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

Comparing libev/ev.pod (file contents):
Revision 1.112 by root, Wed Dec 26 08:06:09 2007 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
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84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head2 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		276
262	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
263	function.	278	function.
264		279
		280	The default loop is the only loop that can handle C<ev_signal> and
		281	C<ev_child> watchers, and to do this, it always registers a handler
		282	for C<SIGCHLD>. If this is a problem for your app you can either
		283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		285	C<ev_default_init>.
		286
265	The flags argument can be used to specify special behaviour or specific	287	The flags argument can be used to specify special behaviour or specific
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		289
268	The following flags are supported:	290	The following flags are supported:
269		291
…		…
290	enabling this flag.	312	enabling this flag.
291		313
292	This works by calling C<getpid ()> on every iteration of the loop,	314	This works by calling C<getpid ()> on every iteration of the loop,
293	and thus this might slow down your event loop if you do a lot of loop	315	and thus this might slow down your event loop if you do a lot of loop
294	iterations and little real work, but is usually not noticeable (on my	316	iterations and little real work, but is usually not noticeable (on my
295	Linux system for example, C<getpid> is actually a simple 5-insn sequence	317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
296	without a syscall and thus I<very> fast, but my Linux system also has	318	without a syscall and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
298		320
299	The big advantage of this flag is that you can forget about fork (and	321	The big advantage of this flag is that you can forget about fork (and
300	forget about forgetting to tell libev about forking) when you use this	322	forget about forgetting to tell libev about forking) when you use this
301	flag.	323	flag.
…		…
403	While this backend scales well, it requires one system call per active	425	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	426	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	428	might perform better.
407		429
		430	On the positive side, ignoring the spurious readyness notifications, this
		431	backend actually performed to specification in all tests and is fully
		432	embeddable, which is a rare feat among the OS-specific backends.
		433
408	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
409		435
410	Try all backends (even potentially broken ones that wouldn't be tried	436	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	437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
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414	It is definitely not recommended to use this flag.	440	It is definitely not recommended to use this flag.
415		441
416	=back	442	=back
417		443
418	If one or more of these are ored into the flags value, then only these	444	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	445	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	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		447
423	The most typical usage is like this:	448	The most typical usage is like this:
424		449
425	if (!ev_default_loop (0))	450	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	498	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	499	earlier call to C<ev_loop_new>.
475		500
476	=item ev_default_fork ()	501	=item ev_default_fork ()
477		502
		503	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	504	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	505	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	506	the child process (or both child and parent, but that again makes little
481	again makes little sense).	507	sense). You I<must> call it in the child before using any of the libev
		508	functions, and it will only take effect at the next C<ev_loop> iteration.
482		509
483	You I<must> call this function in the child process after forking if and	510	On the other hand, you only need to call this function in the child
484	only if you want to use the event library in both processes. If you just	511	process if and only if you want to use the event library in the child. If
485	fork+exec, you don't have to call it.	512	you just fork+exec, you don't have to call it at all.
486		513
487	The function itself is quite fast and it's usually not a problem to call	514	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	515	it just in case after a fork. To make this easy, the function will fit in
489	quite nicely into a call to C<pthread_atfork>:	516	quite nicely into a call to C<pthread_atfork>:
490		517
491	pthread_atfork (0, 0, ev_default_fork);	518	pthread_atfork (0, 0, ev_default_fork);
492		519
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)	520	=item ev_loop_fork (loop)
498		521
499	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
500	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
501	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.
502		529
503	=item unsigned int ev_loop_count (loop)	530	=item unsigned int ev_loop_count (loop)
504		531
505	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
506	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
…		…
551	usually a better approach for this kind of thing.	578	usually a better approach for this kind of thing.
552		579
553	Here are the gory details of what C<ev_loop> does:	580	Here are the gory details of what C<ev_loop> does:
554		581
555	- Before the first iteration, call any pending watchers.	582	- Before the first iteration, call any pending watchers.
556	* If there are no active watchers (reference count is zero), return.	583	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- Queue all prepare watchers and then call all outstanding watchers.	584	- If a fork was detected, queue and call all fork watchers.
		585	- Queue and call all prepare watchers.
558	- If we have been forked, recreate the kernel state.	586	- If we have been forked, recreate the kernel state.
559	- Update the kernel state with all outstanding changes.	587	- Update the kernel state with all outstanding changes.
560	- Update the "event loop time".	588	- Update the "event loop time".
561	- Calculate for how long to block.	589	- Calculate for how long to sleep or block, if at all
		590	(active idle watchers, EVLOOP_NONBLOCK or not having
		591	any active watchers at all will result in not sleeping).
		592	- Sleep if the I/O and timer collect interval say so.
562	- Block the process, waiting for any events.	593	- Block the process, waiting for any events.
563	- Queue all outstanding I/O (fd) events.	594	- Queue all outstanding I/O (fd) events.
564	- Update the "event loop time" and do time jump handling.	595	- Update the "event loop time" and do time jump handling.
565	- Queue all outstanding timers.	596	- Queue all outstanding timers.
566	- Queue all outstanding periodics.	597	- Queue all outstanding periodics.
567	- If no events are pending now, queue all idle watchers.	598	- If no events are pending now, queue all idle watchers.
568	- Queue all check watchers.	599	- Queue all check watchers.
569	- Call all queued watchers in reverse order (i.e. check watchers first).	600	- Call all queued watchers in reverse order (i.e. check watchers first).
570	Signals and child watchers are implemented as I/O watchers, and will	601	Signals and child watchers are implemented as I/O watchers, and will
571	be handled here by queueing them when their watcher gets executed.	602	be handled here by queueing them when their watcher gets executed.
572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573	were used, return, otherwise continue with step *.	604	were used, or there are no active watchers, return, otherwise
		605	continue with step *.
574		606
575	Example: Queue some jobs and then loop until no events are outsanding	607	Example: Queue some jobs and then loop until no events are outstanding
576	anymore.	608	anymore.
577		609
578	... queue jobs here, make sure they register event watchers as long	610	... queue jobs here, make sure they register event watchers as long
579	... as they still have work to do (even an idle watcher will do..)	611	... as they still have work to do (even an idle watcher will do..)
580	ev_loop (my_loop, 0);	612	ev_loop (my_loop, 0);
…		…
584		616
585	Can be used to make a call to C<ev_loop> return early (but only after it	617	Can be used to make a call to C<ev_loop> return early (but only after it
586	has processed all outstanding events). The C<how> argument must be either	618	has processed all outstanding events). The C<how> argument must be either
587	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	619	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
588	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	620	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		621
		622	This "unloop state" will be cleared when entering C<ev_loop> again.
589		623
590	=item ev_ref (loop)	624	=item ev_ref (loop)
591		625
592	=item ev_unref (loop)	626	=item ev_unref (loop)
593		627
…		…
598	returning, ev_unref() after starting, and ev_ref() before stopping it. For	632	returning, ev_unref() after starting, and ev_ref() before stopping it. For
599	example, libev itself uses this for its internal signal pipe: It is not	633	example, libev itself uses this for its internal signal pipe: It is not
600	visible to the libev user and should not keep C<ev_loop> from exiting if	634	visible to the libev user and should not keep C<ev_loop> from exiting if
601	no event watchers registered by it are active. It is also an excellent	635	no event watchers registered by it are active. It is also an excellent
602	way to do this for generic recurring timers or from within third-party	636	way to do this for generic recurring timers or from within third-party
603	libraries. Just remember to I<unref after start> and I<ref before stop>.	637	libraries. Just remember to I<unref after start> and I<ref before stop>
		638	(but only if the watcher wasn't active before, or was active before,
		639	respectively).
604		640
605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606	running when nothing else is active.	642	running when nothing else is active.
607		643
608	struct ev_signal exitsig;	644	struct ev_signal exitsig;
…		…
756		792
757	=item C<EV_FORK>	793	=item C<EV_FORK>
758		794
759	The event loop has been resumed in the child process after fork (see	795	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	796	C<ev_fork>).
		797
		798	=item C<EV_ASYNC>
		799
		800	The given async watcher has been asynchronously notified (see C<ev_async>).
761		801
762	=item C<EV_ERROR>	802	=item C<EV_ERROR>
763		803
764	An unspecified error has occured, the watcher has been stopped. This might	804	An unspecified error has occured, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	805	happen because the watcher could not be properly started because libev
…		…
1045	To support fork in your programs, you either have to call	1085	To support fork in your programs, you either have to call
1046	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,
1047	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1048	C<EVBACKEND_POLL>.	1088	C<EVBACKEND_POLL>.
1049		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
1050		1102
1051	=head3 Watcher-Specific Functions	1103	=head3 Watcher-Specific Functions
1052		1104
1053	=over 4	1105	=over 4
1054		1106
…		…
1131	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
1132	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
1133	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
1134	timer will not fire more than once per event loop iteration.	1186	timer will not fire more than once per event loop iteration.
1135		1187
1136	=item ev_timer_again (loop)	1188	=item ev_timer_again (loop, ev_timer *)
1137		1189
1138	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
1139	repeating. The exact semantics are:	1191	repeating. The exact semantics are:
1140		1192
1141	If the timer is pending, its pending status is cleared.	1193	If the timer is pending, its pending status is cleared.
…		…
1250	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
1251	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,
1252	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
1253	system time reaches or surpasses this time.	1305	system time reaches or surpasses this time.
1254		1306
1255	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1307	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1256		1308
1257	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
1258	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)
1259	and then repeat, regardless of any time jumps.	1311	and then repeat, regardless of any time jumps.
1260		1312
…		…
1394	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
1395	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
1396	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
1397	SIG_DFL (regardless of what it was set to before).	1449	SIG_DFL (regardless of what it was set to before).
1398		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
1399	=head3 Watcher-Specific Functions and Data Members	1457	=head3 Watcher-Specific Functions and Data Members
1400		1458
1401	=over 4	1459	=over 4
1402		1460
1403	=item ev_signal_init (ev_signal *, callback, int signum)	1461	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1411		1469
1412	The signal the watcher watches out for.	1470	The signal the watcher watches out for.
1413		1471
1414	=back	1472	=back
1415		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
1416		1488
1417	=head2 C<ev_child> - watch out for process status changes	1489	=head2 C<ev_child> - watch out for process status changes
1418		1490
1419	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
1420	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.
1421		1518
1422	=head3 Watcher-Specific Functions and Data Members	1519	=head3 Watcher-Specific Functions and Data Members
1423		1520
1424	=over 4	1521	=over 4
1425		1522
1426	=item ev_child_init (ev_child *, callback, int pid)	1523	=item ev_child_init (ev_child *, callback, int pid, int trace)
1427		1524
1428	=item ev_child_set (ev_child *, int pid)	1525	=item ev_child_set (ev_child *, int pid, int trace)
1429		1526
1430	Configures the watcher to wait for status changes of process C<pid> (or	1527	Configures the watcher to wait for status changes of process C<pid> (or
1431	I<any> process if C<pid> is specified as C<0>). The callback can look	1528	I<any> process if C<pid> is specified as C<0>). The callback can look
1432	at the C<rstatus> member of the C<ev_child> watcher structure to see	1529	at the C<rstatus> member of the C<ev_child> watcher structure to see
1433	the status word (use the macros from C<sys/wait.h> and see your systems	1530	the status word (use the macros from C<sys/wait.h> and see your systems
1434	C<waitpid> documentation). The C<rpid> member contains the pid of the	1531	C<waitpid> documentation). The C<rpid> member contains the pid of the
1435	process causing the status change.	1532	process causing the status change. C<trace> must be either C<0> (only
		1533	activate the watcher when the process terminates) or C<1> (additionally
		1534	activate the watcher when the process is stopped or continued).
1436		1535
1437	=item int pid [read-only]	1536	=item int pid [read-only]
1438		1537
1439	The process id this watcher watches out for, or C<0>, meaning any process id.	1538	The process id this watcher watches out for, or C<0>, meaning any process id.
1440		1539
…		…
1449		1548
1450	=back	1549	=back
1451		1550
1452	=head3 Examples	1551	=head3 Examples
1453		1552
1454	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;
1455		1557
1456	static void	1558	static void
1457	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1559	child_cb (EV_P_ struct ev_child *w, int revents)
1458	{	1560	{
1459	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);
1460	}	1563	}
1461		1564
1462	struct ev_signal signal_watcher;	1565	pid_t pid = fork ();
1463	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1566
1464	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	}
1465		1579
1466		1580
1467	=head2 C<ev_stat> - did the file attributes just change?	1581	=head2 C<ev_stat> - did the file attributes just change?
1468		1582
1469	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
…		…
1498	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
1499	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
1500	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
1501	polling.	1615	polling.
1502		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
1503	=head3 Inotify	1628	=head3 Inotify
1504		1629
1505	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
1506	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
1507	change detection where possible. The inotify descriptor will be created lazily	1632	change detection where possible. The inotify descriptor will be created lazily
…		…
1549		1674
1550	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,
1551	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
1552	last change was detected).	1677	last change was detected).
1553		1678
1554	=item ev_stat_stat (ev_stat *)	1679	=item ev_stat_stat (loop, ev_stat *)
1555		1680
1556	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
1557	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
1558	detecting this change (while introducing a race condition). Can also be	1683	detecting this change (while introducing a race condition). Can also be
1559	useful simply to find out the new values.	1684	useful simply to find out the new values.
…		…
1676	static void	1801	static void
1677	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1802	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1678	{	1803	{
1679	free (w);	1804	free (w);
1680	// now do something you wanted to do when the program has	1805	// now do something you wanted to do when the program has
1681	// no longer asnything immediate to do.	1806	// no longer anything immediate to do.
1682	}	1807	}
1683		1808
1684	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1809	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1685	ev_idle_init (idle_watcher, idle_cb);	1810	ev_idle_init (idle_watcher, idle_cb);
1686	ev_idle_start (loop, idle_cb);	1811	ev_idle_start (loop, idle_cb);
…		…
2027	believe me.	2152	believe me.
2028		2153
2029	=back	2154	=back
2030		2155
2031		2156
		2157	=head2 C<ev_async> - how to wake up another event loop
		2158
		2159	In general, you cannot use an C<ev_loop> from multiple threads or other
		2160	asynchronous sources such as signal handlers (as opposed to multiple event
		2161	loops - those are of course safe to use in different threads).
		2162
		2163	Sometimes, however, you need to wake up another event loop you do not
		2164	control, for example because it belongs to another thread. This is what
		2165	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2166	can signal it by calling C<ev_async_send>, which is thread- and signal
		2167	safe.
		2168
		2169	This functionality is very similar to C<ev_signal> watchers, as signals,
		2170	too, are asynchronous in nature, and signals, too, will be compressed
		2171	(i.e. the number of callback invocations may be less than the number of
		2172	C<ev_async_sent> calls).
		2173
		2174	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2175	just the default loop.
		2176
		2177	=head3 Queueing
		2178
		2179	C<ev_async> does not support queueing of data in any way. The reason
		2180	is that the author does not know of a simple (or any) algorithm for a
		2181	multiple-writer-single-reader queue that works in all cases and doesn't
		2182	need elaborate support such as pthreads.
		2183
		2184	That means that if you want to queue data, you have to provide your own
		2185	queue. But at least I can tell you would implement locking around your
		2186	queue:
		2187
		2188	=over 4
		2189
		2190	=item queueing from a signal handler context
		2191
		2192	To implement race-free queueing, you simply add to the queue in the signal
		2193	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2194	some fictitiuous SIGUSR1 handler:
		2195
		2196	static ev_async mysig;
		2197
		2198	static void
		2199	sigusr1_handler (void)
		2200	{
		2201	sometype data;
		2202
		2203	// no locking etc.
		2204	queue_put (data);
		2205	ev_async_send (EV_DEFAULT_ &mysig);
		2206	}
		2207
		2208	static void
		2209	mysig_cb (EV_P_ ev_async *w, int revents)
		2210	{
		2211	sometype data;
		2212	sigset_t block, prev;
		2213
		2214	sigemptyset (&block);
		2215	sigaddset (&block, SIGUSR1);
		2216	sigprocmask (SIG_BLOCK, &block, &prev);
		2217
		2218	while (queue_get (&data))
		2219	process (data);
		2220
		2221	if (sigismember (&prev, SIGUSR1)
		2222	sigprocmask (SIG_UNBLOCK, &block, 0);
		2223	}
		2224
		2225	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2226	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2227	either...).
		2228
		2229	=item queueing from a thread context
		2230
		2231	The strategy for threads is different, as you cannot (easily) block
		2232	threads but you can easily preempt them, so to queue safely you need to
		2233	employ a traditional mutex lock, such as in this pthread example:
		2234
		2235	static ev_async mysig;
		2236	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2237
		2238	static void
		2239	otherthread (void)
		2240	{
		2241	// only need to lock the actual queueing operation
		2242	pthread_mutex_lock (&mymutex);
		2243	queue_put (data);
		2244	pthread_mutex_unlock (&mymutex);
		2245
		2246	ev_async_send (EV_DEFAULT_ &mysig);
		2247	}
		2248
		2249	static void
		2250	mysig_cb (EV_P_ ev_async *w, int revents)
		2251	{
		2252	pthread_mutex_lock (&mymutex);
		2253
		2254	while (queue_get (&data))
		2255	process (data);
		2256
		2257	pthread_mutex_unlock (&mymutex);
		2258	}
		2259
		2260	=back
		2261
		2262
		2263	=head3 Watcher-Specific Functions and Data Members
		2264
		2265	=over 4
		2266
		2267	=item ev_async_init (ev_async *, callback)
		2268
		2269	Initialises and configures the async watcher - it has no parameters of any
		2270	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2271	believe me.
		2272
		2273	=item ev_async_send (loop, ev_async *)
		2274
		2275	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2276	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2277	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2278	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2279	section below on what exactly this means).
		2280
		2281	This call incurs the overhead of a syscall only once per loop iteration,
		2282	so while the overhead might be noticable, it doesn't apply to repeated
		2283	calls to C<ev_async_send>.
		2284
		2285	=back
		2286
		2287
2032	=head1 OTHER FUNCTIONS	2288	=head1 OTHER FUNCTIONS
2033		2289
2034	There are some other functions of possible interest. Described. Here. Now.	2290	There are some other functions of possible interest. Described. Here. Now.
2035		2291
2036	=over 4	2292	=over 4
…		…
2263	Example: Define a class with an IO and idle watcher, start one of them in	2519	Example: Define a class with an IO and idle watcher, start one of them in
2264	the constructor.	2520	the constructor.
2265		2521
2266	class myclass	2522	class myclass
2267	{	2523	{
2268	ev_io io; void io_cb (ev::io &w, int revents);	2524	ev::io io; void io_cb (ev::io &w, int revents);
2269	ev_idle idle void idle_cb (ev::idle &w, int revents);	2525	ev:idle idle void idle_cb (ev::idle &w, int revents);
2270		2526
2271	myclass ();	2527	myclass (int fd)
2272	}
2273
2274	myclass::myclass (int fd)
2275	{	2528	{
2276	io .set <myclass, &myclass::io_cb > (this);	2529	io .set <myclass, &myclass::io_cb > (this);
2277	idle.set <myclass, &myclass::idle_cb> (this);	2530	idle.set <myclass, &myclass::idle_cb> (this);
2278		2531
2279	io.start (fd, ev::READ);	2532	io.start (fd, ev::READ);
		2533	}
2280	}	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
2281		2570
2282		2571
2283	=head1 MACRO MAGIC	2572	=head1 MACRO MAGIC
2284		2573
2285	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
…		…
2541		2830
2542	If defined to be C<1>, libev will compile in support for the Linux inotify	2831	If defined to be C<1>, libev will compile in support for the Linux inotify
2543	interface to speed up C<ev_stat> watchers. Its actual availability will	2832	interface to speed up C<ev_stat> watchers. Its actual availability will
2544	be detected at runtime.	2833	be detected at runtime.
2545		2834
		2835	=item EV_ATOMIC_T
		2836
		2837	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2838	access is atomic with respect to other threads or signal contexts. No such
		2839	type is easily found in the C language, so you can provide your own type
		2840	that you know is safe for your purposes. It is used both for signal handler "locking"
		2841	as well as for signal and thread safety in C<ev_async> watchers.
		2842
		2843	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2844	(from F<signal.h>), which is usually good enough on most platforms.
		2845
2546	=item EV_H	2846	=item EV_H
2547		2847
2548	The name of the F<ev.h> header file used to include it. The default if	2848	The name of the F<ev.h> header file used to include it. The default if
2549	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	2849	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2550	virtually rename the F<ev.h> header file in case of conflicts.	2850	used to virtually rename the F<ev.h> header file in case of conflicts.
2551		2851
2552	=item EV_CONFIG_H	2852	=item EV_CONFIG_H
2553		2853
2554	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2854	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2555	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2855	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2556	C<EV_H>, above.	2856	C<EV_H>, above.
2557		2857
2558	=item EV_EVENT_H	2858	=item EV_EVENT_H
2559		2859
2560	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2860	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2561	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	2861	of how the F<event.h> header can be found, the default is C<"event.h">.
2562		2862
2563	=item EV_PROTOTYPES	2863	=item EV_PROTOTYPES
2564		2864
2565	If defined to be C<0>, then F<ev.h> will not define any function	2865	If defined to be C<0>, then F<ev.h> will not define any function
2566	prototypes, but still define all the structs and other symbols. This is	2866	prototypes, but still define all the structs and other symbols. This is
…		…
2615	defined to be C<0>, then they are not.	2915	defined to be C<0>, then they are not.
2616		2916
2617	=item EV_FORK_ENABLE	2917	=item EV_FORK_ENABLE
2618		2918
2619	If undefined or defined to be C<1>, then fork watchers are supported. If	2919	If undefined or defined to be C<1>, then fork watchers are supported. If
		2920	defined to be C<0>, then they are not.
		2921
		2922	=item EV_ASYNC_ENABLE
		2923
		2924	If undefined or defined to be C<1>, then async watchers are supported. If
2620	defined to be C<0>, then they are not.	2925	defined to be C<0>, then they are not.
2621		2926
2622	=item EV_MINIMAL	2927	=item EV_MINIMAL
2623		2928
2624	If you need to shave off some kilobytes of code at the expense of some	2929	If you need to shave off some kilobytes of code at the expense of some
…		…
2745	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3050	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2746		3051
2747	That means that changing a timer costs less than removing/adding them	3052	That means that changing a timer costs less than removing/adding them
2748	as only the relative motion in the event queue has to be paid for.	3053	as only the relative motion in the event queue has to be paid for.
2749		3054
2750	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3055	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2751		3056
2752	These just add the watcher into an array or at the head of a list.	3057	These just add the watcher into an array or at the head of a list.
2753		3058
2754	=item Stopping check/prepare/idle watchers: O(1)	3059	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2755		3060
2756	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3061	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2757		3062
2758	These watchers are stored in lists then need to be walked to find the	3063	These watchers are stored in lists then need to be walked to find the
2759	correct watcher to remove. The lists are usually short (you don't usually	3064	correct watcher to remove. The lists are usually short (you don't usually
…		…
2775	=item Priority handling: O(number_of_priorities)	3080	=item Priority handling: O(number_of_priorities)
2776		3081
2777	Priorities are implemented by allocating some space for each	3082	Priorities are implemented by allocating some space for each
2778	priority. When doing priority-based operations, libev usually has to	3083	priority. When doing priority-based operations, libev usually has to
2779	linearly search all the priorities, but starting/stopping and activating	3084	linearly search all the priorities, but starting/stopping and activating
2780	watchers becomes O(1) w.r.t. prioritiy handling.	3085	watchers becomes O(1) w.r.t. priority handling.
		3086
		3087	=item Sending an ev_async: O(1)
		3088
		3089	=item Processing ev_async_send: O(number_of_async_watchers)
		3090
		3091	=item Processing signals: O(max_signal_number)
		3092
		3093	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3094	calls in the current loop iteration. Checking for async and signal events
		3095	involves iterating over all running async watchers or all signal numbers.
2781		3096
2782	=back	3097	=back
2783		3098
2784		3099
2785	=head1 Win32 platform limitations and workarounds	3100	=head1 Win32 platform limitations and workarounds

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Comparing libev/ev.pod (file contents): Revision 1.112 by root, Wed Dec 26 08:06:09 2007 UTC vs. Revision 1.138 by root, Mon Mar 31 01:14:12 2008 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.112 by root, Wed Dec 26 08:06:09 2007 UTC vs.
Revision 1.138 by root, Mon Mar 31 01:14:12 2008 UTC