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Revision 1.109 by root, Mon Dec 24 13:19:12 2007 UTC vs.
Revision 1.158 by root, Wed May 21 12:51:38 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://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
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
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
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
…		…
181	See the description of C<ev_embed> watchers for more info.	196	See the description of C<ev_embed> watchers for more info.
182		197
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
184		199
185	Sets the allocation function to use (the prototype is similar - the	200	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
187	allocate and free memory (no surprises here). If it returns zero when	202	used to allocate and free memory (no surprises here). If it returns zero
188	memory needs to be allocated, the library might abort or take some	203	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	204	or take some potentially destructive action.
190	function.	205
		206	Since some systems (at least OpenBSD and Darwin) fail to implement
		207	correct C<realloc> semantics, libev will use a wrapper around the system
		208	C<realloc> and C<free> functions by default.
191		209
192	You could override this function in high-availability programs to, say,	210	You could override this function in high-availability programs to, say,
193	free some memory if it cannot allocate memory, to use a special allocator,	211	free some memory if it cannot allocate memory, to use a special allocator,
194	or even to sleep a while and retry until some memory is available.	212	or even to sleep a while and retry until some memory is available.
195		213
196	Example: Replace the libev allocator with one that waits a bit and then	214	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	215	retries (example requires a standards-compliant C<realloc>).
198		216
199	static void *	217	static void *
200	persistent_realloc (void *ptr, size_t size)	218	persistent_realloc (void *ptr, size_t size)
201	{	219	{
202	for (;;)	220	for (;;)
…		…
241		259
242	An event loop is described by a C<struct ev_loop *>. The library knows two	260	An event loop is described by a C<struct ev_loop *>. The library knows two
243	types of such loops, the I<default> loop, which supports signals and child	261	types of such loops, the I<default> loop, which supports signals and child
244	events, and dynamically created loops which do not.	262	events, and dynamically created loops which do not.
245		263
246	If you use threads, a common model is to run the default event loop
247	in your main thread (or in a separate thread) and for each thread you
248	create, you also create another event loop. Libev itself does no locking
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252
253	=over 4	264	=over 4
254		265
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	266	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		267
257	This will initialise the default event loop if it hasn't been initialised	268	This will initialise the default event loop if it hasn't been initialised
…		…
259	false. If it already was initialised it simply returns it (and ignores the	270	false. If it already was initialised it simply returns it (and ignores the
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	271	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		272
262	If you don't know what event loop to use, use the one returned from this	273	If you don't know what event loop to use, use the one returned from this
263	function.	274	function.
		275
		276	Note that this function is I<not> thread-safe, so if you want to use it
		277	from multiple threads, you have to lock (note also that this is unlikely,
		278	as loops cannot bes hared easily between threads anyway).
		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>.
264		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:
…		…
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.
…		…
314	To get good performance out of this backend you need a high amount of	336	To get good performance out of this backend you need a high amount of
315	parallelity (most of the file descriptors should be busy). If you are	337	parallelity (most of the file descriptors should be busy). If you are
316	writing a server, you should C<accept ()> in a loop to accept as many	338	writing a server, you should C<accept ()> in a loop to accept as many
317	connections as possible during one iteration. You might also want to have	339	connections as possible during one iteration. You might also want to have
318	a look at C<ev_set_io_collect_interval ()> to increase the amount of	340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
319	readyness notifications you get per iteration.	341	readiness notifications you get per iteration.
320		342
321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
322		344
323	And this is your standard poll(2) backend. It's more complicated	345	And this is your standard poll(2) backend. It's more complicated
324	than select, but handles sparse fds better and has no artificial	346	than select, but handles sparse fds better and has no artificial
…		…
332	For few fds, this backend is a bit little slower than poll and select,	354	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	355	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),	356	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	357	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	358	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	359	cases and requiring a syscall per fd change, no fork support and bad
338	support for dup.	360	support for dup.
339		361
340	While stopping, setting and starting an I/O watcher in the same iteration	362	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	363	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	364	(because the fd could point to a different file description now), so its
…		…
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 readiness 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>.
…		…
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?");
…		…
440		465
441	Similar to C<ev_default_loop>, but always creates a new event loop that is	466	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	467	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	468	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).	469	undefined behaviour (or a failed assertion if assertions are enabled).
		470
		471	Note that this function I<is> thread-safe, and the recommended way to use
		472	libev with threads is indeed to create one loop per thread, and using the
		473	default loop in the "main" or "initial" thread.
445		474
446	Example: Try to create a event loop that uses epoll and nothing else.	475	Example: Try to create a event loop that uses epoll and nothing else.
447		476
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	478	if (!epoller)
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	502	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	503	earlier call to C<ev_loop_new>.
475		504
476	=item ev_default_fork ()	505	=item ev_default_fork ()
477		506
		507	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	508	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	509	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	510	the child process (or both child and parent, but that again makes little
481	again makes little sense).	511	sense). You I<must> call it in the child before using any of the libev
		512	functions, and it will only take effect at the next C<ev_loop> iteration.
482		513
483	You I<must> call this function in the child process after forking if and	514	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	515	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.	516	you just fork+exec, you don't have to call it at all.
486		517
487	The function itself is quite fast and it's usually not a problem to call	518	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	519	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>:	520	quite nicely into a call to C<pthread_atfork>:
490		521
491	pthread_atfork (0, 0, ev_default_fork);	522	pthread_atfork (0, 0, ev_default_fork);
492		523
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)	524	=item ev_loop_fork (loop)
498		525
499	Like C<ev_default_fork>, but acts on an event loop created by	526	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	527	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.	528	after fork, and how you do this is entirely your own problem.
		529
		530	=item int ev_is_default_loop (loop)
		531
		532	Returns true when the given loop actually is the default loop, false otherwise.
502		533
503	=item unsigned int ev_loop_count (loop)	534	=item unsigned int ev_loop_count (loop)
504		535
505	Returns the count of loop iterations for the loop, which is identical to	536	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	537	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.	582	usually a better approach for this kind of thing.
552		583
553	Here are the gory details of what C<ev_loop> does:	584	Here are the gory details of what C<ev_loop> does:
554		585
555	- Before the first iteration, call any pending watchers.	586	- Before the first iteration, call any pending watchers.
556	* If there are no active watchers (reference count is zero), return.	587	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- Queue all prepare watchers and then call all outstanding watchers.	588	- If a fork was detected, queue and call all fork watchers.
		589	- Queue and call all prepare watchers.
558	- If we have been forked, recreate the kernel state.	590	- If we have been forked, recreate the kernel state.
559	- Update the kernel state with all outstanding changes.	591	- Update the kernel state with all outstanding changes.
560	- Update the "event loop time".	592	- Update the "event loop time".
561	- Calculate for how long to block.	593	- Calculate for how long to sleep or block, if at all
		594	(active idle watchers, EVLOOP_NONBLOCK or not having
		595	any active watchers at all will result in not sleeping).
		596	- Sleep if the I/O and timer collect interval say so.
562	- Block the process, waiting for any events.	597	- Block the process, waiting for any events.
563	- Queue all outstanding I/O (fd) events.	598	- Queue all outstanding I/O (fd) events.
564	- Update the "event loop time" and do time jump handling.	599	- Update the "event loop time" and do time jump handling.
565	- Queue all outstanding timers.	600	- Queue all outstanding timers.
566	- Queue all outstanding periodics.	601	- Queue all outstanding periodics.
567	- If no events are pending now, queue all idle watchers.	602	- If no events are pending now, queue all idle watchers.
568	- Queue all check watchers.	603	- Queue all check watchers.
569	- Call all queued watchers in reverse order (i.e. check watchers first).	604	- 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	605	Signals and child watchers are implemented as I/O watchers, and will
571	be handled here by queueing them when their watcher gets executed.	606	be handled here by queueing them when their watcher gets executed.
572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573	were used, return, otherwise continue with step *.	608	were used, or there are no active watchers, return, otherwise
		609	continue with step *.
574		610
575	Example: Queue some jobs and then loop until no events are outsanding	611	Example: Queue some jobs and then loop until no events are outstanding
576	anymore.	612	anymore.
577		613
578	... queue jobs here, make sure they register event watchers as long	614	... 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..)	615	... as they still have work to do (even an idle watcher will do..)
580	ev_loop (my_loop, 0);	616	ev_loop (my_loop, 0);
…		…
584		620
585	Can be used to make a call to C<ev_loop> return early (but only after it	621	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	622	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	623	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.	624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		625
		626	This "unloop state" will be cleared when entering C<ev_loop> again.
589		627
590	=item ev_ref (loop)	628	=item ev_ref (loop)
591		629
592	=item ev_unref (loop)	630	=item ev_unref (loop)
593		631
…		…
598	returning, ev_unref() after starting, and ev_ref() before stopping it. For	636	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	637	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	638	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	639	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	640	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>.	641	libraries. Just remember to I<unref after start> and I<ref before stop>
		642	(but only if the watcher wasn't active before, or was active before,
		643	respectively).
604		644
605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606	running when nothing else is active.	646	running when nothing else is active.
607		647
608	struct ev_signal exitsig;	648	struct ev_signal exitsig;
…		…
756		796
757	=item C<EV_FORK>	797	=item C<EV_FORK>
758		798
759	The event loop has been resumed in the child process after fork (see	799	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	800	C<ev_fork>).
		801
		802	=item C<EV_ASYNC>
		803
		804	The given async watcher has been asynchronously notified (see C<ev_async>).
761		805
762	=item C<EV_ERROR>	806	=item C<EV_ERROR>
763		807
764	An unspecified error has occured, the watcher has been stopped. This might	808	An unspecified error has occured, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	809	happen because the watcher could not be properly started because libev
…		…
988	If you must do this, then force the use of a known-to-be-good backend	1032	If you must do this, then force the use of a known-to-be-good backend
989	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
990	C<EVBACKEND_POLL>).	1034	C<EVBACKEND_POLL>).
991		1035
992	Another thing you have to watch out for is that it is quite easy to	1036	Another thing you have to watch out for is that it is quite easy to
993	receive "spurious" readyness notifications, that is your callback might	1037	receive "spurious" readiness notifications, that is your callback might
994	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
995	because there is no data. Not only are some backends known to create a	1039	because there is no data. Not only are some backends known to create a
996	lot of those (for example solaris ports), it is very easy to get into	1040	lot of those (for example solaris ports), it is very easy to get into
997	this situation even with a relatively standard program structure. Thus	1041	this situation even with a relatively standard program structure. Thus
998	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning
…		…
1045	To support fork in your programs, you either have to call	1089	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,	1090	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	1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1048	C<EVBACKEND_POLL>.	1092	C<EVBACKEND_POLL>.
1049		1093
		1094	=head3 The special problem of SIGPIPE
		1095
		1096	While not really specific to libev, it is easy to forget about SIGPIPE:
		1097	when reading from a pipe whose other end has been closed, your program
		1098	gets send a SIGPIPE, which, by default, aborts your program. For most
		1099	programs this is sensible behaviour, for daemons, this is usually
		1100	undesirable.
		1101
		1102	So when you encounter spurious, unexplained daemon exits, make sure you
		1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1104	somewhere, as that would have given you a big clue).
		1105
1050		1106
1051	=head3 Watcher-Specific Functions	1107	=head3 Watcher-Specific Functions
1052		1108
1053	=over 4	1109	=over 4
1054		1110
…		…
1067	=item int events [read-only]	1123	=item int events [read-only]
1068		1124
1069	The events being watched.	1125	The events being watched.
1070		1126
1071	=back	1127	=back
		1128
		1129	=head3 Examples
1072		1130
1073	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1074	readable, but only once. Since it is likely line-buffered, you could	1132	readable, but only once. Since it is likely line-buffered, you could
1075	attempt to read a whole line in the callback.	1133	attempt to read a whole line in the callback.
1076		1134
…		…
1093		1151
1094	Timer watchers are simple relative timers that generate an event after a	1152	Timer watchers are simple relative timers that generate an event after a
1095	given time, and optionally repeating in regular intervals after that.	1153	given time, and optionally repeating in regular intervals after that.
1096		1154
1097	The timers are based on real time, that is, if you register an event that	1155	The timers are based on real time, that is, if you register an event that
1098	times out after an hour and you reset your system clock to last years	1156	times out after an hour and you reset your system clock to january last
1099	time, it will still time out after (roughly) and hour. "Roughly" because	1157	year, it will still time out after (roughly) and hour. "Roughly" because
1100	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1101	monotonic clock option helps a lot here).	1159	monotonic clock option helps a lot here).
1102		1160
1103	The relative timeouts are calculated relative to the C<ev_now ()>	1161	The relative timeouts are calculated relative to the C<ev_now ()>
1104	time. This is usually the right thing as this timestamp refers to the time	1162	time. This is usually the right thing as this timestamp refers to the time
…		…
1106	you suspect event processing to be delayed and you I<need> to base the timeout	1164	you suspect event processing to be delayed and you I<need> to base the timeout
1107	on the current time, use something like this to adjust for this:	1165	on the current time, use something like this to adjust for this:
1108		1166
1109	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1110		1168
1111	The callback is guarenteed to be invoked only when its timeout has passed,	1169	The callback is guarenteed to be invoked only after its timeout has passed,
1112	but if multiple timers become ready during the same loop iteration then	1170	but if multiple timers become ready during the same loop iteration then
1113	order of execution is undefined.	1171	order of execution is undefined.
1114		1172
1115	=head3 Watcher-Specific Functions and Data Members	1173	=head3 Watcher-Specific Functions and Data Members
1116		1174
…		…
1118		1176
1119	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1120		1178
1121	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1122		1180
1123	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1181	Configure the timer to trigger after C<after> seconds. If C<repeat>
1124	C<0.>, then it will automatically be stopped. If it is positive, then the	1182	is C<0.>, then it will automatically be stopped once the timeout is
1125	timer will automatically be configured to trigger again C<repeat> seconds	1183	reached. If it is positive, then the timer will automatically be
1126	later, again, and again, until stopped manually.	1184	configured to trigger again C<repeat> seconds later, again, and again,
		1185	until stopped manually.
1127		1186
1128	The timer itself will do a best-effort at avoiding drift, that is, if you	1187	The timer itself will do a best-effort at avoiding drift, that is, if
1129	configure a timer to trigger every 10 seconds, then it will trigger at	1188	you configure a timer to trigger every 10 seconds, then it will normally
1130	exactly 10 second intervals. If, however, your program cannot keep up with	1189	trigger at exactly 10 second intervals. If, however, your program cannot
1131	the timer (because it takes longer than those 10 seconds to do stuff) the	1190	keep up with the timer (because it takes longer than those 10 seconds to
1132	timer will not fire more than once per event loop iteration.	1191	do stuff) the timer will not fire more than once per event loop iteration.
1133		1192
1134	=item ev_timer_again (loop)	1193	=item ev_timer_again (loop, ev_timer *)
1135		1194
1136	This will act as if the timer timed out and restart it again if it is	1195	This will act as if the timer timed out and restart it again if it is
1137	repeating. The exact semantics are:	1196	repeating. The exact semantics are:
1138		1197
1139	If the timer is pending, its pending status is cleared.	1198	If the timer is pending, its pending status is cleared.
…		…
1174	or C<ev_timer_again> is called and determines the next timeout (if any),	1233	or C<ev_timer_again> is called and determines the next timeout (if any),
1175	which is also when any modifications are taken into account.	1234	which is also when any modifications are taken into account.
1176		1235
1177	=back	1236	=back
1178		1237
		1238	=head3 Examples
		1239
1179	Example: Create a timer that fires after 60 seconds.	1240	Example: Create a timer that fires after 60 seconds.
1180		1241
1181	static void	1242	static void
1182	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1243	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1183	{	1244	{
…		…
1212	Periodic watchers are also timers of a kind, but they are very versatile	1273	Periodic watchers are also timers of a kind, but they are very versatile
1213	(and unfortunately a bit complex).	1274	(and unfortunately a bit complex).
1214		1275
1215	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1276	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1216	but on wallclock time (absolute time). You can tell a periodic watcher	1277	but on wallclock time (absolute time). You can tell a periodic watcher
1217	to trigger "at" some specific point in time. For example, if you tell a	1278	to trigger after some specific point in time. For example, if you tell a
1218	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1279	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1219	+ 10.>) and then reset your system clock to the last year, then it will	1280	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1281	clock to january of the previous year, then it will take more than year
1220	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1282	to trigger the event (unlike an C<ev_timer>, which would still trigger
1221	roughly 10 seconds later).	1283	roughly 10 seconds later as it uses a relative timeout).
1222		1284
1223	They can also be used to implement vastly more complex timers, such as	1285	C<ev_periodic>s can also be used to implement vastly more complex timers,
1224	triggering an event on each midnight, local time or other, complicated,	1286	such as triggering an event on each "midnight, local time", or other
1225	rules.	1287	complicated, rules.
1226		1288
1227	As with timers, the callback is guarenteed to be invoked only when the	1289	As with timers, the callback is guarenteed to be invoked only when the
1228	time (C<at>) has been passed, but if multiple periodic timers become ready	1290	time (C<at>) has passed, but if multiple periodic timers become ready
1229	during the same loop iteration then order of execution is undefined.	1291	during the same loop iteration then order of execution is undefined.
1230		1292
1231	=head3 Watcher-Specific Functions and Data Members	1293	=head3 Watcher-Specific Functions and Data Members
1232		1294
1233	=over 4	1295	=over 4
…		…
1241		1303
1242	=over 4	1304	=over 4
1243		1305
1244	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1306	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1245		1307
1246	In this configuration the watcher triggers an event at the wallclock time	1308	In this configuration the watcher triggers an event after the wallclock
1247	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1309	time C<at> has passed and doesn't repeat. It will not adjust when a time
1248	that is, if it is to be run at January 1st 2011 then it will run when the	1310	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1249	system time reaches or surpasses this time.	1311	run when the system time reaches or surpasses this time.
1250		1312
1251	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1313	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1252		1314
1253	In this mode the watcher will always be scheduled to time out at the next	1315	In this mode the watcher will always be scheduled to time out at the next
1254	C<at + N * interval> time (for some integer N, which can also be negative)	1316	C<at + N * interval> time (for some integer N, which can also be negative)
1255	and then repeat, regardless of any time jumps.	1317	and then repeat, regardless of any time jumps.
1256		1318
1257	This can be used to create timers that do not drift with respect to system	1319	This can be used to create timers that do not drift with respect to system
1258	time:	1320	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1321	the hour:
1259		1322
1260	ev_periodic_set (&periodic, 0., 3600., 0);	1323	ev_periodic_set (&periodic, 0., 3600., 0);
1261		1324
1262	This doesn't mean there will always be 3600 seconds in between triggers,	1325	This doesn't mean there will always be 3600 seconds in between triggers,
1263	but only that the the callback will be called when the system time shows a	1326	but only that the the callback will be called when the system time shows a
…		…
1268	C<ev_periodic> will try to run the callback in this mode at the next possible	1331	C<ev_periodic> will try to run the callback in this mode at the next possible
1269	time where C<time = at (mod interval)>, regardless of any time jumps.	1332	time where C<time = at (mod interval)>, regardless of any time jumps.
1270		1333
1271	For numerical stability it is preferable that the C<at> value is near	1334	For numerical stability it is preferable that the C<at> value is near
1272	C<ev_now ()> (the current time), but there is no range requirement for	1335	C<ev_now ()> (the current time), but there is no range requirement for
1273	this value.	1336	this value, and in fact is often specified as zero.
		1337
		1338	Note also that there is an upper limit to how often a timer can fire (cpu
		1339	speed for example), so if C<interval> is very small then timing stability
		1340	will of course detoriate. Libev itself tries to be exact to be about one
		1341	millisecond (if the OS supports it and the machine is fast enough).
1274		1342
1275	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1343	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1276		1344
1277	In this mode the values for C<interval> and C<at> are both being	1345	In this mode the values for C<interval> and C<at> are both being
1278	ignored. Instead, each time the periodic watcher gets scheduled, the	1346	ignored. Instead, each time the periodic watcher gets scheduled, the
1279	reschedule callback will be called with the watcher as first, and the	1347	reschedule callback will be called with the watcher as first, and the
1280	current time as second argument.	1348	current time as second argument.
1281		1349
1282	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1350	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1283	ever, or make any event loop modifications>. If you need to stop it,	1351	ever, or make ANY event loop modifications whatsoever>.
1284	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1285	starting an C<ev_prepare> watcher, which is legal).
1286		1352
		1353	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1354	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1355	only event loop modification you are allowed to do).
		1356
1287	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1357	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1288	ev_tstamp now)>, e.g.:	1358	*w, ev_tstamp now)>, e.g.:
1289		1359
1290	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1360	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1291	{	1361	{
1292	return now + 60.;	1362	return now + 60.;
1293	}	1363	}
…		…
1295	It must return the next time to trigger, based on the passed time value	1365	It must return the next time to trigger, based on the passed time value
1296	(that is, the lowest time value larger than to the second argument). It	1366	(that is, the lowest time value larger than to the second argument). It
1297	will usually be called just before the callback will be triggered, but	1367	will usually be called just before the callback will be triggered, but
1298	might be called at other times, too.	1368	might be called at other times, too.
1299		1369
1300	NOTE: I<< This callback must always return a time that is later than the	1370	NOTE: I<< This callback must always return a time that is higher than or
1301	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1371	equal to the passed C<now> value >>.
1302		1372
1303	This can be used to create very complex timers, such as a timer that	1373	This can be used to create very complex timers, such as a timer that
1304	triggers on each midnight, local time. To do this, you would calculate the	1374	triggers on "next midnight, local time". To do this, you would calculate the
1305	next midnight after C<now> and return the timestamp value for this. How	1375	next midnight after C<now> and return the timestamp value for this. How
1306	you do this is, again, up to you (but it is not trivial, which is the main	1376	you do this is, again, up to you (but it is not trivial, which is the main
1307	reason I omitted it as an example).	1377	reason I omitted it as an example).
1308		1378
1309	=back	1379	=back
…		…
1313	Simply stops and restarts the periodic watcher again. This is only useful	1383	Simply stops and restarts the periodic watcher again. This is only useful
1314	when you changed some parameters or the reschedule callback would return	1384	when you changed some parameters or the reschedule callback would return
1315	a different time than the last time it was called (e.g. in a crond like	1385	a different time than the last time it was called (e.g. in a crond like
1316	program when the crontabs have changed).	1386	program when the crontabs have changed).
1317		1387
		1388	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1389
		1390	When active, returns the absolute time that the watcher is supposed to
		1391	trigger next.
		1392
1318	=item ev_tstamp offset [read-write]	1393	=item ev_tstamp offset [read-write]
1319		1394
1320	When repeating, this contains the offset value, otherwise this is the	1395	When repeating, this contains the offset value, otherwise this is the
1321	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1396	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1322		1397
…		…
1333		1408
1334	The current reschedule callback, or C<0>, if this functionality is	1409	The current reschedule callback, or C<0>, if this functionality is
1335	switched off. Can be changed any time, but changes only take effect when	1410	switched off. Can be changed any time, but changes only take effect when
1336	the periodic timer fires or C<ev_periodic_again> is being called.	1411	the periodic timer fires or C<ev_periodic_again> is being called.
1337		1412
1338	=item ev_tstamp at [read-only]
1339
1340	When active, contains the absolute time that the watcher is supposed to
1341	trigger next.
1342
1343	=back	1413	=back
		1414
		1415	=head3 Examples
1344		1416
1345	Example: Call a callback every hour, or, more precisely, whenever the	1417	Example: Call a callback every hour, or, more precisely, whenever the
1346	system clock is divisible by 3600. The callback invocation times have	1418	system clock is divisible by 3600. The callback invocation times have
1347	potentially a lot of jittering, but good long-term stability.	1419	potentially a lot of jittering, but good long-term stability.
1348		1420
…		…
1388	with the kernel (thus it coexists with your own signal handlers as long	1460	with the kernel (thus it coexists with your own signal handlers as long
1389	as you don't register any with libev). Similarly, when the last signal	1461	as you don't register any with libev). Similarly, when the last signal
1390	watcher for a signal is stopped libev will reset the signal handler to	1462	watcher for a signal is stopped libev will reset the signal handler to
1391	SIG_DFL (regardless of what it was set to before).	1463	SIG_DFL (regardless of what it was set to before).
1392		1464
		1465	If possible and supported, libev will install its handlers with
		1466	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1467	interrupted. If you have a problem with syscalls getting interrupted by
		1468	signals you can block all signals in an C<ev_check> watcher and unblock
		1469	them in an C<ev_prepare> watcher.
		1470
1393	=head3 Watcher-Specific Functions and Data Members	1471	=head3 Watcher-Specific Functions and Data Members
1394		1472
1395	=over 4	1473	=over 4
1396		1474
1397	=item ev_signal_init (ev_signal *, callback, int signum)	1475	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1405		1483
1406	The signal the watcher watches out for.	1484	The signal the watcher watches out for.
1407		1485
1408	=back	1486	=back
1409		1487
		1488	=head3 Examples
		1489
		1490	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1491
		1492	static void
		1493	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1494	{
		1495	ev_unloop (loop, EVUNLOOP_ALL);
		1496	}
		1497
		1498	struct ev_signal signal_watcher;
		1499	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1500	ev_signal_start (loop, &sigint_cb);
		1501
1410		1502
1411	=head2 C<ev_child> - watch out for process status changes	1503	=head2 C<ev_child> - watch out for process status changes
1412		1504
1413	Child watchers trigger when your process receives a SIGCHLD in response to	1505	Child watchers trigger when your process receives a SIGCHLD in response to
1414	some child status changes (most typically when a child of yours dies).	1506	some child status changes (most typically when a child of yours dies). It
		1507	is permissible to install a child watcher I<after> the child has been
		1508	forked (which implies it might have already exited), as long as the event
		1509	loop isn't entered (or is continued from a watcher).
		1510
		1511	Only the default event loop is capable of handling signals, and therefore
		1512	you can only rgeister child watchers in the default event loop.
		1513
		1514	=head3 Process Interaction
		1515
		1516	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1517	initialised. This is necessary to guarantee proper behaviour even if
		1518	the first child watcher is started after the child exits. The occurance
		1519	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1520	synchronously as part of the event loop processing. Libev always reaps all
		1521	children, even ones not watched.
		1522
		1523	=head3 Overriding the Built-In Processing
		1524
		1525	Libev offers no special support for overriding the built-in child
		1526	processing, but if your application collides with libev's default child
		1527	handler, you can override it easily by installing your own handler for
		1528	C<SIGCHLD> after initialising the default loop, and making sure the
		1529	default loop never gets destroyed. You are encouraged, however, to use an
		1530	event-based approach to child reaping and thus use libev's support for
		1531	that, so other libev users can use C<ev_child> watchers freely.
1415		1532
1416	=head3 Watcher-Specific Functions and Data Members	1533	=head3 Watcher-Specific Functions and Data Members
1417		1534
1418	=over 4	1535	=over 4
1419		1536
1420	=item ev_child_init (ev_child *, callback, int pid)	1537	=item ev_child_init (ev_child *, callback, int pid, int trace)
1421		1538
1422	=item ev_child_set (ev_child *, int pid)	1539	=item ev_child_set (ev_child *, int pid, int trace)
1423		1540
1424	Configures the watcher to wait for status changes of process C<pid> (or	1541	Configures the watcher to wait for status changes of process C<pid> (or
1425	I<any> process if C<pid> is specified as C<0>). The callback can look	1542	I<any> process if C<pid> is specified as C<0>). The callback can look
1426	at the C<rstatus> member of the C<ev_child> watcher structure to see	1543	at the C<rstatus> member of the C<ev_child> watcher structure to see
1427	the status word (use the macros from C<sys/wait.h> and see your systems	1544	the status word (use the macros from C<sys/wait.h> and see your systems
1428	C<waitpid> documentation). The C<rpid> member contains the pid of the	1545	C<waitpid> documentation). The C<rpid> member contains the pid of the
1429	process causing the status change.	1546	process causing the status change. C<trace> must be either C<0> (only
		1547	activate the watcher when the process terminates) or C<1> (additionally
		1548	activate the watcher when the process is stopped or continued).
1430		1549
1431	=item int pid [read-only]	1550	=item int pid [read-only]
1432		1551
1433	The process id this watcher watches out for, or C<0>, meaning any process id.	1552	The process id this watcher watches out for, or C<0>, meaning any process id.
1434		1553
…		…
1441	The process exit/trace status caused by C<rpid> (see your systems	1560	The process exit/trace status caused by C<rpid> (see your systems
1442	C<waitpid> and C<sys/wait.h> documentation for details).	1561	C<waitpid> and C<sys/wait.h> documentation for details).
1443		1562
1444	=back	1563	=back
1445		1564
1446	Example: Try to exit cleanly on SIGINT and SIGTERM.	1565	=head3 Examples
		1566
		1567	Example: C<fork()> a new process and install a child handler to wait for
		1568	its completion.
		1569
		1570	ev_child cw;
1447		1571
1448	static void	1572	static void
1449	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1573	child_cb (EV_P_ struct ev_child *w, int revents)
1450	{	1574	{
1451	ev_unloop (loop, EVUNLOOP_ALL);	1575	ev_child_stop (EV_A_ w);
		1576	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1452	}	1577	}
1453		1578
1454	struct ev_signal signal_watcher;	1579	pid_t pid = fork ();
1455	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1580
1456	ev_signal_start (loop, &sigint_cb);	1581	if (pid < 0)
		1582	// error
		1583	else if (pid == 0)
		1584	{
		1585	// the forked child executes here
		1586	exit (1);
		1587	}
		1588	else
		1589	{
		1590	ev_child_init (&cw, child_cb, pid, 0);
		1591	ev_child_start (EV_DEFAULT_ &cw);
		1592	}
1457		1593
1458		1594
1459	=head2 C<ev_stat> - did the file attributes just change?	1595	=head2 C<ev_stat> - did the file attributes just change?
1460		1596
1461	This watches a filesystem path for attribute changes. That is, it calls	1597	This watches a filesystem path for attribute changes. That is, it calls
…		…
1484	as even with OS-supported change notifications, this can be	1620	as even with OS-supported change notifications, this can be
1485	resource-intensive.	1621	resource-intensive.
1486		1622
1487	At the time of this writing, only the Linux inotify interface is	1623	At the time of this writing, only the Linux inotify interface is
1488	implemented (implementing kqueue support is left as an exercise for the	1624	implemented (implementing kqueue support is left as an exercise for the
		1625	reader, note, however, that the author sees no way of implementing ev_stat
1489	reader). Inotify will be used to give hints only and should not change the	1626	semantics with kqueue). Inotify will be used to give hints only and should
1490	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1627	not change the semantics of C<ev_stat> watchers, which means that libev
1491	to fall back to regular polling again even with inotify, but changes are	1628	sometimes needs to fall back to regular polling again even with inotify,
1492	usually detected immediately, and if the file exists there will be no	1629	but changes are usually detected immediately, and if the file exists there
1493	polling.	1630	will be no polling.
		1631
		1632	=head3 ABI Issues (Largefile Support)
		1633
		1634	Libev by default (unless the user overrides this) uses the default
		1635	compilation environment, which means that on systems with optionally
		1636	disabled large file support, you get the 32 bit version of the stat
		1637	structure. When using the library from programs that change the ABI to
		1638	use 64 bit file offsets the programs will fail. In that case you have to
		1639	compile libev with the same flags to get binary compatibility. This is
		1640	obviously the case with any flags that change the ABI, but the problem is
		1641	most noticably with ev_stat and largefile support.
1494		1642
1495	=head3 Inotify	1643	=head3 Inotify
1496		1644
1497	When C<inotify (7)> support has been compiled into libev (generally only	1645	When C<inotify (7)> support has been compiled into libev (generally only
1498	available on Linux) and present at runtime, it will be used to speed up	1646	available on Linux) and present at runtime, it will be used to speed up
1499	change detection where possible. The inotify descriptor will be created lazily	1647	change detection where possible. The inotify descriptor will be created lazily
1500	when the first C<ev_stat> watcher is being started.	1648	when the first C<ev_stat> watcher is being started.
1501		1649
1502	Inotify presense does not change the semantics of C<ev_stat> watchers	1650	Inotify presence does not change the semantics of C<ev_stat> watchers
1503	except that changes might be detected earlier, and in some cases, to avoid	1651	except that changes might be detected earlier, and in some cases, to avoid
1504	making regular C<stat> calls. Even in the presense of inotify support	1652	making regular C<stat> calls. Even in the presence of inotify support
1505	there are many cases where libev has to resort to regular C<stat> polling.	1653	there are many cases where libev has to resort to regular C<stat> polling.
1506		1654
1507	(There is no support for kqueue, as apparently it cannot be used to	1655	(There is no support for kqueue, as apparently it cannot be used to
1508	implement this functionality, due to the requirement of having a file	1656	implement this functionality, due to the requirement of having a file
1509	descriptor open on the object at all times).	1657	descriptor open on the object at all times).
…		…
1512		1660
1513	The C<stat ()> syscall only supports full-second resolution portably, and	1661	The C<stat ()> syscall only supports full-second resolution portably, and
1514	even on systems where the resolution is higher, many filesystems still	1662	even on systems where the resolution is higher, many filesystems still
1515	only support whole seconds.	1663	only support whole seconds.
1516		1664
1517	That means that, if the time is the only thing that changes, you might	1665	That means that, if the time is the only thing that changes, you can
1518	miss updates: on the first update, C<ev_stat> detects a change and calls	1666	easily miss updates: on the first update, C<ev_stat> detects a change and
1519	your callback, which does something. When there is another update within	1667	calls your callback, which does something. When there is another update
1520	the same second, C<ev_stat> will be unable to detect it.	1668	within the same second, C<ev_stat> will be unable to detect it as the stat
		1669	data does not change.
1521		1670
1522	The solution to this is to delay acting on a change for a second (or till	1671	The solution to this is to delay acting on a change for slightly more
1523	the next second boundary), using a roughly one-second delay C<ev_timer>	1672	than a second (or till slightly after the next full second boundary), using
1524	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1673	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1525	is added to work around small timing inconsistencies of some operating	1674	ev_timer_again (loop, w)>).
1526	systems.	1675
		1676	The C<.02> offset is added to work around small timing inconsistencies
		1677	of some operating systems (where the second counter of the current time
		1678	might be be delayed. One such system is the Linux kernel, where a call to
		1679	C<gettimeofday> might return a timestamp with a full second later than
		1680	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1681	update file times then there will be a small window where the kernel uses
		1682	the previous second to update file times but libev might already execute
		1683	the timer callback).
1527		1684
1528	=head3 Watcher-Specific Functions and Data Members	1685	=head3 Watcher-Specific Functions and Data Members
1529		1686
1530	=over 4	1687	=over 4
1531		1688
…		…
1537	C<path>. The C<interval> is a hint on how quickly a change is expected to	1694	C<path>. The C<interval> is a hint on how quickly a change is expected to
1538	be detected and should normally be specified as C<0> to let libev choose	1695	be detected and should normally be specified as C<0> to let libev choose
1539	a suitable value. The memory pointed to by C<path> must point to the same	1696	a suitable value. The memory pointed to by C<path> must point to the same
1540	path for as long as the watcher is active.	1697	path for as long as the watcher is active.
1541		1698
1542	The callback will be receive C<EV_STAT> when a change was detected,	1699	The callback will receive C<EV_STAT> when a change was detected, relative
1543	relative to the attributes at the time the watcher was started (or the	1700	to the attributes at the time the watcher was started (or the last change
1544	last change was detected).	1701	was detected).
1545		1702
1546	=item ev_stat_stat (ev_stat *)	1703	=item ev_stat_stat (loop, ev_stat *)
1547		1704
1548	Updates the stat buffer immediately with new values. If you change the	1705	Updates the stat buffer immediately with new values. If you change the
1549	watched path in your callback, you could call this fucntion to avoid	1706	watched path in your callback, you could call this function to avoid
1550	detecting this change (while introducing a race condition). Can also be	1707	detecting this change (while introducing a race condition if you are not
1551	useful simply to find out the new values.	1708	the only one changing the path). Can also be useful simply to find out the
		1709	new values.
1552		1710
1553	=item ev_statdata attr [read-only]	1711	=item ev_statdata attr [read-only]
1554		1712
1555	The most-recently detected attributes of the file. Although the type is of	1713	The most-recently detected attributes of the file. Although the type is
1556	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1714	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1557	suitable for your system. If the C<st_nlink> member is C<0>, then there	1715	suitable for your system, but you can only rely on the POSIX-standardised
		1716	members to be present. If the C<st_nlink> member is C<0>, then there was
1558	was some error while C<stat>ing the file.	1717	some error while C<stat>ing the file.
1559		1718
1560	=item ev_statdata prev [read-only]	1719	=item ev_statdata prev [read-only]
1561		1720
1562	The previous attributes of the file. The callback gets invoked whenever	1721	The previous attributes of the file. The callback gets invoked whenever
1563	C<prev> != C<attr>.	1722	C<prev> != C<attr>, or, more precisely, one or more of these members
		1723	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1724	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1564		1725
1565	=item ev_tstamp interval [read-only]	1726	=item ev_tstamp interval [read-only]
1566		1727
1567	The specified interval.	1728	The specified interval.
1568		1729
…		…
1622	}	1783	}
1623		1784
1624	...	1785	...
1625	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1786	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1626	ev_stat_start (loop, &passwd);	1787	ev_stat_start (loop, &passwd);
1627	ev_timer_init (&timer, timer_cb, 0., 1.01);	1788	ev_timer_init (&timer, timer_cb, 0., 1.02);
1628		1789
1629		1790
1630	=head2 C<ev_idle> - when you've got nothing better to do...	1791	=head2 C<ev_idle> - when you've got nothing better to do...
1631		1792
1632	Idle watchers trigger events when no other events of the same or higher	1793	Idle watchers trigger events when no other events of the same or higher
…		…
1658	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1819	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1659	believe me.	1820	believe me.
1660		1821
1661	=back	1822	=back
1662		1823
		1824	=head3 Examples
		1825
1663	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1826	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1664	callback, free it. Also, use no error checking, as usual.	1827	callback, free it. Also, use no error checking, as usual.
1665		1828
1666	static void	1829	static void
1667	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1830	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1668	{	1831	{
1669	free (w);	1832	free (w);
1670	// now do something you wanted to do when the program has	1833	// now do something you wanted to do when the program has
1671	// no longer asnything immediate to do.	1834	// no longer anything immediate to do.
1672	}	1835	}
1673		1836
1674	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1837	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1675	ev_idle_init (idle_watcher, idle_cb);	1838	ev_idle_init (idle_watcher, idle_cb);
1676	ev_idle_start (loop, idle_cb);	1839	ev_idle_start (loop, idle_cb);
…		…
1718		1881
1719	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1882	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1720	priority, to ensure that they are being run before any other watchers	1883	priority, to ensure that they are being run before any other watchers
1721	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1884	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1722	too) should not activate ("feed") events into libev. While libev fully	1885	too) should not activate ("feed") events into libev. While libev fully
1723	supports this, they will be called before other C<ev_check> watchers	1886	supports this, they might get executed before other C<ev_check> watchers
1724	did their job. As C<ev_check> watchers are often used to embed other	1887	did their job. As C<ev_check> watchers are often used to embed other
1725	(non-libev) event loops those other event loops might be in an unusable	1888	(non-libev) event loops those other event loops might be in an unusable
1726	state until their C<ev_check> watcher ran (always remind yourself to	1889	state until their C<ev_check> watcher ran (always remind yourself to
1727	coexist peacefully with others).	1890	coexist peacefully with others).
1728		1891
…		…
1738	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1901	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1739	macros, but using them is utterly, utterly and completely pointless.	1902	macros, but using them is utterly, utterly and completely pointless.
1740		1903
1741	=back	1904	=back
1742		1905
		1906	=head3 Examples
		1907
1743	There are a number of principal ways to embed other event loops or modules	1908	There are a number of principal ways to embed other event loops or modules
1744	into libev. Here are some ideas on how to include libadns into libev	1909	into libev. Here are some ideas on how to include libadns into libev
1745	(there is a Perl module named C<EV::ADNS> that does this, which you could	1910	(there is a Perl module named C<EV::ADNS> that does this, which you could
1746	use for an actually working example. Another Perl module named C<EV::Glib>	1911	use as a working example. Another Perl module named C<EV::Glib> embeds a
1747	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1912	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1748	into the Glib event loop).	1913	Glib event loop).
1749		1914
1750	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1915	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1751	and in a check watcher, destroy them and call into libadns. What follows	1916	and in a check watcher, destroy them and call into libadns. What follows
1752	is pseudo-code only of course. This requires you to either use a low	1917	is pseudo-code only of course. This requires you to either use a low
1753	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1918	priority for the check watcher or use C<ev_clear_pending> explicitly, as
…		…
1915	portable one.	2080	portable one.
1916		2081
1917	So when you want to use this feature you will always have to be prepared	2082	So when you want to use this feature you will always have to be prepared
1918	that you cannot get an embeddable loop. The recommended way to get around	2083	that you cannot get an embeddable loop. The recommended way to get around
1919	this is to have a separate variables for your embeddable loop, try to	2084	this is to have a separate variables for your embeddable loop, try to
1920	create it, and if that fails, use the normal loop for everything:	2085	create it, and if that fails, use the normal loop for everything.
		2086
		2087	=head3 Watcher-Specific Functions and Data Members
		2088
		2089	=over 4
		2090
		2091	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2092
		2093	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2094
		2095	Configures the watcher to embed the given loop, which must be
		2096	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2097	invoked automatically, otherwise it is the responsibility of the callback
		2098	to invoke it (it will continue to be called until the sweep has been done,
		2099	if you do not want thta, you need to temporarily stop the embed watcher).
		2100
		2101	=item ev_embed_sweep (loop, ev_embed *)
		2102
		2103	Make a single, non-blocking sweep over the embedded loop. This works
		2104	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2105	apropriate way for embedded loops.
		2106
		2107	=item struct ev_loop *other [read-only]
		2108
		2109	The embedded event loop.
		2110
		2111	=back
		2112
		2113	=head3 Examples
		2114
		2115	Example: Try to get an embeddable event loop and embed it into the default
		2116	event loop. If that is not possible, use the default loop. The default
		2117	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2118	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2119	used).
1921		2120
1922	struct ev_loop *loop_hi = ev_default_init (0);	2121	struct ev_loop *loop_hi = ev_default_init (0);
1923	struct ev_loop *loop_lo = 0;	2122	struct ev_loop *loop_lo = 0;
1924	struct ev_embed embed;	2123	struct ev_embed embed;
1925		2124
…		…
1936	ev_embed_start (loop_hi, &embed);	2135	ev_embed_start (loop_hi, &embed);
1937	}	2136	}
1938	else	2137	else
1939	loop_lo = loop_hi;	2138	loop_lo = loop_hi;
1940		2139
1941	=head3 Watcher-Specific Functions and Data Members	2140	Example: Check if kqueue is available but not recommended and create
		2141	a kqueue backend for use with sockets (which usually work with any
		2142	kqueue implementation). Store the kqueue/socket-only event loop in
		2143	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1942		2144
1943	=over 4	2145	struct ev_loop *loop = ev_default_init (0);
		2146	struct ev_loop *loop_socket = 0;
		2147	struct ev_embed embed;
		2148
		2149	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2150	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2151	{
		2152	ev_embed_init (&embed, 0, loop_socket);
		2153	ev_embed_start (loop, &embed);
		2154	}
1944		2155
1945	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2156	if (!loop_socket)
		2157	loop_socket = loop;
1946		2158
1947	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2159	// now use loop_socket for all sockets, and loop for everything else
1948
1949	Configures the watcher to embed the given loop, which must be
1950	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1951	invoked automatically, otherwise it is the responsibility of the callback
1952	to invoke it (it will continue to be called until the sweep has been done,
1953	if you do not want thta, you need to temporarily stop the embed watcher).
1954
1955	=item ev_embed_sweep (loop, ev_embed *)
1956
1957	Make a single, non-blocking sweep over the embedded loop. This works
1958	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1959	apropriate way for embedded loops.
1960
1961	=item struct ev_loop *other [read-only]
1962
1963	The embedded event loop.
1964
1965	=back
1966		2160
1967		2161
1968	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2162	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1969		2163
1970	Fork watchers are called when a C<fork ()> was detected (usually because	2164	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1986	believe me.	2180	believe me.
1987		2181
1988	=back	2182	=back
1989		2183
1990		2184
		2185	=head2 C<ev_async> - how to wake up another event loop
		2186
		2187	In general, you cannot use an C<ev_loop> from multiple threads or other
		2188	asynchronous sources such as signal handlers (as opposed to multiple event
		2189	loops - those are of course safe to use in different threads).
		2190
		2191	Sometimes, however, you need to wake up another event loop you do not
		2192	control, for example because it belongs to another thread. This is what
		2193	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2194	can signal it by calling C<ev_async_send>, which is thread- and signal
		2195	safe.
		2196
		2197	This functionality is very similar to C<ev_signal> watchers, as signals,
		2198	too, are asynchronous in nature, and signals, too, will be compressed
		2199	(i.e. the number of callback invocations may be less than the number of
		2200	C<ev_async_sent> calls).
		2201
		2202	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2203	just the default loop.
		2204
		2205	=head3 Queueing
		2206
		2207	C<ev_async> does not support queueing of data in any way. The reason
		2208	is that the author does not know of a simple (or any) algorithm for a
		2209	multiple-writer-single-reader queue that works in all cases and doesn't
		2210	need elaborate support such as pthreads.
		2211
		2212	That means that if you want to queue data, you have to provide your own
		2213	queue. But at least I can tell you would implement locking around your
		2214	queue:
		2215
		2216	=over 4
		2217
		2218	=item queueing from a signal handler context
		2219
		2220	To implement race-free queueing, you simply add to the queue in the signal
		2221	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2222	some fictitiuous SIGUSR1 handler:
		2223
		2224	static ev_async mysig;
		2225
		2226	static void
		2227	sigusr1_handler (void)
		2228	{
		2229	sometype data;
		2230
		2231	// no locking etc.
		2232	queue_put (data);
		2233	ev_async_send (EV_DEFAULT_ &mysig);
		2234	}
		2235
		2236	static void
		2237	mysig_cb (EV_P_ ev_async *w, int revents)
		2238	{
		2239	sometype data;
		2240	sigset_t block, prev;
		2241
		2242	sigemptyset (&block);
		2243	sigaddset (&block, SIGUSR1);
		2244	sigprocmask (SIG_BLOCK, &block, &prev);
		2245
		2246	while (queue_get (&data))
		2247	process (data);
		2248
		2249	if (sigismember (&prev, SIGUSR1)
		2250	sigprocmask (SIG_UNBLOCK, &block, 0);
		2251	}
		2252
		2253	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2254	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2255	either...).
		2256
		2257	=item queueing from a thread context
		2258
		2259	The strategy for threads is different, as you cannot (easily) block
		2260	threads but you can easily preempt them, so to queue safely you need to
		2261	employ a traditional mutex lock, such as in this pthread example:
		2262
		2263	static ev_async mysig;
		2264	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2265
		2266	static void
		2267	otherthread (void)
		2268	{
		2269	// only need to lock the actual queueing operation
		2270	pthread_mutex_lock (&mymutex);
		2271	queue_put (data);
		2272	pthread_mutex_unlock (&mymutex);
		2273
		2274	ev_async_send (EV_DEFAULT_ &mysig);
		2275	}
		2276
		2277	static void
		2278	mysig_cb (EV_P_ ev_async *w, int revents)
		2279	{
		2280	pthread_mutex_lock (&mymutex);
		2281
		2282	while (queue_get (&data))
		2283	process (data);
		2284
		2285	pthread_mutex_unlock (&mymutex);
		2286	}
		2287
		2288	=back
		2289
		2290
		2291	=head3 Watcher-Specific Functions and Data Members
		2292
		2293	=over 4
		2294
		2295	=item ev_async_init (ev_async *, callback)
		2296
		2297	Initialises and configures the async watcher - it has no parameters of any
		2298	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2299	believe me.
		2300
		2301	=item ev_async_send (loop, ev_async *)
		2302
		2303	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2304	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2305	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2306	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2307	section below on what exactly this means).
		2308
		2309	This call incurs the overhead of a syscall only once per loop iteration,
		2310	so while the overhead might be noticable, it doesn't apply to repeated
		2311	calls to C<ev_async_send>.
		2312
		2313	=item bool = ev_async_pending (ev_async *)
		2314
		2315	Returns a non-zero value when C<ev_async_send> has been called on the
		2316	watcher but the event has not yet been processed (or even noted) by the
		2317	event loop.
		2318
		2319	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2320	the loop iterates next and checks for the watcher to have become active,
		2321	it will reset the flag again. C<ev_async_pending> can be used to very
		2322	quickly check wether invoking the loop might be a good idea.
		2323
		2324	Not that this does I<not> check wether the watcher itself is pending, only
		2325	wether it has been requested to make this watcher pending.
		2326
		2327	=back
		2328
		2329
1991	=head1 OTHER FUNCTIONS	2330	=head1 OTHER FUNCTIONS
1992		2331
1993	There are some other functions of possible interest. Described. Here. Now.	2332	There are some other functions of possible interest. Described. Here. Now.
1994		2333
1995	=over 4	2334	=over 4
…		…
2063		2402
2064	=item * Priorities are not currently supported. Initialising priorities	2403	=item * Priorities are not currently supported. Initialising priorities
2065	will fail and all watchers will have the same priority, even though there	2404	will fail and all watchers will have the same priority, even though there
2066	is an ev_pri field.	2405	is an ev_pri field.
2067		2406
		2407	=item * In libevent, the last base created gets the signals, in libev, the
		2408	first base created (== the default loop) gets the signals.
		2409
2068	=item * Other members are not supported.	2410	=item * Other members are not supported.
2069		2411
2070	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2412	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2071	to use the libev header file and library.	2413	to use the libev header file and library.
2072		2414
…		…
2222	Example: Define a class with an IO and idle watcher, start one of them in	2564	Example: Define a class with an IO and idle watcher, start one of them in
2223	the constructor.	2565	the constructor.
2224		2566
2225	class myclass	2567	class myclass
2226	{	2568	{
2227	ev_io io; void io_cb (ev::io &w, int revents);	2569	ev::io io; void io_cb (ev::io &w, int revents);
2228	ev_idle idle void idle_cb (ev::idle &w, int revents);	2570	ev:idle idle void idle_cb (ev::idle &w, int revents);
2229		2571
2230	myclass ();	2572	myclass (int fd)
2231	}
2232
2233	myclass::myclass (int fd)
2234	{	2573	{
2235	io .set <myclass, &myclass::io_cb > (this);	2574	io .set <myclass, &myclass::io_cb > (this);
2236	idle.set <myclass, &myclass::idle_cb> (this);	2575	idle.set <myclass, &myclass::idle_cb> (this);
2237		2576
2238	io.start (fd, ev::READ);	2577	io.start (fd, ev::READ);
		2578	}
2239	}	2579	};
		2580
		2581
		2582	=head1 OTHER LANGUAGE BINDINGS
		2583
		2584	Libev does not offer other language bindings itself, but bindings for a
		2585	numbe rof languages exist in the form of third-party packages. If you know
		2586	any interesting language binding in addition to the ones listed here, drop
		2587	me a note.
		2588
		2589	=over 4
		2590
		2591	=item Perl
		2592
		2593	The EV module implements the full libev API and is actually used to test
		2594	libev. EV is developed together with libev. Apart from the EV core module,
		2595	there are additional modules that implement libev-compatible interfaces
		2596	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2597	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2598
		2599	It can be found and installed via CPAN, its homepage is found at
		2600	L<http://software.schmorp.de/pkg/EV>.
		2601
		2602	=item Ruby
		2603
		2604	Tony Arcieri has written a ruby extension that offers access to a subset
		2605	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2606	more on top of it. It can be found via gem servers. Its homepage is at
		2607	L<http://rev.rubyforge.org/>.
		2608
		2609	=item D
		2610
		2611	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2612	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2613
		2614	=back
2240		2615
2241		2616
2242	=head1 MACRO MAGIC	2617	=head1 MACRO MAGIC
2243		2618
2244	Libev can be compiled with a variety of options, the most fundamantal	2619	Libev can be compiled with a variety of options, the most fundamantal
…		…
2280		2655
2281	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2656	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2282		2657
2283	Similar to the other two macros, this gives you the value of the default	2658	Similar to the other two macros, this gives you the value of the default
2284	loop, if multiple loops are supported ("ev loop default").	2659	loop, if multiple loops are supported ("ev loop default").
		2660
		2661	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2662
		2663	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2664	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2665	is undefined when the default loop has not been initialised by a previous
		2666	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2667
		2668	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2669	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2285		2670
2286	=back	2671	=back
2287		2672
2288	Example: Declare and initialise a check watcher, utilising the above	2673	Example: Declare and initialise a check watcher, utilising the above
2289	macros so it will work regardless of whether multiple loops are supported	2674	macros so it will work regardless of whether multiple loops are supported
…		…
2385		2770
2386	libev.m4	2771	libev.m4
2387		2772
2388	=head2 PREPROCESSOR SYMBOLS/MACROS	2773	=head2 PREPROCESSOR SYMBOLS/MACROS
2389		2774
2390	Libev can be configured via a variety of preprocessor symbols you have to define	2775	Libev can be configured via a variety of preprocessor symbols you have to
2391	before including any of its files. The default is not to build for multiplicity	2776	define before including any of its files. The default in the absense of
2392	and only include the select backend.	2777	autoconf is noted for every option.
2393		2778
2394	=over 4	2779	=over 4
2395		2780
2396	=item EV_STANDALONE	2781	=item EV_STANDALONE
2397		2782
…		…
2423	=item EV_USE_NANOSLEEP	2808	=item EV_USE_NANOSLEEP
2424		2809
2425	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2810	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2426	and will use it for delays. Otherwise it will use C<select ()>.	2811	and will use it for delays. Otherwise it will use C<select ()>.
2427		2812
		2813	=item EV_USE_EVENTFD
		2814
		2815	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2816	available and will probe for kernel support at runtime. This will improve
		2817	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2818	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2819	2.7 or newer, otherwise disabled.
		2820
2428	=item EV_USE_SELECT	2821	=item EV_USE_SELECT
2429		2822
2430	If undefined or defined to be C<1>, libev will compile in support for the	2823	If undefined or defined to be C<1>, libev will compile in support for the
2431	C<select>(2) backend. No attempt at autodetection will be done: if no	2824	C<select>(2) backend. No attempt at autodetection will be done: if no
2432	other method takes over, select will be it. Otherwise the select backend	2825	other method takes over, select will be it. Otherwise the select backend
…		…
2450	be used is the winsock select). This means that it will call	2843	be used is the winsock select). This means that it will call
2451	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2844	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2452	it is assumed that all these functions actually work on fds, even	2845	it is assumed that all these functions actually work on fds, even
2453	on win32. Should not be defined on non-win32 platforms.	2846	on win32. Should not be defined on non-win32 platforms.
2454		2847
		2848	=item EV_FD_TO_WIN32_HANDLE
		2849
		2850	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2851	file descriptors to socket handles. When not defining this symbol (the
		2852	default), then libev will call C<_get_osfhandle>, which is usually
		2853	correct. In some cases, programs use their own file descriptor management,
		2854	in which case they can provide this function to map fds to socket handles.
		2855
2455	=item EV_USE_POLL	2856	=item EV_USE_POLL
2456		2857
2457	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2858	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2458	backend. Otherwise it will be enabled on non-win32 platforms. It	2859	backend. Otherwise it will be enabled on non-win32 platforms. It
2459	takes precedence over select.	2860	takes precedence over select.
2460		2861
2461	=item EV_USE_EPOLL	2862	=item EV_USE_EPOLL
2462		2863
2463	If defined to be C<1>, libev will compile in support for the Linux	2864	If defined to be C<1>, libev will compile in support for the Linux
2464	C<epoll>(7) backend. Its availability will be detected at runtime,	2865	C<epoll>(7) backend. Its availability will be detected at runtime,
2465	otherwise another method will be used as fallback. This is the	2866	otherwise another method will be used as fallback. This is the preferred
2466	preferred backend for GNU/Linux systems.	2867	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2868	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2467		2869
2468	=item EV_USE_KQUEUE	2870	=item EV_USE_KQUEUE
2469		2871
2470	If defined to be C<1>, libev will compile in support for the BSD style	2872	If defined to be C<1>, libev will compile in support for the BSD style
2471	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2873	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2490		2892
2491	=item EV_USE_INOTIFY	2893	=item EV_USE_INOTIFY
2492		2894
2493	If defined to be C<1>, libev will compile in support for the Linux inotify	2895	If defined to be C<1>, libev will compile in support for the Linux inotify
2494	interface to speed up C<ev_stat> watchers. Its actual availability will	2896	interface to speed up C<ev_stat> watchers. Its actual availability will
2495	be detected at runtime.	2897	be detected at runtime. If undefined, it will be enabled if the headers
		2898	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2899
		2900	=item EV_ATOMIC_T
		2901
		2902	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2903	access is atomic with respect to other threads or signal contexts. No such
		2904	type is easily found in the C language, so you can provide your own type
		2905	that you know is safe for your purposes. It is used both for signal handler "locking"
		2906	as well as for signal and thread safety in C<ev_async> watchers.
		2907
		2908	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2909	(from F<signal.h>), which is usually good enough on most platforms.
2496		2910
2497	=item EV_H	2911	=item EV_H
2498		2912
2499	The name of the F<ev.h> header file used to include it. The default if	2913	The name of the F<ev.h> header file used to include it. The default if
2500	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2914	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2501	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2915	used to virtually rename the F<ev.h> header file in case of conflicts.
2502		2916
2503	=item EV_CONFIG_H	2917	=item EV_CONFIG_H
2504		2918
2505	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2919	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2506	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2920	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2507	C<EV_H>, above.	2921	C<EV_H>, above.
2508		2922
2509	=item EV_EVENT_H	2923	=item EV_EVENT_H
2510		2924
2511	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2925	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2512	of how the F<event.h> header can be found.	2926	of how the F<event.h> header can be found, the default is C<"event.h">.
2513		2927
2514	=item EV_PROTOTYPES	2928	=item EV_PROTOTYPES
2515		2929
2516	If defined to be C<0>, then F<ev.h> will not define any function	2930	If defined to be C<0>, then F<ev.h> will not define any function
2517	prototypes, but still define all the structs and other symbols. This is	2931	prototypes, but still define all the structs and other symbols. This is
…		…
2568	=item EV_FORK_ENABLE	2982	=item EV_FORK_ENABLE
2569		2983
2570	If undefined or defined to be C<1>, then fork watchers are supported. If	2984	If undefined or defined to be C<1>, then fork watchers are supported. If
2571	defined to be C<0>, then they are not.	2985	defined to be C<0>, then they are not.
2572		2986
		2987	=item EV_ASYNC_ENABLE
		2988
		2989	If undefined or defined to be C<1>, then async watchers are supported. If
		2990	defined to be C<0>, then they are not.
		2991
2573	=item EV_MINIMAL	2992	=item EV_MINIMAL
2574		2993
2575	If you need to shave off some kilobytes of code at the expense of some	2994	If you need to shave off some kilobytes of code at the expense of some
2576	speed, define this symbol to C<1>. Currently only used for gcc to override	2995	speed, define this symbol to C<1>. Currently this is used to override some
2577	some inlining decisions, saves roughly 30% codesize of amd64.	2996	inlining decisions, saves roughly 30% codesize of amd64. It also selects a
		2997	much smaller 2-heap for timer management over the default 4-heap.
2578		2998
2579	=item EV_PID_HASHSIZE	2999	=item EV_PID_HASHSIZE
2580		3000
2581	C<ev_child> watchers use a small hash table to distribute workload by	3001	C<ev_child> watchers use a small hash table to distribute workload by
2582	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3002	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2588	C<ev_stat> watchers use a small hash table to distribute workload by	3008	C<ev_stat> watchers use a small hash table to distribute workload by
2589	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3009	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2590	usually more than enough. If you need to manage thousands of C<ev_stat>	3010	usually more than enough. If you need to manage thousands of C<ev_stat>
2591	watchers you might want to increase this value (I<must> be a power of	3011	watchers you might want to increase this value (I<must> be a power of
2592	two).	3012	two).
		3013
		3014	=item EV_USE_4HEAP
		3015
		3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3017	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3018	to C<1>. The 4-heap uses more complicated (longer) code but has
		3019	noticably faster performance with many (thousands) of watchers.
		3020
		3021	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3022	(disabled).
		3023
		3024	=item EV_HEAP_CACHE_AT
		3025
		3026	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3027	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3028	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3029	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3030	but avoids random read accesses on heap changes. This improves performance
		3031	noticably with with many (hundreds) of watchers.
		3032
		3033	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3034	(disabled).
2593		3035
2594	=item EV_COMMON	3036	=item EV_COMMON
2595		3037
2596	By default, all watchers have a C<void *data> member. By redefining	3038	By default, all watchers have a C<void *data> member. By redefining
2597	this macro to a something else you can include more and other types of	3039	this macro to a something else you can include more and other types of
…		…
2671		3113
2672	#include "ev_cpp.h"	3114	#include "ev_cpp.h"
2673	#include "ev.c"	3115	#include "ev.c"
2674		3116
2675		3117
		3118	=head1 THREADS AND COROUTINES
		3119
		3120	=head2 THREADS
		3121
		3122	Libev itself is completely threadsafe, but it uses no locking. This
		3123	means that you can use as many loops as you want in parallel, as long as
		3124	only one thread ever calls into one libev function with the same loop
		3125	parameter.
		3126
		3127	Or put differently: calls with different loop parameters can be done in
		3128	parallel from multiple threads, calls with the same loop parameter must be
		3129	done serially (but can be done from different threads, as long as only one
		3130	thread ever is inside a call at any point in time, e.g. by using a mutex
		3131	per loop).
		3132
		3133	If you want to know which design is best for your problem, then I cannot
		3134	help you but by giving some generic advice:
		3135
		3136	=over 4
		3137
		3138	=item * most applications have a main thread: use the default libev loop
		3139	in that thread, or create a seperate thread running only the default loop.
		3140
		3141	This helps integrating other libraries or software modules that use libev
		3142	themselves and don't care/know about threading.
		3143
		3144	=item * one loop per thread is usually a good model.
		3145
		3146	Doing this is almost never wrong, sometimes a better-performance model
		3147	exists, but it is always a good start.
		3148
		3149	=item * other models exist, such as the leader/follower pattern, where one
		3150	loop is handed through multiple threads in a kind of round-robbin fashion.
		3151
		3152	Chosing a model is hard - look around, learn, know that usually you cna do
		3153	better than you currently do :-)
		3154
		3155	=item * often you need to talk to some other thread which blocks in the
		3156	event loop - C<ev_async> watchers can be used to wake them up from other
		3157	threads safely (or from signal contexts...).
		3158
		3159	=back
		3160
		3161	=head2 COROUTINES
		3162
		3163	Libev is much more accomodating to coroutines ("cooperative threads"):
		3164	libev fully supports nesting calls to it's functions from different
		3165	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3166	different coroutines and switch freely between both coroutines running the
		3167	loop, as long as you don't confuse yourself). The only exception is that
		3168	you must not do this from C<ev_periodic> reschedule callbacks.
		3169
		3170	Care has been invested into making sure that libev does not keep local
		3171	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3172	switches.
		3173
		3174
2676	=head1 COMPLEXITIES	3175	=head1 COMPLEXITIES
2677		3176
2678	In this section the complexities of (many of) the algorithms used inside	3177	In this section the complexities of (many of) the algorithms used inside
2679	libev will be explained. For complexity discussions about backends see the	3178	libev will be explained. For complexity discussions about backends see the
2680	documentation for C<ev_default_init>.	3179	documentation for C<ev_default_init>.
…		…
2696	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3195	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2697		3196
2698	That means that changing a timer costs less than removing/adding them	3197	That means that changing a timer costs less than removing/adding them
2699	as only the relative motion in the event queue has to be paid for.	3198	as only the relative motion in the event queue has to be paid for.
2700		3199
2701	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3200	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2702		3201
2703	These just add the watcher into an array or at the head of a list.	3202	These just add the watcher into an array or at the head of a list.
2704		3203
2705	=item Stopping check/prepare/idle watchers: O(1)	3204	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2706		3205
2707	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3206	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2708		3207
2709	These watchers are stored in lists then need to be walked to find the	3208	These watchers are stored in lists then need to be walked to find the
2710	correct watcher to remove. The lists are usually short (you don't usually	3209	correct watcher to remove. The lists are usually short (you don't usually
2711	have many watchers waiting for the same fd or signal).	3210	have many watchers waiting for the same fd or signal).
2712		3211
2713	=item Finding the next timer in each loop iteration: O(1)	3212	=item Finding the next timer in each loop iteration: O(1)
2714		3213
2715	By virtue of using a binary heap, the next timer is always found at the	3214	By virtue of using a binary or 4-heap, the next timer is always found at a
2716	beginning of the storage array.	3215	fixed position in the storage array.
2717		3216
2718	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3217	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2719		3218
2720	A change means an I/O watcher gets started or stopped, which requires	3219	A change means an I/O watcher gets started or stopped, which requires
2721	libev to recalculate its status (and possibly tell the kernel, depending	3220	libev to recalculate its status (and possibly tell the kernel, depending
…		…
2726	=item Priority handling: O(number_of_priorities)	3225	=item Priority handling: O(number_of_priorities)
2727		3226
2728	Priorities are implemented by allocating some space for each	3227	Priorities are implemented by allocating some space for each
2729	priority. When doing priority-based operations, libev usually has to	3228	priority. When doing priority-based operations, libev usually has to
2730	linearly search all the priorities, but starting/stopping and activating	3229	linearly search all the priorities, but starting/stopping and activating
2731	watchers becomes O(1) w.r.t. prioritiy handling.	3230	watchers becomes O(1) w.r.t. priority handling.
		3231
		3232	=item Sending an ev_async: O(1)
		3233
		3234	=item Processing ev_async_send: O(number_of_async_watchers)
		3235
		3236	=item Processing signals: O(max_signal_number)
		3237
		3238	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3239	calls in the current loop iteration. Checking for async and signal events
		3240	involves iterating over all running async watchers or all signal numbers.
2732		3241
2733	=back	3242	=back
2734		3243
2735		3244
		3245	=head1 Win32 platform limitations and workarounds
		3246
		3247	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3248	requires, and its I/O model is fundamentally incompatible with the POSIX
		3249	model. Libev still offers limited functionality on this platform in
		3250	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3251	descriptors. This only applies when using Win32 natively, not when using
		3252	e.g. cygwin.
		3253
		3254	Lifting these limitations would basically require the full
		3255	re-implementation of the I/O system. If you are into these kinds of
		3256	things, then note that glib does exactly that for you in a very portable
		3257	way (note also that glib is the slowest event library known to man).
		3258
		3259	There is no supported compilation method available on windows except
		3260	embedding it into other applications.
		3261
		3262	Due to the many, low, and arbitrary limits on the win32 platform and
		3263	the abysmal performance of winsockets, using a large number of sockets
		3264	is not recommended (and not reasonable). If your program needs to use
		3265	more than a hundred or so sockets, then likely it needs to use a totally
		3266	different implementation for windows, as libev offers the POSIX readiness
		3267	notification model, which cannot be implemented efficiently on windows
		3268	(microsoft monopoly games).
		3269
		3270	=over 4
		3271
		3272	=item The winsocket select function
		3273
		3274	The winsocket C<select> function doesn't follow POSIX in that it requires
		3275	socket I<handles> and not socket I<file descriptors>. This makes select
		3276	very inefficient, and also requires a mapping from file descriptors
		3277	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3278	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3279	symbols for more info.
		3280
		3281	The configuration for a "naked" win32 using the microsoft runtime
		3282	libraries and raw winsocket select is:
		3283
		3284	#define EV_USE_SELECT 1
		3285	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3286
		3287	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3288	complexity in the O(n²) range when using win32.
		3289
		3290	=item Limited number of file descriptors
		3291
		3292	Windows has numerous arbitrary (and low) limits on things.
		3293
		3294	Early versions of winsocket's select only supported waiting for a maximum
		3295	of C<64> handles (probably owning to the fact that all windows kernels
		3296	can only wait for C<64> things at the same time internally; microsoft
		3297	recommends spawning a chain of threads and wait for 63 handles and the
		3298	previous thread in each. Great).
		3299
		3300	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3301	to some high number (e.g. C<2048>) before compiling the winsocket select
		3302	call (which might be in libev or elsewhere, for example, perl does its own
		3303	select emulation on windows).
		3304
		3305	Another limit is the number of file descriptors in the microsoft runtime
		3306	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3307	or something like this inside microsoft). You can increase this by calling
		3308	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3309	arbitrary limit), but is broken in many versions of the microsoft runtime
		3310	libraries.
		3311
		3312	This might get you to about C<512> or C<2048> sockets (depending on
		3313	windows version and/or the phase of the moon). To get more, you need to
		3314	wrap all I/O functions and provide your own fd management, but the cost of
		3315	calling select (O(n²)) will likely make this unworkable.
		3316
		3317	=back
		3318
		3319
		3320	=head1 PORTABILITY REQUIREMENTS
		3321
		3322	In addition to a working ISO-C implementation, libev relies on a few
		3323	additional extensions:
		3324
		3325	=over 4
		3326
		3327	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3328
		3329	The type C<sig_atomic_t volatile> (or whatever is defined as
		3330	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3331	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3332	believed to be sufficiently portable.
		3333
		3334	=item C<sigprocmask> must work in a threaded environment
		3335
		3336	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3337	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3338	pthread implementations will either allow C<sigprocmask> in the "main
		3339	thread" or will block signals process-wide, both behaviours would
		3340	be compatible with libev. Interaction between C<sigprocmask> and
		3341	C<pthread_sigmask> could complicate things, however.
		3342
		3343	The most portable way to handle signals is to block signals in all threads
		3344	except the initial one, and run the default loop in the initial thread as
		3345	well.
		3346
		3347	=item C<long> must be large enough for common memory allocation sizes
		3348
		3349	To improve portability and simplify using libev, libev uses C<long>
		3350	internally instead of C<size_t> when allocating its data structures. On
		3351	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3352	is still at least 31 bits everywhere, which is enough for hundreds of
		3353	millions of watchers.
		3354
		3355	=item C<double> must hold a time value in seconds with enough accuracy
		3356
		3357	The type C<double> is used to represent timestamps. It is required to
		3358	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3359	enough for at least into the year 4000. This requirement is fulfilled by
		3360	implementations implementing IEEE 754 (basically all existing ones).
		3361
		3362	=back
		3363
		3364	If you know of other additional requirements drop me a note.
		3365
		3366
		3367	=head1 VALGRIND
		3368
		3369	Valgrind has a special section here because it is a popular tool that is
		3370	highly useful, but valgrind reports are very hard to interpret.
		3371
		3372	If you think you found a bug (memory leak, uninitialised data access etc.)
		3373	in libev, then check twice: If valgrind reports something like:
		3374
		3375	==2274== definitely lost: 0 bytes in 0 blocks.
		3376	==2274== possibly lost: 0 bytes in 0 blocks.
		3377	==2274== still reachable: 256 bytes in 1 blocks.
		3378
		3379	then there is no memory leak. Similarly, under some circumstances,
		3380	valgrind might report kernel bugs as if it were a bug in libev, or it
		3381	might be confused (it is a very good tool, but only a tool).
		3382
		3383	If you are unsure about something, feel free to contact the mailing list
		3384	with the full valgrind report and an explanation on why you think this is
		3385	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3386	no bug" answer and take the chance of learning how to interpret valgrind
		3387	properly.
		3388
		3389	If you need, for some reason, empty reports from valgrind for your project
		3390	I suggest using suppression lists.
		3391
		3392
2736	=head1 AUTHOR	3393	=head1 AUTHOR
2737		3394
2738	Marc Lehmann <libev@schmorp.de>.	3395	Marc Lehmann <libev@schmorp.de>.
2739		3396

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