[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 1.142 by root, Sun Apr 6 09:53:18 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	Note that this function is I<not> thread-safe, so if you want to use it
		281	from multiple threads, you have to lock (note also that this is unlikely,
		282	as loops cannot bes hared easily between threads anyway).
		283
		284	The default loop is the only loop that can handle C<ev_signal> and
		285	C<ev_child> watchers, and to do this, it always registers a handler
		286	for C<SIGCHLD>. If this is a problem for your app you can either
		287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		289	C<ev_default_init>.
		290
265	The flags argument can be used to specify special behaviour or specific	291	The flags argument can be used to specify special behaviour or specific
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	292	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		293
268	The following flags are supported:	294	The following flags are supported:
269		295
…		…
290	enabling this flag.	316	enabling this flag.
291		317
292	This works by calling C<getpid ()> on every iteration of the loop,	318	This works by calling C<getpid ()> on every iteration of the loop,
293	and thus this might slow down your event loop if you do a lot of loop	319	and thus this might slow down your event loop if you do a lot of loop
294	iterations and little real work, but is usually not noticeable (on my	320	iterations and little real work, but is usually not noticeable (on my
295	Linux system for example, C<getpid> is actually a simple 5-insn sequence	321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
296	without a syscall and thus I<very> fast, but my Linux system also has	322	without a syscall and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	323	C<pthread_atfork> which is even faster).
298		324
299	The big advantage of this flag is that you can forget about fork (and	325	The big advantage of this flag is that you can forget about fork (and
300	forget about forgetting to tell libev about forking) when you use this	326	forget about forgetting to tell libev about forking) when you use this
301	flag.	327	flag.
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332	For few fds, this backend is a bit little slower than poll and select,	358	For few fds, this backend is a bit little slower than poll and select,
333	but it scales phenomenally better. While poll and select usually scale	359	but it scales phenomenally better. While poll and select usually scale
334	like O(total_fds) where n is the total number of fds (or the highest fd),	360	like O(total_fds) where n is the total number of fds (or the highest fd),
335	epoll scales either O(1) or O(active_fds). The epoll design has a number	361	epoll scales either O(1) or O(active_fds). The epoll design has a number
336	of shortcomings, such as silently dropping events in some hard-to-detect	362	of shortcomings, such as silently dropping events in some hard-to-detect
337	cases and rewiring a syscall per fd change, no fork support and bad	363	cases and requiring a syscall per fd change, no fork support and bad
338	support for dup.	364	support for dup.
339		365
340	While stopping, setting and starting an I/O watcher in the same iteration	366	While stopping, setting and starting an I/O watcher in the same iteration
341	will result in some caching, there is still a syscall per such incident	367	will result in some caching, there is still a syscall per such incident
342	(because the fd could point to a different file description now), so its	368	(because the fd could point to a different file description now), so its
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403	While this backend scales well, it requires one system call per active	429	While this backend scales well, it requires one system call per active
404	file descriptor per loop iteration. For small and medium numbers of file	430	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	432	might perform better.
407		433
		434	On the positive side, ignoring the spurious readyness notifications, this
		435	backend actually performed to specification in all tests and is fully
		436	embeddable, which is a rare feat among the OS-specific backends.
		437
408	=item C<EVBACKEND_ALL>	438	=item C<EVBACKEND_ALL>
409		439
410	Try all backends (even potentially broken ones that wouldn't be tried	440	Try all backends (even potentially broken ones that wouldn't be tried
411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
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414	It is definitely not recommended to use this flag.	444	It is definitely not recommended to use this flag.
415		445
416	=back	446	=back
417		447
418	If one or more of these are ored into the flags value, then only these	448	If one or more of these are ored into the flags value, then only these
419	backends will be tried (in the reverse order as given here). If none are	449	backends will be tried (in the reverse order as listed here). If none are
420	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		451
423	The most typical usage is like this:	452	The most typical usage is like this:
424		453
425	if (!ev_default_loop (0))	454	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
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440		469
441	Similar to C<ev_default_loop>, but always creates a new event loop that is	470	Similar to C<ev_default_loop>, but always creates a new event loop that is
442	always distinct from the default loop. Unlike the default loop, it cannot	471	always distinct from the default loop. Unlike the default loop, it cannot
443	handle signal and child watchers, and attempts to do so will be greeted by	472	handle signal and child watchers, and attempts to do so will be greeted by
444	undefined behaviour (or a failed assertion if assertions are enabled).	473	undefined behaviour (or a failed assertion if assertions are enabled).
		474
		475	Note that this function I<is> thread-safe, and the recommended way to use
		476	libev with threads is indeed to create one loop per thread, and using the
		477	default loop in the "main" or "initial" thread.
445		478
446	Example: Try to create a event loop that uses epoll and nothing else.	479	Example: Try to create a event loop that uses epoll and nothing else.
447		480
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
449	if (!epoller)	482	if (!epoller)
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	506	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
475		508
476	=item ev_default_fork ()	509	=item ev_default_fork ()
477		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	512	to reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	513	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	514	the child process (or both child and parent, but that again makes little
481	again makes little sense).	515	sense). You I<must> call it in the child before using any of the libev
		516	functions, and it will only take effect at the next C<ev_loop> iteration.
482		517
483	You I<must> call this function in the child process after forking if and	518	On the other hand, you only need to call this function in the child
484	only if you want to use the event library in both processes. If you just	519	process if and only if you want to use the event library in the child. If
485	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
486		521
487	The function itself is quite fast and it's usually not a problem to call	522	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	523	it just in case after a fork. To make this easy, the function will fit in
489	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
490		525
491	pthread_atfork (0, 0, ev_default_fork);	526	pthread_atfork (0, 0, ev_default_fork);
492		527
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496
497	=item ev_loop_fork (loop)	528	=item ev_loop_fork (loop)
498		529
499	Like C<ev_default_fork>, but acts on an event loop created by	530	Like C<ev_default_fork>, but acts on an event loop created by
500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
501	after fork, and how you do this is entirely your own problem.	532	after fork, and how you do this is entirely your own problem.
		533
		534	=item int ev_is_default_loop (loop)
		535
		536	Returns true when the given loop actually is the default loop, false otherwise.
502		537
503	=item unsigned int ev_loop_count (loop)	538	=item unsigned int ev_loop_count (loop)
504		539
505	Returns the count of loop iterations for the loop, which is identical to	540	Returns the count of loop iterations for the loop, which is identical to
506	the number of times libev did poll for new events. It starts at C<0> and	541	the number of times libev did poll for new events. It starts at C<0> and
…		…
551	usually a better approach for this kind of thing.	586	usually a better approach for this kind of thing.
552		587
553	Here are the gory details of what C<ev_loop> does:	588	Here are the gory details of what C<ev_loop> does:
554		589
555	- Before the first iteration, call any pending watchers.	590	- Before the first iteration, call any pending watchers.
556	* If there are no active watchers (reference count is zero), return.	591	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- Queue all prepare watchers and then call all outstanding watchers.	592	- If a fork was detected, queue and call all fork watchers.
		593	- Queue and call all prepare watchers.
558	- If we have been forked, recreate the kernel state.	594	- If we have been forked, recreate the kernel state.
559	- Update the kernel state with all outstanding changes.	595	- Update the kernel state with all outstanding changes.
560	- Update the "event loop time".	596	- Update the "event loop time".
561	- Calculate for how long to block.	597	- Calculate for how long to sleep or block, if at all
		598	(active idle watchers, EVLOOP_NONBLOCK or not having
		599	any active watchers at all will result in not sleeping).
		600	- Sleep if the I/O and timer collect interval say so.
562	- Block the process, waiting for any events.	601	- Block the process, waiting for any events.
563	- Queue all outstanding I/O (fd) events.	602	- Queue all outstanding I/O (fd) events.
564	- Update the "event loop time" and do time jump handling.	603	- Update the "event loop time" and do time jump handling.
565	- Queue all outstanding timers.	604	- Queue all outstanding timers.
566	- Queue all outstanding periodics.	605	- Queue all outstanding periodics.
567	- If no events are pending now, queue all idle watchers.	606	- If no events are pending now, queue all idle watchers.
568	- Queue all check watchers.	607	- Queue all check watchers.
569	- Call all queued watchers in reverse order (i.e. check watchers first).	608	- 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	609	Signals and child watchers are implemented as I/O watchers, and will
571	be handled here by queueing them when their watcher gets executed.	610	be handled here by queueing them when their watcher gets executed.
572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573	were used, return, otherwise continue with step *.	612	were used, or there are no active watchers, return, otherwise
		613	continue with step *.
574		614
575	Example: Queue some jobs and then loop until no events are outsanding	615	Example: Queue some jobs and then loop until no events are outstanding
576	anymore.	616	anymore.
577		617
578	... queue jobs here, make sure they register event watchers as long	618	... 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..)	619	... as they still have work to do (even an idle watcher will do..)
580	ev_loop (my_loop, 0);	620	ev_loop (my_loop, 0);
…		…
584		624
585	Can be used to make a call to C<ev_loop> return early (but only after it	625	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	626	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	627	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.	628	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		629
		630	This "unloop state" will be cleared when entering C<ev_loop> again.
589		631
590	=item ev_ref (loop)	632	=item ev_ref (loop)
591		633
592	=item ev_unref (loop)	634	=item ev_unref (loop)
593		635
…		…
598	returning, ev_unref() after starting, and ev_ref() before stopping it. For	640	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	641	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	642	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	643	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	644	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>.	645	libraries. Just remember to I<unref after start> and I<ref before stop>
		646	(but only if the watcher wasn't active before, or was active before,
		647	respectively).
604		648
605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606	running when nothing else is active.	650	running when nothing else is active.
607		651
608	struct ev_signal exitsig;	652	struct ev_signal exitsig;
…		…
756		800
757	=item C<EV_FORK>	801	=item C<EV_FORK>
758		802
759	The event loop has been resumed in the child process after fork (see	803	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	804	C<ev_fork>).
		805
		806	=item C<EV_ASYNC>
		807
		808	The given async watcher has been asynchronously notified (see C<ev_async>).
761		809
762	=item C<EV_ERROR>	810	=item C<EV_ERROR>
763		811
764	An unspecified error has occured, the watcher has been stopped. This might	812	An unspecified error has occured, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	813	happen because the watcher could not be properly started because libev
…		…
1045	To support fork in your programs, you either have to call	1093	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,	1094	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	1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1048	C<EVBACKEND_POLL>.	1096	C<EVBACKEND_POLL>.
1049		1097
		1098	=head3 The special problem of SIGPIPE
		1099
		1100	While not really specific to libev, it is easy to forget about SIGPIPE:
		1101	when reading from a pipe whose other end has been closed, your program
		1102	gets send a SIGPIPE, which, by default, aborts your program. For most
		1103	programs this is sensible behaviour, for daemons, this is usually
		1104	undesirable.
		1105
		1106	So when you encounter spurious, unexplained daemon exits, make sure you
		1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1108	somewhere, as that would have given you a big clue).
		1109
1050		1110
1051	=head3 Watcher-Specific Functions	1111	=head3 Watcher-Specific Functions
1052		1112
1053	=over 4	1113	=over 4
1054		1114
…		…
1131	configure a timer to trigger every 10 seconds, then it will trigger at	1191	configure a timer to trigger every 10 seconds, then it will trigger at
1132	exactly 10 second intervals. If, however, your program cannot keep up with	1192	exactly 10 second intervals. If, however, your program cannot keep up with
1133	the timer (because it takes longer than those 10 seconds to do stuff) the	1193	the timer (because it takes longer than those 10 seconds to do stuff) the
1134	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
1135		1195
1136	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
1137		1197
1138	This will act as if the timer timed out and restart it again if it is	1198	This will act as if the timer timed out and restart it again if it is
1139	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
1140		1200
1141	If the timer is pending, its pending status is cleared.	1201	If the timer is pending, its pending status is cleared.
…		…
1250	In this configuration the watcher triggers an event at the wallclock time	1310	In this configuration the watcher triggers an event at the wallclock time
1251	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1252	that is, if it is to be run at January 1st 2011 then it will run when the	1312	that is, if it is to be run at January 1st 2011 then it will run when the
1253	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
1254		1314
1255	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1256		1316
1257	In this mode the watcher will always be scheduled to time out at the next	1317	In this mode the watcher will always be scheduled to time out at the next
1258	C<at + N * interval> time (for some integer N, which can also be negative)	1318	C<at + N * interval> time (for some integer N, which can also be negative)
1259	and then repeat, regardless of any time jumps.	1319	and then repeat, regardless of any time jumps.
1260		1320
…		…
1394	with the kernel (thus it coexists with your own signal handlers as long	1454	with the kernel (thus it coexists with your own signal handlers as long
1395	as you don't register any with libev). Similarly, when the last signal	1455	as you don't register any with libev). Similarly, when the last signal
1396	watcher for a signal is stopped libev will reset the signal handler to	1456	watcher for a signal is stopped libev will reset the signal handler to
1397	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
1398		1458
		1459	If possible and supported, libev will install its handlers with
		1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1461	interrupted. If you have a problem with syscalls getting interrupted by
		1462	signals you can block all signals in an C<ev_check> watcher and unblock
		1463	them in an C<ev_prepare> watcher.
		1464
1399	=head3 Watcher-Specific Functions and Data Members	1465	=head3 Watcher-Specific Functions and Data Members
1400		1466
1401	=over 4	1467	=over 4
1402		1468
1403	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1411		1477
1412	The signal the watcher watches out for.	1478	The signal the watcher watches out for.
1413		1479
1414	=back	1480	=back
1415		1481
		1482	=head3 Examples
		1483
		1484	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1485
		1486	static void
		1487	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1488	{
		1489	ev_unloop (loop, EVUNLOOP_ALL);
		1490	}
		1491
		1492	struct ev_signal signal_watcher;
		1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1494	ev_signal_start (loop, &sigint_cb);
		1495
1416		1496
1417	=head2 C<ev_child> - watch out for process status changes	1497	=head2 C<ev_child> - watch out for process status changes
1418		1498
1419	Child watchers trigger when your process receives a SIGCHLD in response to	1499	Child watchers trigger when your process receives a SIGCHLD in response to
1420	some child status changes (most typically when a child of yours dies).	1500	some child status changes (most typically when a child of yours dies). It
		1501	is permissible to install a child watcher I<after> the child has been
		1502	forked (which implies it might have already exited), as long as the event
		1503	loop isn't entered (or is continued from a watcher).
		1504
		1505	Only the default event loop is capable of handling signals, and therefore
		1506	you can only rgeister child watchers in the default event loop.
		1507
		1508	=head3 Process Interaction
		1509
		1510	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1511	initialised. This is necessary to guarantee proper behaviour even if
		1512	the first child watcher is started after the child exits. The occurance
		1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1514	synchronously as part of the event loop processing. Libev always reaps all
		1515	children, even ones not watched.
		1516
		1517	=head3 Overriding the Built-In Processing
		1518
		1519	Libev offers no special support for overriding the built-in child
		1520	processing, but if your application collides with libev's default child
		1521	handler, you can override it easily by installing your own handler for
		1522	C<SIGCHLD> after initialising the default loop, and making sure the
		1523	default loop never gets destroyed. You are encouraged, however, to use an
		1524	event-based approach to child reaping and thus use libev's support for
		1525	that, so other libev users can use C<ev_child> watchers freely.
1421		1526
1422	=head3 Watcher-Specific Functions and Data Members	1527	=head3 Watcher-Specific Functions and Data Members
1423		1528
1424	=over 4	1529	=over 4
1425		1530
1426	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
1427		1532
1428	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
1429		1534
1430	Configures the watcher to wait for status changes of process C<pid> (or	1535	Configures the watcher to wait for status changes of process C<pid> (or
1431	I<any> process if C<pid> is specified as C<0>). The callback can look	1536	I<any> process if C<pid> is specified as C<0>). The callback can look
1432	at the C<rstatus> member of the C<ev_child> watcher structure to see	1537	at the C<rstatus> member of the C<ev_child> watcher structure to see
1433	the status word (use the macros from C<sys/wait.h> and see your systems	1538	the status word (use the macros from C<sys/wait.h> and see your systems
1434	C<waitpid> documentation). The C<rpid> member contains the pid of the	1539	C<waitpid> documentation). The C<rpid> member contains the pid of the
1435	process causing the status change.	1540	process causing the status change. C<trace> must be either C<0> (only
		1541	activate the watcher when the process terminates) or C<1> (additionally
		1542	activate the watcher when the process is stopped or continued).
1436		1543
1437	=item int pid [read-only]	1544	=item int pid [read-only]
1438		1545
1439	The process id this watcher watches out for, or C<0>, meaning any process id.	1546	The process id this watcher watches out for, or C<0>, meaning any process id.
1440		1547
…		…
1449		1556
1450	=back	1557	=back
1451		1558
1452	=head3 Examples	1559	=head3 Examples
1453		1560
1454	Example: Try to exit cleanly on SIGINT and SIGTERM.	1561	Example: C<fork()> a new process and install a child handler to wait for
		1562	its completion.
		1563
		1564	ev_child cw;
1455		1565
1456	static void	1566	static void
1457	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1567	child_cb (EV_P_ struct ev_child *w, int revents)
1458	{	1568	{
1459	ev_unloop (loop, EVUNLOOP_ALL);	1569	ev_child_stop (EV_A_ w);
		1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1460	}	1571	}
1461		1572
1462	struct ev_signal signal_watcher;	1573	pid_t pid = fork ();
1463	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1574
1464	ev_signal_start (loop, &sigint_cb);	1575	if (pid < 0)
		1576	// error
		1577	else if (pid == 0)
		1578	{
		1579	// the forked child executes here
		1580	exit (1);
		1581	}
		1582	else
		1583	{
		1584	ev_child_init (&cw, child_cb, pid, 0);
		1585	ev_child_start (EV_DEFAULT_ &cw);
		1586	}
1465		1587
1466		1588
1467	=head2 C<ev_stat> - did the file attributes just change?	1589	=head2 C<ev_stat> - did the file attributes just change?
1468		1590
1469	This watches a filesystem path for attribute changes. That is, it calls	1591	This watches a filesystem path for attribute changes. That is, it calls
…		…
1498	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1499	to fall back to regular polling again even with inotify, but changes are	1621	to fall back to regular polling again even with inotify, but changes are
1500	usually detected immediately, and if the file exists there will be no	1622	usually detected immediately, and if the file exists there will be no
1501	polling.	1623	polling.
1502		1624
		1625	=head3 ABI Issues (Largefile Support)
		1626
		1627	Libev by default (unless the user overrides this) uses the default
		1628	compilation environment, which means that on systems with optionally
		1629	disabled large file support, you get the 32 bit version of the stat
		1630	structure. When using the library from programs that change the ABI to
		1631	use 64 bit file offsets the programs will fail. In that case you have to
		1632	compile libev with the same flags to get binary compatibility. This is
		1633	obviously the case with any flags that change the ABI, but the problem is
		1634	most noticably with ev_stat and largefile support.
		1635
1503	=head3 Inotify	1636	=head3 Inotify
1504		1637
1505	When C<inotify (7)> support has been compiled into libev (generally only	1638	When C<inotify (7)> support has been compiled into libev (generally only
1506	available on Linux) and present at runtime, it will be used to speed up	1639	available on Linux) and present at runtime, it will be used to speed up
1507	change detection where possible. The inotify descriptor will be created lazily	1640	change detection where possible. The inotify descriptor will be created lazily
…		…
1549		1682
1550	The callback will be receive C<EV_STAT> when a change was detected,	1683	The callback will be receive C<EV_STAT> when a change was detected,
1551	relative to the attributes at the time the watcher was started (or the	1684	relative to the attributes at the time the watcher was started (or the
1552	last change was detected).	1685	last change was detected).
1553		1686
1554	=item ev_stat_stat (ev_stat *)	1687	=item ev_stat_stat (loop, ev_stat *)
1555		1688
1556	Updates the stat buffer immediately with new values. If you change the	1689	Updates the stat buffer immediately with new values. If you change the
1557	watched path in your callback, you could call this fucntion to avoid	1690	watched path in your callback, you could call this fucntion to avoid
1558	detecting this change (while introducing a race condition). Can also be	1691	detecting this change (while introducing a race condition). Can also be
1559	useful simply to find out the new values.	1692	useful simply to find out the new values.
…		…
1676	static void	1809	static void
1677	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1810	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1678	{	1811	{
1679	free (w);	1812	free (w);
1680	// now do something you wanted to do when the program has	1813	// now do something you wanted to do when the program has
1681	// no longer asnything immediate to do.	1814	// no longer anything immediate to do.
1682	}	1815	}
1683		1816
1684	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1685	ev_idle_init (idle_watcher, idle_cb);	1818	ev_idle_init (idle_watcher, idle_cb);
1686	ev_idle_start (loop, idle_cb);	1819	ev_idle_start (loop, idle_cb);
…		…
2027	believe me.	2160	believe me.
2028		2161
2029	=back	2162	=back
2030		2163
2031		2164
		2165	=head2 C<ev_async> - how to wake up another event loop
		2166
		2167	In general, you cannot use an C<ev_loop> from multiple threads or other
		2168	asynchronous sources such as signal handlers (as opposed to multiple event
		2169	loops - those are of course safe to use in different threads).
		2170
		2171	Sometimes, however, you need to wake up another event loop you do not
		2172	control, for example because it belongs to another thread. This is what
		2173	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2174	can signal it by calling C<ev_async_send>, which is thread- and signal
		2175	safe.
		2176
		2177	This functionality is very similar to C<ev_signal> watchers, as signals,
		2178	too, are asynchronous in nature, and signals, too, will be compressed
		2179	(i.e. the number of callback invocations may be less than the number of
		2180	C<ev_async_sent> calls).
		2181
		2182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2183	just the default loop.
		2184
		2185	=head3 Queueing
		2186
		2187	C<ev_async> does not support queueing of data in any way. The reason
		2188	is that the author does not know of a simple (or any) algorithm for a
		2189	multiple-writer-single-reader queue that works in all cases and doesn't
		2190	need elaborate support such as pthreads.
		2191
		2192	That means that if you want to queue data, you have to provide your own
		2193	queue. But at least I can tell you would implement locking around your
		2194	queue:
		2195
		2196	=over 4
		2197
		2198	=item queueing from a signal handler context
		2199
		2200	To implement race-free queueing, you simply add to the queue in the signal
		2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2202	some fictitiuous SIGUSR1 handler:
		2203
		2204	static ev_async mysig;
		2205
		2206	static void
		2207	sigusr1_handler (void)
		2208	{
		2209	sometype data;
		2210
		2211	// no locking etc.
		2212	queue_put (data);
		2213	ev_async_send (EV_DEFAULT_ &mysig);
		2214	}
		2215
		2216	static void
		2217	mysig_cb (EV_P_ ev_async *w, int revents)
		2218	{
		2219	sometype data;
		2220	sigset_t block, prev;
		2221
		2222	sigemptyset (&block);
		2223	sigaddset (&block, SIGUSR1);
		2224	sigprocmask (SIG_BLOCK, &block, &prev);
		2225
		2226	while (queue_get (&data))
		2227	process (data);
		2228
		2229	if (sigismember (&prev, SIGUSR1)
		2230	sigprocmask (SIG_UNBLOCK, &block, 0);
		2231	}
		2232
		2233	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2234	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2235	either...).
		2236
		2237	=item queueing from a thread context
		2238
		2239	The strategy for threads is different, as you cannot (easily) block
		2240	threads but you can easily preempt them, so to queue safely you need to
		2241	employ a traditional mutex lock, such as in this pthread example:
		2242
		2243	static ev_async mysig;
		2244	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2245
		2246	static void
		2247	otherthread (void)
		2248	{
		2249	// only need to lock the actual queueing operation
		2250	pthread_mutex_lock (&mymutex);
		2251	queue_put (data);
		2252	pthread_mutex_unlock (&mymutex);
		2253
		2254	ev_async_send (EV_DEFAULT_ &mysig);
		2255	}
		2256
		2257	static void
		2258	mysig_cb (EV_P_ ev_async *w, int revents)
		2259	{
		2260	pthread_mutex_lock (&mymutex);
		2261
		2262	while (queue_get (&data))
		2263	process (data);
		2264
		2265	pthread_mutex_unlock (&mymutex);
		2266	}
		2267
		2268	=back
		2269
		2270
		2271	=head3 Watcher-Specific Functions and Data Members
		2272
		2273	=over 4
		2274
		2275	=item ev_async_init (ev_async *, callback)
		2276
		2277	Initialises and configures the async watcher - it has no parameters of any
		2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2279	believe me.
		2280
		2281	=item ev_async_send (loop, ev_async *)
		2282
		2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2285	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2287	section below on what exactly this means).
		2288
		2289	This call incurs the overhead of a syscall only once per loop iteration,
		2290	so while the overhead might be noticable, it doesn't apply to repeated
		2291	calls to C<ev_async_send>.
		2292
		2293	=item bool = ev_async_pending (ev_async *)
		2294
		2295	Returns a non-zero value when C<ev_async_send> has been called on the
		2296	watcher but the event has not yet been processed (or even noted) by the
		2297	event loop.
		2298
		2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2300	the loop iterates next and checks for the watcher to have become active,
		2301	it will reset the flag again. C<ev_async_pending> can be used to very
		2302	quickly check wether invoking the loop might be a good idea.
		2303
		2304	Not that this does I<not> check wether the watcher itself is pending, only
		2305	wether it has been requested to make this watcher pending.
		2306
		2307	=back
		2308
		2309
2032	=head1 OTHER FUNCTIONS	2310	=head1 OTHER FUNCTIONS
2033		2311
2034	There are some other functions of possible interest. Described. Here. Now.	2312	There are some other functions of possible interest. Described. Here. Now.
2035		2313
2036	=over 4	2314	=over 4
…		…
2263	Example: Define a class with an IO and idle watcher, start one of them in	2541	Example: Define a class with an IO and idle watcher, start one of them in
2264	the constructor.	2542	the constructor.
2265		2543
2266	class myclass	2544	class myclass
2267	{	2545	{
2268	ev_io io; void io_cb (ev::io &w, int revents);	2546	ev::io io; void io_cb (ev::io &w, int revents);
2269	ev_idle idle void idle_cb (ev::idle &w, int revents);	2547	ev:idle idle void idle_cb (ev::idle &w, int revents);
2270		2548
2271	myclass ();	2549	myclass (int fd)
2272	}
2273
2274	myclass::myclass (int fd)
2275	{	2550	{
2276	io .set <myclass, &myclass::io_cb > (this);	2551	io .set <myclass, &myclass::io_cb > (this);
2277	idle.set <myclass, &myclass::idle_cb> (this);	2552	idle.set <myclass, &myclass::idle_cb> (this);
2278		2553
2279	io.start (fd, ev::READ);	2554	io.start (fd, ev::READ);
		2555	}
2280	}	2556	};
		2557
		2558
		2559	=head1 OTHER LANGUAGE BINDINGS
		2560
		2561	Libev does not offer other language bindings itself, but bindings for a
		2562	numbe rof languages exist in the form of third-party packages. If you know
		2563	any interesting language binding in addition to the ones listed here, drop
		2564	me a note.
		2565
		2566	=over 4
		2567
		2568	=item Perl
		2569
		2570	The EV module implements the full libev API and is actually used to test
		2571	libev. EV is developed together with libev. Apart from the EV core module,
		2572	there are additional modules that implement libev-compatible interfaces
		2573	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2574	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2575
		2576	It can be found and installed via CPAN, its homepage is found at
		2577	L<http://software.schmorp.de/pkg/EV>.
		2578
		2579	=item Ruby
		2580
		2581	Tony Arcieri has written a ruby extension that offers access to a subset
		2582	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2583	more on top of it. It can be found via gem servers. Its homepage is at
		2584	L<http://rev.rubyforge.org/>.
		2585
		2586	=item D
		2587
		2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2589	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2590
		2591	=back
2281		2592
2282		2593
2283	=head1 MACRO MAGIC	2594	=head1 MACRO MAGIC
2284		2595
2285	Libev can be compiled with a variety of options, the most fundamantal	2596	Libev can be compiled with a variety of options, the most fundamantal
…		…
2426		2737
2427	libev.m4	2738	libev.m4
2428		2739
2429	=head2 PREPROCESSOR SYMBOLS/MACROS	2740	=head2 PREPROCESSOR SYMBOLS/MACROS
2430		2741
2431	Libev can be configured via a variety of preprocessor symbols you have to define	2742	Libev can be configured via a variety of preprocessor symbols you have to
2432	before including any of its files. The default is not to build for multiplicity	2743	define before including any of its files. The default in the absense of
2433	and only include the select backend.	2744	autoconf is noted for every option.
2434		2745
2435	=over 4	2746	=over 4
2436		2747
2437	=item EV_STANDALONE	2748	=item EV_STANDALONE
2438		2749
…		…
2464	=item EV_USE_NANOSLEEP	2775	=item EV_USE_NANOSLEEP
2465		2776
2466	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2777	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2467	and will use it for delays. Otherwise it will use C<select ()>.	2778	and will use it for delays. Otherwise it will use C<select ()>.
2468		2779
		2780	=item EV_USE_EVENTFD
		2781
		2782	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2783	available and will probe for kernel support at runtime. This will improve
		2784	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2785	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2786	2.7 or newer, otherwise disabled.
		2787
2469	=item EV_USE_SELECT	2788	=item EV_USE_SELECT
2470		2789
2471	If undefined or defined to be C<1>, libev will compile in support for the	2790	If undefined or defined to be C<1>, libev will compile in support for the
2472	C<select>(2) backend. No attempt at autodetection will be done: if no	2791	C<select>(2) backend. No attempt at autodetection will be done: if no
2473	other method takes over, select will be it. Otherwise the select backend	2792	other method takes over, select will be it. Otherwise the select backend
…		…
2491	be used is the winsock select). This means that it will call	2810	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,	2811	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	2812	it is assumed that all these functions actually work on fds, even
2494	on win32. Should not be defined on non-win32 platforms.	2813	on win32. Should not be defined on non-win32 platforms.
2495		2814
		2815	=item EV_FD_TO_WIN32_HANDLE
		2816
		2817	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2818	file descriptors to socket handles. When not defining this symbol (the
		2819	default), then libev will call C<_get_osfhandle>, which is usually
		2820	correct. In some cases, programs use their own file descriptor management,
		2821	in which case they can provide this function to map fds to socket handles.
		2822
2496	=item EV_USE_POLL	2823	=item EV_USE_POLL
2497		2824
2498	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2825	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	2826	backend. Otherwise it will be enabled on non-win32 platforms. It
2500	takes precedence over select.	2827	takes precedence over select.
2501		2828
2502	=item EV_USE_EPOLL	2829	=item EV_USE_EPOLL
2503		2830
2504	If defined to be C<1>, libev will compile in support for the Linux	2831	If defined to be C<1>, libev will compile in support for the Linux
2505	C<epoll>(7) backend. Its availability will be detected at runtime,	2832	C<epoll>(7) backend. Its availability will be detected at runtime,
2506	otherwise another method will be used as fallback. This is the	2833	otherwise another method will be used as fallback. This is the preferred
2507	preferred backend for GNU/Linux systems.	2834	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2835	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2508		2836
2509	=item EV_USE_KQUEUE	2837	=item EV_USE_KQUEUE
2510		2838
2511	If defined to be C<1>, libev will compile in support for the BSD style	2839	If defined to be C<1>, libev will compile in support for the BSD style
2512	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2840	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2531		2859
2532	=item EV_USE_INOTIFY	2860	=item EV_USE_INOTIFY
2533		2861
2534	If defined to be C<1>, libev will compile in support for the Linux inotify	2862	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	2863	interface to speed up C<ev_stat> watchers. Its actual availability will
2536	be detected at runtime.	2864	be detected at runtime. If undefined, it will be enabled if the headers
		2865	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2866
		2867	=item EV_ATOMIC_T
		2868
		2869	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2870	access is atomic with respect to other threads or signal contexts. No such
		2871	type is easily found in the C language, so you can provide your own type
		2872	that you know is safe for your purposes. It is used both for signal handler "locking"
		2873	as well as for signal and thread safety in C<ev_async> watchers.
		2874
		2875	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2876	(from F<signal.h>), which is usually good enough on most platforms.
2537		2877
2538	=item EV_H	2878	=item EV_H
2539		2879
2540	The name of the F<ev.h> header file used to include it. The default if	2880	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	2881	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.	2882	used to virtually rename the F<ev.h> header file in case of conflicts.
2543		2883
2544	=item EV_CONFIG_H	2884	=item EV_CONFIG_H
2545		2885
2546	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2886	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	2887	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2548	C<EV_H>, above.	2888	C<EV_H>, above.
2549		2889
2550	=item EV_EVENT_H	2890	=item EV_EVENT_H
2551		2891
2552	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2892	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">.	2893	of how the F<event.h> header can be found, the default is C<"event.h">.
2554		2894
2555	=item EV_PROTOTYPES	2895	=item EV_PROTOTYPES
2556		2896
2557	If defined to be C<0>, then F<ev.h> will not define any function	2897	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	2898	prototypes, but still define all the structs and other symbols. This is
…		…
2607	defined to be C<0>, then they are not.	2947	defined to be C<0>, then they are not.
2608		2948
2609	=item EV_FORK_ENABLE	2949	=item EV_FORK_ENABLE
2610		2950
2611	If undefined or defined to be C<1>, then fork watchers are supported. If	2951	If undefined or defined to be C<1>, then fork watchers are supported. If
		2952	defined to be C<0>, then they are not.
		2953
		2954	=item EV_ASYNC_ENABLE
		2955
		2956	If undefined or defined to be C<1>, then async watchers are supported. If
2612	defined to be C<0>, then they are not.	2957	defined to be C<0>, then they are not.
2613		2958
2614	=item EV_MINIMAL	2959	=item EV_MINIMAL
2615		2960
2616	If you need to shave off some kilobytes of code at the expense of some	2961	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)	3082	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2738		3083
2739	That means that changing a timer costs less than removing/adding them	3084	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.	3085	as only the relative motion in the event queue has to be paid for.
2741		3086
2742	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3087	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2743		3088
2744	These just add the watcher into an array or at the head of a list.	3089	These just add the watcher into an array or at the head of a list.
2745		3090
2746	=item Stopping check/prepare/idle watchers: O(1)	3091	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2747		3092
2748	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3093	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2749		3094
2750	These watchers are stored in lists then need to be walked to find the	3095	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	3096	correct watcher to remove. The lists are usually short (you don't usually
…		…
2767	=item Priority handling: O(number_of_priorities)	3112	=item Priority handling: O(number_of_priorities)
2768		3113
2769	Priorities are implemented by allocating some space for each	3114	Priorities are implemented by allocating some space for each
2770	priority. When doing priority-based operations, libev usually has to	3115	priority. When doing priority-based operations, libev usually has to
2771	linearly search all the priorities, but starting/stopping and activating	3116	linearly search all the priorities, but starting/stopping and activating
2772	watchers becomes O(1) w.r.t. prioritiy handling.	3117	watchers becomes O(1) w.r.t. priority handling.
		3118
		3119	=item Sending an ev_async: O(1)
		3120
		3121	=item Processing ev_async_send: O(number_of_async_watchers)
		3122
		3123	=item Processing signals: O(max_signal_number)
		3124
		3125	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3126	calls in the current loop iteration. Checking for async and signal events
		3127	involves iterating over all running async watchers or all signal numbers.
2773		3128
2774	=back	3129	=back
2775		3130
2776		3131
		3132	=head1 Win32 platform limitations and workarounds
		3133
		3134	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3135	requires, and its I/O model is fundamentally incompatible with the POSIX
		3136	model. Libev still offers limited functionality on this platform in
		3137	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3138	descriptors. This only applies when using Win32 natively, not when using
		3139	e.g. cygwin.
		3140
		3141	There is no supported compilation method available on windows except
		3142	embedding it into other applications.
		3143
		3144	Due to the many, low, and arbitrary limits on the win32 platform and the
		3145	abysmal performance of winsockets, using a large number of sockets is not
		3146	recommended (and not reasonable). If your program needs to use more than
		3147	a hundred or so sockets, then likely it needs to use a totally different
		3148	implementation for windows, as libev offers the POSIX model, which cannot
		3149	be implemented efficiently on windows (microsoft monopoly games).
		3150
		3151	=over 4
		3152
		3153	=item The winsocket select function
		3154
		3155	The winsocket C<select> function doesn't follow POSIX in that it requires
		3156	socket I<handles> and not socket I<file descriptors>. This makes select
		3157	very inefficient, and also requires a mapping from file descriptors
		3158	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3159	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3160	symbols for more info.
		3161
		3162	The configuration for a "naked" win32 using the microsoft runtime
		3163	libraries and raw winsocket select is:
		3164
		3165	#define EV_USE_SELECT 1
		3166	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3167
		3168	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3169	complexity in the O(n²) range when using win32.
		3170
		3171	=item Limited number of file descriptors
		3172
		3173	Windows has numerous arbitrary (and low) limits on things. Early versions
		3174	of winsocket's select only supported waiting for a max. of C<64> handles
		3175	(probably owning to the fact that all windows kernels can only wait for
		3176	C<64> things at the same time internally; microsoft recommends spawning a
		3177	chain of threads and wait for 63 handles and the previous thread in each).
		3178
		3179	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3180	to some high number (e.g. C<2048>) before compiling the winsocket select
		3181	call (which might be in libev or elsewhere, for example, perl does its own
		3182	select emulation on windows).
		3183
		3184	Another limit is the number of file descriptors in the microsoft runtime
		3185	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3186	or something like this inside microsoft). You can increase this by calling
		3187	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3188	arbitrary limit), but is broken in many versions of the microsoft runtime
		3189	libraries.
		3190
		3191	This might get you to about C<512> or C<2048> sockets (depending on
		3192	windows version and/or the phase of the moon). To get more, you need to
		3193	wrap all I/O functions and provide your own fd management, but the cost of
		3194	calling select (O(n²)) will likely make this unworkable.
		3195
		3196	=back
		3197
		3198
2777	=head1 AUTHOR	3199	=head1 AUTHOR
2778		3200
2779	Marc Lehmann <libev@schmorp.de>.	3201	Marc Lehmann <libev@schmorp.de>.
2780		3202

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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 1.142 by root, Sun Apr 6 09:53:18 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 1.142 by root, Sun Apr 6 09:53:18 2008 UTC