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

Comparing libev/ev.pod (file contents):
Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs.
Revision 1.199 by root, Thu Oct 23 07:18:21 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
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void (cb)(void *ptr, long size))	219	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (cb)(const char msg));	255	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
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 involve some kind of timeout, 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	What follows are some ways to handle this problem, from obvious and
		1298	inefficient to smart and efficient.
		1299
		1300	In the following, a 60 second activity timeout is assumed - a timeout that
		1301	gets reset to 60 seconds each time there is activity (e.g. each time some
		1302	data or other life sign was received).
		1303
		1304	=over 4
		1305
		1306	=item 1. Use a timer and stop, reinitialise and 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> it, initialise it
		1315	and start it again:
		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 is
		1322	some activity, libev will first have to remove the timer from its internal
		1323	data structure and then add it again. Libev tries to be fast, but it's
		1324	still not a constant-time operation.
		1325
		1326	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1327
		1328	This is the easiest way, and involves using C<ev_timer_again> instead of
		1329	C<ev_timer_start>.
		1330
		1331	To implement this, configure an C<ev_timer> with a C<repeat> value
		1332	of C<60> and then call C<ev_timer_again> at start and each time you
		1333	successfully read or write some data. If you go into an idle state where
		1334	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1335	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1336
		1337	That means you can ignore both the C<ev_timer_start> function and the
		1338	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1339	member and C<ev_timer_again>.
		1340
		1341	At start:
		1342
		1343	ev_timer_init (timer, callback);
		1344	timer->repeat = 60.;
		1345	ev_timer_again (loop, timer);
		1346
		1347	Each time there is some activity:
		1348
		1349	ev_timer_again (loop, timer);
		1350
		1351	It is even possible to change the time-out on the fly, regardless of
		1352	whether the watcher is active or not:
		1353
		1354	timer->repeat = 30.;
		1355	ev_timer_again (loop, timer);
		1356
		1357	This is slightly more efficient then stopping/starting the timer each time
		1358	you want to modify its timeout value, as libev does not have to completely
		1359	remove and re-insert the timer from/into its internal data structure.
		1360
		1361	It is, however, even simpler than the "obvious" way to do it.
		1362
		1363	=item 3. Let the timer time out, but then re-arm it as required.
		1364
		1365	This method is more tricky, but usually most efficient: Most timeouts are
		1366	relatively long compared to the intervals between other activity - in
		1367	our example, within 60 seconds, there are usually many I/O events with
		1368	associated activity resets.
		1369
		1370	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1371	but remember the time of last activity, and check for a real timeout only
		1372	within the callback:
		1373
		1374	ev_tstamp last_activity; // time of last activity
		1375
		1376	static void
		1377	callback (EV_P_ ev_timer *w, int revents)
		1378	{
		1379	ev_tstamp now = ev_now (EV_A);
		1380	ev_tstamp timeout = last_activity + 60.;
		1381
		1382	// if last_activity + 60. is older than now, we did time out
		1383	if (timeout < now)
		1384	{
		1385	// timeout occured, take action
		1386	}
		1387	else
		1388	{
		1389	// callback was invoked, but there was some activity, re-arm
		1390	// the watcher to fire in last_activity + 60, which is
		1391	// guaranteed to be in the future, so "again" is positive:
		1392	w->again = timeout - now;
		1393	ev_timer_again (EV_A_ w);
		1394	}
		1395	}
		1396
		1397	To summarise the callback: first calculate the real timeout (defined
		1398	as "60 seconds after the last activity"), then check if that time has
		1399	been reached, which means something I<did>, in fact, time out. Otherwise
		1400	the callback was invoked too early (C<timeout> is in the future), so
		1401	re-schedule the timer to fire at that future time, to see if maybe we have
		1402	a timeout then.
		1403
		1404	Note how C<ev_timer_again> is used, taking advantage of the
		1405	C<ev_timer_again> optimisation when the timer is already running.
		1406
		1407	This scheme causes more callback invocations (about one every 60 seconds
		1408	minus half the average time between activity), but virtually no calls to
		1409	libev to change the timeout.
		1410
		1411	To start the timer, simply initialise the watcher and set C<last_activity>
		1412	to the current time (meaning we just have some activity :), then call the
		1413	callback, which will "do the right thing" and start the timer:
		1414
		1415	ev_timer_init (timer, callback);
		1416	last_activity = ev_now (loop);
		1417	callback (loop, timer, EV_TIMEOUT);
		1418
		1419	And when there is some activity, simply store the current time in
		1420	C<last_activity>, no libev calls at all:
		1421
		1422	last_actiivty = ev_now (loop);
		1423
		1424	This technique is slightly more complex, but in most cases where the
		1425	time-out is unlikely to be triggered, much more efficient.
		1426
		1427	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1428	callback :) - just change the timeout and invoke the callback, which will
		1429	fix things for you.
		1430
		1431	=item 4. Whee, use a double-linked list for your timeouts.
		1432
		1433	If there is not one request, but many thousands, all employing some kind
		1434	of timeout with the same timeout value, then one can do even better:
		1435
		1436	When starting the timeout, calculate the timeout value and put the timeout
		1437	at the I<end> of the list.
		1438
		1439	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1440	the list is expected to fire (for example, using the technique #3).
		1441
		1442	When there is some activity, remove the timer from the list, recalculate
		1443	the timeout, append it to the end of the list again, and make sure to
		1444	update the C<ev_timer> if it was taken from the beginning of the list.
		1445
		1446	This way, one can manage an unlimited number of timeouts in O(1) time for
		1447	starting, stopping and updating the timers, at the expense of a major
		1448	complication, and having to use a constant timeout. The constant timeout
		1449	ensures that the list stays sorted.
		1450
		1451	=back
		1452
		1453	So what method is the best?
		1454
		1455	The method #2 is a simple no-brain-required solution that is adequate in
		1456	most situations. Method #3 requires a bit more thinking, but handles many
		1457	cases better, and isn't very complicated either. In most case, choosing
		1458	either one is fine.
		1459
		1460	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1461	rather complicated, but extremely efficient, something that really pays
		1462	off after the first or so million of active timers, i.e. it's usually
		1463	overkill :)
		1464
1283	=head3 The special problem of time updates	1465	=head3 The special problem of time updates
1284		1466
1285	Establishing the current time is a costly operation (it usually takes at	1467	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	1468	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	1469	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).	1512	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1513
1332	If the timer is repeating, either start it if necessary (with the	1514	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.	1515	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1516
1335	This sounds a bit complicated, but here is a useful and typical	1517	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	1518	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		1519
1366	=item ev_tstamp repeat [read-write]	1520	=item ev_tstamp repeat [read-write]
1367		1521
1368	The current C<repeat> value. Will be used each time the watcher times out	1522	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),	1523	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1528	=head3 Examples
1375		1529
1376	Example: Create a timer that fires after 60 seconds.	1530	Example: Create a timer that fires after 60 seconds.
1377		1531
1378	static void	1532	static void
1379	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1533	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1380	{	1534	{
1381	.. one minute over, w is actually stopped right here	1535	.. one minute over, w is actually stopped right here
1382	}	1536	}
1383		1537
1384	struct ev_timer mytimer;	1538	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1539	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1540	ev_timer_start (loop, &mytimer);
1387		1541
1388	Example: Create a timeout timer that times out after 10 seconds of	1542	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1543	inactivity.
1390		1544
1391	static void	1545	static void
1392	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1546	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1393	{	1547	{
1394	.. ten seconds without any activity	1548	.. ten seconds without any activity
1395	}	1549	}
1396		1550
1397	struct ev_timer mytimer;	1551	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1552	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1553	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1554	ev_loop (loop, 0);
1401		1555
1402	// and in some piece of code that gets executed on any "activity":	1556	// and in some piece of code that gets executed on any "activity":
…		…
1488		1642
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1643	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	1644	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1645	only event loop modification you are allowed to do).
1492		1646
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1647	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1648	*w, ev_tstamp now)>, e.g.:
1495		1649
		1650	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1651	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1652	{
1498	return now + 60.;	1653	return now + 60.;
1499	}	1654	}
1500		1655
1501	It must return the next time to trigger, based on the passed time value	1656	It must return the next time to trigger, based on the passed time value
…		…
1538		1693
1539	The current interval value. Can be modified any time, but changes only	1694	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	1695	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1696	called.
1542		1697
1543	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1698	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1544		1699
1545	The current reschedule callback, or C<0>, if this functionality is	1700	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	1701	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.	1702	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1703
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1708	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1709	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1710	potentially a lot of jitter, but good long-term stability.
1556		1711
1557	static void	1712	static void
1558	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1713	clock_cb (struct ev_loop loop, ev_io w, int revents)
1559	{	1714	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1715	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1716	}
1562		1717
1563	struct ev_periodic hourly_tick;	1718	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1719	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1720	ev_periodic_start (loop, &hourly_tick);
1566		1721
1567	Example: The same as above, but use a reschedule callback to do it:	1722	Example: The same as above, but use a reschedule callback to do it:
1568		1723
1569	#include <math.h>	1724	#include <math.h>
1570		1725
1571	static ev_tstamp	1726	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1727	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1728	{
1574	return now + (3600. - fmod (now, 3600.));	1729	return now + (3600. - fmod (now, 3600.));
1575	}	1730	}
1576		1731
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1732	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1733
1579	Example: Call a callback every hour, starting now:	1734	Example: Call a callback every hour, starting now:
1580		1735
1581	struct ev_periodic hourly_tick;	1736	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1737	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1738	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1739	ev_periodic_start (loop, &hourly_tick);
1585		1740
1586		1741
…		…
1625		1780
1626	=back	1781	=back
1627		1782
1628	=head3 Examples	1783	=head3 Examples
1629		1784
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1785	Example: Try to exit cleanly on SIGINT.
1631		1786
1632	static void	1787	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1788	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1634	{	1789	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1790	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1791	}
1637		1792
1638	struct ev_signal signal_watcher;	1793	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1794	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1795	ev_signal_start (loop, &signal_watcher);
1641		1796
1642		1797
1643	=head2 C<ev_child> - watch out for process status changes	1798	=head2 C<ev_child> - watch out for process status changes
1644		1799
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1800	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1873	its completion.
1719		1874
1720	ev_child cw;	1875	ev_child cw;
1721		1876
1722	static void	1877	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1878	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1879	{
1725	ev_child_stop (EV_A_ w);	1880	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1881	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1882	}
1728		1883
…		…
1792	to exchange stat structures with application programs compiled using the	1947	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	1948	default compilation environment.
1794		1949
1795	=head3 Inotify and Kqueue	1950	=head3 Inotify and Kqueue
1796		1951
1797	When C<inotify (7)> support has been compiled into libev (generally only	1952	When C<inotify (7)> support has been compiled into libev (generally
		1953	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	1954	implementations) and present at runtime, it will be used to speed up
1799	change detection where possible. The inotify descriptor will be created lazily	1955	change detection where possible. The inotify descriptor will be created
1800	when the first C<ev_stat> watcher is being started.	1956	lazily when the first C<ev_stat> watcher is being started.
1801		1957
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	1958	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	1959	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	1960	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,	1961	there are many cases where libev has to resort to regular C<stat> polling,
…		…
1979		2135
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2136	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2137	callback, free it. Also, use no error checking, as usual.
1982		2138
1983	static void	2139	static void
1984	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2140	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1985	{	2141	{
1986	free (w);	2142	free (w);
1987	// now do something you wanted to do when the program has	2143	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2144	// no longer anything immediate to do.
1989	}	2145	}
1990		2146
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2147	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2148	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2149	ev_idle_start (loop, idle_cb);
1994		2150
1995		2151
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2152	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2233
2078	static ev_io iow [nfd];	2234	static ev_io iow [nfd];
2079	static ev_timer tw;	2235	static ev_timer tw;
2080		2236
2081	static void	2237	static void
2082	io_cb (ev_loop loop, ev_io w, int revents)	2238	io_cb (struct ev_loop loop, ev_io w, int revents)
2083	{	2239	{
2084	}	2240	}
2085		2241
2086	// create io watchers for each fd and a timer before blocking	2242	// create io watchers for each fd and a timer before blocking
2087	static void	2243	static void
2088	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2244	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2089	{	2245	{
2090	int timeout = 3600000;	2246	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2247	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2248	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2249	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2264	}
2109	}	2265	}
2110		2266
2111	// stop all watchers after blocking	2267	// stop all watchers after blocking
2112	static void	2268	static void
2113	adns_check_cb (ev_loop loop, ev_check w, int revents)	2269	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2114	{	2270	{
2115	ev_timer_stop (loop, &tw);	2271	ev_timer_stop (loop, &tw);
2116		2272
2117	for (int i = 0; i < nfd; ++i)	2273	for (int i = 0; i < nfd; ++i)
2118	{	2274	{
…		…
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2389	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2234	but you will also have to stop and restart any C<ev_embed> watchers	2390	but you will also have to stop and restart any C<ev_embed> watchers
2235	yourself - but you can use a fork watcher to handle this automatically,	2391	yourself - but you can use a fork watcher to handle this automatically,
2236	and future versions of libev might do just that.	2392	and future versions of libev might do just that.
2237		2393
2238	Unfortunately, not all backends are embeddable, only the ones returned by	2394	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2395	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2396	portable one.
2241		2397
2242	So when you want to use this feature you will always have to be prepared	2398	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	2399	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	2400	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.	2401	create it, and if that fails, use the normal loop for everything.
		2402
		2403	=head3 C<ev_embed> and fork
		2404
		2405	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2406	automatically be applied to the embedded loop as well, so no special
		2407	fork handling is required in that case. When the watcher is not running,
		2408	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2409	as applicable.
2246		2410
2247	=head3 Watcher-Specific Functions and Data Members	2411	=head3 Watcher-Specific Functions and Data Members
2248		2412
2249	=over 4	2413	=over 4
2250		2414
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2442	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2443	used).
2280		2444
2281	struct ev_loop *loop_hi = ev_default_init (0);	2445	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2446	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2447	ev_embed embed;
2284		2448
2285	// see if there is a chance of getting one that works	2449	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2450	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2451	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2452	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2466	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2467	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2468
2305	struct ev_loop *loop = ev_default_init (0);	2469	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2470	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2471	ev_embed embed;
2308		2472
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2473	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2474	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2475	{
2312	ev_embed_init (&embed, 0, loop_socket);	2476	ev_embed_init (&embed, 0, loop_socket);
…		…
2368	is that the author does not know of a simple (or any) algorithm for a	2532	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	2533	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	2534	need elaborate support such as pthreads.
2371		2535
2372	That means that if you want to queue data, you have to provide your own	2536	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you would implement locking around your	2537	queue. But at least I can tell you how to implement locking around your
2374	queue:	2538	queue:
2375		2539
2376	=over 4	2540	=over 4
2377		2541
2378	=item queueing from a signal handler context	2542	=item queueing from a signal handler context
2379		2543
2380	To implement race-free queueing, you simply add to the queue in the signal	2544	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	2545	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2546	an example that does that for some fictitious SIGUSR1 handler:
2383		2547
2384	static ev_async mysig;	2548	static ev_async mysig;
2385		2549
2386	static void	2550	static void
2387	sigusr1_handler (void)	2551	sigusr1_handler (void)
…		…
2454		2618
2455	=item ev_async_init (ev_async *, callback)	2619	=item ev_async_init (ev_async *, callback)
2456		2620
2457	Initialises and configures the async watcher - it has no parameters of any	2621	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2622	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2459	believe me.	2623	trust me.
2460		2624
2461	=item ev_async_send (loop, ev_async *)	2625	=item ev_async_send (loop, ev_async *)
2462		2626
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2627	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2628	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do in other threads, signal or	2629	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2630	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2631	section below on what exactly this means).
2468		2632
2469	This call incurs the overhead of a system call only once per loop iteration,	2633	This call incurs the overhead of a system call only once per loop iteration,
2470	so while the overhead might be noticeable, it doesn't apply to repeated	2634	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2494	=over 4	2658	=over 4
2495		2659
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2660	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2661
2498	This function combines a simple timer and an I/O watcher, calls your	2662	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2663	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	2664	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	2665	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2666	more watchers yourself.
2503		2667
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2668	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	2669	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2670	the given C<fd> and C<events> set will be created and started.
2507		2671
2508	If C<timeout> is less than 0, then no timeout watcher will be	2672	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	2673	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	2674	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2675
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2676	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	2677	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>	2678	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2679	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2680	a timeout and an io event at the same time - you probably should give io
		2681	events precedence.
		2682
		2683	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2684
2518	static void stdin_ready (int revents, void *arg)	2685	static void stdin_ready (int revents, void *arg)
2519	{	2686	{
		2687	if (revents & EV_READ)
		2688	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2689	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2690	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2691	}
2525		2692
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2693	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2694
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2695	=item ev_feed_event (struct ev_loop , watcher , int revents)
2529		2696
2530	Feeds the given event set into the event loop, as if the specified event	2697	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	2698	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2699	initialised but not necessarily started event watcher).
2533		2700
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2701	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2702
2536	Feed an event on the given fd, as if a file descriptor backend detected	2703	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2704	the given events it.
2538		2705
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2706	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2707
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2708	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2709	loop!).
2543		2710
2544	=back	2711	=back
…		…
2676		2843
2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2844	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2678		2845
2679	See the method-C<set> above for more details.	2846	See the method-C<set> above for more details.
2680		2847
2681	Example:	2848	Example: Use a plain function as callback.
2682		2849
2683	static void io_cb (ev::io &w, int revents) { }	2850	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	2851	iow.set <io_cb> ();
2685		2852
2686	=item w->set (struct ev_loop *)	2853	=item w->set (struct ev_loop *)
…		…
2724	Example: Define a class with an IO and idle watcher, start one of them in	2891	Example: Define a class with an IO and idle watcher, start one of them in
2725	the constructor.	2892	the constructor.
2726		2893
2727	class myclass	2894	class myclass
2728	{	2895	{
2729	ev::io io; void io_cb (ev::io &w, int revents);	2896	ev::io io ; void io_cb (ev::io &w, int revents);
2730	ev:idle idle void idle_cb (ev::idle &w, int revents);	2897	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		2898
2732	myclass (int fd)	2899	myclass (int fd)
2733	{	2900	{
2734	io .set <myclass, &myclass::io_cb > (this);	2901	io .set <myclass, &myclass::io_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	2902	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2751	=item Perl	2918	=item Perl
2752		2919
2753	The EV module implements the full libev API and is actually used to test	2920	The EV module implements the full libev API and is actually used to test
2754	libev. EV is developed together with libev. Apart from the EV core module,	2921	libev. EV is developed together with libev. Apart from the EV core module,
2755	there are additional modules that implement libev-compatible interfaces	2922	there are additional modules that implement libev-compatible interfaces
2756	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2923	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2757	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2924	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2925	and C<EV::Glib>).
2758		2926
2759	It can be found and installed via CPAN, its homepage is at	2927	It can be found and installed via CPAN, its homepage is at
2760	L<http://software.schmorp.de/pkg/EV>.	2928	L<http://software.schmorp.de/pkg/EV>.
2761		2929
2762	=item Python	2930	=item Python
…		…
2941		3109
2942	=head2 PREPROCESSOR SYMBOLS/MACROS	3110	=head2 PREPROCESSOR SYMBOLS/MACROS
2943		3111
2944	Libev can be configured via a variety of preprocessor symbols you have to	3112	Libev can be configured via a variety of preprocessor symbols you have to
2945	define before including any of its files. The default in the absence of	3113	define before including any of its files. The default in the absence of
2946	autoconf is noted for every option.	3114	autoconf is documented for every option.
2947		3115
2948	=over 4	3116	=over 4
2949		3117
2950	=item EV_STANDALONE	3118	=item EV_STANDALONE
2951		3119
…		…
3121	When doing priority-based operations, libev usually has to linearly search	3289	When doing priority-based operations, libev usually has to linearly search
3122	all the priorities, so having many of them (hundreds) uses a lot of space	3290	all the priorities, so having many of them (hundreds) uses a lot of space
3123	and time, so using the defaults of five priorities (-2 .. +2) is usually	3291	and time, so using the defaults of five priorities (-2 .. +2) is usually
3124	fine.	3292	fine.
3125		3293
3126	If your embedding application does not need any priorities, defining these both to	3294	If your embedding application does not need any priorities, defining these
3127	C<0> will save some memory and CPU.	3295	both to C<0> will save some memory and CPU.
3128		3296
3129	=item EV_PERIODIC_ENABLE	3297	=item EV_PERIODIC_ENABLE
3130		3298
3131	If undefined or defined to be C<1>, then periodic timers are supported. If	3299	If undefined or defined to be C<1>, then periodic timers are supported. If
3132	defined to be C<0>, then they are not. Disabling them saves a few kB of	3300	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3139	code.	3307	code.
3140		3308
3141	=item EV_EMBED_ENABLE	3309	=item EV_EMBED_ENABLE
3142		3310
3143	If undefined or defined to be C<1>, then embed watchers are supported. If	3311	If undefined or defined to be C<1>, then embed watchers are supported. If
3144	defined to be C<0>, then they are not.	3312	defined to be C<0>, then they are not. Embed watchers rely on most other
		3313	watcher types, which therefore must not be disabled.
3145		3314
3146	=item EV_STAT_ENABLE	3315	=item EV_STAT_ENABLE
3147		3316
3148	If undefined or defined to be C<1>, then stat watchers are supported. If	3317	If undefined or defined to be C<1>, then stat watchers are supported. If
3149	defined to be C<0>, then they are not.	3318	defined to be C<0>, then they are not.
…		…
3181	two).	3350	two).
3182		3351
3183	=item EV_USE_4HEAP	3352	=item EV_USE_4HEAP
3184		3353
3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3354	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3186	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3355	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3187	to C<1>. The 4-heap uses more complicated (longer) code but has	3356	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3188	noticeably faster performance with many (thousands) of watchers.	3357	faster performance with many (thousands) of watchers.
3189		3358
3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3359	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3191	(disabled).	3360	(disabled).
3192		3361
3193	=item EV_HEAP_CACHE_AT	3362	=item EV_HEAP_CACHE_AT
3194		3363
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3364	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3196	timer and periodics heap, libev can cache the timestamp (I<at>) within	3365	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3197	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3366	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3198	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3367	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3199	but avoids random read accesses on heap changes. This improves performance	3368	but avoids random read accesses on heap changes. This improves performance
3200	noticeably with with many (hundreds) of watchers.	3369	noticeably with many (hundreds) of watchers.
3201		3370
3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3371	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3203	(disabled).	3372	(disabled).
3204		3373
3205	=item EV_VERIFY	3374	=item EV_VERIFY
…		…
3211	called once per loop, which can slow down libev. If set to C<3>, then the	3380	called once per loop, which can slow down libev. If set to C<3>, then the
3212	verification code will be called very frequently, which will slow down	3381	verification code will be called very frequently, which will slow down
3213	libev considerably.	3382	libev considerably.
3214		3383
3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3384	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3216	C<0.>	3385	C<0>.
3217		3386
3218	=item EV_COMMON	3387	=item EV_COMMON
3219		3388
3220	By default, all watchers have a C<void *data> member. By redefining	3389	By default, all watchers have a C<void *data> member. By redefining
3221	this macro to a something else you can include more and other types of	3390	this macro to a something else you can include more and other types of
…		…
3238	and the way callbacks are invoked and set. Must expand to a struct member	3407	and the way callbacks are invoked and set. Must expand to a struct member
3239	definition and a statement, respectively. See the F<ev.h> header file for	3408	definition and a statement, respectively. See the F<ev.h> header file for
3240	their default definitions. One possible use for overriding these is to	3409	their default definitions. One possible use for overriding these is to
3241	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3410	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3242	method calls instead of plain function calls in C++.	3411	method calls instead of plain function calls in C++.
		3412
		3413	=back
3243		3414
3244	=head2 EXPORTED API SYMBOLS	3415	=head2 EXPORTED API SYMBOLS
3245		3416
3246	If you need to re-export the API (e.g. via a DLL) and you need a list of	3417	If you need to re-export the API (e.g. via a DLL) and you need a list of
3247	exported symbols, you can use the provided F<Symbol.*> files which list	3418	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3294	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3465	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3295		3466
3296	#include "ev_cpp.h"	3467	#include "ev_cpp.h"
3297	#include "ev.c"	3468	#include "ev.c"
3298		3469
		3470	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3299		3471
3300	=head1 THREADS AND COROUTINES	3472	=head2 THREADS AND COROUTINES
3301		3473
3302	=head2 THREADS	3474	=head3 THREADS
3303		3475
3304	Libev itself is thread-safe (unless the opposite is specifically	3476	All libev functions are reentrant and thread-safe unless explicitly
3305	documented for a function), but it uses no locking itself. This means that	3477	documented otherwise, but libev implements no locking itself. This means
3306	you can use as many loops as you want in parallel, as long as only one	3478	that you can use as many loops as you want in parallel, as long as there
3307	thread ever calls into one libev function with the same loop parameter:	3479	are no concurrent calls into any libev function with the same loop
		3480	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3308	libev guarentees that different event loops share no data structures that	3481	of course): libev guarantees that different event loops share no data
3309	need locking.	3482	structures that need any locking.
3310		3483
3311	Or to put it differently: calls with different loop parameters can be done	3484	Or to put it differently: calls with different loop parameters can be done
3312	concurrently from multiple threads, calls with the same loop parameter	3485	concurrently from multiple threads, calls with the same loop parameter
3313	must be done serially (but can be done from different threads, as long as	3486	must be done serially (but can be done from different threads, as long as
3314	only one thread ever is inside a call at any point in time, e.g. by using	3487	only one thread ever is inside a call at any point in time, e.g. by using
3315	a mutex per loop).	3488	a mutex per loop).
3316		3489
3317	Specifically to support threads (and signal handlers), libev implements	3490	Specifically to support threads (and signal handlers), libev implements
3318	so-called C<ev_async> watchers, which allow some limited form of	3491	so-called C<ev_async> watchers, which allow some limited form of
3319	concurrency on the same event loop.	3492	concurrency on the same event loop, namely waking it up "from the
		3493	outside".
3320		3494
3321	If you want to know which design (one loop, locking, or multiple loops	3495	If you want to know which design (one loop, locking, or multiple loops
3322	without or something else still) is best for your problem, then I cannot	3496	without or something else still) is best for your problem, then I cannot
3323	help you. I can give some generic advice however:	3497	help you, but here is some generic advice:
3324		3498
3325	=over 4	3499	=over 4
3326		3500
3327	=item * most applications have a main thread: use the default libev loop	3501	=item * most applications have a main thread: use the default libev loop
3328	in that thread, or create a separate thread running only the default loop.	3502	in that thread, or create a separate thread running only the default loop.
…		…
3352	default loop and triggering an C<ev_async> watcher from the default loop	3526	default loop and triggering an C<ev_async> watcher from the default loop
3353	watcher callback into the event loop interested in the signal.	3527	watcher callback into the event loop interested in the signal.
3354		3528
3355	=back	3529	=back
3356		3530
3357	=head2 COROUTINES	3531	=head3 COROUTINES
3358		3532
3359	Libev is much more accommodating to coroutines ("cooperative threads"):	3533	Libev is very accommodating to coroutines ("cooperative threads"):
3360	libev fully supports nesting calls to it's functions from different	3534	libev fully supports nesting calls to its functions from different
3361	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3535	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3362	different coroutines and switch freely between both coroutines running the	3536	different coroutines, and switch freely between both coroutines running the
3363	loop, as long as you don't confuse yourself). The only exception is that	3537	loop, as long as you don't confuse yourself). The only exception is that
3364	you must not do this from C<ev_periodic> reschedule callbacks.	3538	you must not do this from C<ev_periodic> reschedule callbacks.
3365		3539
3366	Care has been taken to ensure that libev does not keep local state inside	3540	Care has been taken to ensure that libev does not keep local state inside
3367	C<ev_loop>, and other calls do not usually allow coroutine switches.	3541	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3542	they do not clal any callbacks.
3368		3543
		3544	=head2 COMPILER WARNINGS
3369		3545
3370	=head1 COMPLEXITIES	3546	Depending on your compiler and compiler settings, you might get no or a
		3547	lot of warnings when compiling libev code. Some people are apparently
		3548	scared by this.
3371		3549
3372	In this section the complexities of (many of) the algorithms used inside	3550	However, these are unavoidable for many reasons. For one, each compiler
3373	libev will be explained. For complexity discussions about backends see the	3551	has different warnings, and each user has different tastes regarding
3374	documentation for C<ev_default_init>.	3552	warning options. "Warn-free" code therefore cannot be a goal except when
		3553	targeting a specific compiler and compiler-version.
3375		3554
3376	All of the following are about amortised time: If an array needs to be	3555	Another reason is that some compiler warnings require elaborate
3377	extended, libev needs to realloc and move the whole array, but this	3556	workarounds, or other changes to the code that make it less clear and less
3378	happens asymptotically never with higher number of elements, so O(1) might	3557	maintainable.
3379	mean it might do a lengthy realloc operation in rare cases, but on average
3380	it is much faster and asymptotically approaches constant time.
3381		3558
3382	=over 4	3559	And of course, some compiler warnings are just plain stupid, or simply
		3560	wrong (because they don't actually warn about the condition their message
		3561	seems to warn about). For example, certain older gcc versions had some
		3562	warnings that resulted an extreme number of false positives. These have
		3563	been fixed, but some people still insist on making code warn-free with
		3564	such buggy versions.
3383		3565
3384	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3566	While libev is written to generate as few warnings as possible,
		3567	"warn-free" code is not a goal, and it is recommended not to build libev
		3568	with any compiler warnings enabled unless you are prepared to cope with
		3569	them (e.g. by ignoring them). Remember that warnings are just that:
		3570	warnings, not errors, or proof of bugs.
3385		3571
3386	This means that, when you have a watcher that triggers in one hour and
3387	there are 100 watchers that would trigger before that then inserting will
3388	have to skip roughly seven (C<ld 100>) of these watchers.
3389		3572
3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3573	=head2 VALGRIND
3391		3574
3392	That means that changing a timer costs less than removing/adding them	3575	Valgrind has a special section here because it is a popular tool that is
3393	as only the relative motion in the event queue has to be paid for.	3576	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3394		3577
3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3578	If you think you found a bug (memory leak, uninitialised data access etc.)
		3579	in libev, then check twice: If valgrind reports something like:
3396		3580
3397	These just add the watcher into an array or at the head of a list.	3581	==2274== definitely lost: 0 bytes in 0 blocks.
		3582	==2274== possibly lost: 0 bytes in 0 blocks.
		3583	==2274== still reachable: 256 bytes in 1 blocks.
3398		3584
3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3585	Then there is no memory leak, just as memory accounted to global variables
		3586	is not a memleak - the memory is still being refernced, and didn't leak.
3400		3587
3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3588	Similarly, under some circumstances, valgrind might report kernel bugs
		3589	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3590	although an acceptable workaround has been found here), or it might be
		3591	confused.
3402		3592
3403	These watchers are stored in lists then need to be walked to find the	3593	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3404	correct watcher to remove. The lists are usually short (you don't usually	3594	make it into some kind of religion.
3405	have many watchers waiting for the same fd or signal).
3406		3595
3407	=item Finding the next timer in each loop iteration: O(1)	3596	If you are unsure about something, feel free to contact the mailing list
		3597	with the full valgrind report and an explanation on why you think this
		3598	is a bug in libev (best check the archives, too :). However, don't be
		3599	annoyed when you get a brisk "this is no bug" answer and take the chance
		3600	of learning how to interpret valgrind properly.
3408		3601
3409	By virtue of using a binary or 4-heap, the next timer is always found at a	3602	If you need, for some reason, empty reports from valgrind for your project
3410	fixed position in the storage array.	3603	I suggest using suppression lists.
3411		3604
3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3413		3605
3414	A change means an I/O watcher gets started or stopped, which requires	3606	=head1 PORTABILITY NOTES
3415	libev to recalculate its status (and possibly tell the kernel, depending
3416	on backend and whether C<ev_io_set> was used).
3417		3607
3418	=item Activating one watcher (putting it into the pending state): O(1)
3419
3420	=item Priority handling: O(number_of_priorities)
3421
3422	Priorities are implemented by allocating some space for each
3423	priority. When doing priority-based operations, libev usually has to
3424	linearly search all the priorities, but starting/stopping and activating
3425	watchers becomes O(1) w.r.t. priority handling.
3426
3427	=item Sending an ev_async: O(1)
3428
3429	=item Processing ev_async_send: O(number_of_async_watchers)
3430
3431	=item Processing signals: O(max_signal_number)
3432
3433	Sending involves a system call I<iff> there were no other C<ev_async_send>
3434	calls in the current loop iteration. Checking for async and signal events
3435	involves iterating over all running async watchers or all signal numbers.
3436
3437	=back
3438
3439
3440	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3608	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3441		3609
3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3610	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3443	requires, and its I/O model is fundamentally incompatible with the POSIX	3611	requires, and its I/O model is fundamentally incompatible with the POSIX
3444	model. Libev still offers limited functionality on this platform in	3612	model. Libev still offers limited functionality on this platform in
3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3613	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3456		3624
3457	Not a libev limitation but worth mentioning: windows apparently doesn't	3625	Not a libev limitation but worth mentioning: windows apparently doesn't
3458	accept large writes: instead of resulting in a partial write, windows will	3626	accept large writes: instead of resulting in a partial write, windows will
3459	either accept everything or return C<ENOBUFS> if the buffer is too large,	3627	either accept everything or return C<ENOBUFS> if the buffer is too large,
3460	so make sure you only write small amounts into your sockets (less than a	3628	so make sure you only write small amounts into your sockets (less than a
3461	megabyte seems safe, but thsi apparently depends on the amount of memory	3629	megabyte seems safe, but this apparently depends on the amount of memory
3462	available).	3630	available).
3463		3631
3464	Due to the many, low, and arbitrary limits on the win32 platform and	3632	Due to the many, low, and arbitrary limits on the win32 platform and
3465	the abysmal performance of winsockets, using a large number of sockets	3633	the abysmal performance of winsockets, using a large number of sockets
3466	is not recommended (and not reasonable). If your program needs to use	3634	is not recommended (and not reasonable). If your program needs to use
…		…
3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3645	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3478		3646
3479	#include "ev.h"	3647	#include "ev.h"
3480		3648
3481	And compile the following F<evwrap.c> file into your project (make sure	3649	And compile the following F<evwrap.c> file into your project (make sure
3482	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3650	you do I<not> compile the F<ev.c> or any other embedded source files!):
3483		3651
3484	#include "evwrap.h"	3652	#include "evwrap.h"
3485	#include "ev.c"	3653	#include "ev.c"
3486		3654
3487	=over 4	3655	=over 4
…		…
3532	wrap all I/O functions and provide your own fd management, but the cost of	3700	wrap all I/O functions and provide your own fd management, but the cost of
3533	calling select (O(n²)) will likely make this unworkable.	3701	calling select (O(n²)) will likely make this unworkable.
3534		3702
3535	=back	3703	=back
3536		3704
3537
3538	=head1 PORTABILITY REQUIREMENTS	3705	=head2 PORTABILITY REQUIREMENTS
3539		3706
3540	In addition to a working ISO-C implementation, libev relies on a few	3707	In addition to a working ISO-C implementation and of course the
3541	additional extensions:	3708	backend-specific APIs, libev relies on a few additional extensions:
3542		3709
3543	=over 4	3710	=over 4
3544		3711
3545	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3712	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3546	calling conventions regardless of C<ev_watcher_type *>.	3713	calling conventions regardless of C<ev_watcher_type *>.
…		…
3552	calls them using an C<ev_watcher *> internally.	3719	calls them using an C<ev_watcher *> internally.
3553		3720
3554	=item C<sig_atomic_t volatile> must be thread-atomic as well	3721	=item C<sig_atomic_t volatile> must be thread-atomic as well
3555		3722
3556	The type C<sig_atomic_t volatile> (or whatever is defined as	3723	The type C<sig_atomic_t volatile> (or whatever is defined as
3557	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3724	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3558	threads. This is not part of the specification for C<sig_atomic_t>, but is	3725	threads. This is not part of the specification for C<sig_atomic_t>, but is
3559	believed to be sufficiently portable.	3726	believed to be sufficiently portable.
3560		3727
3561	=item C<sigprocmask> must work in a threaded environment	3728	=item C<sigprocmask> must work in a threaded environment
3562		3729
…		…
3571	except the initial one, and run the default loop in the initial thread as	3738	except the initial one, and run the default loop in the initial thread as
3572	well.	3739	well.
3573		3740
3574	=item C<long> must be large enough for common memory allocation sizes	3741	=item C<long> must be large enough for common memory allocation sizes
3575		3742
3576	To improve portability and simplify using libev, libev uses C<long>	3743	To improve portability and simplify its API, libev uses C<long> internally
3577	internally instead of C<size_t> when allocating its data structures. On	3744	instead of C<size_t> when allocating its data structures. On non-POSIX
3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3745	systems (Microsoft...) this might be unexpectedly low, but is still at
3579	is still at least 31 bits everywhere, which is enough for hundreds of	3746	least 31 bits everywhere, which is enough for hundreds of millions of
3580	millions of watchers.	3747	watchers.
3581		3748
3582	=item C<double> must hold a time value in seconds with enough accuracy	3749	=item C<double> must hold a time value in seconds with enough accuracy
3583		3750
3584	The type C<double> is used to represent timestamps. It is required to	3751	The type C<double> is used to represent timestamps. It is required to
3585	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3752	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3589	=back	3756	=back
3590		3757
3591	If you know of other additional requirements drop me a note.	3758	If you know of other additional requirements drop me a note.
3592		3759
3593		3760
3594	=head1 COMPILER WARNINGS	3761	=head1 ALGORITHMIC COMPLEXITIES
3595		3762
3596	Depending on your compiler and compiler settings, you might get no or a	3763	In this section the complexities of (many of) the algorithms used inside
3597	lot of warnings when compiling libev code. Some people are apparently	3764	libev will be documented. For complexity discussions about backends see
3598	scared by this.	3765	the documentation for C<ev_default_init>.
3599		3766
3600	However, these are unavoidable for many reasons. For one, each compiler	3767	All of the following are about amortised time: If an array needs to be
3601	has different warnings, and each user has different tastes regarding	3768	extended, libev needs to realloc and move the whole array, but this
3602	warning options. "Warn-free" code therefore cannot be a goal except when	3769	happens asymptotically rarer with higher number of elements, so O(1) might
3603	targeting a specific compiler and compiler-version.	3770	mean that libev does a lengthy realloc operation in rare cases, but on
		3771	average it is much faster and asymptotically approaches constant time.
3604		3772
3605	Another reason is that some compiler warnings require elaborate	3773	=over 4
3606	workarounds, or other changes to the code that make it less clear and less
3607	maintainable.
3608		3774
3609	And of course, some compiler warnings are just plain stupid, or simply	3775	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3610	wrong (because they don't actually warn about the condition their message
3611	seems to warn about).
3612		3776
3613	While libev is written to generate as few warnings as possible,	3777	This means that, when you have a watcher that triggers in one hour and
3614	"warn-free" code is not a goal, and it is recommended not to build libev	3778	there are 100 watchers that would trigger before that, then inserting will
3615	with any compiler warnings enabled unless you are prepared to cope with	3779	have to skip roughly seven (C<ld 100>) of these watchers.
3616	them (e.g. by ignoring them). Remember that warnings are just that:
3617	warnings, not errors, or proof of bugs.
3618		3780
		3781	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3619		3782
3620	=head1 VALGRIND	3783	That means that changing a timer costs less than removing/adding them,
		3784	as only the relative motion in the event queue has to be paid for.
3621		3785
3622	Valgrind has a special section here because it is a popular tool that is	3786	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3623	highly useful, but valgrind reports are very hard to interpret.
3624		3787
3625	If you think you found a bug (memory leak, uninitialised data access etc.)	3788	These just add the watcher into an array or at the head of a list.
3626	in libev, then check twice: If valgrind reports something like:
3627		3789
3628	==2274== definitely lost: 0 bytes in 0 blocks.	3790	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3629	==2274== possibly lost: 0 bytes in 0 blocks.
3630	==2274== still reachable: 256 bytes in 1 blocks.
3631		3791
3632	Then there is no memory leak. Similarly, under some circumstances,	3792	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3633	valgrind might report kernel bugs as if it were a bug in libev, or it
3634	might be confused (it is a very good tool, but only a tool).
3635		3793
3636	If you are unsure about something, feel free to contact the mailing list	3794	These watchers are stored in lists, so they need to be walked to find the
3637	with the full valgrind report and an explanation on why you think this is	3795	correct watcher to remove. The lists are usually short (you don't usually
3638	a bug in libev. However, don't be annoyed when you get a brisk "this is	3796	have many watchers waiting for the same fd or signal: one is typical, two
3639	no bug" answer and take the chance of learning how to interpret valgrind	3797	is rare).
3640	properly.
3641		3798
3642	If you need, for some reason, empty reports from valgrind for your project	3799	=item Finding the next timer in each loop iteration: O(1)
3643	I suggest using suppression lists.	3800
		3801	By virtue of using a binary or 4-heap, the next timer is always found at a
		3802	fixed position in the storage array.
		3803
		3804	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3805
		3806	A change means an I/O watcher gets started or stopped, which requires
		3807	libev to recalculate its status (and possibly tell the kernel, depending
		3808	on backend and whether C<ev_io_set> was used).
		3809
		3810	=item Activating one watcher (putting it into the pending state): O(1)
		3811
		3812	=item Priority handling: O(number_of_priorities)
		3813
		3814	Priorities are implemented by allocating some space for each
		3815	priority. When doing priority-based operations, libev usually has to
		3816	linearly search all the priorities, but starting/stopping and activating
		3817	watchers becomes O(1) with respect to priority handling.
		3818
		3819	=item Sending an ev_async: O(1)
		3820
		3821	=item Processing ev_async_send: O(number_of_async_watchers)
		3822
		3823	=item Processing signals: O(max_signal_number)
		3824
		3825	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3826	calls in the current loop iteration. Checking for async and signal events
		3827	involves iterating over all running async watchers or all signal numbers.
		3828
		3829	=back
3644		3830
3645		3831
3646	=head1 AUTHOR	3832	=head1 AUTHOR
3647		3833
3648	Marc Lehmann <libev@schmorp.de>.	3834	Marc Lehmann <libev@schmorp.de>.

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Comparing libev/ev.pod (file contents): Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs. Revision 1.199 by root, Thu Oct 23 07:18:21 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs.
Revision 1.199 by root, Thu Oct 23 07:18:21 2008 UTC