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Revision 1.234 by root, Thu Apr 16 07:49:23 2009 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	217	recommended ones.
216		218
217	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
218		220
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		222
221	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	225	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	226	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	252	}
251		253
252	...	254	...
253	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
254		256
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		258
257	Set the callback function to call on a retryable system call error (such	259	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	262	callback is set, then libev will expect it to remedy the situation, no
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		387
382	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,
383	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
384	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),
385	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).
386	of shortcomings, such as silently dropping events in some hard-to-detect	392
387	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
388	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.
389		409
390	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
391	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
392	(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
393	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
394	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
395		415	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		416
400	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	418	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	419	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	420	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	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.
405		428
406	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
407	all kernel versions tested so far.	430	all kernel versions tested so far.
408		431
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	433	C<EVBACKEND_POLL>.
411		434
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		436
414	Kqueue deserves special mention, as at the time of this writing, it was	437	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	439	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	440	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	441	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	442	without API changes to existing programs. For this reason it's not being
		443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		445	system like NetBSD.
420		446
421	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
422	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
423	the target platform). See C<ev_embed> watchers for more info.	449	the target platform). See C<ev_embed> watchers for more info.
424		450
425	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
426	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
427	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
428	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
429	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
430	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
431		458
432	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
433		460
434	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
435	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
436	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
437	(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
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
440		467
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	470	C<NOTE_EOF>.
444		471
…		…
464	might perform better.	491	might perform better.
465		492
466	On the positive side, with the exception of the spurious readiness	493	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	494	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	495	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	496	OS-specific backends (I vastly prefer correctness over speed hacks).
470		497
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	499	C<EVBACKEND_POLL>.
473		500
474	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
528	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
529	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
530	for example).	557	for example).
531		558
532	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
533	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
535		562
536	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
537	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
538	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
539	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
607	very long time without entering the event loop, updating libev's idea of	634	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	635	the current time is a good idea.
609		636
610	See also "The special problem of time updates" in the C<ev_timer> section.	637	See also "The special problem of time updates" in the C<ev_timer> section.
611		638
		639	=item ev_suspend (loop)
		640
		641	=item ev_resume (loop)
		642
		643	These two functions suspend and resume a loop, for use when the loop is
		644	not used for a while and timeouts should not be processed.
		645
		646	A typical use case would be an interactive program such as a game: When
		647	the user presses C<^Z> to suspend the game and resumes it an hour later it
		648	would be best to handle timeouts as if no time had actually passed while
		649	the program was suspended. This can be achieved by calling C<ev_suspend>
		650	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		651	C<ev_resume> directly afterwards to resume timer processing.
		652
		653	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		655	will be rescheduled (that is, they will lose any events that would have
		656	occured while suspended).
		657
		658	After calling C<ev_suspend> you B<must not> call I<any> function on the
		659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		660	without a previous call to C<ev_suspend>.
		661
		662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		663	event loop time (see C<ev_now_update>).
		664
612	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
613		666
614	Finally, this is it, the event handler. This function usually is called	667	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	668	after you initialised all your watchers and you want to start handling
616	events.	669	events.
…		…
631	the loop.	684	the loop.
632		685
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	687	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	688	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	689	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	690	user-registered callback will be called), and will return after one
638	iteration of the loop.	691	iteration of the loop.
639		692
640	This is useful if you are waiting for some external event in conjunction	693	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	694	with something not expressible using other libev watchers (i.e. "roll your
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	738	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		740
688	This "unloop state" will be cleared when entering C<ev_loop> again.	741	This "unloop state" will be cleared when entering C<ev_loop> again.
689		742
		743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		744
690	=item ev_ref (loop)	745	=item ev_ref (loop)
691		746
692	=item ev_unref (loop)	747	=item ev_unref (loop)
693		748
694	Ref/unref can be used to add or remove a reference count on the event	749	Ref/unref can be used to add or remove a reference count on the event
…		…
697		752
698	If you have a watcher you never unregister that should not keep C<ev_loop>	753	If you have a watcher you never unregister that should not keep C<ev_loop>
699	from returning, call ev_unref() after starting, and ev_ref() before	754	from returning, call ev_unref() after starting, and ev_ref() before
700	stopping it.	755	stopping it.
701		756
702	As an example, libev itself uses this for its internal signal pipe: It is	757	As an example, libev itself uses this for its internal signal pipe: It
703	not visible to the libev user and should not keep C<ev_loop> from exiting	758	is not visible to the libev user and should not keep C<ev_loop> from
704	if no event watchers registered by it are active. It is also an excellent	759	exiting if no event watchers registered by it are active. It is also an
705	way to do this for generic recurring timers or from within third-party	760	excellent way to do this for generic recurring timers or from within
706	libraries. Just remember to I<unref after start> and I<ref before stop>	761	third-party libraries. Just remember to I<unref after start> and I<ref
707	(but only if the watcher wasn't active before, or was active before,	762	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	763	before, respectively. Note also that libev might stop watchers itself
		764	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		765	in the callback).
709		766
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	768	running when nothing else is active.
712		769
713	struct ev_signal exitsig;	770	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	771	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	772	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	773	evf_unref (loop);
717		774
718	Example: For some weird reason, unregister the above signal handler again.	775	Example: For some weird reason, unregister the above signal handler again.
…		…
766	they fire on, say, one-second boundaries only.	823	they fire on, say, one-second boundaries only.
767		824
768	=item ev_loop_verify (loop)	825	=item ev_loop_verify (loop)
769		826
770	This function only does something when C<EV_VERIFY> support has been	827	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	828	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	829	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	830	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	831	error and call C<abort ()>.
775		832
776	This can be used to catch bugs inside libev itself: under normal	833	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	837	=back
781		838
782		839
783	=head1 ANATOMY OF A WATCHER	840	=head1 ANATOMY OF A WATCHER
784		841
		842	In the following description, uppercase C<TYPE> in names stands for the
		843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		844	watchers and C<ev_io_start> for I/O watchers.
		845
785	A watcher is a structure that you create and register to record your	846	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	847	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	848	become readable, you would create an C<ev_io> watcher for that:
788		849
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	851	{
791	ev_io_stop (w);	852	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	853	ev_unloop (loop, EVUNLOOP_ALL);
793	}	854	}
794		855
795	struct ev_loop *loop = ev_default_loop (0);	856	struct ev_loop *loop = ev_default_loop (0);
		857
796	struct ev_io stdin_watcher;	858	ev_io stdin_watcher;
		859
797	ev_init (&stdin_watcher, my_cb);	860	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	862	ev_io_start (loop, &stdin_watcher);
		863
800	ev_loop (loop, 0);	864	ev_loop (loop, 0);
801		865
802	As you can see, you are responsible for allocating the memory for your	866	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	867	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	868	stack).
		869
		870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		872
806	Each watcher structure must be initialised by a call to C<ev_init	873	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	874	(watcher *, callback)>, which expects a callback to be provided. This
808	callback gets invoked each time the event occurs (or, in the case of I/O	875	callback gets invoked each time the event occurs (or, in the case of I/O
809	watchers, each time the event loop detects that the file descriptor given	876	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	877	is readable and/or writable).
811		878
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	879	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	880	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	881	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	882	ev_TYPE_init (watcher *, callback, ...) >>.
816		883
817	To make the watcher actually watch out for events, you have to start it	884	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	885	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	886	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	887	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		888
822	As long as your watcher is active (has been started but not stopped) you	889	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	890	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	891	reinitialise it or call its C<ev_TYPE_set> macro.
825		892
826	Each and every callback receives the event loop pointer as first, the	893	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	894	registered watcher structure as second, and a bitset of received events as
828	third argument.	895	third argument.
829		896
…		…
887		954
888	=item C<EV_ASYNC>	955	=item C<EV_ASYNC>
889		956
890	The given async watcher has been asynchronously notified (see C<ev_async>).	957	The given async watcher has been asynchronously notified (see C<ev_async>).
891		958
		959	=item C<EV_CUSTOM>
		960
		961	Not ever sent (or otherwise used) by libev itself, but can be freely used
		962	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		963
892	=item C<EV_ERROR>	964	=item C<EV_ERROR>
893		965
894	An unspecified error has occurred, the watcher has been stopped. This might	966	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	967	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	968	ran out of memory, a file descriptor was found to be closed or any other
		969	problem. Libev considers these application bugs.
		970
897	problem. You best act on it by reporting the problem and somehow coping	971	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	972	watcher being stopped. Note that well-written programs should not receive
		973	an error ever, so when your watcher receives it, this usually indicates a
		974	bug in your program.
899		975
900	Libev will usually signal a few "dummy" events together with an error, for	976	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	977	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	978	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	979	the error from read() or write(). This will not work in multi-threaded
…		…
906		982
907	=back	983	=back
908		984
909	=head2 GENERIC WATCHER FUNCTIONS	985	=head2 GENERIC WATCHER FUNCTIONS
910		986
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	987	=over 4
915		988
916	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
917		990
918	This macro initialises the generic portion of a watcher. The contents	991	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	996	which rolls both calls into one.
924		997
925	You can reinitialise a watcher at any time as long as it has been stopped	998	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	999	(or never started) and there are no pending events outstanding.
927		1000
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1001	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1002	int revents)>.
930		1003
931	Example: Initialise an C<ev_io> watcher in two steps.	1004	Example: Initialise an C<ev_io> watcher in two steps.
932		1005
933	ev_io w;	1006	ev_io w;
…		…
967		1040
968	ev_io_start (EV_DEFAULT_UC, &w);	1041	ev_io_start (EV_DEFAULT_UC, &w);
969		1042
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
971		1044
972	Stops the given watcher again (if active) and clears the pending	1045	Stops the given watcher if active, and clears the pending status (whether
		1046	the watcher was active or not).
		1047
973	status. It is possible that stopped watchers are pending (for example,	1048	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1049	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1050	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1051	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1052	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1053
979	=item bool ev_is_active (ev_TYPE *watcher)	1054	=item bool ev_is_active (ev_TYPE *watcher)
980		1055
981	Returns a true value iff the watcher is active (i.e. it has been started	1056	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1057	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1084	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1085	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1086	from being executed (except for C<ev_idle> watchers).
1012		1087
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	If you need to suppress invocation when higher priority events are pending	1088	If you need to suppress invocation when higher priority events are pending
1019	you need to look at C<ev_idle> watchers, which provide this functionality.	1089	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1090
1021	You I<must not> change the priority of a watcher as long as it is active or	1091	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1092	pending.
1023		1093
		1094	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1095	fine, as long as you do not mind that the priority value you query might
		1096	or might not have been clamped to the valid range.
		1097
1024	The default priority used by watchers when no priority has been set is	1098	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1099	always C<0>, which is supposed to not be too high and not be too low :).
1026		1100
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1101	See L<WATCHER PRIORITIES>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1102	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1103
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1104	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1105
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1106	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1107	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1129	member, you can also "subclass" the watcher type and provide your own
1057	data:	1130	data:
1058		1131
1059	struct my_io	1132	struct my_io
1060	{	1133	{
1061	struct ev_io io;	1134	ev_io io;
1062	int otherfd;	1135	int otherfd;
1063	void *somedata;	1136	void *somedata;
1064	struct whatever *mostinteresting;	1137	struct whatever *mostinteresting;
1065	};	1138	};
1066		1139
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1142	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1143
1071	And since your callback will be called with a pointer to the watcher, you	1144	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1145	can cast it back to your own type:
1073		1146
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1147	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1148	{
1076	struct my_io *w = (struct my_io *)w_;	1149	struct my_io *w = (struct my_io *)w_;
1077	...	1150	...
1078	}	1151	}
1079		1152
…		…
1097	programmers):	1170	programmers):
1098		1171
1099	#include <stddef.h>	1172	#include <stddef.h>
1100		1173
1101	static void	1174	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1175	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1176	{
1104	struct my_biggy big = (struct my_biggy *	1177	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1178	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1179	}
1107		1180
1108	static void	1181	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1182	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1183	{
1111	struct my_biggy big = (struct my_biggy *	1184	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1185	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1186	}
		1187
		1188	=head2 WATCHER PRIORITY MODELS
		1189
		1190	Many event loops support I<watcher priorities>, which are usually small
		1191	integers that influence the ordering of event callback invocation
		1192	between watchers in some way, all else being equal.
		1193
		1194	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1195	description for the more technical details such as the actual priority
		1196	range.
		1197
		1198	There are two common ways how these these priorities are being interpreted
		1199	by event loops:
		1200
		1201	In the more common lock-out model, higher priorities "lock out" invocation
		1202	of lower priority watchers, which means as long as higher priority
		1203	watchers receive events, lower priority watchers are not being invoked.
		1204
		1205	The less common only-for-ordering model uses priorities solely to order
		1206	callback invocation within a single event loop iteration: Higher priority
		1207	watchers are invoked before lower priority ones, but they all get invoked
		1208	before polling for new events.
		1209
		1210	Libev uses the second (only-for-ordering) model for all its watchers
		1211	except for idle watchers (which use the lock-out model).
		1212
		1213	The rationale behind this is that implementing the lock-out model for
		1214	watchers is not well supported by most kernel interfaces, and most event
		1215	libraries will just poll for the same events again and again as long as
		1216	their callbacks have not been executed, which is very inefficient in the
		1217	common case of one high-priority watcher locking out a mass of lower
		1218	priority ones.
		1219
		1220	Static (ordering) priorities are most useful when you have two or more
		1221	watchers handling the same resource: a typical usage example is having an
		1222	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1223	timeouts. Under load, data might be received while the program handles
		1224	other jobs, but since timers normally get invoked first, the timeout
		1225	handler will be executed before checking for data. In that case, giving
		1226	the timer a lower priority than the I/O watcher ensures that I/O will be
		1227	handled first even under adverse conditions (which is usually, but not
		1228	always, what you want).
		1229
		1230	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1231	will only be executed when no same or higher priority watchers have
		1232	received events, they can be used to implement the "lock-out" model when
		1233	required.
		1234
		1235	For example, to emulate how many other event libraries handle priorities,
		1236	you can associate an C<ev_idle> watcher to each such watcher, and in
		1237	the normal watcher callback, you just start the idle watcher. The real
		1238	processing is done in the idle watcher callback. This causes libev to
		1239	continously poll and process kernel event data for the watcher, but when
		1240	the lock-out case is known to be rare (which in turn is rare :), this is
		1241	workable.
		1242
		1243	Usually, however, the lock-out model implemented that way will perform
		1244	miserably under the type of load it was designed to handle. In that case,
		1245	it might be preferable to stop the real watcher before starting the
		1246	idle watcher, so the kernel will not have to process the event in case
		1247	the actual processing will be delayed for considerable time.
		1248
		1249	Here is an example of an I/O watcher that should run at a strictly lower
		1250	priority than the default, and which should only process data when no
		1251	other events are pending:
		1252
		1253	ev_idle idle; // actual processing watcher
		1254	ev_io io; // actual event watcher
		1255
		1256	static void
		1257	io_cb (EV_P_ ev_io *w, int revents)
		1258	{
		1259	// stop the I/O watcher, we received the event, but
		1260	// are not yet ready to handle it.
		1261	ev_io_stop (EV_A_ w);
		1262
		1263	// start the idle watcher to ahndle the actual event.
		1264	// it will not be executed as long as other watchers
		1265	// with the default priority are receiving events.
		1266	ev_idle_start (EV_A_ &idle);
		1267	}
		1268
		1269	static void
		1270	idle-cb (EV_P_ ev_idle *w, int revents)
		1271	{
		1272	// actual processing
		1273	read (STDIN_FILENO, ...);
		1274
		1275	// have to start the I/O watcher again, as
		1276	// we have handled the event
		1277	ev_io_start (EV_P_ &io);
		1278	}
		1279
		1280	// initialisation
		1281	ev_idle_init (&idle, idle_cb);
		1282	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1283	ev_io_start (EV_DEFAULT_ &io);
		1284
		1285	In the "real" world, it might also be beneficial to start a timer, so that
		1286	low-priority connections can not be locked out forever under load. This
		1287	enables your program to keep a lower latency for important connections
		1288	during short periods of high load, while not completely locking out less
		1289	important ones.
1114		1290
1115		1291
1116	=head1 WATCHER TYPES	1292	=head1 WATCHER TYPES
1117		1293
1118	This section describes each watcher in detail, but will not repeat	1294	This section describes each watcher in detail, but will not repeat
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1425	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1426	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1427	attempt to read a whole line in the callback.
1252		1428
1253	static void	1429	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1430	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1431	{
1256	ev_io_stop (loop, w);	1432	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1433	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1434	}
1259		1435
1260	...	1436	...
1261	struct ev_loop *loop = ev_default_init (0);	1437	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1438	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1439	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1440	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1441	ev_loop (loop, 0);
1266		1442
1267		1443
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1451	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1452	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1453	monotonic clock option helps a lot here).
1278		1454
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1455	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1456	passed. If multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1457	then the ones with earlier time-out values are invoked before ones with
		1458	later time-out values (but this is no longer true when a callback calls
		1459	C<ev_loop> recursively).
		1460
		1461	=head3 Be smart about timeouts
		1462
		1463	Many real-world problems involve some kind of timeout, usually for error
		1464	recovery. A typical example is an HTTP request - if the other side hangs,
		1465	you want to raise some error after a while.
		1466
		1467	What follows are some ways to handle this problem, from obvious and
		1468	inefficient to smart and efficient.
		1469
		1470	In the following, a 60 second activity timeout is assumed - a timeout that
		1471	gets reset to 60 seconds each time there is activity (e.g. each time some
		1472	data or other life sign was received).
		1473
		1474	=over 4
		1475
		1476	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1477
		1478	This is the most obvious, but not the most simple way: In the beginning,
		1479	start the watcher:
		1480
		1481	ev_timer_init (timer, callback, 60., 0.);
		1482	ev_timer_start (loop, timer);
		1483
		1484	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1485	and start it again:
		1486
		1487	ev_timer_stop (loop, timer);
		1488	ev_timer_set (timer, 60., 0.);
		1489	ev_timer_start (loop, timer);
		1490
		1491	This is relatively simple to implement, but means that each time there is
		1492	some activity, libev will first have to remove the timer from its internal
		1493	data structure and then add it again. Libev tries to be fast, but it's
		1494	still not a constant-time operation.
		1495
		1496	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1497
		1498	This is the easiest way, and involves using C<ev_timer_again> instead of
		1499	C<ev_timer_start>.
		1500
		1501	To implement this, configure an C<ev_timer> with a C<repeat> value
		1502	of C<60> and then call C<ev_timer_again> at start and each time you
		1503	successfully read or write some data. If you go into an idle state where
		1504	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1505	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1506
		1507	That means you can ignore both the C<ev_timer_start> function and the
		1508	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1509	member and C<ev_timer_again>.
		1510
		1511	At start:
		1512
		1513	ev_timer_init (timer, callback);
		1514	timer->repeat = 60.;
		1515	ev_timer_again (loop, timer);
		1516
		1517	Each time there is some activity:
		1518
		1519	ev_timer_again (loop, timer);
		1520
		1521	It is even possible to change the time-out on the fly, regardless of
		1522	whether the watcher is active or not:
		1523
		1524	timer->repeat = 30.;
		1525	ev_timer_again (loop, timer);
		1526
		1527	This is slightly more efficient then stopping/starting the timer each time
		1528	you want to modify its timeout value, as libev does not have to completely
		1529	remove and re-insert the timer from/into its internal data structure.
		1530
		1531	It is, however, even simpler than the "obvious" way to do it.
		1532
		1533	=item 3. Let the timer time out, but then re-arm it as required.
		1534
		1535	This method is more tricky, but usually most efficient: Most timeouts are
		1536	relatively long compared to the intervals between other activity - in
		1537	our example, within 60 seconds, there are usually many I/O events with
		1538	associated activity resets.
		1539
		1540	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1541	but remember the time of last activity, and check for a real timeout only
		1542	within the callback:
		1543
		1544	ev_tstamp last_activity; // time of last activity
		1545
		1546	static void
		1547	callback (EV_P_ ev_timer *w, int revents)
		1548	{
		1549	ev_tstamp now = ev_now (EV_A);
		1550	ev_tstamp timeout = last_activity + 60.;
		1551
		1552	// if last_activity + 60. is older than now, we did time out
		1553	if (timeout < now)
		1554	{
		1555	// timeout occured, take action
		1556	}
		1557	else
		1558	{
		1559	// callback was invoked, but there was some activity, re-arm
		1560	// the watcher to fire in last_activity + 60, which is
		1561	// guaranteed to be in the future, so "again" is positive:
		1562	w->repeat = timeout - now;
		1563	ev_timer_again (EV_A_ w);
		1564	}
		1565	}
		1566
		1567	To summarise the callback: first calculate the real timeout (defined
		1568	as "60 seconds after the last activity"), then check if that time has
		1569	been reached, which means something I<did>, in fact, time out. Otherwise
		1570	the callback was invoked too early (C<timeout> is in the future), so
		1571	re-schedule the timer to fire at that future time, to see if maybe we have
		1572	a timeout then.
		1573
		1574	Note how C<ev_timer_again> is used, taking advantage of the
		1575	C<ev_timer_again> optimisation when the timer is already running.
		1576
		1577	This scheme causes more callback invocations (about one every 60 seconds
		1578	minus half the average time between activity), but virtually no calls to
		1579	libev to change the timeout.
		1580
		1581	To start the timer, simply initialise the watcher and set C<last_activity>
		1582	to the current time (meaning we just have some activity :), then call the
		1583	callback, which will "do the right thing" and start the timer:
		1584
		1585	ev_timer_init (timer, callback);
		1586	last_activity = ev_now (loop);
		1587	callback (loop, timer, EV_TIMEOUT);
		1588
		1589	And when there is some activity, simply store the current time in
		1590	C<last_activity>, no libev calls at all:
		1591
		1592	last_actiivty = ev_now (loop);
		1593
		1594	This technique is slightly more complex, but in most cases where the
		1595	time-out is unlikely to be triggered, much more efficient.
		1596
		1597	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1598	callback :) - just change the timeout and invoke the callback, which will
		1599	fix things for you.
		1600
		1601	=item 4. Wee, just use a double-linked list for your timeouts.
		1602
		1603	If there is not one request, but many thousands (millions...), all
		1604	employing some kind of timeout with the same timeout value, then one can
		1605	do even better:
		1606
		1607	When starting the timeout, calculate the timeout value and put the timeout
		1608	at the I<end> of the list.
		1609
		1610	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1611	the list is expected to fire (for example, using the technique #3).
		1612
		1613	When there is some activity, remove the timer from the list, recalculate
		1614	the timeout, append it to the end of the list again, and make sure to
		1615	update the C<ev_timer> if it was taken from the beginning of the list.
		1616
		1617	This way, one can manage an unlimited number of timeouts in O(1) time for
		1618	starting, stopping and updating the timers, at the expense of a major
		1619	complication, and having to use a constant timeout. The constant timeout
		1620	ensures that the list stays sorted.
		1621
		1622	=back
		1623
		1624	So which method the best?
		1625
		1626	Method #2 is a simple no-brain-required solution that is adequate in most
		1627	situations. Method #3 requires a bit more thinking, but handles many cases
		1628	better, and isn't very complicated either. In most case, choosing either
		1629	one is fine, with #3 being better in typical situations.
		1630
		1631	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1632	rather complicated, but extremely efficient, something that really pays
		1633	off after the first million or so of active timers, i.e. it's usually
		1634	overkill :)
1282		1635
1283	=head3 The special problem of time updates	1636	=head3 The special problem of time updates
1284		1637
1285	Establishing the current time is a costly operation (it usually takes at	1638	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1639	least two system calls): EV therefore updates its idea of the current
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1683	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1684
1332	If the timer is repeating, either start it if necessary (with the	1685	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1686	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1687
1335	This sounds a bit complicated, but here is a useful and typical	1688	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1689	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344
1345	That means you can ignore the C<after> value and C<ev_timer_start>
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347
1348	ev_timer_init (timer, callback, 0., 5.);
1349	ev_timer_again (loop, timer);
1350	...
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356
1357	This is more slightly efficient then stopping/starting the timer each time
1358	you want to modify its timeout value.
1359
1360	Note, however, that it is often even more efficient to remember the
1361	time of the last activity and let the timer time-out naturally. In the
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1690
1366	=item ev_tstamp repeat [read-write]	1691	=item ev_tstamp repeat [read-write]
1367		1692
1368	The current C<repeat> value. Will be used each time the watcher times out	1693	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1694	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1699	=head3 Examples
1375		1700
1376	Example: Create a timer that fires after 60 seconds.	1701	Example: Create a timer that fires after 60 seconds.
1377		1702
1378	static void	1703	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1704	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1705	{
1381	.. one minute over, w is actually stopped right here	1706	.. one minute over, w is actually stopped right here
1382	}	1707	}
1383		1708
1384	struct ev_timer mytimer;	1709	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1710	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1711	ev_timer_start (loop, &mytimer);
1387		1712
1388	Example: Create a timeout timer that times out after 10 seconds of	1713	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1714	inactivity.
1390		1715
1391	static void	1716	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1717	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1718	{
1394	.. ten seconds without any activity	1719	.. ten seconds without any activity
1395	}	1720	}
1396		1721
1397	struct ev_timer mytimer;	1722	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1723	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1724	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1725	ev_loop (loop, 0);
1401		1726
1402	// and in some piece of code that gets executed on any "activity":	1727	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1732	=head2 C<ev_periodic> - to cron or not to cron?
1408		1733
1409	Periodic watchers are also timers of a kind, but they are very versatile	1734	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1735	(and unfortunately a bit complex).
1411		1736
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1737	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	1738	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	1739	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1740	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	1741	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	1742	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		1743
		1744	You can tell a periodic watcher to trigger after some specific point
		1745	in time: for example, if you tell a periodic watcher to trigger "in 10
		1746	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1747	not a delay) and then reset your system clock to January of the previous
		1748	year, then it will take a year or more to trigger the event (unlike an
		1749	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1750	it, as it uses a relative timeout).
		1751
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1752	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	1753	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1754	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1755	those cannot react to time jumps.
1424		1756
1425	As with timers, the callback is guaranteed to be invoked only when the	1757	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	1758	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	1759	timers become ready during the same loop iteration then the ones with
		1760	earlier time-out values are invoked before ones with later time-out values
		1761	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1762
1429	=head3 Watcher-Specific Functions and Data Members	1763	=head3 Watcher-Specific Functions and Data Members
1430		1764
1431	=over 4	1765	=over 4
1432		1766
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1767	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1768
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1769	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1770
1437	Lots of arguments, lets sort it out... There are basically three modes of	1771	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	1772	operation, and we will explain them from simplest to most complex:
1439		1773
1440	=over 4	1774	=over 4
1441		1775
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1776	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		1777
1444	In this configuration the watcher triggers an event after the wall clock	1778	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	1779	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1780	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	1781	will be stopped and invoked when the system clock reaches or surpasses
		1782	this point in time.
1448		1783
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1784	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		1785
1451	In this mode the watcher will always be scheduled to time out at the next	1786	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	1787	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	1788	negative) and then repeat, regardless of any time jumps. The C<offset>
		1789	argument is merely an offset into the C<interval> periods.
1454		1790
1455	This can be used to create timers that do not drift with respect to the	1791	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	1792	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	1793	hour, on the hour (with respect to UTC):
1458		1794
1459	ev_periodic_set (&periodic, 0., 3600., 0);	1795	ev_periodic_set (&periodic, 0., 3600., 0);
1460		1796
1461	This doesn't mean there will always be 3600 seconds in between triggers,	1797	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	1798	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	1799	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	1800	by 3600.
1465		1801
1466	Another way to think about it (for the mathematically inclined) is that	1802	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	1803	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	1804	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		1805
1470	For numerical stability it is preferable that the C<at> value is near	1806	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	1807	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	1808	this value, and in fact is often specified as zero.
1473		1809
1474	Note also that there is an upper limit to how often a timer can fire (CPU	1810	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	1811	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	1812	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	1813	millisecond (if the OS supports it and the machine is fast enough).
1478		1814
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1815	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		1816
1481	In this mode the values for C<interval> and C<at> are both being	1817	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	1818	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	1819	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	1820	current time as second argument.
1485		1821
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1822	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	1823	or make ANY other event loop modifications whatsoever, unless explicitly
		1824	allowed by documentation here>.
1488		1825
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1826	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1827	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1828	only event loop modification you are allowed to do).
1492		1829
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1830	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1831	*w, ev_tstamp now)>, e.g.:
1495		1832
		1833	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1834	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1835	{
1498	return now + 60.;	1836	return now + 60.;
1499	}	1837	}
1500		1838
1501	It must return the next time to trigger, based on the passed time value	1839	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	1859	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	1860	program when the crontabs have changed).
1523		1861
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	1862	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		1863
1526	When active, returns the absolute time that the watcher is supposed to	1864	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	1865	to trigger next. This is not the same as the C<offset> argument to
		1866	C<ev_periodic_set>, but indeed works even in interval and manual
		1867	rescheduling modes.
1528		1868
1529	=item ev_tstamp offset [read-write]	1869	=item ev_tstamp offset [read-write]
1530		1870
1531	When repeating, this contains the offset value, otherwise this is the	1871	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1872	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1873	although libev might modify this value for better numerical stability).
1533		1874
1534	Can be modified any time, but changes only take effect when the periodic	1875	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	1876	timer fires or C<ev_periodic_again> is being called.
1536		1877
1537	=item ev_tstamp interval [read-write]	1878	=item ev_tstamp interval [read-write]
1538		1879
1539	The current interval value. Can be modified any time, but changes only	1880	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	1881	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1882	called.
1542		1883
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1884	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		1885
1545	The current reschedule callback, or C<0>, if this functionality is	1886	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	1887	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	1888	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1889
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1894	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1895	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1896	potentially a lot of jitter, but good long-term stability.
1556		1897
1557	static void	1898	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1899	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	1900	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1901	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1902	}
1562		1903
1563	struct ev_periodic hourly_tick;	1904	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1905	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1906	ev_periodic_start (loop, &hourly_tick);
1566		1907
1567	Example: The same as above, but use a reschedule callback to do it:	1908	Example: The same as above, but use a reschedule callback to do it:
1568		1909
1569	#include <math.h>	1910	#include <math.h>
1570		1911
1571	static ev_tstamp	1912	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1913	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1914	{
1574	return now + (3600. - fmod (now, 3600.));	1915	return now + (3600. - fmod (now, 3600.));
1575	}	1916	}
1576		1917
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1918	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1919
1579	Example: Call a callback every hour, starting now:	1920	Example: Call a callback every hour, starting now:
1580		1921
1581	struct ev_periodic hourly_tick;	1922	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1923	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1924	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1925	ev_periodic_start (loop, &hourly_tick);
1585		1926
1586		1927
…		…
1625		1966
1626	=back	1967	=back
1627		1968
1628	=head3 Examples	1969	=head3 Examples
1629		1970
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1971	Example: Try to exit cleanly on SIGINT.
1631		1972
1632	static void	1973	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1974	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	1975	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1976	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1977	}
1637		1978
1638	struct ev_signal signal_watcher;	1979	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1980	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1981	ev_signal_start (loop, &signal_watcher);
1641		1982
1642		1983
1643	=head2 C<ev_child> - watch out for process status changes	1984	=head2 C<ev_child> - watch out for process status changes
1644		1985
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1986	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	2059	its completion.
1719		2060
1720	ev_child cw;	2061	ev_child cw;
1721		2062
1722	static void	2063	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2064	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2065	{
1725	ev_child_stop (EV_A_ w);	2066	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2067	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2068	}
1728		2069
…		…
1743		2084
1744		2085
1745	=head2 C<ev_stat> - did the file attributes just change?	2086	=head2 C<ev_stat> - did the file attributes just change?
1746		2087
1747	This watches a file system path for attribute changes. That is, it calls	2088	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2089	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2090	and sees if it changed compared to the last time, invoking the callback if
		2091	it did.
1750		2092
1751	The path does not need to exist: changing from "path exists" to "path does	2093	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	2094	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	2095	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	2096	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2097	least one) and all the other fields of the stat buffer having unspecified
		2098	contents.
1756		2099
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2100	The path I<must not> end in a slash or contain special components such as
		2101	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2102	your working directory changes, then the behaviour is undefined.
1759		2103
1760	Since there is no standard kernel interface to do this, the portable	2104	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2105	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2106	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2107	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2108	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2109	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2110	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2111	currently around C<0.1>, but that's usually overkill.
1768		2112
1769	This watcher type is not meant for massive numbers of stat watchers,	2113	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2114	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2115	resource-intensive.
1772		2116
1773	At the time of this writing, the only OS-specific interface implemented	2117	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2118	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	2119	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2120	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2121
1778	=head3 ABI Issues (Largefile Support)	2122	=head3 ABI Issues (Largefile Support)
1779		2123
1780	Libev by default (unless the user overrides this) uses the default	2124	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2125	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2126	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2127	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2128	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2129	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2130	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2131	most noticeably displayed with ev_stat and large file support.
1788		2132
1789	The solution for this is to lobby your distribution maker to make large	2133	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2134	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2135	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2136	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2137	default compilation environment.
1794		2138
1795	=head3 Inotify and Kqueue	2139	=head3 Inotify and Kqueue
1796		2140
1797	When C<inotify (7)> support has been compiled into libev (generally only	2141	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2142	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2143	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2144	watcher is being started.
1801		2145
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2146	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2147	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2148	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2149	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2150	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2151	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2152	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2153	xfs are fully working) libev usually gets away without polling.
1807		2154
1808	There is no support for kqueue, as apparently it cannot be used to	2155	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2156	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2157	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2158	etc. is difficult.
1812		2159
		2160	=head3 C<stat ()> is a synchronous operation
		2161
		2162	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2163	the process. The exception are C<ev_stat> watchers - those call C<stat
		2164	()>, which is a synchronous operation.
		2165
		2166	For local paths, this usually doesn't matter: unless the system is very
		2167	busy or the intervals between stat's are large, a stat call will be fast,
		2168	as the path data is usually in memory already (except when starting the
		2169	watcher).
		2170
		2171	For networked file systems, calling C<stat ()> can block an indefinite
		2172	time due to network issues, and even under good conditions, a stat call
		2173	often takes multiple milliseconds.
		2174
		2175	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2176	paths, although this is fully supported by libev.
		2177
1813	=head3 The special problem of stat time resolution	2178	=head3 The special problem of stat time resolution
1814		2179
1815	The C<stat ()> system call only supports full-second resolution portably, and	2180	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2181	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2182	still only support whole seconds.
1818		2183
1819	That means that, if the time is the only thing that changes, you can	2184	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2185	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2186	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2187	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2330
1966	=head3 Watcher-Specific Functions and Data Members	2331	=head3 Watcher-Specific Functions and Data Members
1967		2332
1968	=over 4	2333	=over 4
1969		2334
1970	=item ev_idle_init (ev_signal *, callback)	2335	=item ev_idle_init (ev_idle *, callback)
1971		2336
1972	Initialises and configures the idle watcher - it has no parameters of any	2337	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2338	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2339	believe me.
1975		2340
…		…
1979		2344
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2345	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2346	callback, free it. Also, use no error checking, as usual.
1982		2347
1983	static void	2348	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2349	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2350	{
1986	free (w);	2351	free (w);
1987	// now do something you wanted to do when the program has	2352	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2353	// no longer anything immediate to do.
1989	}	2354	}
1990		2355
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2356	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2357	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2358	ev_idle_start (loop, idle_cb);
1994		2359
1995		2360
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2361	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2442
2078	static ev_io iow [nfd];	2443	static ev_io iow [nfd];
2079	static ev_timer tw;	2444	static ev_timer tw;
2080		2445
2081	static void	2446	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2447	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2448	{
2084	}	2449	}
2085		2450
2086	// create io watchers for each fd and a timer before blocking	2451	// create io watchers for each fd and a timer before blocking
2087	static void	2452	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2453	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2454	{
2090	int timeout = 3600000;	2455	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2456	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2457	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2458	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2473	}
2109	}	2474	}
2110		2475
2111	// stop all watchers after blocking	2476	// stop all watchers after blocking
2112	static void	2477	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2478	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2479	{
2115	ev_timer_stop (loop, &tw);	2480	ev_timer_stop (loop, &tw);
2116		2481
2117	for (int i = 0; i < nfd; ++i)	2482	for (int i = 0; i < nfd; ++i)
2118	{	2483	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2579	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2580	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2581	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2582	the rest in a second one, and embed the second one in the first.
2218		2583
2219	As long as the watcher is active, the callback will be invoked every time	2584	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2585	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2586	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2587	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2588	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2589	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2590
2227	As long as the watcher is started it will automatically handle events. The	2591	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2592	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2593
2232	Also, there have not currently been made special provisions for forking:	2594	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2595	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2596	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2597	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2598
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2599	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2600	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2601	portable one.
2241		2602
2242	So when you want to use this feature you will always have to be prepared	2603	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2604	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2605	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2606	create it, and if that fails, use the normal loop for everything.
		2607
		2608	=head3 C<ev_embed> and fork
		2609
		2610	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2611	automatically be applied to the embedded loop as well, so no special
		2612	fork handling is required in that case. When the watcher is not running,
		2613	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2614	as applicable.
2246		2615
2247	=head3 Watcher-Specific Functions and Data Members	2616	=head3 Watcher-Specific Functions and Data Members
2248		2617
2249	=over 4	2618	=over 4
2250		2619
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2647	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2648	used).
2280		2649
2281	struct ev_loop *loop_hi = ev_default_init (0);	2650	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2651	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2652	ev_embed embed;
2284		2653
2285	// see if there is a chance of getting one that works	2654	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2655	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2656	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2657	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2671	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2672	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2673
2305	struct ev_loop *loop = ev_default_init (0);	2674	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2675	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2676	ev_embed embed;
2308		2677
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2678	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2679	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2680	{
2312	ev_embed_init (&embed, 0, loop_socket);	2681	ev_embed_init (&embed, 0, loop_socket);
…		…
2376	=over 4	2745	=over 4
2377		2746
2378	=item queueing from a signal handler context	2747	=item queueing from a signal handler context
2379		2748
2380	To implement race-free queueing, you simply add to the queue in the signal	2749	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2750	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2751	an example that does that for some fictitious SIGUSR1 handler:
2383		2752
2384	static ev_async mysig;	2753	static ev_async mysig;
2385		2754
2386	static void	2755	static void
2387	sigusr1_handler (void)	2756	sigusr1_handler (void)
…		…
2453	=over 4	2822	=over 4
2454		2823
2455	=item ev_async_init (ev_async *, callback)	2824	=item ev_async_init (ev_async *, callback)
2456		2825
2457	Initialises and configures the async watcher - it has no parameters of any	2826	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2827	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	trust me.	2828	trust me.
2460		2829
2461	=item ev_async_send (loop, ev_async *)	2830	=item ev_async_send (loop, ev_async *)
2462		2831
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2832	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2833	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do from other threads, signal or	2834	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2835	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2836	section below on what exactly this means).
2468		2837
		2838	Note that, as with other watchers in libev, multiple events might get
		2839	compressed into a single callback invocation (another way to look at this
		2840	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2841	reset when the event loop detects that).
		2842
2469	This call incurs the overhead of a system call only once per loop iteration,	2843	This call incurs the overhead of a system call only once per event loop
2470	so while the overhead might be noticeable, it doesn't apply to repeated	2844	iteration, so while the overhead might be noticeable, it doesn't apply to
2471	calls to C<ev_async_send>.	2845	repeated calls to C<ev_async_send> for the same event loop.
2472		2846
2473	=item bool = ev_async_pending (ev_async *)	2847	=item bool = ev_async_pending (ev_async *)
2474		2848
2475	Returns a non-zero value when C<ev_async_send> has been called on the	2849	Returns a non-zero value when C<ev_async_send> has been called on the
2476	watcher but the event has not yet been processed (or even noted) by the	2850	watcher but the event has not yet been processed (or even noted) by the
…		…
2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2853	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2480	the loop iterates next and checks for the watcher to have become active,	2854	the loop iterates next and checks for the watcher to have become active,
2481	it will reset the flag again. C<ev_async_pending> can be used to very	2855	it will reset the flag again. C<ev_async_pending> can be used to very
2482	quickly check whether invoking the loop might be a good idea.	2856	quickly check whether invoking the loop might be a good idea.
2483		2857
2484	Not that this does I<not> check whether the watcher itself is pending, only	2858	Not that this does I<not> check whether the watcher itself is pending,
2485	whether it has been requested to make this watcher pending.	2859	only whether it has been requested to make this watcher pending: there
		2860	is a time window between the event loop checking and resetting the async
		2861	notification, and the callback being invoked.
2486		2862
2487	=back	2863	=back
2488		2864
2489		2865
2490	=head1 OTHER FUNCTIONS	2866	=head1 OTHER FUNCTIONS
…		…
2494	=over 4	2870	=over 4
2495		2871
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2872	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2873
2498	This function combines a simple timer and an I/O watcher, calls your	2874	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2875	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	2876	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	2877	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2878	more watchers yourself.
2503		2879
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2880	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2881	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2882	the given C<fd> and C<events> set will be created and started.
2507		2883
2508	If C<timeout> is less than 0, then no timeout watcher will be	2884	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2885	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2886	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2887
2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2888	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2514	passed an C<revents> set like normal event callbacks (a combination of	2889	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2890	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2891	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2892	a timeout and an io event at the same time - you probably should give io
		2893	events precedence.
		2894
		2895	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2896
2518	static void stdin_ready (int revents, void *arg)	2897	static void stdin_ready (int revents, void *arg)
2519	{	2898	{
		2899	if (revents & EV_READ)
		2900	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2901	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2902	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2903	}
2525		2904
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2905	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2906
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)	2907	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2529		2908
2530	Feeds the given event set into the event loop, as if the specified event	2909	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an	2910	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2911	initialised but not necessarily started event watcher).
2533		2912
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2913	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2914
2536	Feed an event on the given fd, as if a file descriptor backend detected	2915	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2916	the given events it.
2538		2917
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2918	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2919
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2920	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2921	loop!).
2543		2922
2544	=back	2923	=back
…		…
2665	}	3044	}
2666		3045
2667	myclass obj;	3046	myclass obj;
2668	ev::io iow;	3047	ev::io iow;
2669	iow.set <myclass, &myclass::io_cb> (&obj);	3048	iow.set <myclass, &myclass::io_cb> (&obj);
		3049
		3050	=item w->set (object *)
		3051
		3052	This is an B<experimental> feature that might go away in a future version.
		3053
		3054	This is a variation of a method callback - leaving out the method to call
		3055	will default the method to C<operator ()>, which makes it possible to use
		3056	functor objects without having to manually specify the C<operator ()> all
		3057	the time. Incidentally, you can then also leave out the template argument
		3058	list.
		3059
		3060	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3061	int revents)>.
		3062
		3063	See the method-C<set> above for more details.
		3064
		3065	Example: use a functor object as callback.
		3066
		3067	struct myfunctor
		3068	{
		3069	void operator() (ev::io &w, int revents)
		3070	{
		3071	...
		3072	}
		3073	}
		3074
		3075	myfunctor f;
		3076
		3077	ev::io w;
		3078	w.set (&f);
2670		3079
2671	=item w->set<function> (void *data = 0)	3080	=item w->set<function> (void *data = 0)
2672		3081
2673	Also sets a callback, but uses a static method or plain function as	3082	Also sets a callback, but uses a static method or plain function as
2674	callback. The optional C<data> argument will be stored in the watcher's	3083	callback. The optional C<data> argument will be stored in the watcher's
…		…
2761	L<http://software.schmorp.de/pkg/EV>.	3170	L<http://software.schmorp.de/pkg/EV>.
2762		3171
2763	=item Python	3172	=item Python
2764		3173
2765	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3174	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2766	seems to be quite complete and well-documented. Note, however, that the	3175	seems to be quite complete and well-documented.
2767	patch they require for libev is outright dangerous as it breaks the ABI
2768	for everybody else, and therefore, should never be applied in an installed
2769	libev (if python requires an incompatible ABI then it needs to embed
2770	libev).
2771		3176
2772	=item Ruby	3177	=item Ruby
2773		3178
2774	Tony Arcieri has written a ruby extension that offers access to a subset	3179	Tony Arcieri has written a ruby extension that offers access to a subset
2775	of the libev API and adds file handle abstractions, asynchronous DNS and	3180	of the libev API and adds file handle abstractions, asynchronous DNS and
2776	more on top of it. It can be found via gem servers. Its homepage is at	3181	more on top of it. It can be found via gem servers. Its homepage is at
2777	L<http://rev.rubyforge.org/>.	3182	L<http://rev.rubyforge.org/>.
2778		3183
		3184	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3185	makes rev work even on mingw.
		3186
		3187	=item Haskell
		3188
		3189	A haskell binding to libev is available at
		3190	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3191
2779	=item D	3192	=item D
2780		3193
2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3194	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3195	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3196
		3197	=item Ocaml
		3198
		3199	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3200	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2783		3201
2784	=back	3202	=back
2785		3203
2786		3204
2787	=head1 MACRO MAGIC	3205	=head1 MACRO MAGIC
…		…
2888		3306
2889	#define EV_STANDALONE 1	3307	#define EV_STANDALONE 1
2890	#include "ev.h"	3308	#include "ev.h"
2891		3309
2892	Both header files and implementation files can be compiled with a C++	3310	Both header files and implementation files can be compiled with a C++
2893	compiler (at least, thats a stated goal, and breakage will be treated	3311	compiler (at least, that's a stated goal, and breakage will be treated
2894	as a bug).	3312	as a bug).
2895		3313
2896	You need the following files in your source tree, or in a directory	3314	You need the following files in your source tree, or in a directory
2897	in your include path (e.g. in libev/ when using -Ilibev):	3315	in your include path (e.g. in libev/ when using -Ilibev):
2898		3316
…		…
2954	keeps libev from including F<config.h>, and it also defines dummy	3372	keeps libev from including F<config.h>, and it also defines dummy
2955	implementations for some libevent functions (such as logging, which is not	3373	implementations for some libevent functions (such as logging, which is not
2956	supported). It will also not define any of the structs usually found in	3374	supported). It will also not define any of the structs usually found in
2957	F<event.h> that are not directly supported by the libev core alone.	3375	F<event.h> that are not directly supported by the libev core alone.
2958		3376
		3377	In stanbdalone mode, libev will still try to automatically deduce the
		3378	configuration, but has to be more conservative.
		3379
2959	=item EV_USE_MONOTONIC	3380	=item EV_USE_MONOTONIC
2960		3381
2961	If defined to be C<1>, libev will try to detect the availability of the	3382	If defined to be C<1>, libev will try to detect the availability of the
2962	monotonic clock option at both compile time and runtime. Otherwise no use	3383	monotonic clock option at both compile time and runtime. Otherwise no
2963	of the monotonic clock option will be attempted. If you enable this, you	3384	use of the monotonic clock option will be attempted. If you enable this,
2964	usually have to link against librt or something similar. Enabling it when	3385	you usually have to link against librt or something similar. Enabling it
2965	the functionality isn't available is safe, though, although you have	3386	when the functionality isn't available is safe, though, although you have
2966	to make sure you link against any libraries where the C<clock_gettime>	3387	to make sure you link against any libraries where the C<clock_gettime>
2967	function is hiding in (often F<-lrt>).	3388	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2968		3389
2969	=item EV_USE_REALTIME	3390	=item EV_USE_REALTIME
2970		3391
2971	If defined to be C<1>, libev will try to detect the availability of the	3392	If defined to be C<1>, libev will try to detect the availability of the
2972	real-time clock option at compile time (and assume its availability at	3393	real-time clock option at compile time (and assume its availability
2973	runtime if successful). Otherwise no use of the real-time clock option will	3394	at runtime if successful). Otherwise no use of the real-time clock
2974	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3395	option will be attempted. This effectively replaces C<gettimeofday>
2975	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3396	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2976	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3397	correctness. See the note about libraries in the description of
		3398	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3399	C<EV_USE_CLOCK_SYSCALL>.
		3400
		3401	=item EV_USE_CLOCK_SYSCALL
		3402
		3403	If defined to be C<1>, libev will try to use a direct syscall instead
		3404	of calling the system-provided C<clock_gettime> function. This option
		3405	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3406	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3407	programs needlessly. Using a direct syscall is slightly slower (in
		3408	theory), because no optimised vdso implementation can be used, but avoids
		3409	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3410	higher, as it simplifies linking (no need for C<-lrt>).
2977		3411
2978	=item EV_USE_NANOSLEEP	3412	=item EV_USE_NANOSLEEP
2979		3413
2980	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3414	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2981	and will use it for delays. Otherwise it will use C<select ()>.	3415	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2997		3431
2998	=item EV_SELECT_USE_FD_SET	3432	=item EV_SELECT_USE_FD_SET
2999		3433
3000	If defined to C<1>, then the select backend will use the system C<fd_set>	3434	If defined to C<1>, then the select backend will use the system C<fd_set>
3001	structure. This is useful if libev doesn't compile due to a missing	3435	structure. This is useful if libev doesn't compile due to a missing
3002	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3436	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3003	exotic systems. This usually limits the range of file descriptors to some	3437	on exotic systems. This usually limits the range of file descriptors to
3004	low limit such as 1024 or might have other limitations (winsocket only	3438	some low limit such as 1024 or might have other limitations (winsocket
3005	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3439	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3006	influence the size of the C<fd_set> used.	3440	configures the maximum size of the C<fd_set>.
3007		3441
3008	=item EV_SELECT_IS_WINSOCKET	3442	=item EV_SELECT_IS_WINSOCKET
3009		3443
3010	When defined to C<1>, the select backend will assume that	3444	When defined to C<1>, the select backend will assume that
3011	select/socket/connect etc. don't understand file descriptors but	3445	select/socket/connect etc. don't understand file descriptors but
…		…
3298	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3732	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3299		3733
3300	#include "ev_cpp.h"	3734	#include "ev_cpp.h"
3301	#include "ev.c"	3735	#include "ev.c"
3302		3736
		3737	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3303		3738
3304	=head1 THREADS AND COROUTINES	3739	=head2 THREADS AND COROUTINES
3305		3740
3306	=head2 THREADS	3741	=head3 THREADS
3307		3742
3308	Libev itself is thread-safe (unless the opposite is specifically	3743	All libev functions are reentrant and thread-safe unless explicitly
3309	documented for a function), but it uses no locking itself. This means that	3744	documented otherwise, but libev implements no locking itself. This means
3310	you can use as many loops as you want in parallel, as long as only one	3745	that you can use as many loops as you want in parallel, as long as there
3311	thread ever calls into one libev function with the same loop parameter:	3746	are no concurrent calls into any libev function with the same loop
		3747	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3312	libev guarantees that different event loops share no data structures that	3748	of course): libev guarantees that different event loops share no data
3313	need locking.	3749	structures that need any locking.
3314		3750
3315	Or to put it differently: calls with different loop parameters can be done	3751	Or to put it differently: calls with different loop parameters can be done
3316	concurrently from multiple threads, calls with the same loop parameter	3752	concurrently from multiple threads, calls with the same loop parameter
3317	must be done serially (but can be done from different threads, as long as	3753	must be done serially (but can be done from different threads, as long as
3318	only one thread ever is inside a call at any point in time, e.g. by using	3754	only one thread ever is inside a call at any point in time, e.g. by using
3319	a mutex per loop).	3755	a mutex per loop).
3320		3756
3321	Specifically to support threads (and signal handlers), libev implements	3757	Specifically to support threads (and signal handlers), libev implements
3322	so-called C<ev_async> watchers, which allow some limited form of	3758	so-called C<ev_async> watchers, which allow some limited form of
3323	concurrency on the same event loop.	3759	concurrency on the same event loop, namely waking it up "from the
		3760	outside".
3324		3761
3325	If you want to know which design (one loop, locking, or multiple loops	3762	If you want to know which design (one loop, locking, or multiple loops
3326	without or something else still) is best for your problem, then I cannot	3763	without or something else still) is best for your problem, then I cannot
3327	help you. I can give some generic advice however:	3764	help you, but here is some generic advice:
3328		3765
3329	=over 4	3766	=over 4
3330		3767
3331	=item * most applications have a main thread: use the default libev loop	3768	=item * most applications have a main thread: use the default libev loop
3332	in that thread, or create a separate thread running only the default loop.	3769	in that thread, or create a separate thread running only the default loop.
…		…
3356	default loop and triggering an C<ev_async> watcher from the default loop	3793	default loop and triggering an C<ev_async> watcher from the default loop
3357	watcher callback into the event loop interested in the signal.	3794	watcher callback into the event loop interested in the signal.
3358		3795
3359	=back	3796	=back
3360		3797
3361	=head2 COROUTINES	3798	=head3 COROUTINES
3362		3799
3363	Libev is much more accommodating to coroutines ("cooperative threads"):	3800	Libev is very accommodating to coroutines ("cooperative threads"):
3364	libev fully supports nesting calls to it's functions from different	3801	libev fully supports nesting calls to its functions from different
3365	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3802	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3366	different coroutines and switch freely between both coroutines running the	3803	different coroutines, and switch freely between both coroutines running the
3367	loop, as long as you don't confuse yourself). The only exception is that	3804	loop, as long as you don't confuse yourself). The only exception is that
3368	you must not do this from C<ev_periodic> reschedule callbacks.	3805	you must not do this from C<ev_periodic> reschedule callbacks.
3369		3806
3370	Care has been taken to ensure that libev does not keep local state inside	3807	Care has been taken to ensure that libev does not keep local state inside
3371	C<ev_loop>, and other calls do not usually allow coroutine switches.	3808	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3809	they do not call any callbacks.
3372		3810
		3811	=head2 COMPILER WARNINGS
3373		3812
3374	=head1 COMPLEXITIES	3813	Depending on your compiler and compiler settings, you might get no or a
		3814	lot of warnings when compiling libev code. Some people are apparently
		3815	scared by this.
3375		3816
3376	In this section the complexities of (many of) the algorithms used inside	3817	However, these are unavoidable for many reasons. For one, each compiler
3377	libev will be explained. For complexity discussions about backends see the	3818	has different warnings, and each user has different tastes regarding
3378	documentation for C<ev_default_init>.	3819	warning options. "Warn-free" code therefore cannot be a goal except when
		3820	targeting a specific compiler and compiler-version.
3379		3821
3380	All of the following are about amortised time: If an array needs to be	3822	Another reason is that some compiler warnings require elaborate
3381	extended, libev needs to realloc and move the whole array, but this	3823	workarounds, or other changes to the code that make it less clear and less
3382	happens asymptotically never with higher number of elements, so O(1) might	3824	maintainable.
3383	mean it might do a lengthy realloc operation in rare cases, but on average
3384	it is much faster and asymptotically approaches constant time.
3385		3825
3386	=over 4	3826	And of course, some compiler warnings are just plain stupid, or simply
		3827	wrong (because they don't actually warn about the condition their message
		3828	seems to warn about). For example, certain older gcc versions had some
		3829	warnings that resulted an extreme number of false positives. These have
		3830	been fixed, but some people still insist on making code warn-free with
		3831	such buggy versions.
3387		3832
3388	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3833	While libev is written to generate as few warnings as possible,
		3834	"warn-free" code is not a goal, and it is recommended not to build libev
		3835	with any compiler warnings enabled unless you are prepared to cope with
		3836	them (e.g. by ignoring them). Remember that warnings are just that:
		3837	warnings, not errors, or proof of bugs.
3389		3838
3390	This means that, when you have a watcher that triggers in one hour and
3391	there are 100 watchers that would trigger before that then inserting will
3392	have to skip roughly seven (C<ld 100>) of these watchers.
3393		3839
3394	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3840	=head2 VALGRIND
3395		3841
3396	That means that changing a timer costs less than removing/adding them	3842	Valgrind has a special section here because it is a popular tool that is
3397	as only the relative motion in the event queue has to be paid for.	3843	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3398		3844
3399	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3845	If you think you found a bug (memory leak, uninitialised data access etc.)
		3846	in libev, then check twice: If valgrind reports something like:
3400		3847
3401	These just add the watcher into an array or at the head of a list.	3848	==2274== definitely lost: 0 bytes in 0 blocks.
		3849	==2274== possibly lost: 0 bytes in 0 blocks.
		3850	==2274== still reachable: 256 bytes in 1 blocks.
3402		3851
3403	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3852	Then there is no memory leak, just as memory accounted to global variables
		3853	is not a memleak - the memory is still being referenced, and didn't leak.
3404		3854
3405	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3855	Similarly, under some circumstances, valgrind might report kernel bugs
		3856	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3857	although an acceptable workaround has been found here), or it might be
		3858	confused.
3406		3859
3407	These watchers are stored in lists then need to be walked to find the	3860	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3408	correct watcher to remove. The lists are usually short (you don't usually	3861	make it into some kind of religion.
3409	have many watchers waiting for the same fd or signal).
3410		3862
3411	=item Finding the next timer in each loop iteration: O(1)	3863	If you are unsure about something, feel free to contact the mailing list
		3864	with the full valgrind report and an explanation on why you think this
		3865	is a bug in libev (best check the archives, too :). However, don't be
		3866	annoyed when you get a brisk "this is no bug" answer and take the chance
		3867	of learning how to interpret valgrind properly.
3412		3868
3413	By virtue of using a binary or 4-heap, the next timer is always found at a	3869	If you need, for some reason, empty reports from valgrind for your project
3414	fixed position in the storage array.	3870	I suggest using suppression lists.
3415		3871
3416	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3417		3872
3418	A change means an I/O watcher gets started or stopped, which requires	3873	=head1 PORTABILITY NOTES
3419	libev to recalculate its status (and possibly tell the kernel, depending
3420	on backend and whether C<ev_io_set> was used).
3421		3874
3422	=item Activating one watcher (putting it into the pending state): O(1)
3423
3424	=item Priority handling: O(number_of_priorities)
3425
3426	Priorities are implemented by allocating some space for each
3427	priority. When doing priority-based operations, libev usually has to
3428	linearly search all the priorities, but starting/stopping and activating
3429	watchers becomes O(1) with respect to priority handling.
3430
3431	=item Sending an ev_async: O(1)
3432
3433	=item Processing ev_async_send: O(number_of_async_watchers)
3434
3435	=item Processing signals: O(max_signal_number)
3436
3437	Sending involves a system call I<iff> there were no other C<ev_async_send>
3438	calls in the current loop iteration. Checking for async and signal events
3439	involves iterating over all running async watchers or all signal numbers.
3440
3441	=back
3442
3443
3444	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3875	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3445		3876
3446	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3877	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3447	requires, and its I/O model is fundamentally incompatible with the POSIX	3878	requires, and its I/O model is fundamentally incompatible with the POSIX
3448	model. Libev still offers limited functionality on this platform in	3879	model. Libev still offers limited functionality on this platform in
3449	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3880	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3536	wrap all I/O functions and provide your own fd management, but the cost of	3967	wrap all I/O functions and provide your own fd management, but the cost of
3537	calling select (O(n²)) will likely make this unworkable.	3968	calling select (O(n²)) will likely make this unworkable.
3538		3969
3539	=back	3970	=back
3540		3971
3541
3542	=head1 PORTABILITY REQUIREMENTS	3972	=head2 PORTABILITY REQUIREMENTS
3543		3973
3544	In addition to a working ISO-C implementation, libev relies on a few	3974	In addition to a working ISO-C implementation and of course the
3545	additional extensions:	3975	backend-specific APIs, libev relies on a few additional extensions:
3546		3976
3547	=over 4	3977	=over 4
3548		3978
3549	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3979	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3550	calling conventions regardless of C<ev_watcher_type *>.	3980	calling conventions regardless of C<ev_watcher_type *>.
…		…
3575	except the initial one, and run the default loop in the initial thread as	4005	except the initial one, and run the default loop in the initial thread as
3576	well.	4006	well.
3577		4007
3578	=item C<long> must be large enough for common memory allocation sizes	4008	=item C<long> must be large enough for common memory allocation sizes
3579		4009
3580	To improve portability and simplify using libev, libev uses C<long>	4010	To improve portability and simplify its API, libev uses C<long> internally
3581	internally instead of C<size_t> when allocating its data structures. On	4011	instead of C<size_t> when allocating its data structures. On non-POSIX
3582	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4012	systems (Microsoft...) this might be unexpectedly low, but is still at
3583	is still at least 31 bits everywhere, which is enough for hundreds of	4013	least 31 bits everywhere, which is enough for hundreds of millions of
3584	millions of watchers.	4014	watchers.
3585		4015
3586	=item C<double> must hold a time value in seconds with enough accuracy	4016	=item C<double> must hold a time value in seconds with enough accuracy
3587		4017
3588	The type C<double> is used to represent timestamps. It is required to	4018	The type C<double> is used to represent timestamps. It is required to
3589	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4019	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3593	=back	4023	=back
3594		4024
3595	If you know of other additional requirements drop me a note.	4025	If you know of other additional requirements drop me a note.
3596		4026
3597		4027
3598	=head1 COMPILER WARNINGS	4028	=head1 ALGORITHMIC COMPLEXITIES
3599		4029
3600	Depending on your compiler and compiler settings, you might get no or a	4030	In this section the complexities of (many of) the algorithms used inside
3601	lot of warnings when compiling libev code. Some people are apparently	4031	libev will be documented. For complexity discussions about backends see
3602	scared by this.	4032	the documentation for C<ev_default_init>.
3603		4033
3604	However, these are unavoidable for many reasons. For one, each compiler	4034	All of the following are about amortised time: If an array needs to be
3605	has different warnings, and each user has different tastes regarding	4035	extended, libev needs to realloc and move the whole array, but this
3606	warning options. "Warn-free" code therefore cannot be a goal except when	4036	happens asymptotically rarer with higher number of elements, so O(1) might
3607	targeting a specific compiler and compiler-version.	4037	mean that libev does a lengthy realloc operation in rare cases, but on
		4038	average it is much faster and asymptotically approaches constant time.
3608		4039
3609	Another reason is that some compiler warnings require elaborate	4040	=over 4
3610	workarounds, or other changes to the code that make it less clear and less
3611	maintainable.
3612		4041
3613	And of course, some compiler warnings are just plain stupid, or simply	4042	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3614	wrong (because they don't actually warn about the condition their message
3615	seems to warn about).
3616		4043
3617	While libev is written to generate as few warnings as possible,	4044	This means that, when you have a watcher that triggers in one hour and
3618	"warn-free" code is not a goal, and it is recommended not to build libev	4045	there are 100 watchers that would trigger before that, then inserting will
3619	with any compiler warnings enabled unless you are prepared to cope with	4046	have to skip roughly seven (C<ld 100>) of these watchers.
3620	them (e.g. by ignoring them). Remember that warnings are just that:
3621	warnings, not errors, or proof of bugs.
3622		4047
		4048	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3623		4049
3624	=head1 VALGRIND	4050	That means that changing a timer costs less than removing/adding them,
		4051	as only the relative motion in the event queue has to be paid for.
3625		4052
3626	Valgrind has a special section here because it is a popular tool that is	4053	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3627	highly useful, but valgrind reports are very hard to interpret.
3628		4054
3629	If you think you found a bug (memory leak, uninitialised data access etc.)	4055	These just add the watcher into an array or at the head of a list.
3630	in libev, then check twice: If valgrind reports something like:
3631		4056
3632	==2274== definitely lost: 0 bytes in 0 blocks.	4057	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3633	==2274== possibly lost: 0 bytes in 0 blocks.
3634	==2274== still reachable: 256 bytes in 1 blocks.
3635		4058
3636	Then there is no memory leak. Similarly, under some circumstances,	4059	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3637	valgrind might report kernel bugs as if it were a bug in libev, or it
3638	might be confused (it is a very good tool, but only a tool).
3639		4060
3640	If you are unsure about something, feel free to contact the mailing list	4061	These watchers are stored in lists, so they need to be walked to find the
3641	with the full valgrind report and an explanation on why you think this is	4062	correct watcher to remove. The lists are usually short (you don't usually
3642	a bug in libev. However, don't be annoyed when you get a brisk "this is	4063	have many watchers waiting for the same fd or signal: one is typical, two
3643	no bug" answer and take the chance of learning how to interpret valgrind	4064	is rare).
3644	properly.
3645		4065
3646	If you need, for some reason, empty reports from valgrind for your project	4066	=item Finding the next timer in each loop iteration: O(1)
3647	I suggest using suppression lists.
3648		4067
		4068	By virtue of using a binary or 4-heap, the next timer is always found at a
		4069	fixed position in the storage array.
		4070
		4071	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4072
		4073	A change means an I/O watcher gets started or stopped, which requires
		4074	libev to recalculate its status (and possibly tell the kernel, depending
		4075	on backend and whether C<ev_io_set> was used).
		4076
		4077	=item Activating one watcher (putting it into the pending state): O(1)
		4078
		4079	=item Priority handling: O(number_of_priorities)
		4080
		4081	Priorities are implemented by allocating some space for each
		4082	priority. When doing priority-based operations, libev usually has to
		4083	linearly search all the priorities, but starting/stopping and activating
		4084	watchers becomes O(1) with respect to priority handling.
		4085
		4086	=item Sending an ev_async: O(1)
		4087
		4088	=item Processing ev_async_send: O(number_of_async_watchers)
		4089
		4090	=item Processing signals: O(max_signal_number)
		4091
		4092	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4093	calls in the current loop iteration. Checking for async and signal events
		4094	involves iterating over all running async watchers or all signal numbers.
		4095
		4096	=back
		4097
		4098
		4099	=head1 GLOSSARY
		4100
		4101	=over 4
		4102
		4103	=item active
		4104
		4105	A watcher is active as long as it has been started (has been attached to
		4106	an event loop) but not yet stopped (disassociated from the event loop).
		4107
		4108	=item application
		4109
		4110	In this document, an application is whatever is using libev.
		4111
		4112	=item callback
		4113
		4114	The address of a function that is called when some event has been
		4115	detected. Callbacks are being passed the event loop, the watcher that
		4116	received the event, and the actual event bitset.
		4117
		4118	=item callback invocation
		4119
		4120	The act of calling the callback associated with a watcher.
		4121
		4122	=item event
		4123
		4124	A change of state of some external event, such as data now being available
		4125	for reading on a file descriptor, time having passed or simply not having
		4126	any other events happening anymore.
		4127
		4128	In libev, events are represented as single bits (such as C<EV_READ> or
		4129	C<EV_TIMEOUT>).
		4130
		4131	=item event library
		4132
		4133	A software package implementing an event model and loop.
		4134
		4135	=item event loop
		4136
		4137	An entity that handles and processes external events and converts them
		4138	into callback invocations.
		4139
		4140	=item event model
		4141
		4142	The model used to describe how an event loop handles and processes
		4143	watchers and events.
		4144
		4145	=item pending
		4146
		4147	A watcher is pending as soon as the corresponding event has been detected,
		4148	and stops being pending as soon as the watcher will be invoked or its
		4149	pending status is explicitly cleared by the application.
		4150
		4151	A watcher can be pending, but not active. Stopping a watcher also clears
		4152	its pending status.
		4153
		4154	=item real time
		4155
		4156	The physical time that is observed. It is apparently strictly monotonic :)
		4157
		4158	=item wall-clock time
		4159
		4160	The time and date as shown on clocks. Unlike real time, it can actually
		4161	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4162	clock.
		4163
		4164	=item watcher
		4165
		4166	A data structure that describes interest in certain events. Watchers need
		4167	to be started (attached to an event loop) before they can receive events.
		4168
		4169	=item watcher invocation
		4170
		4171	The act of calling the callback associated with a watcher.
		4172
		4173	=back
3649		4174
3650	=head1 AUTHOR	4175	=head1 AUTHOR
3651		4176
3652	Marc Lehmann <libev@schmorp.de>.	4177	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3653		4178

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