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

Comparing libev/ev.pod (file contents):
Revision 1.117 by root, Wed Jan 9 04:15:39 2008 UTC vs.
Revision 1.138 by root, Mon Mar 31 01:14:12 2008 UTC

…		…
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
		19	// all watcher callbacks have a similar signature
16	/* called when data readable on stdin */	20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* 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
38	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);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
…		…
84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head2 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		276
262	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
263	function.	278	function.
264		279
		280	The default loop is the only loop that can handle C<ev_signal> and
		281	C<ev_child> watchers, and to do this, it always registers a handler
		282	for C<SIGCHLD>. If this is a problem for your app you can either
		283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		285	C<ev_default_init>.
		286
265	The flags argument can be used to specify special behaviour or specific	287	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>).	288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		289
268	The following flags are supported:	290	The following flags are supported:
269		291
…		…
290	enabling this flag.	312	enabling this flag.
291		313
292	This works by calling C<getpid ()> on every iteration of the loop,	314	This works by calling C<getpid ()> on every iteration of the loop,
293	and thus this might slow down your event loop if you do a lot of loop	315	and thus this might slow down your event loop if you do a lot of loop
294	iterations and little real work, but is usually not noticeable (on my	316	iterations and little real work, but is usually not noticeable (on my
295	Linux system for example, C<getpid> is actually a simple 5-insn sequence	317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
296	without a syscall and thus I<very> fast, but my Linux system also has	318	without a syscall and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
298		320
299	The big advantage of this flag is that you can forget about fork (and	321	The big advantage of this flag is that you can forget about fork (and
300	forget about forgetting to tell libev about forking) when you use this	322	forget about forgetting to tell libev about forking) when you use this
301	flag.	323	flag.
…		…
476	Like C<ev_default_destroy>, but destroys an event loop created by an	498	Like C<ev_default_destroy>, but destroys an event loop created by an
477	earlier call to C<ev_loop_new>.	499	earlier call to C<ev_loop_new>.
478		500
479	=item ev_default_fork ()	501	=item ev_default_fork ()
480		502
		503	This function sets a flag that causes subsequent C<ev_loop> iterations
481	This function reinitialises the kernel state for backends that have	504	to reinitialise the kernel state for backends that have one. Despite the
482	one. Despite the name, you can call it anytime, but it makes most sense	505	name, you can call it anytime, but it makes most sense after forking, in
483	after forking, in either the parent or child process (or both, but that	506	the child process (or both child and parent, but that again makes little
484	again makes little sense).	507	sense). You I<must> call it in the child before using any of the libev
		508	functions, and it will only take effect at the next C<ev_loop> iteration.
485		509
486	You I<must> call this function in the child process after forking if and	510	On the other hand, you only need to call this function in the child
487	only if you want to use the event library in both processes. If you just	511	process if and only if you want to use the event library in the child. If
488	fork+exec, you don't have to call it.	512	you just fork+exec, you don't have to call it at all.
489		513
490	The function itself is quite fast and it's usually not a problem to call	514	The function itself is quite fast and it's usually not a problem to call
491	it just in case after a fork. To make this easy, the function will fit in	515	it just in case after a fork. To make this easy, the function will fit in
492	quite nicely into a call to C<pthread_atfork>:	516	quite nicely into a call to C<pthread_atfork>:
493		517
494	pthread_atfork (0, 0, ev_default_fork);	518	pthread_atfork (0, 0, ev_default_fork);
495		519
496	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
497	without calling this function, so if you force one of those backends you
498	do not need to care.
499
500	=item ev_loop_fork (loop)	520	=item ev_loop_fork (loop)
501		521
502	Like C<ev_default_fork>, but acts on an event loop created by	522	Like C<ev_default_fork>, but acts on an event loop created by
503	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	523	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
504	after fork, and how you do this is entirely your own problem.	524	after fork, and how you do this is entirely your own problem.
		525
		526	=item int ev_is_default_loop (loop)
		527
		528	Returns true when the given loop actually is the default loop, false otherwise.
505		529
506	=item unsigned int ev_loop_count (loop)	530	=item unsigned int ev_loop_count (loop)
507		531
508	Returns the count of loop iterations for the loop, which is identical to	532	Returns the count of loop iterations for the loop, which is identical to
509	the number of times libev did poll for new events. It starts at C<0> and	533	the number of times libev did poll for new events. It starts at C<0> and
…		…
769	=item C<EV_FORK>	793	=item C<EV_FORK>
770		794
771	The event loop has been resumed in the child process after fork (see	795	The event loop has been resumed in the child process after fork (see
772	C<ev_fork>).	796	C<ev_fork>).
773		797
		798	=item C<EV_ASYNC>
		799
		800	The given async watcher has been asynchronously notified (see C<ev_async>).
		801
774	=item C<EV_ERROR>	802	=item C<EV_ERROR>
775		803
776	An unspecified error has occured, the watcher has been stopped. This might	804	An unspecified error has occured, the watcher has been stopped. This might
777	happen because the watcher could not be properly started because libev	805	happen because the watcher could not be properly started because libev
778	ran out of memory, a file descriptor was found to be closed or any other	806	ran out of memory, a file descriptor was found to be closed or any other
…		…
1057	To support fork in your programs, you either have to call	1085	To support fork in your programs, you either have to call
1058	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1059	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1060	C<EVBACKEND_POLL>.	1088	C<EVBACKEND_POLL>.
1061		1089
		1090	=head3 The special problem of SIGPIPE
		1091
		1092	While not really specific to libev, it is easy to forget about SIGPIPE:
		1093	when reading from a pipe whose other end has been closed, your program
		1094	gets send a SIGPIPE, which, by default, aborts your program. For most
		1095	programs this is sensible behaviour, for daemons, this is usually
		1096	undesirable.
		1097
		1098	So when you encounter spurious, unexplained daemon exits, make sure you
		1099	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1100	somewhere, as that would have given you a big clue).
		1101
1062		1102
1063	=head3 Watcher-Specific Functions	1103	=head3 Watcher-Specific Functions
1064		1104
1065	=over 4	1105	=over 4
1066		1106
…		…
1143	configure a timer to trigger every 10 seconds, then it will trigger at	1183	configure a timer to trigger every 10 seconds, then it will trigger at
1144	exactly 10 second intervals. If, however, your program cannot keep up with	1184	exactly 10 second intervals. If, however, your program cannot keep up with
1145	the timer (because it takes longer than those 10 seconds to do stuff) the	1185	the timer (because it takes longer than those 10 seconds to do stuff) the
1146	timer will not fire more than once per event loop iteration.	1186	timer will not fire more than once per event loop iteration.
1147		1187
1148	=item ev_timer_again (loop)	1188	=item ev_timer_again (loop, ev_timer *)
1149		1189
1150	This will act as if the timer timed out and restart it again if it is	1190	This will act as if the timer timed out and restart it again if it is
1151	repeating. The exact semantics are:	1191	repeating. The exact semantics are:
1152		1192
1153	If the timer is pending, its pending status is cleared.	1193	If the timer is pending, its pending status is cleared.
…		…
1262	In this configuration the watcher triggers an event at the wallclock time	1302	In this configuration the watcher triggers an event at the wallclock time
1263	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1303	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1264	that is, if it is to be run at January 1st 2011 then it will run when the	1304	that is, if it is to be run at January 1st 2011 then it will run when the
1265	system time reaches or surpasses this time.	1305	system time reaches or surpasses this time.
1266		1306
1267	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1307	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1268		1308
1269	In this mode the watcher will always be scheduled to time out at the next	1309	In this mode the watcher will always be scheduled to time out at the next
1270	C<at + N * interval> time (for some integer N, which can also be negative)	1310	C<at + N * interval> time (for some integer N, which can also be negative)
1271	and then repeat, regardless of any time jumps.	1311	and then repeat, regardless of any time jumps.
1272		1312
…		…
1406	with the kernel (thus it coexists with your own signal handlers as long	1446	with the kernel (thus it coexists with your own signal handlers as long
1407	as you don't register any with libev). Similarly, when the last signal	1447	as you don't register any with libev). Similarly, when the last signal
1408	watcher for a signal is stopped libev will reset the signal handler to	1448	watcher for a signal is stopped libev will reset the signal handler to
1409	SIG_DFL (regardless of what it was set to before).	1449	SIG_DFL (regardless of what it was set to before).
1410		1450
		1451	If possible and supported, libev will install its handlers with
		1452	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1453	interrupted. If you have a problem with syscalls getting interrupted by
		1454	signals you can block all signals in an C<ev_check> watcher and unblock
		1455	them in an C<ev_prepare> watcher.
		1456
1411	=head3 Watcher-Specific Functions and Data Members	1457	=head3 Watcher-Specific Functions and Data Members
1412		1458
1413	=over 4	1459	=over 4
1414		1460
1415	=item ev_signal_init (ev_signal *, callback, int signum)	1461	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1423		1469
1424	The signal the watcher watches out for.	1470	The signal the watcher watches out for.
1425		1471
1426	=back	1472	=back
1427		1473
		1474	=head3 Examples
		1475
		1476	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1477
		1478	static void
		1479	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1480	{
		1481	ev_unloop (loop, EVUNLOOP_ALL);
		1482	}
		1483
		1484	struct ev_signal signal_watcher;
		1485	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1486	ev_signal_start (loop, &sigint_cb);
		1487
1428		1488
1429	=head2 C<ev_child> - watch out for process status changes	1489	=head2 C<ev_child> - watch out for process status changes
1430		1490
1431	Child watchers trigger when your process receives a SIGCHLD in response to	1491	Child watchers trigger when your process receives a SIGCHLD in response to
1432	some child status changes (most typically when a child of yours dies).	1492	some child status changes (most typically when a child of yours dies). It
		1493	is permissible to install a child watcher I<after> the child has been
		1494	forked (which implies it might have already exited), as long as the event
		1495	loop isn't entered (or is continued from a watcher).
		1496
		1497	Only the default event loop is capable of handling signals, and therefore
		1498	you can only rgeister child watchers in the default event loop.
		1499
		1500	=head3 Process Interaction
		1501
		1502	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1503	initialised. This is necessary to guarantee proper behaviour even if
		1504	the first child watcher is started after the child exits. The occurance
		1505	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1506	synchronously as part of the event loop processing. Libev always reaps all
		1507	children, even ones not watched.
		1508
		1509	=head3 Overriding the Built-In Processing
		1510
		1511	Libev offers no special support for overriding the built-in child
		1512	processing, but if your application collides with libev's default child
		1513	handler, you can override it easily by installing your own handler for
		1514	C<SIGCHLD> after initialising the default loop, and making sure the
		1515	default loop never gets destroyed. You are encouraged, however, to use an
		1516	event-based approach to child reaping and thus use libev's support for
		1517	that, so other libev users can use C<ev_child> watchers freely.
1433		1518
1434	=head3 Watcher-Specific Functions and Data Members	1519	=head3 Watcher-Specific Functions and Data Members
1435		1520
1436	=over 4	1521	=over 4
1437		1522
1438	=item ev_child_init (ev_child *, callback, int pid)	1523	=item ev_child_init (ev_child *, callback, int pid, int trace)
1439		1524
1440	=item ev_child_set (ev_child *, int pid)	1525	=item ev_child_set (ev_child *, int pid, int trace)
1441		1526
1442	Configures the watcher to wait for status changes of process C<pid> (or	1527	Configures the watcher to wait for status changes of process C<pid> (or
1443	I<any> process if C<pid> is specified as C<0>). The callback can look	1528	I<any> process if C<pid> is specified as C<0>). The callback can look
1444	at the C<rstatus> member of the C<ev_child> watcher structure to see	1529	at the C<rstatus> member of the C<ev_child> watcher structure to see
1445	the status word (use the macros from C<sys/wait.h> and see your systems	1530	the status word (use the macros from C<sys/wait.h> and see your systems
1446	C<waitpid> documentation). The C<rpid> member contains the pid of the	1531	C<waitpid> documentation). The C<rpid> member contains the pid of the
1447	process causing the status change.	1532	process causing the status change. C<trace> must be either C<0> (only
		1533	activate the watcher when the process terminates) or C<1> (additionally
		1534	activate the watcher when the process is stopped or continued).
1448		1535
1449	=item int pid [read-only]	1536	=item int pid [read-only]
1450		1537
1451	The process id this watcher watches out for, or C<0>, meaning any process id.	1538	The process id this watcher watches out for, or C<0>, meaning any process id.
1452		1539
…		…
1461		1548
1462	=back	1549	=back
1463		1550
1464	=head3 Examples	1551	=head3 Examples
1465		1552
1466	Example: Try to exit cleanly on SIGINT and SIGTERM.	1553	Example: C<fork()> a new process and install a child handler to wait for
		1554	its completion.
		1555
		1556	ev_child cw;
1467		1557
1468	static void	1558	static void
1469	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1559	child_cb (EV_P_ struct ev_child *w, int revents)
1470	{	1560	{
1471	ev_unloop (loop, EVUNLOOP_ALL);	1561	ev_child_stop (EV_A_ w);
		1562	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1472	}	1563	}
1473		1564
1474	struct ev_signal signal_watcher;	1565	pid_t pid = fork ();
1475	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1566
1476	ev_signal_start (loop, &sigint_cb);	1567	if (pid < 0)
		1568	// error
		1569	else if (pid == 0)
		1570	{
		1571	// the forked child executes here
		1572	exit (1);
		1573	}
		1574	else
		1575	{
		1576	ev_child_init (&cw, child_cb, pid, 0);
		1577	ev_child_start (EV_DEFAULT_ &cw);
		1578	}
1477		1579
1478		1580
1479	=head2 C<ev_stat> - did the file attributes just change?	1581	=head2 C<ev_stat> - did the file attributes just change?
1480		1582
1481	This watches a filesystem path for attribute changes. That is, it calls	1583	This watches a filesystem path for attribute changes. That is, it calls
…		…
1510	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1612	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1511	to fall back to regular polling again even with inotify, but changes are	1613	to fall back to regular polling again even with inotify, but changes are
1512	usually detected immediately, and if the file exists there will be no	1614	usually detected immediately, and if the file exists there will be no
1513	polling.	1615	polling.
1514		1616
		1617	=head3 ABI Issues (Largefile Support)
		1618
		1619	Libev by default (unless the user overrides this) uses the default
		1620	compilation environment, which means that on systems with optionally
		1621	disabled large file support, you get the 32 bit version of the stat
		1622	structure. When using the library from programs that change the ABI to
		1623	use 64 bit file offsets the programs will fail. In that case you have to
		1624	compile libev with the same flags to get binary compatibility. This is
		1625	obviously the case with any flags that change the ABI, but the problem is
		1626	most noticably with ev_stat and largefile support.
		1627
1515	=head3 Inotify	1628	=head3 Inotify
1516		1629
1517	When C<inotify (7)> support has been compiled into libev (generally only	1630	When C<inotify (7)> support has been compiled into libev (generally only
1518	available on Linux) and present at runtime, it will be used to speed up	1631	available on Linux) and present at runtime, it will be used to speed up
1519	change detection where possible. The inotify descriptor will be created lazily	1632	change detection where possible. The inotify descriptor will be created lazily
…		…
1561		1674
1562	The callback will be receive C<EV_STAT> when a change was detected,	1675	The callback will be receive C<EV_STAT> when a change was detected,
1563	relative to the attributes at the time the watcher was started (or the	1676	relative to the attributes at the time the watcher was started (or the
1564	last change was detected).	1677	last change was detected).
1565		1678
1566	=item ev_stat_stat (ev_stat *)	1679	=item ev_stat_stat (loop, ev_stat *)
1567		1680
1568	Updates the stat buffer immediately with new values. If you change the	1681	Updates the stat buffer immediately with new values. If you change the
1569	watched path in your callback, you could call this fucntion to avoid	1682	watched path in your callback, you could call this fucntion to avoid
1570	detecting this change (while introducing a race condition). Can also be	1683	detecting this change (while introducing a race condition). Can also be
1571	useful simply to find out the new values.	1684	useful simply to find out the new values.
…		…
1688	static void	1801	static void
1689	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1802	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1690	{	1803	{
1691	free (w);	1804	free (w);
1692	// now do something you wanted to do when the program has	1805	// now do something you wanted to do when the program has
1693	// no longer asnything immediate to do.	1806	// no longer anything immediate to do.
1694	}	1807	}
1695		1808
1696	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1809	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1697	ev_idle_init (idle_watcher, idle_cb);	1810	ev_idle_init (idle_watcher, idle_cb);
1698	ev_idle_start (loop, idle_cb);	1811	ev_idle_start (loop, idle_cb);
…		…
2039	believe me.	2152	believe me.
2040		2153
2041	=back	2154	=back
2042		2155
2043		2156
		2157	=head2 C<ev_async> - how to wake up another event loop
		2158
		2159	In general, you cannot use an C<ev_loop> from multiple threads or other
		2160	asynchronous sources such as signal handlers (as opposed to multiple event
		2161	loops - those are of course safe to use in different threads).
		2162
		2163	Sometimes, however, you need to wake up another event loop you do not
		2164	control, for example because it belongs to another thread. This is what
		2165	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2166	can signal it by calling C<ev_async_send>, which is thread- and signal
		2167	safe.
		2168
		2169	This functionality is very similar to C<ev_signal> watchers, as signals,
		2170	too, are asynchronous in nature, and signals, too, will be compressed
		2171	(i.e. the number of callback invocations may be less than the number of
		2172	C<ev_async_sent> calls).
		2173
		2174	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2175	just the default loop.
		2176
		2177	=head3 Queueing
		2178
		2179	C<ev_async> does not support queueing of data in any way. The reason
		2180	is that the author does not know of a simple (or any) algorithm for a
		2181	multiple-writer-single-reader queue that works in all cases and doesn't
		2182	need elaborate support such as pthreads.
		2183
		2184	That means that if you want to queue data, you have to provide your own
		2185	queue. But at least I can tell you would implement locking around your
		2186	queue:
		2187
		2188	=over 4
		2189
		2190	=item queueing from a signal handler context
		2191
		2192	To implement race-free queueing, you simply add to the queue in the signal
		2193	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2194	some fictitiuous SIGUSR1 handler:
		2195
		2196	static ev_async mysig;
		2197
		2198	static void
		2199	sigusr1_handler (void)
		2200	{
		2201	sometype data;
		2202
		2203	// no locking etc.
		2204	queue_put (data);
		2205	ev_async_send (EV_DEFAULT_ &mysig);
		2206	}
		2207
		2208	static void
		2209	mysig_cb (EV_P_ ev_async *w, int revents)
		2210	{
		2211	sometype data;
		2212	sigset_t block, prev;
		2213
		2214	sigemptyset (&block);
		2215	sigaddset (&block, SIGUSR1);
		2216	sigprocmask (SIG_BLOCK, &block, &prev);
		2217
		2218	while (queue_get (&data))
		2219	process (data);
		2220
		2221	if (sigismember (&prev, SIGUSR1)
		2222	sigprocmask (SIG_UNBLOCK, &block, 0);
		2223	}
		2224
		2225	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2226	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2227	either...).
		2228
		2229	=item queueing from a thread context
		2230
		2231	The strategy for threads is different, as you cannot (easily) block
		2232	threads but you can easily preempt them, so to queue safely you need to
		2233	employ a traditional mutex lock, such as in this pthread example:
		2234
		2235	static ev_async mysig;
		2236	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2237
		2238	static void
		2239	otherthread (void)
		2240	{
		2241	// only need to lock the actual queueing operation
		2242	pthread_mutex_lock (&mymutex);
		2243	queue_put (data);
		2244	pthread_mutex_unlock (&mymutex);
		2245
		2246	ev_async_send (EV_DEFAULT_ &mysig);
		2247	}
		2248
		2249	static void
		2250	mysig_cb (EV_P_ ev_async *w, int revents)
		2251	{
		2252	pthread_mutex_lock (&mymutex);
		2253
		2254	while (queue_get (&data))
		2255	process (data);
		2256
		2257	pthread_mutex_unlock (&mymutex);
		2258	}
		2259
		2260	=back
		2261
		2262
		2263	=head3 Watcher-Specific Functions and Data Members
		2264
		2265	=over 4
		2266
		2267	=item ev_async_init (ev_async *, callback)
		2268
		2269	Initialises and configures the async watcher - it has no parameters of any
		2270	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2271	believe me.
		2272
		2273	=item ev_async_send (loop, ev_async *)
		2274
		2275	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2276	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2277	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2278	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2279	section below on what exactly this means).
		2280
		2281	This call incurs the overhead of a syscall only once per loop iteration,
		2282	so while the overhead might be noticable, it doesn't apply to repeated
		2283	calls to C<ev_async_send>.
		2284
		2285	=back
		2286
		2287
2044	=head1 OTHER FUNCTIONS	2288	=head1 OTHER FUNCTIONS
2045		2289
2046	There are some other functions of possible interest. Described. Here. Now.	2290	There are some other functions of possible interest. Described. Here. Now.
2047		2291
2048	=over 4	2292	=over 4
…		…
2275	Example: Define a class with an IO and idle watcher, start one of them in	2519	Example: Define a class with an IO and idle watcher, start one of them in
2276	the constructor.	2520	the constructor.
2277		2521
2278	class myclass	2522	class myclass
2279	{	2523	{
2280	ev_io io; void io_cb (ev::io &w, int revents);	2524	ev::io io; void io_cb (ev::io &w, int revents);
2281	ev_idle idle void idle_cb (ev::idle &w, int revents);	2525	ev:idle idle void idle_cb (ev::idle &w, int revents);
2282		2526
2283	myclass ();	2527	myclass (int fd)
2284	}
2285
2286	myclass::myclass (int fd)
2287	{	2528	{
2288	io .set <myclass, &myclass::io_cb > (this);	2529	io .set <myclass, &myclass::io_cb > (this);
2289	idle.set <myclass, &myclass::idle_cb> (this);	2530	idle.set <myclass, &myclass::idle_cb> (this);
2290		2531
2291	io.start (fd, ev::READ);	2532	io.start (fd, ev::READ);
		2533	}
2292	}	2534	};
		2535
		2536
		2537	=head1 OTHER LANGUAGE BINDINGS
		2538
		2539	Libev does not offer other language bindings itself, but bindings for a
		2540	numbe rof languages exist in the form of third-party packages. If you know
		2541	any interesting language binding in addition to the ones listed here, drop
		2542	me a note.
		2543
		2544	=over 4
		2545
		2546	=item Perl
		2547
		2548	The EV module implements the full libev API and is actually used to test
		2549	libev. EV is developed together with libev. Apart from the EV core module,
		2550	there are additional modules that implement libev-compatible interfaces
		2551	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2552	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2553
		2554	It can be found and installed via CPAN, its homepage is found at
		2555	L<http://software.schmorp.de/pkg/EV>.
		2556
		2557	=item Ruby
		2558
		2559	Tony Arcieri has written a ruby extension that offers access to a subset
		2560	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2561	more on top of it. It can be found via gem servers. Its homepage is at
		2562	L<http://rev.rubyforge.org/>.
		2563
		2564	=item D
		2565
		2566	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2567	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2568
		2569	=back
2293		2570
2294		2571
2295	=head1 MACRO MAGIC	2572	=head1 MACRO MAGIC
2296		2573
2297	Libev can be compiled with a variety of options, the most fundamantal	2574	Libev can be compiled with a variety of options, the most fundamantal
…		…
2553		2830
2554	If defined to be C<1>, libev will compile in support for the Linux inotify	2831	If defined to be C<1>, libev will compile in support for the Linux inotify
2555	interface to speed up C<ev_stat> watchers. Its actual availability will	2832	interface to speed up C<ev_stat> watchers. Its actual availability will
2556	be detected at runtime.	2833	be detected at runtime.
2557		2834
		2835	=item EV_ATOMIC_T
		2836
		2837	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2838	access is atomic with respect to other threads or signal contexts. No such
		2839	type is easily found in the C language, so you can provide your own type
		2840	that you know is safe for your purposes. It is used both for signal handler "locking"
		2841	as well as for signal and thread safety in C<ev_async> watchers.
		2842
		2843	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2844	(from F<signal.h>), which is usually good enough on most platforms.
		2845
2558	=item EV_H	2846	=item EV_H
2559		2847
2560	The name of the F<ev.h> header file used to include it. The default if	2848	The name of the F<ev.h> header file used to include it. The default if
2561	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	2849	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2562	virtually rename the F<ev.h> header file in case of conflicts.	2850	used to virtually rename the F<ev.h> header file in case of conflicts.
2563		2851
2564	=item EV_CONFIG_H	2852	=item EV_CONFIG_H
2565		2853
2566	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2854	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2567	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2855	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2568	C<EV_H>, above.	2856	C<EV_H>, above.
2569		2857
2570	=item EV_EVENT_H	2858	=item EV_EVENT_H
2571		2859
2572	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2860	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2573	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	2861	of how the F<event.h> header can be found, the default is C<"event.h">.
2574		2862
2575	=item EV_PROTOTYPES	2863	=item EV_PROTOTYPES
2576		2864
2577	If defined to be C<0>, then F<ev.h> will not define any function	2865	If defined to be C<0>, then F<ev.h> will not define any function
2578	prototypes, but still define all the structs and other symbols. This is	2866	prototypes, but still define all the structs and other symbols. This is
…		…
2627	defined to be C<0>, then they are not.	2915	defined to be C<0>, then they are not.
2628		2916
2629	=item EV_FORK_ENABLE	2917	=item EV_FORK_ENABLE
2630		2918
2631	If undefined or defined to be C<1>, then fork watchers are supported. If	2919	If undefined or defined to be C<1>, then fork watchers are supported. If
		2920	defined to be C<0>, then they are not.
		2921
		2922	=item EV_ASYNC_ENABLE
		2923
		2924	If undefined or defined to be C<1>, then async watchers are supported. If
2632	defined to be C<0>, then they are not.	2925	defined to be C<0>, then they are not.
2633		2926
2634	=item EV_MINIMAL	2927	=item EV_MINIMAL
2635		2928
2636	If you need to shave off some kilobytes of code at the expense of some	2929	If you need to shave off some kilobytes of code at the expense of some
…		…
2757	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3050	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2758		3051
2759	That means that changing a timer costs less than removing/adding them	3052	That means that changing a timer costs less than removing/adding them
2760	as only the relative motion in the event queue has to be paid for.	3053	as only the relative motion in the event queue has to be paid for.
2761		3054
2762	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3055	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2763		3056
2764	These just add the watcher into an array or at the head of a list.	3057	These just add the watcher into an array or at the head of a list.
2765		3058
2766	=item Stopping check/prepare/idle watchers: O(1)	3059	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2767		3060
2768	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3061	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2769		3062
2770	These watchers are stored in lists then need to be walked to find the	3063	These watchers are stored in lists then need to be walked to find the
2771	correct watcher to remove. The lists are usually short (you don't usually	3064	correct watcher to remove. The lists are usually short (you don't usually
…		…
2787	=item Priority handling: O(number_of_priorities)	3080	=item Priority handling: O(number_of_priorities)
2788		3081
2789	Priorities are implemented by allocating some space for each	3082	Priorities are implemented by allocating some space for each
2790	priority. When doing priority-based operations, libev usually has to	3083	priority. When doing priority-based operations, libev usually has to
2791	linearly search all the priorities, but starting/stopping and activating	3084	linearly search all the priorities, but starting/stopping and activating
2792	watchers becomes O(1) w.r.t. prioritiy handling.	3085	watchers becomes O(1) w.r.t. priority handling.
		3086
		3087	=item Sending an ev_async: O(1)
		3088
		3089	=item Processing ev_async_send: O(number_of_async_watchers)
		3090
		3091	=item Processing signals: O(max_signal_number)
		3092
		3093	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3094	calls in the current loop iteration. Checking for async and signal events
		3095	involves iterating over all running async watchers or all signal numbers.
2793		3096
2794	=back	3097	=back
2795		3098
2796		3099
2797	=head1 Win32 platform limitations and workarounds	3100	=head1 Win32 platform limitations and workarounds

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Comparing libev/ev.pod (file contents): Revision 1.117 by root, Wed Jan 9 04:15:39 2008 UTC vs. Revision 1.138 by root, Mon Mar 31 01:14:12 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.117 by root, Wed Jan 9 04:15:39 2008 UTC vs.
Revision 1.138 by root, Mon Mar 31 01:14:12 2008 UTC