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

Comparing libev/ev.pod (file contents):
Revision 1.195 by root, Mon Oct 20 17:50:48 2008 UTC vs.
Revision 1.209 by root, Wed Oct 29 14:12:34 2008 UTC

…		…
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
294	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
295	function.	299	function.
296		300
297	Note that this function is I<not> thread-safe, so if you want to use it	301	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	302	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	303	as loops cannot be shared easily between threads anyway).
300		304
301	The default loop is the only loop that can handle C<ev_signal> and	305	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	306	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	307	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
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 event
388	support for dup.	392	mechanisms: problems include silently dropping fds, requiring a system
		393	call per change per fd (and unnecessary guessing of parameters), problems
		394	with dup and so on. The biggest issue is fork races, however - if a
		395	program forks then I<both> parent and child process have to recreate the
		396	epoll set, which can take considerable time (one syscall per fd) and is of
		397	course hard to detect.
		398
		399	Epoll is also notoriously buggy - embedding epoll fds should work, but
		400	of course doesn't, and epoll just loves to report events for totally
		401	I<different> file descriptors (even already closed ones, so one cannot
		402	even remove them from the set) than registered in the set (especially
		403	on SMP systems). Libev tries to counter these spurious notifications by
		404	employing an additional generation counter and comparing that against the
		405	events to filter out spurious ones.
389		406
390	While stopping, setting and starting an I/O watcher in the same iteration	407	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	408	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	409	(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	410	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
394	very well if you register events for both fds.	411	very well if you register events for both fds.
395		412
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
400	Best performance from this backend is achieved by not unregistering all	413	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	414	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	415	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	416	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	417	extra overhead. A fork can both result in spurious notifications as well
		418	as in libev having to destroy and recreate the epoll object, which can
		419	take considerable time and thus should be avoided.
405		420
406	While nominally embeddable in other event loops, this feature is broken in	421	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	422	all kernel versions tested so far.
408		423
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	424	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
424		439
425	It scales in the same way as the epoll backend, but the interface to the	440	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	441	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	442	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	443	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	444	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	445	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		446	cases
431		447
432	This backend usually performs well under most conditions.	448	This backend usually performs well under most conditions.
433		449
434	While nominally embeddable in other event loops, this doesn't work	450	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	451	everywhere, so you might need to test for this. And since it is broken
…		…
464	might perform better.	480	might perform better.
465		481
466	On the positive side, with the exception of the spurious readiness	482	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	483	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	484	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	485	OS-specific backends (I vastly prefer correctness over speed hacks).
470		486
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	487	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	488	C<EVBACKEND_POLL>.
473		489
474	=item C<EVBACKEND_ALL>	490	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	543	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	544	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	545	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	546	for example).
531		547
532	Note that certain global state, such as signal state, will not be freed by	548	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	549	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	550	as signal and child watchers) would need to be stopped manually.
535		551
536	In general it is not advisable to call this function except in the	552	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	553	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	554	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	555	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
631	the loop.	647	the loop.
632		648
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	649	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	650	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	651	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	652	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	653	user-registered callback will be called), and will return after one
638	iteration of the loop.	654	iteration of the loop.
639		655
640	This is useful if you are waiting for some external event in conjunction	656	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	657	with something not expressible using other libev watchers (i.e. "roll your
…		…
710	respectively).	726	respectively).
711		727
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	728	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	729	running when nothing else is active.
714		730
715	struct ev_signal exitsig;	731	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	732	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	733	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	734	evf_unref (loop);
719		735
720	Example: For some weird reason, unregister the above signal handler again.	736	Example: For some weird reason, unregister the above signal handler again.
…		…
768	they fire on, say, one-second boundaries only.	784	they fire on, say, one-second boundaries only.
769		785
770	=item ev_loop_verify (loop)	786	=item ev_loop_verify (loop)
771		787
772	This function only does something when C<EV_VERIFY> support has been	788	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	789	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	790	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	791	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	792	error and call C<abort ()>.
777		793
778	This can be used to catch bugs inside libev itself: under normal	794	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	798	=back
783		799
784		800
785	=head1 ANATOMY OF A WATCHER	801	=head1 ANATOMY OF A WATCHER
786		802
		803	In the following description, uppercase C<TYPE> in names stands for the
		804	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		805	watchers and C<ev_io_start> for I/O watchers.
		806
787	A watcher is a structure that you create and register to record your	807	A watcher is a structure that you create and register to record your
788	interest in some event. For instance, if you want to wait for STDIN to	808	interest in some event. For instance, if you want to wait for STDIN to
789	become readable, you would create an C<ev_io> watcher for that:	809	become readable, you would create an C<ev_io> watcher for that:
790		810
791	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	811	static void my_cb (struct ev_loop loop, ev_io w, int revents)
792	{	812	{
793	ev_io_stop (w);	813	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	814	ev_unloop (loop, EVUNLOOP_ALL);
795	}	815	}
796		816
797	struct ev_loop *loop = ev_default_loop (0);	817	struct ev_loop *loop = ev_default_loop (0);
		818
798	struct ev_io stdin_watcher;	819	ev_io stdin_watcher;
		820
799	ev_init (&stdin_watcher, my_cb);	821	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	822	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	823	ev_io_start (loop, &stdin_watcher);
		824
802	ev_loop (loop, 0);	825	ev_loop (loop, 0);
803		826
804	As you can see, you are responsible for allocating the memory for your	827	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	828	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	829	stack).
		830
		831	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		832	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		833
808	Each watcher structure must be initialised by a call to C<ev_init	834	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	835	(watcher *, callback)>, which expects a callback to be provided. This
810	callback gets invoked each time the event occurs (or, in the case of I/O	836	callback gets invoked each time the event occurs (or, in the case of I/O
811	watchers, each time the event loop detects that the file descriptor given	837	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	838	is readable and/or writable).
813		839
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	840	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	841	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	842	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	843	ev_TYPE_init (watcher *, callback, ...) >>.
818		844
819	To make the watcher actually watch out for events, you have to start it	845	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	846	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	847	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	848	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		849
824	As long as your watcher is active (has been started but not stopped) you	850	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	851	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	852	reinitialise it or call its C<ev_TYPE_set> macro.
827		853
828	Each and every callback receives the event loop pointer as first, the	854	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	855	registered watcher structure as second, and a bitset of received events as
830	third argument.	856	third argument.
831		857
…		…
894	=item C<EV_ERROR>	920	=item C<EV_ERROR>
895		921
896	An unspecified error has occurred, the watcher has been stopped. This might	922	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	923	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	924	ran out of memory, a file descriptor was found to be closed or any other
		925	problem. Libev considers these application bugs.
		926
899	problem. You best act on it by reporting the problem and somehow coping	927	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	928	watcher being stopped. Note that well-written programs should not receive
		929	an error ever, so when your watcher receives it, this usually indicates a
		930	bug in your program.
901		931
902	Libev will usually signal a few "dummy" events together with an error, for	932	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	933	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	934	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	935	the error from read() or write(). This will not work in multi-threaded
…		…
908		938
909	=back	939	=back
910		940
911	=head2 GENERIC WATCHER FUNCTIONS	941	=head2 GENERIC WATCHER FUNCTIONS
912		942
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915
916	=over 4	943	=over 4
917		944
918	=item C<ev_init> (ev_TYPE *watcher, callback)	945	=item C<ev_init> (ev_TYPE *watcher, callback)
919		946
920	This macro initialises the generic portion of a watcher. The contents	947	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	952	which rolls both calls into one.
926		953
927	You can reinitialise a watcher at any time as long as it has been stopped	954	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	955	(or never started) and there are no pending events outstanding.
929		956
930	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	957	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
931	int revents)>.	958	int revents)>.
932		959
933	Example: Initialise an C<ev_io> watcher in two steps.	960	Example: Initialise an C<ev_io> watcher in two steps.
934		961
935	ev_io w;	962	ev_io w;
…		…
1028	The default priority used by watchers when no priority has been set is	1055	The default priority used by watchers when no priority has been set is
1029	always C<0>, which is supposed to not be too high and not be too low :).	1056	always C<0>, which is supposed to not be too high and not be too low :).
1030		1057
1031	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1058	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1032	fine, as long as you do not mind that the priority value you query might	1059	fine, as long as you do not mind that the priority value you query might
1033	or might not have been adjusted to be within valid range.	1060	or might not have been clamped to the valid range.
1034		1061
1035	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1062	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1036		1063
1037	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1064	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1038	C<loop> nor C<revents> need to be valid as long as the watcher callback	1065	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1060	member, you can also "subclass" the watcher type and provide your own	1087	member, you can also "subclass" the watcher type and provide your own
1061	data:	1088	data:
1062		1089
1063	struct my_io	1090	struct my_io
1064	{	1091	{
1065	struct ev_io io;	1092	ev_io io;
1066	int otherfd;	1093	int otherfd;
1067	void *somedata;	1094	void *somedata;
1068	struct whatever *mostinteresting;	1095	struct whatever *mostinteresting;
1069	};	1096	};
1070		1097
…		…
1073	ev_io_init (&w.io, my_cb, fd, EV_READ);	1100	ev_io_init (&w.io, my_cb, fd, EV_READ);
1074		1101
1075	And since your callback will be called with a pointer to the watcher, you	1102	And since your callback will be called with a pointer to the watcher, you
1076	can cast it back to your own type:	1103	can cast it back to your own type:
1077		1104
1078	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1105	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1079	{	1106	{
1080	struct my_io w = (struct my_io )w_;	1107	struct my_io w = (struct my_io )w_;
1081	...	1108	...
1082	}	1109	}
1083		1110
…		…
1101	programmers):	1128	programmers):
1102		1129
1103	#include <stddef.h>	1130	#include <stddef.h>
1104		1131
1105	static void	1132	static void
1106	t1_cb (EV_P_ struct ev_timer *w, int revents)	1133	t1_cb (EV_P_ ev_timer *w, int revents)
1107	{	1134	{
1108	struct my_biggy big = (struct my_biggy *	1135	struct my_biggy big = (struct my_biggy *
1109	(((char *)w) - offsetof (struct my_biggy, t1));	1136	(((char *)w) - offsetof (struct my_biggy, t1));
1110	}	1137	}
1111		1138
1112	static void	1139	static void
1113	t2_cb (EV_P_ struct ev_timer *w, int revents)	1140	t2_cb (EV_P_ ev_timer *w, int revents)
1114	{	1141	{
1115	struct my_biggy big = (struct my_biggy *	1142	struct my_biggy big = (struct my_biggy *
1116	(((char *)w) - offsetof (struct my_biggy, t2));	1143	(((char *)w) - offsetof (struct my_biggy, t2));
1117	}	1144	}
1118		1145
…		…
1253	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1280	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1254	readable, but only once. Since it is likely line-buffered, you could	1281	readable, but only once. Since it is likely line-buffered, you could
1255	attempt to read a whole line in the callback.	1282	attempt to read a whole line in the callback.
1256		1283
1257	static void	1284	static void
1258	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1285	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1259	{	1286	{
1260	ev_io_stop (loop, w);	1287	ev_io_stop (loop, w);
1261	.. read from stdin here (or from w->fd) and handle any I/O errors	1288	.. read from stdin here (or from w->fd) and handle any I/O errors
1262	}	1289	}
1263		1290
1264	...	1291	...
1265	struct ev_loop *loop = ev_default_init (0);	1292	struct ev_loop *loop = ev_default_init (0);
1266	struct ev_io stdin_readable;	1293	ev_io stdin_readable;
1267	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1294	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1268	ev_io_start (loop, &stdin_readable);	1295	ev_io_start (loop, &stdin_readable);
1269	ev_loop (loop, 0);	1296	ev_loop (loop, 0);
1270		1297
1271		1298
…		…
1282		1309
1283	The callback is guaranteed to be invoked only I<after> its timeout has	1310	The callback is guaranteed to be invoked only I<after> its timeout has
1284	passed, but if multiple timers become ready during the same loop iteration	1311	passed, but if multiple timers become ready during the same loop iteration
1285	then order of execution is undefined.	1312	then order of execution is undefined.
1286		1313
		1314	=head3 Be smart about timeouts
		1315
		1316	Many real-world problems involve some kind of timeout, usually for error
		1317	recovery. A typical example is an HTTP request - if the other side hangs,
		1318	you want to raise some error after a while.
		1319
		1320	What follows are some ways to handle this problem, from obvious and
		1321	inefficient to smart and efficient.
		1322
		1323	In the following, a 60 second activity timeout is assumed - a timeout that
		1324	gets reset to 60 seconds each time there is activity (e.g. each time some
		1325	data or other life sign was received).
		1326
		1327	=over 4
		1328
		1329	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1330
		1331	This is the most obvious, but not the most simple way: In the beginning,
		1332	start the watcher:
		1333
		1334	ev_timer_init (timer, callback, 60., 0.);
		1335	ev_timer_start (loop, timer);
		1336
		1337	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1338	and start it again:
		1339
		1340	ev_timer_stop (loop, timer);
		1341	ev_timer_set (timer, 60., 0.);
		1342	ev_timer_start (loop, timer);
		1343
		1344	This is relatively simple to implement, but means that each time there is
		1345	some activity, libev will first have to remove the timer from its internal
		1346	data structure and then add it again. Libev tries to be fast, but it's
		1347	still not a constant-time operation.
		1348
		1349	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1350
		1351	This is the easiest way, and involves using C<ev_timer_again> instead of
		1352	C<ev_timer_start>.
		1353
		1354	To implement this, configure an C<ev_timer> with a C<repeat> value
		1355	of C<60> and then call C<ev_timer_again> at start and each time you
		1356	successfully read or write some data. If you go into an idle state where
		1357	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1358	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1359
		1360	That means you can ignore both the C<ev_timer_start> function and the
		1361	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1362	member and C<ev_timer_again>.
		1363
		1364	At start:
		1365
		1366	ev_timer_init (timer, callback);
		1367	timer->repeat = 60.;
		1368	ev_timer_again (loop, timer);
		1369
		1370	Each time there is some activity:
		1371
		1372	ev_timer_again (loop, timer);
		1373
		1374	It is even possible to change the time-out on the fly, regardless of
		1375	whether the watcher is active or not:
		1376
		1377	timer->repeat = 30.;
		1378	ev_timer_again (loop, timer);
		1379
		1380	This is slightly more efficient then stopping/starting the timer each time
		1381	you want to modify its timeout value, as libev does not have to completely
		1382	remove and re-insert the timer from/into its internal data structure.
		1383
		1384	It is, however, even simpler than the "obvious" way to do it.
		1385
		1386	=item 3. Let the timer time out, but then re-arm it as required.
		1387
		1388	This method is more tricky, but usually most efficient: Most timeouts are
		1389	relatively long compared to the intervals between other activity - in
		1390	our example, within 60 seconds, there are usually many I/O events with
		1391	associated activity resets.
		1392
		1393	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1394	but remember the time of last activity, and check for a real timeout only
		1395	within the callback:
		1396
		1397	ev_tstamp last_activity; // time of last activity
		1398
		1399	static void
		1400	callback (EV_P_ ev_timer *w, int revents)
		1401	{
		1402	ev_tstamp now = ev_now (EV_A);
		1403	ev_tstamp timeout = last_activity + 60.;
		1404
		1405	// if last_activity + 60. is older than now, we did time out
		1406	if (timeout < now)
		1407	{
		1408	// timeout occured, take action
		1409	}
		1410	else
		1411	{
		1412	// callback was invoked, but there was some activity, re-arm
		1413	// the watcher to fire in last_activity + 60, which is
		1414	// guaranteed to be in the future, so "again" is positive:
		1415	w->again = timeout - now;
		1416	ev_timer_again (EV_A_ w);
		1417	}
		1418	}
		1419
		1420	To summarise the callback: first calculate the real timeout (defined
		1421	as "60 seconds after the last activity"), then check if that time has
		1422	been reached, which means something I<did>, in fact, time out. Otherwise
		1423	the callback was invoked too early (C<timeout> is in the future), so
		1424	re-schedule the timer to fire at that future time, to see if maybe we have
		1425	a timeout then.
		1426
		1427	Note how C<ev_timer_again> is used, taking advantage of the
		1428	C<ev_timer_again> optimisation when the timer is already running.
		1429
		1430	This scheme causes more callback invocations (about one every 60 seconds
		1431	minus half the average time between activity), but virtually no calls to
		1432	libev to change the timeout.
		1433
		1434	To start the timer, simply initialise the watcher and set C<last_activity>
		1435	to the current time (meaning we just have some activity :), then call the
		1436	callback, which will "do the right thing" and start the timer:
		1437
		1438	ev_timer_init (timer, callback);
		1439	last_activity = ev_now (loop);
		1440	callback (loop, timer, EV_TIMEOUT);
		1441
		1442	And when there is some activity, simply store the current time in
		1443	C<last_activity>, no libev calls at all:
		1444
		1445	last_actiivty = ev_now (loop);
		1446
		1447	This technique is slightly more complex, but in most cases where the
		1448	time-out is unlikely to be triggered, much more efficient.
		1449
		1450	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1451	callback :) - just change the timeout and invoke the callback, which will
		1452	fix things for you.
		1453
		1454	=item 4. Wee, just use a double-linked list for your timeouts.
		1455
		1456	If there is not one request, but many thousands (millions...), all
		1457	employing some kind of timeout with the same timeout value, then one can
		1458	do even better:
		1459
		1460	When starting the timeout, calculate the timeout value and put the timeout
		1461	at the I<end> of the list.
		1462
		1463	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1464	the list is expected to fire (for example, using the technique #3).
		1465
		1466	When there is some activity, remove the timer from the list, recalculate
		1467	the timeout, append it to the end of the list again, and make sure to
		1468	update the C<ev_timer> if it was taken from the beginning of the list.
		1469
		1470	This way, one can manage an unlimited number of timeouts in O(1) time for
		1471	starting, stopping and updating the timers, at the expense of a major
		1472	complication, and having to use a constant timeout. The constant timeout
		1473	ensures that the list stays sorted.
		1474
		1475	=back
		1476
		1477	So which method the best?
		1478
		1479	Method #2 is a simple no-brain-required solution that is adequate in most
		1480	situations. Method #3 requires a bit more thinking, but handles many cases
		1481	better, and isn't very complicated either. In most case, choosing either
		1482	one is fine, with #3 being better in typical situations.
		1483
		1484	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1485	rather complicated, but extremely efficient, something that really pays
		1486	off after the first million or so of active timers, i.e. it's usually
		1487	overkill :)
		1488
1287	=head3 The special problem of time updates	1489	=head3 The special problem of time updates
1288		1490
1289	Establishing the current time is a costly operation (it usually takes at	1491	Establishing the current time is a costly operation (it usually takes at
1290	least two system calls): EV therefore updates its idea of the current	1492	least two system calls): EV therefore updates its idea of the current
1291	time only before and after C<ev_loop> collects new events, which causes a	1493	time only before and after C<ev_loop> collects new events, which causes a
…		…
1334	If the timer is started but non-repeating, stop it (as if it timed out).	1536	If the timer is started but non-repeating, stop it (as if it timed out).
1335		1537
1336	If the timer is repeating, either start it if necessary (with the	1538	If the timer is repeating, either start it if necessary (with the
1337	C<repeat> value), or reset the running timer to the C<repeat> value.	1539	C<repeat> value), or reset the running timer to the C<repeat> value.
1338		1540
1339	This sounds a bit complicated, but here is a useful and typical	1541	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1340	example: Imagine you have a TCP connection and you want a so-called idle	1542	usage example.
1341	timeout, that is, you want to be called when there have been, say, 60
1342	seconds of inactivity on the socket. The easiest way to do this is to
1343	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1344	C<ev_timer_again> each time you successfully read or write some data. If
1345	you go into an idle state where you do not expect data to travel on the
1346	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1347	automatically restart it if need be.
1348
1349	That means you can ignore the C<after> value and C<ev_timer_start>
1350	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1351
1352	ev_timer_init (timer, callback, 0., 5.);
1353	ev_timer_again (loop, timer);
1354	...
1355	timer->again = 17.;
1356	ev_timer_again (loop, timer);
1357	...
1358	timer->again = 10.;
1359	ev_timer_again (loop, timer);
1360
1361	This is more slightly efficient then stopping/starting the timer each time
1362	you want to modify its timeout value.
1363
1364	Note, however, that it is often even more efficient to remember the
1365	time of the last activity and let the timer time-out naturally. In the
1366	callback, you then check whether the time-out is real, or, if there was
1367	some activity, you reschedule the watcher to time-out in "last_activity +
1368	timeout - ev_now ()" seconds.
1369		1543
1370	=item ev_tstamp repeat [read-write]	1544	=item ev_tstamp repeat [read-write]
1371		1545
1372	The current C<repeat> value. Will be used each time the watcher times out	1546	The current C<repeat> value. Will be used each time the watcher times out
1373	or C<ev_timer_again> is called, and determines the next timeout (if any),	1547	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1378	=head3 Examples	1552	=head3 Examples
1379		1553
1380	Example: Create a timer that fires after 60 seconds.	1554	Example: Create a timer that fires after 60 seconds.
1381		1555
1382	static void	1556	static void
1383	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1557	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1384	{	1558	{
1385	.. one minute over, w is actually stopped right here	1559	.. one minute over, w is actually stopped right here
1386	}	1560	}
1387		1561
1388	struct ev_timer mytimer;	1562	ev_timer mytimer;
1389	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1563	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1390	ev_timer_start (loop, &mytimer);	1564	ev_timer_start (loop, &mytimer);
1391		1565
1392	Example: Create a timeout timer that times out after 10 seconds of	1566	Example: Create a timeout timer that times out after 10 seconds of
1393	inactivity.	1567	inactivity.
1394		1568
1395	static void	1569	static void
1396	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1570	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1397	{	1571	{
1398	.. ten seconds without any activity	1572	.. ten seconds without any activity
1399	}	1573	}
1400		1574
1401	struct ev_timer mytimer;	1575	ev_timer mytimer;
1402	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1576	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1403	ev_timer_again (&mytimer); /* start timer */	1577	ev_timer_again (&mytimer); /* start timer */
1404	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1405		1579
1406	// and in some piece of code that gets executed on any "activity":	1580	// and in some piece of code that gets executed on any "activity":
…		…
1492		1666
1493	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1667	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1494	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1668	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1495	only event loop modification you are allowed to do).	1669	only event loop modification you are allowed to do).
1496		1670
1497	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1671	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1498	*w, ev_tstamp now)>, e.g.:	1672	*w, ev_tstamp now)>, e.g.:
1499		1673
		1674	static ev_tstamp
1500	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1675	my_rescheduler (ev_periodic *w, ev_tstamp now)
1501	{	1676	{
1502	return now + 60.;	1677	return now + 60.;
1503	}	1678	}
1504		1679
1505	It must return the next time to trigger, based on the passed time value	1680	It must return the next time to trigger, based on the passed time value
…		…
1542		1717
1543	The current interval value. Can be modified any time, but changes only	1718	The current interval value. Can be modified any time, but changes only
1544	take effect when the periodic timer fires or C<ev_periodic_again> is being	1719	take effect when the periodic timer fires or C<ev_periodic_again> is being
1545	called.	1720	called.
1546		1721
1547	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1722	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1548		1723
1549	The current reschedule callback, or C<0>, if this functionality is	1724	The current reschedule callback, or C<0>, if this functionality is
1550	switched off. Can be changed any time, but changes only take effect when	1725	switched off. Can be changed any time, but changes only take effect when
1551	the periodic timer fires or C<ev_periodic_again> is being called.	1726	the periodic timer fires or C<ev_periodic_again> is being called.
1552		1727
…		…
1557	Example: Call a callback every hour, or, more precisely, whenever the	1732	Example: Call a callback every hour, or, more precisely, whenever the
1558	system time is divisible by 3600. The callback invocation times have	1733	system time is divisible by 3600. The callback invocation times have
1559	potentially a lot of jitter, but good long-term stability.	1734	potentially a lot of jitter, but good long-term stability.
1560		1735
1561	static void	1736	static void
1562	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1737	clock_cb (struct ev_loop loop, ev_io w, int revents)
1563	{	1738	{
1564	... its now a full hour (UTC, or TAI or whatever your clock follows)	1739	... its now a full hour (UTC, or TAI or whatever your clock follows)
1565	}	1740	}
1566		1741
1567	struct ev_periodic hourly_tick;	1742	ev_periodic hourly_tick;
1568	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1743	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1569	ev_periodic_start (loop, &hourly_tick);	1744	ev_periodic_start (loop, &hourly_tick);
1570		1745
1571	Example: The same as above, but use a reschedule callback to do it:	1746	Example: The same as above, but use a reschedule callback to do it:
1572		1747
1573	#include <math.h>	1748	#include <math.h>
1574		1749
1575	static ev_tstamp	1750	static ev_tstamp
1576	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1751	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1577	{	1752	{
1578	return now + (3600. - fmod (now, 3600.));	1753	return now + (3600. - fmod (now, 3600.));
1579	}	1754	}
1580		1755
1581	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1756	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1582		1757
1583	Example: Call a callback every hour, starting now:	1758	Example: Call a callback every hour, starting now:
1584		1759
1585	struct ev_periodic hourly_tick;	1760	ev_periodic hourly_tick;
1586	ev_periodic_init (&hourly_tick, clock_cb,	1761	ev_periodic_init (&hourly_tick, clock_cb,
1587	fmod (ev_now (loop), 3600.), 3600., 0);	1762	fmod (ev_now (loop), 3600.), 3600., 0);
1588	ev_periodic_start (loop, &hourly_tick);	1763	ev_periodic_start (loop, &hourly_tick);
1589		1764
1590		1765
…		…
1632	=head3 Examples	1807	=head3 Examples
1633		1808
1634	Example: Try to exit cleanly on SIGINT.	1809	Example: Try to exit cleanly on SIGINT.
1635		1810
1636	static void	1811	static void
1637	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1812	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1638	{	1813	{
1639	ev_unloop (loop, EVUNLOOP_ALL);	1814	ev_unloop (loop, EVUNLOOP_ALL);
1640	}	1815	}
1641		1816
1642	struct ev_signal signal_watcher;	1817	ev_signal signal_watcher;
1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1818	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1644	ev_signal_start (loop, &signal_watcher);	1819	ev_signal_start (loop, &signal_watcher);
1645		1820
1646		1821
1647	=head2 C<ev_child> - watch out for process status changes	1822	=head2 C<ev_child> - watch out for process status changes
…		…
1722	its completion.	1897	its completion.
1723		1898
1724	ev_child cw;	1899	ev_child cw;
1725		1900
1726	static void	1901	static void
1727	child_cb (EV_P_ struct ev_child *w, int revents)	1902	child_cb (EV_P_ ev_child *w, int revents)
1728	{	1903	{
1729	ev_child_stop (EV_A_ w);	1904	ev_child_stop (EV_A_ w);
1730	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1905	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1731	}	1906	}
1732		1907
…		…
1747		1922
1748		1923
1749	=head2 C<ev_stat> - did the file attributes just change?	1924	=head2 C<ev_stat> - did the file attributes just change?
1750		1925
1751	This watches a file system path for attribute changes. That is, it calls	1926	This watches a file system path for attribute changes. That is, it calls
1752	C<stat> regularly (or when the OS says it changed) and sees if it changed	1927	C<stat> on that path in regular intervals (or when the OS says it changed)
1753	compared to the last time, invoking the callback if it did.	1928	and sees if it changed compared to the last time, invoking the callback if
		1929	it did.
1754		1930
1755	The path does not need to exist: changing from "path exists" to "path does	1931	The path does not need to exist: changing from "path exists" to "path does
1756	not exist" is a status change like any other. The condition "path does	1932	not exist" is a status change like any other. The condition "path does
1757	not exist" is signified by the C<st_nlink> field being zero (which is	1933	not exist" is signified by the C<st_nlink> field being zero (which is
1758	otherwise always forced to be at least one) and all the other fields of	1934	otherwise always forced to be at least one) and all the other fields of
1759	the stat buffer having unspecified contents.	1935	the stat buffer having unspecified contents.
1760		1936
1761	The path I<should> be absolute and I<must not> end in a slash. If it is	1937	The path I<must not> end in a slash or contain special components such as
		1938	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1762	relative and your working directory changes, the behaviour is undefined.	1939	your working directory changes, then the behaviour is undefined.
1763		1940
1764	Since there is no standard kernel interface to do this, the portable	1941	Since there is no portable change notification interface available, the
1765	implementation simply calls C<stat (2)> regularly on the path to see if	1942	portable implementation simply calls C<stat(2)> regularly on the path
1766	it changed somehow. You can specify a recommended polling interval for	1943	to see if it changed somehow. You can specify a recommended polling
1767	this case. If you specify a polling interval of C<0> (highly recommended!)	1944	interval for this case. If you specify a polling interval of C<0> (highly
1768	then a I<suitable, unspecified default> value will be used (which	1945	recommended!) then a I<suitable, unspecified default> value will be used
1769	you can expect to be around five seconds, although this might change	1946	(which you can expect to be around five seconds, although this might
1770	dynamically). Libev will also impose a minimum interval which is currently	1947	change dynamically). Libev will also impose a minimum interval which is
1771	around C<0.1>, but thats usually overkill.	1948	currently around C<0.1>, but that's usually overkill.
1772		1949
1773	This watcher type is not meant for massive numbers of stat watchers,	1950	This watcher type is not meant for massive numbers of stat watchers,
1774	as even with OS-supported change notifications, this can be	1951	as even with OS-supported change notifications, this can be
1775	resource-intensive.	1952	resource-intensive.
1776		1953
…		…
1786	support disabled by default, you get the 32 bit version of the stat	1963	support disabled by default, you get the 32 bit version of the stat
1787	structure. When using the library from programs that change the ABI to	1964	structure. When using the library from programs that change the ABI to
1788	use 64 bit file offsets the programs will fail. In that case you have to	1965	use 64 bit file offsets the programs will fail. In that case you have to
1789	compile libev with the same flags to get binary compatibility. This is	1966	compile libev with the same flags to get binary compatibility. This is
1790	obviously the case with any flags that change the ABI, but the problem is	1967	obviously the case with any flags that change the ABI, but the problem is
1791	most noticeably disabled with ev_stat and large file support.	1968	most noticeably displayed with ev_stat and large file support.
1792		1969
1793	The solution for this is to lobby your distribution maker to make large	1970	The solution for this is to lobby your distribution maker to make large
1794	file interfaces available by default (as e.g. FreeBSD does) and not	1971	file interfaces available by default (as e.g. FreeBSD does) and not
1795	optional. Libev cannot simply switch on large file support because it has	1972	optional. Libev cannot simply switch on large file support because it has
1796	to exchange stat structures with application programs compiled using the	1973	to exchange stat structures with application programs compiled using the
1797	default compilation environment.	1974	default compilation environment.
1798		1975
1799	=head3 Inotify and Kqueue	1976	=head3 Inotify and Kqueue
1800		1977
1801	When C<inotify (7)> support has been compiled into libev (generally only	1978	When C<inotify (7)> support has been compiled into libev (generally
		1979	only available with Linux 2.6.25 or above due to bugs in earlier
1802	available with Linux) and present at runtime, it will be used to speed up	1980	implementations) and present at runtime, it will be used to speed up
1803	change detection where possible. The inotify descriptor will be created lazily	1981	change detection where possible. The inotify descriptor will be created
1804	when the first C<ev_stat> watcher is being started.	1982	lazily when the first C<ev_stat> watcher is being started.
1805		1983
1806	Inotify presence does not change the semantics of C<ev_stat> watchers	1984	Inotify presence does not change the semantics of C<ev_stat> watchers
1807	except that changes might be detected earlier, and in some cases, to avoid	1985	except that changes might be detected earlier, and in some cases, to avoid
1808	making regular C<stat> calls. Even in the presence of inotify support	1986	making regular C<stat> calls. Even in the presence of inotify support
1809	there are many cases where libev has to resort to regular C<stat> polling,	1987	there are many cases where libev has to resort to regular C<stat> polling,
…		…
1814	descriptor open on the object at all times, and detecting renames, unlinks	1992	descriptor open on the object at all times, and detecting renames, unlinks
1815	etc. is difficult.	1993	etc. is difficult.
1816		1994
1817	=head3 The special problem of stat time resolution	1995	=head3 The special problem of stat time resolution
1818		1996
1819	The C<stat ()> system call only supports full-second resolution portably, and	1997	The C<stat ()> system call only supports full-second resolution portably,
1820	even on systems where the resolution is higher, most file systems still	1998	and even on systems where the resolution is higher, most file systems
1821	only support whole seconds.	1999	still only support whole seconds.
1822		2000
1823	That means that, if the time is the only thing that changes, you can	2001	That means that, if the time is the only thing that changes, you can
1824	easily miss updates: on the first update, C<ev_stat> detects a change and	2002	easily miss updates: on the first update, C<ev_stat> detects a change and
1825	calls your callback, which does something. When there is another update	2003	calls your callback, which does something. When there is another update
1826	within the same second, C<ev_stat> will be unable to detect unless the	2004	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1983		2161
1984	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2162	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1985	callback, free it. Also, use no error checking, as usual.	2163	callback, free it. Also, use no error checking, as usual.
1986		2164
1987	static void	2165	static void
1988	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2166	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1989	{	2167	{
1990	free (w);	2168	free (w);
1991	// now do something you wanted to do when the program has	2169	// now do something you wanted to do when the program has
1992	// no longer anything immediate to do.	2170	// no longer anything immediate to do.
1993	}	2171	}
1994		2172
1995	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2173	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1996	ev_idle_init (idle_watcher, idle_cb);	2174	ev_idle_init (idle_watcher, idle_cb);
1997	ev_idle_start (loop, idle_cb);	2175	ev_idle_start (loop, idle_cb);
1998		2176
1999		2177
2000	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2178	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2081		2259
2082	static ev_io iow [nfd];	2260	static ev_io iow [nfd];
2083	static ev_timer tw;	2261	static ev_timer tw;
2084		2262
2085	static void	2263	static void
2086	io_cb (ev_loop loop, ev_io w, int revents)	2264	io_cb (struct ev_loop loop, ev_io w, int revents)
2087	{	2265	{
2088	}	2266	}
2089		2267
2090	// create io watchers for each fd and a timer before blocking	2268	// create io watchers for each fd and a timer before blocking
2091	static void	2269	static void
2092	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2270	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2093	{	2271	{
2094	int timeout = 3600000;	2272	int timeout = 3600000;
2095	struct pollfd fds [nfd];	2273	struct pollfd fds [nfd];
2096	// actual code will need to loop here and realloc etc.	2274	// actual code will need to loop here and realloc etc.
2097	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2275	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2112	}	2290	}
2113	}	2291	}
2114		2292
2115	// stop all watchers after blocking	2293	// stop all watchers after blocking
2116	static void	2294	static void
2117	adns_check_cb (ev_loop loop, ev_check w, int revents)	2295	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2118	{	2296	{
2119	ev_timer_stop (loop, &tw);	2297	ev_timer_stop (loop, &tw);
2120		2298
2121	for (int i = 0; i < nfd; ++i)	2299	for (int i = 0; i < nfd; ++i)
2122	{	2300	{
…		…
2290	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2468	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2291	used).	2469	used).
2292		2470
2293	struct ev_loop *loop_hi = ev_default_init (0);	2471	struct ev_loop *loop_hi = ev_default_init (0);
2294	struct ev_loop *loop_lo = 0;	2472	struct ev_loop *loop_lo = 0;
2295	struct ev_embed embed;	2473	ev_embed embed;
2296		2474
2297	// see if there is a chance of getting one that works	2475	// see if there is a chance of getting one that works
2298	// (remember that a flags value of 0 means autodetection)	2476	// (remember that a flags value of 0 means autodetection)
2299	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2477	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2300	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2478	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2314	kqueue implementation). Store the kqueue/socket-only event loop in	2492	kqueue implementation). Store the kqueue/socket-only event loop in
2315	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2493	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2316		2494
2317	struct ev_loop *loop = ev_default_init (0);	2495	struct ev_loop *loop = ev_default_init (0);
2318	struct ev_loop *loop_socket = 0;	2496	struct ev_loop *loop_socket = 0;
2319	struct ev_embed embed;	2497	ev_embed embed;
2320		2498
2321	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2499	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2322	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2500	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2323	{	2501	{
2324	ev_embed_init (&embed, 0, loop_socket);	2502	ev_embed_init (&embed, 0, loop_socket);
…		…
2465	=over 4	2643	=over 4
2466		2644
2467	=item ev_async_init (ev_async *, callback)	2645	=item ev_async_init (ev_async *, callback)
2468		2646
2469	Initialises and configures the async watcher - it has no parameters of any	2647	Initialises and configures the async watcher - it has no parameters of any
2470	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2648	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2471	trust me.	2649	trust me.
2472		2650
2473	=item ev_async_send (loop, ev_async *)	2651	=item ev_async_send (loop, ev_async *)
2474		2652
2475	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2653	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
…		…
2538	/* doh, nothing entered */;	2716	/* doh, nothing entered */;
2539	}	2717	}
2540		2718
2541	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2719	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2542		2720
2543	=item ev_feed_event (ev_loop , watcher , int revents)	2721	=item ev_feed_event (struct ev_loop , watcher , int revents)
2544		2722
2545	Feeds the given event set into the event loop, as if the specified event	2723	Feeds the given event set into the event loop, as if the specified event
2546	had happened for the specified watcher (which must be a pointer to an	2724	had happened for the specified watcher (which must be a pointer to an
2547	initialised but not necessarily started event watcher).	2725	initialised but not necessarily started event watcher).
2548		2726
2549	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2727	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2550		2728
2551	Feed an event on the given fd, as if a file descriptor backend detected	2729	Feed an event on the given fd, as if a file descriptor backend detected
2552	the given events it.	2730	the given events it.
2553		2731
2554	=item ev_feed_signal_event (ev_loop *loop, int signum)	2732	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2555		2733
2556	Feed an event as if the given signal occurred (C<loop> must be the default	2734	Feed an event as if the given signal occurred (C<loop> must be the default
2557	loop!).	2735	loop!).
2558		2736
2559	=back	2737	=back
…		…
2794	=item D	2972	=item D
2795		2973
2796	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2974	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2797	be found at L<http://proj.llucax.com.ar/wiki/evd>.	2975	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2798		2976
		2977	=item Ocaml
		2978
		2979	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2980	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2981
2799	=back	2982	=back
2800		2983
2801		2984
2802	=head1 MACRO MAGIC	2985	=head1 MACRO MAGIC
2803		2986
…		…
2903		3086
2904	#define EV_STANDALONE 1	3087	#define EV_STANDALONE 1
2905	#include "ev.h"	3088	#include "ev.h"
2906		3089
2907	Both header files and implementation files can be compiled with a C++	3090	Both header files and implementation files can be compiled with a C++
2908	compiler (at least, thats a stated goal, and breakage will be treated	3091	compiler (at least, that's a stated goal, and breakage will be treated
2909	as a bug).	3092	as a bug).
2910		3093
2911	You need the following files in your source tree, or in a directory	3094	You need the following files in your source tree, or in a directory
2912	in your include path (e.g. in libev/ when using -Ilibev):	3095	in your include path (e.g. in libev/ when using -Ilibev):
2913		3096
…		…
3385	loop, as long as you don't confuse yourself). The only exception is that	3568	loop, as long as you don't confuse yourself). The only exception is that
3386	you must not do this from C<ev_periodic> reschedule callbacks.	3569	you must not do this from C<ev_periodic> reschedule callbacks.
3387		3570
3388	Care has been taken to ensure that libev does not keep local state inside	3571	Care has been taken to ensure that libev does not keep local state inside
3389	C<ev_loop>, and other calls do not usually allow for coroutine switches as	3572	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3390	they do not clal any callbacks.	3573	they do not call any callbacks.
3391		3574
3392	=head2 COMPILER WARNINGS	3575	=head2 COMPILER WARNINGS
3393		3576
3394	Depending on your compiler and compiler settings, you might get no or a	3577	Depending on your compiler and compiler settings, you might get no or a
3395	lot of warnings when compiling libev code. Some people are apparently	3578	lot of warnings when compiling libev code. Some people are apparently
…		…
3429	==2274== definitely lost: 0 bytes in 0 blocks.	3612	==2274== definitely lost: 0 bytes in 0 blocks.
3430	==2274== possibly lost: 0 bytes in 0 blocks.	3613	==2274== possibly lost: 0 bytes in 0 blocks.
3431	==2274== still reachable: 256 bytes in 1 blocks.	3614	==2274== still reachable: 256 bytes in 1 blocks.
3432		3615
3433	Then there is no memory leak, just as memory accounted to global variables	3616	Then there is no memory leak, just as memory accounted to global variables
3434	is not a memleak - the memory is still being refernced, and didn't leak.	3617	is not a memleak - the memory is still being referenced, and didn't leak.
3435		3618
3436	Similarly, under some circumstances, valgrind might report kernel bugs	3619	Similarly, under some circumstances, valgrind might report kernel bugs
3437	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3620	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3438	although an acceptable workaround has been found here), or it might be	3621	although an acceptable workaround has been found here), or it might be
3439	confused.	3622	confused.
…		…
3677	=back	3860	=back
3678		3861
3679		3862
3680	=head1 AUTHOR	3863	=head1 AUTHOR
3681		3864
3682	Marc Lehmann <libev@schmorp.de>.	3865	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3683		3866

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Comparing libev/ev.pod (file contents): Revision 1.195 by root, Mon Oct 20 17:50:48 2008 UTC vs. Revision 1.209 by root, Wed Oct 29 14:12:34 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.195 by root, Mon Oct 20 17:50:48 2008 UTC vs.
Revision 1.209 by root, Wed Oct 29 14:12:34 2008 UTC