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Revision 1.223 by root, Sun Dec 14 21:58:08 2008 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 is
660	visible to the libev user and should not keep C<ev_loop> from exiting if	732	not visible to the libev user and should not keep C<ev_loop> from exiting
661	no event watchers registered by it are active. It is also an excellent	733	if no event watchers registered by it are active. It is also an excellent
662	way to do this for generic recurring timers or from within third-party	734	way to do this for generic recurring timers or from within third-party
663	libraries. Just remember to I<unref after start> and I<ref before stop>	735	libraries. Just remember to I<unref after start> and I<ref before stop>
664	(but only if the watcher wasn't active before, or was active before,	736	(but only if the watcher wasn't active before, or was active before,
665	respectively).	737	respectively).
666		738
667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
668	running when nothing else is active.	740	running when nothing else is active.
669		741
670	struct ev_signal exitsig;	742	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	743	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	744	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	745	evf_unref (loop);
674		746
675	Example: For some weird reason, unregister the above signal handler again.	747	Example: For some weird reason, unregister the above signal handler again.
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	761	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	762	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	763	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	764	opportunities).
693		765
694	The background is that sometimes your program runs just fast enough to	766	The idea is that sometimes your program runs just fast enough to handle
695	handle one (or very few) event(s) per loop iteration. While this makes	767	one (or very few) event(s) per loop iteration. While this makes the
696	the program responsive, it also wastes a lot of CPU time to poll for new	768	program responsive, it also wastes a lot of CPU time to poll for new
697	events, especially with backends like C<select ()> which have a high	769	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	770	overhead for the actual polling but can deliver many events at once.
699		771
700	By setting a higher I<io collect interval> you allow libev to spend more	772	By setting a higher I<io collect interval> you allow libev to spend more
701	time collecting I/O events, so you can handle more events per iteration,	773	time collecting I/O events, so you can handle more events per iteration,
…		…
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	775	C<ev_timer>) will be not affected. Setting this to a non-null value will
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	776	introduce an additional C<ev_sleep ()> call into most loop iterations.
705		777
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	778	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	779	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	780	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	781	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	782	value will not introduce any overhead in libev.
711		783
712	Many (busy) programs can usually benefit by setting the I/O collect	784	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	785	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	786	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	787	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
723	they fire on, say, one-second boundaries only.	795	they fire on, say, one-second boundaries only.
724		796
725	=item ev_loop_verify (loop)	797	=item ev_loop_verify (loop)
726		798
727	This function only does something when C<EV_VERIFY> support has been	799	This function only does something when C<EV_VERIFY> support has been
728	compiled in. It tries to go through all internal structures and checks	800	compiled in, which is the default for non-minimal builds. It tries to go
729	them for validity. If anything is found to be inconsistent, it will print	801	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	802	is found to be inconsistent, it will print an error message to standard
		803	error and call C<abort ()>.
731		804
732	This can be used to catch bugs inside libev itself: under normal	805	This can be used to catch bugs inside libev itself: under normal
733	circumstances, this function will never abort as of course libev keeps its	806	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	807	data structures consistent.
735		808
736	=back	809	=back
737		810
738		811
739	=head1 ANATOMY OF A WATCHER	812	=head1 ANATOMY OF A WATCHER
740		813
		814	In the following description, uppercase C<TYPE> in names stands for the
		815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		816	watchers and C<ev_io_start> for I/O watchers.
		817
741	A watcher is a structure that you create and register to record your	818	A watcher is a structure that you create and register to record your
742	interest in some event. For instance, if you want to wait for STDIN to	819	interest in some event. For instance, if you want to wait for STDIN to
743	become readable, you would create an C<ev_io> watcher for that:	820	become readable, you would create an C<ev_io> watcher for that:
744		821
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	823	{
747	ev_io_stop (w);	824	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	825	ev_unloop (loop, EVUNLOOP_ALL);
749	}	826	}
750		827
751	struct ev_loop *loop = ev_default_loop (0);	828	struct ev_loop *loop = ev_default_loop (0);
		829
752	struct ev_io stdin_watcher;	830	ev_io stdin_watcher;
		831
753	ev_init (&stdin_watcher, my_cb);	832	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	834	ev_io_start (loop, &stdin_watcher);
		835
756	ev_loop (loop, 0);	836	ev_loop (loop, 0);
757		837
758	As you can see, you are responsible for allocating the memory for your	838	As you can see, you are responsible for allocating the memory for your
759	watcher structures (and it is usually a bad idea to do this on the stack,	839	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	840	stack).
		841
		842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
761		844
762	Each watcher structure must be initialised by a call to C<ev_init	845	Each watcher structure must be initialised by a call to C<ev_init
763	(watcher *, callback)>, which expects a callback to be provided. This	846	(watcher *, callback)>, which expects a callback to be provided. This
764	callback gets invoked each time the event occurs (or, in the case of I/O	847	callback gets invoked each time the event occurs (or, in the case of I/O
765	watchers, each time the event loop detects that the file descriptor given	848	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	849	is readable and/or writable).
767		850
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
769	with arguments specific to this watcher type. There is also a macro	852	macro to configure it, with arguments specific to the watcher type. There
770	to combine initialisation and setting in one call: C<< ev_<type>_init	853	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	854	ev_TYPE_init (watcher *, callback, ...) >>.
772		855
773	To make the watcher actually watch out for events, you have to start it	856	To make the watcher actually watch out for events, you have to start it
774	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	857	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
775	*) >>), and you can stop watching for events at any time by calling the	858	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		860
778	As long as your watcher is active (has been started but not stopped) you	861	As long as your watcher is active (has been started but not stopped) you
779	must not touch the values stored in it. Most specifically you must never	862	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	863	reinitialise it or call its C<ev_TYPE_set> macro.
781		864
782	Each and every callback receives the event loop pointer as first, the	865	Each and every callback receives the event loop pointer as first, the
783	registered watcher structure as second, and a bitset of received events as	866	registered watcher structure as second, and a bitset of received events as
784	third argument.	867	third argument.
785		868
…		…
848	=item C<EV_ERROR>	931	=item C<EV_ERROR>
849		932
850	An unspecified error has occurred, the watcher has been stopped. This might	933	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	934	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	935	ran out of memory, a file descriptor was found to be closed or any other
		936	problem. Libev considers these application bugs.
		937
853	problem. You best act on it by reporting the problem and somehow coping	938	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	939	watcher being stopped. Note that well-written programs should not receive
		940	an error ever, so when your watcher receives it, this usually indicates a
		941	bug in your program.
855		942
856	Libev will usually signal a few "dummy" events together with an error,	943	Libev will usually signal a few "dummy" events together with an error, for
857	for example it might indicate that a fd is readable or writable, and if	944	example it might indicate that a fd is readable or writable, and if your
858	your callbacks is well-written it can just attempt the operation and cope	945	callbacks is well-written it can just attempt the operation and cope with
859	with the error from read() or write(). This will not work in multi-threaded	946	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	947	programs, though, as the fd could already be closed and reused for another
		948	thing, so beware.
861		949
862	=back	950	=back
863		951
864	=head2 GENERIC WATCHER FUNCTIONS	952	=head2 GENERIC WATCHER FUNCTIONS
865
866	In the following description, C<TYPE> stands for the watcher type,
867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
868		953
869	=over 4	954	=over 4
870		955
871	=item C<ev_init> (ev_TYPE *watcher, callback)	956	=item C<ev_init> (ev_TYPE *watcher, callback)
872		957
…		…
878	which rolls both calls into one.	963	which rolls both calls into one.
879		964
880	You can reinitialise a watcher at any time as long as it has been stopped	965	You can reinitialise a watcher at any time as long as it has been stopped
881	(or never started) and there are no pending events outstanding.	966	(or never started) and there are no pending events outstanding.
882		967
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	968	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	969	int revents)>.
		970
		971	Example: Initialise an C<ev_io> watcher in two steps.
		972
		973	ev_io w;
		974	ev_init (&w, my_cb);
		975	ev_io_set (&w, STDIN_FILENO, EV_READ);
885		976
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	977	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		978
888	This macro initialises the type-specific parts of a watcher. You need to	979	This macro initialises the type-specific parts of a watcher. You need to
889	call C<ev_init> at least once before you call this macro, but you can	980	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	983	difference to the C<ev_init> macro).
893		984
894	Although some watcher types do not have type-specific arguments	985	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	986	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		987
		988	See C<ev_init>, above, for an example.
		989
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	990	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		991
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	992	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
900	calls into a single call. This is the most convenient method to initialise	993	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	994	a watcher. The same limitations apply, of course.
902		995
		996	Example: Initialise and set an C<ev_io> watcher in one step.
		997
		998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		999
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1001
905	Starts (activates) the given watcher. Only active watchers will receive	1002	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1003	events. If the watcher is already active nothing will happen.
907		1004
		1005	Example: Start the C<ev_io> watcher that is being abused as example in this
		1006	whole section.
		1007
		1008	ev_io_start (EV_DEFAULT_UC, &w);
		1009
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1011
910	Stops the given watcher again (if active) and clears the pending	1012	Stops the given watcher if active, and clears the pending status (whether
		1013	the watcher was active or not).
		1014
911	status. It is possible that stopped watchers are pending (for example,	1015	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1016	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1017	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	1018	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	1019	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1020
917	=item bool ev_is_active (ev_TYPE *watcher)	1021	=item bool ev_is_active (ev_TYPE *watcher)
918		1022
919	Returns a true value iff the watcher is active (i.e. it has been started	1023	Returns a true value iff the watcher is active (i.e. it has been started
920	and not yet been stopped). As long as a watcher is active you must not modify	1024	and not yet been stopped). As long as a watcher is active you must not modify
…		…
962	The default priority used by watchers when no priority has been set is	1066	The default priority used by watchers when no priority has been set is
963	always C<0>, which is supposed to not be too high and not be too low :).	1067	always C<0>, which is supposed to not be too high and not be too low :).
964		1068
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
966	fine, as long as you do not mind that the priority value you query might	1070	fine, as long as you do not mind that the priority value you query might
967	or might not have been adjusted to be within valid range.	1071	or might not have been clamped to the valid range.
968		1072
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1074
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1076	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1077	can deal with that fact, as both are simply passed through to the
		1078	callback.
974		1079
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1080	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1081
977	If the watcher is pending, this function returns clears its pending status	1082	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1083	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1084	watcher isn't pending it does nothing and returns C<0>.
980		1085
		1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1087	callback to be invoked, which can be accomplished with this function.
		1088
981	=back	1089	=back
982		1090
983		1091
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1093
986	Each watcher has, by default, a member C<void *data> that you can change	1094	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1095	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1096	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1097	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1098	member, you can also "subclass" the watcher type and provide your own
991	data:	1099	data:
992		1100
993	struct my_io	1101	struct my_io
994	{	1102	{
995	struct ev_io io;	1103	ev_io io;
996	int otherfd;	1104	int otherfd;
997	void *somedata;	1105	void *somedata;
998	struct whatever *mostinteresting;	1106	struct whatever *mostinteresting;
999	}	1107	};
		1108
		1109	...
		1110	struct my_io w;
		1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1112
1001	And since your callback will be called with a pointer to the watcher, you	1113	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1114	can cast it back to your own type:
1003		1115
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1117	{
1006	struct my_io *w = (struct my_io *)w_;	1118	struct my_io *w = (struct my_io *)w_;
1007	...	1119	...
1008	}	1120	}
1009		1121
1010	More interesting and less C-conformant ways of casting your callback type	1122	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1123	instead have been omitted.
1012		1124
1013	Another common scenario is having some data structure with multiple	1125	Another common scenario is to use some data structure with multiple
1014	watchers:	1126	embedded watchers:
1015		1127
1016	struct my_biggy	1128	struct my_biggy
1017	{	1129	{
1018	int some_data;	1130	int some_data;
1019	ev_timer t1;	1131	ev_timer t1;
1020	ev_timer t2;	1132	ev_timer t2;
1021	}	1133	}
1022		1134
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1135	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1136	complicated: Either you store the address of your C<my_biggy> struct
		1137	in the C<data> member of the watcher (for woozies), or you need to use
		1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1139	programmers):
1025		1140
1026	#include <stddef.h>	1141	#include <stddef.h>
1027		1142
1028	static void	1143	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1144	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1145	{
1031	struct my_biggy big = (struct my_biggy *	1146	struct my_biggy big = (struct my_biggy *
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1147	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1148	}
1034		1149
1035	static void	1150	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1151	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1152	{
1038	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1154	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1155	}
1041		1156
…		…
1069	In general you can register as many read and/or write event watchers per	1184	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1185	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1186	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1187	required if you know what you are doing).
1073		1188
1074	If you must do this, then force the use of a known-to-be-good backend	1189	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1190	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1077		1192
1078	Another thing you have to watch out for is that it is quite easy to	1193	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1194	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1196	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1197	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1198	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1201
1087	If you cannot run the fd in non-blocking mode (for example you should not	1202	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1203	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1204	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1205	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1206	does this on its own, so its quite safe to use). Some people additionally
		1207	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1208	indefinitely.
		1209
		1210	But really, best use non-blocking mode.
1092		1211
1093	=head3 The special problem of disappearing file descriptors	1212	=head3 The special problem of disappearing file descriptors
1094		1213
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1214	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1215	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1216	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1217	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1218	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1219	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1220	fact, a different file descriptor.
1102		1221
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1253	C<EVBACKEND_POLL>.
1135		1254
1136	=head3 The special problem of SIGPIPE	1255	=head3 The special problem of SIGPIPE
1137		1256
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when reading from a pipe whose other end has been closed, your program	1258	when writing to a pipe whose other end has been closed, your program gets
1140	gets send a SIGPIPE, which, by default, aborts your program. For most	1259	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	programs this is sensible behaviour, for daemons, this is usually	1260	this is sensible behaviour, for daemons, this is usually undesirable.
1142	undesirable.
1143		1261
1144	So when you encounter spurious, unexplained daemon exits, make sure you	1262	So when you encounter spurious, unexplained daemon exits, make sure you
1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1146	somewhere, as that would have given you a big clue).	1264	somewhere, as that would have given you a big clue).
1147		1265
…		…
1153	=item ev_io_init (ev_io *, callback, int fd, int events)	1271	=item ev_io_init (ev_io *, callback, int fd, int events)
1154		1272
1155	=item ev_io_set (ev_io *, int fd, int events)	1273	=item ev_io_set (ev_io *, int fd, int events)
1156		1274
1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1275	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1276	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1159	C<EV_READ | EV_WRITE> to receive the given events.	1277	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1160		1278
1161	=item int fd [read-only]	1279	=item int fd [read-only]
1162		1280
1163	The file descriptor being watched.	1281	The file descriptor being watched.
1164		1282
…		…
1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1291	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1174	readable, but only once. Since it is likely line-buffered, you could	1292	readable, but only once. Since it is likely line-buffered, you could
1175	attempt to read a whole line in the callback.	1293	attempt to read a whole line in the callback.
1176		1294
1177	static void	1295	static void
1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1296	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1179	{	1297	{
1180	ev_io_stop (loop, w);	1298	ev_io_stop (loop, w);
1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1299	.. read from stdin here (or from w->fd) and handle any I/O errors
1182	}	1300	}
1183		1301
1184	...	1302	...
1185	struct ev_loop *loop = ev_default_init (0);	1303	struct ev_loop *loop = ev_default_init (0);
1186	struct ev_io stdin_readable;	1304	ev_io stdin_readable;
1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1188	ev_io_start (loop, &stdin_readable);	1306	ev_io_start (loop, &stdin_readable);
1189	ev_loop (loop, 0);	1307	ev_loop (loop, 0);
1190		1308
1191		1309
…		…
1194	Timer watchers are simple relative timers that generate an event after a	1312	Timer watchers are simple relative timers that generate an event after a
1195	given time, and optionally repeating in regular intervals after that.	1313	given time, and optionally repeating in regular intervals after that.
1196		1314
1197	The timers are based on real time, that is, if you register an event that	1315	The timers are based on real time, that is, if you register an event that
1198	times out after an hour and you reset your system clock to January last	1316	times out after an hour and you reset your system clock to January last
1199	year, it will still time out after (roughly) and hour. "Roughly" because	1317	year, it will still time out after (roughly) one hour. "Roughly" because
1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1201	monotonic clock option helps a lot here).	1319	monotonic clock option helps a lot here).
		1320
		1321	The callback is guaranteed to be invoked only I<after> its timeout has
		1322	passed, but if multiple timers become ready during the same loop iteration
		1323	then order of execution is undefined.
		1324
		1325	=head3 Be smart about timeouts
		1326
		1327	Many real-world problems involve some kind of timeout, usually for error
		1328	recovery. A typical example is an HTTP request - if the other side hangs,
		1329	you want to raise some error after a while.
		1330
		1331	What follows are some ways to handle this problem, from obvious and
		1332	inefficient to smart and efficient.
		1333
		1334	In the following, a 60 second activity timeout is assumed - a timeout that
		1335	gets reset to 60 seconds each time there is activity (e.g. each time some
		1336	data or other life sign was received).
		1337
		1338	=over 4
		1339
		1340	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1341
		1342	This is the most obvious, but not the most simple way: In the beginning,
		1343	start the watcher:
		1344
		1345	ev_timer_init (timer, callback, 60., 0.);
		1346	ev_timer_start (loop, timer);
		1347
		1348	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1349	and start it again:
		1350
		1351	ev_timer_stop (loop, timer);
		1352	ev_timer_set (timer, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	This is relatively simple to implement, but means that each time there is
		1356	some activity, libev will first have to remove the timer from its internal
		1357	data structure and then add it again. Libev tries to be fast, but it's
		1358	still not a constant-time operation.
		1359
		1360	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1361
		1362	This is the easiest way, and involves using C<ev_timer_again> instead of
		1363	C<ev_timer_start>.
		1364
		1365	To implement this, configure an C<ev_timer> with a C<repeat> value
		1366	of C<60> and then call C<ev_timer_again> at start and each time you
		1367	successfully read or write some data. If you go into an idle state where
		1368	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1369	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1370
		1371	That means you can ignore both the C<ev_timer_start> function and the
		1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1373	member and C<ev_timer_again>.
		1374
		1375	At start:
		1376
		1377	ev_timer_init (timer, callback);
		1378	timer->repeat = 60.;
		1379	ev_timer_again (loop, timer);
		1380
		1381	Each time there is some activity:
		1382
		1383	ev_timer_again (loop, timer);
		1384
		1385	It is even possible to change the time-out on the fly, regardless of
		1386	whether the watcher is active or not:
		1387
		1388	timer->repeat = 30.;
		1389	ev_timer_again (loop, timer);
		1390
		1391	This is slightly more efficient then stopping/starting the timer each time
		1392	you want to modify its timeout value, as libev does not have to completely
		1393	remove and re-insert the timer from/into its internal data structure.
		1394
		1395	It is, however, even simpler than the "obvious" way to do it.
		1396
		1397	=item 3. Let the timer time out, but then re-arm it as required.
		1398
		1399	This method is more tricky, but usually most efficient: Most timeouts are
		1400	relatively long compared to the intervals between other activity - in
		1401	our example, within 60 seconds, there are usually many I/O events with
		1402	associated activity resets.
		1403
		1404	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1405	but remember the time of last activity, and check for a real timeout only
		1406	within the callback:
		1407
		1408	ev_tstamp last_activity; // time of last activity
		1409
		1410	static void
		1411	callback (EV_P_ ev_timer *w, int revents)
		1412	{
		1413	ev_tstamp now = ev_now (EV_A);
		1414	ev_tstamp timeout = last_activity + 60.;
		1415
		1416	// if last_activity + 60. is older than now, we did time out
		1417	if (timeout < now)
		1418	{
		1419	// timeout occured, take action
		1420	}
		1421	else
		1422	{
		1423	// callback was invoked, but there was some activity, re-arm
		1424	// the watcher to fire in last_activity + 60, which is
		1425	// guaranteed to be in the future, so "again" is positive:
		1426	w->repeat = timeout - now;
		1427	ev_timer_again (EV_A_ w);
		1428	}
		1429	}
		1430
		1431	To summarise the callback: first calculate the real timeout (defined
		1432	as "60 seconds after the last activity"), then check if that time has
		1433	been reached, which means something I<did>, in fact, time out. Otherwise
		1434	the callback was invoked too early (C<timeout> is in the future), so
		1435	re-schedule the timer to fire at that future time, to see if maybe we have
		1436	a timeout then.
		1437
		1438	Note how C<ev_timer_again> is used, taking advantage of the
		1439	C<ev_timer_again> optimisation when the timer is already running.
		1440
		1441	This scheme causes more callback invocations (about one every 60 seconds
		1442	minus half the average time between activity), but virtually no calls to
		1443	libev to change the timeout.
		1444
		1445	To start the timer, simply initialise the watcher and set C<last_activity>
		1446	to the current time (meaning we just have some activity :), then call the
		1447	callback, which will "do the right thing" and start the timer:
		1448
		1449	ev_timer_init (timer, callback);
		1450	last_activity = ev_now (loop);
		1451	callback (loop, timer, EV_TIMEOUT);
		1452
		1453	And when there is some activity, simply store the current time in
		1454	C<last_activity>, no libev calls at all:
		1455
		1456	last_actiivty = ev_now (loop);
		1457
		1458	This technique is slightly more complex, but in most cases where the
		1459	time-out is unlikely to be triggered, much more efficient.
		1460
		1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1462	callback :) - just change the timeout and invoke the callback, which will
		1463	fix things for you.
		1464
		1465	=item 4. Wee, just use a double-linked list for your timeouts.
		1466
		1467	If there is not one request, but many thousands (millions...), all
		1468	employing some kind of timeout with the same timeout value, then one can
		1469	do even better:
		1470
		1471	When starting the timeout, calculate the timeout value and put the timeout
		1472	at the I<end> of the list.
		1473
		1474	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1475	the list is expected to fire (for example, using the technique #3).
		1476
		1477	When there is some activity, remove the timer from the list, recalculate
		1478	the timeout, append it to the end of the list again, and make sure to
		1479	update the C<ev_timer> if it was taken from the beginning of the list.
		1480
		1481	This way, one can manage an unlimited number of timeouts in O(1) time for
		1482	starting, stopping and updating the timers, at the expense of a major
		1483	complication, and having to use a constant timeout. The constant timeout
		1484	ensures that the list stays sorted.
		1485
		1486	=back
		1487
		1488	So which method the best?
		1489
		1490	Method #2 is a simple no-brain-required solution that is adequate in most
		1491	situations. Method #3 requires a bit more thinking, but handles many cases
		1492	better, and isn't very complicated either. In most case, choosing either
		1493	one is fine, with #3 being better in typical situations.
		1494
		1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1496	rather complicated, but extremely efficient, something that really pays
		1497	off after the first million or so of active timers, i.e. it's usually
		1498	overkill :)
		1499
		1500	=head3 The special problem of time updates
		1501
		1502	Establishing the current time is a costly operation (it usually takes at
		1503	least two system calls): EV therefore updates its idea of the current
		1504	time only before and after C<ev_loop> collects new events, which causes a
		1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1506	lots of events in one iteration.
1202		1507
1203	The relative timeouts are calculated relative to the C<ev_now ()>	1508	The relative timeouts are calculated relative to the C<ev_now ()>
1204	time. This is usually the right thing as this timestamp refers to the time	1509	time. This is usually the right thing as this timestamp refers to the time
1205	of the event triggering whatever timeout you are modifying/starting. If	1510	of the event triggering whatever timeout you are modifying/starting. If
1206	you suspect event processing to be delayed and you I<need> to base the timeout	1511	you suspect event processing to be delayed and you I<need> to base the
1207	on the current time, use something like this to adjust for this:	1512	timeout on the current time, use something like this to adjust for this:
1208		1513
1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1210		1515
1211	The callback is guaranteed to be invoked only after its timeout has passed,	1516	If the event loop is suspended for a long time, you can also force an
1212	but if multiple timers become ready during the same loop iteration then	1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1213	order of execution is undefined.	1518	()>.
1214		1519
1215	=head3 Watcher-Specific Functions and Data Members	1520	=head3 Watcher-Specific Functions and Data Members
1216		1521
1217	=over 4	1522	=over 4
1218		1523
…		…
1242	If the timer is started but non-repeating, stop it (as if it timed out).	1547	If the timer is started but non-repeating, stop it (as if it timed out).
1243		1548
1244	If the timer is repeating, either start it if necessary (with the	1549	If the timer is repeating, either start it if necessary (with the
1245	C<repeat> value), or reset the running timer to the C<repeat> value.	1550	C<repeat> value), or reset the running timer to the C<repeat> value.
1246		1551
1247	This sounds a bit complicated, but here is a useful and typical	1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1248	example: Imagine you have a TCP connection and you want a so-called idle	1553	usage example.
1249	timeout, that is, you want to be called when there have been, say, 60
1250	seconds of inactivity on the socket. The easiest way to do this is to
1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1252	C<ev_timer_again> each time you successfully read or write some data. If
1253	you go into an idle state where you do not expect data to travel on the
1254	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1255	automatically restart it if need be.
1256
1257	That means you can ignore the C<after> value and C<ev_timer_start>
1258	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1259
1260	ev_timer_init (timer, callback, 0., 5.);
1261	ev_timer_again (loop, timer);
1262	...
1263	timer->again = 17.;
1264	ev_timer_again (loop, timer);
1265	...
1266	timer->again = 10.;
1267	ev_timer_again (loop, timer);
1268
1269	This is more slightly efficient then stopping/starting the timer each time
1270	you want to modify its timeout value.
1271		1554
1272	=item ev_tstamp repeat [read-write]	1555	=item ev_tstamp repeat [read-write]
1273		1556
1274	The current C<repeat> value. Will be used each time the watcher times out	1557	The current C<repeat> value. Will be used each time the watcher times out
1275	or C<ev_timer_again> is called and determines the next timeout (if any),	1558	or C<ev_timer_again> is called, and determines the next timeout (if any),
1276	which is also when any modifications are taken into account.	1559	which is also when any modifications are taken into account.
1277		1560
1278	=back	1561	=back
1279		1562
1280	=head3 Examples	1563	=head3 Examples
1281		1564
1282	Example: Create a timer that fires after 60 seconds.	1565	Example: Create a timer that fires after 60 seconds.
1283		1566
1284	static void	1567	static void
1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1568	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1286	{	1569	{
1287	.. one minute over, w is actually stopped right here	1570	.. one minute over, w is actually stopped right here
1288	}	1571	}
1289		1572
1290	struct ev_timer mytimer;	1573	ev_timer mytimer;
1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1574	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1292	ev_timer_start (loop, &mytimer);	1575	ev_timer_start (loop, &mytimer);
1293		1576
1294	Example: Create a timeout timer that times out after 10 seconds of	1577	Example: Create a timeout timer that times out after 10 seconds of
1295	inactivity.	1578	inactivity.
1296		1579
1297	static void	1580	static void
1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1581	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1299	{	1582	{
1300	.. ten seconds without any activity	1583	.. ten seconds without any activity
1301	}	1584	}
1302		1585
1303	struct ev_timer mytimer;	1586	ev_timer mytimer;
1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1305	ev_timer_again (&mytimer); /* start timer */	1588	ev_timer_again (&mytimer); /* start timer */
1306	ev_loop (loop, 0);	1589	ev_loop (loop, 0);
1307		1590
1308	// and in some piece of code that gets executed on any "activity":	1591	// and in some piece of code that gets executed on any "activity":
…		…
1324	to trigger the event (unlike an C<ev_timer>, which would still trigger	1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1325	roughly 10 seconds later as it uses a relative timeout).	1608	roughly 10 seconds later as it uses a relative timeout).
1326		1609
1327	C<ev_periodic>s can also be used to implement vastly more complex timers,	1610	C<ev_periodic>s can also be used to implement vastly more complex timers,
1328	such as triggering an event on each "midnight, local time", or other	1611	such as triggering an event on each "midnight, local time", or other
1329	complicated, rules.	1612	complicated rules.
1330		1613
1331	As with timers, the callback is guaranteed to be invoked only when the	1614	As with timers, the callback is guaranteed to be invoked only when the
1332	time (C<at>) has passed, but if multiple periodic timers become ready	1615	time (C<at>) has passed, but if multiple periodic timers become ready
1333	during the same loop iteration then order of execution is undefined.	1616	during the same loop iteration, then order of execution is undefined.
1334		1617
1335	=head3 Watcher-Specific Functions and Data Members	1618	=head3 Watcher-Specific Functions and Data Members
1336		1619
1337	=over 4	1620	=over 4
1338		1621
1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1340		1623
1341	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1342		1625
1343	Lots of arguments, lets sort it out... There are basically three modes of	1626	Lots of arguments, lets sort it out... There are basically three modes of
1344	operation, and we will explain them from simplest to complex:	1627	operation, and we will explain them from simplest to most complex:
1345		1628
1346	=over 4	1629	=over 4
1347		1630
1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1349		1632
1350	In this configuration the watcher triggers an event after the wall clock	1633	In this configuration the watcher triggers an event after the wall clock
1351	time C<at> has passed and doesn't repeat. It will not adjust when a time	1634	time C<at> has passed. It will not repeat and will not adjust when a time
1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1353	run when the system time reaches or surpasses this time.	1636	only run when the system clock reaches or surpasses this time.
1354		1637
1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1356		1639
1357	In this mode the watcher will always be scheduled to time out at the next	1640	In this mode the watcher will always be scheduled to time out at the next
1358	C<at + N * interval> time (for some integer N, which can also be negative)	1641	C<at + N * interval> time (for some integer N, which can also be negative)
1359	and then repeat, regardless of any time jumps.	1642	and then repeat, regardless of any time jumps.
1360		1643
1361	This can be used to create timers that do not drift with respect to system	1644	This can be used to create timers that do not drift with respect to the
1362	time, for example, here is a C<ev_periodic> that triggers each hour, on	1645	system clock, for example, here is a C<ev_periodic> that triggers each
1363	the hour:	1646	hour, on the hour:
1364		1647
1365	ev_periodic_set (&periodic, 0., 3600., 0);	1648	ev_periodic_set (&periodic, 0., 3600., 0);
1366		1649
1367	This doesn't mean there will always be 3600 seconds in between triggers,	1650	This doesn't mean there will always be 3600 seconds in between triggers,
1368	but only that the callback will be called when the system time shows a	1651	but only that the callback will be called when the system time shows a
…		…
1394		1677
1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1397	only event loop modification you are allowed to do).	1680	only event loop modification you are allowed to do).
1398		1681
1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1682	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1400	*w, ev_tstamp now)>, e.g.:	1683	*w, ev_tstamp now)>, e.g.:
1401		1684
		1685	static ev_tstamp
1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1686	my_rescheduler (ev_periodic *w, ev_tstamp now)
1403	{	1687	{
1404	return now + 60.;	1688	return now + 60.;
1405	}	1689	}
1406		1690
1407	It must return the next time to trigger, based on the passed time value	1691	It must return the next time to trigger, based on the passed time value
…		…
1444		1728
1445	The current interval value. Can be modified any time, but changes only	1729	The current interval value. Can be modified any time, but changes only
1446	take effect when the periodic timer fires or C<ev_periodic_again> is being	1730	take effect when the periodic timer fires or C<ev_periodic_again> is being
1447	called.	1731	called.
1448		1732
1449	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1733	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1450		1734
1451	The current reschedule callback, or C<0>, if this functionality is	1735	The current reschedule callback, or C<0>, if this functionality is
1452	switched off. Can be changed any time, but changes only take effect when	1736	switched off. Can be changed any time, but changes only take effect when
1453	the periodic timer fires or C<ev_periodic_again> is being called.	1737	the periodic timer fires or C<ev_periodic_again> is being called.
1454		1738
1455	=back	1739	=back
1456		1740
1457	=head3 Examples	1741	=head3 Examples
1458		1742
1459	Example: Call a callback every hour, or, more precisely, whenever the	1743	Example: Call a callback every hour, or, more precisely, whenever the
1460	system clock is divisible by 3600. The callback invocation times have	1744	system time is divisible by 3600. The callback invocation times have
1461	potentially a lot of jitter, but good long-term stability.	1745	potentially a lot of jitter, but good long-term stability.
1462		1746
1463	static void	1747	static void
1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1465	{	1749	{
1466	... its now a full hour (UTC, or TAI or whatever your clock follows)	1750	... its now a full hour (UTC, or TAI or whatever your clock follows)
1467	}	1751	}
1468		1752
1469	struct ev_periodic hourly_tick;	1753	ev_periodic hourly_tick;
1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1754	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1471	ev_periodic_start (loop, &hourly_tick);	1755	ev_periodic_start (loop, &hourly_tick);
1472		1756
1473	Example: The same as above, but use a reschedule callback to do it:	1757	Example: The same as above, but use a reschedule callback to do it:
1474		1758
1475	#include <math.h>	1759	#include <math.h>
1476		1760
1477	static ev_tstamp	1761	static ev_tstamp
1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1762	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1479	{	1763	{
1480	return fmod (now, 3600.) + 3600.;	1764	return now + (3600. - fmod (now, 3600.));
1481	}	1765	}
1482		1766
1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1767	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1484		1768
1485	Example: Call a callback every hour, starting now:	1769	Example: Call a callback every hour, starting now:
1486		1770
1487	struct ev_periodic hourly_tick;	1771	ev_periodic hourly_tick;
1488	ev_periodic_init (&hourly_tick, clock_cb,	1772	ev_periodic_init (&hourly_tick, clock_cb,
1489	fmod (ev_now (loop), 3600.), 3600., 0);	1773	fmod (ev_now (loop), 3600.), 3600., 0);
1490	ev_periodic_start (loop, &hourly_tick);	1774	ev_periodic_start (loop, &hourly_tick);
1491		1775
1492		1776
…		…
1495	Signal watchers will trigger an event when the process receives a specific	1779	Signal watchers will trigger an event when the process receives a specific
1496	signal one or more times. Even though signals are very asynchronous, libev	1780	signal one or more times. Even though signals are very asynchronous, libev
1497	will try it's best to deliver signals synchronously, i.e. as part of the	1781	will try it's best to deliver signals synchronously, i.e. as part of the
1498	normal event processing, like any other event.	1782	normal event processing, like any other event.
1499		1783
		1784	If you want signals asynchronously, just use C<sigaction> as you would
		1785	do without libev and forget about sharing the signal. You can even use
		1786	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1787
1500	You can configure as many watchers as you like per signal. Only when the	1788	You can configure as many watchers as you like per signal. Only when the
1501	first watcher gets started will libev actually register a signal watcher	1789	first watcher gets started will libev actually register a signal handler
1502	with the kernel (thus it coexists with your own signal handlers as long	1790	with the kernel (thus it coexists with your own signal handlers as long as
1503	as you don't register any with libev). Similarly, when the last signal	1791	you don't register any with libev for the same signal). Similarly, when
1504	watcher for a signal is stopped libev will reset the signal handler to	1792	the last signal watcher for a signal is stopped, libev will reset the
1505	SIG_DFL (regardless of what it was set to before).	1793	signal handler to SIG_DFL (regardless of what it was set to before).
1506		1794
1507	If possible and supported, libev will install its handlers with	1795	If possible and supported, libev will install its handlers with
1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1509	interrupted. If you have a problem with system calls getting interrupted by	1797	interrupted. If you have a problem with system calls getting interrupted by
1510	signals you can block all signals in an C<ev_check> watcher and unblock	1798	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1527		1815
1528	=back	1816	=back
1529		1817
1530	=head3 Examples	1818	=head3 Examples
1531		1819
1532	Example: Try to exit cleanly on SIGINT and SIGTERM.	1820	Example: Try to exit cleanly on SIGINT.
1533		1821
1534	static void	1822	static void
1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1536	{	1824	{
1537	ev_unloop (loop, EVUNLOOP_ALL);	1825	ev_unloop (loop, EVUNLOOP_ALL);
1538	}	1826	}
1539		1827
1540	struct ev_signal signal_watcher;	1828	ev_signal signal_watcher;
1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1542	ev_signal_start (loop, &sigint_cb);	1830	ev_signal_start (loop, &signal_watcher);
1543		1831
1544		1832
1545	=head2 C<ev_child> - watch out for process status changes	1833	=head2 C<ev_child> - watch out for process status changes
1546		1834
1547	Child watchers trigger when your process receives a SIGCHLD in response to	1835	Child watchers trigger when your process receives a SIGCHLD in response to
1548	some child status changes (most typically when a child of yours dies). It	1836	some child status changes (most typically when a child of yours dies or
1549	is permissible to install a child watcher I<after> the child has been	1837	exits). It is permissible to install a child watcher I<after> the child
1550	forked (which implies it might have already exited), as long as the event	1838	has been forked (which implies it might have already exited), as long
1551	loop isn't entered (or is continued from a watcher).	1839	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1840	forking and then immediately registering a watcher for the child is fine,
		1841	but forking and registering a watcher a few event loop iterations later is
		1842	not.
1552		1843
1553	Only the default event loop is capable of handling signals, and therefore	1844	Only the default event loop is capable of handling signals, and therefore
1554	you can only register child watchers in the default event loop.	1845	you can only register child watchers in the default event loop.
1555		1846
1556	=head3 Process Interaction	1847	=head3 Process Interaction
…		…
1569	handler, you can override it easily by installing your own handler for	1860	handler, you can override it easily by installing your own handler for
1570	C<SIGCHLD> after initialising the default loop, and making sure the	1861	C<SIGCHLD> after initialising the default loop, and making sure the
1571	default loop never gets destroyed. You are encouraged, however, to use an	1862	default loop never gets destroyed. You are encouraged, however, to use an
1572	event-based approach to child reaping and thus use libev's support for	1863	event-based approach to child reaping and thus use libev's support for
1573	that, so other libev users can use C<ev_child> watchers freely.	1864	that, so other libev users can use C<ev_child> watchers freely.
		1865
		1866	=head3 Stopping the Child Watcher
		1867
		1868	Currently, the child watcher never gets stopped, even when the
		1869	child terminates, so normally one needs to stop the watcher in the
		1870	callback. Future versions of libev might stop the watcher automatically
		1871	when a child exit is detected.
1574		1872
1575	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1576		1874
1577	=over 4	1875	=over 4
1578		1876
…		…
1610	its completion.	1908	its completion.
1611		1909
1612	ev_child cw;	1910	ev_child cw;
1613		1911
1614	static void	1912	static void
1615	child_cb (EV_P_ struct ev_child *w, int revents)	1913	child_cb (EV_P_ ev_child *w, int revents)
1616	{	1914	{
1617	ev_child_stop (EV_A_ w);	1915	ev_child_stop (EV_A_ w);
1618	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1916	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1619	}	1917	}
1620		1918
…		…
1635		1933
1636		1934
1637	=head2 C<ev_stat> - did the file attributes just change?	1935	=head2 C<ev_stat> - did the file attributes just change?
1638		1936
1639	This watches a file system path for attribute changes. That is, it calls	1937	This watches a file system path for attribute changes. That is, it calls
1640	C<stat> regularly (or when the OS says it changed) and sees if it changed	1938	C<stat> on that path in regular intervals (or when the OS says it changed)
1641	compared to the last time, invoking the callback if it did.	1939	and sees if it changed compared to the last time, invoking the callback if
		1940	it did.
1642		1941
1643	The path does not need to exist: changing from "path exists" to "path does	1942	The path does not need to exist: changing from "path exists" to "path does
1644	not exist" is a status change like any other. The condition "path does	1943	not exist" is a status change like any other. The condition "path does not
1645	not exist" is signified by the C<st_nlink> field being zero (which is	1944	exist" (or more correctly "path cannot be stat'ed") is signified by the
1646	otherwise always forced to be at least one) and all the other fields of	1945	C<st_nlink> field being zero (which is otherwise always forced to be at
1647	the stat buffer having unspecified contents.	1946	least one) and all the other fields of the stat buffer having unspecified
		1947	contents.
1648		1948
1649	The path I<should> be absolute and I<must not> end in a slash. If it is	1949	The path I<must not> end in a slash or contain special components such as
		1950	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1650	relative and your working directory changes, the behaviour is undefined.	1951	your working directory changes, then the behaviour is undefined.
1651		1952
1652	Since there is no standard to do this, the portable implementation simply	1953	Since there is no portable change notification interface available, the
1653	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1954	portable implementation simply calls C<stat(2)> regularly on the path
1654	can specify a recommended polling interval for this case. If you specify	1955	to see if it changed somehow. You can specify a recommended polling
1655	a polling interval of C<0> (highly recommended!) then a I<suitable,	1956	interval for this case. If you specify a polling interval of C<0> (highly
1656	unspecified default> value will be used (which you can expect to be around	1957	recommended!) then a I<suitable, unspecified default> value will be used
1657	five seconds, although this might change dynamically). Libev will also	1958	(which you can expect to be around five seconds, although this might
1658	impose a minimum interval which is currently around C<0.1>, but thats	1959	change dynamically). Libev will also impose a minimum interval which is
1659	usually overkill.	1960	currently around C<0.1>, but that's usually overkill.
1660		1961
1661	This watcher type is not meant for massive numbers of stat watchers,	1962	This watcher type is not meant for massive numbers of stat watchers,
1662	as even with OS-supported change notifications, this can be	1963	as even with OS-supported change notifications, this can be
1663	resource-intensive.	1964	resource-intensive.
1664		1965
1665	At the time of this writing, only the Linux inotify interface is	1966	At the time of this writing, the only OS-specific interface implemented
1666	implemented (implementing kqueue support is left as an exercise for the	1967	is the Linux inotify interface (implementing kqueue support is left as an
1667	reader, note, however, that the author sees no way of implementing ev_stat	1968	exercise for the reader. Note, however, that the author sees no way of
1668	semantics with kqueue). Inotify will be used to give hints only and should	1969	implementing C<ev_stat> semantics with kqueue, except as a hint).
1669	not change the semantics of C<ev_stat> watchers, which means that libev
1670	sometimes needs to fall back to regular polling again even with inotify,
1671	but changes are usually detected immediately, and if the file exists there
1672	will be no polling.
1673		1970
1674	=head3 ABI Issues (Largefile Support)	1971	=head3 ABI Issues (Largefile Support)
1675		1972
1676	Libev by default (unless the user overrides this) uses the default	1973	Libev by default (unless the user overrides this) uses the default
1677	compilation environment, which means that on systems with large file	1974	compilation environment, which means that on systems with large file
1678	support disabled by default, you get the 32 bit version of the stat	1975	support disabled by default, you get the 32 bit version of the stat
1679	structure. When using the library from programs that change the ABI to	1976	structure. When using the library from programs that change the ABI to
1680	use 64 bit file offsets the programs will fail. In that case you have to	1977	use 64 bit file offsets the programs will fail. In that case you have to
1681	compile libev with the same flags to get binary compatibility. This is	1978	compile libev with the same flags to get binary compatibility. This is
1682	obviously the case with any flags that change the ABI, but the problem is	1979	obviously the case with any flags that change the ABI, but the problem is
1683	most noticeably disabled with ev_stat and large file support.	1980	most noticeably displayed with ev_stat and large file support.
1684		1981
1685	The solution for this is to lobby your distribution maker to make large	1982	The solution for this is to lobby your distribution maker to make large
1686	file interfaces available by default (as e.g. FreeBSD does) and not	1983	file interfaces available by default (as e.g. FreeBSD does) and not
1687	optional. Libev cannot simply switch on large file support because it has	1984	optional. Libev cannot simply switch on large file support because it has
1688	to exchange stat structures with application programs compiled using the	1985	to exchange stat structures with application programs compiled using the
1689	default compilation environment.	1986	default compilation environment.
1690		1987
1691	=head3 Inotify	1988	=head3 Inotify and Kqueue
1692		1989
1693	When C<inotify (7)> support has been compiled into libev (generally only	1990	When C<inotify (7)> support has been compiled into libev and present at
1694	available on Linux) and present at runtime, it will be used to speed up	1991	runtime, it will be used to speed up change detection where possible. The
1695	change detection where possible. The inotify descriptor will be created lazily	1992	inotify descriptor will be created lazily when the first C<ev_stat>
1696	when the first C<ev_stat> watcher is being started.	1993	watcher is being started.
1697		1994
1698	Inotify presence does not change the semantics of C<ev_stat> watchers	1995	Inotify presence does not change the semantics of C<ev_stat> watchers
1699	except that changes might be detected earlier, and in some cases, to avoid	1996	except that changes might be detected earlier, and in some cases, to avoid
1700	making regular C<stat> calls. Even in the presence of inotify support	1997	making regular C<stat> calls. Even in the presence of inotify support
1701	there are many cases where libev has to resort to regular C<stat> polling.	1998	there are many cases where libev has to resort to regular C<stat> polling,
		1999	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2000	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2001	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2002	xfs are fully working) libev usually gets away without polling.
1702		2003
1703	(There is no support for kqueue, as apparently it cannot be used to	2004	There is no support for kqueue, as apparently it cannot be used to
1704	implement this functionality, due to the requirement of having a file	2005	implement this functionality, due to the requirement of having a file
1705	descriptor open on the object at all times).	2006	descriptor open on the object at all times, and detecting renames, unlinks
		2007	etc. is difficult.
		2008
		2009	=head3 C<stat ()> is a synchronous operation
		2010
		2011	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2012	the process. The exception are C<ev_stat> watchers - those call C<stat
		2013	()>, which is a synchronous operation.
		2014
		2015	For local paths, this usually doesn't matter: unless the system is very
		2016	busy or the intervals between stat's are large, a stat call will be fast,
		2017	as the path data is usually in memory already (except when starting the
		2018	watcher).
		2019
		2020	For networked file systems, calling C<stat ()> can block an indefinite
		2021	time due to network issues, and even under good conditions, a stat call
		2022	often takes multiple milliseconds.
		2023
		2024	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2025	paths, although this is fully supported by libev.
1706		2026
1707	=head3 The special problem of stat time resolution	2027	=head3 The special problem of stat time resolution
1708		2028
1709	The C<stat ()> system call only supports full-second resolution portably, and	2029	The C<stat ()> system call only supports full-second resolution portably,
1710	even on systems where the resolution is higher, many file systems still	2030	and even on systems where the resolution is higher, most file systems
1711	only support whole seconds.	2031	still only support whole seconds.
1712		2032
1713	That means that, if the time is the only thing that changes, you can	2033	That means that, if the time is the only thing that changes, you can
1714	easily miss updates: on the first update, C<ev_stat> detects a change and	2034	easily miss updates: on the first update, C<ev_stat> detects a change and
1715	calls your callback, which does something. When there is another update	2035	calls your callback, which does something. When there is another update
1716	within the same second, C<ev_stat> will be unable to detect it as the stat	2036	within the same second, C<ev_stat> will be unable to detect unless the
1717	data does not change.	2037	stat data does change in other ways (e.g. file size).
1718		2038
1719	The solution to this is to delay acting on a change for slightly more	2039	The solution to this is to delay acting on a change for slightly more
1720	than a second (or till slightly after the next full second boundary), using	2040	than a second (or till slightly after the next full second boundary), using
1721	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2041	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1722	ev_timer_again (loop, w)>).	2042	ev_timer_again (loop, w)>).
…		…
1742	C<path>. The C<interval> is a hint on how quickly a change is expected to	2062	C<path>. The C<interval> is a hint on how quickly a change is expected to
1743	be detected and should normally be specified as C<0> to let libev choose	2063	be detected and should normally be specified as C<0> to let libev choose
1744	a suitable value. The memory pointed to by C<path> must point to the same	2064	a suitable value. The memory pointed to by C<path> must point to the same
1745	path for as long as the watcher is active.	2065	path for as long as the watcher is active.
1746		2066
1747	The callback will receive C<EV_STAT> when a change was detected, relative	2067	The callback will receive an C<EV_STAT> event when a change was detected,
1748	to the attributes at the time the watcher was started (or the last change	2068	relative to the attributes at the time the watcher was started (or the
1749	was detected).	2069	last change was detected).
1750		2070
1751	=item ev_stat_stat (loop, ev_stat *)	2071	=item ev_stat_stat (loop, ev_stat *)
1752		2072
1753	Updates the stat buffer immediately with new values. If you change the	2073	Updates the stat buffer immediately with new values. If you change the
1754	watched path in your callback, you could call this function to avoid	2074	watched path in your callback, you could call this function to avoid
…		…
1837		2157
1838		2158
1839	=head2 C<ev_idle> - when you've got nothing better to do...	2159	=head2 C<ev_idle> - when you've got nothing better to do...
1840		2160
1841	Idle watchers trigger events when no other events of the same or higher	2161	Idle watchers trigger events when no other events of the same or higher
1842	priority are pending (prepare, check and other idle watchers do not	2162	priority are pending (prepare, check and other idle watchers do not count
1843	count).	2163	as receiving "events").
1844		2164
1845	That is, as long as your process is busy handling sockets or timeouts	2165	That is, as long as your process is busy handling sockets or timeouts
1846	(or even signals, imagine) of the same or higher priority it will not be	2166	(or even signals, imagine) of the same or higher priority it will not be
1847	triggered. But when your process is idle (or only lower-priority watchers	2167	triggered. But when your process is idle (or only lower-priority watchers
1848	are pending), the idle watchers are being called once per event loop	2168	are pending), the idle watchers are being called once per event loop
…		…
1873		2193
1874	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2194	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1875	callback, free it. Also, use no error checking, as usual.	2195	callback, free it. Also, use no error checking, as usual.
1876		2196
1877	static void	2197	static void
1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1879	{	2199	{
1880	free (w);	2200	free (w);
1881	// now do something you wanted to do when the program has	2201	// now do something you wanted to do when the program has
1882	// no longer anything immediate to do.	2202	// no longer anything immediate to do.
1883	}	2203	}
1884		2204
1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1886	ev_idle_init (idle_watcher, idle_cb);	2206	ev_idle_init (idle_watcher, idle_cb);
1887	ev_idle_start (loop, idle_cb);	2207	ev_idle_start (loop, idle_cb);
1888		2208
1889		2209
1890	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1891		2211
1892	Prepare and check watchers are usually (but not always) used in tandem:	2212	Prepare and check watchers are usually (but not always) used in pairs:
1893	prepare watchers get invoked before the process blocks and check watchers	2213	prepare watchers get invoked before the process blocks and check watchers
1894	afterwards.	2214	afterwards.
1895		2215
1896	You I<must not> call C<ev_loop> or similar functions that enter	2216	You I<must not> call C<ev_loop> or similar functions that enter
1897	the current event loop from either C<ev_prepare> or C<ev_check>	2217	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1900	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1901	C<ev_check> so if you have one watcher of each kind they will always be	2221	C<ev_check> so if you have one watcher of each kind they will always be
1902	called in pairs bracketing the blocking call.	2222	called in pairs bracketing the blocking call.
1903		2223
1904	Their main purpose is to integrate other event mechanisms into libev and	2224	Their main purpose is to integrate other event mechanisms into libev and
1905	their use is somewhat advanced. This could be used, for example, to track	2225	their use is somewhat advanced. They could be used, for example, to track
1906	variable changes, implement your own watchers, integrate net-snmp or a	2226	variable changes, implement your own watchers, integrate net-snmp or a
1907	coroutine library and lots more. They are also occasionally useful if	2227	coroutine library and lots more. They are also occasionally useful if
1908	you cache some data and want to flush it before blocking (for example,	2228	you cache some data and want to flush it before blocking (for example,
1909	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2229	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1910	watcher).	2230	watcher).
1911		2231
1912	This is done by examining in each prepare call which file descriptors need	2232	This is done by examining in each prepare call which file descriptors
1913	to be watched by the other library, registering C<ev_io> watchers for	2233	need to be watched by the other library, registering C<ev_io> watchers
1914	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2234	for them and starting an C<ev_timer> watcher for any timeouts (many
1915	provide just this functionality). Then, in the check watcher you check for	2235	libraries provide exactly this functionality). Then, in the check watcher,
1916	any events that occurred (by checking the pending status of all watchers	2236	you check for any events that occurred (by checking the pending status
1917	and stopping them) and call back into the library. The I/O and timer	2237	of all watchers and stopping them) and call back into the library. The
1918	callbacks will never actually be called (but must be valid nevertheless,	2238	I/O and timer callbacks will never actually be called (but must be valid
1919	because you never know, you know?).	2239	nevertheless, because you never know, you know?).
1920		2240
1921	As another example, the Perl Coro module uses these hooks to integrate	2241	As another example, the Perl Coro module uses these hooks to integrate
1922	coroutines into libev programs, by yielding to other active coroutines	2242	coroutines into libev programs, by yielding to other active coroutines
1923	during each prepare and only letting the process block if no coroutines	2243	during each prepare and only letting the process block if no coroutines
1924	are ready to run (it's actually more complicated: it only runs coroutines	2244	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1927	loop from blocking if lower-priority coroutines are active, thus mapping	2247	loop from blocking if lower-priority coroutines are active, thus mapping
1928	low-priority coroutines to idle/background tasks).	2248	low-priority coroutines to idle/background tasks).
1929		2249
1930	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1931	priority, to ensure that they are being run before any other watchers	2251	priority, to ensure that they are being run before any other watchers
		2252	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2253
1932	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1933	too) should not activate ("feed") events into libev. While libev fully	2255	activate ("feed") events into libev. While libev fully supports this, they
1934	supports this, they might get executed before other C<ev_check> watchers	2256	might get executed before other C<ev_check> watchers did their job. As
1935	did their job. As C<ev_check> watchers are often used to embed other	2257	C<ev_check> watchers are often used to embed other (non-libev) event
1936	(non-libev) event loops those other event loops might be in an unusable	2258	loops those other event loops might be in an unusable state until their
1937	state until their C<ev_check> watcher ran (always remind yourself to	2259	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1938	coexist peacefully with others).	2260	others).
1939		2261
1940	=head3 Watcher-Specific Functions and Data Members	2262	=head3 Watcher-Specific Functions and Data Members
1941		2263
1942	=over 4	2264	=over 4
1943		2265
…		…
1945		2267
1946	=item ev_check_init (ev_check *, callback)	2268	=item ev_check_init (ev_check *, callback)
1947		2269
1948	Initialises and configures the prepare or check watcher - they have no	2270	Initialises and configures the prepare or check watcher - they have no
1949	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2271	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1950	macros, but using them is utterly, utterly and completely pointless.	2272	macros, but using them is utterly, utterly, utterly and completely
		2273	pointless.
1951		2274
1952	=back	2275	=back
1953		2276
1954	=head3 Examples	2277	=head3 Examples
1955		2278
…		…
1968		2291
1969	static ev_io iow [nfd];	2292	static ev_io iow [nfd];
1970	static ev_timer tw;	2293	static ev_timer tw;
1971		2294
1972	static void	2295	static void
1973	io_cb (ev_loop *loop, ev_io *w, int revents)	2296	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1974	{	2297	{
1975	}	2298	}
1976		2299
1977	// create io watchers for each fd and a timer before blocking	2300	// create io watchers for each fd and a timer before blocking
1978	static void	2301	static void
1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2302	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1980	{	2303	{
1981	int timeout = 3600000;	2304	int timeout = 3600000;
1982	struct pollfd fds [nfd];	2305	struct pollfd fds [nfd];
1983	// actual code will need to loop here and realloc etc.	2306	// actual code will need to loop here and realloc etc.
1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
1999	}	2322	}
2000	}	2323	}
2001		2324
2002	// stop all watchers after blocking	2325	// stop all watchers after blocking
2003	static void	2326	static void
2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2327	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2005	{	2328	{
2006	ev_timer_stop (loop, &tw);	2329	ev_timer_stop (loop, &tw);
2007		2330
2008	for (int i = 0; i < nfd; ++i)	2331	for (int i = 0; i < nfd; ++i)
2009	{	2332	{
…		…
2048	}	2371	}
2049		2372
2050	// do not ever call adns_afterpoll	2373	// do not ever call adns_afterpoll
2051		2374
2052	Method 4: Do not use a prepare or check watcher because the module you	2375	Method 4: Do not use a prepare or check watcher because the module you
2053	want to embed is too inflexible to support it. Instead, you can override	2376	want to embed is not flexible enough to support it. Instead, you can
2054	their poll function. The drawback with this solution is that the main	2377	override their poll function. The drawback with this solution is that the
2055	loop is now no longer controllable by EV. The C<Glib::EV> module does	2378	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2056	this.	2379	this approach, effectively embedding EV as a client into the horrible
		2380	libglib event loop.
2057		2381
2058	static gint	2382	static gint
2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2383	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2060	{	2384	{
2061	int got_events = 0;	2385	int got_events = 0;
…		…
2092	prioritise I/O.	2416	prioritise I/O.
2093		2417
2094	As an example for a bug workaround, the kqueue backend might only support	2418	As an example for a bug workaround, the kqueue backend might only support
2095	sockets on some platform, so it is unusable as generic backend, but you	2419	sockets on some platform, so it is unusable as generic backend, but you
2096	still want to make use of it because you have many sockets and it scales	2420	still want to make use of it because you have many sockets and it scales
2097	so nicely. In this case, you would create a kqueue-based loop and embed it	2421	so nicely. In this case, you would create a kqueue-based loop and embed
2098	into your default loop (which might use e.g. poll). Overall operation will	2422	it into your default loop (which might use e.g. poll). Overall operation
2099	be a bit slower because first libev has to poll and then call kevent, but	2423	will be a bit slower because first libev has to call C<poll> and then
2100	at least you can use both at what they are best.	2424	C<kevent>, but at least you can use both mechanisms for what they are
		2425	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2101		2426
2102	As for prioritising I/O: rarely you have the case where some fds have	2427	As for prioritising I/O: under rare circumstances you have the case where
2103	to be watched and handled very quickly (with low latency), and even	2428	some fds have to be watched and handled very quickly (with low latency),
2104	priorities and idle watchers might have too much overhead. In this case	2429	and even priorities and idle watchers might have too much overhead. In
2105	you would put all the high priority stuff in one loop and all the rest in	2430	this case you would put all the high priority stuff in one loop and all
2106	a second one, and embed the second one in the first.	2431	the rest in a second one, and embed the second one in the first.
2107		2432
2108	As long as the watcher is active, the callback will be invoked every time	2433	As long as the watcher is active, the callback will be invoked every
2109	there might be events pending in the embedded loop. The callback must then	2434	time there might be events pending in the embedded loop. The callback
2110	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2435	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2111	their callbacks (you could also start an idle watcher to give the embedded	2436	sweep and invoke their callbacks (the callback doesn't need to invoke the
2112	loop strictly lower priority for example). You can also set the callback	2437	C<ev_embed_sweep> function directly, it could also start an idle watcher
2113	to C<0>, in which case the embed watcher will automatically execute the	2438	to give the embedded loop strictly lower priority for example).
2114	embedded loop sweep.
2115		2439
2116	As long as the watcher is started it will automatically handle events. The	2440	You can also set the callback to C<0>, in which case the embed watcher
2117	callback will be invoked whenever some events have been handled. You can	2441	will automatically execute the embedded loop sweep whenever necessary.
2118	set the callback to C<0> to avoid having to specify one if you are not
2119	interested in that.
2120		2442
2121	Also, there have not currently been made special provisions for forking:	2443	Fork detection will be handled transparently while the C<ev_embed> watcher
2122	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2444	is active, i.e., the embedded loop will automatically be forked when the
2123	but you will also have to stop and restart any C<ev_embed> watchers	2445	embedding loop forks. In other cases, the user is responsible for calling
2124	yourself.	2446	C<ev_loop_fork> on the embedded loop.
2125		2447
2126	Unfortunately, not all backends are embeddable, only the ones returned by	2448	Unfortunately, not all backends are embeddable: only the ones returned by
2127	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2449	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2128	portable one.	2450	portable one.
2129		2451
2130	So when you want to use this feature you will always have to be prepared	2452	So when you want to use this feature you will always have to be prepared
2131	that you cannot get an embeddable loop. The recommended way to get around	2453	that you cannot get an embeddable loop. The recommended way to get around
2132	this is to have a separate variables for your embeddable loop, try to	2454	this is to have a separate variables for your embeddable loop, try to
2133	create it, and if that fails, use the normal loop for everything.	2455	create it, and if that fails, use the normal loop for everything.
		2456
		2457	=head3 C<ev_embed> and fork
		2458
		2459	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2460	automatically be applied to the embedded loop as well, so no special
		2461	fork handling is required in that case. When the watcher is not running,
		2462	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2463	as applicable.
2134		2464
2135	=head3 Watcher-Specific Functions and Data Members	2465	=head3 Watcher-Specific Functions and Data Members
2136		2466
2137	=over 4	2467	=over 4
2138		2468
…		…
2166	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2496	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2167	used).	2497	used).
2168		2498
2169	struct ev_loop *loop_hi = ev_default_init (0);	2499	struct ev_loop *loop_hi = ev_default_init (0);
2170	struct ev_loop *loop_lo = 0;	2500	struct ev_loop *loop_lo = 0;
2171	struct ev_embed embed;	2501	ev_embed embed;
2172		2502
2173	// see if there is a chance of getting one that works	2503	// see if there is a chance of getting one that works
2174	// (remember that a flags value of 0 means autodetection)	2504	// (remember that a flags value of 0 means autodetection)
2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2505	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2506	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2190	kqueue implementation). Store the kqueue/socket-only event loop in	2520	kqueue implementation). Store the kqueue/socket-only event loop in
2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2521	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2192		2522
2193	struct ev_loop *loop = ev_default_init (0);	2523	struct ev_loop *loop = ev_default_init (0);
2194	struct ev_loop *loop_socket = 0;	2524	struct ev_loop *loop_socket = 0;
2195	struct ev_embed embed;	2525	ev_embed embed;
2196		2526
2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2527	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2528	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2199	{	2529	{
2200	ev_embed_init (&embed, 0, loop_socket);	2530	ev_embed_init (&embed, 0, loop_socket);
…		…
2256	is that the author does not know of a simple (or any) algorithm for a	2586	is that the author does not know of a simple (or any) algorithm for a
2257	multiple-writer-single-reader queue that works in all cases and doesn't	2587	multiple-writer-single-reader queue that works in all cases and doesn't
2258	need elaborate support such as pthreads.	2588	need elaborate support such as pthreads.
2259		2589
2260	That means that if you want to queue data, you have to provide your own	2590	That means that if you want to queue data, you have to provide your own
2261	queue. But at least I can tell you would implement locking around your	2591	queue. But at least I can tell you how to implement locking around your
2262	queue:	2592	queue:
2263		2593
2264	=over 4	2594	=over 4
2265		2595
2266	=item queueing from a signal handler context	2596	=item queueing from a signal handler context
2267		2597
2268	To implement race-free queueing, you simply add to the queue in the signal	2598	To implement race-free queueing, you simply add to the queue in the signal
2269	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2599	handler but you block the signal handler in the watcher callback. Here is
2270	some fictitious SIGUSR1 handler:	2600	an example that does that for some fictitious SIGUSR1 handler:
2271		2601
2272	static ev_async mysig;	2602	static ev_async mysig;
2273		2603
2274	static void	2604	static void
2275	sigusr1_handler (void)	2605	sigusr1_handler (void)
…		…
2341	=over 4	2671	=over 4
2342		2672
2343	=item ev_async_init (ev_async *, callback)	2673	=item ev_async_init (ev_async *, callback)
2344		2674
2345	Initialises and configures the async watcher - it has no parameters of any	2675	Initialises and configures the async watcher - it has no parameters of any
2346	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2676	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2347	believe me.	2677	trust me.
2348		2678
2349	=item ev_async_send (loop, ev_async *)	2679	=item ev_async_send (loop, ev_async *)
2350		2680
2351	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2352	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2353	C<ev_feed_event>, this call is safe to do in other threads, signal or	2683	C<ev_feed_event>, this call is safe to do from other threads, signal or
2354	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2355	section below on what exactly this means).	2685	section below on what exactly this means).
2356		2686
2357	This call incurs the overhead of a system call only once per loop iteration,	2687	This call incurs the overhead of a system call only once per loop iteration,
2358	so while the overhead might be noticeable, it doesn't apply to repeated	2688	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2382	=over 4	2712	=over 4
2383		2713
2384	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2714	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2385		2715
2386	This function combines a simple timer and an I/O watcher, calls your	2716	This function combines a simple timer and an I/O watcher, calls your
2387	callback on whichever event happens first and automatically stop both	2717	callback on whichever event happens first and automatically stops both
2388	watchers. This is useful if you want to wait for a single event on an fd	2718	watchers. This is useful if you want to wait for a single event on an fd
2389	or timeout without having to allocate/configure/start/stop/free one or	2719	or timeout without having to allocate/configure/start/stop/free one or
2390	more watchers yourself.	2720	more watchers yourself.
2391		2721
2392	If C<fd> is less than 0, then no I/O watcher will be started and events	2722	If C<fd> is less than 0, then no I/O watcher will be started and the
2393	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2723	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2394	C<events> set will be created and started.	2724	the given C<fd> and C<events> set will be created and started.
2395		2725
2396	If C<timeout> is less than 0, then no timeout watcher will be	2726	If C<timeout> is less than 0, then no timeout watcher will be
2397	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2398	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2728	repeat = 0) will be started. C<0> is a valid timeout.
2399	dubious value.
2400		2729
2401	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2402	passed an C<revents> set like normal event callbacks (a combination of	2731	passed an C<revents> set like normal event callbacks (a combination of
2403	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2404	value passed to C<ev_once>:	2733	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2734	a timeout and an io event at the same time - you probably should give io
		2735	events precedence.
		2736
		2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2405		2738
2406	static void stdin_ready (int revents, void *arg)	2739	static void stdin_ready (int revents, void *arg)
2407	{	2740	{
		2741	if (revents & EV_READ)
		2742	/* stdin might have data for us, joy! */;
2408	if (revents & EV_TIMEOUT)	2743	else if (revents & EV_TIMEOUT)
2409	/* doh, nothing entered */;	2744	/* doh, nothing entered */;
2410	else if (revents & EV_READ)
2411	/* stdin might have data for us, joy! */;
2412	}	2745	}
2413		2746
2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2415		2748
2416	=item ev_feed_event (ev_loop *, watcher *, int revents)	2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2417		2750
2418	Feeds the given event set into the event loop, as if the specified event	2751	Feeds the given event set into the event loop, as if the specified event
2419	had happened for the specified watcher (which must be a pointer to an	2752	had happened for the specified watcher (which must be a pointer to an
2420	initialised but not necessarily started event watcher).	2753	initialised but not necessarily started event watcher).
2421		2754
2422	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2423		2756
2424	Feed an event on the given fd, as if a file descriptor backend detected	2757	Feed an event on the given fd, as if a file descriptor backend detected
2425	the given events it.	2758	the given events it.
2426		2759
2427	=item ev_feed_signal_event (ev_loop *loop, int signum)	2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2428		2761
2429	Feed an event as if the given signal occurred (C<loop> must be the default	2762	Feed an event as if the given signal occurred (C<loop> must be the default
2430	loop!).	2763	loop!).
2431		2764
2432	=back	2765	=back
…		…
2554		2887
2555	myclass obj;	2888	myclass obj;
2556	ev::io iow;	2889	ev::io iow;
2557	iow.set <myclass, &myclass::io_cb> (&obj);	2890	iow.set <myclass, &myclass::io_cb> (&obj);
2558		2891
		2892	=item w->set (object *)
		2893
		2894	This is an B<experimental> feature that might go away in a future version.
		2895
		2896	This is a variation of a method callback - leaving out the method to call
		2897	will default the method to C<operator ()>, which makes it possible to use
		2898	functor objects without having to manually specify the C<operator ()> all
		2899	the time. Incidentally, you can then also leave out the template argument
		2900	list.
		2901
		2902	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2903	int revents)>.
		2904
		2905	See the method-C<set> above for more details.
		2906
		2907	Example: use a functor object as callback.
		2908
		2909	struct myfunctor
		2910	{
		2911	void operator() (ev::io &w, int revents)
		2912	{
		2913	...
		2914	}
		2915	}
		2916
		2917	myfunctor f;
		2918
		2919	ev::io w;
		2920	w.set (&f);
		2921
2559	=item w->set<function> (void *data = 0)	2922	=item w->set<function> (void *data = 0)
2560		2923
2561	Also sets a callback, but uses a static method or plain function as	2924	Also sets a callback, but uses a static method or plain function as
2562	callback. The optional C<data> argument will be stored in the watcher's	2925	callback. The optional C<data> argument will be stored in the watcher's
2563	C<data> member and is free for you to use.	2926	C<data> member and is free for you to use.
2564		2927
2565	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2928	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2566		2929
2567	See the method-C<set> above for more details.	2930	See the method-C<set> above for more details.
2568		2931
2569	Example:	2932	Example: Use a plain function as callback.
2570		2933
2571	static void io_cb (ev::io &w, int revents) { }	2934	static void io_cb (ev::io &w, int revents) { }
2572	iow.set <io_cb> ();	2935	iow.set <io_cb> ();
2573		2936
2574	=item w->set (struct ev_loop *)	2937	=item w->set (struct ev_loop *)
…		…
2612	Example: Define a class with an IO and idle watcher, start one of them in	2975	Example: Define a class with an IO and idle watcher, start one of them in
2613	the constructor.	2976	the constructor.
2614		2977
2615	class myclass	2978	class myclass
2616	{	2979	{
2617	ev::io io; void io_cb (ev::io &w, int revents);	2980	ev::io io ; void io_cb (ev::io &w, int revents);
2618	ev:idle idle void idle_cb (ev::idle &w, int revents);	2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2619		2982
2620	myclass (int fd)	2983	myclass (int fd)
2621	{	2984	{
2622	io .set <myclass, &myclass::io_cb > (this);	2985	io .set <myclass, &myclass::io_cb > (this);
2623	idle.set <myclass, &myclass::idle_cb> (this);	2986	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2639	=item Perl	3002	=item Perl
2640		3003
2641	The EV module implements the full libev API and is actually used to test	3004	The EV module implements the full libev API and is actually used to test
2642	libev. EV is developed together with libev. Apart from the EV core module,	3005	libev. EV is developed together with libev. Apart from the EV core module,
2643	there are additional modules that implement libev-compatible interfaces	3006	there are additional modules that implement libev-compatible interfaces
2644	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3007	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2645	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3008	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3009	and C<EV::Glib>).
2646		3010
2647	It can be found and installed via CPAN, its homepage is at	3011	It can be found and installed via CPAN, its homepage is at
2648	L<http://software.schmorp.de/pkg/EV>.	3012	L<http://software.schmorp.de/pkg/EV>.
2649		3013
2650	=item Python	3014	=item Python
…		…
2661	Tony Arcieri has written a ruby extension that offers access to a subset	3025	Tony Arcieri has written a ruby extension that offers access to a subset
2662	of the libev API and adds file handle abstractions, asynchronous DNS and	3026	of the libev API and adds file handle abstractions, asynchronous DNS and
2663	more on top of it. It can be found via gem servers. Its homepage is at	3027	more on top of it. It can be found via gem servers. Its homepage is at
2664	L<http://rev.rubyforge.org/>.	3028	L<http://rev.rubyforge.org/>.
2665		3029
		3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3031	makes rev work even on mingw.
		3032
2666	=item D	3033	=item D
2667		3034
2668	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2669	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3037
		3038	=item Ocaml
		3039
		3040	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2670		3042
2671	=back	3043	=back
2672		3044
2673		3045
2674	=head1 MACRO MAGIC	3046	=head1 MACRO MAGIC
…		…
2775		3147
2776	#define EV_STANDALONE 1	3148	#define EV_STANDALONE 1
2777	#include "ev.h"	3149	#include "ev.h"
2778		3150
2779	Both header files and implementation files can be compiled with a C++	3151	Both header files and implementation files can be compiled with a C++
2780	compiler (at least, thats a stated goal, and breakage will be treated	3152	compiler (at least, that's a stated goal, and breakage will be treated
2781	as a bug).	3153	as a bug).
2782		3154
2783	You need the following files in your source tree, or in a directory	3155	You need the following files in your source tree, or in a directory
2784	in your include path (e.g. in libev/ when using -Ilibev):	3156	in your include path (e.g. in libev/ when using -Ilibev):
2785		3157
…		…
2829		3201
2830	=head2 PREPROCESSOR SYMBOLS/MACROS	3202	=head2 PREPROCESSOR SYMBOLS/MACROS
2831		3203
2832	Libev can be configured via a variety of preprocessor symbols you have to	3204	Libev can be configured via a variety of preprocessor symbols you have to
2833	define before including any of its files. The default in the absence of	3205	define before including any of its files. The default in the absence of
2834	autoconf is noted for every option.	3206	autoconf is documented for every option.
2835		3207
2836	=over 4	3208	=over 4
2837		3209
2838	=item EV_STANDALONE	3210	=item EV_STANDALONE
2839		3211
…		…
2841	keeps libev from including F<config.h>, and it also defines dummy	3213	keeps libev from including F<config.h>, and it also defines dummy
2842	implementations for some libevent functions (such as logging, which is not	3214	implementations for some libevent functions (such as logging, which is not
2843	supported). It will also not define any of the structs usually found in	3215	supported). It will also not define any of the structs usually found in
2844	F<event.h> that are not directly supported by the libev core alone.	3216	F<event.h> that are not directly supported by the libev core alone.
2845		3217
		3218	In stanbdalone mode, libev will still try to automatically deduce the
		3219	configuration, but has to be more conservative.
		3220
2846	=item EV_USE_MONOTONIC	3221	=item EV_USE_MONOTONIC
2847		3222
2848	If defined to be C<1>, libev will try to detect the availability of the	3223	If defined to be C<1>, libev will try to detect the availability of the
2849	monotonic clock option at both compile time and runtime. Otherwise no use	3224	monotonic clock option at both compile time and runtime. Otherwise no
2850	of the monotonic clock option will be attempted. If you enable this, you	3225	use of the monotonic clock option will be attempted. If you enable this,
2851	usually have to link against librt or something similar. Enabling it when	3226	you usually have to link against librt or something similar. Enabling it
2852	the functionality isn't available is safe, though, although you have	3227	when the functionality isn't available is safe, though, although you have
2853	to make sure you link against any libraries where the C<clock_gettime>	3228	to make sure you link against any libraries where the C<clock_gettime>
2854	function is hiding in (often F<-lrt>).	3229	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2855		3230
2856	=item EV_USE_REALTIME	3231	=item EV_USE_REALTIME
2857		3232
2858	If defined to be C<1>, libev will try to detect the availability of the	3233	If defined to be C<1>, libev will try to detect the availability of the
2859	real-time clock option at compile time (and assume its availability at	3234	real-time clock option at compile time (and assume its availability at
2860	runtime if successful). Otherwise no use of the real-time clock option will	3235	runtime if successful). Otherwise no use of the real-time clock option will
2861	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3236	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2862	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3237	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2863	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3238	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2864		3239
		3240	=item EV_USE_CLOCK_SYSCALL
		3241
		3242	If defined to be C<1>, libev will try to use a direct syscall instead
		3243	of calling the system-provided C<clock_gettime> function. This option
		3244	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3245	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3246	programs needlessly. Using a direct syscall is slightly slower (in
		3247	theory), because no optimised vdso implementation can be used, but avoids
		3248	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3249	higher, as it simplifies linking (no need for C<-lrt>).
		3250
2865	=item EV_USE_NANOSLEEP	3251	=item EV_USE_NANOSLEEP
2866		3252
2867	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3253	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2868	and will use it for delays. Otherwise it will use C<select ()>.	3254	and will use it for delays. Otherwise it will use C<select ()>.
2869		3255
…		…
2884		3270
2885	=item EV_SELECT_USE_FD_SET	3271	=item EV_SELECT_USE_FD_SET
2886		3272
2887	If defined to C<1>, then the select backend will use the system C<fd_set>	3273	If defined to C<1>, then the select backend will use the system C<fd_set>
2888	structure. This is useful if libev doesn't compile due to a missing	3274	structure. This is useful if libev doesn't compile due to a missing
2889	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3275	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2890	exotic systems. This usually limits the range of file descriptors to some	3276	on exotic systems. This usually limits the range of file descriptors to
2891	low limit such as 1024 or might have other limitations (winsocket only	3277	some low limit such as 1024 or might have other limitations (winsocket
2892	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3278	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2893	influence the size of the C<fd_set> used.	3279	configures the maximum size of the C<fd_set>.
2894		3280
2895	=item EV_SELECT_IS_WINSOCKET	3281	=item EV_SELECT_IS_WINSOCKET
2896		3282
2897	When defined to C<1>, the select backend will assume that	3283	When defined to C<1>, the select backend will assume that
2898	select/socket/connect etc. don't understand file descriptors but	3284	select/socket/connect etc. don't understand file descriptors but
…		…
3009	When doing priority-based operations, libev usually has to linearly search	3395	When doing priority-based operations, libev usually has to linearly search
3010	all the priorities, so having many of them (hundreds) uses a lot of space	3396	all the priorities, so having many of them (hundreds) uses a lot of space
3011	and time, so using the defaults of five priorities (-2 .. +2) is usually	3397	and time, so using the defaults of five priorities (-2 .. +2) is usually
3012	fine.	3398	fine.
3013		3399
3014	If your embedding application does not need any priorities, defining these both to	3400	If your embedding application does not need any priorities, defining these
3015	C<0> will save some memory and CPU.	3401	both to C<0> will save some memory and CPU.
3016		3402
3017	=item EV_PERIODIC_ENABLE	3403	=item EV_PERIODIC_ENABLE
3018		3404
3019	If undefined or defined to be C<1>, then periodic timers are supported. If	3405	If undefined or defined to be C<1>, then periodic timers are supported. If
3020	defined to be C<0>, then they are not. Disabling them saves a few kB of	3406	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3027	code.	3413	code.
3028		3414
3029	=item EV_EMBED_ENABLE	3415	=item EV_EMBED_ENABLE
3030		3416
3031	If undefined or defined to be C<1>, then embed watchers are supported. If	3417	If undefined or defined to be C<1>, then embed watchers are supported. If
3032	defined to be C<0>, then they are not.	3418	defined to be C<0>, then they are not. Embed watchers rely on most other
		3419	watcher types, which therefore must not be disabled.
3033		3420
3034	=item EV_STAT_ENABLE	3421	=item EV_STAT_ENABLE
3035		3422
3036	If undefined or defined to be C<1>, then stat watchers are supported. If	3423	If undefined or defined to be C<1>, then stat watchers are supported. If
3037	defined to be C<0>, then they are not.	3424	defined to be C<0>, then they are not.
…		…
3069	two).	3456	two).
3070		3457
3071	=item EV_USE_4HEAP	3458	=item EV_USE_4HEAP
3072		3459
3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3460	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3074	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3461	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3075	to C<1>. The 4-heap uses more complicated (longer) code but has	3462	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3076	noticeably faster performance with many (thousands) of watchers.	3463	faster performance with many (thousands) of watchers.
3077		3464
3078	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3465	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3079	(disabled).	3466	(disabled).
3080		3467
3081	=item EV_HEAP_CACHE_AT	3468	=item EV_HEAP_CACHE_AT
3082		3469
3083	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3470	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3084	timer and periodics heap, libev can cache the timestamp (I<at>) within	3471	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3085	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3472	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3086	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3473	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3087	but avoids random read accesses on heap changes. This improves performance	3474	but avoids random read accesses on heap changes. This improves performance
3088	noticeably with with many (hundreds) of watchers.	3475	noticeably with many (hundreds) of watchers.
3089		3476
3090	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3477	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3091	(disabled).	3478	(disabled).
3092		3479
3093	=item EV_VERIFY	3480	=item EV_VERIFY
…		…
3099	called once per loop, which can slow down libev. If set to C<3>, then the	3486	called once per loop, which can slow down libev. If set to C<3>, then the
3100	verification code will be called very frequently, which will slow down	3487	verification code will be called very frequently, which will slow down
3101	libev considerably.	3488	libev considerably.
3102		3489
3103	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3490	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3104	C<0.>	3491	C<0>.
3105		3492
3106	=item EV_COMMON	3493	=item EV_COMMON
3107		3494
3108	By default, all watchers have a C<void *data> member. By redefining	3495	By default, all watchers have a C<void *data> member. By redefining
3109	this macro to a something else you can include more and other types of	3496	this macro to a something else you can include more and other types of
…		…
3126	and the way callbacks are invoked and set. Must expand to a struct member	3513	and the way callbacks are invoked and set. Must expand to a struct member
3127	definition and a statement, respectively. See the F<ev.h> header file for	3514	definition and a statement, respectively. See the F<ev.h> header file for
3128	their default definitions. One possible use for overriding these is to	3515	their default definitions. One possible use for overriding these is to
3129	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3516	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3130	method calls instead of plain function calls in C++.	3517	method calls instead of plain function calls in C++.
		3518
		3519	=back
3131		3520
3132	=head2 EXPORTED API SYMBOLS	3521	=head2 EXPORTED API SYMBOLS
3133		3522
3134	If you need to re-export the API (e.g. via a DLL) and you need a list of	3523	If you need to re-export the API (e.g. via a DLL) and you need a list of
3135	exported symbols, you can use the provided F<Symbol.*> files which list	3524	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3182	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3571	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3183		3572
3184	#include "ev_cpp.h"	3573	#include "ev_cpp.h"
3185	#include "ev.c"	3574	#include "ev.c"
3186		3575
		3576	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3187		3577
3188	=head1 THREADS AND COROUTINES	3578	=head2 THREADS AND COROUTINES
3189		3579
3190	=head2 THREADS	3580	=head3 THREADS
3191		3581
3192	Libev itself is completely thread-safe, but it uses no locking. This	3582	All libev functions are reentrant and thread-safe unless explicitly
		3583	documented otherwise, but libev implements no locking itself. This means
3193	means that you can use as many loops as you want in parallel, as long as	3584	that you can use as many loops as you want in parallel, as long as there
3194	only one thread ever calls into one libev function with the same loop	3585	are no concurrent calls into any libev function with the same loop
3195	parameter.	3586	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3587	of course): libev guarantees that different event loops share no data
		3588	structures that need any locking.
3196		3589
3197	Or put differently: calls with different loop parameters can be done in	3590	Or to put it differently: calls with different loop parameters can be done
3198	parallel from multiple threads, calls with the same loop parameter must be	3591	concurrently from multiple threads, calls with the same loop parameter
3199	done serially (but can be done from different threads, as long as only one	3592	must be done serially (but can be done from different threads, as long as
3200	thread ever is inside a call at any point in time, e.g. by using a mutex	3593	only one thread ever is inside a call at any point in time, e.g. by using
3201	per loop).	3594	a mutex per loop).
		3595
		3596	Specifically to support threads (and signal handlers), libev implements
		3597	so-called C<ev_async> watchers, which allow some limited form of
		3598	concurrency on the same event loop, namely waking it up "from the
		3599	outside".
3202		3600
3203	If you want to know which design (one loop, locking, or multiple loops	3601	If you want to know which design (one loop, locking, or multiple loops
3204	without or something else still) is best for your problem, then I cannot	3602	without or something else still) is best for your problem, then I cannot
3205	help you. I can give some generic advice however:	3603	help you, but here is some generic advice:
3206		3604
3207	=over 4	3605	=over 4
3208		3606
3209	=item * most applications have a main thread: use the default libev loop	3607	=item * most applications have a main thread: use the default libev loop
3210	in that thread, or create a separate thread running only the default loop.	3608	in that thread, or create a separate thread running only the default loop.
…		…
3222		3620
3223	Choosing a model is hard - look around, learn, know that usually you can do	3621	Choosing a model is hard - look around, learn, know that usually you can do
3224	better than you currently do :-)	3622	better than you currently do :-)
3225		3623
3226	=item * often you need to talk to some other thread which blocks in the	3624	=item * often you need to talk to some other thread which blocks in the
		3625	event loop.
		3626
3227	event loop - C<ev_async> watchers can be used to wake them up from other	3627	C<ev_async> watchers can be used to wake them up from other threads safely
3228	threads safely (or from signal contexts...).	3628	(or from signal contexts...).
		3629
		3630	An example use would be to communicate signals or other events that only
		3631	work in the default loop by registering the signal watcher with the
		3632	default loop and triggering an C<ev_async> watcher from the default loop
		3633	watcher callback into the event loop interested in the signal.
3229		3634
3230	=back	3635	=back
3231		3636
3232	=head2 COROUTINES	3637	=head3 COROUTINES
3233		3638
3234	Libev is much more accommodating to coroutines ("cooperative threads"):	3639	Libev is very accommodating to coroutines ("cooperative threads"):
3235	libev fully supports nesting calls to it's functions from different	3640	libev fully supports nesting calls to its functions from different
3236	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3641	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3237	different coroutines and switch freely between both coroutines running the	3642	different coroutines, and switch freely between both coroutines running the
3238	loop, as long as you don't confuse yourself). The only exception is that	3643	loop, as long as you don't confuse yourself). The only exception is that
3239	you must not do this from C<ev_periodic> reschedule callbacks.	3644	you must not do this from C<ev_periodic> reschedule callbacks.
3240		3645
3241	Care has been invested into making sure that libev does not keep local	3646	Care has been taken to ensure that libev does not keep local state inside
3242	state inside C<ev_loop>, and other calls do not usually allow coroutine	3647	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3243	switches.	3648	they do not call any callbacks.
3244		3649
		3650	=head2 COMPILER WARNINGS
3245		3651
3246	=head1 COMPLEXITIES	3652	Depending on your compiler and compiler settings, you might get no or a
		3653	lot of warnings when compiling libev code. Some people are apparently
		3654	scared by this.
3247		3655
3248	In this section the complexities of (many of) the algorithms used inside	3656	However, these are unavoidable for many reasons. For one, each compiler
3249	libev will be explained. For complexity discussions about backends see the	3657	has different warnings, and each user has different tastes regarding
3250	documentation for C<ev_default_init>.	3658	warning options. "Warn-free" code therefore cannot be a goal except when
		3659	targeting a specific compiler and compiler-version.
3251		3660
3252	All of the following are about amortised time: If an array needs to be	3661	Another reason is that some compiler warnings require elaborate
3253	extended, libev needs to realloc and move the whole array, but this	3662	workarounds, or other changes to the code that make it less clear and less
3254	happens asymptotically never with higher number of elements, so O(1) might	3663	maintainable.
3255	mean it might do a lengthy realloc operation in rare cases, but on average
3256	it is much faster and asymptotically approaches constant time.
3257		3664
3258	=over 4	3665	And of course, some compiler warnings are just plain stupid, or simply
		3666	wrong (because they don't actually warn about the condition their message
		3667	seems to warn about). For example, certain older gcc versions had some
		3668	warnings that resulted an extreme number of false positives. These have
		3669	been fixed, but some people still insist on making code warn-free with
		3670	such buggy versions.
3259		3671
3260	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3672	While libev is written to generate as few warnings as possible,
		3673	"warn-free" code is not a goal, and it is recommended not to build libev
		3674	with any compiler warnings enabled unless you are prepared to cope with
		3675	them (e.g. by ignoring them). Remember that warnings are just that:
		3676	warnings, not errors, or proof of bugs.
3261		3677
3262	This means that, when you have a watcher that triggers in one hour and
3263	there are 100 watchers that would trigger before that then inserting will
3264	have to skip roughly seven (C<ld 100>) of these watchers.
3265		3678
3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3679	=head2 VALGRIND
3267		3680
3268	That means that changing a timer costs less than removing/adding them	3681	Valgrind has a special section here because it is a popular tool that is
3269	as only the relative motion in the event queue has to be paid for.	3682	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3270		3683
3271	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3684	If you think you found a bug (memory leak, uninitialised data access etc.)
		3685	in libev, then check twice: If valgrind reports something like:
3272		3686
3273	These just add the watcher into an array or at the head of a list.	3687	==2274== definitely lost: 0 bytes in 0 blocks.
		3688	==2274== possibly lost: 0 bytes in 0 blocks.
		3689	==2274== still reachable: 256 bytes in 1 blocks.
3274		3690
3275	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3691	Then there is no memory leak, just as memory accounted to global variables
		3692	is not a memleak - the memory is still being referenced, and didn't leak.
3276		3693
3277	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3694	Similarly, under some circumstances, valgrind might report kernel bugs
		3695	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3696	although an acceptable workaround has been found here), or it might be
		3697	confused.
3278		3698
3279	These watchers are stored in lists then need to be walked to find the	3699	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3280	correct watcher to remove. The lists are usually short (you don't usually	3700	make it into some kind of religion.
3281	have many watchers waiting for the same fd or signal).
3282		3701
3283	=item Finding the next timer in each loop iteration: O(1)	3702	If you are unsure about something, feel free to contact the mailing list
		3703	with the full valgrind report and an explanation on why you think this
		3704	is a bug in libev (best check the archives, too :). However, don't be
		3705	annoyed when you get a brisk "this is no bug" answer and take the chance
		3706	of learning how to interpret valgrind properly.
3284		3707
3285	By virtue of using a binary or 4-heap, the next timer is always found at a	3708	If you need, for some reason, empty reports from valgrind for your project
3286	fixed position in the storage array.	3709	I suggest using suppression lists.
3287		3710
3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3289		3711
3290	A change means an I/O watcher gets started or stopped, which requires	3712	=head1 PORTABILITY NOTES
3291	libev to recalculate its status (and possibly tell the kernel, depending
3292	on backend and whether C<ev_io_set> was used).
3293		3713
3294	=item Activating one watcher (putting it into the pending state): O(1)
3295
3296	=item Priority handling: O(number_of_priorities)
3297
3298	Priorities are implemented by allocating some space for each
3299	priority. When doing priority-based operations, libev usually has to
3300	linearly search all the priorities, but starting/stopping and activating
3301	watchers becomes O(1) w.r.t. priority handling.
3302
3303	=item Sending an ev_async: O(1)
3304
3305	=item Processing ev_async_send: O(number_of_async_watchers)
3306
3307	=item Processing signals: O(max_signal_number)
3308
3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
3310	calls in the current loop iteration. Checking for async and signal events
3311	involves iterating over all running async watchers or all signal numbers.
3312
3313	=back
3314
3315
3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3714	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3317		3715
3318	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3716	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3319	requires, and its I/O model is fundamentally incompatible with the POSIX	3717	requires, and its I/O model is fundamentally incompatible with the POSIX
3320	model. Libev still offers limited functionality on this platform in	3718	model. Libev still offers limited functionality on this platform in
3321	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3719	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3332		3730
3333	Not a libev limitation but worth mentioning: windows apparently doesn't	3731	Not a libev limitation but worth mentioning: windows apparently doesn't
3334	accept large writes: instead of resulting in a partial write, windows will	3732	accept large writes: instead of resulting in a partial write, windows will
3335	either accept everything or return C<ENOBUFS> if the buffer is too large,	3733	either accept everything or return C<ENOBUFS> if the buffer is too large,
3336	so make sure you only write small amounts into your sockets (less than a	3734	so make sure you only write small amounts into your sockets (less than a
3337	megabyte seems safe, but thsi apparently depends on the amount of memory	3735	megabyte seems safe, but this apparently depends on the amount of memory
3338	available).	3736	available).
3339		3737
3340	Due to the many, low, and arbitrary limits on the win32 platform and	3738	Due to the many, low, and arbitrary limits on the win32 platform and
3341	the abysmal performance of winsockets, using a large number of sockets	3739	the abysmal performance of winsockets, using a large number of sockets
3342	is not recommended (and not reasonable). If your program needs to use	3740	is not recommended (and not reasonable). If your program needs to use
…		…
3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3751	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3354		3752
3355	#include "ev.h"	3753	#include "ev.h"
3356		3754
3357	And compile the following F<evwrap.c> file into your project (make sure	3755	And compile the following F<evwrap.c> file into your project (make sure
3358	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3756	you do I<not> compile the F<ev.c> or any other embedded source files!):
3359		3757
3360	#include "evwrap.h"	3758	#include "evwrap.h"
3361	#include "ev.c"	3759	#include "ev.c"
3362		3760
3363	=over 4	3761	=over 4
…		…
3408	wrap all I/O functions and provide your own fd management, but the cost of	3806	wrap all I/O functions and provide your own fd management, but the cost of
3409	calling select (O(n²)) will likely make this unworkable.	3807	calling select (O(n²)) will likely make this unworkable.
3410		3808
3411	=back	3809	=back
3412		3810
3413
3414	=head1 PORTABILITY REQUIREMENTS	3811	=head2 PORTABILITY REQUIREMENTS
3415		3812
3416	In addition to a working ISO-C implementation, libev relies on a few	3813	In addition to a working ISO-C implementation and of course the
3417	additional extensions:	3814	backend-specific APIs, libev relies on a few additional extensions:
3418		3815
3419	=over 4	3816	=over 4
3420		3817
3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3818	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3422	calling conventions regardless of C<ev_watcher_type *>.	3819	calling conventions regardless of C<ev_watcher_type *>.
…		…
3428	calls them using an C<ev_watcher *> internally.	3825	calls them using an C<ev_watcher *> internally.
3429		3826
3430	=item C<sig_atomic_t volatile> must be thread-atomic as well	3827	=item C<sig_atomic_t volatile> must be thread-atomic as well
3431		3828
3432	The type C<sig_atomic_t volatile> (or whatever is defined as	3829	The type C<sig_atomic_t volatile> (or whatever is defined as
3433	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3830	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3434	threads. This is not part of the specification for C<sig_atomic_t>, but is	3831	threads. This is not part of the specification for C<sig_atomic_t>, but is
3435	believed to be sufficiently portable.	3832	believed to be sufficiently portable.
3436		3833
3437	=item C<sigprocmask> must work in a threaded environment	3834	=item C<sigprocmask> must work in a threaded environment
3438		3835
…		…
3447	except the initial one, and run the default loop in the initial thread as	3844	except the initial one, and run the default loop in the initial thread as
3448	well.	3845	well.
3449		3846
3450	=item C<long> must be large enough for common memory allocation sizes	3847	=item C<long> must be large enough for common memory allocation sizes
3451		3848
3452	To improve portability and simplify using libev, libev uses C<long>	3849	To improve portability and simplify its API, libev uses C<long> internally
3453	internally instead of C<size_t> when allocating its data structures. On	3850	instead of C<size_t> when allocating its data structures. On non-POSIX
3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3851	systems (Microsoft...) this might be unexpectedly low, but is still at
3455	is still at least 31 bits everywhere, which is enough for hundreds of	3852	least 31 bits everywhere, which is enough for hundreds of millions of
3456	millions of watchers.	3853	watchers.
3457		3854
3458	=item C<double> must hold a time value in seconds with enough accuracy	3855	=item C<double> must hold a time value in seconds with enough accuracy
3459		3856
3460	The type C<double> is used to represent timestamps. It is required to	3857	The type C<double> is used to represent timestamps. It is required to
3461	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3858	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3465	=back	3862	=back
3466		3863
3467	If you know of other additional requirements drop me a note.	3864	If you know of other additional requirements drop me a note.
3468		3865
3469		3866
3470	=head1 COMPILER WARNINGS	3867	=head1 ALGORITHMIC COMPLEXITIES
3471		3868
3472	Depending on your compiler and compiler settings, you might get no or a	3869	In this section the complexities of (many of) the algorithms used inside
3473	lot of warnings when compiling libev code. Some people are apparently	3870	libev will be documented. For complexity discussions about backends see
3474	scared by this.	3871	the documentation for C<ev_default_init>.
3475		3872
3476	However, these are unavoidable for many reasons. For one, each compiler	3873	All of the following are about amortised time: If an array needs to be
3477	has different warnings, and each user has different tastes regarding	3874	extended, libev needs to realloc and move the whole array, but this
3478	warning options. "Warn-free" code therefore cannot be a goal except when	3875	happens asymptotically rarer with higher number of elements, so O(1) might
3479	targeting a specific compiler and compiler-version.	3876	mean that libev does a lengthy realloc operation in rare cases, but on
		3877	average it is much faster and asymptotically approaches constant time.
3480		3878
3481	Another reason is that some compiler warnings require elaborate	3879	=over 4
3482	workarounds, or other changes to the code that make it less clear and less
3483	maintainable.
3484		3880
3485	And of course, some compiler warnings are just plain stupid, or simply	3881	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3486	wrong (because they don't actually warn about the condition their message
3487	seems to warn about).
3488		3882
3489	While libev is written to generate as few warnings as possible,	3883	This means that, when you have a watcher that triggers in one hour and
3490	"warn-free" code is not a goal, and it is recommended not to build libev	3884	there are 100 watchers that would trigger before that, then inserting will
3491	with any compiler warnings enabled unless you are prepared to cope with	3885	have to skip roughly seven (C<ld 100>) of these watchers.
3492	them (e.g. by ignoring them). Remember that warnings are just that:
3493	warnings, not errors, or proof of bugs.
3494		3886
		3887	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3495		3888
3496	=head1 VALGRIND	3889	That means that changing a timer costs less than removing/adding them,
		3890	as only the relative motion in the event queue has to be paid for.
3497		3891
3498	Valgrind has a special section here because it is a popular tool that is	3892	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3499	highly useful, but valgrind reports are very hard to interpret.
3500		3893
3501	If you think you found a bug (memory leak, uninitialised data access etc.)	3894	These just add the watcher into an array or at the head of a list.
3502	in libev, then check twice: If valgrind reports something like:
3503		3895
3504	==2274== definitely lost: 0 bytes in 0 blocks.	3896	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3505	==2274== possibly lost: 0 bytes in 0 blocks.
3506	==2274== still reachable: 256 bytes in 1 blocks.
3507		3897
3508	Then there is no memory leak. Similarly, under some circumstances,	3898	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3509	valgrind might report kernel bugs as if it were a bug in libev, or it
3510	might be confused (it is a very good tool, but only a tool).
3511		3899
3512	If you are unsure about something, feel free to contact the mailing list	3900	These watchers are stored in lists, so they need to be walked to find the
3513	with the full valgrind report and an explanation on why you think this is	3901	correct watcher to remove. The lists are usually short (you don't usually
3514	a bug in libev. However, don't be annoyed when you get a brisk "this is	3902	have many watchers waiting for the same fd or signal: one is typical, two
3515	no bug" answer and take the chance of learning how to interpret valgrind	3903	is rare).
3516	properly.
3517		3904
3518	If you need, for some reason, empty reports from valgrind for your project	3905	=item Finding the next timer in each loop iteration: O(1)
3519	I suggest using suppression lists.	3906
		3907	By virtue of using a binary or 4-heap, the next timer is always found at a
		3908	fixed position in the storage array.
		3909
		3910	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3911
		3912	A change means an I/O watcher gets started or stopped, which requires
		3913	libev to recalculate its status (and possibly tell the kernel, depending
		3914	on backend and whether C<ev_io_set> was used).
		3915
		3916	=item Activating one watcher (putting it into the pending state): O(1)
		3917
		3918	=item Priority handling: O(number_of_priorities)
		3919
		3920	Priorities are implemented by allocating some space for each
		3921	priority. When doing priority-based operations, libev usually has to
		3922	linearly search all the priorities, but starting/stopping and activating
		3923	watchers becomes O(1) with respect to priority handling.
		3924
		3925	=item Sending an ev_async: O(1)
		3926
		3927	=item Processing ev_async_send: O(number_of_async_watchers)
		3928
		3929	=item Processing signals: O(max_signal_number)
		3930
		3931	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3932	calls in the current loop iteration. Checking for async and signal events
		3933	involves iterating over all running async watchers or all signal numbers.
		3934
		3935	=back
3520		3936
3521		3937
3522	=head1 AUTHOR	3938	=head1 AUTHOR
3523		3939
3524	Marc Lehmann <libev@schmorp.de>.	3940	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3525		3941

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