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

Comparing libev/ev.pod (file contents):
Revision 1.110 by root, Tue Dec 25 07:05:45 2007 UTC vs.
Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC

…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		261
262	If you don't know what event loop to use, use the one returned from this	262	If you don't know what event loop to use, use the one returned from this
263	function.	263	function.
264		264
		265	The default loop is the only loop that can handle C<ev_signal> and
		266	C<ev_child> watchers, and to do this, it always registers a handler
		267	for C<SIGCHLD>. If this is a problem for your app you can either
		268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		270	C<ev_default_init>.
		271
265	The flags argument can be used to specify special behaviour or specific	272	The flags argument can be used to specify special behaviour or specific
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	273	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		274
268	The following flags are supported:	275	The following flags are supported:
269		276
…		…
403	While this backend scales well, it requires one system call per active	410	While this backend scales well, it requires one system call per active
404	file descriptor per loop iteration. For small and medium numbers of file	411	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	413	might perform better.
407		414
		415	On the positive side, ignoring the spurious readyness notifications, this
		416	backend actually performed to specification in all tests and is fully
		417	embeddable, which is a rare feat among the OS-specific backends.
		418
408	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
409		420
410	Try all backends (even potentially broken ones that wouldn't be tried	421	Try all backends (even potentially broken ones that wouldn't be tried
411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
…		…
414	It is definitely not recommended to use this flag.	425	It is definitely not recommended to use this flag.
415		426
416	=back	427	=back
417		428
418	If one or more of these are ored into the flags value, then only these	429	If one or more of these are ored into the flags value, then only these
419	backends will be tried (in the reverse order as given here). If none are	430	backends will be tried (in the reverse order as listed here). If none are
420	specified, most compiled-in backend will be tried, usually in reverse	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		432
423	The most typical usage is like this:	433	The most typical usage is like this:
424		434
425	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	483	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
475		485
476	=item ev_default_fork ()	486	=item ev_default_fork ()
477		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	490	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	491	the child process (or both child and parent, but that again makes little
481	again makes little sense).	492	sense). You I<must> call it in the child before using any of the libev
		493	functions, and it will only take effect at the next C<ev_loop> iteration.
482		494
483	You I<must> call this function in the child process after forking if and	495	On the other hand, you only need to call this function in the child
484	only if you want to use the event library in both processes. If you just	496	process if and only if you want to use the event library in the child. If
485	fork+exec, you don't have to call it.	497	you just fork+exec, you don't have to call it at all.
486		498
487	The function itself is quite fast and it's usually not a problem to call	499	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	500	it just in case after a fork. To make this easy, the function will fit in
489	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
490		502
491	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
492		504
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496
497	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
498		506
499	Like C<ev_default_fork>, but acts on an event loop created by	507	Like C<ev_default_fork>, but acts on an event loop created by
500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
501	after fork, and how you do this is entirely your own problem.	509	after fork, and how you do this is entirely your own problem.
		510
		511	=item int ev_is_default_loop (loop)
		512
		513	Returns true when the given loop actually is the default loop, false otherwise.
502		514
503	=item unsigned int ev_loop_count (loop)	515	=item unsigned int ev_loop_count (loop)
504		516
505	Returns the count of loop iterations for the loop, which is identical to	517	Returns the count of loop iterations for the loop, which is identical to
506	the number of times libev did poll for new events. It starts at C<0> and	518	the number of times libev did poll for new events. It starts at C<0> and
…		…
551	usually a better approach for this kind of thing.	563	usually a better approach for this kind of thing.
552		564
553	Here are the gory details of what C<ev_loop> does:	565	Here are the gory details of what C<ev_loop> does:
554		566
555	- Before the first iteration, call any pending watchers.	567	- Before the first iteration, call any pending watchers.
556	* If there are no active watchers (reference count is zero), return.	568	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- Queue all prepare watchers and then call all outstanding watchers.	569	- If a fork was detected, queue and call all fork watchers.
		570	- Queue and call all prepare watchers.
558	- If we have been forked, recreate the kernel state.	571	- If we have been forked, recreate the kernel state.
559	- Update the kernel state with all outstanding changes.	572	- Update the kernel state with all outstanding changes.
560	- Update the "event loop time".	573	- Update the "event loop time".
561	- Calculate for how long to block.	574	- Calculate for how long to sleep or block, if at all
		575	(active idle watchers, EVLOOP_NONBLOCK or not having
		576	any active watchers at all will result in not sleeping).
		577	- Sleep if the I/O and timer collect interval say so.
562	- Block the process, waiting for any events.	578	- Block the process, waiting for any events.
563	- Queue all outstanding I/O (fd) events.	579	- Queue all outstanding I/O (fd) events.
564	- Update the "event loop time" and do time jump handling.	580	- Update the "event loop time" and do time jump handling.
565	- Queue all outstanding timers.	581	- Queue all outstanding timers.
566	- Queue all outstanding periodics.	582	- Queue all outstanding periodics.
567	- If no events are pending now, queue all idle watchers.	583	- If no events are pending now, queue all idle watchers.
568	- Queue all check watchers.	584	- Queue all check watchers.
569	- Call all queued watchers in reverse order (i.e. check watchers first).	585	- Call all queued watchers in reverse order (i.e. check watchers first).
570	Signals and child watchers are implemented as I/O watchers, and will	586	Signals and child watchers are implemented as I/O watchers, and will
571	be handled here by queueing them when their watcher gets executed.	587	be handled here by queueing them when their watcher gets executed.
572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	588	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573	were used, return, otherwise continue with step *.	589	were used, or there are no active watchers, return, otherwise
		590	continue with step *.
574		591
575	Example: Queue some jobs and then loop until no events are outsanding	592	Example: Queue some jobs and then loop until no events are outstanding
576	anymore.	593	anymore.
577		594
578	... queue jobs here, make sure they register event watchers as long	595	... queue jobs here, make sure they register event watchers as long
579	... as they still have work to do (even an idle watcher will do..)	596	... as they still have work to do (even an idle watcher will do..)
580	ev_loop (my_loop, 0);	597	ev_loop (my_loop, 0);
…		…
584		601
585	Can be used to make a call to C<ev_loop> return early (but only after it	602	Can be used to make a call to C<ev_loop> return early (but only after it
586	has processed all outstanding events). The C<how> argument must be either	603	has processed all outstanding events). The C<how> argument must be either
587	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	604	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
588	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	605	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		606
		607	This "unloop state" will be cleared when entering C<ev_loop> again.
589		608
590	=item ev_ref (loop)	609	=item ev_ref (loop)
591		610
592	=item ev_unref (loop)	611	=item ev_unref (loop)
593		612
…		…
598	returning, ev_unref() after starting, and ev_ref() before stopping it. For	617	returning, ev_unref() after starting, and ev_ref() before stopping it. For
599	example, libev itself uses this for its internal signal pipe: It is not	618	example, libev itself uses this for its internal signal pipe: It is not
600	visible to the libev user and should not keep C<ev_loop> from exiting if	619	visible to the libev user and should not keep C<ev_loop> from exiting if
601	no event watchers registered by it are active. It is also an excellent	620	no event watchers registered by it are active. It is also an excellent
602	way to do this for generic recurring timers or from within third-party	621	way to do this for generic recurring timers or from within third-party
603	libraries. Just remember to I<unref after start> and I<ref before stop>.	622	libraries. Just remember to I<unref after start> and I<ref before stop>
		623	(but only if the watcher wasn't active before, or was active before,
		624	respectively).
604		625
605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	626	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606	running when nothing else is active.	627	running when nothing else is active.
607		628
608	struct ev_signal exitsig;	629	struct ev_signal exitsig;
…		…
756		777
757	=item C<EV_FORK>	778	=item C<EV_FORK>
758		779
759	The event loop has been resumed in the child process after fork (see	780	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	781	C<ev_fork>).
		782
		783	=item C<EV_ASYNC>
		784
		785	The given async watcher has been asynchronously notified (see C<ev_async>).
761		786
762	=item C<EV_ERROR>	787	=item C<EV_ERROR>
763		788
764	An unspecified error has occured, the watcher has been stopped. This might	789	An unspecified error has occured, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	790	happen because the watcher could not be properly started because libev
…		…
1068		1093
1069	The events being watched.	1094	The events being watched.
1070		1095
1071	=back	1096	=back
1072		1097
		1098	=head3 Examples
		1099
1073	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1100	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1074	readable, but only once. Since it is likely line-buffered, you could	1101	readable, but only once. Since it is likely line-buffered, you could
1075	attempt to read a whole line in the callback.	1102	attempt to read a whole line in the callback.
1076		1103
1077	static void	1104	static void
…		…
1129	configure a timer to trigger every 10 seconds, then it will trigger at	1156	configure a timer to trigger every 10 seconds, then it will trigger at
1130	exactly 10 second intervals. If, however, your program cannot keep up with	1157	exactly 10 second intervals. If, however, your program cannot keep up with
1131	the timer (because it takes longer than those 10 seconds to do stuff) the	1158	the timer (because it takes longer than those 10 seconds to do stuff) the
1132	timer will not fire more than once per event loop iteration.	1159	timer will not fire more than once per event loop iteration.
1133		1160
1134	=item ev_timer_again (loop)	1161	=item ev_timer_again (loop, ev_timer *)
1135		1162
1136	This will act as if the timer timed out and restart it again if it is	1163	This will act as if the timer timed out and restart it again if it is
1137	repeating. The exact semantics are:	1164	repeating. The exact semantics are:
1138		1165
1139	If the timer is pending, its pending status is cleared.	1166	If the timer is pending, its pending status is cleared.
…		…
1174	or C<ev_timer_again> is called and determines the next timeout (if any),	1201	or C<ev_timer_again> is called and determines the next timeout (if any),
1175	which is also when any modifications are taken into account.	1202	which is also when any modifications are taken into account.
1176		1203
1177	=back	1204	=back
1178		1205
		1206	=head3 Examples
		1207
1179	Example: Create a timer that fires after 60 seconds.	1208	Example: Create a timer that fires after 60 seconds.
1180		1209
1181	static void	1210	static void
1182	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1211	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
1183	{	1212	{
…		…
1246	In this configuration the watcher triggers an event at the wallclock time	1275	In this configuration the watcher triggers an event at the wallclock time
1247	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1276	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1248	that is, if it is to be run at January 1st 2011 then it will run when the	1277	that is, if it is to be run at January 1st 2011 then it will run when the
1249	system time reaches or surpasses this time.	1278	system time reaches or surpasses this time.
1250		1279
1251	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1280	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1252		1281
1253	In this mode the watcher will always be scheduled to time out at the next	1282	In this mode the watcher will always be scheduled to time out at the next
1254	C<at + N * interval> time (for some integer N, which can also be negative)	1283	C<at + N * interval> time (for some integer N, which can also be negative)
1255	and then repeat, regardless of any time jumps.	1284	and then repeat, regardless of any time jumps.
1256		1285
…		…
1339		1368
1340	When active, contains the absolute time that the watcher is supposed to	1369	When active, contains the absolute time that the watcher is supposed to
1341	trigger next.	1370	trigger next.
1342		1371
1343	=back	1372	=back
		1373
		1374	=head3 Examples
1344		1375
1345	Example: Call a callback every hour, or, more precisely, whenever the	1376	Example: Call a callback every hour, or, more precisely, whenever the
1346	system clock is divisible by 3600. The callback invocation times have	1377	system clock is divisible by 3600. The callback invocation times have
1347	potentially a lot of jittering, but good long-term stability.	1378	potentially a lot of jittering, but good long-term stability.
1348		1379
…		…
1405		1436
1406	The signal the watcher watches out for.	1437	The signal the watcher watches out for.
1407		1438
1408	=back	1439	=back
1409		1440
		1441	=head3 Examples
		1442
		1443	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1444
		1445	static void
		1446	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1447	{
		1448	ev_unloop (loop, EVUNLOOP_ALL);
		1449	}
		1450
		1451	struct ev_signal signal_watcher;
		1452	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1453	ev_signal_start (loop, &sigint_cb);
		1454
1410		1455
1411	=head2 C<ev_child> - watch out for process status changes	1456	=head2 C<ev_child> - watch out for process status changes
1412		1457
1413	Child watchers trigger when your process receives a SIGCHLD in response to	1458	Child watchers trigger when your process receives a SIGCHLD in response to
1414	some child status changes (most typically when a child of yours dies).	1459	some child status changes (most typically when a child of yours dies). It
		1460	is permissible to install a child watcher I<after> the child has been
		1461	forked (which implies it might have already exited), as long as the event
		1462	loop isn't entered (or is continued from a watcher).
		1463
		1464	Only the default event loop is capable of handling signals, and therefore
		1465	you can only rgeister child watchers in the default event loop.
		1466
		1467	=head3 Process Interaction
		1468
		1469	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1470	initialised. This is necessary to guarantee proper behaviour even if
		1471	the first child watcher is started after the child exits. The occurance
		1472	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1473	synchronously as part of the event loop processing. Libev always reaps all
		1474	children, even ones not watched.
		1475
		1476	=head3 Overriding the Built-In Processing
		1477
		1478	Libev offers no special support for overriding the built-in child
		1479	processing, but if your application collides with libev's default child
		1480	handler, you can override it easily by installing your own handler for
		1481	C<SIGCHLD> after initialising the default loop, and making sure the
		1482	default loop never gets destroyed. You are encouraged, however, to use an
		1483	event-based approach to child reaping and thus use libev's support for
		1484	that, so other libev users can use C<ev_child> watchers freely.
1415		1485
1416	=head3 Watcher-Specific Functions and Data Members	1486	=head3 Watcher-Specific Functions and Data Members
1417		1487
1418	=over 4	1488	=over 4
1419		1489
1420	=item ev_child_init (ev_child *, callback, int pid)	1490	=item ev_child_init (ev_child *, callback, int pid, int trace)
1421		1491
1422	=item ev_child_set (ev_child *, int pid)	1492	=item ev_child_set (ev_child *, int pid, int trace)
1423		1493
1424	Configures the watcher to wait for status changes of process C<pid> (or	1494	Configures the watcher to wait for status changes of process C<pid> (or
1425	I<any> process if C<pid> is specified as C<0>). The callback can look	1495	I<any> process if C<pid> is specified as C<0>). The callback can look
1426	at the C<rstatus> member of the C<ev_child> watcher structure to see	1496	at the C<rstatus> member of the C<ev_child> watcher structure to see
1427	the status word (use the macros from C<sys/wait.h> and see your systems	1497	the status word (use the macros from C<sys/wait.h> and see your systems
1428	C<waitpid> documentation). The C<rpid> member contains the pid of the	1498	C<waitpid> documentation). The C<rpid> member contains the pid of the
1429	process causing the status change.	1499	process causing the status change. C<trace> must be either C<0> (only
		1500	activate the watcher when the process terminates) or C<1> (additionally
		1501	activate the watcher when the process is stopped or continued).
1430		1502
1431	=item int pid [read-only]	1503	=item int pid [read-only]
1432		1504
1433	The process id this watcher watches out for, or C<0>, meaning any process id.	1505	The process id this watcher watches out for, or C<0>, meaning any process id.
1434		1506
…		…
1441	The process exit/trace status caused by C<rpid> (see your systems	1513	The process exit/trace status caused by C<rpid> (see your systems
1442	C<waitpid> and C<sys/wait.h> documentation for details).	1514	C<waitpid> and C<sys/wait.h> documentation for details).
1443		1515
1444	=back	1516	=back
1445		1517
1446	Example: Try to exit cleanly on SIGINT and SIGTERM.	1518	=head3 Examples
		1519
		1520	Example: C<fork()> a new process and install a child handler to wait for
		1521	its completion.
		1522
		1523	ev_child cw;
1447		1524
1448	static void	1525	static void
1449	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1526	child_cb (EV_P_ struct ev_child *w, int revents)
1450	{	1527	{
1451	ev_unloop (loop, EVUNLOOP_ALL);	1528	ev_child_stop (EV_A_ w);
		1529	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1452	}	1530	}
1453		1531
1454	struct ev_signal signal_watcher;	1532	pid_t pid = fork ();
1455	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1533
1456	ev_signal_start (loop, &sigint_cb);	1534	if (pid < 0)
		1535	// error
		1536	else if (pid == 0)
		1537	{
		1538	// the forked child executes here
		1539	exit (1);
		1540	}
		1541	else
		1542	{
		1543	ev_child_init (&cw, child_cb, pid, 0);
		1544	ev_child_start (EV_DEFAULT_ &cw);
		1545	}
1457		1546
1458		1547
1459	=head2 C<ev_stat> - did the file attributes just change?	1548	=head2 C<ev_stat> - did the file attributes just change?
1460		1549
1461	This watches a filesystem path for attribute changes. That is, it calls	1550	This watches a filesystem path for attribute changes. That is, it calls
…		…
1541		1630
1542	The callback will be receive C<EV_STAT> when a change was detected,	1631	The callback will be receive C<EV_STAT> when a change was detected,
1543	relative to the attributes at the time the watcher was started (or the	1632	relative to the attributes at the time the watcher was started (or the
1544	last change was detected).	1633	last change was detected).
1545		1634
1546	=item ev_stat_stat (ev_stat *)	1635	=item ev_stat_stat (loop, ev_stat *)
1547		1636
1548	Updates the stat buffer immediately with new values. If you change the	1637	Updates the stat buffer immediately with new values. If you change the
1549	watched path in your callback, you could call this fucntion to avoid	1638	watched path in your callback, you could call this fucntion to avoid
1550	detecting this change (while introducing a race condition). Can also be	1639	detecting this change (while introducing a race condition). Can also be
1551	useful simply to find out the new values.	1640	useful simply to find out the new values.
…		…
1658	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1747	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1659	believe me.	1748	believe me.
1660		1749
1661	=back	1750	=back
1662		1751
		1752	=head3 Examples
		1753
1663	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1754	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1664	callback, free it. Also, use no error checking, as usual.	1755	callback, free it. Also, use no error checking, as usual.
1665		1756
1666	static void	1757	static void
1667	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1758	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1668	{	1759	{
1669	free (w);	1760	free (w);
1670	// now do something you wanted to do when the program has	1761	// now do something you wanted to do when the program has
1671	// no longer asnything immediate to do.	1762	// no longer anything immediate to do.
1672	}	1763	}
1673		1764
1674	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1765	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1675	ev_idle_init (idle_watcher, idle_cb);	1766	ev_idle_init (idle_watcher, idle_cb);
1676	ev_idle_start (loop, idle_cb);	1767	ev_idle_start (loop, idle_cb);
…		…
1738	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1829	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1739	macros, but using them is utterly, utterly and completely pointless.	1830	macros, but using them is utterly, utterly and completely pointless.
1740		1831
1741	=back	1832	=back
1742		1833
		1834	=head3 Examples
		1835
1743	There are a number of principal ways to embed other event loops or modules	1836	There are a number of principal ways to embed other event loops or modules
1744	into libev. Here are some ideas on how to include libadns into libev	1837	into libev. Here are some ideas on how to include libadns into libev
1745	(there is a Perl module named C<EV::ADNS> that does this, which you could	1838	(there is a Perl module named C<EV::ADNS> that does this, which you could
1746	use for an actually working example. Another Perl module named C<EV::Glib>	1839	use for an actually working example. Another Perl module named C<EV::Glib>
1747	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1840	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
…		…
1915	portable one.	2008	portable one.
1916		2009
1917	So when you want to use this feature you will always have to be prepared	2010	So when you want to use this feature you will always have to be prepared
1918	that you cannot get an embeddable loop. The recommended way to get around	2011	that you cannot get an embeddable loop. The recommended way to get around
1919	this is to have a separate variables for your embeddable loop, try to	2012	this is to have a separate variables for your embeddable loop, try to
1920	create it, and if that fails, use the normal loop for everything:	2013	create it, and if that fails, use the normal loop for everything.
		2014
		2015	=head3 Watcher-Specific Functions and Data Members
		2016
		2017	=over 4
		2018
		2019	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		2020
		2021	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		2022
		2023	Configures the watcher to embed the given loop, which must be
		2024	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2025	invoked automatically, otherwise it is the responsibility of the callback
		2026	to invoke it (it will continue to be called until the sweep has been done,
		2027	if you do not want thta, you need to temporarily stop the embed watcher).
		2028
		2029	=item ev_embed_sweep (loop, ev_embed *)
		2030
		2031	Make a single, non-blocking sweep over the embedded loop. This works
		2032	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2033	apropriate way for embedded loops.
		2034
		2035	=item struct ev_loop *other [read-only]
		2036
		2037	The embedded event loop.
		2038
		2039	=back
		2040
		2041	=head3 Examples
		2042
		2043	Example: Try to get an embeddable event loop and embed it into the default
		2044	event loop. If that is not possible, use the default loop. The default
		2045	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2046	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2047	used).
1921		2048
1922	struct ev_loop *loop_hi = ev_default_init (0);	2049	struct ev_loop *loop_hi = ev_default_init (0);
1923	struct ev_loop *loop_lo = 0;	2050	struct ev_loop *loop_lo = 0;
1924	struct ev_embed embed;	2051	struct ev_embed embed;
1925		2052
…		…
1936	ev_embed_start (loop_hi, &embed);	2063	ev_embed_start (loop_hi, &embed);
1937	}	2064	}
1938	else	2065	else
1939	loop_lo = loop_hi;	2066	loop_lo = loop_hi;
1940		2067
1941	=head3 Watcher-Specific Functions and Data Members	2068	Example: Check if kqueue is available but not recommended and create
		2069	a kqueue backend for use with sockets (which usually work with any
		2070	kqueue implementation). Store the kqueue/socket-only event loop in
		2071	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1942		2072
1943	=over 4	2073	struct ev_loop *loop = ev_default_init (0);
		2074	struct ev_loop *loop_socket = 0;
		2075	struct ev_embed embed;
		2076
		2077	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2078	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2079	{
		2080	ev_embed_init (&embed, 0, loop_socket);
		2081	ev_embed_start (loop, &embed);
		2082	}
1944		2083
1945	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2084	if (!loop_socket)
		2085	loop_socket = loop;
1946		2086
1947	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	2087	// now use loop_socket for all sockets, and loop for everything else
1948
1949	Configures the watcher to embed the given loop, which must be
1950	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1951	invoked automatically, otherwise it is the responsibility of the callback
1952	to invoke it (it will continue to be called until the sweep has been done,
1953	if you do not want thta, you need to temporarily stop the embed watcher).
1954
1955	=item ev_embed_sweep (loop, ev_embed *)
1956
1957	Make a single, non-blocking sweep over the embedded loop. This works
1958	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1959	apropriate way for embedded loops.
1960
1961	=item struct ev_loop *other [read-only]
1962
1963	The embedded event loop.
1964
1965	=back
1966		2088
1967		2089
1968	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2090	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1969		2091
1970	Fork watchers are called when a C<fork ()> was detected (usually because	2092	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1986	believe me.	2108	believe me.
1987		2109
1988	=back	2110	=back
1989		2111
1990		2112
		2113	=head2 C<ev_async> - how to wake up another event loop
		2114
		2115	In general, you cannot use an C<ev_loop> from multiple threads or other
		2116	asynchronous sources such as signal handlers (as opposed to multiple event
		2117	loops - those are of course safe to use in different threads).
		2118
		2119	Sometimes, however, you need to wake up another event loop you do not
		2120	control, for example because it belongs to another thread. This is what
		2121	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2122	can signal it by calling C<ev_async_send>, which is thread- and signal
		2123	safe.
		2124
		2125	This functionality is very similar to C<ev_signal> watchers, as signals,
		2126	too, are asynchronous in nature, and signals, too, will be compressed
		2127	(i.e. the number of callback invocations may be less than the number of
		2128	C<ev_async_sent> calls).
		2129
		2130	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2131	just the default loop.
		2132
		2133	=head3 Queueing
		2134
		2135	C<ev_async> does not support queueing of data in any way. The reason
		2136	is that the author does not know of a simple (or any) algorithm for a
		2137	multiple-writer-single-reader queue that works in all cases and doesn't
		2138	need elaborate support such as pthreads.
		2139
		2140	That means that if you want to queue data, you have to provide your own
		2141	queue. But at least I can tell you would implement locking around your
		2142	queue:
		2143
		2144	=over 4
		2145
		2146	=item queueing from a signal handler context
		2147
		2148	To implement race-free queueing, you simply add to the queue in the signal
		2149	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2150	some fictitiuous SIGUSR1 handler:
		2151
		2152	static ev_async mysig;
		2153
		2154	static void
		2155	sigusr1_handler (void)
		2156	{
		2157	sometype data;
		2158
		2159	// no locking etc.
		2160	queue_put (data);
		2161	ev_async_send (EV_DEFAULT_ &mysig);
		2162	}
		2163
		2164	static void
		2165	mysig_cb (EV_P_ ev_async *w, int revents)
		2166	{
		2167	sometype data;
		2168	sigset_t block, prev;
		2169
		2170	sigemptyset (&block);
		2171	sigaddset (&block, SIGUSR1);
		2172	sigprocmask (SIG_BLOCK, &block, &prev);
		2173
		2174	while (queue_get (&data))
		2175	process (data);
		2176
		2177	if (sigismember (&prev, SIGUSR1)
		2178	sigprocmask (SIG_UNBLOCK, &block, 0);
		2179	}
		2180
		2181	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2182	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2183	either...).
		2184
		2185	=item queueing from a thread context
		2186
		2187	The strategy for threads is different, as you cannot (easily) block
		2188	threads but you can easily preempt them, so to queue safely you need to
		2189	employ a traditional mutex lock, such as in this pthread example:
		2190
		2191	static ev_async mysig;
		2192	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2193
		2194	static void
		2195	otherthread (void)
		2196	{
		2197	// only need to lock the actual queueing operation
		2198	pthread_mutex_lock (&mymutex);
		2199	queue_put (data);
		2200	pthread_mutex_unlock (&mymutex);
		2201
		2202	ev_async_send (EV_DEFAULT_ &mysig);
		2203	}
		2204
		2205	static void
		2206	mysig_cb (EV_P_ ev_async *w, int revents)
		2207	{
		2208	pthread_mutex_lock (&mymutex);
		2209
		2210	while (queue_get (&data))
		2211	process (data);
		2212
		2213	pthread_mutex_unlock (&mymutex);
		2214	}
		2215
		2216	=back
		2217
		2218
		2219	=head3 Watcher-Specific Functions and Data Members
		2220
		2221	=over 4
		2222
		2223	=item ev_async_init (ev_async *, callback)
		2224
		2225	Initialises and configures the async watcher - it has no parameters of any
		2226	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2227	believe me.
		2228
		2229	=item ev_async_send (loop, ev_async *)
		2230
		2231	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2232	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2233	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2234	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2235	section below on what exactly this means).
		2236
		2237	This call incurs the overhead of a syscall only once per loop iteration,
		2238	so while the overhead might be noticable, it doesn't apply to repeated
		2239	calls to C<ev_async_send>.
		2240
		2241	=back
		2242
		2243
1991	=head1 OTHER FUNCTIONS	2244	=head1 OTHER FUNCTIONS
1992		2245
1993	There are some other functions of possible interest. Described. Here. Now.	2246	There are some other functions of possible interest. Described. Here. Now.
1994		2247
1995	=over 4	2248	=over 4
…		…
2222	Example: Define a class with an IO and idle watcher, start one of them in	2475	Example: Define a class with an IO and idle watcher, start one of them in
2223	the constructor.	2476	the constructor.
2224		2477
2225	class myclass	2478	class myclass
2226	{	2479	{
2227	ev_io io; void io_cb (ev::io &w, int revents);	2480	ev::io io; void io_cb (ev::io &w, int revents);
2228	ev_idle idle void idle_cb (ev::idle &w, int revents);	2481	ev:idle idle void idle_cb (ev::idle &w, int revents);
2229		2482
2230	myclass ();	2483	myclass (int fd)
2231	}
2232
2233	myclass::myclass (int fd)
2234	{	2484	{
2235	io .set <myclass, &myclass::io_cb > (this);	2485	io .set <myclass, &myclass::io_cb > (this);
2236	idle.set <myclass, &myclass::idle_cb> (this);	2486	idle.set <myclass, &myclass::idle_cb> (this);
2237		2487
2238	io.start (fd, ev::READ);	2488	io.start (fd, ev::READ);
		2489	}
2239	}	2490	};
2240		2491
2241		2492
2242	=head1 MACRO MAGIC	2493	=head1 MACRO MAGIC
2243		2494
2244	Libev can be compiled with a variety of options, the most fundamantal	2495	Libev can be compiled with a variety of options, the most fundamantal
…		…
2449	wants osf handles on win32 (this is the case when the select to	2700	wants osf handles on win32 (this is the case when the select to
2450	be used is the winsock select). This means that it will call	2701	be used is the winsock select). This means that it will call
2451	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2702	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2452	it is assumed that all these functions actually work on fds, even	2703	it is assumed that all these functions actually work on fds, even
2453	on win32. Should not be defined on non-win32 platforms.	2704	on win32. Should not be defined on non-win32 platforms.
		2705
		2706	=item EV_FD_TO_WIN32_HANDLE
		2707
		2708	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2709	file descriptors to socket handles. When not defining this symbol (the
		2710	default), then libev will call C<_get_osfhandle>, which is usually
		2711	correct. In some cases, programs use their own file descriptor management,
		2712	in which case they can provide this function to map fds to socket handles.
2454		2713
2455	=item EV_USE_POLL	2714	=item EV_USE_POLL
2456		2715
2457	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2716	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2458	backend. Otherwise it will be enabled on non-win32 platforms. It	2717	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2492		2751
2493	If defined to be C<1>, libev will compile in support for the Linux inotify	2752	If defined to be C<1>, libev will compile in support for the Linux inotify
2494	interface to speed up C<ev_stat> watchers. Its actual availability will	2753	interface to speed up C<ev_stat> watchers. Its actual availability will
2495	be detected at runtime.	2754	be detected at runtime.
2496		2755
		2756	=item EV_ATOMIC_T
		2757
		2758	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2759	access is atomic with respect to other threads or signal contexts. No such
		2760	type is easily found in the C language, so you can provide your own type
		2761	that you know is safe for your purposes. It is used both for signal handler "locking"
		2762	as well as for signal and thread safety in C<ev_async> watchers.
		2763
		2764	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2765	(from F<signal.h>), which is usually good enough on most platforms.
		2766
2497	=item EV_H	2767	=item EV_H
2498		2768
2499	The name of the F<ev.h> header file used to include it. The default if	2769	The name of the F<ev.h> header file used to include it. The default if
2500	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	2770	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2501	virtually rename the F<ev.h> header file in case of conflicts.	2771	used to virtually rename the F<ev.h> header file in case of conflicts.
2502		2772
2503	=item EV_CONFIG_H	2773	=item EV_CONFIG_H
2504		2774
2505	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2775	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2506	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2776	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2507	C<EV_H>, above.	2777	C<EV_H>, above.
2508		2778
2509	=item EV_EVENT_H	2779	=item EV_EVENT_H
2510		2780
2511	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2781	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2512	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	2782	of how the F<event.h> header can be found, the default is C<"event.h">.
2513		2783
2514	=item EV_PROTOTYPES	2784	=item EV_PROTOTYPES
2515		2785
2516	If defined to be C<0>, then F<ev.h> will not define any function	2786	If defined to be C<0>, then F<ev.h> will not define any function
2517	prototypes, but still define all the structs and other symbols. This is	2787	prototypes, but still define all the structs and other symbols. This is
…		…
2566	defined to be C<0>, then they are not.	2836	defined to be C<0>, then they are not.
2567		2837
2568	=item EV_FORK_ENABLE	2838	=item EV_FORK_ENABLE
2569		2839
2570	If undefined or defined to be C<1>, then fork watchers are supported. If	2840	If undefined or defined to be C<1>, then fork watchers are supported. If
		2841	defined to be C<0>, then they are not.
		2842
		2843	=item EV_ASYNC_ENABLE
		2844
		2845	If undefined or defined to be C<1>, then async watchers are supported. If
2571	defined to be C<0>, then they are not.	2846	defined to be C<0>, then they are not.
2572		2847
2573	=item EV_MINIMAL	2848	=item EV_MINIMAL
2574		2849
2575	If you need to shave off some kilobytes of code at the expense of some	2850	If you need to shave off some kilobytes of code at the expense of some
…		…
2696	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	2971	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2697		2972
2698	That means that changing a timer costs less than removing/adding them	2973	That means that changing a timer costs less than removing/adding them
2699	as only the relative motion in the event queue has to be paid for.	2974	as only the relative motion in the event queue has to be paid for.
2700		2975
2701	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2976	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2702		2977
2703	These just add the watcher into an array or at the head of a list.	2978	These just add the watcher into an array or at the head of a list.
2704		2979
2705	=item Stopping check/prepare/idle watchers: O(1)	2980	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2706		2981
2707	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2982	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2708		2983
2709	These watchers are stored in lists then need to be walked to find the	2984	These watchers are stored in lists then need to be walked to find the
2710	correct watcher to remove. The lists are usually short (you don't usually	2985	correct watcher to remove. The lists are usually short (you don't usually
…		…
2726	=item Priority handling: O(number_of_priorities)	3001	=item Priority handling: O(number_of_priorities)
2727		3002
2728	Priorities are implemented by allocating some space for each	3003	Priorities are implemented by allocating some space for each
2729	priority. When doing priority-based operations, libev usually has to	3004	priority. When doing priority-based operations, libev usually has to
2730	linearly search all the priorities, but starting/stopping and activating	3005	linearly search all the priorities, but starting/stopping and activating
2731	watchers becomes O(1) w.r.t. prioritiy handling.	3006	watchers becomes O(1) w.r.t. priority handling.
		3007
		3008	=item Sending an ev_async: O(1)
		3009
		3010	=item Processing ev_async_send: O(number_of_async_watchers)
		3011
		3012	=item Processing signals: O(max_signal_number)
		3013
		3014	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3015	calls in the current loop iteration. Checking for async and signal events
		3016	involves iterating over all running async watchers or all signal numbers.
2732		3017
2733	=back	3018	=back
2734		3019
2735		3020
		3021	=head1 Win32 platform limitations and workarounds
		3022
		3023	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3024	requires, and its I/O model is fundamentally incompatible with the POSIX
		3025	model. Libev still offers limited functionality on this platform in
		3026	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3027	descriptors. This only applies when using Win32 natively, not when using
		3028	e.g. cygwin.
		3029
		3030	There is no supported compilation method available on windows except
		3031	embedding it into other applications.
		3032
		3033	Due to the many, low, and arbitrary limits on the win32 platform and the
		3034	abysmal performance of winsockets, using a large number of sockets is not
		3035	recommended (and not reasonable). If your program needs to use more than
		3036	a hundred or so sockets, then likely it needs to use a totally different
		3037	implementation for windows, as libev offers the POSIX model, which cannot
		3038	be implemented efficiently on windows (microsoft monopoly games).
		3039
		3040	=over 4
		3041
		3042	=item The winsocket select function
		3043
		3044	The winsocket C<select> function doesn't follow POSIX in that it requires
		3045	socket I<handles> and not socket I<file descriptors>. This makes select
		3046	very inefficient, and also requires a mapping from file descriptors
		3047	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3048	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3049	symbols for more info.
		3050
		3051	The configuration for a "naked" win32 using the microsoft runtime
		3052	libraries and raw winsocket select is:
		3053
		3054	#define EV_USE_SELECT 1
		3055	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3056
		3057	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3058	complexity in the O(n²) range when using win32.
		3059
		3060	=item Limited number of file descriptors
		3061
		3062	Windows has numerous arbitrary (and low) limits on things. Early versions
		3063	of winsocket's select only supported waiting for a max. of C<64> handles
		3064	(probably owning to the fact that all windows kernels can only wait for
		3065	C<64> things at the same time internally; microsoft recommends spawning a
		3066	chain of threads and wait for 63 handles and the previous thread in each).
		3067
		3068	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3069	to some high number (e.g. C<2048>) before compiling the winsocket select
		3070	call (which might be in libev or elsewhere, for example, perl does its own
		3071	select emulation on windows).
		3072
		3073	Another limit is the number of file descriptors in the microsoft runtime
		3074	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3075	or something like this inside microsoft). You can increase this by calling
		3076	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3077	arbitrary limit), but is broken in many versions of the microsoft runtime
		3078	libraries.
		3079
		3080	This might get you to about C<512> or C<2048> sockets (depending on
		3081	windows version and/or the phase of the moon). To get more, you need to
		3082	wrap all I/O functions and provide your own fd management, but the cost of
		3083	calling select (O(n²)) will likely make this unworkable.
		3084
		3085	=back
		3086
		3087
2736	=head1 AUTHOR	3088	=head1 AUTHOR
2737		3089
2738	Marc Lehmann <libev@schmorp.de>.	3090	Marc Lehmann <libev@schmorp.de>.
2739		3091

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Comparing libev/ev.pod (file contents): Revision 1.110 by root, Tue Dec 25 07:05:45 2007 UTC vs. Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.110 by root, Tue Dec 25 07:05:45 2007 UTC vs.
Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC