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Revision 1.175 by root, Mon Sep 8 16:36:14 2008 UTC vs.
Revision 1.230 by root, Wed Apr 15 18:47:07 2009 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	217	recommended ones.
216		218
217	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
218		220
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		222
221	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	225	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	226	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	252	}
251		253
252	...	254	...
253	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
254		256
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		258
257	Set the callback function to call on a retryable system call error (such	259	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	262	callback is set, then libev will expect it to remedy the situation, no
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	365	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	366	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	368	readiness notifications you get per iteration.
363		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
		373
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		375
366	And this is your standard poll(2) backend. It's more complicated	376	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	377	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	378	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	379	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	381	performance tips.
372		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		385
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		387
375	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	392
380	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
382		409
383	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	411	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
388		415	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		416
393	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	418	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
396		428
397	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
399		434
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		436
402	Kqueue deserves special mention, as at the time of this writing, it	437	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	439	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	445	system like NetBSD.
409		446
410	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		450
414	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
420		458
421	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
422		460
423	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
429		471
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		473
432	This is not implemented yet (and might never be, unless you send me an	474	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	475	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	488	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	489	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	491	might perform better.
450		492
451	On the positive side, ignoring the spurious readiness notifications, this	493	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
454		500
455	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
456		502
457	Try all backends (even potentially broken ones that wouldn't be tried	503	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		510
465	If one or more of these are or'ed into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		514
469	The most typical usage is like this:	515	Example: This is the most typical usage.
470		516
471	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		519
474	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	521	environment settings to be taken into account:
476		522
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		524
479	Use whatever libev has to offer, but make sure that kqueue is used if	525	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	527	private event loop and only if you know the OS supports your types of
		528	fds):
482		529
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		531
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		533
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	557	for example).
511		558
512	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
515		562
516	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		591
545	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
546		593
547	Like C<ev_default_fork>, but acts on an event loop created by	594	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
550		598
551	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
552		600
553	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
554		603
555	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
556		605
557	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
573	received events and started processing them. This timestamp does not	622	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	623	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	624	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	625	event occurring (or more correctly, libev finding out about it).
577		626
		627	=item ev_now_update (loop)
		628
		629	Establishes the current time by querying the kernel, updating the time
		630	returned by C<ev_now ()> in the progress. This is a costly operation and
		631	is usually done automatically within C<ev_loop ()>.
		632
		633	This function is rarely useful, but when some event callback runs for a
		634	very long time without entering the event loop, updating libev's idea of
		635	the current time is a good idea.
		636
		637	See also "The special problem of time updates" in the C<ev_timer> section.
		638
578	=item ev_loop (loop, int flags)	639	=item ev_loop (loop, int flags)
579		640
580	Finally, this is it, the event handler. This function usually is called	641	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	642	after you initialised all your watchers and you want to start handling
582	events.	643	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	645	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	646	either no event watchers are active anymore or C<ev_unloop> was called.
586		647
587	Please note that an explicit C<ev_unloop> is usually better than	648	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	649	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	650	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	651	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	652	of relying on its watchers stopping correctly, that is truly a thing of
		653	beauty.
592		654
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	656	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	657	process in case there are no events and will return after one iteration of
		658	the loop.
596		659
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	661	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	662	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	663	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	664	user-registered callback will be called), and will return after one
		665	iteration of the loop.
		666
		667	This is useful if you are waiting for some external event in conjunction
		668	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	670	usually a better approach for this kind of thing.
604		671
605	Here are the gory details of what C<ev_loop> does:	672	Here are the gory details of what C<ev_loop> does:
606		673
607	- Before the first iteration, call any pending watchers.	674	- Before the first iteration, call any pending watchers.
…		…
617	any active watchers at all will result in not sleeping).	684	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	685	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	686	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	687	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	689	- Queue all expired timers.
623	- Queue all outstanding periodics.	690	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	691	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	692	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	693	- Call all queued watchers in reverse order (i.e. check watchers first).
627	Signals and child watchers are implemented as I/O watchers, and will	694	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	695	be handled here by queueing them when their watcher gets executed.
…		…
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		714
648	This "unloop state" will be cleared when entering C<ev_loop> again.	715	This "unloop state" will be cleared when entering C<ev_loop> again.
649		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
650	=item ev_ref (loop)	719	=item ev_ref (loop)
651		720
652	=item ev_unref (loop)	721	=item ev_unref (loop)
653		722
654	Ref/unref can be used to add or remove a reference count on the event	723	Ref/unref can be used to add or remove a reference count on the event
655	loop: Every watcher keeps one reference, and as long as the reference	724	loop: Every watcher keeps one reference, and as long as the reference
656	count is nonzero, C<ev_loop> will not return on its own. If you have	725	count is nonzero, C<ev_loop> will not return on its own.
		726
657	a watcher you never unregister that should not keep C<ev_loop> from	727	If you have a watcher you never unregister that should not keep C<ev_loop>
658	returning, ev_unref() after starting, and ev_ref() before stopping it. For	728	from returning, call ev_unref() after starting, and ev_ref() before
		729	stopping it.
		730
659	example, libev itself uses this for its internal signal pipe: It is not	731	As an example, libev itself uses this for its internal signal pipe: It
660	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
661	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
662	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
663	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
664	(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
665	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).
666		740
667	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>
668	running when nothing else is active.	742	running when nothing else is active.
669		743
670	struct ev_signal exitsig;	744	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	745	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	746	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	747	evf_unref (loop);
674		748
675	Example: For some weird reason, unregister the above signal handler again.	749	Example: For some weird reason, unregister the above signal handler again.
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	763	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	764	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	765	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	766	opportunities).
693		767
694	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
695	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
696	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
697	events, especially with backends like C<select ()> which have a high	771	events, especially with backends like C<select ()> which have a high
698	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.
699		773
700	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
701	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,
…		…
703	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
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	778	introduce an additional C<ev_sleep ()> call into most loop iterations.
705		779
706	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
707	to spend more time collecting timeouts, at the expense of increased	781	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	782	latency/jitter/inexactness (the watcher callback will be called
709	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
710	any overhead in libev.	784	value will not introduce any overhead in libev.
711		785
712	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
713	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
714	interactive servers (of course not for games), likewise for timeouts. It	788	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	789	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
723	they fire on, say, one-second boundaries only.	797	they fire on, say, one-second boundaries only.
724		798
725	=item ev_loop_verify (loop)	799	=item ev_loop_verify (loop)
726		800
727	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
728	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
729	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
730	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 ()>.
731		806
732	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
733	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
734	data structures consistent.	809	data structures consistent.
735		810
736	=back	811	=back
737		812
738		813
739	=head1 ANATOMY OF A WATCHER	814	=head1 ANATOMY OF A WATCHER
740		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
741	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
742	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
743	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:
744		823
745	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)
746	{	825	{
747	ev_io_stop (w);	826	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	827	ev_unloop (loop, EVUNLOOP_ALL);
749	}	828	}
750		829
751	struct ev_loop *loop = ev_default_loop (0);	830	struct ev_loop *loop = ev_default_loop (0);
		831
752	struct ev_io stdin_watcher;	832	ev_io stdin_watcher;
		833
753	ev_init (&stdin_watcher, my_cb);	834	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	835	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	836	ev_io_start (loop, &stdin_watcher);
		837
756	ev_loop (loop, 0);	838	ev_loop (loop, 0);
757		839
758	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
759	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
760	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).
761		846
762	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
763	(watcher *, callback)>, which expects a callback to be provided. This	848	(watcher *, callback)>, which expects a callback to be provided. This
764	callback gets invoked each time the event occurs (or, in the case of I/O	849	callback gets invoked each time the event occurs (or, in the case of I/O
765	watchers, each time the event loop detects that the file descriptor given	850	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	851	is readable and/or writable).
767		852
768	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 *, ...) >>
769	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
770	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<<
771	(watcher *, callback, ...) >>.	856	ev_TYPE_init (watcher *, callback, ...) >>.
772		857
773	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
774	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
775	*) >>), 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
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	861	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		862
778	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
779	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
780	reinitialise it or call its C<set> macro.	865	reinitialise it or call its C<ev_TYPE_set> macro.
781		866
782	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
783	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
784	third argument.	869	third argument.
785		870
…		…
843		928
844	=item C<EV_ASYNC>	929	=item C<EV_ASYNC>
845		930
846	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>).
847		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
848	=item C<EV_ERROR>	938	=item C<EV_ERROR>
849		939
850	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
851	happen because the watcher could not be properly started because libev	941	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	942	ran out of memory, a file descriptor was found to be closed or any other
		943	problem. Libev considers these application bugs.
		944
853	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
854	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.
855		949
856	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
857	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
858	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
859	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
860	programs, though, so beware.	954	programs, though, as the fd could already be closed and reused for another
		955	thing, so beware.
861		956
862	=back	957	=back
863		958
864	=head2 GENERIC WATCHER FUNCTIONS	959	=head2 GENERIC WATCHER FUNCTIONS
865
866	In the following description, C<TYPE> stands for the watcher type,
867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
868		960
869	=over 4	961	=over 4
870		962
871	=item C<ev_init> (ev_TYPE *watcher, callback)	963	=item C<ev_init> (ev_TYPE *watcher, callback)
872		964
…		…
878	which rolls both calls into one.	970	which rolls both calls into one.
879		971
880	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
881	(or never started) and there are no pending events outstanding.	973	(or never started) and there are no pending events outstanding.
882		974
883	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,
884	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);
885		983
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	984	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		985
888	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
889	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
…		…
892	difference to the C<ev_init> macro).	990	difference to the C<ev_init> macro).
893		991
894	Although some watcher types do not have type-specific arguments	992	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	993	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		994
		995	See C<ev_init>, above, for an example.
		996
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	997	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		998
899	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
900	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
901	a watcher. The same limitations apply, of course.	1001	a watcher. The same limitations apply, of course.
902		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
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1007	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1008
905	Starts (activates) the given watcher. Only active watchers will receive	1009	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1010	events. If the watcher is already active nothing will happen.
907		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
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1017	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1018
910	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
911	status. It is possible that stopped watchers are pending (for example,	1022	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1023	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1024	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	1025	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	1026	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1027
917	=item bool ev_is_active (ev_TYPE *watcher)	1028	=item bool ev_is_active (ev_TYPE *watcher)
918		1029
919	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
920	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
…		…
962	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
963	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 :).
964		1075
965	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
966	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
967	or might not have been adjusted to be within valid range.	1078	or might not have been clamped to the valid range.
968		1079
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1080	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1081
971	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
972	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
973	can deal with that fact.	1084	can deal with that fact, as both are simply passed through to the
		1085	callback.
974		1086
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1087	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1088
977	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
978	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
979	watcher isn't pending it does nothing and returns C<0>.	1091	watcher isn't pending it does nothing and returns C<0>.
980		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
981	=back	1096	=back
982		1097
983		1098
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1099	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1100
986	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
987	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
988	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
989	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
990	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
991	data:	1106	data:
992		1107
993	struct my_io	1108	struct my_io
994	{	1109	{
995	struct ev_io io;	1110	ev_io io;
996	int otherfd;	1111	int otherfd;
997	void *somedata;	1112	void *somedata;
998	struct whatever *mostinteresting;	1113	struct whatever *mostinteresting;
999	}	1114	};
		1115
		1116	...
		1117	struct my_io w;
		1118	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1119
1001	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
1002	can cast it back to your own type:	1121	can cast it back to your own type:
1003		1122
1004	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)
1005	{	1124	{
1006	struct my_io *w = (struct my_io *)w_;	1125	struct my_io *w = (struct my_io *)w_;
1007	...	1126	...
1008	}	1127	}
1009		1128
1010	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
1011	instead have been omitted.	1130	instead have been omitted.
1012		1131
1013	Another common scenario is having some data structure with multiple	1132	Another common scenario is to use some data structure with multiple
1014	watchers:	1133	embedded watchers:
1015		1134
1016	struct my_biggy	1135	struct my_biggy
1017	{	1136	{
1018	int some_data;	1137	int some_data;
1019	ev_timer t1;	1138	ev_timer t1;
1020	ev_timer t2;	1139	ev_timer t2;
1021	}	1140	}
1022		1141
1023	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
1024	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):
1025		1147
1026	#include <stddef.h>	1148	#include <stddef.h>
1027		1149
1028	static void	1150	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1151	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1152	{
1031	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1154	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1155	}
1034		1156
1035	static void	1157	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1158	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1159	{
1038	struct my_biggy big = (struct my_biggy *	1160	struct my_biggy big = (struct my_biggy *
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1161	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1162	}
1041		1163
…		…
1069	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
1070	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
1071	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
1072	required if you know what you are doing).	1194	required if you know what you are doing).
1073		1195
1074	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
1075	(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
1076	C<EVBACKEND_POLL>).	1198	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1077		1199
1078	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
1079	receive "spurious" readiness notifications, that is your callback might	1201	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1202	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1203	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1204	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1205	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1206	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1207	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1208
1087	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
1088	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
1089	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
1090	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
1091	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.
1092		1218
1093	=head3 The special problem of disappearing file descriptors	1219	=head3 The special problem of disappearing file descriptors
1094		1220
1095	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
1096	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,
1097	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
1098	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
1099	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
1100	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
1101	fact, a different file descriptor.	1227	fact, a different file descriptor.
1102		1228
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1259	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1260	C<EVBACKEND_POLL>.
1135		1261
1136	=head3 The special problem of SIGPIPE	1262	=head3 The special problem of SIGPIPE
1137		1263
1138	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>:
1139	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
1140	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
1141	this is sensible behaviour, for daemons, this is usually undesirable.	1267	this is sensible behaviour, for daemons, this is usually undesirable.
1142		1268
1143	So when you encounter spurious, unexplained daemon exits, make sure you	1269	So when you encounter spurious, unexplained daemon exits, make sure you
1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1270	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1145	somewhere, as that would have given you a big clue).	1271	somewhere, as that would have given you a big clue).
…		…
1152	=item ev_io_init (ev_io *, callback, int fd, int events)	1278	=item ev_io_init (ev_io *, callback, int fd, int events)
1153		1279
1154	=item ev_io_set (ev_io *, int fd, int events)	1280	=item ev_io_set (ev_io *, int fd, int events)
1155		1281
1156	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
1157	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
1158	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.
1159		1285
1160	=item int fd [read-only]	1286	=item int fd [read-only]
1161		1287
1162	The file descriptor being watched.	1288	The file descriptor being watched.
1163		1289
…		…
1172	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
1173	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
1174	attempt to read a whole line in the callback.	1300	attempt to read a whole line in the callback.
1175		1301
1176	static void	1302	static void
1177	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)
1178	{	1304	{
1179	ev_io_stop (loop, w);	1305	ev_io_stop (loop, w);
1180	.. 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
1181	}	1307	}
1182		1308
1183	...	1309	...
1184	struct ev_loop *loop = ev_default_init (0);	1310	struct ev_loop *loop = ev_default_init (0);
1185	struct ev_io stdin_readable;	1311	ev_io stdin_readable;
1186	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);
1187	ev_io_start (loop, &stdin_readable);	1313	ev_io_start (loop, &stdin_readable);
1188	ev_loop (loop, 0);	1314	ev_loop (loop, 0);
1189		1315
1190		1316
…		…
1193	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
1194	given time, and optionally repeating in regular intervals after that.	1320	given time, and optionally repeating in regular intervals after that.
1195		1321
1196	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
1197	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
1198	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
1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1325	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1200	monotonic clock option helps a lot here).	1326	monotonic clock option helps a lot here).
1201		1327
1202	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
1203	but if multiple timers become ready during the same loop iteration then	1329	passed. If multiple timers become ready during the same loop iteration
1204	order of execution is undefined.	1330	then the ones with earlier time-out values are invoked before ones with
		1331	later time-out values (but this is no longer true when a callback calls
		1332	C<ev_loop> recursively).
		1333
		1334	=head3 Be smart about timeouts
		1335
		1336	Many real-world problems involve some kind of timeout, usually for error
		1337	recovery. A typical example is an HTTP request - if the other side hangs,
		1338	you want to raise some error after a while.
		1339
		1340	What follows are some ways to handle this problem, from obvious and
		1341	inefficient to smart and efficient.
		1342
		1343	In the following, a 60 second activity timeout is assumed - a timeout that
		1344	gets reset to 60 seconds each time there is activity (e.g. each time some
		1345	data or other life sign was received).
		1346
		1347	=over 4
		1348
		1349	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1350
		1351	This is the most obvious, but not the most simple way: In the beginning,
		1352	start the watcher:
		1353
		1354	ev_timer_init (timer, callback, 60., 0.);
		1355	ev_timer_start (loop, timer);
		1356
		1357	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1358	and start it again:
		1359
		1360	ev_timer_stop (loop, timer);
		1361	ev_timer_set (timer, 60., 0.);
		1362	ev_timer_start (loop, timer);
		1363
		1364	This is relatively simple to implement, but means that each time there is
		1365	some activity, libev will first have to remove the timer from its internal
		1366	data structure and then add it again. Libev tries to be fast, but it's
		1367	still not a constant-time operation.
		1368
		1369	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1370
		1371	This is the easiest way, and involves using C<ev_timer_again> instead of
		1372	C<ev_timer_start>.
		1373
		1374	To implement this, configure an C<ev_timer> with a C<repeat> value
		1375	of C<60> and then call C<ev_timer_again> at start and each time you
		1376	successfully read or write some data. If you go into an idle state where
		1377	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1378	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1379
		1380	That means you can ignore both the C<ev_timer_start> function and the
		1381	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1382	member and C<ev_timer_again>.
		1383
		1384	At start:
		1385
		1386	ev_timer_init (timer, callback);
		1387	timer->repeat = 60.;
		1388	ev_timer_again (loop, timer);
		1389
		1390	Each time there is some activity:
		1391
		1392	ev_timer_again (loop, timer);
		1393
		1394	It is even possible to change the time-out on the fly, regardless of
		1395	whether the watcher is active or not:
		1396
		1397	timer->repeat = 30.;
		1398	ev_timer_again (loop, timer);
		1399
		1400	This is slightly more efficient then stopping/starting the timer each time
		1401	you want to modify its timeout value, as libev does not have to completely
		1402	remove and re-insert the timer from/into its internal data structure.
		1403
		1404	It is, however, even simpler than the "obvious" way to do it.
		1405
		1406	=item 3. Let the timer time out, but then re-arm it as required.
		1407
		1408	This method is more tricky, but usually most efficient: Most timeouts are
		1409	relatively long compared to the intervals between other activity - in
		1410	our example, within 60 seconds, there are usually many I/O events with
		1411	associated activity resets.
		1412
		1413	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1414	but remember the time of last activity, and check for a real timeout only
		1415	within the callback:
		1416
		1417	ev_tstamp last_activity; // time of last activity
		1418
		1419	static void
		1420	callback (EV_P_ ev_timer *w, int revents)
		1421	{
		1422	ev_tstamp now = ev_now (EV_A);
		1423	ev_tstamp timeout = last_activity + 60.;
		1424
		1425	// if last_activity + 60. is older than now, we did time out
		1426	if (timeout < now)
		1427	{
		1428	// timeout occured, take action
		1429	}
		1430	else
		1431	{
		1432	// callback was invoked, but there was some activity, re-arm
		1433	// the watcher to fire in last_activity + 60, which is
		1434	// guaranteed to be in the future, so "again" is positive:
		1435	w->repeat = timeout - now;
		1436	ev_timer_again (EV_A_ w);
		1437	}
		1438	}
		1439
		1440	To summarise the callback: first calculate the real timeout (defined
		1441	as "60 seconds after the last activity"), then check if that time has
		1442	been reached, which means something I<did>, in fact, time out. Otherwise
		1443	the callback was invoked too early (C<timeout> is in the future), so
		1444	re-schedule the timer to fire at that future time, to see if maybe we have
		1445	a timeout then.
		1446
		1447	Note how C<ev_timer_again> is used, taking advantage of the
		1448	C<ev_timer_again> optimisation when the timer is already running.
		1449
		1450	This scheme causes more callback invocations (about one every 60 seconds
		1451	minus half the average time between activity), but virtually no calls to
		1452	libev to change the timeout.
		1453
		1454	To start the timer, simply initialise the watcher and set C<last_activity>
		1455	to the current time (meaning we just have some activity :), then call the
		1456	callback, which will "do the right thing" and start the timer:
		1457
		1458	ev_timer_init (timer, callback);
		1459	last_activity = ev_now (loop);
		1460	callback (loop, timer, EV_TIMEOUT);
		1461
		1462	And when there is some activity, simply store the current time in
		1463	C<last_activity>, no libev calls at all:
		1464
		1465	last_actiivty = ev_now (loop);
		1466
		1467	This technique is slightly more complex, but in most cases where the
		1468	time-out is unlikely to be triggered, much more efficient.
		1469
		1470	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1471	callback :) - just change the timeout and invoke the callback, which will
		1472	fix things for you.
		1473
		1474	=item 4. Wee, just use a double-linked list for your timeouts.
		1475
		1476	If there is not one request, but many thousands (millions...), all
		1477	employing some kind of timeout with the same timeout value, then one can
		1478	do even better:
		1479
		1480	When starting the timeout, calculate the timeout value and put the timeout
		1481	at the I<end> of the list.
		1482
		1483	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1484	the list is expected to fire (for example, using the technique #3).
		1485
		1486	When there is some activity, remove the timer from the list, recalculate
		1487	the timeout, append it to the end of the list again, and make sure to
		1488	update the C<ev_timer> if it was taken from the beginning of the list.
		1489
		1490	This way, one can manage an unlimited number of timeouts in O(1) time for
		1491	starting, stopping and updating the timers, at the expense of a major
		1492	complication, and having to use a constant timeout. The constant timeout
		1493	ensures that the list stays sorted.
		1494
		1495	=back
		1496
		1497	So which method the best?
		1498
		1499	Method #2 is a simple no-brain-required solution that is adequate in most
		1500	situations. Method #3 requires a bit more thinking, but handles many cases
		1501	better, and isn't very complicated either. In most case, choosing either
		1502	one is fine, with #3 being better in typical situations.
		1503
		1504	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1505	rather complicated, but extremely efficient, something that really pays
		1506	off after the first million or so of active timers, i.e. it's usually
		1507	overkill :)
1205		1508
1206	=head3 The special problem of time updates	1509	=head3 The special problem of time updates
1207		1510
1208	Requesting the current time is a costly operation (it usually takes at	1511	Establishing the current time is a costly operation (it usually takes at
1209	least two syscalls): EV therefore updates it's idea of the current time	1512	least two system calls): EV therefore updates its idea of the current
1210	only before and after C<ev_loop> polls for new events, which causes the	1513	time only before and after C<ev_loop> collects new events, which causes a
1211	difference between C<ev_now ()> and C<ev_time ()>.	1514	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1515	lots of events in one iteration.
1212		1516
1213	The relative timeouts are calculated relative to the C<ev_now ()>	1517	The relative timeouts are calculated relative to the C<ev_now ()>
1214	time. This is usually the right thing as this timestamp refers to the time	1518	time. This is usually the right thing as this timestamp refers to the time
1215	of the event triggering whatever timeout you are modifying/starting. If	1519	of the event triggering whatever timeout you are modifying/starting. If
1216	you suspect event processing to be delayed and you I<need> to base the	1520	you suspect event processing to be delayed and you I<need> to base the
1217	timeout on the current time, use something like this to adjust for this:	1521	timeout on the current time, use something like this to adjust for this:
1218		1522
1219	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1523	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1220		1524
		1525	If the event loop is suspended for a long time, you can also force an
		1526	update of the time returned by C<ev_now ()> by calling C<ev_now_update
		1527	()>.
		1528
1221	=head3 Watcher-Specific Functions and Data Members	1529	=head3 Watcher-Specific Functions and Data Members
1222		1530
1223	=over 4	1531	=over 4
1224		1532
1225	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1533	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1248	If the timer is started but non-repeating, stop it (as if it timed out).	1556	If the timer is started but non-repeating, stop it (as if it timed out).
1249		1557
1250	If the timer is repeating, either start it if necessary (with the	1558	If the timer is repeating, either start it if necessary (with the
1251	C<repeat> value), or reset the running timer to the C<repeat> value.	1559	C<repeat> value), or reset the running timer to the C<repeat> value.
1252		1560
1253	This sounds a bit complicated, but here is a useful and typical	1561	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1254	example: Imagine you have a TCP connection and you want a so-called idle	1562	usage example.
1255	timeout, that is, you want to be called when there have been, say, 60
1256	seconds of inactivity on the socket. The easiest way to do this is to
1257	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1258	C<ev_timer_again> each time you successfully read or write some data. If
1259	you go into an idle state where you do not expect data to travel on the
1260	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1261	automatically restart it if need be.
1262
1263	That means you can ignore the C<after> value and C<ev_timer_start>
1264	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1265
1266	ev_timer_init (timer, callback, 0., 5.);
1267	ev_timer_again (loop, timer);
1268	...
1269	timer->again = 17.;
1270	ev_timer_again (loop, timer);
1271	...
1272	timer->again = 10.;
1273	ev_timer_again (loop, timer);
1274
1275	This is more slightly efficient then stopping/starting the timer each time
1276	you want to modify its timeout value.
1277		1563
1278	=item ev_tstamp repeat [read-write]	1564	=item ev_tstamp repeat [read-write]
1279		1565
1280	The current C<repeat> value. Will be used each time the watcher times out	1566	The current C<repeat> value. Will be used each time the watcher times out
1281	or C<ev_timer_again> is called and determines the next timeout (if any),	1567	or C<ev_timer_again> is called, and determines the next timeout (if any),
1282	which is also when any modifications are taken into account.	1568	which is also when any modifications are taken into account.
1283		1569
1284	=back	1570	=back
1285		1571
1286	=head3 Examples	1572	=head3 Examples
1287		1573
1288	Example: Create a timer that fires after 60 seconds.	1574	Example: Create a timer that fires after 60 seconds.
1289		1575
1290	static void	1576	static void
1291	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1577	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1292	{	1578	{
1293	.. one minute over, w is actually stopped right here	1579	.. one minute over, w is actually stopped right here
1294	}	1580	}
1295		1581
1296	struct ev_timer mytimer;	1582	ev_timer mytimer;
1297	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1583	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1298	ev_timer_start (loop, &mytimer);	1584	ev_timer_start (loop, &mytimer);
1299		1585
1300	Example: Create a timeout timer that times out after 10 seconds of	1586	Example: Create a timeout timer that times out after 10 seconds of
1301	inactivity.	1587	inactivity.
1302		1588
1303	static void	1589	static void
1304	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1590	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1305	{	1591	{
1306	.. ten seconds without any activity	1592	.. ten seconds without any activity
1307	}	1593	}
1308		1594
1309	struct ev_timer mytimer;	1595	ev_timer mytimer;
1310	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1596	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1311	ev_timer_again (&mytimer); /* start timer */	1597	ev_timer_again (&mytimer); /* start timer */
1312	ev_loop (loop, 0);	1598	ev_loop (loop, 0);
1313		1599
1314	// and in some piece of code that gets executed on any "activity":	1600	// and in some piece of code that gets executed on any "activity":
…		…
1319	=head2 C<ev_periodic> - to cron or not to cron?	1605	=head2 C<ev_periodic> - to cron or not to cron?
1320		1606
1321	Periodic watchers are also timers of a kind, but they are very versatile	1607	Periodic watchers are also timers of a kind, but they are very versatile
1322	(and unfortunately a bit complex).	1608	(and unfortunately a bit complex).
1323		1609
1324	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1610	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1325	but on wall clock time (absolute time). You can tell a periodic watcher	1611	relative time, the physical time that passes) but on wall clock time
1326	to trigger after some specific point in time. For example, if you tell a	1612	(absolute time, the thing you can read on your calender or clock). The
1327	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1613	difference is that wall clock time can run faster or slower than real
1328	+ 10.>, that is, an absolute time not a delay) and then reset your system	1614	time, and time jumps are not uncommon (e.g. when you adjust your
1329	clock to January of the previous year, then it will take more than year	1615	wrist-watch).
1330	to trigger the event (unlike an C<ev_timer>, which would still trigger
1331	roughly 10 seconds later as it uses a relative timeout).
1332		1616
		1617	You can tell a periodic watcher to trigger after some specific point
		1618	in time: for example, if you tell a periodic watcher to trigger "in 10
		1619	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1620	not a delay) and then reset your system clock to January of the previous
		1621	year, then it will take a year or more to trigger the event (unlike an
		1622	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1623	it, as it uses a relative timeout).
		1624
1333	C<ev_periodic>s can also be used to implement vastly more complex timers,	1625	C<ev_periodic> watchers can also be used to implement vastly more complex
1334	such as triggering an event on each "midnight, local time", or other	1626	timers, such as triggering an event on each "midnight, local time", or
1335	complicated, rules.	1627	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1628	those cannot react to time jumps.
1336		1629
1337	As with timers, the callback is guaranteed to be invoked only when the	1630	As with timers, the callback is guaranteed to be invoked only when the
1338	time (C<at>) has passed, but if multiple periodic timers become ready	1631	point in time where it is supposed to trigger has passed. If multiple
1339	during the same loop iteration then order of execution is undefined.	1632	timers become ready during the same loop iteration then the ones with
		1633	earlier time-out values are invoked before ones with later time-out values
		1634	(but this is no longer true when a callback calls C<ev_loop> recursively).
1340		1635
1341	=head3 Watcher-Specific Functions and Data Members	1636	=head3 Watcher-Specific Functions and Data Members
1342		1637
1343	=over 4	1638	=over 4
1344		1639
1345	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1640	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1346		1641
1347	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1642	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1348		1643
1349	Lots of arguments, lets sort it out... There are basically three modes of	1644	Lots of arguments, let's sort it out... There are basically three modes of
1350	operation, and we will explain them from simplest to complex:	1645	operation, and we will explain them from simplest to most complex:
1351		1646
1352	=over 4	1647	=over 4
1353		1648
1354	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1649	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1355		1650
1356	In this configuration the watcher triggers an event after the wall clock	1651	In this configuration the watcher triggers an event after the wall clock
1357	time C<at> has passed and doesn't repeat. It will not adjust when a time	1652	time C<offset> has passed. It will not repeat and will not adjust when a
1358	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1653	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1359	run when the system time reaches or surpasses this time.	1654	will be stopped and invoked when the system clock reaches or surpasses
		1655	this point in time.
1360		1656
1361	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1657	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1362		1658
1363	In this mode the watcher will always be scheduled to time out at the next	1659	In this mode the watcher will always be scheduled to time out at the next
1364	C<at + N * interval> time (for some integer N, which can also be negative)	1660	C<offset + N * interval> time (for some integer N, which can also be
1365	and then repeat, regardless of any time jumps.	1661	negative) and then repeat, regardless of any time jumps. The C<offset>
		1662	argument is merely an offset into the C<interval> periods.
1366		1663
1367	This can be used to create timers that do not drift with respect to system	1664	This can be used to create timers that do not drift with respect to the
1368	time, for example, here is a C<ev_periodic> that triggers each hour, on	1665	system clock, for example, here is an C<ev_periodic> that triggers each
1369	the hour:	1666	hour, on the hour (with respect to UTC):
1370		1667
1371	ev_periodic_set (&periodic, 0., 3600., 0);	1668	ev_periodic_set (&periodic, 0., 3600., 0);
1372		1669
1373	This doesn't mean there will always be 3600 seconds in between triggers,	1670	This doesn't mean there will always be 3600 seconds in between triggers,
1374	but only that the callback will be called when the system time shows a	1671	but only that the callback will be called when the system time shows a
1375	full hour (UTC), or more correctly, when the system time is evenly divisible	1672	full hour (UTC), or more correctly, when the system time is evenly divisible
1376	by 3600.	1673	by 3600.
1377		1674
1378	Another way to think about it (for the mathematically inclined) is that	1675	Another way to think about it (for the mathematically inclined) is that
1379	C<ev_periodic> will try to run the callback in this mode at the next possible	1676	C<ev_periodic> will try to run the callback in this mode at the next possible
1380	time where C<time = at (mod interval)>, regardless of any time jumps.	1677	time where C<time = offset (mod interval)>, regardless of any time jumps.
1381		1678
1382	For numerical stability it is preferable that the C<at> value is near	1679	For numerical stability it is preferable that the C<offset> value is near
1383	C<ev_now ()> (the current time), but there is no range requirement for	1680	C<ev_now ()> (the current time), but there is no range requirement for
1384	this value, and in fact is often specified as zero.	1681	this value, and in fact is often specified as zero.
1385		1682
1386	Note also that there is an upper limit to how often a timer can fire (CPU	1683	Note also that there is an upper limit to how often a timer can fire (CPU
1387	speed for example), so if C<interval> is very small then timing stability	1684	speed for example), so if C<interval> is very small then timing stability
1388	will of course deteriorate. Libev itself tries to be exact to be about one	1685	will of course deteriorate. Libev itself tries to be exact to be about one
1389	millisecond (if the OS supports it and the machine is fast enough).	1686	millisecond (if the OS supports it and the machine is fast enough).
1390		1687
1391	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1688	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1392		1689
1393	In this mode the values for C<interval> and C<at> are both being	1690	In this mode the values for C<interval> and C<offset> are both being
1394	ignored. Instead, each time the periodic watcher gets scheduled, the	1691	ignored. Instead, each time the periodic watcher gets scheduled, the
1395	reschedule callback will be called with the watcher as first, and the	1692	reschedule callback will be called with the watcher as first, and the
1396	current time as second argument.	1693	current time as second argument.
1397		1694
1398	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1695	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1399	ever, or make ANY event loop modifications whatsoever>.	1696	or make ANY other event loop modifications whatsoever, unless explicitly
		1697	allowed by documentation here>.
1400		1698
1401	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1699	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1402	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1700	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1403	only event loop modification you are allowed to do).	1701	only event loop modification you are allowed to do).
1404		1702
1405	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1703	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1406	*w, ev_tstamp now)>, e.g.:	1704	*w, ev_tstamp now)>, e.g.:
1407		1705
		1706	static ev_tstamp
1408	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1707	my_rescheduler (ev_periodic *w, ev_tstamp now)
1409	{	1708	{
1410	return now + 60.;	1709	return now + 60.;
1411	}	1710	}
1412		1711
1413	It must return the next time to trigger, based on the passed time value	1712	It must return the next time to trigger, based on the passed time value
…		…
1433	a different time than the last time it was called (e.g. in a crond like	1732	a different time than the last time it was called (e.g. in a crond like
1434	program when the crontabs have changed).	1733	program when the crontabs have changed).
1435		1734
1436	=item ev_tstamp ev_periodic_at (ev_periodic *)	1735	=item ev_tstamp ev_periodic_at (ev_periodic *)
1437		1736
1438	When active, returns the absolute time that the watcher is supposed to	1737	When active, returns the absolute time that the watcher is supposed
1439	trigger next.	1738	to trigger next. This is not the same as the C<offset> argument to
		1739	C<ev_periodic_set>, but indeed works even in interval and manual
		1740	rescheduling modes.
1440		1741
1441	=item ev_tstamp offset [read-write]	1742	=item ev_tstamp offset [read-write]
1442		1743
1443	When repeating, this contains the offset value, otherwise this is the	1744	When repeating, this contains the offset value, otherwise this is the
1444	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1745	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1746	although libev might modify this value for better numerical stability).
1445		1747
1446	Can be modified any time, but changes only take effect when the periodic	1748	Can be modified any time, but changes only take effect when the periodic
1447	timer fires or C<ev_periodic_again> is being called.	1749	timer fires or C<ev_periodic_again> is being called.
1448		1750
1449	=item ev_tstamp interval [read-write]	1751	=item ev_tstamp interval [read-write]
1450		1752
1451	The current interval value. Can be modified any time, but changes only	1753	The current interval value. Can be modified any time, but changes only
1452	take effect when the periodic timer fires or C<ev_periodic_again> is being	1754	take effect when the periodic timer fires or C<ev_periodic_again> is being
1453	called.	1755	called.
1454		1756
1455	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1757	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1456		1758
1457	The current reschedule callback, or C<0>, if this functionality is	1759	The current reschedule callback, or C<0>, if this functionality is
1458	switched off. Can be changed any time, but changes only take effect when	1760	switched off. Can be changed any time, but changes only take effect when
1459	the periodic timer fires or C<ev_periodic_again> is being called.	1761	the periodic timer fires or C<ev_periodic_again> is being called.
1460		1762
1461	=back	1763	=back
1462		1764
1463	=head3 Examples	1765	=head3 Examples
1464		1766
1465	Example: Call a callback every hour, or, more precisely, whenever the	1767	Example: Call a callback every hour, or, more precisely, whenever the
1466	system clock is divisible by 3600. The callback invocation times have	1768	system time is divisible by 3600. The callback invocation times have
1467	potentially a lot of jitter, but good long-term stability.	1769	potentially a lot of jitter, but good long-term stability.
1468		1770
1469	static void	1771	static void
1470	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1772	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1471	{	1773	{
1472	... its now a full hour (UTC, or TAI or whatever your clock follows)	1774	... its now a full hour (UTC, or TAI or whatever your clock follows)
1473	}	1775	}
1474		1776
1475	struct ev_periodic hourly_tick;	1777	ev_periodic hourly_tick;
1476	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1778	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1477	ev_periodic_start (loop, &hourly_tick);	1779	ev_periodic_start (loop, &hourly_tick);
1478		1780
1479	Example: The same as above, but use a reschedule callback to do it:	1781	Example: The same as above, but use a reschedule callback to do it:
1480		1782
1481	#include <math.h>	1783	#include <math.h>
1482		1784
1483	static ev_tstamp	1785	static ev_tstamp
1484	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1786	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1485	{	1787	{
1486	return fmod (now, 3600.) + 3600.;	1788	return now + (3600. - fmod (now, 3600.));
1487	}	1789	}
1488		1790
1489	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1791	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1490		1792
1491	Example: Call a callback every hour, starting now:	1793	Example: Call a callback every hour, starting now:
1492		1794
1493	struct ev_periodic hourly_tick;	1795	ev_periodic hourly_tick;
1494	ev_periodic_init (&hourly_tick, clock_cb,	1796	ev_periodic_init (&hourly_tick, clock_cb,
1495	fmod (ev_now (loop), 3600.), 3600., 0);	1797	fmod (ev_now (loop), 3600.), 3600., 0);
1496	ev_periodic_start (loop, &hourly_tick);	1798	ev_periodic_start (loop, &hourly_tick);
1497		1799
1498		1800
…		…
1501	Signal watchers will trigger an event when the process receives a specific	1803	Signal watchers will trigger an event when the process receives a specific
1502	signal one or more times. Even though signals are very asynchronous, libev	1804	signal one or more times. Even though signals are very asynchronous, libev
1503	will try it's best to deliver signals synchronously, i.e. as part of the	1805	will try it's best to deliver signals synchronously, i.e. as part of the
1504	normal event processing, like any other event.	1806	normal event processing, like any other event.
1505		1807
		1808	If you want signals asynchronously, just use C<sigaction> as you would
		1809	do without libev and forget about sharing the signal. You can even use
		1810	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1811
1506	You can configure as many watchers as you like per signal. Only when the	1812	You can configure as many watchers as you like per signal. Only when the
1507	first watcher gets started will libev actually register a signal watcher	1813	first watcher gets started will libev actually register a signal handler
1508	with the kernel (thus it coexists with your own signal handlers as long	1814	with the kernel (thus it coexists with your own signal handlers as long as
1509	as you don't register any with libev). Similarly, when the last signal	1815	you don't register any with libev for the same signal). Similarly, when
1510	watcher for a signal is stopped libev will reset the signal handler to	1816	the last signal watcher for a signal is stopped, libev will reset the
1511	SIG_DFL (regardless of what it was set to before).	1817	signal handler to SIG_DFL (regardless of what it was set to before).
1512		1818
1513	If possible and supported, libev will install its handlers with	1819	If possible and supported, libev will install its handlers with
1514	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1820	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1515	interrupted. If you have a problem with system calls getting interrupted by	1821	interrupted. If you have a problem with system calls getting interrupted by
1516	signals you can block all signals in an C<ev_check> watcher and unblock	1822	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1533		1839
1534	=back	1840	=back
1535		1841
1536	=head3 Examples	1842	=head3 Examples
1537		1843
1538	Example: Try to exit cleanly on SIGINT and SIGTERM.	1844	Example: Try to exit cleanly on SIGINT.
1539		1845
1540	static void	1846	static void
1541	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1847	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1542	{	1848	{
1543	ev_unloop (loop, EVUNLOOP_ALL);	1849	ev_unloop (loop, EVUNLOOP_ALL);
1544	}	1850	}
1545		1851
1546	struct ev_signal signal_watcher;	1852	ev_signal signal_watcher;
1547	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1853	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1548	ev_signal_start (loop, &sigint_cb);	1854	ev_signal_start (loop, &signal_watcher);
1549		1855
1550		1856
1551	=head2 C<ev_child> - watch out for process status changes	1857	=head2 C<ev_child> - watch out for process status changes
1552		1858
1553	Child watchers trigger when your process receives a SIGCHLD in response to	1859	Child watchers trigger when your process receives a SIGCHLD in response to
1554	some child status changes (most typically when a child of yours dies). It	1860	some child status changes (most typically when a child of yours dies or
1555	is permissible to install a child watcher I<after> the child has been	1861	exits). It is permissible to install a child watcher I<after> the child
1556	forked (which implies it might have already exited), as long as the event	1862	has been forked (which implies it might have already exited), as long
1557	loop isn't entered (or is continued from a watcher).	1863	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1864	forking and then immediately registering a watcher for the child is fine,
		1865	but forking and registering a watcher a few event loop iterations later is
		1866	not.
1558		1867
1559	Only the default event loop is capable of handling signals, and therefore	1868	Only the default event loop is capable of handling signals, and therefore
1560	you can only register child watchers in the default event loop.	1869	you can only register child watchers in the default event loop.
1561		1870
1562	=head3 Process Interaction	1871	=head3 Process Interaction
…		…
1623	its completion.	1932	its completion.
1624		1933
1625	ev_child cw;	1934	ev_child cw;
1626		1935
1627	static void	1936	static void
1628	child_cb (EV_P_ struct ev_child *w, int revents)	1937	child_cb (EV_P_ ev_child *w, int revents)
1629	{	1938	{
1630	ev_child_stop (EV_A_ w);	1939	ev_child_stop (EV_A_ w);
1631	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1940	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1632	}	1941	}
1633		1942
…		…
1648		1957
1649		1958
1650	=head2 C<ev_stat> - did the file attributes just change?	1959	=head2 C<ev_stat> - did the file attributes just change?
1651		1960
1652	This watches a file system path for attribute changes. That is, it calls	1961	This watches a file system path for attribute changes. That is, it calls
1653	C<stat> regularly (or when the OS says it changed) and sees if it changed	1962	C<stat> on that path in regular intervals (or when the OS says it changed)
1654	compared to the last time, invoking the callback if it did.	1963	and sees if it changed compared to the last time, invoking the callback if
		1964	it did.
1655		1965
1656	The path does not need to exist: changing from "path exists" to "path does	1966	The path does not need to exist: changing from "path exists" to "path does
1657	not exist" is a status change like any other. The condition "path does	1967	not exist" is a status change like any other. The condition "path does not
1658	not exist" is signified by the C<st_nlink> field being zero (which is	1968	exist" (or more correctly "path cannot be stat'ed") is signified by the
1659	otherwise always forced to be at least one) and all the other fields of	1969	C<st_nlink> field being zero (which is otherwise always forced to be at
1660	the stat buffer having unspecified contents.	1970	least one) and all the other fields of the stat buffer having unspecified
		1971	contents.
1661		1972
1662	The path I<should> be absolute and I<must not> end in a slash. If it is	1973	The path I<must not> end in a slash or contain special components such as
		1974	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1663	relative and your working directory changes, the behaviour is undefined.	1975	your working directory changes, then the behaviour is undefined.
1664		1976
1665	Since there is no standard to do this, the portable implementation simply	1977	Since there is no portable change notification interface available, the
1666	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1978	portable implementation simply calls C<stat(2)> regularly on the path
1667	can specify a recommended polling interval for this case. If you specify	1979	to see if it changed somehow. You can specify a recommended polling
1668	a polling interval of C<0> (highly recommended!) then a I<suitable,	1980	interval for this case. If you specify a polling interval of C<0> (highly
1669	unspecified default> value will be used (which you can expect to be around	1981	recommended!) then a I<suitable, unspecified default> value will be used
1670	five seconds, although this might change dynamically). Libev will also	1982	(which you can expect to be around five seconds, although this might
1671	impose a minimum interval which is currently around C<0.1>, but thats	1983	change dynamically). Libev will also impose a minimum interval which is
1672	usually overkill.	1984	currently around C<0.1>, but that's usually overkill.
1673		1985
1674	This watcher type is not meant for massive numbers of stat watchers,	1986	This watcher type is not meant for massive numbers of stat watchers,
1675	as even with OS-supported change notifications, this can be	1987	as even with OS-supported change notifications, this can be
1676	resource-intensive.	1988	resource-intensive.
1677		1989
1678	At the time of this writing, only the Linux inotify interface is	1990	At the time of this writing, the only OS-specific interface implemented
1679	implemented (implementing kqueue support is left as an exercise for the	1991	is the Linux inotify interface (implementing kqueue support is left as an
1680	reader, note, however, that the author sees no way of implementing ev_stat	1992	exercise for the reader. Note, however, that the author sees no way of
1681	semantics with kqueue). Inotify will be used to give hints only and should	1993	implementing C<ev_stat> semantics with kqueue, except as a hint).
1682	not change the semantics of C<ev_stat> watchers, which means that libev
1683	sometimes needs to fall back to regular polling again even with inotify,
1684	but changes are usually detected immediately, and if the file exists there
1685	will be no polling.
1686		1994
1687	=head3 ABI Issues (Largefile Support)	1995	=head3 ABI Issues (Largefile Support)
1688		1996
1689	Libev by default (unless the user overrides this) uses the default	1997	Libev by default (unless the user overrides this) uses the default
1690	compilation environment, which means that on systems with large file	1998	compilation environment, which means that on systems with large file
1691	support disabled by default, you get the 32 bit version of the stat	1999	support disabled by default, you get the 32 bit version of the stat
1692	structure. When using the library from programs that change the ABI to	2000	structure. When using the library from programs that change the ABI to
1693	use 64 bit file offsets the programs will fail. In that case you have to	2001	use 64 bit file offsets the programs will fail. In that case you have to
1694	compile libev with the same flags to get binary compatibility. This is	2002	compile libev with the same flags to get binary compatibility. This is
1695	obviously the case with any flags that change the ABI, but the problem is	2003	obviously the case with any flags that change the ABI, but the problem is
1696	most noticeably disabled with ev_stat and large file support.	2004	most noticeably displayed with ev_stat and large file support.
1697		2005
1698	The solution for this is to lobby your distribution maker to make large	2006	The solution for this is to lobby your distribution maker to make large
1699	file interfaces available by default (as e.g. FreeBSD does) and not	2007	file interfaces available by default (as e.g. FreeBSD does) and not
1700	optional. Libev cannot simply switch on large file support because it has	2008	optional. Libev cannot simply switch on large file support because it has
1701	to exchange stat structures with application programs compiled using the	2009	to exchange stat structures with application programs compiled using the
1702	default compilation environment.	2010	default compilation environment.
1703		2011
1704	=head3 Inotify	2012	=head3 Inotify and Kqueue
1705		2013
1706	When C<inotify (7)> support has been compiled into libev (generally only	2014	When C<inotify (7)> support has been compiled into libev and present at
1707	available on Linux) and present at runtime, it will be used to speed up	2015	runtime, it will be used to speed up change detection where possible. The
1708	change detection where possible. The inotify descriptor will be created lazily	2016	inotify descriptor will be created lazily when the first C<ev_stat>
1709	when the first C<ev_stat> watcher is being started.	2017	watcher is being started.
1710		2018
1711	Inotify presence does not change the semantics of C<ev_stat> watchers	2019	Inotify presence does not change the semantics of C<ev_stat> watchers
1712	except that changes might be detected earlier, and in some cases, to avoid	2020	except that changes might be detected earlier, and in some cases, to avoid
1713	making regular C<stat> calls. Even in the presence of inotify support	2021	making regular C<stat> calls. Even in the presence of inotify support
1714	there are many cases where libev has to resort to regular C<stat> polling.	2022	there are many cases where libev has to resort to regular C<stat> polling,
		2023	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2024	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2025	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2026	xfs are fully working) libev usually gets away without polling.
1715		2027
1716	(There is no support for kqueue, as apparently it cannot be used to	2028	There is no support for kqueue, as apparently it cannot be used to
1717	implement this functionality, due to the requirement of having a file	2029	implement this functionality, due to the requirement of having a file
1718	descriptor open on the object at all times).	2030	descriptor open on the object at all times, and detecting renames, unlinks
		2031	etc. is difficult.
		2032
		2033	=head3 C<stat ()> is a synchronous operation
		2034
		2035	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2036	the process. The exception are C<ev_stat> watchers - those call C<stat
		2037	()>, which is a synchronous operation.
		2038
		2039	For local paths, this usually doesn't matter: unless the system is very
		2040	busy or the intervals between stat's are large, a stat call will be fast,
		2041	as the path data is usually in memory already (except when starting the
		2042	watcher).
		2043
		2044	For networked file systems, calling C<stat ()> can block an indefinite
		2045	time due to network issues, and even under good conditions, a stat call
		2046	often takes multiple milliseconds.
		2047
		2048	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2049	paths, although this is fully supported by libev.
1719		2050
1720	=head3 The special problem of stat time resolution	2051	=head3 The special problem of stat time resolution
1721		2052
1722	The C<stat ()> system call only supports full-second resolution portably, and	2053	The C<stat ()> system call only supports full-second resolution portably,
1723	even on systems where the resolution is higher, many file systems still	2054	and even on systems where the resolution is higher, most file systems
1724	only support whole seconds.	2055	still only support whole seconds.
1725		2056
1726	That means that, if the time is the only thing that changes, you can	2057	That means that, if the time is the only thing that changes, you can
1727	easily miss updates: on the first update, C<ev_stat> detects a change and	2058	easily miss updates: on the first update, C<ev_stat> detects a change and
1728	calls your callback, which does something. When there is another update	2059	calls your callback, which does something. When there is another update
1729	within the same second, C<ev_stat> will be unable to detect it as the stat	2060	within the same second, C<ev_stat> will be unable to detect unless the
1730	data does not change.	2061	stat data does change in other ways (e.g. file size).
1731		2062
1732	The solution to this is to delay acting on a change for slightly more	2063	The solution to this is to delay acting on a change for slightly more
1733	than a second (or till slightly after the next full second boundary), using	2064	than a second (or till slightly after the next full second boundary), using
1734	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2065	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1735	ev_timer_again (loop, w)>).	2066	ev_timer_again (loop, w)>).
…		…
1755	C<path>. The C<interval> is a hint on how quickly a change is expected to	2086	C<path>. The C<interval> is a hint on how quickly a change is expected to
1756	be detected and should normally be specified as C<0> to let libev choose	2087	be detected and should normally be specified as C<0> to let libev choose
1757	a suitable value. The memory pointed to by C<path> must point to the same	2088	a suitable value. The memory pointed to by C<path> must point to the same
1758	path for as long as the watcher is active.	2089	path for as long as the watcher is active.
1759		2090
1760	The callback will receive C<EV_STAT> when a change was detected, relative	2091	The callback will receive an C<EV_STAT> event when a change was detected,
1761	to the attributes at the time the watcher was started (or the last change	2092	relative to the attributes at the time the watcher was started (or the
1762	was detected).	2093	last change was detected).
1763		2094
1764	=item ev_stat_stat (loop, ev_stat *)	2095	=item ev_stat_stat (loop, ev_stat *)
1765		2096
1766	Updates the stat buffer immediately with new values. If you change the	2097	Updates the stat buffer immediately with new values. If you change the
1767	watched path in your callback, you could call this function to avoid	2098	watched path in your callback, you could call this function to avoid
…		…
1850		2181
1851		2182
1852	=head2 C<ev_idle> - when you've got nothing better to do...	2183	=head2 C<ev_idle> - when you've got nothing better to do...
1853		2184
1854	Idle watchers trigger events when no other events of the same or higher	2185	Idle watchers trigger events when no other events of the same or higher
1855	priority are pending (prepare, check and other idle watchers do not	2186	priority are pending (prepare, check and other idle watchers do not count
1856	count).	2187	as receiving "events").
1857		2188
1858	That is, as long as your process is busy handling sockets or timeouts	2189	That is, as long as your process is busy handling sockets or timeouts
1859	(or even signals, imagine) of the same or higher priority it will not be	2190	(or even signals, imagine) of the same or higher priority it will not be
1860	triggered. But when your process is idle (or only lower-priority watchers	2191	triggered. But when your process is idle (or only lower-priority watchers
1861	are pending), the idle watchers are being called once per event loop	2192	are pending), the idle watchers are being called once per event loop
…		…
1872		2203
1873	=head3 Watcher-Specific Functions and Data Members	2204	=head3 Watcher-Specific Functions and Data Members
1874		2205
1875	=over 4	2206	=over 4
1876		2207
1877	=item ev_idle_init (ev_signal *, callback)	2208	=item ev_idle_init (ev_idle *, callback)
1878		2209
1879	Initialises and configures the idle watcher - it has no parameters of any	2210	Initialises and configures the idle watcher - it has no parameters of any
1880	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2211	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1881	believe me.	2212	believe me.
1882		2213
…		…
1886		2217
1887	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2218	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1888	callback, free it. Also, use no error checking, as usual.	2219	callback, free it. Also, use no error checking, as usual.
1889		2220
1890	static void	2221	static void
1891	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2222	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1892	{	2223	{
1893	free (w);	2224	free (w);
1894	// now do something you wanted to do when the program has	2225	// now do something you wanted to do when the program has
1895	// no longer anything immediate to do.	2226	// no longer anything immediate to do.
1896	}	2227	}
1897		2228
1898	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2229	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1899	ev_idle_init (idle_watcher, idle_cb);	2230	ev_idle_init (idle_watcher, idle_cb);
1900	ev_idle_start (loop, idle_cb);	2231	ev_idle_start (loop, idle_cb);
1901		2232
1902		2233
1903	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2234	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1904		2235
1905	Prepare and check watchers are usually (but not always) used in tandem:	2236	Prepare and check watchers are usually (but not always) used in pairs:
1906	prepare watchers get invoked before the process blocks and check watchers	2237	prepare watchers get invoked before the process blocks and check watchers
1907	afterwards.	2238	afterwards.
1908		2239
1909	You I<must not> call C<ev_loop> or similar functions that enter	2240	You I<must not> call C<ev_loop> or similar functions that enter
1910	the current event loop from either C<ev_prepare> or C<ev_check>	2241	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1913	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2244	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1914	C<ev_check> so if you have one watcher of each kind they will always be	2245	C<ev_check> so if you have one watcher of each kind they will always be
1915	called in pairs bracketing the blocking call.	2246	called in pairs bracketing the blocking call.
1916		2247
1917	Their main purpose is to integrate other event mechanisms into libev and	2248	Their main purpose is to integrate other event mechanisms into libev and
1918	their use is somewhat advanced. This could be used, for example, to track	2249	their use is somewhat advanced. They could be used, for example, to track
1919	variable changes, implement your own watchers, integrate net-snmp or a	2250	variable changes, implement your own watchers, integrate net-snmp or a
1920	coroutine library and lots more. They are also occasionally useful if	2251	coroutine library and lots more. They are also occasionally useful if
1921	you cache some data and want to flush it before blocking (for example,	2252	you cache some data and want to flush it before blocking (for example,
1922	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2253	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1923	watcher).	2254	watcher).
1924		2255
1925	This is done by examining in each prepare call which file descriptors need	2256	This is done by examining in each prepare call which file descriptors
1926	to be watched by the other library, registering C<ev_io> watchers for	2257	need to be watched by the other library, registering C<ev_io> watchers
1927	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2258	for them and starting an C<ev_timer> watcher for any timeouts (many
1928	provide just this functionality). Then, in the check watcher you check for	2259	libraries provide exactly this functionality). Then, in the check watcher,
1929	any events that occurred (by checking the pending status of all watchers	2260	you check for any events that occurred (by checking the pending status
1930	and stopping them) and call back into the library. The I/O and timer	2261	of all watchers and stopping them) and call back into the library. The
1931	callbacks will never actually be called (but must be valid nevertheless,	2262	I/O and timer callbacks will never actually be called (but must be valid
1932	because you never know, you know?).	2263	nevertheless, because you never know, you know?).
1933		2264
1934	As another example, the Perl Coro module uses these hooks to integrate	2265	As another example, the Perl Coro module uses these hooks to integrate
1935	coroutines into libev programs, by yielding to other active coroutines	2266	coroutines into libev programs, by yielding to other active coroutines
1936	during each prepare and only letting the process block if no coroutines	2267	during each prepare and only letting the process block if no coroutines
1937	are ready to run (it's actually more complicated: it only runs coroutines	2268	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1940	loop from blocking if lower-priority coroutines are active, thus mapping	2271	loop from blocking if lower-priority coroutines are active, thus mapping
1941	low-priority coroutines to idle/background tasks).	2272	low-priority coroutines to idle/background tasks).
1942		2273
1943	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2274	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1944	priority, to ensure that they are being run before any other watchers	2275	priority, to ensure that they are being run before any other watchers
		2276	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2277
1945	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2278	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1946	too) should not activate ("feed") events into libev. While libev fully	2279	activate ("feed") events into libev. While libev fully supports this, they
1947	supports this, they might get executed before other C<ev_check> watchers	2280	might get executed before other C<ev_check> watchers did their job. As
1948	did their job. As C<ev_check> watchers are often used to embed other	2281	C<ev_check> watchers are often used to embed other (non-libev) event
1949	(non-libev) event loops those other event loops might be in an unusable	2282	loops those other event loops might be in an unusable state until their
1950	state until their C<ev_check> watcher ran (always remind yourself to	2283	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1951	coexist peacefully with others).	2284	others).
1952		2285
1953	=head3 Watcher-Specific Functions and Data Members	2286	=head3 Watcher-Specific Functions and Data Members
1954		2287
1955	=over 4	2288	=over 4
1956		2289
…		…
1958		2291
1959	=item ev_check_init (ev_check *, callback)	2292	=item ev_check_init (ev_check *, callback)
1960		2293
1961	Initialises and configures the prepare or check watcher - they have no	2294	Initialises and configures the prepare or check watcher - they have no
1962	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2295	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1963	macros, but using them is utterly, utterly and completely pointless.	2296	macros, but using them is utterly, utterly, utterly and completely
		2297	pointless.
1964		2298
1965	=back	2299	=back
1966		2300
1967	=head3 Examples	2301	=head3 Examples
1968		2302
…		…
1981		2315
1982	static ev_io iow [nfd];	2316	static ev_io iow [nfd];
1983	static ev_timer tw;	2317	static ev_timer tw;
1984		2318
1985	static void	2319	static void
1986	io_cb (ev_loop *loop, ev_io *w, int revents)	2320	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1987	{	2321	{
1988	}	2322	}
1989		2323
1990	// create io watchers for each fd and a timer before blocking	2324	// create io watchers for each fd and a timer before blocking
1991	static void	2325	static void
1992	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2326	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1993	{	2327	{
1994	int timeout = 3600000;	2328	int timeout = 3600000;
1995	struct pollfd fds [nfd];	2329	struct pollfd fds [nfd];
1996	// actual code will need to loop here and realloc etc.	2330	// actual code will need to loop here and realloc etc.
1997	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2331	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2012	}	2346	}
2013	}	2347	}
2014		2348
2015	// stop all watchers after blocking	2349	// stop all watchers after blocking
2016	static void	2350	static void
2017	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2351	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2018	{	2352	{
2019	ev_timer_stop (loop, &tw);	2353	ev_timer_stop (loop, &tw);
2020		2354
2021	for (int i = 0; i < nfd; ++i)	2355	for (int i = 0; i < nfd; ++i)
2022	{	2356	{
…		…
2061	}	2395	}
2062		2396
2063	// do not ever call adns_afterpoll	2397	// do not ever call adns_afterpoll
2064		2398
2065	Method 4: Do not use a prepare or check watcher because the module you	2399	Method 4: Do not use a prepare or check watcher because the module you
2066	want to embed is too inflexible to support it. Instead, you can override	2400	want to embed is not flexible enough to support it. Instead, you can
2067	their poll function. The drawback with this solution is that the main	2401	override their poll function. The drawback with this solution is that the
2068	loop is now no longer controllable by EV. The C<Glib::EV> module does	2402	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2069	this.	2403	this approach, effectively embedding EV as a client into the horrible
		2404	libglib event loop.
2070		2405
2071	static gint	2406	static gint
2072	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2407	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2073	{	2408	{
2074	int got_events = 0;	2409	int got_events = 0;
…		…
2105	prioritise I/O.	2440	prioritise I/O.
2106		2441
2107	As an example for a bug workaround, the kqueue backend might only support	2442	As an example for a bug workaround, the kqueue backend might only support
2108	sockets on some platform, so it is unusable as generic backend, but you	2443	sockets on some platform, so it is unusable as generic backend, but you
2109	still want to make use of it because you have many sockets and it scales	2444	still want to make use of it because you have many sockets and it scales
2110	so nicely. In this case, you would create a kqueue-based loop and embed it	2445	so nicely. In this case, you would create a kqueue-based loop and embed
2111	into your default loop (which might use e.g. poll). Overall operation will	2446	it into your default loop (which might use e.g. poll). Overall operation
2112	be a bit slower because first libev has to poll and then call kevent, but	2447	will be a bit slower because first libev has to call C<poll> and then
2113	at least you can use both at what they are best.	2448	C<kevent>, but at least you can use both mechanisms for what they are
		2449	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2114		2450
2115	As for prioritising I/O: rarely you have the case where some fds have	2451	As for prioritising I/O: under rare circumstances you have the case where
2116	to be watched and handled very quickly (with low latency), and even	2452	some fds have to be watched and handled very quickly (with low latency),
2117	priorities and idle watchers might have too much overhead. In this case	2453	and even priorities and idle watchers might have too much overhead. In
2118	you would put all the high priority stuff in one loop and all the rest in	2454	this case you would put all the high priority stuff in one loop and all
2119	a second one, and embed the second one in the first.	2455	the rest in a second one, and embed the second one in the first.
2120		2456
2121	As long as the watcher is active, the callback will be invoked every time	2457	As long as the watcher is active, the callback will be invoked every
2122	there might be events pending in the embedded loop. The callback must then	2458	time there might be events pending in the embedded loop. The callback
2123	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2459	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2124	their callbacks (you could also start an idle watcher to give the embedded	2460	sweep and invoke their callbacks (the callback doesn't need to invoke the
2125	loop strictly lower priority for example). You can also set the callback	2461	C<ev_embed_sweep> function directly, it could also start an idle watcher
2126	to C<0>, in which case the embed watcher will automatically execute the	2462	to give the embedded loop strictly lower priority for example).
2127	embedded loop sweep.
2128		2463
2129	As long as the watcher is started it will automatically handle events. The	2464	You can also set the callback to C<0>, in which case the embed watcher
2130	callback will be invoked whenever some events have been handled. You can	2465	will automatically execute the embedded loop sweep whenever necessary.
2131	set the callback to C<0> to avoid having to specify one if you are not
2132	interested in that.
2133		2466
2134	Also, there have not currently been made special provisions for forking:	2467	Fork detection will be handled transparently while the C<ev_embed> watcher
2135	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2468	is active, i.e., the embedded loop will automatically be forked when the
2136	but you will also have to stop and restart any C<ev_embed> watchers	2469	embedding loop forks. In other cases, the user is responsible for calling
2137	yourself.	2470	C<ev_loop_fork> on the embedded loop.
2138		2471
2139	Unfortunately, not all backends are embeddable, only the ones returned by	2472	Unfortunately, not all backends are embeddable: only the ones returned by
2140	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2473	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2141	portable one.	2474	portable one.
2142		2475
2143	So when you want to use this feature you will always have to be prepared	2476	So when you want to use this feature you will always have to be prepared
2144	that you cannot get an embeddable loop. The recommended way to get around	2477	that you cannot get an embeddable loop. The recommended way to get around
2145	this is to have a separate variables for your embeddable loop, try to	2478	this is to have a separate variables for your embeddable loop, try to
2146	create it, and if that fails, use the normal loop for everything.	2479	create it, and if that fails, use the normal loop for everything.
		2480
		2481	=head3 C<ev_embed> and fork
		2482
		2483	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2484	automatically be applied to the embedded loop as well, so no special
		2485	fork handling is required in that case. When the watcher is not running,
		2486	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2487	as applicable.
2147		2488
2148	=head3 Watcher-Specific Functions and Data Members	2489	=head3 Watcher-Specific Functions and Data Members
2149		2490
2150	=over 4	2491	=over 4
2151		2492
…		…
2179	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2520	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2180	used).	2521	used).
2181		2522
2182	struct ev_loop *loop_hi = ev_default_init (0);	2523	struct ev_loop *loop_hi = ev_default_init (0);
2183	struct ev_loop *loop_lo = 0;	2524	struct ev_loop *loop_lo = 0;
2184	struct ev_embed embed;	2525	ev_embed embed;
2185		2526
2186	// see if there is a chance of getting one that works	2527	// see if there is a chance of getting one that works
2187	// (remember that a flags value of 0 means autodetection)	2528	// (remember that a flags value of 0 means autodetection)
2188	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2529	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2189	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2530	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2203	kqueue implementation). Store the kqueue/socket-only event loop in	2544	kqueue implementation). Store the kqueue/socket-only event loop in
2204	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2545	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2205		2546
2206	struct ev_loop *loop = ev_default_init (0);	2547	struct ev_loop *loop = ev_default_init (0);
2207	struct ev_loop *loop_socket = 0;	2548	struct ev_loop *loop_socket = 0;
2208	struct ev_embed embed;	2549	ev_embed embed;
2209		2550
2210	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2551	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2211	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2552	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2212	{	2553	{
2213	ev_embed_init (&embed, 0, loop_socket);	2554	ev_embed_init (&embed, 0, loop_socket);
…		…
2269	is that the author does not know of a simple (or any) algorithm for a	2610	is that the author does not know of a simple (or any) algorithm for a
2270	multiple-writer-single-reader queue that works in all cases and doesn't	2611	multiple-writer-single-reader queue that works in all cases and doesn't
2271	need elaborate support such as pthreads.	2612	need elaborate support such as pthreads.
2272		2613
2273	That means that if you want to queue data, you have to provide your own	2614	That means that if you want to queue data, you have to provide your own
2274	queue. But at least I can tell you would implement locking around your	2615	queue. But at least I can tell you how to implement locking around your
2275	queue:	2616	queue:
2276		2617
2277	=over 4	2618	=over 4
2278		2619
2279	=item queueing from a signal handler context	2620	=item queueing from a signal handler context
2280		2621
2281	To implement race-free queueing, you simply add to the queue in the signal	2622	To implement race-free queueing, you simply add to the queue in the signal
2282	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2623	handler but you block the signal handler in the watcher callback. Here is
2283	some fictitious SIGUSR1 handler:	2624	an example that does that for some fictitious SIGUSR1 handler:
2284		2625
2285	static ev_async mysig;	2626	static ev_async mysig;
2286		2627
2287	static void	2628	static void
2288	sigusr1_handler (void)	2629	sigusr1_handler (void)
…		…
2354	=over 4	2695	=over 4
2355		2696
2356	=item ev_async_init (ev_async *, callback)	2697	=item ev_async_init (ev_async *, callback)
2357		2698
2358	Initialises and configures the async watcher - it has no parameters of any	2699	Initialises and configures the async watcher - it has no parameters of any
2359	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2700	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2360	believe me.	2701	trust me.
2361		2702
2362	=item ev_async_send (loop, ev_async *)	2703	=item ev_async_send (loop, ev_async *)
2363		2704
2364	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2705	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2365	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2706	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2366	C<ev_feed_event>, this call is safe to do in other threads, signal or	2707	C<ev_feed_event>, this call is safe to do from other threads, signal or
2367	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2708	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2368	section below on what exactly this means).	2709	section below on what exactly this means).
2369		2710
		2711	Note that, as with other watchers in libev, multiple events might get
		2712	compressed into a single callback invocation (another way to look at this
		2713	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2714	reset when the event loop detects that).
		2715
2370	This call incurs the overhead of a system call only once per loop iteration,	2716	This call incurs the overhead of a system call only once per event loop
2371	so while the overhead might be noticeable, it doesn't apply to repeated	2717	iteration, so while the overhead might be noticeable, it doesn't apply to
2372	calls to C<ev_async_send>.	2718	repeated calls to C<ev_async_send> for the same event loop.
2373		2719
2374	=item bool = ev_async_pending (ev_async *)	2720	=item bool = ev_async_pending (ev_async *)
2375		2721
2376	Returns a non-zero value when C<ev_async_send> has been called on the	2722	Returns a non-zero value when C<ev_async_send> has been called on the
2377	watcher but the event has not yet been processed (or even noted) by the	2723	watcher but the event has not yet been processed (or even noted) by the
…		…
2380	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2726	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2381	the loop iterates next and checks for the watcher to have become active,	2727	the loop iterates next and checks for the watcher to have become active,
2382	it will reset the flag again. C<ev_async_pending> can be used to very	2728	it will reset the flag again. C<ev_async_pending> can be used to very
2383	quickly check whether invoking the loop might be a good idea.	2729	quickly check whether invoking the loop might be a good idea.
2384		2730
2385	Not that this does I<not> check whether the watcher itself is pending, only	2731	Not that this does I<not> check whether the watcher itself is pending,
2386	whether it has been requested to make this watcher pending.	2732	only whether it has been requested to make this watcher pending: there
		2733	is a time window between the event loop checking and resetting the async
		2734	notification, and the callback being invoked.
2387		2735
2388	=back	2736	=back
2389		2737
2390		2738
2391	=head1 OTHER FUNCTIONS	2739	=head1 OTHER FUNCTIONS
…		…
2395	=over 4	2743	=over 4
2396		2744
2397	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2745	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2398		2746
2399	This function combines a simple timer and an I/O watcher, calls your	2747	This function combines a simple timer and an I/O watcher, calls your
2400	callback on whichever event happens first and automatically stop both	2748	callback on whichever event happens first and automatically stops both
2401	watchers. This is useful if you want to wait for a single event on an fd	2749	watchers. This is useful if you want to wait for a single event on an fd
2402	or timeout without having to allocate/configure/start/stop/free one or	2750	or timeout without having to allocate/configure/start/stop/free one or
2403	more watchers yourself.	2751	more watchers yourself.
2404		2752
2405	If C<fd> is less than 0, then no I/O watcher will be started and events	2753	If C<fd> is less than 0, then no I/O watcher will be started and the
2406	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2754	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2407	C<events> set will be created and started.	2755	the given C<fd> and C<events> set will be created and started.
2408		2756
2409	If C<timeout> is less than 0, then no timeout watcher will be	2757	If C<timeout> is less than 0, then no timeout watcher will be
2410	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2758	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2411	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2759	repeat = 0) will be started. C<0> is a valid timeout.
2412	dubious value.
2413		2760
2414	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2761	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2415	passed an C<revents> set like normal event callbacks (a combination of	2762	passed an C<revents> set like normal event callbacks (a combination of
2416	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2763	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2417	value passed to C<ev_once>:	2764	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2765	a timeout and an io event at the same time - you probably should give io
		2766	events precedence.
		2767
		2768	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2418		2769
2419	static void stdin_ready (int revents, void *arg)	2770	static void stdin_ready (int revents, void *arg)
2420	{	2771	{
		2772	if (revents & EV_READ)
		2773	/* stdin might have data for us, joy! */;
2421	if (revents & EV_TIMEOUT)	2774	else if (revents & EV_TIMEOUT)
2422	/* doh, nothing entered */;	2775	/* doh, nothing entered */;
2423	else if (revents & EV_READ)
2424	/* stdin might have data for us, joy! */;
2425	}	2776	}
2426		2777
2427	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2778	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2428		2779
2429	=item ev_feed_event (ev_loop *, watcher *, int revents)	2780	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2430		2781
2431	Feeds the given event set into the event loop, as if the specified event	2782	Feeds the given event set into the event loop, as if the specified event
2432	had happened for the specified watcher (which must be a pointer to an	2783	had happened for the specified watcher (which must be a pointer to an
2433	initialised but not necessarily started event watcher).	2784	initialised but not necessarily started event watcher).
2434		2785
2435	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2786	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2436		2787
2437	Feed an event on the given fd, as if a file descriptor backend detected	2788	Feed an event on the given fd, as if a file descriptor backend detected
2438	the given events it.	2789	the given events it.
2439		2790
2440	=item ev_feed_signal_event (ev_loop *loop, int signum)	2791	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2441		2792
2442	Feed an event as if the given signal occurred (C<loop> must be the default	2793	Feed an event as if the given signal occurred (C<loop> must be the default
2443	loop!).	2794	loop!).
2444		2795
2445	=back	2796	=back
…		…
2567		2918
2568	myclass obj;	2919	myclass obj;
2569	ev::io iow;	2920	ev::io iow;
2570	iow.set <myclass, &myclass::io_cb> (&obj);	2921	iow.set <myclass, &myclass::io_cb> (&obj);
2571		2922
		2923	=item w->set (object *)
		2924
		2925	This is an B<experimental> feature that might go away in a future version.
		2926
		2927	This is a variation of a method callback - leaving out the method to call
		2928	will default the method to C<operator ()>, which makes it possible to use
		2929	functor objects without having to manually specify the C<operator ()> all
		2930	the time. Incidentally, you can then also leave out the template argument
		2931	list.
		2932
		2933	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2934	int revents)>.
		2935
		2936	See the method-C<set> above for more details.
		2937
		2938	Example: use a functor object as callback.
		2939
		2940	struct myfunctor
		2941	{
		2942	void operator() (ev::io &w, int revents)
		2943	{
		2944	...
		2945	}
		2946	}
		2947
		2948	myfunctor f;
		2949
		2950	ev::io w;
		2951	w.set (&f);
		2952
2572	=item w->set<function> (void *data = 0)	2953	=item w->set<function> (void *data = 0)
2573		2954
2574	Also sets a callback, but uses a static method or plain function as	2955	Also sets a callback, but uses a static method or plain function as
2575	callback. The optional C<data> argument will be stored in the watcher's	2956	callback. The optional C<data> argument will be stored in the watcher's
2576	C<data> member and is free for you to use.	2957	C<data> member and is free for you to use.
2577		2958
2578	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2959	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2579		2960
2580	See the method-C<set> above for more details.	2961	See the method-C<set> above for more details.
2581		2962
2582	Example:	2963	Example: Use a plain function as callback.
2583		2964
2584	static void io_cb (ev::io &w, int revents) { }	2965	static void io_cb (ev::io &w, int revents) { }
2585	iow.set <io_cb> ();	2966	iow.set <io_cb> ();
2586		2967
2587	=item w->set (struct ev_loop *)	2968	=item w->set (struct ev_loop *)
…		…
2625	Example: Define a class with an IO and idle watcher, start one of them in	3006	Example: Define a class with an IO and idle watcher, start one of them in
2626	the constructor.	3007	the constructor.
2627		3008
2628	class myclass	3009	class myclass
2629	{	3010	{
2630	ev::io io; void io_cb (ev::io &w, int revents);	3011	ev::io io ; void io_cb (ev::io &w, int revents);
2631	ev:idle idle void idle_cb (ev::idle &w, int revents);	3012	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2632		3013
2633	myclass (int fd)	3014	myclass (int fd)
2634	{	3015	{
2635	io .set <myclass, &myclass::io_cb > (this);	3016	io .set <myclass, &myclass::io_cb > (this);
2636	idle.set <myclass, &myclass::idle_cb> (this);	3017	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2652	=item Perl	3033	=item Perl
2653		3034
2654	The EV module implements the full libev API and is actually used to test	3035	The EV module implements the full libev API and is actually used to test
2655	libev. EV is developed together with libev. Apart from the EV core module,	3036	libev. EV is developed together with libev. Apart from the EV core module,
2656	there are additional modules that implement libev-compatible interfaces	3037	there are additional modules that implement libev-compatible interfaces
2657	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3038	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2658	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3039	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3040	and C<EV::Glib>).
2659		3041
2660	It can be found and installed via CPAN, its homepage is at	3042	It can be found and installed via CPAN, its homepage is at
2661	L<http://software.schmorp.de/pkg/EV>.	3043	L<http://software.schmorp.de/pkg/EV>.
2662		3044
2663	=item Python	3045	=item Python
2664		3046
2665	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3047	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2666	seems to be quite complete and well-documented. Note, however, that the	3048	seems to be quite complete and well-documented.
2667	patch they require for libev is outright dangerous as it breaks the ABI
2668	for everybody else, and therefore, should never be applied in an installed
2669	libev (if python requires an incompatible ABI then it needs to embed
2670	libev).
2671		3049
2672	=item Ruby	3050	=item Ruby
2673		3051
2674	Tony Arcieri has written a ruby extension that offers access to a subset	3052	Tony Arcieri has written a ruby extension that offers access to a subset
2675	of the libev API and adds file handle abstractions, asynchronous DNS and	3053	of the libev API and adds file handle abstractions, asynchronous DNS and
2676	more on top of it. It can be found via gem servers. Its homepage is at	3054	more on top of it. It can be found via gem servers. Its homepage is at
2677	L<http://rev.rubyforge.org/>.	3055	L<http://rev.rubyforge.org/>.
2678		3056
		3057	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3058	makes rev work even on mingw.
		3059
		3060	=item Haskell
		3061
		3062	A haskell binding to libev is available at
		3063	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3064
2679	=item D	3065	=item D
2680		3066
2681	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3067	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2682	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3068	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3069
		3070	=item Ocaml
		3071
		3072	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3073	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2683		3074
2684	=back	3075	=back
2685		3076
2686		3077
2687	=head1 MACRO MAGIC	3078	=head1 MACRO MAGIC
…		…
2788		3179
2789	#define EV_STANDALONE 1	3180	#define EV_STANDALONE 1
2790	#include "ev.h"	3181	#include "ev.h"
2791		3182
2792	Both header files and implementation files can be compiled with a C++	3183	Both header files and implementation files can be compiled with a C++
2793	compiler (at least, thats a stated goal, and breakage will be treated	3184	compiler (at least, that's a stated goal, and breakage will be treated
2794	as a bug).	3185	as a bug).
2795		3186
2796	You need the following files in your source tree, or in a directory	3187	You need the following files in your source tree, or in a directory
2797	in your include path (e.g. in libev/ when using -Ilibev):	3188	in your include path (e.g. in libev/ when using -Ilibev):
2798		3189
…		…
2842		3233
2843	=head2 PREPROCESSOR SYMBOLS/MACROS	3234	=head2 PREPROCESSOR SYMBOLS/MACROS
2844		3235
2845	Libev can be configured via a variety of preprocessor symbols you have to	3236	Libev can be configured via a variety of preprocessor symbols you have to
2846	define before including any of its files. The default in the absence of	3237	define before including any of its files. The default in the absence of
2847	autoconf is noted for every option.	3238	autoconf is documented for every option.
2848		3239
2849	=over 4	3240	=over 4
2850		3241
2851	=item EV_STANDALONE	3242	=item EV_STANDALONE
2852		3243
…		…
2854	keeps libev from including F<config.h>, and it also defines dummy	3245	keeps libev from including F<config.h>, and it also defines dummy
2855	implementations for some libevent functions (such as logging, which is not	3246	implementations for some libevent functions (such as logging, which is not
2856	supported). It will also not define any of the structs usually found in	3247	supported). It will also not define any of the structs usually found in
2857	F<event.h> that are not directly supported by the libev core alone.	3248	F<event.h> that are not directly supported by the libev core alone.
2858		3249
		3250	In stanbdalone mode, libev will still try to automatically deduce the
		3251	configuration, but has to be more conservative.
		3252
2859	=item EV_USE_MONOTONIC	3253	=item EV_USE_MONOTONIC
2860		3254
2861	If defined to be C<1>, libev will try to detect the availability of the	3255	If defined to be C<1>, libev will try to detect the availability of the
2862	monotonic clock option at both compile time and runtime. Otherwise no use	3256	monotonic clock option at both compile time and runtime. Otherwise no
2863	of the monotonic clock option will be attempted. If you enable this, you	3257	use of the monotonic clock option will be attempted. If you enable this,
2864	usually have to link against librt or something similar. Enabling it when	3258	you usually have to link against librt or something similar. Enabling it
2865	the functionality isn't available is safe, though, although you have	3259	when the functionality isn't available is safe, though, although you have
2866	to make sure you link against any libraries where the C<clock_gettime>	3260	to make sure you link against any libraries where the C<clock_gettime>
2867	function is hiding in (often F<-lrt>).	3261	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2868		3262
2869	=item EV_USE_REALTIME	3263	=item EV_USE_REALTIME
2870		3264
2871	If defined to be C<1>, libev will try to detect the availability of the	3265	If defined to be C<1>, libev will try to detect the availability of the
2872	real-time clock option at compile time (and assume its availability at	3266	real-time clock option at compile time (and assume its availability
2873	runtime if successful). Otherwise no use of the real-time clock option will	3267	at runtime if successful). Otherwise no use of the real-time clock
2874	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3268	option will be attempted. This effectively replaces C<gettimeofday>
2875	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3269	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2876	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3270	correctness. See the note about libraries in the description of
		3271	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3272	C<EV_USE_CLOCK_SYSCALL>.
		3273
		3274	=item EV_USE_CLOCK_SYSCALL
		3275
		3276	If defined to be C<1>, libev will try to use a direct syscall instead
		3277	of calling the system-provided C<clock_gettime> function. This option
		3278	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3279	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3280	programs needlessly. Using a direct syscall is slightly slower (in
		3281	theory), because no optimised vdso implementation can be used, but avoids
		3282	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3283	higher, as it simplifies linking (no need for C<-lrt>).
2877		3284
2878	=item EV_USE_NANOSLEEP	3285	=item EV_USE_NANOSLEEP
2879		3286
2880	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3287	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2881	and will use it for delays. Otherwise it will use C<select ()>.	3288	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2897		3304
2898	=item EV_SELECT_USE_FD_SET	3305	=item EV_SELECT_USE_FD_SET
2899		3306
2900	If defined to C<1>, then the select backend will use the system C<fd_set>	3307	If defined to C<1>, then the select backend will use the system C<fd_set>
2901	structure. This is useful if libev doesn't compile due to a missing	3308	structure. This is useful if libev doesn't compile due to a missing
2902	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3309	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2903	exotic systems. This usually limits the range of file descriptors to some	3310	on exotic systems. This usually limits the range of file descriptors to
2904	low limit such as 1024 or might have other limitations (winsocket only	3311	some low limit such as 1024 or might have other limitations (winsocket
2905	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3312	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2906	influence the size of the C<fd_set> used.	3313	configures the maximum size of the C<fd_set>.
2907		3314
2908	=item EV_SELECT_IS_WINSOCKET	3315	=item EV_SELECT_IS_WINSOCKET
2909		3316
2910	When defined to C<1>, the select backend will assume that	3317	When defined to C<1>, the select backend will assume that
2911	select/socket/connect etc. don't understand file descriptors but	3318	select/socket/connect etc. don't understand file descriptors but
…		…
3022	When doing priority-based operations, libev usually has to linearly search	3429	When doing priority-based operations, libev usually has to linearly search
3023	all the priorities, so having many of them (hundreds) uses a lot of space	3430	all the priorities, so having many of them (hundreds) uses a lot of space
3024	and time, so using the defaults of five priorities (-2 .. +2) is usually	3431	and time, so using the defaults of five priorities (-2 .. +2) is usually
3025	fine.	3432	fine.
3026		3433
3027	If your embedding application does not need any priorities, defining these both to	3434	If your embedding application does not need any priorities, defining these
3028	C<0> will save some memory and CPU.	3435	both to C<0> will save some memory and CPU.
3029		3436
3030	=item EV_PERIODIC_ENABLE	3437	=item EV_PERIODIC_ENABLE
3031		3438
3032	If undefined or defined to be C<1>, then periodic timers are supported. If	3439	If undefined or defined to be C<1>, then periodic timers are supported. If
3033	defined to be C<0>, then they are not. Disabling them saves a few kB of	3440	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3040	code.	3447	code.
3041		3448
3042	=item EV_EMBED_ENABLE	3449	=item EV_EMBED_ENABLE
3043		3450
3044	If undefined or defined to be C<1>, then embed watchers are supported. If	3451	If undefined or defined to be C<1>, then embed watchers are supported. If
3045	defined to be C<0>, then they are not.	3452	defined to be C<0>, then they are not. Embed watchers rely on most other
		3453	watcher types, which therefore must not be disabled.
3046		3454
3047	=item EV_STAT_ENABLE	3455	=item EV_STAT_ENABLE
3048		3456
3049	If undefined or defined to be C<1>, then stat watchers are supported. If	3457	If undefined or defined to be C<1>, then stat watchers are supported. If
3050	defined to be C<0>, then they are not.	3458	defined to be C<0>, then they are not.
…		…
3082	two).	3490	two).
3083		3491
3084	=item EV_USE_4HEAP	3492	=item EV_USE_4HEAP
3085		3493
3086	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3494	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3087	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3495	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3088	to C<1>. The 4-heap uses more complicated (longer) code but has	3496	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3089	noticeably faster performance with many (thousands) of watchers.	3497	faster performance with many (thousands) of watchers.
3090		3498
3091	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3499	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3092	(disabled).	3500	(disabled).
3093		3501
3094	=item EV_HEAP_CACHE_AT	3502	=item EV_HEAP_CACHE_AT
3095		3503
3096	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3504	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3097	timer and periodics heap, libev can cache the timestamp (I<at>) within	3505	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3098	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3506	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3099	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3507	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3100	but avoids random read accesses on heap changes. This improves performance	3508	but avoids random read accesses on heap changes. This improves performance
3101	noticeably with with many (hundreds) of watchers.	3509	noticeably with many (hundreds) of watchers.
3102		3510
3103	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3511	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3104	(disabled).	3512	(disabled).
3105		3513
3106	=item EV_VERIFY	3514	=item EV_VERIFY
…		…
3112	called once per loop, which can slow down libev. If set to C<3>, then the	3520	called once per loop, which can slow down libev. If set to C<3>, then the
3113	verification code will be called very frequently, which will slow down	3521	verification code will be called very frequently, which will slow down
3114	libev considerably.	3522	libev considerably.
3115		3523
3116	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3524	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3117	C<0.>	3525	C<0>.
3118		3526
3119	=item EV_COMMON	3527	=item EV_COMMON
3120		3528
3121	By default, all watchers have a C<void *data> member. By redefining	3529	By default, all watchers have a C<void *data> member. By redefining
3122	this macro to a something else you can include more and other types of	3530	this macro to a something else you can include more and other types of
…		…
3139	and the way callbacks are invoked and set. Must expand to a struct member	3547	and the way callbacks are invoked and set. Must expand to a struct member
3140	definition and a statement, respectively. See the F<ev.h> header file for	3548	definition and a statement, respectively. See the F<ev.h> header file for
3141	their default definitions. One possible use for overriding these is to	3549	their default definitions. One possible use for overriding these is to
3142	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3550	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3143	method calls instead of plain function calls in C++.	3551	method calls instead of plain function calls in C++.
		3552
		3553	=back
3144		3554
3145	=head2 EXPORTED API SYMBOLS	3555	=head2 EXPORTED API SYMBOLS
3146		3556
3147	If you need to re-export the API (e.g. via a DLL) and you need a list of	3557	If you need to re-export the API (e.g. via a DLL) and you need a list of
3148	exported symbols, you can use the provided F<Symbol.*> files which list	3558	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3195	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3605	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3196		3606
3197	#include "ev_cpp.h"	3607	#include "ev_cpp.h"
3198	#include "ev.c"	3608	#include "ev.c"
3199		3609
		3610	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3200		3611
3201	=head1 THREADS AND COROUTINES	3612	=head2 THREADS AND COROUTINES
3202		3613
3203	=head2 THREADS	3614	=head3 THREADS
3204		3615
3205	Libev itself is completely thread-safe, but it uses no locking. This	3616	All libev functions are reentrant and thread-safe unless explicitly
		3617	documented otherwise, but libev implements no locking itself. This means
3206	means that you can use as many loops as you want in parallel, as long as	3618	that you can use as many loops as you want in parallel, as long as there
3207	only one thread ever calls into one libev function with the same loop	3619	are no concurrent calls into any libev function with the same loop
3208	parameter.	3620	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3621	of course): libev guarantees that different event loops share no data
		3622	structures that need any locking.
3209		3623
3210	Or put differently: calls with different loop parameters can be done in	3624	Or to put it differently: calls with different loop parameters can be done
3211	parallel from multiple threads, calls with the same loop parameter must be	3625	concurrently from multiple threads, calls with the same loop parameter
3212	done serially (but can be done from different threads, as long as only one	3626	must be done serially (but can be done from different threads, as long as
3213	thread ever is inside a call at any point in time, e.g. by using a mutex	3627	only one thread ever is inside a call at any point in time, e.g. by using
3214	per loop).	3628	a mutex per loop).
		3629
		3630	Specifically to support threads (and signal handlers), libev implements
		3631	so-called C<ev_async> watchers, which allow some limited form of
		3632	concurrency on the same event loop, namely waking it up "from the
		3633	outside".
3215		3634
3216	If you want to know which design (one loop, locking, or multiple loops	3635	If you want to know which design (one loop, locking, or multiple loops
3217	without or something else still) is best for your problem, then I cannot	3636	without or something else still) is best for your problem, then I cannot
3218	help you. I can give some generic advice however:	3637	help you, but here is some generic advice:
3219		3638
3220	=over 4	3639	=over 4
3221		3640
3222	=item * most applications have a main thread: use the default libev loop	3641	=item * most applications have a main thread: use the default libev loop
3223	in that thread, or create a separate thread running only the default loop.	3642	in that thread, or create a separate thread running only the default loop.
…		…
3235		3654
3236	Choosing a model is hard - look around, learn, know that usually you can do	3655	Choosing a model is hard - look around, learn, know that usually you can do
3237	better than you currently do :-)	3656	better than you currently do :-)
3238		3657
3239	=item * often you need to talk to some other thread which blocks in the	3658	=item * often you need to talk to some other thread which blocks in the
		3659	event loop.
		3660
3240	event loop - C<ev_async> watchers can be used to wake them up from other	3661	C<ev_async> watchers can be used to wake them up from other threads safely
3241	threads safely (or from signal contexts...).	3662	(or from signal contexts...).
		3663
		3664	An example use would be to communicate signals or other events that only
		3665	work in the default loop by registering the signal watcher with the
		3666	default loop and triggering an C<ev_async> watcher from the default loop
		3667	watcher callback into the event loop interested in the signal.
3242		3668
3243	=back	3669	=back
3244		3670
3245	=head2 COROUTINES	3671	=head3 COROUTINES
3246		3672
3247	Libev is much more accommodating to coroutines ("cooperative threads"):	3673	Libev is very accommodating to coroutines ("cooperative threads"):
3248	libev fully supports nesting calls to it's functions from different	3674	libev fully supports nesting calls to its functions from different
3249	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3675	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3250	different coroutines and switch freely between both coroutines running the	3676	different coroutines, and switch freely between both coroutines running the
3251	loop, as long as you don't confuse yourself). The only exception is that	3677	loop, as long as you don't confuse yourself). The only exception is that
3252	you must not do this from C<ev_periodic> reschedule callbacks.	3678	you must not do this from C<ev_periodic> reschedule callbacks.
3253		3679
3254	Care has been invested into making sure that libev does not keep local	3680	Care has been taken to ensure that libev does not keep local state inside
3255	state inside C<ev_loop>, and other calls do not usually allow coroutine	3681	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3256	switches.	3682	they do not call any callbacks.
3257		3683
		3684	=head2 COMPILER WARNINGS
3258		3685
3259	=head1 COMPLEXITIES	3686	Depending on your compiler and compiler settings, you might get no or a
		3687	lot of warnings when compiling libev code. Some people are apparently
		3688	scared by this.
3260		3689
3261	In this section the complexities of (many of) the algorithms used inside	3690	However, these are unavoidable for many reasons. For one, each compiler
3262	libev will be explained. For complexity discussions about backends see the	3691	has different warnings, and each user has different tastes regarding
3263	documentation for C<ev_default_init>.	3692	warning options. "Warn-free" code therefore cannot be a goal except when
		3693	targeting a specific compiler and compiler-version.
3264		3694
3265	All of the following are about amortised time: If an array needs to be	3695	Another reason is that some compiler warnings require elaborate
3266	extended, libev needs to realloc and move the whole array, but this	3696	workarounds, or other changes to the code that make it less clear and less
3267	happens asymptotically never with higher number of elements, so O(1) might	3697	maintainable.
3268	mean it might do a lengthy realloc operation in rare cases, but on average
3269	it is much faster and asymptotically approaches constant time.
3270		3698
3271	=over 4	3699	And of course, some compiler warnings are just plain stupid, or simply
		3700	wrong (because they don't actually warn about the condition their message
		3701	seems to warn about). For example, certain older gcc versions had some
		3702	warnings that resulted an extreme number of false positives. These have
		3703	been fixed, but some people still insist on making code warn-free with
		3704	such buggy versions.
3272		3705
3273	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3706	While libev is written to generate as few warnings as possible,
		3707	"warn-free" code is not a goal, and it is recommended not to build libev
		3708	with any compiler warnings enabled unless you are prepared to cope with
		3709	them (e.g. by ignoring them). Remember that warnings are just that:
		3710	warnings, not errors, or proof of bugs.
3274		3711
3275	This means that, when you have a watcher that triggers in one hour and
3276	there are 100 watchers that would trigger before that then inserting will
3277	have to skip roughly seven (C<ld 100>) of these watchers.
3278		3712
3279	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3713	=head2 VALGRIND
3280		3714
3281	That means that changing a timer costs less than removing/adding them	3715	Valgrind has a special section here because it is a popular tool that is
3282	as only the relative motion in the event queue has to be paid for.	3716	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3283		3717
3284	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3718	If you think you found a bug (memory leak, uninitialised data access etc.)
		3719	in libev, then check twice: If valgrind reports something like:
3285		3720
3286	These just add the watcher into an array or at the head of a list.	3721	==2274== definitely lost: 0 bytes in 0 blocks.
		3722	==2274== possibly lost: 0 bytes in 0 blocks.
		3723	==2274== still reachable: 256 bytes in 1 blocks.
3287		3724
3288	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3725	Then there is no memory leak, just as memory accounted to global variables
		3726	is not a memleak - the memory is still being referenced, and didn't leak.
3289		3727
3290	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3728	Similarly, under some circumstances, valgrind might report kernel bugs
		3729	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3730	although an acceptable workaround has been found here), or it might be
		3731	confused.
3291		3732
3292	These watchers are stored in lists then need to be walked to find the	3733	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3293	correct watcher to remove. The lists are usually short (you don't usually	3734	make it into some kind of religion.
3294	have many watchers waiting for the same fd or signal).
3295		3735
3296	=item Finding the next timer in each loop iteration: O(1)	3736	If you are unsure about something, feel free to contact the mailing list
		3737	with the full valgrind report and an explanation on why you think this
		3738	is a bug in libev (best check the archives, too :). However, don't be
		3739	annoyed when you get a brisk "this is no bug" answer and take the chance
		3740	of learning how to interpret valgrind properly.
3297		3741
3298	By virtue of using a binary or 4-heap, the next timer is always found at a	3742	If you need, for some reason, empty reports from valgrind for your project
3299	fixed position in the storage array.	3743	I suggest using suppression lists.
3300		3744
3301	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3302		3745
3303	A change means an I/O watcher gets started or stopped, which requires	3746	=head1 PORTABILITY NOTES
3304	libev to recalculate its status (and possibly tell the kernel, depending
3305	on backend and whether C<ev_io_set> was used).
3306		3747
3307	=item Activating one watcher (putting it into the pending state): O(1)
3308
3309	=item Priority handling: O(number_of_priorities)
3310
3311	Priorities are implemented by allocating some space for each
3312	priority. When doing priority-based operations, libev usually has to
3313	linearly search all the priorities, but starting/stopping and activating
3314	watchers becomes O(1) w.r.t. priority handling.
3315
3316	=item Sending an ev_async: O(1)
3317
3318	=item Processing ev_async_send: O(number_of_async_watchers)
3319
3320	=item Processing signals: O(max_signal_number)
3321
3322	Sending involves a system call I<iff> there were no other C<ev_async_send>
3323	calls in the current loop iteration. Checking for async and signal events
3324	involves iterating over all running async watchers or all signal numbers.
3325
3326	=back
3327
3328
3329	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3748	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3330		3749
3331	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3750	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3332	requires, and its I/O model is fundamentally incompatible with the POSIX	3751	requires, and its I/O model is fundamentally incompatible with the POSIX
3333	model. Libev still offers limited functionality on this platform in	3752	model. Libev still offers limited functionality on this platform in
3334	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3753	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3345		3764
3346	Not a libev limitation but worth mentioning: windows apparently doesn't	3765	Not a libev limitation but worth mentioning: windows apparently doesn't
3347	accept large writes: instead of resulting in a partial write, windows will	3766	accept large writes: instead of resulting in a partial write, windows will
3348	either accept everything or return C<ENOBUFS> if the buffer is too large,	3767	either accept everything or return C<ENOBUFS> if the buffer is too large,
3349	so make sure you only write small amounts into your sockets (less than a	3768	so make sure you only write small amounts into your sockets (less than a
3350	megabyte seems safe, but thsi apparently depends on the amount of memory	3769	megabyte seems safe, but this apparently depends on the amount of memory
3351	available).	3770	available).
3352		3771
3353	Due to the many, low, and arbitrary limits on the win32 platform and	3772	Due to the many, low, and arbitrary limits on the win32 platform and
3354	the abysmal performance of winsockets, using a large number of sockets	3773	the abysmal performance of winsockets, using a large number of sockets
3355	is not recommended (and not reasonable). If your program needs to use	3774	is not recommended (and not reasonable). If your program needs to use
…		…
3366	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3785	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3367		3786
3368	#include "ev.h"	3787	#include "ev.h"
3369		3788
3370	And compile the following F<evwrap.c> file into your project (make sure	3789	And compile the following F<evwrap.c> file into your project (make sure
3371	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3790	you do I<not> compile the F<ev.c> or any other embedded source files!):
3372		3791
3373	#include "evwrap.h"	3792	#include "evwrap.h"
3374	#include "ev.c"	3793	#include "ev.c"
3375		3794
3376	=over 4	3795	=over 4
…		…
3421	wrap all I/O functions and provide your own fd management, but the cost of	3840	wrap all I/O functions and provide your own fd management, but the cost of
3422	calling select (O(n²)) will likely make this unworkable.	3841	calling select (O(n²)) will likely make this unworkable.
3423		3842
3424	=back	3843	=back
3425		3844
3426
3427	=head1 PORTABILITY REQUIREMENTS	3845	=head2 PORTABILITY REQUIREMENTS
3428		3846
3429	In addition to a working ISO-C implementation, libev relies on a few	3847	In addition to a working ISO-C implementation and of course the
3430	additional extensions:	3848	backend-specific APIs, libev relies on a few additional extensions:
3431		3849
3432	=over 4	3850	=over 4
3433		3851
3434	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3852	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3435	calling conventions regardless of C<ev_watcher_type *>.	3853	calling conventions regardless of C<ev_watcher_type *>.
…		…
3441	calls them using an C<ev_watcher *> internally.	3859	calls them using an C<ev_watcher *> internally.
3442		3860
3443	=item C<sig_atomic_t volatile> must be thread-atomic as well	3861	=item C<sig_atomic_t volatile> must be thread-atomic as well
3444		3862
3445	The type C<sig_atomic_t volatile> (or whatever is defined as	3863	The type C<sig_atomic_t volatile> (or whatever is defined as
3446	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3864	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3447	threads. This is not part of the specification for C<sig_atomic_t>, but is	3865	threads. This is not part of the specification for C<sig_atomic_t>, but is
3448	believed to be sufficiently portable.	3866	believed to be sufficiently portable.
3449		3867
3450	=item C<sigprocmask> must work in a threaded environment	3868	=item C<sigprocmask> must work in a threaded environment
3451		3869
…		…
3460	except the initial one, and run the default loop in the initial thread as	3878	except the initial one, and run the default loop in the initial thread as
3461	well.	3879	well.
3462		3880
3463	=item C<long> must be large enough for common memory allocation sizes	3881	=item C<long> must be large enough for common memory allocation sizes
3464		3882
3465	To improve portability and simplify using libev, libev uses C<long>	3883	To improve portability and simplify its API, libev uses C<long> internally
3466	internally instead of C<size_t> when allocating its data structures. On	3884	instead of C<size_t> when allocating its data structures. On non-POSIX
3467	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3885	systems (Microsoft...) this might be unexpectedly low, but is still at
3468	is still at least 31 bits everywhere, which is enough for hundreds of	3886	least 31 bits everywhere, which is enough for hundreds of millions of
3469	millions of watchers.	3887	watchers.
3470		3888
3471	=item C<double> must hold a time value in seconds with enough accuracy	3889	=item C<double> must hold a time value in seconds with enough accuracy
3472		3890
3473	The type C<double> is used to represent timestamps. It is required to	3891	The type C<double> is used to represent timestamps. It is required to
3474	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3892	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3478	=back	3896	=back
3479		3897
3480	If you know of other additional requirements drop me a note.	3898	If you know of other additional requirements drop me a note.
3481		3899
3482		3900
3483	=head1 COMPILER WARNINGS	3901	=head1 ALGORITHMIC COMPLEXITIES
3484		3902
3485	Depending on your compiler and compiler settings, you might get no or a	3903	In this section the complexities of (many of) the algorithms used inside
3486	lot of warnings when compiling libev code. Some people are apparently	3904	libev will be documented. For complexity discussions about backends see
3487	scared by this.	3905	the documentation for C<ev_default_init>.
3488		3906
3489	However, these are unavoidable for many reasons. For one, each compiler	3907	All of the following are about amortised time: If an array needs to be
3490	has different warnings, and each user has different tastes regarding	3908	extended, libev needs to realloc and move the whole array, but this
3491	warning options. "Warn-free" code therefore cannot be a goal except when	3909	happens asymptotically rarer with higher number of elements, so O(1) might
3492	targeting a specific compiler and compiler-version.	3910	mean that libev does a lengthy realloc operation in rare cases, but on
		3911	average it is much faster and asymptotically approaches constant time.
3493		3912
3494	Another reason is that some compiler warnings require elaborate	3913	=over 4
3495	workarounds, or other changes to the code that make it less clear and less
3496	maintainable.
3497		3914
3498	And of course, some compiler warnings are just plain stupid, or simply	3915	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3499	wrong (because they don't actually warn about the condition their message
3500	seems to warn about).
3501		3916
3502	While libev is written to generate as few warnings as possible,	3917	This means that, when you have a watcher that triggers in one hour and
3503	"warn-free" code is not a goal, and it is recommended not to build libev	3918	there are 100 watchers that would trigger before that, then inserting will
3504	with any compiler warnings enabled unless you are prepared to cope with	3919	have to skip roughly seven (C<ld 100>) of these watchers.
3505	them (e.g. by ignoring them). Remember that warnings are just that:
3506	warnings, not errors, or proof of bugs.
3507		3920
		3921	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3508		3922
3509	=head1 VALGRIND	3923	That means that changing a timer costs less than removing/adding them,
		3924	as only the relative motion in the event queue has to be paid for.
3510		3925
3511	Valgrind has a special section here because it is a popular tool that is	3926	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3512	highly useful, but valgrind reports are very hard to interpret.
3513		3927
3514	If you think you found a bug (memory leak, uninitialised data access etc.)	3928	These just add the watcher into an array or at the head of a list.
3515	in libev, then check twice: If valgrind reports something like:
3516		3929
3517	==2274== definitely lost: 0 bytes in 0 blocks.	3930	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3518	==2274== possibly lost: 0 bytes in 0 blocks.
3519	==2274== still reachable: 256 bytes in 1 blocks.
3520		3931
3521	Then there is no memory leak. Similarly, under some circumstances,	3932	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3522	valgrind might report kernel bugs as if it were a bug in libev, or it
3523	might be confused (it is a very good tool, but only a tool).
3524		3933
3525	If you are unsure about something, feel free to contact the mailing list	3934	These watchers are stored in lists, so they need to be walked to find the
3526	with the full valgrind report and an explanation on why you think this is	3935	correct watcher to remove. The lists are usually short (you don't usually
3527	a bug in libev. However, don't be annoyed when you get a brisk "this is	3936	have many watchers waiting for the same fd or signal: one is typical, two
3528	no bug" answer and take the chance of learning how to interpret valgrind	3937	is rare).
3529	properly.
3530		3938
3531	If you need, for some reason, empty reports from valgrind for your project	3939	=item Finding the next timer in each loop iteration: O(1)
3532	I suggest using suppression lists.	3940
		3941	By virtue of using a binary or 4-heap, the next timer is always found at a
		3942	fixed position in the storage array.
		3943
		3944	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3945
		3946	A change means an I/O watcher gets started or stopped, which requires
		3947	libev to recalculate its status (and possibly tell the kernel, depending
		3948	on backend and whether C<ev_io_set> was used).
		3949
		3950	=item Activating one watcher (putting it into the pending state): O(1)
		3951
		3952	=item Priority handling: O(number_of_priorities)
		3953
		3954	Priorities are implemented by allocating some space for each
		3955	priority. When doing priority-based operations, libev usually has to
		3956	linearly search all the priorities, but starting/stopping and activating
		3957	watchers becomes O(1) with respect to priority handling.
		3958
		3959	=item Sending an ev_async: O(1)
		3960
		3961	=item Processing ev_async_send: O(number_of_async_watchers)
		3962
		3963	=item Processing signals: O(max_signal_number)
		3964
		3965	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3966	calls in the current loop iteration. Checking for async and signal events
		3967	involves iterating over all running async watchers or all signal numbers.
		3968
		3969	=back
3533		3970
3534		3971
3535	=head1 AUTHOR	3972	=head1 AUTHOR
3536		3973
3537	Marc Lehmann <libev@schmorp.de>.	3974	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3538		3975

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