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

Comparing libev/ev.pod (file contents):
Revision 1.128 by root, Fri Feb 1 13:53:56 2008 UTC vs.
Revision 1.148 by root, Thu Apr 24 01:42:11 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
…		…
181	See the description of C<ev_embed> watchers for more info.	196	See the description of C<ev_embed> watchers for more info.
182		197
183	=item ev_set_allocator (void (cb)(void *ptr, long size))	198	=item ev_set_allocator (void (cb)(void *ptr, long size))
184		199
185	Sets the allocation function to use (the prototype is similar - the	200	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
187	allocate and free memory (no surprises here). If it returns zero when	202	used to allocate and free memory (no surprises here). If it returns zero
188	memory needs to be allocated, the library might abort or take some	203	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	204	or take some potentially destructive action.
190	function.	205
		206	Since some systems (at least OpenBSD and Darwin) fail to implement
		207	correct C<realloc> semantics, libev will use a wrapper around the system
		208	C<realloc> and C<free> functions by default.
191		209
192	You could override this function in high-availability programs to, say,	210	You could override this function in high-availability programs to, say,
193	free some memory if it cannot allocate memory, to use a special allocator,	211	free some memory if it cannot allocate memory, to use a special allocator,
194	or even to sleep a while and retry until some memory is available.	212	or even to sleep a while and retry until some memory is available.
195		213
196	Example: Replace the libev allocator with one that waits a bit and then	214	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	215	retries (example requires a standards-compliant C<realloc>).
198		216
199	static void *	217	static void *
200	persistent_realloc (void *ptr, size_t size)	218	persistent_realloc (void *ptr, size_t size)
201	{	219	{
202	for (;;)	220	for (;;)
…		…
241		259
242	An event loop is described by a C<struct ev_loop *>. The library knows two	260	An event loop is described by a C<struct ev_loop *>. The library knows two
243	types of such loops, the I<default> loop, which supports signals and child	261	types of such loops, the I<default> loop, which supports signals and child
244	events, and dynamically created loops which do not.	262	events, and dynamically created loops which do not.
245		263
246	If you use threads, a common model is to run the default event loop
247	in your main thread (or in a separate thread) and for each thread you
248	create, you also create another event loop. Libev itself does no locking
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252
253	=over 4	264	=over 4
254		265
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	266	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		267
257	This will initialise the default event loop if it hasn't been initialised	268	This will initialise the default event loop if it hasn't been initialised
…		…
259	false. If it already was initialised it simply returns it (and ignores the	270	false. If it already was initialised it simply returns it (and ignores the
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	271	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		272
262	If you don't know what event loop to use, use the one returned from this	273	If you don't know what event loop to use, use the one returned from this
263	function.	274	function.
		275
		276	Note that this function is I<not> thread-safe, so if you want to use it
		277	from multiple threads, you have to lock (note also that this is unlikely,
		278	as loops cannot bes hared easily between threads anyway).
264		279
265	The default loop is the only loop that can handle C<ev_signal> and	280	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	281	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	282	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	283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
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.
…		…
339	For few fds, this backend is a bit little slower than poll and select,	354	For few fds, this backend is a bit little slower than poll and select,
340	but it scales phenomenally better. While poll and select usually scale	355	but it scales phenomenally better. While poll and select usually scale
341	like O(total_fds) where n is the total number of fds (or the highest fd),	356	like O(total_fds) where n is the total number of fds (or the highest fd),
342	epoll scales either O(1) or O(active_fds). The epoll design has a number	357	epoll scales either O(1) or O(active_fds). The epoll design has a number
343	of shortcomings, such as silently dropping events in some hard-to-detect	358	of shortcomings, such as silently dropping events in some hard-to-detect
344	cases and rewiring a syscall per fd change, no fork support and bad	359	cases and requiring a syscall per fd change, no fork support and bad
345	support for dup.	360	support for dup.
346		361
347	While stopping, setting and starting an I/O watcher in the same iteration	362	While stopping, setting and starting an I/O watcher in the same iteration
348	will result in some caching, there is still a syscall per such incident	363	will result in some caching, there is still a syscall per such incident
349	(because the fd could point to a different file description now), so its	364	(because the fd could point to a different file description now), so its
…		…
451	Similar to C<ev_default_loop>, but always creates a new event loop that is	466	Similar to C<ev_default_loop>, but always creates a new event loop that is
452	always distinct from the default loop. Unlike the default loop, it cannot	467	always distinct from the default loop. Unlike the default loop, it cannot
453	handle signal and child watchers, and attempts to do so will be greeted by	468	handle signal and child watchers, and attempts to do so will be greeted by
454	undefined behaviour (or a failed assertion if assertions are enabled).	469	undefined behaviour (or a failed assertion if assertions are enabled).
455		470
		471	Note that this function I<is> thread-safe, and the recommended way to use
		472	libev with threads is indeed to create one loop per thread, and using the
		473	default loop in the "main" or "initial" thread.
		474
456	Example: Try to create a event loop that uses epoll and nothing else.	475	Example: Try to create a event loop that uses epoll and nothing else.
457		476
458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
459	if (!epoller)	478	if (!epoller)
460	fatal ("no epoll found here, maybe it hides under your chair");	479	fatal ("no epoll found here, maybe it hides under your chair");
…		…
505	=item ev_loop_fork (loop)	524	=item ev_loop_fork (loop)
506		525
507	Like C<ev_default_fork>, but acts on an event loop created by	526	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	527	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.	528	after fork, and how you do this is entirely your own problem.
		529
		530	=item int ev_is_default_loop (loop)
		531
		532	Returns true when the given loop actually is the default loop, false otherwise.
510		533
511	=item unsigned int ev_loop_count (loop)	534	=item unsigned int ev_loop_count (loop)
512		535
513	Returns the count of loop iterations for the loop, which is identical to	536	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	537	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	1089	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,	1090	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	1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1069	C<EVBACKEND_POLL>.	1092	C<EVBACKEND_POLL>.
1070		1093
		1094	=head3 The special problem of SIGPIPE
		1095
		1096	While not really specific to libev, it is easy to forget about SIGPIPE:
		1097	when reading from a pipe whose other end has been closed, your program
		1098	gets send a SIGPIPE, which, by default, aborts your program. For most
		1099	programs this is sensible behaviour, for daemons, this is usually
		1100	undesirable.
		1101
		1102	So when you encounter spurious, unexplained daemon exits, make sure you
		1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1104	somewhere, as that would have given you a big clue).
		1105
1071		1106
1072	=head3 Watcher-Specific Functions	1107	=head3 Watcher-Specific Functions
1073		1108
1074	=over 4	1109	=over 4
1075		1110
…		…
1152	configure a timer to trigger every 10 seconds, then it will trigger at	1187	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	1188	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	1189	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.	1190	timer will not fire more than once per event loop iteration.
1156		1191
1157	=item ev_timer_again (loop)	1192	=item ev_timer_again (loop, ev_timer *)
1158		1193
1159	This will act as if the timer timed out and restart it again if it is	1194	This will act as if the timer timed out and restart it again if it is
1160	repeating. The exact semantics are:	1195	repeating. The exact semantics are:
1161		1196
1162	If the timer is pending, its pending status is cleared.	1197	If the timer is pending, its pending status is cleared.
…		…
1271	In this configuration the watcher triggers an event at the wallclock time	1306	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,	1307	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	1308	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.	1309	system time reaches or surpasses this time.
1275		1310
1276	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1277		1312
1278	In this mode the watcher will always be scheduled to time out at the next	1313	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)	1314	C<at + N * interval> time (for some integer N, which can also be negative)
1280	and then repeat, regardless of any time jumps.	1315	and then repeat, regardless of any time jumps.
1281		1316
…		…
1415	with the kernel (thus it coexists with your own signal handlers as long	1450	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	1451	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	1452	watcher for a signal is stopped libev will reset the signal handler to
1418	SIG_DFL (regardless of what it was set to before).	1453	SIG_DFL (regardless of what it was set to before).
1419		1454
		1455	If possible and supported, libev will install its handlers with
		1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1457	interrupted. If you have a problem with syscalls getting interrupted by
		1458	signals you can block all signals in an C<ev_check> watcher and unblock
		1459	them in an C<ev_prepare> watcher.
		1460
1420	=head3 Watcher-Specific Functions and Data Members	1461	=head3 Watcher-Specific Functions and Data Members
1421		1462
1422	=over 4	1463	=over 4
1423		1464
1424	=item ev_signal_init (ev_signal *, callback, int signum)	1465	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1432		1473
1433	The signal the watcher watches out for.	1474	The signal the watcher watches out for.
1434		1475
1435	=back	1476	=back
1436		1477
		1478	=head3 Examples
		1479
		1480	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1481
		1482	static void
		1483	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1484	{
		1485	ev_unloop (loop, EVUNLOOP_ALL);
		1486	}
		1487
		1488	struct ev_signal signal_watcher;
		1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1490	ev_signal_start (loop, &sigint_cb);
		1491
1437		1492
1438	=head2 C<ev_child> - watch out for process status changes	1493	=head2 C<ev_child> - watch out for process status changes
1439		1494
1440	Child watchers trigger when your process receives a SIGCHLD in response to	1495	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).	1496	some child status changes (most typically when a child of yours dies). It
		1497	is permissible to install a child watcher I<after> the child has been
		1498	forked (which implies it might have already exited), as long as the event
		1499	loop isn't entered (or is continued from a watcher).
		1500
		1501	Only the default event loop is capable of handling signals, and therefore
		1502	you can only rgeister child watchers in the default event loop.
		1503
		1504	=head3 Process Interaction
		1505
		1506	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1507	initialised. This is necessary to guarantee proper behaviour even if
		1508	the first child watcher is started after the child exits. The occurance
		1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1510	synchronously as part of the event loop processing. Libev always reaps all
		1511	children, even ones not watched.
		1512
		1513	=head3 Overriding the Built-In Processing
		1514
		1515	Libev offers no special support for overriding the built-in child
		1516	processing, but if your application collides with libev's default child
		1517	handler, you can override it easily by installing your own handler for
		1518	C<SIGCHLD> after initialising the default loop, and making sure the
		1519	default loop never gets destroyed. You are encouraged, however, to use an
		1520	event-based approach to child reaping and thus use libev's support for
		1521	that, so other libev users can use C<ev_child> watchers freely.
1442		1522
1443	=head3 Watcher-Specific Functions and Data Members	1523	=head3 Watcher-Specific Functions and Data Members
1444		1524
1445	=over 4	1525	=over 4
1446		1526
…		…
1472		1552
1473	=back	1553	=back
1474		1554
1475	=head3 Examples	1555	=head3 Examples
1476		1556
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	1557	Example: C<fork()> a new process and install a child handler to wait for
		1558	its completion.
		1559
		1560	ev_child cw;
1478		1561
1479	static void	1562	static void
1480	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1563	child_cb (EV_P_ struct ev_child *w, int revents)
1481	{	1564	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	1565	ev_child_stop (EV_A_ w);
		1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1483	}	1567	}
1484		1568
1485	struct ev_signal signal_watcher;	1569	pid_t pid = fork ();
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1570
1487	ev_signal_start (loop, &sigint_cb);	1571	if (pid < 0)
		1572	// error
		1573	else if (pid == 0)
		1574	{
		1575	// the forked child executes here
		1576	exit (1);
		1577	}
		1578	else
		1579	{
		1580	ev_child_init (&cw, child_cb, pid, 0);
		1581	ev_child_start (EV_DEFAULT_ &cw);
		1582	}
1488		1583
1489		1584
1490	=head2 C<ev_stat> - did the file attributes just change?	1585	=head2 C<ev_stat> - did the file attributes just change?
1491		1586
1492	This watches a filesystem path for attribute changes. That is, it calls	1587	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	1616	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	1617	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	1618	usually detected immediately, and if the file exists there will be no
1524	polling.	1619	polling.
1525		1620
		1621	=head3 ABI Issues (Largefile Support)
		1622
		1623	Libev by default (unless the user overrides this) uses the default
		1624	compilation environment, which means that on systems with optionally
		1625	disabled large file support, you get the 32 bit version of the stat
		1626	structure. When using the library from programs that change the ABI to
		1627	use 64 bit file offsets the programs will fail. In that case you have to
		1628	compile libev with the same flags to get binary compatibility. This is
		1629	obviously the case with any flags that change the ABI, but the problem is
		1630	most noticably with ev_stat and largefile support.
		1631
1526	=head3 Inotify	1632	=head3 Inotify
1527		1633
1528	When C<inotify (7)> support has been compiled into libev (generally only	1634	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	1635	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	1636	change detection where possible. The inotify descriptor will be created lazily
1531	when the first C<ev_stat> watcher is being started.	1637	when the first C<ev_stat> watcher is being started.
1532		1638
1533	Inotify presense does not change the semantics of C<ev_stat> watchers	1639	Inotify presence does not change the semantics of C<ev_stat> watchers
1534	except that changes might be detected earlier, and in some cases, to avoid	1640	except that changes might be detected earlier, and in some cases, to avoid
1535	making regular C<stat> calls. Even in the presense of inotify support	1641	making regular C<stat> calls. Even in the presence of inotify support
1536	there are many cases where libev has to resort to regular C<stat> polling.	1642	there are many cases where libev has to resort to regular C<stat> polling.
1537		1643
1538	(There is no support for kqueue, as apparently it cannot be used to	1644	(There is no support for kqueue, as apparently it cannot be used to
1539	implement this functionality, due to the requirement of having a file	1645	implement this functionality, due to the requirement of having a file
1540	descriptor open on the object at all times).	1646	descriptor open on the object at all times).
…		…
1572		1678
1573	The callback will be receive C<EV_STAT> when a change was detected,	1679	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	1680	relative to the attributes at the time the watcher was started (or the
1575	last change was detected).	1681	last change was detected).
1576		1682
1577	=item ev_stat_stat (ev_stat *)	1683	=item ev_stat_stat (loop, ev_stat *)
1578		1684
1579	Updates the stat buffer immediately with new values. If you change the	1685	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	1686	watched path in your callback, you could call this fucntion to avoid
1581	detecting this change (while introducing a race condition). Can also be	1687	detecting this change (while introducing a race condition). Can also be
1582	useful simply to find out the new values.	1688	useful simply to find out the new values.
…		…
2078	is that the author does not know of a simple (or any) algorithm for a	2184	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	2185	multiple-writer-single-reader queue that works in all cases and doesn't
2080	need elaborate support such as pthreads.	2186	need elaborate support such as pthreads.
2081		2187
2082	That means that if you want to queue data, you have to provide your own	2188	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:	2189	queue. But at least I can tell you would implement locking around your
		2190	queue:
2084		2191
2085	=over 4	2192	=over 4
2086		2193
2087	=item queueing from a signal handler context	2194	=item queueing from a signal handler context
2088		2195
…		…
2097	{	2204	{
2098	sometype data;	2205	sometype data;
2099		2206
2100	// no locking etc.	2207	// no locking etc.
2101	queue_put (data);	2208	queue_put (data);
2102	ev_async_send (DEFAULT_ &mysig);	2209	ev_async_send (EV_DEFAULT_ &mysig);
2103	}	2210	}
2104		2211
2105	static void	2212	static void
2106	mysig_cb (EV_P_ ev_async *w, int revents)	2213	mysig_cb (EV_P_ ev_async *w, int revents)
2107	{	2214	{
…		…
2125		2232
2126	=item queueing from a thread context	2233	=item queueing from a thread context
2127		2234
2128	The strategy for threads is different, as you cannot (easily) block	2235	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	2236	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:	2237	employ a traditional mutex lock, such as in this pthread example:
2131		2238
2132	static ev_async mysig;	2239	static ev_async mysig;
2133	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;	2240	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2134		2241
2135	static void	2242	static void
…		…
2138	// only need to lock the actual queueing operation	2245	// only need to lock the actual queueing operation
2139	pthread_mutex_lock (&mymutex);	2246	pthread_mutex_lock (&mymutex);
2140	queue_put (data);	2247	queue_put (data);
2141	pthread_mutex_unlock (&mymutex);	2248	pthread_mutex_unlock (&mymutex);
2142		2249
2143	ev_async_send (DEFAULT_ &mysig);	2250	ev_async_send (EV_DEFAULT_ &mysig);
2144	}	2251	}
2145		2252
2146	static void	2253	static void
2147	mysig_cb (EV_P_ ev_async *w, int revents)	2254	mysig_cb (EV_P_ ev_async *w, int revents)
2148	{	2255	{
…		…
2176	section below on what exactly this means).	2283	section below on what exactly this means).
2177		2284
2178	This call incurs the overhead of a syscall only once per loop iteration,	2285	This call incurs the overhead of a syscall only once per loop iteration,
2179	so while the overhead might be noticable, it doesn't apply to repeated	2286	so while the overhead might be noticable, it doesn't apply to repeated
2180	calls to C<ev_async_send>.	2287	calls to C<ev_async_send>.
		2288
		2289	=item bool = ev_async_pending (ev_async *)
		2290
		2291	Returns a non-zero value when C<ev_async_send> has been called on the
		2292	watcher but the event has not yet been processed (or even noted) by the
		2293	event loop.
		2294
		2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2296	the loop iterates next and checks for the watcher to have become active,
		2297	it will reset the flag again. C<ev_async_pending> can be used to very
		2298	quickly check wether invoking the loop might be a good idea.
		2299
		2300	Not that this does I<not> check wether the watcher itself is pending, only
		2301	wether it has been requested to make this watcher pending.
2181		2302
2182	=back	2303	=back
2183		2304
2184		2305
2185	=head1 OTHER FUNCTIONS	2306	=head1 OTHER FUNCTIONS
…		…
2257		2378
2258	=item * Priorities are not currently supported. Initialising priorities	2379	=item * Priorities are not currently supported. Initialising priorities
2259	will fail and all watchers will have the same priority, even though there	2380	will fail and all watchers will have the same priority, even though there
2260	is an ev_pri field.	2381	is an ev_pri field.
2261		2382
		2383	=item * In libevent, the last base created gets the signals, in libev, the
		2384	first base created (== the default loop) gets the signals.
		2385
2262	=item * Other members are not supported.	2386	=item * Other members are not supported.
2263		2387
2264	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2388	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2265	to use the libev header file and library.	2389	to use the libev header file and library.
2266		2390
…		…
2429	io.start (fd, ev::READ);	2553	io.start (fd, ev::READ);
2430	}	2554	}
2431	};	2555	};
2432		2556
2433		2557
		2558	=head1 OTHER LANGUAGE BINDINGS
		2559
		2560	Libev does not offer other language bindings itself, but bindings for a
		2561	numbe rof languages exist in the form of third-party packages. If you know
		2562	any interesting language binding in addition to the ones listed here, drop
		2563	me a note.
		2564
		2565	=over 4
		2566
		2567	=item Perl
		2568
		2569	The EV module implements the full libev API and is actually used to test
		2570	libev. EV is developed together with libev. Apart from the EV core module,
		2571	there are additional modules that implement libev-compatible interfaces
		2572	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2573	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2574
		2575	It can be found and installed via CPAN, its homepage is found at
		2576	L<http://software.schmorp.de/pkg/EV>.
		2577
		2578	=item Ruby
		2579
		2580	Tony Arcieri has written a ruby extension that offers access to a subset
		2581	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2582	more on top of it. It can be found via gem servers. Its homepage is at
		2583	L<http://rev.rubyforge.org/>.
		2584
		2585	=item D
		2586
		2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2588	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2589
		2590	=back
		2591
		2592
2434	=head1 MACRO MAGIC	2593	=head1 MACRO MAGIC
2435		2594
2436	Libev can be compiled with a variety of options, the most fundamantal	2595	Libev can be compiled with a variety of options, the most fundamantal
2437	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2438	functions and callbacks have an initial C<struct ev_loop *> argument.	2597	functions and callbacks have an initial C<struct ev_loop *> argument.
…		…
2472		2631
2473	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2474		2633
2475	Similar to the other two macros, this gives you the value of the default	2634	Similar to the other two macros, this gives you the value of the default
2476	loop, if multiple loops are supported ("ev loop default").	2635	loop, if multiple loops are supported ("ev loop default").
		2636
		2637	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2638
		2639	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2640	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2641	is undefined when the default loop has not been initialised by a previous
		2642	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2643
		2644	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2645	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2477		2646
2478	=back	2647	=back
2479		2648
2480	Example: Declare and initialise a check watcher, utilising the above	2649	Example: Declare and initialise a check watcher, utilising the above
2481	macros so it will work regardless of whether multiple loops are supported	2650	macros so it will work regardless of whether multiple loops are supported
…		…
2577		2746
2578	libev.m4	2747	libev.m4
2579		2748
2580	=head2 PREPROCESSOR SYMBOLS/MACROS	2749	=head2 PREPROCESSOR SYMBOLS/MACROS
2581		2750
2582	Libev can be configured via a variety of preprocessor symbols you have to define	2751	Libev can be configured via a variety of preprocessor symbols you have to
2583	before including any of its files. The default is not to build for multiplicity	2752	define before including any of its files. The default in the absense of
2584	and only include the select backend.	2753	autoconf is noted for every option.
2585		2754
2586	=over 4	2755	=over 4
2587		2756
2588	=item EV_STANDALONE	2757	=item EV_STANDALONE
2589		2758
…		…
2615	=item EV_USE_NANOSLEEP	2784	=item EV_USE_NANOSLEEP
2616		2785
2617	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2786	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2618	and will use it for delays. Otherwise it will use C<select ()>.	2787	and will use it for delays. Otherwise it will use C<select ()>.
2619		2788
		2789	=item EV_USE_EVENTFD
		2790
		2791	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2792	available and will probe for kernel support at runtime. This will improve
		2793	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2794	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2795	2.7 or newer, otherwise disabled.
		2796
2620	=item EV_USE_SELECT	2797	=item EV_USE_SELECT
2621		2798
2622	If undefined or defined to be C<1>, libev will compile in support for the	2799	If undefined or defined to be C<1>, libev will compile in support for the
2623	C<select>(2) backend. No attempt at autodetection will be done: if no	2800	C<select>(2) backend. No attempt at autodetection will be done: if no
2624	other method takes over, select will be it. Otherwise the select backend	2801	other method takes over, select will be it. Otherwise the select backend
…		…
2660		2837
2661	=item EV_USE_EPOLL	2838	=item EV_USE_EPOLL
2662		2839
2663	If defined to be C<1>, libev will compile in support for the Linux	2840	If defined to be C<1>, libev will compile in support for the Linux
2664	C<epoll>(7) backend. Its availability will be detected at runtime,	2841	C<epoll>(7) backend. Its availability will be detected at runtime,
2665	otherwise another method will be used as fallback. This is the	2842	otherwise another method will be used as fallback. This is the preferred
2666	preferred backend for GNU/Linux systems.	2843	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2844	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2667		2845
2668	=item EV_USE_KQUEUE	2846	=item EV_USE_KQUEUE
2669		2847
2670	If defined to be C<1>, libev will compile in support for the BSD style	2848	If defined to be C<1>, libev will compile in support for the BSD style
2671	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2849	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2690		2868
2691	=item EV_USE_INOTIFY	2869	=item EV_USE_INOTIFY
2692		2870
2693	If defined to be C<1>, libev will compile in support for the Linux inotify	2871	If defined to be C<1>, libev will compile in support for the Linux inotify
2694	interface to speed up C<ev_stat> watchers. Its actual availability will	2872	interface to speed up C<ev_stat> watchers. Its actual availability will
2695	be detected at runtime.	2873	be detected at runtime. If undefined, it will be enabled if the headers
		2874	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2696		2875
2697	=item EV_ATOMIC_T	2876	=item EV_ATOMIC_T
2698		2877
2699	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	2878	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2700	access is atomic with respect to other threads or signal contexts. No such	2879	access is atomic with respect to other threads or signal contexts. No such
…		…
2887		3066
2888	#include "ev_cpp.h"	3067	#include "ev_cpp.h"
2889	#include "ev.c"	3068	#include "ev.c"
2890		3069
2891		3070
		3071	=head1 THREADS AND COROUTINES
		3072
		3073	=head2 THREADS
		3074
		3075	Libev itself is completely threadsafe, but it uses no locking. This
		3076	means that you can use as many loops as you want in parallel, as long as
		3077	only one thread ever calls into one libev function with the same loop
		3078	parameter.
		3079
		3080	Or put differently: calls with different loop parameters can be done in
		3081	parallel from multiple threads, calls with the same loop parameter must be
		3082	done serially (but can be done from different threads, as long as only one
		3083	thread ever is inside a call at any point in time, e.g. by using a mutex
		3084	per loop).
		3085
		3086	If you want to know which design is best for your problem, then I cannot
		3087	help you but by giving some generic advice:
		3088
		3089	=over 4
		3090
		3091	=item * most applications have a main thread: use the default libev loop
		3092	in that thread, or create a seperate thread running only the default loop.
		3093
		3094	This helps integrating other libraries or software modules that use libev
		3095	themselves and don't care/know about threading.
		3096
		3097	=item * one loop per thread is usually a good model.
		3098
		3099	Doing this is almost never wrong, sometimes a better-performance model
		3100	exists, but it is always a good start.
		3101
		3102	=item * other models exist, such as the leader/follower pattern, where one
		3103	loop is handed through multiple threads in a kind of round-robbin fashion.
		3104
		3105	Chosing a model is hard - look around, learn, know that usually you cna do
		3106	better than you currently do :-)
		3107
		3108	=item * often you need to talk to some other thread which blocks in the
		3109	event loop - C<ev_async> watchers can be used to wake them up from other
		3110	threads safely (or from signal contexts...).
		3111
		3112	=back
		3113
		3114	=head2 COROUTINES
		3115
		3116	Libev is much more accomodating to coroutines ("cooperative threads"):
		3117	libev fully supports nesting calls to it's functions from different
		3118	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3119	different coroutines and switch freely between both coroutines running the
		3120	loop, as long as you don't confuse yourself). The only exception is that
		3121	you must not do this from C<ev_periodic> reschedule callbacks.
		3122
		3123	Care has been invested into making sure that libev does not keep local
		3124	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3125	switches.
		3126
		3127
2892	=head1 COMPLEXITIES	3128	=head1 COMPLEXITIES
2893		3129
2894	In this section the complexities of (many of) the algorithms used inside	3130	In this section the complexities of (many of) the algorithms used inside
2895	libev will be explained. For complexity discussions about backends see the	3131	libev will be explained. For complexity discussions about backends see the
2896	documentation for C<ev_default_init>.	3132	documentation for C<ev_default_init>.
…		…
2942	=item Priority handling: O(number_of_priorities)	3178	=item Priority handling: O(number_of_priorities)
2943		3179
2944	Priorities are implemented by allocating some space for each	3180	Priorities are implemented by allocating some space for each
2945	priority. When doing priority-based operations, libev usually has to	3181	priority. When doing priority-based operations, libev usually has to
2946	linearly search all the priorities, but starting/stopping and activating	3182	linearly search all the priorities, but starting/stopping and activating
2947	watchers becomes O(1) w.r.t. prioritiy handling.	3183	watchers becomes O(1) w.r.t. priority handling.
2948		3184
2949	=item Sending an ev_async: O(1)	3185	=item Sending an ev_async: O(1)
2950		3186
2951	=item Processing ev_async_send: O(number_of_async_watchers)	3187	=item Processing ev_async_send: O(number_of_async_watchers)
2952		3188
…		…
3024	calling select (O(n²)) will likely make this unworkable.	3260	calling select (O(n²)) will likely make this unworkable.
3025		3261
3026	=back	3262	=back
3027		3263
3028		3264
		3265	=head1 PORTABILITY REQUIREMENTS
		3266
		3267	In addition to a working ISO-C implementation, libev relies on a few
		3268	additional extensions:
		3269
		3270	=over 4
		3271
		3272	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3273
		3274	The type C<sig_atomic_t volatile> (or whatever is defined as
		3275	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3276	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3277	believed to be sufficiently portable.
		3278
		3279	=item C<sigprocmask> must work in a threaded environment
		3280
		3281	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3282	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3283	pthread implementations will either allow C<sigprocmask> in the "main
		3284	thread" or will block signals process-wide, both behaviours would
		3285	be compatible with libev. Interaction between C<sigprocmask> and
		3286	C<pthread_sigmask> could complicate things, however.
		3287
		3288	The most portable way to handle signals is to block signals in all threads
		3289	except the initial one, and run the default loop in the initial thread as
		3290	well.
		3291
		3292	=back
		3293
		3294	If you know of other additional requirements drop me a note.
		3295
		3296
3029	=head1 AUTHOR	3297	=head1 AUTHOR
3030		3298
3031	Marc Lehmann <libev@schmorp.de>.	3299	Marc Lehmann <libev@schmorp.de>.
3032		3300

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Revision 1.128 by root, Fri Feb 1 13:53:56 2008 UTC vs.
Revision 1.148 by root, Thu Apr 24 01:42:11 2008 UTC