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

Comparing libev/ev.pod (file contents):
Revision 1.129 by root, Tue Feb 5 23:56:33 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
…		…
297	enabling this flag.	312	enabling this flag.
298		313
299	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,
300	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
301	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
302	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
303	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
304	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
305		320
306	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
307	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
308	flag.	323	flag.
…		…
505	=item ev_loop_fork (loop)	520	=item ev_loop_fork (loop)
506		521
507	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
508	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
509	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.
510		529
511	=item unsigned int ev_loop_count (loop)	530	=item unsigned int ev_loop_count (loop)
512		531
513	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
514	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
…		…
1066	To support fork in your programs, you either have to call	1085	To support fork in your programs, you either have to call
1067	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,
1068	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1069	C<EVBACKEND_POLL>.	1088	C<EVBACKEND_POLL>.
1070		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
1071		1102
1072	=head3 Watcher-Specific Functions	1103	=head3 Watcher-Specific Functions
1073		1104
1074	=over 4	1105	=over 4
1075		1106
…		…
1152	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
1153	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
1154	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
1155	timer will not fire more than once per event loop iteration.	1186	timer will not fire more than once per event loop iteration.
1156		1187
1157	=item ev_timer_again (loop)	1188	=item ev_timer_again (loop, ev_timer *)
1158		1189
1159	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
1160	repeating. The exact semantics are:	1191	repeating. The exact semantics are:
1161		1192
1162	If the timer is pending, its pending status is cleared.	1193	If the timer is pending, its pending status is cleared.
…		…
1271	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
1272	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,
1273	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
1274	system time reaches or surpasses this time.	1305	system time reaches or surpasses this time.
1275		1306
1276	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1307	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1277		1308
1278	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
1279	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)
1280	and then repeat, regardless of any time jumps.	1311	and then repeat, regardless of any time jumps.
1281		1312
…		…
1415	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
1416	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
1417	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
1418	SIG_DFL (regardless of what it was set to before).	1449	SIG_DFL (regardless of what it was set to before).
1419		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
1420	=head3 Watcher-Specific Functions and Data Members	1457	=head3 Watcher-Specific Functions and Data Members
1421		1458
1422	=over 4	1459	=over 4
1423		1460
1424	=item ev_signal_init (ev_signal *, callback, int signum)	1461	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1432		1469
1433	The signal the watcher watches out for.	1470	The signal the watcher watches out for.
1434		1471
1435	=back	1472	=back
1436		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
1437		1488
1438	=head2 C<ev_child> - watch out for process status changes	1489	=head2 C<ev_child> - watch out for process status changes
1439		1490
1440	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
1441	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.
1442		1518
1443	=head3 Watcher-Specific Functions and Data Members	1519	=head3 Watcher-Specific Functions and Data Members
1444		1520
1445	=over 4	1521	=over 4
1446		1522
…		…
1472		1548
1473	=back	1549	=back
1474		1550
1475	=head3 Examples	1551	=head3 Examples
1476		1552
1477	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;
1478		1557
1479	static void	1558	static void
1480	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1559	child_cb (EV_P_ struct ev_child *w, int revents)
1481	{	1560	{
1482	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);
1483	}	1563	}
1484		1564
1485	struct ev_signal signal_watcher;	1565	pid_t pid = fork ();
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1566
1487	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	}
1488		1579
1489		1580
1490	=head2 C<ev_stat> - did the file attributes just change?	1581	=head2 C<ev_stat> - did the file attributes just change?
1491		1582
1492	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
…		…
1521	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
1522	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
1523	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
1524	polling.	1615	polling.
1525		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
1526	=head3 Inotify	1628	=head3 Inotify
1527		1629
1528	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
1529	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
1530	change detection where possible. The inotify descriptor will be created lazily	1632	change detection where possible. The inotify descriptor will be created lazily
…		…
1572		1674
1573	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,
1574	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
1575	last change was detected).	1677	last change was detected).
1576		1678
1577	=item ev_stat_stat (ev_stat *)	1679	=item ev_stat_stat (loop, ev_stat *)
1578		1680
1579	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
1580	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
1581	detecting this change (while introducing a race condition). Can also be	1683	detecting this change (while introducing a race condition). Can also be
1582	useful simply to find out the new values.	1684	useful simply to find out the new values.
…		…
2078	is that the author does not know of a simple (or any) algorithm for a	2180	is that the author does not know of a simple (or any) algorithm for a
2079	multiple-writer-single-reader queue that works in all cases and doesn't	2181	multiple-writer-single-reader queue that works in all cases and doesn't
2080	need elaborate support such as pthreads.	2182	need elaborate support such as pthreads.
2081		2183
2082	That means that if you want to queue data, you have to provide your own	2184	That means that if you want to queue data, you have to provide your own
2083	queue. And here is how you would implement locking:	2185	queue. But at least I can tell you would implement locking around your
		2186	queue:
2084		2187
2085	=over 4	2188	=over 4
2086		2189
2087	=item queueing from a signal handler context	2190	=item queueing from a signal handler context
2088		2191
…		…
2097	{	2200	{
2098	sometype data;	2201	sometype data;
2099		2202
2100	// no locking etc.	2203	// no locking etc.
2101	queue_put (data);	2204	queue_put (data);
2102	ev_async_send (DEFAULT_ &mysig);	2205	ev_async_send (EV_DEFAULT_ &mysig);
2103	}	2206	}
2104		2207
2105	static void	2208	static void
2106	mysig_cb (EV_P_ ev_async *w, int revents)	2209	mysig_cb (EV_P_ ev_async *w, int revents)
2107	{	2210	{
…		…
2125		2228
2126	=item queueing from a thread context	2229	=item queueing from a thread context
2127		2230
2128	The strategy for threads is different, as you cannot (easily) block	2231	The strategy for threads is different, as you cannot (easily) block
2129	threads but you can easily preempt them, so to queue safely you need to	2232	threads but you can easily preempt them, so to queue safely you need to
2130	emply a traditional mutex lock, such as in this pthread example:	2233	employ a traditional mutex lock, such as in this pthread example:
2131		2234
2132	static ev_async mysig;	2235	static ev_async mysig;
2133	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;	2236	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2134		2237
2135	static void	2238	static void
…		…
2138	// only need to lock the actual queueing operation	2241	// only need to lock the actual queueing operation
2139	pthread_mutex_lock (&mymutex);	2242	pthread_mutex_lock (&mymutex);
2140	queue_put (data);	2243	queue_put (data);
2141	pthread_mutex_unlock (&mymutex);	2244	pthread_mutex_unlock (&mymutex);
2142		2245
2143	ev_async_send (DEFAULT_ &mysig);	2246	ev_async_send (EV_DEFAULT_ &mysig);
2144	}	2247	}
2145		2248
2146	static void	2249	static void
2147	mysig_cb (EV_P_ ev_async *w, int revents)	2250	mysig_cb (EV_P_ ev_async *w, int revents)
2148	{	2251	{
…		…
2427	idle.set <myclass, &myclass::idle_cb> (this);	2530	idle.set <myclass, &myclass::idle_cb> (this);
2428		2531
2429	io.start (fd, ev::READ);	2532	io.start (fd, ev::READ);
2430	}	2533	}
2431	};	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
2432		2570
2433		2571
2434	=head1 MACRO MAGIC	2572	=head1 MACRO MAGIC
2435		2573
2436	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

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Comparing libev/ev.pod (file contents): Revision 1.129 by root, Tue Feb 5 23:56:33 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 1.129 by root, Tue Feb 5 23:56:33 2008 UTC vs.
Revision 1.138 by root, Mon Mar 31 01:14:12 2008 UTC