[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.190 by root, Tue Sep 30 19:34:14 2008 UTC vs.
Revision 1.230 by root, Wed Apr 15 18:47:07 2009 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
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>).
…		…
631	the loop.	658	the loop.
632		659
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	661	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	662	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	663	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	664	user-registered callback will be called), and will return after one
638	iteration of the loop.	665	iteration of the loop.
639		666
640	This is useful if you are waiting for some external event in conjunction	667	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	668	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	712	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.	713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		714
688	This "unloop state" will be cleared when entering C<ev_loop> again.	715	This "unloop state" will be cleared when entering C<ev_loop> again.
689		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
690	=item ev_ref (loop)	719	=item ev_ref (loop)
691		720
692	=item ev_unref (loop)	721	=item ev_unref (loop)
693		722
694	Ref/unref can be used to add or remove a reference count on the event	723	Ref/unref can be used to add or remove a reference count on the event
…		…
697		726
698	If you have a watcher you never unregister that should not keep C<ev_loop>	727	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	728	from returning, call ev_unref() after starting, and ev_ref() before
700	stopping it.	729	stopping it.
701		730
702	As an example, libev itself uses this for its internal signal pipe: It is	731	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	732	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	733	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	734	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>	735	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,	736	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	737	before, respectively. Note also that libev might stop watchers itself
		738	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		739	in the callback).
709		740
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	741	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	742	running when nothing else is active.
712		743
713	struct ev_signal exitsig;	744	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	745	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	746	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	747	evf_unref (loop);
717		748
718	Example: For some weird reason, unregister the above signal handler again.	749	Example: For some weird reason, unregister the above signal handler again.
…		…
766	they fire on, say, one-second boundaries only.	797	they fire on, say, one-second boundaries only.
767		798
768	=item ev_loop_verify (loop)	799	=item ev_loop_verify (loop)
769		800
770	This function only does something when C<EV_VERIFY> support has been	801	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	802	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	803	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	804	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	805	error and call C<abort ()>.
775		806
776	This can be used to catch bugs inside libev itself: under normal	807	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	811	=back
781		812
782		813
783	=head1 ANATOMY OF A WATCHER	814	=head1 ANATOMY OF A WATCHER
784		815
		816	In the following description, uppercase C<TYPE> in names stands for the
		817	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		818	watchers and C<ev_io_start> for I/O watchers.
		819
785	A watcher is a structure that you create and register to record your	820	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	821	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	822	become readable, you would create an C<ev_io> watcher for that:
788		823
789	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	824	static void my_cb (struct ev_loop loop, ev_io w, int revents)
790	{	825	{
791	ev_io_stop (w);	826	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	827	ev_unloop (loop, EVUNLOOP_ALL);
793	}	828	}
794		829
795	struct ev_loop *loop = ev_default_loop (0);	830	struct ev_loop *loop = ev_default_loop (0);
		831
796	struct ev_io stdin_watcher;	832	ev_io stdin_watcher;
		833
797	ev_init (&stdin_watcher, my_cb);	834	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	835	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	836	ev_io_start (loop, &stdin_watcher);
		837
800	ev_loop (loop, 0);	838	ev_loop (loop, 0);
801		839
802	As you can see, you are responsible for allocating the memory for your	840	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	841	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	842	stack).
		843
		844	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		845	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		846
806	Each watcher structure must be initialised by a call to C<ev_init	847	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	848	(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	849	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	850	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	851	is readable and/or writable).
811		852
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	853	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	854	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	855	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	856	ev_TYPE_init (watcher *, callback, ...) >>.
816		857
817	To make the watcher actually watch out for events, you have to start it	858	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	859	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	860	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	861	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		862
822	As long as your watcher is active (has been started but not stopped) you	863	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	864	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	865	reinitialise it or call its C<ev_TYPE_set> macro.
825		866
826	Each and every callback receives the event loop pointer as first, the	867	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	868	registered watcher structure as second, and a bitset of received events as
828	third argument.	869	third argument.
829		870
…		…
887		928
888	=item C<EV_ASYNC>	929	=item C<EV_ASYNC>
889		930
890	The given async watcher has been asynchronously notified (see C<ev_async>).	931	The given async watcher has been asynchronously notified (see C<ev_async>).
891		932
		933	=item C<EV_CUSTOM>
		934
		935	Not ever sent (or otherwise used) by libev itself, but can be freely used
		936	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		937
892	=item C<EV_ERROR>	938	=item C<EV_ERROR>
893		939
894	An unspecified error has occurred, the watcher has been stopped. This might	940	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	941	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	942	ran out of memory, a file descriptor was found to be closed or any other
		943	problem. Libev considers these application bugs.
		944
897	problem. You best act on it by reporting the problem and somehow coping	945	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	946	watcher being stopped. Note that well-written programs should not receive
		947	an error ever, so when your watcher receives it, this usually indicates a
		948	bug in your program.
899		949
900	Libev will usually signal a few "dummy" events together with an error, for	950	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	951	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	952	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	953	the error from read() or write(). This will not work in multi-threaded
…		…
906		956
907	=back	957	=back
908		958
909	=head2 GENERIC WATCHER FUNCTIONS	959	=head2 GENERIC WATCHER FUNCTIONS
910		960
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	961	=over 4
915		962
916	=item C<ev_init> (ev_TYPE *watcher, callback)	963	=item C<ev_init> (ev_TYPE *watcher, callback)
917		964
918	This macro initialises the generic portion of a watcher. The contents	965	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	970	which rolls both calls into one.
924		971
925	You can reinitialise a watcher at any time as long as it has been stopped	972	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	973	(or never started) and there are no pending events outstanding.
927		974
928	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	975	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
929	int revents)>.	976	int revents)>.
930		977
931	Example: Initialise an C<ev_io> watcher in two steps.	978	Example: Initialise an C<ev_io> watcher in two steps.
932		979
933	ev_io w;	980	ev_io w;
…		…
967		1014
968	ev_io_start (EV_DEFAULT_UC, &w);	1015	ev_io_start (EV_DEFAULT_UC, &w);
969		1016
970	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1017	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
971		1018
972	Stops the given watcher again (if active) and clears the pending	1019	Stops the given watcher if active, and clears the pending status (whether
		1020	the watcher was active or not).
		1021
973	status. It is possible that stopped watchers are pending (for example,	1022	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1023	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	1024	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	1025	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.	1026	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1027
979	=item bool ev_is_active (ev_TYPE *watcher)	1028	=item bool ev_is_active (ev_TYPE *watcher)
980		1029
981	Returns a true value iff the watcher is active (i.e. it has been started	1030	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1031	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1024	The default priority used by watchers when no priority has been set is	1073	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1074	always C<0>, which is supposed to not be too high and not be too low :).
1026		1075
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1076	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1028	fine, as long as you do not mind that the priority value you query might	1077	fine, as long as you do not mind that the priority value you query might
1029	or might not have been adjusted to be within valid range.	1078	or might not have been clamped to the valid range.
1030		1079
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1080	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1081
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1082	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1083	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1105	member, you can also "subclass" the watcher type and provide your own
1057	data:	1106	data:
1058		1107
1059	struct my_io	1108	struct my_io
1060	{	1109	{
1061	struct ev_io io;	1110	ev_io io;
1062	int otherfd;	1111	int otherfd;
1063	void *somedata;	1112	void *somedata;
1064	struct whatever *mostinteresting;	1113	struct whatever *mostinteresting;
1065	};	1114	};
1066		1115
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1118	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1119
1071	And since your callback will be called with a pointer to the watcher, you	1120	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1121	can cast it back to your own type:
1073		1122
1074	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1123	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1075	{	1124	{
1076	struct my_io w = (struct my_io )w_;	1125	struct my_io w = (struct my_io )w_;
1077	...	1126	...
1078	}	1127	}
1079		1128
…		…
1097	programmers):	1146	programmers):
1098		1147
1099	#include <stddef.h>	1148	#include <stddef.h>
1100		1149
1101	static void	1150	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1151	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1152	{
1104	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1154	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1155	}
1107		1156
1108	static void	1157	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1158	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1159	{
1111	struct my_biggy big = (struct my_biggy *	1160	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1161	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1162	}
1114		1163
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1298	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1299	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1300	attempt to read a whole line in the callback.
1252		1301
1253	static void	1302	static void
1254	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1303	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1255	{	1304	{
1256	ev_io_stop (loop, w);	1305	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1306	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1307	}
1259		1308
1260	...	1309	...
1261	struct ev_loop *loop = ev_default_init (0);	1310	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1311	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1312	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1313	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1314	ev_loop (loop, 0);
1266		1315
1267		1316
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1324	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1325	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1326	monotonic clock option helps a lot here).
1278		1327
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1328	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	1329	passed. If multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1330	then the ones with earlier time-out values are invoked before ones with
		1331	later time-out values (but this is no longer true when a callback calls
		1332	C<ev_loop> recursively).
		1333
		1334	=head3 Be smart about timeouts
		1335
		1336	Many real-world problems involve some kind of timeout, usually for error
		1337	recovery. A typical example is an HTTP request - if the other side hangs,
		1338	you want to raise some error after a while.
		1339
		1340	What follows are some ways to handle this problem, from obvious and
		1341	inefficient to smart and efficient.
		1342
		1343	In the following, a 60 second activity timeout is assumed - a timeout that
		1344	gets reset to 60 seconds each time there is activity (e.g. each time some
		1345	data or other life sign was received).
		1346
		1347	=over 4
		1348
		1349	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1350
		1351	This is the most obvious, but not the most simple way: In the beginning,
		1352	start the watcher:
		1353
		1354	ev_timer_init (timer, callback, 60., 0.);
		1355	ev_timer_start (loop, timer);
		1356
		1357	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1358	and start it again:
		1359
		1360	ev_timer_stop (loop, timer);
		1361	ev_timer_set (timer, 60., 0.);
		1362	ev_timer_start (loop, timer);
		1363
		1364	This is relatively simple to implement, but means that each time there is
		1365	some activity, libev will first have to remove the timer from its internal
		1366	data structure and then add it again. Libev tries to be fast, but it's
		1367	still not a constant-time operation.
		1368
		1369	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1370
		1371	This is the easiest way, and involves using C<ev_timer_again> instead of
		1372	C<ev_timer_start>.
		1373
		1374	To implement this, configure an C<ev_timer> with a C<repeat> value
		1375	of C<60> and then call C<ev_timer_again> at start and each time you
		1376	successfully read or write some data. If you go into an idle state where
		1377	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1378	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1379
		1380	That means you can ignore both the C<ev_timer_start> function and the
		1381	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1382	member and C<ev_timer_again>.
		1383
		1384	At start:
		1385
		1386	ev_timer_init (timer, callback);
		1387	timer->repeat = 60.;
		1388	ev_timer_again (loop, timer);
		1389
		1390	Each time there is some activity:
		1391
		1392	ev_timer_again (loop, timer);
		1393
		1394	It is even possible to change the time-out on the fly, regardless of
		1395	whether the watcher is active or not:
		1396
		1397	timer->repeat = 30.;
		1398	ev_timer_again (loop, timer);
		1399
		1400	This is slightly more efficient then stopping/starting the timer each time
		1401	you want to modify its timeout value, as libev does not have to completely
		1402	remove and re-insert the timer from/into its internal data structure.
		1403
		1404	It is, however, even simpler than the "obvious" way to do it.
		1405
		1406	=item 3. Let the timer time out, but then re-arm it as required.
		1407
		1408	This method is more tricky, but usually most efficient: Most timeouts are
		1409	relatively long compared to the intervals between other activity - in
		1410	our example, within 60 seconds, there are usually many I/O events with
		1411	associated activity resets.
		1412
		1413	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1414	but remember the time of last activity, and check for a real timeout only
		1415	within the callback:
		1416
		1417	ev_tstamp last_activity; // time of last activity
		1418
		1419	static void
		1420	callback (EV_P_ ev_timer *w, int revents)
		1421	{
		1422	ev_tstamp now = ev_now (EV_A);
		1423	ev_tstamp timeout = last_activity + 60.;
		1424
		1425	// if last_activity + 60. is older than now, we did time out
		1426	if (timeout < now)
		1427	{
		1428	// timeout occured, take action
		1429	}
		1430	else
		1431	{
		1432	// callback was invoked, but there was some activity, re-arm
		1433	// the watcher to fire in last_activity + 60, which is
		1434	// guaranteed to be in the future, so "again" is positive:
		1435	w->repeat = timeout - now;
		1436	ev_timer_again (EV_A_ w);
		1437	}
		1438	}
		1439
		1440	To summarise the callback: first calculate the real timeout (defined
		1441	as "60 seconds after the last activity"), then check if that time has
		1442	been reached, which means something I<did>, in fact, time out. Otherwise
		1443	the callback was invoked too early (C<timeout> is in the future), so
		1444	re-schedule the timer to fire at that future time, to see if maybe we have
		1445	a timeout then.
		1446
		1447	Note how C<ev_timer_again> is used, taking advantage of the
		1448	C<ev_timer_again> optimisation when the timer is already running.
		1449
		1450	This scheme causes more callback invocations (about one every 60 seconds
		1451	minus half the average time between activity), but virtually no calls to
		1452	libev to change the timeout.
		1453
		1454	To start the timer, simply initialise the watcher and set C<last_activity>
		1455	to the current time (meaning we just have some activity :), then call the
		1456	callback, which will "do the right thing" and start the timer:
		1457
		1458	ev_timer_init (timer, callback);
		1459	last_activity = ev_now (loop);
		1460	callback (loop, timer, EV_TIMEOUT);
		1461
		1462	And when there is some activity, simply store the current time in
		1463	C<last_activity>, no libev calls at all:
		1464
		1465	last_actiivty = ev_now (loop);
		1466
		1467	This technique is slightly more complex, but in most cases where the
		1468	time-out is unlikely to be triggered, much more efficient.
		1469
		1470	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1471	callback :) - just change the timeout and invoke the callback, which will
		1472	fix things for you.
		1473
		1474	=item 4. Wee, just use a double-linked list for your timeouts.
		1475
		1476	If there is not one request, but many thousands (millions...), all
		1477	employing some kind of timeout with the same timeout value, then one can
		1478	do even better:
		1479
		1480	When starting the timeout, calculate the timeout value and put the timeout
		1481	at the I<end> of the list.
		1482
		1483	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1484	the list is expected to fire (for example, using the technique #3).
		1485
		1486	When there is some activity, remove the timer from the list, recalculate
		1487	the timeout, append it to the end of the list again, and make sure to
		1488	update the C<ev_timer> if it was taken from the beginning of the list.
		1489
		1490	This way, one can manage an unlimited number of timeouts in O(1) time for
		1491	starting, stopping and updating the timers, at the expense of a major
		1492	complication, and having to use a constant timeout. The constant timeout
		1493	ensures that the list stays sorted.
		1494
		1495	=back
		1496
		1497	So which method the best?
		1498
		1499	Method #2 is a simple no-brain-required solution that is adequate in most
		1500	situations. Method #3 requires a bit more thinking, but handles many cases
		1501	better, and isn't very complicated either. In most case, choosing either
		1502	one is fine, with #3 being better in typical situations.
		1503
		1504	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1505	rather complicated, but extremely efficient, something that really pays
		1506	off after the first million or so of active timers, i.e. it's usually
		1507	overkill :)
1282		1508
1283	=head3 The special problem of time updates	1509	=head3 The special problem of time updates
1284		1510
1285	Establishing the current time is a costly operation (it usually takes at	1511	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	1512	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).	1556	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1557
1332	If the timer is repeating, either start it if necessary (with the	1558	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1559	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1560
1335	This sounds a bit complicated, but here is a useful and typical	1561	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1562	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		1563
1366	=item ev_tstamp repeat [read-write]	1564	=item ev_tstamp repeat [read-write]
1367		1565
1368	The current C<repeat> value. Will be used each time the watcher times out	1566	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1567	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1572	=head3 Examples
1375		1573
1376	Example: Create a timer that fires after 60 seconds.	1574	Example: Create a timer that fires after 60 seconds.
1377		1575
1378	static void	1576	static void
1379	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1577	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1380	{	1578	{
1381	.. one minute over, w is actually stopped right here	1579	.. one minute over, w is actually stopped right here
1382	}	1580	}
1383		1581
1384	struct ev_timer mytimer;	1582	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1583	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1584	ev_timer_start (loop, &mytimer);
1387		1585
1388	Example: Create a timeout timer that times out after 10 seconds of	1586	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1587	inactivity.
1390		1588
1391	static void	1589	static void
1392	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1590	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1393	{	1591	{
1394	.. ten seconds without any activity	1592	.. ten seconds without any activity
1395	}	1593	}
1396		1594
1397	struct ev_timer mytimer;	1595	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1596	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1597	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1598	ev_loop (loop, 0);
1401		1599
1402	// and in some piece of code that gets executed on any "activity":	1600	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1605	=head2 C<ev_periodic> - to cron or not to cron?
1408		1606
1409	Periodic watchers are also timers of a kind, but they are very versatile	1607	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1608	(and unfortunately a bit complex).
1411		1609
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1610	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	1611	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	1612	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1613	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	1614	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	1615	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		1616
		1617	You can tell a periodic watcher to trigger after some specific point
		1618	in time: for example, if you tell a periodic watcher to trigger "in 10
		1619	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1620	not a delay) and then reset your system clock to January of the previous
		1621	year, then it will take a year or more to trigger the event (unlike an
		1622	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1623	it, as it uses a relative timeout).
		1624
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1625	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	1626	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1627	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1628	those cannot react to time jumps.
1424		1629
1425	As with timers, the callback is guaranteed to be invoked only when the	1630	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	1631	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	1632	timers become ready during the same loop iteration then the ones with
		1633	earlier time-out values are invoked before ones with later time-out values
		1634	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1635
1429	=head3 Watcher-Specific Functions and Data Members	1636	=head3 Watcher-Specific Functions and Data Members
1430		1637
1431	=over 4	1638	=over 4
1432		1639
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1640	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1641
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1642	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1643
1437	Lots of arguments, lets sort it out... There are basically three modes of	1644	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	1645	operation, and we will explain them from simplest to most complex:
1439		1646
1440	=over 4	1647	=over 4
1441		1648
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1649	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		1650
1444	In this configuration the watcher triggers an event after the wall clock	1651	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	1652	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	1653	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.	1654	will be stopped and invoked when the system clock reaches or surpasses
		1655	this point in time.
1448		1656
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1657	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		1658
1451	In this mode the watcher will always be scheduled to time out at the next	1659	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	1660	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	1661	negative) and then repeat, regardless of any time jumps. The C<offset>
		1662	argument is merely an offset into the C<interval> periods.
1454		1663
1455	This can be used to create timers that do not drift with respect to the	1664	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	1665	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	1666	hour, on the hour (with respect to UTC):
1458		1667
1459	ev_periodic_set (&periodic, 0., 3600., 0);	1668	ev_periodic_set (&periodic, 0., 3600., 0);
1460		1669
1461	This doesn't mean there will always be 3600 seconds in between triggers,	1670	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	1671	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	1672	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	1673	by 3600.
1465		1674
1466	Another way to think about it (for the mathematically inclined) is that	1675	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	1676	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	1677	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		1678
1470	For numerical stability it is preferable that the C<at> value is near	1679	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	1680	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	1681	this value, and in fact is often specified as zero.
1473		1682
1474	Note also that there is an upper limit to how often a timer can fire (CPU	1683	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	1684	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	1685	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	1686	millisecond (if the OS supports it and the machine is fast enough).
1478		1687
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1688	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		1689
1481	In this mode the values for C<interval> and C<at> are both being	1690	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	1691	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	1692	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	1693	current time as second argument.
1485		1694
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1695	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	1696	or make ANY other event loop modifications whatsoever, unless explicitly
		1697	allowed by documentation here>.
1488		1698
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1699	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1700	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1701	only event loop modification you are allowed to do).
1492		1702
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1703	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1704	*w, ev_tstamp now)>, e.g.:
1495		1705
		1706	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1707	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1708	{
1498	return now + 60.;	1709	return now + 60.;
1499	}	1710	}
1500		1711
1501	It must return the next time to trigger, based on the passed time value	1712	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	1732	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	1733	program when the crontabs have changed).
1523		1734
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	1735	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		1736
1526	When active, returns the absolute time that the watcher is supposed to	1737	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	1738	to trigger next. This is not the same as the C<offset> argument to
		1739	C<ev_periodic_set>, but indeed works even in interval and manual
		1740	rescheduling modes.
1528		1741
1529	=item ev_tstamp offset [read-write]	1742	=item ev_tstamp offset [read-write]
1530		1743
1531	When repeating, this contains the offset value, otherwise this is the	1744	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>).	1745	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1746	although libev might modify this value for better numerical stability).
1533		1747
1534	Can be modified any time, but changes only take effect when the periodic	1748	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	1749	timer fires or C<ev_periodic_again> is being called.
1536		1750
1537	=item ev_tstamp interval [read-write]	1751	=item ev_tstamp interval [read-write]
1538		1752
1539	The current interval value. Can be modified any time, but changes only	1753	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	1754	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1755	called.
1542		1756
1543	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1757	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1544		1758
1545	The current reschedule callback, or C<0>, if this functionality is	1759	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	1760	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.	1761	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1762
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1767	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1768	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1769	potentially a lot of jitter, but good long-term stability.
1556		1770
1557	static void	1771	static void
1558	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1772	clock_cb (struct ev_loop loop, ev_io w, int revents)
1559	{	1773	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1774	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1775	}
1562		1776
1563	struct ev_periodic hourly_tick;	1777	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1778	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1779	ev_periodic_start (loop, &hourly_tick);
1566		1780
1567	Example: The same as above, but use a reschedule callback to do it:	1781	Example: The same as above, but use a reschedule callback to do it:
1568		1782
1569	#include <math.h>	1783	#include <math.h>
1570		1784
1571	static ev_tstamp	1785	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1786	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1787	{
1574	return now + (3600. - fmod (now, 3600.));	1788	return now + (3600. - fmod (now, 3600.));
1575	}	1789	}
1576		1790
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1791	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1792
1579	Example: Call a callback every hour, starting now:	1793	Example: Call a callback every hour, starting now:
1580		1794
1581	struct ev_periodic hourly_tick;	1795	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1796	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1797	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1798	ev_periodic_start (loop, &hourly_tick);
1585		1799
1586		1800
…		…
1628	=head3 Examples	1842	=head3 Examples
1629		1843
1630	Example: Try to exit cleanly on SIGINT.	1844	Example: Try to exit cleanly on SIGINT.
1631		1845
1632	static void	1846	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1847	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1634	{	1848	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1849	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1850	}
1637		1851
1638	struct ev_signal signal_watcher;	1852	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1853	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &signal_watcher);	1854	ev_signal_start (loop, &signal_watcher);
1641		1855
1642		1856
1643	=head2 C<ev_child> - watch out for process status changes	1857	=head2 C<ev_child> - watch out for process status changes
…		…
1718	its completion.	1932	its completion.
1719		1933
1720	ev_child cw;	1934	ev_child cw;
1721		1935
1722	static void	1936	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1937	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1938	{
1725	ev_child_stop (EV_A_ w);	1939	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1940	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1941	}
1728		1942
…		…
1743		1957
1744		1958
1745	=head2 C<ev_stat> - did the file attributes just change?	1959	=head2 C<ev_stat> - did the file attributes just change?
1746		1960
1747	This watches a file system path for attribute changes. That is, it calls	1961	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	1962	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	1963	and sees if it changed compared to the last time, invoking the callback if
		1964	it did.
1750		1965
1751	The path does not need to exist: changing from "path exists" to "path does	1966	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	1967	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	1968	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	1969	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	1970	least one) and all the other fields of the stat buffer having unspecified
		1971	contents.
1756		1972
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	1973	The path I<must not> end in a slash or contain special components such as
		1974	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	1975	your working directory changes, then the behaviour is undefined.
1759		1976
1760	Since there is no standard kernel interface to do this, the portable	1977	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	1978	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	1979	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!)	1980	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	1981	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	1982	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	1983	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	1984	currently around C<0.1>, but that's usually overkill.
1768		1985
1769	This watcher type is not meant for massive numbers of stat watchers,	1986	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	1987	as even with OS-supported change notifications, this can be
1771	resource-intensive.	1988	resource-intensive.
1772		1989
1773	At the time of this writing, the only OS-specific interface implemented	1990	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	1991	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	1992	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	1993	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		1994
1778	=head3 ABI Issues (Largefile Support)	1995	=head3 ABI Issues (Largefile Support)
1779		1996
1780	Libev by default (unless the user overrides this) uses the default	1997	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	1998	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	1999	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2000	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2001	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2002	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2003	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2004	most noticeably displayed with ev_stat and large file support.
1788		2005
1789	The solution for this is to lobby your distribution maker to make large	2006	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2007	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2008	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2009	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2010	default compilation environment.
1794		2011
1795	=head3 Inotify and Kqueue	2012	=head3 Inotify and Kqueue
1796		2013
1797	When C<inotify (7)> support has been compiled into libev (generally only	2014	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2015	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2016	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2017	watcher is being started.
1801		2018
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2019	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2020	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2021	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2022	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2023	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2024	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2025	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2026	xfs are fully working) libev usually gets away without polling.
1807		2027
1808	There is no support for kqueue, as apparently it cannot be used to	2028	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2029	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2030	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2031	etc. is difficult.
1812		2032
		2033	=head3 C<stat ()> is a synchronous operation
		2034
		2035	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2036	the process. The exception are C<ev_stat> watchers - those call C<stat
		2037	()>, which is a synchronous operation.
		2038
		2039	For local paths, this usually doesn't matter: unless the system is very
		2040	busy or the intervals between stat's are large, a stat call will be fast,
		2041	as the path data is usually in memory already (except when starting the
		2042	watcher).
		2043
		2044	For networked file systems, calling C<stat ()> can block an indefinite
		2045	time due to network issues, and even under good conditions, a stat call
		2046	often takes multiple milliseconds.
		2047
		2048	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2049	paths, although this is fully supported by libev.
		2050
1813	=head3 The special problem of stat time resolution	2051	=head3 The special problem of stat time resolution
1814		2052
1815	The C<stat ()> system call only supports full-second resolution portably, and	2053	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2054	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2055	still only support whole seconds.
1818		2056
1819	That means that, if the time is the only thing that changes, you can	2057	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2058	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2059	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	2060	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2203
1966	=head3 Watcher-Specific Functions and Data Members	2204	=head3 Watcher-Specific Functions and Data Members
1967		2205
1968	=over 4	2206	=over 4
1969		2207
1970	=item ev_idle_init (ev_signal *, callback)	2208	=item ev_idle_init (ev_idle *, callback)
1971		2209
1972	Initialises and configures the idle watcher - it has no parameters of any	2210	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2211	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2212	believe me.
1975		2213
…		…
1979		2217
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2218	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2219	callback, free it. Also, use no error checking, as usual.
1982		2220
1983	static void	2221	static void
1984	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2222	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1985	{	2223	{
1986	free (w);	2224	free (w);
1987	// now do something you wanted to do when the program has	2225	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2226	// no longer anything immediate to do.
1989	}	2227	}
1990		2228
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2229	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2230	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2231	ev_idle_start (loop, idle_cb);
1994		2232
1995		2233
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2234	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2315
2078	static ev_io iow [nfd];	2316	static ev_io iow [nfd];
2079	static ev_timer tw;	2317	static ev_timer tw;
2080		2318
2081	static void	2319	static void
2082	io_cb (ev_loop loop, ev_io w, int revents)	2320	io_cb (struct ev_loop loop, ev_io w, int revents)
2083	{	2321	{
2084	}	2322	}
2085		2323
2086	// create io watchers for each fd and a timer before blocking	2324	// create io watchers for each fd and a timer before blocking
2087	static void	2325	static void
2088	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2326	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2089	{	2327	{
2090	int timeout = 3600000;	2328	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2329	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2330	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2331	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2346	}
2109	}	2347	}
2110		2348
2111	// stop all watchers after blocking	2349	// stop all watchers after blocking
2112	static void	2350	static void
2113	adns_check_cb (ev_loop loop, ev_check w, int revents)	2351	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2114	{	2352	{
2115	ev_timer_stop (loop, &tw);	2353	ev_timer_stop (loop, &tw);
2116		2354
2117	for (int i = 0; i < nfd; ++i)	2355	for (int i = 0; i < nfd; ++i)
2118	{	2356	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2452	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	2453	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	2454	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.	2455	the rest in a second one, and embed the second one in the first.
2218		2456
2219	As long as the watcher is active, the callback will be invoked every time	2457	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2458	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2459	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2460	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2461	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2462	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2463
2227	As long as the watcher is started it will automatically handle events. The	2464	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2465	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		2466
2232	Also, there have not currently been made special provisions for forking:	2467	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,	2468	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	2469	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,	2470	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2471
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2472	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2473	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2474	portable one.
2241		2475
…		…
2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2520	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2287	used).	2521	used).
2288		2522
2289	struct ev_loop *loop_hi = ev_default_init (0);	2523	struct ev_loop *loop_hi = ev_default_init (0);
2290	struct ev_loop *loop_lo = 0;	2524	struct ev_loop *loop_lo = 0;
2291	struct ev_embed embed;	2525	ev_embed embed;
2292		2526
2293	// see if there is a chance of getting one that works	2527	// see if there is a chance of getting one that works
2294	// (remember that a flags value of 0 means autodetection)	2528	// (remember that a flags value of 0 means autodetection)
2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2529	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2530	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2310	kqueue implementation). Store the kqueue/socket-only event loop in	2544	kqueue implementation). Store the kqueue/socket-only event loop in
2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2545	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2312		2546
2313	struct ev_loop *loop = ev_default_init (0);	2547	struct ev_loop *loop = ev_default_init (0);
2314	struct ev_loop *loop_socket = 0;	2548	struct ev_loop *loop_socket = 0;
2315	struct ev_embed embed;	2549	ev_embed embed;
2316		2550
2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2551	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2552	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2319	{	2553	{
2320	ev_embed_init (&embed, 0, loop_socket);	2554	ev_embed_init (&embed, 0, loop_socket);
…		…
2384	=over 4	2618	=over 4
2385		2619
2386	=item queueing from a signal handler context	2620	=item queueing from a signal handler context
2387		2621
2388	To implement race-free queueing, you simply add to the queue in the signal	2622	To implement race-free queueing, you simply add to the queue in the signal
2389	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2623	handler but you block the signal handler in the watcher callback. Here is
2390	some fictitious SIGUSR1 handler:	2624	an example that does that for some fictitious SIGUSR1 handler:
2391		2625
2392	static ev_async mysig;	2626	static ev_async mysig;
2393		2627
2394	static void	2628	static void
2395	sigusr1_handler (void)	2629	sigusr1_handler (void)
…		…
2461	=over 4	2695	=over 4
2462		2696
2463	=item ev_async_init (ev_async *, callback)	2697	=item ev_async_init (ev_async *, callback)
2464		2698
2465	Initialises and configures the async watcher - it has no parameters of any	2699	Initialises and configures the async watcher - it has no parameters of any
2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2700	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2467	trust me.	2701	trust me.
2468		2702
2469	=item ev_async_send (loop, ev_async *)	2703	=item ev_async_send (loop, ev_async *)
2470		2704
2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2705	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2706	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2473	C<ev_feed_event>, this call is safe to do from other threads, signal or	2707	C<ev_feed_event>, this call is safe to do from other threads, signal or
2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2708	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2475	section below on what exactly this means).	2709	section below on what exactly this means).
2476		2710
		2711	Note that, as with other watchers in libev, multiple events might get
		2712	compressed into a single callback invocation (another way to look at this
		2713	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2714	reset when the event loop detects that).
		2715
2477	This call incurs the overhead of a system call only once per loop iteration,	2716	This call incurs the overhead of a system call only once per event loop
2478	so while the overhead might be noticeable, it doesn't apply to repeated	2717	iteration, so while the overhead might be noticeable, it doesn't apply to
2479	calls to C<ev_async_send>.	2718	repeated calls to C<ev_async_send> for the same event loop.
2480		2719
2481	=item bool = ev_async_pending (ev_async *)	2720	=item bool = ev_async_pending (ev_async *)
2482		2721
2483	Returns a non-zero value when C<ev_async_send> has been called on the	2722	Returns a non-zero value when C<ev_async_send> has been called on the
2484	watcher but the event has not yet been processed (or even noted) by the	2723	watcher but the event has not yet been processed (or even noted) by the
…		…
2487	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2726	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2488	the loop iterates next and checks for the watcher to have become active,	2727	the loop iterates next and checks for the watcher to have become active,
2489	it will reset the flag again. C<ev_async_pending> can be used to very	2728	it will reset the flag again. C<ev_async_pending> can be used to very
2490	quickly check whether invoking the loop might be a good idea.	2729	quickly check whether invoking the loop might be a good idea.
2491		2730
2492	Not that this does I<not> check whether the watcher itself is pending, only	2731	Not that this does I<not> check whether the watcher itself is pending,
2493	whether it has been requested to make this watcher pending.	2732	only whether it has been requested to make this watcher pending: there
		2733	is a time window between the event loop checking and resetting the async
		2734	notification, and the callback being invoked.
2494		2735
2495	=back	2736	=back
2496		2737
2497		2738
2498	=head1 OTHER FUNCTIONS	2739	=head1 OTHER FUNCTIONS
…		…
2502	=over 4	2743	=over 4
2503		2744
2504	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2745	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2505		2746
2506	This function combines a simple timer and an I/O watcher, calls your	2747	This function combines a simple timer and an I/O watcher, calls your
2507	callback on whichever event happens first and automatically stop both	2748	callback on whichever event happens first and automatically stops both
2508	watchers. This is useful if you want to wait for a single event on an fd	2749	watchers. This is useful if you want to wait for a single event on an fd
2509	or timeout without having to allocate/configure/start/stop/free one or	2750	or timeout without having to allocate/configure/start/stop/free one or
2510	more watchers yourself.	2751	more watchers yourself.
2511		2752
2512	If C<fd> is less than 0, then no I/O watcher will be started and events	2753	If C<fd> is less than 0, then no I/O watcher will be started and the
2513	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2754	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514	C<events> set will be created and started.	2755	the given C<fd> and C<events> set will be created and started.
2515		2756
2516	If C<timeout> is less than 0, then no timeout watcher will be	2757	If C<timeout> is less than 0, then no timeout watcher will be
2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2758	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2759	repeat = 0) will be started. C<0> is a valid timeout.
2519	dubious value.
2520		2760
2521	The callback has the type C<void (cb)(int revents, void arg)> and gets	2761	The callback has the type C<void (cb)(int revents, void arg)> and gets
2522	passed an C<revents> set like normal event callbacks (a combination of	2762	passed an C<revents> set like normal event callbacks (a combination of
2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2763	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2524	value passed to C<ev_once>:	2764	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2765	a timeout and an io event at the same time - you probably should give io
		2766	events precedence.
		2767
		2768	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525		2769
2526	static void stdin_ready (int revents, void *arg)	2770	static void stdin_ready (int revents, void *arg)
2527	{	2771	{
		2772	if (revents & EV_READ)
		2773	/* stdin might have data for us, joy! */;
2528	if (revents & EV_TIMEOUT)	2774	else if (revents & EV_TIMEOUT)
2529	/* doh, nothing entered */;	2775	/* doh, nothing entered */;
2530	else if (revents & EV_READ)
2531	/* stdin might have data for us, joy! */;
2532	}	2776	}
2533		2777
2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2778	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535		2779
2536	=item ev_feed_event (ev_loop , watcher , int revents)	2780	=item ev_feed_event (struct ev_loop , watcher , int revents)
2537		2781
2538	Feeds the given event set into the event loop, as if the specified event	2782	Feeds the given event set into the event loop, as if the specified event
2539	had happened for the specified watcher (which must be a pointer to an	2783	had happened for the specified watcher (which must be a pointer to an
2540	initialised but not necessarily started event watcher).	2784	initialised but not necessarily started event watcher).
2541		2785
2542	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2786	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2543		2787
2544	Feed an event on the given fd, as if a file descriptor backend detected	2788	Feed an event on the given fd, as if a file descriptor backend detected
2545	the given events it.	2789	the given events it.
2546		2790
2547	=item ev_feed_signal_event (ev_loop *loop, int signum)	2791	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2548		2792
2549	Feed an event as if the given signal occurred (C<loop> must be the default	2793	Feed an event as if the given signal occurred (C<loop> must be the default
2550	loop!).	2794	loop!).
2551		2795
2552	=back	2796	=back
…		…
2673	}	2917	}
2674		2918
2675	myclass obj;	2919	myclass obj;
2676	ev::io iow;	2920	ev::io iow;
2677	iow.set <myclass, &myclass::io_cb> (&obj);	2921	iow.set <myclass, &myclass::io_cb> (&obj);
		2922
		2923	=item w->set (object *)
		2924
		2925	This is an B<experimental> feature that might go away in a future version.
		2926
		2927	This is a variation of a method callback - leaving out the method to call
		2928	will default the method to C<operator ()>, which makes it possible to use
		2929	functor objects without having to manually specify the C<operator ()> all
		2930	the time. Incidentally, you can then also leave out the template argument
		2931	list.
		2932
		2933	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2934	int revents)>.
		2935
		2936	See the method-C<set> above for more details.
		2937
		2938	Example: use a functor object as callback.
		2939
		2940	struct myfunctor
		2941	{
		2942	void operator() (ev::io &w, int revents)
		2943	{
		2944	...
		2945	}
		2946	}
		2947
		2948	myfunctor f;
		2949
		2950	ev::io w;
		2951	w.set (&f);
2678		2952
2679	=item w->set<function> (void *data = 0)	2953	=item w->set<function> (void *data = 0)
2680		2954
2681	Also sets a callback, but uses a static method or plain function as	2955	Also sets a callback, but uses a static method or plain function as
2682	callback. The optional C<data> argument will be stored in the watcher's	2956	callback. The optional C<data> argument will be stored in the watcher's
…		…
2769	L<http://software.schmorp.de/pkg/EV>.	3043	L<http://software.schmorp.de/pkg/EV>.
2770		3044
2771	=item Python	3045	=item Python
2772		3046
2773	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3047	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2774	seems to be quite complete and well-documented. Note, however, that the	3048	seems to be quite complete and well-documented.
2775	patch they require for libev is outright dangerous as it breaks the ABI
2776	for everybody else, and therefore, should never be applied in an installed
2777	libev (if python requires an incompatible ABI then it needs to embed
2778	libev).
2779		3049
2780	=item Ruby	3050	=item Ruby
2781		3051
2782	Tony Arcieri has written a ruby extension that offers access to a subset	3052	Tony Arcieri has written a ruby extension that offers access to a subset
2783	of the libev API and adds file handle abstractions, asynchronous DNS and	3053	of the libev API and adds file handle abstractions, asynchronous DNS and
2784	more on top of it. It can be found via gem servers. Its homepage is at	3054	more on top of it. It can be found via gem servers. Its homepage is at
2785	L<http://rev.rubyforge.org/>.	3055	L<http://rev.rubyforge.org/>.
2786		3056
		3057	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3058	makes rev work even on mingw.
		3059
		3060	=item Haskell
		3061
		3062	A haskell binding to libev is available at
		3063	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3064
2787	=item D	3065	=item D
2788		3066
2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3067	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3068	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3069
		3070	=item Ocaml
		3071
		3072	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3073	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2791		3074
2792	=back	3075	=back
2793		3076
2794		3077
2795	=head1 MACRO MAGIC	3078	=head1 MACRO MAGIC
…		…
2896		3179
2897	#define EV_STANDALONE 1	3180	#define EV_STANDALONE 1
2898	#include "ev.h"	3181	#include "ev.h"
2899		3182
2900	Both header files and implementation files can be compiled with a C++	3183	Both header files and implementation files can be compiled with a C++
2901	compiler (at least, thats a stated goal, and breakage will be treated	3184	compiler (at least, that's a stated goal, and breakage will be treated
2902	as a bug).	3185	as a bug).
2903		3186
2904	You need the following files in your source tree, or in a directory	3187	You need the following files in your source tree, or in a directory
2905	in your include path (e.g. in libev/ when using -Ilibev):	3188	in your include path (e.g. in libev/ when using -Ilibev):
2906		3189
…		…
2962	keeps libev from including F<config.h>, and it also defines dummy	3245	keeps libev from including F<config.h>, and it also defines dummy
2963	implementations for some libevent functions (such as logging, which is not	3246	implementations for some libevent functions (such as logging, which is not
2964	supported). It will also not define any of the structs usually found in	3247	supported). It will also not define any of the structs usually found in
2965	F<event.h> that are not directly supported by the libev core alone.	3248	F<event.h> that are not directly supported by the libev core alone.
2966		3249
		3250	In stanbdalone mode, libev will still try to automatically deduce the
		3251	configuration, but has to be more conservative.
		3252
2967	=item EV_USE_MONOTONIC	3253	=item EV_USE_MONOTONIC
2968		3254
2969	If defined to be C<1>, libev will try to detect the availability of the	3255	If defined to be C<1>, libev will try to detect the availability of the
2970	monotonic clock option at both compile time and runtime. Otherwise no use	3256	monotonic clock option at both compile time and runtime. Otherwise no
2971	of the monotonic clock option will be attempted. If you enable this, you	3257	use of the monotonic clock option will be attempted. If you enable this,
2972	usually have to link against librt or something similar. Enabling it when	3258	you usually have to link against librt or something similar. Enabling it
2973	the functionality isn't available is safe, though, although you have	3259	when the functionality isn't available is safe, though, although you have
2974	to make sure you link against any libraries where the C<clock_gettime>	3260	to make sure you link against any libraries where the C<clock_gettime>
2975	function is hiding in (often F<-lrt>).	3261	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2976		3262
2977	=item EV_USE_REALTIME	3263	=item EV_USE_REALTIME
2978		3264
2979	If defined to be C<1>, libev will try to detect the availability of the	3265	If defined to be C<1>, libev will try to detect the availability of the
2980	real-time clock option at compile time (and assume its availability at	3266	real-time clock option at compile time (and assume its availability
2981	runtime if successful). Otherwise no use of the real-time clock option will	3267	at runtime if successful). Otherwise no use of the real-time clock
2982	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3268	option will be attempted. This effectively replaces C<gettimeofday>
2983	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3269	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2984	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3270	correctness. See the note about libraries in the description of
		3271	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3272	C<EV_USE_CLOCK_SYSCALL>.
		3273
		3274	=item EV_USE_CLOCK_SYSCALL
		3275
		3276	If defined to be C<1>, libev will try to use a direct syscall instead
		3277	of calling the system-provided C<clock_gettime> function. This option
		3278	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3279	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3280	programs needlessly. Using a direct syscall is slightly slower (in
		3281	theory), because no optimised vdso implementation can be used, but avoids
		3282	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3283	higher, as it simplifies linking (no need for C<-lrt>).
2985		3284
2986	=item EV_USE_NANOSLEEP	3285	=item EV_USE_NANOSLEEP
2987		3286
2988	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3287	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2989	and will use it for delays. Otherwise it will use C<select ()>.	3288	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3005		3304
3006	=item EV_SELECT_USE_FD_SET	3305	=item EV_SELECT_USE_FD_SET
3007		3306
3008	If defined to C<1>, then the select backend will use the system C<fd_set>	3307	If defined to C<1>, then the select backend will use the system C<fd_set>
3009	structure. This is useful if libev doesn't compile due to a missing	3308	structure. This is useful if libev doesn't compile due to a missing
3010	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3309	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3011	exotic systems. This usually limits the range of file descriptors to some	3310	on exotic systems. This usually limits the range of file descriptors to
3012	low limit such as 1024 or might have other limitations (winsocket only	3311	some low limit such as 1024 or might have other limitations (winsocket
3013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3312	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3014	influence the size of the C<fd_set> used.	3313	configures the maximum size of the C<fd_set>.
3015		3314
3016	=item EV_SELECT_IS_WINSOCKET	3315	=item EV_SELECT_IS_WINSOCKET
3017		3316
3018	When defined to C<1>, the select backend will assume that	3317	When defined to C<1>, the select backend will assume that
3019	select/socket/connect etc. don't understand file descriptors but	3318	select/socket/connect etc. don't understand file descriptors but
…		…
3313	=head2 THREADS AND COROUTINES	3612	=head2 THREADS AND COROUTINES
3314		3613
3315	=head3 THREADS	3614	=head3 THREADS
3316		3615
3317	All libev functions are reentrant and thread-safe unless explicitly	3616	All libev functions are reentrant and thread-safe unless explicitly
3318	documented otherwise, but it uses no locking itself. This means that you	3617	documented otherwise, but libev implements no locking itself. This means
3319	can use as many loops as you want in parallel, as long as there are no	3618	that you can use as many loops as you want in parallel, as long as there
3320	concurrent calls into any libev function with the same loop parameter	3619	are no concurrent calls into any libev function with the same loop
3321	(C<ev_default_*> calls have an implicit default loop parameter, of	3620	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3322	course): libev guarantees that different event loops share no data	3621	of course): libev guarantees that different event loops share no data
3323	structures that need any locking.	3622	structures that need any locking.
3324		3623
3325	Or to put it differently: calls with different loop parameters can be done	3624	Or to put it differently: calls with different loop parameters can be done
3326	concurrently from multiple threads, calls with the same loop parameter	3625	concurrently from multiple threads, calls with the same loop parameter
3327	must be done serially (but can be done from different threads, as long as	3626	must be done serially (but can be done from different threads, as long as
…		…
3369		3668
3370	=back	3669	=back
3371		3670
3372	=head3 COROUTINES	3671	=head3 COROUTINES
3373		3672
3374	Libev is much more accommodating to coroutines ("cooperative threads"):	3673	Libev is very accommodating to coroutines ("cooperative threads"):
3375	libev fully supports nesting calls to it's functions from different	3674	libev fully supports nesting calls to its functions from different
3376	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3675	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3377	different coroutines and switch freely between both coroutines running the	3676	different coroutines, and switch freely between both coroutines running the
3378	loop, as long as you don't confuse yourself). The only exception is that	3677	loop, as long as you don't confuse yourself). The only exception is that
3379	you must not do this from C<ev_periodic> reschedule callbacks.	3678	you must not do this from C<ev_periodic> reschedule callbacks.
3380		3679
3381	Care has been taken to ensure that libev does not keep local state inside	3680	Care has been taken to ensure that libev does not keep local state inside
3382	C<ev_loop>, and other calls do not usually allow coroutine switches.	3681	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3682	they do not call any callbacks.
3383		3683
3384	=head2 COMPILER WARNINGS	3684	=head2 COMPILER WARNINGS
3385		3685
3386	Depending on your compiler and compiler settings, you might get no or a	3686	Depending on your compiler and compiler settings, you might get no or a
3387	lot of warnings when compiling libev code. Some people are apparently	3687	lot of warnings when compiling libev code. Some people are apparently
…		…
3421	==2274== definitely lost: 0 bytes in 0 blocks.	3721	==2274== definitely lost: 0 bytes in 0 blocks.
3422	==2274== possibly lost: 0 bytes in 0 blocks.	3722	==2274== possibly lost: 0 bytes in 0 blocks.
3423	==2274== still reachable: 256 bytes in 1 blocks.	3723	==2274== still reachable: 256 bytes in 1 blocks.
3424		3724
3425	Then there is no memory leak, just as memory accounted to global variables	3725	Then there is no memory leak, just as memory accounted to global variables
3426	is not a memleak - the memory is still being refernced, and didn't leak.	3726	is not a memleak - the memory is still being referenced, and didn't leak.
3427		3727
3428	Similarly, under some circumstances, valgrind might report kernel bugs	3728	Similarly, under some circumstances, valgrind might report kernel bugs
3429	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3729	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3430	although an acceptable workaround has been found here), or it might be	3730	although an acceptable workaround has been found here), or it might be
3431	confused.	3731	confused.
…		…
3439	annoyed when you get a brisk "this is no bug" answer and take the chance	3739	annoyed when you get a brisk "this is no bug" answer and take the chance
3440	of learning how to interpret valgrind properly.	3740	of learning how to interpret valgrind properly.
3441		3741
3442	If you need, for some reason, empty reports from valgrind for your project	3742	If you need, for some reason, empty reports from valgrind for your project
3443	I suggest using suppression lists.	3743	I suggest using suppression lists.
3444
3445
3446
3447	=head1 COMPLEXITIES
3448
3449	In this section the complexities of (many of) the algorithms used inside
3450	libev will be explained. For complexity discussions about backends see the
3451	documentation for C<ev_default_init>.
3452
3453	All of the following are about amortised time: If an array needs to be
3454	extended, libev needs to realloc and move the whole array, but this
3455	happens asymptotically never with higher number of elements, so O(1) might
3456	mean it might do a lengthy realloc operation in rare cases, but on average
3457	it is much faster and asymptotically approaches constant time.
3458
3459	=over 4
3460
3461	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3462
3463	This means that, when you have a watcher that triggers in one hour and
3464	there are 100 watchers that would trigger before that then inserting will
3465	have to skip roughly seven (C<ld 100>) of these watchers.
3466
3467	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3468
3469	That means that changing a timer costs less than removing/adding them
3470	as only the relative motion in the event queue has to be paid for.
3471
3472	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3473
3474	These just add the watcher into an array or at the head of a list.
3475
3476	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3477
3478	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3479
3480	These watchers are stored in lists then need to be walked to find the
3481	correct watcher to remove. The lists are usually short (you don't usually
3482	have many watchers waiting for the same fd or signal).
3483
3484	=item Finding the next timer in each loop iteration: O(1)
3485
3486	By virtue of using a binary or 4-heap, the next timer is always found at a
3487	fixed position in the storage array.
3488
3489	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3490
3491	A change means an I/O watcher gets started or stopped, which requires
3492	libev to recalculate its status (and possibly tell the kernel, depending
3493	on backend and whether C<ev_io_set> was used).
3494
3495	=item Activating one watcher (putting it into the pending state): O(1)
3496
3497	=item Priority handling: O(number_of_priorities)
3498
3499	Priorities are implemented by allocating some space for each
3500	priority. When doing priority-based operations, libev usually has to
3501	linearly search all the priorities, but starting/stopping and activating
3502	watchers becomes O(1) with respect to priority handling.
3503
3504	=item Sending an ev_async: O(1)
3505
3506	=item Processing ev_async_send: O(number_of_async_watchers)
3507
3508	=item Processing signals: O(max_signal_number)
3509
3510	Sending involves a system call I<iff> there were no other C<ev_async_send>
3511	calls in the current loop iteration. Checking for async and signal events
3512	involves iterating over all running async watchers or all signal numbers.
3513
3514	=back
3515		3744
3516		3745
3517	=head1 PORTABILITY NOTES	3746	=head1 PORTABILITY NOTES
3518		3747
3519	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3748	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
…		…
3667	=back	3896	=back
3668		3897
3669	If you know of other additional requirements drop me a note.	3898	If you know of other additional requirements drop me a note.
3670		3899
3671		3900
		3901	=head1 ALGORITHMIC COMPLEXITIES
		3902
		3903	In this section the complexities of (many of) the algorithms used inside
		3904	libev will be documented. For complexity discussions about backends see
		3905	the documentation for C<ev_default_init>.
		3906
		3907	All of the following are about amortised time: If an array needs to be
		3908	extended, libev needs to realloc and move the whole array, but this
		3909	happens asymptotically rarer with higher number of elements, so O(1) might
		3910	mean that libev does a lengthy realloc operation in rare cases, but on
		3911	average it is much faster and asymptotically approaches constant time.
		3912
		3913	=over 4
		3914
		3915	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3916
		3917	This means that, when you have a watcher that triggers in one hour and
		3918	there are 100 watchers that would trigger before that, then inserting will
		3919	have to skip roughly seven (C<ld 100>) of these watchers.
		3920
		3921	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3922
		3923	That means that changing a timer costs less than removing/adding them,
		3924	as only the relative motion in the event queue has to be paid for.
		3925
		3926	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3927
		3928	These just add the watcher into an array or at the head of a list.
		3929
		3930	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3931
		3932	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3933
		3934	These watchers are stored in lists, so they need to be walked to find the
		3935	correct watcher to remove. The lists are usually short (you don't usually
		3936	have many watchers waiting for the same fd or signal: one is typical, two
		3937	is rare).
		3938
		3939	=item Finding the next timer in each loop iteration: O(1)
		3940
		3941	By virtue of using a binary or 4-heap, the next timer is always found at a
		3942	fixed position in the storage array.
		3943
		3944	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3945
		3946	A change means an I/O watcher gets started or stopped, which requires
		3947	libev to recalculate its status (and possibly tell the kernel, depending
		3948	on backend and whether C<ev_io_set> was used).
		3949
		3950	=item Activating one watcher (putting it into the pending state): O(1)
		3951
		3952	=item Priority handling: O(number_of_priorities)
		3953
		3954	Priorities are implemented by allocating some space for each
		3955	priority. When doing priority-based operations, libev usually has to
		3956	linearly search all the priorities, but starting/stopping and activating
		3957	watchers becomes O(1) with respect to priority handling.
		3958
		3959	=item Sending an ev_async: O(1)
		3960
		3961	=item Processing ev_async_send: O(number_of_async_watchers)
		3962
		3963	=item Processing signals: O(max_signal_number)
		3964
		3965	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3966	calls in the current loop iteration. Checking for async and signal events
		3967	involves iterating over all running async watchers or all signal numbers.
		3968
		3969	=back
		3970
		3971
3672	=head1 AUTHOR	3972	=head1 AUTHOR
3673		3973
3674	Marc Lehmann <libev@schmorp.de>.	3974	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3675		3975

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Comparing libev/ev.pod (file contents): Revision 1.190 by root, Tue Sep 30 19:34:14 2008 UTC vs. Revision 1.230 by root, Wed Apr 15 18:47:07 2009 UTC

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Revision 1.190 by root, Tue Sep 30 19:34:14 2008 UTC vs.
Revision 1.230 by root, Wed Apr 15 18:47:07 2009 UTC