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

Comparing libev/ev.pod (file contents):
Revision 1.111 by root, Tue Dec 25 18:01:20 2007 UTC vs.
Revision 1.136 by root, Thu Mar 13 13:06:16 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.
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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?");
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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
…		…
1131	configure a timer to trigger every 10 seconds, then it will trigger at	1171	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	1172	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	1173	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.	1174	timer will not fire more than once per event loop iteration.
1135		1175
1136	=item ev_timer_again (loop)	1176	=item ev_timer_again (loop, ev_timer *)
1137		1177
1138	This will act as if the timer timed out and restart it again if it is	1178	This will act as if the timer timed out and restart it again if it is
1139	repeating. The exact semantics are:	1179	repeating. The exact semantics are:
1140		1180
1141	If the timer is pending, its pending status is cleared.	1181	If the timer is pending, its pending status is cleared.
…		…
1250	In this configuration the watcher triggers an event at the wallclock time	1290	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,	1291	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	1292	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.	1293	system time reaches or surpasses this time.
1254		1294
1255	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1256		1296
1257	In this mode the watcher will always be scheduled to time out at the next	1297	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)	1298	C<at + N * interval> time (for some integer N, which can also be negative)
1259	and then repeat, regardless of any time jumps.	1299	and then repeat, regardless of any time jumps.
1260		1300
…		…
1394	with the kernel (thus it coexists with your own signal handlers as long	1434	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	1435	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	1436	watcher for a signal is stopped libev will reset the signal handler to
1397	SIG_DFL (regardless of what it was set to before).	1437	SIG_DFL (regardless of what it was set to before).
1398		1438
		1439	If possible and supported, libev will install its handlers with
		1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1441	interrupted. If you have a problem with syscalls getting interrupted by
		1442	signals you can block all signals in an C<ev_check> watcher and unblock
		1443	them in an C<ev_prepare> watcher.
		1444
1399	=head3 Watcher-Specific Functions and Data Members	1445	=head3 Watcher-Specific Functions and Data Members
1400		1446
1401	=over 4	1447	=over 4
1402		1448
1403	=item ev_signal_init (ev_signal *, callback, int signum)	1449	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1411		1457
1412	The signal the watcher watches out for.	1458	The signal the watcher watches out for.
1413		1459
1414	=back	1460	=back
1415		1461
		1462	=head3 Examples
		1463
		1464	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1465
		1466	static void
		1467	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1468	{
		1469	ev_unloop (loop, EVUNLOOP_ALL);
		1470	}
		1471
		1472	struct ev_signal signal_watcher;
		1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1474	ev_signal_start (loop, &sigint_cb);
		1475
1416		1476
1417	=head2 C<ev_child> - watch out for process status changes	1477	=head2 C<ev_child> - watch out for process status changes
1418		1478
1419	Child watchers trigger when your process receives a SIGCHLD in response to	1479	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).	1480	some child status changes (most typically when a child of yours dies). It
		1481	is permissible to install a child watcher I<after> the child has been
		1482	forked (which implies it might have already exited), as long as the event
		1483	loop isn't entered (or is continued from a watcher).
		1484
		1485	Only the default event loop is capable of handling signals, and therefore
		1486	you can only rgeister child watchers in the default event loop.
		1487
		1488	=head3 Process Interaction
		1489
		1490	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1491	initialised. This is necessary to guarantee proper behaviour even if
		1492	the first child watcher is started after the child exits. The occurance
		1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1494	synchronously as part of the event loop processing. Libev always reaps all
		1495	children, even ones not watched.
		1496
		1497	=head3 Overriding the Built-In Processing
		1498
		1499	Libev offers no special support for overriding the built-in child
		1500	processing, but if your application collides with libev's default child
		1501	handler, you can override it easily by installing your own handler for
		1502	C<SIGCHLD> after initialising the default loop, and making sure the
		1503	default loop never gets destroyed. You are encouraged, however, to use an
		1504	event-based approach to child reaping and thus use libev's support for
		1505	that, so other libev users can use C<ev_child> watchers freely.
1421		1506
1422	=head3 Watcher-Specific Functions and Data Members	1507	=head3 Watcher-Specific Functions and Data Members
1423		1508
1424	=over 4	1509	=over 4
1425		1510
1426	=item ev_child_init (ev_child *, callback, int pid)	1511	=item ev_child_init (ev_child *, callback, int pid, int trace)
1427		1512
1428	=item ev_child_set (ev_child *, int pid)	1513	=item ev_child_set (ev_child *, int pid, int trace)
1429		1514
1430	Configures the watcher to wait for status changes of process C<pid> (or	1515	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	1516	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	1517	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	1518	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	1519	C<waitpid> documentation). The C<rpid> member contains the pid of the
1435	process causing the status change.	1520	process causing the status change. C<trace> must be either C<0> (only
		1521	activate the watcher when the process terminates) or C<1> (additionally
		1522	activate the watcher when the process is stopped or continued).
1436		1523
1437	=item int pid [read-only]	1524	=item int pid [read-only]
1438		1525
1439	The process id this watcher watches out for, or C<0>, meaning any process id.	1526	The process id this watcher watches out for, or C<0>, meaning any process id.
1440		1527
…		…
1449		1536
1450	=back	1537	=back
1451		1538
1452	=head3 Examples	1539	=head3 Examples
1453		1540
1454	Example: Try to exit cleanly on SIGINT and SIGTERM.	1541	Example: C<fork()> a new process and install a child handler to wait for
		1542	its completion.
		1543
		1544	ev_child cw;
1455		1545
1456	static void	1546	static void
1457	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1547	child_cb (EV_P_ struct ev_child *w, int revents)
1458	{	1548	{
1459	ev_unloop (loop, EVUNLOOP_ALL);	1549	ev_child_stop (EV_A_ w);
		1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1460	}	1551	}
1461		1552
1462	struct ev_signal signal_watcher;	1553	pid_t pid = fork ();
1463	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1554
1464	ev_signal_start (loop, &sigint_cb);	1555	if (pid < 0)
		1556	// error
		1557	else if (pid == 0)
		1558	{
		1559	// the forked child executes here
		1560	exit (1);
		1561	}
		1562	else
		1563	{
		1564	ev_child_init (&cw, child_cb, pid, 0);
		1565	ev_child_start (EV_DEFAULT_ &cw);
		1566	}
1465		1567
1466		1568
1467	=head2 C<ev_stat> - did the file attributes just change?	1569	=head2 C<ev_stat> - did the file attributes just change?
1468		1570
1469	This watches a filesystem path for attribute changes. That is, it calls	1571	This watches a filesystem path for attribute changes. That is, it calls
…		…
1549		1651
1550	The callback will be receive C<EV_STAT> when a change was detected,	1652	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	1653	relative to the attributes at the time the watcher was started (or the
1552	last change was detected).	1654	last change was detected).
1553		1655
1554	=item ev_stat_stat (ev_stat *)	1656	=item ev_stat_stat (loop, ev_stat *)
1555		1657
1556	Updates the stat buffer immediately with new values. If you change the	1658	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	1659	watched path in your callback, you could call this fucntion to avoid
1558	detecting this change (while introducing a race condition). Can also be	1660	detecting this change (while introducing a race condition). Can also be
1559	useful simply to find out the new values.	1661	useful simply to find out the new values.
…		…
1676	static void	1778	static void
1677	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1779	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1678	{	1780	{
1679	free (w);	1781	free (w);
1680	// now do something you wanted to do when the program has	1782	// now do something you wanted to do when the program has
1681	// no longer asnything immediate to do.	1783	// no longer anything immediate to do.
1682	}	1784	}
1683		1785
1684	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1786	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1685	ev_idle_init (idle_watcher, idle_cb);	1787	ev_idle_init (idle_watcher, idle_cb);
1686	ev_idle_start (loop, idle_cb);	1788	ev_idle_start (loop, idle_cb);
…		…
2027	believe me.	2129	believe me.
2028		2130
2029	=back	2131	=back
2030		2132
2031		2133
		2134	=head2 C<ev_async> - how to wake up another event loop
		2135
		2136	In general, you cannot use an C<ev_loop> from multiple threads or other
		2137	asynchronous sources such as signal handlers (as opposed to multiple event
		2138	loops - those are of course safe to use in different threads).
		2139
		2140	Sometimes, however, you need to wake up another event loop you do not
		2141	control, for example because it belongs to another thread. This is what
		2142	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2143	can signal it by calling C<ev_async_send>, which is thread- and signal
		2144	safe.
		2145
		2146	This functionality is very similar to C<ev_signal> watchers, as signals,
		2147	too, are asynchronous in nature, and signals, too, will be compressed
		2148	(i.e. the number of callback invocations may be less than the number of
		2149	C<ev_async_sent> calls).
		2150
		2151	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2152	just the default loop.
		2153
		2154	=head3 Queueing
		2155
		2156	C<ev_async> does not support queueing of data in any way. The reason
		2157	is that the author does not know of a simple (or any) algorithm for a
		2158	multiple-writer-single-reader queue that works in all cases and doesn't
		2159	need elaborate support such as pthreads.
		2160
		2161	That means that if you want to queue data, you have to provide your own
		2162	queue. But at least I can tell you would implement locking around your
		2163	queue:
		2164
		2165	=over 4
		2166
		2167	=item queueing from a signal handler context
		2168
		2169	To implement race-free queueing, you simply add to the queue in the signal
		2170	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2171	some fictitiuous SIGUSR1 handler:
		2172
		2173	static ev_async mysig;
		2174
		2175	static void
		2176	sigusr1_handler (void)
		2177	{
		2178	sometype data;
		2179
		2180	// no locking etc.
		2181	queue_put (data);
		2182	ev_async_send (EV_DEFAULT_ &mysig);
		2183	}
		2184
		2185	static void
		2186	mysig_cb (EV_P_ ev_async *w, int revents)
		2187	{
		2188	sometype data;
		2189	sigset_t block, prev;
		2190
		2191	sigemptyset (&block);
		2192	sigaddset (&block, SIGUSR1);
		2193	sigprocmask (SIG_BLOCK, &block, &prev);
		2194
		2195	while (queue_get (&data))
		2196	process (data);
		2197
		2198	if (sigismember (&prev, SIGUSR1)
		2199	sigprocmask (SIG_UNBLOCK, &block, 0);
		2200	}
		2201
		2202	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2203	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2204	either...).
		2205
		2206	=item queueing from a thread context
		2207
		2208	The strategy for threads is different, as you cannot (easily) block
		2209	threads but you can easily preempt them, so to queue safely you need to
		2210	employ a traditional mutex lock, such as in this pthread example:
		2211
		2212	static ev_async mysig;
		2213	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2214
		2215	static void
		2216	otherthread (void)
		2217	{
		2218	// only need to lock the actual queueing operation
		2219	pthread_mutex_lock (&mymutex);
		2220	queue_put (data);
		2221	pthread_mutex_unlock (&mymutex);
		2222
		2223	ev_async_send (EV_DEFAULT_ &mysig);
		2224	}
		2225
		2226	static void
		2227	mysig_cb (EV_P_ ev_async *w, int revents)
		2228	{
		2229	pthread_mutex_lock (&mymutex);
		2230
		2231	while (queue_get (&data))
		2232	process (data);
		2233
		2234	pthread_mutex_unlock (&mymutex);
		2235	}
		2236
		2237	=back
		2238
		2239
		2240	=head3 Watcher-Specific Functions and Data Members
		2241
		2242	=over 4
		2243
		2244	=item ev_async_init (ev_async *, callback)
		2245
		2246	Initialises and configures the async watcher - it has no parameters of any
		2247	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2248	believe me.
		2249
		2250	=item ev_async_send (loop, ev_async *)
		2251
		2252	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2253	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2254	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2255	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2256	section below on what exactly this means).
		2257
		2258	This call incurs the overhead of a syscall only once per loop iteration,
		2259	so while the overhead might be noticable, it doesn't apply to repeated
		2260	calls to C<ev_async_send>.
		2261
		2262	=back
		2263
		2264
2032	=head1 OTHER FUNCTIONS	2265	=head1 OTHER FUNCTIONS
2033		2266
2034	There are some other functions of possible interest. Described. Here. Now.	2267	There are some other functions of possible interest. Described. Here. Now.
2035		2268
2036	=over 4	2269	=over 4
…		…
2263	Example: Define a class with an IO and idle watcher, start one of them in	2496	Example: Define a class with an IO and idle watcher, start one of them in
2264	the constructor.	2497	the constructor.
2265		2498
2266	class myclass	2499	class myclass
2267	{	2500	{
2268	ev_io io; void io_cb (ev::io &w, int revents);	2501	ev::io io; void io_cb (ev::io &w, int revents);
2269	ev_idle idle void idle_cb (ev::idle &w, int revents);	2502	ev:idle idle void idle_cb (ev::idle &w, int revents);
2270		2503
2271	myclass ();	2504	myclass (int fd)
2272	}
2273
2274	myclass::myclass (int fd)
2275	{	2505	{
2276	io .set <myclass, &myclass::io_cb > (this);	2506	io .set <myclass, &myclass::io_cb > (this);
2277	idle.set <myclass, &myclass::idle_cb> (this);	2507	idle.set <myclass, &myclass::idle_cb> (this);
2278		2508
2279	io.start (fd, ev::READ);	2509	io.start (fd, ev::READ);
		2510	}
2280	}	2511	};
		2512
		2513
		2514	=head1 OTHER LANGUAGE BINDINGS
		2515
		2516	Libev does not offer other language bindings itself, but bindings for a
		2517	numbe rof languages exist in the form of third-party packages. If you know
		2518	any interesting language binding in addition to the ones listed here, drop
		2519	me a note.
		2520
		2521	=over 4
		2522
		2523	=item Perl
		2524
		2525	The EV module implements the full libev API and is actually used to test
		2526	libev. EV is developed together with libev. Apart from the EV core module,
		2527	there are additional modules that implement libev-compatible interfaces
		2528	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2529	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2530
		2531	It can be found and installed via CPAN, its homepage is found at
		2532	L<http://software.schmorp.de/pkg/EV>.
		2533
		2534	=item Ruby
		2535
		2536	Tony Arcieri has written a ruby extension that offers access to a subset
		2537	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2538	more on top of it. It can be found via gem servers. Its homepage is at
		2539	L<http://rev.rubyforge.org/>.
		2540
		2541	=item D
		2542
		2543	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2544	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2545
		2546	=back
2281		2547
2282		2548
2283	=head1 MACRO MAGIC	2549	=head1 MACRO MAGIC
2284		2550
2285	Libev can be compiled with a variety of options, the most fundamantal	2551	Libev can be compiled with a variety of options, the most fundamantal
…		…
2490	wants osf handles on win32 (this is the case when the select to	2756	wants osf handles on win32 (this is the case when the select to
2491	be used is the winsock select). This means that it will call	2757	be used is the winsock select). This means that it will call
2492	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2758	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2493	it is assumed that all these functions actually work on fds, even	2759	it is assumed that all these functions actually work on fds, even
2494	on win32. Should not be defined on non-win32 platforms.	2760	on win32. Should not be defined on non-win32 platforms.
		2761
		2762	=item EV_FD_TO_WIN32_HANDLE
		2763
		2764	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2765	file descriptors to socket handles. When not defining this symbol (the
		2766	default), then libev will call C<_get_osfhandle>, which is usually
		2767	correct. In some cases, programs use their own file descriptor management,
		2768	in which case they can provide this function to map fds to socket handles.
2495		2769
2496	=item EV_USE_POLL	2770	=item EV_USE_POLL
2497		2771
2498	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2772	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2499	backend. Otherwise it will be enabled on non-win32 platforms. It	2773	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2533		2807
2534	If defined to be C<1>, libev will compile in support for the Linux inotify	2808	If defined to be C<1>, libev will compile in support for the Linux inotify
2535	interface to speed up C<ev_stat> watchers. Its actual availability will	2809	interface to speed up C<ev_stat> watchers. Its actual availability will
2536	be detected at runtime.	2810	be detected at runtime.
2537		2811
		2812	=item EV_ATOMIC_T
		2813
		2814	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2815	access is atomic with respect to other threads or signal contexts. No such
		2816	type is easily found in the C language, so you can provide your own type
		2817	that you know is safe for your purposes. It is used both for signal handler "locking"
		2818	as well as for signal and thread safety in C<ev_async> watchers.
		2819
		2820	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2821	(from F<signal.h>), which is usually good enough on most platforms.
		2822
2538	=item EV_H	2823	=item EV_H
2539		2824
2540	The name of the F<ev.h> header file used to include it. The default if	2825	The name of the F<ev.h> header file used to include it. The default if
2541	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	2826	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2542	virtually rename the F<ev.h> header file in case of conflicts.	2827	used to virtually rename the F<ev.h> header file in case of conflicts.
2543		2828
2544	=item EV_CONFIG_H	2829	=item EV_CONFIG_H
2545		2830
2546	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2831	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2547	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2832	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2548	C<EV_H>, above.	2833	C<EV_H>, above.
2549		2834
2550	=item EV_EVENT_H	2835	=item EV_EVENT_H
2551		2836
2552	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2837	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2553	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	2838	of how the F<event.h> header can be found, the default is C<"event.h">.
2554		2839
2555	=item EV_PROTOTYPES	2840	=item EV_PROTOTYPES
2556		2841
2557	If defined to be C<0>, then F<ev.h> will not define any function	2842	If defined to be C<0>, then F<ev.h> will not define any function
2558	prototypes, but still define all the structs and other symbols. This is	2843	prototypes, but still define all the structs and other symbols. This is
…		…
2607	defined to be C<0>, then they are not.	2892	defined to be C<0>, then they are not.
2608		2893
2609	=item EV_FORK_ENABLE	2894	=item EV_FORK_ENABLE
2610		2895
2611	If undefined or defined to be C<1>, then fork watchers are supported. If	2896	If undefined or defined to be C<1>, then fork watchers are supported. If
		2897	defined to be C<0>, then they are not.
		2898
		2899	=item EV_ASYNC_ENABLE
		2900
		2901	If undefined or defined to be C<1>, then async watchers are supported. If
2612	defined to be C<0>, then they are not.	2902	defined to be C<0>, then they are not.
2613		2903
2614	=item EV_MINIMAL	2904	=item EV_MINIMAL
2615		2905
2616	If you need to shave off some kilobytes of code at the expense of some	2906	If you need to shave off some kilobytes of code at the expense of some
…		…
2737	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3027	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2738		3028
2739	That means that changing a timer costs less than removing/adding them	3029	That means that changing a timer costs less than removing/adding them
2740	as only the relative motion in the event queue has to be paid for.	3030	as only the relative motion in the event queue has to be paid for.
2741		3031
2742	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3032	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2743		3033
2744	These just add the watcher into an array or at the head of a list.	3034	These just add the watcher into an array or at the head of a list.
2745		3035
2746	=item Stopping check/prepare/idle watchers: O(1)	3036	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2747		3037
2748	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3038	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2749		3039
2750	These watchers are stored in lists then need to be walked to find the	3040	These watchers are stored in lists then need to be walked to find the
2751	correct watcher to remove. The lists are usually short (you don't usually	3041	correct watcher to remove. The lists are usually short (you don't usually
…		…
2767	=item Priority handling: O(number_of_priorities)	3057	=item Priority handling: O(number_of_priorities)
2768		3058
2769	Priorities are implemented by allocating some space for each	3059	Priorities are implemented by allocating some space for each
2770	priority. When doing priority-based operations, libev usually has to	3060	priority. When doing priority-based operations, libev usually has to
2771	linearly search all the priorities, but starting/stopping and activating	3061	linearly search all the priorities, but starting/stopping and activating
2772	watchers becomes O(1) w.r.t. prioritiy handling.	3062	watchers becomes O(1) w.r.t. priority handling.
		3063
		3064	=item Sending an ev_async: O(1)
		3065
		3066	=item Processing ev_async_send: O(number_of_async_watchers)
		3067
		3068	=item Processing signals: O(max_signal_number)
		3069
		3070	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3071	calls in the current loop iteration. Checking for async and signal events
		3072	involves iterating over all running async watchers or all signal numbers.
2773		3073
2774	=back	3074	=back
2775		3075
2776		3076
		3077	=head1 Win32 platform limitations and workarounds
		3078
		3079	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3080	requires, and its I/O model is fundamentally incompatible with the POSIX
		3081	model. Libev still offers limited functionality on this platform in
		3082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3083	descriptors. This only applies when using Win32 natively, not when using
		3084	e.g. cygwin.
		3085
		3086	There is no supported compilation method available on windows except
		3087	embedding it into other applications.
		3088
		3089	Due to the many, low, and arbitrary limits on the win32 platform and the
		3090	abysmal performance of winsockets, using a large number of sockets is not
		3091	recommended (and not reasonable). If your program needs to use more than
		3092	a hundred or so sockets, then likely it needs to use a totally different
		3093	implementation for windows, as libev offers the POSIX model, which cannot
		3094	be implemented efficiently on windows (microsoft monopoly games).
		3095
		3096	=over 4
		3097
		3098	=item The winsocket select function
		3099
		3100	The winsocket C<select> function doesn't follow POSIX in that it requires
		3101	socket I<handles> and not socket I<file descriptors>. This makes select
		3102	very inefficient, and also requires a mapping from file descriptors
		3103	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3104	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3105	symbols for more info.
		3106
		3107	The configuration for a "naked" win32 using the microsoft runtime
		3108	libraries and raw winsocket select is:
		3109
		3110	#define EV_USE_SELECT 1
		3111	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3112
		3113	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3114	complexity in the O(n²) range when using win32.
		3115
		3116	=item Limited number of file descriptors
		3117
		3118	Windows has numerous arbitrary (and low) limits on things. Early versions
		3119	of winsocket's select only supported waiting for a max. of C<64> handles
		3120	(probably owning to the fact that all windows kernels can only wait for
		3121	C<64> things at the same time internally; microsoft recommends spawning a
		3122	chain of threads and wait for 63 handles and the previous thread in each).
		3123
		3124	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3125	to some high number (e.g. C<2048>) before compiling the winsocket select
		3126	call (which might be in libev or elsewhere, for example, perl does its own
		3127	select emulation on windows).
		3128
		3129	Another limit is the number of file descriptors in the microsoft runtime
		3130	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3131	or something like this inside microsoft). You can increase this by calling
		3132	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3133	arbitrary limit), but is broken in many versions of the microsoft runtime
		3134	libraries.
		3135
		3136	This might get you to about C<512> or C<2048> sockets (depending on
		3137	windows version and/or the phase of the moon). To get more, you need to
		3138	wrap all I/O functions and provide your own fd management, but the cost of
		3139	calling select (O(n²)) will likely make this unworkable.
		3140
		3141	=back
		3142
		3143
2777	=head1 AUTHOR	3144	=head1 AUTHOR
2778		3145
2779	Marc Lehmann <libev@schmorp.de>.	3146	Marc Lehmann <libev@schmorp.de>.
2780		3147

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Comparing libev/ev.pod (file contents): Revision 1.111 by root, Tue Dec 25 18:01:20 2007 UTC vs. Revision 1.136 by root, Thu Mar 13 13:06:16 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.111 by root, Tue Dec 25 18:01:20 2007 UTC vs.
Revision 1.136 by root, Thu Mar 13 13:06:16 2008 UTC