[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 1.80 by root, Sun Dec 9 19:47:30 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
…		…
45		47
46	return 0;	48	return 0;
47	}	49	}
48		50
49	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		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>.
50		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
…		…
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
…		…
105		117
106	=item int ev_version_major ()	118	=item int ev_version_major ()
107		119
108	=item int ev_version_minor ()	120	=item int ev_version_minor ()
109		121
110	You can find out the major and minor version numbers of the library	122	You can find out the major and minor ABI version numbers of the library
111	you linked against by calling the functions C<ev_version_major> and	123	you linked against by calling the functions C<ev_version_major> and
112	C<ev_version_minor>. If you want, you can compare against the global	124	C<ev_version_minor>. If you want, you can compare against the global
113	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
114	version of the library your program was compiled against.	126	version of the library your program was compiled against.
115		127
		128	These version numbers refer to the ABI version of the library, not the
		129	release version.
		130
116	Usually, it's a good idea to terminate if the major versions mismatch,	131	Usually, it's a good idea to terminate if the major versions mismatch,
117	as this indicates an incompatible change. Minor versions are usually	132	as this indicates an incompatible change. Minor versions are usually
118	compatible to older versions, so a larger minor version alone is usually	133	compatible to older versions, so a larger minor version alone is usually
119	not a problem.	134	not a problem.
120		135
121	Example: make sure we haven't accidentally been linked against the wrong	136	Example: Make sure we haven't accidentally been linked against the wrong
122	version:	137	version.
123		138
124	assert (("libev version mismatch",	139	assert (("libev version mismatch",
125	ev_version_major () == EV_VERSION_MAJOR	140	ev_version_major () == EV_VERSION_MAJOR
126	&& ev_version_minor () >= EV_VERSION_MINOR));	141	&& ev_version_minor () >= EV_VERSION_MINOR));
127		142
…		…
155	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	170	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
156	recommended ones.	171	recommended ones.
157		172
158	See the description of C<ev_embed> watchers for more info.	173	See the description of C<ev_embed> watchers for more info.
159		174
160	=item ev_set_allocator (void (cb)(void *ptr, size_t size))	175	=item ev_set_allocator (void (cb)(void *ptr, long size))
161		176
162	Sets the allocation function to use (the prototype and semantics are	177	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	178	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	179	allocate and free memory (no surprises here). If it returns zero when
165	allocated, the library might abort or take some potentially destructive	180	memory needs to be allocated, the library might abort or take some
166	action. The default is your system realloc function.	181	potentially destructive action. The default is your system realloc
		182	function.
167		183
168	You could override this function in high-availability programs to, say,	184	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,	185	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.	186	or even to sleep a while and retry until some memory is available.
171		187
172	Example: replace the libev allocator with one that waits a bit and then	188	Example: Replace the libev allocator with one that waits a bit and then
173	retries: better than mine).	189	retries).
174		190
175	static void *	191	static void *
176	persistent_realloc (void *ptr, size_t size)	192	persistent_realloc (void *ptr, size_t size)
177	{	193	{
178	for (;;)	194	for (;;)
…		…
197	callback is set, then libev will expect it to remedy the sitution, no	213	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	214	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	215	requested operation, or, if the condition doesn't go away, do bad stuff
200	(such as abort).	216	(such as abort).
201		217
202	Example: do the same thing as libev does internally:	218	Example: This is basically the same thing that libev does internally, too.
203		219
204	static void	220	static void
205	fatal_error (const char *msg)	221	fatal_error (const char *msg)
206	{	222	{
207	perror (msg);	223	perror (msg);
…		…
257	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
258	override the flags completely if it is found in the environment. This is	274	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	275	useful to try out specific backends to test their performance, or to work
260	around bugs.	276	around bugs.
261		277
		278	=item C<EVFLAG_FORKCHECK>
		279
		280	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		281	a fork, you can also make libev check for a fork in each iteration by
		282	enabling this flag.
		283
		284	This works by calling C<getpid ()> on every iteration of the loop,
		285	and thus this might slow down your event loop if you do a lot of loop
		286	iterations and little real work, but is usually not noticeable (on my
		287	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		288	without a syscall and thus I<very> fast, but my Linux system also has
		289	C<pthread_atfork> which is even faster).
		290
		291	The big advantage of this flag is that you can forget about fork (and
		292	forget about forgetting to tell libev about forking) when you use this
		293	flag.
		294
		295	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		296	environment variable.
		297
262	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
263		299
264	This is your standard select(2) backend. Not I<completely> standard, as	300	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,	301	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	302	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	389	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	390	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	391	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).	392	undefined behaviour (or a failed assertion if assertions are enabled).
357		393
358	Example: try to create a event loop that uses epoll and nothing else.	394	Example: Try to create a event loop that uses epoll and nothing else.
359		395
360	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
361	if (!epoller)	397	if (!epoller)
362	fatal ("no epoll found here, maybe it hides under your chair");	398	fatal ("no epoll found here, maybe it hides under your chair");
363		399
…		…
401		437
402	Like C<ev_default_fork>, but acts on an event loop created by	438	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	439	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.	440	after fork, and how you do this is entirely your own problem.
405		441
		442	=item unsigned int ev_loop_count (loop)
		443
		444	Returns the count of loop iterations for the loop, which is identical to
		445	the number of times libev did poll for new events. It starts at C<0> and
		446	happily wraps around with enough iterations.
		447
		448	This value can sometimes be useful as a generation counter of sorts (it
		449	"ticks" the number of loop iterations), as it roughly corresponds with
		450	C<ev_prepare> and C<ev_check> calls.
		451
406	=item unsigned int ev_backend (loop)	452	=item unsigned int ev_backend (loop)
407		453
408	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	454	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
409	use.	455	use.
410		456
…		…
443	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
444	usually a better approach for this kind of thing.	490	usually a better approach for this kind of thing.
445		491
446	Here are the gory details of what C<ev_loop> does:	492	Here are the gory details of what C<ev_loop> does:
447		493
		494	- Before the first iteration, call any pending watchers.
448	* If there are no active watchers (reference count is zero), return.	495	* If there are no active watchers (reference count is zero), return.
449	- Queue prepare watchers and then call all outstanding watchers.	496	- Queue all prepare watchers and then call all outstanding watchers.
450	- If we have been forked, recreate the kernel state.	497	- If we have been forked, recreate the kernel state.
451	- Update the kernel state with all outstanding changes.	498	- Update the kernel state with all outstanding changes.
452	- Update the "event loop time".	499	- Update the "event loop time".
453	- Calculate for how long to block.	500	- Calculate for how long to block.
454	- Block the process, waiting for any events.	501	- Block the process, waiting for any events.
…		…
462	Signals and child watchers are implemented as I/O watchers, and will	509	Signals and child watchers are implemented as I/O watchers, and will
463	be handled here by queueing them when their watcher gets executed.	510	be handled here by queueing them when their watcher gets executed.
464	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
465	were used, return, otherwise continue with step *.	512	were used, return, otherwise continue with step *.
466		513
467	Example: queue some jobs and then loop until no events are outsanding	514	Example: Queue some jobs and then loop until no events are outsanding
468	anymore.	515	anymore.
469		516
470	... queue jobs here, make sure they register event watchers as long	517	... 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..)	518	... as they still have work to do (even an idle watcher will do..)
472	ev_loop (my_loop, 0);	519	ev_loop (my_loop, 0);
…		…
492	visible to the libev user and should not keep C<ev_loop> from exiting if	539	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	540	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	541	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>.	542	libraries. Just remember to I<unref after start> and I<ref before stop>.
496		543
497	Example: create a signal watcher, but keep it from keeping C<ev_loop>	544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
498	running when nothing else is active.	545	running when nothing else is active.
499		546
500	struct dv_signal exitsig;	547	struct ev_signal exitsig;
501	ev_signal_init (&exitsig, sig_cb, SIGINT);	548	ev_signal_init (&exitsig, sig_cb, SIGINT);
502	ev_signal_start (myloop, &exitsig);	549	ev_signal_start (loop, &exitsig);
503	evf_unref (myloop);	550	evf_unref (loop);
504		551
505	Example: for some weird reason, unregister the above signal handler again.	552	Example: For some weird reason, unregister the above signal handler again.
506		553
507	ev_ref (myloop);	554	ev_ref (loop);
508	ev_signal_stop (myloop, &exitsig);	555	ev_signal_stop (loop, &exitsig);
509		556
510	=back	557	=back
511		558
512		559
513	=head1 ANATOMY OF A WATCHER	560	=head1 ANATOMY OF A WATCHER
…		…
693	=item bool ev_is_pending (ev_TYPE *watcher)	740	=item bool ev_is_pending (ev_TYPE *watcher)
694		741
695	Returns a true value iff the watcher is pending, (i.e. it has outstanding	742	Returns a true value iff the watcher is pending, (i.e. it has outstanding
696	events but its callback has not yet been invoked). As long as a watcher	743	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	744	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	745	C<ev_TYPE_set> is safe), you must not change its priority, and you must
699	libev (e.g. you cnanot C<free ()> it).	746	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		747	it).
700		748
701	=item callback = ev_cb (ev_TYPE *watcher)	749	=item callback ev_cb (ev_TYPE *watcher)
702		750
703	Returns the callback currently set on the watcher.	751	Returns the callback currently set on the watcher.
704		752
705	=item ev_cb_set (ev_TYPE *watcher, callback)	753	=item ev_cb_set (ev_TYPE *watcher, callback)
706		754
707	Change the callback. You can change the callback at virtually any time	755	Change the callback. You can change the callback at virtually any time
708	(modulo threads).	756	(modulo threads).
		757
		758	=item ev_set_priority (ev_TYPE *watcher, priority)
		759
		760	=item int ev_priority (ev_TYPE *watcher)
		761
		762	Set and query the priority of the watcher. The priority is a small
		763	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		764	(default: C<-2>). Pending watchers with higher priority will be invoked
		765	before watchers with lower priority, but priority will not keep watchers
		766	from being executed (except for C<ev_idle> watchers).
		767
		768	This means that priorities are I<only> used for ordering callback
		769	invocation after new events have been received. This is useful, for
		770	example, to reduce latency after idling, or more often, to bind two
		771	watchers on the same event and make sure one is called first.
		772
		773	If you need to suppress invocation when higher priority events are pending
		774	you need to look at C<ev_idle> watchers, which provide this functionality.
		775
		776	You I<must not> change the priority of a watcher as long as it is active or
		777	pending.
		778
		779	The default priority used by watchers when no priority has been set is
		780	always C<0>, which is supposed to not be too high and not be too low :).
		781
		782	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		783	fine, as long as you do not mind that the priority value you query might
		784	or might not have been adjusted to be within valid range.
		785
		786	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		787
		788	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		789	C<loop> nor C<revents> need to be valid as long as the watcher callback
		790	can deal with that fact.
		791
		792	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		793
		794	If the watcher is pending, this function returns clears its pending status
		795	and returns its C<revents> bitset (as if its callback was invoked). If the
		796	watcher isn't pending it does nothing and returns C<0>.
709		797
710	=back	798	=back
711		799
712		800
713	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
734	{	822	{
735	struct my_io w = (struct my_io )w_;	823	struct my_io w = (struct my_io )w_;
736	...	824	...
737	}	825	}
738		826
739	More interesting and less C-conformant ways of catsing your callback type	827	More interesting and less C-conformant ways of casting your callback type
740	have been omitted....	828	instead have been omitted.
		829
		830	Another common scenario is having some data structure with multiple
		831	watchers:
		832
		833	struct my_biggy
		834	{
		835	int some_data;
		836	ev_timer t1;
		837	ev_timer t2;
		838	}
		839
		840	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		841	you need to use C<offsetof>:
		842
		843	#include <stddef.h>
		844
		845	static void
		846	t1_cb (EV_P_ struct ev_timer *w, int revents)
		847	{
		848	struct my_biggy big = (struct my_biggy *
		849	(((char *)w) - offsetof (struct my_biggy, t1));
		850	}
		851
		852	static void
		853	t2_cb (EV_P_ struct ev_timer *w, int revents)
		854	{
		855	struct my_biggy big = (struct my_biggy *
		856	(((char *)w) - offsetof (struct my_biggy, t2));
		857	}
741		858
742		859
743	=head1 WATCHER TYPES	860	=head1 WATCHER TYPES
744		861
745	This section describes each watcher in detail, but will not repeat	862	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	907	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.	908	C<EAGAIN> is far preferable to a program hanging until some data arrives.
792		909
793	If you cannot run the fd in non-blocking mode (for example you should not	910	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	911	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	912	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	913	such as poll (fortunately in our Xlib example, Xlib already does this on
797	its own, so its quite safe to use).	914	its own, so its quite safe to use).
798		915
799	=over 4	916	=over 4
800		917
…		…
814		931
815	The events being watched.	932	The events being watched.
816		933
817	=back	934	=back
818		935
819	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	936	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	937	readable, but only once. Since it is likely line-buffered, you could
821	attempt to read a whole line in the callback:	938	attempt to read a whole line in the callback.
822		939
823	static void	940	static void
824	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	941	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
825	{	942	{
826	ev_io_stop (loop, w);	943	ev_io_stop (loop, w);
…		…
878	=item ev_timer_again (loop)	995	=item ev_timer_again (loop)
879		996
880	This will act as if the timer timed out and restart it again if it is	997	This will act as if the timer timed out and restart it again if it is
881	repeating. The exact semantics are:	998	repeating. The exact semantics are:
882		999
		1000	If the timer is pending, its pending status is cleared.
		1001
883	If the timer is started but nonrepeating, stop it.	1002	If the timer is started but nonrepeating, stop it (as if it timed out).
884		1003
885	If the timer is repeating, either start it if necessary (with the repeat	1004	If the timer is repeating, either start it if necessary (with the
886	value), or reset the running timer to the repeat value.	1005	C<repeat> value), or reset the running timer to the C<repeat> value.
887		1006
888	This sounds a bit complicated, but here is a useful and typical	1007	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	1008	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,	1009	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	1010	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	1011	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	1012	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	1013	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	1014	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
896	need be.	1015	automatically restart it if need be.
897		1016
898	You can also ignore the C<after> value and C<ev_timer_start> altogether	1017	That means you can ignore the C<after> value and C<ev_timer_start>
899	and only ever use the C<repeat> value:	1018	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
900		1019
901	ev_timer_init (timer, callback, 0., 5.);	1020	ev_timer_init (timer, callback, 0., 5.);
902	ev_timer_again (loop, timer);	1021	ev_timer_again (loop, timer);
903	...	1022	...
904	timer->again = 17.;	1023	timer->again = 17.;
905	ev_timer_again (loop, timer);	1024	ev_timer_again (loop, timer);
906	...	1025	...
907	timer->again = 10.;	1026	timer->again = 10.;
908	ev_timer_again (loop, timer);	1027	ev_timer_again (loop, timer);
909		1028
910	This is more efficient then stopping/starting the timer eahc time you want	1029	This is more slightly efficient then stopping/starting the timer each time
911	to modify its timeout value.	1030	you want to modify its timeout value.
912		1031
913	=item ev_tstamp repeat [read-write]	1032	=item ev_tstamp repeat [read-write]
914		1033
915	The current C<repeat> value. Will be used each time the watcher times out	1034	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),	1035	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.	1036	which is also when any modifications are taken into account.
918		1037
919	=back	1038	=back
920		1039
921	Example: create a timer that fires after 60 seconds.	1040	Example: Create a timer that fires after 60 seconds.
922		1041
923	static void	1042	static void
924	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1043	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
925	{	1044	{
926	.. one minute over, w is actually stopped right here	1045	.. one minute over, w is actually stopped right here
…		…
928		1047
929	struct ev_timer mytimer;	1048	struct ev_timer mytimer;
930	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1049	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
931	ev_timer_start (loop, &mytimer);	1050	ev_timer_start (loop, &mytimer);
932		1051
933	Example: create a timeout timer that times out after 10 seconds of	1052	Example: Create a timeout timer that times out after 10 seconds of
934	inactivity.	1053	inactivity.
935		1054
936	static void	1055	static void
937	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1056	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
938	{	1057	{
…		…
958	but on wallclock time (absolute time). You can tell a periodic watcher	1077	but on wallclock time (absolute time). You can tell a periodic watcher
959	to trigger "at" some specific point in time. For example, if you tell a	1078	to trigger "at" some specific point in time. For example, if you tell a
960	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1079	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
961	+ 10.>) and then reset your system clock to the last year, then it will	1080	+ 10.>) and then reset your system clock to the last year, then it will
962	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1081	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
963	roughly 10 seconds later and of course not if you reset your system time	1082	roughly 10 seconds later).
964	again).
965		1083
966	They can also be used to implement vastly more complex timers, such as	1084	They can also be used to implement vastly more complex timers, such as
967	triggering an event on eahc midnight, local time.	1085	triggering an event on each midnight, local time or other, complicated,
		1086	rules.
968		1087
969	As with timers, the callback is guarenteed to be invoked only when the	1088	As with timers, the callback is guarenteed to be invoked only when the
970	time (C<at>) has been passed, but if multiple periodic timers become ready	1089	time (C<at>) has been passed, but if multiple periodic timers become ready
971	during the same loop iteration then order of execution is undefined.	1090	during the same loop iteration then order of execution is undefined.
972		1091
…		…
979	Lots of arguments, lets sort it out... There are basically three modes of	1098	Lots of arguments, lets sort it out... There are basically three modes of
980	operation, and we will explain them from simplest to complex:	1099	operation, and we will explain them from simplest to complex:
981		1100
982	=over 4	1101	=over 4
983		1102
984	=item * absolute timer (interval = reschedule_cb = 0)	1103	=item * absolute timer (at = time, interval = reschedule_cb = 0)
985		1104
986	In this configuration the watcher triggers an event at the wallclock time	1105	In this configuration the watcher triggers an event at the wallclock time
987	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1106	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
988	that is, if it is to be run at January 1st 2011 then it will run when the	1107	that is, if it is to be run at January 1st 2011 then it will run when the
989	system time reaches or surpasses this time.	1108	system time reaches or surpasses this time.
990		1109
991	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1110	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
992		1111
993	In this mode the watcher will always be scheduled to time out at the next	1112	In this mode the watcher will always be scheduled to time out at the next
994	C<at + N * interval> time (for some integer N) and then repeat, regardless	1113	C<at + N * interval> time (for some integer N, which can also be negative)
995	of any time jumps.	1114	and then repeat, regardless of any time jumps.
996		1115
997	This can be used to create timers that do not drift with respect to system	1116	This can be used to create timers that do not drift with respect to system
998	time:	1117	time:
999		1118
1000	ev_periodic_set (&periodic, 0., 3600., 0);	1119	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1006		1125
1007	Another way to think about it (for the mathematically inclined) is that	1126	Another way to think about it (for the mathematically inclined) is that
1008	C<ev_periodic> will try to run the callback in this mode at the next possible	1127	C<ev_periodic> will try to run the callback in this mode at the next possible
1009	time where C<time = at (mod interval)>, regardless of any time jumps.	1128	time where C<time = at (mod interval)>, regardless of any time jumps.
1010		1129
		1130	For numerical stability it is preferable that the C<at> value is near
		1131	C<ev_now ()> (the current time), but there is no range requirement for
		1132	this value.
		1133
1011	=item * manual reschedule mode (reschedule_cb = callback)	1134	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1012		1135
1013	In this mode the values for C<interval> and C<at> are both being	1136	In this mode the values for C<interval> and C<at> are both being
1014	ignored. Instead, each time the periodic watcher gets scheduled, the	1137	ignored. Instead, each time the periodic watcher gets scheduled, the
1015	reschedule callback will be called with the watcher as first, and the	1138	reschedule callback will be called with the watcher as first, and the
1016	current time as second argument.	1139	current time as second argument.
1017		1140
1018	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1141	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1019	ever, or make any event loop modifications>. If you need to stop it,	1142	ever, or make any event loop modifications>. If you need to stop it,
1020	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1143	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1021	starting a prepare watcher).	1144	starting an C<ev_prepare> watcher, which is legal).
1022		1145
1023	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1146	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1024	ev_tstamp now)>, e.g.:	1147	ev_tstamp now)>, e.g.:
1025		1148
1026	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1149	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1049	Simply stops and restarts the periodic watcher again. This is only useful	1172	Simply stops and restarts the periodic watcher again. This is only useful
1050	when you changed some parameters or the reschedule callback would return	1173	when you changed some parameters or the reschedule callback would return
1051	a different time than the last time it was called (e.g. in a crond like	1174	a different time than the last time it was called (e.g. in a crond like
1052	program when the crontabs have changed).	1175	program when the crontabs have changed).
1053		1176
		1177	=item ev_tstamp offset [read-write]
		1178
		1179	When repeating, this contains the offset value, otherwise this is the
		1180	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1181
		1182	Can be modified any time, but changes only take effect when the periodic
		1183	timer fires or C<ev_periodic_again> is being called.
		1184
1054	=item ev_tstamp interval [read-write]	1185	=item ev_tstamp interval [read-write]
1055		1186
1056	The current interval value. Can be modified any time, but changes only	1187	The current interval value. Can be modified any time, but changes only
1057	take effect when the periodic timer fires or C<ev_periodic_again> is being	1188	take effect when the periodic timer fires or C<ev_periodic_again> is being
1058	called.	1189	called.
…		…
1063	switched off. Can be changed any time, but changes only take effect when	1194	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.	1195	the periodic timer fires or C<ev_periodic_again> is being called.
1065		1196
1066	=back	1197	=back
1067		1198
1068	Example: call a callback every hour, or, more precisely, whenever the	1199	Example: Call a callback every hour, or, more precisely, whenever the
1069	system clock is divisible by 3600. The callback invocation times have	1200	system clock is divisible by 3600. The callback invocation times have
1070	potentially a lot of jittering, but good long-term stability.	1201	potentially a lot of jittering, but good long-term stability.
1071		1202
1072	static void	1203	static void
1073	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1204	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
…		…
1077		1208
1078	struct ev_periodic hourly_tick;	1209	struct ev_periodic hourly_tick;
1079	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1210	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1080	ev_periodic_start (loop, &hourly_tick);	1211	ev_periodic_start (loop, &hourly_tick);
1081		1212
1082	Example: the same as above, but use a reschedule callback to do it:	1213	Example: The same as above, but use a reschedule callback to do it:
1083		1214
1084	#include <math.h>	1215	#include <math.h>
1085		1216
1086	static ev_tstamp	1217	static ev_tstamp
1087	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1218	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
1089	return fmod (now, 3600.) + 3600.;	1220	return fmod (now, 3600.) + 3600.;
1090	}	1221	}
1091		1222
1092	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1223	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1093		1224
1094	Example: call a callback every hour, starting now:	1225	Example: Call a callback every hour, starting now:
1095		1226
1096	struct ev_periodic hourly_tick;	1227	struct ev_periodic hourly_tick;
1097	ev_periodic_init (&hourly_tick, clock_cb,	1228	ev_periodic_init (&hourly_tick, clock_cb,
1098	fmod (ev_now (loop), 3600.), 3600., 0);	1229	fmod (ev_now (loop), 3600.), 3600., 0);
1099	ev_periodic_start (loop, &hourly_tick);	1230	ev_periodic_start (loop, &hourly_tick);
…		…
1160	The process exit/trace status caused by C<rpid> (see your systems	1291	The process exit/trace status caused by C<rpid> (see your systems
1161	C<waitpid> and C<sys/wait.h> documentation for details).	1292	C<waitpid> and C<sys/wait.h> documentation for details).
1162		1293
1163	=back	1294	=back
1164		1295
1165	Example: try to exit cleanly on SIGINT and SIGTERM.	1296	Example: Try to exit cleanly on SIGINT and SIGTERM.
1166		1297
1167	static void	1298	static void
1168	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1299	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1169	{	1300	{
1170	ev_unloop (loop, EVUNLOOP_ALL);	1301	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1185	not exist" is a status change like any other. The condition "path does	1316	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	1317	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	1318	otherwise always forced to be at least one) and all the other fields of
1188	the stat buffer having unspecified contents.	1319	the stat buffer having unspecified contents.
1189		1320
		1321	The path I<should> be absolute and I<must not> end in a slash. If it is
		1322	relative and your working directory changes, the behaviour is undefined.
		1323
1190	Since there is no standard to do this, the portable implementation simply	1324	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	1325	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	1326	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,	1327	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	1328	unspecified default> value will be used (which you can expect to be around
1195	five seconds, although this might change dynamically). Libev will also	1329	five seconds, although this might change dynamically). Libev will also
1196	impose a minimum interval which is currently around C<0.1>, but thats	1330	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1198		1332
1199	This watcher type is not meant for massive numbers of stat watchers,	1333	This watcher type is not meant for massive numbers of stat watchers,
1200	as even with OS-supported change notifications, this can be	1334	as even with OS-supported change notifications, this can be
1201	resource-intensive.	1335	resource-intensive.
1202		1336
1203	At the time of this writing, no specific OS backends are implemented, but	1337	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.	1338	implemented (implementing kqueue support is left as an exercise for the
		1339	reader). Inotify will be used to give hints only and should not change the
		1340	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1341	to fall back to regular polling again even with inotify, but changes are
		1342	usually detected immediately, and if the file exists there will be no
		1343	polling.
1205		1344
1206	=over 4	1345	=over 4
1207		1346
1208	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1347	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1209		1348
…		…
1273	ev_stat_start (loop, &passwd);	1412	ev_stat_start (loop, &passwd);
1274		1413
1275		1414
1276	=head2 C<ev_idle> - when you've got nothing better to do...	1415	=head2 C<ev_idle> - when you've got nothing better to do...
1277		1416
1278	Idle watchers trigger events when there are no other events are pending	1417	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	1418	priority are pending (prepare, check and other idle watchers do not
1280	as your process is busy handling sockets or timeouts (or even signals,	1419	count).
1281	imagine) it will not be triggered. But when your process is idle all idle	1420
1282	watchers are being called again and again, once per event loop iteration -	1421	That is, as long as your process is busy handling sockets or timeouts
		1422	(or even signals, imagine) of the same or higher priority it will not be
		1423	triggered. But when your process is idle (or only lower-priority watchers
		1424	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	1425	iteration - until stopped, that is, or your process receives more events
1284	busy.	1426	and becomes busy again with higher priority stuff.
1285		1427
1286	The most noteworthy effect is that as long as any idle watchers are	1428	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.	1429	active, the process will not block when waiting for new events.
1288		1430
1289	Apart from keeping your process non-blocking (which is a useful	1431	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,	1441	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1300	believe me.	1442	believe me.
1301		1443
1302	=back	1444	=back
1303		1445
1304	Example: dynamically allocate an C<ev_idle>, start it, and in the	1446	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1305	callback, free it. Alos, use no error checking, as usual.	1447	callback, free it. Also, use no error checking, as usual.
1306		1448
1307	static void	1449	static void
1308	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1450	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1309	{	1451	{
1310	free (w);	1452	free (w);
…		…
1355	with priority higher than or equal to the event loop and one coroutine	1497	with priority higher than or equal to the event loop and one coroutine
1356	of lower priority, but only once, using idle watchers to keep the event	1498	of lower priority, but only once, using idle watchers to keep the event
1357	loop from blocking if lower-priority coroutines are active, thus mapping	1499	loop from blocking if lower-priority coroutines are active, thus mapping
1358	low-priority coroutines to idle/background tasks).	1500	low-priority coroutines to idle/background tasks).
1359		1501
		1502	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1503	priority, to ensure that they are being run before any other watchers
		1504	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1505	too) should not activate ("feed") events into libev. While libev fully
		1506	supports this, they will be called before other C<ev_check> watchers did
		1507	their job. As C<ev_check> watchers are often used to embed other event
		1508	loops those other event loops might be in an unusable state until their
		1509	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1510	others).
		1511
1360	=over 4	1512	=over 4
1361		1513
1362	=item ev_prepare_init (ev_prepare *, callback)	1514	=item ev_prepare_init (ev_prepare *, callback)
1363		1515
1364	=item ev_check_init (ev_check *, callback)	1516	=item ev_check_init (ev_check *, callback)
…		…
1367	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1519	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1368	macros, but using them is utterly, utterly and completely pointless.	1520	macros, but using them is utterly, utterly and completely pointless.
1369		1521
1370	=back	1522	=back
1371		1523
1372	Example: To include a library such as adns, you would add IO watchers	1524	There are a number of principal ways to embed other event loops or modules
1373	and a timeout watcher in a prepare handler, as required by libadns, and	1525	into libev. Here are some ideas on how to include libadns into libev
		1526	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1527	use for an actually working example. Another Perl module named C<EV::Glib>
		1528	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1529	into the Glib event loop).
		1530
		1531	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1374	in a check watcher, destroy them and call into libadns. What follows is	1532	and in a check watcher, destroy them and call into libadns. What follows
1375	pseudo-code only of course:	1533	is pseudo-code only of course. This requires you to either use a low
		1534	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1535	the callbacks for the IO/timeout watchers might not have been called yet.
1376		1536
1377	static ev_io iow [nfd];	1537	static ev_io iow [nfd];
1378	static ev_timer tw;	1538	static ev_timer tw;
1379		1539
1380	static void	1540	static void
1381	io_cb (ev_loop loop, ev_io w, int revents)	1541	io_cb (ev_loop loop, ev_io w, int revents)
1382	{	1542	{
1383	// set the relevant poll flags
1384	// could also call adns_processreadable etc. here
1385	struct pollfd fd = (struct pollfd )w->data;
1386	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1387	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1388	}	1543	}
1389		1544
1390	// create io watchers for each fd and a timer before blocking	1545	// create io watchers for each fd and a timer before blocking
1391	static void	1546	static void
1392	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1547	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1393	{	1548	{
1394	int timeout = 3600000;truct pollfd fds [nfd];	1549	int timeout = 3600000;
		1550	struct pollfd fds [nfd];
1395	// actual code will need to loop here and realloc etc.	1551	// actual code will need to loop here and realloc etc.
1396	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1552	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1397		1553
1398	/* the callback is illegal, but won't be called as we stop during check */	1554	/* the callback is illegal, but won't be called as we stop during check */
1399	ev_timer_init (&tw, 0, timeout * 1e-3);	1555	ev_timer_init (&tw, 0, timeout * 1e-3);
1400	ev_timer_start (loop, &tw);	1556	ev_timer_start (loop, &tw);
1401		1557
1402	// create on ev_io per pollfd	1558	// create one ev_io per pollfd
1403	for (int i = 0; i < nfd; ++i)	1559	for (int i = 0; i < nfd; ++i)
1404	{	1560	{
1405	ev_io_init (iow + i, io_cb, fds [i].fd,	1561	ev_io_init (iow + i, io_cb, fds [i].fd,
1406	((fds [i].events & POLLIN ? EV_READ : 0)	1562	((fds [i].events & POLLIN ? EV_READ : 0)
1407	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1563	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1408		1564
1409	fds [i].revents = 0;	1565	fds [i].revents = 0;
1410	iow [i].data = fds + i;
1411	ev_io_start (loop, iow + i);	1566	ev_io_start (loop, iow + i);
1412	}	1567	}
1413	}	1568	}
1414		1569
1415	// stop all watchers after blocking	1570	// stop all watchers after blocking
…		…
1417	adns_check_cb (ev_loop loop, ev_check w, int revents)	1572	adns_check_cb (ev_loop loop, ev_check w, int revents)
1418	{	1573	{
1419	ev_timer_stop (loop, &tw);	1574	ev_timer_stop (loop, &tw);
1420		1575
1421	for (int i = 0; i < nfd; ++i)	1576	for (int i = 0; i < nfd; ++i)
		1577	{
		1578	// set the relevant poll flags
		1579	// could also call adns_processreadable etc. here
		1580	struct pollfd *fd = fds + i;
		1581	int revents = ev_clear_pending (iow + i);
		1582	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1583	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1584
		1585	// now stop the watcher
1422	ev_io_stop (loop, iow + i);	1586	ev_io_stop (loop, iow + i);
		1587	}
1423		1588
1424	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1589	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1590	}
		1591
		1592	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1593	in the prepare watcher and would dispose of the check watcher.
		1594
		1595	Method 3: If the module to be embedded supports explicit event
		1596	notification (adns does), you can also make use of the actual watcher
		1597	callbacks, and only destroy/create the watchers in the prepare watcher.
		1598
		1599	static void
		1600	timer_cb (EV_P_ ev_timer *w, int revents)
		1601	{
		1602	adns_state ads = (adns_state)w->data;
		1603	update_now (EV_A);
		1604
		1605	adns_processtimeouts (ads, &tv_now);
		1606	}
		1607
		1608	static void
		1609	io_cb (EV_P_ ev_io *w, int revents)
		1610	{
		1611	adns_state ads = (adns_state)w->data;
		1612	update_now (EV_A);
		1613
		1614	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1615	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1616	}
		1617
		1618	// do not ever call adns_afterpoll
		1619
		1620	Method 4: Do not use a prepare or check watcher because the module you
		1621	want to embed is too inflexible to support it. Instead, youc na override
		1622	their poll function. The drawback with this solution is that the main
		1623	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1624	this.
		1625
		1626	static gint
		1627	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1628	{
		1629	int got_events = 0;
		1630
		1631	for (n = 0; n < nfds; ++n)
		1632	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1633
		1634	if (timeout >= 0)
		1635	// create/start timer
		1636
		1637	// poll
		1638	ev_loop (EV_A_ 0);
		1639
		1640	// stop timer again
		1641	if (timeout >= 0)
		1642	ev_timer_stop (EV_A_ &to);
		1643
		1644	// stop io watchers again - their callbacks should have set
		1645	for (n = 0; n < nfds; ++n)
		1646	ev_io_stop (EV_A_ iow [n]);
		1647
		1648	return got_events;
1425	}	1649	}
1426		1650
1427		1651
1428	=head2 C<ev_embed> - when one backend isn't enough...	1652	=head2 C<ev_embed> - when one backend isn't enough...
1429		1653
…		…
1633		1857
1634	To use it,	1858	To use it,
1635		1859
1636	#include <ev++.h>	1860	#include <ev++.h>
1637		1861
1638	(it is not installed by default). This automatically includes F<ev.h>	1862	This automatically includes F<ev.h> and puts all of its definitions (many
1639	and puts all of its definitions (many of them macros) into the global	1863	of them macros) into the global namespace. All C++ specific things are
1640	namespace. All C++ specific things are put into the C<ev> namespace.	1864	put into the C<ev> namespace. It should support all the same embedding
		1865	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1641		1866
1642	It should support all the same embedding options as F<ev.h>, most notably	1867	Care has been taken to keep the overhead low. The only data member the C++
1643	C<EV_MULTIPLICITY>.	1868	classes add (compared to plain C-style watchers) is the event loop pointer
		1869	that the watcher is associated with (or no additional members at all if
		1870	you disable C<EV_MULTIPLICITY> when embedding libev).
		1871
		1872	Currently, functions, and static and non-static member functions can be
		1873	used as callbacks. Other types should be easy to add as long as they only
		1874	need one additional pointer for context. If you need support for other
		1875	types of functors please contact the author (preferably after implementing
		1876	it).
1644		1877
1645	Here is a list of things available in the C<ev> namespace:	1878	Here is a list of things available in the C<ev> namespace:
1646		1879
1647	=over 4	1880	=over 4
1648		1881
…		…
1664		1897
1665	All of those classes have these methods:	1898	All of those classes have these methods:
1666		1899
1667	=over 4	1900	=over 4
1668		1901
1669	=item ev::TYPE::TYPE (object , object::method )	1902	=item ev::TYPE::TYPE ()
1670		1903
1671	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1904	=item ev::TYPE::TYPE (struct ev_loop *)
1672		1905
1673	=item ev::TYPE::~TYPE	1906	=item ev::TYPE::~TYPE
1674		1907
1675	The constructor takes a pointer to an object and a method pointer to	1908	The constructor (optionally) takes an event loop to associate the watcher
1676	the event handler callback to call in this class. The constructor calls	1909	with. If it is omitted, it will use C<EV_DEFAULT>.
1677	C<ev_init> for you, which means you have to call the C<set> method	1910
1678	before starting it. If you do not specify a loop then the constructor	1911	The constructor calls C<ev_init> for you, which means you have to call the
1679	automatically associates the default loop with this watcher.	1912	C<set> method before starting it.
		1913
		1914	It will not set a callback, however: You have to call the templated C<set>
		1915	method to set a callback before you can start the watcher.
		1916
		1917	(The reason why you have to use a method is a limitation in C++ which does
		1918	not allow explicit template arguments for constructors).
1680		1919
1681	The destructor automatically stops the watcher if it is active.	1920	The destructor automatically stops the watcher if it is active.
		1921
		1922	=item w->set<class, &class::method> (object *)
		1923
		1924	This method sets the callback method to call. The method has to have a
		1925	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1926	first argument and the C<revents> as second. The object must be given as
		1927	parameter and is stored in the C<data> member of the watcher.
		1928
		1929	This method synthesizes efficient thunking code to call your method from
		1930	the C callback that libev requires. If your compiler can inline your
		1931	callback (i.e. it is visible to it at the place of the C<set> call and
		1932	your compiler is good :), then the method will be fully inlined into the
		1933	thunking function, making it as fast as a direct C callback.
		1934
		1935	Example: simple class declaration and watcher initialisation
		1936
		1937	struct myclass
		1938	{
		1939	void io_cb (ev::io &w, int revents) { }
		1940	}
		1941
		1942	myclass obj;
		1943	ev::io iow;
		1944	iow.set <myclass, &myclass::io_cb> (&obj);
		1945
		1946	=item w->set<function> (void *data = 0)
		1947
		1948	Also sets a callback, but uses a static method or plain function as
		1949	callback. The optional C<data> argument will be stored in the watcher's
		1950	C<data> member and is free for you to use.
		1951
		1952	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1953
		1954	See the method-C<set> above for more details.
		1955
		1956	Example:
		1957
		1958	static void io_cb (ev::io &w, int revents) { }
		1959	iow.set <io_cb> ();
1682		1960
1683	=item w->set (struct ev_loop *)	1961	=item w->set (struct ev_loop *)
1684		1962
1685	Associates a different C<struct ev_loop> with this watcher. You can only	1963	Associates a different C<struct ev_loop> with this watcher. You can only
1686	do this when the watcher is inactive (and not pending either).	1964	do this when the watcher is inactive (and not pending either).
1687		1965
1688	=item w->set ([args])	1966	=item w->set ([args])
1689		1967
1690	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1968	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1691	called at least once. Unlike the C counterpart, an active watcher gets	1969	called at least once. Unlike the C counterpart, an active watcher gets
1692	automatically stopped and restarted.	1970	automatically stopped and restarted when reconfiguring it with this
		1971	method.
1693		1972
1694	=item w->start ()	1973	=item w->start ()
1695		1974
1696	Starts the watcher. Note that there is no C<loop> argument as the	1975	Starts the watcher. Note that there is no C<loop> argument, as the
1697	constructor already takes the loop.	1976	constructor already stores the event loop.
1698		1977
1699	=item w->stop ()	1978	=item w->stop ()
1700		1979
1701	Stops the watcher if it is active. Again, no C<loop> argument.	1980	Stops the watcher if it is active. Again, no C<loop> argument.
1702		1981
…		…
1727		2006
1728	myclass ();	2007	myclass ();
1729	}	2008	}
1730		2009
1731	myclass::myclass (int fd)	2010	myclass::myclass (int fd)
1732	: io (this, &myclass::io_cb),
1733	idle (this, &myclass::idle_cb)
1734	{	2011	{
		2012	io .set <myclass, &myclass::io_cb > (this);
		2013	idle.set <myclass, &myclass::idle_cb> (this);
		2014
1735	io.start (fd, ev::READ);	2015	io.start (fd, ev::READ);
1736	}	2016	}
1737		2017
1738		2018
1739	=head1 MACRO MAGIC	2019	=head1 MACRO MAGIC
1740		2020
1741	Libev can be compiled with a variety of options, the most fundemantal is	2021	Libev can be compiled with a variety of options, the most fundemantal is
1742	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2022	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1743	callbacks have an initial C<struct ev_loop *> argument.	2023	callbacks have an initial C<struct ev_loop *> argument.
1744		2024
1745	To make it easier to write programs that cope with either variant, the	2025	To make it easier to write programs that cope with either variant, the
1746	following macros are defined:	2026	following macros are defined:
1747		2027
…		…
1780	Similar to the other two macros, this gives you the value of the default	2060	Similar to the other two macros, this gives you the value of the default
1781	loop, if multiple loops are supported ("ev loop default").	2061	loop, if multiple loops are supported ("ev loop default").
1782		2062
1783	=back	2063	=back
1784		2064
1785	Example: Declare and initialise a check watcher, working regardless of	2065	Example: Declare and initialise a check watcher, utilising the above
1786	wether multiple loops are supported or not.	2066	macros so it will work regardless of whether multiple loops are supported
		2067	or not.
1787		2068
1788	static void	2069	static void
1789	check_cb (EV_P_ ev_timer *w, int revents)	2070	check_cb (EV_P_ ev_timer *w, int revents)
1790	{	2071	{
1791	ev_check_stop (EV_A_ w);	2072	ev_check_stop (EV_A_ w);
…		…
1793		2074
1794	ev_check check;	2075	ev_check check;
1795	ev_check_init (&check, check_cb);	2076	ev_check_init (&check, check_cb);
1796	ev_check_start (EV_DEFAULT_ &check);	2077	ev_check_start (EV_DEFAULT_ &check);
1797	ev_loop (EV_DEFAULT_ 0);	2078	ev_loop (EV_DEFAULT_ 0);
1798
1799		2079
1800	=head1 EMBEDDING	2080	=head1 EMBEDDING
1801		2081
1802	Libev can (and often is) directly embedded into host	2082	Libev can (and often is) directly embedded into host
1803	applications. Examples of applications that embed it include the Deliantra	2083	applications. Examples of applications that embed it include the Deliantra
…		…
1843	ev_vars.h	2123	ev_vars.h
1844	ev_wrap.h	2124	ev_wrap.h
1845		2125
1846	ev_win32.c required on win32 platforms only	2126	ev_win32.c required on win32 platforms only
1847		2127
1848	ev_select.c only when select backend is enabled (which is by default)	2128	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)	2129	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)	2130	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)	2131	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)	2132	ev_port.c only when the solaris port backend is enabled (disabled by default)
1853		2133
…		…
1978		2258
1979	=item EV_USE_DEVPOLL	2259	=item EV_USE_DEVPOLL
1980		2260
1981	reserved for future expansion, works like the USE symbols above.	2261	reserved for future expansion, works like the USE symbols above.
1982		2262
		2263	=item EV_USE_INOTIFY
		2264
		2265	If defined to be C<1>, libev will compile in support for the Linux inotify
		2266	interface to speed up C<ev_stat> watchers. Its actual availability will
		2267	be detected at runtime.
		2268
1983	=item EV_H	2269	=item EV_H
1984		2270
1985	The name of the F<ev.h> header file used to include it. The default if	2271	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	2272	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.	2273	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	2296	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	2297	additional independent event loops. Otherwise there will be no support
2012	for multiple event loops and there is no first event loop pointer	2298	for multiple event loops and there is no first event loop pointer
2013	argument. Instead, all functions act on the single default loop.	2299	argument. Instead, all functions act on the single default loop.
2014		2300
		2301	=item EV_MINPRI
		2302
		2303	=item EV_MAXPRI
		2304
		2305	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2306	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2307	provide for more priorities by overriding those symbols (usually defined
		2308	to be C<-2> and C<2>, respectively).
		2309
		2310	When doing priority-based operations, libev usually has to linearly search
		2311	all the priorities, so having many of them (hundreds) uses a lot of space
		2312	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2313	fine.
		2314
		2315	If your embedding app does not need any priorities, defining these both to
		2316	C<0> will save some memory and cpu.
		2317
2015	=item EV_PERIODIC_ENABLE	2318	=item EV_PERIODIC_ENABLE
2016		2319
2017	If undefined or defined to be C<1>, then periodic timers are supported. If	2320	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	2321	defined to be C<0>, then they are not. Disabling them saves a few kB of
2019	code.	2322	code.
2020		2323
		2324	=item EV_IDLE_ENABLE
		2325
		2326	If undefined or defined to be C<1>, then idle watchers are supported. If
		2327	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2328	code.
		2329
2021	=item EV_EMBED_ENABLE	2330	=item EV_EMBED_ENABLE
2022		2331
2023	If undefined or defined to be C<1>, then embed watchers are supported. If	2332	If undefined or defined to be C<1>, then embed watchers are supported. If
2024	defined to be C<0>, then they are not.	2333	defined to be C<0>, then they are not.
2025		2334
…		…
2042	=item EV_PID_HASHSIZE	2351	=item EV_PID_HASHSIZE
2043		2352
2044	C<ev_child> watchers use a small hash table to distribute workload by	2353	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	2354	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	2355	than enough. If you need to manage thousands of children you might want to
2047	increase this value.	2356	increase this value (I<must> be a power of two).
		2357
		2358	=item EV_INOTIFY_HASHSIZE
		2359
		2360	C<ev_staz> watchers use a small hash table to distribute workload by
		2361	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2362	usually more than enough. If you need to manage thousands of C<ev_stat>
		2363	watchers you might want to increase this value (I<must> be a power of
		2364	two).
2048		2365
2049	=item EV_COMMON	2366	=item EV_COMMON
2050		2367
2051	By default, all watchers have a C<void *data> member. By redefining	2368	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	2369	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	2398	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	2399	will be compiled. It is pretty complex because it provides its own header
2083	file.	2400	file.
2084		2401
2085	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2402	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:	2403	that everybody includes and which overrides some configure choices:
2087		2404
		2405	#define EV_MINIMAL 1
2088	#define EV_USE_POLL 0	2406	#define EV_USE_POLL 0
2089	#define EV_MULTIPLICITY 0	2407	#define EV_MULTIPLICITY 0
2090	#define EV_PERIODICS 0	2408	#define EV_PERIODIC_ENABLE 0
		2409	#define EV_STAT_ENABLE 0
		2410	#define EV_FORK_ENABLE 0
2091	#define EV_CONFIG_H <config.h>	2411	#define EV_CONFIG_H <config.h>
		2412	#define EV_MINPRI 0
		2413	#define EV_MAXPRI 0
2092		2414
2093	#include "ev++.h"	2415	#include "ev++.h"
2094		2416
2095	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2417	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2096		2418
…		…
2102		2424
2103	In this section the complexities of (many of) the algorithms used inside	2425	In this section the complexities of (many of) the algorithms used inside
2104	libev will be explained. For complexity discussions about backends see the	2426	libev will be explained. For complexity discussions about backends see the
2105	documentation for C<ev_default_init>.	2427	documentation for C<ev_default_init>.
2106		2428
		2429	All of the following are about amortised time: If an array needs to be
		2430	extended, libev needs to realloc and move the whole array, but this
		2431	happens asymptotically never with higher number of elements, so O(1) might
		2432	mean it might do a lengthy realloc operation in rare cases, but on average
		2433	it is much faster and asymptotically approaches constant time.
		2434
2107	=over 4	2435	=over 4
2108		2436
2109	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2437	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2110		2438
		2439	This means that, when you have a watcher that triggers in one hour and
		2440	there are 100 watchers that would trigger before that then inserting will
		2441	have to skip those 100 watchers.
		2442
2111	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2443	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2112		2444
		2445	That means that for changing a timer costs less than removing/adding them
		2446	as only the relative motion in the event queue has to be paid for.
		2447
2113	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2448	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2114		2449
		2450	These just add the watcher into an array or at the head of a list.
2115	=item Stopping check/prepare/idle watchers: O(1)	2451	=item Stopping check/prepare/idle watchers: O(1)
2116		2452
2117	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2453	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2454
		2455	These watchers are stored in lists then need to be walked to find the
		2456	correct watcher to remove. The lists are usually short (you don't usually
		2457	have many watchers waiting for the same fd or signal).
2118		2458
2119	=item Finding the next timer per loop iteration: O(1)	2459	=item Finding the next timer per loop iteration: O(1)
2120		2460
2121	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2461	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2122		2462
		2463	A change means an I/O watcher gets started or stopped, which requires
		2464	libev to recalculate its status (and possibly tell the kernel).
		2465
2123	=item Activating one watcher: O(1)	2466	=item Activating one watcher: O(1)
2124		2467
		2468	=item Priority handling: O(number_of_priorities)
		2469
		2470	Priorities are implemented by allocating some space for each
		2471	priority. When doing priority-based operations, libev usually has to
		2472	linearly search all the priorities.
		2473
2125	=back	2474	=back
2126		2475
2127		2476
2128	=head1 AUTHOR	2477	=head1 AUTHOR
2129		2478

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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 1.80 by root, Sun Dec 9 19:47:30 2007 UTC

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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 1.80 by root, Sun Dec 9 19:47:30 2007 UTC