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Revision 1.114 by root, Mon Dec 31 01:31:30 2007 UTC vs.
Revision 1.160 by root, Thu May 22 03:06:58 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
…		…
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floatingpoint value. Unlike the name
104	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	120	throughout libev.
106		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a syscall indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
111		147
…		…
181	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
182		218
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
184		220
185	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	222	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	223	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	224	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
190	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
191		230
192	You could override this function in high-availability programs to, say,	231	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,	232	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.	233	or even to sleep a while and retry until some memory is available.
195		234
196	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	236	retries (example requires a standards-compliant C<realloc>).
198		237
199	static void *	238	static void *
200	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
201	{	240	{
202	for (;;)	241	for (;;)
…		…
241		280
242	An event loop is described by a C<struct ev_loop *>. The library knows two	281	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	282	types of such loops, the I<default> loop, which supports signals and child
244	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
245		284
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	285	=over 4
254		286
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		288
257	This will initialise the default event loop if it hasn't been initialised	289	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	291	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).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		293
262	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
263	function.	295	function.
		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your app you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
264		307
265	The flags argument can be used to specify special behaviour or specific	308	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>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		310
268	The following flags are supported:	311	The following flags are supported:
…		…
290	enabling this flag.	333	enabling this flag.
291		334
292	This works by calling C<getpid ()> on every iteration of the loop,	335	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	336	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	337	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	338	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	339	without a syscall and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
298		341
299	The big advantage of this flag is that you can forget about fork (and	342	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	343	forget about forgetting to tell libev about forking) when you use this
301	flag.	344	flag.
…		…
314	To get good performance out of this backend you need a high amount of	357	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	358	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	359	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	360	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	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
319	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
320		363
321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
322		365
323	And this is your standard poll(2) backend. It's more complicated	366	And this is your standard poll(2) backend. It's more complicated
324	than select, but handles sparse fds better and has no artificial	367	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,	375	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	376	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),	377	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	378	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	379	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	380	cases and requiring a syscall per fd change, no fork support and bad
338	support for dup.	381	support for dup.
339		382
340	While stopping, setting and starting an I/O watcher in the same iteration	383	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	384	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	385	(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	446	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	447	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	449	might perform better.
407		450
		451	On the positive side, ignoring the spurious readiness notifications, this
		452	backend actually performed to specification in all tests and is fully
		453	embeddable, which is a rare feat among the OS-specific backends.
		454
408	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
409		456
410	Try all backends (even potentially broken ones that wouldn't be tried	457	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	458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
…		…
414	It is definitely not recommended to use this flag.	461	It is definitely not recommended to use this flag.
415		462
416	=back	463	=back
417		464
418	If one or more of these are ored into the flags value, then only these	465	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	466	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	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		468
423	The most typical usage is like this:	469	The most typical usage is like this:
424		470
425	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
440		486
441	Similar to C<ev_default_loop>, but always creates a new event loop that is	487	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	488	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	489	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).	490	undefined behaviour (or a failed assertion if assertions are enabled).
		491
		492	Note that this function I<is> thread-safe, and the recommended way to use
		493	libev with threads is indeed to create one loop per thread, and using the
		494	default loop in the "main" or "initial" thread.
445		495
446	Example: Try to create a event loop that uses epoll and nothing else.	496	Example: Try to create a event loop that uses epoll and nothing else.
447		497
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	499	if (!epoller)
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	523	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
475		525
476	=item ev_default_fork ()	526	=item ev_default_fork ()
477		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	529	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	530	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	531	the child process (or both child and parent, but that again makes little
481	again makes little sense).	532	sense). You I<must> call it in the child before using any of the libev
		533	functions, and it will only take effect at the next C<ev_loop> iteration.
482		534
483	You I<must> call this function in the child process after forking if and	535	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	536	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.	537	you just fork+exec, you don't have to call it at all.
486		538
487	The function itself is quite fast and it's usually not a problem to call	539	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	540	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>:	541	quite nicely into a call to C<pthread_atfork>:
490		542
491	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
492		544
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)	545	=item ev_loop_fork (loop)
498		546
499	Like C<ev_default_fork>, but acts on an event loop created by	547	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	548	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.	549	after fork, and how you do this is entirely your own problem.
		550
		551	=item int ev_is_default_loop (loop)
		552
		553	Returns true when the given loop actually is the default loop, false otherwise.
502		554
503	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
504		556
505	Returns the count of loop iterations for the loop, which is identical to	557	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	558	the number of times libev did poll for new events. It starts at C<0> and
…		…
590	Can be used to make a call to C<ev_loop> return early (but only after it	642	Can be used to make a call to C<ev_loop> return early (but only after it
591	has processed all outstanding events). The C<how> argument must be either	643	has processed all outstanding events). The C<how> argument must be either
592	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
593	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
594		646
		647	This "unloop state" will be cleared when entering C<ev_loop> again.
		648
595	=item ev_ref (loop)	649	=item ev_ref (loop)
596		650
597	=item ev_unref (loop)	651	=item ev_unref (loop)
598		652
599	Ref/unref can be used to add or remove a reference count on the event	653	Ref/unref can be used to add or remove a reference count on the event
…		…
603	returning, ev_unref() after starting, and ev_ref() before stopping it. For	657	returning, ev_unref() after starting, and ev_ref() before stopping it. For
604	example, libev itself uses this for its internal signal pipe: It is not	658	example, libev itself uses this for its internal signal pipe: It is not
605	visible to the libev user and should not keep C<ev_loop> from exiting if	659	visible to the libev user and should not keep C<ev_loop> from exiting if
606	no event watchers registered by it are active. It is also an excellent	660	no event watchers registered by it are active. It is also an excellent
607	way to do this for generic recurring timers or from within third-party	661	way to do this for generic recurring timers or from within third-party
608	libraries. Just remember to I<unref after start> and I<ref before stop>.	662	libraries. Just remember to I<unref after start> and I<ref before stop>
		663	(but only if the watcher wasn't active before, or was active before,
		664	respectively).
609		665
610	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
611	running when nothing else is active.	667	running when nothing else is active.
612		668
613	struct ev_signal exitsig;	669	struct ev_signal exitsig;
…		…
653	Many (busy) programs can usually benefit by setting the io collect	709	Many (busy) programs can usually benefit by setting the io collect
654	interval to a value near C<0.1> or so, which is often enough for	710	interval to a value near C<0.1> or so, which is often enough for
655	interactive servers (of course not for games), likewise for timeouts. It	711	interactive servers (of course not for games), likewise for timeouts. It
656	usually doesn't make much sense to set it to a lower value than C<0.01>,	712	usually doesn't make much sense to set it to a lower value than C<0.01>,
657	as this approsaches the timing granularity of most systems.	713	as this approsaches the timing granularity of most systems.
		714
		715	=item ev_loop_verify (loop)
		716
		717	This function only does something when C<EV_VERIFY> support has been
		718	compiled in. It tries to go through all internal structures and checks
		719	them for validity. If anything is found to be inconsistent, it will print
		720	an error message to standard error and call C<abort ()>.
		721
		722	This can be used to catch bugs inside libev itself: under normal
		723	circumstances, this function will never abort as of course libev keeps its
		724	data structures consistent.
658		725
659	=back	726	=back
660		727
661		728
662	=head1 ANATOMY OF A WATCHER	729	=head1 ANATOMY OF A WATCHER
…		…
761		828
762	=item C<EV_FORK>	829	=item C<EV_FORK>
763		830
764	The event loop has been resumed in the child process after fork (see	831	The event loop has been resumed in the child process after fork (see
765	C<ev_fork>).	832	C<ev_fork>).
		833
		834	=item C<EV_ASYNC>
		835
		836	The given async watcher has been asynchronously notified (see C<ev_async>).
766		837
767	=item C<EV_ERROR>	838	=item C<EV_ERROR>
768		839
769	An unspecified error has occured, the watcher has been stopped. This might	840	An unspecified error has occured, the watcher has been stopped. This might
770	happen because the watcher could not be properly started because libev	841	happen because the watcher could not be properly started because libev
…		…
993	If you must do this, then force the use of a known-to-be-good backend	1064	If you must do this, then force the use of a known-to-be-good backend
994	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
995	C<EVBACKEND_POLL>).	1066	C<EVBACKEND_POLL>).
996		1067
997	Another thing you have to watch out for is that it is quite easy to	1068	Another thing you have to watch out for is that it is quite easy to
998	receive "spurious" readyness notifications, that is your callback might	1069	receive "spurious" readiness notifications, that is your callback might
999	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1000	because there is no data. Not only are some backends known to create a	1071	because there is no data. Not only are some backends known to create a
1001	lot of those (for example solaris ports), it is very easy to get into	1072	lot of those (for example solaris ports), it is very easy to get into
1002	this situation even with a relatively standard program structure. Thus	1073	this situation even with a relatively standard program structure. Thus
1003	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning
…		…
1050	To support fork in your programs, you either have to call	1121	To support fork in your programs, you either have to call
1051	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1122	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1052	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1053	C<EVBACKEND_POLL>.	1124	C<EVBACKEND_POLL>.
1054		1125
		1126	=head3 The special problem of SIGPIPE
		1127
		1128	While not really specific to libev, it is easy to forget about SIGPIPE:
		1129	when reading from a pipe whose other end has been closed, your program
		1130	gets send a SIGPIPE, which, by default, aborts your program. For most
		1131	programs this is sensible behaviour, for daemons, this is usually
		1132	undesirable.
		1133
		1134	So when you encounter spurious, unexplained daemon exits, make sure you
		1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1136	somewhere, as that would have given you a big clue).
		1137
1055		1138
1056	=head3 Watcher-Specific Functions	1139	=head3 Watcher-Specific Functions
1057		1140
1058	=over 4	1141	=over 4
1059		1142
…		…
1100		1183
1101	Timer watchers are simple relative timers that generate an event after a	1184	Timer watchers are simple relative timers that generate an event after a
1102	given time, and optionally repeating in regular intervals after that.	1185	given time, and optionally repeating in regular intervals after that.
1103		1186
1104	The timers are based on real time, that is, if you register an event that	1187	The timers are based on real time, that is, if you register an event that
1105	times out after an hour and you reset your system clock to last years	1188	times out after an hour and you reset your system clock to january last
1106	time, it will still time out after (roughly) and hour. "Roughly" because	1189	year, it will still time out after (roughly) and hour. "Roughly" because
1107	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1108	monotonic clock option helps a lot here).	1191	monotonic clock option helps a lot here).
1109		1192
1110	The relative timeouts are calculated relative to the C<ev_now ()>	1193	The relative timeouts are calculated relative to the C<ev_now ()>
1111	time. This is usually the right thing as this timestamp refers to the time	1194	time. This is usually the right thing as this timestamp refers to the time
…		…
1113	you suspect event processing to be delayed and you I<need> to base the timeout	1196	you suspect event processing to be delayed and you I<need> to base the timeout
1114	on the current time, use something like this to adjust for this:	1197	on the current time, use something like this to adjust for this:
1115		1198
1116	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1117		1200
1118	The callback is guarenteed to be invoked only when its timeout has passed,	1201	The callback is guarenteed to be invoked only after its timeout has passed,
1119	but if multiple timers become ready during the same loop iteration then	1202	but if multiple timers become ready during the same loop iteration then
1120	order of execution is undefined.	1203	order of execution is undefined.
1121		1204
1122	=head3 Watcher-Specific Functions and Data Members	1205	=head3 Watcher-Specific Functions and Data Members
1123		1206
…		…
1125		1208
1126	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1209	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1127		1210
1128	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1211	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1129		1212
1130	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1213	Configure the timer to trigger after C<after> seconds. If C<repeat>
1131	C<0.>, then it will automatically be stopped. If it is positive, then the	1214	is C<0.>, then it will automatically be stopped once the timeout is
1132	timer will automatically be configured to trigger again C<repeat> seconds	1215	reached. If it is positive, then the timer will automatically be
1133	later, again, and again, until stopped manually.	1216	configured to trigger again C<repeat> seconds later, again, and again,
		1217	until stopped manually.
1134		1218
1135	The timer itself will do a best-effort at avoiding drift, that is, if you	1219	The timer itself will do a best-effort at avoiding drift, that is, if
1136	configure a timer to trigger every 10 seconds, then it will trigger at	1220	you configure a timer to trigger every 10 seconds, then it will normally
1137	exactly 10 second intervals. If, however, your program cannot keep up with	1221	trigger at exactly 10 second intervals. If, however, your program cannot
1138	the timer (because it takes longer than those 10 seconds to do stuff) the	1222	keep up with the timer (because it takes longer than those 10 seconds to
1139	timer will not fire more than once per event loop iteration.	1223	do stuff) the timer will not fire more than once per event loop iteration.
1140		1224
1141	=item ev_timer_again (loop)	1225	=item ev_timer_again (loop, ev_timer *)
1142		1226
1143	This will act as if the timer timed out and restart it again if it is	1227	This will act as if the timer timed out and restart it again if it is
1144	repeating. The exact semantics are:	1228	repeating. The exact semantics are:
1145		1229
1146	If the timer is pending, its pending status is cleared.	1230	If the timer is pending, its pending status is cleared.
…		…
1221	Periodic watchers are also timers of a kind, but they are very versatile	1305	Periodic watchers are also timers of a kind, but they are very versatile
1222	(and unfortunately a bit complex).	1306	(and unfortunately a bit complex).
1223		1307
1224	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1225	but on wallclock time (absolute time). You can tell a periodic watcher	1309	but on wallclock time (absolute time). You can tell a periodic watcher
1226	to trigger "at" some specific point in time. For example, if you tell a	1310	to trigger after some specific point in time. For example, if you tell a
1227	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1311	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1228	+ 10.>) and then reset your system clock to the last year, then it will	1312	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1313	clock to january of the previous year, then it will take more than year
1229	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1230	roughly 10 seconds later).	1315	roughly 10 seconds later as it uses a relative timeout).
1231		1316
1232	They can also be used to implement vastly more complex timers, such as	1317	C<ev_periodic>s can also be used to implement vastly more complex timers,
1233	triggering an event on each midnight, local time or other, complicated,	1318	such as triggering an event on each "midnight, local time", or other
1234	rules.	1319	complicated, rules.
1235		1320
1236	As with timers, the callback is guarenteed to be invoked only when the	1321	As with timers, the callback is guarenteed to be invoked only when the
1237	time (C<at>) has been passed, but if multiple periodic timers become ready	1322	time (C<at>) has passed, but if multiple periodic timers become ready
1238	during the same loop iteration then order of execution is undefined.	1323	during the same loop iteration then order of execution is undefined.
1239		1324
1240	=head3 Watcher-Specific Functions and Data Members	1325	=head3 Watcher-Specific Functions and Data Members
1241		1326
1242	=over 4	1327	=over 4
…		…
1250		1335
1251	=over 4	1336	=over 4
1252		1337
1253	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1254		1339
1255	In this configuration the watcher triggers an event at the wallclock time	1340	In this configuration the watcher triggers an event after the wallclock
1256	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1341	time C<at> has passed and doesn't repeat. It will not adjust when a time
1257	that is, if it is to be run at January 1st 2011 then it will run when the	1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1258	system time reaches or surpasses this time.	1343	run when the system time reaches or surpasses this time.
1259		1344
1260	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1261		1346
1262	In this mode the watcher will always be scheduled to time out at the next	1347	In this mode the watcher will always be scheduled to time out at the next
1263	C<at + N * interval> time (for some integer N, which can also be negative)	1348	C<at + N * interval> time (for some integer N, which can also be negative)
1264	and then repeat, regardless of any time jumps.	1349	and then repeat, regardless of any time jumps.
1265		1350
1266	This can be used to create timers that do not drift with respect to system	1351	This can be used to create timers that do not drift with respect to system
1267	time:	1352	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1353	the hour:
1268		1354
1269	ev_periodic_set (&periodic, 0., 3600., 0);	1355	ev_periodic_set (&periodic, 0., 3600., 0);
1270		1356
1271	This doesn't mean there will always be 3600 seconds in between triggers,	1357	This doesn't mean there will always be 3600 seconds in between triggers,
1272	but only that the the callback will be called when the system time shows a	1358	but only that the the callback will be called when the system time shows a
…		…
1277	C<ev_periodic> will try to run the callback in this mode at the next possible	1363	C<ev_periodic> will try to run the callback in this mode at the next possible
1278	time where C<time = at (mod interval)>, regardless of any time jumps.	1364	time where C<time = at (mod interval)>, regardless of any time jumps.
1279		1365
1280	For numerical stability it is preferable that the C<at> value is near	1366	For numerical stability it is preferable that the C<at> value is near
1281	C<ev_now ()> (the current time), but there is no range requirement for	1367	C<ev_now ()> (the current time), but there is no range requirement for
1282	this value.	1368	this value, and in fact is often specified as zero.
		1369
		1370	Note also that there is an upper limit to how often a timer can fire (cpu
		1371	speed for example), so if C<interval> is very small then timing stability
		1372	will of course detoriate. Libev itself tries to be exact to be about one
		1373	millisecond (if the OS supports it and the machine is fast enough).
1283		1374
1284	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1285		1376
1286	In this mode the values for C<interval> and C<at> are both being	1377	In this mode the values for C<interval> and C<at> are both being
1287	ignored. Instead, each time the periodic watcher gets scheduled, the	1378	ignored. Instead, each time the periodic watcher gets scheduled, the
1288	reschedule callback will be called with the watcher as first, and the	1379	reschedule callback will be called with the watcher as first, and the
1289	current time as second argument.	1380	current time as second argument.
1290		1381
1291	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1292	ever, or make any event loop modifications>. If you need to stop it,	1383	ever, or make ANY event loop modifications whatsoever>.
1293	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1294	starting an C<ev_prepare> watcher, which is legal).
1295		1384
		1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1387	only event loop modification you are allowed to do).
		1388
1296	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1297	ev_tstamp now)>, e.g.:	1390	*w, ev_tstamp now)>, e.g.:
1298		1391
1299	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1300	{	1393	{
1301	return now + 60.;	1394	return now + 60.;
1302	}	1395	}
…		…
1304	It must return the next time to trigger, based on the passed time value	1397	It must return the next time to trigger, based on the passed time value
1305	(that is, the lowest time value larger than to the second argument). It	1398	(that is, the lowest time value larger than to the second argument). It
1306	will usually be called just before the callback will be triggered, but	1399	will usually be called just before the callback will be triggered, but
1307	might be called at other times, too.	1400	might be called at other times, too.
1308		1401
1309	NOTE: I<< This callback must always return a time that is later than the	1402	NOTE: I<< This callback must always return a time that is higher than or
1310	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1403	equal to the passed C<now> value >>.
1311		1404
1312	This can be used to create very complex timers, such as a timer that	1405	This can be used to create very complex timers, such as a timer that
1313	triggers on each midnight, local time. To do this, you would calculate the	1406	triggers on "next midnight, local time". To do this, you would calculate the
1314	next midnight after C<now> and return the timestamp value for this. How	1407	next midnight after C<now> and return the timestamp value for this. How
1315	you do this is, again, up to you (but it is not trivial, which is the main	1408	you do this is, again, up to you (but it is not trivial, which is the main
1316	reason I omitted it as an example).	1409	reason I omitted it as an example).
1317		1410
1318	=back	1411	=back
…		…
1322	Simply stops and restarts the periodic watcher again. This is only useful	1415	Simply stops and restarts the periodic watcher again. This is only useful
1323	when you changed some parameters or the reschedule callback would return	1416	when you changed some parameters or the reschedule callback would return
1324	a different time than the last time it was called (e.g. in a crond like	1417	a different time than the last time it was called (e.g. in a crond like
1325	program when the crontabs have changed).	1418	program when the crontabs have changed).
1326		1419
		1420	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1421
		1422	When active, returns the absolute time that the watcher is supposed to
		1423	trigger next.
		1424
1327	=item ev_tstamp offset [read-write]	1425	=item ev_tstamp offset [read-write]
1328		1426
1329	When repeating, this contains the offset value, otherwise this is the	1427	When repeating, this contains the offset value, otherwise this is the
1330	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1331		1429
…		…
1341	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
1342		1440
1343	The current reschedule callback, or C<0>, if this functionality is	1441	The current reschedule callback, or C<0>, if this functionality is
1344	switched off. Can be changed any time, but changes only take effect when	1442	switched off. Can be changed any time, but changes only take effect when
1345	the periodic timer fires or C<ev_periodic_again> is being called.	1443	the periodic timer fires or C<ev_periodic_again> is being called.
1346
1347	=item ev_tstamp at [read-only]
1348
1349	When active, contains the absolute time that the watcher is supposed to
1350	trigger next.
1351		1444
1352	=back	1445	=back
1353		1446
1354	=head3 Examples	1447	=head3 Examples
1355		1448
…		…
1399	with the kernel (thus it coexists with your own signal handlers as long	1492	with the kernel (thus it coexists with your own signal handlers as long
1400	as you don't register any with libev). Similarly, when the last signal	1493	as you don't register any with libev). Similarly, when the last signal
1401	watcher for a signal is stopped libev will reset the signal handler to	1494	watcher for a signal is stopped libev will reset the signal handler to
1402	SIG_DFL (regardless of what it was set to before).	1495	SIG_DFL (regardless of what it was set to before).
1403		1496
		1497	If possible and supported, libev will install its handlers with
		1498	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1499	interrupted. If you have a problem with syscalls getting interrupted by
		1500	signals you can block all signals in an C<ev_check> watcher and unblock
		1501	them in an C<ev_prepare> watcher.
		1502
1404	=head3 Watcher-Specific Functions and Data Members	1503	=head3 Watcher-Specific Functions and Data Members
1405		1504
1406	=over 4	1505	=over 4
1407		1506
1408	=item ev_signal_init (ev_signal *, callback, int signum)	1507	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1416		1515
1417	The signal the watcher watches out for.	1516	The signal the watcher watches out for.
1418		1517
1419	=back	1518	=back
1420		1519
		1520	=head3 Examples
		1521
		1522	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1523
		1524	static void
		1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1526	{
		1527	ev_unloop (loop, EVUNLOOP_ALL);
		1528	}
		1529
		1530	struct ev_signal signal_watcher;
		1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1532	ev_signal_start (loop, &sigint_cb);
		1533
1421		1534
1422	=head2 C<ev_child> - watch out for process status changes	1535	=head2 C<ev_child> - watch out for process status changes
1423		1536
1424	Child watchers trigger when your process receives a SIGCHLD in response to	1537	Child watchers trigger when your process receives a SIGCHLD in response to
1425	some child status changes (most typically when a child of yours dies).	1538	some child status changes (most typically when a child of yours dies). It
		1539	is permissible to install a child watcher I<after> the child has been
		1540	forked (which implies it might have already exited), as long as the event
		1541	loop isn't entered (or is continued from a watcher).
		1542
		1543	Only the default event loop is capable of handling signals, and therefore
		1544	you can only rgeister child watchers in the default event loop.
		1545
		1546	=head3 Process Interaction
		1547
		1548	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1549	initialised. This is necessary to guarantee proper behaviour even if
		1550	the first child watcher is started after the child exits. The occurance
		1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1552	synchronously as part of the event loop processing. Libev always reaps all
		1553	children, even ones not watched.
		1554
		1555	=head3 Overriding the Built-In Processing
		1556
		1557	Libev offers no special support for overriding the built-in child
		1558	processing, but if your application collides with libev's default child
		1559	handler, you can override it easily by installing your own handler for
		1560	C<SIGCHLD> after initialising the default loop, and making sure the
		1561	default loop never gets destroyed. You are encouraged, however, to use an
		1562	event-based approach to child reaping and thus use libev's support for
		1563	that, so other libev users can use C<ev_child> watchers freely.
1426		1564
1427	=head3 Watcher-Specific Functions and Data Members	1565	=head3 Watcher-Specific Functions and Data Members
1428		1566
1429	=over 4	1567	=over 4
1430		1568
1431	=item ev_child_init (ev_child *, callback, int pid)	1569	=item ev_child_init (ev_child *, callback, int pid, int trace)
1432		1570
1433	=item ev_child_set (ev_child *, int pid)	1571	=item ev_child_set (ev_child *, int pid, int trace)
1434		1572
1435	Configures the watcher to wait for status changes of process C<pid> (or	1573	Configures the watcher to wait for status changes of process C<pid> (or
1436	I<any> process if C<pid> is specified as C<0>). The callback can look	1574	I<any> process if C<pid> is specified as C<0>). The callback can look
1437	at the C<rstatus> member of the C<ev_child> watcher structure to see	1575	at the C<rstatus> member of the C<ev_child> watcher structure to see
1438	the status word (use the macros from C<sys/wait.h> and see your systems	1576	the status word (use the macros from C<sys/wait.h> and see your systems
1439	C<waitpid> documentation). The C<rpid> member contains the pid of the	1577	C<waitpid> documentation). The C<rpid> member contains the pid of the
1440	process causing the status change.	1578	process causing the status change. C<trace> must be either C<0> (only
		1579	activate the watcher when the process terminates) or C<1> (additionally
		1580	activate the watcher when the process is stopped or continued).
1441		1581
1442	=item int pid [read-only]	1582	=item int pid [read-only]
1443		1583
1444	The process id this watcher watches out for, or C<0>, meaning any process id.	1584	The process id this watcher watches out for, or C<0>, meaning any process id.
1445		1585
…		…
1454		1594
1455	=back	1595	=back
1456		1596
1457	=head3 Examples	1597	=head3 Examples
1458		1598
1459	Example: Try to exit cleanly on SIGINT and SIGTERM.	1599	Example: C<fork()> a new process and install a child handler to wait for
		1600	its completion.
		1601
		1602	ev_child cw;
1460		1603
1461	static void	1604	static void
1462	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1605	child_cb (EV_P_ struct ev_child *w, int revents)
1463	{	1606	{
1464	ev_unloop (loop, EVUNLOOP_ALL);	1607	ev_child_stop (EV_A_ w);
		1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1465	}	1609	}
1466		1610
1467	struct ev_signal signal_watcher;	1611	pid_t pid = fork ();
1468	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1612
1469	ev_signal_start (loop, &sigint_cb);	1613	if (pid < 0)
		1614	// error
		1615	else if (pid == 0)
		1616	{
		1617	// the forked child executes here
		1618	exit (1);
		1619	}
		1620	else
		1621	{
		1622	ev_child_init (&cw, child_cb, pid, 0);
		1623	ev_child_start (EV_DEFAULT_ &cw);
		1624	}
1470		1625
1471		1626
1472	=head2 C<ev_stat> - did the file attributes just change?	1627	=head2 C<ev_stat> - did the file attributes just change?
1473		1628
1474	This watches a filesystem path for attribute changes. That is, it calls	1629	This watches a filesystem path for attribute changes. That is, it calls
…		…
1497	as even with OS-supported change notifications, this can be	1652	as even with OS-supported change notifications, this can be
1498	resource-intensive.	1653	resource-intensive.
1499		1654
1500	At the time of this writing, only the Linux inotify interface is	1655	At the time of this writing, only the Linux inotify interface is
1501	implemented (implementing kqueue support is left as an exercise for the	1656	implemented (implementing kqueue support is left as an exercise for the
		1657	reader, note, however, that the author sees no way of implementing ev_stat
1502	reader). Inotify will be used to give hints only and should not change the	1658	semantics with kqueue). Inotify will be used to give hints only and should
1503	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1659	not change the semantics of C<ev_stat> watchers, which means that libev
1504	to fall back to regular polling again even with inotify, but changes are	1660	sometimes needs to fall back to regular polling again even with inotify,
1505	usually detected immediately, and if the file exists there will be no	1661	but changes are usually detected immediately, and if the file exists there
1506	polling.	1662	will be no polling.
		1663
		1664	=head3 ABI Issues (Largefile Support)
		1665
		1666	Libev by default (unless the user overrides this) uses the default
		1667	compilation environment, which means that on systems with optionally
		1668	disabled large file support, you get the 32 bit version of the stat
		1669	structure. When using the library from programs that change the ABI to
		1670	use 64 bit file offsets the programs will fail. In that case you have to
		1671	compile libev with the same flags to get binary compatibility. This is
		1672	obviously the case with any flags that change the ABI, but the problem is
		1673	most noticably with ev_stat and largefile support.
1507		1674
1508	=head3 Inotify	1675	=head3 Inotify
1509		1676
1510	When C<inotify (7)> support has been compiled into libev (generally only	1677	When C<inotify (7)> support has been compiled into libev (generally only
1511	available on Linux) and present at runtime, it will be used to speed up	1678	available on Linux) and present at runtime, it will be used to speed up
1512	change detection where possible. The inotify descriptor will be created lazily	1679	change detection where possible. The inotify descriptor will be created lazily
1513	when the first C<ev_stat> watcher is being started.	1680	when the first C<ev_stat> watcher is being started.
1514		1681
1515	Inotify presense does not change the semantics of C<ev_stat> watchers	1682	Inotify presence does not change the semantics of C<ev_stat> watchers
1516	except that changes might be detected earlier, and in some cases, to avoid	1683	except that changes might be detected earlier, and in some cases, to avoid
1517	making regular C<stat> calls. Even in the presense of inotify support	1684	making regular C<stat> calls. Even in the presence of inotify support
1518	there are many cases where libev has to resort to regular C<stat> polling.	1685	there are many cases where libev has to resort to regular C<stat> polling.
1519		1686
1520	(There is no support for kqueue, as apparently it cannot be used to	1687	(There is no support for kqueue, as apparently it cannot be used to
1521	implement this functionality, due to the requirement of having a file	1688	implement this functionality, due to the requirement of having a file
1522	descriptor open on the object at all times).	1689	descriptor open on the object at all times).
…		…
1525		1692
1526	The C<stat ()> syscall only supports full-second resolution portably, and	1693	The C<stat ()> syscall only supports full-second resolution portably, and
1527	even on systems where the resolution is higher, many filesystems still	1694	even on systems where the resolution is higher, many filesystems still
1528	only support whole seconds.	1695	only support whole seconds.
1529		1696
1530	That means that, if the time is the only thing that changes, you might	1697	That means that, if the time is the only thing that changes, you can
1531	miss updates: on the first update, C<ev_stat> detects a change and calls	1698	easily miss updates: on the first update, C<ev_stat> detects a change and
1532	your callback, which does something. When there is another update within	1699	calls your callback, which does something. When there is another update
1533	the same second, C<ev_stat> will be unable to detect it.	1700	within the same second, C<ev_stat> will be unable to detect it as the stat
		1701	data does not change.
1534		1702
1535	The solution to this is to delay acting on a change for a second (or till	1703	The solution to this is to delay acting on a change for slightly more
1536	the next second boundary), using a roughly one-second delay C<ev_timer>	1704	than a second (or till slightly after the next full second boundary), using
1537	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1538	is added to work around small timing inconsistencies of some operating	1706	ev_timer_again (loop, w)>).
1539	systems.	1707
		1708	The C<.02> offset is added to work around small timing inconsistencies
		1709	of some operating systems (where the second counter of the current time
		1710	might be be delayed. One such system is the Linux kernel, where a call to
		1711	C<gettimeofday> might return a timestamp with a full second later than
		1712	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1713	update file times then there will be a small window where the kernel uses
		1714	the previous second to update file times but libev might already execute
		1715	the timer callback).
1540		1716
1541	=head3 Watcher-Specific Functions and Data Members	1717	=head3 Watcher-Specific Functions and Data Members
1542		1718
1543	=over 4	1719	=over 4
1544		1720
…		…
1550	C<path>. The C<interval> is a hint on how quickly a change is expected to	1726	C<path>. The C<interval> is a hint on how quickly a change is expected to
1551	be detected and should normally be specified as C<0> to let libev choose	1727	be detected and should normally be specified as C<0> to let libev choose
1552	a suitable value. The memory pointed to by C<path> must point to the same	1728	a suitable value. The memory pointed to by C<path> must point to the same
1553	path for as long as the watcher is active.	1729	path for as long as the watcher is active.
1554		1730
1555	The callback will be receive C<EV_STAT> when a change was detected,	1731	The callback will receive C<EV_STAT> when a change was detected, relative
1556	relative to the attributes at the time the watcher was started (or the	1732	to the attributes at the time the watcher was started (or the last change
1557	last change was detected).	1733	was detected).
1558		1734
1559	=item ev_stat_stat (ev_stat *)	1735	=item ev_stat_stat (loop, ev_stat *)
1560		1736
1561	Updates the stat buffer immediately with new values. If you change the	1737	Updates the stat buffer immediately with new values. If you change the
1562	watched path in your callback, you could call this fucntion to avoid	1738	watched path in your callback, you could call this function to avoid
1563	detecting this change (while introducing a race condition). Can also be	1739	detecting this change (while introducing a race condition if you are not
1564	useful simply to find out the new values.	1740	the only one changing the path). Can also be useful simply to find out the
		1741	new values.
1565		1742
1566	=item ev_statdata attr [read-only]	1743	=item ev_statdata attr [read-only]
1567		1744
1568	The most-recently detected attributes of the file. Although the type is of	1745	The most-recently detected attributes of the file. Although the type is
1569	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1746	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1570	suitable for your system. If the C<st_nlink> member is C<0>, then there	1747	suitable for your system, but you can only rely on the POSIX-standardised
		1748	members to be present. If the C<st_nlink> member is C<0>, then there was
1571	was some error while C<stat>ing the file.	1749	some error while C<stat>ing the file.
1572		1750
1573	=item ev_statdata prev [read-only]	1751	=item ev_statdata prev [read-only]
1574		1752
1575	The previous attributes of the file. The callback gets invoked whenever	1753	The previous attributes of the file. The callback gets invoked whenever
1576	C<prev> != C<attr>.	1754	C<prev> != C<attr>, or, more precisely, one or more of these members
		1755	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1756	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1577		1757
1578	=item ev_tstamp interval [read-only]	1758	=item ev_tstamp interval [read-only]
1579		1759
1580	The specified interval.	1760	The specified interval.
1581		1761
…		…
1635	}	1815	}
1636		1816
1637	...	1817	...
1638	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1639	ev_stat_start (loop, &passwd);	1819	ev_stat_start (loop, &passwd);
1640	ev_timer_init (&timer, timer_cb, 0., 1.01);	1820	ev_timer_init (&timer, timer_cb, 0., 1.02);
1641		1821
1642		1822
1643	=head2 C<ev_idle> - when you've got nothing better to do...	1823	=head2 C<ev_idle> - when you've got nothing better to do...
1644		1824
1645	Idle watchers trigger events when no other events of the same or higher	1825	Idle watchers trigger events when no other events of the same or higher
…		…
1681	static void	1861	static void
1682	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1683	{	1863	{
1684	free (w);	1864	free (w);
1685	// now do something you wanted to do when the program has	1865	// now do something you wanted to do when the program has
1686	// no longer asnything immediate to do.	1866	// no longer anything immediate to do.
1687	}	1867	}
1688		1868
1689	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1690	ev_idle_init (idle_watcher, idle_cb);	1870	ev_idle_init (idle_watcher, idle_cb);
1691	ev_idle_start (loop, idle_cb);	1871	ev_idle_start (loop, idle_cb);
…		…
1733		1913
1734	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1735	priority, to ensure that they are being run before any other watchers	1915	priority, to ensure that they are being run before any other watchers
1736	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1737	too) should not activate ("feed") events into libev. While libev fully	1917	too) should not activate ("feed") events into libev. While libev fully
1738	supports this, they will be called before other C<ev_check> watchers	1918	supports this, they might get executed before other C<ev_check> watchers
1739	did their job. As C<ev_check> watchers are often used to embed other	1919	did their job. As C<ev_check> watchers are often used to embed other
1740	(non-libev) event loops those other event loops might be in an unusable	1920	(non-libev) event loops those other event loops might be in an unusable
1741	state until their C<ev_check> watcher ran (always remind yourself to	1921	state until their C<ev_check> watcher ran (always remind yourself to
1742	coexist peacefully with others).	1922	coexist peacefully with others).
1743		1923
…		…
1758	=head3 Examples	1938	=head3 Examples
1759		1939
1760	There are a number of principal ways to embed other event loops or modules	1940	There are a number of principal ways to embed other event loops or modules
1761	into libev. Here are some ideas on how to include libadns into libev	1941	into libev. Here are some ideas on how to include libadns into libev
1762	(there is a Perl module named C<EV::ADNS> that does this, which you could	1942	(there is a Perl module named C<EV::ADNS> that does this, which you could
1763	use for an actually working example. Another Perl module named C<EV::Glib>	1943	use as a working example. Another Perl module named C<EV::Glib> embeds a
1764	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1944	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1765	into the Glib event loop).	1945	Glib event loop).
1766		1946
1767	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1947	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1768	and in a check watcher, destroy them and call into libadns. What follows	1948	and in a check watcher, destroy them and call into libadns. What follows
1769	is pseudo-code only of course. This requires you to either use a low	1949	is pseudo-code only of course. This requires you to either use a low
1770	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as
…		…
2032	believe me.	2212	believe me.
2033		2213
2034	=back	2214	=back
2035		2215
2036		2216
		2217	=head2 C<ev_async> - how to wake up another event loop
		2218
		2219	In general, you cannot use an C<ev_loop> from multiple threads or other
		2220	asynchronous sources such as signal handlers (as opposed to multiple event
		2221	loops - those are of course safe to use in different threads).
		2222
		2223	Sometimes, however, you need to wake up another event loop you do not
		2224	control, for example because it belongs to another thread. This is what
		2225	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2226	can signal it by calling C<ev_async_send>, which is thread- and signal
		2227	safe.
		2228
		2229	This functionality is very similar to C<ev_signal> watchers, as signals,
		2230	too, are asynchronous in nature, and signals, too, will be compressed
		2231	(i.e. the number of callback invocations may be less than the number of
		2232	C<ev_async_sent> calls).
		2233
		2234	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2235	just the default loop.
		2236
		2237	=head3 Queueing
		2238
		2239	C<ev_async> does not support queueing of data in any way. The reason
		2240	is that the author does not know of a simple (or any) algorithm for a
		2241	multiple-writer-single-reader queue that works in all cases and doesn't
		2242	need elaborate support such as pthreads.
		2243
		2244	That means that if you want to queue data, you have to provide your own
		2245	queue. But at least I can tell you would implement locking around your
		2246	queue:
		2247
		2248	=over 4
		2249
		2250	=item queueing from a signal handler context
		2251
		2252	To implement race-free queueing, you simply add to the queue in the signal
		2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2254	some fictitiuous SIGUSR1 handler:
		2255
		2256	static ev_async mysig;
		2257
		2258	static void
		2259	sigusr1_handler (void)
		2260	{
		2261	sometype data;
		2262
		2263	// no locking etc.
		2264	queue_put (data);
		2265	ev_async_send (EV_DEFAULT_ &mysig);
		2266	}
		2267
		2268	static void
		2269	mysig_cb (EV_P_ ev_async *w, int revents)
		2270	{
		2271	sometype data;
		2272	sigset_t block, prev;
		2273
		2274	sigemptyset (&block);
		2275	sigaddset (&block, SIGUSR1);
		2276	sigprocmask (SIG_BLOCK, &block, &prev);
		2277
		2278	while (queue_get (&data))
		2279	process (data);
		2280
		2281	if (sigismember (&prev, SIGUSR1)
		2282	sigprocmask (SIG_UNBLOCK, &block, 0);
		2283	}
		2284
		2285	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2286	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2287	either...).
		2288
		2289	=item queueing from a thread context
		2290
		2291	The strategy for threads is different, as you cannot (easily) block
		2292	threads but you can easily preempt them, so to queue safely you need to
		2293	employ a traditional mutex lock, such as in this pthread example:
		2294
		2295	static ev_async mysig;
		2296	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2297
		2298	static void
		2299	otherthread (void)
		2300	{
		2301	// only need to lock the actual queueing operation
		2302	pthread_mutex_lock (&mymutex);
		2303	queue_put (data);
		2304	pthread_mutex_unlock (&mymutex);
		2305
		2306	ev_async_send (EV_DEFAULT_ &mysig);
		2307	}
		2308
		2309	static void
		2310	mysig_cb (EV_P_ ev_async *w, int revents)
		2311	{
		2312	pthread_mutex_lock (&mymutex);
		2313
		2314	while (queue_get (&data))
		2315	process (data);
		2316
		2317	pthread_mutex_unlock (&mymutex);
		2318	}
		2319
		2320	=back
		2321
		2322
		2323	=head3 Watcher-Specific Functions and Data Members
		2324
		2325	=over 4
		2326
		2327	=item ev_async_init (ev_async *, callback)
		2328
		2329	Initialises and configures the async watcher - it has no parameters of any
		2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2331	believe me.
		2332
		2333	=item ev_async_send (loop, ev_async *)
		2334
		2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2337	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2338	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2339	section below on what exactly this means).
		2340
		2341	This call incurs the overhead of a syscall only once per loop iteration,
		2342	so while the overhead might be noticable, it doesn't apply to repeated
		2343	calls to C<ev_async_send>.
		2344
		2345	=item bool = ev_async_pending (ev_async *)
		2346
		2347	Returns a non-zero value when C<ev_async_send> has been called on the
		2348	watcher but the event has not yet been processed (or even noted) by the
		2349	event loop.
		2350
		2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2352	the loop iterates next and checks for the watcher to have become active,
		2353	it will reset the flag again. C<ev_async_pending> can be used to very
		2354	quickly check wether invoking the loop might be a good idea.
		2355
		2356	Not that this does I<not> check wether the watcher itself is pending, only
		2357	wether it has been requested to make this watcher pending.
		2358
		2359	=back
		2360
		2361
2037	=head1 OTHER FUNCTIONS	2362	=head1 OTHER FUNCTIONS
2038		2363
2039	There are some other functions of possible interest. Described. Here. Now.	2364	There are some other functions of possible interest. Described. Here. Now.
2040		2365
2041	=over 4	2366	=over 4
…		…
2109		2434
2110	=item * Priorities are not currently supported. Initialising priorities	2435	=item * Priorities are not currently supported. Initialising priorities
2111	will fail and all watchers will have the same priority, even though there	2436	will fail and all watchers will have the same priority, even though there
2112	is an ev_pri field.	2437	is an ev_pri field.
2113		2438
		2439	=item * In libevent, the last base created gets the signals, in libev, the
		2440	first base created (== the default loop) gets the signals.
		2441
2114	=item * Other members are not supported.	2442	=item * Other members are not supported.
2115		2443
2116	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2444	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2117	to use the libev header file and library.	2445	to use the libev header file and library.
2118		2446
…		…
2268	Example: Define a class with an IO and idle watcher, start one of them in	2596	Example: Define a class with an IO and idle watcher, start one of them in
2269	the constructor.	2597	the constructor.
2270		2598
2271	class myclass	2599	class myclass
2272	{	2600	{
2273	ev_io io; void io_cb (ev::io &w, int revents);	2601	ev::io io; void io_cb (ev::io &w, int revents);
2274	ev_idle idle void idle_cb (ev::idle &w, int revents);	2602	ev:idle idle void idle_cb (ev::idle &w, int revents);
2275		2603
2276	myclass ();	2604	myclass (int fd)
2277	}
2278
2279	myclass::myclass (int fd)
2280	{	2605	{
2281	io .set <myclass, &myclass::io_cb > (this);	2606	io .set <myclass, &myclass::io_cb > (this);
2282	idle.set <myclass, &myclass::idle_cb> (this);	2607	idle.set <myclass, &myclass::idle_cb> (this);
2283		2608
2284	io.start (fd, ev::READ);	2609	io.start (fd, ev::READ);
		2610	}
2285	}	2611	};
		2612
		2613
		2614	=head1 OTHER LANGUAGE BINDINGS
		2615
		2616	Libev does not offer other language bindings itself, but bindings for a
		2617	numbe rof languages exist in the form of third-party packages. If you know
		2618	any interesting language binding in addition to the ones listed here, drop
		2619	me a note.
		2620
		2621	=over 4
		2622
		2623	=item Perl
		2624
		2625	The EV module implements the full libev API and is actually used to test
		2626	libev. EV is developed together with libev. Apart from the EV core module,
		2627	there are additional modules that implement libev-compatible interfaces
		2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2630
		2631	It can be found and installed via CPAN, its homepage is found at
		2632	L<http://software.schmorp.de/pkg/EV>.
		2633
		2634	=item Ruby
		2635
		2636	Tony Arcieri has written a ruby extension that offers access to a subset
		2637	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2638	more on top of it. It can be found via gem servers. Its homepage is at
		2639	L<http://rev.rubyforge.org/>.
		2640
		2641	=item D
		2642
		2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2645
		2646	=back
2286		2647
2287		2648
2288	=head1 MACRO MAGIC	2649	=head1 MACRO MAGIC
2289		2650
2290	Libev can be compiled with a variety of options, the most fundamantal	2651	Libev can be compiled with a variety of options, the most fundamantal
…		…
2326		2687
2327	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2328		2689
2329	Similar to the other two macros, this gives you the value of the default	2690	Similar to the other two macros, this gives you the value of the default
2330	loop, if multiple loops are supported ("ev loop default").	2691	loop, if multiple loops are supported ("ev loop default").
		2692
		2693	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2694
		2695	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2696	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2697	is undefined when the default loop has not been initialised by a previous
		2698	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2699
		2700	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2701	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2331		2702
2332	=back	2703	=back
2333		2704
2334	Example: Declare and initialise a check watcher, utilising the above	2705	Example: Declare and initialise a check watcher, utilising the above
2335	macros so it will work regardless of whether multiple loops are supported	2706	macros so it will work regardless of whether multiple loops are supported
…		…
2431		2802
2432	libev.m4	2803	libev.m4
2433		2804
2434	=head2 PREPROCESSOR SYMBOLS/MACROS	2805	=head2 PREPROCESSOR SYMBOLS/MACROS
2435		2806
2436	Libev can be configured via a variety of preprocessor symbols you have to define	2807	Libev can be configured via a variety of preprocessor symbols you have to
2437	before including any of its files. The default is not to build for multiplicity	2808	define before including any of its files. The default in the absense of
2438	and only include the select backend.	2809	autoconf is noted for every option.
2439		2810
2440	=over 4	2811	=over 4
2441		2812
2442	=item EV_STANDALONE	2813	=item EV_STANDALONE
2443		2814
…		…
2469	=item EV_USE_NANOSLEEP	2840	=item EV_USE_NANOSLEEP
2470		2841
2471	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2472	and will use it for delays. Otherwise it will use C<select ()>.	2843	and will use it for delays. Otherwise it will use C<select ()>.
2473		2844
		2845	=item EV_USE_EVENTFD
		2846
		2847	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2848	available and will probe for kernel support at runtime. This will improve
		2849	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2850	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2851	2.7 or newer, otherwise disabled.
		2852
2474	=item EV_USE_SELECT	2853	=item EV_USE_SELECT
2475		2854
2476	If undefined or defined to be C<1>, libev will compile in support for the	2855	If undefined or defined to be C<1>, libev will compile in support for the
2477	C<select>(2) backend. No attempt at autodetection will be done: if no	2856	C<select>(2) backend. No attempt at autodetection will be done: if no
2478	other method takes over, select will be it. Otherwise the select backend	2857	other method takes over, select will be it. Otherwise the select backend
…		…
2514		2893
2515	=item EV_USE_EPOLL	2894	=item EV_USE_EPOLL
2516		2895
2517	If defined to be C<1>, libev will compile in support for the Linux	2896	If defined to be C<1>, libev will compile in support for the Linux
2518	C<epoll>(7) backend. Its availability will be detected at runtime,	2897	C<epoll>(7) backend. Its availability will be detected at runtime,
2519	otherwise another method will be used as fallback. This is the	2898	otherwise another method will be used as fallback. This is the preferred
2520	preferred backend for GNU/Linux systems.	2899	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2900	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2521		2901
2522	=item EV_USE_KQUEUE	2902	=item EV_USE_KQUEUE
2523		2903
2524	If defined to be C<1>, libev will compile in support for the BSD style	2904	If defined to be C<1>, libev will compile in support for the BSD style
2525	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2905	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2544		2924
2545	=item EV_USE_INOTIFY	2925	=item EV_USE_INOTIFY
2546		2926
2547	If defined to be C<1>, libev will compile in support for the Linux inotify	2927	If defined to be C<1>, libev will compile in support for the Linux inotify
2548	interface to speed up C<ev_stat> watchers. Its actual availability will	2928	interface to speed up C<ev_stat> watchers. Its actual availability will
2549	be detected at runtime.	2929	be detected at runtime. If undefined, it will be enabled if the headers
		2930	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2931
		2932	=item EV_ATOMIC_T
		2933
		2934	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2935	access is atomic with respect to other threads or signal contexts. No such
		2936	type is easily found in the C language, so you can provide your own type
		2937	that you know is safe for your purposes. It is used both for signal handler "locking"
		2938	as well as for signal and thread safety in C<ev_async> watchers.
		2939
		2940	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2941	(from F<signal.h>), which is usually good enough on most platforms.
2550		2942
2551	=item EV_H	2943	=item EV_H
2552		2944
2553	The name of the F<ev.h> header file used to include it. The default if	2945	The name of the F<ev.h> header file used to include it. The default if
2554	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to	2946	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2555	virtually rename the F<ev.h> header file in case of conflicts.	2947	used to virtually rename the F<ev.h> header file in case of conflicts.
2556		2948
2557	=item EV_CONFIG_H	2949	=item EV_CONFIG_H
2558		2950
2559	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2560	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2561	C<EV_H>, above.	2953	C<EV_H>, above.
2562		2954
2563	=item EV_EVENT_H	2955	=item EV_EVENT_H
2564		2956
2565	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2566	of how the F<event.h> header can be found, the dfeault is C<"event.h">.	2958	of how the F<event.h> header can be found, the default is C<"event.h">.
2567		2959
2568	=item EV_PROTOTYPES	2960	=item EV_PROTOTYPES
2569		2961
2570	If defined to be C<0>, then F<ev.h> will not define any function	2962	If defined to be C<0>, then F<ev.h> will not define any function
2571	prototypes, but still define all the structs and other symbols. This is	2963	prototypes, but still define all the structs and other symbols. This is
…		…
2622	=item EV_FORK_ENABLE	3014	=item EV_FORK_ENABLE
2623		3015
2624	If undefined or defined to be C<1>, then fork watchers are supported. If	3016	If undefined or defined to be C<1>, then fork watchers are supported. If
2625	defined to be C<0>, then they are not.	3017	defined to be C<0>, then they are not.
2626		3018
		3019	=item EV_ASYNC_ENABLE
		3020
		3021	If undefined or defined to be C<1>, then async watchers are supported. If
		3022	defined to be C<0>, then they are not.
		3023
2627	=item EV_MINIMAL	3024	=item EV_MINIMAL
2628		3025
2629	If you need to shave off some kilobytes of code at the expense of some	3026	If you need to shave off some kilobytes of code at the expense of some
2630	speed, define this symbol to C<1>. Currently only used for gcc to override	3027	speed, define this symbol to C<1>. Currently this is used to override some
2631	some inlining decisions, saves roughly 30% codesize of amd64.	3028	inlining decisions, saves roughly 30% codesize of amd64. It also selects a
		3029	much smaller 2-heap for timer management over the default 4-heap.
2632		3030
2633	=item EV_PID_HASHSIZE	3031	=item EV_PID_HASHSIZE
2634		3032
2635	C<ev_child> watchers use a small hash table to distribute workload by	3033	C<ev_child> watchers use a small hash table to distribute workload by
2636	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2642	C<ev_stat> watchers use a small hash table to distribute workload by	3040	C<ev_stat> watchers use a small hash table to distribute workload by
2643	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2644	usually more than enough. If you need to manage thousands of C<ev_stat>	3042	usually more than enough. If you need to manage thousands of C<ev_stat>
2645	watchers you might want to increase this value (I<must> be a power of	3043	watchers you might want to increase this value (I<must> be a power of
2646	two).	3044	two).
		3045
		3046	=item EV_USE_4HEAP
		3047
		3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3050	to C<1>. The 4-heap uses more complicated (longer) code but has
		3051	noticably faster performance with many (thousands) of watchers.
		3052
		3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3054	(disabled).
		3055
		3056	=item EV_HEAP_CACHE_AT
		3057
		3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3059	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3062	but avoids random read accesses on heap changes. This improves performance
		3063	noticably with with many (hundreds) of watchers.
		3064
		3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3066	(disabled).
		3067
		3068	=item EV_VERIFY
		3069
		3070	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3071	be done: If set to C<0>, no internal verification code will be compiled
		3072	in. If set to C<1>, then verification code will be compiled in, but not
		3073	called. If set to C<2>, then the internal verification code will be
		3074	called once per loop, which can slow down libev. If set to C<3>, then the
		3075	verification code will be called very frequently, which will slow down
		3076	libev considerably.
		3077
		3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3079	C<0.>
2647		3080
2648	=item EV_COMMON	3081	=item EV_COMMON
2649		3082
2650	By default, all watchers have a C<void *data> member. By redefining	3083	By default, all watchers have a C<void *data> member. By redefining
2651	this macro to a something else you can include more and other types of	3084	this macro to a something else you can include more and other types of
…		…
2725		3158
2726	#include "ev_cpp.h"	3159	#include "ev_cpp.h"
2727	#include "ev.c"	3160	#include "ev.c"
2728		3161
2729		3162
		3163	=head1 THREADS AND COROUTINES
		3164
		3165	=head2 THREADS
		3166
		3167	Libev itself is completely threadsafe, but it uses no locking. This
		3168	means that you can use as many loops as you want in parallel, as long as
		3169	only one thread ever calls into one libev function with the same loop
		3170	parameter.
		3171
		3172	Or put differently: calls with different loop parameters can be done in
		3173	parallel from multiple threads, calls with the same loop parameter must be
		3174	done serially (but can be done from different threads, as long as only one
		3175	thread ever is inside a call at any point in time, e.g. by using a mutex
		3176	per loop).
		3177
		3178	If you want to know which design is best for your problem, then I cannot
		3179	help you but by giving some generic advice:
		3180
		3181	=over 4
		3182
		3183	=item * most applications have a main thread: use the default libev loop
		3184	in that thread, or create a seperate thread running only the default loop.
		3185
		3186	This helps integrating other libraries or software modules that use libev
		3187	themselves and don't care/know about threading.
		3188
		3189	=item * one loop per thread is usually a good model.
		3190
		3191	Doing this is almost never wrong, sometimes a better-performance model
		3192	exists, but it is always a good start.
		3193
		3194	=item * other models exist, such as the leader/follower pattern, where one
		3195	loop is handed through multiple threads in a kind of round-robbin fashion.
		3196
		3197	Chosing a model is hard - look around, learn, know that usually you cna do
		3198	better than you currently do :-)
		3199
		3200	=item * often you need to talk to some other thread which blocks in the
		3201	event loop - C<ev_async> watchers can be used to wake them up from other
		3202	threads safely (or from signal contexts...).
		3203
		3204	=back
		3205
		3206	=head2 COROUTINES
		3207
		3208	Libev is much more accomodating to coroutines ("cooperative threads"):
		3209	libev fully supports nesting calls to it's functions from different
		3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3211	different coroutines and switch freely between both coroutines running the
		3212	loop, as long as you don't confuse yourself). The only exception is that
		3213	you must not do this from C<ev_periodic> reschedule callbacks.
		3214
		3215	Care has been invested into making sure that libev does not keep local
		3216	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3217	switches.
		3218
		3219
2730	=head1 COMPLEXITIES	3220	=head1 COMPLEXITIES
2731		3221
2732	In this section the complexities of (many of) the algorithms used inside	3222	In this section the complexities of (many of) the algorithms used inside
2733	libev will be explained. For complexity discussions about backends see the	3223	libev will be explained. For complexity discussions about backends see the
2734	documentation for C<ev_default_init>.	3224	documentation for C<ev_default_init>.
…		…
2750	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2751		3241
2752	That means that changing a timer costs less than removing/adding them	3242	That means that changing a timer costs less than removing/adding them
2753	as only the relative motion in the event queue has to be paid for.	3243	as only the relative motion in the event queue has to be paid for.
2754		3244
2755	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2756		3246
2757	These just add the watcher into an array or at the head of a list.	3247	These just add the watcher into an array or at the head of a list.
2758		3248
2759	=item Stopping check/prepare/idle watchers: O(1)	3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2760		3250
2761	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2762		3252
2763	These watchers are stored in lists then need to be walked to find the	3253	These watchers are stored in lists then need to be walked to find the
2764	correct watcher to remove. The lists are usually short (you don't usually	3254	correct watcher to remove. The lists are usually short (you don't usually
2765	have many watchers waiting for the same fd or signal).	3255	have many watchers waiting for the same fd or signal).
2766		3256
2767	=item Finding the next timer in each loop iteration: O(1)	3257	=item Finding the next timer in each loop iteration: O(1)
2768		3258
2769	By virtue of using a binary heap, the next timer is always found at the	3259	By virtue of using a binary or 4-heap, the next timer is always found at a
2770	beginning of the storage array.	3260	fixed position in the storage array.
2771		3261
2772	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2773		3263
2774	A change means an I/O watcher gets started or stopped, which requires	3264	A change means an I/O watcher gets started or stopped, which requires
2775	libev to recalculate its status (and possibly tell the kernel, depending	3265	libev to recalculate its status (and possibly tell the kernel, depending
…		…
2780	=item Priority handling: O(number_of_priorities)	3270	=item Priority handling: O(number_of_priorities)
2781		3271
2782	Priorities are implemented by allocating some space for each	3272	Priorities are implemented by allocating some space for each
2783	priority. When doing priority-based operations, libev usually has to	3273	priority. When doing priority-based operations, libev usually has to
2784	linearly search all the priorities, but starting/stopping and activating	3274	linearly search all the priorities, but starting/stopping and activating
2785	watchers becomes O(1) w.r.t. prioritiy handling.	3275	watchers becomes O(1) w.r.t. priority handling.
		3276
		3277	=item Sending an ev_async: O(1)
		3278
		3279	=item Processing ev_async_send: O(number_of_async_watchers)
		3280
		3281	=item Processing signals: O(max_signal_number)
		3282
		3283	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3284	calls in the current loop iteration. Checking for async and signal events
		3285	involves iterating over all running async watchers or all signal numbers.
2786		3286
2787	=back	3287	=back
2788		3288
2789		3289
2790	=head1 Win32 platform limitations and workarounds	3290	=head1 Win32 platform limitations and workarounds
…		…
2794	model. Libev still offers limited functionality on this platform in	3294	model. Libev still offers limited functionality on this platform in
2795	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2796	descriptors. This only applies when using Win32 natively, not when using	3296	descriptors. This only applies when using Win32 natively, not when using
2797	e.g. cygwin.	3297	e.g. cygwin.
2798		3298
		3299	Lifting these limitations would basically require the full
		3300	re-implementation of the I/O system. If you are into these kinds of
		3301	things, then note that glib does exactly that for you in a very portable
		3302	way (note also that glib is the slowest event library known to man).
		3303
2799	There is no supported compilation method available on windows except	3304	There is no supported compilation method available on windows except
2800	embedding it into other applications.	3305	embedding it into other applications.
2801		3306
2802	Due to the many, low, and arbitrary limits on the win32 platform and the	3307	Due to the many, low, and arbitrary limits on the win32 platform and
2803	abysmal performance of winsockets, using a large number of sockets is not	3308	the abysmal performance of winsockets, using a large number of sockets
2804	recommended (and not reasonable). If your program needs to use more than	3309	is not recommended (and not reasonable). If your program needs to use
2805	a hundred or so sockets, then likely it needs to use a totally different	3310	more than a hundred or so sockets, then likely it needs to use a totally
2806	implementation for windows, as libev offers the POSIX model, which cannot	3311	different implementation for windows, as libev offers the POSIX readiness
2807	be implemented efficiently on windows (microsoft monopoly games).	3312	notification model, which cannot be implemented efficiently on windows
		3313	(microsoft monopoly games).
2808		3314
2809	=over 4	3315	=over 4
2810		3316
2811	=item The winsocket select function	3317	=item The winsocket select function
2812		3318
2813	The winsocket C<select> function doesn't follow POSIX in that it requires	3319	The winsocket C<select> function doesn't follow POSIX in that it
2814	socket I<handles> and not socket I<file descriptors>. This makes select	3320	requires socket I<handles> and not socket I<file descriptors> (it is
2815	very inefficient, and also requires a mapping from file descriptors	3321	also extremely buggy). This makes select very inefficient, and also
2816	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3322	requires a mapping from file descriptors to socket handles. See the
2817	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3323	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
2818	symbols for more info.	3324	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2819		3325
2820	The configuration for a "naked" win32 using the microsoft runtime	3326	The configuration for a "naked" win32 using the microsoft runtime
2821	libraries and raw winsocket select is:	3327	libraries and raw winsocket select is:
2822		3328
2823	#define EV_USE_SELECT 1	3329	#define EV_USE_SELECT 1
…		…
2826	Note that winsockets handling of fd sets is O(n), so you can easily get a	3332	Note that winsockets handling of fd sets is O(n), so you can easily get a
2827	complexity in the O(n²) range when using win32.	3333	complexity in the O(n²) range when using win32.
2828		3334
2829	=item Limited number of file descriptors	3335	=item Limited number of file descriptors
2830		3336
2831	Windows has numerous arbitrary (and low) limits on things. Early versions	3337	Windows has numerous arbitrary (and low) limits on things.
2832	of winsocket's select only supported waiting for a max. of C<64> handles	3338
		3339	Early versions of winsocket's select only supported waiting for a maximum
2833	(probably owning to the fact that all windows kernels can only wait for	3340	of C<64> handles (probably owning to the fact that all windows kernels
2834	C<64> things at the same time internally; microsoft recommends spawning a	3341	can only wait for C<64> things at the same time internally; microsoft
2835	chain of threads and wait for 63 handles and the previous thread in each).	3342	recommends spawning a chain of threads and wait for 63 handles and the
		3343	previous thread in each. Great).
2836		3344
2837	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3345	Newer versions support more handles, but you need to define C<FD_SETSIZE>
2838	to some high number (e.g. C<2048>) before compiling the winsocket select	3346	to some high number (e.g. C<2048>) before compiling the winsocket select
2839	call (which might be in libev or elsewhere, for example, perl does its own	3347	call (which might be in libev or elsewhere, for example, perl does its own
2840	select emulation on windows).	3348	select emulation on windows).
…		…
2852	calling select (O(n²)) will likely make this unworkable.	3360	calling select (O(n²)) will likely make this unworkable.
2853		3361
2854	=back	3362	=back
2855		3363
2856		3364
		3365	=head1 PORTABILITY REQUIREMENTS
		3366
		3367	In addition to a working ISO-C implementation, libev relies on a few
		3368	additional extensions:
		3369
		3370	=over 4
		3371
		3372	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3373
		3374	The type C<sig_atomic_t volatile> (or whatever is defined as
		3375	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3376	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3377	believed to be sufficiently portable.
		3378
		3379	=item C<sigprocmask> must work in a threaded environment
		3380
		3381	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3382	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3383	pthread implementations will either allow C<sigprocmask> in the "main
		3384	thread" or will block signals process-wide, both behaviours would
		3385	be compatible with libev. Interaction between C<sigprocmask> and
		3386	C<pthread_sigmask> could complicate things, however.
		3387
		3388	The most portable way to handle signals is to block signals in all threads
		3389	except the initial one, and run the default loop in the initial thread as
		3390	well.
		3391
		3392	=item C<long> must be large enough for common memory allocation sizes
		3393
		3394	To improve portability and simplify using libev, libev uses C<long>
		3395	internally instead of C<size_t> when allocating its data structures. On
		3396	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3397	is still at least 31 bits everywhere, which is enough for hundreds of
		3398	millions of watchers.
		3399
		3400	=item C<double> must hold a time value in seconds with enough accuracy
		3401
		3402	The type C<double> is used to represent timestamps. It is required to
		3403	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3404	enough for at least into the year 4000. This requirement is fulfilled by
		3405	implementations implementing IEEE 754 (basically all existing ones).
		3406
		3407	=back
		3408
		3409	If you know of other additional requirements drop me a note.
		3410
		3411
		3412	=head1 COMPILER WARNINGS
		3413
		3414	Depending on your compiler and compiler settings, you might get no or a
		3415	lot of warnings when compiling libev code. Some people are apparently
		3416	scared by this.
		3417
		3418	However, these are unavoidable for many reasons. For one, each compiler
		3419	has different warnings, and each user has different tastes regarding
		3420	warning options. "Warn-free" code therefore cannot be a goal except when
		3421	targetting a specific compiler and compiler-version.
		3422
		3423	Another reason is that some compiler warnings require elaborate
		3424	workarounds, or other changes to the code that make it less clear and less
		3425	maintainable.
		3426
		3427	And of course, some compiler warnings are just plain stupid, or simply
		3428	wrong (because they don't actually warn about the cindition their message
		3429	seems to warn about).
		3430
		3431	While libev is written to generate as few warnings as possible,
		3432	"warn-free" code is not a goal, and it is recommended not to build libev
		3433	with any compiler warnings enabled unless you are prepared to cope with
		3434	them (e.g. by ignoring them). Remember that warnings are just that:
		3435	warnings, not errors, or proof of bugs.
		3436
		3437
		3438	=head1 VALGRIND
		3439
		3440	Valgrind has a special section here because it is a popular tool that is
		3441	highly useful, but valgrind reports are very hard to interpret.
		3442
		3443	If you think you found a bug (memory leak, uninitialised data access etc.)
		3444	in libev, then check twice: If valgrind reports something like:
		3445
		3446	==2274== definitely lost: 0 bytes in 0 blocks.
		3447	==2274== possibly lost: 0 bytes in 0 blocks.
		3448	==2274== still reachable: 256 bytes in 1 blocks.
		3449
		3450	then there is no memory leak. Similarly, under some circumstances,
		3451	valgrind might report kernel bugs as if it were a bug in libev, or it
		3452	might be confused (it is a very good tool, but only a tool).
		3453
		3454	If you are unsure about something, feel free to contact the mailing list
		3455	with the full valgrind report and an explanation on why you think this is
		3456	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3457	no bug" answer and take the chance of learning how to interpret valgrind
		3458	properly.
		3459
		3460	If you need, for some reason, empty reports from valgrind for your project
		3461	I suggest using suppression lists.
		3462
		3463
2857	=head1 AUTHOR	3464	=head1 AUTHOR
2858		3465
2859	Marc Lehmann <libev@schmorp.de>.	3466	Marc Lehmann <libev@schmorp.de>.
2860		3467

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