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Revision 1.111 by root, Tue Dec 25 18:01:20 2007 UTC vs.
Revision 1.159 by root, Thu May 22 02:44:57 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;
…		…
648	Many (busy) programs can usually benefit by setting the io collect	688	Many (busy) programs can usually benefit by setting the io collect
649	interval to a value near C<0.1> or so, which is often enough for	689	interval to a value near C<0.1> or so, which is often enough for
650	interactive servers (of course not for games), likewise for timeouts. It	690	interactive servers (of course not for games), likewise for timeouts. It
651	usually doesn't make much sense to set it to a lower value than C<0.01>,	691	usually doesn't make much sense to set it to a lower value than C<0.01>,
652	as this approsaches the timing granularity of most systems.	692	as this approsaches the timing granularity of most systems.
		693
		694	=item ev_loop_verify (loop)
		695
		696	This function only does something when C<EV_VERIFY> support has been
		697	compiled in. It tries to go through all internal structures and checks
		698	them for validity. If anything is found to be inconsistent, it will print
		699	an error message to standard error and call C<abort ()>.
		700
		701	This can be used to catch bugs inside libev itself: under normal
		702	circumstances, this function will never abort as of course libev keeps its
		703	data structures consistent.
653		704
654	=back	705	=back
655		706
656		707
657	=head1 ANATOMY OF A WATCHER	708	=head1 ANATOMY OF A WATCHER
…		…
756		807
757	=item C<EV_FORK>	808	=item C<EV_FORK>
758		809
759	The event loop has been resumed in the child process after fork (see	810	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	811	C<ev_fork>).
		812
		813	=item C<EV_ASYNC>
		814
		815	The given async watcher has been asynchronously notified (see C<ev_async>).
761		816
762	=item C<EV_ERROR>	817	=item C<EV_ERROR>
763		818
764	An unspecified error has occured, the watcher has been stopped. This might	819	An unspecified error has occured, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	820	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	1043	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	1044	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
990	C<EVBACKEND_POLL>).	1045	C<EVBACKEND_POLL>).
991		1046
992	Another thing you have to watch out for is that it is quite easy to	1047	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	1048	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	1049	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	1050	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	1051	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	1052	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	1053	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	1100	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,	1101	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	1102	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1048	C<EVBACKEND_POLL>.	1103	C<EVBACKEND_POLL>.
1049		1104
		1105	=head3 The special problem of SIGPIPE
		1106
		1107	While not really specific to libev, it is easy to forget about SIGPIPE:
		1108	when reading from a pipe whose other end has been closed, your program
		1109	gets send a SIGPIPE, which, by default, aborts your program. For most
		1110	programs this is sensible behaviour, for daemons, this is usually
		1111	undesirable.
		1112
		1113	So when you encounter spurious, unexplained daemon exits, make sure you
		1114	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1115	somewhere, as that would have given you a big clue).
		1116
1050		1117
1051	=head3 Watcher-Specific Functions	1118	=head3 Watcher-Specific Functions
1052		1119
1053	=over 4	1120	=over 4
1054		1121
…		…
1095		1162
1096	Timer watchers are simple relative timers that generate an event after a	1163	Timer watchers are simple relative timers that generate an event after a
1097	given time, and optionally repeating in regular intervals after that.	1164	given time, and optionally repeating in regular intervals after that.
1098		1165
1099	The timers are based on real time, that is, if you register an event that	1166	The timers are based on real time, that is, if you register an event that
1100	times out after an hour and you reset your system clock to last years	1167	times out after an hour and you reset your system clock to january last
1101	time, it will still time out after (roughly) and hour. "Roughly" because	1168	year, it will still time out after (roughly) and hour. "Roughly" because
1102	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1169	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1103	monotonic clock option helps a lot here).	1170	monotonic clock option helps a lot here).
1104		1171
1105	The relative timeouts are calculated relative to the C<ev_now ()>	1172	The relative timeouts are calculated relative to the C<ev_now ()>
1106	time. This is usually the right thing as this timestamp refers to the time	1173	time. This is usually the right thing as this timestamp refers to the time
…		…
1108	you suspect event processing to be delayed and you I<need> to base the timeout	1175	you suspect event processing to be delayed and you I<need> to base the timeout
1109	on the current time, use something like this to adjust for this:	1176	on the current time, use something like this to adjust for this:
1110		1177
1111	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1178	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1112		1179
1113	The callback is guarenteed to be invoked only when its timeout has passed,	1180	The callback is guarenteed to be invoked only after its timeout has passed,
1114	but if multiple timers become ready during the same loop iteration then	1181	but if multiple timers become ready during the same loop iteration then
1115	order of execution is undefined.	1182	order of execution is undefined.
1116		1183
1117	=head3 Watcher-Specific Functions and Data Members	1184	=head3 Watcher-Specific Functions and Data Members
1118		1185
…		…
1120		1187
1121	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1188	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1122		1189
1123	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1190	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1124		1191
1125	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1192	Configure the timer to trigger after C<after> seconds. If C<repeat>
1126	C<0.>, then it will automatically be stopped. If it is positive, then the	1193	is C<0.>, then it will automatically be stopped once the timeout is
1127	timer will automatically be configured to trigger again C<repeat> seconds	1194	reached. If it is positive, then the timer will automatically be
1128	later, again, and again, until stopped manually.	1195	configured to trigger again C<repeat> seconds later, again, and again,
		1196	until stopped manually.
1129		1197
1130	The timer itself will do a best-effort at avoiding drift, that is, if you	1198	The timer itself will do a best-effort at avoiding drift, that is, if
1131	configure a timer to trigger every 10 seconds, then it will trigger at	1199	you configure a timer to trigger every 10 seconds, then it will normally
1132	exactly 10 second intervals. If, however, your program cannot keep up with	1200	trigger at exactly 10 second intervals. If, however, your program cannot
1133	the timer (because it takes longer than those 10 seconds to do stuff) the	1201	keep up with the timer (because it takes longer than those 10 seconds to
1134	timer will not fire more than once per event loop iteration.	1202	do stuff) the timer will not fire more than once per event loop iteration.
1135		1203
1136	=item ev_timer_again (loop)	1204	=item ev_timer_again (loop, ev_timer *)
1137		1205
1138	This will act as if the timer timed out and restart it again if it is	1206	This will act as if the timer timed out and restart it again if it is
1139	repeating. The exact semantics are:	1207	repeating. The exact semantics are:
1140		1208
1141	If the timer is pending, its pending status is cleared.	1209	If the timer is pending, its pending status is cleared.
…		…
1216	Periodic watchers are also timers of a kind, but they are very versatile	1284	Periodic watchers are also timers of a kind, but they are very versatile
1217	(and unfortunately a bit complex).	1285	(and unfortunately a bit complex).
1218		1286
1219	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1287	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1220	but on wallclock time (absolute time). You can tell a periodic watcher	1288	but on wallclock time (absolute time). You can tell a periodic watcher
1221	to trigger "at" some specific point in time. For example, if you tell a	1289	to trigger after some specific point in time. For example, if you tell a
1222	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1290	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1223	+ 10.>) and then reset your system clock to the last year, then it will	1291	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1292	clock to january of the previous year, then it will take more than year
1224	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1293	to trigger the event (unlike an C<ev_timer>, which would still trigger
1225	roughly 10 seconds later).	1294	roughly 10 seconds later as it uses a relative timeout).
1226		1295
1227	They can also be used to implement vastly more complex timers, such as	1296	C<ev_periodic>s can also be used to implement vastly more complex timers,
1228	triggering an event on each midnight, local time or other, complicated,	1297	such as triggering an event on each "midnight, local time", or other
1229	rules.	1298	complicated, rules.
1230		1299
1231	As with timers, the callback is guarenteed to be invoked only when the	1300	As with timers, the callback is guarenteed to be invoked only when the
1232	time (C<at>) has been passed, but if multiple periodic timers become ready	1301	time (C<at>) has passed, but if multiple periodic timers become ready
1233	during the same loop iteration then order of execution is undefined.	1302	during the same loop iteration then order of execution is undefined.
1234		1303
1235	=head3 Watcher-Specific Functions and Data Members	1304	=head3 Watcher-Specific Functions and Data Members
1236		1305
1237	=over 4	1306	=over 4
…		…
1245		1314
1246	=over 4	1315	=over 4
1247		1316
1248	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1317	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1249		1318
1250	In this configuration the watcher triggers an event at the wallclock time	1319	In this configuration the watcher triggers an event after the wallclock
1251	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1320	time C<at> has passed and doesn't repeat. It will not adjust when a time
1252	that is, if it is to be run at January 1st 2011 then it will run when the	1321	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1253	system time reaches or surpasses this time.	1322	run when the system time reaches or surpasses this time.
1254		1323
1255	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1324	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1256		1325
1257	In this mode the watcher will always be scheduled to time out at the next	1326	In this mode the watcher will always be scheduled to time out at the next
1258	C<at + N * interval> time (for some integer N, which can also be negative)	1327	C<at + N * interval> time (for some integer N, which can also be negative)
1259	and then repeat, regardless of any time jumps.	1328	and then repeat, regardless of any time jumps.
1260		1329
1261	This can be used to create timers that do not drift with respect to system	1330	This can be used to create timers that do not drift with respect to system
1262	time:	1331	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1332	the hour:
1263		1333
1264	ev_periodic_set (&periodic, 0., 3600., 0);	1334	ev_periodic_set (&periodic, 0., 3600., 0);
1265		1335
1266	This doesn't mean there will always be 3600 seconds in between triggers,	1336	This doesn't mean there will always be 3600 seconds in between triggers,
1267	but only that the the callback will be called when the system time shows a	1337	but only that the the callback will be called when the system time shows a
…		…
1272	C<ev_periodic> will try to run the callback in this mode at the next possible	1342	C<ev_periodic> will try to run the callback in this mode at the next possible
1273	time where C<time = at (mod interval)>, regardless of any time jumps.	1343	time where C<time = at (mod interval)>, regardless of any time jumps.
1274		1344
1275	For numerical stability it is preferable that the C<at> value is near	1345	For numerical stability it is preferable that the C<at> value is near
1276	C<ev_now ()> (the current time), but there is no range requirement for	1346	C<ev_now ()> (the current time), but there is no range requirement for
1277	this value.	1347	this value, and in fact is often specified as zero.
		1348
		1349	Note also that there is an upper limit to how often a timer can fire (cpu
		1350	speed for example), so if C<interval> is very small then timing stability
		1351	will of course detoriate. Libev itself tries to be exact to be about one
		1352	millisecond (if the OS supports it and the machine is fast enough).
1278		1353
1279	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1354	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1280		1355
1281	In this mode the values for C<interval> and C<at> are both being	1356	In this mode the values for C<interval> and C<at> are both being
1282	ignored. Instead, each time the periodic watcher gets scheduled, the	1357	ignored. Instead, each time the periodic watcher gets scheduled, the
1283	reschedule callback will be called with the watcher as first, and the	1358	reschedule callback will be called with the watcher as first, and the
1284	current time as second argument.	1359	current time as second argument.
1285		1360
1286	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1361	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1287	ever, or make any event loop modifications>. If you need to stop it,	1362	ever, or make ANY event loop modifications whatsoever>.
1288	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1289	starting an C<ev_prepare> watcher, which is legal).
1290		1363
		1364	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1365	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1366	only event loop modification you are allowed to do).
		1367
1291	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1368	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1292	ev_tstamp now)>, e.g.:	1369	*w, ev_tstamp now)>, e.g.:
1293		1370
1294	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1371	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1295	{	1372	{
1296	return now + 60.;	1373	return now + 60.;
1297	}	1374	}
…		…
1299	It must return the next time to trigger, based on the passed time value	1376	It must return the next time to trigger, based on the passed time value
1300	(that is, the lowest time value larger than to the second argument). It	1377	(that is, the lowest time value larger than to the second argument). It
1301	will usually be called just before the callback will be triggered, but	1378	will usually be called just before the callback will be triggered, but
1302	might be called at other times, too.	1379	might be called at other times, too.
1303		1380
1304	NOTE: I<< This callback must always return a time that is later than the	1381	NOTE: I<< This callback must always return a time that is higher than or
1305	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1382	equal to the passed C<now> value >>.
1306		1383
1307	This can be used to create very complex timers, such as a timer that	1384	This can be used to create very complex timers, such as a timer that
1308	triggers on each midnight, local time. To do this, you would calculate the	1385	triggers on "next midnight, local time". To do this, you would calculate the
1309	next midnight after C<now> and return the timestamp value for this. How	1386	next midnight after C<now> and return the timestamp value for this. How
1310	you do this is, again, up to you (but it is not trivial, which is the main	1387	you do this is, again, up to you (but it is not trivial, which is the main
1311	reason I omitted it as an example).	1388	reason I omitted it as an example).
1312		1389
1313	=back	1390	=back
…		…
1317	Simply stops and restarts the periodic watcher again. This is only useful	1394	Simply stops and restarts the periodic watcher again. This is only useful
1318	when you changed some parameters or the reschedule callback would return	1395	when you changed some parameters or the reschedule callback would return
1319	a different time than the last time it was called (e.g. in a crond like	1396	a different time than the last time it was called (e.g. in a crond like
1320	program when the crontabs have changed).	1397	program when the crontabs have changed).
1321		1398
		1399	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1400
		1401	When active, returns the absolute time that the watcher is supposed to
		1402	trigger next.
		1403
1322	=item ev_tstamp offset [read-write]	1404	=item ev_tstamp offset [read-write]
1323		1405
1324	When repeating, this contains the offset value, otherwise this is the	1406	When repeating, this contains the offset value, otherwise this is the
1325	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1407	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1326		1408
…		…
1336	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1418	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
1337		1419
1338	The current reschedule callback, or C<0>, if this functionality is	1420	The current reschedule callback, or C<0>, if this functionality is
1339	switched off. Can be changed any time, but changes only take effect when	1421	switched off. Can be changed any time, but changes only take effect when
1340	the periodic timer fires or C<ev_periodic_again> is being called.	1422	the periodic timer fires or C<ev_periodic_again> is being called.
1341
1342	=item ev_tstamp at [read-only]
1343
1344	When active, contains the absolute time that the watcher is supposed to
1345	trigger next.
1346		1423
1347	=back	1424	=back
1348		1425
1349	=head3 Examples	1426	=head3 Examples
1350		1427
…		…
1394	with the kernel (thus it coexists with your own signal handlers as long	1471	with the kernel (thus it coexists with your own signal handlers as long
1395	as you don't register any with libev). Similarly, when the last signal	1472	as you don't register any with libev). Similarly, when the last signal
1396	watcher for a signal is stopped libev will reset the signal handler to	1473	watcher for a signal is stopped libev will reset the signal handler to
1397	SIG_DFL (regardless of what it was set to before).	1474	SIG_DFL (regardless of what it was set to before).
1398		1475
		1476	If possible and supported, libev will install its handlers with
		1477	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1478	interrupted. If you have a problem with syscalls getting interrupted by
		1479	signals you can block all signals in an C<ev_check> watcher and unblock
		1480	them in an C<ev_prepare> watcher.
		1481
1399	=head3 Watcher-Specific Functions and Data Members	1482	=head3 Watcher-Specific Functions and Data Members
1400		1483
1401	=over 4	1484	=over 4
1402		1485
1403	=item ev_signal_init (ev_signal *, callback, int signum)	1486	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1411		1494
1412	The signal the watcher watches out for.	1495	The signal the watcher watches out for.
1413		1496
1414	=back	1497	=back
1415		1498
		1499	=head3 Examples
		1500
		1501	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1502
		1503	static void
		1504	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1505	{
		1506	ev_unloop (loop, EVUNLOOP_ALL);
		1507	}
		1508
		1509	struct ev_signal signal_watcher;
		1510	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1511	ev_signal_start (loop, &sigint_cb);
		1512
1416		1513
1417	=head2 C<ev_child> - watch out for process status changes	1514	=head2 C<ev_child> - watch out for process status changes
1418		1515
1419	Child watchers trigger when your process receives a SIGCHLD in response to	1516	Child watchers trigger when your process receives a SIGCHLD in response to
1420	some child status changes (most typically when a child of yours dies).	1517	some child status changes (most typically when a child of yours dies). It
		1518	is permissible to install a child watcher I<after> the child has been
		1519	forked (which implies it might have already exited), as long as the event
		1520	loop isn't entered (or is continued from a watcher).
		1521
		1522	Only the default event loop is capable of handling signals, and therefore
		1523	you can only rgeister child watchers in the default event loop.
		1524
		1525	=head3 Process Interaction
		1526
		1527	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1528	initialised. This is necessary to guarantee proper behaviour even if
		1529	the first child watcher is started after the child exits. The occurance
		1530	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1531	synchronously as part of the event loop processing. Libev always reaps all
		1532	children, even ones not watched.
		1533
		1534	=head3 Overriding the Built-In Processing
		1535
		1536	Libev offers no special support for overriding the built-in child
		1537	processing, but if your application collides with libev's default child
		1538	handler, you can override it easily by installing your own handler for
		1539	C<SIGCHLD> after initialising the default loop, and making sure the
		1540	default loop never gets destroyed. You are encouraged, however, to use an
		1541	event-based approach to child reaping and thus use libev's support for
		1542	that, so other libev users can use C<ev_child> watchers freely.
1421		1543
1422	=head3 Watcher-Specific Functions and Data Members	1544	=head3 Watcher-Specific Functions and Data Members
1423		1545
1424	=over 4	1546	=over 4
1425		1547
1426	=item ev_child_init (ev_child *, callback, int pid)	1548	=item ev_child_init (ev_child *, callback, int pid, int trace)
1427		1549
1428	=item ev_child_set (ev_child *, int pid)	1550	=item ev_child_set (ev_child *, int pid, int trace)
1429		1551
1430	Configures the watcher to wait for status changes of process C<pid> (or	1552	Configures the watcher to wait for status changes of process C<pid> (or
1431	I<any> process if C<pid> is specified as C<0>). The callback can look	1553	I<any> process if C<pid> is specified as C<0>). The callback can look
1432	at the C<rstatus> member of the C<ev_child> watcher structure to see	1554	at the C<rstatus> member of the C<ev_child> watcher structure to see
1433	the status word (use the macros from C<sys/wait.h> and see your systems	1555	the status word (use the macros from C<sys/wait.h> and see your systems
1434	C<waitpid> documentation). The C<rpid> member contains the pid of the	1556	C<waitpid> documentation). The C<rpid> member contains the pid of the
1435	process causing the status change.	1557	process causing the status change. C<trace> must be either C<0> (only
		1558	activate the watcher when the process terminates) or C<1> (additionally
		1559	activate the watcher when the process is stopped or continued).
1436		1560
1437	=item int pid [read-only]	1561	=item int pid [read-only]
1438		1562
1439	The process id this watcher watches out for, or C<0>, meaning any process id.	1563	The process id this watcher watches out for, or C<0>, meaning any process id.
1440		1564
…		…
1449		1573
1450	=back	1574	=back
1451		1575
1452	=head3 Examples	1576	=head3 Examples
1453		1577
1454	Example: Try to exit cleanly on SIGINT and SIGTERM.	1578	Example: C<fork()> a new process and install a child handler to wait for
		1579	its completion.
		1580
		1581	ev_child cw;
1455		1582
1456	static void	1583	static void
1457	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1584	child_cb (EV_P_ struct ev_child *w, int revents)
1458	{	1585	{
1459	ev_unloop (loop, EVUNLOOP_ALL);	1586	ev_child_stop (EV_A_ w);
		1587	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1460	}	1588	}
1461		1589
1462	struct ev_signal signal_watcher;	1590	pid_t pid = fork ();
1463	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1591
1464	ev_signal_start (loop, &sigint_cb);	1592	if (pid < 0)
		1593	// error
		1594	else if (pid == 0)
		1595	{
		1596	// the forked child executes here
		1597	exit (1);
		1598	}
		1599	else
		1600	{
		1601	ev_child_init (&cw, child_cb, pid, 0);
		1602	ev_child_start (EV_DEFAULT_ &cw);
		1603	}
1465		1604
1466		1605
1467	=head2 C<ev_stat> - did the file attributes just change?	1606	=head2 C<ev_stat> - did the file attributes just change?
1468		1607
1469	This watches a filesystem path for attribute changes. That is, it calls	1608	This watches a filesystem path for attribute changes. That is, it calls
…		…
1492	as even with OS-supported change notifications, this can be	1631	as even with OS-supported change notifications, this can be
1493	resource-intensive.	1632	resource-intensive.
1494		1633
1495	At the time of this writing, only the Linux inotify interface is	1634	At the time of this writing, only the Linux inotify interface is
1496	implemented (implementing kqueue support is left as an exercise for the	1635	implemented (implementing kqueue support is left as an exercise for the
		1636	reader, note, however, that the author sees no way of implementing ev_stat
1497	reader). Inotify will be used to give hints only and should not change the	1637	semantics with kqueue). Inotify will be used to give hints only and should
1498	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1638	not change the semantics of C<ev_stat> watchers, which means that libev
1499	to fall back to regular polling again even with inotify, but changes are	1639	sometimes needs to fall back to regular polling again even with inotify,
1500	usually detected immediately, and if the file exists there will be no	1640	but changes are usually detected immediately, and if the file exists there
1501	polling.	1641	will be no polling.
		1642
		1643	=head3 ABI Issues (Largefile Support)
		1644
		1645	Libev by default (unless the user overrides this) uses the default
		1646	compilation environment, which means that on systems with optionally
		1647	disabled large file support, you get the 32 bit version of the stat
		1648	structure. When using the library from programs that change the ABI to
		1649	use 64 bit file offsets the programs will fail. In that case you have to
		1650	compile libev with the same flags to get binary compatibility. This is
		1651	obviously the case with any flags that change the ABI, but the problem is
		1652	most noticably with ev_stat and largefile support.
1502		1653
1503	=head3 Inotify	1654	=head3 Inotify
1504		1655
1505	When C<inotify (7)> support has been compiled into libev (generally only	1656	When C<inotify (7)> support has been compiled into libev (generally only
1506	available on Linux) and present at runtime, it will be used to speed up	1657	available on Linux) and present at runtime, it will be used to speed up
1507	change detection where possible. The inotify descriptor will be created lazily	1658	change detection where possible. The inotify descriptor will be created lazily
1508	when the first C<ev_stat> watcher is being started.	1659	when the first C<ev_stat> watcher is being started.
1509		1660
1510	Inotify presense does not change the semantics of C<ev_stat> watchers	1661	Inotify presence does not change the semantics of C<ev_stat> watchers
1511	except that changes might be detected earlier, and in some cases, to avoid	1662	except that changes might be detected earlier, and in some cases, to avoid
1512	making regular C<stat> calls. Even in the presense of inotify support	1663	making regular C<stat> calls. Even in the presence of inotify support
1513	there are many cases where libev has to resort to regular C<stat> polling.	1664	there are many cases where libev has to resort to regular C<stat> polling.
1514		1665
1515	(There is no support for kqueue, as apparently it cannot be used to	1666	(There is no support for kqueue, as apparently it cannot be used to
1516	implement this functionality, due to the requirement of having a file	1667	implement this functionality, due to the requirement of having a file
1517	descriptor open on the object at all times).	1668	descriptor open on the object at all times).
…		…
1520		1671
1521	The C<stat ()> syscall only supports full-second resolution portably, and	1672	The C<stat ()> syscall only supports full-second resolution portably, and
1522	even on systems where the resolution is higher, many filesystems still	1673	even on systems where the resolution is higher, many filesystems still
1523	only support whole seconds.	1674	only support whole seconds.
1524		1675
1525	That means that, if the time is the only thing that changes, you might	1676	That means that, if the time is the only thing that changes, you can
1526	miss updates: on the first update, C<ev_stat> detects a change and calls	1677	easily miss updates: on the first update, C<ev_stat> detects a change and
1527	your callback, which does something. When there is another update within	1678	calls your callback, which does something. When there is another update
1528	the same second, C<ev_stat> will be unable to detect it.	1679	within the same second, C<ev_stat> will be unable to detect it as the stat
		1680	data does not change.
1529		1681
1530	The solution to this is to delay acting on a change for a second (or till	1682	The solution to this is to delay acting on a change for slightly more
1531	the next second boundary), using a roughly one-second delay C<ev_timer>	1683	than a second (or till slightly after the next full second boundary), using
1532	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1684	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1533	is added to work around small timing inconsistencies of some operating	1685	ev_timer_again (loop, w)>).
1534	systems.	1686
		1687	The C<.02> offset is added to work around small timing inconsistencies
		1688	of some operating systems (where the second counter of the current time
		1689	might be be delayed. One such system is the Linux kernel, where a call to
		1690	C<gettimeofday> might return a timestamp with a full second later than
		1691	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1692	update file times then there will be a small window where the kernel uses
		1693	the previous second to update file times but libev might already execute
		1694	the timer callback).
1535		1695
1536	=head3 Watcher-Specific Functions and Data Members	1696	=head3 Watcher-Specific Functions and Data Members
1537		1697
1538	=over 4	1698	=over 4
1539		1699
…		…
1545	C<path>. The C<interval> is a hint on how quickly a change is expected to	1705	C<path>. The C<interval> is a hint on how quickly a change is expected to
1546	be detected and should normally be specified as C<0> to let libev choose	1706	be detected and should normally be specified as C<0> to let libev choose
1547	a suitable value. The memory pointed to by C<path> must point to the same	1707	a suitable value. The memory pointed to by C<path> must point to the same
1548	path for as long as the watcher is active.	1708	path for as long as the watcher is active.
1549		1709
1550	The callback will be receive C<EV_STAT> when a change was detected,	1710	The callback will receive C<EV_STAT> when a change was detected, relative
1551	relative to the attributes at the time the watcher was started (or the	1711	to the attributes at the time the watcher was started (or the last change
1552	last change was detected).	1712	was detected).
1553		1713
1554	=item ev_stat_stat (ev_stat *)	1714	=item ev_stat_stat (loop, ev_stat *)
1555		1715
1556	Updates the stat buffer immediately with new values. If you change the	1716	Updates the stat buffer immediately with new values. If you change the
1557	watched path in your callback, you could call this fucntion to avoid	1717	watched path in your callback, you could call this function to avoid
1558	detecting this change (while introducing a race condition). Can also be	1718	detecting this change (while introducing a race condition if you are not
1559	useful simply to find out the new values.	1719	the only one changing the path). Can also be useful simply to find out the
		1720	new values.
1560		1721
1561	=item ev_statdata attr [read-only]	1722	=item ev_statdata attr [read-only]
1562		1723
1563	The most-recently detected attributes of the file. Although the type is of	1724	The most-recently detected attributes of the file. Although the type is
1564	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1725	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1565	suitable for your system. If the C<st_nlink> member is C<0>, then there	1726	suitable for your system, but you can only rely on the POSIX-standardised
		1727	members to be present. If the C<st_nlink> member is C<0>, then there was
1566	was some error while C<stat>ing the file.	1728	some error while C<stat>ing the file.
1567		1729
1568	=item ev_statdata prev [read-only]	1730	=item ev_statdata prev [read-only]
1569		1731
1570	The previous attributes of the file. The callback gets invoked whenever	1732	The previous attributes of the file. The callback gets invoked whenever
1571	C<prev> != C<attr>.	1733	C<prev> != C<attr>, or, more precisely, one or more of these members
		1734	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1735	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1572		1736
1573	=item ev_tstamp interval [read-only]	1737	=item ev_tstamp interval [read-only]
1574		1738
1575	The specified interval.	1739	The specified interval.
1576		1740
…		…
1630	}	1794	}
1631		1795
1632	...	1796	...
1633	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1797	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1634	ev_stat_start (loop, &passwd);	1798	ev_stat_start (loop, &passwd);
1635	ev_timer_init (&timer, timer_cb, 0., 1.01);	1799	ev_timer_init (&timer, timer_cb, 0., 1.02);
1636		1800
1637		1801
1638	=head2 C<ev_idle> - when you've got nothing better to do...	1802	=head2 C<ev_idle> - when you've got nothing better to do...
1639		1803
1640	Idle watchers trigger events when no other events of the same or higher	1804	Idle watchers trigger events when no other events of the same or higher
…		…
1676	static void	1840	static void
1677	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1841	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1678	{	1842	{
1679	free (w);	1843	free (w);
1680	// now do something you wanted to do when the program has	1844	// now do something you wanted to do when the program has
1681	// no longer asnything immediate to do.	1845	// no longer anything immediate to do.
1682	}	1846	}
1683		1847
1684	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1848	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1685	ev_idle_init (idle_watcher, idle_cb);	1849	ev_idle_init (idle_watcher, idle_cb);
1686	ev_idle_start (loop, idle_cb);	1850	ev_idle_start (loop, idle_cb);
…		…
1728		1892
1729	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1893	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1730	priority, to ensure that they are being run before any other watchers	1894	priority, to ensure that they are being run before any other watchers
1731	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1895	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1732	too) should not activate ("feed") events into libev. While libev fully	1896	too) should not activate ("feed") events into libev. While libev fully
1733	supports this, they will be called before other C<ev_check> watchers	1897	supports this, they might get executed before other C<ev_check> watchers
1734	did their job. As C<ev_check> watchers are often used to embed other	1898	did their job. As C<ev_check> watchers are often used to embed other
1735	(non-libev) event loops those other event loops might be in an unusable	1899	(non-libev) event loops those other event loops might be in an unusable
1736	state until their C<ev_check> watcher ran (always remind yourself to	1900	state until their C<ev_check> watcher ran (always remind yourself to
1737	coexist peacefully with others).	1901	coexist peacefully with others).
1738		1902
…		…
1753	=head3 Examples	1917	=head3 Examples
1754		1918
1755	There are a number of principal ways to embed other event loops or modules	1919	There are a number of principal ways to embed other event loops or modules
1756	into libev. Here are some ideas on how to include libadns into libev	1920	into libev. Here are some ideas on how to include libadns into libev
1757	(there is a Perl module named C<EV::ADNS> that does this, which you could	1921	(there is a Perl module named C<EV::ADNS> that does this, which you could
1758	use for an actually working example. Another Perl module named C<EV::Glib>	1922	use as a working example. Another Perl module named C<EV::Glib> embeds a
1759	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1923	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1760	into the Glib event loop).	1924	Glib event loop).
1761		1925
1762	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1926	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1763	and in a check watcher, destroy them and call into libadns. What follows	1927	and in a check watcher, destroy them and call into libadns. What follows
1764	is pseudo-code only of course. This requires you to either use a low	1928	is pseudo-code only of course. This requires you to either use a low
1765	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1929	priority for the check watcher or use C<ev_clear_pending> explicitly, as
…		…
2027	believe me.	2191	believe me.
2028		2192
2029	=back	2193	=back
2030		2194
2031		2195
		2196	=head2 C<ev_async> - how to wake up another event loop
		2197
		2198	In general, you cannot use an C<ev_loop> from multiple threads or other
		2199	asynchronous sources such as signal handlers (as opposed to multiple event
		2200	loops - those are of course safe to use in different threads).
		2201
		2202	Sometimes, however, you need to wake up another event loop you do not
		2203	control, for example because it belongs to another thread. This is what
		2204	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2205	can signal it by calling C<ev_async_send>, which is thread- and signal
		2206	safe.
		2207
		2208	This functionality is very similar to C<ev_signal> watchers, as signals,
		2209	too, are asynchronous in nature, and signals, too, will be compressed
		2210	(i.e. the number of callback invocations may be less than the number of
		2211	C<ev_async_sent> calls).
		2212
		2213	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2214	just the default loop.
		2215
		2216	=head3 Queueing
		2217
		2218	C<ev_async> does not support queueing of data in any way. The reason
		2219	is that the author does not know of a simple (or any) algorithm for a
		2220	multiple-writer-single-reader queue that works in all cases and doesn't
		2221	need elaborate support such as pthreads.
		2222
		2223	That means that if you want to queue data, you have to provide your own
		2224	queue. But at least I can tell you would implement locking around your
		2225	queue:
		2226
		2227	=over 4
		2228
		2229	=item queueing from a signal handler context
		2230
		2231	To implement race-free queueing, you simply add to the queue in the signal
		2232	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2233	some fictitiuous SIGUSR1 handler:
		2234
		2235	static ev_async mysig;
		2236
		2237	static void
		2238	sigusr1_handler (void)
		2239	{
		2240	sometype data;
		2241
		2242	// no locking etc.
		2243	queue_put (data);
		2244	ev_async_send (EV_DEFAULT_ &mysig);
		2245	}
		2246
		2247	static void
		2248	mysig_cb (EV_P_ ev_async *w, int revents)
		2249	{
		2250	sometype data;
		2251	sigset_t block, prev;
		2252
		2253	sigemptyset (&block);
		2254	sigaddset (&block, SIGUSR1);
		2255	sigprocmask (SIG_BLOCK, &block, &prev);
		2256
		2257	while (queue_get (&data))
		2258	process (data);
		2259
		2260	if (sigismember (&prev, SIGUSR1)
		2261	sigprocmask (SIG_UNBLOCK, &block, 0);
		2262	}
		2263
		2264	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2265	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2266	either...).
		2267
		2268	=item queueing from a thread context
		2269
		2270	The strategy for threads is different, as you cannot (easily) block
		2271	threads but you can easily preempt them, so to queue safely you need to
		2272	employ a traditional mutex lock, such as in this pthread example:
		2273
		2274	static ev_async mysig;
		2275	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2276
		2277	static void
		2278	otherthread (void)
		2279	{
		2280	// only need to lock the actual queueing operation
		2281	pthread_mutex_lock (&mymutex);
		2282	queue_put (data);
		2283	pthread_mutex_unlock (&mymutex);
		2284
		2285	ev_async_send (EV_DEFAULT_ &mysig);
		2286	}
		2287
		2288	static void
		2289	mysig_cb (EV_P_ ev_async *w, int revents)
		2290	{
		2291	pthread_mutex_lock (&mymutex);
		2292
		2293	while (queue_get (&data))
		2294	process (data);
		2295
		2296	pthread_mutex_unlock (&mymutex);
		2297	}
		2298
		2299	=back
		2300
		2301
		2302	=head3 Watcher-Specific Functions and Data Members
		2303
		2304	=over 4
		2305
		2306	=item ev_async_init (ev_async *, callback)
		2307
		2308	Initialises and configures the async watcher - it has no parameters of any
		2309	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2310	believe me.
		2311
		2312	=item ev_async_send (loop, ev_async *)
		2313
		2314	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2315	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2316	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2317	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2318	section below on what exactly this means).
		2319
		2320	This call incurs the overhead of a syscall only once per loop iteration,
		2321	so while the overhead might be noticable, it doesn't apply to repeated
		2322	calls to C<ev_async_send>.
		2323
		2324	=item bool = ev_async_pending (ev_async *)
		2325
		2326	Returns a non-zero value when C<ev_async_send> has been called on the
		2327	watcher but the event has not yet been processed (or even noted) by the
		2328	event loop.
		2329
		2330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2331	the loop iterates next and checks for the watcher to have become active,
		2332	it will reset the flag again. C<ev_async_pending> can be used to very
		2333	quickly check wether invoking the loop might be a good idea.
		2334
		2335	Not that this does I<not> check wether the watcher itself is pending, only
		2336	wether it has been requested to make this watcher pending.
		2337
		2338	=back
		2339
		2340
2032	=head1 OTHER FUNCTIONS	2341	=head1 OTHER FUNCTIONS
2033		2342
2034	There are some other functions of possible interest. Described. Here. Now.	2343	There are some other functions of possible interest. Described. Here. Now.
2035		2344
2036	=over 4	2345	=over 4
…		…
2104		2413
2105	=item * Priorities are not currently supported. Initialising priorities	2414	=item * Priorities are not currently supported. Initialising priorities
2106	will fail and all watchers will have the same priority, even though there	2415	will fail and all watchers will have the same priority, even though there
2107	is an ev_pri field.	2416	is an ev_pri field.
2108		2417
		2418	=item * In libevent, the last base created gets the signals, in libev, the
		2419	first base created (== the default loop) gets the signals.
		2420
2109	=item * Other members are not supported.	2421	=item * Other members are not supported.
2110		2422
2111	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2423	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2112	to use the libev header file and library.	2424	to use the libev header file and library.
2113		2425
…		…
2263	Example: Define a class with an IO and idle watcher, start one of them in	2575	Example: Define a class with an IO and idle watcher, start one of them in
2264	the constructor.	2576	the constructor.
2265		2577
2266	class myclass	2578	class myclass
2267	{	2579	{
2268	ev_io io; void io_cb (ev::io &w, int revents);	2580	ev::io io; void io_cb (ev::io &w, int revents);
2269	ev_idle idle void idle_cb (ev::idle &w, int revents);	2581	ev:idle idle void idle_cb (ev::idle &w, int revents);
2270		2582
2271	myclass ();	2583	myclass (int fd)
2272	}
2273
2274	myclass::myclass (int fd)
2275	{	2584	{
2276	io .set <myclass, &myclass::io_cb > (this);	2585	io .set <myclass, &myclass::io_cb > (this);
2277	idle.set <myclass, &myclass::idle_cb> (this);	2586	idle.set <myclass, &myclass::idle_cb> (this);
2278		2587
2279	io.start (fd, ev::READ);	2588	io.start (fd, ev::READ);
		2589	}
2280	}	2590	};
		2591
		2592
		2593	=head1 OTHER LANGUAGE BINDINGS
		2594
		2595	Libev does not offer other language bindings itself, but bindings for a
		2596	numbe rof languages exist in the form of third-party packages. If you know
		2597	any interesting language binding in addition to the ones listed here, drop
		2598	me a note.
		2599
		2600	=over 4
		2601
		2602	=item Perl
		2603
		2604	The EV module implements the full libev API and is actually used to test
		2605	libev. EV is developed together with libev. Apart from the EV core module,
		2606	there are additional modules that implement libev-compatible interfaces
		2607	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2608	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2609
		2610	It can be found and installed via CPAN, its homepage is found at
		2611	L<http://software.schmorp.de/pkg/EV>.
		2612
		2613	=item Ruby
		2614
		2615	Tony Arcieri has written a ruby extension that offers access to a subset
		2616	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2617	more on top of it. It can be found via gem servers. Its homepage is at
		2618	L<http://rev.rubyforge.org/>.
		2619
		2620	=item D
		2621
		2622	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2623	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2624
		2625	=back
2281		2626
2282		2627
2283	=head1 MACRO MAGIC	2628	=head1 MACRO MAGIC
2284		2629
2285	Libev can be compiled with a variety of options, the most fundamantal	2630	Libev can be compiled with a variety of options, the most fundamantal
…		…
2321		2666
2322	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2667	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2323		2668
2324	Similar to the other two macros, this gives you the value of the default	2669	Similar to the other two macros, this gives you the value of the default
2325	loop, if multiple loops are supported ("ev loop default").	2670	loop, if multiple loops are supported ("ev loop default").
		2671
		2672	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2673
		2674	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2675	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2676	is undefined when the default loop has not been initialised by a previous
		2677	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2678
		2679	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2680	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2326		2681
2327	=back	2682	=back
2328		2683
2329	Example: Declare and initialise a check watcher, utilising the above	2684	Example: Declare and initialise a check watcher, utilising the above
2330	macros so it will work regardless of whether multiple loops are supported	2685	macros so it will work regardless of whether multiple loops are supported
…		…
2426		2781
2427	libev.m4	2782	libev.m4
2428		2783
2429	=head2 PREPROCESSOR SYMBOLS/MACROS	2784	=head2 PREPROCESSOR SYMBOLS/MACROS
2430		2785
2431	Libev can be configured via a variety of preprocessor symbols you have to define	2786	Libev can be configured via a variety of preprocessor symbols you have to
2432	before including any of its files. The default is not to build for multiplicity	2787	define before including any of its files. The default in the absense of
2433	and only include the select backend.	2788	autoconf is noted for every option.
2434		2789
2435	=over 4	2790	=over 4
2436		2791
2437	=item EV_STANDALONE	2792	=item EV_STANDALONE
2438		2793
…		…
2464	=item EV_USE_NANOSLEEP	2819	=item EV_USE_NANOSLEEP
2465		2820
2466	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2821	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2467	and will use it for delays. Otherwise it will use C<select ()>.	2822	and will use it for delays. Otherwise it will use C<select ()>.
2468		2823
		2824	=item EV_USE_EVENTFD
		2825
		2826	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2827	available and will probe for kernel support at runtime. This will improve
		2828	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2829	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2830	2.7 or newer, otherwise disabled.
		2831
2469	=item EV_USE_SELECT	2832	=item EV_USE_SELECT
2470		2833
2471	If undefined or defined to be C<1>, libev will compile in support for the	2834	If undefined or defined to be C<1>, libev will compile in support for the
2472	C<select>(2) backend. No attempt at autodetection will be done: if no	2835	C<select>(2) backend. No attempt at autodetection will be done: if no
2473	other method takes over, select will be it. Otherwise the select backend	2836	other method takes over, select will be it. Otherwise the select backend
…		…
2491	be used is the winsock select). This means that it will call	2854	be used is the winsock select). This means that it will call
2492	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2855	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2493	it is assumed that all these functions actually work on fds, even	2856	it is assumed that all these functions actually work on fds, even
2494	on win32. Should not be defined on non-win32 platforms.	2857	on win32. Should not be defined on non-win32 platforms.
2495		2858
		2859	=item EV_FD_TO_WIN32_HANDLE
		2860
		2861	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2862	file descriptors to socket handles. When not defining this symbol (the
		2863	default), then libev will call C<_get_osfhandle>, which is usually
		2864	correct. In some cases, programs use their own file descriptor management,
		2865	in which case they can provide this function to map fds to socket handles.
		2866
2496	=item EV_USE_POLL	2867	=item EV_USE_POLL
2497		2868
2498	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2869	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2499	backend. Otherwise it will be enabled on non-win32 platforms. It	2870	backend. Otherwise it will be enabled on non-win32 platforms. It
2500	takes precedence over select.	2871	takes precedence over select.
2501		2872
2502	=item EV_USE_EPOLL	2873	=item EV_USE_EPOLL
2503		2874
2504	If defined to be C<1>, libev will compile in support for the Linux	2875	If defined to be C<1>, libev will compile in support for the Linux
2505	C<epoll>(7) backend. Its availability will be detected at runtime,	2876	C<epoll>(7) backend. Its availability will be detected at runtime,
2506	otherwise another method will be used as fallback. This is the	2877	otherwise another method will be used as fallback. This is the preferred
2507	preferred backend for GNU/Linux systems.	2878	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2879	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2508		2880
2509	=item EV_USE_KQUEUE	2881	=item EV_USE_KQUEUE
2510		2882
2511	If defined to be C<1>, libev will compile in support for the BSD style	2883	If defined to be C<1>, libev will compile in support for the BSD style
2512	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2884	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2531		2903
2532	=item EV_USE_INOTIFY	2904	=item EV_USE_INOTIFY
2533		2905
2534	If defined to be C<1>, libev will compile in support for the Linux inotify	2906	If defined to be C<1>, libev will compile in support for the Linux inotify
2535	interface to speed up C<ev_stat> watchers. Its actual availability will	2907	interface to speed up C<ev_stat> watchers. Its actual availability will
2536	be detected at runtime.	2908	be detected at runtime. If undefined, it will be enabled if the headers
		2909	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2910
		2911	=item EV_ATOMIC_T
		2912
		2913	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2914	access is atomic with respect to other threads or signal contexts. No such
		2915	type is easily found in the C language, so you can provide your own type
		2916	that you know is safe for your purposes. It is used both for signal handler "locking"
		2917	as well as for signal and thread safety in C<ev_async> watchers.
		2918
		2919	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2920	(from F<signal.h>), which is usually good enough on most platforms.
2537		2921
2538	=item EV_H	2922	=item EV_H
2539		2923
2540	The name of the F<ev.h> header file used to include it. The default if	2924	The name of the F<ev.h> header file used to include it. The default if
2541	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	2925	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2542	virtually rename the F<ev.h> header file in case of conflicts.	2926	used to virtually rename the F<ev.h> header file in case of conflicts.
2543		2927
2544	=item EV_CONFIG_H	2928	=item EV_CONFIG_H
2545		2929
2546	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2930	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2547	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2931	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2548	C<EV_H>, above.	2932	C<EV_H>, above.
2549		2933
2550	=item EV_EVENT_H	2934	=item EV_EVENT_H
2551		2935
2552	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2936	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2553	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	2937	of how the F<event.h> header can be found, the default is C<"event.h">.
2554		2938
2555	=item EV_PROTOTYPES	2939	=item EV_PROTOTYPES
2556		2940
2557	If defined to be C<0>, then F<ev.h> will not define any function	2941	If defined to be C<0>, then F<ev.h> will not define any function
2558	prototypes, but still define all the structs and other symbols. This is	2942	prototypes, but still define all the structs and other symbols. This is
…		…
2609	=item EV_FORK_ENABLE	2993	=item EV_FORK_ENABLE
2610		2994
2611	If undefined or defined to be C<1>, then fork watchers are supported. If	2995	If undefined or defined to be C<1>, then fork watchers are supported. If
2612	defined to be C<0>, then they are not.	2996	defined to be C<0>, then they are not.
2613		2997
		2998	=item EV_ASYNC_ENABLE
		2999
		3000	If undefined or defined to be C<1>, then async watchers are supported. If
		3001	defined to be C<0>, then they are not.
		3002
2614	=item EV_MINIMAL	3003	=item EV_MINIMAL
2615		3004
2616	If you need to shave off some kilobytes of code at the expense of some	3005	If you need to shave off some kilobytes of code at the expense of some
2617	speed, define this symbol to C<1>. Currently only used for gcc to override	3006	speed, define this symbol to C<1>. Currently this is used to override some
2618	some inlining decisions, saves roughly 30% codesize of amd64.	3007	inlining decisions, saves roughly 30% codesize of amd64. It also selects a
		3008	much smaller 2-heap for timer management over the default 4-heap.
2619		3009
2620	=item EV_PID_HASHSIZE	3010	=item EV_PID_HASHSIZE
2621		3011
2622	C<ev_child> watchers use a small hash table to distribute workload by	3012	C<ev_child> watchers use a small hash table to distribute workload by
2623	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3013	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2629	C<ev_stat> watchers use a small hash table to distribute workload by	3019	C<ev_stat> watchers use a small hash table to distribute workload by
2630	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3020	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2631	usually more than enough. If you need to manage thousands of C<ev_stat>	3021	usually more than enough. If you need to manage thousands of C<ev_stat>
2632	watchers you might want to increase this value (I<must> be a power of	3022	watchers you might want to increase this value (I<must> be a power of
2633	two).	3023	two).
		3024
		3025	=item EV_USE_4HEAP
		3026
		3027	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3028	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3029	to C<1>. The 4-heap uses more complicated (longer) code but has
		3030	noticably faster performance with many (thousands) of watchers.
		3031
		3032	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3033	(disabled).
		3034
		3035	=item EV_HEAP_CACHE_AT
		3036
		3037	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3038	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3039	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3040	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3041	but avoids random read accesses on heap changes. This improves performance
		3042	noticably with with many (hundreds) of watchers.
		3043
		3044	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3045	(disabled).
		3046
		3047	=item EV_VERIFY
		3048
		3049	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3050	be done: If set to C<0>, no internal verification code will be compiled
		3051	in. If set to C<1>, then verification code will be compiled in, but not
		3052	called. If set to C<2>, then the internal verification code will be
		3053	called once per loop, which can slow down libev. If set to C<3>, then the
		3054	verification code will be called very frequently, which will slow down
		3055	libev considerably.
		3056
		3057	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3058	C<0.>
2634		3059
2635	=item EV_COMMON	3060	=item EV_COMMON
2636		3061
2637	By default, all watchers have a C<void *data> member. By redefining	3062	By default, all watchers have a C<void *data> member. By redefining
2638	this macro to a something else you can include more and other types of	3063	this macro to a something else you can include more and other types of
…		…
2712		3137
2713	#include "ev_cpp.h"	3138	#include "ev_cpp.h"
2714	#include "ev.c"	3139	#include "ev.c"
2715		3140
2716		3141
		3142	=head1 THREADS AND COROUTINES
		3143
		3144	=head2 THREADS
		3145
		3146	Libev itself is completely threadsafe, but it uses no locking. This
		3147	means that you can use as many loops as you want in parallel, as long as
		3148	only one thread ever calls into one libev function with the same loop
		3149	parameter.
		3150
		3151	Or put differently: calls with different loop parameters can be done in
		3152	parallel from multiple threads, calls with the same loop parameter must be
		3153	done serially (but can be done from different threads, as long as only one
		3154	thread ever is inside a call at any point in time, e.g. by using a mutex
		3155	per loop).
		3156
		3157	If you want to know which design is best for your problem, then I cannot
		3158	help you but by giving some generic advice:
		3159
		3160	=over 4
		3161
		3162	=item * most applications have a main thread: use the default libev loop
		3163	in that thread, or create a seperate thread running only the default loop.
		3164
		3165	This helps integrating other libraries or software modules that use libev
		3166	themselves and don't care/know about threading.
		3167
		3168	=item * one loop per thread is usually a good model.
		3169
		3170	Doing this is almost never wrong, sometimes a better-performance model
		3171	exists, but it is always a good start.
		3172
		3173	=item * other models exist, such as the leader/follower pattern, where one
		3174	loop is handed through multiple threads in a kind of round-robbin fashion.
		3175
		3176	Chosing a model is hard - look around, learn, know that usually you cna do
		3177	better than you currently do :-)
		3178
		3179	=item * often you need to talk to some other thread which blocks in the
		3180	event loop - C<ev_async> watchers can be used to wake them up from other
		3181	threads safely (or from signal contexts...).
		3182
		3183	=back
		3184
		3185	=head2 COROUTINES
		3186
		3187	Libev is much more accomodating to coroutines ("cooperative threads"):
		3188	libev fully supports nesting calls to it's functions from different
		3189	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3190	different coroutines and switch freely between both coroutines running the
		3191	loop, as long as you don't confuse yourself). The only exception is that
		3192	you must not do this from C<ev_periodic> reschedule callbacks.
		3193
		3194	Care has been invested into making sure that libev does not keep local
		3195	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3196	switches.
		3197
		3198
2717	=head1 COMPLEXITIES	3199	=head1 COMPLEXITIES
2718		3200
2719	In this section the complexities of (many of) the algorithms used inside	3201	In this section the complexities of (many of) the algorithms used inside
2720	libev will be explained. For complexity discussions about backends see the	3202	libev will be explained. For complexity discussions about backends see the
2721	documentation for C<ev_default_init>.	3203	documentation for C<ev_default_init>.
…		…
2737	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3219	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2738		3220
2739	That means that changing a timer costs less than removing/adding them	3221	That means that changing a timer costs less than removing/adding them
2740	as only the relative motion in the event queue has to be paid for.	3222	as only the relative motion in the event queue has to be paid for.
2741		3223
2742	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3224	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2743		3225
2744	These just add the watcher into an array or at the head of a list.	3226	These just add the watcher into an array or at the head of a list.
2745		3227
2746	=item Stopping check/prepare/idle watchers: O(1)	3228	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2747		3229
2748	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3230	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2749		3231
2750	These watchers are stored in lists then need to be walked to find the	3232	These watchers are stored in lists then need to be walked to find the
2751	correct watcher to remove. The lists are usually short (you don't usually	3233	correct watcher to remove. The lists are usually short (you don't usually
2752	have many watchers waiting for the same fd or signal).	3234	have many watchers waiting for the same fd or signal).
2753		3235
2754	=item Finding the next timer in each loop iteration: O(1)	3236	=item Finding the next timer in each loop iteration: O(1)
2755		3237
2756	By virtue of using a binary heap, the next timer is always found at the	3238	By virtue of using a binary or 4-heap, the next timer is always found at a
2757	beginning of the storage array.	3239	fixed position in the storage array.
2758		3240
2759	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3241	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2760		3242
2761	A change means an I/O watcher gets started or stopped, which requires	3243	A change means an I/O watcher gets started or stopped, which requires
2762	libev to recalculate its status (and possibly tell the kernel, depending	3244	libev to recalculate its status (and possibly tell the kernel, depending
…		…
2767	=item Priority handling: O(number_of_priorities)	3249	=item Priority handling: O(number_of_priorities)
2768		3250
2769	Priorities are implemented by allocating some space for each	3251	Priorities are implemented by allocating some space for each
2770	priority. When doing priority-based operations, libev usually has to	3252	priority. When doing priority-based operations, libev usually has to
2771	linearly search all the priorities, but starting/stopping and activating	3253	linearly search all the priorities, but starting/stopping and activating
2772	watchers becomes O(1) w.r.t. prioritiy handling.	3254	watchers becomes O(1) w.r.t. priority handling.
		3255
		3256	=item Sending an ev_async: O(1)
		3257
		3258	=item Processing ev_async_send: O(number_of_async_watchers)
		3259
		3260	=item Processing signals: O(max_signal_number)
		3261
		3262	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3263	calls in the current loop iteration. Checking for async and signal events
		3264	involves iterating over all running async watchers or all signal numbers.
2773		3265
2774	=back	3266	=back
2775		3267
2776		3268
		3269	=head1 Win32 platform limitations and workarounds
		3270
		3271	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3272	requires, and its I/O model is fundamentally incompatible with the POSIX
		3273	model. Libev still offers limited functionality on this platform in
		3274	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3275	descriptors. This only applies when using Win32 natively, not when using
		3276	e.g. cygwin.
		3277
		3278	Lifting these limitations would basically require the full
		3279	re-implementation of the I/O system. If you are into these kinds of
		3280	things, then note that glib does exactly that for you in a very portable
		3281	way (note also that glib is the slowest event library known to man).
		3282
		3283	There is no supported compilation method available on windows except
		3284	embedding it into other applications.
		3285
		3286	Due to the many, low, and arbitrary limits on the win32 platform and
		3287	the abysmal performance of winsockets, using a large number of sockets
		3288	is not recommended (and not reasonable). If your program needs to use
		3289	more than a hundred or so sockets, then likely it needs to use a totally
		3290	different implementation for windows, as libev offers the POSIX readiness
		3291	notification model, which cannot be implemented efficiently on windows
		3292	(microsoft monopoly games).
		3293
		3294	=over 4
		3295
		3296	=item The winsocket select function
		3297
		3298	The winsocket C<select> function doesn't follow POSIX in that it requires
		3299	socket I<handles> and not socket I<file descriptors>. This makes select
		3300	very inefficient, and also requires a mapping from file descriptors
		3301	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3302	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3303	symbols for more info.
		3304
		3305	The configuration for a "naked" win32 using the microsoft runtime
		3306	libraries and raw winsocket select is:
		3307
		3308	#define EV_USE_SELECT 1
		3309	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3310
		3311	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3312	complexity in the O(n²) range when using win32.
		3313
		3314	=item Limited number of file descriptors
		3315
		3316	Windows has numerous arbitrary (and low) limits on things.
		3317
		3318	Early versions of winsocket's select only supported waiting for a maximum
		3319	of C<64> handles (probably owning to the fact that all windows kernels
		3320	can only wait for C<64> things at the same time internally; microsoft
		3321	recommends spawning a chain of threads and wait for 63 handles and the
		3322	previous thread in each. Great).
		3323
		3324	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3325	to some high number (e.g. C<2048>) before compiling the winsocket select
		3326	call (which might be in libev or elsewhere, for example, perl does its own
		3327	select emulation on windows).
		3328
		3329	Another limit is the number of file descriptors in the microsoft runtime
		3330	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3331	or something like this inside microsoft). You can increase this by calling
		3332	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3333	arbitrary limit), but is broken in many versions of the microsoft runtime
		3334	libraries.
		3335
		3336	This might get you to about C<512> or C<2048> sockets (depending on
		3337	windows version and/or the phase of the moon). To get more, you need to
		3338	wrap all I/O functions and provide your own fd management, but the cost of
		3339	calling select (O(n²)) will likely make this unworkable.
		3340
		3341	=back
		3342
		3343
		3344	=head1 PORTABILITY REQUIREMENTS
		3345
		3346	In addition to a working ISO-C implementation, libev relies on a few
		3347	additional extensions:
		3348
		3349	=over 4
		3350
		3351	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3352
		3353	The type C<sig_atomic_t volatile> (or whatever is defined as
		3354	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3355	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3356	believed to be sufficiently portable.
		3357
		3358	=item C<sigprocmask> must work in a threaded environment
		3359
		3360	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3361	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3362	pthread implementations will either allow C<sigprocmask> in the "main
		3363	thread" or will block signals process-wide, both behaviours would
		3364	be compatible with libev. Interaction between C<sigprocmask> and
		3365	C<pthread_sigmask> could complicate things, however.
		3366
		3367	The most portable way to handle signals is to block signals in all threads
		3368	except the initial one, and run the default loop in the initial thread as
		3369	well.
		3370
		3371	=item C<long> must be large enough for common memory allocation sizes
		3372
		3373	To improve portability and simplify using libev, libev uses C<long>
		3374	internally instead of C<size_t> when allocating its data structures. On
		3375	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3376	is still at least 31 bits everywhere, which is enough for hundreds of
		3377	millions of watchers.
		3378
		3379	=item C<double> must hold a time value in seconds with enough accuracy
		3380
		3381	The type C<double> is used to represent timestamps. It is required to
		3382	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3383	enough for at least into the year 4000. This requirement is fulfilled by
		3384	implementations implementing IEEE 754 (basically all existing ones).
		3385
		3386	=back
		3387
		3388	If you know of other additional requirements drop me a note.
		3389
		3390
		3391	=head1 VALGRIND
		3392
		3393	Valgrind has a special section here because it is a popular tool that is
		3394	highly useful, but valgrind reports are very hard to interpret.
		3395
		3396	If you think you found a bug (memory leak, uninitialised data access etc.)
		3397	in libev, then check twice: If valgrind reports something like:
		3398
		3399	==2274== definitely lost: 0 bytes in 0 blocks.
		3400	==2274== possibly lost: 0 bytes in 0 blocks.
		3401	==2274== still reachable: 256 bytes in 1 blocks.
		3402
		3403	then there is no memory leak. Similarly, under some circumstances,
		3404	valgrind might report kernel bugs as if it were a bug in libev, or it
		3405	might be confused (it is a very good tool, but only a tool).
		3406
		3407	If you are unsure about something, feel free to contact the mailing list
		3408	with the full valgrind report and an explanation on why you think this is
		3409	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3410	no bug" answer and take the chance of learning how to interpret valgrind
		3411	properly.
		3412
		3413	If you need, for some reason, empty reports from valgrind for your project
		3414	I suggest using suppression lists.
		3415
		3416
2777	=head1 AUTHOR	3417	=head1 AUTHOR
2778		3418
2779	Marc Lehmann <libev@schmorp.de>.	3419	Marc Lehmann <libev@schmorp.de>.
2780		3420

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