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

Comparing libev/ev.pod (file contents):
Revision 1.186 by root, Wed Sep 24 07:56:14 2008 UTC vs.
Revision 1.198 by root, Thu Oct 23 06:30:48 2008 UTC

…		…
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<ev_loop *>. The library knows two
282	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
283	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
284		284
285	=over 4	285	=over 4
286		286
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		687
688	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
689		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
690	=item ev_ref (loop)	692	=item ev_ref (loop)
691		693
692	=item ev_unref (loop)	694	=item ev_unref (loop)
693		695
694	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
…		…
708	respectively).	710	respectively).
709		711
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	713	running when nothing else is active.
712		714
713	struct ev_signal exitsig;	715	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	718	evf_unref (loop);
717		719
718	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
…		…
784		786
785	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
788		790
789	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	791	static void my_cb (struct ev_loop loop, ev_io w, int revents)
790	{	792	{
791	ev_io_stop (w);	793	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
793	}	795	}
794		796
795	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
796	struct ev_io stdin_watcher;	798	ev_io stdin_watcher;
797	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
800	ev_loop (loop, 0);	802	ev_loop (loop, 0);
801		803
…		…
892	=item C<EV_ERROR>	894	=item C<EV_ERROR>
893		895
894	An unspecified error has occurred, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
897	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
899		905
900	Libev will usually signal a few "dummy" events together with an error, for	906	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	907	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	908	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	909	the error from read() or write(). This will not work in multi-threaded
…		…
923	which rolls both calls into one.	929	which rolls both calls into one.
924		930
925	You can reinitialise a watcher at any time as long as it has been stopped	931	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
927		933
928	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	934	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
929	int revents)>.	935	int revents)>.
930		936
931	Example: Initialise an C<ev_io> watcher in two steps.	937	Example: Initialise an C<ev_io> watcher in two steps.
932		938
933	ev_io w;	939	ev_io w;
…		…
967		973
968	ev_io_start (EV_DEFAULT_UC, &w);	974	ev_io_start (EV_DEFAULT_UC, &w);
969		975
970	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	976	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
971		977
972	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
973	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		986
979	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
980		988
981	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
1057	data:	1065	data:
1058		1066
1059	struct my_io	1067	struct my_io
1060	{	1068	{
1061	struct ev_io io;	1069	ev_io io;
1062	int otherfd;	1070	int otherfd;
1063	void *somedata;	1071	void *somedata;
1064	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
1065	};	1073	};
1066		1074
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1078
1071	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1080	can cast it back to your own type:
1073		1081
1074	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1082	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1075	{	1083	{
1076	struct my_io w = (struct my_io )w_;	1084	struct my_io w = (struct my_io )w_;
1077	...	1085	...
1078	}	1086	}
1079		1087
…		…
1097	programmers):	1105	programmers):
1098		1106
1099	#include <stddef.h>	1107	#include <stddef.h>
1100		1108
1101	static void	1109	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1111	{
1104	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1114	}
1107		1115
1108	static void	1116	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1118	{
1111	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1121	}
1114		1122
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
1252		1260
1253	static void	1261	static void
1254	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1262	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1255	{	1263	{
1256	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1266	}
1259		1267
1260	...	1268	...
1261	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1270	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
1266		1274
1267		1275
…		…
1278		1286
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1287	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1288	passed, but if multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1289	then order of execution is undefined.
1282		1290
		1291	=head3 Be smart about timeouts
		1292
		1293	Many real-world problems invole some kind of time-out, usually for error
		1294	recovery. A typical example is an HTTP request - if the other side hangs,
		1295	you want to raise some error after a while.
		1296
		1297	Here are some ways on how to handle this problem, from simple and
		1298	inefficient to very efficient.
		1299
		1300	In the following examples a 60 second activity timeout is assumed - a
		1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")
		1302	was received.
		1303
		1304	=over 4
		1305
		1306	=item 1. Use a timer and stop, reinitialise, start it on activity.
		1307
		1308	This is the most obvious, but not the most simple way: In the beginning,
		1309	start the watcher:
		1310
		1311	ev_timer_init (timer, callback, 60., 0.);
		1312	ev_timer_start (loop, timer);
		1313
		1314	Then, each time there is some activity, C<ev_timer_stop> the timer,
		1315	initialise it again, and start it:
		1316
		1317	ev_timer_stop (loop, timer);
		1318	ev_timer_set (timer, 60., 0.);
		1319	ev_timer_start (loop, timer);
		1320
		1321	This is relatively simple to implement, but means that each time there
		1322	is some activity, libev will first have to remove the timer from it's
		1323	internal data strcuture and then add it again.
		1324
		1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1326
		1327	This is the easiest way, and involves using C<ev_timer_again> instead of
		1328	C<ev_timer_start>.
		1329
		1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and
		1331	then call C<ev_timer_again> at start and each time you successfully read
		1332	or write some data. If you go into an idle state where you do not expect
		1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and
		1334	C<ev_timer_again> will automatically restart it if need be.
		1335
		1336	That means you can ignore the C<after> value and C<ev_timer_start>
		1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.
		1338
		1339	At start:
		1340
		1341	ev_timer_init (timer, callback, 0., 60.);
		1342	ev_timer_again (loop, timer);
		1343
		1344	Each time you receive some data:
		1345
		1346	ev_timer_again (loop, timer);
		1347
		1348	It is even possible to change the time-out on the fly:
		1349
		1350	timer->repeat = 30.;
		1351	ev_timer_again (loop, timer);
		1352
		1353	This is slightly more efficient then stopping/starting the timer each time
		1354	you want to modify its timeout value, as libev does not have to completely
		1355	remove and re-insert the timer from/into it's internal data structure.
		1356
		1357	=item 3. Let the timer time out, but then re-arm it as required.
		1358
		1359	This method is more tricky, but usually most efficient: Most timeouts are
		1360	relatively long compared to the loop iteration time - in our example,
		1361	within 60 seconds, there are usually many I/O events with associated
		1362	activity resets.
		1363
		1364	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1365	but remember the time of last activity, and check for a real timeout only
		1366	within the callback:
		1367
		1368	ev_tstamp last_activity; // time of last activity
		1369
		1370	static void
		1371	callback (EV_P_ ev_timer *w, int revents)
		1372	{
		1373	ev_tstamp now = ev_now (EV_A);
		1374	ev_tstamp timeout = last_activity + 60.;
		1375
		1376	// if last_activity is older than now - timeout, we did time out
		1377	if (timeout < now)
		1378	{
		1379	// timeout occured, take action
		1380	}
		1381	else
		1382	{
		1383	// callback was invoked, but there was some activity, re-arm
		1384	// to fire in last_activity + 60.
		1385	w->again = timeout - now;
		1386	ev_timer_again (EV_A_ w);
		1387	}
		1388	}
		1389
		1390	To summarise the callback: first calculate the real time-out (defined as
		1391	"60 seconds after the last activity"), then check if that time has been
		1392	reached, which means there was a real timeout. Otherwise the callback was
		1393	invoked too early (timeout is in the future), so re-schedule the timer to
		1394	fire at that future time.
		1395
		1396	Note how C<ev_timer_again> is used, taking advantage of the
		1397	C<ev_timer_again> optimisation when the timer is already running.
		1398
		1399	This scheme causes more callback invocations (about one every 60 seconds),
		1400	but virtually no calls to libev to change the timeout.
		1401
		1402	To start the timer, simply intiialise the watcher and C<last_activity>,
		1403	then call the callback:
		1404
		1405	ev_timer_init (timer, callback);
		1406	last_activity = ev_now (loop);
		1407	callback (loop, timer, EV_TIMEOUT);
		1408
		1409	And when there is some activity, simply remember the time in
		1410	C<last_activity>:
		1411
		1412	last_actiivty = ev_now (loop);
		1413
		1414	This technique is slightly more complex, but in most cases where the
		1415	time-out is unlikely to be triggered, much more efficient.
		1416
		1417	=back
		1418
1283	=head3 The special problem of time updates	1419	=head3 The special problem of time updates
1284		1420
1285	Establishing the current time is a costly operation (it usually takes at	1421	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1422	least two system calls): EV therefore updates its idea of the current
1287	time only before and after C<ev_loop> collects new events, which causes a	1423	time only before and after C<ev_loop> collects new events, which causes a
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1466	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1467
1332	If the timer is repeating, either start it if necessary (with the	1468	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1469	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1470
1335	This sounds a bit complicated, but here is a useful and typical	1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1472	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344
1345	That means you can ignore the C<after> value and C<ev_timer_start>
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347
1348	ev_timer_init (timer, callback, 0., 5.);
1349	ev_timer_again (loop, timer);
1350	...
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356
1357	This is more slightly efficient then stopping/starting the timer each time
1358	you want to modify its timeout value.
1359
1360	Note, however, that it is often even more efficient to remember the
1361	time of the last activity and let the timer time-out naturally. In the
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1473
1366	=item ev_tstamp repeat [read-write]	1474	=item ev_tstamp repeat [read-write]
1367		1475
1368	The current C<repeat> value. Will be used each time the watcher times out	1476	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1477	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1482	=head3 Examples
1375		1483
1376	Example: Create a timer that fires after 60 seconds.	1484	Example: Create a timer that fires after 60 seconds.
1377		1485
1378	static void	1486	static void
1379	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1487	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1380	{	1488	{
1381	.. one minute over, w is actually stopped right here	1489	.. one minute over, w is actually stopped right here
1382	}	1490	}
1383		1491
1384	struct ev_timer mytimer;	1492	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1493	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1494	ev_timer_start (loop, &mytimer);
1387		1495
1388	Example: Create a timeout timer that times out after 10 seconds of	1496	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1497	inactivity.
1390		1498
1391	static void	1499	static void
1392	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1500	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1393	{	1501	{
1394	.. ten seconds without any activity	1502	.. ten seconds without any activity
1395	}	1503	}
1396		1504
1397	struct ev_timer mytimer;	1505	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1507	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1508	ev_loop (loop, 0);
1401		1509
1402	// and in some piece of code that gets executed on any "activity":	1510	// and in some piece of code that gets executed on any "activity":
…		…
1488		1596
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1599	only event loop modification you are allowed to do).
1492		1600
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1601	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1602	*w, ev_tstamp now)>, e.g.:
1495		1603
		1604	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1605	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1606	{
1498	return now + 60.;	1607	return now + 60.;
1499	}	1608	}
1500		1609
1501	It must return the next time to trigger, based on the passed time value	1610	It must return the next time to trigger, based on the passed time value
…		…
1538		1647
1539	The current interval value. Can be modified any time, but changes only	1648	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	1649	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1650	called.
1542		1651
1543	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1652	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1544		1653
1545	The current reschedule callback, or C<0>, if this functionality is	1654	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	1655	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	1656	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1657
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1662	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1663	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1664	potentially a lot of jitter, but good long-term stability.
1556		1665
1557	static void	1666	static void
1558	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1667	clock_cb (struct ev_loop loop, ev_io w, int revents)
1559	{	1668	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1669	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1670	}
1562		1671
1563	struct ev_periodic hourly_tick;	1672	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1673	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1674	ev_periodic_start (loop, &hourly_tick);
1566		1675
1567	Example: The same as above, but use a reschedule callback to do it:	1676	Example: The same as above, but use a reschedule callback to do it:
1568		1677
1569	#include <math.h>	1678	#include <math.h>
1570		1679
1571	static ev_tstamp	1680	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1681	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1682	{
1574	return now + (3600. - fmod (now, 3600.));	1683	return now + (3600. - fmod (now, 3600.));
1575	}	1684	}
1576		1685
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1686	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1687
1579	Example: Call a callback every hour, starting now:	1688	Example: Call a callback every hour, starting now:
1580		1689
1581	struct ev_periodic hourly_tick;	1690	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1691	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1692	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1693	ev_periodic_start (loop, &hourly_tick);
1585		1694
1586		1695
…		…
1625		1734
1626	=back	1735	=back
1627		1736
1628	=head3 Examples	1737	=head3 Examples
1629		1738
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1739	Example: Try to exit cleanly on SIGINT.
1631		1740
1632	static void	1741	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1742	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1634	{	1743	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1744	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1745	}
1637		1746
1638	struct ev_signal signal_watcher;	1747	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1749	ev_signal_start (loop, &signal_watcher);
1641		1750
1642		1751
1643	=head2 C<ev_child> - watch out for process status changes	1752	=head2 C<ev_child> - watch out for process status changes
1644		1753
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1754	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1827	its completion.
1719		1828
1720	ev_child cw;	1829	ev_child cw;
1721		1830
1722	static void	1831	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1832	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1833	{
1725	ev_child_stop (EV_A_ w);	1834	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1835	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1836	}
1728		1837
…		…
1792	to exchange stat structures with application programs compiled using the	1901	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	1902	default compilation environment.
1794		1903
1795	=head3 Inotify and Kqueue	1904	=head3 Inotify and Kqueue
1796		1905
1797	When C<inotify (7)> support has been compiled into libev (generally only	1906	When C<inotify (7)> support has been compiled into libev (generally
		1907	only available with Linux 2.6.25 or above due to bugs in earlier
1798	available with Linux) and present at runtime, it will be used to speed up	1908	implementations) and present at runtime, it will be used to speed up
1799	change detection where possible. The inotify descriptor will be created lazily	1909	change detection where possible. The inotify descriptor will be created
1800	when the first C<ev_stat> watcher is being started.	1910	lazily when the first C<ev_stat> watcher is being started.
1801		1911
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	1912	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	1913	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	1914	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	1915	there are many cases where libev has to resort to regular C<stat> polling,
…		…
1979		2089
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2090	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2091	callback, free it. Also, use no error checking, as usual.
1982		2092
1983	static void	2093	static void
1984	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2094	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1985	{	2095	{
1986	free (w);	2096	free (w);
1987	// now do something you wanted to do when the program has	2097	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2098	// no longer anything immediate to do.
1989	}	2099	}
1990		2100
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2102	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2103	ev_idle_start (loop, idle_cb);
1994		2104
1995		2105
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2187
2078	static ev_io iow [nfd];	2188	static ev_io iow [nfd];
2079	static ev_timer tw;	2189	static ev_timer tw;
2080		2190
2081	static void	2191	static void
2082	io_cb (ev_loop loop, ev_io w, int revents)	2192	io_cb (struct ev_loop loop, ev_io w, int revents)
2083	{	2193	{
2084	}	2194	}
2085		2195
2086	// create io watchers for each fd and a timer before blocking	2196	// create io watchers for each fd and a timer before blocking
2087	static void	2197	static void
2088	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2198	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2089	{	2199	{
2090	int timeout = 3600000;	2200	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2201	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2202	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2218	}
2109	}	2219	}
2110		2220
2111	// stop all watchers after blocking	2221	// stop all watchers after blocking
2112	static void	2222	static void
2113	adns_check_cb (ev_loop loop, ev_check w, int revents)	2223	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2114	{	2224	{
2115	ev_timer_stop (loop, &tw);	2225	ev_timer_stop (loop, &tw);
2116		2226
2117	for (int i = 0; i < nfd; ++i)	2227	for (int i = 0; i < nfd; ++i)
2118	{	2228	{
…		…
2242	So when you want to use this feature you will always have to be prepared	2352	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2353	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2354	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2355	create it, and if that fails, use the normal loop for everything.
2246		2356
		2357	=head3 C<ev_embed> and fork
		2358
		2359	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2360	automatically be applied to the embedded loop as well, so no special
		2361	fork handling is required in that case. When the watcher is not running,
		2362	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2363	as applicable.
		2364
2247	=head3 Watcher-Specific Functions and Data Members	2365	=head3 Watcher-Specific Functions and Data Members
2248		2366
2249	=over 4	2367	=over 4
2250		2368
2251	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2369	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2396	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2397	used).
2280		2398
2281	struct ev_loop *loop_hi = ev_default_init (0);	2399	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2400	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2401	ev_embed embed;
2284		2402
2285	// see if there is a chance of getting one that works	2403	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2404	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2405	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2406	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2420	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2421	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2422
2305	struct ev_loop *loop = ev_default_init (0);	2423	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2424	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2425	ev_embed embed;
2308		2426
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2427	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2428	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2429	{
2312	ev_embed_init (&embed, 0, loop_socket);	2430	ev_embed_init (&embed, 0, loop_socket);
…		…
2376	=over 4	2494	=over 4
2377		2495
2378	=item queueing from a signal handler context	2496	=item queueing from a signal handler context
2379		2497
2380	To implement race-free queueing, you simply add to the queue in the signal	2498	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2499	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2500	an example that does that for some fictitious SIGUSR1 handler:
2383		2501
2384	static ev_async mysig;	2502	static ev_async mysig;
2385		2503
2386	static void	2504	static void
2387	sigusr1_handler (void)	2505	sigusr1_handler (void)
…		…
2494	=over 4	2612	=over 4
2495		2613
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2614	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2615
2498	This function combines a simple timer and an I/O watcher, calls your	2616	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2617	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	2618	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	2619	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2620	more watchers yourself.
2503		2621
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2622	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2623	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2624	the given C<fd> and C<events> set will be created and started.
2507		2625
2508	If C<timeout> is less than 0, then no timeout watcher will be	2626	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2628	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2629
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2630	The callback has the type C<void (cb)(int revents, void arg)> and gets
2514	passed an C<revents> set like normal event callbacks (a combination of	2631	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2633	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2634	a timeout and an io event at the same time - you probably should give io
		2635	events precedence.
		2636
		2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2638
2518	static void stdin_ready (int revents, void *arg)	2639	static void stdin_ready (int revents, void *arg)
2519	{	2640	{
		2641	if (revents & EV_READ)
		2642	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2643	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2644	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2645	}
2525		2646
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2648
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2649	=item ev_feed_event (struct ev_loop , watcher , int revents)
2529		2650
2530	Feeds the given event set into the event loop, as if the specified event	2651	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an	2652	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2653	initialised but not necessarily started event watcher).
2533		2654
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2656
2536	Feed an event on the given fd, as if a file descriptor backend detected	2657	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2658	the given events it.
2538		2659
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2661
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2662	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2663	loop!).
2543		2664
2544	=back	2665	=back
…		…
3298	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3299		3420
3300	#include "ev_cpp.h"	3421	#include "ev_cpp.h"
3301	#include "ev.c"	3422	#include "ev.c"
3302		3423
		3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3303		3425
3304	=head1 THREADS AND COROUTINES	3426	=head2 THREADS AND COROUTINES
3305		3427
3306	=head2 THREADS	3428	=head3 THREADS
3307		3429
3308	All libev functions are reentrant and thread-safe unless explicitly	3430	All libev functions are reentrant and thread-safe unless explicitly
3309	documented otherwise, but it uses no locking itself. This means that you	3431	documented otherwise, but libev implements no locking itself. This means
3310	can use as many loops as you want in parallel, as long as there are no	3432	that you can use as many loops as you want in parallel, as long as there
3311	concurrent calls into any libev function with the same loop parameter	3433	are no concurrent calls into any libev function with the same loop
3312	(C<ev_default_*> calls have an implicit default loop parameter, of	3434	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3313	course): libev guarantees that different event loops share no data	3435	of course): libev guarantees that different event loops share no data
3314	structures that need any locking.	3436	structures that need any locking.
3315		3437
3316	Or to put it differently: calls with different loop parameters can be done	3438	Or to put it differently: calls with different loop parameters can be done
3317	concurrently from multiple threads, calls with the same loop parameter	3439	concurrently from multiple threads, calls with the same loop parameter
3318	must be done serially (but can be done from different threads, as long as	3440	must be done serially (but can be done from different threads, as long as
…		…
3358	default loop and triggering an C<ev_async> watcher from the default loop	3480	default loop and triggering an C<ev_async> watcher from the default loop
3359	watcher callback into the event loop interested in the signal.	3481	watcher callback into the event loop interested in the signal.
3360		3482
3361	=back	3483	=back
3362		3484
3363	=head2 COROUTINES	3485	=head3 COROUTINES
3364		3486
3365	Libev is much more accommodating to coroutines ("cooperative threads"):	3487	Libev is very accommodating to coroutines ("cooperative threads"):
3366	libev fully supports nesting calls to it's functions from different	3488	libev fully supports nesting calls to its functions from different
3367	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3368	different coroutines and switch freely between both coroutines running the	3490	different coroutines, and switch freely between both coroutines running the
3369	loop, as long as you don't confuse yourself). The only exception is that	3491	loop, as long as you don't confuse yourself). The only exception is that
3370	you must not do this from C<ev_periodic> reschedule callbacks.	3492	you must not do this from C<ev_periodic> reschedule callbacks.
3371		3493
3372	Care has been taken to ensure that libev does not keep local state inside	3494	Care has been taken to ensure that libev does not keep local state inside
3373	C<ev_loop>, and other calls do not usually allow coroutine switches.	3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3496	they do not clal any callbacks.
3374		3497
		3498	=head2 COMPILER WARNINGS
3375		3499
3376	=head1 COMPLEXITIES	3500	Depending on your compiler and compiler settings, you might get no or a
		3501	lot of warnings when compiling libev code. Some people are apparently
		3502	scared by this.
3377		3503
3378	In this section the complexities of (many of) the algorithms used inside	3504	However, these are unavoidable for many reasons. For one, each compiler
3379	libev will be explained. For complexity discussions about backends see the	3505	has different warnings, and each user has different tastes regarding
3380	documentation for C<ev_default_init>.	3506	warning options. "Warn-free" code therefore cannot be a goal except when
		3507	targeting a specific compiler and compiler-version.
3381		3508
3382	All of the following are about amortised time: If an array needs to be	3509	Another reason is that some compiler warnings require elaborate
3383	extended, libev needs to realloc and move the whole array, but this	3510	workarounds, or other changes to the code that make it less clear and less
3384	happens asymptotically never with higher number of elements, so O(1) might	3511	maintainable.
3385	mean it might do a lengthy realloc operation in rare cases, but on average
3386	it is much faster and asymptotically approaches constant time.
3387		3512
3388	=over 4	3513	And of course, some compiler warnings are just plain stupid, or simply
		3514	wrong (because they don't actually warn about the condition their message
		3515	seems to warn about). For example, certain older gcc versions had some
		3516	warnings that resulted an extreme number of false positives. These have
		3517	been fixed, but some people still insist on making code warn-free with
		3518	such buggy versions.
3389		3519
3390	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3520	While libev is written to generate as few warnings as possible,
		3521	"warn-free" code is not a goal, and it is recommended not to build libev
		3522	with any compiler warnings enabled unless you are prepared to cope with
		3523	them (e.g. by ignoring them). Remember that warnings are just that:
		3524	warnings, not errors, or proof of bugs.
3391		3525
3392	This means that, when you have a watcher that triggers in one hour and
3393	there are 100 watchers that would trigger before that then inserting will
3394	have to skip roughly seven (C<ld 100>) of these watchers.
3395		3526
3396	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3527	=head2 VALGRIND
3397		3528
3398	That means that changing a timer costs less than removing/adding them	3529	Valgrind has a special section here because it is a popular tool that is
3399	as only the relative motion in the event queue has to be paid for.	3530	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3400		3531
3401	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3532	If you think you found a bug (memory leak, uninitialised data access etc.)
		3533	in libev, then check twice: If valgrind reports something like:
3402		3534
3403	These just add the watcher into an array or at the head of a list.	3535	==2274== definitely lost: 0 bytes in 0 blocks.
		3536	==2274== possibly lost: 0 bytes in 0 blocks.
		3537	==2274== still reachable: 256 bytes in 1 blocks.
3404		3538
3405	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3539	Then there is no memory leak, just as memory accounted to global variables
		3540	is not a memleak - the memory is still being refernced, and didn't leak.
3406		3541
3407	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3542	Similarly, under some circumstances, valgrind might report kernel bugs
		3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3544	although an acceptable workaround has been found here), or it might be
		3545	confused.
3408		3546
3409	These watchers are stored in lists then need to be walked to find the	3547	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3410	correct watcher to remove. The lists are usually short (you don't usually	3548	make it into some kind of religion.
3411	have many watchers waiting for the same fd or signal).
3412		3549
3413	=item Finding the next timer in each loop iteration: O(1)	3550	If you are unsure about something, feel free to contact the mailing list
		3551	with the full valgrind report and an explanation on why you think this
		3552	is a bug in libev (best check the archives, too :). However, don't be
		3553	annoyed when you get a brisk "this is no bug" answer and take the chance
		3554	of learning how to interpret valgrind properly.
3414		3555
3415	By virtue of using a binary or 4-heap, the next timer is always found at a	3556	If you need, for some reason, empty reports from valgrind for your project
3416	fixed position in the storage array.	3557	I suggest using suppression lists.
3417		3558
3418	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3419		3559
3420	A change means an I/O watcher gets started or stopped, which requires	3560	=head1 PORTABILITY NOTES
3421	libev to recalculate its status (and possibly tell the kernel, depending
3422	on backend and whether C<ev_io_set> was used).
3423		3561
3424	=item Activating one watcher (putting it into the pending state): O(1)
3425
3426	=item Priority handling: O(number_of_priorities)
3427
3428	Priorities are implemented by allocating some space for each
3429	priority. When doing priority-based operations, libev usually has to
3430	linearly search all the priorities, but starting/stopping and activating
3431	watchers becomes O(1) with respect to priority handling.
3432
3433	=item Sending an ev_async: O(1)
3434
3435	=item Processing ev_async_send: O(number_of_async_watchers)
3436
3437	=item Processing signals: O(max_signal_number)
3438
3439	Sending involves a system call I<iff> there were no other C<ev_async_send>
3440	calls in the current loop iteration. Checking for async and signal events
3441	involves iterating over all running async watchers or all signal numbers.
3442
3443	=back
3444
3445
3446	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3447		3563
3448	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3449	requires, and its I/O model is fundamentally incompatible with the POSIX	3565	requires, and its I/O model is fundamentally incompatible with the POSIX
3450	model. Libev still offers limited functionality on this platform in	3566	model. Libev still offers limited functionality on this platform in
3451	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3538	wrap all I/O functions and provide your own fd management, but the cost of	3654	wrap all I/O functions and provide your own fd management, but the cost of
3539	calling select (O(n²)) will likely make this unworkable.	3655	calling select (O(n²)) will likely make this unworkable.
3540		3656
3541	=back	3657	=back
3542		3658
3543
3544	=head1 PORTABILITY REQUIREMENTS	3659	=head2 PORTABILITY REQUIREMENTS
3545		3660
3546	In addition to a working ISO-C implementation, libev relies on a few	3661	In addition to a working ISO-C implementation and of course the
3547	additional extensions:	3662	backend-specific APIs, libev relies on a few additional extensions:
3548		3663
3549	=over 4	3664	=over 4
3550		3665
3551	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3666	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3552	calling conventions regardless of C<ev_watcher_type *>.	3667	calling conventions regardless of C<ev_watcher_type *>.
…		…
3577	except the initial one, and run the default loop in the initial thread as	3692	except the initial one, and run the default loop in the initial thread as
3578	well.	3693	well.
3579		3694
3580	=item C<long> must be large enough for common memory allocation sizes	3695	=item C<long> must be large enough for common memory allocation sizes
3581		3696
3582	To improve portability and simplify using libev, libev uses C<long>	3697	To improve portability and simplify its API, libev uses C<long> internally
3583	internally instead of C<size_t> when allocating its data structures. On	3698	instead of C<size_t> when allocating its data structures. On non-POSIX
3584	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3699	systems (Microsoft...) this might be unexpectedly low, but is still at
3585	is still at least 31 bits everywhere, which is enough for hundreds of	3700	least 31 bits everywhere, which is enough for hundreds of millions of
3586	millions of watchers.	3701	watchers.
3587		3702
3588	=item C<double> must hold a time value in seconds with enough accuracy	3703	=item C<double> must hold a time value in seconds with enough accuracy
3589		3704
3590	The type C<double> is used to represent timestamps. It is required to	3705	The type C<double> is used to represent timestamps. It is required to
3591	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3595	=back	3710	=back
3596		3711
3597	If you know of other additional requirements drop me a note.	3712	If you know of other additional requirements drop me a note.
3598		3713
3599		3714
3600	=head1 COMPILER WARNINGS	3715	=head1 ALGORITHMIC COMPLEXITIES
3601		3716
3602	Depending on your compiler and compiler settings, you might get no or a	3717	In this section the complexities of (many of) the algorithms used inside
3603	lot of warnings when compiling libev code. Some people are apparently	3718	libev will be documented. For complexity discussions about backends see
3604	scared by this.	3719	the documentation for C<ev_default_init>.
3605		3720
3606	However, these are unavoidable for many reasons. For one, each compiler	3721	All of the following are about amortised time: If an array needs to be
3607	has different warnings, and each user has different tastes regarding	3722	extended, libev needs to realloc and move the whole array, but this
3608	warning options. "Warn-free" code therefore cannot be a goal except when	3723	happens asymptotically rarer with higher number of elements, so O(1) might
3609	targeting a specific compiler and compiler-version.	3724	mean that libev does a lengthy realloc operation in rare cases, but on
		3725	average it is much faster and asymptotically approaches constant time.
3610		3726
3611	Another reason is that some compiler warnings require elaborate	3727	=over 4
3612	workarounds, or other changes to the code that make it less clear and less
3613	maintainable.
3614		3728
3615	And of course, some compiler warnings are just plain stupid, or simply	3729	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3616	wrong (because they don't actually warn about the condition their message
3617	seems to warn about).
3618		3730
3619	While libev is written to generate as few warnings as possible,	3731	This means that, when you have a watcher that triggers in one hour and
3620	"warn-free" code is not a goal, and it is recommended not to build libev	3732	there are 100 watchers that would trigger before that, then inserting will
3621	with any compiler warnings enabled unless you are prepared to cope with	3733	have to skip roughly seven (C<ld 100>) of these watchers.
3622	them (e.g. by ignoring them). Remember that warnings are just that:
3623	warnings, not errors, or proof of bugs.
3624		3734
		3735	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3625		3736
3626	=head1 VALGRIND	3737	That means that changing a timer costs less than removing/adding them,
		3738	as only the relative motion in the event queue has to be paid for.
3627		3739
3628	Valgrind has a special section here because it is a popular tool that is	3740	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3629	highly useful, but valgrind reports are very hard to interpret.
3630		3741
3631	If you think you found a bug (memory leak, uninitialised data access etc.)	3742	These just add the watcher into an array or at the head of a list.
3632	in libev, then check twice: If valgrind reports something like:
3633		3743
3634	==2274== definitely lost: 0 bytes in 0 blocks.	3744	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3635	==2274== possibly lost: 0 bytes in 0 blocks.
3636	==2274== still reachable: 256 bytes in 1 blocks.
3637		3745
3638	Then there is no memory leak. Similarly, under some circumstances,	3746	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3639	valgrind might report kernel bugs as if it were a bug in libev, or it
3640	might be confused (it is a very good tool, but only a tool).
3641		3747
3642	If you are unsure about something, feel free to contact the mailing list	3748	These watchers are stored in lists, so they need to be walked to find the
3643	with the full valgrind report and an explanation on why you think this is	3749	correct watcher to remove. The lists are usually short (you don't usually
3644	a bug in libev. However, don't be annoyed when you get a brisk "this is	3750	have many watchers waiting for the same fd or signal: one is typical, two
3645	no bug" answer and take the chance of learning how to interpret valgrind	3751	is rare).
3646	properly.
3647		3752
3648	If you need, for some reason, empty reports from valgrind for your project	3753	=item Finding the next timer in each loop iteration: O(1)
3649	I suggest using suppression lists.	3754
		3755	By virtue of using a binary or 4-heap, the next timer is always found at a
		3756	fixed position in the storage array.
		3757
		3758	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3759
		3760	A change means an I/O watcher gets started or stopped, which requires
		3761	libev to recalculate its status (and possibly tell the kernel, depending
		3762	on backend and whether C<ev_io_set> was used).
		3763
		3764	=item Activating one watcher (putting it into the pending state): O(1)
		3765
		3766	=item Priority handling: O(number_of_priorities)
		3767
		3768	Priorities are implemented by allocating some space for each
		3769	priority. When doing priority-based operations, libev usually has to
		3770	linearly search all the priorities, but starting/stopping and activating
		3771	watchers becomes O(1) with respect to priority handling.
		3772
		3773	=item Sending an ev_async: O(1)
		3774
		3775	=item Processing ev_async_send: O(number_of_async_watchers)
		3776
		3777	=item Processing signals: O(max_signal_number)
		3778
		3779	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3780	calls in the current loop iteration. Checking for async and signal events
		3781	involves iterating over all running async watchers or all signal numbers.
		3782
		3783	=back
3650		3784
3651		3785
3652	=head1 AUTHOR	3786	=head1 AUTHOR
3653		3787
3654	Marc Lehmann <libev@schmorp.de>.	3788	Marc Lehmann <libev@schmorp.de>.

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Revision 1.186 by root, Wed Sep 24 07:56:14 2008 UTC vs.
Revision 1.198 by root, Thu Oct 23 06:30:48 2008 UTC