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

Comparing libev/ev.pod (file contents):
Revision 1.53 by root, Tue Nov 27 20:15:02 2007 UTC vs.
Revision 1.70 by root, Fri Dec 7 19:23:48 2007 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	/* this is the only header you need */
8	#include <ev.h>	7	#include <ev.h>
9		8
10	/* what follows is a fully working example program */	9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
11	ev_io stdin_watcher;	13	ev_io stdin_watcher;
12	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
13		15
14	/* called when data readable on stdin */	16	/* called when data readable on stdin */
15	static void	17	static void
…		…
46	return 0;	48	return 0;
47	}	49	}
48		50
49	=head1 DESCRIPTION	51	=head1 DESCRIPTION
50		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
51	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
52	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
53	these event sources and provide your program with events.	59	these event sources and provide your program with events.
54		60
55	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
…		…
61	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
62	watcher.	68	watcher.
63		69
64	=head1 FEATURES	70	=head1 FEATURES
65		71
66	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
67	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
68	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
69	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
70	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
71	fast (see this L<benchmark\|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
72	it to libevent for example).	85	for example).
73		86
74	=head1 CONVENTIONS	87	=head1 CONVENTIONS
75		88
76	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
77	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
78	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
79	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
80	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
81	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
82	will not have this argument.
83		95
84	=head1 TIME REPRESENTATION	96	=head1 TIME REPRESENTATION
85		97
86	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
87	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
…		…
116	Usually, it's a good idea to terminate if the major versions mismatch,	128	Usually, it's a good idea to terminate if the major versions mismatch,
117	as this indicates an incompatible change. Minor versions are usually	129	as this indicates an incompatible change. Minor versions are usually
118	compatible to older versions, so a larger minor version alone is usually	130	compatible to older versions, so a larger minor version alone is usually
119	not a problem.	131	not a problem.
120		132
121	Example: make sure we haven't accidentally been linked against the wrong	133	Example: Make sure we haven't accidentally been linked against the wrong
122	version:	134	version.
123		135
124	assert (("libev version mismatch",	136	assert (("libev version mismatch",
125	ev_version_major () == EV_VERSION_MAJOR	137	ev_version_major () == EV_VERSION_MAJOR
126	&& ev_version_minor () >= EV_VERSION_MINOR));	138	&& ev_version_minor () >= EV_VERSION_MINOR));
127		139
…		…
155	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	167	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
156	recommended ones.	168	recommended ones.
157		169
158	See the description of C<ev_embed> watchers for more info.	170	See the description of C<ev_embed> watchers for more info.
159		171
160	=item ev_set_allocator (void (cb)(void *ptr, size_t size))	172	=item ev_set_allocator (void (cb)(void *ptr, long size))
161		173
162	Sets the allocation function to use (the prototype and semantics are	174	Sets the allocation function to use (the prototype is similar - the
163	identical to the realloc C function). It is used to allocate and free	175	semantics is identical - to the realloc C function). It is used to
164	memory (no surprises here). If it returns zero when memory needs to be	176	allocate and free memory (no surprises here). If it returns zero when
165	allocated, the library might abort or take some potentially destructive	177	memory needs to be allocated, the library might abort or take some
166	action. The default is your system realloc function.	178	potentially destructive action. The default is your system realloc
		179	function.
167		180
168	You could override this function in high-availability programs to, say,	181	You could override this function in high-availability programs to, say,
169	free some memory if it cannot allocate memory, to use a special allocator,	182	free some memory if it cannot allocate memory, to use a special allocator,
170	or even to sleep a while and retry until some memory is available.	183	or even to sleep a while and retry until some memory is available.
171		184
172	Example: replace the libev allocator with one that waits a bit and then	185	Example: Replace the libev allocator with one that waits a bit and then
173	retries: better than mine).	186	retries).
174		187
175	static void *	188	static void *
176	persistent_realloc (void *ptr, size_t size)	189	persistent_realloc (void *ptr, size_t size)
177	{	190	{
178	for (;;)	191	for (;;)
…		…
197	callback is set, then libev will expect it to remedy the sitution, no	210	callback is set, then libev will expect it to remedy the sitution, no
198	matter what, when it returns. That is, libev will generally retry the	211	matter what, when it returns. That is, libev will generally retry the
199	requested operation, or, if the condition doesn't go away, do bad stuff	212	requested operation, or, if the condition doesn't go away, do bad stuff
200	(such as abort).	213	(such as abort).
201		214
202	Example: do the same thing as libev does internally:	215	Example: This is basically the same thing that libev does internally, too.
203		216
204	static void	217	static void
205	fatal_error (const char *msg)	218	fatal_error (const char *msg)
206	{	219	{
207	perror (msg);	220	perror (msg);
…		…
257	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
258	override the flags completely if it is found in the environment. This is	271	override the flags completely if it is found in the environment. This is
259	useful to try out specific backends to test their performance, or to work	272	useful to try out specific backends to test their performance, or to work
260	around bugs.	273	around bugs.
261		274
		275	=item C<EVFLAG_FORKCHECK>
		276
		277	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		278	a fork, you can also make libev check for a fork in each iteration by
		279	enabling this flag.
		280
		281	This works by calling C<getpid ()> on every iteration of the loop,
		282	and thus this might slow down your event loop if you do a lot of loop
		283	iterations and little real work, but is usually not noticeable (on my
		284	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		285	without a syscall and thus I<very> fast, but my Linux system also has
		286	C<pthread_atfork> which is even faster).
		287
		288	The big advantage of this flag is that you can forget about fork (and
		289	forget about forgetting to tell libev about forking) when you use this
		290	flag.
		291
		292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		293	environment variable.
		294
262	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
263		296
264	This is your standard select(2) backend. Not I<completely> standard, as	297	This is your standard select(2) backend. Not I<completely> standard, as
265	libev tries to roll its own fd_set with no limits on the number of fds,	298	libev tries to roll its own fd_set with no limits on the number of fds,
266	but if that fails, expect a fairly low limit on the number of fds when	299	but if that fails, expect a fairly low limit on the number of fds when
…		…
353	Similar to C<ev_default_loop>, but always creates a new event loop that is	386	Similar to C<ev_default_loop>, but always creates a new event loop that is
354	always distinct from the default loop. Unlike the default loop, it cannot	387	always distinct from the default loop. Unlike the default loop, it cannot
355	handle signal and child watchers, and attempts to do so will be greeted by	388	handle signal and child watchers, and attempts to do so will be greeted by
356	undefined behaviour (or a failed assertion if assertions are enabled).	389	undefined behaviour (or a failed assertion if assertions are enabled).
357		390
358	Example: try to create a event loop that uses epoll and nothing else.	391	Example: Try to create a event loop that uses epoll and nothing else.
359		392
360	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
361	if (!epoller)	394	if (!epoller)
362	fatal ("no epoll found here, maybe it hides under your chair");	395	fatal ("no epoll found here, maybe it hides under your chair");
363		396
…		…
400	=item ev_loop_fork (loop)	433	=item ev_loop_fork (loop)
401		434
402	Like C<ev_default_fork>, but acts on an event loop created by	435	Like C<ev_default_fork>, but acts on an event loop created by
403	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
404	after fork, and how you do this is entirely your own problem.	437	after fork, and how you do this is entirely your own problem.
		438
		439	=item unsigned int ev_loop_count (loop)
		440
		441	Returns the count of loop iterations for the loop, which is identical to
		442	the number of times libev did poll for new events. It starts at C<0> and
		443	happily wraps around with enough iterations.
		444
		445	This value can sometimes be useful as a generation counter of sorts (it
		446	"ticks" the number of loop iterations), as it roughly corresponds with
		447	C<ev_prepare> and C<ev_check> calls.
405		448
406	=item unsigned int ev_backend (loop)	449	=item unsigned int ev_backend (loop)
407		450
408	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	451	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
409	use.	452	use.
…		…
462	Signals and child watchers are implemented as I/O watchers, and will	505	Signals and child watchers are implemented as I/O watchers, and will
463	be handled here by queueing them when their watcher gets executed.	506	be handled here by queueing them when their watcher gets executed.
464	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
465	were used, return, otherwise continue with step *.	508	were used, return, otherwise continue with step *.
466		509
467	Example: queue some jobs and then loop until no events are outsanding	510	Example: Queue some jobs and then loop until no events are outsanding
468	anymore.	511	anymore.
469		512
470	... queue jobs here, make sure they register event watchers as long	513	... queue jobs here, make sure they register event watchers as long
471	... as they still have work to do (even an idle watcher will do..)	514	... as they still have work to do (even an idle watcher will do..)
472	ev_loop (my_loop, 0);	515	ev_loop (my_loop, 0);
…		…
492	visible to the libev user and should not keep C<ev_loop> from exiting if	535	visible to the libev user and should not keep C<ev_loop> from exiting if
493	no event watchers registered by it are active. It is also an excellent	536	no event watchers registered by it are active. It is also an excellent
494	way to do this for generic recurring timers or from within third-party	537	way to do this for generic recurring timers or from within third-party
495	libraries. Just remember to I<unref after start> and I<ref before stop>.	538	libraries. Just remember to I<unref after start> and I<ref before stop>.
496		539
497	Example: create a signal watcher, but keep it from keeping C<ev_loop>	540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
498	running when nothing else is active.	541	running when nothing else is active.
499		542
500	struct dv_signal exitsig;	543	struct ev_signal exitsig;
501	ev_signal_init (&exitsig, sig_cb, SIGINT);	544	ev_signal_init (&exitsig, sig_cb, SIGINT);
502	ev_signal_start (myloop, &exitsig);	545	ev_signal_start (loop, &exitsig);
503	evf_unref (myloop);	546	evf_unref (loop);
504		547
505	Example: for some weird reason, unregister the above signal handler again.	548	Example: For some weird reason, unregister the above signal handler again.
506		549
507	ev_ref (myloop);	550	ev_ref (loop);
508	ev_signal_stop (myloop, &exitsig);	551	ev_signal_stop (loop, &exitsig);
509		552
510	=back	553	=back
511		554
512		555
513	=head1 ANATOMY OF A WATCHER	556	=head1 ANATOMY OF A WATCHER
…		…
696	events but its callback has not yet been invoked). As long as a watcher	739	events but its callback has not yet been invoked). As long as a watcher
697	is pending (but not active) you must not call an init function on it (but	740	is pending (but not active) you must not call an init function on it (but
698	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	741	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
699	libev (e.g. you cnanot C<free ()> it).	742	libev (e.g. you cnanot C<free ()> it).
700		743
701	=item callback = ev_cb (ev_TYPE *watcher)	744	=item callback ev_cb (ev_TYPE *watcher)
702		745
703	Returns the callback currently set on the watcher.	746	Returns the callback currently set on the watcher.
704		747
705	=item ev_cb_set (ev_TYPE *watcher, callback)	748	=item ev_cb_set (ev_TYPE *watcher, callback)
706		749
707	Change the callback. You can change the callback at virtually any time	750	Change the callback. You can change the callback at virtually any time
708	(modulo threads).	751	(modulo threads).
		752
		753	=item ev_set_priority (ev_TYPE *watcher, priority)
		754
		755	=item int ev_priority (ev_TYPE *watcher)
		756
		757	Set and query the priority of the watcher. The priority is a small
		758	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		759	(default: C<-2>). Pending watchers with higher priority will be invoked
		760	before watchers with lower priority, but priority will not keep watchers
		761	from being executed (except for C<ev_idle> watchers).
		762
		763	This means that priorities are I<only> used for ordering callback
		764	invocation after new events have been received. This is useful, for
		765	example, to reduce latency after idling, or more often, to bind two
		766	watchers on the same event and make sure one is called first.
		767
		768	If you need to suppress invocation when higher priority events are pending
		769	you need to look at C<ev_idle> watchers, which provide this functionality.
		770
		771	The default priority used by watchers when no priority has been set is
		772	always C<0>, which is supposed to not be too high and not be too low :).
		773
		774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		775	fine, as long as you do not mind that the priority value you query might
		776	or might not have been adjusted to be within valid range.
709		777
710	=back	778	=back
711		779
712		780
713	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
734	{	802	{
735	struct my_io w = (struct my_io )w_;	803	struct my_io w = (struct my_io )w_;
736	...	804	...
737	}	805	}
738		806
739	More interesting and less C-conformant ways of catsing your callback type	807	More interesting and less C-conformant ways of casting your callback type
740	have been omitted....	808	instead have been omitted.
		809
		810	Another common scenario is having some data structure with multiple
		811	watchers:
		812
		813	struct my_biggy
		814	{
		815	int some_data;
		816	ev_timer t1;
		817	ev_timer t2;
		818	}
		819
		820	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		821	you need to use C<offsetof>:
		822
		823	#include <stddef.h>
		824
		825	static void
		826	t1_cb (EV_P_ struct ev_timer *w, int revents)
		827	{
		828	struct my_biggy big = (struct my_biggy *
		829	(((char *)w) - offsetof (struct my_biggy, t1));
		830	}
		831
		832	static void
		833	t2_cb (EV_P_ struct ev_timer *w, int revents)
		834	{
		835	struct my_biggy big = (struct my_biggy *
		836	(((char *)w) - offsetof (struct my_biggy, t2));
		837	}
741		838
742		839
743	=head1 WATCHER TYPES	840	=head1 WATCHER TYPES
744		841
745	This section describes each watcher in detail, but will not repeat	842	This section describes each watcher in detail, but will not repeat
…		…
790	it is best to always use non-blocking I/O: An extra C<read>(2) returning	887	it is best to always use non-blocking I/O: An extra C<read>(2) returning
791	C<EAGAIN> is far preferable to a program hanging until some data arrives.	888	C<EAGAIN> is far preferable to a program hanging until some data arrives.
792		889
793	If you cannot run the fd in non-blocking mode (for example you should not	890	If you cannot run the fd in non-blocking mode (for example you should not
794	play around with an Xlib connection), then you have to seperately re-test	891	play around with an Xlib connection), then you have to seperately re-test
795	wether a file descriptor is really ready with a known-to-be good interface	892	whether a file descriptor is really ready with a known-to-be good interface
796	such as poll (fortunately in our Xlib example, Xlib already does this on	893	such as poll (fortunately in our Xlib example, Xlib already does this on
797	its own, so its quite safe to use).	894	its own, so its quite safe to use).
798		895
799	=over 4	896	=over 4
800		897
…		…
814		911
815	The events being watched.	912	The events being watched.
816		913
817	=back	914	=back
818		915
819	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	916	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
820	readable, but only once. Since it is likely line-buffered, you could	917	readable, but only once. Since it is likely line-buffered, you could
821	attempt to read a whole line in the callback:	918	attempt to read a whole line in the callback.
822		919
823	static void	920	static void
824	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	921	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
825	{	922	{
826	ev_io_stop (loop, w);	923	ev_io_stop (loop, w);
…		…
878	=item ev_timer_again (loop)	975	=item ev_timer_again (loop)
879		976
880	This will act as if the timer timed out and restart it again if it is	977	This will act as if the timer timed out and restart it again if it is
881	repeating. The exact semantics are:	978	repeating. The exact semantics are:
882		979
		980	If the timer is pending, its pending status is cleared.
		981
883	If the timer is started but nonrepeating, stop it.	982	If the timer is started but nonrepeating, stop it (as if it timed out).
884		983
885	If the timer is repeating, either start it if necessary (with the repeat	984	If the timer is repeating, either start it if necessary (with the
886	value), or reset the running timer to the repeat value.	985	C<repeat> value), or reset the running timer to the C<repeat> value.
887		986
888	This sounds a bit complicated, but here is a useful and typical	987	This sounds a bit complicated, but here is a useful and typical
889	example: Imagine you have a tcp connection and you want a so-called	988	example: Imagine you have a tcp connection and you want a so-called idle
890	idle timeout, that is, you want to be called when there have been,	989	timeout, that is, you want to be called when there have been, say, 60
891	say, 60 seconds of inactivity on the socket. The easiest way to do	990	seconds of inactivity on the socket. The easiest way to do this is to
892	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	991	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
893	C<ev_timer_again> each time you successfully read or write some data. If	992	C<ev_timer_again> each time you successfully read or write some data. If
894	you go into an idle state where you do not expect data to travel on the	993	you go into an idle state where you do not expect data to travel on the
895	socket, you can stop the timer, and again will automatically restart it if	994	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
896	need be.	995	automatically restart it if need be.
897		996
898	You can also ignore the C<after> value and C<ev_timer_start> altogether	997	That means you can ignore the C<after> value and C<ev_timer_start>
899	and only ever use the C<repeat> value:	998	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
900		999
901	ev_timer_init (timer, callback, 0., 5.);	1000	ev_timer_init (timer, callback, 0., 5.);
902	ev_timer_again (loop, timer);	1001	ev_timer_again (loop, timer);
903	...	1002	...
904	timer->again = 17.;	1003	timer->again = 17.;
905	ev_timer_again (loop, timer);	1004	ev_timer_again (loop, timer);
906	...	1005	...
907	timer->again = 10.;	1006	timer->again = 10.;
908	ev_timer_again (loop, timer);	1007	ev_timer_again (loop, timer);
909		1008
910	This is more efficient then stopping/starting the timer eahc time you want	1009	This is more slightly efficient then stopping/starting the timer each time
911	to modify its timeout value.	1010	you want to modify its timeout value.
912		1011
913	=item ev_tstamp repeat [read-write]	1012	=item ev_tstamp repeat [read-write]
914		1013
915	The current C<repeat> value. Will be used each time the watcher times out	1014	The current C<repeat> value. Will be used each time the watcher times out
916	or C<ev_timer_again> is called and determines the next timeout (if any),	1015	or C<ev_timer_again> is called and determines the next timeout (if any),
917	which is also when any modifications are taken into account.	1016	which is also when any modifications are taken into account.
918		1017
919	=back	1018	=back
920		1019
921	Example: create a timer that fires after 60 seconds.	1020	Example: Create a timer that fires after 60 seconds.
922		1021
923	static void	1022	static void
924	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1023	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
925	{	1024	{
926	.. one minute over, w is actually stopped right here	1025	.. one minute over, w is actually stopped right here
…		…
928		1027
929	struct ev_timer mytimer;	1028	struct ev_timer mytimer;
930	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1029	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
931	ev_timer_start (loop, &mytimer);	1030	ev_timer_start (loop, &mytimer);
932		1031
933	Example: create a timeout timer that times out after 10 seconds of	1032	Example: Create a timeout timer that times out after 10 seconds of
934	inactivity.	1033	inactivity.
935		1034
936	static void	1035	static void
937	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1036	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
938	{	1037	{
…		…
1063	switched off. Can be changed any time, but changes only take effect when	1162	switched off. Can be changed any time, but changes only take effect when
1064	the periodic timer fires or C<ev_periodic_again> is being called.	1163	the periodic timer fires or C<ev_periodic_again> is being called.
1065		1164
1066	=back	1165	=back
1067		1166
1068	Example: call a callback every hour, or, more precisely, whenever the	1167	Example: Call a callback every hour, or, more precisely, whenever the
1069	system clock is divisible by 3600. The callback invocation times have	1168	system clock is divisible by 3600. The callback invocation times have
1070	potentially a lot of jittering, but good long-term stability.	1169	potentially a lot of jittering, but good long-term stability.
1071		1170
1072	static void	1171	static void
1073	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1172	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
…		…
1077		1176
1078	struct ev_periodic hourly_tick;	1177	struct ev_periodic hourly_tick;
1079	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1178	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1080	ev_periodic_start (loop, &hourly_tick);	1179	ev_periodic_start (loop, &hourly_tick);
1081		1180
1082	Example: the same as above, but use a reschedule callback to do it:	1181	Example: The same as above, but use a reschedule callback to do it:
1083		1182
1084	#include <math.h>	1183	#include <math.h>
1085		1184
1086	static ev_tstamp	1185	static ev_tstamp
1087	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1186	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
1089	return fmod (now, 3600.) + 3600.;	1188	return fmod (now, 3600.) + 3600.;
1090	}	1189	}
1091		1190
1092	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1191	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1093		1192
1094	Example: call a callback every hour, starting now:	1193	Example: Call a callback every hour, starting now:
1095		1194
1096	struct ev_periodic hourly_tick;	1195	struct ev_periodic hourly_tick;
1097	ev_periodic_init (&hourly_tick, clock_cb,	1196	ev_periodic_init (&hourly_tick, clock_cb,
1098	fmod (ev_now (loop), 3600.), 3600., 0);	1197	fmod (ev_now (loop), 3600.), 3600., 0);
1099	ev_periodic_start (loop, &hourly_tick);	1198	ev_periodic_start (loop, &hourly_tick);
…		…
1160	The process exit/trace status caused by C<rpid> (see your systems	1259	The process exit/trace status caused by C<rpid> (see your systems
1161	C<waitpid> and C<sys/wait.h> documentation for details).	1260	C<waitpid> and C<sys/wait.h> documentation for details).
1162		1261
1163	=back	1262	=back
1164		1263
1165	Example: try to exit cleanly on SIGINT and SIGTERM.	1264	Example: Try to exit cleanly on SIGINT and SIGTERM.
1166		1265
1167	static void	1266	static void
1168	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1267	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1169	{	1268	{
1170	ev_unloop (loop, EVUNLOOP_ALL);	1269	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1185	not exist" is a status change like any other. The condition "path does	1284	not exist" is a status change like any other. The condition "path does
1186	not exist" is signified by the C<st_nlink> field being zero (which is	1285	not exist" is signified by the C<st_nlink> field being zero (which is
1187	otherwise always forced to be at least one) and all the other fields of	1286	otherwise always forced to be at least one) and all the other fields of
1188	the stat buffer having unspecified contents.	1287	the stat buffer having unspecified contents.
1189		1288
		1289	The path I<should> be absolute and I<must not> end in a slash. If it is
		1290	relative and your working directory changes, the behaviour is undefined.
		1291
1190	Since there is no standard to do this, the portable implementation simply	1292	Since there is no standard to do this, the portable implementation simply
1191	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1293	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1192	can specify a recommended polling interval for this case. If you specify	1294	can specify a recommended polling interval for this case. If you specify
1193	a polling interval of C<0> (highly recommended!) then a I<suitable,	1295	a polling interval of C<0> (highly recommended!) then a I<suitable,
1194	unspecified default> value will be used (which you can expect to be around	1296	unspecified default> value will be used (which you can expect to be around
1195	five seconds, although this might change dynamically). Libev will also	1297	five seconds, although this might change dynamically). Libev will also
1196	impose a minimum interval which is currently around C<0.1>, but thats	1298	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1198		1300
1199	This watcher type is not meant for massive numbers of stat watchers,	1301	This watcher type is not meant for massive numbers of stat watchers,
1200	as even with OS-supported change notifications, this can be	1302	as even with OS-supported change notifications, this can be
1201	resource-intensive.	1303	resource-intensive.
1202		1304
1203	At the time of this writing, no specific OS backends are implemented, but	1305	At the time of this writing, only the Linux inotify interface is
1204	if demand increases, at least a kqueue and inotify backend will be added.	1306	implemented (implementing kqueue support is left as an exercise for the
		1307	reader). Inotify will be used to give hints only and should not change the
		1308	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1309	to fall back to regular polling again even with inotify, but changes are
		1310	usually detected immediately, and if the file exists there will be no
		1311	polling.
1205		1312
1206	=over 4	1313	=over 4
1207		1314
1208	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1315	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1209		1316
…		…
1273	ev_stat_start (loop, &passwd);	1380	ev_stat_start (loop, &passwd);
1274		1381
1275		1382
1276	=head2 C<ev_idle> - when you've got nothing better to do...	1383	=head2 C<ev_idle> - when you've got nothing better to do...
1277		1384
1278	Idle watchers trigger events when there are no other events are pending	1385	Idle watchers trigger events when no other events of the same or higher
1279	(prepare, check and other idle watchers do not count). That is, as long	1386	priority are pending (prepare, check and other idle watchers do not
1280	as your process is busy handling sockets or timeouts (or even signals,	1387	count).
1281	imagine) it will not be triggered. But when your process is idle all idle	1388
1282	watchers are being called again and again, once per event loop iteration -	1389	That is, as long as your process is busy handling sockets or timeouts
		1390	(or even signals, imagine) of the same or higher priority it will not be
		1391	triggered. But when your process is idle (or only lower-priority watchers
		1392	are pending), the idle watchers are being called once per event loop
1283	until stopped, that is, or your process receives more events and becomes	1393	iteration - until stopped, that is, or your process receives more events
1284	busy.	1394	and becomes busy again with higher priority stuff.
1285		1395
1286	The most noteworthy effect is that as long as any idle watchers are	1396	The most noteworthy effect is that as long as any idle watchers are
1287	active, the process will not block when waiting for new events.	1397	active, the process will not block when waiting for new events.
1288		1398
1289	Apart from keeping your process non-blocking (which is a useful	1399	Apart from keeping your process non-blocking (which is a useful
…		…
1299	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1409	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1300	believe me.	1410	believe me.
1301		1411
1302	=back	1412	=back
1303		1413
1304	Example: dynamically allocate an C<ev_idle>, start it, and in the	1414	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1305	callback, free it. Alos, use no error checking, as usual.	1415	callback, free it. Also, use no error checking, as usual.
1306		1416
1307	static void	1417	static void
1308	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1418	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1309	{	1419	{
1310	free (w);	1420	free (w);
…		…
1389		1499
1390	// create io watchers for each fd and a timer before blocking	1500	// create io watchers for each fd and a timer before blocking
1391	static void	1501	static void
1392	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1502	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1393	{	1503	{
1394	int timeout = 3600000;truct pollfd fds [nfd];	1504	int timeout = 3600000;
		1505	struct pollfd fds [nfd];
1395	// actual code will need to loop here and realloc etc.	1506	// actual code will need to loop here and realloc etc.
1396	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1507	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1397		1508
1398	/* the callback is illegal, but won't be called as we stop during check */	1509	/* the callback is illegal, but won't be called as we stop during check */
1399	ev_timer_init (&tw, 0, timeout * 1e-3);	1510	ev_timer_init (&tw, 0, timeout * 1e-3);
…		…
1737		1848
1738		1849
1739	=head1 MACRO MAGIC	1850	=head1 MACRO MAGIC
1740		1851
1741	Libev can be compiled with a variety of options, the most fundemantal is	1852	Libev can be compiled with a variety of options, the most fundemantal is
1742	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	1853	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1743	callbacks have an initial C<struct ev_loop *> argument.	1854	callbacks have an initial C<struct ev_loop *> argument.
1744		1855
1745	To make it easier to write programs that cope with either variant, the	1856	To make it easier to write programs that cope with either variant, the
1746	following macros are defined:	1857	following macros are defined:
1747		1858
…		…
1780	Similar to the other two macros, this gives you the value of the default	1891	Similar to the other two macros, this gives you the value of the default
1781	loop, if multiple loops are supported ("ev loop default").	1892	loop, if multiple loops are supported ("ev loop default").
1782		1893
1783	=back	1894	=back
1784		1895
1785	Example: Declare and initialise a check watcher, working regardless of	1896	Example: Declare and initialise a check watcher, utilising the above
1786	wether multiple loops are supported or not.	1897	macros so it will work regardless of whether multiple loops are supported
		1898	or not.
1787		1899
1788	static void	1900	static void
1789	check_cb (EV_P_ ev_timer *w, int revents)	1901	check_cb (EV_P_ ev_timer *w, int revents)
1790	{	1902	{
1791	ev_check_stop (EV_A_ w);	1903	ev_check_stop (EV_A_ w);
…		…
1794	ev_check check;	1906	ev_check check;
1795	ev_check_init (&check, check_cb);	1907	ev_check_init (&check, check_cb);
1796	ev_check_start (EV_DEFAULT_ &check);	1908	ev_check_start (EV_DEFAULT_ &check);
1797	ev_loop (EV_DEFAULT_ 0);	1909	ev_loop (EV_DEFAULT_ 0);
1798		1910
1799
1800	=head1 EMBEDDING	1911	=head1 EMBEDDING
1801		1912
1802	Libev can (and often is) directly embedded into host	1913	Libev can (and often is) directly embedded into host
1803	applications. Examples of applications that embed it include the Deliantra	1914	applications. Examples of applications that embed it include the Deliantra
1804	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	1915	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
…		…
1843	ev_vars.h	1954	ev_vars.h
1844	ev_wrap.h	1955	ev_wrap.h
1845		1956
1846	ev_win32.c required on win32 platforms only	1957	ev_win32.c required on win32 platforms only
1847		1958
1848	ev_select.c only when select backend is enabled (which is by default)	1959	ev_select.c only when select backend is enabled (which is enabled by default)
1849	ev_poll.c only when poll backend is enabled (disabled by default)	1960	ev_poll.c only when poll backend is enabled (disabled by default)
1850	ev_epoll.c only when the epoll backend is enabled (disabled by default)	1961	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1851	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	1962	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1852	ev_port.c only when the solaris port backend is enabled (disabled by default)	1963	ev_port.c only when the solaris port backend is enabled (disabled by default)
1853		1964
…		…
1978		2089
1979	=item EV_USE_DEVPOLL	2090	=item EV_USE_DEVPOLL
1980		2091
1981	reserved for future expansion, works like the USE symbols above.	2092	reserved for future expansion, works like the USE symbols above.
1982		2093
		2094	=item EV_USE_INOTIFY
		2095
		2096	If defined to be C<1>, libev will compile in support for the Linux inotify
		2097	interface to speed up C<ev_stat> watchers. Its actual availability will
		2098	be detected at runtime.
		2099
1983	=item EV_H	2100	=item EV_H
1984		2101
1985	The name of the F<ev.h> header file used to include it. The default if	2102	The name of the F<ev.h> header file used to include it. The default if
1986	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2103	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
1987	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2104	can be used to virtually rename the F<ev.h> header file in case of conflicts.
…		…
2010	will have the C<struct ev_loop *> as first argument, and you can create	2127	will have the C<struct ev_loop *> as first argument, and you can create
2011	additional independent event loops. Otherwise there will be no support	2128	additional independent event loops. Otherwise there will be no support
2012	for multiple event loops and there is no first event loop pointer	2129	for multiple event loops and there is no first event loop pointer
2013	argument. Instead, all functions act on the single default loop.	2130	argument. Instead, all functions act on the single default loop.
2014		2131
		2132	=item EV_MINPRI
		2133
		2134	=item EV_MAXPRI
		2135
		2136	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2137	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2138	provide for more priorities by overriding those symbols (usually defined
		2139	to be C<-2> and C<2>, respectively).
		2140
		2141	When doing priority-based operations, libev usually has to linearly search
		2142	all the priorities, so having many of them (hundreds) uses a lot of space
		2143	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2144	fine.
		2145
		2146	If your embedding app does not need any priorities, defining these both to
		2147	C<0> will save some memory and cpu.
		2148
2015	=item EV_PERIODIC_ENABLE	2149	=item EV_PERIODIC_ENABLE
2016		2150
2017	If undefined or defined to be C<1>, then periodic timers are supported. If	2151	If undefined or defined to be C<1>, then periodic timers are supported. If
2018	defined to be C<0>, then they are not. Disabling them saves a few kB of	2152	defined to be C<0>, then they are not. Disabling them saves a few kB of
2019	code.	2153	code.
2020		2154
		2155	=item EV_IDLE_ENABLE
		2156
		2157	If undefined or defined to be C<1>, then idle watchers are supported. If
		2158	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2159	code.
		2160
2021	=item EV_EMBED_ENABLE	2161	=item EV_EMBED_ENABLE
2022		2162
2023	If undefined or defined to be C<1>, then embed watchers are supported. If	2163	If undefined or defined to be C<1>, then embed watchers are supported. If
2024	defined to be C<0>, then they are not.	2164	defined to be C<0>, then they are not.
2025		2165
…		…
2042	=item EV_PID_HASHSIZE	2182	=item EV_PID_HASHSIZE
2043		2183
2044	C<ev_child> watchers use a small hash table to distribute workload by	2184	C<ev_child> watchers use a small hash table to distribute workload by
2045	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	2185	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2046	than enough. If you need to manage thousands of children you might want to	2186	than enough. If you need to manage thousands of children you might want to
2047	increase this value.	2187	increase this value (I<must> be a power of two).
		2188
		2189	=item EV_INOTIFY_HASHSIZE
		2190
		2191	C<ev_staz> watchers use a small hash table to distribute workload by
		2192	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2193	usually more than enough. If you need to manage thousands of C<ev_stat>
		2194	watchers you might want to increase this value (I<must> be a power of
		2195	two).
2048		2196
2049	=item EV_COMMON	2197	=item EV_COMMON
2050		2198
2051	By default, all watchers have a C<void *data> member. By redefining	2199	By default, all watchers have a C<void *data> member. By redefining
2052	this macro to a something else you can include more and other types of	2200	this macro to a something else you can include more and other types of
…		…
2081	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2229	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2082	will be compiled. It is pretty complex because it provides its own header	2230	will be compiled. It is pretty complex because it provides its own header
2083	file.	2231	file.
2084		2232
2085	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2233	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2086	that everybody includes and which overrides some autoconf choices:	2234	that everybody includes and which overrides some configure choices:
2087		2235
		2236	#define EV_MINIMAL 1
2088	#define EV_USE_POLL 0	2237	#define EV_USE_POLL 0
2089	#define EV_MULTIPLICITY 0	2238	#define EV_MULTIPLICITY 0
2090	#define EV_PERIODICS 0	2239	#define EV_PERIODIC_ENABLE 0
		2240	#define EV_STAT_ENABLE 0
		2241	#define EV_FORK_ENABLE 0
2091	#define EV_CONFIG_H <config.h>	2242	#define EV_CONFIG_H <config.h>
		2243	#define EV_MINPRI 0
		2244	#define EV_MAXPRI 0
2092		2245
2093	#include "ev++.h"	2246	#include "ev++.h"
2094		2247
2095	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2248	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2096		2249
…		…
2102		2255
2103	In this section the complexities of (many of) the algorithms used inside	2256	In this section the complexities of (many of) the algorithms used inside
2104	libev will be explained. For complexity discussions about backends see the	2257	libev will be explained. For complexity discussions about backends see the
2105	documentation for C<ev_default_init>.	2258	documentation for C<ev_default_init>.
2106		2259
		2260	All of the following are about amortised time: If an array needs to be
		2261	extended, libev needs to realloc and move the whole array, but this
		2262	happens asymptotically never with higher number of elements, so O(1) might
		2263	mean it might do a lengthy realloc operation in rare cases, but on average
		2264	it is much faster and asymptotically approaches constant time.
		2265
2107	=over 4	2266	=over 4
2108		2267
2109	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2268	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2110		2269
		2270	This means that, when you have a watcher that triggers in one hour and
		2271	there are 100 watchers that would trigger before that then inserting will
		2272	have to skip those 100 watchers.
		2273
2111	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2274	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2112		2275
		2276	That means that for changing a timer costs less than removing/adding them
		2277	as only the relative motion in the event queue has to be paid for.
		2278
2113	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2279	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2114		2280
		2281	These just add the watcher into an array or at the head of a list.
2115	=item Stopping check/prepare/idle watchers: O(1)	2282	=item Stopping check/prepare/idle watchers: O(1)
2116		2283
2117	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2284	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2285
		2286	These watchers are stored in lists then need to be walked to find the
		2287	correct watcher to remove. The lists are usually short (you don't usually
		2288	have many watchers waiting for the same fd or signal).
2118		2289
2119	=item Finding the next timer per loop iteration: O(1)	2290	=item Finding the next timer per loop iteration: O(1)
2120		2291
2121	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2292	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2122		2293
		2294	A change means an I/O watcher gets started or stopped, which requires
		2295	libev to recalculate its status (and possibly tell the kernel).
		2296
2123	=item Activating one watcher: O(1)	2297	=item Activating one watcher: O(1)
2124		2298
		2299	=item Priority handling: O(number_of_priorities)
		2300
		2301	Priorities are implemented by allocating some space for each
		2302	priority. When doing priority-based operations, libev usually has to
		2303	linearly search all the priorities.
		2304
2125	=back	2305	=back
2126		2306
2127		2307
2128	=head1 AUTHOR	2308	=head1 AUTHOR
2129		2309

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Comparing libev/ev.pod (file contents): Revision 1.53 by root, Tue Nov 27 20:15:02 2007 UTC vs. Revision 1.70 by root, Fri Dec 7 19:23:48 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.53 by root, Tue Nov 27 20:15:02 2007 UTC vs.
Revision 1.70 by root, Fri Dec 7 19:23:48 2007 UTC