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

Comparing libev/ev.pod (file contents):
Revision 1.183 by root, Tue Sep 23 08:37:38 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
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void (cb)(void *ptr, long size))	219	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (cb)(const char msg));	255	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
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	{
…		…
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2407	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2234	but you will also have to stop and restart any C<ev_embed> watchers	2408	but you will also have to stop and restart any C<ev_embed> watchers
2235	yourself - but you can use a fork watcher to handle this automatically,	2409	yourself - but you can use a fork watcher to handle this automatically,
2236	and future versions of libev might do just that.	2410	and future versions of libev might do just that.
2237		2411
2238	Unfortunately, not all backends are embeddable, only the ones returned by	2412	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2413	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2414	portable one.
2241		2415
2242	So when you want to use this feature you will always have to be prepared	2416	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2417	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2418	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2419	create it, and if that fails, use the normal loop for everything.
		2420
		2421	=head3 C<ev_embed> and fork
		2422
		2423	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2424	automatically be applied to the embedded loop as well, so no special
		2425	fork handling is required in that case. When the watcher is not running,
		2426	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2427	as applicable.
2246		2428
2247	=head3 Watcher-Specific Functions and Data Members	2429	=head3 Watcher-Specific Functions and Data Members
2248		2430
2249	=over 4	2431	=over 4
2250		2432
…		…
2278	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
2279	used).	2461	used).
2280		2462
2281	struct ev_loop *loop_hi = ev_default_init (0);	2463	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2464	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2465	ev_embed embed;
2284		2466
2285	// see if there is a chance of getting one that works	2467	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2468	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2469	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2470	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2484	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2485	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2486
2305	struct ev_loop *loop = ev_default_init (0);	2487	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2488	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2489	ev_embed embed;
2308		2490
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2491	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2492	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2493	{
2312	ev_embed_init (&embed, 0, loop_socket);	2494	ev_embed_init (&embed, 0, loop_socket);
…		…
2368	is that the author does not know of a simple (or any) algorithm for a	2550	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	2551	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	2552	need elaborate support such as pthreads.
2371		2553
2372	That means that if you want to queue data, you have to provide your own	2554	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you would implement locking around your	2555	queue. But at least I can tell you how to implement locking around your
2374	queue:	2556	queue:
2375		2557
2376	=over 4	2558	=over 4
2377		2559
2378	=item queueing from a signal handler context	2560	=item queueing from a signal handler context
2379		2561
2380	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
2381	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
2382	some fictitious SIGUSR1 handler:	2564	an example that does that for some fictitious SIGUSR1 handler:
2383		2565
2384	static ev_async mysig;	2566	static ev_async mysig;
2385		2567
2386	static void	2568	static void
2387	sigusr1_handler (void)	2569	sigusr1_handler (void)
…		…
2454		2636
2455	=item ev_async_init (ev_async *, callback)	2637	=item ev_async_init (ev_async *, callback)
2456		2638
2457	Initialises and configures the async watcher - it has no parameters of any	2639	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2640	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2459	believe me.	2641	trust me.
2460		2642
2461	=item ev_async_send (loop, ev_async *)	2643	=item ev_async_send (loop, ev_async *)
2462		2644
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2645	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2646	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do in other threads, signal or	2647	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2648	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2649	section below on what exactly this means).
2468		2650
2469	This call incurs the overhead of a system call only once per loop iteration,	2651	This call incurs the overhead of a system call only once per loop iteration,
2470	so while the overhead might be noticeable, it doesn't apply to repeated	2652	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2494	=over 4	2676	=over 4
2495		2677
2496	=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)
2497		2679
2498	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
2499	callback on whichever event happens first and automatically stop both	2681	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	2682	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	2683	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2684	more watchers yourself.
2503		2685
2504	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
2505	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
2506	C<events> set will be created and started.	2688	the given C<fd> and C<events> set will be created and started.
2507		2689
2508	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
2509	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
2510	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.
2511	dubious value.
2512		2693
2513	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
2514	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
2515	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>
2516	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.
2517		2702
2518	static void stdin_ready (int revents, void *arg)	2703	static void stdin_ready (int revents, void *arg)
2519	{	2704	{
		2705	if (revents & EV_READ)
		2706	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2707	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2708	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2709	}
2525		2710
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2711	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2712
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2713	=item ev_feed_event (struct ev_loop , watcher , int revents)
2529		2714
2530	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
2531	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
2532	initialised but not necessarily started event watcher).	2717	initialised but not necessarily started event watcher).
2533		2718
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2719	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2720
2536	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
2537	the given events it.	2722	the given events it.
2538		2723
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2724	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2725
2541	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
2542	loop!).	2727	loop!).
2543		2728
2544	=back	2729	=back
…		…
2676		2861
2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2862	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2678		2863
2679	See the method-C<set> above for more details.	2864	See the method-C<set> above for more details.
2680		2865
2681	Example:	2866	Example: Use a plain function as callback.
2682		2867
2683	static void io_cb (ev::io &w, int revents) { }	2868	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	2869	iow.set <io_cb> ();
2685		2870
2686	=item w->set (struct ev_loop *)	2871	=item w->set (struct ev_loop *)
…		…
2724	Example: Define a class with an IO and idle watcher, start one of them in	2909	Example: Define a class with an IO and idle watcher, start one of them in
2725	the constructor.	2910	the constructor.
2726		2911
2727	class myclass	2912	class myclass
2728	{	2913	{
2729	ev::io io; void io_cb (ev::io &w, int revents);	2914	ev::io io ; void io_cb (ev::io &w, int revents);
2730	ev:idle idle void idle_cb (ev::idle &w, int revents);	2915	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		2916
2732	myclass (int fd)	2917	myclass (int fd)
2733	{	2918	{
2734	io .set <myclass, &myclass::io_cb > (this);	2919	io .set <myclass, &myclass::io_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	2920	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2751	=item Perl	2936	=item Perl
2752		2937
2753	The EV module implements the full libev API and is actually used to test	2938	The EV module implements the full libev API and is actually used to test
2754	libev. EV is developed together with libev. Apart from the EV core module,	2939	libev. EV is developed together with libev. Apart from the EV core module,
2755	there are additional modules that implement libev-compatible interfaces	2940	there are additional modules that implement libev-compatible interfaces
2756	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2941	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2757	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2942	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2943	and C<EV::Glib>).
2758		2944
2759	It can be found and installed via CPAN, its homepage is at	2945	It can be found and installed via CPAN, its homepage is at
2760	L<http://software.schmorp.de/pkg/EV>.	2946	L<http://software.schmorp.de/pkg/EV>.
2761		2947
2762	=item Python	2948	=item Python
…		…
2778	=item D	2964	=item D
2779		2965
2780	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
2781	be found at L<http://proj.llucax.com.ar/wiki/evd>.	2967	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2782		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/>.
		2973
2783	=back	2974	=back
2784		2975
2785		2976
2786	=head1 MACRO MAGIC	2977	=head1 MACRO MAGIC
2787		2978
…		…
2941		3132
2942	=head2 PREPROCESSOR SYMBOLS/MACROS	3133	=head2 PREPROCESSOR SYMBOLS/MACROS
2943		3134
2944	Libev can be configured via a variety of preprocessor symbols you have to	3135	Libev can be configured via a variety of preprocessor symbols you have to
2945	define before including any of its files. The default in the absence of	3136	define before including any of its files. The default in the absence of
2946	autoconf is noted for every option.	3137	autoconf is documented for every option.
2947		3138
2948	=over 4	3139	=over 4
2949		3140
2950	=item EV_STANDALONE	3141	=item EV_STANDALONE
2951		3142
…		…
3121	When doing priority-based operations, libev usually has to linearly search	3312	When doing priority-based operations, libev usually has to linearly search
3122	all the priorities, so having many of them (hundreds) uses a lot of space	3313	all the priorities, so having many of them (hundreds) uses a lot of space
3123	and time, so using the defaults of five priorities (-2 .. +2) is usually	3314	and time, so using the defaults of five priorities (-2 .. +2) is usually
3124	fine.	3315	fine.
3125		3316
3126	If your embedding application does not need any priorities, defining these both to	3317	If your embedding application does not need any priorities, defining these
3127	C<0> will save some memory and CPU.	3318	both to C<0> will save some memory and CPU.
3128		3319
3129	=item EV_PERIODIC_ENABLE	3320	=item EV_PERIODIC_ENABLE
3130		3321
3131	If undefined or defined to be C<1>, then periodic timers are supported. If	3322	If undefined or defined to be C<1>, then periodic timers are supported. If
3132	defined to be C<0>, then they are not. Disabling them saves a few kB of	3323	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3139	code.	3330	code.
3140		3331
3141	=item EV_EMBED_ENABLE	3332	=item EV_EMBED_ENABLE
3142		3333
3143	If undefined or defined to be C<1>, then embed watchers are supported. If	3334	If undefined or defined to be C<1>, then embed watchers are supported. If
3144	defined to be C<0>, then they are not.	3335	defined to be C<0>, then they are not. Embed watchers rely on most other
		3336	watcher types, which therefore must not be disabled.
3145		3337
3146	=item EV_STAT_ENABLE	3338	=item EV_STAT_ENABLE
3147		3339
3148	If undefined or defined to be C<1>, then stat watchers are supported. If	3340	If undefined or defined to be C<1>, then stat watchers are supported. If
3149	defined to be C<0>, then they are not.	3341	defined to be C<0>, then they are not.
…		…
3181	two).	3373	two).
3182		3374
3183	=item EV_USE_4HEAP	3375	=item EV_USE_4HEAP
3184		3376
3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3377	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3186	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3378	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3187	to C<1>. The 4-heap uses more complicated (longer) code but has	3379	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3188	noticeably faster performance with many (thousands) of watchers.	3380	faster performance with many (thousands) of watchers.
3189		3381
3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3382	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3191	(disabled).	3383	(disabled).
3192		3384
3193	=item EV_HEAP_CACHE_AT	3385	=item EV_HEAP_CACHE_AT
3194		3386
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3387	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3196	timer and periodics heap, libev can cache the timestamp (I<at>) within	3388	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3197	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3389	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3198	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3390	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3199	but avoids random read accesses on heap changes. This improves performance	3391	but avoids random read accesses on heap changes. This improves performance
3200	noticeably with with many (hundreds) of watchers.	3392	noticeably with many (hundreds) of watchers.
3201		3393
3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3394	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3203	(disabled).	3395	(disabled).
3204		3396
3205	=item EV_VERIFY	3397	=item EV_VERIFY
…		…
3211	called once per loop, which can slow down libev. If set to C<3>, then the	3403	called once per loop, which can slow down libev. If set to C<3>, then the
3212	verification code will be called very frequently, which will slow down	3404	verification code will be called very frequently, which will slow down
3213	libev considerably.	3405	libev considerably.
3214		3406
3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3407	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3216	C<0.>	3408	C<0>.
3217		3409
3218	=item EV_COMMON	3410	=item EV_COMMON
3219		3411
3220	By default, all watchers have a C<void *data> member. By redefining	3412	By default, all watchers have a C<void *data> member. By redefining
3221	this macro to a something else you can include more and other types of	3413	this macro to a something else you can include more and other types of
…		…
3238	and the way callbacks are invoked and set. Must expand to a struct member	3430	and the way callbacks are invoked and set. Must expand to a struct member
3239	definition and a statement, respectively. See the F<ev.h> header file for	3431	definition and a statement, respectively. See the F<ev.h> header file for
3240	their default definitions. One possible use for overriding these is to	3432	their default definitions. One possible use for overriding these is to
3241	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3433	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3242	method calls instead of plain function calls in C++.	3434	method calls instead of plain function calls in C++.
		3435
		3436	=back
3243		3437
3244	=head2 EXPORTED API SYMBOLS	3438	=head2 EXPORTED API SYMBOLS
3245		3439
3246	If you need to re-export the API (e.g. via a DLL) and you need a list of	3440	If you need to re-export the API (e.g. via a DLL) and you need a list of
3247	exported symbols, you can use the provided F<Symbol.*> files which list	3441	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3294	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3488	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3295		3489
3296	#include "ev_cpp.h"	3490	#include "ev_cpp.h"
3297	#include "ev.c"	3491	#include "ev.c"
3298		3492
		3493	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3299		3494
3300	=head1 THREADS AND COROUTINES	3495	=head2 THREADS AND COROUTINES
3301		3496
3302	=head2 THREADS	3497	=head3 THREADS
3303		3498
3304	Libev itself is thread-safe (unless the opposite is specifically	3499	All libev functions are reentrant and thread-safe unless explicitly
3305	documented for a function), but it uses no locking itself. This means that	3500	documented otherwise, but libev implements no locking itself. This means
3306	you can use as many loops as you want in parallel, as long as only one	3501	that you can use as many loops as you want in parallel, as long as there
3307	thread ever calls into one libev function with the same loop parameter:	3502	are no concurrent calls into any libev function with the same loop
		3503	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3308	libev guarentees that different event loops share no data structures that	3504	of course): libev guarantees that different event loops share no data
3309	need locking.	3505	structures that need any locking.
3310		3506
3311	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
3312	concurrently from multiple threads, calls with the same loop parameter	3508	concurrently from multiple threads, calls with the same loop parameter
3313	must be done serially (but can be done from different threads, as long as	3509	must be done serially (but can be done from different threads, as long as
3314	only one thread ever is inside a call at any point in time, e.g. by using	3510	only one thread ever is inside a call at any point in time, e.g. by using
3315	a mutex per loop).	3511	a mutex per loop).
3316		3512
3317	Specifically to support threads (and signal handlers), libev implements	3513	Specifically to support threads (and signal handlers), libev implements
3318	so-called C<ev_async> watchers, which allow some limited form of	3514	so-called C<ev_async> watchers, which allow some limited form of
3319	concurrency on the same event loop.	3515	concurrency on the same event loop, namely waking it up "from the
		3516	outside".
3320		3517
3321	If you want to know which design (one loop, locking, or multiple loops	3518	If you want to know which design (one loop, locking, or multiple loops
3322	without or something else still) is best for your problem, then I cannot	3519	without or something else still) is best for your problem, then I cannot
3323	help you. I can give some generic advice however:	3520	help you, but here is some generic advice:
3324		3521
3325	=over 4	3522	=over 4
3326		3523
3327	=item * most applications have a main thread: use the default libev loop	3524	=item * most applications have a main thread: use the default libev loop
3328	in that thread, or create a separate thread running only the default loop.	3525	in that thread, or create a separate thread running only the default loop.
…		…
3352	default loop and triggering an C<ev_async> watcher from the default loop	3549	default loop and triggering an C<ev_async> watcher from the default loop
3353	watcher callback into the event loop interested in the signal.	3550	watcher callback into the event loop interested in the signal.
3354		3551
3355	=back	3552	=back
3356		3553
3357	=head2 COROUTINES	3554	=head3 COROUTINES
3358		3555
3359	Libev is much more accommodating to coroutines ("cooperative threads"):	3556	Libev is very accommodating to coroutines ("cooperative threads"):
3360	libev fully supports nesting calls to it's functions from different	3557	libev fully supports nesting calls to its functions from different
3361	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3558	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3362	different coroutines and switch freely between both coroutines running the	3559	different coroutines, and switch freely between both coroutines running the
3363	loop, as long as you don't confuse yourself). The only exception is that	3560	loop, as long as you don't confuse yourself). The only exception is that
3364	you must not do this from C<ev_periodic> reschedule callbacks.	3561	you must not do this from C<ev_periodic> reschedule callbacks.
3365		3562
3366	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
3367	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.
3368		3566
		3567	=head2 COMPILER WARNINGS
3369		3568
3370	=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.
3371		3572
3372	In this section the complexities of (many of) the algorithms used inside	3573	However, these are unavoidable for many reasons. For one, each compiler
3373	libev will be explained. For complexity discussions about backends see the	3574	has different warnings, and each user has different tastes regarding
3374	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.
3375		3577
3376	All of the following are about amortised time: If an array needs to be	3578	Another reason is that some compiler warnings require elaborate
3377	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
3378	happens asymptotically never with higher number of elements, so O(1) might	3580	maintainable.
3379	mean it might do a lengthy realloc operation in rare cases, but on average
3380	it is much faster and asymptotically approaches constant time.
3381		3581
3382	=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.
3383		3588
3384	=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.
3385		3594
3386	This means that, when you have a watcher that triggers in one hour and
3387	there are 100 watchers that would trigger before that then inserting will
3388	have to skip roughly seven (C<ld 100>) of these watchers.
3389		3595
3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3596	=head2 VALGRIND
3391		3597
3392	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
3393	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.
3394		3600
3395	=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:
3396		3603
3397	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.
3398		3607
3399	=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.
3400		3610
3401	=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.
3402		3615
3403	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
3404	correct watcher to remove. The lists are usually short (you don't usually	3617	make it into some kind of religion.
3405	have many watchers waiting for the same fd or signal).
3406		3618
3407	=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.
3408		3624
3409	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
3410	fixed position in the storage array.	3626	I suggest using suppression lists.
3411		3627
3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3413		3628
3414	A change means an I/O watcher gets started or stopped, which requires	3629	=head1 PORTABILITY NOTES
3415	libev to recalculate its status (and possibly tell the kernel, depending
3416	on backend and whether C<ev_io_set> was used).
3417		3630
3418	=item Activating one watcher (putting it into the pending state): O(1)
3419
3420	=item Priority handling: O(number_of_priorities)
3421
3422	Priorities are implemented by allocating some space for each
3423	priority. When doing priority-based operations, libev usually has to
3424	linearly search all the priorities, but starting/stopping and activating
3425	watchers becomes O(1) w.r.t. priority handling.
3426
3427	=item Sending an ev_async: O(1)
3428
3429	=item Processing ev_async_send: O(number_of_async_watchers)
3430
3431	=item Processing signals: O(max_signal_number)
3432
3433	Sending involves a system call I<iff> there were no other C<ev_async_send>
3434	calls in the current loop iteration. Checking for async and signal events
3435	involves iterating over all running async watchers or all signal numbers.
3436
3437	=back
3438
3439
3440	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3631	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3441		3632
3442	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
3443	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
3444	model. Libev still offers limited functionality on this platform in	3635	model. Libev still offers limited functionality on this platform in
3445	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
…		…
3456		3647
3457	Not a libev limitation but worth mentioning: windows apparently doesn't	3648	Not a libev limitation but worth mentioning: windows apparently doesn't
3458	accept large writes: instead of resulting in a partial write, windows will	3649	accept large writes: instead of resulting in a partial write, windows will
3459	either accept everything or return C<ENOBUFS> if the buffer is too large,	3650	either accept everything or return C<ENOBUFS> if the buffer is too large,
3460	so make sure you only write small amounts into your sockets (less than a	3651	so make sure you only write small amounts into your sockets (less than a
3461	megabyte seems safe, but thsi apparently depends on the amount of memory	3652	megabyte seems safe, but this apparently depends on the amount of memory
3462	available).	3653	available).
3463		3654
3464	Due to the many, low, and arbitrary limits on the win32 platform and	3655	Due to the many, low, and arbitrary limits on the win32 platform and
3465	the abysmal performance of winsockets, using a large number of sockets	3656	the abysmal performance of winsockets, using a large number of sockets
3466	is not recommended (and not reasonable). If your program needs to use	3657	is not recommended (and not reasonable). If your program needs to use
…		…
3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3668	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3478		3669
3479	#include "ev.h"	3670	#include "ev.h"
3480		3671
3481	And compile the following F<evwrap.c> file into your project (make sure	3672	And compile the following F<evwrap.c> file into your project (make sure
3482	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3673	you do I<not> compile the F<ev.c> or any other embedded source files!):
3483		3674
3484	#include "evwrap.h"	3675	#include "evwrap.h"
3485	#include "ev.c"	3676	#include "ev.c"
3486		3677
3487	=over 4	3678	=over 4
…		…
3532	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
3533	calling select (O(n²)) will likely make this unworkable.	3724	calling select (O(n²)) will likely make this unworkable.
3534		3725
3535	=back	3726	=back
3536		3727
3537
3538	=head1 PORTABILITY REQUIREMENTS	3728	=head2 PORTABILITY REQUIREMENTS
3539		3729
3540	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
3541	additional extensions:	3731	backend-specific APIs, libev relies on a few additional extensions:
3542		3732
3543	=over 4	3733	=over 4
3544		3734
3545	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3735	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3546	calling conventions regardless of C<ev_watcher_type *>.	3736	calling conventions regardless of C<ev_watcher_type *>.
…		…
3552	calls them using an C<ev_watcher *> internally.	3742	calls them using an C<ev_watcher *> internally.
3553		3743
3554	=item C<sig_atomic_t volatile> must be thread-atomic as well	3744	=item C<sig_atomic_t volatile> must be thread-atomic as well
3555		3745
3556	The type C<sig_atomic_t volatile> (or whatever is defined as	3746	The type C<sig_atomic_t volatile> (or whatever is defined as
3557	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3747	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3558	threads. This is not part of the specification for C<sig_atomic_t>, but is	3748	threads. This is not part of the specification for C<sig_atomic_t>, but is
3559	believed to be sufficiently portable.	3749	believed to be sufficiently portable.
3560		3750
3561	=item C<sigprocmask> must work in a threaded environment	3751	=item C<sigprocmask> must work in a threaded environment
3562		3752
…		…
3571	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
3572	well.	3762	well.
3573		3763
3574	=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
3575		3765
3576	To improve portability and simplify using libev, libev uses C<long>	3766	To improve portability and simplify its API, libev uses C<long> internally
3577	internally instead of C<size_t> when allocating its data structures. On	3767	instead of C<size_t> when allocating its data structures. On non-POSIX
3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3768	systems (Microsoft...) this might be unexpectedly low, but is still at
3579	is still at least 31 bits everywhere, which is enough for hundreds of	3769	least 31 bits everywhere, which is enough for hundreds of millions of
3580	millions of watchers.	3770	watchers.
3581		3771
3582	=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
3583		3773
3584	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
3585	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
…		…
3589	=back	3779	=back
3590		3780
3591	If you know of other additional requirements drop me a note.	3781	If you know of other additional requirements drop me a note.
3592		3782
3593		3783
3594	=head1 COMPILER WARNINGS	3784	=head1 ALGORITHMIC COMPLEXITIES
3595		3785
3596	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
3597	lot of warnings when compiling libev code. Some people are apparently	3787	libev will be documented. For complexity discussions about backends see
3598	scared by this.	3788	the documentation for C<ev_default_init>.
3599		3789
3600	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
3601	has different warnings, and each user has different tastes regarding	3791	extended, libev needs to realloc and move the whole array, but this
3602	warning options. "Warn-free" code therefore cannot be a goal except when	3792	happens asymptotically rarer with higher number of elements, so O(1) might
3603	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.
3604		3795
3605	Another reason is that some compiler warnings require elaborate	3796	=over 4
3606	workarounds, or other changes to the code that make it less clear and less
3607	maintainable.
3608		3797
3609	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)
3610	wrong (because they don't actually warn about the condition their message
3611	seems to warn about).
3612		3799
3613	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
3614	"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
3615	with any compiler warnings enabled unless you are prepared to cope with	3802	have to skip roughly seven (C<ld 100>) of these watchers.
3616	them (e.g. by ignoring them). Remember that warnings are just that:
3617	warnings, not errors, or proof of bugs.
3618		3803
		3804	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3619		3805
3620	=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.
3621		3808
3622	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)
3623	highly useful, but valgrind reports are very hard to interpret.
3624		3810
3625	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.
3626	in libev, then check twice: If valgrind reports something like:
3627		3812
3628	==2274== definitely lost: 0 bytes in 0 blocks.	3813	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3629	==2274== possibly lost: 0 bytes in 0 blocks.
3630	==2274== still reachable: 256 bytes in 1 blocks.
3631		3814
3632	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))
3633	valgrind might report kernel bugs as if it were a bug in libev, or it
3634	might be confused (it is a very good tool, but only a tool).
3635		3816
3636	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
3637	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
3638	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
3639	no bug" answer and take the chance of learning how to interpret valgrind	3820	is rare).
3640	properly.
3641		3821
3642	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)
3643	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
3644		3853
3645		3854
3646	=head1 AUTHOR	3855	=head1 AUTHOR
3647		3856
3648	Marc Lehmann <libev@schmorp.de>.	3857	Marc Lehmann <libev@schmorp.de>.

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Comparing libev/ev.pod (file contents): Revision 1.183 by root, Tue Sep 23 08:37:38 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 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs.
Revision 1.205 by root, Mon Oct 27 12:20:32 2008 UTC