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

Comparing libev/ev.pod (file contents):
Revision 1.187 by root, Mon Sep 29 03:31:14 2008 UTC vs.
Revision 1.205 by root, Mon Oct 27 12:20:32 2008 UTC

…		…
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	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	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	107	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	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	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	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		385
382	For few fds, this backend is a bit little slower than poll and select,	386	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	387	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),	388	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	389	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	390
387	cases and requiring a system call per fd change, no fork support and bad	391	The epoll syscalls are the most misdesigned of the more advanced
388	support for dup.	392	event mechanisms: probelsm include silently dropping events in some
		393	hard-to-detect cases, requiring a system call per fd change, no fork
		394	support, problems with dup and so on.
		395
		396	Epoll is also notoriously buggy - embedding epoll fds should work, but
		397	of course doesn't, and epoll just loves to report events for totally
		398	I<different> file descriptors (even already closed ones, so one cannot
		399	even remove them from the set) than registered in the set (especially
		400	on SMP systems). Libev tries to counter these spurious notifications by
		401	employing an additional generation counter and comparing that against the
		402	events to filter out spurious ones.
389		403
390	While stopping, setting and starting an I/O watcher in the same iteration	404	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	405	will result in some caching, there is still a system call per such incident
392	(because the fd could point to a different file description now), so its	406	(because the fd could point to a different file description now), so its
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	407	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
394	very well if you register events for both fds.	408	very well if you register events for both fds.
395
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		409
400	Best performance from this backend is achieved by not unregistering all	410	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	411	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	412	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	413	starting a watcher (without re-setting it) also usually doesn't cause
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	537	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	538	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	539	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	540	for example).
531		541
532	Note that certain global state, such as signal state, will not be freed by	542	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	543	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	544	as signal and child watchers) would need to be stopped manually.
535		545
536	In general it is not advisable to call this function except in the	546	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	547	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	548	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	549	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	695	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.	696	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		697
688	This "unloop state" will be cleared when entering C<ev_loop> again.	698	This "unloop state" will be cleared when entering C<ev_loop> again.
689		699
		700	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		701
690	=item ev_ref (loop)	702	=item ev_ref (loop)
691		703
692	=item ev_unref (loop)	704	=item ev_unref (loop)
693		705
694	Ref/unref can be used to add or remove a reference count on the event	706	Ref/unref can be used to add or remove a reference count on the event
…		…
708	respectively).	720	respectively).
709		721
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	722	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	723	running when nothing else is active.
712		724
713	struct ev_signal exitsig;	725	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	726	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	727	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	728	evf_unref (loop);
717		729
718	Example: For some weird reason, unregister the above signal handler again.	730	Example: For some weird reason, unregister the above signal handler again.
…		…
766	they fire on, say, one-second boundaries only.	778	they fire on, say, one-second boundaries only.
767		779
768	=item ev_loop_verify (loop)	780	=item ev_loop_verify (loop)
769		781
770	This function only does something when C<EV_VERIFY> support has been	782	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	783	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	784	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	785	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	786	error and call C<abort ()>.
775		787
776	This can be used to catch bugs inside libev itself: under normal	788	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	792	=back
781		793
782		794
783	=head1 ANATOMY OF A WATCHER	795	=head1 ANATOMY OF A WATCHER
784		796
		797	In the following description, uppercase C<TYPE> in names stands for the
		798	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		799	watchers and C<ev_io_start> for I/O watchers.
		800
785	A watcher is a structure that you create and register to record your	801	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	802	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:	803	become readable, you would create an C<ev_io> watcher for that:
788		804
789	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	805	static void my_cb (struct ev_loop loop, ev_io w, int revents)
790	{	806	{
791	ev_io_stop (w);	807	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	808	ev_unloop (loop, EVUNLOOP_ALL);
793	}	809	}
794		810
795	struct ev_loop *loop = ev_default_loop (0);	811	struct ev_loop *loop = ev_default_loop (0);
		812
796	struct ev_io stdin_watcher;	813	ev_io stdin_watcher;
		814
797	ev_init (&stdin_watcher, my_cb);	815	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	816	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	817	ev_io_start (loop, &stdin_watcher);
		818
800	ev_loop (loop, 0);	819	ev_loop (loop, 0);
801		820
802	As you can see, you are responsible for allocating the memory for your	821	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,	822	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	823	stack).
		824
		825	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		826	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		827
806	Each watcher structure must be initialised by a call to C<ev_init	828	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	829	(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	830	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	831	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	832	is readable and/or writable).
811		833
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	834	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	835	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	836	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	837	ev_TYPE_init (watcher *, callback, ...) >>.
816		838
817	To make the watcher actually watch out for events, you have to start it	839	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	840	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	841	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	842	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		843
822	As long as your watcher is active (has been started but not stopped) you	844	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	845	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	846	reinitialise it or call its C<ev_TYPE_set> macro.
825		847
826	Each and every callback receives the event loop pointer as first, the	848	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	849	registered watcher structure as second, and a bitset of received events as
828	third argument.	850	third argument.
829		851
…		…
892	=item C<EV_ERROR>	914	=item C<EV_ERROR>
893		915
894	An unspecified error has occurred, the watcher has been stopped. This might	916	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	917	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	918	ran out of memory, a file descriptor was found to be closed or any other
		919	problem. Libev considers these application bugs.
		920
897	problem. You best act on it by reporting the problem and somehow coping	921	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	922	watcher being stopped. Note that well-written programs should not receive
		923	an error ever, so when your watcher receives it, this usually indicates a
		924	bug in your program.
899		925
900	Libev will usually signal a few "dummy" events together with an error, for	926	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	927	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	928	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	929	the error from read() or write(). This will not work in multi-threaded
…		…
906		932
907	=back	933	=back
908		934
909	=head2 GENERIC WATCHER FUNCTIONS	935	=head2 GENERIC WATCHER FUNCTIONS
910		936
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	937	=over 4
915		938
916	=item C<ev_init> (ev_TYPE *watcher, callback)	939	=item C<ev_init> (ev_TYPE *watcher, callback)
917		940
918	This macro initialises the generic portion of a watcher. The contents	941	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	946	which rolls both calls into one.
924		947
925	You can reinitialise a watcher at any time as long as it has been stopped	948	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.	949	(or never started) and there are no pending events outstanding.
927		950
928	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	951	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
929	int revents)>.	952	int revents)>.
930		953
931	Example: Initialise an C<ev_io> watcher in two steps.	954	Example: Initialise an C<ev_io> watcher in two steps.
932		955
933	ev_io w;	956	ev_io w;
…		…
967		990
968	ev_io_start (EV_DEFAULT_UC, &w);	991	ev_io_start (EV_DEFAULT_UC, &w);
969		992
970	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	993	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
971		994
972	Stops the given watcher again (if active) and clears the pending	995	Stops the given watcher if active, and clears the pending status (whether
		996	the watcher was active or not).
		997
973	status. It is possible that stopped watchers are pending (for example,	998	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	999	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	1000	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	1001	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.	1002	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1003
979	=item bool ev_is_active (ev_TYPE *watcher)	1004	=item bool ev_is_active (ev_TYPE *watcher)
980		1005
981	Returns a true value iff the watcher is active (i.e. it has been started	1006	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	1007	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	1049	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 :).	1050	always C<0>, which is supposed to not be too high and not be too low :).
1026		1051
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1052	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	1053	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.	1054	or might not have been clamped to the valid range.
1030		1055
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1056	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1057
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1058	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	1059	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	1081	member, you can also "subclass" the watcher type and provide your own
1057	data:	1082	data:
1058		1083
1059	struct my_io	1084	struct my_io
1060	{	1085	{
1061	struct ev_io io;	1086	ev_io io;
1062	int otherfd;	1087	int otherfd;
1063	void *somedata;	1088	void *somedata;
1064	struct whatever *mostinteresting;	1089	struct whatever *mostinteresting;
1065	};	1090	};
1066		1091
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1094	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1095
1071	And since your callback will be called with a pointer to the watcher, you	1096	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1097	can cast it back to your own type:
1073		1098
1074	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1099	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1075	{	1100	{
1076	struct my_io w = (struct my_io )w_;	1101	struct my_io w = (struct my_io )w_;
1077	...	1102	...
1078	}	1103	}
1079		1104
…		…
1097	programmers):	1122	programmers):
1098		1123
1099	#include <stddef.h>	1124	#include <stddef.h>
1100		1125
1101	static void	1126	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1127	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1128	{
1104	struct my_biggy big = (struct my_biggy *	1129	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1130	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1131	}
1107		1132
1108	static void	1133	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1134	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1135	{
1111	struct my_biggy big = (struct my_biggy *	1136	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1137	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1138	}
1114		1139
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1274	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	1275	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1276	attempt to read a whole line in the callback.
1252		1277
1253	static void	1278	static void
1254	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1279	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1255	{	1280	{
1256	ev_io_stop (loop, w);	1281	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1282	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1283	}
1259		1284
1260	...	1285	...
1261	struct ev_loop *loop = ev_default_init (0);	1286	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1287	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1288	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1289	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1290	ev_loop (loop, 0);
1266		1291
1267		1292
…		…
1278		1303
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1304	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	1305	passed, but if multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1306	then order of execution is undefined.
1282		1307
		1308	=head3 Be smart about timeouts
		1309
		1310	Many real-world problems involve some kind of timeout, usually for error
		1311	recovery. A typical example is an HTTP request - if the other side hangs,
		1312	you want to raise some error after a while.
		1313
		1314	What follows are some ways to handle this problem, from obvious and
		1315	inefficient to smart and efficient.
		1316
		1317	In the following, a 60 second activity timeout is assumed - a timeout that
		1318	gets reset to 60 seconds each time there is activity (e.g. each time some
		1319	data or other life sign was received).
		1320
		1321	=over 4
		1322
		1323	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1324
		1325	This is the most obvious, but not the most simple way: In the beginning,
		1326	start the watcher:
		1327
		1328	ev_timer_init (timer, callback, 60., 0.);
		1329	ev_timer_start (loop, timer);
		1330
		1331	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1332	and start it again:
		1333
		1334	ev_timer_stop (loop, timer);
		1335	ev_timer_set (timer, 60., 0.);
		1336	ev_timer_start (loop, timer);
		1337
		1338	This is relatively simple to implement, but means that each time there is
		1339	some activity, libev will first have to remove the timer from its internal
		1340	data structure and then add it again. Libev tries to be fast, but it's
		1341	still not a constant-time operation.
		1342
		1343	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1344
		1345	This is the easiest way, and involves using C<ev_timer_again> instead of
		1346	C<ev_timer_start>.
		1347
		1348	To implement this, configure an C<ev_timer> with a C<repeat> value
		1349	of C<60> and then call C<ev_timer_again> at start and each time you
		1350	successfully read or write some data. If you go into an idle state where
		1351	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1352	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1353
		1354	That means you can ignore both the C<ev_timer_start> function and the
		1355	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1356	member and C<ev_timer_again>.
		1357
		1358	At start:
		1359
		1360	ev_timer_init (timer, callback);
		1361	timer->repeat = 60.;
		1362	ev_timer_again (loop, timer);
		1363
		1364	Each time there is some activity:
		1365
		1366	ev_timer_again (loop, timer);
		1367
		1368	It is even possible to change the time-out on the fly, regardless of
		1369	whether the watcher is active or not:
		1370
		1371	timer->repeat = 30.;
		1372	ev_timer_again (loop, timer);
		1373
		1374	This is slightly more efficient then stopping/starting the timer each time
		1375	you want to modify its timeout value, as libev does not have to completely
		1376	remove and re-insert the timer from/into its internal data structure.
		1377
		1378	It is, however, even simpler than the "obvious" way to do it.
		1379
		1380	=item 3. Let the timer time out, but then re-arm it as required.
		1381
		1382	This method is more tricky, but usually most efficient: Most timeouts are
		1383	relatively long compared to the intervals between other activity - in
		1384	our example, within 60 seconds, there are usually many I/O events with
		1385	associated activity resets.
		1386
		1387	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1388	but remember the time of last activity, and check for a real timeout only
		1389	within the callback:
		1390
		1391	ev_tstamp last_activity; // time of last activity
		1392
		1393	static void
		1394	callback (EV_P_ ev_timer *w, int revents)
		1395	{
		1396	ev_tstamp now = ev_now (EV_A);
		1397	ev_tstamp timeout = last_activity + 60.;
		1398
		1399	// if last_activity + 60. is older than now, we did time out
		1400	if (timeout < now)
		1401	{
		1402	// timeout occured, take action
		1403	}
		1404	else
		1405	{
		1406	// callback was invoked, but there was some activity, re-arm
		1407	// the watcher to fire in last_activity + 60, which is
		1408	// guaranteed to be in the future, so "again" is positive:
		1409	w->again = timeout - now;
		1410	ev_timer_again (EV_A_ w);
		1411	}
		1412	}
		1413
		1414	To summarise the callback: first calculate the real timeout (defined
		1415	as "60 seconds after the last activity"), then check if that time has
		1416	been reached, which means something I<did>, in fact, time out. Otherwise
		1417	the callback was invoked too early (C<timeout> is in the future), so
		1418	re-schedule the timer to fire at that future time, to see if maybe we have
		1419	a timeout then.
		1420
		1421	Note how C<ev_timer_again> is used, taking advantage of the
		1422	C<ev_timer_again> optimisation when the timer is already running.
		1423
		1424	This scheme causes more callback invocations (about one every 60 seconds
		1425	minus half the average time between activity), but virtually no calls to
		1426	libev to change the timeout.
		1427
		1428	To start the timer, simply initialise the watcher and set C<last_activity>
		1429	to the current time (meaning we just have some activity :), then call the
		1430	callback, which will "do the right thing" and start the timer:
		1431
		1432	ev_timer_init (timer, callback);
		1433	last_activity = ev_now (loop);
		1434	callback (loop, timer, EV_TIMEOUT);
		1435
		1436	And when there is some activity, simply store the current time in
		1437	C<last_activity>, no libev calls at all:
		1438
		1439	last_actiivty = ev_now (loop);
		1440
		1441	This technique is slightly more complex, but in most cases where the
		1442	time-out is unlikely to be triggered, much more efficient.
		1443
		1444	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1445	callback :) - just change the timeout and invoke the callback, which will
		1446	fix things for you.
		1447
		1448	=item 4. Wee, just use a double-linked list for your timeouts.
		1449
		1450	If there is not one request, but many thousands (millions...), all
		1451	employing some kind of timeout with the same timeout value, then one can
		1452	do even better:
		1453
		1454	When starting the timeout, calculate the timeout value and put the timeout
		1455	at the I<end> of the list.
		1456
		1457	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1458	the list is expected to fire (for example, using the technique #3).
		1459
		1460	When there is some activity, remove the timer from the list, recalculate
		1461	the timeout, append it to the end of the list again, and make sure to
		1462	update the C<ev_timer> if it was taken from the beginning of the list.
		1463
		1464	This way, one can manage an unlimited number of timeouts in O(1) time for
		1465	starting, stopping and updating the timers, at the expense of a major
		1466	complication, and having to use a constant timeout. The constant timeout
		1467	ensures that the list stays sorted.
		1468
		1469	=back
		1470
		1471	So which method the best?
		1472
		1473	Method #2 is a simple no-brain-required solution that is adequate in most
		1474	situations. Method #3 requires a bit more thinking, but handles many cases
		1475	better, and isn't very complicated either. In most case, choosing either
		1476	one is fine, with #3 being better in typical situations.
		1477
		1478	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1479	rather complicated, but extremely efficient, something that really pays
		1480	off after the first million or so of active timers, i.e. it's usually
		1481	overkill :)
		1482
1283	=head3 The special problem of time updates	1483	=head3 The special problem of time updates
1284		1484
1285	Establishing the current time is a costly operation (it usually takes at	1485	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	1486	least two system calls): EV therefore updates its idea of the current
1287	time only before and after C<ev_loop> collects new events, which causes a	1487	time only before and after C<ev_loop> collects new events, which causes a
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1530	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1531
1332	If the timer is repeating, either start it if necessary (with the	1532	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.	1533	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1534
1335	This sounds a bit complicated, but here is a useful and typical	1535	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	1536	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		1537
1366	=item ev_tstamp repeat [read-write]	1538	=item ev_tstamp repeat [read-write]
1367		1539
1368	The current C<repeat> value. Will be used each time the watcher times out	1540	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),	1541	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1546	=head3 Examples
1375		1547
1376	Example: Create a timer that fires after 60 seconds.	1548	Example: Create a timer that fires after 60 seconds.
1377		1549
1378	static void	1550	static void
1379	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1551	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1380	{	1552	{
1381	.. one minute over, w is actually stopped right here	1553	.. one minute over, w is actually stopped right here
1382	}	1554	}
1383		1555
1384	struct ev_timer mytimer;	1556	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1557	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1558	ev_timer_start (loop, &mytimer);
1387		1559
1388	Example: Create a timeout timer that times out after 10 seconds of	1560	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1561	inactivity.
1390		1562
1391	static void	1563	static void
1392	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1564	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1393	{	1565	{
1394	.. ten seconds without any activity	1566	.. ten seconds without any activity
1395	}	1567	}
1396		1568
1397	struct ev_timer mytimer;	1569	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1570	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1571	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1572	ev_loop (loop, 0);
1401		1573
1402	// and in some piece of code that gets executed on any "activity":	1574	// and in some piece of code that gets executed on any "activity":
…		…
1488		1660
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1661	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	1662	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1663	only event loop modification you are allowed to do).
1492		1664
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1665	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1666	*w, ev_tstamp now)>, e.g.:
1495		1667
		1668	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1669	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1670	{
1498	return now + 60.;	1671	return now + 60.;
1499	}	1672	}
1500		1673
1501	It must return the next time to trigger, based on the passed time value	1674	It must return the next time to trigger, based on the passed time value
…		…
1538		1711
1539	The current interval value. Can be modified any time, but changes only	1712	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	1713	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1714	called.
1542		1715
1543	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1716	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1544		1717
1545	The current reschedule callback, or C<0>, if this functionality is	1718	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	1719	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.	1720	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1721
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1726	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1727	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1728	potentially a lot of jitter, but good long-term stability.
1556		1729
1557	static void	1730	static void
1558	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1731	clock_cb (struct ev_loop loop, ev_io w, int revents)
1559	{	1732	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1733	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1734	}
1562		1735
1563	struct ev_periodic hourly_tick;	1736	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1737	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1738	ev_periodic_start (loop, &hourly_tick);
1566		1739
1567	Example: The same as above, but use a reschedule callback to do it:	1740	Example: The same as above, but use a reschedule callback to do it:
1568		1741
1569	#include <math.h>	1742	#include <math.h>
1570		1743
1571	static ev_tstamp	1744	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1745	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1746	{
1574	return now + (3600. - fmod (now, 3600.));	1747	return now + (3600. - fmod (now, 3600.));
1575	}	1748	}
1576		1749
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1750	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1751
1579	Example: Call a callback every hour, starting now:	1752	Example: Call a callback every hour, starting now:
1580		1753
1581	struct ev_periodic hourly_tick;	1754	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1755	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1756	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1757	ev_periodic_start (loop, &hourly_tick);
1585		1758
1586		1759
…		…
1625		1798
1626	=back	1799	=back
1627		1800
1628	=head3 Examples	1801	=head3 Examples
1629		1802
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1803	Example: Try to exit cleanly on SIGINT.
1631		1804
1632	static void	1805	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1806	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1634	{	1807	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1808	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1809	}
1637		1810
1638	struct ev_signal signal_watcher;	1811	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1812	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1813	ev_signal_start (loop, &signal_watcher);
1641		1814
1642		1815
1643	=head2 C<ev_child> - watch out for process status changes	1816	=head2 C<ev_child> - watch out for process status changes
1644		1817
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1818	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1891	its completion.
1719		1892
1720	ev_child cw;	1893	ev_child cw;
1721		1894
1722	static void	1895	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1896	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1897	{
1725	ev_child_stop (EV_A_ w);	1898	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1899	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1900	}
1728		1901
…		…
1792	to exchange stat structures with application programs compiled using the	1965	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	1966	default compilation environment.
1794		1967
1795	=head3 Inotify and Kqueue	1968	=head3 Inotify and Kqueue
1796		1969
1797	When C<inotify (7)> support has been compiled into libev (generally only	1970	When C<inotify (7)> support has been compiled into libev (generally
		1971	only available with Linux 2.6.25 or above due to bugs in earlier
1798	available with Linux) and present at runtime, it will be used to speed up	1972	implementations) and present at runtime, it will be used to speed up
1799	change detection where possible. The inotify descriptor will be created lazily	1973	change detection where possible. The inotify descriptor will be created
1800	when the first C<ev_stat> watcher is being started.	1974	lazily when the first C<ev_stat> watcher is being started.
1801		1975
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	1976	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	1977	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	1978	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,	1979	there are many cases where libev has to resort to regular C<stat> polling,
…		…
1979		2153
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2154	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2155	callback, free it. Also, use no error checking, as usual.
1982		2156
1983	static void	2157	static void
1984	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2158	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1985	{	2159	{
1986	free (w);	2160	free (w);
1987	// now do something you wanted to do when the program has	2161	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2162	// no longer anything immediate to do.
1989	}	2163	}
1990		2164
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2165	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2166	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2167	ev_idle_start (loop, idle_cb);
1994		2168
1995		2169
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2170	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2251
2078	static ev_io iow [nfd];	2252	static ev_io iow [nfd];
2079	static ev_timer tw;	2253	static ev_timer tw;
2080		2254
2081	static void	2255	static void
2082	io_cb (ev_loop loop, ev_io w, int revents)	2256	io_cb (struct ev_loop loop, ev_io w, int revents)
2083	{	2257	{
2084	}	2258	}
2085		2259
2086	// create io watchers for each fd and a timer before blocking	2260	// create io watchers for each fd and a timer before blocking
2087	static void	2261	static void
2088	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2262	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2089	{	2263	{
2090	int timeout = 3600000;	2264	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2265	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2266	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2267	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2282	}
2109	}	2283	}
2110		2284
2111	// stop all watchers after blocking	2285	// stop all watchers after blocking
2112	static void	2286	static void
2113	adns_check_cb (ev_loop loop, ev_check w, int revents)	2287	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2114	{	2288	{
2115	ev_timer_stop (loop, &tw);	2289	ev_timer_stop (loop, &tw);
2116		2290
2117	for (int i = 0; i < nfd; ++i)	2291	for (int i = 0; i < nfd; ++i)
2118	{	2292	{
…		…
2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2460	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2287	used).	2461	used).
2288		2462
2289	struct ev_loop *loop_hi = ev_default_init (0);	2463	struct ev_loop *loop_hi = ev_default_init (0);
2290	struct ev_loop *loop_lo = 0;	2464	struct ev_loop *loop_lo = 0;
2291	struct ev_embed embed;	2465	ev_embed embed;
2292		2466
2293	// see if there is a chance of getting one that works	2467	// see if there is a chance of getting one that works
2294	// (remember that a flags value of 0 means autodetection)	2468	// (remember that a flags value of 0 means autodetection)
2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2469	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2470	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2310	kqueue implementation). Store the kqueue/socket-only event loop in	2484	kqueue implementation). Store the kqueue/socket-only event loop in
2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2485	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2312		2486
2313	struct ev_loop *loop = ev_default_init (0);	2487	struct ev_loop *loop = ev_default_init (0);
2314	struct ev_loop *loop_socket = 0;	2488	struct ev_loop *loop_socket = 0;
2315	struct ev_embed embed;	2489	ev_embed embed;
2316		2490
2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2491	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2492	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2319	{	2493	{
2320	ev_embed_init (&embed, 0, loop_socket);	2494	ev_embed_init (&embed, 0, loop_socket);
…		…
2384	=over 4	2558	=over 4
2385		2559
2386	=item queueing from a signal handler context	2560	=item queueing from a signal handler context
2387		2561
2388	To implement race-free queueing, you simply add to the queue in the signal	2562	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	2563	handler but you block the signal handler in the watcher callback. Here is
2390	some fictitious SIGUSR1 handler:	2564	an example that does that for some fictitious SIGUSR1 handler:
2391		2565
2392	static ev_async mysig;	2566	static ev_async mysig;
2393		2567
2394	static void	2568	static void
2395	sigusr1_handler (void)	2569	sigusr1_handler (void)
…		…
2502	=over 4	2676	=over 4
2503		2677
2504	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2678	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2505		2679
2506	This function combines a simple timer and an I/O watcher, calls your	2680	This function combines a simple timer and an I/O watcher, calls your
2507	callback on whichever event happens first and automatically stop both	2681	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	2682	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	2683	or timeout without having to allocate/configure/start/stop/free one or
2510	more watchers yourself.	2684	more watchers yourself.
2511		2685
2512	If C<fd> is less than 0, then no I/O watcher will be started and events	2686	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	2687	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514	C<events> set will be created and started.	2688	the given C<fd> and C<events> set will be created and started.
2515		2689
2516	If C<timeout> is less than 0, then no timeout watcher will be	2690	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	2691	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	2692	repeat = 0) will be started. C<0> is a valid timeout.
2519	dubious value.
2520		2693
2521	The callback has the type C<void (cb)(int revents, void arg)> and gets	2694	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	2695	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>	2696	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2524	value passed to C<ev_once>:	2697	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2698	a timeout and an io event at the same time - you probably should give io
		2699	events precedence.
		2700
		2701	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525		2702
2526	static void stdin_ready (int revents, void *arg)	2703	static void stdin_ready (int revents, void *arg)
2527	{	2704	{
		2705	if (revents & EV_READ)
		2706	/* stdin might have data for us, joy! */;
2528	if (revents & EV_TIMEOUT)	2707	else if (revents & EV_TIMEOUT)
2529	/* doh, nothing entered */;	2708	/* doh, nothing entered */;
2530	else if (revents & EV_READ)
2531	/* stdin might have data for us, joy! */;
2532	}	2709	}
2533		2710
2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2711	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535		2712
2536	=item ev_feed_event (ev_loop , watcher , int revents)	2713	=item ev_feed_event (struct ev_loop , watcher , int revents)
2537		2714
2538	Feeds the given event set into the event loop, as if the specified event	2715	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	2716	had happened for the specified watcher (which must be a pointer to an
2540	initialised but not necessarily started event watcher).	2717	initialised but not necessarily started event watcher).
2541		2718
2542	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2719	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2543		2720
2544	Feed an event on the given fd, as if a file descriptor backend detected	2721	Feed an event on the given fd, as if a file descriptor backend detected
2545	the given events it.	2722	the given events it.
2546		2723
2547	=item ev_feed_signal_event (ev_loop *loop, int signum)	2724	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2548		2725
2549	Feed an event as if the given signal occurred (C<loop> must be the default	2726	Feed an event as if the given signal occurred (C<loop> must be the default
2550	loop!).	2727	loop!).
2551		2728
2552	=back	2729	=back
…		…
2786		2963
2787	=item D	2964	=item D
2788		2965
2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2966	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>.	2967	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2968
		2969	=item Ocaml
		2970
		2971	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2972	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2791		2973
2792	=back	2974	=back
2793		2975
2794		2976
2795	=head1 MACRO MAGIC	2977	=head1 MACRO MAGIC
…		…
3306	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3488	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3307		3489
3308	#include "ev_cpp.h"	3490	#include "ev_cpp.h"
3309	#include "ev.c"	3491	#include "ev.c"
3310		3492
		3493	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3311		3494
3312	=head1 THREADS AND COROUTINES	3495	=head2 THREADS AND COROUTINES
3313		3496
3314	=head2 THREADS	3497	=head3 THREADS
3315		3498
3316	All libev functions are reentrant and thread-safe unless explicitly	3499	All libev functions are reentrant and thread-safe unless explicitly
3317	documented otherwise, but it uses no locking itself. This means that you	3500	documented otherwise, but libev implements no locking itself. This means
3318	can use as many loops as you want in parallel, as long as there are no	3501	that you can use as many loops as you want in parallel, as long as there
3319	concurrent calls into any libev function with the same loop parameter	3502	are no concurrent calls into any libev function with the same loop
3320	(C<ev_default_*> calls have an implicit default loop parameter, of	3503	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3321	course): libev guarantees that different event loops share no data	3504	of course): libev guarantees that different event loops share no data
3322	structures that need any locking.	3505	structures that need any locking.
3323		3506
3324	Or to put it differently: calls with different loop parameters can be done	3507	Or to put it differently: calls with different loop parameters can be done
3325	concurrently from multiple threads, calls with the same loop parameter	3508	concurrently from multiple threads, calls with the same loop parameter
3326	must be done serially (but can be done from different threads, as long as	3509	must be done serially (but can be done from different threads, as long as
…		…
3366	default loop and triggering an C<ev_async> watcher from the default loop	3549	default loop and triggering an C<ev_async> watcher from the default loop
3367	watcher callback into the event loop interested in the signal.	3550	watcher callback into the event loop interested in the signal.
3368		3551
3369	=back	3552	=back
3370		3553
3371	=head2 COROUTINES	3554	=head3 COROUTINES
3372		3555
3373	Libev is much more accommodating to coroutines ("cooperative threads"):	3556	Libev is very accommodating to coroutines ("cooperative threads"):
3374	libev fully supports nesting calls to it's functions from different	3557	libev fully supports nesting calls to its functions from different
3375	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3558	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3376	different coroutines and switch freely between both coroutines running the	3559	different coroutines, and switch freely between both coroutines running the
3377	loop, as long as you don't confuse yourself). The only exception is that	3560	loop, as long as you don't confuse yourself). The only exception is that
3378	you must not do this from C<ev_periodic> reschedule callbacks.	3561	you must not do this from C<ev_periodic> reschedule callbacks.
3379		3562
3380	Care has been taken to ensure that libev does not keep local state inside	3563	Care has been taken to ensure that libev does not keep local state inside
3381	C<ev_loop>, and other calls do not usually allow coroutine switches.	3564	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3565	they do not clal any callbacks.
3382		3566
		3567	=head2 COMPILER WARNINGS
3383		3568
3384	=head1 COMPLEXITIES	3569	Depending on your compiler and compiler settings, you might get no or a
		3570	lot of warnings when compiling libev code. Some people are apparently
		3571	scared by this.
3385		3572
3386	In this section the complexities of (many of) the algorithms used inside	3573	However, these are unavoidable for many reasons. For one, each compiler
3387	libev will be explained. For complexity discussions about backends see the	3574	has different warnings, and each user has different tastes regarding
3388	documentation for C<ev_default_init>.	3575	warning options. "Warn-free" code therefore cannot be a goal except when
		3576	targeting a specific compiler and compiler-version.
3389		3577
3390	All of the following are about amortised time: If an array needs to be	3578	Another reason is that some compiler warnings require elaborate
3391	extended, libev needs to realloc and move the whole array, but this	3579	workarounds, or other changes to the code that make it less clear and less
3392	happens asymptotically never with higher number of elements, so O(1) might	3580	maintainable.
3393	mean it might do a lengthy realloc operation in rare cases, but on average
3394	it is much faster and asymptotically approaches constant time.
3395		3581
3396	=over 4	3582	And of course, some compiler warnings are just plain stupid, or simply
		3583	wrong (because they don't actually warn about the condition their message
		3584	seems to warn about). For example, certain older gcc versions had some
		3585	warnings that resulted an extreme number of false positives. These have
		3586	been fixed, but some people still insist on making code warn-free with
		3587	such buggy versions.
3397		3588
3398	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3589	While libev is written to generate as few warnings as possible,
		3590	"warn-free" code is not a goal, and it is recommended not to build libev
		3591	with any compiler warnings enabled unless you are prepared to cope with
		3592	them (e.g. by ignoring them). Remember that warnings are just that:
		3593	warnings, not errors, or proof of bugs.
3399		3594
3400	This means that, when you have a watcher that triggers in one hour and
3401	there are 100 watchers that would trigger before that then inserting will
3402	have to skip roughly seven (C<ld 100>) of these watchers.
3403		3595
3404	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3596	=head2 VALGRIND
3405		3597
3406	That means that changing a timer costs less than removing/adding them	3598	Valgrind has a special section here because it is a popular tool that is
3407	as only the relative motion in the event queue has to be paid for.	3599	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3408		3600
3409	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3601	If you think you found a bug (memory leak, uninitialised data access etc.)
		3602	in libev, then check twice: If valgrind reports something like:
3410		3603
3411	These just add the watcher into an array or at the head of a list.	3604	==2274== definitely lost: 0 bytes in 0 blocks.
		3605	==2274== possibly lost: 0 bytes in 0 blocks.
		3606	==2274== still reachable: 256 bytes in 1 blocks.
3412		3607
3413	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3608	Then there is no memory leak, just as memory accounted to global variables
		3609	is not a memleak - the memory is still being refernced, and didn't leak.
3414		3610
3415	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3611	Similarly, under some circumstances, valgrind might report kernel bugs
		3612	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3613	although an acceptable workaround has been found here), or it might be
		3614	confused.
3416		3615
3417	These watchers are stored in lists then need to be walked to find the	3616	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3418	correct watcher to remove. The lists are usually short (you don't usually	3617	make it into some kind of religion.
3419	have many watchers waiting for the same fd or signal).
3420		3618
3421	=item Finding the next timer in each loop iteration: O(1)	3619	If you are unsure about something, feel free to contact the mailing list
		3620	with the full valgrind report and an explanation on why you think this
		3621	is a bug in libev (best check the archives, too :). However, don't be
		3622	annoyed when you get a brisk "this is no bug" answer and take the chance
		3623	of learning how to interpret valgrind properly.
3422		3624
3423	By virtue of using a binary or 4-heap, the next timer is always found at a	3625	If you need, for some reason, empty reports from valgrind for your project
3424	fixed position in the storage array.	3626	I suggest using suppression lists.
3425		3627
3426	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3427		3628
3428	A change means an I/O watcher gets started or stopped, which requires	3629	=head1 PORTABILITY NOTES
3429	libev to recalculate its status (and possibly tell the kernel, depending
3430	on backend and whether C<ev_io_set> was used).
3431		3630
3432	=item Activating one watcher (putting it into the pending state): O(1)
3433
3434	=item Priority handling: O(number_of_priorities)
3435
3436	Priorities are implemented by allocating some space for each
3437	priority. When doing priority-based operations, libev usually has to
3438	linearly search all the priorities, but starting/stopping and activating
3439	watchers becomes O(1) with respect to priority handling.
3440
3441	=item Sending an ev_async: O(1)
3442
3443	=item Processing ev_async_send: O(number_of_async_watchers)
3444
3445	=item Processing signals: O(max_signal_number)
3446
3447	Sending involves a system call I<iff> there were no other C<ev_async_send>
3448	calls in the current loop iteration. Checking for async and signal events
3449	involves iterating over all running async watchers or all signal numbers.
3450
3451	=back
3452
3453
3454	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3631	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3455		3632
3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3633	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3457	requires, and its I/O model is fundamentally incompatible with the POSIX	3634	requires, and its I/O model is fundamentally incompatible with the POSIX
3458	model. Libev still offers limited functionality on this platform in	3635	model. Libev still offers limited functionality on this platform in
3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3636	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3546	wrap all I/O functions and provide your own fd management, but the cost of	3723	wrap all I/O functions and provide your own fd management, but the cost of
3547	calling select (O(n²)) will likely make this unworkable.	3724	calling select (O(n²)) will likely make this unworkable.
3548		3725
3549	=back	3726	=back
3550		3727
3551
3552	=head1 PORTABILITY REQUIREMENTS	3728	=head2 PORTABILITY REQUIREMENTS
3553		3729
3554	In addition to a working ISO-C implementation, libev relies on a few	3730	In addition to a working ISO-C implementation and of course the
3555	additional extensions:	3731	backend-specific APIs, libev relies on a few additional extensions:
3556		3732
3557	=over 4	3733	=over 4
3558		3734
3559	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3735	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3560	calling conventions regardless of C<ev_watcher_type *>.	3736	calling conventions regardless of C<ev_watcher_type *>.
…		…
3585	except the initial one, and run the default loop in the initial thread as	3761	except the initial one, and run the default loop in the initial thread as
3586	well.	3762	well.
3587		3763
3588	=item C<long> must be large enough for common memory allocation sizes	3764	=item C<long> must be large enough for common memory allocation sizes
3589		3765
3590	To improve portability and simplify using libev, libev uses C<long>	3766	To improve portability and simplify its API, libev uses C<long> internally
3591	internally instead of C<size_t> when allocating its data structures. On	3767	instead of C<size_t> when allocating its data structures. On non-POSIX
3592	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3768	systems (Microsoft...) this might be unexpectedly low, but is still at
3593	is still at least 31 bits everywhere, which is enough for hundreds of	3769	least 31 bits everywhere, which is enough for hundreds of millions of
3594	millions of watchers.	3770	watchers.
3595		3771
3596	=item C<double> must hold a time value in seconds with enough accuracy	3772	=item C<double> must hold a time value in seconds with enough accuracy
3597		3773
3598	The type C<double> is used to represent timestamps. It is required to	3774	The type C<double> is used to represent timestamps. It is required to
3599	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3775	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3603	=back	3779	=back
3604		3780
3605	If you know of other additional requirements drop me a note.	3781	If you know of other additional requirements drop me a note.
3606		3782
3607		3783
3608	=head1 COMPILER WARNINGS	3784	=head1 ALGORITHMIC COMPLEXITIES
3609		3785
3610	Depending on your compiler and compiler settings, you might get no or a	3786	In this section the complexities of (many of) the algorithms used inside
3611	lot of warnings when compiling libev code. Some people are apparently	3787	libev will be documented. For complexity discussions about backends see
3612	scared by this.	3788	the documentation for C<ev_default_init>.
3613		3789
3614	However, these are unavoidable for many reasons. For one, each compiler	3790	All of the following are about amortised time: If an array needs to be
3615	has different warnings, and each user has different tastes regarding	3791	extended, libev needs to realloc and move the whole array, but this
3616	warning options. "Warn-free" code therefore cannot be a goal except when	3792	happens asymptotically rarer with higher number of elements, so O(1) might
3617	targeting a specific compiler and compiler-version.	3793	mean that libev does a lengthy realloc operation in rare cases, but on
		3794	average it is much faster and asymptotically approaches constant time.
3618		3795
3619	Another reason is that some compiler warnings require elaborate	3796	=over 4
3620	workarounds, or other changes to the code that make it less clear and less
3621	maintainable.
3622		3797
3623	And of course, some compiler warnings are just plain stupid, or simply	3798	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3624	wrong (because they don't actually warn about the condition their message
3625	seems to warn about).
3626		3799
3627	While libev is written to generate as few warnings as possible,	3800	This means that, when you have a watcher that triggers in one hour and
3628	"warn-free" code is not a goal, and it is recommended not to build libev	3801	there are 100 watchers that would trigger before that, then inserting will
3629	with any compiler warnings enabled unless you are prepared to cope with	3802	have to skip roughly seven (C<ld 100>) of these watchers.
3630	them (e.g. by ignoring them). Remember that warnings are just that:
3631	warnings, not errors, or proof of bugs.
3632		3803
		3804	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3633		3805
3634	=head1 VALGRIND	3806	That means that changing a timer costs less than removing/adding them,
		3807	as only the relative motion in the event queue has to be paid for.
3635		3808
3636	Valgrind has a special section here because it is a popular tool that is	3809	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3637	highly useful, but valgrind reports are very hard to interpret.
3638		3810
3639	If you think you found a bug (memory leak, uninitialised data access etc.)	3811	These just add the watcher into an array or at the head of a list.
3640	in libev, then check twice: If valgrind reports something like:
3641		3812
3642	==2274== definitely lost: 0 bytes in 0 blocks.	3813	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3643	==2274== possibly lost: 0 bytes in 0 blocks.
3644	==2274== still reachable: 256 bytes in 1 blocks.
3645		3814
3646	Then there is no memory leak. Similarly, under some circumstances,	3815	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3647	valgrind might report kernel bugs as if it were a bug in libev, or it
3648	might be confused (it is a very good tool, but only a tool).
3649		3816
3650	If you are unsure about something, feel free to contact the mailing list	3817	These watchers are stored in lists, so they need to be walked to find the
3651	with the full valgrind report and an explanation on why you think this is	3818	correct watcher to remove. The lists are usually short (you don't usually
3652	a bug in libev. However, don't be annoyed when you get a brisk "this is	3819	have many watchers waiting for the same fd or signal: one is typical, two
3653	no bug" answer and take the chance of learning how to interpret valgrind	3820	is rare).
3654	properly.
3655		3821
3656	If you need, for some reason, empty reports from valgrind for your project	3822	=item Finding the next timer in each loop iteration: O(1)
3657	I suggest using suppression lists.	3823
		3824	By virtue of using a binary or 4-heap, the next timer is always found at a
		3825	fixed position in the storage array.
		3826
		3827	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3828
		3829	A change means an I/O watcher gets started or stopped, which requires
		3830	libev to recalculate its status (and possibly tell the kernel, depending
		3831	on backend and whether C<ev_io_set> was used).
		3832
		3833	=item Activating one watcher (putting it into the pending state): O(1)
		3834
		3835	=item Priority handling: O(number_of_priorities)
		3836
		3837	Priorities are implemented by allocating some space for each
		3838	priority. When doing priority-based operations, libev usually has to
		3839	linearly search all the priorities, but starting/stopping and activating
		3840	watchers becomes O(1) with respect to priority handling.
		3841
		3842	=item Sending an ev_async: O(1)
		3843
		3844	=item Processing ev_async_send: O(number_of_async_watchers)
		3845
		3846	=item Processing signals: O(max_signal_number)
		3847
		3848	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3849	calls in the current loop iteration. Checking for async and signal events
		3850	involves iterating over all running async watchers or all signal numbers.
		3851
		3852	=back
3658		3853
3659		3854
3660	=head1 AUTHOR	3855	=head1 AUTHOR
3661		3856
3662	Marc Lehmann <libev@schmorp.de>.	3857	Marc Lehmann <libev@schmorp.de>.

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Comparing libev/ev.pod (file contents): Revision 1.187 by root, Mon Sep 29 03:31:14 2008 UTC vs. Revision 1.205 by root, Mon Oct 27 12:20:32 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.187 by root, Mon Sep 29 03:31:14 2008 UTC vs.
Revision 1.205 by root, Mon Oct 27 12:20:32 2008 UTC