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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
10		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
…		…
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	103	it, you should treat it as such.
52		104
53
54	=head1 GLOBAL FUNCTIONS	105	=head1 GLOBAL FUNCTIONS
55		106
56	These functions can be called anytime, even before initialising the	107	These functions can be called anytime, even before initialising the
57	library in any way.	108	library in any way.
58		109
…		…
77	Usually, it's a good idea to terminate if the major versions mismatch,	128	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	129	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	130	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	131	not a problem.
81		132
82	Example: make sure we haven't accidentally been linked against the wrong	133	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	134	version.
84		135
85	assert (("libev version mismatch",	136	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	137	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	138	&& ev_version_minor () >= EV_VERSION_MINOR));
88		139
…		…
118		169
119	See the description of C<ev_embed> watchers for more info.	170	See the description of C<ev_embed> watchers for more info.
120		171
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	172	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		173
123	Sets the allocation function to use (the prototype is similar to the	174	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	175	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	176	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	177	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	178	potentially destructive action. The default is your system realloc
		179	function.
128		180
129	You could override this function in high-availability programs to, say,	181	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	182	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	183	or even to sleep a while and retry until some memory is available.
132		184
133	Example: replace the libev allocator with one that waits a bit and then	185	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	186	retries).
135		187
136	static void *	188	static void *
137	persistent_realloc (void *ptr, long size)	189	persistent_realloc (void *ptr, size_t size)
138	{	190	{
139	for (;;)	191	for (;;)
140	{	192	{
141	void *newptr = realloc (ptr, size);	193	void *newptr = realloc (ptr, size);
142		194
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	210	callback is set, then libev will expect it to remedy the sitution, no
159	matter what, when it returns. That is, libev will generally retry the	211	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	212	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	213	(such as abort).
162		214
163	Example: do the same thing as libev does internally:	215	Example: This is basically the same thing that libev does internally, too.
164		216
165	static void	217	static void
166	fatal_error (const char *msg)	218	fatal_error (const char *msg)
167	{	219	{
168	perror (msg);	220	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	271	override the flags completely if it is found in the environment. This is
220	useful to try out specific backends to test their performance, or to work	272	useful to try out specific backends to test their performance, or to work
221	around bugs.	273	around bugs.
222		274
		275	=item C<EVFLAG_FORKCHECK>
		276
		277	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		278	a fork, you can also make libev check for a fork in each iteration by
		279	enabling this flag.
		280
		281	This works by calling C<getpid ()> on every iteration of the loop,
		282	and thus this might slow down your event loop if you do a lot of loop
		283	iterations and little real work, but is usually not noticeable (on my
		284	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		285	without a syscall and thus I<very> fast, but my Linux system also has
		286	C<pthread_atfork> which is even faster).
		287
		288	The big advantage of this flag is that you can forget about fork (and
		289	forget about forgetting to tell libev about forking) when you use this
		290	flag.
		291
		292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		293	environment variable.
		294
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		296
225	This is your standard select(2) backend. Not I<completely> standard, as	297	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	298	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	299	but if that fails, expect a fairly low limit on the number of fds when
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	386	Similar to C<ev_default_loop>, but always creates a new event loop that is
315	always distinct from the default loop. Unlike the default loop, it cannot	387	always distinct from the default loop. Unlike the default loop, it cannot
316	handle signal and child watchers, and attempts to do so will be greeted by	388	handle signal and child watchers, and attempts to do so will be greeted by
317	undefined behaviour (or a failed assertion if assertions are enabled).	389	undefined behaviour (or a failed assertion if assertions are enabled).
318		390
319	Example: try to create a event loop that uses epoll and nothing else.	391	Example: Try to create a event loop that uses epoll and nothing else.
320		392
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	394	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	395	fatal ("no epoll found here, maybe it hides under your chair");
324		396
…		…
362		434
363	Like C<ev_default_fork>, but acts on an event loop created by	435	Like C<ev_default_fork>, but acts on an event loop created by
364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
365	after fork, and how you do this is entirely your own problem.	437	after fork, and how you do this is entirely your own problem.
366		438
		439	=item unsigned int ev_loop_count (loop)
		440
		441	Returns the count of loop iterations for the loop, which is identical to
		442	the number of times libev did poll for new events. It starts at C<0> and
		443	happily wraps around with enough iterations.
		444
		445	This value can sometimes be useful as a generation counter of sorts (it
		446	"ticks" the number of loop iterations), as it roughly corresponds with
		447	C<ev_prepare> and C<ev_check> calls.
		448
367	=item unsigned int ev_backend (loop)	449	=item unsigned int ev_backend (loop)
368		450
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	451	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	452	use.
371		453
…		…
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	487	usually a better approach for this kind of thing.
406		488
407	Here are the gory details of what C<ev_loop> does:	489	Here are the gory details of what C<ev_loop> does:
408		490
		491	- Before the first iteration, call any pending watchers.
409	* If there are no active watchers (reference count is zero), return.	492	* If there are no active watchers (reference count is zero), return.
410	- Queue prepare watchers and then call all outstanding watchers.	493	- Queue all prepare watchers and then call all outstanding watchers.
411	- If we have been forked, recreate the kernel state.	494	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	495	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	496	- Update the "event loop time".
414	- Calculate for how long to block.	497	- Calculate for how long to block.
415	- Block the process, waiting for any events.	498	- Block the process, waiting for any events.
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	506	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	507	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	508	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	509	were used, return, otherwise continue with step *.
427		510
428	Example: queue some jobs and then loop until no events are outsanding	511	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	512	anymore.
430		513
431	... queue jobs here, make sure they register event watchers as long	514	... queue jobs here, make sure they register event watchers as long
432	... as they still have work to do (even an idle watcher will do..)	515	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	516	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	536	visible to the libev user and should not keep C<ev_loop> from exiting if
454	no event watchers registered by it are active. It is also an excellent	537	no event watchers registered by it are active. It is also an excellent
455	way to do this for generic recurring timers or from within third-party	538	way to do this for generic recurring timers or from within third-party
456	libraries. Just remember to I<unref after start> and I<ref before stop>.	539	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		540
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	541	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	542	running when nothing else is active.
460		543
461	struct dv_signal exitsig;	544	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	545	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	546	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	547	evf_unref (loop);
465		548
466	Example: for some weird reason, unregister the above signal handler again.	549	Example: For some weird reason, unregister the above signal handler again.
467		550
468	ev_ref (myloop);	551	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	552	ev_signal_stop (loop, &exitsig);
470		553
471	=back	554	=back
		555
472		556
473	=head1 ANATOMY OF A WATCHER	557	=head1 ANATOMY OF A WATCHER
474		558
475	A watcher is a structure that you create and register to record your	559	A watcher is a structure that you create and register to record your
476	interest in some event. For instance, if you want to wait for STDIN to	560	interest in some event. For instance, if you want to wait for STDIN to
…		…
543	The signal specified in the C<ev_signal> watcher has been received by a thread.	627	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		628
545	=item C<EV_CHILD>	629	=item C<EV_CHILD>
546		630
547	The pid specified in the C<ev_child> watcher has received a status change.	631	The pid specified in the C<ev_child> watcher has received a status change.
		632
		633	=item C<EV_STAT>
		634
		635	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		636
549	=item C<EV_IDLE>	637	=item C<EV_IDLE>
550		638
551	The C<ev_idle> watcher has determined that you have nothing better to do.	639	The C<ev_idle> watcher has determined that you have nothing better to do.
552		640
…		…
560	received events. Callbacks of both watcher types can start and stop as	648	received events. Callbacks of both watcher types can start and stop as
561	many watchers as they want, and all of them will be taken into account	649	many watchers as they want, and all of them will be taken into account
562	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	650	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	651	C<ev_loop> from blocking).
564		652
		653	=item C<EV_EMBED>
		654
		655	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		656
		657	=item C<EV_FORK>
		658
		659	The event loop has been resumed in the child process after fork (see
		660	C<ev_fork>).
		661
565	=item C<EV_ERROR>	662	=item C<EV_ERROR>
566		663
567	An unspecified error has occured, the watcher has been stopped. This might	664	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	665	happen because the watcher could not be properly started because libev
569	ran out of memory, a file descriptor was found to be closed or any other	666	ran out of memory, a file descriptor was found to be closed or any other
…		…
576	with the error from read() or write(). This will not work in multithreaded	673	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	674	programs, though, so beware.
578		675
579	=back	676	=back
580		677
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	678	=head2 GENERIC WATCHER FUNCTIONS
582		679
583	In the following description, C<TYPE> stands for the watcher type,	680	In the following description, C<TYPE> stands for the watcher type,
584	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.	681	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		682
586	=over 4	683	=over 4
…		…
595	which rolls both calls into one.	692	which rolls both calls into one.
596		693
597	You can reinitialise a watcher at any time as long as it has been stopped	694	You can reinitialise a watcher at any time as long as it has been stopped
598	(or never started) and there are no pending events outstanding.	695	(or never started) and there are no pending events outstanding.
599		696
600	The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	697	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
601	int revents)>.	698	int revents)>.
602		699
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	700	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		701
605	This macro initialises the type-specific parts of a watcher. You need to	702	This macro initialises the type-specific parts of a watcher. You need to
…		…
640	=item bool ev_is_pending (ev_TYPE *watcher)	737	=item bool ev_is_pending (ev_TYPE *watcher)
641		738
642	Returns a true value iff the watcher is pending, (i.e. it has outstanding	739	Returns a true value iff the watcher is pending, (i.e. it has outstanding
643	events but its callback has not yet been invoked). As long as a watcher	740	events but its callback has not yet been invoked). As long as a watcher
644	is pending (but not active) you must not call an init function on it (but	741	is pending (but not active) you must not call an init function on it (but
645	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	742	C<ev_TYPE_set> is safe), you must not change its priority, and you must
646	libev (e.g. you cnanot C<free ()> it).	743	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		744	it).
647		745
648	=item callback = ev_cb (ev_TYPE *watcher)	746	=item callback ev_cb (ev_TYPE *watcher)
649		747
650	Returns the callback currently set on the watcher.	748	Returns the callback currently set on the watcher.
651		749
652	=item ev_cb_set (ev_TYPE *watcher, callback)	750	=item ev_cb_set (ev_TYPE *watcher, callback)
653		751
654	Change the callback. You can change the callback at virtually any time	752	Change the callback. You can change the callback at virtually any time
655	(modulo threads).	753	(modulo threads).
		754
		755	=item ev_set_priority (ev_TYPE *watcher, priority)
		756
		757	=item int ev_priority (ev_TYPE *watcher)
		758
		759	Set and query the priority of the watcher. The priority is a small
		760	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		761	(default: C<-2>). Pending watchers with higher priority will be invoked
		762	before watchers with lower priority, but priority will not keep watchers
		763	from being executed (except for C<ev_idle> watchers).
		764
		765	This means that priorities are I<only> used for ordering callback
		766	invocation after new events have been received. This is useful, for
		767	example, to reduce latency after idling, or more often, to bind two
		768	watchers on the same event and make sure one is called first.
		769
		770	If you need to suppress invocation when higher priority events are pending
		771	you need to look at C<ev_idle> watchers, which provide this functionality.
		772
		773	You I<must not> change the priority of a watcher as long as it is active or
		774	pending.
		775
		776	The default priority used by watchers when no priority has been set is
		777	always C<0>, which is supposed to not be too high and not be too low :).
		778
		779	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		780	fine, as long as you do not mind that the priority value you query might
		781	or might not have been adjusted to be within valid range.
		782
		783	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		784
		785	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		786	C<loop> nor C<revents> need to be valid as long as the watcher callback
		787	can deal with that fact.
		788
		789	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		790
		791	If the watcher is pending, this function returns clears its pending status
		792	and returns its C<revents> bitset (as if its callback was invoked). If the
		793	watcher isn't pending it does nothing and returns C<0>.
656		794
657	=back	795	=back
658		796
659		797
660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	798	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
681	{	819	{
682	struct my_io *w = (struct my_io *)w_;	820	struct my_io *w = (struct my_io *)w_;
683	...	821	...
684	}	822	}
685		823
686	More interesting and less C-conformant ways of catsing your callback type	824	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	825	instead have been omitted.
		826
		827	Another common scenario is having some data structure with multiple
		828	watchers:
		829
		830	struct my_biggy
		831	{
		832	int some_data;
		833	ev_timer t1;
		834	ev_timer t2;
		835	}
		836
		837	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		838	you need to use C<offsetof>:
		839
		840	#include <stddef.h>
		841
		842	static void
		843	t1_cb (EV_P_ struct ev_timer *w, int revents)
		844	{
		845	struct my_biggy big = (struct my_biggy *
		846	(((char *)w) - offsetof (struct my_biggy, t1));
		847	}
		848
		849	static void
		850	t2_cb (EV_P_ struct ev_timer *w, int revents)
		851	{
		852	struct my_biggy big = (struct my_biggy *
		853	(((char *)w) - offsetof (struct my_biggy, t2));
		854	}
688		855
689		856
690	=head1 WATCHER TYPES	857	=head1 WATCHER TYPES
691		858
692	This section describes each watcher in detail, but will not repeat	859	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	860	information given in the last section. Any initialisation/set macros,
		861	functions and members specific to the watcher type are explained.
694		862
		863	Members are additionally marked with either I<[read-only]>, meaning that,
		864	while the watcher is active, you can look at the member and expect some
		865	sensible content, but you must not modify it (you can modify it while the
		866	watcher is stopped to your hearts content), or I<[read-write]>, which
		867	means you can expect it to have some sensible content while the watcher
		868	is active, but you can also modify it. Modifying it may not do something
		869	sensible or take immediate effect (or do anything at all), but libev will
		870	not crash or malfunction in any way.
695		871
		872
696	=head2 C<ev_io> - is this file descriptor readable or writable	873	=head2 C<ev_io> - is this file descriptor readable or writable?
697		874
698	I/O watchers check whether a file descriptor is readable or writable	875	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	876	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	877	would not block the process and writing would at least be able to write
701	condition persists. Remember you can stop the watcher if you don't want to	878	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	879	receiving events as long as the condition persists. Remember you can stop
		880	the watcher if you don't want to act on the event and neither want to
		881	receive future events.
703		882
704	In general you can register as many read and/or write event watchers per	883	In general you can register as many read and/or write event watchers per
705	fd as you want (as long as you don't confuse yourself). Setting all file	884	fd as you want (as long as you don't confuse yourself). Setting all file
706	descriptors to non-blocking mode is also usually a good idea (but not	885	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	886	required if you know what you are doing).
708		887
709	You have to be careful with dup'ed file descriptors, though. Some backends	888	You have to be careful with dup'ed file descriptors, though. Some backends
710	(the linux epoll backend is a notable example) cannot handle dup'ed file	889	(the linux epoll backend is a notable example) cannot handle dup'ed file
711	descriptors correctly if you register interest in two or more fds pointing	890	descriptors correctly if you register interest in two or more fds pointing
712	to the same underlying file/socket etc. description (that is, they share	891	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	892	the same underlying "file open").
714		893
715	If you must do this, then force the use of a known-to-be-good backend	894	If you must do this, then force the use of a known-to-be-good backend
716	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	895	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	896	C<EVBACKEND_POLL>).
718		897
		898	Another thing you have to watch out for is that it is quite easy to
		899	receive "spurious" readyness notifications, that is your callback might
		900	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		901	because there is no data. Not only are some backends known to create a
		902	lot of those (for example solaris ports), it is very easy to get into
		903	this situation even with a relatively standard program structure. Thus
		904	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		905	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		906
		907	If you cannot run the fd in non-blocking mode (for example you should not
		908	play around with an Xlib connection), then you have to seperately re-test
		909	whether a file descriptor is really ready with a known-to-be good interface
		910	such as poll (fortunately in our Xlib example, Xlib already does this on
		911	its own, so its quite safe to use).
		912
719	=over 4	913	=over 4
720		914
721	=item ev_io_init (ev_io *, callback, int fd, int events)	915	=item ev_io_init (ev_io *, callback, int fd, int events)
722		916
723	=item ev_io_set (ev_io *, int fd, int events)	917	=item ev_io_set (ev_io *, int fd, int events)
724		918
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	919	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
726	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	920	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	921	C<EV_READ | EV_WRITE> to receive the given events.
728		922
729	Please note that most of the more scalable backend mechanisms (for example	923	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	924
731	for file descriptors, so you practically need to use non-blocking I/O (and	925	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	926
733	interface before doing I/O (XLib can do this), or force the use of either	927	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	928
735	problem. Also note that it is quite easy to have your callback invoked	929	The events being watched.
736	when the readyness condition is no longer valid even when employing
737	typical ways of handling events, so its a good idea to use non-blocking
738	I/O unconditionally.
739		930
740	=back	931	=back
741		932
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	933	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
743	readable, but only once. Since it is likely line-buffered, you could	934	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	935	attempt to read a whole line in the callback.
745		936
746	static void	937	static void
747	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	938	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
748	{	939	{
749	ev_io_stop (loop, w);	940	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	947	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	948	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	949	ev_loop (loop, 0);
759		950
760		951
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	952	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		953
763	Timer watchers are simple relative timers that generate an event after a	954	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	955	given time, and optionally repeating in regular intervals after that.
765		956
766	The timers are based on real time, that is, if you register an event that	957	The timers are based on real time, that is, if you register an event that
…		…
801	=item ev_timer_again (loop)	992	=item ev_timer_again (loop)
802		993
803	This will act as if the timer timed out and restart it again if it is	994	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	995	repeating. The exact semantics are:
805		996
		997	If the timer is pending, its pending status is cleared.
		998
806	If the timer is started but nonrepeating, stop it.	999	If the timer is started but nonrepeating, stop it (as if it timed out).
807		1000
808	If the timer is repeating, either start it if necessary (with the repeat	1001	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	1002	C<repeat> value), or reset the running timer to the C<repeat> value.
810		1003
811	This sounds a bit complicated, but here is a useful and typical	1004	This sounds a bit complicated, but here is a useful and typical
812	example: Imagine you have a tcp connection and you want a so-called idle	1005	example: Imagine you have a tcp connection and you want a so-called idle
813	timeout, that is, you want to be called when there have been, say, 60	1006	timeout, that is, you want to be called when there have been, say, 60
814	seconds of inactivity on the socket. The easiest way to do this is to	1007	seconds of inactivity on the socket. The easiest way to do this is to
815	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1008	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
816	time you successfully read or write some data. If you go into an idle	1009	C<ev_timer_again> each time you successfully read or write some data. If
817	state where you do not expect data to travel on the socket, you can stop	1010	you go into an idle state where you do not expect data to travel on the
818	the timer, and again will automatically restart it if need be.	1011	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1012	automatically restart it if need be.
		1013
		1014	That means you can ignore the C<after> value and C<ev_timer_start>
		1015	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1016
		1017	ev_timer_init (timer, callback, 0., 5.);
		1018	ev_timer_again (loop, timer);
		1019	...
		1020	timer->again = 17.;
		1021	ev_timer_again (loop, timer);
		1022	...
		1023	timer->again = 10.;
		1024	ev_timer_again (loop, timer);
		1025
		1026	This is more slightly efficient then stopping/starting the timer each time
		1027	you want to modify its timeout value.
		1028
		1029	=item ev_tstamp repeat [read-write]
		1030
		1031	The current C<repeat> value. Will be used each time the watcher times out
		1032	or C<ev_timer_again> is called and determines the next timeout (if any),
		1033	which is also when any modifications are taken into account.
819		1034
820	=back	1035	=back
821		1036
822	Example: create a timer that fires after 60 seconds.	1037	Example: Create a timer that fires after 60 seconds.
823		1038
824	static void	1039	static void
825	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1040	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
826	{	1041	{
827	.. one minute over, w is actually stopped right here	1042	.. one minute over, w is actually stopped right here
…		…
829		1044
830	struct ev_timer mytimer;	1045	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1046	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	1047	ev_timer_start (loop, &mytimer);
833		1048
834	Example: create a timeout timer that times out after 10 seconds of	1049	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	1050	inactivity.
836		1051
837	static void	1052	static void
838	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1053	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839	{	1054	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1063	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1064	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1065	ev_timer_again (&mytimer);
851		1066
852		1067
853	=head2 C<ev_periodic> - to cron or not to cron	1068	=head2 C<ev_periodic> - to cron or not to cron?
854		1069
855	Periodic watchers are also timers of a kind, but they are very versatile	1070	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1071	(and unfortunately a bit complex).
857		1072
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1073	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
859	but on wallclock time (absolute time). You can tell a periodic watcher	1074	but on wallclock time (absolute time). You can tell a periodic watcher
860	to trigger "at" some specific point in time. For example, if you tell a	1075	to trigger "at" some specific point in time. For example, if you tell a
861	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1076	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
862	+ 10.>) and then reset your system clock to the last year, then it will	1077	+ 10.>) and then reset your system clock to the last year, then it will
863	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1078	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
864	roughly 10 seconds later and of course not if you reset your system time	1079	roughly 10 seconds later).
865	again).
866		1080
867	They can also be used to implement vastly more complex timers, such as	1081	They can also be used to implement vastly more complex timers, such as
868	triggering an event on eahc midnight, local time.	1082	triggering an event on each midnight, local time or other, complicated,
		1083	rules.
869		1084
870	As with timers, the callback is guarenteed to be invoked only when the	1085	As with timers, the callback is guarenteed to be invoked only when the
871	time (C<at>) has been passed, but if multiple periodic timers become ready	1086	time (C<at>) has been passed, but if multiple periodic timers become ready
872	during the same loop iteration then order of execution is undefined.	1087	during the same loop iteration then order of execution is undefined.
873		1088
…		…
880	Lots of arguments, lets sort it out... There are basically three modes of	1095	Lots of arguments, lets sort it out... There are basically three modes of
881	operation, and we will explain them from simplest to complex:	1096	operation, and we will explain them from simplest to complex:
882		1097
883	=over 4	1098	=over 4
884		1099
885	=item * absolute timer (interval = reschedule_cb = 0)	1100	=item * absolute timer (at = time, interval = reschedule_cb = 0)
886		1101
887	In this configuration the watcher triggers an event at the wallclock time	1102	In this configuration the watcher triggers an event at the wallclock time
888	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1103	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
889	that is, if it is to be run at January 1st 2011 then it will run when the	1104	that is, if it is to be run at January 1st 2011 then it will run when the
890	system time reaches or surpasses this time.	1105	system time reaches or surpasses this time.
891		1106
892	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1107	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
893		1108
894	In this mode the watcher will always be scheduled to time out at the next	1109	In this mode the watcher will always be scheduled to time out at the next
895	C<at + N * interval> time (for some integer N) and then repeat, regardless	1110	C<at + N * interval> time (for some integer N, which can also be negative)
896	of any time jumps.	1111	and then repeat, regardless of any time jumps.
897		1112
898	This can be used to create timers that do not drift with respect to system	1113	This can be used to create timers that do not drift with respect to system
899	time:	1114	time:
900		1115
901	ev_periodic_set (&periodic, 0., 3600., 0);	1116	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
907		1122
908	Another way to think about it (for the mathematically inclined) is that	1123	Another way to think about it (for the mathematically inclined) is that
909	C<ev_periodic> will try to run the callback in this mode at the next possible	1124	C<ev_periodic> will try to run the callback in this mode at the next possible
910	time where C<time = at (mod interval)>, regardless of any time jumps.	1125	time where C<time = at (mod interval)>, regardless of any time jumps.
911		1126
		1127	For numerical stability it is preferable that the C<at> value is near
		1128	C<ev_now ()> (the current time), but there is no range requirement for
		1129	this value.
		1130
912	=item * manual reschedule mode (reschedule_cb = callback)	1131	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
913		1132
914	In this mode the values for C<interval> and C<at> are both being	1133	In this mode the values for C<interval> and C<at> are both being
915	ignored. Instead, each time the periodic watcher gets scheduled, the	1134	ignored. Instead, each time the periodic watcher gets scheduled, the
916	reschedule callback will be called with the watcher as first, and the	1135	reschedule callback will be called with the watcher as first, and the
917	current time as second argument.	1136	current time as second argument.
918		1137
919	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1138	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
920	ever, or make any event loop modifications>. If you need to stop it,	1139	ever, or make any event loop modifications>. If you need to stop it,
921	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1140	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
922	starting a prepare watcher).	1141	starting an C<ev_prepare> watcher, which is legal).
923		1142
924	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1143	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
925	ev_tstamp now)>, e.g.:	1144	ev_tstamp now)>, e.g.:
926		1145
927	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1146	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
950	Simply stops and restarts the periodic watcher again. This is only useful	1169	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1170	when you changed some parameters or the reschedule callback would return
952	a different time than the last time it was called (e.g. in a crond like	1171	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1172	program when the crontabs have changed).
954		1173
		1174	=item ev_tstamp offset [read-write]
		1175
		1176	When repeating, this contains the offset value, otherwise this is the
		1177	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1178
		1179	Can be modified any time, but changes only take effect when the periodic
		1180	timer fires or C<ev_periodic_again> is being called.
		1181
		1182	=item ev_tstamp interval [read-write]
		1183
		1184	The current interval value. Can be modified any time, but changes only
		1185	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1186	called.
		1187
		1188	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1189
		1190	The current reschedule callback, or C<0>, if this functionality is
		1191	switched off. Can be changed any time, but changes only take effect when
		1192	the periodic timer fires or C<ev_periodic_again> is being called.
		1193
955	=back	1194	=back
956		1195
957	Example: call a callback every hour, or, more precisely, whenever the	1196	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1197	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1198	potentially a lot of jittering, but good long-term stability.
960		1199
961	static void	1200	static void
962	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1201	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
966		1205
967	struct ev_periodic hourly_tick;	1206	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1207	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1208	ev_periodic_start (loop, &hourly_tick);
970		1209
971	Example: the same as above, but use a reschedule callback to do it:	1210	Example: The same as above, but use a reschedule callback to do it:
972		1211
973	#include <math.h>	1212	#include <math.h>
974		1213
975	static ev_tstamp	1214	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1215	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1217	return fmod (now, 3600.) + 3600.;
979	}	1218	}
980		1219
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1220	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1221
983	Example: call a callback every hour, starting now:	1222	Example: Call a callback every hour, starting now:
984		1223
985	struct ev_periodic hourly_tick;	1224	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1225	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1226	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1227	ev_periodic_start (loop, &hourly_tick);
989		1228
990		1229
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1230	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1231
993	Signal watchers will trigger an event when the process receives a specific	1232	Signal watchers will trigger an event when the process receives a specific
994	signal one or more times. Even though signals are very asynchronous, libev	1233	signal one or more times. Even though signals are very asynchronous, libev
995	will try it's best to deliver signals synchronously, i.e. as part of the	1234	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1235	normal event processing, like any other event.
…		…
1009	=item ev_signal_set (ev_signal *, int signum)	1248	=item ev_signal_set (ev_signal *, int signum)
1010		1249
1011	Configures the watcher to trigger on the given signal number (usually one	1250	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1251	of the C<SIGxxx> constants).
1013		1252
		1253	=item int signum [read-only]
		1254
		1255	The signal the watcher watches out for.
		1256
1014	=back	1257	=back
1015		1258
1016		1259
1017	=head2 C<ev_child> - wait for pid status changes	1260	=head2 C<ev_child> - watch out for process status changes
1018		1261
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1262	Child watchers trigger when your process receives a SIGCHLD in response to
1020	some child status changes (most typically when a child of yours dies).	1263	some child status changes (most typically when a child of yours dies).
1021		1264
1022	=over 4	1265	=over 4
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1273	at the C<rstatus> member of the C<ev_child> watcher structure to see
1031	the status word (use the macros from C<sys/wait.h> and see your systems	1274	the status word (use the macros from C<sys/wait.h> and see your systems
1032	C<waitpid> documentation). The C<rpid> member contains the pid of the	1275	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1276	process causing the status change.
1034		1277
		1278	=item int pid [read-only]
		1279
		1280	The process id this watcher watches out for, or C<0>, meaning any process id.
		1281
		1282	=item int rpid [read-write]
		1283
		1284	The process id that detected a status change.
		1285
		1286	=item int rstatus [read-write]
		1287
		1288	The process exit/trace status caused by C<rpid> (see your systems
		1289	C<waitpid> and C<sys/wait.h> documentation for details).
		1290
1035	=back	1291	=back
1036		1292
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1293	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1294
1039	static void	1295	static void
1040	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1296	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1041	{	1297	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1298	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1301	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1302	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1303	ev_signal_start (loop, &sigint_cb);
1048		1304
1049		1305
		1306	=head2 C<ev_stat> - did the file attributes just change?
		1307
		1308	This watches a filesystem path for attribute changes. That is, it calls
		1309	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1310	compared to the last time, invoking the callback if it did.
		1311
		1312	The path does not need to exist: changing from "path exists" to "path does
		1313	not exist" is a status change like any other. The condition "path does
		1314	not exist" is signified by the C<st_nlink> field being zero (which is
		1315	otherwise always forced to be at least one) and all the other fields of
		1316	the stat buffer having unspecified contents.
		1317
		1318	The path I<should> be absolute and I<must not> end in a slash. If it is
		1319	relative and your working directory changes, the behaviour is undefined.
		1320
		1321	Since there is no standard to do this, the portable implementation simply
		1322	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1323	can specify a recommended polling interval for this case. If you specify
		1324	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1325	unspecified default> value will be used (which you can expect to be around
		1326	five seconds, although this might change dynamically). Libev will also
		1327	impose a minimum interval which is currently around C<0.1>, but thats
		1328	usually overkill.
		1329
		1330	This watcher type is not meant for massive numbers of stat watchers,
		1331	as even with OS-supported change notifications, this can be
		1332	resource-intensive.
		1333
		1334	At the time of this writing, only the Linux inotify interface is
		1335	implemented (implementing kqueue support is left as an exercise for the
		1336	reader). Inotify will be used to give hints only and should not change the
		1337	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1338	to fall back to regular polling again even with inotify, but changes are
		1339	usually detected immediately, and if the file exists there will be no
		1340	polling.
		1341
		1342	=over 4
		1343
		1344	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1345
		1346	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1347
		1348	Configures the watcher to wait for status changes of the given
		1349	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1350	be detected and should normally be specified as C<0> to let libev choose
		1351	a suitable value. The memory pointed to by C<path> must point to the same
		1352	path for as long as the watcher is active.
		1353
		1354	The callback will be receive C<EV_STAT> when a change was detected,
		1355	relative to the attributes at the time the watcher was started (or the
		1356	last change was detected).
		1357
		1358	=item ev_stat_stat (ev_stat *)
		1359
		1360	Updates the stat buffer immediately with new values. If you change the
		1361	watched path in your callback, you could call this fucntion to avoid
		1362	detecting this change (while introducing a race condition). Can also be
		1363	useful simply to find out the new values.
		1364
		1365	=item ev_statdata attr [read-only]
		1366
		1367	The most-recently detected attributes of the file. Although the type is of
		1368	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1369	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1370	was some error while C<stat>ing the file.
		1371
		1372	=item ev_statdata prev [read-only]
		1373
		1374	The previous attributes of the file. The callback gets invoked whenever
		1375	C<prev> != C<attr>.
		1376
		1377	=item ev_tstamp interval [read-only]
		1378
		1379	The specified interval.
		1380
		1381	=item const char *path [read-only]
		1382
		1383	The filesystem path that is being watched.
		1384
		1385	=back
		1386
		1387	Example: Watch C</etc/passwd> for attribute changes.
		1388
		1389	static void
		1390	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1391	{
		1392	/* /etc/passwd changed in some way */
		1393	if (w->attr.st_nlink)
		1394	{
		1395	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1396	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1397	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1398	}
		1399	else
		1400	/* you shalt not abuse printf for puts */
		1401	puts ("wow, /etc/passwd is not there, expect problems. "
		1402	"if this is windows, they already arrived\n");
		1403	}
		1404
		1405	...
		1406	ev_stat passwd;
		1407
		1408	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1409	ev_stat_start (loop, &passwd);
		1410
		1411
1050	=head2 C<ev_idle> - when you've got nothing better to do	1412	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1413
1052	Idle watchers trigger events when there are no other events are pending	1414	Idle watchers trigger events when no other events of the same or higher
1053	(prepare, check and other idle watchers do not count). That is, as long	1415	priority are pending (prepare, check and other idle watchers do not
1054	as your process is busy handling sockets or timeouts (or even signals,	1416	count).
1055	imagine) it will not be triggered. But when your process is idle all idle	1417
1056	watchers are being called again and again, once per event loop iteration -	1418	That is, as long as your process is busy handling sockets or timeouts
		1419	(or even signals, imagine) of the same or higher priority it will not be
		1420	triggered. But when your process is idle (or only lower-priority watchers
		1421	are pending), the idle watchers are being called once per event loop
1057	until stopped, that is, or your process receives more events and becomes	1422	iteration - until stopped, that is, or your process receives more events
1058	busy.	1423	and becomes busy again with higher priority stuff.
1059		1424
1060	The most noteworthy effect is that as long as any idle watchers are	1425	The most noteworthy effect is that as long as any idle watchers are
1061	active, the process will not block when waiting for new events.	1426	active, the process will not block when waiting for new events.
1062		1427
1063	Apart from keeping your process non-blocking (which is a useful	1428	Apart from keeping your process non-blocking (which is a useful
…		…
1073	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1438	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1439	believe me.
1075		1440
1076	=back	1441	=back
1077		1442
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1443	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1444	callback, free it. Also, use no error checking, as usual.
1080		1445
1081	static void	1446	static void
1082	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1447	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1083	{	1448	{
1084	free (w);	1449	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1454	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1455	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1456	ev_idle_start (loop, idle_cb);
1092		1457
1093		1458
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1459	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1460
1096	Prepare and check watchers are usually (but not always) used in tandem:	1461	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1462	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1463	afterwards.
1099		1464
		1465	You I<must not> call C<ev_loop> or similar functions that enter
		1466	the current event loop from either C<ev_prepare> or C<ev_check>
		1467	watchers. Other loops than the current one are fine, however. The
		1468	rationale behind this is that you do not need to check for recursion in
		1469	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1470	C<ev_check> so if you have one watcher of each kind they will always be
		1471	called in pairs bracketing the blocking call.
		1472
1100	Their main purpose is to integrate other event mechanisms into libev and	1473	Their main purpose is to integrate other event mechanisms into libev and
1101	their use is somewhat advanced. This could be used, for example, to track	1474	their use is somewhat advanced. This could be used, for example, to track
1102	variable changes, implement your own watchers, integrate net-snmp or a	1475	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1476	coroutine library and lots more. They are also occasionally useful if
		1477	you cache some data and want to flush it before blocking (for example,
		1478	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1479	watcher).
1104		1480
1105	This is done by examining in each prepare call which file descriptors need	1481	This is done by examining in each prepare call which file descriptors need
1106	to be watched by the other library, registering C<ev_io> watchers for	1482	to be watched by the other library, registering C<ev_io> watchers for
1107	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1483	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1108	provide just this functionality). Then, in the check watcher you check for	1484	provide just this functionality). Then, in the check watcher you check for
…		…
1118	with priority higher than or equal to the event loop and one coroutine	1494	with priority higher than or equal to the event loop and one coroutine
1119	of lower priority, but only once, using idle watchers to keep the event	1495	of lower priority, but only once, using idle watchers to keep the event
1120	loop from blocking if lower-priority coroutines are active, thus mapping	1496	loop from blocking if lower-priority coroutines are active, thus mapping
1121	low-priority coroutines to idle/background tasks).	1497	low-priority coroutines to idle/background tasks).
1122		1498
		1499	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1500	priority, to ensure that they are being run before any other watchers
		1501	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1502	too) should not activate ("feed") events into libev. While libev fully
		1503	supports this, they will be called before other C<ev_check> watchers did
		1504	their job. As C<ev_check> watchers are often used to embed other event
		1505	loops those other event loops might be in an unusable state until their
		1506	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1507	others).
		1508
1123	=over 4	1509	=over 4
1124		1510
1125	=item ev_prepare_init (ev_prepare *, callback)	1511	=item ev_prepare_init (ev_prepare *, callback)
1126		1512
1127	=item ev_check_init (ev_check *, callback)	1513	=item ev_check_init (ev_check *, callback)
…		…
1130	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1516	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1131	macros, but using them is utterly, utterly and completely pointless.	1517	macros, but using them is utterly, utterly and completely pointless.
1132		1518
1133	=back	1519	=back
1134		1520
1135	Example: *TODO*.	1521	There are a number of principal ways to embed other event loops or modules
		1522	into libev. Here are some ideas on how to include libadns into libev
		1523	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1524	use for an actually working example. Another Perl module named C<EV::Glib>
		1525	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1526	into the Glib event loop).
1136		1527
		1528	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1529	and in a check watcher, destroy them and call into libadns. What follows
		1530	is pseudo-code only of course. This requires you to either use a low
		1531	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1532	the callbacks for the IO/timeout watchers might not have been called yet.
1137		1533
		1534	static ev_io iow [nfd];
		1535	static ev_timer tw;
		1536
		1537	static void
		1538	io_cb (ev_loop *loop, ev_io *w, int revents)
		1539	{
		1540	}
		1541
		1542	// create io watchers for each fd and a timer before blocking
		1543	static void
		1544	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1545	{
		1546	int timeout = 3600000;
		1547	struct pollfd fds [nfd];
		1548	// actual code will need to loop here and realloc etc.
		1549	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1550
		1551	/* the callback is illegal, but won't be called as we stop during check */
		1552	ev_timer_init (&tw, 0, timeout * 1e-3);
		1553	ev_timer_start (loop, &tw);
		1554
		1555	// create one ev_io per pollfd
		1556	for (int i = 0; i < nfd; ++i)
		1557	{
		1558	ev_io_init (iow + i, io_cb, fds [i].fd,
		1559	((fds [i].events & POLLIN ? EV_READ : 0)
		1560	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1561
		1562	fds [i].revents = 0;
		1563	ev_io_start (loop, iow + i);
		1564	}
		1565	}
		1566
		1567	// stop all watchers after blocking
		1568	static void
		1569	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1570	{
		1571	ev_timer_stop (loop, &tw);
		1572
		1573	for (int i = 0; i < nfd; ++i)
		1574	{
		1575	// set the relevant poll flags
		1576	// could also call adns_processreadable etc. here
		1577	struct pollfd *fd = fds + i;
		1578	int revents = ev_clear_pending (iow + i);
		1579	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1580	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1581
		1582	// now stop the watcher
		1583	ev_io_stop (loop, iow + i);
		1584	}
		1585
		1586	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1587	}
		1588
		1589	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1590	in the prepare watcher and would dispose of the check watcher.
		1591
		1592	Method 3: If the module to be embedded supports explicit event
		1593	notification (adns does), you can also make use of the actual watcher
		1594	callbacks, and only destroy/create the watchers in the prepare watcher.
		1595
		1596	static void
		1597	timer_cb (EV_P_ ev_timer *w, int revents)
		1598	{
		1599	adns_state ads = (adns_state)w->data;
		1600	update_now (EV_A);
		1601
		1602	adns_processtimeouts (ads, &tv_now);
		1603	}
		1604
		1605	static void
		1606	io_cb (EV_P_ ev_io *w, int revents)
		1607	{
		1608	adns_state ads = (adns_state)w->data;
		1609	update_now (EV_A);
		1610
		1611	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1612	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1613	}
		1614
		1615	// do not ever call adns_afterpoll
		1616
		1617	Method 4: Do not use a prepare or check watcher because the module you
		1618	want to embed is too inflexible to support it. Instead, youc na override
		1619	their poll function. The drawback with this solution is that the main
		1620	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1621	this.
		1622
		1623	static gint
		1624	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1625	{
		1626	int got_events = 0;
		1627
		1628	for (n = 0; n < nfds; ++n)
		1629	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1630
		1631	if (timeout >= 0)
		1632	// create/start timer
		1633
		1634	// poll
		1635	ev_loop (EV_A_ 0);
		1636
		1637	// stop timer again
		1638	if (timeout >= 0)
		1639	ev_timer_stop (EV_A_ &to);
		1640
		1641	// stop io watchers again - their callbacks should have set
		1642	for (n = 0; n < nfds; ++n)
		1643	ev_io_stop (EV_A_ iow [n]);
		1644
		1645	return got_events;
		1646	}
		1647
		1648
1138	=head2 C<ev_embed> - when one backend isn't enough	1649	=head2 C<ev_embed> - when one backend isn't enough...
1139		1650
1140	This is a rather advanced watcher type that lets you embed one event loop	1651	This is a rather advanced watcher type that lets you embed one event loop
1141	into another (currently only C<ev_io> events are supported in the embedded	1652	into another (currently only C<ev_io> events are supported in the embedded
1142	loop, other types of watchers might be handled in a delayed or incorrect	1653	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1654	fashion and must not be used).
…		…
1221		1732
1222	Make a single, non-blocking sweep over the embedded loop. This works	1733	Make a single, non-blocking sweep over the embedded loop. This works
1223	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1734	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1735	apropriate way for embedded loops.
1225		1736
		1737	=item struct ev_loop *loop [read-only]
		1738
		1739	The embedded event loop.
		1740
		1741	=back
		1742
		1743
		1744	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1745
		1746	Fork watchers are called when a C<fork ()> was detected (usually because
		1747	whoever is a good citizen cared to tell libev about it by calling
		1748	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1749	event loop blocks next and before C<ev_check> watchers are being called,
		1750	and only in the child after the fork. If whoever good citizen calling
		1751	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1752	handlers will be invoked, too, of course.
		1753
		1754	=over 4
		1755
		1756	=item ev_fork_init (ev_signal *, callback)
		1757
		1758	Initialises and configures the fork watcher - it has no parameters of any
		1759	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1760	believe me.
		1761
1226	=back	1762	=back
1227		1763
1228		1764
1229	=head1 OTHER FUNCTIONS	1765	=head1 OTHER FUNCTIONS
1230		1766
…		…
1318		1854
1319	To use it,	1855	To use it,
1320		1856
1321	#include <ev++.h>	1857	#include <ev++.h>
1322		1858
1323	(it is not installed by default). This automatically includes F<ev.h>	1859	This automatically includes F<ev.h> and puts all of its definitions (many
1324	and puts all of its definitions (many of them macros) into the global	1860	of them macros) into the global namespace. All C++ specific things are
1325	namespace. All C++ specific things are put into the C<ev> namespace.	1861	put into the C<ev> namespace. It should support all the same embedding
		1862	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1326		1863
1327	It should support all the same embedding options as F<ev.h>, most notably	1864	Care has been taken to keep the overhead low. The only data member the C++
1328	C<EV_MULTIPLICITY>.	1865	classes add (compared to plain C-style watchers) is the event loop pointer
		1866	that the watcher is associated with (or no additional members at all if
		1867	you disable C<EV_MULTIPLICITY> when embedding libev).
		1868
		1869	Currently, functions, and static and non-static member functions can be
		1870	used as callbacks. Other types should be easy to add as long as they only
		1871	need one additional pointer for context. If you need support for other
		1872	types of functors please contact the author (preferably after implementing
		1873	it).
1329		1874
1330	Here is a list of things available in the C<ev> namespace:	1875	Here is a list of things available in the C<ev> namespace:
1331		1876
1332	=over 4	1877	=over 4
1333		1878
…		…
1349		1894
1350	All of those classes have these methods:	1895	All of those classes have these methods:
1351		1896
1352	=over 4	1897	=over 4
1353		1898
1354	=item ev::TYPE::TYPE (object *, object::method *)	1899	=item ev::TYPE::TYPE ()
1355		1900
1356	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	1901	=item ev::TYPE::TYPE (struct ev_loop *)
1357		1902
1358	=item ev::TYPE::~TYPE	1903	=item ev::TYPE::~TYPE
1359		1904
1360	The constructor takes a pointer to an object and a method pointer to	1905	The constructor (optionally) takes an event loop to associate the watcher
1361	the event handler callback to call in this class. The constructor calls	1906	with. If it is omitted, it will use C<EV_DEFAULT>.
1362	C<ev_init> for you, which means you have to call the C<set> method	1907
1363	before starting it. If you do not specify a loop then the constructor	1908	The constructor calls C<ev_init> for you, which means you have to call the
1364	automatically associates the default loop with this watcher.	1909	C<set> method before starting it.
		1910
		1911	It will not set a callback, however: You have to call the templated C<set>
		1912	method to set a callback before you can start the watcher.
		1913
		1914	(The reason why you have to use a method is a limitation in C++ which does
		1915	not allow explicit template arguments for constructors).
1365		1916
1366	The destructor automatically stops the watcher if it is active.	1917	The destructor automatically stops the watcher if it is active.
		1918
		1919	=item w->set<class, &class::method> (object *)
		1920
		1921	This method sets the callback method to call. The method has to have a
		1922	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1923	first argument and the C<revents> as second. The object must be given as
		1924	parameter and is stored in the C<data> member of the watcher.
		1925
		1926	This method synthesizes efficient thunking code to call your method from
		1927	the C callback that libev requires. If your compiler can inline your
		1928	callback (i.e. it is visible to it at the place of the C<set> call and
		1929	your compiler is good :), then the method will be fully inlined into the
		1930	thunking function, making it as fast as a direct C callback.
		1931
		1932	Example: simple class declaration and watcher initialisation
		1933
		1934	struct myclass
		1935	{
		1936	void io_cb (ev::io &w, int revents) { }
		1937	}
		1938
		1939	myclass obj;
		1940	ev::io iow;
		1941	iow.set <myclass, &myclass::io_cb> (&obj);
		1942
		1943	=item w->set<function> (void *data = 0)
		1944
		1945	Also sets a callback, but uses a static method or plain function as
		1946	callback. The optional C<data> argument will be stored in the watcher's
		1947	C<data> member and is free for you to use.
		1948
		1949	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1950
		1951	See the method-C<set> above for more details.
		1952
		1953	Example:
		1954
		1955	static void io_cb (ev::io &w, int revents) { }
		1956	iow.set <io_cb> ();
1367		1957
1368	=item w->set (struct ev_loop *)	1958	=item w->set (struct ev_loop *)
1369		1959
1370	Associates a different C<struct ev_loop> with this watcher. You can only	1960	Associates a different C<struct ev_loop> with this watcher. You can only
1371	do this when the watcher is inactive (and not pending either).	1961	do this when the watcher is inactive (and not pending either).
1372		1962
1373	=item w->set ([args])	1963	=item w->set ([args])
1374		1964
1375	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1965	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1376	called at least once. Unlike the C counterpart, an active watcher gets	1966	called at least once. Unlike the C counterpart, an active watcher gets
1377	automatically stopped and restarted.	1967	automatically stopped and restarted when reconfiguring it with this
		1968	method.
1378		1969
1379	=item w->start ()	1970	=item w->start ()
1380		1971
1381	Starts the watcher. Note that there is no C<loop> argument as the	1972	Starts the watcher. Note that there is no C<loop> argument, as the
1382	constructor already takes the loop.	1973	constructor already stores the event loop.
1383		1974
1384	=item w->stop ()	1975	=item w->stop ()
1385		1976
1386	Stops the watcher if it is active. Again, no C<loop> argument.	1977	Stops the watcher if it is active. Again, no C<loop> argument.
1387		1978
…		…
1392		1983
1393	=item w->sweep () C<ev::embed> only	1984	=item w->sweep () C<ev::embed> only
1394		1985
1395	Invokes C<ev_embed_sweep>.	1986	Invokes C<ev_embed_sweep>.
1396		1987
		1988	=item w->update () C<ev::stat> only
		1989
		1990	Invokes C<ev_stat_stat>.
		1991
1397	=back	1992	=back
1398		1993
1399	=back	1994	=back
1400		1995
1401	Example: Define a class with an IO and idle watcher, start one of them in	1996	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1408		2003
1409	myclass ();	2004	myclass ();
1410	}	2005	}
1411		2006
1412	myclass::myclass (int fd)	2007	myclass::myclass (int fd)
1413	: io (this, &myclass::io_cb),
1414	idle (this, &myclass::idle_cb)
1415	{	2008	{
		2009	io .set <myclass, &myclass::io_cb > (this);
		2010	idle.set <myclass, &myclass::idle_cb> (this);
		2011
1416	io.start (fd, ev::READ);	2012	io.start (fd, ev::READ);
1417	}	2013	}
1418		2014
		2015
		2016	=head1 MACRO MAGIC
		2017
		2018	Libev can be compiled with a variety of options, the most fundemantal is
		2019	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		2020	callbacks have an initial C<struct ev_loop *> argument.
		2021
		2022	To make it easier to write programs that cope with either variant, the
		2023	following macros are defined:
		2024
		2025	=over 4
		2026
		2027	=item C<EV_A>, C<EV_A_>
		2028
		2029	This provides the loop I<argument> for functions, if one is required ("ev
		2030	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2031	C<EV_A_> is used when other arguments are following. Example:
		2032
		2033	ev_unref (EV_A);
		2034	ev_timer_add (EV_A_ watcher);
		2035	ev_loop (EV_A_ 0);
		2036
		2037	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2038	which is often provided by the following macro.
		2039
		2040	=item C<EV_P>, C<EV_P_>
		2041
		2042	This provides the loop I<parameter> for functions, if one is required ("ev
		2043	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2044	C<EV_P_> is used when other parameters are following. Example:
		2045
		2046	// this is how ev_unref is being declared
		2047	static void ev_unref (EV_P);
		2048
		2049	// this is how you can declare your typical callback
		2050	static void cb (EV_P_ ev_timer *w, int revents)
		2051
		2052	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2053	suitable for use with C<EV_A>.
		2054
		2055	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2056
		2057	Similar to the other two macros, this gives you the value of the default
		2058	loop, if multiple loops are supported ("ev loop default").
		2059
		2060	=back
		2061
		2062	Example: Declare and initialise a check watcher, utilising the above
		2063	macros so it will work regardless of whether multiple loops are supported
		2064	or not.
		2065
		2066	static void
		2067	check_cb (EV_P_ ev_timer *w, int revents)
		2068	{
		2069	ev_check_stop (EV_A_ w);
		2070	}
		2071
		2072	ev_check check;
		2073	ev_check_init (&check, check_cb);
		2074	ev_check_start (EV_DEFAULT_ &check);
		2075	ev_loop (EV_DEFAULT_ 0);
		2076
		2077	=head1 EMBEDDING
		2078
		2079	Libev can (and often is) directly embedded into host
		2080	applications. Examples of applications that embed it include the Deliantra
		2081	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2082	and rxvt-unicode.
		2083
		2084	The goal is to enable you to just copy the neecssary files into your
		2085	source directory without having to change even a single line in them, so
		2086	you can easily upgrade by simply copying (or having a checked-out copy of
		2087	libev somewhere in your source tree).
		2088
		2089	=head2 FILESETS
		2090
		2091	Depending on what features you need you need to include one or more sets of files
		2092	in your app.
		2093
		2094	=head3 CORE EVENT LOOP
		2095
		2096	To include only the libev core (all the C<ev_*> functions), with manual
		2097	configuration (no autoconf):
		2098
		2099	#define EV_STANDALONE 1
		2100	#include "ev.c"
		2101
		2102	This will automatically include F<ev.h>, too, and should be done in a
		2103	single C source file only to provide the function implementations. To use
		2104	it, do the same for F<ev.h> in all files wishing to use this API (best
		2105	done by writing a wrapper around F<ev.h> that you can include instead and
		2106	where you can put other configuration options):
		2107
		2108	#define EV_STANDALONE 1
		2109	#include "ev.h"
		2110
		2111	Both header files and implementation files can be compiled with a C++
		2112	compiler (at least, thats a stated goal, and breakage will be treated
		2113	as a bug).
		2114
		2115	You need the following files in your source tree, or in a directory
		2116	in your include path (e.g. in libev/ when using -Ilibev):
		2117
		2118	ev.h
		2119	ev.c
		2120	ev_vars.h
		2121	ev_wrap.h
		2122
		2123	ev_win32.c required on win32 platforms only
		2124
		2125	ev_select.c only when select backend is enabled (which is enabled by default)
		2126	ev_poll.c only when poll backend is enabled (disabled by default)
		2127	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2128	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2129	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2130
		2131	F<ev.c> includes the backend files directly when enabled, so you only need
		2132	to compile this single file.
		2133
		2134	=head3 LIBEVENT COMPATIBILITY API
		2135
		2136	To include the libevent compatibility API, also include:
		2137
		2138	#include "event.c"
		2139
		2140	in the file including F<ev.c>, and:
		2141
		2142	#include "event.h"
		2143
		2144	in the files that want to use the libevent API. This also includes F<ev.h>.
		2145
		2146	You need the following additional files for this:
		2147
		2148	event.h
		2149	event.c
		2150
		2151	=head3 AUTOCONF SUPPORT
		2152
		2153	Instead of using C<EV_STANDALONE=1> and providing your config in
		2154	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2155	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2156	include F<config.h> and configure itself accordingly.
		2157
		2158	For this of course you need the m4 file:
		2159
		2160	libev.m4
		2161
		2162	=head2 PREPROCESSOR SYMBOLS/MACROS
		2163
		2164	Libev can be configured via a variety of preprocessor symbols you have to define
		2165	before including any of its files. The default is not to build for multiplicity
		2166	and only include the select backend.
		2167
		2168	=over 4
		2169
		2170	=item EV_STANDALONE
		2171
		2172	Must always be C<1> if you do not use autoconf configuration, which
		2173	keeps libev from including F<config.h>, and it also defines dummy
		2174	implementations for some libevent functions (such as logging, which is not
		2175	supported). It will also not define any of the structs usually found in
		2176	F<event.h> that are not directly supported by the libev core alone.
		2177
		2178	=item EV_USE_MONOTONIC
		2179
		2180	If defined to be C<1>, libev will try to detect the availability of the
		2181	monotonic clock option at both compiletime and runtime. Otherwise no use
		2182	of the monotonic clock option will be attempted. If you enable this, you
		2183	usually have to link against librt or something similar. Enabling it when
		2184	the functionality isn't available is safe, though, althoguh you have
		2185	to make sure you link against any libraries where the C<clock_gettime>
		2186	function is hiding in (often F<-lrt>).
		2187
		2188	=item EV_USE_REALTIME
		2189
		2190	If defined to be C<1>, libev will try to detect the availability of the
		2191	realtime clock option at compiletime (and assume its availability at
		2192	runtime if successful). Otherwise no use of the realtime clock option will
		2193	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2194	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2195	in the description of C<EV_USE_MONOTONIC>, though.
		2196
		2197	=item EV_USE_SELECT
		2198
		2199	If undefined or defined to be C<1>, libev will compile in support for the
		2200	C<select>(2) backend. No attempt at autodetection will be done: if no
		2201	other method takes over, select will be it. Otherwise the select backend
		2202	will not be compiled in.
		2203
		2204	=item EV_SELECT_USE_FD_SET
		2205
		2206	If defined to C<1>, then the select backend will use the system C<fd_set>
		2207	structure. This is useful if libev doesn't compile due to a missing
		2208	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2209	exotic systems. This usually limits the range of file descriptors to some
		2210	low limit such as 1024 or might have other limitations (winsocket only
		2211	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2212	influence the size of the C<fd_set> used.
		2213
		2214	=item EV_SELECT_IS_WINSOCKET
		2215
		2216	When defined to C<1>, the select backend will assume that
		2217	select/socket/connect etc. don't understand file descriptors but
		2218	wants osf handles on win32 (this is the case when the select to
		2219	be used is the winsock select). This means that it will call
		2220	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2221	it is assumed that all these functions actually work on fds, even
		2222	on win32. Should not be defined on non-win32 platforms.
		2223
		2224	=item EV_USE_POLL
		2225
		2226	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2227	backend. Otherwise it will be enabled on non-win32 platforms. It
		2228	takes precedence over select.
		2229
		2230	=item EV_USE_EPOLL
		2231
		2232	If defined to be C<1>, libev will compile in support for the Linux
		2233	C<epoll>(7) backend. Its availability will be detected at runtime,
		2234	otherwise another method will be used as fallback. This is the
		2235	preferred backend for GNU/Linux systems.
		2236
		2237	=item EV_USE_KQUEUE
		2238
		2239	If defined to be C<1>, libev will compile in support for the BSD style
		2240	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2241	otherwise another method will be used as fallback. This is the preferred
		2242	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2243	supports some types of fds correctly (the only platform we found that
		2244	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2245	not be used unless explicitly requested. The best way to use it is to find
		2246	out whether kqueue supports your type of fd properly and use an embedded
		2247	kqueue loop.
		2248
		2249	=item EV_USE_PORT
		2250
		2251	If defined to be C<1>, libev will compile in support for the Solaris
		2252	10 port style backend. Its availability will be detected at runtime,
		2253	otherwise another method will be used as fallback. This is the preferred
		2254	backend for Solaris 10 systems.
		2255
		2256	=item EV_USE_DEVPOLL
		2257
		2258	reserved for future expansion, works like the USE symbols above.
		2259
		2260	=item EV_USE_INOTIFY
		2261
		2262	If defined to be C<1>, libev will compile in support for the Linux inotify
		2263	interface to speed up C<ev_stat> watchers. Its actual availability will
		2264	be detected at runtime.
		2265
		2266	=item EV_H
		2267
		2268	The name of the F<ev.h> header file used to include it. The default if
		2269	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2270	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2271
		2272	=item EV_CONFIG_H
		2273
		2274	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2275	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2276	C<EV_H>, above.
		2277
		2278	=item EV_EVENT_H
		2279
		2280	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2281	of how the F<event.h> header can be found.
		2282
		2283	=item EV_PROTOTYPES
		2284
		2285	If defined to be C<0>, then F<ev.h> will not define any function
		2286	prototypes, but still define all the structs and other symbols. This is
		2287	occasionally useful if you want to provide your own wrapper functions
		2288	around libev functions.
		2289
		2290	=item EV_MULTIPLICITY
		2291
		2292	If undefined or defined to C<1>, then all event-loop-specific functions
		2293	will have the C<struct ev_loop *> as first argument, and you can create
		2294	additional independent event loops. Otherwise there will be no support
		2295	for multiple event loops and there is no first event loop pointer
		2296	argument. Instead, all functions act on the single default loop.
		2297
		2298	=item EV_MINPRI
		2299
		2300	=item EV_MAXPRI
		2301
		2302	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2303	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2304	provide for more priorities by overriding those symbols (usually defined
		2305	to be C<-2> and C<2>, respectively).
		2306
		2307	When doing priority-based operations, libev usually has to linearly search
		2308	all the priorities, so having many of them (hundreds) uses a lot of space
		2309	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2310	fine.
		2311
		2312	If your embedding app does not need any priorities, defining these both to
		2313	C<0> will save some memory and cpu.
		2314
		2315	=item EV_PERIODIC_ENABLE
		2316
		2317	If undefined or defined to be C<1>, then periodic timers are supported. If
		2318	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2319	code.
		2320
		2321	=item EV_IDLE_ENABLE
		2322
		2323	If undefined or defined to be C<1>, then idle watchers are supported. If
		2324	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2325	code.
		2326
		2327	=item EV_EMBED_ENABLE
		2328
		2329	If undefined or defined to be C<1>, then embed watchers are supported. If
		2330	defined to be C<0>, then they are not.
		2331
		2332	=item EV_STAT_ENABLE
		2333
		2334	If undefined or defined to be C<1>, then stat watchers are supported. If
		2335	defined to be C<0>, then they are not.
		2336
		2337	=item EV_FORK_ENABLE
		2338
		2339	If undefined or defined to be C<1>, then fork watchers are supported. If
		2340	defined to be C<0>, then they are not.
		2341
		2342	=item EV_MINIMAL
		2343
		2344	If you need to shave off some kilobytes of code at the expense of some
		2345	speed, define this symbol to C<1>. Currently only used for gcc to override
		2346	some inlining decisions, saves roughly 30% codesize of amd64.
		2347
		2348	=item EV_PID_HASHSIZE
		2349
		2350	C<ev_child> watchers use a small hash table to distribute workload by
		2351	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2352	than enough. If you need to manage thousands of children you might want to
		2353	increase this value (I<must> be a power of two).
		2354
		2355	=item EV_INOTIFY_HASHSIZE
		2356
		2357	C<ev_staz> watchers use a small hash table to distribute workload by
		2358	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2359	usually more than enough. If you need to manage thousands of C<ev_stat>
		2360	watchers you might want to increase this value (I<must> be a power of
		2361	two).
		2362
		2363	=item EV_COMMON
		2364
		2365	By default, all watchers have a C<void *data> member. By redefining
		2366	this macro to a something else you can include more and other types of
		2367	members. You have to define it each time you include one of the files,
		2368	though, and it must be identical each time.
		2369
		2370	For example, the perl EV module uses something like this:
		2371
		2372	#define EV_COMMON \
		2373	SV *self; /* contains this struct */ \
		2374	SV *cb_sv, *fh /* note no trailing ";" */
		2375
		2376	=item EV_CB_DECLARE (type)
		2377
		2378	=item EV_CB_INVOKE (watcher, revents)
		2379
		2380	=item ev_set_cb (ev, cb)
		2381
		2382	Can be used to change the callback member declaration in each watcher,
		2383	and the way callbacks are invoked and set. Must expand to a struct member
		2384	definition and a statement, respectively. See the F<ev.v> header file for
		2385	their default definitions. One possible use for overriding these is to
		2386	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2387	method calls instead of plain function calls in C++.
		2388
		2389	=head2 EXAMPLES
		2390
		2391	For a real-world example of a program the includes libev
		2392	verbatim, you can have a look at the EV perl module
		2393	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2394	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2395	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2396	will be compiled. It is pretty complex because it provides its own header
		2397	file.
		2398
		2399	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2400	that everybody includes and which overrides some configure choices:
		2401
		2402	#define EV_MINIMAL 1
		2403	#define EV_USE_POLL 0
		2404	#define EV_MULTIPLICITY 0
		2405	#define EV_PERIODIC_ENABLE 0
		2406	#define EV_STAT_ENABLE 0
		2407	#define EV_FORK_ENABLE 0
		2408	#define EV_CONFIG_H <config.h>
		2409	#define EV_MINPRI 0
		2410	#define EV_MAXPRI 0
		2411
		2412	#include "ev++.h"
		2413
		2414	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2415
		2416	#include "ev_cpp.h"
		2417	#include "ev.c"
		2418
		2419
		2420	=head1 COMPLEXITIES
		2421
		2422	In this section the complexities of (many of) the algorithms used inside
		2423	libev will be explained. For complexity discussions about backends see the
		2424	documentation for C<ev_default_init>.
		2425
		2426	All of the following are about amortised time: If an array needs to be
		2427	extended, libev needs to realloc and move the whole array, but this
		2428	happens asymptotically never with higher number of elements, so O(1) might
		2429	mean it might do a lengthy realloc operation in rare cases, but on average
		2430	it is much faster and asymptotically approaches constant time.
		2431
		2432	=over 4
		2433
		2434	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2435
		2436	This means that, when you have a watcher that triggers in one hour and
		2437	there are 100 watchers that would trigger before that then inserting will
		2438	have to skip those 100 watchers.
		2439
		2440	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2441
		2442	That means that for changing a timer costs less than removing/adding them
		2443	as only the relative motion in the event queue has to be paid for.
		2444
		2445	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2446
		2447	These just add the watcher into an array or at the head of a list.
		2448	=item Stopping check/prepare/idle watchers: O(1)
		2449
		2450	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2451
		2452	These watchers are stored in lists then need to be walked to find the
		2453	correct watcher to remove. The lists are usually short (you don't usually
		2454	have many watchers waiting for the same fd or signal).
		2455
		2456	=item Finding the next timer per loop iteration: O(1)
		2457
		2458	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2459
		2460	A change means an I/O watcher gets started or stopped, which requires
		2461	libev to recalculate its status (and possibly tell the kernel).
		2462
		2463	=item Activating one watcher: O(1)
		2464
		2465	=item Priority handling: O(number_of_priorities)
		2466
		2467	Priorities are implemented by allocating some space for each
		2468	priority. When doing priority-based operations, libev usually has to
		2469	linearly search all the priorities.
		2470
		2471	=back
		2472
		2473
1419	=head1 AUTHOR	2474	=head1 AUTHOR
1420		2475
1421	Marc Lehmann <libev@schmorp.de>.	2476	Marc Lehmann <libev@schmorp.de>.
1422		2477

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