set> above for more details.
2598		2959
2599	Example:	2960	Example: Use a plain function as callback.
2600		2961
2601	static void io_cb (ev::io &w, int revents) { }	2962	static void io_cb (ev::io &w, int revents) { }
2602	iow.set <io_cb> ();	2963	iow.set <io_cb> ();
2603		2964
2604	=item w->set (struct ev_loop *)	2965	=item w->set (struct ev_loop *)
…		…
2642	Example: Define a class with an IO and idle watcher, start one of them in	3003	Example: Define a class with an IO and idle watcher, start one of them in
2643	the constructor.	3004	the constructor.
2644		3005
2645	class myclass	3006	class myclass
2646	{	3007	{
2647	ev::io io; void io_cb (ev::io &w, int revents);	3008	ev::io io ; void io_cb (ev::io &w, int revents);
2648	ev:idle idle void idle_cb (ev::idle &w, int revents);	3009	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2649		3010
2650	myclass (int fd)	3011	myclass (int fd)
2651	{	3012	{
2652	io .set <myclass, &myclass::io_cb > (this);	3013	io .set <myclass, &myclass::io_cb > (this);
2653	idle.set <myclass, &myclass::idle_cb> (this);	3014	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2669	=item Perl	3030	=item Perl
2670		3031
2671	The EV module implements the full libev API and is actually used to test	3032	The EV module implements the full libev API and is actually used to test
2672	libev. EV is developed together with libev. Apart from the EV core module,	3033	libev. EV is developed together with libev. Apart from the EV core module,
2673	there are additional modules that implement libev-compatible interfaces	3034	there are additional modules that implement libev-compatible interfaces
2674	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3035	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2675	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3036	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3037	and C<EV::Glib>).
2676		3038
2677	It can be found and installed via CPAN, its homepage is at	3039	It can be found and installed via CPAN, its homepage is at
2678	L<http://software.schmorp.de/pkg/EV>.	3040	L<http://software.schmorp.de/pkg/EV>.
2679		3041
2680	=item Python	3042	=item Python
2681		3043
2682	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3044	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2683	seems to be quite complete and well-documented. Note, however, that the	3045	seems to be quite complete and well-documented.
2684	patch they require for libev is outright dangerous as it breaks the ABI
2685	for everybody else, and therefore, should never be applied in an installed
2686	libev (if python requires an incompatible ABI then it needs to embed
2687	libev).
2688		3046
2689	=item Ruby	3047	=item Ruby
2690		3048
2691	Tony Arcieri has written a ruby extension that offers access to a subset	3049	Tony Arcieri has written a ruby extension that offers access to a subset
2692	of the libev API and adds file handle abstractions, asynchronous DNS and	3050	of the libev API and adds file handle abstractions, asynchronous DNS and
2693	more on top of it. It can be found via gem servers. Its homepage is at	3051	more on top of it. It can be found via gem servers. Its homepage is at
2694	L<http://rev.rubyforge.org/>.	3052	L<http://rev.rubyforge.org/>.
2695		3053
		3054	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3055	makes rev work even on mingw.
		3056
		3057	=item Haskell
		3058
		3059	A haskell binding to libev is available at
		3060	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3061
2696	=item D	3062	=item D
2697		3063
2698	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3064	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2699	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3065	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3066
		3067	=item Ocaml
		3068
		3069	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3070	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2700		3071
2701	=back	3072	=back
2702		3073
2703		3074
2704	=head1 MACRO MAGIC	3075	=head1 MACRO MAGIC
…		…
2805		3176
2806	#define EV_STANDALONE 1	3177	#define EV_STANDALONE 1
2807	#include "ev.h"	3178	#include "ev.h"
2808		3179
2809	Both header files and implementation files can be compiled with a C++	3180	Both header files and implementation files can be compiled with a C++
2810	compiler (at least, thats a stated goal, and breakage will be treated	3181	compiler (at least, that's a stated goal, and breakage will be treated
2811	as a bug).	3182	as a bug).
2812		3183
2813	You need the following files in your source tree, or in a directory	3184	You need the following files in your source tree, or in a directory
2814	in your include path (e.g. in libev/ when using -Ilibev):	3185	in your include path (e.g. in libev/ when using -Ilibev):
2815		3186
…		…
2859		3230
2860	=head2 PREPROCESSOR SYMBOLS/MACROS	3231	=head2 PREPROCESSOR SYMBOLS/MACROS
2861		3232
2862	Libev can be configured via a variety of preprocessor symbols you have to	3233	Libev can be configured via a variety of preprocessor symbols you have to
2863	define before including any of its files. The default in the absence of	3234	define before including any of its files. The default in the absence of
2864	autoconf is noted for every option.	3235	autoconf is documented for every option.
2865		3236
2866	=over 4	3237	=over 4
2867		3238
2868	=item EV_STANDALONE	3239	=item EV_STANDALONE
2869		3240
…		…
2871	keeps libev from including F<config.h>, and it also defines dummy	3242	keeps libev from including F<config.h>, and it also defines dummy
2872	implementations for some libevent functions (such as logging, which is not	3243	implementations for some libevent functions (such as logging, which is not
2873	supported). It will also not define any of the structs usually found in	3244	supported). It will also not define any of the structs usually found in
2874	F<event.h> that are not directly supported by the libev core alone.	3245	F<event.h> that are not directly supported by the libev core alone.
2875		3246
		3247	In stanbdalone mode, libev will still try to automatically deduce the
		3248	configuration, but has to be more conservative.
		3249
2876	=item EV_USE_MONOTONIC	3250	=item EV_USE_MONOTONIC
2877		3251
2878	If defined to be C<1>, libev will try to detect the availability of the	3252	If defined to be C<1>, libev will try to detect the availability of the
2879	monotonic clock option at both compile time and runtime. Otherwise no use	3253	monotonic clock option at both compile time and runtime. Otherwise no
2880	of the monotonic clock option will be attempted. If you enable this, you	3254	use of the monotonic clock option will be attempted. If you enable this,
2881	usually have to link against librt or something similar. Enabling it when	3255	you usually have to link against librt or something similar. Enabling it
2882	the functionality isn't available is safe, though, although you have	3256	when the functionality isn't available is safe, though, although you have
2883	to make sure you link against any libraries where the C<clock_gettime>	3257	to make sure you link against any libraries where the C<clock_gettime>
2884	function is hiding in (often F<-lrt>).	3258	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2885		3259
2886	=item EV_USE_REALTIME	3260	=item EV_USE_REALTIME
2887		3261
2888	If defined to be C<1>, libev will try to detect the availability of the	3262	If defined to be C<1>, libev will try to detect the availability of the
2889	real-time clock option at compile time (and assume its availability at	3263	real-time clock option at compile time (and assume its availability
2890	runtime if successful). Otherwise no use of the real-time clock option will	3264	at runtime if successful). Otherwise no use of the real-time clock
2891	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3265	option will be attempted. This effectively replaces C<gettimeofday>
2892	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3266	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2893	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3267	correctness. See the note about libraries in the description of
		3268	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3269	C<EV_USE_CLOCK_SYSCALL>.
		3270
		3271	=item EV_USE_CLOCK_SYSCALL
		3272
		3273	If defined to be C<1>, libev will try to use a direct syscall instead
		3274	of calling the system-provided C<clock_gettime> function. This option
		3275	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3276	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3277	programs needlessly. Using a direct syscall is slightly slower (in
		3278	theory), because no optimised vdso implementation can be used, but avoids
		3279	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3280	higher, as it simplifies linking (no need for C<-lrt>).
2894		3281
2895	=item EV_USE_NANOSLEEP	3282	=item EV_USE_NANOSLEEP
2896		3283
2897	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3284	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2898	and will use it for delays. Otherwise it will use C<select ()>.	3285	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2914		3301
2915	=item EV_SELECT_USE_FD_SET	3302	=item EV_SELECT_USE_FD_SET
2916		3303
2917	If defined to C<1>, then the select backend will use the system C<fd_set>	3304	If defined to C<1>, then the select backend will use the system C<fd_set>
2918	structure. This is useful if libev doesn't compile due to a missing	3305	structure. This is useful if libev doesn't compile due to a missing
2919	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3306	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2920	exotic systems. This usually limits the range of file descriptors to some	3307	on exotic systems. This usually limits the range of file descriptors to
2921	low limit such as 1024 or might have other limitations (winsocket only	3308	some low limit such as 1024 or might have other limitations (winsocket
2922	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3309	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2923	influence the size of the C<fd_set> used.	3310	configures the maximum size of the C<fd_set>.
2924		3311
2925	=item EV_SELECT_IS_WINSOCKET	3312	=item EV_SELECT_IS_WINSOCKET
2926		3313
2927	When defined to C<1>, the select backend will assume that	3314	When defined to C<1>, the select backend will assume that
2928	select/socket/connect etc. don't understand file descriptors but	3315	select/socket/connect etc. don't understand file descriptors but
…		…
3039	When doing priority-based operations, libev usually has to linearly search	3426	When doing priority-based operations, libev usually has to linearly search
3040	all the priorities, so having many of them (hundreds) uses a lot of space	3427	all the priorities, so having many of them (hundreds) uses a lot of space
3041	and time, so using the defaults of five priorities (-2 .. +2) is usually	3428	and time, so using the defaults of five priorities (-2 .. +2) is usually
3042	fine.	3429	fine.
3043		3430
3044	If your embedding application does not need any priorities, defining these both to	3431	If your embedding application does not need any priorities, defining these
3045	C<0> will save some memory and CPU.	3432	both to C<0> will save some memory and CPU.
3046		3433
3047	=item EV_PERIODIC_ENABLE	3434	=item EV_PERIODIC_ENABLE
3048		3435
3049	If undefined or defined to be C<1>, then periodic timers are supported. If	3436	If undefined or defined to be C<1>, then periodic timers are supported. If
3050	defined to be C<0>, then they are not. Disabling them saves a few kB of	3437	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3057	code.	3444	code.
3058		3445
3059	=item EV_EMBED_ENABLE	3446	=item EV_EMBED_ENABLE
3060		3447
3061	If undefined or defined to be C<1>, then embed watchers are supported. If	3448	If undefined or defined to be C<1>, then embed watchers are supported. If
3062	defined to be C<0>, then they are not.	3449	defined to be C<0>, then they are not. Embed watchers rely on most other
		3450	watcher types, which therefore must not be disabled.
3063		3451
3064	=item EV_STAT_ENABLE	3452	=item EV_STAT_ENABLE
3065		3453
3066	If undefined or defined to be C<1>, then stat watchers are supported. If	3454	If undefined or defined to be C<1>, then stat watchers are supported. If
3067	defined to be C<0>, then they are not.	3455	defined to be C<0>, then they are not.
…		…
3099	two).	3487	two).
3100		3488
3101	=item EV_USE_4HEAP	3489	=item EV_USE_4HEAP
3102		3490
3103	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3491	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3104	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3492	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3105	to C<1>. The 4-heap uses more complicated (longer) code but has	3493	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3106	noticeably faster performance with many (thousands) of watchers.	3494	faster performance with many (thousands) of watchers.
3107		3495
3108	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3496	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3109	(disabled).	3497	(disabled).
3110		3498
3111	=item EV_HEAP_CACHE_AT	3499	=item EV_HEAP_CACHE_AT
3112		3500
3113	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3501	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3114	timer and periodics heap, libev can cache the timestamp (I<at>) within	3502	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3115	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3503	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3116	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3504	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3117	but avoids random read accesses on heap changes. This improves performance	3505	but avoids random read accesses on heap changes. This improves performance
3118	noticeably with with many (hundreds) of watchers.	3506	noticeably with many (hundreds) of watchers.
3119		3507
3120	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3508	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3121	(disabled).	3509	(disabled).
3122		3510
3123	=item EV_VERIFY	3511	=item EV_VERIFY
…		…
3129	called once per loop, which can slow down libev. If set to C<3>, then the	3517	called once per loop, which can slow down libev. If set to C<3>, then the
3130	verification code will be called very frequently, which will slow down	3518	verification code will be called very frequently, which will slow down
3131	libev considerably.	3519	libev considerably.
3132		3520
3133	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3521	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3134	C<0.>	3522	C<0>.
3135		3523
3136	=item EV_COMMON	3524	=item EV_COMMON
3137		3525
3138	By default, all watchers have a C<void *data> member. By redefining	3526	By default, all watchers have a C<void *data> member. By redefining
3139	this macro to a something else you can include more and other types of	3527	this macro to a something else you can include more and other types of
…		…
3156	and the way callbacks are invoked and set. Must expand to a struct member	3544	and the way callbacks are invoked and set. Must expand to a struct member
3157	definition and a statement, respectively. See the F<ev.h> header file for	3545	definition and a statement, respectively. See the F<ev.h> header file for
3158	their default definitions. One possible use for overriding these is to	3546	their default definitions. One possible use for overriding these is to
3159	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3547	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3160	method calls instead of plain function calls in C++.	3548	method calls instead of plain function calls in C++.
		3549
		3550	=back
3161		3551
3162	=head2 EXPORTED API SYMBOLS	3552	=head2 EXPORTED API SYMBOLS
3163		3553
3164	If you need to re-export the API (e.g. via a DLL) and you need a list of	3554	If you need to re-export the API (e.g. via a DLL) and you need a list of
3165	exported symbols, you can use the provided F<Symbol.*> files which list	3555	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3212	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3602	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3213		3603
3214	#include "ev_cpp.h"	3604	#include "ev_cpp.h"
3215	#include "ev.c"	3605	#include "ev.c"
3216		3606
		3607	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3217		3608
3218	=head1 THREADS AND COROUTINES	3609	=head2 THREADS AND COROUTINES
3219		3610
3220	=head2 THREADS	3611	=head3 THREADS
3221		3612
3222	Libev itself is completely thread-safe, but it uses no locking. This	3613	All libev functions are reentrant and thread-safe unless explicitly
		3614	documented otherwise, but libev implements no locking itself. This means
3223	means that you can use as many loops as you want in parallel, as long as	3615	that you can use as many loops as you want in parallel, as long as there
3224	only one thread ever calls into one libev function with the same loop	3616	are no concurrent calls into any libev function with the same loop
3225	parameter.	3617	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3618	of course): libev guarantees that different event loops share no data
		3619	structures that need any locking.
3226		3620
3227	Or put differently: calls with different loop parameters can be done in	3621	Or to put it differently: calls with different loop parameters can be done
3228	parallel from multiple threads, calls with the same loop parameter must be	3622	concurrently from multiple threads, calls with the same loop parameter
3229	done serially (but can be done from different threads, as long as only one	3623	must be done serially (but can be done from different threads, as long as
3230	thread ever is inside a call at any point in time, e.g. by using a mutex	3624	only one thread ever is inside a call at any point in time, e.g. by using
3231	per loop).	3625	a mutex per loop).
		3626
		3627	Specifically to support threads (and signal handlers), libev implements
		3628	so-called C<ev_async> watchers, which allow some limited form of
		3629	concurrency on the same event loop, namely waking it up "from the
		3630	outside".
3232		3631
3233	If you want to know which design (one loop, locking, or multiple loops	3632	If you want to know which design (one loop, locking, or multiple loops
3234	without or something else still) is best for your problem, then I cannot	3633	without or something else still) is best for your problem, then I cannot
3235	help you. I can give some generic advice however:	3634	help you, but here is some generic advice:
3236		3635
3237	=over 4	3636	=over 4
3238		3637
3239	=item * most applications have a main thread: use the default libev loop	3638	=item * most applications have a main thread: use the default libev loop
3240	in that thread, or create a separate thread running only the default loop.	3639	in that thread, or create a separate thread running only the default loop.
…		…
3252		3651
3253	Choosing a model is hard - look around, learn, know that usually you can do	3652	Choosing a model is hard - look around, learn, know that usually you can do
3254	better than you currently do :-)	3653	better than you currently do :-)
3255		3654
3256	=item * often you need to talk to some other thread which blocks in the	3655	=item * often you need to talk to some other thread which blocks in the
		3656	event loop.
		3657
3257	event loop - C<ev_async> watchers can be used to wake them up from other	3658	C<ev_async> watchers can be used to wake them up from other threads safely
3258	threads safely (or from signal contexts...).	3659	(or from signal contexts...).
		3660
		3661	An example use would be to communicate signals or other events that only
		3662	work in the default loop by registering the signal watcher with the
		3663	default loop and triggering an C<ev_async> watcher from the default loop
		3664	watcher callback into the event loop interested in the signal.
3259		3665
3260	=back	3666	=back
3261		3667
3262	=head2 COROUTINES	3668	=head3 COROUTINES
3263		3669
3264	Libev is much more accommodating to coroutines ("cooperative threads"):	3670	Libev is very accommodating to coroutines ("cooperative threads"):
3265	libev fully supports nesting calls to it's functions from different	3671	libev fully supports nesting calls to its functions from different
3266	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3672	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3267	different coroutines and switch freely between both coroutines running the	3673	different coroutines, and switch freely between both coroutines running the
3268	loop, as long as you don't confuse yourself). The only exception is that	3674	loop, as long as you don't confuse yourself). The only exception is that
3269	you must not do this from C<ev_periodic> reschedule callbacks.	3675	you must not do this from C<ev_periodic> reschedule callbacks.
3270		3676
3271	Care has been invested into making sure that libev does not keep local	3677	Care has been taken to ensure that libev does not keep local state inside
3272	state inside C<ev_loop>, and other calls do not usually allow coroutine	3678	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3273	switches.	3679	they do not call any callbacks.
3274		3680
		3681	=head2 COMPILER WARNINGS
3275		3682
3276	=head1 COMPLEXITIES	3683	Depending on your compiler and compiler settings, you might get no or a
		3684	lot of warnings when compiling libev code. Some people are apparently
		3685	scared by this.
3277		3686
3278	In this section the complexities of (many of) the algorithms used inside	3687	However, these are unavoidable for many reasons. For one, each compiler
3279	libev will be explained. For complexity discussions about backends see the	3688	has different warnings, and each user has different tastes regarding
3280	documentation for C<ev_default_init>.	3689	warning options. "Warn-free" code therefore cannot be a goal except when
		3690	targeting a specific compiler and compiler-version.
3281		3691
3282	All of the following are about amortised time: If an array needs to be	3692	Another reason is that some compiler warnings require elaborate
3283	extended, libev needs to realloc and move the whole array, but this	3693	workarounds, or other changes to the code that make it less clear and less
3284	happens asymptotically never with higher number of elements, so O(1) might	3694	maintainable.
3285	mean it might do a lengthy realloc operation in rare cases, but on average
3286	it is much faster and asymptotically approaches constant time.
3287		3695
3288	=over 4	3696	And of course, some compiler warnings are just plain stupid, or simply
		3697	wrong (because they don't actually warn about the condition their message
		3698	seems to warn about). For example, certain older gcc versions had some
		3699	warnings that resulted an extreme number of false positives. These have
		3700	been fixed, but some people still insist on making code warn-free with
		3701	such buggy versions.
3289		3702
3290	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3703	While libev is written to generate as few warnings as possible,
		3704	"warn-free" code is not a goal, and it is recommended not to build libev
		3705	with any compiler warnings enabled unless you are prepared to cope with
		3706	them (e.g. by ignoring them). Remember that warnings are just that:
		3707	warnings, not errors, or proof of bugs.
3291		3708
3292	This means that, when you have a watcher that triggers in one hour and
3293	there are 100 watchers that would trigger before that then inserting will
3294	have to skip roughly seven (C<ld 100>) of these watchers.
3295		3709
3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3710	=head2 VALGRIND
3297		3711
3298	That means that changing a timer costs less than removing/adding them	3712	Valgrind has a special section here because it is a popular tool that is
3299	as only the relative motion in the event queue has to be paid for.	3713	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3300		3714
3301	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3715	If you think you found a bug (memory leak, uninitialised data access etc.)
		3716	in libev, then check twice: If valgrind reports something like:
3302		3717
3303	These just add the watcher into an array or at the head of a list.	3718	==2274== definitely lost: 0 bytes in 0 blocks.
		3719	==2274== possibly lost: 0 bytes in 0 blocks.
		3720	==2274== still reachable: 256 bytes in 1 blocks.
3304		3721
3305	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3722	Then there is no memory leak, just as memory accounted to global variables
		3723	is not a memleak - the memory is still being referenced, and didn't leak.
3306		3724
3307	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3725	Similarly, under some circumstances, valgrind might report kernel bugs
		3726	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3727	although an acceptable workaround has been found here), or it might be
		3728	confused.
3308		3729
3309	These watchers are stored in lists then need to be walked to find the	3730	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3310	correct watcher to remove. The lists are usually short (you don't usually	3731	make it into some kind of religion.
3311	have many watchers waiting for the same fd or signal).
3312		3732
3313	=item Finding the next timer in each loop iteration: O(1)	3733	If you are unsure about something, feel free to contact the mailing list
		3734	with the full valgrind report and an explanation on why you think this
		3735	is a bug in libev (best check the archives, too :). However, don't be
		3736	annoyed when you get a brisk "this is no bug" answer and take the chance
		3737	of learning how to interpret valgrind properly.
3314		3738
3315	By virtue of using a binary or 4-heap, the next timer is always found at a	3739	If you need, for some reason, empty reports from valgrind for your project
3316	fixed position in the storage array.	3740	I suggest using suppression lists.
3317		3741
3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3319		3742
3320	A change means an I/O watcher gets started or stopped, which requires	3743	=head1 PORTABILITY NOTES
3321	libev to recalculate its status (and possibly tell the kernel, depending
3322	on backend and whether C<ev_io_set> was used).
3323		3744
3324	=item Activating one watcher (putting it into the pending state): O(1)
3325
3326	=item Priority handling: O(number_of_priorities)
3327
3328	Priorities are implemented by allocating some space for each
3329	priority. When doing priority-based operations, libev usually has to
3330	linearly search all the priorities, but starting/stopping and activating
3331	watchers becomes O(1) w.r.t. priority handling.
3332
3333	=item Sending an ev_async: O(1)
3334
3335	=item Processing ev_async_send: O(number_of_async_watchers)
3336
3337	=item Processing signals: O(max_signal_number)
3338
3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
3340	calls in the current loop iteration. Checking for async and signal events
3341	involves iterating over all running async watchers or all signal numbers.
3342
3343	=back
3344
3345
3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3745	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3347		3746
3348	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3747	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3349	requires, and its I/O model is fundamentally incompatible with the POSIX	3748	requires, and its I/O model is fundamentally incompatible with the POSIX
3350	model. Libev still offers limited functionality on this platform in	3749	model. Libev still offers limited functionality on this platform in
3351	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3750	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3362		3761
3363	Not a libev limitation but worth mentioning: windows apparently doesn't	3762	Not a libev limitation but worth mentioning: windows apparently doesn't
3364	accept large writes: instead of resulting in a partial write, windows will	3763	accept large writes: instead of resulting in a partial write, windows will
3365	either accept everything or return C<ENOBUFS> if the buffer is too large,	3764	either accept everything or return C<ENOBUFS> if the buffer is too large,
3366	so make sure you only write small amounts into your sockets (less than a	3765	so make sure you only write small amounts into your sockets (less than a
3367	megabyte seems safe, but thsi apparently depends on the amount of memory	3766	megabyte seems safe, but this apparently depends on the amount of memory
3368	available).	3767	available).
3369		3768
3370	Due to the many, low, and arbitrary limits on the win32 platform and	3769	Due to the many, low, and arbitrary limits on the win32 platform and
3371	the abysmal performance of winsockets, using a large number of sockets	3770	the abysmal performance of winsockets, using a large number of sockets
3372	is not recommended (and not reasonable). If your program needs to use	3771	is not recommended (and not reasonable). If your program needs to use
…		…
3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3782	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3384		3783
3385	#include "ev.h"	3784	#include "ev.h"
3386		3785
3387	And compile the following F<evwrap.c> file into your project (make sure	3786	And compile the following F<evwrap.c> file into your project (make sure
3388	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3787	you do I<not> compile the F<ev.c> or any other embedded source files!):
3389		3788
3390	#include "evwrap.h"	3789	#include "evwrap.h"
3391	#include "ev.c"	3790	#include "ev.c"
3392		3791
3393	=over 4	3792	=over 4
…		…
3438	wrap all I/O functions and provide your own fd management, but the cost of	3837	wrap all I/O functions and provide your own fd management, but the cost of
3439	calling select (O(n²)) will likely make this unworkable.	3838	calling select (O(n²)) will likely make this unworkable.
3440		3839
3441	=back	3840	=back
3442		3841
3443
3444	=head1 PORTABILITY REQUIREMENTS	3842	=head2 PORTABILITY REQUIREMENTS
3445		3843
3446	In addition to a working ISO-C implementation, libev relies on a few	3844	In addition to a working ISO-C implementation and of course the
3447	additional extensions:	3845	backend-specific APIs, libev relies on a few additional extensions:
3448		3846
3449	=over 4	3847	=over 4
3450		3848
3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3849	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3452	calling conventions regardless of C<ev_watcher_type *>.	3850	calling conventions regardless of C<ev_watcher_type *>.
…		…
3458	calls them using an C<ev_watcher *> internally.	3856	calls them using an C<ev_watcher *> internally.
3459		3857
3460	=item C<sig_atomic_t volatile> must be thread-atomic as well	3858	=item C<sig_atomic_t volatile> must be thread-atomic as well
3461		3859
3462	The type C<sig_atomic_t volatile> (or whatever is defined as	3860	The type C<sig_atomic_t volatile> (or whatever is defined as
3463	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3861	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3464	threads. This is not part of the specification for C<sig_atomic_t>, but is	3862	threads. This is not part of the specification for C<sig_atomic_t>, but is
3465	believed to be sufficiently portable.	3863	believed to be sufficiently portable.
3466		3864
3467	=item C<sigprocmask> must work in a threaded environment	3865	=item C<sigprocmask> must work in a threaded environment
3468		3866
…		…
3477	except the initial one, and run the default loop in the initial thread as	3875	except the initial one, and run the default loop in the initial thread as
3478	well.	3876	well.
3479		3877
3480	=item C<long> must be large enough for common memory allocation sizes	3878	=item C<long> must be large enough for common memory allocation sizes
3481		3879
3482	To improve portability and simplify using libev, libev uses C<long>	3880	To improve portability and simplify its API, libev uses C<long> internally
3483	internally instead of C<size_t> when allocating its data structures. On	3881	instead of C<size_t> when allocating its data structures. On non-POSIX
3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3882	systems (Microsoft...) this might be unexpectedly low, but is still at
3485	is still at least 31 bits everywhere, which is enough for hundreds of	3883	least 31 bits everywhere, which is enough for hundreds of millions of
3486	millions of watchers.	3884	watchers.
3487		3885
3488	=item C<double> must hold a time value in seconds with enough accuracy	3886	=item C<double> must hold a time value in seconds with enough accuracy
3489		3887
3490	The type C<double> is used to represent timestamps. It is required to	3888	The type C<double> is used to represent timestamps. It is required to
3491	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3889	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3495	=back	3893	=back
3496		3894
3497	If you know of other additional requirements drop me a note.	3895	If you know of other additional requirements drop me a note.
3498		3896
3499		3897
3500	=head1 COMPILER WARNINGS	3898	=head1 ALGORITHMIC COMPLEXITIES
3501		3899
3502	Depending on your compiler and compiler settings, you might get no or a	3900	In this section the complexities of (many of) the algorithms used inside
3503	lot of warnings when compiling libev code. Some people are apparently	3901	libev will be documented. For complexity discussions about backends see
3504	scared by this.	3902	the documentation for C<ev_default_init>.
3505		3903
3506	However, these are unavoidable for many reasons. For one, each compiler	3904	All of the following are about amortised time: If an array needs to be
3507	has different warnings, and each user has different tastes regarding	3905	extended, libev needs to realloc and move the whole array, but this
3508	warning options. "Warn-free" code therefore cannot be a goal except when	3906	happens asymptotically rarer with higher number of elements, so O(1) might
3509	targeting a specific compiler and compiler-version.	3907	mean that libev does a lengthy realloc operation in rare cases, but on
		3908	average it is much faster and asymptotically approaches constant time.
3510		3909
3511	Another reason is that some compiler warnings require elaborate	3910	=over 4
3512	workarounds, or other changes to the code that make it less clear and less
3513	maintainable.
3514		3911
3515	And of course, some compiler warnings are just plain stupid, or simply	3912	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3516	wrong (because they don't actually warn about the condition their message
3517	seems to warn about).
3518		3913
3519	While libev is written to generate as few warnings as possible,	3914	This means that, when you have a watcher that triggers in one hour and
3520	"warn-free" code is not a goal, and it is recommended not to build libev	3915	there are 100 watchers that would trigger before that, then inserting will
3521	with any compiler warnings enabled unless you are prepared to cope with	3916	have to skip roughly seven (C<ld 100>) of these watchers.
3522	them (e.g. by ignoring them). Remember that warnings are just that:
3523	warnings, not errors, or proof of bugs.
3524		3917
		3918	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3525		3919
3526	=head1 VALGRIND	3920	That means that changing a timer costs less than removing/adding them,
		3921	as only the relative motion in the event queue has to be paid for.
3527		3922
3528	Valgrind has a special section here because it is a popular tool that is	3923	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3529	highly useful, but valgrind reports are very hard to interpret.
3530		3924
3531	If you think you found a bug (memory leak, uninitialised data access etc.)	3925	These just add the watcher into an array or at the head of a list.
3532	in libev, then check twice: If valgrind reports something like:
3533		3926
3534	==2274== definitely lost: 0 bytes in 0 blocks.	3927	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3535	==2274== possibly lost: 0 bytes in 0 blocks.
3536	==2274== still reachable: 256 bytes in 1 blocks.
3537		3928
3538	Then there is no memory leak. Similarly, under some circumstances,	3929	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3539	valgrind might report kernel bugs as if it were a bug in libev, or it
3540	might be confused (it is a very good tool, but only a tool).
3541		3930
3542	If you are unsure about something, feel free to contact the mailing list	3931	These watchers are stored in lists, so they need to be walked to find the
3543	with the full valgrind report and an explanation on why you think this is	3932	correct watcher to remove. The lists are usually short (you don't usually
3544	a bug in libev. However, don't be annoyed when you get a brisk "this is	3933	have many watchers waiting for the same fd or signal: one is typical, two
3545	no bug" answer and take the chance of learning how to interpret valgrind	3934	is rare).
3546	properly.
3547		3935
3548	If you need, for some reason, empty reports from valgrind for your project	3936	=item Finding the next timer in each loop iteration: O(1)
3549	I suggest using suppression lists.	3937
		3938	By virtue of using a binary or 4-heap, the next timer is always found at a
		3939	fixed position in the storage array.
		3940
		3941	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3942
		3943	A change means an I/O watcher gets started or stopped, which requires
		3944	libev to recalculate its status (and possibly tell the kernel, depending
		3945	on backend and whether C<ev_io_set> was used).
		3946
		3947	=item Activating one watcher (putting it into the pending state): O(1)
		3948
		3949	=item Priority handling: O(number_of_priorities)
		3950
		3951	Priorities are implemented by allocating some space for each
		3952	priority. When doing priority-based operations, libev usually has to
		3953	linearly search all the priorities, but starting/stopping and activating
		3954	watchers becomes O(1) with respect to priority handling.
		3955
		3956	=item Sending an ev_async: O(1)
		3957
		3958	=item Processing ev_async_send: O(number_of_async_watchers)
		3959
		3960	=item Processing signals: O(max_signal_number)
		3961
		3962	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3963	calls in the current loop iteration. Checking for async and signal events
		3964	involves iterating over all running async watchers or all signal numbers.
		3965
		3966	=back
3550		3967
3551		3968
3552	=head1 AUTHOR	3969	=head1 AUTHOR
3553		3970
3554	Marc Lehmann <libev@schmorp.de>.	3971	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3555		3972

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