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

Comparing libev/ev.pod (file contents):
Revision 1.116 by root, Mon Dec 31 01:34:09 2007 UTC vs.
Revision 1.140 by root, Wed Apr 2 06:34:51 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	Note that this function is I<not> thread-safe, so if you want to use it
		281	from multiple threads, you have to lock (note also that this is unlikely,
		282	as loops cannot bes hared easily between threads anyway).
		283
		284	The default loop is the only loop that can handle C<ev_signal> and
		285	C<ev_child> watchers, and to do this, it always registers a handler
		286	for C<SIGCHLD>. If this is a problem for your app you can either
		287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		289	C<ev_default_init>.
		290
265	The flags argument can be used to specify special behaviour or specific	291	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>).	292	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		293
268	The following flags are supported:	294	The following flags are supported:
269		295
…		…
290	enabling this flag.	316	enabling this flag.
291		317
292	This works by calling C<getpid ()> on every iteration of the loop,	318	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	319	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	320	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	321	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	322	without a syscall and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	323	C<pthread_atfork> which is even faster).
298		324
299	The big advantage of this flag is that you can forget about fork (and	325	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	326	forget about forgetting to tell libev about forking) when you use this
301	flag.	327	flag.
…		…
403	While this backend scales well, it requires one system call per active	429	While this backend scales well, it requires one system call per active
404	file descriptor per loop iteration. For small and medium numbers of file	430	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	432	might perform better.
407		433
		434	On the positive side, ignoring the spurious readyness notifications, this
		435	backend actually performed to specification in all tests and is fully
		436	embeddable, which is a rare feat among the OS-specific backends.
		437
408	=item C<EVBACKEND_ALL>	438	=item C<EVBACKEND_ALL>
409		439
410	Try all backends (even potentially broken ones that wouldn't be tried	440	Try all backends (even potentially broken ones that wouldn't be tried
411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
…		…
414	It is definitely not recommended to use this flag.	444	It is definitely not recommended to use this flag.
415		445
416	=back	446	=back
417		447
418	If one or more of these are ored into the flags value, then only these	448	If one or more of these are ored into the flags value, then only these
419	backends will be tried (in the reverse order as given here). If none are	449	backends will be tried (in the reverse order as listed here). If none are
420	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		451
423	The most typical usage is like this:	452	The most typical usage is like this:
424		453
425	if (!ev_default_loop (0))	454	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
440		469
441	Similar to C<ev_default_loop>, but always creates a new event loop that is	470	Similar to C<ev_default_loop>, but always creates a new event loop that is
442	always distinct from the default loop. Unlike the default loop, it cannot	471	always distinct from the default loop. Unlike the default loop, it cannot
443	handle signal and child watchers, and attempts to do so will be greeted by	472	handle signal and child watchers, and attempts to do so will be greeted by
444	undefined behaviour (or a failed assertion if assertions are enabled).	473	undefined behaviour (or a failed assertion if assertions are enabled).
		474
		475	Note that this function I<is> thread-safe, and the recommended way to use
		476	libev with threads is indeed to create one loop per thread, and using the
		477	default loop in the "main" or "initial" thread.
445		478
446	Example: Try to create a event loop that uses epoll and nothing else.	479	Example: Try to create a event loop that uses epoll and nothing else.
447		480
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
449	if (!epoller)	482	if (!epoller)
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	506	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
475		508
476	=item ev_default_fork ()	509	=item ev_default_fork ()
477		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	512	to reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	513	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	514	the child process (or both child and parent, but that again makes little
481	again makes little sense).	515	sense). You I<must> call it in the child before using any of the libev
		516	functions, and it will only take effect at the next C<ev_loop> iteration.
482		517
483	You I<must> call this function in the child process after forking if and	518	On the other hand, you only need to call this function in the child
484	only if you want to use the event library in both processes. If you just	519	process if and only if you want to use the event library in the child. If
485	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
486		521
487	The function itself is quite fast and it's usually not a problem to call	522	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	523	it just in case after a fork. To make this easy, the function will fit in
489	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
490		525
491	pthread_atfork (0, 0, ev_default_fork);	526	pthread_atfork (0, 0, ev_default_fork);
492		527
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496
497	=item ev_loop_fork (loop)	528	=item ev_loop_fork (loop)
498		529
499	Like C<ev_default_fork>, but acts on an event loop created by	530	Like C<ev_default_fork>, but acts on an event loop created by
500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
501	after fork, and how you do this is entirely your own problem.	532	after fork, and how you do this is entirely your own problem.
		533
		534	=item int ev_is_default_loop (loop)
		535
		536	Returns true when the given loop actually is the default loop, false otherwise.
502		537
503	=item unsigned int ev_loop_count (loop)	538	=item unsigned int ev_loop_count (loop)
504		539
505	Returns the count of loop iterations for the loop, which is identical to	540	Returns the count of loop iterations for the loop, which is identical to
506	the number of times libev did poll for new events. It starts at C<0> and	541	the number of times libev did poll for new events. It starts at C<0> and
…		…
766	=item C<EV_FORK>	801	=item C<EV_FORK>
767		802
768	The event loop has been resumed in the child process after fork (see	803	The event loop has been resumed in the child process after fork (see
769	C<ev_fork>).	804	C<ev_fork>).
770		805
		806	=item C<EV_ASYNC>
		807
		808	The given async watcher has been asynchronously notified (see C<ev_async>).
		809
771	=item C<EV_ERROR>	810	=item C<EV_ERROR>
772		811
773	An unspecified error has occured, the watcher has been stopped. This might	812	An unspecified error has occured, the watcher has been stopped. This might
774	happen because the watcher could not be properly started because libev	813	happen because the watcher could not be properly started because libev
775	ran out of memory, a file descriptor was found to be closed or any other	814	ran out of memory, a file descriptor was found to be closed or any other
…		…
1054	To support fork in your programs, you either have to call	1093	To support fork in your programs, you either have to call
1055	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1094	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1056	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1057	C<EVBACKEND_POLL>.	1096	C<EVBACKEND_POLL>.
1058		1097
		1098	=head3 The special problem of SIGPIPE
		1099
		1100	While not really specific to libev, it is easy to forget about SIGPIPE:
		1101	when reading from a pipe whose other end has been closed, your program
		1102	gets send a SIGPIPE, which, by default, aborts your program. For most
		1103	programs this is sensible behaviour, for daemons, this is usually
		1104	undesirable.
		1105
		1106	So when you encounter spurious, unexplained daemon exits, make sure you
		1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1108	somewhere, as that would have given you a big clue).
		1109
1059		1110
1060	=head3 Watcher-Specific Functions	1111	=head3 Watcher-Specific Functions
1061		1112
1062	=over 4	1113	=over 4
1063		1114
…		…
1140	configure a timer to trigger every 10 seconds, then it will trigger at	1191	configure a timer to trigger every 10 seconds, then it will trigger at
1141	exactly 10 second intervals. If, however, your program cannot keep up with	1192	exactly 10 second intervals. If, however, your program cannot keep up with
1142	the timer (because it takes longer than those 10 seconds to do stuff) the	1193	the timer (because it takes longer than those 10 seconds to do stuff) the
1143	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
1144		1195
1145	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
1146		1197
1147	This will act as if the timer timed out and restart it again if it is	1198	This will act as if the timer timed out and restart it again if it is
1148	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
1149		1200
1150	If the timer is pending, its pending status is cleared.	1201	If the timer is pending, its pending status is cleared.
…		…
1259	In this configuration the watcher triggers an event at the wallclock time	1310	In this configuration the watcher triggers an event at the wallclock time
1260	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1261	that is, if it is to be run at January 1st 2011 then it will run when the	1312	that is, if it is to be run at January 1st 2011 then it will run when the
1262	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
1263		1314
1264	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1265		1316
1266	In this mode the watcher will always be scheduled to time out at the next	1317	In this mode the watcher will always be scheduled to time out at the next
1267	C<at + N * interval> time (for some integer N, which can also be negative)	1318	C<at + N * interval> time (for some integer N, which can also be negative)
1268	and then repeat, regardless of any time jumps.	1319	and then repeat, regardless of any time jumps.
1269		1320
…		…
1403	with the kernel (thus it coexists with your own signal handlers as long	1454	with the kernel (thus it coexists with your own signal handlers as long
1404	as you don't register any with libev). Similarly, when the last signal	1455	as you don't register any with libev). Similarly, when the last signal
1405	watcher for a signal is stopped libev will reset the signal handler to	1456	watcher for a signal is stopped libev will reset the signal handler to
1406	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
1407		1458
		1459	If possible and supported, libev will install its handlers with
		1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1461	interrupted. If you have a problem with syscalls getting interrupted by
		1462	signals you can block all signals in an C<ev_check> watcher and unblock
		1463	them in an C<ev_prepare> watcher.
		1464
1408	=head3 Watcher-Specific Functions and Data Members	1465	=head3 Watcher-Specific Functions and Data Members
1409		1466
1410	=over 4	1467	=over 4
1411		1468
1412	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1420		1477
1421	The signal the watcher watches out for.	1478	The signal the watcher watches out for.
1422		1479
1423	=back	1480	=back
1424		1481
		1482	=head3 Examples
		1483
		1484	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1485
		1486	static void
		1487	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1488	{
		1489	ev_unloop (loop, EVUNLOOP_ALL);
		1490	}
		1491
		1492	struct ev_signal signal_watcher;
		1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1494	ev_signal_start (loop, &sigint_cb);
		1495
1425		1496
1426	=head2 C<ev_child> - watch out for process status changes	1497	=head2 C<ev_child> - watch out for process status changes
1427		1498
1428	Child watchers trigger when your process receives a SIGCHLD in response to	1499	Child watchers trigger when your process receives a SIGCHLD in response to
1429	some child status changes (most typically when a child of yours dies).	1500	some child status changes (most typically when a child of yours dies). It
		1501	is permissible to install a child watcher I<after> the child has been
		1502	forked (which implies it might have already exited), as long as the event
		1503	loop isn't entered (or is continued from a watcher).
		1504
		1505	Only the default event loop is capable of handling signals, and therefore
		1506	you can only rgeister child watchers in the default event loop.
		1507
		1508	=head3 Process Interaction
		1509
		1510	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1511	initialised. This is necessary to guarantee proper behaviour even if
		1512	the first child watcher is started after the child exits. The occurance
		1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1514	synchronously as part of the event loop processing. Libev always reaps all
		1515	children, even ones not watched.
		1516
		1517	=head3 Overriding the Built-In Processing
		1518
		1519	Libev offers no special support for overriding the built-in child
		1520	processing, but if your application collides with libev's default child
		1521	handler, you can override it easily by installing your own handler for
		1522	C<SIGCHLD> after initialising the default loop, and making sure the
		1523	default loop never gets destroyed. You are encouraged, however, to use an
		1524	event-based approach to child reaping and thus use libev's support for
		1525	that, so other libev users can use C<ev_child> watchers freely.
1430		1526
1431	=head3 Watcher-Specific Functions and Data Members	1527	=head3 Watcher-Specific Functions and Data Members
1432		1528
1433	=over 4	1529	=over 4
1434		1530
1435	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
1436		1532
1437	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
1438		1534
1439	Configures the watcher to wait for status changes of process C<pid> (or	1535	Configures the watcher to wait for status changes of process C<pid> (or
1440	I<any> process if C<pid> is specified as C<0>). The callback can look	1536	I<any> process if C<pid> is specified as C<0>). The callback can look
1441	at the C<rstatus> member of the C<ev_child> watcher structure to see	1537	at the C<rstatus> member of the C<ev_child> watcher structure to see
1442	the status word (use the macros from C<sys/wait.h> and see your systems	1538	the status word (use the macros from C<sys/wait.h> and see your systems
1443	C<waitpid> documentation). The C<rpid> member contains the pid of the	1539	C<waitpid> documentation). The C<rpid> member contains the pid of the
1444	process causing the status change.	1540	process causing the status change. C<trace> must be either C<0> (only
		1541	activate the watcher when the process terminates) or C<1> (additionally
		1542	activate the watcher when the process is stopped or continued).
1445		1543
1446	=item int pid [read-only]	1544	=item int pid [read-only]
1447		1545
1448	The process id this watcher watches out for, or C<0>, meaning any process id.	1546	The process id this watcher watches out for, or C<0>, meaning any process id.
1449		1547
…		…
1458		1556
1459	=back	1557	=back
1460		1558
1461	=head3 Examples	1559	=head3 Examples
1462		1560
1463	Example: Try to exit cleanly on SIGINT and SIGTERM.	1561	Example: C<fork()> a new process and install a child handler to wait for
		1562	its completion.
		1563
		1564	ev_child cw;
1464		1565
1465	static void	1566	static void
1466	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1567	child_cb (EV_P_ struct ev_child *w, int revents)
1467	{	1568	{
1468	ev_unloop (loop, EVUNLOOP_ALL);	1569	ev_child_stop (EV_A_ w);
		1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1469	}	1571	}
1470		1572
1471	struct ev_signal signal_watcher;	1573	pid_t pid = fork ();
1472	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1574
1473	ev_signal_start (loop, &sigint_cb);	1575	if (pid < 0)
		1576	// error
		1577	else if (pid == 0)
		1578	{
		1579	// the forked child executes here
		1580	exit (1);
		1581	}
		1582	else
		1583	{
		1584	ev_child_init (&cw, child_cb, pid, 0);
		1585	ev_child_start (EV_DEFAULT_ &cw);
		1586	}
1474		1587
1475		1588
1476	=head2 C<ev_stat> - did the file attributes just change?	1589	=head2 C<ev_stat> - did the file attributes just change?
1477		1590
1478	This watches a filesystem path for attribute changes. That is, it calls	1591	This watches a filesystem path for attribute changes. That is, it calls
…		…
1507	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1508	to fall back to regular polling again even with inotify, but changes are	1621	to fall back to regular polling again even with inotify, but changes are
1509	usually detected immediately, and if the file exists there will be no	1622	usually detected immediately, and if the file exists there will be no
1510	polling.	1623	polling.
1511		1624
		1625	=head3 ABI Issues (Largefile Support)
		1626
		1627	Libev by default (unless the user overrides this) uses the default
		1628	compilation environment, which means that on systems with optionally
		1629	disabled large file support, you get the 32 bit version of the stat
		1630	structure. When using the library from programs that change the ABI to
		1631	use 64 bit file offsets the programs will fail. In that case you have to
		1632	compile libev with the same flags to get binary compatibility. This is
		1633	obviously the case with any flags that change the ABI, but the problem is
		1634	most noticably with ev_stat and largefile support.
		1635
1512	=head3 Inotify	1636	=head3 Inotify
1513		1637
1514	When C<inotify (7)> support has been compiled into libev (generally only	1638	When C<inotify (7)> support has been compiled into libev (generally only
1515	available on Linux) and present at runtime, it will be used to speed up	1639	available on Linux) and present at runtime, it will be used to speed up
1516	change detection where possible. The inotify descriptor will be created lazily	1640	change detection where possible. The inotify descriptor will be created lazily
…		…
1558		1682
1559	The callback will be receive C<EV_STAT> when a change was detected,	1683	The callback will be receive C<EV_STAT> when a change was detected,
1560	relative to the attributes at the time the watcher was started (or the	1684	relative to the attributes at the time the watcher was started (or the
1561	last change was detected).	1685	last change was detected).
1562		1686
1563	=item ev_stat_stat (ev_stat *)	1687	=item ev_stat_stat (loop, ev_stat *)
1564		1688
1565	Updates the stat buffer immediately with new values. If you change the	1689	Updates the stat buffer immediately with new values. If you change the
1566	watched path in your callback, you could call this fucntion to avoid	1690	watched path in your callback, you could call this fucntion to avoid
1567	detecting this change (while introducing a race condition). Can also be	1691	detecting this change (while introducing a race condition). Can also be
1568	useful simply to find out the new values.	1692	useful simply to find out the new values.
…		…
1685	static void	1809	static void
1686	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1810	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1687	{	1811	{
1688	free (w);	1812	free (w);
1689	// now do something you wanted to do when the program has	1813	// now do something you wanted to do when the program has
1690	// no longer asnything immediate to do.	1814	// no longer anything immediate to do.
1691	}	1815	}
1692		1816
1693	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1694	ev_idle_init (idle_watcher, idle_cb);	1818	ev_idle_init (idle_watcher, idle_cb);
1695	ev_idle_start (loop, idle_cb);	1819	ev_idle_start (loop, idle_cb);
…		…
2036	believe me.	2160	believe me.
2037		2161
2038	=back	2162	=back
2039		2163
2040		2164
		2165	=head2 C<ev_async> - how to wake up another event loop
		2166
		2167	In general, you cannot use an C<ev_loop> from multiple threads or other
		2168	asynchronous sources such as signal handlers (as opposed to multiple event
		2169	loops - those are of course safe to use in different threads).
		2170
		2171	Sometimes, however, you need to wake up another event loop you do not
		2172	control, for example because it belongs to another thread. This is what
		2173	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2174	can signal it by calling C<ev_async_send>, which is thread- and signal
		2175	safe.
		2176
		2177	This functionality is very similar to C<ev_signal> watchers, as signals,
		2178	too, are asynchronous in nature, and signals, too, will be compressed
		2179	(i.e. the number of callback invocations may be less than the number of
		2180	C<ev_async_sent> calls).
		2181
		2182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2183	just the default loop.
		2184
		2185	=head3 Queueing
		2186
		2187	C<ev_async> does not support queueing of data in any way. The reason
		2188	is that the author does not know of a simple (or any) algorithm for a
		2189	multiple-writer-single-reader queue that works in all cases and doesn't
		2190	need elaborate support such as pthreads.
		2191
		2192	That means that if you want to queue data, you have to provide your own
		2193	queue. But at least I can tell you would implement locking around your
		2194	queue:
		2195
		2196	=over 4
		2197
		2198	=item queueing from a signal handler context
		2199
		2200	To implement race-free queueing, you simply add to the queue in the signal
		2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2202	some fictitiuous SIGUSR1 handler:
		2203
		2204	static ev_async mysig;
		2205
		2206	static void
		2207	sigusr1_handler (void)
		2208	{
		2209	sometype data;
		2210
		2211	// no locking etc.
		2212	queue_put (data);
		2213	ev_async_send (EV_DEFAULT_ &mysig);
		2214	}
		2215
		2216	static void
		2217	mysig_cb (EV_P_ ev_async *w, int revents)
		2218	{
		2219	sometype data;
		2220	sigset_t block, prev;
		2221
		2222	sigemptyset (&block);
		2223	sigaddset (&block, SIGUSR1);
		2224	sigprocmask (SIG_BLOCK, &block, &prev);
		2225
		2226	while (queue_get (&data))
		2227	process (data);
		2228
		2229	if (sigismember (&prev, SIGUSR1)
		2230	sigprocmask (SIG_UNBLOCK, &block, 0);
		2231	}
		2232
		2233	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2234	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2235	either...).
		2236
		2237	=item queueing from a thread context
		2238
		2239	The strategy for threads is different, as you cannot (easily) block
		2240	threads but you can easily preempt them, so to queue safely you need to
		2241	employ a traditional mutex lock, such as in this pthread example:
		2242
		2243	static ev_async mysig;
		2244	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2245
		2246	static void
		2247	otherthread (void)
		2248	{
		2249	// only need to lock the actual queueing operation
		2250	pthread_mutex_lock (&mymutex);
		2251	queue_put (data);
		2252	pthread_mutex_unlock (&mymutex);
		2253
		2254	ev_async_send (EV_DEFAULT_ &mysig);
		2255	}
		2256
		2257	static void
		2258	mysig_cb (EV_P_ ev_async *w, int revents)
		2259	{
		2260	pthread_mutex_lock (&mymutex);
		2261
		2262	while (queue_get (&data))
		2263	process (data);
		2264
		2265	pthread_mutex_unlock (&mymutex);
		2266	}
		2267
		2268	=back
		2269
		2270
		2271	=head3 Watcher-Specific Functions and Data Members
		2272
		2273	=over 4
		2274
		2275	=item ev_async_init (ev_async *, callback)
		2276
		2277	Initialises and configures the async watcher - it has no parameters of any
		2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2279	believe me.
		2280
		2281	=item ev_async_send (loop, ev_async *)
		2282
		2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2285	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2287	section below on what exactly this means).
		2288
		2289	This call incurs the overhead of a syscall only once per loop iteration,
		2290	so while the overhead might be noticable, it doesn't apply to repeated
		2291	calls to C<ev_async_send>.
		2292
		2293	=item bool = ev_async_pending (ev_async *)
		2294
		2295	Returns a non-zero value when C<ev_async_send> has been called on the
		2296	watcher but the event has not yet been processed (or even noted) by the
		2297	event loop.
		2298
		2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2300	the loop iterates next and checks for the watcher to have become active,
		2301	it will reset the flag again. C<ev_async_pending> can be used to very
		2302	quickly check wether invoking the loop might be a good idea.
		2303
		2304	Not that this does I<not> check wether the watcher itself is pending, only
		2305	wether it has been requested to make this watcher pending.
		2306
		2307	=back
		2308
		2309
2041	=head1 OTHER FUNCTIONS	2310	=head1 OTHER FUNCTIONS
2042		2311
2043	There are some other functions of possible interest. Described. Here. Now.	2312	There are some other functions of possible interest. Described. Here. Now.
2044		2313
2045	=over 4	2314	=over 4
…		…
2272	Example: Define a class with an IO and idle watcher, start one of them in	2541	Example: Define a class with an IO and idle watcher, start one of them in
2273	the constructor.	2542	the constructor.
2274		2543
2275	class myclass	2544	class myclass
2276	{	2545	{
2277	ev_io io; void io_cb (ev::io &w, int revents);	2546	ev::io io; void io_cb (ev::io &w, int revents);
2278	ev_idle idle void idle_cb (ev::idle &w, int revents);	2547	ev:idle idle void idle_cb (ev::idle &w, int revents);
2279		2548
2280	myclass ();	2549	myclass (int fd)
2281	}
2282
2283	myclass::myclass (int fd)
2284	{	2550	{
2285	io .set <myclass, &myclass::io_cb > (this);	2551	io .set <myclass, &myclass::io_cb > (this);
2286	idle.set <myclass, &myclass::idle_cb> (this);	2552	idle.set <myclass, &myclass::idle_cb> (this);
2287		2553
2288	io.start (fd, ev::READ);	2554	io.start (fd, ev::READ);
		2555	}
2289	}	2556	};
		2557
		2558
		2559	=head1 OTHER LANGUAGE BINDINGS
		2560
		2561	Libev does not offer other language bindings itself, but bindings for a
		2562	numbe rof languages exist in the form of third-party packages. If you know
		2563	any interesting language binding in addition to the ones listed here, drop
		2564	me a note.
		2565
		2566	=over 4
		2567
		2568	=item Perl
		2569
		2570	The EV module implements the full libev API and is actually used to test
		2571	libev. EV is developed together with libev. Apart from the EV core module,
		2572	there are additional modules that implement libev-compatible interfaces
		2573	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2574	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2575
		2576	It can be found and installed via CPAN, its homepage is found at
		2577	L<http://software.schmorp.de/pkg/EV>.
		2578
		2579	=item Ruby
		2580
		2581	Tony Arcieri has written a ruby extension that offers access to a subset
		2582	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2583	more on top of it. It can be found via gem servers. Its homepage is at
		2584	L<http://rev.rubyforge.org/>.
		2585
		2586	=item D
		2587
		2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2589	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2590
		2591	=back
2290		2592
2291		2593
2292	=head1 MACRO MAGIC	2594	=head1 MACRO MAGIC
2293		2595
2294	Libev can be compiled with a variety of options, the most fundamantal	2596	Libev can be compiled with a variety of options, the most fundamantal
…		…
2550		2852
2551	If defined to be C<1>, libev will compile in support for the Linux inotify	2853	If defined to be C<1>, libev will compile in support for the Linux inotify
2552	interface to speed up C<ev_stat> watchers. Its actual availability will	2854	interface to speed up C<ev_stat> watchers. Its actual availability will
2553	be detected at runtime.	2855	be detected at runtime.
2554		2856
		2857	=item EV_ATOMIC_T
		2858
		2859	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2860	access is atomic with respect to other threads or signal contexts. No such
		2861	type is easily found in the C language, so you can provide your own type
		2862	that you know is safe for your purposes. It is used both for signal handler "locking"
		2863	as well as for signal and thread safety in C<ev_async> watchers.
		2864
		2865	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2866	(from F<signal.h>), which is usually good enough on most platforms.
		2867
2555	=item EV_H	2868	=item EV_H
2556		2869
2557	The name of the F<ev.h> header file used to include it. The default if	2870	The name of the F<ev.h> header file used to include it. The default if
2558	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	2871	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2559	virtually rename the F<ev.h> header file in case of conflicts.	2872	used to virtually rename the F<ev.h> header file in case of conflicts.
2560		2873
2561	=item EV_CONFIG_H	2874	=item EV_CONFIG_H
2562		2875
2563	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2876	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2564	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2877	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2565	C<EV_H>, above.	2878	C<EV_H>, above.
2566		2879
2567	=item EV_EVENT_H	2880	=item EV_EVENT_H
2568		2881
2569	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2882	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2570	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	2883	of how the F<event.h> header can be found, the default is C<"event.h">.
2571		2884
2572	=item EV_PROTOTYPES	2885	=item EV_PROTOTYPES
2573		2886
2574	If defined to be C<0>, then F<ev.h> will not define any function	2887	If defined to be C<0>, then F<ev.h> will not define any function
2575	prototypes, but still define all the structs and other symbols. This is	2888	prototypes, but still define all the structs and other symbols. This is
…		…
2624	defined to be C<0>, then they are not.	2937	defined to be C<0>, then they are not.
2625		2938
2626	=item EV_FORK_ENABLE	2939	=item EV_FORK_ENABLE
2627		2940
2628	If undefined or defined to be C<1>, then fork watchers are supported. If	2941	If undefined or defined to be C<1>, then fork watchers are supported. If
		2942	defined to be C<0>, then they are not.
		2943
		2944	=item EV_ASYNC_ENABLE
		2945
		2946	If undefined or defined to be C<1>, then async watchers are supported. If
2629	defined to be C<0>, then they are not.	2947	defined to be C<0>, then they are not.
2630		2948
2631	=item EV_MINIMAL	2949	=item EV_MINIMAL
2632		2950
2633	If you need to shave off some kilobytes of code at the expense of some	2951	If you need to shave off some kilobytes of code at the expense of some
…		…
2754	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3072	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2755		3073
2756	That means that changing a timer costs less than removing/adding them	3074	That means that changing a timer costs less than removing/adding them
2757	as only the relative motion in the event queue has to be paid for.	3075	as only the relative motion in the event queue has to be paid for.
2758		3076
2759	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3077	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2760		3078
2761	These just add the watcher into an array or at the head of a list.	3079	These just add the watcher into an array or at the head of a list.
2762		3080
2763	=item Stopping check/prepare/idle watchers: O(1)	3081	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2764		3082
2765	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3083	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2766		3084
2767	These watchers are stored in lists then need to be walked to find the	3085	These watchers are stored in lists then need to be walked to find the
2768	correct watcher to remove. The lists are usually short (you don't usually	3086	correct watcher to remove. The lists are usually short (you don't usually
…		…
2784	=item Priority handling: O(number_of_priorities)	3102	=item Priority handling: O(number_of_priorities)
2785		3103
2786	Priorities are implemented by allocating some space for each	3104	Priorities are implemented by allocating some space for each
2787	priority. When doing priority-based operations, libev usually has to	3105	priority. When doing priority-based operations, libev usually has to
2788	linearly search all the priorities, but starting/stopping and activating	3106	linearly search all the priorities, but starting/stopping and activating
2789	watchers becomes O(1) w.r.t. prioritiy handling.	3107	watchers becomes O(1) w.r.t. priority handling.
		3108
		3109	=item Sending an ev_async: O(1)
		3110
		3111	=item Processing ev_async_send: O(number_of_async_watchers)
		3112
		3113	=item Processing signals: O(max_signal_number)
		3114
		3115	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3116	calls in the current loop iteration. Checking for async and signal events
		3117	involves iterating over all running async watchers or all signal numbers.
2790		3118
2791	=back	3119	=back
2792		3120
2793		3121
2794	=head1 Win32 platform limitations and workarounds	3122	=head1 Win32 platform limitations and workarounds

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Comparing libev/ev.pod (file contents): Revision 1.116 by root, Mon Dec 31 01:34:09 2007 UTC vs. Revision 1.140 by root, Wed Apr 2 06:34:51 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.116 by root, Mon Dec 31 01:34:09 2007 UTC vs.
Revision 1.140 by root, Wed Apr 2 06:34:51 2008 UTC