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Revision 1.231 by root, Wed Apr 15 19:35:53 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
…		…
1024	The default priority used by watchers when no priority has been set is	1099	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 :).	1100	always C<0>, which is supposed to not be too high and not be too low :).
1026		1101
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1028	fine, as long as you do not mind that the priority value you query might	1103	fine, as long as you do not mind that the priority value you query might
1029	or might not have been adjusted to be within valid range.	1104	or might not have been clamped to the valid range.
1030		1105
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1107
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1108	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	1109	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	1131	member, you can also "subclass" the watcher type and provide your own
1057	data:	1132	data:
1058		1133
1059	struct my_io	1134	struct my_io
1060	{	1135	{
1061	struct ev_io io;	1136	ev_io io;
1062	int otherfd;	1137	int otherfd;
1063	void *somedata;	1138	void *somedata;
1064	struct whatever *mostinteresting;	1139	struct whatever *mostinteresting;
1065	};	1140	};
1066		1141
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1144	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1145
1071	And since your callback will be called with a pointer to the watcher, you	1146	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1147	can cast it back to your own type:
1073		1148
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1149	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1150	{
1076	struct my_io *w = (struct my_io *)w_;	1151	struct my_io *w = (struct my_io *)w_;
1077	...	1152	...
1078	}	1153	}
1079		1154
…		…
1097	programmers):	1172	programmers):
1098		1173
1099	#include <stddef.h>	1174	#include <stddef.h>
1100		1175
1101	static void	1176	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1177	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1178	{
1104	struct my_biggy big = (struct my_biggy *	1179	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1180	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1181	}
1107		1182
1108	static void	1183	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1184	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1185	{
1111	struct my_biggy big = (struct my_biggy *	1186	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1187	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1188	}
1114		1189
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1324	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	1325	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1326	attempt to read a whole line in the callback.
1252		1327
1253	static void	1328	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1329	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1330	{
1256	ev_io_stop (loop, w);	1331	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1332	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1333	}
1259		1334
1260	...	1335	...
1261	struct ev_loop *loop = ev_default_init (0);	1336	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1337	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1338	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1339	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1340	ev_loop (loop, 0);
1266		1341
1267		1342
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1350	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1352	monotonic clock option helps a lot here).
1278		1353
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1354	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	1355	passed. If multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1356	then the ones with earlier time-out values are invoked before ones with
		1357	later time-out values (but this is no longer true when a callback calls
		1358	C<ev_loop> recursively).
		1359
		1360	=head3 Be smart about timeouts
		1361
		1362	Many real-world problems involve some kind of timeout, usually for error
		1363	recovery. A typical example is an HTTP request - if the other side hangs,
		1364	you want to raise some error after a while.
		1365
		1366	What follows are some ways to handle this problem, from obvious and
		1367	inefficient to smart and efficient.
		1368
		1369	In the following, a 60 second activity timeout is assumed - a timeout that
		1370	gets reset to 60 seconds each time there is activity (e.g. each time some
		1371	data or other life sign was received).
		1372
		1373	=over 4
		1374
		1375	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1376
		1377	This is the most obvious, but not the most simple way: In the beginning,
		1378	start the watcher:
		1379
		1380	ev_timer_init (timer, callback, 60., 0.);
		1381	ev_timer_start (loop, timer);
		1382
		1383	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1384	and start it again:
		1385
		1386	ev_timer_stop (loop, timer);
		1387	ev_timer_set (timer, 60., 0.);
		1388	ev_timer_start (loop, timer);
		1389
		1390	This is relatively simple to implement, but means that each time there is
		1391	some activity, libev will first have to remove the timer from its internal
		1392	data structure and then add it again. Libev tries to be fast, but it's
		1393	still not a constant-time operation.
		1394
		1395	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1396
		1397	This is the easiest way, and involves using C<ev_timer_again> instead of
		1398	C<ev_timer_start>.
		1399
		1400	To implement this, configure an C<ev_timer> with a C<repeat> value
		1401	of C<60> and then call C<ev_timer_again> at start and each time you
		1402	successfully read or write some data. If you go into an idle state where
		1403	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1404	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1405
		1406	That means you can ignore both the C<ev_timer_start> function and the
		1407	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1408	member and C<ev_timer_again>.
		1409
		1410	At start:
		1411
		1412	ev_timer_init (timer, callback);
		1413	timer->repeat = 60.;
		1414	ev_timer_again (loop, timer);
		1415
		1416	Each time there is some activity:
		1417
		1418	ev_timer_again (loop, timer);
		1419
		1420	It is even possible to change the time-out on the fly, regardless of
		1421	whether the watcher is active or not:
		1422
		1423	timer->repeat = 30.;
		1424	ev_timer_again (loop, timer);
		1425
		1426	This is slightly more efficient then stopping/starting the timer each time
		1427	you want to modify its timeout value, as libev does not have to completely
		1428	remove and re-insert the timer from/into its internal data structure.
		1429
		1430	It is, however, even simpler than the "obvious" way to do it.
		1431
		1432	=item 3. Let the timer time out, but then re-arm it as required.
		1433
		1434	This method is more tricky, but usually most efficient: Most timeouts are
		1435	relatively long compared to the intervals between other activity - in
		1436	our example, within 60 seconds, there are usually many I/O events with
		1437	associated activity resets.
		1438
		1439	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1440	but remember the time of last activity, and check for a real timeout only
		1441	within the callback:
		1442
		1443	ev_tstamp last_activity; // time of last activity
		1444
		1445	static void
		1446	callback (EV_P_ ev_timer *w, int revents)
		1447	{
		1448	ev_tstamp now = ev_now (EV_A);
		1449	ev_tstamp timeout = last_activity + 60.;
		1450
		1451	// if last_activity + 60. is older than now, we did time out
		1452	if (timeout < now)
		1453	{
		1454	// timeout occured, take action
		1455	}
		1456	else
		1457	{
		1458	// callback was invoked, but there was some activity, re-arm
		1459	// the watcher to fire in last_activity + 60, which is
		1460	// guaranteed to be in the future, so "again" is positive:
		1461	w->repeat = timeout - now;
		1462	ev_timer_again (EV_A_ w);
		1463	}
		1464	}
		1465
		1466	To summarise the callback: first calculate the real timeout (defined
		1467	as "60 seconds after the last activity"), then check if that time has
		1468	been reached, which means something I<did>, in fact, time out. Otherwise
		1469	the callback was invoked too early (C<timeout> is in the future), so
		1470	re-schedule the timer to fire at that future time, to see if maybe we have
		1471	a timeout then.
		1472
		1473	Note how C<ev_timer_again> is used, taking advantage of the
		1474	C<ev_timer_again> optimisation when the timer is already running.
		1475
		1476	This scheme causes more callback invocations (about one every 60 seconds
		1477	minus half the average time between activity), but virtually no calls to
		1478	libev to change the timeout.
		1479
		1480	To start the timer, simply initialise the watcher and set C<last_activity>
		1481	to the current time (meaning we just have some activity :), then call the
		1482	callback, which will "do the right thing" and start the timer:
		1483
		1484	ev_timer_init (timer, callback);
		1485	last_activity = ev_now (loop);
		1486	callback (loop, timer, EV_TIMEOUT);
		1487
		1488	And when there is some activity, simply store the current time in
		1489	C<last_activity>, no libev calls at all:
		1490
		1491	last_actiivty = ev_now (loop);
		1492
		1493	This technique is slightly more complex, but in most cases where the
		1494	time-out is unlikely to be triggered, much more efficient.
		1495
		1496	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1497	callback :) - just change the timeout and invoke the callback, which will
		1498	fix things for you.
		1499
		1500	=item 4. Wee, just use a double-linked list for your timeouts.
		1501
		1502	If there is not one request, but many thousands (millions...), all
		1503	employing some kind of timeout with the same timeout value, then one can
		1504	do even better:
		1505
		1506	When starting the timeout, calculate the timeout value and put the timeout
		1507	at the I<end> of the list.
		1508
		1509	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1510	the list is expected to fire (for example, using the technique #3).
		1511
		1512	When there is some activity, remove the timer from the list, recalculate
		1513	the timeout, append it to the end of the list again, and make sure to
		1514	update the C<ev_timer> if it was taken from the beginning of the list.
		1515
		1516	This way, one can manage an unlimited number of timeouts in O(1) time for
		1517	starting, stopping and updating the timers, at the expense of a major
		1518	complication, and having to use a constant timeout. The constant timeout
		1519	ensures that the list stays sorted.
		1520
		1521	=back
		1522
		1523	So which method the best?
		1524
		1525	Method #2 is a simple no-brain-required solution that is adequate in most
		1526	situations. Method #3 requires a bit more thinking, but handles many cases
		1527	better, and isn't very complicated either. In most case, choosing either
		1528	one is fine, with #3 being better in typical situations.
		1529
		1530	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1531	rather complicated, but extremely efficient, something that really pays
		1532	off after the first million or so of active timers, i.e. it's usually
		1533	overkill :)
1282		1534
1283	=head3 The special problem of time updates	1535	=head3 The special problem of time updates
1284		1536
1285	Establishing the current time is a costly operation (it usually takes at	1537	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	1538	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).	1582	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1583
1332	If the timer is repeating, either start it if necessary (with the	1584	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.	1585	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1586
1335	This sounds a bit complicated, but here is a useful and typical	1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1588	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		1589
1366	=item ev_tstamp repeat [read-write]	1590	=item ev_tstamp repeat [read-write]
1367		1591
1368	The current C<repeat> value. Will be used each time the watcher times out	1592	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),	1593	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1598	=head3 Examples
1375		1599
1376	Example: Create a timer that fires after 60 seconds.	1600	Example: Create a timer that fires after 60 seconds.
1377		1601
1378	static void	1602	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1603	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1604	{
1381	.. one minute over, w is actually stopped right here	1605	.. one minute over, w is actually stopped right here
1382	}	1606	}
1383		1607
1384	struct ev_timer mytimer;	1608	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1609	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1610	ev_timer_start (loop, &mytimer);
1387		1611
1388	Example: Create a timeout timer that times out after 10 seconds of	1612	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1613	inactivity.
1390		1614
1391	static void	1615	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1616	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1617	{
1394	.. ten seconds without any activity	1618	.. ten seconds without any activity
1395	}	1619	}
1396		1620
1397	struct ev_timer mytimer;	1621	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1622	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1623	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1624	ev_loop (loop, 0);
1401		1625
1402	// and in some piece of code that gets executed on any "activity":	1626	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1631	=head2 C<ev_periodic> - to cron or not to cron?
1408		1632
1409	Periodic watchers are also timers of a kind, but they are very versatile	1633	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1634	(and unfortunately a bit complex).
1411		1635
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1636	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	1637	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	1638	(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 ()	1639	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	1640	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	1641	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		1642
		1643	You can tell a periodic watcher to trigger after some specific point
		1644	in time: for example, if you tell a periodic watcher to trigger "in 10
		1645	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1646	not a delay) and then reset your system clock to January of the previous
		1647	year, then it will take a year or more to trigger the event (unlike an
		1648	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1649	it, as it uses a relative timeout).
		1650
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1651	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	1652	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1653	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1654	those cannot react to time jumps.
1424		1655
1425	As with timers, the callback is guaranteed to be invoked only when the	1656	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	1657	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.	1658	timers become ready during the same loop iteration then the ones with
		1659	earlier time-out values are invoked before ones with later time-out values
		1660	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1661
1429	=head3 Watcher-Specific Functions and Data Members	1662	=head3 Watcher-Specific Functions and Data Members
1430		1663
1431	=over 4	1664	=over 4
1432		1665
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1666	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1667
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1668	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1669
1437	Lots of arguments, lets sort it out... There are basically three modes of	1670	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:	1671	operation, and we will explain them from simplest to most complex:
1439		1672
1440	=over 4	1673	=over 4
1441		1674
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1675	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		1676
1444	In this configuration the watcher triggers an event after the wall clock	1677	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	1678	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	1679	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.	1680	will be stopped and invoked when the system clock reaches or surpasses
		1681	this point in time.
1448		1682
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1683	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		1684
1451	In this mode the watcher will always be scheduled to time out at the next	1685	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)	1686	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	1687	negative) and then repeat, regardless of any time jumps. The C<offset>
		1688	argument is merely an offset into the C<interval> periods.
1454		1689
1455	This can be used to create timers that do not drift with respect to the	1690	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	1691	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	1692	hour, on the hour (with respect to UTC):
1458		1693
1459	ev_periodic_set (&periodic, 0., 3600., 0);	1694	ev_periodic_set (&periodic, 0., 3600., 0);
1460		1695
1461	This doesn't mean there will always be 3600 seconds in between triggers,	1696	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	1697	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	1698	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	1699	by 3600.
1465		1700
1466	Another way to think about it (for the mathematically inclined) is that	1701	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	1702	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.	1703	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		1704
1470	For numerical stability it is preferable that the C<at> value is near	1705	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	1706	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	1707	this value, and in fact is often specified as zero.
1473		1708
1474	Note also that there is an upper limit to how often a timer can fire (CPU	1709	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	1710	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	1711	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).	1712	millisecond (if the OS supports it and the machine is fast enough).
1478		1713
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1714	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		1715
1481	In this mode the values for C<interval> and C<at> are both being	1716	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	1717	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	1718	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	1719	current time as second argument.
1485		1720
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1721	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	1722	or make ANY other event loop modifications whatsoever, unless explicitly
		1723	allowed by documentation here>.
1488		1724
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1725	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	1726	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1727	only event loop modification you are allowed to do).
1492		1728
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1729	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1730	*w, ev_tstamp now)>, e.g.:
1495		1731
		1732	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1733	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1734	{
1498	return now + 60.;	1735	return now + 60.;
1499	}	1736	}
1500		1737
1501	It must return the next time to trigger, based on the passed time value	1738	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	1758	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	1759	program when the crontabs have changed).
1523		1760
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	1761	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		1762
1526	When active, returns the absolute time that the watcher is supposed to	1763	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	1764	to trigger next. This is not the same as the C<offset> argument to
		1765	C<ev_periodic_set>, but indeed works even in interval and manual
		1766	rescheduling modes.
1528		1767
1529	=item ev_tstamp offset [read-write]	1768	=item ev_tstamp offset [read-write]
1530		1769
1531	When repeating, this contains the offset value, otherwise this is the	1770	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>).	1771	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1772	although libev might modify this value for better numerical stability).
1533		1773
1534	Can be modified any time, but changes only take effect when the periodic	1774	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	1775	timer fires or C<ev_periodic_again> is being called.
1536		1776
1537	=item ev_tstamp interval [read-write]	1777	=item ev_tstamp interval [read-write]
1538		1778
1539	The current interval value. Can be modified any time, but changes only	1779	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	1780	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1781	called.
1542		1782
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1783	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		1784
1545	The current reschedule callback, or C<0>, if this functionality is	1785	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	1786	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.	1787	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1788
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1793	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1794	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1795	potentially a lot of jitter, but good long-term stability.
1556		1796
1557	static void	1797	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1798	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	1799	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1800	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1801	}
1562		1802
1563	struct ev_periodic hourly_tick;	1803	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1804	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1805	ev_periodic_start (loop, &hourly_tick);
1566		1806
1567	Example: The same as above, but use a reschedule callback to do it:	1807	Example: The same as above, but use a reschedule callback to do it:
1568		1808
1569	#include <math.h>	1809	#include <math.h>
1570		1810
1571	static ev_tstamp	1811	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1812	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1813	{
1574	return now + (3600. - fmod (now, 3600.));	1814	return now + (3600. - fmod (now, 3600.));
1575	}	1815	}
1576		1816
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1817	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1818
1579	Example: Call a callback every hour, starting now:	1819	Example: Call a callback every hour, starting now:
1580		1820
1581	struct ev_periodic hourly_tick;	1821	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1822	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1823	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1824	ev_periodic_start (loop, &hourly_tick);
1585		1825
1586		1826
…		…
1625		1865
1626	=back	1866	=back
1627		1867
1628	=head3 Examples	1868	=head3 Examples
1629		1869
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1870	Example: Try to exit cleanly on SIGINT.
1631		1871
1632	static void	1872	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1873	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	1874	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1875	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1876	}
1637		1877
1638	struct ev_signal signal_watcher;	1878	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1879	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1880	ev_signal_start (loop, &signal_watcher);
1641		1881
1642		1882
1643	=head2 C<ev_child> - watch out for process status changes	1883	=head2 C<ev_child> - watch out for process status changes
1644		1884
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1885	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1958	its completion.
1719		1959
1720	ev_child cw;	1960	ev_child cw;
1721		1961
1722	static void	1962	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1963	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1964	{
1725	ev_child_stop (EV_A_ w);	1965	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1966	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1967	}
1728		1968
…		…
1743		1983
1744		1984
1745	=head2 C<ev_stat> - did the file attributes just change?	1985	=head2 C<ev_stat> - did the file attributes just change?
1746		1986
1747	This watches a file system path for attribute changes. That is, it calls	1987	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	1988	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.	1989	and sees if it changed compared to the last time, invoking the callback if
		1990	it did.
1750		1991
1751	The path does not need to exist: changing from "path exists" to "path does	1992	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	1993	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	1994	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	1995	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	1996	least one) and all the other fields of the stat buffer having unspecified
		1997	contents.
1756		1998
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	1999	The path I<must not> end in a slash or contain special components such as
		2000	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.	2001	your working directory changes, then the behaviour is undefined.
1759		2002
1760	Since there is no standard kernel interface to do this, the portable	2003	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2004	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2005	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!)	2006	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	2007	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2008	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2009	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2010	currently around C<0.1>, but that's usually overkill.
1768		2011
1769	This watcher type is not meant for massive numbers of stat watchers,	2012	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2013	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2014	resource-intensive.
1772		2015
1773	At the time of this writing, the only OS-specific interface implemented	2016	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2017	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	2018	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2019	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2020
1778	=head3 ABI Issues (Largefile Support)	2021	=head3 ABI Issues (Largefile Support)
1779		2022
1780	Libev by default (unless the user overrides this) uses the default	2023	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2024	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2025	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	2026	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	2027	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	2028	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	2029	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.	2030	most noticeably displayed with ev_stat and large file support.
1788		2031
1789	The solution for this is to lobby your distribution maker to make large	2032	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	2033	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	2034	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2035	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2036	default compilation environment.
1794		2037
1795	=head3 Inotify and Kqueue	2038	=head3 Inotify and Kqueue
1796		2039
1797	When C<inotify (7)> support has been compiled into libev (generally only	2040	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	2041	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	2042	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2043	watcher is being started.
1801		2044
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2045	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	2046	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	2047	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,	2048	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.	2049	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2050	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2051	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2052	xfs are fully working) libev usually gets away without polling.
1807		2053
1808	There is no support for kqueue, as apparently it cannot be used to	2054	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	2055	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2056	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2057	etc. is difficult.
1812		2058
		2059	=head3 C<stat ()> is a synchronous operation
		2060
		2061	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2062	the process. The exception are C<ev_stat> watchers - those call C<stat
		2063	()>, which is a synchronous operation.
		2064
		2065	For local paths, this usually doesn't matter: unless the system is very
		2066	busy or the intervals between stat's are large, a stat call will be fast,
		2067	as the path data is usually in memory already (except when starting the
		2068	watcher).
		2069
		2070	For networked file systems, calling C<stat ()> can block an indefinite
		2071	time due to network issues, and even under good conditions, a stat call
		2072	often takes multiple milliseconds.
		2073
		2074	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2075	paths, although this is fully supported by libev.
		2076
1813	=head3 The special problem of stat time resolution	2077	=head3 The special problem of stat time resolution
1814		2078
1815	The C<stat ()> system call only supports full-second resolution portably, and	2079	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2080	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2081	still only support whole seconds.
1818		2082
1819	That means that, if the time is the only thing that changes, you can	2083	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	2084	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	2085	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	2086	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2229
1966	=head3 Watcher-Specific Functions and Data Members	2230	=head3 Watcher-Specific Functions and Data Members
1967		2231
1968	=over 4	2232	=over 4
1969		2233
1970	=item ev_idle_init (ev_signal *, callback)	2234	=item ev_idle_init (ev_idle *, callback)
1971		2235
1972	Initialises and configures the idle watcher - it has no parameters of any	2236	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,	2237	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2238	believe me.
1975		2239
…		…
1979		2243
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2244	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2245	callback, free it. Also, use no error checking, as usual.
1982		2246
1983	static void	2247	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2248	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2249	{
1986	free (w);	2250	free (w);
1987	// now do something you wanted to do when the program has	2251	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2252	// no longer anything immediate to do.
1989	}	2253	}
1990		2254
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2256	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2257	ev_idle_start (loop, idle_cb);
1994		2258
1995		2259
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2341
2078	static ev_io iow [nfd];	2342	static ev_io iow [nfd];
2079	static ev_timer tw;	2343	static ev_timer tw;
2080		2344
2081	static void	2345	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2346	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2347	{
2084	}	2348	}
2085		2349
2086	// create io watchers for each fd and a timer before blocking	2350	// create io watchers for each fd and a timer before blocking
2087	static void	2351	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2352	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2353	{
2090	int timeout = 3600000;	2354	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2355	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2356	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2372	}
2109	}	2373	}
2110		2374
2111	// stop all watchers after blocking	2375	// stop all watchers after blocking
2112	static void	2376	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2377	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2378	{
2115	ev_timer_stop (loop, &tw);	2379	ev_timer_stop (loop, &tw);
2116		2380
2117	for (int i = 0; i < nfd; ++i)	2381	for (int i = 0; i < nfd; ++i)
2118	{	2382	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2478	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	2479	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	2480	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.	2481	the rest in a second one, and embed the second one in the first.
2218		2482
2219	As long as the watcher is active, the callback will be invoked every time	2483	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	2484	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	2485	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	2486	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	2487	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	2488	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2489
2227	As long as the watcher is started it will automatically handle events. The	2490	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	2491	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		2492
2232	Also, there have not currently been made special provisions for forking:	2493	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,	2494	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	2495	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,	2496	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2497
2238	Unfortunately, not all backends are embeddable, only the ones returned by	2498	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2499	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2500	portable one.
2241		2501
2242	So when you want to use this feature you will always have to be prepared	2502	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	2503	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	2504	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.	2505	create it, and if that fails, use the normal loop for everything.
		2506
		2507	=head3 C<ev_embed> and fork
		2508
		2509	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2510	automatically be applied to the embedded loop as well, so no special
		2511	fork handling is required in that case. When the watcher is not running,
		2512	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2513	as applicable.
2246		2514
2247	=head3 Watcher-Specific Functions and Data Members	2515	=head3 Watcher-Specific Functions and Data Members
2248		2516
2249	=over 4	2517	=over 4
2250		2518
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2546	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2547	used).
2280		2548
2281	struct ev_loop *loop_hi = ev_default_init (0);	2549	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2550	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2551	ev_embed embed;
2284		2552
2285	// see if there is a chance of getting one that works	2553	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2554	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2555	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2556	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2570	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2571	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2572
2305	struct ev_loop *loop = ev_default_init (0);	2573	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2574	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2575	ev_embed embed;
2308		2576
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2577	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2578	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2579	{
2312	ev_embed_init (&embed, 0, loop_socket);	2580	ev_embed_init (&embed, 0, loop_socket);
…		…
2368	is that the author does not know of a simple (or any) algorithm for a	2636	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	2637	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	2638	need elaborate support such as pthreads.
2371		2639
2372	That means that if you want to queue data, you have to provide your own	2640	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you would implement locking around your	2641	queue. But at least I can tell you how to implement locking around your
2374	queue:	2642	queue:
2375		2643
2376	=over 4	2644	=over 4
2377		2645
2378	=item queueing from a signal handler context	2646	=item queueing from a signal handler context
2379		2647
2380	To implement race-free queueing, you simply add to the queue in the signal	2648	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	2649	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2650	an example that does that for some fictitious SIGUSR1 handler:
2383		2651
2384	static ev_async mysig;	2652	static ev_async mysig;
2385		2653
2386	static void	2654	static void
2387	sigusr1_handler (void)	2655	sigusr1_handler (void)
…		…
2453	=over 4	2721	=over 4
2454		2722
2455	=item ev_async_init (ev_async *, callback)	2723	=item ev_async_init (ev_async *, callback)
2456		2724
2457	Initialises and configures the async watcher - it has no parameters of any	2725	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,	2726	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	believe me.	2727	trust me.
2460		2728
2461	=item ev_async_send (loop, ev_async *)	2729	=item ev_async_send (loop, ev_async *)
2462		2730
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2731	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	2732	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do in other threads, signal or	2733	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	2734	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2735	section below on what exactly this means).
2468		2736
		2737	Note that, as with other watchers in libev, multiple events might get
		2738	compressed into a single callback invocation (another way to look at this
		2739	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2740	reset when the event loop detects that).
		2741
2469	This call incurs the overhead of a system call only once per loop iteration,	2742	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	2743	iteration, so while the overhead might be noticeable, it doesn't apply to
2471	calls to C<ev_async_send>.	2744	repeated calls to C<ev_async_send> for the same event loop.
2472		2745
2473	=item bool = ev_async_pending (ev_async *)	2746	=item bool = ev_async_pending (ev_async *)
2474		2747
2475	Returns a non-zero value when C<ev_async_send> has been called on the	2748	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	2749	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	2752	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,	2753	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	2754	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.	2755	quickly check whether invoking the loop might be a good idea.
2483		2756
2484	Not that this does I<not> check whether the watcher itself is pending, only	2757	Not that this does I<not> check whether the watcher itself is pending,
2485	whether it has been requested to make this watcher pending.	2758	only whether it has been requested to make this watcher pending: there
		2759	is a time window between the event loop checking and resetting the async
		2760	notification, and the callback being invoked.
2486		2761
2487	=back	2762	=back
2488		2763
2489		2764
2490	=head1 OTHER FUNCTIONS	2765	=head1 OTHER FUNCTIONS
…		…
2494	=over 4	2769	=over 4
2495		2770
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2771	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2772
2498	This function combines a simple timer and an I/O watcher, calls your	2773	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2774	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	2775	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	2776	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2777	more watchers yourself.
2503		2778
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2779	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	2780	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2781	the given C<fd> and C<events> set will be created and started.
2507		2782
2508	If C<timeout> is less than 0, then no timeout watcher will be	2783	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	2784	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	2785	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2786
2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2787	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	2788	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>	2789	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2790	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2791	a timeout and an io event at the same time - you probably should give io
		2792	events precedence.
		2793
		2794	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2795
2518	static void stdin_ready (int revents, void *arg)	2796	static void stdin_ready (int revents, void *arg)
2519	{	2797	{
		2798	if (revents & EV_READ)
		2799	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2800	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2801	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2802	}
2525		2803
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2805
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)	2806	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2529		2807
2530	Feeds the given event set into the event loop, as if the specified event	2808	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	2809	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2810	initialised but not necessarily started event watcher).
2533		2811
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2813
2536	Feed an event on the given fd, as if a file descriptor backend detected	2814	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2815	the given events it.
2538		2816
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2817	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2818
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2819	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2820	loop!).
2543		2821
2544	=back	2822	=back
…		…
2666		2944
2667	myclass obj;	2945	myclass obj;
2668	ev::io iow;	2946	ev::io iow;
2669	iow.set <myclass, &myclass::io_cb> (&obj);	2947	iow.set <myclass, &myclass::io_cb> (&obj);
2670		2948
		2949	=item w->set (object *)
		2950
		2951	This is an B<experimental> feature that might go away in a future version.
		2952
		2953	This is a variation of a method callback - leaving out the method to call
		2954	will default the method to C<operator ()>, which makes it possible to use
		2955	functor objects without having to manually specify the C<operator ()> all
		2956	the time. Incidentally, you can then also leave out the template argument
		2957	list.
		2958
		2959	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2960	int revents)>.
		2961
		2962	See the method-C<set> above for more details.
		2963
		2964	Example: use a functor object as callback.
		2965
		2966	struct myfunctor
		2967	{
		2968	void operator() (ev::io &w, int revents)
		2969	{
		2970	...
		2971	}
		2972	}
		2973
		2974	myfunctor f;
		2975
		2976	ev::io w;
		2977	w.set (&f);
		2978
2671	=item w->set<function> (void *data = 0)	2979	=item w->set<function> (void *data = 0)
2672		2980
2673	Also sets a callback, but uses a static method or plain function as	2981	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	2982	callback. The optional C<data> argument will be stored in the watcher's
2675	C<data> member and is free for you to use.	2983	C<data> member and is free for you to use.
2676		2984
2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2985	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2678		2986
2679	See the method-C<set> above for more details.	2987	See the method-C<set> above for more details.
2680		2988
2681	Example:	2989	Example: Use a plain function as callback.
2682		2990
2683	static void io_cb (ev::io &w, int revents) { }	2991	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	2992	iow.set <io_cb> ();
2685		2993
2686	=item w->set (struct ev_loop *)	2994	=item w->set (struct ev_loop *)
…		…
2724	Example: Define a class with an IO and idle watcher, start one of them in	3032	Example: Define a class with an IO and idle watcher, start one of them in
2725	the constructor.	3033	the constructor.
2726		3034
2727	class myclass	3035	class myclass
2728	{	3036	{
2729	ev::io io; void io_cb (ev::io &w, int revents);	3037	ev::io io ; void io_cb (ev::io &w, int revents);
2730	ev:idle idle void idle_cb (ev::idle &w, int revents);	3038	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		3039
2732	myclass (int fd)	3040	myclass (int fd)
2733	{	3041	{
2734	io .set <myclass, &myclass::io_cb > (this);	3042	io .set <myclass, &myclass::io_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	3043	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2751	=item Perl	3059	=item Perl
2752		3060
2753	The EV module implements the full libev API and is actually used to test	3061	The EV module implements the full libev API and is actually used to test
2754	libev. EV is developed together with libev. Apart from the EV core module,	3062	libev. EV is developed together with libev. Apart from the EV core module,
2755	there are additional modules that implement libev-compatible interfaces	3063	there are additional modules that implement libev-compatible interfaces
2756	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3064	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2757	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3065	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3066	and C<EV::Glib>).
2758		3067
2759	It can be found and installed via CPAN, its homepage is at	3068	It can be found and installed via CPAN, its homepage is at
2760	L<http://software.schmorp.de/pkg/EV>.	3069	L<http://software.schmorp.de/pkg/EV>.
2761		3070
2762	=item Python	3071	=item Python
2763		3072
2764	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3073	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2765	seems to be quite complete and well-documented. Note, however, that the	3074	seems to be quite complete and well-documented.
2766	patch they require for libev is outright dangerous as it breaks the ABI
2767	for everybody else, and therefore, should never be applied in an installed
2768	libev (if python requires an incompatible ABI then it needs to embed
2769	libev).
2770		3075
2771	=item Ruby	3076	=item Ruby
2772		3077
2773	Tony Arcieri has written a ruby extension that offers access to a subset	3078	Tony Arcieri has written a ruby extension that offers access to a subset
2774	of the libev API and adds file handle abstractions, asynchronous DNS and	3079	of the libev API and adds file handle abstractions, asynchronous DNS and
2775	more on top of it. It can be found via gem servers. Its homepage is at	3080	more on top of it. It can be found via gem servers. Its homepage is at
2776	L<http://rev.rubyforge.org/>.	3081	L<http://rev.rubyforge.org/>.
2777		3082
		3083	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3084	makes rev work even on mingw.
		3085
		3086	=item Haskell
		3087
		3088	A haskell binding to libev is available at
		3089	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3090
2778	=item D	3091	=item D
2779		3092
2780	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3093	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2781	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3094	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3095
		3096	=item Ocaml
		3097
		3098	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2782		3100
2783	=back	3101	=back
2784		3102
2785		3103
2786	=head1 MACRO MAGIC	3104	=head1 MACRO MAGIC
…		…
2887		3205
2888	#define EV_STANDALONE 1	3206	#define EV_STANDALONE 1
2889	#include "ev.h"	3207	#include "ev.h"
2890		3208
2891	Both header files and implementation files can be compiled with a C++	3209	Both header files and implementation files can be compiled with a C++
2892	compiler (at least, thats a stated goal, and breakage will be treated	3210	compiler (at least, that's a stated goal, and breakage will be treated
2893	as a bug).	3211	as a bug).
2894		3212
2895	You need the following files in your source tree, or in a directory	3213	You need the following files in your source tree, or in a directory
2896	in your include path (e.g. in libev/ when using -Ilibev):	3214	in your include path (e.g. in libev/ when using -Ilibev):
2897		3215
…		…
2941		3259
2942	=head2 PREPROCESSOR SYMBOLS/MACROS	3260	=head2 PREPROCESSOR SYMBOLS/MACROS
2943		3261
2944	Libev can be configured via a variety of preprocessor symbols you have to	3262	Libev can be configured via a variety of preprocessor symbols you have to
2945	define before including any of its files. The default in the absence of	3263	define before including any of its files. The default in the absence of
2946	autoconf is noted for every option.	3264	autoconf is documented for every option.
2947		3265
2948	=over 4	3266	=over 4
2949		3267
2950	=item EV_STANDALONE	3268	=item EV_STANDALONE
2951		3269
…		…
2953	keeps libev from including F<config.h>, and it also defines dummy	3271	keeps libev from including F<config.h>, and it also defines dummy
2954	implementations for some libevent functions (such as logging, which is not	3272	implementations for some libevent functions (such as logging, which is not
2955	supported). It will also not define any of the structs usually found in	3273	supported). It will also not define any of the structs usually found in
2956	F<event.h> that are not directly supported by the libev core alone.	3274	F<event.h> that are not directly supported by the libev core alone.
2957		3275
		3276	In stanbdalone mode, libev will still try to automatically deduce the
		3277	configuration, but has to be more conservative.
		3278
2958	=item EV_USE_MONOTONIC	3279	=item EV_USE_MONOTONIC
2959		3280
2960	If defined to be C<1>, libev will try to detect the availability of the	3281	If defined to be C<1>, libev will try to detect the availability of the
2961	monotonic clock option at both compile time and runtime. Otherwise no use	3282	monotonic clock option at both compile time and runtime. Otherwise no
2962	of the monotonic clock option will be attempted. If you enable this, you	3283	use of the monotonic clock option will be attempted. If you enable this,
2963	usually have to link against librt or something similar. Enabling it when	3284	you usually have to link against librt or something similar. Enabling it
2964	the functionality isn't available is safe, though, although you have	3285	when the functionality isn't available is safe, though, although you have
2965	to make sure you link against any libraries where the C<clock_gettime>	3286	to make sure you link against any libraries where the C<clock_gettime>
2966	function is hiding in (often F<-lrt>).	3287	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2967		3288
2968	=item EV_USE_REALTIME	3289	=item EV_USE_REALTIME
2969		3290
2970	If defined to be C<1>, libev will try to detect the availability of the	3291	If defined to be C<1>, libev will try to detect the availability of the
2971	real-time clock option at compile time (and assume its availability at	3292	real-time clock option at compile time (and assume its availability
2972	runtime if successful). Otherwise no use of the real-time clock option will	3293	at runtime if successful). Otherwise no use of the real-time clock
2973	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3294	option will be attempted. This effectively replaces C<gettimeofday>
2974	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3295	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2975	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3296	correctness. See the note about libraries in the description of
		3297	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3298	C<EV_USE_CLOCK_SYSCALL>.
		3299
		3300	=item EV_USE_CLOCK_SYSCALL
		3301
		3302	If defined to be C<1>, libev will try to use a direct syscall instead
		3303	of calling the system-provided C<clock_gettime> function. This option
		3304	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3305	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3306	programs needlessly. Using a direct syscall is slightly slower (in
		3307	theory), because no optimised vdso implementation can be used, but avoids
		3308	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3309	higher, as it simplifies linking (no need for C<-lrt>).
2976		3310
2977	=item EV_USE_NANOSLEEP	3311	=item EV_USE_NANOSLEEP
2978		3312
2979	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3313	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2980	and will use it for delays. Otherwise it will use C<select ()>.	3314	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2996		3330
2997	=item EV_SELECT_USE_FD_SET	3331	=item EV_SELECT_USE_FD_SET
2998		3332
2999	If defined to C<1>, then the select backend will use the system C<fd_set>	3333	If defined to C<1>, then the select backend will use the system C<fd_set>
3000	structure. This is useful if libev doesn't compile due to a missing	3334	structure. This is useful if libev doesn't compile due to a missing
3001	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3335	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3002	exotic systems. This usually limits the range of file descriptors to some	3336	on exotic systems. This usually limits the range of file descriptors to
3003	low limit such as 1024 or might have other limitations (winsocket only	3337	some low limit such as 1024 or might have other limitations (winsocket
3004	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3338	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3005	influence the size of the C<fd_set> used.	3339	configures the maximum size of the C<fd_set>.
3006		3340
3007	=item EV_SELECT_IS_WINSOCKET	3341	=item EV_SELECT_IS_WINSOCKET
3008		3342
3009	When defined to C<1>, the select backend will assume that	3343	When defined to C<1>, the select backend will assume that
3010	select/socket/connect etc. don't understand file descriptors but	3344	select/socket/connect etc. don't understand file descriptors but
…		…
3121	When doing priority-based operations, libev usually has to linearly search	3455	When doing priority-based operations, libev usually has to linearly search
3122	all the priorities, so having many of them (hundreds) uses a lot of space	3456	all the priorities, so having many of them (hundreds) uses a lot of space
3123	and time, so using the defaults of five priorities (-2 .. +2) is usually	3457	and time, so using the defaults of five priorities (-2 .. +2) is usually
3124	fine.	3458	fine.
3125		3459
3126	If your embedding application does not need any priorities, defining these both to	3460	If your embedding application does not need any priorities, defining these
3127	C<0> will save some memory and CPU.	3461	both to C<0> will save some memory and CPU.
3128		3462
3129	=item EV_PERIODIC_ENABLE	3463	=item EV_PERIODIC_ENABLE
3130		3464
3131	If undefined or defined to be C<1>, then periodic timers are supported. If	3465	If undefined or defined to be C<1>, then periodic timers are supported. If
3132	defined to be C<0>, then they are not. Disabling them saves a few kB of	3466	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3139	code.	3473	code.
3140		3474
3141	=item EV_EMBED_ENABLE	3475	=item EV_EMBED_ENABLE
3142		3476
3143	If undefined or defined to be C<1>, then embed watchers are supported. If	3477	If undefined or defined to be C<1>, then embed watchers are supported. If
3144	defined to be C<0>, then they are not.	3478	defined to be C<0>, then they are not. Embed watchers rely on most other
		3479	watcher types, which therefore must not be disabled.
3145		3480
3146	=item EV_STAT_ENABLE	3481	=item EV_STAT_ENABLE
3147		3482
3148	If undefined or defined to be C<1>, then stat watchers are supported. If	3483	If undefined or defined to be C<1>, then stat watchers are supported. If
3149	defined to be C<0>, then they are not.	3484	defined to be C<0>, then they are not.
…		…
3181	two).	3516	two).
3182		3517
3183	=item EV_USE_4HEAP	3518	=item EV_USE_4HEAP
3184		3519
3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3520	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3186	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3521	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3187	to C<1>. The 4-heap uses more complicated (longer) code but has	3522	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3188	noticeably faster performance with many (thousands) of watchers.	3523	faster performance with many (thousands) of watchers.
3189		3524
3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3525	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3191	(disabled).	3526	(disabled).
3192		3527
3193	=item EV_HEAP_CACHE_AT	3528	=item EV_HEAP_CACHE_AT
3194		3529
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3530	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3196	timer and periodics heap, libev can cache the timestamp (I<at>) within	3531	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3197	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3532	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3198	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3533	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3199	but avoids random read accesses on heap changes. This improves performance	3534	but avoids random read accesses on heap changes. This improves performance
3200	noticeably with with many (hundreds) of watchers.	3535	noticeably with many (hundreds) of watchers.
3201		3536
3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3537	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3203	(disabled).	3538	(disabled).
3204		3539
3205	=item EV_VERIFY	3540	=item EV_VERIFY
…		…
3211	called once per loop, which can slow down libev. If set to C<3>, then the	3546	called once per loop, which can slow down libev. If set to C<3>, then the
3212	verification code will be called very frequently, which will slow down	3547	verification code will be called very frequently, which will slow down
3213	libev considerably.	3548	libev considerably.
3214		3549
3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3550	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3216	C<0.>	3551	C<0>.
3217		3552
3218	=item EV_COMMON	3553	=item EV_COMMON
3219		3554
3220	By default, all watchers have a C<void *data> member. By redefining	3555	By default, all watchers have a C<void *data> member. By redefining
3221	this macro to a something else you can include more and other types of	3556	this macro to a something else you can include more and other types of
…		…
3238	and the way callbacks are invoked and set. Must expand to a struct member	3573	and the way callbacks are invoked and set. Must expand to a struct member
3239	definition and a statement, respectively. See the F<ev.h> header file for	3574	definition and a statement, respectively. See the F<ev.h> header file for
3240	their default definitions. One possible use for overriding these is to	3575	their default definitions. One possible use for overriding these is to
3241	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3576	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3242	method calls instead of plain function calls in C++.	3577	method calls instead of plain function calls in C++.
		3578
		3579	=back
3243		3580
3244	=head2 EXPORTED API SYMBOLS	3581	=head2 EXPORTED API SYMBOLS
3245		3582
3246	If you need to re-export the API (e.g. via a DLL) and you need a list of	3583	If you need to re-export the API (e.g. via a DLL) and you need a list of
3247	exported symbols, you can use the provided F<Symbol.*> files which list	3584	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3294	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3631	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3295		3632
3296	#include "ev_cpp.h"	3633	#include "ev_cpp.h"
3297	#include "ev.c"	3634	#include "ev.c"
3298		3635
		3636	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3299		3637
3300	=head1 THREADS AND COROUTINES	3638	=head2 THREADS AND COROUTINES
3301		3639
3302	=head2 THREADS	3640	=head3 THREADS
3303		3641
3304	Libev itself is thread-safe (unless the opposite is specifically	3642	All libev functions are reentrant and thread-safe unless explicitly
3305	documented for a function), but it uses no locking itself. This means that	3643	documented otherwise, but libev implements no locking itself. This means
3306	you can use as many loops as you want in parallel, as long as only one	3644	that you can use as many loops as you want in parallel, as long as there
3307	thread ever calls into one libev function with the same loop parameter:	3645	are no concurrent calls into any libev function with the same loop
		3646	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3308	libev guarentees that different event loops share no data structures that	3647	of course): libev guarantees that different event loops share no data
3309	need locking.	3648	structures that need any locking.
3310		3649
3311	Or to put it differently: calls with different loop parameters can be done	3650	Or to put it differently: calls with different loop parameters can be done
3312	concurrently from multiple threads, calls with the same loop parameter	3651	concurrently from multiple threads, calls with the same loop parameter
3313	must be done serially (but can be done from different threads, as long as	3652	must be done serially (but can be done from different threads, as long as
3314	only one thread ever is inside a call at any point in time, e.g. by using	3653	only one thread ever is inside a call at any point in time, e.g. by using
3315	a mutex per loop).	3654	a mutex per loop).
3316		3655
3317	Specifically to support threads (and signal handlers), libev implements	3656	Specifically to support threads (and signal handlers), libev implements
3318	so-called C<ev_async> watchers, which allow some limited form of	3657	so-called C<ev_async> watchers, which allow some limited form of
3319	concurrency on the same event loop.	3658	concurrency on the same event loop, namely waking it up "from the
		3659	outside".
3320		3660
3321	If you want to know which design (one loop, locking, or multiple loops	3661	If you want to know which design (one loop, locking, or multiple loops
3322	without or something else still) is best for your problem, then I cannot	3662	without or something else still) is best for your problem, then I cannot
3323	help you. I can give some generic advice however:	3663	help you, but here is some generic advice:
3324		3664
3325	=over 4	3665	=over 4
3326		3666
3327	=item * most applications have a main thread: use the default libev loop	3667	=item * most applications have a main thread: use the default libev loop
3328	in that thread, or create a separate thread running only the default loop.	3668	in that thread, or create a separate thread running only the default loop.
…		…
3352	default loop and triggering an C<ev_async> watcher from the default loop	3692	default loop and triggering an C<ev_async> watcher from the default loop
3353	watcher callback into the event loop interested in the signal.	3693	watcher callback into the event loop interested in the signal.
3354		3694
3355	=back	3695	=back
3356		3696
3357	=head2 COROUTINES	3697	=head3 COROUTINES
3358		3698
3359	Libev is much more accommodating to coroutines ("cooperative threads"):	3699	Libev is very accommodating to coroutines ("cooperative threads"):
3360	libev fully supports nesting calls to it's functions from different	3700	libev fully supports nesting calls to its functions from different
3361	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3701	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3362	different coroutines and switch freely between both coroutines running the	3702	different coroutines, and switch freely between both coroutines running the
3363	loop, as long as you don't confuse yourself). The only exception is that	3703	loop, as long as you don't confuse yourself). The only exception is that
3364	you must not do this from C<ev_periodic> reschedule callbacks.	3704	you must not do this from C<ev_periodic> reschedule callbacks.
3365		3705
3366	Care has been taken to ensure that libev does not keep local state inside	3706	Care has been taken to ensure that libev does not keep local state inside
3367	C<ev_loop>, and other calls do not usually allow coroutine switches.	3707	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3708	they do not call any callbacks.
3368		3709
		3710	=head2 COMPILER WARNINGS
3369		3711
3370	=head1 COMPLEXITIES	3712	Depending on your compiler and compiler settings, you might get no or a
		3713	lot of warnings when compiling libev code. Some people are apparently
		3714	scared by this.
3371		3715
3372	In this section the complexities of (many of) the algorithms used inside	3716	However, these are unavoidable for many reasons. For one, each compiler
3373	libev will be explained. For complexity discussions about backends see the	3717	has different warnings, and each user has different tastes regarding
3374	documentation for C<ev_default_init>.	3718	warning options. "Warn-free" code therefore cannot be a goal except when
		3719	targeting a specific compiler and compiler-version.
3375		3720
3376	All of the following are about amortised time: If an array needs to be	3721	Another reason is that some compiler warnings require elaborate
3377	extended, libev needs to realloc and move the whole array, but this	3722	workarounds, or other changes to the code that make it less clear and less
3378	happens asymptotically never with higher number of elements, so O(1) might	3723	maintainable.
3379	mean it might do a lengthy realloc operation in rare cases, but on average
3380	it is much faster and asymptotically approaches constant time.
3381		3724
3382	=over 4	3725	And of course, some compiler warnings are just plain stupid, or simply
		3726	wrong (because they don't actually warn about the condition their message
		3727	seems to warn about). For example, certain older gcc versions had some
		3728	warnings that resulted an extreme number of false positives. These have
		3729	been fixed, but some people still insist on making code warn-free with
		3730	such buggy versions.
3383		3731
3384	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3732	While libev is written to generate as few warnings as possible,
		3733	"warn-free" code is not a goal, and it is recommended not to build libev
		3734	with any compiler warnings enabled unless you are prepared to cope with
		3735	them (e.g. by ignoring them). Remember that warnings are just that:
		3736	warnings, not errors, or proof of bugs.
3385		3737
3386	This means that, when you have a watcher that triggers in one hour and
3387	there are 100 watchers that would trigger before that then inserting will
3388	have to skip roughly seven (C<ld 100>) of these watchers.
3389		3738
3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3739	=head2 VALGRIND
3391		3740
3392	That means that changing a timer costs less than removing/adding them	3741	Valgrind has a special section here because it is a popular tool that is
3393	as only the relative motion in the event queue has to be paid for.	3742	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3394		3743
3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3744	If you think you found a bug (memory leak, uninitialised data access etc.)
		3745	in libev, then check twice: If valgrind reports something like:
3396		3746
3397	These just add the watcher into an array or at the head of a list.	3747	==2274== definitely lost: 0 bytes in 0 blocks.
		3748	==2274== possibly lost: 0 bytes in 0 blocks.
		3749	==2274== still reachable: 256 bytes in 1 blocks.
3398		3750
3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3751	Then there is no memory leak, just as memory accounted to global variables
		3752	is not a memleak - the memory is still being referenced, and didn't leak.
3400		3753
3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3754	Similarly, under some circumstances, valgrind might report kernel bugs
		3755	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3756	although an acceptable workaround has been found here), or it might be
		3757	confused.
3402		3758
3403	These watchers are stored in lists then need to be walked to find the	3759	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3404	correct watcher to remove. The lists are usually short (you don't usually	3760	make it into some kind of religion.
3405	have many watchers waiting for the same fd or signal).
3406		3761
3407	=item Finding the next timer in each loop iteration: O(1)	3762	If you are unsure about something, feel free to contact the mailing list
		3763	with the full valgrind report and an explanation on why you think this
		3764	is a bug in libev (best check the archives, too :). However, don't be
		3765	annoyed when you get a brisk "this is no bug" answer and take the chance
		3766	of learning how to interpret valgrind properly.
3408		3767
3409	By virtue of using a binary or 4-heap, the next timer is always found at a	3768	If you need, for some reason, empty reports from valgrind for your project
3410	fixed position in the storage array.	3769	I suggest using suppression lists.
3411		3770
3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3413		3771
3414	A change means an I/O watcher gets started or stopped, which requires	3772	=head1 PORTABILITY NOTES
3415	libev to recalculate its status (and possibly tell the kernel, depending
3416	on backend and whether C<ev_io_set> was used).
3417		3773
3418	=item Activating one watcher (putting it into the pending state): O(1)
3419
3420	=item Priority handling: O(number_of_priorities)
3421
3422	Priorities are implemented by allocating some space for each
3423	priority. When doing priority-based operations, libev usually has to
3424	linearly search all the priorities, but starting/stopping and activating
3425	watchers becomes O(1) w.r.t. priority handling.
3426
3427	=item Sending an ev_async: O(1)
3428
3429	=item Processing ev_async_send: O(number_of_async_watchers)
3430
3431	=item Processing signals: O(max_signal_number)
3432
3433	Sending involves a system call I<iff> there were no other C<ev_async_send>
3434	calls in the current loop iteration. Checking for async and signal events
3435	involves iterating over all running async watchers or all signal numbers.
3436
3437	=back
3438
3439
3440	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3774	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3441		3775
3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3776	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3443	requires, and its I/O model is fundamentally incompatible with the POSIX	3777	requires, and its I/O model is fundamentally incompatible with the POSIX
3444	model. Libev still offers limited functionality on this platform in	3778	model. Libev still offers limited functionality on this platform in
3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3779	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3456		3790
3457	Not a libev limitation but worth mentioning: windows apparently doesn't	3791	Not a libev limitation but worth mentioning: windows apparently doesn't
3458	accept large writes: instead of resulting in a partial write, windows will	3792	accept large writes: instead of resulting in a partial write, windows will
3459	either accept everything or return C<ENOBUFS> if the buffer is too large,	3793	either accept everything or return C<ENOBUFS> if the buffer is too large,
3460	so make sure you only write small amounts into your sockets (less than a	3794	so make sure you only write small amounts into your sockets (less than a
3461	megabyte seems safe, but thsi apparently depends on the amount of memory	3795	megabyte seems safe, but this apparently depends on the amount of memory
3462	available).	3796	available).
3463		3797
3464	Due to the many, low, and arbitrary limits on the win32 platform and	3798	Due to the many, low, and arbitrary limits on the win32 platform and
3465	the abysmal performance of winsockets, using a large number of sockets	3799	the abysmal performance of winsockets, using a large number of sockets
3466	is not recommended (and not reasonable). If your program needs to use	3800	is not recommended (and not reasonable). If your program needs to use
…		…
3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3811	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3478		3812
3479	#include "ev.h"	3813	#include "ev.h"
3480		3814
3481	And compile the following F<evwrap.c> file into your project (make sure	3815	And compile the following F<evwrap.c> file into your project (make sure
3482	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3816	you do I<not> compile the F<ev.c> or any other embedded source files!):
3483		3817
3484	#include "evwrap.h"	3818	#include "evwrap.h"
3485	#include "ev.c"	3819	#include "ev.c"
3486		3820
3487	=over 4	3821	=over 4
…		…
3532	wrap all I/O functions and provide your own fd management, but the cost of	3866	wrap all I/O functions and provide your own fd management, but the cost of
3533	calling select (O(n²)) will likely make this unworkable.	3867	calling select (O(n²)) will likely make this unworkable.
3534		3868
3535	=back	3869	=back
3536		3870
3537
3538	=head1 PORTABILITY REQUIREMENTS	3871	=head2 PORTABILITY REQUIREMENTS
3539		3872
3540	In addition to a working ISO-C implementation, libev relies on a few	3873	In addition to a working ISO-C implementation and of course the
3541	additional extensions:	3874	backend-specific APIs, libev relies on a few additional extensions:
3542		3875
3543	=over 4	3876	=over 4
3544		3877
3545	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3878	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3546	calling conventions regardless of C<ev_watcher_type *>.	3879	calling conventions regardless of C<ev_watcher_type *>.
…		…
3552	calls them using an C<ev_watcher *> internally.	3885	calls them using an C<ev_watcher *> internally.
3553		3886
3554	=item C<sig_atomic_t volatile> must be thread-atomic as well	3887	=item C<sig_atomic_t volatile> must be thread-atomic as well
3555		3888
3556	The type C<sig_atomic_t volatile> (or whatever is defined as	3889	The type C<sig_atomic_t volatile> (or whatever is defined as
3557	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3890	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3558	threads. This is not part of the specification for C<sig_atomic_t>, but is	3891	threads. This is not part of the specification for C<sig_atomic_t>, but is
3559	believed to be sufficiently portable.	3892	believed to be sufficiently portable.
3560		3893
3561	=item C<sigprocmask> must work in a threaded environment	3894	=item C<sigprocmask> must work in a threaded environment
3562		3895
…		…
3571	except the initial one, and run the default loop in the initial thread as	3904	except the initial one, and run the default loop in the initial thread as
3572	well.	3905	well.
3573		3906
3574	=item C<long> must be large enough for common memory allocation sizes	3907	=item C<long> must be large enough for common memory allocation sizes
3575		3908
3576	To improve portability and simplify using libev, libev uses C<long>	3909	To improve portability and simplify its API, libev uses C<long> internally
3577	internally instead of C<size_t> when allocating its data structures. On	3910	instead of C<size_t> when allocating its data structures. On non-POSIX
3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3911	systems (Microsoft...) this might be unexpectedly low, but is still at
3579	is still at least 31 bits everywhere, which is enough for hundreds of	3912	least 31 bits everywhere, which is enough for hundreds of millions of
3580	millions of watchers.	3913	watchers.
3581		3914
3582	=item C<double> must hold a time value in seconds with enough accuracy	3915	=item C<double> must hold a time value in seconds with enough accuracy
3583		3916
3584	The type C<double> is used to represent timestamps. It is required to	3917	The type C<double> is used to represent timestamps. It is required to
3585	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3918	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3589	=back	3922	=back
3590		3923
3591	If you know of other additional requirements drop me a note.	3924	If you know of other additional requirements drop me a note.
3592		3925
3593		3926
3594	=head1 COMPILER WARNINGS	3927	=head1 ALGORITHMIC COMPLEXITIES
3595		3928
3596	Depending on your compiler and compiler settings, you might get no or a	3929	In this section the complexities of (many of) the algorithms used inside
3597	lot of warnings when compiling libev code. Some people are apparently	3930	libev will be documented. For complexity discussions about backends see
3598	scared by this.	3931	the documentation for C<ev_default_init>.
3599		3932
3600	However, these are unavoidable for many reasons. For one, each compiler	3933	All of the following are about amortised time: If an array needs to be
3601	has different warnings, and each user has different tastes regarding	3934	extended, libev needs to realloc and move the whole array, but this
3602	warning options. "Warn-free" code therefore cannot be a goal except when	3935	happens asymptotically rarer with higher number of elements, so O(1) might
3603	targeting a specific compiler and compiler-version.	3936	mean that libev does a lengthy realloc operation in rare cases, but on
		3937	average it is much faster and asymptotically approaches constant time.
3604		3938
3605	Another reason is that some compiler warnings require elaborate	3939	=over 4
3606	workarounds, or other changes to the code that make it less clear and less
3607	maintainable.
3608		3940
3609	And of course, some compiler warnings are just plain stupid, or simply	3941	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3610	wrong (because they don't actually warn about the condition their message
3611	seems to warn about).
3612		3942
3613	While libev is written to generate as few warnings as possible,	3943	This means that, when you have a watcher that triggers in one hour and
3614	"warn-free" code is not a goal, and it is recommended not to build libev	3944	there are 100 watchers that would trigger before that, then inserting will
3615	with any compiler warnings enabled unless you are prepared to cope with	3945	have to skip roughly seven (C<ld 100>) of these watchers.
3616	them (e.g. by ignoring them). Remember that warnings are just that:
3617	warnings, not errors, or proof of bugs.
3618		3946
		3947	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3619		3948
3620	=head1 VALGRIND	3949	That means that changing a timer costs less than removing/adding them,
		3950	as only the relative motion in the event queue has to be paid for.
3621		3951
3622	Valgrind has a special section here because it is a popular tool that is	3952	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3623	highly useful, but valgrind reports are very hard to interpret.
3624		3953
3625	If you think you found a bug (memory leak, uninitialised data access etc.)	3954	These just add the watcher into an array or at the head of a list.
3626	in libev, then check twice: If valgrind reports something like:
3627		3955
3628	==2274== definitely lost: 0 bytes in 0 blocks.	3956	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3629	==2274== possibly lost: 0 bytes in 0 blocks.
3630	==2274== still reachable: 256 bytes in 1 blocks.
3631		3957
3632	Then there is no memory leak. Similarly, under some circumstances,	3958	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3633	valgrind might report kernel bugs as if it were a bug in libev, or it
3634	might be confused (it is a very good tool, but only a tool).
3635		3959
3636	If you are unsure about something, feel free to contact the mailing list	3960	These watchers are stored in lists, so they need to be walked to find the
3637	with the full valgrind report and an explanation on why you think this is	3961	correct watcher to remove. The lists are usually short (you don't usually
3638	a bug in libev. However, don't be annoyed when you get a brisk "this is	3962	have many watchers waiting for the same fd or signal: one is typical, two
3639	no bug" answer and take the chance of learning how to interpret valgrind	3963	is rare).
3640	properly.
3641		3964
3642	If you need, for some reason, empty reports from valgrind for your project	3965	=item Finding the next timer in each loop iteration: O(1)
3643	I suggest using suppression lists.	3966
		3967	By virtue of using a binary or 4-heap, the next timer is always found at a
		3968	fixed position in the storage array.
		3969
		3970	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3971
		3972	A change means an I/O watcher gets started or stopped, which requires
		3973	libev to recalculate its status (and possibly tell the kernel, depending
		3974	on backend and whether C<ev_io_set> was used).
		3975
		3976	=item Activating one watcher (putting it into the pending state): O(1)
		3977
		3978	=item Priority handling: O(number_of_priorities)
		3979
		3980	Priorities are implemented by allocating some space for each
		3981	priority. When doing priority-based operations, libev usually has to
		3982	linearly search all the priorities, but starting/stopping and activating
		3983	watchers becomes O(1) with respect to priority handling.
		3984
		3985	=item Sending an ev_async: O(1)
		3986
		3987	=item Processing ev_async_send: O(number_of_async_watchers)
		3988
		3989	=item Processing signals: O(max_signal_number)
		3990
		3991	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3992	calls in the current loop iteration. Checking for async and signal events
		3993	involves iterating over all running async watchers or all signal numbers.
		3994
		3995	=back
3644		3996
3645		3997
3646	=head1 AUTHOR	3998	=head1 AUTHOR
3647		3999
3648	Marc Lehmann <libev@schmorp.de>.	4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3649		4001

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