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

Comparing libev/ev.pod (file contents):
Revision 1.58 by root, Wed Nov 28 11:31:34 2007 UTC vs.
Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC

…		…
47		47
48	return 0;	48	return 0;
49	}	49	}
50		50
51	=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>.
52		56
53	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
54	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
55	these event sources and provide your program with events.	59	these event sources and provide your program with events.
56		60
…		…
163	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	167	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
164	recommended ones.	168	recommended ones.
165		169
166	See the description of C<ev_embed> watchers for more info.	170	See the description of C<ev_embed> watchers for more info.
167		171
168	=item ev_set_allocator (void (cb)(void *ptr, size_t size))	172	=item ev_set_allocator (void (cb)(void *ptr, long size))
169		173
170	Sets the allocation function to use (the prototype and semantics are	174	Sets the allocation function to use (the prototype is similar - the
171	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
172	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
173	allocated, the library might abort or take some potentially destructive	177	memory needs to be allocated, the library might abort or take some
174	action. The default is your system realloc function.	178	potentially destructive action. The default is your system realloc
		179	function.
175		180
176	You could override this function in high-availability programs to, say,	181	You could override this function in high-availability programs to, say,
177	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,
178	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.
179		184
…		…
265	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
266	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
267	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
268	around bugs.	273	around bugs.
269		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
270	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
271		296
272	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
273	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,
274	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
…		…
409		434
410	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
411	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
412	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.
413		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.
		448
414	=item unsigned int ev_backend (loop)	449	=item unsigned int ev_backend (loop)
415		450
416	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
417	use.	452	use.
418		453
…		…
451	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
452	usually a better approach for this kind of thing.	487	usually a better approach for this kind of thing.
453		488
454	Here are the gory details of what C<ev_loop> does:	489	Here are the gory details of what C<ev_loop> does:
455		490
		491	- Before the first iteration, call any pending watchers.
456	* If there are no active watchers (reference count is zero), return.	492	* If there are no active watchers (reference count is zero), return.
457	- Queue prepare watchers and then call all outstanding watchers.	493	- Queue all prepare watchers and then call all outstanding watchers.
458	- If we have been forked, recreate the kernel state.	494	- If we have been forked, recreate the kernel state.
459	- Update the kernel state with all outstanding changes.	495	- Update the kernel state with all outstanding changes.
460	- Update the "event loop time".	496	- Update the "event loop time".
461	- Calculate for how long to block.	497	- Calculate for how long to block.
462	- Block the process, waiting for any events.	498	- Block the process, waiting for any events.
…		…
701	=item bool ev_is_pending (ev_TYPE *watcher)	737	=item bool ev_is_pending (ev_TYPE *watcher)
702		738
703	Returns a true value iff the watcher is pending, (i.e. it has outstanding	739	Returns a true value iff the watcher is pending, (i.e. it has outstanding
704	events but its callback has not yet been invoked). As long as a watcher	740	events but its callback has not yet been invoked). As long as a watcher
705	is pending (but not active) you must not call an init function on it (but	741	is pending (but not active) you must not call an init function on it (but
706	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	742	C<ev_TYPE_set> is safe), you must not change its priority, and you must
707	libev (e.g. you cnanot C<free ()> it).	743	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		744	it).
708		745
709	=item callback ev_cb (ev_TYPE *watcher)	746	=item callback ev_cb (ev_TYPE *watcher)
710		747
711	Returns the callback currently set on the watcher.	748	Returns the callback currently set on the watcher.
712		749
713	=item ev_cb_set (ev_TYPE *watcher, callback)	750	=item ev_cb_set (ev_TYPE *watcher, callback)
714		751
715	Change the callback. You can change the callback at virtually any time	752	Change the callback. You can change the callback at virtually any time
716	(modulo threads).	753	(modulo threads).
		754
		755	=item ev_set_priority (ev_TYPE *watcher, priority)
		756
		757	=item int ev_priority (ev_TYPE *watcher)
		758
		759	Set and query the priority of the watcher. The priority is a small
		760	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		761	(default: C<-2>). Pending watchers with higher priority will be invoked
		762	before watchers with lower priority, but priority will not keep watchers
		763	from being executed (except for C<ev_idle> watchers).
		764
		765	This means that priorities are I<only> used for ordering callback
		766	invocation after new events have been received. This is useful, for
		767	example, to reduce latency after idling, or more often, to bind two
		768	watchers on the same event and make sure one is called first.
		769
		770	If you need to suppress invocation when higher priority events are pending
		771	you need to look at C<ev_idle> watchers, which provide this functionality.
		772
		773	You I<must not> change the priority of a watcher as long as it is active or
		774	pending.
		775
		776	The default priority used by watchers when no priority has been set is
		777	always C<0>, which is supposed to not be too high and not be too low :).
		778
		779	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		780	fine, as long as you do not mind that the priority value you query might
		781	or might not have been adjusted to be within valid range.
		782
		783	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		784
		785	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		786	C<loop> nor C<revents> need to be valid as long as the watcher callback
		787	can deal with that fact.
		788
		789	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		790
		791	If the watcher is pending, this function returns clears its pending status
		792	and returns its C<revents> bitset (as if its callback was invoked). If the
		793	watcher isn't pending it does nothing and returns C<0>.
717		794
718	=back	795	=back
719		796
720		797
721	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	798	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
827	it is best to always use non-blocking I/O: An extra C<read>(2) returning	904	it is best to always use non-blocking I/O: An extra C<read>(2) returning
828	C<EAGAIN> is far preferable to a program hanging until some data arrives.	905	C<EAGAIN> is far preferable to a program hanging until some data arrives.
829		906
830	If you cannot run the fd in non-blocking mode (for example you should not	907	If you cannot run the fd in non-blocking mode (for example you should not
831	play around with an Xlib connection), then you have to seperately re-test	908	play around with an Xlib connection), then you have to seperately re-test
832	wether a file descriptor is really ready with a known-to-be good interface	909	whether a file descriptor is really ready with a known-to-be good interface
833	such as poll (fortunately in our Xlib example, Xlib already does this on	910	such as poll (fortunately in our Xlib example, Xlib already does this on
834	its own, so its quite safe to use).	911	its own, so its quite safe to use).
835		912
836	=over 4	913	=over 4
837		914
…		…
915	=item ev_timer_again (loop)	992	=item ev_timer_again (loop)
916		993
917	This will act as if the timer timed out and restart it again if it is	994	This will act as if the timer timed out and restart it again if it is
918	repeating. The exact semantics are:	995	repeating. The exact semantics are:
919		996
		997	If the timer is pending, its pending status is cleared.
		998
920	If the timer is started but nonrepeating, stop it.	999	If the timer is started but nonrepeating, stop it (as if it timed out).
921		1000
922	If the timer is repeating, either start it if necessary (with the repeat	1001	If the timer is repeating, either start it if necessary (with the
923	value), or reset the running timer to the repeat value.	1002	C<repeat> value), or reset the running timer to the C<repeat> value.
924		1003
925	This sounds a bit complicated, but here is a useful and typical	1004	This sounds a bit complicated, but here is a useful and typical
926	example: Imagine you have a tcp connection and you want a so-called	1005	example: Imagine you have a tcp connection and you want a so-called idle
927	idle timeout, that is, you want to be called when there have been,	1006	timeout, that is, you want to be called when there have been, say, 60
928	say, 60 seconds of inactivity on the socket. The easiest way to do	1007	seconds of inactivity on the socket. The easiest way to do this is to
929	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1008	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
930	C<ev_timer_again> each time you successfully read or write some data. If	1009	C<ev_timer_again> each time you successfully read or write some data. If
931	you go into an idle state where you do not expect data to travel on the	1010	you go into an idle state where you do not expect data to travel on the
932	socket, you can stop the timer, and again will automatically restart it if	1011	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
933	need be.	1012	automatically restart it if need be.
934		1013
935	You can also ignore the C<after> value and C<ev_timer_start> altogether	1014	That means you can ignore the C<after> value and C<ev_timer_start>
936	and only ever use the C<repeat> value:	1015	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
937		1016
938	ev_timer_init (timer, callback, 0., 5.);	1017	ev_timer_init (timer, callback, 0., 5.);
939	ev_timer_again (loop, timer);	1018	ev_timer_again (loop, timer);
940	...	1019	...
941	timer->again = 17.;	1020	timer->again = 17.;
942	ev_timer_again (loop, timer);	1021	ev_timer_again (loop, timer);
943	...	1022	...
944	timer->again = 10.;	1023	timer->again = 10.;
945	ev_timer_again (loop, timer);	1024	ev_timer_again (loop, timer);
946		1025
947	This is more efficient then stopping/starting the timer eahc time you want	1026	This is more slightly efficient then stopping/starting the timer each time
948	to modify its timeout value.	1027	you want to modify its timeout value.
949		1028
950	=item ev_tstamp repeat [read-write]	1029	=item ev_tstamp repeat [read-write]
951		1030
952	The current C<repeat> value. Will be used each time the watcher times out	1031	The current C<repeat> value. Will be used each time the watcher times out
953	or C<ev_timer_again> is called and determines the next timeout (if any),	1032	or C<ev_timer_again> is called and determines the next timeout (if any),
…		…
1221	The path does not need to exist: changing from "path exists" to "path does	1300	The path does not need to exist: changing from "path exists" to "path does
1222	not exist" is a status change like any other. The condition "path does	1301	not exist" is a status change like any other. The condition "path does
1223	not exist" is signified by the C<st_nlink> field being zero (which is	1302	not exist" is signified by the C<st_nlink> field being zero (which is
1224	otherwise always forced to be at least one) and all the other fields of	1303	otherwise always forced to be at least one) and all the other fields of
1225	the stat buffer having unspecified contents.	1304	the stat buffer having unspecified contents.
		1305
		1306	The path I<should> be absolute and I<must not> end in a slash. If it is
		1307	relative and your working directory changes, the behaviour is undefined.
1226		1308
1227	Since there is no standard to do this, the portable implementation simply	1309	Since there is no standard to do this, the portable implementation simply
1228	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1310	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1229	can specify a recommended polling interval for this case. If you specify	1311	can specify a recommended polling interval for this case. If you specify
1230	a polling interval of C<0> (highly recommended!) then a I<suitable,	1312	a polling interval of C<0> (highly recommended!) then a I<suitable,
…		…
1315	ev_stat_start (loop, &passwd);	1397	ev_stat_start (loop, &passwd);
1316		1398
1317		1399
1318	=head2 C<ev_idle> - when you've got nothing better to do...	1400	=head2 C<ev_idle> - when you've got nothing better to do...
1319		1401
1320	Idle watchers trigger events when there are no other events are pending	1402	Idle watchers trigger events when no other events of the same or higher
1321	(prepare, check and other idle watchers do not count). That is, as long	1403	priority are pending (prepare, check and other idle watchers do not
1322	as your process is busy handling sockets or timeouts (or even signals,	1404	count).
1323	imagine) it will not be triggered. But when your process is idle all idle	1405
1324	watchers are being called again and again, once per event loop iteration -	1406	That is, as long as your process is busy handling sockets or timeouts
		1407	(or even signals, imagine) of the same or higher priority it will not be
		1408	triggered. But when your process is idle (or only lower-priority watchers
		1409	are pending), the idle watchers are being called once per event loop
1325	until stopped, that is, or your process receives more events and becomes	1410	iteration - until stopped, that is, or your process receives more events
1326	busy.	1411	and becomes busy again with higher priority stuff.
1327		1412
1328	The most noteworthy effect is that as long as any idle watchers are	1413	The most noteworthy effect is that as long as any idle watchers are
1329	active, the process will not block when waiting for new events.	1414	active, the process will not block when waiting for new events.
1330		1415
1331	Apart from keeping your process non-blocking (which is a useful	1416	Apart from keeping your process non-blocking (which is a useful
…		…
1397	with priority higher than or equal to the event loop and one coroutine	1482	with priority higher than or equal to the event loop and one coroutine
1398	of lower priority, but only once, using idle watchers to keep the event	1483	of lower priority, but only once, using idle watchers to keep the event
1399	loop from blocking if lower-priority coroutines are active, thus mapping	1484	loop from blocking if lower-priority coroutines are active, thus mapping
1400	low-priority coroutines to idle/background tasks).	1485	low-priority coroutines to idle/background tasks).
1401		1486
		1487	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1488	priority, to ensure that they are being run before any other watchers
		1489	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1490	too) should not activate ("feed") events into libev. While libev fully
		1491	supports this, they will be called before other C<ev_check> watchers did
		1492	their job. As C<ev_check> watchers are often used to embed other event
		1493	loops those other event loops might be in an unusable state until their
		1494	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1495	others).
		1496
1402	=over 4	1497	=over 4
1403		1498
1404	=item ev_prepare_init (ev_prepare *, callback)	1499	=item ev_prepare_init (ev_prepare *, callback)
1405		1500
1406	=item ev_check_init (ev_check *, callback)	1501	=item ev_check_init (ev_check *, callback)
…		…
1409	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1504	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1410	macros, but using them is utterly, utterly and completely pointless.	1505	macros, but using them is utterly, utterly and completely pointless.
1411		1506
1412	=back	1507	=back
1413		1508
1414	Example: To include a library such as adns, you would add IO watchers	1509	There are a number of principal ways to embed other event loops or modules
1415	and a timeout watcher in a prepare handler, as required by libadns, and	1510	into libev. Here are some ideas on how to include libadns into libev
		1511	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1512	use for an actually working example. Another Perl module named C<EV::Glib>
		1513	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1514	into the Glib event loop).
		1515
		1516	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1416	in a check watcher, destroy them and call into libadns. What follows is	1517	and in a check watcher, destroy them and call into libadns. What follows
1417	pseudo-code only of course:	1518	is pseudo-code only of course. This requires you to either use a low
		1519	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1520	the callbacks for the IO/timeout watchers might not have been called yet.
1418		1521
1419	static ev_io iow [nfd];	1522	static ev_io iow [nfd];
1420	static ev_timer tw;	1523	static ev_timer tw;
1421		1524
1422	static void	1525	static void
1423	io_cb (ev_loop loop, ev_io w, int revents)	1526	io_cb (ev_loop loop, ev_io w, int revents)
1424	{	1527	{
1425	// set the relevant poll flags
1426	// could also call adns_processreadable etc. here
1427	struct pollfd fd = (struct pollfd )w->data;
1428	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1429	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1430	}	1528	}
1431		1529
1432	// create io watchers for each fd and a timer before blocking	1530	// create io watchers for each fd and a timer before blocking
1433	static void	1531	static void
1434	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1532	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1435	{	1533	{
1436	int timeout = 3600000;truct pollfd fds [nfd];	1534	int timeout = 3600000;
		1535	struct pollfd fds [nfd];
1437	// actual code will need to loop here and realloc etc.	1536	// actual code will need to loop here and realloc etc.
1438	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1537	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1439		1538
1440	/* the callback is illegal, but won't be called as we stop during check */	1539	/* the callback is illegal, but won't be called as we stop during check */
1441	ev_timer_init (&tw, 0, timeout * 1e-3);	1540	ev_timer_init (&tw, 0, timeout * 1e-3);
1442	ev_timer_start (loop, &tw);	1541	ev_timer_start (loop, &tw);
1443		1542
1444	// create on ev_io per pollfd	1543	// create one ev_io per pollfd
1445	for (int i = 0; i < nfd; ++i)	1544	for (int i = 0; i < nfd; ++i)
1446	{	1545	{
1447	ev_io_init (iow + i, io_cb, fds [i].fd,	1546	ev_io_init (iow + i, io_cb, fds [i].fd,
1448	((fds [i].events & POLLIN ? EV_READ : 0)	1547	((fds [i].events & POLLIN ? EV_READ : 0)
1449	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1548	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1450		1549
1451	fds [i].revents = 0;	1550	fds [i].revents = 0;
1452	iow [i].data = fds + i;
1453	ev_io_start (loop, iow + i);	1551	ev_io_start (loop, iow + i);
1454	}	1552	}
1455	}	1553	}
1456		1554
1457	// stop all watchers after blocking	1555	// stop all watchers after blocking
…		…
1459	adns_check_cb (ev_loop loop, ev_check w, int revents)	1557	adns_check_cb (ev_loop loop, ev_check w, int revents)
1460	{	1558	{
1461	ev_timer_stop (loop, &tw);	1559	ev_timer_stop (loop, &tw);
1462		1560
1463	for (int i = 0; i < nfd; ++i)	1561	for (int i = 0; i < nfd; ++i)
		1562	{
		1563	// set the relevant poll flags
		1564	// could also call adns_processreadable etc. here
		1565	struct pollfd *fd = fds + i;
		1566	int revents = ev_clear_pending (iow + i);
		1567	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1568	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1569
		1570	// now stop the watcher
1464	ev_io_stop (loop, iow + i);	1571	ev_io_stop (loop, iow + i);
		1572	}
1465		1573
1466	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1574	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1575	}
		1576
		1577	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1578	in the prepare watcher and would dispose of the check watcher.
		1579
		1580	Method 3: If the module to be embedded supports explicit event
		1581	notification (adns does), you can also make use of the actual watcher
		1582	callbacks, and only destroy/create the watchers in the prepare watcher.
		1583
		1584	static void
		1585	timer_cb (EV_P_ ev_timer *w, int revents)
		1586	{
		1587	adns_state ads = (adns_state)w->data;
		1588	update_now (EV_A);
		1589
		1590	adns_processtimeouts (ads, &tv_now);
		1591	}
		1592
		1593	static void
		1594	io_cb (EV_P_ ev_io *w, int revents)
		1595	{
		1596	adns_state ads = (adns_state)w->data;
		1597	update_now (EV_A);
		1598
		1599	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1600	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1601	}
		1602
		1603	// do not ever call adns_afterpoll
		1604
		1605	Method 4: Do not use a prepare or check watcher because the module you
		1606	want to embed is too inflexible to support it. Instead, youc na override
		1607	their poll function. The drawback with this solution is that the main
		1608	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1609	this.
		1610
		1611	static gint
		1612	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1613	{
		1614	int got_events = 0;
		1615
		1616	for (n = 0; n < nfds; ++n)
		1617	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1618
		1619	if (timeout >= 0)
		1620	// create/start timer
		1621
		1622	// poll
		1623	ev_loop (EV_A_ 0);
		1624
		1625	// stop timer again
		1626	if (timeout >= 0)
		1627	ev_timer_stop (EV_A_ &to);
		1628
		1629	// stop io watchers again - their callbacks should have set
		1630	for (n = 0; n < nfds; ++n)
		1631	ev_io_stop (EV_A_ iow [n]);
		1632
		1633	return got_events;
1467	}	1634	}
1468		1635
1469		1636
1470	=head2 C<ev_embed> - when one backend isn't enough...	1637	=head2 C<ev_embed> - when one backend isn't enough...
1471		1638
…		…
1675		1842
1676	To use it,	1843	To use it,
1677		1844
1678	#include <ev++.h>	1845	#include <ev++.h>
1679		1846
1680	(it is not installed by default). This automatically includes F<ev.h>	1847	This automatically includes F<ev.h> and puts all of its definitions (many
1681	and puts all of its definitions (many of them macros) into the global	1848	of them macros) into the global namespace. All C++ specific things are
1682	namespace. All C++ specific things are put into the C<ev> namespace.	1849	put into the C<ev> namespace. It should support all the same embedding
		1850	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1683		1851
1684	It should support all the same embedding options as F<ev.h>, most notably	1852	Care has been taken to keep the overhead low. The only data member the C++
1685	C<EV_MULTIPLICITY>.	1853	classes add (compared to plain C-style watchers) is the event loop pointer
		1854	that the watcher is associated with (or no additional members at all if
		1855	you disable C<EV_MULTIPLICITY> when embedding libev).
		1856
		1857	Currently, functions, and static and non-static member functions can be
		1858	used as callbacks. Other types should be easy to add as long as they only
		1859	need one additional pointer for context. If you need support for other
		1860	types of functors please contact the author (preferably after implementing
		1861	it).
1686		1862
1687	Here is a list of things available in the C<ev> namespace:	1863	Here is a list of things available in the C<ev> namespace:
1688		1864
1689	=over 4	1865	=over 4
1690		1866
…		…
1706		1882
1707	All of those classes have these methods:	1883	All of those classes have these methods:
1708		1884
1709	=over 4	1885	=over 4
1710		1886
1711	=item ev::TYPE::TYPE (object , object::method )	1887	=item ev::TYPE::TYPE ()
1712		1888
1713	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1889	=item ev::TYPE::TYPE (struct ev_loop *)
1714		1890
1715	=item ev::TYPE::~TYPE	1891	=item ev::TYPE::~TYPE
1716		1892
1717	The constructor takes a pointer to an object and a method pointer to	1893	The constructor (optionally) takes an event loop to associate the watcher
1718	the event handler callback to call in this class. The constructor calls	1894	with. If it is omitted, it will use C<EV_DEFAULT>.
1719	C<ev_init> for you, which means you have to call the C<set> method	1895
1720	before starting it. If you do not specify a loop then the constructor	1896	The constructor calls C<ev_init> for you, which means you have to call the
1721	automatically associates the default loop with this watcher.	1897	C<set> method before starting it.
		1898
		1899	It will not set a callback, however: You have to call the templated C<set>
		1900	method to set a callback before you can start the watcher.
		1901
		1902	(The reason why you have to use a method is a limitation in C++ which does
		1903	not allow explicit template arguments for constructors).
1722		1904
1723	The destructor automatically stops the watcher if it is active.	1905	The destructor automatically stops the watcher if it is active.
		1906
		1907	=item w->set<class, &class::method> (object *)
		1908
		1909	This method sets the callback method to call. The method has to have a
		1910	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1911	first argument and the C<revents> as second. The object must be given as
		1912	parameter and is stored in the C<data> member of the watcher.
		1913
		1914	This method synthesizes efficient thunking code to call your method from
		1915	the C callback that libev requires. If your compiler can inline your
		1916	callback (i.e. it is visible to it at the place of the C<set> call and
		1917	your compiler is good :), then the method will be fully inlined into the
		1918	thunking function, making it as fast as a direct C callback.
		1919
		1920	Example: simple class declaration and watcher initialisation
		1921
		1922	struct myclass
		1923	{
		1924	void io_cb (ev::io &w, int revents) { }
		1925	}
		1926
		1927	myclass obj;
		1928	ev::io iow;
		1929	iow.set <myclass, &myclass::io_cb> (&obj);
		1930
		1931	=item w->set<function> (void *data = 0)
		1932
		1933	Also sets a callback, but uses a static method or plain function as
		1934	callback. The optional C<data> argument will be stored in the watcher's
		1935	C<data> member and is free for you to use.
		1936
		1937	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1938
		1939	See the method-C<set> above for more details.
		1940
		1941	Example:
		1942
		1943	static void io_cb (ev::io &w, int revents) { }
		1944	iow.set <io_cb> ();
1724		1945
1725	=item w->set (struct ev_loop *)	1946	=item w->set (struct ev_loop *)
1726		1947
1727	Associates a different C<struct ev_loop> with this watcher. You can only	1948	Associates a different C<struct ev_loop> with this watcher. You can only
1728	do this when the watcher is inactive (and not pending either).	1949	do this when the watcher is inactive (and not pending either).
1729		1950
1730	=item w->set ([args])	1951	=item w->set ([args])
1731		1952
1732	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1953	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1733	called at least once. Unlike the C counterpart, an active watcher gets	1954	called at least once. Unlike the C counterpart, an active watcher gets
1734	automatically stopped and restarted.	1955	automatically stopped and restarted when reconfiguring it with this
		1956	method.
1735		1957
1736	=item w->start ()	1958	=item w->start ()
1737		1959
1738	Starts the watcher. Note that there is no C<loop> argument as the	1960	Starts the watcher. Note that there is no C<loop> argument, as the
1739	constructor already takes the loop.	1961	constructor already stores the event loop.
1740		1962
1741	=item w->stop ()	1963	=item w->stop ()
1742		1964
1743	Stops the watcher if it is active. Again, no C<loop> argument.	1965	Stops the watcher if it is active. Again, no C<loop> argument.
1744		1966
…		…
1769		1991
1770	myclass ();	1992	myclass ();
1771	}	1993	}
1772		1994
1773	myclass::myclass (int fd)	1995	myclass::myclass (int fd)
1774	: io (this, &myclass::io_cb),
1775	idle (this, &myclass::idle_cb)
1776	{	1996	{
		1997	io .set <myclass, &myclass::io_cb > (this);
		1998	idle.set <myclass, &myclass::idle_cb> (this);
		1999
1777	io.start (fd, ev::READ);	2000	io.start (fd, ev::READ);
1778	}	2001	}
1779		2002
1780		2003
1781	=head1 MACRO MAGIC	2004	=head1 MACRO MAGIC
1782		2005
1783	Libev can be compiled with a variety of options, the most fundemantal is	2006	Libev can be compiled with a variety of options, the most fundemantal is
1784	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2007	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1785	callbacks have an initial C<struct ev_loop *> argument.	2008	callbacks have an initial C<struct ev_loop *> argument.
1786		2009
1787	To make it easier to write programs that cope with either variant, the	2010	To make it easier to write programs that cope with either variant, the
1788	following macros are defined:	2011	following macros are defined:
1789		2012
…		…
1822	Similar to the other two macros, this gives you the value of the default	2045	Similar to the other two macros, this gives you the value of the default
1823	loop, if multiple loops are supported ("ev loop default").	2046	loop, if multiple loops are supported ("ev loop default").
1824		2047
1825	=back	2048	=back
1826		2049
1827	Example: Declare and initialise a check watcher, working regardless of	2050	Example: Declare and initialise a check watcher, utilising the above
1828	wether multiple loops are supported or not.	2051	macros so it will work regardless of whether multiple loops are supported
		2052	or not.
1829		2053
1830	static void	2054	static void
1831	check_cb (EV_P_ ev_timer *w, int revents)	2055	check_cb (EV_P_ ev_timer *w, int revents)
1832	{	2056	{
1833	ev_check_stop (EV_A_ w);	2057	ev_check_stop (EV_A_ w);
…		…
1835		2059
1836	ev_check check;	2060	ev_check check;
1837	ev_check_init (&check, check_cb);	2061	ev_check_init (&check, check_cb);
1838	ev_check_start (EV_DEFAULT_ &check);	2062	ev_check_start (EV_DEFAULT_ &check);
1839	ev_loop (EV_DEFAULT_ 0);	2063	ev_loop (EV_DEFAULT_ 0);
1840
1841		2064
1842	=head1 EMBEDDING	2065	=head1 EMBEDDING
1843		2066
1844	Libev can (and often is) directly embedded into host	2067	Libev can (and often is) directly embedded into host
1845	applications. Examples of applications that embed it include the Deliantra	2068	applications. Examples of applications that embed it include the Deliantra
…		…
1885	ev_vars.h	2108	ev_vars.h
1886	ev_wrap.h	2109	ev_wrap.h
1887		2110
1888	ev_win32.c required on win32 platforms only	2111	ev_win32.c required on win32 platforms only
1889		2112
1890	ev_select.c only when select backend is enabled (which is by default)	2113	ev_select.c only when select backend is enabled (which is enabled by default)
1891	ev_poll.c only when poll backend is enabled (disabled by default)	2114	ev_poll.c only when poll backend is enabled (disabled by default)
1892	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2115	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1893	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2116	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1894	ev_port.c only when the solaris port backend is enabled (disabled by default)	2117	ev_port.c only when the solaris port backend is enabled (disabled by default)
1895		2118
…		…
2058	will have the C<struct ev_loop *> as first argument, and you can create	2281	will have the C<struct ev_loop *> as first argument, and you can create
2059	additional independent event loops. Otherwise there will be no support	2282	additional independent event loops. Otherwise there will be no support
2060	for multiple event loops and there is no first event loop pointer	2283	for multiple event loops and there is no first event loop pointer
2061	argument. Instead, all functions act on the single default loop.	2284	argument. Instead, all functions act on the single default loop.
2062		2285
		2286	=item EV_MINPRI
		2287
		2288	=item EV_MAXPRI
		2289
		2290	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2291	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2292	provide for more priorities by overriding those symbols (usually defined
		2293	to be C<-2> and C<2>, respectively).
		2294
		2295	When doing priority-based operations, libev usually has to linearly search
		2296	all the priorities, so having many of them (hundreds) uses a lot of space
		2297	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2298	fine.
		2299
		2300	If your embedding app does not need any priorities, defining these both to
		2301	C<0> will save some memory and cpu.
		2302
2063	=item EV_PERIODIC_ENABLE	2303	=item EV_PERIODIC_ENABLE
2064		2304
2065	If undefined or defined to be C<1>, then periodic timers are supported. If	2305	If undefined or defined to be C<1>, then periodic timers are supported. If
		2306	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2307	code.
		2308
		2309	=item EV_IDLE_ENABLE
		2310
		2311	If undefined or defined to be C<1>, then idle watchers are supported. If
2066	defined to be C<0>, then they are not. Disabling them saves a few kB of	2312	defined to be C<0>, then they are not. Disabling them saves a few kB of
2067	code.	2313	code.
2068		2314
2069	=item EV_EMBED_ENABLE	2315	=item EV_EMBED_ENABLE
2070		2316
…		…
2137	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2383	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2138	will be compiled. It is pretty complex because it provides its own header	2384	will be compiled. It is pretty complex because it provides its own header
2139	file.	2385	file.
2140		2386
2141	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2387	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2142	that everybody includes and which overrides some autoconf choices:	2388	that everybody includes and which overrides some configure choices:
2143		2389
		2390	#define EV_MINIMAL 1
2144	#define EV_USE_POLL 0	2391	#define EV_USE_POLL 0
2145	#define EV_MULTIPLICITY 0	2392	#define EV_MULTIPLICITY 0
2146	#define EV_PERIODICS 0	2393	#define EV_PERIODIC_ENABLE 0
		2394	#define EV_STAT_ENABLE 0
		2395	#define EV_FORK_ENABLE 0
2147	#define EV_CONFIG_H <config.h>	2396	#define EV_CONFIG_H <config.h>
		2397	#define EV_MINPRI 0
		2398	#define EV_MAXPRI 0
2148		2399
2149	#include "ev++.h"	2400	#include "ev++.h"
2150		2401
2151	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2402	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2152		2403
…		…
2158		2409
2159	In this section the complexities of (many of) the algorithms used inside	2410	In this section the complexities of (many of) the algorithms used inside
2160	libev will be explained. For complexity discussions about backends see the	2411	libev will be explained. For complexity discussions about backends see the
2161	documentation for C<ev_default_init>.	2412	documentation for C<ev_default_init>.
2162		2413
		2414	All of the following are about amortised time: If an array needs to be
		2415	extended, libev needs to realloc and move the whole array, but this
		2416	happens asymptotically never with higher number of elements, so O(1) might
		2417	mean it might do a lengthy realloc operation in rare cases, but on average
		2418	it is much faster and asymptotically approaches constant time.
		2419
2163	=over 4	2420	=over 4
2164		2421
2165	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2422	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2166		2423
		2424	This means that, when you have a watcher that triggers in one hour and
		2425	there are 100 watchers that would trigger before that then inserting will
		2426	have to skip those 100 watchers.
		2427
2167	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2428	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2168		2429
		2430	That means that for changing a timer costs less than removing/adding them
		2431	as only the relative motion in the event queue has to be paid for.
		2432
2169	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2433	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2170		2434
		2435	These just add the watcher into an array or at the head of a list.
2171	=item Stopping check/prepare/idle watchers: O(1)	2436	=item Stopping check/prepare/idle watchers: O(1)
2172		2437
2173	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2438	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2174		2439
		2440	These watchers are stored in lists then need to be walked to find the
		2441	correct watcher to remove. The lists are usually short (you don't usually
		2442	have many watchers waiting for the same fd or signal).
		2443
2175	=item Finding the next timer per loop iteration: O(1)	2444	=item Finding the next timer per loop iteration: O(1)
2176		2445
2177	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2446	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2178		2447
		2448	A change means an I/O watcher gets started or stopped, which requires
		2449	libev to recalculate its status (and possibly tell the kernel).
		2450
2179	=item Activating one watcher: O(1)	2451	=item Activating one watcher: O(1)
2180		2452
		2453	=item Priority handling: O(number_of_priorities)
		2454
		2455	Priorities are implemented by allocating some space for each
		2456	priority. When doing priority-based operations, libev usually has to
		2457	linearly search all the priorities.
		2458
2181	=back	2459	=back
2182		2460
2183		2461
2184	=head1 AUTHOR	2462	=head1 AUTHOR
2185		2463

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Comparing libev/ev.pod (file contents): Revision 1.58 by root, Wed Nov 28 11:31:34 2007 UTC vs. Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.58 by root, Wed Nov 28 11:31:34 2007 UTC vs.
Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC