ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.38 by root, Sat Nov 24 09:48:38 2007 UTC vs.
Revision 1.74 by root, Sat Dec 8 14:12:08 2007 UTC

…		…
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
…		…
361	=item ev_loop_fork (loop)	433	=item ev_loop_fork (loop)
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.
		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.
366		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.
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	505	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	506	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	508	were used, return, otherwise continue with step *.
427		509
428	Example: queue some jobs and then loop until no events are outsanding	510	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	511	anymore.
430		512
431	... queue jobs here, make sure they register event watchers as long	513	... 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..)	514	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	515	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	535	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	536	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	537	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>.	538	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		539
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	541	running when nothing else is active.
460		542
461	struct dv_signal exitsig;	543	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	544	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	545	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	546	evf_unref (loop);
465		547
466	Example: for some weird reason, unregister the above signal handler again.	548	Example: For some weird reason, unregister the above signal handler again.
467		549
468	ev_ref (myloop);	550	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	551	ev_signal_stop (loop, &exitsig);
470		552
471	=back	553	=back
		554
472		555
473	=head1 ANATOMY OF A WATCHER	556	=head1 ANATOMY OF A WATCHER
474		557
475	A watcher is a structure that you create and register to record your	558	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	559	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.	626	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		627
545	=item C<EV_CHILD>	628	=item C<EV_CHILD>
546		629
547	The pid specified in the C<ev_child> watcher has received a status change.	630	The pid specified in the C<ev_child> watcher has received a status change.
		631
		632	=item C<EV_STAT>
		633
		634	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		635
549	=item C<EV_IDLE>	636	=item C<EV_IDLE>
550		637
551	The C<ev_idle> watcher has determined that you have nothing better to do.	638	The C<ev_idle> watcher has determined that you have nothing better to do.
552		639
…		…
560	received events. Callbacks of both watcher types can start and stop as	647	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	648	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	649	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	650	C<ev_loop> from blocking).
564		651
		652	=item C<EV_EMBED>
		653
		654	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		655
		656	=item C<EV_FORK>
		657
		658	The event loop has been resumed in the child process after fork (see
		659	C<ev_fork>).
		660
565	=item C<EV_ERROR>	661	=item C<EV_ERROR>
566		662
567	An unspecified error has occured, the watcher has been stopped. This might	663	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	664	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	665	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	672	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	673	programs, though, so beware.
578		674
579	=back	675	=back
580		676
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	677	=head2 GENERIC WATCHER FUNCTIONS
582		678
583	In the following description, C<TYPE> stands for the watcher type,	679	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.	680	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		681
586	=over 4	682	=over 4
…		…
595	which rolls both calls into one.	691	which rolls both calls into one.
596		692
597	You can reinitialise a watcher at any time as long as it has been stopped	693	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.	694	(or never started) and there are no pending events outstanding.
599		695
600	The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	696	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
601	int revents)>.	697	int revents)>.
602		698
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	699	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		700
605	This macro initialises the type-specific parts of a watcher. You need to	701	This macro initialises the type-specific parts of a watcher. You need to
…		…
640	=item bool ev_is_pending (ev_TYPE *watcher)	736	=item bool ev_is_pending (ev_TYPE *watcher)
641		737
642	Returns a true value iff the watcher is pending, (i.e. it has outstanding	738	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	739	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	740	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	741	C<ev_TYPE_set> is safe), you must not change its priority, and you must
646	libev (e.g. you cnanot C<free ()> it).	742	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		743	it).
647		744
648	=item callback = ev_cb (ev_TYPE *watcher)	745	=item callback ev_cb (ev_TYPE *watcher)
649		746
650	Returns the callback currently set on the watcher.	747	Returns the callback currently set on the watcher.
651		748
652	=item ev_cb_set (ev_TYPE *watcher, callback)	749	=item ev_cb_set (ev_TYPE *watcher, callback)
653		750
654	Change the callback. You can change the callback at virtually any time	751	Change the callback. You can change the callback at virtually any time
655	(modulo threads).	752	(modulo threads).
		753
		754	=item ev_set_priority (ev_TYPE *watcher, priority)
		755
		756	=item int ev_priority (ev_TYPE *watcher)
		757
		758	Set and query the priority of the watcher. The priority is a small
		759	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		760	(default: C<-2>). Pending watchers with higher priority will be invoked
		761	before watchers with lower priority, but priority will not keep watchers
		762	from being executed (except for C<ev_idle> watchers).
		763
		764	This means that priorities are I<only> used for ordering callback
		765	invocation after new events have been received. This is useful, for
		766	example, to reduce latency after idling, or more often, to bind two
		767	watchers on the same event and make sure one is called first.
		768
		769	If you need to suppress invocation when higher priority events are pending
		770	you need to look at C<ev_idle> watchers, which provide this functionality.
		771
		772	You I<must not> change the priority of a watcher as long as it is active or
		773	pending.
		774
		775	The default priority used by watchers when no priority has been set is
		776	always C<0>, which is supposed to not be too high and not be too low :).
		777
		778	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		779	fine, as long as you do not mind that the priority value you query might
		780	or might not have been adjusted to be within valid range.
		781
		782	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		783
		784	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		785	C<loop> nor C<revents> need to be valid as long as the watcher callback
		786	can deal with that fact.
		787
		788	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		789
		790	If the watcher is pending, this function returns clears its pending status
		791	and returns its C<revents> bitset (as if its callback was invoked). If the
		792	watcher isn't pending it does nothing and returns C<0>.
656		793
657	=back	794	=back
658		795
659		796
660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	797	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
681	{	818	{
682	struct my_io *w = (struct my_io *)w_;	819	struct my_io *w = (struct my_io *)w_;
683	...	820	...
684	}	821	}
685		822
686	More interesting and less C-conformant ways of catsing your callback type	823	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	824	instead have been omitted.
		825
		826	Another common scenario is having some data structure with multiple
		827	watchers:
		828
		829	struct my_biggy
		830	{
		831	int some_data;
		832	ev_timer t1;
		833	ev_timer t2;
		834	}
		835
		836	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		837	you need to use C<offsetof>:
		838
		839	#include <stddef.h>
		840
		841	static void
		842	t1_cb (EV_P_ struct ev_timer *w, int revents)
		843	{
		844	struct my_biggy big = (struct my_biggy *
		845	(((char *)w) - offsetof (struct my_biggy, t1));
		846	}
		847
		848	static void
		849	t2_cb (EV_P_ struct ev_timer *w, int revents)
		850	{
		851	struct my_biggy big = (struct my_biggy *
		852	(((char *)w) - offsetof (struct my_biggy, t2));
		853	}
688		854
689		855
690	=head1 WATCHER TYPES	856	=head1 WATCHER TYPES
691		857
692	This section describes each watcher in detail, but will not repeat	858	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	859	information given in the last section. Any initialisation/set macros,
		860	functions and members specific to the watcher type are explained.
694		861
		862	Members are additionally marked with either I<[read-only]>, meaning that,
		863	while the watcher is active, you can look at the member and expect some
		864	sensible content, but you must not modify it (you can modify it while the
		865	watcher is stopped to your hearts content), or I<[read-write]>, which
		866	means you can expect it to have some sensible content while the watcher
		867	is active, but you can also modify it. Modifying it may not do something
		868	sensible or take immediate effect (or do anything at all), but libev will
		869	not crash or malfunction in any way.
695		870
		871
696	=head2 C<ev_io> - is this file descriptor readable or writable	872	=head2 C<ev_io> - is this file descriptor readable or writable?
697		873
698	I/O watchers check whether a file descriptor is readable or writable	874	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	875	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	876	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	877	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	878	receiving events as long as the condition persists. Remember you can stop
		879	the watcher if you don't want to act on the event and neither want to
		880	receive future events.
703		881
704	In general you can register as many read and/or write event watchers per	882	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	883	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	884	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	885	required if you know what you are doing).
708		886
709	You have to be careful with dup'ed file descriptors, though. Some backends	887	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	888	(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	889	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	890	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	891	the same underlying "file open").
714		892
715	If you must do this, then force the use of a known-to-be-good backend	893	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	894	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	895	C<EVBACKEND_POLL>).
718		896
		897	Another thing you have to watch out for is that it is quite easy to
		898	receive "spurious" readyness notifications, that is your callback might
		899	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		900	because there is no data. Not only are some backends known to create a
		901	lot of those (for example solaris ports), it is very easy to get into
		902	this situation even with a relatively standard program structure. Thus
		903	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		904	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		905
		906	If you cannot run the fd in non-blocking mode (for example you should not
		907	play around with an Xlib connection), then you have to seperately re-test
		908	whether a file descriptor is really ready with a known-to-be good interface
		909	such as poll (fortunately in our Xlib example, Xlib already does this on
		910	its own, so its quite safe to use).
		911
719	=over 4	912	=over 4
720		913
721	=item ev_io_init (ev_io *, callback, int fd, int events)	914	=item ev_io_init (ev_io *, callback, int fd, int events)
722		915
723	=item ev_io_set (ev_io *, int fd, int events)	916	=item ev_io_set (ev_io *, int fd, int events)
724		917
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	918	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 |	919	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	920	C<EV_READ | EV_WRITE> to receive the given events.
728		921
729	Please note that most of the more scalable backend mechanisms (for example	922	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	923
731	for file descriptors, so you practically need to use non-blocking I/O (and	924	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	925
733	interface before doing I/O (XLib can do this), or force the use of either	926	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	927
735	problem. Also note that it is quite easy to have your callback invoked	928	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		929
740	=back	930	=back
741		931
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	932	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	933	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	934	attempt to read a whole line in the callback.
745		935
746	static void	936	static void
747	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	937	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
748	{	938	{
749	ev_io_stop (loop, w);	939	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	946	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	947	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	948	ev_loop (loop, 0);
759		949
760		950
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	951	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		952
763	Timer watchers are simple relative timers that generate an event after a	953	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	954	given time, and optionally repeating in regular intervals after that.
765		955
766	The timers are based on real time, that is, if you register an event that	956	The timers are based on real time, that is, if you register an event that
…		…
801	=item ev_timer_again (loop)	991	=item ev_timer_again (loop)
802		992
803	This will act as if the timer timed out and restart it again if it is	993	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	994	repeating. The exact semantics are:
805		995
		996	If the timer is pending, its pending status is cleared.
		997
806	If the timer is started but nonrepeating, stop it.	998	If the timer is started but nonrepeating, stop it (as if it timed out).
807		999
808	If the timer is repeating, either start it if necessary (with the repeat	1000	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	1001	C<repeat> value), or reset the running timer to the C<repeat> value.
810		1002
811	This sounds a bit complicated, but here is a useful and typical	1003	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	1004	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	1005	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	1006	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	1007	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	1008	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	1009	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.	1010	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1011	automatically restart it if need be.
		1012
		1013	That means you can ignore the C<after> value and C<ev_timer_start>
		1014	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1015
		1016	ev_timer_init (timer, callback, 0., 5.);
		1017	ev_timer_again (loop, timer);
		1018	...
		1019	timer->again = 17.;
		1020	ev_timer_again (loop, timer);
		1021	...
		1022	timer->again = 10.;
		1023	ev_timer_again (loop, timer);
		1024
		1025	This is more slightly efficient then stopping/starting the timer each time
		1026	you want to modify its timeout value.
		1027
		1028	=item ev_tstamp repeat [read-write]
		1029
		1030	The current C<repeat> value. Will be used each time the watcher times out
		1031	or C<ev_timer_again> is called and determines the next timeout (if any),
		1032	which is also when any modifications are taken into account.
819		1033
820	=back	1034	=back
821		1035
822	Example: create a timer that fires after 60 seconds.	1036	Example: Create a timer that fires after 60 seconds.
823		1037
824	static void	1038	static void
825	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1039	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
826	{	1040	{
827	.. one minute over, w is actually stopped right here	1041	.. one minute over, w is actually stopped right here
…		…
829		1043
830	struct ev_timer mytimer;	1044	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1045	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	1046	ev_timer_start (loop, &mytimer);
833		1047
834	Example: create a timeout timer that times out after 10 seconds of	1048	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	1049	inactivity.
836		1050
837	static void	1051	static void
838	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1052	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839	{	1053	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1062	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1063	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1064	ev_timer_again (&mytimer);
851		1065
852		1066
853	=head2 C<ev_periodic> - to cron or not to cron	1067	=head2 C<ev_periodic> - to cron or not to cron?
854		1068
855	Periodic watchers are also timers of a kind, but they are very versatile	1069	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1070	(and unfortunately a bit complex).
857		1071
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1072	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
…		…
950	Simply stops and restarts the periodic watcher again. This is only useful	1164	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1165	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	1166	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1167	program when the crontabs have changed).
954		1168
		1169	=item ev_tstamp interval [read-write]
		1170
		1171	The current interval value. Can be modified any time, but changes only
		1172	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1173	called.
		1174
		1175	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1176
		1177	The current reschedule callback, or C<0>, if this functionality is
		1178	switched off. Can be changed any time, but changes only take effect when
		1179	the periodic timer fires or C<ev_periodic_again> is being called.
		1180
955	=back	1181	=back
956		1182
957	Example: call a callback every hour, or, more precisely, whenever the	1183	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1184	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1185	potentially a lot of jittering, but good long-term stability.
960		1186
961	static void	1187	static void
962	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1188	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
966		1192
967	struct ev_periodic hourly_tick;	1193	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1194	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1195	ev_periodic_start (loop, &hourly_tick);
970		1196
971	Example: the same as above, but use a reschedule callback to do it:	1197	Example: The same as above, but use a reschedule callback to do it:
972		1198
973	#include <math.h>	1199	#include <math.h>
974		1200
975	static ev_tstamp	1201	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1202	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1204	return fmod (now, 3600.) + 3600.;
979	}	1205	}
980		1206
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1207	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1208
983	Example: call a callback every hour, starting now:	1209	Example: Call a callback every hour, starting now:
984		1210
985	struct ev_periodic hourly_tick;	1211	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1212	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1213	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1214	ev_periodic_start (loop, &hourly_tick);
989		1215
990		1216
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1217	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1218
993	Signal watchers will trigger an event when the process receives a specific	1219	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	1220	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	1221	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1222	normal event processing, like any other event.
…		…
1009	=item ev_signal_set (ev_signal *, int signum)	1235	=item ev_signal_set (ev_signal *, int signum)
1010		1236
1011	Configures the watcher to trigger on the given signal number (usually one	1237	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1238	of the C<SIGxxx> constants).
1013		1239
		1240	=item int signum [read-only]
		1241
		1242	The signal the watcher watches out for.
		1243
1014	=back	1244	=back
1015		1245
1016		1246
1017	=head2 C<ev_child> - wait for pid status changes	1247	=head2 C<ev_child> - watch out for process status changes
1018		1248
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1249	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).	1250	some child status changes (most typically when a child of yours dies).
1021		1251
1022	=over 4	1252	=over 4
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1260	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	1261	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	1262	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1263	process causing the status change.
1034		1264
		1265	=item int pid [read-only]
		1266
		1267	The process id this watcher watches out for, or C<0>, meaning any process id.
		1268
		1269	=item int rpid [read-write]
		1270
		1271	The process id that detected a status change.
		1272
		1273	=item int rstatus [read-write]
		1274
		1275	The process exit/trace status caused by C<rpid> (see your systems
		1276	C<waitpid> and C<sys/wait.h> documentation for details).
		1277
1035	=back	1278	=back
1036		1279
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1280	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1281
1039	static void	1282	static void
1040	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1283	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1041	{	1284	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1285	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1288	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1289	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1290	ev_signal_start (loop, &sigint_cb);
1048		1291
1049		1292
		1293	=head2 C<ev_stat> - did the file attributes just change?
		1294
		1295	This watches a filesystem path for attribute changes. That is, it calls
		1296	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1297	compared to the last time, invoking the callback if it did.
		1298
		1299	The path does not need to exist: changing from "path exists" to "path does
		1300	not exist" is a status change like any other. The condition "path does
		1301	not exist" is signified by the C<st_nlink> field being zero (which is
		1302	otherwise always forced to be at least one) and all the other fields of
		1303	the stat buffer having unspecified contents.
		1304
		1305	The path I<should> be absolute and I<must not> end in a slash. If it is
		1306	relative and your working directory changes, the behaviour is undefined.
		1307
		1308	Since there is no standard to do this, the portable implementation simply
		1309	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1310	can specify a recommended polling interval for this case. If you specify
		1311	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1312	unspecified default> value will be used (which you can expect to be around
		1313	five seconds, although this might change dynamically). Libev will also
		1314	impose a minimum interval which is currently around C<0.1>, but thats
		1315	usually overkill.
		1316
		1317	This watcher type is not meant for massive numbers of stat watchers,
		1318	as even with OS-supported change notifications, this can be
		1319	resource-intensive.
		1320
		1321	At the time of this writing, only the Linux inotify interface is
		1322	implemented (implementing kqueue support is left as an exercise for the
		1323	reader). Inotify will be used to give hints only and should not change the
		1324	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1325	to fall back to regular polling again even with inotify, but changes are
		1326	usually detected immediately, and if the file exists there will be no
		1327	polling.
		1328
		1329	=over 4
		1330
		1331	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1332
		1333	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1334
		1335	Configures the watcher to wait for status changes of the given
		1336	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1337	be detected and should normally be specified as C<0> to let libev choose
		1338	a suitable value. The memory pointed to by C<path> must point to the same
		1339	path for as long as the watcher is active.
		1340
		1341	The callback will be receive C<EV_STAT> when a change was detected,
		1342	relative to the attributes at the time the watcher was started (or the
		1343	last change was detected).
		1344
		1345	=item ev_stat_stat (ev_stat *)
		1346
		1347	Updates the stat buffer immediately with new values. If you change the
		1348	watched path in your callback, you could call this fucntion to avoid
		1349	detecting this change (while introducing a race condition). Can also be
		1350	useful simply to find out the new values.
		1351
		1352	=item ev_statdata attr [read-only]
		1353
		1354	The most-recently detected attributes of the file. Although the type is of
		1355	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1356	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1357	was some error while C<stat>ing the file.
		1358
		1359	=item ev_statdata prev [read-only]
		1360
		1361	The previous attributes of the file. The callback gets invoked whenever
		1362	C<prev> != C<attr>.
		1363
		1364	=item ev_tstamp interval [read-only]
		1365
		1366	The specified interval.
		1367
		1368	=item const char *path [read-only]
		1369
		1370	The filesystem path that is being watched.
		1371
		1372	=back
		1373
		1374	Example: Watch C</etc/passwd> for attribute changes.
		1375
		1376	static void
		1377	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1378	{
		1379	/* /etc/passwd changed in some way */
		1380	if (w->attr.st_nlink)
		1381	{
		1382	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1383	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1384	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1385	}
		1386	else
		1387	/* you shalt not abuse printf for puts */
		1388	puts ("wow, /etc/passwd is not there, expect problems. "
		1389	"if this is windows, they already arrived\n");
		1390	}
		1391
		1392	...
		1393	ev_stat passwd;
		1394
		1395	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1396	ev_stat_start (loop, &passwd);
		1397
		1398
1050	=head2 C<ev_idle> - when you've got nothing better to do	1399	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1400
1052	Idle watchers trigger events when there are no other events are pending	1401	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	1402	priority are pending (prepare, check and other idle watchers do not
1054	as your process is busy handling sockets or timeouts (or even signals,	1403	count).
1055	imagine) it will not be triggered. But when your process is idle all idle	1404
1056	watchers are being called again and again, once per event loop iteration -	1405	That is, as long as your process is busy handling sockets or timeouts
		1406	(or even signals, imagine) of the same or higher priority it will not be
		1407	triggered. But when your process is idle (or only lower-priority watchers
		1408	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	1409	iteration - until stopped, that is, or your process receives more events
1058	busy.	1410	and becomes busy again with higher priority stuff.
1059		1411
1060	The most noteworthy effect is that as long as any idle watchers are	1412	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.	1413	active, the process will not block when waiting for new events.
1062		1414
1063	Apart from keeping your process non-blocking (which is a useful	1415	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,	1425	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1426	believe me.
1075		1427
1076	=back	1428	=back
1077		1429
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1430	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1431	callback, free it. Also, use no error checking, as usual.
1080		1432
1081	static void	1433	static void
1082	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1434	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1083	{	1435	{
1084	free (w);	1436	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1441	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1442	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1443	ev_idle_start (loop, idle_cb);
1092		1444
1093		1445
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1446	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1447
1096	Prepare and check watchers are usually (but not always) used in tandem:	1448	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1449	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1450	afterwards.
1099		1451
		1452	You I<must not> call C<ev_loop> or similar functions that enter
		1453	the current event loop from either C<ev_prepare> or C<ev_check>
		1454	watchers. Other loops than the current one are fine, however. The
		1455	rationale behind this is that you do not need to check for recursion in
		1456	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1457	C<ev_check> so if you have one watcher of each kind they will always be
		1458	called in pairs bracketing the blocking call.
		1459
1100	Their main purpose is to integrate other event mechanisms into libev and	1460	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	1461	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	1462	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1463	coroutine library and lots more. They are also occasionally useful if
		1464	you cache some data and want to flush it before blocking (for example,
		1465	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1466	watcher).
1104		1467
1105	This is done by examining in each prepare call which file descriptors need	1468	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	1469	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	1470	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	1471	provide just this functionality). Then, in the check watcher you check for
…		…
1130	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1493	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.	1494	macros, but using them is utterly, utterly and completely pointless.
1132		1495
1133	=back	1496	=back
1134		1497
1135	Example: *TODO*.	1498	Example: To include a library such as adns, you would add IO watchers
		1499	and a timeout watcher in a prepare handler, as required by libadns, and
		1500	in a check watcher, destroy them and call into libadns. What follows is
		1501	pseudo-code only of course:
1136		1502
		1503	static ev_io iow [nfd];
		1504	static ev_timer tw;
1137		1505
		1506	static void
		1507	io_cb (ev_loop *loop, ev_io *w, int revents)
		1508	{
		1509	// set the relevant poll flags
		1510	// could also call adns_processreadable etc. here
		1511	struct pollfd *fd = (struct pollfd *)w->data;
		1512	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1513	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1514	}
		1515
		1516	// create io watchers for each fd and a timer before blocking
		1517	static void
		1518	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1519	{
		1520	int timeout = 3600000;
		1521	struct pollfd fds [nfd];
		1522	// actual code will need to loop here and realloc etc.
		1523	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1524
		1525	/* the callback is illegal, but won't be called as we stop during check */
		1526	ev_timer_init (&tw, 0, timeout * 1e-3);
		1527	ev_timer_start (loop, &tw);
		1528
		1529	// create on ev_io per pollfd
		1530	for (int i = 0; i < nfd; ++i)
		1531	{
		1532	ev_io_init (iow + i, io_cb, fds [i].fd,
		1533	((fds [i].events & POLLIN ? EV_READ : 0)
		1534	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1535
		1536	fds [i].revents = 0;
		1537	iow [i].data = fds + i;
		1538	ev_io_start (loop, iow + i);
		1539	}
		1540	}
		1541
		1542	// stop all watchers after blocking
		1543	static void
		1544	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1545	{
		1546	ev_timer_stop (loop, &tw);
		1547
		1548	for (int i = 0; i < nfd; ++i)
		1549	ev_io_stop (loop, iow + i);
		1550
		1551	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1552	}
		1553
		1554
1138	=head2 C<ev_embed> - when one backend isn't enough	1555	=head2 C<ev_embed> - when one backend isn't enough...
1139		1556
1140	This is a rather advanced watcher type that lets you embed one event loop	1557	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	1558	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	1559	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1560	fashion and must not be used).
…		…
1221		1638
1222	Make a single, non-blocking sweep over the embedded loop. This works	1639	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	1640	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1641	apropriate way for embedded loops.
1225		1642
		1643	=item struct ev_loop *loop [read-only]
		1644
		1645	The embedded event loop.
		1646
		1647	=back
		1648
		1649
		1650	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1651
		1652	Fork watchers are called when a C<fork ()> was detected (usually because
		1653	whoever is a good citizen cared to tell libev about it by calling
		1654	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1655	event loop blocks next and before C<ev_check> watchers are being called,
		1656	and only in the child after the fork. If whoever good citizen calling
		1657	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1658	handlers will be invoked, too, of course.
		1659
		1660	=over 4
		1661
		1662	=item ev_fork_init (ev_signal *, callback)
		1663
		1664	Initialises and configures the fork watcher - it has no parameters of any
		1665	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1666	believe me.
		1667
1226	=back	1668	=back
1227		1669
1228		1670
1229	=head1 OTHER FUNCTIONS	1671	=head1 OTHER FUNCTIONS
1230		1672
…		…
1318		1760
1319	To use it,	1761	To use it,
1320		1762
1321	#include <ev++.h>	1763	#include <ev++.h>
1322		1764
1323	(it is not installed by default). This automatically includes F<ev.h>	1765	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	1766	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.	1767	put into the C<ev> namespace. It should support all the same embedding
		1768	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1326		1769
1327	It should support all the same embedding options as F<ev.h>, most notably	1770	Care has been taken to keep the overhead low. The only data member the C++
1328	C<EV_MULTIPLICITY>.	1771	classes add (compared to plain C-style watchers) is the event loop pointer
		1772	that the watcher is associated with (or no additional members at all if
		1773	you disable C<EV_MULTIPLICITY> when embedding libev).
		1774
		1775	Currently, functions, and static and non-static member functions can be
		1776	used as callbacks. Other types should be easy to add as long as they only
		1777	need one additional pointer for context. If you need support for other
		1778	types of functors please contact the author (preferably after implementing
		1779	it).
1329		1780
1330	Here is a list of things available in the C<ev> namespace:	1781	Here is a list of things available in the C<ev> namespace:
1331		1782
1332	=over 4	1783	=over 4
1333		1784
…		…
1349		1800
1350	All of those classes have these methods:	1801	All of those classes have these methods:
1351		1802
1352	=over 4	1803	=over 4
1353		1804
1354	=item ev::TYPE::TYPE (object *, object::method *)	1805	=item ev::TYPE::TYPE ()
1355		1806
1356	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	1807	=item ev::TYPE::TYPE (struct ev_loop *)
1357		1808
1358	=item ev::TYPE::~TYPE	1809	=item ev::TYPE::~TYPE
1359		1810
1360	The constructor takes a pointer to an object and a method pointer to	1811	The constructor (optionally) takes an event loop to associate the watcher
1361	the event handler callback to call in this class. The constructor calls	1812	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	1813
1363	before starting it. If you do not specify a loop then the constructor	1814	The constructor calls C<ev_init> for you, which means you have to call the
1364	automatically associates the default loop with this watcher.	1815	C<set> method before starting it.
		1816
		1817	It will not set a callback, however: You have to call the templated C<set>
		1818	method to set a callback before you can start the watcher.
		1819
		1820	(The reason why you have to use a method is a limitation in C++ which does
		1821	not allow explicit template arguments for constructors).
1365		1822
1366	The destructor automatically stops the watcher if it is active.	1823	The destructor automatically stops the watcher if it is active.
		1824
		1825	=item w->set<class, &class::method> (object *)
		1826
		1827	This method sets the callback method to call. The method has to have a
		1828	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1829	first argument and the C<revents> as second. The object must be given as
		1830	parameter and is stored in the C<data> member of the watcher.
		1831
		1832	This method synthesizes efficient thunking code to call your method from
		1833	the C callback that libev requires. If your compiler can inline your
		1834	callback (i.e. it is visible to it at the place of the C<set> call and
		1835	your compiler is good :), then the method will be fully inlined into the
		1836	thunking function, making it as fast as a direct C callback.
		1837
		1838	Example: simple class declaration and watcher initialisation
		1839
		1840	struct myclass
		1841	{
		1842	void io_cb (ev::io &w, int revents) { }
		1843	}
		1844
		1845	myclass obj;
		1846	ev::io iow;
		1847	iow.set <myclass, &myclass::io_cb> (&obj);
		1848
		1849	=item w->set (void (*function)(watcher &w, int), void *data = 0)
		1850
		1851	Also sets a callback, but uses a static method or plain function as
		1852	callback. The optional C<data> argument will be stored in the watcher's
		1853	C<data> member and is free for you to use.
		1854
		1855	See the method-C<set> above for more details.
1367		1856
1368	=item w->set (struct ev_loop *)	1857	=item w->set (struct ev_loop *)
1369		1858
1370	Associates a different C<struct ev_loop> with this watcher. You can only	1859	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).	1860	do this when the watcher is inactive (and not pending either).
1372		1861
1373	=item w->set ([args])	1862	=item w->set ([args])
1374		1863
1375	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1864	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	1865	called at least once. Unlike the C counterpart, an active watcher gets
1377	automatically stopped and restarted.	1866	automatically stopped and restarted when reconfiguring it with this
		1867	method.
1378		1868
1379	=item w->start ()	1869	=item w->start ()
1380		1870
1381	Starts the watcher. Note that there is no C<loop> argument as the	1871	Starts the watcher. Note that there is no C<loop> argument, as the
1382	constructor already takes the loop.	1872	constructor already stores the event loop.
1383		1873
1384	=item w->stop ()	1874	=item w->stop ()
1385		1875
1386	Stops the watcher if it is active. Again, no C<loop> argument.	1876	Stops the watcher if it is active. Again, no C<loop> argument.
1387		1877
…		…
1392		1882
1393	=item w->sweep () C<ev::embed> only	1883	=item w->sweep () C<ev::embed> only
1394		1884
1395	Invokes C<ev_embed_sweep>.	1885	Invokes C<ev_embed_sweep>.
1396		1886
		1887	=item w->update () C<ev::stat> only
		1888
		1889	Invokes C<ev_stat_stat>.
		1890
1397	=back	1891	=back
1398		1892
1399	=back	1893	=back
1400		1894
1401	Example: Define a class with an IO and idle watcher, start one of them in	1895	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1408		1902
1409	myclass ();	1903	myclass ();
1410	}	1904	}
1411		1905
1412	myclass::myclass (int fd)	1906	myclass::myclass (int fd)
1413	: io (this, &myclass::io_cb),
1414	idle (this, &myclass::idle_cb)
1415	{	1907	{
		1908	io .set <myclass, &myclass::io_cb > (this);
		1909	idle.set <myclass, &myclass::idle_cb> (this);
		1910
1416	io.start (fd, ev::READ);	1911	io.start (fd, ev::READ);
1417	}	1912	}
1418		1913
		1914
		1915	=head1 MACRO MAGIC
		1916
		1917	Libev can be compiled with a variety of options, the most fundemantal is
		1918	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		1919	callbacks have an initial C<struct ev_loop *> argument.
		1920
		1921	To make it easier to write programs that cope with either variant, the
		1922	following macros are defined:
		1923
		1924	=over 4
		1925
		1926	=item C<EV_A>, C<EV_A_>
		1927
		1928	This provides the loop I<argument> for functions, if one is required ("ev
		1929	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1930	C<EV_A_> is used when other arguments are following. Example:
		1931
		1932	ev_unref (EV_A);
		1933	ev_timer_add (EV_A_ watcher);
		1934	ev_loop (EV_A_ 0);
		1935
		1936	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1937	which is often provided by the following macro.
		1938
		1939	=item C<EV_P>, C<EV_P_>
		1940
		1941	This provides the loop I<parameter> for functions, if one is required ("ev
		1942	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1943	C<EV_P_> is used when other parameters are following. Example:
		1944
		1945	// this is how ev_unref is being declared
		1946	static void ev_unref (EV_P);
		1947
		1948	// this is how you can declare your typical callback
		1949	static void cb (EV_P_ ev_timer *w, int revents)
		1950
		1951	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1952	suitable for use with C<EV_A>.
		1953
		1954	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1955
		1956	Similar to the other two macros, this gives you the value of the default
		1957	loop, if multiple loops are supported ("ev loop default").
		1958
		1959	=back
		1960
		1961	Example: Declare and initialise a check watcher, utilising the above
		1962	macros so it will work regardless of whether multiple loops are supported
		1963	or not.
		1964
		1965	static void
		1966	check_cb (EV_P_ ev_timer *w, int revents)
		1967	{
		1968	ev_check_stop (EV_A_ w);
		1969	}
		1970
		1971	ev_check check;
		1972	ev_check_init (&check, check_cb);
		1973	ev_check_start (EV_DEFAULT_ &check);
		1974	ev_loop (EV_DEFAULT_ 0);
		1975
		1976	=head1 EMBEDDING
		1977
		1978	Libev can (and often is) directly embedded into host
		1979	applications. Examples of applications that embed it include the Deliantra
		1980	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1981	and rxvt-unicode.
		1982
		1983	The goal is to enable you to just copy the neecssary files into your
		1984	source directory without having to change even a single line in them, so
		1985	you can easily upgrade by simply copying (or having a checked-out copy of
		1986	libev somewhere in your source tree).
		1987
		1988	=head2 FILESETS
		1989
		1990	Depending on what features you need you need to include one or more sets of files
		1991	in your app.
		1992
		1993	=head3 CORE EVENT LOOP
		1994
		1995	To include only the libev core (all the C<ev_*> functions), with manual
		1996	configuration (no autoconf):
		1997
		1998	#define EV_STANDALONE 1
		1999	#include "ev.c"
		2000
		2001	This will automatically include F<ev.h>, too, and should be done in a
		2002	single C source file only to provide the function implementations. To use
		2003	it, do the same for F<ev.h> in all files wishing to use this API (best
		2004	done by writing a wrapper around F<ev.h> that you can include instead and
		2005	where you can put other configuration options):
		2006
		2007	#define EV_STANDALONE 1
		2008	#include "ev.h"
		2009
		2010	Both header files and implementation files can be compiled with a C++
		2011	compiler (at least, thats a stated goal, and breakage will be treated
		2012	as a bug).
		2013
		2014	You need the following files in your source tree, or in a directory
		2015	in your include path (e.g. in libev/ when using -Ilibev):
		2016
		2017	ev.h
		2018	ev.c
		2019	ev_vars.h
		2020	ev_wrap.h
		2021
		2022	ev_win32.c required on win32 platforms only
		2023
		2024	ev_select.c only when select backend is enabled (which is enabled by default)
		2025	ev_poll.c only when poll backend is enabled (disabled by default)
		2026	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2027	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2028	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2029
		2030	F<ev.c> includes the backend files directly when enabled, so you only need
		2031	to compile this single file.
		2032
		2033	=head3 LIBEVENT COMPATIBILITY API
		2034
		2035	To include the libevent compatibility API, also include:
		2036
		2037	#include "event.c"
		2038
		2039	in the file including F<ev.c>, and:
		2040
		2041	#include "event.h"
		2042
		2043	in the files that want to use the libevent API. This also includes F<ev.h>.
		2044
		2045	You need the following additional files for this:
		2046
		2047	event.h
		2048	event.c
		2049
		2050	=head3 AUTOCONF SUPPORT
		2051
		2052	Instead of using C<EV_STANDALONE=1> and providing your config in
		2053	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2054	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2055	include F<config.h> and configure itself accordingly.
		2056
		2057	For this of course you need the m4 file:
		2058
		2059	libev.m4
		2060
		2061	=head2 PREPROCESSOR SYMBOLS/MACROS
		2062
		2063	Libev can be configured via a variety of preprocessor symbols you have to define
		2064	before including any of its files. The default is not to build for multiplicity
		2065	and only include the select backend.
		2066
		2067	=over 4
		2068
		2069	=item EV_STANDALONE
		2070
		2071	Must always be C<1> if you do not use autoconf configuration, which
		2072	keeps libev from including F<config.h>, and it also defines dummy
		2073	implementations for some libevent functions (such as logging, which is not
		2074	supported). It will also not define any of the structs usually found in
		2075	F<event.h> that are not directly supported by the libev core alone.
		2076
		2077	=item EV_USE_MONOTONIC
		2078
		2079	If defined to be C<1>, libev will try to detect the availability of the
		2080	monotonic clock option at both compiletime and runtime. Otherwise no use
		2081	of the monotonic clock option will be attempted. If you enable this, you
		2082	usually have to link against librt or something similar. Enabling it when
		2083	the functionality isn't available is safe, though, althoguh you have
		2084	to make sure you link against any libraries where the C<clock_gettime>
		2085	function is hiding in (often F<-lrt>).
		2086
		2087	=item EV_USE_REALTIME
		2088
		2089	If defined to be C<1>, libev will try to detect the availability of the
		2090	realtime clock option at compiletime (and assume its availability at
		2091	runtime if successful). Otherwise no use of the realtime clock option will
		2092	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2093	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2094	in the description of C<EV_USE_MONOTONIC>, though.
		2095
		2096	=item EV_USE_SELECT
		2097
		2098	If undefined or defined to be C<1>, libev will compile in support for the
		2099	C<select>(2) backend. No attempt at autodetection will be done: if no
		2100	other method takes over, select will be it. Otherwise the select backend
		2101	will not be compiled in.
		2102
		2103	=item EV_SELECT_USE_FD_SET
		2104
		2105	If defined to C<1>, then the select backend will use the system C<fd_set>
		2106	structure. This is useful if libev doesn't compile due to a missing
		2107	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2108	exotic systems. This usually limits the range of file descriptors to some
		2109	low limit such as 1024 or might have other limitations (winsocket only
		2110	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2111	influence the size of the C<fd_set> used.
		2112
		2113	=item EV_SELECT_IS_WINSOCKET
		2114
		2115	When defined to C<1>, the select backend will assume that
		2116	select/socket/connect etc. don't understand file descriptors but
		2117	wants osf handles on win32 (this is the case when the select to
		2118	be used is the winsock select). This means that it will call
		2119	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2120	it is assumed that all these functions actually work on fds, even
		2121	on win32. Should not be defined on non-win32 platforms.
		2122
		2123	=item EV_USE_POLL
		2124
		2125	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2126	backend. Otherwise it will be enabled on non-win32 platforms. It
		2127	takes precedence over select.
		2128
		2129	=item EV_USE_EPOLL
		2130
		2131	If defined to be C<1>, libev will compile in support for the Linux
		2132	C<epoll>(7) backend. Its availability will be detected at runtime,
		2133	otherwise another method will be used as fallback. This is the
		2134	preferred backend for GNU/Linux systems.
		2135
		2136	=item EV_USE_KQUEUE
		2137
		2138	If defined to be C<1>, libev will compile in support for the BSD style
		2139	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2140	otherwise another method will be used as fallback. This is the preferred
		2141	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2142	supports some types of fds correctly (the only platform we found that
		2143	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2144	not be used unless explicitly requested. The best way to use it is to find
		2145	out whether kqueue supports your type of fd properly and use an embedded
		2146	kqueue loop.
		2147
		2148	=item EV_USE_PORT
		2149
		2150	If defined to be C<1>, libev will compile in support for the Solaris
		2151	10 port style backend. Its availability will be detected at runtime,
		2152	otherwise another method will be used as fallback. This is the preferred
		2153	backend for Solaris 10 systems.
		2154
		2155	=item EV_USE_DEVPOLL
		2156
		2157	reserved for future expansion, works like the USE symbols above.
		2158
		2159	=item EV_USE_INOTIFY
		2160
		2161	If defined to be C<1>, libev will compile in support for the Linux inotify
		2162	interface to speed up C<ev_stat> watchers. Its actual availability will
		2163	be detected at runtime.
		2164
		2165	=item EV_H
		2166
		2167	The name of the F<ev.h> header file used to include it. The default if
		2168	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2169	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2170
		2171	=item EV_CONFIG_H
		2172
		2173	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2174	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2175	C<EV_H>, above.
		2176
		2177	=item EV_EVENT_H
		2178
		2179	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2180	of how the F<event.h> header can be found.
		2181
		2182	=item EV_PROTOTYPES
		2183
		2184	If defined to be C<0>, then F<ev.h> will not define any function
		2185	prototypes, but still define all the structs and other symbols. This is
		2186	occasionally useful if you want to provide your own wrapper functions
		2187	around libev functions.
		2188
		2189	=item EV_MULTIPLICITY
		2190
		2191	If undefined or defined to C<1>, then all event-loop-specific functions
		2192	will have the C<struct ev_loop *> as first argument, and you can create
		2193	additional independent event loops. Otherwise there will be no support
		2194	for multiple event loops and there is no first event loop pointer
		2195	argument. Instead, all functions act on the single default loop.
		2196
		2197	=item EV_MINPRI
		2198
		2199	=item EV_MAXPRI
		2200
		2201	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2202	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2203	provide for more priorities by overriding those symbols (usually defined
		2204	to be C<-2> and C<2>, respectively).
		2205
		2206	When doing priority-based operations, libev usually has to linearly search
		2207	all the priorities, so having many of them (hundreds) uses a lot of space
		2208	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2209	fine.
		2210
		2211	If your embedding app does not need any priorities, defining these both to
		2212	C<0> will save some memory and cpu.
		2213
		2214	=item EV_PERIODIC_ENABLE
		2215
		2216	If undefined or defined to be C<1>, then periodic timers are supported. If
		2217	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2218	code.
		2219
		2220	=item EV_IDLE_ENABLE
		2221
		2222	If undefined or defined to be C<1>, then idle watchers are supported. If
		2223	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2224	code.
		2225
		2226	=item EV_EMBED_ENABLE
		2227
		2228	If undefined or defined to be C<1>, then embed watchers are supported. If
		2229	defined to be C<0>, then they are not.
		2230
		2231	=item EV_STAT_ENABLE
		2232
		2233	If undefined or defined to be C<1>, then stat watchers are supported. If
		2234	defined to be C<0>, then they are not.
		2235
		2236	=item EV_FORK_ENABLE
		2237
		2238	If undefined or defined to be C<1>, then fork watchers are supported. If
		2239	defined to be C<0>, then they are not.
		2240
		2241	=item EV_MINIMAL
		2242
		2243	If you need to shave off some kilobytes of code at the expense of some
		2244	speed, define this symbol to C<1>. Currently only used for gcc to override
		2245	some inlining decisions, saves roughly 30% codesize of amd64.
		2246
		2247	=item EV_PID_HASHSIZE
		2248
		2249	C<ev_child> watchers use a small hash table to distribute workload by
		2250	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2251	than enough. If you need to manage thousands of children you might want to
		2252	increase this value (I<must> be a power of two).
		2253
		2254	=item EV_INOTIFY_HASHSIZE
		2255
		2256	C<ev_staz> watchers use a small hash table to distribute workload by
		2257	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2258	usually more than enough. If you need to manage thousands of C<ev_stat>
		2259	watchers you might want to increase this value (I<must> be a power of
		2260	two).
		2261
		2262	=item EV_COMMON
		2263
		2264	By default, all watchers have a C<void *data> member. By redefining
		2265	this macro to a something else you can include more and other types of
		2266	members. You have to define it each time you include one of the files,
		2267	though, and it must be identical each time.
		2268
		2269	For example, the perl EV module uses something like this:
		2270
		2271	#define EV_COMMON \
		2272	SV *self; /* contains this struct */ \
		2273	SV *cb_sv, *fh /* note no trailing ";" */
		2274
		2275	=item EV_CB_DECLARE (type)
		2276
		2277	=item EV_CB_INVOKE (watcher, revents)
		2278
		2279	=item ev_set_cb (ev, cb)
		2280
		2281	Can be used to change the callback member declaration in each watcher,
		2282	and the way callbacks are invoked and set. Must expand to a struct member
		2283	definition and a statement, respectively. See the F<ev.v> header file for
		2284	their default definitions. One possible use for overriding these is to
		2285	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2286	method calls instead of plain function calls in C++.
		2287
		2288	=head2 EXAMPLES
		2289
		2290	For a real-world example of a program the includes libev
		2291	verbatim, you can have a look at the EV perl module
		2292	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2293	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2294	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2295	will be compiled. It is pretty complex because it provides its own header
		2296	file.
		2297
		2298	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2299	that everybody includes and which overrides some configure choices:
		2300
		2301	#define EV_MINIMAL 1
		2302	#define EV_USE_POLL 0
		2303	#define EV_MULTIPLICITY 0
		2304	#define EV_PERIODIC_ENABLE 0
		2305	#define EV_STAT_ENABLE 0
		2306	#define EV_FORK_ENABLE 0
		2307	#define EV_CONFIG_H <config.h>
		2308	#define EV_MINPRI 0
		2309	#define EV_MAXPRI 0
		2310
		2311	#include "ev++.h"
		2312
		2313	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2314
		2315	#include "ev_cpp.h"
		2316	#include "ev.c"
		2317
		2318
		2319	=head1 COMPLEXITIES
		2320
		2321	In this section the complexities of (many of) the algorithms used inside
		2322	libev will be explained. For complexity discussions about backends see the
		2323	documentation for C<ev_default_init>.
		2324
		2325	All of the following are about amortised time: If an array needs to be
		2326	extended, libev needs to realloc and move the whole array, but this
		2327	happens asymptotically never with higher number of elements, so O(1) might
		2328	mean it might do a lengthy realloc operation in rare cases, but on average
		2329	it is much faster and asymptotically approaches constant time.
		2330
		2331	=over 4
		2332
		2333	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2334
		2335	This means that, when you have a watcher that triggers in one hour and
		2336	there are 100 watchers that would trigger before that then inserting will
		2337	have to skip those 100 watchers.
		2338
		2339	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2340
		2341	That means that for changing a timer costs less than removing/adding them
		2342	as only the relative motion in the event queue has to be paid for.
		2343
		2344	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2345
		2346	These just add the watcher into an array or at the head of a list.
		2347	=item Stopping check/prepare/idle watchers: O(1)
		2348
		2349	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2350
		2351	These watchers are stored in lists then need to be walked to find the
		2352	correct watcher to remove. The lists are usually short (you don't usually
		2353	have many watchers waiting for the same fd or signal).
		2354
		2355	=item Finding the next timer per loop iteration: O(1)
		2356
		2357	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2358
		2359	A change means an I/O watcher gets started or stopped, which requires
		2360	libev to recalculate its status (and possibly tell the kernel).
		2361
		2362	=item Activating one watcher: O(1)
		2363
		2364	=item Priority handling: O(number_of_priorities)
		2365
		2366	Priorities are implemented by allocating some space for each
		2367	priority. When doing priority-based operations, libev usually has to
		2368	linearly search all the priorities.
		2369
		2370	=back
		2371
		2372
1419	=head1 AUTHOR	2373	=head1 AUTHOR
1420		2374
1421	Marc Lehmann <libev@schmorp.de>.	2375	Marc Lehmann <libev@schmorp.de>.
1422		2376

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines