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

Comparing libev/ev.pod (file contents):
Revision 1.122 by root, Thu Jan 31 13:10:56 2008 UTC vs.
Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC

…		…
505	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
506		506
507	Like C<ev_default_fork>, but acts on an event loop created by	507	Like C<ev_default_fork>, but acts on an event loop created by
508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
509	after fork, and how you do this is entirely your own problem.	509	after fork, and how you do this is entirely your own problem.
		510
		511	=item int ev_is_default_loop (loop)
		512
		513	Returns true when the given loop actually is the default loop, false otherwise.
510		514
511	=item unsigned int ev_loop_count (loop)	515	=item unsigned int ev_loop_count (loop)
512		516
513	Returns the count of loop iterations for the loop, which is identical to	517	Returns the count of loop iterations for the loop, which is identical to
514	the number of times libev did poll for new events. It starts at C<0> and	518	the number of times libev did poll for new events. It starts at C<0> and
…		…
1152	configure a timer to trigger every 10 seconds, then it will trigger at	1156	configure a timer to trigger every 10 seconds, then it will trigger at
1153	exactly 10 second intervals. If, however, your program cannot keep up with	1157	exactly 10 second intervals. If, however, your program cannot keep up with
1154	the timer (because it takes longer than those 10 seconds to do stuff) the	1158	the timer (because it takes longer than those 10 seconds to do stuff) the
1155	timer will not fire more than once per event loop iteration.	1159	timer will not fire more than once per event loop iteration.
1156		1160
1157	=item ev_timer_again (loop)	1161	=item ev_timer_again (loop, ev_timer *)
1158		1162
1159	This will act as if the timer timed out and restart it again if it is	1163	This will act as if the timer timed out and restart it again if it is
1160	repeating. The exact semantics are:	1164	repeating. The exact semantics are:
1161		1165
1162	If the timer is pending, its pending status is cleared.	1166	If the timer is pending, its pending status is cleared.
…		…
1271	In this configuration the watcher triggers an event at the wallclock time	1275	In this configuration the watcher triggers an event at the wallclock time
1272	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1276	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1273	that is, if it is to be run at January 1st 2011 then it will run when the	1277	that is, if it is to be run at January 1st 2011 then it will run when the
1274	system time reaches or surpasses this time.	1278	system time reaches or surpasses this time.
1275		1279
1276	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1280	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1277		1281
1278	In this mode the watcher will always be scheduled to time out at the next	1282	In this mode the watcher will always be scheduled to time out at the next
1279	C<at + N * interval> time (for some integer N, which can also be negative)	1283	C<at + N * interval> time (for some integer N, which can also be negative)
1280	and then repeat, regardless of any time jumps.	1284	and then repeat, regardless of any time jumps.
1281		1285
…		…
1432		1436
1433	The signal the watcher watches out for.	1437	The signal the watcher watches out for.
1434		1438
1435	=back	1439	=back
1436		1440
		1441	=head3 Examples
		1442
		1443	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1444
		1445	static void
		1446	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1447	{
		1448	ev_unloop (loop, EVUNLOOP_ALL);
		1449	}
		1450
		1451	struct ev_signal signal_watcher;
		1452	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1453	ev_signal_start (loop, &sigint_cb);
		1454
1437		1455
1438	=head2 C<ev_child> - watch out for process status changes	1456	=head2 C<ev_child> - watch out for process status changes
1439		1457
1440	Child watchers trigger when your process receives a SIGCHLD in response to	1458	Child watchers trigger when your process receives a SIGCHLD in response to
1441	some child status changes (most typically when a child of yours dies).	1459	some child status changes (most typically when a child of yours dies). It
		1460	is permissible to install a child watcher I<after> the child has been
		1461	forked (which implies it might have already exited), as long as the event
		1462	loop isn't entered (or is continued from a watcher).
		1463
		1464	Only the default event loop is capable of handling signals, and therefore
		1465	you can only rgeister child watchers in the default event loop.
		1466
		1467	=head3 Process Interaction
		1468
		1469	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1470	initialised. This is necessary to guarantee proper behaviour even if
		1471	the first child watcher is started after the child exits. The occurance
		1472	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1473	synchronously as part of the event loop processing. Libev always reaps all
		1474	children, even ones not watched.
		1475
		1476	=head3 Overriding the Built-In Processing
		1477
		1478	Libev offers no special support for overriding the built-in child
		1479	processing, but if your application collides with libev's default child
		1480	handler, you can override it easily by installing your own handler for
		1481	C<SIGCHLD> after initialising the default loop, and making sure the
		1482	default loop never gets destroyed. You are encouraged, however, to use an
		1483	event-based approach to child reaping and thus use libev's support for
		1484	that, so other libev users can use C<ev_child> watchers freely.
1442		1485
1443	=head3 Watcher-Specific Functions and Data Members	1486	=head3 Watcher-Specific Functions and Data Members
1444		1487
1445	=over 4	1488	=over 4
1446		1489
…		…
1472		1515
1473	=back	1516	=back
1474		1517
1475	=head3 Examples	1518	=head3 Examples
1476		1519
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	1520	Example: C<fork()> a new process and install a child handler to wait for
		1521	its completion.
		1522
		1523	ev_child cw;
1478		1524
1479	static void	1525	static void
1480	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1526	child_cb (EV_P_ struct ev_child *w, int revents)
1481	{	1527	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	1528	ev_child_stop (EV_A_ w);
		1529	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1483	}	1530	}
1484		1531
1485	struct ev_signal signal_watcher;	1532	pid_t pid = fork ();
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1533
1487	ev_signal_start (loop, &sigint_cb);	1534	if (pid < 0)
		1535	// error
		1536	else if (pid == 0)
		1537	{
		1538	// the forked child executes here
		1539	exit (1);
		1540	}
		1541	else
		1542	{
		1543	ev_child_init (&cw, child_cb, pid, 0);
		1544	ev_child_start (EV_DEFAULT_ &cw);
		1545	}
1488		1546
1489		1547
1490	=head2 C<ev_stat> - did the file attributes just change?	1548	=head2 C<ev_stat> - did the file attributes just change?
1491		1549
1492	This watches a filesystem path for attribute changes. That is, it calls	1550	This watches a filesystem path for attribute changes. That is, it calls
…		…
1572		1630
1573	The callback will be receive C<EV_STAT> when a change was detected,	1631	The callback will be receive C<EV_STAT> when a change was detected,
1574	relative to the attributes at the time the watcher was started (or the	1632	relative to the attributes at the time the watcher was started (or the
1575	last change was detected).	1633	last change was detected).
1576		1634
1577	=item ev_stat_stat (ev_stat *)	1635	=item ev_stat_stat (loop, ev_stat *)
1578		1636
1579	Updates the stat buffer immediately with new values. If you change the	1637	Updates the stat buffer immediately with new values. If you change the
1580	watched path in your callback, you could call this fucntion to avoid	1638	watched path in your callback, you could call this fucntion to avoid
1581	detecting this change (while introducing a race condition). Can also be	1639	detecting this change (while introducing a race condition). Can also be
1582	useful simply to find out the new values.	1640	useful simply to find out the new values.
…		…
2070	C<ev_async_sent> calls).	2128	C<ev_async_sent> calls).
2071		2129
2072	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	2130	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2073	just the default loop.	2131	just the default loop.
2074		2132
		2133	=head3 Queueing
		2134
		2135	C<ev_async> does not support queueing of data in any way. The reason
		2136	is that the author does not know of a simple (or any) algorithm for a
		2137	multiple-writer-single-reader queue that works in all cases and doesn't
		2138	need elaborate support such as pthreads.
		2139
		2140	That means that if you want to queue data, you have to provide your own
		2141	queue. But at least I can tell you would implement locking around your
		2142	queue:
		2143
		2144	=over 4
		2145
		2146	=item queueing from a signal handler context
		2147
		2148	To implement race-free queueing, you simply add to the queue in the signal
		2149	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2150	some fictitiuous SIGUSR1 handler:
		2151
		2152	static ev_async mysig;
		2153
		2154	static void
		2155	sigusr1_handler (void)
		2156	{
		2157	sometype data;
		2158
		2159	// no locking etc.
		2160	queue_put (data);
		2161	ev_async_send (EV_DEFAULT_ &mysig);
		2162	}
		2163
		2164	static void
		2165	mysig_cb (EV_P_ ev_async *w, int revents)
		2166	{
		2167	sometype data;
		2168	sigset_t block, prev;
		2169
		2170	sigemptyset (&block);
		2171	sigaddset (&block, SIGUSR1);
		2172	sigprocmask (SIG_BLOCK, &block, &prev);
		2173
		2174	while (queue_get (&data))
		2175	process (data);
		2176
		2177	if (sigismember (&prev, SIGUSR1)
		2178	sigprocmask (SIG_UNBLOCK, &block, 0);
		2179	}
		2180
		2181	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2182	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2183	either...).
		2184
		2185	=item queueing from a thread context
		2186
		2187	The strategy for threads is different, as you cannot (easily) block
		2188	threads but you can easily preempt them, so to queue safely you need to
		2189	employ a traditional mutex lock, such as in this pthread example:
		2190
		2191	static ev_async mysig;
		2192	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2193
		2194	static void
		2195	otherthread (void)
		2196	{
		2197	// only need to lock the actual queueing operation
		2198	pthread_mutex_lock (&mymutex);
		2199	queue_put (data);
		2200	pthread_mutex_unlock (&mymutex);
		2201
		2202	ev_async_send (EV_DEFAULT_ &mysig);
		2203	}
		2204
		2205	static void
		2206	mysig_cb (EV_P_ ev_async *w, int revents)
		2207	{
		2208	pthread_mutex_lock (&mymutex);
		2209
		2210	while (queue_get (&data))
		2211	process (data);
		2212
		2213	pthread_mutex_unlock (&mymutex);
		2214	}
		2215
		2216	=back
		2217
		2218
2075	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
2076		2220
2077	=over 4	2221	=over 4
2078		2222
2079	=item ev_async_init (ev_async *, callback)	2223	=item ev_async_init (ev_async *, callback)
…		…
2607		2751
2608	If defined to be C<1>, libev will compile in support for the Linux inotify	2752	If defined to be C<1>, libev will compile in support for the Linux inotify
2609	interface to speed up C<ev_stat> watchers. Its actual availability will	2753	interface to speed up C<ev_stat> watchers. Its actual availability will
2610	be detected at runtime.	2754	be detected at runtime.
2611		2755
		2756	=item EV_ATOMIC_T
		2757
		2758	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2759	access is atomic with respect to other threads or signal contexts. No such
		2760	type is easily found in the C language, so you can provide your own type
		2761	that you know is safe for your purposes. It is used both for signal handler "locking"
		2762	as well as for signal and thread safety in C<ev_async> watchers.
		2763
		2764	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2765	(from F<signal.h>), which is usually good enough on most platforms.
		2766
2612	=item EV_H	2767	=item EV_H
2613		2768
2614	The name of the F<ev.h> header file used to include it. The default if	2769	The name of the F<ev.h> header file used to include it. The default if
2615	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	2770	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2616	used to virtually rename the F<ev.h> header file in case of conflicts.	2771	used to virtually rename the F<ev.h> header file in case of conflicts.
…		…
2681	defined to be C<0>, then they are not.	2836	defined to be C<0>, then they are not.
2682		2837
2683	=item EV_FORK_ENABLE	2838	=item EV_FORK_ENABLE
2684		2839
2685	If undefined or defined to be C<1>, then fork watchers are supported. If	2840	If undefined or defined to be C<1>, then fork watchers are supported. If
		2841	defined to be C<0>, then they are not.
		2842
		2843	=item EV_ASYNC_ENABLE
		2844
		2845	If undefined or defined to be C<1>, then async watchers are supported. If
2686	defined to be C<0>, then they are not.	2846	defined to be C<0>, then they are not.
2687		2847
2688	=item EV_MINIMAL	2848	=item EV_MINIMAL
2689		2849
2690	If you need to shave off some kilobytes of code at the expense of some	2850	If you need to shave off some kilobytes of code at the expense of some
…		…
2811	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	2971	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2812		2972
2813	That means that changing a timer costs less than removing/adding them	2973	That means that changing a timer costs less than removing/adding them
2814	as only the relative motion in the event queue has to be paid for.	2974	as only the relative motion in the event queue has to be paid for.
2815		2975
2816	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2976	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2817		2977
2818	These just add the watcher into an array or at the head of a list.	2978	These just add the watcher into an array or at the head of a list.
2819		2979
2820	=item Stopping check/prepare/idle watchers: O(1)	2980	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2821		2981
2822	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2982	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2823		2983
2824	These watchers are stored in lists then need to be walked to find the	2984	These watchers are stored in lists then need to be walked to find the
2825	correct watcher to remove. The lists are usually short (you don't usually	2985	correct watcher to remove. The lists are usually short (you don't usually
…		…
2841	=item Priority handling: O(number_of_priorities)	3001	=item Priority handling: O(number_of_priorities)
2842		3002
2843	Priorities are implemented by allocating some space for each	3003	Priorities are implemented by allocating some space for each
2844	priority. When doing priority-based operations, libev usually has to	3004	priority. When doing priority-based operations, libev usually has to
2845	linearly search all the priorities, but starting/stopping and activating	3005	linearly search all the priorities, but starting/stopping and activating
2846	watchers becomes O(1) w.r.t. prioritiy handling.	3006	watchers becomes O(1) w.r.t. priority handling.
		3007
		3008	=item Sending an ev_async: O(1)
		3009
		3010	=item Processing ev_async_send: O(number_of_async_watchers)
		3011
		3012	=item Processing signals: O(max_signal_number)
		3013
		3014	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3015	calls in the current loop iteration. Checking for async and signal events
		3016	involves iterating over all running async watchers or all signal numbers.
2847		3017
2848	=back	3018	=back
2849		3019
2850		3020
2851	=head1 Win32 platform limitations and workarounds	3021	=head1 Win32 platform limitations and workarounds

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Comparing libev/ev.pod (file contents): Revision 1.122 by root, Thu Jan 31 13:10:56 2008 UTC vs. Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.122 by root, Thu Jan 31 13:10:56 2008 UTC vs.
Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC